Boeing and the United Launch Alliance (ULA) successfully completed a Wet Dress Rehearsal (WDR) test today in preparation for the uncrewed flight test of the CST-100 Starliner to the International Space Station (ISS). ULA announced, however, that the launch itself will slip another day, to December 20.

Boeing is developing CST-100 Starliner for NASA’s commercial crew program to take astronauts to and from ISS. The imminent Orbital Flight Test (OFT) will send the spacecraft to ISS atop a ULA Atlas V rocket. No one will be aboard.

Starliner is currently on top of its Atlas V rocket at Cape Canaveral Air Force Station, adjacent to NASA’s Kennedy Space Center in Florida. Today was the “Integrated Day of Launch” where the rocket is fueled and a countdown conducted, but no command is given to start the engine. It is also called a Wet Dress Rehearsal (“wet” because it is fueled) and is a precursor to a static fire test where all of that is done and the engine is fired, but hold down clamps keep the rocket on the pad. Once that test is successfully completed, the rocket is ready for launch.

Today’s #AtlasV #Starliner launch day rehearsal has been successfully accomplished, taking the countdown to the final second at Cape Canaveral. The rocket will be drained of fuel and safed this afternoon before rollback to the Vertical Integration Facility tomorrow. pic.twitter.com/W8rasLXPAr — ULA (@ulalaunch) December 6, 2019



Boeing and ULA were working towards December 17 for the launch, but on Tuesday announced a two-day slip for technical reasons. Today, it was delayed another day. ULA issued the following statement.

The Atlas V rocket has a 100 percent success record. It is powered by Russian RD-180 engines as the Russians reminded everyone in a pair of tweets. The first was from the Twitter account associated with a Russian robot, Fedor, that traveled to and from ISS earlier this year stating: “New American Manned Ship #Starliner in crewless mode prepares for its first test flight to #МКС [ISS] December 19th. The launch will be carried out using the ATLAS V LV on the Russian RD-180 engine. And here is the hand of Moscow!” That was retweeted by Glavkosmos, a wholly owned subsidiary of the Russian space state corporation, Roscosmos, showing a Russian bear peeking from the bushes and saying “RD-180.”

The Roscosmos Twitter account itself was silent about Starliner/Atlas V, focusing instead on the successful launch this morning of a cargo resupply mission, Progress MS-13, to the ISS.

After Russia annexed Crimea in 2014, Congress imposed restrictions on ULA’s use of the Atlas V for national security space launches because of concerns about reliance on those Russian engines, but they do not apply to commercial or civil launches like this one. ULA is developing a new rocket, Vulcan, that will use U.S.-built engines (Blue Origin’s BE-4) to replace the Atlas V, but it will not be operational for several years.