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Applying Nicoll's Law
October 2, 2013 8:54 AM   Subscribe

"Voyager's main transmitter shines at a feeble 22 watts, which is comparable to a car-mounted police radio or -- in visible light -- a refrigerator light bulb. Though incredibly weak by the standards of modern wireless communications, Voyager's signal is astoundingly bright when compared to most natural objects studied by radio telescopes." -- Even as Voyager 1 has left the Solar System (again), it can still be easily detected by telescopes on Earth, showing once again there ain't no stealth in space.
posted by MartinWisse (51 comments total) 20 users marked this as a favorite

I thought Nicoll's Law involved improbable, nearly lethal accidents?
posted by happyroach at 9:04 AM on October 2, 2013 [2 favorites]

My first objection was at least 3 points down...

"Well FINE!!", you say, "I'll turn off the engines and run silent like a submarine in a World War II movie. I'll be invisible." Unfortunately that won't work either.

Although I suspect there will be at some point some very very cold dark sleeping satellites on odd unexpected orbits , if there isn't already.
posted by sammyo at 9:52 AM on October 2, 2013

One of my favorite parts of the Mass Effect series was the thought and detail someone had gone into on the physics, thermal and electric charge management concerns, and stealth aspects of starships with their FTL MacGuffin drive and how it informed flight operations and combat. It was rarely mentioned in the actual gameplay, but the in-game encyclopedia had page after page exploring it. Obviously, this was all in service to the plot. The Normandy needed to be a stealth ship, and there needed to be great big space opera fleet battles, but the justifications for how it all worked were fantastic.

I always figured someone at Bioware was heavily browsing Atomic Rockets at the time.
posted by figurant at 10:00 AM on October 2, 2013 [3 favorites]

When I worked at Green Bank, the Mars Phoenix mission was just about to land. That mission was designed with no direct-to-earth communications; it only had enough transmitter power to relay signals up to the mars reconnaissance orbiter, which then had the power transmit back to the deep space network on Earth. The problem was that Mars missions had experienced a series of failures right before then, so it was basically a requirement from NASA that there be continuous telemetry coverage of entry, descent, and landing in the event of a failure. Since the DSN couldn't provide this, NASA had to step up to the largest fully-steerable antenna in the world, the GBT.

So while the folks at JPL and the Lunar and Planetary Lab are all watching their detailed telemetry relayed via MRO, covered by media from all over, a handful of us are sitting in the Faraday cage that the GBT is controlled from staring at a waterfall plot of the tiny signal from this tiny lander that just happens to be falling towards Mars. We can't decode most of the transmitted data, but we can see the spacecraft slowing as the doppler shift moves the signal around in frequency, and specific transmitter behaviors relay the stage of the descent; separation of various parts, parachute deployment (big doppler shift), and eventually the signal that the lander was on the ground and alive. A handful of seconds later the folks at JPL would learn that same fact after it had been relayed to the MRO and then Goldstone and then Pasadena, but we saw it first.

The folks who did this tracking of Voyager are friends of mine, so I'm glad to hear they're still hunting down various space missions.
posted by kiltedtaco at 10:02 AM on October 2, 2013 [42 favorites]

Cool story, kiltedtaco, thanks for sharing!
posted by Triplanetary at 10:12 AM on October 2, 2013

Receiving it ain't all that easy. For Voyager 2's Uranus and Neptune encounters, the only receiver on earth sensitive enough to pick up its signal was the VLA. NSF let NASA use it ten hours each day.
posted by Chocolate Pickle at 10:21 AM on October 2, 2013

My objection was dealt with in item 5. So I guess I won't be posting about it here... or building any giant directional heat sinks for my spaceship.
posted by Triplanetary at 10:22 AM on October 2, 2013

Jocelyn Bell, the discoverer of pulsars, handed out little slips of paper at a talk I was lucky enough to attend.

On the paper, paraphrased: "In picking up this piece of paper, you have spent more energy that all the energy received from every known pulsar since their discovery."

And it wasn't even close.

