Advanced Nuclear Thermal Propulsion Design for 90 Days Trip to Mars

Ultra Safe Nuclear Technologies (USNC-Tech) has delivered a design concept to NASA as part of a study on nuclear thermal propulsion (NTP) flight demonstration. Fully Ceramic Micro-encapsulated (FCM™) fuel will enable a safer nuclear rocket with double the performance of chemical rockets.

Despite doubling the ISP (fuel efficiency in space) with nuclear thermal, it is possible for large chemical rockets to also achieve 60-90 day trip times to Mars from Earth. SpaceX is developing orbital refueling and the Super Heavy Starship. A fully refueled Super Heavy Starship could achieve a massive delta-V that would enable a superior orbital transfer and faster trip times than were ever achieved when small vehicles are boosted to orbit on smaller rockets.

However, it would still be good to fully develop safe nuclear thermal propulsion. There will be space missions where this capability will be useful.

There was previous work on nuclear thermal propulsion starting with the NERVA project back in the 1960s. They actually built the hardware. There has been numerous projects to update nuclear thermal propulsion. The technology would clearly work and it is a matter of actually fully funding and pushing through to putting actual systems in space. There have also been nuclear thermal designs to launch massive payloads from the earth. The nuclear materials is enclosed so there would be no radiation problems.

A problem is that nuclear thermal only doubles or in some cases triples the ISP that is possible from chemical rockets. This means making beginner nuclear thermal systems that are smaller than the chemical rockets may not give any benefit. SpaceX mass producing fully reusable rockets and have orbital refueling means that any nuclear rocket has a higher bar to clear for any advantage. SpaceX driving launch costs down also makes it more challenging to introduce a clearly superior new space propulsion technology.

FCM Fuel Kernel
The fuel packaging starts with a Uranium Fuel Kernel measuring less than 1 mm across.

TRISO Particle Fuel
The kernel is coated with special layers designed like tiny pressure vessels. The layers contain fission products inside and ensure mechanical and chemical stability during irradiation and temperature changes. This is called a TRISO Particle. Developed in the 1960’s for gas-cooled reactors, TRISO has enjoyed continued international development resulting in an excellent starting point for the Ultra Safe reactor.

FCM™ Fuel
Ultra Safe Nuclear’s breakthrough is encasing the TRISO Particles within a dense Silicon Carbide matrix, which we call Fully Ceramic Micro-Encapsulated Fuel, or FCM™ Fuel

Pellet Stacks
FCM™ Fuel Pellets are stacked…

Graphite Blocks
…and placed into Graphite Blocks. Graphite is the moderator which slows down neutrons and increases the likelihood that neutrons will cause fission reactions in the fuel. Cooling channels are built into the Graphite Blocks. Cold helium flows through the cooling channels and picks up heat.

Reactor Core Cartridge
The Reactor Core is made up of several hundred such Graphite Blocks with a few tons of fuel. Various openings and channels are used for control rods and coolant flow.

The Reactor can be adapted for space propulsion and for ground based nuclear power. High temperature capabilities make it ideal for hydrogen production, space reactors and space nuclear propulsion.

SOURCES- Ultra Safe Nuclear Technologies (USNC-Tech), NASA
Written By Brian Wang,