Anni wrote:
OK if the shuttle is going the same orbital velocity required to get at into
orbital velocity.
Then cannot it be slowed down while in orbit where you would not need a
massive amount of energy to slow it down from 22700mph if done over a few
days which I take it is its approximate speed while in orbit
Could this work? And if it was slowed down could they not use parachutes to
keep it from reentry problems

I'm having trouble reading that, but I think this is the core of your
question:

"while in orbit can it be slowed down over a few days?"

The answer is no. This is one of those things that's very easy to
explain with a diagram, but very difficult to explain with just words.

Imagine a nice circular orbit. If you turn your spaceship so that it
faces in the direction you're going, and you fire your engines, that's
called a prograde burn. Prograde means, "in the direction you're
going." If you turn your spaceship so that it faces opposite the
direction you're going, and you fire your engines, that's called a
retrograde burn.

Once again, imagine that nice circular orbit. Pick a point on the
circle. That's where your spaceship is. If you make prograde burn at
that spot, do you know what happens to the orbit? Nothing at all
happens at the spot where your spaceship is. Instead, the part of the
orbit on the opposite side of the planet moves outward. If you make a
retrograde burn, nothing at all happens to the spot in the orbit where
you made that burn. Instead, the part of the orbit on the opposite
side of the planet moves inward.

This is rule number one of orbital maneuvering. When you make a
prograde or a retrograde burn, nothing at all happens to your orbit at
the spot where you made the burn. Instead, the other side of your
orbit moves in or out.

And that gets us to the reason why you can't slow down gradually over
several days. Once you slow down enough that the opposite side of your
orbit touches the atmosphere, you *will* hit the atmosphere in exactly
one half of one orbit. At the altitude that the shuttle orbits, it
only takes 90 minutes for a complete orbit, so once it slows enough to
touch the atmosphere, it is coming home in 90/2 minutes. End of story.
It doesn't have several days left to slow down gradually. Once it
touches the atmosphere that's it.

If you had a lot of thrust, you could make a very powerful retrograde
burn and lower your speed as much as you want, all the way down to zero
if you wanted to, but you have to do all of that in one half of one
orbit.

Like I said, this is very easy to understand if someone can draw it on
a chalkboard.