Six months since it last lofted a Cygnus cargo vessel toward the International Space Station (ISS), Orbital Sciences Corp. is primed to fly the second mission (designated “ORB-2”) under its $1.9 billion Commercial Resupply Services (CRS) contract with NASA. Liftoff of the company’s two-stage Antares booster—making its fourth flight in less than 15 months—is presently scheduled to occur from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va., at 12:52 p.m. EDT Sunday, 13 July. Assuming an on-time launch, the already long-delayed ORB-2 flight should produce a rendezvous and berthing at the Earth-facing (or “nadir”) port of the station’s Harmony node on Wednesday, 16 July. Named in honor of the late shuttle astronaut Janice Voss, Cygnus will remain attached to the ISS until mid-August and will deliver 3,293 pounds (1,493.8 kg) of equipment and supplies to the incumbent Expedition 40 crew.
It has been a dramatic 15 months for Orbital, following the initial flight test of Antares (the so-called “A-ONE” mission) back in April 2013. The success of A-ONE provided a much-needed shot in the arm for the Dulles, Va.-based company, since the 133-foot-tall (40.5-meter) Antares represents its biggest home-grown launch vehicle and its first foray into large-scale cryogenic rocketry. Antares’ first stage is propelled by a pair of Aerojet-built AJ-26 engines—whose heritage extends back to the Soviet era, having originated as the NK-33 powerplants for the ill-fated N-1 lunar booster—and is fed by a combination of liquid oxygen and a refined form of rocket-grade kerosene, known as “RP-1.” Thirty-six of these engines were procured from Russia in the mid-1990s, at a cost of $1.1 million apiece, to which Orbital added more modern electronics and other performance enhancements. At the instant of liftoff, the two AJ-26 engines produce a combined sea-level propulsive yield of about 734,000 pounds (332,930 kg).
In spite of its eventual success, Antares underwent a tortured development process. The AJ-26 engines performed well on the test stand in 2010, although one of them caught fire in June 2011, following a kerosene leak, apparently caused by stress-corrosion cracking in the 40-year-old metal. Moreover, Orbital’s MARS launch site was experiencing its own headaches; notably, these included difficulties with the construction of new cryogenic tankage systems and with the certification of propellant-loading operations. These problems conspired to delay the A-ONE inaugural flight of the booster—which had, by now, gained the name “Antares,” in place of its developmental name of “Taurus II”—from spring 2012 until the second quarter of the following year. When A-ONE finally launched on 21 April 2013, it delivered an instrumented “mass simulator” of the Cygnus cargo craft into an orbit of 155 x 186 miles (250 x 300 km), inclined 51.6 degrees to the equator, thereby providing a close analog for the opening minutes of a “real” ISS delivery mission.
Five months after A-ONE, under the language and requirements of the Commercial Orbital Transportation Services (COTS) contract between Orbital and NASA, the second Antares successfully boosted the first “real” Cygnus on the first “real” mission to the space station. Since this mission was Orbital’s “Demonstration” flight of the cargo ship’s capabilities, it was designated “ORB-D.” Launched on 18 September, the cargo craft was successfully grappled and berthed at the ISS about 11 days later and spent more than three weeks attached to the nadir port of the Harmony node. In late October, Cygnus departed the station and was intentionally destroyed during a fiery re-entry into the upper atmosphere.
With the completion of ORB-D, the road was clear for Orbital to fly a total of eight Commercial Resupply Services (CRS) missions by 2016, which were tasked to deliver upward of 44,000 pounds (20,000 kg) of equipment and supplies for successive ISS crews. The $1.9 billion contract with NASA to stage these missions had been signed in December 2008. The first mission, designated “ORB-1,” was originally planned for launch in mid-December 2013, but was postponed by almost a month, due to problems aboard the station which necessitated a pair of contingency spacewalks. Launched on 9 January 2014, the ORB-1 Cygnus was successfully berthed at the ISS on 12 January and spent more than five weeks attached to the orbital outpost. It was eventually unberthed on 18 February and deliberately destroyed in the upper atmosphere a day later.
Following the triumphant ORB-1 mission, plans were well underway for ORB-2, whose launch date eventually crystallized for no earlier than 6 May. Unfortunately, delays to the launch of the third Dragon cargo mission to the ISS—conducted under the auspices of NASA’s second CRS partner, SpaceX—from mid-March until 18 April correspondingly pushed the start date of the ORB-2 flight to no earlier than 10 June. However, more trouble was afoot. Late in May, Orbital announced a further postponement of at least one week, caused by the failure of an AJ-26 engine during an acceptance test firing at NASA’s Stennis Space Center in Hancock County, Miss. Although the engine was destined for one of Antares’ planned 2015 missions, its failure and the subsequent investigation (which included representatives of Aerojet, Orbital and NASA) obliged a further delay until such time as the problem had been resolved. By mid-June, Orbital was targeting no earlier than 1 July, and, by the month’s end, this date had shifted to the 10th.
