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View Full Version : Theorhetical questions regarding deep space fighting



Ivonia
04-21-2005, 08:00 AM
If you were to travel into deep space, where you were nowhere near a star for a source of visible light, would it be hard to see things, say a spaceship (particularly a non-reflective one)? And how could you overcome it? Keep in mind that although I would like to learn what it would be like, my story isn't going to be hard sci-fi. But I would like to know what it would be like out there in these situations. And yeah, I know, above all it has to be entertaining, and I want it to be as well. But I would like to know if these scenarios are possible and what they would be like.

I'm sure this has been done already, but I was thinking about having a deep space battle where there is no nearby star to emit visible light, just for a change of pace (the majority of battles otherwise are near stars and planets). What kind of technical difficulties would the combatants face out there?

I was thinking that maybe they could have some kind of infrared/sonar like device that emits a signal, and then when the ships bounce it back, the computer then displays a on the pilot's viewscreen where the ships roughly are at, and if they're friendly or not. So basically the fighters and ships out there would not see any ships visibly there (unless something was lighting up, say an ion cannon charging up, which in my story is very bright while charging). Instead they'd see red (enemy) and blue (friendly) ships flying around kind of like on those tactical screens. The obvious problem would be that if they use it continously, the enemy can pick up their signal, and therefore their location as well (although I suppose I can also encrypt the signals too). How feasible do you think that would be?

Conversely, what would fighting near a supergiant star be like? I like reading about huge stars that are like 500 times the size of our sun, simply because thinking about that stuff is pretty mind-boggling when we think of how big the sun is compared to Earth. What kind of problems would ships face fighting near them (would they also emit a lot more radiation as well)?

Another scenario I was thinking about doing was fighting in a dust cloud/nebula. Would it be like fighting in fog, or would it be worse, as shots could potentially set off an explosion in those hydrogen clouds? I think I saw a couple of Star Trek episodes where they hide in the clouds, but what if actual fighting took place there? What kinds of hazards do you think could fighting there could pose?

Again, I'm not trying for hard science stuff, but I would like to add these scenarios in my story if possible, again just for a change of pace (cause I imagine that fights in space will not always neccessarily be near a strong source of visible light such as a star or planet). Not that I have anything against a regular straight on battle near a planet that's reflecting a lot of light onto the ships and what not, but I think it would be interesting to make the environment of space another factor that both sides have to deal with.

Also, I know that Newton's laws really apply there. I was imagining another scenario where the hero, despite everything he's tried, can't shake the bad guy chasing him. So I would have the hero simply turn his ship around, while still going in the same direction, and then shoot at the bad guy head on (I'm sure this has been done already). I guess in this case I'd like to show kids how an object in motion tends to stay in motion hehe (and at least one version of the ship I currently have designed would allow them to turn the ship around while still heading in the same direction. Of course this will only work in space, and in atmospheric fights the system is disabled so the pilot doesn't accidentally activate it).

And again, I know, in the end it won't matter as long as the story is good. But again, I would like to try something different if possible when the fights occur, rather than always just having straight on fights where both sides can see each other clearly. After all, fighting on the ground sucks when there's inclement weather (and I have some of those fights too, it can't always be a sunny day hehe), so I'd like to put my characters in dangerous situations in space as well (no fighting near black holes though, because they'd have to go past the event horizon for any real danger anyway, and no one in their right mind is going to fly near them).

whitehound
04-21-2005, 08:20 AM
Surely being in deep space would be the equivalent of being on earth when neither moon nor sun was in the sky but the sky was clear - i.e. seeing only by distant starlight. You would be able to see a little bit with the naked eye, and more if you enhanced it. In particular you would always know there was *something* there because it would occlude the stars behind it.

You don't need to bounce infrared off another ship - unless that ship's insulation was totally efficient, which is unlikely, it should have some sort of infrared signal of its own (i.e. it would be warmer than the depths of space around it) and you could detect that. Probably different classes of ships would have slightly different energy signatures.

Jamesaritchie
04-21-2005, 01:49 PM
If you were to travel into deep space, where you were nowhere near a star for a source of visible light, would it be hard to see things, say a spaceship (particularly a non-reflective one)? And how could you overcome it? Keep in mind that although I would like to learn what it would be like, my story isn't going to be hard sci-fi. But I would like to know what it would be like out there in these situations. And yeah, I know, above all it has to be entertaining, and I want it to be as well. But I would like to know if these scenarios are possible and what they would be like.

