Airborne laser success

ERRORIST · 2004-11-15 15:25:05

It can hit a target hundreds of miles away.
http://www.spacedaily.com/news/laser-04 … r-04v.html

GCNRevenger · 2004-11-15 16:51:34

For propulsion...

-Its only 1MW, you'd need a hundred times this energy
-It has enough fuel to fire for minutes, not months

ERRORIST · 2004-11-15 17:17:32

Once in space?

GCNRevenger · 2004-11-15 17:39:39

You would get away with a slightly smaller laser, but the cooling system will be much bigger. Otherwise, same deal. A chemical laser can't sustain a beam long enough.

ERRORIST · 2004-11-15 19:09:29

Why?

GCNRevenger · 2004-11-15 19:14:17

You won't have to contend with atmospheric scattering anymore, so you will need a little less laser power. Since chemical lasers can't pack enough energy per pound for an extended (read: months) firing in a reasonable mass, then the laser would have to be electically powerd and the electricity generated though some high-density or remote means.

Anyway, lasers aren't very efficent, and most of the energy that goes into them winds up lost as waste heat. And that heat has to go some place or the laser will melt... Since space has no convienant supply of air or other working fluid, the only solution is radiators. BIG radiators.

ERRORIST · 2004-11-15 19:18:27

how about a sun shade?

GCNRevenger · 2004-11-15 19:24:31

No no no, the problem is not heat from the sun, its waste heat from the laser. Shielding light from the sun won't help much at all.

ERRORIST · 2004-11-16 16:40:21

its waste heat from the laser.

Cool the waste heat from the laser with a sun shield that environment is -250 degrees.

Austin Stanley · 2004-11-16 20:27:21

There are three ways to get rid of heat, convection, radiation, and conduction. I'll go over each of them in term.

Convection is the difusion of hot molecules from a hot area to cooler areas, primarily in liquid or gasses. On Earth this is the primary method of getting rid of heat, as it is the most efficent. You move cold air/water by something that is hot, and you cool it. The problem is in space, there are no large quantities of air or water to dilute your high temperatures with, and bringing such quantities up with you is very inefficent. Sometimes convection is used as a means to transfer heat from a region that has a lot of it (like a laser or a reactor), to an area that can get rid of it (like a radiator), because convection is the most efficent means to transport heat, but in any case, it is not an effective means of heat disposal in space at least.

The secound method of heat transfer in radiation. And it is the primary means by which heat is delt with in space. Excited molecules emit photons, which take the heat energy away with them. However, this method of heat transfer is fairly small scale, and you often need very big radiators to get rid of the vast amounts of heat you have.

The thrid method of heat transfer is conduction, which is the movment of heat by moleculor action. Exited (hot) molecules bump into other molecules, giving away some of there heat energy in the process. This method is most prevelant within crystline solids, like most metals. Now, while conduction can transport the heat away from it source, or give it to a gas in order to be rid of it via convection, all it realy does is spread your heat around your spacecraft, not get rid of it.

So you see, just because space is realy cold, doesn't mean it is the best enviroment for cooling things off. In fact, vacume is the best insulator in existance.

GCNRevenger · 2004-11-16 20:45:18

Just blocking out heat from the sun won't remove heat from the laser Errorist. The heat from the laser and its reactor needs to be removed from the lasing station and dissapated. Since you have no coolant in space, the only option is to remove it by radiating it away into space. When its "cold" on Earth, the low temperature air is effective at removing heat, but in space there is no "temperature" persay because there is nothing to be hot or cold.

ERRORIST · 2004-11-16 23:19:57

Or you could use the laser fuel as a coolant before it is used for the laser. It would warm up some but it is going to do that anyways once it is used.

GCNRevenger · 2004-11-17 06:49:32

Can't do that, because you can't use a chemical laser. There is no possible way you could keep a large laser stocked with enough laser fuel for continuous beams like you would need for propulsion. The laser must be powerd only by electricity, heat, or radiation from the power source.

Don't forget, you also have to get rid of heat from the cluster of nuclear reactors you'll need to power the thing, and they don't use any expendable substance either.

SpaceNut · 2004-11-17 08:05:33

The Power of Light: An Airborne Laser for Missile Defense

With the successful ground test in the bag, the Missile Defense Agency is pushing forward with plans for an Airborne Laser (ABL), a Boeing 747 freighter aircraft with a laser-tipped nose designed to destroy ballistic missiles as they rocket through the sky. In the ultimate version of laser tag.

ERRORIST · 2004-11-17 16:54:07

If this is a 1MW ABL mirror would the mirror for 100 MW laser be 100 times as big???

http://www.space.com/php/multimedia/ima … t+Assembly
+for+the+Airborne+Laser.+The+window+is+the+exit+for+the+High+Energy+Laser+and+exit+and+ret
urn+window+for+the+Beacon+Illuminator+and+Tracker+Illuminator+lasers.+Credit%3A+Lockheed+Martin.+Click+to+enlarge.%0D%0A]http://www.space.com/php.....%0D%0A

GCNRevenger · 2004-11-17 17:12:21

It would be substantially larger, but probobly not far bigger if its space based. It depends if the big 100MW laser you have in mind is a single beam or not.

John Creighton · 2004-11-20 10:42:20

We should agree that solar ion is a practical method of space travel. So the question then becomes if you build a ship that has solar ion propulsion how much of a boost can you give it if you can augment the solar energy with a laser. Clearly this has the advantage of not having to carry the power plant with you. Initially it may not be practical to build a solar powered ion propulsion system that can intercept a beam all the way to mars. However perhaps maybe over 5 times the distance between the earth and the moon the laser can add significant delta V to the ship. As more powerful beams with less dispersion and more accuracy are developed along with ships with a bigger area of solar cells the distance over which it is practical to augment the solar power with the laser will increase.

GCNRevenger · 2004-11-21 11:44:10

I think that solar ion propulsion is practical to within about 1AU, but out at Martian distances the sun gets pretty dim to generate bulk electricity.

Using a laser beam instead of light from the sun would offer a performance boost, but I think that the investment in the laser(s) needed would be pretty high, and ought to be weighed against the bennefits of a reduced array weight.

New Mars Forums

Announcement

#1 2004-11-15 15:25:05

Re: Airborne laser success

#2 2004-11-15 16:51:34

Re: Airborne laser success

#3 2004-11-15 17:17:32

Re: Airborne laser success

#4 2004-11-15 17:39:39

Re: Airborne laser success

#5 2004-11-15 19:09:29

Re: Airborne laser success

#6 2004-11-15 19:14:17

Re: Airborne laser success

#7 2004-11-15 19:18:27

Re: Airborne laser success

#8 2004-11-15 19:24:31

Re: Airborne laser success

#9 2004-11-16 16:40:21

Re: Airborne laser success

#10 2004-11-16 20:27:21

Re: Airborne laser success

#11 2004-11-16 20:45:18

Re: Airborne laser success

#12 2004-11-16 23:19:57

Re: Airborne laser success

#13 2004-11-17 06:49:32

Re: Airborne laser success

#14 2004-11-17 08:05:33

Re: Airborne laser success

#15 2004-11-17 16:54:07

Re: Airborne laser success

#16 2004-11-17 17:12:21

Re: Airborne laser success

#17 2004-11-20 10:42:20

Re: Airborne laser success

#18 2004-11-21 11:44:10

Re: Airborne laser success

Board footer