Mirror-armed missiles

Joat42 wrote:Lord Skimper, is that you?

My exact thought.

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I don't exactly know how 41st century directed energy weapons would work. But I strongly suspect that you couldn't use a mirror or any kind of lens to effectively extend their range.

Any kind of directed energy weapon is going to suffer from some level of attenuation as the range increases. Unless your lens is really big you won't be able to significantly increase your range, and even with a really really big lens you would begin to have efficiency losses related to just using a lens (or a mirror) as well.

Put another way, you might be able to double or triple the effective range of energy weapons with this technique (although I'd even be skeptical of that in practice), but you'd never be able to increase the range by the factor of 100 that separates energy weapons ranges from missile ranges.

Dear god, the skimpers are multiplying. Isn't one source of insane ideas enough?

Anyway, you're either forgetting or not understanding the problems of beam divergence.

Consider - photons do not lose energy as they travel, and yet energy weapons have a maximum effective range beyond which they cannot burn through a target's sidewall. Why is this? Because you cannot perfectly collimate a photon beam. There will *always* be some degree of spreading of the beam, and so the delivered energy *density* on target drops with distance until it is insufficient to penetrate. And this is one of those pesky 'the laws of physics say so' limits, not a mere technical challenge. If you want to argue that, you'll have to find a different reality.

Why is this relevant to the mirror idea? Because it dictates the size of mirror you need. Namely, if you actually want to use the mirror to refocus the beam onto the target, it needs to be at least as large as the beam, otherwise it will only intercept and redirect a small fraction of the beam's energy. And if you're trying to use this at ranges significantly beyond normal energy weapon range, then by definition you're using them at ranges where the beams have greatly spread out from their original sizes.

And that means you need larger mirrors, relatively speaking, especially if you also want to allow for any level of inaccuracy in the firing ship's beam pointing ability at such extreme ranges. And *that* means that fewer of them fit into whatever your delivery mechanism is, they get more expensive, they get increasingly cumbersome to maneuver, and - especially - that they are giant obvious glaring radar targets which by definition must maneuver on predictable trajectories so that your beam ships can hit them and hence become trivially easy for your target's point defense clusters to pick off by the thousands. (And, to counter the obvious objection, a point defense laser cluster's range against such a bone-naked target is going to be vastly greater than its range against a missile, especially since all it has to do to mission kill it is scorch the surface enough to prevent reflection.)

The problem of beam divergence is also why you can't simply go to visible or UV lasers to get around the *other* fundamental flaw of 'you can't build an x-ray mirror'. As mentioned, In Fire Forged notes that longer wavelength lasers aren't used due to focusing reasons. That's not just a throwaway line either - what that's referring to is that those same pesky laws of physics not only prevent you from perfectly collimating your laser beam, but also dictate that the degree of beam spread increases as your wavelength increases. Which means that if you switch from x-ray lasers to visible or UV lasers in order to actually be able to use mirrors, your beam width and required size of mirror increase *again* in direct proportion to the wavelength.

Let's do a little math here. Assume a SD laser projector has an emitter diameter of 3 meters. This is probably too big, but we'll be generous. The divergence in radians is very roughly wavelength/beam diameter, and let's say you're using UV light at 100 nanometers. This gives you a divergence of about 3e-8 radians. Let's say your mirror is 10 million km from your ship, since the entire point of this idea is to extend beam ranges. In that case, your beam is now over 300 meters across by the time it reaches your mirror. Good luck trying to make *that* into a useful weapon system.

Physics.

Cost effectiveness would be an issue. While a mirror missile is possible would it really be more effective then a laser head missile in a battle especially when you add Apollo to the mix?

Another issue is jitter. At the proposed distances, any kind of movement in the mirror will cause a miss simply because the reflected energy (assuming you can actually build something to reflect that much energy*) will be directed in a slightly different direction.

So, how do you counter jitter? Flywheels were suggested, except they're slow to start up and slow to stop and go in the other direction to stop the motion already imparted when they were first started up. RCS is out as that's never as smooth as you might think. Any other thoughts?

Stiffness. These things need to pack up into a missile that can be launched from (I assume) a standard missile tube. At the sizes needed (someone else did the math for that), that would have to be some very thin, flimsy material, which means it's going to flop and wave and distort all over the place (science at home - try to make a mylar blanket (AKA "Space Blankets") hang perfectly flat and point a laser pointer at it, trying to aim at a spot on a wall), so it will need stiffeners, adding to costs and bulk.

