Concorde Vs Bullet

rick_little99 wrote:

OK, i think you are looking at the problem a little too simply. It is
not just a relative motion issue. Air travelling towards the aircraft
would not be able to enter the muzzle (as it has nowhere to go). The
bullet would then travel down the muzzle at the speed of sound say (I
know it has to accelerate but lets just say it travels at a constant
speed) relative to the muzzle (i.e. the bullet would be travelling its
velocity plus that of concorde). Upon reaching the end of the muzzle
it would hit a wall of air travelling at the same speed as it so would
effectively instantaneously slow down to the speed of concorde. It
then could go one of 3 ways, it could bobble about in the space between
the end of the muzzle and the air around (the boundary layer), fly back
past the aircraft and possibly hitting the aircraft on the way past or
it could go bounce back down the muzzle.


Do you have any idea how much energy it would take to stop a bullet in
an inch or two when the bullet is traveling 3,000+ fps?


Matt

In article .com,
"rick_little99" wrote:

A friend and I were having a debate on a rumour that we once heard.
The rumour went along the lines, If concorde (or and other supersonic
aircraft for that matter) was fitted with guns then the bullets would
not be able to leave the muzzle or it would shoot itself if it fired
them while cruising. Assuming that the bullets velocity and the speed
of the aircraft are the same, what are your thoughts on what would
happen?


It could happen, but not in the way described. The bullets will have an
initial velocity (in air) of aircraft velocity + muzzle velocity.

The problem arises after they leave the gun barrel and are exposed to
drag. The bullets will slow down, due to high supersonic drag and fall
downward. At some time, the aircraft velocity will exceed the bullets'
velocity. There was a case of a Grumman F-11F Tiger shooting itself
down when it fired at a target and dived into its own rounds.

If concorde (or and other supersonic
aircraft for that matter) was fitted with guns then the bullets would
not be able to leave the muzzle

I don't think there's anything special about being supersonic to the
basic physics involved (though it will add some wrinkles). Before
firing, there will be ram air pressure in the (forward facing) muzzle.
When the bullet is fired, there will be explosive chemical pressure
behind the bullet which will exceed the ram air pressure in the muzzle -
this difference will cause the bullet to accelerate down the muzzle. At
some point the pressure behind the bullet will begin to decrease (as the
reaction ends and the volume continues to increase), while the ram air
pressure will increase further up the muzzle (due to the bullet pushing
the air away). Given a sufficient charge, the bullet will exit the
muzzle and become a projectile. The speed of exit depends on the size
of the charge - obviously a dud would not eject the bullet (but this is
true of anything).

Once the bullet exits the muzzle, it will slow down and descend at a
rate typical of a bullet. The plane flying behind or next to it is
independent and largely irrelevant, though it will maintain speed and
altitude due to its engines.

Bullets typically are supersonic to begin with, so there's nothing
special here. Coming out of the concorde it will have an initially
higher airspeed than a typical bullet shot from the ground, so it will
decelerate more quickly. My gut feeling (I have never shot a gun
however) is that the bullet will have enough excess forward speed that
by the time it slows down to the concorde's speed, it will be way ahead
of the plane.

Do fighter planes have guns that fire at supersonic speeds? I suspect so.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

The 50 caliber Browning machine gun bullet has a muzzle
velocity of about 2700-3000 fps, about Mach 2.5 but it is
slow by jet standards and has been replaced for aircraft use
by the 20 mm with higher velocity. The 45 ACP pistol has a
velocity of about 800 fps and is sub-sonic, the .22 LR HV is
just above Mach 1 but slows to below Mach 1 by 25-50 yards.
The 30/06 and other modern rifles have velocities from
2700-4000 fps depending on caliber and bullet weight. The
drag coefficient of a bullet of the heavy bullets used in
the 50 BMG and the 20 mm is such that the bullet does not
slow below Mach 1 for about 1/2 to 1 mile.

The bullet at a hyper speed exiting the muzzle would slow
faster than the same bullet fired from a stationary platform
because the drag increases by the square of the airspeed.


--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"Jose" wrote in message
. ..
| If concorde (or and other supersonic
| aircraft for that matter) was fitted with guns then the
bullets would
| not be able to leave the muzzle
|
| I don't think there's anything special about being
supersonic to the
| basic physics involved (though it will add some wrinkles).
Before
| firing, there will be ram air pressure in the (forward
facing) muzzle.
| When the bullet is fired, there will be explosive chemical
pressure
| behind the bullet which will exceed the ram air pressure
in the muzzle -
| this difference will cause the bullet to accelerate down
the muzzle. At
| some point the pressure behind the bullet will begin to
decrease (as the
| reaction ends and the volume continues to increase), while
the ram air
| pressure will increase further up the muzzle (due to the
bullet pushing
| the air away). Given a sufficient charge, the bullet will
exit the
| muzzle and become a projectile. The speed of exit depends
on the size
| of the charge - obviously a dud would not eject the bullet
(but this is
| true of anything).
|
| Once the bullet exits the muzzle, it will slow down and
descend at a
| rate typical of a bullet. The plane flying behind or next
to it is
| independent and largely irrelevant, though it will
maintain speed and
| altitude due to its engines.
|
| Bullets typically are supersonic to begin with, so there's
nothing
| special here. Coming out of the concorde it will have an
initially
| higher airspeed than a typical bullet shot from the
ground, so it will
| decelerate more quickly. My gut feeling (I have never
shot a gun
| however) is that the bullet will have enough excess
forward speed that
| by the time it slows down to the concorde's speed, it will
be way ahead
| of the plane.
|
| Do fighter planes have guns that fire at supersonic
speeds? I suspect so.
|
| Jose
| --
| Money: what you need when you run out of brains.
| for Email, make the obvious change in the address.

