Orbital Sciences Corp. will wait a little longer to launch its first dedicated Cygnus cargo mission to the International Space Station (ISS), following yesterday’s massive solar flare. Originally scheduled for liftoff atop the company’s Antares rocket from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va., at 1:32 p.m. EST today (Wednesday), a new target launch date has yet to be announced. “The Antares launch today has been scrubbed because of solar activity,” NASA tweeted. “More info on the issue and a new launch date will be forthcoming.”
The delay is another bitter disappointment in a frustrating month-long campaign to get the ORB-1 mission of Cygnus into orbit. Last month, on 11 December, the starboard pump module on one of the space station’s external ammonia coolant loops automatically shut down when it reached pre-set temperature limits, prompting a postponement of Cygnus’ planned 19 December liftoff and a pair of lengthy EVAs by Expedition 38 astronauts Rick Mastracchio and Mike Hopkins during Christmas week to remove and replace the failed hardware. A new target launch date of 7 January was announced, but that too slipped by 24 hours, due to predicted cold temperatures at the MARS site on the Virginia coast. After the Antares rocket boosts Cygnus into orbit, the cargo craft will rendezvous and be berthed at the ISS for about three weeks and will deliver approximately 3,230 pounds (1,465 kg) of supplies and equipment to the station’s crew.
However, yesterday’s massive solar flare—which emanated from one of the largest sunspot groups seen on the Sun’s surface in a decade—proved to be of such severity that NASA and Orbital managers elected to stand down from today’s planned launch attempt. “Early this morning,” Orbital announced Wednesday, 8 January, “the Antares launch team decided to scrub today’s launch attempt, due to an unusually high level of space radiation that exceeded by a considerable margin the constraints imposed on the mission to ensure the rocket’s electronic systems are not impacted by the harsh radiation environment.” The Dulles, Va.-based company, which is one of NASA’s two Commercial Resupply Services (CRS) partners, tasked with transporting cargo to the ISS, added that its engineers and radiation experts “ran numerous models to ensure that all possibilities to preserve the launch were examined,” but that the “significantly elevated flux levels” made it prudent to postpone the launch and “spend the day further examining the potential effects of the space radiation on the rocket’s avionics suite.”
Although no new launch date has been formally announced, ORB-1 passed its Launch Readiness Review with flying colors on Tuesday, 7 January, and Orbital noted that “if we are able” the mission may fly tomorrow (Thursday, 9 January), during a 5-minute “window,” which opens at 1:10 p.m. EST. If the mission does fly tomorrow, it is expected to produce a rendezvous and berthing at the space station’s Harmony node on Sunday morning. According to Space.com, Tuesday’s solar flare was an X1.2-class event—one of the most powerful storm emissions from the Sun, known to disrupt telecommunications and present a danger to astronauts and cosmonauts in Earth orbit—and occurred a 1:32 p.m. EST, exactly 24 hours ahead of today’s scheduled liftoff time. “Space weather officials at the Space Weather Prediction Center overseen by NOAA [the National Oceanic and Atmospheric Administration] are expecting the flare to spark geomagnetic storms in Earth’s magnetic field,” it was noted, “when a wave of super-hot solar plasma associated with the flare … reaches Earth in the next few days.”
In the meantime, the 133-foot-tall (40-meter) Antares rocket remains in a safe condition on Pad 0A at MARS. Carrying Cygnus in its payload shroud, the vehicle rolled out of the Horizontal Integration Facility (HIF) on the afternoon of Sunday, 5 January, and its Transporter-Erector-Launcher (TEL) structure raised it into a vertical orientation by about 10:40 p.m. EST. On Monday, Orbital engineers and technicians worked to connect commodity lines and performed various systems checks, ahead of the Launch Readiness Review on Tuesday. This produced a unanimous “Go” to proceed with an opening launch attempt on Wednesday.
The ORB-1 mission has been a long time in the planning. As part of its Commercial Orbital Transportation Services (COTS) commitment to NASA, Orbital Sciences was required to conduct a full-up Cygnus Demonstration mission (ORB-D) to the ISS, which it triumphantly completed last September-October. The success of this mission cleared the way for the company to set its feet firmly on the road to stage eight dedicated Cygnus cargo flights (ORB-1 through 8) by 2016, under the provisions of a $1.9 billion contract signed with NASA back in December 2008.
