...Or task SpaceX with making a wide LOX/CH4 fueled stage, powered by a pair of (subscale) Raptor engines...
Quote from: ncb1397 on 12/16/2017 06:59 pmReally?QuoteAccording to information the redesign reduced the number of parts needed to assemble the accumulator from twenty-eight to six, eliminated 123 welds and one bolted joint. The extensive changes would have been impractical or impossible using conventional manufacturing means, and have also reduced the unit cost by a third.https://www.nasaspaceflight.com/2017/12/rs-25-next-phase-testing-stennis-hot-fire/Not good enough. The price target is to eventually reach 50 or 60 million dollars per engine https://spaceflightnow.com/2015/11/27/aerojet-rocketdyne-wins-propulsion-contracts-worth-nearly-1-4-billion/ . Not on the initial production run either, but eventually. 200-240 million dollars per flight is still a lot of money. These upgrades can probably get them to that ballpark, but they still need another factor of 5 or so cost reduction on top of that to make SLS sorta competitive (or, at least, not have its engines for a single stage cost more than most entire launch systems). Probably the only fix viable at this point would be to implement a scaled up version of SMART engine recovery (which most Shuttle derived superheavy launchers before SLS assumed anyway, for exactly this reason)Quote from: oldAtlas_Eguy on 12/16/2017 08:33 pmIf a RFI about engines to use on EUS just came out then the pick for which engine would no t occur until contract award sometime after about 9 months from now. Putting the CDR for EUS at about 6 months later or around Apr 2019. Then 3-4 years to build/qualify and that is NET Apr 2022 to as late as Apr 2023 for delivery of first EUS flight hardware. EUS could become the critical path for SLS 1B flights.I thought they had decided on engines for EUS. This RFI says that the design work on EUS is still very preliminary and the detailed design is on hold until a decision on engines.The RFI specifies that the first 2 missions will use RL10C as previously planned, and they don't need it ready until mid-2023. So that gives some scheduling margin for the change
Really?QuoteAccording to information the redesign reduced the number of parts needed to assemble the accumulator from twenty-eight to six, eliminated 123 welds and one bolted joint. The extensive changes would have been impractical or impossible using conventional manufacturing means, and have also reduced the unit cost by a third.https://www.nasaspaceflight.com/2017/12/rs-25-next-phase-testing-stennis-hot-fire/
According to information the redesign reduced the number of parts needed to assemble the accumulator from twenty-eight to six, eliminated 123 welds and one bolted joint. The extensive changes would have been impractical or impossible using conventional manufacturing means, and have also reduced the unit cost by a third.
If a RFI about engines to use on EUS just came out then the pick for which engine would no t occur until contract award sometime after about 9 months from now. Putting the CDR for EUS at about 6 months later or around Apr 2019. Then 3-4 years to build/qualify and that is NET Apr 2022 to as late as Apr 2023 for delivery of first EUS flight hardware. EUS could become the critical path for SLS 1B flights.I thought they had decided on engines for EUS. This RFI says that the design work on EUS is still very preliminary and the detailed design is on hold until a decision on engines.
Leaving the core stage as is for the most part as is, the other possible change could be to make the side boosters either flyback or boost back. It has been demonstrated in "serial staging" by SpaceX's Falcon 9 and soon to be demonstrated by Falcon Heavy's "parallel staging". Technically feasibility is not the issue; but politically feasibility is the main question. The issue of the low flight rate may also begs the question why bother at this point?
Quote from: Rocket Science on 12/19/2017 01:29 pmLeaving the core stage as is for the most part as is, the other possible change could be to make the side boosters either flyback or boost back. It has been demonstrated in "serial staging" by SpaceX's Falcon 9 and soon to be demonstrated by Falcon Heavy's "parallel staging". Technically feasibility is not the issue; but politically feasibility is the main question. The issue of the low flight rate may also begs the question why bother at this point?The technical feasibility is certainly an issue (for launch, not landing), but the main problem is that the Congress contingent from Utah would have a fit over ditching the solids.
