Technical Ben Posted April 20, 2017 Share Posted April 20, 2017 Some form of engines would help... the strains on the fuel tank would want to be reduced, a net alone would not do that. A net has a larger area to catch it from. Though a mix of the two ideas, a cradle on pulleys may work. Link to comment Share on other sites More sharing options...
cubinator Posted April 20, 2017 Share Posted April 20, 2017 12 minutes ago, sevenperforce said: It can land upright in a static cradle with vertical arms. Pinpoint landing isn't a problem, never has been. Hide contents EDIT: Wait a minute. If it can RTLS and control its descent with grid fins enough to pinpoint a landing, it can literally just land in a net, suspended above the ground. No SuperDracos required. Terminal velocity would not be very high. They should hire Black Hat: https://xkcd.com/1243/ If you did land it in a net, you'd have you worry about it bouncing and flipping onto the engine, which would crush it for sure. Link to comment Share on other sites More sharing options...
magnemoe Posted April 20, 2017 Share Posted April 20, 2017 5 hours ago, cubinator said: What about, in place of landing legs, some sort of "catcher" platform that would attach to the second stage and stabilize it as it finishes it's landing? They're already working on something similar for the first stage. That way you don't have the added mass of landing legs during flight, but you still don't tip over when you land. Far to complex and second stage is only 4 ton and with an nose landing the legs don't have to be long. 5 hours ago, sevenperforce said: Another idea that is particularly promising... Autorotation. Terminal velocity on the first stage is (at present) slightly subsonic. I'm guessing it's somewhere around 300 m/s. The first stage masses four times the second stage, but since grid fin drag and pressure drag are the majority, this suggests terminal velocity that's roughly a quarter of that, or 75 m/s. It would actually be slightly higher because of the square term in the drag equation, but the new grid fins are larger so that's probably not much of a difference. The new grid fins are supposed to be able to provide a 1:1 lift-to-drag ratio on the first stage. And that's where things get interesting. L/D on the second stage with the same size grid fins would be on the order of 4:1 or maybe even 5:1. So if the second stage was allowed to autorotate, it could conceivably get enough lift to reduce impact speed to something on the order of 15 m/s, which might be bouncy-castle-survivable. This would require landing wheels as it will rotate on landing Course correction for something rotating sounds complex but they aim smart artillery shells who move and rotate faster If its stupid and work its not stupid. Link to comment Share on other sites More sharing options...
Wjolcz Posted April 20, 2017 Share Posted April 20, 2017 (edited) 5 hours ago, sevenperforce said: The RoombaX I just went into this thread, saw this and had a genuine laugh for a couple of minutes. 3 hours ago, sevenperforce said: It can land upright in a static cradle with vertical arms. Pinpoint landing isn't a problem, never has been. Reveal hidden contents The cradle would have wide open spaces for the exhaust plumes to exit through. EDIT: Wait a minute. If it can RTLS and control its descent with grid fins enough to pinpoint a landing, it can literally just land in a net, suspended above the ground. No SuperDracos required. Terminal velocity would not be very high. Case in point: https://www.youtube.com/watch?v=6qF_fzEI4wU What kind of net and how big would it have to be though? What if they used the interstage fairing to protect the engine bell during the catch? Edited April 20, 2017 by Veeltch Link to comment Share on other sites More sharing options...
sojourner Posted April 20, 2017 Share Posted April 20, 2017 (edited) 7 hours ago, sevenperforce said: The consumables tanks could probably be much smaller, but getting fold-out landing legs requires a lot of space. Don't use fold out legs. Use popout peg legs like on Crew Dragon. EDIT: Hehe, this is sort of weird having this conversation across two forums. Though I am more of a lurker on NSF. Edited April 21, 2017 by sojourner Link to comment Share on other sites More sharing options...
kerbiloid Posted April 21, 2017 Share Posted April 21, 2017 Who needs those legs? Spoiler Link to comment Share on other sites More sharing options...
sojourner Posted April 21, 2017 Share Posted April 21, 2017 (edited) 1 hour ago, kerbiloid said: Who needs those legs? Hide contents Well, if the second stage looked anything like that, it would work, but since it doesn't....... Edited April 21, 2017 by sojourner Link to comment Share on other sites More sharing options...
sevenperforce Posted April 21, 2017 Share Posted April 21, 2017 Random thought. Once the ITS system is up and running, it may actually prove cheaper (dV-wise) to send a fleet of tankers to Mars and use ISRU there to provide transfer fuel. You only need a fuel fraction of 65.7% to SSTO from Mars (including enough residuals for landing), meaning that a single, full tanker can lift 888 tonnes of fuel into Martian orbit via SSTO, more than twice as much as an Earth-based tanker launched by the ITS booster. Link to comment Share on other sites More sharing options...
Streetwind Posted April 21, 2017 Share Posted April 21, 2017 I think the idea is that the crewed ITS spacecraft itself gets filled up on the Martian surface, takes off under its own power, and makes the transfer back to Earth without needing refueling at all. Link to comment Share on other sites More sharing options...
sevenperforce Posted April 21, 2017 Share Posted April 21, 2017 20 minutes ago, Streetwind said: I think the idea is that the crewed ITS spacecraft itself gets filled up on the Martian surface, takes off under its own power, and makes the transfer back to Earth without needing refueling at all. Yes, that's entirely possible. But my point was that collecting propellant on Mars via ISRU and transferring it back to Earth orbit in a tanker might be more efficient than simply launching it on Earth. Link to comment Share on other sites More sharing options...
cantab Posted April 21, 2017 Share Posted April 21, 2017 I rather thing we're a long way off that being cost-effective considering how much harder doing anything on Mars will be. Link to comment Share on other sites More sharing options...
