AR bullet speed from plane

[JeffsSig]

Ok your in a jet traveling 1841 MPH ( or 2700 FPS) and your AR will shoot its bullet at 2700 FPS (or 1841 MPH) and you take a shot from in the plane out of the front of it will the bullet just set in front of the plane for a moment as it will do the same speed? Or will it go way out in front as if you shot it on the ground when your stationary?

To make it easy what will the bullet do as it is going the same rate of speed as the plane?

Edited May 18, 2012 by JeffsSig

[bubbadavis]

The bullet will travel 2700 FPS from its frame of reference (e.g. the plane) so the bullet will behave as if it was shot on the ground. Relative to the ground, the bullet will be traveling at 5400 FPS.

Better question, where do I find one of these Mach 2.5 planes?

[Dolomite_supafly]

The bullet will exit the bore at the muzzle velocity. Then the airplane's velocity will be added to that velocity.

Now if you were shooting out the back of the plane the bullet would pretty much stand still upon exit providing both velocities were the same.

Dolomite

[Rightwinger]

Copper jackets or lead?

(been listening to Steven Wright again Jeff?)

[gjohnsoniv]

How is this relevant?

[Lumber_Jack]

First off how'd you get the rifle on the plane?

If you shoot, from a stationary point, at the instant the plane passes they will travel side by side until the bullet looses energy and falls.

What if you are in the cockpit and shoot towards the tail. That means in relation to the earth the bullet would be standing still, again assuming the bullet and plane are traveling at exactly the same speed.

[peejman]

The bullet will travel 2700 FPS from its frame of reference (e.g. the plane) so the bullet will behave as if it was shot on the ground. Relative to the ground, the bullet will be traveling at 5400 FPS.

This, but only briefly. The aerodynamic heating caused by the near hypersonic velocity would destroy the bullet almost immediately.

Better question, where do I find one of these Mach 2.5 planes?

Faster than a speeding bullet.

[peejman]

If you shoot, from a stationary point, at the instant the plane passes they will travel side by side until the bullet looses energy and falls.

Which will happen almost immediately. The plane has propulsion to maintain it's speed. The bullet doesn't.

What if you are in the cockpit and shoot towards the tail. That means in relation to the earth the bullet would be standing still, again assuming the bullet and plane are traveling at exactly the same speed.

Yes, the bullet would be stationary (briefly) relative to the Earth. However, if you're in the cockpit,you've just shot a hole in the back of your plane while traveling 1800 mph. I suspect you'd have bigger worries.

[Rightwinger]

This, but only briefly. The aerodynamic heating caused by the near hypersonic velocity would destroy the bullet almost immediately.

Faster than a speeding bullet.

This is why I asked copper jacket or lead.

Lead bullets would begin to vaporize immediately. Copper jackets might make it several hundred yards before becoming FOD for your intakes.

That's why its relevant.

(perhaps you need to listen to Steven Wright)

[mcurrier]

Ok your in a jet traveling 1841 MPH ( or 2700 FPS) and your AR will shoot its bullet at 2700 FPS (or 1841 MPH) and you take a shot from in the plane out of the front of it will the bullet just set in front of the plane for a moment as it will do the same speed? Or will it go way out in front as if you shot it on the ground when your stationary?

To make it easy what will the bullet do as it is going the same rate of speed as the plane?

That sounds like the Bugs Bunny or Wiley Coyote version.

Remember when Bugs Bunny would step out of a falling elevator right before it hit ground level and he wouldn't get hurt? Doesn't work like that in real life unfortunately.

[peejman]

This is why I asked copper jacket or lead.

Lead bullets would begin to vaporize immediately. Copper jackets might make it several hundred yards before becoming FOD for your intakes.

That's why its relevant.

(perhaps you need to listen to Steven Wright)

The stagnation temp at hypersonic velocity can exceed 1400 deg C. Copper melts at 1000 deg C. The jacket will begin to vaporize when the bullet exits the muzzle. I be surprised if it makes it 100 ft, much less 100 yds.