Our routinely observed pulsars have flux densities measured in milliJanskys, where a Jansky is 1E-26 watts per square metre per Hertz. Use the world's largest telescopes (say 1E4 square meters, an overestimate even for the Green Bank telescope with a 100m diameter) and collect the flux over a full GHz of bandwidth (1E9 Hz) and you're still getting 1E-16 Watts from a 1 mJy pulsar. You'd have to integrate for about 3 billion years (if I'm doing my math right) to get ONE measly Joule of energy.
posted by RedOrGreen at 10:43 AM on October 2, 2013 [6 favorites]

So looking over the arguments about stealth in future/scifi combat, it would then seem to be best that one scrap the idea of stealth, and go with using an asteroid or very small moon as either an enormous protective shell/armored hangar that either conceals and protects a smaller ship inside of it, or as the ship itself, in something like a combat-oriented version of the UESC Marathon. Using a asteroid/moon made of layers of different aggregate materials could provide different protection against different weapons systems. A thick outer layer of loose, dusty aggrigate against explosive weapons, which would not only minimize structural damage, but the ensuing dust from the explosion would surround the area with particulate matter that would interfere with both directed energy weapons as well as targeting and scanning equipment. A layer of harder, larger aggrigate rocks would provide further explosive absoption, and a very dense, perhaps some sort of crystalline structure would be the innermost layer - maximizing the benefits of the strength of the structure, while the outer layers minimize the weaknesses of the material, not unlike how a gem cutter exploits the structure of a diamond to cut it down.

So really, it seems that one needs to make something so well protected that stealth really doesn't matter.
posted by chambers at 10:44 AM on October 2, 2013

Yeah, but chambers, how ya gonna move all that mass? You could get it moving in a straight (relative to relativity) line, but Newton help you if you need to turn.
posted by Panjandrum at 11:11 AM on October 2, 2013 [1 favorite]

there ain't no stealth in space.

Voyager's 20W signal is visible primarily because it's being transmitted through a high gain parabolic dish aimed at earth. That tiny signal would be much, much harder to spot if it was more or less omnidirectional.

Stealth specifics:

1)Against passive electromagnetic sensors, wrap your ship in a Faraday cage. Search for your enemies a) by briefly extending sensor packages through the cage and/or b) aiming a telescope through a copper mesh. B) will degrade telescope performance but you'll still be dead quiet electromagnetically on anything except very low frequencies.

2) Passive optical? Minimize the effective albedo. Paint it black as the Stones say, hough there are more sophisticated options. Position heat sinks on one side of the ship only, pointed away from the expected direction of enemy approach. Pretty effective so long as you maintain...

3) Distance. Reflected light and thermal signature are both reduced by the inverse square law and an omnidirecional signal at great range would no be easy to spot. Distance is even more effective against active sensors which (according to the radar equation) lose effectiveness at a rate of distance^4. Ouch. Therefore a sensible space battle would take place from at least light seconds away, preferably light minutes. Expect battles to be fought with laser weapons, railgun projectiles travelling at a significant fraction of c or (if you're patient) drones that toodle to their targets over the course of a few months.

Yes, it's possible in principle to dodge lasers at that distance, but an enemy who's doing evasive maneuvers is going to show up like a strobe light on passive infrared sensors. It's not something they'll be doing all the time unless they're very stupid, so course prediction should be easy if you've spotted them by other means. Their first warning that laser light is on its way will be getting hit.

4) Red Baron it and dive at your enemy with a star or planet at your back. It's a trade-off (your enemy might notice that a star's gotten a tad dimmer) but it's pretty classy.

By all means, O my enemy, believe that it's impossible to stealth a space warship. Besides, as far as you know you don't have any enemies.
posted by justsomebodythatyouusedtoknow at 11:16 AM on October 2, 2013 [2 favorites]

Yeah, but chambers, how ya gonna move all that mass? You could get it moving in a straight (relative to relativity) line, but Newton help you if you need to turn.

hmm.. uh, ummm. Reverse the polarity of... that thingy that makes you go. Something something sour the milk... Something something get a cup of really hot coffee... maybe turn it off and on again...

I don't know, that's the engineering department's problem. I'm just here to push buttons and blow stuff up in space.

But seriously, I was more focused on figuring out a solution to the varied problems of detection and combat in space. At least with those variables there is a reasonable amount of current scientific data to play with fairly well. As far as actually making the propulsion and such work in a realistic sense in a projected future of technological advancement, I leave that to those more well trained than I. I was just starting from the idea that spaceships and some form of near-FTL or FTL tech is present, and a large enough economy and presence in space is sufficiently large enough to support large scale battles between planets and/or solar systems.
posted by chambers at 11:33 AM on October 2, 2013

Chambers, your argument is plausible against directed energy and explosive weapons but I think you're underestimating the firepower of projectiles travelling at semi-relativistic speeds. A railgun-launched ball bearing travelling at even a tiny fraction of c would punch a neat hole through even a large asteroid. Well, not a neat hole because it will be losing a bit of energy all the way through; expect a much larger exit wound. If I have the energy budget to go rapid fire and/or launch shotgun blasts of small projectiles my alpha-strike will reduce your base to a fine cloud of dust.

