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International Space Station (ISS) => In-Space Hardware Section => Topic started by: clongton on 03/18/2008 04:25 pm

Title: Propellant Depots - General Discussion
Post by: clongton on 03/18/2008 04:25 pm
Over on the "Griffin Blames Atlas for Ares Dissent" thread the discussion of propellant depots has started to take on a life of its own, so I started this thread so that topic can be pursued and the original thread get back to Mike Griffin. I am going to ask Chris to grab all the relavant posts and move them here, then I'll post a link to here from that thread in case anybody goes looking for them.

Here's the original topic location:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=11786#M258022
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 05:09 pm
I don`t understand something. Someone still have to send all the fuel to the depot.

And if you send the fuel up to the depot by several launches, why not to send them straight to your empty spacecraft to fuel it? It will amount to the same number of dockings, only you dock with the spacecraft, and not with the depot.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/18/2008 05:35 pm
Eerie,
Quote
I don`t understand something. Someone still have to send all the fuel to the depot.

And if you send the fuel up to the depot by several launches, why not to send them straight to your empty spacecraft to fuel it? It will amount to the same number of dockings, only you dock with the spacecraft, and not with the depot.

That's a good question.  Here's the reasons I can think of right now:

1. The depot, since it doesn't need to move constantly back and forth from LEO to GEO/L*/LLO/etc, doesn't have anywhere near as much mass constraints.  Therefore you can add more insulation, you can add zero boiloff systems, in order to reduce the boiloff further than you could with a typical flight stage.

2. The depot can have more facilities (including tugs or robot arms) to make receiving and transferring propellants easier.  If you have to actually "dock" stages together for transfer, that's going to have a lot higher parasitic mass on your outbound vehicle than if you could be berthed to a station using robotic arms and such.

3. Related to two, the station can be built more robustly, such that a berthing mishap is less likely to damage your probably much more fragile outbound stage.  Now your outbound stage has only *one* docking event, even if your depot has tons of them--this makes it easier to take propellants in whatever sized package ends up being most economical.

There are probably other reasons, but those are a few.

The key thing to remember is that propellant depots don't have to be $20B ISS-sized monstrosities.  It may be cheaper to have an actual depot than to try and do without one.  If you do it right.  YMMV, etc.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/18/2008 05:38 pm
Quote
Eerie - 18/3/2008  2:09 PM

I don`t understand something. Someone still have to send all the fuel to the depot.

And if you send the fuel up to the depot by several launches, why not to send them straight to your empty spacecraft to fuel it? It will amount to the same number of dockings, only you dock with the spacecraft, and not with the depot.
It's a gas station. The depot owner keeps it full, just like the gas station owner keeps his tanks full. The expectation is that traffic will eventually require a steady stream of delivery from multiple propellant sources to fill the demand for propellant supply.

There will be lots of small spacecraft that take on 10-15mT of propellant. But there will also be the large mission spacecraft that take on 100mT at a time. That kind of supply can only be made available on-orbit from a depot that carries that much supply. Right now, nobody can deliver that in one shot; but lots of smaller launchers could do that, and a lot of people would make a lot of money doing it.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/18/2008 05:47 pm
It's practically useless to pretend a gas station model as there is only one customer, NASA. Nobody else has enough bucks to buy any significant amount of propellants in LEO every year.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 05:51 pm
Quote
clongton - 18/3/2008  1:38 PM

Quote
Eerie - 18/3/2008  2:09 PM

I don`t understand something. Someone still have to send all the fuel to the depot.

And if you send the fuel up to the depot by several launches, why not to send them straight to your empty spacecraft to fuel it? It will amount to the same number of dockings, only you dock with the spacecraft, and not with the depot.
It's a gas station. The depot owner keeps it full, just like the gas station owner keeps his tanks full. The expectation is that traffic will eventually require a steady stream of delivery from multiple propellant sources to fill the demand for propellant supply.

There will be lots of small spacecraft that take on 10-15mT of propellant. But there will also be the large mission spacecraft that take on 100mT at a time. That kind of supply can only be made available on-orbit from a depot that carries that much supply. Right now, nobody can deliver that in one shot; but lots of smaller launchers could do that, and a lot of people would make a lot of money doing it.

But by the same logic, you could just keep a full "depot" of rockets with fuel tanks on earth, and launch them when necessary. A big hangar with a hundred stored Falcon-9. When you need, you take 1\5\20, fill them with fuel and send one by one.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 05:56 pm
Quote
meiza - 18/3/2008  1:47 PM

It's practically useless to pretend a gas station model as there is only one customer, NASA. Nobody else has enough bucks to buy any significant amount of propellants in LEO every year.

Well, it could be International Space Depot...
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/18/2008 05:59 pm
Quote
meiza - 18/3/2008  2:47 PM

It's practically useless to pretend a gas station model as there is only one customer, NASA. Nobody else has enough bucks to buy any significant amount of propellants in LEO every year.
There are three customers: NASA, ESA and Russia. All would start making use of it once it is available. I would not be surprised to see India and Japan show interest, and once China gets its feet a little wetter, it will also begin to take advantage of it. Once the spacefaring nations begin to grasp what the availability of this technology means to their efforts, they will most assuredly wish to avail themselves of it.

What we are seeing here is the potential, very real potential, for a paradigm shift in how nations view their space efforts, and how smaller nations begin to view their “potential” participation.

The depot can be kept full by any combination of these plus other NGOs like LM, Boeing, and potentially SpaceX if they become successful. This is an enabling technology for everybody’s use.

Yes, it will begin slowly. But that will change. There is simply far too much advantage to making use of the depot to ignore it, especially if other nations are using it.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/18/2008 05:59 pm
Quote
Eerie - 18/3/2008  2:56 PM

Well, it could be International Space Depot...
As good a name as any.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/18/2008 06:25 pm
How much and how often are you envisioning for this international space depot (good name!)?

I'm afraid it doesn't work out. We are talking some tens of tonnes per year at most. Existing satellite launchers can put that up in one piece, no depot is needed.
ESA and RSA are drafting some lunar co-operation already which includes no heavy lift, but the missions are intermittent and small. These space agencies simply don't have enough money. NASA would have, but it has decided to put it on heavy lift so no depot there either.

Also, Europe has been burned before when it has relied on mission critical US hardware to achieve something in space, although there are many successes too.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 06:41 pm
Meiza, if Depot makes space flight cheaper, use rate may rise.

There must be some point where investment in space will start to pay off, after all.

Problem is, we don`t know...
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/18/2008 06:50 pm
What do you technical people view as minimum gauge issues in propellant depots? The docking hardware and sensors and maneuvering capability for the tankers costs mass, and the depot of course has to be insulated, possibly actively cooled and probably have even more docking hardware etc.

The major space powers have existing launchers that can put about 20 - 25 t to LEO (Ariane 5, Delta IV heavy, the future CZ-5). About 10 t of that could be propellant if you try to cram everything into one launch. ESA has looked at 23 t mini EDS stages, launched by Ariane and Angara rockets. Chain two and you can send a reasonable payload towards the moon.

So, I'd hunch that these things mean that a propellant depot is
-certainly only a useless complication if it holds only 10 t of propellants
-quite useless if it holds only 20 t
-breakeven and possibly redundant perhaps with 40 t of propellants (2 Ariane class launches)

So, if we assume that the players could afford an architecture using 40 t of LEO propellant once a year (the budgets would probably have to increase from current), what would the savings be in using a propellant depot instead of chained mini-EDS stages? You could perhaps get partners to launch propellant with small rockets 7 t or 10 t at a time if we want to up flight rates, meaning 4-6 propellant launches, or 8-12 flights a year. That's nice, probably a significant percentage in LEO equivalent mass compared to the total worldwide commercial launch market.

A Soyuz class 8 ton RLV would gain perhaps 12 flights per year from this.

I don't think it's very comparable to the 100-200 ton NASA market that would have transformed space launch.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/18/2008 06:58 pm
Lets try a mission that will be hard without a space depot - sending 100 metric tons to Low Lunar Orbit in one go.
ISP of RL-10-2 burning LOX & LH2 is 462
delta-v LEO to LLO = 4.04 km/s

m0 = m1 exp(delta-v/(ISP * g)) = 100 * exp( 4040 / (462 * 9.81)) = 244 mT
Mass of fuel = 244 - 100 = 144 mT

This option would require 3 launches in a short timescale without a fuel depot.
I am not certain that KSC is set up for machining gunning off Ares-V/J-232 rockets.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/18/2008 07:03 pm
No one pretends that this will be an easy transition or without its false starts. The United States, Russia, ESA, China, India and Japan will all eventually make use of the capability, whether by using International depots or native ones, but most likely by a combination of the two. It will be a time-consuming process, not a reportable “event”.

Missions are sized what they are today because that’s what the available launch vehicles will support. The prime driving force behind mission limitation is the requirement to carry the mission propellant up the earths gravity well together with the mission spacecraft, a mass that typically accounts for anywhere from 50% to 80% of the total mission mass. Eliminating the necessity to do that will transform the way mission planners design their spacecraft. Making that transformation will take time. This will not happen overnight.

A prime example of how this depot architecture could be of near term value is the Mars Sample Return mission. The mission planners are having a very difficult time of it trying to match everything they need to make the mission a minimum success with the lift capacity of the available launch vehicles. They will pull this off, but the mission capabilities will be diminished by the necessity of carrying their mission propellant up with the spacecraft. This problem would be totally eliminated if a depot were available for the spacecraft to fly to before departing for Mars. The mission planners would be able to concentrate more on creating capability than on down-sizing to the launch vehicle.

That’s just a single example that pops to mind. I’m sure if I thought about it there would be others as well. But as time moves forward, and new missions are planned (a long and time-consuming process), the availability of a depot will begin to take on more and more significance in how missions are put together. Possessing the ability to use the launch vehicle to loft the spacecraft instead of spacecraft and propellant will change the face of exploration forever. Purchasing the propellant on-orbit will always be more expensive than purchasing the propellant on the ground, but the tradeoff is the ability to create spacecraft that are freed from the necessity of including their mission propellant in their liftoff weight. Spaceflight will never be the same again.

Edit: Just did a quick calculation on a particular launch system, no names being mentioned because I do NOT want to change the topic, but as a second example ONLY, if the current 2-launch solution to the moon were to have a propellant depot available, the mission could be done with a single launch. Not only that, but the size of the mission works out thus:
18.6mT EDS
20.2mT CEV
182.0mT LSAM gross
231.0mT depot propellant
All pushed thru TLI at a dV of 3150 meters per second
That puts an approximate 60mT LSAM on the lunar surface, 3x NASA's desired target for Ares-V mission.

Please note that these numbers are "ballpark" numbers, not exact, but they are not far off what "exact" numbers would produce.

That's an example of how a depot can completely change the dynamics of space exploration. Any launch vehicle can see these types of efficiencies of scale if they make use of a depot architecture.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/18/2008 07:35 pm
Quote
clongton - 18/3/2008  9:03 PM

A prime example of how this depot architecture could be of near term value is the Mars Sample Return mission. The mission planners are having a very difficult time of it trying to match everything they need to make the mission a minimum success with the lift capacity of the available launch vehicles. They will pull this off, but the mission capabilities will be diminished by the necessity of carrying their mission propellant up with the spacecraft. This problem would be totally eliminated if a depot were available for the spacecraft to fly to before departing for Mars. The mission planners would be able to concentrate more on creating capability than on down-sizing to the launch vehicle.

I wonder if a firm could charge the Mars Sample Return say 90% of the cost of building the fuel depot?  Then they would only need a second sale to complete paying for the construction and to make a profit.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 07:44 pm
Clongton, again, if your LV is too small, why not launch two? It will be the same thing exactly, only you won`t need to create the fuel depot first.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/18/2008 07:45 pm
Quote
Eerie - 18/3/2008  4:44 PM

Clongton, again, if your LV is too small, why not launch two? It will be the same thing exactly, only you won`t need to create the fuel depot first.
Eerie - see the edit to my last post.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 08:14 pm
I still don`t get it.

At some point, you send rockets with tanks, to fuel the depot, right? You can`t avoid it.

Why don`t you just leave those tanks in a special orbit? You will get lots of small depots instead of a big one, and spare building a dedicated spacestation. Your spacecraft then will suck fuel from them in turn, until it is fueled, and the empty tanks will be deorbited, as they will anyway, even if the depot exists.

Of course, you could just keep all those rockets on Earth and launch them when necessary. This way, you store the fuel on Earth, which is much easier (because you can just create it on the spot ). :)

Problem is, both approaches needs MORE LAUNCHES. Once you will have MORE LAUNCHES, you can build depots, shmepost and whatever. It is not about depot at all, but about economy of scale...
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/18/2008 08:19 pm
Quote
Eerie - 18/3/2008  5:14 PM

I still don`t get it.

At some point, you send rocket to fuel the depot, right? You can`t avoid it.

Why don`t you just leave those tanks in a special orbit? You will get lots of small depots instead of a big one, and spare building a dedicated spacestation.

Of course, you could just keep all those rockets on Earth and launch them when necessary...
When you go to a gas station with your car, do you just fill your tank from the pump, or do you go all around the property picking up 1 liter containers, one at a time and dumping them into your tank and then going to find the next one and dumping it into the tank, and the next one and dumping it into the tank, and the next one and dumping it into the tank, and the next one and dumping it into the tank, and the next one and dumping it into the tank and so on etc, etc, etc?

It's a gas station, not a warehouse. And it is not a spacestation; it is unmanned and fully automated.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 08:26 pm
Quote
clongton - 18/3/2008  4:19 PM
When you go to a gas station with your car, do you just fill your tank from the pump, or do you go all around the property picking up 1 liter containers, one at a time and dumping them into your tank and then going to find the next one and dumping it into the tank, and the next one and dumping it into the tank, and the next one and dumping it into the tank, and the next one and dumping it into the tank, and the next one and dumping it into the tank and so on etc, etc, etc?

It's a gas station, not a warehouse. And it is not a spacestation; it is unmanned and fully automated.

Entirely wrong analogy. Gas station is fueled by huge trucks or by pipes. In translation to space, by Super Heavy LV or by Space Elevator.

Space depot will be fueled by "1 liter containers", because fueling it by Super Heavy LV is pointless - with it you can just lift your spacecraft already fueled.

So it is actually easier to fuel directly by "1 liter containers", without bringing them through the Depot first. "Cut the middleman", you know?
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/18/2008 08:32 pm
It is definitely about economies of scale.

Initially, you just want to launch fuel for any given mission with that mission.   You don't explicitly need the depot to do that.   Agreed.

But to grow the architecture significantly, or to bring in partnership contributions which aren't just simple cash, there aren't many things in an Exploration architecture allows which are worthwhile considering.

But lifting half the initial mass at the start of the mission is a significant contribution which is *very* achievable for any other space faring nation out there.

With that capability, we can then also begin to create new architectures the initial one is incapable of supporting.

These are two cases where the Depot Architecture makes a worthwhile impact.


As an aside, I think that the *active* involvement of foreign partners into missions can have far greater advantages than just for the space missions themselves.

Space has historically been just about the only area where even massively opposing countries (USA and USSR being the prime example) have been able to find common ground and common purpose.

Apollo-Soyuz, MIR-Shuttle and ISS have all been examples of how nations can cooperate to the greater benefit of us all.   Sure, ISS isn't the best example, but it has achieved something very special - it brought together a large collection of nations under one banner in the first 'baby steps' attempt humanity has ever tried, in order to create a permanent human presence in space - and essentially it is succeeding, albeit over budget and over schedule.    The principle is the more important thing though.

The precedent of such wide-spread international cooperation is ultimately going to be more important than the actual dollar/yen/Euro/Pound value of this first project.   ISS should be considered as a development project - a pathfinder project.   In that light, it has been very successful and has taught us an enormous amount.

The mistakes of ISS obviously need to be learned, so they can be avoided in the future.   But from this starting point we are ALL in a very strong position to create the next generation of cooperative international effort - this time in a far more affordable fashion.

The VSE/USSEP offers a platform potentially capable of taking not just the USA, but "all mankind" out to the stars - Apollo's dream finally realized.

That's not a bad target for all these cooperating nations to get behind IMHO.   I think almost every other nation in the world would like the chance to really take part, and send members of their nation along, just as long as the cost isn't prohibitively high.

A Propellant Depot, continually filled by international partners, offers a very valuable form of participation and contribution towards each mission which every one of those nations are capable of providing, whether they have a domestic space program or not.

And the beauty is that the USA can still retain all of the key elements needed to perform the missions regardless of international cooperation - definitely something the USA will not want to give up.


Perhaps the tangible benefits are difficult to identify in the realm of "international cooperation", but I think we could all agree that anything which bring countries together, especially competing and potentially conflicting countries, into something significant and beneficial to us all is a worthwhile goal we should pursue.

PD is just one option which fits this quite nicely.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 08:44 pm
Kraisee, you need a REASON for the expansion first. You can`t build the Depot before there are any plans to use it.

I suppose commercial space tourism may be such a reason. But it will come first. THEN, after space tourism already exists, Depot may be built to make it cheaper\easier.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/18/2008 08:59 pm
The requirement we have identified in the DIRECT work is based upon the number of missions we can launch from KSC.

We can launch about 16 launches per year on the infrastructure and budget being allocated for Ares - supporting up to 8 Lunar missions per year (each mission uses one Crew/Cargo flight & one Propellant flight) without a Propellant Depot architecture.

To launch more will require both additional infrastructure and budget.

Or we need to change the paradigm somehow.

PD allows us to remove the requirement for some of those launches (the Propellant ones) and replace them via international partnerships.

This free's up resources and cash here in the US to pay for other things.

If we can 'farm out' the Propellant flights, and spend the money building extra spacecraft instead (fixed costs already paid, only additional per-unit costs need to be covered) we can switch over to launching, say 12 spacecraft launches per year (some LV money goes to pay for the extra LSAMs), with international partners essentially providing all of the matching Propellant flights - making the equivalent of 24 launches - a 50% increase in capability.

And the US Budget for the program has not required any increase to get this improvement.


In the greater picture, a Mars mission would be the equivalent to about 5 Lunar missions, so with International cooperation we could have a program flying up to 7 Lunar missions at the same time as also having a Mars mission fly.

This is the basis of a truly robust expansion of humanity into space.   It isn't Moon or Mars or NEO - its Moon and Mars and NEO's, all at the same time.

Even half this maximum flight rate (at significantly less cost than Ares I might add), would still be robust and affordable.

But you can't do this if the International Partners never take up some of the cost strain.   And history shows that foreign countries don't easily part with just cash in return for flights on Shuttle.   Cold hard cash has not worked.   We need something else.   ISS shows they will pay for hardware and flights.   So lets use that willingness to everyone's advantage.

And launching Propellant isn't all that hard.   It is therefore quite achievable and affordable for any - and all - partners.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 09:08 pm
I still don`t see what the Depot has to do with the Paradigm. You could use Depot money to enlarge the infrastructure and launch more per year.

Yes, international cooperation is (arguably) good, and more launches is good. But this thread is not about that. It is about the Depot, and I can`t see how the Depot alone can revolutionize space industry.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/18/2008 09:25 pm
Also, no matter what the International Partners are asked to do - bring fuel or develop a lander - it will invariably demand them to PAY MORE. Once you find a way to make them do that, everything else is peanuts.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/18/2008 10:03 pm
Quote
clongton - 18/3/2008  9:03 PM
Missions are sized what they are today because that’s what the available launch vehicles will support.

They're limited by money.

For example ESA uses the Soyuz launcher for many missions since it's much cheaper than Ariane 5 - and most of the costs are in the cost of the payload.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/18/2008 10:07 pm
Ross, you get into crazy territory like more than 8 lunar missions per year with Directs to justify a depot.
In all other cases a depot filled by others will just reduce the flight rate of direct / whatyouhave NASA custom heavy lifter and not save much money at all.
Title: Re: Propellant Depots - General Discussion
Post by: on 03/18/2008 10:25 pm
The strategic value of the PD is much larger than the ISS was, plus it is coming at a time when soon to be new space fairing nations (including but not limited to China and India) need to make certain decisions.

They mirror the decisions the US has to make about its priorities - do each want to build competitive HLV capacity or not. Economic analysis does not support either RLV or HLV in the near future. With a PD, this pressing issue gets postponed til it is really needed (and economically justified).

It puts China in a double bind, and makes it far more likely that they will sign the agreements and also become an ISS partner. For again they increasingly fall behind what they can do as a country or in cooperation with one or two countries. This would come at a time when they are strapped in pushing out a next generation launch vehicle, and can look to the troubles that Russia has had with developing Angara and getting off the hypergolics.

Yes other countries can do PD's , just as they can do space stations, but they won't rush to, because like the ISS, once you have something in place, its easier to leverage the one that's present because all the overhead that isn't shared to have your own. Also, its actually easier to deal for props than something like ISS participation, because there may not be any ongoing requirement to maintain, just  a series of on-shot deals.

And as for usage, realize its a changing game with a PD in place. LEO capacity of launchers to get the payload to the PD drives the kinds of missions any government or commercial interest might have. The ability to move from LEO to GTO effectively might move all the commercial business thru a PD simply due to competitive pressure alone.
Title: Re: Propellant Depots - General Discussion
Post by: Smatcha on 03/18/2008 10:51 pm
The location of the depot is also an important question if international participation is desired.  Remember the lowest orbital inclination you can rendezvous with is equal to or lower than your launch site Latitude without serious plane change penalties.  For example if the depot was at 28.5 Russia could not dock with it from their current launch sites.  EML1 or EML2 on the other hand have at least one departure window from every point on the Earth surface every 24 hours.  While there is a plane change required from most launch sites they can occur at very low apogee velocities and can be done in coordination with EML1 or EML2 insertion burn.

If we established 28.5 as the location based on KSC then nations would need to launch from 28.5 or below to provide propellant.
Title: Re: Propellant Depots - General Discussion
Post by: mike robel on 03/18/2008 11:11 pm
Quote
A_M_Swallow - 18/3/2008  3:58 PMLets try a mission that will be hard without a space depot - sending 100 metric tons to Low Lunar Orbit in one go.ISP of RL-10-2 burning LOX & LH2 is 462delta-v LEO to LLO = 4.04 km/sm0 = m1 exp(delta-v/(ISP * g)) = 100 * exp( 4040 / (462 * 9.81)) = 244 mTMass of fuel = 244 - 100 = 144 mTThis option would require 3 launches in a short timescale without a fuel depot.I am not certain that KSC is set up for machining gunning off Ares-V/J-232 rockets.
In spite of all the discussion, I still don't get this PD stuff.  :)  So let us examine the above requirement.OK, let us examine this 100 Ton fuel requirement.100 Tons = 90,718 KGCost of LH2/KG = 0.335Cost of LOX/GL = 0.22Average Cost = 0.275Cost of Fuel = .275 * 90718 = $24,947 ProductionAtlas V Payload = 20,500Atlas V required = 5Atlas V Cost / Launch = 192,000,0005 Atlas V =  $960,000,000total Campaign Cost (Launches + Fuel) = 960,024,947Profit (assume profit will be regulated by US government to 15% - pick your own figure.  If you let law of supply and demand go, profit could easily be 100% or more.)144,034,742Total Campaign Cost = 1,104,028,689 dollars.Fuel cost / KG =  12, 169.Ross' estimate for a Jupiter 232 Launch = 496,833,333, but it carries a 105,895 KG payload and is 50% cheaper.So, it seems to me, in this case, that if we assume the payload to be delivered to the moon is launched on a Jupter 232 and we can orbit the fuel on another Jupiter 232, we have accompished the whole mission with 2 launches, for about the same price, and the launch campaign is much simpler.Of course, we would have to have the capability to either fire off 5 Atlas V in very short order or 2 Jupiter 232.  However, if we are building Jupiters, then Pad 39A and B can both support launches and we demonstrated on Skylab we can launch vehicles from both pads at a relatively short order.What have I missed in my very cursory analysis?
Title: Re: Propellant Depots - General Discussion
Post by: mike robel on 03/18/2008 11:27 pm
Chuck said " Not to put too fine a point on it, but by way of example, the Jupiter-232 can do the entire ESAS lunar mission, with Global Access and Anytime Return, in a SINGLE  launch, if it can fill its mission tanks at a depot rather than on the ground. Without the depot, it takes 2 launch vehicles, with the mission elements divided among them, that must rendezvous in LEO before proceding to the moon. Even accounting for paying more for the propellant on-orbit, that single-launch solution will cost far less than the 2-launch solution flying all its own propellant."

But, as I demonstrate in my above example, we either need 1 Jupiter 232 Launch and 5 Atlas V launches OR 2 Jupiter 232 Launches.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/18/2008 11:58 pm
Quote
mike robel - 18/3/2008  8:27 PM

But, as I demonstrate in my above example, we either need 1 Jupiter 232 Launch and 5 Atlas V launches OR 2 Jupiter 232 Launches.

What you're missing is what I get to do with my propellant. If I drag it up with my spacecraft, I only have 25% left to do my mission with. If I buy it on orbit, I get to use it all for the mission. That is not included in your figures. You're trying to make it come out as if it were economically better or not. That's not the point.

Yes, 1xJ-232 + 5xAtlas-V. but we don't count the costs of the Atlas-V flights because they are not our costs. The ONLY thing we pay for from the Atlas flights is the propellant payload they deliver. It could be 5xAtlas, 10xFalcon-9, 7xSoyuz, or 50xBalloon; we don't care what brings up the propellant. We just buy the propellant. We pay a premium for it, but we buy it at the mission starting point, not the garage.

It's just like buying gasoline at a filling station. I could care less how many tankers, pickup trucks or station wagons it takes for the station owner to fill his storage tanks. I just buy the gas. He operates on completely different economies of scale than I do so the cost of the gas to me is very different than if I were dragging a 500 gallon tank of gasoline around with me hitched to my ball hitch trailer hitch. The trade off is that I only need to launch a single spacecraft to do my mission, not 2. I can purchase more propellant at the depot than I can drag up thru the gravity well. If I drag it all up myself on 2xJupiter launches, I will have used at least 75% of it just to get there, leaving me only 25% of the original propellant load to do my mission with. But at the depot I can fill my tanks and go thru TLI with 100% of the propellant load. I can't do that if I launch my propellant WITH my spacecraft because I burn 3/4 of it up just to get to LEO. The depot enables me to go to the gas station, fill my tanks and start my mission with full tanks. It's not always about the COST of the propellant. I know I will pay more for it in orbit than on the ground, but by buying it in orbit, I get to use ALL of it for the mission, instead of burning 3/4 of it just to get to the starting line. The depot lets me do more with my spacecraft, that I can't otherwise do. Do I pay for the propellant? Yes, I do, and I pay more for it than if I bought it on the ground, but now I get to use all of it for the actual mission, something I can't do with propellant that goes up with the spacecraft.
Title: Re: Propellant Depots - General Discussion
Post by: mike robel on 03/19/2008 12:34 am
Chuck,

OK, I see what I missed.  Thanks for that.  But you said "Yes, 1xJ-232 + 5xAtlas-V. but we don't count the costs of the Atlas-V flights because they are not our costs. The ONLY thing we pay for from the Atlas flights is the propellant payload they deliver. "

This is not true.  When you buy a gallon of gas at the gas station, you are paying for refining it, storing it, transporting it, the drivers pay, the gas station owners pay, and some of his rent/mortage, etc., plus his (very slim) profit on sellilng you a gallon of gas.  If you want to get the payload to orbit, you are going to pay for all that:  Launch vehicle costs, launch costs, propellent cost, and profit.  They are not going to give that fuel away to you for the cost of the fuel.  And, like I said, if the laws of supply and demand are allowed to function, then you will be paying a lot more than 15% profit to them because you are the only customer and there will be a limited number of suppliers.

And, the 2nd 232 puts 100tons of fuel into orbit and burns none of it.  You only burn only what it takes to get your primary payload into orbit, not 3/4s of the fuel that is being carried as cargo.
Title: Re: Propellant Depots - General Discussion
Post by: on 03/19/2008 12:53 am
The other aspect of this is the second stage is reused as the transfer stage, so the vehicle is simpler. Which is very attractive also for more recent launchers/countries.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/19/2008 01:17 am
Quote
clongton - 19/3/2008  1:58 AM
What you're missing is what I get to do with my propellant. If I drag it up with my spacecraft, I only have 25% left to do my mission with. If I buy it on orbit, I get to use it all for the mission. That is not included in your figures. You're trying to make it come out as if it were economically better or not. That's not the point.

Part of what Mike Robot is saying is that the second J-232 has a cost of
$496,833,333 / 105,895 KG =  $4, 692 per KG

The depot would charge NASA $12, 169 per KG

If the figures are realistic NASA may not wish to pay twice the price.

Using 10 Falcon-9 I estmate $7, 716 per kilogram.  This assumes that the private sector has to  carry the construction cost of the propellent depot.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/19/2008 01:18 am
Quote
mike robel - 18/3/2008  9:34 PM

And, the 2nd 232 puts 100tons of fuel into orbit and burns none of it.  You only burn only what it takes to get your primary payload into orbit, not 3/4s of the fuel that is being carried as cargo.
Mike, the 2nd stage is not a delivered payload, it actually completes the ascent to orbit. It does that by burning off a significant portion of its own propellant load. By the time it reaches orbit, there is just enough left for us to close the ESAS mission, no more. Most of the 2nd stage propellant was burned getting to orbit. That's what's so great about the depot. We get to refill it so the lunar mission can begin at TLI with full tanks.

The only way a full tank would be delivered on the launch vehicle is if it were a completely separate stage, that only used enough of the propellant to circularize the orbit, a 3rd stage if you will. That would be a Jupiter-3XX, not a Jupiter-232. We have no plans for a 3-stage Jupiter at this time. Our goal was to show that we could actually do ESAS with the 2-stage launch vehicle that ESAS required.

Yes, of course we pay for the delivery method, you're right, but that is partially offset by the completely different economies of scale from the depot suppliers. When I said that we pay more for the propellant per mT on orbit than we do on the ground, that difference is what picks up the cost. I could have been a little clearer about that.

But now we're starting to do what I do NOT want to do: get specific about the Jupiter. Please, anything further about Jupiter should go over to the Direct thread. Let's keep this one about Propellant depots. It is such an enabling concept that there is a lot we can explore about it. For example, does anyone have ideas they would like to share on how propellant transfer would occur from tanker to depot, and from depot to mission stage? What about boiloff control? How should we control it? These and other depot-specific topics, please.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/19/2008 01:20 am
I suspect the figures are a little different for a depot at EML2.  Does anyone have an estimated development and launch cost of a SEP tug with say a 20 mT payload?
Title: Re: Propellant Depots - General Discussion
Post by: mike robel on 03/19/2008 01:24 am
Chuck,Once again I am a little lost.  If a 232 can put 105,00 KG into orbit when the payload is a CEV + LSAM, why can't one put 105,000 KG into orbit when the payload is a fuel tank with, as you say, a small engine to circulize the orbit and stabalize the tank?  Then the whole fuel payload would be available to refuel?I am not trying to drive this to Jupiter, but to examikng the cost of orbiting the depot, hence my orginal computation based on 5 Atlas V launches and how the same effect is carried out by a single Jupiter.I'm done.  :)
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/19/2008 01:54 am
Given boil-off issues, is there any advantage to LOX / kerosene engines for a reusable lunar lander?

It seems to me that the choice of H2 as the fuel to be stockpiled at a depot (especially an EML-2 depot) is far from obvious. But with kerosene from Earth and lunar LOX (from the moon, of course) sending some tanks of kerosene on a long slow SEP ride along a Belbruno trajectory would be perfectly acceptable.

Title: Re: Propellant Depots - General Discussion
Post by: mike robel on 03/19/2008 01:56 am
Rough concept of the depot.  11 docking ports for LH2, LOX, and Helium gas (in the proper proprtion to fill a fuel tank).  Two probes somewhat like a KC-45 tanker fueling probe to connect to the stage to be refueled.  A small engine - about like a shuttle OMS to maintain the orbit, burning LOX/LH2, with an RCS system.

Fuel transfer to be by pressurized feed from the tanks holding the helium gas to move the propellent from the tanks to the rocket stage.  Robotic arms controlled by humans from the spacecraft being refueled, telepresense from Earth, or computer with human monitoring?  Maybe easier once we have cargo delivery to ISS worked out with multiple types of cargo carriers.

No idea how much gas that would take?  Would gasous nitrogen work instead of helium?  Would straight pumps work?  We re taking huge quanties of fuel here, not like topping up the ISS tanks.

I guess we might need a sun shade like skylab?  Perhaps flexible/retractable so it can be furled while spacecraft dock with it?

Micrometeroid protection a necessity.  Radiators like the ISS to get rid of excess heat?
Title: Re: Propellant Depots - General Discussion
Post by: MichaelF on 03/19/2008 02:08 am
Unattended depots? Maintenance/PMCS/Troubleshooting comes from where?

This would be a giant concern if someone was betting their $Billion+ probe or mission on their being fuel ready to go....

Secondly, where are these fuel-intensive missions headed?  There are none (nor any requirement for such) in the forseeable future.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/19/2008 02:13 am
Wouldn't micro-gravity transfers of cryogenic fuels (H2 in particular) be a real bleep to accomplish?

Dry, rocket engines are rather light. An RL-10B-2 only masses ~664 pound (dry).

Rather than pump fuel as the Air Force does from a tanker to an F-15 (non-cryo fuel, inside the atmosphere, with gravity) why not stockpile Earth-built Centaur stages (or something similar) at the depot and simply swap out the entire propulsion module?

If it is a crewed depot, the engines that are turned in are cleaned and refurbished and mated to another filled fuel tank (filled at the depot's leisure rather than in "underway replenishment" mode) prior to the arrival of a vessel needing to tank up on fuel.

This way tanks and engines could be thoroughly inspected between uses.

= = =

What types of spacecraft do you foresee using a depot? Since on orbit fuel transfer has yet to be invented perhaps it would be easier to invent modular spacecraft that permit rapid swapping out and replacement of filled fuel tanks  (like glass milk bottles) or filled fuel tanks pre-mated to fully inspected and refurbished engines.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/19/2008 03:00 am
Quote
MichaelF - 19/3/2008  4:08 AM

Secondly, where are these fuel-intensive missions headed?  There are none (nor any requirement for such) in the forseeable future.

The missions are headed to the Moon and Mars mostly.  Human transfer vehicles, manned landers and cargo landers are the vehicles that need to use chemical fuel.

As for the shortage of missions that is one of the public embarrassments we are trying to fix.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/19/2008 04:27 am
Quote
MichaelF - 18/3/2008  11:08 PM

Unattended depots? Maintenance/PMCS/Troubleshooting comes from where?
From the ground, like they do now for ISS. You use the RMS and an SPDM to swap out ORUs of any of the systems, including things like docking collars, tanks, cooling systems, RMS, whatever.

We showed we could do this for the Hubble Servicng Mission using SPDM to remove instruments that were never designed to be opened on orbit. Surely we could plan to do it for everything on the spacecraft if given the chance right from the start. Once the business case closes for a depot, you would design it to be as robust as possible with all the systems being capable of being replaced on orbit. Spares would be delivered by the unpressurised equivalent of an HTV or ATV.

Quote
Secondly, where are these fuel-intensive missions headed?  There are none (nor any requirement for such) in the forseeable future.

The point is all missions are fuel intensive if only because you've been forced to buy a Delta IV instead of a Delta II because you are lugging your GEO fuel up with the spacecraft. If you are bringing your fuel up with the spacecraft, then you are buying a larger launcher than you need to if the fuel is on orbit already.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/19/2008 04:51 am
One thing that we haven't touched on is the use of the truly low cost launcher to pitch fuel at the depot.

We've been talking Atlas, Jupiter, Delta as if this design paradigm is the only way.

If there was a market for fuel in orbit, I can see a smart group looking at the whole launcher business & thinking "there has to be a better way." Maybe there is. It's been mentioned elsewhere before, but I'm going to do it again here. Modern launchers have grown up in the realm of really expensive payloads and the need for ultimate reliability to prevent these payloads, be they breathing or not, from being spread over a greater part of the earth's surface. If you are launching fuel and nothing but fuel, do you really care if you pitch some of it in the ocean if the launcher costs are cheap? I mean really cheap. No, cheaper than that. I'm talking cheap as dirt. So cheap that you can afford to lose one in 20 and still sell fuel at a profit.

Think a slightly modified V2 with commercial grade electronincs, a GPS based nav system, orbital control from the ground, pressure fed engines and a 2 tonnes of fuel to orbit payload. The Germans managed to launch roughly 2500 V2s in 8-9 months with about a 60% success rate in the middle of losing a war. If you had a stable economy and business behind you and were tooled up to make 100 per year & launch them from a TEL with a ground crew of 100 (like a V2 launch battery) how cheap could you really make them if you were willing to lose 1 in 20? Launch 100, lose 5, get 190 mT of go juice to orbit per year.

If a nameless 100mT launcher is estimated at about $4500/kg in orbit, then I have to be able to launch a 2 tonne payload for something like $8.55 million, including launcher, development ammortisation and profit and assuming a loss rate of 1 in 20.

Anyone want to design the "Cessna 172 of space" around those numbers? It's really tight, in fact, obscenely tight in aerospace terms. But might it be able to be done?

If you are buying propellant at $7500/kg you get to play with $14.25 million per launch.

Anyone? Anyone? Beuler? Anyone?


Paul
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/19/2008 05:59 am
OK, Rick, I had a think on your depot and herby submit one of my own. :)

- I've separated the docking & control centre from the tankage for safety. Don't want a slighly missed docking attempt to take out the depot.
- There's an RMS to berth the vehicles to the depot.
- An OMS and RCC at the back for stationkeeping Mounting the RCC at the control Centre may be better from a maintenance POV. Time for a trade study on that one.
- The docking port is universal, propellants in and out through the same mechanism. This doesn't mean the same lines are used, just that they all congregate at one port. Slide up, whip out the credit card (first, please, don't want any "dine & dash" customers) and then take your fill of whatever is on tap.
- There are PDGFs all over the depot to allow the RMS to roam around & do maintenance as required.
- All of the depot systems are in ORUs mounted at the control centre. They can be swapped in or out as needed. This includes things like the radiators & solar panels.
- All of the berthing hardware is on the depot. The coarse work is done by the vehicle but the depot does the final little bit, including berthing the vehicle to the depot.

Whattaya think?

Paul
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 06:35 am
Quote
clongton - 18/3/2008  7:58 PM

It's just like buying gasoline at a filling station. I could care less how many tankers, pickup trucks or station wagons it takes for the station owner to fill his storage tanks. I just buy the gas. He operates on completely different economies of scale than I do so the cost of the gas to me is very different than if I were dragging a 500 gallon tank of gasoline around with me hitched to my ball hitch trailer hitch.

Clongton, even if station owner (NASA+?) wil operate on "completely different economies of scale" - and he won`t, because there is no market - there is still the question of why to keep the fuel in orbit and not on Earth. With "completely different economies of scale" you can just store a surplus of rockets.
Title: Re: Propellant Depots - General Discussion
Post by: jeff.findley on 03/19/2008 01:52 pm
Don't forget that if NASA actually goes back to the moon that it has to "invent" something for the international partners to do.  The fuel depot provides a handy way to do this.  You get Russia, ESA, and JSA to provide "free" fuel for the depot in exchange for their astronauts getting to participate in lunar missions.  One of the unwritten rules for this sort of thing is that money ought not cross international borders when doing this sort of thing.  This is why ESA and JSA provide their own labs for ISS and will be providing their own supply vehicles (ATV and HTV).  This isn't the most *globally* cost efficient way of doing things since now you have three unmanned resupply vehicles for ISS (four if you think NASA COTS will work), but it works politically.

Also, this keeps the international partners off the "critical path" since you could still use the most cost efficient US launch vehicles to provide fuel for the depot, if needed.  US launch vehicles for this task could be Jupiter, Atlas, Delta, Falcon, or whatever is cheapest and/or available.  NASA (and the US in general) tends to be a bit of a control freak when it comes to internaional "cooperation", so they won't want anyone but themselves on "the critical path".
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 01:59 pm
Did any international partner approach NASA to participate in the Constellation project?

Does NASA wants any international partners?
Title: Re: Propellant Depots - General Discussion
Post by: MichaelF on 03/19/2008 03:12 pm
Quote
jeff.findley - 19/3/2008  9:52 AM

Don't forget that if NASA actually goes back to the moon that it has to "invent" something for the international partners to do.  .

No, it doesn't.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/19/2008 03:13 pm
Okay, this thread title is supposed to be general discussion about propellant depots by the title but has been so far about a single narrow idea: NASA flying a heavy lifter launcher and using a propellant depot on the side. This isn't very sensible.

What propellant depots are really the best at, is decoupling beyond LEO mass from launcher size, thus eliminating the need for a heavy lifter altogether. The three different spacecraft of ESAS origin, the Orion capsule, the Artemis lander and the EDS stage all weigh less than 25 t empty, which can be lifted by launchers that exist today and have flown many times.

You could achieve similar things by chaining up mini-EDS stages, but that has some problems, like boiloff, bad mass ratio and reliability regarding so many stagings and ignitions. Not insurmountable. A propellant depot can also avoid boiloff by being well insulated, having a sunshield or even being actively cooled: it can afford this mass since it is not going to the moon itself.

Also, with numerous redundant launchers available for sending tankers to the depot, the approach is inherently improvable. You get high flight rate which means low costs. You can enter better launchers that are cheaper or more reliable for example. This is because the mass launched at one time is a reasonable chunk like ten or twenty tonnes, that the launchers can still have other viable missions as well. Ultimately, a propellant depot could be a market for a reusable launch vehicle that could drop the cost of space travel substantially. The biggest hurdle for RLV economics has been lack of market and thus a low flight rate. A depot could change all that. Only NASA has enough money to buy so much propellant on orbit that an RLV becomes feasible.

If NASA builds a heavy lifter, all this becomes moot. Most of the propellant is lifted by the heavy lifter, and thus it makes no sense to make a propellant depot for just the few intermittent refueling tonnes, it is much cheaper to launch another heavy lifter. A purpose built heavy lifter will have big fixed costs and low launch rate, meaning adding more launches will not add much more cost anymore, the savings were missed when the thing was built in the first place.
Also, a purpose built NASA heavy lifter is not an agile system which could easily be improved and it is in practice an irreplaceable monolith. Griffin himself has said how the launchers that are built now will stick for decades. (Well, that has happened with the exception of Saturn.)

Most of the arguments have been hashed before, for example in this thread about an alternative for ESAS replacing heavy lift with a liquid oxygen propellant depot:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=4047

To put the effects of high fixed costs and low flight rate in nine words:
No savings from depot unless you scrap heavy lift.
Title: Re: Propellant Depots - General Discussion
Post by: MichaelF on 03/19/2008 03:21 pm
Quote
tankmodeler - 19/3/2008  12:27 AM

Quote
MichaelF - 18/3/2008  11:08 PM

Unattended depots? Maintenance/PMCS/Troubleshooting comes from where?
From the ground, like they do now for ISS. You use the RMS and an SPDM to swap out ORUs of any of the systems, including things like docking collars, tanks, cooling systems, RMS, whatever.
.

So, a kink (rather, frozen propellant, most likely) in the fuel line will cost you a manned launch (including booster, spacecraft and ground infrastructure) and an EVA (or several).

That's an expensive piece of frozen gas.

It's also a bullet in the head of your business model.  Never mind the expense of your maintenance mission (which is going to gobble up your profit margin, or budget, if your NASA),  you've got an on-orbit customer waiting on fuel (who might have missed his mission window).  He's all frowny, and potential customers take note.

Also, launches, even "emergency" missions, aren't exactly quick.  Months.  If you're NASA (who operate on a budget),  a non crew-fatal emergency could wait years until a launch is scheduled (Hubble, to reference your example).  

Title: Re: Propellant Depots - General Discussion
Post by: MichaelF on 03/19/2008 03:27 pm
Quote
meiza - 19/3/2008  11:13 AM


What propellant depots are really the best at, is decoupling beyond LEO mass from launcher size, thus eliminating the need for a heavy lifter altogether. .

This assumes that no missions will require the volume that Ares V can provide (fairing diam.).  This is not a safe assumption.

If nothing else, it artificially constrains missions.

I can take many times the mass of my couch across town in my car, given 4-5 trips.  I still can't take my couch across town in my car (which was a pain, the last time I moved.  I swear I'm getting a furnished apartment next time).
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/19/2008 03:52 pm
Well the LSAM with the hydrogen tanks is the only diameter constrained thing (EDS is just a stage and Orion is 5 m in diameter), if it wants to be wide for a vertical landing with a low climb to the surface. But there are multiple ways to design around that, for example the LM Centaur-style dual axis lander with one big common bulkhead tank (good for reduced boiloff!), or a lander with a spherical tank on each side of the hab, launched sideways.
I've heard that EELV:s can be fitted with quite big fairings if need be, they have good control authority.

Having a monolithic launcher constrains missions actually more, as you can't grow or shrink so easily.
Title: Re: Propellant Depots - General Discussion
Post by: William Barton on 03/19/2008 04:16 pm
It seems to non-engineer me, for a fuel depot to really decouple mass in LEO from LV payload, it would need to be part of a permanent manned orbital assembly facility. Pretty much what Von Braun proposed close to sixty years ago.
Title: Re: Propellant Depots - General Discussion
Post by: Gary on 03/19/2008 04:16 pm
Lugging fuel from the Earth to LEO for a depot makes no sense. What makes more sense is fuel production on the moon and a lunar fuel depot with regular trips of tanker craft from the moon to the depot keeping it topped up.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/19/2008 04:26 pm
Quote
MichaelF - 19/3/2008  11:27 AM

Quote
meiza - 19/3/2008  11:13 AM


What propellant depots are really the best at, is decoupling beyond LEO mass from launcher size, thus eliminating the need for a heavy lifter altogether. .

This assumes that no missions will require the volume that Ares V can provide (fairing diam.).  This is not a safe assumption.

If nothing else, it artificially constrains missions.

I can take many times the mass of my couch across town in my car, given 4-5 trips.  I still can't take my couch across town in my car (which was a pain, the last time I moved.  I swear I'm getting a furnished apartment next time).

This also assumes NASA can retain its funding levels once the heavy lift infrastructure and related jobs are scrapped.

Perhaps the fuel depot advocates should focus on non-NASA users and non-NASA funding sources.
Title: Re: Propellant Depots - General Discussion
Post by: Smatcha on 03/19/2008 04:42 pm
Quote
meiza - 19/3/2008  9:13 AM

What propellant depots are really the best at, is decoupling beyond LEO mass from launcher size, thus eliminating the need for a heavy lifter altogether.

Actually no, that is not what they are good at nor is that debate relevant to the topic of propellant depots.  What propellant depots enable is the staging of the dominate component of mission mass which is cheap propellant.  The extremely expensive dry spacecraft then rendezvous with the depot taking on the amount of propellant required by the mission.

Aerial tankers don’t eliminate the need for large bombers or smaller jet fighters they both have a utility independent of the tanker.  The aerial tanker like the propellant depot is a force or mission multiplier respectively.

As soon as COTS or EELV can beat a $2K/kg variable cost to LEO let me know.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/19/2008 04:49 pm
Michael,
Quote
This assumes that no missions will require the volume that Ares V can provide (fairing diam.).  This is not a safe assumption.

In engineering "needs" are very rarely decoupled from what's attainable.   What I mean is, that extra payload volume comes with a *very* large price tag--tens of billions worth of development cost and billions a year worth of operations costs.  Very few missions actually absolutely need a fairing that big.  Some could take advantage of it, if they didn't actually have to pay for the capability themselves.  But when you include the cost of that extra volume into the equation, I bet you most people who say right now that they "need" the extra volume can find much cheaper alternative approaches.

There may be a couple of minor missions that just can't be done without a 10m diameter fairing, but the question becomes, in a world of finite resources, is it better to forgo a few missions in exchange for a much more sustainable, robust, and cost-effective architecture?

Quote
If nothing else, it artificially constrains missions.

I can take many times the mass of my couch across town in my car, given 4-5 trips.  I still can't take my couch across town in my car (which was a pain, the last time I moved.  I swear I'm getting a furnished apartment next time).

But that's not the reality of the situation.  Every single component of the ESAS architecture is independently launchable on non-HLV existing boosters.  There's nothing too big to fit in the car.  The reason they want HLVs is because most of the mass involved in moving that couch around is propellant in this case.  Why build a huge new vehicle that is mostly just lifting propellants?

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Smatcha on 03/19/2008 04:57 pm
Quote
Gary - 19/3/2008  10:16 AM

Lugging fuel from the Earth to LEO for a depot makes no sense. What makes more sense is fuel production on the moon and a lunar fuel depot with regular trips of tanker craft from the moon to the depot keeping it topped up.

I agree once we have production level of ISRU working on the Moon along with a transportation infrastructure.  At which point one logical position for the propellant depot would be the EML1 and/or EML2 point being serviced by a recycling lunar lander.  The only question (depending on if there is a high enough concentration of ice at the lunar poles) is if we can also get Hydrogen from the Moon or do we need to still send that up from Earth to keep the system cycling away delivering Lunar LOX to the depot.  Of course Hydrogen is not ideal for long duration storage and transfer so LCH4 may be the best choice.  But Carbon is very rare on the Moon as well.

Once you pencil up all the development costs, system start-up mass, and mass required to run this system though the benefits are still their but not as great as you would expect vs. the incremental cost of a few more Jupiter-232 launches.

The incremental cost per additional kg to LEO once you have committed to a heavy launch system is not very high so the high upfront cost for ISRU will have to be traded against a comparatively low cost avoidance.
Title: Re: Propellant Depots - General Discussion
Post by: josh_simonson on 03/19/2008 05:09 pm
The lunar program aims to have the US provide the end-to-end logistics system itself, while international partners would contribute to a lunar base, and redundant logistic elements.  

A fuel depot in LEO is relatively unattractive because all rockets reach LEO the same way and the 'larger rocket with better $/LB' argument tends to win out.  Fuel depots in higher orbits allow for fuel and cargo to travel through more efficient (and cost effective) means.  Fuel in cis-lunar space is worth about twice what it is in LEO, but a re-useable SEP fuel tug may be able to move fuel from LEO to cis-lunar space with 10% of the fuel/cost.  If the tug is large it may make sense to stockpile fuel in LEO while the tug is in transit.  A mars mission will pretty much require stages/fuel to be staged on the surface and in LMO for the return trip to improve mission reliability and keep the manned craft from ballooning into monstrous proportions.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 05:10 pm
Quote
MichaelF - 19/3/2008  11:21 AM
So, a kink (rather, frozen propellant, most likely) in the fuel line will cost you a manned launch (including booster, spacecraft and ground infrastructure) and an EVA (or several).

That's an expensive piece of frozen gas.

It's also a bullet in the head of your business model.  Never mind the expense of your maintenance mission (which is going to gobble up your profit margin, or budget, if your NASA),  you've got an on-orbit customer waiting on fuel (who might have missed his mission window).  He's all frowny, and potential customers take note.

Also, launches, even "emergency" missions, aren't exactly quick.  Months.  If you're NASA (who operate on a budget),  a non crew-fatal emergency could wait years until a launch is scheduled (Hubble, to reference your example).  


What are you talking about? Where is this elusive customer, that wish to buy tons of propellant - and to buy them RIGHT NOW, and not according to pre-planned agreement? Are we talking year 2100+?
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/19/2008 05:26 pm
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Gary - 19/3/2008  1:16 PM

Lugging fuel from the Earth to LEO for a depot makes no sense. What makes more sense is fuel production on the moon and a lunar fuel depot with regular trips of tanker craft from the moon to the depot keeping it topped up.
A lunar LOX ISRU plant is many years and many billions of dollars away and even then does not address the LH2; and that is assuming that the next president doesn't actually take executive action to delay it even further. In the mean time, LOX and LH2 from earth is the only option.

But the biggest misconception here is that the depot has to make propellant "cheaper". That is just not the case. In fact, the missions that use the depot will most likely pay a premium for the propellant. In exchange, they get better value for their propellant because they don’t have to burn it just to get into orbit. The "savings" come from getting that better value out of the purchase, not in paying less for the propellant. It can be used for the mission instead. This decouples the mission from the launch vehicle. It’s like choosing between a Hummer and a high mileage car. Getting better gas mileage means you get to either go a lot further on a tank of gas – or – carry a lot heavier cargo. The depot gives you that choice while the launcher does not. The purpose of the depot is to make better missions possible by avoiding the necessity to drag your mission propellant up to LEO along with your mission spacecraft. The depot is a mission enhancer, not a bargain basement propellant supplier. It allows smaller launch vehicles to launch really meaningful spacecraft that either weigh more or go further or longer and large launchers to multiply the mission profiles of large spacecraft to potentially combine 2 or 3 missions into a single mission, a time multiplier. For example, think of 60mT being landed on the lunar surface. What would that kind of capability do for the effort to jump start a lunar ISRU effort? Sure, you could do it in several smaller mission launches, but it would take several years longer. That’s the kind of flexibility this depot architecture provides.

To assert that the mission of the depot is to eliminate the heavy lift is not correct. The mission of the depot is to enhance the capabilities of missions of all sizes and to allow more players into the game. All kinds of missions, small, medium and large, are benefited by the use of a depot. The focus of the depot is NOT the launch vehicles, but the MISSION. The mission, not the depot, will be the determining factor in which launch system makes the most sense for that specific mission, and it will be different for each and every mission.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/19/2008 05:43 pm
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SMetch - 19/3/2008  6:42 PM

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meiza - 19/3/2008  9:13 AM

What propellant depots are really the best at, is decoupling beyond LEO mass from launcher size, thus eliminating the need for a heavy lifter altogether.

Actually no, that is not what they are good at nor is that debate relevant to the topic of propellant depots.  What propellant depots enable is the staging of the dominate component of mission mass which is cheap propellant.  The extremely expensive dry spacecraft then rendezvous with the depot taking on the amount of propellant required by the mission.

Aerial tankers don’t eliminate the need for large bombers or smaller jet fighters they both have a utility independent of the tanker.  The aerial tanker like the propellant depot is a force or mission multiplier respectively.

No. You don't need the big launcher as the exploration hardware is small 25 t chunks, and propellant divides even more easily. It can not be any more clear than that.
Ares V and Direct are practically either
1) must launch all propellant in one - launchers. Liquid oxygen to be precise. Needless to say, this is not required.
or
2) must launch Orion & LSAM in one - launchers. This is not required either.

Spin it anyway you want, but you're not saying really anything in your paragraphs. Just save a lot of time and words and take the last step holding Direct people from the logical conclusion: LSAM and Orion can go on separate launchers.
You already have admitted EDS can. And now with the propellant depot you say the LOX can come on many launchers too.
You're left noticing that there is no need for a custom NASA huge launcher for big payloads - since there aren't any!

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As soon as COTS or EELV can beat a $2K/kg variable cost to LEO let me know.

Nobody knows or can gauge the real and projected fixed and variable costs with variable flight rates very well unfortunately. And anyway that is a different question, you were trying to refute if heavy lift is needed when you have a depot, this is just a claim that it would be more economical, a very different one.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 05:49 pm
Clongton, who is going to build the depot and fuel it? I suppose you mean NASA to do it. But first you will have to ensure that someone will use it in large scale.

Basically, you still require more funding for space WORLDWIDE, to pay for more launches. I don`t think it is going to happen just because of the depot. Or at all.
Title: Re: Propellant Depots - General Discussion
Post by: MichaelF on 03/19/2008 06:14 pm
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Eerie - 19/3/2008  1:10 PM

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MichaelF - 19/3/2008  11:21 AM
So, a kink (rather, frozen propellant, most likely) in the fuel line will cost you a manned launch (including booster, spacecraft and ground infrastructure) and an EVA (or several).

That's an expensive piece of frozen gas.

It's also a bullet in the head of your business model.  Never mind the expense of your maintenance mission (which is going to gobble up your profit margin, or budget, if your NASA),  you've got an on-orbit customer waiting on fuel (who might have missed his mission window).  He's all frowny, and potential customers take note.

Also, launches, even "emergency" missions, aren't exactly quick.  Months.  If you're NASA (who operate on a budget),  a non crew-fatal emergency could wait years until a launch is scheduled (Hubble, to reference your example).  


What are you talking about? Where is this elusive customer, that wish to buy tons of propellant - and to buy them RIGHT NOW, and not according to pre-planned agreement? Are we talking year 2100+?

I'm going off of the stated operation model.  That doesn't mean I endorse it (IOW, it's not my argument, I'm just addressing it).

Orbital propellant depots don't make operational or economic sense in the near-term.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/19/2008 06:24 pm
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Eerie - 19/3/2008  2:49 PM

Clongton, who is going to build the depot and fuel it? I suppose you mean NASA to do it. But first you will have to ensure that someone will use it in large scale.

Basically, you still require more funding for space WORLDWIDE, to pay for more launches. I don’t think it is going to happen just because of the depot. Or at all.
Anatoly;
I would imagine that the first depot would actually be a modified EDS from the lunar program, with some technologies onboard for proving. I can actually envision an X-plane type of approach to deploying a depot architecture that is funded by the savings NASA would realize by switching to DIRECT, if they do. Over time, NASA would transition its lunar program to take advantage of the depot and more of them would be deployed to EML-1 & EML-2, to service interplanetary missions, like the manned effort to go to Mars. In addition, deep space science would begin to design their probes and landers to also make use of the depot.

The first example that comes to mind is NASA’s New Horizons probe bound for Pluto. It will be a flyby instead of an orbiter because it couldn’t carry engines and enough propellant up to LEO from the launch pad on its launch vehicle. That is exactly the kind of thing the depot would address. Had a depot been available when New Horizons was being designed, it could have been much larger, with a service engine and propellant to break it into orbit and been an orbiter instead of just a flyby.  While I marvel that we are actually going to Pluto, I am saddened that the entire effort is focused on just a few minutes of the decades-long journey as the probe speeds past the planetoid at breakneck speed. Had New Horizons been an orbiter, we would be able to study this Keiper belt object and its moon in minute detail for years.

For the first few years of operation, I can see NASA maintaining control of the asset, but beginning to allow other nations or NGOs with launch vehicles to rendezvous and deliver propellant, in exchange for some value yet TBD.

Over time, as NASA begins to transition the depot to commercial operations, other nations will begin, gradually, to also design their probes around the availability of a depot. Spacecraft and Mission design takes a very long time and often can consume an entire career, so this will be a slow process. Eventually, manned spacecraft from other nations or NGOs will also begin to use it.

But this is very long term thinking here. There are very valid tradeoffs between the mission size and intent vs. the additional expense of on-orbit propellant purchase. Some space operations will not be advantaged by a depot, while others most definitely will. Just because the depot(s) exist, does not automatically mean all missions will use them. It is very mission specific. There are no illusions about that. But for those missions that do use them, the value added for having the depots available will be quite large and more than worth the additional currency expense. It will begin as a trickle, and end being a flood.
Title: Re: Propellant Depots - General Discussion
Post by: Smatcha on 03/19/2008 06:31 pm
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meiza - 19/3/2008  11:43 AM

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SMetch - 19/3/2008  6:42 PM

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meiza - 19/3/2008  9:13 AM

What propellant depots are really the best at, is decoupling beyond LEO mass from launcher size, thus eliminating the need for a heavy lifter altogether.

Actually no, that is not what they are good at nor is that debate relevant to the topic of propellant depots.  What propellant depots enable is the staging of the dominate component of mission mass which is cheap propellant.  The extremely expensive dry spacecraft then rendezvous with the depot taking on the amount of propellant required by the mission.

Aerial tankers don’t eliminate the need for large bombers or smaller jet fighters they both have a utility independent of the tanker.  The aerial tanker like the propellant depot is a force or mission multiplier respectively.

No. You don't need the big launcher as the exploration hardware is small 25 t chunks, and propellant divides even more easily. It can not be any more clear than that.
Ares V and Direct are practically either
1) must launch all propellant in one - launchers. Liquid oxygen to be precise. Needless to say, this is not required.
or
2) must launch Orion & LSAM in one - launchers. This is not required either.

Spin it anyway you want, but you're not saying really anything in your paragraphs. Just save a lot of time and words and take the last step holding Direct people from the logical conclusion: LSAM and Orion can go on separate launchers.
You already have admitted EDS can. And now with the propellant depot you say the LOX can come on many launchers too.
You're left noticing that there is no need for a custom NASA huge launcher for big payloads - since there aren't any!

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As soon as COTS or EELV can beat a $2K/kg variable cost to LEO let me know.

Nobody knows or can gauge the real and projected fixed and variable costs with variable flight rates very well unfortunately. And anyway that is a different question, you were trying to refute if heavy lift is needed when you have a depot, this is just a claim that it would be more economical, a very different one.

Wrong again, the Jupiter-120 and 232 bring forward a number of fixed and variable cost structures that we already have over twenty years of experience and hard data on.  While we need to project for new components like the upper stage about 80% of our cost structure is very well know or is easily extrapolated from flying systems.

In addition, while an HLV system can have a comparatively high fixed cost vs. say SpaceX its variable launch cost is very low.  As such to show any real savings in moving mass off of the Jupiter onto something else the price to orbit would need to be around $2K/kg to LEO.  While magnetic rail guns that launch blocks of ice into LEO might be able to go below this using small scale traditional approaches will not be able to go below this.

What secures heavy lift for propellant is the lower cost per kg to orbit.

What secures heavy lift for spacecraft is the lower cost to develop/build ground integrated spacecraft placed in space as lower mass single element dry.  In addition a lot of expense is incurred trying to shoe horn spacecraft into a 5m vs. 12m diameter PLF.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/19/2008 06:40 pm
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MichaelF - 19/3/2008  3:14 PM

Orbital propellant depots don't make operational or economic sense in the near-term.

A fair assessment.   The question comes down to where you define the transition between near term and long term then.

I would prefer to make the near term as short as possible and move straight into a wider expansion program.   With the ~$20bn in savings compared to Ares thru 2020, I believe we can afford to do so too.   IMHO, Ares won't make the transition until 2030.   But I believe DIRECT could afford to do such a transition somewhere around 2020-2022 - 3-5 years after we re-establish a human presence on the moon.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/19/2008 07:10 pm
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SMetch - 19/3/2008  8:31 PM

Wrong again, the Jupiter-120 and 232 bring forward a number of fixed and variable cost structures that we already have over twenty years of experience and hard data on.  While we need to project for new components like the upper stage about 80% of our cost structure is very well know or is easily extrapolated from flying systems.

In addition, while an HLV system can have a comparatively high fixed cost vs. say SpaceX its variable launch cost is very low.  As such to show any real savings in moving mass off of the Jupiter onto something else the price to orbit would need to be around $2K/kg to LEO.  While magnetic rail guns that launch blocks of ice into LEO might be able to go below this using small scale traditional approaches will not be able to go below this.


Exactly my point. If you take as an axiom that you will have heavy lift, of course you damn well will fly it, and a depot is probably just a distraction, that's what I've been telling Chuck and Ross. You could of course go further back and your assumptions about "we have heavy lift".

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What secures heavy lift for propellant is the lower cost per kg to orbit.

That is debatable, but nevertheless it is a far better point that the original one that you need one for certain.

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What secures heavy lift for spacecraft is the lower cost to develop/build ground integrated spacecraft placed in space as lower mass single element dry.  In addition a lot of expense is incurred trying to shoe horn spacecraft into a 5m vs. 12m diameter PLF.

The LSAM and Orion are separate spacecraft with completely independent systems which need to dock and undock multiple times anyway, and are proposed to launch un-docked anyway even with Direct, just in the same launcher (and separate launchers in ESAS Ares I & Ares V)! This "we need ground integration" is getting ridiculous grasping for straws. Even with Apollo the CSM turned around and fetched the LM after TLI.

So let me untie this knot for the dear readers here.

Heavy lift lobby thinking:
EDS&LSAM + CEV - Fine (Ares I & V)
CEV&LSAM + EDS - Fine (2x Jupiter-232)
CEV&EDS + LSAM - Fine (Miscellaneous Direct scenarios)
CEV&LSAM + EDS + DEPOT - Fine (Miscellaneous Direct scenarios)
CEV + LSAM + EDS + DEPOT - Nonono! Completely unworkable, we need to ground integrate at least two spacecraft

Why? There is some invisible barrier I cannot see.
Title: Re: Propellant Depots - General Discussion
Post by: renclod on 03/19/2008 07:22 pm
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meiza - 19/3/2008  11:10 PM

So let me untie this knot for the dear readers here.

Heavy lift lobby thinking:
EDS&LSAM + CEV - Fine (Ares I & V)
CEV&LSAM + EDS - Fine (2x Jupiter-232)
CEV&EDS + LSAM - Fine (Miscellaneous Direct scenarios)
CEV&LSAM + EDS + DEPOT - Fine (Miscellaneous Direct scenarios)
CEV + LSAM + EDS + DEPOT - Nonono! Completely unworkable, we need to ground integrate at least two spacecraft

Why? There is some invisible barrier I cannot see.

How about the non-CEV mission: the most logical scenario for the near term - unmanned cargo to Luna.

The one that can dispense of any rendezvous, any LEM extraction, any refuelling... and still do the most needed novel mission: put some usefull stuff on the surface.

Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/19/2008 07:47 pm
We already have fuel depot in orbit. It's called ISS. Progress (and in the future ATV) regularly transfers propellant to the Russian side of ISS, to be used by maneuvering thrusters. We would only need bigger tanks and a process of transferring propellant back into visiting spaceships to make things complete. Cryogenic transfer is also doable, since we do that every time we fire engines in space.

Then we need tugs that would have everything critical quadruple redundant, be capable of many things but would not have to be built, lifted and burned every time we would want to get something into space. That would Progress or better yet ATV. For an extra “cool factor” and capability stick one or even two robotic arms on it. That Dextre that was put on the ISS would be just fine for the job.

With that in place you can send any thing into orbit without having to spend tens of billions of $ to build new heavy lifter plus more billions to pay for fixed costs of running that thing. Since US basically already pays for fixed and variable costs for Delta and Atlas, that is pretty good deal. It could maybe even make those two things completive on the world commercial market thus help reduce running costs even more. If anyone needs to take a lesson on how it is done look at equatorial part of the South America..

After this is done, you take all that money that you didn’t spend on building fancy new rocket and put it into things that are not that beautiful too watch but would be equally impressive. Like a fleet of SEPs that would have 50 m x 200 m solar wing and high isp to reduce the number of rockets needed to lift all that mass into LEO. They would take months to deliver that fuel to lunar orbit or L1/L2 but it’s not like anyone cares if they do. Launch parts for Moon/Mars mission and keep them at depot/station. They are all under 25 mT, so at most they would need bigger fairing (for Mars lander) on existing rockets. Since there are many hammerhead rockets flying around that doesn’t seem to be that big of a deal either.

Want to go to the Mars? Put few (3-6 depending on how fast and how secure you want to go) SEPs together into structure that would be able to withstand “enormous stress” of continuous 100 N of thrust, put landers, crew quarters, life support, supplies and anything else that you need on it, get it to some HEO orbit (EML2?) over the course of few months then send the crew there with Orion that was refueled at depot. Go to Mars and back. Reuse SEPs and maybe even landers for a next mission. While you are in Mars orbit, why not extract oxygen from those Phobos or Deimos rocks that are orbiting Mars. I am sure it could come very handy when the crew would return back to HEO or even as propellant for those SEPs.

Space depot would be part of the whole transportation system that could be soon extended by another depot in HEO, another around Mars (if we got really interested into that), supplied by slow moving SEPs and fast moving human rockets, helped by moving robotic arms and tugs and paid for by having costs reduced for missions beyond LEO.

But the fact that it doesn’t include big rockets probably makes this plan completely unacceptable to US. That concept is way too sensible and cost effective.. it’s way too Russian or European..
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/19/2008 07:47 pm
If you want to use a normal LSAM for that and don't want to dock, you need a big 100 t + launcher. I don't know how much Jupiter-232 can put on the surface directly.
NASA has talked about 3 manned and 1 unmanned mission per year.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 08:00 pm
Neviden;

You will still need to send dozens of not-"fancy new" rockets to fuel the depot. And they are not free, you know. Where will the money for MANY Delta and Atlas come from?
Title: Re: Propellant Depots - General Discussion
Post by: Firehawk153 on 03/19/2008 08:08 pm
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meiza - 19/3/2008  3:10 PM


The LSAM and Orion are separate spacecraft with completely independent systems which need to dock and undock multiple times anyway, and are proposed to launch un-docked anyway even with Direct, just in the same launcher (and separate launchers in ESAS Ares I & Ares V)! This "we need ground integration" is getting ridiculous grasping for straws. Even with Apollo the CSM turned around and fetched the LM after TLI.



Isn't there a component of safety to consider?  I would think that the fewer spacecraft components parts that you have to integrate (especially on the ground where it can be tested)  the fewer points of failure that you have.
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/19/2008 08:14 pm
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Eerie - 19/3/2008  11:00 PM
You will still need to send dozens of not-"fancy new" rockets to fuel the depot. And they are not free, you know. Where will the money for MANY Delta and Atlas come from?
First from the money saved in the form of development and fixed costs for two new rockets and its infrastructure. Extra price reduction for US government (DoD included) would come if they managed to poach Arianespace’s payloads and thus spread fixed costs to parties other then itself.

Later from the reduced number of rockets needed since SEPs would vastly reduce IMLEO by using far less propellant, by supplying propellant from HEO (delivered there by SEPs, if not from the moon itself) and by reusing stuff that was already delivered to orbit.

GEO satellites routinely work for 15 years – that is until they ran out of station keeping propellant. SEPs are basically GEO satellites with huge wings and some serious electric propulsion system (MWs).
Title: Re: Propellant Depots - General Discussion
Post by: renclod on 03/19/2008 08:20 pm
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meiza - 19/3/2008  11:47 PM

If you want to use a normal LSAM for that and don't want to dock, you need a big 100 t + launcher. I don't know how much Jupiter-232 can put on the surface directly.

The proper name is Ares-V.

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NASA has talked about 3 manned and 1 unmanned mission per year.

NASA "talks" all the time. See :

http://www.nasa.gov/pdf/214597main_Culbert2-26-08.pdf

Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 08:26 pm
neviden, I thought price reduction comes from large scale production. Poaching Arianespace will create the opposite effect - less USA rockets produced.

And the question remains - who else needs the Depot and willing to pay for it? Do ESA and russians wish to expand their space budgets? Will they commit to it for any lenght of time?

Another question that no one answered me yet - why not just produce and store rockets on Earth, and launch them on demand, to directly fuel the empty spacecraft? Storing things on Earth is much safer than in space. No boiloff whatsoever.

Of course the question is moot, because no one yet funded neither the Depot, nor additional rockets...
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/19/2008 08:31 pm
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meiza - 19/3/2008  4:47 PM

If you want to use a normal LSAM for that and don't want to dock, you need a big 100 t + launcher. I don't know how much Jupiter-232 can put on the surface directly.
NASA has talked about 3 manned and 1 unmanned mission per year.
A single Jupiter-232 launch that utilized the depot to (re)fill the tanks before earth departure can put an approximately 182mT LSAM thru TLI at 3150 dV, which equates to roughly 60mT landed on the lunar surface.
Title: Re: Propellant Depots - General Discussion
Post by: on 03/19/2008 08:35 pm
PD's take a cost distortion away from LV's - that of adding the mass fraction of propellant necessary for the given mission. Unfortunately much of what a HLV has historically been used for is this.

Why this is important is that it distorts the need for HLVs by artificially reducing flight rate. When it drops too low, the expense of ANY HLV is too high and the program is killed.

So the prime benefit of PD's is to remove the propellant distortion from the LV dependency. LV's then compete fairly against each other in support of a specific mission. As a given LV becomes cost effective for a mission, its flight rate dominates and it claims the niche. Very darwinian
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/19/2008 08:37 pm
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Eerie - 19/3/2008  11:00 PM
You will still need to send dozens of not-"fancy new" rockets to fuel the depot. And they are not free, you know. Where will the money for MANY Delta and Atlas come from?
Who says they have to be Atlas or Deltas? As was suggested a couple of pages back, the commercial operators will most likely develop really simple, dumb, pressure fed launchers that will deliver ~5mT of propellant at a time, on the cheap, with an expected loss rate of 1 in 20.

The most expensive part of any launch is not the launch vehicle, its the spacecraft/payload. But in this case the payload is propellant, which is dirt cheap, comparitively speaking. Insurance rates will be low and the launchers will go up by the dozens. Very, very low tech, and very inexpensive.
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/19/2008 08:41 pm
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Eerie - 19/3/2008  11:26 PM
neviden, I thought price reduction comes from large scale production. Poaching Arianespace will create the opposite effect - less USA rockets produced.
The price will also come down from large scale production, but I looked only at marginal extra costs. More rockets = less fixed costs per rocket, higher production rate = more competitive with Ariane 5 = more foreigners that will pay to have their satellites delivered into space by money that is not from US government.  

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Eerie - 19/3/2008  11:26 PM
And the question remains - who else needs the Depot and willing to pay for it? Do ESA and russians wish to expand their space budgets? Will they commit to it for any lenght of time?
That depends.. can ESA and the Russians depend on US too sell and supply them with propellant at all times? ESA probably can, Russians I am not that sure..

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Eerie - 19/3/2008  11:26 PM
Another question that no one answered me yet - why not just produce and store rockets on Earth, and launch them on demand, to directly fuel the empty spacecraft? Storing things on Earth is much safer than in space. No boiloff whatsoever.
Because, you need that propellant in space not on Earth. You need a lot of it (100+ mT) it all at the beginning of a mission. You can achieve that by either building one or two big rockets, meet in LEO and precede further or by doing more missions with existing rockets and wait until you have enough of it. If you wait you have to make sure your propellant doesn't boil away in the mean time = depot.

Propellant sitting on Earth in some tank is useless for doing missions in space.

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Eerie - 19/3/2008  11:26 PM
Of course the question is moot, because no one yet funded neither the Depot, nor additional rockets...
NASA is paying for Ares I and hopes to pay for Ares V. And we are not talking about peanuts. We are talking about dozens of billions of $ and more billions of $ to actually pay for yearly fixed costs for those things.

So, money apparently is there. It’s only being spent wastefully. Remember the old proverb.. penny saved is penny earned.. NASA (and US government) could save quite a few pennies if they only did what was needed and would work to reduce future costs…
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 08:42 pm
nobodyofconsequence, you don`t need PD to enlarge flight rate. To enlarge flight rate, you just need to use cheaper LVs.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 08:48 pm
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neviden - 19/3/2008  4:41 PM
Because, you need that propellant in space not on Earth. You need a lot of it (100+ mT) it all at the beginning of a mission. You can achieve that by either building one (or two) big rocket, meet in LEO and precede further or by doing more missions with existing rockets and wait until you have enough of it.

Propellant sitting on Earth in some tank is useless for doing missions in space.

Do you actually read what I write? I`m talking about storing ROCKETS, not just fuel.

This way, when you need it, you send several rockets (not one or two) during a short lenght of time, to fuel your spacecraft.

Of course, you will need to enlarge the infrastructure. But it will be on Earth, not in space. You don`t have to worry about boilloff, because fuel is in storage right until you send it.

I agree that much money can be saved. That is true about any governmental organisation. But what PD have to do with it?
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/19/2008 08:56 pm
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clongton - 19/3/2008  11:37 PM
Who says they have to be Atlas or Deltas? As was suggested a couple of pages back, the commercial operators will most likely develop really simple, dumb, pressure fed launchers that will deliver ~5mT of propellant at a time, on the cheap, with an expected loss rate of 1 in 20.
Exactly. Everyone that can shoot rockets into space for cheap will do that. If it blows – it blows. No big deal since the payload would be enlarged upper stage that would be caught by some tug in LEO. We are talking about very good opportunity for testing new things. I am sure the makers of Proton would love to “test” 10 Protons right now by delivering propellant to depot.

Things that do matter you send on the most expensive, reliable and checked out rocket that you can find.

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Eerie - 19/3/2008  11:48 PM
Do you actually read what I write? I`m talking about storing ROCKETS, not just fuel.
Rockets need time to be prepared and launched.

If you then transfer propelant onto one big rocket that was sent to LEO first (empty tank basically) you are talking about depot. ISS is already a depot only that nobody uses that cappability. The true depot would differ only by having tanks even better shielded and having extra equipement that is needed to better keep propellant.

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Eerie - 19/3/2008  11:48 PM
I agree that much money can be saved. That is true about any governmental organisation. But what PD have to do with it?
If you have PD you don't need Ares V. Ares V = money. Don't spend money on things that you don't need, so that you can spend money on things that you do need. Simple.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/19/2008 09:03 pm
Eerie, good questions. There are technical reasons why it's probably more convenient to store the "intermediate product", LEO propellant than the rockets on earth. This is by no means a comprehensive handling of the subject:
-For every 20 t of LEO propellant you need about a 800 t rocket. So storing the stuff at ground has a 40x mass disadvantage.
-If you want to launch the rockets slowly, the propellant will tend to boil off. So you have to insulate the EDS -> it becomes heavy.
-If you want to launch them very fast to avoid boiloff, there are possibly launch site issues -> you need more of those expensive launch sites.
-There are other things where a depot wants to be different from what an EDS wants to be, like the possibility for a robot arm, various docking and pumping accessories.

Of course, none of these are absolute impossibilities, just something that must be traded and should help one see the viability of a propellant depot. ESAS didn't analyze a depot by the way, it looked only at refueling the EDS.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 09:06 pm
Quote
neviden - 19/3/2008  4:56 PM

Rockets need time to be prepared and launched.

If you then transfer propelant onto one big rocket that was sent to LEO first (empty tank basically) you are talking about depot. ISS is already a depot only that nobody uses that cappability. The true depot would differ only by having tanks even better shielded and having extra equipement that is needed to better keep propellant.

Yes, thats what I`m talking about. Only instead of building a dedicated PD, you will need to learn to launch rockets faster. And in the end, it will be the same number of launches and dockings.

But what will be easier - to maintain a large PD for decades in orbit, or to maintain a hangar with 100 Deltas\Altases\Falcons and small dedicated fueltanks for decades on Earth? Imo, the latter. You can have regular workers to dust the equipment and upgrade the electronics. After all, USA can maintain hundreds of ICBMs.
Title: Re: Propellant Depots - General Discussion
Post by: on 03/19/2008 09:10 pm

Quote
Eerie - 19/3/2008  4:42 PM  nobodyofconsequence, you don`t need PD to enlarge flight rate. To enlarge flight rate, you just need to use cheaper LVs.

Wrong - never said you needed PD's solely to enlarge flight rate.

Point was around the accounting term of art called "cost distortion". This has killed Saturn V and Shuttle, and will kill more.

As for cheaper LV's, have been waiting for them all my life. Don't hold your breath. 

Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 09:11 pm
meiza, there is no mass disadvantage on the ground, because of course you don`t keep the fuel in the rockets. You fuel your tankers before you launch.

And it really has to be evaluated what is better - expensive launch sites or expensive DP.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 09:13 pm
nobodyofconsequence, I meant distribution of mass. My mistake, not cheaper LV - SMALLER LV.

Instead of launching 2 LV with 100 tons each, you send 10 with 20 tons. This way you enlarge flight rate by a factor of 5.

But will it make those tons cheaper?
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/19/2008 09:18 pm
Quote
Eerie - 19/3/2008  12:06 AM
Yes, thats what I`m talking about. Only instead of building a dedicated PD, you will need to learn to launch rockets faster. And in the end, it will be the same number of launches and dockings.
What is the difference between a dedicated PD and an improvised PD? What would make a dedicated PD that much more expensive then an improvised PD?

You need everything in both of them only in dedicated PD you leave all your PD stuff behind too be used next time and in improvised PD you must carry it along (or throw it away at LEO). Its probably better to have heavy dedicated PD with multiple spares and to leave that in LEO. It costs money to build it and put it there.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 09:27 pm
neviden, what so important must a dedicated PD have? You don`t need robotic arms to dock. ATV will be the ultimate proof to it (unless it will crash into ISS...)

And the "improvised PD" is simply your empty spacecraft. But less heavy, because you don`t need to keep fuel in orbit for years. You fuel your spacecraft swiftly, and fly to your destination.
Title: Re: Propellant Depots - General Discussion
Post by: on 03/19/2008 09:33 pm

Quote
Eerie - 19/3/2008  5:13 PM  nobodyofconsequence, I meant distribution of mass. My mistake, not cheaper LV - SMALLER LV.  Instead of launching 2 LV with 100 tons each, you send 10 with 20 tons. This way you enlarge flight rate by a factor of 5.  But will it make those tons cheaper?

Don't think you yet understand the point made.

What distorts LV costing - **ANY LV, SMALL, LARGE OR WHATEVER** is the working consumable mass that it carries along.

If you can replenish it independently, you can change the economics of how the total cost adds up.

The cost distortion is where we consider the wet mass fraction more than the dry - we then size things with the inherent, embedded wet cost - when the two are quite different.

For the purpose of this only here's an example - if I launch the dry mass and wet mass seperate, and the wet mass takes several tries (cheap less reliable, but the dry mass (reliable more costly) goes the first time, its still cheaper than wet+dry combined (must be reliable more costly and large).

As to launching wet small or large - it's a question of technology and costing. 

Hell, if you could launch frozen bricks of propellant with a mass driver, that might be a brillant choice. Don't contest it.

But you want to decouple the two to avoid "cost distortion". It comes up in cost accounting all the time. 

Title: Re: Propellant Depots - General Discussion
Post by: on 03/19/2008 09:36 pm
By the way, you can get to GSO with commercial use of a PD. It is **very** cost effective. This is more important for the viability of a LEO PD than lunar or interplanetary prop consumption, because that depends on budgets that are not approved.
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/19/2008 09:38 pm
Quote
Eerie - 20/3/2008  12:27 AM
neviden, what so important must a dedicated PD have? You don`t need robotic arms to dock. ATV will be the ultimate proof to it (unless it will crash into ISS...)
Robotic arm is not needed. It's there to keep the costs down. It's not that expensive either. Dextre is $200M. That is cheap as far as space costs go.

ATV weighs 12 tons so that it could deliver 8 tons of useful cargo.. It's a good ship but it would be much better as a dedicated tug that would grab 2 tons dumb payload that would carry 18 tons of useful cargo and maneuver them further..

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Eerie - 20/3/2008  12:27 AM
And the "improvised PD" is simply your empty spacecraft. But less heavy, because you don`t need to keep fuel in orbit for years. You fuel your spacecraft swiftly, and fly to your destination.
You don't need to keep fuel in orbit for "proper PD" either.. You need to have only as much propellant as you will need in the near future.. launching on many rocket pads that are already existing will be cheaper then having many more pads with them sitting idle for most of the time..

And it will not be less heavy then the spacecraft that will dock to a “proper PD” without shielded tanks (weight) and docking and transferring equipment (weight). Transfer fuel, undock, burn.. no need for heavy shielding since the propellant will have no time to boil off.
Title: Re: Propellant Depots - General Discussion
Post by: MichaelF on 03/19/2008 09:38 pm
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kraisee - 19/3/2008  2:40 PM

Quote
MichaelF - 19/3/2008  3:14 PM

Orbital propellant depots don't make operational or economic sense in the near-term.

A fair assessment.   The question comes down to where you define the transition between near term and long term then.

That's a question that has, at best, a nebulous non-answer like "it'll be obvious when we approach that juncture".

At best, it's a rule-of-thumb decision that is dependant on technical (i.e. where we are in our program path), budgetary and political contexts that aren't apparent yet.

A more definite, but less optimal answer is "when we absolutely cannot progress without it, we'll develop the capability".  This strategy has it's own drawbacks (program is static while awaiting critical developments, etc).

No perfect solution presents itself.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/19/2008 09:40 pm
nobodyofconsequence, I see your point. But you will have to have a separate budget for DP refuelling and maintaince. You will need to send rockets to DP at some constant rate. Do you think USA will fund such thing, that is independent of any specific mission?

Oh, and the same separate budget can be used for what I proposed - storing rockets on Earth.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/19/2008 09:49 pm
If you are fuelling an LSAM from a depot the simplest way is to send the fuel is in sealed tanks.  They are filled at the factory and only opened when attached to the LSAM.  This is similar to the way batteries are inserted into a radio.

The tanks can be transferred from the LV to the SEP tug, SEP to depot and depot to LSAM using robot arms.  The drop tanks are attached to the top of the lander including its plumbing.  Since the attachment is performed in a vacuum there are few width restrictions beyond symmetry.

Hydrogen can be cooled through the skin of the tank.
Title: Re: Propellant Depots - General Discussion
Post by: renclod on 03/19/2008 09:54 pm
Quote
neviden - 20/3/2008  1:38 AM
ATV weighs 12 tons
Not 12... 21 !
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/19/2008 09:55 pm
Quote
MichaelF - 20/3/2008  12:38 AM
A more definite, but less optimal answer is "when we absolutely cannot progress without it, we'll develop the capability".  This strategy has it's own drawbacks (program is static while awaiting critical developments, etc).
This approach has a an extra drawback.

when we absolutely cannot progress without it is usually the money. If you don't have the money but you still want to do something you cut "non-essential" and that is usually the long-term things. And then things slow down, political interests in status quo (those who build stuff want to build stuff in the future and have the money and influence to try to make sure they do. Case and point: shuttle solid boosters) prevail even more and then things come to a grinding stop..

Quote
renclod - 20/3/2008  12:54 AM

Quote
neviden - 20/3/2008  1:38 AM
ATV weighs 12 tons
Not 12... 21 !
It weighs 12 tons empty and carries 8 tons of payload..
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/19/2008 10:19 pm
Quote
Eerie - 19/3/2008  11:40 PM

Oh, and the same separate budget can be used for what I proposed - storing rockets on Earth.

A large number of launches is a big problem.  The US Air Force solved the ICBM multiple launch problem by giving each rocket its own launch pad.  This is expensive.  The other way of doing it is a string of launches.  This has been done by the Russians, they launched a Soyuz a week; for 10 launches that will take 10 weeks.  The Earth Departure Stage would have to stand around in orbit for at least 10 weeks, longer if the weather turns bad.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/19/2008 10:21 pm
There is a point everyone seems to be missing, when speaking about the economic value of using the depot, in terms of heavy lift or not and that is this:

Unless NASA changes its mind, or has its mind changed for it, NASA is proceeding with a heavy lift architecture because that is what the Congress, who pays the bills, instructed them to do, and all the economies of scale will not change that decision. It's cast in stone unless, like I said, something dramatic occurs in NASA. They have determined, by Congressional mandate (Authorization Act) that CxP will be a heavy lift architecture. So the presence, or absence, of a propellant depot is not going to change "that". What might change is how NASA's missions get configured. So for purposes of this conversation, we should be figuring out ways to capitalize on what NASA is going to do, while holding everything else up as a "separate market" that "also" gets serviced by the depot.

So we have two completely separate markets:
1. NASA Heavy Lift CxP
2. Everybody else.

So how do we capitalize on that?
Ideas?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/19/2008 11:00 pm
Quote
clongton - 20/3/2008  12:21 AM

So we have two completely separate markets:
1. NASA Heavy Lift CxP
2. Everybody else.

So how do we capitalize on that?
Ideas?

Ares-I (June 2011) is 3 years away.  The Ares-V is a decade away.  There is plenty of time to launch a small depot suitable for everyone else before then.  The bugs should be fixed by the time Ares/Jupiter needs a bigger depot.

By keeping the dry weight down to about 20 metric tons the first depot can be launched on an EELV and supplied using COTS rockets.  Using one of the current arm designs and a docking system similar to the ISS will save development costs.  A tug to collect customer payloads and refilling tanks can go up on a second launch.

Budgeting 5 tons for avionics, structure, station keeping, power, cooling, docking, sun shield, pumps, fuel in connector, fuel out connector and arm gives 10 to 15 metric tons for the fuel tank.

How much propellant (LOX?) can a 15 mT tank hold?
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/19/2008 11:14 pm
ATV is heavy since it is in essence an ISS module. A propellant tanker doesn't need a pressurized section, nor any of that human stuff.
Title: Re: Propellant Depots - General Discussion
Post by: mike robel on 03/19/2008 11:37 pm
I expect the only way a propellent depot will ever be established is if we someday build craft that cycle between earth orbit and the Lunar surface, as in 2001.  For one way flights I think it will make more sense to send large unmanned payloads direct to the surface of the moon and then use minimum sized vehicles and LOR to man them.

The other way it may make sense is to fuel up a Mars spacecraft as in the book Voyage or if we build a Mars Cycler.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/19/2008 11:47 pm
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MichaelF - 19/3/2008  12:21 PM

Quote
tankmodeler - 19/3/2008  12:27 AM

Quote
MichaelF - 18/3/2008  11:08 PM

Unattended depots? Maintenance/PMCS/Troubleshooting comes from where?
From the ground, like they do now for ISS. You use the RMS and an SPDM to swap out ORUs of any of the systems, including things like docking collars, tanks, cooling systems, RMS, whatever.
.

So, a kink (rather, frozen propellant, most likely) in the fuel line will cost you a manned launch (including booster, spacecraft and ground infrastructure) and an EVA (or several).
No, you've missed my point entirely.

The trouble shooting comes from the ground, the replacement & repair are done robotically on orbit with spares you launched with the empty depot. _That_ is what we showed we could do for the Hubble repair mission; robotic repair. Once you are in danger of depleting your on-board spares, you launch the unpressurised HTV with new ORUs that the RMS slots back into place.

No rescue missions, no manned EVAs, no shot business model. Everything done robotically with stocks held on orbit for just that possibility. Resupply only when convenient.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/20/2008 12:43 am
Quote
nobodyofconsequence - 19/3/2008  6:10 PM
As for cheaper LV's, have been waiting for them all my life. Don't hold your breath. 

One of the key problems with any existing or projected launcher is that they are all designed for launching incredibly expensive spacecraft and, as a consequence, are designed to be incredibly reliable and that costs an incredible amount of money.

Now, if you are launching fuel, the paradigm shifts (incredibly!). If you can afford to lose 1 in 20 launches, your design, manufacture, test and reliability overheads on the entire launcher infrastructure has just been turned on it's head. No-one has ever built a launcher on that basis. There is no experience in it. You'd probably be nuts to hire experienced aerospace people to do it unless you have a program leadership that completely "groked" the cost-based design concept.

On a cost-based design you do _nothing_ if it adds cost. No redundancy, no funky machining, no triple fly-by-wire systems, no fancy launch towers, no cast of thousands at the Cape. Nothing. Sheet metal. Welding. Sand castings. Added weight. Commerical electronics. Standard GPS systems. Anything and everything to keep the launcher costs down. As long as X tonnes of liquid get to orbit for Y dollars, nothing else matters, including loss rate.

No-one has ever done it that way before.

Boy, it would be cool to try, though, wouldn't it?

Paul
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/20/2008 12:45 am
Quote
mike robel - 20/3/2008  1:37 AM

I expect the only way a propellent depot will ever be established is if we someday build craft that cycle between earth orbit and the Lunar surface, as in 2001.  For one way flights I think it will make more sense to send large unmanned payloads direct to the surface of the moon and then use minimum sized vehicles and LOR to man them.

Taking cargo to Moon orbit/EML2 is one of the jobs of the SEP tug.
http://www.entechsolar.com/IACSEP.pdf

If a manned cycler is build it is worth while refuelling the cycler at both ends.  Hall Effect engines are that much more efficient than hydrogen engines.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/20/2008 03:03 am
I love the idea of a tug to do jobs repeatedly.

For a fuel depot I'd make the booster as stupidly simple as absolutely possible and put all the gubbins necessary for final orbital adjustment & docking in a tug. The quality of the tug would be high, but the aim would be to make the boosters as close to the equivalent of a 2000 litre space jerrycan as possible; no guidance once in orbit, no approach radar, no real RCC, just enough to keep it stable until the tug arrived and snagged it for the ride to the depot. the tug then does all the tough work.

If you're going to get fuel to the depot for near $4500 per docked kilo, it's gotta be simple.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: on 03/20/2008 03:07 am

Quote
Eerie - 19/3/2008  5:40 PM  nobodyofconsequence, I see your point. But you will have to have a separate budget for DP refuelling and maintaince. You will need to send rockets to DP at some constant rate. Do you think USA will fund such thing, that is independent of any specific mission?

Oh, and the same separate budget can be used for what I proposed - storing rockets on Earth.

Am not advocating any budget for anything - too soon to do so.

Merely want to point out an economic structural issue that keeps killing the industry over and over again. It''s like watching a cartoon character hammering itself with an enormous mallet over and over again into the ground.

Of course its an economic trade-off, and you can do it many ways. If you'd like my own favorite, its to do Jupiter-120 (and eventually 232) as in the AIAA paper and use PD's as a way to enhance VSE's effectiveness. That's very complementary to the existing political landscape.

As to mission rates to make a PD an economic proposition, that's a different question. Would suggest a study of using LEO PD's as an alternative to GTO. The big money on the commercial side is here and only here. The cost reduction/reliability improvement comes in a much smaller LV with a single engine first stage and a single engine second stage. You refuel at the PD, and inject into GTO and circularize - this has ramifactions for where you put a LEO PD. Perhaps both the DIRECT and commercial as well as the other cases Chuck has already described can occur with the same PD.

Like anything in space, you have to subsidize the initial PD until it becomes cross leveraged into the economics of the industry, which works down the costs long time. To begin with, you do a PD not for cost purposes but to enhance capabilities you already possess independently. Then other missions leverage that capability simply to use up excess capacity. As this subsidy attracts users, then the economics scale to the point that the cost gap closes and volume drives things down.

You've heard this before - but please note that we're only talking props here. Not vehicles. You allow market dynamics to solve which vehicles are best at doing this. Which changes over time.

Purposely constraining this to economics, because its central to how to get out of this boom and bust cycle in space that is so disappointing.

Why not a fan of your approach is that have lived through many ultimate LV scenarios, including the multi decade fan dance of Kistler. LV's come and go, and you can never rely on their ability to justify long term such a broad vision. They are better used very narrowly, for the specific purpose for what they are defined for. A general purpose LV is a contradiction in terms. So doubt your rocket store will find enough applicability across an industry. But everyone uses props.

Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/20/2008 03:59 am
One option I like for the PD architecture is when coupled with crasher stages for landers.

You can use essentially the same size lander each time (assuming the LSAM throttle can handle the variance of course), but change the size of the crasher stage to allow the payload capacity to grow.

Refueling the crasher in space makes for a vast array of mission sizes.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: MichaelF on 03/20/2008 04:07 am
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tankmodeler - 19/3/2008  7:47 PM

Quote
MichaelF - 19/3/2008  12:21 PM

Quote
tankmodeler - 19/3/2008  12:27 AM

Quote
MichaelF - 18/3/2008  11:08 PM

Unattended depots? Maintenance/PMCS/Troubleshooting comes from where?
From the ground, like they do now for ISS. You use the RMS and an SPDM to swap out ORUs of any of the systems, including things like docking collars, tanks, cooling systems, RMS, whatever.
.

So, a kink (rather, frozen propellant, most likely) in the fuel line will cost you a manned launch (including booster, spacecraft and ground infrastructure) and an EVA (or several).


The trouble shooting comes from the ground, the replacement & repair are done robotically on orbit with spares you launched with the empty depot. _That_ is what we showed we could do for the Hubble repair mission; robotic repair. Once you are in danger of depleting your on-board spares, you launch the unpressurised HTV with new ORUs that the RMS slots back into place.

Really?  That's several degrees more advanced than the cutting edge of remote manipulation systems.  Consider the fuel line problem (which is what came off the top of my head, and is not representative of all technical issues):

Remove any obstructing components (hull plates, insulation, etc).
Control those components while they are removed (can't just let them float).
Perform fine manipulation.
Perform multistep detach/install process.
Return all removed components to operating condition.

That's way, way, way beyond anything we've got now. DEXTRE doesn't even approach that kind of sophistication.  Never mind the fact that the RMS would have to operate and maneuver along the entire hull area.  Nothing of the like is currently operational.

Yet more $$$.

Robotic repair, on that scale and with that level of flexibility and precision is a capability that does not yet exist.  And is unlikely to be initiated as an ancillary program for a space depot.

Show me a current terrestrial RMS that can, say, disassemble and reassemble a car.  That would be the minimum proof-of-concept that you would need in order to simply say "oh, repairs will be done on-orbit by RMS".  
Once you have the aforementioned car-building RMS, you still need to space-rate it, match it up with the depot's systems (power, etc).....oh, and enable it to reach all critical areas of the depot (with sufficient reach to access critical components).

If you cannot show the above capability, I'd be less quick to bring up RMS-based maintenance.
Title: Re: Propellant Depots - General Discussion
Post by: MichaelF on 03/20/2008 04:25 am
No project exists in a vacuum.  If your pet project (in this case, orbital fuel depots) needs a system IOT function (such as advanced RMS, capable of handling most critical systems issues, or SEP tugs to move stuff around), which does not yet exist as a deployable system, you have two choices:

Choice 1: Go ahead with the main project and hope that the vital secondary systems are available (developed elsewhere) when you need them.  This is dumb, for many reasons, especially in a narrow niche industry like space operations (where it is relatively unlikely that someone else will be developing a specific capability at a rate which will coincide with your requirements).

Choice 2: Develop them yourself, as an additional project.  This costs time and money.  Big money, as these are specialized systems that have no market to absorb cost of development, and a small production run (meaning of development and production must be amortized over a small number of items, meaning each item is super expensive).

Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/20/2008 04:29 am
The tank itself is a relatively inert module - based on a stage already in production.   It wouldn't have any moving parts to repair.   The biggest problem it will face is being punctured by a large enough bit of MMOD.   If that happens you lose it - just like most other space modules!   You always want to have a backup ready to fly.   You need to put sufficient protection on it to protect it from all but the worst incidents and hope the Chinese don't go blowing any more cra* up in LEO.

The RCS system would be based on existing hardware with long-duration use already proven.   We've had 40 years of experience building such things.   It would obviously include multiple redundant backups - that's pretty routine for such systems.

If there is active cooling (first version probably not, later versions maybe), then you have two redundant solar arrays in case one fails.   You also have multiple backup cooling and control systems for redundancy too.   Everyone knows that multiple-redundancy is SOP in this business.

The transfer lines would need to be designed as bolt-on, bolt-off units to enable easy replacement.   Lines which become frozen are replaced.   Disconnected frozen lines can easily be cleared by exposing them to sunlight for a period of time - prop. just melts slowly and evaporates away from the disconnected line.   Line is then placed back into storage and can even be re-used later if undamaged.   Kink potential must be designed out of the system as much as possible, but if a kink occurs the line is simply swapped out for a good one.

At the tank end, there would need to be two or more parallel valves on each tank to guarantee flow even if one of the fixed valves permanently attached to the tank failed before the transfer line separation plane.   Everything beyond that separation plane would be dual-line (a primary and backup) and be designed to be routinely replaced before its design limits are ever reached.   It shouldn't be too much of an engineering challenge to ensure 10-20 refills per line.   Launch with ten LOX lines and ten LH2 lines (better still if they can be common design) and you've got 100-200 uses.

The RMS would *not* need to be a complex unit.   Something smaller and simpler than Shuttle's would be more than sufficient.   All you need is enough to grab a replacement line and place it carefully in position where multiple (redundant) latches seat it correctly.   It wouldn't need to do anything else (unless it is also to be used to grapple docking spacecraft - but that's a totally different requirement).   A backup might be worthwhile if the cost isn't too high.


An empty PD unit masses a small fraction of what can be lifted by a Heavy Lifter like Jupiter, so could be launched with dozens of spare transfer lines on-board.   Chances are that the service life of the PD would come up (5-10 years maybe) before you used all your spare lines.   And next generation PD could be a continually improved design.   Perhaps the unused lines could be transfered if needed.

These are all fairly standard approaches when it comes to PD systems.   There are a number of papers/articles out there describing all these sorts of technologies and techniques, and nothing particular here is not in use somewhere else already.   Apollo did most of the groundwork.

It's rocket science, but it ain't brain surgery :)

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/20/2008 05:31 am
Quote
MichaelF - 20/3/2008  1:07 AM

Quote
tankmodeler - 19/3/2008  7:47 PM

Quote
MichaelF - 19/3/2008  12:21 PM

Quote
tankmodeler - 19/3/2008  12:27 AM

Quote
MichaelF - 18/3/2008  11:08 PM

Unattended depots? Maintenance/PMCS/Troubleshooting comes from where?
From the ground, like they do now for ISS. You use the RMS and an SPDM to swap out ORUs of any of the systems, including things like docking collars, tanks, cooling systems, RMS, whatever.
.

So, a kink (rather, frozen propellant, most likely) in the fuel line will cost you a manned launch (including booster, spacecraft and ground infrastructure) and an EVA (or several).


The trouble shooting comes from the ground, the replacement & repair are done robotically on orbit with spares you launched with the empty depot. _That_ is what we showed we could do for the Hubble repair mission; robotic repair. Once you are in danger of depleting your on-board spares, you launch the unpressurised HTV with new ORUs that the RMS slots back into place.

Really?  That's several degrees more advanced than the cutting edge of remote manipulation systems.  Consider the fuel line problem (which is what came off the top of my head, and is not representative of all technical issues):

Again, you underestimate what currently exists. I work at MDA. I know exactly what the SPDM & SSRMS can currently do and swapping out purposely designed ORUs is exactly what they do. For the proposed Hubble rescue mission we showed that with special tooling and an existing SPDM we could remove cover plates that had never been designed for orbital removal, cross connect cables that had never been designed for robotic or orbital changeout and "hotwire" the whole thing to a new designed battery that would have been located in the rescue vehicle via a set of space jumper cables.

We currently operate the SSRMS from Earth while the astronauts on station are sleeping to increase the availability of the system and decrease their workload.

This is all absolutely current capability. nothing new at all. Build another SSRMS & SPDM and you get this for free.

If you build a new depot with all the systems designed form the start as ORUs that the SPDM can handle, then you are doing nothing that the current system can't handle. Designing the depot becomes harder, but, then again, it's always harder to design for maintainability and most space stuff has never had to be designed for that.

Quote
Remove any obstructing components (hull plates, insulation, etc).
Can do.
Quote
Control those components while they are removed (can't just let them float).
can do
Quote
Perform fine manipulation.
can do
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Perform multistep detach/install process.
Can do
Quote
Return all removed components to operating condition.
can do

Come on, suggest something we don't do already, will ya??

:)

Quote
Show me a current terrestrial RMS that can, say, disassemble and reassemble a car.  That would be the minimum proof-of-concept that you would need in order to simply say "oh, repairs will be done on-orbit by RMS".  
Sure, can't do that, but then again, the car wasn't designed from the start to be disassembeld by a robot. Design the car that way from the get go and a robot can certainly perform it. You just change the requirements of the car design.  Now, it might not be the prettiest car when you're done, but if you need it to be disassembled by a robot, then that's what you get. So design the depot precicely so that it can be maintained on orbit by the SPDM and it shall work that way.

Quote
Once you have the aforementioned car-building RMS, you still need to space-rate it, match it up with the depot's systems (power, etc).....oh, and enable it to reach all critical areas of the depot (with sufficient reach to access critical components).
As the British might say, "Piece of p*ss, mate." At MDA we do it every day of the week and twice on Sundays. We're naot talking an "off the shelf" Fanuc or ABB robot here, all our stuff is designed from the start for space applications.

The SSRMS walks all over the ISS, from grapple fixture to grapple fixture to virtually any spot on the entire station. It's carried long distance by the Mobile Base Structure (a rail car for space robotics). With the SPDM in place it can perform fine motor skills to a level that the human hand (in EVA gloves, I'll grant) can't manage as repeatedly and can perform much heavier tasks than any astronaut.

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If you cannot show the above capability, I'd be less quick to bring up RMS-based maintenance.
I can show all the above capabilities and more.

And that's why I bring up RMS based repair. We can do it. We _do_ do it. Right now.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/20/2008 05:36 am
Quote
kraisee - 20/3/2008  1:29 AM
It's rocket science, but it ain't brain surgery :)
Who amongst us is old enough to remember Jethro Bodene going through a phase of wanting to grow up to be a "Rocket Surgeon"? Come on, fess up!

:)

Paul
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/20/2008 06:48 am
Quote
meiza - 20/3/2008  2:14 AM
ATV is heavy since it is in essence an ISS module. A propellant tanker doesn't need a pressurized section, nor any of that human stuff.
Remove pressurized section, stick robotic arm instead, add extra tanks and option to refuel both ways and add even more redundant electronics (so that it will work for a decade or even more) and you have a good tug. You could even add extra docking port and make it work like Parom. You could do all that and would be hard pressed to come anywhere near the 20 MT (empty) limit for Ariane.

It can go fetch things that don’t require large delta-v, but are too dumb (cheap) to be trusted to come anywhere near a PD. It could be used to do “space repairs”. And if you put big empty tanks on it you can make pretty large delta-v to get to other places (thou it would probably be better to use cryogenic propulsion for that). You could even make it into space rescue vehicle or free flying now this is what I call 0 gravity – none of those constant resupply dockings and people moving around man tended station.

And if anyone thinks that NASA couldn’t possibly do that – ESA designed and built ATV for €1,3B ($2B). It will build 5 of them and all of them will burn up when their mission is finished. That’s not starving Russian rocket scientists that work for peanuts wages but real expensive western engineer price wages and costs..

Quote
kraisee - 20/3/2008  7:29 AM
It's rocket science, but it ain't brain surgery :)
Exactly. Nothing about PD is impossible or that hard. It’s a sensible approach that doesn’t require untold billions to make. You get to use existing equipment and get to spend money and time on developing new things that will make a difference. You know.. like SEP tugs that would be able to do high delta-v, high isp, low thrust missions. That way you could move your overengineered (=durable, reliable) space station/PD to HEO, L2, Mars orbit or anywhere else.. imagine “ISS light” in orbit around Mars supporting Mars surface mission while checking out if it can extract propellant from it’s moons with ATV tug..

You would only have to design PD once and plan on building few of them from the start. That way if a rocket carrying it explodes – ah well, who cares – send another one.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/20/2008 09:12 am
How about an inflated Depot? Could you fill Bigelow modules with fuel?
Title: Re: Propellant Depots - General Discussion
Post by: Gary on 03/20/2008 09:42 am
Quote
Eerie - 20/3/2008  11:12 AM

How about an inflated Depot? Could you fill Bigelow modules with fuel?

yes but you couldn't inflate the support infrastructure for it!
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/20/2008 10:07 am
Quote
Gary - 20/3/2008  5:42 AM
yes but you couldn't inflate the support infrastructure for it!

But how heavy will it be, anyway?
Title: Re: Propellant Depots - General Discussion
Post by: Gary on 03/20/2008 10:12 am
I have no idea but I'd guess it would be just the weight of the inflatable structure but the gas necessary to inflate it once on orbit. After that it's a matter of robotic or spacewalkers to add the necessary hardware to support it as a depot and then the rockets to fuel it.
You would also need to be careful of the material used. You wouldn't want your propellent to damage the structure. Again, I have no idea how much tolerance an inflatable structure has to the heat and cold of space or the cold of the propellant.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/20/2008 11:55 am
Quote
tankmodeler - 20/3/2008  7:31 AM

Come on, suggest something we don't do already, will ya??

Repair a a meteor strike hole in a fuel tank?
Say 2 inches across.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/20/2008 12:04 pm
The depot's tug will need to be able to refuel at the depot.

The SEP tugs will need a Xenon tank at the Earth orbit propellant depot to refuel from.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/20/2008 12:28 pm
As a supporter of depots since a few years (I think "depot" is a far better short word for it than yet another acronym, "PD"), I'm delighted by the enthusiasm in this thread. Surely now this idea will finally become generally known.

And there are a lot of things around and relating to the use of depots that have to be looked at too:
-tugs (that help stages to dock the depot)
-ferries (use electric propulsion to move propellant long distances)
-EML1 and EML2 depots and rendezvous there for global lunar anytime access and departure (and slow interplanetary highway missions)
-high launch rate low fixed cost proportion launchers, streamlined manufacture, integration and launch procedures (benefits for all space users)
-launcher agnostic or easily customizable tanker spacecraft
-eventually RLV:s

Overall, a big stimulation in a breadth of space activities, all helping exploration and commercial use too.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/20/2008 12:35 pm
Quote
A_M_Swallow - 20/3/2008  7:55 AM
Repair a a meteor strike hole in a fuel tank?
Say 2 inches across.

I have a feeling that, with all those launches of propellant already availiable, it will be easier to send a new fuel tank, instead of repairing an existing one.

I suppose PD won`t be composed of just one tank, right?
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/20/2008 01:15 pm
Quote
A_M_Swallow - 20/3/2008  3:04 PM
The SEP tugs will need a Xenon tank at the Earth orbit propellant depot to refuel from.
Xenon isn’t the only propellant that could be used. There are many combinations of propellants and thrusters. Hydrogen, Xenon, Argon, Lithium, hydrazine, ammonia,.. You might get less thrust for certain power at certain isp, but that can be easily fixed by having more power then it’s strictly necessary. Some solar cell designs are very promising as far as W/kg is concerned.

Quote
meiza - 20/3/2008  3:28 PM
Surely now this idea will finally become generally known.
I also notice the difference in acceptance of those ideas. In the past when you mentioned SEP, depots, tugs and things like that you got general “it’s impossible – you are crazy” response, now nobody talks how this is impossible.

I am still not that optimistic since the one that needs to be convinced (NASA, US government) still works and acts like they live in the 60’s. It’s all still about doing another Apollo to them. If that changes somehow, then I will be optimistic but the way I see it is: if NASA gets Ares V, then we can all forget about any of this (from NASA at least). It will be “cheaper” to just launch another rocket then to develop “complicated and dangerous new technologies”.

But yes, when I first started looking at spaceships with huge solar wings they seemed crazy to me too.. But high isp from SEPs together with propellant transfers (and later even ISRU) remove the need to save every last gram on the spaceships. That means that we could design SSTO landers for the Moon and Mars. 3 and 4 km/s delta-v SSTO is quite doable. Add ISRU powered by those big solar wings (and MWs they provide) and you have everything you need for permanent and economical exploration and eventually even exploitation of space (PGMs maybe?) and its resources. If you want to go beyond the asteroid belt you would need different power source of course, but the half in the NEP would be already operational (electric propulsion part).

Propellant depot would be just a first step in that direction. NASA plans on building tugs (EDS), transport ships (Orion), transit ships (MTV) and landers anyway, so why don’t they do it right the first time? Ares V is a good rocket, but the new rocket is the last thing NASA really needs. Let those engineers and workers do something useful for a change and not just another white elephant..
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/20/2008 02:01 pm
Quote
Eerie - 20/3/2008  2:35 PM

I suppose PD won`t be composed of just one tank, right?

I predict that the third depot will probably have lots of tanks.  The first one may have to be very simple and low cost, particularly in the beginning.  Connectors on the side that permit extra tanks to be added may be useful.

Edit: added "I predict that"
Title: Re: Propellant Depots - General Discussion
Post by: Marsman on 03/20/2008 02:23 pm
Quote
A_M_Swallow - 20/3/2008  11:01 AM

Quote
Eerie - 20/3/2008  2:35 PM

I suppose PD won`t be composed of just one tank, right?

The third depot will probably have lots of tanks.  The first one may have to be very simple and low cost, particularly in the beginning.  Connectors on the side that permit extra tanks to be added may be useful.

I would create an expandable system with the "base" version coming with the hardware and two tanks for use at L1 or L2 and the "heavy" version with the base hardware and maybe 6 tanks in LEO. All components use a common design, and are designed to be rearranged and expanded. If a tank is punctured or fails, just replace it and send up a new one.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/20/2008 06:13 pm
Marsman, I would create nuclear propulsion engines. Just give me world domination...

Why this thread is in "ORION (CEV) / ARES I (CLV)", anyway?
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/20/2008 06:20 pm
Quote
Eerie - 20/3/2008  3:13 PM

Why this thread is in "ORION (CEV) / ARES I (CLV)", anyway?
This topic was "touched on" (by me) over in the "Griffin Blames Atlas for Ares Dissent" thread and began to take on a life of its own. It was off topic for that thread so I just hit the "New Thread" button on the top of the page to have a place for this conversation to continue. In hindsight, I probably should have selected the location first before doing that. But it's the first time I actually created a thread.  :o Anyway, here it is.
Title: Re: Propellant Depots - General Discussion
Post by: marsavian on 03/20/2008 06:36 pm
Better now placed in Exploration Alternatives don't you think because that's what it is. We also had an earlier thread which is in the Ares V section, perhaps it's also better to merge them under your new title too ?

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=9981&posts=325&start=1
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/20/2008 07:18 pm
Quote
Eerie - 20/3/2008  9:35 AM

I suppose PD won`t be composed of just one tank, right?

IMHO that depends on what tanking structures you have available in production already and what your mission requirements are likely to be.

Obviously in the DIRECT camp we've been basing our PD with the capacity of one of our upper stages modified for the purpose (they can even be barrel stretched) and we found we can use a single one of these for all-but the Mars missions.   A single one of these would enable one-launch missions in the size-range of >200mT of payload to be sent through TLI.   I can't imagine any realistic requirement for more than that.

Two of these modules can even provide enough for a hypothetical Mars mission to simply use regular LOX/LH2 propellant systems *both ways* instead of something more exotic.


Existing Centaur and Delta-IV U/S aren't very large, so multiple units would be needed if we used them.   WBC variants are possible too, as well as all-new structures.   Essentially the list of options is endless.

The requirements will drive the hardware IMHO.

Currently, the baseline 4-person, 7-day, Global Access, Anytime Return requirement NASA wants is driving a need for ~100mT of TLI propellant for each Lunar mission.   100mT requirements would mean a fully loaded Jupiter-derived single tank could comfortably support two missions.   Using existing EELV-derived tanking, we would need about 5 propellant modules to support each mission.

IMHO, early PD's would only need a little more than 100mT capacity.   Later ones might need much greater capacity.   500mT capacity is well within the ballpark, although the 'market' is not easy to judge at this point.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/20/2008 08:51 pm
Quote
A_M_Swallow - 20/3/2008  8:55 AM

Quote
tankmodeler - 20/3/2008  7:31 AM

Come on, suggest something we don't do already, will ya??

Repair a a meteor strike hole in a fuel tank?
Say 2 inches across.

OK, ya got me on that one. Of course, a 2" hole in the ISS would put paid to that as well.

Of course, there are two solutions, working in parallel. the first is to armour the tank so that your chances of a LOM strike are greatly reduced. The second is to move the PD just like the ISS is moved now for pieces of debris that are large enough to be tracked.

There are a number of pretty light weight methods of "armouring" a space structure to survive relatively large high velocity impacts. In combination with orbital changes you can be at least qas asafe as the ISS is now for manned ops. Let's face it, that has to be pretty safe, even from a business risk point of view.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/20/2008 11:41 pm
Quote
tankmodeler - 20/3/2008  10:51 PM

OK, ya got me on that one. Of course, a 2" hole in the ISS would put paid to that as well.

We can fix 2" bullet holes in people.  There may be some way of lining the inside of the tank to stop the leak.  There will probably be a pair of holes.

Replacing an empty tank may be the easiest solution.  However manned spaceships and space stations need a way of fixing holes.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/21/2008 12:42 am
Quote
neviden - 20/3/2008  3:15 PM


Quote
meiza - 20/3/2008  3:28 PM
Surely now this idea will finally become generally known.
I also notice the difference in acceptance of those ideas. In the past when you mentioned SEP, depots, tugs and things like that you got general “it’s impossible – you are crazy” response, now nobody talks how this is impossible.

I am still not that optimistic since the one that needs to be convinced (NASA, US government) still works and acts like they live in the 60’s. It’s all still about doing another Apollo to them. If that changes somehow, then I will be optimistic but the way I see it is: if NASA gets Ares V, then we can all forget about any of this (from NASA at least). It will be “cheaper” to just launch another rocket then to develop “complicated and dangerous new technologies”.

But yes, when I first started looking at spaceships with huge solar wings they seemed crazy to me too.. But high isp from SEPs together with propellant transfers (and later even ISRU) remove the need to save every last gram on the spaceships. That means that we could design SSTO landers for the Moon and Mars. 3 and 4 km/s delta-v SSTO is quite doable. Add ISRU powered by those big solar wings (and MWs they provide) and you have everything you need for permanent and economical exploration and eventually even exploitation of space (PGMs maybe?) and its resources. If you want to go beyond the asteroid belt you would need different power source of course, but the half in the NEP would be already operational (electric propulsion part).

Propellant depot would be just a first step in that direction. NASA plans on building tugs (EDS), transport ships (Orion), transit ships (MTV) and landers anyway, so why don’t they do it right the first time? Ares V is a good rocket, but the new rocket is the last thing NASA really needs. Let those engineers and workers do something useful for a change and not just another white elephant..

Griffin, being a very smart and straightforward engineering man, must have surely known about propellant depots (and Doug Stanley as well) and all these other things too, there might be other undisclosed, nontechnical reasons why they have been so unmentionable...

If NASA money goes to workforce (mainly contractor people) then if NASA budget is kept constant the number of jobs is kept constant, and you can choose the most efficient architecture and it doesn't diminish jobs. You just get more and faster.

Though of course other people who know it better know if technicians can actually move for example from SRB to EELV or spacecraft work that easily, perhaps not?
There have been examples right on this forum about higher level engineers who have worked on STS and then moved on to other jobs (Athena in that particular example).
So it's not as if you need absolutely shuttle to keep workforce. Money means jobs, and if NASA budget is what it is, the money is what it is and the jobs are what they are - in a broad overview of course, it's always easy to say from the sidelines.  :o
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/21/2008 01:00 am
Quote
meiza - 20/3/2008  9:42 PM

Griffin, being a very smart and straightforward engineering man, must have surely known about propellant depots (and Doug Stanley as well) and all these other things too, there might be other undisclosed, nontechnical reasons why they have been so unmentionable...
Yes, they both know. However, a depot does not help the intent of the Ares program, which is to build and fly the biggest heavy lift rocket ever flown. That's what he wants. He wants to be remembered, like Von Braun was for the Saturn-V, as the builder of the biggest rocket ever, even bigger than the Saturn-V. That's his goal. A propellant depot negates the need for such a monster, thus it has no place in Griffin's plans. He wants the biggest launch vehicle, not the most efficient architecture. If he brought the depot online before the Ares-V, nobody would build the Ares-V because it wouldn't be needed. Thus he avoids discussing it.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/21/2008 05:11 am
Quote
Gary - 20/3/2008  3:42 AM

Quote
Eerie - 20/3/2008  11:12 AM

How about an inflated Depot? Could you fill Bigelow modules with fuel?

yes but you couldn't inflate the support infrastructure for it!

True, but it's important to remember that Bigelow modules do have an internal core structure for packing equipment into, and they're also planning at least one external "node" module of sorts for linking their inflatable modules together.  Personally, I think that if you're trying to do a low-cost first or second generation propellant depot, there are far worse places to start than with a Bigelow Module.  An important thing to remember is that a single Bigelow Nautilus module has more internal volume than the SIV-B stage (330m^3 vs ~300m^3 for SIV-B).  They ain't small by any stretch of the imagination.  Now, in reality, you're going to want to probably have the oxidizers and fuels in separate modules (just for safety purposes), and you're not going to be able to use the full internal volume for tanks (some of that space is going to be taken up by other hardware).  But even after you factor in stuff like that it's still an intriguing idea.

Now, there are some drawbacks of course.  For instance, there isn't much experience out there yet on flexible cryogenic tanks (there was some work on polymer films for use in cyrogenic propellant bladders back in the day--some of the PET films IIRC were still flexible enough at LH2 temps to do the trick, the problem was that they had too high of a permeability rate or something like that), and the outer pressure shell of the Bigelow station is probably not going to want to be at LH2 temperatures.  Not to mention the fact that you need a method for settling the propellant, you need hardware as you mentioned for transferring it, and possibly some active cooling systems and mass gauging systems.  It's not a trivial problem by any stretch of the imagination, but there are potential solutions for most of the challenges.

Just some food for thought.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/21/2008 11:42 am
Quote
jongoff - 21/3/2008  2:11 AM

Quote
Gary - 20/3/2008  3:42 AM

Quote
Eerie - 20/3/2008  11:12 AM

How about an inflated Depot? Could you fill Bigelow modules with fuel?

yes but you couldn't inflate the support infrastructure for it!

True, but it's important to remember that Bigelow modules do have an internal core structure for packing equipment into, and they're also planning at least one external "node" module of sorts for linking their inflatable modules together.  Personally, I think that if you're trying to do a low-cost first or second generation propellant depot, there are far worse places to start than with a Bigelow Module.  An important thing to remember is that a single Bigelow Nautilus module has more internal volume than the SIV-B stage (330m^3 vs ~300m^3 for SIV-B).  They ain't small by any stretch of the imagination.  Now, in reality, you're going to want to probably have the oxidizers and fuels in separate modules (just for safety purposes), and you're not going to be able to use the full internal volume for tanks (some of that space is going to be taken up by other hardware).  But even after you factor in stuff like that it's still an intriguing idea.

Now, there are some drawbacks of course.  For instance, there isn't much experience out there yet on flexible cryogenic tanks (there was some work on polymer films for use in cryogenic propellant bladders back in the day--some of the PET films IIRC were still flexible enough at LH2 temps to do the trick, the problem was that they had too high of a permeability rate or something like that), and the outer pressure shell of the Bigelow station is probably not going to want to be at LH2 temperatures.  Not to mention the fact that you need a method for settling the propellant, you need hardware as you mentioned for transferring it, and possibly some active cooling systems and mass gouging systems.  It's not a trivial problem by any stretch of the imagination, but there are potential solutions for most of the challenges.

Just some food for thought.

