[HN Gopher] Webb flies Ariane 5: watch the launch live on 25 Dec...
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Webb flies Ariane 5: watch the launch live on 25 December
Author : cos2pi
Score : 198 points
Date : 2021-12-24 14:34 UTC (8 hours ago)
(HTM) web link (www.esa.int)
(TXT) w3m dump (www.esa.int)
| keewee7 wrote:
| How much did NASA, ESA and CSA each contribute to this project?
| jacquesm wrote:
| From the JWST wikipedia page:
|
| "In the 2005 re-plan, the life-cycle cost of the project was
| estimated at US$4.5 billion. This comprised approximately
| US$3.5 billion for design, development, launch and
| commissioning, and approximately US$1.0 billion for ten years
| of operations.[18] ESA is contributing about EUR300 million,
| including the launch.[84] The Canadian Space Agency pledged $39
| million Canadian in 2007[85] and in 2012 delivered its
| contributions in equipment to point the telescope and detect
| atmospheric conditions on distant planets."
|
| https://en.wikipedia.org/wiki/James_Webb_Space_Telescope
| gautamcgoel wrote:
| Those numbers are completely obsolete; the final price tag
| was over $10B.
| geenew wrote:
| The CSA is contributing staff to operations as well, afaik.
|
| A more recent source says this (found through wikipedia).
| Values all appear to be up to launch, and do not include
| operations. NASA: 8,800m ESA : 850m
| CSA : 200m ------------ All : 9,850m
|
| (No epoch given to dollars; presumably they are 2021 USD)
|
| _" Gunther Hasinger, ESA director of science, estimated
| that Europe's contributions to JWST, in the form of
| instruments and the Ariane 5 launch, to be about 700
| million euros ($850 million), roughly the same as an ESA
| "M-class" science mission.
|
| Gilles Leclerc, director general for space exploration at
| the Canadian Space Agency, said Canada's contribution of an
| instrument and fine guidance sensors cost the agency about
| $200 million Canadian ($165 million) over 20 years. "This
| is an investment in discoveries of the universe," he said.
|
| NASA now estimates it will spend $8.8 billion on JWST
| through the spacecraft's launch."_[1][2]
|
| Those numbers line up with a summary the Planetary Society
| put out.[3] That source includes info on the operations
| cost, at least for the US:
|
| " _The James Webb Space Telescope (JWST) is expected to
| cost NASA $9.7 billion over 24 years. Of that amount, $8.8
| billion was spent on spacecraft development between 2003
| and 2021; $861 million is planned to support five years of
| operations. Adjusted for inflation to 2020 dollars, the
| lifetime cost to NASA will be approximately $10.8 billion.
|
| That is only NASA's portion. The European Space Agency
| provided the Ariane 5 launch vehicle and two of the four
| science instruments for an estimated cost of EUR700
| million. The Canadian Space Agency contributed sensors and
| scientific instrumentation, which cost approximately CA$200
| million._"
|
| All three agencies will supply staff to support operations,
| which I guess makes sense since they've all contributed
| different instruments.[4]
|
| [1] https://spacenews.com/jwst-launch-slips-to-november/
|
| [2] https://en.wikipedia.org/wiki/James_Webb_Space_Telescop
| e#Cos...
|
| [3] https://www.planetary.org/articles/cost-of-the-jwst
|
| [4] https://en.wikipedia.org/wiki/James_Webb_Space_Telescop
| e#Par...
| jacquesm wrote:
| Then maybe you should update that wikipedia page.
| kitd wrote:
| All the best to everyone working on this tomorrow. Hope you get
| some suitably generous TOIL in January.
| _joel wrote:
| A fantastic Christmas treat, best of luck to all the teams
| involved :)
| gfodor wrote:
| Interesting they found a way to add a hidden risk variable to the
| launch, by sending it up on a day people are having to choose to
| not be with their families. Have a bad feeling about this :/
| [deleted]
| daenney wrote:
| "They" didn't find anything. It wasn't originally planned for
| tomorrow. The weather found a way. There's only so much wiggle
| room and launch windows.
| gfodor wrote:
| I didn't imply they did it on purpose. The they here is in
| the spirit of Murphy's Law. Seriously: launching on Christmas
| seems like a bad and unnecessary source of entropy.
| rrss wrote:
| > It wasn't originally planned for tomorrow
|
| Right, it was originally planned for 2007.
|
| It is sorta funny that after 14 years of delays they picked
| the week of Christmas.
| mrtksn wrote:
| They didn't pick that either, it was supposed to launch
| earlier but a clamp broke down when attaching the telescope
| to the rocket sending vibrations all over it and and as a
| result they had to inspect for damages, further delaying
| the launch. Then the weather wasn't good and delayed once
| more.
| rrss wrote:
| They did though. It was delayed, they chose to delay it
| from October to December 18 to December 22 to Christmas
| instead of like the first week of January or whatever.
|
| It's not like this thing is launching to Mars and they'd
| have to wait a couple years if they miss this week - it
| could launch on 210 days of each year.
|
| https://jwst.nasa.gov/content/about/faqs/faq.html#launchW
| ind...
|
| I don't mind at all, I just think it's a bit funny.
| myself248 wrote:
| what's funny about it? You think there's anyone working
| on this project who isn't super excited to see it go up
| on Christmas?
|
| No better gift than a successful launch. The folks
| working on preparations overnight surely see themselves
| as Santa's Elves in some fashion.
| gfodor wrote:
| Exactly - you highlight the problem. Launching on
| Christmas introduces unique situational entropy. They
| should do it later.
| foobarian wrote:
| Decades of meticulous planning and they couldn't give their teams
| a day off on Christmas? Of course it could be that consensus was
| this beats any other kind of activity that day in which case fair
| enough. :-)
| malermeister wrote:
| Lots of European countries celebrate Christmas Evening (Dec 24)
| more than Christmas Day (Dec 25).
| CoastalCoder wrote:
| I wish for our Canadian friends that the telescope unfurls on
| Boxing Day.
