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tetrion
August 3rd, 2007, 10:43 PM
Hi,
A while ago I remember reading a webpage that specifically talked about real space physics when it came to space battles, like for example 'there is no 'up' in space, how then does a ship meet another right side up?' and 'you can't dodge lasers, let alone see them'
Unfortunately I cannot remember what the site was. Could someone please post a link, as I'm interested in creating some 'more' realistic cgi.
thanks
Tetrion:cool:

Emperor Tippy
August 3rd, 2007, 10:50 PM
Hi,
A while ago I remember reading a webpage that specifically talked about real space physics when it came to space battles, like for example 'there is no 'up' in space, how then does a ship meet another right side up?' and 'you can't dodge lasers, let alone see them'
Unfortunately I cannot remember what the site was. Could someone please post a link, as I'm interested in creating some 'more' realistic cgi.
thanks
Tetrion:cool:

Watch Andromeda for "realistic" space battles. As for the dodging thing, lasers aren't what you want to use in a real space battle. They are unguided once fired and only an idiot would come closer than at least 30 light seconds to their enemy, allowing plenty of time to dodge the unguided laser.

What you want are guided missiles traveling at around .9 c, almost as fast and a lot harder to dodge. Lasers are relegated to a point defense role.

Don't know what site you mean but those are just a few general points.

Emperor Tippy
August 3rd, 2007, 10:54 PM
This thread deals with it in a secondary manner but it hits the high points.

http://forum.gateworld.net/showthread.php?t=42313

Orion's Star
August 4th, 2007, 12:14 AM
This is a good site for information on "accurate" space battle physics. It is a fairly detailed anaylsis of just about any form of weaponry you can think of. I have no idea how truly accurate it is (as I am not a physicist) but it at least comes across as being relatively well founded.

http://www.projectrho.com/rocket/rocket3x.html#lasermiss

Wordsmit2
August 4th, 2007, 12:34 AM
This site might be the one you're thinking of: Insultingly Stupid Movie Physics (http://www.intuitor.com/moviephysics/). Most of the page discusses common film industry idiocies. Scroll down to the bottom for specific movies.

And my pick for decent space scenes: I noticed in watching some Babylon 5 Starfury flight scenes that often they fly at different orientations. (Hey, any show that requires "matching rotation" for two ships to join up had *better* think of that.) I can't name specific episodes, but I can list a couple of videos with such scenes if anyone wants examples.

Also, for some decent use of Newtonian physics, these videos on YouTube have some good bits:

The Physics of Starship Battles- Laws of Motion and Momentum (http://www.youtube.com/watch?v=GihlZ0Mnq-k), especially from 3:10 onwards.

Whitestar Music Video (http://www.youtube.com/watch?v=nLDEA0MDYFw)

As for 'you can't dodge lasers, let alone see them', there is the problem of letting the audience know what is happening. The only alternatives to glowy beams are missiles, whether self-propelled or propelled by the launcher. But if you don't have a good sense of what draws the audience's eye, the audience may end up so busy trying to figure out exactly what's going on they won't have time to invest emotionally in the scene. Mind you, it's not necessary for the audience to be able to easily make out every detail. Seeing a chunk of rock launched at a planet, then seeing a streak of light or a break in the clouds traced on that planet can be just as effective as having an insert of the rock whizzing by the "camera". So can the look of horror on the face of a witness (Babylon 5 again).

As for dodging, yes it looks really stupid to dodge a "beam" that has already been fired. But you the director can play with that timing by having the target evade before the beam is fired, or you could have the beam sweep an arc (as with the Shadow ship weapons used in Babylon 5), so there is some audience interest generated in seeing a moving ship avoid those sweeping beams.

A lot of making space maneuvers work is building the audience's assumptions beforehand. In watching Babylon 5 we become conditioned to the notion that there is a lot of computer control. We also know which ships have artificial gravity and which ones don't. So when a Whitestar seems to bump while doing evasive action, we assume that's a natural consquence of the computerized firing of multiple thrusters and we know no one aboard felt anything. But if a Starfury lurches sharply we think "Oh no, the poor pilot!"

Arania
August 4th, 2007, 03:04 AM
As for the dodging thing, lasers aren't what you want to use in a real space battle. They are unguided once fired and only an idiot would come closer than at least 30 light seconds to their enemy, allowing plenty of time to dodge the unguided laser.

