[Draft 6-11-2025]
Epigraph
Over time … more with more … became more with less … and then just making do.
Prologue
Initial deployments of the Webb Space Telescope were among the most critical, and the riskiest. 344 single-point failures were identified in the spacecraft, 80% of which were associated with deployment (release) mechanisms.
Yet, risk mitigation aside, vast networks of coordinated effort and relationships pose similar points of failure as well. And success may depend on moments where one person’s action or one decision is such a point.
An anthology inspired by chats with Ben at the gym. He worked 10 years on the Webb Space Telescope program.
Tales of single point moments
VENT BEFORE OPENING
• Mindful of margins
High over Paris there was a crunch. Ben’s sleeping brain wove that sound into his dream, a scene of doom, as another note in the stress & excitement of his mission.
That note jolted him awake. Across the aisle a young boy had crushed a soda can. The kid looked pleased with his show of strength. Perhaps he’d seen social vids of young men crushing beer cans against their foreheads.
But for Ben it was a reminder of the pressurized cabin in which he flew, the consequences of changes in air pressure [1], the margins of safety.
There was a carefully boxed item in the plane’s cargo. It contained a spare part for something going into space.
Ben used the time during descent and the delays before deplaning to ponder the swirl of recent events.
• No pearl inside
•• The review meeting
The meeting had started okay, but Eric felt increasingly irritated. The discomfort in his gut came on whenever he sat in on one of John’s department meetings. Perhaps like a clam when a small particle is introduced inside its shell. But no pearl would result from this stress.
Both of them had graduated from MIT. While their management styles differed, it was John’s incessant, repeated use of the phrase “if you will” that drove Eric crazy.
The agenda for the department meeting was posted earlier in the week. So, Eric didn’t expect anything unusual. His department followed regular order as well. He recognized the section heads seated around the large conference table. Today, as an observer, he sat near the wall in the back, near the door. His lead systems engineer Ben sat next to him.
Basically everyone was there to once again cover a checklist of revisions to the launch vehicle fairing. Ben was agitated as well, and whispered, “Eric, can you believe how John bullies his team?”
“Yeah, that seems so old school, like he really doesn’t want anyone rocking the boat with new questions,” Eric replied.
Ben nodded, then remarked, “I’ve been looking at some new data.”
“Okay, let’s talk at lunch.” After a few more “if you will” moments, they both quietly left the room.
•• The lunch chat
“So, Ben, tell me more about this new data.”
Ben said, “Sure.” After looking around the cafeteria, he continued, “Eric, you might say that it deals with assumptions. The improved honeycomb design of the interior fairing wall makes sense because of the new dimensions. But the vent valves … well, the data shows that they probably flutter and close. The Webb’s sunshield stack is something new, quite fragile. Like a tightly packed, layered sandwich. Remember that tear during recent tests? So, I’ve been thinking more about pressure differentials, possible air pockets inside the stack if all the vents don’t stay open before the fairing opens.”
“I see. Anyone else looking at this?”
“Not that I’m aware of. Knowing how to run sim’s is one thing, but there’s the time, and everyone’s already stressed out,” Ben explained.
“Sounds like this might be appropriate to raise at the next ‘all hands’ meeting. If there’s an opportunity.”
• One raised hand (‘all hands’ holdout)
This was a larger pow-wow. A larger conference room. More staff members in rows of chairs around the walls. More projected visuals, as each technical department head presented. Bill (‘no drama’ Gama), the lab chief, stuck to regular order. Until … just before lunch …
Bill said, “I appreciate all of you going over things yet again. Sounds like subcontractors have been responsive to all your queries. Particularly the fairing contractor. We need to be sure there’re no loose ends. There’s a limited window of opportunity to tweak the design. That opportunity is provided by other customers using the same launcher for their upcoming missions. So, I’d like a show of hands. Raise you hand if you feel there’s something we’ve missed, something to look at further?”
Everyone there looked around. Some picked up their backpacks. Ben nudged Eric and cleared his throat. Eric reflexively raised his hand, and said, “Well …”
John had a smirk on his face, as if saying, “You really put your foot in it this time.” Eric’s was the only hand raised.
• Executive caution
• Contractor rebuff (fairing contractor)
• A good day to garden (cold call)
• The pitch
• Reducing risk
• The long wait
SCREWED BARELY?
- One raised hand (is ball in or out?)
- “Analyze this!”