| Ostrogodsky wrote:
| Yeah, 25th is the day to nurse the hangover
| jpgvm wrote:
| I think spending Christmas wringing your hands unsure if your
| $10B decades-in-development baby is going to make it to orbit
| sounds incredibly stressful...
|
| It's going to be awesome for us to watch but I feel for all the
| folks that worked on this.
| ajross wrote:
| FWIW: given the extraordinarily complicated mechanical
| design, merely reaching orbit is the "easy part". The real
| imagined disasters won't happen until the mirrors assemble.
| mortenjorck wrote:
| True, though it's also worth considering that Webb is going
| far beyond "orbit" as we generally think of it. I don't
| know how much has been launched all the way out to L2
| before, but it's probably an order of magnitude less than
| what's in Earth orbit.
| krisoft wrote:
| > I don't know how much has been launched all the way out
| to L2 before...
|
| There is a handy list on wikipedia: https://en.wikipedia.
| org/wiki/List_of_objects_at_Lagrange_po...
|
| Your intuition is quite right, there is way less
| satellites parked around L2 than in low earth orbit for
| example.
|
| But that doesn't really pose too big of a challenges in
| itself. It is of course far, both distance wise and
| energetically.
|
| The main complication often mentioned is if something is
| wrong with the telescope it makes it very unlikely that a
| crew can visit it to fix it. The way for example how they
| repaired Hubble is unlikely to happen with Webb.
| ajross wrote:
| Meh, but there's nothing to hit in space. The energy
| required to reach a routine geosynchronous orbit is
| already ~85% of escape velocity. The added boost is
| minimally more dangerous and the trip is just empty
| hours. "Time" does kill spacecraft, but not often.
|
| The Webb self-assembly is absolutely where the scary bits
| lurk.
| jpgvm wrote:
| Yeah valid. Though the whole "hurtling upwards on top of
| a bomb" part is still definitely scary in it's own right.
| argiopetech wrote:
| Particularly given the launch record of the Ariane 5
| platform. I did some quick research, and no modern launch
| platform has as high a mission failure rate (4.5%.) The
| Delta family comes close at 4.4%, but that's a 50yr
| launch history. The Delta 4 iteration has had no
| failures.
| jacquesm wrote:
| As I wrote elsewhere, the bulk of those failures were in
| the first 15 launches, after that it was a very long
| string of one success after another with one partial
| failure in 2018.
| Symmetry wrote:
| The Ariane 5 is batting 106 for 111 which is pretty good
| odds and perfectly respectable for a heavy lift vehicle...
| but not so much so that I don't wish it was launching on an
| Atlas 5 instead.
| jacquesm wrote:
| Four of those were in the first 15, the last recent one
| was in 2018, and was a partial failure.
| GuB-42 wrote:
| Ariane 5 had some early problems, the first failure even
| became a case study in critical software development. But
| it had only had one partial failure after the 17th
| launch: the payload was launched to the wrong orbit
| because the wrong coordinates were put in the computer. A
| huge QA problem but not the fault of the launcher which
| did exactly as told.
|
| Now, both Ariane 5 and Atlas 5 are extremely reliable,
| mature rockets.
| _ph_ wrote:
| Well, according to the original planning it should have
| launched before Christmas. It was only the weather delaying it
| by one day. I guess once they were ready for the launch, they
| want to avoid to delay it any longer than needed. Not sure, how
| long the rocket can be "stored" in launch-ready state before it
| has to be serviced again.
| sp332 wrote:
| It was scheduled for Wednesday and then postponed for bad
| weather.
| [deleted]
| jacquesm wrote:
| If you start planning your rocket launches around religious
| holidays then that is going to be a bit of a problem, there are
| just too many of them:
|
| https://nationaltoday.com/religious-holidays/
| rrss wrote:
| How about planning around the single most celebrated holiday
| in the US, religious or not: https://en.m.wikipedia.org/wiki/
| Public_holidays_in_the_Unite...
| jacquesm wrote:
| Ariane 5 is a European effort, not a US effort, it will
| launch from French Guyana, not from the US.
|
| https://en.wikipedia.org/wiki/Ariane_5
| rrss wrote:
| Cool.
|
| Webb will be monitored and operated by NASA in Maryland.
|
| https://en.m.wikipedia.org/wiki/James_Webb_Space_Telescop
| e#T...
|
| https://en.m.wikipedia.org/wiki/Space_Telescope_Science_I
| nst...
| jacquesm wrote:
| I really don't get your fixation about this: the people
| involved are all most likely extremely happy to see their
| creation fly and to have Christmas take a backseat to
| that.
|
| Let's just hope it all goes well, this is one of the most
| complex space endeavors we've ever tried, and if it fails
| it will have many negative long term implications.
| rrss wrote:
| I did not get your real or feigned ignorance that
| Christmas is a much more significant holiday to the vast
| majority of the people involved than the Feast of the
| Ass.
|
| I also hope all goes well. Cheers.
| jacquesm wrote:
| I couldn't care less about Christmas, but I _do_ care
| about the JWST, and I can 't wait for first light.
| soperj wrote:
| If you worked on something since 1996, do you think you
| would give two flying figs what day it launches on?
| rrss wrote:
| my personal preference is irrelevant. my comment was
| regarding whether it is tractable to plan around
| Christmas, or unreasonable because there are too many
| holidays of comparable significance.
| desmosxxx wrote:
| Too many holidays might be a factor but I really doubt
| it's a large one. The bigger reason is you just don't
| delay a 20 year $10billion project for any holiday.
|
| Some of the grunts might be disappointed but having
| worked on way less important things that were launched on
| holidays, I can guarantee anyone significantly involved
| in the project is just happy to see it get off the ground
| no matter what day. You have a good window for launch,
| you take it
| [deleted]
| furyofantares wrote:
| Newton's birthday sounds like the perfect day for a rocket
| launch to me
| kibwen wrote:
| Since Isaac Newton was actually born extremely prematurely,
| at less than 30 weeks of pregnancy, maybe he was the one
| rushing to match the date of the JWST launch. :P
| makira wrote:
| He was born January 4th, using modern calendars.