What you want are guided missiles traveling at around .9 c, almost as fast and a lot harder to dodge. Lasers are relegated to a point defense role.


For one, at 30 light-seconds, any active non-FTL sensor array would take at least one minute to acquire a target, plus another thirty seconds MINIMUM to hit the target with said relatavistic kill missiles, assuming that the system can process the sensor return, arm a missile, and fire with no delay.

Not only that, but the amount of energy that the sensor will be putting out in order to actually work at that range will pretty much paint a gigantic 'I AM HERE' bullseye right on top of you. As soon as the target ship's passive sensors detect your active sensor pulse, they are probably going to arm thier own missiles and fire them at you. Assuming that they are ALSO relatavistic kill missiles, they will probably impact around the same time that your computer processes the return.
Best case scenario, You fire at them, and thier missiles hit you shortly afterwards.
Worst case scenario, They have a cloak or some other equivelant stealth system, get the drop on you, and reduce your ship into so much scrap metal.
Either way, you are at a disadvantage.

My point is that there is alot more to space combat than putting distance between you and them. Andromeda Is slightly less unrealistic than most other soft-sci fi, but it still has a fair few implausable technologies of its own (The GFG is #1)

As for lasers, you cant actually 'dodge' a laser, as any non-FTL sensor will be unable to detect the beam before it hits. What you probably mean is that the unguided laser beam will be unable to adapt to sudden target acceleration. However, this assumes that the target is aware of you in the first place, and has commenced evasive maneuvers. Otherwise, they are travelling in a straight line, which is absurdly easy to hit.

Emperor Tippy
August 4th, 2007, 07:06 AM
For one, at 30 light-seconds, any active non-FTL sensor array would take at least one minute to acquire a target, plus another thirty seconds MINIMUM to hit the target with said relatavistic kill missiles, assuming that the system can process the sensor return, arm a missile, and fire with no delay.
Yes, you use sensor drones with FTL communication abilities. Or FTL capable sensors.

As for the delays, thats why you use missiles and not lasers. A missile can be guided a laser can't.


Not only that, but the amount of energy that the sensor will be putting out in order to actually work at that range will pretty much paint a gigantic 'I AM HERE' bullseye right on top of you. As soon as the target ship's passive sensors detect your active sensor pulse, they are probably going to arm thier own missiles and fire them at you. Assuming that they are ALSO relatavistic kill missiles, they will probably impact around the same time that your computer processes the return.
See above. And Passive sensors are a better idea anyways.


Best case scenario, You fire at them, and thier missiles hit you shortly afterwards.
Worst case scenario, They have a cloak or some other equivelant stealth system, get the drop on you, and reduce your ship into so much scrap metal.
Either way, you are at a disadvantage.
Um, only if they are actually a **** with halfway decent tactics. Start naming Sci-Fi movies and shows where combat takes place at these kinds of ranges. It's a short list. No ship shown in Stagate can fight at those ranges, same for Starwars and Star Trek.


My point is that there is alot more to space combat than putting distance between you and them. Andromeda Is slightly less unrealistic than most other soft-sci fi, but it still has a fair few implausable technologies of its own (The GFG is #1)
Every technology used in pretty much all futuristic Sci-FI is highly implausible.


As for lasers, you cant actually 'dodge' a laser, as any non-FTL sensor will be unable to detect the beam before it hits. What you probably mean is that the unguided laser beam will be unable to adapt to sudden target acceleration. However, this assumes that the target is aware of you in the first place, and has commenced evasive maneuvers. Otherwise, they are travelling in a straight line, which is absurdly easy to hit.

Um, if you are in combat and staying still you deserve to get hit with a laser beam. The Reason laser beams are worthless in any half way decent space battle is that the odds of one actually hitting a target ship even 10 lightseconds away are astronomically small.

gopher65
August 4th, 2007, 07:24 AM
Um, if you are in combat and staying still you deserve to get hit with a laser beam. The Reason laser beams are worthless in any half way decent space battle is that the odds of one actually hitting a target ship even 10 lightseconds away are astronomically small.
If you're talking about a ship as big as the Andromeda (4 km across IIRC), then even if it has inertial dampeners (which don't exist) that are 99% effective it is still going to have a huge amount of inertia. You don't just instantly change course with that much inertia unless you want to tear your ship to pieces. Especially a "collapsible" ship like Andromeda, which was specifically made weak.

