sh1pman Posted December 27, 2018 Share Posted December 27, 2018 8 minutes ago, Ultimate Steve said: *Starship is on the pad ready for first test flight *At T-10 Elon cancels liftoff and announces extensive changes to the architecture Finally liftoff, stage sep, at T+178 Elon calls for abort and RTLS for radical redesign Quote Link to comment Share on other sites More sharing options...
Ultimate Steve Posted December 27, 2018 Share Posted December 27, 2018 35 minutes ago, sh1pman said: Finally liftoff, stage sep, at T+178 Elon calls for abort and RTLS for radical redesign First unmanned Starship to reach Mars is falling through the Martian Atmosphere after a successful entry. Elon orders it not to start its landing burn in favor of a redesign. Quote Link to comment Share on other sites More sharing options...
nasa legolas Posted December 27, 2018 Share Posted December 27, 2018 On 17 de diciembre de 2018 at 5:05 PM, Ozymandias_the_Goat said: A quick squirt of WD-40 will easily amend that. Seriously, if its moving and it's not supposed to move, use duct tape. If it's not moving and it's supposed to move, used WD-40. true Quote Link to comment Share on other sites More sharing options...
Spaceception Posted December 27, 2018 Share Posted December 27, 2018 1 hour ago, Ultimate Steve said: First unmanned Starship to reach Mars is falling through the Martian Atmosphere after a successful entry. Elon orders it not to start its landing burn in favor of a redesign. Bold of you to assume it's even possible to make it to Mars without some redesigns forcing an abort. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted December 27, 2018 Share Posted December 27, 2018 I am curious to know how exactly SpaceX plans to pump methane through an actively-cooled windward Starship skin. Analogy to expander cycle? Quote Link to comment Share on other sites More sharing options...
tater Posted December 27, 2018 Share Posted December 27, 2018 Exciting times... Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted December 27, 2018 Share Posted December 27, 2018 5 minutes ago, tater said: Exciting times... You know, this is spectacularly ambitious speculation, but... ...what if the actively-cooled stainless-steel skin acted as a radiator and condenser on orbit? Quote Link to comment Share on other sites More sharing options...
tater Posted December 28, 2018 Share Posted December 28, 2018 4 minutes ago, sevenperforce said: You know, this is spectacularly ambitious speculation, but... ...what if the actively-cooled stainless-steel skin acted as a radiator and condenser on orbit? Think of what they now have some experience with... The D2 trunk is PVs on one side, radiators on the other (design experience, soon to be flight, unsure about D1 in this regard).. The have been messing with variant stage 2 deorbits for a while. Some are to increase time between burns for alternate orbital insertions, but they have loads of sensors everywhere, they must have a ton of data on the progression of events on S2 EDL (the "L" bit being a crash in the ocean, lol). I have to wonder about them testing how cryo stages behave with different ullage on reentry, if they let S2 burst if heating increases tank pressures, or if they have let it vent to see what that does for heat removal, etc. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted December 28, 2018 Share Posted December 28, 2018 Elon was tweeting recently about the regenerative braking on Teslas, which is pretty awesome, though not any differently than with any hybrid. Run the motors and drain the battery, and the car moves; invert, and you charge the battery while slowing the car. The Starship already has hot-gas RCS motors fed from the header tanks, which are autogenously pressurized by the actively-cooled engine bells. It will also need electric batteries to run onboard systems and provide for spark ignition. Presumably, the working fluid in the actively-cooled heatshield will be circulated by electric motors. A heat cycle and dynamo is a Carnot engine. Thus, methane could run through the loops while oriented belly-sunward to pressurize the header tanks, and then recirculated while in the opposite orientation to condense the methane back down to a liquid. Two different Carnot cycles so you can generate power from both. Same deal during re-entry. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted December 28, 2018 Share Posted December 28, 2018 11 minutes ago, sevenperforce said: Two different Carnot cycles so you can generate power from both. So... solar power minus the solar cells? Quote Link to comment Share on other sites More sharing options...
RedKraken Posted December 28, 2018 Share Posted December 28, 2018 (edited) 51 minutes ago, sevenperforce said: how exactly SpaceX plans to pump methane through an actively-cooled windward Starship skin I've seen rough estimates on reddit specify 5000kg methane over 200s for (earth?) reentry with most (80%) of the hot methane vented. If correct, this requires 25kg/s average pumped thru the windward skin. Peak might be a good deal more. A single raptor 2000kN/330s fuel turbopump moves about 130kg/s CH4. I assume you would have dedicated, redundant pumps for this. Not the raptor turbopumps. Edited December 28, 2018 by RedKraken Quote Link to comment Share on other sites More sharing options...
Mad Rocket Scientist Posted December 28, 2018 Share Posted December 28, 2018 41 minutes ago, sevenperforce said: I am curious to know how exactly SpaceX plans to pump methane through an actively-cooled windward Starship skin. Analogy to expander cycle? There was some good estimates on r/SpaceX about reentry cooling: https://old.reddit.com/r/spacex/comments/a9y9r0/an_energy_budget_for_starship_reentry/ Summary: 35GJ of energy going into BFR from 8 km/s reentry, boiling half the estimated landing fuel absorbs ~3.5 GJ, the steel structure can absorb 30GJ (if you're willing to heat it to nearly red hot), and 28-29GJ radiates away. There are some big assumptions being made (magic conduction, no reflection), but it looks like surprisingly little heat capacity in the propellant. Quote Link to comment Share on other sites More sharing options...
tater Posted December 28, 2018 Share Posted December 28, 2018 Quote Link to comment Share on other sites More sharing options...
