As for the paperwork, I’m going to follow-up tomorrow to make sure that they have everything entered in correctly. However, as of Monday they told me that I had everything in, so it looks like I’ll be graduating after all. Thanks everyone for your support and encouragement!

[Note: We're back in California now, so you can expect more bloggy goodness in the near future. At least once I've caught up at work, and caught up on sleeping...]

Unfortunately this delay means two things. First, I’m not going to be walking at graduation. After missing almost a full month of work, I really can’t afford another big road trip in only a few weeks. Second, this also means I won’t be able to make it to the Small Sat Conference that week either. With how much we need to get done at work between now and October, I can’t really justify taking any more time off until after the X-Prize Cup. But once that’s all over, I’ll try and find a conference I can go to for all those who chipped in money so I could go to ISDC. I haven’t forgotten you all, just have had to change plans several times.

Anyhow, hopefully on Monday I’ll be able to post the last words of this whole thesis saga. Until then, the continuing story continues…

The response curve this time around was a lot closer to what was expected, and by varying some of the material properties around within the tolerances given by the manufacturer, I was able to get this good of a matchup:

Much better than last time. Now that I’ve got this working, the next step is to tie it all together. Of course, the fact that I came down with something nasty today is going to help…

On the happy side, it’s been wonderful to have my family back. I still don’t get to spend too much time with them (except on the 4th and 5th), but it’s so much better having them here than hundreds of miles away. Here’s a picture of James, who figured out how to crawl this week:

…so, don’t expect to hear from me for a while.

[Update: I just heard back from my thesis advisor. It turns out that I have a whole week less to make all the changes then I thought. The department needs the final draft by the 13th in order to get all the signatures and get everything off to the library for the final deadline. So, I only have a week and a half. The good news however, is that because of that, they're dropping the requirement for me to redefend. I just need to make all the changes soon enough that I can get it to all my committee members and have them reread it and actually sign off on it by the 13th. Which means I've really only got a couple of days to rewrite a 175pg paper...]

[Update2: In reality, even though the deadline is moved up, this isn't really that much worse than I expected. "Pass with qualifications" is by far the most common result, I just had a few more changes necessary than I had originally thought.]

Tiff and the boys have been gone for the past two weeks being up with Tiff’s parents in Oregon, and they’ll be driving down with my sister Monday to meet up with me. It’ll be really nice to see them all again–”baching it” is so overrated.

On a thesis related note, last week I stumbled on one last piezoceramic ring while digging through an old box of receipts, and was able to get the nozzle machined to match. Mike Massee and Charles Pooley came over to help me run the last experiment. The results were mixed, but generally positive. We were able to get the jet to modulate, but the modulations appear to have damped out after a short distance:

This was with glycerin at about 500psi feed pressure, and about a 120-150V driving voltage just below the electrical resonance point. The good news is that it is very clear that there was jet modulation going on. It just would’ve been better had it broken up into droplets. In hindsight, it appears that by using a fluid as viscous as glycerin, that the viscous effects dominated the inertial ones enough to cause the jet to resmoth. Water on the other hand (as you could see from my previous post) caused an unsteady enough “steady” jet to make measurements difficult. Maybe I could’ve split the difference and tried a water-glycerin solution.

Anyhow, while it wasn’t ideal, and while it definitely points to the need for some future model refinements, it did validate part of the concept, and some of the observed behavior matched the expected trends, even if the amplitudes were off in magnitude….

Anyhow, that’s a lot of data for me to finish absorbing and wrapping into my thesis, but wish me luck!

I’ll keep you all posted as new developments come up.

[Update: The form is in, and I'm officially scheduled for oral defense on the 3rd of July, 10am in the Mechanical Engineering Department Conference Room at BYU. I've still got to do a lot of polishing work on this paper, especially with cleaning up the format, and fixing any grammatical errors or confusing parts. And then I need to prepare my thesis defense presentation. And all this while we're doing the last few things at work before we get air underneath and a slack tether above XA-0.1...so the it looks like I'll be busy for some time yet.]

This was with one of my abrasive flow machined nozzles (flow machined by Extrude Hone Corporation), using the slower strobe (pulse duration 250 microseconds).

This was the same nozzle, but with the much faster Strobotac (0.5 microsecond flash duration).

And this is the same nozzle flowing glycerin, using the Strobotac strobe. Amazing what a ~650x increase in kinematic viscosity can do eh? It’s hard to believe, but the glycerin jet in this photo is going somewhere between 30-35 meters per second!

For comparison, here are two pictures of a new nozzle that wasn’t abrasive flow machined:

Notice that in spite of the fact that the second nozzle was much rougher with the water flow, that both of them were perfectly smooth for the glycerin flow. This is good because it means that for experimentation and verifying the pulsation characteristics, you can demonstrate the concept using a more viscous fluid first, then once you have the concept figured out, you can go back and do all the fancy manufacturing processes to your nozzles to make them flow smoother. It also shows that our photographic test rig is totally up to the task.

