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NASA Announces SLS/Orion Flight Slide
JF Mezei wrote:
On 2017-05-21 14:43, Fred J. McCall wrote: capsule does, with some minimal lift, gives you 3g or more with jolts much higher. Note that the Shuttle still restrained occupants in seats, not just a mattress and some bungee cords. I never heard about such jolts or hard variations in air density that would create such jolts. So you're ignorant. We knew that. How big do you think a density change needs to be at Mach 25 to ruin your day? Also, if you are at 3G and then go to 4G for a second and back to 3G, everything remains "glued" to the floor. Nothing flies all over the place. You assume all accelerations are in the same direction and normal to the 'floor'. You assume wrong. Capsules 'wobble' on reentry. You,d have to suddently go from 3G to 0G and stay there long enough for gear to start floating, and at 0G, a mere bungee cord would be more than enough to keep gear on the floor. At de-orbit burn, floating stuff would fall to the floor, then go back to floating in 0G until atmosphere starts to generate G forces, at which point they would fall slowly to floor as G forces increase slowly. So I really do not unerstand your argument that a nominal re-entry is violent. Your lack of understanding doesn't change the facts. You have your answer. You think you know better. Go sod yourself. Granted, if the capsule starts tumbling, things will be violent, but isn't the shape designed to prevent this? Actually, US capsules are typically biconic, which means they have two semi-stable attitudes. One is with the heat shield 'down'. The other is with the nose 'down'. Capsules are NOT perfectly stable on reentry, which means they 'wobble' on the way down and that will throw **** inside the capsule around if it isn't properly restrained. If they ever 'wobble' far enough so that they flip to the other stable configuration, you're all dead because that end has no heat shield on it. In fact, biconic capsules have a certain amount of lift. This means two things: 1) They actually 'fly' a little bit on the way down, which reduces the deceleration forces so you only get 3-5 g instead of 9+. 2) Because they actually 'fly' a little bit, down isn't constant. Now, because there is lift, the decelleration vector isn't straight through the floor and varies based on angle of attack. Again, a biconic body is not perfectly stable, so it will also tend to 'wobble' a bit. But you know better, so why do you bother to ask questions in the first place? -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
#53
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NASA Announces SLS/Orion Flight Slide
On Sun, 21 May 2017 13:06:01 -0400, JF Mezei wrote:
On 2017-05-21 05:27, Fred J. McCall wrote: And dies from being sliced to ribbons by bungee cords and jellied against the sides of the capsule. Precisely what phase of re-entry would cause that? Seats. With restraint systems. And shock absorbers. You don't seem to understand that a capsule reentry can be a fairly violent trip as such things go. Which was the goal of my question, but you respond with silly arguments such as "jellied against the sides of the capsule". You're talking about peak deceleration of 3g-5g with random hard jolts in random directions. It's not a nice smooth trip like you seem to think it is. Hard jolts? looking at space shuttle re-entry videos, the crew didn't seem any rougher than on a bus. Which is the difference between a lifting re-entry by a winged vehicle, (Well, OK, some other non-winged shapes do perform lifting re-entries while hypersonic - the Apollo CM, and the Soyuz (Much of the time) and a ballistic re-entry where your're plummeting out of the sky like a badly thrown rock. A shuttle re-entry was typically around 3 Gs. A Soyuz or Apollo, as Fred says, 5-6. A fully ballistic descent, peak Gs of around 9-12 G, sustained over a fairly significant period of time (As in multiple 10s of seconds - when you effectively weigh 2000# (900 Kg), that's damage time. I've pulled significant Gs in airplanes - good seats, solid structure, secure (As in a 200 lb crew chief helping haul on the shoulder straps to get them properly tight) and a G-suit, and you can tolerate High Gs for a while - _If_ you know that they are coming, what direction they're going to be, and G onset isn't too sudden. Rattling around in a jackleg rig is just not going to work. Think of it this way - one of the biggest killers in airliner crashes has been seat failure - the relatively low impacts of a crash landing break the seats away from the structure and impact with bulkheads or the seats in front of you kills you. Frankly, you'd be better off with something like MOOSE - (Man Out Of Space, Easiest) - explored in the early '60s as an "Orbital Parachute" - A system with a retro-rocket that encapsulates a suited astronaut in an ablatable capsule, which will, if properly aimed, give you a chance to use a personal parachute over the right continent. It isn't like there are flying pigs that get hit by the capsule during re-entry, is it ? No, just gravity turns into dense air at high speeds. You don't need pigs then. -- Pete Stickney Struggle no more! I'm here to solve it with ALGORITHMS! |
#54
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NASA Announces SLS/Orion Flight Slide
i believe a dragon could safely return one or 2 astronauts safely..
first theres a large lead time, in the event of a soyuz family failure some back up is prudent.. given that today its clear we might need to return astronauts russian or american in a emergency....... |
#55
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NASA Announces SLS/Orion Flight Slide
bob haller wrote:
i believe a dragon could safely return one or 2 astronauts safely.. first theres a large lead time, in the event of a soyuz family failure some back up is prudent.. given that today its clear we might need to return astronauts russian or american in a emergency....... That's part of what the Commercial Manned Space efforts (SpaceX and Boeing) are supposed to produce. Meanwhile, a Soyuz family failure that prevents using them to reenter is unlikely. If said 'failure' coincides with an ISS failure and you HAVE to get off, you'd use the Soyuz anyway (after all, whatever might be wrong, they've been used a lot so the risk is still low). If it doesn't, you've got half a year to work it out. -- "Rule Number One for Slayers - Don't die." -- Buffy, the Vampire Slayer |
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