Comments on Rocketpunk Manifesto: Battle of the Spherical War Cows: Purple v Green

>And, finally, what would you call a combat spa...

2011-01-17T13:45:02.494-08:00

>And, finally, what would you call a combat spacecraft the size of a Laserstar/Kineticstar but armed with rocket driven morters tipped with bomb-pumped X-ray laers and/or nuclear shaped charges?

Nukestars?

Speaking of which: I know the cost would go up a lot, but bomb-pumped lasers on the front would mean a lot less distance to close before being able to wreck the defending 'star, meaning less of them need to be launched. Maybe if the lasing could work with a shaped charge, then a small warhead and laser right behind the nose armor.

Couple thoughts on kinetic design:

How expensive would it be to put a small, tunable laser on the front of every bus? With a bright light being shined on the enemy's sensors, hopefully targeting would be a little more difficult. Plus, if you either find the wavelength your enemy uses or randomly go through the spectrum, then the enemies point defense optics get a little toasty.

Of course, if you use disposable, one-shot buses, might as well turn them into penetration-aids. Leave the missiles as semi-dumb hunks of metal (maybe a small warhead on the front to make a hole in any whipple shielding) while the bus tries to confuse / kill any defending sensor or laser..

In my universe, quite the opposite. Kinetics are w...

2010-10-05T06:19:54.671-07:00

In my universe, quite the opposite. Kinetics are weak to lasers unless used in massive amounts, in each shot. Since every ship capable of fighting uses a laser, with laserships just the warships with the biggest baddest lasers, Kinetic craft are expensive and rare, while lasers commonplace.

Check my scenarios in ground warfare. The pirates use a kinetic craft, while cargo ships can be refitted with lasers very quickly for combat.

In my universe, quite the opposite. Kinetics are w...

2010-10-05T06:19:48.014-07:00

Yes. With a sort of meta strategic implication. Le...

2010-08-24T18:55:33.670-07:00

Yes. With a sort of meta strategic implication. Less militarized societies or communities may tend to favor kinetics as requiring less defense investment - just the actual kinetics, with a 'civil reserve' of ordinary spacecraft doing the pre-release positioning.

I haven't finished reading through the comment...

2010-08-24T15:46:49.474-07:00

I haven't finished reading through the comments but I'm left with the impression of a rock-scissors-paper type battlefield.

The best weapon to use against a laserless craft (e.g. a KEW bus) would be a single high delta V (long range) guided missile.

But a single guided missile/torpedo would be useless against a laser armed opponent.

The best weapon to use against a laser armed craft would be the KEW weapons bus (swamp the defenses).

The best weapon to use against a missile / torpedo boat would be the laser ship (if it had enough delta V to catch them).

Of course there's no reason that each of these craft can't carry a couple of auxiliary missiles or smaller weapons buses!

BUT a ship with a laser as the primary weapon will always be a warship first and everything else would be secondary.

The other weapons can simply be loaded into anything with cargo hard points (interior and exterior) and some extra delta V.

Jim

I did some caluclations on a recoverable bus, and ...

2010-03-30T06:04:06.216-07:00

I did some caluclations on a recoverable bus, and the numbers aren't as bad as they look. If I assume the same tech as given here, and wish to throw the projectiles at 10 km/s, the ship might break down as follows:
50% kenetics
10.8% recoverable ship
28.4% launch fuel
10.8% return fuel

The actual delta-v is 30 km/s for the recoverable part, while still being able to launch 50% of the launch mass in kenetics.

I would appreciate more visual materials, to make ...

2010-03-09T15:07:16.280-08:00

I would appreciate more visual materials, to make your blog more attractive, but your writing style really compensates it. But there is always place for improvement

One general difference between laser and kinetic c...

2009-09-10T21:23:32.598-07:00

One general difference between laser and kinetic components is that there is no particular reason for big kinetics platforms (except to be big and impressive). They can just as well be deployed from multiple smaller bus vehicles, allowing some more flexibility.

But I'd expect laser stars to be big, with the largest practical power supply and weapon installation, because one maximum laser can outrange two smaller ones of equal combined power, whereas kinetics are simply additive.

On the other hand, there's reason for kinetic buses to be fast, whereas speed does not add to the direct fighting power of a laser star.

