Build Your Own Cruise Missile

WegianWarrior writes "Bruce Simpson, the man behind one of the more interesting site about pulsejets on the web, has launched a project to build a US$5000 DIY cruisemissile - just to prove that it can be done, since some said his earlier article about it was off the peg. Bruce has also designed and placed on his site a non-weld pulsejet you can build with simple tools, a 2D airflow modeling rig and a new valve/injector design for conventional pulsejets (according to the first page on his site, this new design is placed in the public domain)." We linked to his pulsejet pages about two years ago.

Comments

this raises some interesting questions indeed ...

[DataShark]

besides the obvious *geek* factor this kind of *experiments* and demonstrations should make us all stop to think a bit ...

how do we prevent terrorist from using this kind of stuff ?

limiting acces to knowledge (with DMCA style laws)?

creating a orwellian policial state where all are suspect ans subject to vigilance (and who controls the vigilantes) ?

limitating the publication of (now) public-domain stuff ('cause it can be used to devilish ends) ?

the RIAA/DMCA people already want to control what could go on the net, and that is, maybe, only the beggining (see China - although there 's hope there - see the massive failure of the SARS coverup) so maybe it is time to start thinking about how to mantain the net free and at the same time this planet a safe planet to stay ...

just my two uros,

cheers from Portugal

Not too hard

[Animats]

He's really just building a model airplane with a pulse-jet engine. The engine technology is basically that of a WWII V-1. But the guidance will be far, far better. V-1 "buzz bombs" had trouble hitting the right city.

The impressive thing about cruise missiles is the multi-thousand mile range. That's achieved with very clever turbojet engine design, and some of that technology is still classified. Still, it's decades old.

(It's annoying that general aviation is still putt-putting around on reciprocating engines, decades after everything big went turbine.)

Re:this raises some interesting questions indeed .

[gfilion]

how do we prevent terrorist from using this kind of stuff ?

Dammit, a bunch of teenagers with box cutters have fly jumbo jets in the WTC. They had about 200 times more explosive in these jets than in one of these missiles and their equipement cost was box cutters and airplane tickets. Why would they want to build one of those missiles?

You have to solve the weakest link, not the sexy link.

Now I'm putting my aluminium foil beanie back on.

Williams Jet Engine

[Latent Heat]

I heard (in Aviation Week - aka AvLeak) that some dotcom entrepreneur dudes crossed over to work on a 7-person jet taxi -- the idea was for the price of first class airfare you would have a nationwide version of a ride-share cab system. They were going for some ridiculous price point (like half a million for a jet -- you can hardly get a prop plane for those bucks these days). They were going to use a pair of Williams mini fanjet engines of the type used on cruise missiles. Those Williams engines are a whole 'nother story just by themselves -- like they take solid blocks of titanium and use an NC machine to mill out the whole rotor assembly for one of these things in one piece.

Anyway, the aircraft went through its inevitable weight growth (like software bloat when you keep adding features to a package) and it has outgrown the Williams jet engines, and they begged Williams to come up with a higher thrust version, but Williams has a good thing going with the cruise missile and said nothing doing about changing their design. Trouble is that the next tier of jet engine costs ten times as much which means the half mil price tag on the jet plane is out the windows, so I don't know what is happening.

Re:Good luck

[uberdave]

It is not difficult at all, and he is using off the shelf technology. This will give him straight, level flight regardless of wind, or minor design imbalances. GPS units are relatively cheap. The only other thing you need is a microcomputer to glue it all together. A PIC microcontroller can do the job for less than $20.

As a matter of fact, check out this site. GPS navigation of model airplanes has been around for at least seven years already.

Before a flight, Montgomery programs into a laptop computer the path that he wants the aircraft to follow. This information then is downloaded into the airplane's onboard computer. After placing the plane on the runway and starting the engine, he pushes a single button, the aircraft takes off, flies the preprogrammed course and then lands all by itself.

Averaged over a kilometer course, the deviation in the aircraft's position from the programmed course was typically less than 0.5 meter horizontally, 0.25 meter vertically and 0.25 meters per second in air speed, Montgomery reported.

"Carrier differential GPS is accurate enough for most purposes, so you don't need a lot of expensive equipment," he said.

The only difference I see is that this guy is using a jet powered craft, and is calling it a cruise missile. Other than that, it is the same thing.

Oh, and by the way, the FAA has no jurisdiction in New Zealand.

Re:this raises some interesting questions indeed .

