Kinetic impactors and other space weapons

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Arioch
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Re: Kinetic impactors and other space weapons

Post by Arioch »

Ordinary kinetic missiles (either AMM-style missiles or mass driver rounds) do plenty of damage to a planetary target, and don't suffer from the problems of trying to jockey asteroids around (especially while the enemy is right there looking at you), and are much cheaper than something like a torpedo (which would also be devastating to a ground target). Especially if the launching vehicle has a 1-2% lightspeed starting velocity (which is prefectly doable in Outsider terms) a kinetic missile will do nuclear-weapon scale damage to any ground target, while being very difficult to intercept or deflect. Assuming that you'd like to capture the planet someday (habitable worlds being a valuable commodity), using more precise weaponry is probably more desirable than the ecological catastrophe that an ELE-type asteroid would trigger. And even if total catastrophe is what you're after, a hundred or so AMM-D's would cause roughly the same size mess, but much more effectively. They wouldn't be as massive, but they'd have a much higher impact velocity.

KE=1/2mv^2 is a bitch.
entity2636 wrote:You could take a small fast ship, a courier or scout corvette and have it carry a couple of capital ship size antimatter torpedoes on external mounts. You jump into an enemy system, accelerate on a course toward your target, release the torpedoes without firing their engines practically from the edge of the star system, then turn away and jump out. Space is big so it's highly unlikely that you'll be caught and the torps you released will travel on inertia towards their target without emitting an engine signature and could go completely unnoticed or being mistaken for space junk until too late.
Space is big, but the jump points are well-known and carefully watched in an inhabited system. Turning around from a jump requires, in most cases, a full-power burn of more than an hour. The odds that you could jump in and out of an inhabited, defended enemy system without being detected are essentially zero. But again, you don't have easy access to these systems in the first place.

Destroying planet surfaces at this tech level is easy. Getting access to inhabited enemy systems that are well behind the lines is the hard part.

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Re: Kinetic impactors and other space weapons

Post by icekatze »

hi hi
Gorbash wrote:...And keep in mind, this is a "lot" of power.
Everything you just pointed out applies to bombarding a planet with mass drivers too. This is a basic consideration of thermodynamics, energy in, energy out. I realize that this is has gotten away from the topic of Outsider, but the Warhammer 40k people need to check their math if they want to make general predictions about realistic costs/benefits.

Much of the point of using an asteroid as a weapon is to apply a low level of energy for a long period of time in advance, and sometimes taking advantage of an already high potential energy.

----
Getting back to Outsider, given that both sides are still trying to win the war, generational relativistic weapons don't seem like something they would try. Although, between the two of them it does seem like a more Umiak strategy than something the Loroi would do.

I could maybe see the Umiak launching some revenge weapons if they realized that they were certain to lose the conventional war. At which point, the Loroi would probably want to capture intel on the trajectories and guidance systems, and then launch some counter missiles. Instead of just destroying the surface. On the other hand, if the Umiak thought they might convince the hypothetically victorious Loroi to show them mercy, launching revenge weapons would be a bad move.

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Re: Kinetic impactors and other space weapons

Post by LegioCI »

Someone is posting about relativistic bombardment and my spidey sense tingled.

I always liked the idea, in-universe, of combining a relativistic bombardment with hyperspace travel.

As stated in the comic resources, jumping through hyperspace is a bit like playing darts- when a ship enters hyperspace its flung on a ballistic course in an attempt to hit a narrow target within the gravity well, too shallow and you skip back off into hyperspace again and who knows where you'll end up, too deep and you get "libera tu tutame ex infernus". Not only that but you need to avoid landing in a star or even inside a planet.

What this is, more than anything, is a game of odds; what are the chances that you'll land where you want to land? The shorter the jump, the easier it is to calculate to a high degree of accuracy where you're landing, the longer the jump, the larger the margin of error and the greater the odds of something bad happening. This is why jumps are kept to a few light years at a time; its better to make lots of shorter, safer jumps.

This begs the question: How far could you jump if you didn't have to worry about the crew? What are considered "safe" odds for a hyperspace jump and how far could you jump if you were willing to accept a 1-in-1000 risk of a failed jump? 1-in-100? 1-in-10? Hell, depending on the easy of manufacture of hyperspace drives, how far could you go if you were willing to accept that 90% of your weapons would fail the jump?

