While growing up in Cedar Rapids, Iowa, Milton Wright, the Wright Brothers' father, liked to purchase toys for his sons that he hoped would stimulate their imagination. One of the most memorable gifts was a toy helicopter that was designed by the French aeronautical experimenter Alphonse Penaud. Milton gave his sons this gift in 1878, and, though it was a simple device with a stick bound to a four-blade rotor set in a spindle, it had the intended effect-it caused them to dream. Twenty-five years separated the gift of this toy and their invention of the airplane, yet the Wright brothers were convinced it had exerted an important influence. Tom Crouch argued in The Bishop's Boys that toys like these perfectly illustrated the significance of play for technological innovation. He wrote, "rotary-wing toys were to intrigue and inspire generations of children, a few of whom would, as adults, attempt to realize the dream of flight for themselves." If the first powered flight on 17 December 1903 represented a childhood dream realized, it was only the first step in the rapid evolution of the airplane from their flimsy kite-like contraption of wood and cloth to jet airliners and rockets in space. And, as extraordinary as the achievement of powered flight seemed in 1903, before the end of the century, space travel also would become a dream realized. Soviet astronaut Yuri Gagarin first circumnavigated Earth in April 1961, and, eight years later, American astronauts took the first steps for humankind on the Moon. It is with great pleasure that we introduce Realizing the Dream: Biographical Essays in Honor of the Centennial of Flight. These essays in celebration of the Wright brothers' first flight 100 years ago grew out of presentations by a group of prominent scholars in 2003 at a conference sponsored by the NASA History Division and held at the Great Lakes Science Center in Cleveland, Ohio. The volume focuses on the careers of some of the many men and women who helped to realize the dream of flight both through the atmosphere and beyond. These accounts are original and compelling because they examine the history of flight through the lens of biography. Collectively, these individuals helped to shape American aerospace history. There are obviously many other individuals that could, and arguably should, have been included in this collection, but we believe that the cross section of diverse individuals contained in this volume is important because it is symbolic of the dream of flight as a whole. These people all devoted their lives, and sometimes even sacrificed them, to the demands required for its realization. The reasons behind the dreams were diverse. The technological potential first demonstrated by the Wright brothers enabled those who followed them to use flight as a means of racial uplift, gender equalization, personal adventure, commercial gain, military superiority, and space exploration. The history of flight is more than a story of technology; it had important cultural consequences as well, and these are some of the themes that the following biographies explore. We have arranged the essays roughly chronologically, though the careers of the people described here often span more than one period of history. None of the people in this volume were inventors like the Wright brothers, but their contributions to flight were nevertheless significant. They were daredevil pilots, entrepreneurs, business men and women, military strategists, and managers of large-scale technology who advanced the art, science, and business of air and space travel, often through sheer force of character. The final paper serves as an epilogue as well as a tribute to the Wright brothers. It describes a reenactment of their important glider experiments at Kitty Hawk, North Carolina, where the Wrights' childhood dream was first realized.

The NASA History Program was first established in 1959 (a year after NASA itself was formed) and has continued to document and preserve the agency's remarkable history through a variety of products. The NASA History Division serves two key functions: fulfilling the mandate of the 1958 "Space Act" calling for NASA to disseminate aerospace information as widely as possible, and helping NASA managers understand and thus benefit from the study of past accomplishment and difficulties. NASA publishes documents on topics such as: Documentary History, Memoirs, Aeronautics and Space Report of the President, and many more. This is one of those documents.

"Science in Flux" traces the history of one of the most powerful nuclear test reactors in the United States and the only nuclear facility ever built by NASA. In the late 1950s NASA constructed Plum Brook Station on a vast tract of undeveloped land near Sandusky, Ohio. Once fully operational in 1963, it supported basic research for NASA's nuclear rocket program (NERVA). Plum Brook represents a significant, if largely forgotten, story of nuclear research, political change, and the professional culture of the scientists and engineers who devoted their lives to construct and operate the facility. In 1973, after only a decade of research, the government shut Plum Brook down before many of its experiments could be completed. Even the valiant attempt to redefine the reactor as an environmental analysis tool failed, and the facility went silent. The reactors lay in costly, but quiet standby for nearly a quarter-century before the Nuclear Regulatory Commission decided to decommission the reactors and clean up the site. The history of Plum Brook reveals the perils and potentials of that nuclear technology. As NASA, Congress, and space enthusiasts all begin looking once again at the nuclear option for sending humans to Mars, the echoes of Plum Brook's past will resonate with current policy and space initiatives.

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.

During its maiden voyage in May 1962, a Centaur upper stage rocket, mated to an At l a sb o o s t e r, exploded 54 seconds after launch, engulfing the rocket in a huge fireball. In ve s t i g a t i o nre vealed that Centaur's light, stainless-steel tank had split open, spilling its liquid-hyd rogen fueld own its sides, where the flame of the rocket exhaust immediately ignited it. Coming less thana year after President Kennedy had made landing human beings on the Moon a national p r i o r i t y, the loss of Centaur was regarded as a serious setback for the National Aeronautics and Space Administration (NASA). During the failure investigation, Homer Newell, Di rector of Space Sciences, ruefully declared: "Taming liquid hydrogen to the point where expensive oper-ational space missions can be committed to it has turned out to be more difficult than anyone supposed at the outset."