At 10 light seconds all you'd have to do would be to point your laser at their centre of mass. They would never be able to move fast enough to dodge it, especially if they are already moving toward you at 10psl (to use Andromeda terminology). The faster you are moving, the harder it is to change course. Remember, they only have 10 seconds, and those are bigs ships. Just hope they don't have a mirror with them:P.

Emperor Tippy
August 4th, 2007, 07:33 AM
A **** traveling at 10% of lightspeed would move more than 3 kilometers in 10 seconds, meaning that even if you aimed at the center of a 4 KM long ship you wouldn't hit it.

With inertial dampeners (which almost all space based sci-fi uses) the problem exacerbated. And with Andromeda style ones it is non existent (they are apparently 100% effective)

As for Mirrors, we have magnets :D

Dutch_Razor
August 4th, 2007, 02:41 PM
Watch Andromeda for "realistic" space battles. As for the dodging thing, lasers aren't what you want to use in a real space battle. They are unguided once fired and only an idiot would come closer than at least 30 light seconds to their enemy, allowing plenty of time to dodge the unguided laser.

What you want are guided missiles traveling at around .9 c, almost as fast and a lot harder to dodge. Lasers are relegated to a point defense role.

Don't know what site you mean but those are just a few general points.


That's 8 993 773.74 km, or 23 times the distance betweem the Earth and it's moon..

Emperor Tippy
August 4th, 2007, 02:51 PM
That's 8 993 773.74 km, or 23 times the distance betweem the Earth and it's moon..
Yes it is, and when you are using laser weapons and missiles traveling at relativistic speeds it is a minimum distance for a fight.

And if you are fighting with weapons that move at slower speeds the odds of you being able to be effective in a battle, even if your enemies are confined to the same weapons, are astronomically low.

s09119
August 4th, 2007, 03:13 PM
Yes it is, and when you are using laser weapons and missiles traveling at relativistic speeds it is a minimum distance for a fight.

And if you are fighting with weapons that move at slower speeds the odds of you being able to be effective in a battle, even if your enemies are confined to the same weapons, are astronomically low.

Have you even WATCHED Stargate...?

Emperor Tippy
August 4th, 2007, 03:27 PM
Have you even WATCHED Stargate...?
Yes. And just like Star Wars and Star Trek it sucks at presenting an even half way accurate picture of what space warfare would be like.

The OP wanted to talk about the physics of space battle in general, not necessarily in the Stargate Universe.

And the comment about you being effective in battle is in reference to the fact that your enemy never has to meet you on the field of battle. In space warfare stellar bodies are the only real important things. Sometimes a space station can make the list but thats a rarity. Now space is big, real big. The attacker always has the advantage because you can never cover all of the liens of attack. You are also fighting in 4 dimensions, not 2. Flanking and surrounding an enemy isn't possible unless you have enough ships to make it a non issue. Any weapon you use will be dodged at any range greater than a few light seconds under the best circumstances (unless it is a guided missile capable of traveling as fast or faster than its target).

I could go on for hours about all the differences between space battle and land based battle but I'll just give 1 more explanation. Look at how the US navy and Air Force fight wars any more. In an Air to Air dog fight the US planes launch their first salvo of missiles at ranges exceeding 50 miles (and in some cases up to a hundred+ miles). They generally consider a fight at 5-10 miles to be close in knife fight range. 10 miles being 1 minutes flight time at Mach 1. And most missiles are traveling Mach 5+. The navy fights at ranges exceeding a hundred miles regularly.

gopher65
August 4th, 2007, 04:35 PM
A **** traveling at 10% of lightspeed would move more than 3 kilometers in 10 seconds, meaning that even if you aimed at the center of a 4 KM long ship you wouldn't hit it.

With inertial dampeners (which almost all space based sci-fi uses) the problem exacerbated. And with Andromeda style ones it is non existent (they are apparently 100% effective)

As for Mirrors, we have magnets :D
I'm guessing that you misspelled "ship" with the **** up there heh. Woo for the auto-censor!;)

You lead the target. And they aren't 100% effective, else they wouldn't be getting jostled around every time there is a nearby explosion (the ship would simply compensate with artificial gravity and inertia dampners *perfectly*. The reason they get jostled is because of inertia. Their ship moves, but they don't). Assuming you someone see a laser the instant it is fired, and that you can avoid it by an emergency thrust, what is to stop them from firing 2 lasers in slightly different directions? If you avoid the first, the second hits you. If you stay where you are, the second one misses, but the first one hits you. Bad either way.

