Saturday, June 20, 2009

QinetiQ Ion Engine

I don't know how you feel about space, but I love it. It excites me, and seeing new technology making in-orbit first time qualifications is incredibly exciting, even if I had no part in getting it there.

The is a picture of the European Space Agency's (ESA) Gravity and steady-state Ocean Circulation Exploroer (GOCE) launched in March.

That beautiful blue artists rendition (photo courtesy of ESA's website) is the trail of ions produced by QinetiQ's T5 ion thruster. And forgive me for sounding a little biased here, but it is just my excitement for this program and the fact that QinetiQ has an association with it. I don't know who works for QinetiQ, but everything I have seen come out of that company has been extraordinary, and this is no exception.

SAE's Aerospace magazine has an article (written by Jean L. Broge) about QinetiQ's ion engines, which provoked this blog post. I don't want to plagerize the article, so please read it to get the details about the project.

To summarize: The GOCE spacecraft is a part of ESA's living planet program and is designed to measure the Earth's gravitational field. It orbits at the outer reaches of the atmosphere, about 260 to 280km and therefore does experience disturbances from atmospheric drag. QinetiQ's ion engines must counteract those disturbances in order for the gravitational sensors to function properly. Here's the part of the article that really grabbed my attention.
"This mission would not be possible without QinetiQ's electric engines," said Mary Carver, Managing Director of QinetiQ's Integrated Systems business. "Our space engineers have overcome a challenge that has been likened to compensating for the impact of an insect landing on the windscreen of a car traveling at 100 mph."
How would you like your cruise control to be able to do that?

SAE Collegiate Design Challenges

I know what you're thinking. Why am I talking about collegiate challenges when school is out? Well, it's because many of the challenges happen at the end of the school year, and the results are not that old (2009 Aero Design East Results). Also, many design teams don't take the summer off. I speak from experience when I say that it is a LOT of work to design and manufacture everything necessary for the competition. More to the point, it is expensive. Years full of Ramen Noodles dinners does not prepare you for the added expense of being able to compete.

You see, most teams like the one I was on pay for everything that goes into the airplane, formula, mini-baja, or snow mobile out of pocket. Costs can exceed $5000 plus travel expenses. And the students participating in these challenges spend some time looking for sponsors, but most of the time are busy with school work and designing or fabricating the competition vehicle. They don't have time to market themselves. But the sacrifice is worth it.

I remember my senior year working on the Aero Design Challenge, open class. I won't tell you which one in the picture is me. But, that washed out piece of cardboard at the front of the plane is the award check for getting 1st place and a new world record!
I was on campus by 8:00am each morning. If I didn't have class, I was in the computer lab that early. It was the only time I could find a terminal open to compile my Fortran code. In between classes I was in the student commons area, working on all the homework I just got. After the last class, it was down to the lab building the airplane you see above. The team was there until 1:00, 2:00, and sometimes 3:00 in the morning. Just enough time to get back to the apartment, sleep for a couple hours, shower, and do it all over again. I stayed as long as I could until I started dropping screwdrivers and utility knives on my feet. That's when I knew it was time to go. Steel-toed boots are the best!

Because the aero competition is all about lifting weight, the design you see above is a lifting tail configuration. Anyone who is in the industry knows that lifting tail designs are inherently unstable. My kudos goes out to our pilot to be able to control such a monster, but even he couldn't correct for the first hard learned lesson.

You see, that carbon composite wound boom was designed to be strong and light weight. In our haste, we forgot to consider deflection. We're on the runway for our first test flight. The pilot starts the roll-out and we can see the wing tips starting to lift. Then the tail starts to lift. And then the boom deflects to compensate. And the tail lifts more. And the boom bends more. And the tail lifts until it flips the plane over, smashing the vertical fin and cracking other parts. Flight testing over, back to the lab.

