perfidy

Now I have to really think some...

Speculation is such great fun.

Is there any reason the orion ships wouldn't be double enders, much as some triremes were in ancient days? It would enhance manueverability as well as protection.

Also, a factor that isn't ( and probably can't be) taken into account is the development of unforseen technologies.

Sort of like old time futurists trying to picture a modern city without anticipating the elevator.

The only reason I can think of is weight considerations - and a pusher plate would be very heavy - even on a ship as big as an Orion battleship, that would be the single most massive element. But who knows? Maybe someone would build one that way.

I bet that the Europans would have surrounded their moon with a minefield of dormant missles, similar to the "smart rocks" SDI system. It would be hard for the Titanian fleet to detect the objects without using something like active radar, so the missiles could have a good chance of disabling some of the attacking vessels.

On the other hand, a disabled Titanian vessel would still be a problem for the Europans if its massive bulk was still speeding towards Europa. Maybe the mines could be nuclear ...

Has anyone else has read Lem's "Peace on Earth?" The one where weapons escalation on earth led to the partitioning of the moon so that nations could fight proxy wars with robot armies?

And then the robots went radio silent?

And then a few years later, their threat-assessment software realized that the real threat was the meatsacks back on the blue planet?

All that is to say, I know we're spinning deep into speculative territory here, but don't remote "smart rocks" have dangers all their own, e.g. subvertible by a canny enemy with good hackers?

When the era of space warfare comes, if I'm still alive, I'm moving the Perfidious Compound from the coast of Nova Scotia to the asteroid belt where I can hide undetected. Then I'm mining all the asteroids around me with EMP's, molten-metal ejectors, decoy bases, and area explosives.

All y'all can keep your Orion drives and interplanetary campaigns. You want my asteroid mines, you come into my hizzouse and try and get them!

Actually, I think that mines will be pretty rare. A mine, if it is to be useful - kills the enemy; and safe, doesn't pose an enormous threat to friendly ships - it needs to be somewhat stationary. It would need to stay more or less in the same place. In space, this would be difficult to say the least. Orbital mechanics would constantly be moving your mines away from whatever they're protecting. And if you beef them up, give them fuel to move around, you're really not talking mines anymore.

Further, I think speed differentials would render them harmless. If a mine is in an orbit around, say, and I come cruising by at seven or eight km/s, how is it going to get me? The chances that the direction of its orbit would put it in a position to come after me is slim. Space being so big, the chance that I come near it is slim. Unless you literally saturated space with mines, it's not going to work.

Remember that here on Earth, we mine harbors and narrow passages. You can't mine the ocean, and space is incomparably bigger.

If much more effective (fusion, A/M) drives were developed, dormant missiles would work in some cases.

In light of Tim's comments on the first post, I think that the Pyle would have deployed decoys as well. However, being targeted by dozens of battleships would quickly saturate her defenses.

You brought out some good points which I had not thought about which would make mines less useful, but I think there might still be a place for them in space combat.

Some of the drifting problem for mines could be avoided by frequent replacement of the mines (and having the older mines fly themselves home if they are too valuable to discard). The danger to friendly ships could be minimized either by having the mines lay dormant until activated by the proper signal or by giving friendly ships a "password" that changed with time and perhaps with location. The mines could also be programmed to deactivate if they fell outside of the areas assigned to them.

The problem of empty space is trickier, but might be accomodated. First, certain routes would tend to be preferred over others due to the positions of the planets and tactical considerations; this would especially be the case in the final approach to Europa. Secondly, a minefield could be quietly sown at short notice and from a distance in space, especially if there were vessels stationed in Jupiter or Solar orbit for that purpose -- so that after the Titanian fleet was spotted a spread of mines could be thrown along the fleet's probable approach path (though you might call this "artillery" rather than "minelaying"). Finally, the effective distance of mines could be increased if they could maneuver themselves (as subtly as possible, of course) in response to the estimated course of the approaching fleet (perhaps given in coded broadcasts from Europa).

In the scenario imagined here, a minefield would still be valuable even if it did nothing more than make the Titanian fleet change its course to avoid the mines, giving away more information about their position and gaining valuable time for the Europans.

So would this battle be any different if both sides had fusion powerplants?

Perhaps the mines could be tethered to a sattelite which would launch them when an attack was suspected and reel them in when freindly ships wanted to pass. Of course then the sattelite would need to be refueled in order to re-launch them, but you would solve the problem of drift and keep the individual mines from becoming ridiculously expensive.

