Stealth in Space

[Markdoc]

Re: Stealth in Space

 

These types of arguments truly baffle me. Does it really have to be specified that a drone disguised as a ship would be designed to generate the heat of a ship? Can you honestly not think of a reason drones might be used as decoys instead of missiles? Maybe I'm expecting too much' date=' but dismissals like these read to me like you're not really thinking about the situation.[/quote']

 

I think it's more that these arguments have been rehashed over and over and it always ends the same way: people are simply wearily responding to each post. Yes, you could make your drone radiate heat (OK, stealth has gone out the window). But that makes it blindingly obvious, so it's gonna draw attention. If it's radiating, it's going have a spectrum, so you have to build it out of the same material as your ship. OK, so far so good. On radar it's gonna need a similar profile to your ship - this you can fake a variety of ways. If it makes any kind of maneuver, it's going to need the same mass/thrust ratio as your ship. That's trickier, but you might be able to fake that, depending on what your drive is, but really you've apparently now gone to a good deal of trouble to build a large, expensive, complex missile. Why not just put a warhead in the sucker and be done with it?

 

These arguments (and lord knows they're all over teh interwebz) always run the same course. Stealth is possible in Space! Response: Ok, how? Increasingly convoluted arguments. Response: devastating counter arguments. Well, OK, but you can build drones! Response: drones don't give you stealth: the opposite in fact, as you are now magnifying your signal - and it will be difficult to hold the deception up for more than very short periods. You could so make drones! Response: Sigh. Yes, if you were prepared to spend enough you could make drones. That's still not going to give you stealth. It's almost like Stealth! Response: Facepalm.

You could apply all the drone arguments here to current technology: you could build drones that look just like real planes and use them to protect your planes on high threat missions. The idea has been suggested multiple times in real life. The reason it's never been done in real life, is always the same: by the time you make a drone that looks to contemporary sensors just like a real plane, you've spent enough that you might as well stick weapons in it and call it ... oh, I dunno, Taranis sounds like a good name.

 

cheers, Mark

[austenandrews]

Re: Stealth in Space

 

(OK' date=' stealth has gone out the window[/i'])

The conversation shifts. Is that a horror? People take a "no stealth" stance, and when the topic shifts to drones, they say "Who needs drones!" as if drones weaken their stealth argument. Huh? The reason we shifted to drones is because the "no stealth" argument is so strong. Then interesting drone discussions are met with "But drones aren't stealth!" Response: Facepalm.

 

You could apply all the drone arguments here to current technology: you could build drones that look just like real planes and use them to protect your planes on high threat missions. The idea has been suggested multiple times in real life. The reason it's never been done in real life, is always the same: by the time you make a drone that looks to contemporary sensors just like a real plane, you've spent enough that you might as well stick weapons in it and call it ... oh, I dunno, Taranis sounds like a good name.

I refer you back to Jhamin's good point about environmental differences. Making something fly in an atmosphere is hard. In space, not nearly as much. Plus the distances and targeting opportunities are orders of magnitude different. When you don't have much stealth in space, the topic shifts to "What else is there?" I apologize if "Nothing, dadgummit!" isn't much of an answer.

 

Honestly, what's so awful about the concept of decoys that they don't even warrant idle speculation? I'm baffled by the offhand dismissal.

[austenandrews]

Re: Stealth in Space

 

Okay, since my previous post was nonconstructive pre-coffee grumbling, allow me to add to the discussion: It occurs to me that we're making the assumption (often considered erroneous, even for modern aerial warfare) that any craft in question will be of the "people riding in a tin can" variety. I wonder if it's not reasonable to presume that unmanned drones would be the norm rather than the exception in a space engagement, and that drones would be easier and cheaper to mass-produce.

