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Townopolis
2010-05-03, 03:44 PM
So I'm working on the world and lore for a campaign I'd like to run - probably in GURPS or M&M, but that's beside the point - and I want to get the sci-fi as hard as possible while setting it in the far future and keeping one or two things that I consider too handy to lose. However, I'm not so good with the science and am not sure where to look to find it, so I'm asking here if anyone can either inform me or point me in the direction of a handy repository of hard sci-fi science & theory.

Currently, the questions that I know I need help with are:

What are the effects of moving really, really fast in space? The plan is to set the game in a generation ship (well, fleet). Because space is big, the trip would take a long time, giving them plenty of time during the first third or so of the voyage to accelerate a lot. My (extremely rudimentary) understanding of inertia suggests that, once the fleet reaches their top speed, they won't experience any sensation of moving. Also, movement within the fleet will all happen relative to a base velocity and is possible (if the fleet is traveling at N speed, a docked shuttle is also traveling at N speed. If said shuttle takes off towards the front of the fleet, accelerating to M speed, it will be traveling at N+M (but appear to be traveling at M within the fleet). On the shuttle's return trip at M speed, it is actually traveling at N-M. A person standing on a ship's hull is moving at N. If he walks forward along the hull at speed W, he moves at N+W but only experiences W.)

Does inertia work this way? Will the fleet appear to be at rest relative to itself and is flight between ships possible during the voyage?
Can humans indeed live normally while moving at high speeds?
Does anyone know how time dilation works, how its magnitude is determined and whatnot?
What would be needed to accurately strike at a fleet moving fast enough to experience time dilation, and how would the dilation and locomotive speed of the fleet affect any attempt at combat from a stationary (or just much slower-moving) force?
Anything else I need to know about life at high velocity?


Folding Space? Probably the one bit of really soft science I'll use. The idea is that the fleet, upon reaching its destination, will set up a "warp gate" thing that will allow them to create a wormhole and another gate that's idling in their home port. While I'm alright to use this as a piece of soft science, I'd like to harden it up as much as possible.

What's the most plausible explanation for warp gates/jump gates/wormholes? I'm thinking space folding, but only because I once saw something on it in a Scientific American. Also, if we try to harden this up, will it end up being theoretically easier to do away with the generation fleet (turns out it's easy enough to fold space from just one location)?
Is there any "hard" concept for how you would sync up two gates? At present, I'm assuming I'll have to use some arcane pseudosience based on relativity that allows a carefully constructed and calibrated set of gates to become close enough to "the same thing" that they can interact regardless of physical dystance. Of course I'm looking for something harder.


Are force fields a plausible technology and at what scale? this is much less important to the plot and premise than the other two questions, although it might be important for a vanguard ship protecting the fleet from unforeseen debris, but I like shields a lot as a device, while I don't know of any scientific justification for them. Luckily for me, I can always salvage the idea of "shields" as being a colloquial term for a high-tech suit's firewall etc... however:

Is there any scientific justification for an energy-based kinetic barrier? Is it practical/might it be given forseeable advances in energy storage/production etc?
How would they work, theoretically, compared to what we often see in fiction?
Is there any reason at all to make them visible ever?
Would it be more likely to have projected (bubble) shields or shielding that "clings" to the shielding object's surface?


Guns... I'm looking at particle beams and other kinetic weapons, right?

Answers, explanations, links to places with these things, any of the above regarding things I didn't ask but should have, and unsolicited advice are all appreciated.

pffh
2010-05-03, 03:55 PM
I'll answer some of your questions in random order as I think of the answers:

Shields: Modern militaries are experimenting with two types of shields, a sort of magnetic shield that bounces bullets and missiles back and a shield that detects and forces missiles to blow up a few meters from the vehicle.

Time dilation is also quite simple it's simply: T = t/(sqr(1-(v/c)^2))
Where
T = time passed for the non moving stuff
t = time passed for the moving ship
(v/c) = the fraction of the speed of light the ship is moving at (80% speed of light = 0.8, 90% = 0.9 etc)

So if a ship is traveling at 99% the speed of light for 1 year the time that has passed for the non moving stuff is:
T = 1/(sqr(1-0.99^2)) = 7.09 years

Also for moving in space it's good to remember that in space bigger ships are faster since they can fit more and larger thrusters since there is no friction so they don't slow down so the longer and harder you push the faster the ship moves.

Combat with a slow moving enemy: The enemy would appear frozen for the fast ship and I doubt the slow ship could do anything about the fast ship.
Another thing you may want to consider with space ships and space combat is that you don't want to be close to the ship you're blowing up since that scrap metal flying through space is doing so at some silly speed and could theoretically tear a hole in your ship. So ship to ship combat would most likely be on the opposite ends of a solar system.

Oh and one final thing before I go to bed, heat. Getting rid of heat is a major problem in space since there is no matter for it to radiate to. This means that weapons that generate a lot of heat (fx lasers) would not be viable in space and ships would rather use railguns.

ko_sct
2010-05-03, 04:02 PM
Inertia work pretty much like you said but keep in mind that work is always applied to at least 2 objects, which mean that if you are in space, if you kick someone of shoot a normal gun, you'll start flying in the other direction (Also technically work in your spaceship but its little nobody care).

Humans are perfectly fine moving at high speed in space as they don’t feel it, though the acceleration/deceleration might kill them if it is done to fast (I think the max is around 10G, but you’re going to have special seat for that)

For the guns, might I suggest your normal gun whit bullet containing oxygen? I think there a type of bullet where the gun powder contains enough oxygen to burn even in vacuum, though; you might want something more sci-fi.

Also I remember in a book I've read, artificial gravity was done by having a slight acceleration during half of the travel, after wich they went for slight deceleration, might be something to consider.

Noedig
2010-05-03, 04:12 PM
As far warping or space folding, I've found that this (http://www.eveonline.com/background/jump/jump_03.asp) is a good article for the science involved. Now this is of course pseudo science for another game, but it seems logically thought out enough and largely believable. The sight contains many good science-y articles that deal with cloning, FTL communication, genetic modification and other things scifi

Noedig
2010-05-03, 04:18 PM
Oh and as for guns, I like the mass effect approach. Hyper velocity kinetic slugs in a mass reducing field accelerated to near the speed of light do bad things to people, which makes, and I quote "Sir Issac Newton the deadliest sonofabitch in space."

RiOrius
2010-05-03, 04:20 PM
Also for moving in space it's good to remember that in space bigger ships are faster since they can fit more and larger thrusters since there is no friction they don't slow down so the longer and harder you push the faster the ship moves.

Quick correction there: the spaceship does have inertia (and in fact that's why it keeps going). It's the lack of friction (including air resistance) that means a huge spaceship doesn't have to worry about unintended deceleration.


Inertia work pretty much like you said but keep in mind that work is always applied to at least 2 objects, which mean that if you are in space, if you kick someone of shoot a normal gun, you'll start flying in the other direction (Also technically work in your spaceship but its little nobody care).

I think you're confused. What you've described occurs on the earth just as it does in space: if you shoot a gun on earth, you feel the recoil. The difference is whether you're standing (and thus bracing yourself on the ground) or in zero-gravity.

If the spaceship the OP is talking about has artificial gravity, then physics will work the same on the ship as they would on a planet with similar gravity.

Furthermore, even if there is no gravity, and someone is just floating without anything to hold on to while shooting a gun, the recoil won't move them very far. Based on my calculations, firing a .22 bullet (about 2.5g at 330 m/s, according to wikipedia) would only accelerate a 120lb person 0.159 m/s ( 0.036 mph). Similarly, a giant spaceship firing a cannon with a small bullet (relative to the spaceship) wouldn't be jostled very much.

Yukitsu
2010-05-03, 04:20 PM
Oh and as for guns, I like the mass effect approach. Hyper velocity kinetic slugs in a mass reducing field accelerated to near the speed of light do bad things to people, which makes, and I quote "Sir Issac Newton the deadliest sonofabitch in space."

Though technically, a faster moving object with less mass hits with identical force. Changing the mass midflight doesn't alter the initial F, which is conserved unless opposed.

pffh
2010-05-03, 04:21 PM
Oh and as for guns, I like the mass effect approach. Hyper velocity kinetic slugs in a mass reducing field accelerated to near the speed of light do bad things to people, which makes, and I quote "Sir Issac Newton the deadliest sonofabitch in space."

Why would you want to reduce it's mass? Less mass = less kinetic energy which is 0.5*m*v^2 = less damage


Quick correction there: the spaceship does have inertia (and in fact that's why it keeps going). It's the lack of friction (including air resistance) that means a huge spaceship doesn't have to worry about unintended deceleration.

What are you talking about I said friction :smalltongue:

Thanks for the correction my brain is mushed from studying for my finals so I have an excuse for that mistake.

The Rose Dragon
2010-05-03, 04:24 PM
Why would you want to reduce it's mass? Less mass = less kinetic energy which is 0.5*m*v^2 = less damage

Because it is mass times velocity squared. A higher velocity will mean a higher energy than a higher mass, and due to relativity, things will gain mass as they accelerate, meaning you have to start with a very small mass to use the technology.

