Matt_W
4855
I see it’s already cruised well past the moon’s orbit.
This is why math is cool
https://blogs.nasa.gov/webb/2021/12/29/nasa-says-webbs-excess-fuel-likely-to-extend-its-lifetime-expectations/
After a successful launch of NASA’s James Webb Space Telescope Dec. 25, and completion of two mid-course correction maneuvers, the Webb team has analyzed its initial trajectory and determined the observatory should have enough propellant to allow support of science operations in orbit for significantly more than a 10-year science lifetime. (The minimum baseline for the mission is five years.)
Ephraim
4857
That’s one of the best lines in the movie Don’t Look Up. It’s not much of a spoiler, roughly paraphrasing a conversation about orbital dynamics:
Dr. Oglethorpe: And don’t talk about the math!
Dr. Mindy: It’s all math!
Combination plane change/orbital insertion burn, maybe? I’ve done that in KSP often enough, although from low inclination to a higher one rather than higher to low.
Matt_W
4859
Makes sense. They did do like a 60 minute insertion burn once in space. I’m curious what that inclination is relative to. Thinking about it, the telescope has to be in the Earth’s sun-relative orbital plane (because that’s where L2 is, and it’s where the Earth’s shadow lies, which is the whole point.) We usually measure orbital inclinations relative to the Earth’s equator, but the equator is tilted at like 24° relative to the ecliptic. In fact, that’s why we usually launch moon missions from Kennedy: because its latitude (28°) is close to the plane of the ecliptic twice a day. JWST launched from Kourou and has a low inclination. I wonder how that works. Maybe the published inclination number is relative to the ecliptic and not to the equator?
That had to be scary. There was a delay because one of the sensors failed. The good news is both booms have deployed, and the next step is tensioning and separating the layers.
Matt_W
4861
Just for size reference, that whole sunshield has about the area of a tennis court. There’s a human in the lower left of this photo for comparison:
schurem
4862
So fucking awesome. And so far so good. Here’s to as much success on the 2nd half of the deployment as on the first! :beers:
They’ve begun tensioning the sunshield. It’s a process that should take three days, but it could take longer depending on what they encounter.
Tense days, indeed.
Tension, apprehension, and dissension have begun.
jpinard
4865
I’m not following NASA religiously like normal because I’m just stupid stressed about this, so the intermittent posts are great. Hopefully they continue to be positive ones.
Romalar
4866
So they worked out a couple of smaller problems where they needed to orient JWST and its solar panels slightly differently to get the best power and cooling before proceeding to tension the sunshield.
However, after that delay it’s been going quickly and 3/5 layers of the sunshield are now done. Might be done with tensioning all 5 within a day.
https://blogs.nasa.gov/webb/2022/01/03/second-and-third-layers-of-sunshield-fully-tightened/
All the best Half-Life levels!
Matt_W
4868
The shield is 300 square meters. At 1 AU, radiation pressure from the sun is about 9 uPa, so total force on the sunshield will be about 2.7 mN, which is like 0.01 ounce-force. The telescope’s mass is something like 6 metric tons, so you get an acceleration due to radiation pressure of about 45 nanogees, which is not a lot. (It’s approximately 0 to 60mph in 2 years.) But they have that momentum flap thing to counteract radiation pressure. I wonder if they’re mostly worried about developing torque, not linear acceleration.
schurem
4871
Yay! Three cheers for NASA!
