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

[YOyoYOhowsDAjello]

How is it possible though? The Space Shuttle weighs approximately 165,000 lbs empty. How big a parachute would you need to slow it enough to have a cool re-entry? We had parachutes on the capsules we sent up in the 60s but those capsules were tiny compared to the space shuttle and they needed 3 huge chutes to slow those enough to splash down in the ocean and they also needed heat shields to re-enter the Earth's atmosphere from orbit. I think heat resistant tiles is probably the best solution for now.

It's not the space shuttle. It's not the space shuttle. It's not the space shuttle.

This isn't about the best solution for the space shuttle.

This is a theoretical question about whether we could make a space vehicle that could enter the atmosphere and not heat up a lot.



Step 1: Get into orbit with new vehicle
Step 2: Hook up with International space station for refueling and refitting of additional booster rockets
Step 3: Get into the optimal orbit for rapid deceleration and descent
Step 4: Blast the engines and additional booster rockets to slow horizontal velocity and control the descent
Step 5: Once entering the atmosphere, start deploying the series of parachutes designed to slow the descent to augment the slowing effect of the eingines
Step 6: Once altitude is low enough, open larger and larger parachutes to take over for the engines (and jettison the rockets)


I mentioned the SR-71 scenario to show that parachutes are enough to stop a person traveling at mach 3 at 80,000 feet to "re-enter" without the use of any other engines / rockets etc.

Scale that up and you have to get the vehicle to 80,000 feet and traveling at mach 3 and things should be able to meet the requirement for "cool" re-entry (or at lease cooler).

As has been said before, you just need a ton of fuel and you can do it. You could use engines to make the whole descent, or you could use parachutes or some other means to take over once in the atmosphere.

The OP said nothing about practicality or budget. This is an "is it possible" question, and it seems feasible to me. It's a question of how much fuel you can carry to slow yourself down fast enough.

If you can solve that problem with external means, you don't have to carry the solution up from the ground with your vehicle, and you can get rid of the added mass by jettisoning those items. Once you're moving much slower relative to the atmosphere, most of the heat issues of re-entry would be reduces greatly. Since this is not the space shuttle, you could design the thing to have a shape that would work better for slowing itself down for re-entry too.

 

[JulesMaximus]

It's not the space shuttle. It's not the space shuttle. It's not the space shuttle.

This isn't about the best solution for the space shuttle.

This is a theoretical question about whether we could make a space vehicle that could enter the atmosphere and not heat up a lot.

You would think that this type of solution would have been considered by experts since we've been sending space craft up in the atmosphere for over 1/2 a century now.

 

[YOyoYOhowsDAjello]

You would think that this type of solution would have been considered by experts since we've been sending space craft up in the atmosphere for over 1/2 a century now.

DUH, it's not a good solution.

It makes no practical sense.

Why are you using arguments that it's not practical or good to refute the idea that it's possible?

 

[nerp]

Yes. Possible is not always practical. The fact that heat tiles/shields were invented eliminates the need for a hokey parachute system. The current method for the shuttle is the best option right now. That's why it is being used.

 

[JulesMaximus]

DUH, it's not a good solution.

It makes no practical sense.

Why are you using arguments that it's not practical or good to refute the idea that it's possible?

Sure it's possible in theory I guess...

 

[PaperclipGod]

DUH, it's not a good solution.

It makes no practical sense.

Why are you using arguments that it's not practical or good to refute the idea that it's possible?

I think he might be autistic.

 

[JulesMaximus]

It's not the space shuttle. It's not the space shuttle. It's not the space shuttle.

This isn't about the best solution for the space shuttle.

This is a theoretical question about whether we could make a space vehicle that could enter the atmosphere and not heat up a lot.



Step 1: Get into orbit with new vehicle
Step 2: Hook up with International space station for refueling and refitting of additional booster rockets
Step 3: Get into the optimal orbit for rapid deceleration and descent
Step 4: Blast the engines and additional booster rockets to slow horizontal velocity and control the descent
Step 5: Once entering the atmosphere, start deploying the series of parachutes designed to slow the descent to augment the slowing effect of the eingines
Step 6: Once altitude is low enough, open larger and larger parachutes to take over for the engines (and jettison the rockets)


I mentioned the SR-71 scenario to show that parachutes are enough to stop a person traveling at mach 3 at 80,000 feet to "re-enter" without the use of any other engines / rockets etc.

Scale that up and you have to get the vehicle to 80,000 feet and traveling at mach 3 and things should be able to meet the requirement for "cool" re-entry (or at lease cooler).

As has been said before, you just need a ton of fuel and you can do it. You could use engines to make the whole descent, or you could use parachutes or some other means to take over once in the atmosphere.

