gmer412 said:
Wow. I'm in physics one and I just realized how funny that first example is. I think Newton's Third Law requires something to give that equal and opposite reaction...something not found in space.
The Third Law allows for the shuttle to reach space and for it to change speed and direction with rockets and thrusters once there. However, the First Law ensures that it will retain speed and direction until infinity, unless of course some force affects them. Gravity of planets and moons is ridiculously easy to anticipate these days and unless the hypothetical shuttle happens to hit something physically, the aforementioned gravity is pretty much the only thing it has to care about.
Which makes any clip of space craft with burning engines in space quite hilarious if they are not supposed to accelerate.
That is part of the reason why Ion-propulsion engines might be a viable engine for satellites and probes in the near future: the amount of fuel required is ridiculously small because the propulsion is produced by charged ions. Problem is that the acceleration is slow as heck, what with subatomic particles not having much mass to speak of. But if you have...say 5 years of time for that constant acceleration with nothing slowing you down... well, the speeds are beginning to look viable. Problem is naturally that it can't do any drastic course-changes.
They've even tested prototypes and they work. But with the Ion engines the mass of the spacecraft plays an important role in the acceleration curves, so I doubt we'll be seeing such engines on anything designed to hold a man inside.
Just an F-Y-I.