I guess I'm slow, I don't get the reference to Steven Wright (assuming you mean the comedian).

[mcurrier]

The stagnation temp at hypersonic velocity can exceed 1400 deg C. Copper melts at 1000 deg C. The jacket will begin to vaporize when the bullet exits the muzzle. I be surprised if it makes it 100 ft, much less 100 yds.

I guess I'm slow, I don't get the reference to Steven Wright (assuming you mean the comedian).

I'm curious what kind of munitions fighter jets use then?

[Jonnin]

Mcurrier: the F15 used a 20mm gatling gun with just a few rounds of ammo. It was not really for dogfighting, it was for ground targets. Not sure what the f18 and f22 have.

there is more to it than all this. There have been cases of jet fighters, which are much slower than an SR71, running into their own machine gun fire. The bullets lose velocity fast, the plane is still booking it, and they impact out in the distance. For this reason, IIRC, the machine guns on modern fighters are locked out from use at high speeds and are only useful really for a low speed (relatively) "strafing run". There have also been reports of being in a dive, firing at the ground, and hitting their own shots as the dive increased the plane's speed ....!!!

It is hard to tell where fact and fiction mingle in the above. The internet being what it is, the stories of such things could be total BS. Maybe someone here knows for sure.

Edited May 18, 2012 by Jonnin

[Rightwinger]

The stagnation temp at hypersonic velocity can exceed 1400 deg C. Copper melts at 1000 deg C. The jacket will begin to vaporize when the bullet exits the muzzle. I be surprised if it makes it 100 ft, much less 100 yds.

I guess I'm slow, I don't get the reference to Steven Wright (assuming you mean the comedian).

I didn't do a research paper on it or anything, I just know they had to use special metals on the Blackbird just because of the leading edge temperatures. As stated, it's been known that the fastest jets could catch up and fly into their own bullets. I'll try to be more exact next time I'm making a joke.

By the way, those liquid trails on the SR71, that would be fuel, the thing leaked like a sieve at low speeds as it was built to expand under high speed flight and temps to allow for expansion.

Yes, Steven Wright, second joke, enjoy

[media=]

[/media] Edited May 18, 2012 by Rightwinger

[peejman]

I'm curious what kind of munitions fighter jets use then?

Mcurrier: the F15 used a 20mm gatling gun with just a few rounds of ammo. It was not really for dogfighting, it was for ground targets. Not sure what the f18 and f22 have.

there is more to it than all this. There have been cases of jet fighters, which are much slower than an SR71, running into their own machine gun fire. The bullets lose velocity fast, the plane is still booking it, and they impact out in the distance. For this reason, IIRC, the machine guns on modern fighters are locked out from use at high speeds and are only useful really for a low speed (relatively) "strafing run". There have also been reports of being in a dive, firing at the ground, and hitting their own shots as the dive increased the plane's speed ....!!!

It is hard to tell where fact and fiction mingle in the above. The internet being what it is, the stories of such things could be total BS. Maybe someone here knows for sure.

This. The gun can only be used when the plane is flying a relatively low speed. Hypersonic flight is in excess of 3000 mph. The F-22 uses the same (or nearly the same) 20mm Vulcan cannon as everything else (F-18, F-16, F15, F-14, etc... ).

Like I said above, the plane has an engine to maintain its speed, the bullets begin to slow down the moment they exit the muzzle.

I didn't do a research paper on it or anything, I just know they had to use special metals on the Blackbird just because of the leading edge temperatures. As stated, it's been known that the fastest jets could catch up and fly into their own bullets. I'll try to be more exact next time I'm making a joke.

By the way, those liquid trails on the SR71, that would be fuel, the thing leaked like a sieve at low speeds as it was built to expand under high speed flight and temps to allow for expansion.