I remember comments from other teams during the competition itself. To elaborate a bit, you keep your design pretty hush-hush as well as the potential weight you think you can lift. Yeah, that's all calculated out wayyy ahead of time. We go into the competition fully aware of where our plane will start falling apart. There were two classes for the Aero Design Competition. The regular class is smaller planes, and the design is limited to wetted area of the lifting surface and so on. Smaller planes means less weight aloft. The open class had design limitations on fuel. Build as big of plane as you can, but the rules of the competition require it to take off within a certain distance, run the rectangular pattern, and land in the same area you took off in. Too big, and you'll run out of fuel on the downwind. Too small, and you won't be able to carry enough weight to bother competing.

Back to my story. Talking to a competitor in the regular class, they were impressed by an open class competitor that stated they needed about 10 lbs of cargo just to get their weight and balance right for stable flight. The regular class lifts around 10-20 lbs during competition. I didn't have the heart to tell him our plane needed 30 lbs. Yeah, just to get the plane off the ground, we needed more weight than the world record holder in the regular class. Think about this for a minute, a baby is born at 6-10 lbs. We're lifting 3 times that. We're lifting a small child into the air just to get started.

These are just two of the many fond memories I have about the experience. I urge all of you to support your alma mater's or local university's participation in the SAE Collegiate Design Challenges. Sponsor your local team. Be an industry expert or consultant. Provide donations like: tools, storage, work space, even Bologna sandwiches. It all helps and creates a wonderful experience for future engineers.

One more picture, for the road.

Thursday, June 18, 2009

Supersonic Air Travel back on the Horizon

The Concorde is well known for its supersonic commercial air travel "across the pond." Air France and British Airways started supersonic service in 1976 and finally stopped service in 2003 after the fatal accident that killed all 113 people on board. If you know any more of the history of the Concorde, you know it only did water routes because the noise from the sonic boom was deemed too loud to expose anyone or anything on land. Of course, limiting flight only to open seas really diminishes the number of routes available to supersonic flight. Yet, many a weary international traveler, combined with some great engineering and business savvy, opens the door to a future business model that includes supersonic commercial air travel. I have been recently made aware of two companies that are pursuing this goal, and they are not Boeing or Airbus.

Of course, we all know that the Boeing 787 Dreamliner is going to be one of the fastest commercial jets on the market, reaching Mach .85. Each new generation of airplane from those manufacturers are quieter, sleeker, more economical, and faster than their predecessors. No doubt they will one day reach a Mach limit where they will have to deal with supersonic transport. But a little closer to that projected date from companies like Aerion Corp and Supersonic Aerospace International. Both of these companies are starting their business plan small, with business jets. I mean, who other than business travelers could afford $10,000 for a Concorde flight? Might as well cater to where the demand is. But, if those planes take off (pun intended), there is no reason why larger capacity commercial jets will not be on the horizon.

And those two companies must be on the right track, because other companies are continuing to look into supersonic travel as well, just not as closely. Boeing is always looking at supersonic air travel, even if just for military applications. Gulfstream has been rumored to be conducting continuous supersonic research. NASA has a supersonic fundamental aeronautics program.

Look at how much quieter jet engines have gotten in the past decade. We may never be able to get rid of the sonic boom, but it certainly seems possible that research is driving us in a direction to reduce the amplitude of the boom. Who knows, maybe within the next decade or two we'll all be traveling at supersonic speeds.

Friday, June 12, 2009

Salary Survey

NSPE is offering a 12 month free unlimited access to members who participate in the Salary Survey.

If you are not a member, why not? But even if you aren't, taking the survey is free and you do get a free limited access complimentary report for taking it. Pricing for a 12 month, unlimited access subscription to the salary survey is as follows:

NSPE Member/Survey Participant: free
NSPE Member/Nonparticipant: $150
Nonmember/Participant: $375
Nonmember/Nonparticipant: $595

Four Free PDH Hours

NSPE is offering 4 free Professional Development Hours (PDH) in ethics training for NSPE members. And as most of us know, finding those ethics courses to meet the minimum requirements has always been the most difficult.

Go online at to learn more.