 

Here's a scenario: Your primary weapon is an antimatter payload or whatever, loaded into half a dozen drones, which you send inside a volley of several thousand far cheaper secondary drones with identical signatures and much smaller atomic payloads, plus a few thousand more unarmed drones. They all have a package of AI-guided evasive capacity, ECM, etc. (possibly supported remotely by other drones or whatever - not assuming each drone's defenses are entirely self-contained). You blast out this death swarm and they spread over a huge area, in some configuration designed to tax whatever defenses the target has. The atomic warheads will nickel and dime the target, but the antimatter bombs will destroy it. The attacker's job is to make the primary, secondary and decoy drones look identical. The target's job is to choose which drones to focus its attention on. Given what we know, is this kind of approach (a) scientifically possible, ( technologically feasible and © strategically/tactically sound? (Assume for the moment that alternate delivery methods like smuggling in the antimatter isn't an option.)

[Jhamin]

Re: Stealth in Space

 

Here's a scenario: Your primary weapon is an antimatter payload or whatever' date=' loaded into half a dozen drones, which you send inside a volley of several thousand far cheaper secondary drones with identical signatures and much smaller atomic payloads, plus a few thousand more unarmed drones. They all have a package of AI-guided evasive capacity, ECM, etc. (possibly supported remotely by other drones or whatever - not assuming each drone's defenses are entirely self-contained). You blast out this death swarm and they spread over a huge area, in some configuration designed to tax whatever defenses the target has. The atomic warheads will nickel and dime the target, but the antimatter bombs will destroy it. The attacker's job is to make the primary, secondary and decoy drones look identical. The target's job is to choose which drones to focus its attention on. Given what we know, is this kind of approach (a) scientifically possible, ( technologically feasible and © strategically/tactically sound? (Assume for the moment that alternate delivery methods like smuggling in the antimatter isn't an option.)[/quote']

 

A pretty legit scenario. Lets tackle the various pieces of it.

 

1 - How far apart are the launch points and the targets? Interplanetary? (Venus to Mars) Inter-system? (Alpha Centauri to Sol)

1b - How long does it take to get from launch to target? Are these missiles moving at FTL speeds? .99 Light? .5 Light?

 

These first two linked questions tell us a *lot* about how much time the defender has to respond to the attack. If we are moving FTL then physics as we understand it are out the window and we are into super/rubber science type places. Lets avoid that for now. If you can get up to light speed it probably takes a while as all conventional materials known to science would sheer into subatomic particles when hit with instant acceleration (and any "real" engine we can imagine needs to accelerate up over a period of days or weeks).

This leaves us with planet to planet missiles that needs months to travel between launch and destination and solar-system to solar-system missiles that need years.

 

2 - Modern astronomical equipment could detect the launch of the space shuttle from pluto with enough detail to work out the engine power, mass, and velocity of the ship. Any society capable of interplanetary war probably has improved versions of this (just think how far 20 years of cold-war style funding did for radar, between WWII and the height of the cold war. If they spent that much on deep space scanning we would have spooky details on our hypothetical enemies). Assume any ship capable of interplanetary travel will be detected by a society capable of worrying about such things (which is how this thread started). A large fleet of such things will be impossible to miss.

 

Assume our target knows how many attackers are coming, what path they are taking, and how long it will take to get there.

 

3 - What weapons are we defending with?

- If we only have missiles too, then it becomes a race between the economies of the opposing powers. Who can build the most attack devices? The side with the most can fling them into the other sides fleet until they are all killed & then use the rest to kill the home planet of the aggressor. Remember that if you are traveling at interplanetary or inter-system speeds you can't dodge anything without changing your course enough to miss your target entirely. If targeting systems aren't up to hitting incoming missiles with countermeasures then your best tactic is to go with a cold war style "if you launch a cloud of missiles at me, I'll launch a cloud at you and we will both die".

- If we have beam weapons then you get into a situation where you have the months of travel time to work out perfect targeting solutions to hit each and every incoming attacker. Beam weapons in a vacuum aren't limited by range so you can start killing the incoming swarm the moment you detect them. You have to fire your beams at lightspeed & then wait months for them to hit their targets, but a target going at a good % of lightspeed has too much inertia to dodge & then get back on target to hit you, so anyone with a slide rule can predict where to shoot to hit them with your lasers/particle guns. You can start killing them months or years before they get close. This gives you plenty of time to kill thousands of them. If you can't hit them from far away, you are better off going with the cloud of missiles as discussed above.

