James Webb Space Telescope Emerges Successfully From Final Thermal Vacuum Test (phys.org) 82
NASA's James Webb Space Telescope has successfully cleared its final thermal vacuum test meant to ensure that its hardware will function electronically in the vacuum of space, and withstand the extreme temperature variations it will encounter on its mission. Phys.Org reports: One half of the Webb observatory, known as the "spacecraft element," completed this testing at the facilities of Northrop Grumman, the mission's lead industrial partner, in Los Angeles. The other half of Webb, which consists of the telescope and science instruments, has already successfully completed its thermal vacuum testing at NASA's Johnson Space Center in Houston prior to delivery at Northrop Grumman last year.
In the most recent major environmental test, technicians and engineers locked the Webb spacecraft element inside a special thermal vacuum chamber. The testing team drained the atmosphere from the room to replicate the vacuum of space, and exposed the Webb spacecraft element to a wide range of hot and cold temperatures, spanning from minus 235 degrees Fahrenheit (minus 148 degrees Celsius) to a sweltering 215 degrees Fahrenheit (102 degrees Celsius). This variation of temperatures ensures the spacecraft will survive the extreme conditions it will actually experience in space. "The next steps will be to join both halves of Webb to form the fully assembled observatory and complete a final round of deployments, testing and evaluation prior to launch," the report adds. "A full deployment of the spacecraft element will verify that Webb is ready to proceed to the launch site."
In the most recent major environmental test, technicians and engineers locked the Webb spacecraft element inside a special thermal vacuum chamber. The testing team drained the atmosphere from the room to replicate the vacuum of space, and exposed the Webb spacecraft element to a wide range of hot and cold temperatures, spanning from minus 235 degrees Fahrenheit (minus 148 degrees Celsius) to a sweltering 215 degrees Fahrenheit (102 degrees Celsius). This variation of temperatures ensures the spacecraft will survive the extreme conditions it will actually experience in space. "The next steps will be to join both halves of Webb to form the fully assembled observatory and complete a final round of deployments, testing and evaluation prior to launch," the report adds. "A full deployment of the spacecraft element will verify that Webb is ready to proceed to the launch site."
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Wake up and look around, unemployment is bad only in the sense there is almost none! The economy can easily absorb thousands from the military and they might end up doing something beneficial for humanity.
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Dracarys
Why wouldn't electronics work in a vacuum? (Score:2)
I took a few simple electronics classes in college years ago, so I'm not exactly an electrical engineer. But I don't remember atmospheric pressure being something we studied much as affecting electronics. Why would any electronics be expected to function differently in a vacuum?
Re: Why wouldn't electronics work in a vacuum? (Score:5, Informative)
All sorts of things can go wrong, probably largely associated with outgassing -- especially if it built up and then released suddenly. Various epoxies and probably even circuit boards might, I imagine, be potential candidates. Remember: you're removing 14.7 ponds per square inch of pressure that might be (say) helping to hold together layers of a PCB.
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The other thing too is that if you are testing thermal effects, the atmosphere will potentially affect the flow of heat. For example, if you are heating the telescope on one side (to simulate sunlight), you want the opposite side to get no external heat. An atmosphere will increase in temperature and allow heat to flow from it to the cooler side of the telescope .
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Lack of passive cooling, out-gassing of magic pixie fluids, static charge accumulation, massive spontaneous whisker growth, and probably 1001 other things that you don't realise can screw you over until you actually try it.
Oooh. Good point re: static. (Score:2)
Hadn't thought of that. But, yeah: it's one of those "if you DON'T test it, and something goes wrong, boy jeepers, will you have egg on your face" things.
Re:Why wouldn't electronics work in a vacuum? (Score:5, Informative)
I took a few simple electronics classes in college years ago, so I'm not exactly an electrical engineer. But I don't remember atmospheric pressure being something we studied much as affecting electronics. Why would any electronics be expected to function differently in a vacuum?
The issue isn't air pressure; it's temperature. Without airflow and convection, heat moves very differently in vacuum than in air. Spacecraft that do not passively satisfy their thermal needs (which is pretty much anything larger than a CubeSat, and even some of those require thermal mitigations) use heat-pipes to conduct heat from hot parts to radiator panels, but in general these are much less effective at rejecting heat than an equivalently-sized system on Earth.
This is especially challenging for JWST, because its mission is to observe the far infrared (from 600 nm -- red -- out to 27,000 nm), so by Wien's law, you can figure that if there's anything in the optical path as "hot" as ~100 K (-173 C, -280 F) it will swamp the detector with noise. And that's just to get the peak emission wavelength below 27 um; to keep the entire blackbody curve out of the detector's band, everything needs to be kept even colder than that (Wikipedia says 50 K / -220 C / -370 F).
I don't think there are any semiconductors in production that can function at that temperature, so the questions being answered by these thermal-vacuum tests are, can the electronics be kept at their required temperature under all circumstances (whether they are directly exposed to sunlight or are in the shadow of the sunshield), and can that heat be kept away from the optical system?
