Tuesday, July 17, 2007

Energy weapons come of age

From News.com.au:

A MODIFIED Boeing 747 designed to be part of an emerging US antimissile shield has successfully completed an important flight test, the Pentagon's Missile Defence Agency and Boeing said today.

To simulate an intercept, the prototype Airborne Laser actively tracked an airborne target, compensated for atmospheric turbulence and fired a "surrogate" for a missile-zapping high-energy laser, they said.

"We have now demonstrated most of the steps needed for the Airborne Laser to engage a threat missile and deliver precise and lethal effects against it," said Pat Shanahan, a vice president at Boeing, the prime contractor.

[. . .]

The airborne laser is to be the first warplane relying entirely on a directed energy device as a weapon. It is designed to destroy an enemy ballistic missile shortly after it is launched, in the "boost phase" of its flight path.

[. . .]

The aircraft fired the tracking laser at the target aircraft, dubbed Big Crow, for the first time on March 15. The test on Friday demonstrated an ability to go from passive tracking of a simulated missile engine "plume" to active tracking, Boeing said.

In addition, the Lockheed Martin Corp. beam control and fire control system was used to offset atmospheric turbulence in conjunction with the active tracking and firing of the device standing in for the chemical oxygen-iodine laser, the company said.

Engineers will start installing the actual high-energy laser, built by Northrop Grumman Corp, in coming months to prepare for the intercept test.

The biggest problem with using directed energy weapons is the power required to do any serious damage to the target.

Here is how the math works out:

1 joule = 1 watt for 1 second

500,000 joules = 1/10 stick of dynamite

So the equivalent of half a million watts for one second only gets you the energy equivalent of one tenth of a stick of dynamite. To put this in perspective a firecracker called the M-80 was once legal in every state of the union (and is still legal in a couple of states). It had an explosive power equivalent to 1/4 stick of dynamite, or 1,500,000 joules.

In other words a child's toy can produce the equivalent of one million five hundred thousand watts of power for one second.

M-80s were outlawed in most states because they could blow off a hand, or at least fingers, if they were handled carelessly. If you put one inside a cinder block it would blow it apart with enough force to send chunks of the block out fast enough to inflict a fatal wound. So that much energy is nothing to sneeze at. If a laser rifle could be made to operate at that level of energy it would be a great anti-personnel weapon, but to bring down aircraft or missiles will require more power.

Apparently the builders of this anti-missile laser are able to generate this amount of power with chemical reactions. I wonder how many shots they can get from one of their laser planes before it has to land and rearm.