I'm sure this has been done already, but I was thinking about having a deep space battle where there is no nearby star to emit visible light, just for a change of pace (the majority of battles otherwise are near stars and planets). What kind of technical difficulties would the combatants face out there?

I was thinking that maybe they could have some kind of infrared/sonar like device that emits a signal, and then when the ships bounce it back, the computer then displays a on the pilot's viewscreen where the ships roughly are at, and if they're friendly or not. So basically the fighters and ships out there would not see any ships visibly there (unless something was lighting up, say an ion cannon charging up, which in my story is very bright while charging). Instead they'd see red (enemy) and blue (friendly) ships flying around kind of like on those tactical screens. The obvious problem would be that if they use it continously, the enemy can pick up their signal, and therefore their location as well (although I suppose I can also encrypt the signals too). How feasible do you think that would be?

Conversely, what would fighting near a supergiant star be like? I like reading about huge stars that are like 500 times the size of our sun, simply because thinking about that stuff is pretty mind-boggling when we think of how big the sun is compared to Earth. What kind of problems would ships face fighting near them (would they also emit a lot more radiation as well)?

Another scenario I was thinking about doing was fighting in a dust cloud/nebula. Would it be like fighting in fog, or would it be worse, as shots could potentially set off an explosion in those hydrogen clouds? I think I saw a couple of Star Trek episodes where they hide in the clouds, but what if actual fighting took place there? What kinds of hazards do you think could fighting there could pose?

Again, I'm not trying for hard science stuff, but I would like to add these scenarios in my story if possible, again just for a change of pace (cause I imagine that fights in space will not always neccessarily be near a strong source of visible light such as a star or planet). Not that I have anything against a regular straight on battle near a planet that's reflecting a lot of light onto the ships and what not, but I think it would be interesting to make the environment of space another factor that both sides have to deal with.

Also, I know that Newton's laws really apply there. I was imagining another scenario where the hero, despite everything he's tried, can't shake the bad guy chasing him. So I would have the hero simply turn his ship around, while still going in the same direction, and then shoot at the bad guy head on (I'm sure this has been done already). I guess in this case I'd like to show kids how an object in motion tends to stay in motion hehe (and at least one version of the ship I currently have designed would allow them to turn the ship around while still heading in the same direction. Of course this will only work in space, and in atmospheric fights the system is disabled so the pilot doesn't accidentally activate it).

And again, I know, in the end it won't matter as long as the story is good. But again, I would like to try something different if possible when the fights occur, rather than always just having straight on fights where both sides can see each other clearly. After all, fighting on the ground sucks when there's inclement weather (and I have some of those fights too, it can't always be a sunny day hehe), so I'd like to put my characters in dangerous situations in space as well (no fighting near black holes though, because they'd have to go past the event horizon for any real danger anyway, and no one in their right mind is going to fly near them).

Well, sonar wouldn;t work in outer space, of course. Sonar is sound waves, and you can't use sound waves in a vacuum. Radar would be what ships use. It works as well or better in deep space as it does here.

You would also pick up the infrered signatures of any ships. You would not send any sort of beam out to do this. Passive detectors are all you need, and these can paint a very good and detail picture of any ship. It's impossible to insulate a ship so completely that some heat won't escape. Especially in deep space where it's so cold.

I know you aren't after hard SF, but while you can use hinky science is space opera, this doens't mean you can get the science wrong. The only science you're allowed to get wrong is speculative science. If we know how it works, you usually have to get it right.

MadScientistMatt
04-21-2005, 05:34 PM
James is right - you wouldn't need an active infrared scanner, as spaceships are likely to put out a good bit of heat that would make them "glow" in the infrared range. Active infrared scanners could be used, along with radar. But with no other nearby sources of infrared, a passive system may be all you need.

Telling the ships apart would be tricky. The ships may have different looks when viewed in infrared. A computer may be able to distinguish them but may still have some false readings. Your best bet would be to have the computer note the position of all the friendly ships while traveling to the battle. I suppose you could put blinking infared beacons on your ships to identify themselves, at a cost of making the ships more visible. Visually, you may not be able to see much other than the ships making a black spot against the stars. But your ships may have things on them that glow - engines, weapons, or maybe even windows.

Fighting near a supergiant star - well, you would have to contend with the intensity of the light (both visible and infrared, which could heat up the surface of the ships) and radiaton. There would also be particles coming out of the star like solar wind.

