Since higher thrust, regenerative nozzle RS-68s are presumably out of the question...
NASA defends decision to restart RS-25 production, rejects alternativesRe: Is it fair to question the decisions of NASA/Congress? May we reject their decisions and offer superior alternatives? Is it likely NASA would/did agree with said alternatives, but chose to build a Congressional rocket while cowardly keeping silent as to this mistake?A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.Re: That's $2.23 billion down the drain by selecting the RS-25 over RS-68. Additionally, the RS-25 is a brand new engine with zero flight record, both increasing risk of LOM/LOC and requiring EOC. It's lower-performance, less safe, considerably more expensive (both development and operation) and possibly the worst design decision in SHLV's history. Thank you Congress, Augustine and Obama.
NASA defends decision to restart RS-25 production, rejects alternativesRe: Is it fair to question the decisions of NASA/Congress? May we reject their decisions and offer superior alternatives? Is it likely NASA would/did agree with said alternatives, but chose to build a Congressional rocket while cowardly keeping silent as to this mistake?A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.Re: That's $2.23 billion down the drain by selecting the RS-25 over RS-68. Additionally, the RS-25 is a brand new engine with zero flight record, both increasing risk of LOM/LOC and requiring EOC. It's lower-performance, less safe, considerably more expensive (both development and operation) and possibly the worst design decision in SHLV's history. Thank you Congress, Augustine and Obama.Quote from: MATTBLAK on 03/07/2017 11:32 amSince higher thrust, regenerative nozzle RS-68s are presumably out of the question... Re: Regen is not only out of the question, it's unnecessary and always has been unless the core is designed specifically to make regen necessary. For example; Too many RS-68s together heat each other, and the core's base. Spread them apart and they're too close to the SRBs. No argument to the studies that professed such. So use less RS-68s with a bit of thermal mitigation and suddenly they don't heat up, each other, the base or roast by SRBs. You can mail me the $2.23 billion check now.
Quote from: Propylox on 07/08/2017 03:59 amNASA defends decision to restart RS-25 production, rejects alternativesRe: Is it fair to question the decisions of NASA/Congress? May we reject their decisions and offer superior alternatives? Is it likely NASA would/did agree with said alternatives, but chose to build a Congressional rocket while cowardly keeping silent as to this mistake?A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.Re: That's $2.23 billion down the drain by selecting the RS-25 over RS-68. Additionally, the RS-25 is a brand new engine with zero flight record, both increasing risk of LOM/LOC and requiring EOC. It's lower-performance, less safe, considerably more expensive (both development and operation) and possibly the worst design decision in SHLV's history. Thank you Congress, Augustine and Obama.Quote from: MATTBLAK on 03/07/2017 11:32 amSince higher thrust, regenerative nozzle RS-68s are presumably out of the question... Re: Regen is not only out of the question, it's unnecessary and always has been unless the core is designed specifically to make regen necessary. For example; Too many RS-68s together heat each other, and the core's base. Spread them apart and they're too close to the SRBs. No argument to the studies that professed such. So use less RS-68s with a bit of thermal mitigation and suddenly they don't heat up, each other, the base or roast by SRBs. You can mail me the $2.23 billion check now.Complete non-sense. RS-25 is one of the most flight proven engines of all time, most of the current stock has flown multiple missions with 100% reliability. The $2.23 billion was for the design of an equivalent engine to the RS-25, not the RS-25 its self. NASA spent about $1 Billion re-starting RS-25 production including 6 additional production engines.
Quote from: Khadgars on 07/08/2017 08:44 pmQuote from: Propylox on 07/08/2017 03:59 amNASA defends decision to restart RS-25 production, rejects alternativesRe: Is it fair to question the decisions of NASA/Congress? May we reject their decisions and offer superior alternatives? Is it likely NASA would/did agree with said alternatives, but chose to build a Congressional rocket while cowardly keeping silent as to this mistake?A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.Re: That's $2.23 billion down the drain by selecting the RS-25 over RS-68. Additionally, the RS-25 is a brand new engine with zero flight record, both increasing risk of LOM/LOC and requiring EOC. It's lower-performance, less safe, considerably more expensive (both development and operation) and possibly the worst design decision in SHLV's history. Thank you Congress, Augustine and Obama.Quote from: MATTBLAK on 03/07/2017 11:32 amSince higher thrust, regenerative nozzle RS-68s are presumably out of the question... Re: Regen is not only out of the question, it's unnecessary and always has been unless the core is designed specifically to make regen necessary. For example; Too many RS-68s together heat each other, and the core's base. Spread them apart and they're too close to the SRBs. No argument to the studies that professed such. So use less RS-68s with a bit of thermal mitigation and suddenly they don't heat up, each other, the base or roast by SRBs. You can mail me the $2.23 billion check now.Complete non-sense. RS-25 is one of the most flight proven engines of all time, most of the current stock has flown multiple missions with 100% reliability. The $2.23 billion was for the design of an equivalent engine to the RS-25, not the RS-25 its self. NASA spent about $1 Billion re-starting RS-25 production including 6 additional production engines.Actually those 6 engines are only 4 flight, one qual/development engine, and one production/qual/pathfinder. The contract also sets the price per engine and options for additional engines in sets of 4. Options contract duration from execution would be 6 years. The optimal time for the execution of engine option contract would be 1 year after the last set of 2 engines start (5 years before those 2's delivery) or around 2021.There is also a possibility of a separate contract to AJR for additional infrastructure to increase engine production rate for 2/yr to as many as 8/yr. This would be needed to have engine production match the rest of the vehicle manufacture rates. If NASA does this this contract would probably happen about 2020. After the first flight of EM-1. It would be confirmation by the PTBs that SLS is here to stay and that its use in the later half of the 2020's will be 2 flights/yr. Also going to a production rate of 8/yr from 2/yr is liable to reduce unit costs of engines by as much as 50%. If SLS will be used in the late 2020's and into the 2030's then this would be a prudent investment to lower those out year costs making the per flight costs of SLS at 2 per year as low as $600M. That is in 4/kg to LEO equivalent comparison costs of $6,000/kg. Still expensive but not outrageous.
