The Return To Flight (RTF) of Orbital ATK’s Antares rocket is currently waiting on a launch date decision, following resolution work after May’s Static Fire test. The launch, expected to take place in the next four or five weeks, will task Antares with lofting the OA-5 Cygnus en route to a berthing slot in the International Space Station’s increasingly convoluted Visiting Vehicle schedule.
The long-awaited return of Antares will take place almost two years after the CRS-3 mission failed just seconds after lift-off from the Wallops launch site.
Two Cygnus missions have taken place since the loss of Antares – thanks to her ability to launch with multiple launch vehicles.
Those missions – OA-4 and OA-6 – were successfully launched on United Launch Alliance (ULA) Atlas V rockets, flying out of Cape Canaveral Air Force Station SLC-41 in Florida in December 2015 and March 2016, respectively.
The hiring of Atlas V allowed Orbital ATK to continue with its Commercial Resupply Services (CRS) obligations, while work on bringing Cygnus’ natural launch vehicle back into service.
The two RD-181 engines replaced Aerojet AJ-26 engines that were used in the first Antares launches in 2013 and 2014.
The new vehicle configuration is designated as the Antares 200 series, capable of lofting the larger version of the Cygnus spacecraft that debuted with the rides uphill on the Atlas V.
Cygnus flights to the ISS will use the new first stage coupled with Orbital ATK’s CASTOR 30XL solid motor as a second stage in the Antares 230 configuration.
At the time of the test, Antares was targeting a return date of July 6 for the OA-5 mission to the ISS.
Notably, the Antares 230 core stage for OA-5 was not the first stage that underwent the static fire.
The OA-5 rocket remained inside the integration facility, awaiting the results of the tests taking place on her sister that is destined to launch on the OA-7 mission.
Orbital ATK then opted to delay the launch date due to the requirement for “static fire test data analysis to be completed, along with final trajectory shaping work.”
During the interim period, Antares engineers fine-tuned Antares, based on the results of the static fire test. This included the replacement of an engine actuator.
“During the testing and inspection process of the OA-5 vehicle, an unexpected engine actuator response was detected,” noted Trina Helquist, Sr. Manager Communications with Orbital ATK’s Launch Vehicles Division.
“In order to fully understand the occurrence, the unit was removed. We have since replaced the actuator and have completed its initial testing to ensure its readiness for the OA-5 mission.”
The static fire also proved its worth when a hardware review identified a trace amount of particulate in the pneumatic system. However, Orbital ATK noted that was introduced through an interface used for ground testing and which is not used in actual flight operations.
“We have incorporated corrective action into our processes. All other ground systems, both in the launch vehicle assembly facility and at the launch pad, were inspected and confirmed to meet specifications.”
“We will continue to follow our rigorous testing and inspection procedures to ensure mission success.”
Antares’ launch date with the Cygnus spacecraft has the additional challenge of negotiating a slot for arrival in the Station’s busy Visiting Vehicle (VV) schedule, which has become more convoluted over recent weeks.
Japan’s HTV-6 mission to the Station was set to take place in early October and as such provided the main roadblock to Cygnus’ path to the orbital outpost – although the ISS management can request a level of rearrangement to cater for all partners.
Notably, Mitsubishi Heavy Industries, Ltd. and the Japan Aerospace Exploration Agency (JAXA) recently decided to postpone the launch of HTV-6 from its October 1 launch date – to a yet-to-be-determined slot – after a leak was found during processing on the cargo vehicle.
Orbital ATK confirmed an exact launch date for its OA-5 Cygnus has not yet been determined. The current official NET (No Earlier Than) date is late September, although that is expected to change, with the launch expected to take place in the next four to five weeks – which points to an October date.
Cygnus is only expected to make a short visit to the Station, with the most recent Flight Planning Integration Panel (FPIP) manifest (L2) showing Cygnus’ berthed mission is only scheduled for nine days.
The OA-7 Cygnus will enjoy a much longer stay, with a berthed mission of just over two months, per the FPIP manifest document.
The previous plan was for HTV-6 to reside at the ISS for over a month, prior to the arrival of SpaceX’s CRS-10 Dragon spacecraft. However, Dragon’s schedule is also now “under review” as a result of the fallout from the loss of the Falcon 9 with Amos-6 during a Static Fire test this month.
Although the ISS is “well stocked” to cope with the changes to its supply vehicle launch dates, ISS managers are busy realigning their planning schedules, which will eventually provide launch date options for Antares’ return.
(Images: Orbital ATK, ULA, Pratt & Whitney Rocketdyne, NASA and L2 including renders from L2 artist Nathan Koga – The full gallery of Nathan’s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*)
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