I would argue that the only place that space combat is likely to occur, given the stated constraints, would be in the vicinity of each terminus of a flight. As noted above, the geometry of the relevant terminii are continually changing, so that midcourse intercept would be unlikely in the extreme. Add to that that each vehicle may follow a different acceleration profile because of load and propulsion type, and the possible transit orbits would be widely spaced. A solar sail, for example, might accelerate slowly, but continually, so that it reached quite high velocity around mid course before going into "reverse thrust" to decelerate to it's objective. That's not a Hohman trajectory! On the other hand, a chemical rocket might indeed follow a Hohman trajectory from initial burnout to deceleration burn. What all this means is that the only place you are likely to be able to find someone to fight is near either terminus.
I dislike mines as weapons precisely because they are hazardous to both parties. My vote would be for a constellation of large orbiting forts equipped with multiple long range missiles.
As a note, if you are using nuclear-pumped X-ray laser warheads, the solution to target orientation problems is to offset to one side and orient the warhead to fire into the side of the target, rather than into the pusher plate.

Mines are area-denial munitions. This applies to both landmines and seamines, so it is reasonable to project this into space warfare. What this means is that their primary purpose is NOT to destroy or damage the enemy, but rather to prevent him from using a given approach path. Of course, they have to be able to damage the enemy enough to make it preferable to go around them, rather than thru them, in order to accomplish this task. Most minefields, both land and sea, have been effective even when only lightly sown. The *uncertainty* is what makes them effective. Consequently, in this Titan vs Europa scenario, the Europans could, for example, place a bunch of mines in Jupiter orbit in such a way as to limit the possible gravity assist approaches the Titanians could use. This would allow them to place their fleet to cover fewer possible approaches, allowing them to achieve denser weapon coverage of the lower volume of possible Titanian approach paths. Mines would almost certainly be used under those circumstances. A few hundred cheap nuke-pumped x-ray laser mines in jupiter orbit would ensure a few dozen being at the appropriate places in their orbits to do the job, no matter what time the Titanian ships arrived. It only takes 24 GPS sattelites to put 3 in usable positions, everywhere, always, for navigation purposes, here on Earth, so it shouldn't take an unreasonable number to usefully channel the arriving Titanians.

We need to sim this. Put on your thinking caps....

Addendum...another potentially valuable use of mines would be in the role of "dumb sensors" in the following scenario:

1. The enemy fleet could be approaching on one of several feasible courses (these would be fairly close together considering the "hugeness of space", but far enough apart to be significantly apart in the "short term" covered by the time of the engagement) and

2. Your fleet is not able to deploy so as to cover all feasible approaches in a limited time (most likely because you are a Famous Few).

So you deploy "in depth", allowing the enemy to announce his presence by the lighting off of some of your nuclear mines. Once you detect the detonations, you know where to put the fleet (at least at the "coarse" level--you'd need more detailed information for a detailed op-plan).

Another possibility is a 'mine flinger' type of orbiter. Assuming the planet would have bigger and better sensor capabilities, the flinger could throw a swarm of mines into the path of incoming ships. Kind of like leading a moving target with a shotgun. With rudimentary steering control on board the mines, the need for initial accuracy decreases. Make the mines function like some of today's systems, where they destruct after a set period of time (or distance travelled), or even like torpedoes, where they would reverse course and return along a parallel path. Heck, add IFF to 'em and scatter them like grass seed before a battle to cover potential flanking routes and so on.

Ted,
How does this differ from a missile? It goes where you (presumably) want it to go and it blows up a target. I guess that the only difference is that you put the propulsion portion of the problem on the orbiter rather than the weapon. How does the orbiter react all of this impulse it must provide?

Good point John. Essentially they are missiles and I hadn't thought of that.

Dan, Ken,
Dumb question (mine). Why would the Titanian fleet have to use a gravity assist maneuver to attack? Since it seems to be assumed that the Orion battleships have substantial delta-v capability, what is to prevent them from just dropping directly into Europa orbit around Jupiter? If they can do that, where do you put your mines? Seems to me that the approach options are fairly numerous.

John,
Because no matter what kind of delta-v your ship is capable of, a gravity assist maneuver can do it even faster, because it adds in it's delta-v to your propulsion system. Additionally, dropping into Europa orbit would require deceleration, which with an Orion ship would put these zoggin' big nuclear explosions out ahead of your path, acting like a big strobe light advertising "Here we come!!!". Using a gravity assist maneuver for the deceleration would allow you to do it in a somewhat more stealthy manner. Every little bit helps. Which brings up the reason for mining the approaches. Even if they are trying to come in stealthily, the mines going off would scream "Here they come!!!", which could give a significant advantage, even if the mines don't actually do all that much damage.