So a constellation deploying both weapons might have one big laser star, a few smaller laser craft, and a number of kinetics buses, medium sized or smaller.

I would rather have constellations be a main ship ...

2009-09-10T19:55:20.108-07:00

I would rather have constellations be a main ship (Laserstar of Kineticstar) as a command ship for a small flotilla of smaller drones, themselves armed with an assortment of weapons and/or ECM. They can deploy large radar-reflective sails or overly large radiators to mask the thermal signature of your Laserstar. They jamming won't do all that much but might make it just confusing enough you have to add a few seconds for targeting computers to sort through the chaff. Use the kineticdrones to launch some projectiles in the mix to make things confusing to the other side, force them to overheat their lasers, stress their target acquisition software, and play merry hell with the enemy crew's stress levels. the laserdrones can be used as CIWS for the main vessel, or sweep the enemy ships from more angles than they can deal with.

An assault force would combine Laser constellations and Kinetic constellations, coming in from different angles. If you are the attacker and the defender has to protect a specific area, they will be faced with multi-pronged attacks. Because of the implied distances between your constellations, each main ship would be crewed to have command-level decision making in rapid comm range of the flotilla. Since none of these maneuvers can be stealthy, the enemy knows what may be happening. This is the other reason you want command-level decision-making in each constellations: if this is all posturing, there's the chance of someone on one side overreacting. If one captain jumps the gun, you don't necessarily want the whole fleet to commit.

"It was an adder!"

Jim, you might want to use a rail/coilgun to launc...

2009-09-10T19:16:42.792-07:00

Jim, you might want to use a rail/coilgun to launch an NSWR propeled kinetic mini-bus; I, for one, wouldn't want a barely controled fission reaction going off in my face :)

Also, on a slightly different track, the minimum number and make up of a Combat Constellation would be...what? three Laserstars, a Kineticstar, and a Commandstar? or three Kineticstars, one Laserstar, and a Commandstar? Or skip the Commandstar and do three Warstars (smaller, combined arms warships)?

And, finally, what would you call a combat spacecraft the size of a Laserstar/Kineticstar but armed with rocket driven morters tipped with bomb-pumped X-ray laers and/or nuclear shaped charges?
Just some thoughts...

Ferrell

More in the seminar than I can comment on! My un...

2009-09-10T13:57:48.040-07:00

More in the seminar than I can comment on!

My understanding of railguns is that they are limited to a few km/s max. Any faster and you melt the rails, not good. Coilguns may be more complex, but they give higher speed and less waste heat. Without getting into SF magitech, upthread Michael outlined a coilgun about 100 m long and shooting at 10 km/s, with acceleration comparable to a rifle round.

Pretty much keel mounted, but I will argue that primary directed energy weapons will generally be keel mounted, because you can mount a longer range weapon that way. And with long range, and given limited prolonged acceleration, you generally have time to turn and fire.

Particle beams are Nasty. And they don't sound extraordinarily effective, so their use against humans might be the equivalent of gas warfare. Depending on hard it is to armor/harden electronics, they don't sound very useful against robotic ships.

At 10,000 km, not long range in space, even a beam spread of 0.01 percent means a beam diameter of 1 km and a tiny fraction of the beam energy hitting the target (unless it is humongous).

Sabersonic: In a power limited situation (such as ...

2009-09-10T09:04:28.266-07:00

Sabersonic: In a power limited situation (such as the 1 GW reactor we have been talking about) a big (perhaps primary) advantage of the coilgun is that it can convert most of that power into kinetic power of its projectiles rather than heat power dissipated in the plasma arc. With 1 GW available, a coilgun might be able to deliver 900 to 950 MW of power in the form of the motion of the projectiles, while a railgun might only give you 200 MW.

There's also the issue that the electric arc erodes the rail, so the rail will need to be replaced frequently. In some railgun designs, the rail is part of the ammunition, and replaced after every shot.

Jean Remy: A coilgun is simply an electric motor unrolled into a line. As a linear electric motor, it no more needs superconductors than a rotary electric motor. Copper will work fine. Since the main inefficiency of an electric motor is due to electrical resistance, superconductors will increase the efficiency - but well designed electric motors already reach 90% to 95% efficiency.