Unfortunately…I broke my last set of piezoelectric crystals yesterday trying to fit them onto our latest nozzle. I don’t know if I’ll be able to get a new set in time for my thesis defense. So for now, I’m scrambling to finish getting my paper approved for defense without being able to perform the key validation experiment…

…Anyhow, back to work…

Last Sunday, one of the tenants there in Mojave who stores explosives for the local mines had one of their containers explode. So we were locked out of our test area most of the week.

Then Monday, Tiff ended up having a friend take her to the emergency room in Bakersfield. It turns out she had pancreatitis caused by one of her gall stones getting lodged down in the duct leading to her pancreas. So she ended up having two surgeries last week. One to remove the obstruction, and the second to remove her gall bladder. She’s doing a lot better now, and came home on Friday night.

It was a good thing my little sister ended up coming down from Utah. She was able to help out with the boys, and I borrowed her laptop so I could write my thesis stuff while sitting there in the hospital. Honestly, if that hadn’t happened, I don’t think there’s a chance in heck I could have finished things by the deadline. As it is, it’s still going to be nuts next week, but at least I was able to get a lot done last week.

Chapters 1 & 2 are done, Chapter 4 is most of the way done, and Chapter 3 is done except for the experiment I’m going to run on Tuesday or Wednesday. By tomorrow night I should have Chapter 4 done, and Chapter 5 mostly done (also waiting on those experimental results). Chapter 6 and the abstract will have to wait for Wednesday or Thursday. I currently have about 100 pages of actual real content (not counting the University Pages at the front, or the Appendices at the back). After the defense in July, I’m going to see if I can submit the paper electronically, so I can provide a link for anyone here who’s interested. I’m sure you’re all just chomping at the bit to learn more about piezoelectric modulation of water jets…

Anyhow, I need to get to bed.

My parents are bringing my sister down to help out for two weeks (while establishing her position as favorite auntie to two little boys), which should really help. Tiff’s been having medical problems that more or less made it impossible for me to get any thesis work done during the second half of last week. She’s doing a lot better now, but this is going to be tough.

Anyhow, if you guys want some bloggy goodness, Ken seems to be posting a lot of good stuff lately, and Ian over at the MSS blog has been putting up lots of eye-candy. Life’s been a little big crazy, and it’s going to stay crazy for a while, but the end of my thesis is finally in sight.

I’ll post a brief update next Sunday (since I don’t do school or work or space related stuff on Sundays).

The experiment I need to run involves using high-speed photography techniques to determine if the pulsed nozzle is creating a pulsed flow. In order to have a clear comparison, I’m also doing some runs with no driving voltage on the piezoelectric crystal, basically as a control experiment. The smoother and more stable and steady I can get the unpulsed jet, the more obvious even the slightest fluctuations are going to be for the pulsed case.

I was able to enlist the help of XCOR’s Mike Massee for help with the photography portion, but we quickly realized that the nice strobes he had were far too slow for the task at hand. Those strobes were mostly for the entertainment business, so they had a pulse duration of about 250 microseconds. The problem is that I’m trying to detect oscillations on an 0.33mm jet that’s traveling at nearly 60-80m/s when it leaves the nozzle, and in 250 microseconds, the jet travels nearly 15mm (or about 45 jet diameters)! I ran the numbers, and in order to prevent the picture of the jet from completely blurring, I need to have the jet move less than 33 microns (about a tenth of the jet diameter) during the flash. The problem is that this implies a pulse duration of around 0.5 microseconds.

That’s really darned fast.

I discovered while doing some googling after our test run that the strobe I had at BYU that I thought was so crappy actually had a minimum pulse duration in the 0.5-0.8 microseconds range, and that that was actually on the high end for stroboscopes.

Here’s my problem. The thesis draft has to be far enough along that I can get my advisor to agree that I’m ready to schedule my defense by the 18th. This means that the thing is basically written and that I’m in the last minute polishing phase. The experimental validation is very important, and to drop that at the last second will make it a lot harder for me to get my thesis accepted. Since it turns out that the strobes we have just aren’t even close to what I need to pull this project off, I need to come up with another option. That means I need to come up with either a high speed camera setup, or a high speed strobe (with pulse durations less than 1 microsecond) within the next week.

The company that makes the strobes that I used at BYU (They’re General Radio Strobotac strobes) wants almost $6k for the strobes, and doesn’t appear to rent them. There are a couple of places that sell “nano-pulse” systems that use xenon spark flashbulbs to create a flash of light that lasts less than 100 nanoseconds. Those would be even better than a Strobotac (due to the shorter pulse duration), but as far as I couldn’t find any of those for rent, or for sale used on ebay. It is possible to rent high speed cameras, but they tend to run several hundred to a few thousand dollars just for a day or two, which is out of my price range.

So, my question is, does anyone who reads this know a way I could get my hands on something like that within the next week? Anyone have any ideas?

~Jon