|
| https://www.britannica.com/biography/Isaac-Newton
| furyofantares wrote:
| Oh cool, I get to celebrate his birthday twice per year
| now. That said, strangely enough, if the calendar changed
| after my death and people were still celebrating my
| birthday, I'd expect people to celebrate the day on the
| calendar I used rather than the accurate day.
| ape4 wrote:
| For people in North America 12:20 GMT is...
| 4:20 am PST 7:20 am EST
|
| Get up before the children ;)
| jessriedel wrote:
| Are there alternative streams that anyone here would recommend?
| The more technical, the better.
| drunkonvinyl wrote:
| The original title "Webb flies Ariane 5: watch the launch live"
| has a nice ring to it. Here goes!
| notjustanymike wrote:
| And here I am, feeling nervous about a production web deployment.
| Sosh101 wrote:
| Personally I hate launching anything around the Christmas period.
| mulcahey wrote:
| LaunchHN: JWST on Christmas
| Ankaios wrote:
| It's humanity's self-unwrapping Christmas present.
| Mesisio wrote:
| Love it :D
| meepmorp wrote:
| Hopefully.
| amichail wrote:
| Why isn't SpaceX doing this?
| varjag wrote:
| The project and the choice of contractors predates SpaceX.
| ddalex wrote:
| SpaceX wasn't a thing when the project constraints were
| defined.
| NikolaeVarius wrote:
| Because the contracts were made before SpaceX was deemed
| reliable.
| adventured wrote:
| The launch partner/platform wasn't chosen recently and it's
| part of what ESA is providing as a partner in the program.
|
| "In exchange for full partnership, representation and access to
| the observatory for its astronomers, ESA is providing the
| NIRSpec instrument, the Optical Bench Assembly of the MIRI
| instrument, an Ariane 5 ECA launcher, and manpower to support
| operations. The CSA will provide the Fine Guidance Sensor and
| the Near-Infrared Imager Slitless Spectrograph plus manpower to
| support operations."
|
| https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Par...
| khuey wrote:
| "not recently" is underselling it a bit. ESA agreed to launch
| it before Falcon 9 (let alone the Heavy version) had ever
| flown.
| rrss wrote:
| It looks like it was even before Falcon 1's first success.
| [deleted]
| _fizz_buzz_ wrote:
| Ariana 5 can transport a larger/heavier payload than Space X
| rockets. And even then the telescope has to be folded up in
| this really complicated way.
| jcfrei wrote:
| A fair comparison would be to Falcon Heavy (Ariane 5 uses
| boosters as well) which has about twice the payload capacity.
| Just doesn't yet have the launch history required for such an
| important payload.
| sprucely wrote:
| Contracts or momentum? Haven't looked at actual dates, but my
| guess is that this project was established long before SpaceX
| was a viable option.
| fnord77 wrote:
| ariane 5 has had 111 launches. Falcon heavy has had 3.
|
| the falcon heavy probably didn't even exist when they were
| drawing up the contracts
| sidkshatriya wrote:
| I think Falcon heavy is not needed. Webb's weight is ~6200
| kg. Falcon 9 is 8300 kg to GTO (Geostationary transfer
| orbit). This leaves about ~2000 kg fuel equivalent to spare
| which should be more than enough for the special location
| Webb is aiming for.
|
| But yes, the contract for the webb launch was probably locked
| a very long time ago.
|
| (Though it's also possible that Falcon 9's fairing wont be
| able to accommodate Webb)
| ur-whale wrote:
| > Why isn't SpaceX doing this?
|
| Reliability (as in: established track record).
|
| Although, if Ariane decides to explode tomorrow, this comment
| will look ... odd.
| rrss wrote:
| Important to note that the agreement was made in 2007, so
| reliability as a factor would be reliability as assessed in
| 2007, not 2021.
|
| I think that in 2021, Falcon 9 's track record arguably
| suggests it is more reliable than Ariane 5, but it doesn't
| matter because the Falcon fairing is too small for JWST.
| InTheArena wrote:
| This has to be launched by Ariane - it's constraints are
| tightly bound to what that platform can do, and it's fairing
| size. Ariane is optimized for GEO insertion, while Falcon is
| optimized for LEO orbits. You could have used a Falcon, but a
| payload like this was actually built around the rocket's
| capability, and this was designed prior to Falcon being a
| thing.
|
| All that said it's worth nothing that SpaceX's flight success
| rate is 98.5 (135/137), while Ariane V's is 95.5 percent
| (106/111).
|
| The really gobsmaking thing about that is that this is that
| SpaceX's rate is over 11 years, while Ariane's is over 25
| years.
|
| It's time to stop thinking of SpaceX as the plucky,
| untrustworthy startup.
|
| In the future space telescopes like this really need to be
| built in LEO, and then boosted to Lagrange points. The number
| of failure modes beyond the typical rocket / stage / fairing,
| secondary burns that the folding mechanism and the lack of a
| ability to test a ton of new technology in zero-g orbit makes
| this far more likely to fail then anyone is comfortable with,
| given the overall cost to this.
| unethical_ban wrote:
| Does anyone really think of SpaceX as a scrappy startup?
| You seem to recognize that this mission was designed and
| set in stone well before SpaceX was established.
|
| I don't know if JWST needed vertical assembly, but I recall
| that some spy satellites in the past have had to be
| launched on Atlas/Delta because they need to be assembled
| on the rocket vertically (vs. being rolled out to the
| launchpad horizontally).
| architravesty wrote:
| Falcon 9 has a better track record than Ariane 5 at this
| point, but SpaceX wasn't really a thing at the time these
| contracts were signed.
| adgjlsfhk1 wrote:
| also falcon heavy would be required which only has had 3
| launches (all success though)
| guerrilla wrote:
| Countdown with links to livestream and blog here:
| https://www.jwst.nasa.gov/content/webbLaunch/countdown.html
| ourmandave wrote:
| If you want to skip the Super Bowl pre-game, the actual launch
| window starts at 7:20 am EST (12:20 UTC) and lasts for 31
| minutes.
|
| It can launch anytime during that window.
