Author Topic: How should NASA evolve the SLS?  (Read 178656 times)

Offline davey142

  • Member
  • Posts: 78
  • Liked: 9
  • Likes Given: 671
Re: How should NASA evolve the SLS?
« Reply #320 on: 03/20/2013 11:06 pm »
How would NASA convince congress (especially the Senate) to allow them to use a foreign engine, especially one from Russia?

Wouldn't Congress by OK with it if an American company were to build RD-180s in the US?
Wouldn't that negate any cost savings for the RD-180? SLS can't afford any increased cost, especially changing an engine midway through the design. Using them for LRBs could work if an American company modifies them just enough to make it an American derivative, but that means more money!
Atlas V uses the RD-180's so could LRB's for SLS.
SLS is being marketed as the pinnacle of American technology and jobs. so Unless the RD-180 is modified by an American company, it won't be politically correct to use an engine with roots to the Soviet era.
Edit: agree with you that the design should stay the same for the time being.
« Last Edit: 03/20/2013 11:08 pm by davey142 »

Offline spectre9

  • Senior Member
  • *****
  • Posts: 2403
  • Australia
  • Liked: 42
  • Likes Given: 68
Re: How should NASA evolve the SLS?
« Reply #321 on: 03/21/2013 09:33 pm »
50% of all profits from the sale of any RD-180 no matter where or when it might be produced goes to Energomash.

Offline hkultala

  • Full Member
  • ****
  • Posts: 1199
  • Liked: 748
  • Likes Given: 945
Re: How should NASA evolve the SLS?
« Reply #322 on: 03/21/2013 09:48 pm »
How would NASA convince congress (especially the Senate) to allow them to use a foreign engine, especially one from Russia?

Wouldn't Congress by OK with it if an American company were to build RD-180s in the US?
Wouldn't that negate any cost savings for the RD-180? SLS can't afford any increased cost, especially changing an engine midway through the design. Using them for LRBs could work if an American company modifies them just enough to make it an American derivative, but that means more money!
Atlas V uses the RD-180's so could LRB's for SLS.

Edit:
Keep in mind I'm only looking at going to the LRB's now if that is what they are going to do later.

I don't believe they can make the advanced SRB's cheaper than the 5 seg SRB's based on history. For LRB's it does have the advantage of engine throttle for lighter payloads , better rides up, ect. over SRB's.

SRBs are designed so that they automatically throttle to smaller thrust during later stage of their burn. So actually SRB's can throttle down more than LRB's, the throttling just cannot be changed/adjusted.

Quote
I prefer to just keep the design we have and not go to the so called advanced boosters, just add in the US when needed.

Just adding upper stage without making better boosters means that thrust-to-weight ratio during takeoff gets much worse and gravity losses would eat most of the gains the upper stage gives. Upper stage needs the better boosters. (But better boosters can be used without upper stage).


Online sdsds

  • Senior Member
  • *****
  • Posts: 7201
  • “With peace and hope for all mankind.”
  • Seattle
  • Liked: 2050
  • Likes Given: 1962
Re: How should NASA evolve the SLS?
« Reply #323 on: 03/22/2013 04:59 am »
Just adding upper stage without making better boosters means that thrust-to-weight ratio during takeoff gets much worse and gravity losses would eat most of the gains the upper stage gives. Upper stage needs the better boosters. (But better boosters can be used without upper stage).

Can you explain why the T/W ratio gets "much worse?" The GLOW of the so-called "70 ton" vehicle is said to be around 2500 metric tons. Why would the T/W ratio be much effected if its upper stage carried e.g. 200 tons of propellant, rather than 20 tons?

(If the lift-off thrust is 3810 metric tons of force, 3810/2500 ~= 1.52, whereas 3810/2680 ~= 1.42.)

Values derived from "SLS Fun Facts":
http://www.nasa.gov/pdf/588413main_SLS_Fun_Facts.pdf
« Last Edit: 03/22/2013 05:05 am by sdsds »
— 𝐬𝐝𝐒𝐝𝐬 —

Offline Lobo

  • Senior Member
  • *****
  • Posts: 6915
  • Spokane, WA
  • Liked: 672
  • Likes Given: 437
Re: How should NASA evolve the SLS?
« Reply #324 on: 03/22/2013 03:50 pm »

Just adding upper stage without making better boosters means that thrust-to-weight ratio during takeoff gets much worse and gravity losses would eat most of the gains the upper stage gives. Upper stage needs the better boosters. (But better boosters can be used without upper stage).

 

Well, first, they are adding a larger upper stage (Block 1B) to replace the initial smaller upper stage (ICPS), not just putting an upper stage on a stack that didn’t normally have one.  Which is what I assume Rocketman was referring to.  So the added mass will be a net addition vs the ICPS, rather than all new.

Also, I think the Block 1/1B SLS will have enough take off thrust margin for the larger Block 1B upper stage.  The 5-seg booster have 3.6M lbs thrust each.  The RS-25’s are 418klbs each at sea level.  That’s 8.87Mlbs of thrust on take off.  1.37Mlbs more thrust at takeoff than Saturn V. 
I couldn’t find any GLOW number for Block 1B quick, but for Block 1 with ICPS it looks to be 5.82Mlbs per the Space Launch Report link below.
Saturn V was 6.2Mlbs, per the Wikipedia page.

Even if we assume that the Block 1B stage was 200Klbs (91mt) more than the ICPS, for an even 6Mlbs GLOW, SLS will still have a much better T/W ratio at take off than Saturn V.  1.47:1 vs. 1.2:1.
And Saturn V lifted off ok with that 1.2:1 T/W ratio.
And I think that’s due to the massive take off thrust of SRB’s.  That’s probably the reason STS seamed to leap off the pad after SRB ignition, while Saturn V seems to crawl off the pad after F-1 ignition in the old videos I’ve seen. 

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

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

http://www.spacelaunchreport.com/sls0.html

So you don’t need better boosters to get the Block 1B upper stage and extra payload mass off the pad.  Lots of thrust margin for that.  You need better boosters to get the NAA2010 required eventual 130mt to LEO.  5-seg boosters with the SLS core with 4 RS-25’s and the Block 1B upper stage (a CPS/EDS basically rather than a true 2nd stage)  just won’t get you there.

