Is the configuration of SLS/Ares V (large hydrolox core with large solid boosters) mostly a result of the need to use existing shuttle infrastructure, or is it a reasonable HLV design in it's own right?
Quote from: mcdouble on 04/08/2017 06:24 amIs the configuration of SLS/Ares V (large hydrolox core with large solid boosters) mostly a result of the need to use existing shuttle infrastructure, or is it a reasonable HLV design in it's own right?... the RAC-2 kerosene/LOX designs had lower long-term costs, but, critically, they would have cost more to develop because the needed engines didn't exist.
SLS is the design you end up with when you start with RS-25 engines. They are such high-performers that the optimum design wants them to burn a lot of propellant. High-thrust boosters are needed to get the resulting "sustainer" stage started.
Quote from: edkyle99 on 04/18/2017 10:24 pmSLS is the design you end up with when you start with RS-25 engines. They are such high-performers that the optimum design wants them to burn a lot of propellant. High-thrust boosters are needed to get the resulting "sustainer" stage started.Wouldn't it make quite a good upper stage engine for an HLV? More than double the thrust of J-2 used on Saturn V, and 30s better ISP.
Quote from: ArbitraryConstant on 04/19/2017 02:19 amQuote from: edkyle99 on 04/18/2017 10:24 pmSLS is the design you end up with when you start with RS-25 engines. They are such high-performers that the optimum design wants them to burn a lot of propellant. High-thrust boosters are needed to get the resulting "sustainer" stage started.Wouldn't it make quite a good upper stage engine for an HLV? More than double the thrust of J-2 used on Saturn V, and 30s better ISP.Cannot be airstarted without an expensive, major redesign.
Quote from: edkyle99 on 04/18/2017 10:24 pmQuote from: mcdouble on 04/08/2017 06:24 amIs the configuration of SLS/Ares V (large hydrolox core with large solid boosters) mostly a result of the need to use existing shuttle infrastructure, or is it a reasonable HLV design in it's own right?... the RAC-2 kerosene/LOX designs had lower long-term costs, but, critically, they would have cost more to develop because the needed engines didn't exist.... and Aerojet/Rocketdyne, the maker of the RS-25, is building AR-1, at government expense, which was one of the "needed engines", that will soon exist ... and might not have a use.We've come full circle.
Quote from: Space Ghost 1962 on 04/19/2017 12:47 amQuote from: edkyle99 on 04/18/2017 10:24 pmQuote from: mcdouble on 04/08/2017 06:24 amIs the configuration of SLS/Ares V (large hydrolox core with large solid boosters) mostly a result of the need to use existing shuttle infrastructure, or is it a reasonable HLV design in it's own right?... the RAC-2 kerosene/LOX designs had lower long-term costs, but, critically, they would have cost more to develop because the needed engines didn't exist.... and Aerojet/Rocketdyne, the maker of the RS-25, is building AR-1, at government expense, which was one of the "needed engines", that will soon exist ... and might not have a use.We've come full circle. They wouldn't have passed the NASA's reliability requirements, which put too much emphasis on the turbopumps and number of nozzles.
Thus, Even the RD-180 was considered completely unsafe if used on big numbers.
But solids were OK since they are so simple, right?
All part of the thumbs in the scale that SLS RAC process was.
The only engine that might have passed their "safety" requirements were the F-1B. The AR-500 (as was called at that time) most surely wouldn't.
And yes, I have an issue of claiming ridiculous safety levels and then killing the effective numbers with requirement creep and stack complexity.
I'm on the KISS fence.
...At the time NASA was facing a growing realization after so many cancelled efforts that lifecycle cost "doesn't matter" - gov't funding profiles and year-to-year appropriations never allow for the kinds of funding peaks and long term decision-making that lead to efficiency in long term programs, so they decided instead to go for the option that got the nearest term success (equating that to political sustainability) and could be executed under a flat budget profile (political reality). Shuttle derived was the only solution that fit that criteria.
Seeing that Project Constellation was looking at 6 RS-68 engines for the core, which would have been less expensive and more powerful than RS-25, how did SLS get to looking at 4-6 RS-25 engines?Was it merely ablative(RS-68) vs. regenerative nozzle(RS-25) cooling?Thank you In Advance.
Quote from: Hog on 05/27/2017 06:08 pm Seeing that Project Constellation was looking at 6 RS-68 engines for the core, which would have been less expensive and more powerful than RS-25, how did SLS get to looking at 4-6 RS-25 engines?Was it merely ablative(RS-68) vs. regenerative nozzle(RS-25) cooling?Thank you In Advance.As noted above, RS-68 would require some changes, although man-rating wouldn't be needed for Ares V. The real reason Ares V needed 6 uprated RS-68 was that it's payload dwarfed anything SLS will lift. It was designed to put almost triple the mass of a SLS Block 1 payload to TLI. and almost double SLS Block 1B.