An airgel for future nuclear-powered NASA ships?

There NASANASA and nuclear propulsion is a long story. At the beginning of 2023, the American Agency gives new life to some cutting-edge initiatives through his schedule niac (Innovative advanced concepts from NASA). Among these we find, for example, a nuclear propulsion project that combines both a heat engineheat engine and an electric motor, an initiative that would make it possible to reach Mars in 45 days.

Among these selected projects, we find the concept imagined by the engineer Ryan Weed and the American company Positron Dynamics: the propulsion through fragments of fissionfission (FFRE), based on the same type of reaction used in the nuclear centernuclear center current.

Nuclear airgel

This type of nuclear engine would solve the sacrosanct search for the best specific impulsespecific impulse (I_sp), a quantity that summarizes the efficiency of an engine. A nuclear engine would have an I_sp 400 times more powerful than conventional space propulsion, but would cost too much mass. To solve this problem, Positron Dynamics proposes limiting the amount of material for fission and using one of the lightest materials ever designed: airgel, a solidsolid very low density, made up of 98.8%airairthe rest would be fissile material.

Another type of propulsion imagined by Positron Dynamics. ©Positron Dynamics, YouTube

The use of airgel certainly limits the mass constraints, but it also reduces engine power. According to Positron Dynamics the bet would be successful for space propulsion. Distributing fissile material in an airgel matrix is ​​like talking about fission fragments instead of fission. The company therefore proposes to use thepowerpower obtained both to gain thrust, but also to provide energy to the ship. Support from the NIAC program will help develop a small prototype reactor core.