The long awaited launch of the James Webb Space Telescope has slipped another day to Christmas morning. The launch window opens at 7:20 AM EST, 12:20PM UTC. There are no kids around the house to be anxiously awake on the big day, so I guess I'll have to set an alarm.
As we are all eagerly anticipating launch, you might be wondering how to watch the launch and what to expect. Good news! NASA and its partners are planning a launch broadcast celebration that will be viewable in several different ways. Live countdown commentary and launch broadcast will begin at 6 a.m. EST (11:00 UTC) on Dec. 25 and air on NASA Television and the agency’s website, as well as YouTube, Twitter, Facebook, LinkedIn, Twitch, Daily Motion, Theta.TV, and NASA’s App. You can also join the Facebook event to watch the launch live and interact with others watching the launch. The launch broadcast will continue until approximately one hour past launch, to follow the first several critical milestones post-launch. The actual launch window opens at 7:20 a.m. EST (12:20 UTC) and lasts for 31 minutes – we can launch at any point during that window.
—Amber Straughn, Webb deputy project scientist for communications, NASA’s Goddard Space Flight Center.
As a reminder, this launch is by the European Space Agency and is taking place in Kouro, French Guyana, which is important to me because I can't go outside to watch it. This is a scary-complex mission and I did more of an overview of the program in early September, but once launched there's on the order of 300 steps that have to operate as intended if the telescope is to be successful.
The telescope primary mirror is made of hexagonal mirror tiles and is hinged
to be made small enough to fit into the Ariane 5 launch vehicle. Those
need to be unfolded and locked into final position to fractions of a
wavelength of light in order for the telescope to work. It's an
exceptionally sensitive infrared telescope that will be in orbit around the
sun, not the Earth, at the
L2 LaGrange Point
(graphic of the LaGrange points) over 932,000 miles from Earth. That
means there's nothing to shade that exceptionally sensitive heat detector
from the sun - unless they build it onto the telescope. The folded
telescope is on a sun shield base roughly the length and width of a tennis
court - 69.5ft long by 46.5 feet long. That will need to unfold for the
telescope to be shielded from the sun. To borrow from my September post.
This is a high stakes gamble - of your money, if you're an American taxpayer. Most of you will remember that the Hubble Telescope had a poorly made primary mirror that had to be fixed with corrective optics before it could focus properly. That kind of error would end this mission.Unfurling the 21-meter-long telescope in deep space requires 50 major deployments and 178 major release mechanisms. All of these systems must work or the instrument will fail. There is no easy means of servicing the telescope at its location near a Sun-Earth LaGrange point 1.5 million km from Earth, or four times the distance to the Moon.
If you've been watching the activities at Boca Chica, you've seen Booster 4
(B4) get at least two cyrogenic tests; a
partial test last Saturday, and a
more complete set of tests Tuesday.
On December 17th, SpaceX subjected Super Heavy B4 to a cryogenic proof test about twice as ambitious as B3’s, filling the booster maybe a sixth of the way with a few hundred tons of liquid nitrogen (LN2). What isn’t clear is if that test also raised the booster’s propellant tanks to flight pressures (6-8 bar or 90-115 psi). If Booster 4 did reach those pressures, the test is even more significant – partially proving that the rocket is ready for flight. On December 21st, SpaceX performed a similar series of cryogenic tests, again partially filling Booster 4 with about the same amount of liquid nitrogen but doing so two or three times in a row. Again, the Super Heavy survived the several-hour ordeal without any obvious issues. Still, a number of additional tests – some even more important – are still in front of SpaceX and Super Heavy B4.
The obvious tests are to fuel B4 completely. It's possible they'd use liquid nitrogen
(LN2) instead of the actual liquid oxygen (LOx) and methane (LCH4) Super Heavy is designed to fly with for an early test. LN2 is denser than both LOx and LCH4, so partial tank loads of LN2 could get B4 up to full lift off weight, if that's a valuable test.
