Did you ever model a 7 RS-25 core? If so could you point to it?
Since higher thrust, regenerative nozzle RS-68s are presumably out of the question; how feasible/plausible is it that a further iteration of RS-25 could be developed that would notably upgrade the engine in thrust, whilst losing the minimal amount of specific impulse or reliability? Is running them at 115%, 120 or even 130% percent of original design thrust a realistic goal? I think I read in old Shuttle literature that original Block-1 engines were tested to destruction at close to 120% percent throttle settings?
Just reading up on the RS-25, formerly known also as the SSME. This machine is so remarkable as to almost defy belief. The complex plumbing, hydraulic system and helium system all had to come together to work flawlessly over immense temperature ranges. Also to be able to handle the phase change from liquid to gas at the appropriate places and times.So it amazes me even more that NASA would decide that this highly complex and expensive machine could be thrown away. After the various upgrades to the block II version, it seems they were near to the goal of 60 full duration (shuttle 8.5 minutes) firings before major overhaul.
Just reading up on the RS-25, formerly known also as the SSME.
I do remember that early in Constellation they dropped the idea of making it restartable in favor of the J-2X (I think). I guess the complexity of the engine would make that expensive-to-near- impossible. Yet I will still hold out hope.
Always known as RS-25. Latest model is RS-25D. SSME is a categorization of all models. Proposed disposable replacement is designated RS-25E.
Very complex, very expensive. Not at all worth it.
Two points.1. Just because it is an amazing technical achievement does not mean that it is good fit going forward. SLS is really a custom design around it - it makes no sense on any other existing or near future launch vehicle. The liquid propulsion market appears to be shifting towards more affordable and reusable (restart-able) engines.2. Sunk cost fallacy. What is spent on a project is spent. If another choice makes more sense going forward, then it makes sense to put the RS-25 to pasture. (as sad as it sounds)
That's the part I am trying to pin down a bit more. What exactly is required for restart?
. But if spin-up is an issue, could electric spin-up be an option? If they can get a Tesla to go from 0 to 60 in 2.5 seconds, I would think it might not be inconceivable to carry enough power for 4 engine restarts in batteries. (trying to think outside the box).
Quote from: Lars-J on 03/07/2017 10:30 pmTwo points.1. Just because it is an amazing technical achievement does not mean that it is good fit going forward. SLS is really a custom design around it - it makes no sense on any other existing or near future launch vehicle. The liquid propulsion market appears to be shifting towards more affordable and reusable (restart-able) engines.2. Sunk cost fallacy. What is spent on a project is spent. If another choice makes more sense going forward, then it makes sense to put the RS-25 to pasture. (as sad as it sounds)Point 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.
Point 2 - But the RS-25 actually exists and the production line will exist, so we are NOT talking about past costs. And I am just asking if the reusability feature available can be applied to a smaller vehicle, one that would possibly be more likely to be used. This all assumes the 60 flight before overhaul became reality.
Quote from: TomH on 03/08/2017 12:06 amAlways known as RS-25. Latest model is RS-25D. SSME is a categorization of all models. Proposed disposable replacement is designated RS-25E.RS-25 was the Rocketdyne designation, SSME was what NASA called it. For SLS, NASA calls it RS-25, but no distinction is made between RS-25D and E (just remaining inventory and new production units)
Quote from: robert_d on 03/08/2017 04:21 pmQuote from: Lars-J on 03/07/2017 10:30 pmTwo points.1. Just because it is an amazing technical achievement does not mean that it is good fit going forward. SLS is really a custom design around it - it makes no sense on any other existing or near future launch vehicle. The liquid propulsion market appears to be shifting towards more affordable and reusable (restart-able) engines.2. Sunk cost fallacy. What is spent on a project is spent. If another choice makes more sense going forward, then it makes sense to put the RS-25 to pasture. (as sad as it sounds)Point 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.Yes, it is. RS-25 was designed as a sustainer engine that burns to almost orbit. It's use in SLS is the same. Most other engines are designed to be either first or upper stage engines - and virtually no engine would do the job as well for SLS.Quote from: robert_d on 03/08/2017 04:21 pmPoint 2 - But the RS-25 actually exists and the production line will exist, so we are NOT talking about past costs. And I am just asking if the reusability feature available can be applied to a smaller vehicle, one that would possibly be more likely to be used. This all assumes the 60 flight before overhaul became reality.Just the RS-25 existing (and its production line) does not mean that it is free, or will be a lower cost than an alternative from this point on. (the point of the sunk cost fallacy) RS-25 is saved by being such a good fit for SLS (see point 1 above) - if SLS goes away, RS-25 will as well.
What I find disturbing is that the fifth set of engines are only required in 2027, so there will only be four SLS flying in the next 11 years? I was under the impression that they'd be aiming at a somewhat higher launch cadence.
