War in Space, Part Three
Here are parts one and two. And here is a battle in space.
Strategery and Spaceship design
All of this brings us finally to considerations of strategy. What would these warships be used for? Warships are often thought of in terms of how they kill other warships. This is not completely unreasonable. However, in strategic terms, warships exist to exert control over the sea. Historically, this has taken two forms here on Earth: to either protect your own shipping (preserving your use of the seas) or denying the use of the seas for your enemy. More recently, sea power has been used to project military power inland. US carrier battle groups are able to inflict significant amounts of damage to inland targets, and are also able to provide cover for amphibious assaults. To achieve these missions, warships and navies must often defeat other navies, which is why we so often think solely of warships' abilities to kill other warships. But the underlying purposes of navies and warships will drive the development of ship design.
In a solar system that is inhabited by competing powers, these missions will have close analogs. Protect your own interplanetary shipping. Deny it to the enemy. Project military force onto enemy targets on planets, asteroids or moons. Provide cover for space-borne assault on enemy targets. Each of these missions will require different types of warships. We have discussed the different types of warships that could be built with the technology that we have now, or could reasonably develop in the near future. We have seen that they fall into two major categories. How will they be used?
The Orion drive will provide a (very expensive) platform for moving large amounts of men and materials quickly across interplanetary distances. Ships built around less effective drives will be cheaper but much less capable than the Orions. It seems unlikely that any private concern would, in the near future, have the resources or need to build Orion drive commercial ships. Most private, and non-military government transport will use rockets, ion drives or solar sails. Sails will be especially favored by private concerns because of the cheapness of operation - absolutely no fuel costs. Faster transportation for VIPs or urgent cargos will be provided by souped up, stripped down nuclear thermal rocket powered craft.
If a power wishes to impede the shipping of a rival, non-Orion warships will be the most cost-effective commerce raiders. These ships would operate like earthly submarines, and it would be well within their power to effectively attack enemy shipping, or engage in anti-"submarine" warfare. Reconnaissance, intelligence gathering, lurking, stealthily inserting commandos - these are other missions that they might conduct. They could even serve as a sort of destroyer screen for a force of more capable ships. As escorts for friendly shipping, they would be useful in warding off the predations of enemy commerce raiders. But these light warships would be less well suited to the other missions that a space navy would be called upon to fight.
[wik] Side note: in talking about the relative usefulness of Orions and other warships, I am imagining a time when the solar system is somewhat well settled, and rival powers have emerged, and space warfare has had time to evolve. Initially, combat between the smaller classes of warships would be the leading edge - until the first Orion warship is built. I think that the first Orion would be like the British Dreadnought, taking naval warfare to an entirely different level, and possible igniting an arms race. The first interplanetary warships will be commercial or government ships originally designed for other purposes and retrofitted with weaponry. Indeed, ships like that will still be part of navies for a long time after the first purpose-built warships are laid down. But eventually, someone will become sufficiently frustrated with the limitations of conventional ships, and build that first Orion.
Battleship or Carrier?
Since we've been so free with analogies to naval warfare, let's throw out a few more. If the smaller class of warships, using conventional drives, are to be likened to submarines, what is the proper analogy for the Orion drive warships? The obvious choices are Aircraft Carriers and Battleships. Which one it ends up being depends a lot on weapons technology.
On earth, the battleship was surpassed by the carrier because of the advantages of aircraft. The best carrier without its dive-bombers, fighters, and torpedo planes would be a sitting duck for even an awkward, adolescent battleship. Why did aircraft have such advantages? Speed and range. Battleships were not only the largest of warships, they were the fastest and longest ranging. Aircraft trumped that by being able to fly above the water at speeds ten times or more faster than the fastest ship, and then drop bombs on the battleship with impunity from thousands of feet up.
Can we imagine an analogous vehicle in space? We have already seen that an Orion powered ship will be faster and have longer range than any smaller ship. While an Orion-powered ship could indeed carry fighter-equivalent spacecraft, dispersing your firepower into a bevy of smaller and slower ships does not seem to be as great an advantage as it was for wet navies. The same logic that drove the development of ever larger, ever more heavily armed battleships seems to apply to spaceships as well.
