War in Space, Part Two
Part one can be found here, and here is part three. Here can be found a battle in space.
Gravity Gauge
When we think about battles in space, it is useful to draw some parallels to earthly naval warfare. Just as there is a distinction between blue water and brown water navies, there will be a similar divide between warships designed to fight within the gravity well of a planet, and those intended to fight in the depths of interplanetary space. Warships designed to operate in close proximity to bases, and to deal with the rigors of maneuver in a steep gravity well will be very different from those required to make long journeys in flat space between the planets. We can think of the former as river gunboats, the latter as battleships.
Gunboats operating in orbital space around, say, Earth will have powerful, high thrust engines and limited facilities for life support. They will be based in orbital forts, or perhaps launched atop disposable launch vehicles like the Gemini or Apollo rockets of the sixties. The life of the crews of these warships will be more like that of an Air Force fighter pilot than that of a submariner - which I think will be the closest analog for long duration deep space warships.
Gunboats, operating in the constrained space around a planet, will engage at shorter distances than their deep space cousins. In most respects, their armament and sensors will be very like that of a modern jet fighter. In fact, they will probably look something like a modern fighter - as being able to enter the atmosphere (at least the upper reaches of it) will be a very useful thing. Aero-braking, skip-jumping along the top of the atmosphere, and similar tactics will all save fuel while increasing the range and maneuverability of the ship. And being able to land on Earth will be a happy alternative to dying in space in the event of damage to the ship.
Looking beyond the descendants of a marriage between the space shuttle and an F-15, other types of orbital gunboat can be imagined. Light sail ships, boosted by ground or space based lasers might also be developed. Heavier warships, analogous to coast guard cutters might linger in orbit for weeks at a time, before returning to base. If scramjets are ever perfected, then warships operating at the interface between space and the atmosphere might become common. All of these types would have some capacity to attack targets on the ground, and in fact some might be designed around that mission. Erwin Sanger, an Austrian designer in the forties, imagined a rocket-powered bomber that would skip along the top of the atmosphere.
In combat within the gravity well of a large planet, altitude will be the most important tactical consideration. Like the wind gauge for sail-powered warships, gravity gauge will be the dominant factor. Having the advantage of position will be crucial, in that a position higher up the gravity well translates to more options for maneuver. Also, shooting up the gravity well is inherently harder than shooting down. The first pilots of these warships will have to learn the somewhat paradoxical logic of orbital mechanics - slowing down speeds you up, and vice versa. For pilots used to the straightforward maneuvers within an atmosphere will have to adapt quickly.
Deep Space Design Tradeoffs
Deep space will offer vastly different challenges to warship designers. All of the propulsion systems that might be available in the near future have serious limitations. Two tradeoffs will determine the design of all warships. The first is mass/acceleration; the second is power/stealth. I noted in the first part the tradeoffs required by stealth. Most of the tradeoffs for mass and acceleration will push ship design in the same direction.
The major propulsion systems that could be constructed with current or very near future technology are chemical rockets, nuclear fission rockets, nuclear pulse drives, ion drives and solar sails. The first three are high thrust, short duration drives; while the last two are low thrust, long duration. With the exception of nuclear pulse, which I will discuss separately, all of these systems impose the same limitation on warship design: every ounce of mass will reduce the total acceleration the warship is capable of. Space types refer to this as delta-v, or change in velocity. It is a measure of the total change in velocity (speed plus direction) that the ship is capable of with a given drive and fuel supply. It doesn't matter whether your ship accelerates really fast and then coasts, or if it makes a long slow burn, since delta-v measures the total change. This makes it a useful comparison between ships even of vastly different design.
(While solar sails will have effectively infinite delta-v, because they use the solar wind for propulsion, solar sails will not be well suited for combat since the sails are so visible and so fragile. Warships will be confined to the other drives.)
Ship designers will always be striving to make the ship lighter. This will allow engines of a given capacity to achieve a higher delta-v. However, there are things that a warship must have in order to be effective. Weapons, armor, sensors and stealthing; crew, and food, water and life support for voyages lasting months or more; a storm cellar to protect the crew from solar flares; fuel or reaction mass; these are all things you will need to bring along. Rockets and ion drives are low energy, and this balance will place a premium on low mass weapons, small crews (and thus lessened life support requirements) and little or no armor.
Weapons that require vast power plants will be right out. (Both for mass and heat/stealth loss reasons.) Weapons that are themselves heavy will be right out. Missiles will not be very useful in long-range engagements, due to the fact that a rocket capable of propelling a warhead to a target tens of thousands of miles away in time to affect a battle will be almost as large as a small space ship. This would seem to put a premium on beam weapons. However, as we discussed in the previous part, and as Clueless mentioned, power plants capable of powering lasers, masers, and particle beam weapons will be heavy and produce lots of heat.