... Somehow; I feel a sense of deja-vu coming on; writing and reading this stuff...
... The $2.23 billion was for the design of an equivalent engine to the RS-25, not the RS-25 its self. NASA spent about $1 Billion re-starting RS-25 production including 6 additional production engines.
Actually those 6 engines are only 4 flight, one qual/development engine, and one production/qual/pathfinder. The contract also sets the price per engine and options for additional engines in sets of 4. ...
I'm not going to wax poetic about butterflies, but decisions often determine the next set of decisions and weight the following choices. In every type of engineering, key junctions exist that must be robust or the entire system/structure can collapse.
The timeline for launching infrastructure toward a manned, lunar program suddenly jumps from the 30's to whenever the first J-2X launches.
...There is also a possibility of a separate contract to AJR for additional infrastructure to increase engine production rate for 2/yr to as many as 8/yr. This would be needed to have engine production match the rest of the vehicle manufacture rates....
...To change engines now would require a complete redesign of the SLS core and upper stages and would add years plus untold costs to the PoR. ... The core stage is already being fabricated. To go back now means we have to throw away all the design work and tooling that took 6 years to make.
Quote from: oldAtlas_Eguy on 07/09/2017 08:08 pm ...There is also a possibility of a separate contract to AJR for additional infrastructure to increase engine production rate for 2/yr to as many as 8/yr. This would be needed to have engine production match the rest of the vehicle manufacture rates.... With infrastructure for two engines/yr, AR is well positioned to transition that manufacturing capacity and contract from RS-25Es to J-2X, which only need two/flight. With RS-68s powering the core the RS-25Ds could go back into storage as emergency engines to avoid stand down if a future problem occurs with RS-68s.If intransigence prevails we could delay RS-68s until EM-3, but that reduces the emergency stockpile of RS-25s while paying to fly a rocket there's no intention to use (like Ares-1X). It'd be better to delay EM-1 until the new thrust structure and RS-68 configuration, which shouldn't affect EM-2's timeline. It has its own issues.Quote from: Endeavour_01 on 07/11/2017 03:45 am ...To change engines now would require a complete redesign of the SLS core and upper stages and would add years plus untold costs to the PoR. ... The core stage is already being fabricated. To go back now means we have to throw away all the design work and tooling that took 6 years to make.Changing the core isn't a bad idea, as long as the tooling and techniques remain the same. The structural limits are knows and needn't change much, even with new main engines. Fortunately, that's all that's been accomplished so far; knowledge and manufacturing capability - not actual production. Nothing gets "thrown away" other than SLS's poor design and all the time/money wasted on it to date.For example; The LH tank has a humongous and heavy thrust structure to position the main engines low enough for use and far enough away from the LH for safety. That tank could go from five 22ft barrel sections to six (without changing the jig or raising the roof) with an internally-buttressed common bulkhead. That becomes around 1.9mil lbs propellant with main engines and abbreviated thrust structure flush to the LOX tank. A whole lot of weight and cost just got shaved with payloads (single-stage) or US sitting atop the solid's crossbeam.For example; If AR produces J-2X instead of RS-25E we don't need specific tooling for the upper stage. The existing 8.4m LOX jig (no longer in use) can produce an upper stage holding around 420,ooo lbs propellant with a single 22ft barrel section and common bulkhead - both shared with the aforementioned first stage. The budgeting for the Exploration Upper Stage, like the Advanced Booster program, can now go towards these redesigns and/or missions.
Yes. The above is interesting stuff, but old news and more accurately - things that simply are not going to happen. SLS will either fly basically as-is, or will be cancelled. The outcome is binary. There is no third choice. *If it does fly and gets as far as the Block II configuration operational, the only improvements notionally possible after that would be RS-25E upgrades and changing the huge propellant tankage to lighter alloys. In other words; spending a lot more money to tweak an already very expensive booster.
Quote from: MATTBLAK on 07/11/2017 10:32 pmYes. The above is interesting stuff, but old news and more accurately - things that simply are not going to happen. SLS will either fly basically as-is, or will be cancelled. The outcome is binary. There is no third choice. *If it does fly and gets as far as the Block II configuration operational, the only improvements notionally possible after that would be RS-25E upgrades and changing the huge propellant tankage to lighter alloys. In other words; spending a lot more money to tweak an already very expensive booster.Yes even to tweak the infrastructure to be able to build 2 SLS/yr from the current infrastructure level of just 1 SLS/ every 2 years would require more funding (Probably several $Bs) and time. NASA management, in order to appease Congress, went down the rabbit hole from which there is no exit in regards to engine choices. But at the time they had no time and little choice of available engines RS25 or RS68. RS68 had too many insurmountable problems without a lot of funding and engine development time (make the RS68 regeneratively cooled). So that only left RS25 because of the timeline for first launch. Now they are stuck with the engine. With an available time period of what will be 5 years prior to final assembly of the flight SLS from program start vs the initial timeline of only 2/3 years they could have fixed the RS68 problems.