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Forging Takes Flight - Space Travel is Redefined

On June 21, 2004, in the famous words of Neil Armstrong, another "giant leap" for mankind took place 328,491 feet above the California desert, as pilot Mike Melvill became the first civilian to fly a craft beyond the Earth's atmosphere.

The historic launch of SpaceShipOne - the first privately funded craft to successfully reach space - is significant because it opens the doors to private space flight and commercialization. It also represents the first new rocket engine developed for human space flight since 1972.

California-based SpaceDev, contracted by the aerospace development company Scaled Composites, was responsible for the design and manufacture of the solid fuel grain and other major components of the propulsion system.

The launch required a craft constructed of the most dependable and durable materials. When these demands - as well as the project's compressed timeframe - became evident, SpaceDev enlisted the forging expertise of Scot Forge.

The Right Stuff

Some of the components SpaceDev provided for SpaceShipOne's rocket motor, included the igniter, injector and main operating valve. Their design for SpaceShipOne's hybrid propulsion system called for a bulkhead for each solid booster rocket - five in total - that would not only contain and feed the propellant, but also separate and protect it from the motorcase.

"This main oxidizer bulkhead design is what led us to the forging process and, ultimately, Scot Forge," explains Jeff Hickerson, SpaceDev's Mechanical Engineer - Hybrid Propulsion. "Forging brought all the advantages this design required high-strength, structural integrity and the elimination of porosity."

More so than any other available metalworking process, forging provided the consistent material strength necessary for this application. Through forging, the metal is heated and mechanically formed between dies under controlled conditions. In addition to producing the desired shape and dimensions, the forging process also dramatically increases the strength of the material. Structural strength is increased by the elimination of the cast structure, enhanced density and improved homogeneity. The directional strength is improved by aligning the grain flow in specific directions.

Meeting the Deadline with Quality

Once forging was agreed upon, SpaceDev began searching for the right partner for the job. Beyond the quality requirements, this forging provider needed to be able to work with the specified high strength stainless steel (15-5 PH VAR material), and deliver the final product within a 6-week timeframe. The challenge was met by Scot Forge. "Scot Forge offered exactly what we were looking for in terms of quality and material requirements," Hickerson said. "And most critically, they were able to deliver on time."

Headquartered in Illinois, Scot Forge is an open die and rolled ring forging company, and their wide range of experience, including military and aerospace applications, provided an advantage for this project. "Because of our metallurgical expertise," said Tom Schwingbeck, Jr., Dir. of Technical Sales and Services for Scot Forge, "we were familiar with the material, and knew how to forge it to SpaceDev's specifications."

Within the 6-week deadline, Scot Forge delivered five forged blanks, each with an O.D. of 24 3/8". The forging process ensured a lack of voids in the material, which was a chief concern for SpaceDev. "The little cavities - voids - that often appear in cast metals were too much of a performance risk for us," said Hickerson. "We chose a strong stainless steel, with good natural properties. The forging process helped maintain and bolster the strength and consistency of the steel." After being forged, the blanks were solution treated, age hardened and then rough machined. Additionally, Scot Forge performed ultrasonic testing to meet the MIL-STD-2154 Class A standards required for the bulkheads.

"Forging was definitely the right process for the specific and unique demands of this application, and played a role in the success of the mission" said Schwingbeck. "Scot Forge is very proud to have been a part of this historic flight."

Making History and Forging Ahead

The collaboration of SpaceDev and Scot Forge was instrumental in helping the dream of private space flight move quickly from drawing board to launching pad. The groundbreaking flight on June 21, 2004 was the culmination of years of research, preparation, design, and testing. The success of this maiden flight led to two additional launches on September 29 and October 4, which captured the coveted Ansari X-Prize: a ten million-dollar award for consecutive private extra-atmosphere launches.

"The possibilities for this type of flight, and the capabilities of this craft have been demonstrated," said Hickerson, whose group is working on other larger, low cost propulsion systems and further innovation. "The doors are definitely open now. Who knows what the future holds?"