Re: Rocket lift-off questions.

neo asked:

Escape velocity 11 km/s. But certainly rocket does not blast off with
this speed. On tv, i see rocket slowly lifting upward. How much
distance it covers in initial 4-5 seconds?

And is it possible to blast off rocket with acceleration much slower
than g? Will it fall or go upward?

To rise you need at least 1 g to overcome the Earth's gravitation. But
the _relative_ acceleration doesn't decide whether you'll escape.

Can we propel rocket or any body in upward direction with 'constant
velocity', say just 5 centimeter per second?

Possible but inefficient, and to achieve orbit you need 7 Km/sec. To
escape you need a positive velocity away from the Earth "at infinity".

Escape velocity is defined as the velocity required at any given
position to satisfy the inertial equations of motion and achieve
arbitrarily large separation at finite velocity. Of course it is
possible to reach "infinity" at 5 cm/sec, but to do that you need to
maintain this 5 cm/sec all the way out to the radius where the escape
velocity _there_ is 5 cm/sec or less.

One way to define escape velocity is positive total energy:

v^2/2 - GM/r > 0

hence

v > SQRT( 2GM/r )

--
ciao,
Bruce

drift wave turbulence: http://www.rzg.mpg.de/~bds/

.

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