Author Topic: Propellant depot strategy & tactics pow-wow  (Read 50416 times)

Offline mmeijeri

  • Senior Member
  • *****
  • Posts: 7772
  • Martijn Meijering
  • NL
  • Liked: 397
  • Likes Given: 822
Propellant depot strategy & tactics pow-wow
« on: 07/30/2009 05:53 pm »
Here's a thread for those of us who can't wait for propellant depots and want them as soon as possible. Thanks to the Augustine commission prospects are better than they have been for years. We can expect a mountain of FUD from the SDLV people, and this thread is to discuss strategy and tactics for countering that. We don't have much time before the window of opportunity closes. Let's not screw this up people.
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

Offline mmeijeri

  • Senior Member
  • *****
  • Posts: 7772
  • Martijn Meijering
  • NL
  • Liked: 397
  • Likes Given: 822
Re: Propellant depot strategy & tactics pow-wow
« Reply #1 on: 07/30/2009 06:56 pm »
Some context. The good news is that the subcommittee has stated quite bluntly that superheavy lift is not necessary. It has also said depots should be part of any option the commission considers. The bad news is that Jeff Greason has said he is no longer sure 25mT is enough. General Lyles has also said depot technology is still immature.

It sounds as if there may need to be a bigger launcher. What should we argue for? Obvious choices include EELV Phase 1, J-130 and NSC. EELV Phase 1 is very heavy from the point of view of a depot enthusiast, but the good thing is it might also increase the payload capacity of the more reasonably sized Delta Medium. An SDLV would be wasteful, and all EELV might be better, but if we aim too high we may end up with nothing. The commission may recommend depots, but I think we can expect tremendous opposition from the congressional delegations from Alabama and Florida. Resigning ourselves to an SDLV may be the right thing to do.

Another consideration is how to deal with depot development. If MSFC gets involved we would have to be worried they screw up again, especially since this time they'd have an incentive to screw up. Another aspect is the perceived immaturity of depot technology. Augustine himself has said it is pretty difficult to do liquid hydrogen transfer on the ground, let alone in space. He has also said it will be an important topic for discussion next week.

One less ambitious initial target would be to start with in-flight refueling as was proposed by Danny Deger.

As you will know I have been arguing in favour of hypergolic depots at L1 for a while now, in support of an all hypergolic lander. It may not be as sexy as cryogenic depots, but at least it doesn't have the perceived risks. After all, the Russians have been doing hypergolic propellant transfer ever since Salyut-6, way back in 1978. The technology has been in continuous use ever since and is used on ISS today. Hypergolic landers are also a proven technology and Orion uses hypergolic propulsion anyway.

I'm greatly relieved by what happened today and I think the committee will in all likelihood recommend development of cryogenic depots. This is the best news we have had in years. But I'm afraid the committee may hesitate to put cryogenic depots on the critical path and I expect enormous opposition from Florida and Alabama. It seems highly likely there will be funding for cryogenic depots, but the sooner we have operational depots and an exploration program, the bigger the boost to the commercial development of space.

One concern is that the Flexible Path Option would not immediately develop a lander, but a cheaper precursor of a lander could serve as a long duration transit hab and mini space station, which fits perfectly with the Flexible Path option. Hypergolics would also be a very natural fit for long duration missions. Hypergolics for the lander/transfer vehicle only would leave open the possibility of cryogenic depots refueling the EDS as soon as they became available.

J-130/NSC + in-flight refueling of the hypergolic transfer vehicle/lander only sounds like the least ambitious option and EELV Phase 1 and cryogenic depots like the most ambitious one the committee might accept, with a whole range of options in between. All of these options would allow for a commercial propellant market soon.

