Tuesday, August 25, 2009

Space Warfare VI: Kinetics, Part 1

Space travel technology is largely about making vehicles go really, really fast. So it is a bit surprising that kinetic weapons have played such a minor role in science fiction space battles. They never appeared in any story I recall reading when I was growing up - in fact, I don't recall ever reading a story that featured kinetics used against enemy spacecraft. [But see update below.]

'Strategic' kinetic bombardment of planets appeared in Heinlein's The Moon is a Harsh Mistress, and has been popular for slagging planets ever since we learned what an asteroid impact did to the dinosaurs. But using asteroids as bombs is lame. If you are out to wipe out a planet, just nuke the bejeezus out of it rather than spending months or years deflecting an asteroid. So much for kinetic WMD. The remainder of this discussion is about tactical combat between spacecraft, i.e. Space Battles. And because it came out long, I've split it into two posts.

Curiously enough, the first - and often prescient - known attempt to describe Realistic [TM] space tactics, by Malcolm Jameson in 1939 (scroll down a couple of screens) did feature kinetic 'mines,' but the idea was not taken up. Death rays remained far more popular in the early Golden Age, while the rocketpunk era, though more given to missiles, assumed they would carry nukes. It was the 1950s, after all, the age of nuclear hand grenades. At least they were rocket propelled! Current generation ABM technology does use kinetic weapons (kinetic kill vehicles, KKVs, being the favored jargon). But they still haven't caught on in science fiction.

The basic metric of kinetic weapons is that anything hitting you at 3 km/s - a rock, a throw pillow, whatever - delivers 4.5 megajoules of kinetic energy per kg of mass. For comparison, TNT delivers about 4.2 megajoules, meaning that at impact speeds much above 3 km/s a conventional explosive warhead merely adds insult to injury. And kinetic energy goes up with the square of velocity, so an impactor hitting at 100 km/s delivers a whallop equal to about 1000 times its mass in TNT. This is Robinson's First Law, and someone at SFConsim-l duly coined the 'Rick' as a measure of kinetic punch. As a rough and ready measure, Ricks = (Vi / 3)^2, where Vi is impact velocity.

Now, 3 km/s is pretty much the slow end of space speeds. Your encounter speed will probably be at least that much unless you make an orbit matching burn before the shooting starts. Spacecraft with electric drive - which are likely in any setting with regular human interplanetary travel - can be expected to go around ten times faster, give or take, thus delivering a whallop of ~100 Ricks. Smack! That will hurt.

Which actually casts a bit of doubt on the familiar image of kinetic missiles, at least for offensive use. If your encounter speed is 30 km/s (or even a 10 km/s stroll) there is not much need for a booster stage - just toss your kinetics out the hatch. Yes, they'll need a deflect motor to steer them into the target, but your encounter speed will do the heavy work. Guidance issues aside, Jameson had it pretty much right back in 1939.

Purple/Green. This is the popular expression, in the haunts of SFConsim-l and similar places, for the unending debate about missiles v lasers. The argument boils down to saying that while kinetics can be launched from outside laser range, they have to pass through laser range to hit a target, giving defensive lasers a chance to zap them first. The most effective zapping is at relatively long range, wrecking the guidance system and deflect motor so that the kinetic misses. Neener neener neener.

Of course, even a lump of molten wreckage will do it for you if it hits you anyway. A favored solution of mine is kinetic fragmentation, the shotgun approach. Place a small bursting charge in a big kinetic target seeker. If it is crippled it blows itself apart into a cloud of fragments, and (depending on burst range, etc.) one or two will hit, unless they are zapped to a fare-thee-well, vaporizing them. Or at least partly vaporizing them, the flash-off of the vaporized portion (maybe) serving to knock them aside.

As seen by the target, the dangerous fragments are the ones that appears to hang in one place - if a frag shows any lateral drift, it is on its way to missing you. This simplifies defensive targeting - at least in flat space. In orbital space, however, you are swinging at curveballs - and batting .300 probably won't be good enough. In orbital space the problem of determining which frags might hit you is, shall we say, non-trivial.

But for the kinetic attacker, the most effective countermeasure to laser defense may be simply to throw a lot of mass. The more you throw, the more the defender has to zap, and at some point you overwhelm him. Which is why the second part of this discussion will propose a new kinetic weapon: the Killer Bus.

Update: I was mistaken; I did read a book in my teens that featured kinetics: Arthur Clarke's Earthlight. See the comments thread for some details.


Jean Remy said...

I think there are two reasons kinetic weapons don't appear much in SF. One is only related to TV and movies, and the other is more general.

Specifically, in TV and Movies: Space is, quite unfortunately black. Or at least very very dark. While some shows try to mitigate that with nebula background, or even a blue-purplish space background, the fact is still that space is dark, so most likely fast-moving projectiles that are nor carrying their own light source, will be completely invisible. Enter our glow-in-the-dark energy weapons (setting aside the fact that a laser wouldn't glow in space either, of course). In fact I would say that this is what gave rise to the ubiquitous, if impossible, plasma weapon. Plasma weapons make for ballistic characteristics: they need a gun-like barrel rather than a lens, and appear as discrete projectiles. And they come in glow-in-the-dark. I think plasma weapons are attempts to have. in fact, kinetic or ballistic weapons (as opposed to beams) while attempting to make them visible against the background. I won't even blame them, and I fully endorse the spectacle-over-realism inherent in well, a visual medium. For a more PC interpretation: we know getting hit by bullets is messy. It's ugly: Blood flying, bits of people flying, bodies leaking icky stuff all over your shoes. Energy weapons are generally cleaner, from the completely aseptic "vaporization" caused by a phaser (we don't even have a BODY), to the less clean but not really messy flash-cauterization of a PPG or a lightsaber. The horrors of war... just, you know, without all the horror.

In general terms, though, kinetic weapons are not "futuristic" enough. I don't think the reason we don't see them is not that they are not effective. I think instinctively we all know that getting shot by a little metal object moving really really fast is BAD It doesn't really matter that we don't instinctively realize it is worse than being hit by a normal bomb. That's not actually the issue. No, the issue is the perception that firearms are passe, that we can do better than just throwing a little piece of metal out of a tube.
Isn't SF about "Boldly going where no man has gone before"? Well, we've gone to the shooting little bits of metal at people already. A lot.

I think however the winds of change are blowing as, for once, real military science is a little ahead of SF military science. The recent interest in coil- and railguns (not the SF version which so far used railguns as energy weapons) is catching up. Other weapon systems like MetalStorm are showing us we're not quite done with the whole shooting little bits of metal, and that we can do it a lot better than we used to. I wouldn't be surprised if we start seeing more of them.

Anonymous said...