~Jon
I've been toying with the idea of a Bigelow-type "bladder" inside either a hard shell or another Bigelow-style container. This would allow the propellant to be transferred from the tanker or to the spacecraft by mechanically expanding or collapsing the bladder, maybe by twisting to expand or collapse, with the central core being where the propellant is transferred thru, either from the tanker, or to the spacecraft. No pumps, and no gaseous pressurization of the depot. The propellant is always "mechanically" pressurized. So it either sucks the propellant from a pressurized tanker by being mechanically expanded, or squeezes the propellant into the spacecraft by being mechanically collapsed, sort of like wringing out a wet cloth, only the liquid goes into central core plumbing instead of out thru the sides. While the "mechanics" of this would be physically larger, it would be MUCH less complex than doing vacuum pumping because the bladder would always be "full" at whatever state of expansion it was at. Liquid flow in or out would be really simple. Of course, it all would depend upon the state of the art of flexible bladders.

Just an idea.
Title: Re: Propellant Depots - General Discussion
Post by: nacnud on 03/21/2008 12:48 pm
Perhaps you could use surface tension and a pump instead, see corkscrew cups could keep space drinks flowing (http://technology.newscientist.com/channel/tech/dn13194-corkscrew-cups-could-keep-space-drinks-flowing.html) [New Scientist]
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/21/2008 05:45 pm
Chuck,
Quote
I've been toying with the idea of a Bigelow-type "bladder" inside either a hard shell or another Bigelow-style container. This would allow the propellant to be transferred from the tanker or to the spacecraft by mechanically expanding or collapsing the bladder, maybe by twisting to expand or collapse, with the central core being where the propellant is transferred thru, either from the tanker, or to the spacecraft. No pumps, and no gaseous pressurization of the depot. The propellant is always "mechanically" pressurized. So it either sucks the propellant from a pressurized tanker by being mechanically expanded, or squeezes the propellant into the spacecraft by being mechanically collapsed, sort of like wringing out a wet cloth, only the liquid goes into central core plumbing instead of out thru the sides. While the "mechanics" of this would be physically larger, it would be MUCH less complex than doing vacuum pumping because the bladder would always be "full" at whatever state of expansion it was at. Liquid flow in or out would be really simple. Of course, it all would depend upon the state of the art of flexible bladders.

It's been suggested before (google "Murphy Bags" on my blog), but it still has issues for cryogenic propellants.  With cryo propellants, unless you can keep the whole mass subcooled, you're going to get boiloff, which means you'll get gas bubbles in the bag, which means you start having problems with the idea right away.  Plus mechanically squishing a bag is probably not very good at getting all the propellant out.  I'd prefer to have the propellant bladder inside an actual Bigelow shell, and only inflate it once.  Then use pressurization and propellant settling to make sure the liquid goes where you want it to, and the gas goes where you want it to.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/21/2008 05:48 pm
Quote
nacnud - 21/3/2008  6:48 AM

Perhaps you could use surface tension and a pump instead, see corkscrew cups could keep space drinks flowing (http://technology.newscientist.com/channel/tech/dn13194-corkscrew-cups-could-keep-space-drinks-flowing.html) [New Scientist]

Might be doable, but surface tension devices for cryogens can be tricky.  The challenge with such a high surface area to volume ratio is how to avoid turning it into a massive heat exchanger....

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/21/2008 07:12 pm
I like the Advanced Apollo method still.   Dock the two modules firmly together.   Vent a small amount of boiloff gas to create a very small propellant settling effect - 0.0004g was assumed by Apollo.

At which point, adjust the pressure in the source tank vs. the receiving tank so that the source tank is 4psi higher pressure.   Maintain this difference through the process.

This creates a simple pressure differential, and a 'flow' would naturally be created.   Using this technique, and assuming 1.25" ID pipes, this technique can transfer >100mT of LOX/LH2 in less than 60 minutes.   No pumps, no high pressures.   The only moving parts are the valves between the tanks - and they can be designed so as to be 100% redundant.

You lose approximately 0.5% of your total H2 load via the settling/venting to do this entire procedure, but that's not much in the grand scheme of things.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/21/2008 08:48 pm
And 0.0004 g for 1 hour makes 4e-3m/s^2 * 3600 s = 14 m/s. So the wasted propellant wouldn't be that much.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/21/2008 09:02 pm
I can't find it right now, but there's documentation about this on ntrs.nasa.gov

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: MrTim on 03/21/2008 11:43 pm
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clongton - 20/3/2008  7:00 PM
Yes, they both know. However, a depot does not help the intent of the Ares program, which is to build and fly the biggest heavy lift rocket ever flown. That's what he wants. He wants to be remembered, like Von Braun was for the Saturn-V, as the builder of the biggest rocket ever, even bigger than the Saturn-V. That's his goal. A propellant depot negates the need for such a monster, thus it has no place in Griffin's plans. He wants the biggest launch vehicle, not the most efficient architecture. If he brought the depot online before the Ares-V, nobody would build the Ares-V because it wouldn't be needed. Thus he avoids discussing it.

First, Let's avoid asserting an absolute knowledge of somebody's intentions/desires unless we have them on tape or have a few diary pages... I don't think the guy is trying to build a legacy for himself. I think he is planning what he thinks is best and I will give him the benefit of the doubt unless proven wrong.

IMHO the only reason a fuel depot makes sense is as an enabler of participation by other programs into the VSE (unless the depot will be refilled and tended by completely reusable vehicles, then it makes better sense). The economics of the proposed depot are the inverse of what works; The gas station model works on Earth because huge tanker ships, trains and trucks are involved in efficiently getting massive loads of fuel from the well to the refiner and to the stations (plural) where fuel can sit for long periods and then customers pull-up in dinky little vehicles to sip small quantities of fuel from the stations. There are so many customers that an almost universal bulk-discount price applies and the vendors never worry about all the fuel evaporating between customer visits. Multiple stations, operated by private vendors and in competition with one another help keep prices down. None of these things apply to the proposed space depot. A space depot filled by small rockets and providing fuel to big ones would be like a gas station being filled by people in subcompact cars using 2-litre soda bottles, with an occasional visit by a customer in an 18-wheeler who would suck the station dry.

You want the perfect depot for VSE? I give you Ares V.... just launch one with minimal upperstage fuel and the payload, then launch another with no payload (just a fully fueled upper-stage). Have Orion pluck the payload from the first and stick it onto the second before TLI. Unfair? Sure. Adding another launch to the mission? Sure. But a depot and all those launches to fill it need to be counted too... and by using another Ares V as a "depot", you up the flight rate (which some people here seem to think has a magic price reducing effect) while avoiding lots of hassles like worrying about on-orbit fuel boil-off, MMOD risks to the depot, etc. Your "partners" can even use ships or trucks to deliver fuel to the depot instead of rockets ;-)

Sorry, but the depot just smacks of a magic trick to keep the public from noticing the true number of launches used for a mission. If a mission to the moon or mars needs x amount of fuel, then you will pay to put that fuel into orbit whether you use a depot or not...so you may as well use the rocket with the highest payload-to-rocket mass ratio to lift it. If you're gonna lift the fuel in one structure, you might as well store it on-orbit in that container, rather than paying to lift another container (the depot) and then transferring the fuel from one to the other. The question is: how much more money will you spend lifting extra hardware (like the depot and all those re-fuelling rocket bodies, motors, etc) plus extra fuel to allow for boil-off if you go with a depot and keep the fuel on-orbit, instead of just producing it and launching it when needed and on a bulk-carrier.

Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/22/2008 12:16 am
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MrTim - 21/3/2008  8:43 PM

Sorry, but the depot just smacks of a magic trick ...
You are entitled to your opinion.
If you can make it, might I suggest you attend the conference that Jon Goff is chairing next month?
There will be some very smart people there that I think you should talk to.
It will be well worth your time, I promise you.

Copying his post below:

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Just as a FWIW, but I'll be chairing a panel on Propellant Depots at the Space Access 2008 conference in Phoenix two weeks from now. I've got a pretty good lineup (Dallas Bienhoff from Boeing, Frank Zegler from the Centaur team at ULA, and Rand Simberg a blogger from Transterrestrial Musings), and it should be fun. If you're interested in attending, Henry Vanderbilt has details for the conference up at the (rather spartan) Space Access Society website: www.space-access.org

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/22/2008 02:12 pm
Jon is chairing a panel in a conference, he doesn't (yet) chair his own conferences. ;)
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/22/2008 02:16 pm
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meiza - 22/3/2008  11:12 AM

Jon is chairing a panel in a conference, he doesn't (yet) chair his own conferences. ;)
Oops! Fat finger syndrome. But he is certainly qualified to chair his own conference. :)
Title: Re: Propellant Depots - General Discussion
Post by: MrTim on 03/22/2008 04:50 pm
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clongton - 21/3/2008  6:16 PM
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MrTim - 21/3/2008  8:43 PM
Sorry, but the depot just smacks of a magic trick ...
You are entitled to your opinion.
Yes, it's just my opinion, though in reading your response it occurred to me that a reader might have assumed a more negative tone from my "magic" comment, so I'll explain briefly: a magician will often do things with his left hand to get the audience to look at it and not notice his right hand (not as an evil act, but as an artful direction of attention). Therefore, I tend to see a refuelling depot (using current tech and current likely usage) as something that gets people looking at the nice shiny new depot and not noticing that what's really happening is more launches and more fuel consumption. I do not mean to assert any bad intentions, indeed one might well argue that this in-and-of-itself is a positive and useful thing (particularly when one needs to distract congressional critters). I make the argument here though (where all of us post opinions) partly because the conversation is interesting and supporters need to be encouraged to confront and deal with weaknesses in their arguments. I will not ever be in an official position to approve/disapprove a depot, but that does not mean that proponents will not have to face these arguments from somebody who is in that position. I am certainly not going to be the only person to suggest launching an extra Ares V loaded with fuel in place of a depot (it's not that unique of a concept) but depot proponents need to have good answers to various criticisms.

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clongton - 21/3/2008  6:16 PM
If you can make it, might I suggest you attend the conference that Jon Goff is chairing next month?
There will be some very smart people there that I think you should talk to.
It will be well worth your time, I promise you.
I would love to do that, but I got the bug to start my own company and now find no time to spare for such things. The sad truth is that many of the things we discuss on this site (and which are discussed at various space-related conferences) are not going to occur in our lifetimes, so time I spend on such things (including this site) comes from my small budget of recreational time. My business, on the other hand, is a real-world activity that is still at a stage that requires a lot of hands-on time. I am desperately trying to work-in a trip to KSC for one of the remaining shuttle launches, as I was last there for Apollo and would like to personally compare the experiences. Any conference takes a back seat to real rockets spewing real fire ;-)
Title: Re: Propellant Depots - General Discussion
Post by: MrTim on 03/22/2008 05:09 pm
Chuck,
I did not mention it, but I actually think a depot is a very smart thing in a world with a fully re-usable and economical commercial shuttle fleet. If a shuttle fleet could be built and operated with better tech than the current one and done with a far better cost per pound to orbit, then it becomes very complimentary to a program like VSE. The shuttle TPS need not deal with high re-entry speeds of moon and mars missions, nor do you waste energy hauling all the re-usable hardware of a shuttle-type system beyond LEO. The fuel depot (assuming enough customers to keep it busy) then helps to justify the high flight rates that make a fully re-usable shuttle system economical. Also, with a depot being in a stable predictable orbit and not having military requirements, the shuttles do not need the cross-range capability our current orbiters were requited to have, so thin vulnerable wings are out and durable lifting body shapes are back in...

IMHO a fully re-usable unmanned lifting body mated to a fully re-usable fly-back first stage would be the way to make a depot work... provided it was operated by a low-overhead, go-get-em, highly-energized commercial entity and not a government or a big bloated stuck-in-a-rut defense contractor. Perhaps Space-X can consider it in a couple of decades...
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/22/2008 05:17 pm
Ross,
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I like the Advanced Apollo method still.   Dock the two modules firmly together.   Vent a small amount of boiloff gas to create a very small propellant settling effect - 0.0004g was assumed by Apollo.

Yeah, the Centaur guys have demonstrated propulsive propellant settling at accelerations even lower than that (I think down to ~10 micro-g).  It's not a bad way to go, as such small accelerations aren't likely to do much to the orbit of your station.  The only reason I prefer using magnetic tricks is that it also helps with the low-boiloff storage and fluid management side of things.  

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/22/2008 05:43 pm
Mr Tim,
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IMHO the only reason a fuel depot makes sense is as an enabler of participation by other programs into the VSE (unless the depot will be refilled and tended by completely reusable vehicles, then it makes better sense).

Being mostly interested in *commercial* propellant depots, I have to agree that they look best when you have reusable transportation.  But even with existing delivery sources, you can start the ball rolling.  The cool thing is, is that if you do your depot right, it's entirely agnostic as to how you get the propellants there.  Right now there are now commercial RLVs, but as soon as there are, they can start delivering propellants.  And if there's demand for even 25-50 tons of propellant on orbit per year, it might very well help close the business case for a *light* RLV.

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The economics of the proposed depot are the inverse of what works; The gas station model works on Earth because huge tanker ships, trains and trucks are involved in efficiently getting massive loads of fuel from the well to the refiner and to the stations (plural) where fuel can sit for long periods and then customers pull-up in dinky little vehicles to sip small quantities of fuel from the stations. There are so many customers that an almost universal bulk-discount price applies and the vendors never worry about all the fuel evaporating between customer visits. Multiple stations, operated by private vendors and in competition with one another help keep prices down. None of these things apply to the proposed space depot. A space depot filled by small rockets and providing fuel to big ones would be like a gas station being filled by people in subcompact cars using 2-litre soda bottles, with an occasional visit by a customer in an 18-wheeler who would suck the station dry.

Your point?  So analogies are never 100% valid (I personally prefer the "19th/20th century coaling station" analogy myself).  Just because it isn't perfectly analogous doesn't mean it can't still be a good idea in its own right.

But I agree with you, stations need to be sized correctly based on demand, having multiple stations is better than just one, and eventually, if the demand becomes high enough, you might see the case for bigger RLVs open up.  Maybe.  Cars and rockets are different, but that doesn't mean that there isn't at least a little truth in the analogy.

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But a depot and all those launches to fill it need to be counted too...

Why?  Seriously, if it's a non-NASA depot (preferably commercial), do they really care how the propellant was launched, so long as they can buy what they need when they need it for a price they are willing to go with?  Propellant depots, especially if you have ones in both LEO and somewhere in the lunar vicinity (L1/L2 or some LLO), allow a lot more flexibility in mission operations, and a more direct path to continually improving transportation economics.

Ares V on the other hand is a dead end.  You'll never see anything more than minor improvements in cost, you'll never be able to fly more than a certain number of times per year.  You're presetting the limits of your architecture in a way that precludes taking advantage of improvements in commercial launch capabilities.  You're also perpetuating a political empire that will continue to distort NASA's operations for decades to come.

I'm really not a fan of Ares V because it repeats all the same mistakes Apollo made.  I would hope that after 40 years we would've learned a lesson or two.

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Sorry, but the depot just smacks of a magic trick to keep the public from noticing the true number of launches used for a mission.

Why should the public or anyone else for that matter care how many flights it takes?  What matter is how much it costs, what it enables, what it does for commercial industry, etc.  

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If a mission to the moon or mars needs x amount of fuel, then you will pay to put that fuel into orbit whether you use a depot or not...so you may as well use the rocket with the highest payload-to-rocket mass ratio to lift it.

Why?  Wouldn't you rather use whatever is the most cost effective?  

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If you're gonna lift the fuel in one structure, you might as well store it on-orbit in that container, rather than paying to lift another container (the depot) and then transferring the fuel from one to the other.

Why?  Now you have to make your transfer stage carry all the functionality of a depot.  Do you really want to be shipping all that extra weight around?  Do you really want to be expending all of that expensive hardware every time?  

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The question is: how much more money will you spend lifting extra hardware (like the depot and all those re-fuelling rocket bodies, motors, etc) plus extra fuel to allow for boil-off if you go with a depot and keep the fuel on-orbit, instead of just producing it and launching it when needed and on a bulk-carrier.

Once again, mass doesn't matter--cost does.  And quite frankly, I think you'll come out way ahead by reusing your depot structure as opposed to trying to do everything with HLVs.  For one thing, with a depot you can actually build the thing in such a way to eliminate propellant boiloff (or if you don't want to go all the way, you can at least reduce it drastically compared to what you could do with a flight stage).  Second off, a good depot doesn't weigh that much, even if it needs enough propellant for a lunar mission (plus some margin).  And there are methods you can use for a commercial depot that can keep the cost (which is what matters more than mass) down even further.


~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/22/2008 05:47 pm
Mr Tim,

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I would love to do that, but I got the bug to start my own company and now find no time to spare for such things. The sad truth is that many of the things we discuss on this site (and which are discussed at various space-related conferences) are not going to occur in our lifetimes, so time I spend on such things (including this site) comes from my small budget of recreational time. My business, on the other hand, is a real-world activity that is still at a stage that requires a lot of hands-on time. I am desperately trying to work-in a trip to KSC for one of the remaining shuttle launches, as I was last there for Apollo and would like to personally compare the experiences. Any conference takes a back seat to real rockets spewing real fire ;-)

Good luck with your business!  We do only have a finite time available in this life, and we have to make decisions on how to spend that time.  I totally understand.

BTW, sorry if my last reply came off a little flippant.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/22/2008 07:36 pm
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MrTim - 22/3/2008  1:43 AM

You want the perfect depot for VSE? I give you Ares V.... just launch one with minimal upperstage fuel and the payload, then launch another with no payload (just a fully fueled upper-stage). Have Orion pluck the payload from the first and stick it onto the second before TLI. Unfair? Sure. Adding another launch to the mission? Sure. But a depot and all those launches to fill it need to be counted too... and by using another Ares V as a "depot", you up the flight rate (which some people here seem to think has a magic price reducing effect) while avoiding lots of hassles like worrying about on-orbit fuel boil-off, MMOD risks to the depot, etc. Your "partners" can even use ships or trucks to deliver fuel to the depot instead of rockets ;-)

This depends on your mission.  Sending an entire moon base in one go would be a suitable mission for using Ares V as a propellant lifter.
Delta-v of LEO to Low Lunar Orbit is 4.04 km/s
ISP of RL-10-2 using LOX + LH2 is 462 seconds

m0 = m1 exp (4040 / (462 * 9.81)) = m1 * 2.44

So this is going to take 3 Ares V launches.  NASA is only set up to do two at a time, so the fuel will have to be kept cold whilst waiting for the third Ares V launch.

p.s.  The Ares V is a great LV for launching a big depot.

The pumps, RCS, cooling panels, solar panels, avionics, robot arm and tug are all easily reusable.  We do not want/need to launch then again for each mission - that will be a waste of money and fuel.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/22/2008 07:56 pm
Umm, remember you have to land too. Once you design a lander with big money put into reliability and light weight, it is very unlikely you could increase the mass it can land that much. Perhaps 10% or so. Then just keep flying lots of those landers to spread out the high development cost.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/22/2008 08:19 pm
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meiza - 22/3/2008  9:56 PM

Umm, remember you have to land too. Once you design a lander with big money put into reliability and light weight, it is very unlikely you could increase the mass it can land that much. Perhaps 10% or so. Then just keep flying lots of those landers to spread out the high development cost.

One of the main constraints on a lander is the amount of mass you can get to the Moon/Mars.  Use depots and SEP ferries to increase the mass and you can design a bigger lander.  The propellant depots may be on the critical path for a lunar base.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/22/2008 09:06 pm
But it isn't cost effective if you fly the mega-lander once every 5 years. It'd be better to fly 5 regular landers: you could do it sooner, save money etc.
Let's face it that in the current cash situation (NASA budget is 17 billion per year, which is quite a lot), there just isn't enough money for payloads to even overwork a decent roughly 20 ton payload lunar lander.
Maybe later, a lot later...
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/23/2008 02:35 am
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meiza - 22/3/2008  10:06 PM

But it isn't cost effective if you fly the mega-lander once every 5 years. It'd be better to fly 5 regular landers: you could do it sooner, save money etc.

You can use the depot to allow a bigger regular lander.


Or send your cargo up on EELV and transfer using a SEP ferry.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/23/2008 04:21 am
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meiza - 22/3/2008  4:56 PM

Umm, remember you have to land too. Once you design a lander with big money put into reliability and light weight, it is very unlikely you could increase the mass it can land that much. Perhaps 10% or so. Then just keep flying lots of those landers to spread out the high development cost.

Agreed.   Current estimates put the baseline 45mT LSAM Fixed costs in the region of $2.5bn per year with per-unit costs starting around $500m each.

If you only fly one per year, that flight will cost about $3bn.   Two per year drops that sharply to $1.8bn each.   4 per year gets them down to $1.1bn.   If you can squeeze 8 missions out of the entire system (Manufacturing, Ops, LV & Spacecraft all together) each year you could drop individual LSAM costs to about $0.8m.

The key to making this work is finding a viable solution which can realistically support these sorts of flight rate within an affordable total budget and within a reasonable schedule - oh, and keep the politicians on-side to support you at the same time.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/23/2008 09:43 am
I have this crazy idea of a depot that collects oxygen from Earth atmosphere. It will have to have some solar propulsion to keep it in orbit, of course.

What do you think?
Title: Re: Propellant Depots - General Discussion
Post by: MrTim on 03/23/2008 02:14 pm
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jongoff - 22/3/2008  11:43 AM
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The economics of the proposed depot are the inverse of what works; The gas station model works on Earth because huge tanker ships, trains and trucks are involved in efficiently getting massive loads of fuel from the well to the refiner and to the stations (plural) where fuel can sit for long periods and then customers pull-up in dinky little vehicles to sip small quantities of fuel from the stations...(snip)
Your point?  So analogies are never 100% valid (I personally prefer the "19th/20th century coaling station" analogy myself).  Just because it isn't perfectly analogous doesn't mean it can't still be a good idea in its own right.
My point is that all the best experience humans have with distribution of basic liquid and/or powder materials involves bulk transporters with very high cargo-to-vehicle mass ratios hauling the stuff from its origin to the final distribution point where much smaller quantities are distributed to the end user. This is the scheme that works economically. There is no functional model I am aware of that works with the opposite scheme (many small supply vehicles filling a distribution point and then huge bulk consumers).
The model we all live with (gas stations) exists because it works and is efficient, not because it's neat or interesting.

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jongoff - 22/3/2008  11:43 AM
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But a depot and all those launches to fill it need to be counted too...
Why?  Seriously, if it's a non-NASA depot (preferably commercial), do they really care how the propellant was launched, so long as they can buy what they need when they need it for a price they are willing to go with?  Propellant depots, especially if you have ones in both LEO and somewhere in the lunar vicinity (L1/L2 or some LLO), allow a lot more flexibility in mission operations, and a more direct path to continually improving transportation economics.
Basic economics is why. All those launches to loft the depot itself and then fill it must be counted because somebody must pay for them. The entity that paid for them must pass the cost along to the customer or the whole thing goes out of business. Your local gas station did not appear and get filled-up by magic, somebody invested the money to do those things and you are paying him back (plus a profit margin) in small bits each time you buy gas. You and all the other customers are paying for all of that overhead. If you were the only customer, you would have to pay for all of it or the station would go out of business. Most gas stations live on very thin profit margins which would not exist if they were not getting their product delivered by very efficient bulk carrier vehicles and moving large enough volumes of fuel for the tiny profit margins to add-up. Even with those considerations, many stations need to sell other things or provide other services to stay in business.
So the answer is: If the scheme is not economically workable, no vendor will do it and NASA will not be able to buy fuel from a commercial depot... so it's not that NASA must "care" about how the depot or the fuel it holds got into space, but SOMEBODY must pay for and count all those expenses. We do not just get to plug a hole in a spreadsheet for cost of lifting fuel to orbit by saying "insert fuel depot here" with the presumption that somebody will do all that stuff and not charge for it.

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jongoff - 22/3/2008  11:43 AM
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Sorry, but the depot just smacks of a magic trick to keep the public from noticing the true number of launches used for a mission.
Why should the public or anyone else for that matter care how many flights it takes?  What matter is how much it costs, what it enables, what it does for commercial industry, etc.  
Because the total cost of a mission includes the costs of getting the fuel up there whether NASA does it directly or buys the fuel which is sold (at a profit) by a commercial entity who had to pay to put it up there and had to pay for the infrastructure to store it up there and dispense it up there. If a navy ship pulls into a commercial facility and sucks-up a bunch of fuel oil, the government must write somebody a big fat check; the government does not get to simply not count and not pay for the fuel.

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jongoff - 22/3/2008  11:43 AM
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If a mission to the moon or mars needs x amount of fuel, then you will pay to put that fuel into orbit whether you use a depot or not...so you may as well use the rocket with the highest payload-to-rocket mass ratio to lift it.
Why?  Wouldn't you rather use whatever is the most cost effective?  
Absolutely. It's more efficient and cheaper per gallon to ship a million barrels of crude oil from Saudi Arabia to Louisiana by supertanker than by row boat or sail boat, even though those small boats are far cheaper to build and operate than the tanker. (extreme example, but depot proponents need to demonstrate that they can at least break-even while doing something contrary to basic economic norms)

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jongoff - 22/3/2008  11:43 AM
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If you're gonna lift the fuel in one structure, you might as well store it on-orbit in that container, rather than paying to lift another container (the depot) and then transferring the fuel from one to the other.
Why?  Now you have to make your transfer stage carry all the functionality of a depot.  Do you really want to be shipping all that extra weight around?  Do you really want to be expending all of that expensive hardware every time?  
Because you have to pay not just to lift the fuel but also to lift all of the involved structures. If you are going to lift all of that structural mass and then throw it away, it eats into your profit margins. It would be like junking every oil tanker at the end of its first trip; you could do it but it would drive up your per-gallon cost which is the opposite of what you are trying to do. A compromise might be to have the depot be a large frame with all the needed infrastructure and have each vendor loft a tank that gets docked to the frame until pumped empty (at which point tank then gets cast-off). You could have some robot arm crawl around on a grid docking any full tanks as they arrive and casting-off empties as needed. For a depot to work, you have got to find every possible way to reduce the ratio of throw-away mass to fuel-mass.

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jongoff - 22/3/2008  11:43 AM
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The question is: how much more money will you spend lifting extra hardware (like the depot and all those re-fuelling rocket bodies, motors, etc) plus extra fuel to allow for boil-off if you go with a depot and keep the fuel on-orbit, instead of just producing it and launching it when needed and on a bulk-carrier.
Once again, mass doesn't matter--cost does.  (snip)
In spaceflight, mass is cost. It costs money to lift mass into space, so you need to lift as much fuel to space using as little non-fuel mass (which you also must lift) as possible.

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jongoff - 22/3/2008  11:47 AM
(snip)
BTW, sorry if my last reply came off a little flippant.
~Jon
No worries. Your last post was not at all offensive, nor is mine intended to be. This is just a healthy, friendly back-and-forth between people who support manned spaceflight and want it to be done by the best means possible.  :)

BTW: I advanced the extra Ares V launch idea not as something I would push for but more as a devil's advocate position to elicit thoughts by depot supporters about why a depot would be better than that. As I said in another post, I think an argument could be made for a commercial depot
that was filled by completely re-usable automated vehicles (though that's not gonna happen soon).

Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/23/2008 07:21 pm
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MrTim - 23/3/2008  3:14 PM
BTW: I advanced the extra Ares V launch idea not as something I would push for but more as a devil's advocate position to elicit thoughts by depot supporters about why a depot would be better than that. As I said in another post, I think an argument could be made for a commercial depot
that was filled by completely re-usable automated vehicles (though that's not gonna happen soon).


Forget reusable vehicles.  Most of a launch vehicle is a fuel tank.  Tanks are cheap to make on Earth.  Probably cheaper than collecting the tank at sea, repairing the tank & LV and taking them back to the launch pad.  Depending on the costs of heat shields the engines and avionics may be worth recycling.

If your fuel is coming from Phobos then recycling the fuel tank is worth while, there are no tank factories on Phobos.


Something worthy of a trade study.  Which is cheaper?

a. Lift fuel to depot.  Pump fuel into depot tank losing x% of fuel.  Pump fuel from depot tank into customer's rocket-tank losing y% of fuel.  Also z units of helium to flush system.  Discard tank from LV.

b. Lift fuel to depot.  Attach fuel and new fuel tank to depot.  Receive customer rocket and discard its empty fuel tank.  Use robot arm to insert new fuel tank into customer's rocket.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/23/2008 07:29 pm
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MrTim - 23/3/2008  3:14 PM
My point is that all the best experience humans have with distribution of basic liquid and/or powder materials involves bulk transporters with very high cargo-to-vehicle mass ratios hauling the stuff from its origin to the final distribution point where much smaller quantities are distributed to the end user. This is the scheme that works economically. There is no functional model I am aware of that works with the opposite scheme (many small supply vehicles filling a distribution point and then huge bulk consumers).

Try bulk grain carriers.  The grain comes from the farms on ordinary trucks and crosses the water in big ships.  There may be a warehouse in the middle.

Title: Re: Propellant Depots - General Discussion
Post by: MrTim on 03/23/2008 10:34 pm
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A_M_Swallow - 23/3/2008  1:29 PM
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MrTim - 23/3/2008  3:14 PM
My point is that all the best experience humans have with distribution of basic liquid and/or powder materials involves bulk transporters with very high cargo-to-vehicle mass ratios hauling the stuff from its origin to the final distribution point where much smaller quantities are distributed to the end user. This is the scheme that works economically. There is no functional model I am aware of that works with the opposite scheme (many small supply vehicles filling a distribution point and then huge bulk consumers).
Try bulk grain carriers.  The grain comes from the farms on ordinary trucks and crosses the water in big ships.  There may be a warehouse in the middle.
Again, A bulk carrier moves the goods in a special transport vehicle with a huge cargo-to-vehicle ratio. The reason you find smaller vehicles at the head of that chain is that you are harvesting a crop from a widely dispersed area (it would be inefficient to have a massive ship moved around grabbing small quantities from various spots in a field). As soon as practical, the small collected quantities are piled together to make huge piles which are then transported in bulk (big ships, long trains, etc.). Little trucks do not gather the crop and then transport it in little loads all the way to the final distribution points, nor do they transfer small loads to little boats or single-hopper trains.

Nice try though...  ;)

Look, I think space depots would be cool to build and neat to see on NASA TV. They would bring us that much closer to the sci-fi stories many of us read in our younger days... but before they can be a reality they need to make total economic sense; They cannot just be something neat whose construction, launch, and re-fill costs are off-budget and magically not accounted for or payed for. If you want a depot, design one and find a way to fill it that makes the whole exercise cheaper and less expensive than any other method of getting the same fuel mass to orbit... then it will sell itself in the same way that Lunar orbit Rendezvous did (yes, I know Houbolt had to push it at first but it ultimately won because it proved to be the right way to accomplish the task).
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/23/2008 11:26 pm
The final distribution point for fuel tends to be the Moon and Mars.
Title: Re: Propellant Depots - General Discussion
Post by: veedriver22 on 03/24/2008 02:06 am
I would think of a depot as infrastructure.   I know that down here private companies build & refuel the gas stations,  but the goverment does build some of the major components of the system, such as roads, power stations etc.    These private companies could not possiblty build the roads that it uses.  

 WHen it comes to space infrastructure there could be a fuel depot,  and perhaps a basic space station designed to be used and added on to by private companies.  If these pieces were in place,  I am guessing that there would be companies that would take a hard look commercial ventures in space.  

 Here is the question.  If there existed a sizeable depot,  what would be the maximum fuel deliveries that could be made either with ARES or DIRECT?  Design a configuration with no other task than to deliver the maximum load to the depot.  And once that is done, how many moon missions (or other missions) could be accomplished with that fuel?  Would there be any value for deep space probes to fuel up at the depot?   Would mars exploratory missions benefit?
Title: Re: Propellant Depots - General Discussion
Post by: yinzer on 03/24/2008 02:09 am
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MrTim - 23/3/2008  4:34 PM

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A_M_Swallow - 23/3/2008  1:29 PM
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MrTim - 23/3/2008  3:14 PM
My point is that all the best experience humans have with distribution of basic liquid and/or powder materials involves bulk transporters with very high cargo-to-vehicle mass ratios hauling the stuff from its origin to the final distribution point where much smaller quantities are distributed to the end user. This is the scheme that works economically. There is no functional model I am aware of that works with the opposite scheme (many small supply vehicles filling a distribution point and then huge bulk consumers).
Try bulk grain carriers.  The grain comes from the farms on ordinary trucks and crosses the water in big ships.  There may be a warehouse in the middle.
Again, A bulk carrier moves the goods in a special transport vehicle with a huge cargo-to-vehicle ratio. The reason you find smaller vehicles at the head of that chain is that you are harvesting a crop from a widely dispersed area (it would be inefficient to have a massive ship moved around grabbing small quantities from various spots in a field). As soon as practical, the small collected quantities are piled together to make huge piles which are then transported in bulk (big ships, long trains, etc.). Little trucks do not gather the crop and then transport it in little loads all the way to the final distribution points, nor do they transfer small loads to little boats or single-hopper trains.

Nice try though...  ;)


Concrete is about as bulk of a material as there is, the cheapest way to move bulk materials is by conveyor,  then train, then maybe large trucks over prepared roads.  But if you are building the anchorage for the top end of a ski lift way up on a mountain, the concrete gets carried up there by helicopter.  And even though you could carry all the concrete in one shot with one of those huge Russian helicopters, or maybe in two shots with a MH-54E, you'd end up buying a JetRanger and doing it over many days.

It's all about using your capital assets effectively, and in situations where you have to buy them and can't rent them out, that means sizing them small enough that they don't spend most of their time sitting idle.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/24/2008 03:16 am
Quote
veedriver22 - 24/3/2008  3:06 AM
 Here is the question.  If there existed a sizeable depot,  what would be the maximum fuel deliveries that could be made either with ARES or DIRECT?  Design a configuration with no other task than to deliver the maximum load to the depot.  And once that is done, how many moon missions (or other missions) could be accomplished with that fuel?  Would there be any value for deep space probes to fuel up at the depot?   Would mars exploratory missions benefit?

Chemical rockets.  Low lunar orbit - you need about one and a half times as much fuel as cargo plus spacecraft.  So 3 fuel delivers can send 2 full loads to the Moon.  2.5 launches.

SEP ferry.  For 22 mT to moon a 5 mT chemical lander using 17.972 mT chemical fuel and 25.756 mT Xenon (= 71 mT)
A reusable 7 mT SEP plus 2.1 mT solar array are assumed - launched separately.
Using EELV with a 20 mT lift 71 mT / 20 mT = 3.54 launches.  (A single Ares-V or J-232 can do this.)
http://www.entechsolar.com/SPRAT-XX-SLA-SEP.pdf

Deep space probe.  Current probes have to go up on a single rocket, giving a maximum size of about 20 mT including fuel.  A depot would permit 2 launch options so 20 mT dry probe plus fuel.  The fuel may be xenon.

Mars missions.  Larger (20 mT) probes can be sent because the fuel can be sent up separately.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/24/2008 05:24 pm
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Eerie - 23/3/2008  3:43 AM

I have this crazy idea of a depot that collects oxygen from Earth atmosphere. It will have to have some solar propulsion to keep it in orbit, of course.

What do you think?

Google PROFAC.  It's not entirely crazy, though I don't have enough information to truly run the numbers.  There's a guy at Worcester Polytechnic in Massachussetts who's currently trying to push that idea.  There's a lot of question marks though on if you can get the design to close.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/24/2008 06:18 pm
Quote
jongoff - 24/3/2008  1:24 PM

Google PROFAC.  It's not entirely crazy, though I don't have enough information to truly run the numbers.  There's a guy at Worcester Polytechnic in Massachussetts who's currently trying to push that idea.  There's a lot of question marks though on if you can get the design to close.

~Jon

PROPULSIVE FLUID ACCUMULATOR SYSTEMS. Publication: 1960.

Ahhh, the old crazy ideas are the best.  :)
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/24/2008 08:59 pm
MrTim,
Quote
My point is that all the best experience humans have with distribution of basic liquid and/or powder materials involves bulk transporters with very high cargo-to-vehicle mass ratios hauling the stuff from its origin to the final distribution point where much smaller quantities are distributed to the end user. This is the scheme that works economically. There is no functional model I am aware of that works with the opposite scheme (many small supply vehicles filling a distribution point and then huge bulk consumers).

I'm not entirely sure, but I think the 19th-20th century coaling stations in the Pacific might be a closer analogy.  I'll have to study up on it, but AIUI, the ships taking on coal and fresh water (many of them warships) were likely on the same or larger size than the coal delivery ships.  I'm not positive, but that is the one transportation fuel depot type scenario that most closely matches the physical constraints of an orbital depot (and even then it's only a very crude approximation).

Quote
The model we all live with (gas stations) exists because it works and is efficient, not because it's neat or interesting.

It's important to realize though that the reason why gas station logistics works the way they do is entirely dependent upon the technical realities of internal combustion ground transportation.  Rocket orbital transportation has a different set of technical realities, which IMO makes it less likely that the optimal solution for logistics for orbital transports will look exactly like a terrestrial analog like gas stations...

I'm not sure if that makes any sense.

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jongoff - 22/3/2008  11:43 AM
Why should the public or anyone else for that matter care how many flights it takes?  What matter is how much it costs, what it enables, what it does for commercial industry, etc.  
Because the total cost of a mission includes the costs of getting the fuel up there whether NASA does it directly or buys the fuel which is sold (at a profit) by a commercial entity who had to pay to put it up there and had to pay for the infrastructure to store it up there and dispense it up there. If a navy ship pulls into a commercial facility and sucks-up a bunch of fuel oil, the government must write somebody a big fat check; the government does not get to simply not count and not pay for the fuel.

I think I see the root of our miscommunication.  I'm not saying that we can ignore the cost of shipping the fuel--the transportation costs are likely going to dominate the cost of fuel on orbit for the foreseeable future!  What I'm saying is that what matters isn't the *number* of flights it takes to provide that fuel, what matters is the *cost of those flights*.  If someone had a small RLV that could only deliver 500lb worth of payload, but could do it for $250k per flight, it may very well be cheaper to fill it up from 400 flights of a fleet of those than to buy a single Ares-I flight, or 6 EELV-H flights.  I was trying to point out that there isn't a direct connection between number of flights and cost, and that in many cases, splitting it up into small chunks so that your earth-to-orbit transportation system is running at closer to an optimal level may very well result in lower costs.

I agree wholeheartedly that if this is a commercial endeavor, the full cost of propellant delivery to orbit is going to be passed on to customers.  I just think that when all factors are considered, it's going to be cheaper to buy propellants from a depot (even including depot launch and operations costs and amortization of development costs) than it is to build and operate a HLV.

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Absolutely. It's more efficient and cheaper per gallon to ship a million barrels of crude oil from Saudi Arabia to Louisiana by supertanker than by row boat or sail boat, even though those small boats are far cheaper to build and operate than the tanker. (extreme example, but depot proponents need to demonstrate that they can at least break-even while doing something contrary to basic economic norms)

False Analogy.  Just because the economics of ocean transport right now favor a supertanker does not mean that the same applies when you consider the economic and technical realities of current spaceflight.   It *might* turn out that way, but it's highly doubtful.  Especially if you do an *honest* evaluation of all the fixed and development costs.

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Because you have to pay not just to lift the fuel but also to lift all of the involved structures.
 

So?  That structure gets lifted *once* not every single flight.  And you only have to pay for the hardware *once* instead of with every flight.  And most likely the propellant fraction of a depot is still going to be pretty darned high, even with all the fixed systems (think 75-80+% propellant).

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In spaceflight, mass is cost. It costs money to lift mass into space, so you need to lift as much fuel to space using as little non-fuel mass (which you also must lift) as possible.

Well, mass and cost are related, and I do agree you want to maximize your fuel to non-fuel mass ratio.  My point though was that different launch systems have different $/mass at different flight rates.  For instance, even if one vehicle implies you're spending 5% more dry mass per unit wet mass delivered, if it costs 20% less per lb in orbit, the transportation costs will be cheaper.

IOW, you're points are somewhat valid, if and only if all other things are equal, but they aren't.

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No worries. Your last post was not at all offensive, nor is mine intended to be. This is just a healthy, friendly back-and-forth between people who support manned spaceflight and want it to be done by the best means possible.  :)

Good.

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BTW: I advanced the extra Ares V launch idea not as something I would push for but more as a devil's advocate position to elicit thoughts by depot supporters about why a depot would be better than that. As I said in another post, I think an argument could be made for a commercial depot that was filled by completely re-usable automated vehicles (though that's not gonna happen soon).

Yeah, RLVs will likely *follow* the development of significant sources of demand like a depot.  But a depot properly designed really is agnostic about what sort of launcher it is that's sending propellant up, so if you design it to use existing expendables first, you can at least get operations started, and then when reusables come on line, you can adjust your prices accordingly.  I'd rather start with a propellant depot that's marginally better or only comparable to an HLV cost-wise, but that has the potential for much lower costs and much greater capabilities as things like RLVs come on-line.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/25/2008 12:00 am
The other factor effecting the propellant depot is launch rate. If J-232/Ares-V launches are limited to 2 a year it will take an average of 26 weeks to refill a 100 mT depot. Ten launches, once a week, of 10 mT will fill the depot in 10 weeks.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/25/2008 03:23 am
Quote
A_M_Swallow - 24/3/2008  9:00 PM

The other factor effecting the propellant depot is launch rate. If J-232/Ares-V launches are limited to 2 a year it will take an average of 26 weeks to refill a 100 mT depot. Ten launches, once a week, of 10 mT will fill the depot in 10 weeks.

For the record, there is absolutely no point at all in Jupiter-232 or Ares-V if you only intend (or can only afford) 2 flights per year.

That simply replicates the current inefficiency of the Shuttle systems all over again - never being able to fly it enough times each year to ever be able to amortize the fixed costs and make it economical.   This is even crazier since you have managed to get rid of the most costly/time-consuming part - the "Orbiter"!   While I'm sure you are not proposing such a waste of assets, anyone who *seriously* does intend such a thing should be taken out back and shot for the benefit of all mankind IMHO.

As with all launch vehicles, the costs improve dramatically as you increase the flight rate between 1 and 10 flights per year.   Beyond 10 or-so flights per year, the curve flattens out a lot and it takes considerably more flights to see a significant cost difference.



Ares has the problem that together Ares-I and Ares-V replicate the entire Shuttle cost structure all over again - about $4.3bn per year.   Even for this you only get a few flights out of it.   You get 4 Ares-I's and 4 Ares-V's supporting just 6 yearly missions - 2 to ISS, 2 Crew Lunar and 2 Lunar Cargo.   Thus the costs for each Ares launcher - at a flight rate of just 4 per year - are just not getting amortized very well.   If you can somehow double the flight rate you'll be a lot closer, but to do that you'll have to spend about $5.5bn per year - a figure I contend is NOT going to be sustainable.


The key problem to the EELV solution is the sheer number of flights necessary.   Yes, each flight costs less than a Jupiter.   And yes, the fixed costs are only 56% the cost of Jupiter (34% of Ares).   But when you need 7 or 10 flights to do the same thing, the total mission cost goes up a by an order of magnitude.

To replicate the same Ares baseline missions you will need 2 EELV Heavies for ISS, 14 EELV Heavies for the Crew Lunar missions and another 12 EELV Heavies for Lunar Cargo missions.  
This is a total of 28 EELV Heavies to do the same job as 8 Ares or 8 Jupiters.

Ignoring for a second the issue that we only have existing facilities to manufacture 13 Atlas or Delta Heavies per year, the cost for each Heavy at these flight rates only drops to ~$175m each.   So *each* of the Lunar Crew missions are going to cost you a total of $1,225m in launch vehicles every time you go.

The 28 launchers you need to replicate Ares are going to cost you $4.9bn right there - $0.6bn more than Ares and $1.8bn more than Jupiter.   And you will have absolutely no money nor manufacturing capability to build more even if you wanted to.   EELV's will therefore limit you to never more than a handful of missions per year.




To match Ares' baseline flights, Jupiter can do the same missions for about $3.1bn - about $1.2bn less, but by using the same vehicle for all of them we're also flying 8 units per year and pretty-much hit the sweet spot of the cost curve, so additional flights are realistically economical.   To add an extra Jupiter-232 launch to this baseline manifest at this flight rate costs only about $180m.   That's awesome value for launching 100mT of payload - any way you cut it and a pair of J-232's for a full Lunar Crew mission costs only $360m - 29% the cost of the EELV and about 30% the cost of the baseline Ares.

Essentially, this means that for the same $4.3bn you were going to spend flying the same 6 Ares baseline missions, with Jupiter you can still fly the same 2 ISS and 2 Lunar Cargo missions, but can now afford to fly a total of 7 Lunar Crew missions - instead of just 2.

At that point you also amortize the even more expensive LSAM costs across a larger base of units too - making each one far more cost effective also.

I know which option I prefer.




Sorry for taking the thread off-topic, but I just don't like Jupiter-232 being lumped together with Ares-V just because they "look" somewhat similar.   Although performance of Jupiter-232 is about 85% of Ares-V, the costing structures are radically different because of DIRECT being a 1-vehicle solution, and ESAS being a 2-vehicle solution - and that critically important difference can easily be forgotten.

I now return you to your previous discussions.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/25/2008 05:55 am
The two mission types the propellant depot does not help with are trips to the ISS and putting satellites into LEO.  So any Jupiters going to the depot will be on top of those flights.

A good high level design for the depot will work with either rocket type chosen for heavy lift, it just needs tanks able to hold 3 payloads consisting of only fuel.

Mixed rocket type missions are also possible, a possible mixture is to use the heavy lift to lift say the moon base buildings to LEO and the EELV/COTS to lift the fuel.  Important if the number of Jupiters is limited by cost or manufacturing ability or more than one nation is involved.

The 71 mT lift needed to put 22 mT on the Moon's surface using a SEP ferry provides some interesting possibilities for the depot.  This is close to the enhanced lift of the J-120 and can be reached using a J-120 plus an EELV.

Five J-232 plus a depot and SEP ferries can put 154 metric tons of cargo on the Moon (plus lander mass).  The rockets do not need to be launched in the same month.
22 mT * (5 * 100) / 71 = 154 mT
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/25/2008 06:24 am
Purely for reference, the limitations on Jupiter are 21 Core's per year.   Similar Upper Stages.   Current ATK facilities could process up to 80 SRB segments with no changes.   More can be handled with some minor-to-moderate facility alterations in Utah.

KSC facilities are limited by the number of VAB High Bays and the number of MLP's.   Each High Bay would be used for ~6 weeks to stack vehicles.   MLP's an extra 2 weeks thru to launch.

Currently there are two High Bays converted for Shuttle (mostly compatible with Jupiter-120) and two more High Bays not yet converted, but which can be converted for about the cost of one launch.   And there are three MLP's which can be cycled.

Essentially, current facilities (modified to suit) are going to be sufficient to handle 12 Jupiter-232 launches per year which is our baseline number for supporting 6 Lunar missions per year.   Convert one extra High Bay and you can achieve flight rates up to 18 launches per year.   I don't see the budget allowing much more than that.


But getting international partnerships via the Propellant Depot would mean all 18 of those launches out of the US could be carrying spacecraft and performing missions rather than half of them carrying propellant.

At that point US commercial launchers can compete on the world stage for the business of nations wishing to fly, but who do not possess their own space programs.   There are a multitude of European countries, Australia, Canada, South American nations, even some African and Middle Eastern countries could buy sufficient propellant flights in order to secure seats for their citizens.   Not to mention perhaps also any industrial interests who wish to conduct research on the moon.   Corporate money is just as good as foreign governments IMHO.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/25/2008 10:51 am
kraisee;

Have you tried to evaluate how many launches per year will international partners have to do to fuel the depot? How much it will cost them? What they will want in return?
Title: Re: Propellant Depots - General Discussion
Post by: DonEsteban on 03/25/2008 12:30 pm
Hm, to summarize some arguments in favor of propellant depots, which are often forgotten by their opponents:

1) (The main one) Flexibility
    a) you can launch an empty stage and refuel, making possible missions not previously
        possible with single launch
         - this means much less pressure to develop heavy (and costly - R&D) lifter
         - for any Mars missions, you will need this anyway
     b) less operational risks
         - OK, you say that with PD it is not single launch, but there are plenty of refueling launches
         - however, you are launching your empty stage when the fuel is already in the depot, not
           launching several heavy lifters withing short time period and having a  problem if any of
           them failed. The PD works as a buffer against any failures of propellant lifters.
         - (possibly multiple) docking withing limited time window is riskier then berthing at the PD
     c) you might choose LH2 for your TLI stage instead of methane/kerosene/some other
          storable propellant, as the depot can afford the heavy insulation/active refrigeration that
          would be weight-prohibitive on a multiple-dockings architecture

2) Long-term cost savings
    a) a rocket launch carrying only fuel does not need to be insured for loss of cargo
    b) fuel is a perfect cargo for test launches - if your test launch works, you get nicely paid for
        the fuel, if not, well, at least no customer is angry at you for destroying their payload
         - it makes sense to have multiple test (fuel) launches, verifying/tuning  your launcher and
            bringing the insurance costs down for your customers once they decide to trust you with
            their payload
          - or you can keep your costs really down and live with rather pathetic reliability
    c) a guaranteed fuel market will be a huge help for start-ups trying new ideas for reducing the
        launch costs
          - no need for artificial prices, support for everybody, not only the first one, but supports
             those whose vehicles actually work in reality, not the one-off stunts
         
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/25/2008 12:55 pm
Don;
There is an additional benefit: REAL competition based on price.

All the current cost estimates are based on existing, really expensive rockets. Once this technology is in place, it will likely be serviced for propellant delivery by really cheap, really dumb rockets that can be mass produced by the hundreds if needed. The payload is cheap and expendable. All the tanker has to do is get “close” to the depot, and the guidance software on the depot will take over and “fly” the tanker to a berthing dock.

Boeing and LM will have to compete with people who are flying extremely low cost, massed produced rockets. Fuel prices “at the pump” will not be anywhere near the high estimates now floating around because they are based on existing, very expensive rockets which will not be used. Atlas and Delta launch vehicles may very well be among the initial service vehicles, but that won’t last. I expect to see lots of Musk-type attempts, from all over the world. Boeing and LM will have to get into the real cheap launcher business if they want to stay in the game.

I really like the Atlas and Delta rockets, I really do, but there is simply no need to fly real expensive rockets to deliver a real cheap payload. There are lots and lots of entrepreneurs who will see that and will understand the opportunity, and with a real shot at a good ROI, will be lining up to get cheap delivery rockets from other entrepreneurs that will willing to supply them. Commercial space will be underway!
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/25/2008 01:03 pm
Quote
Eerie - 25/3/2008  7:51 AM

kraisee;

Have you tried to evaluate how many launches per year will international partners have to do to fuel the depot? How much it will cost them? What they will want in return?

Well, if a lunar launch was prepared to pay for fuel at a rate equivalent to the ~$4500/kg of a Jupiter 232, then you get 100,000 kg x 4500/kg = $450 million and that would buy X number of seats on a lunar mission. That's where the politics comes in. If the costs of a crew & cargo launch cost 3-4 billion, then paying for a fuel load would possibly buy you one out of the 4 seats. A true pro rated split doesn't work out that way, but the US wants to keep the actual highest tech to themselves and would probably be willing to trade a full share of a seat for that privilige.

If NASA was willing to pay more for fuel on orbit, then the mathmatical ratio of a seat it would buy would increase thus making it even more palatable for NASA to trade a full seat for a fuel load.

To repeate something I wrote earlier in the thread:

"One thing that we haven't touched on is the use of the truly low cost launcher to pitch fuel at the depot.

We've been talking Atlas, Jupiter, Delta as if this design paradigm is the only way.

If there was a market for fuel in orbit, I can see a smart group looking at the whole launcher business & thinking "there has to be a better way." Maybe there is. It's been mentioned elsewhere before, but I'm going to do it again here. Modern launchers have grown up in the realm of really expensive payloads and the need for ultimate reliability to prevent these payloads, be they breathing or not, from being spread over a greater part of the earth's surface. If you are launching fuel and nothing but fuel, do you really care if you pitch some of it in the ocean if the launcher costs are cheap? I mean really cheap. No, cheaper than that. I'm talking cheap as dirt. So cheap that you can afford to lose one in 20 and still sell fuel at a profit.

Think a slightly modified V2 with commercial grade electronincs, a GPS based nav system, orbital control from the ground, pressure fed engines and a 2 tonnes of fuel to orbit payload. The Germans managed to launch roughly 2500 V2s in 8-9 months with about a 60% success rate in the middle of losing a war. If you had a stable economy and business behind you and were tooled up to make 100 per year & launch them from a TEL with a ground crew of 100 (like a V2 launch battery) how cheap could you really make them if you were willing to lose 1 in 20? Launch 100, lose 5, get 190 mT of go juice to orbit per year.

If a nameless 100mT launcher is estimated at about $4500/kg in orbit, then I have to be able to launch a 2 tonne payload for something like $8.55 million, including launcher, development ammortisation and profit and assuming a loss rate of 1 in 20.

Anyone want to design the "Cessna 172 of space" around those numbers? It's really tight, in fact, obscenely tight in aerospace terms. But might it be able to be done?

If you are buying propellant at $7500/kg you get to play with $14.25 million per launch.

Anyone? Anyone? Beuler? Anyone? "



So, at the moment it appears to be very difficult to actually get fuel to orbit this cheaply except as the launchers get larger. However, as was mentioned above, without the need for insurance and with a willingness to accept normally horrendous loss rates in order to minimise costs, it could be possible to build a refueling fleet of really simple and small launchers. To extend my numbers from above, at $4500/kg a 5 tonne payload would allow you ~$21M per launch and at $7500/kg this increases to ~$35.5M. Mmmmm, those numbers are looking much more "doable".

Let's see, 100mt/5 = 20 launches per full fill. 4 lunar mission per year = 80 launches per year. Oooo, I see economies of scale starting to really kick in here. 6 lunar missions per year = 120 fuel launches per year, 10.5 per month, if you allow 1 in 20 to fail.

Set up a production line, a true production line and start churing out fuel transporters the way Convair turned out Atlases in the mid 50's. Heck, maybe it makes sense to update & uprate the Atlas design and use that? Welded balloon tanks, 1.5 stage design, really simple Centaur based upper stage. Could work...

It would be really interesting to see what you could do on that basis. An Atlas built to "round of ammunition" quality standards as opposed to man-rated standards. I wonder what the USAF was paying for Atlas ICBMs (less warhead & silo) in 2007 dollars?

Paul
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/25/2008 01:29 pm
Paul, I think you and I have been reading the same playbook  :)
It's really, really dumb to fly expensive rockets to deliver cheap payload.
There are going to be some smart people who will see that and run off to find a venture capitalist as fast as they can.

Oh - and if ESA gets into the lunar show by using the depot (see ESA manned thread), what's that do to everything?
I LOVE it!
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/25/2008 02:10 pm
Chuck, Paul,
While I agree that large demand for mass in orbit will encourage people to look at different approaches, I'm personally biased to think that the result is going to be high-flight rate, small RLVs, not mass-produced boosters.  I started out thinking the mass produced ELVs would be the ticket, seeing as how my undergraduate training was as a manufacturing engineer.  But the more I got into things, the more I've been convinced that reusability is going to be the key to getting costs way down.  There's lots of ideas for how to get there ("Airlaunched SSTO", Airlaunched TSTO with glideforward, pop-up TSTO, glideback TSTO, boostback TSTO), and probably more than one of them are totally workable.  The reason why nobody has even tried is that the market environment is such that the amount of money available for orbital RLV R&D at the moment is practically non-existent.

So, even if Ross's numbers for EELVs were accurate (which I still contest), what you would likely see is that within short order of once you started priming the pump at that higher price, you'd see truly lower cost options start coming to market.  Sure your first year or two might theoretically be more expensive than flying on DIRECT (but since you wouldn't have to spend all the time and money on DIRECT, you'd probably beat a DIRECT based lunar architecture to market by at least a year or two or three), but by the time DIRECT would be flying at all, you're likely going to see several other options starting to appear.  First, you're going to see a large use of existing foreign low-cost boosters in order to get some of the propellant at a lower price.  Second, you're going to see one or two or three RLV groups trying to service the market.  Third, you're going to see low-cost ELVs like SpaceX, AirLaunch LLC, Microcosm, and SSLoral have been pursuing start coming more onto the market.  Fourth, if the flight rates are that high, ULA has some plans that would allow them to drop their marginal flight costs even further (Last I heard, there might be some interesting stuff out at this year's SPACE 2008 conference).

Assuming that there will be *zero* improvement in the fundamental marginal costs for your competition over a 10-15 year timeframe in spite of increasing the demand by orders of magnitude is unrealistic, IMO.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/25/2008 02:44 pm
Quote
clongton - 25/3/2008  4:29 PM
Oh - and if ESA gets into the lunar show by using the depot (see ESA manned thread), what's that do to everything?
ESA's lunar show is far from certain, but if Europe decides to develop something it will probably all based around ATV and Ariane 5 (no money or interest in big rockets in Europe). Depot would fit really nicely in that combination since it would reduce complexity.

Depot doesn’t fit into NASA plan since it increases complexity. If NASA can launch everything on one or two rockets, why it would want to increase risks by doing more dockings? Far more important thing for NASA then the money is politics. Money is (free) budget money and is not important, but a string of failures (increase in complexity) could lead to a loss of political support. And since NASA knows that the moon mission would depend solely on political support, that means that Depot is undesirable.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/25/2008 03:47 pm
Quote
jongoff - 25/3/2008  11:10 AM

Chuck, Paul,
While I agree that large demand for mass in orbit will encourage people to look at different approaches, I'm personally biased to think that the result is going to be high-flight rate, small RLVs, not mass-produced boosters.
In the beginning, I think that cheap expendables will likely win out for two reasons:
First, they are a known entity. RLVs, not so much.
Second, and I think more critical in the beginning, they are fundamentally much simpler. If you don't have to worry about the "coming down" part of the mission, it has to be a lot easier than a vehicle that has to do both the "going up" and the "coming down" safely.

Once you have a simple tin can booster that's making money, then someone may come along with an even cheaper, yet more complex RLV and make more money, yet that is the way of all businesses, no? I don't have a problem with that, that's the free market, after all.

And, for a depot, I really like the idea of a tug that brings the fuel bowser (I love that British term) up to the Depot. It allows the bowser to be really, really stupid as all the rendevous smarts plus the orbital change muscle stays on the tug and you neither have to boost it nor pay for it more than once. In fact, the cost of the depot & tugs would be such that I would see such a company boosting their infrastructure on someone else's really reliable rockets & concentrating on running the gas station & making cheap bowsers to throw at it.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/25/2008 04:54 pm
Quote
tankmodeler - 25/3/2008  12:47 PM

Quote
jongoff - 25/3/2008  11:10 AM

Chuck, Paul,
While I agree that large demand for mass in orbit will encourage people to look at different approaches, I'm personally biased to think that the result is going to be high-flight rate, small RLVs, not mass-produced boosters.
In the beginning, I think that cheap expendables will likely win out for two reasons:
First, they are a known entity. RLVs, not so much.
Second, and I think more critical in the beginning, they are fundamentally much simpler. If you don't have to worry about the "coming down" part of the mission, it has to be a lot easier than a vehicle that has to do both the "going up" and the "coming down" safely.

Once you have a simple tin can booster that's making money, then someone may come along with an even cheaper, yet more complex RLV and make more money, yet that is the way of all businesses, no? I don't have a problem with that, that's the free market, after all.

And, for a depot, I really like the idea of a tug that brings the fuel bowser (I love that British term) up to the Depot. It allows the bowser to be really, really stupid as all the rendevous smarts plus the orbital change muscle stays on the tug and you neither have to boost it nor pay for it more than once. In fact, the cost of the depot & tugs would be such that I would see such a company boosting their infrastructure on someone else's really reliable rockets & concentrating on running the gas station & making cheap bowsers to throw at it.

Paul
Well said Paul. I have no doubt that we will see, as Jon has suggested, cheap RLVs, but I agree with you that they will come *after* the market is established and functioning - profitably. In fact, I would be suprised if we *didn't* see them, but they will "take over" the market, not "establish" the market. That will be done by the cheap, disposable launcher.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/25/2008 05:43 pm
Quote
Eerie - 25/3/2008  7:51 AM

kraisee;

Have you tried to evaluate how many launches per year will international partners have to do to fuel the depot? How much it will cost them? What they will want in return?

The way we see it is that one "seat" will require about 50mT of propellant to be delivered by that partner.

That could be done in 3 Proton flights by the RSA or 3 Ariane-V flights by ESA.   The Japanese H-2A would enable their program to do such a delivery in about four flights.   China could do that too in about 4 flights with current boosters, but the new CZ-5 series of boosters will be able to do it in just two.

There are quite a few other countries around the world who could also provide launch services, too many to list comprehensively, and many of whom are quite low-cost.   By the time this program is ready, there could be a wealth of nations ready to "get stuck in".

Nations without space programs would simply buy launch services from another spacefaring nation in a globally competitive market.   The US can compete for additional business just like anyone else.   The market could be as large as 400-800mT per year so there's plenty of business to chase.

In return for this contribution, NASA puts one of that country's citizens through the full Astronaut Training program.   While they won't become a US Astronaut (that requires citizenship), they will be fully trained (think Mission Specialist rather than Payload Specialist) and will be an integral member of the 4-person team on the Lunar surface.   They won't be a mere "passenger".

Along with the astronaut, there should also be a payload mass allocation for that astronaut's nation to utilize any way they wish (just as long as it doesn't expose the crew to unnecessary risk) and that astronaut will be allocated sufficient time in the mission schedule to perform the tasks required by that payload also - with or without the assistance of other crew as required by the payload.   Initially flights would be 7-day sortie missions, but if/when full-time habitation becomes established on the lunar surface, that astronaut will be staying for a regular 6-month expedition and the scientific package can then be designed to be a long-duration one too.

A similar arrangement could also be made for Cargo-only flights allowing landing of much larger experiments by any nations who partner - with or without a national astronaut to follow later.

As part of the package, I would encourage a permanent site be planned near the outpost - just like in Antarctica - where each visiting nation gets to bring an identically-sized flag and plant it in the Lunar regolith during a televised ceremony so that as the number of flags increases they begin to form a large circle displaying all the other partner nations as a very important declaration of united cooperation and inclusion for all the nations involved.

As with all missions to ISS, the scientific results of all the experiments are always to be shared with all partners.

At least, that's how we (DIRECT) foresee such a partnership working in our architecture.   I think that would be acceptable to everyone involved.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 03/25/2008 06:19 pm
Well, NASA has decided it won't be a customer and the other agencies don't have enough funding to make it either. So no real hope for propellant depots working as an incentive to improve launch vehicles until either
a) some new huge customer appears from the woodwork or then
b) Ares / Jupiter et al are scrapped.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/25/2008 06:29 pm
Quote
meiza - 25/3/2008  3:19 PM

Well, NASA has decided it won't be a customer and the other agencies don't have enough funding to make it either. So no real hope for propellant depots working as an incentive to improve launch vehicles until either
a) some new huge customer appears from the woodwork or then
b) Ares / Jupiter et al are scrapped.
NASA did not say it would not use a depot. It said it had no plans to include one in the current architecture. ESAS would not build the depot, but DIRECTwould.

Without federal funding, I don't see a Propellant Depot becoming reality for a very, very long time. You should hope that Jupiter gets selected in lieu of Ares, because a depot is part of that architecture.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/25/2008 06:42 pm
DIRECT's first ten missions would not use the Propellant Depot architecture.

But we get through those first ten missions before the end of 2020.   By then we would want the PD in place and ready to use.   So that from 2020 and around Landing #11 or #12 we can expand the architecture by about 20-25% into a Phase-II EOR-LOR architecture enhanced by PD supplies.   This would be the point where partner nations could begin getting really involved although the partnerships need to be established at least 36 months in advance so that the crews can be trained and the partner's delivery systems can be developed to agreeable standards.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/25/2008 07:12 pm
Meiza,
Quote
Well, NASA has decided it won't be a customer and the other agencies don't have enough funding to make it either. So no real hope for propellant depots working as an incentive to improve launch vehicles until either
a) some new huge customer appears from the woodwork or then
b) Ares / Jupiter et al are scrapped.

While I agree that NASA isn't likely going to be a customer of propellant depots (unless it is dragged kicking and screaming), I have no plans of throwing in the towel.  There are potential smaller initial markets for propellant depots that can get the ball rolling.  The key is keeping costs low enough, and finding enough early revenue to last long enough for the market (and eventually NASA and other government agencies) to adapt.  It's a challenge, but to me that's a good thing.  They call them "barriers to entry".  :-)

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/25/2008 07:15 pm
Chuck,
Quote
Without federal funding, I don't see a Propellant Depot becoming reality for a very, very long time.

I think you'll be surprised.  Admittedly the current economic slump is going to slow a lot of things down, but I think there's a real chance that there will be at least a subscale propellant depot on-orbit before there's a manned Orion on orbit (and that's assuming that Orion does ever fly).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/25/2008 07:16 pm
Quote
jongoff - 25/3/2008  4:12 PM

Meiza,
Quote
Well, NASA has decided it won't be a customer and the other agencies don't have enough funding to make it either. So no real hope for propellant depots working as an incentive to improve launch vehicles until either
a) some new huge customer appears from the woodwork or then
b) Ares / Jupiter et al are scrapped.

While I agree that NASA isn't likely going to be a customer of propellant depots (unless it is dragged kicking and screaming), I have no plans of throwing in the towel.  There are potential smaller initial markets for propellant depots that can get the ball rolling.  The key is keeping costs low enough, and finding enough early revenue to last long enough for the market (and eventually NASA and other government agencies) to adapt.  It's a challenge, but to me that's a good thing.  They call them "barriers to entry".  :-)

~Jon
I really don't see a Propellant Depot without Federal (NASA) dollars. There is no one else with pockets deep enough to develop and field the technology. You need federal dollars to get the depot underway.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/25/2008 07:18 pm
Quote
clongton - 25/3/2008  4:16 PM

Quote
jongoff - 25/3/2008  4:12 PM

Meiza,
Quote
Well, NASA has decided it won't be a customer and the other agencies don't have enough funding to make it either. So no real hope for propellant depots working as an incentive to improve launch vehicles until either
a) some new huge customer appears from the woodwork or then
b) Ares / Jupiter et al are scrapped.

While I agree that NASA isn't likely going to be a customer of propellant depots (unless it is dragged kicking and screaming), I have no plans of throwing in the towel.  There are potential smaller initial markets for propellant depots that can get the ball rolling.  The key is keeping costs low enough, and finding enough early revenue to last long enough for the market (and eventually NASA and other government agencies) to adapt.  It's a challenge, but to me that's a good thing.  They call them "barriers to entry".  :-)

~Jon
I really don't see a Propellant Depot without Federal (NASA) dollars. There is no one else with pockets deep enough to develop and field the technology. You need federal dollars to get the depot underway.
Yes, I would be suprised; pleasantly suprised, but suprised none the less.
It will take deep pockets. Unless there's a SkunkWorks effort underway behind the veil?
Title: Re: Propellant Depots - General Discussion
Post by: tnphysics on 03/25/2008 08:35 pm
Doubt it. I can see why DoD would want one (refuel satellites), but I can't see why they would want keep it secret, unless they don't want another country to get access to the technology.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/25/2008 10:28 pm
Chuck,
Quote
I really don't see a Propellant Depot without Federal (NASA) dollars. There is no one else with pockets deep enough to develop and field the technology. You need federal dollars to get the depot underway.

I should've been a little more clear.  There currently are some federal dollars that are going towards depot-related technologies.  Just not *explicitly* so.  Things like SBIR/STTR grants, and other technology demonstrator programs.  Even without NASA explicitly funding a propellant depot development and operations program, there are still ways it can and could help fund the risk reduction portion of things.

The other big thing worth mentioning is that a lot of the question of whether you need large amounts of federal money for a propellant depot revolve around how you actually go about doing the depot.  A full space-station sized depot with all the bells and whistles is likely going to cost Billions.  There may be some ways (and I think I've found at least one) to get an initial operating capability for far less than that.  I could be wrong, I might not ever get the money to find out if I'm wrong, but we'll see.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/26/2008 01:45 am
Using EELV/COTS and a depot launches can 3 payloads of say 10 mT each be delivered to the Moon's surface for less cost than just launching them on big rockets?

Items to be launched = depot, transfer fuel * n, lander fuel * m, cargo * 3, landers * 3

Depending on the items mass and the mixture of LV various items may share the same launch.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/26/2008 02:16 am
Mass to LLO bears a linear relationship to IMLEO.

Mass to the surface bears a linear relationship to mass in LLO - always excepting the CEV mass remains as a constant.

Given the CEV mass doesn't change, mass to IMLEO is therefore closely related to final mass to the surface.

To get the CxP target of 25,300mT of landed mass, plus 20mT of CEV mass circling the moon, your IMLEO will always be pretty similar no matter what launchers you use.

Right now, NASA is pushing for an architecture based around ~180mT IMLEO.   In reality this does not close correctly for the missions they wish to accomplish though.   You really need to launch about 210mT to LEO (LSAM, CEV, EDS, Propellant and ASE) to get this to close properly and enable the full requirement of 4 crew, 7 days, Global Access and Anytime Return capabilities.


The only way to reduce that IMLEO would be to scale-back the size and scope of the program.   You could go back about as far as 130mT IMLEO minimum - but that would only enable replicating the capabilities we had back in 1969 - 2 crew, 3 days max, Lunar equatorial sites only.


3 EELV Heavies can put about 75mT IMLEO up.   It wouldn't enable a mission even the size of Apollo.


Work out the total mass needed (210mT).
Work out how many launches you need to accomplish it with each architecture (Ares 1.5: Can't close yet with 1+1 different launches, DIRECT: 2 near-identical launches, EELV: 8-9 near-identical launches).
Work out the total cost for those launches (Fixed costs per year plus all the flight units).   Compare the results and you will end up with a chart that looks fairly similar to the one I put up earlier.
Only once you have done this does it become pretty simple to compare the lines and tell which is better value for the expected budget you think you will actually get.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/26/2008 03:25 am
Quote
clongton - 25/3/2008  9:29 AM

Paul, I think you and I have been reading the same playbook  :)
It's really, really dumb to fly expensive rockets to deliver cheap payload.
There are going to be some smart people who will see that and run off to find a venture capitalist as fast as they can.

What would an fuel slogging RLV bring back down? An empty fuel tank? Heat shield tiles? Landing gear? Engines?

How often can an RLV's rocket engines be re-used before they are trashed?

(At the NSS Washington lobbying event I was chatting with a fellow from Zero Gravity. He said that the 727 airframes were amazingly inexpensive but the engines wore out fairly rapidly flying parabolas and that fuel costs and insurance were high. Even the airframes wore out but were easily replaced from the "bone yard" and used 727 airframes were cheap. It was the engine maintenance that was expensive.)

A disposable rocket doesn't need to lift heat shields or landing gear in the first place (more fuel instead!) and if the fuel tanks are plug-n-play rather than propellant transfer from tank to tank no one will be throwing away the tanks, either.

A disposable rocket carrying low value fuel does not need insurance (other than liability); an RLV operators' bank will require the RLV to  be insured.

I think a good solution would be to loft Centaur stages, fully fueled tanked mated with NEW engines and stockpile them at the depot. (Or use newer better engines than the RL-10 in that Centaur) Then mate one of stockpiled engine modules with your capsule or space probe and light it up and go on your way. (Maybe use an RLV for crew and high value cargo)

Also, re-used fuel tanks will need regular preventative maintenance. Recall how maintenance intensive passenger airliners are.  

Also, built in bulk, RL-10s, RL-60s and RS-68s will be far cheaper than if built in lower numbers. Building two MER rovers cost about 125% of the cost of building one (as I recall). Building three   might have been 135% of one.

RLVs will require far fewer engines meaning a higher per unit cost PLUS the labor cost of refurbishing and inspecting those engines after every flight.

Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/26/2008 03:26 am
Jon Goff -

With an RLV fuel tanker, what would you predict the ratio to be between total mass at lift off and net payload (fuel) delivered in LEO?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/26/2008 03:51 am
Quote
A_M_Swallow - 26/3/2008  2:45 AM

Using EELV/COTS and a depot launches can 3 payloads of say 10 mT each be delivered to the Moon's surface for less cost than just launching them on big rockets?

Items to be launched = depot, transfer fuel * n, lander fuel * m, cargo * 3, landers * 3

Depending on the items mass and the mixture of LV various items may share the same launch.

These reconnaissance missions may occur whilst the J-232, Orion, EDS and LSAM are being developed.

Assumptions
These are cargo only mission so a CEV is not needed and there is no ascent stage.
(I will leave the manned missions to the Jupiters.)
Cost of the fuel, developing the landers, lunar equipment and depot excluded.

Assume that the Depot is about 20 mT so launch using an Atlas 551 costs $191 million

All cargoes split into 10 mT chunks.
Launch everything else in Falcon 9 which are $35 million plus extras, say $50 million
For a payload of 10 mT that is $50,000,000 / 10,000 kg = $5,000/kg

Assume that the lander has a mass of 5 mT and also acts as the lunar transfer vehicle
Delta-v LEO to lunar surface is 5.93 km/s
ISP of RL-20-2 using LOX+LH2 is 462

m0 = (10 + 5) * exp(5930 /(462 * 9.81)) = 55.5 mT
Mass of fuel = 55.5 - (10 + 5) = 40.5 mT

For 3 mission 3 * 40.5 = 121.5 mT of propellant is needed.
121.5 / 10 = 12 and a bit launches (1.5 mT)

3 * 5 landers = 15 mT
15 / 10 = 1.5 launches

The third lander can be lifted with the 1.5 mT of propellant in its fuel tanks.

3 * 10 mT cargo = 30 mT
30 / 10 = 3 launches (just to be consistent)

So 12 + 1 + 1 + 3 = 17 Falcon 9 needed
17 * $50 million = $850 million

Total launch cost = $191 m + $850 m = $1,041 million to land 30 mT of cargo on the Moon + landers

Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/26/2008 01:05 pm
Quote
Bill White - 26/3/2008  12:25 AM
What would an fuel slogging RLV bring back down? An empty fuel tank? Heat shield tiles? Landing gear? Engines?
Plus the underlying structure, the docking & landing avionics, the docking mechanism and the RCC system.

Quote
How often can an RLV's rocket engines be re-used before they are trashed?
You would design it from the start to go quite some time before replacement or serious overhaul. You'd have to ootherwise you end up like the shuttle, virtually overhauling them each fligha and you can not afford that.

Quote
(At the NSS Washington lobbying event I was chatting with a fellow from Zero Gravity. He said that the 727 airframes were amazingly inexpensive but the engines wore out fairly rapidly flying parabolas and that fuel costs and insurance were high. Even the airframes wore out but were easily replaced from the "bone yard" and used 727 airframes were cheap. It was the engine maintenance that was expensive.)
Engine maintenance is always the largest ongoing expense for any aircraft operator. That's why there are so many big twin engined airliners now. The engines are actually grossly oversized for normal operation becaue of the requirement to be able to safely "go around" after a single engine failure on take-off, but that's still cheaper than maintaining four much smaller engines.

Quote
A disposable rocket doesn't need to lift heat shields or landing gear in the first place (more fuel instead!) and if the fuel tanks are plug-n-play rather than propellant transfer from tank to tank no one will be throwing away the tanks, either.
Well, maybe, but it limits the flexibility to provide fuel to whoever needs it. If I'm a GEO transfer vehicle that needs 3 tonnes and all you have is 10 tonne disposable tanks that I can buy, it doesn't do me any good. I think you need infinitely variable fuel transfer to be viable to a large segment of the potential market.

Quote
A disposable rocket carrying low value fuel does not need insurance (other than liability); an RLV operators' bank will require the RLV to  be insured.
Yep.

Quote
I think a good solution would be to loft Centaur stages, fully fueled tanked mated with NEW engines and stockpile them at the depot. (Or use newer better engines than the RL-10 in that Centaur) Then mate one of stockpiled engine modules with your capsule or space probe and light it up and go on your way. (Maybe use an RLV for crew and high value cargo)
That's still very expensive and also still limits your possible applicaitons. The Centaur will have to be rated for high value payloads and that will really drive up it's cost, plus, like the disposable tank idea above, what if I only need 700 lb of fuel for my little GEO satellite?

Quote
Also, re-used fuel tanks will need regular preventative maintenance. Recall how maintenance intensive passenger airliners are.
You design it from the start for that. Airframe maintenance isn't that big a deal. Engine maintenance is.

Quote
Also, built in bulk, RL-10s, RL-60s and RS-68s will be far cheaper than if built in lower numbers. Building two MER rovers cost about 125% of the cost of building one (as I recall). Building three   might have been 135% of one.
True, but the fundamental design is geared to high value payloads and limited uses. You'll need to provide heat & power to the docked stages while waiting for a customer as well plus the longer exposure to orbital radiation will require "interplanetary mission" levels of hardening of electronics to ensure they are still functioning after an extensive period in orbit.

Plus, it's a lot harder to manage boiloff in a bunch of smaller tanks than in one large and relatively immobile tank. Remember, if the Centaur is going to be use on a mission, you're going to have to carry any additional insulation along for the full ride.

Quote
RLVs will require far fewer engines meaning a higher per unit cost PLUS the labor cost of refurbishing and inspecting those engines after every flight.
Again, the key is to design from the start to minimise this, but, fundamentally, you're right. RLVs will have ongoing maintenance costs, lower specific payloads, higher unit costs, higher ground station costs and higher reliability requirements.

This is why I believe the dirt cheap expendables will be how a depot starts and why I'm not entirely sure that an RLV will replace expendables for a very long time as we currently don't have the technology to make any of the RLV systems cheap enough to deliver something as simple as fuel to orbit at a reasonable cost. Of course, if a market opens up for fuel delivered by expendables and someone thinks thay can make more money on an RLV, that's how these techs will be developed.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/26/2008 02:10 pm
Because of boil off issues and the inherent difficulties of storing and transferring cryogenic hydrogen I am now wondering whether kerosene and ISRU lunar LOX becomes the optimal fuels for a future cis-lunar cartage industry.

Trade low ISP for ease of handling and a more forgiving system. The apocryphal Russian pencil rather than the platinum plated space pen.

Especially at the L points and for that very desirable single stage reusable lunar lander.

Title: Re: Propellant Depots - General Discussion
Post by: AntiKev on 03/26/2008 02:45 pm

Quote
Bill White - 26/3/2008  11:10 AM  Because of boil off issues and the inherent difficulties of storing and transferring cryogenic hydrogen I am now wondering whether kerosene and ISRU lunar LOX becomes the optimal fuels for a future cis-lunar cartage industry.  Trade low ISP for ease of handling and a more forgiving system. The apocryphal Russian pencil rather than the platinum plated space pen.   Especially at the L points and for that very desirable single stage reusable lunar lander.  

I was doing a literature search a couple of weeks ago and came across a bunch of research on zero boil off technologies.  In my estimate we're probably 5 to 10 years away from commercially viable zero-boil off tankage.  Especially if it's only in orbit and we don't have to deal with the mass penalties post launch.  Tanks are relatively light, and if you launch a propellant depot with multiple launches (see the paper in On to Mars II on propellant depots) you shouldn't be as worried about mass. In this case, it seems that LH2/LOX is a reasonable solution if you're designing a depot for LEO, given that by the time a depot is in the design phase we're talking at least 5 to 10 years, meaning ZBO technologies will be available.

Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/26/2008 06:18 pm
Tankmodeler,
Quote
Plus the underlying structure, the docking & landing avionics, the docking mechanism and the RCC system.

Especially early on, RLVs make more sense if you offload the rendezvous/docking complicated bits to a tug.  The RLV would only have a communication system, it's normal flight controls, and some simple mechanical interface.  The tug would have the prox-ops avionics, a robotic arm, the active side of the berthing interface, etc.

Quote
You would design it from the start to go quite some time before replacement or serious overhaul. You'd have to ootherwise you end up like the shuttle, virtually overhauling them each fligha and you can not afford that.

Yeah, we typically go dozens of flights between serious maintenance, and XCOR is claiming 100s of flights for their hardware.

Quote
Well, maybe, but it limits the flexibility to provide fuel to whoever needs it. If I'm a GEO transfer vehicle that needs 3 tonnes and all you have is 10 tonne disposable tanks that I can buy, it doesn't do me any good. I think you need infinitely variable fuel transfer to be viable to a large segment of the potential market.

I wonder why people still bring up the idea of swapping tanks.  Propellant transfer isn't some deep black magic.  The russians have been doing it for decades, and cryo transfer only adds a couple of complications, most of which can be mitigated by settling the propellant first.  Quite frankly once those are ironed out, swapping tanks will be the more complicated, more expensive, more massive, and less reliable way of doing things.

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A disposable rocket carrying low value fuel does not need insurance (other than liability); an RLV operators' bank will require the RLV to  be insured.
Yep.

Well, it depends a lot on how the operation is done.  Most likely for the vehicle itself it will be self-insured for a while yet.  If your RLV ends up destroying itself as often as ELVs, there's no way its going to be economic to operate it.  If it is more reliable, self-insurance shouldn't be that big of a problem.

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Plus, it's a lot harder to manage boiloff in a bunch of smaller tanks than in one large and relatively immobile tank. Remember, if the Centaur is going to be use on a mission, you're going to have to carry any additional insulation along for the full ride.

Exactly.  Unless you provide Zero Boil-Off systems in all your tanks, you're going to be constantly losing propellants with no way to refill them.  Propellant transfer as opposed to tank transfer just fundamentally makes so much more sense.

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RLVs will require far fewer engines meaning a higher per unit cost PLUS the labor cost of refurbishing and inspecting those engines after every flight.

Bill, that's why you design your engine from the start for low-maintenance.  XCOR doesn't have to overhaul their engine after every flight.  It's not an inherent property of rocket engines that they can't be made reliable, it's just that that reliability has to be a higher design priority than raw performance.  And even if your engine costs more per unit, you're reusing it a bunch of times.  That's the point!  RL-10s are supposedly rated for 200 relights.  Say you need two lights per flight.  That's 100 flights in its lifetime.  You'd have to be making 100s of thousands of RL-10s before the per-unit cost per RL-10 was cheaper than the per-flight cost of reusing it 100x.  Even when you factor in the labor time per flight, you're still talking about needing to build 1000s or 10s of thousands per year before you'd get similar economics from mass production.  The numbers just don't add up.

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Again, the key is to design from the start to minimise this, but, fundamentally, you're right. RLVs will have ongoing maintenance costs, lower specific payloads, higher unit costs, higher ground station costs and higher reliability requirements.

This is why I believe the dirt cheap expendables will be how a depot starts and why I'm not entirely sure that an RLV will replace expendables for a very long time as we currently don't have the technology to make any of the RLV systems cheap enough to deliver something as simple as fuel to orbit at a reasonable cost. Of course, if a market opens up for fuel delivered by expendables and someone thinks thay can make more money on an RLV, that's how these techs will be developed.

Coming from the perspective of someone working in the RLV side of the industry, I think you're overoptimistic about the mass-produced ELV approach.  You can get cheaper than existing ELVs for sure, but it's not an easy problem either.  I still think an RLV has a fighting chance of beating low-cost ELVs to the market once there's sufficient demand to close its business case.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/26/2008 06:40 pm
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jongoff - 26/3/2008  3:18 PM

Tankmodeler,
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Plus the underlying structure, the docking & landing avionics, the docking mechanism and the RCC system.

Especially early on, RLVs make more sense if you offload the rendezvous/docking complicated bits to a tug.  The RLV would only have a communication system, it's normal flight controls, and some simple mechanical interface.  The tug would have the prox-ops avionics, a robotic arm, the active side of the berthing interface, etc.
Yes. Doing that makes the most sense for any repeatedly used system.

I really like tugs for these sorts of ops. If you are only going to lift it once, yet use it a lot of times, you can easily make a case for building in triple or even quadruple redundent systems and stupidly high margins to ensure robustness & mission reliability compared to normal space systems. Mass would not be an issue (you define it to be so at the beginning!), so you can avoid some of the expenses of the rocket industry while still getting all the smarts & durability you need for long-term orbital ops. You also design pretty much everything but the structure to be robot-interfaced ORUs to allow unmanned replacement when they eventually need to be replaced.

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Yeah, we typically go dozens of flights between serious maintenance, and XCOR is claiming 100s of flights for their hardware.
There's no fundamental reason that you can't have an engine with low multi-use operating costs, we just tend to optimise designs for things other than the cost for long-term operations.


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Coming from the perspective of someone working in the RLV side of the industry, I think you're overoptimistic about the mass-produced ELV approach.  You can get cheaper than existing ELVs for sure, but it's not an easy problem either.  I still think an RLV has a fighting chance of beating low-cost ELVs to the market once there's sufficient demand to close its business case.

I realise it wouldn't be easy. That's why I actually think you'd be wise to establish such a team with engineers with automotive experience rather than aerospace experience. Technical oversight could be by experienced space people, but program management & the detail work should be done by guys who have made a career of hitting the cost bogey each and every time.

I still think it would be easier than doing it with an RLV, but, hey, if someone wanted to hire me to help an RLV team, I'd be honestly enthusiastic about making that work, too. :)

Paul
Title: Re: Propellant Depots - General Discussion
Post by: MrTim on 03/30/2008 06:01 pm
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tankmodeler - 26/3/2008  12:40 PM
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jongoff - 26/3/2008  3:18 PM
Especially early on, RLVs make more sense if you offload the rendezvous/docking complicated bits to a tug.  The RLV would only have a communication system, it's normal flight controls, and some simple mechanical interface.  The tug would have the prox-ops avionics, a robotic arm, the active side of the berthing interface, etc.
Yes. Doing that makes the most sense for any repeatedly used system.

I really like tugs for these sorts of ops. If you are only going to lift it once, yet use it a lot of times, you can easily make a case for building in triple or even quadruple redundent systems and stupidly high margins to ensure robustness & mission reliability compared to normal space systems. Mass would not be an issue (you define it to be so at the beginning!), so you can avoid some of the expenses of the rocket industry while still getting all the smarts & durability you need for long-term orbital ops. You also design pretty much everything but the structure to be robot-interfaced ORUs to allow unmanned replacement when they eventually need to be replaced.
I like the tug idea... it gets its fuel from the depot (so operating it gets cheaper as the scheme gets more efficient).
The tug idea might actually make the ELV idea better too... it might make things more efficient to have an ELV that does not even get the payload to orbit; An absolutely minimal full-fuel-tank-with-grapple-fixture part of the upper-stage could be ejected from the rest of the upper-stage as the engine shuts down (transferring a bit of energy from the stage remnants to the tank in the process), where a tug that had slowed to match the sub-orbital arc would meet the tank and push it the rest of the way to the orbiting depot. The tug would use a bunch of fuel slowing to meet the tank's arc, and then getting the tank to orbit, but the ELV would not expend fuel lifting any upperstage hardware even to orbital speeds. Other schemes have the ELV putting a complete upperstage into orbit, but this would use the tug's non-payload hardware (engines, guidance, etc.) A slightly better tank might allow the tug to use fuel from the tank during the boost (thereby reducing the mass of the tug during its pre-rendezvous deceleration to meet the tank). The rendezvous & grapple might be tricky but nothing about it would be a mystery and the technique would improve over time. If anybody with a bunch of spare time cares to run the numbers on such a scheme, it would be interesting to see if it would save anything, what sort of tug and ELV flight paths would work best, etc. (I have not done any of the math, so I am not saying it would be worth it...just that it might be)
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/30/2008 07:28 pm
Ehhh, I'm not sure it passes a risk/benefit analysis, still, it could.

The problem with launching to a suborbital trajectory is that you have to be dead right on time to snag the cargo otherwise you lose it. Yes, you are designing to lose 1 in 20, but I think this piles up too much risk on top of the booster risks. You also risk your tug as your tug has to be  suborbital at the time of docking.

From a benefit point of view, well you do boost more fuel for a fixed booster size and, if the tug is more efficient than the booster, the cost to get the tug + booster to orbit and then to the station could be less than the cost to boost to orbit + tug to station.  I'm not sure it would pay for itself, though and even if it did, we are defining the tug as a valuable piece of cargo that we don't want to lose, so I suspect the business risk would be too high to drag up the fuel from a suborbital trajectory. Do the pick-up at the lowest orbit that can be maintained for 2-3 days to give you a chance to address any problems that may arise with the docking while never risking the tug.

Let's face it, you have 2-300 million in the tug and only 30 million in the cargo booster. Where do you think the risk equation may end up? :)

Paul
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/31/2008 01:51 am
If any trade studies are going on about depot height they could usefully include the effect on SEP ferries.  At 400 km the air resistance on the large solar panels is close to the thrust produced by the ion motors.  Consequently using electric propulsion to climb from 400 km to 800 km takes a long time.

Chemical rockets can reach both 400 km and 800 km orbits but the size of the payload may change.  400 km orbits rotate at 7.67 km/s, 800 km orbits are at 7.45 km/s.
Title: Re: Propellant Depots - General Discussion
Post by: Lampyridae on 03/31/2008 03:52 am
Going down, the tug could also drag the empty tank down into a steadily decaying orbit.

With VASIMIR, you could generate more thrust to counteract the drag, as opposed to ion motors which I think don't trade isp and thrust that well. An arcjet would probably be a better bet for low orbit thanks to its higher thrust. STP, which I am a fan of, is also good for LEO.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/31/2008 02:41 pm
Just a heads up to people, I'll be posting the presentations from our Space Access 08 propellant depots panel on my blog in the next few days.  I may even be able to get video of the session to post.  We'll see.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 03/31/2008 04:40 pm
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A_M_Swallow - 30/3/2008  8:51 PM

If any trade studies are going on about depot height they could usefully include the effect on SEP ferries.  At 400 km the air resistance on the large solar panels is close to the thrust produced by the ion motors.  Consequently using electric propulsion to climb from 400 km to 800 km takes a long time.

Chemical rockets can reach both 400 km and 800 km orbits but the size of the payload may change.  400 km orbits rotate at 7.67 km/s, 800 km orbits are at 7.45 km/s.

How about aerodynamic solar panels?
Title: Re: Propellant Depots - General Discussion
Post by: neviden on 03/31/2008 06:42 pm
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A_M_Swallow - 31/3/2008  3:51 AM
Chemical rockets can reach both 400 km and 800 km orbits but the size of the payload may change.  400 km orbits rotate at 7.67 km/s, 800 km orbits are at 7.45 km/s.
SEP could start at 400 km, but you are corect. It's much better to start at slightly higher altitude. You can't avoid the drag. You can overcome that problem with:

a) Seperate tug that would "pick up" payload from 300 km LEO, with everything needed for secure navigation and manipulation, that would do 0.3 m/s delta-v to deliver and attach that to SEP in 800 km LEO orbit.

b) Put small chemical engine on SEP do 0.3 km/s delta-v to raise orbit to 800 km before starting highly efficient (but slow) ion engine.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/01/2008 02:56 am
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jongoff - 31/3/2008  7:41 AM

Just a heads up to people, I'll be posting the presentations from our Space Access 08 propellant depots panel on my blog in the next few days.  I may even be able to get video of the session to post.  We'll see.

For anyone who cares, the presentations are here: http://selenianboondocks.blogspot.com/2008/03/space-access-2008-propellant-depot.html

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/01/2008 04:05 am
Using 4 (or 5) Falcon 9 launches how much mass would a depot permit to be landed on the Moon?
The same for Mars?

A depot in Mars orbit could supply the fuel for the return trip to Earth.  The fuel may be delivered to the depot from the Earth by SEP ferry, ISRU Moon or ISRU Mars.
Title: Re: Propellant Depots - General Discussion
Post by: MrTim on 04/01/2008 03:43 pm
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tankmodeler - 30/3/2008  12:28 PM
Ehhh, I'm not sure it passes a risk/benefit analysis, still, it could.
Neither am I, I just floated it after seeing the tug idea; Don't be so eager to squish the idea without analysis, it got me to think that there might be a way for me to support expendables supplying a depot :)

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tankmodeler - 30/3/2008  12:28 PM
The problem with launching to a suborbital trajectory is that you have to be dead right on time to snag the cargo otherwise you lose it. Yes, you are designing to lose 1 in 20, but I think this piles up too much risk on top of the booster risks. You also risk your tug as your tug has to be  suborbital at the time of docking. (snip) Let's face it, you have 2-300 million in the tug and only 30 million in the cargo booster. Where do you think the risk equation may end up? :)

Paul, I was quite aware of the risky nature of the thing. You'd only get one shot at catching each load of fuel with the tug, and if you used the risky option of having the tug use fuel from the captured payload to re-boost you'd certainly lose the tug if you missed the cargo. ALL of this is based, however, on the premise that we are good at orbital mechanics, rendezvous & docking ops, automated and/or remote control, etc. and the assumption that we will get better at it the more we do it (I'm a well-disguised optimist :) ). As for the risk to the tug, I suppose you could mitigate that by having it carry enough fuel to slow for the capture and then re-boost to orbit on its own if it misses (while still having it use fuel from the cargo object to haul the mass of that cargo should the capture succeed). One might even use this option for several years to build confidence and then transition to the riskier option later. As I indicated in the earlier post, I think a lot of analysis could be done and there are a bunch of possible variations. (possibly have the tug-mated-to-an-empty-tank push-off from the depot, retrograde to give the depot a slight push before going to a new tank, and having the tug push the empty away for a minor kick on the way down? push the empty retrograde for a minor push up after grabbing new tank? how complex should one get for a few fps?) I do not know what options would be optimal, but there seem to be folks here who (a) have the necessary skill sets to consider such things and run the numbers on them, while also (b) having the time and apparently enjoying these activities. Nobody needs to run any further with the idea, but if somebody here chooses to, then please post some results; they would be interesting and might help support the depot idea.


Title: RE: Propellant Depots - General Discussion
Post by: Norm Hartnett on 04/01/2008 06:48 pm
Well I finally got around to reading this thread and a couple of things occur to me.
1) Using any Earth based analogies is a waste of time.  
2) It should be possible to try putting some sort of model together based on current and near term spacecraft, specifically the ATV and Bigelow modules.

All currently operational fuel transfer systems are hypergolic.
Most LEO/geostationary satellite’s station keeping thrusters are hypergolic.

Would it be possible to use a Bigelow station as a test hypergolic fuel depot with an ATV acting as a tug and a stripped down ATV as a fuel cargo transfer vehicle?

 The depot would consist of a Bigelow core (whatever that is) with some station keeping and fuel transfer ability and two BA330 inflatable modules acting as fuel tanks. The tug would be very much like the currently flying ATV with the ability to refuel from the depot. The current cargo capacity would be replaced by extendable/offset rendezvous docking equipment and additional onboard fuel capacity. The stripped ATV would only carry fuel and the simplest and cheapest navigation and maneuvering capabilities. This vehicle would have the rear docking port installed.

Possible operations; Once the empty Bigelow station was assembled and the ATV tug docked to it operations would begin with the launch of the cargo ATV. The cargo ATV reaches LEO and circularizes its orbit. The Tug docks to the rear of the cargo ATV and boosts it into rendezvous orbit and handles all rendezvous and docking maneuvers. Cargo ATV transfers fuel(s) to depot. The tug undocks cargo/tug stack and returns cargo ATV to LEO where it performs its own deorbit burn. The tug returns to the depot and refuels and then goes to a parking orbit.

Customers; possible LEO orbit satellites, most of these are in high angle or polar orbits so for these a polar orbiting depot might be desirable, Geostationary orbital customers might find a GTO orbit to be best for a depot, and interplanetary customers would probably want a equatorial orbit for the depot. For testing and proof of concept the polar orbit is attractive. For the test a special purpose test vehicle could be built or the tug docking mechanism and refueling capability could be piggybacked onto an existing mission. The operation would consist of the launch of the satellite into orbit, tug rendezvous and stack rendezvous with the depot. The satellite would be fueled and place back in orbit by the ATV tug which would then return to the depot. Repeated tests perhaps with multiple participant satellites, would prove the concept that would then encourage the inclusion of refueling and docking equipment on new commercial and military satellites. It might even be possible to develop an add-on pack for existing satellites.

Is this a viable scenario?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/04/2008 03:08 pm
Hey guys,
Just as a follow-up, I added some more detail about some of the technical issues we discussed on the SA'08 panel, and some of my further thoughts: http://selenianboondocks.blogspot.com/2008/04/additional-thoughts-on-sa08-propellant.html

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/04/2008 10:59 pm
Cross reference.

Moon trips using propellent depots as airports supplied by SEP ferries are being discussed in the "Exploration Alternatives (Direct, EELV, Etc.)" thread "Earth-Moon two segment (ion[Cargo]/chemical[Crewed]) mission design".
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=12481
,
Title: Re: Propellant Depots - General Discussion
Post by: Zach on 04/05/2008 01:41 pm
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jongoff - 4/4/2008  10:08 AM

Hey guys,
Just as a follow-up, I added some more detail about some of the technical issues we discussed on the SA'08 panel, and some of my further thoughts: http://selenianboondocks.blogspot.com/2008/04/additional-thoughts-on-sa08-propellant.html

~Jon

Jon,
Thanks for hosting and sharing the propellant depot stuff from Space Access.  Some very interesting information contained there.
Title: RE: Propellant Depots - General Discussion
Post by: AresWatcher on 04/05/2008 04:48 pm
Should this be better on Advanced Concepts section, or alternatives, seen as this will not be used by Constellation?
Title: Re: Propellant Depots - General Discussion
Post by: wingod on 04/05/2008 05:21 pm
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A_M_Swallow - 30/3/2008  8:51 PM

If any trade studies are going on about depot height they could usefully include the effect on SEP ferries.  At 400 km the air resistance on the large solar panels is close to the thrust produced by the ion motors.  Consequently using electric propulsion to climb from 400 km to 800 km takes a long time.

Chemical rockets can reach both 400 km and 800 km orbits but the size of the payload may change.  400 km orbits rotate at 7.67 km/s, 800 km orbits are at 7.45 km/s.

Not for Hall Effect Thrusters.  400 km is a fine orbit to start at, although a high inclination orbit, say 51.6 degrees is superior to a 28.5 degree orbit, enough that the transit time is cut by up to 30%, depending on departure date.


Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/06/2008 03:52 am
Zach,
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Thanks for hosting and sharing the propellant depot stuff from Space Access.  Some very interesting information contained there.

You're welcome.  It was an educational experience for me as well.  Some of the most interesting ideas though came from discussions with people before and after the session.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/10/2008 11:17 am
Being a member of the AIAA, I get a daily news digest and noted that the leadoff story this morning was the USAF recommendation for on orbit refueling of satellites. I thought the story would hold some interest for those who frequent this subject and thread. For those who can't get to the Digest, here's the quote:
{begin}
USAF seeks satellite refueling capability.
Defense News (4/10, Hoffman) reports, "The U.S. Air Force should have the ability to refuel satellites instead of letting them run out of propellant and die in orbit," according to Secretary of the Air Force Michael Wynne, who was speaking at the National Space Symposium being held in Colorado. Gary Payton, the deputy undersecretary of the Air Force for space programs, noted that the "Defense Advanced Research Projects Agency's Orbital Express program tested the ability of one satellite servicing another last year in orbit," and that "two satellites involved in the mission successfully docked and transferred two propellant tanks before there was a software failure." Still, Payton pointed out, "the capability [has been] demonstrated." While current satellites have "rings and external ports [that] could potentially be used" for in-orbit refueling, Peyton "said it would be easier to design the next generation of satellites with a specific in orbit connection point if that capability was further developed."
{end}
For the rest of us, here's the link to the digest:
http://links.mkt751.com/servlet/MailView?ms=MTAzNjgxNAS2&r=MTU4OTU2ODI3MQS2&j=ODM4MjIyMDYS1&mt=2&rj=ODM4MjIyMDYS1
Title: Re: Propellant Depots - General Discussion
Post by: meiza on 04/10/2008 12:17 pm
Would the DoD accept a commercial refueling of a spy sat?
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/10/2008 12:34 pm
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meiza - 10/4/2008  8:17 AM

Would the DoD accept a commercial refueling of a spy sat?
That’s a complete unknown. I would think it is a possibility, depending on many factors. What interested me especially with this story is that they have already done it. Two satellites rendezvoused and propellant transfer was accomplished. I am assuming the propellants were hypergols. The interesting thing is that it is a technology that other parts of the government are obviously interested enough in to design, build and test on orbit. Now they say this is a technology they want to deploy. So much for NASA poo-pooing the idea.
Title: Re: Propellant Depots - General Discussion
Post by: jeff.findley on 04/10/2008 08:59 pm
The US has been very slow in developing these technologies.  These are technologies that the Russians have had for three decades.  Russian Progress resupply ships have routinely refueling Russian space stations since the late 1970's.  This was first demonstrated with the Salyut 6 space station and Progress 1 in early 1978.  This practice became routine for the Russians and was incorporated into the design of Mir and ISS.
Title: Re: Propellant Depots - General Discussion
Post by: on 04/10/2008 09:25 pm
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meiza - 10/4/2008  7:17 AM  Would the DoD accept a commercial refueling of a spy sat?
Yes - they've done similar service arrangements with commercial firms, given qualification/certification requirements.
Title: Re: Propellant Depots - General Discussion
Post by: on 04/10/2008 11:46 pm

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jeff.findley - 10/4/2008  3:59 PM  The US has been very slow in developing these technologies.  These are technologies that the Russians have had for three decades.  Russian Progress resupply ships have routinely refueling Russian space stations since the late 1970's.  This was first demonstrated with the Salyut 6 space station and Progress 1 in early 1978.  This practice became routine for the Russians and was incorporated into the design of Mir and ISS.
Actually the interest for the Russians started with their lunar program a decade before - they wanted to refuel a "EDS" using a Progress-like approach - this is where it came from.

We are not used to thinking of orbital asset reuse. Made all the more difficult by the fact that satellite applications often require specific non overlapping orbital parameters.

However, GSO sats do follow a pattern where you can make use of a depot - we just don't do such a thing. And it would be hard to change the pattern of using a large launcher to inject directly into GTO using a large second stage ISP, since there are fewer steps to "go wrong" (than using a small second stage to LEO, rendezvous with depot, refuel, LEO to GTO burn, GSO circularization burn).

Even though this has the potential to reduce LV costs to get to GSO to almost LEO costs,  any sat you'd fly there would be worth enough for larger launcher anyways, with the current market of sats. So the advantage is moot to them.

But it is the best business case for commercial use of a depot.

Title: Re: Propellant Depots - General Discussion
Post by: Danny Dot on 06/03/2008 11:10 pm
What inclination is the depot kept at?

And, would it be viable for the GPS and geosync market to use the depot?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 06/04/2008 05:58 am
What inclination is the depot kept at?

And, would it be viable for the GPS and geosync market to use the depot?

Well, in all probability, the depot*s* will be wherever there is supply and demand for them.  So, you'll eventually see ones in polar LEO, ones in mid inclination LEOs, possibly some in equatorial LEOs, and probably one or more in L1/L2 or LUNO.  Which will get built first, what propellants will it hold, what inclination, and for servicing what market?  Now thats a better question.  :-)

As for utility for geosync market?  Possibly, though without a very low cost propellant delivery source (like RLVs), its a tough nut to crack for most GEO launchers...

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/13/2008 12:39 am
FYI, I have a review on my blog of a Space 2008 paper that ULA presented on propellant depots that's worth a read if you haven't seen it already:

my review:
http://selenianboondocks.com/2008/11/ula-propellant-depot-paper/
the paper:
http://selenianboondocks.com/wp-content/uploads/2008/11/2008-7644-depot-document.pdf

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/13/2008 03:17 am
The natural clients for a propellant depot are reusable transfer vehicles.  They will need a full set of consumables:

* liquid oxygen
* liquid hydrogen or RP-1
* water for drinking
* oxygen for breathing
* helium or argon to flush the engines and pressurise tanks
* which ever propellant is chosen for the vehicle's reaction control system
* food

The Ares-1 will only just lift the Orion, there is no spare lift for 13 tonnes of hydrogen.  The same applies to the Falcon 9 and Dragon.

VASIMA thrusters can use argon as a propellant.  Unlike helium argon has a similar boiling point to oxygen.
Title: Re: Propellant Depots - General Discussion
Post by: robertross on 11/13/2008 10:54 pm
The natural clients for a propellant depot are reusable transfer vehicles.  They will need a full set of consumables:

* liquid oxygen
* liquid hydrogen or RP-1
* water for drinking
* oxygen for breathing
* helium or argon to flush the engines and pressurise tanks
* which ever propellant is chosen for the vehicle's reaction control system
* food

The Ares-1 will only just lift the Orion, there is no spare lift for 13 tonnes of hydrogen.  The same applies to the Falcon 9 and Dragon.

VASIMA thrusters can use argon as a propellant.  Unlike helium argon has a similar boiling point to oxygen.

I wonder if an electrical re-charge (boost) also fits on that list if they were cheap enough to not have fuel cells, or there is no backup power to control/start them.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/13/2008 11:15 pm
I wonder if an electrical re-charge (boost) also fits on that list if they were cheap enough to not have fuel cells, or there is no backup power to control/start them.

Are you talking about recharging the batteries of satellites and spacecraft?
Possibly by equipping the depot with solar panels too large/heavy for the a small spacecraft to push.

A standard refuelling connection may be needed, hopefully designed so that unneeded pipes can be left as empty spaces.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/17/2008 03:05 pm
Robert,
Most spacecraft have sufficiently sized solar panels to top their own batteries off in short order.  The shuttle is IIRC, pretty unusual in using fuel cells instead of solar panels.  While it's not impossible that there could be some money to be made by providing a little bit of power, most of the money is probably going to be made off of the actual fluids (as well possibly as maintenance/repair services eventually).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: robertross on 11/17/2008 04:22 pm
Robert,
Most spacecraft have sufficiently sized solar panels to top their own batteries off in short order.  The shuttle is IIRC, pretty unusual in using fuel cells instead of solar panels.  While it's not impossible that there could be some money to be made by providing a little bit of power, most of the money is probably going to be made off of the actual fluids (as well possibly as maintenance/repair services eventually).

~Jon

I was only adding that potential 'requirement' to the list. Easier to provide an electrical disconnect to the umbilical 'in case' it's needed, rather than say "I only wish we had...'. Power is everything. If the on-board batteries failed (for either spacecraft), or the solar panel failed to deploy, the APU would need some power to be controlled in the short term before being self-sufficient, not to mention other powered items. Just a contingency measure.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/17/2008 05:24 pm
Robert,
Most spacecraft have sufficiently sized solar panels to top their own batteries off in short order.  The shuttle is IIRC, pretty unusual in using fuel cells instead of solar panels.  While it's not impossible that there could be some money to be made by providing a little bit of power, most of the money is probably going to be made off of the actual fluids (as well possibly as maintenance/repair services eventually).

~Jon

I was only adding that potential 'requirement' to the list. Easier to provide an electrical disconnect to the umbilical 'in case' it's needed, rather than say "I only wish we had...'. Power is everything. If the on-board batteries failed (for either spacecraft), or the solar panel failed to deploy, the APU would need some power to be controlled in the short term before being self-sufficient, not to mention other powered items. Just a contingency measure.

Other reasons for the depot to supply electrical power include keeping the spacecraft's avionics and environmental systems going whilst:
* its batteries are being replaced.
* its solar panels are replaced or repaired.
* its solar panels are being shaded by the depot.
* its solar panels are waiting to be opened for the first time.
* its solar panels are folded back to prevent them from hitting the depot.
* its nuclear reactor is being started.

The depot's own tug, used to help spacecraft and fuel tanks dock, may not be equipped with solar panels because they are heavy and restrict the approach directions.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 11/17/2008 10:03 pm

1. its batteries are being replaced.
2.  its solar panels are replaced or repaired.
3.  its solar panels are being shaded by the depot.
4.  its solar panels are waiting to be opened for the first time.
5.   its solar panels are folded back to prevent them from hitting the depot.
6.  its nuclear reactor is being started.

7.  The depot's own tug, used to help spacecraft and fuel tanks dock, may not be equipped with solar panels because they are heavy and restrict the approach directions.

this about near term and not 50 years from now.

1 &2 No, the depot is for propellant and not hardware and is unmanned.  So no food or air for spacecraft
3.  Go to batteries.  Also sunlight for docked spacecraft would be part of the concept of operations plan
4.  no, they would already opened.  It is too long from launch to docking to survive on batteries
5.  see #3
6.  Nuke engines don't need cryo prop
7.  No tug with the depot
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/18/2008 12:58 am
this about near term and not 50 years from now.

1 &2 No, the depot is for propellant and not hardware and is unmanned.  So no food or air for spacecraft
3.  Go to batteries.  Also sunlight for docked spacecraft would be part of the concept of operations plan
4.  no, they would already opened.  It is too long from launch to docking to survive on batteries
5.  see #3
6.  Nuke engines don't need cryo prop
7.  No tug with the depot

Jim,
While I agree with many of your points (and AM's stuff is mostly silly), I do have to disagree with a few of your statements.

1. A good propellant depot will very likely have a tug.  I do agree that making sure that the tug can get the needed solar power (or has adequate battery power) for normal operations should be planned from the start.  But most of the people I know in industry working on this agree that having one or two small prox ops tugs makes the propellant depot design a *lot* easier.  And it also makes it so your tankers can be a lot closer to a tank than to a satellite (look at the cargo weight vs. the gross weight of a Progress to see what I mean by that).  Lastly, it can offload a lot of hardware from the receiving vehicle as well.  Tugs, especially if done wisely can really make propellant depots a lot easier to implement.

2. Minor nit: many concepts for vehicles with "nuclear engines" involve the use of reaction mass, and LH2 is the reaction mass of choice for most of them.  So, whether it's a NTR, or a Gas Core Nuclear Rocket, or VASIMR, you'll likely need some cryogenic fuels.....but that's pretty far out, so I'm not to worried about it.

3. Depots don't only have to be about propellant, and there may be some ways of making them a lot more useful by allowing them to be at least man-visited.  I'm not going to go into too much detail here, but there are ways that leveraging some of the work that groups like Bigelow are doing could allow for a depot that would be *much* easier and cheaper to implement than concepts like Boeing has presented in the past.

~Jon 
Title: Re: Propellant Depots - General Discussion
Post by: libs0n on 11/18/2008 06:14 pm
LEO is close by.  How about teleoperation rather than automation, or mantending?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/18/2008 08:10 pm
Libs0n,
You'd choose whichever method ends up being cheapest/most-reliable overall.  Conventional wisdom is that this would be a combination of automation/teleoperation, but I think conventional wisdom is wrong in this case.  Assuming the kinds of changes that would have to happen before there'd even be demand for a depot in the first place, I think there's a way of doing a manned depot that would be cheaper, more reliable, and easier to implement than an autonomous or teleoperated station.  But I know I'm playing the heretic on this one.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 11/19/2008 12:28 am
Libs0n,
You'd choose whichever method ends up being cheapest/most-reliable overall.  Conventional wisdom is that this would be a combination of automation/teleoperation, but I think conventional wisdom is wrong in this case.  Assuming the kinds of changes that would have to happen before there'd even be demand for a depot in the first place, I think there's a way of doing a manned depot that would be cheaper, more reliable, and easier to implement than an autonomous or teleoperated station.  But I know I'm playing the heretic on this one.

~Jon

There would be a huge amount of overhead to make it manned.  Also, wouldn't the infrequent visits not close the "business case" for the early ones to be manned. 

Man tended is an option but Orbit Express and Progress show that autonomous or teleoperated is feasible
Title: Re: Propellant Depots - General Discussion
Post by: Vacuum.Head on 11/19/2008 12:29 am
All currently operational fuel transfer systems are hypergolic.
and
* which ever propellant is chosen for the vehicle's reaction control system
A question for fellow Propellant Heads (sorry)
Thinking that to KISS, an initial Propellant Depot might _just_ store hypergolics. So.
What are your favorite Hypergol pairs, assuming that we had to agree on an international standard ;-)
Russian: Unsymmetrical DiMethyHydrazine and NitrogenTetroxide [UDMH/N204]
Europe (ATV) Mono-Methyl Hydrazine and Mixed Oxides of Nitrogen [MMH/MON].
American Aerozine 50 (UDMH:MMH 1:1) / MMH and 'pure' N2O4
Aside ASTRO (DARPA) "Hydrazine" only! Spysats use Monopropellant?
Indian UH 25 (UDMH:MMH 3:1)
IIRC Mixed oxides option is less corrosive. Aerozine 50 is more stable. Is this the answer?
Considerations of long term storage, corrosion, ease of handling and safety are naturally paramount.
And I would refer you to the Russian and European LLO station concepts. With what I assume is hypergolic based lunar architecture some 20 years from now!
PS Another fuel missing from A_M's list:  Xenon for SEP Tugs! cf RASC/OASIS
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/19/2008 04:18 am
There would be a huge amount of overhead to make it manned.  Also, wouldn't the infrequent visits not close the "business case" for the early ones to be manned. 

You're looking at it the wrong way.  I'm not suggesting taking an automated depot, and turning it into a manned station.  I'm suggesting taking a notional manned station (like what Bigelow is trying to do), and converting part of it into a propellant depot.  The difference in approach is important.  I agree that if you did a business as usual propellant depot, and tried to make it a manned station, that it would only drive up the costs.  But I think the approach I'm looking at would take the depot and make it less like a spacecraft, and more like something done for an airplane.  Still expensive, but tens to hundreds of millions expensive, not billions to tens of billions.

Quote
Man tended is an option but Orbit Express and Progress show that autonomous or teleoperated is feasible

I agree to a point, but making something that can be maintained and operated without man tending is a lot harder than making something that can be be maintained in a shirtsleeve environment.

Anyhow, that's all I want to say for now.  I'm thinking about putting together an AIAA paper on the topic for next year's SPACE 2009 conference.  If I can get the bandwidth to pull it off, I'll discuss it in more detail then.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jeff.findley on 11/19/2008 12:39 pm
I'm not sure how a man tended depot would work.  In theory, it would seem to cost the least to develop, especially if the requirements for things like life support and airlocks falls upon the visiting spacecraft.  In that case, you can do things like connecting refueling hoses and such with men in suits rather than with expensive, teleoperated, robotics.

This makes sense when doing something like refueling an EDS, but what about the refueling of the depot?  If refueling the depot requires men in suits, the operations costs could get expensive rather quickly.  I'd think at a minimum, you'd want completely automated refueling of the depot so that any launch vehicle of any size could be used to refuel the depot. 
Title: Re: Propellant Depots - General Discussion
Post by: William Barton on 11/19/2008 12:54 pm
Take a step back from the details of the discussion and consider one point: the purpose of manned spaceflight is "men in space," not science, not ISRO, not economic development. All those things flow from having humans along for the ride. Everything *could* be done with robots, but then what do you have? Robots doing robotic tasks. Back in the 1950s, everything was projected to be manned because robotics was still largely science fiction, and seemed even more far fetched than space travel itself. The point of having a man-tended fuel depot is not to send men up to tend it, but to tend it with men who are already up. Making the fuel depot part of an existing manned space facility is partly right, but also risky and unnecessry. Instead, think of an orbital habitat (a space station whose main purpose is living space for orbiting workers), and mannable space tugs (something along the lines of a Gemini or Soyuz, itself refuellable) that transports workers at need to coorbiting fuel depots (and whatever else happens to be aloft). Infrastructure is what we're really talking about, and having men aloft for any purpose, preferably lots of them, better serves the purpose of creating a space faring civilization than any number of utterly cool and sophisticated "robots in the sky."
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/19/2008 05:42 pm
The point of having a man-tended fuel depot is not to send men up to tend it, but to tend it with men who are already up.

That's exactly where I was going with the thought.

Quote
Making the fuel depot part of an existing manned space facility is partly right, but also risky and unnecessry.

I don't think that's necessarily true that it has to be risky.  You have to design it right, taking the right steps to keep fuels and oxidizers safely separated.  But I don't think it's impossible. 

But the key point here is that *if* you can find a way to safely make a depot part of an existing (commercial) manned facility, it makes a lot of sense to make a lot of the systems have manual backups, and be easily maintainable by people.  If you can't make it part of an existing system, making it man tended is a lot less desirable.

Quote
Instead, think of an orbital habitat (a space station whose main purpose is living space for orbiting workers), and mannable space tugs (something along the lines of a Gemini or Soyuz, itself refuellable) that transports workers at need to coorbiting fuel depots (and whatever else happens to be aloft).

While such an idea isn't bad, it doesn't have all the same benefits as just collocating a depot into an existing station.  One thing to think about is that for any lunar or martian expedition, your vehicle is in effect going to be a "propellant depot collocated with the crew".  Unless you're going one way, or expecting to get all of your return fuel there at the destination, you're going to be toting around a lot of fuel and oxidizer in close proximity to the passengers.  If you can't find a way of safely doing that, you probably shouldn't be going to the Moon or Mars anyway.

Quote
Infrastructure is what we're really talking about, and having men aloft for any purpose, preferably lots of them, better serves the purpose of creating a space faring civilization than any number of utterly cool and sophisticated "robots in the sky."

Well put.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 11/20/2008 07:57 am
I would prefer to have the Depot unmanned, but in the same orbit as a manned station, so it would be relatively "local".

I can't see any real disadvantages to having the crew stationed 100 miles/6-12 hours away by Orion ferry.

But I can see some real advantages to not having a crew sitting aboard Depot in case of emergencies. Something as simple as an MMOD hit could really make a bad day for any crew aboard the Depot.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/20/2008 08:22 pm
But I can see some real advantages to not having a crew sitting aboard Depot in case of emergencies. Something as simple as an MMOD hit could really make a bad day for any crew aboard the Depot.

That depends a lot on design.  As it is, a depot can easily be safer and more MMOD tolerant than the transfer stage, LSAM, or anything else.  It's a lot easier to armor a station that doesn't have to move around than a super light transfer stage.  Also, with a depot it's a lot easier to do sensible things like storing LOX and Hydrogen at opposite ends of the station.  I just don't see why some people think we can safely do a fully-fueled mars craft with people in close proximity to flightweight fully loaded propellant tanks for the better part of a year (and far beyond any hope of rescue), but are scared stiff about having people near a depot.  It's just silly.  While the trades may come out that having people at the depot might end up making sense, dismissing it out of hand is silly.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 11/20/2008 08:35 pm
Perhaps folks should consider RP-1 & LOX as the initial fuel of choice for a LEO depot.

Isn't the Russian RD-58 a proven and reliable engine with decent vacuum ISP?

Wouldn't the on orbit storage of kerosene be very substantially easier than the on orbit storage of liquid hydrogen?

Once the depot economic model is rolling (and enhanced Block D engines are routinely shoving payloads outbound from LEO) move to hydrogen / LOX depots as an upgrade.
 
= = =

The Jupiter 120's excess capacity could also ferry Kevlar & composite bladders of kerosene to LEO on every ISS mission.
Title: Re: Propellant Depots - General Discussion
Post by: William Barton on 11/20/2008 09:04 pm
But I can see some real advantages to not having a crew sitting aboard Depot in case of emergencies. Something as simple as an MMOD hit could really make a bad day for any crew aboard the Depot.

That depends a lot on design.  As it is, a depot can easily be safer and more MMOD tolerant than the transfer stage, LSAM, or anything else.  It's a lot easier to armor a station that doesn't have to move around than a super light transfer stage.  Also, with a depot it's a lot easier to do sensible things like storing LOX and Hydrogen at opposite ends of the station.  I just don't see why some people think we can safely do a fully-fueled mars craft with people in close proximity to flightweight fully loaded propellant tanks for the better part of a year (and far beyond any hope of rescue), but are scared stiff about having people near a depot.  It's just silly.  While the trades may come out that having people at the depot might end up making sense, dismissing it out of hand is silly.

~Jon

I agree with you w/r/t the safety issue, but there is a point about not putting crew at risk unnecessarily. The Mars crew is at risk for a reason (going to Mars), but the fuel depot crew shouldn't be put to the same risk unless they have a reason to be hanging around the fuel when not engaged in fuel-related work. A busy depot would need a full time crew for reasons intrinsic to their task. The main point of having a less busy depot only man tended is, a costly orbital workforce should be busy doing orbital work. If there's no reason for them to be at the depot, then they should be somewhere else doing some other work. And if a depot requires a lot of babysitting, it's probably designed wrong. When I was a kid, the guys at the gas station tended the gas station. Nowadays, the gas station operates itself and the "crew" mainly operates candy bar sales (also unnecessary, and they're really there to keep an eye on the customers).
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 11/20/2008 09:51 pm
Perhaps this is heresy but I cannot shake the idea that the Blue Rhino propane exchange model (http://www.bluerhino.com/) - Drop, Swap & Go - will be far easier to actually deploy at a lower cost than spending the money needed to learn how to pump cryogenic fuel from tank to tank in micro-gravity. Not to mention storing liquid hydrogen for any extended period on orbit.

Sure, on orbit fuel transfer may well be feasible and eventually shall be necessary but for humanity's first ever fuel depot, why not stockpile LOX tanks (perhaps topped off from time to time from a central source) and kerosene tanks and simply integrate those tanks into an outbound payload?

Pre-packaged engines could also be stockpiled to allow custom propulsion solutions for a variety of beyond LEO destinations.

Want to send a telescope to SEL-2? Deliver a pre-packaged scope to the depot where it is mated to an engine & avionics package and the fuel tanks needed to get it to SEL-2.

Space tugs? They arrive at the depot, eject their empty tanks and install filled tanks. Then, the empty tanks are fully inspected for defects at the depot before being re-filled. Swapping out the engines themselves for human tended refurbishment would be a useful feature as well. 

= = =

Back on the kerosene thing, given the very low density of LH2 compared with kerosene, an RLV Earth to LEO fuel tanker would have to be mighty "fluffy" to transport any meaningful amounts of LH2. And would the RLV be bringing an empty LH2 tank back to Earth?

