RealKerbal3x Posted June 20, 2020 Share Posted June 20, 2020 2 minutes ago, tater said: Needless complexity, IMO. SS will survive even a bad reentry long enough to let the escape pod eject the crew, IMO. I'm going to have to test this in KSP Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted June 20, 2020 Share Posted June 20, 2020 (edited) 26 minutes ago, RealKerbal3x said: You have to lug several large abort motors around, which are essentially dead weight after you reach orbit. You can use them to deorbit. Delta-V is comparable, LES ~300 m/s, deorbit from ISS ~250 m/s. They are less efficient, but still better than save some mass but lose the ship. Just don't turn them on all at once. Edited June 20, 2020 by kerbiloid Quote Link to comment Share on other sites More sharing options...
RealKerbal3x Posted June 20, 2020 Share Posted June 20, 2020 Just now, kerbiloid said: You can use them to deorbit. Delta-V is comparable, LES ~300 m/s, deorbit from ISS ~250 m/s. They are less efficient, but still better than save some mass but lose the ship. What about when you're returning from the Moon or Mars? I think a detachable escape pod is a better way to go as it enables a lot more abort modes, including during landing. Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted June 20, 2020 Share Posted June 20, 2020 (edited) 4 minutes ago, RealKerbal3x said: What about when you're returning from the Moon or Mars? Then several SRB is the smallest of your expendables. Upd. Detachable escape pods are nice, but the history of the winged spacecrafts shows than all those cones, semi-cones, needles, saucers finally turned into something like Spiral/DreamChaser. And this shape doesn't fit the cylindric hull well. There are great chances that it will be easier to hide it inside. Also, redundancy. Using regular systems for emergency purposes is not always good. What if the hull lost several tyles like Columbia ? Edited June 20, 2020 by kerbiloid Quote Link to comment Share on other sites More sharing options...
wumpus Posted June 20, 2020 Share Posted June 20, 2020 10 minutes ago, SOXBLOX said: Pretty sure it has just enough thrust with all Raptors to barely ascend once fully fueled. The test articles (and anything point-to-point) will be able to do that, but I'd be shocked if it was really designed to have a TWR>1 once fully fueled. Not that I really know how you could dump propellant, but I assume that it would be necessary during an abort. Quote Link to comment Share on other sites More sharing options...
SOXBLOX Posted June 20, 2020 Share Posted June 20, 2020 Yeah, pretty sure Shadowzone had a video on the topic of Starship aborts a while back. I think he said it could just barely get off the pad. Quote Link to comment Share on other sites More sharing options...
tater Posted June 20, 2020 Share Posted June 20, 2020 Seems like the failure mode of a really bad reentry is already LOM/LOC. We have to assume some baseline reentry profile, then a failure. So a TPS failure, skydiver failure (like the hydraulics on that offshore F9 booster landing), etc. At that point if the entry was survivable (likely a g-load issue on the squishy bits inside), then they can eject the pod instead of landing the wrecked SS. For an ascent abort, I'd imagine the critical bit is aerodynamic forces and g on the crew. Quote Link to comment Share on other sites More sharing options...
SOXBLOX Posted June 20, 2020 Share Posted June 20, 2020 Haven't seen most of this discussion but I'm gonna say that one SS loss with crew on board, when the loss could have been averted with an LES, would wreck public opinion regarding the vehicle. Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted June 20, 2020 Share Posted June 20, 2020 So, for an Earth-landing crewed/passenger Starship, (forgetting Luna/Mars for now), perhaps an emergency landing system (after surviving reentry) comprised of parafoils could work? It would not be comfortable, of course, just trying to turn a crash into a crash-landing. The Starship would have plenty of crumple zone for a belly landing. Perhaps the tankage could be flooded with an inert gas to reduce the risk of explosion or fire? Three or more parafoils on the lee side, with N2 tankage for inerting the tanks, seems like the simplest, cheapest option. Fire the belly RCS/thrusters just before impact to further reduce the impact. Orient the parafoils so the motion is backwards (engine first), which makes it more survivable than if the pax are facing the direction of travel (passengers like to face the direction of travel, but seats offer more crash support facing backwards. Military transports usually have backwards-facing seats). Again, it would be like ejection seats: not pleasant, but better than the alternative. Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted June 20, 2020 Share Posted June 20, 2020 (edited) 4 minutes ago, StrandedonEarth said: The Starship would have plenty of crumple zone for a belly landing. Perhaps the tankage could be flooded with an inert gas to reduce the risk of explosion or fire? It would be safer to completely separate the crew compartment from the tanks making them two different modules. *** Btw, Apollo D-2 design. The capsule is inside the hull. Spoiler Just in a spaceplane/cylinder it could/should be jettisonned radially, then pushed forward. Edited June 20, 2020 by kerbiloid Quote Link to comment Share on other sites More sharing options...
tater Posted June 20, 2020 Share Posted June 20, 2020 KISS. Giant chutes for a 120t (dry) SS make no sense. I'm not gonna talk about airliner levels of passengers, that's way out there, IMO. Just reasonable near future crew levels. Large compared to existing crew vehicles, but not crazy. Crew pod to mitigate some risks. Test vehicle to learn if that is good enough. Quote Link to comment Share on other sites More sharing options...
RCgothic Posted June 20, 2020 Share Posted June 20, 2020 I think all this talk of starship LES is pointless. It's not going to have one. Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted June 20, 2020 Share Posted June 20, 2020 3 minutes ago, kerbiloid said: It would be safer to completely separate the crew compartment from the tanks making them two different modules. But more complex Quote Link to comment Share on other sites More sharing options...
