Orbital skydiving—possible?

[palebluehuh]

Long ago, I read in a science-fiction novel about a guy that went skydiving from orbit. He had on a spacesuit with ablative plating and everything. My question is: with today's technolgy, is it possible to do that? Assuming we had a really well-built spacesuit with ablative plating and some means of deorbiting, can it be done? Assuming it can be done, can we drop the prospective thrill-seeker at a given point on the planet, and if so, how much accuracy can we expect? I'm not picturing landing from orbit onto a moving vehicle, but perhaps getting within a few miles or so of one's destination sounds nice.

 

On a related note, what's the smallest orbital vehicle we have that can withstand a reentry? I remember reading about these really tiny lifepods that were slated to act as an emergency escape for space missions, but they never were built, I think. Now, we have the Soyuz capsule on the ISS, but is there anything smaller?

[5614]

the thing which just entered the earth was smallish [with all the partciles from the sun, i forget the name of it]

 

it is theoretically possible, as the gravitational pull of the earth would pull in the person, so yes its possible, however if brings about many problems.

 

(a) there is a limit to the amount of G-Forces one can withstand, this might be too extreme

(b) the spacesuit would need to be able to withstand a lot

© the parachute would need to come out and slow you down, fabric burns during re-entry, so it would have to be in a totaly seeled container, with metal hinges which wont melt!

(d) you would be going very fast.... very very fast, see 'a', you may red out or black out, depending on which way you are falling.

 

theoretically, yes..... probably not though.... nice idea.

[palebluehuh]

(a) there is a limit to the amount of G-Forces one can withstand, this might be too extreme

 

During freefall, wouldn't the G's be zero? In would only expect to pull G's during the de-orbit burn and the deployment of the parachute.

 

(b) the spacesuit would need to be able to withstand a lot

© the parachute would need to come out and slow you down, fabric burns during re-entry, so it would have to be in a totaly seeled container, with metal hinges which wont melt!

 

True, true. Maybe if the sky-diver maintained a sort of belly-down orientation, and the chute-pack were in the lee of his slipstream, it would keep it from getting too hot. The leading edges, i.e., the belly of the space-diver, would be the hottest part.

[swansont]

During freefall' date=' wouldn't the G's be zero? In would only expect to pull G's during the de-orbit burn and the deployment of the parachute.

[/quote']

 

You would have to pull 1 g for the entire trip just to keep your speed constant. For all the time you are pulling zero g's and speeding up, you will have to pull more g's later on to compensate.

[palebluehuh]

So... I do a de-orbit burn to lower my velocity. Pull G's. I fall for a few minutes. I don't pull G's. Perform maneuvers to bleed airspeed. Pull some G's. I deploy parachute. Pull insane G's. I hit the ground. Potentially fatal G's.

 

How would I maintain 1 G for the entire drop? Rockets?

[Cap'n Refsmmat]

Friction.

You can't go through the atmosphere without friction, which slows you down and is the reason for all of those heat shields.

[swansont]

Friction.

You can't go through the atmosphere without friction' date=' which slows you down and is the reason for all of those heat shields.[/quote']

 

It's technically ram pressure. PV=nRT; P goes up, so T goes up.

[RICHARDBATTY]

You only realy experience g when you are stationary relative to gravity/centrifuge/inertia. Even being slowed by friction you would still be moving with gravity to some extent. An alloy that Thales mentioned in another thread may help as it turns heat into electricity and cools. A good heat sheild and a suit containing this alloy might make it possible. It may take the form of sky surfing. Dude. A board as the entry sheild, wrong shape but you get the idea. Then you would need multi stage chutes starting with small metal ones and working up in size and down in materials. I think a suit of this type would be quite restricting though, the nappy/diaper would get uncomfortable too.

[palebluehuh]

Hmm... Thermoelectric alloys; I like that. But how the heck are you going to cool a spacesuit already heated to incandescence; you'd need a mad-sized radiator. I want something that's marginally mobile (I mean, a person can stand up and walk, even with difficulty; I don't expect a marathon here). But all the heat shielding and life-support components would be bulky, as well as the parachute(s) and such. That much weight would call for servo motor-enhancements, and that would add further to the bulk.

 

Has anyone ever drawn up plans for such a thing?

[YT2095]

I can`t see any reason, that from a geo stationary orbit, and using a sequence of parachutes from very small to the normal size needed, that it couldn`t be done.

there was one guy a few years back that went up to the edge of space in a helium balloon (he`de got a puncture in his space suit glove too, that how I rem it) that did exactly that, he got the world record for freefall too, and his hand was fine eventualy.

[jsatan]

lol you don't burn up on re-entry because of friction. you burn because the speed you are going is above the speed of sound and so the air in front of you compresses and what happens then? it gets hot. very hot in this case.