[mkldev]

With a little bit of effort, assuming the engine can be started and stopped at will and has reasonably accurate guidance, this could be used for other things... like replacing traffic helicopters over urban areas with relatively safe rocket-powered cameras that fly around over the city until they're low on fuel, then fly to an appropriate location and land for refueling.

Before you say that this is nuts, think about this: helicopters are far more dangerous than any airplane. There have been a total of 21 deaths to date in U.S. commercial airplanes this year according to the NTSB. That's based on up to 150,000 flights per day.

So far, the U.S. Military, has already seen 29 helicopter deaths (and 8 additional British casualties in one of those crashes), and at least one other minor crash with no fatalities, and this is not including any that resulted from being under fire. That's based on a few hundred flights per day in Iraq, so I'm guessing a few thousand worldwide. Oh, and that's total flights, not helicopter flights. I doubt the percentage of helicopter flights is particularly high... maybe a couple of hundred helicopter flights per day as a high estimate.

That would make helicopters about 1,000 times as dangerous as airplanes. Lest you think this is a fluke of the way the military uses aircraft, the statistics on the crash rate of helicopters in Alaska should tell you otherwise. The only problem is that airplanes fly too fast for people to get a good view of what's going on in terms of ground traffic.

Enter the cruise missile. Fly ten of them around, snapping pictures and shooting video clips and periodically dumping the footage back via 802.11b networks on the ground. Near-instant gratification, and without putting your staff at risk.

Not to mention that if a blimp is cool, a missile must be... well, really cool. :-)

Re:Good luck

[drinkypoo]

Perhaps a short description of the actual process involved will illustrate your point as well.

As you say, you could use a PIC. You can't get something as accurate as a tomahawk this way; you will have to settle for hitting a building as opposed to flying it through a window of a building. (Since GPS is supposed to be accurate to about 15 meters or so, worst case, with SA off, and most buildings are more than 30 meters in at least one dimension, hitting the building is pretty reasonable.)

The craft will of course not always be making a straight, level flight. There are environmental issues. But a course correction every second or two should be sufficient.

The GPS can deliver hyper-accurate time, and fairly accurate position. From these things one can compute one's airspeed and the direction one is heading. It is then a simple matter to determine which direction one needs to turn to correct one's course.

One would plot a series of waypoints with some sort of computer software, possibly some sort of freely available GIS package, using maps available from the USGS. Once the craft is launched it will immediately begin determining which way it must turn to head to the waypoint. The little gyro replacement will provide straight and level flight when desired. Servos are trivial to control with off the shelf hardware, like a basic stamp for example, it's nice to use a dedicated microcontroller just for servo control so you don't have to tie up your primary microprocessor doing something that silly. You could also just build some custom hardware for it since they're pulse rate (or pulse width?) controlled. It would be a relatively uncomplicated task.

Now, a tomahawk missile is capable of recognizing its target by image, and it can dodge things in its path. Obviously it has significantly more processing power than the machine we're describing. However, my point was hitting a building is easy, not flying through a window, again, as the tomahawk supposedly can. (They claim a 1 meter square hit box.) All we really need to do is follow waypoints, which we can precompute on our launch control system. As the comment above this one points out, doing so will be amazingly trivial. I suspect the poster mentioned a PIC chip because they are insanely cheap and they speak RS232 serial with nothing more than something to raise voltages, for which there are several standard solutions readily available. This allows trivial interfacing to the GPS. IIRC the Basic Stamp also provides RS232, so a pic with enough legs could speak serial to both the servo controller (at a suitably high speed) and the GPS. You only need TX and RX for each connection, because the only other connection to do about 19.2k on a good day is a ground. With four wires to the servo controller you could do higher transfer rates, or reliably get 19.2k, which should be plenty.

In other words, using GPS makes this fairly trivial. The only real defense against it is GPS jamming, since it will be small and reasonably radar-transparent to the point where if it is flying low enough the only way you will spot it is visually, and good luck to you on that front.

The next step beyond this is using radar or laser imaging to find the ground and various obstacles, and apply enough processing power to the problem to make it able to dodge trees, phone poles, aircraft (unless they're your target), and so on. That does make the problem dramatically harder, and raises the cost of the electronics by several orders of magnitude, but of course it is still within the ability and budget of the more determined and wealthy hobbyists. This necessarily means that a hostile organization with some fairly lucrative funding source, such as drugs or oil (similar compounds from a financial standpoint) could put whole fleets of them into the air.

The next step after that would be inertial tracking so that it could still operate when GPS is jammed. After that, you want to do EMP hardening, which is probably more expensive than everything else put together.