"Obsolete SDs" Waste not...

The E wrote:

drinksmuchcoffee wrote:There would also be no blast effects in a vacuum.

There would be a pretty big energy release though, remember that bomb-pumped lasers are a pretty real concept.

There are still no blast effects in a vacuum. The laser heads would be destroyed by the same prompt radiation that produces the lasing effect.

There is still considerable debate about whether actual lasing occurred in the Excalibur tests. While theoretically valid, nobody has put all the pieces together to actually make a working weapon.

Also, given that light travels 300m in a microsecond, steps 7-10 in MaxQQQ's description would take much much less than a millisecond, given a separation of 150m.

The missile is approaching at more than 50% of C. So the range at detonation is 50,000 km, but it is closing at more then 150,000 km/sec.

And if you are going after the sidewalls on a rolled ship the equation changes. The sidewalls are deep inside the wedge, so they can't be seen until the missile is looking past the wedge. But as the missile is flashing by at up to 240,000 km/sec the entire cycle from acquisition to firing needs to take place in something like 50 milliseconds, though it is range dependent.

robert132 wrote:
Indeed they are. In the Honorverse those lasers, bomb-pumped or shipboard release enough energy that they don't just heat up a spot like today's do. The descriptions I've read say that the energy released striking a target is very similar to a kinetic strike, it doesn't "burn" or "melt" through the target, it smashes through it like a tank's penetrator round of sufficient size might.

Actually, current lasers in the multi-Megawatt class do impart kinetic effects. Light, after all, has momentum and when megawatts of energy are imparted in a fraction of a second, there are large amounts of kinetic energy imparted into the target. In a test of a multi-megawatt COIL in the 90s, an empty Titan II target missile body was dented by the test - The target area was a polished area of stainless steel reflecting a good portion of the laser. (Actually, reflecting the laser imparts the most energy via momentum - As Newton proved, all that momentum has to go somewhere, and to rebound at light speed just means it kicks off you that much harder)

In addition, absorbed energy has physical effects, as chemical bonds are abruptly sheared by the laser and solids are boiled into gases - Maxwell's laws of gas's behaviors have explosive potential when matter abruptly changes states. Really all a chemical explosion is is the SUDDEN release of bound gases and the chemical energy of the bonds heating the gas, pressurizing it. A high powered laser will do the same thing to ANY solid - not just one with special unsteady bonds.

And all this is just in the Megawatt range - in the Honorverse, we're talking Penta- and Exa-watt weapons, delivering over a million or billion times the power we are capable of dealing in our largest laser installations today in insanely short periods of times. Yes, the effects will be explosive....

There is if you're close enough to the warhead that the fireball still contains sufficiently dense material at sufficiently high temperature.

Without knowing what BuNine is postulating for explosion conditions, I can't determine that, but a bit of playing around using adiabatic simplifications leads to some skepticism, to be honest.

drinksmuchcoffee wrote:There would also be no blast effects in a vacuum.

drinksmuchcoffee wrote:

MaxxQ wrote:...
Let's see if I can explain it in a way you can understand.

1. Missile launch
2. Powered flight sequence towards target (for DDM and MDM missiles, there may or may not be a coast phase between drive (wedge) initiation)
3. At a certain amount of time before detonation, the wedge shuts down to allow attitude adjustment of the entire missile - this is to point the nose of the missile more or less in the direction of the target. If the missile is coming in from the side of the target, but trying for a throat or kilt shot, this means the missile is now travelling sideways. If attempting to burn through the sidewalls, then very little adjustment is required.
4. Protective shrouds ejected
5. Laserhead release
6. Laserheads, using built in RCS, move forward approximately 150 meters, while also attempting final, more precise, targeting.
7. Warhead (still back on the missile) detonation (between 30,000 and 50,000 km from target). Grav lenses built into the missile behind the warhead focus as much X-Ray energy from the warhead detonation as possible forward towards the laserheads.
8. X-Ray wavefront reaches the laserheads milliseconds before the blast, and the X-Ray energy is focussed onto the lasing rod using a Wolter Mirror-style reflector.
9. Lasing rod releases it's energy at the target.
10. Laserheads destroyed by nuclear warhead blast front.

Steps 3-6 occur over just a few seconds. Steps 7-10 take just a few milliseconds or less (I'll let someone else do the exact math, if they feel it's necessary).

This sequence raises a big question I always had about laser heads. If steps 3-6 take a few seconds, light speed roundtrip time at 50000 km is less than 350ms. So the target has quite a bit of time to deploy point defense laser clusters on a non-maneuvering target that is not protected by a wedge. So if laser heads work this way it is a wonder they can hit anything at all.

There would also be no blast effects in a vacuum.

You don't re-orient the missile, you eject the lasing rods so they end up at the optimum position to hit a target before the "nuke" goes off, this takes a very short time. At least that's how I understand how bomb pumped lasers are supposed to work in a combat effective way.

And you get something of a blast effect from the vaporized missile materials although the area of effect is minuscule compared to the distances involved in space battles.

You still have the particle wave-front from the nuclear explosion and it's secondary effects but it also has to follow the inverse-square law.

Louis R wrote:There is if you're close enough to the warhead that the fireball still contains sufficiently dense material at sufficiently high temperature.

Without knowing what BuNine is postulating for explosion conditions, I can't determine that, but a bit of playing around using adiabatic simplifications leads to some skepticism, to be honest.

