Back From Utah

For those who are wondering, I finally got the thesis wrapped up and submitted for publication on Monday. My final thesis committee member got back from camping, signed the thing off, and after an afternoon of running around, I had the thesis in and all the rest of the paperwork in for graduation. The paper was a lot more solid this time, and a lot more focused. I think I cut the main body back by over 1/3 compared to what I submitted for defense. Unfortunately, I won't be able to publish it on my blog anytime soon, because the Tech Transfer Office wanted to keep it under wraps for at least long enough to file a provisional patent. I'll make sure to put it up here once they're done. Also, I'm planning on continuing the work a bit in my spare time.

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...]

Thesis Update: The Continuing Story Continues...

It's been a while since I posted anything, and I figured it was time to give an update. After the defense on the 3rd, I spent most of the next week pretty much rewriting my whole paper, and redoing one of the key experiments. Although it was a lot more rework than I expected, it was definitely worth it--the thesis is a lot more solid, and a lot more concise. I think I cut the main body of the thesis down to about 80 pages, with about 40 pages of appendices. I made the prints on the nice paper, and now have all but one signature needed. Unfortunately, the last committee member is out of town until Monday (and has been out of town almost the whole time since my thesis defense), so I'm pretty much stuck waiting around until he gets back. The annoying thing is that he may very well have some feedback he wants me to incorporate, so I might be stuck around here even longer. It's kind of amusing how one-week trips to Utah tend to turn into month long trips when it's my family.

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...

Thesis Progress and Jimmy Bloggin

Well, the long hard thesis slog continues. I'm just finished analyzing data from one of the main experiments that I had to redo as part of the thesis revision. In this experiment, I measure the magnitude of the impedance of the coupled piezoelectric/nozzle system at a whole bunch of different frequencies, and then compare that frequency response against what my model predicts. I've made several improvements since last time including using a digital camera to catch both voltages and the frequency from the oscilliscopes instead of trying to pick an average value and write it down. I'm also taking more data points at more frequencies. This should give me a better curve, and better data on the experimental error. It also helps that I stumbled across the fact that I've been using the wrong data from the wrong type of piezoceramic for the past few years. I thought I had bought Pz-28's from Ferroperm, when in reality I had bought Pz-26s. Both materials are hard PZT type ceramics with low dielectric and mechanical losses, but the Pz-26 material is slightly stiffer, and has a few minor differences.

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:

Not Out Of The Woods

So, I defended my thesis today. And "passed with qualifications", which means that they had some things they wanted me to fix before they'd sign off on it. Unfortunately, the qualifications include basically rewriting much of the thesis, and then coming back to re-defend it sometime soon. Oh, and did I mention that the absolute hard deadline for having the thesis defended, approved, and submitted for binding is the 20th?

...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.]

Safely in Utah

Just wanted to let everyone know that I made it out to Utah today. I'll be defending my thesis on Tuesday, so I've got a couple of days to put together my presentation, and polish up the thesis a bit. I'll be out here till around the 7th or so, with the hope being that after the defense, I can take care of any needed paperwork, as well as possibly getting the final thesis revision polished and submitted to the Library. If all goes well, I may head home with everything signed off for graduation in August.

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!

Thesis Update

Just wanted to let everyone know that I got my thesis sent off to my committee today. I still need to get all of them to sign off by tomorrow on it being ready for defense, but the it looks like I've made it! If all goes well, on the 3rd of next month I'll be defending my thesis, and I should have it submitted for publication by the middle of July. Once I have an electronic copy of it online there at BYU, I will post a link here. The paper came in shorter than I expected, with only 174 pages including the university pages at the front, and the reference list and Appendices at the back. I think the modeling approach I took is something I can be confident defending. I wasn't able to perform the final validation experiment due to the piezoceramic rings breaking (due to me being retarded during assembly), and it's unclear if I'll have replacements in time for the defense date, but otherwise I think I did pretty well.

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.]

Thesis Photos

I just thought I'd show you some of what I've been up to lately. Before we could do the jet pulsation tests, we needed some good steady-flow tests to demonstrate that we had a system that could accurately detect jet modulation photographically, and that our steady-state jets were smooth enough for easy comparison. Mike Massee from XCOR helped me take the following set of pictures:


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...