Increased volume means increased surface area means increased atmospheric drag going up and greater design challenges in maintaining structural integrity of a large empty container coming down.

An RLV RP-1 tanker could carry the same mass of fuel in a very much smaller package.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/21/2008 01:28 am
Perhaps this is heresy but I cannot shake the idea that the Blue Rhino propane exchange model (http://www.bluerhino.com/) - Drop, Swap & Go - will be far easier to actually deploy at a lower cost than spending the money needed to learn how to pump cryogenic fuel from tank to tank in micro-gravity. Not to mention storing liquid hydrogen for any extended period on orbit.

Well, I don't think it's a heresy.  I just think it's wrong.  ;-)

Seriously, trying to do tank swaps in orbit with massive propellant tanks is not going to be easier than just pumping propellants.  If you have a way of storing LOX on orbit in tanks like that, you already have all the tools you need to do a regular depot.  And a regular depot is going to be lighter, simpler, more robust, and easier to develop.  I mean, it sounds like a good idea until you get into the details, but the more you look, the more you realize you aren't saving yourself any trouble.

For non-cryo fuels, there are already techniques for doing the transfer, so having pre-filled tanks doesn't do you anything other than make your life a lot more complicated.  For cryo propellants, if you can handle keeping them cool, venting them without spraying propellants out, and "topping them off", you really are already doing an honest to goodness depot anyway, so why not go with a simpler system?

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/21/2008 01:45 am
Perhaps folks should consider RP-1 & LOX as the initial fuel of choice for a LEO depot.

Isn't the Russian RD-58 a proven and reliable engine with decent vacuum ISP?

Wouldn't the on orbit storage of kerosene be very substantially easier than the on orbit storage of liquid hydrogen?

Once the depot economic model is rolling (and enhanced Block D engines are routinely shoving payloads outbound from LEO) move to hydrogen / LOX depots as an upgrade.

Kerosene isn't a bad idea if there's an actual customer for it.  Like, if SpaceX modified a Falcon upper stage for orbital refueling, or if some Russian stage like the Block D that used the RD-58 for refueling.  But otherwise, once you've figured out LOX, you've gone most of the way to figuring out LH2 when it comes to depot work.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jeff.findley on 11/21/2008 05:21 pm
Or if you really don't want to bother with LH2, there are always other gasses, like methane, which are mildly cryogenic as a liquid, which you can use for fuel.

http://science.nasa.gov/headlines/y2007/04may_methaneblast.htm
Title: Re: Propellant Depots - General Discussion
Post by: HIP2BSQRE on 11/22/2008 12:01 am
looking at the coal station like a PD I found the following information looking at US Coal ships:

USS Leonidas  displacement 4200 tons.

Warships:

USS Texas (battleship) --commissioned: 1895  Displacement 6682 tons
Iowa Class                                                 Displacement 11,000 tons


Crusier class

New Orleans--built 1898  Displacement 3400 tons
Newark                         Displacement 4500 tons

Later in the 20Century, battleships are alot larger, but coal ships are getting to be around 11,000 tons. 

In essance--the coal ships had the same displacement or were larger expect for the battleships. 1905/6 saw the Dreadnaught battleships with a displacement over 18,000 tons.  In the US Navy' white Elephant crusie around the world, most of the collers look to be smaller than the largest battleships.
Title: Re: Propellant Depots - General Discussion
Post by: HIP2BSQRE on 11/22/2008 12:07 am
Jon,

When do you expect to see a demo PD--5 years time or shorter? Given techological advances and demostrations--I expect it will happen before 2013, that most of the pieces will be there, and it will be up to someone to put the pieces together.   But even if the pieces are there, will anyone come looking for fuel?  If it is not, do you see NASA doing a COTS like contract saying I want x tons of fuel at XYZ place in 3 years, what is the price?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/23/2008 01:49 am
When do you expect to see a demo PD--5 years time or shorter? Given techological advances and demostrations--I expect it will happen before 2013, that most of the pieces will be there, and it will be up to someone to put the pieces together.   But even if the pieces are there, will anyone come looking for fuel?  If it is not, do you see NASA doing a COTS like contract saying I want x tons of fuel at XYZ place in 3 years, what is the price?

Well, bearing in mind the old joke about how it's hard to make predictions--especially about the future, my guess is no.  If there is a "demo PD" before 2013, it's probably going to be quite a bit different from the cryo propellant depots most of us have been talking about for lunar transportation.

It's totally possible, but the main problems are customers, educating customers, and money.  This recession we're sliding into is likely going to take some time to wind itself down.  And until we know what direction the new administration is going to take regarding space, all bets are off.  If NASA or the DoD decided that PD's were a critical technology and seriously pursued it, it could happen much sooner. 

IOW, I really don't have the foggiest.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 11/23/2008 08:49 am
Centaur have been planning to fly a PD Demo for a while now, as a secondary payload added to any upcoming flight.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060049150_2006251226.pdf


Pretty-much everything is based on 'off the shelf' parts so the costs are pretty low (well, compared to most rocket science anyway!).   The only thing they really need is a budget allocation to do it.   DoD has no use for it, so they won't fund it.   So Centaur have been waiting for some NASA money to trickle down.   It hasn't happened yet.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: jeff.findley on 11/24/2008 03:19 pm
Centaur have been planning to fly a PD Demo for a while now, as a secondary payload added to any upcoming flight.

...

So Centaur have been waiting for some NASA money to trickle down.   It hasn't happened yet.

It won't happen with Mike Griffin in charge.  This technology would make his Ares V obsolete.  Why go down in history as the NASA administrator who funded an orbit refueling demo when you can go down in history as the NASA administrator who one-upped von-Braun and built a huge, new HLV.  :(

Jeff
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 11/24/2008 09:29 pm
Exactly Jeff,
That seems to be the only "reason" for Ares which seems to hold any real water at all.

If all Griffin wanted was that title, he should have just man-rated an EELV to close the gap, and then put all NASA's other resources into building something like Sea Dragon.   If he had started that work back in 2005, I bet it could have been ready before Ares-V's 2019 current (hopeful) schedule.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/25/2008 03:32 am
Centaur have been planning to fly a PD Demo for a while now, as a secondary payload added to any upcoming flight.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060049150_2006251226.pdf


Pretty-much everything is based on 'off the shelf' parts so the costs are pretty low (well, compared to most rocket science anyway!).   The only thing they really need is a budget allocation to do it.   DoD has no use for it, so they won't fund it.   So Centaur have been waiting for some NASA money to trickle down.   It hasn't happened yet.

Well, I guess if you're talking propellant depot demonstrators on that scale, then yeah I think that's likely to happen sooner rather than later.  I think there's a nonzero chance that a suborbital version of that might fly even sooner.  I know that's one of the things I want to do once we have a suborbital vehicle with enough performance to make it happen.  We almost got an SBIR to work with LM and a few other groups doing just that, but alas we missed it.

I had been more thinking about a full demo system that included docking/berthing hardware as well as transfer hookups.  The CTB would be an *awesome* tool for testing out various subsystems, but at least the versions I've seen aren't a full subscale depot--it's still lacking a little functionality that you would need for a depot.  None of that functionality is particularly low TRL mind you.  I guess I was more thinking of a subscale pilot-plant PD when the question was originally asked.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 11/25/2008 05:19 am
Jon,
I'd love to see someone in the New Space arena do this first.

It might actually inspire some serious funding along these lines for the first time since Apollo Applications was shut-down.   If you guys can do it first; more power to you!

And yes, I'd also love to see a larger scale demonstrator.   But we will probably need an initial small-scale test bed like this just to prove the basic concept.   We can cheaply (relatively) test the systems this way and then scale-up from there with a much higher degree of confidence.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/25/2008 06:47 am
And yes, I'd also love to see a larger scale demonstrator.   But we will probably need an initial small-scale test bed like this just to prove the basic concept.   We can cheaply (relatively) test the systems this way and then scale-up from there with a much higher degree of confidence.

Exactly.  Having an easy way of testing various subsystems and approaches can allow you to mature technologies and retire risks a *lot* faster.  That's more or less the key reason why I'm still at MSS--I really think that the capabilities we're offering can really change the game.  Not just for CFM (cryo fluid management) technologies, but also things like TPS techniques and systems, advanced propulsion techniques, and even reusability approaches. 

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: HIP2BSQRE on 11/25/2008 02:11 pm
How much money are we talking here to do a PD demo?  Tens of millions, 100 million+?  Let's say it is $50 million, and the demo goes great, then what would be the next step?  How would you close the business case?  Since if I am investing x million dollars, I want to be sure you have a customer or protential customers within x years.
Title: Re: Propellant Depots - General Discussion
Post by: HIP2BSQRE on 11/25/2008 02:17 pm
Do you think that the new NASA admin will be more open to look at a PD demo flight?
Title: Re: Propellant Depots - General Discussion
Post by: HIP2BSQRE on 11/25/2008 02:18 pm
Do you think there is much chance of getting money for a new space prize for a small PD demo?
Title: Re: Propellant Depots - General Discussion
Post by: HIP2BSQRE on 11/25/2008 02:21 pm
If people really believe in PD, and the future that it holds are they willing to pay?  Form a non-profit corporation, have members pay $x for a share--maybe even parternship with a university and Boeing.  Then use that money to launch a PD demo and maybe go in partnership with DOD and NASA.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/25/2008 04:19 pm
How much money are we talking here to do a PD demo?  Tens of millions, 100 million+?

Depends a lot on what you're trying to demonstrate.  If you're talking a suborbital test bed to test out various approaches, it could be under a million.  For an orbital test bed, maybe in the single digit to low-tens of millions.  And an actual stand-alone depot can cost a lot more depending on what approach you take.

Quote
Let's say it is $50 million, and the demo goes great, then what would be the next step?  How would you close the business case?  Since if I am investing x million dollars, I want to be sure you have a customer or protential customers within x years.

If there was an obvious and straightforward business case, do you think we'd be talking about it on NSF?  No, someone would be doing it.  That said, there are some potential, non-NASA early markets I've identified, but none of them is going to be easy.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/25/2008 04:29 pm
Do you think there is much chance of getting money for a new space prize for a small PD demo?

There were related Centennial Challenges proposed, but CC never got funded after their first year. 

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 11/25/2008 08:11 pm
Propellant depots, per se, are a chicken & egg thing. You aren't going to get much funding unless you have customers. You're not going to get customers until you've proven the technology works. Catch 22.

At MDA, we were on DARPA's Orbital Express program and helped prove that robotic docking, refueling and vehicle module replacement were eminently achievable and at a relatviely low cost.

Perhaps the way forward is to service satellites and then as the technology becomes more mature, customers can be convinced to come to your servicing satellite as opposed to you going to them. Voila, you're a propellant depot!

Once you have customers who are willing to come to you, you can dispense with your own maneuvering capability and focus on refueling your depots tanks, thus completing the concept.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/28/2008 05:36 am
How much money are we talking here to do a PD demo?  Tens of millions, 100 million+?  Let's say it is $50 million, and the demo goes great, then what would be the next step?  How would you close the business case?  Since if I am investing x million dollars, I want to be sure you have a customer or protential customers within x years.

Refuelling satellites already in LEO and GSO would require a different type of architecture - the refueller flies to the satellite.  So the customers for this Propellant Depot (PD) are sending things to high orbit, Moon, Mars and beyond.

I suspect that the main customers for the PD will be reusable transfer vehicles and reusable landers.  They would fly to a PD in orbit around the planet.  Docking with a PD means that transfer vehicles would not need to carry the heat shields and parachutes needed for re-entering the Earth and Mars.  Landers/ascent stages can be equipped with chemical rockets rather than ion thrusters used on transfer vehicles and can be small like taxis, removing the need for walking around areas.

At the PD both types of vehicles would unload passengers and say ISRU materials.  They would refuel, including consumables, and collect passengers and cargo.  These vehicles are in the future but would probably need a PD placing in LEO first.


Commercial customers are only going to be interested if it permits them to do something they can only do that way or if it saves them money.  The same applies to small budget projects within NASA.

Saving money basically implies a smaller launch vehicle.  So the customer would want to say land a large item on the Moon using an EELV rather than an Ares V.  The small demo PD may allow a scientific package to be sent to the Moon using a Falcon 1 or Taurus II rather than an EELV.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/28/2008 05:42 am
PS Another fuel missing from A_M's list:  Xenon for SEP Tugs! cf RASC/OASIS

When I wrote the list I assumed the Xenon will be too expensive.  So the SEP Tugs will follow the VASIMR Tugs and use Argon as the propellant.  Argon can be extracted from the atmospheres of the Earth and Mars by refrigeration.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/28/2008 09:31 pm
Propellant depots, per se, are a chicken & egg thing. You aren't going to get much funding unless you have customers. You're not going to get customers until you've proven the technology works. Catch 22.

It's even a little worse than that in some ways.  It's not just that it's hard to get customers without a proven solution, it's that many of the potential markets for depots can't exist without them.  Fortunately, I have seen a *few* potential markets that tap demand from existing systems that could benefit from the availability of propellant on orbit.  But it is still hard to line up customers until they're convinced that you're real (both technically capable and that you have the money that you'll actually field the product).

Quote
At MDA, we were on DARPA's Orbital Express program and helped prove that robotic docking, refueling and vehicle module replacement were eminently achievable and at a relatively low cost.

Perhaps the way forward is to service satellites and then as the technology becomes more mature, customers can be convinced to come to your servicing satellite as opposed to you going to them. Voila, you're a propellant depot!

Once you have customers who are willing to come to you, you can dispense with your own maneuvering capability and focus on refueling your depots tanks, thus completing the concept.

There's other approaches that might make more sense operationally.  I don't see too many satellites wanting to move out of their orbit and reposition themselves to a centralized depot.  But with tugs, I could see tug satellites taking propellant from a central depot to individual satellites and tanking them up there.  Just like how many pieces of heavy equipment have fueler trucks come to them to refuel instead of them going to the gas station.  The gas station doesn't move to the construction equipment, and the construction equipment doesn't move to the gas station, but a small intermediary truck with all the necessary fueling hardware does all the hard work.  I think that for refueling satellites that that is the more likely model.



Of course, with almost no existing satellites designed for refueling, both of those ideas are somewhat academic.

One other point worth mentioning is that refueling satellites per se may be a less lucrative market than providing fuel to emplace satellites in the first place.   You need a source of propellant delivery cheaper than just buying a bigger launcher, but the amount of propellant used for placing a satellite in GEO or sending a deep space probe out, is typically much greater than the amount of propellant needed for stationkeeping over the satellite's useful lifetime.

Just some food for thought.  But I definitely agree that the work you guys have done at MDA helps lower the hurdle in making this happen.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 12/03/2008 03:53 am
Most of this Propellant Depot discussion has been about large payload missions, where a single payload needs several propellant launches.  There may be a use for the inverse - single propellant launch supplying multiple payloads.  This is the space equivalent of an inflight refuelling tanker supplying several fighter aircraft.

If the propellant depot has zero boil-off facilities then the payload launches do not have to be in the same month.  A big advantage in an industry where the launch of your payload may be delayed because a second payload sharing your big launch vehicles is late.  Time is money.

Falcon-1 can lift 420 kg to LEO for $7.9M
Falcon-9 can lift 9900 kg (increasing to 12,500 kg) to LEO for $36.8M
M = million

9900 / 420 = 23.6
$36.8M / $7.9M = 4.66

The size of payload is increasing faster than the cost of launch vehicle, so there are economies of scale that someone can use to make a profit.

Putting a 420 kg payload (including motor) in low lunar orbit using a 304 second ISP rocket needs about 1250 kg of propellant.

9900 / 1250 = 7.92 fuel loads

Pessimistically rounding down, including allowing for the tug's fuel, the Depot can put 6 off 420 kg satellites in low lunar orbit using fuel brought on a single Falcon-9.

User launch costs on Falcon-1 is 6 * $7.9M = $47.4M + propellant

An alternative customer launch method is 6 off Falcon-9 carrying payload and fuel
cost is 6 * $36.8M =$220.8M

To save the customer money the propellant will have to cost less than
($220.8M - $47.4M) / (6 * 1250 kg) = $23,120 per kg

Money available for the Depot operator including labour and share of development cost is
$220.8M - $47.4M - $36.8M = $136.6M

The 6 launches do not have to come from the same customer and do not need to have the same destination.
The quantity of propellant supplied to each customer can vary.
The Depot can be refilled.
The Depot could supply Argon or Xenon to an ion thruster tug.

I used Falcons for this example but rival launch vehicles at other prices are available including Pegasus, upgraded Falcons direct to TLI, Long March, Delta and Atlas.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 12/10/2008 07:39 am
I put some thoughts up on ways that the government could help encourage the private development of propellant depots without spending billions of dollars to create another NASA-run space station.

http://selenianboondocks.com/2008/12/propellant-depot-policy-thoughts/

Any thoughts, feedback, or suggestions are welcome. 

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 12/16/2008 01:59 pm
{snip}
I used Falcons for this example but rival launch vehicles at other prices are available including Pegasus, upgraded Falcons direct to TLI, Long March, Delta and Atlas.

Mixed LV missions are also possible, for instance launching the propellant on an Atlas and reusing the Falcon-1's upper stage as a mini Earth Departure Stage by refuelling it.
Title: Re: Propellant Depots - General Discussion
Post by: Lars_J on 12/24/2008 11:19 pm
Newcomer to this thread here... I've skimmed the thread, but I have not seen much discussion on these questions...

 - Which orbit should a PD be in? The more launch sites you cover, the more expensive it will be to fill it up - and to reach it for customers. And if it will be used primarily for moon missions, are there not certain orbits that are better than others?

 - Why the focus on cryogenic fuels? Why not follow the KISS rule (keep it simple stupid) and go for non-cryogenic and/or hypergolic fuels? Is it worth the extra complexity?

 - If shipping cargo to the moon using a ion thruster, what fuels could be used by a Earth-Moon ion propelled tug?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 12/25/2008 05:46 am
Newcomer to this thread here... I've skimmed the thread, but I have not seen much discussion on these questions...

 - Which orbit should a PD be in? The more launch sites you cover, the more expensive it will be to fill it up - and to reach it for customers. And if it will be used primarily for moon missions, are there not certain orbits that are better than others?

As you mention, it's a tradeoff.  A lot will depend on who does a given propellant depot (there probably will eventually be several of them, not just one).  If you want to let the Russians participate, you're stuck with 51.6 degrees.  If you only need to let say the Japanese, Americans, Europeans, and Indians, you can probably get away with something quite a bit lower.  Me personally, if I were doing a propellant depot would probably compromise on a "resonant orbit" in the mid latitudes (say 30-40 degrees).  Something high enough to not just catch Canaveral, but also to allow future potential RLV launch locations as well.

Quote
- Why the focus on cryogenic fuels? Why not follow the KISS rule (keep it simple stupid) and go for non-cryogenic and/or hypergolic fuels? Is it worth the extra complexity?

A lot depends on what the customer wants/needs.  Right now, the vast majority of potential upper stages that could be modified to have refueling capabilities, use at least one cryogenic propellant (LOX), and many of them use LH2 as the fuel.  Now, there are some potential depot applications that absolutely want to be storables/hypergols, but it doesn't do much good to provide something "because it's easier" if people aren't as willing to buy it.  I've studied out the problem of cryogenic storage on orbit, and I think that there are some straightforward technologies that can make LH2 not that much of a hassle.  Sure, it isn't proven technology, but there's a lot more potential demand if you can pull it off.

For commercial depots, we don't do whatever is easiest, we do what we think is most profitable.  And my bet is that that will entail storing at least LOX and probably LH2 (though I wouldn't be surprised if there was also decent demand for N2O4, MMH, and Kerosene).

Quote
- If shipping cargo to the moon using a ion thruster, what fuels could be used by a Earth-Moon ion propelled tug?

Ion thrusters typically use something like Xenon, Mercury, Krypton, or Argon I think.  That said, if you can figure out how to do reuse and aerocapture of the tanker stage, I think a chemical one could actually work out to be cheaper than the ion one.  Especially as launch prices come down.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Eerie on 12/25/2008 02:21 pm
I still don`t see any business case for the depot. Maybe in the far future, when you need to send lots of stuff, and on short notice, it will be cost effective to keep fuel in orbit.

But right now, if NASA is going to launch one huge exploration spacecraft in a several years, it makes much more sense to fuel the spacecraft itself, without a middleman.
Title: Re: Propellant Depots - General Discussion
Post by: Jorge on 12/25/2008 05:49 pm
Newcomer to this thread here... I've skimmed the thread, but I have not seen much discussion on these questions...

 - Which orbit should a PD be in? The more launch sites you cover, the more expensive it will be to fill it up - and to reach it for customers. And if it will be used primarily for moon missions, are there not certain orbits that are better than others?

 - Why the focus on cryogenic fuels? Why not follow the KISS rule (keep it simple stupid) and go for non-cryogenic and/or hypergolic fuels? Is it worth the extra complexity?

Realistically speaking, any viable business plan for a propellant depot is going to rely on NASA as a major customer (and quite likely, in the early years, the sole customer). Since LEO missions have no use for a PD, the main driver is going to be NASA manned lunar/Mars missions. That means the PD must fit the NASA lunar architecture: 28.5 degree inclination orbit, LOX/LH2 propellant. Simple as that.
Title: Re: Propellant Depots - General Discussion
Post by: Will on 12/26/2008 04:45 pm
Newcomer to this thread here... I've skimmed the thread, but I have not seen much discussion on these questions...

 - Which orbit should a PD be in? The more launch sites you cover, the more expensive it will be to fill it up - and to reach it for customers. And if it will be used primarily for moon missions, are there not certain orbits that are better than others?

As you mention, it's a tradeoff.  A lot will depend on who does a given propellant depot (there probably will eventually be several of them, not just one).  If you want to let the Russians participate, you're stuck with 51.6 degrees.  If you only need to let say the Japanese, Americans, Europeans, and Indians, you can probably get away with something quite a bit lower.  Me personally, if I were doing a propellant depot would probably compromise on a "resonant orbit" in the mid latitudes (say 30-40 degrees).  Something high enough to not just catch Canaveral, but also to allow future potential RLV launch locations as well.



~Jon

Once the Soyuz pad at Kourou is completed, Russians will be able to launch from there.
Title: Re: Propellant Depots - General Discussion
Post by: Will on 12/26/2008 05:02 pm
I'm surprised there hasn't been more attention paid to the potential benefits of orbital propellant transfer for the Orion/Ares I mission. Storage and transfer of storable propellant is relatively mature technology. If Orion refilled its tanks in orbit, six tons or more of margin would be added to the the trip to LEO. This would allow a lot more leeway either for Ares ! performance or to restore Orion functionality that has been pared back to meet mass saving goals for Orion. Six tons is a lot.
Title: Re: Propellant Depots - General Discussion
Post by: spacedem on 12/26/2008 05:45 pm
Here's an interesting paper sponsored by DOE in '92 talking about using NEO's for resources to stock fuel depots.  The authors seemed to think that they could make LOX/LH2 available in LEO for $100/kg.

http://nsdl.org/resource/2200/20080812125652878T


It would seem like it would be cheaper to move the NEO into some close location before mining it, but that might raise issues of international law.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 12/27/2008 06:38 am
Once the Soyuz pad at Kourou is completed, Russians will be able to launch from there.

Yes for Soyuz, but not for Proton, Dnepr, or Zenit Land Launch.  IOW, it's a tradeoff.  Soyuz is a start, and with Arianne V, Zenit SL, as well as Atlas V, Delta IV, Falcon, and possibly at least the Indians as well...23.8 might be good enough.  But I think there's something to be said for at least going high enough latitude that you can also get Wallops (for Taurus II), as that also gets you IIRC the Japanese and Chinese facilities, and most potential RLV sites in the US as well.

As I said, it's a tradeoff.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 12/27/2008 04:20 pm
China? Look to Wenchang City on Hainan Island at 19 degrees

Quote
China is currently building a new space launch facility near Wenchang City on the Hainan Island. Once completed, it will be the country’s fourth satellite launch centre and replace the Xichang Satellite Launch Centre (XSLC) for geosynchronous orbit (GEO) and other space launch missions. It will also be the only space launch facility capable of supporting China’s new-generation ChangZheng 5 (CZ-5) heavy-load space launch vehicle, as the 5m diameter core stage of the launch vehicle exceeds the size limit for rail transportation from the launcher manufacture plant to any of the existing inland launch centres.

The new Wenchang launch centre will launch satellites and other spacecraft for a wide range of domestic and foreign customers. Hainan Island’s proximity to the equator gives the new launch centre a distinctive advantage over three existing launch centres in China. Located only 19 degrees north, the new launch centre allows a substantial increase of payload mass. For example, compared to the existing Xichang launch centre, a GEO satellite launched from Wenchang will be able to extend its service life by three years as a result of the fuel saved from the shorter manoeuvre from the transit orbit to GEO.

http://www.sinodefence.com/space/facility/wenchang.asp
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 12/27/2008 04:35 pm
Jon -

I have two question categories concerning using RLVs to fill a propellant depot - orbital mechanics and pilots.

(1)      Let us assume the technology issues are solved, and there exist RLVs capable of landing on a a runway, refueling both launch propellant and depot propellant as payload and then taking off all within a short time window.

Solely in terms of the restrictions imposed by orbital mechanics - how frequently could such an RLV accomplish a round trip journey?

Have you ever sketched out what the schedule might look like. How many hours shall elapse between launch, arrival at the depot, propellant transfer, re-entry landing and subsequent re-launch, assuming the ground crews can work with NASCAR-like efficiency keeping those times to a minimum? 

In other words, how short and infrequent are the launch windows and how long might it take an RLV to arrive at the depot even after attaining orbit?

(2)       Wouldn't a pilot-less RLV be vastly more efficient at performing the task of ferrying fuel?
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 12/27/2008 04:46 pm
Jon -

I have two question categories concerning using RLVs to fill a propellant depot - orbital mechanics and pilots.

(1)      Let us assume the technology issues are solved, and there exist RLVs capable of landing on a a runway, refueling both launch propellant and depot propellant as payload and then taking off all within a short time window.

Solely in terms of the restrictions imposed by orbital mechanics - how frequently could such an RLV accomplish a round trip journey?

Have you ever sketched out what the schedule might look like. How many hours shall elapse between launch, arrival at the depot, propellant transfer, re-entry landing and subsequent re-launch, assuming the ground crews can work with NASCAR-like efficiency keeping those times to a minimum? 

In other words, how short and infrequent are the launch windows and how long might it take an RLV to arrive at the depot even after attaining orbit?

(2)       Wouldn't a pilot-less RLV be vastly more efficient at performing the task of ferrying fuel?

It is very depended on the inclination of the depot and the amount of maneuvering delta-V available on the RLV.

The ISS is only available once a day for a ascending node (twice if there is no azimuth limitations)

As for rendevous time duration, it depends on how many delta-V is available and can the depot take a lot of plume impingement.  gemini vs shuttle, ISS vs GATV
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 12/28/2008 05:59 am
Jon -

I have two question categories concerning using RLVs to fill a propellant depot - orbital mechanics and pilots.

(1)      Let us assume the technology issues are solved, and there exist RLVs capable of landing on a a runway, refueling both launch propellant and depot propellant as payload and then taking off all within a short time window.

Solely in terms of the restrictions imposed by orbital mechanics - how frequently could such an RLV accomplish a round trip journey?

Have you ever sketched out what the schedule might look like. How many hours shall elapse between launch, arrival at the depot, propellant transfer, re-entry landing and subsequent re-launch, assuming the ground crews can work with NASCAR-like efficiency keeping those times to a minimum? 

In other words, how short and infrequent are the launch windows and how long might it take an RLV to arrive at the depot even after attaining orbit?

(2)       Wouldn't a pilot-less RLV be vastly more efficient at performing the task of ferrying fuel?

It is very depended on the inclination of the depot and the amount of maneuvering delta-V available on the RLV.

The ISS is only available once a day for a ascending node (twice if there is no azimuth limitations)

As for rendevous time duration, it depends on how many delta-V is available and can the depot take a lot of plume impingement.  gemini vs shuttle, ISS vs GATV

As Jim mentioned, unless your depot is in an equatorial orbit (with equatorial launch sites), you'll get at most 2 windows per day.  That's why I'm somewhat a fan of resonant mid-inclination orbits (in the 23.8-~42 degree range).  The more launch sites that can reach your station, the more frequent you can do deliveries.

Of course, for small depot tanker RLVs, hopefully we can get to the point where they can operate away from the main ELV launch ranges.  There still aren't a huge amount of locations in the US for instance where you can safely launch even a reliable RLV, but there are enough to be very interesting. 

So, yeah 1-2 launch window per day.  If the orbit phasing is right, you might be able to get a rendezvous in the first few orbits...but you'd have to wait about half a day to a day to get another deorbit opportunity (unless you have lots of cross range).  So realistically, the theoretical maximum flight rate of one RLV at one launch site to one depot is twice a day......which is so far beyond where we're at right now that it is entirely academic.

Realistically, I would expect a lower flight rate per vehicle (starting out around once per week and maybe working up to once per day), but going to a few tail numbers once you have the basic design proved out.  Even one small RLV is capable of drastically changing the economics environment of propellant depots.

~Jon

PS Sorry if this isn't entirely coherent.  Caught a nasty cold on vacation.  Headed home tomorrow.
Title: Re: Propellant Depots - General Discussion
Post by: Will on 12/28/2008 04:24 pm
Jon -

I have two question categories concerning using RLVs to fill a propellant depot - orbital mechanics and pilots.

(1)      Let us assume the technology issues are solved, and there exist RLVs capable of landing on a a runway, refueling both launch propellant and depot propellant as payload and then taking off all within a short time window.

Solely in terms of the restrictions imposed by orbital mechanics - how frequently could such an RLV accomplish a round trip journey?

Have you ever sketched out what the schedule might look like. How many hours shall elapse between launch, arrival at the depot, propellant transfer, re-entry landing and subsequent re-launch, assuming the ground crews can work with NASCAR-like efficiency keeping those times to a minimum? 

In other words, how short and infrequent are the launch windows and how long might it take an RLV to arrive at the depot even after attaining orbit?

(2)       Wouldn't a pilot-less RLV be vastly more efficient at performing the task of ferrying fuel?

(2) Depends very much on the design. Historically, unmanned aircraft have had a much worse loss rate than manned ones. A pilot might pay for himself in spite of the reduced payload.

However, if you're building a simple Kistler style RLV, having a pilot may not provide the same benefits as on a winged vehicle or lifting body.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 12/28/2008 05:00 pm
My thanks to Jon & Jim, and yet I fear I may have focused on the wrong question first.

If it takes 2 to 3 days for the orbiter to reach ISS and dock - after lift off - a launch window of once per day isn't an enormous constraint.

Presumably, a fuel tanker could expend additional delta v and shorten that time however don't you then face potential diminishing returns and a non-trivial analysis of a delta v versus delta t trade? Lowering the altitude of your depot adds in even more factors.

It seems to me that if an RLV fuel tanker can launch, match orbits with the depot, dock, off load fuel, depart, re-enter and land with total elapsed time of 72 hours to 96 hours from lift off to wheels stopped, we'd be doing about as good as is feasible.   

Then we add time on the ground to check out the RLV, re-fuel and refurbish and the total gets us up to a 4 to 5 day total trip time, per mission. Average in occasional extended trips to the service hanger for repairs and maintenance and if an RLV actually flies 50 fuel missions per year, wouldn't that be a fantastic result? Once we factor in the launch window constraints, it seems to me that budgeting 24 hours on the ground between missions (as an average) would be the absolute minimum.

How much hanger time versus flight time does an F-22 require? Or a B-1?

If your RLV is flying a 72 to 96 hour mission, how soon (on average) can it go up again after the wheels stop after landing?

Sketch out that figure and we can begin to compares using RLVs versus EELVs or the COTS vehicles (SpaceX and Orbital's evolved Zenit) in terms of cost comparisons.

= = =

As for pilots, providing life support for 3 or 4 days will require significant mass that eats into your payload margins, right? 

= = =

Edit to add:

In another thread, Jim posted this concerning Orion:

Quote
Daylight landing opportunities there are only available 1-2 orbits per day, much like the shuttle.

But what about these hypothetical RLVs? Are there landing window constraints as well as launch window constraints? Routine night landings for these RLV tankers?

As I requested above, a pro forma flight schedule would be very helpful to help visualize the issues involved:

Suppose lift off is at 8:00 a.m.

When would the tanker reach the depot?

When would the tanker leave the depot?

When would the tanker land?

How fast can the tanker lift off again?

From an operational perspective, once per week strikes me as pretty darn optimistic even for a mature flight proven system.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 12/29/2008 05:01 pm
My thanks to Jon & Jim, and yet I fear I may have focused on the wrong question first.

If it takes 2 to 3 days for the orbiter to reach ISS and dock - after lift off - a launch window of once per day isn't an enormous constraint.

*snip*

Average in occasional extended trips to the service hanger for repairs and maintenance and if an RLV actually flies 50 fuel missions per year, wouldn't that be a fantastic result?

*snip*

As for pilots, providing life support for 3 or 4 days will require significant mass that eats into your payload margins, right?

Bill,
A couple of thoughts:
1-It is possible with the right combination of resonant orbits (orbits that have a "ground track" that repeats on some frequent period), launch site location, and/or air launch to get daily opportunities for a 1st/2nd orbit rendezvous.  Ie 2-3 hrs from launch to docking not 2-3 days. 
2-Even without that though, getting 50 flights per year per RLV isn't that shabby.  Even with a 1-ton capability, a fleet of 3 airframes like that would be putting up a lot of mass every year.
3-Also remember that unless the RLV is an SSTO, you've got two stages, and the first stage is the bigger one, and will be back at the launch site sooner.  So you can be prepping that for reflight while you're waiting for the upper stage to come back.  Also you'll likely have a different number of upper stages vs. first stages for that reason.
4-Pilots might make sense for tanker trips if you can get 1st/2nd orbit rendezvous.  Especially if the RLV is also used for other things that need a pilot anyway (say crew/cargo delivery).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 12/29/2008 06:30 pm
Thanks, Jon . . .

Quote
1-It is possible with the right combination of resonant orbits (orbits that have a "ground track" that repeats on some frequent period), launch site location, and/or air launch to get daily opportunities for a 1st/2nd orbit rendezvous.  Ie 2-3 hrs from launch to docking not 2-3 days.

I agree that such orbits (1st or 2nd orbit rendezvous) would be of great value for a depot and greatly aid the feasibility of your concepts. The shorter the round trip, the more "net" leverage RLVs offer.  Do you agree on that point?

Maybe propellant depot advocates should identify and publicize those orbits sooner rather than later so that work can begin to encourage political awareness of the value of such orbits since the restrictions imposed by orbital inclination affects optimal locations for future launch sites and spaceports. I don't see any potential trade secrets here since anyone capable of doing the math can figure out those orbits for themselves -- or am I wrong about that?

But because of daily (or twice daily) windows going down as well as up, elapsed mission times of at least 24 hours would seem to be a theoretical minimum for an RLV to launch, dock with a depot and return, before we factor in hanger time, unless equatorial orbits are used. 

And launching every other day would require (a) substantial operational experience and (b) substantial demand for delivery of mass to LEO.

Quote
2-Even without that though, getting 50 flights per year per RLV isn't that shabby.  Even with a 1-ton capability, a fleet of 3 airframes like that would be putting up a lot of mass every year.

Agreed, if there was someone willing to purchase the mass being lifted by those RLVs.

Whether NASA's needs (on a stand alone basis) would be sufficient to justify developing those RLVs is something I find doubtful, especially if SpaceX and Orbital (for example) are bidding on the same delivery contract using Falcons and Taurus IIs or their successors.

But I'd love to be proven wrong.

In addition, it seems to me that building 300 airframes would greatly lower the incremental acquisition cost of the 3 airframes you mention, but who might possibly absorb those levels of Earth-to-LEO launch capability?

Quote
3-Also remember that unless the RLV is an SSTO, you've got two stages, and the first stage is the bigger one, and will be back at the launch site sooner.  So you can be prepping that for reflight while you're waiting for the upper stage to come back. Also you'll likely have a different number of upper stages vs. first stages for that reason.

If there were a tug deployed on orbit, perhaps a crew-less disposable upper stage fuel tanker mated with a fully reusable first stage in a TSTO system makes more sense insofar as fuel tanks are not themselves inherently valuable. A fully reusable first stage in a TSTO system could greatly reduce the cost of placing an otherwise disposable propulsion module on orbit. If a robotic science mission were headed out beyond cis-lunar space (for example) we aren't recovering the Centaur or Proton Block D or KVRB used to propel that mission, in any event and therefore a market could exist for delivery of a pre-packaged engine module capable of being mated to any number of disposable fuel tanks.

A non-recoverable 2nd stage would seem more economical for delivering those payloads.

RLVs for crew transport make far more sense to me since a human rated cockpit and the associated life support systems do have substantial inherent value; far more inherent value than a fuel tank and a single RL-10 or equivalent.

Be wary of "target fixation" on the RLV concept. ;-)

Quote
4-Pilots might make sense for tanker trips if you can get 1st/2nd orbit rendezvous.  Especially if the RLV is also used for other things that need a pilot anyway (say crew/cargo delivery).

Agreed, but not necessarily for all applications.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 12/29/2008 07:11 pm
Thanks, Jon . . .

Quote
1-It is possible with the right combination of resonant orbits (orbits that have a "ground track" that repeats on some frequent period), launch site location, and/or air launch to get daily opportunities for a 1st/2nd orbit rendezvous.  Ie 2-3 hrs from launch to docking not 2-3 days.

I agree that such orbits (1st or 2nd orbit rendezvous) would be of great value for a depot and greatly aid the feasibility of your concepts. The shorter the round trip, the more "net" leverage RLVs offer.  Do you agree on that point?

Well...I would more say that such orbits are nice to have's not have to have's.  Even if you had to do 2-3 day rendezvous ops, and could only get 50 flights per airframe per year because of that, RLVs would still likely win hands-down on a price basis compared to launching a smaller number of bigger EELVs.

If by using resonant orbits, and 1st/2nd orbit rendezvous you can increase the number of flights per airframe per year from 50 to 150-250, that would just be icing on the cake.

Quote
Maybe propellant depot advocates should identify and publicize those orbits sooner rather than later so that work can begin to encourage political awareness of the value of such orbits since the restrictions imposed by orbital inclination affects optimal locations for future launch sites and spaceports. I don't see any potential trade secrets here since anyone capable of doing the math can figure out those orbits for themselves -- or am I wrong about that?

Yeah, it could make a good paper.  It's not in my primary area of expertise though.  Maybe someone is looking for a topic for a dissertation or thesis?

Quote
But because of daily (or twice daily) windows going down as well as up, elapsed mission times of at least 24 hours would seem to be a theoretical minimum for an RLV to launch, dock with a depot and return, before we factor in hanger time, unless equatorial orbits are used.

Not necessarily.  Theoretically, you could probably wring two flights per day per airframe out of an RLV, if it either had good reentry cross range, air launch, or was at a site that had two daily windows.  But still 24 hours would be amazingly good compared to where we are at now, and trying to squeeze an extra flight in per day would be a problem I really wish we had.

Quote
And launching every other day would require (a) substantial operational experience and (b) substantial demand for delivery of mass to LEO.

Exactly, we're a long way off before the physics itself starts becoming the limiter on RLV flight rates.  And there are other things that can be done even at that point.  One simple one would be multiple launch/landing sites and multiple depots (in the same orbit, but staggered so their ground track overpasses are spaced out more evenly during the day).  Once again though, that's getting into the "problems I would love to have" category.

Quote
Quote
2-Even without that though, getting 50 flights per year per RLV isn't that shabby.  Even with a 1-ton capability, a fleet of 3 airframes like that would be putting up a lot of mass every year.

Agreed, if there was someone willing to purchase the mass being lifted by those RLVs.

Whether NASA's needs (on a stand alone basis) would be sufficient to justify developing those RLVs is something I find doubtful, especially if SpaceX and Orbital (for example) are bidding on the same delivery contract using Falcons and Taurus IIs or their successors.

A lot depends on the size of the RLV.  There's nothing that says the RLV, if it's main primary markets are people, some light cargo, or propellants, has to be as big as either of those other launchers.  And in fact, there's a lot to suggest keeping it in the 0.5-2.5 ton range.  You don't need a lot of propellant depot demand to provide 50 flights per year of an RLV if it's small enough.  And a true RLV is likely going to be a lot less expensive than either of those vehicles, unless Falcon IX reuse goes *very* well.

Quote
In addition, it seems to me that building 300 airframes would greatly lower the incremental acquisition cost of the 3 airframes you mention, but who might possibly absorb those levels of Earth-to-LEO launch capability?

Yeah, 300 airframes is well beyond the point I'm looking at.  Just getting those first few is going to change things enough that any predictions past that point are going to be wildly inaccurate.

Quote
If there were a tug deployed on orbit, perhaps a crew-less disposable upper stage fuel tanker mated with a fully reusable first stage in a TSTO system makes more sense insofar as fuel tanks are not themselves inherently valuable. A fully reusable first stage in a TSTO system could greatly reduce the cost of placing an otherwise disposable propulsion module on orbit.

Maybe.  I'm not convinced, but not positive it wouldn't make sense.  "cheap throwaway upper stages" sound great in theory, but I don't know how well they'd work in practice.  Plus, there are other markets you could serve with a fully reusable vehicle that aren't as easy to serve if the upper stage is expendable.

Quote
RLVs for crew transport make far more sense to me since a human rated cockpit and the associated life support systems do have substantial inherent value; far more inherent value than a fuel tank and a single RL-10 or equivalent.

Be wary of "target fixation" on the RLV concept. ;-)

Fair enough.  I'm just not convinced though that it would be cheaper in the long run to do a half reusable vehicle like that than to bite the bullet and make it fully reusable.  After all, RL-10s aren't cheap, and having to make a new upper stage for each flight is going to lower your realistically attainable max flight rates.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 12/31/2008 06:31 pm
Jon & I have discussed this before. Personally, I think that the first step in this sort of a depot architecture will be the development of a really cheap expendable fuel tanker. Something that can be made by the hundreds on a production line and that can get something between 1 & 5 tons of propellant to orbit for less than $7,000 or $8,000 per kg so that a profit can be made selling it for $10,000 per kg. A booster so cheap that you can afford to lose 1 in 20 & still make money.

However, before that gets going, someone is going to have to convince the markets that this technology is possible and I think a much smaller depot or mobile refueler is more likely than a multi-ton depot for the big boys. Once the docking & autonomous refueling tech is proven to the open market, then the commercial interests will be much more willing to risk their high value payloads around a depot.

BTW, in order to keep the boosters dead cheap I'd use a tug to do all the maneuvering/docking/berthing so that the boosters would actually carry none of the required instruments or maneuver capability. The tug then becomes a single "high value" mobile component in the system while the boosters are little more than bladders with engines attached.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: spacedem on 01/09/2009 12:48 pm
This proposal http://sbir.nasa.gov/SBIR/abstracts/04/sbir/phase1/SBIR-04-1-X2.04-7565.html (http://sbir.nasa.gov/SBIR/abstracts/04/sbir/phase1/SBIR-04-1-X2.04-7565.html)

For an expandable cryo depot was awarded an SBIR Phase I contract in '04, according to http://technology.ksc.nasa.gov/static/SttR.htm.

Does anyone have any info on whether this made any progress?  I can't find any additional info on it.


Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/09/2009 01:53 pm
This proposal http://sbir.nasa.gov/SBIR/abstracts/04/sbir/phase1/SBIR-04-1-X2.04-7565.html (http://sbir.nasa.gov/SBIR/abstracts/04/sbir/phase1/SBIR-04-1-X2.04-7565.html)

For an expandable cryo depot was awarded an SBIR Phase I contract in '04, according to http://technology.ksc.nasa.gov/static/SttR.htm.

Does anyone have any info on whether this made any progress?  I can't find any additional info on it.

Not sure, but I've also looked into similar concepts.  I don't know if my SBIR proposal from 07 would show up (since I don't know if they keep public record of unsuccessful proposals--ED: Apparently they don't), but my latest thinking was combining the idea of cryogenic propellant bladders, and the passive cooling system I had proposed in my 07 proposal, with active cooling work that's been done by Boeing and a few others.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/14/2009 08:18 am
OK I haven't waded through the previous 20 pages of this thread so apologies if this came up before.

I've often seen depots proposed as an enabler for Mars missions, and have to disagree with the sentiment. Requiring depots assumes all-chemical propulsion which in turn assumes a massive IMLEO (500t+?). Presumably, due to packaging issues, the IMLEO of a depot-fuelled mission will actually be greater because the propellant is sent up in smaller chunks which need some form of 'tanker' to deliver them.

IMHO, we have no business attempting to go to Mars in this manner. Unless somebody can greatly reduce launch costs, then we would be tied in to an unsustainably expensive mission architecture.

So, rather than use propellant depots for Mars, why not develop high-isp propulsion? This would slash IMLEO- by at least a half, even for conservative estimates. The JPL study which used a spinning NEP craft gives a good insight into this technology. Solar-electric propulsion would represent a scaling up of well-known technologies, whilst NEP would require a nuclear power source- but we would need one of these for Mars surface operations and ISRU anyway.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 01/14/2009 08:34 pm
For a manned Mars mission the depot can store the fuel in several different tanks.

The cost of a Mars transfer vehicle, need for the structure to be launched in several parts and smallness of the launch window suggest that to reduce risk the fuel should be launched in advance and not kept in the vehicle's own fuel tanks.  A depot would be a good storage place whilst handling the complex delivery times and quantities of several different tanker vehicles.

Ion thrusters are covered by other threads, although the say Argon propellant for a VASIMR thruster could be supplied by the depot.  The boiling point of Argon is 3oC lower than LOX so similar equipment can be used to make and handle liquid Argon.

ed: add apostrophe s
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/15/2009 02:25 am
IMHO, we have no business attempting to go to Mars in this manner. Unless somebody can greatly reduce launch costs, then we would be tied in to an unsustainably expensive mission architecture.

See http://www.thespacereview.com/article/544/1 for an approach to lowering costs to LEO by trading reliability for price. Obviously, this only works for low value cargo, not for expensive hardware, let alone people. But since for now most of the mass that would be launched would be propellant anyway, this can lead to enormous improvements. When high ISP freighters finally come into service, this will change, but it would probably still make sense to launch the argon on cheap unreliable launchers.

So, rather than use propellant depots for Mars, why not develop high-isp propulsion? This would slash IMLEO- by at least a half, even for conservative estimates. The JPL study which used a spinning NEP craft gives a good insight into this technology. Solar-electric propulsion would represent a scaling up of well-known technologies, whilst NEP would require a nuclear power source- but we would need one of these for Mars surface operations and ISRU anyway.

I agree with the high-ISP suggestion, especially for cargo. I read a proposal for a VASIMR powered solar electric lunar cargo tug a while ago. Power density of the solar arrays and their bad radiation resistance were the main bottlenecks. Nuclear propulsion would solve that, but would delay progress until consensus is reached on using nuclear power in space.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/15/2009 10:21 am
IMHO, we have no business attempting to go to Mars in this manner. Unless somebody can greatly reduce launch costs, then we would be tied in to an unsustainably expensive mission architecture.

See http://www.thespacereview.com/article/544/1 for an approach to lowering costs to LEO by trading reliability for price. Obviously, this only works for low value cargo, not for expensive hardware, let alone people. But since for now most of the mass that would be launched would be propellant anyway, this can lead to enormous improvements. When high ISP freighters finally come into service, this will change, but it would probably still make sense to launch the argon on cheap unreliable launchers.

So, rather than use propellant depots for Mars, why not develop high-isp propulsion? This would slash IMLEO- by at least a half, even for conservative estimates. The JPL study which used a spinning NEP craft gives a good insight into this technology. Solar-electric propulsion would represent a scaling up of well-known technologies, whilst NEP would require a nuclear power source- but we would need one of these for Mars surface operations and ISRU anyway.

I agree with the high-ISP suggestion, especially for cargo. I read a proposal for a VASIMR powered solar electric lunar cargo tug a while ago. Power density of the solar arrays and their bad radiation resistance were the main bottlenecks. Nuclear propulsion would solve that, but would delay progress until consensus is reached on using nuclear power in space.

If we go with high-isp propulsion, there is no need for depots. I've attached some back-of-envelope calculations showing how much the IMLEO can fall if you use the right technologies. For an all-NEP mission, the propellant is only 12.7% of the IMLEO, or about 17,000kg in my example. Contrast with a zero boil-off all-cryogenic mission where the propellant accounts for over 70% of the IMLEO (around 275,000kg). Extra propellant would, in practise,be needed to account for boil-off, or extra mass allocated to cooling equipment.
Title: Re: Propellant Depots - General Discussion
Post by: khallow on 01/15/2009 10:56 am

If we go with high-isp propulsion, there is no need for depots. I've attached some back-of-envelope calculations showing how much the IMLEO can fall if you use the right technologies. For an all-NEP mission, the propellant is only 12.7% of the IMLEO, or about 17,000kg in my example. Contrast with a zero boil-off all-cryogenic mission where the propellant accounts for over 70% of the IMLEO (around 275,000kg). Extra propellant would, in practise,be needed to account for boil-off, or extra mass allocated to cooling equipment.

The thing is, propellant depots are synergistic with all propellant-based propulsion systems. For example, the 17,000 kg of NEP propellant could be inserted into a LEO propellant depot by an EELV class rocket seperate from the rest of the vehicle. It also allows you to reuse the vehicle. You could set up similar depots in Mars orbit too and fly all-NEP vehicles on a continuous loop. WIth that sort of infrastructure in place, it should open up a considerable portion of the Solar System to exploration.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/15/2009 11:11 am

If we go with high-isp propulsion, there is no need for depots. I've attached some back-of-envelope calculations showing how much the IMLEO can fall if you use the right technologies. For an all-NEP mission, the propellant is only 12.7% of the IMLEO, or about 17,000kg in my example. Contrast with a zero boil-off all-cryogenic mission where the propellant accounts for over 70% of the IMLEO (around 275,000kg). Extra propellant would, in practise,be needed to account for boil-off, or extra mass allocated to cooling equipment.

The thing is, propellant depots are synergistic with all propellant-based propulsion systems. For example, the 17,000 kg of NEP propellant could be inserted into a LEO propellant depot by an EELV class rocket seperate from the rest of the vehicle. It also allows you to reuse the vehicle. You could set up similar depots in Mars orbit too and fly all-NEP vehicles on a continuous loop. WIth that sort of infrastructure in place, it should open up a considerable portion of the Solar System to exploration.

But why bother??
To conduct the Mars mission, you need to launch bulky payloads like Mars landers, which cannot be practically assembled after launch. If you can launch these bulky payloads, you likely have the services of a launcher in 50,000kg+ class. Incidentally this class of launcher would also prove to be perfectly sized for launching a crew to meet an outbound Mars craft in High Earth Orbit. When you are launching the rest of the mission on ths size of launcher, what's the point in seperating off 12% of the total mission mass for launch on another vehicle, when that ties you into depot development and additional docking operations?
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 01/15/2009 05:12 pm
I agree with you, _if_ you have a high ISP engine, use it for Mars. Heck, use it for long duration cislunar shuttles. However, until such an engine is available, depots do a lot for you. Whether a depot is needed for Mars depends entirely upon whether a high ISP (usually nuke) engine is funded by NASA/the government. It becomes a political issue far more than an engineering one. If you have a high ISP engine, you don't need a depot. If you don't have the engine, you need the depot.

At least as far as Mars is concerned.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/15/2009 05:20 pm
If you have a high ISP engine, you don't need a depot. If you don't have the engine, you need the depot.

But supposing you have the depot, would there be any reason not to use it? You can always use the extra launch mass saved for something useful.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 01/15/2009 06:05 pm
Jon Goff and Ferrris Valyn have posted a propellant depot essay at the "Great Orange Satan" also known as "The Daily Kos" and have submitted it to the Obama transition team.

Becoming Spacefaring: Technology investment (http://www.dailykos.com/story/2009/1/14/205851/891)

While I am in general agreement with the authors concerning the needful-ness and/or desirability of these technologies:

Quote
#Orbital Propellant Transfer and Storage Infrastructure aka Orbital Propellant depots

#Proximity Operations Vehicles aka Space Tugs

#High Flight Rate Reusable Launch Vehicles


I am uncertain what the authors (and everyone else) believe as to how propellant depot development fits into the larger plans:

For example,

==> With ESAS (Ares I and Ares V) there simply is no NASA money available to fund propellant depots. I believe Mike Griffin has said that if the private sector builds a depot, he'd buy fuel (or would have) but depots are simply not part of his vision.


==> I have encountered arguments claiming that it would be foolish and wasteful to venture beyond LEO before depots and genuine RLVs are developed. Cancel everything and spend all of NASA's money on propellant depot research and development and RLV research and development.


==> EELV-only plus propellant depots. The original Boeing CEV proposal (pre-Griffin) included L-point stations and fuel depots and heavy reliance on Delta IVH as NASA's new workhorse. Other variants include COTS players and Atlas V but call for termination of all shuttle derived launch components. Use the money saved from terminating everything associated with STS to fund depot technology development.

I believe the Space Access Society can be said to fall into this category.


==> The Direct 2.0 proposal asserts that using Jupiters rather than Ares saves sufficient money to keep shuttle derived launchers AND fund propellant depot development and deployment AND other cool ancillary projects as well.



Therefore, even if we all agree that propellant depots  are a terrific idea, there remains plenty of disagreement concerning what percentage of focus and budget should be devoted to depots.

Any thoughts on this overview of options?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 01/15/2009 07:09 pm
Ad Astra's high ISP engine is the VASIMR.  Currently they are testing the VX-200 version of the VASIMR thruster.  They claim that nominally, the VX-200 will produce 5 N (~1.1lbf) at a 5,000 s Isp.  It uses 200 kW and argon as a propellant.  They have a contract to attach a VX-200 to the ISS.

Mars is sufficiently near the sun that SEP (Solar Electric Propulsion) can be used.  Basically a Mars SEP tug is a Moon SEP tug pointed in a different direction with more solar panels.  One big engine or several small ones can be used.

Solar power at Mars is about 0.4 of its value at Earth, so SLASR solar arrays producing 3 kg/kW at Earth would mass 3 / 0.4 = 7.5 kg/kW at Mars.

Solar arrays to produce 1 MW at Mars would mass 1000000 * 7.5 / 1000 = 7 500 kg

Paper on VASIMR lunar tug, with 100 tonne cargo delivery vehicle
http://www.adastrarocket.com/Tim_IEPC07.pdf


VASIMR on ISS thread
http://forum.nasaspaceflight.com/index.php?topic=13968.0

p.s. correct * to /
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/15/2009 08:28 pm
I agree with you, _if_ you have a high ISP engine, use it for Mars. Heck, use it for long duration cislunar shuttles. However, until such an engine is available, depots do a lot for you. Whether a depot is needed for Mars depends entirely upon whether a high ISP (usually nuke) engine is funded by NASA/the government. It becomes a political issue far more than an engineering one. If you have a high ISP engine, you don't need a depot. If you don't have the engine, you need the depot.

At least as far as Mars is concerned.

Paul

Why all the uncertainty over high-isp engines? We don't need a warp drive. Just a scaled up hall thruster system as already proven on Smart-1, DS1, etc.
As to powering it, well, nuclear is the best option in many ways but within the Earth/Moon system solar could be viable and politically much more palatable. In fact, IMHO we should not be operating nuclear reactors in spacecraft which stand any chance of impacting Earth- which means no nukes aboard a tug craft spiralling or aerobraking down to LEO.

A SEP tug delivering spacecraft to high Earth orbit would slash an enormous amount off of the fuel bill for a Mars mission, certainly enough to make the necessity of depots questionable.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/15/2009 08:34 pm
==> I have encountered arguments claiming that it would be foolish and wasteful to venture beyond LEO before depots and genuine RLVs are developed.
If I understand correctly, the idea is to have a small RLV launching propellant and benefiting from high flight rate. Sounds good, until you realise that your beyond LEO plans tend to need larger single payloads too- specifically, Mars entry vehicles, which would then require a dedicated wide-body rocket to launch them. The 'Mars rocket' will suffer a dismally poor flight rate if it never gets to launch anything else, and will be so horrendously expensive to fund that it will be in constant risk of program cancellation.
Quote
Therefore, even if we all agree that propellant depots  are a terrific idea, there remains plenty of disagreement concerning what percentage of focus and budget should be devoted to depots.
Well, I don't think they are a terrific idea. Space-based nuclear reactors, high isp propulsion and better atmospheric entry technologies will get us to Mars, and should be higher priority.  :P
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/15/2009 08:36 pm
Ad Astra's high ISP engine is the VASIMR.  Currently they are testing the VX-200 version of the VASIMR thruster.  They claim that nominally, the VX-200 will produce 5 N (~1.1lbf) at a 5,000 s Isp.  It uses 200 kW and argon as a propellant.  They have a contract to attach a VX-200 to the ISS.

Mars is sufficiently near the sun that SEP (Solar Electric Propulsion) can be used.  Basically a Mars SEP tug is a Moon SEP tug pointed in a different direction with more solar panels.  One big engine or several small ones can be used.

Solar power at Mars is about 0.4 of its value at Earth, so SLASR solar arrays producing 3 kg/kW at Earth would produce 3 * 0.4 = 7.5 kg/kW.

Solar arrays to produce 1 MW at Mars would mass 1000000 * 7.5 / 1000 = 7 500 kg

Paper on VASIMR lunar tug, with 100 tonne cargo delivery vehicle
http://www.adastrarocket.com/Tim_IEPC07.pdf


VASIMR on ISS thread
http://forum.nasaspaceflight.com/index.php?topic=13968.0

My main quibble with VASIMR is the huge power consumption. Additionally, it is a new technology. By contrast hall thrusters have been in use for decades and are well known and proven.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/15/2009 08:38 pm
If you have a high ISP engine, you don't need a depot. If you don't have the engine, you need the depot.

But supposing you have the depot, would there be any reason not to use it? You can always use the extra launch mass saved for something useful.

The depot would handle LOX and LH2. The high-isp propellant of choice is Xenon or some other inert gas. So you'd need a separate tank and different transfer technologies.
Incidentally, on-orbit transfer of noble gas propellant would be desirable to get the most out of a SEP or NEP tug architecture. However, IMHO this will be a technique more akin to the current state of the art than to the proposed cryogenic transfer systems.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/15/2009 09:27 pm
The depot would handle LOX and LH2. The high-isp propellant of choice is Xenon or some other inert gas. So you'd need a separate tank and different transfer technologies.
Incidentally, on-orbit transfer of noble gas propellant would be desirable to get the most out of a SEP or NEP tug architecture. However, IMHO this will be a technique more akin to the current state of the art than to the proposed cryogenic transfer systems.

Let's compare the atmospheric boiling points of some relevant gases. According to Wikipedia they are:

hydrogen 20.28 K
argon 87.30 K
oxygen 90.20 K
methane 112 K
krypton 119.93 K
xenon 165.03 K

If you are going to use argon, the difficulty should be on the same order as oxygen. But as I understand it, oxygen transfer is already easier than hydrogen transfer, so you may well be right that it falls into the "relatively easy" category. Methane is often described as a lighter cryogen, so krypton and xenon are probably a lot easier than hydrogen. Xenon is apparently very expensive though.

You were thinking of Mars, I'm thinking more of the moon. I'd like to see argon and oxygen depots at both ends, one in LEO, the other in LLO or perhaps at L1. The argon would be used for cargo transport, the oxygen for quick manned transport.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 02:26 am
To conduct the Mars mission, you need to launch bulky payloads like Mars landers, which cannot be practically assembled after launch.

I think that's an assumption, not a fact.  I'll admit that I haven't focused as much time on Mars (mostly because we aren't going to be going there anytime soon), but I'd be surprised if there weren't some options for landers that didn't take an HLV if you can tank up the stage in orbit.  I remember lots of people saying you couldn't do good lunar landers without the bigger Ares V fairings, but there's plenty of good options for those, like the LM horizontal lander that would work fine.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: sandrot on 01/16/2009 02:36 am
[...] but there's plenty of good options for those, like the LM horizontal lander that would work fine.

Is NASA going for multiple engines for landing?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 02:37 am
I agree with you, _if_ you have a high ISP engine, use it for Mars. Heck, use it for long duration cislunar shuttles. However, until such an engine is available, depots do a lot for you. Whether a depot is needed for Mars depends entirely upon whether a high ISP (usually nuke) engine is funded by NASA/the government. It becomes a political issue far more than an engineering one. If you have a high ISP engine, you don't need a depot. If you don't have the engine, you need the depot.

Even then it's not an open and shut case.  I can quite frankly see cases where a much higher IMLEO chemical propulsion system might very well have a lower costs per pound on mars than a very high Isp NEP system would.  Sure, if 30+ years from now when we have an NEP system large enough for missions like that, launch costs to LEO haven't gone down, depots don't exist, RLVs are still a pipe dream, etc.

But if depots and RLVs do happen, and the cost of launch goes down very much, the situation changes completely.  With an NEP system, your vehicle hardware costs are going to be *very* high compared to a chemical propulsion system.  And you're not going to get many flights to amortize that cost over.  And the development costs are going to be very high.  Sure, the IMLEO is going to be lower, but that doesn't save you as much if launch costs go down.

There's a launch cost point above which the cost of getting stuff into orbit is high enough that it makes sense to spend a lot more on up-front investment, higher hardware cost, etc to lower that initial launch mass.  However, if you get your launch costs below that, it's no longer clear that the IMLEO savings alone would justify a higher-Isp system.

Sure, there are other possible benefits (shorter trip times, etc), but it's not clear that the IMLEO savings really actually equate out to net $$$ savings for an NEP system.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 02:38 am
[...] but there's plenty of good options for those, like the LM horizontal lander that would work fine.

Is NASA going for multiple engines for landing?

Huh?

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: sandrot on 01/16/2009 02:41 am
Is NASA going for multiple engines for landing?

Huh?

~Jon

Doesn't the horizontal lander need more than one engine for landing?

(on top of my mind it does)

And, do you think NASA would like a lander with multiple engines?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 02:52 am
==> With ESAS (Ares I and Ares V) there simply is no NASA money available to fund propellant depots. I believe Mike Griffin has said that if the private sector builds a depot, he'd buy fuel (or would have) but depots are simply not part of his vision.

We didn't suggest that NASA should fund a depot.  We suggested that NASA should spend some money on tech development, and should encourage the private development of depots by buying propellant if they are fielded, but we explicitly do not want NASA building the depot itself (or cutting a contract for a contractor to do such).

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==> I have encountered arguments claiming that it would be foolish and wasteful to venture beyond LEO before depots and genuine RLVs are developed. Cancel everything and spend all of NASA's money on propellant depot research and development and RLV research and development.

I don't think NASA needs to wait for RLVs.  I do think though that if NASA is going to be waiting for something to explore beyond LEO, that waiting for depots is better than waiting for HLVs.  But the reality is that you don't even necessarily need depots at first--just fuel transfer.  And fuel transfer is pretty much a proven process by now. 

You're fine with having NASA wait 10-15 years to develop HLVs?  Why not develop something that actually make spaceflight affordable?

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==> EELV-only plus propellant depots. The original Boeing CEV proposal (pre-Griffin) included L-point stations and fuel depots and heavy reliance on Delta IVH as NASA's new workhorse. Other variants include COTS players and Atlas V but call for termination of all shuttle derived launch components. Use the money saved from terminating everything associated with STS to fund depot technology development.

You don't need that much money to "fund depot technology development".  I'm pretty sure even Boeing or Lockheed could do a demonstration depot for less than the COTS budget.  If STS stuff was shut down to fund a depot-centric mission, most of that money would be going to lunar transfer vehicles and lunar landers (you know, actual exploration hardware, unlike Ares-I and Ares-V), not to developing depot technology.  If you're spending billions on depot tech dev, you're doing something wrong.

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==> The Direct 2.0 proposal asserts that using Jupiters rather than Ares saves sufficient money to keep shuttle derived launchers AND fund propellant depot development and deployment AND other cool ancillary projects as well.

It's quite possible.  You don't need to save much to be able to fund propellant depot development.  Even deployment, though I'm still a huge anti-fan of NASA directly contracting for a depot to be emplaced. 

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Therefore, even if we all agree that propellant depots  are a terrific idea, there remains plenty of disagreement concerning what percentage of focus and budget should be devoted to depots.

I think I'm one of the main proponents of depots, and I really don't think that need *that* much investment to bring to light.  A few H&RT sized development projects (most of those were in the $5-20M range) could prove out most of the remaining questions.  Toss in a few prizes like the Propellant Depot Challenge that the Centennial Challenges team had come up with but never got money for.  If you really want to pay someone to do a demo depot, do it like COTS, with a COTS-like budget.

Depots don't have to be an ISS-sized investment if done right.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 02:53 am
Doesn't the horizontal lander need more than one engine for landing?

(on top of my mind it does)

And, do you think NASA would like a lander with multiple engines?

Yeah, the horizontal lander has a decent number of redundant landing engines.  AIUI, it can actually lose several of them and still land safely.  Some of us actually like engine-out capability, instead of betting one's butt on a single engine that's never been used before the landing.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: sandrot on 01/16/2009 02:56 am
Yes, but with just one engine it's not impossible to escape a gloom fate through an abort... (kind of Apollo 10 LM test).
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/16/2009 02:57 am
With an NEP system, your vehicle hardware costs are going to be *very* high compared to a chemical propulsion system.  And you're not going to get many flights to amortize that cost over.  And the development costs are going to be very high.  Sure, the IMLEO is going to be lower, but that doesn't save you as much if launch costs go down.

Why aren't you going to get many flights? I'd love to see a VASIMR lunar tug, either solar or nuclear. Imagine how much more mass you could put on the moon with an electric propulsion tug, especially in combination with reusable landers and ISRU.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 01/16/2009 03:56 am
If you have a high ISP engine, you don't need a depot. If you don't have the engine, you need the depot.

But supposing you have the depot, would there be any reason not to use it? You can always use the extra launch mass saved for something useful.
_IF_ you have boosters large enough to haul up the propellant along with the rest of a Mars mission without a depot, then not using it means that you reduce mission risk through reducing the number of docking & prox ops. This isn't a small issue. If you can stay away from any particular operation, then it is very wise to do so for mission safety reasons.

It really is a dangerous place out there and eliminating mission complexity is a major way of decreasing your LOM numbers.

Don't get me wrong, I like the idea of depots & tugs and I think they are far more likely than not, but it is always wrong in space ops to do something just because you can instead of doing only those things you need to do. If having a depot of propellant for a high ISP engine is a sensible thing to do, then, by all means, do it. But if you can get all of your mssion hardware on the way to mars without a depot, and without developing a new bigger booster just for that job, then don't increase your mission payload just to develop a depot.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 01/16/2009 04:14 am
Why all the uncertainty over high-isp engines?

Well, as I said, think the majority of the problem with high ISP engines is whether they will be funded sufficiently to be developed enough to be used as engines on a long duration, interplanetary manned mission. We are a very, very, very long way away from having that technology today, no matter how much a new drive is based on any currently existing technology. We are even longer away from that day at the level of funding new drive techs are receiving right now.

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A SEP tug delivering spacecraft to high Earth orbit would slash an enormous amount off of the fuel bill for a Mars mission, certainly enough to make the necessity of depots questionable.
Sure, why not. Not enough is known about the specifics of any particular mission architecture right now to say that you absolutley will or will not need a depot. If you need one, you need one. If you don't, you don't. I do believe that the very low amounts of propellants for many high ISP engine types will mean that a depot is not required.

To be honest, as long as NASA is open to the concept and makes the best use of the potential for depots as required, then we'll see them where they are needed.

Certainly, when there are reusable shuttles between the Earth & the Moon, then depots of some sort will be absolutely required.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 01/16/2009 04:28 am
Sure, there are other possible benefits (shorter trip times, etc), but it's not clear that the IMLEO savings really actually equate out to net $$$ savings for an NEP system.
Absolutely true. It's all about the numbers. Let's face it, even the current NASA concepts for a Mars mission will require storing propellant in space until the entire vehicle can be filled prior to a launch. It is a depot, whether it has that name or not.

Still, for the near and medium future, where chemical boosters have limited launch capability and there is an opportunity to lift commodities for far less money than high value  payloads, depots make a huge amount of sense. Fuel in orbit and a way to transfer it is worth a lot of money. Lots.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 04:30 am
Yes, but with just one engine it's not impossible to escape a gloom fate through an abort... (kind of Apollo 10 LM test).

I'm more a fan of having a system that's robust enough to complete the mission instead of having to abort.  Also, what do you do on ascent if the engine fails?

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 04:57 am
A SEP tug delivering spacecraft to high Earth orbit would slash an enormous amount off of the fuel bill for a Mars mission, certainly enough to make the necessity of depots questionable.

But the question is, would it really be cheaper?  Sure it would save launch mass, but would it really save cost?  Especially for use in the earth-moon system, I think electric propulsion tugs make very little sense.  Do the math.  You have an electric tug.  Say it takes say 6 months to do a round trip (it's 9 to get to the moon and back, but HEO may be quicker).  With the amount of time you spend in the Van Allen belts, you'd be lucky to get 20 flights out of such a system.  The up-front development cost is huge (you're talking an ISS sized set of solar arrays, and a bigger electric engine than has ever flown by a longshot), and the cost for the stage is going to be much higher than for a chemical stage.  Sure, the chemical stage requires more launch mass per flight, but a) it's development cost will be much simpler, b) it spends less time in the van allen belts so you'll likely be able to get more uses out of it, and c) it can complete missions in only a week instead of 6 months, so you can fly 24x more frequently.

On a per mission basis, the chemical stage is going to have a much lower amortized development and hardware cost, but is going to require more launch mass.  It should be obvious though that there is a price point where launch costs have dropped enough where the higher launch costs are compensated for by the lower up-front and hardware costs.  And if you're doing any sort of lunar exploration and development program, you're going to provide enough demand to reach that price point very quickly.

Mass isn't necessarily cost.  And ultimately it's cost that matters.

Electric propulsion may make sense if launch costs don't ever change (they will), or if you're going much further than the Moon or maybe even Mars.  And I think that continuing to fund research into space nuclear power isn't a wasted development.  I just think you're spending too much time looking at engineering quantities, and not enough time looking at economic ones.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 05:14 am
If I understand correctly, the idea is to have a small RLV launching propellant and benefiting from high flight rate. Sounds good, until you realise that your beyond LEO plans tend to need larger single payloads too- specifically, Mars entry vehicles, which would then require a dedicated wide-body rocket to launch them. The 'Mars rocket' will suffer a dismally poor flight rate if it never gets to launch anything else, and will be so horrendously expensive to fund that it will be in constant risk of program cancellation.

You don't necessarily need a "wide body" rocket for launching mars landers.  There are many options ranging from "make the landers smaller and split the mission up into chunks", to "use a modified (VTVL) RLV upper stage as your lander", and many others.

And once again, Mars isn't the only thing in space, and Mars exploration is a long way off.  Depots make a lot more sense for the here and now, for lunar missions, and space commercialization.  You'll never see more than a few flags and footprints missions if you're relying on HLVs and NEPs.  That may be good enough for you, but to me that's a bloody waste.

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Well, I don't think they are a terrific idea. Space-based nuclear reactors, high isp propulsion and better atmospheric entry technologies will get us to Mars, and should be higher priority.  :P

I agree that better atmospheric reentry technology, space nuclear reactors, and high Isp propulsion are good, but you're going to need depots if you want to be able to do reusable space transportation.  And landers are going to be chemical propulsion for a long time.  Depots make a lot of sense for them too. 

Depots don't have to be big ISS-style mutli tens of billions of dollars debacles.  I just really don't see why you don't think having the capability to refuel and reuse spacecraft makes sense.  Are you just going to throw away that multi billion dollar NEP after every flight?  And you think that'll somehow be cheaper?  I don't get your logic.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 05:20 am
The depot would handle LOX and LH2. The high-isp propellant of choice is Xenon or some other inert gas. So you'd need a separate tank and different transfer technologies.

Depots will be designed to handle whatever fluids people want to buy.  If they want Xenon, they'll also store Xenon (btw, you do realize that a single flight of your NEP would use 1/4 of the yearly global supply of Xenon).  They may store it as a liquid and gasify it before transfer or they may store it as a gas.  Gas and storable propellant transfer are demonstrated technologies, and there's nothing incompatible with storing those at a LOX/LH2 propellant depot.

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Incidentally, on-orbit transfer of noble gas propellant would be desirable to get the most out of a SEP or NEP tug architecture. However, IMHO this will be a technique more akin to the current state of the art than to the proposed cryogenic transfer systems.

There's nothing about depots that says they can only be LOX/LH2 or that they can't hold multiple fluids.  And really, even with an electric propulsion architecture, you're going to need cryogens and/or storables in many locations, and being able to transfer and store those is going to be needed as well. 

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/16/2009 10:28 am
I just think you're spending too much time looking at engineering quantities, and not enough time looking at economic ones.

I agree on the importance of looking at economic variables. I do wonder what you think the various costs are going to be in the future. What do you think cost per kg to LEO will be? What do you think it will cost to develop a VASIMR tug like the one proposed by Ad Astra? Specifically one for cargo and for Earth-Moon use.

My own guess would be that around 2025 $1000/kg is possible for most consumables (not Xenon :-) ). I would expect valuable cargo and people to remain significantly more expensive than that, $3000 - $5000 / kg sounds optimistic to me. I have no idea how much it would cost to develop a VASIMR tug. I think the unit price is estimated to be in the hundreds of millions. I'm surprised to hear you think it will be incredibly expensive to develop. After all, it hardly has any moving parts, it only has to carry cargo, not crew and it only needs to deal with tiny forces. I think the main uncertainty lies in its economics, due to the high power requirements and the degradation of solar panels in the van Allen belts and due to the long round-trip times.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 01/16/2009 11:21 am
Ad Astra is testing the VX-200 VASIMR with Argon instead of Xenon so a SEP/NEP tug would have no problems with the availability of Xenon.

A depot in orbit around Mars could supply the return chemical fuel for the manned Mars transfer vehicle.  If the SEP is used to fill the Mars depot then a significant amount of chemical fuel will be saved.

A high ISP manned Mars vehicle may need a big electric thruster developing to get the trip down to 39 days but the tugs can use the thrusters currently being tested.  The trip will simply take something like 2 years.  The launch order and timing would have to be carefully planned.

A tug using thrusters, solar panels and arm that exist in 5 years is likely to cost the same to develop as a science probe.  After all it is just a big one.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/16/2009 02:39 pm
To conduct the Mars mission, you need to launch bulky payloads like Mars landers, which cannot be practically assembled after launch.

I think that's an assumption, not a fact.  I'll admit that I haven't focused as much time on Mars (mostly because we aren't going to be going there anytime soon), but I'd be surprised if there weren't some options for landers that didn't take an HLV if you can tank up the stage in orbit.  I remember lots of people saying you couldn't do good lunar landers without the bigger Ares V fairings, but there's plenty of good options for those, like the LM horizontal lander that would work fine.

~Jon
You don't necessarily need a "wide body" rocket for launching mars landers.  There are many options ranging from "make the landers smaller and split the mission up into chunks", to "use a modified (VTVL) RLV upper stage as your lander", and many others.

A Mars entry vehicle must have a large surface area relative to its mass, to ensure rapid decceleration. 'Tanking up' is just not an issue because a Mars entry vehicle is a big fluffy thing, mostly empty space. A descent-only payload may only weigh 10t yet still need a 10m PLF to fit it in.
A conventional heatshield is unsuitable for on-orbit assembly- imagine piecing together a shuttle orbiter on orbit and then trusting it to deliver a crew safely home.
There are potential ways around this- inflatable or rigid deployable structures, or potentially some form of biconic lifting design. All of these represent a compromise over a standard rigid system because they add mass, complexity, risk, and an awful lot of development cost.
Splitting up the surface elements also helps greatly, but can only be taken so far. Economies of scale work against multiple smaller payloads, and some things, like the ascent vehicle, cannot be broken down below a certain size limit. It would be unwise for the crew's safe return to be dependent on them assembling their ascent vehicle when they arrive.

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Mars isn't the only thing in space, and Mars exploration is a long way off.  Depots make a lot more sense for the here and now, for lunar missions, and space commercialization.  You'll never see more than a few flags and footprints missions if you're relying on HLVs and NEPs.  That may be good enough for you, but to me that's a bloody waste.
Yes, the moon is closer, but the whole reason I started posting on this thread was in response to a widespread belief by many people that depots are an enabler for Mars missions. I contend that they are not. In fact, they are probably more use to a lunar program which can feasibly be all-cryogenic.

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I agree that better atmospheric reentry technology, space nuclear reactors, and high Isp propulsion are good, but you're going to need depots if you want to be able to do reusable space transportation.  And landers are going to be chemical propulsion for a long time.  Depots make a lot of sense for them too. 
Are you confusing propellant transfers with propellant depots? I agree that propellant transfer is necessary. Fortunately, it is also a decades-old technology, in use since Salyut.
I presume you are referring to lunar landers there. Mars landers will work best with ISRU, no depots required. Reuse of Mars landers is a very long term prospect.

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Depots don't have to be big ISS-style mutli tens of billions of dollars debacles.  I just really don't see why you don't think having the capability to refuel and reuse spacecraft makes sense.  Are you just going to throw away that multi billion dollar NEP after every flight?  And you think that'll somehow be cheaper?  I don't get your logic.

~Jon

No, of course I don't propose throwing away the NEP craft. But again, I think you are lumping propellant transfer in with depots, and they are not the same thing. A NEP tug can easily be refuelled by a single EELV-class launch, tanking up the tug directly, no depot required. In my mind this is no different to an ATV refuelling the ISS.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/16/2009 02:56 pm
There are potential ways around this- inflatable or rigid deployable structures, or potentially some form of biconic lifting design. All of these represent a compromise over a standard rigid system because they add mass, complexity, risk, and an awful lot of development cost.

I was going to ask about lifting reentries.  So the trick is that since the Martian atmosphere is so thin, you want a low ballistic coefficient so you can slow down fast enough to not auger-in.  Lift would seem to be a good way to spread that decelleration out over a longer period of time. 

And remember, you're also proposing technologies (NEP) that add lots of complexity, risk, and development cost.  Going to Mars near-term is going to entail risk cost and complexity however you go about it, the question is which approach gives you the best balance of risk vs. reward.

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Yes, the moon is closer, but the whole reason I started posting on this thread was in response to a widespread belief by many people that depots are an enabler for Mars missions. I contend that they are not. In fact, they are probably more use to a lunar program which can feasibly be all-cryogenic.

My point was that since if we build depots for the moon, they'll be there by the time we do a martian program, so finding ways to leverage that technology makes sense.  With depot infrastructure, the cost of launch to orbit for propellant is probably not going to be anywhere near as high as it is today, which means we need to be careful about economic assumptions in the future.

It should also be remembered that a "cryogenic depot" is going to also store things like hypergols for RCS systems, and helium for pressurization systems.  So storing other gasses for electric propulsion systems won't be a big stretch.  And also remember that a big part of the mass you'll need for a Mars program is going to be the landing and ascent mass--especially if you want to eventually go with reusable landers.  And those will want a small depot in Martian orbit.  Can't use electric propulsion for a lander after all.

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Are you confusing propellant transfers with propellant depots? I agree that propellant transfer is necessary. Fortunately, it is also a decades-old technology, in use since Salyut.

It depends.  If your tanker vehicles are much smaller than the tank capacity, using a depot as an intermediary makes sense.  Less rendezvous and docking events with your more fragile transport vehicle.  No need for the propellant to be delivered directly to HEO or L1/L2 or wherever you're going from.  You drop it off at a depot in LEO, then once there's enough you send a freight delivery to your assembly facility/depot in HEO.

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I presume you are referring to lunar landers there. Mars landers will work best with ISRU, no depots required. Reuse of Mars landers is a very long term prospect.

Mars landers work best with ISRU *and* depots.  You refuel on both ends.  Ie you ship up propellant on some propellant flights (or get them locally from Phobos/Deimos if possible) to a small depot, and tank them up with landing propellants before going down, and then retank them on the surface.  That maximizes your payload both ways.

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No, of course I don't propose throwing away the NEP craft. But again, I think you are lumping propellant transfer in with depots, and they are not the same thing. A NEP tug can easily be refuelled by a single EELV-class launch, tanking up the tug directly, no depot required. In my mind this is no different to an ATV refuelling the ISS.

By the time we go to mars, I don't think EELV sized missions will be the cheapest for launching consumables like propellant.  And your landers need propellant too.  I think you have some preconceived ideas about what depots need to be, but there's actually a lot of flexibility.  And they can/should be collocated with facilities for assembling bigger missions, doing maintenance/repairs, etc.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Will on 01/16/2009 03:05 pm
Here's a thought. Launch a prototype on an Ares I test flight, with launch cost coming out of the Constellation budget. Get some more early Ares flight experience without putting a crew at risk.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 01/16/2009 03:17 pm
Jon,

Another approach is to be aggressive about lunar ISRU LOX extraction. If there are easily harvested cold traps, well then, good -- but even if there are not any easily harvested cold traps, LOX can be collected from lunar regolith pretty much globally.

Once lunar LOX comes on-line (even if fuel sources such as ISRU H2 remain elusive) a single stage reusable lander can shuttle between the surface (where it fully loads LOX) and an orbiting transfer station (LLO or EML 1 & 2) where it fills up with fuel (H2, CH4, RP-1).

Land with partial LOX tanks and lift off with partial fuel tanks.

The larger viability of lunar ISRU LOX however does depend on launch costs from Earth. While I find it hard to imagine it ever being cheaper to ship LOX from Earth to the lunar surface rather than developing ISRU, no matter inexpensive RLV technology can potentially become, RLV prices do impact the source of LOX for LEO depots and lunar orbit depots.

But to merge this thread with comments made by NSF poster "vanilla" in other threads, if lunar LOX were sent to LEO and tethers were used to decelerate the incoming canisters of LOX, that same kinetic energy captured by the tethers could be sold as delta v to outbound cargo payloads, adding another revenue stream to the lunar LOX operation.

Whether that is worthwhile depends on where we predict RLV launch costs will end up and is it prudent to "bet the farm" on such predictions?


Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/16/2009 03:22 pm
I was going to ask about lifting reentries.  So the trick is that since the Martian atmosphere is so thin, you want a low ballistic coefficient so you can slow down fast enough to not auger-in.  Lift would seem to be a good way to spread that decelleration out over a longer period of time. 

And remember, you're also proposing technologies (NEP) that add lots of complexity, risk, and development cost.  Going to Mars near-term is going to entail risk cost and complexity however you go about it, the question is which approach gives you the best balance of risk vs. reward.
Mars entry will be the riskiest single point of the mission, so the 'risk' is of a different sort to a TMI propulsion system failure, where you have time and multiple abort options. I really like the idea of keeping the entry vehicle quite simple- ballistic entry, no rotation before landing, favourable payload fraction, heritage from existing systems.
NEP may be able to share costs with development of Martian surface nuclear power which will be needed for ISRU. A high-tech lifting Mars entry vehicle cannot share that technology with anything else.

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My point was that since if we build depots for the moon, they'll be there by the time we do a martian program, so finding ways to leverage that technology makes sense.  With depot infrastructure, the cost of launch to orbit for propellant is probably not going to be anywhere near as high as it is today, which means we need to be careful about economic assumptions in the future.
And my point is that I see people arguing whether the lunar program should or shouldn't use depots, with some saying that 'we will need depots for Mars anyway, so lets develop them for the moon'. If they are available, then consider them, but don't use Mars as a justification.

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a big part of the mass you'll need for a Mars program is going to be the landing and ascent mass
No, it isn't. My BOTE mission plan involves an IMLEO of 186t, of which about 3t is the descent propellant for the four landers. Ascent propellant is ISRU, with a feedstock of about 700kg of H2. Zubrin's numbers are similar but he had a bigger feedstock because his ERV was far larger.
This comparativley miniscule amount of fuel is best loaded aboard each vehicle before launch, so that the entry system can be sealed up.

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--especially if you want to eventually go with reusable landers.  And those will want a small depot in Martian orbit.  Can't use electric propulsion for a lander after all.
A reusable Mars lander is an RLV on another planet. I consider it to fall on the virge of sci-fi, and not something that we need to worry about for a long, long time. If and when an outpost is established, a second generation ascent vehicle utilising an off-board ISRU plant could prove cheap enough that the RLV lander wouldn't be needed. The first generation ascent vehicle, with onboard ISRU, will of course be expensive.

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It depends.  If your tanker vehicles are much smaller than the tank capacity, using a depot as an intermediary makes sense.  Less rendezvous and docking events with your more fragile transport vehicle.
Again based on my BOTE plan, the total propellant mass is 30t. Since a 50t launcher (J120) is needed for the other payloads, this can be launched in one shot for loading directly aboard the tug.
If propellant is being launched in smaller packages, then we clearly aren't going to Mars since we will have nothing to launch the landers with.

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Mars landers work best with ISRU *and* depots.  You refuel on both ends.  Ie you ship up propellant on some propellant flights (or get them locally from Phobos/Deimos if possible) to a small depot, and tank them up with landing propellants before going down, and then retank them on the surface.  That maximizes your payload both ways.
Sci-fi timescales though. In the near-term (or as near as we can contemplate with Mars in mind) I'd propose a pre-loaded lander, with it's very small mass of hypergolic propellants already aboard, and ISRU for ascent, without reuse. If the ISRU plant, and its power supply, can be reused most of the cost of the lander can be avoided.

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By the time we go to mars, I don't think EELV sized missions will be the cheapest for launching consumables like propellant.  And your landers need propellant too.  I think you have some preconceived ideas about what depots need to be, but there's actually a lot of flexibility.  And they can/should be collocated with facilities for assembling bigger missions, doing maintenance/repairs, etc.

~Jon

I think we both suffer from preconceived ideas!
By the time we go Mars, sure there may be cheaper LVs than EELV-sized. But these smaller vehicles might have prevented the development of a larger LV, and without that Mars goes from very difficult to nigh impossible.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/21/2009 08:28 am
I came across this link the other day:

http://spacecraft.ssl.umd.edu/design_lib/OASISEXEC_97.pdf

It discusses some old NASA sponsored ideas for orbital infrastructure, including simple depots / fuel transfer.
Title: Re: Propellant Depots - General Discussion
Post by: khallow on 01/25/2009 04:31 am

I think we both suffer from preconceived ideas!
By the time we go Mars, sure there may be cheaper LVs than EELV-sized. But these smaller vehicles might have prevented the development of a larger LV, and without that Mars goes from very difficult to nigh impossible.

I'm not sure what you are trying to say here. The "cheaper LVs" are going to be cheaper per kg than the "larger LV". So starting with a more affordable lift capacity to LEO isn't a step towards "nigh impossible". Moving on, there's been a decades long trend among commercial launch vehicles to larger vehicles. All four launch providers (ULA's two branches, Orbital, SpaceX) in the US are moving to larger vehicles now.

In that light, it doesn't make sense to me to think that commercial vehicles are going to top out at 25 tons to LEO, unless of course, NASA or other government agencies block private industry from developing vehicles past that cap. If there is an active propellant depot system in orbit, that will provide incentives to develope larger vehicles as well.

At some point, NASA needs to rely on US launch capabilities rather than maintain a rival launch infrastructure. The development of things like an orbital propellant depots aid that process by reducing the reliance on a particular launch vehicle and guaranteeing the market for commercial launch vehicles.

Once you consider using commercial launch vehicles, it then makes sense to ask what will the capabilities of the commercial launch market be by the time you want to go to the Moon or Mars? Are we still going to have merely EELV-class launch vehicles? Or with encouragement from NASA can we grow them to say 50 or even 100 ton lift capacity? Recall that we probably aren't going to have manned lunar missions before 2020 or manned martian missions before 2030. That's plenty of time to grow private launch infrastructure to meet the US government's (including NASA's) needs.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/25/2009 12:49 pm
... starting with a more affordable lift capacity to LEO isn't a step towards "nigh impossible"...

The justification for HLLV is that it avoids the need for PDs and on-orbit assembly. If you choose to incorporate those options though, the case for HLLV is weakened and certainly for lunar missions goes away entirely. That leaves Mars missions without a key essential piece of hardware.

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If there is an active propellant depot system in orbit, that will provide incentives to develope larger vehicles as well.
Surely it does the opposite? If launching things in big chunks was the way to go, you'd just fuel up on Earth and launch in one go. PDs are supposedly sensible because they provie a market for smaller vehicles, perhaps even an RLV, which can benefit from high flight rates.

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Once you consider using commercial launch vehicles, it then makes sense to ask what will the capabilities of the commercial launch market be by the time you want to go to the Moon or Mars? Are we still going to have merely EELV-class launch vehicles? Or with encouragement from NASA can we grow them to say 50 or even 100 ton lift capacity?
At the moment, the commercial (GEO) market seems to support a small number of launches in the 15-20,000kg LEO-equivalent class. The DIVH only flies on government missions- there are no comsats that big. With increasing reliance on surface data transmission networks (e.g. fibre optic) plus miniaturisation of components, I don't know if we can expect commercial sattelites to grow much in size.
That leaves it up to NASA to push forward the size of LVs. However, a PD is exactly the wrong way to do that. It would encourage commercial companies to simply fly their comsat-sized launcher more often, giving better reliability and costs, to fill up the depot in a series of flights. That's kind of the point of a PD, isn't it?
The only way that NASA could directly instigate the building of large commercial LVs would be to specify their requirements precisely. Probably a smart move, of course, since the commercial sector can likely produce a vehcle cheaper than NASA can in-house. But it's going in the oposite direction for propellant depots.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/25/2009 01:18 pm
The justification for HLLV is that it avoids the need for PDs and on-orbit assembly. If you choose to incorporate those options though, the case for HLLV is weakened and certainly for lunar missions goes away entirely.

Probably. On the other hand, having a HLV makes it easier to deploy orbital infrastructure. Perhaps even cheaper. Does anyone know how much cheaper you could make things like ISS modules if you had much bigger mass budgets?
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 01/25/2009 02:48 pm
. Does anyone know how much cheaper you could make things like ISS modules if you had much bigger mass budgets?

They would be more expensive.
Title: Re: Propellant Depots - General Discussion
Post by: khallow on 01/25/2009 04:03 pm
If there is an active propellant depot system in orbit, that will provide incentives to develope larger vehicles as well.
Surely it does the opposite? If launching things in big chunks was the way to go, you'd just fuel up on Earth and launch in one go. PDs are supposedly sensible because they provie a market for smaller vehicles, perhaps even an RLV, which can benefit from high flight rates.

There are economies of scale from a larger launch vehicle. I don't consider it as significant as higher launch rates in terms of driving down cost per kg. But once EELV-class launchers are heavily used, it'll provide incentives to build larger vehicles.

Moving on, I consider small, well-used, frequently  launched RLVs more important to space development than large, poorly-used HLVs. My take is cost to orbit is more important to overall cost of a mission than activity in orbit. Cheap launch infrastructure means all space activities including orbital assembly and manufacture are relatively cheap, while expensive launch infrastructure means space activities will be expensive, even if great effort is made to minimize the non-essential activity in space.

It is worth repeating that we don't need an HLV. As has been noted in these forums before, the largest indivisible payload that we know we'll need for a manned Martian expedition currently is the human body. The larger fairing size and lift capacity of an HLV could be convenient and valuable in that it replaces considerable expense in the form of additional orbital assembly, docking events, and even manufacture. But it is not necessary. We have alternate routes to constructing large structures in space.

These capabilities, orbital propellant depots and orbital assembly are going to be necessary down the road anyway, whether we go with a cheap launch infrastructure or not.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/25/2009 04:14 pm
. Does anyone know how much cheaper you could make things like ISS modules if you had much bigger mass budgets?

They would be more expensive.

Why is that?
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/25/2009 05:26 pm
It is worth repeating that we don't need an HLV. As has been noted in these forums before, the largest indivisible payload that we know we'll need for a manned Martian expedition currently is the human body. The larger fairing size and lift capacity of an HLV could be convenient and valuable in that it replaces considerable expense in the form of additional orbital assembly, docking events, and even manufacture. But it is not necessary. We have alternate routes to constructing large structures in space.

Where was that noted?
You could use the same argument for LEO activities. Assemble you space shuttle orbiter once you're up there.
There is a trade-off between the cost of HLV development and the cost and risks of developing other means of getting to Mars. IMHO, a HLV is a damn sight easier, cheaper, and safer than whatever orbital assembly inflatable modular lifting body Mars entry vehicle might be necessary if we don't have access to a HLV.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 01/25/2009 08:48 pm
The most expensive part of any mission is the spacecraft itself, not the launch vehicle. One of the things that drives the cost of the spacecraft up, and sometimes high enough to trigger cancellation, is the expense and complexity of trying to fit the mission needs on the existing launch vehicles. It's like asking a Volkswagen to move a baby grand piano across town. Sure it can be done. With some modularization and clever packaging  plus some expensive off-site reconstruction at the end destination, it is certainly doable. But it's much easier to wrap it in bubble wrap and ship it on a truck, just once. Just don't plan on using the truck for the family car. Use the Volkswagen for that and save the less often used truck for the pianos.

Why are so many people so convinced that we do not need heavy lift and some say we do not need light lift? Both points of view ignore real life, where both are needed, in appropriate usages.
Title: Re: Propellant Depots - General Discussion
Post by: Khadgars on 01/25/2009 10:00 pm
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Why are so many people so convinced that we do not need heavy lift and some say we do not need light lift? Both points of view ignore real life, where both are needed, in appropriate usages.


I have too totally agree and that's what makes DIRECT so attractive.  With some modifications to Ares it could be done as well.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 01/25/2009 10:52 pm
Again based on my BOTE plan, the total propellant mass is 30t. Since a 50t launcher (J120) is needed for the other payloads, this can be launched in one shot for loading directly aboard the tug.
If propellant is being launched in smaller packages, then we clearly aren't going to Mars since we will have nothing to launch the landers with.

We may be using small launch vehicles to lift the propellant because all the big LV we can make are being used to lift wide heavy things like landers, rovers and transfer vehicles.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/26/2009 10:32 am
We may be using small launch vehicles to lift the propellant because all the big LV we can make are being used to lift wide heavy things like landers, rovers and transfer vehicles.

It seems unlikely. If the propellant is only 15-30% of the total IMLEO, it wouldn't seem to justify the additional docking operations. Certainly, it is far removed from the notion that depots are an 'enabler' for Mars missions.

Such a situation could happen if, say, the IMLEO fell into awkwardly sized chunks and the propellant just happened to equate to a single smaller LV launch. Fine. Or if the mission is international and one partner wanted to launch the propellant on their own EELV-class LV. But these situations are just kludges and compromises, and not arguments for the development of a depot.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 01/26/2009 10:35 am
If the propellant is only 15-30% of the total IMLEO

Just FYI:   For Lunar missions the TLI Propellant load alone is more like 55% of IMLEO.   LOI+Descent represents another 20% or so.   Add Ascent and TEI propellants as well and you're talking over 90% of IMLEO is Propellant.

It's an even larger portion for TMI, more like 65%.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/26/2009 10:58 am
If the propellant is only 15-30% of the total IMLEO

Just FYI:   For Lunar missions the TLI Propellant load alone is more like 55% of IMLEO.   LOI+Descent represents another 20% or so.   Add Ascent and TEI propellants as well and you're talking over 90% of IMLEO is Propellant.

It's an even larger portion for TMI, more like 65%.

Ross.

The 15-30% number relates to a BOTE plan I drew up using 4000s ion thrusters as the main propulsion system. The lower range would be for non-reuse of the MTV, the higher number for a reusable architecture.
Title: Re: Propellant Depots - General Discussion
Post by: William Barton on 01/26/2009 11:24 am
How do propellant depot development and EELV-class launch operations compare, hypothetically speaking, of course, to HLLV development/operations cost? Depot always seems like the best idea, in the long run, but I have to ask myself, is it really? There's some disconnect between cost estimates in various places, and I don't have a good way of evaluating various estimates. It's like the K-1 development budget, with estimates running from $1bln to $10bln, and Kistler itself always seeming to say something like $300mln. How much would it cost to develop and operate a 500mT LV, for example?
Title: Re: Propellant Depots - General Discussion
Post by: khallow on 01/26/2009 11:59 am
It is worth repeating that we don't need an HLV. As has been noted in these forums before, the largest indivisible payload that we know we'll need for a manned Martian expedition currently is the human body. The larger fairing size and lift capacity of an HLV could be convenient and valuable in that it replaces considerable expense in the form of additional orbital assembly, docking events, and even manufacture. But it is not necessary. We have alternate routes to constructing large structures in space.

Where was that noted?

Can't locate a good reference. But it is noted now. This thread (http://"http://forum.nasaspaceflight.com/index.php?topic=13055.0") discusses similar issues though there, the largest indivisible pieces considered are 20-30 metric tons.

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You could use the same argument for LEO activities. Assemble you space shuttle orbiter once you're up there.

What would be the point of assembling in orbit a large vehicle whose sole purpose is to reenter and land on an air strip? Might as well give each vehicle the capability to land on its own and eliminate the assembly step.

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There is a trade-off between the cost of HLV development and the cost and risks of developing other means of getting to Mars. IMHO, a HLV is a damn sight easier, cheaper, and safer than whatever orbital assembly inflatable modular lifting body Mars entry vehicle might be necessary if we don't have access to a HLV.

The trade off is between HLV capability and mission complexity. A mission that requires little assembly (just some automated docking) is going to be simpler than something dependent on a large number of relatively small launches. Still I think cheaper launch costs to LEO will be the greatest influence on the overall cost of a mission and will be more important than the higher cost and risk due to increased complexity of the mission.

We also have that the combination of propellant depots, orbital assembly, and other tricks like inflatables means that mission setup is much more scalable and reliable than for an HLV. For example, once you have the techniques for snapping together a 500 ton (fueled) vehicle supplied by an EELV-class launcher, that's a lot easier to scale up to assembly and fueling of 5,000 ton vehicles than a HLV infrastructure that doesn't have this orbital infrastructure.

Further, the mission isn't dependent on a single vehicle. There would be at least two launch vehicles and perhaps up to six (Delta IV Heavy, Atlas V Heavy, Ariane 5, Falcon 9 Heavy, Angara, and Chenzhou 5) to chose from.
Title: Re: Propellant Depots - General Discussion
Post by: khallow on 01/26/2009 12:18 pm

Why are so many people so convinced that we do not need heavy lift and some say we do not need light lift? Both points of view ignore real life, where both are needed, in appropriate usages.

I have to disagree. We don't need either. I don't mean that we don't need to go to Mars. Rather that I see three doable options (using the general choices mentioned above):

1. Heavy lift only.
2. Light lift only.
3. Both.

Chosing to use a platform requires some commitment from someone, that is, fixed costs. We can't just decide to use one HLV every two years and expect the costs to be 5% of using the same HLV ten times a year. My take is that the Ares V launch frequency of three times a year just doesn't make the cut. Especially if the Ares I is discontinued. DIRECT has higher launch frequency so I like it better.

In any case, committing to using both light and heavy lift means trade offs. I don't see choice 3. being automatically better especially if bad choices are made for launch vehicles.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 01/26/2009 12:23 pm
How do propellant depot development and EELV-class launch operations compare, hypothetically speaking, of course, to HLLV development/operations cost? Depot always seems like the best idea, in the long run, but I have to ask myself, is it really? There's some disconnect between cost estimates in various places, and I don't have a good way of evaluating various estimates. It's like the K-1 development budget, with estimates running from $1bln to $10bln, and Kistler itself always seeming to say something like $300mln. How much would it cost to develop and operate a 500mT LV, for example?

That's an awfully complex question to answer.

Development wise, an HLLV is significantly more expensive than using the existing EELV's.   Somewhere in the order of a billion dollars of expenditure is required to get one EELV fully prepared for NASA's human program -- more if NASA decides not to use the existing launch infrastructure.   Jupiter-120 will cost around $9.5bn, with Jupiter-232 an additional $4bn.   Ares-I will be roughly $14bn with Ares-V at least another $15bn more.   So if you measure it by up-front development dollars alone: EELV wins hands down.   This is why a scaled-back program which cancels the moon would most definitely put EELV in the driving seat.


Operationally, the fixed costs are pretty similar when comparing the smaller CLV systems -- all in the ballpark of ~$1bn per year including all of the various human-specific systems which need to be added such as the spacecraft recovery systems in the Eastern Test Range, the Atlantic Ocean and the Pacific Coast to name just one of the extra costs.   This cost figure assumes that both Jupiter-120 and Ares-I are being operated in conjunction with their respective 'partner' vehicles to share some of the overheads.

But when you include the CaLV the fixed costs are quite different.    EELV has no big partner vehicle, so there are no additional fixed costs for them.   Ares-I has a vast big brother which costs an addition $2.8bn to feed each year.   And Jupiter has additional fixed overheads of around $900m for its EDS.


The flight costs are another story again.   For ISS missions alone, the per-flight costs are fairly similar for all three systems.

But for Lunar missions the reverse of the development costs is the case.   An EELV-based mission launching a CxP-size mission (~210mT IMLEO) would require either 9 Delta-IV Heavy's or 1 DIVH plus 10 Atlas-V 551's.   That's over a billion dollars worth of launch vehicles there and the production and launch facilities both hit their maximum capacities supporting just a few Lunar missions each year, so there is no room for expansion in the future without replicating all of the fixed costs all over again.

Ares-I and Ares-V together would cost around $500m per mission so a ~$500m saving per mission is expected compared to EELV -- and this is the reason why Griffin, Hanley and Cook keep banging-on about how Ares will be cheaper than EELV.   Yes, it will be -- but ONLY if you ignore the extra $30+ billion you have to throw in the Ares pot at the very start!   By my calculations Ares will 'break even' against EELV after about 60 missions, which will take 15 years to achieve at the expected baseline mission rates.   So yeah, by 2036 Ares' lifecycle costs *will* be cheaper than EELV.   But that sounds like a pretty silly argument to be making to me.   YMMV.

Two Jupiter-232's would also cost around $500m per mission.   Their break-even point is significantly sooner though, because they had less than half the up-front development costs.   The break-even point comes after 28 missions.   At CxP's baseline that would be after 7 years -- 2024 or thereabouts.   But DIRECT is planning a significantly higher baseline flight rate than CxP suggests -- with 6-8 missions each year.   Splitting the difference and assuming 7 missions per year, the break-even point comes in just 4 operational years compared to EELV.


So the question really comes down to:

1) Are you willing to pay low up-front costs, medium up-front costs or high up-front costs?

2) How is that to balance against the respective *LONG TERM* High Operational costs, Medium Operational Costs or Low Operational costs?

3) Which of those two questions is the most important?   In other words, is the break-even point the primary driving factor in determining how much you're willing to spend now in order to create the long-term Vision?

4) What do you intend to do about Mars?

When you chart it all together (including 1 Mars mission every 2 years starting 2031), accounting for all the various costs and things like economies of scale and factor in the Orion and Altair as well, the charts below are what you end up with as Total Constellation Program Cost Sandcharts  for each of the three solutions flying the exact same number of Baseline missions...

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/26/2009 12:25 pm
the largest indivisible pieces considered are 20-30 metric tons.
Oh, I'd go considerably lower than that :P
Smallest indivisible component is a dry ascent stage at about 4t. But it needs to have an ISRU plant and H2 feedstock onboard, and preferably an onboard power source. Then it needs to have a descent stage to deliver it to the ground. You're probably talking 10t by this point. This whole kaboodle needs to be packaged into an entry vehicle with heatshield, backshell, parachutes, and RCS, which will get you up to about 20t (or more).
A 20t entry vehicle needs a heatshield area of about 133m2- i.e. about 13m diameter. That's never going to fit onto an EELV.
At launch, it will also need a bus module to provide in-space power, control, and a docking point, taking you up to around 25t.

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What would be the point of assembling in orbit a large vehicle whose sole purpose is to reenter and land on an air strip? Might as well give each vehicle the capability to land on its own and eliminate the assembly step.
It was an illustration of the limits of on-orbit assembly. I believe that the only way to get to Mars will be with multiple entry vehicles and surface rendezvous. However you can't go too far down that route and have dozens of Viking-sized payloads all landing individually- it's just ridiculous. Yet that is what EELV architectures would require (without much development in new entry vehicles).

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The trade off is between HLV capability and mission complexity. A mission that requires little assembly (just some automated docking) is going to be simpler than something dependent on a large number of relatively small launches.
Yes, I agree. But there is a tipping point: if the LV is not big enough to allow a single-piece heatshield (i.e. 13m payload capacity as in the above example) then you are well past the point of 'simple' orbital assembly operations like dockings or propellant transfer. IMHO the complexity of having to assemble the heatshields after launch is a step too far.

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Still I think cheaper launch costs to LEO will be the greatest influence on the overall cost of a mission and will be more important than the higher cost and risk due to increased complexity of the mission.
I doubt it. The payloads will be the most expensive element of a manned Mars mission. This is true today for most payloads anyway.

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We also have that the combination of propellant depots, orbital assembly, and other tricks like inflatables means that mission setup is much more scalable and reliable than for an HLV. For example, once you have the techniques for snapping together a 500 ton (fueled) vehicle supplied by an EELV-class launcher, that's a lot easier to scale up to assembly and fueling of 5,000 ton vehicles than a HLV infrastructure that doesn't have this orbital infrastructure.
The EELV-class launcher simply doesn't have the PLF size to get us to Mars. End of story.
Title: Re: Propellant Depots - General Discussion
Post by: khallow on 01/26/2009 12:26 pm
How do propellant depot development and EELV-class launch operations compare, hypothetically speaking, of course, to HLLV development/operations cost? Depot always seems like the best idea, in the long run, but I have to ask myself, is it really? There's some disconnect between cost estimates in various places, and I don't have a good way of evaluating various estimates. It's like the K-1 development budget, with estimates running from $1bln to $10bln, and Kistler itself always seeming to say something like $300mln. How much would it cost to develop and operate a 500mT LV, for example?

What do you intend to do with it? If all you intend is a few sorties to Mars, then low fixed costs are likely to be more important than low marginal costs. That favors heavy lift vehicles with no orbital infrastructure. If you're running dozens of smallish missions a year (to Mars and elsewhere) perhaps with some private customers as well, then the orbital depot approach makes more sense.
Title: Re: Propellant Depots - General Discussion
Post by: khallow on 01/26/2009 12:56 pm
The trade off is between HLV capability and mission complexity. A mission that requires little assembly (just some automated docking) is going to be simpler than something dependent on a large number of relatively small launches.

Yes, I agree. But there is a tipping point: if the LV is not big enough to allow a single-piece heatshield (i.e. 13m payload capacity as in the above example) then you are well past the point of 'simple' orbital assembly operations like dockings or propellant transfer. IMHO the complexity of having to assemble the heatshields after launch is a step too far.

I absolutely disagree here. As I see it, there are heat shields (for example, Phenolic Impregnated Carbon Ablator or PICA composite) that can be assembled in orbit. For example, the 13 meter diameter heat shield could be sent up on an Atlas 5 (with 5.4 meter fairing) as 10-12 wedges plus some center pieces and glued together with an appropriate high temperature resin. Also, there are inflatable heat shield designs. These would not require a large fairing size.

Added:
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Still I think cheaper launch costs to LEO will be the greatest influence on the overall cost of a mission and will be more important than the higher cost and risk due to increased complexity of the mission.

I doubt it. The payloads will be the most expensive element of a manned Mars mission. This is true today for most payloads anyway.

That's not what I said. I said that launch costs are the greatest influence on overall cost of a mission. By this, I mean that for a mission of fixed capability, the overall cost of the mission will be roughly proportional to the cost of getting the mission into space. I believe for most activities, private or government, that there's an optimal trade off between the overall cost of the mission and the price per kg of getting that mission into orbit. The sweet spot appears to be around 13% (1 in 8) with launch cost share ranging from 10% to 20% for virtually every serious mission. Some very expensive satellites (eg, spy satellites) can have unusually low launch cost shares, but that wouldn't make sense for manned missions.

I've heard it referred to colloquially as payload impedance matching. The idea is that if you're too far off the sweet spot, then it's an indication that you can redesign the payload. If the launch costs are relatively too high, that means you can shave some mass (at increased cost) to squeeze more into your payload. If the launch costs are too low, then either you can reduce capability or spread the mission over more launches.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/26/2009 01:06 pm
The trade off is between HLV capability and mission complexity. A mission that requires little assembly (just some automated docking) is going to be simpler than something dependent on a large number of relatively small launches.

Yes, I agree. But there is a tipping point: if the LV is not big enough to allow a single-piece heatshield (i.e. 13m payload capacity as in the above example) then you are well past the point of 'simple' orbital assembly operations like dockings or propellant transfer. IMHO the complexity of having to assemble the heatshields after launch is a step too far.

I absolutely disagree here. As I see it, there are heat shields (for example, Phenolic Impregnated Carbon Ablator or PICA composite) that can be assembled in orbit. For example, the 13 meter diameter heat shield could be sent up on an Atlas 5 (with 5.4 meter fairing) as 10-12 wedges plus some center pieces and glued together with an appropriate high temperature resin. Also, there are inflatable heat shield designs. These would not require a large fairing size.


This raises a lot of issues.
EVAs for assembly? Assumed usage of a RMS, and if so, attached to what spacecraft and operated by whom?
Quality control for the work?
Confidence in the work? Do you entrust crews lives' to it?
Performance of the adhesive in the temperature environment of LEO? And in vaccum conditions?
What would the mass of the shield be compared to one built on Earth?
How much time and money would need to spent on this technology before it was mature enough?

Inflatables are somewhat closer to reality. However AFAIK they are only compatible with ballistic entries, which loses you some performance and more importantly prevents precision landings. Even inflatables are a barely-tested technology and how much will it cost to conduct tests in Mars atmopsheric conditions? They will also likely weigh more than a normal heatshield, and depending on MMOD or RCS plume requirements may have to be inflated after the spacecraft has performed its de-orbit burn- a phase of the mission in which there is no abort capability.
Title: Re: Propellant Depots - General Discussion
Post by: khallow on 01/26/2009 01:52 pm

This raises a lot of issues.
EVAs for assembly? Assumed usage of a RMS, and if so, attached to what spacecraft and operated by whom?
Quality control for the work?
Confidence in the work? Do you entrust crews lives' to it?
Performance of the adhesive in the temperature environment of LEO? And in vaccum conditions?
What would the mass of the shield be compared to one built on Earth?
How much time and money would need to spent on this technology before it was mature enough?

1. EVAs seem bad for an operation that is somewhat delicate and possibly time consuming. Probably a remote manipulator system (RMS) would be better. Could be operated from the ground.

2. Good question. The RMS could come with appropriate sensing tools (eg, microwave system for finding voids in the seams of the heat shield and repairing said voids with an appropriate tool).

3. Deorbit a large batch of them and check them on the ground. Also covers the next section about the performance of the adhesive.

4. Probably very close. Some mass can be saved by manufacturing the shield in one block. But I don't see the weight savings as being significant. The seams just don't contribute that much (I'm assuming the width of the seams would be at worst a few millimeters) to the overall volume of the heat shield, hence they can't contribute much to the mass.

5. Launch and assemble a few batches in orbit. Deorbit the finished heat shield and check its tolerances. Build up data.

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Inflatables are somewhat closer to reality. However AFAIK they are only compatible with ballistic entries, which loses you some performance and more importantly prevents precision landings. Even inflatables are a barely-tested technology and how much will it cost to conduct tests in Mars atmospheric conditions? They will also likely weigh more than a normal heatshield, and depending on MMOD or RCS plume requirements may have to be inflated after the spacecraft has performed its de-orbit burn- a phase of the mission in which there is no abort capability.

There's some serious trade offs here. I'm not clear on how these are less precise than other reentries since reentry at the point you are using the heatshield is uncontrolled either way. The inflatable heatshield may be deformable too in which case you'd have a crude control mechanism.
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 01/26/2009 02:24 pm
1. EVAs seem bad for an operation that is somewhat delicate and possibly time consuming. Probably a remote manipulator system (RMS) would be better. Could be operated from the ground.
But attached to what spacecraft?

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4. Probably very close. Some mass can be saved by manufacturing the shield in one block. But I don't see the weight savings as being significant. The seams just don't contribute that much (I'm assuming the width of the seams would be at worst a few millimeters) to the overall volume of the heat shield, hence they can't contribute much to the mass.
Intuition would tell me that at the very least you'd want some margin in the design to allow for errors in construction or to compensate for the inherently weaker fragmented shield design.
Actually that puts in mind another point- presumably both types of heatshield would need a framework behind them to distribute loads. The way in which this attaches to the shield material is critical as these point loads are potential spots for failure. Anyway, it's one more thing that would have to be assembled and checked on orbit.

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There's some serious trade offs here. I'm not clear on how these are less precise than other reentries since reentry at the point you are using the heatshield is uncontrolled either way. The inflatable heatshield may be deformable too in which case you'd have a crude control mechanism.

An inflatable heatshield is deformable, but only by the forces acting on it. If you try to 'bank' the craft (i.e. a lifting entry) the shield will just deform in response to the unbalanced forces. So the entry has to be ballistic, hence un-steerable, hence imprecise.
Title: Re: Propellant Depots - General Discussion
Post by: Will on 01/27/2009 03:14 pm
How do propellant depot development and EELV-class launch operations compare, hypothetically speaking, of course, to HLLV development/operations cost? Depot always seems like the best idea, in the long run, but I have to ask myself, is it really? There's some disconnect between cost estimates in various places, and I don't have a good way of evaluating various estimates. It's like the K-1 development budget, with estimates running from $1bln to $10bln, and Kistler itself always seeming to say something like $300mln. How much would it cost to develop and operate a 500mT LV, for example?

That's an awfully complex question to answer.

Development wise, an HLLV is significantly more expensive than using the existing EELV's.   Somewhere in the order of a billion dollars of expenditure is required to get one EELV fully prepared for NASA's human program -- more if NASA decides not to use the existing launch infrastructure.   Jupiter-120 will cost around $9.5bn, with Jupiter-232 an additional $4bn.   Ares-I will be roughly $14bn with Ares-V at least another $15bn more.   So if you measure it by up-front development dollars alone: EELV wins hands down.   This is why a scaled-back program which cancels the moon would most definitely put EELV in the driving seat.


Operationally, the fixed costs are pretty similar when comparing the smaller CLV systems -- all in the ballpark of ~$1bn per year including all of the various human-specific systems which need to be added such as the spacecraft recovery systems in the Eastern Test Range, the Atlantic Ocean and the Pacific Coast to name just one of the extra costs.   This cost figure assumes that both Jupiter-120 and Ares-I are being operated in conjunction with their respective 'partner' vehicles to share some of the overheads.

But when you include the CaLV the fixed costs are quite different.    EELV has no big partner vehicle, so there are no additional fixed costs for them.   Ares-I has a vast big brother which costs an addition $2.8bn to feed each year.   And Jupiter has additional fixed overheads of around $900m for its EDS.


The flight costs are another story again.   For ISS missions alone, the per-flight costs are fairly similar for all three systems.

But for Lunar missions the reverse of the development costs is the case.   An EELV-based mission launching a CxP-size mission (~210mT IMLEO) would require either 9 Delta-IV Heavy's or 1 DIVH plus 10 Atlas-V 551's.   That's over a billion dollars worth of launch vehicles there and the production and launch facilities both hit their maximum capacities supporting just a few Lunar missions each year, so there is no room for expansion in the future without replicating all of the fixed costs all over again.



It's important to remember that a propellant depot will have some additional costs. You'll need to develop the technology and you'll probably want a reusable tug as well.

You'll have some added operating costs: operating the depot, shipping up fuel for proximity operations, replacement tugs from time to time. I expect there will be some losses in propellant transfer, and you'll probably be using some propellant as reaction mass to settle the tanks for transfer.

This isn't necessarily a show stopper, but it is part of the tradeoff, and I don't know of anybody that has a really good estimate of what the cost of depot operations will be.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 01/27/2009 05:28 pm
This raises a lot of issues.
EVAs for assembly? Assumed usage of a RMS, and if so, attached to what spacecraft and operated by whom?
Quality control for the work?
Confidence in the work? Do you entrust crews lives' to it?
Performance of the adhesive in the temperature environment of LEO? And in vaccum conditions?
What would the mass of the shield be compared to one built on Earth?
How much time and money would need to spent on this technology before it was mature enough?

1. EVAs seem bad for an operation that is somewhat delicate and possibly time consuming. Probably a remote manipulator system (RMS) would be better. Could be operated from the ground.
I can tell you that such an RMS (probably a couple of arms to get the job done) would be exceedingly complex and expensive and, as was mentioned above, would need an acompanying spacecraft to anchor it all to while the assembly was taking place.

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2. Good question. The RMS could come with appropriate sensing tools (eg, microwave system for finding voids in the seams of the heat shield and repairing said voids with an appropriate tool).
I'm afraid you don't seem to appreciate the difficulties of doing proper bonding here on Earth, much less in space. Getting a good bond is paramount, making sure that there are no voids is the key and, if you have very narrow bondlines (well under 1mm and usually in the .1mm range), there will be no repairs. It's gotta be good, or it doesn't go.

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3. Deorbit a large batch of them and check them on the ground. Also covers the next section about the performance of the adhesive.
Have you any idea of the sort of process development program you are implying? Hundreds of millions of $ would be a conservative number. Possibly over a billion. At most, this is the sort of thing that would be built in as few sections as possible on earth and assembled as simply as possible in orbit. Manufacturing process development in orbit for a manned flight just isn't on. Not in my lifetime or mine and yours put together.
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4. Probably very close. Some mass can be saved by manufacturing the shield in one block. But I don't see the weight savings as being significant. The seams just don't contribute that much (I'm assuming the width of the seams would be at worst a few millimeters) to the overall volume of the heat shield, hence they can't contribute much to the mass.
The fact that you have more joints, and joints that you are not sure of without the development program, means that the rest of the support structure needs to be stronger/weightier to compensate.
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5. Launch and assemble a few batches in orbit. Deorbit the finished heat shield and check its tolerances. Build up data.
See process development costs, above.

Having some knowledge of bonding, machine design & robotic operations, I can tell you that this idea is a non-starter unless the program is forced into a corner at gunpoint. There are so many programmatic risks & potential schedule & budget black holes that it really is a non-starter.

If you need to build a big heatshield in space (and we probably will need to at some point) it must be in as few pieces as possible. Inflatables are much better and an inflatable that you catually inflate in earth orbit prior to the trip & then just use on landing is better still.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/27/2009 09:20 pm
Hi Chuck,

I don't know if what you wrote was in response to my question, but it does seem to answer it in part.

The most expensive part of any mission is the spacecraft itself, not the launch vehicle. One of the things that drives the cost of the spacecraft up, and sometimes high enough to trigger cancellation, is the expense and complexity of trying to fit the mission needs on the existing launch vehicles. It's like asking a Volkswagen to move a baby grand piano across town. Sure it can be done. With some modularization and clever packaging  plus some expensive off-site reconstruction at the end destination, it is certainly doable. But it's much easier to wrap it in bubble wrap and ship it on a truck, just once. Just don't plan on using the truck for the family car. Use the Volkswagen for that and save the less often used truck for the pianos.

There must be economies of scale too. I imagine the design cost of existing ISS modules was quite high, so building ten identical modules would be much less than ten times as expensive as designing and building a single one. Do you happen to know any numbers for the existing modules?

Suppose you didn't have to shave off every last ounce, how much cheaper could you make the design of a module? And by how much could you reduce the production cost of a single module? I imagine both savings would be substantial, but what do I know.

On a related note: suppose that, purely hypothetically, you had to design a self launching ISS module. I'm not saying that would be a good idea, I would just like to understand the trade-offs better. Wouldn't that be a whole lot simpler to design than a J-120? If you just used the 50mT payload of J-120 and put it all into making the "hull" (is that the right word?) nice and sturdy. Wouldn't that be Really Easy, comparatively speaking?
Title: Re: Propellant Depots - General Discussion
Post by: Phil-Space on 02/02/2009 12:36 am
One way to start using/benefiting from depots is through the lunar robotic program.  Even with development of Ares I & V, near term robotic missions are limited by the Atlas 552 (21 T LEO) and Delta HLV (26 T) performance capable of delivering a few tons to the lunar surface.  However, if at least the LO2 for the lander were provided in LEO, this limitation is largely mitigated.

In this scenario, the EELV launches the lander, payload and LH2.  In LEO the lander rendezvous with the LO2 depot and on loads enough LO2 to provide a 6:1 propellant ratio.  The lander then performs the TLI, LOI and Lunar descent burns.

If an Atlas 552 is used for launch, simplistically the numbers work out to:
Mpayload = 9,800 Kg
Mstage = 4,900 Kg
Mlh2 = 6,300 Kg
Mlo2 =  37,500 Kg  (provided by depot)

For the Delta HLV the payload mass goes up to 12 T.

I’m assuming an ISP of 460 sec and a slightly optimistic lander mass fraction of 0.9.

Being able to land 9 to 12 T of payload on the lunar surface using strictly existing EELV’s is huge.  This would provide extremely robust robotic exploration  Or even more importantly could start laying the foundation of a lunar base before the first Ares V launch and people once again return to the moon. 
Title: Re: Propellant Depots - General Discussion
Post by: khallow on 02/02/2009 11:44 am
tankmodeler, I don't feel qualified to argue your points. However, I think the bit about "proper bonding" is a bit of a red herring. It seems to me possible to build a heat shield that doesn't use any sort of bonding at all. Somehow "snap" it together. I won't bother past this very weak idea except to note that the mass budget is healthier with orbital assembly. Heavier heatshields aren't necessarily an unreasonable tradeoff for forgoing a heavy lift vehicle. So if an idea like this only works with a heavier heat shield, that doesn't mean it is less viable. Assembling a heavier heatshield in orbit (with the added constraints that puts on the rest of the mission) may still in the long run be cheaper than making a full sized one on the ground and lifting it with a heavy launch vehicle.

