I think there needs to be a defined mission before the LV is evolved.
The first step would be to upgrade the "figure of merit" measure by which alternatives are analysed. For SLS as NASA intends to use it, mass delivered to LEO is not as useful a measure as mass delivered to a cis-lunar rendezvous orbit.
I would also fund a common CPS between the EELVs and SLS on the theme of ULA's ACES system. By sharing the U/S development costs with DoD for the EELV Phase-I project, more cash can be spared for payloads. It would not greatly impair the performance of SLS as the SLS core could launch the entire spacecraft/ACES combo into initial parking orbit with little or no use of the CPS's engines. So, you'd be able to get the full 40t+ through escape.
So the question again is, how would you evolve the SLS for NASA's maximum benefit?
My understanding of the current SLS evolution path was this (excuse me if I'm wrong).Block-I - Three SSMEs, iCPS (modified DCSS) and 5-seg RSRM-V solid boosters; 70t IMLEO, 30t TLIBlock-IA - Four or five RS-25E, CPS and 5-seg RSRM-V; 105t IMELO, 40t+ TLIBlock-IB - As Block-IA but with Next-generation boosters (NGBs); 120t IMLEO, 50t TLIBlock-II - Includes 3 x J-2X upper stage & CPS becomes third stage, if included in stack; 130t IMLEO
Quote from: Hyperion5 on 12/06/2012 11:28 pmSo the question again is, how would you evolve the SLS for NASA's maximum benefit? Develop Block I, then add an improved second stage to make Block 1B. The result will be a highly capable launch vehicle, the world's most capable, developed using propulsion that essentially already exists. After that, stop forever "developing" and just fly the thing.
My understanding of the current SLS evolution path was this (excuse me if I'm wrong).Block-I - Three SSMEs
Quote from: Ben the Space Brit on 12/07/2012 09:45 amMy understanding of the current SLS evolution path was this (excuse me if I'm wrong).Block-I - Three SSMEsI wish that were true, but am pretty sure the plan of record calls for all of the initial SLS cores to fly with four SSME. With four per vehicle, NASA will need to "upgrade" to new-production core engines sooner.
Boeing's already designing for a Block 1B Core Stage, which envelopes Block 1A loads as well. So the real question is how do you get from a Block 1B vehicle to a Block 2 vehicle? I think given the current funding levels, NASA will figure out how to "shoe-horn" a Block 2 Core Stage from the Block 1B design through some combination of load reduction (uncertainty reduction from flight data from the first couple of Block 1 launches), reduced factors of safety, modification of the trajectory, etc...
Quote from: Hyperion5 on 12/06/2012 11:28 pmSo the question again is, how would you evolve the SLS for NASA's maximum benefit? Develop Block I, then add an improved second stage to make Block 1B. The result will be a highly capable launch vehicle, the world's most capable, developed using propulsion that essentially already exists. After that, stop forever "developing" and just fly the thing. - Ed Kyle
Once evaluations have been done, NASA will choose what will succeed Block 1, Block 1A or Block 1B. And then they’ll choose what succeeds that. A “Block IIB” would probably add powerful enough advanced boosters to Block 1B in order to get 130mt to LEO, and then they can eliminate the current PoR of a 5th RS-25 and the J2X powered Large upper stage. I think the current Block II PoR concept was before Dynetics came out with their super booster concept that opened the door to the boosters being powerful enough to not have to upgrade the core again and develop a brand new J2X powered Large upper stage. And I’d be pretty surprised if it didn’t get axed soon considering the developments over the last year, and replaced with basically a Block II with powerful enough advanced boosters to only need a new Block 1B style upper stage, and the same four RS-25’s on the core as Block 1. But that will probably wait until NASA’s finished with it’s evaluations of the different 1A and 1B options. And that’s really the best way to go. That means the core only gets designed once, and is designed for the Block 1B or 1A loads (although the booster interfaces will need to be upgraded for the advanced boosters). One new upper stage, and that’s it. That drops several development paths from the current Block II PoR.
Quote from: edkyle99 on 12/07/2012 02:50 pmQuote from: Hyperion5 on 12/06/2012 11:28 pmSo the question again is, how would you evolve the SLS for NASA's maximum benefit? Develop Block I, then add an improved second stage to make Block 1B. The result will be a highly capable launch vehicle, the world's most capable, developed using propulsion that essentially already exists. After that, stop forever "developing" and just fly the thing. - Ed KyleATK isn't advantaged in the booster comp. That's the law. It has to be fair. It doesn't matter if it benefits NASA. It matters that private companies get a fair chance to break this booster monopoly that's older than I am.
So compete the five-segment boosters. ATK doesn't have to build them. Just don't spend $10 billion more, or whatever, to develop an all-new design, again.