Kerbal01 Posted April 22, 2017 Share Posted April 22, 2017 bringing this back to SpaceX discussion: and: lastly B1035 is at 39A: Link to comment Share on other sites More sharing options...
TheEpicSquared Posted April 22, 2017 Share Posted April 22, 2017 https://mobile.twitter.com/SpaceX/status/855830651303538690 Awesome! Link to comment Share on other sites More sharing options...
Kerbal01 Posted April 22, 2017 Share Posted April 22, 2017 18 minutes ago, TheEpicSquared said: https://mobile.twitter.com/SpaceX/status/855830651303538690 Awesome! posted above Link to comment Share on other sites More sharing options...
Ten Key Posted April 22, 2017 Share Posted April 22, 2017 That fairing picture is incredible. I would love to have that one up on the wall. Link to comment Share on other sites More sharing options...
Wjolcz Posted April 22, 2017 Share Posted April 22, 2017 (edited) How much a fully reusable F9 (first and second stage) could put into LEO? About 20 metric tonnes? Extra question: Could a F9 or FH launch from Boca Chica and land at Florida? I'd imagine this would be the case with FH because I really can't imagine how the middle core could go back to the launch site like in their FH video. Edited April 22, 2017 by Veeltch Link to comment Share on other sites More sharing options...
Kerbal01 Posted April 22, 2017 Share Posted April 22, 2017 FAA overflight rules would forbid that. Link to comment Share on other sites More sharing options...
IncongruousGoat Posted April 22, 2017 Share Posted April 22, 2017 59 minutes ago, Veeltch said: How much a fully reusable F9 (first and second stage) could put into LKO? About 20 metric tonnes? Into LKO? Probably closer to a hundred, given KSP's lowered orbital velocities. In all seriousness, though, it depends on how SpaceX goes about reusing the second stage, and what kind of mass penalty that incurs. Although I suspect it would probably be closer to 15 tons. Link to comment Share on other sites More sharing options...
Wjolcz Posted April 22, 2017 Share Posted April 22, 2017 (edited) 34 minutes ago, IncongruousGoat said: Into LKO? Probably closer to a hundred, given KSP's lowered orbital velocities. In all seriousness, though, it depends on how SpaceX goes about reusing the second stage, and what kind of mass penalty that incurs. Although I suspect it would probably be closer to 15 tons. OH NOOO! I did it again! I seriously should stop posting in this thread after 10 pm. 15 tons for a fully reusable rocket is still pretty good though, isn't it? Edited April 22, 2017 by Veeltch Link to comment Share on other sites More sharing options...
sevenperforce Posted April 22, 2017 Share Posted April 22, 2017 15 minutes ago, Veeltch said: OH NOOO! I did it again! I seriously should stop posting in this thread after 10 pm. 15 tons for a fully reusable rocket is still pretty good though, isn't it? Recovery mode for the second stage is the tricky part. Link to comment Share on other sites More sharing options...
_Augustus_ Posted April 23, 2017 Share Posted April 23, 2017 (edited) 3 hours ago, DarthVader said: FAA overflight rules would forbid that. NVM oops I'm an idiot Edited April 23, 2017 by _Augustus_ Link to comment Share on other sites More sharing options...
Kryten Posted April 23, 2017 Share Posted April 23, 2017 (edited) 12 minutes ago, _Augustus_ said: But launches from Vandenberg fly over a large chunk of North America. Launching from Texas and landing in Florida would only mean flying over Florida. Almost all payloads from Vandenberg fly southwest. At worst, they overfly some barrier islands. Edited April 23, 2017 by Kryten Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted April 23, 2017 Share Posted April 23, 2017 2 minutes ago, Kryten said: Almost all payloads from Vandenberg fly southwest. At worst, they overfly some barrier islands. IIRC, the lowest inclination Vandenburg can launch to is 50*, due to those overflight rules. Link to comment Share on other sites More sharing options...
monophonic Posted April 23, 2017 Share Posted April 23, 2017 9 hours ago, DarthVader said: FAA overflight rules would forbid that. Rules can be changed. After all, airliners are allowed to overfly cities and they come down wrong occasionally too. But those particular rules won't change easily, or soon. I'll guess we have to be into daily launches with perfect record before any overflight permits will start to get issued. And those will be special cases for single launches at first too. 8 hours ago, Veeltch said: 15 tons for a fully reusable rocket is still pretty good though, isn't it? Depend entirely on the refurbishment costs. STS failed there but SpaceX seems to be doing better. Link to comment Share on other sites More sharing options...
mikegarrison Posted April 23, 2017 Share Posted April 23, 2017 1 hour ago, monophonic said: Rules can be changed. After all, airliners are allowed to overfly cities and they come down wrong occasionally too. But those particular rules won't change easily, or soon. I'll guess we have to be into daily launches with perfect record before any overflight permits will start to get issued. And those will be special cases for single launches at first too. Airline flight safety reliability is at least a million times better than rocket booster flight safety reliability. Six orders of magnitude is a conservative estimate. Link to comment Share on other sites More sharing options...
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