4 ms·

The JWT launch and deployment is going to be terrifying. Peeking between my fingers for that one.

by robin_reala 6y ago

deleted 6y ago
[deleted]
hashmymustache 6y ago
Picking Halloween is an interesting launch date. That said it’s hard to believe any timeline or budget at this point.
nickserv 6y ago
Yes! Deployment in particular, as it's never been done before. Launch is on an Ariane 5, and those have become very reliable.
bumby 6y ago
This part makes my nether-regions pucker: 307 single point failure components. I do not envy the reliability or systems engineers on that project. http://spaceref.com/news/viewsr.html?pid=51617 http://spaceref.com/news/viewsr.html?pid=51617
- koheripbal 6y ago
  This data point is not useful without knowing the failure rate for each of them. For example, the Sun is a single point of failure for us each day. ...but the odds of the Sun being destroyed per day are so infinitesimally small, that it's not meaningful to say I have a single point of failure each day for the next 20,000 days.
  - vlovich123 6y ago
    That’s a logical albeit unhelpful argument. My observation of how engineering is done and the economic pressures involved make me think that such cost cutting is inevitable. So the short term “we’ll just make this single point of failure component more reliable” is not an effective strategy as “design in depth” that assumes any single component will fail. It can be more expensive but in some ways (maintenance, up-front cost) but can also be cheaper since the individual components don’t need as much testing/validation/reliability. That being said, engineering is all about trade offs so the takeaway I have from something like this is blind faith/hope that the domain experts make these decisions better than an outsider (me) and that when mistakes are made they’re corrected in the longer-term. I don’t know a better way than that.
  - bumby 6y ago
    This is fair. Single point of failures denote a severity (loss of mission) but risk is defined as severity x probability. To extend your example to the extreme, everything on the JWST has a failure probability > 0, even the systems with redundancies. What ends up happening is each failure is plotted on a severity x probability matrix with a resulting score. Depending on the requirements, the exact probability category thresholds may be defined quantitatively (e.g. 1/10,000 chance) or they may be more qualitative (e.g., ‘likely’ vs. ‘may happen’ vs. ‘improbable’). The resulting risk has to accepted by someone (usually a program or project manager). To your point, they have obviously found each to be an acceptable (but perhaps uncomfortable) risk. Some projects will define the acceptable level of risk at the requirements stage to drive design (e.g., no single points of failure that can result in loss of crew). With all that said, it is still an abnormally high number of single point failures in a complex system and reliability is generally not linearly related to complexity (just think about what happens to cyclomatic complexity as you add more variables and the resulting number of test cases you need for full coverage) In my opinion, the real dangerous part of this process is that humans are notoriously poor at thinking in probabilistic terms. Challenger, Columbia, EVA 23 etc. are all attributable, in part, to bad assessments of probability. Human biases are all but guaranteed to affect these probabilities and thus affect our understanding of the associated risk.
- tedd4u 6y ago
  I happen to know someone working in the area of reliability and testing on JWT. Personally, I couldn't take the stress. The design as you point out seems to be unlike other missions where the very design limits failures. My understanding is the people who made these decisions are long gone, leaving the current team to make it work or $20B and two decades will be flushed down the drain. I think people on this team are aging at 5x real-time.
  - deleted 6y ago
    [deleted]
nickff 6y ago
I am quite skeptical that it will take place this year. The project is already 14 years late and ~20x over the original budget. I expect them to announce a shocking delay later this year, blaming COVID. https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Cost_and_schedule_issues https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Cos... https://xkcd.com/2014/ https://xkcd.com/2014/
- koheripbal 6y ago
  14 years "late" is not exactly accurate as the initial time projections were based upon full funding from the initial moments of the project - which was never a realistic goal. Similarly, the 20x budget overrun number makes two errors - 1. that the initial numbers were in today's inflation adjusted dollars (which they were not), and that project scope remained exactly the same - which it has not. Numerous aspects of the telescope have been enhanced/improved to accommodate additional science.
  - nickff 6y ago
    The project was supposed to take 10 years and is already at 24! That's simply atrocious, and saying that they didn't get everything they wanted to is a poor excuse. I ran the numbers for inflation adjustment, and 500MM in 1997 is equivalent to ~811MM today. That means the project is between 12x-20x over budget... not much of an improvement in my mind.
black6 6y ago
At least the Ariane 5 is a proven launch vehicle. Artemis 1 is going to be the real knuckle-biter, if NASA defies all odds and meets schedule.
_ph_ 6y ago
I am looking so much forward to this. Hubble has been launched in 1990 and look what insane amount of great science and pictures it brought. JWT should be a huge step upwards from this, especially as it looks into different wavelengths. This could deliver an amazing amount of science. I also hope, that if the Starship becomes operational, it could deliver much larger telescopes to space and start a new era of astronomy.