110 Pages Down...

Just thought I'd give an update real quick. Last week was a blur.

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.

Busy Out of My Mind

Hey guys, I'm going to be busy out of my mind as I start the last two weeks before my thesis has to be finished and ready to defend, most likely pulling 40-50 hours a week on that on top of the 40 hours a week I'm working at MSS. I was able to get a strobelight (actually the university is shipping out the exact one I had been using previously), so I should be in business again as far as that is concerned, but most of the work I have left to do (all ~55 remaining tasks) is writing, and revising some of the old stuff I've previously written. I've got a much better feel for how I want to write the thing, and it might just be possible for me to get this done.

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).

Another Thesis Bleg: Short Pulse Duration Stroboscope

I figured it might be a good idea to bring this one up on the blog, just in case. Over the weekend, I finally got my flow test rig setup for my thesis. The rig is pretty similar to the fuel half of our igniter cart--basically it's just a fluid tank with a regulated pressure input, some fill plumbing, and a valve between it and the water jet nozzle. I should have the linear amplifier for driving the piezoelectric crystal fairly soon (Charles Pooley of Microlaunchers is helping me out with the design--he's very good at analog electronics design).

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

Thesis Layout Bleg

So, I've been slogging along with my thesis, trying to get everything wrapped up on time. I have a month from yesterday to get the experiments, models, and paper wrapped up to the point that my advisers are willing to sign off on me being ready to defend. I've gone back through my thesis, trying to add in all the stuff I've done since I last stopped writing (back in 2004 or so). I originally had about 70 pages worth of stuff written, and I'm almost through bringing the first 50 pages or so (Chapters 1 and 2) up to snuff. However I'm now running into a challenge in the layout of the paper, and I was wondering if I could get some suggestions (seeing as how my whole thesis committee is out of town).

As I understand it, the general format recommended goes something like this:

• Chapter One: Introduction--Here you give a basic introduction to what the problem is you're trying to solve, what benefits it would provide, what specific question you are trying to answer (the thesis statement), what other applications there might be for the topic, and what delimitations you're putting in to prevent the thesis from getting too nasty.
• Chapter Two: Literature Review--Here you discuss all the papers and books that you've found on the topic that are relevant, and give a basic introduction to the specific areas of specialized knowledge you're going to be using in your thesis.
• Chapter Three: Methodology--Here you lay out the experimental and analytical methodology you're going to use in your thesis, including discussions of your models, and what tests you will perform (and how).
• Chapter Four: Results--Here you discuss the results that you get from carrying out your methodology. You discuss the experiments and the data, you discuss the models and what they predict, etc.
• Chapter Five: Conclusions--Here you basically try to tie everything together and determine if you were able to answer the question, and if so what was the answer
• Chapter Six: Future Work--Here you lay out areas that you either delimited in chapter one or that came up during research that might be interesting to investigate in the future. You can also discuss what other steps need to be taken before your technology can be applied in the real world.
  

Or something to that effect.

However, I have a bit of a problem. For me, I didn't know much about the problem at hand when I started (nor did any of my advisers), so I had to take a much more iterative approach. I made several prototypes, trying to figure out what would work and what wouldn't. Some of that fed back into the modeling. I also ended up iterating several times on the models as data came in showing I needed to add complexities like damping, or was able to determine that the amplitude of the displacements was small enough that I could drop some terms in some of the models.

My original plan was to just add an additional two chapters: preliminary methodology, and preliminary results before the model refinement and final results chapters. However that seems really kind of kludgy. Not to mention the fact that after Chapter 2, I already have about 50 pages of text and graphics (not counting the 12 pages worth of stuff from the title page till Chapter 1 starts or the several pages worth of bibliography, or any of the apendices). I'm worried that at the rate I'm going, my thesis may end up being a whopping 150-200 pages thick by the time I'm done with it (if I manage to finish it at all).

So does anyone have any thoughts or suggestions? Anyone else been down this road? Any examples of a good thesis that I could look at for ideas?

ISDC Regrets

I should've put this up a few days ago when I first made up my mind, but I've been so busy I haven't even had time to think. Basically, due to how close my thesis deadline is, I'm not going to be able to go to ISDC.