Depending on the answer to that question you could potentially use unmanned hyperspace drones; for example you could pop a few dozen drones into a system far beyond enemy lines, have them monitor the system for a few hours before jumping back- even if jump points are known and observed, there's probably at least a few hours reaction time unless each point is watched by its own dedicated picket; something that would generally be unwise since it would be safer to keep a larger mass of warships at a central point further in-system to potentially guard multiple vectors. A few might doink off into hyper space or be intercepted, but if even one makes the jump back successfully you could have a powerful reconnaissance tool.

Even scarier, you could potentially plop a RKV into orbit on the outer edges of an enemy system deep behind their lines, have it light up a H-bar reaction drive. (Most expensive thing about it is the fuel.) Depending on the costs involved, you could potentially send hundred of semi-guided relativistic projectiles on a one-way trip into an enemy staging system to hit orbital docks and supply/repair stations, inhabited planets, etc. But y'know, that's just my inner strategic pragmatist/mad scientist talking.
"But notice how the Human thinks. 'Interesting... how can I use this as a weapon?'" - Arioch

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Re: Kinetic impactors and other space weapons

Post by entity2636 »

Arioch wrote:Space is big, but the jump points are well-known and carefully watched in an inhabited system. Turning around from a jump requires, in most cases, a full-power burn of more than an hour. The odds that you could jump in and out of an inhabited, defended enemy system without being detected are essentially zero. But again, you don't have easy access to these systems in the first place.

Destroying planet surfaces at this tech level is easy. Getting access to inhabited enemy systems that are well behind the lines is the hard part.
The idea is not to jump in and out undetected, rather jump in release the unpowered ordnance on the appropriate course, *Hai, just passing through, bye!", and either going for another jump zone or doing a powered turn and jumping out. Of course the ship would be detected and interceptors would be launched, but it will also take them considerable time to catch the ship, and by that time the enemy ship may have jumped back out again.

The ordnance will travel on it's own inertia for days or weeks until it gets close to it's target where it will then start it's engines for a final approach course adjustments, release MIRVs and *boom* 8-)

@LegioCI - The problem is the cost and bulk of hyperdrives. Such drone ships will cost comparable to scout ships and be of similar size (~100 metres long) because hyperdrives are rather large and have substantial energy requirements. You'll save on life support systems, but an automated ship will be vulnerable to EW and unforeseen circumstances.

By the way, I like the quote in your signature :) Humans do make very uncomfortable enemies to fight as every one of them will find 101 ways of using anything as a weapon :lol:

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Re: Kinetic impactors and other space weapons

Post by Arioch »

LegioCI wrote:I always liked the idea, in-universe, of combining a relativistic bombardment with hyperspace travel.
Velocity is an important component in the success of a hyperspace jump. As with varying jump position, varying jump velocity will affect the exit location in the destination system. Jumping with higher than optimal velocity will bring you out of hyperspace deeper into the system (this is exactly what the new Umiak "deep jump" group is doing in page 129). Too much velocity will push you into the bottom of the destination gravity well, and you will collide with the star. Jumping at a high fraction of lightspeed will result in a star collision pretty much 100% of the time, so relativistic attack and hyperspace travel don't go well together.

Using unmanned starships to try to jump farther than normal could work, but even if you double normal range, that still doesn't reach you any juicy targets. It's quite possible to bull-rush a border system to try to overwhelm the defenders and get to the next interior system; this has been done many times in the past, and so any major population center within 1 or 2 jumps of the front has already been hit or evacuated in the past. Major infrastructure or population centers tend to be at least 4 jumps from any uncontrolled system, and well defended.

Because of the power requirements of the jump field generator and inertial dampers, the smallest possible jump-capable "drone" is still a very substantial vessel (at the tech level of the Loroi or Umiak) in the 75 meter range. This is a fairly expensive piece of hardware to deploy in the thousands that you'd need to reliably reach difficult jump targets. But even for those few that make it, they are still subject to interception by defenders. They might catch the defenses off-guard by arriving at an unexpected location in the system (jump points that are considered impossible won't have nearby defenses), but they will still have to penetrate the local defenses of any planet or other infrastructure that they attack. As reconnaissance, each drone would have to survive two consecutive highly improbably jumps; if I remember my combinatorics correctly, the odds of surviving two 1-in-100 events is 1-in-10,000.

