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Lasers may be able to propel spacecraft to Mars at a significant fraction of the speed of light

By Shawn Knight ยท 112 replies
Feb 26, 2016
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  1. NASA late last year outlined a three-phase plan to send astronauts to Mars. The ambitious undertaking, much of which involves ongoing space research and developing methods to harvest resources from Mars to sustain human life, is on schedule to unfold over the next several years.

    Those challenges aside, perhaps the most pressing question then becomes how to transport astronauts to the red planet in the most efficient – and of course, safe – manner. Although Mars is one of our closest neighbors, it would still take a modern spacecraft several months to get there using traditional thrust-based propulsion methods.

    Philip Lubin, a US Santa Barbara physics professor and NASA employee, believes the key to timely space travel lies in an alternative propulsion technology known as photonic propulsion.

    In its simplest explanation, Lubin proposes a spacecraft with a reflective sail that could be pushed through space at an incredibly high speed (a significant fraction of the speed of light) by firing a laser directly at the sail. If successful, Lubin believes the method could send a 100 kilogram robotic craft to Mars in just three days. A larger craft occupied by humans could make the trip in about a month.

    As Wired notes, photonic propulsion could allow us to explore other solar systems in search of potentially habitable planets. Maintaining communication with a robotic craft that far away, however, would still be a problem given modern technology.

    Lubin says there's no known reason why we could not do this although there are several hurdles that must be overcome beforehand. For example, how would we slow down a spacecraft as it approaches its destination?

    Those interested in delving deeper into Lubin's proposal can check out his 52-page paper on the matter by clicking here.

    Permalink to story.

  2. TomSEA

    TomSEA TechSpot Chancellor Posts: 2,633   +695

    "For example, how would we slow down a spacecraft as it approaches its destination?"

    Do what they've always done in space. Turn the aircraft around and use the propulsion in the opposite direction.
  3. JacekM

    JacekM TS Rookie

    The laser would be earth based, right? So how they suppose to stop at the destination?
  4. fps4ever

    fps4ever TS Booster Posts: 95   +66

    It will slow down when it hits the surface.
    Misagt likes this.
  5. davislane1

    davislane1 Inquisitor Posts: 4,500   +3,499

    "A significant fraction of the speed of light"

    Now there's a marketing phrase.
    Makson likes this.
  6. Technician

    Technician TS Addict Posts: 677   +113

    And I can drive my car to the store at a significant fraction of that speed.
  7. Technician

    Technician TS Addict Posts: 677   +113

    I already see a problem with that paper, you don't 'fly' in space, you travel. No air = no flight.
    That is an interesting read, thanks. I like that the lasers are only 5kg and about 8.5 x 11 inches in size. It beats the older theory of use a huge laser.
    Last edited: Feb 26, 2016
    stewi0001 likes this.
  8. yRaz

    yRaz TS Evangelist Posts: 2,146   +1,223

    But it's being propelled by lasers based on or around earth. We'd have to put earth in front of the spacecraft to slow it down
  9. Ivangela

    Ivangela TS Rookie

    no you can't
  10. Ivangela

    Ivangela TS Rookie

    If the laser are only 5Kg why aren't they on the craft, then one can do as Raz says
  11. CrisisDog

    CrisisDog TS Booster Posts: 134   +28

    Air brakes. I'm sure everyone's seen the movie 2010?
  12. I presume it's because the power source would be the grid due to the immense power requirements and therefore have to be Earth based.
  13. Technician

    Technician TS Addict Posts: 677   +113

    Yes, I can, what is significant to me is the issue, you cannot know what that means.
  14. Dennis Young

    Dennis Young TS Rookie

    For slowing down, gravity drag in the Martian atmosphere will work, but if the craft is traveling at the speeds discussed, would likely take weeks or months to slow down. The other way would be to whip around Mars and use the laser to slow it down every time it comes out from the planet's shadow. This, too, would take time.
    treetops likes this.
  15. psycros

    psycros TS Evangelist Posts: 1,685   +1,081

    The reason you can't put the propulsion lasers on the ship is the same reason you can't move a sailboat by taking a fan on board and then pointing at the sail - well, outside of a cartoon, anyway. As for the slowing down part...if the ship doesn't need to carry a big engine and fuel to get it up to speed (particularity if its assembled in space) then its got plenty of room left for deceleration and maneuvering rockets. Incidentally, this concept has been around since at least the mid-1960's.
  16. Technician

    Technician TS Addict Posts: 677   +113

    More like the 40's
  17. yRaz

    yRaz TS Evangelist Posts: 2,146   +1,223

    What is equal and opposite reaction. The 5kg laser would propel itself away from the 100kg craft faster than it would slow the craft down.
  18. Ivangela

    Ivangela TS Rookie

    I suppose that makes sense

    I still don't think Technicians car can achieve a significant fraction of the speed of light, lol
  19. cliffordcooley

    cliffordcooley TS Guardian Fighter Posts: 9,171   +3,263

    That's also a significant fraction of genius.
  20. Squid Surprise

    Squid Surprise TS Evangelist Posts: 1,315   +537

    They can use "normal" fuel/propulsion to slow down... you wouldn't need that much (unlike the insane amount you'd need to make the entire voyage).

    Once Mars has been "colonized", they could build equivalent lasers on the red planet for future voyages perhaps... would take crazy math skills to calculate orbits, but should be possible...
  21. cliffordcooley

    cliffordcooley TS Guardian Fighter Posts: 9,171   +3,263

    What I want to know is how long would it take to gain that much speed. We should all know we are limited to the amount of acceleration our bodies can withstand. So how long would we be under physical stress while accelerating or decelerating?
  22. Ralph Dratman

    Ralph Dratman TS Rookie

    If complete gram-scale spacecraft are really possible, they might also help answer the question "Where are all the extraterrestrials?" Alien wafers might be stationed all around the Solar System at this very moment. Remember, we sometimes miss incoming asteroids until the last moment. How are we going to spot tiny robots from other star systems?
  23. hitech0101

    hitech0101 TS Guru Posts: 451   +32

    Feedback - I checked in FF & chrome, the video container has height specified in such a manner that I was not able to view the entire content it was slightly cut off, tried scrolling up and down could not get entire content to fit on my screen. Maybe happening only for me.
  24. NotSoFast

    NotSoFast TS Rookie

    1/14,911.111 isn't significant, it's negligible.
  25. NotSoFast

    NotSoFast TS Rookie


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