Orbital ATK’s Antares rocket returned to flight in a new configuration on Monday, two years after its previous mission ended in an explosion seconds after liftoff. Monday’s launch took place from the Mid-Atlantic Regional Spaceport on Wallops Island, Virginia – at the end of a five-minute window at 19:45 EDT (23:45 UTC).
Returning Antares Launch:
The launch was the sixth flight of the Antares, but it was first to use the Antares-230 configuration, differing from previous rockets by the use of RD-181 first stage engines in place of the AJ-26-62 motors used in the 110, 120 and 130 configurations.
Replacing the AJ-26 – which was a refurbishment of NK-33 engines built in the early 1970s Soviet Union – was already part of Orbital’s plans at the time of the 2014 failure, however after the loss of that mission and the failure of an AJ-26 during a test firing earlier in 2014, these plans were moved forwards.
Antares was developed, along with Orbital’s Cygnus spacecraft, under NASA’s Commercial Orbital Transportation Services (COTS) program. The Antares rocket first flew in April 2013, carrying a mass simulator designed to mimic a Cygnus vehicle, along with four CubeSats.
Its next launch, in September of the same year, marked the first flight of Cygnus with the SS G. David Low successfully completing all of Orbital’s remaining COTS demonstration objectives including berthing at the International Space Station (ISS).
Having completed its demonstration flight, Cygnus was cleared to begin an eight-mission Commercial Resupply Services (CRS) contract to deliver cargo to the Space Station, which NASA had awarded to Orbital Sciences Corporation in December 2008. The first two missions under this contract were flown successfully in January and July 2014.
At 18:22 local time (22:22 UTC) on 28 October 2014, Antares lifted off from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) to begin Cygnus’ third CRS mission. Fifteen seconds into the mission an explosion occurred at the base of the first stage, the rocket lost thrust and fell back to Earth close to its launch pad.
Investigations by Orbital and by NASA determined that the anomaly had been caused by the failure of a turbopump in the rocket’s number one engine. NASA’s investigation identified three possible root causes of the turbopump failure – although determined that evidence was inconclusive as to which scenario or combination of scenarios caused the failure.
The three failure modes identified were that turbopump’s hydraulic balance assembly and turbine bearing were not sufficiently robust, that foreign object debris had been ingested by the turbopump or that the failure was the result of a manufacturing fault in the turbine housing. Orbital’s review concluded that a manufacturing fault in the turbine assembly was the most likely cause.
The AJ-26 engines were derived from the NK-33 engines developed by the Soviet Union’s Kuznetsov Design Bureau, or OKB-276, for the N-1F rocket.
An upgraded operational version of the N-1, which had been developed in the late 1960s with the intent of launching manned missions to the Moon, the N-1F was abandoned in the early 1970s following the failure of all four N-1 test flights and the Soviet Union being beaten to the Moon by the United States. NK-33s were to have replaced the thirty NK-15 engines that powered the N-1’s first stage.
Despite their destruction being ordered, the NK-33 engines were stored following the abandonment of the N-1 program and were subsequently proposed for several different rocket programs before finally flying in 2013 – first aboard Antares in April and then Russia’s Soyuz-2-1v in December.
The engines used on Antares were refurbished by Aerojet Rocketdyne, who assigned them the AJ-26 designation. With original production having ended in the 1970s, the stockpile of NK-33s was limited to around sixty examples, thirty-six of which were purchased by Aerojet for projects in the United States. Orbital ATK expected to continue flying out its initial CRS missions with the AJ-26 before transitioning to another engine for subsequent missions.
The RD-181 that will debut on the launch is derived from the RD-191 engine used by Russia’s Angara rocket and was developed by NPO Energomash. The RD-191 is itself a single-chamber version of the RD-170 series engine which was originally built for the Zenit and Energia rockets, with the RD-180 used by United Launch Alliance’s Atlas V a twin-chamber version of the same family.
Antares now uses a pair of RD-181s in place of its two AJ-26s. The RD-181s burn the same propellant type as the AJ-26 – RP-1 oxidized by liquid oxygen – allowing stages which were under construction for AJ-26-engined vehicles to be converted for the RD-181. The new engines are more powerful than their predecessors, increasing Antares’ payload capacity.
The first stage of Antares was designed and constructed by Ukraine’s Yuzhnoye and Yuzhmash design bureaus and is based on the first stage of the Zenit rocket that was developed by the same bureaus. Antares’ second stage is a Castor-30XL solid rocket motor, introduced on the unsuccessful 2014 launch as an upgrade in place of the Castor-30B that had been used for the previous two missions.
