Artillery Question.

[Kirill S.]

Can someone explain to me how thw VT works?

[Agua Perdido]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Kirill S.:

Can someone explain to me how thw VT works?<HR></BLOCKQUOTE>

VT artillery has a special fuze so the shells always airburst (unlike normal point-detonating shells which have to hit a tree or something to burst in the air). Before VT, gunners would try to do this by setting a time fuze to detonate the shell just before it hit the ground. Given how fast the shell is going, and how close it is to the ground when you want it to go off (at least compared to its total flight time), you can see where this would be tricky, to say the least. The gunners would set the fuses for a certain time, and hope it worked out it.

VT stands for "variable time," although the fuzes weren't actually clocks at all. VT fuzes were small radar sets in the nose of the projectile. They'd be set to go off a certain distance above ground level. When the fuze detects that the shell is 20 feet above the ground (or whatever), it sets off the shell.

VT fuzes were originally developed for anti-aircraft use, where you have the same problem. You either have to hit a small, fast plane dead-on, or set the timer to detonate the shell when you think it'll be close to the plane. With the VT fuze, the radar in the shell detects if passes within so many feet of a metal object (the plane), and sets off the shell. You're now faced with the much-easier problem of trying to get your shell close to the plane, instead of hitting it dead-on, or guessing exactly how many seconds it'll take the shell to get to it.

And, yes, the shells would take some finite amount of time to arm, so they wouldn't be triggered by radar return from the ground as they were being shot out of the gun.

Hope this helps.

Agua Perdido

[Edited because I haven't had enough coffee yet. Grogs are welcome to fill in appropriate details. Yes, they really had the technology to created a miniaturized radar set that would fit in the nose of an artillery shell. This is only enough electronics to say, "hey, there's something 20 feet away!" We're not talking AWACS.]

[ 09-19-2001: Message edited by: Agua Perdido ]

[chrisl]

Here's a few pages from a quick search on yahoo. I saw a page a while back (from a URL posted on this board) that had the whole history of the development of the VT fuze and its application, but didn't bookmark it.

fuzes and shells

more fuzes

site with good details

Essentially they're a simple RF (radio frequency) transmitter and receiver. When the fuze approaches something (a plane or treetops or the ground) the amplitude of the reflected signal is increased. The reflected signal (picked up by a simple receiver) is mixed with the transmitted signal, probably resulting in something like an audio frequency signal (easier to make circuits for) which is used to fire a detonator. This is based on a quick skim of the last site listed. Do a little reading on the web for more detail.

(I hadn't scrolled all the way down when I started typing, but it looks like the last link I listed is the one (or pretty similar) with the whole history and details of the VT fuze. Enjoy.)

[ 09-19-2001: Message edited by: chrisl ]

[xerxes]

VT shells are supposed to always go off in the air, but they don't. I'm not sure about exact %'s but maybe around 1/2 hit the ground in CM. This confused me about what artillery was hitting me until I tested and found out that they don't all go off in the air.

-marc

[Kirill S.]

Thanks all!