A nuclear rocket to go to Mars: NASA and Darpa study the fission engine

There’s also nuclear power, in the plan to return to the Moon and then head for Mars. Both destinations need a lot of energy to send men and equipment, supplies and habitable structures. Heavy loads, environments suitable for human permanence, therefore larger and more difficult to transport.

In theory, the power already exists, but much more can be exploited using fission to propel rockets towards the goal, even for human missions: NASA and Darpa (the acronym stands for Defense advanced Research projects agency) are convinced of this, which have announced a collaboration to develop a nuclear thermal propulsion prototype in space. In summary: the upper stage of a rocket that exploits the heat generated by fission. The project is called Draco (Demonstration rocket for agile cislunar operations), and according to NASA reports, it could be tested as early as 2027.

A small reactor in the engine

Rockets, mechanically, all work in the same way: after combustion, the gas is expelled downwards through nozzles and this generates upward thrust, it is the principle of action and reaction. Even a thermonuclear engine works like this, only that to heat the gas we don’t use a chemical reaction (as in the case of hydrogen and oxygen, for example) but the heat generated by nuclear fission. According to NASA, the thermonuclear engine will be “at least 3 times more efficient compared to traditional chemical propulsion”. It means reduction of time and costs.

The effort to find ever better solutions to travel faster and with more power responds to the needs of future space programs, both American and European. First of all the Moon: the Artemis program aims to land in 2025 with a crew, but in the following years there will be heavy traffic to and from our satellite. An orbital space station, the Gateway, will be built, and there are plans to build a settlement, a sort of Moon Village, on its surface. The loads to be carried will be many and heavy: “The ability to obtain extraordinary advances in space technology through Draco’s thermonuclear propulsion program will be essential for the more efficient and rapid transportation of materials to the Moon and people to Mars,” he said. Stefanie Tompkins, director of Darpa.

“With the help of this new technology, astronauts could travel to and from deep space faster than ever before,” he stressed NASA Director Bill Nelson.

Go to Mars in 45 days

How much faster? The US Space Agency doesn’t say. The outward journey to Mars takes between 6 and 9 months and the launch window opens only every 26 months, because we have to wait for the Earth and the Red Planet to be at the minimum distance from each other. An engine that much more efficient would be a revolution.

Even more than for the Moon, for one manned mission to Mars you will probably need to bring materials and supplies in advance. A mission is expected to last 21 months. Shortening travel time by two-thirds or more would reduce the risk to astronauts. There is another project for a rocket that uses both thermal nuclear and electric nuclear (heat is transformed into electrical energy which powers an ion thruster, it has a much longer but weaker impulse). IS included in NASA’s Innovative Advanced Concepts (NIA) program by Ryan Gosse of the University of Florida, Gainesville, and promises to get to Mars in just 45 days.

But we are talking about prototype engines that have never flown. Although thermonuclear propulsion is object of study and experimentation since the 50s, that is, since man began to make use of nuclear power also for civilian purposes, in any case a legacy of the study for military applications. Both America and the USSR studied solutions of this type, there were also tests (in particular in the Nerva program, Nuclear engine for Rocket vehicle application and rover, also by NASA) in the hypothesis that a type of nuclear fission rocket could form the upper stage of the Apollo program rocket. But it never made its way to heaven: “The engineers – we read on the NASA website – failed to solve the problems relating to shielding for the crew and the fear of radiation in the places of (possible, ed) accidents”. Problems that the engineers working on Draco will probably also have to deal with.

Space

Artemis III, the NASA shuttle and the SpaceX lander: back to the Moon

by Matteo Marino

January 18, 2023

Nuclear power in space

Nuclear fission is also a solution for producing energy on the surface of other worlds. Starting with the moon. The Human Exploration of Artemis program plans to land at the South Pole, where there are special conditions. Margins of craters such as Shackleton have the advantage of being practically always touched by sunlight, to be exploited with panels, right next to depressions that are always in the shade. In other places, however, the lunar day lasts two weeks, and then there are two weeks of darkness. There is no way to use renewables (the Moon has no atmosphere, so no wind). NASA has been evaluating for some time the use of mini nuclear power plants, small fission plants to connect lunar and Martian settlements.

In June 2022 the US Space Agency has announced the signing of 3 contracts for as many development projects of prototypes to be tested on the Moon “by the end of the decade”, a phase that will therefore see fission for propulsion and that for energy supply proceed in parallel. And which will then perhaps be used on Mars, where the day lasts more or less like that of the Earth, but the Sun is up to 100 million kilometers further away and the amount of energy that arrives is inferior. Additionally, the Martian atmosphere has a nasty habit of kicking up planetary dust storms that can blind any solar panel. This has already happened with a couple of probes, the last Insight, which died suffocated by a red veil who left her no escape.

However, atomic energy is already used in space missions, albeit in a much less harsh way than the fission process: the Curiosity and Perseverance rovers have a plutonium heart. The heat of the decay of the nucleus of the radioactive element, in addition to heating the circuits in the Martian frost, is transformed into electricity by a radioisotope thermoelectric generator. This system currently also keeps the Voyager 1 and 2 probes on (which took off 45 years ago (they still transmit data from the borders of the Solar System) and New Horizonswhich after showing us Pluto up close for the first time, is flying towards new objects in the Kuiper belt.