In movies and games involving ships fighting in space, I''ve often thought that the ships were pretty darn close to one another. In movies, the closeness is to make the battle look better and in games it is to make the battle both interesting to watch and relatively easy to play. But what if someone wanted to simulate "actual" space combat and they needed to know what sort of distances are involved. I''ve roughly worked out some distances based on some initial assumptions. Let''s take a capital ship with a radius of 100 meters (for simplisity''s sake, it is spherical) for our target. Our ship is located distance D away and will be firing a projectile at a velocity V. This projectile will take time T to reach the target and is unguided (aside from initial aiming). During this time T, the target ship can try to dodge out of the way by applying an acceleration A in some random direction. By applying A over time T, there will be a sphere with radius R (with R = A * T * T) that contains the possible postion of the target. The ratio of the area of the cross-section of this sphere divided by the area of the cross-section of the target ship gives us the probability P of the shell hitting the target. For this example we are interested in the cases where P(1) = 50%, P(2) = 10% and P(3) = 1%. Doing the math, we work out that R(1) = 141 meters, R(2) = 316 m and R(3) = 1000 m. Since capital ships are large and unwieldly, we make the assumption that its acceleration A = 1.0 m/s(squared), or about 1/10 of a g (acceleration of earth''s gravity). Knowing R and A we work out T to be: T(1) = 12 secs, T(2) = 18 s, T(3) = 32 s. We make one last assumption in that the projectile is moving at 1/10 the speed of light or 30,000 kilometres / second. Knowing V and T, we work out D to be: D(1) = 360,000 km, D(2) = 540,000 km, D(3) = 960,000 km. So, even at the large distance of 360,000 km, you''d have a 50% chance of hitting the target. In fact, reduce the distance to 300,000 km and you get a 90% chance of hitting. That''s one hell of a point blank range. Working out these distances was easy compared to working out the gameplay that can deal with them. I wonder how a 100m sphere looks 300,000 km away. I''d be surprized if it''s even one pixel in size. Guess a 1st person perspective is out .

With projectiles, you also have to factor in ballistics. In space, the only thing that really might affect the projectile is slight misalignment of the gun barrel, or in the case of non-magnetically propelled projectiles, the possibility of the escaping gasses disturbing the bullet trajectory. Also, since I didn''t see the formula you were using, are you also making the projectile move in vector fashion? I.E. is the projectile taking the sum of the vectors of the projectile plus the firing platform''s movement?

With energy weapons, unless they are non-attenuating (lasers) then basically there will be no error at all since for most intents and purposes, you will not have to consider trajectory or sums of vectors.

Still your calculations are interesting. But what if the target obect can accelerate more than 1m/s*2? Also, what of the firing ship''s own heading? I suppose the targeting computer could be tied into the navigational helm, so that it will always know what course and heading the vessel will be at and compensate for it. If it does not have that capability, then the gunner''s job will be a bit more diffucult.

I also would imagine that passive sensors would be best...since although they can be spoofed, at least the observing vessel isn''t making it easier for the other vessels to see him. But still, optical tracking can be fooled simply by painting the vessel black. IR or other visual spectrum detection can be spoofed by flares, or other decoys. Emissions detections can be spoofed as well.

What other ways could vessels essentially make themselves harder to be discovered and hit?

I''ve always wondered about this. To make situational awareness possible in these environments, it might be worth trying to create a visual in which each pixel does not represent a constant angular distance, but a distance relative to its "interest". A capital ship would generate a lot of interest, so the angular distance of the capital ship would get a disproportionate number of pixels in relation to its angular distance, whereas empty space is extremely uninteresting, so it would get very few pixels. A fighter is less interesting than a capital ship, but more interesting than empty space.

This would distort distance perception(even though things that are close are more interesting), but with a complete enough altereation of the perception of physics, the actual distance would be unimportant.