That's the tactic they use with missiles on Andromeda. If you fire one missile, the Point Defences take it out. If you fire 10, one might get through.

Emperor Tippy
August 4th, 2007, 04:48 PM
I'm guessing that you misspelled "ship" with the **** up there heh. Woo for the auto-censor!;)

Yep. Although flinging **** at .1 c would most likely be fairly deadly.


You lead the target. And they aren't 100% effective, else they wouldn't be getting jostled around every time there is a nearby explosion (the ship would simply compensate with artificial gravity and inertia dampners *perfectly*. The reason they get jostled is because of inertia. Their ship moves, but they don't). Assuming you someone see a laser the instant it is fired, and that you can avoid it by an emergency thrust, what is to stop them from firing 2 lasers in slightly different directions? If you avoid the first, the second hits you. If you stay where you are, the second one misses, but the first one hits you. Bad either way.

The problem with leading the target is the vast area you have to cover. Space battles are fought in 4 dimensions and in distances measured in light seconds or even light minutes. With ships capable of sublight speeds measured in percentages of c. Even from 10 Light seconds out you are talking about an area millions of square kilometers in diameter. And the ship (which is 4 KM long) can be at any location inside that box.


That's the tactic they use with missiles on Andromeda. If you fire one missile, the Point Defences take it out. If you fire 10, one might get through.
Yeah,and those missiles were traveling at 95 psl are were guided. It was also salvos of more like 50 to a hundred missiles and hope 1 gets through.

gopher65
August 4th, 2007, 04:54 PM
Another thing about those missiles. It takes a lot of energy to accelerate a missile up to 90% the speed of light. Let's assume that they also use Inertia Dampeners on their missiles as well (makes sense unless it is a kinetic warhead, where it would be counter-productive). Since they get jostled on their ship, we know that their IDs are good, but not perfect.

Let's take a random guess and say they are nearly perfect: 99% effective. That seems reasonable, but the number could be anything. I'm just using this for demo purposes. Now let's choose a mass for the missile and its propulsion system. I'm going to say they are a LOT more advanced than us, and that they can make a warhead with a ginormous yield really small, and that the mass of their propulsion system, guidance system, the inertia dampeners themselves, and the warhead itself, all totals at 100kg. That seems reasonable to me too, though the real number could be much higher.

So 1% of 100kg is 1 kg. You'd need to dump about 10^17 joules of energy into it to accelerate it up to 90% of the speed of light. That's 100 THOUSAND TERAWATTS.

First question:
How much damage could you do with a 100 thousand Terawatt laser? Or, if you wanted to make sure they didn't evade you, how much damage could you do with ten 10,000 Terawatt lasers (or particle cannons, etc)? EDIT: Or, if you wanted to make SURE you didn't miss them:P, how much damage could you do with 100,000 one Terawatt lasers?

Second Question:
With 10^17 joules of kinetic energy behind it (keep in mind, that this is what is left *after* the inertial dampeners do their thing), what is that missile going to do if its target evades, and it has to turn around? That's right, it will have to use 10^17 joules of energy to stop, and then it will have to use 10^17 joules of energy to speed back up again to catch its target. Which might well be able to evade again, since you only have one missile chasing it. If you have ten, then you just used exawatt of energy to fire a few missiles.

That's why non-kinetic missiles make absolutely no sense (unless you equip them with a faster than light drive).

Emperor Tippy
August 4th, 2007, 05:05 PM
Considering the manipulation they can do with gravitational masses and inertial masses (the Andromeda has an effective gravitational mass of 1 kg) I think they might have solved some of the problems associated with changes in directions at those kinds of speeds.

Oh that gives me an interesting idea. As you said, accelerating the missile up to .9 c takes 100 Thousand Terawatts of energy. What happens if you increase the mass of the object after it is launched? Since you have the same amount of energy and energy can't be created or destroyed does the object lose its velocity? If so what happens if you pump its mass up so high that it stops instantly, accelerate it just a bit the other direction, and then dump its mass way back down? Can you effectively move that massive amount of energy in any direction?

And if the increased mass doesn't slow the object down then why not give it a mass of 1 nanogram or even less at launch? You need vastly less energy t accelerate it up to .9c and once its moving you can just dump the mass back on for impact time.

