Fun With: Sensor arms race

[rhoenix]

This thread is directly inspired by the Scifi Sensors thread, and specifically is regarding the sensor arms race.

So, the beginning is with what sensors are available for a hard scifi craft. In this case, I'm going to start with a few basic sensor suites (I'm open to suggestions for specifics):

(passive sensors)
- Infrared Aperature System: Inspired from the F-35 DAS system, this passive sensor array would be responsible for omnidirectional viewing around the craft.

- Electromagnetic Sensing Array: Another passive sensor array, designed specifically to detect electromagnetic fields. Like the IAS, E/M sensors are distributed around the hull of the craft for omnidirectional sensing.

(active sensors)
- LIDAR (LIght Detection And Ranging) Array: Designed to be able to generate short pulses from the infrared, visible, ultraviolet, and microwave frequencies to resolve a target.

Given the above sensors available (and more if suggested), how could those sensors be defeated to render another craft undetectable by those sensors?

[Batman]

Um-IR is merely a subset of the EM spectrum you know and microwave means we're talking RADAR.

[rhoenix]

Um-IR is merely a subset of the EM spectrum you know...

I do. They are meant to be separate systems, for resolution at different ranges.

If you have a better solution to accomplish this goal, I'd like to read it.

..and microwave means we're talking RADAR.

As far as I'm aware, RADAR systems use microwaves exclusively. This LIDAR system would be capable of using microwaves in addition to using other frequencies for the sensor ping.

[Batman]

If it's using microwaves it's NOT LIDAR. LIDAR as the acronym says uses light, or at least wavelengths that are reasonably close to it (like UV/IR).
And radar most certainly DOESN'T exclusively use microwaves. Radar being ABLE to use that particular bandwidth is actually a reasonably recent development.

[rhoenix]

If it's using microwaves it's NOT LIDAR. LIDAR as the acronym says uses light, or at least wavelengths that are reasonably close to it (like UV/IR).

So a LIDAR system being capable of UV/IR wavelengths only means it's still LIDAR, but adding the ability to go into the microwave wavelength as well makes it necessarily something else?

Okay, then this is a LIDAR+M (for LIDAR with microwave capability) system.

So back to the OP, how would you defeat each or any of these sensors?

[Stark]

Why are you arguing over acronyms when you could just say 'active EM sensor'? I'm sure others could describe why using one EM array for everything might be a bad idea on a warship.

[rhoenix]

Why are you arguing over acronyms when you could just say 'active EM sensor'? I'm sure others could describe why using one EM array for everything might be a bad idea on a warship.

That would work. Since I can't edit the OP, where one sees "LIDAR," please mentally replace with "Active E/M Sensor."

As for "one EM array for everything," I can see that having all sensors be in one physical place makes them all vulnerable; so, would distributing the sensors all over the craft (as with the passive sensors) make more sense?

[Stark]

Well, you need different wavelengths to detect different things at different ranges doing different things, if I understand correctly.

[rhoenix]

Well, you need different wavelengths to detect different things at different ranges doing different things, if I understand correctly.

I understand that, which is why I tried to add different capabilities to the systems above; the ones listed in the OP were given as examples.

Given the lack of responses, I gather that there is no feasible solution to defeat these sorts of sensors and allow another craft to proceed undetected. Is this correct?

[JGregory32]

Given the lack of responses, I gather that there is no feasible solution to defeat these sorts of sensors and allow another craft to proceed undetected. Is this correct?

There are always methods around something. read the section at atomic rocket about stealth for a good summary of the "no stealth in space" argument.
Back to the OP, nothing can prevent a ship from being detected given a great enough amount of time and eyes on the sky. As a last resort you can always look for star being occuled by a passing object, which would give away position and bearing if observed.
The problem becomes matters of scale and timing. a solar system is a big place and all detection systems will suffer from lightspeed lag, ie no detection system can function faster than the speed of light and in the case of active sensors slower than the speed of light. So the ability to detect a ship from the other side of the solar system is useless if you have no ability to act on the information in a timely manner.
Can you give us some ideas on the scales and timeframes your going to be working with?