Yukitsu
2010-05-03, 04:25 PM
Because it is mass times velocity squared. A higher velocity will mean a higher energy than a higher mass, and due to relativity, things will gain mass as they accelerate, meaning you have to start with a very small mass to use the technology.

The problem being, you start with an initial force, and get an increase in the square root of the velocity to your decrease in weight. The force remains constant while the other two variables alter to accomodate it.

Noedig
2010-05-03, 04:26 PM
Forgive my lack of hard math for this but IIRC the fluff says that a slug held in a mass reducing field can be fired at proportionally (or expoentially? big difference i know) greater velocity with less recoil. An example was a paint chip accelerated to a velocity so great that impacted with the force of a nuclear warhead. The recoil would still be absolutely tremendous but less so than if you fired an appropriately sized slug at a slower speed.

Ill look this up again.

pffh
2010-05-03, 04:26 PM
Because it is mass times velocity squared. A higher velocity will mean a higher energy than a higher mass, and due to relativity, things will gain mass as they accelerate, meaning you have to start with a very small mass to use the technology.

Oh yeah, been some time since I studied this I had completely forgotten about the mass increase.

DSCrankshaw
2010-05-03, 04:26 PM
The formula for time dilation has already been stated, but to clarify: when you approach the speed of light, you experience something called length contraction--distances along your direction of travel seem shorter. What this means if you approach the speed of light, you can travel vast distances in short times. So, at 99% light speed, you can travel 7.09 light years in what seems to you to be one year. (The reason you're not traveling faster than the speed of light from your perspective is because the distance is only one light-year in your frame of reference.)

One sci-fi book which actually uses this is Orson Scott Card's Speaker for the Dead.

The Rose Dragon
2010-05-03, 04:27 PM
The mass isn't decreased during flight. You start with a very low mass and accelerate it to very high velocities. The computer onboard the gun cuts off a bullet shaped to explode like a hollow-point but at the size of a sand grain.

Noedig
2010-05-03, 04:30 PM
Found it on the Mass Effect wiki, which consequently has a good article on shield science.


Codex Image
A mass accelerator propels a solid metal slug using precisely-controlled electromagnetic attraction and repulsion. The slug is designed to squash or shatter on impact, increasing the energy it transfers to the target. If this were not the case, it would simply punch a hole right through, doing minimal damage.

Accelerator design was revolutionized by element zero. A slug lightened by a mass effect field can be accelerated to greater speeds, permitting projectile velocities that were previously unattainable. If accelerated to a high enough velocity, a simple paint chip can impact with the same destructive force as a nuclear weapon. However, mass accelerators produce recoil equal to their impact energy. This is mitigated somewhat by the mass effect fields that rounds are suspended within, but weapon recoil is still the prime limiting factor on slug velocity.

ko_sct
2010-05-03, 04:30 PM
I think you're confused. What you've described occurs on the earth just as it does in space: if you shoot a gun on earth, you feel the recoil. The difference is whether you're standing (and thus bracing yourself on the ground) or in zero-gravity.

If the spaceship the OP is talking about has artificial gravity, then physics will work the same on the ship as they would on a planet with similar gravity.

Furthermore, even if there is no gravity, and someone is just floating without anything to hold on to while shooting a gun, the recoil won't move them very far. Based on my calculations, firing a .22 bullet (about 2.5g at 330 m/s, according to wikipedia) would only accelerate a 120lb person 0.159 m/s ( 0.036 mph). Similarly, a giant spaceship firing a cannon with a small bullet (relative to the spaceship) wouldn't be jostled very much.

I know it work the same way, but for example, if you’re on the top of your space ship and kick someone (it wouldn’t be really effective in a fight in vacuum but meh) you’re going to send yourself in the opposite direction, which may have nothing for you to catch and again for the gun (I was more thinking of a repeating shotgun but the effect is still small), your sending yourself in the opposite direction, which may or may not (probably not as you've shown it as very little effect) send yourself away from your ship

On earth, even though you’re sending yourself in the opposite direction, it has pretty much no effect; you won’t send yourself away from earth with a little kick (unless you’re Chuck Norris, which I doubt you are)

Noedig
2010-05-03, 04:32 PM
Magnet boots solve that little vaccum fighting thing

Yukitsu
2010-05-03, 04:34 PM
The mass isn't decreased during flight. You start with a very low mass and accelerate it to very high velocities. The computer onboard the gun cuts off a bullet shaped to explode like a hollow-point but at the size of a sand grain.

Given the description below, it should actually experience a massive reduction in velocity upon exiting the field, as it will travel with a total kinetic energy equal to the imparted energy of the gun. In other words, once it weighs something again, it has to accelerate the mass it now suddenly has. Unless it never actually leaves the field, but if that's the case, the impact force is still the exit force.

The Rose Dragon
2010-05-03, 04:36 PM
Given the description below, it should actually experience a massive reduction in velocity upon exiting the field, as it will travel with a total kinetic energy equal to the imparted energy of the gun. In other words, once it weighs something again, it has to accelerate the mass it now suddenly has. Unless it never actually leaves the field, but if that's the case, the impact force is still the exit force.

And the exit force is very high. What's so hard to understand?

Yukitsu
2010-05-03, 04:37 PM
And the exit force is very high. What's so hard to understand?

Because the exit force isn't increased by the mass reducer. Conservation of force takes precedence over conservation of velocity. Even if it's a high velocity, high force slug, the force total is no different than a standard slug propelled using the same method without the mass reducer.

Basically, I don't understand why a mass reducer would increase force. It shouldn't.

The Rose Dragon
2010-05-03, 04:51 PM
It doesn't increase force, it increases efficiency. Compare a magazine filled with real life sized bullet to a tiny grain of sand chipped from a block of metal the size of a magazine with the same force. Which one would last longer in a firefight?

Yukitsu
2010-05-03, 04:52 PM
It doesn't increase force, it increases efficiency. Compare a magazine filled with real life sized bullet to a tiny grain of sand chipped from a block of metal the size of a magazine with the same force. Which one would last longer in a firefight?

Yes, but I was arguing when people were saying it was more effective per hit.

The Rose Dragon
2010-05-03, 04:54 PM
I don't know about that. It may be said to be more effective and I might have missed that in the codex. I just know that reason for why they use mass effect fields in guns.

Darius Rae
2010-05-03, 04:57 PM
The thing to remember is that space is VERY big. So big, that when you think of big, you are nowhere close. To get from our sun to the closest star, Proxima Centari it would take at least 4 years going at the speed of light. Many generations could conceivably pass before you reach another system. (or you cheat and go faster than light like the Destiny from SGU)




Also for moving in space it's good to remember that in space bigger ships are faster since they can fit more and larger thrusters since there is no friction so they don't slow down so the longer and harder you push the faster the ship moves.


Except that you would want a ship with lower mass to increase available force according to F=MA. Engine size is less relevant than mass flow. If you have one small engine that pumps a lot of mass out, it will be better than a lot of less efficient ones. Having said that, big engines give you a better chance to produce more thrust.

Relativity
I haven't checked to see if those equations are right, but I would default to say they were. I have nothing to add.

Artificial Gravity
2 easy ways to do this
1: You have the ships accelerate at 1G (about 9.8 meters per second squared) once you get half way to your destination you decelerate at 1G. This means that the "ground" will be perpendicular to the thrust.

2: Spinning torus rings, you can google it for more information but it works by creating a force that acts as gravity.

Weapons
Lasers - Very sci-fi, except they probably will not use visible light

Rail Gun (or coil gun or gauss gun) - You use a magnet to propel a slug forward at high velocity.

Wormholes and Jump Drives
To make a wormhole you generally need
A: Lots of mass (a few of our suns)
B: Exotic matter, matter that by definition holds wormholes open

Alternatively you could "accelerate" something by sending it through the 4th dimension. This is the idea behind folding space-time. (or at least the physics idea, I cannot account for bad sci-fi explanations)

I will edit it in a bit to include more stuff...

(btw studying aerospace engineering)

Edit: Included Wormholes and a talk of how big space is

Math_Mage
2010-05-03, 05:00 PM
Why would you want to reduce it's mass? Less mass = less kinetic energy which is 0.5*m*v^2 = less damage

It makes sense if the gun applies the same amount of force to any projectile. Let's run the numbers. Force is change in momentum. If you apply the same amount of force over the same amount of time, you get the same change in momentum. Initial momentum for both projectiles is 0, final momentum is mass*velocity. Half the mass <==> double the velocity. But the kinetic energy is mv^2*0.5, so the smaller projectile will have a higher kinetic energy.

Now, relativity is going to have a retarding effect of some kind on this, and I don't know how Newtonian physics is going to interact with mass reducer fields--what's conserved, momentum or velocity or energy or...? But the basic math checks out.

Siosilvar
2010-05-03, 05:12 PM
Weapons
Lasers - Very sci-fi, except they probably will not use visible light

And even if they are, you won't be able to see them unless you're looking straight down the "barrel", in which case you've now been blinded by the beam.

