Stealth in Space

Few concepts of space warfare have inspired as much controversy (and hate mail) as discussing stealth in space, so I figured it’s time to have an article about that.

apollo 8 translunar plume.png
The bright Apollo 8 plume observed from Earth, as it makes a Trans-lunar Injection.

For starters, though, I’d recommend checking out Winchell Chung’s website, Atomic Rockets, which has an excellent discussion on this topic, aptly titled There Ain’t No Stealth in Space. I will summarize the main points about stealth here, but for an in-depth discussion of them, see the above link.

  • Carefully scanning the entire celestial sphere takes 4 hours or less.
  • Thruster burns of any drive with reasonable power can be detected all the way across the solar system (billions of km away).
  • Even with engines cold, the heat from radiators attached to life support will be detectable at tens of millions of km away, which is still far too large to get any sort of surprise.
  • Radiating heat in a single direction (away from the enemy) is easily defeated by fielding a number of tiny detector probes which idly coast about the system. Additionally, the narrower of a cone in which you radiate heat, the larger and larger of radiators you need to field. A 60 degree cone of radiation is roughly 10% as efficient, and it only gets worse the tighter of a cone you have.
  • Making a huge burn and then trying to stealthily coast for months to the target is do-able, but as long as your enemy can track your first burn, they can very accurately predict where you’ll be as you coast across the solar system. And you still have to worry about radiating your heat for months.
  • Decoys are only really viable on really short time scales, such as in combat. Over the long term, study of a decoy’s signature over time will reveal it’s true nature. It would need a power source and engine identical to the ship it’s trying to conceal, as well identical mass, otherwise the exhaust plume will behave differently. This means your decoy needs to be the same mass, same power, same engine as your real ship, so at that point, why not just build a real ship instead?
plume diagram.png
Anti-stealth detection measures was developed heavily during the cold war for detecting ICBMs. In space, without a horizon or an atmosphere, it’s far easier.

There are a few more points that are not mentioned but I get messaged about them a lot, so I’ll put them here.

  • Hiding behind a planet to make a burn is not really feasible. All it takes is two detectors at opposite sides of this planet to catch this. In reality, a web of tiny, cheap detectors spread across the solar system will catch almost all such cases.
  • A combat-ready ship will require very hot radiators for its nuclear powerplant for use in combat. If these radiators are going to be completely cold for the journey, they will suffer enormous thermal expansion stress when activated. In order to avoid this, very exotic and expensive materials for your radiators will be needed to get from 10 K to 1000 K without shattering. Not only that, your radiator armor will need to be similarly exotic, which means it will likely not be very good at armoring your radiators anyways.
plume in atmo.png
Rocket exhaust plumes can be uncoupled from atmosphere using modern technology after some study. This step can be skipped in space.

Now there are plenty of dissenting views (as Atomic Rockets is good to point out, as well as rebuttals to the rebuttals). Certain partial solutions, such as using internal heatsinks, and so on, are pointed out, but they all are very limited.

Ultimately, stealth in space is somewhat possible, but current proposed solutions are either ridiculously expensive, impractical, or require you to accept limitations that defeat the purpose of stealth in the first place. Indeed, rather than consider it a ‘yes-or-no’ question, it’s simply a matter of how close you can get to the enemy before they detect you.

In practice, ‘how close’ generally means halfway across the solar system, with expensive stealth solutions reducing that distance only partially. Given this, Children of a Dead Earth runs with the assumption that stealth is not a reasonable military tactic for near future space warfare.

But let’s look at an example of possible stealth: replacing your main engine (nuclear rocket or combustion rocket) with a solar sail. Your exhaust plume is now nonexistent, but now you have to take decades to centuries deliver a military payload anywhere (troops or weaponry). Your best bet is to keep your payload very small if you want to get anywhere in reasonable time. And you still have to worry about your radiators.

solar-sail
Concept art of a solar sail. Abysmal thrust, and basically useless in the outer solar system, but it’s stealthy.

Suppose replace your crew module with basic electronics, and do away entirely with the crew and their hot radiators. This is reasonable for any short term space travel, but over the course of months where things can and will go wrong with the ship or the strategic situation, having a human element is necessary. Alternatively, if Strong AI can be developed, this is another possible solution, but this assumes that such an AI won’t require lots of power and heat to radiate as well.

cryosleep
A different idea to get around this problem is to put everyone in cryosleep and keep the ship basically frozen. Comes with a host of it’s own problems as well, chiefly that the technology does not exist yet.

Given a solar sail and crewless ‘dumb’ ships with miniature payloads, you can build ships that can sneak across the solar system and do very little. Such ships would be unable to respond to complex and unexpected tactical decisions, and would be very easy to outsmart, as well as easy to spoof with electronic warfare. They could perhaps be used as mines, given a tiny amount of a delta-v and a small nuclear payload.

Ironically, this specification of tiny, ‘dumb’ stealth crafts is exactly what you need to build a web of detectors scattered about the solar system. This means the field of cheap detectors you want spanning the solar system can be created stealthily.

The Hubble Space Telescope in orbit
The Hubble Space Telescope. Much smaller and cheaper versions can be scattered about the solar system stealthily if using solar sails.

Defensive stealth in space exists in full force. When you enter orbit of an the enemy’s planet, they might have an inordinate amount military hardware and spacecrafts hidden beneath the surface. But as soon as they launch, the secret is out.

This idea plays a major role in Children of a Dead Earth, as when the enemy drops into orbit around your planet, one must always be wary that the enemy fleet is simply trying to draw out your forces to get a tally on what you actually have. This constantly requires balancing of launching just enough firepower to deal with the enemy without revealing too much about one’s own reserves.

titan-missile
A Titan Missile Silo from the cold war. Similar silos could be littered across planets, moons, and asteroids with full fledged capital ships, ready to launch when the enemy enters low orbit.

The easiest way to conceal a large amount of military hardware for a long distance invasion is to hide it amongst commercial traffic. Of course, this requires complicity with the civilian traders, either bought with money or intimidation, but it is possible. And such perfidy also plays a key role in Children of a Dead Earth.

With that all in mind, I will admit that at the beginning of my project, I was dead set on getting stealth to work in space warfare. Ultimately, I came to the conclusion that while stealth in space is certainly possible, it is not feasible given mass, cost, and time constraints. If you want stealth, you need to pay the price of decades-long travel times, enormously massive ships, vastly reduced military effectiveness, or all of the above all at once.

