If humans intend to become an interplanetary species (or even an interstellar), we need new propulsion methods that combine significant levels of thrust with fuel efficiency. One option NASA has been investigating for decades is spacecraft that rely on nuclear power and that can be in the form of a nuclear-electric or nuclear-thermal propulsion (NEP / NTP).
In the current era of space exploration, other space agencies are also exploring this technology. The British space agency recently signed a contract with the British automobile manufacturer Rolls-Royce. Rolls-Royce will investigate nuclear and propulsion applications in accordance with their assignments. Given the company's record of mechanical, electrical, and nuclear power solutions
This contract is the first step in a process to define and shape nuclear power solutions for the UK Space Agency and the European Space Agency (ESA). Based on previous studies and experiments from the early era of space racing, nuclear energy has proven to be an effective propulsion means and relies (best of all) on proven and validated technology.
Artist's impression of the Rolls-Royce nuclear propulsion concept. Photo credit: Rolls-Royce
Today there is no shortage of researchers extolling the benefits of nuclear energy as a means of exploring space. However, research into possible applications has been somewhat limited since the end of the Apollo era. So recent efforts to get the ball rolling again have met with great excitement. Dave Gordon, senior vice president of Rolls-Royce Defense in the UK, stated in a company press release:
“We are excited to be working with the UK Space Agency on this landmark project to define future nuclear power technologies for space. We believe there is real niche capacity in the UK in this area and this initiative can build on the UK's strong nuclear network and supply chain.
"We look forward to developing this and other exciting space projects in the future as we develop the power to protect our planet, secure our world and explore our universe."
As mentioned earlier, research into nuclear propulsion dates back to the early space age. Between 1959 and 1972, NASA's Space Nuclear Propulsion Office (SNPO) conducted 23 reactor tests at the Nuclear Rocket Development Station at the AEC Nevada test site in Jackass Flats, Nevada. In 1961, NASA and the Atomic Energy Commission (AEC) came together to launch the Nuclear Engine for Rocket Vehicle Applications (NERVA) program.
The aim of this program was to develop a nuclear thermal rocket (NTP) that could enable rapid transport to the moon, Mars and other places in space. In an NTP rocket, uranium or deuterium reactions are used to heat liquid hydrogen in a reactor, thereby ionizing it into a hot plasma, which is then passed through nozzles to create thrust.
In contrast, an NEP missile involves the same basic reactions that generate heat, which is then used to create the electricity that powers an electric motor (like a Hall Effect thruster). Unfortunately, changing priorities and a changing budget environment resulted in cuts that forced NASA to cease its nuclear propulsion work by late 1972.
According to a technical report by Doctor Michael G. Houts (the NTP lead researcher at NASA Marshall), an NTP rocket could produce 200 kWt of electricity over a period of 13 years using a single kilogram of uranium – resulting in a fuel efficiency of around 45 grams per 1000 MWh (twice as high as chemical missiles). At this speed, a nuclear thermal missile could travel to Mars in half the time (100 days!).
In recent years, research on nuclear propulsion has resumed at NASA's Marshall Space Flight Center. With the UK space agency on board now, ESA is likely to look into nuclear propulsion for future missions as well. Roscosmos is also pursuing NEP technology with its TEM (Transport and Energy Module) program and plans to conduct the first reactor tests in the early 2020s and the first orbital flight test by 2030.
An artist's conception shows a Mars transit habitat with a nuclear propulsion system. Photo credit: NASA
In 2017, China Aerospace Science and Technology Corp. (CASC) – the main contractor of the Chinese National Space Agency (CNSA) – their "Road Transportation Roadmap". In addition to developing a reusable spacecraft (similar to the X-37B), that document also called for the creation of a single stage spacecraft (SSTO) and fully reusable missiles by 2030, as well as a nuclear-powered shuttle by 2045.
Between NASA, ESA, Roscomos, China and India, there are some very ambitious plans for space exploration in the coming decades. This includes returning to the moon (or sending astronauts for the first time) and building bases that allow for an ongoing human presence. Between the 2030s and 2040s, all the great space players hope to have left footprints (and possibly habitats) on Mars as well.
As Dr. Graham Turnock, chief executive of the UK space agency, said in a press release from the agency:
“Nuclear power and propulsion in space is a groundbreaking concept that could unlock future space missions that will take us to Mars and beyond. This study will help us understand the exciting potential of nuclear-powered spaceships and whether this emerging technology could help us travel further and faster than ever before. "
Artist's concept of a bimodal nuclear missile on its way to the moon, Mars and other targets in the solar system. Photo credit: NASA
According to UK Science Secretary Amanda Solloway, this research also presents an opportunity for the aerospace industry. As government and industry find ways to build on more solid and sustainable economic models, space exploration could use this time to introduce new and far-sighted thinking:
“If we better recover from the pandemic, it will be partnerships like this between business, industry and government that will help create jobs and drive game-changing innovation that will drive space travel in the UK.
"Nuclear energy offers transformative opportunities for space exploration. This innovative study with Rolls-Royce could help move our next generation of astronauts into space faster and longer and significantly expand our knowledge of the universe."
The first crewed mission beyond Low Earth Orbit (LEO) in three years, for the first time since the end of the Apollo era (1972). By the end of the decade, we hope to have permanent infrastructure on and around the moon that will facilitate missions to Mars. By the middle of the century, we could even send astronauts to the main belt and have a permanent outpost on Mars.
There is a possibility that spacecraft powered by NTP or NEC engines could begin the journey, carrying crews and cargo to and from Earth.
Further reading: Rolls-Royce, UK Space Agency