ULA will launch its second Vulcan rocket without a real payload

The second flight of United Launch Alliance's Vulcan rocket will take off in September with a dummy payload in place of Sierra Space's Dream Chaser spaceplane, preserving a chance for ULA to begin launching US military satellites on the new rocket by the end of the year, officials announced Wednesday.

Tory Bruno, ULA's CEO, announced the change in flight plan for the second Vulcan rocket in a conference call with reporters. There was little hope Sierra Space's Dream Chaser would be ready to make its first resupply run to the International Space Station before the end of the summer.

Dream Chaser had been booked to launch on the second test flight of ULA's Vulcan rocket for the last five years. With the near-flawless inaugural flight of Vulcan in January and a successful second flight later this year, ULA's Vulcan will be certified by the US Space Force to loft the military's most sensitive national security satellites into orbit.

The Space Force is eager for Vulcan to become available for a backlog of 25 military launches it awarded to ULA beginning in 2020, when the first Vulcan flight was scheduled to happen in 2021. Instead, Vulcan didn't fly until this year, and there is urgency for ULA to complete the second Vulcan certification flight, known as Cert-2, as soon as possible.

There's still a lot of work for Sierra Space to do to prepare the Dream Chaser spaceplane for launch. Sierra Space's chief executive, Tom Vice, recently told ULA that the Dream Chaser spaceplane will not be ready to fly by September, when ULA will have the next Vulcan rocket ready to go.

“Timing is everything," Bruno said. "We waited as long as possible on Dream Chaser because we really, really wanted to fly them. It’s a very exciting mission.”

“Certification at our own expense”

ULA's other big customer, Amazon's Project Kuiper broadband constellation, also won't be ready to launch its first batch of operational satellites on a Vulcan rocket this fall. Bruno said no other payloads could be ready to launch by September, so ULA will put a dummy satellite on the second Vulcan rocket.

This dummy payload, or mass simulator, will mimic the weight of a functional spacecraft, but won't deploy from the Vulcan rocket's Centaur upper stage. ULA built the mass simulator as a backup to launch on the first Vulcan test flight earlier this year if its main payload, Astrobotic's Peregrine lunar lander, missed its ride. Now, it will take the place of Dream Chaser on the Cert-2 mission.

Ars first reported in April that ULA, a 50-50 joint venture between Boeing and Lockheed Martin, was considering flying the Cert-2 mission with a dummy payload due to delays with the Dream Chaser spaceplane.

On Cert-2, the Vulcan rocket will fly in the same configuration as it did on the debut launch in January, with two strap-on solid rocket boosters to provide additional thrust alongside two methane-fueled BE-4 main engines made by Blue Origin, Jeff Bezos' space company. Vulcan's upper stage, called the Centaur V, will accelerate into low-Earth orbit a few hundred miles above Earth, then perform several experiments and maneuvers to demonstrate the upper stage's capabilities for future operational missions.

"We'll do some maneuvers with the upper stage just to fully characterize the limits of what Centaur V can do," Bruno said. Future Vulcan missions will require the Centaur V upper stage to fly in space for six or more hours to place national security payloads directly into geosynchronous orbit more than 22,000 miles (nearly 36,000 kilometers) over the equator.