You'll have to click on the photo to really see anything. It's FM0 (FM1 and FM2 are much better) when it was close to completion. '1' points to the inner mandrel, the internal cylinder upon which the optic is built. I don't know what it's made of, but maybe someone will reveal that in a comment, or I could ask, if anyone is curious. (I probably know more about it, but at the moment I can't locate that information in the thorny tangle of my brain.) The first step in building an optic is to mount the inner mandrel in a lathe. It is then precisely aligned with the carriage.
Once the inner mandrel is in place, the optic is built entirely of spacers, glass, and epoxy.
Above is an actual spacer, beside which I have cleverly placed a metric ruler. As you can see, the spacer is about 22.5 cm in length. Its height is 1.5 mm and its width is 1.2 cm. It is made of graphite. You can write with one, just as you could with a pencil, but it would be a #1 pencil or harder. Almost all of the spacers in the optic are like this. There are two exceptions. The first 6 layers of spacers are 1.6 mm wide. (I have a story about that, but I'll tell it later.) That's to add strength. (Optic components are designed with both strength and weight taken into consideration.) The other exception occurs at the intermediate mandrel, which is pointed to by '2' in the first photo. I need a better photo to explain the intermediate mandrel - I'll take one tomorrow.
(Is that a crack in the glass on the surface above where '2' is pointing? I don't remember, but I think it's a reflection.)
Once spacers are epoxied to the inner mandrel, glass is epoxied to those spacers, then more spacers are epoxied to that glass. The procedure is repeated until the optic is complete.
I'll explain what '3' points to tomorrow.
...to be continued.
3 comments:
http://www.nustar.caltech.edu/uploads/files/hailey_spie2010_7732_28.pdf
says the support mandrels are titanium.
The paper above was presented at a meeting on 28June2010. It said that FM1 would be done in December and FM2 would be done now. A 3 month slip after only 6 months seems like a pretty big deal. If I were to blindly project it out, I'd have to guess that FM2 won't actually be done until mid to late May. Blind projections aren't worth much, though, especially since there's a good chance you've all gone quite a ways up the learning curve. Even if it's 'only' a 3 month slip, it's pretty hard to make up time on the schedule when the project is only one year away from launch.
Given the fact that the James Webb Telescope (successor to Hubble) is $1.5B over budget and years behind schedule, there's not a lot of money at NASA to throw at late projects, especially with the current Congress. I'm guessing it is not impossible that a behind-schedule Small Explorer project like NuStar could be canceled if it goes over budget or is too far behind schedule.
I should stress that I don't have any inside information on this topic and this is total speculation on my part. I do know that this project was canceled back in 2006 via a press conference. Yes, it was done in such a tacky fashion, they didn't even tell the lead scientist. She found out when someone from Europe called and said "I was sorry to hear your project was canceled. Why didn't you tell us?" (BTW, this is NASA's first scientist led mission in which the head scientist is a woman. The "old-boy" network has been slow to admit women in science.)
Those numbers cannot be correct. FM2 wasn't even started until more than a month after FM1 was started. Even if they flipped those, FM1 is now on Layer 104 or so, which means that it will be finished in one month (depending on how long repairs take). FM2 will be finished one month after that. The biggest delays so far have been caused by not getting glass in a timely fashion, although that might be irrelevant.
The December projection could not have been right in any case. I don't remember when we started FM1, exactly, but it was several weeks after I started work in the beginning of July. 133 layers at 6 layers per week is 22 weeks, meaning that FM1 would have been finished, at best, on Dec 25 or so, allowing for no downtime for any reason, including holidays and vacations.
Furthermore, barring further disasters, the final optic, FM2, will be finished by mid-March. It will have to be calibrated and tested. Nevertheless, it will be finished well in advance of the scheduled Feb 2012 launch date.
The maniacal republicans now in control in the House of Representatives are a concern, of course. But I think that most, if not all, of the money for NuSTAR has already been allocated.
Post a Comment