So, it may very well be that early spaceships will be armed with rapid-fire cannon and machine-guns. With some effort, a high velocity, rapid-fire cannon could be developed for use in spaceships. Rate of fire would be important, as I discussed in the first part. The more rounds put in the general vicinity of the target will increase the chance of a hit. One of the most promising technologies is the Metalstorm system invented by the Australian O'Dwyer. This system stacks bullets in the barrel, and fires them electronically. By bundling several barrels together, it can achieve rates of fire approaching millions of rounds per minute. Gunners on warships would fire hundreds of rounds at a time, laying patterns that would (hopefully) intersect the course of the target. Variations might include sub-munitions, target seeking or sensor rounds, and explosive rounds. After firing all its rounds, individual Metalstorm units could be discarded, increasing available delta-v. Rapid-fire, self contained, requiring effectively no external power, and disposable after use - Metalstorm cannon seem an ideal fit for spaceships.
As technology advances, smaller and more efficient power plants will allow warships to move toward beam weapons that will be more accurate than the cannon described above. Unless radically better drives are developed, missiles will remain the weapons of orbital gunboats, and not deep space navies. The mass penalty for missiles with adequate range will simply be too great. Warships of these types will be armed with cannon; and, if they can be developed, standoff x-ray lasers.
Deep space warships built around rockets or ion drives will tend toward small. Small is better for mass and stealth both. In all likelihood, they will be narrow, to provide a smaller radar and IR signature for enemies to detect. (That is, as long as the ship is pointing in the right direction.) They will be covered with stealth materials, and the rear of the ship will have complicated and fragile fractal heat radiators as well as the drive exhaust. Weapons will be concealed beneath the stealth covering. Life for the crew will be hard, living in cramped spaces for months at a time. I imagine it will be rather like a submarine.
Orion Drive The exception to much of the mass considerations discussed above is the nuclear pulse, or Orion drive. This concept involves building a very large ship with a heavy base plate attached to the back of the ship by some very serious shock absorbers. Then, you light off a small nuke behind the ship. Repeat as necessary. This is an over-the-top propulsion scheme. With this, you could accelerate very large masses very quickly. Ships using an Orion drive would simply have to be big just to make the acceleration survivable. Since you need a big ship; adding armor, huge power plants, or anything else you want is not such a big deal. An Orion powered warship would be a huge hulking brute. It would not be subtle, and stealth would be a lost cause.
No other type of spaceship (based on current technology) could match the Orion for speed and payload. It will be in a class by itself until and unless someone invents fusion or antimatter drives. Meanwhile, the inherent limitations of the other propulsion types will limit the kinds of warships that can be built around them. (As will the existence of Orion powered warships.) And given the requirement for (large numbers of) nuclear devices for propulsion in an Orion, and the stupendous expense of putting that much mass in orbit will probably mean that only governments will ever have them.
Life for a crewman on an Orion warship will be easy, by comparison. The generous payloads of an Orion will make for more comfortable quarters, and better life support. Large amounts of armor will likely contribute to the peace of mind of the crew as well. Rotating crew quarters providing artificial gravity might even be possible. The speed of Orion will also mean shorter journeys - weeks instead of months between planets.
In the next part, we'll look at strategic considerations, and how these ships might be employed.
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B,
B,
In considering Orion drive vessels, what kind of acceleration are we talkling about? That is, is it enough to turn the crew into moist red goop? And the reverse is true- how does such a vehicle maneuver, slow down, or stop without "gooping" the crew?
And why have human crews at all, when machines without crews could make the sick, envelope-pushing maneuvers that would otherwise goop a pilot?
The inertia of a large,
The inertia of a large, massive ship will tame the acceleration down to a very large jerk. If it were smaller, accelerations could be in the range of strawberry jam making.
Human crews will be necessary for a couple reasons - at least in the absence of real artificial intelligence. Unlike here on earth, where we can communicate in real time with and give guidance to "autonomous" drones that will soon make their appearance, time delays will require the presence of at least some humans in the ship. Second, we don't want berserkers running madly around the solar system, autonomously destroying stuff.
The first class of ships I described will be automated as much as possible - crews might be as small as ten or so. Further, each ship will be accompanied by autonomous drones, which will participate in the fight, but will be close enough so that they can be effectively controlled by the human crew on the warship.
I'll be talking a bit more about autonomous drones and such in the final part.
B,
B,
OK, nice reference to berserkers which indeed must be averted at all costs. What was that series again? Was it just "Berserkers"?
What's the scale of these warships you have in mind? If the Orion drive vessels are to be the "Dreadnought" of their age, it seems most of the design would be propulsion and support for them- like John said, a power plant with guns.
