Author Topic: Propellant depot strategy & tactics pow-wow  (Read 50424 times)

Offline MZ

  • Member
  • Posts: 5
  • Liked: 0
  • Likes Given: 1
Re: Propellant depot strategy & tactics pow-wow
« Reply #20 on: 08/03/2009 10:07 pm »
Thanks.  So it isn't that the other fuels perform badly it is just that they haven't been used for in space propulsion before...a new engine development would be needed.

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

Offline neilh

  • Senior Member
  • *****
  • Posts: 2365
  • Pasadena, CA
  • Liked: 46
  • Likes Given: 149
Re: Propellant depot strategy & tactics pow-wow
« Reply #21 on: 08/03/2009 10:10 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.

Just to add to what others have said, the white paper Jon Goff submitted to the Augustine Commission is an excellent explanation of the merits of propellant depots. I particularly like the chart which compares a depot-centric architecture with an HLV-centric one in terms of ability to meet the committee's objectives:

http://selenianboondocks.com/wp-content/uploads/2009/07/Depot-Centric_Human_Spaceflight.pdf
http://selenianboondocks.com/2009/07/depot-centric-human-spaceflight/
Someone is wrong on the Internet.
http://xkcd.com/386/

Offline Danny Dot

  • Rocket Scientist, NOT Retired
  • Senior Member
  • *****
  • Posts: 2792
  • Houston, Texas
  • Liked: 17
  • Likes Given: 1
Re: Propellant depot strategy & tactics pow-wow
« Reply #22 on: 08/03/2009 10:12 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.

Someone crank the numbers on kw-hours to turn 30mT of water into rocket fuel?  I am too busy right now. 

My guess is a REALLY big number.  I looked a site on using electrolysis at gas stations to make hydrogen and the power requirements were HUGE.  They also stated the process is only 50% efficient and large quantities of waste heat is produced.  This means huge radiators. 

Danny Deger
Danny Deger

Offline neilh

  • Senior Member
  • *****
  • Posts: 2365
  • Pasadena, CA
  • Liked: 46
  • Likes Given: 149
Re: Propellant depot strategy & tactics pow-wow
« Reply #23 on: 08/03/2009 10:14 pm »
On a related note, the wikipedia article on propellant depots could use a lot of improvement:

http://en.wikipedia.org/wiki/Propellant_depot

Just remember to cite your sources and maintain a NPOV!
Someone is wrong on the Internet.
http://xkcd.com/386/

Offline loomy

  • Full Member
  • *
  • Posts: 172
  • Liked: 0
  • Likes Given: 0
Re: Propellant depot strategy & tactics pow-wow
« Reply #24 on: 08/03/2009 10:15 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.

LOL!  The large rocket doesn't exist yet.  Is that a good place to start!

And how about this:  Orbital and SpaceX can use propellant depots.  They can't use Ares V.

Hat trick:  SpaceX says it'll take 2+ years and the $300,000,000 from COTS-D to develop a crew abort system.  Cargo doesn't need crew abort systems!

Bonus point:  In some places the competition NASA has with the private sector would be illegal or cause an international event, see: Softwood lumber dispute.  Depots are the first step in NASA transitioning from ridiculous socialism (NASA chose to build its own rockets over buying EELV when the mere existence of EELV should have ended NASA's medium lift business) to the american entrepreneur's capitalism you hear about on TV.

Offline butters

  • Senior Member
  • *****
  • Posts: 2399
  • Liked: 1693
  • Likes Given: 598
Re: Propellant depot strategy & tactics pow-wow
« Reply #25 on: 08/04/2009 01:37 am »
Is there really any advantage to LCH4 over RP-1 for refillable upper stages?  The specific impulse is 3% higher, but the density is 20% lower.  This reduces the propellant mass ratio of each supply tanker, so it takes more IMLEO to deliver the same propellant mass.

LCH4 is promising for Mars ISRU, so it makes sense for a mars ascent stage, but I don't see any benefit for the rest of the trip, including return from low mars orbit (cheaper to send propellant from earth than to land a much bigger ascent stage and then haul it back out of the gravity well).

