Scorpius Space Launch Co. (SSLC) is capitalizing on—and contributing to—a growing trend in the aerospace industry: the increasing use of composite materials in place of more traditional metals. One has to look no further than the Boeing 787 Dreamliner, which according to market research company Lucintel uses about 50% composites by structural weight, as evidence.
Last fall, SSLC, in partnership with Microcosm, delivered a pair of next-generation all-composite cryogenic propellant tanks for integration into a prototype reusable launch vehicle in development by Garvey Spacecraft under a Phase II SBIR project for the Air Force Research Laboratory’s Propulsion Directorate. When Garvey’s Prospector 9 begins flight testing, which is planned for this month, it will be the first time that a launch vehicle has flown with two such all-composite propellant tanks, according to SSLC.
The Pressurmaxx tanks, which in the Prospector 9 are being used for fuel and oxidizer, conform to ASME (American Society of Mechanical Engineers) standards, and their liner-less design reduces cost and weight compared to metal tanks, explained Markus Rufer, Scorpius’ Executive Vice President and Chief Operating Officer. “Depending on application, size, and pressure requirements, both cost and weight savings are in the 30-50% range,” he said.
The tanks also offer performance enhancements compared to traditional aluminum structures, Rufer noted. “All-composite tanks eliminate the problems concerning delamination and corrosion issues that carbon fiber over-wrapped metal tanks have,” he said, adding that they are also structurally stronger and have shorter manufacturing lead times.
“What’s unique about our all-composite tanks is that they can hold up to several thousand psi pressure under cryogenic conditions—an achievement that has never been attained before without resorting to the use of metal liners,” said Rufer. “We are not aware of any other production all-composite liner-less tanks on the market that are made for high-pressure cryogenic applications.”
The current composite-fuel-tank program builds upon previous cooperative efforts between the two companies. In 2000, Garvey Spacecraft accomplished the first-ever flight demonstration of a composite cryogenic tank carrying liquid oxygen, using a prototype test tank supplied by SSLC.
Many advancements have been made to the composite-tank technology since earlier development programs. “Major progress was achieved in weight optimization by reducing wall thickness,” Rufer said. “Also, compatibility was expanded to include alcohol- and natural gas-based propellants and pressurants. [And] high-load, sealed Y-joints were developed for the mounting skirts.”
According to Garvey Spacecraft’s John Garvey, “When we first defined the P-9 vehicle configuration, we assumed it would feature aluminum tanks to minimize risk. However, Scorpius’ recent progress in refining, testing, and producing their latest generation of composite tanks gave us enough confidence to make the switch now rather than waiting until a future vehicle.
“One of the goals of our work with AFRL is to evaluate and, if possible, increase the technology readiness levels of candidate advanced launch vehicle technologies, with all-composite tanks like the Pressurmaxx being right near the top of the list,” Garvey added.
In 2007, Pressurmaxx tank products were ordered by a variety of companies, “from small aerospace component manufacturers to the nation’s largest defense contractors,” Rufer said. They have been selected for applications in launch vehicles, experimental spacecraft, sub-orbital vehicles, sounding rockets, lunar and Mars-lander vehicle concepts, as well as superconductor coil technology.
Microcosm’s Scorpius family of launch vehicles uses Pressurmaxx technology to increase the payload-to-orbit by 30% with no increase in cost.