At the beginning of the project, I did explore some more exotic solutions to stealth, but I ultimately wasn’t keen on implementing technologies that were not heavily reviewed and published in scientific articles. At some point though in future posts, I will go over all of the more ‘out there’ technologies I considered for all aspects of space warfare (like a hypothetical nuclear rocket which generates an exhaust plume at 30 K, for instance). Stay tuned!

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56 thoughts on “Stealth in Space

  1. Have you considered using a small, stealthy probe with a solar sail and panels as a sort of long range missile bus, or a remote control ‘boomer’?

    The idea being that in the decades leading up to the war, you send these out in ones and twos into enemy territory, and then send a signal to them to launch when you think the time is right.(While you could use a laser comm for this, you could just as easily broadcast an encoded message over the radio-by the time anyone figures out it’s a launch code, they can see the missiles launching anyway.)

    You could either use this to support an invasion directly, disrupt enemy movements, or attack strategic targets with nukes.

    Also: are James Webb style sun shields not really usable as a stealth thing? Not to block the sun, but to block your infrared signature in one direction and present a chilled side to the enemy.
    And burning on the other side of a planet could work if it’s your home planet and your target is another planet. I don’t imagine there’s a way to ensure there are detectors minding all sides of an enemy held planet, especially in a shooting war where the enemy’ll be doing his damnedest to deny you intel.

    So a sneaky invasion fleet with some good timing could conceivably make the transfer burn on the other side of their home planet, extend ‘stealth shields’ and face the target, and not get spotted until it’s too late to call reinforcements from elsewhere.
    It’s an Operation Chariot tier gamble, but it’s the sort that wins wars.

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    1. You cover all sides of a planet by launching your sensor probes into things like solar polar orbits. It’s also kind of hard for, let’s say, the Grand Duchy of Venus to stop the Martian Republic from placing probes inside the orbit of Venus, (or for the Martians to stop the Venusians from placing stuff outside or Mars’s orbit).

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    2. Small, stealthy probes with a missile payload are essentially the “mines” I mentioned earlier in the article.

      About the cold shields, this is essentially the same concept as reducing your cone of radiation, only by half, as mentioned in the article.

      The main issue is that the enemy won’t have detectors only on their main planet. All factions will have detectors scattered across the solar system, in every single planetary orbit, as well as multiple out of solar plane. Easily accomplished by using Statites: https://en.wikipedia.org/wiki/Statite

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      1. What’s the point of having a telescope out of the ecliptic? Besides spy satellites that need to orbit the target directly, you want your detection spacecraft on a solar orbit inferior to Venus and looking outward. Otherwise the Sun will heat up your sensitive optics, and any target not elongated very far away from the Sun will get lost in its glare anyway.

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        1. It is for spacecrafts that try to achieve stealth by reducing their radiator emissions cones to small angles, and aim it in a direction where they think no one will be. When doing so, the best place to aim your emissions is directly out of the ecliptic, because that is where there will far less in terms of planets or asteroids that will detect you.

          This means leaving some telescopes out in wide orbits above and below the ecliptic to catch anyone that tries this technique.

          They would also use space sunshades (similar to the James Webb Telescope) to prevent the sun from damaging their optics, even when pointed semi-close to the sun (as long as you don’t point the telescope directly at the sun).

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      2. ‘Mines’ may not be the right word. While they’re immobile in the tactical sense, they’re somewhat mobile in the strategic sense-among other things, they can move into enemy territory given enough time.
        That being said, you could use these to ‘mine’ a transfer trajectory.

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        1. You’re right, I am stretching the terminology a bit. I was referring to them ‘mining’ a trajectory or ‘mining’ common orbits, but it’s a little confusing that way.

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  2. Stealth seems infeasible – but as you mention, obscurity may be achievable. I’d be interested in what it would take to distinguish a warship from a cargo ship at range, for example, given that they’d likely use similar drives and fuels and be similar in size. If we posit a strongly trafficked solar system, with plenty of ships going to and fro at any given time, how difficult would it be to spot a warship or fifteen in among all of these?

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    1. After detecting an exhaust plume, you can deduce the ship’s course, type of engine used, thrust, mass flow, exhaust velocity, and mass of the ship itself. Also, the power supply and crew of the ship can be determined by studying the radiators. If you have a catalog of enemy ship and cargo ship classes, you can very quickly guess what sort of ship you’re dealing with.

      With that said though, if the enemy wishes to confuse this information by tweaking the drives or mass of the ship, they very easily can with some moderate configuration changes. Essentially, if the enemy is not trying, you can easily pick out whether a ship is a warship or not. But with some effort, the enemy can conceal this information entirely. Your enemy could easily decide to primarily develop warships which have engines/power/mass similar to commercial freighters.

      Actually determining what a ship looks like, and finding out exactly what it’s armed with isn’t possible until the ship is very close. More or less, this range is when the enemy drops into orbit around your planet.

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    2. To make a warship look like a civilian cargo ship (there are/can be military cargo ships, e.g. carrying ground troops or supplies), you basically need a civilian cargo ship and change the interior, staying within the same mass range a cargo ship on that route would have. You might want to add more remass, living quarters, stores, life support, high-power reactor & radiators (switched off, retracted and hidden), hidden guns/turrets, fallback systems, maybe heat sinks and/or flow batteries and/or fuel cells …

      Civilian ships are generally unarmed, have small crews, lots of automation but few sensors … and thus a fairly low power reactor — more available mass for cargo is king. They likely have little if any PD, with Whipple shields handling small pieces and active radar and slight course changes avoiding larger bits of space junk.

      With your larger crew (you have to maintain a lot of stuff freighters do not have, like weapons, sensors, drones, missiles, extra reactor(s), extra attitude and manoeuvre engines, munitions, and of course all the extra life support … and never mind being able to fill all combat stations and have a reserve bridge) you need quite a bit more power, even if just for the life support and need to handle that heat as well as the body heat of all the extra people.

      So you draw more power — which means even more heat to handle. Which will show clearly on IR and possibly on visible cameras, available on any good spy microdrone, which the local authorities have seeded everywhere. Which will likely make people suspicious why you have that much more heat than a normal freighter. If you are lucky, they’ll just think you are smuggling illegal immigrants, or carrying slaves of some kind. Or maybe lots of animals (which would need to be inspected for illnesses, of course, if importing them is even allowed.

