Nuclear thermal propulsion (NTP) achieves higher specific impulse than chemical rockets by heating propellant via _______.
- Electric arc
- Nuclear fission reactor
- Radioactive decay
- Fusion plasma
Answer: Nuclear fission reactor
NTP uses fission reactors to heat liquid hydrogen to ~2500 K, achieving Isp ~900 s vs ~450 s for LH2/LOX chemical engines, enabling faster Mars transit.