 

tut tut .

[JohnB]

I'm not sure that too amny parachutes would be needed. The factor not mentioned so far is "Terminal Velocity". For all practical purposes, it doesn't matter if you jump from 500 feet or 5,000 feet. The Terminal Velocity is the same, about 120 mph if in a spreadeagled position.

 

Rather than thinking of air resistance, we can think of the air attempting to slow the falling body to terminal velocity. I suppose the question would be, how fast would the air slow you down? In an ideal case, ignoring the thickness of the atmosphere and heat, the falling person would be slowed at an ever increasing rate until their speed dropped to TV.

 

How quickly would they slow down? And how much heat would be generated? Once the person hits TV, even if 10 miles up, it should become the same as any other parachute jump. I hope.

[Ophiolite]

I wonder if a spherical, ablative cocoon could be used to enclose the Sky Surfer until he got down to a sensible altitude and velocity. You aren't going to be able to see anything through the interval of maximum decelleration anyway. Or give it an aerofoil shape so you have some controllable glide capability.

I think this idea was proposed twenty-five years ago in an SF novel, possibly by Jerry Pournelle in "Jannisary", but I can't put my hand on a copy to check. If it wasn't, then I bag patent rights!

[Geode]

In Starship Troopers the Mobile Infantry dropped from orbit with approximately zero vector. Gravity did all the work. The MI troopers were surrounded by a succession of shells, that might be the way to go in this case. Rudimentary brakes of various designs could bring the assemblage to a reasonable velocity as they ablated away; the challenge might lay in navving the thing to come down over a benign stretch of land. Keeping the 'jumper' supplied with oxygen will also be a challenge.

 

On the other hand, the Air Force did some testing from sub-orbit with a man in a balloon and a pressurized pod. At altitude (100 miles?) the man (in a pressure suit) simply jumped.

 

Maybe right-now tech can't do it, but day-after-tomorrow tech should.

 

 

 

Geode

[swansont]

In Starship Troopers the Mobile Infantry dropped from orbit with approximately zero vector. Gravity did all the work. The MI troopers were surrounded by a succession of shells' date=' that might be the way to go in this case. Rudimentary brakes of various designs could bring the assemblage to a reasonable velocity as they ablated away; the challenge might lay in navving the thing to come down over a benign stretch of land. Keeping the 'jumper' supplied with oxygen will also be a challenge.

 

On the other hand, the Air Force did some testing from sub-orbit with a man in a balloon and a pressurized pod. At altitude (100 miles?) the man (in a pressure suit) simply jumped.

[/quote']

 

Zero vector?

 

A man in a balloon is not in orbit - the huge difference is the tangential speed, and thus energy, that you have to reduce. It's not simply freefall.

[Geode]

swansont wrote: A man in a balloon is not in orbit...

 

Apologies for not being clearer. I had no intention of implying that a man in a balloon was in orbit, and the 'zero vector' comment should have been 'nearly zero lateral vector'.

 

In the book the troops were dropped such that the velocity of the ship doing the dropping is cancelled by the drop. This is supposed to reduce to as near zero as possible the tangential velocity component and thereby minimize the energy-dissipation requirement.

 

 

 

Geode

[JohnB]

Weren't ablative cocoons considered originally as life boats for the ISS? I seem to remember reading something about it yonks ago. It looked like a large, elongated red blood cell. The air supply wasn't a problem as the evacuee was in a full EVA suit.

[Ophiolite]

On the other hand' date=' the Air Force did some testing from sub-orbit with a man in a balloon and a pressurized pod. At altitude (100 miles?) the man (in a pressure suit) simply jumped.

 

Geode[/quote']Minor (?) correction. 100,000' not 100 miles. First attempt was in 1957, and it was beaten by a couple of thousand feet in 1960. I don't think it's been bettered since then.

[ydoaPs]

You only realy experience g when you are stationary relative to gravity/centrifuge/inertia.

 

i am confused as to what you are trying to say. are you saying you only pull g's when you accelerate? if so, you are right. if you are saying you only pull g's when you are stationary, you are wrong.

[5614]

im not sure if this is what he meant, but yourdad is right... maybe richard meant you only experience 0g when you are stationary relative to gravity etc... which is correct.

[Guest Imnothere]

As far as I know the guy that jumped from a balloon from a height of aproximately 30 km was named Joe Kittinger.

 

I'm not sure that too amny parachutes would be needed. The factor not mentioned so far is "Terminal Velocity". For all practical purposes' date=' it doesn't matter if you jump from 500 feet or 5,000 feet. The Terminal Velocity is the same, about 120 mph if in a spreadeagled position.

