concord bullet

Hallo mate, hope all’s well. 🙂

Hi Seafuryfan,

The part of the projectile that sticks out of the case, i.e. the front end, is indeed on most types smooth.
The part of the projectile that is enclosed in the case, the rear end of the projectile, has grooves.
This is certainly so on the .50 machine gun ammo.

Cheers, Transall.

Ex-military: I don’t own a .50!
🙂

“Spock! Analysis.”

Fascinating, and quite funny. Steve’s hypothesis sounds reasonable. IMHO, the main factors that will affect this bullet once it leaves the barrel are:

Gravity. Gravity drop will be a major factor for the bullet. At 1nm at static speeds, the bullet might drop by about 10 feet. Given that Concorde (used to) travel approximately 1 mile every 3 seconds at Mach 2, in 3 seconds the bullet will have dropped by about 10 feet.

Wind and friction. When exposed to the intial windspeed of mach 4.5, the bullet may be unable to sustain a controlled ballistic profile and may tumble when exposed to the aerodynamic forces because of:

a. the change in air pressure and velocity as it passes from turbulent leading edge airflow to the ‘smooth’ air in front

b. base drag (turbulent air which occurs around and behind the bullet) which slows it down

c. skin friction, that is, the friction caused by the interaction of the bullet surface and the surrounding airflow.

Even if tumbling does not occur, the above factors, which are not normally major players on static shoots or at low speeds, become major players (IMHO).

Transall, my understanding for most bullets (although perhaps not for all of them) is that the spiral grooves in the gun barrell alone provide spin to the bullet by the travel of gases along them. To maximise velocity, the bullet itself is smooth.

Now, where are those electrodes? 😀

PS: Hi Steve!

ok lets assume the gun is in the middle of the fuselage pointing forward. fire the gun and shoot yourself in the cockpit.

face the gun backwards and blow the tail off. the end result is a bit of a mess.

these theories are quite interesting but where does the bloke who fires the rifle sit?

😎

“Do you know anything about the Javelin incidents mentioned above?
I’ve recently seen one with your name under it

Cheers, Transall.”

I did an extensive amount of research when I built my Javelin model but I didn’t see anything about Javelins running into thier own bullets,although in theory I suppose it could’ve happenned.I would guess that it is unlikely to have happenned as the Jav was,I beleive,transonic rather than supersonic,ie it would only go supersonic if you were really pushing it(a pre-production machine did a supersonic dive over the outskirts of London to prove that the aircraft could be made to go supersonic without control being lost,as had been suggested by a former Gloster test pilot in the national press,a suggestion which had damaged Gloster’s and the Javelin’s reputation.A loud Javelin-generated sonic boom over London soon restored thier image! :D)
For anyone who doesn’t know what Transall is talking about,here’s the link to a review I wrote of Airfix’s FAW.9 Javelin.

http://m2reviews.cnsi.net/reviews/korean/harringtonjav.htm

Turning this round a bit- If it were going forwards at mach 2 and shot a shell out of the back-a la tail gunner-which left the barrel at mach 2-would it just drop out of the sky?

Wind drift would also have to be taken into account. Plus, as the bullet dropped it may be affected by the change in direction of wind at different levels.

(Absurd, laterally-thought remark, but I cannot resist it – nobody said the rifle was pointing in the same direction as the aircraft’s travel! No need to respond to this – really. :))

[QUOTE]Originally posted by SteveYoung

The round also generates no lift, as the air flowing over it’s upper surface travels at the same velocity as that travelling underneath, hence no pressure differential, and therefore no lift. The round does however have weight, and so will immediately be subjected to the acceleration of gravity at 9.8 metres per second squared (I learned that in school twenty years ago, and frankly I’m amazed I still remember it! :D). So from the very moment that the round leaves the barrel of the weapon, it will be falling.

Hi Steve,

Are you sure there is absolutely no lift? I do not know.
But the bullet is cast with with grooves that interact with the grooves in the barrel in order to make it spin. The spinning is intended to stabilise it in flight. Possibly the spinning grooves on the bullet act as a tiny airfoil and generate minimal lift.

Best regards, Transall.

