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The deployment sequence that takes approx 30 days is terrifying but also probably one of the most complex things we would ever achieve if successful. Have been

by gadnuk 5y ago

The deployment sequence that takes approx 30 days is terrifying but also probably one of the most complex things we would ever achieve if successful. Have been waiting for this since I was a teenager. Can't believe we are almost there (launch on Dec 22). Here's a short 2 min video of that deployment sequence if anyone wants to be fascinated: https://www.youtube.com/watch?v=RzGLKQ7_KZQ https://www.youtube.com/watch?v=RzGLKQ7_KZQ Also a short interview with Dr. John Mather (could listen to him all day) if anyone wants to know how the telescope works: https://www.youtube.com/watch?v=4P8fKd0IVOs https://www.youtube.com/watch?v=4P8fKd0IVOs

peter303 5y ago
They should deploy in Earth orbit near the ISS, then move to L2. Would give option for repair. The shuttle was decommissioned after the primary Webb design was done. What would have known the launch options at the time it was ready?
- steve_taylor 5y ago
  It’s probably too risky given all the debris in orbit.
  - hoseja 5y ago
    Do you have any idea how little "debris" there actually is?
    - samsari 5y ago
      Do you have any idea how little risk "too risky" actually is?
- idontwantthis 5y ago
  You can't just put things in space wherever you want them and then move them whenever you want to or to wherever you want to.
sophacles 5y ago
Cool videos thanks. Do you have any handy links to why it takes 30 days to unfold everything? I assume there are good reasons, but I just can't imagine what they are.
- spaetzleesser 5y ago
  I think there is a lot of testing done after each step. It also may have to do with the cooling.
  - cogman10 5y ago
    AFAIK, the equipment is super sensitive as well. They likely don't want to proceed to the next stage until they are absolutely sure the previous stage happened successfully, otherwise they'll risk damaging things which will hose the whole mission.
- smarx007 5y ago
  I think most critical phases you’d want to happen when the satellite is in direct contact with the ground stations (they probably make extensive use of relay satellites to maximize windows of telemetry/payload data transmission, but here we are talking about issuing critical command sequences). Those windows are not 8 hours long. Further, it apparently takes almost 30 days to travel to the L2 Lagrange point and not all systems deploy until then. Edit: nope, I was wrong, it’s going to deploy a whole range of systems while on the way to the L2. https://youtu.be/RzGLKQ7_KZQ https://youtu.be/RzGLKQ7_KZQ
- gadnuk 5y ago
  Here's another video expanding a bit more on that deployment sequence: https://www.youtube.com/watch?v=WY9KckPI68Y https://www.youtube.com/watch?v=WY9KckPI68Y The observatory has around 7000 moving parts with complex structures for the primary and secondary mirrors and more importantly, the sunshield that would be used to keep the observatory instruments at a specific low temperature. It will take roughly 30 days for Webb to reach the start of its orbit at L2. At the end of 30 days, the telescope should have stabilized itself in an orbit around L2. But I would assume it takes that many days for deployment and unfolding everything because of the sheer number of parts and motions involved coupled with things like getting to L2, stabilizing orbit, temperature stability and all the checks for the instruments on board along with the mirror deployment (since it's not one big sheet of mirror). Here's a link which gives an idea about the logistics involved (along with a cool video series of the journey embedded): https://hackaday.com/2021/11/02/30-days-of-terror-the-logistics-of-launching-the-james-webb-space-telescope/ https://hackaday.com/2021/11/02/30-days-of-terror-the-logist... To fathom how complex the sunshield deployment is (and that's just a part of the whole sequence), from the link above: "Full deployment of the sunshield is without a doubt the sketchiest part of the whole process. The sunshield consists of five separate metalized Kapton sheets, each the size of three tennis courts. Each one must be unrolled, extended to its full size, tightened, and spaced out vertically for the sunshield to do its job. This takes the coordinated action of 140 release mechanisms, 70 hinges, eight deployment motors, about 400 pullies, and nearly 400 meters of cable to accomplish, not to mention the sensors, wiring harnesses, and computers to control everything. It’ll take the better part of two days to complete the sunshield deployment." The whole thing is just insane. From this talk by Dr. John Mather: https://www.youtube.com/watch?v=2RLGx_wgyAw https://www.youtube.com/watch?v=2RLGx_wgyAw Around 1:47 you can see the number of people involved. 3 space agencies (ESA, NASA, CSA), over 3000 engineers and technicians and 100 scientists worldwide.
