Railgun - Sonic Boom

[J-Man5]

Fel,

Will Jason ever figure out why his RailGun (Gauss Rifle) now lacks the sonic boom it originally had?

J-Man5

[Lochar]

Fel,

Will Jason ever figure out why his RailGun (Gauss Rifle) now lacks the sonic boom it originally had?

J-Man5

Couple of ideas.  And remember, I know jack about physics.

Bullet shape is making the sonic boom flow inward, cancelling itself out and not sounding?  

Bullet is small enough that when it pierces the sound barrier, it doesn't create a big enough boom to be heard anymore?

[Shadowhawk]

I don't think in RL even true railgun (Jason's rifle looks more like multicoil gauss rifle), which can produce quite large plasma flash, gives sonic boom. The bullet is too small I think... hear the video of real rail gun experiment at http://www.powerlabs.org/railgun.htm

[Phantom]

Fel,

Will Jason ever figure out why his RailGun (Gauss Rifle) now lacks the sonic boom it originally had?

J-Man5

Well if i had to guess   I would think that the gun orininaly was a little out of alinment and that caused the projectile to vibrate or wobble some what when fired and that was enough to cause the boom.

later he corrected the coils by accident and eliminated the problem.

Personaly i think the projectile he is using is too small to cause a sonic boom ....but i could be wrong.

my thinking on this is the shockwave caused wouldn't be large enough.


Phantom

[canilash]

I concur with Phantom, the bullet should be too small for a sonic boom. Remembering the heat caused by the reentry, the bullet should also disintegrate upon acceleration.

EDIT: Okay, I admit being wrong. And I knew part of the sound of firearms came from a sonic boom. I remember a documentary on TV where they said silencers slowed the bullets down under sonic velocity. I still say the bullet should disintegrate.

[Fiferguy]

I have a lot of experience shooting modern firearms, and contrary to popular belief, the loud noise cause by the shooting of a gun is due to it's supersonic nature. If you've ever fired a blank cartridge, or a muzzle-loader without any kind of projectile, you'll notice this difference. Yes, there is a loud noise, but it is more of a pop than a bang. The rest of the noise comes from the bullet breaking the sound barrier. If you've ever stood downrange of a shooter, you can attest to this as the farther you are from the shooter, the longer the lag from when the bullet hits to when you hear the report of the rifle.

I wonder though, if the hypersonic nature of the railgun causes it not necessarily to break the sound barrier, but to enter a realm of fluid dynamics that we don't understand yet?

Fifer

[Solarstorm]

Well I am not a physists but I would imagine that the sonic boom that we are talking about is the wave effect that shatters windows and eardrums and such. Bullets do create a sonic boom. However they dont displace enough air to generate the wave effect that most of us associcate with a "sonic boom". Maybe Jason's error caused the bullet or gun to generate a larger wave from firing and thus the sonic boom that later disappeared when he did some more work on the gun.

[Fiferguy]

Could be...but from what I remember (and I could be wrong), Fel described it as a "Nee-Yaa" type sound, but none of the bang that we would associate with a normal gun. So that makes me believe that its hypersonic nature and small size are causing the normal fluid dynamics of a high speed projectile to be different. I could be wrong though...

Fifer

[thisandthat]

I concur with Phantom, the bullet should be too small for a sonic boom. Remembering the heat caused by the reentry, the bullet should also disintegrate upon acceleration.

You can get a sonic boom with a .30 cal bullet.
A silenced wepon uses light power charges so it does not make a sonic boom.
If you are in the hills you can here the sonic boom from kids plinking with .22's.
The sonic boom is not a function of size but of speed and shape.

[Shadowhawk]

I don't know enough about physics of sound to "solve" this issue ("Solve" because it is possible that bullet from Jason railgun/gauss rifle should create sonic boom), but perhaps it is because of the size and agnle of sonic cone created by such fast a bullet.

