Author Topic: Griffin speech - EELV would not work for Constellation  (Read 31039 times)

Offline clongton

  • Expert
  • Senior Member
  • *****
  • Posts: 10259
  • Connecticut
    • Direct Launcher
  • Liked: 2020
  • Likes Given: 620
RE: Griffin speech - EELV would not work for Constellation
« Reply #80 on: 01/26/2008 03:14 PM »
David;
In my opinion, see my response to a similar question at
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=11586#M235173
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline meiza

  • Expert
  • Senior Member
  • *****
  • Posts: 3069
  • Where Be Dragons
  • Liked: 2
  • Likes Given: 3
Re: Griffin speech - EELV would not work for Constellation
« Reply #81 on: 01/26/2008 04:31 PM »
David, he probably means nuclear thermal rockets (NTR) which run on hydrogen only. Their use is outlined in the Mars reference mission 3.0.

Offline Zach

  • Member
  • Posts: 94
  • Liked: 0
  • Likes Given: 0
Re: Griffin speech - EELV would not work for Constellation
« Reply #82 on: 01/26/2008 05:18 PM »
Quote
meiza - 26/1/2008  11:31 AM

David, he probably means nuclear thermal rockets (NTR) which run on hydrogen only. Their use is outlined in the Mars reference mission 3.0.

NTR is certainly the likely interpretation of Griffin's comment.  But if Griffin believes that hydrogen boilof is a key limiting technology in an NTR world he has his priorities mixed up: "control of hydrogen boiloff in space is one of the key limiting technologies for deep space exploration".  Development of the reactor, human rating it, getting approval to launch said reactor, and operating it, especially in Earth orbit make hydrogen storage pale in comparison.

Offline sbt

  • Veteran
  • Full Member
  • ***
  • Posts: 328
  • Liked: 0
  • Likes Given: 0
Re: Griffin speech - EELV would not work for Constellation
« Reply #83 on: 01/27/2008 11:23 AM »

Quote
Zach - 26/1/2008  6:18 PM  NTR is certainly the likely interpretation of Griffin's comment.  But if Griffin believes that hydrogen boilof is a key limiting technology in an NTR world he has his priorities mixed up: "control of hydrogen boiloff in space is one of the key limiting technologies for deep space exploration".  Development of the reactor, human rating it, getting approval to launch said reactor, and operating it, especially in Earth orbit make hydrogen storage pale in comparison.

Note that he said 'one of' not 'the'. All the enabling technologies have to be in place for something to be enabled. A reactor that lacks fuel because it has all boiled away is going to look pretty silly, as is a stock of LH with no way to make use of it.

The thing with control of boiloff is that it is 'dual use' - the technology benefits both Chemical and Nuclear Thermal propulsion.

Rick

I am not interested in your political point scoring, Ad Hominem attacks, personal obsessions and vendettas. - No matter how cute and clever you may think your comments are.

Offline Zach

  • Member
  • Posts: 94
  • Liked: 0
  • Likes Given: 0
Re: Griffin speech - EELV would not work for Constellation
« Reply #84 on: 01/27/2008 01:04 PM »
Quote
sbt - 27/1/2008  6:23 AM

Quote
Zach - 26/1/2008  6:18 PM  NTR is certainly the likely interpretation of Griffin's comment.  But if Griffin believes that hydrogen boilof is a key limiting technology in an NTR world he has his priorities mixed up: "control of hydrogen boiloff in space is one of the key limiting technologies for deep space exploration".  Development of the reactor, human rating it, getting approval to launch said reactor, and operating it, especially in Earth orbit make hydrogen storage pale in comparison.

Note that he said 'one of' not 'the'. All the enabling technologies have to be in place for something to be enabled. A reactor that lacks fuel because it has all boiled away is going to look pretty silly, as is a stock of LH with no way to make use of it.

The thing with control of boiloff is that it is 'dual use' - the technology benefits both Chemical and Nuclear Thermal propulsion.

Rick


Fully agree with boiloff control being dual use.  But to use thermal mitigation measures as an excuse for developing Ares V, the "biggest rocket that we can afford", over J-232 or EELV class simply to reduce the duration of storing LH2 is silly:

"But if we split the EOR lunar architecture into two equal but smaller
vehicles, we will need ten or more launches to obtain the same Mars-bound
payload in LEO, and that is without assuming any loss of packaging efficiency for
the launch of smaller payloads. When we consider that maybe half the Mars
mission mass in LEO is liquid hydrogen, and if we understand that the control of
hydrogen boiloff in space is one of the key limiting technologies for deep space
exploration, the need to conduct fewer rather than more launches to LEO for early
Mars missions becomes glaringly apparent.

