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Martlet 3D

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Martlet 3D

Payload: 90 kg (198 lb). Apogee: 1,850 km (1,140 mi).

All previous Martlet sub orbital vehicles were capable of carrying either light or medium payload masses and the addition of a sounding probe with a heavy payload capacity would have greatly increased the 16 inch gun systems versatility as well as the marketability of any future HARP-type service.

The theoretical performance of the Martlet 3D would have allowed payloads of up to 600 pounds(270 kg) to be launched to an altitude of about 700 NM (1300 km)and lighter payloads of 200 pounds (90 kg) to be lifted to an altitude of up to 1000 NM (1850 km).

The development of the Martlet 4 vehicle was never completed and the Martlet 4A stage (M4 first stage) was not available for use as the Martlet 3D conversion. The Martlet 3D vehicle never entered service.

by Richard K Graf

Payload: 90 kg (198 lb) to a 1850 kg altitude.

Stage Data - Martlet 3D

• Stage 0. 1 x HARP Gun. Gross Mass: 450 kg (990 lb). Empty Mass: 1.00 kg (2.20 lb). Thrust (vac): 127,000.000 kN (28,550,000 lbf). Isp: 365 sec. Burn time: 0.0100 sec. Isp(sl): 43 sec. Diameter: 0.42 m (1.37 ft). Span: 0.42 m (1.37 ft). Length: 36.59 m (120.04 ft). Propellants: Guncotton. No Engines: 1. Engine: 16 in gun. Status: Out of production. The HARP gun, a converted 16 inch naval gun, was used during the 1960's to launch the Martlet series of rocket-launched space probes. Using 450 kg of M8M propellant, with optimum web size, and a maximum muzzle pressure of 4100 atmospheres, the gun had the following performance:
  • 250 kg projectile accelerated at 13,000 peak G's to 2,300 m/s muzzle velocity
  • 500 kg projectile accelerated at 9,000 peak G's to 1,900 m/s muzzle velocity
  • 750 kg projectile accelerated at 6,500 peak G's to 1,680 m/s muzzle velocity
  • 1,000 kg projectile accelerated at 5,000 peak G's to 1,550 m/s muzzle velocity
  'Specific impulse' indicated here is effective specific impulse for a 750 kg projectile. Due to muzzle dynamics, value differs for other masses of projectile. Diameter and length are that for the gun bore.

• Stage 1. 1 x Martlet 4A. Gross Mass: 890 kg (1,960 lb). Empty Mass: 155 kg (341 lb). Thrust (vac): 67.600 kN (15,197 lbf). Isp: 300 sec. Burn time: 30 sec. Isp(sl): 210 sec. Diameter: 0.42 m (1.37 ft). Span: 2.20 m (7.20 ft). Length: 4.00 m (13.10 ft). Propellants: Solid. No Engines: 1. Engine: Martlet 4-1. Status: Study 1966.