Antares launch timeline on the NG-12 mission

The Antares launch timeline for the NG-12 mission. Credit: Northrop Grumman

Northrop Grumman’s Antares rocket will deliver a Cygnus supply ship into orbit Saturday to begin a two-day pursuit of the International Space Station.

The rocket’s two RD-181 engines will ignite around 3.7 seconds before liftoff from pad 0A at the Mid-Atlantic Regional Spaceport, a complex owned by the state of Virginia at NASA’s Wallops Flight Facility.

Launch is timed for 9:59 a.m. EDT (1359 GMT) Saturday

The first stage’s two RD-181 engines will power up to 864,000 pounds of thrust and burn for 3 minutes, 14 seconds, then separate from the upper stage’s Castor 30XL motor about eight seconds later. The first stage burn time is approximately 20 seconds shorter than on previous Antares missions because the RD-181 engines will operate at full throttle through most of the early phase of the launch.

The launch, known as NG-12 in Northrop Grumman’s station resupply manifest, will be the sixth Antares mission using new, more powerful RD-181 engines, which the company ordered from the Russian engine-builder NPO Energomash to replace decades-old Russian-built AJ26 engines blamed for an Antares rocket crash seconds after liftoff in October 2014.

Once the first stage finished its job on the NG-12 launch the Antares rocket’s 12.8-foot-diameter (3.9-meter) diameter payload shroud will jettison in two halves at around T+plus 3 minutes, 53 seconds. An interstage adapter that connected the first and second stages will separate at T+plus 3 minutes, 59 seconds.

The launcher’s Castor 30XL solid-fueled upper stage will ignite at T+plus 4 minutes, 5 seconds, and generate up to 104,300 pounds of thrust during a burn lasting approximately 2 minutes, 43 seconds. The second stage motor will burn out at approximately T+plus6 minutes, 48 seconds, then deploy the Cygnus spacecraft at around T+plus 8 minutes, 38 seconds.

The spacecraft’s two cymbal-shaped electricity-generating solar arrays will unfurl in a fan-like motion around two hours into the mission, and the ship’s thrusters will begin fine-tuning its approach to the space station with a series of course-correction burns, setting up for a laser-guided final approach Monday.

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