Ultimate Launch Controller
This project has been on hold for quite a while and is something I may or may not get back to in future.
Most club launch control systems are a more-or-less integrated collection of simple individual launch controllers. There are typically three main parts to the system: the LCO panel, the relay boxes and the power distribution system. In the AERO-PAC system, there are a number of "banks" which fan out to the individual relay boxes. These systems are connected by wires and setting up a large club range takes a lot of time and effort.
Most of us rocketeers know these systems well from repeated setting up and tearing down. There have been periodic discussions about building an updated system from time to time, but nothing has come of it so far. Usually, the discussions fail because of cost concerns (or sometimes the fear of something new), before an actual design gets developed. In early 2005, I started thinking about this again and decided to start by designing the ultimte system first and worring about cost afterwards.
Critical requirements of the any launch control system:
- Safety: it should be possible to explain to everyone why the system won't light a motor in their face.
- Ruggedness: the parts need to be capable of withstanding rain and dust. They also need to survive being tossed into a crate during hasty tear-down.
- Interchangeability: components will break and they need to be easily swapped out.
- Testability: it must be easy to determine if a component is working correctly.
- Ease of use: it must be easy to use the system since many people will need to launch rockets or pull an LCO shift without significant training.
Additional requirements, which make this the "ultimate" system:
- No wires: a wireless system removes the biggest hassle of setup.
- No measuring: the system would help in laying out the range to avoid measuring distances.
- Better feedback: the system would be able to monitor igniter resistance and report it.
The Design
My proposal is to replace two existing parts of the traditional launch control system with entirely new ones. The LCO console and relay boxes would be replaced with smart, wireless units. (The power distribution system could remain much the same.)
The bank controllers and relay boxes would be merged into a single multi-controller (called a "bank controller"). This bank controller would have a power input (for a standard 12v battery) and several igniter lead outputs (5 or perhaps more). Each bank controller would be identical and would be capable of being used in any part of the range.
Each bank controller would be a smart, semi-independent device with:
- a GPS receiver,
- a wireless connection,
- a high-visibility display (2- or 4-line),
- a buzzer or speaker,
- buttons for igniter testing.
The LCO console would turn into a computer with:
- a GPS receiver,
- a wireless connection,
- a touch screen monitor.
The wireless connections are, of course, to replace the currently necessary wired connections. When the range is first set up, the LCO controller is powered on. Various range setups are stored on the LCO controller and one is chosen (or created on the spot). The console uses its GPS unit to position all range components relative to itself.
When a bank controler is powered on, it uses the wireless connection to locate the LCO controller. (This can be something like Blue Tooth coordination if we're worried about "trojan horse" bank contollers.) The console assigns the bank its pad numbers and location on the range. The person setting up the bank then carries the bank to that location, using the display to guide him. Once the bank is placed, the power distribution and launch pads can be set up using the bank as a reference.
Note that power to the bank controller will be intermittent and it does not necessarily need local memory. However, each bank should have a unique permanent ID. The console can remember assignments as the banks come up again and re-integrate them without manual intervention. Power to the console is also intermittent, but it does have local memory (a hard disk or NVRAM).
Bank Controllers
The bank controllers would all be made identical (but with unique IDs). Each bank controller would be a sealed box, made to protect the antennae and connectors when stacked (or tossed) into a create.
When power is applied, a bank controller:
- gets its GPS location,
- locates the LCO console,
- gets its assigned location,
- gets its assigned pad numbers.
If the controller is not in the correct location, it prompts the user to move it by displaying arrows. It also reads out the minimum distance from the flight line continuously for manual range layout.
When powered on, each bank is in one of three states:
- Disabled: The bank has not made contact with the LCO console. All functions are disabled.
- Disarmed: The bank is fully set up, but currently disarmed. Igniter testing is enabled, but the firing circuit is locked out.
- Armed: The bank is armed and ready to launch rockets. The firing circuit is enabled, and will fire one or more pads when commanded to by the console. However, there is no way to fire from the bank itself. A buzzer sounds when the bank is armed to warn people to stay away.
The bank should have A/D converters for each pad to measure the resistance of each igniter. That way, more info can be given the user than just whether or not there is igniter continuity. An open connection (resistance > 1MΩ) still means the same thing, but a short (resistance < 100mΩ) and a bad igniter (resistance > 20Ω) are good things to report in addition. Also, this info can be reported to the console, providing more information to the LCO.
The bank should also indicate when it is armed to warn people away. A buzzer is probably the most effective, but also quite annoying when the range is closed.
The igniter connections should be designed so that they indicate when a connector is plugged in or not. (Perhaps by using a 4-pin connector with two pins shorted together). There should also be LED indicators for each ignitor showing whether the pad is available.
The igniter connectors on the bank can also be used to read data from external devices. This would allow reading data from a load cell for motor testing right through the system. The data would be transmitted to the LCO console and available to the flier immediately through the WiFi network.
Normally, each output is assigned to a separate pad for normal solid motor ignition. For hybrid systems, more than one output can be assigned to the same pad. For example, a hybrid system requires a fill trigger in addition to the launch trigger. HyperTek systems also provide a dump feature which can also be controlled.
The bank controller should also accept video input from a local CCD camera to allow video capture of the launch. This will be a nice to have for the fliers, but also useful for hybrid launches as the LCO will have a close-up view of the fill process and be able to see the liquid nitrous venting.
The LCO Console
The LCO console is basically a rugged computer with a monitor that can be read in sunlight. It controls one or more bank controllers, splitting up the pad numbers between them as configured during range setup.
The console maintains continuous communication with the banks through the wireless network. The banks will act only as long as communication with the console continues. If communication with the console is lost for more than a short period of time (5 seconds?), the bank will switch to disarmed state if it is currently armed.
The console screen displays a map of the range, with each bank shown in its location (as reported by its GPS receiver). The LCO can arm or disarm banks individually. (It may be desirable to enable more than one bank for drag racing.) There is a single control to "open the range," which disarms all banks. In use, the LCO console is much the same as a launch controller made of switches, with the switches all being softkeys through the touch screen monitor.
The LCO console is just a computer so most of the work on this comonent will be the software. There are two modes in which the software operates: range setup and LCO operation.
Range Setup
Range layout involves several things:
- Establishing the flight line,
- Positioning the LCO table,
- Positioning the banks of pads.
The LCO console helps directly with all these things by taking advantage of the fact that the console and the banks know their location.
LCO Operation
In operation, the console displays a map of the whole range, with all the banks in appropriate locations. Banks can be selected on at a time by touching them. For the selected bank, a row of buttons appears on the bottom showing the pads connected to that bank and their individual status (igniter state). Pads can be armed and disarmed through these buttons.
Since the console is implemented in software, the system can be made as easy to use or as flexible as we like. (Mechanical systems have to choose between flexibility and ease of use because they need to be wired a single way.) For example, in normal launching, you only want one pad at a time armed. However, a mechanical system capable of drag racing is harder to use for normal launching becuase you have to remember to turn off the previous pad before going on to the next. The ultimate launch controller doesn't suffer such limitations because it's easy to make it disarm all but the most recently armed pad for normal launching.
Other Devices
Of course, once we have the system going, it can be expanded endlessly.
One idea is to add a remote "launch inhibit" switch. That would allow the RSO or other "official" observers to prevent a rocket from launching. This would run through the network and the LCO would see exactly what was happening.
Another useful device for range setup would be a surveyer box. This small device would just have a GPS and a network connection. It would be told by the LCO console what location to go to and would prompt the user in the same was as the banks to a location. This would direct placing the flight line or any other features that were drawn on the range plan.