I'm thinking SLS may *never* have a stable configuration at this rate. Especially if you count Orion:EM-1: totally new obviouslyEuropa Clipper: first SLS 1BEM-2: first fully integrated SLS 1B/OrionEM-3: Orion gets a new main engine, new EUS engineFlight 5: RS-25EFlight 10 (maybe sooner): Castor 1200Thats 6 major redesigns/unique configurations in the first 10 flights. Not counting the minor component level upgrades needed early on by every launcher. And that still doesn't get SLS to its performance targets, so there may be even more upgrades in between/after those that NASA hasn't decided on yet!
I am sure it would be much cheaper to ask SX to quote them on 2x falcon heavy to get exploration mission components into LEO and doc them. Maybe one falcon heavy and a falcon 9 would do the job. That's about $200 mill. You could do that close to 10 times for the price of SLS. Might require a bit of rengineering on the exploration craft but got to be worth it. SLS is a bad joke from budget point of view.
Quote from: corneliussulla on 12/19/2017 05:25 amI am sure it would be much cheaper to ask SX to quote them on 2x falcon heavy to get exploration mission components into LEO and doc them. Maybe one falcon heavy and a falcon 9 would do the job. That's about $200 mill. You could do that close to 10 times for the price of SLS. Might require a bit of rengineering on the exploration craft but got to be worth it. SLS is a bad joke from budget point of view.This thread is not about SpaceX nor its ability to replace SLS. You can discuss that on 10,000 other threads.
Quote from: Rocket Science on 12/19/2017 01:29 pmLeaving the core stage as is for the most part as is, the other possible change could be to make the side boosters either flyback or boost back. It has been demonstrated in "serial staging" by SpaceX's Falcon 9 and soon to be demonstrated by Falcon Heavy's "parallel staging". Technically feasibility is not the issue; but politically feasibility is the main question. The issue of the low flight rate may also begs the question why bother at this point? A flyback stage with seven BE-4s or AR-1s or nine Raptors would allow SLS to meet it performance targets.I wonder could a modified New Glenn core be used as a booster?
I always thought that 5.5 meter diameter boosters were the largest that NASA seriously considered due to VAB or MLP constraints. But SpaceGhost1962 mentioned studying triple core 8.4 meter vehicles in the VAB, though I'm not sure how many changes that would entail.New Glenn boosters would have considerably higher thrust and ISP than the current solids. How high and fast would they stage? Does downrange landing the boosters help payload (Blue isn't planning on RTLS as far as I can tell)?
Quote from: envy887 on 12/19/2017 11:57 pmI always thought that 5.5 meter diameter boosters were the largest that NASA seriously considered due to VAB or MLP constraints. But SpaceGhost1962 mentioned studying triple core 8.4 meter vehicles in the VAB, though I'm not sure how many changes that would entail.New Glenn boosters would have considerably higher thrust and ISP than the current solids. How high and fast would they stage? Does downrange landing the boosters help payload (Blue isn't planning on RTLS as far as I can tell)?New Glenn has a max thrust 3,850,000lbs which is very close to that of the five segment RSRM which is around 3,600,000lbs.They would stage higher and faster but probably not as much as the Dynetics Pyrios booster would have since they would normally be saving some of the propellant for landing.You probably could deal with it by just throttling back the RS-25s for part of the flight .
New Glenn has a max thrust 3,850,000lbs which is very close to that of the five segment RSRM which is around 3,600,000lbs.They would stage higher and faster but probably not as much as the Dynetics Pyrios booster would have since they would normally be saving some of the propellant for landing.You probably could deal with it by just throttling back the RS-25s for part of the flight .
