Just a few days shy of two full years since one of the worst accidents to befall NASA’s Commercial Resupply Services (CRS) program, Orbital ATK picked up the baton in fine fashion last night, as it successfully launched its revitalized Antares 230 booster on a critical mission to bring science and supplies to the International Space Station (ISS). Bouncing back to operational service after months of launch pad modifications, new engines, and a longer-than-expected wait, due to the ravages of Mother Nature, the two-stages Antares sprang away from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va., at 7:45:46 p.m. EDT Monday, 17 October. The booster is laden with Orbital ATK’s OA-5 Cygnus cargo ship, which is carrying 5,346 pounds (2,425 kg) of equipment, supplies, and research materials to the space station.
Seven hundred and twenty days—more than 102 weeks—have elapsed since the horrific evening of 28 October 2014, when a first-generation Antares 130 vehicle rose ponderously from Pad 0A, carrying the fully-loaded ORB-3 Cygnus cargo ship toward the ISS. No sooner had the booster cleared the launch pad, it suffered a catastrophic turbopump failure within one of its two AJ-26 first-stage engines. A voracious liquid oxygen fire rapidly gorged itself on the 133-foot-tall (40.5-meter) rocket, which promptly lost power and collapsed back onto the pad in a blazing fireball. As outlined in a recent AmericaSpace article, over the course of the next 18 months the damage to Pad 0A was repaired and an upgraded RD-181 engine suite was installed aboard the second-generation Antares 230. Last May, the new engines were test-fired on the pad without incident.
In the meantime, ISS-bound Cygnus missions continued, thanks to contracts signed between Orbital ATK and United Launch Alliance (ULA) in the closing weeks of 2014 to use the Atlas V booster on two occasions. Yet Antares’ return to flight continued to meet with delay through the summer of 2016, with target dates in early July, late August, and the end of September coming and going. At length, a “window” from 9-13 October was announced, with NASA and Orbital ATK eventually settling on the last of these dates. Unfortunately, Mother Nature—via Hurricane Matthew, which battered Bermuda, home to critical radar and tracking assets, and Hurricane Nicole—conspired against Antares, pushing the launch further to the right. This was a pity, for processing of both Cygnus and the rocket had gone exceptionally well: Antares was elevated on Pad 0A last Thursday and over the weekend a Launch Readiness Review (LRR) issued a “Go” to proceed with the flight.
At length, all seemed set for a five-minute “launch window,” opening at 8:03 p.m. EDT Sunday, but Orbital ATK announced a 24-hour delay, due to a problematic Ground Support Equipment (GSE) cable. This was a pity, for the weather outlook for Sunday was 95 percent favorable. According to the Dulles, Va.-headquartered organization, the cable “did not perform as expected during the pre-launch checkout,” but it was stressed that spares were on hand, re-work procedures were in effect, and no other technical issues were apparent. T-0 was re-set for 7:40:40 p.m. EDT Monday.
Weather conditions were predicted to be 100-percent favorable for Monday’s launch attempt, and Orbital ATK’s Antares and Cygnus controllers came to their stations by 1 p.m. EDT. Power-up of the booster got underway shortly thereafter and by 4:15 p.m. the process of chilling-down the liquid oxygen loading system with liquid nitrogen had gotten underway, together with avionics checks. An hour later, the Flight Termination System (FTS)—tasked with destroying Antares in the event of a major malfunction during ascent—completed its final checkout and at 5:40 p.m. the countdown entered a 20-minute-long built-in hold. Coming smoothly out of the hold at the top of the hour, the launch team received a “Go” to commence cryogenic tanking at 6:06 p.m.
Tonight’s mission marked the sixth Antares to depart the launch pad, but only the fifth to successfully deliver its payload into orbit. Originally developed under the nomenclature of “Taurus,” it represented the first foray into large-scale cryogenic rocketry for Orbital Sciences Corp. After a lengthy and tortured development process, Antares flew its maiden mission in April 2013, before successfully lofting three Cygnus cargo ships to the ISS between September 2013 and July 2014. This early success, however, was dramatically cut short in October 2014, when it suffered an explosion, seconds after liftoff. By that time, problems with its aging, Soviet-era AJ-26 engines were well known and efforts were already underway. In December 2014, it was announced that the uprated Antares 230 booster would utilize a pair of RD-181 engines at the base of its first stage. These engines are fed by a combination of liquid oxygen and a highly refined form of rocket-grade kerosene, known as “RP-1.”