Originally posted by Ant Harrington
Cheers Transall,it was the F11F icident I was thinking of.:) Did the guy make it down ok or did he actually get shot down by his own sheels??

Hi Ant,

The F-11F was lost but I think the pilot ejected safely.

Do you know anything about the Javelin incidents mentioned above?
I’ve recently seen one with your name under it;)

Cheers, Transall.

This is all guesswork, but I’d assume that the deceleration of the round would be quite dramatic. Presumably the airflow in the barrel of the weapon would be static, so the round would be propelled down the barrel at the usual velocity. Somebody’s mentioned Mach 2.5, so for the purposes of this exercise we’ll use that. We’ll also assume the rifle barrel to be a metre long. If Concorde is tarvelling at Mach 2, then that makes the total forward velocity of the round Mach 4.5.

However, when it comes into contact with the outside airflow, which is coming towards it at Mach 2, the total forward velocity of the round would very quickly be reduced to Mach 2.5. As Concorde is travelling at Mach 2, there’s only now a Mach 0.5 differential.

But… the principles of flight state that to achieve level flight at a constant velocity, lift must equal weight and thrust must equal drag. We’ll assume that Concorde is in level flight.

Unfortunately for the round, its total thrust is provided in its first metre or so of flight, as the expanding gasses within the cartridge case accelerate it from zero to Mach 2.5 in about a metre. After that, it has no thrust, and so every further metre that it flies, it will encounter drag.

The round also generates no lift, as the air flowing over it’s upper surface travels at the same velocity as that travelling underneath, hence no pressure differential, and therefore no lift. The round does however have weight, and so will immediately be subjected to the acceleration of gravity at 9.8 metres per second squared (I learned that in school twenty years ago, and frankly I’m amazed I still remember it! :D). So from the very moment that the round leaves the barrel of the weapon, it will be falling.

So to summarise, if Concorde were to be in level and unaccelerated flight at Mach 2 when she fired the weapon, the round would initially travel faster than Concorde, but it’s trajectory and ballistics would cause it to decelerate and fall away.

Whether the round would make it past the nose of Concorde, or how far ahead of the aeroplane it would get, are matters for minds far more intelligent than mine… 😀

Cheers Transall,it was the F11F icident I was thinking of.:) Did the guy make it down ok or did he actually get shot down by his own sheels??

I think the early Gloster Javalins had a problem of being hit by there own bullets/cannon shells in a dive

But would you be able to hear the gun firing?:D 😀 😀

Flood.

Indeed, Ant, I just forgot about the bullet drop.
But luckily, it’s all hypothetical:)

It may have happened to a Starfighter too, but it certainly happened to a US NAVY Grumman F-11F Tiger.

Cheers, Transall.

Just to add my penny’s worth to this (slightly strange) discussion, I don’t think Concorde would ever meet the bullets she fired for the simple reason that bullets drop as they slow down. Perhaps Concorde could catch up with them,but in the vertical plane the bullets would be at a lower altitude.
There was a case where a USAF (Starfighter?) was hit by his own cannon shells,but he was in a dive rather than straight and level.

Hi,

Many variables here…like what caliber, what type of rifle?
We must also assume this is only hypothetical…fixing the rifle would not be easy…the airflow at Mach 2 would rip it, and the skin it is attached to, off very quickly. I have no idea if one could fit it inside the boundary layer on Concorde.
Mach 2 flight is really something different. You can get away with antennas and air data probes on Harriers for example that would not have held up to Mach 2 flight in a Phantom.
The muzzle velocity of an infantry rifle bullet can be as high as Mach 2.5 and it bleeds off to 0.0 in less than 3 miles. And that’s at Sea level.
It isn’t even measured in Mach, I’m only familiar with meters per second.
I suppose the speed would be added to Concordes speed. So, I guess the theoretical bullet would leave the muzzle with and airspeed of Mach 4.5.
That would bleed down very soon but less fast than at sea level due to the thin air.
I mentioned the caliber, because I suppose a lighter bullet would lose it’s velocity faster than a heavy bullet.
I guess Concorde would catch up within a mile.

Hope this helps a bit, Transall.

its late at night but i am thinking bullet will be traveling at mach2 plus speed of bullet and concorde won’t catch it until it hits the officials who scrapped her in the head:D