Reconnaissance in Outsider must generally be done in force; if the enemy sees you popping scouts in and out of a jump point, they will station defenses there (if there aren't any already) to attack them.
entity2636 wrote:The idea is not to jump in and out undetected, rather jump in release the unpowered ordnance on the appropriate course, *Hai, just passing through, bye!", and either going for another jump zone or doing a powered turn and jumping out. Of course the ship would be detected and interceptors would be launched, but it will also take them considerable time to catch the ship, and by that time the enemy ship may have jumped back out again.
Any jump point that you expect the enemy might use will have some kind of defenses. Often there is an armed station nearby (as with Leido-Sala Post and Gora Relay in Leido Crossroads), but at the very least there will be a tracking station. Jump travel is not stealthy; the arrival of an object from hyperspace is announced with a bright flash of light that is visible from across the system. Any ship arriving from a known jump point will be observed, as will any weapon launches.

But again, any system that you can reasonably reach with a single jump does not have much in the way of planetary infrastructure for your drone to attack.

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Re: Kinetic impactors and other space weapons

Post by LegioCI »

Out of curiosity, what sort of distances are we looking at for a "safe" jump vs. one that have a significant chance of failure? (Assuming no other factors are taken into account but distance.)
"But notice how the Human thinks. 'Interesting... how can I use this as a weapon?'" - Arioch

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Re: Kinetic impactors and other space weapons

Post by entity2636 »

LegioCI wrote:Out of curiosity, what sort of distances are we looking at for a "safe" jump vs. one that have a significant chance of failure? (Assuming no other factors are taken into account but distance.)
According to the Insider, safe jumps are <10LY, usually less (6...10LY). The safest jumps are between two single stars that have no gas giants around them and have no other massive objects or stellar remnants nearby as every concentration of mass influences your hyperspace trajectory and can pull you "off course". Multiple star systems are more dangerous to jump into because of how the two stars' gravity interacts with one another. Rapidly rotating stellar remnant systems (neutron stars, pulsars, etc.) are dangerous to impossible to jump into because of the gravity waves they generate. Hypothetically, you could safely jump into a lone star system (free floating star that's ejected from the galaxy) that's more than 10LY away, IF there are no gravitational anomalies along your course.

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Re: Kinetic impactors and other space weapons

Post by RedDwarfIV »

Something the WH40K meme did not take into consideration is that if it is expensive for you to push a rock towards a planet, its going to be significantly more expensive for the target to deflect it. The closer the rock gets to the target, the more delta-V is required to change its course.
If every cloud had a silver lining, there would be a lot more plane crashes.

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Re: Kinetic impactors and other space weapons

Post by Absalom »

SVlad wrote:Starship Troopers - either the scenarist was a moron, or humans throw that asteroid themselves in a false flag operation (conspiracy!).
The movie director hated the book, so he intentionally did a bad job with the movie.

So, false flag it is.

icekatze wrote:hi hi
Gorbash wrote:...And keep in mind, this is a "lot" of power.
Everything you just pointed out applies to bombarding a planet with mass drivers too. This is a basic consideration of thermodynamics, energy in, energy out. I realize that this is has gotten away from the topic of Outsider, but the Warhammer 40k people need to check their math if they want to make general predictions about realistic costs/benefits.

Much of the point of using an asteroid as a weapon is to apply a low level of energy for a long period of time in advance, and sometimes taking advantage of an already high potential energy.
Within the 40k setting, it makes some sense.

In essence, anything defenseless enough to be hit with an asteroid is defenseless enough to be unable to oppose an armed landing. Anything dangerous enough to prevent an armed landing is dangerous enough to stop an asteroid if you give them time. So, either you don't need the asteroid, or you want the asteroid faster than it will arrive.

Also, remember that their paperwork is atrocious (armies destroyed decades before the paperwork gets finished), and that they might not be working in a location that they've sufficiently scouted before (or even scouted at all).


Really, the asteroid scenario makes the most sense for terrorists, planetary neighbors, and "trapdoor spider" aliens. As a general interstellar-warfare case, asteroids will always be more like lightning: outwardly impressive, but if your doing it intentionally you]re better off applying the same concepts in a different way (e.g. mine a comet for hydrogen, and use to fuel a fleet of KKV fusion-drives).

Using an asteroid instead of a missile is like using a tree branch instead of a mace: the missile will work better.

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