Stofan joined the Lewis Flight Propulsion Laboratory in 1958, shortly before it became part of the newly formed National Aeronautics and Space Administration (NASA) as the Lewis Research Center. He became a research engineer in the Propulsion Aerodynamics Division, where he researched the use of ejector nozzles in supersonic aircraft. These nozzles subsequently found use in the Lockheed SR-71 Blackbird. As NASA switched its focus from aviation to space-related technologies, he joined the Chemical Rocket Systems Branch in the new Rocket and Aerodynamics Division, where he studied slosh dynamics, the manner in which fuel sloshed about in the propellant tanks of liquid-fuel rockets. Fuel could slosh for many different reasons, and understanding these and their effects was crucial to mitigating them in order to ensure that the fuel could be pumped into the engine.[3][4]
Stofan examines a small propellant tank to study fluid sloshing
Stofan's expertise with sloshing was called upon in 1962 when Lewis took on the development of the Centaurupper-stage vehicle, which was fueled with liquid hydrogen and liquid oxygen.[4][5] Liquid hydrogen was a cryogenic fuel about which there was little empirical knowledge at the time. He played a key role in understanding its behavior: he helped develop internal baffles to control propellant sloshing, gauges to measure the boiling of cryogenic propellants, and a propellant utilization system that ensured that the liquid hydrogen and liquid oxygen would run out at precisely the same time, thereby ensuring that neither was wasted.[4][6] Centaur upper stages were used atop Atlas-Centaur rockets by the Surveyor program, which sent robotic spacecraft to the Moon.[3][4]
Stofan became the head of the Propellant Systems Section in 1966. He tackled the problem of understanding the behavior of liquid hydrogen propellant in microgravity. This was important not just for Centaur, but for the Saturn V rocket that took the first men to the Moon, for it also used liquid hydrogen in its upper stages. The following year, he was the Project Manager of a test program that investigated the Centaur's booster pump, which increased the pressure of the propellant flowing to the engine. Centaur was tested with a full-scale hot firing in the vacuum test facility at Lewis's Plum Brook Station. It was found that the booster pumps were unnecessary, and they were subsequently removed from the design.[3][4]
Stofan chats with Glenn Research Center Associate Director Janet L. Watkins at a Centaur 50th-anniversary event in 2013.
In 1969, Stofan became the Assistant Project Manager for Improved Centaur. This project involved mating the Centaur with the more powerful Titan rocket family. As Manager of the Titan-Centaur Project Office from 1970 to 1974, he oversaw the integration of Titan and Centaur, and was in charge of the Titan-Centaur Proof Flight (TC-1) in February 1974. From 1974 to 1978 he was head of the Launch Vehicles Directorate, responsible for both the Titan-Centaur and Atlas-Centaur offices. He directed the design and engineering of the launch vehicles, and coordinated relations with Air Force, aerospace industry teams, and mission planners. In these years, ten Atlas-Centaur and six Titan-Centaur missions were carried out, including the Pioneer 10 and Pioneer 11 probes to Jupiter and Saturn, the Viking missions to Mars, Helios probes to the Sun, and the Voyager probes to Jupiter and the outer planets.[3][4]
Stofan became Deputy Associate Administrator for the Office of Space Science at NASA Headquarters in 1978, but returned to the Lewis Research Center as its director in 1982.[3][5] Lewis had suffered badly from budget cuts and layoffs in the 1970s, and morale was low. There were even fears that the center might close. Stofan brought in new projects, including the Shuttle-Centaur and the Space Station power system.[7] He went back to NASA headquarters in 1986 to head the Space Station Office, directing the design of the Space Station Freedom.[3][4][8][9] He retired from NASA on April 1, 1988.>[10] For his services, he had received the NASA Exceptional Service Medal in 1975 and the NASA Distinguished Service Medal in 1981. He also received the Presidential Rank Awards of Meritorious Executive in 1982 and Distinguished Executive in 1985.[3][4]
Later life
After retiring from NASA in 1988, Stofan joined Martin Marietta Astronautics as its vice president of Advanced Launch Systems and Technical Operations. In 1991 he returned to Cleveland as the president of Analex Corporation, a firm established and run by ex-NASA employees who provided engineering and management expertise to US agencies. He later served as director of Electro-Optical Systems at Lockheed Missiles and Space Company.[4][11] His daughter, Ellen Stofan, served as Chief Scientist at NASA, assistant director of the National Air and Space Museum and Under Secretary for Science and Research at The Smithsonian.[12]
Titan was a family of United States expendable rockets used between 1959 and 2005. The Titan I and Titan II were part of the US Air Force's intercontinental ballistic missile (ICBM) fleet until 1987. The space launch vehicle versions contributed the majority of the 368 Titan launches, including all the Project Gemini crewed flights of the mid-1960s. Titan vehicles were also used to lift US military payloads as well as civilian agency reconnaissance satellites and to send interplanetary scientific probes throughout the Solar System.
