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Vanguard SLV 2



Vanguard Satellite Launching Vehicle 2 (SLV-2) was launched on 26 June 1958. The flight failed to reach orbit due to premature cutoff of the second stage rocket engine. The program objective was to launch into orbit a fully instrumented "X-ray and environmental satellite" to study maximum variations in intensity of X-rays from the Sun in the 1 to 8 angstrom wavelength bands and to make certain space environment measurements. The purpose of the IGY Vanguard satellite program, run by the U.S. Navy, was to launch one or more satellites into Earth orbit during the International Geophysical Year (IGY).

Mission Profile

Vanguard Satellite Launching Vehicle 2 (SLV-2) was launched from Cape Canaveral, Florida, on 26 June 1958. Liftoff was nominal, but low oxidizer feed pressure caused the second stage rocket engine to shut down after firing for only 8 seconds, 152.6 seconds after launch, resulting in insufficient velocity to arm the third stage for firing and causing termination of the flight. The premature shutdown caused the propellant tank pressures to exceed design values without failing, proving the structural integrity of the tankage.

Spacecraft and Subsystems

The SLV-2 satellite was a 9.75 kg (21.5 lb), 50.8 cm (20 inch) diameter sphere. The spherical shell was magnesium, internally gold-plated and externally covered with an aluminum deposit coated with highly polished silicon monoxide of sufficient thickness to provide thermal control for the instrumentation. 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 the 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. It used an 80 mW transmitter at a frequency of 108.00 megahertz.

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 7200 kg of kerosene (RP-1) and liquid oxygen, with helium pressurant. It also held 152 kg of hydrogen peroxide. It was finless, 13.4 m (44 ft.) tall, 1.14 m (45 in.) in diameter, and had a launch mass of approximately 8090 kg (17,800 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 1520 kg (3350 lbs) Unsymmetrical Dimethylhydrazine (UDMH) and White Inhibited Fuming Nitric Acid (WIFNA) with a helium pressurant tank. It produced a thrust of 7340 pounds (~32,600 N) and had a launch mass of approximately 1990 kg (4390 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 firing for 144 seconds, bringing the rocket to an altitude of 58 km (36 mi), followed by the second stage burn of 120 seconds 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 and including Vanguard SLV-6.

Alternate Names

  • VanguardSLV2

Facts in Brief

Launch Date: 1958-06-26
Launch Vehicle: Vanguard
Launch Site: Cape Canaveral, United States
Mass: 9.75 kg

Funding Agency

  • Department of Defense-Department of the Navy (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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