Encyclopedia Astronautica
Martlet 3E



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Martlet 3E
Canadian sounding rocket. The Martlet 3E vehicle was designed to take advantage of the portability of the HARP 7 inch guns. Unlike the big fixed 16 inch guns the 7 inch HARP guns, were portable and could be relocated to conduct launches from a wide variety of sites. It was soon determined that a gun-launched rocket vehicle for the 7 inch gun would have a similar performance to the Martlet 2 glide probe launched from the fixed 16 inch guns. Launch costs would also be about the same.

The Martlet 3E was a full-bore, rocket-assisted, Fiberglas airframe vehicle 88.5 inches (2.25 m) long and 7.15 inches (18 cm) in diameter. The vehicle used six flip-out fins for stability, a straight tapered nose cone, and the recently-developed hydrostatic containment technique to support the rocket grain during launch. The launch weight of the Martlet 3E vehicle was 135 pound (61 kg) without payload, of which 94 pound (43 kg) was rocket fuel.

The Martlet 3E was initially designed to be launched at a velocity of 1200 m/sec (4000 ft/sec) from the HARP 7 inch guns with a 12 second ignition delay and a seven second rocket motor burn time. The specific impulse of the rocket motor was 280 sec./vacuum. The theoretical performance of the 3E would have allowed a 20 kg payload to be lofted to an altitude of some 250 km - well in excess of the Martlet 2 vehicles performance envelope. Higher launch velocities would have allowed heavier payloads or higher altitudes to be realised.

Considerable research went in to the development of the Martlet 3E with numerous test launches. Individual test programs were conducted to address design concerns with the rocket motor grain hydrostatic-support technique, the structural integrity of the motor's Fiberglas airframe throughout the launch cycle (including case wear), the new flip-out fins, and other aspects.

Most of the development flights of the Martlet 3E were conducted using surplus 155 mm smooth-bore guns (6.25 inch) in place of the 7 inch (7.17 inch actual bore diameter) guns. There were only a limited number of 7 inch guns available. The 155 mm smooth-bore guns were available in larger numbers and were expendable if development problems occurred. Once the primary design problems of the 3E were worked out it was intended to scale the design up from the 6.25 inch to 7.17 inch. The final high altitude vertical flight testing was to be conducted with the 7 inch gun systems.

With the launch costs of the Martlet 3E in the same range as a Martlet 2 vehicles it was intended that once the 3E became operational it would replace the Martlet 2 as the primary atmospheric sounding vehicle for the HARP Program. The use of the 3E over the Martlet 2 would allow portable soundings to be conduced all over the world. This would also free up the 16 inch gun for the future development and operation of a gun-launched satellite vehicle.

by Richard K Graf

Payload: 20 kg (44 lb) to a 250 km altitude.

Stage Data - Martlet 3E

  • Stage 1. 1 x Martlet 3E. Gross Mass: 61 kg (134 lb). Empty Mass: 18 kg (39 lb). Diameter: 0.18 m (0.59 ft). Span: 0.61 m (2.00 ft). Length: 1.48 m (4.85 ft). Propellants: Solid. Status: Study 1963.

Gross mass: 155 kg (341 lb).
Payload: 20 kg (44 lb).
Height: 2.15 m (7.05 ft).
Diameter: 0.18 m (0.59 ft).
Apogee: 250 km (150 mi).

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Associated Countries
See also
  • Gun-launched Artillery dominated military ballistics from the earliest use of gunpowder. In 1865 Jules Verne could only realistically consider a cannon for a moon launch in his influential novel. Even after the rocket established its primacy as a method of accessing space, Canadian Gerald Bull began a life-long struggle to use guns for cheap access to space. His successes could not generate funding to continue. Others since then have pursued the technology, convinced it was the only way for low-cost delivery of payloads to orbit. More...
  • Martlet In 1962-1967 Canada's Gerard Bull led development of the Martlet system for gun-launched access to space. The program was cancelled before the objective of gun launch to orbit was attained. More...

Associated Manufacturers and Agencies
  • Bull Canadian manufacturer of rockets, spacecraft, and rocket engines. Bull, Canada. More...

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