The Construction Diary
| Phase 1: Procurement You can't build a cruise missile without parts -- so the first step was to procure all the bits. One of the key goals in this "proof of concept" project, was to purchase all the necessary parts, materials and tools without raising any suspicion.
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Note that although I don't live in the USA, I decided to buy most of the key components from US-based suppliers -- just as a terrorist operating within US-borders would undoubtedly do.
It struck me that the easiest way to procure some of the key parts would be to buy them from eBay, where there are literally millions of transactions occuring every day. This was also a good way to keep the cost down.
I've drawn up a list of parts, tools and materials necessary to get this project going:
- A GPS system with computer interface
- A single-board computer (flight control)
- A radio control system. (testing and flight control)
- Stainless steel sheet (for building the pulsejet engine)
- Various metal-working tools for building the pulsejet engine)
- Expanded polystyrene sheet (for the basic airframe)
- Fiberglass or kevlar cloth, mat and resins (for the airframe)
The GPS System
I purchased a GPS development system through eBay. This provided me with a GPS receiver, antenna, computer interface and the software needed to interface with a flight-control computer.
The product was delivered by international airmail in less than a week and passed through customs without any problems. Subscribers read more...
Total cost: around US$120
The Radio Control Transmitter
The computerized transmitter was purchased over the Internet from an online hobby store. It was delivered by international courier in less than a week and also passed through customs without query.
Note that although our DIY cruise missile won't actually be radio controlled, this equipment is required so that the airframe and engine can be flight-tested before the onboard guidance system is fitted. Subscribers read more...
Total cost: Around US$230
The Radio Control Flight Pack
The receiver and servos were purchased on eBay. However, since the seller would only ship to a US address, it was consigned to an unrelated third party living in The States who forwarded it to me by international airmail. This took around two weeks and, once again, passed through customs without any problems.
Note also that the servos used to control the flight surfaces have been replaced with units designed for very large "1/4 scale" models. The significantly greater strength and torque offered by these servos is essential to cope with the loads imposed by high-speed flight, even when the control surfaces have a fair degree of aerodynamic balancing. Subscribers read more...
Total cost: Around US$150
Flight Attitude Control System
Rather than go to all the trouble of using gyros (which drift and require a lot more software support), the decision was made to use a much simpler infra-red stability system of the type available for model aircraft.
This unit will ensure that the craft flies "straight and level" between GPS-controlled course corrections initiated by the onboard computer system. Subscribers read more...
Total cost: Around US$119
Video Camera and RF Downlink
I decided to include a video camera with RF downlink. The unit was purchased over the Net and promises a transmitter power of 1.5W, operating at a frequency of 1.2GHz. By my estimates, when the receiver is fitted with a reasonably high-gain antenna, this will provide a line-of-site range of more than 10 miles.
Once the craft becomes autonomous, the value of such a camera is really rather limited -- but I may well use this same RF downlink to carry telemetry from the onbard flight control system. This will be invaluable during the testing phase of the project. Subscribers read more...
Total cost: US$130
The Stainless Steel
A single sheet 8'x4' of 0.035" (0.9mm) stainless steel) is far more than is required to build the simple pulsejet engine for this missile.
Since this is a very readily available material with numerous uses, no reason for anyone to question such a purchase. Subscribers read more...
Total cost: Around US$100
Expanded/foam Polystyrene Sheet
This material is commonly used for insulation in refrigeration units and large chillers. As such, it is readily available from a number of suppliers.
It was chosen as the basic airframe material because it is lightweight, easily shaped with simple tools, has a very low radar signature, and is cheap.
An 8'x4' sheet of 4 inch thick material cost me around US$12 and I bought four of them to be used for creating the fuselage and flying surfaces of the missile. Subscribers read more...
Total cost: US$48
Fiberglass Resin, Cloth and Mat
Although polystyrene foam will be used for the "core" of the airframe, it is far to weak and flimsy to be used on its own. For this reason, a layer of fiberglass cloth and epoxy resin is applied over the foam core.
This "composite" construction makes a very strong yet lightweight structure with a low radar signature and is a variation of that used by many homebuilt aircraft such as those designed by Burt Rutan and others.
Fiberglass cloth and epoxy resins are widely used in the boat-building industry so supply is no problem, most marine stores and large hardware chain stores sell gallons of resin and many yards of cloth/mat every day. Subscribers read more...
Total cost: US$150
Other Items
The items above were the first to arrive and provide enough to get started with the core of the project. Further materials and components will be purchased as/when required. Top of my list right now is obtaining a suitable single-board microcomputer to handle the flight control and guidance tasks.
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