Maybe your name is Dr. Forester and you live in Deep-13, but past a certain muzzle velocity even a planetary crust isn't going to protect you if I know your location. Presumably I've been monitoring you build the thing for months.

You won't be able to do evasive maneuvers with an asteroid base because, as Panjandrum points out, your asteroid base will be near-impossible to maneuver even if you have warning that a shot is coming at you.

If I'm wrong about stealth then a space battle would go to the side that fires first. The situation would be even less stable than the 20th century cold war.
posted by justsomebodythatyouusedtoknow at 11:36 AM on October 2, 2013 [1 favorite]

I think the big takeaway lesson from both the "stealth in space" discussion and the larger Atomic Rockets is that space warfare, if it happens, won't resemble any of the metaphors used to describe it. The laws of physics and engineering mean it won't resemble age of sail combat, or battleship combat, or aerial dogfighting, or submarine warfare, or any of the cliches used to describe space warfare. It will be it's own thing, with tactics and weaponry dictated by the environment and technology, and nearly all descriptions of it in fiction resemble Herodotus trying to describe modern submarine combat in terms of swimming Greek phalanxes.

I feel for SF writers, trying to make make space combat interesting, with things for the humans to do, as opposed to watching ICBMs that take weeks or months to arrive... and damn. Even I had to use a lousy metaphor.
posted by happyroach at 11:41 AM on October 2, 2013 [5 favorites]

While full stealth in space might be really hard, practical and useful stealth can be achieved as long as you can beat existing sensing technology. Which circa 20th century might mean that you deploy a reflective balloon in front of your spacecraft that suppresses your laser, radar, visible, and infrared signatures by reflecting the blackness of space to the earth below. And you add a disinformation campaign in which you lie about the spacecraft blowing up 6 days after it was launched to cover its transition into stealth mode in a new orbit, and you leave a decoy in the old orbit.

"A spy satellite's rise... and faked fall",
"Anatomy of a spy satellite",

The MISTY-class satellites' stealth ability seems to be at least partially directional, however--and if you're unlucky, a Canadian amateur satellite-spotter will notice a mysterious object overhead that isn't listed in the Space Track catalog, and he will eventually put together all the clues and guess that it's your spy satellite that you claimed blew up. And he'll publish his findings, and your only recourse will be to look up his address and command the satellite to treat his location as a hostile zone, so that when it flies over his city it points its stealth balloon right at him and when he looks up from his balcony with binoculars he can't see anything (but his friends in other cities can still see it).

From "I Spy" in Wired 14.02:
"They know where we live," Molczan says excitedly. He believes that when it was originally launched into orbit, the satellite was programmed to be invisible to the Soviets, but the National Reconnaissance Office failed to take the hobbyists into account. Molczan is convinced that after reports of the observers' USA 53 sightings, the satellite was reprogrammed with the coordinates of every area where skilled hobbyists live.
(Trevor Paglen's book Blank Spots on the Map has a great chapter on this story.)
posted by jjwiseman at 11:43 AM on October 2, 2013 [6 favorites]

And justsomebodythatyouusedtoknow just proved Nicoll's law:

"It is a truth universally acknowledged that any thread that begins by pointing out why stealth in space is impossible will rapidly turn into a thread focusing on schemes whereby stealth in space might be achieved."
posted by MartinWisse at 11:47 AM on October 2, 2013 [2 favorites]

I seem to remember that on ST:TOS, Kirk just flew the Enterprise into a handy ionised gas cloud or similar. And the Romulans had cloaking technology, so there's that.

As for Voyager being hard to receive - well, it all depends what you mean by hard, and receive. Back in 2006, a bunch of German radio hams picked up Voyager 1 at 14-odd billion km, albeit with a borrowed 20m dish. (They were practising for a planned ham radio satellite mission to Mars. Deep space missions make very useful beacons for testing stuff; Pioneer 10 was a favourite for many years.) But the hams didn't decode the signal; a scratch on a waterfall is one thing, but solid data lock quite another.

The best bit of this story, I think, is that just about _all_ of the basic techniques that make the radio link of your digital mobile phone work were developed first for deep space comms. There's a very accessible and entertaining account at USC that basically takes you from Sputnik to the iPhone. One of the chief players is one Andrew Viterbi, who designed the eponymous coding method for the Voyager missions (still a mainstay of digital comms), before co-founding a company called Qualcomm - the Intel of mobile phone comms. (It reads as if they had a whale of a time, too. and I fully intend to dig deeper into that story.)

