Maybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.
Quote from: envy887 on 03/04/2017 12:22 pmMaybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".
Quote from: PahTo on 03/04/2017 03:26 pmQuote from: envy887 on 03/04/2017 12:22 pmMaybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".Like Saturn 1/1b with it's 8 H-1s and perfect launch record? Or Saturn V with multiple engine failures but also a perfect launch record? Falcon 9 also hasn't had any propulsion issues leading to LOM, despite having a Merlin blow up on one flight.
Quote from: envy887 on 03/04/2017 04:34 pmQuote from: PahTo on 03/04/2017 03:26 pmQuote from: envy887 on 03/04/2017 12:22 pmMaybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".Like Saturn 1/1b with it's 8 H-1s and perfect launch record? Or Saturn V with multiple engine failures but also a perfect launch record? Falcon 9 also hasn't had any propulsion issues leading to LOM, despite having a Merlin blow up on one flight.Could you define “perfect launch record”? I can sort of see exempting it because it was a test flight, but Apollo 6 was a partial failure, and would have resulted in LOM had it been a crewed lunar flight…
Quote from: WulfTheSaxon on 03/04/2017 06:09 pmQuote from: envy887 on 03/04/2017 04:34 pmQuote from: PahTo on 03/04/2017 03:26 pmQuote from: envy887 on 03/04/2017 12:22 pmMaybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".Like Saturn 1/1b with it's 8 H-1s and perfect launch record? Or Saturn V with multiple engine failures but also a perfect launch record? Falcon 9 also hasn't had any propulsion issues leading to LOM, despite having a Merlin blow up on one flight.Could you define “perfect launch record”? I can sort of see exempting it because it was a test flight, but Apollo 6 was a partial failure, and would have resulted in LOM had it been a crewed lunar flight…Not loss of mission but at least an abort from low earth orbit. The crew would of been safe.
How would an abort from LEO not be LOM? I didn’t say anything about LOC.
And as I pointed out up-thread, and Steven Pietrobon showed in his paper, an SLS core with six engines and a large upper stage will use up its propellants long before it reaches 7.5 km/s. From Steven's charts, I came up with about 4.5 km/s. I'm sure Steven could provide his exact calculations.
Core stage burn out was at 4771 m/s inertial speed.
Any chance you're willing to run calcs on core with 5 RS-25s and a center J-2X, two Dark Knights, and a larger US optimized to match, staging with enough prop for the core to land downrange on the (modified deep throttleable) J-2X (or RTLS on lofted trajectory)? I know, lots of unknowns, but ballpark would be nice to know.
I just keep seeing this position again, from the looks of Russia, and now SpaceX, it seems like it is important to be good at manufacturing, and pumping out large numbers of rocket engines. ...In the mid 90s, Marshall Space Flight Center had the idea of a low cost rocket engine, FASTRAC https://www.nasa.gov/centers/marshall/news/background/facts/fastrac.html Ideas like a low pressure, machine manufactured turbopump, ablative nozzle, and pintle injector. The rs-68 used some of those ideas, and it was cheaper, but the Atlas V ended being the cheaper rocket. We don't know how much an American rd-180 would have ended up costing. The rs-27 was the simplified rocket engine of the 60s, with heritage from the V-2, but users of it, the Atlas and Delta rockets of the 90s, were not cheap rockets. For all the hype the Saturn V gets, it was an expensive rocket. The F-1 required a lot of skilled human labor.
Quote from: Steven Pietrobon on 03/05/2017 04:20 amCore stage burn out was at 4771 m/s inertial speed.Any chance you're willing to run calcs on core with 5 RS-25s and a center J-2X, two Dark Knights, and a larger US optimized to match, staging with enough prop for the core to land downrange on the (modified deep throttleable) J-2X (or RTLS on lofted trajectory)? I know, lots of unknowns, but ballpark would be nice to know.I know this is very unlikely to actually happen, just interested in performance numbers as a hypothetical.