Offline Jorge

  • Senior Member
  • *****
  • Posts: 6404
  • Liked: 529
  • Likes Given: 67
Re: Propellant depot strategy & tactics pow-wow
« Reply #26 on: 08/04/2009 01:41 am »
Is there really any advantage to LCH4 over RP-1 for refillable upper stages?  The specific impulse is 3% higher, but the density is 20% lower.

Easier to keep the prop lines clean, I would think.
JRF

Offline mmeijeri

  • Senior Member
  • *****
  • Posts: 7772
  • Martijn Meijering
  • NL
  • Liked: 397
  • Likes Given: 822
Re: Propellant depot strategy & tactics pow-wow
« Reply #27 on: 08/04/2009 06:46 am »
Easier to keep the prop lines clean, I would think.

Do jet aircraft have similar problems, or is it something specific to rocket engines?
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 #28 on: 08/04/2009 10:03 am »
One important consideration for hypergolic depots / propellant transfer: it really needs a depot or refueling at L1, not just in LEO. Hypergolics are too inefficient for use on an EDS, other than perhaps a one time transfer of a heavy fully reusable spacecraft, where the cost can be amortised. The spacecraft would have to be dry-launched to L1, either in one launch, or preferably in two launches with EOR with an EDS. Only at L1 would it be fueled.

In order to accommodate smaller launchers, especially small RLVs, but also including things like Falcon and potential new vehicles like Aquarius or Scorpius, you would want to have a LEO export depot as well. And since stimulating the launch industry and thereby reducing cost to orbit as soon as possible is the main point of doing all this, the LEO depot would be important. The LEO hypergolics depot could also refuel reusable tugs, which are crucial for making depots (including cryogenic ones) cost effective. These tugs would also make ISS resupply more efficient. Another initial application would be refueling unmanned Orions making trips into the inner van Allen belt and back to do radiation shielding tests.

The main argument in favour of hypergolics depots is that there are no technical obstacles that can be used as a pretext to put them off to the long run. Hypergolic propellant transfer is a mature technology that has seen continuous operational use ever since Salyut-6 in 1978. There are already spacecraft, either operational or in the pipeline (Orion, ATV, HTV, Cygnus, Dragon), that could use them. Based at L1, performance would not be an issue and hypergolics are perfectly suited for the long duration missions envisaged for the Flexible Path option.

The sales pitch is not helped if depot enthusiasts keep stressing cryogenic depots (even midly cryogenic ones like oxygen or methane) are better... They are, but hypergolic ones are good enough to avoid HLV and very useful in the short run anyway.
« Last Edit: 08/04/2009 10:05 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 #29 on: 08/04/2009 08:06 pm »
Anybody think of using solids. I think there was a late-70 MSR study that used two shuttle launch to launch 2 IUS's each and the spacecraft elements. Assembly on orbit.

Offline TOG

  • Full Member
  • **
  • Posts: 223
  • Near Chicago, Illinois
  • Liked: 65
  • Likes Given: 58
Re: Propellant depot strategy & tactics pow-wow
« Reply #30 on: 08/04/2009 08:54 pm »
Team-

This has probably come up elsewhere, but any thought of using one of the expandable modules that Bigelow is developing?

Or how about (if we HAVE to use cryogenic fuels) puling an ET up from a SSTS or SDHLV?

In other words, any thoughts on WHAT would hold our fuels?

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 NUAETIUS

  • Full Member
  • ****
  • Posts: 427
  • Liked: 1
  • Likes Given: 0
Re: Propellant depot strategy & tactics pow-wow
« Reply #31 on: 08/04/2009 09:51 pm »
Team-

This has probably come up elsewhere, but any thought of using one of the expandable modules that Bigelow is developing?

Or how about (if we HAVE to use cryo genic fuels) puling an ET up from a SSTS or SDHLV?

In other words, any thoughts on WHAT would hold our fuels?