Rakaydos Posted December 28, 2018 Share Posted December 28, 2018 2 hours ago, CatastrophicFailure said: So... solar power minus the solar cells? Solar Thermal power. Quote Link to comment Share on other sites More sharing options...
zolotiyeruki Posted December 28, 2018 Share Posted December 28, 2018 4 minutes ago, tater said: 11 more engines = about 35% more mass at liftoff? Or is there something else going on? Quote Link to comment Share on other sites More sharing options...
IncongruousGoat Posted December 28, 2018 Share Posted December 28, 2018 (edited) 1 minute ago, zolotiyeruki said: 11 more engines = about 35% more mass at liftoff? Or is there something else going on? 42 engines. If you still don't get it, go read The Hitchhiker's Guide to the Galaxy. It's well worth your time. Edited December 28, 2018 by IncongruousGoat Spelling Quote Link to comment Share on other sites More sharing options...
DDE Posted December 28, 2018 Share Posted December 28, 2018 5 hours ago, Rakaydos said: Solar Thermal power. The classic. 7 hours ago, sevenperforce said: The Starship already has hot-gas RCS motors fed from the header tanks Where have we heard this? I always wondered what kind of RCS that thing would have. Quote Link to comment Share on other sites More sharing options...
Xd the great Posted December 28, 2018 Share Posted December 28, 2018 5 hours ago, tater said: MOAR ENGINES. Same as MOAR BOOSTER. Elon played ksp too much. Quote Link to comment Share on other sites More sharing options...
tater Posted December 28, 2018 Share Posted December 28, 2018 Quote Link to comment Share on other sites More sharing options...
IncongruousGoat Posted December 28, 2018 Share Posted December 28, 2018 7 hours ago, DDE said: Where have we heard this? I always wondered what kind of RCS that thing would have. I think it's been mentioned at at least one of the IACs, and maybe also the DearMoon announcement. In any case, it's been the definitive plan (along with autogeneous pressurization) for a while now. Quote Link to comment Share on other sites More sharing options...
DDE Posted December 28, 2018 Share Posted December 28, 2018 (edited) 1 hour ago, IncongruousGoat said: I think it's been mentioned at at least one of the IACs, and maybe also the DearMoon announcement. In any case, it's been the definitive plan (along with autogeneous pressurization) for a while now. That seems needlessly low-ISP when proper bipropellant thrusters are an option. Edited December 28, 2018 by DDE Quote Link to comment Share on other sites More sharing options...
tater Posted December 28, 2018 Share Posted December 28, 2018 24 minutes ago, DDE said: That seems needlessly low-ISP when proper bipropellant thrusters are an option. If the goal is rapid turn around, and possibly P2P (something I don't take terribly seriously, but they seem to), then nasty hypergolics are to be avoided. Quote Link to comment Share on other sites More sharing options...
MinimumSky5 Posted December 28, 2018 Share Posted December 28, 2018 High Isp isn't necessarily the best option, depending on what you want. Eliminating the weight of the hypergolic storage systems, and the serious cost savings in not needing to handle them, are a much more important feature for SpaceX than squeezing every last second of performance out of them. Quote Link to comment Share on other sites More sharing options...
IncongruousGoat Posted December 28, 2018 Share Posted December 28, 2018 (edited) 47 minutes ago, DDE said: That seems needlessly low-ISP when proper bipropellant thrusters are an option. Wait, what? I think I must have mis-read something. I thought they were planning on using bipropellant gaseous methane and gaseous LOX thrusters, fed from the tank boiloff. At those small scales spark ignition works, so it's not too much more complicated than a hypergolic thruster. Edited December 28, 2018 by IncongruousGoat Quote Link to comment Share on other sites More sharing options...
DDE Posted December 28, 2018 Share Posted December 28, 2018 22 minutes ago, tater said: If the goal is rapid turn around, and possibly P2P (something I don't take terribly seriously, but they seem to), then nasty hypergolics are to be avoided. 12 minutes ago, MinimumSky5 said: High Isp isn't necessarily the best option, depending on what you want. Eliminating the weight of the hypergolic storage systems, and the serious cost savings in not needing to handle them, are a much more important feature for SpaceX than squeezing every last second of performance out of them. RCS is not necessarily cryo. Both ULA’s IVF and the Buran testify to that. 1 minute ago, IncongruousGoat said: Wait, what? I think I must have mis-read something. I thought they were planning on using bipropellant gaseous methane and gaseous LOX thrusters, fed from the tank boiloff. At those small scales spark ignition works, so it's not too much more complicated than a hypergolic thruster. If it’s what was meant, “hot gas” was a very odd way to describe it. Quote Link to comment Share on other sites More sharing options...
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