8 ms·

The good news is that the trajectory of timeline slip is less than one week per week, and if that holds true, the two will eventually rendezvous. In 1996, it w

The good news is that the trajectory of timeline slip is less than one week per week, and if that holds true, the two will eventually rendezvous. In 1996, it was estimated for 2007, fast forwarding a bit to 2018, it slipped one year from an estimated launch in 2020 to 2021, in 2020 it slipped from March 2021 to July, by January 2021 it slipped to October 31st, and it's been known since June, 14 weeks ago, that it wasn't likely to meet that date. At this rate, I estimate the current date will intercept the target date in early 2022.

tshaddox 5y ago
> The good news is that the trajectory of timeline slip is less than one week per week, and if that holds true, the two will eventually rendezvous. Not if the timeline slips such that at each slip the delta between the current time and the launch time decreases by 50%.
- feoren 5y ago
  It still works in that case, actually; you just have to pass through a singularity where the timeline is delayed infinitely many times, but the total amount of each of those infinite delays is finite. 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + ... = 1. This is the answer to Zeno's paradox. A sports reporter gives an update every time Hercules catches up to where the tortoise was the last time he gave an update. All that happens is the sports reporter eventually needs to talk faster and faster and faster, and eventually try to give infinite updates right as Hercules passes the tortoise. Then the reporter's vocal chords explode, but otherwise the race proceeds as you would expect. (That is, just because a description of an event is infinitely long, does not mean the event itself is infinitely long in any sense.)
  - tshaddox 5y ago
    Lol yeah, that was a goof. I had Zeno’s paradox in mind and intended to choose a divergent series but accidentally used the textbook convergent one. Let’s swap it out for the harmonic series.
irrelative 5y ago
See also: https://xkcd.com/2014 https://xkcd.com/2014
nsxwolf 5y ago
I cannot foresee a timeline where it does not explode on the pad.
- mmazing 5y ago
  I hope you are incorrect. I will be extremely sad if this mission is not successful.
  - chroem- 5y ago
    Although tragic, it would be a fitting end to this boondoggle of a project. JWST was originally marketed as a quick, cheap win for NASA, but it turned into the polar opposite of that.
- khuey 5y ago
  Most of the time and money was spent on design. If it blows up they should be able to build a second one for a fraction of the time/cost of the first one.
  - janmo 5y ago
    In this case, they should have build a half dozen instead of one..
    - oh_sigh 5y ago
      "First rule in government spending: Why build one, when you can build two for twice the price?" -Contact
      - chasd00 5y ago
        I was expecting it to read something like “why build two when you can build one for the price of 5”
  - oh_sigh 5y ago
    Wasn't a major part of the problem that the design kept changing based on the pushed timeline? So what we are getting now is completely different from what was planned in 1996 to be launched in 2007? If that's the case, and the JWST fails to deploy, we probably wouldn't just build another copy of it - we would build a completely new/reworked space telescope that would take another 25 years to design/launch.
perihelions 5y ago
>"trajectory of timeline slip is less than one week per week, and if that holds true, the two will eventually rendezvous." Not mathematically certain. If the timeline slip is a sequence like [1-1/2^k]_{k=1...} = {1/2 week, 3/4 weeks, 7/8 weeks, 15/16 weeks...}, then it's possible the project timeline could diverge forever. (This is just a restatement of Zeno's paradox).
- TeMPOraL 5y ago
  The act of delaying launch takes non-zero amount of time in the real world, so at some point the slippage fraction gets so small that the launch will happen while being about to be rescheduled.
  - perihelions 5y ago
    You just keep observing the quantum superposition of launch/no-launch, using increasingly powerful lasers.
    - halfmatthalfcat 5y ago
      This whole line on conversation made my night, haven’t laughed this hard in a while.
- jhgb 5y ago
  > This is just a restatement of Zeno's paradox I thought Zeno's paradox was caused by lack of understanding of infinitesimal calculus by Ancient Greeks? That is, in situations where a series converges despite an having infinite number of elements. Divergent series like yours shouldn't constitute such a paradox, since they both have an infinite number of elements AND diverge.
- nine_k 5y ago
  There is an old joke. A crate of beer is standing in the end of a magical room; each step towards the crate is half as short as the preceding one. A mathematician and an engineer enter the room. The engineer starts walking towards the chest, while the mathematician stands still. M: Why are you doing this? You can't reach it in finite time anyway! E: But in a few hundred steps I'll be close enough for all practical purposes!
Covzire 5y ago
Why does the launch date keep slipping? I've been looking forward to this launch for a very long time and I'm getting pretty irked at the teams sending this up, to the point where even if they are completely successful I hope they don't get put on another big project like this again. Hopefully the delays have been because it's a lot harder to send this to L2 successfully than anyone thought or could have known, and now we do.
- sp332 5y ago
  Lately, Covid has been the holdup. https://wwwnc.cdc.gov/travel/notices/covid-4/coronavirus-french-guiana https://wwwnc.cdc.gov/travel/notices/covid-4/coronavirus-fre...
  - newnamenewface 5y ago
    This is complete hearsay but I was sat next to a engineer working on the project on a recent flight. He mentioned to me that 1.) it would be delayed past October till December, and probably early into next year, and 2.) COVID, like any good excuse, was being used because it was there and not necessarily because it caused the delays. Maybe the engineer was just telling a story with a bit of flair but I believed him.
    - thehappypm 5y ago
      Anything can be blamed on covid or global warming.
- colechristensen 5y ago
  Why? Time estimation is hard and you’re a pretty bad PM of a scientific missions primary goal is to launch by a date. You keep working until you are confident you can do it right. Failures happen when delivery dates are more important than quality.
slownews45 5y ago
Damn - these are full time employment deals for folks. 25 years on one project! Question - they have a ton of shielding for solar radiation - can they not locate this thing in a shadow area somewhere?
- zardo 5y ago
  Possibly, but they couldn't power it by attaching solar panels.
- causality0 5y ago
  Being in a shadow area would mean it would be in orbit of something, and at best it would be in shadow 50% of the time and still need the same amount of shielding for daylight operations. Being in orbit would also mean its position would be much less stable than it will be at the L2 point.
- perihelions 5y ago
  Related: https://news.ycombinator.com/item?id=10462349 https://news.ycombinator.com/item?id=10462349 ("NASA's last original Voyager engineer retires at 80")
- perihelions 5y ago
  There aren't any permanent shadows in space. Every orbit goes "around" eventually -- and there's no configuration where some combination of objects works to permanently shadow you. (A technical exception is a planetary solar L2 Lagrange point [0], *if* it would occur close enough to a planet to be totally eclipsed. But that doesn't happen (AFAIK) -- they're generally far enough away that although the planet is always in front of the sun, the planet's disk is much smaller than the solar disk. Like a partial eclipse). With cryogenic cooling, you have an even more difficult challenge: the light of a planet's infrared radiation emission is something you also have to shield. That's a major reason JWST (and similar cryogenic telescopes) go to solar L2: its sunshield doesn't only block out the sun -- it simultaneously blocks out the sun and the Earth. That's the unique advantage of the solar L2 point: the sun and Earth are always in the same direction. [0] https://en.wikipedia.org/wiki/Lagrange_point https://en.wikipedia.org/wiki/Lagrange_point
dzhiurgis 5y ago
Had my reddit reminder trigger back in July. I think I've set it up like 6 years ago. Amazed it actually worked.