Venerable
2010-05-03, 06:04 PM
Does inertia work this way? Will the fleet appear to be at rest relative to itself and is flight between ships possible during the voyage?

Yes. If they're traveling at the same velocity, with no acceleration, and no outside forces are acting on them, then flight between ships is as simple as aiming yourself and jumping. Just don't miss!:smallbiggrin:


Can humans indeed live normally while moving at high speeds?

It's not speed that causes damage, it's acceleration. As long as your fleet accelerates at around 1g (or maybe a bit more), everything should be fine.

For the record, to get someplace fast, boost at max acceleration for the first half of the trip, spin the ship 180 degrees, then decelerate for the second half. The only reason to "coast" at constant velocity would be to conserve fuel. But then you have to spin the ship to provide gravity.


Does anyone know how time dilation works, how its magnitude is determined and whatnot?

Don't worry about it, if you're doing stuff between ships traveling at the same speed. If they're not, you can look up the equation for time dilation (http://en.wikipedia.org/wiki/Time_dilation#Overview_of_time_dilation_formulae), but it's not the kind of thing you want to use in-game (unless all your players are physics enthusiasts).


What would be needed to accurately strike at a fleet moving fast enough to experience time dilation, and how would the dilation and locomotive speed of the fleet affect any attempt at combat from a stationary (or just much slower-moving) force?

To strike, you'd need the target's trajectory and speed. It should be pretty simple to determine that.

In an attack between ships moving at different speeds, mass dilation comes into play: the faster something is moving (as you perceive it), the greater its mass. Getting struck by a pebble at 2MPH doesn't hurt much; getting struck by a pebble moving at close to lightspeed would punch a hole through your body. This fact can be used by both attacker and defender. But remember, it's not the absolute speeds of the ships that matters, it's the difference in speeds that causes dilation.


Anything else I need to know about life at high velocity?

One thing: velocities don't add with a simple N+M (http://en.wikipedia.org/wiki/Velocity-addition_formula). Otherwise, if you're moving at 3/4 the speed of light and fire off another rocket at 3/4 lightspeed in the same direction, it would be moving at 1.5c, which violates the "nothing moves faster than light" rule. At velocities we're used to, adding velocities with N+M is an adequate approximation, but when you start moving at a significant fraction of c you need to use (N+M)/(1+NM/c^2).


Is there any "hard" concept for how you would sync up two gates?

Steal from the best: in Ken MacLeod's The Stone Canal, a pair of gates was created simultaneously in the solar system. One was left in orbit near Jupiter, while the other was towed at near-lightspeed to another star system. Since the gates were "birthed" from the same flaw in spacetime, there's no remote sync-up issue.


Are force fields a plausible technology and at what scale?

We use 'em all the time, but we call them "electromagnets". :smallwink: Maybe you could create one from something else (sonic?), but it's pretty much all handwaving aside from electromagnetism. Make it up, go nuts!

a_humble_lich
2010-05-03, 06:10 PM
As far as warping space, what others have said is right but I'd like to add some things. There exist solutions to the equations of general relativity that give wormholes and warp bubbles. However, they all have some "difficulties." They often require masses equivalent to the mass of galaxies (a bit of an engineering problem) or use negative mass (don't know what negative mass is, join the club nobody else does). Massive gravitational forces would also be a problem (after all general relativity is the theory of gravity). Now it is a fairly young field, so if you want to say there are easier solutions go for it.

As far as relativity goes, I'd recommend avoiding it. If you stay below about 20% the speed of light, and effects of relativity will be small enough to be ignored. Once you start messing with relativity things start getting complicated and if you don't know what you're doing it is easy to get stuff wrong. Even if you do know what you are doing it is easy to get stuff wrong :-)

However, for a game you might not mind the science being a little wrong. In that case the equation for time dilation given earlier is correct. You also will have length contraction (the distance the space ship sees to its destination will be shorter). Someone earlier said mass increases, in the modern way of thinking that is not true. Rather an objects energy and momentum increase--which in practical terms means the closer you are to the speed of light the more energy you will need to accelerate faster.

For space combat I feel it will be dominated by lasers and particle beams. Space in big and empty so there is not much to hide behind. If a ship can be detected 5000 km away it will take maybe 2 hours for a bullet to get there. Eve a super hyper velocity railgun shell going at mach 25 will take 10 minutes. If ships can maneuver at all it will be hard to hit them. At those distances you will need weapons that either go the speed of light (lasers) or close to it (particle beams).

Math_Mage
2010-05-03, 06:16 PM
Yes. If they're traveling at the same velocity, with no acceleration, and no outside forces are acting on them, then flight between ships is as simple as aiming yourself and jumping. Just don't miss!:smallbiggrin:

Or splatter yourself against space dust between the ships...:smalleek:

Presumably you'd have to be shielded somehow, probably the same way the ships themselves are shielded.

MachineWraith
2010-05-03, 06:25 PM
http://www.projectrho.com/rocket/index.html


That site is a veritable goldmine for the injection of science into your fiction. It's excellent, and I've used it to great effect myself.

Darius Rae
2010-05-03, 06:26 PM
Steal from the best: in Ken MacLeod's The Stone Canal, a pair of gates was created simultaneously in the solar system. One was left in orbit near Jupiter, while the other was towed at near-lightspeed to another star system. Since the gates were "birthed" from the same flaw in spacetime, there's no remote sync-up issue.

That is a good idea and would work great for what the OP appears to need to do. My only problem (which you can and probably should ignore) is that if you towed the other gate at near-light speed you run into relativity problems (essentially creating a time machine)




For space combat I feel it will be dominated by lasers and particle beams. Space in big and empty so there is not much to hide behind. If a ship can be detected 5000 km away it will take maybe 2 hours for a bullet to get there. Eve a super hyper velocity railgun shell going at mach 25 will take 10 minutes. If ships can maneuver at all it will be hard to hit them. At those distances you will need weapons that either go the speed of light (lasers) or close to it (particle beams).

I fully agree with this (except for one nitpick) While there is no reason that with sufficient energy that you couldn't propel any mass at near C, (they are called "relativistic kill weapons" or any variation of "relativistic kill ___" ) lasers take much less. (again following F=MA, this is the equation you will be living by)

The nitpick, mach number cannot be used in space. Mach number is the speed of an object traveling through a fluid divided by the speed of sound in that fluid. The measurements that you will be best to use will be %C or a C fraction, C being the speed of light.

Jack_Simth
2010-05-03, 06:33 PM
Also for moving in space it's good to remember that in space bigger ships are faster since they can fit more and larger thrusters since there is no friction so they don't slow down so the longer and harder you push the faster the ship moves.
There is *some* fricton ... from the occasional lone hydrogen atom, mostly. Of course, if you hit that at a high fraction of c, well... it's more like heavy radiation. All ships have an absurd amount of radiation shielding, at it all goes at the front of the ship (barring fantasy-tech, of course). Likewise, the distance between starts is ENORMOUS. Space is full of long, long ways, and most of them are stacked end-to-end. Even at a fairly good fraction of c (say, 75%), you're still looking at multi-year journeys to get to the nearest stars... and that's accounting for time dilation for the travelers. If you want to go to anything outside the local cluster, you're looking at sleep ships or multi-generation ships... and stasis isn't something we've got working reliably for long periods of time, so you're pretty much looking at multi-generation ships.

Mind you, if you can get to a high enough fraction of c, the distance doesn't matter, as the speed pauses the traveler.


Combat with a slow moving enemy: The enemy would appear frozen for the fast ship and I doubt the slow ship could do anything about the fast ship.
Another thing you may want to consider with space ships and space combat is that you don't want to be close to the ship you're blowing up since that scrap metal flying through space is doing so at some silly speed and could theoretically tear a hole in your ship. So ship to ship combat would most likely be on the opposite ends of a solar system.

Well... that's a point of contention. For ship A, it's ship B that's moving, and is frozen. For ship B, it's ship A that's moving, and is frozen. Both frames are equally valid.

So which ship blows up because they can't dodge? Ask a physics professor. They *might* be able to give you an answer. Maybe.



Oh and one final thing before I go to bed, heat. Getting rid of heat is a major problem in space since there is no matter for it to radiate to. This means that weapons that generate a lot of heat (fx lasers) would not be viable in space and ships would rather use railguns.

Well... radiating works just fine - that works on light - but you can't dump it directly (which is generally how you cool yourself on earth). You can still dump it fairly effectively - basically use a refrigeration unit to concentrate heat to the point where one side glows - the glow is heat heading off into space. How effective it is depends on:
1) How effective your refrigeration unit is
2) How much heat your radiation zone can handle before it malfunctions.
3) How much surface (in a spherical sense) you can devote to this.

a_humble_lich
2010-05-03, 06:43 PM
I fully agree with this (except for one nitpick) While there is no reason that with sufficient energy that you couldn't propel any mass at near C, (they are called "relativistic kill weapons" or any variation of "relativistic kill ___" ) lasers take much less. (again following F=MA, this is the equation you will be living by)

The nitpick, mach number cannot be used in space. Mach number is the speed of an object traveling through a fluid divided by the speed of sound in that fluid. The measurements that you will be best to use will be %C or a C fraction, C being the speed of light.

