More than four decades after it was last used, the Saturn V rocket—the vehicle that carried the U.S. Apollo astronauts to the moon and back between 1968 and 1972—still holds the title of the most powerful liquid-fueled propulsion system ever created.
The five F-1 engines of the Saturn V’s first stage, known as the S-1C, each packed a staggering 700,000 kilograms (1.5 million pounds) of thrust at liftoff. That’s equivalent to 24 million kilowatts (32 million horsepower) of power or the output of 100,000 sports cars.
After the S-1C stage completed its mission to get the Saturn V to 67 kilometers (42 miles) high in less than 2-1/2 minutes—by achieving speeds greater than Mach 7 (8,600 kilometers per hour or 5,300 miles per hour)—it was unceremoniously dropped into an Atlantic Ocean grave some 4,300 meters (14,000 feet) below the surface.
That is, until 2013, when billionaire entrepreneur and Amazon.com founder Jeff Bezos led an expedition that recovered 11,300 kilograms (25,000 pounds) of components from the F-1 engines that launched the Apollo 11, 12 and 16 lunar landing missions in July 1969, November 1969 and April 1972, respectively. Included were five thrust chambers, one exhaust nozzle, two heat exchangers, four turbines, three turbine manifolds and one gas generator, all of which were taken to the Kansas Cosmosphere and Space Center in Hutchinson, Kansas, for processing.
Preserving the thrust chambers and exhaust nozzle posed a special problem for conservators because they were constructed of a nickel-based superalloy called Inconel X-750 that was designed to withstand temperatures up to 3,300 degrees Celsius (6,000 degrees Fahrenheit). Unfortunately, no one had ever studied the reaction of this material to decades of seawater exposure, so the conservation team did not know how best to treat the artifacts made from it.
National Institute of Standards and Technology (NIST) engineers Tim Foecke and Adam Creuziger were enlisted to help the Kansas Cosmosphere staff identify the corrosion mechanisms that they would be dealing with during conservation of the Iconel X-750 components. The NIST researchers developed a complex sample stabilization technique and examined samples from the corroded artifacts under scanning electron microscopy and X-ray microanalysis. They discovered that the structure of the superalloy was altered by the very thing it was designed to withstand—the incredibly high heat of the F-1 engine exhaust. The Iconel X-750 that started out composed of microscopic cube-shaped elements transformed into a substance made up of tiny branch-like structures called dendrites. Foecke and Creuziger also found that the change made Iconel X-750 easier to stabilize (remove corrosive salts left behind by exposure to seawater) than in its original state, a welcomed bonus for the conservators.
Today, the recovered F-1 engine parts may be seen at the Kansas Cosmosphere; the Smithsonian National Air and Space Museum in Washington, D.C.; the Museum of Flight in Seattle; and the Kent, Washington, headquarters of Blue Origin, the Bezos company developing commercial space vehicles.
– Michael E. Newman