How would an inter-planetary [not inter-stellar] recycling/scavenging team know when ships have crashed?

Question

In my world, there is a certain group of 'scavengers' — people who go around and pick out valuable (and salvageable, of course) objects from ships that have crashed [onto the surface of a moon/planet], had fatal errors, been sabotaged/physically attacked or otherwise rendered unusable and derelict. These 'objects' might be tech, resources from the actual ship itself, freight it was carrying, or even information in the form of physical drives (data storage) and the like (there are strict rules about not viewing other people's info). Another reason for scavenging is to clean up debris from densely [at least by space’s standards] populated areas where it could be a danger. They can either be independent or paid by a recycling company, so costs wouldn't be a super big issue.

Scavenging also doubles as a bit of a search-and-rescue at the same time as it can include rescuing people and supplying others with resources, so it's seen as relatively important.

My issue is that I have no idea how these scavengers would be able to detect that a ship has crashed. The world has pretty decent inter-planetary radio (though this can be changed), although it has some delay. I've thought of things such as the scavenging ship picking up distress signals, or having the ships being reported by colonies (however, there are not colonies everywhere).
Also note this is interplanetary scavenging, interstellar travel still takes ages in this word, so there would be pretty much no ships hanging out in deep space. Probably even more so, it is scavenging between moons orbiting the same planet. There is no FTL.

Conclusion/super-simplified version: how could one ship know that another one has crashed, even if it's a very long way away (if it's even possible)?

Does anyone here have any ideas? If there's anything I need to clarify, please tell me; I'm pretty new.

Answer 1

It's all about being in the know

Even today, oceanic salvage isn't about detecting the existence of a derelict ship. It's about knowing that a ship didn't make port. Why?

Because the ocean is big. Really, really, really big, and when ships crash... they tend to sink, making them really hard to detect.

Space is, of course, really, really, really big. Big in a way that makes finding something in our ocean a lot more like finding your left sock in your bedroom. Worse (and this is important), unless you have something like faster-than-light transportation and/or communication, nothing about the crash will travel faster than the speed of light. In other words, if the derelict lost one light-year from any inhabited planet had a transponder (and if it were working), you wouldn't know where the ship was (in the worst case) until years later when the signal had arrived at not one, but two populated planets (triangulation...).

The idea of using something like radar (using any wavelength along the EM spectrum) is even worse. If you had enough power to pump the signal out constantly (say, one massive, cook-everyone-in-the-system pulse daily), you would be at least one year waiting to detect the ship, and at worst two (remember, the example derelict is 1 LY away).

That's a lot of wishful thinking

On the other hand, if you knew every trade ship's schedule and knew when one didn't make port as scheduled, you'd not only know there was an opportunity, you'd also have a better-than-average idea of where to look.

So, as usual, knowledge is king. And knowing where things should have been is half the battle when it comes to knowing where they are.

But, just as a frame challenge, would it be practical to have interstellar salvage?

I've been working on the assumption that salvage could occur anywhere. That's actually a really bad assumption. Space isn't just really, really big. It's unimaginably humongous. Without some really convenient things (like a continuously operating transponder and generations worth of time), the time to get there plus the cost to get there and back would never be worth the effort. And that assumes you can find it once you get there. If you had to travel a year to get to the last guaranteed-known location, that ship will have moved, possibly a lot, before you could arrive.

But what if we make some practical assumptions?

1. No matter what Hollywood things, even if you have FTL, pirates won't operate in deep space. Even the idea of a shipping lane is a volume of space so ridiculously large that by the time pirates detected a victim's passing, they couldn't get to it before it was out of their control. Besides, there's no support in the middle of the void, and piracy needs support (at least someone to fence the goods to!). That suggests pirates will act at known stopping point like gas giants used for refueling or within star systems that require ships to pause for navigational changes or where there's inhabited planets so ships would be coming and going. So, place to find salvage #1: star systems where there's a reason for shipping to stop or pass through.

2. Deep space stations used for research or waypoints or just because you need a reason in your story to let ships stop would also work.

3. Battlefields... but this is most likely also to be local to a star system or other "fixed point in space" (if that phrase can be used in regard to space). I personally suspect space battles will never take place in the void. Why would they? Unless the two sides agreed to meet at some lonely spot, there'd never be a reason to even be there. And you'd never know someone was there thanks to information being limited to the speed of light (unless you allow FTL).

In other words, salvage shouldn't be assumed to be just anywhere. Oh, it could be... ships go off course. Mysterious wormholes appear out of nowhere... But 99% of salvage will occur in predictable locations, and that means things like Radar suddenly have some value. Rather than waiting for years to find a needle in a massive haystack, you're waiting hours (and hoping the derelict isn't so close to the sun as to interfere with the signal...).