I agree completely a "relativistic kill weapon" that fired a .1g paint chip at 20% the speed of light would take the energy of a small nuclear warhead (.1 kton assuming no energy is wasted). And it would still take about .1 s to reach the target. Much smaller masses are much more practical--you could fire relativistic protons easily, or even a continuous beam of them :-)

As for using mach numbers in space you are right, I was just trying to use units non-physicists would understand.

dspeyer
2010-05-03, 09:08 PM
Well... that's a point of contention. For ship A, it's ship B that's moving, and is frozen. For ship B, it's ship A that's moving, and is frozen. Both frames are equally valid.

So which ship blows up because they can't dodge? Ask a physics professor. They *might* be able to give you an answer. Maybe.


This isn't a complete answer, but I think the time dilation and the space dilation will cancel out, and each ship will experience the same amount of time with the other within targetting range. If you're worrying about relativity and using sane telescopes, that amount of time will be very short.

Math_Mage
2010-05-03, 09:19 PM
Well... that's a point of contention. For ship A, it's ship B that's moving, and is frozen. For ship B, it's ship A that's moving, and is frozen. Both frames are equally valid.

So which ship blows up because they can't dodge? Ask a physics professor. They *might* be able to give you an answer. Maybe.

Law of symmetry. Whatever happens, happens to both of them. Either both can dodge, or neither can. My money's on the latter, but I'm not a physics professor. :smalltongue:

Jack_Simth
2010-05-03, 09:45 PM
This isn't a complete answer, but I think the time dilation and the space dilation will cancel out, and each ship will experience the same amount of time with the other within targetting range. If you're worrying about relativity and using sane telescopes, that amount of time will be very short.
It's the relativistic paradox.

If you throw an 11-foot pole at the correct relativistic velocity, it'll shorten to 9 feet, and will fit in the ten-foot barn you're throwing it through for a very small fraction of an instant.

If you're an 11-foot pole, thrown at relativistic velocities, that ten-foot barn shortens to a little smaller than 9 feet, and you'll never fit, not even for an instant.

But there's one barn, and there's one pole. Both are the exact same scenario, just written from different perspectives. Does it fit, or doesn't it? That's a matter of perspective (pole or barn). Relativity gets it's name partially because it says both are equally valid. It's relative to your perspective.

It's similar to the black hole paradox: The same equations that predict an object observed falling into a black hole superheats and spaghettifies ALSO predict that an observer falling into a black hole is basically fine (from the observer's perspective). The same equations also say both perspectives are equally valid.

Who's frozen and unable to dodge? Well, that's a matter of perspective....

The Pressman
2010-05-03, 09:58 PM
Are force fields a plausible technology and at what scale? this is much less important to the plot and premise than the other two questions, although it might be important for a vanguard ship protecting the fleet from unforeseen debris, but I like shields a lot as a device, while I don't know of any scientific justification for them. Luckily for me, I can always salvage the idea of "shields" as being a colloquial term for a high-tech suit's firewall etc... however:

Is there any scientific justification for an energy-based kinetic barrier? Is it practical/might it be given forseeable advances in energy storage/production etc?
How would they work, theoretically, compared to what we often see in fiction?
Is there any reason at all to make them visible ever?
Would it be more likely to have projected (bubble) shields or shielding that "clings" to the shielding object's surface?


Guns... I'm looking at particle beams and other kinetic weapons, right?

Answers, explanations, links to places with these things, any of the above regarding things I didn't ask but should have, and unsolicited advice are all appreciated.
One way to do this is to have a bubble of plasma contained in a magnetic field.

dspeyer
2010-05-03, 10:17 PM
It's the relativistic paradox.

Relativity doesn't have paradoxes, it just has very confusing things.



If you throw an 11-foot pole at the correct relativistic velocity, it'll shorten to 9 feet, and will fit in the ten-foot barn you're throwing it through for a very small fraction of an instant.

If you're an 11-foot pole, thrown at relativistic velocities, that ten-foot barn shortens to a little smaller than 9 feet, and you'll never fit, not even for an instant.

But there's one barn, and there's one pole. Both are the exact same scenario, just written from different perspectives. Does it fit, or doesn't it? That's a matter of perspective (pole or barn). Relativity gets it's name partially because it says both are equally valid. It's relative to your perspective.


The pole "fitting inside the barn" means that it finishes entering before it starts to leave. Entering and leaving occur at opposite ends of the barn. Events which are close in time and distant in space are not definitively ordered, because which you observe first depends on your location. Therefore fitting inside the barn is not meaningful.



It's similar to the black hole paradox: The same equations that predict an object observed falling into a black hole superheats and spaghettifies ALSO predict that an observer falling into a black hole is basically fine (from the observer's perspective). The same equations also say both perspectives are equally valid.


Black holes crush by tidal forces. Relativity offers no protection.



Who's frozen and unable to dodge? Well, that's a matter of perspective....

No. This is the sort of problem that has a well-defined solution -- it's just one that's difficult to find.

dspeyer
2010-05-03, 10:18 PM
Law of symmetry. Whatever happens, happens to both of them. Either both can dodge, or neither can. My money's on the latter, but I'm not a physics professor. :smalltongue:

There is one asymmetry: one ship has experienced powerful acceleration (i.e. gravity) and the other hasn't. Position in a gravitational field is relevant to time dilation.

It probably isn't relevant here, but it's sometimes important to remember.

Townopolis
2010-05-03, 11:01 PM
Thanks for the responses so far. To recap, what I have at the moment is:

To start with, guns: My original assessment that I'd be looking at particle beams is based on this movie (http://www.youtube.com/watch?v=0AV5aY7HYAk), and it seems to be supported by the responses I've received regarding the issues of bullet lag that slower kinetic weapons have when you're trying to kill other people. Checking out Wikipedia has also led me to this article (http://www.airpower.maxwell.af.mil/airchronicles/aureview/1984/jul-aug/roberds.html) and also this one (http://www.fas.org/spp/starwars/program/npb.htm). They seem promising, although I haven't read them completely yet. Unless there's something that hasn't been mentioned, or there's a reason lasers are going to make a comeback, or someone can tell me what particle beams look like (and why, if you know), I'm mostly satisfied with this.

Force fields to protect ourselves: The military is already working on electromagnetic shielding that's supposed to at least help mitigate kinetic attacks. That's good, and I found this site (http://www.hardsf.org/HSFTForc.htm) (which was actually stupidly easy to find) which has a little more information. Of course there are problems with maneuverability, unless you like living in a hamster ball. Also, the first article on particle beams states that the weapon would be so awesome that shielding would be impractical (although I'm not sure it's thinking about force fields in particular). It doesn't go into details, but that has me worried. A few questions about force fields that are probably a lot harder to answer.

Does anyone understand the ideas behind force fields and particle beams well enough to speculate about whether or not the one would be effective against the other?
Is there any support for creating a force "screen?" Basically, would it be possible to create an array of force fields in the "shape" of plate armor? This was the first idea that came to mind as to how you could have "solid" force fields that protected while still allowing a wide range of motion.


Also, on a somewhat related topic, does anyone have any idea how a particle beam would fare against chobham armor (with or without shielding to help mitigate)?

Moving in space: Another thing I noticed while looking at particle beams was that apparently ions can't be accelerated beyond 10% of c. If this is true, I probably shouldn't have ships moving faster than this. Even if it is not, I like 20% of c as a top speed based on the advice that avoiding relativistic shenanigans is safer. Works for me, especially since this was already planned as being a generation ship.

I didn't think to realize that constant acceleration would create artificial gravity. Thanks for that. Also, as pointed out here (http://www.projectrho.com/rocket/rocket3at.html) (thanks), "down" is the direction of the engines/exhaust. I'm not certain, however, if it makes sense for the ship to resemble more of a skyscraper with he engines on the bottom, or a flying saucer with the engines on the bottom, or perhaps a skyscraper with the engines on the side. I figure that, since people are designed to move horizontally, a "short" ship would be more comfortable to move around it (or at least be a lot less reliant on elevators), but I don't know what else should be taken into consideration. That's actually a good question.

Is there any way an intersteller ship would be built relative to its engines that would be more practical?
I'm also confused by the "no friction in space means bigger = faster" thing. Friction normally (as I understand it) usually manifests as wind/water/ground resistance that is counteracted by being aerodynamic/aquadynamic/having wheels. So, there's no reason for spaceships to be aerodynamic and pointy, but isn't acceleration based more on the amount of energy you are able to exert compared to your mass (so a bigger ship would still take more energy to move)? Also, as pointed out in Machinewraith's link, acceleration in space is done with reaction mass, so it's a matter ship mass vs. remass. If all ships carry the same remass relative to their own mass, wouldn't this mean they all accelerate at the same rate? (now I'm even more confused...)


