After getting rained out yesterday, it’s time to start preparing for the next launch window for the Cygnus spacecraft. If it succeeds, this will be the first launch for the cargo tug since the previous one blew up in October 2014. UPDATE: Gusts of wind caused first delays and finally a scrub for the launch attempt today. The next attempt will be at 5:10pm ET on Saturday. See the bottom of article for more details.

The return to flight mission for Orbital’s Enhanced Cygnus spacecraft is a cargo run to the International Space Station. The launch window begins at 5:33pm EST, and you can watch the launch preparations live here starting at 4:30pm ET:

This is the first flight for the new Enhanced Cygnus spacecraft which has 25% more volume for cargo than previous Cygnus spacecraft. It is carrying 3,349.0 kilograms (7,383.3 pounds) of material. The manifest includes 1,181.0 kilograms of essential crew supplies (food and care packages), 1,007.0 kilograms of hardware (power systems, structural equipment, thermal control hardware, and EVA supplies), 847.0 kilograms of research materials (a new life science facility, microsatellite deployer, metallurgy and flame-resistant textile experiments), 227.0 kilograms of spacewalk equipment, and 87.0 kilograms of computer equipment (cameras and data handling hardware).

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This is also the first time Cygnus is heading to space on a United Launch Alliance Atlas V rocket instead of an Orbital Antares rocket. The Atlas V is unusual in that it allows for an extended 30 minute launch window, allowing time to resolve technical glitches or for foul weather to clear.

Launch schematic for OA-4 from launch to interception with the International Space Station. Image credit: Orbital ATK

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It will take the spacecraft approximately 2.5 days to intercept the space station once it launches. It will stay attached for a month as astronauts unload cargo and refill the spacecraft with garbage. This is a one-way trip for Cygnus: when it undocks, it’ll burn up in the Earth’s atmosphere during destructive reentry.

If today’s launch is also scrubbed, two additional windows are open on December 5th and 6th. After that, mission planners will need to be creative about how to create orbital intercepts, possibly including a launch where the spacecraft will loiter in orbit for a few weeks before intercepting the space station. Due to an annual sun-angle blackout, no spacecraft can dock with the space station between Christmas Eve and January 3, 2016.

This is the fourth commercial cargo mission for Orbital, OA-4, since 2014. The company is contracted to deliver 28,700 kilograms (63,272 pounds) of cargo to the space station over approximately ten missions.

Artist’s concept of the Enhanced Cygnus approaching the International Space Station. Image credit: Orbital ATK

Update 6:03pm: Although the weather was better than during yesterday’s attempt, gusts of wind delayed today’s launch three times. Each failure reset the countdown clock to the final 4-minutes, and the rocket and spacecraft experienced no technical issues. With the final attempt set to the very end of the 30-minute window, that leaves the launch scrubbed for today. United Launch Alliance’s Vernon Thorp explained in the post-event briefing, “The winds were just a couple of knots too high, so we just didn’t feel comfortable launching tonight.”

The next windows open at 5:10pm ET on December 5th, and again at 4:44pm on December 6th. If Cygnus isn’t in orbit by the end of the weekend, mission controllers will need to do fancy planning to get around the orbital constraints of the International Space Station.

Check back with us tomorrow afternoon at 4pm as we follow the third launch attempt!

[NASA | Orbital | Orbital]

Top image: Atlas V rocket with Cygnus on board awaiting launch. The white-capped towers are lightening protection. Credit: NASA


Contact the author at mika.mckinnon@io9.com or follow her at @MikaMcKinnon.

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