You also have the star's gravity. This may be one of the most important factors. Your spaceships would have to be orbiting the sun or constantly firing their thrusters to hold still. If you want a hard SF book, you'll probably want to read up on basic orbital mechanics. The gravity can do funny things - for example, it takes more energy to orbit high and slowly than close and fast. Firing your main engine in a way that would make a spaceship in a vacuum accelerate could sometimes make the ship climb to a higher orbit and lose speed. Orbital mechanics are a bit lengthy to deal with in a message board post - this can amount to a whole chapter in a college physics book.

The outside of the star is actually pretty thin. If your spaceship had good cooling, you could fly it partway into the star before things got too hot for it.

A nebula is actually pretty thin. More like Earth's normal atmosphere than a cloud, or often even thinner. They look thick because they're really, really big. It might make for problems in long range laser combat, but that's about it. Hydrogen gas in a nebula is not going to ignite. If you had a thick enough cloud of hydrogen gas, you could pour some liquid oxygen overboard and start a fire. But a really thin nebula might not even burn then.

You may wish to check out this site for some interesting advice on things you may find in space:

http://www.badastronomy.com/

Julie Worth
04-21-2005, 06:31 PM
(no fighting near black holes though, because they'd have to go past the event horizon for any real danger anyway, and no one in their right mind is going to fly near them).

Ah, but there are all sorts of fun effects outside the event horizon. And the horizon itself is not all that dangerous, particularly if the hole is large enough--the black hole at the center of a galaxy, for instance. There your combatants could continue their silly fight for quite some time before being torn apart by tidal forces near the singularity. Even that's not necessarily the end. You could have the singularity serve as a wormhole, shooting them millions of light-years off course to another galaxy. Or to a different time. Since physics breaks down at the singularity, you can do anything you want.

preyer
04-22-2005, 03:16 AM
i'm not sure why a ship would be designed to fly backwards rather than simply have rotating turrents other than flying backwards would be pretty cool. or even rear-mounted guns. i'd have to research it, but i wouldn't think the guns would have to be uber-huge and powerful to effectively neutralize the enemy ship, assuming i'm right when i say a few quarter-sized holes in a hull would make larger holes as the compartment violently decompressed (if indeed there would be a violent decompression). that is, a weapon with enough power to put in a hole or ten in a ship's heavier gauged steel (or whatever metal) skin would be generally as effective as ripping off half the side of the compartment. could be way wrong on that, though, just an idear to investigate.

as i understand what you're asking, you're not asking about ships being imposed over the background stars rather than there being an utter deficiency of natural light sources, right? in that, i don't think it would be any different than stepping into a closet where there's a total and complete lack of light. can't see your own hand inches in front of you face, right? i don't see why it'd be one lick different in space where there's not even stars visible on any level.

sure, you could have a really fancy detection system, but to simply detect if something's around doesn't require that, as mentioned above, though i'm sure a computer with a host of knowledge could paint a relatively accurate picture of the shape of things with some imaging system. and i reckon that the chances are a ship would know if they're being detected depending on its sophistication. certainly a warship would have something like that, if not some kind of counter to it. in the end, it would amount to which ship had the superior technology, i'd imagine. isn't it the angular quality of stealth bombers that along them to allude detection? maybe the same principle of ship design could help warship to the same, too, not sure.

another thing i'd have to wonder about from a logical perspective is why both sides would feel so compelled to wage war that they'd do so on the cusp of potentially disasterous natural places like black holes.

when kirk entered the nebula, he did so to level the playing field. kahn, despite being given common sense to the contrary, is so demented by bloodlust and revenge that he ignores the warnings and follows anyway. for me to believe both sides would willingly do such a thing, i'd have to be given a scenario where one side is willingly giving away their strategic advantage. that is, two able ships aren't very likely to do battle ten feet from the surface of any sun. like on the high seas, you didn't flee into a reef or area will sand bars unless you were desperate, and most sane commanders would probably just let them go in hopes that their enemy would indeed get themselves stuck. okay, not very dramatic, but that's why you have to give the guy winning the battle enough reason to throw caution to the solar wind and give chase into the asteroid field. given such incentive, it might make for an interesting story to have the pursuer's ship damaged, crew members die, the ship flounder, limp away, get torn up some more by other pirates or natural things, basically the commander who was kicking asss gradually get his butt handed to him, and *still* pursue his prey on an individual level for years.

that's perseverance.