Antares’ twin AJ-26 first stage engines, developed by Aerojet, can trace their heritage back to the Soviet era, having been purchased from Russia in the mid-1990s as part of a consignment of 36 powerplants originally conceived for the ill-fated N-1 lunar rocket. Powered by liquid oxygen and rocket-grade kerosene (known as “RP-1”), they have been extensively upgraded, and at the instant of liftoff each engine produces a sea-level thrust of 338,000 pounds (153,300 kg). Despite a handful of problems, including stress corrosion of the 40-year-old metal, the engines performed generally well on the test stand, but Orbital also struggled with the development of the new MARS launch site and experienced difficulties with the construction of new kerosene and liquid oxygen tankage. These conspired to delay the inaugural test launch of Antares from early 2012 until April 2013.
The last 12 months have proven a banner year for Orbital. Despite many engineering challenges, the company’s Antares rocket completed its maiden test flight on 21 April 2013, successfully lofting a mass simulator of Cygnus into orbit and providing a close analog for the opening minutes of a “real” ISS mission. Five months later, on 18 September, the Demonstration mission, ORB-D, was launched into orbit. Although technical difficulties were encountered during the early rendezvous phase, Cygnus was berthed perfectly at the “nadir” (or Earth-facing) port of the space station’s Harmony node on 29 September. The cargo ship spent three weeks attached to the ISS, before being unberthed on 22 October and commanded to perform a destructive re-entry into the upper atmosphere.
About three hours ahead of launch, all personnel will be cleared from Pad 0A and the process of chilling down the Ground Support Equipment will get underway. Shortly afterward, Antares’ ordnance—including pyrotechnics to separate various components of the vehicle during flight—will be enabled, and at about T-2 hours the cooling of the liquid oxygen transfer lines will commence, ahead of loading propellants into the first stage tanks. Forty-five minutes before launch, the avionics system will be loaded with the flight software to guide its ascent. Propellant loading aboard Antares is timed to begin at about T-90 minutes, due to time limits associated with the rapid boil-off of the cryogenics. This should produce a state with all propellant levels declared to be “Flight Ready,” and the liquid oxygen will remain in a “topping off” mode, being continuously replenished until just before liftoff. Following a final “Go/No-Go” poll of the launch team, Antares and Cygnus systems will be transferred to internal power and the TEL will be armed to execute a rapid retraction at the moment of launch.
At T-5 minutes, the Flight Termination System will be armed, and at T-3 minutes and 30 seconds the Terminal Count will get underway, with Antares’ on-board autosequencer now in primary control of all vehicle critical functions. These will include the final pressurization of the first-stage fuel tanks and the gimbaling of the two AJ-26 engines. Under computer command, the engines will ignite at T-2 seconds, ramping up to full power, with liftoff at 1:32 p.m. EST Wednesday. Seconds after clearing the tower, Antares will execute a pitch and roll program maneuver to establish itself onto the proper flight azimuth for insertion into a low-Earth orbit, inclined 51.6 degrees to the equator.
Maximum aerodynamic turbulence (known as “Max Q”) will be encountered about 80 seconds into the flight, and the AJ-26 engines will continue to burn hot and hard until they finally shut down about 4 minutes after launch. At an altitude of about 70 miles (110 km), and traveling in excess of 10,000 mph (16,000 km/h), the first stage will separate at 1:35 p.m. EST. This will leave the second stage and Cygnus to coast for two minutes, prior to jettisoning the bullet-like payload shroud. Ignition of the second stage’s solid-fueled Castor-30B engine—making its first flight on this launch—will occur soon afterward to inject Cygnus into low-Earth orbit. The cargo ship will separate from the second stage about 10 minutes after launch.
Cygnus will then embark on a 72-hour rendezvous profile, which requires several orbit-raising and “phasing” maneuvers to bring it into the neighborhood of the ISS on Sunday, 12 January. In a manner not dissimilar to September’s ORB-D mission, the ORB-1 profile will see Cygnus showcasing its ability to “hold” position at various distances, before entering the Keep-Out Sphere—a virtual exclusion zone, extending about 660 feet (200 meters) around the space station to prevent a collision—and being grappled by Canadarm2. Under the control of Expedition 38 crewmen Mike Hopkins, Koichi Wakata and Rick Mastracchio, it will be berthed onto the “nadir” port of the Harmony node. Current plans call for Cygnus to remain berthed at the ISS until the end of January, at which time it will be robotically detached and later commanded to execute a destructive re-entry into the upper atmosphere. In so doing, it will dispose of about 2,200 pounds (1,000 kg) of waste material.
Like September’s ORB-D mission, which was named for former Orbital executive G. David Low, the upcoming flight of ORB-1 pays tribute to another shining light in the company’s fortunes. It will bear the name “Spaceship C. Gordon Fullerton” to honor the former shuttle astronaut and research pilot who died last year. Assuming a successful ORB-1 mission, Orbital plans two further Cygnus flights in 2014, with ORB-2 scheduled for May and ORB-3 for October.
Missions » ISS » COTS » CYGNUS » ORB-1 »