Being radio and a bit weird, this side of things rarely gets mentioned in the "What did the space race ever do fo us?" debate, but I reckon modern mobile comms is worth a salute or two.
posted by Devonian at 11:53 AM on October 2, 2013 [5 favorites]

your argument is plausible against directed energy and explosive weapons but I think you're underestimating the firepower of projectiles travelling at semi-relativistic speeds.

Point taken. I was considering railguns and other kinetic kill vehicles, but had not considered those forces when used at semi-relativistic speeds.

When faced with such a weapon, the few options available are interception, deflection, or absorption.

Absorption to any reasonable degree would have to be addressed by some future tech that would vaguely resemble 'shields', which at the current or near-current level of tech are only effective against radiation. Any kinetic reactive material, like those used on tanks today, would not react in time to stop such a fast moving KKV.

Interception would be nigh-impossible, considering the time to acquire, track, and fire would be a few seconds late, and the KKV is several hundred thousand meters away, having already passed through me.

Deflection would require some sort of array of mobile gravity wells spinning around the ship to bend the trajectory enough to cause the KKV to miss, but then again, that same gravity well would have negative effects on the ship itself, not to mention the tech and resources needed to control and contain such an object.
posted by chambers at 11:54 AM on October 2, 2013

MartinWisse, that's not an argument.

Chambers: I was just starting from the idea that spaceships and some form of near-FTL or FTL tech is present

If you've got fantasy FTL technology, expect battles to be taking place at light year ranges. Anything less than that would be like fighting in a Tarantino basement. Here are two scenarios, depending on what fantasy tech you're talking about.

a) Assuming you're talking about jump drives and that there are no FTL sensors or communicators, you get Battlestar Galactica. Scout ships jumping around looking for the enemy main force, searching a sphere of a few light seconds around themselves with every jump. Without FTL communications, fleets and/or capital ships would not be able to jump frequently/unscheduled or they'd lose contact with their scouts. Whichever fleet gets spotted first will fall victim to some kind of ambush attack, hundreds of enemy raiders jumping in at ranges measured in kilometers, and they'd need to jump away very fast or die. The show actually did a pretty good job of thinking through the implications of its fantasy tech.

Capital ship gun battles and ramming -- no. Just no.

b) If you're talking about warp drives (rather than discontinuous travel), FTL communications and FTL sensors you get Star Trek, sort of. Sensible battles would be fought at extreme distances with warp-capable drones (photon torpedoes). Directed energy weapons (phasers) would make sense, but only as CIWS system to shoot down enemy torpedoes moments before impact.

Star Trek battles fought with phasers can't be made plausible in a universe with warp drives even if you add more technobabble. Dodging would be far too easy for a superluminal ship. If nothing else you could fly away and outrun the laser/phaser/whatever.
posted by justsomebodythatyouusedtoknow at 12:05 PM on October 2, 2013 [3 favorites]

Course it's not an argument, it's an observation. I mean, you're still wrong, but I'm not arguing with you about it. If you want to believe in stealth in space, go ahead.
posted by MartinWisse at 12:13 PM on October 2, 2013 [1 favorite]

There is one other scifi scenario to add to your list, wherein FTL travel is possible only through large 'jump gate' facilities, and other forms of propulsion are confined to speeds that are less than relativistic speeds, somewhat like how the EVE Online universe 'works'. That also presents a major strategic problem of choke points and heavy static fortifications surrounding it.
posted by chambers at 12:18 PM on October 2, 2013

wherein FTL travel is possible only through large 'jump gate' facilities

Stargate comes to mind.

I mean, you're still wrong, but I'm not arguing with you about it. If you want to believe in stealth in space, go ahead.

Look, I don't have a religious belief in the possibility of space stealth. I know you're withdrawing from the conversation and that's fine, but I'd honestly like to know what you think I'm wrong about.

I'm quite sure I'm right about the uselessness of active sensors at light minute ranges. The radar equation's punishing 10^-4 distance penalty would rule out almost anything. LIDAR might be an exception - I'd be willing to hear an argument.

As for passive sensors, I could much more easily imagine that I'm wrong but I'd like to hear an argument. If you've got a link about something other than the Voyager probes which are actively trying to be seen, I'd like that.
posted by justsomebodythatyouusedtoknow at 12:34 PM on October 2, 2013

Wasn't there something about a cyrogenic laser a while back? I know it was mentioned in Sundiver by David Brin, but he mostly ignore physics in favour of a good plot. I probably should understand how lasers work, but honestly the whole three energy state thing always made my head hurt, so I learned it well enough for the test and then forgot it.