I suppose, just for the sake of completeness, I will mention that there are two "flavors" of coilgun. The equivalent of a synchronous electric motor requires the projectile to be made out of ferrous metal, and the switching magnets attract the ferrous metal in the projectile. The equivalent of an asynchronous electric motor uses projectiles without ferrous metal, and pushes/pulls on the projectile by inducing eddy currents in the conductors for the magnetic field to push against.

As far as particle beams, a Z-pinch isn't really involved (you only get a Z-pinch when you have a current that is screened from its own electric charge by an ambient material). A good linear accelerator is all you need. particle beams do not self focus in space. Their main range limitation is the random thermal motion of the particles in the beam - the beam may start out a micron wide, but if the particles have an average thermal speed of 0.01 c and the beam is moving at 0.5 c, you get the beam opening in a 50:1 cone (this example is rather unrealistic for illustrative purposes - 0.01 c is not uncommon for the thermal motion in particle beams, but the speed of the particle bunches is likely to be more like 0.99 c to 0.999 c and this introduces relativistic effects into the opening angle. I can go into more details on how to calculate this if others are interested).

A particle beam does not do kinetic damage, not in the sense of a kinetic round. The momentum of a particle beam is about the same as that of a laser of the same energy, and the beam particles do not act as a continuous media to disrupt the target. Rather, each particle punches through individually, losing energy by ionizing the atoms it passes by and occasionally smacking into a nucleus and shattering it into more high speed particles. This does heat the target, but heats it deeply rather than on the surface. It also produces all the effects of ionizing radiation (which it is), such as health effects and amorphizing the crystal structure of delicate electronic components.

A particle beam can be deflected by a magnetic field. You would use a strong magnet for the turret. You would also neutralize the beam just before it left by injecting a co-propagating beam of oppositely charged particles. The primary beam will probably be protons, and it will be neutralized with electrons, giving you a beam of hydrogen plasma.

There is no intrinsic reason a particle beam needs to be inefficient. With high Q superconducting accelerating cavities, you could in principle put most of your energy into the kinetic energy of the particles. The main inefficiencies would then the the refrigeration you need to keep the superconductors cool. In principle, a free electron laser could have very nearly the same efficiency since it is essentially a particle beam that converts its particle beam energy into light energy, so it may be that particle beams and lasers have the same efficiency.

Luke

Jean Remy "I think if we tart throwing in tor...

2009-09-10T08:37:53.614-07:00

Jean Remy
"I think if we tart throwing in torchdrive the kinetic buses will fall by the wayside."

The NSWR ( http://en.wikipedia.org/wiki/Nuclear_salt-water_rocket ) sounds like it would scale down far enough to put in a missile that could track a target that is also using a NSWR to maneuver.

Re: rail guns vs. coil guns.

This technology: http://en.wikipedia.org/wiki/Launch_loop could be adapted to shooting 'cannonballs' at an enemy. BTW If I understand it correctly the waste heat would go into the launching loop & not into mass that is launched, so the 'cannonball' would not be enormously conspicuous in the infrared.

2009-09-10T07:44:28.799-07:00

This comment has been removed by the author.

A minor point, but IC fusion doesn't necessari...

2009-09-10T05:55:51.210-07:00

A minor point, but IC fusion doesn't necessarily require a laser. If the society has managed modest levels of antimatter production, you could do antimatter initiated fusion.

It seems likely that heat will by a problem with a rail gun, but does anybody know how that waste heat would compare with a similarly powered laser?

To weigh in on the particle beams issue: It seems to me that a particle cannon could have similar range and response time as a laser, but has fundamentally different doctrinal issues. Lasers seem to be the weapon to use when you need to project useful power, ie, power that you can use without causing unnecessary damage and without irking allies. Discreet, effective force projection. Particle beams, on the other hand, are the weapons you use when you want people to know that whoever stands against you will be dead, no questions asked. They get one chance to surrender, and if they don't take that chance, they die quickly from the initial damage or die slowly from a heavy radiation dose.

The United States would use lasers.
The Roman Empire would use particle beams.

Michael

Saber: "However I have to ask this question: ...

2009-09-09T23:05:33.858-07:00

Saber: "However I have to ask this question: Would a self-propelled Kinetic round be a better choice over an Electromagneticly Launched Round from a dedicated coilgun either spinal or mounted upon a turret?"

