Heat on re-entry from space?

Question

I have always wondered why spacecraft re-enter the atmosphere at such terrific rates of speed. Wouldn't it be possible to slow down somehow, while in orbit, thus avoiding all the dangers from heat build-up on re-entry? Perhaps by "skimming" the outer atmosphere before descending, or bringing extra propellant?

Answer 1

Think of it in terms of conservation of energy. When the space shuttle launches think of all that fuel it has to burn through. Part of that fuel energy is transformed into kinetic energy in the shuttle which allows it to orbit. If you wanted to slow it down on your own power, you would basically need the same amount of fuel it took to get you up there in the first place which is a lot. When you come back down into the atmosphere, the kinetic energy in the shuttle turns into heat and pressure.

There is some heat created through friction but this is a very small part of it. Friction with air is very low. When objects travel faster than the speed of sound, the air in front of the object compresses because it doesn't have enough time to move out of the way. This compressed air is at very high pressure. So basically you have high pressure in front of the vehicle and not behind it. It will then produce a force causing the craft to slow.

When air compresses it gets hotter, the same as bicycle pump gets hotter when you compress air in it. This is where the heat comes from.

As of right now, there really is no way of avoiding heat when dealing with accelerating or decelerating massive objects at extreme velocities. You will either get the heat from a combustion reaction or other thermal anomalies.

Answer 2

The speed necessary to orbit the earth is about 17,500 miles per hour, almost 5 miles per second.

They do skim the outter atmosphere as they descend, the problem is that they are going so fast they still heat up.

Extra propellent weighs more, and thus will create more heat on reentry.

Answer 3

they do "skim" as best as possible i believe by entering the atmosphere at the optimum angle to cause minimal atmospheric resistance.

the amount of fuel needed to create a reverse thrust capable would most likely be unviable, and it would have to start moving forward again at some point..imagine an aircraft which stopped dead in the air, it'll start plummeting for the ground. a shuttle most likely wants a similiar trajectory to an aircraft in this respect and dosnt want to plummet straight to the ground either..it lands like a plane would.

to conclude, ceramic plates which absorb the heat and help slow the shuttle down anyway are simply more practical.

Answer 4

No, it is impossible. A spacecraft MUST travel at 17,400 mph in order to stay in orbit. Any lower and it will automatically fall into the earth. The heat is from the friction of air particles rubbing against the spacecraft. You could fire your engines to fall slower and reduce heat, but that would waste too much fuel. Heat tiles are a much better option.

Answer 5

The spacecraft or whatever object actually has to have a certain speed or velocity in order to enter Earth Atmosphere or it would skip off.
I honestly do not know why so much money is spent on space rides while people starve and go homeless on this planet.

Answer 6

What the shuttle does is that it glides into the atosphere and in space it travels round the Earth in 90 min. so when u have that speed and u glide into the atmosphere , the particles rub on the skin of the shuttle and heat it up hence why it is hot and glows red. this cant be avoided in any way.

Answer 7

they could stay at station. In a case like Columbia with a hollow contained in the wing. in the journey that they knew the position on the wing it change into and how massive it change into there are diverse techniques/angles/trajectories the holiday can take to re-enter properly. contained with regards to the holiday having this challenge on a project to at least something except the ISS the plan is to have a 2d holiday on standbye in case they could't re-enter. They plan to attempt this if a project to Hubble easily takes position.

Answer 8

Here's the funny thing about orbital dynamics: once in orbit, if you slow down, you move AWAY from the earth, not towards it. To move towards the earth, you have to speed up, and direct your velocity towards the earth.

It would *technically* be possible to leave orbit by heading towards the earth by speeding up, and then once in thick enough atmosphere to fire retro-rockets against gravity and descend slowly. But this would take so much fuel as to be practically impossible. Insted we take advantage of the friction with the atmosphere at high speeds, and let it slow us down without using any fuel -- much more efficient. And it's really not any more dangerous than going UP on rocket engines is. :)