Big Cannon help

[stukearney]

Something like that, but we are more highly constrained for size. Yeah we are going for the M777. Why doesn't that make sense?

[POLAND_SPUD]

you've wrote

The idea is to get the UAV 80km away near instantly

That kind of range suggests a MLRS system

besides rocket launch would put a lot less Gs on the UAV during launch so it seemed more appropiate

anyway...
I used specs you mentioned to model it in GGDT
I assumed:
a 14cm burst disk
1L deadspace
extra 300 g for a sabot (barrel ID is 159mm so you need a sabot)
and the pressure -> 80 psi (100psi gives you 112m/s of MV)

[jackssmirkingrevenge]

That suggests a howitzer but that doesn't make any sense

I agree in that if you want your drone to operate far away, it doesn't make sense to fire a UAV out of a gun when compared to delivering it by rocket.

Rockets not only have much softer acceleration than a gun launch but also require virtually no hardware to launch as Hamas are happy to demonstrate:



...assuming of course that your design actually uses a reduced charge to fire the UAV and not just uses the gun barrel as a launch tube for a rocket.

[stukearney]

Gah, really sorry, make that 25-30km, no idea how 80 got in my head.

We use guns due to ease of integrating into existing defense systems. In a previous iteration I build a UAV for a Zuni rocket.

[jackssmirkingrevenge]

We use guns due to ease of integrating into existing defense systems. In a previous iteration I build a UAV for a Zuni rocket.

Is it going to be shot out by a gun charge though and travel to the target area based on that acceleration alone, or use a rocket motor and just use the gun tube to guide it?

[stukearney]

No rocket, acceleration. I've been having heaps of fun designing everything to withstand ~10,000 - 15,000 g's

[POLAND_SPUD]

@jsr
yup exactly

Gah, really sorry, make that 25-30km

Still that's for projectiles optimised for range (high sectional density and a lot of propelant (as the shells can handle that)), I doubt you could achieve more than 15 km. Please excuse me as you probably know better what you're doing, but that's just what I think.

No rocket, acceleration. I've been having heaps of fun designing everything to withstand ~10,000 - 15,000 g's

same as above - range

and again what's the point of designing stuff to handle 10,000 g's when you can use a rocket?


I don't know maybe I shouldn't be saying this as I don't work in this industry but that's just common sense.

[jackssmirkingrevenge]

I doubt you could achieve more than 15 km. Please excuse me as you probably know better what you're doing, but that's just what I think.

According to GGDT's external ballistics calculator, with a generous drag co-efficient of 0.05, you'll get less than a kilometer at 100 m/s - I assume this is for test purposes and the actual intended velocity is much higher.

[POLAND_SPUD]

you'll get less than a kilometer at 100 m/s

I think it's just for testing of the terminal phase of flight (ie. how well the UAV can transition into normal flight)


Now that I think about this whole design I find it extremally impractical. Some aspects of it match the complexity of the excalibur round. That's going to cost a LOT - not sure if you can find someone willing to pay that much for something that could be X times cheaper and have better operational specs when delivered by a rocket


anyway you've asked a specific question and maybe we should not discuss the feasibility of it as we're not experts on this.
The simulation indicates that you can get that over 100m/s with the setup you described at around 80-90psi
Can your tank handle that much ??

[danielrowell]

Now that I think about this whole design I find it extremally impractical. Some aspects of it match the complexity of the excalibur round. That's going to cost a LOT - not sure if you can find someone willing to pay that much for something that could be X times cheaper and have better operational specs when delivered by a rocket

True, but getting permission to use rocket motors of the impulse he needs is no easy task, I'm sure. He would either have to have a certification or permission from some bigwig corporation to use motors of that size. Plus, from a practical standpoint, launching high-impulse rockets several times a day would be MUCH more expensive than using a gun. Also, if his UAVs can survive being launched from a gun, they can certainly survive being launched from a rocket.

On a side note, kudos for making such an awesome project!

[POLAND_SPUD]

plus, from a practical standpoint, launching high-impulse rockets several times a day would be MUCH more expensive than using a gun.

your talking about delivery methods - I am talking about the price of your cargo

A gun launched UAV is bound to be X times more expensive than a UAV delivered by a rocket. Electronics can probably handle acceleration quite well due to small mass and lack of moving parts
but what about optics, servos and stuff ?

I suspect that G hardened version of this ->
http://www.gs.flir.com/products/unmanned/tacfliriii.cfm
will be substantially more expensive than the standard version

[jackssmirkingrevenge]

maybe we should not discuss the feasibility of it as we're not experts on this.

You're being remarkably diplomatic about this, have you stopped drinking

[POLAND_SPUD]

Lol sorry I can't help discussing it... I wish I had his job

[stukearney]

Haha glad you guys find this interesting. Avionics are being protected by encapsulation.

I think it's just for testing of the terminal phase of flight (ie. how well the UAV can transition into normal flight)

Spot on, we just want to test out the parachute/deployment mechanisms first. We are firing up at 70 degrees to get enough height to give it time to deploy out.

Regarding the Gun vs. Rocket. I'm with the rocket guys, easier to design for, potentially more room and more range. But yes from what we have been told and looked at the gun is going to be cheaper and easier to operate over the long run then rockets. Also a lot easier to integrate into existing systems (just another shell over a whole new system). Customer requirement.

The simulation indicates that you can get that over 100m/s with the setup you described at around 80-90psi

I think so, we are using LPG tanks that were previously certified for higher then 120. Hopefully we can get it re-certified after I've taken to it with a welder.

[POLAND_SPUD]

Can you post pics of it? hmm probably not
anyway if you succede we'll find an article on it or a video somewhere on the internets