So if we want a lunar transportation architecture that looks back to the ISS
LEO logistics requirement, and forward to the first Mars missions, it becomes
apparent that the best approach is a dual-launch EOR mission, but with the total
payload split unequally. The smaller launch vehicle puts a crew in LEO every time
it flies, whether they are going to the ISS or to the Moon. The larger launch
vehicle puts the lunar (or, later, Mars) cargo in orbit. After rendezvous and
docking, they are off to their final destination."

I don't find anything glaringly apparent. An NTR will require LH2 be stored for the better part of 2 years during the trip to and stay at Mars to supply the LH2 propellant for the return trip.  If we don't know how to store LH2 in Earth orbit, where mass and errors aren't nearly as critical as during the Mars journey we need to use a different technology or not go to Mars.

Offline alexterrell

  • Full Member
  • ****
  • Posts: 1500
  • Germany
  • Liked: 41
  • Likes Given: 30
RE: Griffin speech - EELV would not work for Constellation
« Reply #85 on: 03/29/2008 08:45 PM »
Quote
jongoff - 23/1/2008  2:18 PM

While one could definitely draw the conclusion that Griffin drew, ie. that hydrogen boiloff issues imply it would be better to launch the system in fewer pieces, one could also draw a different conclusion.  The conclusion I would draw is that if cryogenic propellant storage technologies are so critical--develop them.


Why develop them? There's a very good technology for storing hydrogen already. Combine it with Carbon and call it Kerosene. Methane or Propane.

Offline A_M_Swallow

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8104
  • South coast of England
  • Liked: 248
  • Likes Given: 99
RE: Griffin speech - EELV would not work for Constellation
« Reply #86 on: 03/30/2008 06:13 AM »
Keeping things simple, a 100 mT (reusable) spacecraft that goes from EML2 to low Mars orbit (LMO) and returns.  In addition 100 mT of cargo is delivered to Mars orbit.  Total 200 mT.
The high delta-v needed (13.47 km/s) to go from the Earth's surface to EML2 is ignored.

Hydrogen engine has an ISP of 462.
Kerosene engine has an ISP of 327.
If used the SEP ferry has a dry weight of 15 mT and an ISP of 2750.  The ferry returns empty.
Delta-v is the same both directions = 0.14 + 0.6 + 0.9 + 0.2 + 0.3 + 0.9 = 3.04 km/s


All hydrogen

Return 100 * exp(3040 / (462 * 9.81)) = 195.6 mT
Out (100 + 195.6) * exp(3040 / (462 * 9.81)) = 578 mT
Hydrogen propellent = 578 - 200 = 378 mT


All kerosene

Return 100 * exp(3040 / (327 * 9.81)) = 258 mT
Out (100 + 258) * exp(3040 / (327 * 9.81)) = 923.5 mT
Kerosene propellent = 923.5 - 200 = 723.5 mT


Hydrogen with SEP Ferries for cargo and return fuel

Return 100 * exp(3040 / (462 * 9.81)) = 195.6 mT
Return hydrogen propellent = 195.6 - 100 = 95.6 mT
SEP return 15 * exp(3040 / (2750 * 9.81)) = 16.79 mT
Return SEP propellent 16.79 - 15 = 1.79 mT

Out 100 * exp(3040 / (462 * 9.81)) = 195.6 mT
Out hydrogen propellent = 195.6 - 100 = 95.6 mT
SEP out (16.79 + 95.6 + 100) * e^(3040 / (2750 * 9.81)) = 237.7
Out SEP propellent = 237.7 - (16.79 + 95.6 + 100) = 25.3 mT

Total hydrogen propellent =  95.6 + 95.6 = 191.2 mT (plus boil off)
Total SEP propellent = 1.79 + 25.3 = 26.1 mT


Kerosene with SEP Ferries for cargo and return fuel

Return 100 * exp(3040 / (327 * 9.81)) = 258 mT
Return kerosene propellent = 258 - 100 = 158 mT
SEP return 15 * exp(3040 / (2750 * 9.81)) = 16.79 mT
Return SEP propellent 16.79 - 15 = 1.79 mT

Out Return 100 * exp(3040 / (327 * 9.81)) = 258 mT
Out kerosene propellent = 258 - 100 = 158 mT
SEP out (16.79 + 158 + 100) * e^(3040 / (2750 * 9.81)) = 307.6
Out SEP propellent = 307.6 - (16.79 + 158 + 100) = 32.81 mT

Total kerosene propellent =  158 + 158 = 316 mT
Total SEP propellent = 1.79 + 32.81 = 34.6 mT


The chemical fuel saved weights more than the SEP ferry.

