OA-4 Cargo Launch to ISS Postponed a Third Time, Next Attempt Sunday

Weather is not cooperating for the launch of Orbital ATK’s OA-4 cargo mission to the International Space Station (ISS) aboard a United Launch Alliance (ULA) Atlas V rocket.  Rain and winds have been the primary factors in the delays.  The next attempt is scheduled for tomorrow, Sunday, December 6, at 4:44:56 pm ET, although the Air Force weather forecast even then is only 40 percent favorable.  Monday is a better weather day, with a 70 percent chance of no weather violations.

After scrubbing on Thursday and Friday, ULA was hoping to launch today.  The launch team was counting down to launch and encountered a couple of technical issues that required extended holds to resolve.  There were five opportunities to launch during a 30-minute launch window between 5:10 and 5:40 pm ET.  By early afternoon, only one of those remained because the extended holds ate into the first parts of the window, and according to CBS News space reporter Bill Harwood (@cbs_spacenews) a collision avoidance period ruled out the last slot.  Only 5:33 pm ET remained and with just a 20 percent probability of acceptable weather, ULA decided to wait another day. 

ULA President Tory Bruno tweeted that crew rest was one of the factors in deciding to wait until tomorrow.  The launch team had been through the countdown on Thursday and Friday, resetting several times within the launch window only to be foiled by weather each time.

Scrub. Saving crew rest for better weather on Sunday and Monday

— Tory Bruno (@torybruno) December 5, 2015

This is the first launch of Orbital ATK’s Cygnus cargo spacecraft since the October 2014 launch failure of the company’s own Antares rocket.  Orbital ATK is retrofitting Antares with a different Russian rocket engine and currently plans to resume flights in May 2016.   Until then, it is using ULA’s Atlas V for two Cygnus launches – this one and another in March.

Orbital Sciences Corporation already launched two operational cargo missions to ISS, Orb-1 and Orb-2.  Orb-3 was the failure.  The company merged with ATK earlier this year and this launch is designated Orbital ATK CRS-4 or OA-4 for short.  CRS refers to the Commercial Resupply Services contract through which NASA purchases ISS cargo resupply services from Orbital ATK and SpaceX.

SpaceX’s last cargo mission also was a failure and a firm date for the next SpaceX launch to ISS has not been set, although NASA ISS program manager Kirk Shireman said this week that it will be no earlier than January 8, 2016.

NASA is anxious to get OA-4 up to ISS not only because the supplies are needed, but it is a very busy time there as NASA and its Russian counterpart, Roscosmos, try to meet a schedule that includes returning three people now on ISS to Earth on December 11, launching and docking a new three-person crew on December 15, undocking and deorbiting a Russian Progress cargo ship on December 18, and launching a new Russian Progress cargo craft on December 21 (it will dock on December 23).  After that, no visiting vehicles can come or go from the ISS because of a “beta angle cutout” from December 24 to January 2 when the Sun’s position relative to ISS does not provide proper lighting conditions for such activities.

The ISS is a partnership among the United States, Russia, Japan, Canada, and 11 European countries acting through the European Space Agency (ESA).   It is typically occupied by six people rotating on approximately 6-month shifts.   The six men currently aboard the ISS are NASA’s Scott Kelly and Kjell Lindgren, Japan’s Kimiya Yui, and Russia’s Mikhail Kornienko, Oleg Kononenko, and Sergei Volkov.   Lindgren, Yui and Kononenko are the three scheduled to return on December 11.   Kelly and Kornienko are on a one-year mission aboard the ISS to test human adaptation to spaceflight in preparation for someday sending crews to Mars.  They are more than half way through their mission, with their return scheduled for March 2016. along with Volkov (who arrived in September).