More than a decade after his mortal life was lost, along with his crew, during the final, tragic re-entry of Shuttle Columbia, veteran astronaut Rick Husband was posthumously granted a second opportunity to visit the International Space Station (ISS) tonight (Tuesday, 22 March). A mighty United Launch Alliance (ULA) Atlas V 401 booster successfully delivered Orbital ATK’s OA-6 Cygnus cargo ship into low-Earth orbit, en-route for a Saturday arrival at the multi-national outpost. Liftoff from Space Launch Complex (SLC)-41 at Cape Canaveral Air Force Station, Fla., took place on-time at 11:05 p.m. EDT. As has become traditional in its Cygnus operations, Orbital ATK named OA-6 in honor of an individual who had contributed substantially to the goals of commercial spaceflight or exploration: in this case, paying tribute to Husband’s unique “spirit for exploration.”
Previous Cygnus missions have also memorialized deceased astronauts—specifically former Orbital senior executive G. David Low, veteran shuttle commander C. Gordon Fullerton, five-time flier Janice Voss, and “Original Seven” Mercury selectee Donald “Deke” Slayton—but for the first time with Husband a Cygnus will be named for an individual who actually boarded the ISS itself. Husband flew as pilot on STS-96, which performed the first docking with the infant station, way back in mid-1999. When the Expedition 47 crew opens the hatch into his spacefaring namesake on Saturday morning, they will be greeted by a welcome sign and a photograph of Husband, pictured on Columbia’s flight deck, during his final, fateful space voyage.
As detailed in yesterday’s AmericaSpace preview article, preparations for OA-6 entered high gear on 23 January, when the 41.5-foot-long (12.6-meter) Centaur upper stage for the Atlas V 401 booster arrived at the Cape. Two weeks later, the 106.5-foot-long (32.5-meter) Common Core Booster (CCB)—the rocket’s first stage, powered by a Russian-built RD-180 engine—also arrived and the pair were mated in the Vertical Integration Facility (VIF) at SLC-41 on 26 February. In the meantime, Cygnus’ Pressurized Cargo Module (PCM) arrived in Florida in mid-January, followed by its Service Module (SM) a few days later. These were integrated in the Space Station Processing Facility (SSPF), transferred to the Payload Hazardous Servicing Facility (PHSF) for fueling, and encapsulated within a 45.3-foot-long (13.8-meter) Extra-Extended Payload Fairing (XEPF). On 14 March, the XEPF was installed atop the Atlas V, topping-off this “barebones” variant of ULA’s booster fleet at an impressive 194 feet (59 meters).
Rollout of the Atlas V—whose “401” nomenclature describes the presence of a 13-foot-diameter (4-meter) payload fairing, no strap-on rockets, and a single-engine Centaur upper stage—took place yesterday (Monday). The approximately quarter-mile (400-meter) distance from the VIF to the SLC-41 pad surface took place under cloud-flecked blue skies and nominally required about 35 minutes to complete. When the vehicle was “hard-down” on the pad, it was carefully centered and propellant umbilicals and electrical and data connections were established. The track mobiles from the Mobile Launch Platform (MLP) were removed and ULA engineers set to work preparing for formal countdown operations. This included the initiation of flight control systems, the bringing online of ground command, control, and communications instrumentation, and the verification of interfaces between the Atlas V and the Launch Control Center (LCC).
Under normal circumstances, ISS-bound missions are required to meet either “instantaneous” or very short (5-10 minutes) launch windows, in order to establish the proper orbital parameters and conditions for rendezvous with the outpost. However, as demonstrated during its OA-4 Cygnus launch, last December, ULA has utilized the flexibility and performance of the Atlas V to meet a longer, 30-minute window. According to Jim Sponnick, ULA’s vice president for Atlas and Delta Programs, instantaneous windows “can significantly limit the probability of an on-time launch,” and in remarks provided to AmericaSpace he stressed that ULA “strives to implement longer launch windows in our mission designs to maximize the probability of a first-day launch for our customers.”
Additionally, ULA and Orbital ATK have worked closely to produce a mission design which not only provides for the longer window, but also accommodates the need to respond to short-notice changes in the space station’s orbit. Such changes might include the late requirement to execute a Debris Avoidance Maneuver (DAM). “The launch design approach accounts for the fact that the ISS orbit can change shortly before the launch, if either an overall orbit adjustment or evasive debris mitigation maneuver is required,” explained Mr. Sponnick in quotes provided to AmericaSpace, prior to the OA-4 mission. “Considering the capabilities inherent in the Atlas design, the late changes that can occur in the ISS orbit and the close co-ordination with the Orbital ATK Cygnus rendezvous design, we have implemented a 30-minute-long window, which will occur within a bounding 50-minute-long window that accounts for the potential late orbital changes for the ISS.”
