fasterfaller 0 #26 June 13, 2006 QuoteSpectre210 survived reentry from bailing out of the shuttle, so I don't see why not. Damn skippy I survived , but then again I am special . Looks like I have been downsized as well . Quote Share this post Link to post Share on other sites
lawrocket 3 #27 June 13, 2006 This is interesting. Most of the speed that needs to be bled off from friction for objects in re-entry IS from horizontal speed. What I'm confused about is how you can have zero groundspeed along with zero velocity. Perhaps you must have zero horizontal velocity with relation to winds. I think that the only way that it COULD be accomplished is to have the fall happen from a height that is minimally into "space" so that the airspeed rarely gets above any terminal velocity that the skydiver may encounter. Damn. It's a tough question, and I think pretty hypothetical with regard to exactly how to get a craft up there that would get things operating within the correct parameters. My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
Andy_Copland 0 #28 June 13, 2006 I dont know if that makes me feel better. Looks like the only person laughing with me is a half orange oompa loompa... I crack me up sorry1338 People aint made of nothin' but water and shit. Until morale improves, the beatings will continue. Quote Share this post Link to post Share on other sites
shaiziel 0 #29 June 13, 2006 Different situation. Again, they were having to slow down from orbital velocity. In my hypothesized situation, you would not be streaking across the sky at 10,000 mph. That is what makes shuttle re-entry so extreme. In this situation we are saying "suppose you had ZERO orbital velocity". Totally different.---------------------------------------- 6.8% - Almost there! Quote Share this post Link to post Share on other sites
micro 0 #30 June 13, 2006 QuoteDifferent situation. Again, they were having to slow down from orbital velocity. In my hypothesized situation, you would not be streaking across the sky at 10,000 mph. That is what makes shuttle re-entry so extreme. In this situation we are saying "suppose you had ZERO orbital velocity". Totally different. color me ignorant, but how does one achieve "zero orbital velocity?" I miss Lee. And JP. And Chris. And... Quote Share this post Link to post Share on other sites
twibbles 0 #31 June 13, 2006 QuoteDidn't a shuttle recently DISprove this as a possibility??? The shuttle needed to lose it's orbital velocity, which was 27,400 Km/h if i remember right, hence needing heat shields to absorb the heat generated by the friction against the atmosphere while aerobraking. If orbital velocity is taken out of the question like shaiziel was saying, it's another question all together Eugene "In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move." Quote Share this post Link to post Share on other sites
Slappie 9 #32 June 13, 2006 QuoteDifferent situation. Again, they were having to slow down from orbital velocity. In my hypothesized situation, you would not be streaking across the sky at 10,000 mph. That is what makes shuttle re-entry so extreme. In this situation we are saying "suppose you had ZERO orbital velocity". Totally different. If this was the case, wouldn't you think NASA would just slow the shuttle down to zero and then let it fall as you say back to earth. Slow enough as to not cause re-entry burns etc.. No is the answer. You must reach a certain amount of speed and the correct angle or you will bounce of the upper atmosphere to become a bb being shot away from he earth with no mean to slow down or direct your trajectory. "Find out just what any people will quietly submit to and you have found out the exact measure of injustice and wrong which will be imposed upon them." Quote Share this post Link to post Share on other sites
twibbles 0 #33 June 13, 2006 QuoteQuoteDifferent situation. Again, they were having to slow down from orbital velocity. In my hypothesized situation, you would not be streaking across the sky at 10,000 mph. That is what makes shuttle re-entry so extreme. In this situation we are saying "suppose you had ZERO orbital velocity". Totally different. color me ignorant, but how does one achieve "zero orbital velocity?" A very big rocket firing against the direction of travel in orbit, or starting on the ground and going straight up in a rocket could do it. Eugene "In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move." Quote Share this post Link to post Share on other sites
