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Why do we need X-ray lasers???

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Why do we need X-ray lasers???
Post by jgnfld   » Thu Mar 27, 2014 10:06 am

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If the terminal velocity of a Mark 23 is .83c (Honorverse wikia) why do we need even bother with an X-ray laser. At relativistic velocities, wouldn't simply colliding with a sidewall generate far more X-rays, gamma rays, and, hell, maybe even low energy cosmic rays that would cascade forward than any mere fusion source + lasing rods could provide?

My physics is pretty old, rusted, and pitted, but I get 1.7*e^11 megajoules as the output of the 40 megatonne bomb (of which only some will be converted to X-rays) while at terminal velocity there would be a release of 1.1*e^16 megajoules of energy upon collision (most of which would be converted to high energy radiation, I would think).

What am I missing?
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Re: Why do we need X-ray lasers???
Post by The E   » Thu Mar 27, 2014 10:11 am

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jgnfld wrote:What am I missing?


That hitting a sidewall is actually not that easy, that laser heads have a greater chance of actually hitting something because they have a standoff range, and last but not least, that all we know about collisions of physical objects against sidewalls is that these are not considered to be a risk for the ship projecting the wall.
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Re: Why do we need X-ray lasers???
Post by munroburton   » Thu Mar 27, 2014 10:43 am

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The missile is moving that way at .83c, the target's moving this way at .4c. The target is 1.3km across its longest axis. Not the easiest thing to intercept, as the target can adjust its acceleration and course.

Putting lasers on the missiles increase their range from point-blank to 50,000km, driving the odds of scoring a hit up. No longer does the missile have to actually hit the target, it just has to get close enough to shoot at it.

Plus the target can roll. Although a SD might take 12 minutes to complete a 90 degree turn, it doesn't need to turn the full 90 to interpose its (300km wide) wedge between the ship and any missiles trying to hit it directly. And any missiles accelerating up to .8c will need a long, noisy run, giving a reasonably alert crew enough time to do so.

So far, the only thing that can destroy a wedge is another wedge of at least equivalent strength.
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Re: Why do we need X-ray lasers???
Post by MaxxQ   » Thu Mar 27, 2014 11:58 am

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munroburton wrote:The missile is moving that way at .83c, the target's moving this way at .4c. The target is 1.3km across its longest axis. Not the easiest thing to intercept, as the target can adjust its acceleration and course.

Putting lasers on the missiles increase their range from point-blank to 50,000km, driving the odds of scoring a hit up. No longer does the missile have to actually hit the target, it just has to get close enough to shoot at it.


Also upping the odds of a hit are the fact that with something like a Mk16, you get six chances to hit the target (six laserheads), and if you're using a Mk23, you get ten shots with a single missile.

This is in contrast with a *single* chance to hit the target by trying to actually hit the target with the missile.

I'll take multiple laserhead chances over a single swing-and-a-miss any day.
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Re: Why do we need X-ray lasers???
Post by namelessfly   » Thu Mar 27, 2014 12:05 pm

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jgnfld wrote:If the terminal velocity of a Mark 23 is .83c (Honorverse wikia) why do we need even bother with an X-ray laser. At relativistic velocities, wouldn't simply colliding with a sidewall generate far more X-rays, gamma rays, and, hell, maybe even low energy cosmic rays that would cascade forward than any mere fusion source + lasing rods could provide?

My physics is pretty old, rusted, and pitted, but I get 1.7*e^11 megajoules as the output of the 40 megatonne bomb (of which only some will be converted to X-rays) while at terminal velocity there would be a release of 1.1*e^16 megajoules of energy upon collision (most of which would be converted to high energy radiation, I would think).

What am I missing?



A 100 ton missile at 1/3 Cee has a KE of

KE = 1/2 x 1eex5 Kg x (1eex8)^2 = 5eex21 Joules.

I think you had a typing boo boo.

In contrast, the yield of a 40 Megaton bomb is 40 x 4eex15 = 1.6eex17 Joules.

Your point is well taken.

However; achieving impact is difficult and the missile can not evade defensive fire. Plus xero stand off range increases defensive hit rate
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Re: Why do we need X-ray lasers???
Post by Whitecold   » Thu Mar 27, 2014 12:06 pm

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In the end it boils down to "because the plot says so."

6 orders of magnitude more energy trump about every targeting consideration, and missiles were used before laser heads were invented, and could achieve kills.
Nukes needed direct hits, and could achieve them, but realistically, a nuke is more a scuttling charge than a warhead when the missile carries a million times more kinetic energy.
It is one of those mess-ups that happened so long ago that it's completely impossible to fix it by now.
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Re: Why do we need X-ray lasers???
Post by SWM   » Thu Mar 27, 2014 1:44 pm

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Impact on a sidewall does no damage. Nuke going off at or near a sidewall damages the sidewall.
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Re: Why do we need X-ray lasers???
Post by crewdude48   » Thu Mar 27, 2014 2:03 pm

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An impeller drive missile does not strike the sidewall. The impeller bands interact with the sidewall, causing the nodes to overload. This causes the nodes to explosively react, destroying the missile body. So, while all of the kinetic energy of the missile would be directed into the sidewall, it would not be at the same time or the same point. A nuke with gravity focusing would put less energy on target in a more directed fashion, allowing higher impulse loads at points.
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Re: Why do we need X-ray lasers???
Post by jgnfld   » Thu Mar 27, 2014 2:13 pm

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SWM wrote:Impact on a sidewall does no damage. Nuke going off at or near a sidewall damages the sidewall.


A relativistic impact IS a nuke. X-ray, gamma, etc. is what is released, is it not?
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Re: Why do we need X-ray lasers???
Post by namelessfly   » Thu Mar 27, 2014 2:26 pm

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jgnfld wrote:
SWM wrote:Impact on a sidewall does no damage. Nuke going off at or near a sidewall damages the sidewall.


A relativistic impact IS a nuke. X-ray, gamma, etc. is what is released, is it not?



Gamma rays are released when nuclei come apart which does occur at high enough temperatures.

I have not yet crunched the numbers. However; my gut would expect that such nuclear dissolution to not occur until impact energy significantly exceeds about 1eex15 Joule per Kg. Think much more than 1/10 Cee, maybe 1/2 Cee.

Given the fact that the KE of a missile at only 1/3 Cee vastly exceeds the yield of a multiple megaton warhead, I think of the nuke as a burster charge that causing the vaporized missile to become a cloud of plasma that expands at a few % Cee as it impacts.
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