tlb wrote:A graser beam is not hair thin; from
War of Honor, chapter 28:
"...So I did exactly what Mister Pirate told me to," Thomas Bachfisch said with an evil grin. "We hove to, opened our personnel locks, and stood by to be boarded. And then, when their boarding shuttles were about five hundred klicks out, we opened the weapons ports and put an eighty-centimeter graser straight through their ship."
Obviously the beam is not the full wide of the graser, instead it has a Gaussian profile (let's guess a quarter of the diameter for the main part of the beam); so about 20 cm for Bachfisch's weapons, which would be small compared to the latest Manticoran weapons for cruisers and SD's (maybe even destroyers). The reflectors are probably based on artificial gravity, which can also provide focusing.
ThinksMarkedly wrote:Is there any evidence of the beam being of comparable width to the dish that emitted it? I don't see any reason why an 80cm emitter can't produce a 1mm thick beam. In fact, there's also something to be said about focusing more the wider it is: if you look at our current telescopes, in any wavelength, the bigger the telescope the better they can resolve smaller angles.
Whether a hair thin beam makes sense is another story. If you make it too thin, will it just punch through the entire ship and come out on the other side? Given that both ships are moving, the beam will still slice, but if it's too focused, it might not hit enough matter once the leading edge has come out on the other side.
Though it would help with staying focused to greater distances. Maybe the focus width is configurable, depending on the enemy ship's distance.
Please do not confuse a laser (at whatever frequency) with an antenna or a telescope. Within the limit of the Rayleigh distance, the beam width of a laser is approximately the same as the width at the source and begins to increase linearly for distances much greater. So there is no need for focusing and it would be wasteful to make a beam smaller than whatever is dictated by the aperture. I had an argument like this before and these are the numbers I produced then:
(Spoilers) Future Technological Developments.tlb wrote:Let's look at the equations for Gaussian beam propagation and see what we can see. For Gaussian beams (where the energy is highest in the center and drops rapidly as you measure to the edge) the beam width follows this equation:
w(z) = w(0) * squareroot(1 + (z/R)**2),
where z is the distance from the source and R is the Rayleigh distance. For distances small compared to R the beam width is about the width at the source (which is some fraction of the size the end of the laser) and for distances much greater than R the beam width increases linearly with distance. The equation for the Rayleigh distance is
R = pi * (w(0)**2 / L),
where L is the wavelength of the emitted radiation. This is a simplification based on the wavelength being much smaller than w(0).
The wavelength of an x-ray is in the vicinity of 0.3 nanometers (exponent of -9) and for gamma rays is in the region of 30 femtometers (exponent of -15). If we try those figures we get distances that are nearly a light minute or more. So we should not worry about getting energy to the target, provided we can actually hit it.
PS. I am having difficulty finding the sizes of the graser aperture for the current classes of ships, although there are passages that indicate that they increase based on ship size; such as LAC, DD, CL, CA and SD. From
Honor Among Enemies, chapter 5:
But the undeniably fertile imagination of Hemphill's allies in BuShips had given her Q-ships some advantages the Peeps had never thought of. For one thing, their energy batteries would come as a major surprise to anyone unfortunate enough to enter their range. The Peeps' Q-ships had settled for projectors heavy enough to deal with cruisers and battlecruisers, but Hemphill had taken advantage of a bottleneck in the superdreadnought building schedule. Weapons production had gotten well ahead of hull construction, so Hemphill had convinced the Admiralty to skim off some of the completed lasers and grasers sitting around in storage. Wayfarer had barely half the energy mounts of her Peep counterparts, but the ones she did have were at least three times as powerful. If she ever got close enough to shoot anyone with those massive beams, her target was going to know it had been kissed.