| neals wrote:
| I can't watch this. So many years and so many man-hours riding on
| top of a rocket is to much for me.
| C19is20 wrote:
| Similar. But more because I can't believe they didn't build two
| - for redundancy.
| anotheryou wrote:
| I wonder what time and cost a rebuild would have. Maybe half
| the original development costs?
| dimtion wrote:
| I do have a question about JWST that I wasn't able to find a fine
| answer in other forums.
|
| A lot of people and engineers are saying that the JWST is a
| marvel of engineering, with truly inovative technical solutions
| and a giant step up compared to Hubble Telescope. And it does
| seems like so!
|
| However, I'm always baffled how everyone seems proud that the
| telescope has something like 200 SPOF during deployment, and if
| even one of them fails the whole mission could fail.
|
| I know that each step has probably been throughoutly tested, and
| that the acceptable probability of failure of each one of those
| steps has been deemed acceptable. But I'm still surprised that
| people are proudly conflating excellent engineering with a design
| that has a large number of spofs.
|
| In my domain this would be considered as a terrible design (aka
| "hope is not a strategy"), even given the constraints of mass and
| volume that such project incur: 200 hundred low probability
| events, chained, can get in the realm of possible.
|
| I can't imagine JSWT team doing "bad engineering", so I'm sure
| I'm missing a piece. Is it only PR that underline this aspect? Is
| JWST as brittle as the news want to make us think? Or are there
| technical reasons or acceptable failure modes that gives
| confidence that those steps are not as critical as the news let
| us people know?
| jacquesm wrote:
| Unlike say, the Apollo program, which had a guaranteed
| successful outcome?
|
| The thing to realize is that these are some of the hardest
| things humanity has tried their hand on and _if_ it all works
| that 's a great thing for all of us, if it fails we will learn
| something and we'll go back to the drawing board (but we won't
| have a JWST and that's a significant loss, besides the obvious
| future calls of 'look at what happened to JWST' which will no
| doubt have negative impact on finding funding for future space
| missions).
|
| Also, I think you're mistaken about people being 'proud about
| the 200 SPOFs', if they could have made it one less they
| certainly would have because everybody involved wants this to
| succeed. Think of these as the ones that they simply could not
| get rid of no matter how hard they tried.
| twistedpair wrote:
| > Unlike say, the Apollo program, which had a guaranteed
| successful outcome?
|
| Apollo was wildly dangerous. Apollo 1 killed the whole crew.
| The contemporary calculated failure odds for a Saturn V
| launch were 1/8. Compare that to the current Dragon 2
| projected LOC risk of 1/276 [1].
|
| [1] https://en.wikipedia.org/wiki/Crew_Dragon_Demo-2#:~:text=
| NAS....
| Stratoscope wrote:
| I think GP was being sarcastic.
| jacquesm wrote:
| Absolutely. Those guys were laying their lives on the
| line with every launch.
| redis_mlc wrote:
| WJW wrote:
| Perhaps it's a case of "we're proud that we got it all the
| way down to _only_ 200 SPOFs in the final design, the earlier
| designs were way worse ".
| jacquesm wrote:
| There is a fair chance of that, actually. If you start
| enumerating the ones that are obvious even to lay people (
| _one_ rocket, _one_ satellite, _one_ set of mirrors and so
| on) then this is probably an extremely impressive low
| number.
| shmageggy wrote:
| I've been binging JWST content and definitely recall John
| Mayer saying in at least one interview that 344 single
| points of failure was as low as they could get it. And I
| can believe it. If you watch some of the more detailed
| interviews, he always stresses how every design choice
| was heavily labored over and reviewed.
| jacquesm wrote:
| It's an absolutely amazing effort, from the design
| through all of the problems they had to deal with along
| the way to seeing it sit there on top of that booster. A
| few months from now we could be in a completely new era
| of astronomy.
| darknavi wrote:
| > However, I'm always baffled how everyone seems proud that the
| telescope has something like 200 SPOF during deployment, and if
| even one of them fails the whole mission could fail.
|
| I'm not sure I've seen anyone who is _proud_ of it, lots of
| people are just setting expectations. Probably due to the
| similarities with Hubble (although JWST can self-align it's
| mirrors!).
|
| It also might be posturing to show how well the thing is built.
| Space is hard, like really hard, and these agencies keep
| knocking it out of the park.
| harshreality wrote:
| I think all the SPOF talk is expectation management in case it
| fails. It's part space telescope mission, part engineering
| challenge. Even if the space telescope part fails, the
| engineering effort that's gone into it means something.
|
| They must've calculated that the overall chance of success, and
| they have a target, and they met their target. Unfortunately,
| tests and theoretical modelling have a tendency to not exactly
| replicate a space environment (or any true production
| environment), nobody's perfect at anticipating everything, and
| management has ways of manipulating engineering estimates.
|
| The Space Review [1] quotes NASA as saying there are 344 SPOF.
| They talk mainly about the sun shield, so that's probably the
| biggest risk, but consider all of them as about equal...
|
| If each SPOF has a 0.1% chance of failure, net success rate is
| only 71%. Presumably most of the estimated failure
| probabilities are less than that, and the sun shield--which
| probably comprises many of the SPOFs--averages (far?) more than
| 0.1% per SPOF, because everyone seems to be particularly
| worried about that working.
|
| I wonder what that figure is. Has it been published anywhere?
| Dear NASA and ESA, what do your engineers say about overall
| chance of failure?
|
| [1] https://www.thespacereview.com/article/4303/1
| sgt101 wrote:
| It has to fit in the fareing, survive launch stress and
| vibration, fly further than the moon and it has to weigh 6000
| kgs +including fuel. If it works it will be one of the greatest
| engineering feats of history.
| nharada wrote:
| I'm guessing it's a case where all the various extreme
| requirements simply do not allow for redundancy in the places
| the engineers would prefer to have it. The options are likely
| (1) okay performance with a lower chance of failure or (2)
| extreme performance with a higher chance of failure.