Tanking is critically timed to begin about 90 minutes before launch, due to temporal limits associated with the rapid boil-off of the cryogens. A final poll of flight controllers occurred in two phases and the liquid oxygen fueling was completed at T-15 minutes, by which time all propellant tanks had attained “Flight Ready” levels. For once, the weather, too, seemed to be playing ball, with upper-level winds remaining “Green,” as the Orbital ATK launch team continued to track no issues with their vehicle. Shortly thereafter, the booster transitioned to Internal Power and at T-11 minutes the Transporter-Erector-Launcher (TEL) “strongback” was armed to allow it to execute a rapid retraction at T-0.
Closing in on the opening of the five-minute launch window, the FTS was placed onto internal power and armed at T-5 minutes. Despite the high levels of confidence in the enhanced Antares, observers at Wallops noted a distinct atmosphere of anxiety and unease as the final hours and minutes ticked away. At 7:36 p.m., with three minutes and 30 seconds remaining on the clock, the “Terminal Count” was initiated. During this period, the rocket’s autosequencer assumed primary command of all vehicle critical functions, controlling all events up to the ignition of the twin RD-181 engines at T-0.
However, in the final couple of minutes, a decision was made to slip until the end of tonight’s launch window, tracking at T-0 at 7:45:46 p.m. EDT. This was apparently associated with a minor error indication with an engine, which was promptly resolved. At 7:41 p.m., the OA-5 Cygnus was transferred to internal battery power and the Orbital ATK teams declared their readiness as “Go for Launch.” Under careful computer control, the engines roared to life, ramping up to a combined thrust of 937,000 pounds (425,000 kg). This represents a 12.5-percent performance hike over the older AJ-26 suite.
An Antares rising again into the night was always going to be a difficult pill to swallow; for only its most recent, catastrophic mission in October 2014 launched in darkness. That said, the ill-fated ORB-3 mission took flight a matter of minutes after sunset, whereas tonight’s launch—which came 71 minutes after sundown—could truly be classified as a fully nocturnal one. The flare of the booster’s twin engines at liftoff caused many hearts to jump into throats, for the sight of the base of the first stage flaring, then failing, two years ago this month, was clearly still fresh in many minds. But on this occasion, Antares performed like a champ, clearing the tower with lumbering ease and powering upward into the darkened Virginia sky.
Seconds after clearing the Pad 0A, to audible relief from the gathered spectators, the rocket began a combined pitch and roll program maneuver to establish itself onto the proper azimuth to inject the OA-5 Cygnus into low-Earth orbit. Maximum aerodynamic turbulence on the vehicle’s airframe was encountered about 80 seconds into the ascent. All told, the first stage and its two flawless RD-181s boosted Antares for 208 seconds, burning 527,522 pounds (239,280 kg) of liquid oxygen and RP-1.
Following shutdown of the engines, the 90.5-foot-long (27.6-meter) first stage was jettisoned, exposing the OA-5 Cygnus and its attached CASTOR-30XL upper stage to continue the journey into low-Earth orbit. Tonight’s launch was the first outing of the CASTOR-30XL, a solid-fueled motor, which measures 19.7 feet (6 meters) long and 7.7 feet (2.3 meters) in diameter and weighs 58,000 pounds (26,300 kg). This burned for the next three minutes to deliver Cygnus to an orbital “slot” with an apogee of 218 miles (352 km) and a perigee of 132 miles (213 km), inclined 51.618 degrees to the equator. The CASTOR-30XL was then shut down and Cygnus separated into free flight at 7:54 p.m. EDT, exactly nine minutes and four seconds after departing Wallops.
Due to the Wednesday’s planned launch—and Friday’s planned docking—of the piloted Soyuz MS-02 spacecraft at the ISS, Cygnus’ own arrival has been pushed back to Sunday, 23 October. The cargo ship will follow a longer-than-normal rendezvous profile, “loitering” in low-Earth orbit, ahead of its final closure toward the space station. It will be grappled by Expedition 49 astronauts Kate Rubins and Takuya Onishi, via the 57.7-foot-long (17.6-meter) Canadarm2, and berthed at the Earth-facing (or “nadir”) port of the Unity node. Cygnus is expected to remain on-station until mid-November.
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