Anyway, lets suppose you can dump all your heat out through a laser, at least temporarily. Then I can shine the laser somewhere that is UNLIKELY to have someone there; say out of plane of the solar system, or directly at the sun. Since lasers are highly directional, doubly so in vacuum, unless someone is in a very narrow cone in the place I'm pointing it, wouldn't I be able to keep my emissions in every other direction near zero?

Also, I love how every physicist assumes that chemistry and materials science are never going to improve, and that current heat-containment materials are as good as they will ever get. Sure, over long timescales things would equilibraite, but if I launch a ship with sufficiently good thermal coating you could keep cool for a certain amount of time. Not forever, but say a few hours, so long as you didn't have any engines on.
posted by Canageek at 12:46 PM on October 2, 2013 [1 favorite]

To elaborate, the main problem I have with the original article is its point 3) regarding thermal signatures when running quiet.

A Russian Oscar submarine is a cylinder 154 meters long and has a beam of 18 meters, which would be a good ballpark estimate of the size of an interplanetary warship. If it was nose on to you the surface area would be 250 square meters.

To keep the lifesystem in the spacecraft at levels where the crew can live, you probably want it above 273 K (where water freezes), and preferably at 285-290 K (room temperature).

Those assumptions only hold if there's spam in the can. A drifting unmanned craft could be orders of magnitude harder to spot.

Even if we assume a giant hot submarine sized ship, the article claims that with current technology that ship could be detected at 129 light-seconds. That's only a couple of light minutes - much longer than usual imagined space battles but ships duking it out in the Kuiper belt could plausibly be further away than that.
posted by justsomebodythatyouusedtoknow at 12:57 PM on October 2, 2013

people think of the doctrine of 'Mutually Assured Destruction' is a function of the power of nuclear weapons, but it's also a function of the relative fragility of the biosphere wrt nuclear warfare.

there won't be any war in space (at least after the first one) because the infrastructure for getting into and surviving in space is just too fragile and too expensive. any war would quickly turn into armageddon. conversely, even more than MAD, no rational actor would even allow the possibility of war in space. and i think this is even independent of whether there is meat in space: sustaining robots runs into the same problems.

conflicts would have to be resolved in a ritual manner, where respecting the outcome is insured by the knowledge of all the participants that the alternative is total destruction.
posted by at 1:17 PM on October 2, 2013 [2 favorites]

Anyway, lets suppose you can dump all your heat out through a laser, at least temporarily.

Also, I love how every physicist assumes that chemistry and materials science are never going to improve,

Angry physicist here to tell you ENTROPY DOES NOT WORK THAT WAY</morbo>. I can't get rid of heat by making something even hotter. Physicists tend to know that chemistry and materials science cannot overcome basic thermodynamics, and to the extent it appears that they do, it's only due to misunderstanding of the chemistry/materials science.
posted by kiltedtaco at 1:20 PM on October 2, 2013 [3 favorites]

How about "tame black hole as heat sink"? I think I heard about that one once, but don't remember the details.
posted by radwolf76 at 1:40 PM on October 2, 2013

You could try giving the job of reversing entropy to Maxwell's Demon, but so far he's refused to take the job on. A quick canter through the history of the Demon in physics, though, is quite a good light to shine on the 'no stealth in space' argument. This shit has history.
posted by Devonian at 2:02 PM on October 2, 2013

Nice to see we have all the usual suspects here today. Hello cooling lasers, nice to see you again. Hi, "But future science!", looking good today.

I 'm going to propose Happyroach's Corollary to Nicoll's Law. It takes the form of the following:

Stealth in space discussions invariably boil down to:

A: "Stealth in space is impractical."

B: " But what about [something invariably impossible from a physics or engineering standpoint]?"

A: "That won't work because of [reasons]."

B: "But what about [something else impossible according to physics or engineering]?"

A: "No, because of [reasons]."

B: "I will argue the math now, though I don't quite understand it."

C: "But what about this [impossible according to physics or engineering] thing I read in a SF novel?"

And so on. It can probably be done as a flow chart with no decision diamonds and a loop from C to A.
posted by happyroach at 3:25 PM on October 2, 2013 [2 favorites]

[something invariably impossible from a physics or engineering standpoint]
"I will argue the math now, though I don't quite understand it."

I'm not sure why a relatively cold, relatively small unmanned ship would be impossible from an engineering standpoint, or why it would be easily detected from several light minutes away. Going unmanned isn't moving the goalposts, it's trying to depict what a realistic warship would have to look like.

Small: having no crew and no life support significantly reduces the cross-section.

Cold: Going from +21 degrees C to -55 degrees C (acceptable for MILSPEC electronics) reduces the thermal signature by ~50% while drifting.

