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NASA Space Transportation Technology

Sorry, But Lasers Aren't Taking You To Mars Anytime Soon 193

An anonymous reader writes: It's long been a dream of humanity to travel interplanetary distances at great speeds, or to make it to another star system within a human lifetime. Until recently, technologies to get us there — antimatter propulsion, wormholes or warp drive — have all been composed of physically unrealistic solutions. But recent developments in laser technology make directed energy propulsion a feasible solution. By building a giant laser array in space and developing a new type of solar sail that reflects the laser light with incredible efficiency, a laser sail, this propulsion system is scalable to arbitrarily large powers. There are many technical obstacles to be overcome, and so it's unlikely we'll see the fruit of this anytime in the next few decades (despite the promises of some), but this may well be the technology that takes us to the stars in the coming centuries.
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Sorry, But Lasers Aren't Taking You To Mars Anytime Soon

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  • Forbes dot com (Score:5, Informative)

    by Dunbal ( 464142 ) * on Wednesday February 24, 2016 @08:59AM (#51574121)
    Lasers would get me to Mars faster than I would click on a Forbes link.
  • by 110010001000 ( 697113 ) on Wednesday February 24, 2016 @09:00AM (#51574127) Homepage Journal
    Another Ethan Siegel blogspam that will take you to Forbes which HAS BEEN KNOWN TO deliver malware via their adserver. Do not follow the Forbes link!
  • by Anonymous Coward on Wednesday February 24, 2016 @09:06AM (#51574151)

    "Scalable to arbitrarily large powers" = "I haven't thought about this very hard"

  • I recall there was some trick at the turnover about charging the sails an using the lasers for deceleration too.

    • Acceleration on the first half of the trip is done & then mandatory deceleration on the last half unless you don't care about stopping.

      • well... if you aim it right you'll stop one way or the other.

        it's really about who decides what the deceleration looks like... and over what time-frame. either you handle it yourself... or physics is certainly up to the task of decelerating your craft for you.

      • then mandatory deceleration on the last half unless you don't care about stopping.

        Stopping without catastrophic results. Stopping is easy.

  • Nuclear is still the best way to get to Mars. If it weren't for the fact that the words "nuclear rocket" in the same sentence is somehow horrifying, we would have been there a while ago. I mean, it isn't even going to be on Earth people. If you really want we can even have it dock with the ISS so we just have to carry it up.
    • by dbIII ( 701233 )
      "Seven Eves" has a bit about the "what could possibly go wrong" aspects of a nuclear rocket on the cheap. Those SF movies with the stuff at the other end of a very very long boom from the living area have got the right idea too. I'm not saying it's a show stopper, but horrifying is the way it has to be treated if used correctly. Being casual about radiation is not the way to work with it - it needs to be kept away from soft squishy organic bits as much as possible so automated to the back of beyond. Tha
  • Rocheworld (Score:3, Interesting)

    by dargaud ( 518470 ) <slashdot2 AT gdargaud DOT net> on Wednesday February 24, 2016 @09:21AM (#51574241) Homepage
    If interested in this potential star-reaching tech, read Robert L. Forward's book Rocheworld [amazon.com].
  • I was always worried about being kidnapped by lasers to another planet.
  • when doing something new, should we begin with an untested unknown technology, or with existing technology modified to meet the need ?
    imo the second method. and in this case, choosing that way would probably get us to mars in decade or three, but choosing first will only delay it ever further (though it would allow us to paint and write cool impotent pictures to pass the time).

    and we are not doing a new potential technology a service by saddling it with solving complex task start with.

  • by jandrese ( 485 ) <kensama@vt.edu> on Wednesday February 24, 2016 @09:36AM (#51574319) Homepage Journal
    XKCD covered this [xkcd.com] and came to the conclusion that laser propulsion just isn't practical, even by the lofty standards of theoretical intrastellar space travel.
    • FTFL, "But you really need lasers for this â" regular light spreads out too fast. Maybe a set of lasing cavities orbiting the sun â¦" Ah, but if you had some way to line up regular light, then you'd really have something. Maybe we'll come up with some kind of snazzy metamaterial to do that soon.

      Anyway, the big argument for laser propulsion is not efficiency of the system. It's mass savings on the spacecraft. It doesn't work unless you have power to waste, so clearly we won't use it any time s

    • by ceoyoyo ( 59147 )

      Not sure where you got "not practical" out of that. It's a piece about an interesting paper to get more efficiency out of the setup. A plain old solar sail (even without the lasers) works pretty well if you're going far enough or you need a little bit of fuel-free thrust for things like station keeping or attitude control.

      You know we've launched solar sails, right?

    • LOL ... "This is awful. If we were lifting the squirrel with a motor, railgun, or electric catapult, with 1.21 gigawatts we could send it screaming upward at ridiculous speeds."

      I live in a place with an overabundance of squirrels ... and I insist someone does the 1.21 gigawatt squirrel railgun thingy ... you know, purely in the name of science.

  • Sorry, But Lasers Aren't Taking You To Mars Anytime Soon

    a) I didn't think they were going to; this is the first I've heard of it at all
    b) Well, not with that attitude.

    C'mon, Slashdot, put a positive spin on it. Lasers might take you to Mars some day.

    • by Viol8 ( 599362 )

      "Lasers might take you to Mars some day."

      Sure, they might take you there, but you'll only be passing by , because unless someone has built another laser array ON mars you won't be stopping until you hit something. Which could be the same day or a billion years later as the dried out dust that used to be your corpse slowly orbits the galaxy.