The JWT launch and deployment is going to be terrifying. Peeking between my fingers for that one.

deleted 6y ago

[deleted]

hashmymustache 6y ago

Picking Halloween is an interesting launch date. That said it’s hard to believe any timeline or budget at this point.

nickserv 6y ago

Yes! Deployment in particular, as it's never been done before. Launch is on an Ariane 5, and those have become very reliable.

bumby 6y ago

This part makes my nether-regions pucker: 307 single point failure components. I do not envy the reliability or systems engineers on that project. http://spaceref.com/news/viewsr.html?pid=51617 http://spaceref.com/news/viewsr.html?pid=51617

koheripbal 6y ago
This data point is not useful without knowing the failure rate for each of them. For example, the Sun is a single point of failure for us each day. ...but the odds of the Sun being destroyed per day are so infinitesimally small, that it's not meaningful to say I have a single point of failure each day for the next 20,000 days.
- vlovich123 6y ago
  That’s a logical albeit unhelpful argument. My observation of how engineering is done and the economic pressures involved make me think that such cost cutting is inevitable. So the short term “we’ll just make this single point of failure component more reliable” is not an effective strategy as “design in depth” that assumes any single component will fail. It can be more expensive but in some ways (maintenance, up-front cost) but can also be cheaper since the individual components don’t need as much testing/validation/reliability. That being said, engineering is all about trade offs so the takeaway I have from something like this is blind faith/hope that the domain experts make these decisions better than an outsider (me) and that when mistakes are made they’re corrected in the longer-term. I don’t know a better way than that.
- bumby 6y ago
  This is fair. Single point of failures denote a severity (loss of mission) but risk is defined as severity x probability. To extend your example to the extreme, everything on the JWST has a failure probability > 0, even the systems with redundancies. What ends up happening is each failure is plotted on a severity x probability matrix with a resulting score. Depending on the requirements, the exact probability category thresholds may be defined quantitatively (e.g. 1/10,000 chance) or they may be more qualitative (e.g., ‘likely’ vs. ‘may happen’ vs. ‘improbable’). The resulting risk has to accepted by someone (usually a program or project manager). To your point, they have obviously found each to be an acceptable (but perhaps uncomfortable) risk. Some projects will define the acceptable level of risk at the requirements stage to drive design (e.g., no single points of failure that can result in loss of crew). With all that said, it is still an abnormally high number of single point failures in a complex system and reliability is generally not linearly related to complexity (just think about what happens to cyclomatic complexity as you add more variables and the resulting number of test cases you need for full coverage) In my opinion, the real dangerous part of this process is that humans are notoriously poor at thinking in probabilistic terms. Challenger, Columbia, EVA 23 etc. are all attributable, in part, to bad assessments of probability. Human biases are all but guaranteed to affect these probabilities and thus affect our understanding of the associated risk.
tedd4u 6y ago
I happen to know someone working in the area of reliability and testing on JWT. Personally, I couldn't take the stress. The design as you point out seems to be unlike other missions where the very design limits failures. My understanding is the people who made these decisions are long gone, leaving the current team to make it work or $20B and two decades will be flushed down the drain. I think people on this team are aging at 5x real-time.
- deleted 6y ago
  [deleted]

nickff 6y ago

I am quite skeptical that it will take place this year. The project is already 14 years late and ~20x over the original budget. I expect them to announce a shocking delay later this year, blaming COVID. https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Cost_and_schedule_issues https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Cos... https://xkcd.com/2014/ https://xkcd.com/2014/

koheripbal 6y ago
14 years "late" is not exactly accurate as the initial time projections were based upon full funding from the initial moments of the project - which was never a realistic goal. Similarly, the 20x budget overrun number makes two errors - 1. that the initial numbers were in today's inflation adjusted dollars (which they were not), and that project scope remained exactly the same - which it has not. Numerous aspects of the telescope have been enhanced/improved to accommodate additional science.
- nickff 6y ago
  The project was supposed to take 10 years and is already at 24! That's simply atrocious, and saying that they didn't get everything they wanted to is a poor excuse. I ran the numbers for inflation adjustment, and 500MM in 1997 is equivalent to ~811MM today. That means the project is between 12x-20x over budget... not much of an improvement in my mind.

black6 6y ago

At least the Ariane 5 is a proven launch vehicle. Artemis 1 is going to be the real knuckle-biter, if NASA defies all odds and meets schedule.

_ph_ 6y ago

I am looking so much forward to this. Hubble has been launched in 1990 and look what insane amount of great science and pictures it brought. JWT should be a huge step upwards from this, especially as it looks into different wavelengths. This could deliver an amazing amount of science. I also hope, that if the Starship becomes operational, it could deliver much larger telescopes to space and start a new era of astronomy.