Interim Cryogenic Propulsion Stage (ICPS) for SLS

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Jim
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 « Reply #30 on: 01/11/2012 04:08 PM »

Is there other plausible candidates for the iCPX contract other than the DCSS?

That was the point of the thread.  Read the first few posts.
Steven Pietrobon
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 « Reply #31 on: 01/12/2012 07:31 AM »

Here are the numbers using a Delta-IV Heavy Second Stage.

ms =  3,488 kg (stage dry mass)
mp = 27,220 kg (propellant mass)
mt = ms+mp = 30,708 kg < 32,386 kg NASA specification
ve = 4501.25 m/s (RL10B-2 exhaust speed)
mc = 24,224 kg (payload mass)
dv = ve*ln(1+mp/(ms+mc)) = 3080 m/s > 3050 m/s requirement.

Pretty much a perfect match!

F = 110,093 N (RL10B-2 thrust)
a_0 = F/(mp+ms+mc) = 2.0 m/s^2 (initial acceleration)
a_f = F/(ms+mc) = 4.0 m/^2 (final acceleration)

so no worries about going over 2g = 19.6 m/s^2.
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 « Reply #32 on: 01/12/2012 09:36 PM »

Here are the numbers using a Delta-IV Heavy Second Stage.

ms =  3,488 kg (stage dry mass)
mp = 27,220 kg (propellant mass)
mt = ms+mp = 30,708 kg < 32,386 kg NASA specification
ve = 4501.25 m/s (RL10B-2 exhaust speed)
mc = 24,224 kg (payload mass)
dv = ve*ln(1+mp/(ms+mc)) = 3080 m/s > 3050 m/s requirement.

Pretty much a perfect match!

F = 110,093 N (RL10B-2 thrust)
a_0 = F/(mp+ms+mc) = 2.0 m/s^2 (initial acceleration)
a_f = F/(ms+mc) = 4.0 m/^2 (final acceleration)

so no worries about going over 2g = 19.6 m/s^2.
Incidentally, if the CPS weight was the maximum (32,386 kg), and the dry mass was just 5% of the wet mass, it would still mean a minimum 397s of isp. If we use a more realistic 10%, that's 430s. So, only H2 fuel would work.
Again, assuming a 10% mass of the 32,386 kg (3,238kg), the maximum thrust of the engine would be 1.07MN (242klbf). I'm not sure if a J-2X at 84% could do that.
So, only H2 upper stages are possible. Only US engine appears to be the RL10. You'd need a Vinci or an LE-5B engine.
The H2A US could almost fit there (it's missing some 20m/s of delta-v). The ESC-A would give a paltry 1,824m/s. The Atlas V (single RL10) only gives 2,537m/s. So, the only competing upper stage that can compete is foreign.
It's a shame nobody else has an H2 stage in advanced development. In particular, a Centaur scaled to 32,386kg would give 3,200m/s.
Robotbeat
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 « Reply #33 on: 01/12/2012 09:38 PM »

No, it's not a "shame" that no other upper stage could compete, they were already betting on exactly a certain stage. IMHO, of course.
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 « Reply #34 on: 01/12/2012 10:02 PM »

No, it's not a "shame" that no other upper stage could compete, they were already betting on exactly a certain stage. IMHO, of course.
The "shame" is that a bigger centaur would give a lot of performance to the Atlas V 551/2 or even an hypothetical Atlas V Heavy. And is sort of a requirement for the Phase II.
A Falcon 9 or even better, a Falcon Heavy with such an US would be formidable.
And Antares is too small, but an H2 would make it enviable good for current planetary missions needs.
Even if ATK went ahead with a son of Liberty, but with an American H2 Upper stage it would make a great rocket.
So my point is that's a shame that the work on new H2 US engines and stages is sort of frozen, while NASA makes not one, but two H2 upper stages (SLS Block 2 US and the CPS).
Robotbeat
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 « Reply #35 on: 01/12/2012 10:15 PM »

I agree with you there. (not so sure about the Liberty part, though )

BTW, work isn't frozen. Blue Origin has been testing their own hydrogen engine and XCor, of course, is working with ULA on a replacement for the RL-10.
Ronsmytheiii
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 « Reply #36 on: 01/12/2012 10:15 PM »

No "shame", NASA is being a prudent consumer and buying an existing stage to fit it's need.  CPS will be the big ticket item, no need to invest a ton of resources on a new stage when only a couple COTS stages will do the job.
MP99
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 « Reply #37 on: 01/12/2012 11:05 PM »

It's OT but I really wonder why this mission is being contemplated, other than to say they've been.  {snip}

For the sound of it the highly elliptical orbit for the Orion followed by Trans-Earth Injection is to test the heat shield.  The heat shield and side walls will not get as hot as during a re-entry from the Moon but close.

EFT-1 accomplishes this.