      • because unless someone has built another laser array ON mars

        Well there you go. Problem solved.

      • "Lasers might take you to Mars some day."

        Sure, they might take you there, but you'll only be passing by , because unless someone has built another laser array ON mars you won't be stopping until you hit something. Which could be the same day or a billion years later as the dried out dust that used to be your corpse slowly orbits the galaxy.

        If you have a laser propulsion system on the moon, you accelerate the ship up to speed, then the ship separates a mirror to go ahead of the ship and the laser hits the forward mirror and is reflected back to the ship, slowing it down. The forward mirror will continue to accelerate on it's way out of the solar system like a Voyager, but so long as it's mass is less than what it would take for equivalent thrust from fuel, it's all good.

  • by jbmartin6 ( 1232050 ) on Wednesday February 24, 2016 @09:58AM (#51574397)
    The biggest technical hurdle to human spaceflight is enabling them to survive the experience. Robots are far more likely, I think, for the next few centuries at least. Of course, some new disruptive technology could change that picture.
    • by k6mfw ( 1182893 )

      The biggest technical hurdle to human spaceflight is enabling them to survive the experience. Robots are far more likely, I think, for the next few centuries at least. Of course, some new disruptive technology could change that picture.

      There is this website "Rocketpunk" retro future like steampunk (I'm too lazy to find the link) which stated back in 1940s and 1950s it was envisioned there will be lots of people in space to manage weather and communication stations in orbit along with orbiting telescopic platforms that look both at earth and into space. And not only that but all these people will be working on the McGuffinite (the Alfred Hitchcock term) But then along comes NASA that is able to replace all these people with just a few kg o

  • by cerberusss ( 660701 ) on Wednesday February 24, 2016 @10:06AM (#51574451) Homepage Journal

    By building a giant laser array in space BLAH BLAH BLAH unlikely we'll see the fruit of this anytime in the next few decades

    You had me at giant laser array 3

  • How do you stop at the other end?

    • You reverse the polarity of the neutron flow.
      • You reverse the polarity of the neutron flow.

        Shit. Are you sure it's not a tachyon pulse?

      • You reverse the polarity of the neutron flow.

        Well, if you're going to do that, might as well reverse the particle flux from the sun.

    • You get there in the first place by using the light sail to speed up or slow down in your orbit around the sun, NOT by lifting straight out. You speed up by reflecting light at a vector that increases your speed, slow down by reflecting it in the other direction.

      Nobody stops in space, unless they want to fall into the sun. You just match up orbital speeds and directions (sometimes for orbits around orbiting objects).

      rgb

  • >> ("lay-zers") may well be the technology that takes us to the stars in the coming centuries

    I, for one, welcome our new shark overlords.

    • by Shark ( 78448 )

      It's *space* shark overlord to you, chum.

      That said, I'm pretty sure exploration isn't the first reason governments would want to put giant lasers in space. They might also want to cook some popcorn, if you get my drift.

  • Nobody reading this today is going to Mars.

    It's time for you all to accept that and just move on.

  • The limiter in space communications, and in the space-sail-propulsion application, is diffraction. Don't think additive diffraction, as in crystallography, but the basic mechanism.

    Waves diffract (change path) when they pass near the edge of an aperture. This is how nature works.

    You might tightly collimate your beam, but the more you do so, the greater the 'spread' of the beam over long distances. For reference, see The Opticks, by I. Newton. (I hope you can read Latin!)

  • It's a well known fact (at least among sailors) that a good boat, you can use the sail like a wing and then use the 'lift' to push you forward faster than the wind is pushing you. Typically done with extremely light catamarans and hydrofoils, you can achieve speeds 3x the wind.

    I will ignore the obvious joke about going faster than the speed of light, but I wonder if we could do a similar effect using a solar sail? Anyone know if you can use a solar sail to get 'lift' as well as push?

    • Anyone know if you can use a solar sail to get 'lift' as well as push?

      "Lift" is defined relative to the direction of motion (it is the component of force on a wind perpendicular to the airflow). The force on a lightsail is defined relative to the incident direction of the beam.

      If you were to define "drag" as force in the direction of the beam, and "lift" as force perpendicular to the beam, then, yes, you can have lift on the sail.

      Nobody actually does define lift and drag on a lightsail that way, but if you think of the laser (or solar) beam as the "incident wind", then in fa

    • This works because you travel faster by eliminating friction by minimizing the surface of the boat in the water.

  • ...Inverse Square Law? Fer ******* sakes! Even a "focused" beam spreads out over distances. Those who dream of "laser propulsion" might think of a huge laser onboard, but the power source to drive it would be immense!

    Is it April 1st, yet?

  • I came to Slashdot many years ago to read about new and exciting technology and when an announcement was made or a proposal was evaluated there was a lot of excitement by everyone, criticism was common, but it was constructive criticism, almost as if the readers were interested and excited.

    Now days, not so much, most posts are either haters that hate everything, or people trying to out negative everyone else by pointing out how "it will never happen".

    sigh...

  • Lasers aren't ever going to lift a ship up from the surface of the earth via a light sail. It is not entirely impossible that ground-bound lasers cannot be directed into an ablative material in the base of a ship that then vaporizes, superheats, and emerges as a plasma drive, but even that is highly speculative and requires extremely precise alignment of thrust vectors and the ship's vertical axis in the presence of both turbulence and coriolis effects during liftoff.

    The place light sails become arguably u

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