The long-awaited inaugural flight of the new Vulcan Centaur rocket is targeting a four-day launch window that will open no later than May 4th from Space Launch Complex-41 (SLC-41), Cape Canaveral Space Force Station (CCSFS), Florida.

Vulcan will carry Astrobotic's Peregrine lunar lander and carry 24 payloads to the moon, including 11 for NASA as part of the agency's Commercial Lunar Payload Services project and two prototype satellites for Amazon's Project Kuiper broadband constellation.

The third payload will be Houston-based Celestis' Memorial "Enterprise Flight," a tribute to Majel Barrett Roddenberry and her husband, Star Trek creator Gene Roddenberry, and other cremated remains. It will also carry hair samples from America's first president and from Presidents Dwight Eisenhower, John F. Kennedy, and Ronald Reagan "beyond the Earth-moon system to orbit the sun forever."

Like most large rocket projects, ULA has been planning to launch Vulcan since 2020, but its debut has been subject to multiple issues, primarily due to the rocket's main engines and the payload.

The next-generation 202-foot-tall (67-meter) rocket will replace ULA's well-established workhorses, the Atlas V and the Delta IV, in launching payloads to space. Its first stage is powered by two BE-4 methane-liquid oxygen engines built by Jeff Bezos' Blue Origin; each engine will generate approximately 550,000 pounds (2.45 meganewtons) of thrust to propel Vulcan into orbit. The rocket is equipped with a Centaur V upper stage and two solid rocket boosters (SRB).

ULA chose May 4th due to a number of factors. Blue Origin's engine arrived more than four years late, but recent tests revealed a potential issue. During a series of tests, Bruno revealed that one of the two engines' oxygen pumps consistently delivered around 5% more oxygen than expected into the engine.

"When the performance of your hardware has even a small shift that you didn't expect, sometimes that is telling us that there could be something else going on in the system that is potentially of greater concern."

"We've come to the conclusion that this is most likely unit-to-unit variation," Bruno added.

"The other engines, including the flight engines that are on rocket right now, are all very similar, and of that earlier family that did not have an extra 5 percent of output coming out of the main oxygen pump. Now we're satisfied, and we'll resume testing shortly with the other engine. That testing sequence will run about six weeks."

Theoretically, Vulcan's pre-launch testing could be completed and ready to blast off by mid-April, but the launch's primary mission, "Cert-1," is to deliver Astrobotic's lunar lander, which has a specific window of only a few days each month to fly its trajectory to the moon.

Bruno said that the two-stage rocket will roll out from ULA's Vertical Integration Facility (VIF) to the launch pad in a few days for tanking tests, followed by at least one wet dress rehearsal where the vehicle is fully loaded with propellants and goes through a practice countdown, stopping just before engine ignition and unloading of fuel.

The testing culminates with a Flight Readiness Firing (FRF) to practice the full day-of-launch timeline, complete with a 3.5-second long ignition of its BE-4 engines at about 70% of rate thrust. After FRF, the rocket will return to the VIF for two strap-on SRBs and payload integration.

"Are we frustrated? No. We're being careful and we're being thoughtful to make sure we have a successful mission," Bruno said "We want very much to get this right, and waiting a few weeks for the first launch does not impact any of those other schedules. We have plenty of time to do this."

"We're going to do this the right way."

Related Links
United Launch Alliance
Rocket Science News at Space-Travel.Com