Tag Archives: U.S. Air Force Ballistic Missile Division

11 October 1958, 08:42:13 UTC

Pioneer 1 is readied for launch aboard a Thor Able I at Launch Complex 17A, Cape Canaveral Air Force Station. (NASA Image Number 73-H-787)

11 October 1958: At 08:42:13 UTC (3:42:13 a.m., Eastern Standard Time), Able 2 (later renamed Pioneer 1) was launched from Launch Complex 17A at the Cape Canaveral Air Force Station on the east coast of Florida., on a mission to orbit The Moon. The launch vehicle was Thor Number 130, DM-1812-6. The mission was carried out by the U.S. Air Force Ballistic Missile Division, the Advanced Research Projects Agency (ARPA), and the newly established National Aeronautics and Space Administration (NASA).

The Thor second stage shut down approximately 10 seconds earlier than planned. An accelerometer had cut off the engine because of an incorrect valve setting. As a result, the space probe did not achieve sufficient velocity to escape Earth’s gravity. It reached a maximum altitude of 71,303 miles (114,751 kilometers) at 11:42 UTC.

An attempt to insert the space probe into a 79,970 × 20,000 mile (128,699 × 32,187 kilometers) orbit failed. The internal temperatures were too cold for the stage’s batteries to ignite the solid fuel rocket engine. 43 hours after launch, Able 2 reentered the atmosphere at 03:46 UTC, 13 October 1958, over the South Pacific Ocean.

The Able 2 space probe is today designated Pioneer 1. It was built by the Ramo-Wooldridge Corporation’s Space Technology Laboratory (STL) in Redondo Beach, California.

The Thor Able was a two-stage orbital launch vehicle which was developed from the Douglas Aircraft Company’s SM-75 Thor intermediate-range ballistic missile.

Designated Thor DM-19, the first stage was 60.43 feet (18.42 meters) long and 8 feet (2.44 meters) in diameter. Fully fueled, the first stage had a gross weight of 108,770 pounds (49,337 kilograms). It was powered by a Rocketdyne LR-79-7 engine which burned liquid oxygen and RP-1 (a highly-refined kerosene rocket fuel) and produced 170,565 pounds of thrust (758.711 kilonewtons). This stage had a burn time of 2 minutes, 45 seconds.

The second stage was an Aerojet General Corporation-built Able, a second stage for the U.S. Navy’s Vanguard rocket. It was 21 feet, 6.6 inches (6.57 meters) long with a maximum diameter of 2 feet, 9 inches (0.84 meters), and had a gross weight of 5,000 pounds (2,268 kilograms). It used an Aerojet AJ10-101 rocket engine which burned a hypergolic mixture of nitric acid and UDMH. The second stage produced 7,711 pounds of thrust (34.300 kilonewtons) and burned for 1 minutes, 55 seconds.

The Altair X248 third stage was developed by the Alleghany Ballistics Laboratory for the U.S. Navy’s Vanguard rocket. It was 4 feet, 11 inches (1.499 meters) long, 2 feet, 7 inches (0.787 meters) in diameter, and weighed 505 pounds (229 kilograms). It was powered by a solid fuel rocket engine producing 2,300 pounds (10.231 kilonewtons) of thrust. Its burn time was 38 seconds.

Arrangement of equipment with the Pioneer lunar orbiter. (Drew ex Machina)
A Pioneer lunar orbiter attached to the third stage of the Thor-Able launch vehicle. (U.S. Air Force)

The lunar probe was the fourth stage of the Thor-Able launch vehicle. It was 74 centimeters (2 feet, 5.13 inches) in diameter, 76 centimeters (2 feet, 5.9 inches) long, and weighed 38.1 kilograms (83.996 pounds). The probe’s external shell was constructed of metal and fiberglass. It carried 11.3 kilograms (24.9 pounds) of instruments designed to measure magnetic fields, radiation and micrometeorites. It also carried an infrared camera system intended to obtain close-up images of The Moon’s surface. Pioneer 1 was spin-stabilized, turning 108 r.p.m.

The probe was equipped with a Thiokol TX-8-6 solid rocket engine to decelerate it for entry into lunar orbit. The rocket engine was the main structural component of the probe. There were 8 vernier rockets to correct its trajectory. The Thiokol TX-8 was produced at the U.S. Army’s Longhorn Army Ammunition Plant near Karnack, Texas. It was designed to power the GAR-1 Falcon radar-homing air-to-air guided missile (later designated AIM-4 Falcon). The rocket motor weighed 11 kilograms (24.3 pounds).

© 2024, Bryan R. Swopes