Orbital ATK has conducted a crucial step in the return of its Antares rocket to flight operations later this year from the Mid-Atlantic Regional Spaceport in Virginia. This crucial step took place on Tuesday at Pad-0A, where the company performed a static fire of the newly redesigned Antares core stage ahead of the rocket family’s return to flight on NET 6 July 2016.
Road to the static fire – upgrading Antares:
The road to the static fire has been one of slow and steady progress for Orbital ATK following the October 2014 mishap during the Orb-3 launch.
That mishap led to a critical redesign of the Antares core stage away from its 100 series configuration with Aerojet AJ26 engines and into its 230 configuration with two RD-181 engines.
To this end, the Antares 230 variant will not only provide better engine reliability for the rocket, but will also increase its overall performance and payload-to-orbit targets.
In all, the upgraded Antares 230 will be capable of providing a 25% increase in payload-to-orbit capability over the Antares 100 series via a 13% higher thrust performance of the RD-181 engines over the AJ26 engines and a 10 second higher Specific Impulse (ISP) of the RD-181s over the AJ26s.
Impressively, this engine changeout, while significant, was done with minimal reconfiguration of the Antares core stage.
While the RD-181s are a higher performance engine over the AJ26s, they nonetheless use the same mixture ratio as the AJ26s, thus eliminating the need to redesign the core stage propellant and oxidizer tanks on Antares.
Moreover, selection of the RD-181s did not require a huge modification effort at the launchpad itself.
As has been noted previously, Orbital ATK was extremely lucky in that the Orb-3 launch mishap did not destroy any of the major structural elements of the launch pad itself.
In fact, most of the critical pad structures escaped major damage during the October 2014 incident, with the cross-country piping receiving the brunt of the destructive force of the launch failure.
This led to a relatively quick repair of the pad alongside the modifications needed for the RD-181 engines.
Notably, these pad modifications for the RD-181 engines were minor and focused on the different services needed for the RD-181s, specifically the need for heated nitrogen to evacuate air from the engine’s combustion chambers prior to ignition.
One of these modifications saw the creation and installation of a heater panel to heat the nitrogen flow and feed it at the correct pressure into the engines.
In this time, in what has proven to be a crucial design configuration for the Cygnus spacecraft, currently Antares’ sole spacecraft, Cygnus has conducted two resupply missions to the International Space Station (ISS) during the Antares rocket’s stand down period.
This was made possible because Cygnus was designed to be compatible with multiple launch vehicles, thus allowing Orbital ATK to contract with United Launch Alliance to launch two Cygnus missions – OA-4 and AO-6 – aboard the veteran Atlas V rocket from the Cape Canaveral Air Force Station in Florida in December 2015 and March 2016, respectively.
With pad and rocket now ready, Orbital ATK is turning their attention toward the final aspects of ground testing before Antares can once again grace the skies this summer.
The first static-fire ready Antares’ 230 core stage was transported to Pad-0A at the Mid-Atlantic Regional Spaceport (MARS) for a slew of pad tests on 12 May.
The prolonged pad stay prior to the targeted static fire has allowed teams to fine-tune various aspects of the vehicle’s integration with pad facilities and to test the pad modifications in advance of the static fire.
For the static fire, Orbital ATK had a 3 hour 15 minute window opening at 17:00 Eastern.
Had the static fire cannot be completed by 20:15 Eastern, Orbital ATK would have made use of their back-up dates that extend through 5 June to conduct the engine test firing.
However, the static fire was achieved early in the window, allowing engineers and technicians to pour over the wealth of data collected by the engine test firing to confirm that the engines, pad, and Antares 230 core stage have all performed as designed.
“Early indications show the upgraded propulsion system, core stage and launch complex all worked together as planned,” said Mike Pinkston, Orbital ATK General Manager and Vice President, Antares Program. “Congratulations to the combined NASA, Orbital ATK and Virginia Space team on what appears to be a successful test.”
If no major issues are detected, Orbital ATK will use the static fire data to fine-tune the Antares 230 core stage that will loft the next Cygnus mission, OA-5, to the Space Station in July.
The Antares 230 core stage for OA-5, however, will not be the same core stage static fired.
Instead, the static fired 230 core will remain on the pad for additional ground support testing following its static fire before being returned to the horizontal position and moved back into Orbital ATK’s integration facility at MARS.
That static fired core will then be prepared for the OA-7 mission, currently set to launch in the extreme late part of December 2016 while a different Antares core 230 stage is prepared for this summer’s OA-5 mission.
The OA-5 Cygnus is currently undergoing integration operations at Orbital ATK’s MARS facility ahead of what is anticipated to be a NET (No Earlier Than) 6 July 2016 launch to the International Space Station – during which, launch duties for Cygnus will once again return solely to Antares.
“The successful stage test, along with the extensive testing of each new RD-181, gives us further confidence in the first stage propulsion and in moving forward to launch,” said Pinkston. “We are now focused on the OA-5 mission and launching the enhanced Cygnus spacecraft to the International Space Station on our upgraded, higher-performing Antares rocket.”
(Images via Orbital ATK and NASA)