I was originally envisioning a single "mothership" generation ship that would be as close to a self-sustaining "moving colony" as possible, with it's own military base (possibly another ship) an escort of military ships (with new personnel coming from future generations from the mother ship of course). However, until I have a better idea of how acceleration works relative to mass, I'm not sure.

Wormholes and stuff: As expected so far, my best bet seems to be good ol' pseudoscience and handwaving.

A new question, less to do with science so much as science-users

Being an engineer in the future: As science and technology progress, it becomes necessary to specialize more and more in order to be relevant as more than a high school teacher. However, when you want to play an engineer, you don't want to play the "astrogation sensors technician" who's fine with astrogation sensors but nothing else. You want to play an "Engineer!"

So is it plausible that, with technological assists, you could have a generalist engineer who could deal with, say, 50%+ of the mechanical situations that might arise on a starship during interstellar travel?

I'm imagining some form of computer, maybe integrated into a suit or helmet or maybe just your skull, that would contain a database of technical information as well as the ability to perform any relevant computations (including knowing relevant formulas). The engineer's education would focus on fundamentals, high-end concepts, and information processing skills. The idea is that the engineer's training focuses more and more on "thinking" while the computer would supply knowledge of specifics. Basically, is it reasonable that the right training + instant wikipedia (only better) could = practical competence in a wide field?

dspeyer
2010-05-03, 11:17 PM
There are two good reasons to make the ship "tall".

First is structural. Picture building the ship on earth, and supporting it only by where the engines are. This is equivalent to firing the engines at 1g. If you picture the building drooping at the edges, then crumbling, it probably would.

The other is space dust. Interstellar space averages 1 million particles / cubic meter. Most of those are hydrogen atoms, but at 0.2c their energy isn't entirely negligible, and you're going to pass through a lot of cubic meters. The shield for this needs to be as large as the ship's cross section.

Math_Mage
2010-05-03, 11:26 PM
There is one asymmetry: one ship has experienced powerful acceleration (i.e. gravity) and the other hasn't. Position in a gravitational field is relevant to time dilation.

It probably isn't relevant here, but it's sometimes important to remember.

In this case, it shouldn't matter, as you say. The reason a person traveling at relativistic speeds away from Earth and back ages slower, gets asymmetric results, is because of the asymmetry in acceleration during the period of measurement. In the given problem, we simply have one ship traveling at a moderate fraction of the speed of light relative to some reference point (perhaps a planet?), and the other ship effectively standing still. Symmetry isn't broken.

Townopolis
2010-05-03, 11:35 PM
In this case, it shouldn't matter, as you say. The reason a person traveling at relativistic speeds away from Earth and back ages slower, gets asymmetric results, is because of the asymmetry in acceleration during the period of measurement. In the given problem, we simply have one ship traveling at a moderate fraction of the speed of light relative to some reference point (perhaps a planet?), and the other ship effectively standing still. Symmetry isn't broken.

I think I actually understood that.

Object A is moving at speed N. Object B is stationary.
Relative to B, A is moving at N.
Relative to A, B is moving at N in the opposite direction.

But now the time dilation... which is really distance dilation... is going to make my head explode.

erikun
2010-05-03, 11:52 PM
These questions are always fun, although I'm not quite sure which ones were already answered and which ones weren't. It is a bit late here. Well, I'll try to answer them to the best of my ability, and the answers should hopefully be the same as everyone else's. :smalltongue:

What are the effects of moving really, really fast in space?

None, effectively. Once you accelerate up to your desired speed, then everything moving at the same relative speed would effectively be standing still. It's much like how you can wander around the cabin of a train or airplane in motion, but you get pushed back when accelerating in a car or airplane. It's the acceleration that has an effect, not the motion.

Unlike the car, there is no air resistance (due to no air) so standing outside won't "blow" you off the ship. Heck, several ships travelling together would be effectively stationary relative to each other, so you could just push off of one to get to the other. Docking to a high-speed moving fleet wouldn't be any stranger than docking to a "stationary" planet: you would just need to match them for speed, and then you're just dealing with relative motion.

Please note that a turn is a form of acceleration, so making a turn during travel would "push off" any loose debris.

The greatest threat for near-light speed travel would be random objects (such as mircometeors, or even loose atomic matter) and solar wind turbulence. Of course, most sci-fi interstellar travel uses energy shield of some sort to dampen or deflect such problems.

Does inertia work this way?

Inertia would only apply during accelerating or deceleration. It is how easy or difficult it is to get an object moving or to stop it. Your starships would have a lot of inertia, meaning they would need to take a long time to get up to full speed, and a long time to slow back down. They would also need to take wide "turns" if they are correcting their course under their own thrusters.

Can humans indeed live normally while moving at high speeds?

High speeds aren't a problem, although high acceleration can be. I think 5G (five times Earth's gravity) starts giving humans large problems for survival, for a reference. Note that if your ship has any kind of psudoscience artifical gravity, it could be used to negate the severity of the ship's acceleration.

Time dilation has been answered far better than I ever could.

What would be needed to accurately strike at a fleet moving fast enough to experience time dilation?

Trajectory and stealth. Assuming you've mastered interstellar travel, it won't be hard to determine how fast a ship is moving, and thus where you would need to aim to hit it.

The problem is getting a weapon unnoticed at the fleet. Objects in deep space can reasonably be seen MONTHS away, if not further. It will be very hard to get anything dangerous close enough to a fleet to start damaging ships. I suppose an energy weapon would work, including a focuses laser, but most current laser technology just works at heating stuff up, not exploding it.

Destroying a ship once you get the object to it won't be a problem. A relatively small asteroid at 90% speed of light will probably obliterate anything less than a small moon. Other people were discussion actual munitions, which will clearly work well if you can convince the travelling fleet to let you close enough to use them.

Folding Space?

The only two type of folding space ideas I'm familiar with are the wormhole (basically a pathway through space) or folding a space "bubble" around a ship and using that for faster-than-light travel. In either case, you are basically bypassing normal space, so you can't be interrupted by anything during your journey.

There is also the fantasy "hyperspace", which is basically like another dimension where the distances between two objects isn't as far. Babylon 5 and Crest of the Stars used hyperspace, for reference. It is generally assumed you can run into other ships in hyperspace, given that it's basically another dimension.

Are force fields a plausible technology and at what scale?

Not really, no. They closest I know of is creating a magnetic field to ward off the worst of interstellar radiation and ionized particles, much like the natural magnetic field on Earth. This wouldn't help against small particles, like micrometeors, punching holes in you hull. (Earth's atmosphere burns up stuff like that.)

I mean, I suppose you could create some kind of plasma-material and run it through the magnetic field, to eat up any small matter that isn't ionized. That was just off the top of my head, though, so I'm not sure if it would work. It would certainly make the ship hazardous to stand on, though.

I would think a Lead/depleted Uranium alloy on the outer hull would also absorb harmful radiation, then radiate it back out into space. Not sure how well that would work practically, though.

erikun
2010-05-04, 12:28 AM
Part two!

To start with, guns:

Yeah, this seems fairly accurate. Don't negate what a good laser can do, though. Being bombarded with Gamma radiation will quickly cook anyone inside a ship, and it has a habit of going through matter, to boot. This is why I recommended magnetic shielding: space has a lot of free Gamma radiation, which will ultimately kill off a human within a month unless you have some way of protecting them. Ironically enough, it also means that a Gamma laser wouldn't be effective unless you knocked out the ship's shielding, or managed to overwhelm it.

We actually have particle beam technology right now. Are you familiar with how plasma is created? It involves taking matter, putting it in a magnetic field, and accelerating it to the point where the atomic bonds fall apart and you end up with electron/proton soup. Oddly enough, if this is how you're getting your particles, then the magnetic shielding would be partially effective against it. Not completely effective, mind you, but the charged particles would still tend to follow the magnetic flow.

You'd probably end up with a space battle rather similar to how it is played on television. Fast, colored particle beams would go after the smaller ships (which have weaker shielding) while the heavier mass driver "missiles" hammer away at the slower, larger ships. Of course, this assumes that such combat is close range. As I mentioned before, you will see an enemy coming from a long ways off...

Force fields:

I think I unintentionally covered this topic already. :smalltongue: An electromagnetic energy field would be partially effective against a particle beam, as the particle beam is made out of charged particles. Not fully effective, though: that is a lot of energy to redirect. It would probably work very similarly to how armor works. If the magnetic field is angled to "catch" and deflect the beam, the ship shouldn't take any damage. If the particle beam is too strong, or hits at a vulnerable angle, the ship would take damage.

That's how I see it, at least.

I'm not sure what chobham armor is. Material armor isn't likely to stand up to a particle beam for long, though.

Being an engineer in the future:

It would be understandable for an engineer to just be familiar with his/her tools, and simply have the repair details "downloaded" to a portable storage device. Most sci-fi settings, such as Shadowrun and Eclipse Phase, assume the characters have access to a wireless infonet to download such material at-will, or have storage devices capable of carrying such information easily.