However, another consideration might yet result in Orion carriers rather than Orion battleships. The development of autonomous reconnaissance and (very soon) combat drones is well under way. There is no reason to believe that these developments will not be carried into space - in fact, all of our robotic space probes could be considered non-combat autonomous drones. The advantages of a non-crewed warship would be many - greater tolerance for acceleration, no need to waste mass on life support and a vulnerable but clever meatsack, and less concern if the drone is lost as opposed to a piloted warship. I don't think that the big warships will ever be unmanned, as the limitations placed on communications by the speed of light will require that humans be present at the battlefield. But that does not mean that drones will not be present on the battlefield. As I mentioned earlier, the line between weapon, sensor, and drone will grow vague. Each ship will be attended by a network of drones, feeding sensor data back to the mother ship; and if opportunity presents - deploying itself as a weapon. A big part of battle management will be the handling of these networks of drones. (I think that will be true here on earth in a very short time as well.) But these drones - be they weapons platforms akin to fighters, sensor drones, or x-ray lasers, will not make the Orion warship into a carrier. The primary focus will I think remain on the primary weaponry of the warship; if only because the autonomous drones of various types could never keep up with the mother ship. It does not pay to deploy millions of dollars of equipment that could be rapidly left behind by a fast moving battle, and play absolutely no part in the battle itself.
So the Orions will be battleships, queens of space. The generous payloads of Orions will likely see them armed with powerful generators, lasers and masers, particle beam weapons, railguns and metalstorm cannon. Bundles of lasing rods like those used in the standoff X-ray lasers could be dropped overboard with propulsion nukes, literally gaining more bang for the buck. The powerful weaponry of an Orion battleship, powered by an onboard fission reactor, would likely outrange as well as outpower any smaller ship. (Just like with traditional battelships, which could shoot farther than any other.) Armor will be possible, making the battleship resistant to many of the weapons capable of being carried by smaller warships, and even to those mounted on orbital bases. (An Orion battleship is in effect a mobile base - considering its size.) Crew complement for an Orion Battleship might number in the hundreds - mostly for damage control, but also to manage all the weapons, sensors, drones and communications that would be required by such a vessel. Next bit will cover what might happen in an actual space battle.
[alsø wik] Side note: The only reasonable variant on the basic battleship that seems likely is an assault version. It would perform the traditional naval missions of projection of force and covering assaults. This vessel would be used to rapidly transport space marines and the means to get them into whatever they're attacking - winged landing craft, zero-gravity assault boats, or whatever is required. This type of ship would also favor the types of weapons that could be used to bombard planetary surfaces. In time, as space navies build more Orions, variations in size and relative power might eventually be grouped into traditional categories such as frigates, cruisers and battleships. Or we might come up with altogether new names.
[alsø alsø wik] I think that in the long run, the traditions of the Navy will be more suited to space warfare than those of the Air Force. But since the Air Force is closer to space - they will likely get there first. And we'll have generals in command of our space fleets. And that would suck.
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I have some questions about
I have some questions about Orion. I can see that Orion would be useful if a flight originated on a planet. I can see how the overpressure from a nuc would provide powerful impulsive thrust in an atmosphere. On the otherhand, I don't see as effective an operative mechanism in a vacuum since blast effect is largely nil. Granted, there would be some residual impulsive effect from the mass of the bomb itself, but I can't help but feel that it would be no more than perhaps one third of the mass flow from the bomb since a substantial portion would be likely to be dissipated laterally to the sides. This suggests to me that the utility of Orion degrades substantially outside the atmosphere.
If the posited warship were to be constructed in orbit, the advantages of Orion would appear to be small. Indeed, if your interest were in maneuvering thrust you would have to carry a substantial number of nuc's to have a reserve for significant delta v, and this would grow roughly as the square of the vehicle weight. When do you reach critical mass? Can you effectively shield the crew from prolonged exposure? Would things like hydrogen embrittlement make the pusher plate lifetime unacceptably short?
