Directed Energy Planetary Defense and Relativistic Probes

Post by mabbo » Thu, Jan 07, 2016, 5:36 PM UTC

jerf wrote: post #20

mabbo wrote: post #15

Earlier quoted context omitted.

The point isn't the vaporize them, it's to nudge them ever so slightly. Consider a comet- you fire one or more lasers to a specific spot on the comet, causing heat. The heat causes the water to expand, and shoot off from the comet. Does this destroy the comet? Certainly not much of it. But as that water vapor shoots away from it, Newtons Third Law comes into play and the comet, ever so slightly, is pushed in the oppo…

For the "larger ones" that fitzwatermellow was mentioning, the problem is that your mental model of a big rock starts breaking down. You'd be closer to think "big gravel pile sort of iced together, sort of held together by local gravity because there's nothing else pulling them apart". You shoot a little pulse at the gravel pile and break a piece off and it may simply fly out into space, taking almost all the momentu…

Post by sandworm101 » Thu, Jan 07, 2016, 6:05 PM UTC

marcosdumay wrote: post #21

sandworm101 wrote: post #19

Earlier quoted context omitted.

But KSP does give a false impression. It is very much a "spheres in a vacuum" approach to orbital physics. It doesn't model many/most of the realworld forces. When dealing with the truly minuscule forces such as would be created by lasers aimed at asteroids, one much accommodate all other similarly-sized forces before taking action. Rocks in space are subject to a force/pressure from the sun, a pressure comparable to…

> Rocks in space are subject to a force/pressure from the sun, a pressure comparable to that from a earthbound laser. Hum, is it? When near the Sun, yes, of course, but when away from it, we can probably throw way more energy on it than the Sun. Yes, it does require details that we currently can't measure. The good new is that the laser doubles as an excellent instrument for measuring those details.

Post by Retric » Thu, Jan 07, 2016, 7:15 PM UTC

jerf wrote: post #20

mabbo wrote: post #15

Earlier quoted context omitted.

The point isn't the vaporize them, it's to nudge them ever so slightly. Consider a comet- you fire one or more lasers to a specific spot on the comet, causing heat. The heat causes the water to expand, and shoot off from the comet. Does this destroy the comet? Certainly not much of it. But as that water vapor shoots away from it, Newtons Third Law comes into play and the comet, ever so slightly, is pushed in the oppo…

For the "larger ones" that fitzwatermellow was mentioning, the problem is that your mental model of a big rock starts breaking down. You'd be closer to think "big gravel pile sort of iced together, sort of held together by local gravity because there's nothing else pulling them apart". You shoot a little pulse at the gravel pile and break a piece off and it may simply fly out into space, taking almost all the momentu…

Post by chr1 » Thu, Jan 07, 2016, 7:36 PM UTC

sandworm101 wrote: post #24

marcosdumay wrote: post #21

Earlier quoted context omitted.

> Rocks in space are subject to a force/pressure from the sun, a pressure comparable to that from a earthbound laser. Hum, is it? When near the Sun, yes, of course, but when away from it, we can probably throw way more energy on it than the Sun. Yes, it does require details that we currently can't measure. The good new is that the laser doubles as an excellent instrument for measuring those details.

That very much depends on the laser. Most of the approaches I've seen discussed involve multiple 'attacks' on a rock spread out over a considerable period of time. You only fire when the rock is far enough above the horizon (say 25-30% of the time if you have 1 ground laser). And then you want to hit it when it is at some sort of apsis, preferably when it is far away with a relatively slow velocity. The sun has a 24/…

Post by bakhy » Thu, Jan 07, 2016, 8:06 PM UTC