Rereading this entire page and the comments, I am reminded that there is an excellent fictional treatment of Orion warship weaponry available: "Footfall" by Larry Niven & Jerry Pournelle. Great story, Check it out...

I have been swamped at work this last week, and I apologize for not finishing the scenario.

Thanks to all for the great comments, and I have integrated many of your comments into my thinking about how the whole thing will turn out. It should be up in a day or so...

Dan,
I'm not arguing about the utility of a slingshot maneuver. On the other hand, if I knew the Europans had mined that approach why not just bypass it? It's not clear that the Europans would not see the Titanians decelerating even if they WERE using a slingshot. By the way, just what are the sensor systems that are going to see these ships/propulsion explosions at such a great range? If you had something like a Hubble with the IR imager I'm sure you could see them if you were looking in the right place, but the field of view is pretty small, making a meaningful sky search difficult. Then too, electromagnetic noise around Jupiter is probably fierce. Could you hide by decelerating only when Europa is on the opposite side of Jupiter?
I did, by the way, read "Footfall". Good book.

John,
There are good answers to your questions, but I will have to think about it a bit to figure out how to describe the situation without the use of diagrams, which are not possible in this forum. I will get back here on this tomorrow or saturday. BTW, Buckethead, It's probably a good thing that you haven't finished it. This is a good discussion. You might get even better input if you stay swamped for another week, before you get back to it...

Would there be any place in this war for giant kamikaze asteroids equipped with Orion drives (or large numbers of smaller objects hurled their home base) aimed at the enemy moon? Their mass would make them immune to some of the more elegant weapons, and the orion drive could keep the things on course if they are hit with nukes. I'm sure that defending planet could counter the approaching masses with dumb objects of its own, but defense would be difficult for the planet with fewer of these missiles -- if nothing else, the swarm of rocks might distract the defender from its fight with a simultaneously approaching fleet.

William,
I guess the answer to your question is dependent on what the Titanians objectives are. Certainly what you propose is possible, and even a very effective strategy if your objective is to completely obliterate the Europans. Usually most civilized (?) combatants (an oxymoron?) seek to exploit the entity they are attacking by taking the products of their labor or by taking their territory. Neither of those is possible if you bash them with a big rock. Considering that life here on Earth has barely survived some encounters with asteroids, a much smaller Europa would likely fare worse.

There is also the fact that using Asteroids as WMD's would probably result with retaliation, and then MAD, similar to the potential outcome of a nuclear war on Earth. So I think retalaition and MAD would likely deter such a strategy.

I see both of your points. I'm sure that use of planet-destroying weapons would also make one unpopular with the rest of the nations of the Solar System. But is there no sure defense to my asteroids of doom? Because if that were the case wouldn't the situation be similar the cold war, where a conventional confrontation was never seriously contemplated because of the fear that any war would eventually go nuclear?

OK, John, so it took me longer than I said, but here's my response to your post of Apr 29 10:21p: First of all, if the Titanians know the Europans had mined a specific approach, why not bypass it; That's the purpose of mining it. As I said before, mines are primarily an area-denial munition. If they make the percieved cost of using the approach too high, the enemy will not use that approach. This allows you to channel the enemy into routes you WANT them to take, for whatever reason your plans make that advantageous to you. Second point, can the Europans see the Titanians coming even if they are using a slingshot; As you mentioned in the last line, if you plan your approach when Europa is on the opposite side, it would mean they could only see you from outposts in different orbits. Said outposts could have their reporting networks jammed or be destroyed in advance, reducing warning time. It may not work, but then again, it might, and it would probably be worth a shot. Additionally, since the Titanian fleet would not be flying in formation, but rather coming in from somewhat different directions and speeds (due to wanting to all arrive at the same time, at the same place, even though all the ships would have different starting places, times, available delta-v, etc), coming in from directions that are hard to see would make it more difficult to get sufficient accurate iformation to be able to trace all the future paths ahead to find out where they are all going. Given this, the Europans would likely mine the most useful jovian gravity assist approaches. That would be the ones closest to jupiter, which gives the greatest velocity change, and the most difficult for the Europans to predict the end result of. This would force the Titanians to use gravity approaches farther out, which would be more predictable (this is the part I wish I could draw a diagram for. It's alot more obvious what I'm talking about if you can see it as a picture). Finally, sensors to see 'em coming; If they are using Orion ships, the nuclear explosions would be obvious to the naked eye from well outside the jovian system. They are really damn bright at any electromagnetic frequency you care to measure. This is why the Titanians would prefer to use a gravity assist so they wouldn't have to use the nuke drive. Without those, the detection problems you mentioned would then be highly significant, possibly giving the Titanians a useful advantage.