A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other.
The Centaur is a family of rocket propelled upper stages that has been in use since 1962. It is currently produced by U.S. launch service provider United Launch Alliance, with one main active version and one version under development. The 3.05 m (10.0 ft) diameter Common Centaur/Centaur III flies as the upper stage of the Atlas V launch vehicle, and the 5.4 m (18 ft) diameter Centaur V has been developed as the upper stage of ULA's new Vulcan rocket. Centaur was the first rocket stage to use liquid hydrogen (LH2) and liquid oxygen (LOX) propellants, a high-energy combination that is ideal for upper stages but has significant handling difficulties.
The Saturn family of American rockets was developed by a team of former German rocket engineers and scientists led by Wernher von Braun to launch heavy payloads to Earth orbit and beyond. The Saturn family used liquid hydrogen as fuel in the upper stages. Originally proposed as a military satellite launcher, they were adopted as the launch vehicles for the Apollo Moon program. Three versions were built and flown: the medium-lift Saturn I, the heavy-lift Saturn IB, and the super heavy-lift Saturn V.
A liquid-propellant rocket or liquid rocket utilizes a rocket engine burning liquid propellants. (Alternate approaches use gaseous or solid propellants.) Liquids are desirable propellants because they have reasonably high density and their combustion products have high specific impulse (Isp). This allows the volume of the propellant tanks to be relatively low.
The Saturn I was a rocket designed as the United States' first medium lift launch vehicle for up to 20,000-pound (9,100 kg) low Earth orbit payloads. The rocket's first stage was built as a cluster of propellant tanks engineered from older rocket tank designs, leading critics to jokingly refer to it as "Cluster's Last Stand". Its development was taken over from the Advanced Research Projects Agency in 1958 by the newly formed civilian NASA. Its design proved sound and flexible. It was successful in initiating the development of liquid hydrogen-fueled rocket propulsion, launching the Pegasus satellites, and flight verification of the Apollo command and service module launch phase aerodynamics. Ten Saturn I rockets were flown before it was replaced by the heavy lift derivative Saturn IB, which used a larger, higher total impulse second stage and an improved guidance and control system. It also led the way to development of the super-heavy lift Saturn V which carried the first men to landings on the Moon in the Apollo program.
The RL10 is a liquid-fuel cryogenic rocket engine built in the United States by Aerojet Rocketdyne that burns cryogenic liquid hydrogen and liquid oxygen propellants. Modern versions produce up to 110 kN (24,729 lbf) of thrust per engine in vacuum. Three RL10 versions are in production for the Centaur upper stage of the Atlas V and the DCSS of the Delta IV. Three more versions are in development for the Exploration Upper Stage of the Space Launch System and the Centaur V of the Vulcan rocket.
Titan IV was a family of heavy-lift space launch vehicles developed by Martin Marietta and operated by the United States Air Force from 1989 to 2005. Launches were conducted from Cape Canaveral Air Force Station, Florida and Vandenberg Air Force Base, California.
The Saturn Vehicle Evaluation Committee, better known as the Silverstein Committee, was a US government commission assembled in 1959 to recommend specific directions that NASA could take with the Saturn rocket program. The committee was chaired by Abe Silverstein, a long-time NASA engineer, with the express intent of selecting upper stages for the Saturn after a disagreement broke out between the Air Force and Army over its development. During the meetings the Committee members outlined a number of different potential designs, including the low-risk solution von Braun was developing with existing ICBM airframes, as well as versions using entirely new upper stages developed to take full advantage of the booster stage. The advantages of using new uppers were so great that the committee won over an initially skeptical von Braun, and the future of the Saturn program changed forever.
