Friday morning’s unberthing and departure of Orbital ATK’s OA-4 Cygnus cargo ship from the International Space Station (ISS)—wrapping up the first U.S. visiting vehicle mission of 2016, as well as marking the longest stay-time of any commercial provider at the orbital outpost—has cleared the way for a busy slate of unpiloted missions from NASA’s commercial partners. Current plans envisage up to five SpaceX Dragon cargo missions between April and December, with as many as three more Cygnuses expected to fly at intervals from March through October. If this schedule is met, the year will close with SpaceX having flown 12 dedicated resupply missions, and seven for Orbital ATK, under the language of their Commercial Orbital Transportation Services (COTS) contracts, signed back in December 2008. This year is expected to see the arrival via CRS vehicles of the long-awaited Bigelow Expandable Activity Module (BEAM) and the first of two International Docking Adapters (IDAs) for Commercial Crew operations, together with a significant quantity of science and supplies for several ISS crews.
In anticipation of the OA-4 departure, the orbit of the space station was raised on Wednesday, 17 February, using the engines of Russia’s Progress M-29M resupply freighter, which is docked at the aft longitudinal port of the Zvezda service module. The “burn,” which took place at 9:44 p.m. EST, served to position the ISS at the proper altitude for the departure of One-Year crewmen Scott Kelly and Mikhail Kornienko, together with cosmonaut Sergei Volkov, who are due to return to Earth early on 2 March. This was followed by the robotic unberthing of the OA-4 Cygnus cargo ship—nicknamed “Spaceship Deke Slayton,” in honor of the former Mercury and Apollo-Soyuz Test Project (ASTP) astronaut—from the Earth-facing (or “nadir”) port of the Unity node at 5:38 a.m. EST Friday, 19 February. Unberthing and positioning of the craft was performed by the 57.7-foot-long (17.6-meter) Canadarm2 robotic arm and was conducted by the Robotics Officer (ROBO) in the Mission Control Center (MCC) at the Johnson Space Center (JSC) in Houston, Texas.
“Honor to give #Cygnus a hand (or arm) in finalizing its mission this morning,” tweeted Expedition 46 Commander Scott Kelly, who oversaw Friday’s departure. Less than two hours later, at 7:26 a.m. EST, Kelly and his Expedition 46 crewmate Tim Kopra oversaw the successful release of Cygnus from Canadarm2. For Kopra, the role of Canadarm2 itself—which was installed onto the station almost 15 years ago and which has played a significant role in the assembly and resupply of the ISS—was of equal importance. “Amazing robotic arm helped build our @Space_Station,” he tweeted to his 52,300 followers. “Next job: unberth and release #Cygnus.” Kopra’s sentiment was shared by British astronaut Tim Peake, who described Canadarm2 as “a true workhorse” and poignantly thanked Canada for its contribution to the ISS Program.
At the time of separation, the station and Cygnus were flying high above Bolivia, as seen in a stunning perspective subsequently tweeted by Kelly. When the cargo ship, loaded with trash and other unwanted items, had reached a safe distance from the ISS, it twice pulsed its hydrazine/nitrogen tetroxide thrusters to push the low point of its orbit deep into Earth’s atmosphere. This will cause it to burn up over a sparsely inhabited stretch of the Pacific Ocean on Saturday, 20 February.
The OA-4 mission now holds the record for the longest stay-time of any commercial visiting vehicle, having been attached to the space station for more than 10 weeks. From the moment of its berthing at the Unity nadir interface at 9:26 a.m. EST last 9 December to the instant of its unberthing and departure at 7:26 a.m. EST Friday, Cygnus had remained in place for 71 days and 22 hours. This is almost twice as long as the next-longest Cygnus stay-time—the ORB-1 flight, named in honor of former shuttle commander C. Gordon Fullerton, which spent almost 37 days berthed at the ISS in January-February 2014—and significantly longer than SpaceX’s longest-ever Dragon resident, CRS-6, which clocked almost 34 days affixed to the ISS in April-May 2015. And when one adds to that Cygnus’ total time since launch, last 6 December, this mission will have spent about 76 days in orbit, more than twice as long as the 37-day launch-to-landing achievement of SpaceX’s CRS-6.
As previously outlined by AmericaSpace, the OA-4 mission marked the inaugural outing of Orbital ATK’s “Enhanced Cygnus” spacecraft, which is visually distinctive from its “Standard” predecessor, primarily due to the presence of two UltraFlex solar arrays. The latter are circular, as opposed to the rectangular arrays utilized aboard Standard Cygnuses, and although they provide the same amount of power—around 3.5 kilowatts—they are significantly less massive. Moreover, the Enhanced Cygnus is much larger: measuring 15.9 feet (4.86 meters) high, about 3.9 feet (1.2 meters) taller than the Standard, and capable of accommodating a much larger payload volume of around 950 cubic feet (27 cubic meters). According to NASA, this enabled OA-4’s Pressurized Cargo Module (PCM) to carry 7,383 pounds (3,349 kg) of total cargo, which represented the heaviest payload ever delivered into space aboard a Cygnus and a 40-percent uplift on any of its predecessors.
