Laser beams could send missions to Mars in just 45 days

A laser thermal propulsion system, using this technology to heat hydrogen fuel, could reduce transit times to Mars to 45 days. This is the conclusion of a team of researchers from McGill University in Montreal who evaluated the potential of this novel propulsion system.

Using current technology the travel time reaches six months. Even with nuclear-thermal or nuclear-electric propulsion (NTP/NEP), a one-way transit could take 100 days to reach Mars.

The research was led by Emmanuel Duplay, a McGill graduate and current MSc student in Aerospace Engineering at TU Delft. The results have recently been submitted to the journal Astronomy & Astronomy and are available on arXiv.

In recent years, directed energy (DE) propulsion has been the subject of considerable research and interest. There is a concept for a laser-electric spacecraft that is being investigated by NASA and as part of a collaborative study between UCSB (University of California Santa Barbara and MIT).

For this application, lasers are used to deliver power to photovoltaic arrays on a spacecraft, which is converted into electricity to power a Hall-effect thruster (ion engine). This idea is similar to a nuclear-electric propulsion (NEP) system, where a laser array takes the place of a nuclear reactor.

As Duplay explained to Universe Today, their concept is related but different: “Our approach is complementary to these concepts, as it uses the same phased array laser concept, but would use a much more intense laser flux on the spacecraft to directly heat the propellant, similar to a giant steam boiler. This allows the spacecraft to accelerate rapidly while still close to Earth, so the laser doesn’t need to be focused as far out in space.”

“Our spacecraft is like a racing car that accelerates very fast while still close to Earth. We think we can even use the same laser-powered rocket engine to return the booster to Earth orbit, after you’ve launched the main rover to Mars, allowing you to quickly recycle it for the next launch.” He said.

In this sense, the concept proposed by Duplay and colleagues is similar to a nuclear-thermal propulsion (NTP) system, where the laser has taken the place of a nuclear reactor. In addition to hydrogen propellant and DE, the mission architecture for a thermal laser spacecraft includes several technologies from other architectures.

As Duplay pointed out, they include “fiber-optic lasers that act as a single optical element, inflatable space structures that can be used to focus the laser beam as it reaches the spacecraft heating chamber, and the development of high-temperature materials that allow the spacecraft to break into the Martian atmosphere on arrival.

This last item is essential since there is no laser array on Mars to slow the spacecraft down once it reaches Mars. “The inflatable reflector is a key to other directed energy architectures: designed to be highly reflective, it can support higher laser power per unit area than a photovoltaic panel, making this mission feasible with an array size of modest laser compared to electric laser propulsion”Duplay added.

By combining these elements, a laser-thermal rocket could enable very fast transits to Mars that would be as short as six weeks, something previously thought to be possible only with nuclear-powered rocket engines. The most immediate benefit is that it presents a solution to the dangers of deep space transits, such as prolonged exposure to radiation and microgravity.