Jean Remy does have some points on the proliferation of Directed Energy beam weaponry over Kinetic Energy Weaponry in most science fiction. There is also the added problem of Kinetic Weaponry having a low rate of acceleration that is effectively sub-c, if not sub-relavistic. That is, like lasers in the previously mentioned blog entry, kinetic energy rounds take some time to cover the distance between the attacker and defender and reach said target. A velocity that is much slower than beam weaponry such as lasers and would likely be outshined by near-c directed energy weapons.

Even the kinetic mine previously mentioned would only be an effective interception weapon if interplanetary drives are rocketing at high accelerations and velocities for the Robinson's First Law to take into effect.

However, there is one property of Kinetic Energy Weapons that Directed Energy Weapons just simply can't duplicate. That property is the complexity and variety of damage a kinetic weapon round can do to a target beyond simply heating a target area, as explained in this website link: http://www.stardestroyer.net/Empire/Tech/Shields/Impact.html

To put it simply, if that thing hits, a ship has a whole set of problems besides thermally weakened bulkheads.

As for that Purple/Green debate, well one can level the laser slugging field by potentially creating a kinetic mine missile that launches at a target but just before it reaches the effective laser damage range of a defending ship, it explodes and fragments into a cloud of tiny and high speed shrapnel (preferably with the majority of the blast pointed away from the attacking ship). Each one of those shrapnel (or at least a majority of them) are still traveling at the velocity of the missile and in the same general direction. Just alot more, smaller, targets for the defending ship to worry about.

If space junk have the potential to cause catastrophic damage to any orbiting spacecraft, then dedicated kinetic weaponry are going to be devastating. Granted, such battles, with or without kinetic energy rounds, will generate a lot of space junk that would make travel to and from space even more hazardous and risky than right now.

Probably easier and cheaper to just psyche an enemy spacecraft into the path of an incoming rocket booster.

- Sabersonic

Citizen Joe said...

An inherent problem with mining space is the same problem you have with conventional landmines. If you miss, there's still a mine out there posing a hazard to navigation. Self destructs on mines won't help either, since that just makes a larger cloud of debris. I'll point out my favorite kinetic medium again, Lithium Deuteride. The Teller-Ulam design for fission/fusion bombs uses a fission explosion to compress and detonate deuterium fuel into a fusion explosion. At orbital speeds, you don't need to fission booster, just let them slam into ships. An added benefit is that Lithium Deuteride is very flammable, thus reentry into an oxygen rich atmosphere will cause it to simply burn up. So you get all the bang you need with planets sweeping the battlefield clean afterwards.

Rick said...

Jean - For written SF, as distinct from film etc., your second point is surely the main one - ray guns are Futuristic, while bullets are not. And possibly the visual image also leaks over into written SF, since the writers have grown up seeing images of (all too colorful) beams zapping away.

I seem to remember that when I was 12 or 13 an uber-geek friend pointed out that good old fashioned round shot would be very effective at space speeds - it is kinda too bad that David Weber didn't think of that when he decided to do Napoleonic Wars in SPAAACE !!!

But I only became a kinetics fan after doing the numbers, which most people, even SF writers, are averse to. (Heinlein wasn't, and he if anyone might have come up with the idea, though he didn't. See my early post, A Little Faux Heinlein.)

Speaking of coilguns, BTW, I just realized that I have read an SF novel, and a pretty old one (1955), that featured kinetics: Clarke's Earthlight. Ships from Mars are attacking a Moon base, which nails them with a 'beam' of molten iron fired from a coilgun type weapon. (Neatly explaining why the beam would be visible in space!)

I didn't think of it when I wrote the post, because my mental image of kinetics is solid target seekers / bullets / frags, and Clarke's weapon is stylistically a beam even though the actual mechanism is kinetic impact.

Sabersonic - I'd quibble with one point: High acceleration isn't needed for effective kinetics, just high speed. It might take a month for an electric drive to push a ship/projectile to 30 km/s, but once it reaches that speed it will smack you as hard as anything else going that fast.

Probably easier and cheaper to just psyche an enemy spacecraft into the path of an incoming rocket booster.

Which gets into two big, related, and interesting areas: Tactics, and the human factor.

Citizen Joe: All depending on the orbit of the kinetics. If an attacker approaching on a hyperbolic solar orbit releases kinetics, any that don't hit on the first past will leave the Solar System - if above planetary escape speed they will at least go into solar orbit and be a minimal problem. But defensive kinetics tossed into the path of a (fast moving) attacker could be left in planetary orbit, posing just the threat you mention.

Will lithium deuteride pellets go off on impact at 'ordinary' space speeds. I would think they'd have to be going uber fast. I believe that ignition temperature for an H-bomb is on order of 100 million K, corresponding to an impact speed on order of 1000 km/s.

Of course, if you have uber fast ships this is not an issue. On the third hand, at 1000 km/s even a throw pillow hits you with near nuclear-equivalent punch. No need for lithium deuteride!

Jean Remy said...

Now I have this vision of a humoristic short story where fast-moving ships launch cute throw pillows at each other as weapons. "Pillow Fight" BOOM

Luke said...

Sabersonic: As I've recently been finding out, directed energy weapons also have various and complex ways to damage a target other than direct heating. As a material heats, its vapor pressure increases - this is the pressure developed as the surface evaporates. When the vapor pressure exceeds the ambient pressure, you can get significant "wind" velocities as the jet of evaporate rockets away from the surface. This has many consequences. For one, like a rocket, in imparts a reaction force on the illuminated material. If the reaction force is high enough, the material can break, resulting in the laser blasting off a disk that flies inward (or at least tangential to the surface, away from the direction of laser radiation. The disk may also fragment in the process). Further, a jet can cause any melted zone to break up into droplets, which are then carried away by the jet. The jet and droplets can erode more material as they shoot out of the hole. Also, if the vapor pressure exceeds the yield strength of the material, the material will plasticly deform (meaning some of the deformation is permanent). If the vapor pressure exceeds the ultimate strength of the material, the material will rupture. If the vapor pressure is more than approximately the latent heat of fusion (per unit mass, not mole - and note that fusion in this case refers to a solid-liquid transition rather than to a nuclear reaction) times the density, the evaporate will have enough pressure to make the material flow like a fluid, carving out a nice crater. At high velocities (essentially, at more than about 2 to 3 Ricks), kinetic impactors have the same damage mechanism as the latter - the energy deposited produces a vapor (from both the impactor and the hull material) with enough energy to make the hull material (and the remains of the impactor) flow like a liquid.

This is all before we get to other types of directed energy weapons, such as x-ray lasers and particle beams, which have different damage mechanisms to take into account.