The numbers in sdsds’s link were a bit different.  I don’t think they included the ICPS, at least it doesn’t mention anything about it.  The GLOW for the Space Launch Report link is a little higher, and maybe that’s the ICPS.  Not sure, I just used those numbers instead.
« Last Edit: 03/22/2013 03:56 pm by Lobo »

Offline Hyperion5

  • Full Member
  • ****
  • Posts: 1681
  • Liked: 1373
  • Likes Given: 302
Re: How should NASA evolve the SLS?
« Reply #325 on: 03/22/2013 04:42 pm »
You need better boosters to get the NAA2010 required eventual 130mt to LEO.  5-seg boosters with the SLS core with 4 RS-25’s and the Block 1B upper stage (a CPS/EDS basically rather than a true 2nd stage)  just won’t get you there.

No, I don't think you do need better boosters to hit the NAA2010 mandate of 130 mt to LEO.  A better upper stage would probably deliver for you, Lobo.  I took a look over at the effect of adding an RL-10A-4-2 engine to the Jupiter's upper stage (thank Chuck for this). 

http://www.directlauncher.org/documents/Baseball_Cards/J246H-41.5003.08001_EDS_090608.jpg

http://www.directlauncher.org/documents/Baseball_Cards/J247H-41.5003.08001_EDS_090608.jpg

Notice that roughly 2.5 mt difference in payload to LEO added with just one additional RL-10 engine?  As it happens, the SLS Bloc IB only has four RL-10 engines up top, space enough to either add two more RL-10B-2 engines, or three more RL-10A-4-2 engines, depending on which is used.  If we figure 3 more RL-10A-4-2 engines are used, we're looking at around a 7-10 mt difference in payload to LEO to the positive.  That would get the SLS into the range of 125-128 mt to LEO.  But could you hit the 130 mt mark with just an upper stage upgrade?  I'm fairly sure you could IF NASA were to use either the J-2X or a quartet of RL-60 engines. 

http://www.directlauncher.org/documents/Baseball_Cards/J241H-41.5002.08001_EDS_090608.jpg

Based on Chuck Longton's work, I'd have to guess a J-2X stage up top would have the SLS Bloc IB either delivering 130 mt to orbit or get exceptionally close.  But the RL-60 engine option I'm fairly sure would deliver the 130 mt NASA is looking to get out of the SLS.  As you'll see, they deliver a couple of mt more to LEO than a J-2X stage would. 

http://www.directlauncher.org/documents/Baseball_Cards/J244H-41.5005.08001_EDS_090608.jpg

So I think the premise is better said, "We can't get to 130 mt mandate with the Bloc IB's upper stage, or even using the max number of RL-10 engines, though adding more would get us very close to the mandate.  But give us a quartet of RL-60 engines, and we will beat the mandate for sure without new boosters." 



« Last Edit: 03/22/2013 04:46 pm by Hyperion5 »

Offline HappyMartian

  • Senior Member
  • *****
  • Posts: 2713
  • Tap the Moon's water!
  • Asia
  • Liked: 16
  • Likes Given: 2
Re: How should NASA evolve the SLS?
« Reply #326 on: 03/22/2013 06:31 pm »
You need better boosters to get the NAA2010 required eventual 130mt to LEO.  5-seg boosters with the SLS core with 4 RS-25’s and the Block 1B upper stage (a CPS/EDS basically rather than a true 2nd stage)  just won’t get you there.

No, I don't think you do need better boosters to hit the NAA2010 mandate of 130 mt to LEO.  A better upper stage would probably deliver for you, Lobo.  I took a look over at the effect of adding an RL-10A-4-2 engine to the Jupiter's upper stage (thank Chuck for this). 

http://www.directlauncher.org/documents/Baseball_Cards/J246H-41.5003.08001_EDS_090608.jpg

http://www.directlauncher.org/documents/Baseball_Cards/J247H-41.5003.08001_EDS_090608.jpg

Notice that roughly 2.5 mt difference in payload to LEO added with just one additional RL-10 engine?  As it happens, the SLS Bloc IB only has four RL-10 engines up top, space enough to either add two more RL-10B-2 engines, or three more RL-10A-4-2 engines, depending on which is used.  If we figure 3 more RL-10A-4-2 engines are used, we're looking at around a 7-10 mt difference in payload to LEO to the positive.  That would get the SLS into the range of 125-128 mt to LEO.  But could you hit the 130 mt mark with just an upper stage upgrade?  I'm fairly sure you could IF NASA were to use either the J-2X or a quartet of RL-60 engines. 

http://www.directlauncher.org/documents/Baseball_Cards/J241H-41.5002.08001_EDS_090608.jpg

Based on Chuck Longton's work, I'd have to guess a J-2X stage up top would have the SLS Bloc IB either delivering 130 mt to orbit or get exceptionally close.  But the RL-60 engine option I'm fairly sure would deliver the 130 mt NASA is looking to get out of the SLS.  As you'll see, they deliver a couple of mt more to LEO than a J-2X stage would. 

http://www.directlauncher.org/documents/Baseball_Cards/J244H-41.5005.08001_EDS_090608.jpg

So I think the premise is better said, "We can't get to 130 mt mandate with the Bloc IB's upper stage, or even using the max number of RL-10 engines, though adding more would get us very close to the mandate.  But give us a quartet of RL-60 engines, and we will beat the mandate for sure without new boosters." 



....

I was a big supporter of DIRECT & J-246, so you're preaching to the converted.
....

PS this is all nibbling around the edges of the argument. Just as DIRECT proposed, NASA should go in with ULA/Boeing/LM and develop an ACES-type upper stage, initially as ICPS 2 as a common u/s for Atlas & Delta, then an 8.4m version as 1BUS. Not gonna happen, though.


Yep. I was a supporter of the J-246, but kind of suspected that the J-241 would get the nod for the political reason that the money was already spent on the development of the J-2X.

