Author Topic: Can SSMEs act as a restartable upper stage engine?  (Read 5776 times)

Offline FinalFrontier

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Could SSMEs could act as a Restartable upper stage engine. 

CXP initially proposed air start SSME: This was yet another fundamental problem with the logic of CXP. Ares 1 was entirley dependent on the engine being convertable to air start. Once that went out the window so to did Ares 1.

Is it theoretically possible to build a restartble SSME? Thats the question we should answer.

Second question: Regardless of air start capability, would it make sense from a cost standpoint to build an air start SSME, and a stage to go around it?


Edit: OP modified to fix large mistake in content (i.e. that SSME cannot be air startable, when in fact it can)
« Last Edit: 07/02/2010 07:28 PM by Chris Bergin »
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Offline HarryM

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Re: Myth: The SSME can act as an upper stage engine
« Reply #1 on: 07/02/2010 04:49 PM »
Can't be emphasized enough with regards to the Ares-1 shambles. As soon as it was realized that the SSME was not a cheap "slam-dunk" as an US engine the whole thing should have been re-evaluated.

In light of the damage to our future HSF plans, I would really like the person/persons (NASA? P&W?) who said how easy it would be to do this to be named/shamed/publicly humiliated.

Offline Jim

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Re: Myth: The SSME can act as an upper stage engine
« Reply #2 on: 07/02/2010 05:35 PM »
This thread is to disband the myth that the SSME could act as an upper stage engine. While I think most of us are already in agreement on this, I would like to ensure that the "myth" of the second stage SSME goes no further.

It might MIGHT be technically possible but the costs would be astronomical and your upper stage would be so overweight with extra equipment that it might not acheive orbit, and if it did preformance would be nil.

CXP initially proposed air start SSME: This was yet another fundamental problem with the logic of CXP. Ares 1 was entirley dependent on the engine being convertable to air start. Once that went out the window so to did Ares 1.

SSME requires complex, heavy, equipment to start properly. It is incapable of restarts. You cannot convert the engine to a restartable engine (and if somehow you had the money and managed to pull it off your preformance would be so bad that it wouldn't be worth it.)

Airstarts and restarts are two different things.  the SSME can be used for an upperstage, just not one that does restarts.

Offline strangequark

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Re: Myth: The SSME can act as an upper stage engine
« Reply #3 on: 07/02/2010 05:46 PM »
Airstarts and restarts are two different things.  the SSME can be used for an upperstage, just not one that does restarts.

I recall reading a paper at one point about using existing, heritage SSMEs for the first Ares I flights, and just modifying the software for the startup valve sequencing. Do you know if this was just wishful thinking by MSFC, or had technical meat behind it?

EDIT: Nevermind, found the paper listed in the other thread, and the mention of reorificing the ASI lines.
« Last Edit: 07/02/2010 06:02 PM by strangequark »

Offline alexw

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Re: Myth: The SSME can act as an upper stage engine
« Reply #4 on: 07/02/2010 05:58 PM »
This thread is to disband the myth that the SSME could act as an upper stage engine. While I think most of us are already in agreement on this, I would like to ensure that the "myth" of the second stage SSME goes no further.

It might MIGHT be technically possible but the costs would be astronomical and your upper stage would be so overweight with extra equipment that it might not acheive orbit, and if it did preformance would be nil.

CXP initially proposed air start SSME: This was yet another fundamental problem with the logic of CXP. Ares 1 was entirley dependent on the engine being convertable to air start. Once that went out the window so to did Ares 1.

SSME requires complex, heavy, equipment to start properly. It is incapable of restarts. You cannot convert the engine to a restartable engine (and if somehow you had the money and managed to pull it off your preformance would be so bad that it wouldn't be worth it.)
    Ahh, a subject of great historical interest and importance -- as you correctly observe, the fate of air-start/re-start SSME is intimately tied to Ares I.
   Regrettably, FinalFrontier, I am unfamiliar with either your academic or industrial background leading to the technical expertise to make such definitive, sweeping statements.  But I am greatly interested, and would be delighted to hear you describe in detail:
       a) The standard SSME start procedure, touching in particular on how the valve sequencing was devised back in the 1970s given the evident problems at the time
       b) GHe (and N2) purge volumes
       c) Initial temperature requirements
       d) The additional "complex, heavy" equipment used in the ground start procedure
       e) The standard SSME "restart" procedure, for example that used after RSLS aborts

     If possible, could you explain where the earlier NASA documents on both air-start and re-start of SSME were obviously in error, and what technical miscalculations led to those conclusions.

