Comments on: Supersonic free-fall http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/ The unbearable lightness of Lex. Enjoy! Sun, 21 Mar 2010 02:51:23 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: nate http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/comment-page-1/#comment-411675 nate Mon, 25 Feb 2008 06:50:44 +0000 http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/#comment-411675 Re B's principle: there is no sucking, only pushing. gravity sucks, its much nicer in space...but the atmosphere only pushes, Gas molecules bangin' around and all that. (press?sure.) N Re B’s principle: there is no sucking, only pushing. gravity sucks, its much nicer in space…but the atmosphere only pushes, Gas molecules bangin’ around and all that. (press?sure.)

N

]]> By: Snake Eater http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/comment-page-1/#comment-411674 Snake Eater Wed, 15 Aug 2007 20:19:01 +0000 http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/#comment-411674 Agree... Michel is crackers...all this effort and expense to ultimately place second in a two man race...but on the up side... I did enjoy the techno/geek discussion. Best Agree… Michel is crackers…all this effort and expense to ultimately place second in a two man race…but on the up side… I did enjoy the techno/geek discussion. Best

]]> By: Hope the Packup Included This - - It’s not random, it’s CHAOS! http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/comment-page-1/#comment-104871 Hope the Packup Included This - - It’s not random, it’s CHAOS! Wed, 15 Aug 2007 19:24:00 +0000 http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/#comment-104871 [...] on the more serious side, think about being a bona fide astronaut and, having scoffed at skydivers all these years (for no real aviator would jump out of a ‘perfectly good’ airplane) and now you are in [...] [...] on the more serious side, think about being a bona fide astronaut and, having scoffed at skydivers all these years (for no real aviator would jump out of a ‘perfectly good’ airplane) and now you are in [...]

]]> By: MaxDamage http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/comment-page-1/#comment-104738 MaxDamage Wed, 15 Aug 2007 05:28:47 +0000 http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/#comment-104738 Exactly, B2. I've been pondering this a bit more. The "golden BB" bit of pollen isn't much of a risk unless there's turbulence in the air, updrafts and the sort. Yes, they're light, and small. So is a bullet. E=MV^2 and he's got a whole bagfull of V. But there's a lot of atmosphere and little of him so what are the odds? One that's causing me to pull what remaining hair I have out is Bernoulli's Principle and how that's going to work with such low pressures and high velocity. ObGeekExplanation: Bernoulli's Principle is why aircraft fly. As you increase the speed of a fluid, and air acts as one, the pressure drops. So far so good. So we make an aircraft wing and we make the bottom flat and the top sort of curved, so it has a longer length than the bottom. We then fly through the air and the air flowing across the top of the wing speeds up, it having a longer length to pass over, thus the pressure drops, and we have lift. You can think of high pressure on the bottom of the wing lifting the aircraft, but it's more accurate to think of the low pressure on the top of the wing sucking the aircraft upwards. So, stick your hand out the window of your car sometime and feel that wind resistance. That's not just the resistance caused by the high pressure of the air ahead of your hand, it's also the low pressure of the air behind your hand working in concert. There are not a lot of square inches to your hand. There are a lot of square inches to his body, especially in some sort of lightweight pressure suit (and carbon fiber tells me they went for light weight and minimal area). Toss in ten times the speed, or 100x the wind resistance, and the equations just start getting surreal real fast. Once past Mach the air doesn't flow around you. It parts, and you're dragging a huge vacuum behind you. This changes things dramatically, and is the reason the speed of sound was indeed a barrier for so long. I wish him luck. With a nice drogue chute deployed soon after the jump he should be fine. If he wants to cowboy his way down the physics rapidly reach numbers we normally don't see in building bridges, but approach those involving explosives. I don't do this sort of work for a living, my calculations could be off a bit, and of course the ascent is probably the most dangerous part for him. Still, while possible, taking such a risk just to be in a record book is not something I could professionally lend my support to. - Max Exactly, B2. I’ve been pondering this a bit more. The “golden BB” bit of pollen isn’t much of a risk unless there’s turbulence in the air, updrafts and the sort. Yes, they’re light, and small. So is a bullet. E=MV^2 and he’s got a whole bagfull of V. But there’s a lot of atmosphere and little of him so what are the odds?

One that’s causing me to pull what remaining hair I have out is Bernoulli’s Principle and how that’s going to work with such low pressures and high velocity.

