Author Topic: Scud missiles and GPS (Read 369 times)

Nilsen · « **on:** July 12, 2005, 04:10:51 AM »

how hard would it really be to install and use and off-the-shelf commerical GPS system in say a Scud missile. I could not do it, but would it be hard for someone with a tech background to do so?

What would the problem be really?

the speed of the missile?
the soft/hardware that uses the GPS signal to control the missile?

On a boat almost everyone could afford a gps/plotter/autopilot combo that could send your boat to anywere in the world just by pressing a few buttons so thats not very high-tech at all these days. Ofcourse the speeds/loads are nowere near that of a missile but still.. i cant imagine you would need a genious to make it work, or am i wrong?

The reliability would not be what you get in a purpose buildt high-tech package but something tells me that those countires that uses the Scud really would not care if only half of them worked properly if the other half would be alot more accurate than they are now.

Any thoughts?

Gh0stFT · « **Reply #1 on:** July 12, 2005, 04:56:23 AM »

whats your future plans Nilsen?

Nilsen · « **Reply #2 on:** July 12, 2005, 05:05:22 AM »

LOL!

There is a place in Italy called Maranello that could use some "attention", and the Tactical Tomahawk is abit over my budget

Nah.. was just wondering, and someone else here must have done the same.

Siaf__csf · « **Reply #3 on:** July 12, 2005, 05:41:24 AM »

I think the biggest challenge would be to connect the soviet tube electronics to the GPS.

Nilsen · « **Reply #4 on:** July 12, 2005, 07:00:13 AM »

Quote

Originally posted by Siaf__csf
I think the biggest challenge would be to connect the soviet tube electronics to the GPS.

I think even my dad could fix that. he is brilliant with converters for various useless uses. Its kinda his hobby. he hasnt coverted sand to gold yet, but i bet hes is working on it.

Chairboy · « **Reply #5 on:** July 12, 2005, 09:20:08 AM »

A few years ago, I remember that the accepted wisdom was that civilian GPS circuits would not work at speeds greater then, say, 1,000 mph for some reason. I find it unlikely that was true for long, considering how many people make the circuits, but for a while, it may have been.

With something like a SCUD (which is, essentially, a V2) is that it is a ballistic weapon. To use GPS for navigation, you would need to be tracking the position during boost and re-calculating your target point. You couldn't really use it to 'steer' the missile, the cone of navigation for it is very very small once the boost phase is complete.

GPS would probably be more useful in conjunction with a cruise missile, which can be steered through all phases of flight.

Nilsen · « **Reply #6 on:** July 12, 2005, 09:32:16 AM »

But with some control finns on the warhead section you would not need to make many adjustments with them to radically increase accuracy would you?
The Scuds are accurate enough as they are to bring it within the general area beeing targeted. Its prolly just the last few seconds (depending on their terminal velocity) that the GPS thingy would be needed to make the last adjustments.

Chairboy · « **Reply #7 on:** July 12, 2005, 09:47:13 AM »

At the speeds a Scud comes in, fins would have a real hard time making a difference without breaking up the rocket.

Keep in mind, the SCUD doesn't deliver just a warhead, the entire launch vehicle is coming with, and the center of pressure calculations take this into consideration.

Take a look at ballistic rockets in the US arsenal and note that, as far as I know, none of them use fins for terminal guidance. The M270 MLRS firing ATACMS, the most advanced battlefield ballistic rocket system I know of, doesn't, for example.

Most of the Iraqi modifications to the R series soviet missiles increased range, but at a cost of payload and reliability. Many of the rounds fired disintegrated mid-flight because of aerodynamic stresses. It is, quite literally, rocket science. When a SCUD is coming in at between 7 mach and 9 mach, you're talking serious Gs and a really short period where you can make adjustments, not to mention dealing with spin stabilization.

If you want to use off the shelf technology for high accuracy against distant targets, cruise missiles seem pretty obvious. The costs of developing a new navigation system for a SCUD would be awful high, especially in testing.