As per the calculation in the article, the range at which such a ship would be detected with current technology is well under a light minute. Rd = (13.4 * sqrt(A) * T^2)

Multiple light minute ranges are ridiculously long (we're only eight light minutes from he sun) but that's no an argument against he idea. It only shows that realistic space battles would need to be fought.

I didn't do myself any favors at the beginning of his discussion by making what I concede was an unrealistic heat sink proposal. What I've proposed here is not impossible (-55 degrees is quite possible as an operating temperature from an engineering standpoint). I did do the math and I have reason to think I do understand it.

You're not making an argument, you're just being insulting.
posted by justsomebodythatyouusedtoknow at 4:24 PM on October 2, 2013

Your post advocates a

( ) technical ( ) strategic ( )

approach to space stealth. Your idea will not work. Here is why it won't work. (One or more of the following may apply to your particular idea.)

( ) Entropy doesn't work like that
( ) Materials science can't do that, no matter hard we try
( ) You'd need to be much further away than you think
( ) It requires fictional technologies that aren't feasible.

Specifically, your plan fails to account for

( ) Physics
( ) Capabilities of sensors
( ) The coldness of space

Furthermore, this is what I think about you:

( ) Sorry dude, but I don't think it would work.
( ) This is a stupid idea, and you're a stupid person for suggesting it.
( ) Nice try, assh0le! I'm going to find out where you live and burn your
house down!

posted by BungaDunga at 4:25 PM on October 2, 2013 [2 favorites]

Space stealth, schmace stealth.

I'm way more excited to have found my new favorite measurement.
posted by Sphinx at 4:47 PM on October 2, 2013 [1 favorite]

The Normandy needed to be a stealth ship, and there needed to be great big space opera fleet battles, but the justifications for how it all worked were fantastic.

One of my favorite bits in Mass Effect 2 had the Normandy sneaking up to a hostile geth (alien robot) space station, and the ship pilot, Joker, says to Legion, the geth crew member, "You know that they can just look out a window and see us, right?" Legion's response: "Windows are a structural weakness. Geth do not use them." Well, that was easy.
posted by Halloween Jack at 7:02 PM on October 2, 2013

You don't know how many times I've heard someone say ergs per second per square centimeter per Hertz per steradian, and nobody even blinks.
posted by kiltedtaco at 7:48 PM on October 2, 2013 [2 favorites]

kiltedtaco: Sorry, I thought you could fairly easily swap heat into another form of energy, say, light, then dump it into another location, say space? It isn't going to be efficient, but I don't see how that violates thermodynamics provided you have an external power source (Say, a very low-heat battery).

Also: You seem to have said 'BAH THERMODYNAMICS' without actually reading my comment. I fail to see why you couldn't have a very good thermal insulator (Which, you know, I've seen; McMaster has one they are patenting that I've seen heated up to red-hot with a blowtorch while someone holds the other hand, just a few inches away. So sure, there is is heat at one end of the rod, but you won't feel it at the other side for a good long while.)

Or here i an idea: Why don't you just store the heat in a chemical substance? There are about a billion endothermic reactions out there that could turn that heat into a more complex chemical structure. Some of them are very endothermic.

I may not know thermodynamics very well, but I do know there are reactions you do that get damn cold, damn fast, so you could suck up heat with them. They aren't very common, but they exist. Couple that with good thermal insulation on certain parts, and I don't see why it isn't possible to hide all the heat a ship is giving off for a few hours. But of course armchair physics geeks will ignore this as they don't know anything about chemistry, and only look at things in a very theoretical model and over long time scale, not you know, short timescales and practical cases.
posted by Canageek at 8:00 PM on October 2, 2013

I find it a little incredulous that you can't do stealth at all in space. I tried looking into various websites and it seems that it boils down to "we can detect even minor variations to the background radiation levels (i.e. empty space at ~3K) and any ship worth its salt will have a lot of radiation being emitted due to thermodynamic considerations."

The two key challenges to stealth are either avoid generating radiation or be able to properly hide the radiation. The linked website suggests that its not possible to do either.

For avoid generating radiation, the argument is that your engines will need to produce significant radiation to be able to impart the required acceleration for tactical maneuvers to large spaceship masses. I don't get why heat producing engines are really needed. How about other means of propulsion like light sails (use two or three far apart heavily guarded master ships as the light source) or gravity based slingshots (send out asteroids or use massive dumb decoys as asteroids and small fighters slingshot around them like comets to change directions) or anything else that ?

