Category Archives: Design

Design and manufacturing. Tools and processes in a computerized age.

Project Spartan Spear

I’m an advisor to a team of aerospace engineering students at San Jose State University. For their senior design project, they are designing a launch vehicle to take nanosatellites (specifically, 1U and 3U CubeSats) to orbit.  Project Spartan Spear now has a Kickstarter campaign which runs to Feb. 27.

My role as mentor/advisor is in computing and avionics. We have others who cover propulsion and structures, and manufacturing. During the first semester, the team of 7 students did preliminary design of the vehicle, including aerodynamic estimates, projected trajectory, and some early CAD and experiments dealing with components of the engine.  Frankly, a launch vehicle project is so overwhelming that the entire team is now focused on just getting the engine designed, built, and tested.  The bulk of it needs to be done by May 2015, when they graduate.  Experience with other senior design projects shows that they have a life of their own, and testing continues into the summer and fall. There website shows progress in CAD models and preliminary experiments.

This is one of three projects in the aerospace senior design class. In my biased opinion, this is the most intriguing and exciting.  (We actually had to turn students away at the beginning of the fall semester in order to balance the teams; the other two are nanosatellites.)

The difference between this and large launch vehicles like Falcon 9 or Atlas V is that on the large vehicles, CubeSats are treated as secondary payloads, subject to the rules of the primary that is funding the bulk of the launch costs.  This new concept allows CubeSats to be primary payloads, and effectively lets users/developers deploy them on their own schedule to their own selected orbits. Furthermore, this is an air-launch design, which reduces the environmental impact normally associated with launch pads; the impact is primarily as an airport user.

In effect, availability of this sort of launch vehicle allows businesses that understand space benefits and spin-offs to pursue iterative development. Rather than waiting 1 or 2 years between flight bookings, this allows a business to plan a cycle of weeks or months.  The ultimate hope is to service many customers, allowing for several launches per week.

The obvious applications of having such a launch vehicle are iterative development involving: small biologicals, materials, small electronics, etc.  Spartan Spear is a step toward getting regular access to  low Earth orbit , with the intent of jumpstarting product development cycles for these types of innovations, which ultimately will find their way into new terrestrial projects and manned space systems.

Design-challenged

With due respect to the “challenged” individuals who have impediments or roadblocks to performing certain tasks… some days, I feel like I am design-challenged. I may have a fair amount of understanding about a particular design goal and how it might be realized, but I can’t do the design.

To clarify, I operate in a couple of technical domains.  I’m doing fine in one (computer systems, especially computer software). But in the other, I have a sense of extreme frustration. Basically, I can’t do aerospace vehicle design.

I’ve come to the conclusion that to do reasonable design work, you need the appropriate 3D mechanical CAD tools, combined with simulation capability, such as static structural analysis, fluid flow, and thermal conductivity. Back of the envelope computation doesn’t cut it for a design that can be built.

What’s the problem with the CAD tools? They cost on the order of $7,000 for CAD and simulation capability. An aspiring designer cannot afford these tools. (This is not the same as having AutoCAD or Sketch-Up for drafting and design.) From here, the CAD system may generate instructions for manufacturing. In fact, for a more coordinated environment of design tools, database, and interface to manufacturing, the software tools may cost $50,000.

These tools are part of a design workflow. Other components of the workflow might include trajectory design and analysis, high fidelity CFD, design of the fuel system. For a vehicle design to work, the different parts of the workflow need to be able to talk to each other. That is, there are data formats and possibly signals agreed upon between tools.

All this introduces a set of workflow challenges. That is, the design-challenged individual may also be workflow-challenged.

To better size up the problem for a small aerospace entrepreneur, I’m hosting a session on “Aerospace Workflow Challenges” at the Hacker Dojo on June 29. I have more notes on the expectations of the session here.

 

Unobtainium and investment

In my last post about “Requirements gone wild” (April 11), I mentioned the mythical material “unobtainium”, a notion that sometimes doesn’t sit well with people. This time, I’m going to do a reality check.

People sometimes seem to think that rocket science represents the pinnacle of human creativity. Watching a rocket launch is awe-inspiring. It is taken as evidence that anything the mind can imagine, human creativity can make real. I’m convinced that people who say that are really trying to say is that the human spirit, along with persistence, can accomplish anything; within a lot of human activity, that may be true.  But I’ve seen this used as a defense that some day we will have warp drive… just because we can imagine it today.  In the broader spectrum of how nature really behaves, this doesn’t hold up.

Fundamentally, science and engineering are about discovering and harnessing the laws of nature. We believe that the world is governed by a self-consistent set of laws of behavior.  We try to discover those laws, and sometimes we draw the wrong conclusions.  Nevertheless, we believe that nature itself is self-consistent in its behavior.  We can improve our understanding, but we cannot demand that nature contradict itself.  (Well, we can demand, but it won’t do any good.)

How well we understand those laws of nature is evident in the types of engineering we now engage in.  Sending a rocket to the Moon or detonating a nuclear device are both extremely dependent on our understanding those laws. Sometimes in engineering development, we don’t really know the answer.  So we have to do experiments to ask nature how it behaves under certain circumstances.  If we like the answer, we incorporate it into our design.  If we don’t, we go back to the drawing board.

“Unobtainium” is a code word for material that borders on violating the laws of physics.  In truth, we may not know how to create the material today.  It may cost us a couple of decades of major sweat to figure it out.  (I’m still waiting on nanotubes for digital circuitry with zero internal resistance.)  If it is possible at all, turning unobtainium into the obtainable takes non-trivial resources.  Sometimes, those resources are very expensive.If you are bringing VCs, angels, or other investors to the table, then what may be unique about your plan is how you convince yourself and investors that unobtainium really isn’t.  The business plan in part amounts to how you can prove it.  On the other hand, if investors smell unaddressed unobtainium (also known as “hand-waving”) in your plan, you can expect them to walk away.

