History of Rockets: Vanguard and Thor

Ethan Wong

July 21, 2023

The Vanguard rocket was developed to put an artificial satellite into space due to the Soviet Union’s success with Sputnik 1 and 2. Designed with a GE X-405 engine, engineers allowed the nozzle to be gimballed, allowing it to be controlled and adjusted without the help of vernier engines. The X-405 engine was powered with kerosine (RP-1) as well as liquid oxygen (LOX) while the 19ft second stage of the rocket used an AJ-10 engine. The rocket itself was tiny despite having three stages (the third stage being only around 5 feet), standing at 72 feet tall and unable to carry a payload larger than 25 lbs. The rocket first launched successfully on March 17th, 1968 carrying Vanguard 1, the fourth-ever satellite in space, which was equipped with solar cells for power. To get an idea of the payload capacity that the Vanguard rocket had, Vanguard 1 was only 16.5 cm in diameter, an extremely tiny spherical spacecraft. While the rocket design never had variations, it did launch three Vanguard satellites throughout 11 launches, featuring 8 defeats in the process. After 4 consecutive failures, Vanguard 2 launched in 1959 on February 17th. Vanguard 3 launched later that year on September 18th. 

Like many rockets, the Thor rocket started its journey as an ICBM. The Thor rockets were left in the hands of the Douglas Aircraft Corporation at the same time the development of the Atlas ICBM rocket was in progress. The missile was a simple design that could be mounted with a warhead, allowing it to be in use as a deterrent during the Cold War, while also being a defense against the Cuban Missile Crisis. Due to the development of the Thor rocket in the 1950s, the U.S. would manufacture the launch vehicle, and transfer it by plane to Great Britain where it could then be targeted toward the Soviet Union at the time. Because of this, the ICBM was less than 70 feet tall because of airplane transportation.

September 20th, 1957 featured the first successful launch of the PGM-17A Thor Intercontinental Ballistic Missile, utilizing kerosene and LOX for propellant. A single LR-79 engine was mounted at the base of the rocket, and two vernier engines were on the sides to help steer the ICBM. A year later, the Thor-Able rocket was launched from Cape Canaveral with no change in the first stage, yet a new Able second stage was also utilized by the Vanguard rockets. Most notably, March 11th, 1980 marked the launch of Pioneer 5 by the Thor-Able; other satellites were launched by the vehicle as well, such as earlier Pioneer tests and Explorer 6. Another variation of the Thor rocket was using an Agena stage for the upper stage, which is commonly used for rockets such as Atlas and Titan.

Thor-Able Star was another variant that enlarged the upper stage while still utilizing its AJ-10 engine. Additionally, it also became the first upper stage capable of re-igniting once in orbit. The Thor-Able Star would carry satellites and serve from 1960 to 1965. The Thor-Delta had its second and potential third stages derived from the Vanguard rocket and launched a total of 12 times with 11 successes. It would later be transformed into the Delta rockets.