Ivonia
04-24-2005, 05:43 AM
Cool replies thanks! Another question came up while I was thinking up more scenarios. If a book has done this already that you know of, or you know the answer, then feel free to let me know.

Similiar to my question about being in deep space, there is a battle in my story where forces are fighting in orbit above a planet on both sides (the side facing the sun, and the side in darkness). The planet is in most respects like Earth, but it has no natural satellites (moons) to reflect light onto the darkside of the planet (and if any of you have ever been out in the middle of nowhere, far from city lights on a moonless night, you know how dark it can be).

What would fighting on the darkside be like, if they weren't near the curavature of the planet to get some of the light bending around it? There are artificial lights on the night side of the planet (from cities on the planet), but would that be enough to light up the dark areas, or would the ships fighting in orbit still essentially be blind (they're fighting in relatively low orbit, so they can't see the sunlight at all from where they're fighting. The planet is blocking it). To make matters worse, the good guys are attempting to evacuate the civilians off the planet, but the bad guys got there sooner than they thought and are attempting to kill them all.

Obviously the forces fighting on the side of the planet facing the sun wouldn't have sight issues, but I'd bet the ones fighting on the other side of the planet would have issues with being able to see their enemy clearly (other than cloaking, but in my story you can't fire while cloaked, or it deactivates due to the power needed to sustain cloaking, so it's really only good for sneaking/spying missions. And yes, I did that on purpose, I hate stories where ships, especially small fighters, can cloak indefinitely and still be able to fire away without the other side being able to spot them. I know, it's not realistic, but hey, I'm just trying to make it more entertaining hehe).

Sorry if I'm asking weird questions, but thanks for answering my other ones. I would just like to know what would happen in these kinds of situations, or what you think would likely happen. Otherwise I'll end up making a story with horribly wrong science, kind like a very old sci-fi movie the Simpsons watched where these guys were in a spaceship, and held their breath when the air became "contaminated" or was leaking out (I forget which), and they couldn't breathe until they put their goggles on lol. And the alien in the movie was a dog on a wire wearing a glass helmet hehe.

Obviously we can't have faster-than-light travel anytime soon (if ever), but for the sake of the story most of us are willing to suspend our beliefs a little to enjoy the story, so long as it's not too implausible (I never understood how all the aliens in Star Trek: Voyager spoke perfect English hehe, but for the most part I was willing to look past since most of the episodes were pretty good). And I hope that in putting my characters through these kinds of hazards, hopefully it'll make the story more entertaining as they try to survive not only the enemy, but also the hazardous environments/situations.

Mr Underhill
04-24-2005, 08:18 AM
Good questions.

The situation with the spacecraft in orbit on the night side of the planet (eclipse is the technical term for this situation) is pretty much the same as for the spacecraft in the dark of interstellar space.

In both cases you do actually have starlight as illumination, and if you go out deep in the country on a night when the moon hasn't risen yet, you'll find that you can actually see things around by starlight, just a little, once your eyes get used to it. Even 21st century military light intensifier goggles can make it a viable source of illumination. But since the light is so faint, this would almost certainly be useless for long-range detection. But if the ships are alongside each other and the space marines are outside getting ready to board, it might work.

The most obvious means of detecting other ships would be infrared or radar. For radar, don't forget to take distance into account. A distance of one astronomical unit (150 million km) is not much in interstellar space, but a radar ping would take eight minutes out and eight minutes to return, unless you have some kind of FTL radar that uses tachyons or something.

Infrared is just light at a lower frequency than humans can see, and comes from the heat of an object. (Look up "blackbody radiation" if you want the details.) Any spaceship inhabited by humans will be radiating a substantial amount of heat, since it will be somewhere around 300 degrees Kelvin inside, as opposed to 3 Kelvin, the background temperature of space. At infrared wavelengths it will stand out like a sore thumb even with engines off and power plant at minimal levels. To get a "stealth" effect under those circumstances would be incredibly difficult. You would have to get the surface of the craft down to 3K, the temperature of liquid helium, but keep the compartments inside warm enough for humans. That would take a hell of a thermal management system. Thing is, the heat has to go somewhere. You could try radiating it out into space on the side away from the ship you're trying to hide from, or else you would have to store the heat internally somehow, which would only work for so long.

Pretty much the same thing applies on the night side of a planet. However, your scene would be "illuminated" in infrared by the heat radiated from the nightside of the planet. The equilibrium temperature of a piece of space junk in the vicinity of an earthlike planet would also be much closer to room temperature, so you have a better chance of being able to cover your waste heat, run silent and pretend to be a rock or dead satellite.