[Starglider]

Why are you arguing over acronyms when you could just say 'active EM sensor'? I'm sure others could describe why using one EM array for everything might be a bad idea on a warship.

Actually it's theoretically possible if we could make a phased array that worked at optical wavelengths. In fact, given sufficiently advanced nanotechnology (not nanorobotics, just complex nanostructure fabrication) it should be possible to make flat panel transceivers that work as wideband passive and active EM sensors as well as point defence lasers and comms arrays; you could coat all of your hull except the radiators with them.

[Stark]

LOL I'm not sure how 'hundreds of sensors' is releva t to 'probably don't want one sensor'.

[rhoenix]

Actually it's theoretically possible if we could make a phased array that worked at optical wavelengths. In fact, given sufficiently advanced nanotechnology (not nanorobotics, just complex nanostructure fabrication) it should be possible to make flat panel transceivers that work as wideband passive and active EM sensors as well as point defence lasers and comms arrays; you could coat all of your hull except the radiators with them.

That's very awesome, and helps immensely. Thank you.

LOL I'm not sure how 'hundreds of sensors' is releva t to 'probably don't want one sensor'.

...What was this in response to?

Given the lack of responses, I gather that there is no feasible solution to defeat these sorts of sensors and allow another craft to proceed undetected. Is this correct?

There are always methods around something. read the section at atomic rocket about stealth for a good summary of the "no stealth in space" argument.
Back to the OP, nothing can prevent a ship from being detected given a great enough amount of time and eyes on the sky. As a last resort you can always look for star being occuled by a passing object, which would give away position and bearing if observed.
The problem becomes matters of scale and timing. a solar system is a big place and all detection systems will suffer from lightspeed lag, ie no detection system can function faster than the speed of light and in the case of active sensors slower than the speed of light. So the ability to detect a ship from the other side of the solar system is useless if you have no ability to act on the information in a timely manner.
Can you give us some ideas on the scales and timeframes your going to be working with?

First of all, thank you for your response - I will reply to it as best I can.

The basics of each scenario are essentially projected forward in time from present day by about a millenia. Technological level at this point is hard scifi style.

One side uses a combination of scramjets (for atmospheric acceleration, and underwater) and fusion engines for their crafts, and has begun experimenting with contragravity to increase the overall efficiency of their engines. The other uses a drive system consisting of photonic, fusion, and chemical rockets. In both cases, the typical warships have about 4G acceleration (for the sake of example), and about 3G for the larger ships. Side 1 has more efficient engines, side 2 has more powerful ones.

Both sides have comparable sensors and weapons. Both sides have relatively equal sensor nets around and within their home systems, but they do have exploitable gaps for smaller ships that don't overtly draw attention to themselves.

======

Scenario 1 is through a short term Cold War sort of scenario, wherein these two different opposing powers, based in different star systems, engage in espionage, spying, and sabotage of one another. Side 1, with the more efficient engines would be the ones trying to sneak about. Side 1 is based in the Sol system (ours), and Side 2 is based in Alpha Centauri. Side 1's goal is to be better at it than Side 2. How would this be accomplished?

Scenario 2 is a longer term scenario, with both Side 1 and Side 2 being based in star systems equidistant to our solar system. A nuclear fusion torchship launch is detected from Earth by both sides, and both want to get their before the other to make contact, without the other side knowing about it. How could this be done?

If you need more information, please let me know.

EDIT: Added quote, and clarified scenario data.

[Starglider]

In fact, given sufficiently advanced nanotechnology (not nanorobotics, just complex nanostructure fabrication) it should be possible to make flat panel transceivers that work as wideband passive and active EM sensors as well as point defence lasers and comms arrays.

That's very awesome, and helps immensely. Thank you.