Further, and this is something I really need to dredge up in a new thread, perhaps we can disengage, for a price, fairing size from payload mass. After all, a heatshield just isn't that heavy, perhaps 5 tons or less, right? It could go up on a rocket, shaped somewhat worse than the Ares I. Modifying one of the EELVs for extremely large fairing sizes might be a viable option. Delta IV heavy looks promising. It has a large diameter anyway so increasing from 5 meters to over 13 meters isn't as bad a stretch. It also has a lower thrust to weight ratio so air resistance is less of an issue.

In our discussions on Lunar and Mars missions, there doesn't seem to be much need for large fairing sizes. The heatshield is the main bit of equipment that is hard to shrink. Other things like buildings, nuclear reactor radiators, and solar panels can be inflated, assembled, or unfolded with little loss of integrity.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 02/03/2009 05:01 am
tankmodeler, I don't feel qualified to argue your points. However, I think the bit about "proper bonding" is a bit of a red herring. It seems to me possible to build a heat shield that doesn't use any sort of bonding at all. Somehow "snap" it together.
Nothing in the aerospace business "snaps" together. Please don't take this the wrong way, but rather casual comments like this hide significant portions of what makes space travel really difficult to do. It is almost always much better to build unitary structures from a safety/structural integrity point of view. They are lighter, much lighter, which then ripples very positively throughout the rest of the program. Optimising things like structure & systems to make them both very light and very, very reliable is the real difficulty in working in space. Let's face it, if the heat shield isn't the most reliable thing it can be, you just better not go to Mars.   
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I won't bother past this very weak idea except to note that the mass budget is healthier with orbital assembly.
Only if we are working within a system that can launch dumb tankers for less than it currently can. Now, this should be true if you design your entire architecture to make this so, but it currently isn't. Launching fuel currently costs as much per pound as launching satellites and at that rate, it's better to launch the entire fuelled spacecraft & lessen on-orbit ops to simplify the mission & reduce mission & crew risks.

Please don't think that just because it sounds easy, that it really is either easy or the right thing to do. In space, that frequently isn't the case.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 02/04/2009 11:40 am
Launching fuel currently costs as much per pound as launching satellites ...
This isnt entirely true. There is quite a wide variation between pound-to-orbit launch costs around the world across different launcher families, and while ITAR and other constraints might dictate a domestic launcher or certain payload shroud, fuel could be launched with pretty much cheapest option available.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 02/04/2009 01:00 pm
Another cost is that of insurance.   It's a lot cheaper for a commercial operator to insure 20 tons of LOX/LH2 than it is to insure a $3bn spy satellite.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 02/04/2009 11:00 pm
While I was talking about the nominal way we currently design & operate launch vehicles being not esspecially different for low value payloads versus high value payloads, I agree with both of you. The differences in launch costs plus reduced or self-insured insurance costs are the current places where there is a wedge in the door for propellant depots. However, if you are already launching your hardware on the low cost launchers, I'm not sure the insurance cost alone is enough to pay for the establishment of a depot so that you can launch your expensive payload empty on a smaller launcher. I think that launch costs probably have to come down somethign like 40-60% from the cheapest available today for a commercial business case to close _and_ to entice satellite makers/operators to launch empty. I could well be very wrong, of course as I haven't seen or worked the numbers and I don't want to make the same error w.r.t. business matters that I decry in others regarding engineering matters.  :)

Paul
Title: Re: Propellant Depots - General Discussion
Post by: spacenut on 02/05/2009 03:30 pm
Why couldn't you just launch a propellant depot with equipment to seperate the hydrogen and oxygen and liquify it and pump it into a docking spacecraft.  Then to refuel the depot, just launch water on EELVs or such and pump it into the depot.  Water might freeze, but with the proper solar panels at the depot, could thaw, seperate and liquify the fuel.  Thus any cheap dumb booster could get water to the station.  Same with the moon.  Launch ice to the moon, let it crash and bury itself under the surface, have robotic equipment to go "mine" it thaw, seperate, and use the fuel at a nearby base. 
Title: Re: Propellant Depots - General Discussion
Post by: Kaputnik on 02/05/2009 07:49 pm
There was a thread already about crashing ice onto the moon. I think there are issues with it evaporating due to the heat of impact, or the sunlight getting to it.

I'm not sure that a LEO depot would gain an awful lot from the idea. You'd still have to develop the technology to liquefy and pump cryogenic fluids, only now you'd need a huge electrolysis system too.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/05/2009 08:56 pm
There was a thread already about crashing ice onto the moon. I think there are issues with it evaporating due to the heat of impact, or the sunlight getting to it.

I'm not sure that a LEO depot would gain an awful lot from the idea. You'd still have to develop the technology to liquefy and pump cryogenic fluids, only now you'd need a huge electrolysis system too.

And quite frankly, an electrolysis system is going to be even more of a pain in the neck than just storing hydrogen.  Now, instead of just having to provide enough energy to pump out what little heat manages to leak into the LH2 through all your insulation, you're having to chill and liquify the hydrogen...

The only time electrolysis of water would be better than just storing and shipping LH2 is if the water is available already in-situ.  If you have to ship it all the way from earth, you'd be better off shipping it as LOX and LH2.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/05/2009 10:21 pm
And quite frankly, an electrolysis system is going to be even more of a pain in the neck than just storing hydrogen.  Now, instead of just having to provide enough energy to pump out what little heat manages to leak into the LH2 through all your insulation, you're having to chill and liquify the hydrogen...

I've been wondering what the biggest problem with long term storage of cryogenic propellants in space is is. Cryogenic equipment has existed on earth for more than a century now (pioneered by Kamerlingh Onnes in my home town of Leiden :-) ). Is power the limiting factor? Or mass, mtbf, something else?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/06/2009 02:20 am
I've been wondering what the biggest problem with long term storage of cryogenic propellants in space is is. Cryogenic equipment has existed on earth for more than a century now (pioneered by Kamerlingh Onnes in my home town of Leiden :-) ). Is power the limiting factor? Or mass, mtbf, something else?

The big issue with cryogenic storage on-orbit is the fact that if you don't have something like gravity to force the propellant to assume a good configuration (liquid over the outlet, only gas near the vent valves), most tasks become a lot  harder, and a lot of our terrestrial experience ends up being less relevant.  So, you have two options:

1) Deal with the weirdness, and find out how to handle things like two-phased flows with uncontrolled propellant orientation.
2) Provide some other means of forcing the propellants to settle.

NASA so far has spent a lot of time focusing on option one.  It makes for much cooler science experiments, and you learn lots about weird phenomena.  But the second option (settled propellant handling) makes everything a lot easier.  This is more or less what all upper stages use to some extent or other, usually using occasional or continuous accelerations from small rockets to keep the liquid where you want it to be.  Once you have the propellant settled, you can use terrestrial cryo-handling techniques and technology.

I'm glossing over a lot of nuances, but that's the basic idea.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/06/2009 02:30 am
1) Deal with the weirdness, and find out how to handle things like two-phased flows with uncontrolled propellant orientation.
2) Provide some other means of forcing the propellants to settle.

OK, that's what I had understood.

You appeared (to me at least) to be suggesting power was a significant problem. Doing some googling leads me to believe that this is indeed somewhat of a problem, in that cooling efficiency goes down the further you go down on the temperature scale. In other words, you need more input power for a given cooling power at a lower temperature. Kind of makes sense.

This led me to a wild idea. What if we set up a really powerful orbital electrical power supply? Maybe nuclear, maybe enormous solar satellites in LEO, maybe power beaming from the surface or enormous solar satellites in GEO. This would be very expensive, but it would also enable a lot of things. So imagine you had lots and lots of power, would this help at all with orbital depots? Could you somehow trade increased power requirements for complexity elsewhere?
Title: Re: Propellant Depots - General Discussion
Post by: Patchouli on 02/06/2009 02:44 am
I think one very important piece of hardware for any propellant depot to work will be a good nuclear or solar electric tug.
It's needed to get your propellants to where they need to be without burning three times as much propellant as you're transporting.
This might be unpopular with some people but I favor storable propellants such as
hypergolics or N2O and propane.
I think high test hydrogen peroxide also could make a good storable oxidizer but it's not as safe as the other two.

As for the propellant settling problem in LEO just use gravity gradient designs or a tether.

Away from LEO spin the depot after the tanker docks even a 1/1000th of g should be enough.

Or if you going to just transport water forget the electrolysis ,cryogenic refrigeration and general weirdness of cryogenic liquids in microgravity and just use a nuclear steam rocket.
Title: Re: Propellant Depots - General Discussion
Post by: robertross on 02/07/2009 04:47 pm
I think one very important piece of hardware for any propellant depot to work will be a good nuclear or solar electric tug.
It's needed to get your propellants to where they need to be without burning three times as much propellant as you're transporting.
This might be unpopular with some people but I favor storable propellants such as
hypergolics or N2O and propane.
I think high test hydrogen peroxide also could make a good storable oxidizer but it's not as safe as the other two.

As for the propellant settling problem in LEO just use gravity gradient designs or a tether.

Away from LEO spin the depot after the tanker docks even a 1/1000th of g should be enough.


I think if we get over our fear of nuclear, it has many benefits for high-volume cryo applications. In terms of settling the propellants, if you remember the dumbell neblua (trying to think of an earth-based alternative) you have your main controls & hardware in the center, and the propellant tanks opposing one another from a central hub. You then spin-up the assembly to settle the propellants in the tanks, using your on-board propellant, drawing off (edit: the interior periphery) of the tanks for fluid handling. For docking, you reverse thrust to null the rotation, pump in the fluids, undock, and spin up again (or let the spacecraft match the rotation of the orbiting depot, which might be easier). In this scenario, the solar idea is questionable.

But I think solar could work just fine if you can find a way to strengthen the arrays & attachment mechanisms. The array size would have to be large enough to account for day/night transitions (assuming LEO).

EDIT: Hypergols are not safe either. Not only for their explosif nature, but their reactivity. If they escaped and contacted a sensitive area, it could be corrosive.
Title: Re: Propellant Depots - General Discussion
Post by: kch on 02/07/2009 05:31 pm

In terms of settling the propellants, if you remember the dumbell neblua (trying to think of an earth-based alternative) you have your main controls & hardware in the center, and the propellant tanks opposing one another from a central hub. You then spin-up the assembly to settle the propellants in the tanks, using your on-board propellant, drawing off (edit: the interior periphery) of the tanks for fluid handling. For docking, you reverse thrust to null the rotation, pump in the fluids, undock, and spin up again (or let the spacecraft match the rotation of the orbiting depot, which might be easier).


It might be useful to consider using CMGs in the central hub for the spin-up and de-spin -- seems like it would be cleaner, safer, and let you retain all your on-board propellants for customers.
Title: Re: Propellant Depots - General Discussion
Post by: Phil-Space on 02/07/2009 09:57 pm

In terms of settling the propellants, if you remember the dumbell neblua (trying to think of an earth-based alternative) you have your main controls & hardware in the center, and the propellant tanks opposing one another from a central hub. You then spin-up the assembly to settle the propellants in the tanks, using your on-board propellant, drawing off (edit: the interior periphery) of the tanks for fluid handling. For docking, you reverse thrust to null the rotation, pump in the fluids, undock, and spin up again (or let the spacecraft match the rotation of the orbiting depot, which might be easier).


It might be useful to consider using CMGs in the central hub for the spin-up and de-spin -- seems like it would be cleaner, safer, and let you retain all your on-board propellants for customers.


I don't see it necessary to stop the spin for docking.  At a revolution every few minutes for small depots and 10's of minutes for larger structures "spinning" rendezvous should not be an issue.  Still, I agree that one would want to include CMGs.
Title: Re: Propellant Depots - General Discussion
Post by: robertross on 02/07/2009 10:03 pm

It might be useful to consider using CMGs in the central hub for the spin-up and de-spin -- seems like it would be cleaner, safer, and let you retain all your on-board propellants for customers.


I don't see it necessary to stop the spin for docking.  At a revolution every few minutes for small depots and 10's of minutes for larger structures "spinning" rendezvous should not be an issue.  Still, I agree that one would want to include CMGs.

That's very true, for both responses. It never even dawned on me. Of course it raises interesting servicing issues for the CMG's, but I guess no different than any other piece of hardware on the PD. Having a dedicated robot arm for orbital repairs of itself (with parts brought up on a specific re-fuelling mission). So much complexity, best to keep it dumb and simple for a reasonably short lifespan. That's where having more than one has benefits.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/10/2009 07:37 pm
FYI,
I just wrote up an article about an orbital mechanics trick that removes one of the key drawbacks of using an LEO depot for lunar missions.  Basically, as vanilla pointed out previously on this site and others, using normal single-burn departures, an LEO depot restricts you to launch windows only every 7-14 days.  But I figured out an approach that gives you at least daily opportunities.  There is a small increase in delta-V (<400m/s) and flight time (<1 day) required.

http://selenianboondocks.com/2009/02/orbital-mechanics-tricksiness-to-increase-the-frequency-of-tli-opportunities-for-leo-depots/

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 02/10/2009 08:02 pm
Jon,
That's an excellent approach.

We've been working on something along those lines for our Depot architecture too, but at a higher apogee than GEO.   It's not a very simple problem :)

A ~400m/s penalty to get daily opportunities would be minor given the fact that the Depot explicitly allows you to fill your tanks to the desired capacity.   It is even more cost effective if you can make the architecture a 1-launch solution (with other nations paying to lift the propellant as their contribution to the effort).

We're currently trying to find some solutions where the plane change burn might possibly be combined with either one of the others -- but that's difficult.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: kfsorensen on 02/10/2009 08:16 pm
FYI,
I just wrote up an article about an orbital mechanics trick that removes one of the key drawbacks of using an LEO depot for lunar missions.  Basically, as vanilla pointed out previously on this site and others, using normal single-burn departures, an LEO depot restricts you to launch windows only every 7-14 days.  But I figured out an approach that gives you at least daily opportunities.  There is a small increase in delta-V (<400m/s) and flight time (<1 day) required.

http://selenianboondocks.com/2009/02/orbital-mechanics-tricksiness-to-increase-the-frequency-of-tli-opportunities-for-leo-depots/

~Jon
Jon, it's more complicated than that.  Your trick can be used to alter orbital inclination, but it doesn't alter the right ascension of the ascending node.  And it is a rather complex interplay of node and inclination that determines a lunar injection opportunity.  I wish it was one of those things that was easily explained in words (it would help if we were sitting together at a white board) but I don't think the scheme you've proposed would make much difference.

Your orbital plane and the Moon's orbital plane don't have to be coplanar for lunar injection.  What actually needs to happen is that the line of apsides of your transfer orbit is roughly collinear with the line formed by the intersection of your orbital plane and the Moon's.  You can do a trans-lunar injection from a polar orbit if you desire.  But your transfer orbit needs to fairly co-apsidal.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/03/2009 11:06 pm
As has been written previously a useful place for a propellant depot is in lunar orbit.  The depot can then sell fuel to cargo lunar landers and manned LSAM.  If the LSAM are launched and transported dry they can be lifted to LEO by 20 MT to 50 mT payload LV such as EELV, removing the need to wait for Ares V.

Using estimated figures from astronautix the manned LSAM uses 19 mT of propellant and the cargo lander up to 27 mT.  If the launch mass problems continue the depot may be able to supply the return propellant for the Orion capsule.
LSAM info
http://www.astronautix.com/craft/lsam.htm (http://www.astronautix.com/craft/lsam.htm)

If liquid hydrogen is transported to lunar orbit in a propellant depot, instead of a normal tank, zero boil off technology can be used to prevent all the hydrogen being boiled off.  A solar electric transfer vehicle can be used to drag the depot from LEO to say Earth Moon L2 and when it is empty take the depot back for refilling.  Similar tugs can carry the LSAM and cargo for the Moon's surface from LEO to L2.

The Wikipedia webpage for the VASIMR has been updated to mention a transfer vehicle able to pull 34 mT to low lunar orbit in 6 months.  The tug uses 8 mT of Argon.  The small depot can have a dry mass of 34 mT - 27 mT = 7 mT.  A heavier depot would take longer than 6 months to get to low lunar orbit or GEO.

VASIMR info
http://en.wikipedia.org/wiki/VASIMR (http://en.wikipedia.org/wiki/VASIMR)

Title: Re: Propellant Depots - General Discussion
Post by: DonEsteban on 03/04/2009 01:26 pm
LEO propellant depot is necessary - the only one reachable by small/simple/cheap means.

For Lunar activity, a depot at L1/L2 would be better. (It should also be easier to thermally shield for long-term storage - no large, warm Earth to deal with).

Wouldn't be better to use Solar Thermal rocket to bring liquid hydrogen from the LEO depot to L1?

You are already carrying your fuel, no need to refuel with argon.

You don't need to worry about repeated passing through Van Allen belts frying your solar arrays.

And you get higher thrust while still having very decent ISP - much shorter transfer times. Even when only transferring fuel, this makes the whole thing operationally simpler.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 03/04/2009 01:33 pm
As has been written previously a useful place for a propellant depot is in lunar orbit.  The depot can then sell fuel to cargo lunar landers and manned LSAM.  If the LSAM are launched and transported dry they can be lifted to LEO by 20 MT to 50 mT payload LV such as EELV, removing the need to wait for Ares V.


ludicrous

1.  LSAM's are not going to use a depot.  LSAM is a specific name for a specific NASA lunar lander that is part of the ESAS.  It is not a generic term.  And as such, the LSAM as part of the ESAS does not use depots. 

2.  If a depot were part of the plan, there won't be any "selling" of the propellant, it would be provided

3.  And only the clueless use astronautix and wiki for space info.  Using them as reference doesn't valid anything.  If the poster wanted to make a valid point, he would use the source for info
http://www.adastrarocket.com/vasimr.html
Title: Re: Propellant Depots - General Discussion
Post by: jeff.findley on 03/04/2009 01:35 pm
I'd say, at least initially, move the propellant with the same propellant being used by the depot.  In other words, LOX/LH2.  There are several high ISP vacuum LOX/LH2 engines to chose from. 

Are there any proven solar thermal engines?
Title: Re: Propellant Depots - General Discussion
Post by: DonEsteban on 03/04/2009 01:42 pm
I'd say, at least initially, move the propellant with the same propellant being used by the depot.  In other words, LOX/LH2. 
Yes, that's my point.

Quote
There are several high ISP vacuum LOX/LH2 engines to chose from. 

Are there any proven solar thermal engines?
No, unfortunately. By the time a depot is up there, there could/should be some. ISP 900 vs ISP ~450 is quite a difference. Especially if you want to cycle between the depots.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/04/2009 04:00 pm
{snip}
3.  And only the clueless use astronautix and wiki for space info.  Using them as reference doesn't valid anything.  If the poster wanted to make a valid point, he would use the source for info
http://www.adastrarocket.com/vasimr.html

There is information about the proposed solar electric tug in wikipeadia that is not available to the general public any where else.

A VASIMR thruster is due to be attached to the ISS for inspace testing in 2011/2012.
Title: Re: Propellant Depots - General Discussion
Post by: Xplor on 03/04/2009 11:49 pm
The combination of propellant depots and high ISP propulsion makes perfect sense.  Load the depot in LEO so that any number of launch options can supply it.  Then use high ISP propulsion to move the depot to L1/2 or LLO, which ever winds up being used for exploration.  One can bring the depot back to LEO for refueling or simply launch another, it’s not at all clear which is more cost effective.

While high area ratio LO2/LH2 engines may eventually get up to 470 sec, this pales compared to 900 sec for solar thermal and >> 1,000 sec for the various electric options.

While CxP currently doesn’t take advantage of depots, we don’t really know what direction President Obama and the next NASA administrator are going to take.  They seem to have a soft side for commercial interests.

What is ludicrous is spending $12B to recreate EELV capabilities, spending another $20B to show that we can build a bigger rocket than they did 40 years ago while saddling America with continuing multi-billion dollar annual infrastructure costs.  What is ludicrous is taking 15 years to get to the moon, when 40 years ago it was done in 8 years with almost no space capability to start with.

The cheapest way to reduce launch costs is to launch less.  The use of propellant depots combined with high ISP in-space propulsion can reduce launch mass by a factor of 2.  This is what I call sustainable and extensible!
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/06/2009 11:59 am
The combination of propellant depots and high ISP propulsion makes perfect sense.  Load the depot in LEO so that any number of launch options can supply it.  Then use high ISP propulsion to move the depot to L1/2 or LLO, which ever winds up being used for exploration.  One can bring the depot back to LEO for refueling or simply launch another, it’s not at all clear which is more cost effective.

If smallish LV are being used to fill the Lunar (and Mars) depot then the depot will have to go up on a separate LV.  That is likely to swing the cost towards refuelling, although a full cost analysis will need performing.  A private sector propellant depot may have problems get authorisation to use the Ares I and V LV.

A lunar depot and SEP tug amount to a partial replacement for the Ares V and EDS described in the ESAS documents.  A significant amount of the fuel mass goes away and ROL becomes viable.  An Altair variant able to accept fuel in orbit, carry extra consumables and having fuel tanks able to reach the depots orbit (L2) would be useful.  A means of get the Orion to L2 becomes important.

Whilst the Orion and the Altair ascend stage are being developed the descent stage can start assembling the lunar outpost and permitting exploration by lunar rovers.

A good SEP tug should be able to carry a filled depot to Mars.  The propellant can then fuel a robotic descend and ascend stages.  Approx 30 mT fuel plus up to 30 mT lander and explorer should permit a significant science mission.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/11/2009 05:32 pm
On the Alternative DIRECT thread I discovered that LOX/Methane and LOX/RP-1 suffer from 0.2% a day boil off, mostly of the LOX.  This implies that even a LOX only propellant depot needs zero boil-off equipment.

Without zero boil-off after 183 days (6 months) the depot would have lost more than 30% of its LOX.
Title: Re: Propellant Depots - General Discussion
Post by: yg1968 on 03/15/2009 12:09 pm
Here is a good interview with Dallas Bienhoff of Boeing on the merits of Propellant Depots:

http://www.thespaceshow.com/detail.asp?q=678

He mentions in the interview that it would take 40 Falcon 9 launches to get enough fuel for a moon mission. 40 missions seems like a lot and it also assumes that Space X can deliver on their cheaper price. 

Edit: as mentionned below, actually the number is 40 lauches per year and therefore 20 per moon mission. Sorry for the mistake.

Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/15/2009 03:21 pm
40 launches every 6 months or so is a lot.  I suspect that given a market that size someone will build bigger rockets.

There may also be a demand for LEO to lunar orbit ion/thermal space tugs.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/15/2009 09:42 pm
At 10,450kg to LEO for each Falcon 9, I don't see why you'd need 40 of them to lift the ~100mT needed for the TLI burn.

When they develop their LOX/LH2 Upper Stage they should get even higher performance, and a stretched version of that with an integrated RCS borrowing design from Dragon would make for a great delivery vehicle.   I can't see that delivering less than 8-10mT of useful LOX/LH2 on every flight.

Another 3 should be able to comfortably lift the ~25mT of LOX/LH2 for the Descent Module.

What more do you need?

I can't see *any* way it would need more than 20 Falcon-9's and IMHO you could probably do it with less than 15.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: Piotr on 03/16/2009 08:58 am
On the Alternative DIRECT thread I discovered that LOX/Methane and LOX/RP-1 suffer from 0.2% a day boil off, mostly of the LOX.  This implies that even a LOX only propellant depot needs zero boil-off equipment.

Without zero boil-off after 183 days (6 months) the depot would have lost more than 30% of its LOX.

A valid point. It gets even worse for LH2, which has current demonstrated capability (Centaur) around 5% boil-off per day (its wrt original propellant load).

I am currently doing research in this area, and ESA is quite interested in it. Surprisingly, there is little work in this field, except few vague papers from LM.

There are several things that can be done to limit the boil-off:

1. Increase vehicle size - heat gets into tank through tank surface and surface increases less than volume with increasing radius. Simple, but limited practically.

2. Apply passive TPS and composite structure - this can effectively eliminate the boil-off for missions around 1-2 months for 20+ tonnes of propellant. Using metal tanks but composite/low conduction interfaces, you can still get around 0.02% daily boil-off (wrt initial load). Insulations includes thick MLI blankets (20+ layers), or sunshield, thou sunshield is limited by orientation wrt Earth and Sun.

3. Vapour cooling - use some of the cold boil-off vapour to cool outside of the tank, and extract the heat. Some propellant is wasted but you can achieve something like 0.01% daily boil-off.

4. Use cryocoolers (active TPS). They are very inefficient thermodynamically (c.a. 5%), but they can remove excess heat from propellant, meaning zero-boil-off. But that costs mass and power.

Regards
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/16/2009 01:02 pm
There are several things that can be done to limit the boil-off:
[...]

Another intriguing but longer-term solution is magnetic propellant positioning. It turns out that both liquid hydrogen and liquid oxygen have interesting magnetic properties. The idea is that with magnetic propellant positioning you can put the propellant "in the middle of the tank" to limit propellant contact with the wall. Interestingly, this magnetic positioning is both a settling technique and an anti-boil-off technique. It doesn't work very well when the tank is accelerating, so it's not very useful for rockets, just for depots.
Title: Re: Propellant Depots - General Discussion
Post by: Celebrimbor on 03/16/2009 01:17 pm
On the Alternative DIRECT thread I discovered that LOX/Methane and LOX/RP-1 suffer from 0.2% a day boil off, mostly of the LOX.  This implies that even a LOX only propellant depot needs zero boil-off equipment.

Without zero boil-off after 183 days (6 months) the depot would have lost more than 30% of its LOX.

A valid point. It gets even worse for LH2, which has current demonstrated capability (Centaur) around 5% boil-off per day (its wrt original propellant load).

I am currently doing research in this area, and ESA is quite interested in it. Surprisingly, there is little work in this field, except few vague papers from LM.

There are several things that can be done to limit the boil-off:

1. Increase vehicle size - heat gets into tank through tank surface and surface increases less than volume with increasing radius. Simple, but limited practically.

2. Apply passive TPS and composite structure - this can effectively eliminate the boil-off for missions around 1-2 months for 20+ tonnes of propellant. Using metal tanks but composite/low conduction interfaces, you can still get around 0.02% daily boil-off (wrt initial load). Insulations includes thick MLI blankets (20+ layers), or sunshield, thou sunshield is limited by orientation wrt Earth and Sun.

3. Vapour cooling - use some of the cold boil-off vapour to cool outside of the tank, and extract the heat. Some propellant is wasted but you can achieve something like 0.01% daily boil-off.

4. Use cryocoolers (active TPS). They are very inefficient thermodynamically (c.a. 5%), but they can remove excess heat from propellant, meaning zero-boil-off. But that costs mass and power.

Regards

It seems like a mixture of 2-4 is the best way, do you agree? A passive solar screen (2) could easily double as a solar array for your active system (4). Then thermodynamic efficiency doesn't matter since the power isn't needed for much else.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/16/2009 07:22 pm
At 10,450kg to LEO for each Falcon 9, I don't see why you'd need 40 of them to lift the ~100mT needed for the TLI burn.

{snip}
I can't see *any* way it would need more than 20 Falcon-9's and IMHO you could probably do it with less than 15.

I listened to the show again, it is 40 launches a year for 2 Moon missions.  That is 20 launches per lunar mission.

20 * 9 tonne = 180 tonne of propellant per mission (rounding errors and boil-off apply)
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/16/2009 07:23 pm
There are several things that can be done to limit the boil-off:
[...]

Another intriguing but longer-term solution is magnetic propellant positioning. It turns out that both liquid hydrogen and liquid oxygen have interesting magnetic properties. The idea is that with magnetic propellant positioning you can put the propellant "in the middle of the tank" to limit propellant contact with the wall. Interestingly, this magnetic positioning is both a settling technique and an anti-boil-off technique.

Yeah, LOX is paramagnetic and LH2 is diamagnetic.  It's an interesting idea, and there should be a fun Space 2009 paper with more info about it coming out... :-)

Quote
It doesn't work very well when the tank is accelerating, so it's not very useful for rockets, just for depots.

You don't need another settling mechanism when the tank is accelerating.  But even rocket stages have long coast-phases that could benefit from the technology.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/16/2009 08:31 pm
Prime customer for a propellant depot could be a GEO satellite company that wants to launch 7 or 8 or more tonne satellites.

Currently the Delta IV claims to be able to get about 25,800 kg to LEO as against 6,275 kg to GEO and 9,306 kg to escape orbit.

Method.
Use a Delta IV or Atlas V to fly the satellite and dry upper stage to LEO.
Fuel the upper stage (or refuel the second stage).
Fly to GEO, delta-v 4.33 km/s KSC.
Title: Re: Propellant Depots - General Discussion
Post by: yg1968 on 03/16/2009 10:35 pm
At 10,450kg to LEO for each Falcon 9, I don't see why you'd need 40 of them to lift the ~100mT needed for the TLI burn.

{snip}
I can't see *any* way it would need more than 20 Falcon-9's and IMHO you could probably do it with less than 15.

I listened to the show again, it is 40 launches a year for 2 Moon missions.  That is 20 launches per lunar mission.

20 * 9 tonne = 180 tonne of propellant per mission (rounding errors and boil-off apply)

Ooups sorry. I had remembered that he had mentionned 40 launches per year. But I did not realize that he was making the calculations for 2 moon missions per year.  Thanks for correcting me on that.
Title: Re: Propellant Depots - General Discussion
Post by: aggelos on 03/17/2009 09:50 am
Hi!I am  new to he forum..I'm greek ,(greece is a member of esa) I want to ask something..with orbital fuel depot ,is possible a single stage to orbit rocket?one stage with strap on liquid boosters like angara,and when reaches fuel depot refuel and go to moon....
Is that impossible?

Title: Re: Propellant Depots - General Discussion
Post by: tankmodeler on 03/17/2009 04:10 pm
Hi!I am  new to he forum..I'm greek ,(greece is a member of esa) I want to ask something..with orbital fuel depot ,is possible a single stage to orbit rocket?one stage with strap on liquid boosters like angara,and when reaches fuel depot refuel and go to moon....
Is that impossible?
Welcome!

Impossible? No, probably not.
Useful? Also no, probably not.

The problem is dragging all that mass (of the core stage) to the moon (and presumably back) means that you'd have pretty much nothing as a payload.

Also, if you have liquid boosters that you drop getting to orbit, then you are already at a two-stage system.

Paul
Title: Re: Propellant Depots - General Discussion
Post by: aggelos on 03/17/2009 06:32 pm
just imagine..a little bigger EDS (of Ares V), alone launch directly from ground,go up ,refuel in LEO  and go to moon...
I think with Ares V is logical to carry an empty eds to LEO?why carry an empty tank?its better without it?
with orbital fuel depots will make new smaller rockets and more reusable rockets...
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/17/2009 06:41 pm
With orbital fuel depots will make new smaller rockets and more reusable rockets...

A propellant depot doesn't really help in RLV design. The issue isn't fuel, it's TPS. Re-entry is exceptionally harsh.
Title: Re: Propellant Depots - General Discussion
Post by: Spacenick on 03/17/2009 11:08 pm
Well reducing boil off in space should be much easier then it is on earth, isn't it? I mean put a solar panel on the depot and keep it pointed to the sun, that should give you energy and reduce boil off simply by putting the tank in the shadow. Then one could cool the LOX with a sterling cooler driven by an electric motor. Maybe also add an isolating aerogel layer between the solar array and the tank. This should also be pretty light weight. As there is nearly no heat transfer to the envrionment other then heat radiation boil off should be minimal and be easily kept at zero with ther stirling cooler.
Title: Re: Propellant Depots - General Discussion
Post by: DonEsteban on 03/18/2009 07:56 am
Reducing boiloff for LOX should be relatively easy.

Reducing boiloff for LH is another matter - the temperatures needed are MUCH lower. Simple sun-shade and simple cryocooler would not be enough.

On Earth, you have advantage of enough mass and enough power.
In space, you want your anti-boiloff infrastructure to be as light as possible (otherwise you lose the benefits of LH).

In LEO, the Earth itself is quite warm and covers essentially half of the sky  - you want to be in the shade from BOTH Sun and Earth - and they are moving relatively to each other - not simple at all.

Further away the Earth becomes smaller and the task is much easier. However, that 'further away' may be out of reach for the 'cheap commercial refueling vehicles' - one of the main selling points for propellant depots.
Title: Re: Propellant Depots - General Discussion
Post by: DonEsteban on 03/18/2009 08:25 am
With orbital fuel depots will make new smaller rockets and more reusable rockets...

A propellant depot doesn't really help in RLV design. The issue isn't fuel, it's TPS. Re-entry is exceptionally harsh.
Hm, maybe a disposable ballute/inflatable heat-shield would help.

I still think the easiest way to get a real benefit out of RLV is to be able to get as close as possible to 'refuel & fly again', without much refurbishing needed. Even if that costs a significant fraction of the payload. Which in turn means you need to start with a MUCH larger rocket.

Perhaps something like:
 - two KEROLOX flyback boosters, flying back to the launch site
 - ET-based LH/LOX - core, returning to the launch site after one orbit, using disposable ballute/inflatable heat shield/some other magic.
 - on top of that perhaps another (disposable, but possibly small/simple/cheap) stage to deliver the payload to the desired orbit

If this is done in expendable way, it would lift 120t? to orbit.
Adding all the recovery HW would perhaps reduce the payload in half.
Now detune the engines/design them with lots of margin so that the whole vehicle can be flown hundreds of times. The payload is further reduced ... perhaps to 15-20t.

But you can fly the vehicle hundreds of times...you actually NEED to fly the vehicle hundreds of times, to make economic sense. So.. why would you fly it that many times? Well -- to fill the propellant depot, for example. :-) In order to deliver the mining machinery to the Moon, NEO, to start the ISRU, which will in turn allow economical SPSs...

Sounds like a BIG upfront investment ... but nothing compared to the current 'bailouts' thrown down the drain ... and with tangible economic/ecologic and geopolitical benefits of abundant cheap energy.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/18/2009 02:31 pm
Reducing boiloff for LOX should be relatively easy.

Reducing boiloff for LH is another matter - the temperatures needed are MUCH lower. Simple sun-shade and simple cryocooler would not be enough.

Actually, from most of the sources I've seen, you can get a zero-boiloff LH2 system, even in LEO.  It may be a bit more complicated than what you need for a LOX system, but it's not impossible.

Quote
On Earth, you have advantage of enough mass and enough power.  In space, you want your anti-boiloff infrastructure to be as light as possible (otherwise you lose the benefits of LH).

Well, you want the cryo storage system on an actual flight vehicle to be as light as possible.  But for a depot?  That only has to be launched once, but can be used for many flights, so it makes all the sense in the world to invest in a better passive/active cooling system.  You transfer the LH2 from the tanker to the depot as quick as possible, and then when a tankee arrives, you only fill the LH2 tanks right before departure.  That way, you can keep the LH2 stored in the most efficient storage system (probably zero boiloff) during the long waits before the mission, and then transfer it into the lighter but less thermally efficient flight systems only briefly before departure (at which point you go and burn most of the hydrogen all in one go.

Quote
In LEO, the Earth itself is quite warm and covers essentially half of the sky  - you want to be in the shade from BOTH Sun and Earth - and they are moving relatively to each other - not simple at all.

Actually, it isn't as hard as you think.  If the angle of your sunshield (using a conical design like ULA is developing) is relatively narrow, and you are in a medium inclination orbit, you just point your sunshield away from the earth.  Sure, some sunlight will get through for a few minutes at a time every several orbits, but you have the rest of that time to slowly pump the heat back out.  I don't have exact numbers, but I'm almost positive its a solveable problem.

Quote
Further away the Earth becomes smaller and the task is much easier. However, that 'further away' may be out of reach for the 'cheap commercial refueling vehicles' - one of the main selling points for propellant depots.

Yeah, for depots further out (L1 or LLO for instance), you really want an LEO depot as well, with tankers going between the two.  But the obstacles to an LEO depot aren't as severe as you seem to think.  Sure it's easier in deep space, but it's not impossible (or even that much harder than anything else we do in space) to do one in LEO.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Piotr on 03/18/2009 02:48 pm
There are several things that can be done to limit the boil-off:
[...]

Another intriguing but longer-term solution is magnetic propellant positioning. It turns out that both liquid hydrogen and liquid oxygen have interesting magnetic properties. The idea is that with magnetic propellant positioning you can put the propellant "in the middle of the tank" to limit propellant contact with the wall. Interestingly, this magnetic positioning is both a settling technique and an anti-boil-off technique.

Yeah, LOX is paramagnetic and LH2 is diamagnetic.  It's an interesting idea, and there should be a fun Space 2009 paper with more info about it coming out... :-)

~Jon

Magnetic settling/contact reduction - a very interesting idea. Does any of you (mmeijeri and Jon) have further info on it? Maybe an abstract of some paper? PM or email me, I would be happy to exchange some of the work I have.

More on boil-off:

1. As for using solar-arrays for sun-shields, that is unfortunately not a good idea. Solar arrays are very hot. Their front has high solar absorbivity (0.9?) - lots of radiation absorbed, they convert about 25% into electricity, and rest goes through the back (IR radiation) or structure (conduction). From the point of view of anything behind, the SA is a big IR source. Since you want high IR emittance/absorbivity for your tank, most of the IR heat from SA would end up in the tank. You can play with shapes and view factors, but that is also limited. And as already mentioned, in LEO sunshields are ADCS nightmare. In Lagrangians however (like ESA's L1 station concept), it makes more sense.

2. Radiation is not a big problem for tanks. MLI and coatings deal with that. Problem is conduction from warm bus. Especially if structure s made out of aluminum. To offset that, its best to have truss interfaces and adapters, preferably composite ones like in Herschel cryostat. However, there are still tank penetrations due to PMD, and those are difficult to offset.

~Piotr
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/18/2009 03:47 pm
Magnetic settling/contact reduction - a very interesting idea. Does any of you (mmeijeri and Jon) have further info on it? Maybe an abstract of some paper? PM or email me, I would be happy to exchange some of the work I have.

I sent you some llinks, but I just found that doing a search for just the term: magnetic propellant (no quotes) comes up with a lot more hits.

Quote
More on boil-off:

1. As for using solar-arrays for sun-shields, that is unfortunately not a good idea. Solar arrays are very hot. Their front has high solar absorbivity (0.9?) - lots of radiation absorbed, they convert about 25% into electricity, and rest goes through the back (IR radiation) or structure (conduction). From the point of view of anything behind, the SA is a big IR source. Since you want high IR emittance/absorbivity for your tank, most of the IR heat from SA would end up in the tank. You can play with shapes and view factors, but that is also limited.

Yeah, you need solar panels for power, but they're not good from a thermal standpoint, so you need to strike a balance.

Quote
And as already mentioned, in LEO sunshields are ADCS nightmare. In Lagrangians however (like ESA's L1 station concept), it makes more sense.

ADCS?  My mind is drawing a blank on that acronym.  The ULA guys seemed to think that sunshields would work fine in LEO.  The analysis they did in their paper was at a fairly high LEO (1000km), but they said that that altitude was more driven by other considerations (the group they worked with had a lot of data for that trajectory and wanted to use it) than limitations on lower altitudes.  They said the main constraint at lower altitudes was atomic oxygen erosion of the sunshield.  That means it needs to be maintainable/repairable, or you have to replace the depot module every few years--whichever is easier/cheaper.  The sunshield design they came up with was actually designed with repair/replacement/redundancy in mind.

Quote
2. Radiation is not a big problem for tanks. MLI and coatings deal with that. Problem is conduction from warm bus. Especially if structure s made out of aluminum. To offset that, its best to have truss interfaces and adapters, preferably composite ones like in Herschel cryostat. However, there are still tank penetrations due to PMD, and those are difficult to offset.

Yeah, that's what I was hearing--it's the intertank heat loads and the tank-to-bus heat loads that tend to dominate.  Magnetic positioning can help a bit with that, as can low-K attachments, vapor cooled points, and using an intermediate "gas" tank between the attachment points and the actual propellant tank...lots of tricks and details, but many of them are now well understood.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: R.Simko on 03/18/2009 04:11 pm
Here are a few thoughts.  Would any of these ideas work? 

1.  Make the depot a tank within a tank.  Put the LH in the inner tank  and the outer for the LOX.  Would that reduce boil off?

2.  Attach any solar array to the depot by a tether.  This would allow the greater distance between solar array and the depot, to reduce heat exchange.

3.  Sinse LH is more problematic, make a depot the carries LOX and RP1, instead of LH.  New rockets using the depot would be based on using  LOX and RP1.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/18/2009 04:48 pm
Magnetic settling/contact reduction - a very interesting idea. Does any of you (mmeijeri and Jon) have further info on it? Maybe an abstract of some paper? PM or email me, I would be happy to exchange some of the work I have.

Hi Piotr,

Jon is a real rocket man and has written a lot about depots, I'm just an amateur. I found an interesting article in Acta Astronautica the other day:

Jeffrey G. Marchetta, Benjamin D. Simmons, John I. Hochstein, Magnetic retention of
LO2 in an accelerating environment, Acta Astronautica, Volume 62, Issues 8-9,
April-May 2008, Pages 478-490, ISSN 0094-5765, DOI: 10.1016/j.actaastro.2008.01.016.
(http://www.sciencedirect.com/science/article/B6V1N-4S1JJXT-2/2/d37d63d2a2128914fed66e59d048ede1)
Abstract:
Recent advances in magnet technology suggest that magnetic positive positioning of
liquids may become a viable technology for future spacecraft systems. Preliminary
simulation results for a subscale tank are presented which illustrate that a magnet
of sufficient strength can retain liquid oxygen (LO2) in an accelerating
environment. Development of a new computational model for simulating equilibrium
free surface shapes in the presence of a magnetic field is presented. Comparisons of
equilibrium simulation predictions to known solutions for simple configurations
support the conclusion that the computational model is suitable for continuing the
investigation of magnetic propellant storage. Results obtained using the equilibrium
simulation are presented to further demonstrate the feasibility of using magnetic
retention to manage cryogenic propellants onboard spacecraft.
Keywords: Magnetic fluid; Cryogenic propellant; Propellant management; Reduced gravity
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/18/2009 04:53 pm
Yeah, that's what I was hearing--it's the intertank heat loads and the tank-to-bus heat loads that tend to dominate.  Magnetic positioning can help a bit with that, as can low-K attachments, vapor cooled points, and using an intermediate "gas" tank between the attachment points and the actual propellant tank...lots of tricks and details, but many of them are now well understood.

Naive question here: why couldn't you just add some possibly heavy cryocoolers to a propellant depot and be done with the cooling aspects (not the settling and transfer)? Mass doesn't seem such a big deal for a structure that's meant to stay in a fixed orbit. You would have to launch it first of course, and there mass could be a problem. I'm thinking in the context of >60 mT launchers.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/18/2009 07:02 pm
Here are a few thoughts.  Would any of these ideas work? 

1.  Make the depot a tank within a tank.  Put the LH in the inner tank  and the outer for the LOX.  Would that reduce boil off?

Actually it would probably make things a whole lot worse.  Once you've gotten a decent sunshield, the two biggest sources of heat leaks into the LH2 for a setup like Centaur are a) from the "hot section" where all the power, control, and communications stuff is held, and b) from the LOX itself!  Surrounding the LH2 tank with a LOX tank would probably be a really bad idea.

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2.  Attach any solar array to the depot by a tether.  This would allow the greater distance between solar array and the depot, to reduce heat exchange.

A lot depends on how much power you need.  If it's small enough, the complexity of a tether is probably more hassle than its worth.  If you need a lot of power though, one benefit of a tether is that it would make "gravity gradient" stabilization easier.

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3.  Sinse LH is more problematic, make a depot the carries LOX and RP1, instead of LH.  New rockets using the depot would be based on using  LOX and RP1.

While tons of people suggest this, I think this is a cop-out.  LH2 is *more* problematic, not impossibly problematic.  I think there's something to be said for basing your storage on what works best for the customer, not what's most convenient for yourself.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/18/2009 08:04 pm
Yeah, that's what I was hearing--it's the intertank heat loads and the tank-to-bus heat loads that tend to dominate.  Magnetic positioning can help a bit with that, as can low-K attachments, vapor cooled points, and using an intermediate "gas" tank between the attachment points and the actual propellant tank...lots of tricks and details, but many of them are now well understood.

Naive question here: why couldn't you just add some possibly heavy cryocoolers to a propellant depot and be done with the cooling aspects (not the settling and transfer)? Mass doesn't seem such a big deal for a structure that's meant to stay in a fixed orbit. You would have to launch it first of course, and there mass could be a problem. I'm thinking in the context of >60 mT launchers.

Well, you don't want to push it too far.  The right way, IMO is get a good passive cooling design to minimize the size and complexity of your active component (and also to make it so that if your active part goes down, you aren't screwed while you try to repair/replace it).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: R.Simko on 03/18/2009 11:38 pm
Thanks for answering my questions Jongoff. 
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/19/2009 04:23 am
Thanks for answering my questions Jongoff. 

No worries.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Piotr on 03/19/2009 09:17 am
Martijn and Jon, thanks for all the papers. I will take a closer look at them over the weekend.

One question that pops-up with magnetic settling is the required magnet strength and resulting mass and power. Any estimates of what would be required? Even a ballpark figure would be nice. I am just trying to get a system engineering angle on that to see how does it compare to cryocoolers or heavy passive TPS.

As for Simko's idea about replacing LH2 with RP1, it would make the TPS simpler, but would severely reduce the performance of whatever propulsion you have. The boil-off problem can be rather easily limited by passive TPS, the problems start once you want to completly eliminate it. It all depends on a whole architecture design. If you are going to fill up and empty the propellant depot once a month, then maybe you dont need zero-boil-off. If you do it once a year, then you do need it.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/19/2009 02:03 pm
While tons of people suggest this, I think this is a cop-out.  LH2 is *more* problematic, not impossibly problematic.  I think there's something to be said for basing your storage on what works best for the customer, not what's most convenient for yourself.

I can understand why you would not want to delay work on cryo depots, but if other depots can be operational sooner I see no reason to delay fielding depots of any kind until the cryogenic problems have been solved. For a long time problems with handling cryogenic propellants have been the major excuse for not starting work on depots and working on monstrous launchers instead.

So I would go further than proposing lox/kerosene depots and say that we should go with hypergolics depots ASAP. ATV, Orion and HTV all use hypergolic fuels, so there would immediately be users for such a depot. HTV uses MON3 instead of NTO though, and I don't know if the thrusters on the existing craft could use an identical oxidiser without changes. Given that MON3 is just NTO with a slight admixture of nitric oxide it may not be a big deal. Maybe the HTV could work with NTO or else Orion and ATV with MON3. And later on, lunar landers could work with hypergolic fuels as well, with acceptable performance and better safety than lox/lh2.

At the same time, start serious work on cryo depots ASAP as well. Whichever could be developed first would be deployed first. I would expect that to be the hypergolic depots.

In this way you can debug the proximity operations, involve commercial and international partners and implant the idea of depots in the public mind as soon as possible.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/19/2009 02:28 pm
Martijn and Jon, thanks for all the papers. I will take a closer look at them over the weekend.

One question that pops-up with magnetic settling is the required magnet strength and resulting mass and power. Any estimates of what would be required? Even a ballpark figure would be nice. I am just trying to get a system engineering angle on that to see how does it compare to cryocoolers or heavy passive TPS.

Honestly, I'm not the one to ask.  Dr Marchetta was suggesting that while LOX can possibly be controlled using just permanent magnets, that you might need superconducting electromagnets for the LH2...but that depends really strongly on what goal you're trying to achieve.  If you're just trying to keep the LH2 away from the vent, you can probably use a much weaker magnet.  If you're trying to do the full job (keeping it away from the vent at all times, keeping it away from the sump except right before transfer ops, and keeping it away from the walls whenever possible....you'd need several superconducting magnets, and some permanent ones as well....Not sure how quickly all that adds up since I don't really have much experience with superconducting magnets.  Also, so far most of Dr Marchetta's work (and most of the empirical data he can correlate his models to) involve LOX.  He's hoping to do some LH2 modeling work this year, but that remains to be seen.

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As for Simko's idea about replacing LH2 with RP1, it would make the TPS simpler, but would severely reduce the performance of whatever propulsion you have. The boil-off problem can be rather easily limited by passive TPS, the problems start once you want to completly eliminate it. It all depends on a whole architecture design. If you are going to fill up and empty the propellant depot once a month, then maybe you dont need zero-boil-off. If you do it once a year, then you do need it.

Yeah, it's a tradeoff.  You have a good point though that high-tempo depots might be more able to tolerate a little LH2 boiloff (especially an LEO depot) than one that is either remote or only used occasionally.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: robertross on 03/19/2009 02:35 pm
Martijn and Jon, thanks for all the papers. I will take a closer look at them over the weekend.

One question that pops-up with magnetic settling is the required magnet strength and resulting mass and power. Any estimates of what would be required? Even a ballpark figure would be nice. I am just trying to get a system engineering angle on that to see how does it compare to cryocoolers or heavy passive TPS.

Honestly, I'm not the one to ask.  Dr Marchetta was suggesting that while LOX can possibly be controlled using just permanent magnets, that you might need superconducting electromagnets for the LH2...but that depends really strongly on what goal you're trying to achieve.  If you're just trying to keep the LH2 away from the vent, you can probably use a much weaker magnet.  If you're trying to do the full job (keeping it away from the vent at all times, keeping it away from the sump except right before transfer ops, and keeping it away from the walls whenever possible....you'd need several superconducting magnets, and some permanent ones as well....Not sure how quickly all that adds up since I don't really have much experience with superconducting magnets.  Also, so far most of Dr Marchetta's work (and most of the empirical data he can correlate his models to) involve LOX.  He's hoping to do some LH2 modeling work this year, but that remains to be seen.

Quote
As for Simko's idea about replacing LH2 with RP1, it would make the TPS simpler, but would severely reduce the performance of whatever propulsion you have. The boil-off problem can be rather easily limited by passive TPS, the problems start once you want to completly eliminate it. It all depends on a whole architecture design. If you are going to fill up and empty the propellant depot once a month, then maybe you dont need zero-boil-off. If you do it once a year, then you do need it.

Yeah, it's a tradeoff.  You have a good point though that high-tempo depots might be more able to tolerate a little LH2 boiloff (especially an LEO depot) than one that is either remote or only used occasionally.

~Jon

The great advantage of superconductors for this application (despite the weight penalty) is that you already have a cryogenic source for magnets operating at this low temperature. I'm sure a balance can be found using higher temperature magnets (somewhere between LOX and LN2 versions I know of) to possibly gain an advantage in mass & cost.

I think this is a great way forward, btw, and makes a lot of sense (superconducting magnets for magnetic settling).
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/19/2009 02:37 pm
I can understand why you would not want to delay work on cryo depots, but if other depots can be operational sooner I see no reason to delay fielding depots of any kind until the cryogenic problems have been solved. For a long time problems with handling cryogenic propellants have been the major excuse for not starting work on depots and working on monstrous launchers instead.

While this is true, and while I personally think there's a good chance that the first depot will be hypergolic storables, I think that a non-cryo depot isn't going to get people to stop wasting money on monstrous launchers.  Nobody who can afford cislunar travel anytime soon is going to build a manned lunar program using anything other than LOX/LH2 for at least the TLI burn.  They aren't going to do a LOX/RP-1 based option just to use a depot.  Even just providing LOX provides plenty of cop-outs.  The problem is that you still end up needing bigger launchers or lots of launches.  If you can provide all of the propellants at a depot you can go with an architecture that uses existing boosters with only two hardware launches....

The other important thing for me is that you have to solve almost all the same problems for LOX as you do for LH2.  The LH2 problem may be more severe, but the solution space is similar.  Sunshields, MLI, vapor cooled points, low-K connections to the hot section, thermodynamic venting, Vacuum insulation panels, settled handling, etc.

Quote
So I would go further than proposing lox/kerosene depots and say that we should go with hypergolics depots ASAP. ATV, Orion and HTV all use hypergolic fuels, so there would immediately be users for such a depot. HTV uses MON3 instead of NTO though, and I don't know if the thrusters on the existing craft could use an identical oxidiser without changes. Given that MON3 is just NTO with a slight admixture of nitric oxide it may not be a big deal. Maybe the HTV could work with NTO or else Orion and ATV with MON3. And later on, lunar landers could work with hypergolic fuels as well, with acceptable performance and better safety than lox/lh2.

Just because they use hypergols doesn't mean that they would have use for buying it from you on orbit.  That's a tougher nut to crack.  Now if ATV were being used as a tug, maybe...but that's a different problem.

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At the same time, start serious work on cryo depots ASAP as well. Whichever could be developed first would be deployed first. I would expect that to be the hypergolic depots.

In this way you can debug the proximity operations, involve commercial and international partners and implant the idea of depots in the public mind as soon as possible.

This might be the case if anyone were ready to start on a depot of any sort right now.  The technology is there, but the business case or government financing isn't there yet.  It could get there quickly, but right now we've got a long way to go before we even get a chance to try.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/19/2009 03:47 pm
While this is true, and while I personally think there's a good chance that the first depot will be hypergolic storables, I think that a non-cryo depot isn't going to get people to stop wasting money on monstrous launchers. 

I agree. On the other hand, if they continue down the road of monstrous launchers, prospects for cryo depots anytime soon look dim. But there are still a couple of years before development on the necessary upper stages begins in earnest, so there is still time to stop this. If depots of any kind (probably hypergolic ones) are fielded before this, there is still a chance. Otherwise it might be another decade before the option is looked at again. So I'd say fielding hypergolic depots and warding off new upper stages is urgent if you want to promote commercial space. It's probably too late to stop J-120, but it might not be too late to save depots.

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Nobody who can afford cislunar travel anytime soon is going to build a manned lunar program using anything other than LOX/LH2 for at least the TLI burn.

I agree. It's not completely impossible with hypergolic depots in LEO, a gateway station and depot at L1 and a >=60 mT J-130, but it is stretching things. If you were to use an existing Delta IV upper stage for transport to L1 it's easy enough. In fact I'm really enthusiastic about that option. But no one who owns a big launcher capable of launching an EDS that will propel an Orion + Altair to the moon is going to want to use depots immediately.

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  They aren't going to do a LOX/RP-1 based option just to use a depot.  Even just providing LOX provides plenty of cop-outs.  The problem is that you still end up needing bigger launchers or lots of launches.  If you can provide all of the propellants at a depot you can go with an architecture that uses existing boosters with only two hardware launches....

And besides isn't the performance of LOX/RP-1 similar to that of MMH/NTO?

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The other important thing for me is that you have to solve almost all the same problems for LOX as you do for LH2.  The LH2 problem may be more severe, but the solution space is similar.  Sunshields, MLI, vapor cooled points, low-K connections to the hot section, thermodynamic venting, Vacuum insulation panels, settled handling, etc.

I agree serious work on LH2 depots should start at once.

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Just because they use hypergols doesn't mean that they would have use for buying it from you on orbit.  That's a tougher nut to crack.  Now if ATV were being used as a tug, maybe...but that's a different problem.

Any ideas on how that could be stimulated?

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This might be the case if anyone were ready to start on a depot of any sort right now.  The technology is there, but the business case or government financing isn't there yet.  It could get there quickly, but right now we've got a long way to go before we even get a chance to try.

I'm afraid you're right, and I wish someone in power would push NASA down this road.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/19/2009 07:49 pm
I agree. On the other hand, if they continue down the road of monstrous launchers, prospects for cryo depots anytime soon look dim. But there are still a couple of years before development on the necessary upper stages begins in earnest, so there is still time to stop this. If depots of any kind (probably hypergolic ones) are fielded before this, there is still a chance. Otherwise it might be another decade before the option is looked at again. So I'd say fielding hypergolic depots and warding off new upper stages is urgent if you want to promote commercial space. It's probably too late to stop J-120, but it might not be too late to save depots.

You're apparently a lot more optimistic than I about the prospects of monster launcher development.  Put simply, I don't think there's a chance in heck of NASA actually getting the money to build Ares V.  And I don't think that the existence of a hypergol depot would do anything to change their minds if they did have the money. 

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Just because they use hypergols doesn't mean that they would have use for buying it from you on orbit.  That's a tougher nut to crack.  Now if ATV were being used as a tug, maybe...but that's a different problem.

Any ideas on how that could be stimulated?

I think the challenge is that barring an actual customer coming along, the first depot may have to be vertically integrated with its first customer.  For instance, say someone found a way to close a business case around space tugs.  A hypergol depot is really not much more than some tanks and plumbing attached to some sort of spacecraft bus.  So, it might make sense for a tug company to also field a refeuling setup to allow them to get more life out of their tugs.

There may be other options, but that ones the most compelling so far.

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I'm afraid you're right, and I wish someone in power would push NASA down this road.

We'll see.  A lot will depend on how the NASA admin pick goes.  If certain pieces of human ballast get their way, propellant depot development may have to be done by routing around the damage.  Remember though, even if NASA's trajectory is almost orthogonal to an intelligent course for space development, the "dot product" of a large angle that isn't quite 90 degrees is still going to be a decent amount of effort headed in the right direction.  Don't look at what percentage of NASA's budget is being spent intelligently, or you'll despair, but if you look in absolute terms at what NASA isn't screwing up, it gives one some hope....

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/19/2009 08:14 pm
Quote
Just because they use hypergols doesn't mean that they would have use for buying it from you on orbit.  That's a tougher nut to crack.  Now if ATV were being used as a tug, maybe...but that's a different problem.

Any ideas on how that could be stimulated?

Find someone who wants a satellite weighting 7 or more tonnes in GEO.  Until the big LV exist a tug is probably the only way to get the satellite into orbit.  The tug, depot and satellite can be launched using existing LV.

Edit: add probably the only
Note: tugs can use chemical or ion thrusters, both can be filled from a depot.
Title: Re: Propellant Depots - General Discussion
Post by: Patchouli on 03/20/2009 12:48 am
On the Alternative DIRECT thread I discovered that LOX/Methane and LOX/RP-1 suffer from 0.2% a day boil off, mostly of the LOX.  This implies that even a LOX only propellant depot needs zero boil-off equipment.

Without zero boil-off after 183 days (6 months) the depot would have lost more than 30% of its LOX.

Wouldn't zero boil-off  be an order of power easier for LOX then LH2 since you can find temps close to possibly even below the boiling temp of LOX in the depot's shadow?

You might be able to get away with running it through a large radiator shielded from the sun by a multilayered mylar shield might as well have the depot tanks also behind said shield.

Or just have a gaseous helium loop cooling system if that is not enough.

LH2 on the other hand probably is still going to boil off even if you stored it on the dark side of Pluto it's still 40K there.

I really wish they would get off using LH2 for any hardware that must be stored in space for any length of time as for those applications it's really just more trouble then it's worth.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 03/20/2009 01:13 am

I really wish they would get off using LH2 for any hardware that must be stored in space for any length of time as for those applications it's really just more trouble then it's worth.

by whose reasoning?  Certainly not the poster's.  No previous proof of knowledge, experience or documentation to back up such a claim
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/20/2009 01:22 am
I really wish they would get off using LH2 for any hardware that must be stored in space for any length of time as for those applications it's really just more trouble then it's worth.

I agree we should not wait to deploy depots of any kind before we've mastered the relatively difficult cryogenic ones. That would just make it take too long and time's running out. I fear that Ares V or J-232 would kill off depots for at least a decade. If we start developing hypergolics depots now, we may be able to get a foot in the door before it's too late.

But hypergolic depots are only of limited use. At L1 they can support somewhat useful operations in the Earth-Moon system and its direct neighbourhood. They can also usefully support lunar landers with better performance than you might expect. But to get to L1 or anywhere else beyond LEO realistically speaking you either need a bigger launcher (harming the prospects of depots and commercial spaceflight in the process) or cryo depots. I'd say cryo depots are pretty urgent too. Start both cryo and hypergolic depots at once.
Title: Re: Propellant Depots - General Discussion
Post by: Patchouli on 03/20/2009 01:58 am
A typical Centaur has 1.8% boil off per day not a serious issue for an upper stage but a disaster for a depot.
LM/ULA claims they can get this to .1% per day if need for a lunar lander configuration.
http://www.unitedlaunchalliance.com/docs/publications/Atlas/Lunar_Lander_Configurations_Incorporating_Accessibility_2006-7284.pdf

Good but still not good enough for a depot unless you have regular propellant top off flights and usage since 18% of the hydrogen will have been lost after 180 days.

Though maintaining a hydrogen depot could be a first killer application for RLVs.

Other issues hydrogen embrittlement and stress cracking.

http://sti.srs.gov/fulltext/WSRC-STI-2008-00062.pdf

This is one reason why I think a hydrogen economy is nothing more then a pipe dream I can't see the gas station on the street or the distribution trucks dealing with these issues.

On RLVs these problems can be dealt with by regular inspection and EELVs who cares you're not reusing it.

But a depot not only has to be reused it has to last years with no large scale maintenance since you can't take it back to a hanger.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/20/2009 04:30 am

I really wish they would get off using LH2 for any hardware that must be stored in space for any length of time as for those applications it's really just more trouble then it's worth.

by whose reasoning?  Certainly not the poster's.  No previous proof of knowledge, experience or documentation to back up such a claim

I'm with Jim here.  While there may be some cases where CH4 is a better solution, there are lots of situations where LH2 just makes a ton more sense.  I wish people wouldn't keep letting their ignorance of the solution space drive them to jump to suboptimal conclusions.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/21/2009 11:29 pm
Remember though, even if NASA's trajectory is almost orthogonal to an intelligent course for space development, the "dot product" of a large angle that isn't quite 90 degrees is still going to be a decent amount of effort headed in the right direction.

It looks as if current plans are the cross product of what NASA used to do and what it ought to be doing...
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/24/2009 02:53 am
Other threads are suggesting that NASA will be having problems with Congress over the next few months, particularly financial problems.  Allowing for presidential terms lasting 4 years and the US Government's financial year starting in September - what sort and size of propellant depot could be placed in LEO within 3 years?
How much would it cost (+/- 100%)?
How massive a payload could it get to GEO or lunar orbit?
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/24/2009 07:26 am
No chance at all of a cryogenic Depot in just 3 years.   6 years minimum -- and that only with a serious budget, on a regular budget call it 8-10 years.

A Hypergolic Depot might be possible in as little as 3 years because the necessary hardware already exists for Progress/Shuttle refueling the ISS.   But a new depot could only be built if you can find the money from somewhere -- and money is proving to be in extraordinarily short supply in NASA circles right now so I don't think its likely.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/24/2009 01:03 pm
Why does it have to be only one fuel?

My local Speedway fuel station offers 3 grades of gasoline, diesel and kerosene and propane exchange for my BBQ grill not to mention gas producing hot dogs and chili.

NASA likes H2. Well, okay, that is a big topic for another thread and an H2 depot would indeed be useful. 

But Russia already has an operational kerosene stage (Block D) and an operational hypergolic tug (Fregat). Building an LH2 only depot would limit the depot to American customers and stiff arm a large potential customer base. 

Can the US -- all by itself -- provide sufficient demand to justify a propellant depot?

For smaller commercial applications, I would also submit that being able to provide Fregats -- on demand -- would be a useful ancillary business line.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/24/2009 01:54 pm
No chance at all of a cryogenic Depot in just 3 years.   6 years minimum -- and that only with a serious budget, on a regular budget call it 8-10 years.

How useful, if at all, would the ISS be for doing cryogenic depot research? The microgravity aspects would be impossible to test on earth, and even with computer simulations it might still be useful to do some experiments. Maybe you could test and tweak a scale model inside the ISS? I guess it would have to be pretty small for it not to be an explosion hazard.

I don't know if the existing ISS has enough space for a workshop. If not, maybe we've found another reason to convert an MPLM for permanent use. :) Would things like CNC machines need major modifications before they could work in microgravity? Even if not, you would pretty much need an MPLM to bring them up to the ISS, since they likely won't fit through a hatch.

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A Hypergolic Depot might be possible in as little as 3 years because the necessary hardware already exists for Progress/Shuttle refueling the ISS.   

An ATV with bigger tanks would basically be a depot. There are a few more changes, but that's about it, right?

Quote
But a new depot could only be built if you can find the money from somewhere -- and money is proving to be in extraordinarily short supply in NASA circles right now so I don't think its likely.

If Ares were cancelled however...
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/24/2009 03:47 pm
Google is your friend:

"A CNC mill was flown aboard NASA's KC-135 ``Weightless Wonder'' microgravity research aircraft to investigate the effect of gravity on the machining process and to demonstrate the feasibility and functionality of a CNC mill in a weightless environment, such as aboard the International Space Station. The experiment hypothesis was that the surface roughness of milling cuts made in microgravity would be of higher quality than cuts made in a gravitational environment due to increased chip removal. The technical problems associated with microgravity machining (such as the chip removal and collection process), and the engineering solutions to these problems were also evaluated in this experiment."
http://adsabs.harvard.edu/abs/2003AIPC..654..882V

You need to pay for the full article unfortunately.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/24/2009 04:17 pm
Turns out this experiment was less impressive than I thought. It was a Space Grant project. The author of the paper, the youthful Graylan Vincent, wants to be the first geologist on Mars. I'd say his career got off to a good start.

http://www.waspacegrant.org/effallwin02.html
Title: Re: Propellant Depots - General Discussion
Post by: aggelos on 03/24/2009 05:57 pm
its possible a iss extension fuel depot?
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/24/2009 06:03 pm
its possible a iss extension fuel depot?

Sorry, No -
A fuel depot is a highly specialized application and the ISS is in no way equipped to take on that kind of duty. A fuel depot would need to be a completely separate operation, most likely in a different orbit as well.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/24/2009 06:07 pm
A fuel depot is a highly specialized application and the ISS is in no way equipped to take on that kind of duty. A fuel depot would need to be a completely separate operation, most likely in a different orbit as well.

I'm not so sure about that. A man-tended fuel depot close to the ISS might not be a bad idea, depending on what you wanted to do with it. For going to the moon with L1 rendez-vous the inclination doesn't matter much.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/24/2009 06:17 pm
its possible a iss extension fuel depot?

Sorry, No -
A fuel depot is a highly specialized application and the ISS is in no way equipped to take on that kind of duty. A fuel depot would need to be a completely separate operation, most likely in a different orbit as well.

Different orbits cross. The same orbit but a little ahead or a little behind might make sense.

Polar orbits would be the worst.

Long term (centuries from now?) if there is substantial and frequent travel to and from cis-lunar space then extensive use of equatorial orbits would help with space debris issues and space traffic control since most everything would be moving in the same direction within a well defined corridor.

Long term, EML-1 and EML-2 are also the premier cis-lunar depot locations.

Smack dab on the "Lo road" entrance/exit ramps together with 24/7 global access to Earth and Luna.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/24/2009 06:36 pm
Long term we'll be nuclear, LEO to lunar surface in 24-hours with no stop-over in LLO, just straight in (I hope).
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/25/2009 02:49 am
No chance at all of a cryogenic Depot in just 3 years.   6 years minimum -- and that only with a serious budget, on a regular budget call it 8-10 years.

A Hypergolic Depot might be possible in as little as 3 years because the necessary hardware already exists for Progress/Shuttle refueling the ISS.   But a new depot could only be built if you can find the money from somewhere -- and money is proving to be in extraordinarily short supply in NASA circles right now so I don't think its likely.

Ross.

Once a Depot is in LEO successfully selling any type of propellant it can be used to publicly show the commercial possibilities.  In later years larger Depots selling other fuels can then be built, possibly paid for by oil companies.

NASA may make a good anchor customer but if Acme Space Fuels Inc is sensible it will find a second customer.

NASA could finance building a Propellant Depot as an ordinary project but there is an alternative issue Space Act Agreements for propellant similar to COTS development and cargo delivery agreements.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/25/2009 02:54 am
Long term we'll be nuclear, LEO to lunar surface in 24-hours with no stop-over in LLO, just straight in (I hope).

To Mars possibly but a safe nuclear reactor lighter than the solar arrays/concentrator suitable for LEO to lunar flights will be difficult to build.

The argon, xenon, nitrogen or hydrogen used as propellent by the nuclear thermal or ion thruster could be refuelled at a Propellant Depot.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/25/2009 03:02 am
its possible a iss extension fuel depot?

The ISS is in a good orbit for a solar electric or solar thermal space tug to take on propellant.  The high latitude means more time in the sun per orbit, particularly during the equinoxes.  A chemical tug is likely to prefer its Depot nearer the equator to save fuel.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/25/2009 10:55 am
Long term we'll be nuclear, LEO to lunar surface in 24-hours with no stop-over in LLO, just straight in (I hope).

To Mars possibly but a safe nuclear reactor lighter than the solar arrays/concentrator suitable for LEO to lunar flights will be difficult to build.

The argon, xenon, nitrogen or hydrogen used as propellent by the nuclear thermal or ion thruster could be refuelled at a Propellant Depot.

What I envision for lunar use is thermal nuclear. Ion engines are PERFECT for solar system travel, like going to Mars etc. But if you want a trip to the lunar surface to take no more than 24 hours you need a LANTR engine; thermal nuclear, LH2 propellant, LUNOX augmented nozzle.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/25/2009 02:53 pm
LANTR engines look like nice engines.
http://www.nss.org/settlement/moon/LANTR.html (http://www.nss.org/settlement/moon/LANTR.html)

I suspect the same boost effect by burning LOX applies to solar thermal engines which have similar ISPs.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/25/2009 10:20 pm
No chance at all of a cryogenic Depot in just 3 years.   6 years minimum -- and that only with a serious budget, on a regular budget call it 8-10 years.

I think that depends a lot on your assumptions (and what scale of fuel depot you do for a first rev)...Some of the concepts I've seen are simple enough that they could probably be flying within 3 years if they had decent funding.  The only problem is that a fuel depot is part of an overall system (need a way of getting propellant to the depot, and need a way of getting it to the customers)--tugs and standardized interfaces would help a lot, but those would also need to be fielded.  Now, on the tug side, pretty much all the needed technology is proven out (Dallas Bienhoff pointed out to me last year that the Orbital Express propellant transfer hardware was also designed to be cryo compatible for instance), we would just need a "commercialized Orbital Express derivative".  For the tanker side as well, you could do things with proven off-the-shelf hardware, but it would also need to be integrated...

You could field something within three years.  The only problem is that the people who could do it aren't the sort who'll just do something like that on speculation.  They'd actually want a firm contract to do so.

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A Hypergolic Depot might be possible in as little as 3 years because the necessary hardware already exists for Progress/Shuttle refueling the ISS.   But a new depot could only be built if you can find the money from somewhere -- and money is proving to be in extraordinarily short supply in NASA circles right now so I don't think its likely.

Yeah, the money is the issue.  There are some potential near-to-medium-term markets for a small hypergolic depot, but for cryo depots, unless you have RLVs working giving a much lower price per lb to orbit, there aren't a huge number of markets outside of human transportation beyond LEO...and that depends strongly on either space tourism (which may be hurting with current market situations, and would require capsules capable of handling higher speed reentries), or on government programs (which tend to want to build bloated oversized launchers to keep bloated oversized ground support crews)...

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/25/2009 10:30 pm
Why does it have to be only one fuel?

My local Speedway fuel station offers 3 grades of gasoline, diesel and kerosene and propane exchange for my BBQ grill not to mention gas producing hot dogs and chili.

NASA likes H2. Well, okay, that is a big topic for another thread and an H2 depot would indeed be useful.

But Russia already has an operational kerosene stage (Block D) and an operational hypergolic tug (Fregat). Building an LH2 only depot would limit the depot to American customers and stiff arm a large potential customer base. 

It depends.  Those "customers" need their own customers.  Who are the russians going to sell refueled Block D or Fregat flights to?  If there are markets for refueling such stages, the next question is what are the destination (and hence departure orbits). 

It's quite possible to have a multi-fuel depot.  But what fuel you have, and where, is going to depend on how the markets play out.  I can see the need for *small* hypergolic tanks on a mid-inclination cryo depot, since most cryo stages still use hypergols for RCS.  But for a mini-depot servicing say tugs in near-polar orbits, it might be entirely hypergols with no cryogens...

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Can the US -- all by itself -- provide sufficient demand to justify a propellant depot?

Yes.  Easily.  Eventually multiple depots.

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For smaller commercial applications, I would also submit that being able to provide Fregats -- on demand -- would be a useful ancillary business line.

Maybe...but I'm skeptical.  You could actually put a small payload into LLO or L1 with a Fregat, or a very small GEO satellite...but I'm not sure if it would be worth the cost or not.  Just because it can be done doesn't mean it can be done profitably.  Just because it can be done profitably doesn't mean that there's enough business to justify the risk of doing so.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/25/2009 10:46 pm
How useful, if at all, would the ISS be for doing cryogenic depot research? The microgravity aspects would be impossible to test on earth, and even with computer simulations it might still be useful to do some experiments. Maybe you could test and tweak a scale model inside the ISS? I guess it would have to be pretty small for it not to be an explosion hazard.

I think you'd be hard pressed to get permission to bring a decent sized LH2 tank inside the ISS.  As it is, there are some options using suborbital vehicles for short-duration microgravity experiments (some such tests have even be done on the Vomit Comet, but there are issues with getting permission to fly volatile fuels or oxidizers inside manned aircraft).  That's one of the things I'm hoping to work on once we have a vehicle at MSS that can get enough "hang time".  Also, at least Lockheed (and possibly Boeing as well), have floated ideas for flying cryo depot experiments as part of their Atlas-V flights.  There's a paper online for the Centaur Test Bed that you can probably find on google or at ntrs.nasa.gov.  There are other options in the works.

In fact, the DMSP launch that's the AF has kept delaying is supposed to have something north of 11,000lb of unused propellants after payload delivery, which Lockheed is planning on using to demonstrate their spin-settling idea after spacecraft delivery.  They were talking about spinning up the tank, demonstrating handling in that orientation, despinning it, transfering to an accelerated settling configuration, then lathering, rinsing, and repeating a few times to verify they have their procedures worked out (and as much data milked out of that flight as they possibly can get).  [Methinks their wives are going to not be seeing them for several days straight when that launch finally goes off].

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An ATV with bigger tanks would basically be a depot. There are a few more changes, but that's about it, right?

Yeah.  There are lots of demonstrated methods for settling storable propellants (pistons, diaphragms, spin settling, propulsive settling, etc, etc).  All a storable depot really needs is a big tank, a transfer interface, and some sort of spacecraft bus for attitude control, communications, and power...

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/25/2009 10:48 pm
its possible a iss extension fuel depot?

Sorry, No -
A fuel depot is a highly specialized application and the ISS is in no way equipped to take on that kind of duty. A fuel depot would need to be a completely separate operation, most likely in a different orbit as well.

Well, it could be done technically, but is probably a political nonstarter.  Most depot operations want frequent dockings, and do weird settling stuff all of which would probably hurt the microgravity environment of a space station.  But as others have pointed out, having it as a relatively close flyer in the same orbit just ahead of or behind ISS wouldn't be a terrible place for putting a depot.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/25/2009 10:58 pm
There's a paper online for the Centaur Test Bed that you can probably find on google or at ntrs.nasa.gov.

Here:   http://gltrs.grc.nasa.gov/reports/2006/CR-2006-214410.pdf


That's a piece of hardware which *really* needs to be funded by someone.

Unfortunately CxP have no intention because if it were successful it would destroy their entire justification for the giant Ares-V and essentially make it obsolete over-night.   CxP's current management doesn't want that at all.

As soon as this technology is flight-proven, the Propellant Depot concept becomes far more plausible and EELV's are *perfectly* placed as a delivery vehicles for them.

Given the potential for additional business which that would generate, I personally think that's sufficient justification for ULA to give serious consideration to funding this first test relatively in-expensive secondary payload entirely out of their own pockets.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/25/2009 11:13 pm
Long term, EML-1 and EML-2 are also the premier cis-lunar depot locations.

Smack dab on the "Lo road" entrance/exit ramps together with 24/7 global access to Earth and Luna.

"If the Good Lord had wanted us to explore the solar system, He would have given us libration points."

I don't remember who said it, but I like it.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/26/2009 12:07 am
There's a paper online for the Centaur Test Bed that you can probably find on google or at ntrs.nasa.gov.

Here:   http://gltrs.grc.nasa.gov/reports/2006/CR-2006-214410.pdf

That's a piece of hardware which *really* needs to be funded by someone.

They've actually got an even cooler cryo testbed concept (sorry for the pun) in the works, but I don't think it's public knowledge yet, so that's all I can say for now.

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Unfortunately CxP have no intention because if it were successful it would destroy their entire justification for the giant Ares-V and essentially make it obsolete over-night.   CxP's current management doesn't want that at all.

As soon as this technology is flight-proven, the Propellant Depot concept becomes far more plausible and EELV's are *perfectly* placed as a delivery vehicles for them.

Exactly.  Until you've demonstrated it beyond any doubt, there's huge incentive for many at NASA to ignore the technology as "unproven".

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Given the potential for additional business which that would generate, I personally think that's sufficient justification for ULA to give serious consideration to funding this first test relatively in-expensive secondary payload entirely out of their own pockets.

I don't think they have as big of IRAD budgets as you might think.  There are other options being investigated, but I haven't personally heard of any breakthroughs funding-wise (but that doesn't mean they haven't happened--just that I may not be as in-the-know on such things as I'd like to think).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/26/2009 02:10 am
Jobs point.  The Shuttle may be launched in Florida but so are the Delta IV, Delta II, Atlas V and Falcon 9 LV.  I suspect that an extra 10 or so flights a year will result is some company recruiting extra staff at the launch pad and rocket factory.
Title: Re: Propellant Depots - General Discussion
Post by: kraisee on 03/26/2009 04:15 am
Not many.

You essentially need the same number of people to process 5 Delta first stages a year as you do for processing 10.

The current EELV workforce and infrastructures could handle at least 15-20 per year with no increases in the workforce at all.   After that only moderate increases would be required up to around 30 per year, per system.

Only if you wish to go beyond that sort of flight rate would you would probably require a second Pad and that's the point where you would need more staff.

Even then, the entire EELV program -- Atlas & Delta, manufacturing in Alabama and launch processing at both CCAFS and VAFB all wrapped-up together, only employs around 3,000 people in total.

KSC is going to be shedding more than 7,000 jobs in just 18 months time.   Even if we maxed-out the EELV program, it isn't ever going to require more than a fraction of those workers.

Ross.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/26/2009 01:35 pm
KSC is going to be shedding more than 7,000 jobs in just 18 months time.   Even if we maxed-out the EELV program, it isn't ever going to require more than a fraction of those workers.

Which in my book is a feature, not a bug.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/26/2009 01:39 pm
KSC is going to be shedding more than 7,000 jobs in just 18 months time.   Even if we maxed-out the EELV program, it isn't ever going to require more than a fraction of those workers.

Which in my book is a feature, not a bug.

~Jon

Congressional mileage varies on this point, and they happen to be the folks with the golden checkbook.


Title: Re: Propellant Depots - General Discussion
Post by: aggelos on 03/26/2009 03:03 pm
could we make  orbit depot only with LOX ?Is 90% I think of thw weight of fuel...lets bring hydrogen from earth...
Title: Re: Propellant Depots - General Discussion
Post by: Patchouli on 03/26/2009 05:39 pm
KSC is going to be shedding more than 7,000 jobs in just 18 months time.   Even if we maxed-out the EELV program, it isn't ever going to require more than a fraction of those workers.

Which in my book is a feature, not a bug.

~Jon

Who's says they would stay jobless?

It may create new jobs to replace those that were lost or the operation could just be ran at a larger scale.

If the launch system requires less people to operate there will be more money for advanced research projects which in turn would need to hire people.

Instead of working on an old SRB some of the people could find themselves working on a VASIMR engine,a new type of ECLSS,solar power demo satellite or scramjet.
Title: Re: Propellant Depots - General Discussion
Post by: Patchouli on 03/26/2009 05:54 pm
could we make  orbit depot only with LOX ?Is 90% I think of thw weight of fuel...lets bring hydrogen from earth...

Hydrocarbon's might be more near therm then hydrogen but regardless the fuel LOX is often the biggest mass.

Main advantage of hydro carbon fuel is you can send 50+T of it to the moon using just 8T of xenon gas and not loose any of it during the six month transit.

You can get hydrogen to an L1 depot on a solar tug if you're willing to loose 18% of it by the time it gets there.

Though the boil off hydrogen could be used for propulsion in some sort of VASIMR or solar thermo engine vs simply being vented.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/26/2009 06:39 pm
could we make  orbit depot only with LOX ?Is 90% I think of thw weight of fuel...lets bring hydrogen from earth...

You can.  In fact, that's what my ULA friends suggest as a much easier first step.  That said, while it does save some complexity, it comes with some real costs as well.  Whether or not the tradeoff is worth it is going to depend on what your goals are, and what your starting resources are.  I've been focusing on trying to make a simple, small, single-EELV-launch LOX/LH2 depot concept close, because I think that in spite of the higher costs, it gives you more flexibility.  But the ULA guys also have some pretty clever and impressive ideas for what you could do with a LOX-only depot...

You Mileage *Will* Vary

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/26/2009 06:46 pm
could we make  orbit depot only with LOX ?Is 90% I think of thw weight of fuel...lets bring hydrogen from earth...

Hydrocarbon's might be more near therm then hydrogen but regardless the fuel LOX is often the biggest mass.

Main advantage of hydro carbon fuel is you can send 50+T of it to the moon using just 8T of xenon gas and not loose any of it during the six month transit.

You can get hydrogen to an L1 depot on a solar tug if you're willing to loose 18% of it by the time it gets there.

Though the boil off hydrogen could be used for propulsion in some sort of VASIMR or solar thermo engine vs simply being vented.

Of course, one important thing to remember is that whether the "slow boat" approach actually ends up being any cheaper for LEO to L1 transport depends on a lot of assumptions.  A lot of assumptions that are very likely to be invalid once you have a depot architecture.  The single biggest one is that earth-to-LEO costs are going to continue to be so high that they swamp all other considerations.  If your solar electric system costs more than a chemical tug (very likely), and is capable of less missions per year, and less missions overall (also very likely), it's quite possible that earth-to-LEO prices don't have to come down very far before solar-electric becomes economically questionable for cislunar transportation.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/26/2009 06:54 pm
could we make  orbit depot only with LOX ?Is 90% I think of thw weight of fuel...lets bring hydrogen from earth...

It depends what you are launching.

A deep space probe on an expendable upper stage can use a LOX only depot.  The mass of the probe can be increased because the main LV does not need to lift the mass of the LOX.

However a reusable space tug will have problems because it will not have any fuel to burn on its second trip.

LOX only depots can be useful in orbit around the Moon and Mars.  If the LOX is taken there using ion thrusters there can be a significant reduction in the total mass launched from the Earth.  (A LOX + fuel Depot would save even more mass.)
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/30/2009 08:27 pm
Legal Aspects

Currently Propellant Depots appear to be outside of national and international law with no regulatory agency having jurisdiction.

The Depot operator and customers may have to voluntary submit to regulation and licensing until international law has caught up. Sales contracts and employment contracts being attached to licensing country's national laws. Criminal laws covering theft, fraud, vandalism, murder, manslaughter, assault, rape, health & safety, trading standards, pollution, navigation, arrest, trial and criminal responsibility will be needed.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 03/30/2009 08:30 pm

Currently Propellant Depots appear to be outside of national and international law with no regulatory agency having jurisdiction.


Incorrect, they fall under the laws of the country of origin, these rules are in affect for the ISS.  No different than ships and planes in international waters except martime vessels have registry and planes have a similar ownership title.  The US Code even has laws for the shuttle and ISS
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/30/2009 08:32 pm
I don't know if this would be a big problem unless and until we have many commercial players in the field. I wonder if US spacecraft are considered US territory just as ships and aircraft are.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 03/30/2009 08:49 pm

Currently Propellant Depots appear to be outside of national and international law with no regulatory agency having jurisdiction.


Incorrect, they fall under the laws of the country of origin, these rules are in affect for the ISS.  No different than ships and planes in international waters except martime vessels have registry and planes have a similar ownership title.  The US Code even has laws for the shuttle and ISS

Jim is correct, here.

Also, under the Outer Space Treaty of 1967, the nation of origin for a facility bears responsibility towards the other signatories of that treaty.

Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/30/2009 10:59 pm
The Shuttles are owned by the US Government.  Any Depots are likely to be private sector, so different rules apply.  Doubly so if the Depot is registered in Singapore or a tax haven.

Extending maritime law to space may be a good idea providing allowance is made for the different ways space and sea ships move.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 03/31/2009 10:29 am
The Shuttles are owned by the US Government.  Any Depots are likely to be private sector, so different rules apply.

No same rules apply
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/31/2009 08:10 pm
Question for EELV-only supporters:

Assuming that realistically, without either cryo depots or bigger launchers you can't go beyond LEO, would you start with bigger launchers or with depots? If depots, what tangible signs of progress can you offer the US public within the >=8 years I'm hearing it would take to develop them? If bigger launchers, how big and what will you do with them until depots become operational?

I have my own ideas of course, but I'd like to know what other people are thinking.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/31/2009 10:40 pm
The Shuttles are owned by the US Government.  Any Depots are likely to be private sector, so different rules apply.

No same rules apply

Not to sea ships.  For instance during peace time you do not arrest sea ships belonging to other governments.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/31/2009 10:50 pm
Question for EELV-only supporters:

Well, I'm less of an "EELV only" supporter and more of a "get NASA out of the damn launch business and make them buy flights on commercial rockets just like everyone else" kind of guy.  I mean seriously, there's very little that NASA is doing at the moment that is as importance as national defense, yet the DoD is perfectly fine flying billion dollar national security payloads on EELVs.  But I digress....

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Assuming that realistically, without either cryo depots or bigger launchers you can't go beyond LEO, would you start with bigger launchers or with depots?

Depots.  With depots and existing stages with some slight modifications (lunar mission kits if you will), we could have people back on the moon.  Without depots, I'm skeptical Congress will keep the funding going long enough and strong enough for us to get back.

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If depots, what tangible signs of progress can you offer the US public within the >=8 years I'm hearing it would take to develop them?

I would say within 8 years you could do the following:
a) a series of suborbital CFM test flights to debug the technologies
b) a series of one or two orbital CFM demo flights to demonstrate the key technologies on orbit (in subscale)
c) launch a medium-scale single-launch depot on an existing EELV
d) maybe do a couple of impressive robotic lunar landings using the depot to enable stuff that wouldn't be possible otherwise or use the depot to send someone on an "Apollo 8" trajectory using a refueled centaur and either an Orion, or a Dragon or Soyuz with uprated heat shield....

8 years is a long time.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/31/2009 11:01 pm
d) maybe do a couple of impressive robotic lunar landings using the depot to enable stuff that wouldn't be possible otherwise or use the depot to send someone on an "Apollo 8" trajectory using a refueled centaur and either an Orion, or a Dragon or Soyuz with uprated heat shield....

This is the most impressive of the four, coming near the end of those 8 years and I'm afraid most people wouldn't even find it very interesting. And you'd need multiple depots (LEO, L1, LLO) and probably multiple Centaurs to make it work, right?

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8 years is a long time.

Two presidential terms, 4 congressional cycles. I think that this is a large part of the reason depots are such a hard sell. Doing the right thing is hard.


---

Edit: re-reading this posting it seems a bit harsh. I didn't mean it that way. I was just expressing frustration.
Title: Re: Propellant Depots - General Discussion
Post by: Jorge on 03/31/2009 11:33 pm
The Shuttles are owned by the US Government.  Any Depots are likely to be private sector, so different rules apply.

No same rules apply

Not to sea ships.  For instance during peace time you do not arrest sea ships belonging to other governments.

Who gives a flip about sea ships and why are you trying to confuse the issue here? The Outer Space Treaty is quite explicit about this issue:

http://www.oosa.unvienna.org/oosa/SpaceLaw/outerspt.html

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Article VI

    States Parties to the Treaty shall bear international responsibility for national activities in outer space, including the moon and other celestial bodies, whether such activities are carried on by governmental agencies or by non-governmental entities, and for assuring that national activities are carried out in conformity with the provisions set forth in the present Treaty. The activities of non-governmental entities in outer space, including the moon and other celestial bodies, shall require authorization and continuing supervision by the appropriate State Party to the Treaty. When activities are carried on in outer space, including the moon and other celestial bodies, by an international organization, responsibility for compliance with this Treaty shall be borne both by the international organization and by the States Parties to the Treaty participating in such organization.

 
Article VII

    Each State Party to the Treaty that launches or procures the launching of an object into outer space, including the moon and other celestial bodies, and each State Party from whose territory or facility an object is launched, is internationally liable for damage to another State Party to the Treaty or to its natural or juridical persons by such object or its component parts on the Earth, in air or in outer space, including the moon and other celestial bodies.

Bottom line: it does not matter one whit whether a private-sector propellant depot is "registered" with Singapore or some tax haven; they are subject to the regulations of the country they launched from, and that country is liable for damages caused by the propellant depot (which gives them a huge incentive to take an active hand in regulating them).
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/31/2009 11:54 pm
Who gives a flip about sea ships and why are you trying to confuse the issue here?
Ask Jim that question.
{snip}
Quote
Bottom line: it does not matter one whit whether a private-sector propellant depot is "registered" with Singapore or some tax haven; they are subject to the regulations of the country they launched from, and that country is liable for damages caused by the propellant depot (which gives them a huge incentive to take an active hand in regulating them).

1. The ESA performs launches but is not owned by a country.  A good lawyer can keep a case going for years.

2. The regulations need writing, particularly the criminal and commercial aspects.  I gave a list earlier.
Title: Re: Propellant Depots - General Discussion
Post by: R.Simko on 04/01/2009 01:05 am
I would think the actual successfull construction of a propellant depot, would be a very "tangible sign of progress" in itself.  To me, that would not only be something that no other country has done before, but would be a sign that we are opening up space to the world. 

Of course saying "the world", sounds a little grandiose, but there are more countries all the time that are making it to space.  A depot will enhance their ability to do deep space missions and our, with smaller rockets.  Depots will open up space to commercial interests, like nothing else we can do.  I can visualize, that in only a few short decades, small commercial companies taking tourists to landings on near Earth objects.

We have tried the massive rocket routine before and it wasn't sustainable.  Let's go where "No Man Has Gone Before",  Lets build a  depot.


Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/01/2009 01:12 am
We have tried the massive rocket routine before and it wasn't sustainable.  Let's go where "No Man Has Gone Before",  Lets build a  depot.

Who do you think should build, own and operate this depot?

Where should the money come from?
Title: Re: Propellant Depots - General Discussion
Post by: R.Simko on 04/01/2009 01:49 am
I feel that the US is very capable of building a depot on its own. The operation can be international.

I can't see us building Ares 5 and using it for more than a handfull of trips to the moon, before it is cut as too expensive.  We don't need another plant the flag and then 5 decades in LEO.  I would do a complete revamp of Constellation, with a propellant depot as its center piece.  The Constellation money would be used, with a shift in its architecture.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/01/2009 02:02 am
I can't see us building Ares 5 and using it for more than a handfull of trips to the moon, before it is cut as too expensive.

Precisely. Which is why anything as massive as the Ares-V is completely unreasonable. A propellant Depot based architecture sets the foundation for all future space travel beyond LEO. Mission planners can utilize the lift capacity of the launch vehicle to fly actual payloads instead of propellant. Quite frankly, by utilizing the depot, I honestly cannot ever envision needing a launch vehicle larger than the Jupiter-241/246. Even the lowly Jupiter-130 lets you put 50mT of actual hardware/spacecraft into orbit. That is a massive improvement over what we can accomplish today and it's all based on the propellant depot.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 04/01/2009 02:24 am
Who gives a flip about sea ships and why are you trying to confuse the issue here?
Ask Jim that question.
{snip}


You are causing the confusion with your asinine comment about arresting ships.

My comment was about the laws ON the spacecraft pertaining to personnel conduct.  They are the same as laws on ship at sea.
I said nothing about ships interacting
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 04/01/2009 02:29 am
Who gives a flip about sea ships and why are you trying to confuse the issue here?
Ask Jim that question.
{snip}
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Bottom line: it does not matter one whit whether a private-sector propellant depot is "registered" with Singapore or some tax haven; they are subject to the regulations of the country they launched from, and that country is liable for damages caused by the propellant depot (which gives them a huge incentive to take an active hand in regulating them).

1. The ESA performs launches but is not owned by a country.  A good lawyer can keep a case going for years.

2. The regulations need writing, particularly the criminal and commercial aspects.  I gave a list earlier.

So what that ESA is not "owed" by a country, that doesn't matter, it is the country where the launch takes place, French Guiana that is responsible

The regulation don't need writing, they already exist.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 04/01/2009 02:33 am

Who's says they would stay jobless?

It may create new jobs to replace those that were lost or the operation could just be ran at a larger scale.

If the launch system requires less people to operate there will be more money for advanced research projects which in turn would need to hire people.

Instead of working on an old SRB some of the people could find themselves working on a VASIMR engine,a new type of ECLSS,solar power demo satellite or scramjet.


None of that work is at the launch site.  And if any were to get launched, it would be for years.  The people will have moved on.

Also believe it or not, most of the work at KSC is not high tech.  It is just wrench turning
Title: Re: Propellant Depots - General Discussion
Post by: kkattula on 04/01/2009 04:14 am

Who's says they would stay jobless?

It may create new jobs to replace those that were lost or the operation could just be ran at a larger scale.

If the launch system requires less people to operate there will be more money for advanced research projects which in turn would need to hire people.

Instead of working on an old SRB some of the people could find themselves working on a VASIMR engine,a new type of ECLSS,solar power demo satellite or scramjet.


None of that work is at the launch site.  And if any were to get launched, it would be for years.  The people will have moved on.

Also believe it or not, most of the work at KSC is not high tech.  It is just wrench turning

A good solution is one that has those people working on 10, 15 or 20 Constellation launches per year instead of 3, 4 or 5 Shuttle launches.

There are two ways to reduce launch costs:

1) Reduce the number of people working per launch -> job losses.

2) Increase the number of launches using the same workforce -> job retention or even growth

Depots are a great way to increase the number of launches, without requiring a lot of extra payload development. i.e. once the depot is in orbit, you just need a standard bus to fill it, with variants for each propellant type, and an adaptor for each LV type.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/01/2009 04:33 am
This is the most impressive of the four, coming near the end of those 8 years and I'm afraid most people wouldn't even find it very interesting. And you'd need multiple depots (LEO, L1, LLO) and probably multiple Centaurs to make it work, right?

Well, it's true that an Apollo 8 mission (loop around the moon without stopping in lunar orbit) might not be *that* exciting all told.  But it'd be useful, and if one or more of the people on-board were space tourists, might pique more interest.

As for whether you would need multiple Centaurs and multiple depots...nope.  If you're not trying to reuse the Centaur ferry, you can toss a ~38klb payload into TLI (assuming you top the Centaur up in LEO).  If you're trying to reuse just the centaur (with the capsule reentering upon earth return), you're probably talking more like 28klb worth of capsule.  In both of those cases, that's more than enough payload for a capsule and possibly some living space.

Now, if you want to go into lunar orbit, and eventually to the lunar surface, that's when the logistics starts getting more complex, and multiple depots start making more sense.

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Two presidential terms, 4 congressional cycles. I think that this is a large part of the reason depots are such a hard sell. Doing the right thing is hard.

Everything NASA does takes multiple years to do.  But I'm not holding my breath for NASA to fund a billion dollar depot project.  There are groups in NASA that might get some low-level funding for some of the demo work, but I'm assuming that a real depot is something that is going to have to be developed commercially.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/01/2009 04:42 am
Who do you think should build, own and operate this depot?

Personally, I think there are lots of benefits from having depots be commercially owned, developed, and operated.  Next best case would be NASA contracting someone to build and operate a depot.

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Where should the money come from?

From whoever's willing to pay for it?  :-)  Seriously, my guess is it most likely will be a mix of a) some government money/incentives for R&D that's mutually useful for other government projects (long-term cryo storage, etc), b) some direct private investment, c) some bootstrapping money from earlier ventures like possibly tugs, and d) some money either from vendor financing, presales, etc.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/01/2009 01:08 pm
Who do you think should build, own and operate this depot?

Personally, I think there are lots of benefits from having depots be commercially owned, developed, and operated.  Next best case would be NASA contracting someone to build and operate a depot.

In an academic setting, or at a conference enjoying beverages, I could agree that there would be benefits to a commercially owned and operated propellant depot, but remember that the ITAR angle on that would be huge.

In real life Washington? It could take years of concerted effort seeking to plow through the bureaucracy and you'd still fail. MirCorp represents the only real precedent for a private facility effort.

So, what should NASA be doing while depot advocates are engaged in trench warfare on Capitol Hill? Should the current space program simply be dismantled and terminated while we wait for Congress to "see the light"

This is why I believe depot advocates should climb on-board DIRECT as DIRECT appears to offer the most viable bureaucratic pathway to depot deployment.

= = =

If the underlying objective is to create demand for high flight rates to facilitate RLV development thereby lowering the cost of LEO access (and that seems to be the core motivation for NewSpace or Space Access calls for a propellant depot architecture) it strikes me that a LEO sports arena would support more frequent regular flights than a propellant depot and therefore a LEO sports arena would better facilitate development of low cost RLVs than would a propellant depot.

But that would require accepting advertising, entertainment and marketing dollars. ;-)
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/01/2009 01:19 pm
If the underlying objective is to create demand for high flight rates to facilitate RLV development ...

I really don’t think that a depot will facilitate the development of a RLV unless the intent is to provide fuel to literally fly it back home under power for reuse.

Launch vehicles, RLV or not, arrive on orbit with propellant tanks empty. They go to the depot to take on a load of fuel for the payload/spacecraft to continue beyond LEO. This doesn’t help a RLV that once on orbit doesn't need any additional propellant from the depot.
Title: Re: Propellant Depots - General Discussion
Post by: kkattula on 04/01/2009 01:58 pm
I believe the idea is to use a smal RLV (or small fleet) to replenish the depot, 1 or 2 tons at a time.

This could provide the high flight rates that RLV's require to be more cost effective than ELV's.

It could also demonstrate the RLV concept on a small scale without needing the massive investment that a Shuttle sized RLV would.
Title: Re: Propellant Depots - General Discussion
Post by: R.Simko on 04/01/2009 02:03 pm
I like Mr. White's idea of building a sports arena in space.  That would stimulate commercial development and it would certainly grab the worlds attention.  Anyone ever read the book "Enders Game?"

Perhaps a COTS  type program for a fuel depot, might get the ball rolling. 
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/01/2009 02:55 pm
In an academic setting, or at a conference enjoying beverages, I could agree that there would be benefits to a commercially owned and operated propellant depot, but remember that the ITAR angle on that would be huge.

Sure, but ITAR is a hassle--not a show stopper.

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In real life Washington? It could take years of concerted effort seeking to plow through the bureaucracy and you'd still fail. MirCorp represents the only real precedent for a private facility effort.

You know what they say about trying to reason from a single data point, right?

Anyway, a first-gen propellant depot could probably be built and launched from the states.  Once you have a passive "fueler" interface, you start putting TAAs in place so you can access the international market.  If your fuel transfer interface is entirely passive, this becomes a lot easier.

I think you're handwaving and overestimating the problem.

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So, what should NASA be doing while depot advocates are engaged in trench warfare on Capitol Hill? Should the current space program simply be dismantled and terminated while we wait for Congress to "see the light"

This is why I believe depot advocates should climb on-board DIRECT as DIRECT appears to offer the most viable bureaucratic pathway to depot deployment.

None of us working on depot stuff are sitting on our hands waiting for Congress and NASA to see the light.  There are already mutual needs being addressed that allow us to move forward even if NASA isn't officially doing a depot-centric architecture.

I'm not hitching my wagon to DIRECT mostly because I think it's still another NASA launch vehicle that shouldn't happen.  Sure, it's better than the status quo, but there's just as good of a chance that there won't be the budget for a depot.  And DIRECT can do a lot without one.

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If the underlying objective is to create demand for high flight rates to facilitate RLV development thereby lowering the cost of LEO access (and that seems to be the core motivation for NewSpace or Space Access calls for a propellant depot architecture) it strikes me that a LEO sports arena would support more frequent regular flights than a propellant depot and therefore a LEO sports arena would better facilitate development of low cost RLVs than would a propellant depot.

Maybe.  But in my book it's not an either-or situation.  There are multiple good initial RLV markets.  I'm looking at it more from an angle of "ok, you want cheap access *beyond* LEO.  That takes more than just RLVs."

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But that would require accepting advertising, entertainment and marketing dollars. ;-)

I have no problem with accepting money, so long as it's real.  I've yet to really see a valid case for "orbital sports arenas".  But if you can actually make a convincing case, then more power to you.  This isn't a zero-sum game.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/01/2009 03:03 pm
I really don’t think that a depot will facilitate the development of a RLV unless the intent is to provide fuel to literally fly it back home under power for reuse.

Launch vehicles, RLV or not, arrive on orbit with propellant tanks empty. They go to the depot to take on a load of fuel for the payload/spacecraft to continue beyond LEO. This doesn’t help a RLV that once on orbit doesn't need any additional propellant from the depot.

Umm...I think you're missing the point entirely Chuck.  RLVs are also presumably going to reach orbit with some payload.  That payload could be a small propellant tank for deliveries to the depot.  The depot helps provide demand for RLV flights that have many good features:

1-the payload is divisible.  Demand for 300 mT/yr can be met with 2x 150mT HLV launches, or as many as 100+ flights of a 3mT RLV (or 300 flights of a 1mT RLV).  There are some practical limitations on the lower end, but even small depots can provide demand for high flight rates (the key to closing the business case for RLVs).
2-the payload doesn't require a lot of hand-holding.  If the station is in a resonant orbit, you're always flying the same trajectory, with the same payload, the same CG, etc, etc.  You only have to analyze the trajectory and get an FAA launch license for that trajectory *once*.  And since the tank is basically reusable, your payload handling costs per mission might be as simple as a couple hour's maintenance and then hooking up the cryo delivery truck.

Depots are a wonderful tool for enabling RLV development.  The number one obstacle in the way of RLV development is the difficulty of raising the money to try (and the money to be able to do some incremental development work).  If you can close the business case with proven, steady demand for a high flight rate, getting the funding becomes a *lot* easier.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/01/2009 03:12 pm
I really don’t think that a depot will facilitate the development of a RLV unless the intent is to provide fuel to literally fly it back home under power for reuse.

Launch vehicles, RLV or not, arrive on orbit with propellant tanks empty. They go to the depot to take on a load of fuel for the payload/spacecraft to continue beyond LEO. This doesn’t help a RLV that once on orbit doesn't need any additional propellant from the depot.

Umm...I think you're missing the point entirely Chuck.  RLVs are also presumably going to reach orbit with some payload.  That payload could be a small propellant tank for deliveries to the depot.  The depot helps provide demand for RLV flights that have many good features:

1-the payload is divisible.  Demand for 300 mT/yr can be met with 2x 150mT HLV launches, or as many as 100+ flights of a 3mT RLV (or 300 flights of a 1mT RLV).  There are some practical limitations on the lower end, but even small depots can provide demand for high flight rates (the key to closing the business case for RLVs).
2-the payload doesn't require a lot of hand-holding.  If the station is in a resonant orbit, you're always flying the same trajectory, with the same payload, the same CG, etc, etc.  You only have to analyze the trajectory and get an FAA launch license for that trajectory *once*.  And since the tank is basically reusable, your payload handling costs per mission might be as simple as a couple hour's maintenance and then hooking up the cryo delivery truck.

Depots are a wonderful tool for enabling RLV development.  The number one obstacle in the way of RLV development is the difficulty of raising the money to try (and the money to be able to do some incremental development work).  If you can close the business case with proven, steady demand for a high flight rate, getting the funding becomes a *lot* easier.

~Jon

Ok, I can see that.

If that’s the case, perhaps getting the USAF/DoD involved might be the route to the funding. Surveillance spacecraft that can be launched to the depot on a moments notice, fuel up and go to the target orbit might provide a quasi-military need that could be funded. End result – a RLV that has need of a depot.

Of course the military is not the aim of all this, just a means to the end.

FWIW
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/02/2009 03:07 am
Everything NASA does takes multiple years to do.  But I'm not holding my breath for NASA to fund a billion dollar depot project.  There are groups in NASA that might get some low-level funding for some of the demo work, but I'm assuming that a real depot is something that is going to have to be developed commercially.~Jon

I agree with this and believe that the above passage is realistic and accurate.

That said, there won't be a commercial business case unless NASA is ordered by Congress to be a captive customer to assure sales for that depot. And I do not see Congress doing that, not when Senator Bill Nelson can (reportedly) disapprove of NASA Administrator choice and as Chris Bergin reports, over a hundred people "blitz" Capitol Hill to lobby for extending the orbiter.

And Jon, other than potential NASA lunar missions, who are the potential customers for an LH2 depot in LEO?

I support 100% (make that 200%) immediate funding to advance the TRLs for propellant depot technologies. However we cannot bet the space program on it, and I return to my earlier question -- what do you think NASA should be doing while we wait for propellant depot technology to mature?

= = =

A big reason I like the sports arena idea is that Congress can order NASA to tolerate the idea WITHOUT taking a dime from NASA's existing budgets.

At best (or worst) simply order NASA to offer cooperation at incremental cost points reasonably negotiated so that NASA is reimbursed for depreciation of facilities used at times they would otherwise be idle.

Bringing in stadium name rights dollars, endorsement deals and advertising (with NASA being involved only at the margins) increases the total amount being spent on human spaceflight without raiding NASA's other budgetary items.

Contrast that with the NewSpace / Space Access concept of terminating all shuttle derived programs and "betting the farm" on propellant depots and RLVs and it should be obvious why the odds of Congress doing that are essentially zero. Even Admiral Steidle was unable to defeat the shuttle lobby and with Bill Nelson (allegedly) having the power to veto an unsatisfactory NASA Administrator, I see no traction for a NewSpace only approach.

Therefore, a LEO sports stadium idea (with Congress merely saying --if you guys raise the money we will order NASA not to obstruct) could offer the best short term potential source of demand for a high flight rate RLV. Even if that is politically unlikely as well.

Therefore, in terms of political realism, the DIRECT Team's approach offers the best opportunity for developing the propellant depots that most of us agree are a good idea worth pursuing.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/02/2009 12:31 pm
I support 100% (make that 200%) immediate funding to advance the TRLs for propellant depot technologies. However we cannot bet the space program on it, and I return to my earlier question -- what do you think NASA should be doing while we wait for propellant depot technology to mature?

That depends on whether or not one believes, like I do, that propellant depots will eventually form the backbone of spaceflight beyond LEO.

•   Do not hold up the program to wait on a depot. Fly as if you weren’t going to get one
•   Do not deploy an architecture that becomes a total waste once the depots are online (Ares-V).
•   DO deploy an architecture that is still useful once a depot is online (Jupiter)

The difference is the size of the launch vehicle. We do not want to build obsolescence into the launch vehicle, which is what the Ares architecture actually does. It makes no sense to spend billions of dollars on a launch vehicle that is immediately obsolete when the depot is deployed. Why is it obsolete? Because once the depot is deployed, the cost of a lunar mission drops considerably by using the depot and a smaller launch vehicle. The Ares-V itself is too big and too expensive to compete.

Until the depot is deployed, we need to continue down the path of moving spaceflight beyond LEO, towards the moon, NEO’s, Mars and beyond. For that effort, without a depot, we definitely need a heavy lift capability. But how big is big enough without being too big? NASA itself gave us the key by defining the lunar mission as being a 2-launch event. Where we differ from NASA is they want to use one small EELV-class crew launcher and one humongous, massive cargo launcher, while we would deploy a single launch vehicle, considerably larger than Ares-I but considerably smaller than Ares-V, and launch the mission on a pair of approximately equally sized launches.

The advantage of this approach is that, while the Ares-V becomes completely useless once the depot is operational, the Jupiter actually begins to shine, because what used to take 2 launches to get a lunar mission underway can now be done with only ONE launch. Everything that is needed for the lunar mission would be on that one, single launch, EXCEPT enough propellant to get beyond LEO. For that, the lunar stack (Orion, LSAM and the EDS) would rendezvous with the depot, fill up all the tanks, and then depart for the moon. In this way the pre-depot hardware is not wasted, it is actually enhanced by the availability on orbit of a propellant depot.

Now if NASA never gets around to deploying a depot, then the 2-launch architecture of 2 approximately identical launch vehicles remains useful, accomplishing the same mission, in the same number of launches, while actually costing less than Ares and at the same time maintaining the foundation for more efficient use when a depot finally does come online. In fact, the lower cost of doing the lunar missions with Jupiter vs. Ares actually makes the funding necessary for development and deployment of the depot available without needing to go back to Congress to ask for more money.

That’s my take on it.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/02/2009 01:49 pm
I support 100% (make that 200%) immediate funding to advance the TRLs for propellant depot technologies. However we cannot bet the space program on it, and I return to my earlier question -- what do you think NASA should be doing while we wait for propellant depot technology to mature?

That depends on whether or not one believes, like I do, that propellant depots will eventually form the backbone of spaceflight beyond LEO.

•   Do not hold up the program to wait on a depot. Fly as if you weren’t going to get one
•   Do not deploy an architecture that becomes a total waste once the depots are online (Ares-V).
•   DO deploy an architecture that is still useful once a depot is online (Jupiter)

 * * *

That’s my take on it.

I agree with pretty much everything posted here, especially those three bullet points.

Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/02/2009 03:44 pm
If that’s the case, perhaps getting the USAF/DoD involved might be the route to the funding. Surveillance spacecraft that can be launched to the depot on a moments notice, fuel up and go to the target orbit might provide a quasi-military need that could be funded. End result – a RLV that has need of a depot.

Of course the military is not the aim of all this, just a means to the end.

I'd think a family of reusable tugs would be a better market then refueling an RLV.  The depot is going to be in a specific orbital plane.  Military satellites are going to be going into several different orbital planes.  Plane changes are expensive.  While you can probably place a depot in an orbital plane that's close to most military customers...

*shrug*

Details.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/02/2009 04:04 pm
That said, there won't be a commercial business case unless NASA is ordered by Congress to be a captive customer to assure sales for that depot. And I do not see Congress doing that, not when Senator Bill Nelson can (reportedly) disapprove of NASA Administrator choice and as Chris Bergin reports, over a hundred people "blitz" Capitol Hill to lobby for extending the orbiter.

There are other, non-NASA markets out there for cryogenic depots.  They're just farther out, take more intermediate steps, and are at a much earlier state than would be desirable.  I think it's possible to bootstrap up to that capability, especially if at least some NASA funding (for mutually needed capabilities like long-duration cryo storage) is available along the way.

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And Jon, other than potential NASA lunar missions, who are the potential customers for an LH2 depot in LEO?

NASA unmanned missions beyond LEO, Non-NASA lunar missions, some GEO launches (particularly from countries like India that don't have launchers big enough to put the biggest satellites into GEO, but could with the help of a depot).  Space tourism.  None of those is a slam dunk.  Yes it would be wonderful if NASA decided to actually take the commercial side of its mandate seriously.  But hope isn't a business plan.

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I support 100% (make that 200%) immediate funding to advance the TRLs for propellant depot technologies. However we cannot bet the space program on it, and I return to my earlier question -- what do you think NASA should be doing while we wait for propellant depot technology to mature?

NASA should be helping develop the technologies needed for making our nation a spacefaring one, instead of just a space visiting one.  Quite frankly "going in circles in LEO" while putting significant investments for a few years into spacefaring technologies would be perfectly fine by me.  NASA is not a spaceline, and shouldn't be.  It should be helping create a strong space industry that's self-sustaining, innovative, and healthy.

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A big reason I like the sports arena idea is that Congress can order NASA to tolerate the idea WITHOUT taking a dime from NASA's existing budgets.

At best (or worst) simply order NASA to offer cooperation at incremental cost points reasonably negotiated so that NASA is reimbursed for depreciation of facilities used at times they would otherwise be idle.

Bringing in stadium name rights dollars, endorsement deals and advertising (with NASA being involved only at the margins) increases the total amount being spent on human spaceflight without raiding NASA's other budgetary items.

My problem with the idea is that it requires a lot of up-front money, and a whole bunch of things to go right at once for it to stand a chance.  You need big station space on orbit (possibly bigger than a Nautilus module), you need better transportation, you need an actual in-space sport, you need to recruit teams, etc.  It's not that it has potential, but look how bad Rocket Racing League has been struggling, and that's just for doing rocket-powered airplane racing that only took single-digit millions to get started....I just don't see orbital sports being an initial market.  Maybe once some of the other pieces are in place, but it isn't a good anchor market, IMO.

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Contrast that with the NewSpace / Space Access concept of terminating all shuttle derived programs and "betting the farm" on propellant depots and RLVs and it should be obvious why the odds of Congress doing that are essentially zero. Even Admiral Steidle was unable to defeat the shuttle lobby and with Bill Nelson (allegedly) having the power to veto an unsatisfactory NASA Administrator, I see no traction for a NewSpace only approach.

Bill, that's a strawman and you know it.  My position has always been to do an architecture that while forward compatible to depots and RLVs can start with just existing boosters (EELVs and eventually Falcon 9 or Taurus II), and maybe propellant transfer (propellant transfer doesn't imply propellant depots).  These are actually closer to prime-time than DIRECT or Constellation.  There's no "betting the farm" on unproven technologies (even ones that had most of the hard parts demonstrated decades ago by the Soviets).

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Therefore, in terms of political realism, the DIRECT Team's approach offers the best opportunity for developing the propellant depots that most of us agree are a good idea worth pursuing.

I doubt it.  The problem is that a depot+RLV+EELV architecture makes DIRECT obsolete.  Sure, DIRECT can use a depot to do cool stuff, but the DIRECT part isn't actually needed anymore.  Do you really think that the forces in NASA that want to perpetuate the status quo are going to go along willingly with depots, when it's just as much of a threat to DIRECT as it is to Constellation?  I'm sorry, I've seen this bait-and-switch before.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 05:33 pm
I doubt it.  The problem is that a depot+RLV+EELV architecture makes DIRECT obsolete.  Sure, DIRECT can use a depot to do cool stuff, but the DIRECT part isn't actually needed anymore.  Do you really think that the forces in NASA that want to perpetuate the status quo are going to go along willingly with depots, when it's just as much of a threat to DIRECT as it is to Constellation?  I'm sorry, I've seen this bait-and-switch before.

That's exactly what I'm afraid of. I've been arguing enthusiastically for "DIRECT Light" and hypergolic depots for a while, because I think that a bigger launcher, while not necessary, does allow us to move the game from LEO to L1 where a simpler hypergolic depot gives you the Earth-Moon system above GEO and the lunar surface.

So a bigger launcher + simpler hypergolic depot at L1 would be almost as useful as EELV + more difficult cryo depots in LEO  and therefore a sensible precursor. Without the bigger launcher you'd be stuck in LEO and a hypergolic depot in LEO isn't much use. In this way the bigger launcher really does add some value and actually helps depots rather than hurting them. It would allow you to get value from your depot development after maybe 4 years instead of 8.

Of course a bigger launcher doesn't necessarily mean DIRECT, it could also mean a bigger EELV. And since I understand there is significant synergy between a wide body Centaur and depots, that might not be a bad idea.

I can't really think of very useful manned applications of hypergolic depots in LEO and I can't think of a different directly usable precursor of cryo depots either.

I had thought about astronaut excursions from ISS to go on repair missions or something, but you can only get a plane change of about 5 degrees with Orion and that's while not bringing any tools along. Multiple depots would be an option (this was proposed in OASIS, though with cryo depots), but I think the phasing for rendez-vous would lead to missions that take too long.

So if, with a hypergolic depot but without a bigger launcher, manned missions beyond LEO are out and manned missions in LEO aren't terribly useful, maybe we could focus on unmanned missions beyond LEO enabled by a hypergolic depot. You can put up and resupply a hypergolic depot at L1 with EELV's. And from there you could transfer propellant to dry-launched unmanned landers. You could also retrieve satellites from GEO, LLO and SEL2 and attempt robotic repairs at L1 a la Orbital Express. It would be more difficult than with astronauts at L1, but not necessarily impossible. L1 is only a light second away.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 06:06 pm
Come to think of it, Orbital Express style unmanned servicing in LEO might be enhanced by hypergolic depots too. This would be a sensible precursor for similar activities at L1.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 06:20 pm
The problem is that a depot+RLV+EELV architecture makes DIRECT obsolete.

With EELVs for launching crew and RLVs for propellant I assume? The EELVs could launch propellant as well, do you include RLVs because you think they will have much lower launch costs per kg?
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/02/2009 06:21 pm
The shuttle infrastructure and the shuttle workforce remain a political legacy that cannot be "hand waved" away.

Unless a plan proposes to (a) keep at least a significant percentage of that workforce employed or (b) explain how Congress might be persuaded to lay off many thousands of people in terrible economic times, that plan has essential;ly zero chance of being adopted for the foreseeable future.

That is why I believe adopting DIRECT while including propellant depot research funding as part of current budgets is the best way to go.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 06:24 pm
Do you really think that the forces in NASA that want to perpetuate the status quo are going to go along willingly with depots, when it's just as much of a threat to DIRECT as it is to Constellation?

In what way would depots be a threat to Constellation as a whole? Or are you just referring to the Ares part of Constellation?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/02/2009 06:27 pm
Come to think of it, Orbital Express style unmanned servicing in LEO might be enhanced by hypergolic depots too. This would be a sensible precursor for similar activities at L1.

Yeah, if NASA doesn't want to go with a depot for lunar missions (or if NASA gets lunar missions taken off its plate), this is the most likely incremental path for purely commercial depot development:

1-tugs for orbital servicing of LEO or GEO assets (different tugs in different orbits--not the same ones going back and forth)
2-small hypergolic "mini depots" to service the tugs
3-then moving to small single-launch cryo depots for sending stuff medium sized stuff beyond LEO for US and international customers.
4-At so weiter

That said, step three is the hardest.  If RLVs come into being it becomes tons easier.  Or if Bigelow gets his space stations working it becomes easier.  Or if orbital space tourism takes off. 

The thing with a depot is it has to give you some clear benefit you can't get some other way. 

For manned missions beyond LEO, the value proposition is obvious--lower development costs, lower operations costs, more flexibility, less limits on maximum size (a depot-centric architecture can easily deliver payloads to the Moon or Mars that would be physically impossible without either a depot or lots of on-orbit assembly).

For GEO satellites, you either need to a) provide the capability to launch satellites that certain actors can't currently (like say enabling India which doesn't have an EELV class booster) to put large GEO comsats up, b) allow them to do it cheaper than launching a heavy version of one of their launchers (depends on RLVs or cheap launchers of some sorts), or c) allow them some set of services that lowers their cost or risk otherwise.

But anyway, that's enough for now...

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/02/2009 06:33 pm
The problem is that a depot+RLV+EELV architecture makes DIRECT obsolete.

With EELVs for launching crew and RLVs for propellant I assume? The EELVs could launch propellant as well, do you include RLVs because you think they will have much lower launch costs per kg?

Actually, I'd have both crew and propellants (and any light cargo) launched by the RLVs.  At the flight rates we're talking about they should be tons cheaper.  EELVs would launch the big, and especially high volume/mass chunks--landers, transfer stages (which are really just the EELV upper stages with special kits added on), the "capsule" or whatever is used for hauling the crew from LEO to the moon and back.  Right now, with basic Constellation design,  using dry launch for everything and loading all the propellants from a depot, you could get all the hardware up in a single launch using existing EELVs.  Then the RLVs would provide all the people, propellants, and provisions.  If you start getting cleverer from there, even more possibilities open themselves up.

But initially, before RLVs are available, sure the EELVs could launch the crew. 

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/02/2009 06:40 pm
The shuttle infrastructure and the shuttle workforce remain a political legacy that cannot be "hand waved" away.

Unless a plan proposes to (a) keep at least a significant percentage of that workforce employed or (b) explain how Congress might be persuaded to lay off many thousands of people in terrible economic times, that plan has essentially zero chance of being adopted for the foreseeable future.

And I'm not expecting them to do the right thing.  So what.  I've already pointed out time and again that I fully expect that depots are only going to happen commercially, because there are too many political interests tied to NASA as a welfare program.

Quote
That is why I believe adopting DIRECT while including propellant depot research funding as part of current budgets is the best way to go.

I don't think that adopting DIRECT is actually going to lead to any more propellant depot funding than the status quo.  When the chips come down, those incentives are still going to want to do what they can to limit funding to alternatives that could obsolete them.

I'm not hostile to DIRECT--I just don't buy the sales job that by somehow providing the right bacon to Senator Ballast's state, we're going to somehow see the coffers open up to doing the right thing.  DIRECT is about as relevant to depots as belly-button lint, in spite of the good intentions of its proponents.

There was a small chance (and still is a small chance) that NASA as a whole will change course to a good direction.  But as you point out, NASA is a poster-boy for all the ills public-choice theory have discovered over the years.  I'm not holding my breath for anything but scraps.  But as I've said before on this thread, $17B/yr times the cosine of 89.9 degrees is still a decent chunk of change.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/02/2009 06:45 pm
In what way would depots be a threat to Constellation as a whole? Or are you just referring to the Ares part of Constellation?

Once you have depots there is no longer any need for NASA to own and operate its own gargantuan launch vehicles.  NASA wants to operate those launch vehicles.  A few politicians want NASA to keep doing something that employs lots and lots of people in their districts (at the expense of the rest of the country).  Right now when there aren't any clear alternatives to NASA, it's a lot easier for certain politicians to take the general low-level interest in space that people have, combine it with a lack of other alternatives, and get lots of money funneled off to their districts and to their campaign contributors.   Once there are clear alternatives that are cheaper and better, it will be harder. 

