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Old 2022-09-27, 13:52   #199
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Quote:
Originally Posted by Dr Sardonicus View Post
The C-130 is nominally a cargo plane which has been around since the Vietnam War.
It has been around since well before the Vietnam war. It has been 68 years since the first flight. It is still in production.
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Hercules is the longest continuously produced military aircraft at more than 60 years, with the updated Lockheed Martin C-130J Super Hercules currently being produced.
It, the An-2, DC-3, and B-52 are among the longest serving craft out there. They are not museum pieces and there are many copies of them doing real work.
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Old 2022-09-27, 13:52   #200
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C-130s go back to the 1950s; LC-130s to 1956. https://en.wikipedia.org/wiki/Lockheed_LC-130
When failure is not an option, as in the last resupply flight of the season to the South Pole Station, it's an LC-130 that doesn't QUITE touch down. They kick cargo out the back at a few feet of altitude above the runway and let the crates slide to a stop on the snow. It's called "drifting". If they were to land and be unable to take off, the air crew would be staying until another could come get them, possibly for months, and there might not be enough provisions on site for that added demand.

Last fiddled with by kriesel on 2022-09-27 at 13:57
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Old 2022-09-27, 16:18   #201
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Originally Posted by kriesel View Post
They kick cargo out the back at a few feet of altitude above the runway and let the crates slide to a stop on the snow. It's called "drifting".
AKA "lithobraking" in the astronautical community.
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Old 2022-09-27, 16:20   #202
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Originally Posted by Batalov View Post
I am quite sure this has been discussed before, but --
I was curious to learn how an order from "a red button" reaches submarines. It is tricky: Communication with submarines .
I have heard extremely plausible rumours that the DoD have conducted experiments with pulsed neutrino beams. They are easy to generate and have global range, even to the antipodes if needed. Detection is tricky, the main problem being background noise from cosmic muons.
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Old 2022-09-27, 17:37   #203
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Originally Posted by xilman View Post
Detection is tricky
That's putting it mildly. The first particle type to exit a star going supernova is neutrinos. Xrays take a long time to get out, but very large quantities of matter are essentially transparent to neutrinos, including planets and stars. The Ice Cube Neutrino Observatory uses the bulk of the earth as a shield against other particles, and deduces which neutrino events arrived through the earth rather than through the ice, by relative timing of detection among the several adjacent modules, rejecting northward-bound detections in favor of southward. It's only what I call the unluckiest neutrinos that get detected; made it ALMOST through the earth, but interacted with the last kilometers of ice before escaping into space again.
https://en.wikipedia.org/wiki/IceCub...no_Observatory was a ~$330 million US construction project (without the dense core).

Fermilab (Batavia Illinois) will be used to drive pulsed neutrino beams aimed at an underground neutrino detector DUNE 1300 km away at Lead South Dakota. Current projections are $2.6 billion US. Much of the excavation & infrastructure was preexisting due to repurposing a long-operating deep gold mine.

How to make a neutrino beam: https://www.symmetrymagazine.org/art...-neutrino-beam

Last fiddled with by kriesel on 2022-09-27 at 17:51
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Old 2022-09-27, 19:29   #204
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Quote:
Originally Posted by kriesel View Post
That's putting it mildly. The first particle type to exit a star going supernova is neutrinos. Xrays take a long time to get out, but very large quantities of matter are essentially transparent to neutrinos, including planets and stars. The Ice Cube Neutrino Observatory uses the bulk of the earth as a shield against other particles, and deduces which neutrino events arrived through the earth rather than through the ice, by relative timing of detection among the several adjacent modules, rejecting northward-bound detections in favor of southward. It's only what I call the unluckiest neutrinos that get detected; made it ALMOST through the earth, but interacted with the last kilometers of ice before escaping into space again.
https://en.wikipedia.org/wiki/IceCub...no_Observatory was a ~$330 million US construction project (without the dense core).

Fermilab (Batavia Illinois) will be used to drive pulsed neutrino beams aimed at an underground neutrino detector DUNE 1300 km away at Lead South Dakota. Current projections are $2.6 billion US. Much of the excavation & infrastructure was preexisting due to repurposing a long-operating deep gold mine.

How to make a neutrino beam: https://www.symmetrymagazine.org/art...-neutrino-beam
However, terrestrial neutrino sources are very much closer than astrophysical source, even the Sun, and the inverse square law is enormously in their favour. Sending neutrinos a few hundred or thousand kilometres through rock to a detector is now routine. Not so long ago an instrumental fault caused a stir by suggesting that neutrinos travelled superluminously.
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Old 2022-09-27, 19:46   #205
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Quote:
Originally Posted by xilman View Post
However, terrestrial neutrino sources are very much closer than astrophysical source, even the Sun, and the inverse square law is enormously in their favour. Sending neutrinos a few hundred or thousand kilometres through rock to a detector is now routine.
Are you suggesting a simple PWM signal might be possible? I assume QAM is not an option.