However, a J-246 isn't what we are getting. Heavy duty versions of the J-241SH or a J-246SH are what is being argued about.

Evolved EELV for Heavy Lift Launch
At: http://spirit.as.utexas.edu/~fiso/telecon/Barr_11-3-10/Barr%2011-3-10.pdf
See Page 6    "ACES Enables Engine-Out"


The above presentation supports the idea of an Advanced Common Evolved Stage (ACES) with four RL10 Engines as having the lowest loss of mission risk on the basis of engine out capability. However, given the heavier payload capability of the J-24?SH/SLS, one would suspect that a stage with a more powerful group of rocket engines such as the six RL10 engines of the J-246SH or a single J-2X of the J-241SH would be a more optimal solution.


See:

Propulsion  "Next Generation Engine (NGE)" "MB-60 Engine" Page 25 of
A Study of CPS Stages for Missions beyond LEO   By Mark Schaffer May 16, 2012
At: http://www.sei.aero/eng/papers/uploads/archive/SpaceWorks%20CPS%20Study%20Final%20Distribution.pdf



"Mitsubishi Heavy Industries (MHI) and Pratt & Whitney Rocketdyne (PWR) have been co-developing the MB-60 cryogenic upper stage engine since 1999."

From: The MB-60 Cryogenic Upper Stage Engine - A World Class Propulsion System  By William Sack, Kenji Kishimoto, Akira Ogawara, Kimito Yoshikawa, and Masahiro Atsumi    2009
At: http://archive.ists.or.jp/upload_pdf/2009-a-03.pdf 

Various upper stages based on four MB-60s would have almost as much thrust than the J-2X. Five MB-60s could provide more thrust than the J-2X. Since this thread is discussing the future, I see no reason that the MB-60, built either by Mitsubishi Heavy Industries or Pratt & Whitney Rocketdyne, could not eventually meet the needs for an upper stage or a CPS for the SLS. Japan and Mitsubishi Heavy Industries should discuss such cooperative possibilities with the American government and Pratt & Whitney Rocketdyne.


.....




Hyperion, currently I'm not sure if even  the "CPS Gamma (Optional)" with an "8.0 m" diameter, "32.1 m" length, "454.3 t" of Propellant, "481.4 t" Wet Mass, and "5x MB-60" (noted on page 29 of Mark Schaffer's above noted A Study of CPS Stages for Missions beyond LEO) would be the optimal upper stage for the SLS. 

An upper stage with two J-2Xs seems to be a bit more reasonable, especially if the LRBs are likely.

How many times do we want to design an SLS upper stage?

Could an upper stage with two J-2Xs also have two RL10s?


Edited.
« Last Edit: 03/22/2013 06:38 pm by HappyMartian »
"The Moon is the most accessible destination for realizing commercial, exploration and scientific objectives beyond low Earth orbit." - LEAG

Offline TomH

  • Senior Member
  • *****
  • Posts: 2938
  • Vancouver, WA
  • Liked: 1868
  • Likes Given: 909
Re: How should NASA evolve the SLS?
« Reply #327 on: 03/22/2013 06:54 pm »
H5,

I just cannot see how all these multiple engines on a second stage to reach orbit makes any sense. You then need a third stage for Earth departure; or you restart a stage that has excess engine mass. The sustainers need to do what they are designed for: take the core to disposal orbit. Jettisoning those sustainers prior to disposal orbit is an immense waste of resources. Any upper stage needs to be an Earth departure stage, one with low engine mass and high ISP. I just cannot see how ATK or AJ advanced boosters and a second stage with multiple engines, all to reach orbit could possibly be more efficient than Dynetics boosters, the core and no additional stage to reach disposal orbit. Atop that you either have cargo for assembly at LEOR or you have cargo atop one upper stage, an upper stage designed for Earth departure with low engine mass and high ISP. Advanced boosters are already required. It is far more sensible just to go with the most powerful boosters available and omit the use of a second stage for reaching disposal orbit.

Offline 93143

  • Senior Member
  • *****
  • Posts: 3054
  • Liked: 312
  • Likes Given: 1
Re: How should NASA evolve the SLS?
« Reply #328 on: 03/22/2013 08:01 pm »
I just cannot see how all these multiple engines on a second stage to reach orbit makes any sense. You then need a third stage for Earth departure; or you restart a stage that has excess engine mass.

Well, apparently the TLI performance of even a multi-RL-10 stage is better with larger tanks and suborbital staging than with tanks small enough to drop off in LEO.  Sharing delta-V between stages more equitably generally helps payload.

Gravity losses are minimal in the last couple km/s before orbit, and they aren't zero during TLI.  There's a reason DIRECT designed the JUS to be far too heavy for a J-130 to deposit in orbit on its own...

Offline Lobo

  • Senior Member
  • *****
  • Posts: 6915
  • Spokane, WA
  • Liked: 672
  • Likes Given: 437
Re: How should NASA evolve the SLS?
« Reply #329 on: 03/22/2013 09:29 pm »
H5,

I just cannot see how all these multiple engines on a second stage to reach orbit makes any sense. You then need a third stage for Earth departure; or you restart a stage that has excess engine mass. The sustainers need to do what they are designed for: take the core to disposal orbit. Jettisoning those sustainers prior to disposal orbit is an immense waste of resources. Any upper stage needs to be an Earth departure stage, one with low engine mass and high ISP. I just cannot see how ATK or AJ advanced boosters and a second stage with multiple engines, all to reach orbit could possibly be more efficient than Dynetics boosters, the core and no additional stage to reach disposal orbit. Atop that you either have cargo for assembly at LEOR or you have cargo atop one upper stage, an upper stage designed for Earth departure with low engine mass and high ISP. Advanced boosters are already required. It is far more sensible just to go with the most powerful boosters available and omit the use of a second stage for reaching disposal orbit.

X2.

I’m no expert on any of this, mind you.  But the more more you grow the upper stage to make up for booster performance, the less optimal it is for BLEO burns because it becomes larger, heavier, with engines that have higher thrust and lower ISP (like J2X).  I think the JUS was sort of a balance of being a 2nd stage and an EDS. 

