Riding a Laser to Mars

Could a laser send a spacecraft to Mars?

That is a proposed mission from a group at McGill University, made to fulfill a solicitation from NASA. The laser, a 10-meter vast array in the world, would certainly heat up hydrogen plasma in a chamber behind the spacecraft, creating thrust from hydrogen gas and sending it to Mars in only 45 days. There, it would be aerobrake in Mars’ atmosphere, shuttling supplies to human colonists or, at some point probably, even human beings themselves.

In 2018, NASA challenged engineers to craft a mission to Mars that would certainly deliver a payload of at the very least 1,000 kilos in no more than 45 days, along with longer trips deep into, as well as out of, the solar system.

The quick delivery time is stimulated by an aspiration to shuttle shipments and, someday, astronauts to Mars while lessening their exposure to the harmful effects of galactic cosmic rays and solar storms. Elon Musk’s SpaceX pictures a human trip to Mars would certainly take six months with its chemical-based rockets.

Concepts behind the theory

McGill’s concept, called laser-thermal propulsion, relies on a variety of infrared lasers based on Earth, 10 meters in diameter, incorporating several invisible infrared beams, each with a wavelength of about one micron, for a powerful total of 100 megawatts– the electric power required for approximately 80,000 U.S. households.

The payload, orbiting in an elliptical medium Earth orbit, would include a reflector that directs the laser beam originating from Earth into a heating chamber containing a hydrogen plasma. With its core afterward heated up as high as 40,000 Kelvin (72,000 degrees Fahrenheit), hydrogen gas circulating around the core would get to 10,000 K (18,000 degrees Fahrenheit) and be ejected out a nozzle, creating thrust to propel the ship away from Earth for 58 minutes. (Side thrusters would maintain the craft aligned with the laser’s beam as Earth rotates.).

When the beaming halts, the payload whisks away at a velocity of nearly 17 kilometers per second relative to Earth– fast enough to transcend the moon’s orbital distance in a mere 8 hours. When it gets to the Martian atmosphere in a month and a half, it will still be traveling at 16 km/s; however, as soon as there, putting the payload in a 150-km orbit around Mars is a difficult issue for the engineering team to address.

It is hard since the payload cannot carry a chemical propellant to fire a rocket to slow itself down– the fuel needed would certainly reduce the payload mass to less than 6 percent of the initial 1,000 kgs. Furthermore, until humans on the red planet can build an identical laser range for the incoming craft to utilize its reflector and plasma chamber to provide reverse thrust, aerocapture is the only way to slow down the payload at Mars.

Also then, the aerocapture, or aerobraking, in Mars’ atmosphere could be a dicey maneuver, with the spacecraft experiencing slowdowns of up to 8 g (where g is the acceleration caused by gravity at Earth’s surface, 9.8 m/s2), about the human limit, for a few minutes, as it is recorded within a single pass around Mars. The big heat fluxes on the craft due to atmospheric friction would be above conventional thermal protection system materials, but not those under active development.

Laser-thermal propulsion

Laser-thermal propulsion of spacecraft right into deep space– Mars and further– contrast with other previously proposed approaches of conveyance, such as:

• laser-electric propulsion, in which a laser beam would certainly impinge on photovoltaic (PV) cells behind the payload;
• solar-electric propulsion, in which sunlight on the PV cells produces the propulsive thrust;
• nuclear-electric propulsion, in which a nuclear reactor develops electricity that produces ions thrust out a thruster;
• nuclear-thermal propulsion, in which a nuclear reactor’s heat converts liquid to a gas that’s propelled out a nozzle to produce thrust.

” Laser-thermal propulsion enables fast transport missions of 1 ton with laser varieties the size of a volleyball court– something laser-electric propulsion can solely do with kilometer-class arrays,” claims Emmanuel Duplay, lead author on the study that worked on the project over two years while part of McGill University’s Summer Undergraduate Research in Engineering Program. Duplay is currently in Delft University of Technology’s Master of Science Program in Aerospace Engineering with a specialization in Spaceflight.

An excellent advantage of laser-thermal propulsion mission concept introduced by Duplay et al. is its extremely low mass-to-power ratio, in the range 0.001– 0.010 kg/kW–” unmatched,” they write, “far below also those cited for advanced nuclear propulsion technologies, due to the reality that the source of power stays on Earth and the delivered flux can be processed by a low-mass inflatable reflector.”.

Application of laser-thermal propulsion

Laser-thermal propulsion had first been studied in the 1970s using 10.6-micron CO2 lasers, the most powerful at the time. Today’s present-day fiber-optic lasers, at one micron, which can be integrated into massively parallel, phased arrays with a big, effective diameter, suggests a focal length of power delivery over two orders of magnitude greater– 50,000 kilometers in Duplay’s laser-thermal propulsion concept.

Duplay explains that architecture for phased-array lasers is being produced by a team led by physicist Philip Lubin at the University of California at Santa Barbara. Lubin’s team’s array utilizes individual laser amplifiers of roughly 100 watts each– each amplifier is a simple loop of fiber optics and an LED light as a pump and can be mass-produced at low costs– so the Mars mission conceived here would certainly need on order of 1 million individual amplifiers.

The first people to Mars most likely will not get there utilizing laser-thermal propulsion technology. “However, as more people make the journey to sustain a long-term colony, we will certainly require propulsion systems that obtain us there much faster– if only to prevent radiation hazards,” Duplay says. He speculates that a laser-thermal mission to Mars might launch ten years after the first human missions, so maybe around 2040.

Read the original article on PHYS.

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