As to detection and countermeasures, a good solution for a capital ship would be to send sensor drones with a complete package of EM and gravitational sensors. The drones would either send their information to the capital ship, or to each other in a relay fashion to protect against jamming. The capital ship would be able to perform extremely accurate triangulation or mapping with half a dozen drones at a reasonable distance from the enemy ship. The countermeasure to that is to destroy the drones. Also, since drones would most likely be expendable, they could use active sensors for detection. Also, active sensors can be spoofed as well for the same reason that EM emissions can be faked. Heck, use passive IR and send out flares. Flares illuminate the area and obscure your own location. Put reflectors on the side facing you to prevent blinding, and if they''re not in the room temperature spectrum, prevent the flares from illuminating you.

The best way, though, is to tag an enemy. By this I mean that a fighter or drone attaches a beacon which broadcasts an easily detectable signal to a ship which will fire at and around the beacon. The counter to this is a nonmagnetic hull or shell or vibrating the hull or various methods of detecting small ruptures in the hull indicative of an attached beacon.(resistance, inductance, capacitance for contact, standard metal detection techniques for nonconductive regions, etc.)

Real world weapons are not likely to be perfectly accurate. Servos that move the weapons into position or chemical thrusters that rotate the ship are not likely to be able to aim well enough to even reach those distances.

Btw, in answer to your previous question:
The ratio of the pixel distance to the width in pixels of the screen is equal to the ratio of the angular distance to the angular width of the field of view. The angular distance in radians is simply the linear distance divided by the radius. Assuming a 100 m ship 360 000km away, the angular distance is 2.77778e-7. Further assuming a 1600x1200 screen resolution and a horizontally oriented ship perpendicular to a ray that bisects the ship as well as the FOV, the resulting pixel width of such a ship is 0.000283 pixels. One would need a screen resolution(assuming a 4:3 screen ratio) of 5654867x4241151 in order for the ship to show as one full pixel. In case you were wondering, modern monitors have 72 pixels/inch. It would require a monitor at least 1994.91 m across in order to display such a vast resolution. And remember, that''s one pixel of such a massive screen.

So, we need to give our interfaces an overhaul. Even improving a monitor''s pixels/inch wouldn''t fix the problem, since it would still be a speck to a viewer.

Btw, Dauntless,

quote: Also, what of the firing ship''s own heading?

In space, your own ship doesn''t have a heading. It has an acceleration, but its velocity is always measured to be zero. Instead, you measure the other ship''s heading and velocity to be different with respect to an outside observer.

I think that from realistic point of view, the weapons of choice in the future are missiles.

Think of the alternatives:
1) energy guns - the favorite of science fiction, but in real world they aren''t very practicle. They consume too much power, and in order to achieve significant damage, it is required that the energy beam stays on the target for a considerable time interval.
2) artillery guns - projectiles are relatively slow, when you think in terms of astronomical distances. It would be very hard to aim, and when projectile is in motion, the target can move.

Missiles on the other hand, have the ability to maneuver and select targets. Missiles can make ship-to-ship combat possible even accross distances spanning the entire solar system. With a smart missile, you wouldn''t even have to lock on the target, you simply fire the missile where you think the target is. While the missile is accelerating, it''s computer and radar can search for targets. The bigger the distance between ships, the more time missile got to accelerate. So when it reaches the target, it would be hard to stop the missile due to it''s speed.

The only problem with that is inertia - if the missile locates the target that is too far from it''s current trajectory, it would be very hard to adjust the course. But on average, guided missile attacks would outdo any static projectiles.

Whatever weapons of the future may be, it''s almost certain they will be able to select targets and adjust velocity.

300000 km, one light second, that''s about the distances used in that tv show Andromeda

assuming that information can only travel as fast as light,
information is
one second using passive sensors
two seconds using active sensors
old
need to have good prediction for small targets capable of great acceleration

of course, I remember one sci-fi novel where the ships would accelerate for days to get to relativistic velocities and only then be able to jump to hyperspace, while accelerating they were subject to pirates, to take care of them they just fired nukes, which makes sense to me

I agree with berserk that missiles are the way to go. If it''s going to be difficult to pin down a target''s exact location, perhaps the missile could explode a short time before reaching the target. This would create a cloud of debris, which should be pretty devastating when moving sufficiently fast. The cloud should expand radially, presenting a circular pattern of debris facing the target ship.

In keeping with this thread''s "fun with math" theme , I wonder how large of a circle you could manage...