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 06:51 pm
Once you have depots there is no longer any need for NASA to own and operate its own gargantuan launch vehicles.  NASA wants to operate those launch vehicles.  A few politicians want NASA to keep doing something that employs lots and lots of people in their districts (at the expense of the rest of the country).  Right now when there aren't any clear alternatives to NASA, it's a lot easier for certain politicians to take the general low-level interest in space that people have, combine it with a lack of other alternatives, and get lots of money funneled off to their districts and to their campaign contributors.   Once there are clear alternatives that are cheaper and better, it will be harder. 

For the launcher part, I agree completely. I thought you were saying depots would be a threat to Altair + Orion too. Politics aside, those parts of Constellation could actually benefit from depots.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/02/2009 07:18 pm

I doubt it.  The problem is that a depot+RLV+EELV architecture makes DIRECT obsolete.

DIRECT is only obsolete if they can can cheaply launch Altair and cargo on an EELV.  Currently something like the J-120 is needed to lift these to LEO in a single launch.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 04/02/2009 07:22 pm

DIRECT is only obsolete if they can can cheaply launch Altair and cargo on an EELV.  Currently something like the J-120 is needed to lift these to LEO in a single launch.

Who says a single launch is required?
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 07:32 pm
Who says a single launch is required?

Do you know where the whole 1.5 launch thing comes from anyway? Why is it such a horrible thing if you need two or more launches? Shouldn't you take the cost of those launches into account? And the benefits too? It isn't obvious to me that one moon mission is worth exactly three (=1.5/0.5) ISS missions, no more no less.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/02/2009 07:34 pm

DIRECT is only obsolete if they can can cheaply launch Altair and cargo on an EELV.  Currently something like the J-120 is needed to lift these to LEO in a single launch.

Who says a single launch is required?

No one says a single launch is needed, however several Delta IV launches plus assembly in space gets rather expensive.  That is just to assemble the lander.  People, Orion and EDS or tug extra.

Edit : Add That is just to assemble the lander.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 07:59 pm
The shuttle infrastructure and the shuttle workforce remain a political legacy that cannot be "hand waved" away.

Unless a plan proposes to (a) keep at least a significant percentage of that workforce employed or (b) explain how Congress might be persuaded to lay off many thousands of people in terrible economic times, that plan has essential;ly zero chance of being adopted for the foreseeable future.

That is why I believe adopting DIRECT while including propellant depot research funding as part of current budgets is the best way to go.

As you know, I think that DIRECT Light + L1 hypergolic depots is a much better way to stay within the political constraints than DIRECT itself, but it is not the only way. Shuttle-B/C/Z, J-120/J-130 or a scaled down Ares V each with either 4 seg or 5 seg boosters would all preserve jobs and lead to depots sooner than EELV + cryo depots would or DIRECT/Ares would. Of these J-120 would merely be the cleanest and cheapest solution. EELV + WBC might be even better, but would not satisfy the political constraints.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/02/2009 08:11 pm

I doubt it.  The problem is that a depot+RLV+EELV architecture makes DIRECT obsolete.

DIRECT is only obsolete if they can can cheaply launch Altair and cargo on an EELV.  Currently something like the J-120 is needed to lift these to LEO in a single launch.

No, you could lift the dry mass of an Altair on a single EELV flight.  If you're using a depot, there's no reason not to also top off the Altair.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/02/2009 08:31 pm
Quick comment: I think NASA has had its fill of a RLV for a while; it’s retiring the only one it ever flew and has no plans to create a new one for the foreseeable future. That’s for a much later period of time. So any mission architecture that has a RLV in the critical path is making the same mistake that Ares did.

Having said that, my main post;

A Propellant Depot is a Death Knell to the Ares-V because once it’s online there is no excuse for flying such a gargantuan monster. Its main purpose, in spite of what anyone at NASA would tell you, is to lift mission propellant to orbit so that a much smaller spacecraft that goes up with its propellant tanks full can go do a mission. That’s because as much as 75% or more of the mass of the spacecraft at launch is its mission propellant. Think about this. If Ares can lift 135mT to orbit, and ~75% of that is propellant, that means that the spacecraft itself only masses ~34mT. That’s an awfully big and expensive rocket just to put a 34mT spacecraft into orbit. On the other hand, there are a couple of existing EELV launchers that are “close” to being able to lift that, provided the spacecraft could get it’s mission propellant somewhere else, say, like at an orbital gas station. You see why NASA is so anxious to “poison pen” the depot idea? Dr Griffin was bound and determined to build the biggest, baddest launch vehicle ever, and an operational propellant depot would have completely ruined his day. So Griffin did not want a propellant depot in the architecture. So far, Jon and I are on the same page.

But neither EELV can actually do that “YET”, so there would still need to be some choices made to provide the necessary dry lift requirement. There are a couple of ways to approach that.

•   We could scale back the size of the lunar mission to redo a 3x crew with 2 on the surface, like Apollo, and scale back the size of everything else so that the existing EELVs could launch the dry spacecraft. The spacecraft then goes to the depot on orbit to get its mission propellant. [or]
•   We could keep the mission size the same and undertake a launch vehicle development program to field a launch vehicle that can lift the dry weight of the spacecraft. The spacecraft then goes to the depot on orbit to get its mission propellant.

Both options would continue to require a multi-launch mission profile.

There is some, but not much support for the first option, so we know that one is DOA. Let’s look at the second. There are two choices.

•   Start with the existing EELV’s and upgrade their lift capabilities to match the required mission mass. This increases the ROI made in developing the EELV launch capability. This will continue to require a multi-launch profile. [or]
•   Start with the existing STS infrastructure, workforce and flight hardware and transition it into a launch system capable of lifting the required mission mass. This increases the ROI in developing Shuttle, PLUS it retains a significant number of voters in their jobs in the districts that the legislators in Congress represent. This will start as a 2-launch mission profile but will transition to a single-launch mission profile once the depot becomes operational.

Ooo, I said the magic word – voters. Remember, and this is key, the Representatives and Senators in Congress were not sent their by their constituents to build the best space program they could. They were sent there to tend to the bread and butter issues that directly affects the people who sent them there and pay their salaries. And in today’s economic climate that translates directly into jobs; who has one and who doesn’t. So the legislators have to choose between Space Program efficiency and Constituency satisfaction with their jobs. It’s a lousy choice to have to make but make it they must.

Ok, now I see a lot of hand waving going on, all over the place, but it is a NAKED TRUTH that this situation cannot be hand-waved away! It must be considered, and it must be part of the equation. That’s just reality folks.

So what do we do? Do we upgrade the EELVs or do we transition the STS elements?
•   The EELV option (my personal favorite is the Atlas-V Phase II) creates a launch system that is efficient and well suited to a depot-centric lunar program but that puts thousands of voters and their families on the street in a terrible economy.
•   The STS option creates a launch vehicle (Jupiter) that is perhaps a little larger than what a depot-centric architecture would like but it keeps a significant percentage of the Legislator’s constituents employed in a terrible economy.

That’s the choice that has to be made. To me, when looking at what is reality, and understanding that there is no way to do this without retaining a significant portion of the workforce, the choice is obvious.

Congress made that choice, and they made it loud and clear. When they passed the 2005 Space Authorization Act they clearly specified that STS was to be the foundation. Because the choice had to be made, they chose jobs over efficiency. It was to be STS.

Griffin’s way of implementing that was the Ares-V, a totally massive and completely useless launch vehicle when a depot capability is finally fielded. DIRECT on the other hand, fields a smaller heavy lift vehicle that is not too big and actually is even more efficient in a depot-centric architecture than it is without a depot.

A lunar program supported by DIRECT actually costs significantly less than its Ares counterpart, and actually frees up the funding needed to develop and deploy a depot. As Jon, who isn’t really thrilled by DIRECT once said: “At least it doesn’t suck all the air out of the room”. In addition, we’ve run the numbers every which way we could imagine, and it always comes back the same: a lunar program supported by a single-launch Jupiter and an on orbit propellant depot will actually cost less to fund annually than a similarly sized EELV-supported program.

So there it is.
In an Ares-supported lunar program, there will be no depot at all because there will be no money to pay for it.

In an EELV-supported lunar program you will get a depot but at the cost of thousands of lost jobs at KSC, MAF, MSFC and JSC. It is extremely unlikely that enough Representatives and Senators will deliberately cut their own throats in order to make this program happen.

But in a DIRECT-supported lunar program, it will start off as a 2-launch lunar program, deploy an on orbit propellant depot, transition to a depot-centric single-launch lunar program and bring the VSE into full bloom. It will also bring the EELV-class launchers into the family by ceding all LEO servicing needs to them, in addition to being the primary propellant launch providers for the depot. The depot will become the backbone of future human spaceflight and NASA will continue to push the boundaries outward.

Where it goes from there is anyone’s guess because once the depot becomes central to spaceflight, and it will become central to spaceflight, we will be able to do a lot more with a lot smaller launch vehicles and more nations will be able to participate. Will the Jupiter survive that transition? I don’t know. All I do know is that it will certainly get us there in no uncertain terms. In addition to getting us back to the moon, it will provide the funding to deploy the propellant depot, all without having to go back to Congress to ask for more money.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/02/2009 08:40 pm
Chuck writes:

Quote
So what do we do? Do we upgrade the EELVs or do we transition the STS elements?
•   The EELV option (my personal favorite is the Atlas-V Phase II) creates a launch system that is efficient and well suited to a depot-centric lunar program but that puts thousands of voters and their families on the street in a terrible economy.
•   The STS option creates a launch vehicle (Jupiter) that is perhaps a little larger than what a depot-centric architecture would like but it keeps a significant percentage of the Legislator’s constituents employed in a terrible economy.

Jon writes:

Quote
I don't think that adopting DIRECT is actually going to lead to any more propellant depot funding than the status quo.  When the chips come down, those incentives are still going to want to do what they can to limit funding to alternatives that could obsolete them.

I'm not hostile to DIRECT--I just don't buy the sales job that by somehow providing the right bacon to Senator Ballast's state, we're going to somehow see the coffers open up to doing the right thing.  DIRECT is about as relevant to depots as belly-button lint, in spite of the good intentions of its proponents.

I assert that the arguments and points of disagreement have been well stated. What matters now is what President Obama wants to do and what Congress can be persuaded to do.

Fortunately, the amounts of money needed over the next two or three fiscal years to materially advance propellant depot TRLs may not be all that significant.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/02/2009 08:44 pm
The shuttle infrastructure and the shuttle workforce remain a political legacy that cannot be "hand waved" away.

Unless a plan proposes to (a) keep at least a significant percentage of that workforce employed or (b) explain how Congress might be persuaded to lay off many thousands of people in terrible economic times, that plan has essential;ly zero chance of being adopted for the foreseeable future.

That is why I believe adopting DIRECT while including propellant depot research funding as part of current budgets is the best way to go.

As you know, I think that DIRECT Light + L1 hypergolic depots is a much better way to stay within the political constraints than DIRECT itself, but it is not the only way. Shuttle-B/C/Z, J-120/J-130 or a scaled down Ares V each with either 4 seg or 5 seg boosters would all preserve jobs and lead to depots sooner than EELV + cryo depots would or DIRECT/Ares would. Of these J-120 would merely be the cleanest and cheapest solution. EELV + WBC might be even better, but would not satisfy the political constraints.

A genuinely international EML-1 depot with

(a) hypergolic landers and/or
(b) kerosene/lunar LOX landers

solves (and raises) a number of other problems.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 08:45 pm
IMO, an STS-derived solution that doesn't absolutely need depots will not lead to depots. It will delay depots even further. If you want to have a launcher that's big enough to go to the moon, don't start with depots. If you want depots, don't start with a launcher that is big enough to go to the moon. Once you have either that big rocket or that depot, it is going to be incredibly difficult to overcome resistance to building the other alternative. Then the rush will be on to build a moon base or to go to Mars.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/02/2009 08:49 pm
IMO, an STS-derived solution that doesn't absolutely need depots will not lead to depots. It will delay depots even further. If you want to have a launcher that's big enough to go to the moon, don't start with depots. If you want depots, don't start with a launcher that is big enough to go to the moon. Once you have either that big rocket or that depot, it is going to be incredibly difficult to overcome resistance to building the other alternative. Then the rush will be on to build a moon base or to go to Mars.

You're being a little shortsighted. If depots are part of the master plan, then depots will happen. Remember, the VSE doesn't stop at the moon. It keeps going out, and out and out. There is no way we are going to do that without depots. They WILL happen. The only real question is selecting a means to the end. Both the EELV and the STS approach WILL deploy depots. The question is which one is most likely to happen?

I submit that in todays economy, it'll be the one that preserves jobs rather than the one that puts thousands of workers and their families on the street.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 08:52 pm
What matters now is what President Obama wants to do and what Congress can be persuaded to do.

It would also be interesting to know what commercial players could do, independently of NASA. I think VSE is a golden opportunity to seek synergies with commercial space, but if that opportunity isn't seized, it doesn't mean it's all over. In fact, maybe it would be for the best if NASA decided to "Stick" with Ares, so it would crash and burn in a few years time. After that there might not be support for NASA building a launcher ever again. A number of times I've fought against things only to have them happen and to realise that maybe it was the best thing that could have happened...
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/02/2009 08:53 pm
The current Jupiters can "do the Moon" with two launches and no depots but they cannot "do Mars" with two launches and no depots.

If Jupiters get built (J232 or J246) and we return to the Moon relatively soon, depots shall be mandatory for Mars.

Which is part of why the Ares V advocates are not backing down. IMHO
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/02/2009 08:56 pm
The current Jupiters can "do the Moon" with two launches and no depots but they cannot "do Mars" with two launches and no depots.

If Jupiters get built (J232 or J246) and we return to the Moon relatively soon, depots shall be mandatory for Mars.

Which is part of why the Ares V advocates are not backing down. IMHO

Ares-V advocates do not want to see depots in any form because they totally destroy the need for anything that large and wasteful.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/02/2009 08:57 pm
What matters now is what President Obama wants to do and what Congress can be persuaded to do.

It would also be interesting to know what commercial players could do, independently of NASA. I think VSE is a golden opportunity to seek synergies with commercial space, but if that opportunity isn't seized, it doesn't mean it's all over. In fact, maybe it would be for the best if NASA decided to "Stick" with Ares, so it would crash and burn in a few years time. After that there might not be support for NASA building a launcher ever again. A number of times I've fought against things only to have them happen and to realise that maybe it was the best thing that could have happened...

Money would be the key issue, here.

I wonder what the television rights would be worth for televising a global consortium (Russia + China + EU + Japan + India) that beat NASA back to the Moon. Without NASA.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 09:08 pm
You're being a little shortsighted. If depots are part of the master plan, then depots will happen. Remember, the VSE doesn't stop at the moon. It keeps going out, and out and out. There is no way we are going to do that without depots. They WILL happen.

Possibly, but I wouldn't say it was certain. For one thing, there is no guarantee the program will not be canceled before it reaches Mars. And we don't know for certain that a Mars mission would be done with chemical propulsion. If I were certain DIRECT would lead to depots within 10 years I wouldn't be worried. But I am.

In addition to 'if' there is 'how soon'. If you start with hypergolic depots, you will have them within 4 years and you will have made it more likely that funding for cryo depots will continue. Especially since you will have been able to get ULA, SpaceX and Orbital to supply depots and they will want to continue doing that, thus putting lobbying power behind the idea.

Quote
The only real question is selecting a means to the end. Both the EELV and the STS approach WILL deploy depots. The question is which one is most likely to happen?

If Ares crashes and burns, the answer is EELV. If it is stopped in time, STS, for political reasons. Since I want to see depots as soon as possible, my preference is STS.

Quote
I submit that in todays economy, it'll be the one that preserves jobs rather than the one that puts thousands of workers and their families on the street.

I agree. And with J-120/J-130 or Shuttle-B/C/Z + hypergolic depots, the only losers out of your list of KSC, MAF, MSFC and JSC would be MSFC. And even there it wouldn't be all bad, since it would be the propulsion branch that would bear the brunt, not the Orion, Altair, ISS and science teams. They would not only be spared, but could be given bigger budgets. And other work could be found for the propulsion people as well. Politicians care about jobs, not about upper stages.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/02/2009 09:35 pm
Money would be the key issue, here.

I wonder what the television rights would be worth for televising a global consortium (Russia + China + EU + Japan + India) that beat NASA back to the Moon. Without NASA.

A lot of money, but is is probably far too risky and too far in the future to be commercially interesting right now. Ten years from now, it might be different. A less ambitious plan might be for tele-operated rovers, especially if you sell tickets that allow people to play with a rover for an hour, under appropriate supervision of course. How much would people be willing to pay to say that they had telerobotically worked on clearing a landing pad and building a berm for the new moon base? I think you could sell television rights for that as well.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/03/2009 01:06 am

I doubt it.  The problem is that a depot+RLV+EELV architecture makes DIRECT obsolete.

DIRECT is only obsolete if they can can cheaply launch Altair and cargo on an EELV.  Currently something like the J-120 is needed to lift these to LEO in a single launch.

No, you could lift the dry mass of an Altair on a single EELV flight.  If you're using a depot, there's no reason not to also top off the Altair.

~Jon

A single launch on EELV would mean that NASA as given up the 17mT of payload to the Moon's surface variant of Altair.
http://www.nasa.gov/pdf/289914main_fs_altair_lunar_lander.pdf (http://www.nasa.gov/pdf/289914main_fs_altair_lunar_lander.pdf)
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 04/03/2009 01:39 am

A single launch on EELV would mean that NASA as given up the 17mT of payload to the Moon's surface variant of Altair.
http://www.nasa.gov/pdf/289914main_fs_altair_lunar_lander.pdf

No it wouldn't and your link pointless,  especially if it is intended to just show the 17mt requirement.
The payload would be on another launch.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/03/2009 02:21 am

A single launch on EELV would mean that NASA as given up the 17mT of payload to the Moon's surface variant of Altair.
http://www.nasa.gov/pdf/289914main_fs_altair_lunar_lander.pdf

No it wouldn't and your link pointless,  especially if it is intended to just show the 17mt requirement.
The payload would be on another launch.

Which tends to invalidate Jongoff's point.
Title: Re: Propellant Depots - General Discussion
Post by: kkattula on 04/03/2009 03:01 am

A single launch on EELV would mean that NASA as given up the 17mT of payload to the Moon's surface variant of Altair.
http://www.nasa.gov/pdf/289914main_fs_altair_lunar_lander.pdf

No it wouldn't and your link pointless,  especially if it is intended to just show the 17mt requirement.
The payload would be on another launch.

Which tends to invalidate Jongoff's point.

I don't think so.  A dry lander plus cargo should still be able to be launched by one EELV Heavy.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/03/2009 04:28 am
Quick comment: I think NASA has had its fill of a RLV for a while; it’s retiring the only one it ever flew and has no plans to create a new one for the foreseeable future. That’s for a much later period of time. So any mission architecture that has a RLV in the critical path is making the same mistake that Ares did.

a) I agree that NASA should never again be allowed to build an operational RLV.  Of course, I don't think NASA should be building any operational rocket vehicles. 

b) With the mission mode I was talking about, an RLV is *not* in the critical path.  Even if RLVs prove to be impossible, a mission architecture that uses EELV class ELVs can still keep going.  It isn't going to be as cheap as it would be with RLVs, but the RLVs are an *improvement* that can be rolled in as time goes on.

c) If there's steady demand for propellant deliveries that are open to commercial providers, NASA won't have to build an RLV.  The single biggest obstacle to RLV development right now is funding.  Without a clear and identified market for RLVs that's big enough to justify their development (and the fact that you'll probably need to do one or two incremental vehicles along the way), they'll never happen commercially.  Now, once there's money, there's still a bunch of other problems, but the biggest problem with commercial RLVs is that none of the commercial companies have even gotten enough money to have a chance at failing technically, let alone succeeding.

d) I want to see a robust market, not *a* RLV, or *a* shuttle derived HLV.  I want to see several competing players, with enough business to go around that you don't get a stagnant monopoly situation.

Quote
Having said that, my main post;

A Propellant Depot is a Death Knell to the Ares-V because once it’s online there is no excuse for flying such a gargantuan monster. Its main purpose, in spite of what anyone at NASA would tell you, is to lift mission propellant to orbit so that a much smaller spacecraft that goes up with its propellant tanks full can go do a mission. That’s because as much as 75% or more of the mass of the spacecraft at launch is its mission propellant. Think about this. If Ares can lift 135mT to orbit, and ~75% of that is propellant, that means that the spacecraft itself only masses ~34mT. That’s an awfully big and expensive rocket just to put a 34mT spacecraft into orbit. On the other hand, there are a couple of existing EELV launchers that are “close” to being able to lift that, provided the spacecraft could get it’s mission propellant somewhere else, say, like at an orbital gas station. You see why NASA is so anxious to “poison pen” the depot idea? Dr Griffin was bound and determined to build the biggest, baddest launch vehicle ever, and an operational propellant depot would have completely ruined his day. So Griffin did not want a propellant depot in the architecture. So far, Jon and I are on the same page.

Yup. 

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But neither EELV can actually do that “YET”, so there would still need to be some choices made to provide the necessary dry lift requirement. There are a couple of ways to approach that.

•   We could scale back the size of the lunar mission to redo a 3x crew with 2 on the surface, like Apollo, and scale back the size of everything else so that the existing EELVs could launch the dry spacecraft. The spacecraft then goes to the depot on orbit to get its mission propellant. [or]
•   We could keep the mission size the same and undertake a launch vehicle development program to field a launch vehicle that can lift the dry weight of the spacecraft. The spacecraft then goes to the depot on orbit to get its mission propellant.

Both options would continue to require a multi-launch mission profile.

There are other options as well.  You're doing what a composites engineer would call a "black aluminum" design.  Once you have depots (and especially with single-launch depots like I've been looking at lately), there's no reason to do things the exact way they are now.  You instead optimize things to take the maximum advantage of refuelability.

For instance: If you can refuel the lander in L1/LLO, you have the option of having it self-ferry.  Or if it's reusable you might not even be sending a lander on every flight.  Or you can send the lander and the CEV separately.  If there's a depot/way station (which can be a 1-2 launch affair--nothing anywhere near as big as even Skylab), a lot of the worries about split missions like that go away....

I could rattle off a dozen different possible approaches that you can only do with a depot that might work a lot better, and that wouldn't require anything bigger than what we have right now (not saying that upgrades like doing a Wide Body Centaur upgrade wouldn't help things a *lot*, just saying that they're icing on the cake, not hard and fast requirements).

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Congress made that choice, and they made it loud and clear. When they passed the 2005 Space Authorization Act they clearly specified that STS was to be the foundation. Because the choice had to be made, they chose jobs over efficiency. It was to be STS.

Well, one thing to remember--when "Congress" passed the Space Authorization Act, do you really think 95% of them cared at all about the technical approach so long as it sounded remotely feasible?  Face it, those guys aren't rocket scientists.  The vast majority of them also don't have many if any shuttle jobs in their districts.  There are two or three senior Congresspeople who represent districts that would lose out if Shuttle were to go away.  Sure, they are in decent positions of power, and can throw monkey-wrenches, but only so long as the majority of Congress doesn't actually care very strongly.

Sure, many of them don't want to see the US government manned space program to end on their watch.  But that's a lot different from actively caring and actively supporting Constellation.  There's a very real chance that if things get botched bad enough (like say sticking with Constellation until someone gets killed by "The Safest Rocket Vehicle EVAR!!!1!!eleven!!"), that some of those other Congress people will start caring.  Or if other people in positions of power in appropriations, who don't happen to have a lot of shuttle jobs on the line but do have a lot of EELV jobs on the line start getting involved...

The only reasons certain Senators can get away with their antics are because most of his colleagues really don't care that much.  That can possibly change very quickly.

That said...I agree that NASA isn't likely to be allowed to do what is best for the country as opposed to what is best for the political careers of a few politicians.  I fully expect it.  My propellant depot plans assume that at best NASA will only provide some funding at the edges for such approaches.  I'm resigned to that.  It still fraks me off that so many career politicians have no problem putting their personal gain ahead of the nation, but what can one do?

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In addition, we’ve run the numbers every which way we could imagine, and it always comes back the same: a lunar program supported by a single-launch Jupiter and an on orbit propellant depot will actually cost less to fund annually than a similarly sized EELV-supported program.

I've never been particularly convinced of this.  I have a hard time seeing how a program that employs a lot more people to do the same thing can possibly cost less.  Also, the EELV guys have more tricks of their sleeves for driving costs down if the flight rate gets high enough to justify it.  But I doubt either of us is going to convince the other.

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But in a DIRECT-supported lunar program, it will start off as a 2-launch lunar program, deploy an on orbit propellant depot, transition to a depot-centric single-launch lunar program and bring the VSE into full bloom. It will also bring the EELV-class launchers into the family by ceding all LEO servicing needs to them, in addition to being the primary propellant launch providers for the depot. The depot will become the backbone of future human spaceflight and NASA will continue to push the boundaries outward.

I highly doubt it.  I know you guys intend it to be so, but the fundamental point keeps coming back to the fact that once you have a depot, anything much bigger than an EELV starts becoming obsolete.  Especially if RLVs come onto the scene.  The very forces that are trying to keep jobs at KSC, etc are going to still be trying to protect their turf even if a SDLV gets built.  I'm not very hopeful that they'll intentionally do a lot to help do something that might put at jeapordy all their attempts at looting the public for their own political gain.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/03/2009 04:30 am
Fortunately, the amounts of money needed over the next two or three fiscal years to materially advance propellant depot TRLs may not be all that significant.

Exactly.  I doubt they'll fund a full depot, but they might just pay for most of the up-front R&D.  Because the reality is that 95% of the technologies needed for depots are also needed to make Constellation work (and for military applications like ORS).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/03/2009 04:40 am
You're being a little shortsighted. If depots are part of the master plan, then depots will happen.

You mean like the OTV that was supposed to be built as part of the Space Transportation System?  NASA never drops features when the budgets get tight.

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Remember, the VSE doesn't stop at the moon. It keeps going out, and out and out. There is no way we are going to do that without depots. They WILL happen. The only real question is selecting a means to the end. Both the EELV and the STS approach WILL deploy depots. The question is which one is most likely to happen?

Well, VSE would *like* to keep going out and out.  Whether NASA is actually capable of doing that or not remains to be seen.  Whether they can do so in a sufficiently cost-effective manner to be given the funding to take future steps remains to be seen.  The fact is that every time in the past that NASA has proposed a big plan for moving out into space that includes a big rocket, almost nothing after the big rocket has gotten funded, even if it got that far.

Now, that said, I do expect depots will happen eventually.  I just think that other than paying for some low-level R&D work, that depots will happen in-spite of NASA, not because of it.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/03/2009 04:42 am
Ares-V advocates do not want to see depots in any form because they totally destroy the need for anything that large and wasteful.

How large is "too large" is in the eye of the beholder.  I'd like to see NASA out of the space launch business.  Commercial space has been doing launches now for over 20 years.  I'd rather see NASA take a more NACA-like role when it comes to launch vehicles, and focus its operational spending on the in-space portion that isn't really the realm of much commercial activity yet.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/03/2009 04:45 am
A single launch on EELV would mean that NASA as given up the 17mT of payload to the Moon's surface variant of Altair.
http://www.nasa.gov/pdf/289914main_fs_altair_lunar_lander.pdf (http://www.nasa.gov/pdf/289914main_fs_altair_lunar_lander.pdf)

Not necessarily.  It depends a lot on how you go about things.  Sure, if you do a "black aluminum" style depot architecture, then you might be limited to a little less than 17mT....but if you actually use depots effectively, your limits for single-piece cargoes is about 26mT, and your limits for multi-piece single-landing cargoes is probably closer to 100mT...but those bigger missions become a lot more logistically complicated.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/03/2009 05:04 pm
Fortunately, the amounts of money needed over the next two or three fiscal years to materially advance propellant depot TRLs may not be all that significant.

Exactly.  I doubt they'll fund a full depot, but they might just pay for most of the up-front R&D.  Because the reality is that 95% of the technologies needed for depots are also needed to make Constellation work (and for military applications like ORS).

~Jon

I would like to suggest that propellant depot advocates are MORE likely to be funded for this early R&D work if propellant depot advocates did not proclaim quite so loudly that their intention is to utterly eviscerate NASA as it presently exists.

I am reminded of the old joke about the college freshman who writes (e-mails?) home near the end of the first semester:

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Dear Mom & Dad -

College has been awesome so far. I've been learning great things here at the "U" especially about how shallow and hypocritical your values are and how badly I have been raised.

I hate you and never want to see you again.

Your son

PS -- Please send $25,000 for next semester's tuition.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/03/2009 09:25 pm
I would like to suggest that propellant depot advocates are MORE likely to be funded for this early R&D work if propellant depot advocates did not proclaim quite so loudly that their intention is to utterly eviscerate NASA as it presently exists.

Umm...I never proclaimed that.  There are large parts of NASA that would benefit greatly from a depot.  Most of the constellation stuff would get much easier (even if you just do a "black aluminum" approach where the only changes to the hardware as planned is a fueling interface).  Heck, even Ares-I could be made to work with a depot to relax the constraints.  I'm just saying that I doubt NASA is going to fund the actual implementation of a depot if the "political realities" are really as set in stone as you claim.  I just doubt that they aren't going to connect the dots.  Even if they don't actively sabotage it, do you really see Senator Nelson going to bat for depots, even if they were done in a way and sold in a way that wasn't threatening to his fiefdom?

I can probably afford to tone down the spleen venting a little, I'm just saying that I think supporting DIRECT because I want depots is a really naive approach that's very likely to not get depots. 

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/03/2009 11:05 pm
NASA should be helping develop the technologies needed for making our nation a spacefaring one, instead of just a space visiting one.  Quite frankly "going in circles in LEO" while putting significant investments for a few years into spacefaring technologies would be perfectly fine by me.  NASA is not a spaceline, and shouldn't be.  It should be helping create a strong space industry that's self-sustaining, innovative, and healthy.

Absolutely. There seems to be an enormous desire on the part of NASA to move beyond LEO. I sympathise with that, but I think there are more important things that should be done first: creating redundant commercial manned access to LEO and enabling commercial LEO stations.

And in order to move beyond LEO in a sensible way, you need depots. Had NASA started work on depots years ago, they could have moved beyond LEO in a way that is not only sustainable, but would have synergies with commercial space. Instead of realising their mistake, they are determined to make it again.

And even if you do go beyond LEO before the other goals are met, it doesn't imply you have to abandon LEO altogether. I don't think the American public is eager to shut down the ISS at all. I think they would be more than happy for that to continue for a while. Expanding activity in LEO would be an excellent way to buy time to develop depots.

Also, moving beyond LEO doesn't mean immediately moving all the way to the lunar surface, let alone constructing a permanent outpost.

Abandoning LEO is one mistake, moving beyond it without depots is a second, moving to the lunar surface without establishing infrastructure at L1 or perhaps LLO first is a third, and building a permanent outpost before depots and beyond-LEO orbital infrastructure is a fourth.

Had NASA wanted to minimise synergies with commercial space it might have been difficult for them to come up with a better plan than Ares, which makes me wonder. DIRECT is a bit better than that, but only by virtue of requiring less money. It is guilty of three of the four mistakes.

I'm not a US taxpayer, so I can't really complain, but it seems like such a waste. If done with synergies with commercial space in mind, the VSE could hasten significant commercial manned spaceflight by one or two decades. It's so frustrating.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/03/2009 11:15 pm
A single launch on EELV would mean that NASA as given up the 17mT of payload to the Moon's surface variant of Altair.
http://www.nasa.gov/pdf/289914main_fs_altair_lunar_lander.pdf (http://www.nasa.gov/pdf/289914main_fs_altair_lunar_lander.pdf)

Not necessarily.  It depends a lot on how you go about things.  Sure, if you do a "black aluminum" style depot architecture, then you might be limited to a little less than 17mT....but if you actually use depots effectively, your limits for single-piece cargoes is about 26mT, and your limits for multi-piece single-landing cargoes is probably closer to 100mT...but those bigger missions become a lot more logistically complicated.

~Jon

I am thinking about the limits of the Earth to Depot part of the journey.  EELV can certainly lift about 26mT to LEO but I suspect less to the ISS.  Like the ISS the LEO Depot is a space station, actual orbital height and angle have yet to be decided.

26mT - 17mT = 9mT for the Altair descent stage, extra docking & fuelling hardware and docking fuel

The Altair descent stage has a main engine and RCS so it should be able to fly the cargo from LEO to the Depot.  The propellant mass will have to come off the cargo mass.  Since the LEM used its ascent stage to perform docking the Altair descent stage will need hardware adding to dock with the refuelling interface of the Depot and accept the propellant.  The guidance system and RCS will need enhancing to find the Depot and perform the docking.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/03/2009 11:32 pm
In an academic setting, or at a conference enjoying beverages, I could agree that there would be benefits to a commercially owned and operated propellant depot, but remember that the ITAR angle on that would be huge.

Sure, but ITAR is a hassle--not a show stopper.


Write and publish the interface standard in a non-ITAR country.  The Depot and spacecraft manufactures then buy licences.  The Europeans can also buy interface licences.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/04/2009 05:29 am

Not necessarily.  It depends a lot on how you go about things.  Sure, if you do a "black aluminum" style depot architecture, then you might be limited to a little less than 17mT....but if you actually use depots effectively, your limits for single-piece cargoes is about 26mT, and your limits for multi-piece single-landing cargoes is probably closer to 100mT...but those bigger missions become a lot more logistically complicated.

~Jon

This suggests using a Propellant Depot at LEO with an optional second in lunar orbit results in a two launch EELV lunar plus propellant architecture.

1. Altair descent stage, Altair ascent stage and Earth Departure stage.
2. Orion Command Module, Orion Service Module and astronauts.

Give the Altair descent stage and the Orion Service Module big fuel tanks and the Earth Departure state is no longer needed.  Some sort of tug to get the fuel to the L1/L2/LLO Depot would be needed.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/04/2009 12:27 pm
This suggests using a Propellant Depot at LEO with an optional second in lunar orbit results in a two launch EELV lunar plus propellant architecture.

Or a single launch Jupiter.
Launch one time, fill up one time and go. No convoy.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/05/2009 06:28 am
We need to find a mission that pay for the prototype Propellant Depot.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/05/2009 04:23 pm
As for whether you would need multiple Centaurs and multiple depots...nope.  If you're not trying to reuse the Centaur ferry, you can toss a ~38klb payload into TLI (assuming you top the Centaur up in LEO).  If you're trying to reuse just the centaur (with the capsule reentering upon earth return), you're probably talking more like 28klb worth of capsule.  In both of those cases, that's more than enough payload for a capsule and possibly some living space.

I see, without stopping at L1 or in lunar orbit that could work. It's a free return trajectory, so you don't need a TEI to get back, you are in effect already on your way back. The Orion probably does need some fuel to descend into the atmosphere, right? Do you know how much delta-v is required? I think Danny Deger said something the other day about the Apollo capsule being able to land ballistically, but only in a dire emergency.

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Now, if you want to go into lunar orbit, and eventually to the lunar surface, that's when the logistics starts getting more complex, and multiple depots start making more sense.

Yeah, I'm having some trouble getting the numbers to add up without 1) shedding radiation shielding which I definitely don't like, 2) mandatory refueling at the gateway station which worries me or 3) using L2 as a waypoint instead of L1, which I'm not entirely happy with either.

I know you've thought a lot about depots, have you considered the implications of mandatory refueling before the return journey for any time abort?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/05/2009 07:57 pm
{snip}
I know you've thought a lot about depots, have you considered the implications of mandatory refueling before the return journey for any time abort?

That is an Abort to Depot.  The spacecraft would need the ability to get to the Depot using either its main engine or its RCS or both.

Following the abort once at the Depot the spacecraft could:
1. refuel.
2. or permit the crew to transfer to a waiting back up craft.
3. or pick up supplies like food, water, air and batteries.
4. or allow the crew to wait for a LON (Launch On Need) to rescue them.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 04/06/2009 03:22 pm
Write and publish the interface standard in a non-ITAR country.  The Depot and spacecraft manufactures then buy licences.  The Europeans can also buy interface licences.

Doesn't fix the issue
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/06/2009 03:36 pm
Write and publish the interface standard in a non-ITAR country.  The Depot and spacecraft manufactures then buy licences.  The Europeans can also buy interface licences.

Doesn't fix the issue

Exactly.  The US government considers a US person or a US firm to always be under ITAR restrictions even if they do the publishing in some other country.  Now, if a non-US company were to publish an interface standard (MDA for instance), they would be outside ITAR, and it could become a global standard.  But whether that will happen first, or whether a US firm will just bite the bullet and get the ITAR approvals to publish that standard publicly is anyone's guess.  Remember, ITAR doesn't say you can't publish technical information, it just says you have to get *permission* before you do so.

It's retarded, but not quite as retarded as some seem to think.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/06/2009 05:09 pm
Write and publish the interface standard in a non-ITAR country.  The Depot and spacecraft manufactures then buy licences.  The Europeans can also buy interface licences.

Doesn't fix the issue

Exactly.  The US government considers a US person or a US firm to always be under ITAR restrictions even if they do the publishing in some other country.  Now, if a non-US company were to publish an interface standard (MDA for instance), they would be outside ITAR, and it could become a global standard.  But whether that will happen first, or whether a US firm will just bite the bullet and get the ITAR approvals to publish that standard publicly is anyone's guess.  Remember, ITAR doesn't say you can't publish technical information, it just says you have to get *permission* before you do so.

It's retarded, but not quite as retarded as some seem to think.

~Jon

I deal with ITAR data every day and I don’t think it’s retarded at all.
In the last few years however, it has been severely abused in order to hide documentation that does not actually fall under ITAR guidelines, documents that were “withheld” solely because their contents were “inconvenient”. None-the-less, once that stamp is on the document, it’s game over.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/07/2009 01:40 am
European companies are designing versions of commercial aircraft components to get around ITAR restrictions.  IMHO To prevent the now normal 'do not buy American ban' an interface specification for space equipment will have to prove in advance beyond reasonable doubt that the documents will not be ITAR .  Evidence that future versions of the specification will not be given ITAR classification will also be needed.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/09/2009 04:49 pm
I see, without stopping at L1 or in lunar orbit that could work. It's a free return trajectory, so you don't need a TEI to get back, you are in effect already on your way back. The Orion probably does need some fuel to descend into the atmosphere, right? Do you know how much delta-v is required? I think Danny Deger said something the other day about the Apollo capsule being able to land ballistically, but only in a dire emergency.

I'm not sure how much delta-V is needed to maintain attitude during a semi-lifting reentry.  But that delta-V budget is usually covered under the capsule itself.

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Yeah, I'm having some trouble getting the numbers to add up without 1) shedding radiation shielding which I definitely don't like, 2) mandatory refueling at the gateway station which worries me or 3) using L2 as a waypoint instead of L1, which I'm not entirely happy with either.

I know you've thought a lot about depots, have you considered the implications of mandatory refueling before the return journey for any time abort?

Yeah, it means that you make sure there's always reserve fuel at the waystation depot.  You preposition your return propellant (and have enough life support/consumables to stay over for a while in case something goes wrong).  At least that's one of the approaches I've looked at.

The thing is that as soon as you add depots to the mix, it opens up *so* many options that it's often hard to pick the "best one".  A lot is going to depend on what everyone else ends up doing between now and then.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/09/2009 05:06 pm
I'm not sure how much delta-V is needed to maintain attitude during a semi-lifting reentry.  But that delta-V budget is usually covered under the capsule itself.

Yeah, I asked Ross the same question and he said all it takes is about 137 kg of propellant. Sounds like a low number, so I may have misunderstood.

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Yeah, it means that you make sure there's always reserve fuel at the waystation depot.  You preposition your return propellant (and have enough life support/consumables to stay over for a while in case something goes wrong).  At least that's one of the approaches I've looked at.

That's what I was thinking of, but it sounds slightly scary. I'd prefer a trip where the Orion itself has the means to get back to Earth safely, without needing assistance from other ships or stations. The Altair doesnt satisfy this condition of course, so it may not be crucial.

A slightly bigger upper stage would be useful, because it would allow the crew to bring the return fuel along. I reread the WBC-as-an-EDS article on your blog and it looks like a perfect compromise: NASA gets to build the J-130 as a first stage and the WBC is used as both an EDS and a more capable upper stage on EELVs.

But you might start with something simpler first. The interesting thing is that the existing DHCSS is just fine for cargo missions to L1, using Belbruno-like trajectories it could get something like 21mT to L1 in four months. Plenty of payload if dry launched and fueled at L1. And with improved boil-off mitigation so it can do the final insertion burn as well as the TLI, it could get a crewed Orion with enough return fuel to L1.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/09/2009 10:22 pm
I've been thinking some more about short-term precursors of cryogenic depots. I've not made a secret of my enthusiasm for hypergolic depots, but I'd like to focus on the cryogenic aspect for a bit.

I'd like to make a list of issues that need solving for cryogenic depots. This includes things like technologies that need to be developed, subsystems that need to be designed, procedures that need to be developed, contracts that need to be awarded etc. I am sure that there are issues I'm unaware of, but I know of the following:

- boil-off
- zero gravity multi-phase fluid transfer issues
- proximity operations
- tugs
- MMOD shielding

My guess is that the last three and things like contractual issues can be addressed relatively quickly during the development and deployment of hypergolic depots. I suspect on orbit hypergolic propellant transfer equipment is a useful precursor to similar cryogenic equipment.

Based on this list, I'd like to see if we can come up with a list of precursors and small incremental steps to get to cryogenic depots from where we are today. I think the trick is to make the steps small enough so that you don't need a massive budget and massive patience on the part of Congress and useful enough to show Congress you're spending the money wisely. Actually, if we can think of a way that might convince private financiers, that might be even better. So the best precursors would be ones that could be deployed on real missions, either commercial or funded by government.

Suggestions anyone?
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/09/2009 10:33 pm
Some precursors that do not require cryogenic fluid transfer, including some potentially crazy ones:

- upper stages with better passive cooling
If you could aggregate them on orbit, you could have some of the benefits of depots without needing fluid transfer. It would allow more payload from LEO to L1 because the Orion would not have to do the expensive insertion maneuver with its hypergolic propulsion system. It could also allow propulsive braking to LEO to allow for inter station transfers and reuse of the SM. It could allow the ISS to function as a LEO port.

- upper stages with better active cooling
Possibly too heavy. Similar benefits to those of the previous suggestion.

- a large, unpressurised orbital shelter with good MMOD that can house existing or slightly modified upper stages.
In this way the upper stages get MMOD shielding without needing to be made more massive.

- a similar orbital shelter with good and possibly heavy cryo-coolers and the power supply to run them. A sort of giant "space fridge".
In this way the upper stages get active cooling without needing to be made more massive.

Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/09/2009 11:02 pm
{snip}
Based on this list, I'd like to see if we can come up with a list of precursors and small incremental steps to get to cryogenic depots from where we are today. I think the trick is to make the steps small enough so that you don't need a massive budget and massive patience on the part of Congress and useful enough to show Congress you're spending the money wisely. Actually, if we can think of a way that might convince private financiers, that might be even better. So the best precursors would be ones that could be deployed on real missions, either commercial or funded by government.

Suggestions anyone?
Simply because the real depot will contain several hundred tons of fuel does not require the test version to be large.  Two tons of test fuel propellant may be sufficient.  The tubes can be full size.
Title: Re: Propellant Depots - General Discussion
Post by: Xplor on 04/10/2009 12:07 pm
I've been thinking some more about short-term precursors of cryogenic depots. I've not made a secret of my enthusiasm for hypergolic depots, but I'd like to focus on the cryogenic aspect for a bit.

I'd like to make a list of issues that need solving for cryogenic depots. This includes things like technologies that need to be developed, subsystems that need to be designed, procedures that need to be developed, contracts that need to be awarded etc. I am sure that there are issues I'm unaware of, but I know of the following:

1) boil-off
2) zero gravity multi-phase fluid transfer issues
3) proximity operations
4) tugs
5) MMOD shielding

My guess is that the last three and things like contractual issues can be addressed relatively quickly during the development and deployment of hypergolic depots. I suspect on orbit hypergolic propellant transfer equipment is a useful precursor to similar cryogenic equipment.

Based on this list, I'd like to see if we can come up with a list of precursors and small incremental steps to get to cryogenic depots from where we are today. I think the trick is to make the steps small enough so that you don't need a massive budget and massive patience on the part of Congress and useful enough to show Congress you're spending the money wisely. Actually, if we can think of a way that might convince private financiers, that might be even better. So the best precursors would be ones that could be deployed on real missions, either commercial or funded by government.

Suggestions anyone?

#1) Boil-off really already needs to be accomplished to support any multi launch architecture using cryogenics.  CxP has chosen to sidestep this at the expense of a 5% LOM!  Just another area where CxP has loosened the requirements because they were “hard”.
#2 zero-g transfer: With settling (at least during transfer) one doesn’t need #2, all rockets already transfer fluid to their engines
#3) I assume you mean automated prox ops?  Already required for Orion, COTS and CRS.
#4) Would be a great addition to all architectures and should absolutely be pursued!
#5) I’d love to see the time on orbit where shielding makes sense.  At a day, no it doesn’t, we haven’t been loosing unshielded upper stages to MMOD.  Also, I’m curious how much a thick MLI blanket helps here.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/10/2009 03:39 pm
I've been thinking some more about short-term precursors of cryogenic depots. I've not made a secret of my enthusiasm for hypergolic depots, but I'd like to focus on the cryogenic aspect for a bit.

I'd like to make a list of issues that need solving for cryogenic depots. This includes things like technologies that need to be developed, subsystems that need to be designed, procedures that need to be developed, contracts that need to be awarded etc. I am sure that there are issues I'm unaware of, but I know of the following:

1) boil-off
2) zero gravity multi-phase fluid transfer issues
3) proximity operations
4) tugs
5) MMOD shielding

My guess is that the last three and things like contractual issues can be addressed relatively quickly during the development and deployment of hypergolic depots. I suspect on orbit hypergolic propellant transfer equipment is a useful precursor to similar cryogenic equipment.

Based on this list, I'd like to see if we can come up with a list of precursors and small incremental steps to get to cryogenic depots from where we are today. I think the trick is to make the steps small enough so that you don't need a massive budget and massive patience on the part of Congress and useful enough to show Congress you're spending the money wisely. Actually, if we can think of a way that might convince private financiers, that might be even better. So the best precursors would be ones that could be deployed on real missions, either commercial or funded by government.

Suggestions anyone?

#1) Boil-off really already needs to be accomplished to support any multi launch architecture using cryogenics.  CxP has chosen to sidestep this at the expense of a 5% LOM!  Just another area where CxP has loosened the requirements because they were “hard”.
#2 zero-g transfer: With settling (at least during transfer) one doesn’t need #2, all rockets already transfer fluid to their engines
#3) I assume you mean automated prox ops?  Already required for Orion, COTS and CRS.
#4) Would be a great addition to all architectures and should absolutely be pursued!
#5) I’d love to see the time on orbit where shielding makes sense.  At a day, no it doesn’t, we haven’t been loosing unshielded upper stages to MMOD.  Also, I’m curious how much a thick MLI blanket helps here.

Thanks XPlor, that was more or less what I was going to say (but I've been...a little sleep deprived lately, and haven't had all the time to respond to all the posts I wanted to).  On the MMOD issue...would it be possible to do something combined with a sunshield?  AIUI, the most effective kinds of MMOD protection are ones where you have an outer layer to vaporize the debris, and then as much space as possible for the vaporized debris to spread out before it hits anything on the inside.  Would it be possible to say put at least one or two of the layers of a sunshield as a Kevlar MMOD layer?  It wouldn't be perfect, but might be interesting.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/14/2009 08:19 pm
Quote
The helium may need topping up as well.

Probably.  And at least at this point the RCS propellant as well.  A full-service depot is likely going to have at least four fluids (LOX, LH2, Helium, and Hydrazine), possibly more.

I had wondered about helium pressurant for hypergolic propulsion. If you make sure you don't use up all propellant, would that mean not losing any helium? And do you know why helium is used instead of say nitrogen? Would nitrogen dissolve in MMH/NTO?
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/14/2009 08:59 pm
Does anyone know reasonable dry mass estimates for large hypergolic tanks such as might be found in a depot? I've been doing some googling and found something on the website of the Technical University of Delft, referring to research done by the University of Maryland:

http://www.lr.tudelft.nl/live/pagina.jsp?id=416497e6-bd6b-44f0-8889-14231a648af4&lang=en

"Large (1000’s of kg) storable propellant tanks: 0.316 (Mp)^0.6  (in kg)"

This gives very low numbers however. For comparison, Ed Kyle's highly reliable launch report* gives a dry mass of 4500 kg and total mass of 39,500 kg for the hypergolic Titan IV second stage, a dry mass fraction of 0.11. The same source leads to a much lower ratio of 0.06 for the Falcon 9 second stage.

So is there a fundamental reason hypergolic stages are heavier than lox/kerosene stages or is it just that hypergolic stages were developed earlier and use less efficient technologies whereas the Falcon 9 is brand new? The Wikipedia page on the Titan IV states that the Titan ultimately used Al-Li, but Ed's page makes no mention of this. Might Ed's numbers predate the conversion to Al-Li (if that ever happened) and might that explain the big difference?

As for the difference between Ed's numbers and the formula above, could it be because the formula is for tanks contained within an external shell, instead of in a monococque construction? I realise that a stage contains more than just tanks, but I had thought, perhaps incorrectly, that the mass of the tanks would dominate. It looks as if upper stage engines are surprisingly light-weight, on the order of hundreds of kg.


* :)
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/14/2009 09:16 pm
So is there a fundamental reason hypergolic stages are heavier than lox/kerosene stages ...

Hypergols are not as energetic as lox/kerosene so it takes significantly more of the propellant to achieve the same delta-V.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/14/2009 09:18 pm
Sorry, I meant to compare dry mass ratio, not total mass for the same payload & delta-v.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 04/15/2009 01:32 am
  IMHO To prevent the now normal 'do not buy American ban' an interface specification for space equipment will have to prove in advance beyond reasonable doubt that the documents will not be ITAR .  Evidence that future versions of the specification will not be given ITAR classification will also be needed.

That is the problem, the "O" of IMHO.  Your "O" is not based on any relevant data.

There is no guaranteed that a document won't be ITAR
Title: Re: Propellant Depots - General Discussion
Post by: Patchouli on 04/15/2009 03:15 am
  IMHO To prevent the now normal 'do not buy American ban' an interface specification for space equipment will have to prove in advance beyond reasonable doubt that the documents will not be ITAR .  Evidence that future versions of the specification will not be given ITAR classification will also be needed.

That is the problem, the "O" of IMHO.  Your "O" is not based on any relevant data.

There is no guaranteed that a document won't be ITAR

ITAR has been a failure in every sense of the word and needs to go as it has done far more harm then good.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/15/2009 03:41 am
  IMHO To prevent the now normal 'do not buy American ban' an interface specification for space equipment will have to prove in advance beyond reasonable doubt that the documents will not be ITAR .  Evidence that future versions of the specification will not be given ITAR classification will also be needed.

That is the problem, the "O" of IMHO.  Your "O" is not based on any relevant data.

There is no guaranteed that a document won't be ITAR

There is plenty of data.  There are major limits on the law making powers of the US Federal Government and the jurisdiction of the FBI.

During prohibition drinking establishments were opened on ships outside the 3 mile limit.  The legal sale of alcohol in Canada, Britain and Mexico continued.

Aircraft components are being made in Europe, including the UK, to avoid ITAR restrictions.

The copyright history of the the book "Lord of the Rings" provides interesting lessons, and US lawyers may know the history.

Unlike previous export controls ITAR is neither NATO nor UN.  The US Government has no mechanism for applying its classifications to a non-US document, written by a non-US person (or team), working for a non-US organisation without a US contract, published by a non-US publisher and printed outside the USA.

Thinking about it we had better warn the publisher not to take a US contract until after the document has been published.

Any hardware built in the USA may be ITAR (someone else will have to do that determination).  ESA will simply have to buy its connectors from say the Chinese.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 04/15/2009 06:27 am
Sorry, I meant to compare dry mass ratio, not total mass for the same payload & delta-v.

I've heard that Centaur style tanks mass about ~4% of the mass of their contents (for LOX/LH2, which admittedly has a crappy bulk density).  Backing things out a bit, that gives you something like a tank mass of ~0.7% of the propellant mass for denser propellants.

But it's worth noting, that even for LOX/LH2, the tanks aren't most of the weight of a lightweight stage.  All the other supporting systems weigh more.  This will likely be even more the case for a depot (unless you count the cooling systems as part of the tank weight instead of counting them separately).  FWIW.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/15/2009 04:45 pm
If someone is really worried about the propellant depot's connector interface standard being non-ITAR they can get the legal equivalent of a trade study written and published by international trade lawyers saying what actions and procedures need performing.

It appears that the islands of Barbados and Cypress never joined the Coordinating Committee for Multilateral Export Controls (CoCom) or signed the Wassenaar Arrangement.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 04/15/2009 05:09 pm
If someone is really worried about the propellant depot's connector interface standard being non-ITAR they can get the legal equivalent of a trade study written and published by international trade lawyers saying what actions and procedures need performing.

It appears that the islands of Barbados and Cypress never joined the Coordinating Committee for Multilateral Export Controls (CoCom) or signed the Wassenaar Arrangement.

Simply clueless again

International trade lawyers  have no say in it nor have any advice that is worth anything
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/15/2009 05:15 pm
If someone is really worried about the propellant depot's connector interface standard being non-ITAR they can get the legal equivalent of a trade study written and published by international trade lawyers saying what actions and procedures need performing.

It appears that the islands of Barbados and Cypress never joined the Coordinating Committee for Multilateral Export Controls (CoCom) or signed the Wassenaar Arrangement.

Simply incorrect again

International trade lawyers  have no say in it nor have any advice that is worth anything

That is a very weird statement to make.  They have been handling ITAR problems for several years.

NASA can use its own lawyers to put itself in the clear.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 04/22/2009 02:00 pm
I've heard that Centaur style tanks mass about ~4% of the mass of their contents (for LOX/LH2, which admittedly has a crappy bulk density).  Backing things out a bit, that gives you something like a tank mass of ~0.7% of the propellant mass for denser propellants.

But it's worth noting, that even for LOX/LH2, the tanks aren't most of the weight of a lightweight stage.  All the other supporting systems weigh more.  This will likely be even more the case for a depot (unless you count the cooling systems as part of the tank weight instead of counting them separately).  FWIW.

~Jon


Jon,

on a related question, would you have any thoughts / guess how the mass of an Altair might scale with the fuel load?

On topic - say if it was fuelled in LLO before performing descent (depends on payload, of course).

Off topic - for a really small fuel load.

Alternate version of same question - what proportion of the existing (proposed / suggested) full-sized Altair is fuel tanks?

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/06/2009 10:14 pm
One potential advantage of LEO propellant depots would be that they would allow new launchers to establish a reliability record without risking very expensive hardware. Another advantage be that they could allow new concepts such as small RLVs or small, cheap, unreliable expendable boosters like the proposed Aquarius or Microcosm Scorpius to prove their worth.

Although I'm very enthusiastic about L1 propellant depots, they would be unreachable for those new types of launchers. That might be solved by having additional depots in LEO that accumulate the propellant before it is taken to L1 by other vehicles. One remaining worry would be that hypergolics or deeply cryogenic hydrogen would be more difficult and therefore more expensive payloads to handle than something simpler like kerosene, food or water.

Would this rule out participation by potential market entrants such as Microcosm, Masten or even SpaceX? I know that Microcosm deliberately avoided using liquid hydrogen because they felt such a deep cryogen would lead to high launch costs. Hypergolics would probably be considerably worse. ULA on the other hand has extensive expertise with both liquid hydrogen and hypergolics and would be at an advantage.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 05/07/2009 12:03 am
Although I'm very enthusiastic about L1 propellant depots, they would be unreachable for those new types of launchers. That might be solved by having additional depots in LEO that accumulate the propellant before it is taken to L1 by other vehicles. One remaining worry would be that hypergolics or deeply cryogenic hydrogen would be more difficult and therefore expensive payloads to handle than something simpler like kerosene, food or water.

Would this rule out participation for potential market entrants such as Microcosm, Masten or even SpaceX? I know that Microcosm deliberately avoided using liquid hydrogen because they felt such a deep cryogen would lead to high launch costs. Hypergolics would probably be considerably worse. ULA on the other hand has extensive expertise with both liquid hydrogen and hypergolics and would be at an advantage.

There is likely to be a market for propellant that boosts satellites from LEO to GSO.  If the Falcon 1 and Falcon 9 upper stages are refuelled using LOX and RP-1 they can boost their own satellites.  The normal EELV upper stages could also take on LOX, and possibly hydrogen at LEO, and lift bigger satellites to GSO than their heavy versions.

All LV can take any of the propellants to a propellant depot in LEO, the bigger ones simply lifting more fuel.

Solar thermal and solar electric tugs could push depots from LEO to L1 (or Mars).  The argon for a VASIMR tug return trip to lunar orbit can be lifted on a single Falcon 9.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 05/07/2009 02:55 am

* * *

Although I'm very enthusiastic about L1 propellant depots, they would be unreachable for those new types of launchers. That might be solved by having additional depots in LEO that accumulate the propellant before it is taken to L1 by other vehicles. One remaining worry would be that hypergolics or deeply cryogenic hydrogen would be more difficult and therefore expensive payloads to handle than something simpler like kerosene, food or water.

* * *

Unreachable in a single throw, maybe but why couldn't Masten (for example) build a mini-depot in LEO to accumulate fuel to send payloads to L1?

Or perhaps in collaboration with others? Couldn't Masten (again, for example) deliver a smallish RP-1 package to LEO and hand it off to a tether operator?

An EML depot and the follow-on lunar or SEL or NEO missions are going to need lots and lots of logistical support creating ample business for anyone who can loft mass to LEO at a lower cost than their competitors.



Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/07/2009 12:33 pm
Unreachable in a single throw, maybe but why couldn't Masten (for example) build a mini-depot in LEO to accumulate fuel to send payloads to L1?

Oh yes, the L1 problem would be solved by an additional LEO depot. I was worried about hazardous/deeply cryogenic material handling. MMH is very toxic and also carcinogenic, NTO is corrosive and toxic, the combination is hypergolic. Liquid hydrogen is deeply cryogenic, extremely flammable, you cannot see, taste or smell it and it burns with a nearly invisible flame. You need special equipment and procedures to deal with these substances safely. I was wondering if that might be too difficult/expensive for small players. For instance are there hypergolics facilities at Kwajalein? Not saying there aren't, just wondering.

Quote
Or perhaps in collaboration with others? Couldn't Masten (again, for example) deliver a smallish RP-1 package to LEO and hand it off to a tether operator?

Agreed, RP-1 and LOX would not be a problem.

Quote
An EML depot and the follow-on lunar or SEL or NEO missions are going to need lots and lots of logistical support creating ample business for anyone who can loft mass to LEO at a lower cost than their competitors.

Absolutely, I saw two problems: L1 is "too far away" in delta-v and liquid hydrogen / hypergolics might be expensive payloads to handle. The first would be solved by having additional LEO depots. I was wondering about the second.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 05/07/2009 01:26 pm
I would hope that the EML-1/2 depots would actually be the "open for business" end of the depot. The other end would be a SEP power plant. Together, these two would form a single spacecraft. I envision the depot being refuled in LEO, making it's way to EML-1/2 for duty, and then returning when empty to be refuled again. I can see 2, perhaps 3 of these in constant cycle between LEO and EML-1/2.

Refuling and any required servicing of the depot would always be performed in LEO. SEP power takes it to and from the EML halo orbit.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/07/2009 01:30 pm
If you refuel the L1 depot by EELV, you don't even need to move it back to LEO. If, for whatever reason, it turns out to be cheaper to do this in LEO, then that's fine. But that's something for the long run. In the short run, resupply by J-130 + DHCSS or EELV would be the least technically risky solution.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 05/07/2009 01:39 pm
If you refuel the L1 depot by EELV, you don't even need to move it back to LEO. If, for whatever reason, it turns out to be cheaper to do this in LEO, then that's fine. But that's something for the long run. In the short run, resupply by J-130 + DHCSS or EELV would be the least technically risky solution.

We need to keep the Jupiter out of the depot business - period. The DIRECT Team vigorously opposes using the Jupiter in this capacity. We do not want to be the competition for the commercial suppliers. We create the business so that the commercial suppliers can start making profits in space. The Jupiter's contribution is launching the depots into orbit and kick-starting the commercial industry. Once the depots are in place, then all kinds of missions to all kinds of places by all kinds of nations become possible. The EELVs would be competing with other similar lift capacities from other commercial concerns and other nations to keep the depots full, enabling a true paradigm shift in space capabilities by a variety of nations and commercial concerns.

The Jupiters should not be involved in any capacity other than as an anchor-store customer.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/07/2009 01:43 pm
We need to keep the Jupiter out of the depot business - period.

I agree, though it would not necessarily be for the DIRECT team to have the last word on that. And note that the DHCSS already provides a measure of synergy with EELVs.

Quote
The Jupiter's contribution is launching the depots into orbit and kick-starting the commercial industry.

Agreed. My point was that EELVs can reach L1 already, and the depot doesn't have to be moved to LEO to be refueled. If that turns out to be efficient in the long run, fine, we can do that as a later upgrade once the basic systems have been proven.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 05/07/2009 07:36 pm

Agreed. My point was that EELVs can reach L1 already, and the depot doesn't have to be moved to LEO to be refueled. If that turns out to be efficient in the long run, fine, we can do that as a later upgrade once the basic systems have been proven.

The EELV's payload to L1 is significantly less than their payload to LEO.  If the mass difference is more than the return SEP fuel then refuelling the depot in LEO is probably worth while.  When determining profitability the cost of the SEP equipment has to be taken into account.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/07/2009 08:27 pm
The EELV's payload to L1 is significantly less than their payload to LEO. 

Sure, but they are GEO vehicles as well, and L1 is cheaper to reach than GEO.

Quote
If the mass difference is more than the return SEP fuel then refuelling the depot in LEO is probably worth while.  When determining profitability the cost of the SEP equipment has to be taken into account.

Sure, eventually, with SEP tugs. But in the mean-time EELVs exist and depots and SEP tugs, especially van Allen crossing ones, don't. I would want to see the cheapest, soonest and least risky depot first and that would be a hypergolic depot that is permanently stationed in L1 orbit. Which conveniently also happens to be the easiest, cheapest and least risky destination beyond LEO. Anything else leads to unnecessary delays before we get any depots (or SEP tugs for that matter), which if NASA has anything to do with it could easily be decades of delay.

Later on, I see a big role for SEP, with degradation in the van Allen belts being a major obstacle to be overcome. Again, I would urge for precursor systems to be developed first, so we don't have to wait ages before work starts on SEP tugs. So let's not wait until we've fixed radiation problems before fielding a SEP tug, let alone make strategically vital depots dependent on them. Let's start with a SEP tug based at L1. Initially it could be used to efficiently supply other hypergolic depots in GEO, LLO, at SEL-2 in support of manned and unmanned science missions. Once we have LUNOX and cryo depots, such beyond LEO depots could be serviced by SEP tugs as well. In the mean-time SEP tug precursors could serve as power beaming satellites at L1 or in highly elliptical lunar orbit, as was proposed recently by ENTECH.

So, if you want to promote the cause of depots and SEP tugs, start first with the simplest possible depot (hypergolic), and with the simplest possible client (Orion). Then either a non-van-Allen-crossing SEP tug or more powerful cryo depots. Then either lunar ISRU or van Allen crossing SEP tugs from LEO. And only then, if at all, a combination of a van Allen crossing SEP tug with a depot, likely a cryogenic one by that time.

If you don't like depots (in which case you probably love monstrous NASA-only launchers, which are safe from commercial competition), then insist on huge cryogenic depots, with non-settled fluid transfer, zero boil-off (not just low boil-off), SEP propulsion, tens of crossings of the van Allens during their service lives, and all the bells and whistles you can think of to make sure the concept is never funded, or if it is funded, likely to go down in flames - especially if MSFC has anything to do with it.

I'm convinced you don't belong to the second group - I just wanted to spell out some consequences.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 05/08/2009 11:38 pm
Unreachable in a single throw, maybe but why couldn't Masten (for example) build a mini-depot in LEO to accumulate fuel to send payloads to L1?

Woah there turbo.  We just finally got our first stable VTVL flight today...give us some time, eh?  ;-)

Seriously, I think that LM and Boeing both have a lot more relevant expertise.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/08/2009 11:53 pm
Woah there turbo.  We just finally got our first stable VTVL flight today...give us some time, eh?  ;-)

Seriously, I think that LM and Boeing both have a lot more relevant expertise.

Once you have an operational RLV, would you guys expect to be able to deal with the safety and handling aspects of hypergolic or cryogenic propellants and expect to be able to deliver them to an existing LEO depot? Let's assume the operator of the depot would be using a tug capable of picking up standardised containers and that those containers could be bought off the shelf.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 05/10/2009 04:20 am
So, if you want to promote the cause of depots and SEP tugs, start first with the simplest possible depot (hypergolic), and with the simplest possible client (Orion). Then either a non-van-Allen-crossing SEP tug or more powerful cryo depots. Then either lunar ISRU or van Allen crossing SEP tugs from LEO. And only then, if at all, a combination of a van Allen crossing SEP tug with a depot, likely a cryogenic one by that time.

Orion is a few years away, we would also have to get it to L1.

A LEO depot is probably easier.  From LEO larger cargoes with refuelled upper stages can be sent to Geostationary Orbit, L1 and lunar orbit.  A depot in polar orbit can refuel reconnaissance satellites, this may get a customer providing the price of the refuelling is less than the cost of a new satellite.
Title: Re: Propellant Depots - General Discussion
Post by: Marisum on 05/10/2009 10:52 am
Hello, I am new to Direct and have a couple of comments. First, have you guys and gals looked at a lunar/mars architecture using only J120? Since the general ideal is to reduce cost, can this be done?

This assumes that propellant deposts could be used to support such a concept.

Perhaps these elements:
Earth Orbiting Deport
Reusable In-space Stages for LEO to Lunar Orbit (Space Tug?)
Reusable Lunar Landers
Lunar Orbiting Station
Cargo Prepositioning in LEO and Lunar/mars orbits

Just wondering



Title: Re: Propellant Depots - General Discussion
Post by: Marisum on 05/10/2009 11:03 am
Okay, this thread title is supposed to be general discussion about propellant depots by the title but has been so far about a single narrow idea: NASA flying a heavy lifter launcher and using a propellant depot on the side. This isn't very sensible.

What propellant depots are really the best at, is decoupling beyond LEO mass from launcher size, thus eliminating the need for a heavy lifter altogether. The three different spacecraft of ESAS origin, the Orion capsule, the Artemis lander and the EDS stage all weigh less than 25 t empty, which can be lifted by launchers that exist today and have flown many times.

You could achieve similar things by chaining up mini-EDS stages, but that has some problems, like boiloff, bad mass ratio and reliability regarding so many stagings and ignitions. Not insurmountable. A propellant depot can also avoid boiloff by being well insulated, having a sunshield or even being actively cooled: it can afford this mass since it is not going to the moon itself.

Also, with numerous redundant launchers available for sending tankers to the depot, the approach is inherently improvable. You get high flight rate which means low costs. You can enter better launchers that are cheaper or more reliable for example. This is because the mass launched at one time is a reasonable chunk like ten or twenty tonnes, that the launchers can still have other viable missions as well. Ultimately, a propellant depot could be a market for a reusable launch vehicle that could drop the cost of space travel substantially. The biggest hurdle for RLV economics has been lack of market and thus a low flight rate. A depot could change all that. Only NASA has enough money to buy so much propellant on orbit that an RLV becomes feasible.

If NASA builds a heavy lifter, all this becomes moot. Most of the propellant is lifted by the heavy lifter, and thus it makes no sense to make a propellant depot for just the few intermittent refueling tonnes, it is much cheaper to launch another heavy lifter. A purpose built heavy lifter will have big fixed costs and low launch rate, meaning adding more launches will not add much more cost anymore, the savings were missed when the thing was built in the first place.
Also, a purpose built NASA heavy lifter is not an agile system which could easily be improved and it is in practice an irreplaceable monolith. Griffin himself has said how the launchers that are built now will stick for decades. (Well, that has happened with the exception of Saturn.)

Most of the arguments have been hashed before, for example in this thread about an alternative for ESAS replacing heavy lift with a liquid oxygen propellant depot:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=4047

To put the effects of high fixed costs and low flight rate in nine words:
No savings from depot unless you scrap heavy lift.


The whole idea behind depots is to refuel in orbit and therefore not need super heavy lift to start with. Additionally, it makes more sense to use the depots for xenon to power ion drives than it does putting up chemical propellants. The ratio is 10:1 in favor of the ion drive. Ion tugs could take cargo to the moon and mars for a fraction of the cost of chemical rockets due to reduced mass alone. Also, propellant transfer would be easier and safer.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/10/2009 11:30 am
Orion is a few years away, we would also have to get it to L1.

Having a LEO depot before Orion is finished sounds very exciting, but is it realistic? Ross has talked about something like three years for a hypergolic depot, though that is clearly not an official estimate.

Quote
A LEO depot is probably easier.  From LEO larger cargoes with refuelled upper stages can be sent to Geostationary Orbit, L1 and lunar orbit.  A depot in polar orbit can refuel reconnaissance satellites, this may get a customer providing the price of the refuelling is less than the cost of a new satellite.

LEO depots are definitely more useful than I initially thought and I would really like to see them. They can support reusable tugs that make launching ISS modules and resupply of consumables more efficient. They can support reusable Orions stationed permanently at the ISS for manned visits to man-tended free flyers. ESA would like to have a man-tended free flyer as a precursor to a space station of their own and a free flyer would also provide a better microgravity environment so there would be clear scientific advantages too.

And even before you have manned access to L1, you could start with an unmanned depot there, fueling or refueling robotic lunar landers or even 'interplanetary kickstages'. If you use a Delta-IV to get a big probe to L1 and then refuel it there, you can send bigger probes. L1 is only 140 m/s or so away from Earth escape.

But in truth, I don't think any of this is likely before at least Orion and probably J-130 is operational.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 05/10/2009 01:09 pm
A depot in polar orbit can refuel reconnaissance satellites,

That is not viable.  The satellites are in too many different planes and at too many different attitudes to be serviced by a depot
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/10/2009 01:23 pm
That is not viable.  The satellites are in too many different planes and at too many different attitudes to be serviced by a depot

Are there any geostationary spy satellites? And would the DoD ever want to involve NASA with national security missions?
Title: Re: Propellant Depots - General Discussion
Post by: Marisum on 05/10/2009 07:23 pm
Unreachable in a single throw, maybe but why couldn't Masten (for example) build a mini-depot in LEO to accumulate fuel to send payloads to L1?

Oh yes, the L1 problem would be solved by an additional LEO depot. I was worried about hazardous/deeply cryogenic material handling. MMH is very toxic and also carcinogenic, NTO is corrosive and toxic, the combination is hypergolic. Liquid hydrogen is deeply cryogenic, extremely flammable, you cannot see, taste or smell it and it burns with a nearly invisible flame. You need special equipment and procedures to deal with these substances safely. I was wondering if that might be too difficult/expensive for small players. For instance are there hypergolics facilities at Kwajalein? Not saying there aren't, just wondering.

[Agreed, RP-1 and LOX would not be a problem.

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An EML depot and the follow-on lunar or SEL or NEO missions are going to need lots and lots of logistical support creating ample business for anyone who can loft mass to LEO at a lower cost than their competitors.

Absolutely, I saw two problems: L1 is "too far away" in delta-v and liquid hydrogen / hypergolics might be expensive payloads to handle. The first would be solved by having additional LEO depots. I was wondering about the second.

Hypergolics are used on most all current and past generation satellites, however, Ion drives are now replacing hypergolics on most new generation satellites. The logical assumption here is that any new Space Tug designed for satellite or lunar/mars cargo missions will be ion. Small hypergolics systems may add some flexibility to the tug. The most likley first tugs in space will be LEO to service ISS and other Space Stations. The tug would use in-space refueling deposts to refuel both the ion and hypergolic propulsion systems. This can be done today with no new technology.
Title: Re: Propellant Depots - General Discussion
Post by: Marisum on 05/10/2009 07:51 pm
Let's build an Ion Drive/Hypergolic Space Tug (on paper :) ) and use in-space refueling to power it. A good place to start would be components/systems from existing satellites so I propose using the Boeing 702 satellite bus. In contains the structure, ion drives/propellant, hypergolic RCS propellant/thrusters, power management, and solar array all in one nice unit. You only need to design/build the docking/refueling system.

We take two of them and do a little reconfiguring, we move all the hypergolic propellants to one bus and all the xenon ion propellant to the other bus. We remove the RCS thrusters from bus #1. We leave the RCS thrusters on bus #2.

We move the 4 ion thrusters on Bus #1 to bus #2 so now bus #2 has all the hypergolic and all (8) ion thrusters.

The solar arrays generate approximately 18kw and we have two sets of the, one set on Bus #1 and one set on bus #2. So with two 702 bus systems we can generate 36 kw of electrical power.

For refueling we place a Fuel Depot in LEO. It carries both hypergolic and ion propellants. The size of the Depot is simply a matter of how many missions you want to support x5, x10 x20, etc. Refuleing is done using a pressurized transfer system.

Boom. you now have a Refuelable LEO Space Tug at low cost and you  can fly it within 2-3 years.

Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/11/2009 12:33 am
Okay, this thread title is supposed to be general discussion about propellant depots by the title but has been so far about a single narrow idea: NASA flying a heavy lifter launcher and using a propellant depot on the side. This isn't very sensible.

Actually, it's been a bit wider than that. Agreed HLV + depot on the side isn't sensible.

Quote
If NASA builds a heavy lifter, all this becomes moot. Most of the propellant is lifted by the heavy lifter, and thus it makes no sense to make a propellant depot for just the few intermittent refueling tonnes, it is much cheaper to launch another heavy lifter. A purpose built heavy lifter will have big fixed costs and low launch rate, meaning adding more launches will not add much more cost anymore, the savings were missed when the thing was built in the first place.

Even with the mighty Ares V, propellant depots still make sense. They would allow more flexibility. With Ares V you have to launch a lot of cargo or propellant in one go. With a propellant depot, you can dry-launch most payloads on a commercial launcher and then load the required amount of propellant from the depot. Ares V + propellant depot makes more sense than Ares V alone. A propellant depot alone makes even more sense. The same holds for other big launchers, Shuttle-derived or otherwise.

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To put the effects of high fixed costs and low flight rate in nine words:
No savings from depot unless you scrap heavy lift.

Little savings. Building the big launcher before the depot makes it less likely the depot will be built and vice versa. Some people would rather lose the big launcher, others would rather lose the depot.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 05/11/2009 01:12 am
If NASA builds a heavy lifter, all this becomes moot. Most of the propellant is lifted by the heavy lifter, and thus it makes no sense to make a propellant depot for just the few intermittent refueling tonnes, it is much cheaper to launch another heavy lifter. A purpose built heavy lifter will have big fixed costs and low launch rate, meaning adding more launches will not add much more cost anymore, the savings were missed when the thing was built in the first place.

Even with the mighty Ares V, propellant depots still make sense. They would allow more flexibility. With Ares V you have to launch a lot of cargo or propellant in one go. With a propellant depot, you can dry-launch most payloads on a commercial launcher and then load the required amount of propellant from the depot. Ares V + propellant depot makes more sense than Ares V alone. A propellant depot alone makes even more sense. The same holds for other big launchers, Shuttle-derived or otherwise.

Team Direct has been VERY explicit that they do not intend that Jupiters be used to fill a depot. They seek 12 Jupiter missions per year to go elsewhere, enabled by commercially supplied fuel

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To put the effects of high fixed costs and low flight rate in nine words: No savings from depot unless you scrap heavy lift.

Little savings. Building the big launcher before the depot makes it less likely the depot will be built and vice versa. Some people would rather lose the big launcher, others would rather lose the depot.

Depots also enable non-NASA players.

Ending a NASA-centric (NASA only) model for human spaceflight is what matters most - IMHO - and I would like to see depot enabled medium lift operated by private companies and non-US nations to help develop the Moon with NASA operated (and depot supplied) heavy lift lofting vessels that will leave cis-lunar space.

Title: Re: Propellant Depots - General Discussion
Post by: Marisum on 05/11/2009 02:56 am
Quote
Team Direct has been VERY explicit that they do not intend that Jupiters be used to fill a depot. They seek 12 Jupiter missions per year to go elsewhere, enabled by commercially supplied fuel

The ideal that you can't use the J120 to launch Space Tugs and Propellant Depots seems bogus to me. The reason I say this is that
without using the vehicle you simply can't launch large commercial payloads like Tugs and Depots. You would have to have an entirely different heavy lift vehicle which would have to be developed entirely by the private sector before they could put these payloads into orbit. This
pretty much kills all commercial development in space.

Also, the only reason placing commercial payloads was outlawed from
the Space Shuttles was to protect the Atlas and Delta LVs. This had two very bad results. 1) It took payloads away from the Shuttle which made the shuttles non-cost effective and 2) It drove all the commercial launch business to the European and Russians vehicles, because the now protected EELVs where not cost effective and no one would buy them.
This is still true today. Very bad, you should rethink this position.

If the goal to encourage commercial space enterprize we will need access. Therefore, the problem is the same as always, getting access.
Currently, private companies can't get access to either the Shuttles or
the ISS.  The most important element missing from all of NASA activities is access. So, why are we paying for them via our tax dollars? And why
should the private sector support Aries 1/Aries 5 or the Direct J120 vehicle concept if we can't use it.

If I build an Propellant Depot with Private Capital and I need to buy a ride
to put it into space, I should be able to do that. Nothing else makes sense, because if the Private Sector knows that they can't get access, THEY WILL NOT INVEST. This means that all your hopes and dreams of
developing space infrastructure is just that and nothing more.





Title: Re: Propellant Depots - General Discussion
Post by: khallow on 05/11/2009 12:58 pm
I just glanced through some of the recent posts in this thread and noticed a lot of assumptions about the use and economics of heavy lift vehicles.

Marisum, the simple answer is that you don't need heavy lift to put a propellant depot (or a tug, for that matter) in space. Even if you did, putting a depot into orbit is a different issue than filling that depot (which is what Bill was speaking of). The former requires a fixed number of launches (presumably no more than a few) while the latter means some number of launches each year. I gather that the HLV would have limited launch frequency and be unable to both support a busy space exploration effort and propellant shipping. But you might be able to squeeze in the launching of a propellant depot, especially if the depot would be partly or fully used for NASA missions.

Second, I think there's a lot of assumptions about the cost of HLVs. My view is that we have absolutely no assurance that HLV will be competitive in cost per kg as compared to smaller vehicles. The three HLVs that have been developed (Saturn V, Space Shuttle, Energia) have not demonstrated any cost advantage over smaller vehicles. Saturn V is the best of the lot (118 metric tons to LEO, $135 million margin (http://www.geocities.com/launchreport/satstg5.html) cost in 1967 dollars which is roughly $8,000 per kg today plus enormous fixed costs). As I dimly recall, Ares V has a similar marginal cost per kg. Point is some rockets beat that figure soundly today.

An HLV with a propellant depot on the side may well be economical. To give a contrived example, if a Falcon 9 can launch propellant for $2,000 per kg and Ares V can launch propellant for $8,000 per kg, then there's a very compelling reason (that $6,000 per kg difference in cost) to use a propellant depot to take advantage of the lower costs of a Falcon 9. If a mission uses 100 tons of propellant and a propellant depot loses a quarter of its propellant to evaporation before it can be used, then that still is a $400 million reduction in cost from using a propellant depot.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 05/11/2009 01:33 pm
There are reasons for HLLV not driven by cost such as payload fairings that allow the launch of pre-assembled large objects. Whether HLLV will be cheaper by the pound has been argued to death and getting people change their minds through paper arguments will be difficult.

Fighting the HLLV political advocates also expends energy perhaps better used in a different manner.

Large lunar landers and pre-assembled regolith moving equipment (big lunar John Deere equipment) are examples of things that need large launchers. Even if the launch costs are more per pound, avoiding on site assembly can also save money and the "best" solution may not always be obvious.
 
Me? I'd love to see a ginormous Bigelow habitat (much larger than a BA-330) as an obstruction free playing volume for micro-gravity sports. Assembling a large interior volume from Lego pieces wouldn't be easy even if lofting the atmosphere and supplies needed to furnish that facility might be better accomplished by numerous small launchers.

One size - whether XL or XS - does not fit all.

Therefore (IMHO) we need an architecture that does not close the door on any approach but rather creates opportunity for EELV launches, NewSpace & COTS-D players and even foreign launches without throwing away the existing STS infrastructure.

Every Jupiter launched slogging fuel is one less Jupiter available for carrying large pre-integrated items and therefore innovative and lower cost alternatives for filling that depot will have a secure market niche.

Title: Re: Propellant Depots - General Discussion
Post by: Marisum on 05/11/2009 02:07 pm

Some items will need Heavy Lift and if these item are developed by the Private Sector they will need a ride into orbit.

Bill White says:
"Large lunar landers and pre-assembled regolith moving equipment (big lunar John Deere equipment) are examples of things that need large launchers. Even if the launch costs are more per pound, avoiding on site assembly can also save money and the "best" solution may not always be obvious."

Another system that is very large and will need many heavy launchers is
Space Solar Power.

Commercial Space Enterprizes will need access to heavy lift to build some of the future space infrastructure. If the Government does not allow access then these things simply can not happen.

Money has never been the driving factor in commercial space. There has always been access to the capital markets. What has been missing is the
support of Government in the form of market systems that are actually workable. Example: NASA COTS, everyone made it clear to NASA that NASA needed to offer launch commitments in order for the private sector to access capital. NASA did not do so (it did much later) and this resulted in only one company (SpaceX) actually being able to match NASA's investment (because they had cash on hand) also (i believe Orbital's bid on the rebid was a pay-as-you-go scheme).

NASA needs a lot of additional money that it will never get to complete its Vision. Cost overruns on Aries 1 and space shuttle extension will drain all the funding for Aries 5. This means that the heavy lifter will never be built.

NASA could get all the systems/components, actually better systems/components, for the exploration vision and do so at less cost, in less time and with plenty of money buy farming these systems/ components out to the private sector. The process is simple, and NASA knows how to do it, they just dont want to. All NASA has to do is agree to lease the systems/componets once they are completed, thereby providing customer base for the Tugs, Lands, Depots, etc, etc.

All of this could have been done many years ago, it is only NASA's anti-commercial position, and unfounded fear that have stoped it.

Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/11/2009 02:11 pm
Team Direct has been VERY explicit that they do not intend that Jupiters be used to fill a depot. They seek 12 Jupiter missions per year to go elsewhere, enabled by commercially supplied fuel

I know, and that is certainly progress. But on the other hand: every launch of a Jupiter lifts a little bit of cargo and a lot of propellant to orbit. That propellant could have been off-loaded and the cargo could have been dry-launched and the propellant launched separately, perhaps in a number of launches. By its very existence Jupiter competes with commercial launchers. Now I can live with J-130, and I still believe a shuttle derived launcher is highly likely, but it is incorrect to say DIRECT avoids competition with commercial launchers. It's technically impossible. But anyway, that's something for the DIRECT threads.

Quote
Depots also enable non-NASA players.

Ending a NASA-centric (NASA only) model for human spaceflight is what matters most - IMHO - and I would like to see depot enabled medium lift operated by private companies and non-US nations to help develop the Moon with NASA operated (and depot supplied) heavy lift lofting vessels that will leave cis-lunar space.

Absolutely, and maybe even the heavy Mars spacecraft could be launched on commercial launchers. What is the dry mass of the biggest piece?
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 05/11/2009 03:01 pm
Team Direct has been VERY explicit that they do not intend that Jupiters be used to fill a depot. They seek 12 Jupiter missions per year to go elsewhere, enabled by commercially supplied fuel

I know, and that is certainly progress. But on the other hand: every launch of a Jupiter lifts a little bit of cargo and a lot of propellant to orbit. That propellant could have been off-loaded and the cargo could have been dry-launched and the propellant launched separately, perhaps in a number of launches. By its very existence Jupiter competes with commercial launchers. Now I can live with J-130, and I still believe a shuttle derived launcher is highly likely, but it is incorrect to say DIRECT avoids competition with commercial launchers. It's technically impossible. But anyway, that's something for the DIRECT threads.

Chickens and eggs -- if Obama simply canceled NASA human spaceflight and spent the $8 or $9 billion thereby saved on education or midnight basketball programs or solar energy research, who would the new commercial players sell their launches to? Unlike ESAS, it appears Direct 3.0 foresees explicit incorporation of propellant depots supported by non-NASA launchers into the architecture and you want to toss Zoe Soldana out of bed for eating crackers? 


Urban Dictionary link - eating crackers in bed (http://www.urbandictionary.com/define.php?term=eating+crakers+in+bed)


The case for human spaceflight is over-determined is the sense used by Althusser . . . over determination is a way of thinking about the multiple, often opposed, forces active at once in any political situation.

Contradictory and overlapping reasons exist for funding human spaceflight (including national prestige, job programs, scientific research, inspiration of the youth, and  others as well as Dennis Wingo's desire to incorporate space into Earth's economic sphere) and therefore a theoretically pure approach such as "NASA should only buy what is commercially available" is neither politically viable nor technologically optimal. 

Also, the existing STS infrastructure represents accumulated capital and design work and a trained work force and to simply throw all that away to sustain a theoretical point would be profoundly wasteful and counterproductive to the larger vision.
 

Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/11/2009 03:30 pm
Chickens and eggs -- if Obama simply canceled NASA human spaceflight and spent the $8 or $9 billion thereby saved on education or midnight basketball programs or solar energy research, who would the new commercial players sell their launches to?

It is true that there won't be propellant depots any time soon without having governments as customers. And you know what? I wouldn't even advocate the government promoting them. I'm sort of libertarian-leaning and I don't think it would be proper for governments to do that. Unlike die-hard libertarians I'm not entirely convinced that there absolutely do not exist any circumstances where collective action might lead to superior results. Maybe extraterrestrial resources are such a case, but I'm not convinced. I am convinced however that governments are highly unlikely not to screw up such an effort.

But if there is going to be a manned space program (and yes that would be exciting!), I say it ought to promote commercial development of space. And guess what, it's not just little old me saying that, it's actually USG policy. Now that's a statement about ideals, but as always there are political realities.

As I've said many times before I believe a shuttle derived launcher is probably inevitable and as shuttle derived launchers go, the Jupiter family is not a bad one. It's nice to see they've incorporated depots and gateway stations in the plan. It's less nice to see that they have made them subordinate to huge launchers. I predict this means the depots will never be built if DIRECT is chosen, despite good intentions that may (or may not) exist.

Quote
Unlike ESAS, it appears Direct 3.0 foresees explicit incorporation of propellant depots supported by non-NASA launchers into the architecture and you want to toss Zoe Soldana out of bed for eating crackers? 

Nice phrase. Beautiful lady. Hadn't heard of either before.

How about this:

- SDLV first and depots later makes no technical sense
- US manned spaceflight beyond LEO will not be funded without an SDLV
- depots will not be funded without manned spaceflight
===> depots will not be funded without an SDLV, so we're going to have to live with an SDLV

I think we agree on this. It may not be what we like, but it is what we believe the world is currently like. There may however be an architecture that gets depots funded that has a smaller SDLV than DIRECT.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 05/11/2009 03:44 pm
Quote
SDLV first and depots later makes no technical sense

Maybe, maybe not. However even we grant the truth of the above assertion, the need to keep the STS workforce occupied adds a constraint that might not exist in a truly clean sheet design space.

For better AND for worse, the shuttle stack exists and provides both opportunity and constraint on future options.

Did NASA make a wrong turn in the early 1970s? Perhaps, but that is a purely academic question.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 05/11/2009 05:26 pm
Quote
SDLV first and depots later makes no technical sense

Maybe, maybe not. However even we grant the truth of the above assertion, the need to keep the STS workforce occupied adds a constraint that might not exist in a truly clean sheet design space.

For better AND for worse, the shuttle stack exists and provides both opportunity and constraint on future options.

Did NASA make a wrong turn in the early 1970s? Perhaps, but that is a purely academic question.

Not entirely.  Remember, sacred cows *do* often get roasted in DC. 

But more importantly SDLV first with depots later is pretty much a guarantee that you only get the SDLV.  It's like the old joke about the difference between the Air Force and the Marines.  When the Marines build and landing strip, they build the landing strip and required buildings first, and then have to go back to beg for money to build some crappy barracks.  When the AF builds an airstrip they build the officer's club, and the nice barracks, and all the amenities first, and then they go back and beg for money to build the actual airstrip.

If you really think that SDLVs are a hard and fast political requirement, then get the *useful* stuff built first, and then go back and bet more money for the politically motivated stuff.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 05/11/2009 05:38 pm
Quote
SDLV first and depots later makes no technical sense

Maybe, maybe not. However even we grant the truth of the above assertion, the need to keep the STS workforce occupied adds a constraint that might not exist in a truly clean sheet design space.

For better AND for worse, the shuttle stack exists and provides both opportunity and constraint on future options.

Did NASA make a wrong turn in the early 1970s? Perhaps, but that is a purely academic question.

Not entirely.  Remember, sacred cows *do* often get roasted in DC. 

But more importantly SDLV first with depots later is pretty much a guarantee that you only get the SDLV.  It's like the old joke about the difference between the Air Force and the Marines.  When the Marines build and landing strip, they build the landing strip and required buildings first, and then have to go back to beg for money to build some crappy barracks.  When the AF builds an airstrip they build the officer's club, and the nice barracks, and all the amenities first, and then they go back and beg for money to build the actual airstrip.

If you really think that SDLVs are a hard and fast political requirement, then get the *useful* stuff built first, and then go back and bet more money for the politically motivated stuff.

~Jon

If you are right, Jon, right now would be a good time for someone to win funding for propellant depots.

That said, the fact that Jim Muncy can speak at Space Access and express potential acceptance of shuttle derived (C, Z, whatever) suggests to me that the odds are low for achieving immediate propellant depot architecture funding without shuttle derived launch vehicles.

By September 2009 Team Obama will have its new course established and thereafter course changes will be difficult to accomplish at least until January 2013 or January 2017 depending on which political crystal ball you prefer.

Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/17/2009 11:27 am
If you really think that SDLVs are a hard and fast political requirement, then get the *useful* stuff built first, and then go back and bet more money for the politically motivated stuff.

That may not be possible. Once depots are operational, there would no longer be a role for an SDLV. There wouldn't be anything left that commercial launchers couldn't lift to orbit or commercial upper stages couldn't get to L1/L2. Heck, even today you could get a Soyuz-sized capsule to L1/L2 with a Centaur, it's only because Orion is so heavy that you'd need a bigger launcher to get the DIV upper stage to LEO. If depots are developed first, then there will never be an SDLV. Politicians will only allow a depot to be built if they are ready to abandon the shuttle stack and shuttle workforce, or if a compelling argument can be found to keep it operational.

If NASA wants to preserve the shuttle workforce, it has to make sure no gateways or depots are developed before it reaches the moon and that no commercial capsules are developed for fear they might reach L1/L2 before NASA reaches the moon. It is against NASA's organisational interest to lead the way into space in any meaningful sense of the word. Right now it is delaying progress by commercial players so it will have the first shot. That's not leading, that's obstructing.

Take Ares I for example. I suspect it isn't just a precursor system to get funding for Ares V, it is also a way to delay man-rating the EELVs. The enthusiasm for SpaceX being awarded a COTS contract may have been slightly misplaced. SpaceX is much further away from having an operational capsule than would have been the case for an established aerospace player with a ULA launcher. If the intent was to delay commercial competition, awarding the contract to SpaceX was a good way to do it. Not funding COTS-D is also a good move from that perspective, as you have pointed out before.

I'm not optimistic about reform from the inside. NASA has shown it is willing to use FUD, lies and intimidation to suppress competition. I doubt having a new administrator or even a new plan will help much. Griffin himself used to advocate EELVs and depots. And who knows, maybe he still thinks they are a good idea. It's not impossible his heart is in the right place. It could be he felt compelled by political forces to discredit them, at least in the short run.

In my opinion the only way to get NASA to build or facilitate depots is for Congress to order them to do that. And unless you believe politicians are willing to abandon the shuttle workforce, that means finding a prominent role for the shuttle stack, and one that is not threatened by depots. If we want depots soon, we must find a way in which depots are synergistic with an SDLV. To the best of my knowledge no pressure group has come up with a proposal for that, the proposals to date have been either disastrous for depots or disastrous for the shuttle stack. If we want depots, we had better get our act together soon.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 05/17/2009 02:26 pm
mmeijeri;

DIRECT Phase-1 and 2 does exactly what you are discussing.
Phase-1 uses a 2-launch architecture to accomplish the lunar missions, getting that part of the VSE operational and established. Then Phase-2 introduces depots in LEO. The justification is that with a depot available in LEO the 2-launch lunar mission can be done with a SINGLE Jupiter launch. That saves NASA $billions of dollars and is a huge incentive for the Congress to approve the funding.

Apollo taught us that going to the moon is very expensive and the Congress will only pay for such an expensive undertaking for just so long. So first we get the exploration going, because Congress is willing to fund that today. It's exciting and they can show progress to their constituancies to justify the money, which is what it takes to maintain public support. Then once we have crew on the surface, then we show Congress how to shave $billions off the price tag. They get to keep the the space exploration program going at a reduced cost. It's just too good an opportunity for them to pass up because they can then show their constituancies what they are doing to be fiscally responsible with the nation's treasure.

Can a depot-based architecture be successfully established without a SDLV? Yes it can. It most assuredly can. The EELV's are more than up to the task. Technically it just is not that difficult, though it is more long term than getting to the moon without it. The public will need to be willing to watch monies being spent without exciting results being visible for some time until we can begin to design spacecraft around the depot later on. History has shown us that the public just does not support that kind of long-term thinking. Establishing a depot-based architecture from the very beginning, without an already established justification for it takes a lot more vision than what I honestly believe we have a right to expect from the Congress. They are all good and hard working people, but their "vision", by necessity, is limited by their terms in office. Very few of them have the luxury of working on projects that likely won't see completion anytime while they are in office, or even, in some cases, their immediate successor. They have to justify their efforts with actual results to their constituencies. Guys like Jon for example will disagree with me, and I honestly respect his point of view, I really do, but my point of view is based on having dealt with some members of Congress for a very long time. The way we all would like to see Congress work rarely lines up with the way it actually does.That in no way should be read as a slap at Congress - it is not. It's an assessment from my experience of the way things actually work inside the beltway. The people who insist that Congress operate the way they think it should rarely get the results they seek. But the people who concede reality and work with it have a much better chance to obtain what they want.

The DIRECT Team is very hopeful that by taking this path, should we all be fortunate enough to have DIRECT, or some flavor if it selected, a Propellant Depot-based architecture will actually become a reality in the foreseeable future, bringing many, many more players into the realm of exploration.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/17/2009 03:23 pm
DIRECT Phase-1 and 2 does exactly what you are discussing.

It does not look that way to me.

Quote
Phase-1 uses a 2-launch architecture to accomplish the lunar missions, getting that part of the VSE operational and established.

This will take a substantial number of years during which there will be no funding for depots. And as long as Orion and an SDLV - any SDLV - are operational in LEO, they will get in the way of commercial alternatives. There just isn't a way around that. As long as it operates in LEO, J-130 is just a massively oversized and slightly less harmful Ares I, albeit one that can likely actually fly. Take it beyond LEO, and it can do exciting new things.

Quote
Then Phase-2 introduces depots in LEO. The justification is that with a depot available in LEO the 2-launch lunar mission can be done with a SINGLE Jupiter launch. That saves NASA $billions of dollars and is a huge incentive for the Congress to approve the funding.

In fact, by that time a mission can be done by EELVs. Phase 2 obsoletes Jupiter, which is why there will be no Phase 2. With LEO and L1 depots, there is no role for the shuttle stack, unless you come up with a new application.

Quote
Apollo taught us that going to the moon is very expensive and the Congress will only pay for such an expensive undertaking for just so long.

Then don't go all the way to the moon initially. Problem solved. And commercial development of space would be facilitated. You would even please Mars and NEO enthusiasts.

Quote
So first we get the exploration going, because Congress is willing to fund that today. It's exciting and they can show progress to their constituancies to justify the money, which is what it takes to maintain public support.

Funding for NASA has been remarkably stable over the years, with the important exception of Apollo. The moon is not needed to continue the space program. The moon may be needed to ensure survival of the shuttle stack and more importantly the workforce. Personally, I don't think that is true, provided you come up with a good plan.

Quote
Then once we have crew on the surface, then we show Congress how to shave $billions off the price tag. They get to keep the the space exploration program going at a reduced cost. It's just too good an opportunity for them to pass up because they can then show their constituancies what they are doing to be fiscally responsible with the nation's treasure.

But they will likely still not want to kill the shuttle stack. Saving money isn't a good enough reason to kill off the shuttle stack now, it will not be a good enough reason then.

Quote
Can a depot-based architecture be successfully established without a SDLV? Yes it can. It most assuredly can. The EELV's are more than up to the task. Technically it just is not that difficult, though it is more long term than getting to the moon without it.

Often asserted, but not self-evident. An EELV based Moon Direct would likely return to the moon sooner and definitely go beyond LEO sooner. Smaller capsule, hypergolic lander, L1 rendez-vous. No new engines, no new launchers. Think Early Lunar Access. I'm not in favour of a mad dash to the moon, but if you wanted to, this is the way you would do it.

Quote
The public will need to be willing to watch monies being spent without exciting results being visible for some time until we can begin to design spacecraft around the depot later on.

False, only if you go about it the wrong way. There is no reason why there wouldn't be exciting results. I wonder why you keep saying that.

Quote
History has shown us that the public just does not support that kind of long-term thinking. Establishing a depot-based architecture from the very beginning, without an already established justification for it takes a lot more vision than what I honestly believe we have a right to expect from the Congress.

All it takes is a bit more vision from space enthusiasts to come up with a plan that will yield exciting results more quickly and in a way that stimulates commercial development of space. Which is part of NASA's official mission by the way.

Quote
But the people who concede reality and work with it have a much better chance to obtain what they want.

Absolutely, which is why I do just that. It means we're going to have to come up with an alternative that preserves the shuttle stack and workforce, gives it a prominent long term role and aligns its interests with depots, gateway stations and the commercial development of space. Despite the technical achievements of the shuttle, for 25 long years the shuttle stack has been an obstacle to progress. If we can realign its interests, we can realign NASA. $1.5B a year is a bargain if we can do that.

But it takes a plan that balances the interests of the shuttle stack, its workforce, supply chain and political supporters with NASA's official mission. DIRECT in its current incarnation most definitely isn't that plan, though elements from it could certainly be part of it, as could some other interesting proposals out there.

Quote
The DIRECT Team is very hopeful that by taking this path, should we all be fortunate enough to have DIRECT, or some flavor if it selected, a Propellant Depot-based architecture will actually become a reality in the foreseeable future, bringing many, many more players into the realm of exploration.

Wanna bet? I predict that what DIRECT will achieve if adopted is preservation of the shuttle stack and a return to the moon. Those who want to see the commercial development of space should resist it with all their might. Or better yet - steer it in a more fruitful and balanced direction because there will be no progress without the shuttle stack.
Title: Re: Propellant Depots - General Discussion
Post by: Marisum on 05/17/2009 04:32 pm
One option would be to keep the Shuttles, but make one or two of them unmanned. This would allow for a much higher flight rate and lower cost, while retaining some manned capability until a replacement that is better and cheaper than Ares 1 is developed.

Interesting thought. If the Russian's asked me to travel to the moon in thier cheapy soyuz vehicle I would probably do it. If NASA asked me to travel there I would most likely decline, because I would not want to get stuck there. The Russian's have manned and serviced the ISS since the beginning and NASA has been lost in space for two decades. How on Earth can we expect them to service a moon base if they can't service a low earth orbit space station?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 05/18/2009 03:24 am

Then don't go all the way to the moon initially. Problem solved. And commercial development of space would be facilitated. You would even please Mars and NEO enthusiasts.

{snip}

Wanna bet? I predict that what DIRECT will achieve if adopted is preservation of the shuttle stack and a return to the moon. Those who want to see the commercial development of space should resist it with all their might. Or better yet - steer it in a more fruitful and balanced direction because there will be no progress without the shuttle stack.

It should be possible to come up with an architecture that uses J-130 and a propellant depot to put large cargoes on the Moon, and possibly Mars.
How soon?

A J-130, propellant depot and Orion (or Human Orbital Transfer Vehicle) may be able to reach a Near Earth Object.  This will keep the astronauts busy going exploration whilst the Altair is developed.
Title: Re: Propellant Depots - General Discussion
Post by: Marisum on 05/18/2009 06:36 am
You could go to the moon with either the J rockets or the shuttles. The architecture would just look a little different, using smaller mods that are docked in space. Docking is not a big problem. In fact, if you use both you could do even better, no need for CEV since the astraunts can return via a shuttle. If you make the whole system reusable that would be even better.

NASA could bid out each component in a type COTS program, doing a 50/50 venture with each commercial company. This alone would cut the governments development cost in half.

Parts might include:
LEO launchers (Shuttle, J-120, SpaceX, Orbital, Other)
Space Booster Section (J2x Powered)
Space Tug Section (RL-10 Powered)
Space Habitats
Lunar Landers
Depots

You could have two different systems, one manned, one un-manned for cargo, but based on many of the same mod components. The un-manned system could use slower ion engines but save tons of mass (smaller depots). The manned system would use a chemical tug.
This would actually be cheaper then current thinking because the mods would be reusable. They could also be smaller and easier to launch.

pics attached.





Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/29/2009 07:24 pm
I had wondered about helium pressurant for hypergolic propulsion. If you make sure you don't use up all propellant, would that mean not losing any helium? And do you know why helium is used instead of say nitrogen? Would nitrogen dissolve in MMH/NTO?

Found the answer to my question here (http://forum.nasaspaceflight.com/index.php?topic=10600.msg413272#msg413272). Nitrogen does indeed dissolve in NTO. You could use it, but you would need more nitrogen.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 01/23/2010 08:48 pm
And here's the old depot thread again.

Martijn, FWIW that post of mine wasn't about cryogenic depots or landers--in fact, I didn't say anything about what propulsion system the landers would use.  They could just as easily be cryogenic ones as storables.

I know and that's precisely my objection. I like the fact your proposal avoids cryogenic propellant transfer and its technological risks. I don't like the fact that it doesn't use propellant transfer at all. It's not that I like hypergolics because they are ideal for landers, I like landers (and their Flexible Path precursors) because they are ideal for hypergolics.

The reason I like hypergolics is that they would enable us to get massive synergy to commercial development of space through NASA exploration and do so as cheaply, quickly and risk free as possible. Storable propellant transfer is TRL 9 and there is no good reason for avoiding it. Commercial propellant flights soon would aid the development of RLVs and other systems to reduce cost to orbit which is the greatest obstacle to commercial development of space. All we would have to do is to find an application that requires lots of hypergolic propellant. Landers and their precursors are the only application I can think of, EDSs are not a realistic candidate for the US since it has the best upper stages in the world and those are cryogenic.

Note that even though hypergolics (or other non-cryogenics) are not necessarily ideal for landers, they do remain excellent candidates, and even more so for long duration Flexible Path missions.

Side note: I do like your proposal very much though, since it would provide a way to beat NASA to beyond LEO which might cause such a political earthquake that all sorts of previously politically impossible things might suddenly become possible. Especially in an era of budget cuts and more interest in international cooperation.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 01/24/2010 05:11 am
I had wondered about helium pressurant for hypergolic propulsion. If you make sure you don't use up all propellant, would that mean not losing any helium? And do you know why helium is used instead of say nitrogen? Would nitrogen dissolve in MMH/NTO?

Found the answer to my question here (http://forum.nasaspaceflight.com/index.php?topic=10600.msg413272#msg413272). Nitrogen does indeed dissolve in NTO. You could use it, but you would need more nitrogen.

If you want an inert alternative to both nitrogen and helium try argon.
Density          (0 °C, 101.325 kPa)  1.784 g/L
Melting point    83.80 K, −189.35 °C, −308.83 °F
Boiling point    87.30 K, −185.85 °C, −302.53 °F
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 03:36 am
Moving this to a more appropriate thread.

According to ESA's documentation ATV transfers 820kg of propellant. Not much, but it only takes half an hour, fully automated.

If that is actually true, I stand corrected, big time. News to me.


It uses the same system and concept the Russians use.

OK, I figured out the discrepancy. 

First off, it is 100% correct that ATV uses the same prop system as Progress, in terms of its prop payload section. What I don't know is if ATV is Progress-M or Progress-M1 flavor.

However, the Russian refueling system is not necessarily a simple blow down system because there is substantial pressure in the receiving prop tanks after each refueling. So ..... there is a very time consuming and energy intensive operation to reduce the back pressure of the receiving tanks prior to the next prop transfer. This is the "24 hours" I mentioned earlier.

I believe that such an operation is required every time that a prop transfer occurs - the pressure from the fueling vehicle is transferred to the receiving vehicle, so that the next time there is a fueling, the pressure must somehow be reduced, or the next tanker must have even higher pressure levels.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 03:40 am
Is there a technical description of the Russian propellant transfer system available online? Last time I checked there was only one Russian paper, which I don't have and which I couldn't read if I did since I don't speak Russian.
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 04:36 am
There is infamous Mir Hardware Heritage, which describes Salyut prop systems in some detail.
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 04:38 am
The key attributes of the Russian system are:

It works, and

They separate the pressurizing gases from the propellant by an elastic membrane.

So, no dissolving the pressurizing gas in the prop for them.
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 04:43 am
Let me provide the best English write up of the Russian prop transfer system:

Journal of the British Interplanetary Society, Vol 38, pp 381 - 384, 1985.

Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 04:43 am
Do you know how often the system could be cycled? I'm particularly interested in a reusable lander which can also serve as a makeshift depot. It doesn't matter much anymore, as the scenario under which this might make sense seems to be evaporating fast, but I'm still curious.
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 04:49 am
Do you know how often the system could be cycled? I'm particularly interested in a reusable lander which can also serve as a makeshift depot. It doesn't matter much anymore, as the scenario under which this might make sense seems to be evaporating fast, but I'm still curious.


The receiving system can be cycled as often as power allows, and there is room in the prop tanks. Note that the receiving system is big and heavy, not good for a lunar lander. When I say "big", I mean in terms of a system that can hold 2 or 3 tons, I am not sure that the Russian system can scale upwards very well.

The tanker system really has one cycle in it, although I do know a way to jimmy Progress to get a 2nd cycle. It voids the warranty.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 04:51 am
You say it's big and heavy, but isn't that just because it is pressure-fed? I'm not convinced a single stage reusable lander could be pressure-fed anyway, so that's not necessarily a big problem.
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 04:54 am
You say it's big and heavy, but isn't that just because it is pressure-fed? I'm not convinced a single stage reusable lander could be pressure-fed anyway, so that's not necessarily a big problem.

Its big and heavy partially due to the redundancy, but also because its pressure fed. The entire system - across ISS and Progress is all pressure fed. I am not sure how a pump fed system would work in this context.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 04:56 am
Even if it was pressure-fed, it wouldn't have to be at full pressure during propellant transfer, would it?
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 04:58 am
Even if it was pressure-fed, it wouldn't have to be at full pressure during propellant transfer, would it?

No, of course the tanker would be at higher pressure.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 05:00 am
I meant it wouldn't have to be at the same pressure level as when the engine is burning. That would likely be a very high level for an ESAS-sized pressure-fed lander.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 02/04/2010 05:27 am
This is a very interesting conversation! I had assumed that they would have used a sort of wetted screen for the prop tanks, not an elastic membrane.

Is there a pdf or link to this british research paper on Russian prop transfer, Danderman, or am I going to have to go to my local University's library to access it?

Thanks!

Also, what sort of pressures are we talking about, exactly?
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 05:30 am
Is there a pdf or link to this british research paper on Russian prop transfer, Danderman, or am I going to have to go to my local University's library to access it?

I couldn't find it and I pay good money to have internet access to scientific journals through my local university library. If anyone can find a link, I'd love to know. The website of the BIS doesn't have anything before 1999 online, so that may be a bad omen.
Title: Re: Propellant Depots - General Discussion
Post by: robertross on 02/04/2010 03:30 pm
This is a very interesting conversation! I had assumed that they would have used a sort of wetted screen for the prop tanks, not an elastic membrane.


Remember, this all depends on the propellants in question.
Membranes crack in cryo conditions.

For hypergols this is essentially a non-issue, so long as the membrane doesn't degrade or get attached by the propellants or their constituent components.
Title: Re: Propellant Depots - General Discussion
Post by: Patchouli on 02/04/2010 04:02 pm
I meant it wouldn't have to be at the same pressure level as when the engine is burning. That would likely be a very high level for an ESAS-sized pressure-fed lander.

There are options in between a pressure fed system or going all the way to a turbo pump.

http://www.xcor.com/products/pumps/index.html

I believe this same pump technology could be useful for propellant transfer as well.
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 07:27 pm
I meant it wouldn't have to be at the same pressure level as when the engine is burning. That would likely be a very high level for an ESAS-sized pressure-fed lander.

I believe that the working pressure level for Russian pressure fed engines is 20 atmospheres. This means that the ISS prop tanks have to change pressures from 3 atmospheres prior to tanking, and 20 atmospheres when operating engines.

This change of pressure requires a boatload of power for the compressor. In the old days, the Russian stations didn't have much available, so this took a long time, and was a problem for the crew. Nowadays, ISS has a lot of power, so its not such a problem.

Future Chinese platforms will require loads and loads of power if they plan to emulate the Russian refueling system for lunar missions.
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 07:28 pm
This is a very interesting conversation! I had assumed that they would have used a sort of wetted screen for the prop tanks, not an elastic membrane.


Remember, this all depends on the propellants in question.
Membranes crack in cryo conditions.

For hypergols this is essentially a non-issue, so long as the membrane doesn't degrade or get attached by the propellants or their constituent components.

The Russians did have such problems, so they switched to a metalized membrane some time ago.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 02/04/2010 08:14 pm
This is a very interesting conversation! I had assumed that they would have used a sort of wetted screen for the prop tanks, not an elastic membrane.


Remember, this all depends on the propellants in question.
Membranes crack in cryo conditions.

For hypergols this is essentially a non-issue, so long as the membrane doesn't degrade or get attached by the propellants or their constituent components.

The Russians did have such problems, so they switched to a metalized membrane some time ago.

Ah-HA! I knew it! You kind of have to do that when your oxidizer is an acid (see, hypergols have their own set of difficulties as well as advantages).
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 08:30 pm
Ah-HA! I knew it! You kind of have to do that when your oxidizer is an acid (see, hypergols have their own set of difficulties as well as advantages).

Obviously. The only reason this could have been of strategic importance is that it is TRL 9. It is strategic as long as all of the following are true:

- no RLVs/cheap expendables yet
- no cryogenic propellant transfer and long term storage yet
- a willingness to go beyond LEO soon
- no HLV
- freely competing commercial launchers
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 08:31 pm
And then there is kerosene/peroxide. I think the main reason people don't like this idea is the same reason I do like it: it works and it would make HLV superfluous.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 08:34 pm
Future Chinese platforms will require loads and loads of power if they plan to emulate the Russian refueling system for lunar missions.

Which means large solar panels or ... APUs! How's that for shuttle-derived goodness? ;)
Title: Re: Propellant Depots - General Discussion
Post by: nooneofconsequence on 02/04/2010 08:39 pm
And then there is kerosene/peroxide. I think the main reason people don't like this idea is the same reason I do like it: it works and it would make HLV superfluous.
Prop depots always kill HLV.

As to peroxide, many like the high ISP of hydrolox. Or the consumables pairing aspect (water and oxygen and power presuming fuel cell).
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 02/04/2010 08:40 pm
Future Chinese platforms will require loads and loads of power if they plan to emulate the Russian refueling system for lunar missions.

Which means large solar panels or ... APUs! How's that for shuttle-derived goodness? ;)
OR, use the Shuttle's fuel cells... since we're going to be going with cryogenic propellants, anyways, you might as well start on it!
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 08:41 pm
Future Chinese platforms will require loads and loads of power if they plan to emulate the Russian refueling system for lunar missions.

Which means large solar panels or ... APUs! How's that for shuttle-derived goodness? ;)

Ummm ... APUs running for a prolonged period. Maybe fuel cells could do the job.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 08:46 pm
Prop depots always kill HLV.

Sure, but the noncryogenics have the advantage of being TRL 9. My concern here is getting rid of SDLV/HLV and getting commercial propellant flights up and running as soon as possible. The immaturity of cryogenic propellant transfer has been used as a pretext for SDLV. But as I said, it only makes sense under a specific set of circumstances, and those are not the circumstances we live in.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 08:48 pm
Ummm ... APUs running for a prolonged period. Maybe fuel cells could do the job.

Just out of curiosity, why would it be a problem to have an APU running for several hours? Don't diesel generators run much longer?
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 09:34 pm
OR, use the Shuttle's fuel cells... since we're going to be going with cryogenic propellants, anyways, you might as well start on it!

Well, that decision hasn't been made yet since there won't be a lander for the foreseeable future. Note that you're letting your preferred launch vehicle determine the propellant used for the lander and not discussing it on its own merits...
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 02/04/2010 09:46 pm
OR, use the Shuttle's fuel cells... since we're going to be going with cryogenic propellants, anyways, you might as well start on it!

Well, that decision hasn't been made yet since there won't be a lander for the foreseeable future. Note that you're letting your preferred launch vehicle determine the propellant used for the lander and not discussing it on its own merits...
If the launch vehicle upper stage can be integrated with the propellant tanker, so the upper stage IS the tanker, then if you start reusing the upper stage (like SpaceX wants to do with the Falcon 9, eventually), then you can also reuse the tanker spacecraft, allowing you to reduce all of the costs to the fuel price and operations costs. That's why it makes sense to use the same propellant for a launch vehicle's upper stage as for your prop depot. The launch vehicle upper stage has to just about enter orbit anyways, so why not make it into the tanker? The two are inter-related, which is why I treat them such.

Otherwise, are we planning on building a new tanker craft for every mission? If we do, we're missing out on a really big opportunity for cost reduction down the road. Also, if the depot uses the same fuel as the upper stage, then the tanker can also go directly to other, higher orbits, if necessary (though with much less fuel). And, it can still reach orbit in case of engine under-performance earlier on.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 09:58 pm
Yes, that's a very nice idea and I want to see that eventually. But I'm getting the feeling that's not your most important reason. If we used hypergolics or kerosene/peroxide, we could go beyond LEO soon. I think you don't like that because you know that would cost you the HLV. Conversely I don't want the HLV because I'm convinced it would cost us RLVs. The reason for RLV is commercial development of space, which seems like an excellent reason. It seems you would rather give up on commercial development of space and even exploration soon than on HLV. The reason for HLV is ... something its proponents aren't even willing to talk about. My guess: excitement with the concept. Yes, I agree completely that large rockets are exciting. But they come at a very high price.

And lest you think this is off-topic for a depot thread: to me the main point of depots is what they could do for near term commercial development of space. That's something I can get really excited about. In this case the enthusiasm for depots is derived from the enthusiasm for commercial development of space.

Another exciting reason might be if we didn't get HLVs and wanted to do exploration anyway. In that case the enthusiasm for depots is derived from the enthusiasm for exploration.

The final reason is the one people focus on and it's the least exciting to me: depots give you flexibility. This is no different from terrestrial gas stations. Useful, sure, but hardly anything to get enthusiastic about.

Commercial development of space and exploration are the main reasons depots are exciting.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 02/04/2010 10:15 pm
Yes, that's a very nice idea and I want to see that eventually. But I'm getting the feeling that's not your most important reason. If we used hypergolics or kerosene/peroxide, we could go beyond LEO soon. I think you don't like that because you know that would cost you the HLV. Conversely I don't want the HLV because I'm convinced it would cost us RLVs. The reason for RLV is commercial development of space, which seems like an excellent reason. It seems you would rather give up on commercial development of space and even exploration soon than on HLV. The reason for HLV is ... something its proponents aren't even willing to talk about. My guess: excitement with the concept. Yes, I agree completely that large rockets are exciting. But they come at a very high price.

And lest you think this is off-topic for a depot thread: to me the main point of depots is what they could do for near term commercial development of space. That's something I can get really excited about. In this case the enthusiasm for depots is derived from the enthusiasm for commercial development of space.

Another exciting reason might be if we didn't get HLVs and wanted to do exploration anyway. In that case  the enthusiasm for depots is derived from the enthusiasm for exploration.

The final reason is the one people focus on and it's the least exciting to me: depots give you flexibility. This is no different from terrestrial gas stations. Useful, sure, but hardly anything to get enthusiastic about.

Commercial development of space and exploration are the main reasons
depots are exciting.

You're wrong. You and Jon Goff have already convinced me that HLV is a luxury of sorts. It's the fact that you can integrate the tanker into the upper stage and hence reuse both of them (when upper stage reusability is possible... we already know that it's possible because of the Shuttle) that has convinced me to use the same fuel for both. Also, the logistical simplicity of using methane/LOX or hydrolox for crew consumption and power.

Look. I know hypergolic prop transfer is TRL-9, but it's obvious that NASA is entering a phase when they want to bring things like cryogenic prop transfer to TRL-9. SpaceX has mentioned that they want to eventually reuse the Falcon 9 upper stage (besides just the lower stage) and also eventually want to make a hydrolox upper stage. Put those two things together (or just use kerolox for the depot), stretch the tank, and you've got yourself a fully reusable propellant delivery architecture that could be online within a decade if you wanted. The DinoSpace companies can do this, too, if they wanted to (Lockheed-Martin is putting a little research into flying scale-model flyback boosters right now).

The ease of hydrolox ISRU (heck, we're doing it right now on the ISS on a very small scale, though without cryogenic cooling, which can be done), the very low toxicity, and the fact that it has basically the highest chemical Isp available are just icing on the cake.

But, I'm not opposed to a hypergolic reusable lander. I'd want to know if hypergolic engines are intrinsically longer lasting than other engines, like kerolox or hydrolox or methane/lox (when you assume you have a way of easily starting the engine basically as many times as you want). That's a very important consideration. Remember also that hypergolic fuels like hydrazine must be actively kept from freezing, which means plenty of power consumption and dual redundant heaters, etc. In space, the average temperature is not necessarily room temperature!

Your idea for kerosene/peroxide is worth consideration, too.
Title: Re: Propellant Depots - General Discussion
Post by: Danderman on 02/04/2010 10:23 pm
Ummm ... APUs running for a prolonged period. Maybe fuel cells could do the job.

Just out of curiosity, why would it be a problem to have an APU running for several hours? Don't diesel generators run much longer?

Diesel generators don't have to carry their own oxidizer with them.

Think about jet engines, they run for hours, but there is a reason why rocket engines do not.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/04/2010 10:50 pm
Think about jet engines, they run for hours, but there is a reason why rocket engines do not.

Ah, that makes sense. Given that noncryogenic propellants typically require heating to prevent them from freezing do you think the propellant itself might be used as a coolant? It would be an interesting form of multiple use for the propellant: propellant for a rocket engine, "fuel" for an APU and coolant. Again, merely curious, not saying we should do it this way.
Title: Re: Propellant Depots - General Discussion
Post by: robertross on 02/05/2010 12:22 am
Think about jet engines, they run for hours, but there is a reason why rocket engines do not.

Ah, that makes sense. Given that noncryogenic propellants typically require heating to prevent them from freezing do you think the propellant itself might be used as a coolant? It would be an interesting form of multiple use for the propellant: propellant for a rocket engine, "fuel" for an APU and coolant. Again, merely curious, not saying we should do it this way.

Depending on the propellant, one problem is that with a rise in temperature, certain chemicals can become more corrosive. Also, the temperature imparted to the metals/materials can cause them to degrade.

Again, this is not true for all chemicals. But seals, fluid conductors, even sensors can be attacked. Hate to see a pressure sensor give you faulty readings during a transfer. Safety valves help, but they can fail too.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/05/2010 12:33 am
Reading about the Shuttle APUs (http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-apu.html#sts-apu), it seems they would be up to the job. They can run for two hours at a time, provide 100kW each and are fairly compact and light-weight. I was surprised they provide so much power. There appears to be a mistake in the text: fuel consumption should be 3 pounds per minute, not 3 pounds per hour, right?

Incidentally they don't use an oxidiser, but hydrazine with a catalyst bed. Something similar could be done with peroxide. Mark Ventura, who is of course a strong proponent of hydrogen peroxide, has argued  (http://www.gkllc.com/lit/gk-authored/AIAA-2006-4547_hydrogen_peroxide_gas_generators.pdf)that this would in fact be preferable, especially since you could regulate temperature by varying the water content.

Again, I'm not saying this is ideal, fuel cells or solar arrays may be much better, I'm just looking for an existence proof. So far it seems as if transfer rates, power requirements and pressure are not show stoppers.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/05/2010 03:12 am
You're wrong. You and Jon Goff have already convinced me that HLV is a luxury of sorts. It's the fact that you can integrate the tanker into the upper stage and hence reuse both of them (when upper stage reusability is possible... we already know that it's possible because of the Shuttle) that has convinced me to use the same fuel for both. Also, the logistical simplicity of using methane/LOX or hydrolox for crew consumption and power.

OK, fair enough. You prefer a better system later, at the risk of it never happening. I prefer the simplest system as soon as possible, at the risk of not getting the better system or only getting it a lot later. The reason is that I think having commercial propellant flights soon is crucial.