And you need to consider what it means to become a derelict

What causes a ship to become derelict? The Apollo 13 moon mission demonstrates the theoretical possibility of a ship being primarily intact even though everyone one it could be dead. So you have the case of a broken resource (like oxygen) leaving the ship intact. But piracy? A battle? A meteor impact? I'll be honest with you. I'd avoid reality when it comes to what makes a ship derelict, because IMO most causes would leave chunks-too-small-to-be-worth-salvaging spinning off into many directions that, with every passing second, are getting too far apart to effectively salvage.

Although that does bring up a point... until they start getting affected by another force (like a star's gravity), all you'd need to do is find two such chunks and trace their route and you'd find the source of the accident and, therefore, be able to predict where other chunks might have gone... Hm....

But, to be fair, that wasn't your question.

Answer 2

Easily, from intrasystem scans.

Voyager is around 18 billion kilometers away. It produces about as much energy as your fridge lamp. It was still easy to spot by a single telescope.

So, just have a telescope scanning the solar system. When people burn huge amounts of fuel to move at massive speeds, you can note where they are, and the red hot engines will tell you where they are for a while after that.

From the energy you should easily be able to tell exactly where they are going, and at what speed. If they fail to do a counterburn to slow down you can tell they'll either fly into deep space past a planet or crash into it.

Answer 3

Sentient wind jellyfish

https://the-scp.foundation/object/scp-312

This planet has aliens. They drift in the upper atmosphere and maybe higher. They come to ground sometimes, for their own reasons. They communicate with each other and they know what is going on. They are pretty mysterious, these things.

But not entirely inscrutable. They can communicate with your scavengers. One (usually one of a recurring few, which the scavengers have named) will show up with news of something. The wind jellyfish generally understand what sort of things the scavengers are interested in, but might also tell them other things they are not interested in, or can barely understand. The jellyfish have their own system of coordinates which your scavengers understand, mostly. There are things the wind jellyfish want and which the scavengers can provide so there is a quid pro quo.

This serves your purpose of getting the news to the scavengers. It also introduces a story element you can use to move things along. The wind jellyfish perspective on things will be interesting in its own right and maybe these creatures have something else going on which will turn out to be relevant.

Answer 4

"I've thought of things such as the scavenging ship picking up distress signals, or having the ships being reported by colonies."

I think this would be one of the things to focus on - sniffing out where wrecks might be, whether through distress signals, or picking up on coms from some government system, like the equivalent of an air traffic control, or coms from a battle.

Something else I'd point to is the idea of a "graveyard orbit." Today, when a satellite in a high orbit of earth has lived its life, it is moved to a graveyard orbit where it won't get in the way of anything. As time goes on you might find not just graveyard orbits, but graveyard asteroids. This could be a source of wreckage to look at.

I'll note however that advancements in mission extension technologies, satellite buses, etc, will reduce as time goes on the likelihood of a ship or a satellite being simply abandoned.

Answer 5

AIS and ADS-B in Space

Airplanes and ocean-going vessels regularly transmit their location, speed, size, and intended destination through systems like AIS and ADS-B. It's a safety measure, that I would expect to come with us to space.

The messages are very short (think like 150 characters) and generally go out at short intervals like 30 seconds. It's cheap, valuable, and easy for the authorities to keep track of and fine violators.

Scavengers would collect and mine this data, and look for anomalies. Things that might catch their eye include:

• Ship Stops Reporting - if the transmitter goes offline, either there's a problem like a crash or equipment failure, or the ship is hiding something.
• Missed the Exit - If a ship fails to turn or maneuver when it should, say it didn't do a burn when the gravity slingshot was needed to keep them on route to their reported destination. Could indicate that the crew is incapacitated.
• Detection without Reporting - If scavengers see a RADAR/IR/LIDAR/whatever return, but no associated AIS/ADS-B transmission, it's either a wreck or a criminal.

There are other potential anomalies, depending on what is normal, what is reported, and what scavengers might be able to guess from that data.

Note that a lot of the things that indicate "potential wreck" could also be indications of "pirates or smugglers." This could be an interesting plot point.

Answer 6

With advances with various methods of detection, such as optical, RADAR, etc. finding wreckage in odd or unstable trajectories may be easier in the future, but detecting small object, such as ships will still be somewhat difficult.

What you can look for is the debris field such a collision would cause. Over time, object broken free of the ship will drift around, making the debris field larger, but will more or less stay fairly close to the wreckage due to minute gravitational attractions and a shared trajectory.