They probably wouldn't be able to perform complex actions, just as a general doctor wouldn't be expected to perform complex brain surgery. However, they should be able to identify and repair pretty much any common machine that their society is familiar with.

Darius Rae
2010-05-04, 12:34 AM
So is it plausible that, with technological assists, you could have a generalist engineer who could deal with, say, 50%+ of the mechanical situations that might arise on a starship during interstellar travel?


Those are what you call mechanical engineers. :smallbiggrin: They will have all the "mechanical" ie moving parts covered. You will probably need a physicist for the big math stuff, and a aerospace (or in this case just space) engineer for propulsion.

If by engineer you mean technician, then yes with AI or human assisted interfaces many many mechanical situations will be fixable. For the other bigger problems, the technician would contact the appropriate engineer.

Edit: ninjaed, a bit...

Townopolis
2010-05-04, 12:56 AM
For reference, Chobham (http://en.wikipedia.org/wiki/Chobham_armour) is simply the most advanced (I think) current ceramic armor, and possibly the most advanced kinetic armor today period. I don't know how it does against energy weapons, although ceramics do get fired at pretty freaking high temperatures.

Regarding engineers, part of my question is actually the assumption that (in the future) nearly every single mechanical object is going to have an integrated electronic component as well, so how reasonable would it be to try and train an effective mechanical & electrical engineer? (As to level of expertise, this would be someone with as much training/education as, say, a neurosurgeon, only more general. I guess I'm looking for the halfway point between technician and engineer that makes for useful PCs and happy players.)

Excession
2010-05-04, 01:01 AM
I don't see "shields" working unless you hand-wave it. Sure, you can use an electric or magnetic field to deflect a charged particle beam, but it won't work against the neutral particle beams which seem more likely. There are a few other options for avoiding fire though:

Point defence. For projectiles and missiles, engage them with your own weapons before they can hit. This might involve something like modern anti-missile weapons, lasers, or smaller more manoeuvrable anti-missile missiles.

Reactive and ablative armours. I've read about a system that mounted shaped charges facing outward under the first layer of armour, when something hits the outer armour hard you set off the appropriate shaped charged to meet and deflect the incoming projectile or explosion shockwave.

Stealth and ECM: Hide. Pretend to be something or somewhere else. Jamming, chaff, flares, decoys. Pretty much whatever you can think of and hope the enemy didn't think of. Come in quiet and hide in a comet to get in-system. There should be a lot of this.

If you have the ability to push a significant mass to relativistic speeds, things get screwy anyway. Just paint a rock black, aim it at your enemies, and switch the engines off half way there. It's mostly invisible, has so much mass it's really hard to deflect, and will kill an entire planet when it hits. Planets become a liability because they're too predictable. Better to hide in mobile ships and habitats.

Personally, I don't see a space battle being much like what you see on movies and TV. Engagement ranges are likely to be measured in light-minutes or hours, if not years if you're lobbing relativistic missiles at each other. A "one shot kill environment" is likely; whoever gets unlucky first loses. Most of the combat is going to be done by robots and computers. Humans are too big, not fast enough, and can't withstand vacuum or serious accelerations.

The better "realistic" science fiction that I've read has tended to involve reasons why large-scale space battles don't happen. It may simply not make economic sense as there's plenty of space to go around. If nobody is used to it the fancy weapon and armour systems don't tend to show up when someone does start shooting. Check out "A Deepness in the Sky" by Vernor Vinge for an example of this. Firefly is another example; it's assumed that the big ships have weapons, but the "player characters" don't get to have them.

I think that's enough rambling for me :smallwink:

GoodbyeSoberDay
2010-05-04, 01:24 AM
If I were you I'd nix the artificial gravity and go with the B5 rotating system setup. By the time you can actually manipulate gravity the way they do in sci-fi you'd realistically be using your magical gravity generator for propulsion, weapons, shields, et cetera, or you'd be holding back the phlebtonium (http://tvtropes.org/pmwiki/pmwiki.php/Main/HoldingBackThePhlebotinum).

Darius Rae
2010-05-04, 02:30 AM
For engineers, there is a lot of book learning (taking finals this week...) but you can get a lot from first hand experience as well. This usually takes 4 years, or longer if you want a masters degree or such. So, it takes less time than learning neurosurgery. Whats the starting age for wizards in DnD 3.5? Characters at an age of about 20 something up would fit the bill.

a_humble_lich
2010-05-04, 04:22 AM
On particle beams and lasers.

First I have no idea why you say ions can't be accelerated part 10% light speed. Right now the RHIC (http://en.wikipedia.org/wiki/Relativistic_Heavy_Ion_Collider) accelerator at Brookhaven accelerates gold ion at 99.995% the speed of light. As for what particle accelerators look like, your TV is one :-) Higher powered ones are building sized or larger. The LHC at CERN is a 8.5 km ring. The SLAC accelerator is 2 miles long (in a line) undernearth the 280 freeway near Stanford. Ship mounted particle beam would most likely be much smaller (and thus lower energy) but with more particles so it makes an effective weapon.

As for particle beams vs. lasers, I'd say they both are equally realistic. We currently have laser weapons in the real world.

I think the big thing to think about isn't armour or weapons, but propulsion. Traveling across interstellar distances is hard. A ship will most likely have enough fuel to get there once, with no fancy maneuvering along the way.

Brother Oni
2010-05-04, 07:00 AM
For the guns, might I suggest your normal gun whit bullet containing oxygen? I think there a type of bullet where the gun powder contains enough oxygen to burn even in vacuum, though; you might want something more sci-fi.



This is a bit of a myth. Gunpowder already contains the oxygen required to burn within its chemical structure. Guns would work fine in a vaccum (there are modern guns which will fire underwater).

There's a Firefly scene where Jayne shoots Vera inside a spacesuit as apparently she needs an atmosphere to fire. Either Vera is a special gun where the propellant needs an external source of oxygen, or Jayne was mistaken.

Two things though - as mentioned before, heat disappation will be an issue, so high rof weapons would have issues with their barrels warping under high heat; the other would be that outside of a gravity well, bullets won't slow down, so you could theoretically fire a round from a few hundred miles away and it'd still hit something at the same force it was fired at.

This would apply to any other physical objects, so artillery, railguns and missiles would be interesting to use in zero/low gravity conditions - just bear in mind engagement ranges and flight velocities.

Townopolis
2010-05-04, 02:42 PM
More excellent answers, thanks everyone.

So particle beams (probably neutral) and gamma lasers would be major weapons. Electromagnetic shielding would protect against radiation and lasers, but not against particle beams and other kinetic weapons. To deal with those, you'd need some form of improved armor.

Because particle beams travel at very near the speed of light, it is very difficult to defend against them with point defenses. Combine this with the damage potential of a very big beam, larger particle cannons that can easily rip through armor and blow cities up would likely be classified as WMD's and only kept around as deterrents.

Either smaller particle cannons, point defense turrets and hand-held assault rifle varieties, would either be weak enough that they can be defended against for a little while, or their power draw would be such that the beams can't be maintained for significant portions of time, or would be replaced by more "normal" mass driver technology. Depending on energy requirements, standard dakka mass drivers might be used for infantry combat anyway because the nigh-instant delivery of a particle beam is mostly only necessitated by the extreme range of ship battles. I should probably get to fully reading those articles on particle beam weapons.

(speaking of extreme range, the fact that we can already target enemies beyond the curvature of the earth, and that targeting technology will likely only get better, really screwed up our exciting space battles.)

Ships would be built fairly classically, like fat cigars with lots of elevators. Turning around mid-journey might be an issue unless the ship had full shielding (or could for the turn). Still not sure on whether or not there's good reason to take one big ship over many smaller ones. Artificial gravity is accomplished through propulsion, with no phlebotinum to hold back.

Issues of heat radiation cause problems, especially with the pew-pew cannons. Ships need ways to vent heat into space. Either through large external radiators or some other way.

I don't suppose there's a way to link heat expulsion with propulsion, say by channeling/dumping system heat into the reaction mass before expelling it?


Computer-assisted electromechanical engineers appear plausible enough.

Jack_Simth
2010-05-04, 06:09 PM
Relativity doesn't have paradoxes, it just has very confusing things.

Close enough, generally.


The pole "fitting inside the barn" means that it finishes entering before it starts to leave. Entering and leaving occur at opposite ends of the barn. Events which are close in time and distant in space are not definitively ordered, because which you observe first depends on your location. Therefore fitting inside the barn is not meaningful.

"It's not meaningful" is a very interesting way of saying "unanswerable".

But where the rubber meets the road, you can align two clocks at distant locations if they have a relative vector of 0 (time round-trip light off of mirrors). You can set sensors in the same frame of reference that will respond identically and record the results to the common clock.

So the barn can have an entrance that notes the exact instant the end of the pole is no longer in the barn. The exit of the barn can have a sensor that notes the exact instant the pole started leaving the barn.

You can do the exact same thing on the pole itself.

They're not exceeding light speed, so they can send each other encoded messages.


Black holes crush by tidal forces. Relativity offers no protection.