I think one of the points we've been discussing is to actually put a self-propelled kinetic in a rail/coilgun to give it that initial kick.

Coilgun v railgun (VERY simplified)

A railgun is a Jacob's ladder on steroids. It's of a (relatively) simple construction as you basically have two conductive rails, you create a plasma arc with the projectile, and you shoot the whole thing downrange. They require a LOT of power and create a LOT of waste heat. We already know how much of a problem waste heat is in space.

A coilgun is a Maglev train, and similarly more complex in construction. The projectile is in suspension inside magnetic coils, and the polarity in the coils is changed very fast, attracting and repulsing the projectile along. They require supraconductors which either need to be cryogenically cooled, or require the invention of "warm" supraconductors. They generate less heat but as far less "brute force" approach have a lower acceleration.

Purple v Green... v Orange?

Orange Option being particle cannons. If the technology to create z-pinched near-light-speed particle cannon exists, they might have greater reach than a laser(self focusing), will not require a vulnerable mirror, will inflict kinetic damage added to thermal damage, and have a time to target close enough to a laser that the difference would be insignificant (especially compared to a kinetic bus). The disadvantages are probably the need to mount a large accelerator, they can't be turreted since deflecting the beam robs it of most of their delicious kinetic energy, requiring the entire ship to swing, and they might be deflected with magnetic shields. Their energy requirements are probably a little off the wall compared to lasers and missiles.

Correct me if I'm wrong, but I have read/heard...

2009-09-09T22:22:16.239-07:00

Correct me if I'm wrong, but I have read/heard somewhere that for a coilgun to have a range equal to that of a railgun then the coilgun's lenght would have to be about two times or more the barrel length of the railgun. However, the chief advantage of a coilgun over a railgun would be a higher Rate of Fire which is perfect for the high volume saturated fire needed to at least keep a target craft busy while it either the attacker or its buddies maneuver themselves towards that target craft's weaker sides.

However I have to ask this question: Would a self-propelled Kinetic round be a better choice over an Electromagneticly Launched Round from a dedicated coilgun either spinal or mounted upon a turret?

I ask because from what I can gather, the chief factor in the cost of the Kinetic Round would be the drive motor that accelerates the mass towards a target and be able to have a high enough DeltaV budget to not only reach the target, but to also make course adjustments to lower its chances of being zapped out of the sky and keep on track with the target craft.

But what if that round only needed enough DeltaV to make course corrections and keep on target while some other external force gave the projectile the velocity needed to cross the distance between the shooter and the target? A Coilgun-launched Kinetic Round does offer that possibility as shown by the following visual examples at 5:57 to 6:02 and 7:44 to 7:58 in the following video clip:

http://www.youtube.com/watch?gl=JP&hl=ja&v=aZ_kGr0EK3M

However I am unsure if it is a viable weapon system layout for orbital space combat, let alone deep space. Then I got this little brain fart: If diffusion of a laser decreases its damage potential of the focal point upon the target and the distance between the laser and the target having its own diffusing properties, then would it not be prudent to launch a Kinetic Round/Missile/whatever towards the enemy craft that deploys a Laser Diffusion Cloud that is closer to the lasing ship than the lased ship?

And since a majority of the combat spacecraft classes are potentially being designed with an armored face plate as evident in the previous replies, would it be too presumptuous of myself to think that a majority of the offensive weapon systems would utilize a mechanized system similar to the Disappearing Gun as this article describes:

http://en.wikipedia.org/wiki/Disappearing_gun

And one other thing:

"In spite of the practical elegance of Michael's layered shutters, for cinematic purposes there is nothing like the order 'Unshutter main mirror!' ... external view, in silence, as the armored shutter slides slowly open to reveal a big laser mirror."

Well there's nothing really stopping one in creating that little visualization. Granted, it doesn't make mention to the inner shutters but then again, how much detail do the reader/audience really need?

- Sabersonic

Railguns and coilguns have very different technica...

2009-09-09T20:54:45.223-07:00

Railguns and coilguns have very different technical details, but in SF the terms are used pretty interchangeably. As I did in my last post, when I wrote 'railgun' even though I'm actually imagining a coilgun.

I think people say 'railgun' because it sends its payload at express highball speed. :-)

I think if we tart throwing in torchdrive the kine...