      So even when nobody would guess you are a warship, you will be inspected closely and likely be boarded. Which will give you away.

      Or maybe you are a passenger carrier, which are bound to be many fewer than freight ships and likely need to state their passenger lists well ahead of arrival time. And in which case the passengers will want to communicate ahead with their business partners, loved ones, employers in spe, etc. and while everything will be encrypted, the recipients will wonder why the messages are not signed properly digitally and why their replies are not generating proper answers. You’d need to have the private keys of many of the individuals you claim to carry … and immigration might just send “please fill out this form” messages — of course encrypted for just these claimed passengers … so you’ll need to really work at this masquerade.

      And you’ll be scanned and possibly boarded well away from your destination.

      You may want some power from chemical storage (batteries, fuel cells) to lower the reactor output heat and you likely want some large heat sinks to dump the extra heat from the extra people and extra life support and all that nice combat stuff. Which will take up mass that’s not available for warship
      purposes.

      It’s even worse posing as a luxury liner — you may have a much better heat budget. And demanding ultra-rich and powerful and celebrity passengers. Which will call ahead to their companies, servants, managers, and so on and so on; and will have constant radio traffic. Without anyone noticing you fake them, so you not only need their cryptographic keys, but also all the knowledge not to trip up. And an effing huge slow rotating torus for them, with large space observation windows for every cabin — lots of useless mass for a combat vessel. Oh, and you better follow the travel itinerary fixed years ago, and really have all these celebrities and politicans board some launch vessel — there *will* be normal journalists showing this CEO or that politician or these celebrities boarding for $whatever, trying to interview some, and of course there will be paparazzi trying everything for a ‘story’, and some of them may manage to be where the passengers board the luxury liner (i.e. in space) — and likely some of the passengers *will be* paparazzi in disguise — and their news organisations hearing nothing from them may be a minor problem.

      Freighters will choose their engine almost solely on “how do I need the least remass to reach my destination in an acceptable time”, which may mean choosing a weaker thrust engine and using multiple burns on separate orbits to get to escape velocity for the planet or to enter a circular orbit at the destination. A couple days extra may well be worth the saving in remass and engine mass — which means more cargo (and less money for reaction mass) for the same trip.

      A warship however will want high(er) thrust on demand, not being outmaneuvered by the enemy is important, as is dodging, even if it means heavier and/or somewhat less efficient engines. A warship will also prefer multiple engines to have some redundancy.

      An engine’s exhaust will trivially show everyone it’s composition (spectrogram) and hence the fuel used, ejected mass (via it’s relative brightness and triangulated distance), exit speed in line of the viewer (shift of the spectrogram peaks) and ship mass (given the exhaust’s known characteristics, how fast does the ship accelerate). So you need a freighter’s typical engine(s) and reaction mass, and yet you may want to pack an extra military engine or two for when the disguise is dropped or fails.

      Since your ‘real’ reactor and it’s (much larger) radiator are both cold. you may need some time heating them up slowly so they do not crack or fail. Which means you become visible as a likely warship minutes or hours before you have the power for combat.

      Most freighters will be tied to a shipping line, which means they will have ground support, which will already have gathered cargo for the next stop and is ready to handle the cargo to be dropped off at the destination, and they likely know at least some of the crew, and will have basic information about the important people from the shipping line. Especially if the freighter follows the same route most of the time, people will get to know each other, and the shipping line headquarters will also be in contact with the ship and their local people at the destination. Might be a bit difficult to fool them, unless the shipping line (or at least the local people) are yours in some way.

      So you might take or impersonate a captain-owned or crew-owned ship, which takes whatever cargo it can get and goes where the most profitable cargo is meant to go. They may or may not be known to the local people, they might have no ties to the place (no lovers/relatives of some crew member, etc). If they are unknown (or crew with ties have changed ship, become grounders, died or whatever, reported around when the ship left, latest), you won’t trip up on some little thing. Of course, these kind of vessels tend to be not quite the largest, best equipped ones.

      Depending on the political and military circumstances, they could be intercepted and inspected by some small, light “customs” boat (which may include boarding) or by a cheap drone or two with highly specialized and very very sensitive and high resolution sensors (visible, IR, UV, SAR, lidar, magnetic, masscon, etc etc etc — and even “pass through” EM radiation measurements in case of a pair of drones taking the ship on opposite sides). So you better be a freighter to that scrutiny or be OK with dropping the masquerade right there and then, when the local defense has decided that you are far enough out to be stopped easily if you turn out to be evil.

      There will also be a ship register of some kind, listing most, if not all vessels known, and it will likely have a number of identification methods, so you better come up right there, too. Which may be easy (many tramp freighters having random changes, some only known by type, …) or a bit harder (ship visited in the past and was mapped by passing check-drones). Of course, if you actually have the original ship instead of impersonating it, it may be easier.

      Remember also that any space ship with a couple km/s dV can almost trivially be turned into a very devastating kinetic weapon against any in-orbit infrastructure and any ground installation unless a thick enough atmosphere protects it.

      And there will also be a *huge* number of very important orbital structures, too: freight needs to be temporarily stored and moved between planetary shuttles and space freighters (and other space freighters), the same is true for civilian travellers from and to the planet which will be using a hub to change over, the military needs to get people on board their vessels and installations, and will likely also want hubs unless there’s a reason not to, fuel/remass depots just make so much stuff easier, and for the military, the same goes for ordnance stockpiles (and these missiles need to have maintenance and inspections so they’ll work when called upon). All these non-atmospheric ships need to be build and repaired, which means either a space dock or an installation on an asteroid (the Moon is likely too deep a gravity well and may have too much gravity for a number of vessels). There will be science labs and factories producing stuff that’s easier/cheaper/only doable in free fall, and likely lots of it. Hospitals will care for those who would suffer too much in a gravity well or would not take returning through the atmosphere well at all — accidents will happen, even without combat. There’ll be space hotels for the merely rich and well to do and honey mooners who want that free fall experience when they choose to, but sleep and eat and use the toilet in full or reduced ‘gravity’ (and there’s that ‘sex in free fall’ thing for those who want additional difficulties and and new experiences. Less pointless than the miles high club, because it really is a difference.). There’ll likely be several free fall games, with some athletes becoming super stars — which means good accommodations for them and the support personal (from MDs to trainers to gear maintenance to camera crews to reporters to very rich fans … and less good accommodations for merely rich fans wanting to see with their own eyes.