One thing though, for Earth the longest you can stay in darkness in low earth orbit is about 45 minutes. You might check the NASA websites and see if they have video and such of folks spacewalking out of the shuttle or space station. One orbit lasts 90 minutes, so every 45 minutes they have sunset, then sunrise 45 minutes later. (Actually it is more sunlight than dark, sometimes it is almost always in sun, but that's a long story.) Now, maybe you could fire your engines to stay in the shadow, but then that will probably give you away.

So that's the other thing: thrusters. If the spacecraft are using any kind of propulsion currently envisioned, they shoot big gobs of energy out in order to maneuver. Spacecraft in Star Trek and Stargate seem to have some kind of reactionless drive, but even those probably emit some kind of energy when they are used. Any military worth their salt will be all over means of detecting it even at low levels and long distances.

And any time you fire weapons you will be visible. If it's a beam weapon, the energy discharge will be visible (I don't care if it's directed energy, there's going to be leakage, and in low orbit you've got the upper ionosphere and magnetic fields you'll be disturbing). If it's missiles or projectiles, you have some kind of exhaust. Firing a weapon will give you away even if the ship itself stays cloaked.

And a quick word about the nebula scenario: the thing to remember is that a nebula looks like a cloud to us from a long, long way away, but it is actually still an incredibly hard vacuum by Earth standards. If you were inside of most nebulas (with the possible exception of accretion disks) it would look just like empty space. You might get some electrostatic buildup from the gas and dust, or magnetic effects, but probably nothing more than a few glitches in your sensors. But since it is a very tenous plasma, anyone moving through a nebula might well be more "visible" than in normal interstellar space.

preyer
04-24-2005, 10:04 AM
you could catapult magnetic mines, eh? low-tech solution to a high-tech problem. :)

Pthom
04-24-2005, 12:39 PM
A catapult is not a reactionless weapon. Using one will displace the vessel that fires it. Also, the projectile need not have a power source (as in a missile) to determine where it came from. Such a thing is done today, after the fact, in crime investigation. In a future with interstellar vessels, surely, such a task would be, as Mr. Underhill suggests, commonplace and more than likely instantaneous.

One great place to hide, depending on the effeciency of your ship's shielding, is inside the corona of a red giant star. The trick is used by Larry Niven in The Mote in God's Eye, and in The Gripping Hand.

DaveKuzminski
04-24-2005, 07:15 PM
Fighting in space will resemble greatly fighting on and in the ocean. Why? Because most battles, probably 99%, will occur near a planet (land mass) because those are strategic positions. You control the seas by controlling ports. You would control space by controlling places from which space craft can be launched. Also, sea traffic naturally goes to ports. Therefore, if you want to cut the enemy's space traffic, you intercept it where you know it will have to occur because once it gets out into deep space, the amount of area to be patrolled and searched or blockaded becomes too large to be practical. Therefore, battles far from land or far from planets will be rare.

preyer
04-25-2005, 01:13 AM
how would a catapult displace a ship? the only way to track down where it would come from is from tracing down its likely origin of trajectory. that's why you'd relocate after firing, eh? or even manually slide out a skiff with a timer on it that shoots the weapon.

i've never read where the enemy sends out remote ships during a battle to inflict more damage, though i'm sure there are plenty of books with that idea. seems pretty smart to me to slip out a couple of insurance policies while engaged, somewhat akin to individual planes just sans the human element, something where the computer stays focused on the vital parts of the ship without loss to like or buckling from common sense or cowardice. it doesn't even have to be particularly electronic, those at those minute electronic levels it may be easy to shield from some kind of scanning equipment or just be too small to detect. if not small enough to detect, makes some kind of sense to release thousands of tiny pulsers to confuse the enemy and keep them constantly on the edge of their seat. i mean, if the slightest detection could possibly mean their destruction, they'd have to investigate each one. each one could even carry a small explosive charge that chips away at some part of the enemy's ship while being effectively too small and in too great a quantity to destroy. you could manufacture these tiny bombs by the millions with no problem, and they might even be some kind of plastic. certainly one of the main targets of such small arms would be the tracking systems and weapons. not much use against a death star or borg ship, though.

i've never seen much value in sending space jets into battle when you could operate them remotely and, not having to build in a cockpit and atmospheric controls, could build them smaller and harder to hit, not to mention not risking a lot of people's lives in the process. it also opens the door for better pilots instead of searching long and hard for just the right type of individual both mentally and physically able to fly. you could have talented handicapped people at the helm of fighters.