Engineering's Grand Challenges

NSPE's PE Magazine had an article in its April 09 edition about the National Academy of Engineering's (NAE) Grand Challenges summit. The think tank of top experts in engineering, science, humanities, and public policy met in March to discuss the biggest engineering challenges of the 21st century. Their key findings include:
  • Americans have high expectations of technological advancement and of U.S. leadership meeting the challenges.
  • Most adults view engineering as less appealing to young people compared to law, medicine, or business.
  • Interest in engineering grows as youngsters learn about the challenges engineers are addressing.
  • To improve competitiveness, higher education standards are necessary.
(Note: Paraphrased directly from the PE Magazine article. No byline is listed for the author of the article.)

The list of 14 Grand Challenges
  1. Make solar energy economical
  2. Provide energy from fusion
  3. Develop carbon sequestration methods
  4. Manage the nitrogen cycle
  5. Provide access to clean water
  6. Restore and improve urban infrastructure
  7. Engineer better medicines
  8. Advance health informatics
  9. Secure cyberspace
  10. Prevent nuclear terror
  11. Reverse-engineer the brain
  12. Enhance virtual reality
  13. Advance personalized learning
  14. Engineer the tools of scientific discovery
It is not just a bunch of talking heads in a room, it is up to all of us to meet these challenges. We must get involved both professionally and personally to continue towards the goal of reaching the goals set by these challenges. Educate, inform, and participate at as many levels as possible. These are not some challenges that we can afford to waste time on, or pass down for the next generation to deal with. I urge all of you to get started by visiting the links I have posted above and learn about these Grand Challenges. Find out where you can help.

Thursday, June 11, 2009

Housekeeping - Scripts

I use Firefox 3 with Adblock+ and NoScript. I'm in the habit when visiting new websites to automatically click on the NoScript icon and allow scripts for that domain. What I don't like is seeing a list of a dozen scripts being blocked that have different domains than the one I'm visiting. That is, after all, why I have NoScript installed.

But, usually the webpage does not view correctly until I allow more scripts on the page. I decided to check out the report on this blog to see what scripts are there and was quite surprised to see how many I actually had. For your benefit, I have traced the scripts on this blog to gadgets on the right side bar. Depending on if you want to see/use the gadget or not, you can enable is disable scripts on this page.

blogger - lets me actually write a blog to the blogspot domain.
blogspot* - the host domain of this blog.
disgus* - the application used for comments to blog posts.
twitter - for the rolling twitter updates.
sitemeter* - a traffic monitoring application so I know how many people actually visit this blog.
google - because everything is owned by google, especially since I'm using google blogspot.
gmodules - on of the gadgets that allows you to "follow" this blog, much like following me on twitter.
googlesyndication - for the google ad services, which I have blocked by adblock+ anyway so I still don't see them even with the script allowed.

I hope that clarifies all the scripts I have running on this blog. No security risks, but you can pick and choose what scripts to run and what scripts to continue blocking. The 3 scripts marked with an asterisk are the ones I recommend allowing. The other ones are optional. Actually, sitemeter is optional, too, but it would help me out if I could measure all the traffic to this blog. Please note: to be able to use the gagdets of gmodules and googlesyndication, you must also allow the google domain.

Tuesday, June 9, 2009

Application of Bi-Linear Material Models

Based on the comment from Burhop on my post about bi-linear material models, I'm expanding on the applications of bi-linear models. This deserves a topic on its own because I need to first clarify a few implied assumptions, mainly on how I would like to see this in "first-past solvers." I made the statement that the math is easy because I'm only switching E1 with E2 in the stiffness matrix after I reach the yield point and therefore should be able to be included in first-pass solvers. Well, it's not really that easy and here's where I need to clarify. I'll define first-pass solvers and typical thresholds of those solvers in terms of linear, nonlinear, static, and dynamic analysis.