In readiness for today’s opening launch attempt, the Florida weather presented a 90-percent likelihood of acceptable conditions, with a slight risk of a violation of the Cumulus Cloud Rule. The Atlas V CCB had been previously fueled with a “storable” form of rocket-grade kerosene (known as “RP-1”) a few days ago, but the loading of liquid oxygen took place relatively late in the countdown, in order that the boiled-off cryogens could be continuously replenished until close to T-0. In tandem, liquid oxygen and hydrogen were loaded aboard the Centaur upper stage, which was tasked with executing a 14-minute “burn,” late in the ascent, to inject the OA-6 Cygnus spacecraft into low-Earth orbit.
With fueling complete, the Atlas V entered its final pre-planned “hold” at T-4 minutes at 10:31 p.m., with the expectation that the clock would be stopped for about 30 minutes, for final checks and a “Go/No-Go” poll of all stations by ULA Launch Conductor Scott Barney. During the course of the hold, Clay Flinn, the 45th Weather Squadron weather officer, delivered his final summary from late weather balloon data and confirmed that meteorological conditions were without mandated parameters. In the meantime, the workhorse Atlas V was clearly ready to go. As cryogenic topping concluded, the CCB turned from a deep copper color to an intense white. “The signature plume of vapor that can be seen streaming from the booster is the boiling fuels venting from the rocket,” noted AmericaSpace’s Launch Tracker at 10:43 p.m. “The booster was a copper color as it stood unfilled on the launch pad, [but] as the fueling process started the booster turned white with ice crystals.”
At 11:01 p.m. EDT, Mr. Barney issued a definitive “Go for Launch” and the countdown clock was released from its final hold at T-4 minutes. During these dwindling few minutes, all propellant tanks aboard the Atlas V were pressurized and the Flight Termination System (FTS)—tasked with destroying the vehicle in the event of a major contingency during ascent—was placed onto internal power and armed.
The RD-180 engine, with a total propulsive yield of 860,000 pounds (390,000 kg), roared to life at T-2.7 seconds, and was subjected to a series of computer-controlled health checks, ahead of leaving the pad at T+1.1 seconds. At precisely 11:05 p.m. EDT, for the 62nd time since its maiden voyage, way back in August 2002, the Atlas V took flight, climbing vertically away from the Cape for the first 16 seconds. Its upward momentum was then arrested, as planned, by a pitch, roll, and yaw program maneuver, commanded by the avionics aboard the Centaur, which established the vehicle onto its proper flight azimuth of 44.4 degrees. The RD-180 engine continued to burn hot and hard for the opening four minutes of the ascent, before shutting down at 11:10 p.m. Following Booster Engine Cut-Off (BECO) at four minutes and 15 seconds, the CCB separated from the vehicle, leaving the Centaur in pole position for its own burn.
The upper stage’s RL-10C engine—capable of 22,900 pounds (10,390 kg) of thrust—ignited four minutes and 31 seconds into the flight. During its lengthy, 14-minute burn, the two-piece (or “bisector”) XEPF was discarded, exposing the OA-6 Cygnus to the space environment for the first time. And by the time the Centaur shut down at 11:24 p.m., just over 18 minutes since leaving the Cape, the spacecraft was in an initial orbit of about 144 miles (232 km), inclined 51.6 degrees to the equator. Cygnus separated from the Centaur at 11:26 p.m., about 21 minutes after liftoff. The departing booster performed a collision avoidance maneuver, ahead of executing a de-orbit burn to ensure that no further contact would be inadvertently made with the Cygnus.
Less than two hours later, the spacecraft’s fan-like pair of circular solar arrays were successfully deployed, setting the ship on course for a three-day chase to reach the space station. “Both #Cygnus solar arrays deployed!” exulted Orbital ATK in a tweet at 1:12 a.m. EDT Wednesday. And the spectacular launch and flight of Spaceship Rick Husband brought a series of tweets from several NASA and international astronauts, many of whom were former colleagues and friends of the man himself. “Godspeed SS Rick D. Husband,” tweeted former ISS Commander Terry Virts, whilst Japan’s first station skipper, Koichi Wakata, added his own congratulations.
“Clearly this team was ready to go do this launch tonight,” said Kenny Todd, NASA’s ISS Operations Integration Manager. “The space station is ready and the crew is ready.” His words were echoed by former astronaut Frank Culbertson, now President of Orbital ATK’s Space Systems Group. “We all know it takes a lot of hard work to make it look easy,” said Mr. Culbertson, “and the team did that.”
The pieces were thus set in motion for a rendezvous and capture of the spacecraft by the station’s 57.7-foot-long (17.6-meter) Canadarm2 on Saturday, 26 March. Leading the effort from inside the multi-windowed cupola will be Expedition 47 Commander Tim Kopra and Britain’s Tim Peake, assisted by newly-arrived NASA astronaut Jeff Williams. Grapple is scheduled to occur at 6:40 a.m. EDT, after which the Robotics Officer (ROBO) in the Mission Control Center (MCC) at the Johnson Space Center (JSC) in Houston, Texas, will command Canadarm2 to maneuver Cygnus to its berthing location at the Earth-facing (or “nadir”) port of the Unity node. According to the present schedule, the entire process is expected to be completed by 9:45 a.m. EDT.
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