pilotdave 0 #34 June 13, 2006 Ok, some quick, dumb calculations... The space station is about 400 km above the surface of earth. 400,000 meters or ~1.3 million feet. So lets say you have basically no drag from exit to about 300,000 feet. That's a million feet of freefall accelerating at ~32 ft/s^2. Probably a little less acceleration because there's less gravity at a million feet than on the surface, but not THAT much less. Long story short... you're doing 5400 (edit) mph when you reach 300,000 feet, and you're still accelerating. Course I probably left something off the calculation (again)... Dave Quote Share this post Link to post Share on other sites
Slappie 9 #35 June 13, 2006 QuoteOk, some quick, dumb calculations... The space station is about 400 km above the surface of earth. 400,000 meters or ~1.3 million feet. So lets say you have basically no drag from exit to about 300,000 feet. That's a million feet of freefall accelerating at ~32 ft/s^2. Long story short... you're doing 3800 mph when you reach 300,000 feet. Dave You also have to take into consideration there is no drag in space. So unless you've some type of mechanical device (rocket or some uber fan) you'll have no way of slowing down before you slam into the earths upper atmosphere. Kind of like a bug on a windshield, cept this car is traveling at 4000mph. "Find out just what any people will quietly submit to and you have found out the exact measure of injustice and wrong which will be imposed upon them." Quote Share this post Link to post Share on other sites
twibbles 0 #36 June 13, 2006 QuoteIf this was the case, wouldn't you think NASA would just slow the shuttle down to zero and then let it fall as you say back to earth. Slow enough as to not cause re-entry burns etc.. No one slows orbital velocity down to zero because it's very expensive to do and technically very challanging. Everyone's seen the shuttle launching. Other then energy lost through drag in the atmosphere, the the boosters and main engines are used to bring it to orbital velocity. Now imagine needing the same rockets and engines to slow it back down to zero. And the only you need the corect angle for re-entry in the first place is because of the orbital velocity of the object. If you shoot BB at an oblique angle to a pool of water, it'll bounce off. If you drop it straight down, there's no problem. Eugene "In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move." Quote Share this post Link to post Share on other sites
lawrocket 3 #37 June 13, 2006 QuoteYou won't be going faster then terminal velocity.As the atmosphere thickens the lower you go, your terminal velocity lowers. Got to go think about it some more. See? That's the problem. In fact, he WAS going faster than terminal velocity for almost the whole flight, which is why the drag slowed him down. Fortunately, this slowdown was controlled over a period of time. (I wonder what Kittenger's G-load was for portions of this). So if you jump above the atmosphere - where there would be no terminal velocity - the further you fall until you hit the atmosphere, the higher your velocity compared to the atmosphere when you hit it, right? It seems that if a person jumped and didn't hit the atmosphere for 60 seconds, that person would be falling at 2,116.8 kilometers per hour. If the person fell 2 kilometer prior to hitting the atmosphere, that person would be traveling at 200 km/hr upon re-entry. (my math may be off. I'm not good at this). But that isn't very far. If you traveled 10 km before re-entry, I'd imagine you are travling at 1,000 km/hr. That would make a bigger burn when you start slowing down. It MAY be possible, but only with the drop done in perfectly measured conditions. So My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
simplyputsi 0 #38 June 13, 2006 Quotet... you're doing 5400 (edit) mph when you reach 300,000 feet, Dave That's not that fast really. Beavis and butthead rule!!Skymama's #2 stalker - Quote Share this post Link to post Share on other sites
twibbles 0 #39 June 13, 2006 QuoteQuoteOk, some quick, dumb calculations... The space station is about 400 km above the surface of earth. 400,000 meters or ~1.3 million feet. So lets say you have basically no drag from exit to about 300,000 feet. That's a million feet of freefall accelerating at ~32 ft/s^2. Long story short... you're doing 3800 mph when you reach 300,000 feet. Dave You also have to take into consideration there is no drag in space. So unless you've some type of mechanical device (rocket or some uber fan) you'll have no way of slowing down before you slam into the earths upper atmosphere. Kind of like a bug on a windshield, cept this car is traveling at 4000mph. But then atmosphere density increases exponetionally towards the ground. And drag is function of density and the squared of velocity, drag would gradually increase the lower you go. The big question is wether the peak deeceleration is survivable. Eugene edited to change "drag is a function of velocity and the squared of velocity" "In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move." Quote Share this post Link to post Share on other sites