RealKerbal3x Posted June 20, 2020 Share Posted June 20, 2020 10 minutes ago, RCgothic said: I think all this talk of starship LES is pointless. It's not going to have one. I agree with you. As has already been demonstrated, an LES for SS is feasible for smaller crews. But crewed Starship could be 10 years out, which is plenty of time for them to fly it thousands of times and remove the need for a complex LES with pure reliability. After all, an LES for 100 people just doesn't make sense. Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted June 20, 2020 Share Posted June 20, 2020 (edited) 7 minutes ago, RealKerbal3x said: After all, an LES for 100 people just doesn't make sense. 100 humans in suits ~= 15 t. Or a sphere 6 m in diameter including the seats. So, not that much for a 100 t dry, 9 m wide ship. Actually somewhat of the Apollo D-2 proportions. Edited June 20, 2020 by kerbiloid Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted June 20, 2020 Share Posted June 20, 2020 (edited) 3 hours ago, Technical Ben said: Doesn't SS already have enough thrust for most aborts it's self? IIRC, Musk said a while back that Starship would have enough thrust itself to abort from Superheavy off the pad, they’d just light the vacuum Raptors, too. There would be a loss of efficiency but that’s not really a concern at that point. I assume the design is such that the engines could tolerate the underexpansion, at least for a time. This would happen in a fraction of a second, too. Seems to be two different trains running here, RE: aborts and safety. Are we talking astronaut-level safety or Joe Schmoe-level safety? I believe the LOCV risk for Dragon 2 is said to be 1:270. It’s worth mentioning that Starship as a system could simply demonstrate this level of safety by flying/returning 270 times in a row without incident. This would be a long pole for any other rocket, but SS could possibly do this within a single year. Add in a decade or so of operations, and you could possibly see 1:thousands reliability demonstrated before passenger ops become a thing. Edited June 20, 2020 by CatastrophicFailure wot the deuce?? Trice? Catorse even? Quote Link to comment Share on other sites More sharing options...
magnemoe Posted June 20, 2020 Share Posted June 20, 2020 50 minutes ago, Nightside said: I like this idea, it is basically a propellant depot, I guess. I suspect refueling operations will be very tricky, given the need for an inertial kick to get the fluids flowing, there are a lot of things that could go catastrophically wrong. Even if the MarsShip is only refueled once, I don't see any reason to risk having crew aboard during that operation anytime soon. Dumping hundreds of tons of props during an emergency separation/ landing seems like it would be hard to do. It seems like you would be descending in a cloud of combustible material, right before your landing burn. The trust then transferring does not to be high, just enough to settle fuel at bottom of tanks. Pretty sure they use pumps too, as this is standard electrical powered pumps gas bobbles is no huge deal. And yes docking is an risk factor but back to back should be pretty safe. Quote Link to comment Share on other sites More sharing options...
tater Posted June 20, 2020 Share Posted June 20, 2020 Also posted this in the Starlink thread: Quote Link to comment Share on other sites More sharing options...
Brotoro Posted June 21, 2020 Share Posted June 21, 2020 Would a single relatively small parachute in the nose of a Starship be a good backup method of ensuring that the ship can turn over before landing burn in case of aerosurface malfunction during descent? Quote Link to comment Share on other sites More sharing options...
tater Posted June 21, 2020 Share Posted June 21, 2020 1 minute ago, Brotoro said: Would a single relatively small parachute in the nose of a Starship be a good backup method of ensuring that the ship can turn over before landing burn in case of aerosurface malfunction during descent? A drogue chute? Interesting idea. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted June 21, 2020 Share Posted June 21, 2020 16 minutes ago, tater said: A drogue chute? Interesting idea. And why not? It works in KSP... Quote Link to comment Share on other sites More sharing options...
Xd the great Posted June 21, 2020 Share Posted June 21, 2020 2 hours ago, Brotoro said: Would a single relatively small parachute in the nose of a Starship be a good backup method of ensuring that the ship can turn over before landing burn in case of aerosurface malfunction during descent? Well, if one of the flaps malfunction, I am not sure if they can survive reentry, and I am not sure if 1 single drouge chute is enough to flip the starship over. Quote Link to comment Share on other sites More sharing options...
magnemoe Posted June 21, 2020 Share Posted June 21, 2020 16 hours ago, RealKerbal3x said: I agree with you. As has already been demonstrated, an LES for SS is feasible for smaller crews. But crewed Starship could be 10 years out, which is plenty of time for them to fly it thousands of times and remove the need for a complex LES with pure reliability. After all, an LES for 100 people just doesn't make sense. Agree with an large crew an LES will not work. However Musk is very interested in getting NASA money and want to start flying it as fast as possible and in that case an LES makes lots of sense. It will take an long time to get an 99.99% safety rating. Quote Link to comment Share on other sites More sharing options...
Guest Posted June 21, 2020 Share Posted June 21, 2020 He'll start flying it with cargo. I don't expect people to fly on Starship in a while. Besides, there's no infrastructure to handle 100+ people being in space at the same time. To build it, it would take a lot of cargo launches, so by the time it's ready, Starship should be good for crew, or we'll have something better. Quote Link to comment Share on other sites More sharing options...
tater Posted June 21, 2020 Share Posted June 21, 2020 50 minutes ago, Dragon01 said: He'll start flying it with cargo. I don't expect people to fly on Starship in a while. Besides, there's no infrastructure to handle 100+ people being in space at the same time. To build it, it would take a lot of cargo launches, so by the time it's ready, Starship should be good for crew, or we'll have something better. Yeah, the large numbers of people on SS is not something I take seriously as a near term event. Quote Link to comment Share on other sites More sharing options...
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