Irene Klotz The booster flew for more than 2 min. despite losing one of four engines.
Irene Klotz
Firefly’s Alpha rocket lost one of its four first-stage engines 15 sec. after liftoff but continued flying for more than 2 min. until it began to tumble, prompting a range safety officer to detonate the booster’s Flight Termination System. Credit: Matt Hartman
The day before Firefly Aerospace launched its first Alpha rocket, Founder and CEO Tom Markusic was most concerned about the hold-down clamps at the base of the booster that must release within milliseconds to allow the vehicle to lift off.
“I can accept if we ultimately find another problem that we could have only found in flight, but I just can’t accept a ground system causing us to lose a mission,” Markusic told reporters on Sept. 1.
The clamps performed flawlessly, and the 97.6-ft.-tall booster lifted off from Space Launch Complex-2 (SLC-2) at Vandenberg Space Force Base in California at 6:59 p.m. local time on Sept. 2.
Markusic’s relief was short-lived. Fifteen seconds after liftoff, one of the rocket’s four liquid-oxygen (LOX) and kerosene-fed Reaver engines shut down, though the ascent continued so cleanly that Markusic initially wondered if the declining pressure reading of Engine 2 was due to loss of telemetry, not the engine.
“The acceleration was perfect,” Markusic tells Aviation Week. “It didn’t seem like anything happened. . . . We really didn’t understand the implications for probably 60 sec. That’s when I started to worry about how it was all going to end.”
The rocket continued climbing for about another minute, heading on a western trajectory that would take it up over the Pacific Ocean before turning south. Upon reaching an orbital perch 186 mi. above Earth and inclined 137 deg. relative to the equator, the booster was to deploy a 57-lb. payload consisting of educational memorabilia and technology demonstrations. The payload included a Purdue University drag sail that would have helped deorbit the rocket’s upper stage and a Firefly plasma thruster the company designed for its upcoming Space Utility Vehicle tug.
But it was not to be. As the Alpha hit supersonic speed about 2 min. after liftoff, it began to cartwheel, prompting a range safety officer to trigger the rocket’s Flight Termination System and end the Alpha’s debut. “In that transonic regime, where you’re going into Max q [the point of maximum dynamic pressure on a vehicle], the drag builds up very precipitously, and that makes it very difficult to control,” Markusic says.
The rocket’s engine compartment was thrown clear of the blast, which occurred at an altitude of about 50,000 ft., and landed about 0.75 mi. away from the launchpad. “That whole truss structure and cluster of engines stayed together all the way to the ground,” Markusic says. “We recovered them, so we have the ability to go look at these components.”
The rocket’s engines were recovered after impact about 0.75 mi. from Space Launch Complex-2 at Vandenberg Space Force Base. Credit: Firefly Aerospace
Preliminary analysis indicates a valve that feeds propellant to Engine 2 closed when it lost its electrical signal. “It’s a relatively simple way that that valve gets its electrical signal—it’s a wire and connectors—and somehow that electrical continuity was interrupted,” Markusic says. “Why it lost its signal is the subject of our investigation.”
Firefly’s unique Reaver engine utilizes a combustion tap-off power cycle in which some of the exhaust energy from the main combustion chamber is diverted to power the engine’s single-shaft turbopumps. While tap-off cycle engines are not new, the Firefly design is the first for an orbital boost engine and the first that uses RP-1 (kerosene) rather than liquid-hydrogen propellant.
The major benefit of the tap-off cycle, which is also a form of open-cycle gas-generator propulsion system, is increased simplicity.
While previous open-cycle engines such as the Saturn’s F1 and current RP-1 fueled systems like SpaceX’s Merlin engine are configured with two combustion devices—one for thrust and the other for powering the LOX/RP-1 turbomachinery—the Alpha’s engines are configured with only a single combustor for both functions. Fuel and oxidizer pumps are initiated for both first- and second-stage engines using an inert gas before ignition, after which the tap-off cycle is self-sustaining.
The Alpha’s engine design also incorporates innovations to offset the usual disadvantage of the tap-off cycle, which normally sacrifices some propellent to cool the combustion chamber gases driving the turbomachinery.
Although the company has previously been reluctant to discuss details of the design, Firefly Co-founder Eric Salwan, director of commercial business development, says the engine incorporates a regenerative cooling system that combines forged copper channels with a protective electroplated nickel jacket.
The design enables fuel to be pumped around the engine, which absorbs the heat of combustion before being injected into the chamber and combusted to provide additional thrust. The copper provides a good heat sink and, because of the special nickel plating, is able to sustain the heat of combustion throughout the engine’s life cycle without ever reaching its melting point.
“We found a way to do this without wasting any fuel for cooling, which was pretty extraordinary and ultimately makes the engine very efficient,” says Markusic.
Previously known as Firefly Space Systems, the company was about to begin full-scale tests of a different Alpha launch vehicle when funding dried up in late 2016. The company shut down in 2017 before venture-capital investor Noosphere revived it. In May, Firefly completed a Series A financing round that raised almost $200 million.
With a lift capacity of 2,200 lb. to low Earth orbit (LEO) or nearly 1,400 lb. to sun-synchronous orbit—about twice the lift capacity of Virgin Orbit’s Launcher-One and more than three times the lift capacity of Rocket Lab’s Electron—the Alpha is designed to address the upper end of the small-satellite market. Starting price is $15 million, positioning Firefly to offer the lowest cost per pound to orbit in its vehicle class.
The company has a second vehicle in production and was prepared to begin commercial launch services as early as December if the flight test was successful. Depending on the mishap investigation, Firefly could conduct a second flight test before year-end.
Firefly also is working on orbital transfer vehicles and a small lunar lander called Blue Ghost, which won a $93.3 million NASA Commercial Lunar Payload Services contract to deliver 10 science payloads to the Moon’s surface in 2023.
Firefly also plans a medium-class booster, called Beta, capable of delivering 5-10 metric tons in LEO, filling a niche opened by the retirement of United Launch Alliance’s Delta II.
—With Guy Norris in Colorado Springs
