A nuclear fission fragment rocket engine (FFRE) that is exponentially more propellent efficient than rocket engines currently used to power today's space vehicles and could eventually achieve very high specific impulse (>100,000 sec) at high power density (>kW/kg). A new NASA NIAC (NASA Innovative Advanced Concepts) project is creating a buildable near term design for a nuclear fission fragment rocket. It would enable manned mission to Mars with 90 day travel times. The fission fragment system would give experience in a technology which could eventually enable interstellar rockets with speeds of 10% of the speed of light.

Current proposed designs for Fission Fragment Rocket Engines are prohibitively massive, have significant thermal constraints, or require implementing complex designs, such as dusty plasma levitation, which limits the near-term viability. Researchers propose to develop a small prototype low-density nuclear reactor core and convert the nuclear energy stored in a fissile material into a high velocity rocket exhaust and electrical power for spacecraft payloads.

The key improvements over previous concepts are:
1. Embed the fissile fuel particles in an ultra-low density aerogel matrix to achieve a critical mass assembly
2. Utilize recent breakthroughs in high field, high temperature superconducting magnets to constrain fission fragment trajectories between moderator elements to minimize reactor mass.