SimScale Blog

Then why not just officially ditch what is, at this point, a quirky anachronism at best, and a potentially really expensive source of mistakes [1] at worst? [1]: https://www.simscale.com/blog/nasa-mars-climate-orbiter-metric/

The problem is one of readability, not memorization. A lot of readability amounts to taking what the initial author already knows and expressing it so that it's easy for everybody who comes after to know too. Making implicit units explicit is a great example of that. Look at Martin Fowler's writings on Money types, for example. Or look at the $125 million failure of a space probe because people used implicit units: https://www.simscale.com/blog/2017/12/nasa-mars-climate-orbiter-metric…

Associate professor in fluid dynamics here. There is typically a split between the people who want good looking simulations for movies/games, and those who need accurate results for engineering. For engineering, you need more effort on how you resolve the complex geometry and how you model the turbulence in the flow. This adds significant complexity both for problem setup and solution time. The only product I’m aware of that is built for real-time, 3D flow design is Ansys Discovery: https://www.ansys.com/products/3d-design/ansys-discovery OpenFOAM is high quality, but as you’ve seen complex to use. There is a web-based GUI that can lighten the burden to get started somewhat: https://www.simscale.com/ I think they give you ~3000 simulation hours for a trial.

Also newtype wrappers. If you have code that deals e.g. with pounds and kilograms, Dollars and Euros, screen coordinates and window coordinates, plain text and HTML and so on, those values are usually encapsulated in safe wrapper structs instead of being passed as raw ints or floats. This prevents you from accidentally passing the wrong kind of value into a function, and potentially blowing up your $125 million spacecraft[1]. I also find that such wrappers also make the code far more readable, as there's no confusion exactly what kind of value is expected. [1] https://www.simscale.com/blog/nasa-mars-climate-orbiter-metric/

So many things are "Typed" but don't appear to be. 3PM (time zone). "Hello" (UTF-8/ASCII). 38.8977,77.0365 (WGS84). It's effectively the "NASA Mars Metric" mistake all over the place: https://www.simscale.com/blog/nasa-mars-climate-orbiter-metric/

Maybe not NASA, but what about its contractors? https://www.simscale.com/blog/nasa-mars-climate-orbiter-metric/

The sad part is that this isn't the last time. https://www.simscale.com/blog/nasa-mars-climate-orbiter-metric/

Thanks for the clarification! This makes sense. I do wonder who is liable if the software used to design a bridge outputs incorrect simulation results and the bridge collapses as a consequence. I suppose it's on the senior project engineer (or whoever ultimately signs off on the design) to verify the results somehow. Edit: This article [0] talks about the "trust" placed in commercial and open-source CAD software by engineers and doesn't mention regulation/certification of the software itself, which seems to imply that there is none. [0] https://www.simscale.com/blog/open-source-software-cae/

I'm sure it was picked a long time ago and it's too costly to switch. I imagine any code going into multi-million dollar missile needs to be incredibly audited and understood. (Not that this never happens! https://www.simscale.com/blog/2017/12/nasa-mars-climate-orbiter-metric…

Reading through Beads author's blog reveals him to be a person with decades of experience. To me it appears that Beads is a well thought out attempt to address the multitude of issues that the author has experienced over the years. NASA lost the Mars Climate Orbiter due to a confusion of values being in feet or meters. https://www.simscale.com/blog/2017/12/nasa-mars-climate-orbiter-metric… That is exactly the sort of mistake that the support for physical measurements mitigates. There probably never will be a programming language that pleases all the syntax camps and all the semantics camps. Why not just use macro-assembler? It is the purest language that isn't binary machine code.

And knowing the difference is an important part of rocket science: https://www.simscale.com/blog/2017/12/nasa-mars-climate-orbiter-metric…

I read comments and many are saying "is it urban legend" I do not think so, we underestimate people ability to complicate things and make mistakes. Does anyone remember story how NASA lost 125 million orbiter because measuring unit mistake> https://www.simscale.com/blog/2017/12/nasa-mars-climate-orbiter-metric…

You mean like the 125m Mars orbiter lost due to engineers forgetting imperial/metric conversion? https://www.simscale.com/blog/2017/12/nasa-mars-climate-orbiter-metric…

Surprising, I thought they do, especially after these kind of incidents: https://www.simscale.com/blog/2017/12/nasa-mars-climate-orbiter-metric…

There's a surprising amount of corner cutting that goes on with large engineering projects. Examples: - A water slide had basic design flaws. That water slide would later go on to decapitate the son of a Congressman [1]; - The Millenium Tower in San Francisco was allowed to be built without the piles going down to bedrock [2]; - A borrowed system from an earlier rocket was never tested on the Ariane 5. An integer overflow basically caused the Ariane 5 to blow up on launch [3]; - Famously, the Challenger disaster came down to some O rings becoming brittle in the cold launch conditions and the launch was approved regardless [4]; - To counter the competition of the Airbus A320neo, Boeing decided against a full redesign of the 737 and instead just updated the aging 737 design by putting more powerful engines on it and moving them forward. This could lead to stalls if the plane angled up too much. To counter this, Boeing added the (now famous) MCAS to keep the 737 type rating [5] and didn't really tell airlines and pilots about it. But the worst part was the system had no redundancy. It relies on a single sensor. Normally for safety-critical sensors there is triple-redundancy. So for something like this you'd have 3 sensors (minimum) and there'd need to be agreement between at least two. That was an optional upgrade. [1]: https://www.nytimes.com/2018/03/26/us/waterslide-boy-decapitated-charg… [2]:…