What should we aim for?
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

Offline rklaehn

  • interplanetary telemetry plumber
  • Full Member
  • ****
  • Posts: 1259
  • germany
  • Liked: 191
  • Likes Given: 318
Re: Propellant depot strategy & tactics pow-wow
« Reply #2 on: 07/30/2009 07:39 pm »
The realistic depot concepts I have seen so far are all based on existing upper stages. The easiest path to a depot would be building the wide body centaur or whatever the concept is currently called. A wide body centaur plus RS68a would get delta IV heavy to 35-40mt to LEO. That should be enough for even the biggest piece of exploration hardware.

If transferring LH2 proves too difficult initially, just limit the propellant transfer to the LOX, which is the majority of propellant mass anyway. LOX is also common in many different propellant combinations, and the only realistic candidate for lunar ISRU.

But ULA seemed relatively confident that they can make LH2 transfer work as well.

If a shuttle derived vehicle is required for political reasons, it should be DIRECT, since it is clear that they see the benefits of depots.   

Offline A_M_Swallow

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8906
  • South coast of England
  • Liked: 500
  • Likes Given: 223
Re: Propellant depot strategy & tactics pow-wow
« Reply #3 on: 07/30/2009 07:48 pm »
Some context. The good news is that the subcommittee has stated quite bluntly that superheavy lift is not necessary. It has also said depots should be part of any option the commission considers. The bad news is that Jeff Greason has said he is no longer sure 25mT is enough. General Lyles has also said depot technology is still immature.

Devise a plan to bring depot technology to TRL 9 within 3 years.  Launch the propellant on say an EELV.  Refuel the upper stage of a Falcon 1 so it can send a communications satellite to L2.  Then refuel a medium EELV's Centaur so it can send a satellite to GSO.

Quote
It sounds as if there may need to be a bigger launcher. What should we argue for? Obvious choices include EELV Phase 1, J-130 and NSC. EELV Phase 1 is very heavy from the point of view of a depot enthusiast, but the good thing is it might also increase the payload capacity of the more reasonably sized Delta Medium. An SDLV would be wasteful, and all EELV might be better, but if we aim too high we may end up with nothing. The commission may recommend depots, but I think we can expect tremendous opposition from the congressional delegations from Alabama and Florida. Resigning ourselves to an SDLV may be the right thing to do.

Which ever one you chose will make its rivals into enemies.  Since depots are compatible with all the LV types the answer is ALL.  For all the LV under consideration produce a page showing how big a cargo can be sent to L1 if they refuel in LEO.

Offline jongoff

  • Recovering Rocket Plumber/Space Entrepreneur
  • Senior Member
  • *****
  • Posts: 6807
  • Lafayette/Broomfield, CO
  • Liked: 3987
  • Likes Given: 1681
Re: Propellant depot strategy & tactics pow-wow
« Reply #4 on: 07/30/2009 08:37 pm »
There are tools being worked on by industry and NASA for doing cryo fluid management technology maturation.  Centaur Test Bed has been mentioned before, but and industry team and NASA are working together on a new project called CRYOTE (CRYogenic Orbital TEstbed) that would be even more capable.  A ground-test version of it is actually funded and being built as we speak.  That's about all I think I'm safe with saying for now, but there should be more details at SPACE 2009.  I've also been doing some work at Masten to see if we can do a suborbital version of the same (CRYOSOTE?) that could fly on our suborbital vehicles, once they're available.

Testbeds like this can help with the rapid maturation of the technology.  It would also be nice if the two depot-related Centennial Challenges would actually get funded. 

NASA has some depot-related SBIR topics out on their solicitation, but adding more, or going with larger "Broad Area Announcement" style contracts would also be very helpful.

The technology is mostly there, and we have or will soon have the tools to retire the rest of the remaining risks quickly if depots end up being put on the critical path, like they ought to.

~Jon

Offline TOG

  • Full Member
  • **
  • Posts: 223
  • Near Chicago, Illinois
  • Liked: 65
  • Likes Given: 58
Re: Propellant depot strategy & tactics pow-wow
« Reply #5 on: 08/03/2009 07:31 pm »
Team-

Any thoughts on this alternative to LH2 - LOX storage: What if the fuel was stored as Stable Water?  Then when the time comes to transfer the fuel the water could be broken into H2 and O2 via energy gathered from solar panels. 