And there’s also this.  The stretched core can sustain four RS-25’s to suborbit, as they will for STS Block 1/1B.  An ET-sized core can sustain three RS-25’s to suborbit, as they did for STS, and would have for J-130.  You can put a larger and more powerful upper stage on top, but you can’t stage any sooner, unless you are jettisoning a partially full core….which doesn’t make much sense.  SLS Block 2 put a 5th RS-25 on the core to drain it faster to make proper staging for the J2X powered large 2nd stage.  J246 had the 4th RS-25 on the ET-sized core for earlier staging of the JUS. 
So I don’t know how you really put a larger and more powerful upper stage on SLS Block 1 with the same 4 RS-25 engines.  Maybe if the SLS core was shrunk back to ET size, and then you could have a J-247H basically. 

But the stretched core has the fuel to get the payload basically to LEO with four RS-25’s.  The RS-25’s can’t drain the tank any faster unless you pump up the % thrust you run them at, but that might get too out of the margins for a crew launch.   Letting the core burn to orbit is the optimal use of a sustainer core platform. And it should be used as such.  Which is why I think NASA is moving away from their 3-stage Block II PoR design, to basically a “Block 2B”. 

Offline Hyperion5

  • Full Member
  • ****
  • Posts: 1681
  • Liked: 1373
  • Likes Given: 302
Re: How should NASA evolve the SLS?
« Reply #330 on: 03/22/2013 09:31 pm »
I post an interesting alternative to advanced boosters without saying it's necessarily the best way forward, and it sure seems to have attracted replies.   8) 

H5,

I just cannot see how all these multiple engines on a second stage to reach orbit makes any sense. You then need a third stage for Earth departure; or you restart a stage that has excess engine mass. The sustainers need to do what they are designed for: take the core to disposal orbit. Jettisoning those sustainers prior to disposal orbit is an immense waste of resources.

It sounds to me like you're not a fan of how both Chuck Longton (clongton) and the legendary and controversial Wernher von Braun did things with the Saturn V and the Jupiter designs.  Chuck's Jupiters with upper stages (all Jupiter 24X-series) would see the core burn out before reaching orbit.  The Saturn V similarly did not have a pure EDS.  I think 93143 has hit the nail on the head by this observation as to why both Chuck and Wernher had similar approaches. 

Well, apparently the TLI performance of even a multi-RL-10 stage is better with larger tanks and suborbital staging than with tanks small enough to drop off in LEO.  Sharing delta-V between stages more equitably generally helps payload.

Gravity losses are minimal in the last couple km/s before orbit, and they aren't zero during TLI.  There's a reason DIRECT designed the JUS to be far too heavy for a J-130 to deposit in orbit on its own...

I should also mention there's a major bonus to having that number of engines on a stage--engine-out capability.  You are far more likely to lose an engine on an upper stage than you are on the boosters.  Because most engines have a maximum burn duration, they can only compensate so much for losing other engines via longer burns.  ULA for instance had a study showing a four RL-10 upper stage that could afford losing an engine was exponentially less likely to fail due to engine failure than the one-engine Centaurs we see today.  I believe the failure rate on that was predicted at 79 per 100,000 flights, while the 4-engine stage would fail at a rate of 5 per 100,000 flights due to engine failure, which is exceptional.  The failure rate rises marginally with 6 engines to 6 failures per 100,000 flights, but notice how slowly the predicted failure rate jumps with more RL-10 engines.  This is one reason why a single J-2X stage might not be so appealing to SLS engineers. 


Any upper stage needs to be an Earth departure stage, one with low engine mass and high ISP. I just cannot see how ATK or AJ advanced boosters and a second stage with multiple engines, all to reach orbit could possibly be more efficient than Dynetics boosters, the core and no additional stage to reach disposal orbit. Atop that you either have cargo for assembly at LEOR or you have cargo atop one upper stage, an upper stage designed for Earth departure with low engine mass and high ISP. Advanced boosters are already required. It is far more sensible just to go with the most powerful boosters available and omit the use of a second stage for reaching disposal orbit.

I personally think it'd actually benefit the SLS' TLI performance to go for a larger upper stage with more engines.  I wouldn't mind having the Dynetics boosters, but we should admit at least that there's nothing fundamentally wrong with the designs of Chuck Longton's Jupiters.  In any case, the SLS is a close cousin of those designs, as the SLS Bloc IB is essentially like a Jupiter 246 Heavy with a stretched core stage, less powerful upper stage and built with heavier alloys.  It would surely benefit, as Chuck's numbers seem to suggest, from adding a few more engines and a bit more propellant up top.  So maybe it'd need to do a 1 km/s change in velocity, but that's fine by me, since it eliminates the hard to simulate disposal orbit for the core stage.  Anyone who's ever tried to simulate a shuttle getting to orbit knows what I'm talking about.   ;)



Hyperion, currently I'm not sure if even  the "CPS Gamma (Optional)" with an "8.0 m" diameter, "32.1 m" length, "454.3 t" of Propellant, "481.4 t" Wet Mass, and "5x MB-60" (noted on page 29 of Mark Schaffer's above noted A Study of CPS Stages for Missions beyond LEO) would be the optimal upper stage for the SLS. 


As much as I admire your advocating for use of the MB-60, I do have to point out that JAXA hasn't pitched in to fund its use on the SLS.  If they had I doubt any of us would be saying the Bloc IB's upper stage seems a tad underpowered, which it is.  I should also mention that I've seen a set of simulations pitting the RL-60 against the MB-60 for TLI performance, and the American rocket engine would win.  It may not have been funded to completion, but the design specs claimed would see it triumph if true.  Aside from that, just think about the politics of putting Japanese engines on the upper stage of a rocket meant to show the pinnacle of America's technical might.  It sounds like a tough sell to me. 


How many times do we want to design an SLS upper stage?

