Hi guys, I ran into a problem on another mailing list and since it's sort of
relevant to the subject matter here, here it is:)
I've been wondering about the acceleration that's placed on a projectile fired
from a modern high velocity tank gun, versus the acceleration that's placed on
a projectile fired from one of those theoretical superguns (conventional, not
electromagnetic) that's supposed to shoot payloads into orbit. I think that
the acceleration placed on the orbital payload would be higher thank on the
tank gun projectile. What does everyone think? Calculations would be welcome:)
This is actually a question I had about the feasibility of launching something
delicate, like a satellite into orbit with a supergun. It seems like the
satellite would have to be specially hardened. But even now high tech missiles
are being launched from tank guns which have electronics comparable in
complexity to some satellites. So can regular
I've been wondering about the acceleration that's placed on a projectile fired
from a modern high velocity tank gun, versus the acceleration that's placed on
a projectile fired from one of those theoretical superguns
The velocity would be lower on a theoretical supergun for a few very basic
reasons. As I learned in the Field Artillery school the big one is gravity,
all things will fall unless enough propellant is placed behind it and it is
given the proper quadrant (up or down) to reach escape velocity or level
flight
Tank Guns and in particular modern smooth bore tank guns are designed to be
fired in an almost a flat trajectory Although this by the laws of ballistics
is impossible, that is always the goal so as to eliminate as much dead space (
the area between where the projectile starts to clime and it falls to hit the
point of aim) as can be done, there by extending the kill zone. The higher the
velocity the flatter the trajectory.
The next factor to be considered is mass Vs propellant, the heavier the object
to be launched the more propellant is needed to reach escape velocity. This
would restrict it to a supergun as the size and weight of any worthwhile pay
load would necessitate a large amount of propellant and a far heavier gun tube
then any tank would like to lug around.
The artillery type supergun would be the way to go, in that they would be big
enough and strong enough to with stand the blast but at a lower velocity
there by negating the need for super reinforcement for the satellite.
To point out the feasibility of this we need look no further then the
W.W.I
German Paris gun, it fired a 307lb shell 24 miles up and 92 miles in range. If
you were to marry this shell up with a RAP (rocket assisted projectile) I see
now reason why it could not achieve orbit.
> At 12:33 AM 5/26/01 -0600, you wrote:
> From what I have seen most of the data on guns capable of puting
Now for some calculations (simplified):
A tank gun shoots a round with muzzle velocity in the 1000 m/sec range
(see "Modern Land Combat" but Miller and Foss). A gun barrel is say appx 5 m
long. Assume (for the sake of serious simplicity) that acceleration in the gun
barrel is constant. The acceleration that the
projectile is subjected to should be about 10,000 g (100,000 m/sec2).
Please notice that I'm using conveniently rounded figures. Also note
that we are talking about a "dumb" round--the guided missile rounds
generally have fairly low velocities (gun-wise).
> From way back when, I seem to remember something about 7miles per
This is significantly greater than 1 km/sec in the tank gun example, but
not unreachable. Furthermore the acceleration, assuming a purpose-built
gun, can be applied over a much longer barrel length (say a buried, limited
traverse gun or a railroad carriage piece). A 12 meter barrel should be able
to throw stuff into orbit (if all of the above assumptions are correct) and
not subject its "package" to any more stress than the tank round previously
mentioned.
> From this, I think you can begin to see that barrel length is VERY
I'm sure Oerjan can come up with better numbers--and probably has the
data on how fast the guided tank rounds come out of the barrel...
Rob
[quoted original message omitted]
> Rob Hofrichter wrote:
> A tank gun shoots a round with muzzle velocity in the 1000 m/sec range
> subjected to should be about 10,000 g (100,000 m/sec2). Please notice
The biggest approximation is that you assume a constant acceleration. With
today's propellant-powered guns it isn't, so the accels for "dumb" tank
main gun rounds peaks around 40-50,000 g.
> Also note that we are talking about a "dumb" round--the guided
[ka-snip]
> From this, I think you can begin to see that barrel length is VERY
Yep, and superguns tend to be very long indeed. But also the
time-acceleration profile - if you can maintain a reasonably constant
acceleration all along the barrel you get away with a far lower peak
acceleration for any given muzzle velocity.
Thanks everyone for giving me the information on various guns. I had no idea
that tank guns gave that much acceleration to the projectiles. But even
assuming constant acceleration and using some simple physics formulae
(s= 1/2*a*t^2, v=at, etc.) I can see the acceleration is in tens of
thousands of gees.
So really, superguns could give a much lower acceleration to its projectiles
than tank guns... that's very surprising to me.
> On Mon, 28 May 2001, Oerjan Ohlson wrote:
> The biggest approximation is that you assume a constant acceleration.
With
> today's propellant-powered guns it isn't, so the accels for "dumb"
tank
> main gun rounds peaks around 40-50,000 g.