Rick: I'd argue that you need both high acceleration and high speed - but at different stages of the attack. High acceleration would be needed for terminal guidance, where you need to outmaneuver the target (which may try to accelerate away from the projectile), plus covering whatever last gap you have between the attacker and target as they flash past at high speeds. Before then, however, it is delta-V you want, and you can build this up slowly.

I really wish I could say more about Li-D projectiles, but this is skirting dangerously close to things I am Not Allowed To Discuss (namely, anything involving nuclear weapons design an implementation).

Jean Remy said...

Luke: some good points there, but I have a little quibble about, quoth "High acceleration would be needed for terminal guidance[...]" That's a missile you're talking about, not that a missile can't be a kinetic impactor, or that we're not allowed to go tangentially off-subject, but so far we'd mostly been talking about ballistic KKV's, as the third option in the "kill the other guy" triumvirate Missile/Beam/Bullet. only mention this because Rick talks of the rarity of the weapon in SF, and missiles are definitely not that, hence my assumption that indeed we're talking about ballistic impactors. In a ballistic weapon, of course, all the acceleration you're going to have stops where the barrel does.

You could do some neat tricks with trajectories in orbit though. If you want to hit something in orbit but on the other side of the planet, you could calculate what orbit your weapon needs, shoot, and watch it curve around and hit the unsuspecting target. "What, me? Nope I was on the other side of the planet, why?"

Rick said...

Jean - Another favorite kinetic example of mine is a carton of skim milk ... food fight!

Luke - Interesting discussion of damage mechanisms (and, at the end, an interesting hint about the nature of your day job. :-)

On terminal guidance, I'll counter-quibble with Jean, since I did mention guided target seekers, which need a deflect acceleration equal to their prospective targets' sidestep acceleration. This might be fairly high, but probably short duration, and unrelated to impact speed, which is imparted earlier.

Unguided kinetics are only likely to hit if flight time (not necessarily range!) of their unguided phase is fairly short, giving the target little time to evade. Even against nonmaneuvering targets there may be a course correction requirement - reduced for frag weapons that blast out a cross section.

Anonymous said...

"You could do some neat tricks with trajectories in orbit though. If you want to hit something in orbit but on the other side of the planet, you could calculate what orbit your weapon needs, shoot, and watch it curve around and hit the unsuspecting target."

There's another advantage kinetic energy rounds have over directed energy weaponry: Directed Energy Weaponry are LoS only, kinetics can take orbital and ballistic trajectories to hit a target hiding behind something. Such as an inhabited space station full of civilians for example.

However, a thought just occurred to me just now, and correct me if I'm wrong. Lasers and similar kinds of directed energy weapons need at least a second or two to stay upon the target to do its damaging effects upon an enemy combat spacecraft. Kinetics, like bullets, perform their damage in mere milliseconds and all the crew has to do is calculate and aim before pulling the trigger.

And I'm not really sure how much of thrust a laser can create when it hits as Luke describes, but one can be certain that a kinetic slug, especially one that is of significant enough mass, will produce a lot more momentum into the target ship than a laser cannon is capable of.

- Sabersonic

Luke said...

Sabersonic: the dwell time of a directed energy weapon depends a lot on its parameters. At very high intensities, the evaporation of target material produces enough pressure to destroy the target as rapidly as an explosive, which can be much more rapid than a second or two. On the other hand lower "heat ray" intensities can require dwell times of seconds or minutes (depending on the parameters of the beam and the target).

At orbital and super-orbital velocities, momentum is going to be essentially insignificant as a mechanism of causing damage. This can be seen partly by noting that momentum increases linearly with velocity while kinetic energy increases quadratically with energy. Thus, as velocities increase you get to a point where kinetic energy overwhelms momentum. At lower speeds (say the 1 km/s of a rifle bullet) momentum is important. Here, material strength matters and the force is in the direction of motion of the projectile. At 10 km/s typical of orbital encounters, matter flows like a fluid, material strength in negligible, and the force is unidirectional.

Roughly, the momentum imparted by a laser evaporation jet will be comparable to a bullet with the same velocity and the same mass of material.

Jean Remy said...

Every weapon system has advantages and disadvantages. A light speed DEW will hit now and can be "swept" across, while a ballistic one is on a fixed trajectory, at a far lower speed, so easier to avoid. I guess circumstance dictates the weapon, but if mass is limited and you're only allowed one type, you have to grab the one that will fit the mission best, ie: long range, high acceleration combat could demand Missiles, Long range low accel could require DEWs and at short range low accel ballistic KKVs will give you more punch.

Luke said...

oops, typo - at high speeds the force will be omnidirectional, pushing in all directions from the explosion, not unidirectional.

M. D. Van Norman said...

I wonder how stealthy kinetic weapons might be. Could a hypervelocity cannon throw a cold, mostly invisible projectile at an unsuspecting target on the other side of the solar system? Or would the gun give off so much waste heat that everyone would know something was up?

Anonymous said...

Luke: Well I guess momentum-based damage is out for Kinetic Energy rounds, however to clarify my previous statement I used the word "momentum" because I'm not sure if "thrust" would be a more accurate a term to what happens to a spacecraft when hit by a high velocity round such as those fired from a rail/coil gun.

And here's another thought that just occurred to me. In this blog entry and the Laser Weapons one, there was never a single notation about Directed Energy Weaponry having the ability to slice through a target. So far, they could only perform surface damage most of the time and could potentially only drill through a few meters of material at most rather then the "hot knife through butter" as seen in several sci-fi film and television.

A kinetic energy round has a possible ability to strike deep into a spacecraft, if not punch a big hole into it and rupture several compartments deep within. This thought occurred to me as I was trying to make a comparison of a car getting hit by an armor penetrating, high velocity rifle round. Said bullet won't cause the car to be pushed back due to a transfer of energy from the bullet to the vehicle, but it does leave a nice, deep hole on the way.

As for that note on Kinetics being a stealth weapon IN SPAAACE!!!!! Well, other then the impossibility of such stealth in space within that particular scale, the heat of the rail/coil gun generating the energy needed to launch said projectile would be enough of a clue that something bad is about to come one's way. It would be more efficient to just set a trajectory to the target and bring the fight to the enemy.

Of course then again, I have been wrong before.

- Sabersonic

Jean Remy said...

--Stealth projectile--

I'm not sure but from what it looks like in clips I've seen of railguns, a lot of the waste heat seems to be caused by friction in the air. I'm not sure how much heat is transferred by conductivity to the projectile during the launch phase. That said, to use my orbital idea again, you could probably fire a "low velocity" shot, or even do a cold release by angling the ship right, and have the projectile follow some form of decaying spiral orbit to intercept your target, assuming a relatively "stationary" one. Use a throw pillow or a carton of milk if you can get a high enough relative velocity to your target, and no one will see it coming. Might be a pain and a half to compute, but for first strike capability...