Quote from: Dante80 on 01/06/2016 04:20 pmQuote from: Lars-J on 01/06/2016 04:15 pmQuote from: Dante80 on 01/06/2016 12:43 pmTo be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that. 5 years to build an engine!?!?!From the JOFOC.ARJ hand builds their engines (at least, that's what I knew they did in the past). This is the production process I imagine for a 5 year build: (see image) It's no wonder the surviving RS-25's are treated like precious commodities.(Meanwhile, another domestic liquid engine producer builds over 100 engines per year)
Quote from: Lars-J on 01/06/2016 04:15 pmQuote from: Dante80 on 01/06/2016 12:43 pmTo be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that. 5 years to build an engine!?!?!From the JOFOC.ARJ hand builds their engines (at least, that's what I knew they did in the past).
Quote from: Dante80 on 01/06/2016 12:43 pmTo be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that. 5 years to build an engine!?!?!
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.
So what about this,A six RS-25D, three BE-3 booster, firing for about 2.33 minutes so that it can return. Restart on 3 BE-4's for boostback/re-entry, then one or two BE-3's for landing. Use a new BE-3 vacuum optimized engine as the upper stage engine.Current inventory is 16 rs-25's. Enough for 2 boosters and 4 spare engines. Proposal would be to build 16 more to get potential total of 4 boosters with 8 spare engines. No modifications except for production efficiencies. Buy 18 BE-4's from B.O. for boosters and spares. Contract for 12 vacuum optimized versions for the upper stage expendable, but put out a contract for a long term second stage/depot development that anyone could bid on that would give good performance to lunar regions using the BE-3 powered second stage. That way nothing is wasted, and a returnable second stage is not required. Since the BE-3 will be used for human suborbital, I would think the entire system could be human rated.So could this system lift a fully fueled Orion to LEO? Could a hydrolox propellant depot be developed?Would be ironic if the supposedly BLEO Orion stayed in LEO while a descendant of the originally intended suborbital BE-3 went on to be part of a reusable cis-lunar transfer system.
Point 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.
Quote from: Hog on 05/11/2017 06:01 pmQuotePoint 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.Yes, it is. RS-25 was designed as a sustainer engine that burns to almost orbit. It's use in SLS is the same. Most other engines are designed to be either first or upper stage engines - and virtually no engine would do the job as well for SLS.They lit the 3 SSMEs at 100%RPL, then lit the 2 SRBs, up to 104.5% at "tower clear", then both liquids and solids decrease thrust, "in the bucket" for Max.Q, then liquids back to 104.5 and solids increase their thrust, then staging at approx. MET-122seconds with Booster Sep, approx. 5 minutes at 104.5%RPL with some OMS firing during OMS-1(depending on mission), then 3 g throttling, then the seats snap forward at MECO.Yes, the RS-25 is a sustainer engine, and it burns during every second of that 0-17,500mph drag race, but as soon as the 25's shutdown at MECO, assuming OMS-2 wasn't required and aside from some minor orbital corrections, is the Orbiter on fully on-orbit?Just clarifying the "RS-25 burns almost to orbit" wording.SLS- go for launch!
QuotePoint 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.Yes, it is. RS-25 was designed as a sustainer engine that burns to almost orbit. It's use in SLS is the same. Most other engines are designed to be either first or upper stage engines - and virtually no engine would do the job as well for SLS.
QuoteQuote from: Hog on 05/11/2017 06:01 pmQuotePoint 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.Yes, it is. RS-25 was designed as a sustainer engine that burns to almost orbit. It's use in SLS is the same. Most other engines are designed to be either first or upper stage engines - and virtually no engine would do the job as well for SLS.They lit the 3 SSMEs at 100%RPL, then lit the 2 SRBs, up to 104.5% at "tower clear", then both liquids and solids decrease thrust, "in the bucket" for Max.Q, then liquids back to 104.5 and solids increase their thrust, then staging at approx. MET-122seconds with Booster Sep, approx. 5 minutes at 104.5%RPL with some OMS firing during OMS-1(depending on mission), then 3 g throttling, then the seats snap forward at MECO.Yes, the RS-25 is a sustainer engine, and it burns during every second of that 0-17,500mph drag race, but as soon as the 25's shutdown at MECO, assuming OMS-2 wasn't required and aside from some minor orbital corrections, is the Orbiter on fully on-orbit?Just clarifying the "RS-25 burns almost to orbit" wording.SLS- go for launch!Can I ask for a point of clarification? It was my (possibly incorrect) understanding that at MECO, the shuttle was still suborbital, so that the ET would reenter upon separation, and that the OMS was used to give the orbiter that extra kick into orbit. "Almost to orbit" is more of a mission constraint rather than performance constraint if my understanding is correct. The various "wet workshop" reuse ideas would have the ET go to orbit with the orbiter, in which case the RS-25s could continue burning provided there was still LH/LOX in the tank.