 |
|
|
|
|
|
| |
| |
|
|
|
|
| |
| |
|
|
scott wrote:
>> Newton's third law still applies, even at relativistic accelerations.
>> If a force is applied to the projectile to make it accelerate at a
>> certain
>> direction, another force will accelerate something else (ie. the gun)
>> at the opposite direction. I can't think of any way of avoiding that.
>
> Bolt it to the Earth, then (assuming you're measuring recoil relative to
> the Earth) the recoil will be avoided.
That wouldn't half spoil the movie's storyline.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Warp wrote:
> Bill Pragnell <bil### [at] hotmail com> wrote:
>> Hollywood gets projectile momentum transfer wrong all the time. Every
>> time somebody gets shot by any kind of weapon, for a start.
> Yes, it's funny how Hollywood physics are so skewed while still not
> appearing completely wacky to the layman.
[snip detail]
Agreed - all of it. Maybe I read too much into realism, but I just can't
take most action films seriously. The other things that are always wrong
are explosions. A big pretty billowing fireball with hardly any force
behind it is definitely not what a hand grenade does, or indeed any
other explosive. A small firework and a gallon of fuel, maybe.
For a significant departure in this regard, watch The Kingdom. There's a
car bomb explosion nearly halfway through that was done using real C4
explosive, and it looks terrifyingly powerful. And very real.
That said, there are some very silly films that manage to mostly get
this sort of thing right - True Lies, for example. Unlikely in the
extreme, but most of the actual action isn't too far-fetched.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
scott wrote:
>> Newton's third law still applies, even at relativistic accelerations.
>> If a force is applied to the projectile to make it accelerate at a
>> certain
>> direction, another force will accelerate something else (ie. the gun)
>> at the opposite direction. I can't think of any way of avoiding that.
>
> Bolt it to the Earth, then (assuming you're measuring recoil relative to
> the Earth) the recoil will be avoided.
http://www.xkcd.com/162/
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Bill Pragnell wrote:
> Agreed - all of it. Maybe I read too much into realism, but I just can't
> take most action films seriously.
Are you kidding?
There's 300 enemy troops with SMGs, grenades and rocket launchers, not
to mention 3 helicopters, and yet 1 lone commando manages to shoot them
all down without dying?
Need I explain further? ;-)
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On Thu, 25 Oct 2007 20:03:36 +0200, Orchid XP v7 <voi### [at] devnull> wrote:
> There's 300 enemy troops with SMGs, grenades and rocket launchers, not
> to mention 3 helicopters, and yet 1 lone commando manages to shoot the
m
> all down without dying?
Not a problem, as long as there are enough RPG rounds conveniently lying
around.
http://www.wasabi.nu/filmklipp_visa.asp?id=771 (Flash required)
--
FE
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Bill Pragnell wrote:
> Darren New wrote:
>> (The railguns in the story actually had to fire for a few thousand
>> rounds to punch a hole in the atmosphere so the needles wouldn't just
>> vaporize.)
>
> That's pretty cool. Relativistic weapons would only really be as useful
> as nukes - to cause almost-total destruction.
>
>>> But anyway, even without relativity, the recoil would be absurd.
>> Yep. If it can go thru a concrete wall coming out the front, the stock
>> can certainly break your shoulder.
>
> It would do more than that. I can't be bothered with the sums right now
> but I imagine the recoil from a relativistic projectile gun would smash
> you to bits. You'd have to design any such gun to be recoilless somehow.
> <insert inertia-absorbing machinery here>
>
> :)
I think it would depend on the mass of the projectile, otherwise
headlights on cars would be pretty useless. Well, except maybe as
propulsion.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Fredrik Eriksson wrote:
> On Thu, 25 Oct 2007 20:03:36 +0200, Orchid XP v7 <voi### [at] devnull> wrote:
>> There's 300 enemy troops with SMGs, grenades and rocket launchers, not
>> to mention 3 helicopters, and yet 1 lone commando manages to shoot
>> them all down without dying?