Luke said...

Re: Stealth kinetics - railguns tend to be rather inefficient. Modern hypervelocity railgun research usually involves striking a plasma arc behind the projectile, and using the force of the magnetic field on the current flowing through the arc to push the projectile. This results in a horrendous muzzle blast of hot plasma and eroded material from the rails and projectile; up to 80% of the energy used can go into the muzzle blast rather than the bullet. This flash of heat and light would likely be easily detectable at reasonable engagement ranges.

Coil guns have the potential to be much more efficient. These are essentially linear electric motors, and electric motors commonly achieve 95% or greater efficiency at turning electric work into mechanical work, with most of the waste heat going in to resistive heating of the coils. If your setting has advanced carbon materials technology, carbon nanotube wires could be an order of magnitude more conductive (resulting in even less heat), while room temperature superconductors or cryogenically cooled superconductors could be even more efficient still. Coil guns have the possibility of being relatively stealthy if no one is using active scanning.

Radar or lidar, of course, could pick up incoming projectiles, although the range of detection when scanning the full sky might be limited. Lidar, at least, would be able to see and resolve any projectile that comes within laser range - but the time to detect an incoming projectile when doing a full sky survey could be an issue (I haven't done the math yet). Lidar might preferentially scan along certain high threat approach vectors - certainly potentially hostile spacecraft in view could be scanned and any launch detected.

Re; lasers cutting things in half - x-ray lasers and particle beams might achieve deeply penetrating strikes, as might lasers that emit a burst of rapid pulses. Actually cutting spacecraft in half seems rather optimistic to me - at least without either a cooperating or dead target or outlandish power requirements.

Kinetics can have issues with penetrating deeply because they tend to explode on the surface. Again, so much energy is released that the projectile vaporizes itself and blasts away in all directions. One way to increase penetration is to use a dense long-rod penetrator - say something like a 3 meter length of tungsten rebar. On impact with the hull, the front end of the rod will explode away, blasting a hole in the hull and allowing the rest of the rod to drift through and explode against anything inside. Shrapnel or shotgun-like blasts are unlikely to do any deep damage, although they could easily crater the surface and blast away exposed equipment.

So far I am surprised no one has mentioned the standard defense against hypervelocity impactors - a stand-off or "Whipple" shield. I will hold off on this in the event Rick decides to discuss it in part 2 of this blog post.

Rick said...

Whipple shields are not something I can fit into the limited space of a blog post, so discussion in these comments is fine!

A variant on longrods that has been discussed is a series of kinetics on the same track, so the first one blows a hole in the Whipple shield, and the following ones go through it. This has the advantage that the initial impact won't send a shock wave up the length of the rod, breaking it up.

Of course either method requires precise alignment, and obviously is ruled out for fragmentation kinetics, or any kinetics that are uncontrolled for more than the last few seconds of flight.

The idea of stealthy kinetics was ventured by commenter 'Z' in comments to Part II of this series, Stealth Reconsidered. They pointed out that for non-prolonged flight times you could chill the kinetic to cryo temperatures.

For high powered coilguns you'd still have the problem of launch heat - even if less than 1 percent of launch energy goes to heating the projectile, that is fairly hot if you're slinging it at several km/s. But Z discussed low power internal coilguns, 'torpedo tubes' imparting a modest kick away from the launching spacecraft.

This could be effective for Lancer style tactics. At minimum it imposes higher scan suite costs.

I used to think that lasers and kinetics had essentially the same damage mechanism - essentially inducing a surface explosion - because I was thinking of lasers as firing one uber pulse rather than a CW beam or (most likely) a train of pulses.

Luke is correct in saying that momentum is only a minor factor in high speed kinetics. As a reference point, a 10 kg kinetic hitting at 30 km/s packs kinetic energy comparable to a 1000-kg bomb, but the momentum is only comparable to a 1000-kg mass hitting at 300 m/s. Which in fact makes the impact very comparable to a bomb hit.

OTOH, even so the momentum is non-trivial - roughly comparable to the impact of an 11" = 28 cm shell. So in World War II terms, battleship grade armor will stop it, but cruiser armor won't.

Jean Remy said...

Could whipple shields be used as a defense against beam weapons? Say a silicon-carbide shield (since it's just a shield hanging on a frame and isn't part of the hull structure) a hull of titanium-carbide (or titanium with a coat of graphite, or something combining structural strength and refractive properties). In between the two, I'd fill segmented baffles with dust or even gas with diffractive properties, so as to scatter the beam, the baffle also absorbing any kinetic-like effect like the rapid expansion of the shield material itself.

(Self-quibble: yes, yes off subject, I know. *sheepish grin*)

Anonymous said...

The Whipple Shield and that self sealing polymer of NASA's are excellent as defense against small, high velocity targets. However they can only scatter the impact effect of an incoming projectile, no matter the origin, up to a specific mass and volume, if not just mass.

A pistol round massed kinetic energy round or smaller against a Whipple Shield is effectively no contest. A bowling ball massed kinetic energy round or larger, and then you got problems.

However, I admit that when I hear the term "Rail Gun" and "Coil Gun", the first thing that pops into my mind are spinal mounted juggernauts that accounts for a quarter of a spacecraft's mass or larger with the size of the weapon and related systems stretching from bow to stern (or in more accurate cases, top to bottom) of the vessel in question.

- Sabersonic

Luke said...

Jean Remy: At the very least, a Whipple shield will be as good as any other armor against beam weapons. For x-ray lasers or particle beams, the stand-off properties will not really help, but they will not hurt either. For high powered continuous lasers in the IR/Vis/UV, it will either not help much but not hurt (when the primary damage mechanism is by melting or evaporation) or it may actually be less effective than a single monolithic slab (for impulsive momentum transfer blasting out a section of armor, where thicker armor provides more support to resist deformation of the slab). For high energy pulsed lasers in the near IR/Vis/UV, the Whipple shield will be as good or better than a monolithic slab - as good for a rapid burst of pulses used to drill deeply, better for a single very high energy pulse that blasts a crater from the surface.

An ideal material would be something like diamondoid or fullerite - carbon has immense bond strength for its weight, giving it both incredible material strength and the best refractory properties of any element. That we cannot actually make these carbon materials in bulk for industrial applications is unfortunate, but don't let that stop your science fiction settings from making use of them.

