Artistic rendition of a laser driven spacecraft. Image: NASA

Lasers might push spacecraft all the way to Mars in just 3 days

Depending on the alignment of Mars and Earth, as well as the speed of propulsion, a spacecraft could reach the Red Planet as soon as 150 days. So far, NASA spacecraft have made 13 trips to Mars, with seven landings. The most recent — that of the Curiosity rover — took 253 days from launch on Earth to touchdown on Mars. There’s now reason to believe, however, that this journey could be significantly made faster to the point it only takes 3 days, according to a NASA researcher.

Artistic rendition of a laser driven spacecraft. Image: NASA

Artistic rendition of a laser driven spacecraft. Image: NASA

This could be possible using a ‘photonic propulsion’ system, says NASA scientist Philip Lubin. A massive laser based on Earth would fire bursts of photons into the ‘sail’ of the spacecraft and accelerated it up to 26% the speed of light, which is unheard of in space flight. But that’s only for a tiny object with a 1 meter solar sail. Larger, more practical crafts, would be accelerated to between 1-3% the speed of light, which is still fantastic.

Spacecraft are launched from Earth by converting the chemical energy in rocket fuel into thrust. This process is inefficient, Lubin says, when compared to electromagnetic acceleration. This technology is currently used in research facilities to accelerate particles close to the speed of light. Transferring this technology that can achieve relativistic speed from the micro to the macro world has proven to be quite a challenge.

Lubin and colleagues have now received a proof-of-concept grant from NASA to assess whether or not a photonic propulsion system for long distance space applications is viable.

Though photons have no mass, they do have momentum and energy. Once these reflect of a receiver, which could look something like a very thin sail, some of that energy is transferred, pushing the craft. While this pressure is minute, the catch is that it builds momentum over time.

The Planetary Society, a non-profit organization founded by Carl Sagan and now coordinated by Bill Nye, is working with a satellite-sized object called the LightSail. The sail is made out of thin Mylar and when stretched out measures 345 square feet. LightSail is scheduled to be delivered to Georgia Tech for integration into the Prox-1 spacecraft in March, and should make for a great test.

While the LightSail will be powered by the sun’s rays, Lubin’s system involves firing a high power laser array called DE-STAR (Directed Energy System for Targeting of Asteroids and ExploRation). Energy would come from a PV solar array. Using the same energy used today to launch rockets into space, Lubin says a 100kg object could reach Mars in three days or one month for a large craft — the kind able to carry humans. “There is no known reason why we could not do this,” said Lubin.

“As an example, on the eventual upper end, a full scale DE-STAR 4 (50-70 GW) will propel a wafer scale spacecraft with a 1 m laser sail to about 26% the speed of light in about 10 minutes (20 kgo accel), reach Mars (1 AU) in 30 minutes, pass Voyager I in less than 3 days, pass 1,000 AU in 12 days and reach Alpha Centauri in about 15 years. The same directed energy driver (DE-STAR 4) can also propel a 100 kg payload to about 2% c and a 10,000 kg payload to more than 1,000 km/s,” Lubin wrote in a paper.

Of course, this could prove to be our best shot at exploring other solar systems as well.

“The human factor of exploring the nearest stars and exoplanets would be a profound voyage for humanity, one whose non-scientific implications would be enormous,” writes Lubin. “It is time to begin this inevitable journey beyond our home.”

How in the world Lubin and team will solve the technical challenges is beyond me at this point, but we will follow these developments with great interest.

20 thoughts on “Lasers might push spacecraft all the way to Mars in just 3 days

  1. S. Smith

    So they get it there in 3 days. Without a propulsion system on board, how are they going to stop it at Mars? Especially at 3% the speed of light? A speed not yet achieved.

  2. HarryKeller

    The “large spacecraft” would take a month and so be at around 0.2%c if the quotes are correct. A large spacecraft would have to have a braking mechanism. It might use a magnetically driven ionic propulsion system that would have to begin slowing the craft far from Mars and so double the trip time to two months. That’s still a large improvement over current transit times. It also opens the launch window considerably.

    Now, the real problems begin. How will you land on Mars? Can you return or will you stay forever as in the Mars One idea? How many supply trips will be necessary before the arrival of humans? How will they live — food, air, water, heat, radiation protection, meteorite protection, etc.?

