Could gravitational wave interference patterns be used for long range sensors detecting advanced spaceships?

Question

Low energy, fantastic range

From HDE in another topic, I learned gravitational waves have an intensity which is inverse proportional to distance, not square distance, like in electromagnetic fields..

$$h\sim\frac{1}{R}\frac{GM}{c^2}\left(\frac{v}{c}\right)^2$$

Because of this, the gravitational wave energy becomes spread over a giant distances and their amplitude is extremely small.

Now suppose future detectors of gravitational waves will be very sensitive. I was thinking of using an array of highly sensitive gravitational wave detectors in orbit around a planet, as a long range sensor for ships that make use of artificial gravity, or Alcubierre drives.

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

An approximate direction to the ships is known

Important thing to keep in mind for this question: we know where to look, the direction: we know in what region of space these aliens are to be expected. So far, they were not particularly hostile to Earth, but we would like to know their capabilities. Distance to earth of the alien ships can be anywhere between 26 and 200 light years.

The source of the gravitational wave used for this

For our detector array, there is a suitable and regular gravitational wave, coming from that direction. The source of this GW is an imminent neutron star collision, which is in progress ca 600,000 light years behind our observation region, as seen from Earth. We expect to be able to use this constellation for about 100 years, before they collide.

https://marvelcinematicuniverse.fandom.com/wiki/Gravity_Field_Generator

Interference patterns

I wonder if an "obstacle" such as an Alcubierre drive, could cause a ripple in the gravitational waves, which could be found invoking interference patterns, like it happens in the water, when you put 2 sticks and disturb the surface.

Alternative method: the bending of light

(thanks @ChristopherJamesHuff for the feedback..)

The linear artificial gravity and the Alcumbiere drive introduce excessive gradients in space time, which could be detected using other means. When the field required for the drive has enough range, it could be detected using the same methods applied for exo-planets: find a disturbance in the starlight characteristic for sudden ST-gradients, like like gravitational lensing. We've chosen to invest in the GW array, because 1) we don't know if these ships emit EM radiation, and 2) whether these ships will be be parked anywhere near a star.

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Question: is it plausible that a ship invoking a space time distortion may form characteristic interference patterns in gravitational waves, that can be detected by my array ?

https://en.wikipedia.org/wiki/Shack%E2%80%93Hartmann_wavefront_sensor

Answers I'll vote for would explain how artificial gravity or other space-time irregularities would disturb gravitational waves, or not. The best answer would make me replace a tag.. I'd like this question to become science-based, now it is not.

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Note 1: the goal of my detector is to find out if FTL or Alcubierre drives or artificial gravity can exist, if it is in use anywhere within our Milky Way, say 100 thousand light years. My sensor has no space-war or defensive purpose. EDIT: You may assume we know in what direction to look.

Note 2: science based frame challenges are very welcome ! When gravitational waves e.g. can't do interference patterns of any kind, please correct me.

Answer 1

Gravitational waves and electromagnetic waves traveling through a gravitational field would behave basically identically in terms of lensing, Shapiro delay, etc. Both are just waves traveling at c through curved spacetime. The gravitational waves are themselves curved spacetime, but to a minuscule degree when speaking of ambient gravitational radiation from sources at astronomical distances.

So, given similar sources, any detection of warp drives or artificial gravity by lensing or other effects could likely be replicated exactly with electromagnetic antennas.

Worse, there are very few gravitational wave sources, and they are all very low frequency, so any instruments will have to be similarly huge to match them, and so will any disturbances you wish to detect. In electromagnetic radiation, there is a thoroughly-studied cosmic microwave background that reaches peak intensity at a wavelength of 1.9 mm, and a sky full of near-black-body stars, interstellar clouds of gas absorbing or emitting with sharp spectral lines, etc. There is far more signal to work with, and the shorter wavelengths will reveal smaller targets or provide a more detailed view of those targets, as well as improving sensitivity to small disturbances.

Gravitational sensors would be more useful for detecting the emissions produced by such ships, which are likely to be quite distinct from any natural ones. They could also provide information on objects that can't be seen electromagnetically due to obstructing dust clouds, though this seems unlikely to be relevant.

Answer 2

Not practically.

Need many sensors to determine if patterns

To reconstruct a pattern you need a matrix/array of sensors. The example given, the 'Hartmann wavefront sensor' is backed by sensing devices that are millions of 1d sensors packed into a 2d array.

So to be able to create an image that makes it clear the patterns that may exist many sensors are needed ideally in 2d or 3d configurations. Each sensor to be one pixel of an image.

How many pixels do you need to clearly determine there is a pattern? Depends on what is attempted to be observed. What frequency, what resolution. It can be assumed that spaceships have less impact then stellar object mergers. My guess Is that millions of LIGO detectors scattered throughout the solar system would be needed to get good resolution of patterns.

Gravity-Radar (gravdar?)

Same idea as radar just with gravity. Much more practical then checking interference patterns.

To merely detect signal source magnitude and direction would require far fewer devices. Perhaps on the order of a dozen sensors. A few on earth plus a few at the L4, L5 points. This would assume they are large enough to be sensitive enough to detect smaller signals. Bare minimum would be three but large sensors in space with separation would allow for much better resolution both in detecting weak signals and for determining angle.

This is already being done. The array just needs to have bigger sensors that are not earthbound to be able to detect something like ships.

Military applications:

Sensor array. High resolution. Enough said.

Answer 3

Maybe

The best warp drive paper I've seen lately comes from the Heisenberg lab at the Swiss Federal Institute of Technology. She says a warp drive could be constructed with just 1/10000 the energy obtainable by converting the sun to pure energy, though this might be improvable by a factor of, say, 10³⁰.

The energy requirement as described, if converted to gravitational waves, is not all that much less than is dissipated in a black hole merger. So if the aliens can't tune their drive well, you might see it. If, of course, they do better than that ... well, keep watching the skies!