During its maiden voyage in May 1962, a Centaur upper stage rocket, mated to an Atlas booster, exploded 54 seconds after launch, engulfing the rocket in a huge fireball. Investigation revealed that Centaur's light, stainless-steel tank had split open, spilling its liquid-hydrogen fuel down its sides, where the flame of the rocket exhaust immediately ignited it. Coming less than a year after President Kennedy had made landing human beings on the Moon a national priority, the loss of Centaur was regarded as a serious setback for the National Aeronautics and Space Administration (NASA). During the failure investigation, Homer Newell, Director of Space Sciences, ruefully declared: "Taming liquid hydrogen to the point where expensive operational space missions can be committed to it has turned out to be more difficult than anyone supposed at the outset." .After this failure, Centaur critics, led by Wernher von Braun, mounted a campaign to cancel the program. In addition to the unknowns associated with liquid hydrogen, he objected to the unusual design of Centaur. Like the Atlas rocket, Centaur depended on pressure to keep its paper thin, stainless-steel shell from collapsing. It was literally inflated with its propellants like a football or balloon and needed no internal structure to give it added strength and stability. The so-called "pressure-stabilized structure" of Centaur, coupled with the light weight of its high-energy cryogenic propellants, made Centaur lighter and more powerful than upper stages that used conventional fuel. But, the critics argued, it would never become the reliable rocket that the United States needed. Others, especially military proponents of Centaur, believed that accepting the challenge of developing liquid-hydrogen technology was an important risk to take. Despite criticism and early technical failures, the taming of liquid hydrogen proved to be one of NASA's most significant technical accomplishments. Centaur not only succeeded in demonstrating the feasibility of liquid hydrogen as a rocket fuel, but it also went on to a brilliant career as an upper stage for a series of spectacular planetary missions in the 1970s. Ironically, this success did little to ensure the future of the Centaur rocket. Once the Shuttle became operational in the early 1980s, all expendable launch vehicles like Centaur were slated for termination. Centaur advocates fought to keep the program alive.

The story of how liquid hydrogen was put to work is told in two great books. Part 1 is this book, "Liquid Hydrogen as a Propulsion Fuel, 1945-1959", by John L. Sloop (NASA SP-4404). Part 2 is "Taming Liquid Hydrogen: The Centaur Upper Stage Rocket: 1958-2002", by Virginia P. Dawson and Mark D. Bowles (NASA SP-2004-4230).

Access—no single word better describes the primary concern of the exploration and development of space. Every participant in space activities—civil, military, scientific, or commercial—needs affordable, reliable, frequent, and flexible access to space. To Reach the High Frontier details the histories of the various space access vehicles developed in the United States since the birth of the space age in 1957. Each case study has been written by a specialist knowledgeable about the vehicle described and places each system in the larger context of the history of spaceflight. The technical challenge of reaching space with chemical rockets, the high costs associated with space launch, the long lead times necessary for scheduling flights, and the poor reliability of the rockets themselves show launch vehicles to be the space program's most difficult challenge.

The book documents Glenn's many research specialties over those 75 years. Among them are early jet engines and rockets; flight safety and fuel efficiency tested in premier icing and wind tunnels; liquid hydrogen fuel which, despite skeptics like aerospace engineer Wernher von Braun, helped the U.S. win the race to the moon; and electric propulsion, considered key to future space flight. Space enthusiasts, aviation personnel, aerospace engineers, and inventors may be interested in this comprehensive and milestone volume. Other related products: NASA at 50: Interviews With NASA\'s Senior Leadership can be found here: https: //bookstore.gpo.gov/products/sku/033-000-01360-4 Other products published by National Aeronautical and Space Administration (NASA) can be found here: https: //bookstore.gpo.gov/agency/550