Design
| Enviro |
Astro | Propulsion
| Power | Thermal
| Structures | AD&C
| CDHS |
Test
These
are technical rocket terms
used in space systems engineering design.
Rockets
Thrust
is based on Newton's Third Law, for every action
there is an equal and opposite reaction and the
conservation of momentum. Essentially, rocket propellant
mass exits in one direction and the spacecraft is
propelled the opposite direction. The product of
propellant mass flow rate and effective exhaust
velocity equal the force of thrust, expressed in
Newtons.
Impulse
is based on Newton's Second Law, the time rate of
change of a body's momentum equals the net applied
force. Momentum is the product of body mass and
velocity. Total impulse is the momentum change caused
by applying thrust over time.
Specific
impulse (Isp)
is used to characterize rocket efficiency. It is
the total impulse divided by the propellant mass
required for that impulse. This term is often used
to compare propulsion systems during preliminary
design trade studies. Isp is expressed in units
of seconds.
Nozzles
produce thrust by converting a rocket's thermal
energy to kinetic energy. Fluid mechanics describe
thermodynamic expansion with challenging partial
differential equations.
Characteristic
exhaust velocity (C*)
is a rocket performance parameter used in design
and testing. It is the product of the chamber pressure
and throat area divided by the exhaust mass flow
rate.