tshaddox 5y ago

> The good news is that the trajectory of timeline slip is less than one week per week, and if that holds true, the two will eventually rendezvous. Not if the timeline slips such that at each slip the delta between the current time and the launch time decreases by 50%.

feoren 5y ago
It still works in that case, actually; you just have to pass through a singularity where the timeline is delayed infinitely many times, but the total amount of each of those infinite delays is finite. 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + ... = 1. This is the answer to Zeno's paradox. A sports reporter gives an update every time Hercules catches up to where the tortoise was the last time he gave an update. All that happens is the sports reporter eventually needs to talk faster and faster and faster, and eventually try to give infinite updates right as Hercules passes the tortoise. Then the reporter's vocal chords explode, but otherwise the race proceeds as you would expect. (That is, just because a description of an event is infinitely long, does not mean the event itself is infinitely long in any sense.)
- tshaddox 5y ago
  Lol yeah, that was a goof. I had Zeno’s paradox in mind and intended to choose a divergent series but accidentally used the textbook convergent one. Let’s swap it out for the harmonic series.

irrelative 5y ago

See also: https://xkcd.com/2014 https://xkcd.com/2014

nsxwolf 5y ago

I cannot foresee a timeline where it does not explode on the pad.

mmazing 5y ago
I hope you are incorrect. I will be extremely sad if this mission is not successful.
- chroem- 5y ago
  Although tragic, it would be a fitting end to this boondoggle of a project. JWST was originally marketed as a quick, cheap win for NASA, but it turned into the polar opposite of that.
khuey 5y ago
Most of the time and money was spent on design. If it blows up they should be able to build a second one for a fraction of the time/cost of the first one.
- janmo 5y ago
  In this case, they should have build a half dozen instead of one..
  - oh_sigh 5y ago
    "First rule in government spending: Why build one, when you can build two for twice the price?" -Contact
    - chasd00 5y ago
      I was expecting it to read something like “why build two when you can build one for the price of 5”
- oh_sigh 5y ago
  Wasn't a major part of the problem that the design kept changing based on the pushed timeline? So what we are getting now is completely different from what was planned in 1996 to be launched in 2007? If that's the case, and the JWST fails to deploy, we probably wouldn't just build another copy of it - we would build a completely new/reworked space telescope that would take another 25 years to design/launch.

perihelions 5y ago

>"trajectory of timeline slip is less than one week per week, and if that holds true, the two will eventually rendezvous." Not mathematically certain. If the timeline slip is a sequence like [1-1/2^k]_{k=1...} = {1/2 week, 3/4 weeks, 7/8 weeks, 15/16 weeks...}, then it's possible the project timeline could diverge forever. (This is just a restatement of Zeno's paradox).

