Super Strypi failure blamed on first stage motor malfunction

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LOGAN, Utah — The failure of the first launch of the U.S. Air Force’s Super Strypi rocket last year was likely caused by a problem with the rocket’s first stage motor, and the future of the small launch vehicle remains uncertain.

The Super Strypi lifted off from the Pacific Missile Range Facility in Kauai, Hawaii, on Nov. 3, 2015, carrying 13 small satellites on a mission for the Operationally Responsive Space (ORS) Office designated ORS-4. The rocket appeared to break up shortly after liftoff, and the U.S. Air Force later declared the launch a failure without providing additional information.

In a presentation at the 30th Annual Conference on Small Satellites at Utah State University here Aug. 8, Jeffry Welsh, the ORS-4 mission director, did not go into specifics about the cause of the failure, referring questions to the ORS Office as the final report on the failure has not been released.

However, he did indicate the failure was caused by an issue with the first stage motor of the spin-stabilized rocket. That spinning, which was within parameters, “doomed the first stage” because the motor was, according his slides, “insufficiently robust.”

The text of the paper being presented by Welsh and others at the conference stated that the Super Strypi broke up 57 seconds after liftoff because of a problem with the vehicle’s first stage motor.

“The most likely cause of the launch vehicle anomaly was breach of the first stage motor case due to slag build up in the aft end of the first stage motor from vehicle rotation leading to increased insulation erosion,” the paper states.

The Super Strypi is a variant of the Strypi sounding rocket developed in the 1960s, using three stages, each powered by a solid rocket motor provided by Aerojet Rocketdyne. The first stage motor, designated LEO-46, is designed to burn for 76 seconds, generating a maximum thrust of nearly 285,000 pounds-force.

The paper notes that first stage motor was built “with a significant design escape in the first stage insulation” that was not noticed until after the motor was built. The paper added, though, that the insulation flaw was not a contributing factor in the failure.

No current missions are currently planned to fly on the Super Strypi. Welsh, who is no longer involved with the vehicle, said he “didn’t have any insight” into the future of the vehicle. Any plans for future launches will likely come after the formal release of the Air Force report into the failure, expected later this year.

While no other missions are currently manifested using the Super Stypri, the Air Force has not ruled out using the vehicle again. Randy Riddle of the Air Force’s Rocket Systems Launch Program said during an Aug. 8 panel session here that the failure of the Super Strypi on its first launch did not disqualify it from consideration in the future.

“I wouldn’t throw them out because they’ve had a failure. Everyone’s had a failure,” he said. However, he said Super Strypi would have to compete with other vehicles, such as the new generation of small launch vehicles being developed commercially, for any future launch opportunities.

The ORS-4 mission failure destroyed its satellite payload, including eight cubesats developed by NASA for a mission called Edison Demonstration of Smallsat Networks (EDSN) to demonstrate intersatellite communications and networking technologies for future smallsat constellations.

Despite the loss of the EDSN satellites, NASA was able to test the technologies in space using a separate cubesat mission called Network & Operation Demonstration Satellites, or Nodes, which used two cubesats built from spare parts left over from EDSN. The Nodes satellites flew to the International Space Station on a Cygnus cargo mission in December 2015 and were deployed from the station in May.

John Hanson, the Nodes project manager at NASA Ames Research Center, said in an Aug. 6 presentation at the 13th Annual Summer CubeSat Developers’ Workshop here that the two Nodes cubesats were able to successfully demonstrate the technologies planned for use on EDSN. “The great thing about cubesats is that we’re robust against launch failures,” he said.