Re:Why wouldn't electronics work in a vacuum? (Score:4, Informative)
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Its still good to do a system level test even if the sub systems have been tested. The telescope and electronics housings are going to expand and contract quite a bit with temperature changes. Electronic connections could work lose, wear against each other etc.
This should all be fixed by design, but its a huge system with a lot of engineers and mistakes can happen. Better to find problems now than when its in orbit.
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Great question.
Analog Devices [analog.com] has an informative answer, and offers more to consider regarding space-compatible devices.
The vacuum of space is a favorable environment for tin whiskers, so prohibited materials are a concern. Pure tin, zinc, and cadmium plating are prohibited on IEEE parts and associated hardware in space. These materials are subject to the spontaneous growth of whiskers that can cause electrical shorts. Tin whiskers are electrically conductive, crystalline structures of tin that sometimes grow from surfaces where tin is used as a final finish. Devices with pure tin leads can suffer from the tin whiskers phenomenon that can cause electrical shorts. Using lead-based solder eliminates the risk of shorts occurring when devices are used in high stress applications. Finally, the space radiation environment can have damaging effects on spacecraft electronics. There are large variations in the levels of and types of radiation a spacecraft may encounter. Missions flying at low Earth orbits, highly elliptical orbits, geostationary orbits, and interplanetary missions have vastly different environments. In addition, those environments are changing. Radiation sources are affected by the activity of the Sun.The vacuum of space is a favorable environment for tin whiskers, so prohibited materials are a concern. Pure tin, zinc, and cadmium plating are prohibited on IEEE parts and associated hardware in space. These materials are subject to the spontaneous growth of whiskers that can cause electrical shorts. Tin whiskers are electrically conductive, crystalline structures of tin that sometimes grow from surfaces where tin is used as a final finish. Devices with pure tin leads can suffer from the tin whiskers phenomenon that can cause electrical shorts.
Using lead-based solder eliminates the risk of shorts occurring when devices are used in high stress applications.
Finally, the space radiation environment can have damaging effects on spacecraft electronics. There are large variations in the levels of and types of radiation a spacecraft may encounter. Missions flying at low Earth orbits, highly elliptical orbits, geostationary orbits, and interplanetary missions have vastly different environments. In addition, those environments are changing. Radiation sources are affected by the activity of the Sun.
Again, great question.
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Great question.
Pure tin, zinc, and cadmium plating are prohibited on IEEE parts and associated hardware in space. These materials are subject to the spontaneous growth of whiskers that can cause electrical shorts.
Well, I need to shave every morning or I look scruffy. So I don't see why hardware in space should be treated like snowflakes.
Teach them proper bodily hygiene, and make them shave every morning. As well as brushing their teeth.
Philips probably has space graded razors and toothbrushes. Otherwise how could folks on the ISS shave and brush their teeth?
Although, Philips will kill the budget with the costs of replacement blades and brushes.
Again, great question.
Thank you, Sir! Seriously, despite my weak humor, your's is a grea
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Thank you. I see that you are Brexit woke. I love that drama. I want what's best for the UK, whatever that is. I binge on www.parliamentlive.tv/Commons and Bercow's interests in explaining stuff along the way interests me very much.
In the spirit of weak humour, which I also enjoy, I, sadly, have to call you an insensitive clod for not including references to cloud, blockchain, AI and deep learning.
But, since you're a respectful bloke, I gift to you the buzz words, "freedom gas," and "molecules of U.S. freed
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The electronics themselves wouldn't be affected, but the encapsulating materials and construction techniques could be vulnerable to the temperature/atmospheric extremes.
Re:Why wouldn't electronics work in a vacuum? (Score:5, Informative)
They don't, generally. The points of thermal vacuum testing are:
- making sure the thermal model of the spacecraft is ok, i.e. it won't overheat or get too chilly, and all parts remain within their designated temperature range. This is called a thermal balance test, and it's a fairly big deal. Sometimes a thermal balance test will result in minor modifications, such as painting a part of it black, or enlarging a radiator or something.
- making sure all parts are able to deal with the stresses of thermal expansion. This is called thermal cycling tests, and typically a spacecraft goes through 8 or 9 hot and cold cycles before it is cleared for launch.
Source: I've been doing thermal vacuum tests for the past 22 years, and I'm in charge of the software that controls thermal vacuum tests in ESA's test center.
When JWST gets first light... (Score:1)
Re:When JWST gets first light... (Score:5, Informative)
I would want it to take 24 hour series of pictures of earth
You know we've had that literal exact thing, for the last 4 years, continuously. [nasa.gov]
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I would want it to take 24 hour series of pictures of earth so that flat earth retards can try to dispute that. Of course I know that flat earth retards do not even believe that JWST is in space, but of course you cannot please flat earth retards.
The only thing that would satisfy them is personal observation but they are too close-minded to accept that such observation is possible from ground-level with a modicum of thought. The obvious one is to measure angle of pole star above the horizon at different latitudes, coupled with the observation of opposite seasons in the northern and southern hemispheres. Anyone can make those measurements and the only explanation for the result is a spherical Earth. No conspiracy can influence the outcome. It's inter
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Or, we could stand on the shoulders of giants.