callumprentice 5y ago
Thank you so much for both of those links. Absolutely fascinating - especially the Smarter Every Day channel which I wasn’t aware of. Excited to watch more of it.
ashika 5y ago
it's wild to me, given all the delays and complexity and risk, that the mission length is only 5-10 years max. but even if it blows up on the launchpad we've learned a ton, if only about the difficulty of manufacturing such devices in the 21st century. i am praying it does work, though, and that we get 10 years of amazing data from it before eagerly deploying a replacement.
- cogman10 5y ago
  Is 10 years a hard max (like does it crash into the moon or something?) or is it just a projected max timeframe? I wonder that mostly because we've managed to use a lot of our other space equipment well past their their mission lengths. I'd be interested if JWST is possibly the same.
  - ditn 5y ago
    It's a hard limit due needing fuel to maintain its orbit. It's in a lagrange point (https://en.wikipedia.org/wiki/Lagrange_point https://en.wikipedia.org/wiki/Lagrange_point) which requires occasional orbital corrections.
    - CuriousCosmic 5y ago
      Well it's not strictly a hard limit but it's currently planned to be a hard limit. If SpaceX can pull off even a fraction of what they claim with Starship, it's not unrealistic to think that it'd be financially viable to attempt a refuelling of the JWST.
      - ditn 5y ago
        That's an event I'd like to see!
    - ortusdux 5y ago
      IIRC, it was also not designed to be serviceable.
kortex 5y ago
How does one even begin to engineer tests for such a sequence of events? Yeah you can test each step individually, but then you have all the integration effects. How do you know you have enough coverage? $10B buys a lot of QA and I'm sure they try to engineer everything with the right margins, but it's still an unfathomable amount of state space. Are there techniques to stay sane and manage risk without just throwing money at it? I feel like that kind of knowledge could be useful for software test development.
- wolverine876 5y ago
  Simple: NASA Systems Engineering Handbook https://ntrs.nasa.gov/citations/20170001761 https://ntrs.nasa.gov/citations/20170001761 That's the 2017 version; maybe there's a later one. IIRC, it's an abridged from NASA Expanded Guidance for SE, but my link to that is broken.
  - qwertyuiop_ 5y ago
    Wait no Agile ?
    - wolverine876 5y ago
      Did you read it all? ;)
- double0jimb0 5y ago
  Systems Engineering is the discipline that oversees this. They define what tests will be required to validate the thing will do what it is supposed to before any hardware is built. I don’t think there is a good analogy to typical software QA, which is usually a “make sure it doesn’t break anything that already works” type of discipline.
- jdiez17 5y ago
  There's no real silver bullet other than applying the systems engineering process diligently. You start by writing down your user requirements (what the system needs to deliver), and you follow the thread of figuring out that "to do X, this subsystem has to provide conditions A, B, C..." recursively, in a breadth-first search. The level of detail codified in these functional, performance and interface requirements depends on the level of assurance you need. Then, you need to validate that each requirement is met by your system. This can be done by test, analysis (mathematically proving some property), review of design, or inspection. It's true that you can't fully validate most space systems on Earth, because we can't simulate all environmental conditions simultaneously. That's why you ideally you want each requirement to be validated by two methods. When you find anomalies due to integration effects, it's usually because your interface requirements are not specified well enough ;)
chasd00 5y ago
the "fabric" tensioning looks really sketchy to me. i can barely get a fitted sheet tensioned correctly on my bed..
- topspin 5y ago
  JWST has something like 300 SPOFs in the deployment phase. Then there are operation issues; the MIRI cryocooler has had a long, troubled development history. Three weeks ago NASA put out a Hollywood production quality disclaimer video[1]. [1] https://www.youtube.com/watch?v=uUAvXYW5bmI https://www.youtube.com/watch?v=uUAvXYW5bmI
belter 5y ago
