After a mission lasting under two months, Orbital ATK’s OA-7 Cygnus spacecraft has conducted its final mission event – deorbit and destructive reentry. After departing the Space Station last week, Cygnus successfully conducted the SAFFIRE III fire in space experiment and deployed Cubesats for NanoRacks. Reentry occurred on Sunday over a remote stretch of the Pacific Ocean at around 13:02 EDT.
End of Mission:
Launched on 18 April 2017 after an almost month-long delay caused by its Atlas V carrier rocket, the flight of OA-7 Cygnus to the International Space Station was a resounding success – with the S.S. John Glenn departing the ISS over a month ahead of schedule.
The decision to release Cygnus early allowed the craft to perform its two post-Station mission objectives in a more timely manner instead of remaining berthed to the ISS for an additional month even though its mission was already complete.
Cygnus’ earlier unberth took advantage of a one-day opening in the ISS crew’s availability to release the craft ahead of schedule following the two-day weather delay to the CRS-11 launch of the SpaceX Dragon capsule.
The opening in the ISS crew’s schedule allowed Cygnus to depart the Station one day ahead of Dragon’s arrival.
Since leaving the Station last week, Cygnus has successfully performed the SAFFIRE III experiment, testing the real-life spread and interaction of fires in space with the various materials from which spacecraft are constructed.
After this experiment last Sunday, the craft continued its post-Station activities with the deployment of four NanoRacks Cubesats on Wednesday afternoon.
Following Cubesat deployment, Cygnus remained in a stable orbit through Saturday.
Yesterday, Cygnus’ controller in the Orbital ATK control room in Dulles, Virginia, began the process of preparing the craft for reentry.
A series of three engine firings on Saturday began at 11:50:19 EDT with the A4DV burn. This 285 second maneuver changed Cygnus’ velocity by 25.42 m/s and began the process of lowering Cygnus’ altitude – which had been raised from the Space Station’s ~400km orbit to 500km for Cubesat deployment.
The A5DV followed at 12:34:36 EDT, a 307 second thruster firing that further altered the OA-7 craft’s velocity by 27.62 m/s.
The final DV burn, A6DV, commenced at 13:20:25 EDT. A relatively small burn by comparison, the 85 second pulse from Cygnus’ engines changed the S.S. John Glenn’s velocity by 7.68 m/s.
These burns set Cygnus up for its farewell.
Deorbit operations then began on Sunday, 11 June at 08:00:47 EDT with the DDV1 burn – a 689 second firing of Cygnus’ thrusters that will reduce the craft’s speed by 62.98 m/s and set the spacecraft on a precise course for its deorbit burn.
The deorbit burn, known as RDV, then commenced at 12:36:59 EDT (16:36:59 GMT).
The burn lasted 5.5 minutes and slowed Cygnus by the final 30.82 m/s needed to send the craft into its death plunge into Earth’s atmosphere.
Entry Interface – the moment Cygnus encounters the first traces of Earth’s upper atmosphere – was set to occur at 13:12 EDT (17:12 GMT), with the destruction of the spacecraft occurring soon thereafter. However, Orbital ATK noted the timeline showed this was advanced by 10 minutes, marked at 13:02 EDT.
Looking ahead to OA-8:
Conclusion of the OA-7 mission will firmly shift attention for Orbital ATK to the next Cygnus flight – the OA-8E mission, which is scheduled to launch later this summer aboard the company’s Antares rocket.
The OA-8E mission represents the first of four flights of Orbital ATK under its extended contract with NASA for Cygnus operations.
The extension to the CRS-1 (Commercial Resupply Services 1) contract award was made by NASA to both SpaceX and Orbital ATK based on delays the CRS-2 contract awards and the commencement of those flights in 2019.
Specifically for OA-8E, preparations are well underway at the Mid-Atlantic Regional Spaceport (MARS) in Virginia.
According to Frank DeMauro, Vice President and General Manager of the Advanced Programs Division for Orbital ATK Space Systems Group, “Preparations for OA-8 are going very well. For Cygnus, the PCM is already at Wallops and the Service Module has completed all testing and is ready to be shipped to Wallops approximately 45 days prior to launch.
“The Antares team is also making great progress towards launch. The hardware is in excellent shape and the team is ready to go.”
Specifically for Antares, the Castor 30XL second stage has been going through mechanical integration including motor cone and avionics structure installations – with everything on track for launch later this year.
While all launches to the Space Station are based on a variety of factors, including crew time, visiting vehicle schedules, and supply needs, Orbital ATK states that they will be ready to support a launch “later this summer.”
According to Mr. DeMauro, “The final launch date will be determined jointly by NASA and Orbital ATK based on hardware readiness and NASA traffic and cargo requirements.”
At the post-launch news conference for the OA-7 mission back in April, it was stated that OA-8E was targeting a launch in the September time frame.
This would place the mission, under the currently understood visiting vehicle schedule for the ISS, between SpaceX’s CRS-12 mission, which is slated to launch No Earlier Than 1 August 2017, and the CRS-13 mission, which is currently targeting a launch sometime in November.
OA-8E will be the second and final flight of Cygnus in 2017, with the OA-9E mission now slated to occur in 2018.
OA-8E will carry ~3,350kg of cargo up to the ISS, marking the heaviest payload yet for the Antares rocket.
(Images: Orbital ATK, NASA)