This could reduce the amount of loss due to the "boil off" effect, and would be more stable and less prone to "unfortunate incidents" on orbit.

Thoughts?

Drew Montgomery AKA TOG.
M's Laws of Aerodynamics:                                    On Physics Exam:
1) if you push anything hard enough it will fly          Q)The allegory of Schrödinger's cat shows what?
2) if you stop pushing it stops flying                        A)That Shrödinger was a sadistic cat hater

Offline jongoff

  • Recovering Rocket Plumber/Space Entrepreneur
  • Senior Member
  • *****
  • Posts: 6807
  • Lafayette/Broomfield, CO
  • Liked: 3987
  • Likes Given: 1681
Re: Propellant depot strategy & tactics pow-wow
« Reply #6 on: 08/03/2009 07:55 pm »
Any thoughts on this alternative to LH2 - LOX storage: What if the fuel was stored as Stable Water?  Then when the time comes to transfer the fuel the water could be broken into H2 and O2 via energy gathered from solar panels. 

This could reduce the amount of loss due to the "boil off" effect, and would be more stable and less prone to "unfortunate incidents" on orbit.

The problem is that electrolyzing water (and then chilling it down to cryo temps) takes a nearly insane amount of energy.  You'd be better off using the much smaller amount of energy it takes to actively cool the LH2/LOX.

~Jon

Offline simon-th

  • Full Member
  • ****
  • Posts: 952
  • Liked: 0
  • Likes Given: 0
Re: Propellant depot strategy & tactics pow-wow
« Reply #7 on: 08/03/2009 08:04 pm »
Team-

Any thoughts on this alternative to LH2 - LOX storage: What if the fuel was stored as Stable Water?  Then when the time comes to transfer the fuel the water could be broken into H2 and O2 via energy gathered from solar panels. 

This could reduce the amount of loss due to the "boil off" effect, and would be more stable and less prone to "unfortunate incidents" on orbit.

Thoughts?

Drew Montgomery AKA TOG.

Interesting idea, but not really viable.

4.4 kilowatt-hours of electricity converts 1 liter of water into 1.59 liters of liquid hydrogen and 0.79 liters of liquid oxygen. With efficiency losses we can think about 7-8 kilowatt-hours of electricity required.

For a metric ton of water converted into H2/O2 you would thus require about 8MWh. The peak output of the ISS' solar panels are 100KW. With these panels it would take 80 hours to convert one 1 metric ton. If you require say 50 metric tons of fuel for one mission, you end up having to wait 4000 hours or 160 days for your fuel depot to convert the water. And while it does so, you got the same boil-off problems you have if you bring up H2 and O2 separated in the first place.

I'd say fuel depots can realistically be a. for hypergolics only or b. for LOX only. Only in the very long run will we be able to build depots with LH2/LOX capability.

Offline yg1968

  • Senior Member
  • *****
  • Posts: 17266
  • Liked: 7123
  • Likes Given: 3064
Re: Propellant depot strategy & tactics pow-wow
« Reply #8 on: 08/03/2009 08:06 pm »
Can someone explain or provide a link as to why propellant depots are such a great idea. Why are they better and cheaper than having a large rocket.  Thanks.

Offline mmeijeri

  • Senior Member
  • *****
  • Posts: 7772
  • Martijn Meijering
  • NL
  • Liked: 397
  • Likes Given: 822
Re: Propellant depot strategy & tactics pow-wow
« Reply #9 on: 08/03/2009 08:17 pm »
I'd say fuel depots can realistically be a. for hypergolics only or b. for LOX only. Only in the very long run will we be able to build depots with LH2/LOX capability.

