Author Topic: Impact Physics  (Read 8515 times)

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Offline fcharton

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Re: Impact Physics
« Reply #30 on: January 30, 2012, 08:13:20 AM »
At double the range, the average distance between projectiles is x2, not x4... isn't it? It's the area of the spherical shell section over which they are spread that increases x4.

Your to-hit probility drops by a factor of 4, yes... but that's because the to-hit probility is proportional to the inverse square of the projectile spread, not because the projectiles themselves spread exponentially.

That's correct, I edited it in the post above...

Francois
 

Offline jseah

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Re: Impact Physics
« Reply #31 on: January 30, 2012, 11:52:02 AM »
As far as efficiency is concerned, a high rate of fire at close range will always beat a longer 'firing window'.
Hm, ok, that's a good point. 

Muzzle velocity increases by sqrt of energy (which goes linear wrt size); minimum range decreases by ratio of muzzle velocity to ship speed

Hence 2x 200ton railguns will fire 2.5 times as fast as 1x 400ton railgun (2 guns with 0.8 cooldown). 

Faster velocity of 400ton railgun marginally decreases inaccuracy, but certainly not by 60%.  Since you will need to have seriously huge railguns before that translates to higher maximum range, I don't think ships would mount big guns, instead of lots of little ones. 

Space stations might though.  The cost of a big gun is mostly in the fuel needed to lug it around. 


Also, wouldn't one-hit-one-kill make missiles mounting a railgun be seriously gamebreaking?  Or if missiles can't mount weapons, then we might see the advent of the suicide fighter. 
 

Offline sublight

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Re: Impact Physics
« Reply #32 on: January 30, 2012, 01:32:58 PM »
Armor: For near misses and lasers.

Currently things look like:
Rail Guns: Potential Instant kill if ship-accelerated for anything stationary that isn't protected by an atmosphere.
Defense: Don't be stationary if there is any chance of a rail gun armed enemy in sensor range.

Lasers: Not an instant kill. For hitting anything too mobile to get a Rail Gun lock on.
Defense: Armor and shields.

Nuclear Missile: For when you need to kill a maneuvering target from outside of laser range.
Defense: Active anti-missile systems.

Alternative Defense for of all: Kill them before they get close enough to kill you.


I'd say having an auto-jink setting may be essential to surviving combat without micromanaging. Lots of small random nudge maneuvers could probably be assumed to have in summation no net effect on ship course and thus neglected for position calculations while adding a miss-chance for non-guided rounds against an otherwise coasting target. If a rail gun refuses to fire for anything less than, say, a 1% hit chance, then no one would have to worry about Golden-BB events turning around key battles.
 

Offline procyon

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Re: Impact Physics
« Reply #33 on: January 31, 2012, 03:24:34 AM »
I think that one hit / one kill will probably be the name of the game in NA.

The real game won't be about surviving the hits.  You just won't see that happen very often.

It will be about not getting hit.

Whoever can acheive the best hit % will be the winner.  If there is one.  MAD will be a real possibility in ship to ship battles in this game.

As I said, I plan on aiming to conduct my battles at ranges measured in AU.  If I get close enough to be firing rail guns with a reasonable probability of hitting the enemy ship - they will likely be doing the same to me.  The best I would hope for is to see that the other guy got destroyed before he kills me.

And on the issue of long rods for slugs, very possible - but I wouldn't bother unless it proved to be the only way you could launch a slug.  Personnally I just want something that deposits the greatest percentage of energy on target.  Penetration will likely be a moot point.  The amount of energy the target will have to absorb should be enormous.  If it was nothing but a shell around a mercury core (not feasable, just an example) that would 'splash' into a target - that would be fine.  Conservation of energy will take care of the rest.  The energy has to go somewhere and do something.  A lot of 'something'....
« Last Edit: January 31, 2012, 03:27:08 AM by procyon »
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Offline UnLimiTeD

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Re: Impact Physics
« Reply #34 on: January 31, 2012, 03:57:53 AM »
I quite honestly think that directional defensive weaponry should be included for this reason.
Like outfitting Ships with Shrapnell tanks dropping a few thousand 5-20 gram metal pieces.
It will barely reduce laser power, not worth modeling at least, but it should fragment railgun projectiles and fore missiles to evade.
Directional shields a small distance from the ship might also be an option.
Basically everything you could think off based on the projected technology or todays to reduce the chance of a direct projectile hit.
 