It's seems like one of those situations has to be true.

Arania
August 4th, 2007, 05:32 PM
Hi,
A while ago I remember reading a webpage that specifically talked about real space physics when it came to space battles, like for example 'there is no 'up' in space, how then does a ship meet another right side up?' and 'you can't dodge lasers, let alone see them'
Unfortunately I cannot remember what the site was. Could someone please post a link, as I'm interested in creating some 'more' realistic cgi.
thanks
Tetrion:cool:

Have a look at Space War (http://everything2.com/index.pl?node_id=738646) on e2. Pretty solid modern space combat ideas.


Considering the manipulation they can do with gravitational masses and inertial masses (the Andromeda has an effective gravitational mass of 1 kg) I think they might have solved some of the problems associated with changes in directions at those kinds of speeds.

Oh that gives me an interesting idea. As you said, accelerating the missile up to .9 c takes 100 Thousand Terawatts of energy. What happens if you increase the mass of the object after it is launched? Since you have the same amount of energy and energy can't be created or destroyed does the object lose its velocity? If so what happens if you pump its mass up so high that it stops instantly, accelerate it just a bit the other direction, and then dump its mass way back down? Can you effectively move that massive amount of energy in any direction?

And if the increased mass doesn't slow the object down then why not give it a mass of 1 nanogram or even less at launch? You need vastly less energy t accelerate it up to .9c and once its moving you can just dump the mass back on for impact time.

It's seems like one of those situations has to be true.

Bearing in mind that what we are looking for here is 'realistic' sci-fi, Mass alteration is basically out of the question. Even at that technological level, it would be far more effective to use a wormhole with a moving exit to impart the required speed to the projectile.

Besides that, there is no known process that can modify the mass of an object, apart from accelerating it to relatavistic velocities, which only serves to increase it, bringing us full circle back to 'how to turn a missile into a Relatavistic kill vehicle'

Perhaps we should stop using sci-fi examples of 'Realistic' combat and come up with our own. Andromeda is just as bad as other Sci-fi when it comes to 'magic' technology. The only difference between Andromeda and Star Wars/trek/gate is that it relies less upon the magic technology for plot, and more upon the magic technology for military benefit.

Emperor Tippy
August 4th, 2007, 05:39 PM
And there is no known way to travel faster than the speed of light, or survive the acceleration necessary to reach the speeds almost all sci-fi ships travel at in any reasonable length of time.

What really annoys me about most of Sci-Fi's take on space battles is they cerate this tech, which I'm fine with and it falls under suspension of disbelief, but then fail to utilize that tech in anything approaching a competent manner.

Wordsmit2
August 5th, 2007, 12:57 AM
Assuming you someone see a laser the instant it is fired

points up something I touched on obliquely in my post and is something that really irks me about movies and TV shows, and even more horribly--reality--these days.

Writers and directors--and Presidents--are so ignorant now that there are virtually no tactics employed. Fights boil down to two parties standing in place throwing punches until the non-"good guy" one collapses. (Goodness only knows how they figure out who's who.) Funny, when I was a child this sort of trial by ordeal on TV and in movies was something only idolatrous savages employed to victimize unwary travelers. My my, haven't we evolved since then!

As to what "seeing" a laser has to do with this: In combat anyone who is not a moron tries to anticipate what others will do, while at the same time trying to be either unpredictable or unstoppable himself. Tacticians or battle computers are making shrewd guesses as to what an opponent's next actions will be and trying to weave their party's goals into that to their advantage. (The opponent is doing the same.) Thus you're not reacting to that shot, you're anticipating. But from the POV of someone observing the fight, you may indeed seem to be dodging each others' blows.

In moviemaking, where this falls down is when the makers are so dumb or incompetent that they design the scene so it actually appears the characters are reacting instead of anticipating. Oh look! An explosion! *run run pant pant* Safe!

Wordsmit2
August 5th, 2007, 01:19 AM
Bearing in mind that what we are looking for here is 'realistic' sci-fi, Mass alteration is basically out of the question.

If you could alter mass, I doubt you'd be slanging missiles at each other anyway. At that level of technology you'd have whole different agendas and therefore whole different ideas of "how combat is *done*". Or *why* it's done, for that matter.

This also connects to Emperor Tippy's comment.