M = mass of missile
D = mass of debris per unit area ("density" of cloud)
r = radius of circle = sqrt( M / ( D * pi ) )

I would think that raking a ship with even 1 gram (1 paperclip) of debris per square meter would be pretty effective. A mass of 1000 kg seems reasonable for a missile; this would give your circular cloud a radius of about 500 meters.

Do a google search for "airborn laser".

I appologize for any spelling mistakes and poor organization, this is just from the top of my head.

The actual theme for Star-Wars and many other space-movies/games/"simulations" is something relative to "WW2 pacific theatre combat in space". I mean, in most space sims there are cruisers, battleships, destroyers and something that is never named aircraft carriers (named only carriers or destroyers instead) that carry fighters. This theme has been chosen just because it is more action.

Actually I believe if there is any space combat in the future it will be less action and more boring (more like some kind of extreme-distance submarine war). Probably the enemies won't fire lots energy/bullets at each other like WW2 fighter pilots, I think targeting and destruction technology have advanced a bit then...

Think about it, firing some sort of nuclear guided missile through a whole solar system makes much more sense (although it is more boring and will not be considered an alternative theme for most movies). It maybe could take weeks for a hit, although a single hit could destroy the whole ship. I think space combat would be more strategical and less impulsive (e.g. firing countermeasures and trying to evade/destroy missiles before they hit days/weeks ahead).

Therefore we can also think: How large does spaceships have to be? The larger = easier to hit. Will spaceships even carry human crews? Probably articifical intelligence will be a VERY good alternative in the future. Why have anything else than freighting spaceships? Why not just send missiles responsible for patrolling and attack enemy transports/missiles? Missiles/spaceships (something combined I think) don't have to be really huge because no human interferance is necesary.

Different missiles could be designed to do different things, for example defending transport vessels from attack, attacking an enemy transport, intercept and reprogram enemy missiles to attack the enemy instead.

I'm still waiting for a different theme than the WW2 one. I hope someone will make something very different some time.

[edited by - Unwise owl on August 7, 2002 11:59:20 AM]

Not to detract from the very interesting ideas thrown out about this subject, but most of the replies have assumed at or around present technology. It is possible new power sources for energy weapons will be found that make them practical, or new and inventive reasons to use projectile technology. If for instance a propulsion system was designed to give spacecraft manuverability such as we see in fighter aircraft today, close up fighting could be a reality since the target would be so manuverable that shots from great distances would have very little chance of hitting. Also, this same idea about distances came up 50 years ago. After WWII it was decided by many nations that guns were obsolete and missiles would be the new weapon of the future. When pilots flew aircraft into Vietnam that had no guns, only missiles, they found that the technology was severely lacking in hit probability, and to this day has not improved enough to become the only means of offense or defense. But hey, you never know, I''m probably completely wrong.
Oh and, space is not a vacuum, so an energy weapon would lose an amount of power proportional to the distance. It would be small, but over extreme distances could have a great effect.

Hmm, it seems like dectection and aiming errors could be the limiting factors in calculating distance. So, I guess it''s not the size of the gun that counts, it''s how well you aim it.

If I were a betting man, I''d wager that space combat would be a lot like modern submarine warfare. Both take place in 3D space and most of the time is spent trying to locate the other guy without giving away your own position. Given the need for a monitor 2 km wide to display ships as a pixel, I''d guess everything would need to be display iconically. Without the need for fancy 3D graphics, all that is needed is to work out the game mechanics and come up with a killer interface. May not have mass market appeal, but I''d bet there''s a few people who would enjoy playing.

I''m not sure how you''d handle the use of "fighter" class ships. The problem is that without resorting to convienient technologies such as inertialless drives, fighters don''t have anywhere near enough reaction mass to get up to a speed to close the distance of hundreds of thousands of kms and then slow down to match velocity of the target. I guess the fighers could be boosted to a high speed by some sort of support vessel and then just make a single charging attack without slowing down at all. The support ship could then round up the fighters after the battle. Ship to ship missiles would require the same sort of boosting, but of course there is no need to pick ''em up after.

The defenders could launch there own cloud of fighters, which would pass through the attacking group and then the survivors would carry on to attack the cap ships.

Korvan