Rocket Technology

In the beginning, the growth of rocket technology in the U.S. received an enormous impetus from the development of the Air Force`s long-range missiles. These programs – Atlas, Thor, Titan, and Minuteman – representing one of the most urgent, complex, and costly tasks ever undertaken by American industry, involved over 200,000 firms as well as many hundreds of thousands of scientists, engineers, and technicians. Selected by the Air Force as systems engineer and technical director, TRW Systems Group coordinated the technical, cost, and schedule aspects of each of these vast efforts.


Atlas, the first U.S. ICBM, was a 1-1/2 stage cryogenic liquid-propellant missile featuring a sustainer engine and two booster engines. The two boosters, visible on each side of the rocket, were jettisoned in flight, leaving the sustainer engine to continue firing until it burned out and the correct ballistic trajectory was achieved. This is why Atlas was called a 1-1/2 stage rocket, it did not truly have a second stage. The reason for this design was that rocket engineers had not completely solved the problem os starting a second stage engine at high altitudes.

The initial flight was made at Cape Canaveral in June of 1957, only a little over 2-1/2 years after development had begun. Athough deactivated in 1965 as a weapon system, Atlas continued to play an active role in the space program for a few years, having served as a versatile and reliable booster for lunar and deep space probes as well as for Project Mercury and Project Gemini, as engine improvements increased its thrust to over 400,000 pounds. Mated with an Agena D upper stage, this vehicle was able to insert in earth orbit a payload of 11,500 pounds.


The intermediate-range Thor, a one-stage cryogenic liquid-propellant missile, took just 13 months to go from drawing board to first flight. It was ready for military operation as an IRBM in December of 1958, just 3 years after starting development – a record for such a vast undertaking. Mated with second and third stages derived from the Navy`s Vanguard booster and dubbed Thor-Able 1, the vehicle saw its first service in the nation`s space effort in August of 1958. In October of the same year, it launched TRW`s Pioneer 1, the world`s first deep space probe. Deactivated as a weapon system in 1963, the Thor became the nation`s most widely used space booster, earning the title of “space-age workhorse”.

It was used with several different upper stage combinations, and was upgraded almost continuously. The early Thor-Delta configuration, based on the original Thor-Able combination, was able to orbit 610 pounds. One of the last improvement in payload capability was seen in Long Tank Thor, which with its three strap-on solid propellant boosters and an Agena D upper stage was able to orbit 2640 pounds.


The Titan program resulted in the development of two weapon systems: Titan I and Titan II. Titan I, a two stage cryogenic liquid propellant missile with first stage thrust of 300,000 pounds and second stage thrust of 80,000 pounds, was first successfully flight tested in February of 1959. Like Atlas, Titan I was deactivated in 1965. The later generation Titan II employed non-cryogenic storable propellants and inertial guidance. With first stage thrust increased to 430,000 pounds and second stage thrust to 100,000 pounds, it offered greater payload weight and increased range, as well as better accuracy.

It could also be launched from underground silos, providing greater security against attack. Still deployed and fully operational as ICBM, Titan II also saw duty in the US space program, notable as the booster for the two-man Gemini capsule. Utilising various improvements to increase thrust, Titan II evolved into an even more powerful vehicle Titan III. One member of this family, the Titan IIIC, featured two 1,2 million-pound-thrust solid propellant boosters, strapped on each side, an improved first stage with thrust increased to 474,000 pounds, and a 16,000-pound-thrust hydrogolic fueled third stage known as a Transtage. Used extensively as by the Air Force as a booster for military communication satellites, TRW`s Vela nuclear detection satellites, and other spacecraft, the Titan IIIC had sufficient thrust to orbit 25,100 pounds.


Studies begun in 1957 to develop a second-generation ICBM which would have less vulnerability to enemy action, be capable of launching in a shorter time, be more mobile and reliable, cost less, and require fewer operating personnel. The ensuing program resulted in the development of the three-stage Minuteman, the first solid-propellant IVBM to become operational in the US. The first version of the missile, Minuteman I, was test-flown from Cape Canaveral in 1961, and later the same year was first launched from an underground silo. The first two flight units (20 missiles) were declared operational at Malstrom AFB, Montana, in 1962.

An improved version, Minuteman II, was first launched in 1964. It incorporated a new second stage engine and an improved guidance system, providing greater range and payload and greater ability to withstand the effects of enemy attack. In 1967, the goal of 1000 operational Minutman was reached.

Development of the next version of the missile, Minuteman III, began in 1967. Minuteman III had an improved third-stage engine and a new re-entry system which allowed even heavier payloads and greater accuracy. A key feature of the new design improvements was their ability to be grafted onto Minuteman II missiles. This resulted in a new weapon system at a fraction of the cost of developing an entirely new one. Dispersed in hardened underground silos throughout seven western states, that prime deterrent force was steadily being updated with the eventual goal of replacing all older models with Minuteman III.

minuteman I

Minuteman I. This image or file is a work of a U.S. Air Force Airman or employee, taken or made as part of that person's official duties. As a work of the U.S. federal government, the image or file is in the public domain