Sabersonic: The standoff armor concept will work against just about any hypervelocity projectile, assuming it is scaled appropriately to the threat. By increasing the thickness and stand-off distance, you can protect against larger threats. Take, for example, a 1 gram steel ball impacting a slab of steel armor at 32 km/s. The kinetic energy of the ball is on the order of 1 MJ, and I estimate it will blow out a crater about 5.5 cm deep and possibly causing material failure or plastic deformation out to a distance of about 9 cm (details on how I did this calculation are here http://www.panoptesv.com/SciFi/DamageInstant.html , where the same principles apply to hypervelocity impacts and normal explosives as to laser pulses). A 10 cm standoff distance will protect the next layer of armor. If the mass of the impactor increases to 1 kg, it will pack 1 GJ of energy at 32 km/s. This will produce a roughly 55 cm crater and possible plastic deformation out to 2 meters, requiring about 2 meters of standoff distance between the shield and the main armor. (The quoted standoff distances are probably a significant underestimate, since the calculation assumes the impact vapor is doing work as it expands against the material, which is not true for simple vacuum spaced shields. Against armor where the space is stuffed with some strong but light and fluffy material such as aramid fibers, ultra-high molecular weight polyethylene, or carbon nanotubes, the estimate will be better). I estimate about half a mm of steel stand-off armor will disintegrate the 1 kg ball of steel at 32 km/s (out of time to estimate performance against a long-rod steel penetrator).

Citizen Joe said...

There is one more advantage to using Lithium Deuteride pellets (LiD). You would be just as correct to arrange it as D-Li... or D-Lithium... and since it is in the form of a crystalline salt, you would be hurling D-Lithium crystals at ships, which would then explode.

(you may have to say that out loud to get it).

Rick said...

I don't really have anything to add except that this is a way cool analysis and discussion!

And for science fiction purposes it seems entirely appropriate to assume that in the midfuture we'll have learned how to produce these materials on an industrial scale. Compared to old SF standbys like 'neutronium' it is a decidedly modest approach to materials tech!

Not to mention a certain inherent coolness to diamond(oid) armor!

There was an old Clarke story, forget the title, where they landed on the Moon and found that big gem quality diamonds were scattered all over the surface. But while they're there, one of the scientists gets notification that his synthesis process has worked. One ironic upshot: His wife divorces him afterwards, because her passion was diamonds, and thanks to his process they become more or less worthless. :-)

Rick said...

Forgot to add:

D-Lithium ... argggh!

And not to worry about 'straying' to protection against beam weapons!

Citizen Joe said...

Try silicon carbide for your diamond like armor. Yes, it isn't quite as strong as real diamonds or fullerene, but it is producible in space. Many of the asteroids are silicon based and there's plenty of carbon out there. If you filter out and build your armor with C-12 and Si-28, then your armor could even absorb neutron radiation up to 3 neutrons per molecule before the atoms become unstable. You can also polish the surface and keep oblique angles which would serve to deflect incoming laser fire.

Jean Remy said...

Silicon-carbide is exactly what I was proposing in fact. It's used as refractory material in nuclear reactors. I thought what's good for a nuclear reactor and has relatively low density could only be good for low-mass anti-laser armor, right?

Doesn't sound quite as cool as diamond armor.

Speaking of, if the wife liked diamonds more than the guy, good riddance. She wasn't worth it.

D-Lithium... 'at pun just brake the laws of physics. I cannae take it 'nymore.

Anonymous said...

The problems with kinetics is one of range. Shooting the target with a slug moving 100 km/s sounds great, until you realize it is going to take about an hour to hit something as close as lunar orbit. Even if you are talking about engaging something say 1000 km out, it is a full 10 seconds to get there. It would have to be a pretty pathetic propulsion system not to be able to get out of the way. You could try putting some kind of fuse on it like modern artillery shells, but then it has the same vulnerabilities those do, and we are developing systems to target those now.
So it would have to be under power and able to track the target. But at that point it is in essence a miniature ship, and faces all the difficulties incumbent with that. As you say, we are developing the technology to take out missiles now. In space they won't have the curvature of the earth to hide behind, and the greater delta V and acceleration required mean they are likely going to be bigger than our current missiles (which themselves are not small). And this doesn't factor in the logistical issues attached with using something with a finite supply.

Kinetic weapons would work fine if you were engaging in near space conditions (eg earth, the moon, and a few of the L points) and had a way to induce very high accelerations in the projectile without dealing with the questions that raises, but beyond that scope they get questionable.

Anonymous said...

The standoff distance of a Whipple Shield can be as large as a designer wishes, but like the argument on the inverse square boom over a shadow shield, there is so much distance that can be placed before it cuts into the mass allowance of the design.

Even if that isn't an issue for spacecraft (until the DeltaV budget gets into the picture that is), the standoff distance only increases the target profile of the spacecraft. I may be off, but in warfare, you don't want to make yourself, especially one that is resource and financially expensive, any easier to be targeted by hostile forces than you need to be. And considering that space-borne threats are not limited to planar, or even hemispherical like on a planetary surface, that whipple shield needs a full 360+ degree of protection around the more important sections of the spacecraft.

And speaking of 360+ degree threats, the angled armor as suggested by Citizen Joe isn't going to be as effective as on the ground if only because the angle of attack isn't limited to planar attacks that made sloped armor such an effective defense for tanks. Thickness, in addition to composition, will predominately dictate how well it can protect a spacecraft against a variety of weapon system projectiles. And thickness will have an upper limit due to the constrains of mass and deltaV budget.

- Sabersonic

Citizen Joe said...

Actually, directional armor would be more effective in space. Since everyone would be able to detect everyone, you could point yourself in the most desirable direction and it would have no effect on your course.

Jean Remy said...

"Actually, directional armor would be more effective in space. Since everyone would be able to detect everyone, you could point yourself in the most desirable direction and it would have no effect on your course."

That's assuming only one threat. However in a three dimensional theater against multiple threats, presenting minimal or ideal profile to one might present you maximum cross-section to another.

Rick said...

Anon throws down on (unguided) kinetics! But for range I would substitute flight time, because that is the critical metric for dodging. A single unguided kinetic is in fact pretty easy to dodge if you have more than a few seconds' warning time, because even a big target only has to move a few dozen meters to get out of the way.

A shotgun blast of fragments is more difficult to dodge, because it has a larger effective cross section - I'll have more on that in Part 2 of this discussion, which I'll be posting soon.

But I pretty much figure that long haul kinetics have to be guided, therefore miniature (or not so miniature!) ships, which does introduce costs and vulnerabilities. On the other hand, if it takes out a target that is more expensive, you have won the exchange.

Armor coverage is an interesting issue. All-round armor will be frightfully expensive in mass, and some important and exposed components - notably drive engine lanterns - are nearly impossible to armor.

So I'll make a case for 'faceplate' armor. Against kinetics it should be sufficient, because it is very hard simultaneous kinetic strikes along two different axes, so a faceplate is sufficient so long as you can pivot in time to receive the second attack.

