Orbital ATK Cygnus OA-5 SS Alan Pointdexter finished its mission in dense layers of atmosphere on November 27. It has spent in space 40 days since reaching orbit on atop of Antares 230 on October 17.
It was successful month in space for SS Alan Pointdexter. In spite of fact of delivering over 2300 kg of supplies for crew of International Space Station, Cygnus served as usual for getting rid off of all unwanted equipment and trash. After undocking from Unity nadir docking port and release from Canadarm2 grab on November 22, spacecraft entered into last phase of OA-5 mission – performing experiments and deploying Cubesat satellites using NanoRacks deployment device.
First phase of last mission of Cygnus was initialization of SAFFIRE-II experiment shortly after leaving International Space Station. It is basically hermetically closed environment filled with flammable materials and oxygen; SAFFIRE-II in spite of its not spectacular look is important step in improving knowledge on dynamic and behaviour of flames in low gravity conditions. Improving our knowledge on physics of flames in low gravity will help in creating more safety space vehicles in future and develop new fire-extinguishing systems for currently used vehicles. This time experiment was focused on nine samples of different materials (with the following dimensions: 5 cm x 30 cm) ignited with steel wire using electricity; experiment was designed to test how low gravity conditions change flammability limits in Maximum Oxygen Concentration (21%, just as inside ISS). SAFFIRE-II was carried out in conditions simulating configuration described in NASA-STD-6001 Test 1. Just as its predecessor onboard of Cygnus OA-6 earlier this year, SAFFIRE-II was conducted after reaching safe distance from ISS to prevent any damage for the Station in case of potential failure of steel container containing flammable material and explosion of spacecraft. It was started at 18:30 UTC on November 22 and was recorded with cameras, microphones and number of sensors installed around container inside Cygnus. Data collected during experiment were transmitted to Earth during following days and until November 25 Cygnus remained on 413.6 km x 422.5 km orbit (five kilometers above ISS). To meet demands of the next point of its mission, Cygnus have been waiting until Friday 25, when it initiated two burns of its BE-4 engine to increase orbit from 417.7 km (final orbit before burn was already circular) to 502.6 km x 511.2 km. First pair of LEMUR-2 satellites (Sokolsky and Xioaqing) was deployed at 21:05 UTC and next pair separated already on Saturday (Anubhavthakur and Wingo) at 01:05 UTC.
This was last part of the OA-5 mission. On Sunday, Cygnus started its main engine once again to reduce speed with two burns. It entered into dense upper layers of atmosphere of Earth around 23:36 UTC on November 27, 2016 over South Pacific.