SUMMARY

   This NAR R&D report describes the concept, design, and construction 
of a complete 32-pad launch control system developed for the Monroe 
Astronautical Rocket Society (MARS), NAR Section #136 in Rochester, NY.   
The project balances a variety of important goals — such as safety, 
reliability, ruggedness, and ease of use  —  as well as the overall 
cost.  The system includes all components for an expandable range 
layout.

    The equipment employs several innovative features which were 
designed to solve common launch system limitations:
  The main control console uses a digital rotary encoder to select the 
pad. This eliminates the accidental launching of multiple rockets with 
the typical array of toggle switches, and it solves the problem of 
finding a 32-position mechanical switch.  A reliable digital control 
circuit replaces the mechanical switches for long-life operation.
  The main control console gives visual continuity indication for all 
pads simultaneously. There is no need to select the pad to check the 
igniter. This feature allows for faster operation on a busy rocket 
range.
  Each pad control box incorporates a high-current relay with the 
option of adding a local pad battery at any launch pad (for clustering, 
or distant pads). All pad boxes are interchangeable   —  for model 
rocket pads, high-impulse pads, or "away cells"  —  allowing the widest 
variety of range layouts using the same equipment.
  Each pad control box has a novel continuity circuit which produces a 
variable pitch tone to indicate igniter quality.  A good (low-
resistance) igniter gives a higher frequency tone, and poor (higher 
resistance) igniter gives a lower frequency tone. Problems such as  weak 
igniters or dirty clips are audible both at the pad and at the main 
controller.
  The pad boxes have several safety features:  3-way toggle switch for 
TEST-OFF-ARMED modes;  a pulsing tone when in the ARMED position; and a 
warning tone for "stuck relay" when in the TEST position.
  The cost of cabling is greatly reduced by using a single pair of 
wires for both the launch signal to a pad and the continuity signal from 
a pad. A third wire is used only when supplying power from a centrally-
located battery; in this case, low-cost standard outdoor power cords are 
used.

    Detailed design information for all system components is included in 
this report.  The appendices contain schematic diagrams, circuit board 
layout drawing, parts lists, and vendor addresses, enabling others to 
reproduce the whole system.

    This project required significant effort by the authors over a 6-
month period to design, build, and test the system.  Much time was spent 
locating quality low-cost parts, and modifying the design to use these 
parts, but maintain ruggedness and reliability.  Many portions of the 
construction effort were shared by several members of the MARS section.

    The new MARS launch system has been used successfully at recent 
launches, including this year's National Sport Launch at Geneseo, NY 
with over 600 flights on the 4th of July weekend.