The OP said nothing about practicality or budget. This is an "is it possible" question, and it seems feasible to me. It's a question of how much fuel you can carry to slow yourself down fast enough.

If you can solve that problem with external means, you don't have to carry the solution up from the ground with your vehicle, and you can get rid of the added mass by jettisoning those items. Once you're moving much slower relative to the atmosphere, most of the heat issues of re-entry would be reduces greatly. Since this is not the space shuttle, you could design the thing to have a shape that would work better for slowing itself down for re-entry too.

Mach 3 is roughly 1500 mph, a satellite in low earth orbit would have to be traveling at around 17,000 mph to keep from falling back into the atmosphere. The farther away from the planet the slower the speed required to hold a stationary orbit. Of course, you'd need more fuel to get to that orbit and more fuel to slow your decent from the higher altitude.

Yeah, I'm back to the practicality thing again...sorry.

 

[irishScott]

Yes, if you had enough fuel and properly positioned thrusters you could negate heat to the point where no heat shield would be required, but it would still create heat like almost every other action/reaction involving friction. Realistic concerns (ie: fuel weight) also prevent such a system from being viable.

 

[yh125d]

Theoretically? Absolutely



Feasibly? Absolutely not



Jules, learn to make a distinction between feasible and theoretically possible. It's obviously nowhere near feasible, but it is absolutely 100% possible. And since that's all that we're talking about here...

 

[Jzero]

Even if you had unlimited fuel to do fire rockets to brake the ship, the rockets themselves generate ridiculous amounts of heat.

Wikipedia says a rocket engine can get as hot as 5800F vs 3000F for a typical STS re-entry....I'm not an astrophysicist so I don't know just how hot the SSME and SRBs get, but it could potentially be hotter than the heat from atmospheric friction.

And since you're pretty much firing the rocket directly against your path of motion, you are moving directly into the heat source as you go...

 

[JulesMaximus]

I think he might be autistic.

Must...resist...urge to post what I really think of paperclipdog...

 

[JulesMaximus]

Theoretically? Absolutely



Feasibly? Absolutely not



Jules, learn to make a distinction between feasible and theoretically possible. It's obviously nowhere near feasible, but it is absolutely 100% possible. And since that's all that we're talking about here...

Yeah, I get it...thanks.

 

[Hayabusa Rider]

The question as stated is "possible". It surely is.

Is it practical? Not with our state of technology.

How do you avoid heating excessively? Apply enough thrust against the pull of gravity. It's not rocket science

 

[sonicdrummer20]

I always assumed it was pure friction that caused heat upon entry/re-entry of the atmosphere, theoretically you could enter at a much slower speed and reduce friction but I'm not sure about a cold entry

 

[DisgruntledVirus]

It's physically impossible to stop something heating up when they move. The act of typing this post out is creating heat from fluid resistance. So no, there is no way you could possibly stop the space shuttle from heating up on re-entry.

And the heat is not produced by it slowing down, it's produced by it speeding up everything else.


I'm not sure why you'd want to waste all that fuel when re-entry for the space shuttle is essentially free. And on a practical note, balancing the thing so it doesn't flip over, as you allude to, would be pretty hard.

While it would not be possible to prevent all heat, you could prevent it from getting "too hot". You could keep it under a few hundred degrees if you were able to reenter slow enough.

Hell a space elevator would work on this principle, and would not require any kind of heat sheilding (provided it moved at a slow enough speed).

 

[Hayabusa Rider]

I always assumed it was pure friction that caused heat upon entry/re-entry of the atmosphere, theoretically you could enter at a much slower speed and reduce friction but I'm not sure about a cold entry

That is correct. The atmosphere resists the motion of the spacecraft, and the momentum is dissipated as heat. The kinetic energy of the shuttle is huge, and the atmosphere has to do the work of slowing it down.

If it did not have to do so, then heating by atmospheric friction would be a non issue.

Imagine descending at a 100 mph. Friction is comparatively nil and therefore no heat.

Of course some alternate means of slowing it must happen. Thrusters would do the trick, but again it's the practicality which is the issue.

Supposing that a HE3 powered ship were built. It could move through the solar system in more or less a straight line, or what was the fastest curve regardless of power consumption. Then it could land as nicely as any helicopter.

Unfortunately that's sci-fi for now.

 

[YOyoYOhowsDAjello]

I always assumed it was pure friction that caused heat upon entry/re-entry of the atmosphere, theoretically you could enter at a much slower speed and reduce friction but I'm not sure about a cold entry

That is correct. The atmosphere resists the motion of the spacecraft, and the momentum is dissipated as heat. The kinetic energy of the shuttle is huge, and the atmosphere has to do the work of slowing it down.

