Why cant a space ship slow down and use its thrusters to enter into the earths atmosphere?

Question

Could this be done with out using heat shields?

Answer 1

Space ships don't really slow down or speed up, per se. If you fire your thrusters to 'slow' the spacecraft, what you're really doing is reducing the kinetic energy. This reduces the total energy of the orbit, which reduces the size of the orbit.

Once you have a new, lower energy orbit, physics takes over and distributes the energy between kinetic energy (speed) and potential energy (position). Because of the relationships involved, the speed of the satellite actually increases as the orbit gets smaller .... which is why it's more accurate to talk about how much energy you're taking out of the orbit or adding to the orbit. 'Slowing down' results in a higher end velocity while 'speeding up' results in a lower end velocity.

If you started in a circular orbit and slowed down, you would create a new smaller, elliptical orbit. Your satellite would be at apogee of the new orbit. The satellite would speed up as it approached perigee in the new, smaller orbit. In fact, at perigee, the satellite would be traveling faster than it was in the original orbit. Slowing down again could create a new, smaller, circular orbit. The new speed would still be faster than your original starting speed.

In other words, reducing a satellite's altitude always results in a net gain in speed.

Answer 2

To slow a spaceship down far enough to enter the atmosphere without shielding would take alot of fuel. Which adds to the launch weight and effectively increases the amount of fuel needed to lift the payload into space. It is much more efficient just to let the friction of earth's atmosphere slow down the spacecraft. Its like the difference between using the friction of brake pads to stop your car (no energy used), and reversing the engine and trying to accelerate your car in the opposite direction to stop (some fuel is consumed).

Answer 3

Why would one want to? It would take a lot of energy and wouldn't the ship want to use the energy it had to get where it was going? I just saw superman and he could enter the atmosphere without heat shields so I bet a space ship could do it too.

Answer 4

This would cost a lot of fuel, and that would have to be carried into space, or launched into space then used to fuel the craft. It is much more efficient to use the heat shields and the resulting friction of the craft while it re-enters the atmosphere.

Answer 5

Expenditure of energy.

You have to take all that fuel you're burning out of the gravity well.

More efficient to shield the craft and let it basically "fall" back to the planet.

Answer 6

because the earth s (gravity) is too high