      Never mind all the satellites for communications, science, weather, forest fire detection, navigation, ship tracking, etc. etc. etc.

      If getting to space is getting less expensive, many more use cases will become feasible and are going to happen, which will probably never enter my mind until it’s announced, so there will be even more and more.

      And ground installations tend to be much larger and have many more people than orbital infrastructures. So you bury your base well under the moon surface — but what happens when even a moderate 500 tons of vessel goes on an impact course at a moderate 3 km/s (and picking up another 2.38 km/s from the Moon’s gravity well)? That’s a nice round one kiloton TNT equivalent, nicely impacting straight down on your rock roof and (unlike a normal nuke) transferring all the lovely energy into the roof of your base, shattering and cracking rock all over the place. How many places will still be airtight, no matter how large your base is, deep underground? How many will be leaking slow enough that people have time to get into suits or rescue balls or into a still airtight place? How many will die in the hours and days following, when the oxygen reserves in the rescue balls run out before anyone can carry you to safety? How many will die because even in their suits they cannot get through the rubble to more oxygen or shelter — or fatally puncture their suit trying? How many will die even in the places still airtight when their oxygen reserves run out? Or having to decide to kill those with no suit or rescue balls — because there is no way to make an airlock and if the suited ones don’t leave everybody dies? How many will die as there’s little chance of getting even the most critical machinery working at least partially, with power and water and air pipes ruptured and torn apart all over — and when getting from any place to anywhere means digging through tons of rubble first? And if people are lucky, they’ll get to experience it second hand via some still working suit radios and the tales of the few ones rescue teams (risking limb, life and sanity) will be able to get to in time …

      There will always be people who think others are capitalist swines, communist traitors, not following their own extremist take on $RELIGION properly, have the wrong skin color, not being patriotic enough, being patriotic for the wrong country, making everyone equal or causing grave inequalities, exploiting consumers, using the wrong editor/operation system/browser/hardware basis/…, being pro/contra abortion/immigration/guns/…, belonging to the wrong country/tribe/company, destroying the ecology (say, of the Moon!!).

      Or that the souls of wrong- or non-believers must be rescued from eternal damnation. If that takes torturing the body, to permanent damage or even death — well, life *is* but a valley of tears, and what days, weeks, months, years or even decades of the worst imaginable pain against ETERNAL!!! DAMNATION!!! IN!!! HELL!!! It is your duty, morally, and you are charged so by your gods and your religious leaders, to be a good human, to be a kind and loving person, to be a friend to all and to be ab enemy to none — and thus to rescue the souls of these poor mis-believers from that horrible terrible, infernal, eternal fate. If you don’t get them on the right path, their soul’s eternal damnation is blood on *your* hands, you failed them, you failed your gods, you failed your community … Worse, if you don’t even try or try with less than all your skill and will, you are evil, you are condemning those you are sworn to help avoid exactly that fate to eternal damnation, to eternal pain much worse than the pain any human body can ever feel, to be cast away from the gods, to be not loved. For ever and ever and ever. Not “till the Earth dies”. Not “till this galaxy burns out”. Not “till the last star stops even glowing slightly”. Not “till the last photon in all the universes stops existing”. Not “till the whole universe crashes together into a reverse big bang (if that ever happens)”. Not “till even the concept of time has no meaning any more, since even space time is no more”. Much much much longer. Eternally.

      How then can you let your fellow humans fall to such a fate, by not applying yourself fully, by not acting, or worse, even preventing soul rescuing torture? You must be the most evil person imaginable! And you should be ashamed of yourself and work hard, hard, hard for forgiveness, that you condemned fellow sentient beings to that fate …

      And given that (and bog standard extortion and so on), a rogue freighter with a suicide crew or robotic control (and maybe a good cargo of chemical or biological weapons, if the target is, say, Earth) will be one of the worst possible nightmares for those trying to save lives.

      Losing the almost finished flagship *and* the dockyard, the crews of both *and* the civilian contractors and specialists to a stupid tramp freighter slamming into it doesn’t look too good on your resume, either. And it does not help that even blasting the whole tramp freighter into smithereens won’t stop all that smithereens crashing through flagship and dockyard either — you have to divert the ship or move the dockyard out of the way. And you may have not much more than a couple minutes to do it — all it takes is an incoming vessel not slowing at perigee, but changing course and accelerating …

      So, yes, there will and must be some sort of safety structure that tries to prevent that from happening constantly, even though it’ll certainly not be preventable in every case. Which means that the less you know about an incoming vessel, the more you will have to check it out. So what if that costs lots of reaction mass/fuel and time? The cost of failing is vastly more expensive materially, and it’s very hard to place too high a value on the hundreds or thousands that can die if you fail to avert the danger.

      And yes, it would likely be an acceptable tactic to use against military installations and vessels, especially if you “raise the real flag” and tell them to get into the rescue capsules (or whatever) or die — that’s basically what’s called a commando raid. (In which case the attackers would try to survive by, say, leaving the ship in time and try to be picked up by another vessel.)

      Which means that hiding an armed ship as a legitimate cargo vessel is possible at a fair distance — but getting close enough to actually use these weapons on valuable targets is going to be a completely different thing. Likely the easiest course of action is being unarmed and a bona fide freighter and hiding (w/heat sinks and/or non-reactor power) a raiding party, and try to take over (for a short time), mine, booby-trap or scuttle whatever you can dock with as that bona fide freighter — and whatever else is (or very soon will) dock with that. So you could assassinate a target that you knew many months ago would be at a place in a reasonably short time frame (you can unload some cargo and try to aquire more cargo for the next stop of the freighter, but not forever …), or (try to) grab some key technology, or do a smash and burn or leave a nice explosive present or poison gas … You might even try to capture a tug that is/comes to where ever you dock and has legitimate business going to some military target and load that up with a couple presents.

      I do not see many chances to fight as an armed vessel, though you could have a good number of drones with weapons — which again will need you to come so close a sufficient reaction is not possible between drone launch and full attack of the drones.

      On the other hand, if all you want is not let the enemy know 6 months ahead of time, but only some weeks (hoping he cannot get reserves in time or recall a fleet etc.) the job is much easier — but you still need a civilian drive and fuel/remass and the right mass range and probably not too much heat radiation — spy sats can be everywhere and likely will be and they must not get readings from you that could give you away.