In order to keep Cygnus flying while Antares was grounded, Orbital ATK purchased two Atlas V missions from United Launch Alliance which were flown in December 2015 and April 2016.
Coinciding with an upgrade of the Cygnus spacecraft to an “enhanced” configuration with a larger pressurized cargo module – as well as redesigned fuel tanks and new solar arrays – the more powerful Atlas rocket allowed Orbital to maximize the cargo Cygnus could carry to the Space Station. The launch will be the first time an enhanced Cygnus launches aboard Antares.
The launch carried the seventh Cygnus spacecraft, designated CRS Orbital ATK 5 (OA-5).
Orbital have chosen to name their Cygnus spacecraft after astronauts, with OA-5 being named the SS Alan Poindexter. Born in November 1961, Poindexter served in the US Navy including as an F-14 pilot in the First Gulf War and later as a test pilot, before joining NASA in 1998. He flew aboard two Space Shuttle missions; the first as pilot of Atlantis during the STS-122 mission that delivered the Columbus module to the International Space Station in February 2008.
His second mission was as the Commander of Discovery during April 2010’s STS-131. In 2010 Poindexter retired from NASA and returned to the Navy. He was killed in a watercraft accident while on vacation in July 2012. The SS Alan Poindexter is the first Cygnus to be named after an astronaut who visited the ISS.
The Cygnus spacecraft consists of a service module whose design draws upon Orbital’s experience of manufacturing commercial communications satellites, and a pressurized cargo module (PCM).
The PCM is constructed by Franco-Italian aerospace contractor Thales Alenia Space and is based on the design of the three Multi-Purpose Logistics Modules (MPLMs) used by the Space Shuttle to deliver cargo to the station. A Common Berthing Mechanism (CBM) at the forward end of the PCM allows Cygnus to be attached to the space station upon arrival.
The 6,173 kilogram (13,608 pound) Cygnus spacecraft is powered by an IHI Aerospace Delta-V engine, derived from the BT-4 propulsion system frequently used by communications satellites.
The Delta-V burns hydrazine propellant and can operate either as a monopropellant thruster or in a bipropellant mode using mixed oxides of nitrogen (MON-3) as oxidiser. Smaller reaction control thrusters facilitate maneuvering and attitude control. Cygnus carries 800 kilograms (1,764 lb) of propellant for its mission.
For the OA-5 mission, the SS Alan Poindexter is carrying 2,342 kilograms (5,163 lb) of cargo for the International Space Station, of which 2,209 kilograms (4,870 lb) is useful mass and the remainder packaging.
This cargo includes 585 kilograms (1,290 lb) of provisions for the crew, 1,023 kilograms (2,255 lb) of hardware for the US segment of the space station, 42 kilograms (93 lb) of hardware for the Russian segment, 56 kilograms (124 lb) of computer equipment and five kilograms (11 lb) of hardware to support spacewalks.
As well as provisions and vehicle hardware, Cygnus will carry 498 kilograms (1,098 lb) of scientific equipment including experiments to be performed aboard the station. The Cool Flame Investigation (CFI) will follow up unexpected results observed during the earlier Flame Extinguishment Experiment (FLEX) aboard the station, which discovered materials continuing to burn at low temperatures and with no visible flame after their normal burning was extinguished.
The Lighting Effects experiment will take advantage of the planned replacement of the International Space Station’s lighting system to study whether crew sleep patterns and alertness can be improved by controlling the station’s lighting environment. Fluorescent lights aboard the space station are being replaced with LED-based lights. NASA will investigate controlling the intensity of the blue component of the lighting to aid sleep and increase alertness at appropriate times.
EveryWear is a French-led European Space Agency experiment which will be conducted by Expedition 50/51 crewmember Thomas Pesquet, who is scheduled to arrive aboard the Soyuz MS-03 mission in November. Pesquet will use an app on a tablet computer to record scientific results, medical information, sleep, exercise and nutritional data which will be transmitted automatically to Earth.
The Fast Neutron Spectrometer (FNS) is a radiation detector which is expected to provide more accurate measurements of neutron flux within the space station’s radiation environment. The new sensor will initially be operated for six months across three different locations; within the Unity, Harmony and Destiny modules. Once its primary mission is complete the sensor is expected to remain in use indefinitely.
Following its departure from the space station, Cygnus will be used for the Saffire-II experiment, studying the effects of a fire aboard a spacecraft. Saffire uses a self-contained experimental package to determine how flammable material samples are in microgravity aboard the spacecraft.
Saffire-II is the second of three Saffire experiments under NASA’s Spacecraft Fire Safety Demonstration Project. The first was performed using the OA-6 spacecraft, SS Rick Husband, following its departure from the ISS in June; the third will be carried by the OA-7 mission that is currently scheduled for launch in late December.
