High cost astronomy

[Sonny Taylor]

I've got my fingers crossed, toes crossed and unspeakable parts of my anatomy crossed in hope of success.

I remember when Hubble's flawed primary mirror was news shortly after Hubble's launch; remember where I was, reading the bad news in the Toronto Sun at the time in the 90's just like I remember my car radio announcing the Challenger disaster in 1986. That disappointed me (but of course it was optically correctable with a later add-on). Widespread "Hubble trouble" jokes were quickly put to rest after the first service mission by the space shuttle.

If JWST doesn't work; naturally I'll be downhearted, but I'll feel even more for the thousands of people who worked on this project for decades, many of them likely wondering if it would ever come to be, what with budget overruns, cancellation threats, re-designs etc.

But here we are 14 years too late and Whoosh! ...she's actually on the way. Can hardly be complacent and satisfied just yet though; too much complexity still to come.

Go JWST GO!

[Sonny Taylor]

Now that I think about it, I've been nerding out about this thing for over 25 years now. I'm grateful that I got to live long enough to see it finally fly

...Yeah, exactly my thoughts.

[Jlabute]

yup, a few tradgedies in the past but many successful missions too. Seeing the thoroughness of modern engineering and all the mistakes we’ve learned from, I am optimistic JWST will work just fine, and with no focus issues. The hubble repair almost didn’t happen. Another thing I hope NASA learned is not to give in to despair.

Certainly there are quite a few steps that need to happen, but just a few minutes ago I turned on an electronics device with 2,000,000,000 transistors in it and every one worked as expected. After working in space for 50 years I think they ought to be pretty confident.

[Sonny Taylor]

but just a few minutes ago I turned on an electronics device with 2,000,000,000 transistors in it and every one worked as expected. After working in space for 50 years I think they ought to be pretty confident.

So let's see... one bit per transistor = 2 Gigabits = 250 Megabytes.

Did you power up a 1990's laptop?

I'm seriously pulling your chain of course with inaccurate or mistaken assumptions. I certainly share your optimism and enthusiasm though.

[Sonny Taylor]

https://www.jwst.nasa.gov/content/webbL ... its=metric

Temperature data is now being displayed (2 points on the hot side of the craft and 2 points on the cold side).

[Sonny Taylor]

About 2.3 times the distance of the moons orbit now. 60% of the distance to L2 orbit has been covered but as it slows down I presume the last 40% will take much longer.

I noticed that the temperature on the cold side of JWST has plunged since the sunshield was recently deployed.

A few days ago the average temperature of the primary mirror was -45C. Now it's dropped quickly to -116C. I assume this is a very good sign (JWST being primarily an infrared telescope needing extreme cold).

GO!!!

[Edit] I also noticed that the hot side temperature shot up. I guess that was probably expected

[Jlabute]

Pretty cool that NASA did such a precision launch with just the right amount of fuel in order to ease in to orbit and make corrections for 10 years. Very thrifty. I don’t think I did so well playing lunar lander.

[Sonny Taylor]

It's hard to wrap my mind around the mechanics of unfolding and fine adjusting the mirror segments, as will happen in the dark beyond the Sun shield in cryogenic temperatures.

Things like (just for example) what kind of lubricants are used in the motors (or whatever form of physical actuators) to move various structures? Are lubricants even necessary for some actuator types in a vacuum at cryogenic temperatures? Maybe they're even solid coatings on bearing surfaces(?)

I tried to answer my own question specifically about that subject by searching Google for "cryogenic lubricants". I came across this vintage 1970 NASA technical paper:
https://ntrs.nasa.gov/api/citations/197 ... 000335.pdf

It's mildly detailed, talkng about "Fluorinated polyether" (not an overly long read, but interestng).

It does talk about dry lubricant:

Present cryogenic systems are lubricated by the transfer of a dry lubricant film from the ball-retainer (cage) pockets to the balls and subsequently to the races of the bearing during operation. This "dry transfer-film" method
of lubrication provides only boundary lubrication. Wear, therefore, occurs on the rolling elements as well as on the races of the bearing. This wear leads to early failure and relatively short bearing life. In addition, wear in the ball pockets of the retainer can be excessive, leading to premature retainer failure and thus catastrophic failure of the bearing.

It doesn't specifically mention vacuum conditions, but since Fluorinated polyether was used in rocket turbo-pumps, perhaps a vacuum is not even relevant. (These ridiculous horsepower turbo-pumps pushing tons of cryogenic rocket fuel alone are a serious piece of tech).