ships that are destroyed still have black boxes that survive the destruction, most likely. once ejected, these boxes open up and release another weapon. better yet, build your ships out of that black box material, lol.

what's always bothered me in stories with all sorts of high-tech gizmos is the weapons systems still rely on humans to press the trigger at just the right time to hit anything. you'd think that by that point you'd have some kind of scanner tracing your eye movements and highlighting the target once you hit the trigger, then adjusting for where the enemy ships you're dogfighting will be in a second and fire *there* instead of the empty space it just left. i mean, good gravy, man, they had systems akin to this on WWII bombers. now, where you can 'paint' a target, why are dogfights still fought with super-high-tech ships using low-tech humans to hit anything, particularly with front-mounted cannons unable to move a single degree? that might work great for strafing runs, but it sure would be hard to actually hit a moving target. and for gawd's sake, can you not put a computerized laser turrent on the *back* of the ship to cover your asss? beats the hell out of losing a plane and pilot, doesn't it?

Mr Underhill
04-25-2005, 06:11 AM
how would a catapult displace a ship? the only way to track down where it would come from is from tracing down its likely origin of trajectory. that's why you'd relocate after firing, eh? or even manually slide out a skiff with a timer on it that shoots the weapon.You'll recall that every action has an equal and opposite reaction, my dear Preyer. Isaac Newton and all that.

If you relocate, you are maneuvering and, I maintain, visible. Sliding out something like a missile rack wouldn't be a bad way to go, but you would have to wait until the ship and the weapon drift apart, so that would work if you can wait an orbit or so.

DaveKuzminski
04-25-2005, 06:49 AM
i've never read where the enemy sends out remote ships during a battle to inflict more damage, though i'm sure there are plenty of books with that idea.

what's always bothered me in stories with all sorts of high-tech gizmos is the weapons systems still rely on humans to press the trigger at just the right time to hit anything.

First off, it's more entertaining in a story, be it in a book, TV show, or movie if someone is doing the action rather than sitting back watching the screen as a remote unit does the fighting. Now with that answered, let's go to the brief, unreferenced history of remote control fighting.

You can go back very far, though one of the best documented incidents occurred when the English attacked the first Spanish Armada with fire ships. Those were set on course and left to the wind to direct. Some of the Spanish ships had to cut their anchors to escape the blaze. Others were caught. Regardless, it caused significant problems for the Spanish.

Fast forward, the first attacks for submarine warfare in the American Revolution and the American Civil War relied upon explosives that were meant to be triggered once the attacking ship withdrew to safety in a remote manner by a trip cord. Crude, but remote.

Fast forward to WWII. Remote units have become sophisticated. The Nazis used sensors on the upper wings of their rocket plane to trigger missiles that were lauched straight up from the plane because the tactic was for it to pass beneath an Allied bomber. The shadow of the bomber would then trigger the sensor. Yes, it worked. A number of bombers were lost that way. However, the rocket plane had to glide to a landing and our fighters picked them off so that they couldn't repeat their missions. Also, the fuel was dangerous to use and several rocket planes exploded on takeoff.

In the Pacific, the US managed to sink a Japanese vessel with a remote controlled missile before the war ended.

There were other examples of remote devices, such as the Japanese balloon bombs, although those weren't extremely sophisticated. Still, those worked and might have succeeded even more had it not been for strict control of the news.

When you come down to it, almost every navy used torpedoes in WWI and WWII. Those are remote devices, though most were at first preprogrammed. However, those and mines were soon developed enough that they could distinguish when a target was near rather than hitting it.

I think that you can probably make the point that a lot of remote devices are now in use. You can probably project just about any weapon as part of a later remote unit for a space opera.

preyer
04-25-2005, 11:25 AM
good reply, DK.

MU, wouldn't the fact that you're weightless affect that law? really, though, if you've got a catapult thing, you're probably a large enough vessal as to not be detectable if indeed you pitched a bomb, eh? hypothetically speaking, of course. :)

Pthom
04-25-2005, 11:33 AM
The condition of weightlessness (a term that means lack of the force of gravity acting on a mass) has nothing to do with the laws of kinetics. Weightless or not, you, your ship, and your catapult (with its ammunition) have mass. Shove a part of that mass in one direction and everything else tends to move off in the opposite direction.