Bear in mind that they may not be able to match optical telescopes for resolving power; a nanostructured phased arrays operating in this mode will use complex algorithms to reconstruct the original wavefront from relatively noisy data from the trillions of individual cells, and the ultimate angular resolution is depends on technical parameters we just can't reliably estimate right now. They should be very good for sky survey though. Also if you have weapons grade lasers as primary anti-ship weapons, hull-mounted flat panels aren't likely to work well in that role due to power density and cooling issues. They should be fine for dazzling enemy sensors and zapping inbound missiles though.

[rhoenix]

Bear in mind that they may not be able to match optical telescopes for resolving power; a nanostructured phased arrays operating in this mode will use complex algorithms to reconstruct the original wavefront from relatively noisy data from the trillions of individual cells, and the ultimate angular resolution is depends on technical parameters we just can't reliably estimate right now. They should be very good for sky survey though. Also if you have weapons grade lasers as primary anti-ship weapons, hull-mounted flat panels aren't likely to work well in that role due to power density and cooling issues. They should be fine for dazzling enemy sensors and zapping inbound missiles though.

Actually, that makes them fit more perfectly. The shorter-range sensors (both active and passive) as well as beam-derived point defense would be managed through this sort of system; longer range sensors, more sensitive sensors, or better guns would need more specialized equipment.

The other reason this helps is because there will be a race of machines in this story, and I could very easily see this being part of their designs.

[JGregory32]

Scenario 1 is through a short term Cold War sort of scenario, wherein these two different opposing powers, based in different star systems, engage in espionage, spying, and sabotage of one another. Side 1, with the more efficient engines would be the ones trying to sneak about. Side 1 is based in the Sol system (ours), and Side 2 is based in Alpha Centauri. Side 1's goal is to be better at it than Side 2. How would this be accomplished?

Scenario 2 is a longer term scenario, with both Side 1 and Side 2 being based in star systems equidistant to our solar system. A nuclear fusion torchship launch is detected from Earth by both sides, and both want to get their before the other to make contact, without the other side knowing about it. How could this be done?

Okay, you've got problems. First of all without some form of FTL your basically looking at either generational ships to make the passage or large computerized ships with no living crew.
The distances involved make fighting any kind of war diffucult as attacks are going to take a very long time to reach their target, here the advantage is going to be heavily on the side of the defenders simple becasue of the long journey time.
As for stealth? The time needed for the journey make stealth impossible, no one is going to miss detecting the ships.

[dragon]

Also some of our earth observation satelites have whats called hyperspectral sensors which allows measurments across hundreds of different narrow bandwidths across the spectrum. THe problem with this is it requires alot of knowledge to be able to read the final products and thats even after various comptuters had a run at it first.

Whats actualy cool about this is that even just changing the bandwidth by a few nm will give you radically different information.

In contrast to multispectral sensors acquiring the reflected radiance in broad bands, hyperspectral sensors record the radiance in many narrow contiguous bands. These bands are spread over the atmospheric windows and cover the entire reflec tive region of the electromagnetic spectrum, i.e. the visible and near infrared (VIS/NIR) and the short wave infrared (SWIR). Some hyperspectral sensors additionally have multispectral bands in the thermal infrared regions (TIR).

Presently, a number of airborne imaging spectrometers has been providing data of successively increasing quality. Acronyms of those sensors are AVIRIS, CASI, DAIS 7915, MIVIS, HYMAP etc. Spaceborne sensors for terrestrial remote sensing are expected to be operating soon.

link




edit- oops pics from link

[Batman]

Why are you arguing over acronyms when you could just say 'active EM sensor'? I'm sure others could describe why using one EM array for everything might be a bad idea on a warship.

Because I'm anal retentive about proper acronym use at times probably.

