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GRASERS

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Re: GRASERS
Post by ThinksMarkedly   » Fri Jul 22, 2022 1:40 am

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Loren Pechtel wrote:Agreed, but note that you're not hauling something like the VLBI along on a raid. I don't think you're even bringing the VLT.


Actually, why not? With a squadron of ships, you can replicate what the Event Horizon Telescope did and with an even better resolution. So single-digit micro-arcseconds should be possible. 1 µas at 1 light-hour away gives a resolution of 5.2 m.
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Re: GRASERS
Post by tlb   » Fri Jul 22, 2022 8:43 am

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Loren Pechtel wrote:First, in modern scientific usage grasers do not exist at least as used in the Honorverse. He's using the old school approach that gamma rays are higher frequency than x-rays, but for some reason the scientific community has shifted towards x-rays being from electron shell activity (generally by kicking loose an electron and then using the photon that is released when it rejoins) and gamma rays being from nucleus activity. Generally gamma rays are higher frequency but there is a substantial overlap region. Since we see no other manifestation of being able to mess with the nucleus of atoms it's pretty clear that Honorverse "grasers" are based on electrons and thus are x-ray.

ThinksMarkedly wrote:We do know it involves gravitational technology somehow. And since the same grav tech can be used to make nuclear fusion, it should be possible to use it to somehow mess with the nuclei and produce gamma rays. Not that I would expect a controlled nuclear fusion happening on the graser emitters.

The point being that we don't know how they do it in the first place, so we can't dismiss the possibility that it is way into the gamma ray range.

Though it's entirely possible that the nomenclature has nothing to do with the scientific principle. Like you're proposing, if they simply achieve a much higher frequency ("towards gamma ray range"), the name "graser" might have simply stuck, like the "lasers" being used where "xrasers" would have probably been more correct but unpronounceable. (You could attempt to pronounce the X as the Greek Chi "Χ", which is the letter the Romans copied in the first place, so it would come out as "khraser" or "chraser" as in "loch" -- or as in LaTeΧ).

The Honorverse has both Grasers and X-ray lasers (the bomb pumped missile warheads), so I expect you are both right to say that the author has sided with the astronomers and is using gamma ray to mean a much high frequency photon (which translates to a much higher energy photon).

Note the previous exchanges which make clear that he does not mean that "they simply achieve a much higher frequency ('towards gamma ray range')", because he does not view gamma rays as being defined by a range (Wikipedia stated that a photon emitted by the nucleus could be in the ultraviolet or longer wavelength).
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Re: GRASERS
Post by Loren Pechtel   » Sat Jul 23, 2022 5:28 pm

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ThinksMarkedly wrote:
Loren Pechtel wrote:Agreed, but note that you're not hauling something like the VLBI along on a raid. I don't think you're even bringing the VLT.


Actually, why not? With a squadron of ships, you can replicate what the Event Horizon Telescope did and with an even better resolution. So single-digit micro-arcseconds should be possible. 1 µas at 1 light-hour away gives a resolution of 5.2 m.


You need to measure the distance between your ships with incredible accuracy to do this. And there's the time factor--it took a long time to integrate all the data to produce those Event Horizon images.
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Re: GRASERS
Post by ThinksMarkedly   » Sun Jul 24, 2022 9:24 pm

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Loren Pechtel wrote:You need to measure the distance between your ships with incredible accuracy to do this. And there's the time factor--it took a long time to integrate all the data to produce those Event Horizon images.


That is also extra easy: just bounce a laser on the other ship and measure the time it takes to get back. We measure the distance to the moon with this technology (they even did it in one episode of The Big Bang Theory), and in space you don't have any atmospheric attenuation that makes you only get a handful of photons back.

Yes, integrating all the data is a difficult part, especially if the HV computers have to warm up their valves.
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Re: GRASERS
Post by Loren Pechtel   » Mon Jul 25, 2022 12:06 am

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ThinksMarkedly wrote:
Loren Pechtel wrote:You need to measure the distance between your ships with incredible accuracy to do this. And there's the time factor--it took a long time to integrate all the data to produce those Event Horizon images.


That is also extra easy: just bounce a laser on the other ship and measure the time it takes to get back. We measure the distance to the moon with this technology (they even did it in one episode of The Big Bang Theory), and in space you don't have any atmospheric attenuation that makes you only get a handful of photons back.

Yes, integrating all the data is a difficult part, especially if the HV computers have to warm up their valves.


You lose most of the energy due to dispersion, not due to the atmosphere.
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Re: GRASERS
Post by ThinksMarkedly   » Mon Jul 25, 2022 4:10 pm

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Loren Pechtel wrote:You lose most of the energy due to dispersion, not due to the atmosphere.


Fair enough, but if they can have effective laser and graser weapons at hundreds of thousands of km, bouncing low-power lasers and getting a few photons back should be easy. As I said, we're doing it right now. And unlike the EHT, those ships would all have line-of-sight to make perfect measurements.

And before its collapse, the Arecibo Observatory was also a transmitter, allowing us to have not only radio astronomy, but radar astronomy. The resolution was horrible, but photons in the radio frequency travel as fast as those in the X-ray range, so for ranging (the second R in RADAR) it was more than enough.

I wouldn't be surprised to find out that VLBI is exactly how those massive arrays detecting hyper signals in Manticore are built. Which in turn means that now that they have FTL signalling, the Manticore-built arrays might be even better than everyone else's.
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Re: GRASERS
Post by Loren Pechtel   » Mon Jul 25, 2022 9:27 pm

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ThinksMarkedly wrote:I wouldn't be surprised to find out that VLBI is exactly how those massive arrays detecting hyper signals in Manticore are built. Which in turn means that now that they have FTL signalling, the Manticore-built arrays might be even better than everyone else's.


The thing is you have a lot of calibration to set up anything of the sort and a lot of computing to turn the results into something useful. FTL comms would get the signal slightly faster but I'd be awfully leery of using grav anything around something so precisely calibrated as a VLBI observatory.

A fleet isn't just popping in and quickly doing it. And note that the difficulty goes up with frequency--you need to know positions to within a small fraction of the wavelength you are observing.
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