TeMPOraL 5y ago
The act of delaying launch takes non-zero amount of time in the real world, so at some point the slippage fraction gets so small that the launch will happen while being about to be rescheduled.
- perihelions 5y ago
  You just keep observing the quantum superposition of launch/no-launch, using increasingly powerful lasers.
  - halfmatthalfcat 5y ago
    This whole line on conversation made my night, haven’t laughed this hard in a while.
jhgb 5y ago
> This is just a restatement of Zeno's paradox I thought Zeno's paradox was caused by lack of understanding of infinitesimal calculus by Ancient Greeks? That is, in situations where a series converges despite an having infinite number of elements. Divergent series like yours shouldn't constitute such a paradox, since they both have an infinite number of elements AND diverge.
nine_k 5y ago
There is an old joke. A crate of beer is standing in the end of a magical room; each step towards the crate is half as short as the preceding one. A mathematician and an engineer enter the room. The engineer starts walking towards the chest, while the mathematician stands still. M: Why are you doing this? You can't reach it in finite time anyway! E: But in a few hundred steps I'll be close enough for all practical purposes!

Covzire 5y ago

Why does the launch date keep slipping? I've been looking forward to this launch for a very long time and I'm getting pretty irked at the teams sending this up, to the point where even if they are completely successful I hope they don't get put on another big project like this again. Hopefully the delays have been because it's a lot harder to send this to L2 successfully than anyone thought or could have known, and now we do.

sp332 5y ago
Lately, Covid has been the holdup. https://wwwnc.cdc.gov/travel/notices/covid-4/coronavirus-french-guiana https://wwwnc.cdc.gov/travel/notices/covid-4/coronavirus-fre...
- newnamenewface 5y ago
  This is complete hearsay but I was sat next to a engineer working on the project on a recent flight. He mentioned to me that 1.) it would be delayed past October till December, and probably early into next year, and 2.) COVID, like any good excuse, was being used because it was there and not necessarily because it caused the delays. Maybe the engineer was just telling a story with a bit of flair but I believed him.
  - thehappypm 5y ago
    Anything can be blamed on covid or global warming.
colechristensen 5y ago
Why? Time estimation is hard and you’re a pretty bad PM of a scientific missions primary goal is to launch by a date. You keep working until you are confident you can do it right. Failures happen when delivery dates are more important than quality.

slownews45 5y ago

Damn - these are full time employment deals for folks. 25 years on one project! Question - they have a ton of shielding for solar radiation - can they not locate this thing in a shadow area somewhere?

zardo 5y ago
Possibly, but they couldn't power it by attaching solar panels.
causality0 5y ago
Being in a shadow area would mean it would be in orbit of something, and at best it would be in shadow 50% of the time and still need the same amount of shielding for daylight operations. Being in orbit would also mean its position would be much less stable than it will be at the L2 point.
perihelions 5y ago
Related: https://news.ycombinator.com/item?id=10462349 https://news.ycombinator.com/item?id=10462349 ("NASA's last original Voyager engineer retires at 80")
perihelions 5y ago
There aren't any permanent shadows in space. Every orbit goes "around" eventually -- and there's no configuration where some combination of objects works to permanently shadow you. (A technical exception is a planetary solar L2 Lagrange point [0], *if* it would occur close enough to a planet to be totally eclipsed. But that doesn't happen (AFAIK) -- they're generally far enough away that although the planet is always in front of the sun, the planet's disk is much smaller than the solar disk. Like a partial eclipse). With cryogenic cooling, you have an even more difficult challenge: the light of a planet's infrared radiation emission is something you also have to shield. That's a major reason JWST (and similar cryogenic telescopes) go to solar L2: its sunshield doesn't only block out the sun -- it simultaneously blocks out the sun and the Earth. That's the unique advantage of the solar L2 point: the sun and Earth are always in the same direction. [0] https://en.wikipedia.org/wiki/Lagrange_point https://en.wikipedia.org/wiki/Lagrange_point

dzhiurgis 5y ago

Had my reddit reminder trigger back in July. I think I've set it up like 6 years ago. Amazed it actually worked.