TOG

Search the forum, it has been talked about ad nausium.
“It has long been recognized that the formation of a committee is a powerful technique for avoiding responsibility, deferring difficult decisions and averting blame….while at the same time maintaining a semblance of action.” Augustine's Law - Norm Augustine

Offline yg1968

  • Senior Member
  • *****
  • Posts: 17267
  • Liked: 7123
  • Likes Given: 3065
Re: Propellant depot strategy & tactics pow-wow
« Reply #32 on: 08/05/2009 04:53 am »
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.

LOL!  The large rocket doesn't exist yet.  Is that a good place to start!

That's a bad argument. Propellant depots don't exist either. But from the hearing on July 30th, probably the strongest proponent on the panel for propellant depots, Jeff Greason said that he was no longer convinced that there wasn't a need for a 75m ton rocket. He said that the next generation HLV should be capable of lifting between 25mt and 75mt. But even with a 75mt rocket, he felt that propellant depots were still a game changer and needed to be a priority but he also felt that a large enough rocket would not need to rely on propellant depots until the propellant depots are ready.
« Last Edit: 08/05/2009 05:04 am by yg1968 »

Offline neilh

  • Senior Member
  • *****
  • Posts: 2365
  • Pasadena, CA
  • Liked: 46
  • Likes Given: 149
Re: Propellant depot strategy & tactics pow-wow
« Reply #33 on: 08/05/2009 05:26 am »
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.

LOL!  The large rocket doesn't exist yet.  Is that a good place to start!

That's a bad argument. Propellant depots don't exist either. But from the hearing on July 30th, probably the strongest proponent on the panel for propellant depots, Jeff Greason said that he was no longer convinced that there wasn't a need for a 75m ton rocket. He said that the next generation HLV should be capable of lifting between 25mt and 75mt. But even with a 75mt rocket, he felt that propellant depots were still a game changer and needed to be a priority but he also felt that a large enough rocket would not need to rely on propellant depots until the propellant depots are ready.

Here's the text from his actual slide:

http://www.nasa.gov/ppt/375965main_03%20-%20Integrated%20beyond%20LEO%20overview_2009july30_without%20backup%20slides.ppt (slide 86)
http://www.nasa.gov/offices/hsf/meetings/07_30_meeting.html#

Quote
Chemical in-space propulsion: Lunar return

* Revolves around some kind of Earth Departure Stage
** Considered three classes, which map to the three classes of launch vehicles (25mT, 75mT, 125mT)
* 25mT vehicles require propellant transfer and a depot for human Lunar exploration
** Still an open question whether mass/volume is sufficient for payloads
** Number of launches requires time to place propellant, vehicles, and mass on orbit; managing boil-off, orbit maintenance, keep-alive power drives need for a depot for missions beyond the first few
* 75mT vehicles can support some exploration missions with “top off” of one EDS by another, but can do significant exploration before depot is ready
** Cannot match Ares V capability without top-off transfer
* 125+ mT vehicles do not require propellant transfer for Lunar missions but would be greatly enhanced by them for Mars
* Point of departure EDSs for these classes provided to NASA for additional architecture analysis now underway
Someone is wrong on the Internet.
http://xkcd.com/386/

Offline JohnFornaro

  • Not an expert
  • Senior Member
  • *****
  • Posts: 10974
  • Delta-t is an important metric.
  • Planet Eaarth
    • Design / Program Associates
  • Liked: 1257
  • Likes Given: 724
Re: Propellant depot strategy & tactics pow-wow
« Reply #34 on: 08/05/2009 01:51 pm »
Water, Water, Water. 

Turns to ice, don't need to refrigerate, shade will do.  Stores forever with no boil-off.  Higher density for launching.  Triple use:  Fuel, Breathing, Drinking.  Requires electrolysis capability, either solar or nuclear. Cheaper to launch. Cheaper to purchase.  Less expensive to manufacture (electrolyze?) in space if the equipment is designed with sufficiently amortized life, and un-attended operation.  Does not rule our hypergolics, or other fuel combinations.  Depot should be multi-fuel capable, as well as able to store supplies, consumables, rescue craft, spare parts, ultimately habitat and micro-gravity & radiation experimentation.

Locate at Emily-1. Start small, build-out to 2400m diameter, rotating ring.

What's not to like?
Sometimes I just flat out don't get it.

