Novel Processes for Advanced Manufacturing: Summary of a Workshop (2013)

Interesting new release from NAP, Novel Processes for Advanced Manufacturing: Summary of a Workshop
Table of Contents

1. Workshop Introduction
2. Additive Manufacturing Session Summary
3. Electromagnetic Field Manipulation of Properties Session Summary
4. Design of Materials
5. Workshop Conclusion

A Defense of Computational Physics

This is a defense a long time in the making (h/t Dan Hughes). Patrick Roache has done short articles along a similar vein defending the Computational Physics enterprise against what amounts to an empty nihilism that seems to be popular among academics.

Here is the publisher's description,
Karl Popper is often considered the most influential philosopher of science of the first half (at least) of the 20th century. His assertion that true science theories are characterized by falsifiability has been used to discriminate between science and pseudo-science, and his assertion that science theories cannot be verified but only falsified have been used to categorically and pre-emptively reject claims of realistic Validation of computational physics models. Both of these assertions are challenged, as well as the applicability of the second assertion to modern computational physics models such as climate models, even if it were considered to be correct for scientific theories. Patrick J. Roache has been active in the broad area of computational physics for over four decades. He wrote the first textbooks in Computational Fluid Dynamics and in Verification and Validation in Computational Science and Engineering, and has been a pioneer in the V&V area since 1985. He is well qualified to confront the mis-application of Popper's philosophy to computational physics from the vantage of one actively engaged and thoroughly familiar with both the genuine problems and normative practice.
Here is a short excerpt from one of Roache's papers that gives a flavor of the argument he is addressing,

In a widely quoted paper that has been recently described as brilliant in an otherwise excellent Scientific American article (Horgan 1995), Oreskes et al (1994) think that we can find the real meaning of a technical term by inquiring about its common meaning. They make much of supposed intrinsic meaning in the words verify and validate and, as in a Greek morality play, agonize over truth. They come to the remarkable conclusion that it is impossible to verify or validate a numerical model of a natural system. Now most of their concern is with groundwater flow codes, and indeed, in geophysics problems, validation is very difficult. But they extend this to all physical sciences. They clearly have no intuitive concept of error tolerance, or of range of applicability, or of common sense. My impression is that they, like most lay readers, actually think Newton’s law of gravity was proven wrong by Einstein, rather than that Einstein defined the limits of applicability of Newton. But Oreskes et al (1994) go much further, quoting with approval (in their footnote 36) various modern philosophers who question not only whether we can prove any hypothesis true, but also “whether we can in fact prove a hypothesis false.” They are talking about physical laws—not just codes but any physical law. Specifically, we can neither validate nor invalidate Newton’s Law of Gravity. (What shall we do? No hazardous waste disposals, no bridges, no airplanes, no...) See also Konikow & Bredehoeft (1992) and a rebuttal discussion by Leijnse & Hassanizadeh (1994). Clearly, we are not interested in such worthless semantics and effete philosophizing, but in practical definitions, applied in the context of engineering and science accuracy.
Quantification of Uncertainty in Computational Fluid Dynamics, Annu. Rev. Fluid. Mech. 1997. 29:123–60

Navier Stokes 12 Step Program

By way of another fine mesh, Boston University’s Prof. Lorena Barba has released a 12 Step Program for Navier-Stokes. It is a self-paced introductory CFD course presented based on IPython Notebooks. From the site:

We announce the public release of online educational materials for self-learners of CFD using IPython Notebooks: the CFD Python Class on Bitbucket

The course starts with simple one dimensional toy problems and progresses through Burger's equation, then to two dimensions and then finally to Navier-Stokes in 2D. Looks neat, can't wait to try out the notebooks.

Topology Optimization in GE Jet Engine Bracket Challenge Entry

There is an interesting contest on GrabCAD for designing a lighter weight engine bracket for a GE engine the winner of which GE will produce and test using an additive manufacturing method (maybe DMLS). One of the contestants used PareTO software (methods based on these matlab scripts I linked previously) to design a pretty nice looking bracket.

Update: There are more entries that are using topology optimization.

• KMWE and TU Delft Team Entry. This comment the team makes is interesting: "Since the optimised topology models are in stl we have started to first create a volume model with stp extension so we meet the competition recuirements. This takes a lot of time!" This bottle neck in the work-flow is similar to the problem CFD analysts have with structured grid generation. While many (most) 3D printers will take an stl format file (which is just a triangulate surface), you still really want the normal CAD formats (parametric) for a couple reasons. Usually for the metal printing processes you have to add support material. This is done more easily / accurately with something other than an stl. Also you want to be able to use the part in larger assemblies, and this is likely to go better using a native CAD format.
• GE Jet Engine Bracket v1.5, Topology Optimized Bracket - V4, by Igor Lins e Silva
• GE-jet engine bracket-opti-design-phase 1, by Cheng.Li
• Engine Bracket V2.1, by Igor Lins e Silva
• GE Challenge, by Charlie Pyott. I like this one because he uses a lattice, which reminds me of the octet truss things I was working on previously. Charlie also has a website with other interesting designs.