- Line call
- Mending manners (moving on)
- The long wait
Notes
[1] A common demonstration in science class.
• Wiki > Collapsing can
https://en.wikipedia.org/wiki/Collapsing_can
Note AI’s response to Google search for “high school science demo the power of vacuum to crush a can.”
[2] Getting a space telescope into space is only part of the drama.
Basically the issue was loading on the spacecraft due to any “pressure differential once the fairing is separated.” That is, failing to adequately equalize pressure inside & outside before exposure to space (vacuum).
• Wiki > James Webb Space Telescope
https://en.wikipedia.org/wiki/James_Webb_Space_Telescope
• Wiki > Ariane 5
https://en.wikipedia.org/wiki/Ariane_5
The VA253 launch on 15 August 2020 introduced two small changes that increased lift capacity by about 85 kg (187 lb); these were a lighter avionics and guidance-equipment bay, and modified pressure vents on the payload fairing, which were required for the subsequent launch of the James Webb Space Telescope. It also debuted a location system using Galileo navigation satellites.
On 25 December 2021, VA256 launched the James Webb Space Telescope towards a Sun–Earth L2 halo orbit. The precision of trajectory following launch led to fuel savings credited with potentially doubling the lifetime of the telescope by leaving more hydrazine propellant on board for station-keeping than was expected. According to Rudiger Albat, the program manager for Ariane 5, efforts had been made to select components for this flight that had performed especially well during pre-flight testing, including “one of the best Vulcain engines that we’ve ever built.”
Google search:
“Ariane 5 modified pressure vents on the payload fairing”
Example result:
• Ariane Group > “Everything You Always Wanted To Know About The Launch Of The James Webb Space Telescope But Were Afraid To Ask” (12-21-2021) – Interview with Stéphane Leboucher, Head of Ariane Mission Preparation and Customization
‘@ArianeGroup – James Webb Télescope Spatial
Is there anything different about the launcher this time?
Yes, the vents on the fairing in particular have been modified to prevent the risk of depressurization that could damage Webb when the fairing is jettisoned. This could have happened if residual air were to be trapped in the folded membranes of the James Webb sunshield. The modifications were successfully tested on the last two Ariane 5 flights on 30 July and 23 October. Our fans will also be happy to know that this time, Ariane 5 is carrying a video system (nicknamed Viki), so that all stages of the launch can be closely followed.
• NASA > Spaceflight > Forum > Ariane 5 fairing separation – includes photo of a fairing vent and diagram showing location of 14 vents
https://forum.nasaspaceflight.com/index.php?topic=53382.0
https://www.nsf.gov/attachments/300822/public/12_James_Webb_Space_Telescope_Update_Eric_Smith.pdf
• ESA > “Ariane 5’s third launch of 2020” (8-16-2020)
https://www.esa.int/Enabling_Support/Space_Transportation/Ariane/Ariane_5_s_third_launch_of_2020
A further modification to Ariane 5’s fairing will minimise depressurisation at separation as this two-part nose cone is jettisoned away from the launch vehicle in space. Manufactured by RUAG Space Switzerland, the fairing protects the customer payloads from the acoustic, thermal and aerodynamic stresses during the ascent. New hardware ensures that venting ports around the base of the fairing remain fully open on the way to space, allowing the pressure to equalise within the fairing prior to opening and falling away from the rocket.
This alteration is part of the preparation for the launch of the NASA/ESA/CSA James Webb Space Telescope (JWST) set for October 2021. These changes mitigate concerns that residual air pressure in the folds of the JWST sunshield membranes could cause high stresses at the time of fairing separation, potentially damaging sensitive components.
[3] JWST Sunshield protection
• Wiki > James Webb SpaceTelescope > Sunshield protection
https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Sunshield_protection
The sunshield consists of five layers, each approximately as thin as a human hair. Each layer is made of Kapton E film, coated with aluminum on both sides. The two outermost layers have an additional coating of doped silicon on the Sun-facing sides, to better reflect the Sun’s heat back into space. Accidental tears of the delicate film structure during deployment testing in 2018 led to further delays to the telescope deployment.
The sunshield was designed to be folded twelve times so that it would fit within the Ariane 5 rocket’s payload fairing, which is 4.57 m (15.0 ft) in diameter, and 16.19 m (53.1 ft) long. The shield’s fully deployed dimensions were planned as 14.162 m × 21.197 m (46.46 ft × 69.54 ft).
