ULA ships Vulcan upper stage to factory for more Ars Technica work

The Centaur V upper stage for the first Vulcan test flight was originally lifted atop its booster at Cape Canaveral in February.
Zoom in / The Centaur V upper stage for the first Vulcan test flight was originally lifted atop its booster at Cape Canaveral in February.

United Launch Alliance technicians in Cape Canaveral, Fla., partially disassembled the first Vulcan rocket to send upper-stage launch vehicles back to its factory for reinforcements to its wafer-thin steel fuel tank.

A test article for the Centaur V upper stage of Vulcan rockets exploded March 29 during a structural test at NASA’s Marshall Space Flight Center in Alabama. After a nearly three-month investigation, ULA engineers have determined that the upper stage already fitted to the first Vulcan rocket with hangar-flight capability in Florida needs more work.

ULA hasn’t ruled out launching the company’s first new Vulcan rocket later this year, but recovery from the testbed explosion in March eliminated any chance of getting the Vulcan off the ground this summer. That also means the Vulcan rocket won’t become operational for the US military until next year, following two certification flights to demonstrate the vehicle’s performance and reliability.

The US Space Force is eager for the Vulcan rocket to enter service. The Pentagon selected ULA and SpaceX in 2020 to launch about 40 of the most critical military surveillance, communications and navigation satellites from 2022 to 2028. ULA has been awarded the rights to launch about 60 percent of missions, mostly using the new rocket Vulcan, with SpaceX taking the remaining 40 percent with its Falcon family of rockets.

The Vulcan rocket will replace the Atlas and Delta launch vehicles piloted by ULA, a 50-50 joint venture between Boeing and Lockheed Martin. Only one Delta rocket remained in ULA’s inventory prior to retirement, and an additional 19 Atlas V launchers remain in ULA’s backlog. All those rockets are already reserved for customers.

Gary Wentz, ULA’s vice president for government and commercial programs, confirmed earlier reports from Ars that the first launch of the Vulcan is now expected no earlier than the fourth quarter of this year.

The Centaur V upper stage for the first Vulcan launch was unstacked from the Vulcan booster to prepare for shipment to the factory, according to ULA spokeswoman Jessica Rye.

In a statement, ULA described the work needed on the Centaur V upper stage as minor reinforcement at the top of the forward cupola, or the uppermost section of the liquid hydrogen tank. The modifications will add strength to the tank, which contains super flammable fuel cooled to minus 423 degrees Fahrenheit (minus 253 degrees Celsius).

Wentz said the March 29 testbed explosion was caused by a leak of liquid hydrogen at the forward bulkhead of the Centaur V upper stage.

So what basically happened is we got a large concentration of hydrogen gas that found an ignition source outside the vehicle and ignited, Wentz said.

The super-thin, high-performance steel skin needs to be a bit thicker near the top of the dome, ULA chief executive Tory Bruno tweeted. The steel walls of the pressure-stabilized propellant tanks of the Centaur’s upper stages are as thin as 0.02 inch, or half a millimeter, in some places.

Wentz said the investigation concluded that the problem is relatively easy to fix. The ULA production team is preparing another Centaur V test article at the Decatur, Alabama factory for a second ground test attempt interrupted by the March explosion.

Vulcan boosters and payloads ready to go

Meanwhile, the ULA launch crew at Cape Canaveral will also remove the Vulcan booster from its launch pad and store it horizontally in another hangar until the company is ready to resume launch preparations. ULA plans to launch a pair of Atlas V rockets this summer and drop off the same launch pad that Vulcan will use.

ULA aimed to launch the first Vulcan rocket in 2019, when the company announced the program in 2015. Problems with developing the first stages of the new methane-fueled BE-4 engines, built by Jeff Bezoss’ Blue Origin space company, are were responsible for most of the delay to the Vulcans’ maiden flight.

But now the first stage, with two flight-ready BE-4 engines, is ready for launch. ULA tested the rocket at its launch pad in Florida on June 7, and the company says the readiness-to-fly launch met all goals.

The main payload for the first Vulcan launch is also complete and in storage until it needs to be transported to Cape Canaveral. The rocket’s debut flight will send an Astrobotic-built commercial lander to the Moon with a package of experiments and technology demo payloads for NASA. Two test satellites for Amazon’s Kuiper broadband network will tour space on the first Vulcan rocket.

It turns out that the problem now keeping Vulcan grounded is part of the rocket with a design rooted in the early years of the space age. The Centaur V is a larger, upgraded twin-engine version of the Centaur upper stage, which has flown 268 missions since 1962.

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Image Source : arstechnica.com

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