Slashdot Mirror

← Back to Stories (view on slashdot.org)

Modular Laser Launch Systems

Posted by michael on from the future's-so-bright-you-gotta-wear-shades dept.

BerntB writes "I don't think Jordin Kare's NIAC article has been covered? It's about using new laser tech to build modular laser launch systems. The modular nature makes it easier to test and build. The only other launch ideas as cool are the Orion Project and the space elevator."

4 of 152 comments (clear)

  1. This is the only orbital platform technology... by Anonymous Coward · · Score: 5, Funny

    ...that offers a built-in light show and 1600x DVD burning.

  2. How Ironic... by Baldrson · · Score: 5, Interesting
    The only other launch ideas as cool are the Orion Project and the space elevator.

    Since the prior story is about Carnegie Mellon its rather ironic that the most intriguing launch technology was left off entirely -- and it is out of the robotics department of CM: the Rotovar(tm) by Hans Moravec.

    We investigate a cheaper system. A satellite in low circular equatorial orbit has two long cables extending in opposite directions. It rotates in the orbital plane, and the cables touch the planet each rotation, with the rotational velocity canceling the orbital velocity. The system acts like two spokes of a giant wheel rolling on the equator.

    The orbit is stable, and the taper is minimized when the satellite's diameter is one third the planet's. On Earth it is 4000 km long and touches down every 20 minutes, every 2 hours at six points. Cable motion near the ground is vertical and uniformly accelerated at 1.4 g. The maximum velocity in the atmosphere is 2 km/sec. One eighth the strength of graphite gives it a taper of 10:1, and it can lift 1/54 of its own mass at each contact.

    The central idea in this paper, of a satellite that rolls like a wheel, was originated and suggested to me by John McCarthy of Stanford. He also encouraged the work and provided many of the resources for it. The symbolic mathematics was done with the MACSYMA system being developed at MIT. This program behaves like a programmable desk calculator that deals with algebraic expressions instead of simply numbers. It is capable of solving equations, integrating formulas, taking limits and much more.

    --
    Seastead this.
  3. Look at the numbers on this by Animats · · Score: 5, Informative
    Laser launch is a nice idea, but the power requirements are huge. The current altitude record is 71 meters (not kilometers), with a 51 gram (not Kg) craft and a 10 kilowatt laser.

    Kare, who's been plugging this idea for decades, writes "A rule of thumb for laser launchers is that the unit payload is 1 kg per MW of laser power." The Apollo lunar module (all the stuff that went to the moon) massed about 6500 Kg, of which 2500Kg made the round trip. So we're going to need several gigawatts of laser power for a moon shot.

    Kare is talking about using continuous diode lasers in the 1KW range. These don't exist, but 60W units are available, so this isn't totally unreasonable. Kare proposes to use maybe 150 of these future 1KW units in a prototype. That only launches a 150g craft.

    Launching something the size of the Apollo lunar module would take six million such units, and about 12 gigawatts of electrical power for several minutes. This is twice the power output of Grand Coulee Dam, the biggest single power source in the US.

    The power storage problem might be overcome using ultracapacitors. You can get 2600 farad capacitors (not ufd, farads) at 2.5V today, and you can take current out fast. Auto engines can be started with six of these things, weighing a total of about 3Kg. With a big budget, a laser launch system could have enough energy storage to do the job.

    Six million lasers, though, is a bit much. The prototype doesn't put enough mass in orbit to be useful, and the real version is too big.

    If you want to launch a microsat, you call Orbital Sciences Corporation, and they launch a Pegasus rocket from a L-1011 for you. The X-prize guys get all the press, but Orbital actually puts stuff in orbit. They've launched 45 payloads so far. Click here for their user manual.

  4. Riding the Highways of Light by s_p_oneil · · Score: 5, Insightful

    Here's a similar, but more interesting article: http://science.nasa.gov/newhome/headlines/prop16ap r99%5F1.htm

    Now that's cool. ;-) A flying saucer that flies straight up by creating a vacuum above it that literally sucks it upward. Plus, it uses no propellant at all, which means significantly less weight to lift.

    Quote:
    "You could go halfway around the world in 45 minutes, or from the Earth to the Moon in about 5-1/2 hours."

    If NASA wants to build a base on the moon, they need something similar to this. Even if technical problems make it difficult to lift people this way (i.e. excessive heat, microwave radiation, or G-forces), it sounds perfect for lifting heavy cargo and supplies into orbit or to the moon.

    Of course, I like the candle-based rocket fuel as well:
    http://science.nasa.gov/headlines/y2003/29j an%5Fen virorocket.htm