Overpopulation

On 5/22/06, panamabob@...
wrote:
> but rockets today don't go through the majority of the atmosphere at escape velocity.... start slow and speed up progressively... sendinga item off a rail accelerator suggest that it would have attained escape velocity + because friction would make it lose part of its umph along the way. escape velocity, some 7 miles per second seems to me to create some serious friction issues.
(...)

In fact current rockets reach escape velocity when they are already
well outside the atmosphere. Consider a "didactic" case where the
rocket accelerates vertically at 3g until reaching escape velocity.
That would happen at an altitude of more than 2,000 kilometers. In a
realistic case (like the Apollos going to the Moon), first the ship
enters orbit, and then accelerates to escape velocity.

And yes, launching something from the Earth surface at escape velocity
would create serious friction issues - *much* more serious than the
ones faced by ships reentering atmosphere. In the case of spacecraft
reentering, atmosphere starts very thin and then goes thicker (which
means that the craft reaches the thicker layers at lower speeds), and
the reentrance angle is very shallow in order to prevent overheating.
In the case of spacecraft shot from Earth surface at escape velocity -
basically a meteor turned upside down... - the craft would get the
thickest of atmosphere first, at maximum speed and (I suspect) at a
straight angle!

That said, I would not be quick to deem that impossible - but it would
be more "challenging" than current heat shielding technology, I
guess...