Why does the Space Shuttle have to be going so fast to re-enter the earth atmosphere?

Answer 1

The shuttle has to be going 17,000 miles per hour to stay in orbit. When it slows down a little bit, it starts to fall back to Earth. That's how they begin re-entry.

Answer 2

Oops...
Did I just see a "Cart" before the "Horse?"

Let's re-group here for a moment...

The problem first off is to get going fast enough to escape the Earth's gravitational field...Right? Okay. And, we all know that speeds like that take a huge amount of fuel to achieve...

So much fuel, in fact, that there is not much left on board the space craft for anything but a little bit of steering this way and that to achieve the right re-entry angle and direction so the craft enters Earth's atmosphere somewhere close to the right spot and doesn't wind up hitting Mount Everest or something.

So the thing is out there banging along at some 25,000 miles per hour when the driver decides to land back on Earth. Guess what... There is not a huge pile of fuel to decelerate the rocket ship back down to maybe one or two thousand miles per hour for a nice little normal jet plane landing. So, what they have to do is slide into the atmosphere at a very precise angle and slowly burn off the excess speed.

Burning of the excess speed (if you have ever touched a race car's brake pads, you will understand) creates heat, and I do mean tons of it. That is why the re-entry vehicles have heat shields built into them, and why everyone is so concerned about any possible damage to them during launch. No heat shield = Giant French Fry Fireball.

Answer 3

The Shuttle is traveling 17,500 miles per hour while in orbit. Obviously it has to slow down before it lands.

However, so far we dont have the technology to build a spacecraft that can carry enough fule to slow down. So the Shuttle does a "re-entrry burn"--a firing of its OMS (orbital maneovering ssytem) rockets, using what fuel it has left to push it into the atmosphere at the end of its stay in space.

Then the Shuttle uses the friction of the atmospher to slow down. That takes a while--the Shuttle actually starts re-entry more than halfway around the world. This technique is called "atmospheric braking.

So--here's the deal--the Shuttle enters the atmosphere so fast because it can't slow down--it has to use the atmosphere itslef to do that.

Answer 4

Actually, the space shuttle is already going fast. It has to slow down to re-enter the Earth's atmosphere.

Answer 5

There is no minimum velocity relative to the earth's surface that is required to re-enter the atmosphere. It can be accomplished by simply falling inward from a location that is static relative to the spinning earth. The reason that most spacecraft re-enter with some significant velocity component is: 1. They are already in orbit, moving at roughly 17,000 mph relative to the surface, and to slow down requires a lot of reverse thrust, which requires a lot of fuel, which is very heavy - so they did not take it along to begin with. 2. They are already in a trajectory inbound from another body (like the Moon), moving at a comparable speed to item 1 above, and they cannot slow to a relatively low speed for the same reasons. 3. They may be falling inward from a nearly "static" location above the earth's surface, but they reach a relatively high speed before hitting the outer edges of the atmosphere. This would be true for - say - suborbital ballistic vehicles. There is a minimum velocity required to attain orbit. This speed varies according to your altitude above the earth. There is also a minimum speed required to escape the earth's gravitational field. At the earth's surface, this is roughly 7 miles per second, but it decreases as you start from higher locations. There is no minimum speed required to re-enter the atmosphere.

Answer 6

The speed the shuttle has when entering the atmosphere is what's left of the velocity it needed to stay in orbit. It is *NOT* required for re-entry and re-entry could be accomplished at much, much lower speeds...and more safely too. The problem is that to slow it way, way down would require much more fuel than it has onboard.

Answer 7

Its designed to be manueverable while going fast. When moving slowly its little wings wouldn't provide any lift. It sort of has to be going fast also because it was going fast when it left the earth (escape velocity) and the only way to slow it down is to fire its rocket engines. It would take a lot of fuel to slow it down enough to sort of free fall back to earth with a parachute.

Answer 8

if it were to come down to earth slow, it would have to fire its rocket engines all the way down, in a controlled decent and its fuel tanks would have to be so much bigger, that it wouldn't be able to get off the ground to begin with, with all the added weight.

Answer 9

It's kind of like a toy space shuttle entering water, if it's too slow, it won't be stable and it'll fall in too many directions, the speed keeps it stable until it lands

Answer 10

It has to in order to escape from the atmospheric aliens....