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      1. While you do raise the important point of “most all vessels will be checked out thoroughly long before they can do something bad, and it’s really hard to disguise yourself under that scrutiny”, I do believe you could’ve said it without a large, rambling essay on just about everything even tangentially related to the subject.

        The rant on the psychology of fanaticism, in particular, wasn’t entirely necessary, particularly since there’s nothing preventing our ‘suicide’ bombers from remote controlling the freighter from another, nondescript vessel with a laser com.

        As for disguising as a freighter, I imagine your nation’s spy network would help with that. A pretty common ploy, I would imagine, would be to load the ‘freighter’ with casaba melons from a fruits and vegetables supplier.
        Except that, upon arrival, the ‘freighter’ turns out to be a warship, the melons are flak missiles, and the supplier disappears overnight. Almost like it was just a front for smuggling munitions as fruit.

        On a question more related to the game, does ship navigation support multiple types of engines, and switching between them?

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      2. Another thing. Are battery sizes above 1kg supported? Or are there other means of power storage?

        Mostly thinking that a Q ship could have a civilian style reactor, and a bank of batteries. The reactor runs at full to power the ship during normal operations, and also to charge the batteries. Said batteries could then supplement the reactor during battle.

        On one hand, it gives the Q ship not a lot in battle endurance- around half an hour, maybe.
        It’d also preclude the use of high energy weapons, limiting the Q ship to missiles, drones, and conventional cannons.

        On the other, you have a Q ship that doesn’t need to slowly warm up a military reactor to war power. The reactor’s already at full power while still undercover-You just kick in the batteries, roll out the gun radiators, and you’re good to go.

        …Come to think of it, this could be useful for military ships too. It’d give you some ability to power weapons and defend yourself while the reactor spools up to war power, reducing the severity of the surprise factor.
        It could also allow slightly smaller reactors, as the batteries can take up the slack during periods of high load and recharge inbetween.

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        1. Because you will see the enemy coming hours away in most cases, time to start up the reactor is not generally an issue. Additionally, the reactor should be kept at at least partial power at all times simply to keep the radiators hot. If the powerplant radiators get too cold, they will crack from thermal expansion stress, so you either need to keep them always warm or build them out of expensive and exotic materials.

          In reality, nuclear reactors can achieve criticality in microseconds, the main problem is the rest of the reactor will suffer strain from the temperature delta. Most modern day reactors use pressurized steam lines through turbines to extract, and the steam pipes are the reason why they take so long to start up. In Children of a Dead Earth, the reactors are thermoelectric (similar to the SNAP reactors from the cold war) rather than relying on turbines, and can be designed for much quicker start up times (minutes at worst).

          For an extreme case, NTRs have microsecond start and stop times. They are limited only by how fast the core can go critical.

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          1. What about for the other two use cases presented: Q ships with civilian reactors that have to punch above their weight, and using batteries to allow a slightly smaller reactor? (you wouldn’t have to make a reactor that can service the entirety of the ship’s power draw during it’s highest peak continuously, just one that can charge batteries fast enough to service that peak when it comes round.)

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            1. Nuclear reactors can be scaled up and down in power based on use (RTGs can not though). Generally, RTGs can be made small enough that they can do the same jobs that a battery would do.

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      3. Who says a interplanetary freighter will be piloted anyway? Or have a reactor? It will probably just be the payload, electronics to run it, solar panels or an RTG to run the electronics, an antenna, and a chemical rocket engine with just enough fuel to stop once it gets to its destination. Like real space freighters! Plus instead of using a fireship, you could aways just push an asteroid into the enemy base, it will plow right thru customs!

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        1. Salvage rules may have an impact here. A lot here depends on the structure of the applicable law. An uncrewed freighter is one unrecoverable computer failure away from being an inert block of salvage, free to the next human to board it, so having a small crew aboard may well be worth it.

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          1. I guess that’s true of most space missions lol. It probably depends on how big the freighters are, smaller ones can be made automated, and losing one is no big deal, but transporting a huge payload all at once is something you can’t afford to lose to a computer error.

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  3. I think the biggest barrier on Stealth in Space is what is the mission for the stealth craft?

    Infiltration? Better off mixing in with the commercial traffic.

    First strike? Barring FTL drives, first strikes typically require speed and overwhelming numbers. If you’ve already infiltrated a system through Q ships mixing in with the commercial traffic, you’d have a good chance of taking down orbital defenses before the target knew what was going on.

    Similar situations have similar alternatives to Stealth.

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    1. In the ocean, stealth (submarines) is pretty much just to force the enemy to have to deal with it. Just suspecting there might be a submarine down there means you have to mobilize a ship with a towed sonar array, or a squadron of helicopters to hunt for it, and you have to delay your mission and stuff. Also for deploying SLBMs but (hopefully) that won’t ever happen. So I agree there’s really no analogue for stealth missions in space!

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  4. Another unrelated question: How well simulated is ammo/fluid/cargo/power transmission within a ship?
    Are they just assumed to be there, or do you have to plan those out?

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    1. Within each subsystem, fluid flows and the like are simulated using turbocompressors, as are power systems, however, between systems, this is handled automatically for you.

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      1. I take it this means no worrying about power lines and pipes getting severed?

        Because I imagine this is how most mission kills for turrets and the like would happen-it’s not that the turret itself got hit, but that the ammunition elevator or some other servicing system got disabled.

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        1. High voltage power lines are made redundant, and so are low-volume fluid pipes. Generally, the only pipes that service heavy flow are from propellant tanks to your engine, radiator coolant is much lower flow.

          Generally, turrets usually are destroyed by the turret or weapon itself getting hit. The internals getting hit requires penetration through the main bulkhead and whipple shields, which is usually far more difficult to get through than the turret mantlet.

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            1. Far more likely is that they will be as short and straight as possible. About the only case for heavy-flow pipes I can see is fuel-to-engines, and those you generally want as short as is manageable.

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            2. Heavy flow pipes from propellant to engine are designed as part of the each engine (so these need to be developed for each engine if you do design your own engine).

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  5. Yet another one: Is multiplayer of any sort planned for the future?

    Preferably player-to-player, but posting missions and fleets with custom actions to fight against could do as a patch solution.