ObGeekExplanation: Bernoulli’s Principle is why aircraft fly. As you increase the speed of a fluid, and air acts as one, the pressure drops. So far so good. So we make an aircraft wing and we make the bottom flat and the top sort of curved, so it has a longer length than the bottom. We then fly through the air and the air flowing across the top of the wing speeds up, it having a longer length to pass over, thus the pressure drops, and we have lift. You can think of high pressure on the bottom of the wing lifting the aircraft, but it’s more accurate to think of the low pressure on the top of the wing sucking the aircraft upwards.

So, stick your hand out the window of your car sometime and feel that wind resistance. That’s not just the resistance caused by the high pressure of the air ahead of your hand, it’s also the low pressure of the air behind your hand working in concert.

There are not a lot of square inches to your hand. There are a lot of square inches to his body, especially in some sort of lightweight pressure suit (and carbon fiber tells me they went for light weight and minimal area). Toss in ten times the speed, or 100x the wind resistance, and the equations just start getting surreal real fast. Once past Mach the air doesn’t flow around you. It parts, and you’re dragging a huge vacuum behind you. This changes things dramatically, and is the reason the speed of sound was indeed a barrier for so long.

I wish him luck. With a nice drogue chute deployed soon after the jump he should be fine. If he wants to cowboy his way down the physics rapidly reach numbers we normally don’t see in building bridges, but approach those involving explosives.

I don’t do this sort of work for a living, my calculations could be off a bit, and of course the ascent is probably the most dangerous part for him. Still, while possible, taking such a risk just to be in a record book is not something I could professionally lend my support to.

– Max

]]> By: b2 http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/comment-page-1/#comment-411673 b2 Tue, 14 Aug 2007 19:39:59 +0000 http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/#comment-411673 <p>Interesting physics. It's all here under Terminal Velocity:</p> <p>http://hypertextbook.com/facts/JianHuang.shtml</p> <p>Got it? Now let us apply the terminal velocity calculator at: </p> <p>http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html:</p> <p>Based on a B2 estimated weight of 250 lbs- (Frenchman+gear ), a nominal cross section of 10 sqft and a start point of 125,000 ft in the ionosphere it is feasible he could reach a terminal velocity of near 1.3M. (nominal 650kts maybe). Terminal velocity for him as he nears the surface is about 145 kts. Theoretically, 15 seconds after he leaps he will reach a terminal velocity of 1.3M, and decelrate/fall over 100000ft until he slows to 145.. Lets see, 650-145= that's only about a 500kt delta worth of friction...This stunt depends on his equipment and pressure suit.</p> <p>Heat from friction, G and cold survivability all factors. He may reach 1.3M but he might not get to tell us how it felt because he could be dead!</p> <p>b2</p> Interesting physics. It’s all here under Terminal Velocity:

http://hypertextbook.com/facts/JianHuang.shtml

Got it? Now let us apply the terminal velocity calculator at:

http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html:

Based on a B2 estimated weight of 250 lbs- (Frenchman+gear ), a nominal cross section of 10 sqft and a start point of 125,000 ft in the ionosphere it is feasible he could reach a terminal velocity of near 1.3M. (nominal 650kts maybe). Terminal velocity for him as he nears the surface is about 145 kts. Theoretically, 15 seconds after he leaps he will reach a terminal velocity of 1.3M, and decelrate/fall over 100000ft until he slows to 145.. Lets see, 650-145= that’s only about a 500kt delta worth of friction…This stunt depends on his equipment and pressure suit.

Heat from friction, G and cold survivability all factors. He may reach 1.3M but he might not get to tell us how it felt because he could be dead!

b2

]]> By: lex http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/comment-page-1/#comment-104596 lex Tue, 14 Aug 2007 16:06:39 +0000 http://www.neptunuslex.com/2007/08/13/supersonic-free-fall/#comment-104596 Theodore, I should have said that you can't hear the shockwave detaching, since it's behind you. Since radio waves travel at the speed of light, and the conductive environment of the airplane is <em>also</em> supersonic you can hear all normal cockpit sounds. Theodore, I should have said that you can’t hear the shockwave detaching, since it’s behind you. Since radio waves travel at the speed of light, and the conductive environment of the airplane is also supersonic you can hear all normal cockpit sounds.

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