Editing Project HARP (section)

=== Martlet 4 ===
By July 1964, the Marlet 4 program pursued developing an orbit capable multi-stage rocket system to be launched from the 16" Barbados gun. Two versions of full-scale orbital launch vehicle projectiles were proposed in the Martlet 4 series. The first was to have used three solid rocket motor stages and was planned to orbit approximately 50 pounds of payload. The second used liquid rocket motors and was planned to have orbited 200 pounds of payload. Both were about {{convert|28|ft|m}} long and {{convert|16|in|mm}} in diameter, weighing about {{convert|2900|lb}} at launch. However, no Martlet 4 vehicles were built; the project was halted before the design was completed.

==== Martlet 4 Control Systems ====
A guidance and control system were developed for the orbital mission by Aviation Electric Limited of Montreal under the direction of McGill-BRL-Harry Diamond Laboratory group. [[Infrared]] horizon sensors and sun sensors were included in calculating [[Spacecraft attitude control|vehicle attitude]]. Information for on-board sensors was to be processed by the logic module, which provided commands to a cold gas thruster system which in turn adjusted the vehicle's orientation. The components of the guidance and control assembly were integrated into a 6.25-inch diameter test projectile. Sun sensors, horizon sensors, telemetry packs, receiving/transmitting antenna, hydraulic systems, logic modules, and gas thruster [[Spacecraft attitude control|attitude control]] systems were all test-fired to approximately 10,000 g's.<ref>{{Cite book|last=Bull, G. V. (Gerald V.)|title=Paris Kanonen--the Paris guns (Wilhelmgeschütze) and Project HARP : the application of major calibre guns to atmospheric and space research|date=1988|publisher=E.S. Mittler|others=Murphy, C. H. (Charles H.)|isbn=3-8132-0304-2|location=Herford [Germany]|oclc=24066021}}</ref>