 

4 - What is more expensive: Antimatter or your Engines?

If we are propelling dozens or hundreds of ships across vast distances how much economic sense does it make to arm only a few of them? How much sense does it make to arm *any* of them?

If antimatter is cheaper than engines (say on a 1:3 scale), every ship will have a full antimatter warhead. Why spend $3 million space bucks for a drone vs. $4 million space bucks ($3M drone + $1M antimatter) for a fully armed killer?

If engines are cheaper than antimatter (on that same 1:3 scale), why send antimatter at all? If you can build a $1 million space buck missile that can get up to light speed you already have all the planet-killing power you need.

According to Wikipedia "A 1 kg mass traveling at 99% of the speed of light would have a kinetic energy of 5.47×1017 joules. In explosive terms, it would be equal to 132 megatons of TNT or approximately 32 megatons more than the theoretical max yield of the tsar bomba, the most powerful nuclear weapon ever detonated. 1 kg of mass-energy is 8.99×1016 joules or about 21.5 megatons of TNT."

That's just 1kg, about 2/3 the weight of a bowling ball. If you slam into your target planet with a 10*ton* lightspeed engine you start wiping out continents or cracking the crust of the planet. Why spend $4 million space bucks for an anti-matter tipped warhead when you could buy 4 of these babies for the same price?

[Narf the Mouse]

Re: Stealth in Space

 

Given that the missile only needs to dodge by its own diameter, it seems plausible that the missiles could dodge regularly, with most of them staying on target.

[Jhamin]

Re: Stealth in Space

 

Given that the missile only needs to dodge by its own diameter' date=' it seems plausible that the missiles could dodge regularly, with most of them staying on target.[/quote']

 

In an atmosphere that would be true. You can use fins to steer and you are only moving a few hundred miles an hour tops. In a vacuum moving at the kind of speeds you need to cross interplanetary or interstellar distances you are moving thousands of meters a *second* and have built up *enormous* amounts of inertia. As we all know from highschool physics the more inertia you have the harder it is to change your course.

 

You would need the full power of your main engine to affect your course and changing course enough to move the diameter of your missile out of the way will change your course enough that you will need to expend even more energy getting back on course. Changing the direction you are traveling by 1 degree when you are in between Venus and Mars will cause you to miss Mars entirely, let alone not hit the part of it you want.

 

Any attempt to change course when traveling at a good % of lightspeed will throw you so far off course that you will not have enough fuel to get back on course! If you do have enough fuel, then why didn't you use it to go faster and cut down how long the other side has to work out the best way of killing you? Turning in space is hard. When the Apollo 13 rocket suffered an explosion on the way to the moon they had to ride out the trip and circle the moon before coming back because even if they were in perfect condition they didn't have the fuel to turn around in mid-flight and go back to earth. And they were not going at anywhere near the speeds we are talking about. (and I know that turning around is a bigger deal than dodging, but at the speeds we are talking about even dodging is too much)

 

This also begs the question of how your missile knows to dodge. If it has sensors capable of detecting the missile coming to kill it then the incoming missile can try see it's target moving and can also try to correct course. This becomes a war of who has the best sensors and maneuvering computers. If the defender is shooting lightspeed beams of energy at you then you are already dead by the time you detect the attack. "Wobbling unpredictably" is only possible in an atmosphere against an enemy with poor sensors.

[dmjalund]

Re: Stealth in Space

 

In an atmosphere that would be true. You can use fins to steer and you are only moving a few hundred miles an hour tops. In a vacuum moving at the kind of speeds you need to cross interplanetary or interstellar distances you are moving thousands of meters a *second* and have built up *enormous* amounts of inertia. As we all know from highschool physics the more inertia you have the harder it is to change your course.

Inertia would affect changing direction - not moving distance. No amount of velocity in the direction of travel (at non-relativistic velocities) affect maneuverability in directions perpendicular to travel.