In the case of lasers, two or more laser craft can nominally form a constellation to engage a target simultaneously. But other things equal, by putting full armor only on a faceplate I can save mass for greater maneuverability, and control the tactical geometry and engage one target at a time.

Also, range advantage of big optics pushes heavily in favor of battlestars with a single primary mirror; one such craft will have the zap range advantage over multiple enemy craft of equal total zapping power.

Yes it is a risk, but I think the tradeoffs favor putting most of your armor mass into a faceplate.

Luke said...

Citizen Joe: Silicon carbide is a good choice for many kinds of armor if advanced carbon materials are not available. Layered SiC and tungsten might also be a good choice - the layers of alternating low density/high density give you something of the effect of stand-off armor, acting to disperse the jet of plasma, vapor, and debris of an impactor, and both are very good refractories. Alloy the tungsten with a bit of steel to increase its toughness (the toughness will not affect the first impactor, but you don't want your armor cracking so as to reduce its effectiveness against follow-ups).

However, for neutron protection, you really want boron doped polyethylene (above neutron energies of about 10 MeV, add a layer of iron on top of it so that the neutrons can lose energy by hitting iron nuclei and putting them in excited nuclear states). Carbon is not all that great of a moderator and has a very low neutron capture cross section, silicon is an even worse moderator and has a fairly moderate neutron capture cross section. Meanwhile, the hydrogen in polyethylene makes an excellent moderator and boron is great for sucking up neutrons as they scatter down in energy from fast to thermal. Ultra-high molecular weight polyethylene is also very strong, similar to aramid fibers in strength and used in bullet-proof vests. It could thus make a good filler to stuff the gaps in whipple shields.

This leads to a good all-around armor of layers of silicon carbide, tungsten, and borated polyethylene fabric.

Anonymous: from any reasonable range, a kinetic will need guidance and some form of propulsion. They don't need high delta-V, just enough acceleration to home in on the target, counter any initial aiming error, and counter the target's evasive maneuvers. High thrust solid or hybrid chemfuel rockets should be fine for this job. You could use the rockets for the initial launch as well, or use some other launch platform (such as a coil gun) with a guided seeker head.

Also note that by your standards, all plausible near to mid term propulsion systems other than chemfuel rockets would not be able to get out of the way of a perfectly aimed unguided round in 10 seconds, and chemfuel is so propellant-thirsty that after dodging a few kinetics the spacecraft would be running on empty (Nuke thermal is an intermediate case - it has a high enough acceleration that dodging is plausible in some cases, but while way more propellant-thirsty than plasma and ion thrusters it would last a bit longer than chemfuel).

Note that the primary technology being developed now to take out missiles in space (that you mentioned) happens to be guided kinetic rounds.

Sabersonic: a high volume stand-off shield doesn't make you any easier to target. It can be easier to hit the shield, but the critical bits still have the same cross section as before, and are now obscured by a large volume but robust and essentially empty shell.

Rick said...

Very good point about the dodging problem. In a midfuture setting, electric drive doesn't have the oomph, and chemfuel you burn through pretty quickly. Which could argue for sporadic small kinetics, not really expected to hit, but to force dodging. (Thus just the opposite of the massive killer bus described in the next post.)

Anonymous said...

Luke: A hit is still a hit in both planetary and orbital combat, the only difference is what happens to the target after it hits. Once an attacker craft figures out that the mass they struck with their kinetics and otherwise is just empty space, then they'll figure out (assuming they survive that is) that little detail, they'll aim their weapon systems a little bit more closer to the center mass than before.

Not only that, but the whipple shield also makes it easier for onboard targeting systems to plot the course of the defending craft and make it all the more easier for gunners to have their mark strike true and hit something vital. And then there's the little issue with radiators if one utilizes a 360+ degree high volume whipple shield. Unless I'm wrong, those radiator systems are going to be stored in armored cubicles just under the shield that is being shot at.

As for that faceplate solution, well it only works effectively if the defending ship has only one hostile craft to point the thing at. When there's more than one hostile craft, then there's a problem. It would probably be easier to have separate Shield Bearing Drones to protect the mother craft's less armored sides if a faceplate-armored craft is facing against a cluster or even an entire constellation of warcrafts.

- Sabersonic

Luke said...

Sabersonic: I am not sure I follow your line of reasoning. Even if the attacker knows where to shoot to get the kinetic debris plume to intersect a vital component, the spacecraft is still better protected with standoff armor than without. While the target profile may be larger, it does not make you any easier to hit (except in non-dangerous areas). I do not see how standoff armor makes it easier for your course to be plotted, and if so, why it would have a significant effect. Lasers will already be shining on a target they can fully resolve, and kinetics will have seeker heads with terminal guidance (except for possibly a few seconds before impact, if they detonate into shrapnel, but for this errors in the target's course will be small and unlikely to affect the outcome).

You have a good point about radiators. For spacecraft designed to enter combat, my guess is they will have damage tolerant radiators that can take quite a few holes before notably degrading. There will also need to be other equipment outside of the armor - sensors, thruster openings, comm arrays.

Jean Remy said...

Damage tolerant radiators:

I'd say droplet radiators would be the best bet. The emitters themselves would have a relatively small cross-section, and the "panels" wouldn't be physical, so a shot through would simply scatter the fluid. It would cut into the coolant reserves, but not be as crippling as losing a solid radiator. The sprays could be shut off during brutal maneuvering so as not to scatter the spray during abrupt vector shifts.

Rick said...

Droplet radiators were considered for Ken Burnside's game, Attack Vector, but ended up not being used. I'm not sure of the reason(s) - possibly because the game was designed to have a lot of 'brutal maneuvering.'

Regarding faceplate shields, yeah, you are in trouble if simultaneously attacked from two widely separated bearings. But as with tanks it is a matter of tradeoffs. Thick all-round shielding will be enormously massive, perhaps too massive for a spacecraft with any maneuver power to speak of. Which makes it a prime target for a killer bus - the bursting charges can be reduced for a tight pattern.

Shield drones offload the problem but don't really change it, because you still have to deal with the mass.

And putting most armor in a faceplate needn't mean no other armor. You might have the heaviest armor in a faceplate, but secondary armor at least along one side, so you have a heavily defended aspect and a medium defended one.

Anonymous said...