    Getting there is less than half of the problem.

  3. Jonnyslide

    I think the initial goal of these systems, as a proof of concept, is to send probes out that can only transmit data and information back. They would carry light-weight sensors and perhaps apertures, data storage systems, etc., to relay information back to Earth. From that standpoint, the investment and return on investment would be…well…astronomical.

    In terms of return systems, that needs to be figured out and is an altogether different application of the technology. If your trip time takes a total of 3 days, relatively half the time needs to be spent trying slow down. I say relatively half because Mars has a much slower orbital velocity than the earth (due to being farther away from the Sun) in reality, one would need to slow down even more, not to mention getting the desired payload into the correct Martian trajectory which would require a lot of delta V – think going in a straight line then needing to make a sharp turn.

    This requires substantial focus in orbital dynamics to model correctly and the paper just illustrates the math, at a high-level, for what the concept can do. I’m fine with this and I think the authors took the correct approach but it is important to properly set expectations for this type of ‘disruptive’ technology so people don’t run off the deep-end with it.

    Also, to add, to decelerate enough to get captured by Mars gravity well, the same or more amount of energy (compensating for the difference in orbital velocities) will be required, in the opposite direction. This would require on-board engines (not an option, VASMIR, plasma drives, chemical thursters, etc., would not work as the speeds mentioned, due to mass and GW power levels, would drastically decrease. Perhaps there is a balance somewhere.

    A couple hundred years from now we will probably have space-based networks of these directed energy lasers that move packages around the solar system. I imagine these being placed at lagrangian points of different orbital systems such as sun-moon-earth, sun-venus, juputer and its moons, etc.

    Interesting thing about this concept though is that in order to do all those things, we gotta do it the hard way first- then setup the infrastructure for future growth…as is all things..

  4. mark

    I have a question, with the orbiting laser the diagram shows the laser orbiting the earth in a way that will block the laser. Could the laser not orbit the earth in a way that will not block the laser? for example going from top, right, bottom, left then back to top. instead of front, right, back, left…

  5. Brian

    Actually you can use the earth laser to slow the craft down at mars by detaching part of the mirror and bouncing the laser off it and onto the spacer craft. This accelerates the mirror fragment away faster.

    The laser would be a huge weapon in orbit. It’s seem like a bad idea.

    Solar ion engines are the best so far.

  6. Jonathan Kolber

    This is exciting. Alpha Centauri in 15 years! If these combinations of probe/spacecraft and propulsion systems can be standardized and made cheap enough (perhaps with detachable robots that can explore and transmit findings, which the spacecraft would then relay back to Earth), we could disperse such probes to all manner of nearby systems and have some good (perhaps amazing!) first-hand knowledge of all of the nearby star systems later in this century. That could be followed by colony ships departing early in the 22nd century, and actual human colonies established in the 23rd.

    But why not build these lasers in space? No atmospheric interference, and it can be powered like SPS with a butterfly wing-like solar array, with everything optimally sized for power transmission. Also, I’m wondering about slowing down the probes as they approach their destinations. If they’re designed to just keep going, the separable robots will have to include significant broadcast capabilities. All solvable details, I’m sure. :)

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  8. Patrick Wiley

    If I know my newtonian physics, an orbiting laser would be pushed backwards by the energy it emits. I’m not sure that such a thing could even stay in orbit. For a terrestrial laser this is no problem because the energy would be absorbed by the Earth.

  9. Patrick Wiley

    Why worry about it’s weapons applications? We still have enough nukes to wipe out the Earth several times over and no one’s finger is getting any closer to the button.

  10. Stephen D. Patterson

    Lasers don’t generate thrust. They generate energy, which is converted into thrust at the receiving end.

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  12. Amna

    I have several questions, if the laser propulsion that is supposed to propel the craft to Mars is in outer space, orbiting the Earth, how is the spacecraft going to actually get to outer space? Is the use of chemical propulsion still going to be needed? Or is the laser beam going to be directed into Earth, where the spacecraft is going to be placed? And won't that laser beam have negative effects, especially if directed into Earth? Also, if the spacecraft was to travel at a speed that's 26% of the speed of light, isn't that going to have any affect on the astronauts? Are they going to be able to survive travelling at such a high speed? Any answers are much appreciated :)

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