The return to flight of Orbital ATK’s Antares rocket will be sometime in August rather than July 6. The company is still analyzing data from its May 31 hot fire test and the timing of the launch also depends on other activities on the International Space Station (ISS).

The July 6 date has always been tentative, but in an emailed statement to SpacePolicyOnline.com today, Orbital ATK confirmed the slip to August.

“We are continuing to prepare for the upcoming launch of the Antares rocket and Cygnus spacecraft for the OA-5 cargo logistics mission to the International Space Station from NASA’s Wallops Flight Facility. Our Antares team recently completed a successful stage test and is wrapping up the test data analysis.



“Final trajectory shaping work is also currently underway, which is likely to result in an updated launch schedule in the August timeframe. A final decision on the mission schedule, which takes into account the space station traffic schedule and cargo requirements, will be made in conjunction with NASA in the next several weeks. Also, our Cygnus spacecraft for the OA-6 mission successfully undocked from the space station and hosted the Spacecraft Fire Experiment-I (Saffire). The team is now performing the final OA-6 mission milestones.”

The delay was first reported by Space News.

Orbital ATK uses Antares to launch Cygnus cargo spacecraft to the ISS. An October 2014 attempt failed 15 seconds after launch because of a problem with its AJ26 engine, a version of a Russian NK-33 engine built in the 1970s and refurbished by Aerojet Rocketdyne. The company decided to replace the AJ26/NK-33 engines with new Russian RD-181s. Two RD-181s are needed for each launch instead of one AJ26/NK-33.

A hot fire test of the re-engined Antares with two RD-181s took place on May 31 at the Mid-Atlantic Regional Spaceport (MARS) at Wallops Island, VA, the launch site for Antares.

While awaiting the Antares return to flight, Orbital ATK has launched two Cygnus cargo craft to ISS using United Launch Alliance (ULA) Atlas V rockets. Those were the Orbital ATK (OA)-4 and OA-6 missions. OA-6 just departed from the ISS and will reenter Earth’s atmosphere on July 22. The Antares return-to-flight mission is OA-5. The sequence is out of order because OA-5 was intended to take place between OA-4 and OA-6, but Antares was delayed and the decision was made to keep the mission designations with their launch vehicles (OA-4 and -6 on ULA’s Atlas V; OA-5 on Orbital ATK’s Antares).