If it did not have to do so, then heating by atmospheric friction would be a non issue.

Imagine descending at a 100 mph. Friction is comparatively nil and therefore no heat.

Of course some alternate means of slowing it must happen. Thrusters would do the trick, but again it's the practicality which is the issue.

Supposing that a HE3 powered ship were built. It could move through the solar system in more or less a straight line, or what was the fastest curve regardless of power consumption. Then it could land as nicely as any helicopter.

Unfortunately that's sci-fi for now.

As Dr. Pizza mentioned, it's not "pure friction".

"Reentry heating differs from the normal atmospheric heating associated with jet aircraft, and this governs TPS design and characteristics. The skin of high-speed jet aircraft can become hot from atmospheric friction, but this frictional heating is similar to rubbing your hands together. The Orbiter reenters the atmosphere as a blunt body by having a very high (40-degree) angle of attack, with its broad lower surface facing the direction of flight. Over 80% of the heating the Orbiter experiences during reentry is caused by compression of the air ahead of the ultrasonic vehicle, in accordance with the basic thermodynamic relation between pressure and temperature."

http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system#Reentry_heating

(But yes, take care of speed and you take care of both issues)

 

[yh125d]

As Dr. Pizza mentioned, it's not "pure friction".

"Reentry heating differs from the normal atmospheric heating associated with jet aircraft, and this governs TPS design and characteristics. The skin of high-speed jet aircraft can become hot from atmospheric friction, but this frictional heating is similar to rubbing your hands together. The Orbiter reenters the atmosphere as a blunt body by having a very high (40-degree) angle of attack, with its broad lower surface facing the direction of flight. Over 80% of the heating the Orbiter experiences during reentry is caused by compression of the air ahead of the ultrasonic vehicle, in accordance with the basic thermodynamic relation between pressure and temperature."

http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system#Reentry_heating

(But yes, take care of speed and you take care of both issues)

Which, on a very fundamental level, is based in friction. On a very simple level the action is similar to rubbing your hands together, and then rubbing them together harder

 

[JTsyo]

I always had this question... obviously I have no knowledge about rocket science...
Why the EFF so we have to enter the atmosphere at that high speed? cant we slow down just before reentry? cant we control the speed? or will it take a lot of thrust to slow down, something equivalent to liftoff? If so, how about we don't accelerate to that speed and instead of one day make it a 5 day trip? will that cause O2 issues?

You need a certain velocity to stay in orbit, less than that and you start dropping. It would be expensive to have to shed that velocity before re-entry. Once you're out of orbit there's W=mg. You reach terminal velocity pretty quick even from rest, though I guess it decreases are you get into thicker and thicker atmosphere. Terminal velocity shouldn't be too much of a problem for heat generation I guess.

Ok I have figured out a way. Create a vaccum field around your space ship. Then you won't heat up.

Kind of like supercavitation in fluids.

 

[SunnyD]

Yep, you can with minimal heat gain - providing you're willing to take a really long, slow trip coming down. It's impractival though.

 

[sonicdrummer20]

As Dr. Pizza mentioned, it's not "pure friction".

"Reentry heating differs from the normal atmospheric heating associated with jet aircraft, and this governs [BOLD] TPS [/BOLD] design and characteristics. The skin of high-speed jet aircraft can become hot from atmospheric friction, but this frictional heating is similar to rubbing your hands together. The Orbiter reenters the atmosphere as a blunt body by having a very high (40-degree) angle of attack, with its broad lower surface facing the direction of flight. Over 80% of the heating the Orbiter experiences during reentry is caused by compression of the air ahead of the ultrasonic vehicle, in accordance with the basic thermodynamic relation between pressure and temperature."

http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system#Reentry_heating

(But yes, take care of speed and you take care of both issues)

I think you have my stapler...

 

[bdude]

a paper airplane

 

[speg]

Yes. Though, as you said you would have to use a lot (i.e., an insane amount) of fuel to slow down and control your decent.

 

[Mr. Pedantic]

While it would not be possible to prevent all heat, you could prevent it from getting "too hot". You could keep it under a few hundred degrees if you were able to reenter slow enough.

Hell a space elevator would work on this principle, and would not require any kind of heat sheilding (provided it moved at a slow enough speed).

But the thing is, that at the moment, for the Space Shuttle, it's not 'too hot'. If it were 'too hot', every space shuttle would do a Columbia every single reentry.

 

[Rubycon]

...Then it could land as nicely as any helicopter.

Please let's keep helicopters out of space. It's bad enough Hollywood has guns in space.