October 18, 2021

ULA readies Vulcan booster for cryogenic tanking tests


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EDITOR’S NOTE: Updating number of Atlas 5 missions remaining.

ULA’s Vulcan pathfinder booster stands on pad 41 Wednesday. Credit: United Launch Alliance

United Launch Alliance rolled a test article for its new Vulcan rocket to a launch pad at Cape Canaveral Wednesday, moving the booster into position for a series of cryogenic tanking tests set to begin in the coming days.

The 110-foot-tall (33.5-meter) Vulcan first stage rode a mobile launch platform along rail tracks from ULA’s Spaceflight Operations Center at Cape Canaveral Space Force Station to pad 41, a seaside launch complex teams have modified to support Vulcan missions and continued flights of ULA’s Atlas 5 rocket.

The Vulcan Centaur launch vehicle, which will ultimately replace ULA’s Atlas and Delta rocket families, is scheduled to lift off for the first time next year. Blue Origin’s delivery of flight-ready BE-4 first stage engines is driving the schedule for the first Vulcan test flight.

While ULA’s factory team in Decatur, Alabama, waits for the engine delivery, the company’s launch team at Cape Canaveral is moving forward with “pathfinder” testing using a first stage test article.

ULA shipped the Vulcan pathfinder booster from Alabama to Florida earlier this year. It’s fitted with two BE-4 engine test units previously used for test-firings at Blue Origin’s facility in West Texas.

Mark Peller, ULA’s vice president of major development, said in an interview with Spaceflight Now that the upcoming cryogenic tanking tests will allow engineers to validate how the company plans to load propellant into the Vulcan rocket during a real countdown.

“We have a tremendous amount of experience with cryogenic propellant,” Peller told Spaceflight Now. “Both Atlas and Delta are cryogenic vehicles. Delta has cryogenic fuel as well as oxidizer.”

The Vulcan first stage is fueled by liquified natural gas, instead of the kerosene and liquid hydrogen fuels that power the Atlas 5 and Delta 4 rockets. ULA will continue to use super-cold liquid oxygen — the same oxidizer used on Atlas and Delta rockets — to allow the Vulcan’s BE-4 engines to fire during the first few minutes of flight.

“There are two things that are unique here,” Peller said. “We’ve modified the systems, so we want to validate them. And two, the vehicle is a little bit different scale. So we want to just take time. It helps us validate all of our analysis and predictions, and any extrapolation of data that we’re bringing over from Atlas and Delta. It might take a little bit longer, or it might be a little bit faster to load the vehicle and chill the tanks down and the engines down.”

This infographic from ULA shows modifications to pad 41 to support Vulcan missions. Credit: United Launch Alliance

The Vulcan core stage measures 17.7 feet (5.4 meters) in diameter, and contains aluminum propellant tanks for methane and liquid oxygen for the dual BE-4 engines. The Vulcan first stage is more than 5 feet (1.5 meters) wider than the Atlas 5’s core stage.

A fully loaded Vulcan core stage will contain more than a million pounds of liquid propellant, about 50 percent more propellant mass than the Atlas 5’s first stage.

“We use ground software to monitor the vehicle throughout these operations to maintain a safe state, and we do extensive simulation of all of this, but it is simulation in the lab, at our integration lab in Denver,” Peller said. “So this gives us the opportunity to do it, not just with hardware in the loop, but cryogenic propellant in the loop.

“For the most part, this is validation of procedures and processes, validation of ground software, and it’s all in an effort to take the time outside of a normal launch campaign, and take the time to work through this and get all of this updated and validated,” Peller said. “So when we get out there with the first vehicle, we have this experience, and that that goes smoothly.”

ULA, a 50-50 joint venture between Boeing and Lockheed Martin, has finished upgrades to pad 41 and the nearby Vertical Integration Facility, where teams assemble rockets, to accommodate the larger Vulcan Centaur rocket.

The liquified natural gas, or methane, fuel burned by the Vulcan’s twin first stage BE-4 engines required ULA to install new storage tanks at pad 41.

The three 100,000-gallon methane storage tanks are located on the north side of pad 41. The company also upgraded the launch pad’s sound suppression water system, which dampens the intense acoustics generated by a rocket launch.

The liquid hydrogen and liquid oxygen propellant storage facilities at pad 41 also had upgrades to accommodate the larger Centaur upper stage that will fly on Vulcan rockets.

ULA’s Vulcan Launch Platform, with the Vulcan pathfinder booster, arrives on pad 41 at Cape Canaveral on Wednesday. Credit: Stephen Clark / Spaceflight Now

After the Vulcan pathfinder rocket arrived at Cape Canaveral, ULA raised the booster vertical on top of the Vulcan Launch Platform.

ULA rolled the rocket to pad 41 earlier this year and flowed propellant from the new ground storage tanks through supply lines leading to the Vulcan Launch Platform. The platform connects the Vulcan booster to the propellant lines through a connection at the base of the pad.

“We’ve already filled these tanks up so we can kind of understand the properties,” said Ron Fortson, ULA’s director and general manager of launch operations, as he guided reporters around the launch pad in May. “We’ve flowed the propellant through all the lines. We call them cold flow tests. We flowed through all the lines all the way up to the connection with the VLP, which is the Vulcan Launch Platform, with the Vulcan rocket sitting on top.”