The Atlas-Centaur was a United States expendable launch vehicle derived from the SM-65 Atlas D missile. The vehicle featured a Centaur upper stage, the first such stage to use high-performance liquid hydrogen as fuel. Launches were conducted from Launch Complex 36 at the Cape Canaveral Air Force Station (CCAFS) in Florida. After a strenuous flight test program, Atlas-Centaur went on to launch several crucial spaceflight missions for the United States, including Surveyor 1, Mariner 4, and Pioneer 10/11. The vehicle would be continuously developed and improved into the 1990s, with the last direct descendant being the highly successful Atlas II.
A modular rocket is a kind of multistage rocket which has components that can interchanged for different missions. Several such rockets use similar concepts such as unified modules to minimize expenses on manufacturing, transportation and for optimization of support infrastructure for flight preparations.
The Inertial Upper Stage (IUS), originally designated the Interim Upper Stage, was a two-stage, solid-fueled space launch system developed by Boeing for the United States Air Force beginning in 1976 for raising payloads from low Earth orbit to higher orbits or interplanetary trajectories following launch aboard a Titan 34D or Titan IV rocket as its upper stage, or from the payload bay of the Space Shuttle as a space tug.
Studied by Marshall Space Flight Center in 1968, the Saturn V-Centaur booster would have been used for deep space missions if it had flown. It consisted of an ordinary Saturn V launch vehicle, except that the Apollo spacecraft would be replaced with a Centaur upper stage, as a high-energy liquid-fueled fourth stage, which would provide a 30% performance improvement over Saturn V-A/Saturn INT-20. This combination never flew.
A parking orbit is a temporary orbit used during the launch of a spacecraft. A launch vehicle boosts into the parking orbit, then coasts for a while, then fires again to enter the final desired trajectory. The alternative to a parking orbit is direct injection, where the rocket fires continuously until its fuel is exhausted, ending with the payload on the final trajectory. The technology was first used by the Soviet Venera 1 mission to Venus.
Milton William Rosen was a United States Navy engineer and project manager in the US space program between the end of World War II and the early days of the Apollo Program. He led development of the Viking and Vanguard rockets, and was influential in the critical decisions early in NASA's history that led to the definition of the Saturn rockets, which were central to the eventual success of the American Moon landing program. He died of prostate cancer in 2014.
The Titan IIIE or Titan 3E, also known as the Titan III-Centaur, was an American expendable launch system. Launched seven times between 1974 and 1977, it enabled several high-profile NASA missions, including the Voyager and Viking planetary probes and the joint West Germany-U.S. Helios spacecraft. All seven launches were conducted from Cape Canaveral Air Force Station Launch Complex 41 in Cape Canaveral, Florida.
The Atlas SLV-3, or SLV-3 Atlas was an American expendable launch system derived from the SM-65 Atlas / SM-65D Atlas missile. It was a member of the Atlas family of rockets.
An orbital propellant depot is a cache of propellant that is placed in orbit around Earth or another body to allow spacecraft or the transfer stage of the spacecraft to be fueled in space. It is one of the types of space resource depots that have been proposed for enabling infrastructure-based space exploration. Many different depot concepts exist depending on the type of fuel to be supplied, location, or type of depot which may also include a propellant tanker that delivers a single load to a spacecraft at a specified orbital location and then departs. In-space fuel depots are not necessarily located near or at a space station.
A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel and oxidizer; that is, both its fuel and oxidizer are gases which have been liquefied and are stored at very low temperatures. These highly efficient engines were first flown on the US Atlas-Centaur and were one of the main factors of NASA's success in reaching the Moon by the Saturn V rocket.
Shuttle-Centaur was a version of the Centaur upper stage rocket designed to be carried aloft inside the Space Shuttle and used to launch satellites into high Earth orbits or probes into deep space. Two variants were developed: Centaur G-Prime, which was planned to launch the Galileo and Ulysses robotic probes to Jupiter, and Centaur G, a shortened version planned for use with United States Department of Defense Milstar satellites and the Magellan Venus probe. The powerful Centaur upper stage allowed for heavier deep space probes, and for them to reach Jupiter sooner, prolonging the operational life of the spacecraft. However, neither variant ever flew on a Shuttle. Support for the project came from the United States Air Force (USAF) and the National Reconnaissance Office, which asserted that its classified satellites required the power of Centaur. The USAF agreed to pay half the design and development costs of Centaur G, and the National Aeronautics and Space Administration (NASA) paid the other half.
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