On Wed, 19 Feb 2003, kilopascal wrote: > ... It is possible they are talking about the specific impulse of a > rocket that is lifting off and not in space away from any sources of gravity. > Maybe specific impulse is dependant on gravity and if no gravity > exists, then the specific impulse is infinite (ge=0) from the formulas > below:
Absolutely not, John. The specific impulse of a rocket motor is a measure of its performance wherever it is. That is: (Thrust times a short time interval) divided by the mass ejected in the exhaust during that short time interval. Check the units as follows: force x time/mass has units (kg m/s^2)s/kg = m/s the exhaust velocity. Equating pounds force and pounds mass is an *error* near the earth or far out in space. Gene.
