Propellant economy

Fissile fuel of a nuclear thermal rockets can last months to years, so the only factor that limits mission time is the amount of propellant and propellant economy.

The propellant economy measures how much propellant the rockets uses for a burn. It's usually measured by kg/s or g/s for smaller thrusters. Better (smaller) propellant economy will allow longer missions on same propellant tanks.

The propellant economy is improved by:

• Higher exhaust velocity and specific impulse inherent to the rocket.
• Lower thrust.

The propellant economy is degraded by:

• Lower exhaust velocity and specific impulse inherent to the rocket.
• Higher thrust.