Yes, Steven Wright, second joke, enjoy

You're right about the SR-71. It's skin was largely made of titanium (same thing exhaust systems are made of these days) and since they couldn't make a fuel bladder that would take the heat, the skin itself is the fuel tank. The plane gets so hot during high speed flight (~950 deg F in spots) that in order to accommodate thermal expansion, it leaks like a sieve when it's cold. I believe the whole plane grows about 1" in length at speed.

Alas, youtube is blocked by big brother so I'll have to watch that later.

[Rightwinger]

Please do, its "relevant". LOL

[Jonnin]

Yea we had an aerospace guy here (sadly he passed a year or so ago) who was in flight school with neal armstrong. He worked on several planes including the xsomething valkarie. He *hated* the sr71 because of its fuel leaking and overall design. He said they got it down to a science about putting in just enough fuel to get it up and expanded, then did a refuel in the air. He said something about it gettting to high speeds with brute force engineering, rather than problem solving. I don't know nothin' bout that, I just think it was a pretty looking design.

[gjohnsoniv]

Yea we had an aerospace guy here (sadly he passed a year or so ago) who was in flight school with neal armstrong. He worked on several planes including the xsomething valkarie. He *hated* the sr71 because of its fuel leaking and overall design. He said they got it down to a science about putting in just enough fuel to get it up and expanded, then did a refuel in the air. He said something about it gettting to high speeds with brute force engineering, rather than problem solving. I don't know nothin' bout that, I just think it was a pretty looking design.

I'm no engineer but I personally like the design as well.

[Rightwinger]

Makes ya wonder what we don't know is flying now. But with the US content to think it will remain top dog with current technology, the defunct black bird project was probably the last of the really fast manned aircraft. It's all RPV now which is good for not losing pilots but you lose something vital without eyes on the target to me.

[gjohnsoniv]

Makes ya wonder what we don't know is flying now. But with the US content to think it will remain top dog with current technology, the defunct black bird project was probably the last of the really fast manned aircraft. It's all RPV now which is good for not losing pilots but you lose something vital without eyes on the target to me.

For all we know they have another type of piloted craft flying now, who knows.

[Jonnin]

Makes ya wonder what we don't know is flying now. But with the US content to think it will remain top dog with current technology, the defunct black bird project was probably the last of the really fast manned aircraft. It's all RPV now which is good for not losing pilots but you lose something vital without eyes on the target to me.

There comes a point where more speed is not helpful. I think the era of speed = king is over, and now they seek innovation in other areas. This is good. There is a lot of military R&D in this country, in every area you can imagine. Not sure what manned craft is flying, but you can bet there are new things being done, even if they are incremental upgrades to the older designs.

[peejman]

I think speed will always be king. The limiting factor these days is the pilot.

I'm fascinated by the design of the SR-71, mostly because of the time in which it was done. They didn't have all the fancy tools we have today. That's probably why it so cool looking.

The Valkyrie you mentioned is likely the XB-70, also a really cool plane. There's one on display at the USAF museum in Dayton OH. I highly recommend a visiting, it's fascinating.

Edited June 18, 2012 by peejman

[Guest BungieCord]

I'm still working on what happens if you're driving your car at the speed of light and you switch on the headlights. Once I've got that one worked out, I'll get back to you.

[leroy]

Thanks for posting the picture peej!! I love the gblackbird. I dont care if it does leak fuel on the ground. It's a great thing. It made the russians and the chinese afraid of us. That's a great thing!!

Thanks again.

leroy

By the way, please give bubba and dolomite an "...A..." in physics and vector addition!!

[Guest Darthlaidher]

This is why I asked copper jacket or lead.

Lead bullets would begin to vaporize immediately. Copper jackets might make it several hundred yards before becoming FOD for your intakes.

That's why its relevant.

(perhaps you need to listen to Steven Wright)

I don't think so, the military can't build a plane faster than the black bird, they tried and the skin ripped off it. Now take a copper cased bullet. It would probably break apart in a couple feet.

Edited June 15, 2012 by Darthlaidher