What matters to me is:

- TRL 9
- commercial propellant flights available to small launchers
- fully reusable single stage lander (even if reusable only for a couple of times)
- lander fits inside an EELV fairing
- lander design suitable for the long term (so no absolutely crappy propellants)
- as simple as possible
- as soon as possible

There are some other issues, but they belong more in the reusable landers thread than here.

Quote
Look. I know hypergolic prop transfer is TRL-9, but it's obvious that NASA is entering a phase when they want to bring things like cryogenic prop transfer to TRL-9. SpaceX has mentioned that they want to eventually reuse the Falcon 9 upper stage (besides just the lower stage) and also eventually want to make a hydrolox upper stage. Put those two things together (or just use kerolox for the depot), stretch the tank, and you've got yourself a fully reusable propellant delivery architecture that could be online within a decade if you wanted. The DinoSpace companies can do this, too, if they wanted to (Lockheed-Martin is putting a little research into flying scale-model flyback boosters right now).

TRL 9 is my only reason. There are other technical tradeoffs and it's fun to talk about those, but nothing strategic as far as I can tell. Perhaps volume requirements inside an EELV fairing are problematic for a fully reusable single stage LOX/LH2 lander, but not for other fuels.

If we're not going beyond LEO soon, then by the time we are ready cryogenic propellant transfer will be TRL 9. At that time I'd see no strategic reason to prefer hypergolics. As long as the TLI propellant is LOX/LH2 it doesn't matter what you use for the lander. Both hypergolics and LOX/LH2 seem like excellent lander propellants. Depending on the applications other propellants like methane or silane could be even better, but I'd be happy to be 'stuck' with either indefinitely. The same list of criteria would apply 10 years from now, but might give different results then. All else being equal I'd rather see the lander ASAP than ten years from now. That also means I'd not at all be opposed to NASA building a lander. If considerations of pork require it, fine. Better spend it on a lander than on a launch vehicle.

Your other points are more appropriate for the reusable lander thread.
Title: Re: Propellant Depots - General Discussion
Post by: nooneofconsequence on 02/05/2010 11:45 pm
My issues with this is that even with TRL-9 they will take it out of critical path as before with other 'improvements'. Because it messes with political justifications for HLV.

We are coming to a crossroads.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/05/2010 11:47 pm
My issues with this is that even with TRL-9 they will take it out of critical path as before with other 'improvements'. Because it messes with political justifications for HLV.

So true. Once they lose the SDLV, it might be different. But I'd be very surprised if we went beyond LEO anytime soon. By the time we do go, cryogenics will be ready.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/08/2010 09:50 pm
This NASA paper describes the current state of the art in cryogenic propellant transfer. It also contains two references to papers describing the Russian noncryogenic system. The paper comes from - where else - Glenn.

Cryogenic Fluid Transfer for Exploration (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080032611_2008032989.pdf)
Title: Re: Propellant Depots - General Discussion
Post by: Patchouli on 02/09/2010 12:50 am
Future Chinese platforms will require loads and loads of power if they plan to emulate the Russian refueling system for lunar missions.

Which means large solar panels or ... APUs! How's that for shuttle-derived goodness? ;)

Ummm ... APUs running for a prolonged period. Maybe fuel cells could do the job.


Solar panels plus battery technology from electric cars like the Tesla Roadster could make APU's completely unnecessary.

If that battery pack can propel a car 244 miles it certainly can run your pump for several hours.

Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/09/2010 12:55 am
I read the other day that hydrazine makes for perfectly decent fuel cells and hydrogen peroxide makes for excellent fuel cells.
Title: Re: Propellant Depots - General Discussion
Post by: kkattula on 02/09/2010 05:20 am
Nitpicks:

TRL-9 for space station re-supply is not the same as TRL-9 for depots supplying large trans-stages and landers. In fact hypergolic transfer for exploration is more like TRL-7.  Cryogenic is 6, hopefully soon to be 7.

http://www.hq.nasa.gov/office/codeq/trl/trl.pdf


Liquid fuel rocket engines can be run for long periods of time. Most wear occurs during startup & shutdown transients. Once they reach steady state, they can generally continue until the propellants run out. (Ablatives excepted).

IIRC, one individual SSME was twice fired for 2017 seconds (34 minutes) at Stennis. 600,000 gallons of liquid hydrogen and 230,000 of liquid oxygen were burned. The limiting factor was the amount of propellant that could be supplied.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/09/2010 07:42 am
You are probably correct on the TRL-7 for noncryogenics. From what I've read in ULA papers I believe that certain aspects of long term cryogenic storage (~year) are still TRL 4. It's somewhere in the papers on the ULA website. It is possible however that this only applies to LEO or LLO and not L1/L2. Such long storage periods would appear to be necessary for Mars exploration and for the use of SEP tugs for propellant.
Title: Re: Propellant Depots - General Discussion
Post by: Hopf on 02/13/2010 06:00 pm
You are probably correct on the TRL-7 for noncryogenics. From what I've read in ULA papers I believe that certain aspects of long term cryogenic storage (~year) are still TRL 4. It's somewhere in the papers on the ULA website. It is possible however that this only applies to LEO or LLO and not L1/L2. Such long storage periods would appear to be necessary for Mars exploration and for the use of SEP tugs for propellant.

With cryo storage and transfer the reason for the low TRL isn't because it is all that hard, it is because it hasn't been demonstrated in large scale.  Science and military satellites already store 100's of pounds of all sorts of cryogens, including liquid helium for multiple years. Now that it appears NASA will have money for technology development the TRL could come up very rapidly.  Something like CRYOTE could be flown in a couple of years and in one flight bring the TRL for cryo transfer up to 7 (System prototyping demonstration in an operational environment).  http://www.ulalaunch.com/docs/publications/CryogenicOrbitalTestbed(CRYOTE)2009.pdf 
A useful scale cryo depot demo could be flown shortly thereafter, providing depot TRL at 8 (Actual system completed and "mission qualified" through test and demonstration in an operational environment). 

Thus, in 3 to 4 years depots could be ready for implementing in an actual beyond Earth orbit architecture.  Just so happens that is also around when a commercial capsule could start flying to ISS.  Combine these and you have a BEO mission early in Obama's second term as shown in this NASA picture!
Title: Re: Propellant Depots - General Discussion
Post by: phred on 02/15/2010 06:15 pm

Quote
Thus, in 3 to 4 years depots could be ready for implementing in an actual beyond Earth orbit architecture.  Just so happens that is also around when a commercial capsule could start flying to ISS.  Combine these and you have a BEO mission early in Obama's second term as shown in this NASA picture!

That picture you attached is an Orion after rendevouz with a Centaur.  This was the proposed configuration for sending the Orion to the Earth/Moon L1 to service an 8 meter far infrared telescope launched by the Ares V.  The Orion and the Centaur/airlock were each to be launched on its own Ares 1.  Thus two Ares 1 launches would have facilitated a BEO flight (without propellant transfer), and still could in Obama's FIRST term, if the money was committed.  Maybe it wouldn't be cheaper, but it could be done.
Title: Re: Propellant Depots - General Discussion
Post by: Hopf on 02/18/2010 02:48 pm
“Thus two Ares 1 launches would have facilitated a BEO flight (without propellant transfer), and still could in Obama's FIRST term, if the money was committed. “

Phred, it is misconceptions like this that have allowed Constellation to survive this long.  A BEO flight prior to 2013…  Any amount of money wouldn’t get Orion/Ares I to ISS by 2013 let alone BEO!

Ares I and Orion have barely passed PDR, which is typically 10% program complete.  So the programs still have 90% of the work to go!  This is why the Augustine commission placed a 2017 date as more realistic for first LEO flight. 

Nobody has started working on a long duration Centaur to support the illustrated mission, or an Ares I payload fairing allowing Ares I to launch Centaur, or on the air-lock mission module.  NASA is only planning on a single launch pad for Ares I, thus there would be a minimum of many months between launches, seriously challenging this kind of mission.

It is time for Constellation supporters to truly understand the program of record, what it has accomplished and where it “is” going.  Continuing to perpetuate myths will not get us to LEO let alone the moon or anywhere else.
Title: Re: Propellant Depots - General Discussion
Post by: spacenut on 02/19/2010 09:01 pm
I think if we are going to do a propellant depot, it should start with hypergolics, then proceed to hydorlox storage, and helium or argon for tugs.  Use a framwork similar to the space station so that a space hotel could be added.  NASA would operate it, but private suppliers would bring the fuel and passengers.  Build another one at L1 or L2, or build it in LEO and use a tug to carry it to L1 or L2.  Use a reusable lander at at L station for moon landings, and use an L2 station to refuel for Mars.  I think this would keep everyone busy, and have goals to reach each stage.  If existing EELV's can do it fine, if not develop heavier lift and phase it in.  The ultimate goal is Mars for now.  We need a 20 year plan we can stick and do it.  Involve as many companies and countries as possible within reason and do it.
Title: Re: Propellant Depots - General Discussion
Post by: Serafeim on 02/19/2010 09:25 pm
Quote
I think if we are going to do a propellant depot, it should start with hypergolics,   

I think that can be done now.hypergoles transfer all day on Iss..
Title: Re: Propellant Depots - General Discussion
Post by: neilh on 04/18/2010 12:12 am
Quote
I want to see exploration and commercial propellant launches as soon as possible.

Propellant launches are not needed until the BEO program is initiated. The BEO program won't be initiated until after ISS is stabilized. Think post 2020.

Therefore, I predict fuel depots will actually get deployed immediately prior to the first BEO mission, some time in early to mid 2020s although preliminary R&D work will be done in the mid 2010s, with finalizing R&D in the late 2010s.

Until the mid 2020s, actually launching a fuel depot that needs any significant number of propellant launches is not necessary, except perhaps for a proof of concept test mission.

Propellant transfer technology is far more mature than a U.S. kero-lox HLV engine and therefore far more R&D dollars shall flow to R&D for that engine than to propellant depot R&D.

Just my prediction, the mileage of your predictions may vary.

(I copied this over to a more appropriate thread. Also, should this thread be moved to a section other than the Orion section?)

You seem to be assuming that a propellant depot would only be used for human BEO missions, but with the development of automated rendezvous (one of the first targets of the FY2011 technology development plan), propellant depots provide multiplier effects to robotic missions as well. After all, the propellant in a depot can be used to fuel an Earth Departure Stage or even a lander, regardless of whether the payload is a human or a robot.

After all, propellant depots offer both human and robotic missions most of the benefits of an HLV (pretty much all except super-large payload fairing). In particular, you're able to design a spacecraft or lander without having to worry as much about mass, allowing you to be much more cost-effective. These benefits can be reaped well before 2020, and also allow the depot technology to be proven on unmanned missions before you use them for human missions.

With propellant depots, it may even be feasible and cost-effective for NASA to launch several finalists for a Lunar/Martian/NEO Centennial Challenge (for ISRU, landers, rovers, etc.) as secondary payloads on an EDS which gets refueled in LEO and/or L1, then deploys those finalists to the extraplanetary body for the "final round" of the Challenge.
Title: Re: Propellant Depots - General Discussion
Post by: Bill White on 04/18/2010 12:50 pm
@ neilh

First let's see if funding for propellant transfer for robotic missions makes it into the FY2011 or FY2012 line item detail. I see lots of arm waving that FY2011 will accomplish "this or that" without such things being in the line item detail.

I do see benefit to such an approach, however my comment was more in response to Martijn, who wanted large scale depots ASAP to create demand for RLV tankers to create ultra low cost Earth-to-LEO lift.

Small scale depots are worth funding but will they create the up-mass demand to support genuine RLVs?

Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/18/2010 12:58 pm
I do see benefit to such an approach, however my comment was more in response to Martijn, who wanted large scale depots ASAP to create demand for RLV tankers to create ultra low cost Earth-to-LEO lift.

Not large scale depots, small refuelable orbital transfer craft. But yes, as soon as possible, life being short and the art being long.

Quote
Small scale depots are worth funding but will they create the up-mass demand to support genuine RLVs?

Depots or their precursors would not create the demand, they would channel it. Exploration would provide the demand. If there's no exploration then depots by themselves won't do you any good. If cheap and reliable access to orbit emerges independently, then the urgency of propellant transfer is diminished, though it would remain valuable.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/18/2010 03:22 pm
{snip}

Small scale depots are worth funding but will they create the up-mass demand to support genuine RLVs?

If you are testing depots by building small ones first make sure that they are useful.  For instance able to send to the Moon a payload for a Pegasus, Taurus II or Falcon 1(e).  This helps generate a market.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 02:49 pm
How much will propellant (hypergolic, say) in LEO cost? I've heard $10,000 per kg. Presumably, that could be considerably lowered for hundreds of tons per year, but even at that high price, I've figured out that a fully chemical hypergolic human Mars architecture (using LMO rendezvous and only MRO-style aerobraking requiring no heat shields for the equipment pre-placed in LMO) would use only 1500 tons of LEO propellent (not counting pre-landed equipment on Mars which is optional if your ascent stage lands pre-fueled), which is "only" $15 billion. Considering that Mars missions typically cost $100 billion or much more, that's pocket change.

Lower it to $4000/kg or $2000/kg, and the same propellant is only $6 billion or $3 billion. But really, even $10,000/kg is plenty to be only a fraction of the Mars mission costs, while lowering a lot of the development risk (because it doesn't require large heatshields or low-boil-off techniques).
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 03:14 pm
I vaguely recall that SEP from a Lagrange point to LMO would take on the order of a year and have a mass ratio of 2:1 including packaging. I can dig up the reference if people are interested. LEO to a Lagrange point is also 2:1 assuming LOX/LH2 and three body trajectories which is current technology for that segment and hypergolic propellant payload. That gives a combined ratio of 4:1 for propellant, and better once you have van Allen crossing tugs. A heatshield on the other hand has to be transported by chemical propulsion. Depending on the delta-v/delta-t trade and the time vs radiation shielding trade it isn't obvious to me which of the approaches would have lower IMLEO. SEP + hypergolics could turn out to be competitive with LOX/LH2 + heatshields. SEP + cryogenics sounds even more promising. Hybrids between propulsive and aerodynamic orbit insertion are also possible and can still avoid problems with hypersonic retropropulsion, but are more difficult to analyse.

Small SEP tugs + hypergolic propellant transfer give you Phobos, Deimos and perhaps Ceres. At a stretch they would give you Mars surface operations (though that would also require ISRU and surface nuclear power). Radiation and prolonged microgravity could still throw a spanner in the works.

It looks as if rocket science suffers from an ailment that also afflicts computer science: novelty vampirism. It's amazing how we haven't even maxed out mature technology for exploration purposes.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 03:24 pm
What is the minimum required for a Mars Transfer Vehicle, not counting main propulsion? 40 tons? Can't you just go in a Sundancer Bigelow module-sized vehicle? That's only 9 tons, plus another 10 tons in supplies. Add in an Orion for a total of 40 tons.

Heck, just pre-orbit the Orion at Mars for more weight savings on the way to Mars.

Anyway, propellant in LEO is really, really cheap compared to almost anything. 1500 tons IMLEO just for propellant sounds like a lot except that it would be just a fraction of the cost of the total mission
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 03:29 pm
What is the minimum required for a Mars Transfer Vehicle, not counting main propulsion? 40 tons? Can't you just go in a Sundancer Bigelow module-sized vehicle? That's only 9 tons, plus another 10 tons in supplies. Add in an Orion for a total of 40 tons.

Unless you want to assume closed-loop life support, it depends a lot on delta-t.

Quote
Anyway, propellant in LEO is really, really cheap compared to almost anything. 1500 tons IMLEO just for propellant sounds like a lot except that it would be just a fraction of the cost of the total mission

Well, the first mission is likely to be the most expensive, since you have to do all hardware development for it. If you do that incrementally with a Flexible Path, you can spread it out over "multiple firsts", which is probably the only way to get things funded.

But once you start using reusable spacecraft and transhabs (and you should do that straight away), launch costs should be the main cost driver, not just a tiny fraction of total costs. If each Mars mission were to cost $100B I'd say it would be outrageous to even try. Even $15B a mission sounds outrageous to me.

With RLVs it might be very different. Its proponents expect an order of magnitude in price reduction or more, which gets us right into Shuttle to ISS territory, even with your all-chemical scenario. Throw in SEP for the propellant and it could be even more affordable - even without cryogenic propellant transfer or massive heatshields. And the good thing is that hypergolic propellant transfer + exploration is good enough to get RLVs started.

Reducing launch costs looks like something that might have a much bigger impact than high tech improvements in in-space propulsion.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 04/26/2010 04:02 pm
What is the minimum required for a Mars Transfer Vehicle, not counting main propulsion? 40 tons? Can't you just go in a Sundancer Bigelow module-sized vehicle? That's only 9 tons, plus another 10 tons in supplies. Add in an Orion for a total of 40 tons.

Orion is 10.6mT (inc crew).

cheers, Martin

(http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=20190.0;attach=194149)
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 04:08 pm
Dual use food is also an interesting option if you want to do propulsive orbit insertion. If you produce methane from human waste products you could use that for orbit insertion. There are all kinds of inappropriate analogies for that which I will not go into...
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 04:19 pm
What is the minimum required for a Mars Transfer Vehicle, not counting main propulsion? 40 tons? Can't you just go in a Sundancer Bigelow module-sized vehicle? That's only 9 tons, plus another 10 tons in supplies. Add in an Orion for a total of 40 tons.

Unless you want to assume closed-loop life support, it depends a lot on delta-t.

Quote
Anyway, propellant in LEO is really, really cheap compared to almost anything. 1500 tons IMLEO just for propellant sounds like a lot except that it would be just a fraction of the cost of the total mission

Well, the first mission is likely to be the most expensive, since you have to do all hardware development for it. If you do that incrementally with a Flexible Path, you can spread it out over "multiple firsts", which is probably the only way to get things funded.

But once you start using reusable spacecraft and transhabs (and you should do that straight away), launch costs should be the main cost driver, not just a tiny fraction of total costs. If each Mars mission were to cost $100B I'd say it would be outrageous to even try. Even $15B a mission sounds outrageous to me.

With RLVs it might be very different. Its proponents expect an order of magnitude in price reduction or more, which gets us right into Shuttle to ISS territory, even with your all-chemical scenario. Throw in SEP for the propellant and it could be even more affordable - even without cryogenic propellant transfer or massive heatshields. And the good thing is that hypergolic propellant transfer + exploration is good enough to get RLVs started.

Reducing launch costs looks like something that might have a much bigger impact than high tech improvements in in-space propulsion.
I've been doing some back-of-the-envelope architectures, and have got about $60 billion for a Mars mission using this hypergolic approach. Half the money is for development and a quarter is for propellant and a quarter for fabricating the spacecraft hardware (including surface instruments and equipment which is pre-landed just using MSL skycrane techniques and EELV Heavies), assuming an average $100,000-per-dry-kg for fabricating landers, hypergolic stages, etc. The recurring mission costs assuming no new development would be about $30 billion. Martian ISRU for the ascent propellant, high-ISP tugs, a hydrolox LEO propellant depot, cryogenic storage, aerocapture, etc would all reduce mission hardware mass, both propellant and fabrication costs (significant cost is needed to fabricate all the hypergolic stages, though the idea of using just cheap propellant tanks versus full stages is interesting).

Pre-orbit the return capsule (or use a more spartan return capsule than the full Orion spacecraft) and your costs reduce pretty far, too. Reduce the crew from 4 to 3 would decrease costs. I assumed 10 tons of supplies, using only water recycling (already to be used on Orion), and even that is unnecessary since 4 crew consume less than 8 tons of water, oxygen, and food every year (and some would be pre-landed on Mars and some could perhaps be pre-orbited in LMO, at least in case of failure of water recycling equipment). With full water recycling, consumables is only about 2 tons annually for 4 crew (of course, some mass must be used for packaging and/or preparing the food and for hygiene, etc).

As for solar particle events, the full hypergolic stages could be used for shielding, at least for the trip to Mars.

If you have a low delta-t for the crewed MTV, mass of the MTV is at a huge premium and Orion is probably too massive to be very practical to lug both ways with the crew, although that's what I assumed (makes sense to me to pre-orbit it around Mars).

Also, I assumed 20 tons for Orion because that includes full prop tanks, though 10 tons is a lot of propellant to lug around... You're right. Best leave it at a 10 ton Orion. That makes it much lighter.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 04:44 pm
For the sake of reducing mass further, how about rendezvous the MTV in high Mars orbit with your return stage and capsule, just inside of Mars' escape velocity? This way, you could board a pre-placed Mars inter-orbit craft that can take you from high Mars orbit to Phobos and back (or from HMO to LMO where you can rendezvous with your lander). An Orion spacecraft (without parachutes and heatshield, saving you at least a couple tons) should be just about perfect for this role. You may even be able to do a little aerobraking, but that'd be optional (and perhaps undesireable).

The extra propellant saved by rendezvous in high Mars orbit could be used to lower the delta-t for the outbound and inbound trips.

So, propellant depots in LEO and HMO (perhaps just pre-depots, just big tanks).

EDIT: I'm sure you could save even more by actually starting your MTV at EML1/2 where you transfer from an Orion spacecraft (and don't bring that Orion with, just use the MTV and the return capsule is already pre-placed in high Mars orbit).
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 04:58 pm
So, your MTV only needs about 1.8km/s outbound for a slow trip (EML1/2 to Earth C3 is .14km/s, Earth C3 to Mars Transfer Orbit is .6, MTO to Mars C3 is .9, Mars C3 to some HMO is, say, another .16 km/s), and any more delta-v can be used for speeding it along faster (though for the trip to Mars, you have to brake any extra delta-v you add). 20 tons for an MTV, not counting main propulsion?

The trip back would have more mass (the 10 ton return capsule for a total of about 30 tons), but doesn't need braking. Only 1.16km/s would be needed for a slow return trip, and more delta-v can be added to reduce transit time (this time, braking propulsion wouldn't be needed).
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 05:00 pm
For the sake of reducing mass further, how about rendezvous the MTV in high Mars orbit with your return stage and capsule, just inside of Mars' escape velocity?

I agree, perhaps even a Mars Lagrange point, although you have to do the delta-v vs delta-t trade again in the light of as yet unknown radiation risks. The MTV does not need to brake into LMO and the lander might be better off by refueling in HMO with relatively cheap propellant than by bringing the LMO insertion fuel along itself. It would definitely want to refuel for the descent propellant. Similarly, on the return trip the MTV should return to L1/L2, not LEO. There is a choice between bringing an Earth entry vehicle along, or depending on another L1/L2 rendez-vous with a return capsule.

The precise details of the transport infrastructure matter a lot. Especially with hypergolics and heavy payloads you pretty much have to use moon Lagrange points. This allows you to use LOX/LH2 almost to Earth escape. An Earth swingby and perhaps a moon swingby as well makes a lot of difference. Every staging point is also a potential refueling point (with SEP-transported propellant!) which is extra important for hypergolics in order to keep effective Isp up. This argues for having as many staging points as practical.

Ideally I would like to see NASA buy storable propellant in LEO, at EML1/2, SEL1/2, in HMO and in LMO (also GEO and LLO in early phases) and buy transportation services between those orbital locations. I expect this would lead to privately developed van Allen crossing SEP tugs, cryogenic depots and refuelable upper stages and EELV Phase 1, perhaps even 2.

I'm working on the delta-v vs delta-t calculations for Mars and next to the delta-t constraints by radiation the plane changes are my biggest uncertainty.

EDIT: heheh, parallel edits...
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 05:02 pm
How much delta-v is needed to reduce the trip time to a certain amount, assuming high-thrust and Oberth effect?

Is adding 2 km/s outbound (plus another 2 km/s for braking and 2km/s back to Earth, maybe a little more because of reduced Oberth effect at Mars) sufficient for reducing trip time to a reasonable level?
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 05:07 pm
...
I'm working on the delta-v vs delta-t calculations for Mars and next to the delta-t constraints by radiation the plane changes are my biggest uncertainty.

EDIT: heheh, parallel edits...
Plane changes are pretty expensive without a swing-by. With a Moon swing-by, it's probably not bad at all.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 05:17 pm
How much delta-v is needed to reduce the trip time to a certain amount, assuming high-thrust and Oberth effect?

That's what I've been trying to figure out. You can get quite spectacular heliocentric delta-v's from a 1-2 km/s powered Earth swingby. No doubt it works nicely on the other end as well, but my spreadsheet doesn't do that yet. Hop_David has a spreadsheet that does however, but it may only do coplanar Hohmann transfers. And we'd still need to translate that to delta-t. I have some rough code to calculate delta-t vs delta-v for the Earth moon system which I intend to upgrade, but that only works with precisely prograde coplanar burns, which is probably too restrictive.

I haven't looked into the plane changes enough to make a reasonable estimate. The difference in inclination is small enough (would lead to ~500m/s delta-v IIRC), but it's the RAAN I know nothing about just yet. I have a link to a table of perturbed orbital elements for the planets somewhere, but I haven't got round to it yet.

I'm working out the bugs in my derivation of a Lambert solver as I think that's what we'd really need. I dislike implementing stuff that I don't fully understand, which why I'm doing a lot of paper and pencil stuff first, but I solemny resolve here and now to actually implement some of this stuff before I have read Apollonius in the original Greek. :-)
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 04/26/2010 05:32 pm
Also, I assumed 20 tons for Orion because that includes full prop tanks, though 10 tons is a lot of propellant to lug around... You're right. Best leave it at a 10 ton Orion. That makes it much lighter.

AIUI, the CEV is carried passively until it undocks from the MTV and performs Earth re-entry. Therefore, the SM is discarded before CEV docks with the MTV.

Alternatively, if you can get the mass of capsule + crew + return samples + SM down to ~3mT, then 7.6mT of hypergolic propellant can brake you sufficiently to perform a LEO-equivalent reenty. AFAICT Soyuz + SM masses quite a bit more than that, and carries only 1/4 of that propellant. Plus crew & returned samples, of course.



This is pretty much the role that Orion was designed to perform. It shouldn't be a surprise that NASA occaisionally gets their sums right on something like this.

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 05:38 pm
Also, I assumed 20 tons for Orion because that includes full prop tanks, though 10 tons is a lot of propellant to lug around... You're right. Best leave it at a 10 ton Orion. That makes it much lighter.

AIUI, the CEV is carried passively until it undocks from the MTV and performs Earth re-entry. Therefore, the SM is discarded before CEV docks with the MTV.

Alternatively, if you can get the mass of capsule + crew + return samples + SM down to ~3mT, then 7.6mT of hypergolic propellant can brake you sufficiently to perform a LEO-equivalent reenty. AFAICT Soyuz + SM masses quite a bit more than that, and carries only 1/4 of that propellant. Plus crew & returned samples, of course.



This is pretty much the role that Orion was designed to perform. It shouldn't be a surprise that NASA occaisionally gets their sums right on something like this.

cheers, Martin
10 tons isn't a lot, but it is more than a Sundancer module. Orion is also useful for other things, like going to EML1/2. IF you leave the MTV in a high Mars orbit, Orion (sans heat shield and parachutes) would also work well zipping around the orbits of Mars, to Phobos and Deimos, to a lander in LMO and back, etc.

If ONLY being used for reentry, even a lunar or interplanetary reentry, then anything much more than 1 ton per astronaut is more than is strictly necessary. If you have, say, 7 astros returning from Mars, then Orion is in the sweet spot. Or, four astros and hundreds of kilograms of samples... It's not too bad, all considered. You go to war with the army you have.
Title: Re: Propellant Depots - General Discussion
Post by: Jorge on 04/26/2010 05:56 pm
Also, I assumed 20 tons for Orion because that includes full prop tanks, though 10 tons is a lot of propellant to lug around... You're right. Best leave it at a 10 ton Orion. That makes it much lighter.

AIUI, the CEV is carried passively until it undocks from the MTV and performs Earth re-entry. Therefore, the SM is discarded before CEV docks with the MTV.

That has never been the plan. SM stays on the CM until after MTV undocking, both to protect the TPS and to provide maneuvering capability post-undocking. The plan you describe would require the MTV to be on a entry trajectory prior to CM undocking, then the MTV would have to maneuver to avoid re-entry.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 06:02 pm
So, the MTV ends up in a solar orbit, right? Is it possible to send a tug out to recover it?
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 06:07 pm
Why not have it brake into L1/L2/SEL-2 propulsively? One more powered swingby.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 06:15 pm
Why not have it brake into L1/L2/SEL-2 propulsively? One more powered swingby.
Because it severely impacts the whole architecture, especially with a high incoming velocity. If you just have it dock with a tug (SEP or otherwise) soon after or just before the crew leave in the Orion, then it need not impact the design of the MTV other than having systems which can survive long enough without people. It could be a separate project bid out to commercial tug operators.

EDIT: Also, the tug need not be finished until after the astronauts are already on their way to Mars.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 06:26 pm
Because it severely impacts the whole architecture, especially with a high incoming velocity.

Well, it would be a powered swingby to a very high orbit with propellant that was prepositioned in HMO by SEP, or maybe even with Mars ISRU propellant so that may not be prohibitive. It would even relax the requirements on the capsule heatshields, though you would probably not want to depend on that. Hang on, isn't that an argument you've made yourself?

This is like the scenario advocated by Huntress and Farquhar, though with aerobraking in their case.

Quote
If you just have it dock with a tug (SEP or otherwise) soon after or just before the crew leave in the Orion, then it need not impact the design of the MTV other than having systems which can survive long enough without people. It could be a separate project bid out to commercial tug operators.

I suppose you could send a tug after it (have it loiter at a Lagrange point and sweep in to rendez-vous with the MTV) and that might not be a bad idea. The timing would be critical though and perigee is the best place for any burn, so you'd get only one chance after which recovery would become a lot more expensive. Of course, under this scenario the propellant would only have to come from a Lagrange point, not HMO, so that could be an advantage.

I'd lean towards having a capsule + lander + MTV complex return to a Lagrange point in nominal cases, propelled by the lander. In an emergency you could ditch the lander + MTV and reenter directly with the capsule and at hyperbolic velocity.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 06:42 pm
I would definitely leave the lander in LMO. Otherwise, you have to bring it through 3km/s Plus whatever extra velocity you use to shorten delta-t for the crew plus at least another 3km/s just to put it back in LMO for the next time. You're likely looking at at least 10km/s for that piece of hardware (although not all at the same time, which makes things far, far easier). If you leave it in LMO, you can use it for the next mission or for backup.

EDIT:And even if you brought it back to EML1/2, it's still at a Lagrange point and we only have infrastructure in LEO (besides, the radiation picture is probably actually worse at EML2 than at LMO). If you're reusing the lander but have to refurbish it extensively before reuse, it may well be cheaper just to launch a new one. Otherwise, you could refurbish it at LMO, possibly. Reuse without refurbish is doubly good because you don't have to haul it anywhere and you don't need to fund a refurbish mission.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 07:01 pm
OK, that's another option. I was originally thinking of a journey like this:

ground -> ISS on a commercial crew taxi
ISS to L1/L2 by Orion + EELV upper stage
L1/L2 to SEL-2 by lander + Orion
SEL-2 -> SML-1 by lander + Orion + MTV
SML-1 -> LMO/Phobos by lander (+Orion?)
LMO -> surface of Mars in just the lander

On the way back you'd do that roughly in reverse, only you wouldn't return the Orion to LEO but to the Earth itself.

NSF poster vanilla pointed out that the scheduling flexibility of L1/L2 would probably be better than an extra stop at SEL-2. In that case you wouldn't have a two week journey from L1/L2 to SEL-2 which is what I wanted the lander for. Two weeks in a capsule in a nominal case seemed a bit much. If you skip SEL-2, you would still need a stage for the TMI, and I thought it would be useful to have the lander double as that stage. But you could also use something like the crasher stage we were discussing in another thread. Leaving the lander in LMO would be more mass-efficient, bringing it along could be safer, although it may not give you all that much more safety.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 07:12 pm
EDIT:And even if you brought it back to EML1/2, it's still at a Lagrange point and we only have infrastructure in LEO (besides, the radiation picture is probably actually worse at EML2 than at LMO). If you're reusing the lander but have to refurbish it extensively before reuse, it may well be cheaper just to launch a new one. Otherwise, you could refurbish it at LMO, possibly. Reuse without refurbish is doubly good because you don't have to haul it anywhere and you don't need to fund a refurbish mission.

Well, the MTV had better be good enough to spend a long time in plus it would only be man-tended once back at a Lagrange point. But I'm not looking at saving costs, I expect that to be a wash, at least as long as launch costs are still high. I'd be looking to transform the nature of the cost structure.

I'd like to go from

fixed costs1 + IMLEO1 * cost/kg + expendable hardware

to

fixed costs2 + IMLEO2 * cost/kg

As long as total costs were similar I'd choose the reusable variant as it seems more likely to get into a virtuous cycle of ever more propellant launches and ever lower launch costs. I believe that's a strategically important consideration. Of course as launch costs go down, the case for reuse actually strengthens. If for whatever reason we couldn't have that, an expendable design could also be fine, but I'd rather not give up on it easily.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 07:41 pm
To be honest, I don't see what the Sun-Earth Lagrange points get you from a HSF perspective. The Earth-Moon ones are just about as good, far easier to get to, and far closer to Earth in case Something Bad Happens, besides fitting in almost perfectly with Moon missions.

Sun-Mars Lagrange points might be different, I don't know.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 07:49 pm
According to Farquhar it saves you more delta-v (MTV only has to move between SEL-2 and SML-1, perigee lowering burn is cheaper, moon flyby is supposedly easier), but I suspect vanilla's argument is more important.

For prepositioning propellant the Earth and Mars Lagrange points could still be relevant. As long as we don't have van Allen crossing tugs you'd have to do the first leg by chemical propulsion and in that case moon and Earth Lagrange points are equally expensive, but the Earth Lagrange points are "closer to Mars" and basing your tugs there could be cheaper. But all that would be unmanned. Apart from a "first" and the occasional servicing mission there probably isn't much point in frequent manned missions to the Earth Lagrange points, unless Farquhar's argument turns out to be weightier than vanilla's.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 07:56 pm
If only, if only, there's water (or oil) on Phobos/Deimos...
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/26/2010 08:10 pm
Isn't the presence of CHON on Phobos and Deimos a given? It might not be, but that's what I vaguely recall. But it could be a while before we were able to extract those. Brute force oxygen from regolith with nuclear power might be a good first step.

And Ceres is a colossal reservoir of water. Imagine bringing propellant from the edge of the inner solar system back inwards to Phobos... That of course lies far in the future.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 08:21 pm
Isn't the presence of CHON on Phobos and Deimos a given? It might not be, but that's what I vaguely recall. But it could be a while before we were able to extract those. Brute force oxygen from regolith with nuclear power might be a good first step.

And Ceres is a colossal reservoir of water. Imagine bringing propellant from the edge of the inner solar system back inwards to Phobos... That of course lies far in the future.
Off-topic a little bit, but man, I can't wait until Dawn gets to Ceres! There could be practically anything there... ANYTHING! And probably with an ocean to explore far closer than Jupiter or Saturn (and without the radiation of Jupiter), I'm quite excited!

We need a standardized SEP bus for sending prop depots and landers to (and from!) places like these. That would be a good "game-changing" technology.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 04/26/2010 08:56 pm
AIUI, the CEV is carried passively until it undocks from the MTV and performs Earth re-entry. Therefore, the SM is discarded before CEV docks with the MTV.

That has never been the plan. SM stays on the CM until after MTV undocking, both to protect the TPS and to provide maneuvering capability post-undocking. The plan you describe would require the MTV to be on a entry trajectory prior to CM undocking, then the MTV would have to maneuver to avoid re-entry.

I went back and checked DRA 5.0 again, and you're quite right.

I've found the source of my confusion:-

Quote
It was not within the scope of the DRA 5.0 activity to recommend specific design upgrades for the Orion vehicle or to develop an upgrade strategy. Instead, a mass estimate of 10 t was used for the vehicle CM to size propulsion stages. An additional 4 t was book-kept for a service module that may be needed to perform an Earth-targeting burn.
(My highlight of the "may be" text that I'd ignored).

Note that the MTV mass budget only accounts for the Orion (10.6mT incl crew) - there is no accommodation for the SM. I had assumed that the internal CEV propulsion performed re-entry positioning, but not if 300m/s is required !

And yes, I had wondered how the heatshield would be protected during the transits & Mars orbit.

(http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=20190.0;attach=194149)

http://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf (http://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf)
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090012109_2009010520.pdf (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090012109_2009010520.pdf)

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 09:02 pm
...
I haven't looked into the plane changes enough to make a reasonable estimate. The difference in inclination is small enough (would lead to ~500m/s delta-v IIRC), but it's the RAAN I know nothing about just yet. I have a link to a table of perturbed orbital elements for the planets somewhere, but I haven't got round to it yet.
...

BTW, the Dawn mission used a Mars flyby for the necessary plane change to visit Vesta:
http://dawn.jpl.nasa.gov/mission/popups/faq_qa_M4.asp
http://dawn.jpl.nasa.gov/mission/faqs.asp
It saved about 2.3km/s for the plane change, 2.6km/s total assist.

Would Phobos and Deimos be any use at all for gravity assists or the Oberth effect?
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/26/2010 11:31 pm
Why not have it brake into L1/L2/SEL-2 propulsively?

My personal thoughts are for a SEP or NEP powered mission departing from and returning to EML-2, under power all the way, both ways. By the time the MTV approaches EML-2 on the return trip, propulsively breaking most of the way in, enough delta-V will have been shed to make capture no more dramatic than a docking event at ISS.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 04/26/2010 11:44 pm
Why not have it brake into L1/L2/SEL-2 propulsively?

My personal thoughts are for a SEP or NEP powered mission departing from and returning to EML-2, under power all the way, both ways. By the time the MTV approaches EML-2 on the return trip, propulsively breaking most of the way in, enough delta-V will have been shed to make capture no more dramatic than a docking event at ISS.
However, that increases the time the crew spends on the way back versus just accelerating and having the crew leave in a capsule and the MTV enter a solar orbit.

However, with SEP, delta-v is pretty cheap, and this sort of thing can be afforded (especially since now you are close to the Sun and have twice as much power available as when you are at Mars).

I would really like more work on electric propulsion and solar power, as well (seems to me that nuclear power can't beat it in the inner solar system, since a solar array could eventually be made as thin as a solar sail, while solar power also has a definite edge when it comes to near-term solutions in the inner solar system). The specific power of the ion engine and power conditioning equipment becomes quite important, as well (the DS-1's total system not counting the Xenon tanks and solar arrays had a specific power of about 71W/kg... Xenon tanks had an impressively low mass that was less than 10% the mass of the Xenon propellant stored... the power conditioning system weighed more than the engine itself).
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 04/27/2010 01:51 am
I suspect that Van Allen crossing SEP counts as a new (low TRL) technology.  Fortunately it is scalable.  If the mini SEP tug masses less than 1 mT it can be launched on a Falcon 1e (or rival) for $10.9 million.  If the full size SEP needs an EELV at $200 million then:

Launch costs for 3 test missions and the real launch are 3 * $10.9M + $200M
= $232.7 million
Development costs and part will be extra.

The tug could use a VASIMR or hall effect thruster.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 04/27/2010 12:13 pm
I would not either advocate NEP or SEP crew between LEO and EML-2 - too slow.
Crew would need to be Rapid Transit.
But all the supplies, indeed even the MTV, could be prositioned at EML-2 via electric propulsion once the propellant tanks were filled at the depot.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 04/30/2010 02:38 pm
Continuing in a more appropriate thread (I think):

That does not apply to propellant supply flights and you know it

It does apply.  A rendezvous and a transfer is a rendezvous and a transfer, no matter what the cargo.

If you lose a propellant flight it's not a big deal. If you lose a crew or a big and expensive EDS or a lander, it is. The 1-(1-p)^n argument only applies if no individual flight is allowed to fail, but propellants flights are expendable. With Constellation, DIRECT or an EELV-based architecture n=3, for Apollo n=2 and if they had gone with direct ascent with a Nova überbooster they would have had n=1.

Note that n>=4 if you used libs0n's idea of using single stick EELV-class launchers without propellant transfer. Still an interesting reference point and libs0n wasn't arguing against propellant transfer, just detailing what could be done without it.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 05/01/2010 06:21 pm
Has there been any analysis of crew-tended depots?  I ask because of the concern about the low level of confidence in uncrewed rendezvous and docking operations.

Consider an architecture where a crew is launched to the depot, inhabits a small (maybe Harmony-sized) node, and awaits the arrival of propellant transfer vehicles from any number of suppliers -- as many as can get their vehicle to the depot during the crew's window of availability.  In a two-week stay, a crew could oversee half a dozen dockings, transfers and undockings.

I'm imagining the habitable node's power needs could be supported by small solar arrays and large battery arrays, since it might be inhabited only 10% of the time.

Of course similarly "tended" operations could be used for on-orbit exploration vehicle assembly too....
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/01/2010 06:50 pm
One consideration that has been mentioned is explosion risk. How easy it would be to shield against that? Wouldn't the shrapnel be launched at low velocities compared to orbital velocities? If so it might help to enclose a depot in an unpressurised inflatable shelter capable of absorbing most of the shrapnel.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 05/01/2010 11:11 pm
One consideration that has been mentioned is explosion risk. How easy it would be to shield against that? Wouldn't the shrapnel be launched at low velocities compared to orbital velocities? If so it might help to enclose a depot in an unpressurised inflatable shelter capable of absorbing most of the shrapnel.

If the depot is connected to the control cabin by a tether then most of the shielding could be an armoured disk on the tether.

The operators could pilot the docking tug, possibly by remote control.  I assume that the same tug can be used for both propellant deliveries and customer rockets.
Title: Re: Propellant Depots - General Discussion
Post by: pathfinder_01 on 05/01/2010 11:17 pm
Has there been any analysis of crew-tended depots?  I ask because of the concern about the low level of confidence in uncrewed rendezvous and docking operations.

Consider an architecture where a crew is launched to the depot, inhabits a small (maybe Harmony-sized) node, and awaits the arrival of propellant transfer vehicles from any number of suppliers -- as many as can get their vehicle to the depot during the crew's window of availability.  In a two-week stay, a crew could oversee half a dozen dockings, transfers and undockings.

I'm imagining the habitable node's power needs could be supported by small solar arrays and large battery arrays, since it might be inhabited only 10% of the time.

Of course similarly "tended" operations could be used for on-orbit exploration vehicle assembly too....


I think one of the useful prerequisites to propellant depots will be automated docking. Having crew will increase expenses and expose him to the danger of both explosion and leak. It might be fine for an exploration craft to dock, but having someone on hand constantly could be a problem.  Having automated ones means you could set up a depot anywhere in the solar system and still have it be useful. Needing it manned limits you to LEO for the for seeable future.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 05/02/2010 08:25 pm
I think one of the useful prerequisites to propellant depots will be automated docking.

I think one of the prerequisites to useful propellant depots will be automated docking.  Is that what you meant?

A "useful propellant depot" in that sense is one which makes missions headed beyond LEO cost less than similar mission designs using heavy-lift or rendezvous (no prop transfer) architectures.

You are right that crew-tended operation would increase costs and create the possibility of missions failing with loss of crew.  What then are the advantages?

First, the "technology readiness level" of automated docking and propellant transfer is low.  (Is "Orbital Express" the only mission where this has been demonstrated?)  Somehow this capability needs to be demonstrated on a larger scale if an automated depot architecture is to gain much traction.  I would love to see a robotic mission "top off" its cryogenic upper stage in LEO before e.g. heading off to land on the Moon.  ULA would dearly love to demonstrate that, too! (http://www.ulalaunch.com/docs/publications/SettledCryogenicPropellantTransfer.pdf)

But here's the thing:  for whatever reason there's funding for crewed missions even when there isn't funding available for robotic missions.  I'm suggesting using NASA human spaceflight funding to support "flexible path" crewed missions to propellant depots.

Quote
Needing it manned limits you to LEO for the for seeable future.

Why do you feel a crewed mission to a depot at an Earth-Moon Lagrange point is beyond the foreseeable future?  I think a crew could get there and back with a dual-EELV launch architecture.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/02/2010 08:28 pm
First, the "technology readiness level" of automated docking and propellant transfer is low.  (Is "Orbital Express" the only mission where this has been demonstrated?)

Actually, it is very high! The Soviets/Russians have been doing it ever since 1978. ESA uses the same technology for ATV, licensed from the Russians.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 05/02/2010 08:40 pm
First, the "technology readiness level" of automated docking and propellant transfer is low.  (Is "Orbital Express" the only mission where this has been demonstrated?)

Actually, it is very high! The Soviets/Russians have been doing it ever since 1978. ESA uses the same technology for ATV, licensed from the Russians.

Yes and no.  For almost every automated docking with Salyut, Mir, or ISS hasn't there has been a crewmember aboard the station overseeing the operation, with the ability to waive off or take control of the approaching vehicle?  That's a crew-tended docking even if it proceeds under fully automated control.  Also, have propellant transfers from Progress to station taken place without human supervision?
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/02/2010 08:55 pm
Yes and no.  For almost every automated docking with Salyut, Mir, or ISS hasn't there has been a crewmember aboard the station overseeing the operation, with the ability to waive off or take control of the approaching vehicle?  That's a crew-tended docking even if it proceeds under fully automated control.

I think so, but it is still fully automated.

Quote
  Also, have propellant transfers from Progress to station taken place without human supervision?

Don't know about Progress, but certainly from ATV and since that uses Russian technology the answer is probably yes for Progress too.

BTW: Orbital Express wasn't fully automated. It required active intervention from the ground, not just wave off.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/02/2010 09:05 pm
A "useful propellant depot" in that sense is one which makes missions headed beyond LEO cost less than similar mission designs using heavy-lift or rendezvous (no prop transfer) architectures.

That's one way depots could be useful. Another way, one that I find much more interesting, is by stimulating development of commercial launch vehicles that can take small payloads (people, propellant, supplies) to LEO an order of magnitude more cheaply than current commercial launch prices. Rand Simberg and Jon Goff among others have been making this argument for a long time and in my opinion it is the decisive argument in favour of choosing to base exploration on propellant transfer. The money would come from funding intended for beyond LEO while stimulating activity in LEO as a free side effect. For a recent explanation see Jon's site, www.selenianboondocks.com (http://www.selenianboondocks.com).

One moon mission a year (or even precursor missions in cis- and translunar space and to NEO's) would be enough to support a thriving industry. And the good news is that we already have all the technology we need for that!

Quote
You are right that crew-tended operation would increase costs and create the possibility of missions failing with loss of crew.  What then are the advantages?

If the depot is co-orbital with the ISS or some future LEO station it needn't increase costs much, assuming the station's primary purpose was something else.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 05/02/2010 09:48 pm
Quote
Needing it manned limits you to LEO for the for seeable future.

Why do you feel a crewed mission to a depot at an Earth-Moon Lagrange point is beyond the foreseeable future?  I think a crew could get there and back with a dual-EELV launch architecture.

I suspect the problem is that we do not send the man/operator to the Lagrange depot until the depot is full.  Filling the unmanned depot needs automated docking.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 05/03/2010 12:27 am
Quote
Needing it manned limits you to LEO for the for seeable future.

Why do you feel a crewed mission to a depot at an Earth-Moon Lagrange point is beyond the foreseeable future?  I think a crew could get there and back with a dual-EELV launch architecture.

I suspect the problem is that we do not send the man/operator to the Lagrange depot until the depot is full.  Filling the unmanned depot needs automated docking.

With hypergolic propellants, filling the depot could have been accomplished by a prior crew.  That prior crew only got as far as the depot, oversaw the dockings and propellant transfers, and then went home.  A subsequent crew, launched months later, can then reach the depot and transfer propellant to their exploration vehicle.  (That vehicle might be a lander, or the service module of their own spacecraft, or a departure stage that had been dry-launched.)

Those early crewed missions that "only" get to the EML depot and back look expensive, but if they use a similar spacecraft (i.e. Orion) they also serve to increase our confidence in that vehicle before we send one on a mission beyond cis-lunar space.  An obvious improvement to the system would be the automated depot replenishment you are suggesting.  I'm all in favor of that, once the depot exists!
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 05/03/2010 01:09 am
A "useful propellant depot" in that sense is one which makes missions headed beyond LEO cost less than similar mission designs using heavy-lift or rendezvous (no prop transfer) architectures.

That's one way depots could be useful. Another way, one that I find much more interesting, is by stimulating development of commercial launch vehicles that can take small payloads (people, propellant, supplies) to LEO an order of magnitude more cheaply than current commercial launch prices.

Good point, and it's a point that's easy to forget!  It only supports LEO depots though, right?  Because there's no nascent industry of entrepreneurs with systems capable of taking propellant to an EML depot?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 05/03/2010 01:15 am
Quote
Needing it manned limits you to LEO for the for seeable future.

Why do you feel a crewed mission to a depot at an Earth-Moon Lagrange point is beyond the foreseeable future?  I think a crew could get there and back with a dual-EELV launch architecture.

I suspect the problem is that we do not send the man/operator to the Lagrange depot until the depot is full.  Filling the unmanned depot needs automated docking.

With hypergolic propellants, filling the depot could have been accomplished by a prior crew.  That prior crew only got as far as the depot, oversaw the dockings and propellant transfers, and then went home.  A subsequent crew, launched months later, can then reach the depot and transfer propellant to their exploration vehicle.  (That vehicle might be a lander, or the service module of their own spacecraft, or a departure stage that had been dry-launched.)

Those early crewed missions that "only" get to the EML depot and back look expensive, but if they use a similar spacecraft (i.e. Orion) they also serve to increase our confidence in that vehicle before we send one on a mission beyond cis-lunar space.  An obvious improvement to the system would be the automated depot replenishment you are suggesting.  I'm all in favor of that, once the depot exists!

You are using recursion.  I am not certain that works in space flight.

An alternative way of building the EML depot is to assemble and fill it in LEO under human control.  Then use a SEP tug to fly it to EML. 

Hopefully there will be a SEP tug around in 5 or 6 years time.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 05/03/2010 02:15 am
A "useful propellant depot" in that sense is one which makes missions headed beyond LEO cost less than similar mission designs using heavy-lift or rendezvous (no prop transfer) architectures.

That's one way depots could be useful. Another way, one that I find much more interesting, is by stimulating development of commercial launch vehicles that can take small payloads (people, propellant, supplies) to LEO an order of magnitude more cheaply than current commercial launch prices.

Good point, and it's a point that's easy to forget!  It only supports LEO depots though, right?  Because there's no nascent industry of entrepreneurs with systems capable of taking propellant to an EML depot?
I see no reason why commercial folks couldn't do such a thing today. Maybe not deep space depots, yet, but EML1 should be fine. The really small folks could fill up a depot in LEO which later gets sent to EML1/2 on a slow ballistic or chaotic trajectory (or via SEP), as well. Actually, I think Orbital possesses all the skill necessary to build a SEP tug, since they have experience with integrating SEP systems to their satellite bus (see: Dawn spacecraft) and also have, or will soon have, experience with unmanned rendezvous and docking (Cygnus). Ion thrusters are commercially available and deployed. The only big issue I see would be high-power thrusters (~50kW, about ten times larger than commercial ones, though those could be clustered), larger arrays than commonly deployed (50kW minimum, more like 100kW or more), and thruster life. Many of these problems could possibly be solved soon by Ad Astra and their VASIMR, but they aren't the only ones. Others besides Orbital could probably do it, as well.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/03/2010 03:32 am
Those early crewed missions that "only" get to the EML depot and back look expensive, but if they use a similar spacecraft (i.e. Orion) they also serve to increase our confidence in that vehicle before we send one on a mission beyond cis-lunar space.  An obvious improvement to the system would be the automated depot replenishment you are suggesting.  I'm all in favor of that, once the depot exists!

That would indeed be rather expensive. If you were in a hurry to do this, you might want to do it Orbital Express style instead, controlled from the ground. L1/L2 is only a light second or so away, and depending on the time of day (night) you could even have direct line of sight communications with the spacecraft.

Another consideration is to have a lander precursor be the depot, saving the cost of a separate vehicle (though increasing the cost of the lander). As long as we are talking precursor missions, it wouldn't even need a separate EDS to get to MEO and back. Once there, storable propulsion wouldn't be so inefficient anymore. And of course you could also use both a Centaur or a Delta upper stage and storable propulsion to get to MEO.

But I prefer initial missions even closer to home. Unmanned round trips of a refuelable capsule precursor and/or a lander precursor that also serves as a makeshift depot between the ISS and the lower van Allen belt to do experiments into the effectiveness of radiation shielding. Having it act as a general purpose man-tended free flyer would be another option.

Or manned servicing missions between ISS and Hubble, especially if Hubble were moved closer to ISS orbit. The moving itself could be done with such a lander, or more efficiently with a SEP tug, although you would have to cough up the necessary funds early.

These early missions could help you get the bugs out of automated rendez-vous, docking, and propellant transfer. Once that was done, we'd be ready for manned missions in supersynchronous space.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/03/2010 03:39 am
Good point, and it's a point that's easy to forget!  It only supports LEO depots though, right?

You could still buy transport services between a LEO depot and an L1/L2 depot. EELVs could provide that service efficiently. Not as efficiently as the eventual systems with TLI propellant supplied by RLV, but unlike those they would be available straight away.

Quote
Because there's no nascent industry of entrepreneurs with systems capable of taking propellant to an EML depot?

I imagine development costs would be correspondingly higher. And high development costs look like the major obstacle to getting this operational, even for LEO RLVs. A high flight rate generated by an exploration program or an exploration precursor program as I described above could help overcome that obstacle. Interestingly, the type of propellant used would then no longer be critical, allowing the use of storable propellant and removing the depence on technological breakthroughs in that department. Cryogenic refueling would remain a very desirable upgrade.

Just LEO -> GEO/GTO tugs as described by Jon in a recent blog post don't seem enough to me, even if you simplify the system a lot (storable propellant, existing spacecraft bus, offloading the spacecraft propellant in addition to the GTO injection propellant, using rendez-vous with a small wet launched cryogenic LEO->GTO stage as a stepping stone, all three maybe in collaboration with Orbital).

Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 05/03/2010 05:00 am
You are using recursion.  I am not certain that works in space flight.

I thought with the analysis in Космические ракетные поезда Tsiolkovsky fairly convincing showed that recursion (in the form of multi-stage rockets) was really the only approach that works in space flight!  (Note an Orion crew can  get to an EML depot relying solely on LEO rendezvous with an appropriate departure stage.  No depot is required for them to get there, so this proposal doesn't depend on circular reasoning, if that's what you meant.)

Quote
An alternative way of building the EML depot is to assemble and fill it in LEO under human control.  Then [...] fly it to EML.

Good point.  This is a mechanism that allows e.g. small RLVs to contribute propellant in LEO that eventually reaches EML.

Quote
use a SEP tug [for this purpose].  Hopefully there will be a SEP tug around in 5 or 6 years time.

SEP is certainly an optimization worthy of consideration for propellant transfer between LEO and EML.  It's difficult to find fault with a factor of 20 improvement over hydrolox in specific impulse!  Did you mean to suggest a suitable SEP tug might exist in 5 or 6 years, or that given the masses and thrusts involved the delta-t to from LEO to EML might be 5 or 6 years?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 05/03/2010 05:41 am
Quote
use a SEP tug [for this purpose].  Hopefully there will be a SEP tug around in 5 or 6 years time.

SEP is certainly an optimization worthy of consideration for propellant transfer between LEO and EML.  It's difficult to find fault with a factor of 20 improvement over hydrolox in specific impulse!  Did you mean to suggest a suitable SEP tug might exist in 5 or 6 years, or that given the masses and thrusts involved the delta-t to from LEO to EML might be 5 or 6 years?

It depends on whether Ad Astra are actually building a space tug or just talking about it.  (The VASIMR on the ISS is under active development.)

From Ad Astra Rocket Executive Summary

"For robotic resupply missions to future human lunar outposts, Ad Astra is designing a 2MW solar powered VASIMR ® lunar tug capable of delivering more than twice the payload to the Moon (~34MT,) as compared to the all-chemical stage presently envisioned (~16MT.) Such enhancements in payload capability could result in savings of up to $400M/year over the present lunar resupply architecture."

http://www.adastrarocket.com/EXECUTIVE%20SUMMARY240110.pdf (http://www.adastrarocket.com/EXECUTIVE%20SUMMARY240110.pdf)

Even if Ad Astra are not going a head there are several firms that can integrate Hall Effect thrusters with solar panels, satellite bus and guidance system.
Title: Re: Propellant Depots - General Discussion
Post by: corrodedNut on 05/03/2010 01:55 pm
Dallas Bienhoff will talk about orbital propellant depots on The Space Show today, 2-3:30 PM PDT:

http://www.thespaceshow.com

His PPT slides from Space Access 2010 via Selenian Boondocks:

http://selenianboondocks.com/wp-content/uploads/2010/04/100408_Space-Access10.pptx
Title: Re: Propellant Depots - General Discussion
Post by: neilh on 05/03/2010 09:06 pm
Dallas Bienhoff will talk about orbital propellant depots on The Space Show today, 2-3:30 PM PDT:

http://www.thespaceshow.com

His PPT slides from Space Access 2010 via Selenian Boondocks:

http://selenianboondocks.com/wp-content/uploads/2010/04/100408_Space-Access10.pptx

Show starting now.
Title: Re: Propellant Depots - General Discussion
Post by: neilh on 05/03/2010 10:28 pm
Dallas Bienhoff will talk about orbital propellant depots on The Space Show today, 2-3:30 PM PDT:

http://www.thespaceshow.com

His PPT slides from Space Access 2010 via Selenian Boondocks:

http://selenianboondocks.com/wp-content/uploads/2010/04/100408_Space-Access10.pptx

Show starting now.

There was an interesting question about what Dallas perceives as the easiest and hardest technical hurdles for a depot. His response:

Easiest: insulation (just add more layers of MLI or mylar),  debris protection (already understand this problem from space station)

Harder: transfer in zero-g environment (want to ensure you get liquid transferred and not gas; done already with storables, not cryogenic yet)
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 05/03/2010 10:37 pm
He should have mentioned pre-placing depots in different places beyond LEO as a good way to multiply the effectiveness of prop depots for BEO exploration, especially if SEP comes along (both lowers the costs because SEP can be one-tenth as powerful yet still be quite effective and gives you much of the benefit of high-Isp propulsion, since it chops up the exponent, while expanding commercial opportunities of selling propellant to NASA beyond Earth orbit and maturing SEP in general).
Title: Re: Propellant Depots - General Discussion
Post by: neilh on 05/21/2010 08:23 pm
There's a -lot- of info on what NASA has in mind for the in-space refueling and storage Flagship Technology Demonstration in this supplementary document from the recent FTD RFI, titled "Cryogenic Propellant Transfer and Storage Demonstration Mission Point-of-Departure":

http://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=230993/PTSD%20WhitePaper.pdf
Title: Re: Propellant Depots - General Discussion
Post by: kkattula on 05/22/2010 10:34 am
Harder: transfer in zero-g environment (want to ensure you get liquid transferred and not gas; done already with storables, not cryogenic yet)

Easy.  You don't.  ULA have already worked out that milli-g is enough to settle the propellant.
Title: Re: Propellant Depots - General Discussion
Post by: Patchouli on 05/22/2010 07:43 pm
Harder: transfer in zero-g environment (want to ensure you get liquid transferred and not gas; done already with storables, not cryogenic yet)

Easy.  You don't.  ULA have already worked out that milli-g is enough to settle the propellant.

You probably can get enough g to settle the propellant with just a modest tether or even the thrusters.

I'd prefer the tether as it would not alter the depot's orbit though one could just have reboost happen during transfers.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 05/27/2010 08:08 pm
If you can launch a 24-29-ton dry GEO bird (60 tons fueled?) and refuel it in LEO and place it in GSO with a LEO-fueled (hypergolic?) stage, that may be something to sell a depot on (or at least tankers) without requiring low-cost access to space. The only other way to do it would be a rather large HLV.

Of course, you're not likely to get many of those... maybe three in a decade if you're REALLY lucky.

You can do the same with a smaller GEO bird, provided you are sufficiently cheaper than the competition. Returning your transfer craft from GTO to LEO is probably not that difficult through aerobraking in multiple passes, especially if your RLV orbiter doubles as a transfer craft. Since you won't have more than a handful of transfers a year, you can afford to go slowly. That's less than 3km/s, below the exhaust velocity of a storable thruster.

Or you could use a ballistic trajectory to L1/L2, and then use SEP to get to and from GEO. It's a bit more expensive, but it would allow you to do the whole LEO->GEO transfer. Lowering your perigee and aerobraking back from L1/L2 isn't too expensive. If your transfer craft is a modified RLV orbiter, you can even get it back on the ground for occasional servicing.

Now you would be spending more delta-v than the exhaust velocity of your thruster, so things start to get appreciably more expensive. You are still avoiding part of the storable (maybe even monopropellant) delta-v normally provided by the spacecraft, though you no longer have the benefit of staging in GTO. You do still have the benefit of LEO staging. It's a nontrivial set of trade-offs.

Arc jets and SEP are yet other ways to skin this cat. There's more than one way to harness the power of cheap small lift and more than one way to get there.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 08/22/2010 05:05 am
There's a -lot- of info on what NASA has in mind for the in-space refueling and storage Flagship Technology Demonstration in this supplementary document from the recent FTD RFI, titled "Cryogenic Propellant Transfer and Storage Demonstration Mission Point-of-Departure":

http://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=230993/PTSD%20WhitePaper.pdf

Can anyone comment on why this proposal is for cryogenic CH4 rather than H2?  I think it is from May of 2010, and suggests a launch in 2015.  When does NASA think H2 transfer and storage might be demonstrated?  Or is CH4 good enough for the foreseeable future?
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 08/22/2010 11:16 am
http://forum.nasaspaceflight.com/index.php?topic=22437.0;all (http://forum.nasaspaceflight.com/index.php?topic=22437.0;all)

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: CommercialSpaceFan on 09/24/2010 12:24 am
I believe that this all chemical DRM demonstrates the need for depots.  This DRM requires 5 launches of individual cryo stages over some lengthy period of time.  Each of the stages requires extremely efficient cryo storage demanding replacement of the entire stage if boil-off happens to be a little too high.  These 5 stages must be hard docked and have their propulsion systems all work months after launch.  5 independent stages will entail much higher mass than a single stage, not to mention 1/5th the reliability since this contraption doesn't provide engine out, but does require all 5 engines to work.

It seems that overcoming the fear of propellant transfer drastically simplifies the entire architecture.  Store the propellant in a depot that is designed for long duration storage where mass is not at as high a priority as the EDS.  Launch sufficient propellant such that high boil-off is accommodated.  If boil-off is too high launch another tanker.  The EDS can be the upper stage of the launch vehicle launching all of the elements, thus spending hours to days in orbit not months.  With engine out reliability is further enhanced.
Title: Re: Propellant Depots - General Discussion
Post by: kkattula on 09/24/2010 05:14 am
You still need low or zero boil-off for the target insertion and departure propellant.

For a destination with regular windows like Mars orbit, you could pre-position a depot.  For a NEO, you could take the zero boil-off equipment with you, and discard it before the departure burn.

This still saves mass because you only need to send, (through transit-injection), enough equipment to conserve the 40% target insertion and departure propellant. Instead of the full 100%.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 09/25/2010 07:44 pm
I believe that this all chemical DRM demonstrates the need for depots.

Agreed.


Quote
This DRM requires 5 launches of individual cryo stages over some lengthy period of time.  Each of the stages requires extremely efficient cryo storage demanding replacement of the entire stage if boil-off happens to be a little too high.  These 5 stages must be hard docked and have their propulsion systems all work months after launch.  5 independent stages will entail much higher mass than a single stage, not to mention 1/5th the reliability since this contraption doesn't provide engine out, but does require all 5 engines to work.

A single RL-10 stage with 300-350mT of prop will have incredibly long engine-burn times, even with no engines out. Also, a stage that big will have to carry a lot of dry mass towards the end of the mission.

A DIRECT J-2xx-style EDS would naturally have a prop capacity of ~170mT. Two of these in chain would have more reasonable engine-lifetime requirements and 2nd-stage burnout mass.

This would obviously require a depot to aggregate the prop from several launches.


Quote
It seems that overcoming the fear of propellant transfer drastically simplifies the entire architecture.

I suspect the fear is partly that commercial could be cheaper to deliver prop to the depot. This is least of a concern for the all-chemical mission, which gets the HLV flight rate up, and the per-Kg costs down.


Quote
Store the propellant in a depot that is designed for long duration storage where mass is not at as high a priority as the EDS.

The mission also has a requirement for low boiloff in the stage that performs rendezvous & TEI. Once this is developed, you only need to mature PT to enable a depot. Maybe a depot could actually dock into the stack to become that stage.

If you have two EDS's, the one that performs injection must only store prop for a few days after being fuelled from the depot. This will keep it's mass down.


Quote
The EDS can be the upper stage of the launch vehicle launching all of the elements, thus spending hours to days in orbit not months.

The upper stage launched with the other elements would more naturally become the injection stage than the low-boiloff rendezvous / TEI stage.

This may require un-docking & re-docking the stack.

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 09/25/2010 08:31 pm
A single RL-10 stage with 300-350mT of prop will have incredibly long engine-burn times [but two J-2xx-style EDS] in chain would have more reasonable engine-lifetime requirements

This line of reasoning deserves analysis in the context of depots.

What are the barriers to development of hydrolox engines that have reliable burn durations more like aircraft engines (i.e. hours rather than minutes)?
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 09/25/2010 08:35 pm
L1/L2 staging will take care of the burn duration requirements. Another non-issue.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 09/26/2010 12:34 am
I think an off-the-shelf RL-10 is rated for something like 4000 seconds of continual firing without maintenance, which is around 100 tons of propellant. The total service life of an RL-10 derivative, the Common Extensible Cryogenic Engine (CECE), is about 10000 seconds, which means around 250 tons of propellant.

I'm sure it could be qualified for, say, 15000 seconds or more if you had a good reason for it. No one does today, which is why it isn't qualified for 15000 seconds.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 09/26/2010 01:25 am
I think an off-the-shelf RL-10 is rated for something like 4000 seconds of continual firing without maintenance, which is around 100 tons of propellant. The total service life of an RL-10 derivative, the Common Extensible Cryogenic Engine (CECE), is about 10000 seconds, which means around 250 tons of propellant.

I'm sure it could be qualified for, say, 15000 seconds or more if you had a good reason for it. No one does today, which is why it isn't qualified for 15000 seconds.

On a reusable spaceship you would want at least 10 trips out of an engine, that is 20 sets of firings.

Depart spacestation, course correction * n and descent.
Ascent, course correction * n and rendezvous with spacestation.
Title: Re: Propellant Depots - General Discussion
Post by: Llian Rhydderch on 02/16/2014 10:36 pm
This thread has been quiet for a very long time, by NSF standards.  Not sure if there is some other, more current, thread for general discussion on propellant depots.

But I thought it would be important to note, in this general prop depot area, that there has been a fair amount of discussion of the concept over on the SpaceX MCT thread recently.  Are propellant depots useful or needed for the Mars Colonial Transporter speculative system?  How so?  Where placed?  Why?

If depots are your interest, you might want to pop over there and view or participate in the discussion.

http://forum.nasaspaceflight.com/index.php?topic=33494.0 (http://forum.nasaspaceflight.com/index.php?topic=33494.0)

Cheers,
Llian
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 02/17/2014 05:49 am
The issue for MCT speculation is that Musk doesn't seem to care about depots and hasn't mentioned them.

Musk has been wrong several times in the past, so that shouldn't count against the concept at all, only if we're trying to do Kremlinology for the MCT.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 02/17/2014 08:51 am
I contend Musk will start talking about an LEO depot and its importance in his MCT architecture as soon as SpaceX has demonstrated second-stage recovery and reuse. The link is that a depot needs to be filled, and the way he sees to do that is with a special "tanker" second-stage that delivers only propellant to orbit before landing on Earth again for reuse.

Until second-stage recovery and reuse is demonstrated he won't talk about depots because he doesn't want to unnecessarily step on the toes of potential allies who might view a depot architecture as an adversary of their favorite BFR architecture.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 02/17/2014 11:02 pm
Just found article on fuel depots/ lunar lander.

http://newpapyrusmagazine.blogspot.co.nz/2014/01/an-sls-launched-cargo-and-crew-lunar.html
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 02/17/2014 11:16 pm
Just found article on fuel depots/ lunar lander.

http://newpapyrusmagazine.blogspot.co.nz/2014/01/an-sls-launched-cargo-and-crew-lunar.html

The old question returns, "Will lunar landers use hydrogen or methane for fuel?"
Title: Re: Propellant Depots - General Discussion
Post by: a_langwich on 02/18/2014 09:17 pm
Is CRYOTE still going?  Anybody seen progress or lessons-learned presentations?
Title: Re: Propellant Depots - General Discussion
Post by: Proponent on 02/19/2014 09:07 am
CRYOTE has, unfortunately, never been more than a proposal.

To my knowledge, the closest thing there's been to a flight demonstration of cryogenic depot technology were the secondary experiments performed with Atlas V AV-017's Centaur stage (http://www.ulalaunch.com/site/docs/publications/SuccessfulFlightDemonstrationConductedbytheAirForceandUnitedLaunchAllianceWillEnhanceSpaceTransportation_.pdf) after it completed its primary mission of launching DMSP-18.  Among other things, rigid-body propellant settling was demonstrated.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/19/2014 08:32 pm
CRYOTE has, unfortunately, never been more than a proposal.

I'm not sure that's accurate. I remembered seeing an update a year or so ago on ground test article work they were doing. I pinged someone at ULA to see if they had any publicly available update info I could share. I could be wrong, but I'm pretty sure this is an active project (just one that's making slow but steady progress).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/19/2014 08:49 pm
The issue for MCT speculation is that Musk doesn't seem to care about depots and hasn't mentioned them.

Musk has been wrong several times in the past, so that shouldn't count against the concept at all, only if we're trying to do Kremlinology for the MCT.

Agreed. One of Elon's strongest suits is the ability to change his mind quickly when someone shows he needs to. He may come across as cocky, but he's demonstrated an unusual knack for learning from others. I can't remember who compared him to the Borg, but it seemed apt.

That said, we shouldn't assume that SpaceX has to build and run a depot in order to use it. There's no reason this should be a one-company "industry".

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/19/2014 08:53 pm
Until second-stage recovery and reuse is demonstrated he won't talk about depots because he doesn't want to unnecessarily step on the toes of potential allies who might view a depot architecture as an adversary of their favorite BFR architecture.

I think the far more likely case is just that he's not convinced yet that depots make sense.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Proponent on 02/19/2014 09:42 pm
CRYOTE has, unfortunately, never been more than a proposal.

I'm not sure that's accurate. I remembered seeing an update a year or so ago on ground test article work they were doing. I pinged someone at ULA to see if they had any publicly available update info I could share. I could be wrong, but I'm pretty sure this is an active project (just one that's making slow but steady progress).

~Jon

Funded by ULA itself?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/19/2014 09:54 pm
CRYOTE has, unfortunately, never been more than a proposal.

I'm not sure that's accurate. I remembered seeing an update a year or so ago on ground test article work they were doing. I pinged someone at ULA to see if they had any publicly available update info I could share. I could be wrong, but I'm pretty sure this is an active project (just one that's making slow but steady progress).

Ok, I did some digging and here's my understanding of the situation with CRYOTE.

ULA built a ground test system and were putting it through its paces when NASA announced their Cryogenic Propellant Storage and Transfer program and solicited industry input/proposals. ULA and their NASA partners on CRYOTE proposed doing CRYOTE as part of that program, but ultimately NASA decided to do CPST entirely in-house. ULA then decided to do a larger-scale follow-on to the CRYOTE ground test system using their own resources (sounds like they're using a full 10ft diameter LH2 tank with a ~3ft barrel section), and have been building hardware and will be working with some interested NASA groups to perform ambient and t-vac tests in the coming months.

So, not sure if that answers the question, but it looks like the program that started with CRYOTE is still making progress, just they've had some twists and turns along the way.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: a_langwich on 02/19/2014 10:04 pm
CRYOTE has, unfortunately, never been more than a proposal.

I'm not sure that's accurate. I remembered seeing an update a year or so ago on ground test article work they were doing. I pinged someone at ULA to see if they had any publicly available update info I could share. I could be wrong, but I'm pretty sure this is an active project (just one that's making slow but steady progress).

~Jon

 This bulletin (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&ved=0CDYQFjAC&url=https%3A%2F%2Fwww.cpiac.jhu.edu%2Fcpiacsearch%2Fdownloadfile%2F%3Ffile_id%3D43841&ei=IjQFU9_uG4rhygG3m4GADw&usg=AFQjCNFtISxZELiix73byCsckB6wmzD-5w&bvm=bv.61535280,d.cWc) is from July 2010.

Quote
The Cryogenic Orbital Testbed (CRYOTE) ground test article remains on schedule for vacuum chamber testing in the latter half of 2010. Atlas V launch opportunities are being evaluated for as early as 2012.
and
Quote
A CRYOTE ground test article has already been fabricated and is being prepared for cryogenic vacuum chamber testing.

There's further mention that the hydrogen in the tank provides opportunities for a very-high-efficiency thrust system, such that CRYOTE mounted in a ULA ESPA adapter might actually be used as a small, high-Isp kick stage.

Sounds promising...note also the same newsletter covers SpaceX's first Falcon 9 launch.  How much ground has CRYOTE covered in the meantime?
Title: Re: Propellant Depots - General Discussion
Post by: a_langwich on 02/19/2014 10:58 pm
Re: CRYOTE

Don't have access to this article from June 2012
http://www.sciencedirect.com/science/article/pii/S0011227512000124
Title: Re: Propellant Depots - General Discussion
Post by: a_langwich on 02/20/2014 12:13 am

Ok, I did some digging and here's my understanding of the situation with CRYOTE.

ULA built a ground test system and were putting it through its paces when NASA announced their Cryogenic Propellant Storage and Transfer program and solicited industry input/proposals. ULA and their NASA partners on CRYOTE proposed doing CRYOTE as part of that program, but ultimately NASA decided to do CPST entirely in-house. ULA then decided to do a larger-scale follow-on to the CRYOTE ground test system using their own resources (sounds like they're using a full 10ft diameter LH2 tank with a ~3ft barrel section), and have been building hardware and will be working with some interested NASA groups to perform ambient and t-vac tests in the coming months.

So, not sure if that answers the question, but it looks like the program that started with CRYOTE is still making progress, just they've had some twists and turns along the way.

~Jon

Ah, thanks! 

NASA and its Not-Invented-Here attitude (where "here" is the sponsoring center or even office inside a center)...   ::)

Interesting, too, that ULA is going for the 10-ft tank...that sounds good, too, but the little tank integrated with an ESPA adapter seemed like it might provide some very useful options for secondary payloads. 
Title: Re: Propellant Depots - General Discussion
Post by: muomega0 on 02/20/2014 01:50 am

Ok, I did some digging and here's my understanding of the situation with CRYOTE.

ULA built a ground test system and were putting it through its paces when NASA announced their Cryogenic Propellant Storage and Transfer program and solicited industry input/proposals. ULA and their NASA partners on CRYOTE proposed doing CRYOTE as part of that program, but ultimately NASA decided to do CPST entirely in-house. ULA then decided to do a larger-scale follow-on to the CRYOTE ground test system using their own resources (sounds like they're using a full 10ft diameter LH2 tank with a ~3ft barrel section), and have been building hardware and will be working with some interested NASA groups to perform ambient and t-vac tests in the coming months.

So, not sure if that answers the question, but it looks like the program that started with CRYOTE is still making progress, just they've had some twists and turns along the way.

~Jon

Ah, thanks! 

NASA and its Not-Invented-Here attitude (where "here" is the sponsoring center or even office inside a ncenter)...   ::) 
NIH is not quite correct.  No funding--all is directed to 130 mT, likely way less shuttle derived.

Technology roadmaps were developed assuming an HLV architecture and hence many things do not make the  list.   EP is also at play, but with limited funding.   IOW funding is redirected to the baseline program and enabling technologies, like baffling issues.
 
Consequently, the technology roadmaps do not include the words 'boiloff' or 'depot'. (http://forum.nasaspaceflight.com/index.php?topic=26625.msg1097422#msg1097422)

There is some rationale for this decision:  if you have no mission, why worry about boiloff or storing prop?

Centaur has over 150 deep space missions over the decades (http://forum.nasaspaceflight.com/index.php?topic=33862.msg1151128#msg1151128) and there a few rocket scientists over the decades who know why this is the case, and what needs to worked in the future depending on the mission set and funding level presented.

The great news is that a ZBO LH2 LEO depot is feasible.  Other factors and organizations prefer different fuel.

Most parts of NASA however recognize the benefits of a depot based architecture and all the efforts put forth to prevent its future for obvious reasons. (http://forum.nasaspaceflight.com/index.php?topic=33864.msg1151158#msg1151158)  More importantly, it shifts the focus to missions and technology development and 100s of thousands of incremental improvements.  Quite an exciting future!     
Title: Re: Propellant Depots - General Discussion
Post by: a_langwich on 02/20/2014 03:35 am
NIH is not quite correct.  No funding--all is directed to 130 mT, likely way less shuttle derived.
 

Did you read the quoted material?  NASA funded the Cryogenic Propellant Storage and Transfer project, but the group involved decided to do it their own way.  No need to pull in all the politics, you can keep all that in the space policy forum.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 02/20/2014 03:54 am
I'm all for depots for doing BLEO missions especially lunar. L2 or LLO depots to suuport landers, but can't see a good case for LEO depot. BLEO missions need a HLV  with payload to LLO of 10t+ or Orion capsule. Ideally this HLV would  have reuse 1st stage while delivering above payloads to depot.

Initially 2nd stage would be expendable, once depot is fueled from moon, it could be refueled and returned to earth surface.

A LEO depot just adds one more expensive link in chain.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 02/20/2014 04:45 am
I'm all for depots for doing BLEO missions especially lunar. L2 or LLO depots to suuport landers, but can't see a good case for LEO depot. BLEO missions need a HLV  with payload to LLO of 10t+ or Orion capsule. Ideally this HLV would  have reuse 1st stage while delivering above payloads to depot.

Initially 2nd stage would be expendable, once depot is fueled from moon, it could be refueled and returned to earth surface.

A LEO depot just adds one more expensive link in chain.

A BA330 weights about 20 tonne, this is near the maximum payload of an EELV.  To use a BA330 as a building on the Moon launch it to LEO dry.  Full the propellant tanks at the LEO depot and the building can fly to the Moon.

Same for the SLS.  A medium sized Mars Transfer vehicle could have a dry weight of 130 tonne.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/20/2014 01:58 pm
I'm all for depots for doing BLEO missions especially lunar. L2 or LLO depots to suuport landers, but can't see a good case for LEO depot. BLEO missions need a HLV  with payload to LLO of 10t+ or Orion capsule. Ideally this HLV would  have reuse 1st stage while delivering above payloads to depot.

Initially 2nd stage would be expendable, once depot is fueled from moon, it could be refueled and returned to earth surface.

A LEO depot just adds one more expensive link in chain.

Why do people assume a LEO depot has to be expensive relative to an HLV? I did a paper with ULA years ago on a dual-fluid depot that was big enough to support useful deep-space missions, and it could be launched on a single EELV launch. I mean, it's true you can make a depot really complex if you try, but there's no reason a useful depot has to be very complex at all. My guess is that a depot, including development, is likely going to cost you less than $1B to put the first one up. And once you combine a depot with a decent upper stage (Centaur is marginal but could do in a pinch, ACES is much better), cislunar transportation starts getting much easier. A LEO depot with a decent upper stage can do everything an HLV can do, but you end up getting much better flight rate with the depot (which likely leads to a lower price per lb delivered to the destination). Also LEO depots are one of the two keys to creating reusable in-space transportation networks (the other one being good aerocapture technology).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 02/20/2014 03:49 pm
Jon. I'm not discounting your work. With existing LVs a LEO depot maybe best option for cislunar.

My scenario only works for a non exist reuseable HLV which may exist by 2020.
Title: Re: Propellant Depots - General Discussion
Post by: muomega0 on 02/20/2014 04:18 pm
NIH is not quite correct.  No funding--all is directed to 130 mT, likely way less shuttle derived.
 

Did you read the quoted material?  NASA funded the Cryogenic Propellant Storage and Transfer project, but the group involved decided to do it their own way.  No need to pull in all the politics, you can keep all that in the space policy forum.

Many programs are simply terminated and personnel are reassigned.   by pulling it in house, it still has a life so to speak, but without funding it has no substantial path forward.   

The politics are important because technically the LEO ZBO depot is the most cost effective approach for many sets of missions forward.
Title: Re: Propellant Depots - General Discussion
Post by: muomega0 on 02/20/2014 04:49 pm
I'm all for depots for doing BLEO missions especially lunar. L2 or LLO depots to suuport landers, but can't see a good case for LEO depot. BLEO missions need a HLV  with payload to LLO of 10t+ or Orion capsule. Ideally this HLV would  have reuse 1st stage while delivering above payloads to depot.

Initially 2nd stage would be expendable, once depot is fueled from moon, it could be refueled and returned to earth surface.

A LEO depot just adds one more expensive link in chain.

Why do people assume a LEO depot has to be expensive relative to an HLV? I did a paper with ULA years ago on a dual-fluid depot that was big enough to support useful deep-space missions, and it could be launched on a single EELV launch. I mean, it's true you can make a depot really complex if you try, but there's no reason a useful depot has to be very complex at all. My guess is that a depot, including development, is likely going to cost you less than $1B to put the first one up. And once you combine a depot with a decent upper stage (Centaur is marginal but could do in a pinch, ACES is much better), cislunar transportation starts getting much easier. A LEO depot with a decent upper stage can do everything an HLV can do, but you end up getting much better flight rate with the depot (which likely leads to a lower price per lb delivered to the destination). Also LEO depots are one of the two keys to creating reusable in-space transportation networks (the other one being good aerocapture technology).

~Jon

A LEO depot allows smaller existing LVs to provide 70% or more of the mass to travel to L2, the moon, or beyond.  If its zero boiloff, then LVs can be launched at anytime prior to the missions, including different fiscal years.  In a flat budget environment this gives the PMs great flexibility to spend $$ on hardware or LVs from one year to the next.

There really is not much to a LEO ZBO LH2 depot:  its an upper stage with no engines with stretched tanks launched empty, a power bus, a refrigeration system, attitude control.    Yes, other configurations exist.

So its basically a ISS power module with a refrigeration system and a couple of empty tanks, where the long life equipment is retained for a long duration.  Its 'simple' only because of the decades of experience gleaned from reducing the boiloff passively.  Showstoppers:  NONE.

The benefits?  For two lunar sorties per year at 2x120 mT, you need at most a 20 mT LV launched 10 times or multiple LVs launched a few times.

Now if you rapidly assemble all the prop in a short time, then boiloff can be managed for a lunar sortie type mission.  Contrast this with Ares V staging five, no six flights for  a Mars DRM mission due to 70 tons of boiloff over a 6 month time frame for a mission every two years.  Now explain to anyone why is the word 'boiloff' not in the technology roadmap (http://forum.nasaspaceflight.com/index.php?topic=26625.msg1097422#msg1097422)?!

yes, one opt for methane or hyrdazines, but then the IMLEO can increase by 40 to 80% depending on the deltaV required.

the politics?  well with ZBO LH2 (rather than methane, etc) depot, it requires less IMLEO and hence less LV business!  it also allows multiple LV participants rather than just a sole source provider--less business!     It also requires less expendable equipment and starts NASA on a path to reusable transfer stages and perhaps SSTO vehicles--less business!  With the FY flexibility, money could go to missions and not LVs--less business!  If you choose LH2, then i cannot sell NASA a hypergolic transfer stage or have prop available for GEO sats--less business!  If you boil away 70 tons of prop more business!       we all get it  :D

Please follow all the sublinks and critique the depot concept (http://forum.nasaspaceflight.com/index.php?topic=33864.msg1151158#msg1151158)  Comments are welcome.
Title: Re: Propellant Depots - General Discussion
Post by: Proponent on 02/20/2014 06:28 pm
So, not sure if that answers the question, but it looks like the program that started with CRYOTE is still making progress, just they've had some twists and turns along the way.

Thanks.  I'm delighted to be wrong!
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/20/2014 08:44 pm
Jon. I'm not discounting your work. With existing LVs a LEO depot maybe best option for cislunar.

My scenario only works for a non exist reuseable HLV which may exist by 2020.

I honestly think that medium sized (reusable) rockets flying very frequently are likely going to be cheaper than HLVs of any flavor (including SpaceX hypothetical ones).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: KelvinZero on 02/21/2014 08:11 am
I honestly think that medium sized (reusable) rockets flying very frequently are likely going to be cheaper than HLVs of any flavor (including SpaceX hypothetical ones).
Although SpaceX does not talk about propellant depots much, it seems an ideal purpose for the F9R. We want a reason to launch something like that repetitively.

Is my basic logic below right? I realise the F9R upper stage is not the beast described here, Im just speculating on what you can potentially do on top of  the F9R first stage alone.

This link claims the F9 v1.1 upper stage is about 100t fueled. http://www.spacelaunchreport.com/falcon9v1-1.html
(Is that right? it also says about double the mass of the block 1 F9 upper stage??)
So just using F9R and a depot should allow departing earth with a 100t stage, plus whatever it was pushing.

More excitingly,  if we were allowed to master something like that asteroid capture SEP tug, we could refuel the upper stage again at the moon and begin descent with from lunar orbit to lunar surface with a 100t wet mass descent stage, which I guess could deliver 50t to the lunar surface, based on Apollo descent/ascent stage masses with mere hypergolic propellant... you would need lunar ISRU for the same mass to lift off again.

In any case here are three totally affordable technologies to at least demonstrate. F9R, Depots, 40Kw SEP tug. Im sure we could do a lot with them, and the knowledge gained in these three areas would have huge ramifications.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 02/21/2014 08:55 am
Jon. I'm not discounting your work. With existing LVs a LEO depot maybe best option for cislunar.

My scenario only works for a non exist reuseable HLV which may exist by 2020.

I honestly think that medium sized (reusable) rockets flying very frequently are likely going to be cheaper than HLVs of any flavor (including SpaceX hypothetical ones).

~Jon
With a LEO depot do you still need a LL0 depot for lunar missions?
Title: Re: Propellant Depots - General Discussion
Post by: Proponent on 02/21/2014 11:40 am
Jon. I'm not discounting your work. With existing LVs a LEO depot maybe best option for cislunar.

My scenario only works for a non exist reuseable HLV which may exist by 2020.

I honestly think that medium sized (reusable) rockets flying very frequently are likely going to be cheaper than HLVs of any flavor (including SpaceX hypothetical ones).

~Jon
With a LEO depot do you still need a LL0 depot for lunar missions?

You don't absolutely need it, but it would help make in-space stages smaller.  Making propellant on the moon (http://www.spudislunarresources.com/Papers/Affordable_Lunar_Base.pdf) will increase the attractiveness of a cis-lunar depot.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/21/2014 12:03 pm
I'm all for depots for doing BLEO missions especially lunar. L2 or LLO depots to suuport landers, but can't see a good case for LEO depot. BLEO missions need a HLV  with payload to LLO of 10t+ or Orion capsule. Ideally this HLV would  have reuse 1st stage while delivering above payloads to depot.

You need neither the depot nor the HLV. You can do lunar missions with just existing launch vehicles and upper stages if you use both LEO rendezvous and L1/L2 rendezvous and if you launch the lander empty.

Quote
A LEO depot just adds one more expensive link in chain.

No, the HLV is the unnecessary expensive link. The depot is also unnecessary, but at least it's useful, because it would provide a destination for small RLVs, which are cheaper to develop than large RLVs. You can get started with refueling at L1/L2, for which you don't need a depot either, since a lander can act as its own depot. A hypergolic refuelable lander is all you need to get started. If you leave refueling to the market, market forces will lead to depots in both LEO and at L1/L2 as soon as traffic warrants it.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/21/2014 12:05 pm
Although SpaceX does not talk about propellant depots much, it seems an ideal purpose for the F9R. We want a reason to launch something like that repetitively.

It's puzzling, but SpaceX is always talking about HLVs, not about depots or refueling.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/21/2014 12:07 pm
You don't absolutely need it, but it would help make in-space stages smaller.

Strictly speaking it's refueling at L1/L2 that makes the stages smaller, and you can do that without a depot if the spacecraft is its own depot. Whether to build a depot is an economic decision depending on levels of traffic and that decision is best left to the market. That also means private players would have to pay for development of the depot, which would only be possible if they could recoup the money from the projected traffic.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 02/21/2014 07:04 pm
I only see depots as viable if fueled from space/moon. Cis-lunar transport would be biggest user of depots.

 A LEO depot could be used for anything from GTO satellite launches to Mars missions. 2nd stages could refuel and return to earth, with full tank a heat shield may not be needed.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/21/2014 07:06 pm
I only see depots as viable if fueled from space/moon.

Why?
Title: Re: Propellant Depots - General Discussion
Post by: muomega0 on 02/21/2014 07:34 pm
I only see depots as viable if fueled from space/moon.

Why?
No real data is provide to back up the statement.  The real reason is that    with a LEO depot it eliminates lots of business for LVs. (http://forum.nasaspaceflight.com/index.php?topic=12338.msg1162195#msg1162195)

You don't absolutely need it, but it would help make in-space stages smaller.
Strictly speaking it's refueling at L1/L2 that makes the stages smaller, and you can do that without a depot if the spacecraft is its own depot. Whether to build a depot is an economic decision depending on levels of traffic and that decision is best left to the market. That also means private players would have to pay for development of the depot, which would only be possible if they could recoup the money from the projected traffic.
Not true.   Without a LEO depot one LV provider gets most of the business.

Depots in LEO first allow mutiple LVs (the world has excess launch capacity (http://forum.nasaspaceflight.com/index.php?topic=32409.msg1162734#msg1162734)) to provide the propellant for all BEO mission, the gas n go architecture.   Hence the billion dollar fixed cost product lines can be shutdown.  Most logical folks understand this.

The LEO depot can eventually be extended to L1/L2 for trips to Mars depending on the role for EP.  With a LEO depot you do not need a lunar depot for the lunar surface.

The program forward should be EP and depots, but the thumbs on the scale trades (ESAS revived with EP) all show EP And HLV, with HLV morphing into yet another beast.  Funding EP is killing depots and retaining the number one cost driver at NASA:  HLV (http://forum.nasaspaceflight.com/index.php?topic=12338.msg1161978#msg1161978)
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/21/2014 11:03 pm
I only see depots as viable if fueled from space/moon.

Why?

I've heard others express this sentiment as well, and I've never understood it either.  Unless you assume that Heavier Lift economies of scale will dominate high-flight-rate reusability economies of scale, or that the delivery cost of handling large numbers of small launchers is going to dominate things, or that the depot somehow has to be really, really expensive... I mean, I guess those might be reasonable assumptions if you haven't looked at the details, but I think they're all wrong. I'm pretty sure that launching 100tons of propellant to LEO will be cheaper using 50 flights of a 2ton to orbit gas-and-go RLV with a depot than launching that 100tons of propellant using an HLV. Even a partially reusable HLV. Even a fully reusable HLV, because you're not going to get as many flights to amortize your development cost over. At least not anytime in the foreseeable future.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: LegendCJS on 02/21/2014 11:20 pm
I only see depots as viable if fueled from space/moon.

Why?

I've heard others express this sentiment as well, and I've never understood it either.  Unless you assume that Heavier Lift economies of scale will dominate high-flight-rate reusability economies of scale, or that the delivery cost of handling large numbers of small launchers is going to dominate things, or that the depot somehow has to be really, really expensive... I mean, I guess those might be reasonable assumptions if you haven't looked at the details, but I think they're all wrong. I'm pretty sure that launching 100tons of propellant to LEO will be cheaper using 50 flights of a 2ton to orbit gas-and-go RLV with a depot than launching that 100tons of propellant using an HLV. Even a partially reusable HLV. Even a fully reusable HLV, because you're not going to get as many flights to amortize your development cost over. At least not anytime in the foreseeable future.

~Jon

I don't think cheaper launch one way or the other even is required to justify depots. Even if you assume that the price per ton (maximum load) for any form of non-maned launch costs the same, I think there is still a benefit.On a high level, the options to deliver mass to orbit are a stair step function due to the mass caps of different launcher options.  You pay the full load price even if you don't use the mass. A depots ability to store fuel on orbit and deliver this mass in a continuously variable (non-stepped) manner opens up a tool to optimize the utilization of the existing launch mass limitations, without being constrained to having mission starting mass equal to that of a particular launcher or combo of launchers, but still get the full use of the payload of the launchers you are paying for.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 02/22/2014 12:02 am

With a LEO depot do you still need a LL0 depot for lunar missions?

Yes.  The moment you have a reusable lunar lander you need a place to refuelling it.

The depot could be at LLO, EML-1, EML-2 or DRO.

The delta-v LEO to lunar surface return is likely to be too high for the refuelling to take place in LEO.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/22/2014 03:07 am
Jon. I'm not discounting your work. With existing LVs a LEO depot maybe best option for cislunar.

My scenario only works for a non exist reuseable HLV which may exist by 2020.

I honestly think that medium sized (reusable) rockets flying very frequently are likely going to be cheaper than HLVs of any flavor (including SpaceX hypothetical ones).

~Jon
With a LEO depot do you still need a LL0 depot for lunar missions?

I think it makes sense to have depots at both ends of the trip. I'm not sold on LLO (as compared to EML-1/2), but I think that the marginal price for a second depot (especially a simple single-launch design) will be low enough that you'd want at least one at both places.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/22/2014 12:49 pm
I'm pretty sure that launching 100tons of propellant to LEO will be cheaper using 50 flights of a 2ton to orbit gas-and-go RLV with a depot than launching that 100tons of propellant using an HLV.

I agree, but I think there is a much more important argument: RLVs, even just very small ones, are so important that they trump considerations of  launch cost for NASA. The question should be: "by how much will this reduce commercial launch prices", not "what will price will NASA have to pay".
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/22/2014 12:54 pm
I think it makes sense to have depots at both ends of the trip.

Agreed, and of the two the LEO depot is more important (more difficult too) in the short term. As an aside, I still believe orbital refueling at L1/L2 without a dedicated depot is even more important than the LEO depot.

Quote
I'm not sold on LLO (as compared to EML-1/2), but I think that the marginal price for a second depot (especially a simple single-launch design) will be low enough that you'd want at least one at both places.

Not sure about the cost, but LLO does seem a lot less useful. It might eventually be useful if you want to export ice or building materials from the moon and want to make use of high Isp propulsion from LLO to L1/L2. Then again, if you have a mass driver, that might be more efficient still. Hard to see as this is all very far in the future. The market can take care of it anyway.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 02/22/2014 02:28 pm
I'm all for depots for doing BLEO missions especially lunar. L2 or LLO depots to suuport landers, but can't see a good case for LEO depot. BLEO missions need a HLV  with payload to LLO of 10t+ or Orion capsule. Ideally this HLV would  have reuse 1st stage while delivering above payloads to depot.

Initially 2nd stage would be expendable, once depot is fueled from moon, it could be refueled and returned to earth surface.

A LEO depot just adds one more expensive link in chain.

Why do people assume a LEO depot has to be expensive relative to an HLV? I did a paper with ULA years ago on a dual-fluid depot that was big enough to support useful deep-space missions, and it could be launched on a single EELV launch. I mean, it's true you can make a depot really complex if you try, but there's no reason a useful depot has to be very complex at all. My guess is that a depot, including development, is likely going to cost you less than $1B to put the first one up. And once you combine a depot with a decent upper stage (Centaur is marginal but could do in a pinch, ACES is much better), cislunar transportation starts getting much easier. A LEO depot with a decent upper stage can do everything an HLV can do, but you end up getting much better flight rate with the depot (which likely leads to a lower price per lb delivered to the destination). Also LEO depots are one of the two keys to creating reusable in-space transportation networks (the other one being good aerocapture technology).

Jon,

ISTR you were doing some work on the orbital mechanics of a LEO depot.

Obviously, current launches often have short windows to carefully setup a staging orbit for onward injection. How will the depot set itself up with the orbital elements for the payload's required staging orbit.

Did I remember that correctly and, if so, how is it / did it go?

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 02/22/2014 06:27 pm
Some BOTE calculations.  For a hypothetical reusable Low Lunar Orbit (LLO) lander.

Delta-V = 1870 m/s one way
payload = 500 kg - descent only
dry mass = 1100 kg
Isp = 321 s
g = 9.81 m/s/s

Assent_fuel = 1100 * (exp(1870 / (321*9.81)) -1) = 892 kg
Descent_fuel = (1100+500+892) * (exp(1870 / (321*9.81)) -1) = 2020 kg
Total_fuel = 2020 + 892 = 2912 kg

Round it up to 3 tonne


Have a simple refueller that can support 3 landings.  Allow 2 tonne for the propellant pumps, solar panel, avionics, RCS and docking port.  Tanks to weigh say 15% of propellant

Mass = (3 * 3 * 1.15) + 2 = 12.35 tonne


edit:spelling
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/22/2014 07:01 pm
ISTR you were doing some work on the orbital mechanics of a LEO depot.

Obviously, current launches often have short windows to carefully setup a staging orbit for onward injection. How will the depot set itself up with the orbital elements for the payload's required staging orbit.

Did I remember that correctly and, if so, how is it / did it go?

You did remember correctly.

I'm actually supposed to be writing an abstract on just that topic today (for the IAC conference in Toronto this fall). We had previously intended to do the paper last year, but the two astrogators I'm working with were heavily involved in the LADEE mission and Inspiration Mars, so were pretty busy last year. So far we think we have a very promising potential solution, but without setting up the detailed analysis and Monte Carlos, it's hard to say how good of an idea we really have. Hopefully this year we'll be able to focus long enough to get the research done. It's not being paid for by anyone so unfortunately it sometimes takes backburner.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 02/23/2014 11:09 pm
Here is my scenario for Reuseable Lunar transport system, I borrowed some of the ideas from elsewhere.
Assume the following, LV is F9R with reuseable LOX/LHX 2nd stage and lunar ISRU is in place.
Up Trip.
Go to LEO depot and fuel 2nd stage then proceed to LLO(L1/L2). Transfer payload to lander. Refuel 2nd stage from a lander or depot(optional).
Down Trip
Proceed to LEO depot using Aerobraking, off load surplus fuel and return to earth.

The max payload to LLO can be same as max LEO payload even if more fuel is required between LLO and LEO than from earth to LEO. Build 2nd stage with larger fuel tanks but only load max fuel required to get to LEO depot.

There is no reason 2nd stage can't do a few round trips between LLO and LEO depot carrying fuel only. Using a SEP tug to tranport a empty 2nd stage from LEO to LLO would allow even more fuel to be delivered to LEO depot, SEP tug would return to LEO by its self.

A small cargo hold in 2nd stage could be used for returning lunar samples or gold(worth $42m mt) to earth.

One advantage I can see to LLO(L1/L2) depot is access to 24hr solar power for processing of lunar water into LOX/LHX. A small processing plant would still be need on lunar surface to fuel lander. 



Title: Re: Propellant Depots - General Discussion
Post by: Oli on 02/27/2014 01:59 pm
I'm pretty sure that launching 100tons of propellant to LEO will be cheaper using 50 flights of a 2ton to orbit gas-and-go RLV with a depot than launching that 100tons of propellant using an HLV.

I agree, but I think there is a much more important argument: RLVs, even just very small ones, are so important that they trump considerations of  launch cost for NASA. The question should be: "by how much will this reduce commercial launch prices", not "what will price will NASA have to pay".

One should not argue for depots with hypothetical RLVs that don't exist. In fact we should be a bit more honest about the costs of filling a propellant depot with small launchers. For a few tons cargo to the ISS NASA pays $130m or more. Is it unreasonable to assume that NASA would have to pay an equal amount to fill a depot with 13t of hydrolox? Suddenly bringing 130t to orbit would cost in the order of $1.3bn and SLS looks almost like a cheap option. I any case, the benefit of using a propellant depot comes for the use of existing launch vehicles and the consequental savings in development/fixed costs of HLVs not necessarily from a reduction in "pure" launch costs.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/27/2014 02:45 pm
One should not argue for depots with hypothetical RLVs that don't exist.

You're completely missing the point. Small RLVs don't exist yet, but creating a large and fiercely competitive propellant launch market can enable private investment to develop them.

My point is precisely that we shouldn't focus on whether smaller launchers are cheaper for NASA, but on whether a program based around orbital propellant transfer would reduce launch costs.

But in fact you are utterly, utterly wrong about what you go on to write as well:

Quote
In fact we should be a bit more honest about the costs of filling a propellant depot with small launchers. For a few tons cargo to the ISS NASA pays $130m or more. Is it unreasonable to assume that NASA would have to pay an equal amount to fill a depot with 13t of hydrolox? Suddenly bringing 130t to orbit would cost in the order of $1.3bn and SLS looks almost like a cheap option. I any case, the benefit of using a propellant depot comes for the use of existing launch vehicles and the consequental savings in development/fixed costs of HLVs not necessarily from a reduction in "pure" launch costs.

RLVs would be an order of magnitude cheaper than expendable launchers, enough to make fully commercial manned spaceflight viable.
Title: Re: Propellant Depots - General Discussion
Post by: Zed_Noir on 02/28/2014 04:31 am
One should not argue for depots with hypothetical RLVs that don't exist. In fact we should be a bit more honest about the costs of filling a propellant depot with small launchers. For a few tons cargo to the ISS NASA pays $130m or more. Is it unreasonable to assume that NASA would have to pay an equal amount to fill a depot with 13t of hydrolox?

You are lumping in the Dragon and it's processing cost on that $130M figure. For bulk cargo like hydrolox on a RLV. The cost per flight will be the cost of the hydrolox, operational costs & the amortized cost fraction of the RLV. So the project cost for a RLV with 13 mT payload to LEO should be a low fraction of the cost of building that RLV.
Title: Re: Propellant Depots - General Discussion
Post by: Oli on 02/28/2014 05:34 am
Quote
In fact we should be a bit more honest about the costs of filling a propellant depot with small launchers. For a few tons cargo to the ISS NASA pays $130m or more. Is it unreasonable to assume that NASA would have to pay an equal amount to fill a depot with 13t of hydrolox? Suddenly bringing 130t to orbit would cost in the order of $1.3bn and SLS looks almost like a cheap option. I any case, the benefit of using a propellant depot comes for the use of existing launch vehicles and the consequental savings in development/fixed costs of HLVs not necessarily from a reduction in "pure" launch costs.

RLVs would be an order of magnitude cheaper than expendable launchers, enough to make fully commercial manned spaceflight viable.

That is simply speculation. In general bigger rockets are more cost-effective per kg to orbit, as long as you have a reasonable launch rate (if you draw the cost curve, it drops fast with a few launches and flattens out). It is not at all given that a smaller RLV would be cheaper, especially not if the existing bigger rockets already exist and fly regularily. In any case, I would like to see a study that says otherwise.

One should not argue for depots with hypothetical RLVs that don't exist. In fact we should be a bit more honest about the costs of filling a propellant depot with small launchers. For a few tons cargo to the ISS NASA pays $130m or more. Is it unreasonable to assume that NASA would have to pay an equal amount to fill a depot with 13t of hydrolox?

You are lumping in the Dragon and it's processing cost on that $130M figure. For bulk cargo like hydrolox on a RLV. The cost per flight will be the cost of the hydrolox, operational costs & the amortized cost fraction of the RLV. So the project cost for a RLV with 13 mT payload to LEO should be a low fraction of the cost of building that RLV.

Falcon 9 would need an additional hydrolox tank that can withstand g-loads and navigate itself to the depot and berth/dock to it. For vehicles like Delta/Atlas the upper stage could be adapted accordingly, but it won't come for free either. Advertised launch prices are one thing, what matters is how much NASA/Air force pay for it.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/28/2014 09:30 am
That is simply speculation. In general bigger rockets are more cost-effective per kg to orbit, as long as you have a reasonable launch rate (if you draw the cost curve, it drops fast with a few launches and flattens out).

That too is speculation and more importantly, we know we don't have the necessary flight rates to keep a large rocket fully utilised. You can be skeptical about an order of magnitude improvement, but at least it would keep EELVs fully employed, which would make them no more expensive and probably cheaper than an HLV. Other than perhaps an EELV-derived EELV which could consolidate the EELVs further and still serve existing markets.

But again, my point was that we shouldn't focus on whether this will be cheaper for NASA (though I think it will be), but on whether this will reduce launch prices by enough to make manned spaceflight commercially viable. Even though launch prices are currently high, that's not an insurmountable obstacle for NASA, the spacecraft would still be much more expensive to build than to launch. High launch prices are an insurmountable obstacle for commercial spaceflight however.

Depots, and more generally propellant transfer, are an opportunity to make space launch radically cheaper and thus open up space for mankind. That's far more important than whether NASA may need to spend 50% more on its initial investment. Not that I think it would have to, but I'm arguing that we need to look at both costs and benefits. Even if we knew the depot route was 50% more expensive, it would still be worth it because of the great benefits.
Title: Re: Propellant Depots - General Discussion
Post by: Oli on 02/28/2014 10:41 am
That too is speculation and more importantly, we know we don't have the necessary flight rates to keep a large rocket fully utilised. You can be skeptical about an order of magnitude improvement, but at least it would keep EELVs fully employed, which would make them no more expensive and probably cheaper than an HLV. Other than perhaps an EELV-derived EELV which could consolidate the EELVs further and still serve existing markets.

But again, my point was that we shouldn't focus on whether this will be cheaper for NASA (though I think it will be), but on whether this will reduce launch prices by enough to make manned spaceflight commercially viable. Even though launch prices are currently high, that's not an insurmountable obstacle for NASA, the spacecraft would still be much more expensive to build than to launch. High launch prices are an insurmountable obstacle for commercial spaceflight however.

Depots, and more generally propellant transfer, are an opportunity to make space launch radically cheaper and thus open up space for mankind. That's far more important than whether NASA may need to spend 50% more on its initial investment. Not that I think it would have to, but I'm arguing that we need to look at both costs and benefits. Even if we knew the depot route was 50% more expensive, it would still be worth it because of the great benefits.

Well with "large rocket" in this context I meant existing ELV. Large compared to potentially smaller RLV with higher flight rate. I think existing ELVs would be well utilized by foreseeable exploration missions. No need to develop new rockets, be it HLV or RLV.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/28/2014 11:30 am
Well with "large rocket" in this context I meant existing ELV. Large compared to potentially smaller RLV with higher flight rate. I think existing ELVs would be well utilized by foreseeable exploration missions. No need to develop new rockets, be it HLV or RLV.

Sure, whether to develop new launch vehicles would be up to the market. If you can offer lower prices, you can take market share away from existing suppliers, so there would be both pressure to reduce costs and revenue to finance R&D from. Apart from Elon Musk entrepreneurs have found it very difficult to get funding for RLV development. This would help. Would it be enough? Maybe not, but that's not a reason not to try.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 02/28/2014 11:36 am
BTW, that same argument applies to depots themselves. Existing launch vehicles and in-flight refueling of the spacecraft rather than the transfer stage are good enough to get started. When to develop depots and / or RLVs is just a question of economics, depending mainly on the amount of traffic.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/28/2014 02:42 pm
One should not argue for depots with hypothetical RLVs that don't exist. In fact we should be a bit more honest about the costs of filling a propellant depot with small launchers. For a few tons cargo to the ISS NASA pays $130m or more. Is it unreasonable to assume that NASA would have to pay an equal amount to fill a depot with 13t of hydrolox?

Is it possible to do a hydrolox tanker that cost that much? Sure. That issue was pointed out by Josh Hopkins about four years ago, and was the main reason I've been working on boom-assisted rendezvous technologies. Even if you use the current approach to rendezvous and docking for the tanker vehicle, just by making it reusable you should get the costs well below $130M/13tonnes. But the techniques I'm working on, if they pan out, should make an even bigger difference in lower delivery cost. Even without RLVs, I think you can get the delivery cost of prop to a depot under the $5000/kg range with even modest depot usage. But if you actually do a high-flight-rate RLV (something that I think we have all the pieces for now), I wouldn't be surprised if you could get the cost below $500/kg.

Small RLVs combined with boom assisted rendezvous techniques to keep the delivery cost down make depots potentially way more affordable than HLVs. But even existing launchers plus depots is better than HLVs if you don't handwave away the billions spent on development of those HLVs. And as soon as you have a depot, you're now setup to use whatever launch solution is the cheapest. It introduces an element of competition into the launch market that makes it far easier to close business cases for new capabilities than the status quo. The biggest reason we don't have RLVs today isn't a lack of technology, or some magic economic infeasibility, it's that without a market that can really benefit from high flight rates, its hard to close the business case and raise the money unless you're already extremely wealthy to start with (see Musk and Bezos).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/02/2014 12:18 am
I am a HUGE supporter of Propellant Depots (I started this thread), and while I agree that RLVs really are what will bring the depots into their own, the simple fact is that there are none, not even as serious power points (discounting F9R). Because of that I think we do the concept of a depot-centric architecture a great dis-service by trying to justify depots on a cost basis dependent on hypothetical and non-existent RLVs, especially sense the depots don't actually need RLVs to make a huge positive contribution to the space program. They can do just fine being serviced by cost effective expendable launch vehicles.


If one desires to interject RLVs into the conversation at least limit it to the F9R which, while it may be too large for this role, may actually work. Beyond the F9R, there is nothing of any consequence out there.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 03/02/2014 01:04 am
F9R [...] may be too large for this role

Eh? What delivered propellant mass do you think a fully reusable F9R would provide? Or are you wanting to eliminate F9R upper stage reuse from discussion as well?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/02/2014 02:13 am
Propellant Depots can work with an entirely expendable architecture they hold the fuel until the expendable inspace vehicles and landers can use it.  The payloads and propellant go up on separate launch vehicles, doubling or trebling the all up inspace mass.

The SLS for instance could launch ~120 tonne of fuel to a LEO depot in one go, that will give the Mars transfer vehicles quite a kick.  Although it may be better to use the SLS to launch the spacecraft dry.

A propellant depot can be filled by expandable LV or reusable LV, it does not care.

The depots become force multipliers for reusable landers, transfer vehicles and tugs because the spacecraft can be reused several times.  Propellants like methane and hydrogen are considerably cheaper to make than spacecraft permitting money to be saved by reuse of the spacecraft.
Title: Re: Propellant Depots - General Discussion
Post by: RocketmanUS on 03/02/2014 02:42 am
Depots/propellant transfer makes crewed Mars missions feasible, plus other BLEO missions. It also helps with having a flex path. We are not locked into a specific design for return craft ( Lunar vs. Mars velocity return ). We could use LEO and EML-2 as a staging point for BLEO crewed missions. It also brings in more global government and commercial partners for multiple types of missions.

Commercial crew taxi to LEO.
In space reusable crew transfer vehicle LEO to EML-2 and back to LEO.
EML-2 to any were in the solar system ( note beyond Mars would need nuclear power instead of solar ).

For the return trip the crew craft can refuel in Mars orbit from propellants sent from Earth.

For satellites using SEP they can be refueled by a reusable tanker that gets it's propellants from a LEO depot.

F9 ( all disposable ) is cost effective. Having the propellant tanks reusable could add some cost savings and is highly plausible. SRB's and orbiter were both reused, so we know it can be done.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 03/02/2014 04:40 am
One issue with supplying depots from expendable LV is fact that expensive cryogenic fuel tanks used to deliver fuel are thrown away every time.
One option would be deliver water, which would be easier to store but would require a electrolysis plant plus a larger solar array on depot.

In regards to BLEO missions. A LEO depot should allow the 70t SLS version to do same missions as 130t version Congress was after.
Title: Re: Propellant Depots - General Discussion
Post by: Hauerg on 03/02/2014 05:10 am
I am a HUGE supporter of Propellant Depots (I started this thread), and while I agree that RLVs really are what will bring the depots into their own, the simple fact is that there are none, not even as serious power points (discounting F9R). Because of that I think we do the concept of a depot-centric architecture a great dis-service by trying to justify depots on a cost basis dependent on hypothetical and non-existent RLVs, especially sense the depots don't actually need RLVs to make a huge positive contribution to the space program. They can do just fine being serviced by cost effective expendable launch vehicles.


If one desires to interject RLVs into the conversation at least limit it to the F9R which, while it may be too large for this role, may actually work. Beyond the F9R, there is nothing of any consequence out there.

I feel that Elon not talking about depots for now has to do with the fact that he sees all expendable launch vehicles as too expensive for filling up the depot. Fuel would be the perfect payload for "used" F9Rs early on.
X
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 03/02/2014 05:36 am
A F9R may only be good for 9t and you have include fuel tanks in that 9t. That is not a lot of fuel per mission.
A F9H at $130m for 53T would be better.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/02/2014 10:29 am
A F9H at $130m for 53T would be better.

So what? High flight rates are needed to make efficient use of any launch vehicle, and very high launch rates for a reusable vehicle. Why do you think an expendable flight would have lower cost / kg?
Title: Re: Propellant Depots - General Discussion
Post by: Hauerg on 03/02/2014 10:38 am
A F9R may only be good for 9t and you have include fuel tanks in that 9t. That is not a lot of fuel per mission.
A F9H at $130m for 53T would be better.

BUT if on one hand you cannot recover the FH core and on the other hand is truly recoverable F9R might still be attractive and it will be a reasonable low risk market for the flown F9R cores. building a flight history for rockets that are not shiny white on the pad.
(Of course a fully reusable FH would be even greater.)
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/02/2014 10:46 am
If an HLV can fly in multiple configurations, including ones that can carry commercial payloads and especially including a small reusable configuration for LEO, then that's fine with me. I don't think the heavy LEO configuration is all that useful, but high energy and reusable LEO configurations are very useful. All excess payload capacity can be used for reusability: use some of the propellant for boost-back, beef up structures, add TPS, landing gear etc.

I'm not a huge fan of EELV Phase 2, though Phase 1 seems like a good idea and there is some industrial logic behind Phase 2 as well. But if it is the basis for an RLV as with FH, that would be awesome. Needs a lot of development money, and that is where depots / propellant transfer come in.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/02/2014 11:17 am
In my opinion an expendable depot architecture is the way to go until such time as RLVs may actually be developed. The payload delivered to LEO by something like a F9H would simply be a huge propellant tank that a mission spacecraft, launched dry, would rendezvous with, gas up and depart. The now empty depot tank would then be de-orbited and splashed. KISS
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/02/2014 11:18 am
That way a depot wouldn't contribute towards development of RLVs. Very bad idea.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/02/2014 11:30 am
One thing to ponder for people who dislike LEO depots because they aren't very suitable for refilling by HLVs: refueling by HLV at L1/L2, either with a dedicated depot or mere in-flight refueling, would be quite possible. So if you're truly convinced HLVs are superior for technical reasons and aren't merely pushing them for ulterior motives, L1/L2 refueling is the way to go. It is agnostic as to the type of propellant used for TLI, whether to use depots and if so in what orbital locations, whether to use small or large launch vehicles, reusable or expendable ones.

It would create enough traffic to allow commercial players to recoup the necessary investment for development of all kinds of infrastructure provided the investment actually makes sense.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/02/2014 10:53 pm
That way a depot wouldn't contribute towards development of RLVs. Very bad idea.

Creating a RLV launch architecture is not the purpose of depots. The reason for depots is to provide mission propellant to orbiting spacecraft. The quickest way to get a depot-centric architecture of any kind going is to use expendables like I described. Once that is established someone like an Elon Musk will see that there is a market for depot services and realize that a refillable depot is a better path and go for it. One way or another permanent refillable depots will eventually become the norm but if you wait for that technology to reach TRL-6 before even trying it then the depots will never happen at all.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/03/2014 12:05 am
One issue with supplying depots from expendable LV is fact that expensive cryogenic fuel tanks used to deliver fuel are thrown away every time.
{snip}

To make the delivery tank reusable you have to equip it with a heat shield and parachute.  That will make the fuel tanks even more expensive and reduce the fuel delivered in each flight.  Some significant cost trades need doing for that design.

A partially reusable LV may be the most economical design.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/03/2014 12:36 am
In my opinion an expendable depot architecture is the way to go until such time as RLVs may actually be developed. The payload delivered to LEO by something like a F9H would simply be a huge propellant tank that a mission spacecraft, launched dry, would rendezvous with, gas up and depart. The now empty depot tank would then be de-orbited and splashed. KISS

That seems kind of silly and wasteful. If you've figured out how to safely transfer cryo props from a depot into a receiving vehicle, you probably also know how to transfer cryo prop from a tanker into a depot. You have all the pieces to reuse the depot. Tankers don't need as good of long-term cryo handling capabilities as a depot (which will have more mass devoted to long-term low-boiloff storage by necessity). Throwing the depot out instead of refueling doesn't make sense. Even if you think Falcon Heavy is the only vehicle that can affordably launch propellants (praise be to Saint Elon!), leaving the depot itself up there, and having subsequent FH's just launch tankers will result in lower overall cost and more propellant delivery. And if it turns out that FH isn't the cheapest way of launching prop, by leaving the depot in orbit you're not locked-in.

What complexity do you think you actually avoid by having a single-use depot like that?

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: RocketmanUS on 03/03/2014 04:52 am
In my opinion an expendable depot architecture is the way to go until such time as RLVs may actually be developed. The payload delivered to LEO by something like a F9H would simply be a huge propellant tank that a mission spacecraft, launched dry, would rendezvous with, gas up and depart. The now empty depot tank would then be de-orbited and splashed. KISS

That seems kind of silly and wasteful. If you've figured out how to safely transfer cryo props from a depot into a receiving vehicle, you probably also know how to transfer cryo prop from a tanker into a depot. You have all the pieces to reuse the depot. Tankers don't need as good of long-term cryo handling capabilities as a depot (which will have more mass devoted to long-term low-boiloff storage by necessity). Throwing the depot out instead of refueling doesn't make sense. Even if you think Falcon Heavy is the only vehicle that can affordably launch propellants (praise be to Saint Elon!), leaving the depot itself up there, and having subsequent FH's just launch tankers will result in lower overall cost and more propellant delivery. And if it turns out that FH isn't the cheapest way of launching prop, by leaving the depot in orbit you're not locked-in.

What complexity do you think you actually avoid by having a single-use depot like that?

~Jon
First generation like clongton said would work. Launch tanker/depot. Then within a given amount of days launch the payload that will need the propellants from the tanker/depot. Also good for orbits not usually used. It is a low cost was to develop the depots that will be refillable and much larger.

Possible first generation use for example:
For FH it's US could be refueled this way if modified to improve it's payload to Mars surface if the US was reusable ( land-landing with heat shield ). So launch the tanker/depot before or after as needed per mission type.

There are a lot of advantage for using depots including placing a BLEO payload in orbit before it's BLEO burn. Use the depot to fill it when the window opens up ( advantage launch before any possible bad weather ).
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/03/2014 03:34 pm
Blue Origin's RLV  is better than a powerpoint.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 04:23 pm
So is Elon Musk's RLV. But regardless of that, the biggest selling point of propellant transfer is that it will accelerate development of RLVs, no matter how far along they are. And we need RLVs badly.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/03/2014 04:52 pm
So is Elon Musk's RLV. But regardless of that, the biggest selling point of propellant transfer is that it will accelerate development of RLVs, no matter how far along they are. And we need RLVs badly.

More generally, a depot that is reusable (which is little harder than a one-use depot) makes the launch market more competitive, regardless of how the launch is done. That's what matters. I think the natural outcome of that will be closing the business case for RLVs and other low-cost launch options, but the competition element is what matters--let the market fund what makes the most sense.

It also makes it international cooperation easier. Instead of say having India or Russia or China or Europe or Brazil put on the critical path for developing a hardware module for a deep space mission (in trade for flying an astronaut), they can just launch propellant on their national launcher.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 05:16 pm
Sure, if HLV proponents are right, that's what will happen. If depot proponents are right, then that's what will happen. No need to prejudge this and to second guess the market.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/03/2014 05:37 pm
Blue Origin's RLV  is better than a powerpoint.

Chris, that vehicle doesn't count and you know it. It is not an orbital LV. It is suborbital. Just because somebody has a "rocket" that can be refueled and reused over again does not make it a RLV. The context of what we're talking about here is a launch vehicle capable of inserting a payload into LEO. Come on Chris. What the heck!
Title: Re: Propellant Depots - General Discussion
Post by: Chalmer on 03/03/2014 05:45 pm
I my mind a propellant depots are the only way to go, if we ever want to get out of LEO in a sustainable matter. But the really great thing is, that even if we don't a propellant depot is still a good idea since it can have many uses.

Commercially operated depots could find many ways to attract a revenue stream; Satellite refueling, refueling of earth departure stages for both unmanned and manned exploration, refuel stages from smaller rockets to deliver satellites to GEO, or what ever use someone can imagine.

The real gem is that a depot would also be rocket agnostic. It does not matter which rocket refills it, as long as it is price competitive per liter fuel or oxidizer delivered.

I think depots in earth orbit, most likely LEO, could be a cornerstone for increased commercialization of space, and exploration of space. Bringing down costs in all energy aspects.

Buy fuel delivered in LEO for x amount of dollars, sell for y>x amount of dollars to anyone who want it, be it space agencies or private corporations. 
Title: Re: Propellant Depots - General Discussion
Post by: Lar on 03/03/2014 06:50 pm
I agree. What should X (the buy price) and Y (the sell price) be? What percentage higher than X should Y be?
Title: Re: Propellant Depots - General Discussion
Post by: Chalmer on 03/03/2014 07:03 pm
I agree. What should X (the buy price) and Y (the sell price) be? What percentage higher than X should Y be?

I don't know what prices should be. But does it matter? The market will figure it out. If it turns out to be a big market with high margins, more companies will enter and drive down prices.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/03/2014 07:35 pm
Blue Origin's RLV  is better than a powerpoint.