There are many steps to go before the first launch of a Starship and Super Heavy mission. They have yet to do a static firing of 29 engines and my guess is they'll probably start with a small number and add more engines gradually until the full 29 get tested. I can see a lot of WDRs (Wet Dress Rehearsals) happening in the next several weeks. It would be crazy to try to peg a date for the first flight, but I think the chances of a launch in the first week of January are about zero. Perhaps by the end of the month.
Watching SpaceX charge forward at this rate has been one of the major highlights of the last two years for me. I'm not in the biz any longer, but I have a pretty good idea of what their test crews are going through, and my hat's off to them!
ReplyDeleteYeah, it has been fun watching them - both Boca Chica and from the yard. I don't think any government or company has put up 31 orbital launches in a year, and they're saying, "hold my beer."
DeleteAll I ever worked on were a few payloads. Very different in that there are always schedule pressures, but the closer you get to launch day the more pressure there is.
We'll see about Webb. I bet it's postponed until next year.
ReplyDeleteAs to SpaceX, glad to see they're charging along. Can't wait to see what's next in store for all of us space watchers.
Next year as in a week from now or as in months and months?
DeleteMy own guess is that postponing a long time isn't very likely. At this point, having worked on the system for nearly 20 years, they either had to say they're ready for launch and ship the thing or keep screwing with it. Time to go for broke. If they did something to it and broke it badly, such that "it has to go back to the shop," that's one thing, but I think we're past that possibility.
I think it's going to launch tomorrow or within a few days.
Whether or not it gets to L2 and operates successfully is a bigger question. I'd like to see it, but I sure wouldn't bet more than a cup of coffee on it.
Anonymous at September 9, 2021 at 10:55 PM commented on the "overview of the program in early September" post with:
ReplyDeleteA friend from the NRO, after [Webb's] existence could be admitted publicly, said some of his co-workers were very nervous when stories cropped up in the news asking how well the lens would have worked if it had pointed down at the earth.
How good was it? Read our license tags or read our phone screens?
If anon 9/9/21 at 1055 would like to answer, I'd love to see a response. As I always say, "In God we trust; everyone else bring data and keep your hands where I can see them."
DeleteI don't buy it.
First off, it's an infrared telescope that means it reads heat sources. It's not going to resolve license plate numbers - unless they are a different temperature than the plate they're on, and it's a sharp temperature differential. It's blind to anything displayed on a phone because the temperatures will be the same.
Second off, optical resolution questions all come down to some well known equations that depend on wavelength. Infrared is longer than visible light so the resolution in infrared is less than the resolution in visible light. I don't know what the shortest wavelength JWST can work at, but it is intended for far infrared (to see objects with the most red-shift (farther away)).
Third off, JWST is going to be almost a million miles from Earth (932,000 miles). That makes the angular size of anything being looked at much, much smaller than a spy telescope would see from low Earth's orbit.
That's why I don't think it would be very useful to look for anything on Earth. Use an Earth-orbiting satellite for that.
Let me add that I'm human like everyone else and I might be missing important facts, which is why I want to see data showing me if I'm wrong.
Beans wrote: As to the Hubble, well, it was a disused spy satellite that was designed to be carried to space in the Shuttle
DeleteOops, I misquoted/edited the comment. The NRO comment was about, 'what if the Hubble had been pointed down at Earth'.
The Webb mission's complexity indicates the need for a manned space station. Complex designs that must deploy in zero G are hard to test in one G. A permanently manned space station factory could allow the parts to be assembled and tested in zero G, and sent on the mission only after the design is proven.
ReplyDeleteExcellent point. Move final test to orbit, before packaging the satellite on an upper stage to go out into the solar system.
DeleteOne word: Galileo. No, not the 16th century scientist, the probe to Jupiter named after him.
In a scenario eerily reminiscent of the problems with the just-launched Lucy (satellite to Jupiter's Trojan asteroids), which had its solar arrays fail to open properly, Galileo's antenna failed to fully deploy. In Galileo's case it handicapped the mission. Since the antenna couldn't work at its designed antenna gain, the signals back to earth were much weaker and data rates had to be slowed down to be decipherable here on Earth. I suspect we got less science out of the mission than we could have.
In both of those cases, if the satellites could have been tested in a hard vacuum in their real thermal environment I'd bet those faults could have been found.