Static vs. Dynamic
Most first-pass solvers, or those built into CAD packages, only run static solvers. Static solvers assume that the load is applied slowly and remains constant, or static. But along with that is the assumption that the deflections of the material are small. So what is a small deflection? Well, small deflection can be defined the same way that sin(theta) = theta for small angles. Basically, it is as small or large as you need it to be while still producing acceptable levels of error in the result.

Dynamic solvers not only solve simulations that require movement or changing loads over time, but they also have less error when solving problems with large deflections. I'll get back to this concept in a minute, so hold this thought.

Linear vs. Nonlinear
In my prior post I commented on linear material models. Linear models assume stresses and strains only within the elastic, or linear, range of the material (E1) and project the same elasticity of the material if the loads exceed yield. Nonlinear models define equations of state for the entire stress-strain curve. Bi-linear material models estimate the plastic range of the material with a linear curve following the slope of the line from yield to ultimate stress/strain points (E2) as shown in this repost of the stress strain curve of a typical steel material.
Where these definitions start to get confusing is that many materials that have large deflections, like rubbers, are defined with non-linear material models and linear material models are assumed to have small deflections. Therefore, FEA analysis tend to fall into two groups: 1)linear-static and 2)nonlinear-dynamic. Why would anyone want to do a non-linear static analysis?

Application of Bi-linear Material Model
That's just it, I'm doing a bi-linear material model in a static analysis. That's my typical application. It crosses the border between static load but with large deflections. If I were to assume linear materials, an increased load does not give large deflections as I'm still following E1, even above the yield point. By switching to E2, a small load causes a large deflection - as typically seen during necking of a metal material - while stress barely rises. In other words, I'm not going to get a strange stress riser in my post processor that I have to explain away. Instead, I'm going to get large deflections that will either a)crash my simulation or b)more accurately represent the system including interactions (interferences) with other components within the assembly.

What are some specific examples?
  • When I'm designing sacrificial parts. My actual design my not ever exceed yield, but if there is an overload condition due to handling or unforeseen use of the product, then I will create a simulation that overloads the assembly. I need to make sure I design in a specific - and safe - failure mode. Shear pins are cheap to replace if it saves the motor!
  • When I'm designing for deflection. Usually when designing for deflection, the parts are so overbuilt that I don't have to worry about stress failure. But as mentioned in my previous post, if I'm doing FEA it is often because the complexity of the part precludes me from being able to visualize load paths or failure modes. If I happen to yield a part, I need to know that the deflection in my simulation accurately represent deflections beyond yield with just a slight increase in load.
  • Always. Yeah, I (almost) always use a bi-linear material model. The overhead to run the stiffness matrix with a bi-linear material model (static analysis) is so low that there is hardly an increase in run-times compared to a linear static analysis. I use a bi-linear material model just for the increased fidelity of the FEA model.

Monday, June 1, 2009

Bi-Linear Material Models

I don't do FEA very often. Most of my designs are fairly simple with hearty factors of safety built in. Therefore, I can get away with closed-form solutions using standard Mechanics of Materials theory, including Roark's Formulas for the more complex boundary conditions, conservative estimates to simplify the problem, and a good use of professional judgement.

But, when I need to run FEA, it is because the problem is too complex for me to make accurate judgements or conservative simplifications. Thus, I need a fairly accurate representation. Most of all, I may be at the point where I pass yield. Running an FEA simulation using the standard linear material models is not sufficient. Yet, for a first-pass analysis I also don't need a fully defined model. I need a good approximation with a fast run-time.

Enter, the bi-linear material model.
The figure above is of a typical stress-strain curve for steel.
The cyan colored line with the slope E1 is your standard Modulus of Elasticity in the elastic range as determined by the .2% offset to find the yield strength (sigma y) at the yield strain (epsilon y). The second cyan line with the slope E2 is the approximated elasticity in the plastic range of the material. It is approximated because, as you can obviously see, contains error above and below the line compared to the actual stress-strain curve. But, it is a much more accurate approximation as to the material's response to a load then continuing with the usual FEA analysis of linear materials as it would continue to follow the Modulus of Elasticity, projected as the green line.