This debris field, being made of metals and other composites, will look differently on scanners in various EM wavelengths so you can differentiate a ship wreckage from a dust cloud, smashed asteroid or comet. With some filters on your sensors and a trained eye of a observer, they can detect such wreckage easily at great distances.

Scavengers may keep a suite of sensors, optics and arrays to look for wreckage to salvage.

Answer 7

Today we can detect the gravitational waves of colliding black holes. With some significant advancement in the detection capabilities, we will be able to detect the collision of much smaller masses, like two spaceships hitting each other head front (traffic lights keep being neglected even in space apparently).

Considering that the information of the collision would propagate at the speed of light, it's natural to think that "exclusive zones" would emerge, were only one company is practically capable of operating, due to the close proximity. The borders between these zones would see some interesting "debate" on who is entitled to the recovery.

Answer 8

You didn't mention if you are considering FTL travel/communication, but to make any of what you are asking reasonable it probably is a necessity.

Intercepting information about spaceship having trouble can be done on several levels - capturing the communication about the ship problems and getting information directly from the ship owning company being the primary two sources. Currently in transportation there are similar ways of signaling issues and I would imagine something similar will exist for space travel once solidly established, especially with FTL communication.

Based on the flight plan and pure calculation one should be able to find more or less accurate position of the wreck. The more accurate the more chances of actual help. If it is less accurate, search is more complicated (and here a bit of luck and experience can help, combined with finding traces like already mentioned in other answers debris fields), meaning something really valuable needs to be salvageable ot someone has to actually be nearby and have some trace helping to find the wreck.

Finally, ships can be equipped in something resembling black boxes of today airplanes. While the primary goal of the black box is to keep record of the last period of the flight, for it to be valuable it has to be found. So all black boxes are equipped with a beacon that emits specific radio signal to help find it. Something similar could be on board of spaceships - of course with different scale and beacon emission time (the black box one emits signal for roughly 1 month only).

If you assume no FTL communication means, the distance alone means that the chances of any rescue mission is close to zero and the scavengers will get the information about the ship after significant amount of time and will be able to reach there after similar or longer period. Even distance between near two stars is counted in light years, 2 ly apart means the scavengers get information after two years and will need at least another 2 years (in practice more) to get there. So without the FTL the same principles for "where do they know from" remain but you are limited to recovering transport only (and only most valuable one probably will be worth salvaging).

Answer 9

Because a fair bit of your business model involves operating as a "Roadside Assistance" company.

In modern-day America, if you have car troubles that make your car inoperable along the side of the freeway you'll typically need to call a tow-truck. However, knowing all the local tow-companies' phone numbers and service areas is a pain (not to mention negotiating price, etc.) so a lot of folks tend to subscribe to a service like AAA so that they only have to call one number and that company will arrange everything as quickly and painlessly as possible.

In your locally-space-faring future, people are likely to have similar "car troubles" that leave them stranded mid-route and in need of rescue. By operating as a "Roadside Assistance" company you will essentially be the first-call for anyone* stranded along any of the main routes. *(Other than maybe bigger shipping firms who operate their own internal tow-fleets.) This business model means that, yeah, you'll have to spend some resources on a customer-service call-center, and possibly have a number of smaller fast-rescue ships constantly deployed, but it'll also mean that you're first on the scene and likely the first to lay claim to the salvage. Heck, as a service you could even let customers install a "black box" device that automatically calls you in event of a catastrophic failure (which you could advertise as life-saving because it lets crew prioritize getting to escape pods before calling a tow company).

And, while this means that most of your day-to-day business will be taxiing stranded motorists to the nearest port while arranging the nearest tow, it also means that you will have first bid when it comes to offering up a price on "total loss" wrecks, and you (assuming the "black box" subscription) will also likely be first to lay full legal claim on any "no survivors" wrecks. (You will have to be top-knotch about not letting people die, though, as doing that would tank the entire front-end of your business, and all the good leads it provides, if word [or rumor] got out.)

Answer 10

Dangerous to Go Alone

You basically have the right setup already, with distress beacons or something similar being the most common way of finding damaged ships. The problem is that a distress beacon is also a big red sign for bandits or other nefarious entities so an injured ship is going to want to make sure they can be found but only by people who know where to look. I would imagine that distress beacons are high powered but (relatively) low ranged. That way anyone who is close enough to help will be able to follow the signal, without blasting it over the entire sector or whatever to cut down on bad guys hearing it.