Offline alexterrell

  • Full Member
  • ****
  • Posts: 1500
  • Germany
  • Liked: 41
  • Likes Given: 30
RE: Griffin speech - EELV would not work for Constellation
« Reply #87 on: 03/30/2008 09:21 PM »
Quote
Norm Hartnett - 23/1/2008  1:30 PM

This speech is one of the reasons I respect Dr. Griffin. The man can really put together a good speech and this year he has done several of them. I still consider him one of the most dynamic leaders NASA has ever had.

I would like to challenge both the DIRECT group and the EELV group to respond to this speech on a point-by-point basis.
Good luck.

Some challenge. I appreciate Griffin's reasoning. I won't do a point by point rebuttal, but some points to consider (numbers are approx):

1. Ares Lift requirement was 23.3 tons? Where did this come from? The Ares 1 selection was made before Orion was specified, so 23.3 tons seems a bit odd. Why not reduce the size of Orion? Orion has double the volume of Apollo, for 33% more crew. OK - I know Americans have got bigger over the last 40 years, but that's a big increase. So why not de-size Orion? This is a bit like a factory house builder deciding to make standard modules 43 feet long when ISO containers are 40 feet.

2. The EELV people now claim that 23.3 tons can be done. Not sure who to believe, but they should know.

3. Safety: The premise was that the SRB had one accident in 200+ flights, and was therefore safer than the EELVs. In reality, Ares I is a new launch vehicle and claims about its safety are just that: claims. Next point: In simple terms, man rating means take a relatively reliable rocket and ensure that in the event of failure, the crew will probably survive. On that latter point, solid rockets don't do very well.

4. Heavy lift requirement, not a point solution for LEO access: There's nothing that can't be delivered in 20+ ton modules.

5. Cost analysis: David Smith posted the CBO estimates elsewhere in this thread and show Ares as the most expensive option.

http://www.cbo.gov/ftpdocs/76xx/doc7635/10-09-SpaceLaunch.pdf

  CBOís results show total costs for development and operation in Table E2 page 51:

  Alternative 1: Delta+ = $27.9B
  Alternative 2: Atlas+ = $26.1B
  Alternative 6: Ares I & V = $32.4B

I think this is false. The alternative is for, say, 4 Ares V and 2 Ares 1 launches, per period (1-2 years?), versus say 24 EELV launches, of which 2 are human, 2 are precious cargo, and 20 are fuel and Earth Departure Stages. You put that out to tender with enough notice and I assure you the price of commercial launches will come down. Even for the EDS tenders (where a launch failure is acceptable if backups are made), Atlas might win round 1. SpaceX might win rounds 2 and 3. Someone you've never heard of might win Round 4. At a cost much lower than current Atlas costs, let alone NASA launch costs.

5. Storing Hydrogen: Griffin presented this as a problem for Mars missions. But single launch does nothing here as the mission is multi-year anyway. So I assume this is a lunar mission problem. On Earth, its pretty clear that using hydrogen doesn't make sense. If we found a big hydrogen well, we'd turn it into something useful like methane. So using methane, propane or kerosene increases the mass to LEO by what: 30%? There is no way, including development costs, that Ares V will be less than 130% the cost of Proton or Falcon 9H, and probably not Atlas V and Delta IV heavy.

Even for a Mars mission, according to AM Swallows calculations (no aerobraking or ISRU), 723 tons of kerosene/LOx on Falcon 9 will be cheaper than 378 tons on Ares V.

6. Future Proofing: Like it or not, I think Obama's the favourite for President, and then its probably bye bye Ares V. I think the development of a market providing multiple options in 20-25 ton class, at a descent rate would be a much better future proofing legacy.

Just some thoughts ....

Alex


Offline Lampyridae

  • Veteran
  • Full Member
  • ****
  • Posts: 1641
  • Liked: 64
  • Likes Given: 114
Re: Griffin speech - EELV would not work for Constellation
« Reply #88 on: 03/31/2008 05:49 AM »
There are other things to feed NTRs... such as Ammonia, Isp of about 600 compared to 800 for LH. That would do for return propellant.
SKYLON... The League of Extraordinary Gentlemen's preferred surface-to-orbit conveyance.

Offline neviden

  • Regular
  • Full Member
  • ****
  • Posts: 411
  • Liked: 1
  • Likes Given: 0
Re: Griffin speech - EELV would not work for Constellation
« Reply #89 on: 03/31/2008 04:23 PM »
Quote
Lampyridae - 31/3/2008  7:49 AM
There are other things to feed NTRs... such as Ammonia, Isp of about 600 compared to 800 for LH. That would do for return propellant.
In that case they are better of with simply using chemical rockets. NTRs are borderline useful as it is with 800 s.

