Propellant Depots - General Discussion

[kraisee]

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.

[Eerie]

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.

[kraisee]

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.

[Eerie]

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.

[Eerie]

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.

[meiza]

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.

[meiza]

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.

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.

[Smatcha]

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.

[mike robel]

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?

[mike robel]

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.

[clongton]

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.

[mike robel]

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.

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.

[A_M_Swallow]

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.

[clongton]

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.

[A_M_Swallow]

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?

[mike robel]

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.  

[Bill White]

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.

[mike robel]

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?