>
> Not a problem, as long as there are enough RPG rounds conveniently lying
> around.
>
> http://www.wasabi.nu/filmklipp_visa.asp?id=771 (Flash required)
>
>
it wasn't a fair fight
he had a plunger!
Tom
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
scott nous apporta ses lumieres en ce 2007/10/25 03:11:
>> Well, in an atmosphere, it would be like being hit by an explosion, as
>> you pile up all the air in front of it.
>
> Wouldn't something going that fast vaporize immediately when it hit the
> air going that fast? Doesn't stuff that going only a fraction of that
> speed burn up in the outer atmosphere?
>
>> Plus, don't forget all that nice gamma-burst radiation. (The railguns
>> in the story actually had to fire for a few thousand rounds to punch a
>> hole in the atmosphere so the needles wouldn't just vaporize.)
>
> Ah yes, ok :-)
>
>>> Well... technically a railgun (not to be confused with a coilgun)
>>> fires projectiles using electrical propolsion. There's nothing in the
>>> definition about how fast. ;-)
>>
>> True. But to get the electrical propultion to work, the projectile
>> needs to be pretty small, which means it needs to go pretty fast.
>> Otherwise it's more of a thrower than a firearm. :-)
>
> In one of our lectures at university the dude had this rail-gun. It was
> about 2 metres long and plugged into the 420V 3-phase power supply. He
> loaded it with a brass (I think) solid lump of metal that was in a
> pointy bullet shape. It wasn't small, about 10cm diameter and 30cm
> long. When he flicked the switch it punched through (and got stuck in)
> a big bit of wood just off the end of the bench he was using. Rig up 10
> or 20 metres of that baby and it would be interesting :-)
>
>
The bullet would have been hypersonic, not relativistic! Anyway, beter protect
your ears when it fires... and don't stand anywhere close to that thing!
--
Alain
-------------------------------------------------
Lutheran: If shit happens, don't talk about it.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Bill Pragnell nous apporta ses lumieres en ce 2007/10/25 06:28:
> Darren New wrote:
>> True. But to get the electrical propultion to work, the projectile
>> needs to be pretty small, which means it needs to go pretty fast.
>> Otherwise it's more of a thrower than a firearm. :-)
>
> A railgun is exactly that - a thrower. A firearm uses chemical reactions
> to provide impulse.
>
> You would never use one as a portable antipersonnel weapon anyway, it's
> probably more useful as a large scale space-based anti-ship or
> planet-busting weapon.
Or as a satelite thrower.
Dig a large tunnel up some mountain near the equator, from about sea level to
near the summit, line it up with proper circuitry. Load a specialy designed
single stage rocket. Launch a 1000 tons payload into stationary orbit for less
than $1 000 000.00! And you could do that every few hours.
--
Alain
-------------------------------------------------
You know you've been raytracing too long when you're starting to find these
quotes more unsettling than funny.
-- Alex McLeod a.k.a. Giant Robot Messiah
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
scott wrote:
>> Well, in an atmosphere, it would be like being hit by an explosion, as
>> you pile up all the air in front of it.
>
> Wouldn't something going that fast vaporize immediately when it hit the
> air going that fast?
Yes. That's why it's like an explosion. :-)
> Doesn't stuff that going only a fraction of that
> speed burn up in the outer atmosphere?
Pretty much.
>> Plus, don't forget all that nice gamma-burst radiation. (The railguns
>> in the story actually had to fire for a few thousand rounds to punch a
>> hole in the atmosphere so the needles wouldn't just vaporize.)
>
> Ah yes, ok :-)
Of course, it was fun when they were sitting out on the airless moon,
trying to shoot down the device orbiting the sun, or at least firing at
the sun to see if they could get enough radiation to shut down the
electronics on the thing orbiting the sun....
--
Darren New / San Diego, CA, USA (PST)
Remember the good old days, when we
used to complain about cryptography
being export-restricted?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
