After 110 days at the International Space Station, the Northrop Grumman Innovation Systems (NGIS) NG-11 Cygnus resupply vehicle has departed the orbital outpost.
But in a significant change from previous missions, Cygnus will not perform a destructive re-entry within the next few weeks, instead remaining on orbit until the end of the year to test new systems aboard the craft that will aid NGIS in their ability to offer Cygnus as a free-flying science platform for ISS, non-Space Station, and future NASA needs.
A prolonged mission for NG-11 Cygnus:
After departing the International Space Station, the NG-11 Cygnus will – as is customary – deploy a series of Cubesats from both a forward hatch-mounted deployer and its standard CubeSat deployer mounted on its service module on the rear of the craft.
Speaking directly to NASASpaceflight, Frank DeMauro, Vice President and General Manager of Space Systems Division at Northrop Grumman Innovation Systems, said “We have seven CubeSats total. Four are going to be from the Slingshot system that mounts on the hatch part of Cygnus, and then three will get launched from the NanoRacks CubeSat deployer which is mounted on the outside of the service module.”
But after these releases, the NG-11 Cygnus will enter new territory.
Instead of changing its orbit to maneuver for a destructive deorbit and reentry over the South Pacific, Cygnus will instead begin a multi-month orbital test campaign to validate several new systems that will greatly aid its ability to serve as a free-flying science platform going forward.
CubeSat deployer and its location on the outside of the Cygnus craft. (Credit: Northrop Grumman)
These new systems include the first flight of a Control Moment Gyro (CMG) on Cygnus that will enable the craft to maintain its attitude instead of using propellant-driven thrusters.
“The goal of this experiment – and I do want to stress that this is an experiment – is to demonstrate our ability to fly Cygnus with a Control Moment Gyroscope, demonstrate that our avionics and software works well with the CMG, and so we’ll spend a couple of weeks actually doing that particular check out,” related Mr. DeMauro.
“The team has got some specific tests they’ll be doing for maneuverability and checking the interfaces between all the avionics. We’ll be looking at the fuel usage with and without the CMG because without the Control Moment Gyroscope, as with all of our missions before, we just use fuel for maneuverability.
“And now with a CMG we’ll use that for pointing the spacecraft and just use fuel for trimming the orbit,” said Mr. DeMauro.
This test will be carried out as part of the NG-11 Cygnus’ extended stay on orbit, something else NGIS is keen to demonstrate with the craft.
“We plan to fly around for about six months,” noted Mr. DeMauro, to show Cygnus’ capability of staying on orbit to serve as a free-flying scientific research platform and/or testbed for government and commercial entities.”
And that all leads to a big end-goal for NG-11 – showing that two Cygnus spacecraft can be operated in orbit at the same time.
To do this, NG-11 will remain in orbit through the end of the year so that its flight can overlap with the NG-12 mission of the next Cygnus this fall.
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“The real goal at the end of the mission is to demonstrate the ability to fly multiple Cygnus vehicles in orbit at the same time,” said Mr. DeMauro. “Our thinking is that in the future, if we have a payload that wants Cygnus to fly around for a longer time, then that mission would most likely overlap with another cargo mission. And so we need to have the ability to control two Cygnus vehicles at the same time.”
But having two Cygnus vehicles in orbit at the same time is not a simple matter of just launching another one. NGIS has spent a great deal of time upgrading Cygnus software, ground software, human-computer interfaces, and training controllers to get to this point.
“The key with the software upgrades is that if we have a single controller and we have two vehicles that we’re controlling, how do we make sure that the commands are going to the correct spacecraft? And then also how do we make sure that the controller, and not only the controller but all of the members of the team for monitoring the two spacecraft, are looking at the right telemetry for each particular spacecraft,” noted Mr. DeMauro.
In terms of human-computer interfaces, NGIS has color coded the data that will come from each Cygnus. For example, NG-11’s telemetry might have a blue background whereas NG-12’s would have a purple background – enabling controllers to instantly recognize which vehicle’s data they are looking at.
The Lunar Gateway – with a Cygnus-derived element. (Credit: NASA)
But more than the above tests, the long-duration orbital stay allows NGIS to learn how Cygnus’ regular systems – systems that will soon be called upon for NASA’s Lunar Gateway – respond to prolonged operation in space.
While a formal announcement is still forthcoming from NASA and NGIS, a publicly released government report has revealed a directive to have the Lunar Gateway’s habitation module come from NGIS using a Cygnus-derived design.
NGIS has tested their design with NASA, as previously reported by this site.
While not speaking directly toward Gateway, Mr. DeMauro did highlight what NGIS can learn of long-duration Cygnus use for potential application to coming NASA needs.
“We have always felt that Cygnus is a great building block for us and NASA to build upon to go beyond Low Earth Orbit. Cygnus gives us a great jumping-off point to design and develop and then deploy systems that go to the Moon and then eventually beyond that,” said Mr. DeMauro.
“Certainly part of our goal is to prove out our systems or learn about our systems as they would operate for much longer times in orbit. Of course the environment out at the moon or at Mars is obviously very different than Low Earth Orbit. So that may limit in some ways how much of this will apply.
“But certainly there are things to be learned and lessons to be applied towards any upgrades to the Cygnus we might make based on this long-duration mission.”