Depends on the size of the black hole (prior to the event horizon, anyway - beyond that, we have no definitive info). It was my college astronomy teacher who pointed this out, curiously. But then, he was also confused by early experiments into the photovoltaic effect and their meaning....

No. This is the sort of problem that has a well-defined solution -- it's just one that's difficult to find.
Cool. So which can't dodge? A or B?

Emmerask
2010-05-04, 06:41 PM
I'm imagining some form of computer, maybe integrated into a suit or helmet or maybe just your skull, that would contain a database of technical information as well as the ability to perform any relevant computations (including knowing relevant formulas). The engineer's education would focus on fundamentals, high-end concepts, and information processing skills. The idea is that the engineer's training focuses more and more on "thinking" while the computer would supply knowledge of specifics. Basically, is it reasonable that the right training + instant wikipedia (only better) could = practical competence in a wide field?

Yep and you may also want to integrate augmented reality into that suit :smallsmile:

here a nice video http://www.youtube.com/watch?v=mn-zvymlSvk&feature=player_embedded

MachineWraith
2010-05-04, 07:00 PM
Stealth and ECM: Hide. Pretend to be something or somewhere else. Jamming, chaff, flares, decoys. Pretty much whatever you can think of and hope the enemy didn't think of. Come in quiet and hide in a comet to get in-system. There should be a lot of this.

Stealth is impossible in space. Reference. (http://www.projectrho.com/rocket/rocket3w.html#nostealth)

Drogorn
2010-05-04, 07:16 PM
Anything moving at a significant fraction of C is a weapon. A very powerful weapon.

As such, relativistic missiles would be a weapon of choice. The warhead on such a missile would be either a bomb-pumped laser, or it would be a dispersal warhead, to spread out relativistic shrapnel just before impact.

If the missile can actually impact the target, then expect the target to be utterly obliterated from the energy release.

Math_Mage
2010-05-04, 08:48 PM
Anything moving at a significant fraction of C is a weapon. A very powerful weapon.

As such, relativistic missiles would be a weapon of choice. The warhead on such a missile would be either a bomb-pumped laser, or it would be a dispersal warhead, to spread out relativistic shrapnel just before impact.

If the missile can actually impact the target, then expect the target to be utterly obliterated from the energy release.

However, since anything moving at such high velocities is so dangerous, you have to expect that any ship expecting to move at even miniscule fractions of lightspeed has some way to deal with such shrapnel, as well as radiation shielding. Whether it's a Langston Field (http://en.wikipedia.org/wiki/The_Mote_in_God%27s_Eye) or a General Products hull (http://en.wikipedia.org/wiki/Known_Space) or something else entirely, ships are going to be protected from simple projectiles.

Dilb
2010-05-05, 04:29 AM
Part two!

To start with, guns:

Yeah, this seems fairly accurate. Don't negate what a good laser can do, though. Being bombarded with Gamma radiation will quickly cook anyone inside a ship, and it has a habit of going through matter, to boot. This is why I recommended magnetic shielding: space has a lot of free Gamma radiation, which will ultimately kill off a human within a month unless you have some way of protecting them. Ironically enough, it also means that a Gamma laser wouldn't be effective unless you knocked out the ship's shielding, or managed to overwhelm it.

Gamma rays are photons, which are neutral particles, so they aren't deflected by magnetic fields. Only charged particles, like protons and electrons, would be deflected. The only way to shield yourself from gamma rays is to have something absorb it, like a big block of lead. Fortunately there aren't a lot of gamma rays in space, most of the time.

Also, LASERs (light amplification by stimulated emission of radiation) produce light, technically. A laser type device that gives off high energy photons would be called an x-ray laser, as gamma rays generally refers to high energy photons from natural sources like nuclear decay or exploding stars.

hewhosaysfish
2010-05-05, 07:09 AM
I didn't think to realize that constant acceleration would create artificial gravity. Thanks for that. Also, as pointed out here (http://www.projectrho.com/rocket/rocket3at.html) (thanks), "down" is the direction of the engines/exhaust. I'm not certain, however, if it makes sense for the ship to resemble more of a skyscraper with he engines on the bottom, or a flying saucer with the engines on the bottom, or perhaps a skyscraper with the engines on the side. I figure that, since people are designed to move horizontally, a "short" ship would be more comfortable to move around it (or at least be a lot less reliant on elevators), but I don't know what else should be taken into consideration. That's actually a good question.


Well a sphere is the 3d shape which contains the most internal volume per unit of surface area so if you're building your hulls out of really expensive phlebotonium, you might want a spherical ship to keep costs down. OTOH, given the problems of radiating heat which others have pointed out, you might want as much surface are as possible in which case a big, flat ship would be more appropriate.

EDIT:

That is a good idea and would work great for what the OP appears to need to do. My only problem (which you can and probably should ignore) is that if you towed the other gate at near-light speed you run into relativity problems (essentially creating a time machine)
Another problem with this idea is that, if the gate is already 'open' when you set out from the system, people will be able to travel freely between the origin planet and the fleet.
This would be very handy for the people who build and operate the ships but less so when you are building and operating the setting. The "generation fleet" is no longer a generation fleet, just a rather exotic space station. Maintenance crew can be rotated in and out over months, rather than being borna and dying on it. Food, materials and fuel can be replaced. There's no need for a genetically diverse population of colonists to live in a closed environment for years/escades/centuries: the entire human population and all the resources of humanity are on hand.
Very handy if you're running a space program but undercuts a lot of the unique attributes of the intended setting.

Telok
2010-05-05, 08:34 AM
Forever War, by Joe Haldeman, speaks on the subjects of shields, C-fractional ship combat, and crew survivability during maneuvers.

http://en.wikipedia.org/wiki/The_Forever_War

You can skip the second half of the book if you're pressed for time. No technical details, just plot.

Thespianus
2010-05-05, 09:59 AM
Something to keep in mind is that, at high speeds time moves at a slower pace, even if the person in the fast moving space ship won't be able to detect it internally.

This means that the people in the fast moving vehicle has less time to react to external threats, not only because of "normal" Newtonian effects such as "If you move fast on a bicycle, it's hard to react in time to avoid a pothole in the road", but because you literally have less time to react.

This is another reason that travelling at the speed of light is hard: You don't have ANY time to brake. At all. You're literally out of time.

So, for someone moving at a large fraction of c, the time available to this person to take (let's say) evasive manouvers is a lot less than for a person in a more or less stationary space ship.

Include this in your game, and it might make high speed travel even less interesting. ;)

hamishspence
2010-05-05, 10:35 AM
The speed of light, and the limitations of mass-energy conversion, do mean some interesting things for realistic spaceflight.

Most of the mass of the ship will be fuel- even with perfect efficiency mass-energy conversion, it still takes many times the mass of the main vehicle, in reaction mass, to get anywhere close to lightspeed.

Plus, the closer you get, the less efficient it becomes- going from 0-90% of the speed of light, is far easier than going from 90-99%. (which would require a vastly higher proportion of reaction mass.)

Mr.Bookworm
2010-05-05, 11:43 AM
I have a science question, if no one minds.

Is there any theoretical way to get to FTL speeds without accelerating (even pseudoscientific ways)?

I was thinking that you would first send a generation or freeze ship over to the destination, at a reasonable fraction of c (.1 or so). When they start out, they broadcast a beacon signal to the destination. Then when they get there, they set up a radio beacon, or something similar that moves at c. They then set up the initial colony while waiting for the signal to travel back to Earth. When it gets there, a ship with a similar machine can enter the machine, and it will tweak your speed without acceleration to FTL speeds. It then gets there, latches onto the signal sent by the beacon way back when on Earth, and bam, FTL travel.

Now, poke holes, please.

The Glyphstone
2010-05-05, 11:48 AM
Well, the strict/pedantic answer is no - the definition of acceleration is a change in speed over time (even negative accel), so if your speed ever changes even a fraction, let alone from rest to lightspeed, you've accelerated.

It sounds like you're describing instantaneous acceleration - moving from rest to lightspeed and beyond in a effectively immeasurable increment of time. I suppose it'd be technically possible, if you put enough energy into it...though I can't imagine anything in existence could survive the sudden inertic stress that'd inflict.

Math_Mage
2010-05-05, 01:10 PM
I have a science question, if no one minds.

Is there any theoretical way to get to FTL speeds without accelerating (even pseudoscientific ways)?

I was thinking that you would first send a generation or freeze ship over to the destination, at a reasonable fraction of c (.1 or so). When they start out, they broadcast a beacon signal to the destination. Then when they get there, they set up a radio beacon, or something similar that moves at c. They then set up the initial colony while waiting for the signal to travel back to Earth. When it gets there, a ship with a similar machine can enter the machine, and it will tweak your speed without acceleration to FTL speeds. It then gets there, latches onto the signal sent by the beacon way back when on Earth, and bam, FTL travel.

Now, poke holes, please.

There certainly isn't anything in known physics that will do that. The closest possibilities are acceleration through higher dimensions, closed timelike curves (basically the same thing), and means of teleportation. All have been examined from an SF perspective before.

