Firefly Aerospace says the premature shutdown of one of its Alpha rocket’s four main engines caused the launcher to lose control as it reached supersonic speed during a test flight over California last week.
In a statement Sunday, the company released preliminary information from the investigation into the launch accident, and emphasized lessons learned from the mission will boost chances the next test flight will reach orbit.
The first test flight of Firefly’s Alpha launcher Sept. 2 ended in a dramatic orange fireball high above Vandenberg Space Force Base, a military facility on California’s Central Coast between Los Angeles and San Francisco.
The privately-developed Alpha rocket is sized to haul payloads of up to 2,200 pounds (1,000 kilograms) into a low-altitude orbit, or up to 1,388 pounds (630 kilograms) of payload to a 310-mile-high (500-kilometer) sun-synchronous polar orbit.
After taking off off from Space Launch Complex 2-West at Vandenberg, the 97.6-foot-tall (29.75-meter) rocket climbed vertically for several seconds before beginning a pitch maneuver to head downrange toward the southwest over the Pacific Ocean.
Firefly said Sunday that the launcher released and cleared the pad correctly, and ground fluid connections and umbilicals detached from the rocket as designed. Thrust vectoring from the rocket’s four kerosene-fueled Reaver engines eliminated tipping and rolling induced at liftoff.
But one of the four Reaver engines, developed in-house at Firefly, shut down about 15 seconds into the flight. A video replay released by the company shows the engine losing thrust.
Firefly called it an “uneventful shutdown” and stressed that the engine “didn’t fail.”
“The propellant main valves on the engine simply closed and thrust terminated from Engine 2,” Firefly said.
Each Reaver engine can generate more than 40,000 pounds of thrust at maximum power, consuming a mix of kerosene fuel and super-cold liquid oxygen. The Reaver engines were supposed to fire for 2 minutes, 47 seconds, before switching off to allow for separation of the spent first stage booster.
A single Lightning engine on the Alpha rocket’s second stage was expected to ignite moments later to power the mission into orbit.
With only three Reavers firing, the rocket climbed slower than anticipated, its guidance computer commanding the remaining powerplants to swivel their nozzles to keep the launcher on course without the help of the dead engine.
“Alpha was able to compensate at subsonic speeds, but as it moved through transonic and into supersonic flight, where control is most challenging, the three engine thrust vector control was insufficient and the vehicle tumbled out of control,” Firefly said Sunday.
Vandenberg Space Force Base officials said in a statement that range safety from Space Launch Delta 30, headquartered at the base, terminated the flight.
Upon command, the rocket’s Flight Termination System fired explosive charges to destroy the vehicle as it tumbled out of control, moments after aerodynamic forces appeared to strip away the launcher’s payload fairing, which contained several small CubeSats from institutions offered a free ride on the inaugural Alpha test flight.
Firefly said it is looking into why the Reaver engine shut down prematurely, and will report the root cause of the “anomaly” at the end of the investigation.
“In collaboration with the FAA (Federal Aviation Administration) and our partners at Space Launch Delta 30, we will return to conduct the second Alpha flight as soon as possible,” Firefly said.
Founded in 2014, Firefly is headquartered in Cedar Park, Texas, just north of Austin. The company developed the Alpha rocket almost exclusively through private funding, with the intention of carving out a slice of the flourishing small satellite launch market.
Firefly Aerospace was previously named Firefly Space Systems before entering bankruptcy. Firefly emerged from bankruptcy proceedings in 2017 under new ownership.
Noosphere Ventures, a Menlo Park, California-based firm led by managing partner Max Polyakov, funded the remainder of the Firefly’s rocket development program with a $200 million investment.
Firefly announced in May it closed a Series A funding round, welcoming new investors that pledged nearly $200 million in additional funding to pay for expanded rocket production capacity.
Firefly’s other projects beyond the Alpha launcher include the Beta rocket, which will use upgraded engines to haul heavier payloads into orbit. Firefly also has ambitions for a robotic lunar lander, a space tug powered by electric thrusters, and a reusable spaceplane.
Firefly is also developing a second launch site would be located at the disused Complex 20 launch pad at Cape Canaveral Space Force Station in Florida.
The first Alpha test flight “marked a major advancement for the Firefly team, as we demonstrated that we ‘arrived’ as a company capable of building and launching rockets,” the company said.
“We also acquired a wealth of flight data that will greatly enhance the likelihood of Alpha achieving orbit during its second flight,” Firefly said. “In short, we had a very successful first flight.”