Remember, velocity in space is still a matter of time, reaction mass, and specific impulse. Any of the vehicles you discussed can be as fast as any other one given the same vehicle mass. The difference is in the acceleration rate of the vehicle, and thus in the time it takes to reach any desired velocity. There is no practical difference in payload capability among the alternatives you listed for a ship built in orbit, just a difference in time to achieve a specific velocity. Isp may be the big swinger in selecting a design for a deep space vehicle, which would provide a bias toward ion propulsion.
If maneuvering capability is the criterion, then perhaps either a nuclear rocket or chemical rocket would be preferable. Or perhaps a hybrid....ion engine for cruising and chemical,or more likely nuclear, rocket, for maneuvering.
I return again to "mission"
I return again to "mission" and the question of whether people will go to space at all. Seems to me you have been reading too much SF. We have yet to colonize Antarctica. Why? No payback to match costs. And Antarctica is more benign than Mars by several orders of magnitude. We also haven't fought a war there. Reason? No people. No people, no resources, no war.
Yes, Orion drives are
Yes, Orion drives are effective in space. The amount of momentum you can expect to get out of a KT isn't as great as in the atmosphere, but it's still MUCH higher than from any chemical propellant, because of the higher exaust velocity.
I suggest you pick up a copy of "Project Orion: The True Story of the Atomic Spaceship", by George Dyson. It's quite a good read.
Given the exponential nature of mass ratios, you wouldn't have to achieve much efficiency before synthysizing anti-hydrogen would be practical. It could be used to energize much larger quantities of hydrogen, for high ISP rockets on a relatively small scale, and for military purposes also would be handy as a small scale explosive or particle source for a beam weapon.
BTW, Bill, the reason we haven't colonized Antarctica isn't because it wouldn't be practical. The mineral resources already discovered there would quite nicely sustain an extractive mining based economy. It's because of a political decision among the major powers that, because they couldn't agree who would get it, nobody would. Colonization of that continent is illegal, not infeasible.
Brett,
Brett,
While I grant that it is illegal to exploit Antarctica, there may also be another factor that is more relevant. to wit:It is still cheaper to get the desired resources other places than Antarctica. We have lots of shale oil in the US, but we buy oil on the open market because it's cheaper than extracting it from shale. There's lots of iron ore remaining in the Messabi(sp?) area of Wisconsin but it's too expensive to refine.
In a space construction scenario, despite the distances involved it may be cheaper to get raw materials from the asteroid belt, or even from the Moon, than to lift them out of Earth's gravity well. Money conquers all!
WRT Orion, I don't have the advantages of having read the book you reference, but I flinch at engineering challenges it poses. For example, to get significant thrust you would have to detonate the "fuel" very close to the pusher plate. Although the thermal effects fall off as one over R squared, the detonation would need to be close enough to the pusher plate to need to have it made of unobtanium if it is to survive thermal erosion for long. Does Dyson address this?
Oops, Meant one over R-cubed!
Oops,
Meant one over R-cubed!
Buckethead,
Buckethead,
Thanks for sharing your insight. Quite well thought out. However, your position here (and SDB's) seems to postulate that there'll be the same technologies in use today, only somewhat more efficient.
Admittedly, it's impractical to assume that we know what the actual limitations of new technologies. Regardless, I'd be curious to hear your comments on some of the technologies beginning to take form.
The obvious (to me) long pole in the tent is nanotechnology - specifically, the ability to generate diamondoid structures.
-John
The biggest problem to me
The biggest problem to me with the Orion concept is that you need a hell of a lot of acceleration out of each nuke(they're expensive buggers, for one), and I don't see any great way to achieve that. Simply because it's such unsustained acceleration, you either need to goop the crew or figure out a way for a nuclear detonation to last something on the order of minutes. One option would be to have the pusher plate be like a mile from the ship and use the shocks to spread out the acceleration over a longer period of time, but there are limits to that. I dunno.
And no, radiation falls off as 1/R^2, not 1/R^3.
Alex,
Alex,
You're right! I was thinking about the VOLUME of a sphere.
Other sources seem to think that you can do the Orion thing without gooping the crew. Dyson can probably answer that. I just don't think that it is a reliable long term system. Impulsive force systems are difficult to engineer.
Fusion rockets might be a better alternative for a vehicle with a substantial maneuvering requirement.
