6
$\begingroup$

Instead of flying say tons of metal and/or water and other raw materials/molecular matter to the Moon or Mars, could we shoot it there in ionized form by accelerating these sufficiently?

Maybe subsequently shooting the previously removed electrons so that the matter can be discharged on-site.

Of course we would need a simple (?) base built there previously that is able to "catch" the beam.

I imagine this could be much cheaper and faster than sending rockets filled with stuff.

Is this in any way feasible? Or would the atmosphere get in the way? In that case, just bringing the stuff into earth orbit and only then shooting it would no longer be much cheaper, but still faster.

That is, if such a beam of reasonable size (a few tens or hundreds of meters) could transport any reasonable amount of mass in reasonable time.

$\endgroup$
  • 4
    $\begingroup$ You'd be better off launching slugs or shells of material from a railgun; you'd have a better chance of catching them at the other end, though that wouldn't be easy either. $\endgroup$ – Monty Wild Feb 26 '15 at 0:41
  • 1
    $\begingroup$ Wouldn't the rotation and motion of the planets mean that the beam's direction have to be continually adjusted to land in the same place? Over millions of kilometers would it be possible maintain a beam with that precision? $\endgroup$ – Matthew Lock Feb 26 '15 at 7:17
3
$\begingroup$

Various forms of this have been proposed as propulsion systems for ships in interplanetary or interstellar space, which should give you some idea of the energy that is contained in the beam.

A neutral particle beam is needed for transmitting matter or energy over long distances since the beam of charged particles would otherwise disperse. The catcher might be a large superconducting ring, but when the "hot beam" passes through the magnetic field it may disperse into ions again, creating a huge radioactive cloud. If the beam impacts directly onto a target like the lunar surface, then extreme heating and inducing radiation in the target might happen. You will be mining radioactive glass for your materials.

A "beam" of macroscopic particles (Smart Dust) might be a better solution. Some proposals make each piece of "smart dust" a tiny solar sail, so sunlight or perhaps a laser in orbit could be used to accelerate the "smart dust" towards the target. Since the macroscopic particles are neither charged nor moving at relativistic velocity, the problem of catching the "beam" of smart dust is also much easier. Perhaps a "pie pan" made from metal or sintered out of regolith would do as your mass catcher. The issue of heat will still be there, only not so severe (maybe you will have to pry off a pile of sintered material from the "pie pan" structure).

Some proposals using "smart dust" to propel a spacecraft suggest that you can use the beam to achieve incredible accelerations (usually by breaking the beam down into a plasma so it can effectively couple to a superconducting magnetic "drive plate"), so it is possible to generate and transport a lot of energy using a macroscopic dust "smart beam" as well.

$\endgroup$
  • $\begingroup$ Thank you for this answer. All the other proposals and elaborations have also been great, but I can pick just one "answer" (and I felt like "helping out" another "novice", if points mean anything/much here?). This was my first post here, but I see I will enjoy this community. Kudos to everyone! Let's keep it up. $\endgroup$ – masterxilo Feb 27 '15 at 11:30
  • $\begingroup$ Imo, such discussions are very fun and interesting, in the words of Carl Sagan: "Science and science fiction have done a kind of dance over the last century, [...]. The scientists make a finding. It inspires science fiction writers to write about it, and [...] people read the science fiction and are excited, and inspired to become scientists to find out more [...], which they do, which then feeds again into another generation of science fiction and science; and that sequence has played major role in our present ability [...]." $\endgroup$ – masterxilo Feb 27 '15 at 11:31
14
$\begingroup$

TL;DR: No.

The problem with charged particle beams is dispersal. Since all the particles have the same charge sign, and like-charged particles repel one another, the beam would disperse before it could reach any target, and much of the material would be lost.

Alternatively, a neutral-particle beam could well serve to deliver particles to a relatively small destination across interplanetary distances, however capturing these particles at the other end would be a problem, and they would arrive with an energy close to that with which they were accelerated in the first place, hence why this system is being considered for use as a weapon.

$\endgroup$
  • 2
    $\begingroup$ Further, Conservation of Charge (a physical law) still applies here. Firing charges from Point A to Point B means that Point A progressively becomes more and more charged. Eventually, the attractive forces of this will pull your fired charged particles back. Solution: Fire two streams of charged particles - one positive, one negative. $\endgroup$ – user6511 Feb 26 '15 at 0:39
5
$\begingroup$

From a physics standpoint, it's essentially irrelevant what mechanism is used to deliver some matter – whether by rocket or by particle stream, you'll still have to accelerate all that matter to the necessary escape velocity, and heaving all that mass out of Earth's gravity well still requires the same amount of physical work.

Rockets have one big disadvantage – they're subject to the rocket equation. They do not only have to lift the payload, but also the rocket engine and all fuel, and all fuel to lift that fuel, which is wildly inefficient[1]. Of course, there are ways to improve on that.

  • Launch the payload with an engine but without an energy source. The energy required for propulsion is provided externally, e.g. via solar panels or a ground-based laser. Reaction mass will still have to be taken along, which is subject to the rocket equation.

  • Use laser propulsion, where light itself transfers impulse onto the payload.

  • Perform all acceleration up front with a stationary device (e.g. a railgun) so that the payload requires neither engines nor fuel. Due to the high accelerations, this tends to be unsuitable for delivering life forms alive, but for raw materials this poses no problem. This would be the most realistic option for cheaply delivering large quantities of low-priority cargo on an interplanetary scale. If you want to launch from Earth directly to the target planet, the friction caused by the atmosphere is a major problem (you do not want your cargo to burn up).

    Depending on a lot of variables (mostly, scale), the most economical solution would be either to use cheap rockets to lift cargo to an orbital railgun, providing initial delta-v to a small rocket via a mass driver, or building a ginormous vacuum tube up into the higher atmosphere through which cargo is accelerated. See for example the Star Tram concept as an interesting example, and the Surface to Orbit page on Project Rho for comparisons of various ground launch concepts.

Accelerating large units (a couple of tons) from a stationary device is logistically easier than accelerating small units (microscopic dust or single molecules, i.e. a gas or a plasma). The latter requires additional energy to break down the materials in the first place, and a lot of effort to slow down, capture, and recombine the transferred matter.

[1]: The technical term is “exponential”

$\endgroup$
1
$\begingroup$

As already stated, like charges repel and therefore a non-neutral beam will spread out.

The closest thing to what you are asking for is to use a rail gun or a catapult to fire finished (or part-finished) products into orbit around the destination planet for collection. You would still need some packaging (with thrusters attached) in case anything went wrong, or to make micro adjustments after launch.

$\endgroup$
0
$\begingroup$

You don't get something for nothing. The energy required to get the stuff anywhere is given to us by e=mc^2. Waiting for antigravity motors myself, then we can use flying saucers for transport. The physics will eventually get there.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.