Is there a sci-fi equivalent of what you have in mind, dimensions-wise? "Discovery" from "2001", say? "Sulaco" from "Aliens"? The Death Star?
Wouldn't maneuverability in
Wouldn't maneuverability in wartime be moot? Incoming (or outgoing) salvos by light-based weaponry would obviate the need for high-speed manuvering as light is faster than any OrionBarge can dogfight. I'd think armor plating would be the prime necessity. Hollow out that asteroid, boys!
Um, where are these big ships going? And who are they fighting?
GP-- the problems with light
GP-- the problems with light-based weaponry are several. 1) you need a HUGE powerplant to provide a beam strong enough to punch a worthwhile hole in anything at distance, 2) beams are hard to focus on one spot over distance, and beam weapons work best when they can burn in on a target, 3) aiming is a nontrivial problem, since beam discharges travel theoretically forever in the direction of the shot, 4) that HUGE powerplant is probably a stationary target-- *kaboom*, 5) if the powerplant is planet-based, the beam would have to be powerful enough to make it out of the atmosphere while remaining ship-lethal.
Now, if it was a MASER sweep, as Steven den Beste has pointed out, you're screwed if your electronics are not hardened. But light-based weaponry just isn't feasible, as I see it anyway.
GP, Johno answered most of
GP, Johno answered most of your question for you - but the key thing is that light speed delays over any distance larger than say, fifty thousand miles, will make targeting a huge problem. (Yet captains will still want to engage at the longest range possible) You don't have to be faster than light to dodge a laser - you just need to be fast enough to not be where your enemy aimed at.
As to who is fighting, well obviously, it'll be us against the godless commies, wherever they ran to. Actually, part three is up, and I will deal with that (a bit) in part four.
Johno, an Orion powered ship would be (at a minimum) battleship sized. Though it would look more like an oil drilling rig, with big shock absorber legs connected to the pusher plate.
Having spent several years
Having spent several years testing Gatling guns, both 20mm and 7.62mm, I have to say that there is no such thing as a free lunch. First, it takes substantial energy to drive these beasts. It took 40hp to drive a 20mm gun and feed system at 6000shots per minute. Ammunition alone weighed about 1000lbs. The reactive thrust for a 20mm weapon was about 2000lbs. If you go to higher muzzle velocity, the reactive thrust goes up. If you go to higher mass flow rate, the reactive thrust goes up. Something has to counteract this. Gun barrels get very hot from both chemical thermal effects and even more from projectile friction. I have seen barrels split from heat....very spectacular.
For your near planet scenario, I am reminded of the Co-orbital Retrograde Attack Program (CRAP). It consisted of putting a mass of almost anything into the same orbit as the target, only retrograde. Fun :-)
Do you envision the requisite
Do you envision the requisite construction facilities for an Orion ship to be up at any point in the forseeable future? If they're in space, how do you build and supply them? If they're on earth, how do you launch a battleship/oil rig sized object into orbit? It seems to me that this is the sort of problem that could only be solved with some form of space elevator, or at least a Heinleinesque space catapault.
And I hacked together some stats on a space catapault(I was planning to use them in defence of the concept, excep t they didn't defend it) - assuming a 100-km launch track, a target in LEO, and a 20-ton payload, you'd need 405 m/ss acceleration(over 40 g's), and 800 GJ imparted over 22 s(a power of 36 GW, about equal to the average electricity use of California), and that would still take 100 days to deliver the weight of a battleship assuming one firing per orbital period.
The above said, if you want to build a fleet of smaller vessels, 1 GW of constant power supply(a moderately large nuke plant) to the aforementioned catapault could deliver about 500 kg per launch(~3000 tons per year), to 243 different orbiting factories - either to produce a fleet of smaller vessels, or to use them as supply points for a geosynchronous factory building a bigger ship. Assuming those LEO plants are intermediate processing, that's 729,000 tons a year being fed into the sky, or perhaps 600-700,000 after life support and equipment replacement requirements. That's the kind of scale to make it all work, but who can loft hundreds of space factories without using the catapault, not to mention finding a 100-km long slope lifted at 10.6 degrees from flat?
And yes, sorry for the long tangent...call me SDB Jr. ;)
Alex,
Alex,
Once there is sufficient motivation and technology, I see almost all major space vessel construction happening in space. Why lift hundreds of thousands or millions of tons of metal per year, when you can refine metal from asteroids already far outside a substantial gravity well? In fact, the only reason we aren't doing it right now is because economy of scale doesn't make it worth it to launch small satellites and a few science probes.
