# James Webb Space Telescope general discussion thread **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Tags:** science-math\ **Created:** [December 25, 2021, 1:18pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624 "2021-12-25T13:18:56Z")\ **Posts on this page:** 20\ **Page:** 14
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [January 19, 2022, 8:15pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/261 "2022-01-19T20:15:53Z")
Yes, it’s slowed down to about common airliner speed, but the distance it has to cover is now of just terrestrial rather than astronomical magnitude. ---
**Author:** ![Fiendish\_Astronaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiendish_astronaut/32/3295_2.png) [@Fiendish\_Astronaut](https://boards.straightdope.com/u/Fiendish_Astronaut)\ **Post date:** [January 19, 2022, 10:22pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/262 "2022-01-19T22:22:13Z")
The telescope has covered close to 95% of the distance to L2, but is now travelling more slowly than a commercial jet. Around 5 days left to go before it inserts itself into the lagrange point. Exciting! ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [January 20, 2022, 12:45am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/263 "2022-01-20T00:45:24Z")
Currently 94.8% there. Exciting! ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [January 20, 2022, 12:53am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/264 "2022-01-20T00:53:09Z")
Once it gets to L2 and enters orbit, are there any further points of possible failure? ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [January 20, 2022, 1:05am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/265 "2022-01-20T01:05:51Z")
It’ll undergo commissioning, which will take several months. ETA — after commissioning, _ **then** _ it will come online and be operational. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 20, 2022, 1:14am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/266 "2022-01-20T01:14:31Z")
> [@Hari\_Seldon](#): > > Once it gets to L2 and enters orbit, are there any further points of possible failure? Well, there’s still the risk of a hotshot fighter pilot hitting the thermal exhaust port, but that’s less than 2 meters in diameter. ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [January 20, 2022, 1:16am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/267 "2022-01-20T01:16:39Z")
R2D2 where are you? ---
**Author:** ![Euphonious\_Polemic](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/euphonious_polemic/32/3002_2.png) [@Euphonious\_Polemic](https://boards.straightdope.com/u/Euphonious_Polemic)\ **Post date:** [January 20, 2022, 1:34am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/268 "2022-01-20T01:34:57Z")
So about the size of a Womp Rat? ---
**Author:** ![squeegee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/squeegee/32/14537_2.png) [@squeegee](https://boards.straightdope.com/u/squeegee)\ **Post date:** [January 20, 2022, 1:35am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/269 "2022-01-20T01:35:59Z")
> [@Bullitt](#): > > _ **then** _ it will come online and be operational [![](https://img.youtube.com/vi/g7-tskP0OzI/hqdefault.jpg "Now Witness the Firepower of this fully Armed and Operational Battle Station") ](https://www.youtube.com/watch?v=g7-tskP0OzI) Fire at will, Commander ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [January 20, 2022, 9:11am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/270 "2022-01-20T09:11:30Z")
It’s now 95.3% to L2. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [January 20, 2022, 12:19pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/271 "2022-01-20T12:19:09Z")
> [@Hari\_Seldon](#): > > Once it gets to L2 and enters orbit, are there any further points of possible failure? The science instruments have only been superficially tested post-launch, if at all. This is a big part of the commissioning process, as well as the fine alignment of the main mirror segments. The Canadian Space Agency provided the JWST with the Near-Infrared Imager and Slitless Spectrograph (NIRISS) scientific instrument and the Fine Guidance Sensor (FGS), which are mission-critical components. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [January 20, 2022, 1:39pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/272 "2022-01-20T13:39:04Z")
I don’t believe that they have tested any of the actual cameras or anything since the launch. It’s possible that it ends up in a perfect orbit, with all mechanical parts functioning perfectly, but with no “picture”. Let’s hope that’s not the case. ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [January 20, 2022, 3:25pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/273 "2022-01-20T15:25:39Z")
> [@k9bfriender](#): > > It’s possible that it ends up in a perfect orbit, with all mechanical parts functioning perfectly, but with no “picture”. “Damn it, who was supposed to take the lens cap off before launch?” ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [January 20, 2022, 8:14pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/274 "2022-01-20T20:14:05Z")
“Film!? Nobody said anything about film!” ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [January 20, 2022, 8:20pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/275 "2022-01-20T20:20:00Z")
The earliest spy satellites didn’t have any sort of digital photography and would occasionally drop canisters of film from orbit that would be snatched up by a plane as it parachuted down. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [January 21, 2022, 9:12am UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/276 "2022-01-21T09:12:56Z")
> [@Dr.Strangelove](#): > > I do wonder why it’s so slow to move. Seems like the coarse adjustment should be pretty quick. Maybe they’re just trying to be gentle. I read somewhere (was it in an earlier post here?) that the deployment of these mirrors was done so slowly because any faster would have generated more heat than they wanted. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [January 21, 2022, 12:20pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/277 "2022-01-21T12:20:05Z")
> [@Senegoid](#): > > I read somewhere (was it in an earlier post here?) that the deployment of these mirrors was done so slowly because any faster would have generated more heat than they wanted. That was I comment I made earlier, though you may have seen it elsewhere, too. I’m not sure what the maximum coarse displacement of the actuators is, but I believe it’s on the order of about a micron. The mirrors were clearly not being moved at the finest 10 nanometer step. They were moving at the overall rate of a little more than 1 mm per day. And yes, heat from the motors was a factor in how they were moved. They were moved sequentially in short bursts to avoid heat build-up in any one area. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [January 21, 2022, 4:08pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/278 "2022-01-21T16:08:14Z")
The NASA Where is Webb web site contains this quote: " Even against beryllium’s strength, which is six times greater than that of steel, these ROC actuators individually shape the curvature of each mirror segment to set the initial parabolic shape of the primary mirror." What are they talking about? Steels are typically stronger than beryllium. Beryllium yields around 240 MPa and breaks around 370 MPa. Even cheap mild steel has a similar yield and a break strength more than twice beryllium. Beryllium’s modulus to density ratio is six times that of steel. Maybe that’s what they got confused with? ---
**Author:** ![Euphonious\_Polemic](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/euphonious_polemic/32/3002_2.png) [@Euphonious\_Polemic](https://boards.straightdope.com/u/Euphonious_Polemic)\ **Post date:** [January 21, 2022, 5:08pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/279 "2022-01-21T17:08:03Z")
> [@k9bfriender](#): > > I don’t believe that they have tested any of the actual cameras or anything since the launch. It’s possible that it ends up in a perfect orbit, with all mechanical parts functioning perfectly, but with no “picture”. Never mind, late to the obvious joke… ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 21, 2022, 5:39pm UTC](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624/280 "2022-01-21T17:39:19Z")
> [@Napier](#): > > Beryllium’s modulus to density ratio is six times that of steel. Maybe that’s what they got confused with? Is that confused, or just an unstated assumption? Without qualification, “strength” could mean a number of things. In context, given that weight is critical for aerospace applications, the fact that they were referring to strength for a given weight doesn’t seem like a huge leap. [Previous page](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624.md?page=13) [Next page](https://boards.straightdope.com/t/james-webb-space-telescope-general-discussion-thread/956624.md?page=15)