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speed of sound

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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speed of sound

Unread postAuthor: Mini Khan » Sat Apr 15, 2006 2:52 pm

how hard is it to reach the speed of sound, wouln't it be posible with a 15 foot 1.5" barral with a 4" by 8 foot chamber with a piston valve, and useing a striped golf ball that ways about 40 grams, its a perfect fit, at 120 psi,what i just discribed was my cannon but i cant download the speed caculating programs, can someone caculate the vilocity for me plz.
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Unread postAuthor: Shrimphead » Sat Apr 15, 2006 3:40 pm

It is physically impossible for normal air (79%nitrogen, 21% oxygen i think) to reach supersonic speeds. It can be done with helium and probably some other gasses, and I think it was spudinator who did it with his hybrid using a 6x mix. You can get really close with a normal pneumatic, but you can't fully reach it.
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Unread postAuthor: jrrdw » Sat Apr 15, 2006 3:58 pm

What i would like to have is very quite and very fast, i want mine so quite you can bearly hear it sitting rite beside it! Flat shooting for at least 250 yrds. Now that is my ideal cannon.
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Unread postAuthor: schmanman » Sat Apr 15, 2006 6:54 pm

What i would like to have is very quite and very fast, i want mine so quite you can bearly hear it sitting rite beside it! Flat shooting for at least 250 yrds. Now that is my ideal cannon.


mine shoots 300 yards with the barrel level with the ground. after going through a carhood,2x4, then 3/4 inch plywood with a 3 pound steel bar. two 6" inch,5' foot long airchambers and a 18 foot,2 inch diameter barrel, and a piston valve should do it,jrrdw. it sounds like a cough when fired,and shoots 400 yards at 30 psi. oops,a little off topic,if I sound like I'm bragging,I'm not.I'm just proud of it :oops: :D :oops: :D



http://www.spudfiles.com/forums/viewtop ... &lighter=&
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Unread postAuthor: jrrdw » Sat Apr 15, 2006 8:36 pm

Yea thats the ticket! Try making some ammo out of ice, i've been wondering how that would turn out. I don't have a cannon rite now, (booowhooowhooo), but soon! I'm collecting parts for one now, i got the chambers/barrel/idea for design, but thats it, SOON!!!!!!!
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Unread postAuthor: spudshot » Sat Apr 15, 2006 11:09 pm

i think it was a 5x mix spudinator used, also joel claims to have broken the sound barrier using a huge cannon with a supah + valve with normal air, though he didnt have a chrony, he said he heard the sonic boom
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Unread postAuthor: drac » Sun Apr 16, 2006 7:24 am

Come to think of it, what does a sonic boom sound like? :oops:
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Unread postAuthor: dragon finder » Sun Apr 16, 2006 7:41 am

Shoot a gun and you will get the idea.
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Unread postAuthor: feral_patriot » Sun Apr 16, 2006 8:00 am

Since they grounded the Concorde SST a couple years ago it is unlikely that people will get to hear a sonic-boom any more. Brings back fond memories of Larson Airforce Base when I was a kid ,wathing that plane take off & land,and "feeling" as well as hearing the sonic-boom as the Concorde passed overhead. :) 8) :(
Indeed,to achieve that with an air-canon would be remarkable!!!
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Unread postAuthor: dragon finder » Sun Apr 16, 2006 10:00 am

As an object moves through the air it creates a series of pressure waves in front of it and behind it, similar to the bow and stern waves created by a boat. These waves travel at the speed of sound, and as the speed of the aircraft increases the waves are forced together or 'compressed' because they cannot "get out of the way" of each other, eventually merging into a single shock wave at the speed of sound. This critical speed is known as Mach 1 and is approximately 1,225 km/h (761 mph) at sea level.
Sonic boom diagram

In smooth flight, the shock wave starts at the nose of the aircraft and ends at the tail. There is a sudden rise in pressure at the nose, decreasing steadily to a negative pressure at the tail, where it suddenly returns to normal. This "overpressure profile" is known as the N-wave due to its shape. We experience the "boom" when there is a sudden rise in pressure, so the N-wave causes two booms, one when the initial pressure rise from the nose hits, and another when the tail passes and the pressure suddenly returns to normal. This leads to a distinctive "double boom" from supersonic aircraft. When maneuvering the pressure distribution changes into different forms, with a characteristic U-wave shape. Since the boom is being generated continually as long as the aircraft is supersonic, it traces out a path on the ground following the aircraft's flight path, known as the boom carpet.
A cage around the engine reflects any shock waves. A spike behind the engine converts them into thrust.
A cage around the engine reflects any shock waves. A spike behind the engine converts them into thrust.
To generate lift a supersonic airplane has to produce at least two shock waves: One over-pressure downwards wave, and one under-pressure upwards wave. Whitcomb area rule states, we can reuse air displacement without generating additional shock waves. In this case the fuselage reuses some displacement of the wings.
To generate lift a supersonic airplane has to produce at least two shock waves: One over-pressure downwards wave, and one under-pressure upwards wave. Whitcomb area rule states, we can reuse air displacement without generating additional shock waves. In this case the fuselage reuses some displacement of the wings.

A sonic boom or "tunnel boom" can also be caused by high-speed trains in tunnels (e.g. the Japanese Shinkansen). In order to reduce the sonic boom effect, a special shape of the traincar and a widened opening of the tunnel entrance is necessary. When a high speed train enters a tunnel, the sonic boom effect occurs at the tunnel exit. In contrast to the (super)sonic boom of an aircraft, this "tunnel boom" is caused by a rapid change of subsonic flow (due to the sudden narrowing of the surrounding space) rather than by a shock wave. In close range to the tunnel exit this phenomenon can cause disturbances to residents.

sonic boom info from wikipedia.com
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Unread postAuthor: drac » Sun Apr 16, 2006 12:00 pm

Ohhhh, I see. I was on vacation, shooting the .22 i got from my great uncle. I heard like a *woosh* and then a couple seconds later, this huge BANG. Is that like it?
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Unread postAuthor: Rambo » Sun Apr 16, 2006 12:05 pm

So how we are going to distinguish the boom from the combustion and the sonic boom?
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Unread postAuthor: Mini Khan » Sun Apr 16, 2006 9:02 pm

i think it is possible to reach the spped of sound with air because really expensive pellet guns that u cock once do it
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Unread postAuthor: boilingleadbath » Mon Apr 17, 2006 1:40 am

Mini Khan, that's a combonation of compressive air heating, possibly deiseling of the lubricant, and most likely shock heating in the barrel.
It's not exactly a typical spudgun system, but don't interpret this reply to mean that I think it's impossible.

That being said, Rambo has a very good point - going on sound alone will be very hard, if not impossible, due to the launch noise.

When shooting a rifle, you can hear the shockwave of the bullet a bit - it's a drawn-out noise after the bang of the rifle.
This might be very hard to hear with our launchers, as we are shooting projectiles with poor aerodynamics at speeds just above the speed of sound - they'll fall back down into the subsonic range very quickly, although how quickly would require calculations I don't feel like doing.
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Unread postAuthor: Jolly Roger » Mon Sep 18, 2006 10:57 am

The sonic boom of projectiles can also alter the accuracy of a shot because of the air pressure distribution in the transonic period. Thats why alot of attempts to enter supersonice speeds in early aircraft were so dangerous as the materials were not engineered to accomodate for this. Projectiles used for potential supersonic cannons will have to be designed with this in mind.
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