Jim M wrote:
The 50 caliber Browning machine gun bullet has a muzzle
velocity of about 2700-3000 fps, about Mach 2.5

Barrettt's new .416 round will do over mach 3 out of the barrel and
keep over mach 2 out to 3000 yds. "Reach out, reach out and touch
someone..."

The Monk

Take that California.

BTW, I've looked at the Barrett website and didn't see the
specs. If I was Barrett I would have done a .495 first and
then when California bans those, make a 458, that caliber is
very popular, from the 45 ACP pistol to the 45/70 rifle and
a lot of others.


--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"Flyingmonk" wrote in message
oups.com...
| Jim M wrote:
| The 50 caliber Browning machine gun bullet has a muzzle
| velocity of about 2700-3000 fps, about Mach 2.5
|
| Barrettt's new .416 round will do over mach 3 out of the
barrel and
| keep over mach 2 out to 3000 yds. "Reach out, reach out
and touch
| someone..."
|
| The Monk
|

One of the driving reasons to the development of air to air missiles in
the jet age was the problem of having the engines ingest the bullets
you fired a few seconds earlier that have now slowed down due to air
drag whilst you kept on motoring along at 500 to 1500 mph - and lumps
of metal hitting a 50,000 rpm fan blade has predictable results... So,
they developed missiles that leap off the rail and gain speed beyond
their initial launch velocity, sparing the ignoble result of shooting
yourself down (actually ramming your own projectiles from behind, which
is technically not 'shooting' yourself)... Further, the missiles very
soon had heat tracking, higher speed, longer range, etc. capabilities,
allowing the pilot to shoot a target moving at supersonic speed from a
standoff distance... Yes, there was joy in Mudville...
Then Vietnam came along... And the Mig-15 was a quick, deadly, street
fighter that outclimbed the US fighters and could turn inside of you in
a fight, and never, ever engaged you at supersonic speeds from 5 miles
away... Instead he dived in tight and rolled onto your tail firing
cannon shells up your butt... And even if you got behind him he was too
close to fire missiles effectively... Our vaunted kill ratio of 30:1
slammed into the ground hitting an eye popping 1:1 ratio... Needless to
say this came as a shock to our cocky fighter jocks... And the shock
was often fatal... So, they began demanding, "gimme some gawddam
guns!"... To their credit the Pentagon listened, equipping Sabres with
50 caliber guns to even the odds, and started the Top Gun fighter
school to teach the obsolete art of dog fighting... Luckily, there were
still fighter jocks from WWII who could show the new kids how to save
their butts in a real gunfight... So, in the end it turned out right
from our point of view and John Wayne was able to swagger down the
street once more...

denny

The F-104, armed with a high velocity 20 mm Vulcan cannon
shot itself down during flight testing ground attack. It
passed the hail of bullets while in a dive. So, the bullets
will leave the barrels, but they slow down since they have
no continuous propulsion. The aircraft can pass the
bullets, something that is handled by training.


--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"rick_little99" wrote in message
oups.com...
|A friend and I were having a debate on a rumour that we
once heard.
| The rumour went along the lines, If concorde (or and other
supersonic
| aircraft for that matter) was fitted with guns then the
bullets would
| not be able to leave the muzzle or it would shoot itself
if it fired
| them while cruising. Assuming that the bullets velocity
and the speed
| of the aircraft are the same, what are your thoughts on
what would
| happen?
|

rick_little99 wrote:

A friend and I were having a debate on a rumour that we once heard.
The rumour went along the lines, If concorde (or and other supersonic
aircraft for that matter) was fitted with guns then the bullets would
not be able to leave the muzzle or it would shoot itself if it fired
them while cruising. Assuming that the bullets velocity and the speed
of the aircraft are the same, what are your thoughts on what would
happen?


It would take a lot of air pressure to stop a bullet just as it was
leaving the muzzle. The bullet would easily exit the barrel and only
then begin to slow down from air resistance. In level flight, it is
very unlikely that the airplane could shoot itself as the bullet would
be falling to earth as it slowed down and would pass under the airplane.


Matt