Astra Space makes conclusion on Canaveral launch
Company changes up rocket design after 2 mission failures
Astra Space only saw failure during its attempts to launch from the Space Coast in 2022 to the point the company shelved its rocket design in favor of a new one.
While it did manage successful orbital flights from Alaska in late 2021 and spring 2022 of the Rocket 3.3 design, it saw two mission failures from its only two attempts from Cape Canaveral Space Force Station, both involving its upper stage. Both missions had NASA payloads, and the latter, the TROPICS-1 mission, was supposed to be the first of three flights last summer to send up six hurricane-tracking satellites.
The remaining four TROPICS satellites will now be launched by competitor Rocket Lab later this summer from Virginia while Astra Space returned to the drawing board to complete the bigger Rocket 4 design not expected to fly until at least 2024.
This week the Alameda, California-based company announced the “mishap” investigation was formally closed by the Federal Aviation Administration, and the company posted its conclusions for why the TROPICS-1 mission failure occurred. It outlined how the sources of the failure, including the upper stage engine design and fuel choice, led to the rocket exhausting its second-stage fuel faster than expected which ultimately led to it not reaching its required orbital velocity and falling back into Earth’s atmosphere.
Early on, Astra Space figured the fuel was exhausted because the combustion chamber of the engine became too hot resulting in “burn-through” of the chilled fuel that flows through the walls of the nozzle instead of up into the top of the engine chamber where it would mix with liquid oxygen to create the normal thrust. The burn-through state that began 18 seconds into the second-stage flight meant the fuel was gone after 250 seconds and sensors showed 20% of the liquid oxygen that was supposed to mix to the fuel was left onboard.
“Shortly after the ignition of the upper stage engine, the upper stage’s fuel consumption rate increased and remained anomalously high for the remainder of the flight,” the report stated. “Flight data showed that the burn-through was precipitated by a substantial blockage of the fuel injector.”
So with less cool fuel flowing through the engine walls, it was easier for it to reach a boiling point.
“If too much of the fuel boils, its cooling capability is significantly and adversely impacted, and the wall temperature can go up and up until the wall fails and ‘burns through,’ dumping a portion of the fuel flow directly into the combustion chamber — essentially wasting it,” the report said.
Just why the fuel injector was blocked resulting in the fuel in the nozzle walls getting too hot and burning through wasn’t as easy to figure out, but after six months of testing and analysis, the company eliminated possible options including the presence of foreign debris and extraneous helium gas.
In the end, the fuel being used for Rocket 3.3, described as “a kerosene-like fuel with a higher vapor pressure” was of lower quality than that used on rockets like SpaceX Falcon 9s. Also, testing of the nozzle design did not take into account the flow of the exhaust plume in the vacuum of space that ultimately led to higher temperatures on the combustion chamber. Finally, teams suspect the launch date in June in the Florida summer heat, combined with these other factors caused the engine fuel to reach a boiling point during liftoff that led to the “burn-through” situation. Also faulted was the lack of a thermal barrier coating in a portion of the upper stage that was part of the rocket’s design.
“This missing coating was in a location that was considered acceptable by engineers at the time, but further analysis showed that we had underestimated the
need for coating in this region under flight conditions,” the report stated.
While the rocket failures were a setback to the company, officials that authored the report, head of mission assurance Andrew Griggs and company founder and chief technical officer and Adam London, said they should not remain an issue for the new rocket design.
“We focused the TROPICS-1 investigation on learning all that we could to inform the design and operation of this new, larger and more reliable rocket,” the report reads. “To that end, Rocket 4 incorporates key architectural choices (most notably, a different upper stage engine design and a different fuel) that completely eliminate the causes of this mishap.”
The company has changed other design features to combat other potential hazards such as foreign debris, but also took its internal processes and culture to task “to increase the reliability of our fourth generation rocket.”
The larger design, doubling the payload capacity of Rocket 3, is targeting the ability to service the sundry commercial internet constellations in the works similar to SpaceX’s Starlink and Amazon’s Project Kuiper. The company stated it intends to keep costs to under $5 million per launch.
“We know that we have room to improve further, so we are implementing dozens of company-wide initiatives designed to ensure the reliability of Rocket 4. These improvements include an overhauled design review process, a more robust test-like-you-fly qualification process, and a refreshed set of Astra core values,” the report reads.
Astra Space was the first new rocket company to launch from the Space Coast since SpaceX came to town. Another new rocket service provider, Relativity Space, is slated to make its first-ever launch with its 3D-printed Terran 1 rocket from Cape Canaveral next week.