Vulcan conducting launch day dress rehearsal as the final Delta IV Heavy arrives at Cape Canaveral

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Action finally returned to the United Launch Alliance’s (ULA) Space Launch Complex 41 (SLC-41) as the Vulcan-Centaur rocket rolled out to the pad on May 11 for further testing ahead of its debut flight. Meanwhile, ULA offloaded its final Delta IV Heavy rocket from their Rocketship vessel.

These events come as ULA enters the home stretch in its preparations for the inaugural launch of its Vulcan-Centaur launch vehicle. Vulcan is designed to replace both Atlas V and Delta IV Heavy, which are currently being phased out.

ULA began the morning on May 11 with the rollout of the upcoming Vulcan rocket from the vertical integration facility (VIF), which is located inside the perimeter of SLC-41 at Cape Canaveral Space Force Station. Ahead of ULA launches from SLC-41, Atlas V and Vulcan rockets are stacked vertically inside the VIF atop mobile launch platforms. By midday, Vulcan arrived at the launch pad, which has been modified to launch both Atlas V and Vulcan. Once at the pad, the mobile launch platform was integrated with the existing pad infrastructure.

In addition to ULA using SLC-41 for Vulcan in Florida, the company is in the process of converting their west coast Atlas V pad, SLC-3 for Vulcan operations out of Vandenberg Space Force Base in California.

The Delta IV Heavy center core for the NROL-70 mission rolls through Cape Canaveral on May 11. (Credit: Max Evans for NSF)

As Vulcan was rolling out of the VIF, the center core and Delta Cryogenic Second Stage for the final Delta IV Heavy mission was hauled off of ULA’s Rocketship from the dock in Port Canaveral. Both spray-on foam insulation (SOFI) orange-colored Delta IV Heavy side core boosters remained on board ULA’s transport ship and will be offloaded at a later date.

The penultimate launch of Delta IV Heavy is scheduled to liftoff from Space Launch Complex 37B no earlier than the end of this month for the NROL-68 mission. The final flight of Delta IV Heavy and any Delta rocket, NROL-70, is scheduled to launch in 2024 from the same pad.

Teams at Cape Canaveral are currently putting Vulcan-Centaur through a final launch day dress rehearsal. Activities include cryogenic propellant loading operations on both the Vulcan first stage and the Centaur V second stage, which is meant to simulate launch day operations in the countdown prior to BE-4 engine ignition. Component and subsystem tests are also being performed on the vehicle.

Assuming the successful completion of the tanking tests, ULA is aiming to perform the flight readiness firing of Vulcan’s twin Blue Origin BE-4 engines next week. This will be the first time that two BE-4 engines are fired at the same time and while integrated with a launch vehicle. During the Space Shuttle program, flight readiness firings were carried out before the maiden flight of each of the orbiters. According to ULA CEO Tory Bruno, ULA intends to livestream the Vulcan flight readiness firing.

Blue Origin’s BE-4 is an oxygen-rich staged combustion cycle engine, the first for a domestically-produced U.S. engine, and runs on liquid oxygen and liquid methane. A reusable version of the BE-4 will be used on the first stage of Blue Origin’s New Glenn launch vehicle.

This is the second time that this particular Vulcan-Centaur stack has been at the pad for testing. On March 10, the vehicle completed a first-stage tanking demonstration. After this, Vulcan was rolled back into the VIF. Both Vulcan and Centaur V were integrated at the VIF back in late January and into early February. Before this Vulcan was stacked in the VIF, a pathfinder first-stage was also used for testing, which will later be refurbished to fly a mission.

On the maiden voyage of Vulcan, the vehicle will launch with Astrobotic’s Peregrine lander and the first two Kuiper constellation internet satellites for Kuiper LLC, which is a subsidiary of Amazon. Vulcan will also carry the cremated remains of approximately 150 people on Celestis’ “Enterprise Flight” mission. The remains include those from American actress Nichelle Nichols, who played the character of Lt. Uhura on Star Trek.

In late March, a Centaur V test article at NASA’s Marshall Space Flight Center in Huntsville, Alabama suffered an anomaly that resulted in a loss of the test article and damage to the test stand. According to Tory Bruno on Twitter, the test consisted of “extreme structural load testing of various worst possible conditions.” Bruno also stated that the anomaly resulted in a hydrogen leak, which eventually found a source of ignition, leading to an overpressure event.

This overpressure event caused a cave-in on the forward dome of the test article and subsequent damage to the test stand. It is unclear how exactly this anomaly has affected the preparations for Vulcan’s debut flight, which has been designated Cert-1.

Centaur V features numerous improvements over the Centaur III, which is currently used on the Atlas V. This includes increased thrust and specific impulse. Furthermore, the Centaur V will fly with two Aerojet Rocketdyne RL-10 engines as standard, while Centaur III typically uses just one single RL10 engine, except for Boeing CST-100 Starliner missions, which utilize two.

(Lead image: The Cert-1 Vulcan-Centaur stack rolls out to the pad at SLC-41 on May 11. Credit: United Launch Alliance)

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