| nkrisc wrote:
| > However, I'm always baffled how everyone seems proud that the
| telescope has something like 200 SPOF during deployment, and if
| even one of them fails the whole mission could fail.
|
| Genuinely curious: how would you have achieved the mission
| goals with fewer SPOF?
| GekkePrutser wrote:
| Every kilo launched costs a proverbial and probably nearly
| literal tonne of fuel so things are not as simple as that.
|
| It's also has to fit on the rocket hence the once off folding
| mechanism. And after deploying it has to be perfectly aligned
| (remember the Hubble with its slightly off mirror)
|
| I think having redundancy for everything would just not make
| for a launchable spacecraft.
| throw0101a wrote:
| > _Is JWST as brittle as the news want to make us think? Or are
| there technical reasons or acceptable failure modes that gives
| confidence that those steps are not as critical as the news let
| us people know?_
|
| There is no room for redundancy in many aspects of the design,
| unlike, say a Boeing 777 or Airbus A350.
|
| How can you have a redundant heat shield, or primary mirror
| (two parts of which swing)? I'm sure some computer systems have
| redundancy and perhaps comms.
|
| But like with a helicopter: how can you have redundancy in the
| tail rotor?
|
| So with the JWST: there's no way around many SPOFs.
| GekkePrutser wrote:
| Does this have a heat shield? It won't re-enter right? It's
| far too far away for that.
| krisoft wrote:
| Not the kind of heat shield you would use to re-enter.
|
| The telescope is designed to image very faint sources of
| infrared light. The problem is that everything (including
| the telescope itself) glows in infrared. The hotter things
| are the more infrared they emit. Because of this you want
| to keep the instrument as cold as possible. (You do this
| because you don't want to drown the faint sources by the
| glow of the telescope itself.)
|
| Now of course there are parts which has to be "hot". At
| least relatively to the very cold instruments. The solar
| panels are heated by the sun, the transmission electronics
| and the processing turns electricity into heat. The
| positioning thrusters burn chemicals which makes them hot.
|
| Because of this they designed the spacecraft with two
| sides, a cold one for the instrument and a hot one for
| everything else. They even choose the orbit cleverly so
| they can keep the sun and the earth and the moon always on
| the hot side of the vehicle.
|
| And then you have this problem that you have to make sure
| that the hot side won't warm up your cold side. This is
| where the heat shield comes into play. Sometimes it is also
| called a sun shield since the sun is the main source of
| heat for it to shield against of course, but it also
| shields the instrument from the heat of the hot side
| equipments.
|
| Structurally it is a 5 layer lassagne. They just replaced
| the pasta with metalized kapton tape and the sauce with the
| vacuum of space. It is about the size of a tennis court,
| launches folded up and will un-fold in space. Hopefully. :)
| akiselev wrote:
| It's actually a sunshield [1]
|
| [1]
| https://webb.nasa.gov/content/observatory/sunshield.html
| mastax wrote:
| Better helicopter example is the Jesus Nut.
| Teknoman117 wrote:
| "Because it it comes off that's who you're seeing next"
| jacquesm wrote:
| Regarding that helicopter example:
|
| https://verticalmag.com/news/bell-electrically-
| distributed-a...
| beamatronic wrote:
| The answer to your redundancy question is: Assembly line.
|
| Instead of ramping up a project, and building 1 of something,
| you would plan to do more than one, and you could iterate
| over time as you learn. SpaceX is doing a good job of this.
|
| If 1 Webb telescope is valuable then wouldn't 3 or 5 also be
| valuable?
|
| We have a number of proven space designs at this point:
| Soyuz, Spirit/Opportunity rovers.
| bernulli wrote:
| It's really not - just by having more hardware available
| (at higher total expenses) doesn't make the pool of money
| available (public research funding) to book time on these
| things more. These things are one-off, you build a new one
| if you expect 10x improvement over the old one.
|
| We don't need a fleet of X1 to break the sound barrier for
| the first time. We do need many Airbus/Boeings to fly
| people and stuff from A to B.
|
| Note that that is the case with the unique research
| hardware you cite as well - we're not sending another
| Spirit/Opportunity, but have graduated to something else.
|
| Soyuz is a different use case, as there is an economic
| demand to be filled - that's why a private company like
| SpaceX is in that sector with its Dragon. On the other
| hand, you don't see SpaceX cranking out Spirits or JWSTs or
| Washington Monuments.
| twistedpair wrote:
| They calculated that. Building a second JWST would have
| added 10% to the budget, but the budget committee nixed
| that.
|
| YOLO (you only launch once).
| devoutsalsa wrote:
| The JWST only has a planned mission duration of 10 years.
| If it's as epic as everyone claims it could be, there
| must be a follow up mission planned. So even if it fails,
| we'll still see a successor at some point.
| dylan604 wrote:
| >there must be a follow up mission planned
|
| https://www.universetoday.com/139461/what-comes-after-
| james-...
|
| The write up goes into detail on how missions are
| planned, and what is in line to follow JWST.
| thebigman433 wrote:
| There are quite a few more telescopes planned, I think
| the next major one is the Nancy Grace Roman telescope,
| which is another infrared scope, made from an old NRO
| telescope. The decade survey called for another massive
| space telescope to look at the optical and UV spectrums,
| so Id expect that to be the next truly big flagship
| telescope.
| wmf wrote:
| Since JWST was delayed ten years the successor will
| probably be delayed 20 years and launch in 2050.
| yk wrote:
| I hope it's just badly thought through marketing. There is
| currently a AWS spot during nfl games, that shows a spectacular
| catch and then proclaims that the catch probability is only
| 3.6% or something. You are meant to be somehow impressed by the
| unlikelihood I believe, but that their model thought the catch
| is unlikely and the guy caught it implies a rejection of their
| model with p=3.6% < 5%.
|
| The JWST marketing seems to work under a similar premise, they
| proudly proclaim that they couldn't mitigate hundreds of single
| points of failure, and you're supposed the be impressed by how
| difficult their task is. Hopefully the engineering did a
| reasonable job and the marketing is just playing up the wrong
| thing.
