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Vanguard SLV 6



Vanguard Satellite Launching Vehicle 6 (SLV-6) was designed to carry a small spherical satellite into Earth orbit to study solar heating of Earth and the heat balance. A faulty second stage pressure valve caused a mission failure.

Mission Profile

Vanguard SLV-6 launched from Cape Canaveral, Florida, at 20:16 UT (4:16 p.m. EDT) on 22 June 1959. The second-stage pressure regulator valve designed to control helium flow, which forces second stage propellant into the engine, did not respond to command and did not fully open. Pressure built up within the helium reservoir and could not be relieved as it heated up, causing rupture about 40 seconds after the second-stage engine separated. The helium tank burst at an altitude of 65 to 80 km (40 to 50 miles). The rocket rolled over in a ballistic trajectory at an altitude of about 145 km (90 miles). The third stage ignited before plunging into the Atlantic Ocean some 500 km (300 miles) northeast of Cape Canaveral.

Spacecraft and Subsystems

The SLV-6 satellite was a 10.8 kg (23.8 lb), 50.8 cm (20 inch) diameter sphere. The shell was composed of magnesium alloy and the interior was pressurized. The payload instrumentation package was mounted in the center of the sphere. The package was arranged in a cylindrical stack with mercury batteries at the bottom, followed by the minitrack tracking system electronics, the environment electronics, the telemetering instrumentation, and the experiment electronics. Below the package at the bottom of the sphere was the separation device, a spring loaded tube with a timer designed to push the satellite away from the third stage after orbit was reached. At the top of the interior of the sphere was a pressure gauge. Four 30-inch spring-loaded metal rods were folded along the equator of the sphere and would protrude radially outward when deployed, acting as a turnstile antenna. Mounted at the end of each antenna rod was a thermistor to measure solar heating processes. Two transmitters were used, one of 10 mW broadcasting at 108.00 MHz and one of 100 mW at 108.03 MHz.

Launch Vehicle

Vanguard was the designation used for both the launch vehicle and the satellite. The first stage of the three-stage Vanguard Test vehicle was powered by a GE X-405 28,000 pound (~125,000 N) thrust liquid rocket engine, propelled by kerosene (RP-1) and liquid oxygen, with helium pressurant. It was finless, 13.4 m (44 ft.) tall, 1.14 m (45 in.) in diameter, and had a launch mass of approximately 8180 kg (18,000 lbs. wt.).

The second stage was a 5.8 m (19 ft.) high, 0.8 m (31.5 in.) diameter Aerojet-General AJ-10 liquid engine burning Unsymmetrical Dimethylhydrazine (UDMH) and White Inhibited Fuming Nitric Acid (WIFNA) with a helium pressurant tank. It produced a thrust of 7500 pounds (~33,300 N) and had a launch mass of approximately 1980 kg (4350 lbs. wt.). This stage contained the complete guidance and control system.

A solid-propellant rocket with 2350 pounds (~ 10,400 N) of thrust (for 30 seconds burn time) was developed by the Grand Central Rocket Co. to satisfy third-stage requirements. The stage was 1.5 m (60 in.) high, 0.8 m (31.5 in.) in diameter, and had a launch mass of 194 kg (428 lbs.). The thin (0.076 cm, 0.03 in.) steel casing for the third stage had a hemispherical forward dome with a shaft at the center to support the satellite and an aft dome fairing into a steel exit nozzle.

The total height of the vehicle with the satellite fairing was about 21.9 meters (72 feet). The payload capacity was 11.3 kg (25 lbs.) to a 555 km (345 mi.) Earth orbit. A nominal launch would have the first stage bringing the rocket to an altitude of 58 km (36 mi), followed by the second stage to 480 km (300 mi), whereupon the third stage would bring the satellite to orbit. This was the same launch vehicle configuration, with minor modifications, as used for Vanguard TV-3 and all succeeding Vanguard flights up to this one.

Alternate Names

  • VanguardSLV6

Facts in Brief

Launch Date: 1959-06-22
Launch Vehicle: Vanguard
Launch Site: Cape Canaveral, United States
Mass: 10.3 kg

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Space Physics
  • Earth Science

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams



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