Suddenly extremely worried about this: "James Webb Telescope will run a proprietary JS interpreter by a bankrupt company " https://news.ycombinator.com/item?id=19737663 https://news.ycombinator.com/item?id=19737663 https://www.researchgate.net/publication/252882358_Event-driven_James_Webb_Space_Telescope_operations_using_on-board_JavaScripts_-_art_no_62740A https://www.researchgate.net/publication/252882358_Event-dri... "The James Webb Space Telescope (JWST) will use an event-driven system architecture to provide efficient and flexible operations as initiated by a simplified, high-level ground command interface. Event-driven operations is provided through the use of an on-board COTS JavaScript engine hosted within the payload flight software..." Edit: Found something ....Is it too late to postpone the launch? https://www.stsci.edu/~idash/pub/dashevsky0607rcsgso.pdf https://www.stsci.edu/~idash/pub/dashevsky0607rcsgso.pdf "...The JWST science operations will be driven by ASCII (instead of binary command blocks) on-board scripts, written in a customized version of JavaScript. The script interpreter is run by the flight software, which is written in C++. The flight software operates the spacecraft and the science instruments. The on-board scripts will autonomously construct and issue commands, as well as telemetry requests, in real-time to the flight software, to direct the Observatory Subsystems (e.g., Science Instruments, Attitude Control, etc.)... The flight software will execute the command sent by the calling on-board script and return telemetry, which will be evaluated in real-time by that on-board script. The calling script will then send status information to a higher-level on-board script, which contains the logic to skip forward in the observing plan in response to certain events (see Section 4.1)... " Found it... "JWST uses an extended version of JavaScript, which was developed as a COTS product called Nombas ScriptEase 5.00e. ScriptEase provides functionality common to many modern software languages and follows the ECMAScript standard." http://brent-noorda.com/nombas/us/toolkit/index.htm http://brent-noorda.com/nombas/us/toolkit/index.htm http://brent-noorda.com/nombas/us/toolkit/isdkdownload.htm http://brent-noorda.com/nombas/us/toolkit/isdkdownload.htm Latest errata from 2004, moving from worried to full panic mode... http://brent-noorda.com/nombas/us/devspace/errata/isdk/index501.htm http://brent-noorda.com/nombas/us/devspace/errata/isdk/index...
- jazzyjackson 5y ago
  it’s not running Node 0.10.0 for gods sake, it’s an interpreter to write jobs that scientists can use for their studies - the flight critical stuff is a different stack
robbiewxyz 5y ago
From that video it appears the unfolding sequence is set to occur prior to the insertion burn into L2. If the JWST will in fact spend almost a month in earth's orbit, does someone have an educated estimate on the magnitude of risk posed by space junk to nominal deployment? Looking at those solar shields I imagine that they could be destroyed entirely by even the smallest of debris fragments. Same with the mirrors. Edit: I'm wrong here (thanks @thethirdone). The burn set to occur after deployment is the L2 insertion burn and not the transfer insertion burn. Most of deployment will occur in the transfer orbit en route to L2, far away from earth-orbiting debris.
- 0x0nyandesu 5y ago
  Basically none cause it's outside the typical orbit
- ProjectArcturis 5y ago
  It will orbit and deploy at the point where the Earth's and sun's gravity cancel out, which is far beyond most anything else, especially space junk.
- thethirdone 5y ago
  I interpreted "orbital insertion burn" to mean the stabilization into L2 burn. With that interpretation the unfolding occurs during its travel to L2 where there is little space debris.
inglor_cz 5y ago
We really need Starship in operation. It should be able to carry much larger objects into space - no need for complicated folding and unfolding mechanisms. Starship could possibly take normal sized heavy equipment to other planets, such as heavy earth movers. (Not those with a combustion engine, but still useful.)
- arlort 5y ago
  I think if they had starship they'd have just built it foldable anyway but with a bigger mirror
- grishka 5y ago
  Not even that — seeing how cheap Starship launches would be per kg of payload (I've seen a figure of $10), we could as well build a huge orbital station and just manufacture and/or assemble arbitrarily sized stuff in there or even in space. No atmosphere, and especially pesky oxygen, to deal with, no contaminants to keep out, no gravity to fight against. I'd imagine that any scientific and fabrication processes that need a deep vacuum would also greatly benefit from being done on a space station.
  - inglor_cz 5y ago
    Zero gravity engineering is going to be an interesting challenge, and a source of many funny videos. (Possibly some less than funny, too.) I would definitely love to see something like the Space Station V from Kubrick's 2001 - A Space Odyssey IRL. AFAIK it was almost a quarter of a mile in diameter. This seems to be suited for in-orbit fabrication and assembly.
- jcims 5y ago
  The one thing that I think starship has proven is that for any major mission that stretches our current launch capanilities, it may be worth investigating developing a new launch vehicle instead of accommodating the ones we have. Just think of all the engineering and risk that’s going into a process that will be used once.
  - 5y ago