2009-09-09T20:53:49.108-07:00

I think if we tart throwing in torchdrive the kinetic buses will fall by the wayside. Now I'm not saying it's impossible to use kinetic in a torchdrive setting, but if starships can easily generate hundreds of km/s (or even Mm/s) you need some very hefty delta-v on your missile. The kinetics will need their own torchdrives to stay competitive, and I don't really see nuke-thermals, fusion reactors or anti-matter engines as small and cheap enough to make them viable. Skewing the purple/green fight even worse, if your trochdrive is an Inertial Containment Fusion system, the fact that it works using a powerful laser actually requires a Laserstar to *start* with, so ironically enough the weapon is determined by the engine, rather than the opposite. Not only would such a system be hard to put on anything very small, but you merely built a minilaserstar rather than a kinetic.

Low main drive acceleration makes Realistic [TM] s...

2009-09-09T20:42:21.611-07:00

Low main drive acceleration makes Realistic [TM] space combat a long slow dance, and the only way to avoid that is to break out the terawatt torch drives.

Powerful chemfuel thrusters can give a spacecraft a short fast kick to one side, but unless you carry a whole lot of chemfuel the thrusting will be brief, and a target seeker can carry just as much delta v (in a vastly smaller tank).

Much of the art of space warfare will be plotting your orbit so it get you to your objective without getting you into avoidable trouble.

If transfer speeds are high, defensive kinetics could end up striking far from the planet they are defending. You want to hit an attacking constellation before it begins its orbit matching burn, which can start a couple of weeks out for high ISP drive ships.

So you may send out your defensive delivery bus a couple of weeks earlier still, to push the kinetics up to a good speed and release them heading down the throat of the attackers. And if you have a high power railgun you can give them some extra kick.

Or alternatively the railgun can give them some side kick, allowing the delivery bus to deliver an oblique attack while staying well clear of the attackers' laser stars.

That last comment was mine. Michael

2009-09-09T20:38:43.057-07:00

That last comment was mine.

Michael

Luke, I'll defer to your knowledge, because I ...

2009-09-09T20:38:04.182-07:00

Luke, I'll defer to your knowledge, because I don't know the engineering of railguns, just the basic science. I was just thinking that a lot of the heat the railgun generated at firing would be due to current resistance on the rails, and that superconducting rails would help a bit. If a coil gun is better, than the rail ship ought to use a coil gun. The way the projectile is propelled is not as important as the fact that it is a projectile.

Michael: Rail guns require current to run down one...

2009-09-09T20:20:00.752-07:00

Michael: Rail guns require current to run down one rail, across the projectile, and back the other rail. The weak point in this system is where the electrical contact between the rails and the projectile. Since the projectile is moving at multiple km/s, you will not have direct physical contact. Instead, you need to arc across a gap to complete your circuit. The high current arc erodes the rails and projectile into plasma. In fact, modern rail gun designs propel the projectile by driving the current through a plasma arc behind the projectile, and the plasma pushes the projectile forward.

If you want superconductors to make a difference, ditch the rail gun in favor of a coil gun. No electrical contact is needed so you can levitate the projectile in the barrel (either using an inductrack design or making use of the perfect diamagnitism of the superconductors).

Luke

If the mini-buses are coming in on slightly diffre...

2009-09-09T18:40:07.954-07:00

If the mini-buses are coming in on slightly diffrent vectors, then trying to get out of the way and still fight the other Laserstar might be impossible...it also might use up all your emergency fuel so you don't have any left over to dodge the next salvo from the Kineticstar later that day. If the object of the battle is to keep the enemy Laserstar and its support Kineticstar occupied with combat to keep them from targeting your troop convoy from relieving/resuppling our strategicly importaint outpost, then all theories about chess games and manuver fall by the wayside...If keeping the outpost in friendly hands out weighs the cost of a Laserstar (or a smaller Warstar), then you might break the rules for a greater payback then the potential loss of a major warship.

Ferrell

This is all great, but where are the nuclear explo...

2009-09-09T14:58:12.111-07:00

This is all great, but where are the nuclear explosions and terawatts of bomb-pumped lasers?

Seriously, though, space warfare will be about maneuver. Its highly predictable outcomes will usually mean that no one fights unless victory is assured. Of course, some will gamble when the odds appear even.