Quote from: davey142 on 03/20/2013 10:46 pmQuote from: deltaV on 03/20/2013 02:28 pmQuote from: davey142 on 03/20/2013 10:55 amHow 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.
Quote from: deltaV on 03/20/2013 02:28 pmQuote from: davey142 on 03/20/2013 10:55 amHow 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!
Quote from: davey142 on 03/20/2013 10:55 amHow 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?
How would NASA convince congress (especially the Senate) to allow them to use a foreign engine, especially one from Russia?
Quote from: davey142 on 03/20/2013 10:46 pmQuote from: deltaV on 03/20/2013 02:28 pmQuote from: davey142 on 03/20/2013 10:55 amHow 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.
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).
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.
Quote from: Lobo on 03/22/2013 03:50 pmYou 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.jpghttp://www.directlauncher.org/documents/Baseball_Cards/J247H-41.5003.08001_EDS_090608.jpgNotice 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.jpgBased 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.jpgSo 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."
Quote from: MP99 on 12/31/2012 10:25 am....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 LaunchAt: 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 ofA Study of CPS Stages for Missions beyond LEO By Mark Schaffer May 16, 2012At: 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. .....
....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.
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.
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.
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.
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...
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.
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.
How many times do we want to design an SLS upper stage?
An upper stage with two J-2Xs seems to be a bit more reasonable, especially if the LRBs are likely.
Could an upper stage with two J-2Xs also have two RL10s?Edited.
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”.
Quote from: TomH on 03/22/2013 06:54 pmI 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...
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.
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.
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.
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.
SLS [...] 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?
I think you are a nice guy, but I respectfully disagree with your propositions. In the SLS paradigm, they are not a logical fit.
Quote from: Hyperion5 on 03/22/2013 09:31 pmIt 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?
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.
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.