"Beam Rider" weapon - attainable now?

I don’t know if this should go here, IMHO, or GQ…but here goes…

Seems to me, a “beam rider” weapon would be attainable, now…I imagine it would consist of a small object, or several small objects, placed in orbit. Something the size of that tool kit that was lost recently, and was able to be tracked visibly in the night sky from land-based telescopes - or maybe smaller because of mass issues. These objects would be light, with a “solar sail” mirrored surface (mylar?) oriented such that it would reflect the energy from a laser. If small enough and light enough, wouldn’t the laser push the solar-sail equipped object? Not only that, but given enough distance, it would build up an enormous amount of energy from the velocity.

Am I just daydreaming? I realize there are a lot of issues with size and weight for a laser to actually be able to push the object…in fact, the “solar wind” might even completely offset the effects of the laser…

Anyone got more info on this?

You can get more info here: http://en.wikipedia.org/wiki/Solar_sail

This idea has been kicked about for a long time. I think the practical limits are keeping a beam of sufficient power focused on the spacecraft. Remember the earth is moving…a lot.

The Earth is moving?? Seems pretty solid and stable to me…



Dirk, I’m not getting what you’re trying to propose here. What are the targets of this weapon? Other satellites? Ground installations? Why do we need this method as opposed to the basic projectile (i.e., firearms) or guided rocket systems we could already use?

I’m not sure about the weapon part, but the concept is that you could use a beam to propel a payload without having to put fuel or even a motor on the device…just a reflector/collector. This would eliminate a big part of the weight on, say, an earth to orbit vehicle, as the only thing on the vehicle itself would be payload, structure and the reflector/collector thingy. Of course, you’d need to build a really big laser facility (or whatever beam you are trying to use for this), and you’d need some fairly hefty computing power to keep it perfectly on target (if you screwed up your vehicle would turn into a brick since it would have no onboard thrust capability).

I’ve seen demos of this on a small scale, where they have what looks like a metallic Frisbee and they hit it with laser pulses…it’s pretty cool seeing it go up (it’s like it’s getting hit by lightning or something), but no idea if you could scale it up to be practical. I’ve also never seen one go higher than a couple hundred feet, though I’m sure that current laser and aiming technology could, in theory at least, reach orbit.


All the light sail proposals I’ve seen deploy the sail in outer space after the spacecraft was put into space via conventional means. Trying to design a craft that could both make it through the atmosphere and act as a light sail via photon propulsion would be a pretty damn difficult design project.

I’m pretty sure to say that what you saw wasn’t a demo of a light sail as the one on the OP. It was probably a (insert name of gizmo that I can’t recall at this moment) that works by either using the incoming laser energy to heat up air around the target area, causing it to expand and propel the gizmo or by ablating some material off the target point, heating it up and using it as reaction mass for propulsion.
Those things usually look like a Frisbee or a spindle.

A photon bouncing light sail wouldn’t go anywhere in Earths atmosphere anyway.

Here you go, something like this?

Now that would be more menacing as a projectile, but it goes up, not down from orbit; it can’t work in a vacuum.

I worked on this for several years. There are basically two ways to use a laser to drive something – light pressure (that’s your solar sail), which is a pretty small push, and wouldn’t be useful on something like a toolbox (that’s the reason you use sails – large area and low weight), and Laser Propulsion using Laser-Sustained Detonation Waves (LSD waves – ha,ha.) Leik Myrabo’s Lightcraft is sorta a version of the latter, only it uises ambient atmosphere, but most LSD wave proposals involve sending up a block of something to use as reaction mass – ideally ice.
Here’s a YouTube of Myrabo’s lightcraf in action. Note that it’s not really very big. The plan was to be able to launch to orbit, but the laser he’s using in this test isn’t anywhere near big enough.

The LSD wave method with self-contained reaction mass would actually work very well in space. Some folks have suggested that this is its natural application – in space there’s no attenuation or Blooming of the laser, and you can keep shooting at your craft for a long time. It’s a great way to change orbits. But Arthur Kantrowitz, one of the proposers of the LSD craft (and founder of the L-5 Society, among other things) wanted to use it to launch things into orbit. And that’s the way it’s used in Jerry Pournelle’s story “High Justice” and in Michael Kube-McDowell’s novel “The Quiet Pools”