Sunday, March 22, 2015

Reliability Growth: Enhancing Defense System Reliability

This report (pdf) from the National academies on reliability growth is interesting. There's a lot of good stuff on design for reliability, physics of failure, highly accelerated life testing, accelerated life testing and reliability growth modeling. Especially useful is the discussion about the suitability of assumptions underlying some of the different reliability growth models.

The authors provide a thorough critique of MIL-HDBK-217, Reliability Prediction of Electronic Equipment, in Appendix D, which is probably worth the price of admission by itself. If you're concerned with product reliability you should read this report (lots of good pointers to the lit).

Tuesday, January 13, 2015

Guidelines for Planning and Evidence for Assessing a Well-Designed Experiment

This paper is full of great guidance for planning a campaign of experimentation, or assessing the sufficiency of a plan that already exists. The authors break up the effort into four phases:
  1. Plan a Series of Experiments to Accelerate Discovery
    1. Design Alternatives to Span the Factor Space
    2. Decide on a Design Strategy to Control the Risk of Wrong Conclusions
  2. Execute the Test
  3. Analyze the Experimental Design
They give a handy checklist for each phase (reproduced below). The checklists are comprehensive (significantly more than my little list of questions) and I think they stand-alone, but the whole paper is well worth a read. Design of experiments is more than just math, as this paper stresses it is a strategy for discovery.

Tuesday, December 30, 2014

Starscraper Sounding Rocket Kickstarter

The Boston University Rocket Propulsion Group (BURPG) is developing a sounding rocket designed to top 150km and funding it partially through a kickstarter campaign. They plan on launching from Blackrock next year like Qu8k, but this is a more ambitious and complex effort.

The rocket will be controlled using fluid injection thrust vectoring. The thrust levels of their hybrid motor are comparable to Qu8k, but it is a significantly larger (30 vs 14ft long, 12 vs 8in diameter) and heavier (1100 vs 320 lbs) and aims higher (150km vs 120kft). It's hard to tell, but it also seems to be an order of magnitude or so more expensive.

The advantage the BURPG folks claim for their concept over traditional solid fuel sounding rockets is a gentler ride for payloads on the longer, smoother burning hybrid.

Saturday, December 6, 2014

Fully Scripted Open Source Topology Optimization

Helical Extruder Gear for Printrbot with Optimized Topology

I've used a couple different methods for stringing together open source tools to do topology optimization, but they have all required some interactive user input. Here are some previous posts demonstrating those manual methods:
Those approaches are fine if you've got time to fiddle with interactive software, but I wanted to do some parametric studies, so I need an automated approach that would be scalable to lots and lots of optimizations.

Thursday, November 20, 2014

119 Open Source Aeronautical Engineering Tools

I posted a list of 33 open source aeronautical engineering tools on LinkedIn a couple days ago. One of the comments was a question about how open they all really were so I added a column to the list for the license and any non-free dependencies (i.e. Matlab). I went ahead and made an entry for each of the pieces of software from Ralph Carmichael's PDAS collection, which added 84 public domain pieces of software. In addition, there are 23 with various flavors of GNU, 4 BSD-style, and 3 NASA open source agreement (NOSA) codes. See the whole list below the fold. Please suggest adds/changes/deletes in the comments.

Monday, August 18, 2014

Validation & Verification in Physics of Plasmas

Physics of Plasmas is making a collection of 20 papers on verification and validation available for free download for a limited time.
Theoretical models, both analytical and numerical, are playing an increasingly important role in predicting complex plasma behavior, and providing a scientific understanding of the underlying physical processes.

Since the ability of a theoretical model to predict plasma behavior is a key measure of the model’s accuracy and its ability to advance scientific understanding, it is Physics of Plasmas’ Editorial Policy to encourage the submission of manuscripts whose primary focus is the verification and/or validation of codes and analytical models aimed at predicting plasma behavior.

Saturday, July 19, 2014

FreeFem++ Topology Optimization Scripts

There are lots of open source topology optimization options out there (e.g. 99 line code, ToPy) that I've written about before. One that I haven't posted about yet is a collection of FreeFem++ scripts by Allaire, et al. that illustrate a variety of topology optimization approaches and problems. FreeFem++ is a partial differential equation solver based on the finite element method. FreeFem++problems are defined in scripts that use a high level language. FreeFem++ itself is written in C++.

Tuesday, July 1, 2014

UAVs for Film and Profit

Yesterday's AIAA Daily Launch had a great round-up of some recent UAV news:
  • Wall Street Journal (6/27, Nicas, Subscription Publication) reported on the ongoing fight over U.S. unmanned aircraft rules, which is pitting high-tech entrepreneurs against major aerospace and defense companies.
  • Washington Post (6/28, Whitlock) reported that a majority of U.S. military UAV accidents occur abroad, but “at least 49 large drones have crashed during test or training flights near domestic bases since 2001, according to a yearlong Washington Post investigation.”
  • AP (6/28, Jelinek) reported that the Pentagon announced armed UAVs are “flying over Baghdad to protect U.S. troops that recently arrived to assess Iraq’s deteriorating security.”
  • South Florida Sun Sentinel (6/29, Anthony) reported that Boynton Beach is dropping plans to ban drones in order to boost its “fledgling image as a technological hot spot — a place that welcomes engineers and innovation.”
  • South Bend (IN) Tribune (6/29, Sheckler) reported that as UAVs become cheaper and more available to the public, and their popularity grows among hobbyists and entrepreneurs, “they will increasingly raise questions about how to best regulate them, and how to balance concerns about safety and privacy.”
  • Hollywood Reporter (6/27, Giardina) reported that Hollywood movie studios are interested in using UAVs in filming “because they hold the promise of new creative options, real cost savings and possibly even safer sets.” Federal law prohibits the commercial use of UAVs, so filmmakers choose to shoot in countries with lax UAV laws to get the shots needed for their films.
Most interesting are the petitions of the seven aerial photography companies for exemptions for commercial filming operations. As the FAA press release says, the seven Section 333 Exemption Applications for Commercial Operations of Unmanned Aircraft are available on I think it is interesting that these companies are taking this approach, because in some fillings by Pirker they specifically call out historical use of remote control aircraft for movies and TV (one of four broad categories of commercial use they cite). The applications have 18 "limitations and conditions" under which commercial operations will take place. They also make this interesting claim: "These limitations provide for at least an equivalent or even higher level of safety to operations under the current regulatory structure because the proposed operations represent a safety enhancement to the already safe movie and television filming operations conducted with conventional aircraft."
To drive that point home they show a couple pictures of a manned helicopter filming as it currently occurs.