A few reasons:1. Whoever ever took a look into the Augustine report (just review page 87...) should know that a 5 RS-68B Ares V Lite based SHLV received a ringing endorsement by the report over any SSME-based SDLV.2. NASA likes the concept. They want as big an HLV (with growth option) as they can get. A 5 RS-68B, 5-segment SRB Ares V Lite provides 145mt to LEO AND still offers 20% in growth at a later stage.3. The RS-68B development effort just has a bigger lobby (at MSFC, at Rocketdyne, at NASA headquarters, in other industry lobbyists) behind it vs. an RS-25e development effort.This is my opinion. If Ares I is canceled and an SHLV only is developed, it will be a RS-68 based, 5-segment, J-2x rocket.
The RS-68B would not be an option due to base heating. You would have to develop a regen version.
The problem comes in that anything based on the RS-68 will not be a SDHLV, but an all new design, new 10m tank. NASA's reports already discuss in detail the performance loss with the RS-68 in detail. Add to it that the Ares V Lite can only lift 145mT vs the Ares V Classic which could do 155mT, to start.
No, NASA is ordered to close the gap, and closing the gap means SSME at this point. They no longer have the time to develop the RS-68 Regen and the 10m tank. If they had begun work in '07, sure, but they wasted time on the Ares I instead.
Analyst has a point. I've been looking at the EELV's, and they could do the growth into HLV if need be.
1. 10m tank - yes.2. Performance loss compared to what? Compared to a 5 SSME based 8.4m Ares V? Not really. Please provide a link for the Ares V Classic (5segment SRB, 5 SSME at core stage, J2x upper stage) having a 155mt lift capacity.
Quote from: ares-mojo on 12/29/2009 12:25 pm1. 10m tank - yes.2. Performance loss compared to what? Compared to a 5 SSME based 8.4m Ares V? Not really. Please provide a link for the Ares V Classic (5segment SRB, 5 SSME at core stage, J2x upper stage) having a 155mt lift capacity. The performance loss is in isp. RS-68 has less isp than SSME, hence the need for a 10m tank to make up.
Quote from: ares-mojo on 12/29/2009 08:21 amA few reasons:1. Whoever ever took a look into the Augustine report (just review page 87...) should know that a 5 RS-68B Ares V Lite based SHLV received a ringing endorsement by the report over any SSME-based SDLV.2. NASA likes the concept. They want as big an HLV (with growth option) as they can get. A 5 RS-68B, 5-segment SRB Ares V Lite provides 145mt to LEO AND still offers 20% in growth at a later stage.3. The RS-68B development effort just has a bigger lobby (at MSFC, at Rocketdyne, at NASA headquarters, in other industry lobbyists) behind it vs. an RS-25e development effort.This is my opinion. If Ares I is canceled and an SHLV only is developed, it will be a RS-68 based, 5-segment, J-2x rocket.The problem is none of these statements have any real meat behind it (obviously you do say it is your opinion) besides *I want a giant mega booster for some reason* and ignore economics, infrastructure changes, facility and tooling changes and, perhaps most importantly, using what we have now that would not require as much development money and a heavily loaded development schedule. Basically, the exact same plan now just sans Ares 1.
This is not correlating well with reality. "Closing the gap" (at least in the sense you appear to use the term "gap") isn't possible. If we are talking about US HSF, there is no gap (US astronauts will fly continuously to the ISS), if we are talking about a US launch vehicle with US manned spacecraft, the gap will not be closed by a SHLV development program but either by Ares I/Orion or by a commercial US dedicated CLV alternative. If we are talking "programmatic gap", we need to look to the end of the ISS program and the start of exploration, in which case there is no reason at all to go for a SSME-based 8.4m core HLV just for schedule reasons over an RS-68B 10m HLV. We'll start operating an HLV at the end of the next decade at the earliest (budget wise) no matter what (yes, I know some folks disagree, but reality dictates that we won't have a 100mt+ vehicle ready before 2018+ AND have lunar hardware or other deep space hardware ready).