      I look forward to reading your numbers!
         -Alex

Online ugordan

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Re: Myth: The SSME can act as an upper stage engine
« Reply #5 on: 07/02/2010 06:00 PM »
Regrettably, FinalFrontier, I am unfamiliar with either your academic or industrial background leading to the technical expertise to make such definitive, sweeping statements.  But I am greatly interested, and would be delighted to hear you describe in detail:
 
<cut>

I look forward to reading your numbers!

Oh, this is going to be fun.

Offline HarryM

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Re: Myth: The SSME can act as an upper stage engine
« Reply #6 on: 07/02/2010 06:24 PM »
So, there is the possibility then that the decision to go J-2X on the A1US was not so much unsuitability of the SSME as to want common engines (cost savings) between Ares-1 and Ares-V upper stage/departure stage? If that is the case then my condemnation of the original study/persons (the 1993 study? http://forum.nasaspaceflight.com/index.php?topic=20475.3060 ) is out of line. 

Offline FinalFrontier

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Re: Myth: The SSME can act as an upper stage engine
« Reply #7 on: 07/02/2010 06:59 PM »
Went back, went over the info again and realized I made a huge mistake with this thread.

Yes, its possible for SSME to be an upper stage engine BUT, its not possible for it to restart. OP will be modified to reflect this.  So its not an issue of the sequencing or the start up equipment, it can be an upper stage.

So here is the "new" question I would like to answer with this thread: If it can't restart, is there any way it could meet the qualifications of a given user to be an upper stage engine? Not sure about that, seems like most upper stages have to have restart capability. 

Edit: OP modified to recognize air start potential.
« Last Edit: 07/02/2010 07:03 PM by FinalFrontier »
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Offline Chris Bergin

Re: Can SSMEs act as a restartable upper stage engine?
« Reply #8 on: 07/02/2010 07:31 PM »
Edited the thread title as we won't be having any "myth" threads on here, other than from professionals in the field of the subject.

Offline Jim

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Re: Myth: The SSME can act as an upper stage engine
« Reply #9 on: 07/02/2010 08:26 PM »


So here is the "new" question I would like to answer with this thread: If it can't restart, is there any way it could meet the qualifications of a given user to be an upper stage engine? Not sure about that, seems like most upper stages have to have restart capability. 


it depends of the vehicle architecture.  Saturn V second stage didn't need to restart, neither does the Proton 2nd and 3rd stages and Soyuz 3rd stage.

Offline edkyle99

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Re: Myth: The SSME can act as an upper stage engine
« Reply #10 on: 07/02/2010 11:37 PM »
So here is the "new" question I would like to answer with this thread: If it can't restart, is there any way it could meet the qualifications of a given user to be an upper stage engine? Not sure about that, seems like most upper stages have to have restart capability. 

I think that any useful upper stage engine developed for the future, especially if it is a high-energy cryogenic fuel engine, needs to be restartable.  Being able to restart an engine makes it do more than one job, giving the possibility of reduced costs.  An even bigger cost advantage would be provided by designing a rocket with only two stages - one big one to boost and a smaller one to both ascend to orbit and to restart for beyond LEO work.

 - Ed Kyle
« Last Edit: 07/02/2010 11:38 PM by edkyle99 »

Offline alexw

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Re: Myth: The SSME can act as an upper stage engine
« Reply #11 on: 07/03/2010 02:07 AM »
So here is the "new" question I would like to answer with this thread: If it can't restart, is there any way it could meet the qualifications of a given user to be an upper stage engine? Not sure about that, seems like most upper stages have to have restart capability. 
     Depends on the mission role; if LEO or below is the final destination of that stage, then restart unneeded -- see Shuttle and Soyuz, and most cases of solid upper stages. For GEO and higher-energy destinations, it seems to be typical to coast in LEO and await phasing before making a second burn. But Ariana V ECA does not -- the HM7B cryogenic engine isn't restartable, and burns for 15 minutes (WP). I presume they take some orbital geometry performance hit from that, but they're also launching nearly equatorially from Guyana.