“The engineering team that is investigating the failure of an AJ-26 engine during an acceptance test at Stennis Space Center recommended that certain inspections be performed on the two AJ-26 engines that are currently integrated on the Antares rocket,” Orbital reported on 3 July. “These inspections were recently completed and program officials have cleared the rocket for flight.” Elsewhere, the Cygnus spacecraft was mated with the Antares booster, preparatory to rollout to Pad 0A on 9 July. In the meantime, liftoff was slightly shifted by 24 hours to the right, tracking an opening launch attempt at 1:40 p.m. EDT on 11 July. According to this flight plan, Cygnus would follow a 90-hour rendezvous profile, ahead of grappling by the space station’s 57.7-foot (17.6-meter) Canadarm2 at 7:24 a.m. EDT on 15 July and subsequent berthing onto the Harmony nadir port.
Yesterday (Tuesday), the payload fairing was installed atop the Antares booster in the Horizontal Integration Facility (HIF) at Wallops. However, the presence of thunderstorms in the area on Tuesday evening prompted Orbital to postpone the rollout until Thursday. The resultant “compression of the operational schedule,” caused by this delay, produced an announcement from Orbital on Wednesday afternoon that the launch would be rescheduled for no earlier than 1:14 p.m. EDT Saturday, 12 July. The presence of continued poor weather conditions forced another 24-hour delay until Sunday. Such a move would allow “for normal launch operations processing,” but it was stressed that Cygnus could accommodate a rendezvous and berthing at the ISS on 16 July. At the same time, the “late loading” of payloads aboard Cygnus’ Pressurized Cargo Module (PCM) was concluded Tuesday and the hatch was closed for flight. In total, the spacecraft will deliver 3,293 pounds (1,493.8 kg) of equipment and supplies to the incumbent Expedition 40 crew of U.S. astronauts Steve Swanson and Reid Wiseman, Russian cosmonauts Aleksandr Skvortsov, Oleg Artemyev, and Maksim Surayev, and Germany’s Alexander Gerst.
The Antares rocket, with the ORB-2 Cygnus tucked inside its payload fairing, was delivered from the HIF to Pad 0A in a horizontal orientation on Thursday, then raised to the vertical, by means of the Transporter-Erector-Launcher (TEL). Assuming that no weather or technical issues impair Sunday’s launch attempt, the Antares/Cygnus flight control team will receive their “Call to Stations” at T-3 hours and 50 minutes. About 45 minutes later, the process of “chilling down” the fuel lines of the rocket’s first stage with liquid nitrogen will get underway, preparatory to the loading of cryogenic propellants. This chill-down protocol serves to avoid catastrophically shocking the equipment by being suddenly hit by a rapid temperature change. After a poll of the launch team at T-1 hour and 30 minutes, propellants will begin flowing into the first stage. The loading process is critically timed to begin about 90 minutes ahead of liftoff, due to temporal limits associated with the rapid boil-off of the cryogenics. A final poll of the launch team will occur in a two-step process, and the fueling operation should conclude at about T-15 minutes. By this stage, all propellants will be at “Flight Ready” levels and a definitive “Go for Launch” will be issued.
Antares will transition to internal power, and at T-11 minutes the TEL will be armed to execute a rapid retraction from the vehicle at the instant of liftoff. At T-5 minutes, the Flight Termination System (FTS)—tasked with destroying the rocket in the event of a major accident during ascent—will be armed and Antares’ avionics will transfer to internal power. With three minutes and 30 seconds remaining on the clock, the “Terminal Count” will be initiated. At this stage, Antares’ autosequencer will assume primary control of all vehicle critical functions, commanding all events up the ignition of the twin AJ-26 engines at T-0. Under careful computer control, the engines will steadily ramp up to full power for two seconds, producing a launch at 12:52 p.m. EDT Sunday.
Shortly after clearing the Pad 0A tower, the rocket will perform a combined pitch and roll program maneuver to establish itself onto the proper flight azimuth to inject Cygnus into low-Earth orbit. Maximum aerodynamic turbulence (colloquially known as “Max Q”) will be experienced throughout the airframe at T+80 seconds and the AJ-26 engines will continue to burn hot and hard, until they are finally shut down about four minutes and 15 seconds into the flight. By this point, the vehicle will have attained an altitude of about 70 miles (112 km) and six seconds later the first stage will be jettisoned, leaving the second stage—powered by a single Castor-30B solid-fueled engine, built by Alliant TechSystems—and Cygnus to coast, preparatory to discarding the bulbous, 32.5-foot-tall (9.9-meter) payload shroud at T+5 minutes and 30 seconds. Ignition of the Castor-30B should occur just under six minutes into the flight, burning for 137 seconds and providing Cygnus with its final push into low-Earth orbit at a mean altitude of about 124 miles (200 km), inclined 51.6 degrees to the equator. Approximately 10 minutes after leaving Wallops, the third Cygnus spacecraft in history should be in orbit.