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Not so long ago an instrumental fault caused a stir by suggesting that neutrinos travelled superluminously.
I remember that. But the team figured out their issue. Damn those BNC connectors!
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Old 2022-09-27, 22:34   #206
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Quote:
Originally Posted by xilman View Post
Sending neutrinos a few hundred or thousand kilometres through rock to a detector is now routine.
Funding and building a major particle production beamline project is not what I would call routine. Using one eventually becomes routine. But this discussion began with the idea of DoD using neutrinos to communicate with mobile receivers (submarines). After a career in producing custom scientific apparatus, including beam line elements and neutrino detectors, and associating with the scientists involved in such physics, the idea of placing a neutrino detector as a long distance communication device in a nuclear powered submarine occurs to me as ludicrous. Neutrino source beamlines such as from Fermilab, CERN, etc, are necessarily statically aimed at their detectors. And they don't so much aim particles at the detectors as spray a 3D fan or plume of neutrinos, with the detector in front of the center of the broad fan. At the Fermilab source, the particle beam producing neutrinos is directed 5.8 degrees downward toward a target to produce the neutrinos, followed by a particle decay pipe, focusing horns for the transient particles, and absorbers to filter out the unwanted particles. The neutrinos themselves can not be focused, redirected, or filtered. They must be created going in about the right direction.

The largest submarines known are Russia's Typhoon class, with 48,000 ton displacement. https://en.wikipedia.org/wiki/Typhoon-class_submarine
Allocating ~2% of its displacement to a neutrino detector's active volume would allow 1 kiloton detector (receiver) size. (Containment structure, shielding/veto of reactor & cosmic backgrounds, cabling, data acquisition etc. would be additional and could exceed 5% in total.)

Table IV of https://www.aps.org/policy/reports/m...king_Group.pdf shows muon neutrino interaction rates of 14. to 180,000 per kiloton-YEAR, depending on energy and distance.
That's not much signal on which to impose modulation no matter how cleverly done.

The Daya Bay neutrino experiment (8 times 20 tons detector size) achieved 5.5 million interactions over 9 years in close proximity to a 6-pack of nuclear reactors used as particle source. http://dayawane.ihep.ac.cn/twiki/bin...blic/DYB_Final That's 5.5E6 interactions/9 years / (8 * .020 kilotons) = 3.8E6. interactions/kiloton-year.

Reactors used as transmitters by frequent modulation of fission rate and power output would require excellent encryption since their neutrino output would likely be nearly isotropic, and could also present problems of grid stabilization. Their output power modulation might be easily inexpensively detectable by a well placed monitoring of grid voltage. The power modulation of a nuclear core can be risky (Chernobyl!) US power slew rates are of order 6-10 MW/sec or less, which would limit signaling rate.

If we suppose modulation was limited to 10% of fission output and signal falls off as inverse square of distance, 3.8E6 /kiloton-year *0.1 * (1.9 km / 1000 km ) ^2 = 1.38 interactions/receiver-year at 1000 km. At 100 km, it's 138., still less than one half interaction per day.

Last fiddled with by kriesel on 2022-09-27 at 22:34
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Old 2022-09-27, 23:03   #207
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Quote:
Originally Posted by kriesel View Post
At 100 km, it's 138., still less than one half interaction per day.
Could you get a signal through?
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Old 2022-09-27, 23:27   #208
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Quote:
Originally Posted by chalsall View Post
Quote:
Originally Posted by kriesel View Post
At 100 km, it's 138., still less than one half interaction per day.
Could you get a signal through?
In the context of communicating with ballistic missile submarines, it depends on the signal. If the signal happened to be the launch order, my guess would be no.

EDIT: It occurred to me that, however unlikely, it is possible that the launch code transmission could continue despite a general nuclear war.

If that happened, what would follow?

It would lead to a barrage of nuclear missiles after the initial exchange by however long it takes to transmit the signal - six months, a year, whatever.

Last fiddled with by Dr Sardonicus on 2022-09-27 at 23:35
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Old 2022-09-28, 00:19   #209
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This US Navy communications station, shut down in 1993, is about a 20 minute drive from my home and was used to communicate with ballistic missile submarines:

https://en.wikipedia.org/wiki/Skaggs...cation_Station
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