So far, only 2 re-flights, both with "hot" re-entries which makes it unlikely those boosters will ever fly again.
Quote from: georgegassaway on 08/18/2017 09:40 pmSo far, only 2 re-flights, both with "hot" re-entries which makes it unlikely those boosters will ever fly again.Is that your supposition, or is this based on information provided by SpaceX?
Quote from: LouScheffer on 08/18/2017 01:28 pmQuote from: woods170 on 08/18/2017 01:07 pmQuote from: deruch on 08/18/2017 07:02 am May have been the 1.7Mlb-f version just flown below the new maximum thrust level though. Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. You don't fly higher-thrust engines for the first time if you do not intend to utilize that higher thrust.This is not obvious to me. At some point you start qualifying your engines to a new, higher, maximum thrust. You incorporate the new engines into new boosters as they are built. Now suppose the first mission for the new booster does not require the new maximum thrust. What are you going to do? Use the new maximum thrust just because you can? That seems wrong, running at higher ratings surely increases the risk. Swap if for a booster with crappier engines? That seems wrong too.I believe the Shuttle had engine settings which were developed, and qualified, but never intended to be used. They were reserved for abort scenarios.Every time SpaceX introduced more powerfull engines on their rockets they immediately made use of the increased power. There is no valid reason not to do so.
Quote from: woods170 on 08/18/2017 01:07 pmQuote from: deruch on 08/18/2017 07:02 am May have been the 1.7Mlb-f version just flown below the new maximum thrust level though. Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. You don't fly higher-thrust engines for the first time if you do not intend to utilize that higher thrust.This is not obvious to me. At some point you start qualifying your engines to a new, higher, maximum thrust. You incorporate the new engines into new boosters as they are built. Now suppose the first mission for the new booster does not require the new maximum thrust. What are you going to do? Use the new maximum thrust just because you can? That seems wrong, running at higher ratings surely increases the risk. Swap if for a booster with crappier engines? That seems wrong too.I believe the Shuttle had engine settings which were developed, and qualified, but never intended to be used. They were reserved for abort scenarios.
Quote from: deruch on 08/18/2017 07:02 am May have been the 1.7Mlb-f version just flown below the new maximum thrust level though. Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. You don't fly higher-thrust engines for the first time if you do not intend to utilize that higher thrust.
May have been the 1.7Mlb-f version just flown below the new maximum thrust level though. Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust.
Quote from: woods170 on 08/18/2017 02:15 pmQuote from: LouScheffer on 08/18/2017 01:28 pmQuote from: woods170 on 08/18/2017 01:07 pmQuote from: deruch on 08/18/2017 07:02 am May have been the 1.7Mlb-f version just flown below the new maximum thrust level though. Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. You don't fly higher-thrust engines for the first time if you do not intend to utilize that higher thrust.This is not obvious to me. At some point you start qualifying your engines to a new, higher, maximum thrust. You incorporate the new engines into new boosters as they are built. Now suppose the first mission for the new booster does not require the new maximum thrust. What are you going to do? Use the new maximum thrust just because you can? That seems wrong, running at higher ratings surely increases the risk. Swap if for a booster with crappier engines? That seems wrong too.I believe the Shuttle had engine settings which were developed, and qualified, but never intended to be used. They were reserved for abort scenarios.Every time SpaceX introduced more powerfull engines on their rockets they immediately made use of the increased power. There is no valid reason not to do so.They flew Merlin 1C at partial thrust on Falcon 1 because it wasn't yet qualified for fuller thrust (that'd be for Falcon 1e, which never flew).
On missions where you don't need the extra performance, maybe they simply reserve the uprated thrust for engine-out scenarios?With the uprated thrust, they still might be able to recover a stage if the affected engine(s) are not the 3 restartable ones.At least in the past, i think an engine-out scenario would almost always result in loss of the first stage because it would use up their landing fuel reserves.
"Continuous Close Up Footage of Launch Through Landing of the CRS-12 Falcon 9!" from Astronomy Live:
Quote from: mme on 08/18/2017 06:02 pm"Continuous Close Up Footage of Launch Through Landing of the CRS-12 Falcon 9!" from Astronomy Live:This video from the Updates thread shows a fast flip of the first stage with a main engine starting before the flip is complete. The flip must throw propellant to the top of the tanks. Do the nitrogen thrusters provide ullage? Or does TEA/TEB give the necessary thrust as well as lighting the engine? Or is there some other mechanism?
Regarding thrust: Higher thrust means higher G-forces, right? How much can the mice take?
Quote from: jpo234 on 08/20/2017 12:44 pmRegarding thrust: Higher thrust means higher G-forces, right? How much can the mice take?Ping! Could it be, that SpaceX had to hold back the higher thrust of Block 4 so that they didn't flatten the mice?
... Since they have 9 engines on the first stage, they could have run 1 (or more?) at the higher thrust and used lower thrust on the remaining to end up with the same overall vehicle thrust. Doing this would allow them an excellent chance to analyze the performance of the uprated engines in comparison to past engines in a range of performances (i.e. higher, equal, and lower thrust). Would be especially nice as they get the engines back for hands-on study post flight.I'm not saying that this was done. Only that it is a scenario that is also compatible with available data.
First reused one to return twice... nice going SpaceX