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    1. Multiplayer (player to player combat) is the number one requested feature amongst playtesters thus far. Unfortunately, it’s a little beyond the scope of this project, however it would definitely be on the table for any future projects.

      Currently, I’m working on getting Steam Workshop support, so mods (including custom missions/fleets/etc.) can be shared easily amongst players.

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  6. By “under the surface”, is it only on small bodies (up to Ceres), or is it possible on larger ones with atmosphere as well? Are there surface installations? Either civilian or concealed guns/missile launchers.
    How is atmosphere modelled? Is aerobrake possible/worth it? If atmosphere composition allows it, are there Sabre-like dual-mode engines? Though if (as the title may suggest) Earth is… unavailable, I’m not sure if others worlds could be used that way. Maybe gas giant ones, by using atmospheric hydrogen instead of oxygen like on Earth.
    While we’re at it, is soft lithobraking possible? (I do expect hard lithobraking to be modelled in some form.)

    One stealth method I don’t remember seeing discussed:
    Launch the craft from a station, and use the station itself to physically hide the departing burn.

    For example, your station is a giant opaque bubble with a catapult inside, that can point in any direction. The bubble is covered with openings that keep busying themselves to try and fool distant sensors (your defensive perimeter made sure there are no close ones), so when your catapult fires the craft, it goes through one of the openings, hopefully undetected. The heat surplus could be hidden by keeping reactors producing heat even when not firing the catapult.
    Obviously, given the initial acceleration, this would be unsuited for crewed vehicles unless extreme body modifications are available.

    The craft itself has been pre-cooled as much as possible, and carries massive heat-sinks to keep it cold while coasting.
    Depending on how good sensors are, it could use a solar sail for manoeuvring. It could also be built around a liquid hydrogen tank, boiling it to keep cold and venting it for manoeuvring. With superblack material coating, you could keep it at a few °K for months if not years, making it indistinguishable from background space, even when exposed to the Sun if its cross-section is small enough – making it the closest thing to invisible, as even occulting won’t work as interplanetary distances.
    So at best hostile forces may guess that you sent something by studying your activities close enough, but they wouldn’t know where and when.
    (That is, if it wasn’t for that spy ring they got right in station management.)

    How possible would that be, both IRL (and at what speculation levels) or in the game?

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    1. The catapult can’t accelerate too quickly, lest it splatter the people against the bulkhead. Even assuming crash couches of some sort and people specially trained for that sort of thing, you can max out at maybe 9 g’s.

      Using basic kinematic equations, given an enormous space station with a 1 km catapult track, you can launch the ship at 420 m/s at most. Let’s say you splurge and get a space station with a 10 km catapult track. That increases your max delta-v to 1.3 km/s. In any case, you can’t really get around the solar system on such little delta-v. Some sources cite 20 g’s as the maximum for very short durations, so that with a 10 km long catapult would get you up to 1.9 km/s. Still not really usable, and insanely expensive to boot (having an electromagnetic catapult that can launch kilotons of mass that’s also 10 km long).

      On the other point about atmospheres, they are very useful for hiding within. However, given that Earth is not a focal point in the setting, only on Titan is atmosphere really relevant. Mars has an atmosphere that allow aerobraking, stealth not so much. As such, most of the game doesn’t really focus on atmospheres much (which is why the ships are not aerodynamic at all).

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      1. For manned crafts, it could give a small boost – useful for a thrust- and delta-V-limited stealth design, but it may not be worth it by itself.

        But I was more thinking about unmanned crafts, who can withstand a far greater acceleration. For example, interplanetary missiles (both anti-ship or anti-cities/habitats). On a 500m catapult with an acceleration of 15500g (today’s rating for artillery shell electronics according to Wikipedia), have more than 12km/s, which should be enough to go places.
        Note that it a first-strike weapon, so building one would probably prompt attacks from anyone else, meaning only a clearly dominant power could build one, as I doubt you could build it covertly.
        Then you have it already, you could also use it to give a small boost to your manned stealth designs, if you ever need them.

        For hiding in Titan’s atmosphere, does it mean atmospheric or aerospace designs are supported? How does it affects combat?
        Given your answer, I guess there is little use hiding in the gas giant’s atmospheres, they are probably too far from interesting things (so it means no He3-extracting plants on Saturn, but then again He3 may be overhyped)

        Also, Titan has seas. Submarine designs? 😉

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        1. For launching unmanned payloads, your solution would be viable. However, it does fall into the category of expensive/difficult methods of stealth.

          A high speed 500 m catapult inside an enormous space station is no small investment, and as you mentioned, it would be hard to build it covertly. Add that to the cost of constantly having to scrub the area of close-range telescopes the enemy may be quietly slipping into high orbit around the system.

          Space stations suffer from the inability to dodge, which means launching projectiles from very far away is feasible. And this giant station would absolutely be a target of priority for any enemy.

          Finally, as you mentioned earlier as well, a simple spy ring would ruin the whole thing.

          It’s a possible stealth design, but I’m not sure any space military would find the benefit to exceed the cost of production and maintenance.

          In game, atmospheric designs are not supported, since the game takes place entirely in space. Neither are submarines. Sorry.

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          1. I actually see one case where someone would build one of those: a system with one vastly more powerful military, probably imperial or hegemonic, essentially unbeatable in conventional conflict. Sort of today’s world if there was only an US-like superpower and Africa.
            For example, Earth vs colonies.

            Earth leaders want to make sure they keep their conventional military advantage, so they build this station. No-one can stop them anyway. They could maybe launch an attack against the construction yard, but that would invite devastating response. (Better have good anti-terror services, though.)
            It would require a significant portion of the Earth military budget, the way developing and maintaining a giant nuclear arsenal does. Once it is completed, it will loom over any upcoming new power or unruly colony like a sword of Damocles, so the leaders may think it is worth the extra cost, and even allows cutting conventional military back a bit.
            It may also be used like drones today, for “precision killing”. If they are feeling particularly unscrupulous, it can even be used as WMD against habitats or cities.
            I’d expect them to put engines on it, so it can dodge at least a little bit. Would be a embarrassing if any suicidal maniac could blow it up by driving a hauler through it.

            Also note that the walls themselves can be pretty thin. Their only use is to prevent others to see inside. There would be a skeleton frame, that would also be used as support for the many ports, but the walls between them could be little more than thin metal plates. I wonder how much the entire station would actually mass?