[Cancer]

Re: Stealth in Space

 

Well, drag forces (which are available to you in an atmosphere, but not in space) can scale as velocity raised to some higher power than 1. This has the potential for giving you deceleration (and asymmetric deceleration, which is a huge part of maneuverability) far beyond the force you can apply directly. Move a control surface, and the resulting force on the entire aircraft is much greater than the force you had to exert on the control surface. Hence, we routinely have much greater maneuverability in the atmosphere than we have in space, even at equivalent speeds.

[Jhamin]

Re: Stealth in Space

 

Well' date=' drag forces (which are available to you in an atmosphere, but not in space) can scale as velocity raised to some higher power than 1. This has the potential for giving you deceleration (and asymmetric deceleration, which is a huge part of maneuverability) far beyond the force you can apply directly. Move a control surface, and the resulting force on the entire aircraft is much greater than the force you had to exert on the control surface. Hence, we routinely have much greater maneuverability in the atmosphere than we have in space, even at equivalent speeds.[/quote']

 

This is of course what I meant when I mentioned atmospheres, I just did a very poor job of saying so. My main point was that any dodging you might do with an interstellar missile wasn't going to involve the kind of acrobatics you can do in an atmosphere and could be matched by an interceptor.

[Narf the Mouse]

Re: Stealth in Space

 

Inertia would affect changing direction - not moving distance. No amount of velocity in the direction of travel (at non-relativistic velocities) affect maneuverability in directions perpendicular to travel.

Thank you, I wasn't sure.

 

And that's what I meant. Jets on the side of the missile, then just wobble back and forth continuously. No change in direction of travel means you can easily wobble enough that, for most of the missiles, their lightspeed defenses are useless. And, it would mean incoming counter-missiles would have to be able to wobble as well and may miss.

[Sundog]

Re: Stealth in Space

 

Not really. Your "wobble" will need to be within a circular error of probability of your target optimum trajectory; and probably not a very big error, unless you're planning on massive reserves of reaction mass (and even then, too great a deviation WILL affect your trajectory, due to gravitational interactions with other bodies in the target's solar system). So a planet that's under attack observes your missile long enough to determine the maximum of it's circle, the saturates that area with energy fire - chances are very good that your mssile gets hit. If not, repeat as needed (it's only energy). As for missiles, they just fly straight into the middle, then set of a conventional explosive charge coupled with 500000 ball bearings. Your expensive evasion system just got owned by an upgunned Claymore.

[Narf the Mouse]

Re: Stealth in Space

 

Not really. Your "wobble" will need to be within a circular error of probability of your target optimum trajectory; and probably not a very big error' date=' unless you're planning on massive reserves of reaction mass (and even then, too great a deviation WILL affect your trajectory, due to gravitational interactions with other bodies in the target's solar system). So a planet that's under attack observes your missile long enough to determine the maximum of it's circle, the saturates that area with energy fire - chances are very good that your mssile gets hit. If not, repeat as needed (it's only energy). As for missiles, they just fly straight into the middle, then set of a conventional explosive charge coupled with 500000 ball bearings. Your expensive evasion system just got owned by an upgunned Claymore.[/quote']

In which case, those are lasers that aren't firing at the *other* missiles. Also, you're completely ignoring beam spread.

 

Expensive? Assuming that each of those ball bearings weighs 0.1 ounce, that's 1.4 kilotons of ball bearings. Your fuel/mass ratio just sunk like a granite boulder.

[Sundog]

Re: Stealth in Space

 

Yeah, I was ignoring beam spread. Mainly because it's a wash - the amount of power loss and the improvement in the chance of actually striking the target cancel out. As for "not targeting other missiles", well, I've probably got, at worst, days to get them all, so firing a burst over a period of say, two minutes, still lets that array hit a LOT of missiles before they get too close.

And okay, a multi-directional burst is probably too heavy. Instead, have the interceptor missile rotate the firing port towards the target at the last minute (rardar systems can show where the target is NOW from that distance) and fire 5 000 ball bearings instead. Target still gets shredded.