by gadnuk 5y ago

peter303 5y ago

They should deploy in Earth orbit near the ISS, then move to L2. Would give option for repair. The shuttle was decommissioned after the primary Webb design was done. What would have known the launch options at the time it was ready?

steve_taylor 5y ago
It’s probably too risky given all the debris in orbit.
- hoseja 5y ago
  Do you have any idea how little "debris" there actually is?
  - samsari 5y ago
    Do you have any idea how little risk "too risky" actually is?
idontwantthis 5y ago
You can't just put things in space wherever you want them and then move them whenever you want to or to wherever you want to.

sophacles 5y ago

Cool videos thanks. Do you have any handy links to why it takes 30 days to unfold everything? I assume there are good reasons, but I just can't imagine what they are.

spaetzleesser 5y ago
I think there is a lot of testing done after each step. It also may have to do with the cooling.
- cogman10 5y ago
  AFAIK, the equipment is super sensitive as well. They likely don't want to proceed to the next stage until they are absolutely sure the previous stage happened successfully, otherwise they'll risk damaging things which will hose the whole mission.
smarx007 5y ago
I think most critical phases you’d want to happen when the satellite is in direct contact with the ground stations (they probably make extensive use of relay satellites to maximize windows of telemetry/payload data transmission, but here we are talking about issuing critical command sequences). Those windows are not 8 hours long. Further, it apparently takes almost 30 days to travel to the L2 Lagrange point and not all systems deploy until then. Edit: nope, I was wrong, it’s going to deploy a whole range of systems while on the way to the L2. https://youtu.be/RzGLKQ7_KZQ https://youtu.be/RzGLKQ7_KZQ
gadnuk 5y ago
Here's another video expanding a bit more on that deployment sequence: https://www.youtube.com/watch?v=WY9KckPI68Y https://www.youtube.com/watch?v=WY9KckPI68Y The observatory has around 7000 moving parts with complex structures for the primary and secondary mirrors and more importantly, the sunshield that would be used to keep the observatory instruments at a specific low temperature. It will take roughly 30 days for Webb to reach the start of its orbit at L2. At the end of 30 days, the telescope should have stabilized itself in an orbit around L2. But I would assume it takes that many days for deployment and unfolding everything because of the sheer number of parts and motions involved coupled with things like getting to L2, stabilizing orbit, temperature stability and all the checks for the instruments on board along with the mirror deployment (since it's not one big sheet of mirror). Here's a link which gives an idea about the logistics involved (along with a cool video series of the journey embedded): https://hackaday.com/2021/11/02/30-days-of-terror-the-logistics-of-launching-the-james-webb-space-telescope/ https://hackaday.com/2021/11/02/30-days-of-terror-the-logist... To fathom how complex the sunshield deployment is (and that's just a part of the whole sequence), from the link above: "Full deployment of the sunshield is without a doubt the sketchiest part of the whole process. The sunshield consists of five separate metalized Kapton sheets, each the size of three tennis courts. Each one must be unrolled, extended to its full size, tightened, and spaced out vertically for the sunshield to do its job. This takes the coordinated action of 140 release mechanisms, 70 hinges, eight deployment motors, about 400 pullies, and nearly 400 meters of cable to accomplish, not to mention the sensors, wiring harnesses, and computers to control everything. It’ll take the better part of two days to complete the sunshield deployment." The whole thing is just insane. From this talk by Dr. John Mather: https://www.youtube.com/watch?v=2RLGx_wgyAw https://www.youtube.com/watch?v=2RLGx_wgyAw Around 1:47 you can see the number of people involved. 3 space agencies (ESA, NASA, CSA), over 3000 engineers and technicians and 100 scientists worldwide.

callumprentice 5y ago

Thank you so much for both of those links. Absolutely fascinating - especially the Smarter Every Day channel which I wasn’t aware of. Excited to watch more of it.

