Total Members Voted: 433
Voting closed: 04/02/2020 08:43 pm
Static fire Apr 1 and 150 hop on Apr 6? It's optimistic, but could be doable. Will need legs installed by then of course. Likely after static fire. I doubt nosecone will be added for this short hop. Would be just duplicating Hopper 1's hop.
The 150m Hop plan is leftover from previous testing... I'd guess that they would start with some "tethered hops" before going for free flight hops. Biggest hurdle to any hopping right now is Thrusters for attitude control. Any evidence so far that these have been installed?
Quote from: IvanDogovich on 03/27/2020 12:30 pmThe 150m Hop plan is leftover from previous testing... I'd guess that they would start with some "tethered hops" before going for free flight hops. Biggest hurdle to any hopping right now is Thrusters for attitude control. Any evidence so far that these have been installed?I'm guessing that since they have had issues with tanks, that tanks, then Raptor fire will be done first before installing additional hardware such as legs and thrusters. It think SpaceX has learned to test components before getting too far into a build. The tanks and Raptor firing are still high risk tests.
Quote from: capoman on 03/27/2020 02:33 pmQuote from: IvanDogovich on 03/27/2020 12:30 pmThe 150m Hop plan is leftover from previous testing... I'd guess that they would start with some "tethered hops" before going for free flight hops. Biggest hurdle to any hopping right now is Thrusters for attitude control. Any evidence so far that these have been installed?I'm guessing that since they have had issues with tanks, that tanks, then Raptor fire will be done first before installing additional hardware such as legs and thrusters. It think SpaceX has learned to test components before getting too far into a build. The tanks and Raptor firing are still high risk tests.Do they strictly need RCS thrusters for a straight up-and-down hop? For more drastic moves, sure. But as long as its a nice, gentle up and down with the fiery bits pointed squarely at the ground, 3-engine TVC gives them at least some control authority on all 6 axes. Might that be enough for initial testing? My recollection from Hopper was that the RCS thruster packs were only needed for roll control, as you can't really get that from only one engine.
[...] My recollection from Hopper was that the RCS thruster packs were only needed for roll control, as you can't really get that from only one engine.
OK, I here submit for review SS SN04 main fluids piping diagram.IMHO OFC
Quote from: DusanC on 03/27/2020 10:04 amOK, I here submit for review SS SN04 main fluids piping diagram.IMHO OFCThe big thing that's missing is that there needs to be high-pressure gox and gch4 tanks between the autogenous pressurization exhaust from the engine and the main tanks. Just pushing the gas directly from the engine to the tank would result in horrible control issues as there would be a lot of lag between "pressure too low/high" and changes at the rate of production at the engines. This would be easy to fix by just putting a small buffer with room in both directions (able to handle much higher pressures than the main tank, always pressed to ~10B or so) between them. With that, you can keep the pressure at the main tanks very controlled and stable.And, those tanks would also be quite useful for the gox/ch4 control thrusters they are building.
Quote from: cdebuhr on 03/27/2020 02:41 pmQuote from: capoman on 03/27/2020 02:33 pmQuote from: IvanDogovich on 03/27/2020 12:30 pmThe 150m Hop plan is leftover from previous testing... That also begs the question, would they use hot or cold thrusters at this point?
Quote from: capoman on 03/27/2020 02:33 pmQuote from: IvanDogovich on 03/27/2020 12:30 pmThe 150m Hop plan is leftover from previous testing... That also begs the question, would they use hot or cold thrusters at this point?
Quote from: IvanDogovich on 03/27/2020 12:30 pmThe 150m Hop plan is leftover from previous testing... That also begs the question, would they use hot or cold thrusters at this point?
The 150m Hop plan is leftover from previous testing... That also begs the question, would they use hot or cold thrusters at this point?
Quote from: Tuna-Fish on 03/27/2020 03:52 pmQuote from: DusanC on 03/27/2020 10:04 amOK, I here submit for review SS SN04 main fluids piping diagram.IMHO OFCThe big thing that's missing is that there needs to be high-pressure gox and gch4 tanks between the autogenous pressurization exhaust from the engine and the main tanks. Just pushing the gas directly from the engine to the tank would result in horrible control issues as there would be a lot of lag between "pressure too low/high" and changes at the rate of production at the engines. This would be easy to fix by just putting a small buffer with room in both directions (able to handle much higher pressures than the main tank, always pressed to ~10B or so) between them. With that, you can keep the pressure at the main tanks very controlled and stable.And, those tanks would also be quite useful for the gox/ch4 control thrusters they are building.A suitably large pipe for the flow volume at reduced pressure and a pressure reduction valve is all that should be needed. Remember the Raptors are producing up to 300 bar pressures. The tanks are at 6 bar. Put the pressure reduction valve at the Raptor, and have it output 50 bar. A relatively small pipe could then deliver that to the propellant tank where there is a valve for controlling the flow into the tank.