I should think once would be a good answer.  I'm not saying the SLS Bloc IB is a bad way to go with evolving the design, but you could hit the mandate's performance targets with only ONE upper stage re-design.  The problem is there is a catch to every possible solution.  A J-2X upper stage would get you to 130 mt to LEO, but it'd have no engine-out margin.  A quartet or quintet of RL-60 engines would easily get you there, but that means more time and money spent developing an all-new engine.  A quartet or quintet of Vinci or MB-60 engines would probably get the SLS to 130 mt to LEO, but then you run into the politically delicate position of having America's premier rocket relying on foreign engines.  However, the SLS Bloc IB has its own catch, which is it needs new boosters to meet the performance mandate.  From where I sit though, adding a robust upper stage sure seems less expensive and difficult than re-doing the boosters. 

If politics weren't a problem, I'd either ask the Japanese or French to use either the MB-60 or Vinci engines on the SLS.  At least with Vinci engines we'd be adding to an existing engine production line.  I can't remember--are MB-60 engines due to be used on any Japanese launcher? 


An upper stage with two J-2Xs seems to be a bit more reasonable, especially if the LRBs are likely.

Wouldn't TLI maneuvering get a tad awkward with that much thrust on tap?

Could an upper stage with two J-2Xs also have two RL10s?
Edited.

So how would that work?  Would you let the J-2X engines do much of the delta-v and have the RL-10 engines handle the rest?  It's an interesting idea, though surely there's a reason why most 2-engine type upper stages are composed of main engines and vernier engines. 
« Last Edit: 03/22/2013 09:32 pm by Hyperion5 »

Offline Hyperion5

  • Full Member
  • ****
  • Posts: 1681
  • Liked: 1373
  • Likes Given: 302
Re: How should NASA evolve the SLS?
« Reply #331 on: 03/22/2013 09:48 pm »

I’m no expert on any of this, mind you.  But the more more you grow the upper stage to make up for booster performance, the less optimal it is for BLEO burns because it becomes larger, heavier, with engines that have higher thrust and lower ISP (like J2X).  I think the JUS was sort of a balance of being a 2nd stage and an EDS. 

And there’s also this.  The stretched core can sustain four RS-25’s to suborbit, as they will for STS Block 1/1B.  An ET-sized core can sustain three RS-25’s to suborbit, as they did for STS, and would have for J-130.  You can put a larger and more powerful upper stage on top, but you can’t stage any sooner, unless you are jettisoning a partially full core….which doesn’t make much sense.  SLS Block 2 put a 5th RS-25 on the core to drain it faster to make proper staging for the J2X powered large 2nd stage.  J246 had the 4th RS-25 on the ET-sized core for earlier staging of the JUS. 
So I don’t know how you really put a larger and more powerful upper stage on SLS Block 1 with the same 4 RS-25 engines.  Maybe if the SLS core was shrunk back to ET size, and then you could have a J-247H basically. 

But the stretched core has the fuel to get the payload basically to LEO with four RS-25’s.  The RS-25’s can’t drain the tank any faster unless you pump up the % thrust you run them at, but that might get too out of the margins for a crew launch.   Letting the core burn to orbit is the optimal use of a sustainer core platform. And it should be used as such.  Which is why I think NASA is moving away from their 3-stage Block II PoR design, to basically a “Block 2B”. 


I believe Boeing has already shown the giant J-2X second stage was axed from the evolution of the design.  You should also remember that not all upper stage engines more powerful than an RL-10 are also less efficient.  Some of them are actually better at putting more payload through TLI & TMI than the RL-10, according to simulations I've seen performed.  The MB-60 according to Astronautix (http://www.astronautix.com/engines/mb60.htm) has 467 seconds of Isp and did very well in the simulations fregate ran for an EDS stage.  Same goes for the RL-60, which beat all the competition in that simulation. 

Mind you, fregate was simulating an EDS for a different rocket, but I'm pretty sure his math will hold up despite 1-2 minor errors.  Those errors would affect all the numbers slightly, but would not alter the finishing position of the engines.  The RL-10B-2 does well, but it would be beaten by any NGE, MB-60 and especially the RL-60. 
« Last Edit: 03/22/2013 09:53 pm by Hyperion5 »

Offline Lobo

  • Senior Member
  • *****
  • Posts: 6915
  • Spokane, WA
  • Liked: 672
  • Likes Given: 437
Re: How should NASA evolve the SLS?
« Reply #332 on: 03/22/2013 09:52 pm »
I just cannot see how all these multiple engines on a second stage to reach orbit makes any sense. You then need a third stage for Earth departure; or you restart a stage that has excess engine mass.

Well, apparently the TLI performance of even a multi-RL-10 stage is better with larger tanks and suborbital staging than with tanks small enough to drop off in LEO.  Sharing delta-V between stages more equitably generally helps payload.

Gravity losses are minimal in the last couple km/s before orbit, and they aren't zero during TLI.  There's a reason DIRECT designed the JUS to be far too heavy for a J-130 to deposit in orbit on its own...

Chuck or one of the Direct guys could probably tell you more accurately, but myself, I always thought the JUS was designed because Direct was always a plan to supplant the 1.5 architecture of CxP with a single common core vehicle.  That meant EOR, which was CxP plan.  Which meant a large EDS was needed to send a 20mt Orion CSM and 45mt LSAM through TLI.  CxP would have the big Ares V upper stage and would launch LSAM to LEO where it would dock with Orion and do the TLI burn.  So Direct was trying to stick with that. 
Also, J-130 could put about 70mt to LEO, so with an optimum sized upper stage, it could put about 30mt maybe through TLI.    Orion was 20-ish mt, so a 5m EELV upper stage could send Orion through TLI.  But the LSAM was like 45mt, so J-130 couldn’t get it plus a probably stretched EELV upper stage to LEO by itself. 
Now Orion and LSAM were elements of CxP and Direct couldn’t change those requirements.  They were just working on an alternate launch system.  So they had to get 65mt through TLI like CxP would.  So they put Orion and the LSAM on a J-130 (with LSAM doing the circ burn), and the JUS on a J-246, for a EOR. 

If you could mess with the sizes of Orion and LSAM, and make them each about 30mt, then they could use two J-130’s, with smaller EELV derived EDS’s, and have a LOR and send the two elements separately.  They came up with something like that as a possibility for Side Mount-SDHLV during the Augustine commission.  But Orion stayed the same size, and the lander was down-sized, so it would be more like an Apollo LEM scale lander, rather than the bigger Altair they envisioned. 