Ok, I've read both posts and sets of comment threads, so now I'll say something (hopefully intelligable): First, something that I heard from an engineer who worked on tank guns (bear with me; I'm a little fuzzy-it was 25 years ago); a penitrator rod is made out of a dense, but low-melting point metal. It also has an optimal length of about 3 to 17 times the cross-section, depending on relitive velocity, so that when it strikes the target, the leading surface is vaporized, but the momentium of the rod behind it pushes it into the target faster than the expandsion rate of the now-gasious metal. As the penitrator fully enters the armor, the gas (being as dense as the solid metal), decelerates throught the solid armor like a bullet through liquid; when it reaches the interior of it's target, the difference in pressure allows the gas penitrator to expand at sonic to supersonic speeds...while it is still traveling forward at about the speed of sound. This blast burns, pulverizes everything in its path, and incenderates all flammable objects inside the target; if the fire is hot enough and the compression just right and the oxygen levels remain high enough, you can conceviblly ignite an oxygen/nitrogen fire as well. And that's just what happens inside a tank, just before the turret blows off (a tank turret is 1/10 to 1/6 the total weight of a tank). So, now lets go back to when a simular round strikes a spacecraft.
At the point when the initial blast occures, one of two things will happen; either a seal, door/hatch, cover, seam, bulkhead/deck, or access panel will fail- in which case the fireball will enter some other space and do bad things to them. Then, all the air, smoke, debris, and what-have-you, will be pushed by pressure to escape out the hole the penitrator came in from. That escaping air will be bad (obscuring your sensors, depleting your breathing supplies, ect) and making part of your spacecraft unusable until you get around to fixing it. If you can. However, if the compartment that the penitrator enters does not fail, then all that flame will shoot out the hole in the hull EXACTLY like a rocket. This is so obviously bad that I'll let you use your imaginations to picture it...

Ok, enought time spent dwelling on that! Here is something else you can think about: Nuclear driven kinetic weapons. I read about them on Atomic Rockets; they are like the propulsion bomb-units from an Orion (1950s version), or bomb-pumped X-ray lasers, but instead of a lasing array, they have a sheet of material that is super-heated and deformed into a bolt or 'spear' of plasma. (oh, no, a 'practical' plasma weapon...) Depending on the material and the thickness of the sheet, it could travel at hundreds (or even a couple of thousand) kilometers per second and have as little as a fraction of a degree of beam devergence. And, I'm sure, the pulse would glow like a lighthouse on fire, not to mention the flash from the where the nuclear detonation vaporizes the casing. Imagine the surprise of the ememy ship when that thing goes off just before it reaches their defensive-fire range! Just 'grazing' your Whipple shield would still put you in a world of hurt when the transfer energy causes it to explode. A 'shaped nuclear charge' indeed!
Well, just some thoughts...


Rick said...

Ferrell - On your first point, this relates to an issue I haven't dealt with at all here yet, whether the interior of manned combatant spacecraft is pressurized, or the crew suits up for combat.

Even if pressurized, though, large spacecraft with multiple compartments won't be quite as vulnerable as the very cramped interior of a tank.

On your second point, remember my 'accidental Orion' post a couple of weeks back? I hadn't made the connection, but that is certainly one compact way to give a projectile a very sudden and powerful kick!

Relating to neither point, but thanks for your comment over at TecTrends Monitor. Much appreciated on a new blog!

Anonymous said...

Rick- one, so I got the jump on your next post...
two- that's what got me to thinking!
Three- you're welcome; I enjoy your TecTrends Monitor very much!
four- It's late here and I'm going to bed now...talk to you later!

Mark said...

If you're using thicker faceplate armor, sloped armor for the faceplate would make sense as well, giving you a conical armored "bow" that you would turn into the attack. if you cover the rest of the hull in a Whipple shield with shutters or doors over the bits that need to be exposed and you suddenly have a surprisingly sleek looking warship.

Rick said...

Mark - I gotta think about sloped armor. My first thought is that it offers no real advantage. Against laser, the thickness of armor WRT the beam path is critical, and the effective thickness of oblique armor is greater ... but in a sloped faceplate you're adding area as you decrease thickness, so it is a wash.

Against kinetics, at terrestrial speeds - whether a lance at 20 m/s or a shell at 1 km/s, sloped armor causes the impactor to bounce off, reducing effective impact force. But at more than a few km/s everything can be treated as a fluid, because impact energy is much greater than any material strength. So again the angle of impact doesn't really matter, and sloping still comes out as a wash.

I could easily be wrong, but that is my first thought.

Luke said...

Ferrell: Your description of the effects of an armor piercing munition on an armored vehicle sounds about right, but the dynamics are a bit off. When uranium, for example, is not available, people use tungsten for their penetrators, and tungsten is the most refractory metal in existence - so clearly ease of vaporization is not a primary driving concern.

In any event, being on the other side of a bulkhead hit by a hypervelocity kinetic strike is not healthy. The cloud of plasma, vapor, condensed grit, and shattered fragments of bulkhead and penetrator will spray out in a hypervelocity cone, smashing anything in the way and producing an instant overpressure that acts like any explosive blast wave.

Jean Remy said...

The advantage of tungsten in a penetrator is its hardness. The advantage of depleted uranium is its density, in the same spirit that lead is used for bullets, besides its low melting point, which made it malleable and allowed soldiers to fabricate bullets in the field--before the introduction of the cartridge soldiers in some armies were issued with a molding set. An armor-piercing bullet for example has a sleeve of steel over a lead core. Ideally a penetrating rod would be a sleeve of hard material (tungsten/steel) with a dense core (lead/uranium), to provide mass and increased kinetic energy.

However those are for relatively low-velocity projectiles. At orbital speeds the hardness is less of an issue since, as Rick says, all materials act fluidly: at the moment of impact matter becomes a plasma.

Luke said...

Jean Remy: Tungsten is denser than uranium: 19.25 g/cm^3 for W compared to 19.1 g/cm^3 for U. Only gold, neptunium, plutonium, and the row 6 platinum group metals are denser than tungsten, and not by much - these are not used because of their cost (and, in some cases, strategic importance and radiological safety). Uranium is marginally better at punching through materials at 2 km/s because when it fails, it shears off into a self-sharpening point, rather than mushrooming into a blunt head as tungsten does, and thus preserves a narrow cross section to its target. It has an interesting side effect that the hot uranium powder produced spontaneously bursts into flame when exposed to oxygen, leading to interesting effects on the inside of armored vehicles after penetration. The self sharpening effect is irrelevant at orbital velocities, though, as the uranium just fluidizes like anything else.

Jean Remy said...

That's what I get for relying on memory rather than checking my Mendeliev Table.

/slap self on fingers.

Anonymous said...

Ok, I'm awake now! Just to shift the discussion a bit, how about when you shoot kinetics at a ship, you shoot a whole pattern of them on an intercept course so that you either have to expend a LOT of manuvering fuel or risk getting hit by one of them, thus ruining your day. What do you all have to say about that?


Rick said...

