The proposed laser-thermal propulsion system relies on an earth-based laser array to emit a beam to heat the fuel core and generate thrust.
A team of engineers has proposed a laser-based propulsion system that could reduce transit time to March up to 45 days only. A trip to Mars is not like taking a car and reaching for the nearest Starbucks. Earth and Mars continue to move in their orbits around the sun, which means the two planets are never the same distance apart. The best way forward for a Mars mission is to target the time when the two worlds are in closest approach, leading to a “minimum cost” trajectory. This particular path is called the Hoeman Transfer Orbit, but the launch window only opens after 26 months, and it would still take about nine months to reach Mars.
Once a team lands on Mars, they will need to spend another three to four months on the planet for Mars and Earth to align for proximity, then embark on the return journey, which will take another nine months. Bringing supplies such as food, water, science equipment and medical aid along with a massive amount of fuel will be a hassle. A crew of six would need to carry around three million pounds of cargo for such a mission. Based on the maximum payload capacity of existing technology, it would take ten of SpaceX’s mighty Starship Super Heavy rocket just to get that cargo into orbit. Transporting it to Mars will require a massive upgrade in capacity and numbers.
However, experts can solve the radiation exposure and cargo problems to a great extent if the engines could be supercharged. And that’s where a laser propulsion system can come to the rescue, cutting Mars travel time down to just 45 days. A team from McGill University has proposed a new propulsion system that relies on lasers to heat hydrogen and propel a spacecraft to Mars. Until now, it was thought that the only possible method to achieve such a short travel window on Mars was a nuclear-powered rocket engine. The whole setup consists of a ground-based laser array 10 meters in size that can deliver 100 MW of power via a focused beam. The spacecraft itself is connected to an inflatable chamber that focuses the incoming laser beam on the hydrogen propellant fuel, heating it to generate thrust.
Many problems, one solution
The team calls it a Laser-Thermal Propulsion System (LTPS) and says the Earth-based laser array can focus on a target up to 50,000 km away. The LTPS, hydrogen booster and payload can be launched separately or together atop a beast like the Falcon 9 rocket. Once the cargo is released to high-energy transfer orbit to Mars, the LTPS returns to the original elliptical orbit. For the actual combustion, the terrestrial laser falls on the inflatable parabolic reflector, which concentrates it and directs it towards the core of the hydrogen plasma, heating it to a temperature of up to 40,000 Kelvin. The core is then used to heat the surrounding stream of hydrogen gas, which is then expelled through a nozzle to generate thrust.
Now the possibility of reaching March doesn’t just have to do with reducing travel time. The longer astronauts stay in a spacecraft, the greater the risk of exposure to galactic cosmic rays (GCR). NASA research has found strong evidence that radiation exposure increases the lifetime risk of cancer and degenerative diseases. And radiation exposure beyond Earth’s orbit is no small number. 1 Milli-Sievert (mSv) of radiation is equivalent to three chest X-rays. In space, the range of ionizing radiation is between 50 and 2,000 mSv, which effectively means going through up to 6,000 x-ray exams. Additionally, there is a risk of space anemia, which was recently documented in NASA-assisted research. Additionally, there is also the potential threat of coronal mass ejections (CMEs) which can compromise the entire mission.
Next: What is a Mars “sol” and how long does it last?
Source: arXiv, NASA
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