Heheh, usually I'm the one to argue hypergolic depots are the way to go for now, not cryogenic ones. Allow me to take the other side for a change. :)

What makes you say cryogenic depots are far in the future? I think the political risks far outweigh the technical ones, especially if development of the depots is left to LM / Boeing / ULA, not MSFC. Other than that the remaining argument would be that hypergolic depots could perhaps be operational sooner, which means the benefits to the launch sector would occur sooner.

Within the context of the Flexible Path / Deep Space option, hypergolics do start to make extra sense because of the long durations involved. They may even offer a greater "depot multiplication factor" than cryogenics, since their density is much greater. Payload fairings constrain the maximum volume for a dry-launched EDS. With hypergolics these constraints would be much less constraining. I think that if you make use of an Earth swingby the Oberth effect reduces the required delta-v's by so much the inefficiency of hypergolics is much reduced. This means you may actually be able to push larger masses towards Mars than with cryogenics. I'm not sure about this, I'm still working on the calculations.
« Last Edit: 08/03/2009 08:31 pm by mmeijeri »
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

Offline marsavian

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 3216
  • Liked: 2
  • Likes Given: 3
Re: Propellant depot strategy & tactics pow-wow
« Reply #10 on: 08/03/2009 08:17 pm »
Propellant Depots - General Discussion

http://forum.nasaspaceflight.com/index.php?topic=12338.0
« Last Edit: 08/03/2009 08:18 pm by marsavian »

Offline mmeijeri

  • Senior Member
  • *****
  • Posts: 7772
  • Martijn Meijering
  • NL
  • Liked: 397
  • Likes Given: 822
Re: Propellant depot strategy & tactics pow-wow
« Reply #11 on: 08/03/2009 08:20 pm »
In a nutshell:

1) they allow you to do exploration without HLVs
2) this can stimulate a thriving commercial launch market, which may drive down costs and eventually lead to RLVs
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

Offline simon-th

  • Full Member
  • ****
  • Posts: 952
  • Liked: 0
  • Likes Given: 0
Re: Propellant depot strategy & tactics pow-wow
« Reply #12 on: 08/03/2009 08:26 pm »
Can someone explain or provide a link as to why propellant depots are such a great idea. Why are they better and cheaper than having a large rocket.  Thanks.

Just a couple of benefits:

1. Costs. You get your fuel up to the depot with a number of smaller launch vehicles. High flight rates (>20 flights per year) reduces cost per launch significantly. On the other hand large rockets do have high fixed costs and only make sense at large flight rates (that you don't get if you have a 120mt vehicle).

2. Flexibility. Your architecture basically involves your flight stack with an empty EDS going up to the depot and be fueled and then you go whereever you want to go. You can have an empty spacecraft (EDS and payload) in the 75mt range and after it's fueled you have a spacecraft with say 200mt ready to propel 60mt to a Mars trajectory.

3. Creating a market for commercial rockets. You get fuel up to your depot constantly. A commercial provider with e.g. a 15mt to LEO rocket may be able to sell 20 launches per year to NASA for the fuel depot. That lowers this providers cost per launch quite significantly. That also means that the DoD and NASA can use these launchers for other payloads for quite a lower price.

Offline TOG

  • Full Member
  • **
  • Posts: 223
  • Near Chicago, Illinois
  • Liked: 65
  • Likes Given: 58
Re: Propellant depot strategy & tactics pow-wow
« Reply #13 on: 08/03/2009 08:27 pm »
Jon & Simon,

Thank you both for your quick responses.  I can see now where this is not practical.  Forgot (briefly) that in this case the conversion of water to their base elements is only an energy transfer, and the amount of energy loss (as well as the time involved in the process) would make this a losing proposition.  I was just looking for a little different way to approach the problem.  The spin off of that solution would be "capturing" a comment and separating the elements for their fuel components. 

But as you both so succinctly pointed out, the amount of energy required to separate the elements is prohibitive.

I understand the attraction of Hypergolics (easier to store for longer periods of time), but was trying to look for alternatives that did not necessarily involve terrestrial sources.

