On Sun, 06 Mar 2005 23:33:48 -0500, Dan Nafe wrote:

In article ,
Ron Wanttaja wrote:

[snip]
So...we have to burn our downward thrusters for four hours. "G" on the Moon
is
about 5.6 ft/Sec^2. We'd need to burn the same to counter that. Total
acceleration required is 5.6 ft/sec^2 x 4 hours x 3600 seconds/hour... about
80,000 FPS, about sixteen times more than a ballistic S/C using a mass driver
for launch, and, as a point of interest, almost three times what a spacecraft
launch from the *Earth* needs. With the accel/decel Delta-V, our 870-pound
spacecraft requires 24.9 *million* pounds of fuel.

Doesn't the vehicle get lighter as fuel and oxidizer are consumed,
requiring less thrust, lowering the consumption rate...

Exactly, but the basic rocket equation takes that into account:

Fuel = Initial Mass * (1 - 1/(e^(Delta-V/(ISP * g)))

Ron Wanttaja