But more to the point, I think, is that IF you have a large enough ship that tossing some mass overboard won't significantly affect its position, then it's surely big enough to obscure stars from the observers on another ship.

Of course, that's why we have the wonderful convenience of cloaking devices. ;)

Galoot
04-25-2005, 11:54 AM
wouldn't the fact that you're weightless affect that law?Come join me in the weightless depths of space. C'mon, you can trust me.

++KICK TO THE GROIN++

Sorry.

Now you're flying away from me. And I'm flying away from you.

If, instead of kicking you, I hurl a heavy rock at your head, my throwing the rock has an opposite reaction on me. I will fly backwards as the rock flies forward.

If, instead of throwing my rock at your head, I climb into my spaceship and point its rocket nozzle toward you and light the fire, the exhaust will burn you to a crisp while I fly off in the opposite direction.

Watch for Learning Physics Through Violence, coming to a store near you.

MadScientistMatt
04-25-2005, 04:22 PM
On a related note, some warships now have automated machine guns to defend against missiles at close range. This is a bit easier than trying to identify if a spaceship is hostile, since a computer can safely assume that anything small and heading toward it at extreme speed is an incoming missile. But if the sensors on a ship can automatically tell a hostile ship from a friendly one - or if the pilot can designate the target - an automated turret would be quite reasonable to put on a spaceship. A logical extension of the manual and remote control turrets from World War II bombers.

whitehound
04-26-2005, 12:32 AM
it also opens the door for better pilots instead of searching long and hard for just the right type of individual both mentally and physically able to fly. you could have talented handicapped people at the helm of fighters. This was the premise of Anne McCaffrey's award-winning novel The Ship Who Sang - children with good brains but severely deformed bodies were turned into cyborgs and actually built into the ship they would fly, growing up with them so that moving the ship's propulsion jets or whatever felt as natural to them as walking would have done if they had been able to.

preyer
04-26-2005, 11:03 AM
that premise sounds familiar. basically, remote controlled arms was a plot of the bad movie, 'toys,' with robin williams. in that movie, children were being trained to use the latest in military gizmology though they didn't know it via free arcade-style games.

anyway, so you put the catapult on a slide. would that not remove the 'displacement'? or even a slingshot, which might work even better anyway.

Galoot
04-26-2005, 11:10 AM
anyway, so you put the catapult on a slide. would that not remove the 'displacement'?Nope. Not if the slide is attached to the ship, anyway.

preyer
04-26-2005, 11:37 AM
then does that mean when the crew moves about the ship opening doors and such, it's being displaced, too?

Galoot
04-26-2005, 12:48 PM
then does that mean when the crew moves about the ship opening doors and such, it's being displaced, too?Yes.

Here's a quickie thought experiment. Float a surfboard on the surface of the water and stand up on it. Now try to walk forward. You'll push the board backward and your face will smuck into the water. Try the same thing on a skateboard, or balanced on a large ball, and lose some teeth.

Empty space has no friction. If your feet are moving you forward, they're also moving whatever they're standing on backward. The ship masses a lot more than you do, of course, so it moves backward only a little bit.*

I remember a story in which someone was wafted by an unfortunate breeze into the middle of a large room while in orbit. They managed to reach one of the chamber's walls by removing their clothes and throwing them in the opposite direction.


*Keep in mind that if you're weightless, you're going to have a hard time walking. You can jump from wall to wall to make your way down a hallway, or you can wear magnetic or velcro shoes. Either way, though, you're exerting a force on the walls or the floor, and your ship will react to it.

whitehound
04-26-2005, 01:52 PM
Just as we exert force, including gravitational force, on the planet as well as it on us - but its mass and momentum are so much greater than ours that the effects are negligible. What about very small bodies? If a reasonably-large ship - say something about the size of a Boeing - took off from an asteroid, would it make the asteroid wobble in orbit, or is the speed of the asteroid through space so great that the effect wouldn't be noticed?

MadScientistMatt
04-26-2005, 04:34 PM
Just as we exert force, including gravitational force, on the planet as well as it on us - but its mass and momentum are so much greater than ours that the effects are negligible. What about very small bodies? If a reasonably-large ship - say something about the size of a Boeing - took off from an asteroid, would it make the asteroid wobble in orbit, or is the speed of the asteroid through space so great that the effect wouldn't be noticed?

Since the ship would probably not be taking off by giving the asteroid a shove, not necessarily. It would depend on how much of the propellant from its rockets hit the asteroid.

