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Launch Control System Plans |
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I designed and built our launch control system during the spring of
2007. After reading a bunch about launch
systems and designs, I eventually combined many needs and a few desires
into a workable design of our own. I prototyped the design and
made still more changes during construction and eventually arrived at
our current working launch control system. The design is
flexible and scaleable to many many pads and for a variety of expected
uses. And it has several safety enhancements in addition to the
required safety features. It uses a Central Control architecture, but
with control for individual independent Pads
too. I hope to expand this in a future design revision to allow
rack or independent launchers for each pad controller.
All pads are centrally controlled, but two pads per launch sequence can be independently owned by members. For example, our system can control launches from external tube, rail, or tower launchers owned by members. Our launcher can control up to 8 pads simultaneously and (by design) is capable of launching all 8 pads (or any combination) at the same time with one fire button. Pads 1-6 are directly mounted on the main rack, with indicators for Pad Select and Launch Current, and Pads 7 and 8 have "Launch Current Only" leads for standalone pads. The design allows Pad Select and Launch Current indicators for all 8 pads, but I haven't determined a simple effect way to put indicator lights on all possible third party pad configurations. That work is ongoing.
Pads 1-6 have interchangeable launch rods of 1/8", 3/16", or 1/4". Rods can be changed on each pad individually between launches as requirements change. Pads 7 and 8 will accommodate virtually any launch system, such as rail or tube launchers. This allows us to launch rockets of reasonable physical size up our max authorized power of G via external pads. Although the current prototype has a fixed launch angle, I have already modified the design to allow adjustable angle by using a second bottom plate attached by piano hinges. Maybe someday I'll modify this prototype! The main rack containing Pads 1-6 is self contained and easy to dismantle and store. To stow the pad, all one has to do is remove the launch rods and store them in the attached rod storage tube, disconnect the control cable, and remove the saw-horse stand using two wing nuts. The entire pad system is highly portable since it is only about 6 feet long by 6" square. I originally selected 1/2" PVC tube with a threaded cap (shown) for the launch rod storage, but later required a change to a 1" tube to accommodate the larger 3/16" and 1/4" rods. Launch current leads for Pads 7 and 8 connect to a terminal strip near pad 6..
DB25 male connectors are used so that standard cables can be used to connect the launch controller. We have a 30' cable currently, but will soon expand to 75' and longer as funds allow, simply by changing out the cable. The cable, of course, connects to the Launch Control Panel. My design includes a Pad Controller with test switches and lights intended to allow high current launches with separate batteries directly at the Pad. The architecture allows for much longer distances between the Launch Control location and the Pad. We expect that as the club requirements grow so will our desire to launch larger and more powerful rockets. Our Launch Control system should provide for this expansion. I've included the circuit diagram for the Pad Controller on this site, but we have not yet built it. I'll leave its functional description for another day. Suffice it to say that the Pad Controller uses relays to switch launch current from local batteries at the Pad to the Launch Clips. I am also working on a continuity test modification to allow flyers to verify igniter continuity when preparing for launch. Eventually, we will expand the launch controller to display continuity to the LCO as well. The Launch Controller itself has all required and several additional features built-in, starting with a Battery Box. The battery box allows simultaneous connection of up to 10 standard 6v lantern batteries to provide 12v of power sufficient for a full day of flying without changing batteries. In our current configuration, Launch current is provided by these batteries in addition to select and status indications both at the pad and on the controller (The Pad Controller modifies this design and places launch pad power separately at the pad). Any standard 12v DC power system will work here, such as a car battery, if needed for still more current. All Launch Control functions, safety features and indicators are located on the Launch Control Panel. We used a standard Pelican 1150 Case to hold all of the bits because -- well, actually it's because it's what we had available. But it perfectly sized for 8 pad select switches, key arming switch, power switch, volt meter, and fire button. The design is scaleable to many pads so expansion requires little more than a bigger box to hold a larger number of switches and indicators. We anticipate that as we grow we will add additional racks of 6 or 8 pads each and apply the same controller design to a bigger launch control box. In addition to standard functionality, our design has a Pad lockout capability so the pad or pads can be independently locked out by people at the pad loading or checking rockets. If the pad is locked out or Ready for Launch, the Launch Control System is notified by signals from the Pad. Launch current is disabled until the Launch Controller Arming Switch and Pad Arming switches are both enabled.
The whole system cost about $500 to build, partly due to the cost of prototyping (ie. parts that didn't work out) and the $35 Pelican Case. I have included the final parts lists for the Pad and Controller on this site. Although the cost seems high for a startup system, we expect it to reap benefits later as we grow. We will be able to launch more with this system in a shorter period of time than if we used individual pads and controllers. Now we can load up 8 Rockets and run a launch sequence for each one without reloading. It should be more interesting for spectators too with less time between launches. The Launch System Debut was at a TRG launch on March 25, 2007. We launched about 40 rockets on A, B and C motors and the system worked great. We used it to control launches from a tiny rail launcher using one of the external pad controls. Other than a healthy coating of black powder smoke dust, it still looks like new.. If anyone out there builds and/or improves our design, please drop me a note and let me know. We're always interested in improving our launch control systems. Thanks in advance. Kevin Yackley, NAR# 86725
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