Northrop Grumman

4:59 p.m.                Begin 30-minute hold at T-4 Minutes
5:03 p.m.                Weather Briefing
5:26 p.m.                Status check to continue countdown
5:29:11 p.m.           T-4 Minutes and counting
5:33:08 p.m.           RD-180 engine ignition
5:33:11 p.m.           Launch
5:33:29 p.m.           Begin pitch/yaw/roll maneuver
5:34:33 p.m.           Mach 1
5:34:44 p.m.           Maximum Dynamic Pressure
5:37:26 p.m.           Atlas booster engine cutoff (BECO)
5:37:32 p.m.           Atlas booster/Centaur separation
5:37:42 p.m.           Centaur first main engine start (MES1)
5:37:50 p.m.           Payload Fairing jettison
5:51:27 p.m.           Centaur first main engine cutoff (MECO1)
5:54:16 p.m.           Cygnus spacecraft separation
~6:33 p.m.              Cygnus solar array deploy
~7:30 p.m.              Post-Launch News Conference on NASA Television

The cryogenic propellant tanks on the United Launch Alliance Atlas V booster stage and Centaur upper stage are loaded now as we move toward a liftoff time of 5:33 p.m. EST from Cape Canaveral Air Force Station in Florida, adjacent to NASA’s Kennedy Space Center. Pumps have slowed to “topping mode.” The booster’s RD-180 engine uses RP-1 fuel and liquid oxygen to generate about 933,000 pounds of thrust. The Centaur stage burns liquid hydrogen and liquid oxygen to place the Orbital ATK enhanced Cygnus spacecraft and its 7,383 pounds of cargo into its initial orbit to get to the International Space Station. The launch window is 30 minutes today.

. . . at Space Launch Complex 41 where a United Launch Alliance Atlas V stands ready to send a cargo-laden Cygnus spacecraft built by Orbital ATK into orbit later this afternoon. As with yesterday, the weather is garnering a large share of attention as we move toward our scheduled launch time of 5:33 p.m. EST. The forecast stands at a 40 percent chance of acceptable conditions today.The launch team has a 30-minute window today to begin the mission that will see more than 7,300 pounds of equipment and supplies to the International Space Station.

As our continuous countdown coverage gets under way here and on NASA TV, look for up-to-date information about the countdown, launch and ascent into space along with background information about what makes this mission important and how the science being conducted off the Earth will advance life on the Earth, as well as prepare the way for future crews making an eventual journey to Mars.

 

Air Force meteorologists offered an improved weather forecast for Friday’s launch of the Orbital ATK CRS-4 resupply mission to the International Space Station. The likelihood of acceptable conditions has grown to 40 percent for launch time at 5:33 p.m. EST, the start of a 30-minute window. Our continuous countdown and launch coverage of the cargo-laden Cygnus spacecraft atop an Atlas V rocket will begin at 4:30 p.m. on this blog and on NASA TV, which can be linked from here or streamed at www.nasa.gov/ntv

Forecasters from the Cape Canaveral Air Force Station 45^th Weather Squadron have issued an updated prediction for today’s launch of an Orbital ATK Cygnus cargo spacecraft at 5:33:11 p.m. EST aboard a United Launch Alliance Atlas V rocket. There are no significant changes from the forecast released Thursday evening. There remains a 30 percent chance of favorable weather today, 30 percent Saturday and 40 percent chance on Sunday.

A launch in the first 7 ½ minutes of today’s 30-minute launch window will result in a rendezvous at the International Space Station and grapple and berthing of Cygnus on Monday, Dec. 7. A launch in the remainder of the window will result in a rendezvous with the station on Tuesday, Dec. 8

Our continuous countdown coverage here and on NASA Television will begin at 4:30 p.m. You can use the link here on the blog to watch or stream directly at https://www.nasa.gov/nasatv.

With no signs poor weather conditions would clear in time for a launch today, the launch managers scrubbed today’s try. The United Launch Alliance Atlas V rocket and Orbital ATK Cygnus spacecraft will be configured to launch tomorrow at 5:33 p.m. EST, the opening of a 30-minute window. The forecast tomorrow calls for a 30 percent chance of acceptable conditions at launch time. Continuous countdown coverage here and on NASA TV will begin at 4:30 p.m. EST.

The launch teams are now working toward a liftoff at 6:25:45 p.m. EST, the end of today’s launch window for the Atlas V rocket and its Cygnus payload.

Launch managers have set a new liftoff time for today at 6:03 p.m. EST. Weather remains the only concern.