For hiding the radiation, the argument is that you cant do that because of thermodynamics (whatever you use to hide the radiation would quickly become hot enough to be detected). That's a weird declaration because it doesn't take into account the fact that different materials have very different heat absorption & release characteristics and its entirely possible to temporarily store heat in some container and jettison the container at convenient moments (say when right next to Jupiter or behind a planet). Stealth is needed temporarily, just the time it takes to get into the right position to make the kill.

Is this correct or am I missing something? The linked website in FPP is a bit too glib and smug to really answer or provide details. A lot of links are dead or outdated or too generic(.

Any suggestions on where to look? What am I missing?
posted by TheLittlePrince at 10:34 PM on October 2, 2013

By all means, O my enemy, believe that it's impossible to stealth a space warship. Besides, as far as you know you don't have any enemies.

If you are warmer than 3K, you are visible. If you aren't, you're dead.
posted by eriko at 11:01 PM on October 2, 2013 [1 favorite]

Happyroach and killedtaco, and others, assuredly, I'm going to make you sad and I understand why, but I'm going to anyway. Simply put, we have no way of knowing if our understanding of science is correct, and what we might discover in however many years or what another life form may know. Yeah, that's an easy way out and probably something a lot of people say. But it's true! We are still searching for the theory that unites quantum physics and general relativity. We could, at some point down the road, discover one or both are wrong. As a lay person, I suspect we will just as we have with other theories thought to be correct.

Yes, I'm sure this is one more thing that is said when the subject comes up, and I'm sure is frustrating. But! It's also the one right now that is the one that can't be disputed, no matter how small the chances are.

But also, there is the never say never principle. Because how many times throughout History have we said something is impossible and someone makes it happen. It ends up being within the theories that exist, just executed in a way not considered.

Which is to say, in all actuality stealth in space is probably impossible and there is no known way it could happen. But to deny that at some point in the future something can't change and make it possible is silly and wrong-headed (history stands by this!) to say Canageeks point about new materials is wrong. Sheet, I grew up being told it would be impossible to map the human genome. Now, within my lifetime, I can pay $100 to get chunks of it analyzed and a basic understanding of those chunks sent back to me.

Yes, I realize this is a cop out, in a way... Because with it, then nothing is impossible. But its not unreasonable to allow for it in a hypothetical discussion. If you were in a room being asked to build such a device, sure. In a thread where people are trying to imagine what might be at our disposal in a few hundred years? Less reasonable.

Or maybe a better question to you physic wonks, how do you see physics shaking out in the next 100, 200, or 300 years?
posted by [insert clever name here] at 12:08 AM on October 3, 2013

kiltedtaco: Sorry, I thought you could fairly easily swap heat into another form of energy, say, light, then dump it into another location, say space? It isn't going to be efficient, but I don't see how that violates thermodynamics provided you have an external power source (Say, a very low-heat battery).

Say I turn on a lightbulb. The light dumps energy elsewhere. What happens to the temperature of the bulb itself, does it cool down or does it heat up? The reasons behind this are thermodynamic and not specific to lightbulbs.

And ok already, yes we all know that insulators exist. Nobody is disagreeing. The problem is jumping from "insulators exist" to magically beaming energy away. The yelling is about the latter, not the former.

Simply put, we have no way of knowing if our understanding of science is correct,

Yeah, this does make me sad, because it's basically a path to disregarding all of the really fucking awesome science we do know in favor of dreaming up fantasies. Which is not inherently bad on its own, but did I mention the really fucking awesome science we do know? It's way cooler.
posted by kiltedtaco at 6:12 AM on October 3, 2013 [4 favorites]

figurant said: I always figured someone at Bioware was heavily browsing Atomic Rockets at the time.

Yes, they were. One of the developers privately contacted me and mentioned it. They also studied Ken Burnside's Attack Vector: Tactical.

This was hinted in an Easter Egg in Mass Effect 2.
posted by Nyrath at 11:43 AM on October 3, 2013 [1 favorite]

[insert clever name here] said: I'm going to make you sad and I understand why, but I'm going to anyway. Simply put, we have no way of knowing if our understanding of science is correct, and what we might discover in however many years

Yes, just like clockwork this tired old trope keeps cropping up. I cover that in the Maybe A Future Scientific Breakthrough Will Let Me Have My Way section of the page Respecting Science.

At the very least, a new scientific breakthrough has a 50% chance of making things worse, not better.
posted by Nyrath at 11:50 AM on October 3, 2013 [2 favorites]

Hah! That's awesome, Nyrath.
posted by figurant at 12:23 PM on October 3, 2013 [1 favorite]

This was hinted in an Easter Egg in Mass Effect 2.