Chris, that vehicle doesn't count and you know it. It is not an orbital LV. It is suborbital. Just because somebody has a "rocket" that can be refueled and reused over again does not make it a RLV. The context of what we're talking about here is a launch vehicle capable of inserting a payload into LEO. Come on Chris. What the heck!

Actually, BO is working on an orbital RLV as well as their suborbital RLV. Now whether their orbital RLV should be taken seriously with Blue's slow development progress to-date is open for debate. But they were a CCDev contractor specifically because they're trying to develop a TSTO orbital RLV.

But...this is veering pretty quickly off topic for a thread on depots.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/03/2014 07:36 pm
Blue Origin's RLV  is better than a powerpoint.

Chris, that vehicle doesn't count and you know it. It is not an orbital LV. It is suborbital. Just because somebody has a "rocket" that can be refueled and reused over again does not make it a RLV. The context of what we're talking about here is a launch vehicle capable of inserting a payload into LEO. Come on Chris. What the heck!
No, their suborbital vehicle is a prelude to a reusable orbital launch vehicle. Because Blue Origin doesn't publicize as much as SpaceX, it's not as widely known, but it's certainly not a secret. In fact it's on their webpage: http://www.blueorigin.com/about/

Come on, Chuck. What the heck! ;)
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/03/2014 07:41 pm
But anyway, the point isn't that any specific company might develop whatever. (I should point out that XCOR also has intentions of a large, hydrogen-powered TSTO vehicle.) Could be Lockheed (they have/had a boost-back booster plan), Darpa's project, mass-produced expendables, Sea Dragon, Skylon, gun launch, lunar or asteroid ISRU, atmospheric orbital scooping, whatever. Exactly how it gets there is left up to competitive forces and can be decoupled from whatever the mission is. That is the depot's strength.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 07:46 pm
That is the depot's strength.

The strength of orbital refueling, not depots, the same argument applies to the depot itself. In-flight refueling at L1/L2 is the most neutral place to start, and conveniently it's the easiest too.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/03/2014 08:02 pm
It's much less strong for orbital refueling vs depots because with orbital refueling, the vehicle itself has to bear the burden of lots of rendezvous, unlike with a depot where the vehicle being refueled just fuels up a single time even if sent via beer keg sized tankers to the depot.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 08:10 pm
I don't think that makes much of a difference, if at all, because the total number of rendez-vous and docking operations remains essentially the same. Also, consider the use of tugs.
Title: Re: Propellant Depots - General Discussion
Post by: Lar on 03/03/2014 08:32 pm
I don't think that makes much of a difference, if at all, because the total number of rendez-vous and docking operations remains essentially the same. Also, consider the use of tugs.

Ya the total remains the same, just about but you move from a bunch of  non critical dockings and one critical one, to all your dockings being critical (the tankers have to loiter and if any of them fails to dock, your mission is scratched. Or else you launched more tankers than you need)

So I agree a depot is a significant difference.

I agree. What should X (the buy price) and Y (the sell price) be? What percentage higher than X should Y be?

I don't know what prices should be. But does it matter? The market will figure it out. If it turns out to be a big market with high margins, more companies will enter and drive down prices.

Well, technically it doesn't matter[1], I was curious as to what people thought.

1 - as long as you're sort of close. As with numerical integration, your initial guess can affect how long it takes to converge to the right answer... if the price for X is WAY WAY off on the low side no one will launch fuel, and if the price for Y is WAY WAY off on the high side no one will buy.

So THAT suggests a starting seed, set X really really high and set Y less than X and run at a loss. Maybe not the best seed but you will get iterations.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 08:51 pm
Ya the total remains the same, just about but you move from a bunch of  non critical dockings and one critical one, to all your dockings being critical (the tankers have to loiter and if any of them fails to dock, your mission is scratched. Or else you launched more tankers than you need)

I don't understand why that should be so. Why is it a problem if one tanker fails to dock to the spacecraft? I see no difference with the case of one tanker failing to dock with a depot.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 08:55 pm
I agree. What should X (the buy price) and Y (the sell price) be? What percentage higher than X should Y be?

I don't think NASA should be in the business of selling propellant, just buying and using it. They could buy the amount of propellant they needed for a fixed set of missions a year based on some sort of reverse auction scheme. Maybe they need 200mT a year. Say company A running a small RLV can deliver 75mT @ $1500/kg, while company B with an expendable launcher can do 300mT @ 3500/kg. Then A would get to sell 75mT at $1500/kg and B the remaining 125mt @ $3500/kg. Both parties (and new entrants) would have an incentive to reduce costs and prices in order to gain market share. Reducing costs would take investment. And if there is enough total volume, they can recoup their investment. It would make it much easier to fund R&D than is currently the case.
Title: Re: Propellant Depots - General Discussion
Post by: Lar on 03/03/2014 08:57 pm
Ya the total remains the same, just about but you move from a bunch of  non critical dockings and one critical one, to all your dockings being critical (the tankers have to loiter and if any of them fails to dock, your mission is scratched. Or else you launched more tankers than you need)

I don't understand why that should be so. Why is it a problem if one tanker fails to dock to the spacecraft? I see no difference with the case of one tanker failing to dock with a depot.

Because you don't launch the mission spacecraft until the depot has enough fuel to fill the mission spacecraft. Depotless, you wiill have to have tankers loiter, and you may want to send a spare. Or be prepared to launch a spare very quickly. Operationally far less flexible if you have a problem with a tanker. Not sure how else to make it any clearer.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 08:59 pm
Because you don't launch the mission spacecraft until the depot has enough fuel to fill the mission spacecraft. Depotless, you wiill have to have tankers loiter, and you may want to send a spare. Or be prepared to launch a spare very quickly. Operationally far less flexible if you have a problem with a tanker. Not sure how else to make it any clearer.

The spacecraft can wait for the tankers just as the depot would. No need for the tankers to loiter. I don't think it would be a problem even if they had to, but they don't. This is basically what happens at the ISS, only at L1/L2.
Title: Re: Propellant Depots - General Discussion
Post by: Lar on 03/03/2014 09:00 pm
Because you don't launch the mission spacecraft until the depot has enough fuel to fill the mission spacecraft. Depotless, you wiill have to have tankers loiter, and you may want to send a spare. Or be prepared to launch a spare very quickly. Operationally far less flexible if you have a problem with a tanker. Not sure how else to make it any clearer.

The spacecraft can wait for the tankers just as the depot would. No need for the tankers to loiter. I don't think it would be a problem even if they had to, but they don't.

You're going to have a manned[1] mission use consumables while it waits around for tankers to launch and possibly for a spare to launch too because one blew up on the way up? I think that misses the point.

1 - the architecture needs to work for manned missions as well as unmanned
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 09:02 pm
You're going to have a manned mission use consumables while it waits? I think that misses the point.

I wouldn't send the crew until after the spacecraft was ready to depart. Not very different from with a depot, where you wouldn't send the crew until the depot was full. The difference is that you wouldn't simultaneously launch the spacecraft. But I'm imagining the spacecraft is too big to fit on an EELV, reusable and in-space only anyway.
Title: Re: Propellant Depots - General Discussion
Post by: Lar on 03/03/2014 09:08 pm
You're going to have a manned mission use consumables while it waits? I think that misses the point.

I wouldn't send the crew until after the spacecraft was ready to depart. Not very different from with a depot, where you wouldn't send the crew until the depot was full. The difference is that you wouldn't simultaneously launch the spacecraft. But I'm imagining the spacecraft is too big to fit on an EELV, reusable and in-space only anyway.

Your tanker only architecture has more constraints than a depot architecture. That seems clear to me. If it doesn't to you? OK. Enough said on this (by me) because continued back and forth seems counterproductive.  Perhaps someone else will have a different perspective, I made the point I wanted to make.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 09:18 pm
Your tanker only architecture has more constraints than a depot architecture. That seems clear to me. If it doesn't to you? OK. Enough said on this.

I was hoping for constructive dialogue, not for you to unilaterally declare the discussion over. Feel free not to participate if you don't want to.

Contrary to your assertion there are no more constraints than with a depot architecture, and the total system of systems will be less complicated than with a depot. Less capable too of course, but it's a good place to start. Every addition will have to pay for itself, and there is no more reason to give depots a free pass than to give HLVs (or RLVs) a free pass.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/03/2014 09:55 pm
A depot can contain an arm, extensive insulation or even active refrigeration, or other things which would significantly increase the mass of a refuelable in-space stage. Also, a depot could be filled up in LEO and tug itself to high energy orbit, providing a big bulk amount of fuel. This increases the efficiency of the operation signficantly since especially for RLVs (but also large inexpensive launch vehicles) you want to launch to as low of an orbit as possible otherwise you eat into your propellant delivered in a non-linear fashion. A depot makes this more feasible. Heck, you could fill up a depot in LEO and put it in orbit around Mars or in low lunar orbit (or vice versa, picking up lunar propellant in LLO, transporting it to LEO or GTO or EML2 via much higher Isp propulsion, greatly improving the bang for the buck of lunar ISRU).
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/03/2014 10:00 pm
A depot provides flexibility that just refueling in orbit alone doesn't provide. I don't know for sure what the cheapest way to get propellant into orbit will be in the future, but providing a place where you can buy it without having to worry about how it got there is a pretty powerful capability.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 10:15 pm
A depot provides flexibility that just refueling in orbit alone doesn't provide.

Sure, but the same goes for RLVs, HLVs, SEP tugs, ISRU etc etc. Eventually we may want all of that, but it's going to take a lot of money we are going to have to prioritise and to allocate our resources wisely. All I'm saying is that in-flight refueling at L1/L2 is about the minimum we need, and we could do that straight away. I'm also arguing it's important we should do it straight away. And then the allocation could be left to the market, which seems optimal to me.

I think it is inconsistent to argue that the market should decide what type of launch vehicle is optimal but to insist we should have a depot, and to determine where we should put it and what type of propellant it should use. There may be good reasons to have different policies for launch vehicles than for orbital infrastructure, and to decide not to impose a launch vehicle while insisting on a depot, but so far I haven't heard any. All I'm hearing is that depots have additional qualities. That is true enough, but it's also true for all the other pieces of infrastructure I mentioned, where you would let the market decide, so it still seems inconsistent.

Quote
I don't know for sure what the cheapest way to get propellant into orbit will be in the future, but providing a place where you can buy it without having to worry about how it got there is a pretty powerful capability.

But that capability is already provided by in-flight refueling. And if you impose only in-flight refueling at a Lagrange point and leave all other variables free, then you leave even more room for optimisation by the market. Depending on the traffic, it could well be that you would want a LEO depot to accept spacecraft propellant from small RLVs and use SEP tugs to take it to L1/L2. If so, a consortium of companies should be able to come up with a business plan for the RLV + depot + SEP tug and include development costs in its price/kg for delivery of spacecraft propellant to L1/L2. Maybe the case for it is compelling enough for commercial players to do so straight away at 200mT of total traffic a year. Or maybe it doesn't make economic sense until after we have 1000mT a year. Who knows? Let the market sort it out.

Again, I'm eager to hear specific suggestions as to why a depot should not be subject to the same market-driven logic as launch vehicles.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/03/2014 11:05 pm
You're basically assuming that 100 dockings for an upper stage is no more difficult than 1 docking.
Title: Re: Propellant Depots - General Discussion
Post by: mmeijeri on 03/03/2014 11:08 pm
You're basically assuming that 100 dockings for an upper stage is no more difficult than 1 docking.

Huh? How am I doing that? I'm talking about in-flight refueling of spacecraft, not upper stages.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 03/04/2014 03:37 am
Martijn is emphasizing again the point he's made numerous times, generalizing from "lander" to "spacecraft." But it is easier to understand when he sticks with "lander."

I'm going to try to channel him! ;)

First, put a dry lander at a rendezvous point. Then send any number of tankers to fuel her up. Then send the crew to rendezvous, board the lander, and voyage to her mission destination.

See how no "depot" was necessary because the lander is the depot?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/04/2014 04:34 am
Martijn is emphasizing again the point he's made numerous times, generalizing from "lander" to "spacecraft." But it is easier to understand when he sticks with "lander."

I'm going to try to channel him! ;)

First, put a dry lander at a rendezvous point. Then send any number of tankers to fuel her up. Then send the crew to rendezvous, board the lander, and voyage to her mission destination.

See how no "depot" was necessary because the lander is the depot?

Yeah, but now either your lander or your tankers have to have all the prox-ops hardware on them, both of which are really inefficient. The lander still needs all the capabilities of a depot--long-term storage, prox-ops/docking, and propellant transfer. But instead of leaving it in orbit and using it a bunch of times, you're now going to do maneuvers with it and haul all that extra dry mass around. Seems a bit silly to me.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Roy_H on 03/06/2014 02:43 pm
You're basically assuming that 100 dockings for an upper stage is no more difficult than 1 docking.

Seems like a reasonable assumption to me.
Title: Re: Propellant Depots - General Discussion
Post by: mfck on 03/13/2014 09:28 am
MIT has given some love to the depot idea
http://web.mit.edu/newsoffice/2014/galactic-gas-stations-0305.html
Title: Re: Propellant Depots - General Discussion
Post by: darkbluenine on 03/13/2014 05:53 pm
Opinion on FY15 budget termination of CPSTE flight:

Quote
The second program going nowhere fast is the Cryogenic Propellant Storage and Transfer Experiment, which according to the budget justification has been downgraded from a sub-scale orbital demonstration to ground level demonstrations in support of SLS. For proponents of economically sustainable space exploration, this change may be particularly disheartening.

Arguably, there is no greater enabling technology to be achieved with less overall investment than cryogenic propellant storage and transfer.  While we currently have the ability to conduct long term deep space missions using storable hypergolic propellants, their relatively low performance is a critical limiting factor in both robotic and crewed space missions.   Developing and demonstrating the ability store high performance cryogenic propellants in space for long periods of time without significant boil-off is nothing less than a necessity for long term exploration.  Taken together with the closely related challenge of transferring cryogenic propellants from one container to another in zero-g, as well as accurately measuring the amount of fluid in a storage vessel, the net result is leveraging effect with stunning capacity.  In fact, as the Augustine commission determined, 

“In the absence of in-space refueling, the U.S. human spaceflight program will require a heavy-lift launcher of significantly greater than 25 mt capability to launch the EDS and its fuel. However the picture changes significantly if in-space refueling is used.” Furthermore “Studies commissioned by the Committee found that in-space refueling could increase by at least two to three times the injection capability from low-Earth orbit of a launcher system, and in some cases more. Thus, an in-space refueling capability would make larger super-heavy lift vehicles even more capable, and would enable smaller ones to inject from low-Earth orbit a mass comparable to what larger launchers can do without in space refueling.”

For a nation and an agency serious about exploring space, it is difficult to think of a single justifiable reason why proceeding with an orbital demonstration of this enabling technology should not be a priority. It is very easy to come up with an unjustifiable reason however.  It represents a viable alternative to SLS. 

NASA, driven by Congress, studiously ignored Augustine’s findings when formulating plans for the Space Launch System, and as other websites have established, effectively buried internal studies showing that propellant deports offer a lower cost alternative on a much quicker time frame.   With a planned sub-scale flight demonstration now off the table, supporters of the “mega booster” will continue to be able to point to the absence of an actual demonstration of cryogenic transfer and storage as the circular justification for pressing on.

http://innerspace.net/nasa/detailed-nasa-budget-bad-news-for-europa-propellant-depot-advocates/

FWIW...
Title: Re: Propellant Depots - General Discussion
Post by: Robert Thompson on 03/16/2014 09:28 am
What could Elon have accomplished if he was driven by a vision of prop depots?
Title: Re: Propellant Depots - General Discussion
Post by: redliox on 03/16/2014 09:58 am
It's good to see support for depots in space, but shouldn't the focus first be on getting the gas versus the gas station?  Then again, of course, setting up the infrastructure for ISRU and exporting it (from Moon or Mars) would take as much time as the numerous flights to fill the depot up with leftover fuel.

Useful, but it might be a while yet.  I tend to favor a straighter approach ala Mars Direct thinking since less infrastructure is needed.

If the depot's design were kept simple, it might more appealing to budget-wary Congress and administrators.  Skylab II is already based on the principle of using SLS' hydrogen tank as a module; keep it as a propellant tank but give it the necessary thrusters and shielding and means to be a mini-station.  Perhaps something like a sunshade added, but no multiple modules or 'tankers'.  Just the deport with a port on each end optimized for craft to visit for a day or 2 and depart with the needed fuel.  Keep it a gas station, not a hotel.

Furthermore, place it at L4 or L5 instead of L1 or L2, those are larger and stable points that would lower the station keeping needs.  How large a difference in delta-V is needed to push a depot to L4/5 versus L1/2?
Title: Re: Propellant Depots - General Discussion
Post by: rklaehn on 03/16/2014 10:00 am
What could Elon have accomplished if he was driven by a vision of prop depots?

I think he will come around to the idea eventually, just like he came around to powered vertical landing after trying parachute recovery for a while. But there might be an opportunity for another company. Not everything can and should be done by SpaceX.
Title: Re: Propellant Depots - General Discussion
Post by: rklaehn on 03/16/2014 10:12 am
It's good to see support for depots in space, but shouldn't the focus first be on getting the gas versus the gas station?  Then again, of course, setting up the infrastructure for ISRU and exporting it (from Moon or Mars) would take as much time as the numerous flights to fill the depot up with leftover fuel.

A propellant depot has huge advantages even without ISRU. It creates a market for propellant in space. It significantly reduces the barrier of entry for new launch vehicles. It allows internaltional cooperation without being dependent on international partners for mission critical parts, etc. But it seems that politics will prevent NASA from doing anything even remotely relevant for space exploration.

Quote
Furthermore, place it at L4 or L5 instead of L1 or L2, those are larger and stable points that would lower the station keeping needs.  How large a difference in delta-V is needed to push a depot to L4/5 versus L1/2?

EML2 is the best staging point for beyond earth orbit exploration. For getting beyond earth orbit with chemical propulsion from a staging point close to C3=0, you need to be able to quickly and cheaply (in terms of delta-v) get back to a highly elliptic orbit for using the Oberth effect. That is not as easy from L4/5 than from L1/2.

The stationkeeping costs are not a problem for a propellant depot where you have a constant supply of propellant to tap into. In fact, you can probably do the station keeping with just the boiloff.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/18/2014 01:31 am
What could Elon have accomplished if he was driven by a vision of prop depots?

Who knows. Personally, I think it's a good thing to have a healthy industry with multiple players approaching problems from multiple directions. Elon shouldn't be expected to solve all problems, and an industry with only one player carrying it is not a healthy industry. It would be nice if we had an "Elon Musk Equivalent" going after depots, in parallel with the actual Elon going after low-cost launch.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: redliox on 03/18/2014 08:10 am
An illustrated scheme pointing out places in CisLunar space.  The various propellant depot locations were what caught my attention and in turn why I thought to post it here.  EML2 seems to be the official favorite nowadays, but only for outbound, BEO missions.  Just as hypothetically, it could be placed closer to Earth in GEO or LEO if you want to apply propellants to all missions.
Title: Re: Propellant Depots - General Discussion
Post by: Lar on 03/18/2014 12:23 pm
An illustrated scheme pointing out places in CisLunar space.  The various propellant depot locations were what caught my attention and in turn why I thought to post it here.  EML2 seems to be the official favorite nowadays, but only for outbound, BEO missions.  Just as hypothetically, it could be placed closer to Earth in GEO or LEO if you want to apply propellants to all missions.
Interesting diagram! What's the provenance? It has that 1970's look to it, a mix of computer printed text and hand drawn components...
Title: Re: Propellant Depots - General Discussion
Post by: RanulfC on 03/18/2014 12:45 pm
An illustrated scheme pointing out places in CisLunar space.  The various propellant depot locations were what caught my attention and in turn why I thought to post it here.  EML2 seems to be the official favorite nowadays, but only for outbound, BEO missions.  Just as hypothetically, it could be placed closer to Earth in GEO or LEO if you want to apply propellants to all missions.
Interesting diagram! What's the provenance? It has that 1970's look to it, a mix of computer printed text and hand drawn components...

"High Frontier" or one of those I'm guessing given the subject material :)

Randy
Title: Re: Propellant Depots - General Discussion
Post by: muomega0 on 03/18/2014 01:03 pm
Good summary graphic on depots and their purpose. 

The stationkeeping costs are not a problem for a propellant depot where you have a constant supply of propellant to tap into. In fact, you can probably do the station keeping with just the boiloff.
Tons of propellant each year is not a problem?!

With LH2 zero boiloff, the station keeping costs can also be kept to zero, using power rather than propellant.

Station keeping will dwarf reboost in LEO and is a tremendous waste of resource.  ULA estimates tons of boiloff for station keeping per year. (http://forum.nasaspaceflight.com/index.php?topic=29757.msg958757#msg958757)

Add the power and the refrigerators.  With power use attitude control based on rotating devices (reaction wheels, cmgs...)  and reduce the station keeping to zero.

Boiloff must be burned continuously, as it expands 851 times and cannot be stored, so the option of reboost after filling tanks, allowing a lower altitude to maximize IMLEO, is not an option  (hence the reason to start with a LEO depot and not an L2 depot).   The L1 depot and single mission DRMs are proposed only to lock out the smaller fleet and justify a HLV- 5th figure in article (http://www.nasaspaceflight.com/2011/12/exploration-gateway-platform-hosting-reusable-lunar-lander-proposed/)

EML2 is the best staging point for beyond earth orbit exploration.
L2 is the the best staging location for cis-lunar space (http://forum.nasaspaceflight.com/index.php?topic=1337.msg1114315#msg1114315).
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/19/2014 10:47 pm
What could Elon have accomplished if he was driven by a vision of prop depots?

Who knows. Personally, I think it's a good thing to have a healthy industry with multiple players approaching problems from multiple directions. Elon shouldn't be expected to solve all problems, and an industry with only one player carrying it is not a healthy industry. It would be nice if we had an "Elon Musk Equivalent" going after depots, in parallel with the actual Elon going after low-cost launch.

~Jon

Perhaps (hoping) there is someone like Bigelow who just needs a ride upstairs who is interested in propellant depots and has the money to give it a shot, so long as the ride is affordable. SpaceX may be that ride.
Title: Re: Propellant Depots - General Discussion
Post by: KelvinZero on 03/20/2014 09:23 am
What could Elon have accomplished if he was driven by a vision of prop depots?

Who knows. Personally, I think it's a good thing to have a healthy industry with multiple players approaching problems from multiple directions. Elon shouldn't be expected to solve all problems, and an industry with only one player carrying it is not a healthy industry. It would be nice if we had an "Elon Musk Equivalent" going after depots, in parallel with the actual Elon going after low-cost launch.

~Jon

Perhaps (hoping) there is someone like Bigelow who just needs a ride upstairs who is interested in propellant depots and has the money to give it a shot, so long as the ride is affordable. SpaceX may be that ride.

Since great minds think alike, I expect he already has seen the same advantages we have but just doesn't want to give ULA any free endorsements. :)

I would really like to see ULA (or related body) doing a bit of speculative investment in this technology on their own initiative as spaceX has done towards developing reusable stages.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/20/2014 11:34 pm

Perhaps (hoping) there is someone like Bigelow who just needs a ride upstairs who is interested in propellant depots and has the money to give it a shot, so long as the ride is affordable. SpaceX may be that ride.

Bigelow will not be able to afford to use an SLS for routine supply missions so he will need a space tug between LEO and his EML-1/2 spacestation.  A reusable tug can be refuelled at the LEO propellant depot.
Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/22/2014 08:08 pm
It never even occurred to me that Bigelow might seek a ride on the SLS.
SLS will likely be far too expensive for him or any other similar commercial operator to afford.
Title: Re: Propellant Depots - General Discussion
Post by: rklaehn on 03/22/2014 08:59 pm
Good summary graphic on depots and their purpose. 

The stationkeeping costs are not a problem for a propellant depot where you have a constant supply of propellant to tap into. In fact, you can probably do the station keeping with just the boiloff.
Tons of propellant each year is not a problem?!

Station keeping cost can be very low. In this presentation (http://spirit.as.utexas.edu/~fiso/telecon/Folta_2-23-11/Folta_2-23-11.pdf) they give "~9 m/s based on routine weekly maneuvers" for EML1 stationkeeping. (This is not exactly at EML1, but some halo orbit. But there is no particular advantage for a propellant depot to be exactly at a lagrange point)

That gives less than 0.5% propellant loss per year for station keeping. I would say that this is completely acceptable. Even if you use the propellant only once every mars synodic period, you have less than 1% propellant loss.

And that is with impulsive station keeping maneuvers every week. If you use continuous thrust you could reduce this even further, so that a small amount of xenon for electric propulsion will be enough for the lifetime of the depot.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/22/2014 11:36 pm
The builder of a Moon Base could use propellant depots.  The Moon buildings will weigh something like 20 tonnes.  So transporting them from the Earth to the Moon would be something like:

EELV to launch building and nearly dry inspace propulsion stage Earth surface to LEO depot.
Fuel inspace propulsion stage.
Fly inspace stage and building to Low Lunar orbit depot.
Refuel inspace stage.
Land building and inspace stage on the Moon's surface.
Title: Re: Propellant Depots - General Discussion
Post by: Robert Thompson on 03/23/2014 01:35 am
This is not exactly at EML1, but some halo orbit. But there is no particular advantage for a propellant depot to be exactly at a lagrange point.

I haven't yet heard the pros and cons of halo orbits versus the point itself, regardless EML1 or 2. My naive assumption is that station keeping parallel to the EM line will be the same dV whether you're on the point or doing a halo orbit. I would also imagine that just because the halo orbit gives you velocity in a plane, the fact that it is perpendicular to the EM line means you have a steep plane change anyway. Is there any savings in dV from either the point or the halo orbit? Reminds me of the gossamer interplanetary highway calculations.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 03/23/2014 04:29 am
It's probably going to be important for propellant depot operators in the vicinity of EML1 or EML2 to define their "station keeping" policy carefully. I believe the orbital dynamics make "holding" at the exact Lagrange point less than optimal.[1] But the so-called "orbits" around Lagrange points don't have the same characteristics as orbits around gravitational bodies. One example: they are not in general planar. Another example: not all trajectories that remain within the vicinity of a Lagrange point are repeating trajectories.

Yet there's nothing intrinsically wrong with having a depot on e.g. a non-repeating Lissajous trajectory. What's important is that the trajectory must provide frequent, similar rendezvous opportunities.[2] Linked to that importance of rendezvous is the importance of navigation, which in an L-point vicinity requires precise knowledge of position and velocity.

As Folta describes in the paper linked above, they used the DSN extensively to get 100 m and 0.1 cm/s accuracy. Wow! They also kept their maneuver execution errors (both performance and pointing) around 1-2%. Again: wow! (Could they do that solely by virtue of ion thrusters?)

I suggest that although a science mission like theirs was an excellent use of the DSN resource, depots used for exploration missions will need to get their precise navigation assistance elsewhere. Is anyone aware of work being done on that? Would/could laser-based navigation tools be used?

--

[1] The Lagrange points themselves are in equilibrium, but not stable. Orbits around the L-points though can/do have both stable and unstable "manifolds." That means that some (but not all) slightly deviating trajectories actually lead back onto the target orbit without requiring any propulsion whatsoever!

[2] The need for regular and similar rendezvous opportunities is for mission planning. If a mission e.g. misses a launch window, there "needs" to be another opportunity "soon" to do the same thing. That's semi-evident for rendezvous after launching from Earth; potentially life-critical if the rendezvous is after a launch e.g. from the lunar surface.

--

Caveat: all this of course is my humble opinion, and only to the best of my knowledge. Reality may vary.
Title: Re: Propellant Depots - General Discussion
Post by: Proponent on 03/23/2014 12:18 pm
I haven't yet heard the pros and cons of halo orbits versus the point itself, regardless EML1 or 2

At L2, an advantage of a sufficiently large halo orbit is remaining in line-of-sight contact with earth.
Title: Re: Propellant Depots - General Discussion
Post by: muomega0 on 03/23/2014 12:48 pm
It's probably going to be important for propellant depot operators in the vicinity of EML1 or EML2 to define their "station keeping" policy carefully.
Caveat: all this of course is my humble opinion, and only to the best of my knowledge. Reality may vary.
Physics, not your opinion, suggest many cheap solutions unless a "policy" is put in place.  It all starts with LEO depot.

The SLS/Orion programs are so badly thought out that they no longer deserve any attention--it is time to move on. (http://forum.nasaspaceflight.com/index.php?topic=34177.msg1172615#msg1172615) Unless of course, congress keeps the two gifts that keep on giving. ;D
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/23/2014 07:04 pm
{snip}
Yet there's nothing intrinsically wrong with having a depot on e.g. a non-repeating Lissajous trajectory. What's important is that the trajectory must provide frequent, similar rendezvous opportunities.[2] Linked to that importance of rendezvous is the importance of navigation, which in an L-point vicinity requires precise knowledge of position and velocity.

As Folta et al. describe in the paper linked above, they used the DSN extensively to get 100 m and 0.1 cm/s accuracy. Wow! They also kept their maneuver execution errors (both performance and pointing) around 1-2%. Again: wow! (Could they do that solely by virtue of ion thrusters?)

I suggest that although a science mission like theirs was an excellent use of the DSN resource, depots used for exploration missions will need to get their precise navigation assistance elsewhere. Is anyone aware of work being done on that? Would/could laser-based navigation tools be used?
{snip}

By its very nature a depot is a large item.  There is plenty of room to give it the same navigation avionics as a manned spacecraft or possibly a rover or lander.  Being a spacestation the depot can also be fitted with transmitters, aerials, accurate clocks and mirrors to simplify flying to it.
Title: Re: Propellant Depots - General Discussion
Post by: rklaehn on 03/23/2014 08:36 pm
This is not exactly at EML1, but some halo orbit. But there is no particular advantage for a propellant depot to be exactly at a lagrange point.

I haven't yet heard the pros and cons of halo orbits versus the point itself, regardless EML1 or 2. My naive assumption is that station keeping parallel to the EM line will be the same dV whether you're on the point or doing a halo orbit. I would also imagine that just because the halo orbit gives you velocity in a plane, the fact that it is perpendicular to the EM line means you have a steep plane change anyway. Is there any savings in dV from either the point or the halo orbit? Reminds me of the gossamer interplanetary highway calculations.

I think a halo orbit offers lower stationkeeping cost and lower rendezvous and departure delta-v, but it adds a (soft) scheduling constraint to rendezvous and departure.

Does anybody know if continuous thrust would significantly reduce the stationkeeping delta-v requirements? It seems intuitive that this would be the case.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 03/24/2014 02:53 am
Here's another paper by Folta (and others) about the ARTEMIS mission, with lots of info on station keeping:
http://www.aerospace.ubi.pt/workshop2012/Folta.pdf

The attached image is taken from the paper, and shows achieved results for the two spacecraft. Note in particular that P2 remained in orbit at L1 for 233 days, and annualized the propulsion required came to 5.09 m/s per year. Even the worst value reported (for P1 at L2) was only 7.39 m/s per year.
Title: Re: Propellant Depots - General Discussion
Post by: Hop_David on 03/24/2014 03:37 pm
Blue Origin's RLV  is better than a powerpoint.

Chris, that vehicle doesn't count and you know it. It is not an orbital LV. It is suborbital. Just because somebody has a "rocket" that can be refueled and reused over again does not make it a RLV. The context of what we're talking about here is a launch vehicle capable of inserting a payload into LEO. Come on Chris. What the heck!
No, their suborbital vehicle is a prelude to a reusable orbital launch vehicle. Because Blue Origin doesn't publicize as much as SpaceX, it's not as widely known, but it's certainly not a secret. In fact it's on their webpage: http://www.blueorigin.com/about/

Come on, Chuck. What the heck! ;)

Yeah, come on! From suborbital to orbital RLV is just a hop and a skip.

Robotbeat, this is furious handwaving.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/24/2014 04:03 pm
Blue Origin's RLV  is better than a powerpoint.

Chris, that vehicle doesn't count and you know it. It is not an orbital LV. It is suborbital. Just because somebody has a "rocket" that can be refueled and reused over again does not make it a RLV. The context of what we're talking about here is a launch vehicle capable of inserting a payload into LEO. Come on Chris. What the heck!
No, their suborbital vehicle is a prelude to a reusable orbital launch vehicle. Because Blue Origin doesn't publicize as much as SpaceX, it's not as widely known, but it's certainly not a secret. In fact it's on their webpage: http://www.blueorigin.com/about/

Come on, Chuck. What the heck! ;)

Yeah, come on! From suborbital to orbital RLV is just a hop and a skip.

Robotbeat, this is furious handwaving.
Furious handwaving??

Chuck clearly wasn't aware that Blue Origin was working on this.

You don't need a hydrogen engine for suborbital. If Blue Origin only cared primarily about suborbital, no way they'd spend the resources to develop a new hydrogen rocket engine.
Title: Re: Propellant Depots - General Discussion
Post by: Hop_David on 03/24/2014 06:01 pm
Yeah, come on! From suborbital to orbital RLV is just a hop and a skip.

Robotbeat, this is furious handwaving.
Furious handwaving??

Chuck clearly wasn't aware that Blue Origin was working on this.

"Working on this" -- Okay. That is much better than Powerpoint.

I'll say it again: furious handwaving.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/26/2014 10:13 pm
Yeah, come on! From suborbital to orbital RLV is just a hop and a skip.

Robotbeat, this is furious handwaving.
Furious handwaving??

Chuck clearly wasn't aware that Blue Origin was working on this.

"Working on this" -- Okay. That is much better than Powerpoint.

I'll say it again: furious handwaving.
Handwaving over what? I'm saying Blue Origin is working towards orbital applications, and their progress is greater than mere powerpoint. They've developed a liquid hydrogen rocket engine (which is unnecessary for suborbital applications). Are you claiming their BE-3 hydrogen engine is powerpoint or are you claiming it isn't planned for orbital use?

https://www.youtube.com/watch?v=T5Xbhw8M5rU
I quote: "Blue Origin's Orbital Launch Vehicle will use the BE-3 engine to launch the company's Space Vehicle into orbit to transport crew and cargo to low-Earth orbit."
Title: Re: Propellant Depots - General Discussion
Post by: Hop_David on 03/27/2014 04:52 pm
Are you claiming their BE-3 hydrogen engine is powerpoint or are you claiming it isn't planned for orbital use?

Ummm.... Neither. You've dropped important context: RLV.

Or are you claiming "orbital use" = "RLV"?

Suborbital RLV is possible. Spaceship 1 demonstrated that awhile back. But orbital RLV is a different story. So far that sort of vehicle is Powerpoint.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/27/2014 07:23 pm
Are you claiming their BE-3 hydrogen engine is powerpoint or are you claiming it isn't planned for orbital use?

Ummm.... Neither. You've dropped important context: RLV.

Or are you claiming "orbital use" = "RLV"?

Suborbital RLV is possible. Spaceship 1 demonstrated that awhile back. But orbital RLV is a different story. So far that sort of vehicle is Powerpoint.

Hop, they actually have talked specifically about developing an orbital RLV, and are actively working towards it. I don't have as high of confidence in their team as SpaceX's team, but it is an active goal that they are working towards at least according to the limited amount we know about BO.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Lar on 03/27/2014 07:57 pm
Suborbital RLV is possible. Spaceship 1 demonstrated that awhile back. But orbital RLV is a different story. So far that sort of vehicle is Powerpoint.

Somebody better tell SpaceX that!

Also, this may be wandering a bit far afield of the thread topic.
Title: Re: Propellant Depots - General Discussion
Post by: Hop_David on 03/27/2014 09:13 pm
Suborbital RLV is possible. Spaceship 1 demonstrated that awhile back. But orbital RLV is a different story. So far that sort of vehicle is Powerpoint.

Somebody better tell SpaceX that!

Same goes for SpaceX. They have a chance to achieve a Grasshopper booster RLV. But that's suborbital.

But a reusable upper stage? With an 8 km/s delta V budget and enduring a an 8 km/s re-entry?

I would put that in the same category as Musk's plans for an 80,000 person Mars colony (http://www.wired.com/wiredscience/2012/11/elon-musk-mars-colony/). Definitely Powerpoint.



Also, this may be wandering a bit far afield of the thread topic.

In my opinion orbital RLVs are relevant to propellant depots.

An economical RLV with an Mf of 90% that can endure a full 8 km/s re-entry is not doable in my opinion.

However, if the upper stage were able to shed some velocity with reaction mass, it would not have to endure the full brunt of an 8 kms re-entry. But this would require propellant depots.





Title: Re: Propellant Depots - General Discussion
Post by: clongton on 03/27/2014 09:18 pm
An economical RLV with an Mf of 90% that can endure a full 8 km/s re-entry is not doable in my opinion.

Sure it is. Dragon and Soyuz do it all the time. Granted they are different vehicles but still, the principle is the same.
Proper shielding, good avionics and a place to land.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/28/2014 12:11 am
But a reusable upper stage? With an 8 km/s delta V budget and enduring a an 8 km/s re-entry?

Definitely Powerpoint.

I think I may have found a good way of making this particularly problem tons easier...but it's only a bit past powerpoint (still pretty low TRL).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/28/2014 12:13 am
An economical RLV with an Mf of 90% that can endure a full 8 km/s re-entry is not doable in my opinion.

Sure it is. Dragon and Soyuz do it all the time. Granted they are different vehicles but still, the principle is the same.
Proper shielding, good avionics and a place to land.

I think his point was the return from orbit with a stage that has a 90% propellant mass fraction (or looking at it the other way, 10% dry fraction). That *is* hard. But I'm starting to think a lot more doable. Maybe. :-)

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/28/2014 12:50 am
If you have at least two stages and hydrogen Isp for the upper stage, 90% mf isn't essential for developing an orbital RLV.

I think people over-estimate the technical "impossibility" of an orbital RLV. It's unquestionably possible. Whether it's worth it economically is certainly NOT a settled point, however. It may very well be that FULL reuse will remain impractical even if/when SpaceX and Blue Origin build their mostly-reusable orbital launch vehicles (SpaceX is far closer, obviously). However, I think propellant markets would tilt the table towards eventual full reuse.

Also, a reusable first stage is suborbital, so the distinction between suborbital and orbital for the vast majority of the launch vehicle (the first stage) isn't as great.
Title: Re: Propellant Depots - General Discussion
Post by: Hop_David on 03/28/2014 01:50 am
An economical RLV with an Mf of 90% that can endure a full 8 km/s re-entry is not doable in my opinion.

Sure it is. Dragon and Soyuz do it all the time.

As did the Apollo capsules decades ago. Are these upper stages? No.

These are payloads for the upper stage, not the upper stage. Their delta V budget is what it takes to lower perigee into the upper atmosphere and let aerobraking kick in. Their delta V budget is far short of 8 km/s. Their propellant mass fraction doesn't have to be anywhere near 90%.

Title: Re: Propellant Depots - General Discussion
Post by: a_langwich on 03/28/2014 02:11 am
An economical RLV with an Mf of 90% that can endure a full 8 km/s re-entry is not doable in my opinion.

Sure it is. Dragon and Soyuz do it all the time. Granted they are different vehicles but still, the principle is the same.
Proper shielding, good avionics and a place to land.

Could you work that 90% mass fraction number again for Dragon and Soyuz?  I'm getting a different number.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/28/2014 03:38 am
These are payloads for the upper stage, not the upper stage. Their delta V budget is what it takes to lower perigee into the upper atmosphere and let aerobraking kick in. Their delta V budget is far short of 8 km/s. Their propellant mass fraction doesn't have to be anywhere near 90%.

A typical upper stage (at least for LEO) tends to have far less than 8km/s of delta-V capability as well. The total delta-V including gravity losses and air drag losses is typically well under 10km/s and sometimes under 9km/s for dense propellants. A decent two-stage system typically has a first stage that knocks out most of the gravity/drag losses and stages with around 2-3km/s of downrange speed (plus whatever fraction of earth's eastward rotation you got from your launch site. Meaning that your upper stage is probably only needing to deliver 6ish km/s of delta-V, which is a lot more doable, even if your reentry system is heavy. And it may not necessarily be the case that the entry system has to be heavy...

But while I think RLVs can be germane to depot logistics, I think RLV feasibility, or enabling RLVs using orbital depots (silly idea IMO) probably belong in different threads.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Hop_David on 03/28/2014 01:59 pm
But while I think RLVs can be germane to depot logistics, I think RLV feasibility, or enabling RLVs using orbital depots (silly idea IMO) probably belong in different threads.

~Jon

Okay. I've responded in another thread (http://forum.nasaspaceflight.com/index.php?topic=30610.30).
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 03/28/2014 02:22 pm
These are payloads for the upper stage, not the upper stage. Their delta V budget is what it takes to lower perigee into the upper atmosphere and let aerobraking kick in. Their delta V budget is far short of 8 km/s. Their propellant mass fraction doesn't have to be anywhere near 90%.

A typical upper stage (at least for LEO) tends to have far less than 8km/s of delta-V capability as well. The total delta-V including gravity losses and air drag losses is typically well under 10km/s and sometimes under 9km/s for dense propellants. A decent two-stage system typically has a first stage that knocks out most of the gravity/drag losses and stages with around 2-3km/s of downrange speed (plus whatever fraction of earth's eastward rotation you got from your launch site. Meaning that your upper stage is probably only needing to deliver 6ish km/s of delta-V, which is a lot more doable, even if your reentry system is heavy. And it may not necessarily be the case that the entry system has to be heavy...

But while I think RLVs can be germane to depot logistics, I think RLV feasibility, or enabling RLVs using orbital depots (silly idea IMO) probably belong in different threads.

~Jon
Orbital depots enable /any/ kind of low cost access to space, commoditizing space launch. That's their greatest advantage, IMO.
Title: Re: Propellant Depots - General Discussion
Post by: Robert Thompson on 03/30/2014 02:04 am
RLV feasibility, or enabling RLVs using orbital depots (silly idea IMO)

A distant infrastructure of many tail numbers: A refueled fleet RLV could change plane and land at a different spaceport, integrate with a different fleet reusable upper stage. Conceivable as soon as 2040. 2045.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/30/2014 02:50 am
RLV feasibility, or enabling RLVs using orbital depots (silly idea IMO)

A distant infrastructure of many tail numbers: A refueled fleet RLV could change plane and land at a different spaceport, integrate with a different fleet reusable upper stage. Conceivable as soon as 2040. 2045.

Ok, using a refueling to enable a plane change might make some sense, but so long as your landing site's inclination is equal to or less than the inclination of the depot, you could just wait for a bit and do the landing...

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 03/31/2014 07:13 pm
...

Jon Goff: "I think I may have found a good way of making this particularly problem tons easier...but it's only a bit past powerpoint (still pretty low TRL)."

Fermat: ""I have a proof of this theorem, but there is not enough space in this margin"

 ;)

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/31/2014 08:28 pm
...

Jon Goff: "I think I may have found a good way of making this particularly problem tons easier...but it's only a bit past powerpoint (still pretty low TRL)."

Fermat: ""I have a proof of this theorem, but there is not enough space in this margin"

 ;)

Sorry for being a tease, it's just a potentially big idea and I'd like to make sure the IP is protected before publicly discussing it--winning arguments on the internet is fun but doesn't pay the bills...

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: JasonAW3 on 03/31/2014 08:44 pm
Ok, assuming we CAN scoop from NEO asteroids,

How good of a Heat Sink would gathered reolith from various asteriods be, in regards to possible cryogenic fuel storage.  Assuming a padded heat transfer blanket against the holding tank, a layer of fine regolith, a layer of courser regolith mixed in with fine regolith to fill in spaces,with an outer layer of mixed course, medium and fine regolith, covered with a reflective blanket both holding in the layers of regolith, and holding the heat distribution piping to dispose of the heat from within, via a heat dissapation panel in the shadow of the propellant depot.

     I figure the gathering and disposition of the various layers of regolith could asily be done either robotically or through teleoperations.

By minimizing human interaction as much as possible during the early stages, you minimize the risk to Human life.  Mind you, this MIGHT be a good idea for a long term fuel depot, but for short term, unless there is enough traffic to warrent such a change over, the current designs seem the best.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/31/2014 10:09 pm
Ok, assuming we CAN scoop from NEO asteroids,

How good of a Heat Sink would gathered reolith from various asteriods be, in regards to possible cryogenic fuel storage.  Assuming a padded heat transfer blanket against the holding tank, a layer of fine regolith, a layer of courser regolith mixed in with fine regolith to fill in spaces,with an outer layer of mixed course, medium and fine regolith, covered with a reflective blanket both holding in the layers of regolith, and holding the heat distribution piping to dispose of the heat from within, via a heat dissapation panel in the shadow of the propellant depot.

     I figure the gathering and disposition of the various layers of regolith could asily be done either robotically or through teleoperations.

By minimizing human interaction as much as possible during the early stages, you minimize the risk to Human life.  Mind you, this MIGHT be a good idea for a long term fuel depot, but for short term, unless there is enough traffic to warrent such a change over, the current designs seem the best.

Regolith from asteroids will be a poor heat sink.  You need to have the depot built into a big asteroid for it to be a good heat sink.  Anything else is an insulator.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 04/16/2014 09:49 pm
What I' m going to describe may have been covered.

Possible uses for a L1 depot supplied with lunar fuel.
1) Have a tanker operating out of this depot that could refuel spent RLV upper stages that have delivered  GEO satellites. A fully or even partially fuelled stage should be able to make a powered landing on earth without needing a heatshield.
2) Use the tanker to collect GEO space junk eg dead upper stages and satellites, then transfer them to a junk yard in L1. The space junk could be used to supply moon with metals, solar panels etc or supply  a space factory.

3) Refuelled upper stages could also be used to return lunar materials eg regolith samples, mined gold to earth. A upper stage with suitable compartment should be able to delivery a tonne or more to earth.

Would anybody care to do calculations on how much fuel would be required to return a upper stage from GEO without a heat shield?
Title: Re: Propellant Depots - General Discussion
Post by: floss on 05/10/2014 10:24 pm
Why return an upper stage to earth at all when they are so valuable in space in the first place is beyond me every pound in space should be reused in space since it cost so much  to put it up there .

For instance tanks on the lunar surface would be incredibly valuable.

A material reprossing site in Leo is essential for the long term health of the orbital environment.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 05/11/2014 02:53 am
What I' m going to describe may have been covered.

Possible uses for a L1 depot supplied with lunar fuel.
1) Have a tanker operating out of this depot that could refuel spent RLV upper stages that have delivered  GEO satellites. A fully or even partially fuelled stage should be able to make a powered landing on earth without needing a heatshield.

I wish this idea would die. The amount of propellant it would take to make it back from GEO to the earth's surface, purely propulsively is simply ludicrous. You're talking about ~12km/s that you have to do in a single stage. Sure you can do most of that in space, but you're still talking about more performance than a Centaur could do even if you filled it all the way up. Numbers matter.

Not that there aren't benefits for bringing stages back to LEO or the earth's surface, I just think that doing that propulsively is the absolutely wrong way to go. The good news is that if the Magnetoshell Aerocapture technology we're going to be working on with MSNW this fall works, I think I have a way to use it to bring stuff back to LEO and maybe even to earth's surface w/o a traditional heat shield, and with really modest amounts of hardware/consumables.

Low-mass, low-maintenance aerobraking/aerocapture is a strongly complementary technology for depots.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 05/11/2014 07:57 pm
...

Jon Goff: "I think I may have found a good way of making this particularly problem tons easier...but it's only a bit past powerpoint (still pretty low TRL)."

Fermat: ""I have a proof of this theorem, but there is not enough space in this margin"

 ;)

Sorry for being a tease, it's just a potentially big idea and I'd like to make sure the IP is protected before publicly discussing it--winning arguments on the internet is fun but doesn't pay the bills...

Gosh, this response passed me by the first time...

Anyway, no problem of course. (I'm sure you noticed the smiley, anyway.) Hope it works out as a really big idea.

Meanwhile>>   :-X

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 05/11/2014 08:23 pm
In response to the query:
https://www.google.com/search?q=Magnetoshell+Aerocapture+MSNW

Google first shows me:
http://msnwllc.com/Papers/Kirtley_MSNW_NIAC_12MAR_final.pdf

Quote
A Magnetoshell doesn’t deflect gas like an aeroshell or plasma like a magnetic decelerator. It captures the hypersonic neutral gas through collisional processes. The momentum of the charge-exchanged gas is absorbed by the magnetic structure.

Followups recommended at:
http://forum.nasaspaceflight.com/index.php?topic=29912.0
Title: Re: Propellant Depots - General Discussion
Post by: Ludus on 06/26/2014 08:27 pm
Has there been any detailed study of depots that store ice and convert it to propellant? Water ice and dry ice stored long term as a stable feedstock, a reactor for power and process heat and basically the same sort of ISRU automated chemical plant that's been studied in detail for Mars and the moon.

I picture a depot that can store delivered water and co2 indefinitely with no real loss and make both lox and a selection of fuel like hydrogen, methane or RP-1 on demand. Just give the depot advanced notice of what you need and your credit card number and you're good for a fill up.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 06/26/2014 08:37 pm
Has there been any detailed study of depots that store ice and convert it to propellant? Water ice and dry ice stored long term as a stable feedstock, a reactor for power and process heat and basically the same sort of ISRU automated chemical plant that's been studied in detail for Mars and the moon.

I picture a depot that can store delivered water and co2 indefinitely with no real loss and make both lox and a selection of fuel like hydrogen, methane or RP-1 on demand. Just give the depot advanced notice of what you need and your credit card number and you're good for a fill up.

Ice and dry ice would have to be kept refrigerated but solar powered refrigeration is not hard.

Melting them will take a lot of energy.  So will converting CO2 into methane.  For the size of solar panels a depot is likely to have this could take weeks.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 06/26/2014 10:54 pm
This depot would convert water to LOX & LH or methane continuously as it can store cryogenic fuels indefinitely with its cryogenic plant.

The great thing about water is it is easy to transport so can be used to topup payloads to max.

I understand Bigelow' s BA330 converts water to H & O and uses them for station keeping. I think they are stored in gas form.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 06/28/2014 09:58 am
Just found this paper by Boeing for fuel depot that converts water to LH & L0X.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010039031.pdf 
Title: Re: Propellant Depots - General Discussion
Post by: oldAtlas_Eguy on 06/28/2014 02:32 pm
Just found this paper by Boeing for fuel depot that converts water to LH & L0X.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010039031.pdf

Interesting find.

I noticed the total weight was estimated at 69mt.  But this also included the concept of 18mt of 8 spent ACES stages repurposed as LOX/LH2 storage.  Leaving 51mt of of everthing else which would possibly fit in a SLS faring.

In order to construct the depot out of spent upper stages you would need an arm with DEXTER like capabilities plus US that has a CBM like addapter under its detacable payload adapter to do mate to the depot superstructure.  Also the US engine would need to be easily detachable so that a docking adapter can be connected at the other end.  Another option would be to leave engines on two of the US out of the 8 so that major repositioning of the depot such as moving it from LEO to L2 could be done just from the water that tankers from Earth took up to the depot.  Once at L2 other sources for water Moon or asteroids could be used.

In order to reposition from LEO to L2 a 70mt dry weigth depot would need ~70mt of water delivered and converted to LOX/LH2.  BTW 2 spent US tanks would hold more than 70mt of LOX/LH2 (2 Centaur's > 80mt).  Max acceleration using 2 RL10 on a 70 MT structure would be ~.3 to .4 g's.
Title: Re: Propellant Depots - General Discussion
Post by: oldAtlas_Eguy on 06/28/2014 02:49 pm
Additional notes about ACES was it's essentially unlimited restart capability.  Making such an US a ready cis-lunar tug.  Using the prop depot as not only for prop but a tug maintenance depot location where engines and other components scroungred off of the eight US used to make the depot can be used to keep a tug going for a lot of missions.  BTW an interesting point is that a streched ACES (71mt prop version) used as tug could take an SLS delivered 70mt paylod and deliver it to L2.  Where at L2 it could fuel up again and then push this 70mt payload on to deep space (Mars,etc). Unfortunatly the tug would be expended so this would be a use for the end-of life last use mission for the tug.

It would be great if Boeing,LM and ULA would actualy spend a little money on doing what they have figured out how to do.  A complete cis-lunar transport infrastructure for large payloads (70mt lots).

Edit (spelling typos)
Title: Re: Propellant Depots - General Discussion
Post by: Burninate on 06/28/2014 09:45 pm
So I've been running the numbers on ion thrusters, and with the new generation of solar array wings at 200w/kg, they are *highly* complementary to the notion of a propellant depot out at the edge of our gravity well - whether L1/L2, lunar retrograde, geosynchronous, whatever.  That ~3.5km/s at 2000s-5000s turns an SLS cargo mission into a Falcon Heavy cargo mission.  Yes, hanging out in the Van Allen belts is not feasible for crew, but even crew capsules can benefit somewhat, if they use high-thrust propulsion to get past the most dangerous areas in one orbit.

I'd always used the numbers for the ISS solar array wing trusses, but this was a bad decision - they are extraordinarily heavier per power than recent developments, and an order of magnitude heavier than even contemporary arrays for unmanned missions of the era in which they were designed.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 06/28/2014 10:20 pm
So I've been running the numbers on ion thrusters, and with the new generation of solar array wings at 200w/kg, they are *highly* complementary to the notion of a propellant depot out at the edge of our gravity well - whether L1/L2, lunar retrograde, geosynchronous, whatever.  That ~3.5km/s at 2000s-5000s turns an SLS cargo mission into a Falcon Heavy cargo mission.  Yes, hanging out in the Van Allen belts is not feasible for crew, but even crew capsules can benefit somewhat, if they use high-thrust propulsion to get past the most dangerous areas in one orbit.

A lunar lander with stretched fuel tanks could be used as a space tug to push SEP through the Van Allen belts.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 06/29/2014 08:28 am
But a reusable upper stage? With an 8 km/s delta V budget and enduring a an 8 km/s re-entry?

Definitely Powerpoint.

I think I may have found a good way of making this particularly problem tons easier...but it's only a bit past powerpoint (still pretty low TRL).

Jon Goff: "I think I may have found a good way of making this particularly problem tons easier...but it's only a bit past powerpoint (still pretty low TRL)."

Fermat: ""I have a proof of this theorem, but there is not enough space in this margin"

 ;)

Sorry for being a tease, it's just a potentially big idea and I'd like to make sure the IP is protected before publicly discussing it--winning arguments on the internet is fun but doesn't pay the bills...

So ... I guess this must have been MAC?

Let's assume we're talking about an F9US using MAC braking to square the RLV circle (so keeping that depot filled up cheaply).

Initial braking will slow orbital speeds, but will also reduce perigee. ISTM a gentle deceleration will just knock off a negligible speed before reenty - no different than today's deorbit thruster burn.

To make a difference, it looks like MAC needs to provide enough braking that by the time a normal reentry altitude is reached, a lot of speed has been knocked off, and to continue staying "far ahead of the curve" in order to avoid lots of heating to the stage. All made more difficult because you don't have the chance to reduce heating / extend the reentry time via L/D.

Do you think MAC could get to the stage where F9US could avoid a heatshield completely (IE like core stage after its reentry burn)? Or does it ultimately just reduce the heatshield requirements a bit? Or somewhere in between?

Unless you're eliminating the heatshield, it's then a matter of whether you're reducing heatshield mass faster than you're adding MAC mass?

Hmm, not sure that was phrased very well as questions. But, basically, does MAC have the potential to make u/s reentry a lot easier?

I also wonder, given some LOX residuals, whether you could reduce power requirements by using high temp superconductors for the magnetic field? I'm thinking embedded in the tank, but wonder if the geometry just means you end up spraying the stage with your generated plasma?

Could you use either O2 or RP-1 residuals as gas to maintain the plasma?

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 06/29/2014 10:34 am
So I've been running the numbers on ion thrusters, and with the new generation of solar array wings at 200w/kg, they are *highly* complementary to the notion of a propellant depot out at the edge of our gravity well - whether L1/L2, lunar retrograde, geosynchronous, whatever.  That ~3.5km/s at 2000s-5000s turns an SLS cargo mission into a Falcon Heavy cargo mission.

Chemical rockets can reach escape with ~3.2 km/s due to Oberth effect.

SEP rockets have much higher Isp, but must perform a much larger dV to reach escape without benefit of Oberth effect.

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 06/30/2014 12:01 am
So I've been running the numbers on ion thrusters, and with the new generation of solar array wings at 200w/kg, they are *highly* complementary to the notion of a propellant depot out at the edge of our gravity well - whether L1/L2, lunar retrograde, geosynchronous, whatever.  That ~3.5km/s at 2000s-5000s turns an SLS cargo mission into a Falcon Heavy cargo mission.

Chemical rockets can reach escape with ~3.2 km/s due to Oberth effect.

SEP rockets have much higher Isp, but must perform a much larger dV to reach escape without benefit of Oberth effect.

cheers, Martin
You can use Oberth to some extent with SEP by just thrusting near perigee and taking extra time.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 06/30/2014 04:32 pm
So ... I guess this must have been MAC?

Yup.

Quote
Let's assume we're talking about an F9US using MAC braking to square the RLV circle (so keeping that depot filled up cheaply).

Or potentially a Centaur or ACES stage. I haven't pitched this to SpaceX, but I'd prefer to keep this technology as one open to all parties. And in some ways Centaur and ACES may be easier to implement MAC for aeroentry with than F9US (though it may be feasible too).

Quote
Initial braking will slow orbital speeds, but will also reduce perigee. ISTM a gentle deceleration will just knock off a negligible speed before reenty - no different than today's deorbit thruster burn.

To make a difference, it looks like MAC needs to provide enough braking that by the time a normal reentry altitude is reached, a lot of speed has been knocked off, and to continue staying "far ahead of the curve" in order to avoid lots of heating to the stage. All made more difficult because you don't have the chance to reduce heating / extend the reentry time via L/D.

Do you think MAC could get to the stage where F9US could avoid a heatshield completely (IE like core stage after its reentry burn)? Or does it ultimately just reduce the heatshield requirements a bit? Or somewhere in between?

I created a fairly ghetto simulation (that I still need to review and vet with MSNW) that indicates it might be possible to bring an upper stage back w/o needing TPS. The key thing is that MAC works in the 85-175ish km altitude band, and it's possible to get really, really big drag cross-sections (ie very low ballistic coefficient). The question is can you do enough of that braking at a high enough altitude that the heating is low? My simulation suggests yes there might be a way to do that. Not vetted, but promising.

Quote
Hmm, not sure that was phrased very well as questions. But, basically, does MAC have the potential to make u/s reentry a lot easier?

Yes, I think so. Still need to prove the technology, and in order to get to the MAC effective radius needed, there is some...cleverness involved... that also need so be proven out.

Quote
I also wonder, given some LOX residuals, whether you could reduce power requirements by using high temp superconductors for the magnetic field? I'm thinking embedded in the tank, but wonder if the geometry just means you end up spraying the stage with your generated plasma?

There's some possibilities there, both with superconductors, and even with chilled pure-metal conductors (cryo cooled pure aluminum or copper has a huge resistivity drop compared to room-temp)... but they're both tons easier if you have LH2 like you do with Centaur. It's also possible to use some variants on our MIDAS technology to do the coil as a deployed structure, though that makes cryo cooling harder...

Quote
Could you use either O2 or RP-1 residuals as gas to maintain the plasma?

You actually shouldn't need much makeup gas to maintain the plasma as the atmospheric neutrals that get ionized will tend to replenish the plasma quickly. Ideally you'd want a plasma seed gas that is similar in composition to the atmospheric neutrals you want to ionize. So Nitrous, Nitrogen Tetroxide, or even compressed air might be better than just LOX, and definitely better than RP-1. But GOX might be good enough for practical purposes.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 06/30/2014 04:35 pm
So I've been running the numbers on ion thrusters, and with the new generation of solar array wings at 200w/kg, they are *highly* complementary to the notion of a propellant depot out at the edge of our gravity well - whether L1/L2, lunar retrograde, geosynchronous, whatever.  That ~3.5km/s at 2000s-5000s turns an SLS cargo mission into a Falcon Heavy cargo mission.

Chemical rockets can reach escape with ~3.2 km/s due to Oberth effect.

SEP rockets have much higher Isp, but must perform a much larger dV to reach escape without benefit of Oberth effect.

cheers, Martin
You can use Oberth to some extent with SEP by just thrusting near perigee and taking extra time.

The problems are that:
a) Most SEP systems scale with peak thruster power rating, so thrusting near perigee means a bigger engine or a much slower departure (MSNW's thrusters may be an exception to this rule).
b) As you do a bunch of mini perigee boosts, your orbital period becomes longer and longer, so you're boosting less and less of the time in an orbit. This may make the boost time excessive.
c) This will probably require a big battery to allow you to effectively utilize the solar panels.

It's possible, but I'd want to see numbers run on it. If it doesn't make sense, spiraling out tends to take around 5km/s.

SEP makes sense in a wide range of areas, but I think people tend to think it's more of a panacea than it is.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 06/30/2014 05:49 pm
If you aren't constrained on time but are constrained on Isp, boosting near perigee is a good idea. It does increase your time, potentially by a lot. The real optimum is probably in the middle somewhere.

I like SEP, but yeah, definitely not a panacea. In fact, I doubt SpaceX will use it much for their colonization plans. It's a powerful force multiplier in some cases, though.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 07/02/2014 02:10 pm
So ... I guess this must have been MAC?

Yup.

Thanks for a comprehensive set of answers


Quote
Let's assume we're talking about an F9US using MAC braking to square the RLV circle (so keeping that depot filled up cheaply).

Or potentially a Centaur or ACES stage. I haven't pitched this to SpaceX, but I'd prefer to keep this technology as one open to all parties. And in some ways Centaur and ACES may be easier to implement MAC for aeroentry with than F9US (though it may be feasible too).

I had a quick think, and F9US was the only thing that came to mind that was talking about doing reentry but doesn't currently have a heatshield.

Would never have occurred to me that Centaur/ACES might want to do the same thing. Didn't mean to imply this should be SpaceX-only.

It occurs to me this might be interesting for Cygnus, too.

cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 07/02/2014 06:05 pm
So ... I guess this must have been MAC?

Yup.

Thanks for a comprehensive set of answers


Quote
Let's assume we're talking about an F9US using MAC braking to square the RLV circle (so keeping that depot filled up cheaply).

Or potentially a Centaur or ACES stage. I haven't pitched this to SpaceX, but I'd prefer to keep this technology as one open to all parties. And in some ways Centaur and ACES may be easier to implement MAC for aeroentry with than F9US (though it may be feasible too).

I had a quick think, and F9US was the only thing that came to mind that was talking about doing reentry but doesn't currently have a heatshield.

Would never have occurred to me that Centaur/ACES might want to do the same thing. Didn't mean to imply this should be SpaceX-only.

It occurs to me this might be interesting for Cygnus, too.

Oh, and just to clarify, MAC is potentially useful for three distinct types of applications: Aerocapture (coming in from a hyperbolic interplanetary trajectory and capturing into an elliptical orbit around a planet), Aerobraking (taking an elliptical orbit, and lowering its apogee via one or more passes through the atmosphere), and Aeroentry (using the atmosphere to bring something back to the surface).

I think that F9US and Centaur/ACES could both benefit from being made reusable. Still need to crunch the numbers, but I think MAC might enable both.

Upper stage reuse might actually entail two or all three of these. For instance, imagine a F9US or Centaur/ACES turned into a cislunar tug. You would boost out with the liquid propulsion (topped off by the depot), travel to the destination, and on the return you'd use MAC to aerocapture into LEO. For missions to LEO (like ISS) the same system could be used for helping bring the stage back. For missions to GEO, you'd want to aerobrake back to LEO first, then aeroentry for return. For a mission beyond cislunar space, you might be able to do a departure burn in a way that allows you to use MAC to capture the boost stage back into earth orbit immediately after separating with the now departing stack. Follow that up with aerocapture into LEO and if desired aeroentry, or reuse in LEO...

MAC (assuming it works anywhere close to as well as predicted when scaled-up) and Depots are like cookies and ice cream--great on their own, but even better together.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mfck on 07/02/2014 06:17 pm
I wonder what a night sky would look like... 
Title: Re: Propellant Depots - General Discussion
Post by: mheney on 07/02/2014 06:17 pm
For those of us late to the conversation - could someone expand "MAC"?

Thanks.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 07/02/2014 08:34 pm
For those of us late to the conversation - could someone expand "MAC"?

Magnetoshell Aerocapture. I give a little overview in this blog post talking about some of the recent contract wins we've had at Altius:

http://blog.altius-space.com/2014/06/recent-altius-contract-wins-what-do-they-mean/

There's also a thread somewhere in the Advanced Concepts section (I'm too lazy to grab a link, but someone else can probably point it out).

The reason we were discussing MAC in the depots thread is that the two are strongly synergistic technologies. Depots work best when you're reusing stuff in space, and MAC makes bringing stuff back a heck of a lot easier (including ISRU propellants).

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: mheney on 07/02/2014 08:55 pm
Very cool stuff.  Thanks!
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 07/02/2014 09:33 pm
A reusable ACES with larger tanks could double as a depot and a OTV.
Attach it to cryogenic plant in orbit which would proved active cooling and station keep with a SEP.  Top it up with additional launches. Once fully fueled it could used as a OTV then returned to earth for recycling and most importantly maintenance.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 07/04/2014 08:53 am


So ... I guess this must have been MAC?

Yup.

Thanks for a comprehensive set of answers


Quote
Let's assume we're talking about an F9US using MAC braking to square the RLV circle (so keeping that depot filled up cheaply).

Or potentially a Centaur or ACES stage. I haven't pitched this to SpaceX, but I'd prefer to keep this technology as one open to all parties. And in some ways Centaur and ACES may be easier to implement MAC for aeroentry with than F9US (though it may be feasible too).

I had a quick think, and F9US was the only thing that came to mind that was talking about doing reentry but doesn't currently have a heatshield.

Would never have occurred to me that Centaur/ACES might want to do the same thing. Didn't mean to imply this should be SpaceX-only.

It occurs to me this might be interesting for Cygnus, too.

Oh, and just to clarify, MAC is potentially useful for three distinct types of applications: Aerocapture (coming in from a hyperbolic interplanetary trajectory and capturing into an elliptical orbit around a planet), Aerobraking (taking an elliptical orbit, and lowering its apogee via one or more passes through the atmosphere), and Aeroentry (using the atmosphere to bring something back to the surface).

I think that F9US and Centaur/ACES could both benefit from being made reusable. Still need to crunch the numbers, but I think MAC might enable both.

Upper stage reuse might actually entail two or all three of these. For instance, imagine a F9US or Centaur/ACES turned into a cislunar tug. You would boost out with the liquid propulsion (topped off by the depot), travel to the destination, and on the return you'd use MAC to aerocapture into LEO. For missions to LEO (like ISS) the same system could be used for helping bring the stage back. For missions to GEO, you'd want to aerobrake back to LEO first, then aeroentry for return. For a mission beyond cislunar space, you might be able to do a departure burn in a way that allows you to use MAC to capture the boost stage back into earth orbit immediately after separating with the now departing stack. Follow that up with aerocapture into LEO and if desired aeroentry, or reuse in LEO...

MAC (assuming it works anywhere close to as well as predicted when scaled-up) and Depots are like cookies and ice cream--great on their own, but even better together.

~Jon

Yeah. The aerobraking of a u/s from GTO back to LEO, followed by aeroentry was another reason I made the original assumption that F9US (more likely FHUS) was the obvious use case for this.

If the system has a high enough drag to perform the no-heatshield reentry as discussed, would it be able to aerobrake from GTO to LEO in one pass? How about return from a Lunar depot mission?

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 07/07/2014 09:48 am
Planetary resources video on using asteriod water as fuel.

http://www.planetaryresources.com/2014/06/fuelspace/

Although none of the existing satellites use water as fuel, there is the option of attaching a water fuelled spacecraft to a satellite. There are a few companies developing propulsion systems that use water as fuel. Some split it and use it as rocket fuel and gas thrusters whiles others use the gases in ion thrusters. Water is great for secondary payload spacecraft as it is inert, launch providers don't like secondary payloads that contain rocket fuel.
Title: Re: Propellant Depots - General Discussion
Post by: jsgirald on 07/07/2014 12:30 pm
Excuse me if this question has already been answered but, what scale of depots are we discussing?
I mean, for large interplanetary missions a la MCT we'd need hundreds or maybe thousands of metric tons of methane/lox per launch window. But how would that work? That's a pretty large infrastructure even with fully reusable FH.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 07/07/2014 06:30 pm
Planetary resources video on using asteriod water as fuel.

http://www.planetaryresources.com/2014/06/fuelspace/

Although none of the existing satellites use water as fuel, there is the option of attaching a water fuelled spacecraft to a satellite. There are a few companies developing propulsion systems that use water as fuel. Some split it and use it as rocket fuel and gas thrusters whiles others use the gases in ion thrusters. Water is great for secondary payload spacecraft as it is inert, launch providers don't like secondary payloads that contain rocket fuel.

Yeah, a water-fueled "jet pack" using either one of the elctrolysis/rocket options or one of the RF plasma thruster options could make a lot of sense... but it won't provide a lot of demand from a mass standpoint.  I think the bigger market will be delivering satellites to destinations beyond LEO (ie MEO, GEO, or further out), not replenishing their stationkeeping propellant.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 07/07/2014 07:15 pm
If they do establish fuel depots the fuel may end up being cheaper in locations like L2 L1 than at LEO.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 07/07/2014 09:21 pm
If they do establish fuel depots the fuel may end up being cheaper in locations like L2 L1 than at LEO.

That's a definite maybe. :-)

In reality, you'll probably want depots in multiple locations--LEO for sure, Earth-Moon L1 or L2, and in orbit around whatever planets you'd like to actually do interesting things at (ie at least Mars, possibly Venus, maybe other places as time goes on). Orbital dynamics makes the first step off of a gravity well a doozy. Having a depot right there so you can refuel right away makes a ton of sense for most missions. Also having a LEO depot helps make reusing in-space hardware (so you can start having honest to goodness spaceships) a lot more feasible. Even if it means that the LEO depots end up getting a lot of their prop from RLVs instead of NEOs or the Moon.

I'm a fan of gas stations on both ends of the trip. :-)

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 07/07/2014 10:00 pm
Excuse me if this question has already been answered but, what scale of depots are we discussing?
I mean, for large interplanetary missions a la MCT we'd need hundreds or maybe thousands of metric tons of methane/lox per launch window. But how would that work? That's a pretty large infrastructure even with fully reusable FH.

Both.  The initial depots will be small.

Since the Mars Transfer Vehicle is very big it is likely to need its own large depot which will take several launches to fill.

To land a tonne on the Moon from LEO will require exp(5930 /(321 * 9.81)) - 1 = 5.58 tonne of methane/LOX so a smaller one can be used.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 07/08/2014 12:21 am
I'm picking PR will have refinery/depot somewhere around L1, L2 to reduce the DV between a mined asteriod and the refinery. The other advantage of positioning a refinery here is access to permanent sunlight for supplying power for converting water into fuel.
There may not be a need for a depot in LEO just a fully fuelled OTV. Have the OTV permanently stationed at the refinery then transfer to LEO when required.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 07/08/2014 02:24 am
I'm picking PR will have refinery/depot somewhere around L1, L2 to reduce the DV between a mined asteriod and the refinery. The other advantage of positioning a refinery here is access to permanent sunlight for supplying power for converting water into fuel.

At least the first point might be mooted if MAC works. In some ways it might be easier to come directly back to LEO instead of going to L1/L2...

The more continuous solar power (and lack of space debris in L1/L2) are more legitimate reasons for basing things there.

Quote
There may not be a need for a depot in LEO just a fully fuelled OTV. Have the OTV permanently stationed at the refinery then transfer to LEO when required.

Sure, you could do that. But I think earth-based RLVs will be here long before PR/DSI or ShackletonEnergy are shipping water back from NEOs or the Moon.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Burninate on 07/08/2014 02:34 am
I'm picking PR will have refinery/depot somewhere around L1, L2 to reduce the DV between a mined asteriod and the refinery. The other advantage of positioning a refinery here is access to permanent sunlight for supplying power for converting water into fuel.

At least the first point might be mooted if MAC works. In some ways it might be easier to come directly back to LEO instead of going to L1/L2...

The more continuous solar power (and lack of space debris in L1/L2) are more legitimate reasons for basing things there.

Quote
There may not be a need for a depot in LEO just a fully fuelled OTV. Have the OTV permanently stationed at the refinery then transfer to LEO when required.

Sure, you could do that. But I think earth-based RLVs will be here long before PR/DSI or ShackletonEnergy are shipping water back from NEOs or the Moon.

~Jon

Why L1/L2 instead of, say, a P/2 lunar resonant high earth orbit, 400,000km x 40,000km? You can still Oberth burn to interplanetary from that, it's stable, it's thermally stable except for brief flybys every few days, and the burn to aerobrake into LEO is not very much.

The idea comes from the TESS mission. (http://arxiv.org/pdf/1306.5333.pdf)

Still not sure I understand the cost/benefits of either option over an LEO depot, if restricted to chemical-only propulsion.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 07/08/2014 03:32 am
{snip}
Still not sure I understand the cost/benefits of either option over an LEO depot, if restricted to chemical-only propulsion.

LEO => EML-2 has a delta-v of 3.43 km/s and 6.86 km/s return
EML-2 => LMO has a delta-v of ~3.7 km/s and ~7.4 km/s return

So with a reusable Mars Transfer Vehicle you can save a delta-v of about 6.86 km/s if it stops at EML-2.  The Earth reentry vehicle can have a much smaller mass since it only needs consumables for a couple of weeks.
edit:typo
Title: Re: Propellant Depots - General Discussion
Post by: Burninate on 07/08/2014 03:58 am
{snip}
Still not sure I understand the cost/benefits of either option over an LEO depot, if restricted to chemical-only propulsion.

LEO => EML-2 has a delta-v of 3.43 km/s and 6.86 km/s return
EML-2 => LLO has a delta-v of ~3.7 km/s and ~7.4 km/s return

So with a reusable Mars Transfer Vehicle you can save a delta-v of about 6.86 km/s if it stops at EML-2.  The Earth reentry vehicle can have a much smaller mass since it only needs consumables for a couple of weeks.
This should probably be obvious to me, but what do the 'return' numbers mean?

Also why is LLO relevant to a Mars mission?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 07/08/2014 04:37 am
{snip}
Still not sure I understand the cost/benefits of either option over an LEO depot, if restricted to chemical-only propulsion.

LEO => EML-2 has a delta-v of 3.43 km/s and 6.86 km/s return
EML-2 => LMO has a delta-v of ~3.7 km/s and ~7.4 km/s return

So with a reusable Mars Transfer Vehicle you can save a delta-v of about 6.86 km/s if it stops at EML-2.  The Earth reentry vehicle can have a much smaller mass since it only needs consumables for a couple of weeks.
edit:typo
This should probably be obvious to me, but what do the 'return' numbers mean?

Also why is LLO relevant to a Mars mission?

LLO should have been LMO.

Manned missions to Mars have to come back, so the planners have to double the delta-v figures.  For a reusable vehicle the engines and fuel tanks are also brought back.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 07/08/2014 04:49 am
[A depot in] a P/2 lunar resonant high earth orbit, 400,000km x 40,000km? You can still Oberth burn to interplanetary from that

That idea is worth thinking about!

Dropping from 400,000x40,000 to 400,000x240 km requires a braking burn of -271 m/s. That leads to a perigee pass 11 days later with a velocity of 10,887 m/s, which is only 88 m/s from escape velocity.

It isn't clear to me how often departure windows occur for e.g. TMI from this kind of orbit, though....
Title: Re: Propellant Depots - General Discussion
Post by: Burninate on 07/08/2014 06:15 am
{snip}
Still not sure I understand the cost/benefits of either option over an LEO depot, if restricted to chemical-only propulsion.

LEO => EML-2 has a delta-v of 3.43 km/s and 6.86 km/s return
EML-2 => LMO has a delta-v of ~3.7 km/s and ~7.4 km/s return

So with a reusable Mars Transfer Vehicle you can save a delta-v of about 6.86 km/s if it stops at EML-2.  The Earth reentry vehicle can have a much smaller mass since it only needs consumables for a couple of weeks.
This should probably be obvious to me, but what do the 'return' numbers mean?
Manned missions to Mars have to come back, so the planners have to double the delta-v figures.  For a reusable vehicle the engines and fuel tanks are also brought back.
Oh, I get it, 'Return' is just the two-way number, 2 * the one-way number.  You're saying that stopping at EML-2 saves the *second* and *Third* Mars mission from making the LEO <-> EML-2 trip.

So from your post:
LEO -> EML2 = 3.43 km/s
EML2 -> MTO -> LMO = ~3.7 km/s
-EDL ignored-
-Ascent ignored-
LMO -> MTO -> EML2 = ~3.7 km/s
EML2 -> LEO = 3.43 km/s

And by the depot, for re-usable tanks and thrusters it's just
EML2 -> MTO -> LMO = ~3.7 km/s
-EDL ignored-
-Ascent ignored-
LMO -> MTO -> EML2 = ~3.7 km/s

But that doesn't account for aerobraking/aerocapture, in which case it becomes, according to WP's charts (http://en.wikipedia.org/wiki/Delta-v_budget):
LEO -> EML2 = 3.43 km/s
EML2 -> MTO < ~1 km/s
MTO -> LMO = 0 km/s
-EDL ignored-
-Ascent ignored-
LMO -> MTO = 2.7km/s
MTO -> EML2 < ~ 1km/s
EML2 -> LEO = 0.33 km/s

But for a direct LEO depot, we would be talking about Oberth-assisted, direct burns, not transitioning to EML2, in which case it becomes:
LEO -> MTO = 4.3 km/s
MTO -> LMO = 0 km/s
-EDL ignored-
-Ascent ignored-
LMO -> MTO = 2.7km/s
MTO -> LEO = 0 km/s

That's still 7km/s for the direct trip, down from 7.2km/s in your description of the benefits of an EML2 depot without aerocapture/aerobraking.  I discount aerocapture mass costs here, which is not compatible with reality yet, but I think it still brings the point into question.

The worst part, though, is that the vehicle is not the bulk of the mission mass, but rather the fuel is.  That fuel has to go through the same expensive LEO -> EML2 maneuvers, at 3.43km/s, as it would if it was sent up in your schedule to EML2 - we don't get to re-use that.

Would it be accurate to say a Mars-Earth cycler does this particular job - re-using habitat modules and engines, but not fuel - a lot better during the Mars transit, as it needs only minimal propulsion once in place?

[A depot in] a P/2 lunar resonant high earth orbit, 400,000km x 40,000km? You can still Oberth burn to interplanetary from that

That idea is worth thinking about!

Dropping from 400,000x40,000 to 400,000x240 km requires a braking burn of -271 m/s. That leads to a perigee pass 11 days later with a velocity of 10,887 m/s, which is only 88 m/s from escape velocity.

It isn't clear to me how often departure windows occur for e.g. TMI from this kind of orbit, though....

I suppose that's a big weakness if all else is equal - the minima in dV to escape into heliocentric orbit only comes once a year instead of once a month.  I'm not clear on how much a multiple-burn or an off-center burn would cost, only that this minima will jump around by +2 months in relation to the 26-month cycle Mars conjunction. 

From the above accounting, all else does not seem to be equal though.

Edit:
Experimental Hohmann Transfer spreadsheet says, in no particular order:
40k x 40k -> 440k x 40k: 1015 m/s
440k x 40k -> 440k x 440k: 535 m/s
440k x 40k -> 440k x 300: 247 m/s
440k x 40k -> C0: 200 m/s
440k x 300 -> C0: 80 m/s
300 x 300 -> 440k x 300: 3121 m/s
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 07/08/2014 07:46 am
Propellant between LEO and EML can be lifted using a SEP which adds more options to the list.

Aerocapture with a time limit of about a week would need to be tested.
Title: Re: Propellant Depots - General Discussion
Post by: Burninate on 07/08/2014 08:45 am
Propellant between LEO and EML can be lifted using a SEP which adds more options to the list.

Aerocapture with a time limit of about a week would need to be tested.

SEP is exactly where I think the benefits lie, but I'm currently grappling with the problem of the Van Allen belts.  Obviously prohibitive to humans, but perhaps even damaging to electronics.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 07/09/2014 02:22 am
Propellant between LEO and EML can be lifted using a SEP which adds more options to the list.

Aerocapture with a time limit of about a week would need to be tested.

SEP is exactly where I think the benefits lie, but I'm currently grappling with the problem of the Van Allen belts.  Obviously prohibitive to humans, but perhaps even damaging to electronics.

SEP avionics is high power so the Van Allen belts have little effect.  The solar panels age.  It is the guidance system, computers, radios and sensors that need protecting.
Title: Re: Propellant Depots - General Discussion
Post by: Burninate on 07/09/2014 04:35 am
How warm would a methane-lox propellant depot be able to operate in practice?

http://forum.nasaspaceflight.com/index.php?topic=35006.msg1217016#msg1217016 says ~100k for 3 bar, but would substantially higher pressure tankage be practical?
Title: Re: Propellant Depots - General Discussion
Post by: RocketmanUS on 07/09/2014 05:11 pm
Would rotating the depot, US, or EDS reduce the boil off rate? ( reduce the time one side receives Sun light while having the other side radiate the energy that was received when it was in the Sun light )
Title: Re: Propellant Depots - General Discussion
Post by: guru on 07/10/2014 12:03 am
Rotating would reduce the boil off rate, partially because of the cooling cycle you described, but more for the fact that rotation settles the propellant.  A settled propellant has less surface area for heat transfer.  (AIUI anyway.)
Title: Re: Propellant Depots - General Discussion
Post by: IslandPlaya on 07/10/2014 12:09 am
Assuming a full tank, I can't see what difference it would make. The heat flux would be the same. I can see a bbq roll being good in other ways but it would not effect the boil off rate as such.
Title: Re: Propellant Depots - General Discussion
Post by: KelvinZero on 07/10/2014 03:14 pm
Is there a discussion or paper anywhere that establishes that boil off is a hard problem to solve given active cooling?

I hope it isn't, because if we can't do that we will never master ISRU for propellant.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 07/10/2014 04:03 pm


Rotating would reduce the boil off rate, partially because of the cooling cycle you described, but more for the fact that rotation settles the propellant.  A settled propellant has less surface area for heat transfer.  (AIUI anyway.)

Hmm, I think that's the wrong way around.

I believe there has been some research into using magnetic fields to pool the prop at the centre of the tank, in order to reduce heat transfer into the liquid. If liquid cools the inward face of the tank skin, it reduces radiative cooling from the space side, IE increases the net inward heat flux. Basically, incoming heat can either be re-radiated to space, or it can boil your cryogen. The only way that passive systems (no cryocooler) can reduce boiloff is by allowing the Sun side to get hot enough to re-radiate as near 100% of the incoming heat as possible, whilst insulating that hot surface from the tank walls.

That's probably best done with a Sunshield and no barbecue roll, I'd have thought.

Cheers, Martin

PS a sphere has the lowest surface area for a volume.
Title: Re: Propellant Depots - General Discussion
Post by: guru on 07/10/2014 10:05 pm


Rotating would reduce the boil off rate, partially because of the cooling cycle you described, but more for the fact that rotation settles the propellant.  A settled propellant has less surface area for heat transfer.  (AIUI anyway.)

Hmm, I think that's the wrong way around.

I believe there has been some research into using magnetic fields to pool the prop at the centre of the tank, in order to reduce heat transfer into the liquid. If liquid cools the inward face of the tank skin, it reduces radiative cooling from the space side, IE increases the net inward heat flux. Basically, incoming heat can either be re-radiated to space, or it can boil your cryogen. The only way that passive systems (no cryocooler) can reduce boiloff is by allowing the Sun side to get hot enough to re-radiate as near 100% of the incoming heat as possible, whilst insulating that hot surface from the tank walls.

That's probably best done with a Sunshield and no barbecue roll, I'd have thought.

Cheers, Martin

All good points, but the ULA design does use a barbecue roll in addition to the sun shade.

http://www.ulalaunch.com/uploads/docs/Published_Papers/Extended_Duration/APracticalAffordableCryogenicPropellantDepotBasedonULAsFlightExperience20087644.pdf

The hot side can absorb / reflect all of the heat, still be insulated from the propellant (via vacuum space between it and the sun shade), and then, as it rotates, radiate heat from the cold side at a higher rate.

Quote
PS a sphere has the lowest surface area for a volume.

True, but only applicable if all of the propellant is in one glob.  If there are 1000 globs of propellant floating around, the unsettled propellant has more surface area.

Edit: Okay, I was wrong.  I will concede, after re-reading the paper, that the rolling motion's advantage was for propellant settling for transfer purposes, not for heat transfer.   The orientation of the depot while rolling clearly shows that they prefer the barbecue roll for heat management meaning I was incorrect in my original response that the rolling motion was less effective than settling.   The same action serves two different purposes.
Title: Re: Propellant Depots - General Discussion
Post by: KelvinZero on 07/15/2014 04:18 am
c) This will probably require a big battery to allow you to effectively utilize the solar panels.
This is off topic but it was thinking about SEP to an EML2 depot that brought me here and the idea is no doubt too easily dismissed for its own thread:

I was just wondering if you could for example exploit your propellant mass to get a battery for free. I don't know whether propellants that are chosen to be cheap to ionize make them more or less appropriate.

It was just a random idea I thought might not have been considered since such a reaction would not need great storage (having tons and tons of mass to store only an orbit's worth of your solar panels) so in other circumstances would be ignored.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 07/17/2014 09:07 am
c) This will probably require a big battery to allow you to effectively utilize the solar panels.
This is off topic but it was thinking about SEP to an EML2 depot that brought me here and the idea is no doubt too easily dismissed for its own thread:

I was just wondering if you could for example exploit your propellant mass to get a battery for free. I don't know whether propellants that are chosen to be cheap to ionize make them more or less appropriate.

It was just a random idea I thought might not have been considered since such a reaction would not need great storage (having tons and tons of mass to store only an orbit's worth of your solar panels) so in other circumstances would be ignored.

Lox & LH2. Run through a fuel cell to generate electricity (both Shuttle & Apollo did this), use electrolysis to break the water back down to gasses using power from the solar panels.

This assumes you already have a cryocooler on board to recycle boiloff gasses.

Cheers, Martin

Edit: not sure this is terribly efficient (too much heating up & then cryocooling).

Edit 2: unless you keep the gasses in gas phase, run them through the cycle many times to perform all the boost manoeuvres, then cryocool them when you're at/near your destination. Now I have an image of a stage with two chuffing great balloons attached that I can't get out of my head. Better hope you don't get an MMOD strike.

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: KelvinZero on 07/17/2014 09:59 am
Duh! I had been thinking only of the SEP propellant for a tug moving the propellant to an EML2 depot.

I had entirely missed the detail that as well as the 10t of SEP propellant you could have something like 40t of conventional propellant plus whatever you need to mitigate boiloff during what could be a multi-year trip out to EML2

I was hoping for something like a big (but not very high power density) capacitor ie it could return all its stored power rapidly.

Come to think of it, a pressure difference between tanks might be enough power storage.  It only needs to store the electric energy from a single orbit and release it during a fraction of that orbit. You might be able to share some mass between whatever you use for boiloff and this.

(edit) Maybe you would need a lot more power storage than I thought. I figure if you are going to EML2 by only thrusting when near earth towards the end you have orbits of around a month? I think you need on the order of a hundred tons of battery to provide 40kWh with typical battery power density?.. In which case I guess only something like a hydrogen/oxygen fuel cell would have the necessary storage to make a difference.

eg Li-ion battary 128Wh/kg. 40kW for SEP tug. hours in month = 720
battery mass = 40k*720/128 = 255 tons.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 07/17/2014 03:27 pm
The battery needs to cover the time when the spacecraft is in shadow.  As the height of the orbit increases this time reduces because the shadow gets smaller.
Title: Re: Propellant Depots - General Discussion
Post by: muomega0 on 07/17/2014 03:53 pm
c) This will probably require a big battery to allow you to effectively utilize the solar panels.
This is off topic but it was thinking about SEP to an EML2 depot that brought me here and the idea is no doubt too easily dismissed for its own thread:

I was just wondering if you could for example exploit your propellant mass to get a battery for free. I don't know whether propellants that are chosen to be cheap to ionize make them more or less appropriate.

It was just a random idea I thought might not have been considered since such a reaction would not need great storage (having tons and tons of mass to store only an orbit's worth of your solar panels) so in other circumstances would be ignored.

Lox & LH2. Run through a fuel cell to generate electricity (both Shuttle & Apollo did this), use electrolysis to break the water back down to gasses using power from the solar panels.

This assumes you already have a cryocooler on board to recycle boiloff gasses.

Cheers, Martin

Edit: not sure this is terribly efficient (too much heating up & then cryocooling).

Edit 2: unless you keep the gasses in gas phase, run them through the cycle many times to perform all the boost manoeuvres, then cryocool them when you're at/near your destination. Now I have an image of a stage with two chuffing great balloons attached that I can't get out of my head. Better hope you don't get an MMOD strike.

Cheers, Martin
the concept of a cryocooler is to reduce the sink temperature below the boiling point (or to remove the heat flow from the environment to the tank) to prevent boiling in the first place.  IOW:  the freezer is kept at ~30F to keep the ice from melting in the first place.

The issue with LEO EP is the starting altitude.  ISS is ~ 60 minutes of sun/30 minutes of shade at 300 to 400 km (yes there are about two orbits a year at 51.6 degree inclination where the eclipse time is zero).   But 1000 km and full sun is too high in the optimization between LV IMLEO, so hence the ~650 km projection--below the belts too.  Another LEO EP issue is the 206 days to travel from LEO to L2 (http://forum.nasaspaceflight.com/index.php?topic=35115.msg1222963#msg1222963).

The batteries are heavy.. one issue with LEO EP along with turning the thrusters on and off.  adding battery weight requires more thrusters and power or the trip time is increased.  It would be fantastic if the technology matured to reduce the trip time and maintained very low costs.

Using propellant for power at $1,000 to $10,000 /kg -- if you are a LV provider, then you should jump all over this option. ;)  Oh..that's right...the ULA tanker acting like a depot option, which BTW, was a significantly better attempt at a sustainable architecture than BFRs.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 07/17/2014 09:06 pm


Duh! I had been thinking only of the SEP propellant for a tug moving the propellant to an EML2 depot.

I had entirely missed the detail that as well as the 10t of SEP propellant you could have something like 40t of conventional propellant plus whatever you need to mitigate boiloff during what could be a multi-year trip out to EML2

:-)

Quote
(edit) Maybe you would need a lot more power storage than I thought. I figure if you are going to EML2 by only thrusting when near earth towards the end you have orbits of around a month?

Lunar transit is about three days each way, so perhaps up to a few days, then transition to perigee raising?

Quote
I think you need on the order of a hundred tons of battery to provide 40kWh with typical battery power density?.. In which case I guess only something like a hydrogen/oxygen fuel cell would have the necessary storage to make a difference.

eg Li-ion battary 128Wh/kg. 40kW for SEP tug. hours in month = 720
battery mass = 40k*720/128 = 255 tons.

Tesla battery is 85 kwh. Only need to store enough power for one perigee burn.

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 07/17/2014 09:35 pm


c) This will probably require a big battery to allow you to effectively utilize the solar panels.
This is off topic but it was thinking about SEP to an EML2 depot that brought me here and the idea is no doubt too easily dismissed for its own thread:

I was just wondering if you could for example exploit your propellant mass to get a battery for free. I don't know whether propellants that are chosen to be cheap to ionize make them more or less appropriate.

It was just a random idea I thought might not have been considered since such a reaction would not need great storage (having tons and tons of mass to store only an orbit's worth of your solar panels) so in other circumstances would be ignored.

Lox & LH2. Run through a fuel cell to generate electricity (both Shuttle & Apollo did this), use electrolysis to break the water back down to gasses using power from the solar panels.

This assumes you already have a cryocooler on board to recycle boiloff gasses.

Cheers, Martin

Edit: not sure this is terribly efficient (too much heating up & then cryocooling).

Edit 2: unless you keep the gasses in gas phase, run them through the cycle many times to perform all the boost manoeuvres, then cryocool them when you're at/near your destination. Now I have an image of a stage with two chuffing great balloons attached that I can't get out of my head. Better hope you don't get an MMOD strike.

Cheers, Martin

the concept of a cryocooler is to reduce the sink temperature below the boiling point (or to remove the heat flow from the environment to the tank) to prevent boiling in the first place.  IOW:  the freezer is kept at ~30F to keep the ice from melting in the first place.

Yeah, but my point was once you have one in place, can you do something else with it?

Common concept seems to be to allow the tank to boiloff some gas, which removes the excess heat from the tank. The gas can then be transported to a remote cryocooler, which is good because the cooler's radiator is itself a heat load which wants to be kept away from the main tanks.

This seems quite compatible with re-liquifying gaseous H2 & O2 once they are not required for power storage.

Quote
The batteries are heavy.. one issue with LEO EP along with turning the thrusters on and off.  adding battery weight requires more thrusters and power or the trip time is increased.  It would be fantastic if the technology matured to reduce the trip time and maintained very low costs.

Batteries are heavy because they require electrodes to meet the maximum power requirement, and sufficient volume of electrolyte to meet the maximum energy storage requirement.

Electrodes are replaced with fuel cell (sized for peak power requirement during boost) and electrolysis (sized for peak power production by the solar panels).

Requirement to carry a lot of electrolyte for the energy storage is replaced by needing some tanking volume for water and gaseous O2 & H2. There is huge chemical energy stored in the separate gasses, and you get to reuse it hundreds of times before finally delivering it to a stage that will just burn it.

Quote
Using propellant for power at $1,000 to $10,000 /kg -- if you are a LV provider, then you should jump all over this option. ;)  Oh..that's right...the ULA tanker acting like a depot option, which BTW, was a significantly better attempt at a sustainable architecture than BFRs.

Not burning the prop to provide power, but just using it as the working fluid in the battery, and repeatedly converting it gas/water and back water/gas.

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: KelvinZero on 07/17/2014 11:38 pm
...
Lunar transit is about three days each way, so perhaps up to a few days, then transition to perigee raising?
...
Tesla battery is 85 kwh. Only need to store enough power for one perigee burn.
...
Although you are only doing a burn at one point, the aim is to store the solar energy collected during the entire preceding orbit to expend at that one point.

I was thinking you would start in a circular obit in LEO, keep boosting at just one point which will become the perigree. The apogee keeps getting further and further from the earth until it gets near the moon. Im imagining from there you get a bit of a slingshot to EML2, something like that.

T=2*Pi*sqrt(a^3/(MG))
a = largest semi axis major of depot on way to intercept moon, = half that of moon.
(moon's semi axis major = 384,399*10^3 meters)
G = 6.67*10^-11 N(m/kg)^2
M = mass of earth = 5.97*10^24

I get about ten days. Much less than the month I guessed at first because I was assuming similar to the lunar period.

btw, this raises an interesting possibility of doing away with your solar panels entirely:
http://en.wikipedia.org/wiki/Photocatalytic_water_splitting
(but that is getting way off topic and I havent seen great efficiencies for them)
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 07/18/2014 10:02 am


...
Lunar transit is about three days each way, so perhaps up to a few days, then transition to perigee raising?
...
Tesla battery is 85 kwh. Only need to store enough power for one perigee burn.
...
Although you are only doing a burn at one point, the aim is to store the solar energy collected during the entire preceding orbit to expend at that one point.

I was thinking you would start in a circular obit in LEO, keep boosting at just one point which will become the perigree. The apogee keeps getting further and further from the earth until it gets near the moon. Im imagining from there you get a bit of a slingshot to EML2, something like that.

If you're looking to store all the energy that the solar panels can acquire in 10 days, then that's one heck of a storage system.

There must come a time where it's better just to start thrusting continuously.

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: KelvinZero on 07/18/2014 10:22 am
Yep, and that isn't even mentioning the uber electric propulsion that is supposedly able to deliver this thrust all at once.. I was just thinking about that one power storage aspect.

I wonder how much just constant power and variable ISP would help with this sort of approach.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 11/16/2014 03:30 pm
There is some useful technology coming out of JWST.
One critical technology for fuel depots is the cryogenic cooler, JWST will flight prove this technology.

http://www.spacenews.com/article/civil-space/42563manufacturing-issues-plague-james-webb-space-telescope
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/16/2014 06:27 pm
There is some useful technology coming out of JWST.
One critical technology for fuel depots is the cryogenic cooler, JWST will flight prove this technology.

http://www.spacenews.com/article/civil-space/42563manufacturing-issues-plague-james-webb-space-telescope

That cooler is probably too small.  It will have been sized to cool the telescope's coolant rather than the main tank of a depot.  However the techniques are likely to be reusable with bigger parts.

edit:grammar
Title: Re: Propellant Depots - General Discussion
Post by: baldusi on 11/21/2014 09:16 pm
A cryocooler to 7Kelvin, well below the 13K for making hydrogen ice? You only need 20Kelvin for an hydrogen depot. And the sloshing might well be a worse problem. Think of the surface to mass ratio and how does that affects your temperature transfer.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/21/2014 11:45 pm
A cryocooler to 7Kelvin, well below the 13K for making hydrogen ice? You only need 20Kelvin for an hydrogen depot. And the sloshing might well be a worse problem. Think of the surface to mass ratio and how does that affects your temperature transfer.

You need a cryocooler that outputs heat/energy as fast as the sun adds it.  So the energy is proportional to the surface area of the tank exposed to sun light plus reflected light plus conduction.  A sunshield helps.
Title: Re: Propellant Depots - General Discussion
Post by: IslandPlaya on 11/22/2014 05:51 am
Yes but I think the point is you don't need to cool to liquid He temps, just H2 which is an order of magnitude easier.
Title: Re: Propellant Depots - General Discussion
Post by: baldusi on 11/28/2014 06:09 pm
A cryocooler to 7Kelvin, well below the 13K for making hydrogen ice? You only need 20Kelvin for an hydrogen depot. And the sloshing might well be a worse problem. Think of the surface to mass ratio and how does that affects your temperature transfer.

You need a cryocooler that outputs heat/energy as fast as the sun adds it.  So the energy is proportional to the surface area of the tank exposed to sun light plus reflected light plus conduction.  A sunshield helps.
It's a dynamic equilibrium. On the one hand you have heat input (sun, electronics, mechanism) and on the other you have heat output (basically your radiating surface * transitivity). For a LH2 depot, the sunshield is required. Look at the ACES proposals with MLI. You need not only to avoid the heat but to reject it. Since the rejection is proportional to the 4th power of the temperature difference, the temperature function is usually concave (you have an equilibrium). But it also means that each extra degree that you have to cool is more difficult to the 4th power. LH2 is liquid at around 20K, and it actually freezes at 14K. So you can't really get cooler than that. And thus requiring a cryocooler down to 7K is counterproductive.
What I meant by surface, is that the heating or cooling of the H2 liquid mass is, at boiling point, directly related to its surface. Thus, by sloshing you can get ridiculously higher ratios of surface to mass wrt all the liquid in a nice single blob. That means that you'll have many times extra heat input (at the same heat flux from the sun and with the same insulation) than if you can control sloshing somehow. In other word, it's easier to attack the sloshing problem than to put ridiculous requirements on the cryocooler.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/29/2014 12:51 am
Attach a thermostat to the cooling system.  When the temperature drops to say 19K turn the cooling system's power off.
Title: Re: Propellant Depots - General Discussion
Post by: baldusi on 11/29/2014 03:07 pm
You can't. Temperature is not uniform, specially with slosh. In no gravity you don't have a nice temperature differential up/down. In fact, if you chill the gaseous H2, you'll liquify it and lose pressure, unless you pressurize with He.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 11/29/2014 05:12 pm


What I meant by surface, is that the heating or cooling of the H2 liquid mass is, at boiling point, directly related to its surface. Thus, by sloshing you can get ridiculously higher ratios of surface to mass wrt all the liquid in a nice single blob. That means that you'll have many times extra heat input (at the same heat flux from the sun and with the same insulation) than if you can control sloshing somehow. In other word, it's easier to attack the sloshing problem than to put ridiculous requirements on the cryocooler.

To put that another way, you're saying that the vacuum provides an additional element of insulation between the liquid mass and the sun-heated external surface of the heatshield. Convection provides a short circuit of that additional insulation.

IIUC, ULA's IVF uses broad area cooling to keep the inner skin of the tank down below the boiling point. Convection then becomes irrelevant - there is no temperature difference, so no heat transfer into the fluid mass.

The issue then becomes providing sufficient insulation between that area-cooled inner skin and the Sun side of the Sunshield - via MLI.

IVF says that any orbiting location will have a certain daily demand of reaction mass for stationkeeping, which is a certain rate of loss of mass per day. It is only necessary to provide enough insulation such that the boiling off of that reaction mass rejects whatever heat gets through the insulation. IE the heat soaking into the system provides a boiloff rate that matches the ongoing rate of propellant demand for stationkeeping.

ZBO is completely pointless, except perhaps in interplanetary transit. But the advantage here is that the boiloff rate is pretty low here, anyway.

The advantage that ULA have is that H2 provides a tremendously amount of cooling per gram of mass boiled off. Other liquids will have a much harder time keeping the boiloff down to manageable rates.

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/30/2014 02:53 am
You can't. Temperature is not uniform, specially with slosh. In no gravity you don't have a nice temperature differential up/down. In fact, if you chill the gaseous H2, you'll liquify it and lose pressure, unless you pressurize with He.

At a depot we want the hydrogen to be a liquid.  Pressure is only needed when pumping the hydrogen.  UP and down can be created by simply rotating the tank to produce artificial gravity.  A couple of baffles will stir the liquid to help produce a uniform temperature.
Title: Re: Propellant Depots - General Discussion
Post by: baldusi on 11/30/2014 12:11 pm

You can't. Temperature is not uniform, specially with slosh. In no gravity you don't have a nice temperature differential up/down. In fact, if you chill the gaseous H2, you'll liquify it and lose pressure, unless you pressurize with He.

At a depot we want the hydrogen to be a liquid.  Pressure is only needed when pumping the hydrogen.  UP and down can be created by simply rotating the tank to produce artificial gravity.  A couple of baffles will stir the liquid to help produce a uniform temperature.
Have you ever seen a phase diagram? Without pressure you get below your vapor pressure and your liquid evaporates. You might add a rotational element, but then you can't easily do attitude control and translation. It might work, but spinning and un spinning plus slosh baffles add mass. You'd have to trade agains other option.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/30/2014 08:43 pm

You can't. Temperature is not uniform, specially with slosh. In no gravity you don't have a nice temperature differential up/down. In fact, if you chill the gaseous H2, you'll liquify it and lose pressure, unless you pressurize with He.

At a depot we want the hydrogen to be a liquid.  Pressure is only needed when pumping the hydrogen.  UP and down can be created by simply rotating the tank to produce artificial gravity.  A couple of baffles will stir the liquid to help produce a uniform temperature.
Have you ever seen a phase diagram? Without pressure you get below your vapor pressure and your liquid evaporates. You might add a rotational element, but then you can't easily do attitude control and translation. It might work, but spinning and un spinning plus slosh baffles add mass. You'd have to trade agains other option.

Depots are spacestations rather than vehicles, once in orbit the about the only movement is station keeping.
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 12/01/2014 12:01 pm

You can't. Temperature is not uniform, specially with slosh. In no gravity you don't have a nice temperature differential up/down. In fact, if you chill the gaseous H2, you'll liquify it and lose pressure, unless you pressurize with He.

At a depot we want the hydrogen to be a liquid.  Pressure is only needed when pumping the hydrogen.  UP and down can be created by simply rotating the tank to produce artificial gravity.  A couple of baffles will stir the liquid to help produce a uniform temperature.
Have you ever seen a phase diagram? Without pressure you get below your vapor pressure and your liquid evaporates. You might add a rotational element, but then you can't easily do attitude control and translation. It might work, but spinning and un spinning plus slosh baffles add mass. You'd have to trade agains other option.

Depots are spacestations rather than vehicles, once in orbit the about the only movement is station keeping.
While a LEO depot will need a Sunshield, a lot of heat comes from the Earth.

If the depot points its Sunshield permanently to the Sun (which is always in the same direction), it might still need to perform some other maneuvers to also shield from the Earth (which direction changes rapidly).

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 12/01/2014 03:39 pm

While a LEO depot will need a Sunshield, a lot of heat comes from the Earth.

If the depot points its Sunshield permanently to the Sun (which is always in the same direction), it might still need to perform some other maneuvers to also shield from the Earth (which direction changes rapidly).

Cheers, Martin

Looking at the picture the problem of heat from the Earth may have already been solved by ULA.
Title: Re: Propellant Depots - General Discussion
Post by: baldusi on 12/02/2014 01:37 am


You can't. Temperature is not uniform, specially with slosh. In no gravity you don't have a nice temperature differential up/down. In fact, if you chill the gaseous H2, you'll liquify it and lose pressure, unless you pressurize with He.

At a depot we want the hydrogen to be a liquid.  Pressure is only needed when pumping the hydrogen.  UP and down can be created by simply rotating the tank to produce artificial gravity.  A couple of baffles will stir the liquid to help produce a uniform temperature.
Have you ever seen a phase diagram? Without pressure you get below your vapor pressure and your liquid evaporates. You might add a rotational element, but then you can't easily do attitude control and translation. It might work, but spinning and un spinning plus slosh baffles add mass. You'd have to trade agains other option.

Depots are spacestations rather than vehicles, once in orbit the about the only movement is station keeping.
If you look at the IVF papers, they propose to use very small thrusters for station keeping that permanently settle the slosh.
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 12/09/2014 01:21 am
By the way, did anyone notice or mention in this thread that NASA STMD effectively killed the CPST cryogenics project ?

http://www.nasa.gov/sites/default/files/files/G-63505_Bridge_Summer_2014%281%29.pdf

Quote
Earlier this year, the Space Technology Mission Directorate (STMD) directed the Cryogenic Propellant Storage and Transfer (CPST) project to reformulate from a spaceflight technology demonstration project to a ground technology demonstration project based on the directorate’s budget environment
and the Space Launch System’s need for quicker, near-term infusion of key technologies

The last real update here was  www.nasa.gov/mission_pages/tdm/main/tdm_newsletter.html

http://www.nasa.gov/sites/default/files/files/TDM_Summer_2013.pdf
Quote
Members of the CPST technology demonstration team from Glenn, NASA’s Marshall Space Flight Center in Huntsville, Ala., and NASA’s Kennedy Space Center , Fla., shared results from four major cryogenic fluid test activities. These tests addressed technologies for passive and active thermal control, liquid acquisition in microgravity and chilldown of transfer lines — all key tests to advance NASA’s ability to safely and cost-effectively store and transfer advanced, cryogenic propellants required to power the nation’s future space vehicles.
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 01/06/2015 08:31 pm
One more very nice presentation from Dr. David J. Chato at Advanced Space Propulsion Workshop November 18th 2014.

List of presentations : http://aspw.jpl.nasa.gov/workshop-proceedings

Quote
We have no proven way to guarantee we can get gas-free liquid cryogens out of a tank in microgravity
- –Only known experience in the world is the single flight of the Russian Buran (liquid oxygen reaction control system)

..
Title: Re: Propellant Depots - General Discussion
Post by: Fsci123 on 01/09/2015 09:09 pm
Are there any papers that state the cost reduction when using propellant depots and other advanced infrastructure(SSTOs, spaceplanes, etc) as opposed to the situation we have now?
Title: Re: Propellant Depots - General Discussion
Post by: CommercialSpaceFan on 01/10/2015 01:47 pm
One more very nice presentation from Dr. David J. Chato at Advanced Space Propulsion Workshop November 18th 2014.

List of presentations : http://aspw.jpl.nasa.gov/workshop-proceedings (http://aspw.jpl.nasa.gov/workshop-proceedings)

Quote
We have no proven way to guarantee we can get gas-free liquid cryogens out of a tank in microgravity
- –Only known experience in the world is the single flight of the Russian Buran (liquid oxygen reaction control system)

..


Dave is off by a factor of 10 on Centaur demonstrated boil-off.  The actual number is about 2%/day.
http://www.ulalaunch.com/uploads/docs/Published_Papers/Upper_Stages/CentaurUpperstageApplicabilityforSeveralDayMissionDurationswithMinorInsulationModificationsAIAA20075845.pdf (http://www.ulalaunch.com/uploads/docs/Published_Papers/Upper_Stages/CentaurUpperstageApplicabilityforSeveralDayMissionDurationswithMinorInsulationModificationsAIAA20075845.pdf)

And this was with only a 3 layer MLI blanket designed to support 8 hour GSO missions.


Also, Dave is fixated on micro G.  In a low accelerated environment vapor free liquid acquisition has been demonstrated on 100's of flights including Saturn SIV, Ariane, Centaur, DCSS, etc.  Ground based experiments transferring cryogen's into a tank are actually conservative due to the reduced ullage/liquid interaction that is necessary to collapse the ullage for no vent fill.
Title: Re: Propellant Depots - General Discussion
Post by: Proponent on 01/10/2015 04:26 pm
Are there any papers that state the cost reduction when using propellant depots and other advanced infrastructure(SSTOs, spaceplanes, etc) as opposed to the situation we have now?

The ten attachments below regarding the advantages of propellant depots actually reflect just six studies, because in some cases I've attached multple papers from more or less the same group of people:

* 2 reports from NASA's OASIS study in the early 2000s.
* A Georgia Tech thesis by a student Young, followed by 2 papers involving his advisor, Alan Wilhite.
* A ULA study from 2010.
* A 2011 paper by an MSFC engineer and Gordon Woodcock.
* A paper by lunar scientist Paul Spudis and another MSFC engineer, Tony Lavoie; this one differs from the others in that the propellants used to fill the depots come principally from the moon rather than from Earth.
* That's it for complete reports, but we have 2 fragments of a study done by NASA's Human Architecture Team.  Without seeing the full study, it's hard rely on these.

If you're looking for clear apples-to-apples comparison of depot-based exploration architectures with heavy-lift alternatives, start with the Georgia Tech studies (attachments 4 & 5), which presents sand charts clearly laying out the cost advantages of depots for low-frequency NEA missions.

Given that NASA is spending tens of billions of dollars on a non-depot-based approach to solar-system exploration, another question that's worth asking is, where are the studies showing that depots are inferior?  On the floor of the House in back in 2012, Administrator Bolden said, in response to a query from Rep. Rohrabacher, that NASA had such study and would provided to Rohrabacher (http://forum.nasaspaceflight.com/index.php?topic=25953.msg777350#msg777350) (see 2:11:00 and following in this video (http://science.edgeboss.net/wmedia/science/sst2011/071211.wvx)).  To my knowledge, neither has the study been made public nor did Rohrabacher ever receive it (http://spacenews.com/policy/110913-lawmaker-asks-nasa-study.html).  If NASA possess a credible study supporting it's program, why would it fail to release it or at least provide it to relvant lawmakers?

In fact, a while ago I opened up a thread specifically for pointers to studies supporting heavy-lift architectures (http://forum.nasaspaceflight.com/index.php?topic=32810.0).  Not much turned up.
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 01/10/2015 09:00 pm
The ten attachments below regarding the advantages of propellant depots actually reflect just six studies, because in some cases I've attached multple papers from more or less the same group of people:
the problem with all the large scale space studies are that testing their falsification criteria would take years and billions. A science nobody can afford.

someone has to come up with a lot cheaper testable theories
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 01/10/2015 11:29 pm
The ten attachments below regarding the advantages of propellant depots actually reflect just six studies, because in some cases I've attached multple papers from more or less the same group of people:
the problem with all the large scale space studies are that testing their falsification criteria would take years and billions. A science nobody can afford.

someone has to come up with a lot cheaper testable theories

Use cubesats to simulate the two architectures.  A 1U cubesat can be launched for about $100,000.  A 3U (or 6U) cubesat could play the part of the depot.  A 6U cubesat can represent the SLS payload. A 2U cubesat with a thruster can represent the space tug that buys the propellant.
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 01/10/2015 11:34 pm
The ten attachments below regarding the advantages of propellant depots actually reflect just six studies, because in some cases I've attached multple papers from more or less the same group of people:
the problem with all the large scale space studies are that testing their falsification criteria would take years and billions. A science nobody can afford.

someone has to come up with a lot cheaper testable theories

Use cubesats to simulate the two architectures.  A 1U cubesat can be launched for about $100,000.  A 3U (or 6U) cubesat could play the part of the depot.  A 6U cubesat can represent the SLS payload. A 2U cubesat with a thruster can represent the space tug that buys the propellant.

Thats more or less what DARPA Phoenix is ( or was ) about.
Title: Re: Propellant Depots - General Discussion
Post by: CommercialSpaceFan on 01/11/2015 06:43 pm
Simplistically:

Giant rockets: Exploration must pay the cost of the rocket development ($20B for SLS) and annual recurring cost ($2B/yr? for SLS for 1 launch/year or about $20K/kg) and any upgrades (Block 1 to 1A to 2).  The investment in the giant rocket infrastructure provides little benefit to other space users (science, national security, commercial).  Sole source programs have a tendency to increase in cost.

Distributed launch and depots:  Rocket development is paid for by commercial and other users (Delta, Atlas, Antares, Falcon).  The infrastructure cost is shared by all users (existing recurring cost is about $10k/kg). The added launch demand of Exploration increases launch rate, reducing costs for all.  Vehicle improvements are funded commercially (or other users) and benefit all users.  Higher launch rate encourages more competition with likely cost reduction. 

The real question in the distributed launch/depot paradigm is what is the cost of the depot.  If it is ISS class, than the Giant rocket solution may be cheaper.  If the depot cost is reasonable than the distributed launch is likely to provide a more flexible and affordable path.
Title: Re: Propellant Depots - General Discussion
Post by: Vultur on 01/11/2015 08:07 pm
Also, I think the SLS program is also 'internally' inefficient - IE if SpaceX developed a rocket with the same capabilities as SLS the development cost would be a lot lower.

If they succeed in developing Raptor/BFR it will be interesting to compare the costs in 2021 or thereabouts...
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 01/11/2015 11:25 pm
Depot development may end up being driven by surplus performance of RLV.

A mini BFR (9 * Raptor) should be able to do 40t to LEO,  if used for ISS or Bigelow Dragon missions, it would have 30t of surplus fuel onboard. Would be a pity not leave it in orbit.
A Blue Origin 6 xBE4 should be capable of 30t leaving 20t of surplus fuel.
In both cases the fuel could be considered as free as Dragon has paid for mission.

Even a ULA expendable NLV should have a few tons of surplus fuel on these missions.

Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 02/02/2015 07:16 pm
I thought was a better place for this great find of Manboy

Cryo transfer demo using Dragon trunk.

I'm unsure if this has been posted. It's a proposal to do a Cryogenic Propellant Storage and Transfer mission using Dragon's trunk.

http://hdl.handle.net/2060/20140017303

There are a few other articles here on fuel depots and cryo transfer demonstration missions. These were based on using Centuar and having demo equipment as secondary payload.

Unfortunately I don't' think any cryo transfer mission has flown yet.
http://spirit.as.utexas.edu/~fiso/archivelist.htm
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 02/02/2015 11:20 pm
I thought was a better place for this great find of Manboy

Cryo transfer demo using Dragon trunk.

I'm unsure if this has been posted. It's a proposal to do a Cryogenic Propellant Storage and Transfer mission using Dragon's trunk.

http://hdl.handle.net/2060/20140017303

There are a few other articles here on fuel depots and cryo transfer demonstration missions. These were based on using Centuar and having demo equipment as secondary payload.

Unfortunately I don't' think any cryo transfer mission has flown yet.
http://spirit.as.utexas.edu/~fiso/archivelist.htm

For safety reasons this experiment proposes testing using nitrogen instead of LOX. Nitrogen is used as a coolant so depots may sell nitrogen as well as LOX. A difference in connector shape could be used to ensure the two substances are not mixed up.
Title: Re: Propellant Depots - General Discussion
Post by: CommercialSpaceFan on 02/07/2015 05:33 pm
By the way, did anyone notice or mention in this thread that NASA STMD effectively killed the CPST cryogenics project ?

http://www.nasa.gov/sites/default/files/files/G-63505_Bridge_Summer_2014%281%29.pdf


Any idea on how much has been spent on the CPST/eCryo program over the past 7 or so years?  Cost of the flight demo grew beyond $300m before being reformulated, but how much was actually spent?
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 02/08/2015 05:02 pm
By the way, did anyone notice or mention in this thread that NASA STMD effectively killed the CPST cryogenics project ?

http://www.nasa.gov/sites/default/files/files/G-63505_Bridge_Summer_2014%281%29.pdf


Any idea on how much has been spent on the CPST/eCryo program over the past 7 or so years?  Cost of the flight demo grew beyond $300m before being reformulated, but how much was actually spent?
They are still working on cryogenic transfer technology but ground based only for now. So it is not dead, just has to wait longer for flight data.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 04/03/2015 04:37 am
ULA and its parent companies have long be advocate s of fuel depots unfortunately their expensive LVs doesn't make economically viable.
Between the 3 companies they are slowly starting to put the technologies in place to make fuel depots possible.
1) The IVF system ULA plan to fly in 2018 means a OTV can be totally powered/ fuelled by LOX and LH.
2) The composites fuel tanks Boeing and NASA have developed mean the OTV can be super lite eg < 10% dry mass.
3) LM Jupiter tug would take care of docking of upper stage tanker to OTV. It could also maintain the OTV in orbit if it is empty.
4) A modified Exoliner could take care of fuel transfer, or even better provide active cryogenic cooling to OTV, with Jupiter providing power.

Even without the critical low cost reusable LV there may still be a case for fuel depot.
At present there are 3 vehicles ( CST100 , Jupiter, and DC) in running to supply crew and cargo to ISS using ULA LV. Between these vehicles ULA could be looking at few flights a year. The fuel depot could be used for surplus fuel off loaded from the visiting upper stages.

Given the NGLV will be capable of around 20t LEO, there should be a few spare tons each ISS visit.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 05/11/2015 02:17 pm
Inflatable insulating shield for Fuel depot.

http://www.parabolicarc.com/2015/05/11/paragon/#more-55245

Add this shield to a ULA ACES or IVF Centuar and we have a fuel depot. The best thing is that NASA doesn't need to spend $100s millions developing a fuel depot.
Title: Re: Propellant Depots - General Discussion
Post by: lamontagne on 07/20/2015 11:44 am
One interesting characteristic of a fuel depot is that it can make use of the excess capacity of many launches.
IT would become the norm to always launch at full load and transfer any leftover fuel to the depot.  That is if the added costs of maneuvering to the depot and of fuel transfer equipment could be offset by the purchase cost payed by the fuel depot owner.
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 07/20/2015 02:18 pm
One interesting characteristic of a fuel depot is that it can make use of the excess capacity of many launches.
IT would become the norm to always launch at full load and transfer any leftover fuel to the depot.  That is if the added costs of maneuvering to the depot and of fuel transfer equipment could be offset by the purchase cost payed by the fuel depot owner.

The main issue with this is that the energy required to match with the fuel depot is almost always going to be higher than that contained in the extra fuel.  IF aerobraking could be used on GTO stages, but then they would have to survive very long term boil off issues. Otherwise how many launches would be to an orbit within 2 or 3 degrees of the plane of the depot and that would have an apogee and perigee close enough energy wise. Also to avoid long periods of boil off potential, launches would have to be closely synched to the location of the depot.
Title: Re: Propellant Depots - General Discussion
Post by: RocketmanUS on 07/20/2015 05:18 pm
One interesting characteristic of a fuel depot is that it can make use of the excess capacity of many launches.
IT would become the norm to always launch at full load and transfer any leftover fuel to the depot.  That is if the added costs of maneuvering to the depot and of fuel transfer equipment could be offset by the purchase cost payed by the fuel depot owner.

The main issue with this is that the energy required to match with the fuel depot is almost always going to be higher than that contained in the extra fuel.  IF aerobraking could be used on GTO stages, but then they would have to survive very long term boil off issues. Otherwise how many launches would be to an orbit within 2 or 3 degrees of the plane of the depot and that would have an apogee and perigee close enough energy wise. Also to avoid long periods of boil off potential, launches would have to be closely synched to the location of the depot.
ACES and SEP

ACES I believe is being designed with propellant transfer. So if the payload used SEP to go from LEO to it's needed orbit then the payload and ACES ( US ) could be launched to the depot. There unneeded propellants for the ACES disposal could be transfered to the depot. The payload would disconnect from the ACES and use it's SEP to it's needed orbit. Would probable need more than one depot for diferent inclinations ( if there is enough flights in a given period of time ).
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/03/2015 08:02 am
A relevant post to the topic I made on another thread: http://forum.nasaspaceflight.com/index.php?topic=37464.msg1412670#msg1412670 (http://forum.nasaspaceflight.com/index.php?topic=37464.msg1412670#msg1412670)
Title: Re: Propellant Depots - General Discussion
Post by: oldAtlas_Eguy on 08/03/2015 06:19 pm
One interesting characteristic of a fuel depot is that it can make use of the excess capacity of many launches.
IT would become the norm to always launch at full load and transfer any leftover fuel to the depot.  That is if the added costs of maneuvering to the depot and of fuel transfer equipment could be offset by the purchase cost payed by the fuel depot owner.

The main issue with this is that the energy required to match with the fuel depot is almost always going to be higher than that contained in the extra fuel.  IF aerobraking could be used on GTO stages, but then they would have to survive very long term boil off issues. Otherwise how many launches would be to an orbit within 2 or 3 degrees of the plane of the depot and that would have an apogee and perigee close enough energy wise. Also to avoid long periods of boil off potential, launches would have to be closely synched to the location of the depot.
ACES and SEP

ACES I believe is being designed with propellant transfer. So if the payload used SEP to go from LEO to it's needed orbit then the payload and ACES ( US ) could be launched to the depot. There unneeded propellants for the ACES disposal could be transfered to the depot. The payload would disconnect from the ACES and use it's SEP to it's needed orbit. Would probable need more than one depot for diferent inclinations ( if there is enough flights in a given period of time ).

