You could fit 5x RS-68s on an 8.4m corestage. But; I'd worry about their exhaust impinging on the SRB plumes and the outer four impinging on the center engine's output and efficiency, which reportedly did happen to an extent to the 10-meter diameter Saturn V. In relation to this, NASA's Ares V team has reportedly changed the engine layout to a "ring" configuration (see attached) to minimise this prospect. Not to mention that 5x RS-68s would drain an 8.4m stage's propellants pretty damn quickly. Would an 8.4m, 5-engine corestage have to be stretched ridiculously to get a decent propellant burntime? Or could you get around that by having a more powerful, capacious upper stage and/or third stage?
I'd think having 4x RS-68s with the maximum, practical stretched corestage might be a good compromise, along with the standard 4-segment SRBs. To get closer to their original payload requirement NASA would likely then need the lately-discussed, second upperstage with its 3x or even 4x J-2X. Would this second, upper stage have a short burntime, because of the need to restrict it's height for the VAB limitations, with the final, 1x J-2X EDS on top?
Incidentally, I still think the 3x RS-68 Jupiter 232 is the best compromise, particularly if those RS-68s become optimised, regeneratively-cooled versions.
Yinzer, Don't forget that we've been proposing to use a "Wide Body Centaur" for the Upper Stage of Jupiter-232 anyway. So such a development investment is broadly "equal" for either program. The physical size of a new stage makes almost no difference in terms of development cost. That decision would mean the only major development cost delta between Atlas and DIRECT would be the re-development of the External Tank into the Core for Jupiter and the development of the J-2X which is already well underway. Ross.Edited by kraisee 7/1/2008 1:33 AM
Quoteyinzer - 7/1/2008 3:23 AM Referring to the Jupiter Upper Stage as a "Wide Body Centaur" is a bit of a stretch, don't you think? It's three times the diameter of the existing Centaur and twice that of the Lockheed-proposed WBC. This will make it harder to have the stage be structurally stable when sitting on the launch pad like the Lockheed one is supposed to be. It's also going to have something like five times the installed thrust. New engines. More extensive pad modifications (an Atlas WBC can use the same launch pad as the Common Centaur), etc.We sourced numbers and details directly from Lockheed's Centaur Development Team for it. Jupiter's U/S is an 8.41m diameter version of Lockheed's Wide Body Centaur, with J-2X engines instead of RL-10's. Lockheed provided us with details and confirmed that the design is quite viable. (EDIT: and masses an awful lot less than what we are actually claiming too!) We have been planning an ICES variant of the WBC ever since we started work on v2.0 of the DIRECT proposal because it offers the best boiloff characteristics of any stage and boiloff was a very high priority for us. Though, at 8.41m diameter, our U/S will not fly on any existing Atlas. Ross.Edited by kraisee 7/1/2008 6:32 AM
yinzer - 7/1/2008 3:23 AM Referring to the Jupiter Upper Stage as a "Wide Body Centaur" is a bit of a stretch, don't you think? It's three times the diameter of the existing Centaur and twice that of the Lockheed-proposed WBC. This will make it harder to have the stage be structurally stable when sitting on the launch pad like the Lockheed one is supposed to be. It's also going to have something like five times the installed thrust. New engines. More extensive pad modifications (an Atlas WBC can use the same launch pad as the Common Centaur), etc.
Trever - 13/1/2008 10:11 AMAs far as I’m aware, the Atlas program has never taken a serious look at the implications of flying a WBC on an in-line SDV such as J-232 and thus I have no idea where the Direct team would have gotten good cost estimates.
One can say similar things about a lot of the rest of the J-232 concept. For example, the RS68 is an engine designed to fly with the environments of up to 3 side by side engines, or a single engine surrounded by 4 small SRB’s. It is likely to require significant redesign and certainly requalification to fly 3 RS68’s near two 2.5m lb SRB’s. This is not today’s RS68 or even the RS68A or even a human rated RS68 flying on Delta.
The above is not intended to mean that the J-232 can’t be developed, just that there are significant technical hurdles to its development.
Trever - 13/1/2008 10:11 AM I’m talking about almost all subsystems being identical to today’s flight certified Centaur subsystems: Avionics: FTINU, remote data unit, snip Flight software
clongton - 13/1/2008 9:54 AMThe upper stage of the J-232 is not only based on a variation of the WBC/ICES, it was designed in conjunction with efforts of members of the Atlas Advanced Systems Development team at LM. We contacted them and asked for their participation in the design effort. They agreed and looked very carefully at it, making suggestions, asking questions, offering alternatives, adjudicated discrepancies, ran analysis after analysis, etc, etc; everything you would expect design team participants to do. In the end, it was they who judged the design to be a workable variant to the WBC/ICES. It was they who provided us with the performance numbers, anticipated costs and masses, and it was they who did the analysis to provide the pmf.
HIP2BSQRE - 13/1/2008 10:31 AMA problem with Direct is that the proponents can claim almost anything since they can say work and data is secret and thus inscrutable.I belive that Direct has been very open with thier numbers and data. If you want thier numbers just ask them. Just remembert that they cannot give you thier contacts. Now--looking at NASA---have they given thier numbers for Ares I and Ares V? Nope. :angry: I did a Freedom of Information Request for the Appendixs that came from the ESAS Study--No response. You can do one yourself and see what you get? Ask NASA for their currant numbers on Ares I, and tell us your response. I believe NASA engineers are the best out there. They have been told to make a PIG fly and they will make it fly. Is it the best solution? I don't think so! Ten years from now when people look at Ares I, what do they think they will say? They will say how did NASA commit $10B+ and to a vicheal that may be flying for 10+ years in that 6 month study? And even when they relized that the study had got things wrong, why did they not go and re-evaluate the program? Ares I might be a classical study why big engineering and IT projects fail---not willing to re-evaluate you assumptions and the choices that you have made, when you relize early that you have major problems.
