Orbital Sciences’ giant Antares booster – destined to launch the company’s Cygnus cargo ships toward the International Space Station as part of a $1.9 billion Commercial Resupply Services contract with NASA – has taken another step toward its inaugural launch. On Monday, the first of its two stages was rolled out to Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Virginia, in anticipation of this maiden flight, currently scheduled for later in 2012. Although Antares will not carry a Cygnus on this occasion, the launch is expected to validate Orbital’s first cryogenically-powered rocket, its largest to date…and a vehicle whose first stage is fed by engines originally manifested for the Soviet Union’s ill-fated N-1 lunar booster.
The triumphant arrival of Antares’ first stage at the pad comes a few weeks ahead of a 30-second ‘hot-fire’ static test of those engines and appears to mark the end of construction woes and other technical difficulties at the MARS site. Orbital is contracted to execute eight flights of its Cygnus craft to the space station, with the first slated for early next year, and although Sunday’s anticipated launch of a Falcon 9 with the Dragon cargo ship appears to leave the Dulles, Virginia-based company 2-0 ‘behind’ SpaceX, a successful maiden voyage for Antares is expected to rapidly regain lost ground.
“Today’s rollout of Orbital’s Antares test vehicle and the upcoming SpaceX mission are significant milestones in our effort to return space station resupply activities to the United States and in-source the jobs associated with this important work,” said David Weaver, NASA’s Associate Administrator for Communications. “NASA’s commercial space programme is helping to ensure American companies launch our astronauts and their supplies from US soil.” That soil, however, has been part of the problem for Antares’ lengthy wait. Launch pad modifications for the vehicle at the MARS site included the construction of a Horizontal Integration Facility and a wheeled transporter, capable of rolling out the entire vehicle a mere 24 hours before liftoff. Moreover, Pad 0A itself was completely demolished and rebuilt as a new facility with kerosene and liquid oxygen tankage.
According to David Thompson, Orbital’s chairman and CEO, speaking in February of this year, difficulties with the pad’s propellant handling and pressurisation systems were the root cause. “The net cause of these problems has been to push our schedule for on-pad stage testing and the first launch by some 8-9 months over the past year,” Thompson explained at the time. “To more effectively address these challenges, Orbital took over day-to-day management of work on the spaceport’s launch pad and its related propellant equipment last fall, assigning a 20-person contingent to direct and oversee the remaining activities.” At the time, Thompson noted that Antares’ maiden launch would likely occur within a month of the successful hot-fire test, which makes an end-of-year target realistic. With Monday’s successful rollout of the booster’s first stage, Thompson was considerably more upbeat, proudly declaring in a statement that the new vehicle and pad hardware represents “the first all-new, large-scale liquid-fuel launch site to be built in the US in decades”.
Next up for Antares is the static firing of the twin AJ-26 engines, which have been developed by Aerojet from a batch of Soviet NK-33 powerplants, originally destined to propel the N-1 rocket. Fuelled by rocket-grade kerosene (RP-1) and liquid oxygen, these old engines have never been used, although Aerojet added modern electronics and incorporated other performance enhancements. Early plans called for a single AJ-26 on the first stage, supplemented by strap-on boosters. However, it was eventually decided to add a second AJ-26 and eliminate the boosters. The engines – each of which produces a sea-level thrust of approximately 338,000 pounds – were repeatedly test-fired by Orbital and Aerojet for a cumulative 600 seconds in March 2010. Much of this work has gone well, with the exception of a failure on the test stand at NASA’s Stennis Space Center in Mississippi in June 2011, when an engine caught fire following a kerosene leak. Investigators blamed stress corrosion cracks in the 40-year-old metal and following the implementation of improved inspection protocols two successful hot-firings were performed last September and November.
Meanwhile, Antares’ upper stage was produced by Alliant Techsystems (ATK) and utilises a solid-fuelled motor known as the Castor-30A, originally part of the Athena and Taurus I first stages and a descendant of the engine which powered the Peacekeeper missile. This engine was test-fired by ATK in December 2009. The first two Antares flights will employ the Castor-30A, after which an uprated motor (the Castor-3B) will be introduced and later a ‘stretched’ version (the Castor-XL) to enable larger Cygnus cargo vehicles.
The eagerly awaited first voyage of the new vehicle has not received a firm target date, although a static test in the next few weeks and a month-long processing flow thereafter produces an estimate of late November or December, almost exactly a year since Antares received its current name. Orbital Sciences has traditionally used Greek-derived names – Pegasus, Taurus, Minotaur – for its rockets and in December 2011 David Thompson explained that the old name of ‘Taurus II’ was being changed to ‘Antares’ because “a launch vehicle of this scale and significance deserves its own name”.
And Antares certainly is both significant and impressive in scale. Standing 133 feet tall and 12.8 feet in diameter, it has the capacity to insert up to 11,000 pounds of payload into low-Earth orbit. On its first flight, it will ferry a Cygnus ‘mass simulator’, heavily instrumented to gather data on the launch environment, together with four tiny ‘picosatellites’ to be deployed from a pair of dispensers. All this will serve as a tantalising prelude for the first Cygnus test mission to the International Space Station, which seems unlikely to occur before January 2013. When it finally flies, Cygnus will spend five or six days undergoing intensive systems tests before it is captured and berthed at the orbital outpost. In a manner not dissimilar to last May’s arrival of Dragon, the critical phase of the Cygnus approach profile will come when it enters the so-called ‘Keep-Out Sphere’ around the station. Like Dragon, the craft must demonstrate its ability to hold position and retreat, before formal permission is granted for it to proceed with the final stages of the rendezvous.
Having been captured and berthed by the station’s Canadarm2 robotic manipulator, Cygnus will remain docked at the Earth-facing (‘nadir’) port of the Harmony node for around a month. It will bring 1,200 pounds of equipment and supplies to the station’s crew and at the end of its mission will dispose of around 2,200 pounds of unneeded trash during a destructive re-entry into the atmosphere. A January 2013 launch means that Cygnus’ arrival will occur a few weeks after the arrival of the final three members of the six-man Expedition 34 crew – Chris Hadfield, Roman Romanenko and Tom Marshburn – to join teammates Oleg Novitsky, Evgeny Tarelkin and Commander Kevin Ford, who are currently scheduled to launch on 23 October. With the completion of a successful Cygnus test mission, Orbital will be in an excellent position to declare Antares ready for operations and the company presently envisages two cargo delivery flights per year until 2016.Missions » A-ONE » Missions » ISS » COTS » Missions » ISS »