Perhaps in our modern day we have much better options than in 1970.

Mirror temperature now down to -132C well on the way to what is considered cryogenic in the USA (-180C) with mostly passive cooling. Gotta get her down to -223C

The more I try to learn about JWST, the more astonished I am about the engineering.

[Edit] The "dry lubricant" above is a little out of context in that it is not related to the newer Fluorinated polyether discussed in the paper.

[Jlabute]

That is an interesting read. So many discoveries required in order to accomplish or improve operating conditions in space. Expansion coefficients of different materials and behavior in weightlessness. Some lubricants can be too viscous for small parts, like in a wrist watch, so we have the concept of ‘jewels’, or a hard surface with a low friction coefficient.

Apparently JWST is using Pennzane oil by Nye Lubricants.

https://www.fuelsandlubes.com/flo-artic ... a-mission/

https://www.designworldonline.com/nye-l ... telescope/

Pennzane oil. I almost read Pennzoil when I first saw it, lol.

[Sonny Taylor]

Sorry, double post deleted.

[Sonny Taylor]

That is an interesting read. So many discoveries required in order to accomplish or improve operating conditions in space. Expansion coefficients of different materials and behavior in weightlessness. Some lubricants can be too viscous for small parts, like in a wrist watch, so we have the concept of ‘jewels’, or a hard surface with a low friction coefficient.

Apparently JWST is using Pennzane oil by Nye Lubricants.

https://www.fuelsandlubes.com/flo-artic ... a-mission/

https://www.designworldonline.com/nye-l ... telescope/

Pennzane oil. I almost read Pennzoil when I first saw it, lol.

I guess I must've tweaked your interest a bit with my post. Thanks for the links. I almost read Pennzane as Pennzoil too.

So I tried to lookup multiply-alkylated cyclopentane (MAC) Pennzane™ oil for more details.

Multiply-alkylated cyclopentanes (MACs) are composed of one cyclopentane ring with two to five alkyl groups substituted on the ring. They are synthesized by reacting dicyclopentadiene with alcohols of various chain lengths producing a lubricant with a selectable range of physical properties.

OK then, that's gettng too deep for my rudimentary knowledge of chemistry, but sounds cool and I guess it works.

A little off topic...

You also tweaked my interest by mentioning "jewels" in a wrist watch. I never thought to try to understand what that meant. Now I know.
https://en.wikipedia.org/wiki/Jewel_bearing

The advantages of jewel bearings include high accuracy, very small size and weight, low and predictable friction, good temperature stability, and the ability to operate without lubrication and in corrosive environments.

Jewel bearings remind me of the (mostly) obsolete use of Journal (or plain) bearings in railroading. The axle end of each wheelset simply rode under a bearing surface with no rollers. They did however support heavy weight, generated lot's of heat, needed lubrication and could hardly be called Jewels.
https://en.wikipedia.org/wiki/Plain_bearing

I learned something today.

[Jlabute]

I learned something today.

Me too! I see the previous Nye Lubrication task was Perseverance on Mars. Living in space is tough. High levels of radiation, temperature extremes, how to get rid of heat, how to generate power, and so forth. All the electronics are radiation hardened and made to withstand hundreds of times more radiation than what would occur on earth. I see the same company, Infineon also provided radiation hardened parts for Hubble. JWST will be more exposed than Hubble.

https://www.embeddedcomputing.com/techn ... -telescope

[Jlabute]

JWST is fully deployed! Yippee. No problems unfolding or opening. Almost there.

[Sonny Taylor]

An old 1971 Carly Simon song lyric comes to mind...

Anticipation, anticip ay ay tion is making me late... It's keepin' me wai ay ay ay ay ting.

I wonder how soon "first light" images will be available to the public? Maybe that should read "first heat" (being primarily an infrared telescope).

[Jlabute]

An old 1971 Carly Simon song lyric comes to mind...

Anticipation, anticip ay ay tion is making me late... It's keepin' me wai ay ay ay ay ting.

I wonder how soon "first light" images will be available to the public? Maybe that should read "first heat" (being primarily an infrared telescope).

The telescope is still reflecting and focussing photons. The temperature of the object causes photons to be emitted. Long infrared will heat, but short infrared won’t. Short infrared is used in TV remotes for example. Long infrared in heat lamps. Heat is the transfer of energy between objects brought together, not separated by lightyears of vacuum.