Anyway, I think it would have been a cheaper and more sustainable way to go to use two J-130’s with 5m EELV ACES/common Centaur upper stages and LOR, and have played with Orion and the lander in order to optimize that.  (Maybe the lander would brake itself into High Lunar orbit, and a 30mt Orion, similar to Apollo, using maybe lighter and more efficient methalox service module propellant would rendezvous with it, and then brake it down to LLO.  Then the crew would board the lander and go to the surface.  That way you effectively transfer 10mt of mass from the lander to Orion, balancing the two payloads to be launched on two J-130’s. 
Because something like Apollo would be hard with two launches of the same sized LV and LOR, because Apollo was 30mt, and the LEM was 15mt.  Orion was 20mt, and the LSAM was 45mt.  Those work for single launch systems, or 1.5 launch systems, but not 2 launch systems (two equal sized launchers).  For a two launch system of equal sized launchers you need to balance the payloads. 
Another way to do it would be EMLP1 rendezvous, with Orion then braking the stack down to LLO from EMLP1.  And that would have meant a more ET-directly derived launcher in J-130 (that J246 would have been), and skipping the need to develop JUS all together.  NASA would just pay ULA to develop ACES.  And have a version of it optimized for J-130, and a version optimized for their EELV fleet, for maximum synergy and cost sharing with EELV's.  (as much as a SDHLV can be anyway)

Offline Lobo

  • Senior Member
  • *****
  • Posts: 6915
  • Spokane, WA
  • Liked: 672
  • Likes Given: 437
Re: How should NASA evolve the SLS?
« Reply #333 on: 03/22/2013 10:02 pm »

I believe Boeing has already shown the giant J-2X second stage was axed from the evolution of the design.  You should also remember that not all upper stage engines more powerful than an RL-10 are also less efficient.  Some of them are actually better at putting more payload through TLI & TMI than the RL-10, according to simulations I've seen performed.  The MB-60 according to Astronautix (http://www.astronautix.com/engines/mb60.htm) has 467 seconds of Isp and did very well in the simulations fregate ran for an EDS stage.  Same goes for the RL-60, which beat all the competition in that simulation. 

Mind you, fregate was simulating an EDS for a different rocket, but I'm pretty sure his math will hold up despite 1-2 minor errors.  Those errors would affect all the numbers slightly, but would not alter the finishing position of the engines.  The RL-10B-2 does well, but it would be beaten by any NGE, MB-60 and especially the RL-60. 

You are correct.  However, I was referring to using existing or soon-to-be existing upper stage engines.  Mainly RL-10 and J2X.  If you put a brand new NGE engine in the mix like RL-60 or MB-60, then that changes the equation.  Although, again, the more you grow the upper stage, the physically bigger and heavier it is, with a heavier thrust structure, etc.  But yes, you can have a higher thrust and higher ISP engine with an NGE.

Offline TomH

  • Senior Member
  • *****
  • Posts: 2938
  • Vancouver, WA
  • Liked: 1868
  • Likes Given: 909
Re: How should NASA evolve the SLS?
« Reply #334 on: 03/22/2013 10:10 pm »
It sounds to me like you're not a fan of how both Chuck Longton (clongton) and the legendary and controversial Wernher von Braun did things with the Saturn V and the Jupiter designs.

You're comparing apples to oranges. The Saturn V was a single stack vehicle and employed serial staging. It took the LOR approach. It did not employ sustainers.

SLS uses parallel staging, sustainers, and at least for Mars, must use LEOR to assemble components. What would you do with three to seven half fueled upper stages while assembling Mars components in LEO?

You are suggesting throwing away sustainers halfway to orbit when they could be used all the way to orbit. You unnecessarily add an unneeded stage. Your appeal to authority names does not add persuasiveness to your argument. If S-II could have gotten everything above it to a V of say 17,460 mph, do you actually believe von Braun would have used a J-2 on the S-IVB? It would have been excess mass at the cost of lower ISP; he would have used an RL-10. RL-10 can't fight gravity loss like J-2 class engines. S-I with F-I needed high ISP DENSITY to get everything off the ground. Since you invoke Chuck Longton, he has stated over and over that the parallel staging and SLS are a better design than Saturn V with its serial staging. I would have to search to find it, but I remember him saying once or twice that for a HLV, SLS is about the best design that can be had.

The core should use the sustainers all the way to disposal orbit. If only assembly components are atop the core, only circularization is required. If the hardware atop the core will depart LEO for deep space, the mass and thrust of J-2X are unnecessary and its lower ISP a disadvantage. With little gravity loss to counter, RL-10 is the right choice.

I think you are a nice guy, but I respectfully disagree with your propositions. In the SLS paradigm, they are not a logical fit.
« Last Edit: 03/22/2013 10:25 pm by TomH »

Offline Lobo

  • Senior Member
  • *****
  • Posts: 6915
  • Spokane, WA
  • Liked: 672
  • Likes Given: 437
Re: How should NASA evolve the SLS?
« Reply #335 on: 03/22/2013 10:20 pm »

It sounds to me like you're not a fan of how both Chuck Longton (clongton) and the legendary and controversial Wernher von Braun did things with the Saturn V and the Jupiter designs.  Chuck's Jupiters with upper stages (all Jupiter 24X-series) would see the core burn out before reaching orbit.  The Saturn V similarly did not have a pure EDS.  I think 93143 has hit the nail on the head by this observation as to why both Chuck and Wernher had similar approaches. 

