I don't think liquid engines are the same in this regard as SRMs. The performance characteristics don't vary as much and engine performance is constrained by the rate of flow of fuel/oxidizer to the engines. SRMs just light off and go, so there is no ability to control the rate of burn dynamically once the motor is cast.In any case, no Merlin-1D has yet flown with the full qualified thrust, that will come with Block 5 (or the ever-mysterious Block 4 perhaps). I would expect that all engines at that point will be able to perform to that level and will not be run "hotter".
Quote from: abaddon on 03/29/2017 02:06 pmI don't think liquid engines are the same in this regard as SRMs. The performance characteristics don't vary as much and engine performance is constrained by the rate of flow of fuel/oxidizer to the engines. SRMs just light off and go, so there is no ability to control the rate of burn dynamically once the motor is cast.In any case, no Merlin-1D has yet flown with the full qualified thrust, that will come with Block 5 (or the ever-mysterious Block 4 perhaps). I would expect that all engines at that point will be able to perform to that level and will not be run "hotter".So for shuttle, they would only choose SRBs that were higher performing (based on the performance of the fuel mix that went into the casting) for missions that needed it?
Quote from: Mike_1179 on 03/29/2017 02:13 pmQuote from: abaddon on 03/29/2017 02:06 pmI don't think liquid engines are the same in this regard as SRMs. The performance characteristics don't vary as much and engine performance is constrained by the rate of flow of fuel/oxidizer to the engines. SRMs just light off and go, so there is no ability to control the rate of burn dynamically once the motor is cast.In any case, no Merlin-1D has yet flown with the full qualified thrust, that will come with Block 5 (or the ever-mysterious Block 4 perhaps). I would expect that all engines at that point will be able to perform to that level and will not be run "hotter".So for shuttle, they would only choose SRBs that were higher performing (based on the performance of the fuel mix that went into the casting) for missions that needed it?Yes. There was some degree of "choice" here. It could be mission specific or based on season of projected launch. Missions in winter had these higher performance SRBs since the atmosphere is denser in winter. IIRC, it was a difference of burning ~10,000lbs of propellant per second vs. ~11,000lbs of propellant per second.
So how did we veer off from SSME to SRB?Mike's original post said "I remember that shuttle missions would choose SSMEs that were "hotter" for missions that were heavier..."So do SSME's AND SRB's have performance differences? and they were choosing for both?P.S. yes this is off topic so feel free to ignore, and we can move on.
So, it is my understanding that this mission will mark the first reuse of a Dragon Mk1 (and may also mark the wind-down of the Mk1 production line). Has any indication been given yet as to which spacecraft will be used?
Quote from: Ben the Space Brit on 03/31/2017 12:26 pmSo, it is my understanding that this mission will mark the first reuse of a Dragon Mk1 (and may also mark the wind-down of the Mk1 production line). Has any indication been given yet as to which spacecraft will be used?It is generally understood to be using the Dragon from the CRS-4 mission. I'm not sure if that has been de-facto confirmed yet though.
In office today: 1st reflown booster on mission cntrl screen, many flown Merlins, 1st reused Dragon ready to ship out ..I'm sensing a theme♻️
My emphasis:QuoteIn office today: 1st reflown booster on mission cntrl screen, many flown Merlins, 1st reused Dragon ready to ship out ..I'm sensing a theme♻️https://twitter.com/rocketjoy/status/847931487437570048
It'll be interesting to see how much they actually refly - IIRC, it is basically only the pressure vessel. No plumbing, heat shield, recovery or docking gear.
Quote from: Bob Shaw on 03/31/2017 11:51 pmIt'll be interesting to see how much they actually refly - IIRC, it is basically only the pressure vessel. No plumbing, heat shield, recovery or docking gear.They have already reused components from Dragons on previous flights, so I think it is more than you think that will be reused.
Quote from: Ben the Space Brit on 03/31/2017 12:26 pmSo, it is my understanding that this mission will mark the first reuse of a Dragon Mk1 (and may also mark the wind-down of the Mk1 production line). Has any indication been given yet as to which spacecraft will be used?It is capsule C106, which had flown the SpX 4 mission.
Quote from: Skyrocket on 03/31/2017 12:28 pmQuote from: Ben the Space Brit on 03/31/2017 12:26 pmSo, it is my understanding that this mission will mark the first reuse of a Dragon Mk1 (and may also mark the wind-down of the Mk1 production line). Has any indication been given yet as to which spacecraft will be used?It is capsule C106, which had flown the SpX 4 mission.Do you have a source for the C1XX numbers?
Quote from: Galactic Penguin SST on 04/01/2017 05:24 amQuote from: Skyrocket on 03/31/2017 12:28 pmQuote from: Ben the Space Brit on 03/31/2017 12:26 pmSo, it is my understanding that this mission will mark the first reuse of a Dragon Mk1 (and may also mark the wind-down of the Mk1 production line). Has any indication been given yet as to which spacecraft will be used?It is capsule C106, which had flown the SpX 4 mission.Do you have a source for the C1XX numbers?The /r/spacex wiki has this info. I can't guarantee it is accurate.