Encyclopedia Astronautica
Martlet 2G



mart2g.jpg
Martlet 2G
Canadian sounding rocket. This derivative of the Martlet 2 gun-fired suborbital space probe achieved a higher scientific payload through use of a lighter sabot. 12 were flown before the program was ended.

Although the Martlet 2 series had adequate payload capacity for its primary scientific mission, it was understood from the first flights that the heavy pusher plate, petal arms, and sabot represented a sub-optimal vehicle configuration . About half of the all-up launch weight consisted of the sabot which was promptly discarded after launch. If more of the launch mass was retained after launch a larger vehicle with a greater payload capacity would result - without an increase in the launch weight and without the need to prototype a new gun propellant configuration.

As the HARP Program proceeded a low-priority development program was conducted for a new vehicle with a much lighter centre sabot. This vehicle was designated the Martlet 2G and its design was substantially based on the probes flown on the smaller 5" and 7" HARP guns.

The Martlet 2G had the same launch weight as the earlier Martlet 2's but nearly twice the flight weight and a substantially increased payload capacity. The flight envelope of the Martlet 2G was intended to be identical to the earlier Martlet 2 with a maximum theoretical apogee of 200 km. Only 12 operational Martlet 2G's were flown. Although none of these flights were high altitude tests, the basic concept of the Martlet 2G vehicle configuration was proven.

The Martlet 2G was a dart shaped vehicle 2.27 m (89.5") long and 18 cm (7") in diameter with a flight weight of 159 kg (350 lb). In the place of the earlier pusher plate and petal arms the Martlet 2G used a much lighter centre sabot. This consisted of four blocks that were attached to the vehicle near the centre of balance with each block occupying 90 degrees of the bore circumference. The Martlet 2G sabot was about 46 cm (18") long and was manufactured from three components:

  • A sabot crown, made of aluminium and mated to the vehicle body using buttress threads.
  • A sabot base, made of polycarbonate and machined slightly oversized so that it could be force-fitted into the bore.
  • A polythene obdurator, to seal the gun gases.

After the vehicle had exited the gun muzzle, aerodynamic forces would peel the sabot sections away from the body, freeing it for ballistic flight to apogee. With this type of sabot the tail end of the vehicle was allowed to trail in the gun gases during the launch. It was found that the short duration exposure to the gun gases posed no substantial hazard to vehicle's flight performance.

by Richard K Graf

Payload: 160 kg (350 lb) to a 200 km altitude. Launch Price $: 0.003 million in 1965 dollars. Total Development Built: 12.

Status: Hardware 1967.
Gross mass: 159 kg (350 lb).
Payload: 160 kg (350 lb).
Height: 2.27 m (7.44 ft).
Diameter: 0.18 m (0.59 ft).
Apogee: 200 km (120 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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