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"China Is Developing A New Laser Satellite That..." Topic


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Tango01 Supporting Member of TMP01 Oct 2018 10:04 p.m. PST

… Will Be Able To Locate U.S. Submarines 500 Meters Below The Surface

"China is developing a satellite with a powerful laser for anti-submarine warfare that researchers hope will be able to pinpoint a target as far as 500 metres below the surface.

It is the latest addition to the country's expanding deep-sea surveillance programme, and aside from targeting submarines most operate at a depth of less than 500 metres it could also be used to collect data on the world's oceans.

Project Guanlan, meaning "watching the big waves", was officially launched in May at the Pilot National Laboratory for Marine Science and Technology in Qingdao, Shandong. It aims to strengthen China's surveillance activities in the world's oceans, according to the laboratory's website…"

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Amicalement
Armand

Stryderg02 Oct 2018 10:32 a.m. PST

But, wouldn't that heat the water and cause global warming (tm)?

Thresher0102 Oct 2018 11:24 a.m. PST

How do we know it isn't a laser designed to kill our subs?

There's a treaty against weapons in space, so it should be banned, right?

Tango01 Supporting Member of TMP02 Oct 2018 11:33 a.m. PST

(smile)

Amicalement
Armand

Lion in the Stars02 Oct 2018 11:16 p.m. PST

Thresher, that treaty only covers nuclear weapons in space.

Rocks or tungsten rods are treaty-compliant.

FatherOfAllLogic03 Oct 2018 6:51 a.m. PST

uh-huh.

Andrew Walters03 Oct 2018 11:06 a.m. PST

Well, that's a *little* scary, but consider…

#1 the laser beam attenuates rapidly under water. Any satellite small enough to launch will be unable to damage anything underwater, only detect. If that.

#2 the laser can search exactly one spot at a time. This means it would take forever to scan an area, so it's a pretty terrible search device. If it works it's a great *tracking* device, which is very serious, but not as serious as a good searching device.

#3 only certain wavelengths can travel underwater well enough to accomplish this goal, and it wouldn't be tough to put sensors on top of the sub to detect those wavelengths. That means that, unlike sonar, the sub's crew will *know* when they're being tracked. Some clever person will figure a way to break contact and then they have to start searching all over again.

#4 if you paint the top of the subs the right color you should be able to greatly reduce the laser reflection. That would greatly reduce the depth to which this satellite could detect subs.

It feels like they're goal is a little optimistic. If we had time we could do some research and figure out how many watts of electricity a satellite can produce/consume, then figure out which wavelength they'd need to use. Figure out how efficient the lasers in that color are, then how much attenuation you'd get from the atmosphere and how much per meter of ocean. Then you'd know how sensitive the detectors would have to be and you could make a guess at whether or not this is practical.

But there are some *really* sensitive detectors around nowadays. You'd have a tough time getting the best ones working on a satellite, but I bet it's possible.

There are two more serious problems with that satellite, though.

First, the US will know where the satellite is. If there comes a day you need to blind it you just hit it with an inexpensive laser from anywhere in theatre. The direct beam from even a modest laser would overwhelm the detector and blind it to the extremely faint reflections from a submarine under the ocean. So when the satellite is most needed it would be useless.

Second, you need to know where your detector is pointing at the moment you get a reflection if you want to know where the submarine is. You would probably want these in a very high geosynchronous orbit so they could watch continually, but let's assume a very low orbit of 1000 miles. If the the satellite is angled off from what it's supposed to be just a hair, say 1mm for a 20' satellite, that similar triangles math we all learned shows us that the position of the sub is 250 meters off. That's not bad, but that's assuming a low orbit and a single millimeter misalignment. If it's a geosynchronous satellite and it's an inch off then your detection is 16 miles off. I guess that's still close enough to send in the helicopters to localize it.

But it's too easy to blind. That will be the Achilles heel.

microgeorge03 Oct 2018 4:03 p.m. PST

Looks like a good target for an ASAT launched from an F-15.

Lion in the Stars03 Oct 2018 9:32 p.m. PST

@Andrew Walters: Yup. The second this satellite launches, the USN will have countermeasures in place. The quickest one would be laser sensors on top of the hull. Repainting a ship is honestly more complicated than sticking a half-dozen off-the-shelf CCD camera chips down the spine of a sub, you'd have to first figure out what surface would work best, then how to get that surface finish to survive salt water, and finally get it to play nice with non-skid.


@Microgeorge: We'd have to build some new ASATs. We retired all those old ones (sadly). Probably wouldn't take much to make one of those nice SM3 missiles mount up and work, though. And SM3s can take down a satellite in a 300km orbit from a surface launch already. Giving an SM3 with the surface-launch booster a ~40,000ft elevation advantage would be wicked, you'd probably be looking at 800km orbits for targets. (Getting above the thickest part of the atmosphere before launch greatly increases range)

Andrew Walters04 Oct 2018 11:47 a.m. PST

They don't mention the attitude. If it's geosynchronous I don't think anything can shoot it down. But if it's in LEO there are lots of ways to kill it. All cost more than just shining a light on it to blind it. Blinding it could also be temporary, deniable…

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