shuttle re entry in to earths atmosphere??

Question

Why is it that when a spaceshuttle or any other spacecraft for that matter need such high speed to re enter earths atmoshere? And why does it need a certian angel to re enter?

Answer 1

It doesn't need the speed to re-enter, it needs the speed NOT to re-enter.

An orbit is basically a path where your foward motion is sufficient that as gravity pulls you back to Earth the Earth's surface itself curves away below you. If you throw a ball straight it follows a curve down: if you throw it fast enough its downward curve matches the curve of the Earth, so it never hits the ground. That's an orbit. In order to maintain an orbit like the shuttle you need to travel at 17,500mph.

To re-enter the spacecraft fires its engines to slow itself down a little, enough that its curve now doesn't match the curve of the Earth, so it hits the upper layers of the atmosphere. At several thousand mph this generates a lot of friction and drag. If you re-enter at too shallow an angle you simply bounce back into space, much like a stone skimming across a pond. If you re-enter too steeply you produce too much friction and heat and burn up.

But why re-enter so quickly? The answer to that is in the fuel costs. To get the shuttle up to 17,500mph in the first place required all the fuel in that big orange tank, plus those two solid rocket boosters, plus a little of the onboard fuel as well. To slow down to a speed where the descent through the atmosphere would not produce so much friction and heat would require almost that amount of fuel again. Getting that into orbit as well as the shuttle would make the whole thing prohibitively expensive, needing multiple launches per mission or an unfeasibly large launch vehicle. However, after the initial deceleration, the friction with the atmosphere will slow you down to a decent speed for a landing at no extra cost. It's a neat solution. Dangerous yes, but so is riding a rocket into space in the first place.

Answer 2

They're traveling at such high speed because they're orbiting. Low Earth Orbital speed is 17,500 MPH, and the Apollo capsules returning from the moon "fell" all the way to Earth, accelerating all the way - to about 25,000 MPH.

If they had the fuel, they *could* slow themselves down, and basically tumble out of orbit - but you'd need enough fuel to slow a 100-ton shuttle from 17,500 to, say, 4,000 MPH - and they just don't carry that with them. So, the energy needs to be spent some way, and they use the atmosphere.

The angle is important because they want to bleed their speed off relatively slowly. If they plowed into the ever-thickening layers of atmosphere TOO fast, they'd create too much heat - and the tiles on the shuttle would literally melt. So, they come in a shallower angle - keeping the heat generated by their slowing at a constant rate.

Answer 3

The simple answer concerning the re-entry velocity of spacecraft is that the velocity is not needed for re-entry but is a result of being in orbit around the earth. There is a specific velocity that is required for an object to orbit the earth at a certain altitude. So, basically, the spacecraft does a re-entry burn to slow the vehicle down so it's orbit decays and it starts re-entering the atmosphere.

Concerning the angle of re-entry, too steep of an angle and the aerodynamic heating of the vehicle becomes too great and the vehicle will burn up. Too shallow of an angle the vehicle could skip off the atmosphere like a rock across the top of a pond.

Answer 4

The bottom of the shuttle is covered with special tiles that protect it from the intense heat. When I was in school, they used to come give science demos, and would perform a really impressive one where they would heat a space shuttle tile with a blow torch until it glowed red. Then just a second or two afterwards, they would place it flat against their bare hand. The re-entry burn is how the space shuttle (and all returning spacecraft) gets rid of all of that speed they had keeping them up in space. It's basically a giant brake pad. If they didn't use the atmosphere for this, then they would need another giant fuel tank and pair of boosters to put an equal amount of retro thrust into the Shuttle to slow down again. Aerobraking is simply much cheaper to do, and much more feasible. Columbia broke apart during re-entry because a tile on one of its wings was damaged by a loose piece of foam breaking off the main tank and striking it during launch. This caused a crack that the super-hot plasma leaked into the wing's internal structure through, and weakend its integrity. It broke off, sending the shuttle out of control, and the aerodynamic forces on the craft then destroyed the rest of it since it was designed to take the pressures only in certain angles.

Answer 5

To remain in orbit you must attain a speed of 17,500 mph--------so when the shuttle gets ready to return it must slow down from that speed. It does this by entering the atmosphere on a very precise angle--------- not to steep(or it will burn up) not too shallow(or it will skip off the atmosphere like a flat rock skipping across water)------- it also does a series of steep turns which serve to further slow the spacecraft during reentry.

Landing speed is a little over 220 mph on average-------- see NASA's Landing 101 instructions at this link:
http://www.nasa.gov/returntoflight/launch/landing101.html

Answer 6

When u get that high in orbit u are traveling 18.000 to 25 000 mph.
Normally they fire the retro rockets over Hawaii when it is traveling at 18,000 mph . The resistance of the atmosphere slow es the shuttle a 1000 mph for each Minuit and u will be on the ground in 18 minutes.

Answer 7

the high rate of speed comes from the speed needed to maintain orbit around the earth. to steep of an angle and the friction with the steadily thickening atmosphere creates too much heat and you burn up, too shallow an angle and you just "skip" off the atmosphere and continue back into space.