Dan,
Good points, but I can't help still having a few questions. (1)Since transfer orbits are likely going to have excess energy to dispose of, compared to Europan orbital velocity, what we are looking for should be a velocity decrement. While I can't rule it out, I've never heard of a slingshot maneuver being used for anything but a velocity increase? (2)You didn't say that the origins for the transfer orbits would be widely disbursed, but if they are, then the corresponding transfer orbits would have significantly different apsides, making the mining operation difficult at best? Indeed, how would Europa know where they might come from? A three corner orbit around Mars? (3)Since Jupiter is generally held to be a failed brown dwarf, it's vicinity is likely to be electromagnetically extremely noisy. The consequence of this is that communications circum Jove are probably going to be by laser tight beam. Lasers are almost impossible to jam except by another laser saturating the receiver, something which is both difficult to do and a dead giveaway.

Finally, as you may see from my other posts I am not enamoured of the Orion concept as being really viable for a long term force in being. I can't help seeing fusion rockets, ion rockets, and solar sails(in the inner solar system) as being more likely solutions. Considering the work being done on the nature of gravity, I would not rule out some form of gravity drive, depending on the era under consideration. 2100c.e. probably not. 2500c.e., maybe. If my guess is right, the problem of reliable detection is much more severe.

John,
OK, Here Goes for (1): While the numbers work out substantially the same using either Newtonian or Einsteinian gravity equations, the Einsteinian way of looking at it gives us a nice, easy to understand picture of the situation, so I will use that: Imagine the funnel-shape pictures you always see in magazine articles and tv shows about black holes. That's a gravity well, which is what we are dealing with, here. The funnel-shaped grid lines represent space-time, distorted by the gravity of the object in the center. Now, imagine that the object in the center, which is providing the gravity, is rotating. It will drag those grid lines around with it. Now imagine a marble rolling along on the flat part of the grid, and then coming upon the distorted part. If it enters the funnel shaped part going in the same direction as the gravity source is rotating, it will be dragged along with the grid lines, which will give it a bit of a boost. The boost comes at the expense of the object in the center's rotational energy. But if it comes from the other direction, so it's moving against the rotation of the grid lines, it will be dragged backwards, along with the grid lines, which will take some energy away from it. That energy will wind up in the object in the center, as an increase in it's rotational energy. If your marble comes closely enough to the object in the center, enough energy will be stolen by the rotation so that the marble won't have enough energy to get back out of the gravity well, and will, instead be captured into orbit around the center object. That's what the Titanians are trying to do: be captured into jupiter orbit, somewhere in the vicinity of Europa. As far as examples of this having been used in practice, the Galileo probe used gravity assists in the inner solar system to gain energy to get to jupiter (the type of maneuver you mentioned being familiar with), but once it got there, it used a gravity assist to slow down, and enter jupiter orbit. All the recent mars probes used gravity slow-downs to enter mars orbit. It's been used repeatedly by NASA, but the news media tends to concentrate on the speed increase aspect, because that sounds like getting "something-for-nothing", which is about the highest intellectual speed your average journalist can manage.

The comment software only allows 5k, and the stuff I tried to post is larger, so see the next post for the rest...

