A new era of space exploration is dawning. With the resumption of NASA’s Artemis lunar program, our eyes are also on Mars, with a manned mission in the near future, on the 2030s horizon. With SpaceX offering its Starship, NASA is exploring a way to shorten spacetime using nuclear propulsion.
One of the biggest challenges on a Mars mission is travel time. With current liquid-liquid fuel propulsion technologies, this can be achieved in at least six months. For a manned mission, this remains a significant problem for the physical and mental aspects of the astronauts (particularly radiation exposure), and this immediately closes the door to further manned exploration of the solar system.
Given that we won’t have either the USS Enterprise or the Millennium Falcon anytime soon, we still need to find a way to drastically reduce astronauts’ travel time to the Red Planet without burdening the spacecraft with tens of tons of liquid propellant. Core drive is a very advantageous solution.
The revival of the race for the atomic engine
A first race for this technology took place during the Cold War, then the programs were discontinued. However, in recent years, Russia, China and the United States have again become involved in these projects. NasaNasa has restarted a bimodal nuclear propulsion program that combines both a nuclear thermal propulsion system (NTP) and another nuclear electric propulsion system (NEP).
The goal is to reach Mars in 100 days, instead of 180 today. The Niac program – Nasa Innovative Advanced Concepts – is in its first phase, collecting concepts and supporting their maturation before moving on to more concrete phases transforms.
Rally core thermal and core electrics
These are the two nuclear propulsion concepts examined so far. The NTP is based on a conventional propellant using liquid hydrogen (LH2) as the propellant, which would be heated by an onboard nuclear reactor. Due to this strong heating, the hydrogen changes into a gaseous state, which drastically increases the pressure passed with a nozzle. The thrust generated is very effective. The concept was studied as early as the 1950s by NASA and the US AirAir Force and between 1965 and 1980 by the USSR.
The NEP drive is based on a nuclear reactor that powers an ion engine (Hall Effect engine). This creates an electromagnetic field that accelerates gas particles to create thrust. The commonly used gas is XenonXenon.
Did you know ?
Nuclear power has been used in space for decades! Nuclear batteries power several probes such as Voyager 1 or Cassini because their distance from the sun did not allow them to have enough solar energy. This is also the case with the Mars rovers Curiosity and Perseverance, which do not need a solar panel!
Combining these two drives for a single mission makes it possible to be more flexible in the amount of thrust required. In fact, interplanetary travel requires both large thrusts (departure and arrival for braking) and small trajectory corrections. In addition, the thrust must not be too strong for the comfort of the astronauts. On the other hand, it must be able to last longer. For example, a CIP concept can maintain thrust for almost three hours.
The innovation that reduces travel time to 45 days
The “Bimodal NTP/NEP with a Wave Rotor Topping Cycle” concept selected in Phase I of NASA’s Niac program, proposed by Professor Ryan Goose, director of the Hypersonics program at the University of Florida, proposes the addition of a pressure wave compressor. In conjunction with the NTP engine, the supercharger uses the pressure generated by the heating of the LH2LH2 to compress it even more, thus further increasing thrust. With a CIP engine, thrust is also improved. According to Goose, adding this compressor to a bimodal system combining NTP and CIP can cut the travel time to Mars to 45 days.