Of course that means that your salvage crew is going to need some way to know the general area of any ships in distress. The simplest way would be for them to be hired by whoever is sitting around waiting for their shipment to show up. Assume that the injured ship's full route is known by someone at either end of the trip. One of those people can then hire your salvage crew and say "look somewhere between Alpha Centauri II and Beta Kerotine IV". Once the crew gets close enough the distress beacon is found and away they go.

When the crew doesn't have a good lead or is not on a job, they can do some basic traveling along common routes where people get into trouble. That should be a last resort though since there is no guarantee of a return on investment of time/fuel.

Answer 11

Salvage

Most salvage operations do not involve retrieving sunken wreckage from the deep. Those wrecks are hard to find, so looking for them is expensive. In most cases it simply isn't worth the effort to dig them up, unless they are of historical significance.

No, most salvage operations at sea involve someone saying "please come and rescue us". The owner (or captain) of the vessel in distress has to ask for it, and commonly they'll sign a contract or at least verbally accept the terms of the rescue, which is typically between 10% and 25% of the value of vessel and cargo.

So I think your instincts of these people looking for distress signals is exactly right. The scavenger is guaranteed to get a return on their investment of time, money, fuel and whatever else, which they would be unlikely to get by scrounging off crashed and fully destroyed ships.

Answer 12

Radio transponders work just fine on this scale

Just like in real life, all legitimate ships will be regularly transmitting their positions (and distress messages as necessary) using their radio. So, you simply need to know if a radio signal can cross a solar system fast enough to provide data that is recent enough to be useful, and you need to know if a ship can transmit a signal powerful enough to be picked up over those distances.

The entire diameter of our Solar System is only about 8.3 light hours across; however, nothing farther out than some of Saturn's moons really looks that worth colonizing; so, my guess is that it will be very rare for you to need to transmit this distance. Worst case likely scenario, you will need to send a message between Saturn and Jupiter while they are at opposite sides of the solar system which is a distance of about 70 light minutes. So, whenever a disaster happens, (either the transmission unexpectedly ends, or they send a distress signal), nearly every scavenger in the solar system will be able to notice this within an hour. In the grand scheme of things, this not not a very long delay.

Figuring out if you can transmit and receive a signal that is powerful enough is a bit more complicated. Basically, your signal just has to be more powerful than the background noise of space which is on average about 4e-23 W/Hz/m^2. With a total distance to cover of 1.259e+12 m we can determine the surface area of an omni-directional transmission at that range to be about 2e25m^2; so, if you are using a 1 square meter radio reciever, you can pick up that signal as long as it is being transmitted at something greater than 800 W/Hz.

Since transponders don't need to transmit complex data, you can use very low frequency signals. Using an alternating current transmitter, you can reduce this signal down to arbitrarily low frequencies so your actual transmission may just be a Morris Code like 0.5 Hz being transmitted from a 400 W emitter. This is about the same amount of power that a typical fighter jet needs for its onboard radar system; so, I think it is safe to say you could fit something this powerful on just about any spaceship worth salvaging.

Answer 13

The ship drive is easily detectable

Those spaceships leave a very conspicuous trace when they enter and exit hyper drive, the light speed version of the sonic boom, but not constant as the sonic boom. The scavengers check all the signals and when a signal comes from an unknown location far from any spaceport they check it carefully.

However ship hitting a rock at high speed would be completely destroyed, scavenging that would not be credible. More credible would be ships stopped by a failure in their drive and maybe later falling on a planet or on an asteroid.

Answer 14

Quantum Internet! If your world was based on ours just x years in the future then it's not unlikely they will of mastered quantum internet in some form or another as it is a science we are beginning understand and are trying to develop right now.

So what is 'Quantum Internet'? I will preface this with I have no formal education in quantum physics, just an interest and a hope of working in the field one day! Here's the Wikipedia article:https://en.wikipedia.org/wiki/Quantum_network TL:DR using quantum entanglement to transfer data instantaneously across infinite distances. Sounds crazy and very bs? yeah, welcome to quantum physics.

So how can I use it for a salvage ship? If the ship get's shut down the qbit becomes un-entangled and the other end knows the ship has some form of problem. We can use it to actually communicate between quantum computers in the present day, maybe they could send an actual distress signal or maybe it just sounds an alarm when the 'beacon' goes offline(a qbit pair collapses). Currently we would need a central hub(Like 1 single server or a small network of servers) to have this kind of system work but I don't doubt someone somewhere is working on that problem, meaning a traditional internet like setup is would be possible. Notice a ship goes down and get a move on! Might need some small repairs or might be lovely salvage!

Hope this idea helps or is at least interesting. It's one of the more science fiction sounding but actually(mostly) real in the present day ideas out there for FTL communication. I know you said no FTL but this is physically possible and it's being proven all the time.