Anuclear electric rocket (more properlynuclear electric propulsion) is a type ofspacecraft propulsion system wherethermal energy from anuclear reactor is converted toelectrical energy, which is used to drive anion thruster or other electricalspacecraft propulsion technology.[1][2][3][4][5][6][7][8] The nuclear electric rocket terminology is slightly inconsistent, as technically the "rocket" part of the propulsion system is non-nuclear and could also be driven bysolar panels. This is in contrast with anuclear thermal rocket, which directly uses reactor heat to add energy to aworking fluid, which is then expelled out of a rocket nozzle.
The key elements to NEP are:
SNAP-10A, launched into orbit by USAF in 1965, was the first use of a nuclear reactor in space and of anion thruster in orbit.
A 1963 paper byMyron Levoy proposed a hybrid nuclear-electric engine design, which would have been able to work both in open-cycle mode as anuclear thermal engine during mission phases requiring high thrust, as well as in closed-cycle mode as a nuclear-electric engine with low thrust, buthigh efficiency during remaining mission phases. The proposed application of this engine design was for a fasthuman-crewed round-trip mission to Mars.[9]
In 2001, theSafe affordable fission engine was under development, with a tested 30 kW nuclear heat source intended to lead to the development of a 400 kW thermal reactor withBrayton cycle gas turbines to produce electric power. Waste heat rejection was intended to be accomplished using low-massheat pipe technology. Safety was intended to be assured by a rugged design.[citation needed]
Project Prometheus was an early 2000sNASA study on nuclear electric spacecraft.[citation needed]
Kilopower is the latest NASA reactor development program, but is intended for surface use only.[citation needed]
Proposed cuts by the second Donald Trump administration in the FY2026 budget has no funding for nuclear electric propulsion and nuclear thermal propulsion, raising the possibility that, given the current political climate, NTP and NEP could be banned, with all research could possibly be destroyed.[10][11]
US-A satellite series, launched by into orbit by the USSR, includedKosmos 1818 andKosmos 1867 in 1987, using theTOPAZ nuclear reactor and a "Plazma-2 SPT"Hall-effect thruster.
The TEM project started in 2009 with the goal of powering a Mars engine.
March 2016 - First batch of nuclear fuel received[citation needed]
Apebble bed reactor using high mass-flow gaseousnitrogen coolant near normal atmospheric pressures is a possible heat source. Power generation could be accomplished withgas turbine technology, which is well developed.Nuclear fuel would be highly enricheduranium encapsulated in low-borongraphite balls probably 5–10 cm in diameter. The graphite would also moderate theneutrons of the nuclear reaction.
This style of reactor can be designed to be inherently safe. As it heats, the graphite expands, separating the fuel and reducing the reactor's criticality. This property can simplify the operating controls to a single valve throttling the turbine. When closed, the reactor heats, but produces less power. When open, the reactor cools, but becomes more critical and produces more power.
The graphite encapsulation simplifies refueling and waste handling. Graphite is mechanically strong, and resists high temperatures. This reduces the risk of an unplanned release of radioactive elements, includingfission products. Since this style of reactor produces high power without heavy castings to contain high pressures, it is well suited to power spacecraft.[12]
A variety of electric propulsion technologies have been proposed for use with high power nuclear electrical generation systems, includingVASIMR,DS4G, andpulsed inductive thruster (PIT). PIT and VASIMR are unique in their ability to trade between power usage, specific impulse (a measure of efficiency, seespecific impulse) and thrust in-flight. PIT has the additional advantage of not needing conditioned power.[citation needed]
A number of heat-to-electricity schemes have been proposed. In the near term,Rankine cycle,Brayton cycle, andStirling cycle generators go through an intermediate mechanical phase, with attendant energy losses. More exotic technologies have also been proposed:thermoelectric (includinggraphene-based thermal power conversion[13][14][15]),pyroelectric,thermophotovoltaic,thermionic andmagnetohydrodynamic typethermoelectric materials.
Radioisotope thermoelectric generators,radioisotope heater units,radioisotope piezoelectric generators, and theradioisotope rocket all use the heat from a static radioactive source (usuallyPlutonium-238) for a low level of electric or direct propulsion power. Other concepts include thenuclear thermal rocket, the fission fragment rocket,nuclear pulse propulsion, and the possibility of afusion rocket, assuming thatnuclear fusion technology is developed at some point in the near future.[citation needed]
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