MITEE - A Miniature Nuclear Propulsion Engine Chemical rockets have reached their limits. The hydrogen/oxygen chemical rocket can only deliver a specific impulse of about 450 seconds. The specific impulse is a measure of the thrust delivered by the rocket per unit mass of propellant consumed. Increasing the specific impulse to 1000 seconds, which is possible with Nuclear Thermal Propulsion, enables the spacecraft velocity to be over 2 times greater than that for a hydrogen/oxygen rocket, for the same mass of propellant consumed. Sidebar 1 compares the IMLEO (Initial Mass in Low Earth Orbit) for hydrogen/oxygen rockets with those for...