Last, and most obvious thing that no one has mentioned is that...

If there were a material capable of doing what is proposed here, then why not cover the ships with it? It's a wondrous material that is thin and lightweight (no appreciable mass addition to the ship), and can stand up to gigawatts (if not terawatts) of energy without being affected. Seems to me that this Wondersheet would be better used for passive ship defense. Why, since it's so strong and reflective, warships could do away with all that pesky and mass-intensive armor, which means there's now enough room to try stuffing everything Skimper wants into a battlecruiser, including 5 squadrons of LACs, four KHIIs, four pod rails, 1000000000 missiles, and a few dozen lasers. Oh, and there might be just enough room to squeeze in a destroyer and some cargo, so that this SuperBattlecruiser can be a Q-Ship carrying it's own escort.**

*It's free-floating in space. That much energy hitting it, if it doesn't vaporize it instantly, is going to send it flying off in some odd direction. See: Solar sails

**I know I missed a few things. Feel free to add more Skippy ridiculousness.

Nanoscopic imperfections in the reflective surface would cause trouble in redirecting the beam over such a long range for a mirror large enough to use in such a way. Then how do you protect such a large reflector from microscopic impacts in a way that is cost effective.

Combat ranges are measured in light minutes now. Just think of the number of variables you would have to account for in the chaos of a battle at such ranges to reflect a laser accurately enough to be useful as a weapon.

Dilandu wrote:So, let's arm our missile with mirror. Just large parabolic mirror, amde from thin foil.......SNIP
fireballed.

Introducing the tinfoil Skimpy missile extraordinaire!

Psst! Its reusable!

At the kind of energy levels we are talking about for Honourverse lasers (even PD lasers) they are actually kinetic weapons as they vaporise the target and that mass becomes a superheated ball of explosive plasma that transmits impact damage to the target. This will happen before more than a fraction of the pulse can be reflected, even assuming that you can build a mirror for the wavelength in question.

This is why honorverse armour depth is measured in metres so as to absorb this impact and insulate the core hull from the plasma.

If you use a dielectric mirror with 99.999% reflectivity you are still absorbing an awful lot of energy into a mass far smaller than the ammount of mass vaporised on the target.

Dielectric Mirrors https://en.wikipedia.org/wiki/Dielectric_mirror at least have the advantage of being tuned to a target wavelength
Even minor imperfections such as grease smudges will also castrophically effect reflectivity and accuracy.

Silverwall wrote:At the kind of energy levels we are talking about for Honourverse lasers (even PD lasers) they are actually kinetic weapons as they vaporise the target and that mass becomes a superheated ball of explosive plasma that transmits impact damage to the target. This will happen before more than a fraction of the pulse can be reflected, even assuming that you can build a mirror for the wavelength in question.

This is why honorverse armour depth is measured in metres so as to absorb this impact and insulate the core hull from the plasma.

If you use a dielectric mirror with 99.999% reflectivity you are still absorbing an awful lot of energy into a mass far smaller than the ammount of mass vaporised on the target.

Dielectric Mirrors https://en.wikipedia.org/wiki/Dielectric_mirror at least have the advantage of being tuned to a target wavelength
Even minor imperfections such as grease smudges will also castrophically effect reflectivity and accuracy.

And for those wondering, a grease smudge in this context is the oil of a fingerprint. Which is why you see optics destined for space (such as the Hubble telescope mirrors) being worked on in clean rooms, with the technicians doing the work dressed up in corresponding clean room suits.

MuonNeutrino wrote:
Let's do a little math here. Assume a SD laser projector has an emitter diameter of 3 meters. This is probably too big, but we'll be generous.

Think you may actually be conservative rather than generous with SD laser emitter size. When the Shrike class was originally introduced in EoH, their spinal graser was described as:

Echoes of Honor, Ch Three wrote:"A one-point-five-meter spinal mount equipped with the latest grav lenses," she told them, watching their eyes, "which permits her to carry a graser— not a laser—approximately as powerful as that mounted in our Homer -class battlecruisers."

And Homer's were almost 40 years old by the time the wars broke out, and pre-Grayson contact so they were still built on the old rules "cruisers get cruiser weapons, battlecruisers get extra cruiser weapons, and wallers get waller weapons" rule.