After many delays, Orbital Sciences Corp. has successfully launched its second dedicated Cygnus cargo mission toward the International Space Station (ISS). Liftoff of the two-stage Antares booster, carrying Cygnus—whose mission, designated “ORB-2”, is named in honor of the late NASA astronaut Janice Voss—took place on time at 12:52 p.m. EDT Sunday, 13 July, from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va. Within ten minutes of leaving Earth, Antares had boosted Cygnus into an initial orbit of 125 x 185 miles (200 x 300 km), inclined 51.6 degrees to the equator, allowing the unpiloted craft to begin deploying its solar arrays and communications appendages, ahead of rendezvous and berthing at the ISS on Wednesday morning.
As described in AmericaSpace’s ORB-2 preview article, this mission has been waiting in the wings for some considerable time. Originally targeted for launch in early May, it was postponed into June by delays incurred by SpaceX’s third Dragon cargo mission (SpX-3) and later into July, following the failure of an Antares AJ-26 first-stage engine on the test stand at NASA’s Stennis Space Center, Miss. At length, Orbital Sciences and NASA settled on a new launch date of Friday, 11 July, which was slipped firstly until the Saturday, 12 July, and ultimately until Sunday, 13 July, due to severe thunderstorms in the Wallops area. Meteorological conditions for Sunday’s launch were reported as 90 percent favorable and televised views of Antares on its seaside launch pad showed beautiful weather conditions and waves gently lapping the shore.
The booster, which stands 133 feet (40.5 meters) tall, with the ORB-2 Cygnus encapsulated within its bulbous payload fairing, was rolled horizontally from Wallops’ Horizontal Integration Facility (HIF) over to the nearby Pad 0A on Thursday, 10 July, after which the Transporter-Erector-Launcher (TEL) carrier raised it slowly to a vertical configuration. According to John Steinmeyer, the Senior Program Manager for Orbital’s Launch Systems Group, the Antares/Cygnus flight control received their “Call to Stations” at about 8:00 a.m. EDT Sunday. Shortly thereafter, the process of “chilling down” the fuel lines of the rocket’s first stage with liquid nitrogen got underway, ahead of loading the cryogenic propellants. Antares is Orbital’s largest home-grown launch vehicle, as well as being the Dulles, Va.-based company’s first foray into cryogenic rocketry. The first stage is powered to two Aerojet-built AJ-26 engines, which utilize a mixture of liquid oxygen and a highly-refined form of rocket-grade kerosene, known as “RP-1”.
Chilling down the engines—which were purchased from Russia in the mid-1990s and extensively upgraded by Aerojet with more modern electronics and systems—in this manner helped to prevent catastrophically “shocking” the equipment by being suddenly hit by a rapid temperature change. After a poll of the launch team at T-90 minutes, the liquid oxygen and RP-1 began flowing into the first stage tanks. The timing of the 75-minute loading protocol was critical, due to temporal limits associated with the rapid boil-off of the super-cold propellants, and a final poll of the launch team occurred in a two-step process.
In the meantime, at 12:20 p.m. EDT, the final balloon data was received by the flight control team and verified that upper-level winds were “Green” (“Go”) for launch. For a time, the Range declared itself as “Red” (“No-Go”), due to the presence of an unauthorized boat in the launch danger area; this was shooed away by the U.S. Coast Guard and the Range adjusted its status to “Green”. By 12:37 p.m., with 15 minutes remaining before the opening of the five-minute “launch window”, fueling of Antares’ first stage was concluded, with all propellants confirmed at “Flight Ready” levels, and at 12:41 p.m. the launch team completed its final poll and reported a definitive “Go for Launch”.
Four minutes later, at 12:45 p.m. the TEL was 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 vehicle in the event of a major accident during ascent—was armed and Antares’ avionics were transitioned from ground supplies to internal power. At T-3 minutes and 30 seconds, the “Terminal Count” was initiated and the rocket’s autosequencer assumed primary control of vehicle critical functions, commanding all events up to the ignition of the twin AJ-26 engines at T-0. In the final 60 seconds of the countdown, the fuel tanks were pressurized, the gimbal navigation controls of the AJ-26 engines were tested and, finally, the TEL was retracted from the vehicle.