shaiziel 0 #40 June 13, 2006 Well we're basing it on the theory of getting as close to zero orbital velocity, not zero ground speed. I guess a point to account for is the rotation speed of the atmosphere. Whatever the case is, your best bet is to match the lateral speed of the atmosphere.---------------------------------------- 6.8% - Almost there! Quote Share this post Link to post Share on other sites
twibbles 0 #41 June 13, 2006 Ahh.. I see your point. I knew i was missing something Eugene "In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move." Quote Share this post Link to post Share on other sites
pilotdave 0 #42 June 13, 2006 Comparison... concorde does ~1400 mph. That pointy nose reaches about ~260 degrees F. I think you'd be toast (well done toast at that) by the time you slowed to 1400 mph. Dave Quote Share this post Link to post Share on other sites
lawrocket 3 #43 June 13, 2006 Quotewouldn't you think NASA would just slow the shuttle down to zero and then let it fall as you say back to earth. Slow enough as to not cause re-entry burns etc.. The energy requirements to do this make it unfeasible. You'd practically have to have haul another one or two fully groundlaunch-ready space shuttles up there with it to slow it down like that and maintain altitude. My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
stitch 0 #44 June 13, 2006 QuoteQuotet... you're doing 5400 (edit) mph when you reach 300,000 feet, Dave That's not that fast really. Beavis and butthead rule!!Yeah!!!! When you re-enter the atmosphere, just deploy your drogue."No cookies for you"- GFD "I don't think I like the sound of that" ~ MB65 Don't be a "Racer Hater" Quote Share this post Link to post Share on other sites
shaiziel 0 #45 June 13, 2006 Exactly. Of course the structure of the behavior and nature of the atmosphere is important here. I assume it rotates with the planet as "holes in the ozone" don't seem to move across the surface. So the atmosphere is moving through space at... roughly 1,000mph laterally. So you'd need to maintain orbital speed equivalent to the speed of the upper atmosphere in a best case scenario.---------------------------------------- 6.8% - Almost there! Quote Share this post Link to post Share on other sites
normiss 620 #46 June 13, 2006 STAND on the atmosphere??? Quote Share this post Link to post Share on other sites
shaiziel 0 #47 June 13, 2006 So if you're going to be experiencing some heat, could it be mitigated with a small capsule like suit encased in thermal ceramic? You probably couldn't afford to have limbs sticking out as they may be ripped off.---------------------------------------- 6.8% - Almost there! Quote Share this post Link to post Share on other sites
simplyputsi 0 #48 June 13, 2006 QuoteQuoteQuotet... you're doing 5400 (edit) mph when you reach 300,000 feet, Dave That's not that fast really. Beavis and butthead rule!!Yeah!!!! When you re-enter the atmosphere, just deploy your drogue. a little mach 7.5 never hurt anyone. not a drogue dude, you have to fire your chest mounted retro rocket, then you can deploy your drogue. Now what size drogue to use??Skymama's #2 stalker - Quote Share this post Link to post Share on other sites
twibbles 0 #49 June 13, 2006 QuoteExactly. Of course the structure of the behavior and nature of the atmosphere is important here. I assume it rotates with the planet as "holes in the ozone" don't seem to move across the surface. So the atmosphere is moving through space at... roughly 1,000mph laterally. So you'd need to maintain orbital speed equivalent to the speed of the upper atmosphere in a best case scenario. Yeah, that's why most rockets are launched east-wards, so they don't have to go against Earth's rotation. I suppose i could do a spredsheet, with atmosphere density against height. With the velocities from gravational acceleration at different heights, i could work out the drag at different altitudes, and get a graph out of it, but it sounds like proper work That is assuming a straight line fall in relation to the Earth's and the atmosphere's rotation of course. Eugene "In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move." Quote Share this post Link to post Share on other sites
twibbles 0 #50 June 13, 2006 QuoteSo if you're going to be experiencing some heat, could it be mitigated with a small capsule like suit encased in thermal ceramic? You probably couldn't afford to have limbs sticking out as they may be ripped off. Or something ablative, absorbing heat by vaporising Eugene "In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move." Quote Share this post Link to post Share on other sites