ashika 5y ago

it's wild to me, given all the delays and complexity and risk, that the mission length is only 5-10 years max. but even if it blows up on the launchpad we've learned a ton, if only about the difficulty of manufacturing such devices in the 21st century. i am praying it does work, though, and that we get 10 years of amazing data from it before eagerly deploying a replacement.

cogman10 5y ago
Is 10 years a hard max (like does it crash into the moon or something?) or is it just a projected max timeframe? I wonder that mostly because we've managed to use a lot of our other space equipment well past their their mission lengths. I'd be interested if JWST is possibly the same.
- ditn 5y ago
  It's a hard limit due needing fuel to maintain its orbit. It's in a lagrange point (https://en.wikipedia.org/wiki/Lagrange_point https://en.wikipedia.org/wiki/Lagrange_point) which requires occasional orbital corrections.
  - CuriousCosmic 5y ago
    Well it's not strictly a hard limit but it's currently planned to be a hard limit. If SpaceX can pull off even a fraction of what they claim with Starship, it's not unrealistic to think that it'd be financially viable to attempt a refuelling of the JWST.
    - ditn 5y ago
      That's an event I'd like to see!
  - ortusdux 5y ago
    IIRC, it was also not designed to be serviceable.

kortex 5y ago

How does one even begin to engineer tests for such a sequence of events? Yeah you can test each step individually, but then you have all the integration effects. How do you know you have enough coverage? $10B buys a lot of QA and I'm sure they try to engineer everything with the right margins, but it's still an unfathomable amount of state space. Are there techniques to stay sane and manage risk without just throwing money at it? I feel like that kind of knowledge could be useful for software test development.

wolverine876 5y ago
Simple: NASA Systems Engineering Handbook https://ntrs.nasa.gov/citations/20170001761 https://ntrs.nasa.gov/citations/20170001761 That's the 2017 version; maybe there's a later one. IIRC, it's an abridged from NASA Expanded Guidance for SE, but my link to that is broken.
- qwertyuiop_ 5y ago
  Wait no Agile ?
  - wolverine876 5y ago
    Did you read it all? ;)
double0jimb0 5y ago
Systems Engineering is the discipline that oversees this. They define what tests will be required to validate the thing will do what it is supposed to before any hardware is built. I don’t think there is a good analogy to typical software QA, which is usually a “make sure it doesn’t break anything that already works” type of discipline.
jdiez17 5y ago
There's no real silver bullet other than applying the systems engineering process diligently. You start by writing down your user requirements (what the system needs to deliver), and you follow the thread of figuring out that "to do X, this subsystem has to provide conditions A, B, C..." recursively, in a breadth-first search. The level of detail codified in these functional, performance and interface requirements depends on the level of assurance you need. Then, you need to validate that each requirement is met by your system. This can be done by test, analysis (mathematically proving some property), review of design, or inspection. It's true that you can't fully validate most space systems on Earth, because we can't simulate all environmental conditions simultaneously. That's why you ideally you want each requirement to be validated by two methods. When you find anomalies due to integration effects, it's usually because your interface requirements are not specified well enough ;)

chasd00 5y ago

the "fabric" tensioning looks really sketchy to me. i can barely get a fitted sheet tensioned correctly on my bed..

topspin 5y ago
JWST has something like 300 SPOFs in the deployment phase. Then there are operation issues; the MIRI cryocooler has had a long, troubled development history. Three weeks ago NASA put out a Hollywood production quality disclaimer video[1]. [1] https://www.youtube.com/watch?v=uUAvXYW5bmI https://www.youtube.com/watch?v=uUAvXYW5bmI

