Ep 50 James Webb Space Telescope

Engineering News – Improved Solar Electricity Performance (1:35)

It’s episode 50! This week we’re talking about an engineering marvel, the James Webb Space Telescope (7:30). The telescope took decades to build (14:00), but it was worth it because it has a lot of really interesting features (25:05)


Engineering News

James Webb Space Telescope

Episode Summary

Hi and welcome to Failurology; a podcast about engineering failures. I’m your host, NicoleAnd I’m Brian. And we’re both from Calgary, AB. It’s episode 50!! The episode number of how old I feel!Thank you again to our Patreon subscribers! For more or less than the cost of a baseball (the MLB ones), you can hear us talk about more interesting engineering failures! That’s $5, and we have a dedicated RSS feed that gets you all of our regular and mini fail episodes in your favourite podcast app. This week in engineering news, improved solar electricity performance.Current solar electricity panels are made from silicone, which is reliable, inexpensive and the structure and performance are well understood. But silicone is also only 20% efficient in converting sunlight to electricity. On top of that, while the panel materials are inexpensive, production can be expensive and complicated.In an effort to lower technology costs, researchers have been exploring the potential of CadTel, which is a mixture of Cadmium, Selenium and Telluride, and currently makes up about 5% of the photovoltaic market. CadTel is 40 times thinner than silicon cells and can be applied directly onto the front glass of the solar panel with vapour transport disposition. These factors can significantly change the manufacturing process and reduce costs of these panels.However, we don’t know enough about the performance, specifically voltage deficits. Researchers at the Arizona State University, Holman Research Group, in partnership with the Centre for Next Generation Photovoltaics at Colorado State University, the National Renewable Energy Laboratory in Golden Colorado, and First Solar In in Tempe, Arizona are working to better understand CadTel and how we can use it to improve solar electricity generation.They are using a measurement technique called external radiative efficiency (ERE) to gather more information. What they have found is that the voltage deficits are not related to interfaces between different materials, which is the common assumption. The issues are related to selectivity, essentially the electrons within the cell go the wrong way and cancel each other out. The selectivity issues tell researchers that the semipermeable membranes are imperfect, which was previously assumed to not be an issue and was overlooked.By doping the absorbers, it can help improve selectivity by only letting the electrons flow one way through the membrane.The external radiative efficiency measurement technique is really the star of this study, because it will allow researchers to test many other advanced materials and monitor device degradation in the field.If you want to read more about the CadTel study, check out the links on the webpage for this episode at failurology.caFake AdNow onto this week's episode. we’re talking about another engineering marvel; the James Webb Space Telescope.There is a lot of information on the telescope. The Wikipedia article alone is over 20,000 words. We can’t possibly cover everything. We are instead focusing on the things we think are most interesting, including an overview of the telescope and its purpose and mission, and then the construction of the telescope. Launched December 25, 2021 at 12:20 Greenwich mean time from Guyana Space Centre, a European spaceport located in French Guyana in South America.It entered service in February 2022JWST was designed primarily to conduct infrared astronomyDevelopment was led by NASA in collaboration with the European Space Agency and the Canadian Space Agency. And cost 9.7 billion USD.Several thousand scientists, engineers and technicians spanning 15 countries contributed to building, testing and integration of the JWST, as well as 258 companies, government agencies and academic institutions participated in the pre-launch project.It was launched on an ESA Ariane 5 rocketJames E Webb was the administrator of NASA from 1961-1968 during the Mercury, Gemini and many Apollo programs.Naming ControversyScientific American released an article in March 2021 urging NASA to reconsider the name based on Webb’s alleged complicity during the Lavender Scare persecution of LGBTQ employees during the Harry Truman administration. For those, like myself, who may not have heard of the Lavender Scare - gay men and lesbians were said to be a national security risk and communist sympathizers with led to a call to remove them from state employment. NASA declined to rename the telescope claiming that there was no evidence that Webb participated in the Lavender Scare. Honestly, I wasn’t there, I don’t know. I have to assume the claim to change the name wasn’t baseless. But as we know from other episodes we’ve done, NASA has made some questionable decisions when it comes to crew safety. ConstructionDevelopment of the telescope began in 1996 with a planned launch in 2007. But the telescope underwent a major redesign in 2005. There were many other delays and cost overruns throughout design and construction, such as a ripped sunshield during practice deployment, an independent review board recommendation, a threat from US congress to cancel the project, problems with the rocket and the telescope itself, communication glitches between the telescope and launch vehicle, and of course covid. Construction was completed in 2016, followed by 5 years of extensive testing.The prime contractor was Northrop Grumman Aerospace Systems (The Grumman part of the company built the Apollo Lunar Module as well as the Grumman LLV, the mail truck that is used by both the USPS and CanadaPost among other things). who developed and built the spacecraft element, including the satellite bus, sunshield, deployable tower assembly connecting the optical telescope element to the spacecraft bus, and the mid boom assembly which deploys the large sunshield.Ball Aerospace & Technologies developed and built the optical telescope element itself and the integrated science instrument module. TelescopeIntended to succeed the Hubble Space Telescope, which was launched in 1990 and still remains in operation. The JWSB will be the largest, most powerful space telescope ever