 

Well, someone can correct me if I’m wrong here, but I think the two are different.  Von Braun’s design in the Saturn V was a serial staged design, not a parallel staged design.  With the existing gas generator kerolox technology of the time in the US, the 1st stage couldn’t generate both enough thrust and ISP to have a combination 2nd stage and EDS like a JUS.  So they went with high thrust, and gave the Saturn V a hydrolox 2nd stage to get that ISP.  And then a 3rd stage for EDS.  If Saturn V had had a hydrolox sustainer core stage powered by J2’s, and say Titan SRB’s strapped on, or big kerolox parallel boosters, then they could have gotten away with a “2.5” stage LV, like SLS Block 1B will be. 
But, when you are starting from a clean sheet design, and money is no object, and you aren’t looking for economic sustainability, just the best and fastest way to put a man on the moon, then a 3 stage serial staged wide-body LV is more efficient than a parallel staged machine.  And that’s what he went with.

Direct and SLS were working within shuttle derived legacy hardware.  And STS was parallel staged for different reasons.   (reusable boosters, reusable engines on the orbiter which means the Orbiter needs to be placed low on the stack, etc).  Direct and SLS were inheriting legacy systems that didn’t apply to them.  Which is why the RAC-2 team really won the RAC competition, but RAC-1 won for political reasons of being “shuttle derived”. 

So anyway, to make a short story long, I don’t know that your comparison is quite applicable.  :-)
And as far as why Direct had a JUS and the J24x series staged before suborbit, in my previous post I address why I think that is.  Of course, Chuck Logton could comment on if I understood their reasoning correctly, or if I have totally wrong.  (which is certainly possible!) But I –think- the JUS concept was maybe more due to Direct trying to work within the CxP framework, but making it a more feasible two-launch system.  Rather than it being the absolutely cheapest and most sustainable method period (which would require reworking Orion and LSAM designs, and they couldn’t do that).
I think their concept with JUS probably was actually a little more mass efficient, as it probably can push more mass through TLI as the JUS probably weighs less than two smaller EELV derived stages.  But by other metrics, like development costs of JUS, and costs of a low flight-rate JUS versus the shared costs and much higher flight rate of a common EELV upper stage, might mean it’s actually a more affordable system up front, and in the long run, to go with two similar sized launches with two EDS’s, and LOR.

I –think- anyway…I could be wrong…  ;-)

Offline Lobo

  • Senior Member
  • *****
  • Posts: 6915
  • Spokane, WA
  • Liked: 672
  • Likes Given: 437
Re: How should NASA evolve the SLS?
« Reply #336 on: 03/22/2013 10:30 pm »

You are suggesting throwing away sustainers halfway to orbit when they could be used all the way to orbit. You unnecessarily add an unneeded stage.


Yea, when you think about it, the current Block II Por, the SLS core with a 5th RS-25, a J2X powered LUS, and a CPS on top of that, is actually a 4-stage rocket when you count the boosters.  SLS Block 1B and Saturn V are both actually 3- stage rockets. The core of SLS Block 1B is really a gournd lit 2nd stage.  So you want that 2nd stage to burn clear to suborbit the way the S-II stage did.  To make the Block 1B stage bigger, would be like making the S-IVB bigger, and staging before it did, rather than letting that stage get most of the way to orbit.

Really, I think in a parallel staged system with a hydrolox core, if you don’t want to let the sustainer stage go clear to suborbit, then might as well do a 3 stage system and use a higher thrust propellant like kerolox for the first stage and then let a hydrolox 2nd stage to get you that high ISP to orbit.  Like Saturn V or RAC-2.
The RS-25, if you are going to use it, is a complex but great sustainer engine.  Great ISP in vacuum…almost as good as a true in-space engine.  Yet high thrust to overcome gravity losses.  Jettisoning it early is a waste I think.  Might as well use RS-68’s then.  If you switched the boosters to liquid, switched the core to RS-68’s, and then created a large JUS-style combo upper stage/EDS with RL-60’s or MB-60’s…then that’s a different animal, as RS-68’s aren’t all that great all the way to orbit like the RS-25’s.

Online sdsds

  • Senior Member
  • *****
  • Posts: 7201
  • “With peace and hope for all mankind.”
  • Seattle
  • Liked: 2050
  • Likes Given: 1962
Re: How should NASA evolve the SLS?
« Reply #337 on: 03/22/2013 10:44 pm »
SLS [...] at least for Mars, must use LEOR to assemble components.

What rules out Lagrange point assembly?

Quote
What would you do with three to seven half fueled upper stages while assembling Mars components in LEO?

That's not a problem ... for Lagrange point assembly!  ;)
— 𝐬𝐝𝐒𝐝𝐬 —

Offline Hyperion5

  • Full Member
  • ****
  • Posts: 1681
  • Liked: 1373
  • Likes Given: 302
Re: How should NASA evolve the SLS?
« Reply #338 on: 03/23/2013 12:42 am »
I think you are a nice guy, but I respectfully disagree with your propositions. In the SLS paradigm, they are not a logical fit.

Ah thanks.  I'm just pointing out that the proposition that we need advanced boosters to meet the NAA2010 mandate isn't actually true.  It isn't that the SLS Bloc IB is a bad design, far from it.  However, we should all note an interesting part about that mandate.  It's a mandate to LEO rather than TLI or TMI.  Given budgeting realities, I simply think we should acknowledge that if meeting the mandate is what matters, you can do it faster with one upper stage upgrade than you can with new boosters.  Whether that's ideal for the SLS, well, it depends on your point of view. 

Btw, I just noticed the huge gap in capability between the SLS Bloc II (with Bloc IB upper stage) and Bloc IIA to LEO.  The first would put up 155 mt to LEO, and the latter 178 mt, which suggests that a J-2X up top of a SLS Bloc I would easily meet the NASA mandate.  Whether it'd be worth it to add yet another NASA-only engine, lose engine-out capability and see the TLI performance trimmed a few mt is another matter. 


It sounds to me like you're not a fan of how both Chuck Longton (clongton) and the legendary and controversial Wernher von Braun did things with the Saturn V and the Jupiter designs.

You're comparing apples to oranges. The Saturn V was a single stack vehicle and employed serial staging. It took the LOR approach. It did not employ sustainers.

SLS uses parallel staging, sustainers, and at least for Mars, must use LEOR to assemble components. What would you do with three to seven half fueled upper stages while assembling Mars components in LEO?