Is that the "Isaac Newton is the deadliest sonofabitch" one?
posted by ROU_Xenophobe at 12:28 PM on October 3, 2013 [1 favorite]

Yes, the "Isaac Newton is the deadliest sonofabitch" clip. The one with Serviceman Burnside and Serviceman Chung.
posted by Nyrath at 12:54 PM on October 3, 2013

Nicoll's law is like the flip side of the Turing Tarpit: In the former science says that your ultimate goal is impossible even as governments are launching stealth spy spacecraft, while in the latter the math works out so that you can do anything but it's so impractical that you will never actually do it. What they have in common is a lot of repetitive discussion sucking the air away from the interesting bits.
posted by jjwiseman at 2:24 PM on October 3, 2013 [1 favorite]

Yes, just like clockwork this tired old trope keeps cropping up. I cover that in the Maybe A Future Scientific Breakthrough Will Let Me Have My Way section of the page Respecting Science.

Nyrath, but like it or not, this is what our history has shown to be true of our understanding of physics. What makes you think NOW we have it right? Because the maths work? It did before too. That's the part that turns science into dogma. Yes, as the respecting science page says, we'd have to come up with a different theory that makes all the same numbers work, but that's what we did, and that's what string theory tried to do (and came close to doing it).

Again, I'm not saying this as someone sitting in on the discussion in a room to build a super stealth space-mobile right now, but as someone part of a hypothetical discussion of technology that might be able to be made in the future. To deny the idea that we may just have it all wrong again is to deny science. Trope or not.

But a more likely solution will come out of my second point, the thing we didn't realize could work until somebody thinks it up. This happens All The Time in science. Something that shouldn't work, does, and then we realize that oh yeah, it's not that the science is bad, is that we didn't think about it that way.

With either idea I'm not suggesting we just put all our eggs in "The future will figure it out!" bucket, but rather I stand in opposition to the idea that it's impossible and what we know now is what we'll know forever.
posted by [insert clever name here] at 9:24 PM on October 3, 2013

(Or, put better than I ever could:
Clarke's First Law: When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.)
posted by [insert clever name here] at 9:29 PM on October 3, 2013

Clarke's First Law:

Clarke wrote fiction.
posted by KathrynT at 4:44 PM on October 4, 2013 [1 favorite]

Yep, it's good to see my corollary is going strong.

To follow up on what KathrynT said, Clark's little homily is pretty much BS. Distinguished scientists do in fact say some things are impossible that are in fact, impossible. Like for instance, no amount of wistful thinking is going to allow people to levitate, no matter what certain gurus say. Likewise, distinguished scientists saying breathing vacuum is impossible, will not mean that eventually average humans will learn the trick of taking a stroll in orbit without technological assistance. But, stealth in space and FTL are two things that people are emotionally very attracted to. I get why people desperately want FTL, but stealth in space just seems like such a weird technical area for people to argue in favor of. It's like if I said the equations for gas buoyancy say lighter-than-air craft have to have a captain volume/mass ratio and people argued that no, the laws don't actually say that, and zepplins armored like M-1 tanks are totally feasible. I suppose we as a society have the idea of progress so intended we can't accept any technological or physical constraint.

That said, there can be edge cases. The NROL sats can be stealthed to a degree in a narrow direction, though the fact that amateur astronomers have been spotting those stealth sats is actually an argument against the practicality of the idea. If we had a decent space infrastructure, with observation satellites in higher orbits, the NROLs would be very vulnerable. One should also be careful of arguing from a specific case to the general: NROL doesnt mean large, powered interplanetary craft could be practically stealthed. The success of house cabernet against early tanks doesn't mean the modern army should invest in anti-tank horses.
posted by happyroach at 10:28 PM on October 4, 2013

The success of house cabernet against early tanks doesn't mean the modern army should invest in anti-tank horses.

I'm going to assume that horse cavalry got autocorrected somewhere in there and just enjoy the mental image.
posted by figurant at 11:58 PM on October 4, 2013 [2 favorites]

Has anyone suggested having combat ships built away from their centre of mass, with variable inertial mass distribution?

Predicting where a 'brick' of a ship will be by the time your rounds cross the distance isn't hard; having a ship divided into at least two distant central masses that are actively modifying their relative distance and therefore rate of rotation (even if not doing it dynamically with something like a twin pendulum system) would make it much harder.

Possibly hard enough to justify the increased engineering requirements?

I think it would make for a unique ship design at least... not just another pointy flying brick.
posted by Tzarius at 3:41 AM on October 6, 2013

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