If NASA thinks about going nuclear then NEP presents much better option. But if they would develop electric propulsion system in MW range, they could even remove the need for nuclear reactor and go with SEP.

Offline clongton

  • Expert
  • Senior Member
  • *****
  • Posts: 10259
  • Connecticut
    • Direct Launcher
  • Liked: 2020
  • Likes Given: 620
Re: Griffin speech - EELV would not work for Constellation
« Reply #90 on: 03/31/2008 05:19 PM »
Quote
neviden - 31/3/2008  12:23 PM

Quote
Lampyridae - 31/3/2008  7:49 AM
There are other things to feed NTRs... such as Ammonia, Isp of about 600 compared to 800 for LH. That would do for return propellant.
In that case they are better of with simply using chemical rockets. NTRs are borderline useful as it is with 800 s.

If NASA thinks about going nuclear then NEP presents much better option. But if they would develop electric propulsion system in MW range, they could even remove the need for nuclear reactor and go with SEP.
I have posted a reply to this over in a more appropriate thread. Let's try to keep on topic.
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=9905&posts=128#M263546
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline Lampyridae

  • Veteran
  • Full Member
  • ****
  • Posts: 1641
  • Liked: 64
  • Likes Given: 114
Re: Griffin speech - EELV would not work for Constellation
« Reply #91 on: 04/01/2008 01:36 AM »
OK, back on track...

While LH, either for chemical engines or NTR, is a really good idea for propulsion but a pain to store, I still don't think it's necessarily a showstopper for an EELV solution. The same anti-boiloff technology, as others have pointed out, can just as easily be redirected to EELV. What I think is the real issue is the possibility of a LV failure and some critical component winding up in the ocean with a launch window 3 months away and the LV fleet grounded while the review board figures out what's wrong.

You are putting all your eggs in one basket with a big launcher, but unlike eggs you can't make a Mars ship omelette with 5 eggs instead of 6. ISS is a 4 egg omelette when it was meant to be 6, after all. And it's still not ready to be served.

That being said... (I hate it when I shoot down my own arguments) you can still have backup modules on the ground and only one extra LV waiting to go, as opposed to two complete Mars ships and one big LV ready for LON. But I don't think we will have the money for spare spacecraft anyway.

Now, with the Europeans and Russians, neither seem about to stump for a new, larger launcher but both are keen on the moon. The only approach I've ever seriously heard is along the lines of EELV.
SKYLON... The League of Extraordinary Gentlemen's preferred surface-to-orbit conveyance.

Offline neviden

  • Regular
  • Full Member
  • ****
  • Posts: 411
  • Liked: 1
  • Likes Given: 0
Re: Griffin speech - EELV would not work for Constellation
« Reply #92 on: 04/01/2008 11:50 AM »
Quote
Lampyridae - 1/4/2008  3:36 AM
You are putting all your eggs in one basket with a big launcher, but unlike eggs you can't make a Mars ship omelette with 5 eggs instead of 6. ISS is a 4 egg omelette when it was meant to be 6, after all. And it's still not ready to be served.
I don't get the egg omlette metaphor. Mars ship could be built like ISS. You would need quite a few pieces, but there is no reason why any single piece should have to weigh more then 20 mT empty.

The only reason why ISS is still not served is that NASA *must* use the Shuttle with its low flight rate and year long shutdowns following accident. If the 20 mT pieces that the Shuttle delivers to the ISS were built to be launched on regular rockets you would have built it ages ago. Even shuttle shutdown wouldnít affect ISS construction since you could simply use any number of other 20 mT rockets on the market.

If you would go with ďchemical only / use onceĒ system you would initially need quite a lot of 20mT rockets. This number could be cut drastically with the use of depot, long term cryogenic storage, tugs, SEPs, ISRU,.. That way NASA would end up with reusable transportation infrastructure that could reduce costs in the long run, instead of moon littered with abandoned landers.

Quote
Lampyridae - 1/4/2008  3:36 AM
Now, with the Europeans and Russians, neither seem about to stump for a new, larger launcher but both are keen on the moon. The only approach I've ever seriously heard is along the lines of EELV.
Itís no wonder they donít want that. They donít want to repeat US experience of ending up with *very* expensive system that has no use beyond human spaceflight. Even human spaceflight for the sake of human spaceflight has a problem of convincing taxpayers that itís good idea to spend money on it.

The only way European and Russian will end up on the moon is if their engineers develop cost effective solutions to do that. Big rockets are very useful and convenient, but they arenít exactly cost effective.

Tags: