Is it possible to re-enter the earths atmosphere without heating up?

[Mr. Pedantic]

Throw a bullet in a fire and see how far the slug goes.

What? What does that have to do with this?

You have an open-ended tube. In the middle is some mass of combustible propellant. On one side is the bullet. On the other side is a lot of air.

When the propellant explodes, because of the nature of the tube, it will go in two directions:
1) In the direction of the bullet
2) In the direction of the air

It will propel both of these with equal momentum.

Because of the nature of air (in that the amount of it inside the tube is a lot lighter than the bullet) the bullet will not travel as far as the air from the inside of the tube. HOWEVER. The bullet will go somewhere.

 

[HybridSquirrel]

Was going to mention kittinger...100k+ jump and no burn up

 

[JD50]

Was going to mention kittinger...100k+ jump and no burn up

Wow, that's crazy.

 

[DrPizza]

Was going to mention kittinger...100k+ jump and no burn up

But, he's not in orbit. To maintain orbit, you have to be going a hell of a lot faster than he's going.

 

[The Boston Dangler]

But, he's not in orbit. To maintain orbit, you have to be going a hell of a lot faster than he's going.

if you were going a hell of a lot faster, you wouldn't hit the earth in the first place

 

[HybridSquirrel]

But, he's not in orbit. To maintain orbit, you have to be going a hell of a lot faster than he's going.

the question was "Is it possible to re-enter the earths atmosphere without heating up?" as noted from the thread title. the answer in a nut shell is yes, because kittinger did it. He was technically considered to be outside the atmosphere

 

[ElFenix]

But, he's not in orbit. To maintain orbit, you have to be going a hell of a lot faster than he's going.

he's not even in space per the 100 km rule (which is a completely arbitrary bright line rule, as the atmospheric effects of re-entry are noticeable at 120 km per wikipedia)

 

[HybridSquirrel]

he's not even in space per the 100 km rule (which is a completely arbitrary bright line rule, as the atmospheric effects of re-entry are noticeable at 120 km per wikipedia)

32km is still basically in space...

 

[DrPizza]

32km is still basically in space...

Your post is still basically just making up numbers about where space begins. 32 km is no where near the upper portion of the atmosphere. Troposphere, sure, but not atmosphere.


The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. An altitude of 120 km (75 mi) is where atmospheric effects become noticeable during atmospheric reentry of spacecraft. The Kármán line, at 100 km (62 mi), also is often regarded as the boundary between atmosphere and outer space.

 

[EJ257]

I'm probably going to make myself look retarded (again), but after you finish laughing, kindly answer the question.

------

So, I was just thinking about how hot the space shuttle gets when it re-enters the atmosphere. AFAIK, this is due to the shuttle slowing down as it hits the atmosphere, and that speed is dissipated in the form of drag/heat. I was wondering...

What if instead of trying to hurtle through the atmosphere at warp 9, a shuttle actually fired its rockets in the opposite direction (pretend it has gigantic gas tanks, too), and slowed its re-entry? And as it re-entered, it slowly adjusted the direction of its thrust to oppose the now predominantly "vertical" force of gravity. i.e., it'd be balancing on it's tail.

Mmm... yeah, so I guess this doesn't even remotely resemble the space shuttle anymore. But if such a vehicle existed -- is that kind of "cold" re-entry possible?

In theory if power/fuel is no object then yes you could do it. Take Space Ship One for example. That was the first privately funded, manned spacecraft to reach space (100km high) and snagged the Anzari X Prize iirc. That ship was essentially above 99.9% of the Earth's atmosphere when it reached it highest point on the accent. It did NOT have a heat shield like the space shuttle simply because it was going too slow at that point to create enough friction to require one. It glided back down to the spaceport in New Mexico and they did it again a few days later. The ship is now hanging in the Smithsonian in DC when you walk in the door. So yes if you could slow your orbital vehicle down enough it will be able to make a cool reentry like you described.

 

[daw123]

I'm sorry if this has been discussed previously (I didn't read the thread in its entirety), but is there anyway that you can use the heat generated by the friction to your advantage as an energy source (thinking along the lines that heat = energy)?

It just seems to me that you are generating a shitload of energy, which is effectively wasted (the insides of the spaceship is shielded from the heat using insulation).

Again, sorry if this has already been discussed.

 

[TractorMan]

Reference tv show "Salvage 1".

 

[BoomerD]

Fucking necroposters...

 

[Cerpin Taxt]

Ok, but what if the shuttle was on a treadmill while it was re-entering the atmosphere?

 

[AMCRambler]

Is that box strapped to his ass to catch the shit when he shits his pants?

 

[JeffMD]

This thread is way to long and mostly wrong. Most people assumed the object was the nasa shuttle, but it was not part of the initial question. If you used a propulsion system that could control your descent against gravity and keep speeds down then the friction would be minimal. The shuttle needs to re enter the way it does because of small fuel resources and limitations on its shielding.

 

[Fritzo]

You could do a low-heat reentry if you were able to create a system that kept you from descending by more than a couple hundred mph. Once you start approaching the speed of sound in the atmosphere, things get hot really quick.

This would involve some sort of retro-rocket, and it would be incredibly wasteful. Heat shielding is simply more efficient.

 

[Yongsta]

Some rockets / propulsion to counteract your descent speed (acceptable speed so much heat isn't generated) but like others have said it would be impractical / wasteful.

 

[jagec]

Ok, but what if the shuttle was on a treadmill while it was re-entering the atmosphere?

This is the obvious solution to the problem. Just put a treadmill up there, spin it up until you bring the shuttle to a halt, and then slowly lower it back down to the earth's surface.

 

[Newbian]

I wonder how much heat this necro is making.

 

[ElFenix]

for all of fusetalk's problems it was at least difficult to necro threads due to the auto archiving feature.

 

[AmdEmAll]

This may have been posted already but here is a way to re-enter without much heat. I think it only works from a certain distance up though, not sure exactly.

http://www.slideshare.net/davidtowers/commercial-space-travel-feathering-technology

 

[Jeff7]

for all of fusetalk's problems it was at least difficult to necro threads due to the auto archiving feature.

My ideal solution:
- Be able to post to old threads, to help reduce the incidence of this problem.
- Posting to old threads won't bump them, unless an admin specifically re-enables it.

 

[DrPizza]

My ideal solution:
- Be able to post to old threads, to help reduce the incidence of this problem.
- Posting to old threads won't bump them, unless an admin specifically re-enables it.

It would make it harder to catch spam. I'll toss out the auto-archive idea again in the mod forums. I'm not sure what the software capabilities are in vB.

This thread is way to long and mostly wrong. Most people assumed the object was the nasa shuttle, but it was not part of the initial question. If you used a propulsion system that could control your descent against gravity and keep speeds down then the friction would be minimal. The shuttle needs to re enter the way it does because of small fuel resources and limitations on its shielding.

Speaking of mostly wrong, (not to even point out "to") it wasn't friction that caused most of the heating on the space shuttle during reentry. The heating is caused by compressing the air in front of it as it descends. As the shuttle is moving at supersonic speeds, it compresses the air in front of it. I think this video will give most people a more intuitive understanding of where the heat comes from:
http://www.youtube.com/watch?v=4qe1Ueifekg

One non-intuitive understanding is how objects are shaped when they're reentering the atmosphere. Intuitively, most people would think that a more aerodynamic shape is better - it would "reduce air resistance." "But, it won't slow down in time!" Well, simply re-enter at a shallower angle so that you travel further through the atmosphere. The advantage of non-aerodynamic shapes is that they end up with a sort of vapor barrier forming in front of them which slows the conduction of heat into the vehicle (the air can't get out of the way, because the vehicle is moving so fast.) Whereas, aerodynamic objects would have increased heating, because they wouldn't maintain a bubble of air in front of them. That is, the greater the drag coefficient, the less the vehicle heats up. Heating is inversely proportional to friction! (This throws out the idea that friction is the prime reason for the heating - shapes that cause more friction (drag) with the atmosphere have a lower heating load.)

So, it's not friction that you'd be keeping down; it's the compression of air that you're keeping down. Thus, you would need to slow your vehicle BEFORE you reached the atmosphere.

 

[Brovane]

I think you could minimize the heat load.

The key is to shed your orbital velocity slowly. Usually during re-entry you shed your orbital velocity quickly and you see a lot of heating up. Even then the Apollo capsules came in much faster than the shuttle and experienced a lot more heating than the shuttle. If you could pricesly control and dip down into the upper atmosphere enough to sheed some velocity and the go back up again. Then dip back down and shed more velocity and then go backup again. Basically you flight plan shows a wave motion going up and down. You dip down shed velocity and then use your remaining velocity to stear yourself back up again and then keep repeating.