built. It will allow scientists to look at what our universe was like about 200 million years after the Big Bang. The Hubble telescope was great for its time, but now we need a stronger telescope, one that can view objects too old and distant, or sometimes up to 100 times fainter, than what the Hubble can view.It is big. Really big. The sunshield is about 21.2m by 14.2m and 8 meters tall. Scientists are hoping to enable a broad range of investigations in astronomy and cosmology. Hopefully viewing the first stars or formations of the first galaxies. Maybe we will even find other species or a replacement planet. Possibly, but very long duration, light speed travel issues will need to be solved first before colonisation can occur. JWST’s primary mirror, called the Optical Telescope Element or OTE, has 18 hexagonal mirror sections that make up a 6.5m diameter mirror. For comparison, Hubble has a 2.5m diameter mirror. The mirror segments are made of gold plated beryllium. The gold plating provides infrared reflectivity and durability, 48 grams of gold was used in Webb’s mirror construction. The gold plating is 100 nanometers thick. Gold is used as it is highly reflective at infrared wavelengths. The OTE has a diameter almost 3x that of the Hubble, giving JWST a light collecting area about 6.25 times that of the Hubble.The Hubble uses new UV, visible, and near infrared spectra, while JWST uses long wavelength visible light through mid-infrared.JWST has to be kept below 50 Kelvin, or -223C in order to observe faint signals without interference from other sources of warmth. Good thing it’s in space, because fortunate for humans, unfortunate for the JWST, it's not that cold on earth. The Hubble operates at 15C which radiates strongly in the infrared bands.The telescope is orbiting the sun about 550km from earth's surface. Its orbit is such that it keeps out of the Earth and Moon’s shadow. Its five layer kite shaped sunshield protects it from warming by the sun, moon and earth.FeaturesThe telescope design emphasis the near to mid-infrared for three main reasonsHigh redshift (very old and distant) objects have visible emissions in the infrared, meaning they can only be observed with infrared astronomy. Colder objects such as debris and plants emit most strongly in in the infrared The infrared bands are too difficult to study from on earth or with the Hubble.Telescopes on earth have to look through the Earth’s atmosphere which is opaque in many infrared bands. Even where it is transparent, there are many other chemical compounds such as water, carbon dioxide, and methane that exist in the atmosphere.JWST can also view nearby objects and opportunistic and unplanned targets within 48 hours of a decision to do so. The sunshield blocks light and heat from the sun, earth and moon. And its position keeps the sunshield between those objects and the telescope at all times.The sunshield has 5 layers, each as thin as a human hair. It's made from Kapton E, a polyamide film, with aluminium coated membranes and a layer of doped silicon on the sun facing side of the two hottest layers to reflect heat.Accidental tears of the delicate film structure occurred during testing in 2018, delaying the project. The sunshield was hand assembled and designed to fold 12 times to fit in the rocket’s payload.The sunshield blocks about 60% of the sky from one position, but JWST can see all of the sky over a 6 month period.The sunshield is also helped by a cryocooler to make sure the mid infrared instrument stays at its optimal supercool temperature. Can downlink 57.2 gigabytes of recorded data every day with a maximum data rate of 28 megabits per secondAs we mentioned, the telescope's primary mirror is made up of 18 hexagonal segments.Constructing it as a single mirror wouldn't have fit in an existing launch vehicle.There are 132 small motors or actuators that position and occasionally adjust the optics to combat environmental disturbances. The JWST configuration only needs occasional updates every few days to maintain focus, whereas other telescopes have to continually adjust their mirror segments. Each of the 18 segments have 6 positional actuators with another at the centre to adjust curvature of the primary mirrors and another 6 actuators for the secondary mirrors. 18x7+6 = 132.The actuators can position within 10 millionths of a millimetre accuracy.The optical design is referred to as three mirror anastigmat. This is similar to a satellite dish. There is a large primary mirror that collects information and reflects it to the secondary mirror that sits in front of it, which then dials that back to a third mirror either in front of or slightly behind the primary. The secondary mirror is 0.74m diameter and has a fine steering motor.The integrated science instrument module holds four science instruments and a guide cameraA near infrared cameraNear infrared spectrographMid infrared instrumentFine guidance sensor and near infrared imager and slitless spectrographThe spacecraft bus hosts computing, communication, electric power, propulsion and structural parts. The bus is 350kg and supports the 6,200 kg telescopeIt's made of a graphite composite materialMission goalsThe JWST has four key goalsSearch for light from the first stars and galaxies that formed in the universe after the Big BangStudy galaxy formation and evolutionUnderstand star formation and planet formationStudy planetary systems and the origins of life So there you have it, a telescope 26 years in the making. The James Webb Space Telescope is a promising addition to our efforts of space exploration and the fields of astronomy and cosmology. For photos, sources and an episode summary from this week’s episode head to Failurology.ca. If you’re enjoying what you’re hearing, please rate, review and subscribe to Failurology, so more people can find it. If you want to chat with us, our Twitter handle is @failurology, you can email us thefailurologypodcast@gmail.com, or you can connect with us on Linked In. Check out the show notes for links to all of these. Thanks, everyone for listening. And tune into the next episode where we will talk about the Teton Dam. A completely preventable dam failure that decimated towns downstream. Bye everyone, talk soon! Sources:Engineering Newshttps://www.sciencedaily.com/releases/2022/03/220304090344.htmEngineering Failurehttps://en.wikipedia.org/wiki/James_Webb_Space_Telescopehttps://en.wikipedia.org/wiki/Guiana_Space_CentreJames webb space telescope is out of stock