     (BTW, thank you, FF, for constructively re-purposing the thread, and thanks also ChrisB for editing the title and setting policy precedent.)

I think that any useful upper stage engine developed for the future, especially if it is a high-energy cryogenic fuel engine, needs to be restartable.  Being able to restart an engine makes it do more than one job, giving the possibility of reduced costs.  An even bigger cost advantage would be provided by designing a rocket with only two stages - one big one to boost and a smaller one to both ascend to orbit and to restart for beyond LEO work. - Ed Kyle
     Ed, are you alluding to Concept-103? I would assume (not having calculated it) that the heavy dual-J2X upper stage makes for a poor EDS.
     -Alex

Offline FinalFrontier

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Re: Myth: The SSME can act as an upper stage engine
« Reply #12 on: 07/03/2010 05:12 PM »
So here is the "new" question I would like to answer with this thread: If it can't restart, is there any way it could meet the qualifications of a given user to be an upper stage engine? Not sure about that, seems like most upper stages have to have restart capability. 
     Depends on the mission role; if LEO or below is the final destination of that stage, then restart unneeded -- see Shuttle and Soyuz, and most cases of solid upper stages. For GEO and higher-energy destinations, it seems to be typical to coast in LEO and await phasing before making a second burn. But Ariana V ECA does not -- the HM7B cryogenic engine isn't restartable, and burns for 15 minutes (WP). I presume they take some orbital geometry performance hit from that, but they're also launching nearly equatorially from Guyana.

     (BTW, thank you, FF, for constructively re-purposing the thread, and thanks also ChrisB for editing the title and setting policy precedent.)

I think that any useful upper stage engine developed for the future, especially if it is a high-energy cryogenic fuel engine, needs to be restartable.  Being able to restart an engine makes it do more than one job, giving the possibility of reduced costs.  An even bigger cost advantage would be provided by designing a rocket with only two stages - one big one to boost and a smaller one to both ascend to orbit and to restart for beyond LEO work. - Ed Kyle
     Ed, are you alluding to Concept-103? I would assume (not having calculated it) that the heavy dual-J2X upper stage makes for a poor EDS.
     -Alex
On the repurposing your welcome. Inital thread was a disaster, my apologies.

I thought that NASA would want any future second stage engine to have restart capability. Ares 1 was leo only, but they still want restart capability. I guess its a safety thing.
« Last Edit: 07/03/2010 05:32 PM by FinalFrontier »
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Offline edkyle99

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Re: Myth: The SSME can act as an upper stage engine
« Reply #13 on: 07/03/2010 05:30 PM »
     Ed, are you alluding to Concept-103? I would assume (not having calculated it) that the heavy dual-J2X upper stage makes for a poor EDS.
     -Alex
I thought so too, but was surprised when I did some calculations.  It really should be able to do the claimed 45 tonnes to escape.  The "heavy" is all relative.  I figured a 260 tonne gross upper stage atop a nearly 3,100 tonne gross first stage.  That is roughly (+/- 1%) the same ratio of Centaur to Atlas CCB gross mass - another rocket that can do escape with only two stages.  (My guess is that Concept 103 is, roughly-speaking, a back of the envelope Atlas super-scale-up).

 - Ed Kyle
« Last Edit: 07/03/2010 05:33 PM by edkyle99 »

Offline FinalFrontier

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Re: Myth: The SSME can act as an upper stage engine
« Reply #14 on: 07/03/2010 05:33 PM »
     Ed, are you alluding to Concept-103? I would assume (not having calculated it) that the heavy dual-J2X upper stage makes for a poor EDS.
     -Alex
I thought so too, but was surprised when I did some calculations.  It really should be able to do the claimed 45 tonnes to escape.  The "heavy" is all relative.  I figured a 260 tonne gross upper stage atop a nearly 3,100 tonne gross first stage.  That is roughly (+/- 1%) the same ratio of Centaur to Atlas CCB gross mass - another rocket that can do escape with only two stages.

 - Ed Kyle
How does it stack up against a JUS (6 rl10b2) for TLI preformance?
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Offline edkyle99

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Re: Myth: The SSME can act as an upper stage engine
« Reply #15 on: 07/03/2010 05:46 PM »
     Ed, are you alluding to Concept-103? I would assume (not having calculated it) that the heavy dual-J2X upper stage makes for a poor EDS.
     -Alex
I thought so too, but was surprised when I did some calculations.  It really should be able to do the claimed 45 tonnes to escape.  The "heavy" is all relative.  I figured a 260 tonne gross upper stage atop a nearly 3,100 tonne gross first stage.  That is roughly (+/- 1%) the same ratio of Centaur to Atlas CCB gross mass - another rocket that can do escape with only two stages.

