(ORDO NEWS) — NASA and China are planning a crewed mission to Mars in the next decade. While this represents a huge leap forward in space exploration, it also poses significant logistical and technological challenges.
For starters, missions can only launch to Mars once every 26 months, when our planets are at their closest points in orbit to each other (during “opposition”). With current technology, a transit from Earth to Mars would take six to nine months.
Even using a nuclear thermal or nuclear electric propulsion system (NTP/NPP), it can take 100 days to get to Mars one way.
However, a team of researchers from Montreal’s McGill University has assessed the potential of a laser-thermal propulsion system. According to their study, a spacecraft using a new propulsion system that uses lasers to heat hydrogen fuel could reduce the time it takes to travel to Mars to just 45 days!
The study was led by Emmanuel Duplay, a McGill alumnus and current MA student in aerospace engineering at TU Delft. He was joined by Associate Professor Andrew Higgins and several researchers from the Mechanical Engineering Department at McGill University.
Their study, titled “Design for a rapid transit mission to Mars using laser-thermal propulsion,” was recently presented in the journal Astronomy & Astronomy.
In recent years, directed energy (DE) propulsion has become the subject of significant research and interest. An example is the Starlight program, also known as the Directed Energy Propulsion for Interstellar Exploration (DEEP-IN) and Directed Energy Interstellar Studies (DEIS) programs, developed by Professor Philip Lubin and the UCSB Experimental Cosmology Group (ECG).
As part of NASA-funded research that began in 2009, these programs aim to tailor large-scale DE applications for interstellar missions.
There are also the Breakthrough Starshot and Project Dragonfly projects, both of which originated from a design study conducted by the Interstellar Science Initiative (i4iS) in 2013.
These concepts involve using a gigawatt laser array to accelerate a light sail and a small spacecraft to fractions of the speed of light (relativistic speeds) to reach nearby star systems in decades rather than centuries or millennia.
But while these concepts are interstellar, Duplay and colleagues have explored the possibility of an interplanetary concept.
As Duplay explained to Universe Today via email:
“The ultimate application of directed energy could propel a light sail to the stars for true interstellar travel, and this possibility motivated our team that conducted this study. We were interested in how the same laser technology could be used to travel quickly in the solar system, which , hopefully will be a closer stepping stone to showcase this technology.”
In addition to laser sail propulsion, DE is being explored for several other applications in space exploration. These include transferring power to spacecraft and permanently shadowed habitats (such as the Artemis program), communications, asteroid defense, and searching for possible technosignatures.
There is also a laser-electric spacecraft concept that is being studied by NASA and is part of a joint UCSB and MIT ECG study.
In this case, lasers are used to supply energy to the spacecraft’s photovoltaic grids, which is converted into electricity to power the Hall thruster (ion thruster). This idea is similar to a nuclear electric propulsion system (NPP), where a laser system replaces a nuclear reactor. As Duplay explained, their concept is related but different:
“Our approach complements these concepts in the sense that it uses the same laser phased array concept, but uses the much more intense laser beam on the spacecraft to directly heat the propellant, similar to a giant steam kettle. This allows the spacecraft to rapidly accelerate while it is still is close to the Earth, so the laser does not need to be focused as far into space.
“Our spacecraft is like a dragster that accelerates very quickly while staying close to the Earth. We believe we can even use the same laser-powered rocket engine to return the booster to Earth orbit after it has thrown the main vehicle to Mars , which will allow you to quickly dispose of it for the next launch.”
In this respect, the concept proposed by Duplay and his colleagues is reminiscent of a nuclear thermal propulsion system (NTP), where the laser has taken the place of a nuclear reactor.
In addition to OE and hydrogen fuel, the mission architecture for the laser-thermal spacecraft incorporates several technologies from other architectures. As Duplay pointed out, they include:
“fibre-optic laser beams that act as a single optical element, inflatable space structures that can be used to focus a laser beam as it arrives on a spacecraft into a heating chamber, and the development of high-temperature materials that would allow a spacecraft to crash into the Martian atmosphere on arrival”.
The last element is very important, given that there is no laser array on Mars to slow down the spacecraft once it reaches Mars.
“The inflatable reflector is the key to distinguishing it from other directed energy architectures: designed for high reflectivity, it can handle more laser power per unit area than a photovoltaic panel, making this mission feasible with a modest laser setup compared to a laser- electric motors,” Duplay added.
By combining these elements, a laser-thermal rocket could provide very fast flights to Mars that would last only six weeks – something that was previously thought only possible with nuclear-fueled rocket engines.
The most immediate advantage is that it represents a solution to the problems associated with the hazards associated with deep space flight, such as prolonged exposure to radiation and microgravity.
At the same time, says Duplay, the mission comes with some challenges, as many of the technologies involved are cutting-edge and have not yet been tested:
“The laser heating chamber is probably the biggest challenge: Can we keep hydrogen gas, our fuel, when it is heated by a laser beam to over 10,000 K, and at the same time keep the walls of the chamber cool? Our models say it is feasible, but experimental testing on a full scale is not yet possible because we have not yet built the necessary 100 MW lasers.”
While much of the technology in this proposed mission architecture – and other similar proposals – is still in theory and development, their potential is undeniable.
Reducing the time it takes to get to Mars to weeks instead of months would solve two of the biggest problems for Martian missions – logistical and medical.
In addition, the creation of a rapid transit system between Earth and Mars will accelerate the creation of infrastructure between Earth and Mars. This could include a Gateway-type space station orbiting Mars, similar to the Mars Base Camp proposed by Lockheed Martin, as well as a laser array to slow incoming spacecraft.
The presence of these objects will also speed up plans to create a permanent human presence on the surface of Mars.
Professor Higgins concluded by saying:
“The Mars in 45 Days study led by Emmanuel was motivated by the study of other, near-term applications of phased array laser technology being developed by Philip Lubin’s group.
The ability to deliver energy into deep space using a laser would be a revolutionary technology for propulsion and Our study looked at a laser thermal approach, which looks promising, but the laser technology itself is a real game-changer.”
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