Updated 3 p.m. Eastern Dec. 5.
KENNEDY SPACE CENTER, Fla. — For the third day in a row, poor weather postponed the Atlas 5 launch of an Orbital ATK Cygnus cargo spacecraft Dec. 5, further delaying the delivery of cargo to the International Space Station.
NASA said launch managers postponed the attempt more than three hours before the scheduled 5:10 p.m. Eastern launch time at Cape Canaveral, Florida, because forecasts predicted winds would remain too high throughout the 30-minute launch window. Clouds and rain prevented the first launch attempt Dec. 3, and winds just higher than limits postponed a second attempt Dec. 4.
“The winds were just a couple of knots too high,” said Vern Thorp, program manager for NASA missions at ULA, in an interview on NASA TV immediately after the Dec. 4 launch attempt was postponed. “We just did not feel comfortable launching tonight.”
NASA announced that the launch will be rescheduled for Dec. 6 at 4:44 p.m. Eastern time at the beginning of another 30-minute launch window. Forecasts call for a 40 percent chance of acceptable weather at launch time.
Cygnus, carrying more than 3,500 kilograms of supplies, equipment and experiments for the ISS on a mission designated OA-4, will arrive at the station on Dec. 9 if it launches Dec. 6.
The delays in the Cygnus launch threaten to create a traffic jam at the ISS this month because of the planned arrival and departure of four other spacecraft. “This is actually the beginning of an extremely busy time for the International Space Station,” said Kirk Shireman, NASA ISS program manager, during a pre-launch press conference here Dec. 2.
The arrival of the Cygnus on Dec. 9 or later would give the crew only limited time to unload the module before the Dec. 11 undocking of a Soyuz spacecraft returning three members of the ISS crew to Earth: Oleg Kononenko, Kjell Lindgren and Kimiya Yui. A Soyuz will launch Dec. 15 with three crew crewmembers: Timothy Kopra, Yuri Malenchenko and Timothy Peake.
Besides the departing and arriving Soyuz spacecraft, a Progress cargo spacecraft will undock from the station Dec. 18. A new Progress spacecraft, the first of the Progress-MS version, will launch Dec. 21 and dock with the station two weeks later.
Shireman said that, in addition to the Progress and Soyuz spacecraft arriving and departing the station, station managers had a “beta cutout” period from Dec. 24 to Jan. 2 when high solar illumination would prohibit spacecraft from traveling to and from the station. “It’ll be a time to catch our breath,” he said.
Frank Culbertson, president of Orbital ATK’s Space Systems Group, said Dec. 2 that the optimal time to launch was between Dec. 3 and 5, but that they could launch later and wait for an opening in visiting vehicle traffic to arrive at the station.
“We could loiter for quite a while in orbit until they opened up a window for us to approach the station,” he said, something he said the company had already brought up with NASA. “We’re ready to have that discussion if necessary.”