“We spent [that] time determining the correct thermal configuration and the right attitude to get to that configuration,” answered Joe. “We had a range that we expect to perform in, and there’s a min temperature and max temperature, and we were examining how strict those temperatures needed to be for the operation and what changes we may need to make to be within that range.”
The plan and extra day allowed for the full tensioning of the sunshield and retirement of approximately 75% of the mission’s total single-point failure risk.
Marc enthused: “The fact that it went off really with no concerns or issues at the end was just fantastic. It’s such an incredible accomplishment… millions of hours and people’s lives dedicated to it to get us to this point… that’s really hard to summarize and give credit to all the work that was done to get us to this point.”
Joe concurred: “I have worked on other programs and followed other programs over my career at Northrop, and all of them were difficult. But I will say none as equally difficult in dealing with the soft structure nature of the sunshield deployables and all the interactions of maintaining the configuration.”
Hillary picked up on the idea of the complexity of the soft structure, harkening back to the ground testing and development work Northrop Grumman poured into the sunshield for decades.
“It was so huge to have the ground testing because all of these interactions were brand new to us. We were able to test it for truly the first time because it’s not heritage, and to learn so much through the ground tests of how all of these soft structure parts interact… it’s a balancing act. To have that opportunity, sort of a sandbox, to develop a soft structure deployable system, was invaluable.”
Speaking to the sunshield’s history, Joe recalled, “So maybe 15 years ago, we had the concept design review for the sunshield. Fundamentally, the design did go through some changes. It used to look quite different, but functionally, it performed the same role. It just took a different form over time due to design considerations and needs for supporting the membranes as they were folded.”
“I think where the design itself changed a lot was the specifics in the system involved in the control of the membrane when it was on the vehicle for launch, and then the deployment,” continued Marc.
“That’s really where I think people had to do a lot of new and novel design work to come up with: ‘how do you fold and manage a membrane for a launch configuration and how do you unfold and individually tension and work your way through all the different layers when you go to perform the tensioning process?’”
And testing on the ground was key, and unlike some elements of Webb, the sunshield could be taken through multiple deployment tests on the ground.
“I guess our benefit was that we had multiple of those deployments that we were able to perform on the ground,” said Joe. “There was a lot of analytical predictions that were basically confirming on the ground with that one-G to zero-G analytical prediction that sets everything going on while we’re pushing out a boom or while we’re running motors to bring the layers up into position.”
1/ Good news keep coming. Mike Menzel @NASA Webb Mission Systems Engineer said yesterday in press brief that #Webb might have "quite a bit of fuel margin (…) Roughly speaking, it’s around 20 years of propellant”, adding that’s still TBD.
Credit: @esa / @cnes / @arianespace pic.twitter.com/inpBOyDcNr
— ESA Webb Telescope (@ESA_Webb) January 9, 2022
“While we’re assessing motor telemetry, there’s other stuff going on in the background that is providing control of the membranes, control of the many, many cables we have that tension the system while reducing our billowing of the membrane itself because one of the big things we were assessing on the ground was snag.”
“Really, during that final build phase when we had many engineers supporting every day in the high bay, they were verifying the worst-case configurations that the membranes and cables could have been in to make sure that nothing could snag on something else and hold up a deployment.”
In the end, nothing snagged. It all worked.
Joe continued: “I would say everything that went into the folding and how to position five layers together and then hold them all to a structure as well as how to then unfold and tension, I don’t really think that we have done — or anyone has really done –anything like that before for a space vehicle.”
“Obviously, individuals take all of their own knowledge in design and analysis work to build towards something so they can take ideas out over time or concepts that they’ve used in other places, but the way they came together for this subsystem, I don’t think there’s anything we would say that’s a heritage subsystem that we, or probably anybody else, has really ever developed.”
“We have a telescope.” JWST teams completed the observatory’s unfolding process on Saturday, January 8, 2022. Over five months of commissioning and calibration remain. (Credit: NASA GSFC/CIL/Adriana Manrique Gutierrez)
T+10 days saw the successful deployment of the Secondary Mirror Support Structure (SMSS) and secondary mirror. The following day, the Aft Deployable Instrument Radiator (ADIR) was deployed successfully.
The final major deployments of JWST began on T+12 days, when the port primary mirror wing successfully swung out from its launch position and latched to the primary mirror structure.
Throughout the next days and weeks, teams on the ground will begin aligning Webb’s mirror and performing initial system checkouts as JWST prepares to bring its instruments online.
The entire commissioning phase is expected to last at least six months, with the first returns from Webb expected in the middle of 2022.
(Lead image: Sunshield deployment test. Credit: Northrop Grumman)