reply to post by Manasseh
Manasseh....allow me to change tactics.
Imagine a jet airplane....(I flew them for more that two decades)
The air doesn't 'hold up' an airplane in flight. It is the motion THROUGH the air, and the airfoil shape of the wing, that provide lift...lift
counter-acts weight.
This is the way of airplanes, designed to operate in air.
If you could magically transport a jet into space it would be useless.
No air to run the engines, nor the APU (which is really just a smaller jet engine) You'd have some electricity for a short while, from the batteries
(maybe...they might explode in a vacuum)
Point is, a spacecraft is designed to operate in a vacuum....AND, in the case of the STS, also in the atmosphere.
You see, after re-entering, the Shuttle is simply a glider. It IS aerodynamic, and controllable in ways similar to airplanes....but it is a very,
very non-efficient 'glider' (some have called it a brick with wings)....hence, it's rate of descent is far, far higher than a 'real'
glider....the ones with the long wings.
The Shuttle has NO engines, once it re-enters.
There are basically four forces that act on a regular airplane....Lift, Weight (gravity), Thrust and Drag.
LIFT is provided by an airfoil...a wing. Gravity is obvious. THRUST, from the engine/engines....and DRAG is the resistance of the object through the
air (see a Physics text). OR, just wave your hand through the air, then through some water. Which provides more resistance?? BTW, air, although
it's a gas, is in an aerodynamic sense, similar to fluid in its dynamics.
OK, the Four Forces....I know the next question....the Shuttle (or any other glider) has no THRUST. True. In this instance, gravity and forward
momentum provide the 'thrust'....at the expense of, a loss of altitude. Basically, Kinetic and Potetential energy, when combined, will allow the
vehicle to continue forward. Sometimes you will hear a term called 'Conservation of Energy' when applied to the Shuttle. It refers to the
'potential energy' (altitude above the ground) and 'kinetic energy' is the speed, or better, the velocity.
Velocity can be sacrificed, to reduce descent rate....but only up to a point. Altitude can be sacrificed, in increase velocity. THIS is conservation
of energy, since we do NOT have the other energy source, in this example....THRUST! (and drag, in an atmosphere, is always there....)
Take an object....expel a mass away from it, and the motion of THAT mass will result in an opposite motion.....simple as pie!!!! The masses react to
each other!!!