 

Rather than thinking of air resistance, we can think of the air attempting to slow the falling body to terminal velocity. I suppose the question would be, how fast would the air slow you down? In an ideal case, ignoring the thickness of the atmosphere and heat, the falling person would be slowed at an ever increasing rate until their speed dropped to TV.

 

How quickly would they slow down? And how much heat would be generated? Once the person hits TV, even if 10 miles up, it should become the same as any other parachute jump. I hope.[/quote']

 

Although I never have done any skydiving myself there are some remarks I'd like to make.

It may be true that there is no difference between terminal velocity whether you jump from 200 m or 2 km. But if you jump from 30 km there will be a difference, because there is no (or hardly any) atmosphere at that height, you will fall faster then 200 km/h.

 

Joe Kittinger used one stabilizing chute before deploying his main chute. But before deploying his stabilizing chute he did manage to break the speed of sound.

 

Jumping from the International Space Station (about 400 km up) I think you would hit the atmosphere at pretty much the same speed as the space shuttle would, so it will be hot and you will need shielding.

 

So as far as I can see it the question that remains simply is : Are there materials available today that can handle the amount of heat generated, yet is light enough to be worn?

[Geode]

JohnB wrote: Weren't ablative cocoons considered originally as life boats for the ISS?

 

Never heard of that one. The design specs for the ISS originally (or eventually) incorporated a lifting-body escape boat that would more or less auto-nav its way to a soft landing, the terminal stage of this descent mediated by a parachute.

 

 

Geode

[[Tycho?]]

Yeah I was going to mention that super-high balloon jump as well.

 

The trick is terminal veloctiy. Just because you are falling from space doesn't mean you are moving at rediculously high speeds. If you are stationary relative to the atmosphere you are falling into, I'd think you'd be able to do it with no need for heat shields. You would need specially designed parachutes I would think, since you do get moving pretty fast (the record holder broke the sound barrier I think, this is possible because the atmosphere was so thin up there).

[Halash]

Long ago' date=' I read in a science-fiction novel about a guy that went skydiving from orbit. He had on a spacesuit with ablative plating and everything. My question is: with today's technolgy, is it possible to do that? Assuming we had a really well-built spacesuit with ablative plating and some means of deorbiting, can it be done? Assuming it can be done, can we drop the prospective thrill-seeker at a given point on the planet, and if so, how much accuracy can we expect? I'm not picturing landing from orbit onto a moving vehicle, but perhaps getting within a few miles or so of one's destination sounds nice.

 

On a related note, what's the smallest orbital vehicle we have that can withstand a reentry? I remember reading about these really tiny lifepods that were slated to act as an emergency escape for space missions, but they never were built, I think. Now, we have the Soyuz capsule on the ISS, but is there anything smaller?[/quote']

 

 

dude i had that idea at school... hah . i was inisioning me flying in a space craft and then bailing out and going superfast... it prolly possible with lots of thruster fuel to slow your descent.

 

 

the g-force and hitting the atmosphere couold rip limbs off

[Peterpanskydive]

I'm not sure that too amny parachutes would be needed. The factor not mentioned so far is "Terminal Velocity". For all practical purposes, it doesn't matter if you jump from 500 feet or 5,000 feet. The Terminal Velocity is the same, about 120 mph if in a spreadeagled position.

 

Rather than thinking of air resistance, we can think of the air attempting to slow the falling body to terminal velocity. I suppose the question would be, how fast would the air slow you down? In an ideal case, ignoring the thickness of the atmosphere and heat, the falling person would be slowed at an ever increasing rate until their speed dropped to TV.

 

How quickly would they slow down? And how much heat would be generated? Once the person hits TV, even if 10 miles up, it should become the same as any other parachute jump. I hope.

John B quote "I'm not sure that too amny parachutes would be needed. The factor not mentioned so far is "Terminal Velocity". For all practical purposes, it doesn't matter if you jump from 500 feet or 5,000 feet. The Terminal Velocity is the same, about 120 mph if in a spreadeagled position."

 

Hi John, the terminal velocity is giverned by mass/surface area presented to atmosphere. Higher altitude = less density of atmosphere, therefore higher speed. Your figure would be at around sea level. Kittinger, Joseph W, Jr. "The Long, Lonely Leap." National Geographic. December 1960: 854-873.

 

"An hour and thirty-one minutes after launch, my pressure altimeter halts at 103,300 feet. At ground control the radar altimeters also have stopped-on readings of 102,800 feet, the figure that we later agree upon as the more reliable. It is 7 o'clock in the morning, and I have reached float altitude …. Though my stabilization chute opens at 96,000 feet, I accelerate for 6,000 feet more before hitting a peak of 614 miles an hour, nine-tenths the speed of sound at my altitude."

 

Hope this helps.