During its free flight, Cygnus will also deploy four CubeSats for Spire Global.
The Spire, or Lemur-2, satellites, which will be used for meteorological research. Spire’s filing with the US Federal Communications Commission states that these will be deployed into an orbit at least 45 kilometres (28 miles, 24 nautical miles) above that of the space station, provided Cygnus has sufficient fuel remaining to reach this orbit; otherwise they will be released at least 15 kilometres (9 miles, 8 nautical miles) below and ahead of the station.
Each Spire satellite carries a payload named STRATOS, which will be used to study the occultation of signals from Global Positioning System (GPS) navigation satellites as they pass through Earth’s atmosphere. By studying how these signals are affected as they pass through the atmosphere, the temperature, humidity and atmospheric pressure of that atmospheric region can be inferred.
Each satellite has a mass of four kilograms (9 lb). The total mass of the satellites, their NanoRacks deployer and supporting equipment is listed as 83 kilograms (183 lb).
These four satellites are the third group of operational spacecraft in Spire’s constellation; following the deployment of the first four satellites by a PSLV in September 2015, and nine further satellites were launched with the OA-6 Cygnus mission to the International Space Station in March.
Four of these spacecraft were transferred to the space station and deployed from the Kibo module, while four of the remaining five were deployed by Cygnus after its departure. The final satellite failed to separate from Cygnus.
The launch took place from Pad 0A of the Mid-Atlantic Regional Spaceport (MARS). Originally constructed for the short-lived Conestoga rocket, which made a single unsuccessful launch in 1995, pad 0A was rebuilt for Antares once Orbital had been awarded its Commercial Orbital Transportation Services contract.
Pad 0A was damaged in September 2014’s launch failure, with the launch its first since returning to service.
Antares’ mission began with ignition of the RD-181 main engines at the zero mark in the countdown. Liftoff occurred 3.6 seconds later, with the first stage burning for three minutes and 29 seconds. First stage main engine cutoff occurred at an altitude of 104 kilometers (65 miles, 56 nautical miles), with the rocket traveling downrange at a velocity of 3.69 kilometers per second (8,250 mph, 13,300 kph).
Six seconds after first stage cutoff, the spent stage separated from the vehicle. The payload fairing separated from around Cygnus 35 seconds after staging, with the interstage between the first and second stages jettisoned five seconds later. The second stage ignited seven seconds after interstage separation, ending a 53-second coast.
The second stage motor, a Castor-30XL, burned for two minutes and forty-three seconds, injecting Cygnus into orbit. Its burnout at seven minutes and five seconds mission elapsed time marked the end of powered flight for the mission. The Castor-30XL’s only previous launch was the September 2014 Antares mission that failed during first stage flight.
The SS Alan Poindexter separated from Antares two minutes after second stage burnout to continue its journey to the International Space Station.
The expected orbital parameters at spacecraft separation are a perigee of 209 kilometers (130 miles, 113 nautical miles), an apogee of 288 kilometers (179 miles, 156 nautical miles) and inclination of 51.64 degrees. An hour and a half after launch, Cygnus will deploy its solar arrays.
Over the first two and a half days of its flight, Cygnus will perform a series of orbit adjustment maneuvers to bring its orbit close to that of the space station. However, Cygnus will loiter until after the arrival of the next Soyuz spacecraft later this week, following a one day delay caused by a ground support issues during the attempt to launch on Sunday.
Astronauts aboard the station will grapple Cygnus using the station’s CanadArm2 arm and bring Cygnus on to the nadir – or Earth-facing – port of the Unity module. Cygnus is expected to remain at the station for a month, while cargo is unloaded and the spacecraft is filled with equipment and waste for disposal. At the end of its stay, Cygnus will be unberthed and released – again using CanadArm2 – to begin the free flight part of its mission.
In late November, following CubeSat deployment and the conclusion of the Saffire-II experiment, Cygnus will be deorbited and destroyed during reentry into Earth’s atmosphere. Unlike SpaceX’s Dragon spacecraft, Cygnus is not designed to be recovered.
The company’s next launch is expected to take place in mid-November, with an air-launched Pegasus-XL rocket, which will deploy NASA’s eight-satellite CYGNSS weather research constellation.
The next Antares launch is expected to occur at the very end of the year, with the OA-7 Cygnus mission.
Following the Cygnus launch, the next mission to the International Space Station is expected to begin on Wednesday, with Soyuz MS-02 lifting off from the Baikonur Cosmodrome with three cosmonauts to join the Expedition 50 crew in orbit. The next resupply mission will be Russia’s Progress MS-04, due to launch at the start of December.
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