The departure of OA-4 opens the gates for a busy 2016 of visiting vehicle traffic, which is expected to get underway later in March, following the departure of Kelly, Kornienko, and Volkov and the mid-month arrival of the next increment, Soyuz TMA-20M cosmonauts Alexei Ovchinin and Oleg Skripochka, together with NASA astronaut Jeff Williams. The station’s next planned visitor will be the OA-6 Cygnus—the second ISS-bound commercial vehicle to be lofted by a United Launch Alliance (ULA) Atlas V booster, whilst Orbital ATK awaits the return to flight of its homegrown Antares rocket—whose launch was recently moved from 10 March until No Earlier Than (NET) 22 March.
During a routine inspection of cargo bags for the OA-6 mission, microbial analyses revealed evidence of common black mold and a decision was taken to disinfect all cargo, including that already loaded aboard Cygnus, before moving into the final phase of payload packing. “The initial mold response is complete with the full re-disinfection of all cargo bays in the initial cargo shipment for OA-6,” NASA told AmericaSpace on Wednesday. “In addition, the teams verified full disinfection of a planned second shipment of cargo currently being packed for transport to KSC. The investigation will be ongoing to determine root cause and proper future mitigations.”
Although the OA-6 cargo manifest is still being finalized, it is understood that the mission will rise from Space Launch Complex (SLC)-41 at Cape Canaveral Air Force Station, Fla., in the third week of March, with Novosti Kosmonavtiki suggesting a 30-minute “window” on the 22nd, which extends from 10:02-10:32 p.m. EST. Although ISS-bound missions ordinarily require short or “instantaneous” windows, usually no longer than 5-10 minutes, the OA-4 launch campaign demonstrated ULA’s capability to enhance its “mission design capabilities and operational processes” and “make good use of the launch vehicle performance to provide the flexibility to accomplish launch window objectives.” Assuming an on-time launch, Cygnus will be robotically captured, again via Canadarm2, and berthed at the Unity nadir interface on 26 March, where it will remain until May.
Dovetailed into this manifest will be the return to flight of SpaceX’s Dragon cargo ship, which has already supported one “demo” and six successful “dedicated” resupply flights to the space station since May 2012, before being stalled by the high-altitude failure of CRS-7, last 28 June. At present, the CRS-8 mission—bearing the Bigelow Expandable Activity Module (BEAM) in Dragon’s unpressurized “trunk,” together with a pressurized cargo of food, water, equipment, and supplies for the Expedition 47 crew—is officially “still in review,” with NASA noting that “downstream effects from the OA-6 delay are still being worked out.” That said, Novosti has suggested a tentative launch date as early as 2 April. After two days in free flight, the Dragon will be robotically captured by Canadarm2 and berthed at the nadir port of the Harmony node, thus marking the first instance that unpiloted visiting vehicles will be located simultaneously at both nodes.
Although the Unity node was one of the earliest ISS components to reach orbit—launched aboard STS-88 in December 1998—it has been occupied at various points during its 17 years aloft. It provided an early home for Pressurized Mating Adapter (PMA)-3, enabling the shuttle dockings of STS-97 and STS-98 in the winter of 2000-2001, and routinely supported Italian-built MPLMs during several flights prior to and after the Columbia disaster, before being occupied by the Leonardo Permanent Multipurpose Module (PMM) in February 2011. This “permanence” ended in May 2015, when the Leonardo PMM was robotically relocated to a new home on the station’s Tranquility node, allowing the Unity nadir interface to once again become available for visiting cargo craft. As a result, the ISS now has two berthing locations—one at Unity nadir, the other at the nadir port of the Harmony node—for unpiloted Cygnuses from Orbital ATK, Dragons from SpaceX, and H-II Transfer Vehicles (HTVs) from the Japan Aerospace Exploration Agency (JAXA).
With CRS-8 expected to remain in orbit for about a month, it can be anticipated that both the Dragon and Cygnus spacecraft will depart the station in relatively short order, sometime in May, only weeks before Orbital ATK plans to return its Antares booster to flight, carrying OA-5 from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va. Unused for a rocket launch since the catastrophic loss of the ORB-3 Cygnus vehicle on 28 October 2014, this will not only mark the return of Antares, but also the inaugural mission of its new “230” configuration, boasting enhanced, Russian-built RD-181 first-stage engines and a second stage powered by the Castor-30XL solid-fueled motor. According to Novosti, two Antares-230 boosters will deliver the OA-5 Cygnus toward the ISS on 31 May and the OA-7 Cygnus on 4 October. The 230 booster is reportedly capable of delivering a Cygnus laden with up to 7,100 pounds (3,200 kg) of payloads and supplies to low-Earth orbit and enables Orbital ATK to make good on its pledge to complete its original eight-mission CRS contract with NASA by early 2017.