 - Ed Kyle
How does it stack up against a JUS (6 rl10b2) for TLI preformance?

Not sure about "JUS", but the HLLV study compared Concept 103 to a 2x5SRB/5xSSME/4xRL10 in-line.  The Shuttle-derived in-line could lift more to TLI/escape, but much less to LEO.  It was projected to cost more, however, than 103, which makes sense because 103 only needs two stages versus the four propulsion units of SDV in-line. 

 - Ed Kyle

Offline FinalFrontier

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Re: Myth: The SSME can act as an upper stage engine
« Reply #16 on: 07/03/2010 05:49 PM »
     Ed, are you alluding to Concept-103? I would assume (not having calculated it) that the heavy dual-J2X upper stage makes for a poor EDS.
     -Alex
I thought so too, but was surprised when I did some calculations.  It really should be able to do the claimed 45 tonnes to escape.  The "heavy" is all relative.  I figured a 260 tonne gross upper stage atop a nearly 3,100 tonne gross first stage.  That is roughly (+/- 1%) the same ratio of Centaur to Atlas CCB gross mass - another rocket that can do escape with only two stages.

 - Ed Kyle
How does it stack up against a JUS (6 rl10b2) for TLI preformance?

Not sure about "JUS", but the HLLV study compared Concept 103 to a 2x5SRB/5xSSME/4xRL10 in-line.  The Shuttle-derived in-line could lift more to TLI/escape, but much less to LEO.  It was projected to cost more, however, than 103, which makes sense because 103 only needs two stages versus the four propulsion units of SDV in-line. 

 - Ed Kyle

What if: For the SSME you used 4, and they were from the existing 17 SSME stockpile (so no cost to buld them), and you used a standard 4 seg SRM.

so what exactly is 103? A core with a second stage using 2 j2x (rs 68 first stage?) A bit confused, I though 103 was a proposal to use 2 j2xs on the EDS for ares v.......
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Offline dks13827

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Re: Myth: The SSME can act as an upper stage engine
« Reply #17 on: 07/03/2010 05:54 PM »
 
It was interesting that Apollo 7 did not have the restart stuff on their S-IVB.  That saves some weight, not sure how much.  It would have been interesting to  restart that engine  for a few seconds as a test but they obviously didnt think that was necessary.

Offline MP99

Re: Myth: The SSME can act as an upper stage engine
« Reply #18 on: 07/04/2010 01:29 AM »
So here is the "new" question I would like to answer with this thread: If it can't restart, is there any way it could meet the qualifications of a given user to be an upper stage engine? Not sure about that, seems like most upper stages have to have restart capability. 
     Depends on the mission role; if LEO or below is the final destination of that stage, then restart unneeded -- see Shuttle and Soyuz, and most cases of solid upper stages. For GEO and higher-energy destinations, it seems to be typical to coast in LEO and await phasing before making a second burn. But Ariana V ECA does not -- the HM7B cryogenic engine isn't restartable, and burns for 15 minutes (WP). I presume they take some orbital geometry performance hit from that, but they're also launching nearly equatorially from Guyana.

     (BTW, thank you, FF, for constructively re-purposing the thread, and thanks also ChrisB for editing the title and setting policy precedent.)

I think that any useful upper stage engine developed for the future, especially if it is a high-energy cryogenic fuel engine, needs to be restartable.  Being able to restart an engine makes it do more than one job, giving the possibility of reduced costs.  An even bigger cost advantage would be provided by designing a rocket with only two stages - one big one to boost and a smaller one to both ascend to orbit and to restart for beyond LEO work. - Ed Kyle
     Ed, are you alluding to Concept-103? I would assume (not having calculated it) that the heavy dual-J2X upper stage makes for a poor EDS.
     -Alex


ISTR Ross saying that a three-stage Jupiter could improve TLI performance (at much greater expense). Not sure if the third stage (RL-10) would be used during ascent or just for circularisation & TLI.