| jdiez17 wrote:
| I don't think you are supposed to be impressed by the number
| of things that could go wrong. At least, that's not how I see
| it. They talk about the deployment phase with all these
| complex things that have to go exactly right as "the 30 days
| of terror." And that's a pretty accurate description of what
| many people with a stake in the JWST will be feeling. Not
| awe, but terror. This is a big part of space missions at the
| bleeding edge of science and technology, and I think it's
| great that many people are hearing about it!
| jcims wrote:
| I think this is your earnest attempt at it but its a good place
| to apply the story from yesterday 'be curious, not
| judgemental'.
| dimtion wrote:
| I'd like to apologize if this sounded judgmental. English is
| not my main language, and perhaps my phrasing sounded like I
| assumed my domain specific opinion is better than the actual
| people working on the the project.
|
| Reading the other comments, and maybe to contextualize to my
| question better, I'm more surprised by how the project is
| presented as marvelous to the public, rather than thinking
| that any technical part were overlooked.
|
| While I'm sure that engineering teams at NASA and ESA have
| countless contingency plans, procedures and failure models.
| Medias around the project seem to focus on how fragile the
| deployment procedure is. Great engineering is an act of
| finding the best balance between opposing constrains, by
| building technically sound systems but also more importantly
| designing robust human or automated procedures.
|
| In this story, in my opinion, the media presents a skewed
| explanation of why the project is incredible by highlighting
| that it would be incredible that such a brittle deployment
| procedure would even work.
| kataklasm wrote:
| That's literally what he is doing, isn't it? He thought
| something was off, and instead of spewing his opinion all
| over the place he requested information from folks more
| versed in the domain than him. He is literally being curious,
| not judgemental.
| jacquesm wrote:
| > I'm always baffled how everyone seems proud that the
| telescope has something like 200 SPOF during deployment,
| and if even one of them fails the whole mission could fail
|
| I see this as judgmental, am I wrong in that?
| MobiusHorizons wrote:
| It expresses an opinion, but I don't think that has to be
| judgmental. The OP has to explain their position in order
| to ask for additional information.
| twistedpair wrote:
| While a farm tractor might have a factor of safety of 10,
| spacecraft are usually closer to 1.3, due to mass and
| efficiency constraints.
|
| Space is hard.
| wslack wrote:
| I suggest the book "Failure is not an option" by Gene Kranz, an
| Apollo flight director (played by Ed Harris in Apollo 13). He
| describes how the primary work of flight controllers in all
| missions is risk management. You are constantly balancing
| mission needs, fuel needs, mass needs, temperature needs, and
| etc etc.
|
| I don't think that a raw metric of the number of SPOF is the
| right way to measure the risk of this spacecraft. It's a fun
| term for PR purposes (and emphasizing the risk here) but the
| actual risk posture is more complex.
|
| I imagine that in the course of developing this, they worked
| out a possible strategy without all of those SPOF - but doing
| so doesn't eliminate the risk, and the impact to mission is
| likely massive.
| onphonenow wrote:
| What I don't understand is for $11 billion - can't we do 3
| $3B space telescopes that work reasonably well? Spread risk?
| More science?
|
| Let's say a Falcon 9 launch is $90M. Falcon heavy let's say
| $200M.
|
| So you take your 3x $3B. Put $200M/instrument into launch,
| have $2.8B per telescope leftover.
|
| There just seems to be something wrong that it costs THIS
| much to build a telescope.
|
| That said, the Thirty Meter Telescope is also a sort of
| "forever" job, the delays have stretched on and on.
|
| I wonder if you did something like bid out and paid just on
| performance instead of this forever cost reimbursement thing.
| Right now if you can get onto one of these mega projects, and
| can stretch it out with delays, it basically can cover your
| career (ie, 20 year projects).
| foobarian wrote:
| I think this is because of how the various constraints work
| against each other. We need the telescope to be as large as
| possible to work as well as possible. But the rockets can
| only be so big (i.e. we're constrained by the largest
| available booster). The only thing here under our control
| is how hard we work on fitting the biggest possible
| instrument in the available payload envelope, and that is
| exactly what happened.
|
| With a machine this complex I think it's also not easy to
| crank out multiple copies since I'm imagining most of it is
| made by hand without the benefit of a production line.
| lamontcg wrote:
| JWST is driven by the size of the mirror, the need for an
| IR instrument and the temperature you need to keep the
| instrument at to do the observations. Spamming a bunch of
| hubble-sized instruments up into orbit won't accomplish the
| same thing. And I don't think you can do space VLBI in the
| optical/IR or it would have been done already (but I don't
| know why?).
|
| It is kind of like asking why 5 Ford Rangers can't replace
| one Lamborghini or something.
| CamperBob2 wrote:
| _Spamming a bunch of hubble-sized instruments up into
| orbit won 't accomplish the same thing._
|
| It will, and then some, once we get optical
| interferometry nailed down. JWST is great, and needed to
| be done, and I'm glad it's finally getting deployed. But
| if I had an argument to make against it, it would be,
| "Let's wait until we know how to do this properly. We're
| not there yet."
|
| That's a weak argument and should almost never be heeded,
| but it's also not wrong.
| aargh_aargh wrote:
| The reason we can't achieve the same resolution as JWST
| with interferometry has been mentioned in a recent
| startalk podcast. The distance between the telescopes
| would have to be coordinated to a precision somewhere on
| the order of nanometers.
| petschge wrote:
| The reason why we are barely getting started into VLBI in
| the IR on the ground (and nothing that I have heard of
| yet in space) is that the different apertures need to be
| stable relative to each other with a precision better
| than a small fraction of a wavelength. (One tenth, one
| twelves and one twenties are often used, depending
| basically on which performance drop relative to the
| theoretical optimum you are willing to live with.)
|
| For radio astronomy, where we do VLBI everyday, we have
| to handle waves of wavelength 1 cm and position antennas
| to a precision better than a millimeter. Not easy when
| the antennas are scattered across the country, but
| something we can pull off.