But I do wonder about other thing. If the bullet is very fast, shouldn't it create joinized/plasma trail, like meteors do?

[canilash]

I don't know enough about physics of sound to "solve" this issue ("Solve" because it is possible that bullet from Jason railgun/gauss rifle should create sonic boom), but perhaps it is because of the size and agnle of sonic cone created by such fast a bullet.

But I do wonder about other thing. If the bullet is very fast, shouldn't it create joinized/plasma trail, like meteors do?

You mean ionized, right? I thought that at the speed it goes, it could compress the air enough to detonate, ionize, or maybe even fusion it. Or fusion itself. Or the hydrogen of water molecules, at least.

Added: I was just thinking, at the speed the railgun shoots, it must need a lot of energy. I do know tat PPGs are powerful, but It just occured to me that maybe a single PPG could power a city block. Jason could simply use the magnetic field created by a railgun, reduce its amperage and use it to create current in a wire. I must return studying my course on electricity and magnetism...

[Blyker]

The Quake2 railgun has a corkscrew tail, and thus this weapon has it as well.

[furry_wolf2001b]

Umm, are we shure that it is the bullet itself thats making(was making) the sound?

Simply traveling thrue the air to be more specifick.

Culd it be something with the gun itself that is making the sound, when it is firing.

Hmm, i dont remeber, is the bullet accelerated in vacume? (the barrell empthy of air)

The coils themselves(and other workings of the gun), are they making anny noise?


Ok these are just some grasping at straws things.

[Lochar]

http://sennadar.plebian.net/forum/viewtopic.php?t=496

[Fiferguy]

Umm, are we shure that it is the bullet itself thats making(was making) the sound?

Simply traveling thrue the air to be more specifick.

Culd it be something with the gun itself that is making the sound, when it is firing.

Hmm, i dont remeber, is the bullet accelerated in vacume? (the barrell empthy of air)

The coils themselves(and other workings of the gun), are they making anny noise?


Ok these are just some grasping at straws things.

It would have to be the passage of the bullet that makes the noise. In a normal gun, there is a small bang from the gun powder burning, but the main noise from the gun comes from the bullet breaking the speed of sound. There are special subsonic rounds that you can buy, but most of these are such low velocities that true shooters won't use them, because their trajectories are like rainbows. Think about it like this, the harder you throw a ball, the straighter the arc. Same goes with a rifle bullet. You want a faster projectile so you can hit at more ranges. Typically, you will sight in a weapon at a set distance, and know what the bullet is going to do for other distances. This gives you an order of accuracy that you know you can hit a target, say hunting. The slower the round, the more the bullet moves, reducing your effective accuracy. Ok...sorry about that tangent. But there is nothing in the rail gun to make any kind of loud boom, by Fel's description. About all you would get, I imagine, is an electronic whine, similar to the toy "Ray guns" that some played with as children.

It wouldn't work to have the bullet start in a vacuum then hit the air as it exits the gun. The change in density at the muzzle would blow the gun up. Forensics experts use a similar property to collect bullet samples from suspects' weapons. They shoot the gun into a large tank of water, then collect the bullet from the bottom. In fact, it's been shown that the more energy the bullet has behind it, the more sudden the stop. It's another reason that you shouldn't hold a gun barrel up to anything and shoot it. It'll blow the muzzle apart on you, potentially injuring you and bystanders.

I still hold to the belief that the projectile is moving so fast as to enter a realm of fluid dynamics that I don't know about. Long range target shooters use a specially shaped bullet to reduce the effect of wind on their shots. I wonder if the velocity of this bullet causes it to instead of breaking the air, to part it--similar to the way an airfoil works.

But if I've learned anything about Fel, it's that he delights in not only torturing his readers, but giving them surprises. Maybe eventually he'll let us in on the secret...*wink wink nudge nudge*

Fifer

P.S. The above comments come from 20 years of gunsmithing and target shooting, so they should be fairly accurate.