Nuclear technology for future space missions

With nuclear power and its related technologies, interplanetary missions will be faster, more efficient, and cheaper. Thanks to this, humanity is ever closer to a new era of space travel to Mars, the solar system and even beyond.

These are some of the conclusions of a panel of international experts who participated in the webinar of the International Atomic Energy Agency (IAEA): “Atoms for Space: Nuclear Systems for Space Exploration”.

With nuclear energy and its related technologies, interplanetary missions will be faster, more efficient and cheaper.

International experts agreed that further progress in nuclear fission and fusion is necessary for deep space travel (beyond our solar system). Nuclear power could supply electricity for onboard systems and instrumentation, and could also make possible a sustainable human presence on other planets in the solar system.

The experts described technologies that use both nuclear fission and fusion, with three main purposes: the propulsion of spacecraft, the generation of energy in missions on the extraterrestrial surface and the electrical supply of on-board systems.

spacecraft propulsion
For the foreseeable future, ships launched into space will continue to rely on fossil fuels for propulsion. However, once in orbit, nuclear engines could take over and create propulsion to accelerate speed.

Key nuclear technologies

There are two key nuclear technologies for propulsion: thermonuclear propulsion (NTP) and nuclear electropropulsion (NEP).

Thermonuclear propulsion involves using a nuclear fission reactor to heat a liquid propellant, such as hydrogen. The heat turns the liquid into a gas that expands through a nozzle to generate thrust and propel the spacecraft. One of its main advantages is that space flights would need to load less fuel, and NTP engines would make the trip shorter. For example, a trip to Mars would be reduced by 25% compared to traditional chemical rockets. In addition, a reduced time in space also reduces the astronauts’ exposure to cosmic radiation.

With electronuclear propulsion technology, thrust is produced by converting thermal energy from a nuclear reactor into electrical energy. With this type of technology the boost is less but continuous, and the fuel efficiency is much higher. Speed is increased, with a more than 60% reduction in transit time to Mars compared to traditional chemical rockets.

The spacecraft company Ad Astra Rocket Company is building a NEP system: the Variable Specific Impulse Magnetoplasma Rocket (VASIMR). It is a plasma craft in which electric fields heat and accelerate a propellant to shape a plasma. When the plasma shoots out of the engine, magnetic fields direct it in the right direction and the impulse is generated. The VASIMR design would allow large amounts of energy to be processed while maintaining the high fuel efficiency that characterizes electric ships.

converteArtistic illustration of the VASIMR spacecraft (Photo: Ad Astra Rockets)

In the short term, they indicate from Ad Astra, the VASIMR engine is expected to be used for a wide range of high-energy applications, from solar electricity in cislunar space to nuclear electricity in interplanetary space. In the longer term, the VASIMR could be the precursor to future fusion spacecraft, which are still in the conceptual phase.

VASIMR, an electronuclear propulsion technology ship, could be the precursor to future fusion ships

fusion ships

Fusion craft like the Reverse Field Configuration Reactor (PFRC) being developed at Princeton’s Plasma Physics Laboratory could produce a direct fusion drive (DFD), which directly converts energy from charged particles produced in the fusion reactions in propulsion for the spacecraft.

The PFRC reactor at the Princeton Plasma Physics Laboratory (Photo: Princeton Fusion Systems)

The possibilities of DFD technology open the door to interstellar space, human missions to Mars and a stable supply of energy for a future lunar base, indicate from the company Princeton Satellite Systems. Other advantages are that they are small in size and require very little fuel. Just a few kilos can power a spacecraft for ten years.

The possibilities of nuclear fusion technology open the door to interstellar space, human missions to Mars and a stable supply of energy for a future lunar base.

Energy for the alien surface
Nuclear reactors could also be used to provide a reliable source of surface power for extended exploration missions, facilitating a sustainable human presence on other planetary bodies. Fission surface power reactor designs are micro-reactors that could supply electrical power in the tens of kW range for decades. The current focus is on using either low-enriched uranium fuels or high-enriched uranium fuels for peaceful use.

In the words of NASA’s Space Nuclear Technology Portfolio representative, the Agency’s priority is to “design, build, and demonstrate a low-enriched uranium fission surface power system with a wide range of applications for the surface of the Moon and for a future mission to Mars with humans, scalable to energy levels above 100 kWe; it must also be able to cover the needs of the NEP system.”

NASA is working on the design of a fission surface power system for applications on the surface of the Moon and for a future mission to Mars with humans

Power for systems on board the spacecraft
Spacecraft not only need electrical power for propulsion, but also to maintain their life support systems, communications, and other equipment and systems. Special emphasis was made at the expert meeting on radioisotope thermoelectric generators (RTGs), which have powered the Voyager spacecraft for decades far beyond the Sun thanks to their potential to provide heat and electricity for long periods of time to systems aboard spacecraft in the cold temperatures of space.

Future nuclear solutions such as DFD technology could supply electricity simultaneously. According to NASA studies, a fusion-powered direct-drive engine can produce power and thrust with the best performance, generating electrical power and propulsion with a single engine.

With the support of nuclear energy, future space missions will be able to count on a much greater number of applications. In the words of Mikhail Chudakov of the IAEA’s Department of Nuclear Energy, “our path to the stars goes through the atom.”