DaveKuzminski
04-26-2005, 05:05 PM
One writer decades ago made use of displacement in space for a short story. In the story, a ship came upon another that was believed to be a derelict anchored in space. They were surprised when the anchor shifted from one end of the derelict to the other. Upon investigation, they discovered there were still people on board and they were moving their ship length by length by locking the anchor into place and then shoving the internal mechanism inside the ship to move it one length so they could work their way back to the regular shipping lanes where they could be rescued. The story was interesting for that feature alone.

Pthom
04-26-2005, 09:59 PM
and this anchor...similar in function to a sky hook, right?
;)

As for momentum and moving a ship by walking around inside it (or bouncing, in the case of no gravity), we come to the subject of the inertial reference frame. Both the ship and the occupants are in the same inertial frame, just as the Earth and we who live here are. When you take a step in one direction, you exert a force upon the Earth in the opposite direction. Of course, the Earth is many times greater in mass than all the humans, horses, elephants and ants, etc, who exert forces on it, so we observe little to no change in the Earth's position.

But let's look at astronauts on the International Space Station. They move about inside it, pushing off walls, and so on, yet the station stays put in orbit. The idea that one could move a vessel to the right by continually banging on the left wall of it is akin to the old Popeye cartoon where he could make his sailboat move by blowing into the sails. The force applied to the walls of the space station by astronauts moving about inside it is balanced by the station pushing back on the astronauts. The entire assembly stays put. Now, when the astronauts eject waste materials...THEN the station moves, since some of its mass leaves the inertial frame. This is exactly what happened to Apollo 13 when the cyro tank exploded.

Moving torpedos around inside a warship changes nothing as far as the warship's position in space...but fire one at an enemy, and you'll need to adjust for the loss of mass and for the change in momentum. Popeye should not blow at his own sails, but turn around and blow into the air behind him.

If the Popeye trick would work, we could make a ship move across the ocean by walking from bow to stern. Problem is, even if that did work, once everyone was at the stern, then what? Walking back to the bow would counter any advantage gained. 'Course, if you have an unlimited number of passengers, and could convince them to jump off the stern, you'd have what amounts to a rocket engine: mass ejected from one side pushes the vessel in the opposite direction.

DaveKuzminski
04-26-2005, 10:32 PM
Well, in the simplest terms possible, they basically turned the ship into a slinky operating in deep space. So long as one end was anchored, the other end could be moved until it became the end that was anchored.

I believe that when you're in orbit, it's significantly different from being in deep space since there are different forces and degrees of those forces at work on any objects.

Pthom
04-27-2005, 12:00 AM
I believe that when you're in orbit, it's significantly different from being in deep space since there are different forces and degrees of those forces at work on any objects.

An orbit is just the path one object makes about another body. That other body can be a planet, moon or asteroid, or a star, or a galaxy. In other words, it's pretty darn tough to not be in an orbit of one kind or another when in space. Granted, the effects galaxies might have on a space ship located between them is so negligible as to be non-existant. But then, we're talking about fighting battles in space, no? And the participants in such battles come from somewhere (a planet, most likely), and are defending or beseiging it, depending.

Basically, the only force applicable to any object in orbit is gravity, and that of a nearby celestial object, at that. Current spaceflight depends on arranging simple to complex orbits to achieve an objective, whether it be a satellite (the Moon) or another ship (the ISS) ... or another planet (Mars). A low earth orbit such as used by the Space Shuttle is about 90 minutes in duration...changing direction to evade an attacker or to attack an invader requires one of two things: a lot of time or a lot of energy. If I recall correctly, when the shuttle had a dual mission to visit a satellite and to repair Hubble, it took most of their time just to change from one orbit to another.

In other words, using technology we have at our disposal now, or that even within reach in the near future, the jet fighter-like space battles we see in movies and on TV are highly unlikely.

But science fiction isn't limited to the near future, nor to currently available technology. I think it's important to keep track of how physics works, but not to the point where doing so prevents telling a darned good yarn. In a short piece I wrote recently, I needed my protags to go from Earth to Mars, and not to gain a year in age doing so. The theme of the story prevented me from using such bolognium as FTL, but not from some creative chemistry. I 'invented' PAN fuel (poly aluminum nitrate) which can be used only in a vacuum, but is cheap enough and hot enough that it doesn't take huge quantities of it to boost a ship at 0.5 g most of the way from Earth to Mars. I got my team there in a week, and they enjoyed the false gravity of the constant acceleration.