I know.  I’m such a spoil-sport. :-/

As for warp drive, the notion is in fact being investigated, but as a possible extension of the current laws of physics, using devices whose behavior we understand in current physics.  (Look up “Alcubierre drive” and Harold “Sonny” White.)  This approach amounts to looking for more subtle behavior in what we would otherwise consider as “noise”.  Can we then tweak the signal out of that noise and harness it in a new way?  Time will tell. That time may be decades.  It may be centuries.  It may be never because nature doesn’t behave that way.  But it will be interesting to see what clues can be discovered on Earth in the next few years.

Requirements gone wild

And now for something completely different.

A colleague and I were trying to explain the basics of rocket propulsion to someone.  The subject of putting nuclear bombs behind a thick plate to produce thrust came up.  (We didn’t say “Project Orion“. But if you know what that is, that is effectively how the discussion went.)

When we discussed exploding the bomb very close to the plate, we were asked what sort of material would be used that wouldn’t be slowly destroyed in the process.  The conversation then went…

“Unobtainium.”
“What’s that?”
“It’s what you can’t obtain!”

At this point, we were berated for being scientists and engineers with no creativity.  Now, of course, we laughed it off.  I later pointed that there is a nice video that describes the predicament that engineers get thrown into with impossible requirements.  Engineers here will understand.

Sometimes, the demands of rocket science feel a little bit like this. :-)

As for lacking creativity, I thought about going to multi-dimensional space and red-shifting the color.  The part that really gave me grief was the kitten.

A month of drafting (and why would I do this?)

Here’s a piece of artwork that is probably familiar to many who are learning to do drafting and design by computer.

CDI60-Proj1-CustomerAssembly

There is nothing special about it, except that I drew this one, following the instructions in the workbook as precisely as possible.1 Actually, I drew half of it. The thin vertical plate, with two bolts, the rod it attaches to, and the guide assembly in the foreground were drawn by me. The vertical block in the back and the darker plate that it connects to were provided as part of the homework exercise.

This drawing is the result of about four weeks of CAD practice using SolidWorks. Half of this was done in the CAD lab at De Anza College, in Cupertino, California.2 The other half was done on my home machine, which I hastily modified to run Windows 7. To my surprise, I was told that SolidWorks requires Excel to manage its bill of materials. The user interface on SolidWorks, and many other CAD programs, is very rich.  By comparison, simple spreadsheet functions (not full Excel) are fairly trivial.

For those of you who think that I am primarily a computer scientist who is picking up engineering, that is perhaps partly true. On the other hand, my diversion into computer science started from engineering.  Decades ago, I grew up using mechanical drawing pencils, T-square, right triangles, a variety of scales, compass, and French curves. (The latter refers to a piece of plastic, not a people or person.)

All this was well before the invention of the personal computer. The programming I did professionally started on IBM System/370 and Amdahl 470  computers, although I had learned on IBM 360.  There was no AutoCAD, no Adobe Photoshop or Illustrator.  These tools came much later with the invention of the raster graphics workstation.  (By contrast, there were tools like CADAM, but I’m told they required mainframe computers.)  So in doing nearly four decades of computing, I managed to miss the computer-aided drafting and design revolution. A better way to say it is, I knew about the revolution, but I had no access.3

Why SolidWorks?  Why not Creo or AutoCAD?  The simple answer is that most of the aerospace groups that I’ve personally dealt with in the last three years were doing mechanical design using SolidWorks. Both SolidWorks and Creo (formerly Pro/Engineer) are parametric modeling tools.  So is AutoDesk Inventor.  AutoCAD is not.

After a career of computing, with an excursion into VLSI design, why do this now?  There are several reasons for this.

  1. Back in high school, you could divide up prospective engineering students taking shop courses into two major camps: those with electrical circuit skills and those with mechanical design skills.  I was in the latter camp.  I would much rather deal with Newton’s Laws than Kirchhoff’s Laws.  (A couple of decades later, I decided that a serious engineer should be grounded in both. However, I should caution that I know very few engineers who actually deal in both.)
  2. In recent years, I’ve gotten into discussions with aerospace people about various aspects of vehicle design. This includes small launch vehicles, and small satellites and making them survive re-entry.  We’ve even talked about exploration of planetary bodies and their moons with dense atmospheres.  One of these projects is progressing beyond the design concept phase.  I’ve discovered that in doing a vehicle design, I am very hampered by not having a drafting table or CAD software.  Furthermore, analysis of some of these designs will require computerized finite element methods.
  3. The technology of 3D printing (also known as additive manufacturing) is emerging beyond rapid prototyping.  Industrial use of 3D printing is taking off, and consumer 3D printers are beginning to emerge.  For space exploration, it is even more important.  It provides an alternative to continually bring up finished products from Earth to orbit, and then launching them onto interplanetary trajectories.  It makes more sense to process raw material in very little gravity and energy, and utilize the resulting feedstock in 3D printers to create space structures.

For the immediate future, my goal is to work on small vehicle designs and hopefully explore 3D printing.  And perhaps design my own furniture.

Footnotes:

1. The design exercise for the drawing is from Engineering Desgn with SolidWorks 2012 by David C. Planchard & Marie P. Planchard.

2. Yes, I now have a real student ID card and student parking permit.  And I am feeling the pain of homework deadlines.

3. Strangely, in the late 1980s, I ended up working with senior designers on full-custom design of VLSI circuits. For a while, I had pretty good access to VLSI CAD, although I didn’t have any prior training in the field.  A little over a decade later, I supplemented that with courses in VLSI and ASIC design.