With as many as three Cygnuses expected to fly this year, SpaceX anticipates as many as five Dragons, which will be the largest number of visiting vehicles ever despatched to the ISS by the Hawthorne, Calif.-based launch services provider in its history. (Previously, it has flown a peak of two successful missions per annum in 2012, 2014 and 2015.) Following the arrival of CRS-8, the BEAM module will be robotically removed from Dragon’s trunk and attached to the aft-facing port of the Tranquility node, where it will remain for up to two years. “BEAM is a combined ground and crew operation,” NASA’s Rob Navias told AmericaSpace, “somewhere around five days or so after Dragon berthing.”
It was also pointed out that the movement of the inflatable module—which measures about 13 feet (4 meters) in length and 10.5 feet (3.2 meters) in diameter, offering a habitable internal volume of 565 cubic feet (16 cubic meters)—will be conducted remotely from the ground. The operation to transfer BEAM from Dragon’s unpressurized trunk and rigidly attach it to the Common Berthing Mechanism (CBM) of Tranquility’s aft port is expected to require about eight hours, although the actual “expansion” of the module will not occur immediately and is scheduled to take place “within four months” of its arrival. Mr. Navias has stressed that “no timetable” has been set for the first crew ingress or activity inside BEAM, but that “it will not be immediately.”
Following the departure of CRS-8, the long-awaited CRS-9 mission is tentatively planned for May, bringing the IDA-2 payload to the station. This Boeing-built docking adapter will be installed onto Pressurized Mating Adapter (PMA)-2, at the forward end of the Harmony node, during a joint robotics/EVA operation, planned for U.S. EVA-36. Spacewalkers for this excursion are as-yet undetermined, as are the precise tasks of the EVA itself, and since it will likely occur close to the change-over between the Expedition 47 and 48 increments, it remains to be seen who will perform U.S. EVA-36.
IDA-2 was originally intended to be the “backup” Commercial Crew docking adapter, attached to the zenith port of Harmony, the loss of IDA-1 in June 2015 has pressed it into the “primary” role. It will therefore be mounted onto the forward port of Harmony. A replacement (IDA-3) is in the process of being assembled from spare parts and will be launched in the spring of 2017, possibly aboard SpaceX’s CRS-14 Dragon to take IDA-2’s original position. However, NASA recently advised AmericaSpace that “We are working with Boeing to finalize plans for IDA-3 fabrication.”
Shortly after the CRS-9 Dragon berths at the station, the crew and ground controllers will remove the 1,150-pound (520-kg) IDA-2 from the spacecraft’s trunk and “temp-stow” it onto Canadarm2’s Dextre Special Purpose Dextrous Manipulator (SPDM), to await installation onto Harmony’s forward port during a combined EVA/robotics operation. IDA-2 will be positioned between 10 inches (25 cm) and two feet (60 cm) from the forward end of PMA-2 at the front end of Harmony, whereupon U.S. EVA-36 spacewalkers will maneuver it into position, closing external connectors, internal switches, and driven hook-motors. This will open the way for the arrival of Boeing’s CST-100 Starliner and SpaceX’s Crew Dragon vehicles, both of which are expected to stage their inaugural piloted missions in 2017, restoring the United States’ ability to launch its own astronauts from U.S. soil for the first time since the end of the Space Shuttle era.
Rounding out 2016, three other Dragons are tentatively scheduled to fly on 12 June, 15 August and 15 December; an ambitious schedule, indeed. The first of these missions, CRS-10, will deliver the Department of Defense (DoD) Space Test Program (STP)-H5, which will host the Lightning Imaging Sensor (LIS) for 24-hour global lightning measurements. It will be robotically installed in a nadir-facing position on ExPRESS Logistics Carrier (ELC)-1 on the P-3 truss, remaining operational for about two years. Other CRS-10 payloads include the Stratospheric Aerosol and Gas Experiment (SAGE)-III—equipped with Instrument Payload (IP) and Nadir-Viewing Platform (NVP)—which will be robotically installed onto ELC-4 on the S-3 truss, thereby providing a continuous and unobstructed view of Earth’s atmospheric limb as it seeks to undertake long-term measurements of ozone, aerosols, water vapor, and associated gases.
Next up, CRS-11 in August will deliver the Neutron Star Interior Composition Explorer (NICER), the Multiple User System for Earth Sensing Facility (MUSES)—tasked with monitoring stratospheric aerosols, lightning imaging, and high-resolution observations of the Home Planet—and testing of a Roll-Out Solar Array (ROSA). The latter will roll open in space, like a party favor, offers greater compactness than current rigid-panel solar-array designs. ROSA will be robotically detached from Dragon’s trunk and “temp-stowed” onto an ELC. It will later be transferred by Canadarm2 to its operational location for around a week of deployment activities. All commanding of ROSA will be done by the Robotics Officer (ROBO) in Houston. Closing out 2016, SpaceX’s CRS-12 mission will launch in mid-December, carrying the Cosmic Ray Energetics and Mass (CREAM) cosmic-ray detection payload.
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