Author Topic: Ariane 5 VA256 - James Webb Space Telescope - NET 25 December 2021 (12:20 UTC)  (Read 82201 times)

Offline Josh_from_Canada

https://spaceflightnow.com/2021/12/10/webb-telescope-fueled-for-flight-ready-for-lifting-atop-launcher/
Some of the important milestones remaining during the launch campaign:
Dec 11: Stacking Webb on Ariane
Dec 12: "Remove before flight" parts are removed
Dec 13: Payload fairing put over the spacecraft (last time anyone will see it)
Dec 15: Dress rehearsal
Dec 17: Launch readiness review
Dec 20: Rollout to the pad
Dec 21: Beginning of the countdown
Dec 22: DÉCOLLAGE!!!
Launches Seen: Atlas-V OA-7,

Offline centaurinasa

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Online Herb Schaltegger

Pretty good segment on the JWST this morning on CBS Sunday Morning here in the US. (Might be region-limited - sorry, non-USA’ians).

https://www.cbsnews.com/video/the-revolutionary-james-webb-space-telescope/

One soundbite dropped was that the mechanism has over 300 single-point failures. That’s encouraging. :)
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Offline GWR64

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Offline matthewkantar

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Pretty good segment on the JWST this morning on CBS Sunday Morning here in the US. (Might be region-limited - sorry, non-USA’ians).

https://www.cbsnews.com/video/the-revolutionary-james-webb-space-telescope/

One soundbite dropped was that the mechanism has over 300 single-point failures. That’s encouraging. :)

Good example for a statistics prof. How reliable do each of the 300 steps need to be to have 50/50 shot at everything going to plan?

Offline Robotbeat

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Pretty good segment on the JWST this morning on CBS Sunday Morning here in the US. (Might be region-limited - sorry, non-USA’ians).

https://www.cbsnews.com/video/the-revolutionary-james-webb-space-telescope/

One soundbite dropped was that the mechanism has over 300 single-point failures. That’s encouraging. :)

Good example for a statistics prof. How reliable do each of the 300 steps need to be to have 50/50 shot at everything going to plan?
about 99.8%.

Which is high, but not impossibly so. …of course 50/50 is hardly great odds! To get 95% chance of success, you need each to have 99.983% success rate… a lot harder.
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Online Greg Hullender

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about 99.8%.

Which is high, but not impossibly so. …of course 50/50 is hardly great odds! To get 95% chance of success, you need each to have 99.983% success rate… a lot harder.
Yep, I get the same answer (exp(-300*ln(2)) is about 0.9977).

It would be nice if, as the deployment proceeded, they told us how many single points of failure remained. But I'm sure they're not set up to report that.

Offline Lewis007

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VA256 launch sticker

Offline Josh_from_Canada

Launches Seen: Atlas-V OA-7,

Online dsmillman

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From the JWST Blog:

The James Webb Space Telescope team is working a communication issue between the observatory and the launch vehicle system. This will delay the launch date to no earlier than Friday, Dec. 24. We will provide more information about the new launch date no later than Friday, Dec. 17.
[dated Dec 14]
« Last Edit: 12/15/2021 12:54 am by zubenelgenubi »

Offline Fmedici

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Offline Barley

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Good example for a statistics prof. How reliable do each of the 300 steps need to be to have 50/50 shot at everything going to plan?
about 99.8%.

Which is high, but not impossibly so. …of course 50/50 is hardly great odds! To get 95% chance of success, you need each to have 99.983% success rate… a lot harder.
99.8% is not high.  For items used once per day it's a failure every year and a half.  Many common devices are better than that.  Door locks and car starter motors for two.  Most are better than 99.99%.  Six sigma is 99.9997% and there's a lot of that about.

Reliability is not rocket science.

Offline baldusi

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Good example for a statistics prof. How reliable do each of the 300 steps need to be to have 50/50 shot at everything going to plan?
about 99.8%.

Which is high, but not impossibly so. …of course 50/50 is hardly great odds! To get 95% chance of success, you need each to have 99.983% success rate… a lot harder.
99.8% is not high.  For items used once per day it's a failure every year and a half.  Many common devices are better than that.  Door locks and car starter motors for two.  Most are better than 99.99%.  Six sigma is 99.9997% and there's a lot of that about.

Reliability is not rocket science.

AIUI, those single point of failure points are on deployment mechanisms. Only used once.