|
| For IR astronomy we are talking wavelength in the range
| of 1000 nanometers to 30 microns. So at the easiest end
| of the spectrum you would have to position satellites to
| a precision better than 3 microns relative to each other,
| while flying on orbit and being pulled and pushed by
| tidal forces, gradients in the graviational fields and
| solar wind pressure (which contains turbulent
| fluctuations). For it to actually work in near IR you
| would have to get the positioning right to within 100nm.
|
| For comparison: The mirrors of JWST itself are flat to
| within about 25nm. And in some sense we ARE doing IR VLBI
| with JWST since we have separate mirror segments that we
| all position correctly relatively to each other. But
| doing so we separate freeflying satellites is something
| we just aren't capable of yet.
|
| PS: Yes, LISA Pathfinder has demonstrated measurements of
| spacecraft separation down to a few picometer, so we are
| slowly getting there.
| sjburt wrote:
| There are many people in NASA and around that have made
| similar arguments.
|
| I think the real reason that they never have a lot of
| traction, sadly, is that if you propose 3, Congress will
| give you 2. And then when 2 are over budget, it will get
| trimmed to one. Better to propose one big mission and get
| it to the point where it can't be cut easily.
| dwohnitmok wrote:
| Yeah when you have a fickle funding source often the only
| way to get any long-term project done is to make it too
| big to fail, but then you see all the other terrible
| waste, corruption, etc. that accompanies that.
| azalemeth wrote:
| I'd bet that the vast majority of that cost isn't going to
| be materials -- it'll be staff time to design and optimise
| the telescope and make something that can work, including
| where necessary how to make new materials or processes to
| make that telescope. I'm not saying the actual hardware is
| cheap by any stretch of the imagination, but making three
| different telescopes isn't a linear function of that
| budget. They're literally pushing the envelope of what's
| possible here. If something terrible happens to the rocket,
| lots of forms will be written and people will be sad but
| fundamentally I think they'll build something a bit better
| on a few years and nail it. A bit like New Horizons
| (awesome Mars rover) vs Beagle 2 (awesome Mars rover that
| died on arrival to Mars).
| rtsil wrote:
| JWST was (re)launched in 2005, the very idea of cheap
| spaceflight didn't exist back then, so you'd have ended up
| with three expensive flights. Also consider that the
| expected cost back then was $4.5 billion.
| mongol wrote:
| Perhaps that is what will happen from now on. But when JWST
| was initiated, the options looked different.
| Mesisio wrote:
| Will this be visually tracked? Like can we watch it to it's
| journey?
| BurningFrog wrote:
| We're told that since JWT will travel very far away before it
| unfolds and activates all its systems, there is no practical way
| to service it if something would go wrong.
|
| Why can't it unfold etc in Earth orbit, where a repair mission
| can be sent if needed, and _then_ travel to its Lagrange point?
| ufmace wrote:
| Absent all of the other practical considerations, even in LEO,
| a repair mission would probably be so expensive that it would
| be cheaper to build and launch a new one instead.
| whiteboardr wrote:
| Orbiting around earth would require it to constantly course
| correct / rotate in order to avoid the device from getting to
| hot from the sun's radiation - there isn't enough fuel to "play
| it safe" around earth for this long since it will be needed at
| L2.
|
| Let alone the current lack of in orbit service capabilities
| like we had when the space shuttle was still around.
| Symmetry wrote:
| It doesn't have enough fuel onboard to go from LEO to the
| Lagrange point itself.
| CyanBird wrote:
| It wouldn't need to, you could park it there a secondary
| liquid fuel booster attached, and then after the origami
| shenanigans if it unfolds correctly the second booster could
| send it away to its final position
|
| I saw some interviews of engineers of the jwst and few of
| them had similar ideas, or at least to assemble them in leo
| then slingshot them to their final positions/orbits
| bendhoefs wrote:
| What booster would you use?
|
| Another booster up in the fairing? That would need to be
| quite heavy. It would be a totally custom thing for this
| specific mission. You would need a suitable storable
| propellant.
|
| Leave the booster from the Ariane attached? The lh2 and lox
| would boil off after a few days.
|
| What do you do if the deployment fails? SpaceX's dragon
| can't do space-walks on its own, it doesn't have an
| airlock. There would be no way to fix it short of
| developing a whole new space craft for that task.
| samwillis wrote:
| For space walk accessibility maybe they should have
| docked it to the ISS for initial setup before then
| boosting it to its final point?
| zrail wrote:
| ISS is in a very low and eccentric orbit. I think
| boosting from ISS to a geo transfer orbit, let alone
| escape, is more expensive than just going straight to
| escape velocity.
| devoutsalsa wrote:
| We probably wouldn't have a way to service it in earth orbit
| either. We needed a space shuttle to operate on Hubble. And
| using some other commenter's estimate a 2nd JWST would cost 10%
| of the 10 billion USD price of the first one. A billion dollars
| is ballpark what it costed to launch a space shuttle. So even
| if we had the shuttle, would we fix the first one or just build
| & launch a second one?
| mabbo wrote:
| Can we crowdfund 3 more this way, I wonder?
| ultramegachurch wrote:
| I suspect the deployed structure cannot handle the acceleration
| required for escape velocity. That also may require much more
| propellant. Then on top of that, we don't have the capability
| for humans to service satellites other than the ISS. So this is
| all a moot point.
| Mesisio wrote:
| Interesting though.
|
| Does that really matter without air resistance?
|
| Depending on how high you actually bring it. Like 500km away
| from earth is still an orbit (I think that's Hubble's orbit)
| but how much force do you need or will happen?
| MobiusHorizons wrote:
| When rockets are firing lots of acceleration is applied
| that the delicate structures are only designed to handle
| when stowed. Think long arms on hinges. They can take
| acceleration in one axis, but not at 90 degrees to it.
| Mesisio wrote:
| I guess the acceleration needed to leave orbit might need
| so much more fuel if you need to do it slowly than doing
| it fast?
|
| Otherwise it would just take longer.
| aliher1911 wrote:
| Rocket engines could only be throttled down to certain
| power and manoeuvring thrusters would run out of
| propellant way before it reaches any orbit. Maybe
| something like electric propulsion can do it but it will
| take very long time to make it practical imho.