Offline simon-th

  • Full Member
  • ****
  • Posts: 952
  • Liked: 0
  • Likes Given: 0
Re: Propellant depot strategy & tactics pow-wow
« Reply #35 on: 08/05/2009 01:57 pm »
Water, Water, Water. 

Locate at Emily-1. Start small, build-out to 2400m diameter, rotating ring.


You want a large, rotating swimming pool at EML-1?  ;) ;) ;)

Sorry, couldn't resist...

Offline JohnFornaro

  • Not an expert
  • Senior Member
  • *****
  • Posts: 10974
  • Delta-t is an important metric.
  • Planet Eaarth
    • Design / Program Associates
  • Liked: 1257
  • Likes Given: 724
Re: Propellant depot strategy & tactics pow-wow
« Reply #36 on: 08/05/2009 02:07 pm »
Uhh... actually ice rink.
Sometimes I just flat out don't get it.

Offline jongoff

  • Recovering Rocket Plumber/Space Entrepreneur
  • Senior Member
  • *****
  • Posts: 6807
  • Lafayette/Broomfield, CO
  • Liked: 3987
  • Likes Given: 1684
Re: Propellant depot strategy & tactics pow-wow
« Reply #37 on: 08/05/2009 07:39 pm »
That's a bad argument. Propellant depots don't exist either. But from the hearing on July 30th, probably the strongest proponent on the panel for propellant depots, Jeff Greason said that he was no longer convinced that there wasn't a need for a 75m ton rocket. He said that the next generation HLV should be capable of lifting between 25mt and 75mt. But even with a 75mt rocket, he felt that propellant depots were still a game changer and needed to be a priority but he also felt that a large enough rocket would not need to rely on propellant depots until the propellant depots are ready.

I think you're misreading what Jeff said.  I thought he said that he was no longer 100% certain that 25mT would be enough.  That it might, but might be marginal.  That's completely different from saying we need a 75mT vehicle.  If 25mT is marginal for the "biggest smallest piece", but 30-35mT is ok, there are other options that don't involve building a big HLV.

~Jon

Offline loomy

  • Full Member
  • *
  • Posts: 172
  • Liked: 0
  • Likes Given: 0
Re: Propellant depot strategy & tactics pow-wow
« Reply #38 on: 08/05/2009 08:04 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.

LOL!  The large rocket doesn't exist yet.  Is that a good place to start!

That's a bad argument. Propellant depots don't exist either.

It is an awesome argument.  Depots could cost what, 5x less? 10x less to develop than Ares V?  (Remember that some of the Ares V cost is built into the cost of Ares I, and will be added back into the cost of Ares V when Ares I is gone)

And the resulting volume production of smaller rockets, the ones that would use the depots, would lower costs.

And the competition between suppliers of smaller rockets would lower costs. 

Oh, and those same rockets that use the depots will also launch the depots themselves.  Even more launches! 

And more frequent successful launches mean more safety guaranteed.

OH and entities other than NASA and its suppliers can use the depots.  Virgin Galactic hotel rockets can use depots for fuel and have nothing else to do with NASA.

Or you could do none of that and be socialist and build one big government rocket.  The soviet bear is alive and well in the united states.
« Last Edit: 08/05/2009 08:05 pm by loomy »

Offline JohnFornaro

  • Not an expert
  • Senior Member
  • *****
  • Posts: 10974
  • Delta-t is an important metric.
  • Planet Eaarth
    • Design / Program Associates
  • Liked: 1257
  • Likes Given: 724
Re: Propellant depot strategy & tactics pow-wow
« Reply #39 on: 08/05/2009 08:39 pm »
Give up on the "Soviet bear" analogy.  The PTB like BFR's, perhaps even to the detriment of long term HSF. 

But Loomy's argument makes sense to a certain extent.  More smaller rockets are a good thing; it spreads the wealth, the saftety, the cost, the experience, the manufacturing capability.  It encourages private industry, minimizes investment capital, allows faster returns, spreads risk.

Just a few big 'uns.  Waterboys, if you will.

I think 25mt may be too low:  50?
Sometimes I just flat out don't get it.

Tags:
 

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