Graser Quesions

Hello,
I did try a search for the answer to these two question was not able to find them. Apologies if they have already been answered and I was unable to find them.

1) When the size of the graser weapon is mentioned, is that the size of the weapon emplacement/focusing element or the dimensions of the weapon beam itself?

2) Damage from lasers/grasers - in the descriptions some of it sounds like damage from a solid object impacting or a kinetic round. But light doesn't have any mass. Have I missed something or is this descriptive freedom for the sake of the story?

technoDaleks wrote:Hello,
I did try a search for the answer to these two question was not able to find them. Apologies if they have already been answered and I was unable to find them.

1) When the size of the graser weapon is mentioned, is that the size of the weapon emplacement/focusing element or the dimensions of the weapon beam itself?

2) Damage from lasers/grasers - in the descriptions some of it sounds like damage from a solid object impacting or a kinetic round. But light doesn't have any mass. Have I missed something or is this descriptive freedom for the sake of the story?

The size is the emitter. Yes, that is very large. And despite the face that you should be able to snipe at an orbital platform with an 8 meter grader from the hyperlimit if you run the math, you can’t.

There is an essay in one of the collections on Honorvere armor systems that goes into this in great detail, but there the short version: when the honorverse uses the term laser they mean X-ray lasers. Both X-ray and gamma rays are not immediately absorbed at the surface of a target, they get absorbed some distance inside the target. The energy levels are insanely huge. So what you have is a petawatt pulse that strikes a 2 meter thick armor plate (which isn’t exactly that, but anyway) it interacts with say the first meter of the armor and heats it say 50 million degrees in a spot 4 meters wide. Which results in extremely energetic plasma that really wants to expand really really fast.

So the inner meter of the armor is blown into the ship at multiple km/sec. The rest of the armor system is designed to catch this and greatly attenuate the energy before it gets to really really important parts.

1) both? Larger emplacements have larger focal apertures which have wider beams. But there has also been a lot of behind-the-scenes weapon development over the series, so a later graser with more powerful grav-lenses, etc. may well be more powerful than a much earlier graser with a larger focal length.

2) Light is both a particle and a wave, particles have mass. Actually, the point being made is about how much energy is being transferred rather than the mechanism. When target material absorbs more energy than it can ignore-deflect-disperse, it fails. In the case of something hit by a graser circa 1900 P.D., it fails catastrophically, explosively, as it transfers the remainder to everything around it.

technoDaleks wrote:Hello,
I did try a search for the answer to these two question was not able to find them. Apologies if they have already been answered and I was unable to find them.

1) When the size of the graser weapon is mentioned, is that the size of the weapon emplacement/focusing element or the dimensions of the weapon beam itself?

2) Damage from lasers/grasers - in the descriptions some of it sounds like damage from a solid object impacting or a kinetic round. But light doesn't have any mass. Have I missed something or is this descriptive freedom for the sake of the story?

1) I believe the size is supposed to be the aperture of the weapon, hence initial beam width. The physical size of the laser/graser assembly is dependent the base tech it is built from. A Silesian 24 cm laser assembly may be the physical size of a Manticorian 60 cm laser (in 1900pd), due to the base tech.

2) Light has momentum, it's a basic Physics fact from Einsteinian Physics - a single light photon behaves both like a wave AND a particle. So, when a concentrated beam of light hits a target, it will hit with kinetic energy. And when we are discussing gigawatt beams, that is a lot of kinetic energy, Also, some light is absorbed by the target - and at these levels it is too much for materials to readily absorb, so they are superheated and explode, again with kinetic energy.

If you'd like to see the momentum in sunlight, search the internet for a "radiometer", they are usually less than $10 US.

Even if you polish a missile to reflect the beam, the initial kinetic energy will damage the weapon. There is a picture floating around of one of the SDI tests of a multi-megawatt laser against a Titan II missile body at White Sands in the early 90s. The polished metal missile body was dented by the beam impact in the test.

Edit: the above is just about lasers in general, KZT is correct, these weapons are in the x-ray range and impact with not only the surface, but deep into the armor causing volumes to explode as they attempt to absorb the energy.

Graser’s and high energy X-rays can’t be focused by physical systems, it’s all magic gravitic stuff and it is apparently done in free space between the sidewall and the emitter.

Though if you look at the math, there isn’t any need to focus grasers if the gamma rays are emitted as a coherent beam. Though fine tuning aiming might be helpful. X-rays diverge significantly faster as it’s related to something like the square of the wavelength.

