Scientists say solar energy tops nuclear for powering crewed missions to Mars

Crewed Mars missions have been the talk of the town for the past few years. But first, lessons learned from the upcoming Artemis program will be imperative to prepare for future trips to Mars. And one of them will involve figuring out the power systems, including ones that haven't been tested on the moon's surface, such as nuclear energy, that would support future settlements. 

But what if we told you that crewed missions on the Red Planet could be powered by harvesting energy from the sun?

Researchers at the University of California, Berkeley, published a paper in the journal Frontiers in Astronomy and Space Sciences that argues a human expedition to Mars can be fueled by photovoltaics-based power systems, instead of nuclear energy.

Comparing various options

The concept isn't entirely new. In fact, the primary source of power for some NASA Mars rovers comes from a multi-panel solar array. These rover solar arrays generate about 140 watts of power for up to four hours per sol, a Martian day. 

But, in the past decade, it was assumed that nuclear power would be a better option than solar energy for human missions. Though solar arrays have delivered renewable power in space, they could be pointless in places that never get any light. It was also argued that solar panels may struggle to collect sufficient light on the dusty surface of Mars. 

However, in the current study, researchers weighed the options - they compared different ways to generate power. The calculations observed the amount of equipment mass needed to be transported from Earth to the Martian surface for a six-person mission. Specifically, they quantified the requirements of a nuclear-powered system against different photovoltaic and even photoelectrochemical devices.

Photovoltaics-based power systems practical to sustain a crewed mission

The productivity of solar-powered solutions depends on solar intensity, surface temperature, and other factors that would determine where a non-nuclear outpost would be optimally located. This took into account several factors, such as the absorption and scattering of light in the atmosphere, which would affect the amount of solar radiation at the planet’s surface.

A photovoltaic array that uses compressed hydrogen for energy storage eventually emerged as the winner. The “carry-along mass” of such a system is about 8.3 tons versus about 9.5 tons for nuclear power at the equator. Usage of the solar-based system becomes less sustainable closer to the equator at more than 22 tons, but it outperforms fission energy across about 50 percent of the Martian surface.

“I think it’s nice that the result was split pretty close down the middle,” co-lead author Aaron Berliner, a bioengineering graduate student in the Arkin Laboratory at UC Berkeley, said. “Nearer the equator, solar wins out; nearer the poles, nuclear wins.”

The system uses electricity to split water molecules to produce hydrogen, which can be stored in pressurized vessels and then re-electrified in fuel cells for power.

Got Mars on their mind

Hydrogen can also be combined with nitrogen to produce ammonia for fertilizers. Though technologies like water electrolysis to produce hydrogen and hydrogen fuel are less common on Earth, they can be a game-changer for the human occupation of Mars. 

“Compressed hydrogen energy storage falls into this category as well,” co-lead author Anthony Abel, a chemical and biomolecular engineering Ph.D. student at UC Berkeley, said. “For grid-scale energy storage, it’s not used commonly, although that is projected to change in the next decade.”

Abel and Berliner are members of the Center for the Utilization of Biological Engineering in Space (CUBES), a project developing biotechnologies to support space exploration. 

“Now that we have an idea of how much power is available, we can start connecting that availability to the biotechnologies in CUBES,” Berliner said. “The hope is ultimately to build out a full model of the system, with all of the components included, which we envision as helping to plan a mission to Mars, evaluate tradeoffs, identify risks, and come up with mitigation strategies either beforehand or during the mission.”