Just like the Modulus if Elasticity (E1) is the slope of the line to the yield point
the modulus of "plasticity" (E2) is the slope of the line from the yield point to the ultimate point.
The benefit of using a bi-linear material model is
  1. You can easily define the two equations of state with the data you already have from the material properties.
  2. It solves relatively quickly because it uses the same matrix & solver as a linear static analysis, but changes the modulus value if the yield point is reached.
  3. It is more accurate than assuming a non-yielding analysis.

The biggest problem with the bi-linear material model is that it is considered a nonlinear material model. For most FEA applications, that requires me to purchase the nonlinear package. In other words, to get a reasonable approximation, I have to spend a whole lot of money for material models I'll never use. It's not like I'm defining the equations of state for rubbers or amorphous solids. I'm just approximating the stress strain curve of isotropic materials beyond yield with a linear function. How is that nonlinear?

So why don't "express" versions of FEA software - the ones that come with the CAD software - have a the ability to solve bi-linear materials models without forcing me to purchase a bloated piece of non-linear material code I won't use? Bi-Linear material models are great for first-pass analysis and ballpark figures. Given enough margin for error, they can even be used for final approvals, but they are more in-line with comparative analysis and "warm fuzzies." Why not include them with express FEA solvers?

Disparity of Technological Advance

Humans tend to fear what they do not know and to destroy what they fear. And I think many of us are aware that there are a whole lot of things we don't know.

Perhaps that is why there is such a disparity in our ability to create things that destroy rather than things that preserve. Just look at the items around you and realize how many things had to be destroyed in order to make it happen. Also look at how that item could be used to hurt, maim, or destroy if given in the wrong hands - and no I'm not turning this into a "green" post.

As engineers, our prime directive is to hold paramount the safety and well-being of the public. Yet, how easy is it for us to create things that can easily destroy when placed in the wrong hands? Worse yet, look at all the medical tools we have that are designed to radiate, cut, remove, or otherwise destroy living tissue. Yes, usually remove infected tissue, but there is always collateral damage with healthy tissue. Why is our first instinct in medicine to destroy? Of all the fields of study, I would think medicine would be the field focused on creation, sustainability, and longevity. Look back at doctor's medical kits as shortly as the civil war period and you'll see something more along the lines of a carpenter's toolbox than a med kit.

Personally, I think the best tool we have to overcome disease of the human body is the human body itself. Our immune system, if working properly, can fight off any disease. So why would a sick individual use a treatment method that destroys a part of their body? Well, I can name a few: education, availability of alternate treatments, financial ability, and other methods that we have just come to accept as being state-of-the-art medical care. Well I say poo-poo to that. I think it is time that we engineers (bio-medical specifically) challenge the perspective of our learned brethren in the medical field and come up with ways to treat disease without having to eradicate healthy tissue in the process. If our military has changed its perspective on acceptable collateral damage, it's high time the medical field does as well. Radiation, drugs, chemo, and other treatments that have side effects as bad as the disease itself really shouldn't be offered, much less advertised on television. Let's come up with better ways to create health rather than destroy disease.

I happen to have a personal experience with one such device currently on the market. Short of turning my soapbox post into a shameless plug, I will simply link you to Ed Skilling's Photon Genie.
Basically, this device enhances our body's ability to heal itself and fend off disease. It does so without destroying any healthy tissue in the process. Pretty cool stuff, really. But why aren't more people informed of this option for chronic disease treatment? Why must it always be harmful drugs or surgeries that destroy healthy tissue along with the infected tissue? If you are on maintenance meds, why not ask your doctor about alternative treatment options? Bring up the Photon Genie, and I'm sure your orthodox medical professional will give you a strange look and blow off your question. Don't be intimidated. Remember, (s)he is only "practicing" medicine and doctors are humans, too, capable of making mistakes. Read, learn, educate yourself and take control of your own health. If you can't find medical care that suits your needs, look elsewhere. It's out there, you just have to be open to it and hopefully, engineers will find new methods that will be acceptable by orthodox medicine that follow the benefit rather than hurt philosophy. (Sorry, I'm starting to sound preachy. But I really want to note that some scientist had to come up with the theory on how the Photon Genie works and an engineer had to come up with the means to apply it. This exemplifies the philosophical change in thinking we need today - build up the good rather than destroy the bad.)