"I return again to "mission"
"I return again to "mission" and the question of whether people will go to space at all. Seems to me you have been reading too much SF. We have yet to colonize Antarctica. Why? No payback to match costs. And Antarctica is more benign than Mars by several orders of magnitude. We also haven't fought a war there. Reason? No people. No people, no resources, no war." -- William M Goetsch
What kind of tweeb are you? Do you have ANY idea the resources that are in space!?!?! The Moon alone has all kinds of crap we need!(helium 3 for one damnit!) and the stuff on mars... There are TRILLIONS AND TRILLIONS OF $ OF STUFF OUT THERE! GERRRRR! you don't know what you're talking about.
(Don't take this personal, I forgot me meds today)
On Orion version one, the
On Orion version one, the primary impulse was a specialized "package" designed by Theodore Taylor, essentially a nuclear "shaped charge". The bomb went off some distance behind the plate, but the side nearest the plate was full of some plastic material which was vaporized and ejected at high velocity towards the plate to impart momentum.
Orion drive plates were to be lens shaped in cross section in order to use mass most efficiently and reduce overall stress. Militaraly, Orion was offered to the Air Force in an attempt to get funding, but no one could think of a military task that was not already done faster and cheaper by existing or near term weapons (remember, this was 1959).
In the future, the Orion principle might be revived with microfusion explosions, where a powerful laser or electron beam array detonates tiny capsules of Dt-He3 fuel in the thrust chamber. Estimated performance of such a system running at @ 100 Hz would be a max velocity of 3 percent of the speed of light (3 PSOL), a fairly respectable velocity inside a solar system. This would still be a big ship as well (ranging from Saturn 5 sized to really huge).
Retractable radiators will probably be the major design feature of fusion powered ships. They would be retracted when running in "stealth" mode (i.e. powered down and cold), extended in cruise mode, and withdrawn again in combat. During combat, heat would be dumped into thermal storage tanks of heavy oil or molten salt which ring the outside of the hull. When the heat load is too great, the tank is ejected, but until then, it can serve as extra armour against beam weapons and absorb a certain amount of damage from kinetic energy weapons. This limits combat manoeuvres to very short bursts of activity, probably resulting in the use of missile swarms or metalstorm volleys as the primary offensive mode.
The primary targets would probably be space commerce, which is another kettle of fish altogether. In a mature space economy, the money would be in life support materials: carbon, hydrogen, oxygen and nitrogen, as well as He3 for fusion fuel. Bulk cargos of ice or liquified gasses would be sent as cheaply (read slowly) as possible, since Delta V is expensive. Robotic "supertankers" ambling along behind a lightsail or pushed slowly by a mass driver or similar high ISP/low thrust drive would be the main form of commerce, crewed by a bored AI leafing through the equivalent of a porn magazine. Humans would be sent by smaller fusion powered "fast ships".
Targeting "supertankers" will require either massive changes in velocity between the fusion powered warship and the lightsail or mass driver to capture the materials, or adopting a policy of "unrestricted submarine warfare" to destroy all enemy space commerce with kinetic energy pebbles launched during a flyby at 3 PSOL. The AI might be programmed with some interesting surprises and defense routines to defeat these tactics.
Running down a passenger ship might be difficult, since it will probably be smaller, faster and lighter than a Dreadnaught, while small, stripped down commerce raiders have to finish the job before being led to the heavily defended home port. Convoy escorts of passenger ships may happen (depending on the volume of passenger traffic), but the mismatch in performance and life support issues would mean only a very wealthy power could dispatch robotic warships as convoy escorts for cargo ships, or have fleet units do flybys at fairly regular intervals.
Since cargo ships may be dacades in transit, warships would probably be parked in the asteroid hanger unless a crisis situation developed, otherwise the fleet operations would suck up all your funds, and the ships may not be in the right position when the crisis happens (think of the dreadnaught fleets of the UK and Imperial Germany during WWI).
All of this presupposses that
All of this presupposses that defense by armor is possable but railguns negate this entirely by the mass ( almost two tons/sq.M.) required to deffend against a smart one gram projectile at only 10 klicks/sec.
How does it survive a 100 gram one at 20Km/S?