The interesting point about ACES is that add a sun shield and solar cell arrays with heat sink and it becomes a short duration depot (several months at least). Enough for it to be used to gather prop from other ACES until it is full such that it could then travel out to L2 where it would have almost half its propellant still on-board for use to support Lunar operations or other deep space missions. Once empty they may be thrown away by the RL-10 performing a disposal burn with the last of the residual prop. Or they could be collected to create a larger farm of tanks in a much larger permanent depot where the engines are unmounted and saved for use on such things as reusable landers where the engines don't outlast the structure or other systems meaning repacing just the engines prolongs the life of the lander by several factors.

ACES has everything except a long term power source, heat rejection, and sun/radiant heat shield to lower boil-off rates. It would not take much to add them. This poor man's depot would literally be available to wherever the ACES drops it payloads off at on a regular basis [LEO, GTO, GEO, L2, LLO, Sun Sync LEO, etc.].
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 08/03/2015 10:20 pm
ULA have recently received some funding from NASA to develop inflatable sun/heat shields for depots.

With sun shield and better insulation, ACES depot can last months without significant boil off if stationed at L2. LEO depots are not so good as they have to deal with heat from earth.
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/04/2015 02:27 pm
While the 'tanker' approach to propellant depots lends itself to the possibility of depot's serving different orbits. Most of the eventual uses of a depot would probably be served best with a prograde equatorial or near equatorial orbit. As has been pointed out, for a depot the $/Kg is the most important consideration, and from my point of view as important is reducing the ΔV so for many BLEO missions starting in LEO you reduce the ΔV requirement somewhat by launching from equatorial orbit just as you increase the fuel load that can make orbit to stock up your depot if it can launch into equatorial orbit from a near equatorial launch platform.

However there is still the potential for wanting a propellant depot to serve a different inclination of orbit.
Title: Re: Propellant Depots - General Discussion
Post by: spacenut on 08/04/2015 04:40 pm
Propellant depots would most likely be used for Earth-moon travel, or Earth-Mars travel.  So, that would mean one in LEO and one at L2 initially.  The one in LEO could also contain propellants for SEP tugs going to GSO or going to L2.  From L2 a SEP tug could refuel and go to Mars and back.  The other fuels like methane, oxygen, or hydrogen would be used for large human rated deep space transports or for Earth-moon transports. 

The fuel depot could become a very large space station, not only for fuel, but for human and cargo transfers, thus a space infrastructure system.  It should be designed modular so all launch providers could dock, deliver fuel or cargo, and receive fuel and cargo.  It could be built using all launch providers, thus utilizing all aspects of space exploration, from SEP technology, possibly EM propulsion technology, solar panels technology, etc. 
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 08/11/2015 12:10 am
It looks like ISS expedition 45/46 is going to get a microgravity glovebox experiment called ZBOT-1, aka Zero Boil-Off Tank. From what i understand it should be on near term cargo manifest already.

Pretty cool and relevant for the thread.

http://www.nasa.gov/mission_pages/station/research/experiments/1270.html
https://spaceflightsystems.grc.nasa.gov/sopo/ihho/psrp/msg/zbot/
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150002710.pdf
Title: Re: Propellant Depots - General Discussion
Post by: Burninate on 08/11/2015 06:26 am
While the 'tanker' approach to propellant depots lends itself to the possibility of depot's serving different orbits. Most of the eventual uses of a depot would probably be served best with a prograde equatorial or near equatorial orbit. As has been pointed out, for a depot the $/Kg is the most important consideration, and from my point of view as important is reducing the ΔV so for many BLEO missions starting in LEO you reduce the ΔV requirement somewhat by launching from equatorial orbit just as you increase the fuel load that can make orbit to stock up your depot if it can launch into equatorial orbit from a near equatorial launch platform.

However there is still the potential for wanting a propellant depot to serve a different inclination of orbit.
For low orbits:
Only in the abstract distant future when everybody has assured access to an equatorial launchsite.

Reaching an equatorial LEO from the equator is just slightly more efficient than reaching a latitude-inclination orbit from higher latitudes.  Reaching an equatorial LEO from higher latitudes is damn-near impossible, delta V goes up by kilometers per second and payload mass shrinks to a small fraction of its former value.

For high orbits it doesn't matter all that much - GTO or SSTO's apo boost only differs a little with latitude.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 08/11/2015 07:36 am
Only in the abstract distant future when everybody has assured access to an equatorial launchsite.

A floating launch platform (like Sea Launch) needn't be relegated to an abstract distant future. Add the notions of first stage RTLS and second stage once-around return, and payload integration while at sea.... A single floating platform at the equator could supply depots at multiple inclinations!
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/11/2015 05:48 pm
While the 'tanker' approach to propellant depots lends itself to the possibility of depot's serving different orbits. Most of the eventual uses of a depot would probably be served best with a prograde equatorial or near equatorial orbit. As has been pointed out, for a depot the $/Kg is the most important consideration, and from my point of view as important is reducing the ΔV so for many BLEO missions starting in LEO you reduce the ΔV requirement somewhat by launching from equatorial orbit just as you increase the fuel load that can make orbit to stock up your depot if it can launch into equatorial orbit from a near equatorial launch platform.

However there is still the potential for wanting a propellant depot to serve a different inclination of orbit.
For low orbits:
Only in the abstract distant future when everybody has assured access to an equatorial launchsite.


Why everyone? Why not just those who would choose to participate in the use of a fuel depot and where an equatorial orbit would make sense.

As I stated in my original post on this topic, I think there might be justification for depots or tankers servicing inclined or even highly inclined orbits as well (SSO for example). However, currently we have Kwajalein and Kourou close enough to the equator to be considered. If you are going to use a propellant depot at all it is because your mission would save money doing so, the largest historical volume of missions that a depot might make sense for are geosynchronous orbit boosts, these would save considerably if they were launched from an equatorial LEO depot and if, rather than having their upper stage refueled, they were being brought by a tug that returned to the depot. Launching the 'bird' to equatorial LEO on a vehicle optimized for its total cargo to LEO, then having it taken to GEO by a tug that returns to the depot for future use, could in theory make sense and would be much cheaper from LEO if that depot and tug were in equatorial orbit. You can use aerobraking for part of the return ΔV but you can't adjust inclination with aerobraking.

For flights to Mars or the asteroids, you certainly can save on ΔV and increase possible launch windows from a fixed orbit depot by having that depot in equatorial orbit.  It doesn't so much matter on cis-lunar flight, but if the depot is already there ...
Title: Re: Propellant Depots - General Discussion
Post by: Burninate on 08/13/2015 05:15 am
While the 'tanker' approach to propellant depots lends itself to the possibility of depot's serving different orbits. Most of the eventual uses of a depot would probably be served best with a prograde equatorial or near equatorial orbit. As has been pointed out, for a depot the $/Kg is the most important consideration, and from my point of view as important is reducing the ΔV so for many BLEO missions starting in LEO you reduce the ΔV requirement somewhat by launching from equatorial orbit just as you increase the fuel load that can make orbit to stock up your depot if it can launch into equatorial orbit from a near equatorial launch platform.

However there is still the potential for wanting a propellant depot to serve a different inclination of orbit.
For low orbits:
Only in the abstract distant future when everybody has assured access to an equatorial launchsite.


Why everyone? Why not just those who would choose to participate in the use of a fuel depot and where an equatorial orbit would make sense.

As I stated in my original post on this topic, I think there might be justification for depots or tankers servicing inclined or even highly inclined orbits as well (SSO for example). However, currently we have Kwajalein and Kourou close enough to the equator to be considered. If you are going to use a propellant depot at all it is because your mission would save money doing so, the largest historical volume of missions that a depot might make sense for are geosynchronous orbit boosts, these would save considerably if they were launched from an equatorial LEO depot and if, rather than having their upper stage refueled, they were being brought by a tug that returned to the depot. Launching the 'bird' to equatorial LEO on a vehicle optimized for its total cargo to LEO, then having it taken to GEO by a tug that returns to the depot for future use, could in theory make sense and would be much cheaper from LEO if that depot and tug were in equatorial orbit. You can use aerobraking for part of the return ΔV but you can't adjust inclination with aerobraking.

For flights to Mars or the asteroids, you certainly can save on ΔV and increase possible launch windows from a fixed orbit depot by having that depot in equatorial orbit.  It doesn't so much matter on cis-lunar flight, but if the depot is already there ...

I also believed something in this vicinity, but it turns out the math isn't nearly so rosy.

The equator rotates at about 464m/s.  Launching from an equatorial launchsite to an equatorial orbit gives a 464m/s boost to launches, over a launch to orbit from Non-Rotating Model Earth.  Launching from a 30 degree latitude launchsite to a 30 degree latitude orbit gives 464m/s * cos(30deg) = 402m/s boost to launches over Non-Rotating Model Earth.

NRME orbits give (very nearly) the same figures as launching to a polar orbit from anywhere on Earth.

At 340s Isp, a rocket that gets 62m/s "for free" can loft about 1.88% extra payload.

Do you think running a Mars program out of Kwaj using 98 launches per decade, is more credible than running a Mars program out of KSC using 100 launches per decade for the same payload?  Note also that you're almost completely cutting off collaboration possibilities with Japan, China, India, and Russia, leaving only ESA.
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/13/2015 05:57 am
I also believed something in this vicinity, but it turns out the math isn't nearly so rosy.

The equator rotates at about 464m/s.  Launching from an equatorial launchsite to an equatorial orbit gives a 464m/s boost to launches, over a launch to orbit from Non-Rotating Model Earth.  Launching from a 30 degree latitude launchsite to a 30 degree latitude orbit gives 464m/s * cos(30deg) = 402m/s boost to launches over Non-Rotating Model Earth.

NRME orbits give (very nearly) the same figures as launching to a polar orbit from anywhere on Earth.

At 340s Isp, a rocket that gets 62m/s "for free" can loft about 1.88% extra payload.

Do you think running a Mars program out of Kwaj using 98 launches per decade, is more credible than running a Mars program out of KSC using 100 launches per decade for the same payload?  Note also that you're almost completely cutting off collaboration possibilities with Japan, China, India, and Russia, leaving only ESA.

You don't see where I am talking about the savings. It is not savings of launch from the Equator to LEO but the savings of launching from LEO equatorial orbit to Mars or to GEO/GTO.   There is hardly any energy penalty launching from any inclination orbit in LEO to the moon, L1, or L2. But there is a substantial disadvantage in launching from an inclined orbit to TMI or to GEO/GTO. So if you need 100 launches from Earth to fuel 25 cargo flights to Mars starting from a 28degree inclined orbit you might get by with 75 flights to fuel 25 cargo flights launching from an equatorial orbit.

And yes there is the possibility of starting by doing a boost to a highly elliptical orbit stretching out nearly as far out as the moon, or going by way of L2, but the simplest solution that requires less risk, exposure to radiation etc is to start for Mars with a single burn from an equatorial or near equatorial orbit (peak efficiency from a 1.83° orbit).
Title: Re: Propellant Depots - General Discussion
Post by: douglas100 on 08/13/2015 09:05 am
I think the inclination of a LEO depot will be set by the latitude of the most northerly or southerly  launch site supplying it. An inclined orbit is more flexible for departures to different destinations beyond LEO, where orbital mechanics can dictate injection points well away from the equator.

I don't see any US launch provider establishing a major launch facility at Kwajalein just to gain a couple of percent of payload performance. It would be expensive to set up and more expensive to run than existing spaceports with their well established infrastructure and cheaper logistics. At one time SpaceX were talking about launching F9 from Kwajalein but changed their mind when SLC-40 became available.

When you look at the trades, I just don't see equatorial orbital depots as being necessary.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 08/13/2015 02:53 pm
An inclined orbit is more flexible for departures to different destinations beyond LEO, where orbital mechanics can dictate injection points well away from the equator.

Yes, and for a depot serving missions headed to arbitrary destinations this is compelling. But for a depot serving as the first stop on a pathway where the next stop is another depot near the Moon? Aren't there regular lunar transfer opportunities from equatorial LEO?
Title: Re: Propellant Depots - General Discussion
Post by: douglas100 on 08/13/2015 04:03 pm

Yes, and for a depot serving missions headed to arbitrary destinations this is compelling. But for a depot serving as the first stop on a pathway where the next stop is another depot near the Moon? Aren't there regular lunar transfer opportunities from equatorial LEO?

There are two opportunities a month to reach the Moon each month from parking orbits of any inclination. Equatorial orbit isn't specially favoured for lunar trajectories. The problem arises if the destination does not lie in the Earth's equatorial plane during the planetary launch window. Some Mars missions have used parking orbits with inclinations up to 52 degrees (Mars Odyssey, I believe.) So again, equatorial orbit gives no special benefit. Only geosynchronous orbit is a favoured destination from equatorial orbit.

Equatorial  has two benefits I can think of. The first is the one nadrec has been advocating: maximum payload to LEO. The second is, for a destination in low equatorial orbit from an equatorial launch site, there are no launch window constraints.

If you already have a spaceport like CSG at Kourou, great. But as I already argued, the small loss of performance caused by launching from CCFS, does not justify the great expense of the US setting up and operating a major launch facility at Kwajalein.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 08/13/2015 05:01 pm

Yes, and for a depot serving missions headed to arbitrary destinations this is compelling. But for a depot serving as the first stop on a pathway where the next stop is another depot near the Moon? Aren't there regular lunar transfer opportunities from equatorial LEO?

There are two opportunities a month to reach the Moon each month from parking orbits of any inclination. Equatorial orbit isn't specially favoured for lunar trajectories. The problem arises if the destination does not lie in the Earth's equatorial plane during the planetary launch window. Some Mars missions have used parking orbits with inclinations up to 52 degrees (Mars Odyssey, I believe.) So again, equatorial orbit gives no special benefit. Only geosynchronous orbit is a favoured destination from equatorial orbit.

Equatorial  has two benefits I can think of. The first is the one nadrec has been advocating: maximum payload to LEO. The second is, for a destination in low equatorial orbit from an equatorial launch site, there are no launch window constraints.

If you already have a spaceport like CSG at Kourou, great. But as I already argued, the small loss of performance caused by launching from CCFS, does not justify the great expense of the US setting up and operating a major launch facility at Kwajalein.

I'm not a fan of putting a depot in equatorial orbit (I'd rather have infrastructure in places where the widest range of launch sites can access it), but one other benefit for a low equatorial orbit is that the radiation levels there are tons lower even than ISS, since they don't pass through the South Atlantic Anomaly. There was a recent paper about space settlements (by Al Globus of NASA Ames, IIRC) making that point.

But setting up launch infrastructure for equatorial launch by multiple players (not just a point solution for one company) sounds daunting. Especially with how politically unstable most equatorial nations are.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/14/2015 09:41 pm
Ok, looking into this some more, and realizing that I had *face palm* been an idiot and forgot (despite having lived near the arctic circle for 15 years at one time) that the earth's axis of rotation is tilted to the ecliptic by 23.5°. So lets try this again: the ideal location for a depot serving Mars launches would be an orbit matching the inclination of the ecliptic to the equator (as opposed to the other possible orbit that is inclined 23.5° the opposite direction from the equator). A depot supporting GTO/GSO launches would of course still be best served in an equatorial orbit. Either of those depot's would be just as useful supporting lunar operations.

Given the slight difference from KSC latitude an orbit with a plane close to the ecliptic would be possible with launches from KSC.

Still if we do consider a depot to service GSO, GTO, then the equator does make sense. And given that Kourou already supports several countries and launch vehicles it would make sense to expand it rather than go to Kwajalein.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 08/15/2015 04:10 am
Um.... The orbit of Mars is not in the plane of the ecliptic. So direct-to-Mars injection points can end up far from the plane of the ecliptic too. Did you read what douglas100 wrote upthread, "[...] parking orbits with inclinations up to 52 degrees (Mars Odyssey)?" (See http://www.astronautix.com/craft/maryssey.htm#chrono for corroboration.)

But this whole notion of direct-LEO-to-Mars injection doesn't really play well with the theme of depots. If you have a propulsion system that can stop along the way and refuel, why take advantage of that only once during the trip?
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 08/15/2015 08:09 am
One interesting characteristic of a fuel depot is that it can make use of the excess capacity of many launches.
IT would become the norm to always launch at full load and transfer any leftover fuel to the depot.  That is if the added costs of maneuvering to the depot and of fuel transfer equipment could be offset by the purchase cost payed by the fuel depot owner.

The main issue with this is that the energy required to match with the fuel depot is almost always going to be higher than that contained in the extra fuel.  IF aerobraking could be used on GTO stages, but then they would have to survive very long term boil off issues. Otherwise how many launches would be to an orbit within 2 or 3 degrees of the plane of the depot and that would have an apogee and perigee close enough energy wise. Also to avoid long periods of boil off potential, launches would have to be closely synched to the location of the depot.
ACES and SEP

ACES I believe is being designed with propellant transfer. So if the payload used SEP to go from LEO to it's needed orbit then the payload and ACES ( US ) could be launched to the depot. There unneeded propellants for the ACES disposal could be transfered to the depot. The payload would disconnect from the ACES and use it's SEP to it's needed orbit. Would probable need more than one depot for diferent inclinations ( if there is enough flights in a given period of time ).

The interesting point about ACES is that add a sun shield and solar cell arrays with heat sink and it becomes a short duration depot (several months at least). Enough for it to be used to gather prop from other ACES until it is full such that it could then travel out to L2 where it would have almost half its propellant still on-board for use to support Lunar operations or other deep space missions.

Hmm, that is an interesting thought.

Assume that you want a depot at L2, and ACES are being used largely for GTO missions. That leaves each ACES in GTO after disposal.

This spends a lot of time distant from the Earth, so heating would be relatively low in terms of triggering boiloff.

ISTM that this is an ideal orbit for assembling multiple ACES together so they can pool their prop into one full load. As a downside, I believe these would require plane change and phasing burns in order to rendezvous. But then that's needed for LEO rendezvous anyway, and is easier with a high Apogee?

On the upside, the burn from GTO to TLI is pretty small if the starting inclination and phasing is correct.

In terms of the cost of using Vulcan to lift this residual prop, is the assumption that each would launch in its heaviest configuration (equivalent of Atlas 551), to maximise residuals on orbit? Would the extra risk to the primary payload of multiple solids be balanced by a large extra margin during the u/s burn?

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/15/2015 04:44 pm
Um.... The orbit of Mars is not in the plane of the ecliptic. So direct-to-Mars injection points can end up far from the plane of the ecliptic too. Did you read what douglas100 wrote upthread, "[...] parking orbits with inclinations up to 52 degrees (Mars Odyssey)?" (See http://www.astronautix.com/craft/maryssey.htm#chrono for corroboration.)

But this whole notion of direct-LEO-to-Mars injection doesn't really play well with the theme of depots. If you have a propulsion system that can stop along the way and refuel, why take advantage of that only once during the trip?


Mars is only about 1.75° off of the ecliptic. 

Not withstanding the fact that a space craft in the right polar or any other inclination orbit can have a launch window that takes it out tangential to the Earth's orbit around the sun, there is no orbit other than one that is in the same plane as the ecliptic that will always have relatively efficient launch windows throughout the launch season and in every subsequent season.  There is no advantage to a depot that has to shift planes throughout the launch season.

You do have to launch close to the ecliptic plane, either because you are in a matching plane or you can come out along that path at the right time from an inclined orbit or because you change the direction as part of your exit burn (which still has advantages over making a significant plane change later in flight. Now if you used a perfect Hohmann orbit you could get away (with a energy penalty at both ends) with being off the ecliptic, but as soon as you vary significantly from the half orbit style Hohmann and use a higher energy shorter (or longer) flight time orbit with an ellipse that takes you outside the orbit of Mars you must stay in the plane of Mars orbit or have a very large plane correction at the appropriate plane crossing node along your trajectory.

So for a depot to be effective launching many missions over a full, 10 - 12 week launch season, to Mars, the most energy ( ΔV) efficient location for that depot is one in the same plane as the ecliptic.
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/15/2015 04:49 pm

But this whole notion of direct-LEO-to-Mars injection doesn't really play well with the theme of depots. If you have a propulsion system that can stop along the way and refuel, why take advantage of that only once during the trip?

Where else (except in Earth orbit or cis lunar space) could it be?  You could have a depot in a Mars orbit of course and I expect there to be one, for the purposes I see for exploring Mars I expect that depot to be in a fairly high inclination orbit as well.

But you can't with out using a lot of energy rendezvous with a depot on some sort of solar orbit between Earth and Mars, and while you can have an L2 depot or some other location, you are adding to the energy, complexity and radiation exposure (for crewed flights) to use the depot effectively.
Title: Re: Propellant Depots - General Discussion
Post by: douglas100 on 08/15/2015 05:14 pm

...So for a depot to be effective launching many missions over a full, 10 - 12 week launch season, to Mars, the most energy ( ΔV) efficient location for that depot is one in the same plane as the ecliptic.

A couple of points.

A depot orbiting the Earth in the plane of the ecliptic, with an inclination of 23.5 degrees will not stay in the ecliptic plane. Although it will remain at that inclination, the orbit will slowly precess out of the ecliptic plane. I think there is little to be gained by using such an orbit.

The important point for vehicles departing the depot for BEO is the direction the departure trajectory must take relative to the celestial sphere. If you are heading for something even a degree or so out of the ecliptic you may have to aim at points quite far from the celestial equator in order to get a solar orbit which intersects that of the target.

Basically, what it comes down to is what the depot is used for. All destinations apart from GSO are constantly changing their relative positions to the Earth. A depot serving multiple users must be flexible. Departures from such a depot might have to be set up some time in advance by orbital phasing, depending on destination. This would be similar to the way the ISS sets itself up to receive Soyuz and Progress 6 hour transfers. A flexible depot would then best be at a fairly high inclination to allow the injection points of departure trajectories to be as far from the equator as required.

So I don't think there will be one giant depot where everyone comes to fuel up before departing every which way. Rather, I would expect smaller depots (ACES sized?), deployed to inclinations which best suit their users.

The exception to that is the one you already mentioned: an equatorial depot supplying the GSO traffic. But that would be a specialist application rather than a general one.
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/15/2015 05:23 pm

...So for a depot to be effective launching many missions over a full, 10 - 12 week launch season, to Mars, the most energy ( ΔV) efficient location for that depot is one in the same plane as the ecliptic.

A couple of points.

A depot orbiting the Earth in the plane of the ecliptic, with an inclination of 23.5 degrees will not stay in the ecliptic plane. Although it will remain at that inclination, the orbit will slowly precess out of the ecliptic plane. I think there is little to be gained by using such an orbit.

The important point for vehicles departing the depot for BEO is the direction the departure trajectory must take relative to the celestial sphere. If you are heading for something even a degree or so out of the ecliptic you may have to aim at points quite far from the celestial equator in order to get a solar orbit which intersects that of the target.

Basically, what it comes down to is what the depot is used for. All destinations apart from GSO are constantly changing their relative positions to the Earth. A depot serving multiple users must be flexible. Departures from such a depot might have to be set up some time in advance by orbital phasing, depending on destination. This would be similar to the way the ISS sets itself up to receive Soyuz and Progress 6 hour transfers. A flexible depot would then best be at a fairly high inclination to allow the injection points of departure trajectories to be as far from the equator as required.

So I don't think there will be one giant depot where everyone comes to fuel up before departing every which way. Rather, I would expect smaller depots (ACES sized?), deployed to inclinations which best suit their users.

The exception to that is the one you already mentioned: an equatorial depot supplying the GSO traffic. But that would be a specialist application rather than a general one.

So is the precession so fast as to preclude the use of a single depot for the 10-12 week launch window to Mars?
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/15/2015 05:31 pm
Oh and one other point, any orbit is good at least twice a month for cis-lunar operations, equatorial any time of the month with a maximum penalty of 700m/s - so the GSO depot can just as easily serve lunar operations as any other orbit could, but more conveniently. Would combining lunar operations with GSO not make sense for a specialized depot.
Title: Re: Propellant Depots - General Discussion
Post by: douglas100 on 08/15/2015 05:37 pm
My general point is that there is no "fixed" orbit for this kind of operation. It depends on many factors. I wouldn't let maximum payload to LEO and minimum delta V drive your conclusions exclusively. These can be traded against operational efficiencies such as using existing vehicles and launch sites and having multiple users and suppliers for the depot(s).
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/15/2015 05:44 pm
But many people posting here are completely dismissive of Kourou which would seem to me (and to several launch providers) to have a definite advantage.
Title: Re: Propellant Depots - General Discussion
Post by: douglas100 on 08/15/2015 07:24 pm
I'm not sure who has been dismissive of Kourou.

There have been only two commercial launch operators using equatorial launch sites, Arianespace and Sea Launch. Zenit's GTO payload was considerable increased by equatorial launch but they're currently out of the game for reasons other than performance.

Which leaves Ariane. Although Arianespace have been very successful, their equatorial advantage has not put them beyond the reach of other competitors, as SpaceX has shown. And what other launch provider has said, "Look at Arianespace's performance advantage, we must build an equatorial launch pad somewhere to compete?" Only Sea Launch. (And it's not clear if their marine infrastructure was cheaper than a comparative land based equivalent.) Not SpaceX (who briefly considered Omalek), not ULA....

Actually, this point about equatorial launch costs is slightly OT, because it is irrelevant whether depots are used or not. It comes down to whether it is financially worthwhile for launch providers to build new equatorial launch sites for performance gain only, for whatever the operational purpose. I don't believe it is for several reasons. Jon Goff gave one of them upthread.

Edit: added "commercial."
Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/15/2015 10:21 pm
I'm not sure who has been dismissive of Kourou.

There have been only two commercial launch operators using equatorial launch sites, Arianespace and Sea Launch. Zenit's GTO payload was considerable increased by equatorial launch but they're currently out of the game for reasons other than performance.

Which leaves Ariane. Although Arianespace have been very successful, their equatorial advantage has not put them beyond the reach of other competitors, as SpaceX has shown. And what other launch provider has said, "Look at Arianespace's performance advantage, we must build an equatorial launch pad somewhere to compete?" Only Sea Launch. (And it's not clear if their marine infrastructure was cheaper than a comparative land based equivalent.) Not SpaceX (who briefly considered Omalek), not ULA....

Actually, this point about equatorial launch costs is slightly OT, because it is irrelevant whether depots are used or not. It comes down to whether it is financially worthwhile for launch providers to build new equatorial launch sites for performance gain only, for whatever the operational purpose. I don't believe it is for several reasons. Jon Goff gave one of them upthread.

Edit: added "commercial."

Now you are being dismissive of Kourou, why would anyone have to build a new equatorial launch site, Kourou can have more pads developed. Currently several vehicles launch from there.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 08/16/2015 04:42 am
Umm...  ESA pays CNES something like €435 million for 5 years use of CSG.
http://www.esa.int/Our_Activities/Launchers/ESA_and_CNES_sign_contract_on_Guiana_Space_Centre_CSG
Title: Re: Propellant Depots - General Discussion
Post by: douglas100 on 08/17/2015 08:36 am

Now you are being dismissive of Kourou, why would anyone have to build a new equatorial launch site, Kourou can have more pads developed. Currently several vehicles launch from there.

Yep, Ariane 5, Soyuz ST and Vega. All operated by...guess who?

The answer to your question is politics. The French government will not allow any competitor to Arianespace  to operate from their territory.

If we are talking about a non commercial international collaboration like ISS involving depots (like maybe human lunar exploration) then the depot will be at an inclination suitable to the partners. It won't be equatorial because in the real messy world of compromise and trades, the small gain in performance in launching from the equator is offset by other factors.

And I misunderstood what you meant by "dismissing" Kourou. I thought you meant folks were criticising Korou as a good launch site in general (which it is.) But I am most certainly dismissing it in the sense you meant.
 



Title: Re: Propellant Depots - General Discussion
Post by: nadreck on 08/17/2015 07:59 pm

Now you are being dismissive of Kourou, why would anyone have to build a new equatorial launch site, Kourou can have more pads developed. Currently several vehicles launch from there.

Yep, Ariane 5, Soyuz ST and Vega. All operated by...guess who?

The answer to your question is politics. The French government will not allow any competitor to Arianespace  to operate from their territory.

If we are talking about a non commercial international collaboration like ISS involving depots (like maybe human lunar exploration) then the depot will be at an inclination suitable to the partners. It won't be equatorial because in the real messy world of compromise and trades, the small gain in performance in launching from the equator is offset by other factors.

And I misunderstood what you meant by "dismissing" Kourou. I thought you meant folks were criticising Korou as a good launch site in general (which it is.) But I am most certainly dismissing it in the sense you meant.


To me the advantage of using Kourou for a launch site outweighs the political issues. If we presume that Arianespace works with Soyuz, they could work with any other launch vehicle, and if they could turn the location advantage to their advantage having an equatorial depot themselves or co-operating with another agency or company that has one but wants to share it for the access advantage from Kourou it certainly could happen.
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 10/21/2015 10:30 pm
It looks like ISS expedition 45/46 is going to get a microgravity glovebox experiment called ZBOT-1, aka Zero Boil-Off Tank. From what i understand it should be on near term cargo manifest already.

ZBOT is scheduled to launch on CRS-8 ( i.e. sometime in 2016~ish )

http://www.spacestationresearch.com/wp-content/uploads/ZIN-ZBOT-Summary.pdf

Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 10/23/2015 07:58 am


A depot orbiting the Earth in the plane of the ecliptic, with an inclination of 23.5 degrees will not stay in the ecliptic plane. Although it will remain at that inclination, the orbit will slowly precess out of the ecliptic plane. I think there is little to be gained by using such an orbit.

What would cause that precession?

Cheers, Martin
Title: Re: Propellant Depots - General Discussion
Post by: douglas100 on 10/23/2015 08:54 am
The oblateness of the Earth. The same effect causes sun synchronous orbits to precess in such a way that the orbital plane remains fixed relative to the Sun-Earth direction.

https://en.wikipedia.org/wiki/Nodal_precession (https://en.wikipedia.org/wiki/Nodal_precession)
Title: Re: Propellant Depots - General Discussion
Post by: MP99 on 10/23/2015 09:47 pm
OK, thanks.
Title: Re: Propellant Depots - General Discussion
Post by: Robotbeat on 10/26/2015 12:17 am
Um.... The orbit of Mars is not in the plane of the ecliptic. So direct-to-Mars injection points can end up far from the plane of the ecliptic too. Did you read what douglas100 wrote upthread, "[...] parking orbits with inclinations up to 52 degrees (Mars Odyssey)?" (See http://www.astronautix.com/craft/maryssey.htm#chrono for corroboration.)

But this whole notion of direct-LEO-to-Mars injection doesn't really play well with the theme of depots. If you have a propulsion system that can stop along the way and refuel, why take advantage of that only once during the trip?
Agreed. Or at least, agreed that LEO-to-Mars makes a lot less sense than some high-Earth/cislunar-orbit-to-Mars.

Gather propellant in LEO launched by RLVs, then use SEP to push that propellant to a depot in some high energy orbit. That allows you to cheaply get to Mars quickly.
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 04/14/2016 06:00 pm
An interesting report

https://www.cryogenicsociety.org/csa_highlights/26th_space_cryogenics_workshop/

Full pdf with abstracts on NTRS (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160001109.pdf)
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 04/15/2016 01:03 am
The New Shepard should offer larger scale testing of LH and LOX transfers without expense of going to orbit.

Sent from my ALCATEL ONE TOUCH 6030X using Tapatalk

Title: Re: Propellant Depots - General Discussion
Post by: oldAtlas_Eguy on 04/18/2016 02:43 pm
The New Shepard should offer larger scale testing of LH and LOX transfers without expense of going to orbit.

Sent from my ALCATEL ONE TOUCH 6030X using Tapatalk
That would imply that if done BO would develop a fuel transfer capable US for their orbital LV system. That would also imply that that BO would develop a LEO LOX/LH2 depot. So far there has been no information or hints that BO has any such intentions.

But maybe someone should point out to them what this tech could do for their transportation system.
Title: Re: Propellant Depots - General Discussion
Post by: GWH on 04/18/2016 03:00 pm
....Or it could just be a science payload that BO hosts for a paying customer.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 04/18/2016 05:35 pm
The New Shepard should offer larger scale testing of LH and LOX transfers without expense of going to orbit.

Sent from my ALCATEL ONE TOUCH 6030X using Tapatalk
That would imply that if done BO would develop a fuel transfer capable US for their orbital LV system. That would also imply that that BO would develop a LEO LOX/LH2 depot. So far there has been no information or hints that BO has any such intentions.

But maybe someone should point out to them what this tech could do for their transportation system.
I was think payload experiment in capsule, that can use >100kg fuel.


Sent from my ALCATEL ONE TOUCH 6030X using Tapatalk

Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 05/04/2016 11:03 pm

http://www.parabolicarc.com/2016/05/04/nasa-selects-paragons-inspace-fuel-depot-tech-sbir-phase-award/

Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 05/04/2016 11:07 pm
Altius cryogenic coupler for fuel transfer.

http://sbir.nasa.gov/SBIR/abstracts/16/sbir/phase1/SBIR-16-1-H2.04-8454.html

In Phase I, Altius and its team will focus on developing and testing a proof-of-concept of this innovative new cryogenic sealing architecture, including performing insertion/extraction and leak testing, to compare with a more traditional spring-energized polymer seal concept. Altius will then update the coupling design based on lessons learned-from these tests, raising the TRL from 2 to 3 at the end of Phase I.
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 09/18/2016 12:32 am
Just to note, the number of propellant depots in LEO went from 1 to 2 a few days ago (https://forum.nasaspaceflight.com/index.php?topic=30224.0). One operational, one prototype.

It probably looks and works very similar to the one described here (http://ntrs.nasa.gov/search.jsp?R=19870012563)
Title: Re: Propellant Depots - General Discussion
Post by: Lar on 01/19/2017 05:42 pm
Crosslinking for reference:

http://forum.nasaspaceflight.com/index.php?topic=40815.msg1631777#msg1631777 and the next few posts have information on the ZBOT experiment to be flown shortly.

NASA link on ZBOT

https://www.nasa.gov/mission_pages/station/research/experiments/1270.html
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 01/19/2017 06:12 pm
Altius cryogenic coupler for fuel transfer.

http://sbir.nasa.gov/SBIR/abstracts/16/sbir/phase1/SBIR-16-1-H2.04-8454.html

In Phase I, Altius and its team will focus on developing and testing a proof-of-concept of this innovative new cryogenic sealing architecture, including performing insertion/extraction and leak testing, to compare with a more traditional spring-energized polymer seal concept. Altius will then update the coupling design based on lessons learned-from these tests, raising the TRL from 2 to 3 at the end of Phase I.

I just saw this from mid last year. The Phase I went pretty well, and we have a Phase II proposal in for evaluation. We won't know if we have the Phase II until mid-March. If we win the Phase II, but if we do get it, it will be an important step in making upper stages for several launch vehicles inherently refuelable.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Space Ghost 1962 on 01/19/2017 06:37 pm
Altius cryogenic coupler for fuel transfer.

http://sbir.nasa.gov/SBIR/abstracts/16/sbir/phase1/SBIR-16-1-H2.04-8454.html

In Phase I, Altius and its team will focus on developing and testing a proof-of-concept of this innovative new cryogenic sealing architecture, including performing insertion/extraction and leak testing, to compare with a more traditional spring-energized polymer seal concept. Altius will then update the coupling design based on lessons learned-from these tests, raising the TRL from 2 to 3 at the end of Phase I.


I just saw this from mid last year. The Phase I went pretty well, and we have a Phase II proposal in for evaluation. We won't know if we have the Phase II until mid-March. If we win the Phase II, but if we do get it, it will be an important step in making upper stages for several launch vehicles inherently refuelable.

~Jon

Congrats Jon to you and your Altius team.

Edit/Lar: demangled quotes
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/11/2017 04:37 am
As I mentioned in this other post and the blog article it links to (http://forum.nasaspaceflight.com/index.php?topic=22738.msg1652524#msg1652524), Altius was just awarded an SBIR Phase II to continue work on the cryogenic propellant coupler. We should have the contract started by some time in late April or early May. I'll post more details on the Altius thread when I have them.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: AncientU on 03/12/2017 09:24 pm
As I mentioned in this other post and the blog article it links to (http://forum.nasaspaceflight.com/index.php?topic=22738.msg1652524#msg1652524), Altius was just awarded an SBIR Phase II to continue work on the cryogenic propellant coupler. We should have the contract started by some time in late April or early May. I'll post more details on the Altius thread when I have them.

~Jon

Congrats Jon!

Is the idea to make universal couplers following the docking adaptor concept?  Fuel specific or general cryogens?  What types of flow rates/volume transfer rates are targeted (large craft or small)?
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/15/2017 03:40 pm
As I mentioned in this other post and the blog article it links to (http://forum.nasaspaceflight.com/index.php?topic=22738.msg1652524#msg1652524), Altius was just awarded an SBIR Phase II to continue work on the cryogenic propellant coupler. We should have the contract started by some time in late April or early May. I'll post more details on the Altius thread when I have them.

~Jon

Congrats Jon!

Is the idea to make universal couplers following the docking adaptor concept?  Fuel specific or general cryogens?  What types of flow rates/volume transfer rates are targeted (large craft or small)?

I'm not sure what you mean by your first question. But for the second question, the architecture we're developing should work for any cryogenic propellant (LOX, LH2, liquid methane, liquid propane, liquid helium, etc). And for the other question, the coupling should be scalable from smallsat launch vehicle application sizes all the way up to ACES, EUS, ITS, or New Glenn's upper stage. In Phase II we're focusing on something on the smaller end of that spectrum, but we could probably make this work for any flow rate realistically imaginable.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/15/2017 06:57 pm
As I mentioned in this other post and the blog article it links to (http://forum.nasaspaceflight.com/index.php?topic=22738.msg1652524#msg1652524), Altius was just awarded an SBIR Phase II to continue work on the cryogenic propellant coupler. We should have the contract started by some time in late April or early May. I'll post more details on the Altius thread when I have them.

~Jon

Congrats Jon!

Is the idea to make universal couplers following the docking adaptor concept?  Fuel specific or general cryogens?  What types of flow rates/volume transfer rates are targeted (large craft or small)?

I'm not sure what you mean by your first question. But for the second question, the architecture we're developing should work for any cryogenic propellant (LOX, LH2, liquid methane, liquid propane, liquid helium, etc). And for the other question, the coupling should be scalable from smallsat launch vehicle application sizes all the way up to ACES, EUS, ITS, or New Glenn's upper stage. In Phase II we're focusing on something on the smaller end of that spectrum, but we could probably make this work for any flow rate realistically imaginable.

~Jon

The NASA Docking System, which implements the International Docking System Standard (IDSS). The standard has a planned extension "... in future implementations will be able to transfer water, fuel, oxidizer and pressurant as well."

The IDSS is currently at Revision E October 2016. The appropriate pages are 3-38 and 3-59. Currently the actual size and shape of the connectors is undefined.
http://www.internationaldockingstandard.com (http://www.internationaldockingstandard.com)
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 03/15/2017 08:03 pm
The IDSS is currently at Revision E October 2016. The appropriate pages are 3-38 and 3-59. Currently the actual size and shape of the connectors is undefined.
Relevant thread plug (http://forum.nasaspaceflight.com/index.php?topic=42501.0) where proposed fluid and electrical coupling standard interface is being defined for satellites.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/15/2017 10:15 pm
The NASA Docking System, which implements the International Docking System Standard (IDSS). The standard has a planned extension "... in future implementations will be able to transfer water, fuel, oxidizer and pressurant as well."

The IDSS is currently at Revision E October 2016. The appropriate pages are 3-38 and 3-59. Currently the actual size and shape of the connectors is undefined.
http://www.internationaldockingstandard.com (http://www.internationaldockingstandard.com)

I'm familiar with IDS/NDS, but it wasn't clear that was what he was asking. Yes, you could use this coupler with something like that. But that isn't the planned operational mode unless a customer wants it done that way. My notional approach would be to have a soft-capture using magnetic versions of our sticky boom, followed by a robotic connection. Trying to do a traditional docking operation requires more prox-ops capability than upper stages typically have.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/16/2017 05:00 am
The NASA Docking System, which implements the International Docking System Standard (IDSS). The standard has a planned extension "... in future implementations will be able to transfer water, fuel, oxidizer and pressurant as well."

The IDSS is currently at Revision E October 2016. The appropriate pages are 3-38 and 3-59. Currently the actual size and shape of the connectors is undefined.
http://www.internationaldockingstandard.com (http://www.internationaldockingstandard.com)

I'm familiar with IDS/NDS, but it wasn't clear that was what he was asking. Yes, you could use this coupler with something like that. But that isn't the planned operational mode unless a customer wants it done that way. My notional approach would be to have a soft-capture using magnetic versions of our sticky boom, followed by a robotic connection. Trying to do a traditional docking operation requires more prox-ops capability than upper stages typically have.

~Jon

Upper stages may have insufficient prox-ops but landers and capsules are very nimble and will have NDS. Reusable landers need to refuel.
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/16/2017 09:21 am
Thinking about it a spacestation is likely to have both docking ports and arms.

Docking ports are expensive and heavy because they provide access for people and power. The extended version supplies a simple way of providing fuel, LOX and water to a lander.

An upper stage does not carry people (unlike the capsule) so saving mass getting the spacestation's arm to grab the stage would be a valid attachment system. There would have to be pipes to carry the propellant from the arm to the lander, possibly via fuel tanks.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/17/2017 02:18 pm
The NASA Docking System, which implements the International Docking System Standard (IDSS). The standard has a planned extension "... in future implementations will be able to transfer water, fuel, oxidizer and pressurant as well."

The IDSS is currently at Revision E October 2016. The appropriate pages are 3-38 and 3-59. Currently the actual size and shape of the connectors is undefined.
http://www.internationaldockingstandard.com (http://www.internationaldockingstandard.com)

I'm familiar with IDS/NDS, but it wasn't clear that was what he was asking. Yes, you could use this coupler with something like that. But that isn't the planned operational mode unless a customer wants it done that way. My notional approach would be to have a soft-capture using magnetic versions of our sticky boom, followed by a robotic connection. Trying to do a traditional docking operation requires more prox-ops capability than upper stages typically have.

~Jon

Upper stages may have insufficient prox-ops but landers and capsules are very nimble and will have NDS. Reusable landers need to refuel.

As I said, there's nothing to preclude using this coupler as part of an NDS. It's just a simple tube-in-tube design with some magic in the seal design. I just also think that unless you need to seal a large diameter pressure hatch (like you would for a capsule or a lander), that a hard docking ring isn't the right approach compared to a soft-dock approach. Fortunately the coupler can support either method quite easily.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/17/2017 02:21 pm
An upper stage does not carry people (unlike the capsule) so saving mass getting the spacestation's arm to grab the stage would be a valid attachment system. There would have to be pipes to carry the propellant from the arm to the lander, possibly via fuel tanks.

We're also talking about multiple much lighter weight arms than the station arms. Like was shown in the picture in my blog post:

http://www.altius-space.com/wp-content/uploads/2017/03/DistributedLaunchFauxArt.png

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: oldAtlas_Eguy on 03/17/2017 02:33 pm
What is really needed is a lightweight NDS that offers power and fluid transfers but has no people access ability. A reusable tug (re-purposed US) would need the structural docking offered by NDS to latch onto payloads and get them to other orbits. An interface to dock to the depot and the same to then dock to the payload would simplify the use of such a tug. Also if a vehicle that wants to refuel uses an NDS (with fluids transfer standard) then no arms are necessary on the depot unless they are needed to perform maintenance on the depot itself.

Standardize the interfaces. Simplyfy the system and methods/procedures. Use of an arm increases complexity, time, and cost of attaching to the depot. An automated docking is the lowest cost procedure wise.

Look at the system from the depot provider's point of view. Make the attachment and fueling of vehicles as automated/standard and simple as possible.

Put the requirement onto the users to comply with standards if they want the fuel. Also this simplifies the prop up-load deliveries such that they use the same docking mechanisms/ports. So that only one port type exists on the depot.

A BTW fluid transfers are halted during docking. So it is in everyone's interest if the depot is servicing multiple vehicles simultaneous (tanker and tugs/Upper Stages) that docking is done in the shortest amount of time. Arm capture and berthing is a very long process.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/17/2017 11:30 pm
What is really needed is a lightweight NDS that offers power and fluid transfers but has no people access ability. A reusable tug (re-purposed US) would need the structural docking offered by NDS to latch onto payloads and get them to other orbits. An interface to dock to the depot and the same to then dock to the payload would simplify the use of such a tug. Also if a vehicle that wants to refuel uses an NDS (with fluids transfer standard) then no arms are necessary on the depot unless they are needed to perform maintenance on the depot itself.

Standardize the interfaces. Simplyfy the system and methods/procedures. Use of an arm increases complexity, time, and cost of attaching to the depot. An automated docking is the lowest cost procedure wise.

Look at the system from the depot provider's point of view. Make the attachment and fueling of vehicles as automated/standard and simple as possible.

Put the requirement onto the users to comply with standards if they want the fuel. Also this simplifies the prop up-load deliveries such that they use the same docking mechanisms/ports. So that only one port type exists on the depot

I'm just not sure an NDS-style connector, even without the pressure port, is the right way to do this. I think I could do a multi-Sticky Boom solution for less mass and complexity, especially on the receiving side.

On the receiving side, the DogTags (capture targets for the Electropermanent Magnetic Sticky Booms) we're developing weigh less than 100g each, and you could probably get away with 6 of them per vehicle for an upper stage. Even if you wanted to make them bigger to enable even sloppier capture connections, you're talking low single digit kg per captured vehicle, not 100s of kg for an NDS-style adapter sized for an ACES to ACES connection.

NDS requires precision prox-ops to get the two pieces together, while I'm trying to design Sticky Booms to handle an upper stage rendezvousing directly with another upper stage or with a depot. Ie something that can handle modest relative velocities and position mismatches, doesn't require stationkeeping, doesn't require formation flying, etc. I still need to do some work on sizing, but my guess is I can get 4 Sticky Booms in for less mass than a single NDS on the capturing side.

For cargo or spacecraft that need to be tugged around, adding three DogTags on the back would still likely be <1kg of added mass even for a big payload.

I know NDS is what people are used to, I just don't think it's the end-all-be-all of connecting things in space. Especially if you don't need to seal a large diameter pressure-tight connection for passing people back and forth. That's what NDS shines for. Not for soft capturing upper stages or payloads for cargo or propellant transfer.

Quote
A BTW fluid transfers are halted during docking. So it is in everyone's interest if the depot is servicing multiple vehicles simultaneous (tanker and tugs/Upper Stages) that docking is done in the shortest amount of time. Arm capture and berthing is a very long process.

With Canadarm maybe, but primarily because they have an irreplaceable arm that they don't trust to do the captures autonomously, so they have a human sticky flying the arm (as I understand it). There's no reason why you can't have capture operations be much quicker with proper supervised autonomy. Once again, I don't think NDS is the answer *unless* you need a pressurized hatch that people can go through, in which case it's great.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 03/18/2017 06:02 am
An upper stage does not carry people (unlike the capsule) so saving mass getting the spacestation's arm to grab the stage would be a valid attachment system. There would have to be pipes to carry the propellant from the arm to the lander, possibly via fuel tanks.

We're also talking about multiple much lighter weight arms than the station arms. Like was shown in the picture in my blog post:

http://www.altius-space.com/wp-content/uploads/2017/03/DistributedLaunchFauxArt.png

~Jon
Jon is transfer done under very small thrust to settle fluid? If so how much thrust in Gs and which stage provides thrust.

How do booms hold up to thrust?.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/19/2017 03:57 am
Jon is transfer done under very small thrust to settle fluid? If so how much thrust in Gs and which stage provides thrust.

The details will likely depend on the vehicles transfering propellants, but generally I think it would be better if both vehicles were providing settling thrust (as otherwise you'd create a torque). ULA found that very low thrust levels (IIRC 10s of µGs) was enough for propellant settling, so you're not talking a lot of thrust.

Quote
How do booms hold up to thrust?.

One nice thing about these booms is that they're extendable and rectractable. So after the initial soft capture, you can pull them in all or most of the way to make the connection very stiff in spite of being lightweight. Definitely robust enough to handle the minor forces due to settling thrusters.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/19/2017 11:32 am

The details will likely depend on the vehicles transfering propellants, but generally I think it would be better if both vehicles were providing settling thrust (as otherwise you'd create a torque). ULA found that very low thrust levels (IIRC 10s of µGs) was enough for propellant settling, so you're not talking a lot of thrust.

{snip}
~Jon

10 µGs = 10 * 10-6 * 9.81 = approx 10-4 m/s2

Using F = m a
on a 50 tonne wet vehicle

F = 50,000 * 10-4 = 5 N (or 1.1 lbf)

There are several thrusters in the 5 N range. Normally aimed at station keeping for satellites. So cold thrusters, mono-propellants, ion thrusters and solar thermal thrusters are available. Since refuelling can take several hours the engineers may wish to use the same fuel as the main engines, the Morpheus lander had methane/LOX RCS thrusters in that thrust range.

If the settling thruster comes with an accurate accelerometer it can be used to measure the change in mass of the vehicle m = F/a

IMHO the FAA will want the equipment calibrated (see aircraft refuelling) and require allowance for propellant burnt and the mass of any people and cargo transferred.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/21/2017 03:32 am

The details will likely depend on the vehicles transfering propellants, but generally I think it would be better if both vehicles were providing settling thrust (as otherwise you'd create a torque). ULA found that very low thrust levels (IIRC 10s of µGs) was enough for propellant settling, so you're not talking a lot of thrust.

{snip}
~Jon

10 µGs = 10 * 10-6 * 9.81 = approx 10-4 m/s2

Using F = m a
on a 50 tonne wet vehicle

F = 50,000 * 10-4 = 5 N (or 1.1 lbf)

There are several thrusters in the 5 N range. Normally aimed at station keeping for satellites. So cold thrusters, mono-propellants, ion thrusters and solar thermal thrusters are available. Since refuelling can take several hours the engineers may wish to use the same fuel as the main engines, the Morpheus lander had methane/LOX RCS thrusters in that thrust range.

If the settling thruster comes with an accurate accelerometer it can be used to measure the change in mass of the vehicle m = F/a

IMHO the FAA will want the equipment calibrated (see aircraft refuelling) and require allowance for propellant burnt and the mass of any people and cargo transferred.

For ACES the IVF GOX/GH2 thrusters are more than adequate for settling.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 03/21/2017 04:22 am

For ACES the IVF GOX/GH2 thrusters are more than adequate for settling.

~Jon

Good.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/29/2017 05:39 pm
I'll be doing a FISO telecon presentation today (3pm EDT) about some aspects of using propellant depots. I'll upload a copy of my presentation once I'm done if people are interested.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 03/29/2017 09:05 pm
I'll be doing a FISO telecon presentation today (3pm EDT) about some aspects of using propellant depots. I'll upload a copy of my presentation once I'm done if people are interested.

~Jon

The presentation went well. While direct links from Twitter don't appear to work, they do seem to work here on the NSF forum.

Presentation: http://spirit.as.utexas.edu/%7Efiso/telecon/Goff_3-29-17/Goff_3-29-17.pptx

The audio isn't up yet, but I'll post a link later when it's up.

Edit: Here's the audio to go with the presentation: http://spirit.as.utexas.edu/%7Efiso/telecon/Goff_3-29-17/Goff.mp3

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: savuporo on 06/16/2017 11:57 pm
http://parabolicarc.com/2017/06/15/chinese-supply-ship-refuels-tiangong2-space-station/
Title: Re: Propellant Depots - General Discussion
Post by: Space Colonist on 07/12/2017 07:15 am
I am new to the forums and have not had time to read the past 10 years of post on this thread but one thing I have yet to see. Has anyone suggested getting a majority of the propellant from the Moon?
The main reason I ask is that the element that makes up 40% of the Moon's surface also accounts for 80% of the mass of rocket propellant.
As an example, if SpaceX were to use a propellant depot supplied by the Moon they would only need one launch of the tanker variant to provide the fuel for the journey to Mars rather than the 5 suggested by Musk. This would make the entire venture much more feasible.
Title: Re: Propellant Depots - General Discussion
Post by: MATTBLAK on 07/12/2017 07:35 am
http://www.nss.org/settlement/moon/LUNOX.html

http://wiki.developspace.net/Human_Lunar_Exploration_Architecture_Studies

https://www.wired.com/2013/07/international-lunar-resources-exploration-concept-1993/
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 07/12/2017 10:44 am
Google "cislunar 1000".
Title: Re: Propellant Depots - General Discussion
Post by: titusou on 07/12/2017 03:05 pm
Well, I just happened to finished reading from page1, yes call me crazy :)

I would suggest you start from p31, which will teleport you back to ~2010.

Before 2010 there is a lot of debate about Direct/Jupiter HLV, but those are really not relevant to what we have today: SLS is a done deal, Falcon9 become reuse-able.

Also, if you see jongoff post, read his stuff in detail. I personally think he has most knowledge regarding PD within this thread.

I think moving forward the key thing is how to realize the concept. The benefit is clearly there, technology is also there (if utilize settling, non-settling is a different story). How to make it happen is probably the most challenging part, aka: who is going to pay for the first PD?


Titus
Title: Re: Propellant Depots - General Discussion
Post by: Zed_Noir on 07/13/2017 09:56 am
I am new to the forums and have not had time to read the past 10 years of post on this thread but one thing I have yet to see. Has anyone suggested getting a majority of the propellant from the Moon?
The main reason I ask is that the element that makes up 40% of the Moon's surface also accounts for 80% of the mass of rocket propellant.
....

Getting propellant from the Moon in the short term (next dozen years) will not be very variable.

The main issues are setting up Lunar mining operations, Lunar propellants processing & storage facilities, Lunar surface mobility systems, Lunar spaceport, cis-Lunar transport logistics and finally some kind of orbital propellant depot. IMO all these issues require just about as much budget each as either the SpaceX BFR or the SpaceX BFS, which you have to do to go Mars anyways.

The current SpaceX Mars plan only requires the BFR, the BFS spacecraft & the BFS tanker plus a lot of bulk propellants. So only 3 budget line items as compares to the over a dozen line items for getting propellants from the Moon.

Maybe when there is a fleet of 300 mT reusable launch vehicles available you could set up a Lunar propellants supply system to an orbital propellant depot.
Title: Re: Propellant Depots - General Discussion
Post by: MATTBLAK on 07/13/2017 12:25 pm
I have often thought that the best use of lunar oxygen production in the short term would be as breathing gas for Outpost inhabitants. Of course; if polar ice is actually found to be more plentiful than expected, the infrastructure could grow on from there.
Title: Re: Propellant Depots - General Discussion
Post by: oldAtlas_Eguy on 07/13/2017 10:30 pm
In the long run ITS would probably spur the development of Lunar propellants and the creation of L2 depots. It would make the transport of cargo and personnel to the Lunar surface much cheaper enableing a tremendous lowering of the costs of the infrastructure which would then be bootstrapping by fueling ITS on the surface then using a ITS tanker variant (no reentry shielding since it would never return to Earth) to transfer liquids to L2 and return to Lunar surface. 100 flights by the tanker would transport ~ 38,000mt in just 1 year of operations. This is not a small scale operations. At $10/kg for the liquids purchased at the Lunar surface is $380M in purchases from the "miners". In fact the liquids prices at the Lunar surface could be as high as $30/kg and still be cheaper than prop delivered to L2 from Earth. At $30/kg that is > $1B/yr in sales for just payload + another $3B in propellant sales to the tanker to deliver the liquids to L2 which then would have a Value/price of <$150/kg at L2. So the total sales of all liquids from the "miners" could be as much as $4B with just a single ITS tanker in operation which is replaced each year.

At which when this takes place the investments into infrastructure and exploration/development of resources would probably be more than $10B per year for all of cis-Lunar space. To put this into perspective this level of commercial development funding would be equivalent to the NASA budget for government centered contracted activities for just operations and exploration (which is only $8B currently) would be like having $40+B sized budget for these areas of activities in NASA.

But we will have to wait. The private investment funds have yet to freely flow.
Title: Re: Propellant Depots - General Discussion
Post by: Archibald on 10/06/2017 01:27 pm
If BFR can lift 150 mt, and needs 1100 mt to refuel, then it would take 8 flights, and that would left some margin for boiloff (although methane and LOX boils less than LH2).

I've been on this forum since 2008 and closely followed the quest for propellant depots by JohnGoff and many others.
I think SpaceX architecture validates the usefulness of prop depots. It is an enormous force multiplier.
Title: Re: Propellant Depots - General Discussion
Post by: oldAtlas_Eguy on 10/07/2017 01:26 am
If BFR can lift 150 mt, and needs 1100 mt to refuel, then it would take 8 flights, and that would left some margin for boiloff (although methane and LOX boils less than LH2).

I've been on this forum since 2008 and closely followed the quest for propellant depots by JohnGoff and many others.
I think SpaceX architecture validates the usefulness of prop depots. It is an enormous force multiplier.
Actually the tanker can lift 220mt of prop. So only 5 for 1,100mt.
Title: Re: Propellant Depots - General Discussion
Post by: Archibald on 10/07/2017 11:02 am
thank you.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 08/11/2018 04:22 am
I know this thread is a little old, but I wanted to mention we'll be presenting a paper on the orbital dynamics of using a LEO propellant depot for interplanetary missions at this year's AAS Astrodynamics Specialists Conference in Snowbird, UT on the 22nd. This is a follow-on to a paper we did last year (that I blogged about here on Selenian Boondocks: https://selenianboondocks.com/2018/02/aas-paper-review-practical-methodologies-for-low-delta-v-penalty-on-time-departures-to-arbitrary-interplanetary-destinations-from-a-medium-inclination-low-earth-orbit-depot/)

This year's paper "RAAN Agnostic 3-Burn Departure Methodology for Deep Space Missions from LEO Depots" extends the methodology in the previous paper to show that a mid-inclination depot (say ISS-like orbit) can support missions to a wide range of destinations with only modest dV penalties even though the depot plane doesn't line up with the desired departure asymptote at the desired departure date. We're illustrating the concept showing how a LEO micro-depot could refuel LauncherOne-class small rocket upper stages (and small storable kick stages) to enable a string of 8 back-to-back missions to 4 planets and 4 NEOs in a five month timeframe. It's pretty sweet. I'll make sure to post the paper, the presentation slides, and a writeup on Selenian Boondocks once it's done, but I figured I'd mention it here.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: MATTBLAK on 08/11/2018 05:28 am
Propellant Depots: hey NASA etc... Just do it!!
Title: Re: Propellant Depots - General Discussion
Post by: GWH on 08/11/2018 06:55 am
Jon, what would the viability of launching from a high inclination orbit like the ISS be?

An idea I have been fascinated by (but never researched the viability of) is fueling departure stages for small payloads via utilizing rideshare and excess capacity on visiting vehicles.
Title: Re: Propellant Depots - General Discussion
Post by: speedevil on 08/11/2018 09:42 am
Jon, what would the viability of launching from a high inclination orbit like the ISS be?

An idea I have been fascinated by (but never researched the viability of) is fueling departure stages for small payloads via utilizing rideshare and excess capacity on visiting vehicles.
The related idea of rideshare payloads of low value having oxidiser added only shortly after the main payload has been delivered by the upper stage departs occurred to me.
This could considerably reduce the risk profile of small ride-alongs with propellant, eliminating any risk to the primary payload, and simplifying the flight approval process.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 08/11/2018 07:05 pm
Jon, what would the viability of launching from a high inclination orbit like the ISS be?

An idea I have been fascinated by (but never researched the viability of) is fueling departure stages for small payloads via utilizing rideshare and excess capacity on visiting vehicles.

That's pretty much the very idea I've been looking at for the last few years. I actually like an ISS coorbital depot location a lot. ISS orbit is high enough inclination that except for very low C3 targets, you can make a low-penalty three-burn departure work for even pretty gnarly departure asymptotes, and since there's a lot of traffic to the altitude that is usually volume instead of mass limited, it gives you a lot of options for buying leftover propellant.

In the case of SpaceX, they ought to have a few tonnes of leftover LOX/Kero and Helium in their upper stage after dropping Dragon off. Any money from that excess propellant would basically be pure profit. ULA, once they're flying Vulcan, should also have a lot of excess prop capacity in an ISS-like orbit. If you say had to give NGIS a $10M discount to fly on Vulcan instead of Antares, and you added an extra 2-3 solids, you could get somewhere in the neighborhood of 15 tonnes of excess propellant as a secondary payload for a delta-cost in the range of $25M--which is also cheaper than bulk launch on a reusable Falcon 9.

And going to your last point, when you combine those benefits with refueling smallsat launcher upper stages (and possibly storable kick stages for the more challenging destinations), an ISS coorbital depot would allow the Rocketlabs, Virgin Orbits, and Fireflys of the world send smallsat payloads to anywhere in the solar system at not a huge premium to the cost of launching those payloads to LEO.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 08/11/2018 07:06 pm
Propellant Depots: hey NASA etc... Just do it!!

If NASA doesn't do it, I wouldn't be surprised if a foreign space agency decided to go after something like this. It would be a good niche for a country to carve out for itself.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Proponent on 08/28/2018 05:34 pm
Jeff Foust at SpaceNews:  "Startup plans 'gas stations' for satellite servicing." (https://spacenews.com/startup-plans-gas-stations-for-satellite-servicing/)
Title: Re: Propellant Depots - General Discussion
Post by: Asteroza on 08/29/2018 12:51 am
Propellant Depots: hey NASA etc... Just do it!!

If NASA doesn't do it, I wouldn't be surprised if a foreign space agency decided to go after something like this. It would be a good niche for a country to carve out for itself.

~Jon

Since you are advising Orbit Fab, I assume they are trying to implement the ISS co-orbital propellant depot with the 3 burn exit strategy you mentioned...

How would a similar strategy work out for a prop depot parked in sun terminator riding SSO orbit to work with SSO bound customers? Those usually aren't so volume limited so rideshare prop hauling is harder, but then again such a depot can double as a space corral type platform for cubesat class sensors as an expandable single platform version of the A-train earth observation fleet...
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 08/29/2018 01:44 am
Since you are advising Orbit Fab, I assume they are trying to implement the ISS co-orbital propellant depot with the 3 burn exit strategy you mentioned...

Actually, I haven't explicitly been working with OrbitFab on the ISS co-orbiting depot/3-burn departure concept, though I think one of my coauthors has been working with them a little. The depot in our paper was more of a pet concept I've been working on for the past few years, focused on bigger things--refueling microsat launcher upper stages with LOX/Kero/storables to enable dedicated BLEO launches. Though the two ideas aren't mutually exclusive.

Quote
How would a similar strategy work out for a prop depot parked in sun terminator riding SSO orbit to work with SSO bound customers? Those usually aren't so volume limited so rideshare prop hauling is harder, but then again such a depot can double as a space corral type platform for cubesat class sensors as an expandable single platform version of the A-train earth observation fleet...

From a standpoint of refueling spacecraft, SSO and near-ISS are the two areas I would focus on, as that's where the most existing/planned spacecraft are. From what I've heard talking with smallsat launch providers, most of them expect to have leftover mass on most flights, and having something dense and inert like a water tank or Xenon tank that can takeup spare space probably makes a lot of sense. Is that what you were asking?

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Asteroza on 08/29/2018 07:31 am
Quote
How would a similar strategy work out for a prop depot parked in sun terminator riding SSO orbit to work with SSO bound customers? Those usually aren't so volume limited so rideshare prop hauling is harder, but then again such a depot can double as a space corral type platform for cubesat class sensors as an expandable single platform version of the A-train earth observation fleet...

From a standpoint of refueling spacecraft, SSO and near-ISS are the two areas I would focus on, as that's where the most existing/planned spacecraft are. From what I've heard talking with smallsat launch providers, most of them expect to have leftover mass on most flights, and having something dense and inert like a water tank or Xenon tank that can takeup spare space probably makes a lot of sense. Is that what you were asking?

~Jon

Sort of. Larger launches could expect a larger rideshare prop tug to propel itself+tank to a depot (Sherpa comes to mind), but what are your thoughts on the smaller launchers? The amount of rideshare mass isn't that high, which cuts into chances of a tug+tank, and some of the potential providers don't have restartable upper stages to rendezvous with a depot which would suggest mere rideshare tank separation like a cubesat ejection. Does that end up needing an OTV to go catch rideshare tanks with StickyBooms? Or is there a fundamental expectation that normally, restartable upper stages will come to the depot (grappled by a depot StickyBoom and perhaps hard berthed to a visiting vehicle mount) to do two way propellant transfers (deposit or pickup)?

Err, let me split that and say pure prop delivery when the rideshare provider can't come themselves, and the restartable upper stage club, who are expected to deposit regularly by visiting themselves before disposal (with a nice tether drop opportunity for depot reboost) but might occasionally come for pickup (not only to refuel themselves and depart with original BLEO payload, but perhaps refuel after dropping the original LEO payload and pickup the actual smaller departure BLEO payload from the depot itself, which was a cargo deposit left earlier). There's also the case of depositing propellant for a waiting cargo deposit (propellants for electric thruster payloads that are cargo deposits at the depot) rather than the upper stage itself (think cubesats with a stack of ejectable 3U water tanks).

Which I suppose quickly devolves into the cases for scavengable ullage from liquid upper stages themselves (LOx, hydrogen or kerosene)(hypergols?), delivered storable propellants to be converted for upper stages (aka water delivery being slowly converted to LOx/LH2 at the depot), and delivered storable for electric driven payloads (so water, and noble gases like xenon?)
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 08/29/2018 10:05 pm
Sort of. Larger launches could expect a larger rideshare prop tug to propel itself+tank to a depot (Sherpa comes to mind), but what are your thoughts on the smaller launchers? The amount of rideshare mass isn't that high, which cuts into chances of a tug+tank, and some of the potential providers don't have restartable upper stages to rendezvous with a depot which would suggest mere rideshare tank separation like a cubesat ejection. Does that end up needing an OTV to go catch rideshare tanks with StickyBooms? Or is there a fundamental expectation that normally, restartable upper stages will come to the depot (grappled by a depot StickyBoom and perhaps hard berthed to a visiting vehicle mount) to do two way propellant transfers (deposit or pickup)?

I'm not positive on OrbitFab's latest plans (I've been heads down in Altius stuff lately), and not sure what I'm allowed to say, but I think the general idea is that their depots work together with satellite servicing vehicles--both to get launched materials from the launcher to the depot, and then to take the propellant from the depot to the customers (if the customer isn't the servicing vehicle itself).

For the micro-depot concept I was discussing in my AAS paper, I'd have the upper stages rendezvous directly with the depot (we think it's possible with the depot housing the prox-ops smarts, remote controlling the upper stage through the RPO maneuvers, and then having the depot's Sticky Boom systems capture the upper stage). But I think that's a bit of a different case from what OrbitFab is working on.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 09/16/2018 05:23 am
We completed the AAS paper on Monday, and I finally got time to start writing up a review on Selenian Boondocks:

https://selenianboondocks.com/2018/09/aas-paper-review-raan-agnostic-3-burn-departure-methodology-for-deep-space-missions-from-leo-depots-part-1-of-2/

That link includes a link to the full-text of the paper. I'll be doing the second part of the writeup early next week, but for those of you who want to slog through the paper, it's there.

~Jon

PS and for fun, I'm including the Brian Versteeg propellant depot artwork we used in the paper. Brian is the guy who did the artwork for Deep Space Industries, and we commissioned him to do this depot concept picture for a proposal we were writing earlier this year.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 09/17/2018 04:15 pm
And here's the second half of the paper review:
https://selenianboondocks.com/2018/09/aas-paper-review-raan-agnostic-3-burn-departure-methodology-for-deep-space-missions-from-leo-depots-part-2-of-2/

Long-story short, our analysis shows how an ISS-coorbital depot could enable a LauncherOne-class vehicle to send 90-450kg payloads to almost anywhere in the solar system as dedicated launch missions, for ~$25M or less per mission...

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: brickmack on 09/18/2018 01:49 pm
Quote
This is much cheaper than buying a whole Falcon 9 mission anytime in the foreseeable future, and to many of these destinations, if you want to go at all, you’re unlikely to get many secondary payloads who can use your trajectory, so your main alternative would be buying a full Falcon 9.

Since all these launches would have to go to the same staging orbit anyway to reach the depot, what about using a single large rocket to carry a bunch of separate upper stage/payload stacks, and using the same method to allow several departures in quick succession? If you used F9, you'd still need the LauncherOne upper stage, and you add the expendable F9 upper stage, but eliminate the expendable LauncherOne first stage and you can probably save most of the support costs. With a LauncherOne S2 dry mass of 329 kg, and 470 kg payload, and say 200 kg for the dry mass of the largest storable stage you considered, thats basically 1 ton per stack dry, so F9 could carry like 16 of those to LEO by mass. Volumetrically, LO S2 is 1.3 meters wide and looks to be ~3 meters long. Call it 5 meters with payload. In F9's 4.6 meter internal diameter you can pack 8 of those per level. Probably can't stack 2 levels though, but the difference can be made up by fueling some of those, which also reduces the demand on the depot. LauncherOne is 10 million a flight, if we assume 1/3 of that is the upper stage (probably much less, half is generally operations/overhead) thats 27 million for 8 stages, plus the F9 at 50 million, so 77 million total, vs 80 million with equivalent number of LauncherOnes. Not a huge savings, but nonzero, and I'd say thats pretty conservative (probably-excessive cost for LO S2, no reusable fairing on F9). If you include fuel (probably just for the storable stages, you'd still want to get your semi-cryogenic fuel from the depot) thats up to 750*8 = 6000 kg extra mass carried in the same volume at no additional cost (equals 6000 kg less propellant that has to be carried separately to the depot, which if you're using Atlas V or Vulcan with extra boosters to rideshare that propellant up could be up to like 8 million dollars in extra boosters, if using GEM-63 at ~half the cost of AJ60), and it still fits in F9s reusable mass capacity. New Glenn is likely even better because this arrangement seems to be mainly volume-limited (with a 6.5 meter internal diameter fairing, you could carry 19 LauncherOne S2s per layer, and as tall as it is you may be able to fit a second layer in there), but we don't know enough about its cost and payload yet
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 09/18/2018 07:03 pm
Quote
This is much cheaper than buying a whole Falcon 9 mission anytime in the foreseeable future, and to many of these destinations, if you want to go at all, you’re unlikely to get many secondary payloads who can use your trajectory, so your main alternative would be buying a full Falcon 9.

Since all these launches would have to go to the same staging orbit anyway to reach the depot, what about using a single large rocket to carry a bunch of separate upper stage/payload stacks, and using the same method to allow several departures in quick succession? If you used F9, you'd still need the LauncherOne upper stage, and you add the expendable F9 upper stage, but eliminate the expendable LauncherOne first stage and you can probably save most of the support costs. With a LauncherOne S2 dry mass of 329 kg, and 470 kg payload, and say 200 kg for the dry mass of the largest storable stage you considered, thats basically 1 ton per stack dry, so F9 could carry like 16 of those to LEO by mass. Volumetrically, LO S2 is 1.3 meters wide and looks to be ~3 meters long. Call it 5 meters with payload. In F9's 4.6 meter internal diameter you can pack 8 of those per level. Probably can't stack 2 levels though, but the difference can be made up by fueling some of those, which also reduces the demand on the depot. LauncherOne is 10 million a flight, if we assume 1/3 of that is the upper stage (probably much less, half is generally operations/overhead) thats 27 million for 8 stages, plus the F9 at 50 million, so 77 million total, vs 80 million with equivalent number of LauncherOnes. Not a huge savings, but nonzero, and I'd say thats pretty conservative (probably-excessive cost for LO S2, no reusable fairing on F9). If you include fuel (probably just for the storable stages, you'd still want to get your semi-cryogenic fuel from the depot) thats up to 750*8 = 6000 kg extra mass carried in the same volume at no additional cost (equals 6000 kg less propellant that has to be carried separately to the depot, which if you're using Atlas V or Vulcan with extra boosters to rideshare that propellant up could be up to like 8 million dollars in extra boosters, if using GEM-63 at ~half the cost of AJ60), and it still fits in F9s reusable mass capacity. New Glenn is likely even better because this arrangement seems to be mainly volume-limited (with a 6.5 meter internal diameter fairing, you could carry 19 LauncherOne S2s per layer, and as tall as it is you may be able to fit a second layer in there), but we don't know enough about its cost and payload yet
With small LV you can fly when ready not have to wait for another dozen payloads to be ready to fill large LV. Launch windows can be limited for some BLEO which is even more reason to use small LV.

Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 09/18/2018 08:00 pm
Quote
This is much cheaper than buying a whole Falcon 9 mission anytime in the foreseeable future, and to many of these destinations, if you want to go at all, you’re unlikely to get many secondary payloads who can use your trajectory, so your main alternative would be buying a full Falcon 9.

Since all these launches would have to go to the same staging orbit anyway to reach the depot, what about using a single large rocket to carry a bunch of separate upper stage/payload stacks, and using the same method to allow several departures in quick succession? If you used F9, you'd still need the LauncherOne upper stage, and you add the expendable F9 upper stage, but eliminate the expendable LauncherOne first stage and you can probably save most of the support costs. With a LauncherOne S2 dry mass of 329 kg, and 470 kg payload, and say 200 kg for the dry mass of the largest storable stage you considered, thats basically 1 ton per stack dry, so F9 could carry like 16 of those to LEO by mass. Volumetrically, LO S2 is 1.3 meters wide and looks to be ~3 meters long. Call it 5 meters with payload. In F9's 4.6 meter internal diameter you can pack 8 of those per level. Probably can't stack 2 levels though, but the difference can be made up by fueling some of those, which also reduces the demand on the depot. LauncherOne is 10 million a flight, if we assume 1/3 of that is the upper stage (probably much less, half is generally operations/overhead) thats 27 million for 8 stages, plus the F9 at 50 million, so 77 million total, vs 80 million with equivalent number of LauncherOnes. Not a huge savings, but nonzero, and I'd say thats pretty conservative (probably-excessive cost for LO S2, no reusable fairing on F9). If you include fuel (probably just for the storable stages, you'd still want to get your semi-cryogenic fuel from the depot) thats up to 750*8 = 6000 kg extra mass carried in the same volume at no additional cost (equals 6000 kg less propellant that has to be carried separately to the depot, which if you're using Atlas V or Vulcan with extra boosters to rideshare that propellant up could be up to like 8 million dollars in extra boosters, if using GEM-63 at ~half the cost of AJ60), and it still fits in F9s reusable mass capacity. New Glenn is likely even better because this arrangement seems to be mainly volume-limited (with a 6.5 meter internal diameter fairing, you could carry 19 LauncherOne S2s per layer, and as tall as it is you may be able to fit a second layer in there), but we don't know enough about its cost and payload yet

A couple issues I can see:
1- How do you mechanically support those stages/payload stacks against launch loads inside the fairing? How heavy is that support structure? I mean, it may be physically possible, but doing this in a way that doesn't load the stages/payloads wrong sounds like a coupled loads analysis nightmare.
2- How long can the stages and payloads be stored in LEO waiting to be loaded? They weren't designed for hanging out for five months like that. How expensive is it to modify them to handle that thermal, AO, and MMOD environment?

Color me skeptical that there'd be any real net benefit. A much bigger benefit would be if VO or RL could be convinced to go reusable for their first stages...

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/14/2018 05:37 am
FYI for those interested, I'll be doing a FISO telecon on propellant depots (with Mike Loucks and John Carrico) the afternoon of November 28th. I'll be expanding on the work we did for the AAS paper.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Asteroza on 11/26/2018 10:46 pm
How well would a 3 burn prop depot fit with the recent work on VENUS (Vega new upper stage), which is pushing towards a initially a Space Rider AVUM+ service module modified with both liquid and electric thrusters (and an evolution towards a larger SEP tug/upper stage)?

I suppose in the context of mixed mode propulsion, what are your feelings on an upper stage that is a mix between a water plasma thruster and a gaseous oxygen/hydrogen engine, the idea being the 3 burn departure requires hard high thrust modes, but electric propulsion elsewhere using a "common" water propellant tank (and something to handle the oxygen/hydrogen from cracking water during the 60 day loiter between burns)?
Title: Re: Propellant Depots - General Discussion
Post by: A_M_Swallow on 11/27/2018 02:17 am
How well would a 3 burn prop depot fit with the recent work on VENUS (Vega new upper stage), which is pushing towards a initially a Space Rider AVUM+ service module modified with both liquid and electric thrusters (and an evolution towards a larger SEP tug/upper stage)?

I suppose in the context of mixed mode propulsion, what are your feelings on an upper stage that is a mix between a water plasma thruster and a gaseous oxygen/hydrogen engine, the idea being the 3 burn departure requires hard high thrust modes, but electric propulsion elsewhere using a "common" water propellant tank (and something to handle the oxygen/hydrogen from cracking water during the 60 day loiter between burns)?

The depot would need a water tank to store the water. Rotate the tank to settle the liquid and attach the drain to the side allowing gravity feed. A pump will still be needed.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/28/2018 08:44 pm
FYI for those interested, I'll be doing a FISO telecon on propellant depots (with Mike Loucks and John Carrico) the afternoon of November 28th. I'll be expanding on the work we did for the AAS paper.

~Jon

For those interested, here's a link to the Future In-Space Operations working group presentation I gave on propellant depots today, and the recording of the talk/Q&A:

http://fiso.spiritastro.net/telecon/Goff_11-28-18/

Hopefully this works better than Twitter. Something about their t.co link shortener doesn't play well with the FISO telecon archive.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Asteroza on 11/29/2018 12:04 am
FYI for those interested, I'll be doing a FISO telecon on propellant depots (with Mike Loucks and John Carrico) the afternoon of November 28th. I'll be expanding on the work we did for the AAS paper.

~Jon

For those interested, here's a link to the Future In-Space Operations working group presentation I gave on propellant depots today, and the recording of the talk/Q&A:

http://fiso.spiritastro.net/telecon/Goff_11-28-18/

Hopefully this works better than Twitter. Something about their t.co link shortener doesn't play well with the FISO telecon archive.

~Jon

FISO archive has some protection mechanisms such as checking referrer tags to make sure people come directly to get presentations, rather than leeching papers via hotlinking.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 11/29/2018 02:40 am
FYI for those interested, I'll be doing a FISO telecon on propellant depots (with Mike Loucks and John Carrico) the afternoon of November 28th. I'll be expanding on the work we did for the AAS paper.

~Jon

For those interested, here's a link to the Future In-Space Operations working group presentation I gave on propellant depots today, and the recording of the talk/Q&A:

http://fiso.spiritastro.net/telecon/Goff_11-28-18/

Hopefully this works better than Twitter. Something about their t.co link shortener doesn't play well with the FISO telecon archive.

~Jon

FISO archive has some protection mechanisms such as checking referrer tags to make sure people come directly to get presentations, rather than leeching papers via hotlinking.

That would make sense. Both Twitter and Facebook didn't work, but a link from my blog did. Did you get a chance to listen? Have any questions or comments?

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: Asteroza on 11/30/2018 01:27 am
Have any questions or comments?

~Jon

One of the final questions on the telecon (by Gary?) indicated interest in using 3 burn plus ultra low deltaV trajectories (aka Interplanetary Superhighway) style navigation, along with some comments regarding dry kick stages and water propulsion coming into vogue.

In that context, if you consider that many of the alleged water propulsion systems are largely a workaround for needing an inert propellant for secondary payload delivered smallsats, when the end game is electrolysis to gaseous hydrogen for a plasma thruster (and what becomes of the oxygen?), it makes me think over the comments on dry kick stages. Assuming a smallsat launcher is delivering effectively a primary payload of (main payload)+(1 or 2 kick stages) to the prop depot, where the kick stage might stick around with the payload to become a service bus after the third burn, and that smallsat launcher payload fairings aren't that big, there are some unique freedoms/restraints to kick stage design.

For example, a kick stage using gaseous oxygen/hydrogen for the kick burns could arrive at the depot dry and be fueled. For gaseous fueling, is there merit to having kick stage tankage be collapsible, as it would come dry, freeing up smallsat launcher payload fairing volume? Say something extreme like the solar array being like a solar sail, where the deployment booms are effectively hollow tubes doing double duty as large 3D structures to stiffen the sail and be propellant storage, using fueling pressure to deploy them?

Since those water thrusters are effectively hydrogen plasma thrusters, is there merit to oversizing the hydrogen tank on a gaseous oxy/hydro kick stage to fuel the plasma thruster later, versus water electrolysis just before use? Say something like a cross between a piston and a common bulkhead tank, where sucking down oxygen retracts the hydrogen tank into the shell of the oxygen tank?

With mixed combustion/electric, one could foresee a situation where you burn for departure, electric during cruise, then burn for capture (or burn to land). The lander bit makes me think you could do electrolysis in route near the destination, and do a gaseous oxy/hydro lander. Which would favor water as storage and only temporarily use gaseous tanks, but those tanks are kinda a problem, as any damage holing them means you are screwed, but you would be equally screwed if you had stored gaseous continually, the only workaround being multiple tanks. Which makes the idea of using gaseous tanks as solar array booms work as you would have multiple tanks though you increase the debris hit cross sectional area.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 10/16/2020 05:42 pm
Finally depots are getting some love after Shelby, Boeing and others black listed them.



Torys presentation.
https://youtu.be/d5mPfbyzdF0
https://spacenews.com/ulas-tory-bruno-argues-for-u-s-investments-in-the-production-of-fuel-in-space/
Tory Bruno has pitched the idea of a "strategic propellant reserve" to the National Space Council. This approach might have hope of getting funded.




http://www.parabolicarc.com/2020/10/14/nasa-tipping-point-selections-include-cryogenic-fluid-lunar-surface-and-landing-tech/

https://www.lockheedmartin.com/content/lockheed-martin/en-us/news/features/2020/cryogenic-nasa-moon.html




https://arstechnica.com/scienc...on-orbit-spacecraft-refueling/

Eta Space of Merritt Island, Florida, $27 million. Small-scale flight demonstration of a complete cryogenic oxygen fluid management system. System will be the primary payload on a Rocket Lab Photon satellite and collect critical cryogenic fluid management data in orbit for nine months.
Title: Re: Propellant Depots - General Discussion
Post by: Proponent on 11/18/2020 04:12 pm
From SpaceNews: Orbit Fab to launch first fuel tanker in 2021 with Spaceflight (https://spacenews.com/orbit-fab-to-launch-with-spaceflight/).
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 02/24/2021 02:34 am
For those of you who haven't seen it already, I'm most of the way through a blog post series talking about different types of orbital propellant depots, how they're different from each other (application, location, size, propellant type, and other considerations):

https://selenianboondocks.com/2020/09/an-updated-propellant-depot-taxonomy

I figured if you are reading this thread, and hadn't seen this yet, you might find it interesting/useful. At some point I'd love to do some explainer videos to go with the written descriptions, but I figured that better was the enemy of good enough.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 03/18/2021 01:14 am
In the Earth-Moon system there are a set of looping periodic trajectories (orbits, if you will) that look like the one in the attached graphic.
(It is taken from https://ntrs.nasa.gov/api/citations/19670017845/downloads/19670017845.pdf) The trajectory loops around both the Earth and the Moon on each cycle.

The proposed application then was a rescue vehicle that could come to the aid of an Apollo mission during its trans-lunar (or presumably trans-Earth) coast phase. But the implications for a propellant depot are pretty clear: an outward bound mission to the cislunar vicinity could leave LEO and inject onto a trajectory that would facilitate rendezvous with a depot that was more or less non-propulsively following one of these looping trajectories. After plenty of time (days) refueling at the depot the outbound mission would perform a smallish maneuver at or near perilune so that it stayed in the lunar vicinity while the depot went on about its next loop. Tanker flights sent to replenish the depot would also maneuver there, but instead of remaining in the lunar vicinity they would inject onto trajectories which take them back to the Earth's surface.

I'm curious whether people see value in a depot on this kind of looping trajectory? Are they explicitly discussed someplace?
Title: Re: Propellant Depots - General Discussion
Post by: Eric Hedman on 03/18/2021 11:12 pm
In the Earth-Moon system there are a set of looping periodic trajectories (orbits, if you will) that look like the one in the attached graphic.
(It is taken from https://ntrs.nasa.gov/api/citations/19670017845/downloads/19670017845.pdf) The trajectory loops around both the Earth and the Moon on each cycle.

The proposed application then was a rescue vehicle that could come to the aid of an Apollo mission during its trans-lunar (or presumably trans-Earth) coast phase. But the implications for a propellant depot are pretty clear: an outward bound mission to the cislunar vicinity could leave LEO and inject onto a trajectory that would facilitate rendezvous with a depot that was more or less non-propulsively following one of these looping trajectories. After plenty of time (days) refueling at the depot the outbound mission would perform a smallish maneuver at or near perilune so that it stayed in the lunar vicinity while the depot went on about its next loop. Tanker flights sent to replenish the depot would also maneuver there, but instead of remaining in the lunar vicinity they would inject onto trajectories which take them back to the Earth's surface.

I'm curious whether people see value in a depot on this kind of looping trajectory? Are they explicitly discussed someplace?
I think there needs to be a fair amount of analysis done on an orbit like this to see all the costs and opportunities involved to see if there is an advantage to this idea.  It does kind of fall into the cycler concept Buzz Aldrin was advocating for going to Mars and back except for carrying propellant instead of people and cargo.I know Buzz has also explored the concept of cyclers to and from the Moon.
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 03/18/2021 11:18 pm
It does kind of fall into the cycler concept Buzz Aldrin was advocating for going to Mars and back except for carrying propellant instead of people and cargo. I know Buzz has also explored the concept of cyclers to and from the Moon.

Yours is the second comment I've seen describing this as a cycler, and that seems like a catchy name at least! And sure enough, some kind wikipedia editor has already started an article on the topic: https://en.wikipedia.org/wiki/Lunar_cycler
Title: Re: Propellant Depots - General Discussion
Post by: Asteroza on 03/19/2021 01:16 am
In the Earth-Moon system there are a set of looping periodic trajectories (orbits, if you will) that look like the one in the attached graphic.
(It is taken from https://ntrs.nasa.gov/api/citations/19670017845/downloads/19670017845.pdf) The trajectory loops around both the Earth and the Moon on each cycle.

The proposed application then was a rescue vehicle that could come to the aid of an Apollo mission during its trans-lunar (or presumably trans-Earth) coast phase. But the implications for a propellant depot are pretty clear: an outward bound mission to the cislunar vicinity could leave LEO and inject onto a trajectory that would facilitate rendezvous with a depot that was more or less non-propulsively following one of these looping trajectories. After plenty of time (days) refueling at the depot the outbound mission would perform a smallish maneuver at or near perilune so that it stayed in the lunar vicinity while the depot went on about its next loop. Tanker flights sent to replenish the depot would also maneuver there, but instead of remaining in the lunar vicinity they would inject onto trajectories which take them back to the Earth's surface.

I'm curious whether people see value in a depot on this kind of looping trajectory? Are they explicitly discussed someplace?

Seems like it would also be hanging out near L3 a fair bit. I wonder if there would be any merit to pre-staging such a depot at L3 and send it down when needed, but returns to standby at L3...
Title: Re: Propellant Depots - General Discussion
Post by: MATTBLAK on 03/19/2021 01:29 am
Propellant Depots: I'm all for them. Those, propellant ISRU and Solar Electric Propulsion (plus perhaps NEP) will open the Solar System to Exploration and exploitation. It's way past time this was done. Or perhaps; it's an idea whose time has come...
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 03/19/2021 07:44 pm
Propellant Depots: I'm all for them. Those, propellant ISRU and Solar Electric Propulsion (plus perhaps NEP) will open the Solar System to Exploration and exploitation. It's way past time this was done. Or perhaps; it's an idea whose time has come...
NASA are funding a few in space cryo fuel transfer and storage experiments. All three HLSs need these technologies. They are same technologies that threaten SLS future which is why NASA wasn't able fund them in past.

There are other companies targeting small storable fuel depots to service LEO smallsat market.

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Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 03/21/2021 08:54 am
Seems like it would also be hanging out near L3 a fair bit.

Ouch, that's a keen observation!

I tried to reproduce an orbit like this with rather crude tools (see attached image) and — if I understand my units of time correctly ― the period of the orbit (as plotted) is around 6 months. That's a long time to wait for your depot to be in the right location....
Title: Re: Propellant Depots - General Discussion
Post by: sdsds on 03/24/2021 11:38 am
if I understand my units of time correctly ― the period of the orbit (as plotted) is around 6 months.

Nope, my units of time were off by a factor of 2π. A much better estimate for the period of the orbit is 0.869 sidereal months. That's only 23.7 days!
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 04/29/2021 07:37 pm
LOXSAT1 demo mission is all go and received NSSA funding.

Sounds like they have some small LV customers for LOXSAT2 operational depot.

https://techtodaynewspaper.com/nasa-awards-eta-space-contract-for-gas-stations-in-space/

The contract includes funding for the initial design of LOXSAT 2, a full-scale operational depot intended for launch in 2025. LOXSAT 2 will provide liquid oxygen and RP-1 to refuel the upper stages of multiple small launch vehicles. “We are working with several launch providers to develop standardized interfaces, promote orbital refueling into mission profiles, and develop supply and demand projections for this new market,” said Dr. Notardonato. “This capability will then be used to open the inner solar system to exploration by small satellites at reduced costs.”



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Title: Re: Propellant Depots - General Discussion
Post by: Ronsmytheiii on 09/03/2021 10:17 am
https://twitter.com/hugo_blair/status/1433320987592835073?s=20
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 09/03/2021 11:16 am
https://twitter.com/hugo_blair/status/1433320987592835073?s=20
Here is youtube link, presentation starts at 1:00:00 mark.
https://youtu.be/rW2crjkvmmo

NB Jon and I had discussion about this back in Mar in RL "What Next for RL" thread. (Sorry no link). Jon Goff had some input to presentation as concept of refuelling small LV upper stages is one of his areas of interest.

Reusing US as earth departure stage makes lot sense and may not be that expensive given fuel will be delivered by lower cost RLV like F9R or SS. The modifications shouldn't be that expensive for Electron  US. Photon will provide guidance and top end control thruster, may need few additional ones on base of US.
Other modifications are a power point to recharge engine battery and refuelling ports. Assuming $5M for mods and refuelling and $5M for reuseable Electron thats $10M to deliver 220kg to earth escape. Only expendable parts are fairing and US which is reused as EDS.

Boiloff of LOX in US after departing depot is an issue. To afford significant modifications to US it would be case of ED burn soon after leaving depot, multiple burns are probably off the cards especially if hours apart.








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Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 09/06/2021 09:00 pm
https://twitter.com/hugo_blair/status/1433320987592835073?s=20

I'm glad someone on Twitter saw that. I was a coauthor on the presentation, and wanted to see the concept get more attention. Let me know if any of you have questions.

~Jon
Title: Re: Propellant Depots - General Discussion
Post by: OTV Booster on 09/13/2021 07:13 pm
https://twitter.com/hugo_blair/status/1433320987592835073?s=20 (https://twitter.com/hugo_blair/status/1433320987592835073?s=20)

I'm glad someone on Twitter saw that. I was a coauthor on the presentation, and wanted to see the concept get more attention. Let me know if any of you have questions.

~Jon
Jon, I just worked up through this thread from 2017 and read your boondocks articles on taxonomy. Nice work. Some thoughts.


The RL and SX concepts are similar in that they are not agnostic. A commercial depot can not afford this. That said, a startup has to find a niche that closes the business case with some small number of customers. To make this work, all interfaces, electronic, logical, physical and orbital must ultimately be standardized. A first attempt can get away with ad hoc solutions but ultimately it has to be industry standard. Is there any industry movement in this direction?


A depot pioneer faces a chicken/egg problem. I can think of some ways to bootstrap but like so many engineering and business ideas it all hinges on 'it depends'. It's a hard nut to crack.


ISTM a first effort might get its best mileage by carefully targeting limited services. One thought is LOX and He/N2 only. The customer can short LOX at launch (assuming they have the launch flexibility) and pile on the fuel. This admittedly limits the initial customer base to those who find it useful. To its credit, with H2 and CH4, LOX is the heavy part. Not sure about kerosene.


There are too many fuels in use to target them all on a first try, but everybody uses LOX except those few who use and are phasing out hypergolics.


I likes Chickens
And I likes eggs
But gettin that cycle started
Has some pretty weak legs.  ::)
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 09/13/2021 07:29 pm
https://twitter.com/hugo_blair/status/1433320987592835073?s=20 (https://twitter.com/hugo_blair/status/1433320987592835073?s=20)

I'm glad someone on Twitter saw that. I was a coauthor on the presentation, and wanted to see the concept get more attention. Let me know if any of you have questions.

~Jon
Jon, I just worked up through this thread from 2017 and read your boondocks articles on taxonomy. Nice work. Some thoughts.


The RL and SX concepts are similar in that they are not agnostic. A commercial depot can not afford this. That said, a startup has to find a niche that closes the business case with some small number of customers. To make this work, all interfaces, electronic, logical, physical and orbital must ultimately be standardized. A first attempt can get away with ad hoc solutions but ultimately it has to be industry standard. Is there any industry movement in this direction?


A depot pioneer faces a chicken/egg problem. I can think of some ways to bootstrap but like so many engineering and business ideas it all hinges on 'it depends'. It's a hard nut to crack.


ISTM a first effort might get its best mileage by carefully targeting limited services. One thought is LOX and He/N2 only. The customer can short LOX at launch (assuming they have the launch flexibility) and pile on the fuel. This admittedly limits the initial customer base to those who find it useful. To its credit, with H2 and CH4, LOX is the heavy part. Not sure about kerosene.


There are too many fuels in use to target them all on a first try, but everybody uses LOX except those few who use and are phasing out hypergolics.


I likes Chickens
And I likes eggs
But gettin that cycle started
Has some pretty weak legs.  ::)
Orbital Fab are making start and have developed refueling port that some satellite manufacturers are using.

https://spacenews.com/orbit-fab-to-launch-with-spaceflight/


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Title: Re: Propellant Depots - General Discussion
Post by: OTV Booster on 09/14/2021 02:10 am
https://twitter.com/hugo_blair/status/1433320987592835073?s=20 (https://twitter.com/hugo_blair/status/1433320987592835073?s=20)

I'm glad someone on Twitter saw that. I was a coauthor on the presentation, and wanted to see the concept get more attention. Let me know if any of you have questions.

~Jon
Jon, I just worked up through this thread from 2017 and read your boondocks articles on taxonomy. Nice work. Some thoughts.


The RL and SX concepts are similar in that they are not agnostic. A commercial depot can not afford this. That said, a startup has to find a niche that closes the business case with some small number of customers. To make this work, all interfaces, electronic, logical, physical and orbital must ultimately be standardized. A first attempt can get away with ad hoc solutions but ultimately it has to be industry standard. Is there any industry movement in this direction?


A depot pioneer faces a chicken/egg problem. I can think of some ways to bootstrap but like so many engineering and business ideas it all hinges on 'it depends'. It's a hard nut to crack.


ISTM a first effort might get its best mileage by carefully targeting limited services. One thought is LOX and He/N2 only. The customer can short LOX at launch (assuming they have the launch flexibility) and pile on the fuel. This admittedly limits the initial customer base to those who find it useful. To its credit, with H2 and CH4, LOX is the heavy part. Not sure about kerosene.


There are too many fuels in use to target them all on a first try, but everybody uses LOX except those few who use and are phasing out hypergolics.


I likes Chickens
And I likes eggs
But gettin that cycle started
Has some pretty weak legs.  ::)
Orbital Fab are making start and have developed refueling port that some satellite manufacturers are using.

https://spacenews.com/orbit-fab-to-launch-with-spaceflight/ (https://spacenews.com/orbit-fab-to-launch-with-spaceflight/)


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Thanks for the link. Read it and googled a bit more. It launched in June but I didn't find any hard mission results. Just PR stuff.


Where did you find info on sat builders using the refueling ports? I saw nothing but I skimmed more than read.


Ports are a good start. Need a lot more but it's only intended as a minimum viable demo.
Title: Re: Propellant Depots - General Discussion
Post by: tbellman on 09/14/2021 09:45 am
ISTM a first effort might get its best mileage by carefully targeting limited services. One thought is LOX and He/N2 only. The customer can short LOX at launch (assuming they have the launch flexibility) and pile on the fuel. This admittedly limits the initial customer base to those who find it useful. To its credit, with H2 and CH4, LOX is the heavy part. Not sure about kerosene.

That might work somewhat for methane and kerosene(*).  Hydrogen-fuelled rockets, however, have the extra problem that while hydrogen tends to be around a sixth of the oxygen by mass, hydrogen will take up more than twice the volume of oxygen.  The space shuttle external tank, e.g, was 553 m³ for oxygen, but 1497 m³ for hydrogen.

Any rocket that wants to fill its empty oxygen tank at the depot, will need to carry double the amount of fuel, and thus have twice as large fuel tank.  For methalox, the total tank volume would need to increase by about 40%(†), but for hydrolox it would need to increase by 70%(‡).  40% increase can be hard enough, but 70% increase seems like it would be a stretch (pun intended), especially since a hydrogen-fueled rocket is already disadvantaged by needing large tanks.

On top of that, since the rocket is carrying more fuel, it needs more propellant to just reach the depot.  The prototypical refuelling rocket, Starship, would need to carry 250 tonnes methane to orbit if it is to just refuel oxygen (full tank).  That's more than its payload capacity...

Of course, it's still better than carrying all the required propellant up from Earth in a single launch.  But I'm not convinced that it is enough to make sense to have a LOX-only depot, regardless of fuel type, but especially for hydrogen.

When I started writing this reply, I thought it would work out reasonably OK for methane- and kerosene-fuelled rockets, but as I ran the numbers, I got more pessimistic...  Could work out better if you only need half a tank-load of propellant on orbit instead of a full tank-load, so for example refuelling only (edit: ISRU-produced) oxygen on the Moon for return to Earth may work out.




(*) I believe typical oxygen-kerosene ratios are a bit more than twice as much oxygen as kerosene by mass.  The first stage of Saturn V used a 2.3:1 ratio, for example.

(†) At a 3.7:1 ratio by mass, LOX density of 1080 g/l, LCH₄ density of 400 g/l (at their respective 3 bar boiling points), tanks would be about 3.4:2.5 by volume.  Double the amount of methane, and you get a volume ratio of 3.4:5.0.  (3.4+5.0) / (3.4+2.5) ≈ 1.4.

(‡) 6:1 ratio by mass, LH₂ density of 66.3 g/l (at 3 bar boiling), tanks are about 5.6:15 by volume.  Double the amount of hydrogen, and you get a volume ratio of 5.6:30 by volume.  (5.6+30) / (5.6+15) ≈ 1.7.
Title: Re: Propellant Depots - General Discussion
Post by: OTV Booster on 09/14/2021 02:22 pm
ISTM a first effort might get its best mileage by carefully targeting limited services. One thought is LOX and He/N2 only. The customer can short LOX at launch (assuming they have the launch flexibility) and pile on the fuel. This admittedly limits the initial customer base to those who find it useful. To its credit, with H2 and CH4, LOX is the heavy part. Not sure about kerosene.

That might work somewhat for methane and kerosene(*).  Hydrogen-fuelled rockets, however, have the extra problem that while hydrogen tends to be around a sixth of the oxygen by mass, hydrogen will take up more than twice the volume of oxygen.  The space shuttle external tank, e.g, was 553 m³ for oxygen, but 1497 m³ for hydrogen.

Any rocket that wants to fill its empty oxygen tank at the depot, will need to carry double the amount of fuel, and thus have twice as large fuel tank.  For methalox, the total tank volume would need to increase by about 40%(†), but for hydrolox it would need to increase by 70%(‡).  40% increase can be hard enough, but 70% increase seems like it would be a stretch (pun intended), especially since a hydrogen-fueled rocket is already disadvantaged by needing large tanks.

On top of that, since the rocket is carrying more fuel, it needs more propellant to just reach the depot.  The prototypical refuelling rocket, Starship, would need to carry 250 tonnes methane to orbit if it is to just refuel oxygen (full tank).  That's more than its payload capacity...

Of course, it's still better than carrying all the required propellant up from Earth in a single launch.  But I'm not convinced that it is enough to make sense to have a LOX-only depot, regardless of fuel type, but especially for hydrogen.

When I started writing this reply, I thought it would work out reasonably OK for methane- and kerosene-fuelled rockets, but as I ran the numbers, I got more pessimistic...  Could work out better if you only need half a tank-load of propellant on orbit instead of a full tank-load, so for example refuelling only (edit: ISRU-produced) oxygen on the Moon for return to Earth may work out.




(*) I believe typical oxygen-kerosene ratios are a bit more than twice as much oxygen as kerosene by mass.  The first stage of Saturn V used a 2.3:1 ratio, for example.

(†) At a 3.7:1 ratio by mass, LOX density of 1080 g/l, LCH₄ density of 400 g/l (at their respective 3 bar boiling points), tanks would be about 3.4:2.5 by volume.  Double the amount of methane, and you get a volume ratio of 3.4:5.0.  (3.4+5.0) / (3.4+2.5) ≈ 1.4.

(‡) 6:1 ratio by mass, LH₂ density of 66.3 g/l (at 3 bar boiling), tanks are about 5.6:15 by volume.  Double the amount of hydrogen, and you get a volume ratio of 5.6:30 by volume.  (5.6+30) / (5.6+15) ≈ 1.7.
I just finished reading Jon Goffs [size=78%]https://selenianboondocks.com/2020/09/an-updated-propellant-depot-taxonomy (https://selenianboondocks.com/2020/09/an-updated-propellant-depot-taxonomy)[/size] and was thinking of several possible depot scenarios. Refueling a big rocket wasn't one I was thinking of. Cubesats and OTVs were more in line with my thoughts. And even then, more of a proof of concept/Kickstarter than a full service depot.


One thing Jon mused on was separate O2 and fuel depots for safety reasons. With different fuels out there this makes good operational sense from the depot operators POV.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 09/14/2021 04:33 pm
Orbital Fab are placing a fuel depot in GEO. Delivery is via SpaceFlights OTV which is flying as rideshare on CLPS launch.

https://spaceflight.com/spaceflight-inc-announces-first-lunar-and-geo-rideshare-mission-geo-pathfinder/

Not sure what satellites they plan to refuel given GEO smallsat market is very new.

On separate subject, this OTV rideshare should help lower cost of future CLPS missions. In most cases F9 and Vulcan are     to big for these landers and surplus performance is going to waste.

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Title: Re: Propellant Depots - General Discussion
Post by: tbellman on 09/14/2021 05:33 pm
I just finished reading Jon Goffs [size=78%]https://selenianboondocks.com/2020/09/an-updated-propellant-depot-taxonomy (https://selenianboondocks.com/2020/09/an-updated-propellant-depot-taxonomy)[/size] and was thinking of several possible depot scenarios. Refueling a big rocket wasn't one I was thinking of. Cubesats and OTVs were more in line with my thoughts. And even then, more of a proof of concept/Kickstarter than a full service depot.

Satellites and orbital tugs are probably not a good fit for a LOX-only depot.

Very few satellites, and especially so cubesats, are likely to be consumers of oxygen at all.  They mostly are monopropellant with some heavy noble gas like xenon for ion thrusters, or hydrazine.  Those that are bi-propellant are most likely using storable hypergols, and want nitrogen tetroxide or so for their oxidizer.

Orbital tugs would presumably be designed to have a fairly long life-time on orbit, and want to be refuelled not just once, but ten or twenty times, or even more.  If the depot brings only oxygen, the tug will need to be launched with tens of times more fuel than if the depot can bring both oxygen and fuel, and that will almost certainly kill the business case.

Quote from: OTV Booster
One thing Jon mused on was separate O2 and fuel depots for safety reasons. With different fuels out there this makes good operational sense from the depot operators POV.

That could make more sense.  But then it's not really a case of limiting what services are provided; it's just separating those two services to separate pit stops.
Title: Re: Propellant Depots - General Discussion
Post by: jongoff on 10/09/2021 06:36 am
I need to find time to respond to some of these posts before this thread goes too stale...
Title: Re: Propellant Depots - General Discussion
Post by: Asteroza on 10/10/2021 10:52 pm
Wouldn't a LOX/LH2 depot fundamentally also be a water depot, compatible with water plasma thruster based services? This, plus a potential capability to manufacture LOX/LH2 from water deliveries (which are a reasonably dense cargo, thus easy rideshare fodder), provides a secondary delivery market that is amenable to adhoc delivery?
Title: Re: Propellant Depots - General Discussion
Post by: brickmack on 01/02/2022 07:07 pm
Wouldn't a LOX/LH2 depot fundamentally also be a water depot, compatible with water plasma thruster based services? This, plus a potential capability to manufacture LOX/LH2 from water deliveries (which are a reasonably dense cargo, thus easy rideshare fodder), provides a secondary delivery market that is amenable to adhoc delivery?

Yeah. Propellant production from pre-placed water was a feature of Lockheed's Mars Base Camp architecture, no reason you couldn't use some of that water for other purposes. With any water-derived hydrolox production, you do have the problem of excess oxygen having to be dumped (since engines always burn fuel-rich), but accounting for the storability and density of water you might still come out ahead on a mass-to-orbit basis. And directly using water for propellant would skip that whole problem.
Title: Re: Propellant Depots - General Discussion
Post by: DanClemmensen on 01/02/2022 09:46 pm
Wouldn't a LOX/LH2 depot fundamentally also be a water depot, compatible with water plasma thruster based services? This, plus a potential capability to manufacture LOX/LH2 from water deliveries (which are a reasonably dense cargo, thus easy rideshare fodder), provides a secondary delivery market that is amenable to adhoc delivery?

Yeah. Propellant production from pre-placed water was a feature of Lockheed's Mars Base Camp architecture, no reason you couldn't use some of that water for other purposes. With any water-derived hydrolox production, you do have the problem of excess oxygen having to be dumped (since engines always burn fuel-rich), but accounting for the storability and density of water you might still come out ahead on a mass-to-orbit basis. And directly using water for propellant would skip that whole problem.
For crewed spacecraft depot customers, that surplus oxygen is a valuable asset. Otherwise, the depot or the customer spacecraft can use the extra oxygen for cold gas thrusters for station keeping and angular momentum dumping.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 01/02/2022 10:47 pm
Wouldn't a LOX/LH2 depot fundamentally also be a water depot, compatible with water plasma thruster based services? This, plus a potential capability to manufacture LOX/LH2 from water deliveries (which are a reasonably dense cargo, thus easy rideshare fodder), provides a secondary delivery market that is amenable to adhoc delivery?

Yeah. Propellant production from pre-placed water was a feature of Lockheed's Mars Base Camp architecture, no reason you couldn't use some of that water for other purposes. With any water-derived hydrolox production, you do have the problem of excess oxygen having to be dumped (since engines always burn fuel-rich), but accounting for the storability and density of water you might still come out ahead on a mass-to-orbit basis. And directly using water for propellant would skip that whole problem.
For crewed spacecraft depot customers, that surplus oxygen is a valuable asset. Otherwise, the depot or the customer spacecraft can use the extra oxygen for cold gas thrusters for station keeping and angular momentum dumping.

No, not a good idea.  Requires additional systems on the receiver spacecraft. 

The depot can use it itself for those purposes.
Title: Re: Propellant Depots - General Discussion
Post by: DanClemmensen on 01/02/2022 11:42 pm
Wouldn't a LOX/LH2 depot fundamentally also be a water depot, compatible with water plasma thruster based services? This, plus a potential capability to manufacture LOX/LH2 from water deliveries (which are a reasonably dense cargo, thus easy rideshare fodder), provides a secondary delivery market that is amenable to adhoc delivery?

Yeah. Propellant production from pre-placed water was a feature of Lockheed's Mars Base Camp architecture, no reason you couldn't use some of that water for other purposes. With any water-derived hydrolox production, you do have the problem of excess oxygen having to be dumped (since engines always burn fuel-rich), but accounting for the storability and density of water you might still come out ahead on a mass-to-orbit basis. And directly using water for propellant would skip that whole problem.
For crewed spacecraft depot customers, that surplus oxygen is a valuable asset. Otherwise, the depot or the customer spacecraft can use the extra oxygen for cold gas thrusters for station keeping and angular momentum dumping.

No, not a good idea.  Requires additional systems on the receiver spacecraft. 

The depot can use it itself for those purposes.
I am speculating here: The crewed craft would not have a separate receiver for the "extra" oxygen. Instead, it would receive more LOX than it needs for propellant use, and it would have a system to tap its LOX tank for crew atmosphere or for its cold gas thrusters. And you are right, it may in fact not be a good idea, it's just speculation based on the point made in the prior post.
Title: Re: Propellant Depots - General Discussion
Post by: Jim on 01/02/2022 11:56 pm
No.  Crew vehicles don’t have cold gas thrusters, much less oxygen ones.  It would require separate tanks.

Also, LOX can not be used in cold gas thrusters, not high enough pressure.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 01/03/2022 12:45 am
There are pros and cons for shipping and converting water in orbit.
Pros
More compact tanks on tanker, makes for lighter tanker which is big plus for lunar landers taking fuel to LO.
No issues with boiloff so trip times can be months.
Access to 24/7 solar power. Which is plus for lunar fuel.
Lot cheaper to deliver equipment to lunar orbit than lunar surface.

Cons
Depot is now complex processing plant.
Excess Oxygen, but this can be used with hydrogen or methane for earth or moon.
In case of LEO that 24/7 solar power becomes more like 12/7.

With lunar fuel going need to create some fuel on surface for landers to get into orbit.  Fuel BLLO and descents to surface can be extracted from water in orbit.

For LEO depots iy may work out cheaper to deliver fuel instead of water from earth.

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Title: Re: Propellant Depots - General Discussion
Post by: mandrewa on 01/03/2022 02:23 am
There are pros and cons for shipping and converting water in orbit.
Pros
More compact tanks on tanker, makes for lighter tanker which is big plus for lunar landers taking fuel to LO.
No issues with boiloff so trip times can be months.
Access to 24/7 solar power. Which is plus for lunar fuel.
Lot cheaper to deliver equipment to lunar orbit than lunar surface.

Another advantage of water is that every launch to the depot can go up full, or close to it.  Many payloads don't use the full capacity of the rocket.  Water is very compact.  If you have different size water tanks that would mount underneath the main payload, then every launch can go up full.
Title: Re: Propellant Depots - General Discussion
Post by: Asteroza on 01/05/2022 04:18 am
There are pros and cons for shipping and converting water in orbit.
Pros
More compact tanks on tanker, makes for lighter tanker which is big plus for lunar landers taking fuel to LO.
No issues with boiloff so trip times can be months.
Access to 24/7 solar power. Which is plus for lunar fuel.
Lot cheaper to deliver equipment to lunar orbit than lunar surface.

Another advantage of water is that every launch to the depot can go up full, or close to it.  Many payloads don't use the full capacity of the rocket.  Water is very compact.  If you have different size water tanks that would mount underneath the main payload, then every launch can go up full.

This is the core part of a question I had rolling around in the back of my mind; Why isn't Dragon using surplus upmass to fill water bladders in the trunk for delivery to ISS? Why is this potential market being ignored/avoided currently? I feel like the answers to those questions has relevance to the overall propellant depot marketplace.
Title: Re: Propellant Depots - General Discussion
Post by: Redclaws on 01/05/2022 04:38 am
What would the ISS do with the water?  And where would they store it?
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 01/05/2022 10:19 am
Hydrolox is really only useful to a handful of upper stages which currently don't support refuelling. Only time they'd need a top is for BLEO which are far few between.

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Title: Re: Propellant Depots - General Discussion
Post by: brickmack on 01/05/2022 09:55 pm
This is the core part of a question I had rolling around in the back of my mind; Why isn't Dragon using surplus upmass to fill water bladders in the trunk for delivery to ISS? Why is this potential market being ignored/avoided currently? I feel like the answers to those questions has relevance to the overall propellant depot marketplace.

I think Momentus was interested in doing this. Send small payloads (like the ones already deployed from JEM-AL and Bishop) up in cargo vehicles, use whatever capacity is left over for water to fuel their tugs, use the station's crew and robotics to integrate everything and mate it to a tug that goes off and brings the payloads to more useful orbits.

Really would be nice if it works out, solves a lot of different problems for multiple parties. But Momentus' future looks pretty questionable right now. And their propulsion tech is expected to produce a ton of radio interference right? Might not be able to use it in proximity to the station, so operations might have to be one-way (release new tugs and payloads, but no refueling and reuse), kinda hard to justify then

Either way, until someone actually does this, theres no point and no capability for bringing up substantial amounts of water to the station
Title: Re: Propellant Depots - General Discussion
Post by: su27k on 08/29/2022 02:27 pm
https://twitter.com/rocketrepreneur/status/1563372802484211712

Quote
For those who were asking, I wrote a blog post about the @AIAA/@AerospaceCorp Cislunar Depot Workshop I participated in this last week, including key takeaways, and a copy of my presentation.
When @mmealling finishes uploading his presentation, I'll update the post with a link.



My Independent Perspectives on Cislunar Depots (https://starbrighteng.com/my-independent-perspectives-on-cislunar-depots/)


https://twitter.com/mmealling/status/1563758299920699393

Quote
Here are my slightly modified slides. I used animations that don't translate well so they needed to be updated. The last slide includes a summary of the Commodities Reserve.

An Investor’s Perspective on Cislunar Depots (https://medium.com/@rocketforge/an-investors-view-b4c91a10e888)
Title: Re: Propellant Depots - General Discussion
Post by: su27k on 09/03/2022 03:54 am
Fill ’er up (https://aerospaceamerica.aiaa.org/features/filler-up/)

Quote from: aerospaceamerica.aiaa.org
The push to expand Earth’s economy into space has prompted NASA to pump millions of dollars into the old idea of establishing propellant depots in Earth orbit for satellites or passenger transports and cargo tugs headed for deep space. Jon Kelvey looks at the reasons for the renewed interest — and the hurdles ahead.
Title: Re: Propellant Depots - General Discussion
Post by: su27k on 09/03/2022 05:30 am
Fill ’er up (https://aerospaceamerica.aiaa.org/features/filler-up/)

Quote from: aerospaceamerica.aiaa.org
The push to expand Earth’s economy into space has prompted NASA to pump millions of dollars into the old idea of establishing propellant depots in Earth orbit for satellites or passenger transports and cargo tugs headed for deep space. Jon Kelvey looks at the reasons for the renewed interest — and the hurdles ahead.

https://twitter.com/davehuntsman/status/1565905499828133890

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Reasonable summary article vis a vis in-space fuel depots. Only 1 tweak: sayings ‘depots’ was ‘verboten’ 12yrs ago inside NASA an understatement; have direct knowledge of 2 good NASA depot advocates- at 2 different Centers 100s miles apart-receiving firing orders on same day.



Even easy to remember date: the firing orders, dated end of Nov giving obligatory 30-day warnings of firing- noted that termination of the two civil servants would be effective “commencing Dec 25, 2011” - for both. The two felt a message was being sent. One had 35+yrs in NASA.
Title: Re: Propellant Depots - General Discussion
Post by: su27k on 10/21/2022 01:16 pm
https://twitter.com/jeff_foust/status/1583126543068725248

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Interesting comment by Orbit Fab’s Daniel Faber at #GSSF22: ability to refuel will result a shift from electric to chemical propulsion; can trade efficiency for getting you into revenue service the fastest. (Also, price of xenon is now “terrifying,” he says.)
Title: Re: Propellant Depots - General Discussion
Post by: JayWee on 10/21/2022 02:56 pm
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Interesting comment by Orbit Fab’s Daniel Faber at #GSSF22: ability to refuel will result a shift from electric to chemical propulsion; can trade efficiency for getting you into revenue service the fastest. (Also, price of xenon is now “terrifying,” he says.)
Any idea how much Xenon a GEO satellite has?
Title: Re: Propellant Depots - General Discussion
Post by: spacenut on 10/21/2022 06:49 pm
It may be cheaper in the long run to make lox from lunar soil and launch to lunar orbit or to L1 or L2.  Lox has more mass or weight so launching from earth would be more expensive in the long run. 

Launching liquid methane or even liquid hydrogen from earth would be cheaper due to their mass or weight getting to orbit or to the moon. 

Water would have more mass due to the oxygen content if launched from earth.  Water may also have a tendency to freeze in space causing expansion that could lead to leaks.  Methane is widely handled in liquid form already on earth, unlike hydrogen which tends to leak more due to the small atom.  Pound for pound methane or hydrogen would be cheaper to launch than water. 

Hydrogen is also not a good long term storage unless you have refrigeration equipment at the depot due to faster boil off. 

I think setting up lox manufacturing on the moon should be a priority for any type of moon base to cut down on transportation costs to launch to a depot.  Then only methane would have to be brought from earth. 
Title: Re: Propellant Depots - General Discussion
Post by: Zed_Noir on 10/21/2022 07:40 pm
It may be cheaper in the long run to make lox from lunar soil and launch to lunar orbit or to L1 or L2.  Lox has more mass or weight so launching from earth would be more expensive in the long run. 

Launching liquid methane or even liquid hydrogen from earth would be cheaper due to their mass or weight getting to orbit or to the moon. 

Water would have more mass due to the oxygen content if launched from earth.  Water may also have a tendency to freeze in space causing expansion that could lead to leaks.  Methane is widely handled in liquid form already on earth, unlike hydrogen which tends to leak more due to the small atom.  Pound for pound methane or hydrogen would be cheaper to launch than water. 

Hydrogen is also not a good long term storage unless you have refrigeration equipment at the depot due to faster boil off. 

I think setting up lox manufacturing on the moon should be a priority for any type of moon base to cut down on transportation costs to launch to a depot.  Then only methane would have to be brought from earth.
Disagree for the short to medium term, maybe even the long term. It will be cheaper to bring propellants from Earth then setting up ISRU LOX production on the Moon and the logistics of delivering it to Earth orbit.

Propellants is cheap. Off Earth facilities and cislunar logistics are expensive.

Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 10/22/2022 04:53 am
It may be cheaper in the long run to make lox from lunar soil and launch to lunar orbit or to L1 or L2.  Lox has more mass or weight so launching from earth would be more expensive in the long run. 

Launching liquid methane or even liquid hydrogen from earth would be cheaper due to their mass or weight getting to orbit or to the moon. 

Water would have more mass due to the oxygen content if launched from earth.  Water may also have a tendency to freeze in space causing expansion that could lead to leaks.  Methane is widely handled in liquid form already on earth, unlike hydrogen which tends to leak more due to the small atom.  Pound for pound methane or hydrogen would be cheaper to launch than water. 

Hydrogen is also not a good long term storage unless you have refrigeration equipment at the depot due to faster boil off. 

I think setting up lox manufacturing on the moon should be a priority for any type of moon base to cut down on transportation costs to launch to a depot.  Then only methane would have to be brought from earth.
Disagree for the short to medium term, maybe even the long term. It will be cheaper to bring propellants from Earth then setting up ISRU LOX production on the Moon and the logistics of delivering it to Earth orbit.

Propellants is cheap. Off Earth facilities and cislunar logistics are expensive.
Start with earth supplied depot and build a customer base. Eventually depot operator will put out a tender for supply which should contain quantity and max price.
Investors in lunar ISRU facility will then have an ideal if it is feasible.

Depots do make setting up lunar facility cheaper. Would also create new markets as access is lot cheaper when landers (human or cargo) can refuel on surface from lunar ISRU.

While demand for LH is limited someone like ULA or Blue may pay depot to provide storage facilities(cyrocooler). Either company could provide LH, they may choose buy LOX from depot if its cheaper than they can supply it.
If this is case one Vulcan LH tanker mission could support multiple refuellings of Centaurs.

Title: Re: Propellant Depots - General Discussion
Post by: oldAtlas_Eguy on 10/23/2022 05:30 pm
For HydroLOX, 1 ton of LH results in 5 tons of prop if LOX is local sourced.

For MethaLOX, 1 ton of LNG results in 4 tons of prop if LOX is local sourced.

A Starship Tanker is possible in the future if all of Starship operational goals are met. Deliver ~500t of LNG to Lunar orbit from LEO. That = 2000t of prop when local Lunar LOX is added.

The key is that 500t of LNG when Lunar produced LOX is mixed in the equations creates a heavy and very active Lunar orbit to Lunar surface round trip transport rate.

Some of the interesting items is that the Delta V to get LNG from LEO to the Lunar surface takes ~5.8 km/s. To get LOX from Lunar surface to LEO takes ~2.8 km/s.

If the cost of producing LOX on the Lunar surface gets cheap enough then delivering LOX to LEO may  end cheaper than delivering LOX from Earth. If a Tanker from Earth delivering 200t of prop (LOX or LNG or 3 to 1 mix) costs $10M then per ton that is a cost of $50,000/ton. SO LOX at LEO has a value of $50,000/ton.

This is where I need to do a cost model for the complete infrastructure with some amount of excess prop at all 3 locations LEO, Lunar Orbit, Lunar Surface from the amounts of shifted around LNG and LOX. If Lunar LOX drops at LEO to half the cost of LOX from Earth then total prop cost at LEO drops by 37%.

When I finish the cost model I will add my info either to this post or a later one.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 10/23/2022 06:02 pm
You are assuming tanker can use aerobraking into LEO on return trip with few 100ts of LOX. While heatshield is rated for higher DV that is mostly empty Tanker.
Title: Re: Propellant Depots - General Discussion
Post by: TrevorMonty on 10/23/2022 06:16 pm
Lunar LOX is going come from electrolysis of water or molten regolith with metal byproduct. I'm assuming energy requirements are similar in which case may as well use water and make LH. Now we have 2000ts of Hydrolox which is far superior fuel for CIS- lunar space travel.