Octet Truss Improved Time Cost

Previously, I did a quick and dirty scaling study on how long it takes to make a 3D cube of octet truss unit cells in BRLCAD. I posted some questions about the results to the list and got some good recommendations on speeding things up. The approach I used previously was just unioning a big, flat list of primitives. The main recomendation to get speed-up was to introduce a bit of spatial organization in the way the primitives are grouped. I did this by making each unit cell a region, and then making an assembly combination of the unit cells. This is only two levels of hierarchy, so ultimately the scaling is still quadratic. The speed-up is pretty dramatic though. To get the \( N log(N) \) scaling mentioned on the email list would require an octree structure with an adaptive number of subdivision levels. Here's a plot showing the improved time scaling:

ITAR Craziness in the News

First it was the almost good news story on NASA's NTRS service coming back online

The website of the NASA Technical Reports Server (NTRS), a massive collection of aerospace-related records, was disabled in March due to congressional concerns that it had inadvertently disclosed export-controlled information. (“NASA Technical Reports Database Goes Dark,” Secrecy News, March 21; “Database Is Shut Down by NASA for a Review,” New York Times, March 22.)

The site is now active again, though hundreds of thousands of previously released documents have been withheld pending review.

Rather than conducting a focused search for actual export-controlled information and then removing it, as would have seemed appropriate, NASA blocked access to the entire collection. The agency acted under pressure from Rep. Frank Wolf (R-VA) of the House Appropriations Committee while it assessed the situation.
NTRS Back Online

The FAS also got some emails describing the process for NASA to return the rest of the reports to public availability. Getting that error message back in March that the server was down was a pretty big shock. It's a very commonly used resource in the Aeronautical / Astronautical Engineering community. I hope they are able to get things restored rapidly!

As if the NTRS fiasco wasn't enough export control weirdness for your week we also got a bit of a spectacle courtesy of Defense Distributed and the Directorate of Defense Trade Controls.

the Directorate of Defense Trade Controls (“DDTC”) told Defense Distributed to take down the plans that it had posted for producing a crappy plastic handgun using an expensive 3-D printer. You can read the letter by clicking this link.
[...]
But leaving aside whether or not these plans are controlled technical data that cannot be put on the Internet without a DDTC license, this whole brouhaha seems to be a waste of time by DDTC. Real guns that won’t blow up in your hand, can fire multiple shots before falling apart, and which can be much more cheaply manufactured are readily available outside the United States, so the danger posed by exporting these plans is, well, non-existent. Foreign militaries aren’t very likely to abandon their AK47s now that they can print their own plastic handguns. Worse yet, the plans had apparently been downloaded more than a 100,000 times before the Feds dropped the ban hammer. There is no way that DDTC can now stuff all that toothpaste back in the tube.
DDTC Slams Stable Door After The Horses Have Bolted

The striking similarity in both cases is that the information in question had already been made widely available to the public, and the public had availed itself to it. In the NTRS case those reports had been available for years, and are widely used in engineering education and referenced in textbooks. The Defcad files were only available for a matter of weeks (the latest files were only added to the archive in the past few days), but had already been downloaded more than 100k times and were hosted on servers in New Zealand. Of course for a political animal like Cody Wilson getting a take-down order from the State Dept. is exactly the sort of thing he wants

Orbital Sciences Antares Launch Success

A New Nuclear Rocket Concept

The folks at University of Washington and MSWNW LLC. have a new Fusion Driven Rocket concept. It combines magnetic and inertial confinement to achieve fusion and subsequent fuel heating for high exhaust velocity.

UAV Crash Course

NASA released a report on UAV mishaps, Crash Course:
Lessons Learned from Accidents Involving Remotely Piloted and Autonomous Aircraft

The findings echo decades of flight operations experience: mishaps are usually the result of a "chain" of circumstances that individually would probably not cause a problem. Here's NASA's description of Crash Course:

This volume contains an investigation of remotely piloted research vehicle (RPRV) and unmanned aircraft system (UAS) mishaps and will examine their causes, consequences, resultant corrective actions, and lessons learned. Most undesired outcomes usually do not occur because of a single event, but rather from a series of events and actions involving equipment malfunctions and/or human factors. This book comprises a series of case studies focusing mostly on accidents and incidents involving experimental aircraft. The information provided should be of use to flight-test organizations, aircraft operators, educators, and students, among others. These lessons are not unique to the UAS environment and are also applicable to human aviation and space flight activities. Common elements include crew resource management, training, mission planning issues, management and programmatic pressures (e.g., schedule, budget, resources), cockpit/control station design, and other factors.