Norm Hartnett - 13/1/2008 1:23 PMTrever could you clarify a couple of points for me?Your concern about the environment that the RS68s would be operating in would seem to apply to both the DIRECT and Constellation program wouldn’t it? The environment that the Jupiter 120 and 232 would be operating in would seem to be, if anything, somewhat more benign that that of the Ares V. While the DIRECT Team is claiming that they can operate with the existing RS68 and accelerate the fielding of the Jupiter 120, even if they are incorrect wouldn’t the delay and additional cost of developing the enhanced RS68 still be less than the current Constellation program?Your concerns about the claims of the DIRECT Team’s EDS may be valid, but even if they need to return to a clean sheet design they are in no worse a situation than NASA is with their Ares EDS development. If the claims can be taken as accurate for the performance of the Jupiter 230 and for the overall cost savings of the program wouldn’t DIRECT actually leave NASA with sufficient margin in lift, time, and cost to address these EDS concerns?
SMetch - 13/1/2008 7:28 PMFor those who selected;“If accepted the DIRECT would require major overhaul.”…. could you elaborate on the areas in the DIRECT v2 proposal that would require a ‘major overhaul’. Unlike what happened to Skip recently we believe that informed disagreement makes a concept stronger not weaker. It’s our secret weapon don’t tell NASA upper management.
JonSBerndt - 12/1/2008 11:55 AMQuoteclongton - 12/1/2008 10:21 AMQuoteYegor - 12/1/2008 11:00 AMHmm… All of sudden the number of people voted “If accepted the DIRECT would require major overhaul” doubled overnight (somewhere from midnight – in a very short time) from 19 to 38. When “If accepted the DIRECT would require only sensible, peer-studied changes” gain only 10% - 11 more votes at the same time.IMHO there is something fishy in this.Why would you say that? It's pretty standard that when it comes to polling, a lot of people don't make up their minds until they see some of the early responses. There is something to be said for listening a LOT before you open your mouth. In actual matter of fact, DIRECT actually got its start that way. There was a WHOLE LOT of listening to people who know what they're talking about before the design even began to gel.It does sort of seem strange. Particularly if no other votes were cast for the other items in the same overnight period - especially considering this poll has already been out there for a while.Jon
clongton - 12/1/2008 10:21 AMQuoteYegor - 12/1/2008 11:00 AMHmm… All of sudden the number of people voted “If accepted the DIRECT would require major overhaul” doubled overnight (somewhere from midnight – in a very short time) from 19 to 38. When “If accepted the DIRECT would require only sensible, peer-studied changes” gain only 10% - 11 more votes at the same time.IMHO there is something fishy in this.Why would you say that? It's pretty standard that when it comes to polling, a lot of people don't make up their minds until they see some of the early responses. There is something to be said for listening a LOT before you open your mouth. In actual matter of fact, DIRECT actually got its start that way. There was a WHOLE LOT of listening to people who know what they're talking about before the design even began to gel.
Yegor - 12/1/2008 11:00 AMHmm… All of sudden the number of people voted “If accepted the DIRECT would require major overhaul” doubled overnight (somewhere from midnight – in a very short time) from 19 to 38. When “If accepted the DIRECT would require only sensible, peer-studied changes” gain only 10% - 11 more votes at the same time.IMHO there is something fishy in this.
Yegor - 13/1/2008 10:34 PMQuoteJonSBerndt - 12/1/2008 11:55 AMQuoteclongton - 12/1/2008 10:21 AMQuoteYegor - 12/1/2008 11:00 AMHmm… All of sudden the number of people voted “If accepted the DIRECT would require major overhaul” doubled overnight (somewhere from midnight – in a very short time) from 19 to 38. When “If accepted the DIRECT would require only sensible, peer-studied changes” gain only 10% - 11 more votes at the same time.IMHO there is something fishy in this.Why would you say that? It's pretty standard that when it comes to polling, a lot of people don't make up their minds until they see some of the early responses. There is something to be said for listening a LOT before you open your mouth. In actual matter of fact, DIRECT actually got its start that way. There was a WHOLE LOT of listening to people who know what they're talking about before the design even began to gel.It does sort of seem strange. Particularly if no other votes were cast for the other items in the same overnight period - especially considering this poll has already been out there for a while.JonThe majority of people voted in the first couple of days. Then there was something like 7 votes a day. “If accepted the DIRECT would require major overhaul” was getting steady 10% of votes all that time.Then all of sudden 30 new people voted overnight where “If accepted the DIRECT would require major overhaul” got 65% of votes. In that “If accepted the DIRECT would require major overhaul” number doubled. Then again there were 7 votes a day with the old distribution.1. Unusually high activity in a short time period.2. Totally different distribution.3. Out of 19 peoples voted “If accepted the DIRECT would require major overhaul” just one voiced his opinion.IMHO with the probability of 99% these votes were fabricated – someone just created many user profiles and voted.