Ferrell - On one level that is the idea behind a killer bus, or any fragmentation kinetic. But in that case it is only dealing with the final, unguided phase of flight after a target seeker has (presumably) been slagged by defensive fire, whether zaps or counter-kinetics.

But yes, the same principle could be applied to guided kinetics, firing them in a spread so that the target either has to take its chances or make an evasion burn that effectively takes it out of the fight.

In kinetics-dominant combat that could be a primary tactic, perhaps the primary tactic. (Though it is expensive if you are using a lot of fairly complex guided weapons.

Jean Remy said...

Well some countries have been known to use several million dollars worth of guided missiles to destroy 50 dollars worth or tents and donkeys.

Or so I heard...

Rick said...

Though in fairness (?), if the guy you want to nail is in the tent or riding the donkey, the missile is cheap at the price. If he isn't, well, that's a failure of intelligence ... and yes, I'm aware of the implicit pun. :-)

Luke said...

Ferrell: That seems about right. Plausible near to mid future kinetic warfare will probably involve high delta-V but low acceleration carrier spacecraft (likely propelled by plasma thrusters of some flavor) and low delta-V but high thrust seeker heads (probably chemfuel, and which may or may not be launched from a "gun" of some sort for an additional 2 to 3 km/s of delta-V). Thus, there will be a range where if you launch, it takes enough time for your seekers to drift to the intercept that the target can put on more delta-V than the seekers have available. Beyond this range, the target can avoid any singe seeker. To engage at longer ranges, as you say, you launch seekers in a spread so if the target evades one, it will move into a zone threatened by another.

One probably counter-intuitive aspect of kinetics warfare is that you don't launch your ordinance in the direction of the target. You are already flashing past at something like 10 to 30 km/s, adding an additional 2 to 5 km/s of velocity by shooting the munitions straight ahead will not do much. Instead, you set your course such that your spacecraft has a distance of closest approach of, say, 1000 km from the target (perhaps this keeps you out of laser range, and gives you the opportunity to dodge his kinetic munitions). You then launch your seekers perpendicular to your direction of motion, towards where the target will be when both of you pass the plane normal to your relative velocity vector. This gives you the greatest range, and keeps you the farthest from enemy weapons.

Going back to composition of the kinetic penetrators - in asteroidal material, the platinum group metals are much more common than on earth. Since platinum, iridium and osmium are the densest elements, perhaps the penetrator rods or buckshot or whatever will be made out of these metals. (Oh, and one correction, rhenium is also denser than tungsten, but then again, rhenium is also about as expensive as gold, so it doesn't help much).

Rick said...

Luke - One probably counter-intuitive aspect of kinetics warfare is that you don't launch your ordinance in the direction of the target ... You then launch your seekers perpendicular to your direction of motion


Anonymous said...

"In kinetics-dominant combat that could be a primary tactic, perhaps the primary tactic. (Though it is expensive if you are using a lot of fairly complex guided weapons."

I got the idea from (of all things), submarine warfare--a 'full spred' of WWII torpedos to hit a high speed, very manuverable target used much the same principle. Time and velosity determine if and when you intercept another object. Dodge them or zap them, or both, you might wind up missing your 'mark' and the mission is a scrub. Miss the 'launch window' and your target is outside the range of your weapons; miss your 'burn' window and you can't intercept your target. A weapon not used is just as good (for you) as if your enemy didn't have one in the first place.


Rick said...

Ferrell - Well, submarines are one of the two basic metaphors for space warcraft, the other one being aircraft. The stealth aspect of subs is obviously absent, but otherwise it is easy to imagine kinetic-armed space warcraft as rather like submarines from the crew's point of view.

Anonymous said...

Something that occures to me about space warfare in orbit, is that in the cluttered space, and high-tension enviornment, that it may be possible to 'lose' a chunk of debris or a kinetic round...historical accounts of combat are filled with those lucky (or unlucky) occurances that have resulted in a battle going in a completely different direction than expected.


Jean Remy said...

It probably won't be as easy to "lose" a weapon as it is on Earth. Space combat will not have much in the way of fog of war because of drifting clouds of obscuring gun smoke, nor stormy weather or foggy weather, or even night-and-day, which make battles on Earth so fluid. That said, orbital battles are bound to be messy, and the more developed the orbit is (ie: a fledgling colony will not have the space infrastructure of an industrialized super-power) the more messy it will be.

However a radar blip on CBDR had better identify itself or it gets blown up.

Turbo10k said...

Found this on for hypervelocity impacts:
Sounds okay.

Anonymous said...

Just a quick comment on the use of Lasers as PD against KEW.

Consider a KEW projectile as primarily a rod at high velocity. As others have pointed out, adding a basic seeker with some delta-V could significantly improve your hit probability.

However, adding that sensor and engine means your KEW is now vulnerable to PD (which can easily kill your sensors).

However, killing a KEW projectile's sensor does not in anyway decrease the odds of it hitting the target! It just keeps the projectile from performing any course correction.

This also neatly counters the laser PD in flat space strategy of only shooting at projectiles with zero relative motion, since those with small relative motion must now also be targeted.

This leads to an obvious counter tactic of including a small charge to turn your single projectile into a shotgun round when it loses its sensing capability (hey, I'm being targeted by laser PD and will lose all course correction capability, better detonate so I still have a chance of hitting).

With a little thought, multiple charges could be included that could *directionally* detonate trying to throw the most mass in the right direction.

This tactic - counter-tactic should be a key component of any long lasting war (hot or cold).


Turbo10k said...

What's that crap before me?:

Jim, it's a complicated failsafe you've come up with. You're making sure that the missile hits after it's been destroyed. Strange things happen in space...


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Anonymous said...

Я тоже бывало такое замечала, однако как-то заранее не придавала этому значения.

Daniel said...

I see Whipple shields becoming the equivalent of reactive armor. Modern missiles are designed with reactive armor in mind: they carry /two/ warheads. First one fires and either sets off the reactive armor or makes a small hole, then the second, bigger one fires and carves through the remaining armor. Similarly, one could mount a small warhead (either explosively formed penetrator or explosively propelled penetrator) which would then make a hole in the whipple shield. After that the main penetrator comes through and deals with the main ship.

Or one could take a page from modern infantry weapons and have your kinetic launchers fire bursts of 2-5 penetrators that all land on the same spot.

Jeff said...

I'm not a physicist or an engi-neer. Just an old-line grunt. But, it sounds like your Whipple shield is similar to reactive armor. So, to defeat this, you'd use a tan-dem, or HESH , warhead. The first charge would detonate the reactive charge and the second would deto-nate against the armor. HESH rounds have been around since the 60s, if not before. I much prefer a blast/frag continuous rod war-head. It's too difficult to burn all the fragments with a DEW beam. All it takes is for one to get through... , yuck. Messy messy.