| HideousKojima wrote:
| The parts of a ship that thrusters are directly attached to
| experience acceleration first, the other parts that are
| further out from the thrusters won't accelerate immediately
| and if the acceleration is too sudden or extreme could be
| damaged or break off entirely.
|
| And to answer your question in the other response, many
| thrusters have a minimum thrust, and even that minimum may
| be too much for the parts when deployed.
| martyvis wrote:
| By definition, as long as thrusters are firing, you are
| accelerating.
| chriswarbo wrote:
| Acceleration is defined as the change in velocity, and
| velocity is defined as the change in position (w.r.t.
| some inertial reference frame). There will _always_ be
| some bending when thrust is applied at one part of a
| body; nothing is perfectly rigid.
|
| As an extreme example, imagine a stick one lightyear in
| length: if we ignite a rocket on one end, firing
| perpendicular to the stick's length, then the other end
| cannot start moving for at least a year.
| twistedpair wrote:
| Rockets can easily accelerate with enough force to kill a
| human (cargo flights and unmanned flights use different
| launch profiles for this reason).
|
| The less Gs you need to design a component for, the
| lighter/simpler it can be, so why unfurl early and add that
| extra mass and complexity to the design?
| BurningFrog wrote:
| We had the capability in 1993, and could of course develop it
| again.
|
| A broken JWT could wait a few years in orbit.
| ultramegachurch wrote:
| That may be true, but designing a mission based off that
| hypothetical is a bad idea. The reality is we currently
| don't have the capability for humans to service satellites,
| and developing that capability would probably take years
| and cost >$100 million. And NASA can't just decide to take
| on that endeavor, it would require congress and months of
| political bickering. JWST was designed for what is
| currently feasible and practical.
| kaashif wrote:
| > developing that capability would probably take years
| and cost >$100 million. And NASA can't just decide to
| take on that endeavor
|
| So what you're saying is, this could easily be funded by
| some billionaire, e.g. Jeff Bezos who already sells
| billions of dollars in Amazon stock per year to fund Blue
| Origin?
|
| Not saying this _should_ be done privately, but if
| funding is the problem, that problem can be solved.
|
| Space travel is less expensive than most people think, it
| just isn't very high up on our list of priorities.
| ultramegachurch wrote:
| "Maybe Jeff Bezos could fund this" is not a good
| parameter to design a mission around.
| BurningFrog wrote:
| $100M is 1% of what JWST cost.
|
| Looks like a reasonable repair cost (and only if) it
| turns out to be broken.
| ultramegachurch wrote:
| It's still not that simple, unfortunately. Ironically,
| there are too many single pint failures. Maybe JWST broke
| in a way that can't be repaired. Maybe congress doesn't
| approve the repair mission. Maybe the repair mission
| would actually cost $1 billion. Maybe the repair mission
| fails. Now imagine you're the mission designer. You could
| trade increased complexity for some small chance of a
| repair mission maybe being possible. Or you you could
| decrease complexity and just accept that repair won't be
| possible. The answer becomes pretty clear.
| superjan wrote:
| Referring to hubble? The JWT is designed to observe from
| the Lagrange point in permanent shadow of the earth. It
| won't work from earth orbit. First parking it in orbit, and
| then restarting the engine after unfolding comes with a
| whole new set of risks and tradeoffs.
| alserio wrote:
| What about an unmanned mission to fix it? And maybe to refuel
| it.
| nexuist wrote:
| But who repairs the repairers?
| ultramegachurch wrote:
| Incredibly unlikely. First, it would have to fail in a way
| that's possible to fix. We don't have robots that can
| replace screws, solder joints, and polish mirrors in space.
| Then we'd have to design a brand new spacecraft and
| mission. That would take years, lots of money, and
| political will. NASA would likely cut its losses, document
| the lessons learned, and try again.
| mabbo wrote:
| It's a problem of energy and orbits.
|
| To get from low-earth orbit to the sun-earth Lagrange point 2
| (where the JWT is headed) takes around 7 km/s of delta-v[0].
| That's a lot of speed.
|
| You could try to do this gently enough that the unfurled JWT
| won't be damaged by the acceleration. This isn't totally
| impossible, but you'd need a good Hall thruster (ion engine)
| with a huge amount of reaction mass, since the JWT is so big
| itself. It would need to run for longer than any other such
| thruster has. It would need massive solar panels to power
| it.[1]
|
| Or you could have the original rocket just be bigger, and throw
| it all the way to the right orbit while everything is packed
| tight.
|
| [0] https://en.wikipedia.org/wiki/Delta-v_budget [1] I'm
| guessing at this, but that's my intuition. I encourage anyone
| to correct me because space is too cool to be upset that I was
| wrong.
| [deleted]
| eterm wrote:
| How feasible is a repair mission without the shuttle?
| twistedpair wrote:
| L2 is very far from earth, well beyond the Moon. The Shuttle
| could never leave Low Earth Orbit, so it's a non-factor in
| repair missions once JWST is on station.
| usrusr wrote:
| I believe what was GP was getting at is that even in a
| "convenience orbit", a repair mission would be very
| unlikely.
| buryat wrote:
| in Armageddon the Shuttles flew over the moon
| dragonwriter wrote:
| The shuttle-like craft were explicitly special, more
| capable craft (visually hinted at by the extra set of
| boosters and other design differences.)
|
| Not that Armageddon was particularly focussed on reality.
| BurningFrog wrote:
| The scenario we're talking about is having JWT unfold in
| Low Earth Orbit, so it can be repaired there, if need be.
| justin66 wrote:
| > Why can't it unfold etc in Earth orbit, where a repair
| mission can be sent if needed, and then travel to its Lagrange
| point?
|
| Another comment mentioned that it's not designed to accelerate
| while it's fully deployed, and that's true enough. You'd wreck
| it.
|
| The other essential thing is that there's no way to give it and
| its instruments anything like their designed operating
| parameters (pretty hot on one side of the sunshade, something
| like 40 kelvin on the other side) in Earth orbit.
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