WASHINGTON — The return to flight of Europe’s Vega C small launch vehicle has slipped to late 2024 after the European Space Agency concluded a rocket motor nozzle must be redesigned.
ESA announced Oct. 2 the completion of an independent investigation into an anomaly that took place during a static-fire test of a Zefiro 40 motor June 28. That test was a part of efforts to return the Vega C to flight after a December 2022 launch failure blamed on that motor.
Giovanni Colangelo, ESA’s inspector general and chair of the committee that investigated the incident, said at a briefing that the performance of the motor was “roughly normal” until 39.7 seconds after ignition. At that time, a brand new throat insert product of carbon-carbon material was expelled from the nozzle, together with other pieces of the nozzle. The motor continued to burn, although at far lower pressures, until the fuel was exhausted.
The test was intended to verify the performance of the throat insert, which prime contractor Avio had replaced as a part of the recommendations into the December 2022 launch failure. That investigation, released in March, concluded that carbon-carbon material from the unique supplier, Ukrainian company Yuzhnoye, didn’t meet specifications. ArianeGroup now supplies the throat insert. On the time ESA hoped to resume Vega C flights by the tip of 2023.
The June test anomaly was not linked to that launch failure, ESA concluded. “The failure of the test is expounded to the design of the nozzle that was not upgraded with the change within the carbon-carbon supplier for the throat insert,” Colangelo said. The geometry of the brand new throat insert and its different thermo-mechanical properties contributed to the failure. “The consequences had not been identified as critical in the course of the redesign.”
He said that as early as one second into the test, debonding of the throat insert from the metallic nozzle had began, which grew progressively worse. Eventually, hot gas from the exhaust got into gaps within the nozzle, causing the ejection of the throat insert and other nozzle components.
ESA advisable that the Zefiro 40 nozzle be redesigned, together with improved modeling of its performance and two static-fire tests of that recent design. A joint task force of Avio and ESA personnel has already began that work, said Giulio Ranzo, chief executive of Avio. “Now we have to conduct, I’d say, an adjustment of the design, a modification of the design of a part of the nozzle.”
That redesign will lead to at least one static-fire test within the second quarter of 2024, he said, which might be used to each confirm the performance of the redesigned nozzle in addition to refined numerical models. That might be followed by a second static-fire test before Vega C is able to return to flight.
That return to flight of Vega C is now planned for the fourth quarter of 2024. “We plan to check on the bottom as much as we are able to prior to flight to secure that we’ve done an excellent job in adapting the design,” said Ranzo.
Before the Vega C return to flight might be two launches of the unique version of the Vega, which doesn’t use the Zefiro 40 motor. The primary is scheduled for Oct. 6, and can place into orbit the THEOS-2 Earth statement satellite for Thailand, the FORMOSAR-7R/TRITON radio occultation satellite for Taiwan and 10 smallsat second payloads.
The second, and final, Vega launch is scheduled for the second quarter of 2024. Stéphane Israël, chief executive of Arianespace, said the payload for that mission, together with the Vega C return to flight, have yet to be identified. Arianespace expects to perform 4 Vega C flights in 2025 and subsequent years, with the potential for increasing that launch rate to 5 or 6 a 12 months.
The Vega C manifest includes several launches for Copernicus, the joint Earth statement program of ESA and the European Commission. Amongst them is Sentinel-1C, a radar imaging satellite considered so critical that, at one point, ESA has discussed moving up its launch from the primary half of 2023 before the Vega C launch failure took place last December. The spacecraft is simply too large to launch on the unique Vega.
“We’re discussing with the European Commission and in addition with ESA how you can best accommodate this case,” Israël said. That features, he said, finding “the perfect solutions to hurry up what we are able to speed up.”
ESA Director General Josef Aschbacher said any decision to maneuver Sentinel-1C to a distinct launch vehicle, including a non-European one, might be within the hands of the European Commission, which takes ownership of the satellite before launch. “They’ll determine where and when to launch this satellite,” he said.
Israël said that Arianespace was working with other Vega C customers to debate the implications of this latest delay. “We don’t expect that many will leave,” he said.
ESA said that the price of the extra work to return the Vega C to flight might be funded inside existing budgets. Toni Tolker-Nielsen, ESA’s director of space transportation, said the total return-to-flight costs were about 25–30 million euros ($26.3–31.6 million.)