Mr.Bookworm
2010-05-05, 02:01 PM
Well, the strict/pedantic answer is no - the definition of acceleration is a change in speed over time (even negative accel), so if your speed ever changes even a fraction, let alone from rest to lightspeed, you've accelerated.

It sounds like you're describing instantaneous acceleration - moving from rest to lightspeed and beyond in a effectively immeasurable increment of time. I suppose it'd be technically possible, if you put enough energy into it...though I can't imagine anything in existence could survive the sudden inertic stress that'd inflict.


Not quite. What I mean is, bypass the accelearation part of the equation by doing... something.

If you could somehow do that, you could completely bypass the energy requirements needed to accelerate to even a fraction of a speed of light.

It wouldn't hurt anyone on the ship, either, since they would be shifted to FTL speeds at the same time as the ship.

Of course, by the time a civilization could muck around with the laws of the universe like this, they could probably just make their own. But a boy can dream.

Gravitron5000
2010-05-05, 02:01 PM
More excellent answers, thanks everyone.
So particle beams (probably neutral) and gamma lasers would be major weapons. Electromagnetic shielding would protect against radiation and lasers, but not against particle beams and other kinetic weapons. To deal with those, you'd need some form of improved armor.


You need some way to accelerate your particles to a velocity that will do damage. It's much easier to accelerate a charged particle using a EM field than it is to accelerate an uncharged particle. I think that your particle of choice would likely be a proton (+ve charged ion).

hamishspence
2010-05-05, 02:03 PM
Not quite. What I mean is, bypass the accelearation part of the equation by doing... something.

If you could somehow do that, you could completely bypass the energy requirements needed to accelerate to even a fraction of a speed of light.

It wouldn't hurt anyone on the ship, either, since they would be shifted to FTL speeds at the same time as the ship.

Of course, by the time a civilization could muck around with the laws of the universe like this, they could probably just make their own. But a boy can dream.

The Necrons in WH40K do this: "inertialess drive" allowing them to accelerate without any issues of having to carry lots of fuel

erikun
2010-05-05, 02:24 PM
Gamma rays are photons, which are neutral particles, so they aren't deflected by magnetic fields. Only charged particles, like protons and electrons, would be deflected. The only way to shield yourself from gamma rays is to have something absorb it, like a big block of lead. Fortunately there aren't a lot of gamma rays in space, most of the time.
Thanks for the correction. I'd thought that the Earth's magnetic field was what protected the planet from gamma radiation. I guess it's some other function, or we just don't receive enough to worry about. Math Mage did have a good point, though: anything moving at such high speeds will already have methods of dealing with heavy gamma ray and small shrapnel bombardment.


So particle beams (probably neutral) and gamma lasers would be major weapons.

Still not sure on whether or not there's good reason to take one big ship over many smaller ones. Artificial gravity is accomplished through propulsion, with no phlebotinum to hold back.

I don't suppose there's a way to link heat expulsion with propulsion, say by channeling/dumping system heat into the reaction mass before expelling it?

How are you planning on accelerating atomic particles to near-light speeds? The most likely way I can think of is magnitizing them, spinning them around a circuit to gain speed and then firing them out the nozzle. The next closest method that doesn't require magnets would be simply heating matter to extreme temperatures and firing the matter in one direction, much like an exahust engine. I doubt you'd be reaching near-light speeds that way, though.

Larger ships require more extraneous matter to hold everything together. You need more structure to house everything and more pathways for people to walk around inside. Multiple smaller ships would (possibly) need less material total for the same purpose, thus needing less fuel to travel. It would certainly be easier to accelerate/decelerate each smaller ship than a single large one. I suppose it really depends on design, though.

A simple steam turbine (http://en.wikipedia.org/wiki/Steam_turbine) is a way to turn heat into electrical power. You still have major problems with directing the heat into the turbine and removing it quickly enough, but it is one way to easily remove heat.


I have a science question, if no one minds.

Is there any theoretical way to get to FTL speeds without accelerating (even pseudoscientific ways)?
That is going to be very high-science fiction. If you could somehow ignore acceleration and just change speed as desired, it would be very useful. However, the only way I could think of doing so would involve teleportation (teleport an object into a different frame of reference) or time travel (travel to a future point when you are moving at that speed). Neither are very well backed by science, understandably.

Math_Mage
2010-05-05, 03:43 PM
The Necrons in WH40K do this: "inertialess drive" allowing them to accelerate without any issues of having to carry lots of fuel

Larry Niven's Kzinti (http://en.wikipedia.org/wiki/Kzin), too.

Regarding gamma rays, it is the Earth's atmosphere, rather than its magnetic field, which offers protection. Like Dilb says, the key is a large amount of mass. Doesn't necessarily have to be lead, but that's one of the most effective.

Thane of Fife
2010-05-05, 03:44 PM
Not quite. What I mean is, bypass the accelearation part of the equation by doing... something.

If you could somehow do that, you could completely bypass the energy requirements needed to accelerate to even a fraction of a speed of light.

This is sort of what is meant by "folding" through other dimensions. It just skips the FTL part and moves you somewhere else. I recommend watching this (http://www.tenthdimension.com/medialinks.php) if you want a better idea of folding through higher dimensions.

Math_Mage
2010-05-05, 04:30 PM
This is sort of what is meant by "folding" through other dimensions. It just skips the FTL part and moves you somewhere else. I recommend watching this (http://www.tenthdimension.com/medialinks.php) if you want a better idea of folding through higher dimensions.

I love that vid. However, I'm not sure it's a viable comparison. Sure, moving through the fifth dimension allows you to, say, move between possible timelines--but what you want to do is move around a lot in the first three dimensions without moving around much in the fourth dimension or the fifth dimension, because you want to stay in the same timeline. OTOH, maybe higher-dimensional travel lets you find a universe where the time dimension runs backwards? But it still takes a lot of personal time to get anywhere, it just isn't expressed in your net travel time. Hmmm...

Ormur
2010-05-05, 06:51 PM
The most sensible imbibed FTL drives I've seen in Sci-fi are jump drives. You just make jumps of limited length depending on the power source and you retain velocity. You have to calculate a lot and can only jump outside of gravity wells or something. Not that there is any real science behind it. Of course huge ships approaching c towing wormhole gateways between systems is even more hard science sounding. The Algebraist by Iain M. Banks has a good description of space travel with that technology. I think the coolest description is of a fleet of high sub light-speed ships attacking a system. They turn around midway after accelerating and then a few weeks before arriving they turn on their drives again to de-accelerate and light up the sky like stars in an orderly pattern from lightweeks away signalling to everyone that they're coming.

If you want a some kind of warp drive then the Alcubierre drive (http://en.wikipedia.org/wiki/Alcubierre_drive) is the best shot at plausibility. I think someone proved it wouldn't be possible even with exotic matter (something about never being able to turn it of from inside since the front of the warp bubble is an event horizon away, plus it uses more power than is available in the universe) but that can always be chalked up as us not having discovered any workarounds yet.

Ubercaledor
2010-05-05, 08:31 PM
Here's a question:

At relativistic speeds, shouldn't the Heisenberg uncertainty principle (or an analogous effect) apply in regards to locating/tracking crafts?

Drogorn
2010-05-05, 08:43 PM
No. The uncertainty principle only applies to subatomic particles.

Darius Rae
2010-05-05, 09:18 PM
Not quite. What I mean is, bypass the accelearation part of the equation by doing... something.


You cant bypass the acceleration part and wind up going faster than you did before because that change in velocity is, by definition, acceleration.

However, this might work...

http://upload.wikimedia.org/wikipedia/commons/8/8f/TARDIS1.jpg

Dilb
2010-05-05, 11:39 PM
No. The uncertainty principle only applies to subatomic particles.

It applies to everything, it just doesn't matter for anything larger than a molecule. Plus, it's related to the uncertainty in speed, so going faster doesn't change anything. It's just as hard to localized something not moving as it is to localize something moving at 0.99c.

In regards to time dilation, remember it works both ways. Someone on a ship seems the earth moving just as slowly as the earth sees the ship moving. They disagree because they interpret time differently, and until they meet up (which involves one of them changing the way they see time) it doesn't matter that they disagree.

Even without that, if you fire gamma rays at each other, neither one of you can dodge because gamma rays travel at the speed of light. It's literally impossible to receive any warning, because the warning is travelling slower than the weapon.

Math_Mage
2010-05-06, 04:01 AM
It applies to everything, it just doesn't matter for anything larger than a molecule.

Uncertainty phenomena have been observed in objects the naked eye can see, according to an NPR special I heard recently. [/nitpick]

But yeah, it won't have any impact on tracking spacecraft at any speed.

Ravens_cry
2010-05-06, 04:39 AM
It just might be possible, but we are talking near-deity level energies here, to use what has been called an Alcubierre Drive (http://en.wikipedia.org/wiki/Alcubierre_drive) to go FTL, though some studies show that instabilities arise at attempts to go faster then light with such a method (http://www.technologyreview.com/blog/arxiv/23292/).