“That was the final test of those ground systems and the mobile launch platform, the VLP,” Peller said Monday. “But we stopped short of actually pulling propellant into the vehicle. We went back to the SPOC, where we established limited vehicle processing capability to do some more checkouts.

“So our next step here, coming up soon, is to go back out and start flowing propellant to the actual vehicle,” Peller said. “So ground systems and the VLP are checked out. Now let’s start getting experience loading propellant on the vehicle, validating procedures, timelines, ground software, all the things we need to do to help burn down our risk and ensure readiness to proceed into our first launch campaign.”

Peller said ULA’s launch team, stationed in the Atlas Spaceflight Operations Center at Cape Canaveral, will run the Vulcan pathfinder booster through standard checkouts after arriving at the pad.

Engineers will take a cautious approach with the tanking tests, first loading liquid oxygen into the Vulcan booster and assessing the response of the rocket. After draining the oxidizer, ULA teams will evaluate data before proceeding to the next step of testing.

“Then, if we’re ready, we’ll go forward and do LNG (liquefied natural gas) only, take day or so to evaluate that data, and then we’ll go and do a combined test where we’ll load both propellants,” Peller said. “We’ll do it on a timeline to a procedure that is consistent with a day of launch countdown.”

ULA will run through the multi-hour countdown before simulating an abort at around T-minus 10 seconds, before the BE-4 engines would ignite for a real launch, Peller said.

During the final phase of the countdown, the rocket’s propellant tanks will be pressurized, and the BE-4 engines will go through chilldown conditioning, a procedure that involves flowing small amounts of super-cold propellants through fluid lines before ignition.

“We can verify chilldown times for the engines, and we can gimbal the engine and do all sorts of other things, but we’ll stop short of hotfiring,” Peller said.

 

Artist’s concept of United Launch Alliance’s Vulcan rocket. Credit: ULA

ULA is taking advantage in a break in Atlas 5 launch operations at Cape Canaveral to complete the Vulcan pathfinder testing. ULA planned to launch an Atlas 5 rocket on an unpiloted test flight of Boeing’s Starliner crew capsule earlier this month, but Boeing called off the mission due to spacecraft valve problems.

The first stage of the Atlas 5 rocket assigned to the Starliner test flight will now be used for ULA’s next launch from Florida. That mission, set for liftoff Oct. 16, will carry NASA’s robotic Lucy asteroid probe into space.

Once the pathfinder tanking tests are complete, ULA will send the Vulcan booster back to the company’s factory in Alabama to be outfitted for a future launch. Meanwhile, factory workers are finishing assembly of a different Vulcan rocket that will launch on the first test flight next year.

The Vulcan rocket can fly with zero, two, four, or six solid rocket boosters. ULA has developed an upgraded dual-engine version of the venerable hydrogen-fueled Centaur upper stage to fly atop the Vulcan rocket.

Ultimately, further upgrades to the new “Centaur 5” upper stage will allow a “single-stick” Vulcan Centaur rocket to outlift ULA’s Delta 4-Heavy rocket, which combines three Delta 4 rocket core stages to give heavy payloads an extra boost into space.

Peller said ULA expects to receive the first pair of flight-ready BE-4 engines from Blue Origin at the end of the year, allowing the company to ship the first flight-rated booster to Cape Canaveral in early 2022.

That will kick off another series of tests at the Vulcan launch pad, culminating in a full-up countdown rehearsal that will end with a hold-down test-firing of the two BE-4 engines.

Once the flight readiness firing is complete, ground crews will install a pair of Northrop Grumman solid rocket boosters to the Vulcan core stage and prep the launcher for its first flight.

The inaugural Vulcan launch will loft a commercial lunar lander built by Astrobotic, which will fly science payloads to the moon’s surface under contract to NASA. A second Vulcan Centaur launch scheduled in late 2022 will launch a cargo-carrying spaceplane from Sierra Nevada on a resupply mission to the International Space Station.

If the first two missions are successful, the U.S. Space Force will clear the Vulcan Centaur rocket to start launching critical military satellites.

ULA unveiled the Vulcan rocket in 2015. It’s designed for a new era in the U.S. launch industry marked by increased competition, particularly from SpaceX, and a changing market.

The U.S. military is an anchor customer for ULA. Pentagon officials announced last August that ULA will get 60 percent of the military’s most critical satellite launch contracts awarded through late 2024 for missions that will take off between 2022 and late 2027.

SpaceX will receive 40 percent of the national security launch contracts over the same period, giving the Pentagon two independent companies capable of serving all the military’s medium- and heavy-lift launch needs.

The agreements with ULA and SpaceX cover contracts to launch satellites for the U.S. Space Force, the National Reconnaissance Office, the Missile Defense Agency, and other military services and agencies.

But the Atlas 5 rocket is not going away immediately, and pad 41 will support launches of both types of rockets for several years. ULA has contracts for at least 29 more Atlas 5 missions before retiring the rocket in favor of the Vulcan Centaur.

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Follow Stephen Clark on Twitter: @StephenClark1.


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