If your warhead is a sphere 2m in diameter, at 100m from the detonation the density would be one one-millionth of the density of your warhead. So for all practical purposes, unless you are extremely close to the detonation (on the order of 10-20 meters or less), there would be no blast effects.

Joat42 wrote:You don't re-orient the missile, you eject the lasing rods so they end up at the optimum position to hit a target before the "nuke" goes off, this takes a very short time. At least that's how I understand how bomb pumped lasers are supposed to work in a combat effective way.

And you get something of a blast effect from the vaporized missile materials although the area of effect is minuscule compared to the distances involved in space battles.

You still have the particle wave-front from the nuclear explosion and it's secondary effects but it also has to follow the inverse-square law.

No, you want the coarse aiming done by the missile. For one reason the grav lens used needs to be between the bomb and the laser heads. But there are more.

Consider the case of a missile targeting a rolled ship. You are going to pass 30,000 km away from the target. With the missile aimed roughly where it expects the target to be the laser heads need to move a fixed distance at a fixed velocity and fixed vector to reach firing position, so you can easily determine when that will be and provide appropriate vibration dampening etc.

If the missile is aimed 90 degrees to the target you need to have the laser rods all get to exactly the right spot at exactly the right time. Each of them needs to spin, then travel a different distance, at a different vector and using different amounts of thrust to get there. So you now require a much more complex engine. And since you are having them turn about 90 degrees and the actual laser rod is 5 meters long and about 0.06 millimeters in diameter, vibration is probably going to be a lot bigger problem.

kzt wrote:

Joat42 wrote:You don't re-orient the missile, you eject the lasing rods so they end up at the optimum position to hit a target before the "nuke" goes off, this takes a very short time. At least that's how I understand how bomb pumped lasers are supposed to work in a combat effective way.

And you get something of a blast effect from the vaporized missile materials although the area of effect is minuscule compared to the distances involved in space battles.

You still have the particle wave-front from the nuclear explosion and it's secondary effects but it also has to follow the inverse-square law.

No, you want the coarse aiming done by the missile. For one reason the grav lens used needs to be between the bomb and the laser heads. But there are more.

Consider the case of a missile targeting a rolled ship. You are going to pass 30,000 km away from the target. With the missile aimed roughly where it expects the target to be the laser heads need to move a fixed distance at a fixed velocity and fixed vector to reach firing position, so you can easily determine when that will be and provide appropriate vibration dampening etc.

If the missile is aimed 90 degrees to the target you need to have the laser rods all get to exactly the right spot at exactly the right time. Each of them needs to spin, then travel a different distance, at a different vector and using different amounts of thrust to get there. So you now require a much more complex engine. And since you are having them turn about 90 degrees and the actual laser rod is 5 meters long and about 0.06 millimeters in diameter, vibration is probably going to be a lot bigger problem.

Yeah... vibration is something we've already been trying to decide how to dampen. Last I heard, the missile reorienting could be considered (as you said, kzt) coarse, the laserhead maneuvering after release is medium, and gyroscopic-like dampening inside the laserhead is the fine tuning.

As for my milliseconds (or less) comment, I already said someone else could do the math. The point was that a LOT happens in very tiny fractions of a second. Regarding the "blast wave" I mentioned, I realize that that was a poor choice of words, but then, I'm not a wordsmith - I'm a silversmith. I know there's no such thing as a shockwave in space, but I couldn't come up with the correct term(s), and I was too lazy to go to thesaurus.com.

Louis R wrote:There is if you're close enough to the warhead that the fireball still contains sufficiently dense material at sufficiently high temperature.

Without knowing what BuNine is postulating for explosion conditions, I can't determine that, but a bit of playing around using adiabatic simplifications leads to some skepticism, to be honest.

drinksmuchcoffee wrote:There would also be no blast effects in a vacuum.

As far as I know, it's just a basic nuclear detonation, with the added effects of the grav lenses focusing all the X-Ray energy forward towards the laserheads. I'm assuming (although I'm sure someone here will point out that I'm wrong) that the grav lenses would also focus any OTHER detonation effects in that general direction as well. OTOH, maybe the grav lenses are tuned to only focus X-Rays... <shrug>

More thinking on laser heads...

Figuring out the optimum distance that the lasing medium needs to be from the explosion is kind of fraught. Obviously, with a higher yield the optimum distance would be further away. Equally obviously, the power of your x-ray laser will be, all other things being equal, higher the closer you are to your explosion.

There are three things that are not so obvious.

One is that it takes a finite amount of time before your lasing material will begin to lase. So if you are too close to the warhead you won't get any laser effect at all.

Another is that the closer you are to the warhead, the less lasing time you will have before prompt radiation effects vaporize your lasing medium. This is important because while power is nice, it is actually the amount of energy you transfer to your target that will do damage. Energy being the time-power product. So it might well be that the optimum distance from a destructiveness standpoint is not the closest possible distance you can be to the warhead and still get a lasing effect.

The final one is that a bigger warhead yield is not necessarily better. Given that the optimum lasing distance increases with warhead yield, and getting further away from the warhead takes a finite amount of time -- time when the missile has its wedge off and cannot maneuver and is easy meat for point defense. So there probably is some rapidly diminishing return on increasing warhead yield. That might be somewhat mitigated by being able to engage from further away from the target.