            Then again, a dominant imperial military with a big, spherical, slightly mobile station armed with one unstoppable central gun as the symbol of their power, we all know how this will turn out.
            They blow an unarmed habitat to make an example/kill “terrorist” leaders, then resistance movements who managed to steal the schematics use unconventional means to lob a nuke or two down an exhaust port and blow the damn thing – being too focused on conventional military supremacy, they neglected unconventional attack vectors.
            Resistance gets hunted down to a Kuiper planetoid, then on a Saturn He3 mining station, but manages to escape. Major resistance figure is revealed to be the lost son of Earth chief of staff. Earth decides to build a new one in Triton orbit, Earth chairman and senior staff move there to oversee it, leak info to try and ensnare remaining resistance forces. Resistance still manages to blow the thing up with the help of local population and thus decapitate Earth upper echelons.
            Earth falls apart, charismatic resistance figure who wanted a System Republic disappears, armed movements turn against each other and general Republic of China-style chaos follows, leaving entire system infrastructure crippled.

            About building one covertly, depending on the exact details, it may be just possible enough that some would try it, for example by camouflaging it as a conventional military base built from an asteroid. I wouldn’t bet on it personally, though, way too much potential to end with a Space Cuba missile crisis and, at best, have to scrub it anyway.

            And no atmospheric designs?
            Why you wouldn’t add something as trivial as a complete aerodynamic model with lift and drag models, air flow at sub-, trans- and supersonic regimes depending on atmosphere composition and temperature as well as gravity, weather patterns and turbulences, air-breathing engines specialised for each type of atmosphere, corrosion, types of precipitations/dust and their effects on components… this is truly an incomprehensible decision.
            Seriously though, how useful can be aerobraking in scenarios?

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            1. Ha! Yeah, you hit the nail on the head with atmospheric designs. If Titan is the only body with a significant and relevant atmosphere (Mars’s atmosphere is so thin comparatively), the additional work needed wasn’t quite worth it.

              As for aerobraking, it is useful for civilian operations with low delta-v. Ultimately, though, it’s a technique that takes a very long time to do to make it useful. Swinging through Mars’ atmosphere 10+ times with a very wide, highly eccentric orbit is extremely slow, too slow for military operations. Plus, it gives your enemy a nice window every few weeks to take potshots at you as you swing by for each aerobrake.

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  7. Short note on thermal expansion stress:

    Steel Young’s Modulus: 30
    Steel expansion coefficient: 9.9
    Temperature difference: 1000K
    Stress: 287kPa, or about 2.8 atmospheres. Negligible.

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    1. Your calculation yields about 300 MPa, so your answer is off by a factor of 1000 (assuming you meant GPa for the Young’s Modulus, and you accidentally dropped the 10^-6 factor for the expansion coefficient).

      Regardless, steel’s Young’s Modulus is 200 GPa, so the actual thermal expansion stress is around 2 GPa (20,000 atmospheres), which is enough to shatter nearly all steels with ease.

      Finally, steel is generally not used in radiators because of how dense it is. Steel radiators would kill your mass ratio. High strength ceramics are used because of the low density and ability to shrug off damage. On the flip side, ceramics tend to suffer even worse thermal expansion stress than steels.

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  8. Hm… there is, possibly, one way to overcame point 5:

    “Making a huge burn and then trying to stealthily coast for months to the target is do-able, but as long as your enemy can track your first burn, they can very accurately predict where you’ll be as you coast across the solar system.”

    Well, we could use gravity assist in combination with some “cold” engines (like cold-gas thrusters) to make SOME course corrections which the enemy would not be able to evaluate correctly. Of course, cold-gas thrusters are tremendously inefficient, but even a slight trajectory correction would eventually lead to the exponential increase in the volume of space where our ship could possibly be. But… it would took quite a lot of time for our ship to became unpredictable on the level necessary to give us any military advantages. So, again, it’s impractical.

    And, of course, the problem “how to hide residual heat” still looms above. There isn’t much use for hard-to-detect thruster, if the ship itself could be detected by residual radiation.

    P.S. As far as I could recall, there was some talks about “pulsed spaceship” with the ajustable center of gravity. Basically, the spaceship was supposed to be constructed of two parts, that could detach from each other and connect again.

    The idea was, that the ship would be placed on elliptical orbit around massive body, and ship’s two parts should be detached in perigee, and re-connected in apogee – thus affecting the resultant force. As far as I recall, this engine could really work… the only problem was, that it’s even more slow than photon engine. I.e. it would took years to accelerate (and the effectiveness of the method decreases with increasing distance from the massive body)

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  9. Thinking about tactics is hard! There are entire schools dedicated to this.

    Let’s try to systematize a bit. There are two types of military craft possible in space.

    1. the Ice Cube as per Eth’s post above (starts cold, keeps cold by dumping (heated) mass, maneuvers slowly and sparingly with some sort of propellant-less drive). ALL your space-based sensor platforms are going to be ice cubes. No exceptions. Having a lot of hydrogen onboard might enable some interesting detection strategies as well, such as a neutron or even neutrino detector. An interesting variation is to just use an icy asteroid to hide in.

    2. the Cold Umbrella (also discussed itt, uses emissions shaping, perhaps to an extreme extent http://physicscentral.com/explore/action/led.cfm , but essentially consists of a chilled shield and a way to efficiently radiate heat in a direction the enemy isn’t, presumably, looking). This is going to be ALL your manned platforms. No exceptions.

    Both work. Exceedingly well, in fact. Radar is useless over space distances. Starfield occultation doesn’t work at all for small-ish things.

    Now, to make our Ice Cube useful, we need to get it to where it can do some harm. The obvious but painful way is with a mass driver, as previously discussed. Interesting variations occur, such as building your accelerator rail inside the Europan ice sheet. The less obvious is to just use a reaction drive where the enemy can’t see it, such as deep inside an atmosphere (think open cycle nuclear (sc)ramjet booster with a small chemical upper stage). This is somewhat inefficient, but we’re working on a military budget, and has the advantage that you can use “fast” orbital tracks to get where you’re going

    The higher you can get its aphelion, the less probable it is that your Cold Umbrella will be detected while doing course adjustments so it can fall back into the gravity well towards just the right spot in spacetime. Note that the higher you are, the cheaper orbit changes become, to the point where you need to spend mere meters of dV to effect degrees of orbital plane change!

