Why does the space shuttle have to reach such a great speed to re-enter the atmosphere?

Answer 1

It doesn't have to reach a great speed to re-enter the atmosphere. It must have a great speed to LEAVE the atmosphere, i.e. leave earth's surface and get into orbit. It has a great speed when it re-enters because it uses the earths atmosphere to slow itself down rather than use a lot of expensive rocket fuel to do so.

Answer 2

>>Itis well known that to leave the earth's gravitational force the space shuttle needs to be sent up on a rocket at high speed.<< The shuttle does not leave Earth'd gravitational force. It is the balance between Earth's gravity and the shuttle's speed that allows it to remain in orbit. >>The question is when the space shuttle is re-entering the earth's gravitational influence and atmosphere, why does it have to do so at super high speed.<< Because slowing down is very hard. It takes both solid rocket boosters plus all the fuel in the external tank plus a little kick from the orbital manoeuvring engines to get the shuttle up to that speed. Slowing it significantly would require almost as much fuel again, and it can't carry that much. Even if it could, it can only stay up because it is going so fast. The moment it slows down even slightly it begins to drop back to Earth and hits the upper atmosphere. That's hw re-entry is achieved: the orbital manoeuvring engines fire to slow the shuttle slightly so it drops into the upper atmosphere. The rest of the speed is bled off by friction with the air. >>It is this super high speed that led to the burning up and disintegration of Columbia. What did the NASA people learn from it.<< They learned that you need to design a spacecraft that is not vulnerable to bits falling off and damaging the thermal protection system. >>In my opinion, such high speeds are NOT required to re-enter the earth's atmosphere.<< With the greatest respect, your opinion is irrelevant, and franlkly it is a bit arrogant to declare your iopinion in regard to a system designed and built by people who have been working on spacecraft systems for a long time and make their living doing it. Do you honestly think that if there was a viable way to bring a spacecraft back to Earth without hitting the upper atmosphere at high speed and generating huge temperatures and aerodynamic forces that they would not actually be using it by now? Yes, re-entry is dangerous, but it is still the best way to get home that there is.

Answer 3

The space shuttle is travelling at great speed to keep itself in orbit around Earth. Upon re-entry it needs to slow down. The easiest way to do this is to use the friction of Earth's atmosphere to slow itself down. This creates a huge amount of heat.

If the shuttle could slow itself down before entering the atmosphere, the heat wouldn't be generated and there would be no need for expensive heat shields. However, this would take a huge amount fuel which costs money. And it would also add weight to the shuttle at lift off which means more fuel to lift off which means more money.

Answer 4

A couple of really ignorant answers here. Jonsmarth is correct.

The purpose of getting the shuttle up to 17,000 mph or so has nothing to do with re-entering the atmosphere. In fact, the problem is to get rid of that speed during the re-entry process.

The high speed is required for the shuttle to remain in orbit and dock with the space station.

Answer 5

It doesn't. But it needs that great speed to maintain orbit. If they could do it, a much less dangerous way of coming home would be to fire their engines until they have almost no speed, then simply drop, the way Burt Rutan's Space Ship1 did a couple of years ago - he didn't have to worry about heat build up from atmospheric friction, because he never achieved orbital velocity.

But the fact is, it's HARD and EXPENSIVE to launch all that fuel; so, what you do is, carry just enough fuel to slow down a little, then let the atmospheric drag reduce your speed.

It's dangerous, but there's no method for the shuttle to loft *two* external tanks - one with fuel for the ascent, one with fuel for he descent.

Answer 6

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It doesn't have to reach a great speed to re-enter the atmosphere. It must have a great speed to LEAVE the atmosphere, i.e. leave earth's surface and get into orbit. It has a great speed when it re-enters because it uses the earths atmosphere to slow itself down rather than use a lot of expensive rocket fuel to do so.

Answer 7

its not overcoming gravity or friction it is coming down at that speed because that is the speed it needs to move at to stay in orbit. it slows down some nin order to come down to earth but it cannot slow down that much, the atmosphere does most of the braking for the shuttle.

Answer 8

When re-entering the atmosphere I think it could have something to do with overcoming the friction and resistance caused by the atmosphere. It is going from a less dense atmosphere in space to a more dense atmosphere on earth and it needs to "break through" it.

Answer 9

Because it has to go pass the Ozone layer which is hard to do.

Answer 10

It will lose momentum as it enters.