Why is the re-entry of spacecrafts always a big deal?

Question

Why do they always enter up-side-down? Is it gravity or what?

Answer 1

The entry, currently designed spacecrafts with llimited fuel and power, into teh Earth's atmosphere is a "big deal" since it is entering the atmosphere unpowered. By that I mean that the rocket engines are not decreasing its speed, it would take too much fuel, thus they let the friction of the atmosphere slow it down. Since the spacecraft is travelling very fast (about 8km/sec) the air it encounters ionizes and becomes a plasma. Current spacecraft designs use heat shields, which are placed on the bottom of the spacecraft since teh top is reserved for viewing and work, and the center of gravity is such that re-entry forces do not flip the spacecraft (remember that most of the piping and heavy equipment is not where the crew is thus the center of gravity tends to be near the "bottom."

Thus during the intial stages of re-entry the temperature is high, and if the heat shield fails then parts of the spaeccraft melt and likely the spacecraft is destroyed.

In addition the plasma has alot of free electrons floating around, and any communication signals get bounced back. Thus during re-entry there is a communication blackout. When the spacecraft slows down enough where the plasma decreases, then communications is possible.

Hope this helps

Answer 2

Well they do not enter upside down at least the shuttle doesnt. Its heat tiles are on the bottom. Starting with the early programs, the heatshield was on the bottom of the capsule, so they had to come in bottom first.

The big deal is : the times when the lives on board may be in danger and no one can do anything about it.

Launch - the time between ignition and the height that the escape pod or system will work. In the older programs, there was an escape rocket on top of the capsule that would take the crew away from the main rocket, the shuttle, the flight deck can jettison.

Orbit departure burn (Lunar flights) mis calculations could cause the rocket to leave earth orbit and mis the moon without power to get back.

LOS loss of signal - anytime the capsule is behind the moon, "not knowing" is the biggest fear in space program

Lunar orbit burn - again to come home, something wrong and deep spoace here we come

LOS - Re entry into the atmosphere - ionization blocks radio so again, not knowing - cant help

The team in flight control breath again at AOS or aquisition of signal -

Final big deal - touch down and roll stop (splashdown and stable one) End of flight

Answer 3

It should be, but here is why.

You have an spaceship (space shuttle) that weights around 50,000 lbs (ball park figure) going at 23,000 mph, NO BRAKES diving into the atmosphere.

As long as they remain high enough no thin happens. But as get closer to the ground the density of the atmosphere increases (become thicker) thus the friction of air molecules and the spacecraft increases. The more friction, the more heat. The denser the air the harder it becomes to push the air away to let the spacecraft go through. This is aero braking. In the process there is so much friction and heat that it burns. The engineers design the ship so the shape is used to slow it down, that's why they go belly first. Once they slow down to about 2,000 mph or so they are no longer in fire and they start flying like a regular plane.

The alternative?

Slow down using engines in a controlled powered descend, that way there will be no friction issues to deal with.

The catch!

They will have to carry additional fuel adding weight, space, and cost.

So we go with the cheaper alternative!

Some times we pay the price!

Answer 4

1) Because it's the final, and most dangerous, stage of a successful mission, and it's always good to have a crew come home safe.
2) They turn around to get the best effect from firing the rockets to slow the shuttle for re-entry, and this is best accomplished by a flip that inverts the craft. The firing sequence slows, then flips, the craft back to an upright position to enter the atmosphere right-side up at a nose-high angle. This allows the belly heat tiles absorb most of the friction of re-entry as the wings act as a parachute to help slow the shuttle prior to assuming the glide path. Fuel expended, the rockets are not necessary and the shuttle heads for the landing point as the world's largest glider.

Answer 5

They enter with the "heat shield", usually a side of the vehicle that has materials which are good insulators of heat, down due to the fact that the friction bewtween the air particles and the vehicle at the vehicle's high speeds turns the air into a super heated air or plasma. If you were to stand un-protected in a plasma field, you would be a bright flash about the duration of a typical camera flash before you burned up to nothing--not even very much ash would be left of you at those temperatures.

Answer 6

Conservation of energy.

The Space Shuttle and other spacecraft gain considerable amounts of potential and kinetic energy going into orbit, starting at 0 velocity and getting up to 8 km/s.

ALL this energy must be dumped to get back to Earth at 0 velocity. This requires ENORMOUS brakes, e.g., the entire bottom of the Space Shuttle is a giant air brake. The heating of the Shuttle tiles and the air around is a manifestation of dumping all that energy.

Answer 7

Space craft are going 17,500 miles per hour in orbit, any slower and they would fall to Earth. That speed is only possible in the vacuum of space. Any attempt to go so fast in the air would result in the wind tearing the space craft apart. Drive a car very fast and put your hand out the window and feel the force of the wind. Now imagine going 300 times faster than any car and you have some idea of the force of the air at such high speeds. To return to the ground, rockets are used to slow down very slightly, maybe to 16,500 miles per hour, which causes the space craft to fall toward the ground. As it enters the atmosphere that same force you feel on your hand out the car window, only 300 times more, tries to tear the space craft apart, and in doing so it slows down the craft until it is flying as slowly as a normal airplane.

Answer 8

something shifting for the time of the ambience reports friction. You journey friction once you walk. The commute basically needs a warmth shelter by way of fact its stepping into the ambience at mach 20. in case you are able to desire to decelerate the descent to a minimum of a few thing greater reminiscent of what a jet fighter does then heating of the outer epidermis does no longer be an argument.

Answer 9

Because of the enourmous friction and heat on the shuttle from our atmosphere you see we are spinning at 1000mi an hour and so is the atmosphere around us and upon re-entry they are instantly exposed to that.

Answer 10

I dont know