Air-start SSME sounds like it would be ideal for such a second stage - compared to twin J-2X it has better Isp, 2/3rds the mass and nearly as much thrust. It's also throttleable.

I can't envisage this as part of any initial HLV proposal (except maybe a Kero 1st stage, RS-25"V" 2nd stage & RL-10 EDS), but it seems to provide a growth option for an SSME-based architecture, which is always nice to have in your back pocket.



I'd also be interested whether an upper-stage SSME could be further vacuum-optimised with a nozzle extension - I'd guess it already has the chamber pressures to cope with this.

cheers, Martin

Offline Jorge

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Re: Myth: The SSME can act as an upper stage engine
« Reply #19 on: 07/04/2010 02:30 AM »

It was interesting that Apollo 7 did not have the restart stuff on their S-IVB.  That saves some weight, not sure how much.

1500 lbm.
JRF

Offline jjknap

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Re: Can SSMEs act as a restartable upper stage engine?
« Reply #20 on: 07/04/2010 02:40 AM »
I am not an expert, but a couple things come to mind when you talk about restart of a SSME:
1.  If you are using liquid hydrogen and oxygen, wouldn't you have a limited time to restart anyway based on the ability of the stage to keep the fuel at the correct temperature?

2.  I remember that the Saturn V third stage had to have small rocket engines that had to fire prior to the restart in order to push the fuel towards the engine.  I would think you would need this same type of setup if using liquid hydrogen and oxygen on a stage that you wanted to use for other things beyond LEO.
« Last Edit: 07/04/2010 02:41 AM by jjknap »

Offline FinalFrontier

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Re: Can SSMEs act as a restartable upper stage engine?
« Reply #21 on: 07/04/2010 03:10 AM »
I am not an expert, but a couple things come to mind when you talk about restart of a SSME:
1.  If you are using liquid hydrogen and oxygen, wouldn't you have a limited time to restart anyway based on the ability of the stage to keep the fuel at the correct temperature?

2.  I remember that the Saturn V third stage had to have small rocket engines that had to fire prior to the restart in order to push the fuel towards the engine.  I would think you would need this same type of setup if using liquid hydrogen and oxygen on a stage that you wanted to use for other things beyond LEO.
We were discussing options that would not require restart capability. Also discussing whether such a capability is feasible, although Ares 1 is a fair demonstration of why its probably not.....
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Offline kch

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Re: Myth: The SSME can act as an upper stage engine
« Reply #22 on: 07/04/2010 03:20 AM »

It was interesting that Apollo 7 did not have the restart stuff on their S-IVB.  That saves some weight, not sure how much.

1500 lbm.


IIRC, all the S-IVBs used on Saturn IBs were that way (no TLI, so no need to restart).

Offline Jorge

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Re: Myth: The SSME can act as an upper stage engine
« Reply #23 on: 07/04/2010 03:32 AM »

It was interesting that Apollo 7 did not have the restart stuff on their S-IVB.  That saves some weight, not sure how much.

1500 lbm.


IIRC, all the S-IVBs used on Saturn IBs were that way (no TLI, so no need to restart).

I believe that is correct.
JRF

Offline edkyle99

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Re: Myth: The SSME can act as an upper stage engine
« Reply #24 on: 07/04/2010 03:57 AM »

so what exactly is 103? A core with a second stage using 2 j2x (rs 68 first stage?) A bit confused, I though 103 was a proposal to use 2 j2xs on the EDS for ares v.......
Concept 103, the kerosene rocket idea, was first publicly described in the following document.  It illustrates the cost savings potential of entirely abandoning Shuttle-Derived.
http://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=238644/HLLV%20Study.pdf

 - Ed Kyle
« Last Edit: 07/04/2010 03:57 AM by edkyle99 »

Offline JosephB

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Re: Can SSMEs act as a restartable upper stage engine?
« Reply #25 on: 07/04/2010 07:35 PM »
One of many things that are very interesting in that document is the Upper Stage engine possibility noted for concept 103. RS-68B E/O. Uffda!

Offline JosephB

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Re: Can SSMEs act as a restartable upper stage engine?
« Reply #26 on: 07/04/2010 07:48 PM »
I agree with Ed though. A dual US/EDS makes a lot of sense.

Better yet, how about both?
J-2X for BEO
68B for heavy LEO payloads?
« Last Edit: 07/04/2010 08:01 PM by JosephB »

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