The Science of Cooking

We all have our hobbies outside of design and engineering. Although I wouldn't consider cooking a hobby of mine, I do enjoy cooking and find myself pretty good at it. And even though this post is just about sharing my recipe I recently tweeted about, I wanted to put a little substance in here to keep it on topic.

One of my favorite cooking websites is They do a fine job of explaining recipes for the analytical mind. I also find it educational and informative and the information I have learned from their website has made developing my own recipes easier since I have a better understanding of the complex interaction of components within a mixture. (Sorry, tried to put some jargon in here to make it sound all "engineery.") Cooking for Engineers is also the website that I got my Grilled Turkey recipe from that I use each Thanksgiving.

Now that the formal stuff is out of the way, here's my recipe for quesadillas. A little background... my wife and I were in the mood for Mexican but didn't want to go out. We hadn't gone grocery shopping yet so we had some jumbo prawns in the freezer as well as some frozen chicken breasts, but not much else. Since my wife and son like shrimp, but my daughter and I don't, it worked out well to make some shrimp and chicken quesadillas. Well, shrimp quesadillas and chicken quesadillas, not chicken & shrimp quesadillas. I was originally looking for a "saucy quesadilla" or at least some sort of fajita-style quesadilla.

I also have to warn you that I'm one of those cooks, who when in the mood to really cook, doesn't measure a thing. I go by smell and taste, adding a bit more here and there until I like what I have in the pan. So, for those of you who need to have specific measurements, I'm only guessing as to how much I really used. Don't blame me if it doesn't taste as good for you as it did for me, try adjusting the recipe a bit.

Shrimp Quesadillas
12 jumbo prawns - cleaned and shelled (thawed, of course)
4 Tblsp butter
1 Tblsp Lime Juice
3/4 tsp Garlic Salt (I like using Simply Organic)
1/2 tsp Cumin
1/2 tsp Chili Powder
1 tsp Paprika
1 Tblsp Flour (or Corn Starch)

Large (burrito-size) tortillas
Monteray Jack cheese (shredded)
Sharp Cheddar cheese (shredded)
Green onion
Tomato (diced with seeds removed)
Sour Cream

Saute the shrimp in the butter on medium heat until done. (I prefer to saute these covered. They cook a little faster and keep the stove top clean from splattering butter. I originally sauteed the shrimp in 3 Tblsp butter, but added another tablespoon after sauteing because I didn't have a enough left in the pan and wanted to freshen it up a bit.) Remove shrimp from frying pan and keep butter in pan.
Add lime juice, garlic salt, cumin, chili powder, and paprika to butter remaining in pan. Stir until well mixed. Heat still on medium. Add flour (or corn starch) to thicken sauce.
Return shrimp to pan. Heat through, turning often to coat the shrimp.

While the shrimp is cooking, prepare your tortilla.
I used shredded cheeses because they melt easier on the tortilla. Diced blocks of cheese will also work, but you run the risk of scorching your tortilla before all the cheese is melted.
Cover one tortilla - to the edges - with: Monteray Jack, sharp cheddar, tomato and green onion.
Place battered shrimp on tortilla.
In a clean frying pan, heat the tortilla on medium until the cheese is melted or tortilla starts getting crispy. Place another tortilla on top and flip over to toast second tortilla until crispy.

Remove, cut, and garnish with sour cream, guacamole, and your favorite salsa.

Chicken Quesadillas
For the chicken quesadillas, follow the same recipe. I cut my chicken breasts into strips and cooked them with light Olive Oil instead of butter.