what if we could reach Mars in just 45 days?

Currently, sending humans to Mars would involve months-long missions launched at specific times. However, such long journeys would not be without risk for the astronauts on board and the best way to avoid them would be to shorten the travel time. To do this, nuclear power seems ideal.

To leave the Earth, we have always relied on chemical rockets. The technology is not perfect, but it will still have enabled human exploration of the Moon. However, NASA, China and SpaceX have another target in mind: Mars. With chemical propulsion, we would then have to deal with a limiting factor: time. It would take approximately six to nine months (and a phenomenal amount of propellants) to send men to the red planet.

Under these conditions, Mars would then probably mark some kind of limit beyond which we could not go. To travel further, you have to go faster with less fuel. And if the solution came from nuclear power?

Thermal and electrical nuclear

The idea is not new. NASA and the Soviet space program spent years working on the subject, but no project really came to fruition.

There are two types of nuclear propulsion. Let’s start with the nuclear-thermal propulsion (NTP) which involves a rocket engine in which a nuclear reactor replaces the combustion chamber. The latter burns liquid hydrogen as fuel to make ionized hydrogen gas (plasma). This gas is then channeled through nozzles to generate thrust.

NASA became interested in the concept as early as the end of the 1950s with its program Nuclear Engine for Rocket Vehicle Application (NERVA). It had resulted in the development of a successfully tested solid-core nuclear reactor. With the end of the Apollo era in 1973, funding for the program had subsequently been significantly reduced. The project was then finally canceled even before flight tests were carried out. The Soviets had also developed their own concept (RD-0410) between 1965 and 1980, before also canceling their program.

For its part, the nuclear-electric propulsion (NEP) is essentially based on a nuclear reactor supplying electricity to a Hall effect thruster (ion engine). The latter then generates an electromagnetic field which ionizes and accelerates an inert gas (such as xenon). NEP designs are distinguished by being able to deliver over 10,000 seconds of specific impulse (I sp), meaning they can sustain thrust for almost three hours. However, the thrust level is still quite low compared to other options.

Both of these concepts have their pros and cons. This is why researchers favor solutions that include two modes of propulsion (bimodal).

A few years ago, with Mars in sight, NASA relaunched its nuclear program with the aim of developing bimodal propulsion. According to the agency, such a rocket could allow transits to the Red Planet in just 100 days. However, a new concept proposes to do even better.

Artist’s concept of a bimodal nuclear rocket. Credits: NASA

March in 45 days

As part of the NASA Innovative Advanced Concepts (NIAC) program for 2023, NASA has selected a nuclear concept for Phase I development. This new class of bimodal nuclear propulsion system uses a “wave rotor topping cycle” and could reduce transit times to Mars to just 45 days.

The proposal is signed by Professor Ryan Gosse of the University of Florida. It incorporates one of the fourteen concepts selected for phase 1 of this year’s NIAC (NASA Innovative Advanced Concepts) program, which aims to nurture visionary ideas. All teams will benefit from an envelope of $12,500 to help mature the technology and methods involved.

Ryan Gosse’s proposal is a bimodal design based on a solid-core NERVA reactor (mentioned earlier). The latter would provide a specific impulse (I sp) of 900 seconds, which is double the current performance of chemical rockets. The proposed cycle also includes a pressure wave compressor – or Wave Rotor (WR). The technology, used in internal combustion engines, harnesses pressure waves produced by reactions to compress intake air.

Combined with a nuclear thermal engine (NTP), the WR would use the pressure created by the heating of liquid hydrogen by the reactor to further compress the reaction mass. According to the researcher, this could provide levels of thrust comparable to those of a NERVA-class NTP concept, but with an intensity of 1400 to 2000 seconds of Specific Impulse. Combined with a CIP cycle, thrust levels would then be further improved.

Ideally, the researcher promises that such a design could make it possible to reach Mars by only 45 days and potentially revolutionize human exploration of deep space. Such a transit would not only reduce the overall duration of the mission, but also considerably major risks associated with missions to Marsincluding radiation exposure and time spent in microgravity.

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