There will probably be highly automated refineriers right near the asteroid belt which will work on converting the raw materials into iron, gold, and all the other available materiels. Then it will launch payloads towards the manufacturing plants (probably by using slow but efficient ion drives attached to the ore blocks) where the ores will be turned into ships, space stations, weapons, etc. Finally, the process will be completed with a shipment of consumables that absolutely have to come from earth (things like water, food supplies, oxygen).
At first, most of the manufacturing capacity would go to building more refineries and construction factories, which would in turn increase capacity at a geometric rate.
I don't see any of this requiring any major technology we don't already have, although new technology could definitely make things alot easier and better.
That may or may not be
That may or may not be possible, I dunno. Refineries require massive amounts of electricity in some cases(e.g., aluminum), messy non-asteroid chemicals(e.g., I think cyanide is a necessary component of any gold mining other than the ancient "Grab the nuggets" method), or simply vast quantities of things that are common enough here but aren't big in space(e.g., where do you find enough coal to make steel in large quantity?). You'll still need supplies from Earth in vast quantity if you want to do anything in space in bvast quantity, and I don't just mean O2.
Re: Orion drive. Maybe I'm
Re: Orion drive. Maybe I'm missing something but exploding a nuke behind a big mother space ship wouldn't give you much push: No blast wave (no air) and little mass except for the slight mass of the nuke device itself which would go in all directions. Some little push from radiation maybe.
Alex,
Alex,
Actually, you don't need electricity to smelt aluminum, you need heat. A fair sized solar furnace would probably provide what would be needed, at least in Earth orbit. Same thing is true of smelting iron. Yes you would probably need catalysts and alloying materials for some operations, but they might very likely be available in the asteroid belt as well as the basic ores. Getting started is the hard part. Once you get established in orbit and learn how to function there, it will probably become easier in time to bootstrap to an almost exclusively space based system. You're basically right that energy is the critical component, so nearer the sun would be better. Perhaps the logical place would be in orbit around Venus. Mercury orbit is likely to be too hot for manned operations, but robotic foundries might work.
My understanding was that
My understanding was that aluminum-smelting was done with ungodly amounts of electricity, but that knowledge comes from a half-remembered passage in a Chem text several years ago, so I'll hand you that. One questions seems obvious with regards to orbital smelting though - we've been discussing coolant problems rather extensively in this debate, and if there's anything that requires more cooling than industrial-sized quantities of liquid metal, I'd be hard-pressed to think of it. How do you stop the station from melting? I would almost think that putting it on an asteroid is better - even if you're further from everything, you also have a base, not to mention a FAR better way to cool yourself. Anyone feel like towing a good-sized asteroid into LEO? Maybe LVO?
Alex,
Alex,
Actually, many scenarios for space manufacturing involve dragging the right asteroid into orbit where you plan to do the work. Then your waste heat can be used to preheat the portions of the asteroid that you plan to get your raw materials from. Eventually, of course, you eat up all of your asteroid real estate, and need to go get another one. Still, a medium sized nickel iron asteroid would probably yield more raw materials than we have already mined here on Earth to date. I don't want to downplay the difficulties in getting such a process started and operating routinely, but ultimately it should be preferable to doing the same thing here on Earth.
Re: Orion ships
Re: Orion ships
Anyone wishing to read an excellent fictional account of an Orion-powered warship (and, actually, a good near-earth combat sequence), should look at Footfall, by Larry Niven and Jerry Pournelle.
In their story, earth is under siege by aliens of a slightly higher level of technology (say 50-100 years into the future here). Mankind covertly (okay, suspend your disbelief) an Orion ship in the Pacific Northwest and launches it into orbit. The theory, of course, is that as long as the second bomb lights off properly, you'll continue moving upward after the initial thrust of the first. Not being an engineer, physicist, or mathematician, it made sense to me (although they may have used considerable dramatic license). The ensuring combat took place in the space between the earth and the moon. The Orion could correct its course by launching the propulsion bombs off-center. They also made use of the bomb-driven X-ray lasers (although I believe they were Gamma ray lasers in the book) mentioned earlier in this thread (or the previous thread).
The one other interesting vessel in the book was called a Stovepipe. Essentially it was a battleship gun with a pilot cabin and solid fuel rockets attached. Stovepipes were carried into orbit by the Orion (lots of cargo capacity) but, as far as I could tell, were good for a single use (and the pilot had little hope of returning). I suppose when your planet is besieged, you'll go to any length to be freed.
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I enjoy the discussion. Yet I
I enjoy the discussion. Yet I think that Space will never be heavily militarized. There is minimal economic return and the ships will be so vulnerable. I think on a small scale such as interceptors and police action it will happen. I believe that conquering other worlds will always be cost prohibitive. Trade would be a much better tool. Wars are fought for money first, territory is used as a function of economic growth or control of markets.