Here's part two, in re: point (2): Actually, the mining operation would be extremely easy. The most important approach paths for the Titanians to use jupiter for gravity slow-down are extremely close to jupiter. The closer they go, the greater the effect. Picture the gravity well diagram you imagined for number (1), above. The deeper you go, the steeper the gravity well, and the greater the effect of going with or against the rotation of the grid lines. No matter what direction the Titanians are coming from, that principle will always apply. The Europans will place their mines in close orbit around jupiter. The closer the Titanians come to the jovian atmosphere, the more Europan mines they are likely to encounter, and the more damage they will take from them. If you do a web search on GPS (Global Positioning System) you will should find a diagram that shows the 24 sattelites (plus some spares) in orbit around Earth, and that gives 3 above the horizon for any point on earth at any given time. Use a similar distribution of mine sattelites in jupiter orbit, and approximately 1/8th of them will be above the horizion for any point at any time. Put 240 in orbit, for example, and that makes roughly 30 capable of attacking any ship in range at any time. Use nuclear bomb pumped x-ray laser mines and the explosion of the mines will tell the Europans that the Titanians are on their way, do some damage to the Titanian's ships, and with a little bit of luck and some computer orbital calculation it may give the Europans a good idea of the Titanian's planned area of operations. It wouldn't take all that much computer power, either. The AEGIS missle system the US Navy has on it's most recent CGs & DDGs is capable of tracking 96 different targets simultaneously, directing weapons toward each of those targets, and continuing to scan the airspace around the ship for further targets, all at the same time. The system was designed to use the Intel 80286 processor. The navy had to upgrade to the 386 processor during the first maintenance cycle after deploying the system only because no-one was making 286s anymore. If you are not drawing fancy pictures on the screen for game players to admire, the actual mathematics of the problem are relatively simple, when compared to even currently available processor power, and can be handled by processors that were being used on desktops in the late 80s. It would be trivial for processors available when this scenario is actually possible. Which brings me back to the area-denial munition concept. If near-jovian space is heavily mined, the Titanians have to go farther out, recieving less benefit from gravity-assist, requiring them to expend more of their on-board delta-v. Their use of the on-board propulsion is potentially detectable by the Europans, giving them more info on what the Titanians are doing. It also uses up Titanian delta-v, which will then be unavailable for the coming battle. In warfare, any little advantage might make the crucial difference in who wins and who dies. I can give an arbitrarily large number of historical examples where seemingly trivial issues made the difference between a win and a loss.

OK, That's it for tonight, I've had enough. I will continue tomorrow with the rest of your post.

Dan,
Great explanations so far, given that you don't have a common blackboard to draw on. I think the point I missed was to not think about the rotation of Jupiter. Obviously, the closer you get the less the effect is like a (huge) point mass and more like a (huge) distributed mass, which would have the effect of dragging you in the direction of rotation (my non-mathematical visualization). I can see that if you mine essentially all of the near-Jupiter orbits it would have the effects you describe.

What about ordinary civil commerce? Commercial ships are usually even more interested in conserving delta-v as a cost of operation. Obviously, you could have a command link that would arm or disarm the mines on command, but that is also another failure mode, as well, either technical or human. Then too, how about spies or saboteurs?

An autonomous system is more reliable as a weapon, but tougher on peaceful friendlies, either economically or physically. A decent IFF equivalent could work, but then you have a key distribution problem to deal with. Deployment and (possibly) maintenance are non-trivial tasks as well. Obviously, as I said before, I don't like mines :-). Sounds like you are, or were, in Navy R&D. Waiting with 'bated breath for your next installment.

Dan:

Your description of gravity assist is _almost_ correct. It isn't the rotation of the planet that provides the assist, it's the movement of the planet in it's orbit. If the path of the spacecraft passes behind the planet, the spacecraft will pick up some kinetic energy and the planet will lose some. If the spacecraft passes in front of the planet, it will lose energy and the planet will gain. The effect is exactly the same, whether the planet is rotating or not, and even works for a non-rotating point mass.

John,
OK, sounds reasonable. On the other hand, is it not also reasonable that a large rotating mass will also have an incremental effect on the velocity change of a nearby smaller mass like a ship? I guess the question is: Would not both phenomena provide a combined velocity increment? I don't have a good estimate of relative effect, and I can see that they might reinforce, counter or offset each other to some extent. My guess is that the orbital effect would be substantially larger than the rotation effect, but what do I know?

You're right, kick myself. While both have an effect, "reference-frame dragging" (the technical term for what I was describing) is only significant where there is a very high gravity gradient, like around a neutron star or black hole. In the more normal areas of the universe, like around jupiter, the way you described is the only one that has enough effect to be useful. What can I say, I tend to live in the more extreme parts of the universe :-)

Dan:

I learned something too - I didn't realize "reference-frame dragging" existed at all... I guess I've been thinking of Newtonian physics only. (The new stuff like relativity and quantum physics makes my head spin.)

John

John,
There may be a sort of Newtonian way of looking at frame dragging. For a ship in near planet orbit (say 1/4 planetary radius or less) the portion of the planet that is nearest you has more gravitational effect than the half on the other side of the spin axis since it is closest. Although as Dan points out it would be pretty small the net effect would be non-zero, tending to drag you in the direction of rotation.

Reasonable?