Nilsen · « **Reply #8 on:** July 12, 2005, 09:58:13 AM »

Makes sense Chariboy.

What if they made the tip of the missile detachable with a warhead and guidance package?

slimm50 · « **Reply #9 on:** July 12, 2005, 10:15:07 AM »

Quote

Originally posted by Nilsen
Nah.. was just wondering,

That's not the sort of thing most normal people just "wonder" about. I'm reporting you right now, mister I-was-just-wondering.

Chairboy · « **Reply #10 on:** July 12, 2005, 10:25:41 AM »

IANARS, but as far as I can tell, you would still have limited terminal guidance at the cost of significant payload.

A better investment is usually going to be with launch precision and boost phase navigation. For every dollar spent on improving the precision of the course during boost you're gonna get the equivalent of hundreds of dollars spent on terminal guidance with this sort of projectile, as far as I can tell. It seems backwards, but seriously, the challenge of steering something at 9 mach without destroying it is pretty significant, especially considering the type of buffeting you'd have. If you could increase the accuracy of an Iraqi SCUD by more then 10% through terminal guidance, I would be amazed, but again, IANARS, so someone else here might have a better answer.

The way I figure it, you need to start with the CEP of the existing round, then design a system that will maneuver within that circle.

The CEP for the SCUD A was over two miles. It is travelling at one mile per second coming in. You'd need to write a navigation system that would deal with the thickening air during the final few seconds and give appropraite control impulses to avoid overstressing the mechanism. You might be able to improve the SCUD A because of the relatively low speed and high CEP, but nobody uses the SCUD A anymore, it was withdrawn from service in the late 70s.

Take the SCUD D, on the other hand. Coming in at 9-10 mach, it's covering two miles a second at a 45 degree or so angle... but already has a documented CEP of 50 meters (according to some online sources, I don't know the actual numbers). Terminal guidance will give you little return, AND it's harder to implement. Not a winning combination, especially considering the already limited payload size.

Have I mentioned how well suited cruise missiles are yet for low cost, off the shelf, super high precision munitions yet?

Nilsen · « **Reply #11 on:** July 12, 2005, 10:32:24 AM »

Quote

Originally posted by Chairboy

Have I mentioned how well suited cruise missiles are yet for low cost, off the shelf, super high precision munitions yet?

I belive you have.. but but..ah nevermind

Cruise missiles are so dull.. they juts kinda cruise to their target. No real shock and awe!

But ok, ill settle for making me a cruise missile if you are gonna make that much of a fuss.

LOL Slimm! My intentions are pure as snow.. promise.

Chairboy · « **Reply #12 on:** July 12, 2005, 10:44:00 AM »

I expect this conversation is part of a business plan you have on offering high speed package courier service to companies that absolutely positively must have that parcel posted post-haste to Peoria for Patterson?

One of my blue-sky ideas has been to adapt a cruise missile project I built a few years ago into a personal courier. I'd leave it ready in a vertical launcher in the backyard (it used a .44 size trainer as the vehicle) and then, to impress my friends, I'd call my wife and say 'Hey honey, I left my office keys at home on the counter, could you drop 'em in the courier? I'm at (latitude/longitude)'. She'd put it in the little parachute egg attached to the bomb-release, then type in the target and press the launch button. Electric starter/glow plug umbilical would start up the motor, my OOPIC launch circuit would run it for a few seconds to get it warmed up and verify RPMs and upload the coordinates through the break-away serial connector, then a servo would pull the pin on the bungee launcher. It'd throw it up in the air, the autopilot would circle it up to 500-1000 feet or so and then beeline towards my coordinates, dropping the payload over me. Then it'd fly back home and fire the off-the shelf R/C recovery chute and drift down to somewhere in my backyard for recovery.

Some day, I'll dust off the ol' girl. The FMA Co-pilot really simplifies a lot of the stabilization needs it has, I should be able to steer by rudder alone for course instead of trying to actively keep it on keel using the accelerometers I was using before.