Theemile wrote:2) Light has momentum, it's a basic Physics fact from Einsteinian Physics - a single light photon behaves both like a wave AND a particle. ...

If you'd like to see the momentum in sunlight, search the internet for a "radiometer", they are usually less than $10 US.

A popular, but incorrect, explanation of the observed effect.

Crookes incorrectly suggested that the force was due to the pressure of light.[5] This theory was originally supported by James Clerk Maxwell, who had predicted this force. This explanation is still often seen in leaflets packaged with the device. ... [But] Finally, if light pressure were the motive force, the radiometer would spin in the opposite direction, as the photons on the shiny side being reflected would deposit more momentum than on the black side where the photons are absorbed.

https://en.wikipedia.org/wiki/Crookes_radiometer

While light does have momentum, it is negligible in this context: a gigajoule pulse has momentum of ~3.3 kgm/s. Roughly half that of a 96mph fastball.

Theemile wrote:

technoDaleks wrote:Hello,
I did try a search for the answer to these two question was not able to find them. Apologies if they have already been answered and I was unable to find them.

1) When the size of the graser weapon is mentioned, is that the size of the weapon emplacement/focusing element or the dimensions of the weapon beam itself?

2) Damage from lasers/grasers - in the descriptions some of it sounds like damage from a solid object impacting or a kinetic round. But light doesn't have any mass. Have I missed something or is this descriptive freedom for the sake of the story?

1) I believe the size is supposed to be the aperture of the weapon, hence initial beam width. The physical size of the laser/graser assembly is dependent the base tech it is built from. A Silesian 24 cm laser assembly may be the physical size of a Manticorian 60 cm laser (in 1900pd), due to the base tech.

2) Light has momentum, it's a basic Physics fact from Einsteinian Physics - a single light photon behaves both like a wave AND a particle. So, when a concentrated beam of light hits a target, it will hit with kinetic energy. And when we are discussing gigawatt beams, that is a lot of kinetic energy, Also, some light is absorbed by the target - and at these levels it is too much for materials to readily absorb, so they are superheated and explode, again with kinetic energy.

If you'd like to see the momentum in sunlight, search the internet for a "radiometer", they are usually less than $10 US.

Even if you polish a missile to reflect the beam, the initial kinetic energy will damage the weapon. There is a picture floating around of one of the SDI tests of a multi-megawatt laser against a Titan II missile body at White Sands in the early 90s. The polished metal missile body was dented by the beam impact in the test.

Edit: the above is just about lasers in general, KZT is correct, these weapons are in the x-ray range and impact with not only the surface, but deep into the armor causing volumes to explode as they attempt to absorb the energy.

Anyhow, so the SD works by absorbing the energy in it's enormous amounts of armor. This results in lots of chunks of armor (generally metal) and pieces of the carbon nano-composite called battlesteel (which forms structural elements of the ship) moving at high velocity, hopefully to be contained by further layers of the armor system.

When say a destroyer gets hit by that same graser you don't have to worry about being killed by fragments of your armor.
Apparently instead the graser converts a 4m cylinder all the way through the destroyer to a few million degrees plasma. This then has roughly the effect of having a good sized nuclear weapon go off inside the ship. This generally results in an overall bad day for everyone on board, often involving the phrase 'lost with all hands'.

I am working with a laser cutting machine at my job. It is Fiber Laser, so, the Laser Generator is outside the maschine and the laser is leaded into the machine by a glass fiber.

I wonder if you have to move the whole weapon into the direction of your target, like a normal gun, or if they have the emitter inside the ship and only some kind of lenses at the hull!

Maybe it depends on the weapon. Main energy weapon = normal gun, Laser cluster = emitter and lenses/glass fiber.

kzt wrote:Graser’s and high energy X-rays can’t be focused by physical systems, it’s all magic gravitic stuff and it is apparently done in free space between the sidewall and the emitter.

Though if you look at the math, there isn’t any need to focus grasers if the gamma rays are emitted as a coherent beam. Though fine tuning aiming might be helpful. X-rays diverge significantly faster as it’s related to something like the square of the wavelength.

I suspect that a good deal of the reason for the granitic lens is aiming, These things would be pretty useless if they couldn't be aimed, or if aiming them involved moving several tons of emitter hardware on 3-dimensional gimbals to aim them.