Precisely on time, at 12:52:14 p.m., the two AJ-26 engines roared to life and gradually ramped up thrust to their combined propulsive yield of about 734,000 pounds (332,930 kg), as computers continuously monitored their health and start-up performance. Two seconds later, at T+2 seconds (and 12:52:16 p.m.), liftoff was confirmed and Antares was released from Pad 0A to commence its ten-minute climb to orbit. Shortly after clearing the launch complex, at T+13 seconds, the rocket performed a combined pitch and roll program maneuver to establish itself onto the proper flight azimuth to insert the ORB-2 Cygnus into low-Earth orbit. A minute into the flight, Antares was already at an altitude of 3 miles (4.8 km) and traveling in excess of 500 mph (800 km/h), going supersonic a few seconds later. Maximum aerodynamic turbulence (colloquially known as “Max Q”) was experienced throughout the airframe at T+80 seconds and the AJ-26 engines continued to burn hot and hard, until they were finally shut down at T+4 minutes and 15 seconds.
By this point, the vehicle had attained an altitude of about 66 miles (106 km) and the first stage was 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 fairing at T+5 minutes and 30 seconds. According to AmericaSpace’s Launch Tracker, this descended to a splashdown in the Atlantic Ocean. Meanwhile, ignition of the Castor-30B took place at exactly 12:58 p.m., six minutes after launch, and provided Cygnus with its final push into low-Earth orbit and a ‘low point’ (or ‘perigee’) of about 125 miles (200 km), inclined 51.6 degrees to the equator.
The Castor-30B burned out after two minutes, at 1:00 p.m., leaving the stack to coast for a further two minutes, until Cygnus separated at 1:02 p.m. A mere ten minutes had elapsed since Antares rocketed away from Wallops Island and Orbital Sciences Corp. could boast that the second dedicated Cygnus mission under its $1.9 billion Commercial Resupply Services (CRS) contract with NASA—signed back in December 2008—was safely in orbit and ready for its three-day trek to the ISS. Separation from the second stage of the rocket occurred high above the Atlantic Ocean, to the east of Brazil, and at 1:08:29 p.m. Cygnus’ first electricity-generating solar array was reported to be successfully deployed, with the second following shortly thereafter.
Yet this is merely the first step of a complex series of phasing and rendezvous maneuvers which Cygnus must complete, before Wednesday morning’s scheduled berthing at the Earth-facing (or “nadir”) port of the space station’s Harmony node. Like its predecessor Cygnuses, the ORB-2 mission is named for a deceased astronaut: the ORB-D (“Demonstration”) mission in September-October 2013 honored G. David Low, whilst ORB-1 in January-February 2014 paid tribute to C. Gordon Fullerton. Today’s launch remembers five-time shuttle astronaut Janice Voss, who died of cancer two years ago. In the minutes after ORB-2 achieved orbit, the tributes began flooding in, via Twitter. Shuttle astronaut and ISS resident Nicole Stott called Voss “a wonderful human being – on her way to #ISS”, whilst Expedition 40 crewman Reid Wiseman tweeted from the ISS: “Nicely done @Orbital Sciences – looking forward to #Cygnus arrival on Wednesday!”
With its twin gallium arsenide solar arrays providing a total of 3.5 kW of electrical capability, Voss’ mechanized namesake will gradually close the distance with the ISS, ahead of capture by the station’s 57.7-foot-long (17.6-meter) Canadarm2 at about 6:37 a.m. EDT Wednesday, 16 July. ORB-2 boasts several upgraded rendezvous tools, including a new Triangulation LIDAR (known as “TriDAR”), which provides a model-based laser navigation sensor, being trialed on this flight. It will compare its readings with a Computer Aided Design (CAD) of the station to determine relative positions and attitudes. “Cygnus will employ one TriDAR unit for the ORB-2 mission,” NASA explained in its ORB-2 mission press kit. “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.
Early Wednesday, the spacecraft will hold position at a distance of 39.4 feet (12 meters) from the space station. At this stage, Expedition 40 Commander Steve Swanson—based in the multi-windowed cupola and assisted Germany’s Alexander Gerst—will grapple Cygnus, via Canadarm2. With Cygnus denoting the Latin word for “swan”, the first handful of letters of Swanson’s surname, Orbital could not resist a cheeky tweet: “When #Cygnus (Latin for swan) arrives at the #ISS on the 16th, #AstroSwanson will be leading the grapple. Coincidence?” Less than two hours after the grapple, at 8:30 a.m. EDT, if all goes well, Swanson and Gerst will 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).
In an interview with NASA’s Pat Ryan, Orbital’s ORB-2 Visiting Vehicle Lead Floyd Booker remarked that long-range planning for payloads aboard Cygnus missions typically gets underway about 12 months ahead of launch. This mission carries a total of 3,293 pounds (1,493.8 kg) of supplies and equipment for the Expedition 40 crew, which, in addition to Swanson, Gerst and Wiseman, also features Russian cosmonauts Aleksandr Skvortsov, Oleg Artemyev and Maksim Surayev. The payload includes 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 space station’s 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.” To be 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 is 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.
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