Monday, December 6, 2010

It's Only Rocket Science

Well, SpaceX finally got their static fire test after three attempts (one yesterday, one at 9:40 AM EST or so this morning, and the final success at 10:50 AM EST). The issue appears to have been startup transients in the engines and being unsure exactly how much to allow before an automatic abort (with the number six engine proving to the hurdle in both aborts, first due to over-pressure and then under-pressure), so they were trying out several configuration files to get one that did the job.

Anyway, this reminded me of the "crash the code until it stops failing" approach that's sometimes required in coding, so I thought I'd talk some about what I've been up to in the last few weeks. One major thing I've had in the works is the TransHab module calculator that is now live on the Atomic Rockets website. (Thanks to Adam Schwaninger for his assistance with the interface, and to Winchell Chung for providing the web space.)

As I mentioned a while back, I'm very interested in the possibilities of inflatable modules and find the work Bigelow Aerospace has done in advancing the readiness of the TransHab design to be of particular interest. (That is, a rigid central core with an inflatable outer section, as seen below.)
Looking at the Biglowe modules in a cross-section, I realized I could break down the cross-section into segments defined by geometric relations and then use formulas I learned in Statics last year to convert this into a formula for the volume of a module of given radius and length. This formula, in various re-solved forms, is the basis of the calculator. An "equivalent density" term allows me to relate the volume of the module to a mass and thus with certain parameters (density and any other two, with certain exceptions) I can solve for all parameters. The completed calculator can therefore be used to at least estimate details about potential future applications of TransHa-derived modules.

I'm very satisfied with how the calculator turned out--in testing against AutoCAD Inventor models of modules, the volume equation works to <1% error, which is pretty good in my book. The input model is inspired somewhat by Theodore Hall's SpinCalc, and though the graphic interface that Adam helped me put together is not quite as slick as the inspiration, I think it works pretty well.

In the future, I'd like to add the multi-unit support at some point, but it can wait until v2.0. Other things I'm thinking of adding are a launch fairing diameter parameter, which would require looking over data for the ratio of the diameter of the rigid core to the fairings used to encapsulate the payload, which should be an easier addition, and so may be my first revision goal.

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