Tom, I think the size of those MTV components is going to be huge, so chances are the SLS would need to use nearly all of the upper stage propellants to get them into orbit.  Once away, you then simply do de-orbit burns over the Pacific and that little problem's taken care of quickly.  NASA is hardly going to let a bunch of partly fueled stages sit around in LEO acting like space junk after all. 


You are suggesting throwing away sustainers halfway to orbit when they could be used all the way to orbit. You unnecessarily add an unneeded stage.

Wait a minute, since when have I said anything about adding another stage?  We're simply talking about using a single upper stage upgrade to meet the NAA2010 mandate, not simply "throwing away sustainers halfway to orbit".  Besides, by going from the Bloc I to the Bloc IB, you are already cutting into the ability of the core to make it to a disposal orbit.  The Bloc I upper stage is going to be about 30.7 mt in gross mass.  If the SLS Bloc IB keeps its t/w ratio the same, you're looking at an upper stage of around 123 mt, though it may be less than that.  The upgrade we're talking about is not going to see the core run out of propellants halfway to orbit.  It'll be far closer to orbital speeds than that. 

http://www.directlauncher.org/documents/Baseball_Cards/J246-41.4004.08001_EDS_090606.jpg

A Jupiter 246's upper stage has a mass of almost 187 mt, a roughly 52% increase in mass over the theoretical mass of an SLS Bloc IB's upper stage.  This makes sense, as the stage has 50% more thrust and would have a superior propellant mass fraction to boot.  Thankfully, due to the SLS' elongated core stage, we don't need as much propellant to do the same job.  The Jupiters had to compensate for having four engines with a tank sized for three, so we could probably keep the stage mass increase down to 10-30 mt, which would still see the SLS stage quite high and fast.  After that you've got a quartet of RL-60 engines taking over, which given their superior Isp, you'd probably want firing at that final part of the ascent burn anyways.  Sustainer engines are great if they've got excellent Isp, but if you're 80-90% of the way to orbital speed, the higher Isp of a dedicated upper stage engine starts improving performance rather than detracting from it. 


Your appeal to authority names does not add persuasiveness to your argument. If S-II could have gotten everything above it to a V of say 17,460 mph, do you actually believe von Braun would have used a J-2 on the S-IVB? It would have been excess mass at the cost of lower ISP; he would have used an RL-10. RL-10 can't fight gravity loss like J-2 class engines.

Well it's the internet, Tom, so I've given up thinking my arguments are always going to be truly persuasive.  ;D  There's just one problem with your Saturn V plan, Tom.  It doesn't take into account the needs of lifting the Apollo CSM on the Saturn IB.  Even six RL-10 engines in that era stood no chance of getting an Apollo CSM to orbit on that rocket, hence the J-2.  Supposing though that Wernher had the Saturn V S-II staging at nearly orbital speed, the obvious solution is simply adding a nozzle extension to the S-IVB's J-2.  It's only got a 27.5 expansion ratio, and it was achieving 420 seconds of vac Isp with that.  Hike that expansion ratio to 100 and I bet it'd top 435 seconds of vac Isp at least, which is barely less than that of the 1960s-era RL-10 engines. 

S-I with F-I needed high ISP DENSITY to get everything off the ground. Since you invoke Chuck Longton, he has stated over and over that the parallel staging and SLS are a better design than Saturn V with its serial staging. I would have to search to find it, but I remember him saying once or twice that for a HLV, SLS is about the best design that can be had.

It's also the same Chuck Longton who designed the Jupiters' upper stages, none of which could be put in a disposal orbit by the core stage.  If the SLS was what he dreamed up to be the ideal HLV, I dare say his Jupiters would look quite a bit different.  I've heard Chuck say many things, but saying the SLS design as it stands is the best HLV design that can be had?  Why then would Chuck have come up with these enormous upper stage designs for his Jupiters if the SLS approach was the way to go? 



The core should use the sustainers all the way to disposal orbit. If only assembly components are atop the core, only circularization is required. If the hardware atop the core will depart LEO for deep space, the mass and thrust of J-2X are unnecessary and its lower ISP a disadvantage. With little gravity loss to counter, RL-10 is the right choice.

You don't necessarily have to use a J-2X, which has inferior Vac Isp compared to the RS-25.  As I'm sure HappyMartian will remind you, the MB-60 might be an even better choice for that job.  Regardless, won't the SLS Bloc IB have such a large upper stage that it'll be straining this possibility of the core doing all but the circularization burn?  Given the SLS Bloc I will only put around 95 mt into LEO, I don't think the Bloc IB will be able to not have its upper stage do the latter part of the ascent burn.  If that's the case, then we're arguing over a matter of degrees, not some fundamental difference. 

Offline llanitedave

  • Senior Member
  • *****
  • Posts: 2286
  • Nevada Desert
  • Liked: 1545
  • Likes Given: 2052
Re: How should NASA evolve the SLS?
« Reply #339 on: 03/23/2013 01:01 am »
As much as I admire your advocating for use of the MB-60, I do have to point out that JAXA hasn't pitched in to fund its use on the SLS.  If they had I doubt any of us would be saying the Bloc IB's upper stage seems a tad underpowered, which it is.  I should also mention that I've seen a set of simulations pitting the RL-60 against the MB-60 for TLI performance, and the American rocket engine would win.  It may not have been funded to completion, but the design specs claimed would see it triumph if true.  Aside from that, just think about the politics of putting Japanese engines on the upper stage of a rocket meant to show the pinnacle of America's technical might.  It sounds like a tough sell to me. 

I pretty much agree with this.  In an ideal world, a heavy launcher would be a truly international effort, with multiple nations supplying tanks, engines, software, fairings, and even launch facilities.  But we aren't there yet, and until we are, if the SLS is a national effort, then it should use national components.  Working out a deal with ESA for solar panels is one thing, buying Russian engines is something else.

If Russia and China and Europe and India and Japan and South Korea(and hey, maybe even Iran and North Korea and Ukraine in a few years) ever become mutual stakeholders in this evolution, so much the better.  But until then, I don't think it's worth the wait.  We've got great technology here, and we need the jobs, let's use it.
"I've just abducted an alien -- now what?"

Tags:
 

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