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After watching an official JWST video https://www.youtube.com/watch?v=uUAvXYW5bmI https://www.youtube.com/watch?v=uUAvXYW5bmI, they seem almost proud of having

After watching an official JWST video https://www.youtube.com/watch?v=uUAvXYW5bmI https://www.youtube.com/watch?v=uUAvXYW5bmI, they seem almost proud of having several hundred of single points of failure and an immensely complex deployment process that takes several weeks and must work perfectly. I don't know what engineer could be proud of coming up with a design like that.

NikolaeVarius 5y ago
Its a machine that is extremely mass limited, has many different groups of people influencing different systems, and is extremely complex. If the HARD requirement is "you have this much mass and volume to make a thing to a particular confidence score" you make the damn thing and hope you are on the correct side of the dice. No single engineer gives a shit about the entire system because no single person is equipped with the human ability of comprehending each individual part that has whatever confidence rating that is required.
- spaetzleesser 5y ago
  Makes me wonder if the future is in launching things in parts and assembling things in space. This probably has its own set of problems though.
  - sgtnoodle 5y ago
    That would be pretty cool if it could be done inside a pressurized workspace. Humans could do the work of massive cranes.
Out_of_Characte 5y ago
Single points of failure are inevitable. engineers could always make a copy of the entire design but that would double the costs and you would still be left with unknown points of failure that the telescope double would have. The solar shield is like rolling out five layers of tightly packed tinfoil from several points without tearing. Claiming that you would do away with single points of failure if you were the one designing it is too easy to say on HN
- shantara 5y ago
  I'm not arguing you could completely go away with single points of failure when designing a spacecraft while being limited by the payload mass and volume. But the whole JWST unfolding sequence looks like a way too risky gamble to me. Maybe, it was worthwhile to sacrifice some of the scientific payload mass to add more redundancies into the solar shield design and increase the chances the telescope would be able to reach the beginning of its observation process. There's also the whole "what if we could avoid mass and volume constraints" tangent, that was discussed in the yesterday's Starship article, but it's more of a theoretical consideration for now.
  - jdmichal 5y ago
    Honestly, I thought the same about the whole Perseverance landing sequence on Mars. But now it's done, and the rover is running around doing its thing. So, what I learned is that single points of failure on initial deployment -- which by definition only has to run once -- is a drastically different cost vs risk calculation than something that happens during normal operations.
  - idlewords 5y ago
    The unfolding sequence looked complicated to me, too, and then I remembered I am just a guy online. You are right that a magical rocket could solve many of NASAs problems (just launch ten Webbs and use the ones that don't work as sunshades for the rest!) but I think NASA is being pretty practical in not waiting for one to be invented.
- dylan604 5y ago
  >entire design but that would double the costs What was the original budget for JWST? Where's it at now? From your assessment and the numbers, it sounds like there's not just double but triple redundancy now.
  - ZeikJT 5y ago
    In 1996 when it was a proposed idea the estimated cost was 500 million USD and the proposed launch was 2007. But the design kept getting more and more lofty and the project got more and more complex. The initial estimate was a bit off, it has cost about 9.6 billion USD so far. Still though, if everything works and we learn more about the universe, I think it'll have been worth it.
alanbernstein 5y ago
If I skipped reading the first clause in your comment, I would definitely think you were talking about modern software systems. Plenty of pride there. (Ok, "weeks" isn't quite applicable in that case... Unless you're counting the time for updates to propagate through all upstream dependencies.)
idlewords 5y ago
The question is what engineer could be proud of finding a solution within such difficult constraints, and the answer is a really good bunch of engineers.
mdoms 5y ago
Very aggravating to hear them use units like "thousandths of an inch thick" and "feet of cables". Does NASA really still work with imperial units of measure?
shlurpy 5y ago
The mass constraint in space engineering is a real killer, unfortunately. I doubt they want so many single points of failure, but I also understand it can be effectively impossible to add redundancy within mass window.
spaetzleesser 5y ago
These people aren’t dumb. I am pretty sure they went through a lot of options before settling on a design. Keep in mind that a lot of space devices are outdated by the time they are being deployed.

NikolaeVarius 5y ago

Its a machine that is extremely mass limited, has many different groups of people influencing different systems, and is extremely complex. If the HARD requirement is "you have this much mass and volume to make a thing to a particular confidence score" you make the damn thing and hope you are on the correct side of the dice. No single engineer gives a shit about the entire system because no single person is equipped with the human ability of comprehending each individual part that has whatever confidence rating that is required.

spaetzleesser 5y ago
Makes me wonder if the future is in launching things in parts and assembling things in space. This probably has its own set of problems though.
- sgtnoodle 5y ago
  That would be pretty cool if it could be done inside a pressurized workspace. Humans could do the work of massive cranes.

Out_of_Characte 5y ago

Single points of failure are inevitable. engineers could always make a copy of the entire design but that would double the costs and you would still be left with unknown points of failure that the telescope double would have. The solar shield is like rolling out five layers of tightly packed tinfoil from several points without tearing. Claiming that you would do away with single points of failure if you were the one designing it is too easy to say on HN

shantara 5y ago
I'm not arguing you could completely go away with single points of failure when designing a spacecraft while being limited by the payload mass and volume. But the whole JWST unfolding sequence looks like a way too risky gamble to me. Maybe, it was worthwhile to sacrifice some of the scientific payload mass to add more redundancies into the solar shield design and increase the chances the telescope would be able to reach the beginning of its observation process. There's also the whole "what if we could avoid mass and volume constraints" tangent, that was discussed in the yesterday's Starship article, but it's more of a theoretical consideration for now.
- jdmichal 5y ago
  Honestly, I thought the same about the whole Perseverance landing sequence on Mars. But now it's done, and the rover is running around doing its thing. So, what I learned is that single points of failure on initial deployment -- which by definition only has to run once -- is a drastically different cost vs risk calculation than something that happens during normal operations.
- idlewords 5y ago
  The unfolding sequence looked complicated to me, too, and then I remembered I am just a guy online. You are right that a magical rocket could solve many of NASAs problems (just launch ten Webbs and use the ones that don't work as sunshades for the rest!) but I think NASA is being pretty practical in not waiting for one to be invented.
dylan604 5y ago
>entire design but that would double the costs What was the original budget for JWST? Where's it at now? From your assessment and the numbers, it sounds like there's not just double but triple redundancy now.
- ZeikJT 5y ago
  In 1996 when it was a proposed idea the estimated cost was 500 million USD and the proposed launch was 2007. But the design kept getting more and more lofty and the project got more and more complex. The initial estimate was a bit off, it has cost about 9.6 billion USD so far. Still though, if everything works and we learn more about the universe, I think it'll have been worth it.

alanbernstein 5y ago

If I skipped reading the first clause in your comment, I would definitely think you were talking about modern software systems. Plenty of pride there. (Ok, "weeks" isn't quite applicable in that case... Unless you're counting the time for updates to propagate through all upstream dependencies.)

idlewords 5y ago

The question is what engineer could be proud of finding a solution within such difficult constraints, and the answer is a really good bunch of engineers.

mdoms 5y ago

Very aggravating to hear them use units like "thousandths of an inch thick" and "feet of cables". Does NASA really still work with imperial units of measure?

shlurpy 5y ago

The mass constraint in space engineering is a real killer, unfortunately. I doubt they want so many single points of failure, but I also understand it can be effectively impossible to add redundancy within mass window.

spaetzleesser 5y ago

These people aren’t dumb. I am pretty sure they went through a lot of options before settling on a design. Keep in mind that a lot of space devices are outdated by the time they are being deployed.