And Jgregory32 is right. Even if we assume those ships can keep the acceleration up FOREVER (and with the given technology there's no way that works-hell with ANY remotely realistic technology, there's no way that works, and that's completely ignoring what it would do to the crew) we're talking travel times measured in YEARS. In fact no matter WHAT the acceleration we're talking travel times measured in years. That'd be the pesky lightspeed limit. If you WANT an interstellar war, you need some form of FTL.

[rhoenix]

Ok, points taken about interstellar distances and lack of FTL - let's skip past this particular point for now, as it's obvious some chicanery will be needed. I already had a mechanism ready just in case, but that's the subject of another thread.

So, for now - how would those sensors be defeated, or prevented from doing their job properly (e.g. detecting a ship that doesn't want to be found)?

The only ideas I'm coming up with currently are either "flashbulb" missiles (basically to temporarily overload the ship's sensors), or upscaling that to the real flashbulb nuclear missiles used to generate an EMP, thereby disabling the other ship. However, if at all possible, I'd like to find more subtle and elegant ways of dodging detection.

[Starglider]

or upscaling that to the real flashbulb nuclear missiles used to generate an EMP, thereby disabling the other ship.

The EMP effect in contemporary nuclear warfare is caused by the interaction of X-rays from the nuclear device with the upper atmosphere and the planetary magnetic field. It won't work in deep space. It may be possible to make a nuclear-pumped EM pulse generator equivalent to the ones you can make using conventional explosives - though difficult since a nuclear device would blow itself apart orders of magnitude faster. That's good for an ultra-high-power one-shot radar image, but unless you can also also make it very highly directional it won't do you much good as a weapon, because even a nuclear-pumped pulse would be ineffective against hardened military electronics after quite a short distance.

[rhoenix]

The EMP effect in contemporary nuclear warfare is caused by the interaction of X-rays from the nuclear device with the upper atmosphere and the planetary magnetic field. It won't work in deep space.

So much for that, then.

But onto figuring out a way to accomplish that anyway...

It may be possible to make a nuclear-pumped EM pulse generator equivalent to the ones you can make using conventional explosives - though difficult since a nuclear device would blow itself apart orders of magnitude faster. That's good for an ultra-high-power one-shot radar image, but unless you can also also make it very highly directional it won't do you much good as a weapon, because even a nuclear-pumped pulse would be ineffective against hardened military electronics after quite a short distance.

Actually, if built into a missile designed with a small blast radius and maneuvering thrusters, that could still work.

[Starglider]

Actually, if built into a missile designed with a small blast radius and maneuvering thrusters, that could still work.

If you can get a nuke that close, why not give it an X-ray laser head (as featured in the Honorverse) and actually damage the enemy as opposed to maybe possbily overloading some of their sensors?

[Batman]

Just to be my nitpicky self, a missile WITHOUT maneuvering thrusters is useless ANYWAY on account of being totally unable to compensate for the target trying to get out of the way. And there's no such thing as limited blast radius in space OR WRT EMP. You either have the oomph to fry enemy sensors or you don't. Inverse square rule.

[JGregory32]

There are measures to defeat active systems, they've been developed for the various stealth fighter and bomber programs so I don't see a problem with assuming that as time go on more methods are found.
It's also possible to jam sensors but that would tell people that SOMETHING is there. Don't forget the old mrk I eyeball and it's equivalent optical sensors. Ships large enough to make the journey are going to be noticable when they occlude the stars behind them.
Also unless the ships are on a kamikaze run then when they perform their braking manuvers they are going to light up like christmas trees.
Best idea? Tunnel out a moonlet and shove it in the direction of the enemy, rogue planets might be more common than we think and they can be armed and armored in excess of realistic ship design.

[Junghalli]

If you WANT an interstellar war, you need some form of FTL.

Or commanders and policymakers with much longer planning horizons than we have. Considering that by the time we can build c-fractional manned ships we probably should have cracked aging, I don't think this is particularly unrealistic.

Of course, you could point out that there are realistically few plausible incentives for interstellar warfare, but this is true with FTL as well.