Thank you again,
TOG.
M's Laws of Aerodynamics:                                    On Physics Exam:
1) if you push anything hard enough it will fly          Q)The allegory of Schrödinger's cat shows what?
2) if you stop pushing it stops flying                        A)That Shrödinger was a sadistic cat hater

Offline yg1968

  • Senior Member
  • *****
  • Posts: 17266
  • Liked: 7123
  • Likes Given: 3064
Re: Propellant depot strategy & tactics pow-wow
« Reply #14 on: 08/03/2009 08:36 pm »
Can someone explain or provide a link as to why propellant depots are such a great idea. Why are they better and cheaper than having a large rocket.  Thanks.

Just a couple of benefits:

1. Costs. You get your fuel up to the depot with a number of smaller launch vehicles. High flight rates (>20 flights per year) reduces cost per launch significantly. On the other hand large rockets do have high fixed costs and only make sense at large flight rates (that you don't get if you have a 120mt vehicle).

2. Flexibility. Your architecture basically involves your flight stack with an empty EDS going up to the depot and be fueled and then you go whereever you want to go. You can have an empty spacecraft (EDS and payload) in the 75mt range and after it's fueled you have a spacecraft with say 200mt ready to propel 60mt to a Mars trajectory.

3. Creating a market for commercial rockets. You get fuel up to your depot constantly. A commercial provider with e.g. a 15mt to LEO rocket may be able to sell 20 launches per year to NASA for the fuel depot. That lowers this providers cost per launch quite significantly. That also means that the DoD and NASA can use these launchers for other payloads for quite a lower price.

Thanks for all of the answers.

Offline mmeijeri

  • Senior Member
  • *****
  • Posts: 7772
  • Martijn Meijering
  • NL
  • Liked: 397
  • Likes Given: 822
Re: Propellant depot strategy & tactics pow-wow
« Reply #15 on: 08/03/2009 08:40 pm »
The problem is that electrolyzing water (and then chilling it down to cryo temps) takes a nearly insane amount of energy.  You'd be better off using the much smaller amount of energy it takes to actively cool the LH2/LOX.

This idea does make sense for propulsion systems for space stations. The quantities involved are much smaller. Plans for Space Station Freedom included LOX/LH2 propulsion with propellant stored as water. Bigelow is considering something similar for his planned stations.

EDIT: I think both plans were for gaseous H2 and O2, which makes sense for the small quantities and burns involved.
« Last Edit: 08/04/2009 07:03 am by mmeijeri »
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

Offline agman25

  • Full Member
  • ****
  • Posts: 452
  • Liked: 0
  • Likes Given: 2
Re: Propellant depot strategy & tactics pow-wow
« Reply #16 on: 08/03/2009 08:44 pm »
Team-

Any thoughts on this alternative to LH2 - LOX storage: What if the fuel was stored as Stable Water?  Then when the time comes to transfer the fuel the water could be broken into H2 and O2 via energy gathered from solar panels. 

This could reduce the amount of loss due to the "boil off" effect, and would be more stable and less prone to "unfortunate incidents" on orbit.

Thoughts?

Drew Montgomery AKA TOG.

Interesting idea, but not really viable.

4.4 kilowatt-hours of electricity converts 1 liter of water into 1.59 liters of liquid hydrogen and 0.79 liters of liquid oxygen. With efficiency losses we can think about 7-8 kilowatt-hours of electricity required.

For a metric ton of water converted into H2/O2 you would thus require about 8MWh. The peak output of the ISS' solar panels are 100KW. With these panels it would take 80 hours to convert one 1 metric ton. If you require say 50 metric tons of fuel for one mission, you end up having to wait 4000 hours or 160 days for your fuel depot to convert the water. And while it does so, you got the same boil-off problems you have if you bring up H2 and O2 separated in the first place.

I'd say fuel depots can realistically be a. for hypergolics only or b. for LOX only. Only in the very long run will we be able to build depots with LH2/LOX capability.