Quote from: OV-106 on 12/29/2009 12:29 pmQuote from: ares-mojo on 12/29/2009 08:21 amA few reasons:1. Whoever ever took a look into the Augustine report (just review page 87...) should know that a 5 RS-68B Ares V Lite based SHLV received a ringing endorsement by the report over any SSME-based SDLV.2. NASA likes the concept. They want as big an HLV (with growth option) as they can get. A 5 RS-68B, 5-segment SRB Ares V Lite provides 145mt to LEO AND still offers 20% in growth at a later stage.3. The RS-68B development effort just has a bigger lobby (at MSFC, at Rocketdyne, at NASA headquarters, in other industry lobbyists) behind it vs. an RS-25e development effort.This is my opinion. If Ares I is canceled and an SHLV only is developed, it will be a RS-68 based, 5-segment, J-2x rocket.The problem is none of these statements have any real meat behind it (obviously you do say it is your opinion) besides *I want a giant mega booster for some reason* and ignore economics, infrastructure changes, facility and tooling changes and, perhaps most importantly, using what we have now that would not require as much development money and a heavily loaded development schedule. Basically, the exact same plan now just sans Ares 1. I recommend that you look at the AC report in detail again. I know people around here think it is a flawed report and everyone has long forgotten about it already, but that is just not the case. There are valid reasons why the conclusions in the report were made - including taking into account infrastructure changes, facility and tooling changes, development schedule, risk assessment, schedule etc. etc.And yes, what I said is basically the current plan without Ares 1. Do I think this would be the best way forward back in 2004/2005? No. But I strongly believe this is what NASA, the WH and Congress will go for.
If this wasn't the best way forward in 2004/2005, then why on earth would it be the best way forward in 2009 when the situation is even more urgent?
10m RS-68B just wins the trade.
Quote from: OV-106 on 12/29/2009 12:39 pmIf this wasn't the best way forward in 2004/2005, then why on earth would it be the best way forward in 2009 when the situation is even more urgent?Decisions have been made already, development contracts awarded, program continuity is more important than getting it right "perfectly" by canceling everything just to go for an architecture that we right now believe fits the budget we expect to have in the next 10 years best. The programmatic risk for a complete architecture change is just too high. A lot of Ares I development work can be salvaged. The question that really remains is 8.4m SSME-core or 10m RS-68B core and due to schedule not being a factor any more for HLV development (we got 10 years in any event), 10m RS-68B just wins the trade.
Quote from: ares-mojo on 12/29/2009 12:54 pmQuote from: OV-106 on 12/29/2009 12:39 pmIf this wasn't the best way forward in 2004/2005, then why on earth would it be the best way forward in 2009 when the situation is even more urgent?Decisions have been made already, development contracts awarded, program continuity is more important than getting it right "perfectly" by canceling everything just to go for an architecture that we right now believe fits the budget we expect to have in the next 10 years best. The programmatic risk for a complete architecture change is just too high. A lot of Ares I development work can be salvaged. The question that really remains is 8.4m SSME-core or 10m RS-68B core and due to schedule not being a factor any more for HLV development (we got 10 years in any event), 10m RS-68B just wins the trade.I don't know jack about chemical rocket engineering, so I probably shouldn't voice an opinion about this, but I have to agree somewhat with ares-mojo for the following reasons:1. According to the Obama/Bolden meeting "leak" (to the best of my knowledge), the President looked at four options, and all without Ares 1 in them. So the consensus is that Ares 1 is headed for the scrap-pile, but most of the work can be salvaged if:2. A "simpler" heavy-lift launch vehicle is chosen, which in local parlance means an "Ares V lite" or whatever "lite" means.Thus this:3. The date for the "simpler" HLV is 2018, so eight to nine years, more likely ten given the budget. So this fits in ares-mojo time frame for the 10m RS-68B since the lead time is ten years anyway.But the "simpler" could really mean the 8.4m SSME core, so this falls well within 8-9 years.Just MHO y'see.But these "leaks" have a purpose. Does that mean they come true?No.But I give it 60/40.
Your tag line at the bottom is "if it ain't broke, don't fix it". Why front load a new HLV with more development, where major problems can always arise, if not necessary? We have the tooling for an 8.4 meter core now. We have SSME's where it has been studied for years on how to make expendable versions. We have all the infrastructure in place to accomodate that configurationm, etc. So use 5 segment boosters someday if necessary, fine and that gives you a little more performance. However, those are not ready and we have 4 segments today. The simple fact is there is no reason to throw the baby out with the bath water and fund MSFC for a decade to maybe eventually field a new mega booster that will not be cost effective when complete just because MSFC employees *think* we need it. This is about power at their center and their center alone. Don't fool yourself that it is anything else.