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Aviation Forum / General / Aviation / February 2006Concorde Vs Bullet
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? Next time you're on a plane, toss a bag of peanuts to someone in front of you. Never knew you could throw a bag of peanuts 500MPH, did you? > 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 [quoted text clipped - 3 lines] > of the aircraft are the same, what are your thoughts on what would > happen? > Next time you're on a plane, toss a bag of peanuts to someone in front of > you. I assume you mean in an open cockpit plane against the wind. Bullets don't get to travel in a vessel like you and I do. -Robert From: Robert M. Gary - view profile Date: Fri, Feb 17 2006 10:43 am Email: "Robert M. Gary" <N70...@gmail.com> Groups: rec.aviation.piloting Not yet ratedRating: show options Reply | Reply to Author | Forward | Print | Individual Message | Show original | Report Abuse | Find messages by this author > Next time you're on a plane, toss a bag of peanuts to someone in front of > you. I assume you mean in an open cockpit plane against the wind. Bullets don't get to travel in a vessel like you and I do. -Robert They do if you are a terrorist...... Ben > 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 [quoted text clipped - 3 lines] > of the aircraft are the same, what are your thoughts on what would > happen? Only if it's on a conveyor belt also going the speed of sound in the opposite direction. ;^) 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. NOt quite. The bullet would not 'instantaneously' slow down. It has a given amount of energy and is capable of supersonic speeds. The question would be how long would it take to slow down to the Concorde's speed. If you guess a second, and the bullet was fired along the flight path of the airplane, it would have fallen 16 feet be the time it was traveling the same speed, and another number of feet before it slowed down enough for the airplane to catch up to it. During WW2 some airplanes were said to have hit themselves with their own bullets, but I think you can work out how that might happen with an airplane diving under its own line of fire. Finally, if you think you knew the answer, why did you post the question? I posted the question because i wanted to canvas opinion and spark debate.....the very reason that these groups exist! > I posted the question because i wanted to canvas opinion and spark > debate.....the very reason that these groups exist! In other words, you're a a troll... If its travelling at its own velocity plus the velocity of Concorde, why would it instantly slow down to the speed of Concorde after exiting the muzzle? Seems to me it would continue out the muzzle at whatever its combined velocity was. > 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 [quoted text clipped - 9 lines] > 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 > 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 [quoted text clipped - 3 lines] > 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  SignatureMoney: 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. SignatureThe 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. |> If concorde (or and other supersonic | > aircraft for that matter) was fitted with guns then the bullets would [quoted text clipped - 30 lines] | | Jose 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. SignatureThe 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. | Jim M wrote: | >The 50 caliber Browning machine gun bullet has a muzzle [quoted text clipped - 5 lines] | | 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 Denny, I think you're right, but a few details are off a tad: >>>Then Vietnam came along... And the Mig-15 was a quick, deadly, street fighter ...<<< MiG-15 flew in Korea, MiG-17 flew in Vietnam. As did the MiG-19 and MiG-21. The -17 was the last of the gunships with twin 23mm and a single 37mm gun. >>>and never, ever engaged you at supersonic speeds from 5 miles away..<<< Correct, the reason being the -17 wasn't a supersonic fighter. AFAIK it'd only go Mach in a dive. >>>To their credit the Pentagon listened, equipping Sabres with 50 caliber guns to even the odds<<< The F-86 Sabre had 6 .50cal Brownings from the get-go and flew in Korea. The F-100 Super Sabre had 4 20mm revolver cannon and was the last of the USAF's gunships IIRC. Ditto for the USN's F-8 Crusader. When the F-4 Phantom became the front line fighter for the Air Force & Navy it was a missile-only bird until the pilots bitched enough that gun pods were hung on the centerline. The F-4E was the first Phantom variant with an internal 20mm. Now I read the gun debate is going on yet again with the F-35 JSF. Maybe the designers should read up on their history? Whew. Sorry about the thread creep, got carried away with my history.. (kingfish@hotmail.com wrote) > MiG-15 flew in Korea, MiG-17 flew in Vietnam. As did the MiG-19 and > MiG-21. The -17 was the last of the gunships with twin 23mm and a single > 37mm gun. Did the VC throw 'old' MiG-15's into the breach, early in the war? Montblack It's, "Into the breach" like a break in the wall or dike, correct? Not, "Into the breech" like the rear of a cannon or a gun, ready to be fired - right? >>>Did the VC throw 'old' MiG-15's into the breach, early in the war? Montblack It's, "Into the breach" like a break in the wall or dike, correct? Not, "Into the breech" like the rear of a cannon or a gun, ready to be fired - right? <<< Good question Mont. I've never read anything about MiG-15s flying in Vietnam, but I guess there may have been a few kicking around, maybe early in the war like you suggested. All the North Vietnamese aces flew MiG-17s IIRC. And yeah, it is "Once more into the breach dear friends" from that Shakespeare guy (kingfish@hotmail.com wrote) > Good question Mont. I've never read anything about MiG-15s flying in > Vietnam, but I guess there may have been a few kicking around, maybe early > in the war like you suggested. All the North Vietnamese aces flew MiG-17s > IIRC. When you consider some of the hardware from earlier wars we had sitting around on airfields over there... Montblack MiG 19 and 21 too. | (kingfish@hotmail.com wrote) | > Good question Mont. I've never read anything about MiG-15s flying in [quoted text clipped - 6 lines] | | Montblack 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. SignatureThe 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. |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 [quoted text clipped - 3 lines] | of the aircraft are the same, what are your thoughts on what would | happen? > 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 [quoted text clipped - 3 lines] > 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 |
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