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The fission process occurs because incident neutrons are “absorbed” in a fissile nucleus, and an excited state is produced. During the past NERVA Rover NTP development, highly enriched uranium (HEU) was used in order to achieve fission.Ĭurrent NTP designs are using low enriched uranium (LEU) or high-assay low enriched uranium (HALEU) for non-proliferation and security considerations while still achieving fission. In an NTP system, that heat is generated by flowing hydrogen through a reactor that is enriched with the fissile nucleus Uranium-235 in order to achieve fission.

To generate the heat and thrust for a thermal propulsion system like NTP, a source of energy is needed. Figure 2: Breakdown of Different Types of Rocket Propulsion Description of the Nuclear Fission Process Figure 3: Typical Fission Process of a Fissile Uranium-235 Atom Related to Nuclear Thermal Propulsion is Chemical Propulsion. This is different from “Electric Propulsion” where electric or magnetic fields are used to accelerate propellants (typically gases), or “Solid Propulsion” where a solid fuel/oxidizer blend is burned. To maintain hydrogen in the liquid state, the hydrogen fuel must be stored at temperatures well below the normal freezing point of water (20K), and at those temperatures, they are considered “Cryogenic” propellants. H2 provides ~900 seconds I SP at a fuel temperature of ~2800K, while comparably using H2O in an NTP system would only result in ~375 seconds I SP at the same temperatures. Typically when the term “Nuclear Thermal Propulsion” (or NTP) is used, it is in reference to in-space propulsion systems that rely upon a low molecular weight (typically hydrogen) fuel that flows through a reactor to generate heat due to the nuclear fission processes and eventual thrust.Ī low molecular weight propellant is desirable because for a given chamber temperature, the lower the molecular weight, the higher the resulting I SP (or Specific Impulse, a measure of rocket engine efficiency) e.g. What is Nuclear Thermal Propulsion? Figure 1: CAD Model of a Nuclear Thermal Propulsion (NTP) Engine Assembly

Artificial academy 2 hongfire outer space