Re: Cannon in space, how much more propellent efficent are they than missiles?
- From: IsaacKuo <mechdan@xxxxxxxxx>
- Date: Mon, 12 Jan 2009 17:26:39 -0800 (PST)
On Jan 12, 4:50 pm, "n...@xxxxxxx" <Alien8...@xxxxxxxxx> wrote:
On Jan 11, 11:27 pm, IsaacKuo <mech...@xxxxxxxxx> wrote:
This really isn't a problem, since you can turn the entire ship to the
desired direction on a dime (given realistic time/space scales of
space combat). Also, the amount of torque is not significant.
I'll mention for the OP's benefit that this can be handled with
flywheels to avoid expending propellant.
The mass you save in propellant is much less than the mass
you're spending in ammunition.
Far more of a problem is the sheer mass of the cannon or railgun.
A cannon hardly ever makes any sense because you can get more
velocity with less mass simply by giving the missiles more fuel and
launching them out of lightweight launch tubes. A railgun has a
chance to make sense, but it's a challenge.
I don't quite see where the railgun's "chance" is; a fired railgun
round is basically a dumb slug that leaves its "fuel tank" etc. behind
just like a cannon shell does.
A railgun can be used to launch a missile, and has the potential
to maximize delivered payload if the ammunition mass dominates
over the railgun's mass.
Not even close...the AC130 has a 105mm howitzer (not pointed
forward, either). The big issue is one of mass--not just of the gun
itself but the amount of ammunition to make it worth the trouble.
I would argue that the mission profile determines what "worth the
trouble" means in this context. Frinst, why does the aircraft carry
that large a gun? Because somebody determined it was the best tool for
a particular job.
It can only be the best tool for a particular job if it's superior to
the alternatives.
If you don't have dozens/hundreds of rounds, it makes more sense
to use rockets/missiles.
We're talking relatively realistic space combat at standoff range, a
longer-range version of Battlestar Galactica volleys/broadsides minus
the fighters, right?
No, I'm talking about aircraft weaponry. Aircraft weapons are
(not surprisingly) meant to be used within Earth's atmosphere.
As such, atmospheric drag is a problem. This means that a gun
can, under the proper circumstances, be a superior weapon to
rockets/missiles. Since a gun weighs so much, this typically only
happens when you want a lot of ammunition.
I'll point out that BatGal used both missiles _and_ railguns to good
effect, and I note that missiles generally should be easier to see
coming than railgun slugs.
Battlestar Galactica? So what? It's not realistic or anything.
Besides, the guns seem to be familiar gunpowder guns.
Besides, didn't we in
an ancestor to this thread decide that such slugs could make good area-
denial weapons, if fired into possible enemy attack vectors?
Some people think so. I don't. All it takes is a simple BOE
calculation
to realize the ridiculously large amounts of mass required in order to
have a hope of a single hit (and this hit will not be very damaging).
(why turrets suck)
This is why non-fixed gun mounts are limited to helicopters and
specialized slow flying "gunship" aircraft.
And useta be standard equipment on even large WWII bombers which
are, as you say, slow movers by today's standards. Hell, even the B-52
carried tail-mounted twin .50's for point defense against
interceptors.
The tail gun was utterly useless, and dropped. It only made some
marginal amount of sense when primitive night fighting radar
tactics involved simply heading straight for the centroid of the
return signal. This puts the interceptor on a very inefficient tail
chase--which is adequate if the interceptor is much faster than
the target. A B-52 would have been almost as fast as the interceptor,
so a primitive interceptor might spend a long time slowly
catching up with the bomber before it got within range of its
own guns.
This is one of the things I've mentioned that I liked about BatGal;
the use of such maneuvering by their fighters. OTOH the big ships
didn't make use of such, they used turreted weapons. ISTM there's
going to be a breakeven point between aim-at-need small ships and
turret-equipped large ships. IOW a large ship can afford the extra
complexity and maintenance resources to have turrets, while a smaller
ship cannot. However, for _realistic_ space combat (beyond a semi-
suicide mission like the Orion in _Footfall_), we're already talking
fairly large ships with realistic (i. e. "weak") drives and life
support etc., so I'm guessing turrets will be the way to go.
Turrets can be realistic for beam weapons, because they are not
too heavy. The beam generating hardware can remain fixed while
a lightweight turret directs the beam. But for any sort of "gun", it
starts getting questionable. With realistic time/space scales, you
could have many minutes or hours to rotate the ship into the desired
firing angle.
Battlestar Galactica is different, because of the flexible "jump"
technology. You don't see the enemy coming from hours away.
They can just jump right next to you, and vice versa. This means
the space equivalent of point blank knife fighting.
Isaac Kuo
.
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