Offline eeergo

The communication issue has been traced back to a cable between the launcher and JWST, which delayed an "aliveness test" needed before fairing encapsulation.

https://twitter.com/jeff_foust/status/1471506057851592719
-DaviD-

Offline Rik ISS-fan

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Wiring from the USA :-X
« Last Edit: 12/16/2021 06:45 pm by Rik ISS-fan »

Offline Barley

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Good example for a statistics prof. How reliable do each of the 300 steps need to be to have 50/50 shot at everything going to plan?
about 99.8%.

Which is high, but not impossibly so. …of course 50/50 is hardly great odds! To get 95% chance of success, you need each to have 99.983% success rate… a lot harder.
99.8% is not high.  For items used once per day it's a failure every year and a half.  Many common devices are better than that.  Door locks and car starter motors for two.  Most are better than 99.99%.  Six sigma is 99.9997% and there's a lot of that about.

Reliability is not rocket science.

AIUI, those single point of failure points are on deployment mechanisms. Only used once.

They are not using pyros; all those devices will have been tested multiple times.

In any case it's the same number sliced a different way.  But it's hard to find devices that many individuals buy thousands of.  Things bought in those quantities are not exactly devices (perhaps disposable coffee cups).  And few people have sat at the end of an assembly line watching hundreds of thousands of units being powered up and working first time.  Or more usually, being shipped without being tested because it's better to do deeper, often destructive, inspections of a small fraction of units to find problems before they occur than to do superficial 100% testing.  In many companies six sigma is consumer grade, not some special high reliability voodoo.

Offline Ken the Bin

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NGA notice for December 22 through January 21.  Obliviously they didn't get the word about the delay to NET December 24, so I expect a cancel-and-replace notice to come out at some point, after the new targeted launch date is firm.

Quote from: NGA
170411Z DEC 21
HYDROLANT 3083/21(24).
WESTERN NORTH ATLANTIC.
DNC 01.
1. HAZARDOUS OPERATIONS, ROCKET LAUNCHING
   1120Z TO 1416Z DAILY 22 DEC THRU 21 JAN 22
   IN AREAS BOUND BY:
   A. 05-27N 048-06W, 05-26N 047-11W,
      04-54N 047-11W, 04-55N 048-06W.
   B. 05-09N 046-30W, 05-04N 044-46W,
      04-46N 044-47W, 04-52N 046-31W.
2. CANCEL THIS MSG 211516Z JAN 22.

Edit: Two additional notices ...

Quote from: NGA
170427Z DEC 21
NAVAREA IV 1129/21(24).
WESTERN NORTH ATLANTIC.
FRENCH GUIANA.
1. HAZARDOUS OPERATIONS, ROCKET LAUNCHING
   1210Z TO 1416Z DAILY 22 DEC THRU 21 JAN 22
   IN AREA BOUND BY
   05-18.00N 052-47.40W, 05-22.35N 052-33.83W,
   05-11.16N 052-24.63W, 05-09.00N 052-36.00W.
2. CANCEL THIS MSG 211516Z JAN 22.
Quote from: NGA
170417Z DEC 21
HYDROLANT 3084/21(57).
EASTERN NORTH ATLANTIC.
EASTERN SOUTH ATLANTIC.
DNC 01.
1. HAZARDOUS OPERATIONS, SPACE DEBRIS
   1219Z TO 1501Z DAILY 22 DEC THRU 21 JAN 22
   IN AREA BOUND BY
   02-03N 014-35W, 00-07S 001-57E,
   01-54S 001-43E, 00-16N 014-49W.
2. CANCEL THIS MSG 211601Z JAN 22.
« Last Edit: 12/17/2021 04:25 am by Ken the Bin »

Online Galactic Penguin SST

Astronomy & spaceflight geek penguin. In a relationship w/ Space Shuttle Discovery. Current Priority: Chasing the Chinese Spaceflight Wonder Egg & A Certain Chinese Mars Rover

Online Galactic Penguin SST

For some reason the above tweet from ESA’s chief, and several others saying the same thing, are now deleted…

https://twitter.com/dutchspace/status/1471798763379474436?s=21
Astronomy & spaceflight geek penguin. In a relationship w/ Space Shuttle Discovery. Current Priority: Chasing the Chinese Spaceflight Wonder Egg & A Certain Chinese Mars Rover

 

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