[4] JWST sunshield deployment – deployment tower assembly (DTA) – ball screw assembly bearings (friction margins for extended operation)
• Wiki > Ball screw
https://en.wikipedia.org/wiki/Ball_screw
• Google search: “jwst sunshield mechanism screw drive”
AI Overview
The James Webb Space Telescope (JWST) sunshield deployment involved a complex mechanical system, including screw drives as part of its deployment tower assembly (DTA). This mechanism played a crucial role in the initial deployment and tensioning of the sunshield layers.
Here’s how the screw drive mechanism is used:
Deployment Tower Assembly (DTA): The DTA consists of inner and outer tubes that translate relative to each other.
Ball Screw: A 6-foot ball screw is mounted within the DTA, acting as the primary driver for translating the tubes.
Stepper Motor: A gear motor, specifically a 3-phase, 4-pole, permanent-magnet stepper motor, drives the ball screw.
Planetary Gearbox: The motor is connected to a 576:1 planetary gearbox, which increases the motor’s torque to provide sufficient power for driving the ball screw.
Actuation Sequence: The stepper motor rotates the ball screw, causing the ball screw nut to translate along the screw. This translation of the nut then either pulls a flexure to achieve the stowed preload or pushes it to achieve the deployed preload.
Deployment Steps related to the screw drive:
Stow Preload: The stepper motor rotates clockwise to achieve the desired preload in the stowed position, reaching a flexure load of at least 1750 lbs.
Motor Off: The motor power is turned off once the flexure strain limit is reached in the stow preload.
Unload and Deploy: The stepper motor rotates counter-clockwise to unload the flexure and extend the ball screw, enabling the sunshield deployment.
Deployed Preload: The ball screw continues to advance past the end-of-travel stop to preload the flexure to a minimum of 1350 lbs, ensuring the sunshield is properly tensioned.
In essence, the screw drive mechanism, driven by a stepper motor and planetary gearbox, is vital for the initial deployment and tensioning of the JWST sunshield by precisely translating the DTA tubes and applying the required preload to the flexure.
AI responses may include mistakes.
[5] Deployment involved a series of first-of-its-kind complex deployments and maneuvers once the spacecraft separated from the upper stage.
• Space News > “JWST launch marks only the start of a risky deployment process” by Jeff Foust (December 23, 2021) – The liftoff marks only the beginning of the riskiest part of the mission.
• Northrop Grumman > “One Shot to do the Impossible” by Adam Stone – The Intense Testing of the James Webb Space Telescope
[6] Regular order entails doing things in an agreed upon way. This agreement may be based upon tradition. Or on institutional culture, as in “the NASA way.” Our modern political culture has the same mindset (at least until quite recently).
• CBS News > Face The Nation > “John’s Notebook: What is ‘regular order’? by John Dickerson (September 24, 2017)
https://www.cbsnews.com/news/johns-notebook-what-is-regular-order
Regular order is Washington jargon, but it basically means doing things the agreed upon way.
In Congress, regular order is the process for tackling tough problems – studying them, applying expertise and arguing them on the merits without personal attacks.
It’s also a mindset for a place where everyone has to work together the next day. It sets the conditions for heated arguments so everyone feels heard and respected. It grounds debates in the values of the institution – fairness, equality, justice – which temper the passions of the moment.
Regular order doesn’t always lead to compromise. But compromise is less likely without it. Regular order doesn’t always mean less partisanship. Partisan hotheads can still hijack the public process.
But without regular order people get suspicious of the final product. Losers feel cheated and invited to undermine the law.
[7] Systems engineering is another agreed upon way to tackle the development of complex systems. Across the complete life cycle of those systems. It uses an interdisciplinary framework to choreograph a shared vision across all stakeholders, technical disciplines, engineering teams, manufacturers, and end users.
https://en.wikipedia.org/wiki/Systems_engineering
• Wiki > Systems engineering
Systems engineering is an interdisciplinary field of engineering and engineering management that focuses on how to design, integrate, and manage complex systems over their life cycles.
The systems engineering process is a discovery process that is quite unlike a manufacturing process. A manufacturing process is focused on repetitive activities that achieve high-quality outputs with minimum cost and time. The systems engineering process must begin by discovering the real problems that need to be resolved and identifying the most probable or highest-impact failures that can occur. Systems engineering involves finding solutions to these problems.
Systems engineering encourages the use of modeling and simulation to validate assumptions or theories on systems and the interactions within them.