Of course, calling ORB-2 merely a “spacecraft” is something of a misnomer, for Orbital has religiously attached a name to each of its Cygnus missions. Last year’s ORB-D was named in honor of the late G. David Low, a former shuttle astronaut and Orbital senior executive, under whose leadership the architecture of the COTS program was assembled and refined in 2006-2008. Following hard on its heels, the ORB-1 mission paid tribute to former shuttle commander C. Gordon Fullerton, who died last August, and the forthcoming ORB-2 will fly in memory of the late Janice Voss, another veteran astronaut, who passed away in February 2012.
Following its arrival in orbit, Voss’ mechanized namesake will begin a three-day flight profile to rendezvous with the ISS. Cygnus’ twin gallium arsenide solar arrays will be deployed, generating a total of 3.5 kW of electrical capability, and it will be commanded to execute a series of “phasing” maneuvers to bring it closer to the station. Upgrades for ORB-2 include a new Triangulation LIDAR (known as “TriDAR”), a model-based laser navigation sensor, which is being trialed on this flight and will compare its readings with a Computer Aided Design (CAD) model of the space station to determine relative positions and attitudes. “Cygnus will employ one TriDAR unit for the ORB-2 mission,” NASA explained. “Future missions will incorporate two TriDARs and one LIDAR.” Cygnus will also employ a Quasonix lightweight, high-powered S-band radio for telemetry and commanding capability. The spacecraft will hold position at a distance of 39.4 feet (12 meters) from the space station, early Tuesday, 15 July. At this stage, Expedition 40 Commander Steve Swanson—based in the multi-windowed cupola and assisted by Reid Wiseman and Alexander Gerst—will grapple Cygnus, via Canadarm2, at 6:37 a.m. EDT Wednesday, 16 July. They will subsequently berth the spacecraft at the Harmony nadir port and open the hatches to begin unloading its cargo. Cygnus is a two-piece vehicle, comprising a Pressurized Cargo Module (PCM)—fabricated by Thales Alenia Space and based in design upon the Multi-Purpose Logistics Module, used for cargo deliveries on 12 shuttle flights between March 2001 and July 2011—and Orbital’s home-built Service Module (SM).
Aboard Cygnus for the ORB-2 mission are 1,684 pounds (764.2 kg) of crew supplies, including “crew care packages”—among them gifts from the crew’s families—and provisions, including foodstuffs. A further 783 pounds (355.1 kg) is devoted to vehicle hardware, including health care products, Environmental Control and Life Support System (ECLSS) equipment, EVA tools, equipment for the ISS electrical system, and others. Scientific experiments will comprise 721 pounds (327.0 kg) and include no fewer than 28 CubeSats. Known as “Flock 1b” and developed by Planet Labs of San Francisco, Calif., these are part of an expansive initiative to obtain imagery of Earth. “On the ORB-1 mission in January, Planet Labs … launched an initial fleet of 28 CubeSats, individually known as Dove satellites, from the space station,” NASA explained. “This collective group of small, relatively inexpensive nanosatellites, known as ‘Flock 1,’ will be joined by 28 additional Dove satellites, Flock 1b, on the ORB-2 mission.” Deployed from the airlock of Japan’s Kibo laboratory, the satellites’ imagery “can be used to help identify and track natural disasters and responses to them,” as well as helping to “improve environmental and agricultural monitoring and management.”
Also hitching a ride into space aboard Cygnus will be TechEdSat-4, to be deployed by Kibo’s Small Satellite Orbital Deployer, which seeks to develop a tension-based drag device, known as “Exo-Brake,” and demonstrate frequent uplink and downlink capabilities. “Engineers believe exo-brakes eventually will enable small samples return from the station or other orbital platforms to Earth,” it was noted by NASA. Elsewhere, in association with the Student Spaceflight Experiment Program (SSEP), the National Center for Earth and Space Science “Charlie Brown” payload includes 15 investigations, selected from 1,344 student team proposals, focusing upon food growth and consumption to the effect of microgravity on the oxidation process and even the production of penicillin on the space station.
According to NASA’s ORB-2 press kit, Cygnus will remain berthed at the ISS for 36 days. It will be detached, again by means of Canadarm2, on 15 August. It will then “be guided to a safe distance away from the orbiting laboratory.” However, unlike its ORB-D and ORB-1 predecessors, it will not be immediately plunged to a destructive re-entry. “The Cygnus spacecraft will fly an additional 15 days after departure to conduct spacecraft engineering tests to support future mission objectives,” it was explained. “At the end of that free-flight period, Cygnus will perform a series of engine burns so that it will re-enter Earth’s atmosphere for a destructive re-entry over the South Pacific Ocean.” Cygnus will carry about 2,967 pounds (1,346 kg) of unneeded equipment for disposal during re-entry.