    So a typical mission profile for such a craft (or indeed fleet) on a Pearl Harbor style mission would be

    – get accelerated extremely hard out of some planet/planetoid’s gravity well
    – spend months or years coasting
    – effect a course change near aphelion, using a propellantless drive
    – swing back in to where your target actually is, keeping your nose towards it and emissions at a minimum
    – turn on your nuclear lightbulb engine to decelerate at the last possible moment
    – unleash hell when in tactical range

    if you’re detected on the inbound leg, can you tell? probably not, as sensors are all passive and a smart enemy will send an Ice Cube drone out to meet you, you will not see it, your friends will not see it, you will die an ignominous but mercifully short death. So if you too are smart, you will probably jink constantly with said propellantless drive, to complicate targeting and force the Ice Cube to go hot for terminal guidance/maneuver; note that jinking gets less and less effective as you get closer…

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    1. Or send a Q-Ship that has the same general cross section and same order of mass as a civilian craft along an unremarkable orbital route, or spend years doing peaceful navigational training with your warships so your attack appears no different from the previous ten innocent passages.

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  10. It is a conceit to assume that the theoretical opponent has an already deployed modern sensor network. The reality might be much like the USA’s Satellite Network. Lots of civilian communication relays, a mostly outdated, but slowly being replaced military communication relay (and leasing of civilian relays) and a much smaller number of observation satellites for weather, science, mapping and intelligence gathering many of which are decades old.

    Governments don’t have unlimited funds and they don’t know when space-war will break out. So they’re prepared only for previous wars and painfully lagging towards what their most recent wargames told them.

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  11. I have no idea where to ask this, but this seems like a decent place, given it gives one answer to my question in terms of what we wouldn’t do –

    What color would we paint ships?

    Obviously, camouflage is right out; not black, but also not gray. Ships and planes are gray for camouflage. Given space is optically transparent, and (from my understanding) optical ranging can in some ways reach farther than radar given it’s passive, I’m seeing a number of possible options –

    1) Anti-flash white, to protect against nukes

    2) Some sort of heraldic color, recognizable through spectrometry so you could identify a ship’s affiliation from a single pixel signature. (This might suggest different radiator arrangements for IFF purposes; I understand modern-day tanks have something similar.)

    3) Dazzle patterning, a la World War 1 ships, to foil optical ranging and tracking – this seems really unlikely given you’d have a stationary backdrop of stars to compare it to

    Would love any input!

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    1. Actually, no paint is most likely. As mentioned in a different article, the space shuttle main tank was originally painted white. NASA discovered they could save 272 kg (600 lb) of mass by not painting it, giving them a bit more delta-v.

      Generally, anything to foil sensors would probably be ineffective since ships would be tracked by engine plume and radiators (and even gun flashes). Anti-flash paint would actually be less effective against nukes than many raw metals. In game, most ships run with an aluminum whipple shield, which is far more reflective than most paints.

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      1. Tangential question, sorry-
        Do visible insignia have a purpose on ships, or would IFF be completely electronic / by profile? Would we have big Normandy stripes on ships, or the chevrons on IDF helicopters and US tanks, or would it just not be worth the trouble?
        (Also, wanting to recheck if unique radiator folding patterns would work for IFF, or if there’s an optimal solution that these would deviate from, or if it’d be impossible to tell at a distance.)

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        1. At a distance, most ships are a single pixel of light, though the single pixel can be very clearly identified based on the distribution of wavelengths. So the placement of radiators and the like doesn’t matter so much as the temperature and materials used.

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  12. You mentioned drone ships as being impractical – open to electronic warfare, and being out-strategised. How practical is the idea of a fleet of stealthed drone ships, spaced thousands of km apart, with strategies and tactics being beamed to them via a tight laser from a single manned (non stealth) command ship?

    I was originally thinking of this as a sort of inter-system invasion. The mothership parks on the edge of the Oort cloud (and yes, I know anything that massive would be visible the second it turned around and started slowing down), starts harvesting asteroids to replenish resources, and destroys any satellites it’s detected coming out to meet it. It then launches the invasion fleet of drones and the command ship – far enough out that burns are able to focus all radiation away from any possible sensors, the ships themselves are able to cool down from the burn enough over the years it would take to come in-system, and minor burns with cold engines would be enough to radically change their course.

    The idea would be that the command ship sits thousands of km away, perhaps tens of thousands of km away, safely out of reach of any incoming fire, while using the drones as both shields for incoming missiles and drones, and… well, an invasion fleet to sweep the system clear of anything capable of fighting back.

    Problems with electronic warfare could be reduced by having the drones essentially be in standby mode outside of combat mode – having brief preprogrammed ‘windows’ where they’re listening for new commands. This could also be used for scanner drones – if they are only scanning their surroundings 1/20th of the time, they would be a lot less vulnerable to their sensors being destroyed by EM bursts, lasers, etc

    I’m relatively new to hard space combat, and my science and maths is very basic, so please excuse (but point out!) any gaping holes in this…

    One very obvious problem is the strategic inflexibilty of it. You essentially have your entire fleet coast through the system for 5 – 20 years on an inflexible pre-planned invasion route. And your opponents would know something is coming, because the command ship wouldn’t be stealthed at all (no point – it’d be impossible to hide the heat signature of a manned ship)

    Another problem is that any society capable of sending ships from one star to another is likely to have technologies that make the entire debate worthless. It would be far easier for them just to drop rocks on their opponents heads, use their advanced weapons, never bother to enter the inner system, etc…. But sidestepping these issues…

    Once again, I’m no scientist. The following problems may not be an issue, depending on the maths. Could someone who does know the math tell me if these are issues or not?

    – Sensors may be able to detect reflections from the comms lasers from the dishes that receive them

    – Since the command ship wouldn’t be stealthed, it’s likely that high powered telescopes would be looking in that general area anyway. Which raises it’s own question – what is the relation between size and distance, for spotting ‘cold’ objects? (how far away could a dead car be spotted in space? how far away a soda can? How far away a dead aircraft carrier?)

    – There’s nothing stopping the defending side from using ‘active radar’, or the equivalent. Shooting powerful lasers out so they can pick up the reflection of incoming ships. This would drastically increase their range. But would active detection systems work over interplanetary distances? I have no idea.

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