Quote from: Patchouli on 12/20/2017 01:48 amNew Glenn has a max thrust 3,850,000lbs which is very close to that of the five segment RSRM which is around 3,600,000lbs.They would stage higher and faster but probably not as much as the Dynetics Pyrios booster would have since they would normally be saving some of the propellant for landing.You probably could deal with it by just throttling back the RS-25s for part of the flight .At shutdown it'll be producing a lot of thrust still (while solids "throttle" almost to zero), unless they shut down all but the center engine or something. This was a problem for all previously-studied liquid boosters, the loads from the boosters pushing on the core stage just before BECO are too high. Even with RSRMV they've already had to alter the core stage throttle profile to mitigate this, but with any liquid option they'll probably have to add a 5th RS-25 to minimize the relative acceleration (and, unless thats coupled with some sort of engine reuse, this only exacerbates the most critical cost and schedule problem of the program)
Quote from: brickmack on 12/20/2017 03:59 amQuote from: Patchouli on 12/20/2017 01:48 amNew Glenn has a max thrust 3,850,000lbs which is very close to that of the five segment RSRM which is around 3,600,000lbs.They would stage higher and faster but probably not as much as the Dynetics Pyrios booster would have since they would normally be saving some of the propellant for landing.You probably could deal with it by just throttling back the RS-25s for part of the flight .At shutdown it'll be producing a lot of thrust still (while solids "throttle" almost to zero), unless they shut down all but the center engine or something. This was a problem for all previously-studied liquid boosters, the loads from the boosters pushing on the core stage just before BECO are too high. Even with RSRMV they've already had to alter the core stage throttle profile to mitigate this, but with any liquid option they'll probably have to add a 5th RS-25 to minimize the relative acceleration (and, unless thats coupled with some sort of engine reuse, this only exacerbates the most critical cost and schedule problem of the program)The F-1B only had two throttle settings, and the lowest was 72% of max. And with two off-center engines on Pyrios they could not shut some of them down to "throttle".BE-4 will throttle much lower, somewhere around 30%, and is much more controllable since it's a requirement for landing. If they need to, they can shut down 2, 4 or 6 engines leading up to separation. The extra 80+ seconds of burn time will allow the RS-25s to burn an extra 140 tonnes of fuel, increasing the core stage TWR at booster sep and further reducing the difference in acceleration of the boosters and core.With the relatively slow liftoff (~1.23 TWR at liftoff) and the large mass of the core stage (at staging it will mass 50% more than two NG upper stages), the boosters should be going fairly slow at staging compared to New Glenn, although much faster than RSRMs will be. I figure about 2.3 km/s at booster sep for NG booster SLS, vs 2.5 km/s for NG, vs 1.4 km/s for RSRM boosted SLS.The extra velocity at staging with NG boosters is sufficient to put the entire EUS and Orion in orbit with only a small circularization burn from the EUS (even with downrange recovery of the boosters).
Quote from: envy887 on 12/20/2017 12:59 pmQuote from: brickmack on 12/20/2017 03:59 amQuote from: Patchouli on 12/20/2017 01:48 amNew Glenn has a max thrust 3,850,000lbs which is very close to that of the five segment RSRM which is around 3,600,000lbs.They would stage higher and faster but probably not as much as the Dynetics Pyrios booster would have since they would normally be saving some of the propellant for landing.You probably could deal with it by just throttling back the RS-25s for part of the flight .At shutdown it'll be producing a lot of thrust still (while solids "throttle" almost to zero), unless they shut down all but the center engine or something. This was a problem for all previously-studied liquid boosters, the loads from the boosters pushing on the core stage just before BECO are too high. Even with RSRMV they've already had to alter the core stage throttle profile to mitigate this, but with any liquid option they'll probably have to add a 5th RS-25 to minimize the relative acceleration (and, unless thats coupled with some sort of engine reuse, this only exacerbates the most critical cost and schedule problem of the program)The F-1B only had two throttle settings, and the lowest was 72% of max. And with two off-center engines on Pyrios they could not shut some of them down to "throttle".BE-4 will throttle much lower, somewhere around 30%, and is much more controllable since it's a requirement for landing. If they need to, they can shut down 2, 4 or 6 engines leading up to separation. The extra 80+ seconds of burn time will allow the RS-25s to burn an extra 140 tonnes of fuel, increasing the core stage TWR at booster sep and further reducing the difference in acceleration of the boosters and core.With the relatively slow liftoff (~1.23 TWR at liftoff) and the large mass of the core stage (at staging it will mass 50% more than two NG upper stages), the boosters should be going fairly slow at staging compared to New Glenn, although much faster than RSRMs will be. I figure about 2.3 km/s at booster sep for NG booster SLS, vs 2.5 km/s for NG, vs 1.4 km/s for RSRM boosted SLS.The extra velocity at staging with NG boosters is sufficient to put the entire EUS and Orion in orbit with only a small circularization burn from the EUS (even with downrange recovery of the boosters).Now if we can recover the core main engines in a "pod" as has been studied over the years we will begin to see potentially real cost savings in the out years with a flyback/boostback architecture...