belter 5y ago

Suddenly extremely worried about this: "James Webb Telescope will run a proprietary JS interpreter by a bankrupt company " https://news.ycombinator.com/item?id=19737663 https://news.ycombinator.com/item?id=19737663 https://www.researchgate.net/publication/252882358_Event-driven_James_Webb_Space_Telescope_operations_using_on-board_JavaScripts_-_art_no_62740A https://www.researchgate.net/publication/252882358_Event-dri... "The James Webb Space Telescope (JWST) will use an event-driven system architecture to provide efficient and flexible operations as initiated by a simplified, high-level ground command interface. Event-driven operations is provided through the use of an on-board COTS JavaScript engine hosted within the payload flight software..." Edit: Found something ....Is it too late to postpone the launch? https://www.stsci.edu/~idash/pub/dashevsky0607rcsgso.pdf https://www.stsci.edu/~idash/pub/dashevsky0607rcsgso.pdf "...The JWST science operations will be driven by ASCII (instead of binary command blocks) on-board scripts, written in a customized version of JavaScript. The script interpreter is run by the flight software, which is written in C++. The flight software operates the spacecraft and the science instruments. The on-board scripts will autonomously construct and issue commands, as well as telemetry requests, in real-time to the flight software, to direct the Observatory Subsystems (e.g., Science Instruments, Attitude Control, etc.)... The flight software will execute the command sent by the calling on-board script and return telemetry, which will be evaluated in real-time by that on-board script. The calling script will then send status information to a higher-level on-board script, which contains the logic to skip forward in the observing plan in response to certain events (see Section 4.1)... " Found it... "JWST uses an extended version of JavaScript, which was developed as a COTS product called Nombas ScriptEase 5.00e. ScriptEase provides functionality common to many modern software languages and follows the ECMAScript standard." http://brent-noorda.com/nombas/us/toolkit/index.htm http://brent-noorda.com/nombas/us/toolkit/index.htm http://brent-noorda.com/nombas/us/toolkit/isdkdownload.htm http://brent-noorda.com/nombas/us/toolkit/isdkdownload.htm Latest errata from 2004, moving from worried to full panic mode... http://brent-noorda.com/nombas/us/devspace/errata/isdk/index501.htm http://brent-noorda.com/nombas/us/devspace/errata/isdk/index...

jazzyjackson 5y ago
it’s not running Node 0.10.0 for gods sake, it’s an interpreter to write jobs that scientists can use for their studies - the flight critical stuff is a different stack

robbiewxyz 5y ago

From that video it appears the unfolding sequence is set to occur prior to the insertion burn into L2. If the JWST will in fact spend almost a month in earth's orbit, does someone have an educated estimate on the magnitude of risk posed by space junk to nominal deployment? Looking at those solar shields I imagine that they could be destroyed entirely by even the smallest of debris fragments. Same with the mirrors. Edit: I'm wrong here (thanks @thethirdone). The burn set to occur after deployment is the L2 insertion burn and not the transfer insertion burn. Most of deployment will occur in the transfer orbit en route to L2, far away from earth-orbiting debris.

0x0nyandesu 5y ago
Basically none cause it's outside the typical orbit
ProjectArcturis 5y ago
It will orbit and deploy at the point where the Earth's and sun's gravity cancel out, which is far beyond most anything else, especially space junk.
thethirdone 5y ago
I interpreted "orbital insertion burn" to mean the stabilization into L2 burn. With that interpretation the unfolding occurs during its travel to L2 where there is little space debris.

inglor_cz 5y ago

We really need Starship in operation. It should be able to carry much larger objects into space - no need for complicated folding and unfolding mechanisms. Starship could possibly take normal sized heavy equipment to other planets, such as heavy earth movers. (Not those with a combustion engine, but still useful.)

arlort 5y ago
I think if they had starship they'd have just built it foldable anyway but with a bigger mirror
grishka 5y ago
Not even that — seeing how cheap Starship launches would be per kg of payload (I've seen a figure of $10), we could as well build a huge orbital station and just manufacture and/or assemble arbitrarily sized stuff in there or even in space. No atmosphere, and especially pesky oxygen, to deal with, no contaminants to keep out, no gravity to fight against. I'd imagine that any scientific and fabrication processes that need a deep vacuum would also greatly benefit from being done on a space station.
- inglor_cz 5y ago
  Zero gravity engineering is going to be an interesting challenge, and a source of many funny videos. (Possibly some less than funny, too.) I would definitely love to see something like the Space Station V from Kubrick's 2001 - A Space Odyssey IRL. AFAIK it was almost a quarter of a mile in diameter. This seems to be suited for in-orbit fabrication and assembly.
jcims 5y ago
The one thing that I think starship has proven is that for any major mission that stretches our current launch capanilities, it may be worth investigating developing a new launch vehicle instead of accommodating the ones we have. Just think of all the engineering and risk that’s going into a process that will be used once.
- 5y ago