The earliest reliably documented mention of the spherical Earth concept dates from around the 6th century BC when it appeared in ancient Greek philosophy, but remained a matter of speculation until the 3rd century BC, when Hellenistic astronomy established the spherical shape of the Earth as a physical given and calculated Earth's circumference.
The paradigm was gradually adopted throughout the Old World during Late Antiquity and the Middle Ages. A practical demonstration of Earth's sphericity was achieved by Ferdinand Magellan and Juan Sebastián Elcano's expedition's circumnavigation (1519–1522).
More at this Wikipedia article [wikipedia.org].
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Why waste time on them, someone has to flip our burgers so if they are fine with not getting an education, don't disturb them.
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so that flat earth retards can try to dispute that.
What exactly is wrong with you that those idiots are even on your radar??
Just hope they don't botch the mirror... (Score:1)
They goofed on how microgravity would impact Hubbell, and it was almost disastrous. I'm sure they learned from that, but my fingers are crossed nonetheless.
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It was the orbit and attitude that oh so precisely doomed the Hubble.
There was a defect in the mirror and you're making up dumb shit.
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Welcome to /. We're glad to have you here.
I, too, way long time ago, posted random bullshit so I could see my work on the Internet.
We all have done that (I'm talking to you, "me too," AOL newbies).
Anyway, you're wrong and I'm going to take the time to teach you how I got the answer I posted.
In your search engine (if that term is confusing, let me know in a reply) type "1990 Hubble Space Telescope" without the quotes.
Among the "answers," (results of the search) I found this snippet from https://www.history.n [nasa.gov]
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Uhhhh ... My response was to the AC, not Slartibartfast ( 3395 ).
Re:Just hope they don't botch the mirror... (Score:5, Informative)
They goofed on how microgravity would impact Hubbell
Em, no, not at all. They had their optical test stand on Earth set to the wrong focus so the mirror was ground to the wrong focal point.
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I'm with you.
My biggest fear is that the mission will be scrubbed. My fingers are crossed, as well.
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I suppose if they scrub the Webb they can keep the space station floating for a few extra months.
Ordinary people understand a space station. It has people in it. But a cold and distant telescope? We already have lots of pretty pictures of stars.
I am actually pleasantly surprised that NASA does any science at all.
"final" test? (Score:3)
"The next steps will be to join both halves of Webb to form the fully assembled observatory and complete a final round of deployments, testing and evaluation prior to launch,"
So it's still not ready to launch, and there are potentially many more opportunities for issues to crop up pushing it's budget even higher then its already astronomical 10 Billion dollar price tag. Don't get me wrong, I think NASAs budget should be doubled and a lot of the strings that Congress attaches to various projects (build the engine in my district, open a research center in mine, etc or no money) should be cut, but the procurement process needs a complete overhaul. The cost plus contracts need to be ended and contractors shouldn't get a dime until they achieve verifiable project milestones. If they fail at any stage of a contract all of the hardware, software and documentation developed up to that point is turned over to NASA to rebid the contract without losing the previous work. It's to be expected that projects will run over-budget once in a while, but lately every major NASA project has doubled (or more) it's initial budget (Constellation, SLS, JWST, etc).
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"The next steps will be to join both halves of Webb to form the fully assembled observatory and complete a final round of deployments, testing and evaluation prior to launch,"
So it's still not ready to launch, and there are potentially many more opportunities for issues to crop up pushing it's budget even higher then its already astronomical 10 Billion dollar price tag. Don't get me wrong, I think NASAs budget should be doubled and a lot of the strings that Congress attaches to various projects (build the engine in my district, open a research center in mine, etc or no money) should be cut, but the procurement process needs a complete overhaul. The cost plus contracts need to be ended and contractors shouldn't get a dime until they achieve verifiable project milestones. If they fail at any stage of a contract all of the hardware, software and documentation developed up to that point is turned over to NASA to rebid the contract without losing the previous work. It's to be expected that projects will run over-budget once in a while, but lately every major NASA project has doubled (or more) it's initial budget (Constellation, SLS, JWST, etc).
The overhaul for certain, but there's a few major points that are ignored or contradictory in your statements.
With initial budget under-bid and undercut, it is automatically going to cause over-budgets when reality sets in. Also, what is criticized as "over-budget" today is often simply reaffirmation that originally approved budgets were truly undercut (and originally estimates were indeed more accurate than the over-estimations claims the critics throw around at the time).
The various aspects to a pr
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This type of project is generally pushing the envelope on performance and that sort of work hard and unpredictable. Sometimes problems are uncovered that no one expected. There is also no magical way to do an accurate estimate of engineering effort.
When engineers are making a new device that is similar to many others, they can make reasonable predictions of effort, but not for something liie this.
If a company did this, they would have to charge an enormous amount to absorb that risk. The budgeting is als
wake me up when it's done (Score:2)
boom (Score:2)
I just hope it doesn't explode on its way to space.