That wasn't me...

cheers, Martin
Ben the Space Brit
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 « Reply #38 on: 01/13/2012 11:38 AM »

No "shame", NASA is being a prudent consumer and buying an existing stage to fit it's need.  CPS will be the big ticket item, no need to invest a ton of resources on a new stage when only a couple COTS stages will do the job.

Of course, a lot depends on whether CPS happens.  As matters stand, yes, iCPS is only planned for one flight at the moment, the Lunar HEO demonstrator.  So it makes sense to use an existing upper stage with the absolute minimum modifications.  The laws being what they are, the appearance of competition must be observed but, in practice, if NASA's engineers have already identified an upper stage that fits the bill then they might as well use it rather than delay an already rather long-term project any further.

However, is CPS a sure thing? Given the current economic situation, if I were NASA, I would certainly want to hedge my bets rather than hope that Congress doesn't blink in the face of the deficit and makes easy-sounding cuts.  Being able to share an upper stage with a general EELV upgrade (Common Centaur) or with one of the other 'newspace' contractors might reduce costs and streamline testing and production somewhat.

In the end, it requires a bit of crystal-balling and, in the end, a call.
Robotbeat
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 « Reply #39 on: 01/13/2012 03:23 PM »

No "shame", NASA is being a prudent consumer and buying an existing stage to fit it's need.  CPS will be the big ticket item, no need to invest a ton of resources on a new stage when only a couple COTS stages will do the job.

Of course, a lot depends on whether CPS happens.  As matters stand, yes, iCPS is only planned for one flight at the moment, the Lunar HEO demonstrator.  So it makes sense to use an existing upper stage with the absolute minimum modifications.  The laws being what they are, the appearance of competition must be observed but, in practice, if NASA's engineers have already identified an upper stage that fits the bill then they might as well use it rather than delay an already rather long-term project any further.

However, is CPS a sure thing? Given the current economic situation, if I were NASA, I would certainly want to hedge my bets rather than hope that Congress doesn't blink in the face of the deficit and makes easy-sounding cuts.  Being able to share an upper stage with a general EELV upgrade (Common Centaur) or with one of the other 'newspace' contractors might reduce costs and streamline testing and production somewhat.

In the end, it requires a bit of crystal-balling and, in the end, a call.
iCPS has at very least 2 flights, according to the original post in this thread.
yg1968
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 « Reply #40 on: 01/15/2012 03:19 PM »

Here is an article on this topic:
http://www.spacenews.com/civil/120113-orion-human-rated-upper-stage.html
Ronsmytheiii
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 « Reply #41 on: 01/15/2012 03:29 PM »

Here is an article on this topic:
http://www.spacenews.com/civil/120113-orion-human-rated-upper-stage.html

Hmmm

Quote
SpaceX chief Elon Musk, for one, isn’t worried that NASA’s Orion test program will eat into efforts to develop commercial transportation systems to fly astronauts to and from the space station.

“I think this is really aimed at some variant of the (Atlas 5) Centaur upper-stage,” Musk wrote in an email to Space News. “I don’t think this affects the Commercial Crew program in any way.”

Think someone should tell Mr Musk that it is aimed at DHUS and not Centaur....
ciscosdad
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 « Reply #42 on: 01/15/2012 09:32 PM »

I think the bottom line is that this is going to be used for a very few missions (interim). They've identified a stage that will allow them to do something useful and want to use it. I work for a government department and must adhere to similar restrictions. If there were a stage that gave higher performance, that would have been purchased and the mission designed to make full use of those numbers.
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 « Reply #43 on: 01/16/2012 01:14 AM »

Here is an article on this topic:
http://www.spacenews.com/civil/120113-orion-human-rated-upper-stage.html

From the article:  Responses to the announcement are due Feb. 7. The agency plans to follow up its request for sources with a solicitation for proposals by Sept. 30

There goes NASA rushing forward again at the speed of a slug on Valium!  Will it really need to take the better part of 8 months to react to the response they get to this?  (To be fair, iCPS probably isn't anywhere near the SLS critical path.)

[EDIT:  Jim's answer below explains this quite adequately.  --sdsds]
spectre9
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 « Reply #44 on: 01/16/2012 01:54 AM »

Thanks for linking that article.

"Delta IV not getting human rated"

Just because it keeps getting said doesn't mean it's true.

Or at least not that I will believe it anyway.

DIV-H will launch the Orion safer, cheaper with a real rocket and without a 300ft+ crew access tower.

I know the solution, LIBERTY!!!!

I can really understand EELV fanboys because these rockets are real and do exist.

Every plan to build a new rocket to do something one that already exists can do just makes me ask WHY?

I'm not trying to troll, I seriously don't know why.

The reason why shuttle was so expensive is because it was a massive cost just to launch a few astronauts.

SLS wants to do the same and not do it until 2021.

WHY!!!!!!!!!!!!!!!!!!!
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