Offline procyon

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Re: Impact Physics
« Reply #35 on: January 31, 2012, 04:56:55 AM »
Quote from: UnLimiTeD
I quite honestly think that directional defensive weaponry should be included for this reason.
Like outfitting Ships with Shrapnell tanks dropping a few thousand 5-20 gram metal pieces.

Your 'drop tanks' ought to be easy enough to model with a shrapnel warhead missile, depending on how Steve puts them together.

Just make one with a small / no engine, release, and have 'detonate'.  Should produce a fair cloud of projectiles.

Then accel in a direction that will put the 'cloud' between you and incoming ordinance.  If it is in a path that enemy ships would like to use - all the better.

I could even see dropping spreads of these missiles toward incoming vehicles.  Harder to see than a ship with a rail gun and should create quite a bit of havoc if something blunders into them.  I could also see them as 'escort missiles' used to accompany ship killing missiles and throwing out clouds of shrapnel to intercept incoming AMMs.  Might be useful if nuclear 'escort missiles' are expensive.
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Offline Mel Vixen

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Re: Impact Physics
« Reply #36 on: January 31, 2012, 06:38:05 AM »
And while railguns have some massive punch they are much slower then a laser thus would need more time to reach the targed if they arent fired on point blank range. I could see Smaller lasers and rails as point defence weapons if the targeting can be justified.
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Offline sublight

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Re: Impact Physics
« Reply #37 on: January 31, 2012, 07:08:06 AM »
I'm not sure about point defenses against rail guns. Last time I tried plugging 1kg shells into the the Newtonian Sensor formula the detection range was something like 34 km for the sample Missile detection scanner. That's less than 0.5s reaction time against just a slow muzzle velocity only railgun round. Maybe single-use reactive explosive devices (reactive armor) could intercept an incoming round in time.

I'm worried about shipyards. Slow ship maneuvers can greatly limit effective railgun range, but if our massive unmoving shipyards are vulnerable to kinetic rains of death they could become dead yards walking as soon as any opposing railgun armed ship gets an active sensor ping. A reactive explosive device might protect against rare unlucky hits, but a lot of railgun rounds can get fired before a defensive missiles wave could close with the attackers.
 

Offline UnLimiTeD

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Re: Impact Physics
« Reply #38 on: January 31, 2012, 07:36:45 AM »
Against the speeds projected, reactive armor doesn't work.
 

Offline sublight

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Re: Impact Physics
« Reply #39 on: January 31, 2012, 09:51:07 AM »
Against the speeds projected, reactive armor doesn't work.

My bad on the name. I meant something closer to plastering the hull with computer triggered claymore mines.

If hypervelocity Projectile + small obstruction = nuclear-like boom, then disrupting the incoming round 50m out would significantly reduce the damage.

If hypervelocity Projectile + small obstruction = very hot expanding plasma ball, then this wouldn't help much since most of the plasma would still hit the ship still at hypervelocity speeds.

EDIT: On further thought, while we may not know the exact rate of plasma expansion from such an intercept, we can calculate the maximum uniform expansion rate by converting the impact energy entirely into kinetic expansion rather than pure thermal. If a 1kg 1,000 km/s hyperveolocity round begins expanding into a spherical shell after striking 100g of oncoming shrapnel traveling at 10 km/s, then the combined mass ends up as a cloud traveling at 908.2 km/s toward the target while expanding at 290.4 km/s. If a 100m distant intercept was made, and the cloud is treated as a disk of uniform density, then the ship gets sandblasted with 0.32 g/m2 containing 128.2 MJ/m2 of impact energy. Actual dispersal rate would probably be lower and impact energy density higher.

The feasibility of 'operation short stop' depends on where a kinetic round would be detected and how fast a defense system could react.
« Last Edit: January 31, 2012, 11:21:24 AM by sublight »
 

Offline fcharton

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Re: Impact Physics
« Reply #40 on: January 31, 2012, 10:20:26 AM »
Also, wouldn't one-hit-one-kill make missiles mounting a railgun be seriously gamebreaking?  Or if missiles can't mount weapons, then we might see the advent of the suicide fighter. 

Actually, I think an interesting weapon could be a "railgun toting ballistic drone" (RTBD). A projectile you'd send on a ballistic course towards a target, equipped with a passive sensor, which would close into range, and activate and shoot. Such a small object, on a ballistic course, would be extremely hard to detect, but very deadly once it activates (if it can close in).

