High-performance ultra-light nuclear rockets for near-earth objects interaction missions

The performance capabilities and technology features of ultra compact nuclear thermal rockets based on very high power density (30 Megawatts per liter) fuel elements are described. Nuclear rockets appear particularly attractive for carrying out missions to investigate or intercept near-Earth objects (NEOs) that potentially could impact on the Earth. Many of these NEO threats, whether asteroids or comets, have extremely high closing velocities, i.e., tens of kilometers per second relative to the Earth. Nuclear rockets using hydrogen propellant enable flight velocities 2 to 3 times those achievable with chemical rockets, allowing interaction with a potential NEO threat at a much shorter time, and at much greater range. Two versions of an ultra compact nuclear rocket based on very high heat transfer rates are described: the PBR (Particle Bed Reactor), which has undergone substantial hardware development effort, and MITEE (MIniature ReacTor EnginE) which is a design derivative of the PBR. Nominal performance capabilities for the PBR are: thermal power similar or equal to 1000 MW thrust similar or equal to 45,000 lbsf, and weight similar or equal to 500 kg. For MITEE, nominal capabilities are: thermal power 100 MW; thrust similar or equal to 4500 lbsf, and weight similar or equal to 50 kg. Development of operational PBR/MITEE systems would enable spacecraft launched from LEO (low-Earth orbit) to investigate intercept NEO's at a range of similar to 100 million kilometers in times of similar to 30 days.