shooting yourself down - more physics?

Smitty Two wrote:

1. I didn't stipulate a vacuum. My engine and wing don't work very well
without air. I said, to simplify calculations, ignore the effects of
friction on the projectile. We are flying above the earth.

You said discounting air friction. This is key to the problem. No air
friction would be the physical equivalent of being in a vacuum.

If there were no air friction, the projectile would continue ahead with
a forward speed of 1500 mph - its own 500 mph from its spent propellant
charge, and the 1000 mph imparted to it from the airframe.

Air friction, however, acts on the projectile from the moment it departs
the muzzle, and acts to slow the projectile in a continuous manner. The
aircraft continues to maintain its 1000 mph since it has a propulsive
device that is assumed to continue to operate. Air friction (along with
gravity) are the forces that conspire to ALLOW the aircraft to overtake
its projectile and contribute to shooting itself down.

So... are we or are we not including air friction? If we are, I am not
going to hazard a guess.. my math gland atrophied long ago after I
passed calculus. If we are not, then the problem is unsolvable in level
flight on earth.

Dave

In article t,
Dave S wrote:

Smitty Two wrote:

1. I didn't stipulate a vacuum. My engine and wing don't work very well
without air. I said, to simplify calculations, ignore the effects of
friction on the projectile. We are flying above the earth.

You said discounting air friction. This is key to the problem. No air
friction would be the physical equivalent of being in a vacuum.

If there were no air friction, the projectile would continue ahead with
a forward speed of 1500 mph - its own 500 mph from its spent propellant
charge, and the 1000 mph imparted to it from the airframe.

Air friction, however, acts on the projectile from the moment it departs
the muzzle, and acts to slow the projectile in a continuous manner. The
aircraft continues to maintain its 1000 mph since it has a propulsive
device that is assumed to continue to operate. Air friction (along with
gravity) are the forces that conspire to ALLOW the aircraft to overtake
its projectile and contribute to shooting itself down.

So... are we or are we not including air friction? If we are, I am not
going to hazard a guess.. my math gland atrophied long ago after I
passed calculus. If we are not, then the problem is unsolvable in level
flight on earth.

Dave

It's a hypothetical question, of course. I think I stated it fairly
clearly. Bill has already answered it correctly, with a second from
Alex. My calculus skills have also eroded over the years, which is one
reason I wanted to discount friction. But, I'd be curious to learn what
the real world answer would be, including friction, which of course is
dependent on a whole host of factors. (Of course, by the time the plane
caught up with the bullet in the real world, the friction would likely
have reduced its speed to something *relatively* harmless.)

Now, for some practical math, I hope one of these WW1 guys around here
can help me not shoot the prop off my RV when I put the .50 on the front.

Has nothing to do with physics, but it is possible for a helicopter to shoot
himself down in several different ways. Fire a pair of 2.75" rockets at the
same time with proximity fuses while doing running fire and it could get
ugly.

Running fire while shooting the gun (or rockets) at close ranges could
easily produce ricochets that could hit the helicopter. I have seen the 50
caliber machine gun on an OH-58D blow out the copilot chin bubble before.

Another good way to shoot yourself down is for one helicopter to remote
LASER designate for another helicopter firing a Hellfire missile while you
are inside a certain fan in front of the firing helicopter. The Hellfire
can lock on to the laser designating source rather than the target.

Jeff
recently retired Army CW4 Master Army Aviator

"Smitty Two" wrote in message
news
If you guys aren't tired of arithmetic, I'm wondering if any fighter
pilots have shot themselves down. Probably not, but imagine you're
flying straight and level at 1000 mph and fire a 500 mph projectile at
an enemy that's directly ahead but at a higher altitude. You miss him;
the bullet follows a parabolic path, returning to your altitude just as
you overtake it. Discounting air friction, at what angle was the bullet
fired?

(extra credit question -- how many rivets could you have installed in
the time you wasted thinking about this question?)

Jeff wrote:
Has nothing to do with physics, but it is possible for a helicopter to shoot
himself down in several different ways. Fire a pair of 2.75" rockets at the
same time with proximity fuses while doing running fire and it could get
ugly.

Running fire while shooting the gun (or rockets) at close ranges could
easily produce ricochets that could hit the helicopter. I have seen the 50
caliber machine gun on an OH-58D blow out the copilot chin bubble before.

Another good way to shoot yourself down is for one helicopter to remote
LASER designate for another helicopter firing a Hellfire missile while you
are inside a certain fan in front of the firing helicopter. The Hellfire
can lock on to the laser designating source rather than the target.

Jeff
recently retired Army CW4 Master Army Aviator

During WW2 P-51s shot them selvesdown when making low level passes
and debris got scooped into the oil cooler.

Dan, U.S. Air Force, retired

(snip)
... my math gland atrophied long ago after I passed calculus.
(snip)

That calculus was *nasty* stuff ...
and matrix algebra was *worse*

I haven't recovered either, after 35+ years!

Peter

Smitty Two wrote:

If you guys aren't tired of arithmetic, I'm wondering if any fighter
pilots have shot themselves down. Probably not, but imagine you're
flying straight and level at 1000 mph and fire a 500 mph projectile at
an enemy that's directly ahead but at a higher altitude. You miss him;
the bullet follows a parabolic path, returning to your altitude just as
you overtake it. Discounting air friction, at what angle was the bullet
fired?

(extra credit question -- how many rivets could you have installed in
the time you wasted thinking about this question?)

What kind of gun do *you* have with a muzzle velocity of only 733 fps ?

....Ken

Jeff wrote:

The Hellfire
can lock on to the laser designating source rather than the target.

This is what the post-accident investigators refer to as "a very bad
thing" (TM).

Dave

..22 shooting CB caps.

Peter Dohm wrote:
(snip)
... my math gland atrophied long ago after I passed calculus.
(snip)

That calculus was *nasty* stuff ...
and matrix algebra was *worse*

I haven't recovered either, after 35+ years!

Peter


Geeze, a buncha light weights. The calculus series and linear
algebra you guys took were rough? Differential equations? Hah! Take a
course in imaginary variables.

Dan, U.S. Air Force, retired

Ken Chaddock wrote:

Smitty Two wrote:

If you guys aren't tired of arithmetic, I'm wondering if any fighter
pilots have shot themselves down. Probably not, but imagine you're
flying straight and level at 1000 mph and fire a 500 mph projectile at
an enemy that's directly ahead but at a higher altitude. You miss him;
the bullet follows a parabolic path, returning to your altitude just
as you overtake it. Discounting air friction, at what angle was the
bullet fired?

(extra credit question -- how many rivets could you have installed in
the time you wasted thinking about this question?)


What kind of gun do *you* have with a muzzle velocity of only 733 fps ?

...Ken

A light 45, old 38 S&W, 38 rimfire, 45-70....

Dan, U.S. Air Force, retired