Thinking of it, it might mean that the old "non newtonian" idea of ships expending fuel for distance travelled and not acceleration might not be as irrealistic as we'd have thought. Against such railgun drones, the best strategy for a ship under threat would be make small course changes at all times, and this would use fuel on a "per distance" basis...

Francois


 

Offline jseah

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Re: Impact Physics
« Reply #41 on: January 31, 2012, 11:50:53 AM »
My vision of railgun drones (because missiles with weapons may as well be called drones) involves them accelerating all the way to the target. 
(depending on how the damages work out, they might not have to do this.  Burn 50% of delta-v then reserve for course correction might be more than enough)

Drones can pack much higher fuel to mass ratio since they are one-shot (and can burn all their delta-v) which means the closing speed of the drone will be obscene, the drone can then fire its railgun shells at all targets and then attempt to ram something. 

If the drone itself hits, that thing is gone.  Armour, fancy shields, uber big moon-sized battlestation, all gone.  Nothing will survive a 5ton object hitting it at 60kkm/s.  Maybe not even planets (the planet itself will live, not sure about anything on it)

And at 60kkm/s relative speed, any hit from railguns will also likely blow away vast amounts of opposition. 

...

You know, when this all comes out, I'm totally going to make fighters.  No carriers, just really really small ships.  Single weapon or missile launcher, that's it.  Jumpships and support (like radar and coillers) will probably be bigger, but I don't intend to put those on the line of battle. 

When every shot is lethal, you want your enemy's shots to overkill as much as possible.  Why build big battleships when they die to one shot anyway?  Better to have many tiny ships and eat the inefficiencies.  They'll pay you back when the lucky 30% of your stuff comes back, instead of 1 lonely ship that lived through a mid-range nuke. 
 

Offline Steve Walmsley

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Re: Impact Physics
« Reply #42 on: February 01, 2012, 03:50:11 PM »
With regard to the cloud of 1000 kilogram objects. Something like that will be in the game, initially as a missile warhead but I am sure that will be adapted to a variety of uses, both offensive and defensive.

Every time I think "OMG these weapons are going to be too powerful", I remind myself that this is reasonably realistic physics and that future combat spacecraft will have to deal with these type of weapons. I am sure tactics will evolve to deal with the situation. I just don't know what they will be :). As several posters have mentioned, spacecraft speed is often going to be more important in terms of damage than railgun launch speed, although railgun launch speed may be more important in terms of controlling the engagement and the ability to set up a potential intercept shot. Personally, I think I would probably move as slowly as tactically feasible if I am likely to encounter hostile railgun fire.

Steve
 

Offline jseah

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Re: Impact Physics
« Reply #43 on: February 02, 2012, 09:00:28 AM »
Personally, I think I would probably move as slowly as tactically feasible if I am likely to encounter hostile railgun fire.
Or play chicken with your enemy by suicide running your ships into his.  And hoping yours are cheaper. 

Who says fighters aren't feasible?  They're *totally* feasible and even cost efficient!

Would like a railgun drone though.  (weight penalty for automated systems?)
 

Offline byron

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Re: Impact Physics
« Reply #44 on: February 02, 2012, 03:30:12 PM »
Or play chicken with your enemy by suicide running your ships into his.  And hoping yours are cheaper. 

Who says fighters aren't feasible?  They're *totally* feasible and even cost efficient!

That's called a missile.

With regard to the cloud of 1000 kilogram objects. Something like that will be in the game, initially as a missile warhead but I am sure that will be adapted to a variety of uses, both offensive and defensive.

Every time I think "OMG these weapons are going to be too powerful", I remind myself that this is reasonably realistic physics and that future combat spacecraft will have to deal with these type of weapons. I am sure tactics will evolve to deal with the situation. I just don't know what they will be :). As several posters have mentioned, spacecraft speed is often going to be more important in terms of damage than railgun launch speed, although railgun launch speed may be more important in terms of controlling the engagement and the ability to set up a potential intercept shot. Personally, I think I would probably move as slowly as tactically feasible if I am likely to encounter hostile railgun fire.

Steve
I would like to point out that, while the physics are entirely realistic (and bravo for that, Steve) the engineering is way out there.  Massive kinetic kill is a fact of life at the sort of velocities we expect here.  The scenario is more balanced at lower velocities. 
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