🚀 go-pugleaf

Ben Clifford wrote:
> 
> 
snip

> 
> Imagine getting something up high on a smaller scale - throwing a ball
> all the way to the top of a skyscraper.
> 
> If you are standing on the ground and want to give the ball all of it's
> energy at once (when you throw it), you have to throw it pretty fast for
> it to get all the way up to the top of the skyscraper.
> 
> Alternatively, you can plod up the staircase holding the ball - the ball
> never travels faster than about half a metre per second but still
> manages to reach the top of the apartment block. Why? Because it is
> being supplied energy all the time, by you carrying it.
> 
> The "escape velocity" is the speed that the object needs to be if you
> are giving one massive throw to begin with, eg throwing the ball from
> the ground.
> 
> If you are carrying the ball up, by putting rockets on the bottom of
> your space craft that keep going all the way up, your spacecraft can be
> travel very slowly, as long as the rockets are always there lifting it.
> 
> Does this help?
> 

Yes, very much!  Great example.   This is quite easy to understand...Let
me rephrase...so long as rocket engine is providing lift (thrust to
weight ratio greater than 1) any object can escape Earth's gravitational
field just so long as the engines can burn long enough.