I finally have all the of the models just about done (with all the hard parts done, just some tidy-up work needed), and I have most of the hardware I need to run the validation tests I wanted to. But I'm down to a month to get all the paperwork done, run the experiments, finish writing the actual paper, etc. I went back through and am almost done with revising my first and second chapter (which will probably account for 50 pages by the time I'm done), but I have a lot of work to do. Particularly, I'm trying to simplify the paper and combine the preliminary work I did into the methodology section in a way that works...and my brain is about to give up for the night.

Anyhow, I'm sorry to let you all down, especially after the absolutely amazing response I got when I first put up the Tip Jar. I actually raised more than enough money to go. But it was a foolish decision on my part, I should've known that signing up for a conference right before I need to have my thesis done was a bad idea.

I want to make it up to the people who donated money so I could go by offering to go to a different conference instead. NewSpace 2007 happens right at the end of my post-defense deadline for getting everything 100% wrapped up, so I probably can't attend that one, but there's the Smallsat conference in August or the AIAA Space 2007 conference in September. I've always wanted to go to SmallSat conference, and it happens to be the same week as graduation (with the conference ending the day before graduation), so I'll actually be up in the area anyway. Space 2007 on the other hand is just down in Long Beach, so it's fairly close. What do you all think?

Why Blogging Has Been a Little Light Lately

Thesis Bleg: Bessel Functions and Complex Numbers Question

A couple months ago, I posted about endurance, and when it is best to stay the course vs when it's best to cut bait. One of the examples I gave was my thesis. I wasn't sure if staying the course made sense, or if I should change topics. After a lot of deliberation, last month I determined that staying the course was the best route, and have been slogging away at the thing (which is a big part of why blogging has skimped out lately). I'm starting to get some real traction in several areas, having found some very useful papers, and making some progress on the modeling side of things.

So I have a question for any hardcore math nerds.

In my model for radial vibration of a piezoelectric crystal, I get an equation for the radial displacement as a function of the radial location (at rest), and time:

ur(r,t) = [A * J0 (k * r) + B * Y0 (k *r)] * cos (omega * t)

Where J0 and Y0 are Bessel functions of the first and second kind (0th order) respectively, k is omega/vp, omega is the driving frequency for the piezoelectric crystal, and vp is the speed of sound of the crystal in I think the thickness direction. Vp = sqrt (c11/rho), where c11 is the stiffness in the thickness direction, and rho is density. The problem is that in order to model losses, c11 is really a complex number, with the real part being analogous to the static stiffness, and the imaginary part being the "loss modulus".

Anyhow, the problem I have is that the complex number is inside the Bessel Function, and I was having a hard time figuring out how to handle that for my model. I've came up with an idea, but wanted to run it past some more eyes.

Ok, so since the stiffness, c11, is complex, the velocity is also complex, so you can sub in vp = vr - i * vi, where vr is the real component of velocity, and vi is the imaginary component. So the term inside the Bessel function becomes:

(omega * r) / (vr - i * vi)

My thought was, what happens if you multiply the top and bottom by (vr + i * vi)? If I'm doing the math right, I get:

(omega * r * (vr + i * vi))/(vr^2 + vi^2)

The bottom term is just the square of the magnitude of the complex velocity, ie |vp|^2. Splitting things up a bit, and subbing in term |k| = omega/|vp| you get:

|k| * r * vr/|vp| + i * |k| * r * vi/|vp|

Basically, the left hand side looks just like the "k * r" term in the original formula multiplied by a term that is just the magnitude of the real over the magnitude of the complex velocities. The right hand side is just the imaginary version of the same. Now, |k|, vr, vi, and |vp| are all just constants based on the density, the static stiffness, the quality factor of the material, and the driving frequency of the system.

So, the Bessel functions appear to be in a form like this:

J0 ((A + i * B) *r)

The two big questions I have (other than have I made any obvious math errors so far?) are:

1. Are Bessel Functions distributive?

Ie, does J0 ((A + i * B) *r) = J0 (A*r) + J0 (i*B*r)?

2. Since the Modified Bessel Function (I), is represented as In(x)=(-1)^n * Jn(ix), can I then rewrite this all as: J0((A+i*B) * r) = J0 (A*r) + I0(B*r)?

If both of those are true, I may finally have figured this out. Can anyone shed any light on that?