That is only if you use ecotrolysis. Other approaches such as Photocatalysis has zero power requirements. The work very well with UV light. Guess where UV is abundant.

Offline MZ

  • Member
  • Posts: 5
  • Liked: 0
  • Likes Given: 1
Re: Propellant depot strategy & tactics pow-wow
« Reply #17 on: 08/03/2009 08:59 pm »
Why is the choice of fuels at a depot between hypergolics and LH2?  I would think that there are fuels that are more easily stored and transferred than LH2, and that also has a better Isp than hypergolics.
Just curious why the other options have been discarded.

Offline neilh

  • Senior Member
  • *****
  • Posts: 2365
  • Pasadena, CA
  • Liked: 46
  • Likes Given: 149
Re: Propellant depot strategy & tactics pow-wow
« Reply #18 on: 08/03/2009 09:40 pm »
Why is the choice of fuels at a depot between hypergolics and LH2?  I would think that there are fuels that are more easily stored and transferred than LH2, and that also has a better Isp than hypergolics.
Just curious why the other options have been discarded.

Methane, for example, which I believe doesn't need cooling. Both Armadillo Aerospace and XCOR (Jeff Greason's company) have recently constructed LOX/Methane engines:

http://www.xcor.com/products/engines/5M15_LOX-Methane_rocket_engine.html
http://www.hobbyspace.com/nucleus/index.php?itemid=14018

The CEV was "originally" planned to use methane, but was switched to hypergolics in 2006:

http://www.space.com/spacenews/archive06/Methane_013006.html

Quote
Hypergols such as the nitrogen tetroxide and monomethyl hydrazine combination the space shuttle burns to maneuver on orbit are considered highly reliable and easier to store than other propellants. But they offer lower performance than methane and other so-called green propellants and are highly caustic, requiring painstakingly careful -- and therefore expensive -- handling by workers on the ground who have to be extremely careful to avoid potentially lethal exposure.

Scott Horowitz, NASA associate administrator for space exploration, said the decision to drop the methane-engine requirement from the CEV program came down to changing assumptions about the performance advantages and technical risk. There are no methane-fueled space propulsion systems in service today. Hypergolic systems, on the other hand, were used on board the Apollo command and service modules and the lunar landers.

This paper on scalable depot design (the first one which came up from some googling) lists the following propellant options: LOX, LH2, LCH4, kerosene, H2O2, liquid xenon.

http://www.ssdl.gatech.edu/Papers/Masters/Street_8900.pdf

On a related note, I'm not sure if anybody linked to this yet, but I came across a presentation by Boeing in 2007 on the "Potential Impact of a LEO Propellant on the NASA ESAS Architecture":

http://www.boeing.com/defense-space/space/constellation/references/presentations/Potential_Impact_of_LEO_Propellant_on_NASA_ESAS_Architecture.pdf
« Last Edit: 08/03/2009 09:46 pm by neilh »
Someone is wrong on the Internet.
http://xkcd.com/386/

Offline fotoguzzi

  • Full Member
  • ***
  • Posts: 335
  • Phobos first!
  • PDX, Oregon, USA
  • Liked: 0
  • Likes Given: 0
Re: Propellant depot strategy & tactics pow-wow
« Reply #19 on: 08/03/2009 09:47 pm »
Can someone explain or provide a link as to why propellant depots are such a great idea. Why are they better and cheaper than having a large rocket.  Thanks.
I know this has been gone over before, but to simplify clongton's points,

Take the fuel up in the cheapest form possible.  It could be dozens of small, cheap rockets or one big giant cheap rocket--whatever works.  If a stable market can be developed, a candidate rocket will emerge.  There is less time pressure, and if it fails to reach orbit, you are only out one cheap rocket and some cheap propellant.

Then send as much precious crew and time-sensitive, expensive exploration gear, and a large propellant tank as you can afford to launch to the depot.
My other rocket is a DIRECT Project 2

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0