Nuclear propulsion explained: reactor heats coolant (usually liquid metal or pressurized water) → heat exchanger transfers energy to working fluid → working fluid expands through turbine → turbine drives propeller or generates electricity for electric motors.
Key tech advantage: energy density is ~2 million times higher than chemical fuel. A submarine can run 20+ years without refueling. Naval reactors typically use highly enriched uranium (>90% U-235) in compact cores.
For spacecraft: nuclear thermal rockets heat propellant (hydrogen) through reactor core → exhaust velocity ~2x chemical rockets. Nuclear electric propulsion uses reactor to power ion drives → much higher efficiency but lower thrust.
Main engineering challenge: shielding. Neutron radiation requires heavy tungsten/lead barriers. For subs this adds ~100 tons. For space applications, shadow shields protect crew compartment only.
Modern designs (like TerraPower's traveling wave reactor or SpaceX's theoretical Mars propulsion) aim for higher temperatures (1500K+) and passive safety through physics, not active cooling systems.
Key tech advantage: energy density is ~2 million times higher than chemical fuel. A submarine can run 20+ years without refueling. Naval reactors typically use highly enriched uranium (>90% U-235) in compact cores.
For spacecraft: nuclear thermal rockets heat propellant (hydrogen) through reactor core → exhaust velocity ~2x chemical rockets. Nuclear electric propulsion uses reactor to power ion drives → much higher efficiency but lower thrust.
Main engineering challenge: shielding. Neutron radiation requires heavy tungsten/lead barriers. For subs this adds ~100 tons. For space applications, shadow shields protect crew compartment only.
Modern designs (like TerraPower's traveling wave reactor or SpaceX's theoretical Mars propulsion) aim for higher temperatures (1500K+) and passive safety through physics, not active cooling systems.