Cygnus ISS mission delayed until January – Three EVAs planned
Orbital’s Antares rocket rolled out to its launch pad on Tuesday. However, due to the uncertainty surrounding the cooling system issue on the International Space Station (ISS) – which will require three EVAs – the ORB-1/CRS-1 mission to launch the Cygnus spacecraft on its first operational mission to the orbital outpost has been delayed until January.
Antares is the first cryogenically powered rocket to be produced by Orbital Sciences. She’s also the largest rocket they have ever produced.
The first stage of the Antares was developed jointly between Orbital Sciences Corporation and KB Yuzhnoye and PO Yuzhmash of Ukraine, with the propulsion provided by two AJ26-62 engines burning RP-1 propellant in liquid oxygen, which generate 3.3 meganewtons (740,000 pounds) of thrust.
The AJ26 engines powering the first stage began life as NK-33s, constructed in the 1960s to power the rockets which would have taken Soviet cosmonauts to the Moon via the massive N1 rocket. The engines were rebuilt by Aerojet to optimize their performance for the Antares.
The Upper Stage is an upgraded version called the ATK Castor 30, with the 30B set to be used for the first two Commercial Resupply Services (CRS) missions – CRS-1 (Orb-1) and CRS-2 (Orb-2).
The final transition for the rocket will come via the use of the CASTOR 30XL, which will power the last six CRS flights scheduled for the Antares – allowing for the transition towards the launch of extra cargo on a larger Cygnus Spacecraft.
Orbital successfully ticked the boxes for the A-ONE mission objectives, with a flawless launch of Antares on its debut mission into space.
With the A-ONE mission achieving all of its validation tasks – successfully lofting a Cygnus Mass Simulator into space – Orbital then conducted a post-flight performance review, in order to confirm everything proceeded as plan during Antares’ launch out of Wallops.
Antares then launched the first Cygnus spacecraft on the ORB-D mission to the ISS, again performing without issue as it sent the spacecraft en route to the orbital outpost for her debut arrival at the Station.
This third launch of Antares is set to conduct the ORB-1/CRS-1 mission, lofting a Cygnus full of supplies to the ISS on the first operational mission under their Commercial Resupply Services (CRS) contract with NASA.
One of the key milestones ahead of the launch was the rollout of the integrated Antares and Cygnus stack, with the rocket first emerging from its Horizontal Integration Facility in the early hours of Tuesday morning.
The rocket was then transported about one mile to the Mid-Atlantic Regional Spaceport (MARS) launch complex, known as Pad 0A, aboard the Transporter/Erector/Launcher (TEL), a specialized vehicle that also raised the rocket to a vertical position on the launch pad and serves as a support interface between the rocket and the launch complex’s systems.
Antares rolled out without a confirmed launch date, as NASA teams continue to work an issue with one of two cooling loops on the Station.
The issue is specific to a Flow Control Valve (FCV) in the loop A coolant system, used to regulate the temperature of ammonia coolant in the ISS’ external cooling loops.
It is likely that several EVAs will be required to replace a Pump Module with a spare staged on the ISS. However, engineers are continuing to work an interim solution, by commanding an isolation valve on the cooling system to control the flow of ammonia.
While that valve was not specifically designed for such a task, the vendor and controllers on the ground believe software should be able to command the valve to carry out this new role on a temporary basis.
Testing of this method is ongoing, although – per L2’s extensive dedicated section on the problem – the teams are still working on this interim fix.
It was hoped that this alternative method would allow for the loop to be brought back on line with full confidence in its near term ability. This may have allowed for Cygnus to berth, prior to ISS managers then switching focus to the schedule of the required spacewalks early in the new year, as opposed to this month.
Unfortunately, the ISS team are not yet fully confident they can bring Loop A back into action ahead of Cygnus’ arrival on December 22. As such, the launch has been postponed until at least the New Year.
“The decision was just made to stand down from the launch,” noted a memo sent out on Tuesday evening (L2).
“The ISS Program is not confident we will be able to manage the cooling loop for the Cygnus to berth. Also, we will focus the team on the EVA task, which is the highest priority to get the cooling loop fully functional.
“Will target the first opportunity in January, which is NET January 9th.”
However, the NET (No Earlier Than) date was then moved to January 13, per Orbital’s release, which added the vehicle will be removed from the pad, prior to being moved back to January 7.
“The Antares rocket that is currently on the launch pad at Wallops Island, Virginia, will be returned to a horizontal position and transported back to the Horizontal Integration Facility (HIF),” the company noted.
“At the HIF, the Antares payload fairing will be removed to allow the Cygnus team to open the payload module hatch and remove time-critical payloads for safekeeping until the next launch attempt, which will occur no earlier than January 13, 2014.
With Cygnus stood down, Station teams set a near-term schedule for three spacewalks to replace the Pump Module, to take place on December 21, 23 and 25. An article overviewing the latest plans will be published later this week.
Once the Station’s cooling ability via Loop A is returned into a stable configuration – thus returning full functionality and redundancy to the ISS’ cooling needs – Orbital will be provided with a green light to press towards the realigned launch date in early January.
Should there be a further delay, discussions will need to take place on the near-term Visiting Vehicle schedule, given Cygnus will need to depart from the ISS in time to make way for SpaceX’s Dragon spacecraft, which is scheduled for the middle of February.
(Images: via L2’s Cygnus Section – Containing presentations, videos, a vast set of unreleased hi-res images, interactive high level updates and more, with additional images via Orbital and NASA).
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