[Narf the Mouse]

Re: Stealth in Space

 

Yeah' date=' I was ignoring beam spread. Mainly because it's a wash - the amount of power loss and the [i']improvement[/i] in the chance of actually striking the target cancel out. As for "not targeting other missiles", well, I've probably got, at worst, days to get them all, so firing a burst over a period of say, two minutes, still lets that array hit a LOT of missiles before they get too close.

And okay, a multi-directional burst is probably too heavy. Instead, have the interceptor missile rotate the firing port towards the target at the last minute (rardar systems can show where the target is NOW from that distance) and fire 5 000 ball bearings instead. Target still gets shredded.

The decline in the chances of the laser actually doing anything is not canceled out, particularly on a dodging missile with mirror coating (why not? It's not stealthy in the first place).

 

140 kg is a lot more doable. Of course, at that range, the missile can also afford to do something like flip 90' degrees on one axis and have its main engine fire a short burst. Of course, then it has to cancel out that movement, but it's also canceled out your missile.

[Jhamin]

Re: Stealth in Space

 

The decline in the chances of the laser actually doing anything is not canceled out' date=' particularly on a dodging missile with mirror coating (why not? It's not stealthy in the first place).[/quote']

 

Once again, you are not going to dodge lasers. If they can see you they can hit you with a laser & there is no non-superscience way of knowing when an incoming laser is about to hit you. You can't wait until you see the gun shoot at you as by the time you see it you have been hit by the laser. You can dodge the entire way to your target, but then you are burning fuel continuously for months or years and I just can't envision a missile with that much fuel.

 

And mirrors only work on low power lasers. If your mirror is 99.8% perfect (and it won't be) that .2% of energy getting through will still kill you if the beam is strong enough. And if I was defending my planet with beam weapons knowing how bad even one getting through would be I'd spring for the beams powerful enough to kill you with .2% of their energy.

 

140 kg is a lot more doable. Of course' date=' at that range, the missile can also afford to do something like flip 90' degrees on one axis and have its main engine fire a short burst. Of course, then it has to cancel out that movement, but it's also canceled out your missile.[/quote']

 

When you are moving at interstellar speeds in a vacuum you do not have time to do "last second" maneuvers. Any maneuver that will get you away in time will have to happen far enough ahead of time that the interceptor will have time to adjust for it or at least burst as it goes by & kill you anyway.

[Narf the Mouse]

Re: Stealth in Space

 

Nonsense. Start with one evasion every month; link the frequency of evasions to remaining distance. It'll make the missile bulky, but a bulky missile that hits is worth far more than a slim missile that doesn't.

 

If they're that powerful, why don't you just aim them at my planet, instead of wasting them shooting down missiles? And let's try some numbers, here. According to Wikipedia, a common Helium-Neon laser would spread to ~500 km by the time it hits the moon. Assuming that's diameter, assuming the beam grows from a 1 cm diameter (on the large size), ((4/3) * (500/2) * 3.141^2) / ((4/3) * (0.001/2) * 3.141^2)) = 500,000 (this is the very round-about way, but it shows the work). Attentuation of 1/500,000 would render almost any known laser ineffective.

 

But let's say that you've got a super-laser. Let's say it only spreads by x2 over 450,000 km. And let's say I'm launching from Alpha Centauri, that you detect the launch immediately as the energy of it reaches you (4.26? years later). Let's say you have 4.16 years to intercept my missile. Let's say you need to have 0.02% of the energy arrive to have a kill. I'm using more generous figures than yours, here.

 

x = (((4.16 * 365 * 24 * 60 * 60 * 300,000) / 450,000) / 0.0002) log 2 = 130,000,000,000. You can start intercepting my missiles at 130 billion kilometers with a reasonable chance of success. Doable, I must admit. You'll even have 130,000,000,000 / 290,000 / 60 / 60 / 24 = 5 days to shoot them down.

 

 

Given that my missile has likewise known your missile is coming almost since it left your solar system, it has had literal computer ages to prepare. It comes down to whether yours times it's burst release better or mine times its evasion better.