NASA EAS - Final Update

Last crawled date: 1 year, 10 months ago

NASA Experiment Attachement System - EAS

https://grabcad.com/challenges/nasa-experiment-attachment-system-eas-challenge

At first I would like to thank NASA for bringing this challenge ( perhaps much more in the future ) and allowing me be part of this endeavor.

Here are some considerations and reasons of my design:

1- My main goal was create a system easy to use, with minimum number of assembly steps in orbit. 2 sub-assembly was the objective. And line-up the design with main goal of the NASA Logistics Reduction.

2-Avoid the use of sheet metal. The reason sheet metal under stress exhibit local buckling, and this is very hard to detect without using a buckling FEA model. Sheet metals have another problem: After laser cutting, the edges are sharp and you need do rework on that, increasing the cost.

3-Reduce to minimum the use of metals with complex form. The reason for that is that with the increase in complexity of the part, it is less likely to be reused in other way, since the complex geometry don't allow that. Because of that i decided use the same external profile as the handrails of the previous NASA challenge ( https://grabcad.com/challenges/nasa-handrail-clamp-assembly-challenge ), allowing other use after the end of experiment.

4-Since I am using the handrails, it is possible to modify in order to get other EAS geometry for other future experiments? The ABS joins allow easy customization, with the R3DO and AMF, it is possible to produce these parts inside the ISS. Just been necessary launch new rails for the structure. This way reducing the weight in future missions.

5-The surface interface with the seat track was designed wide to reduce the moments and convert it to force. Hand calculations showed that force limits wouldn't be a problem, but the moment would be. A self-lock system was placed for the purpose of reducing the use of tools.

6-I didn't add the threaded inserts for the abs parts in the .step, the reason I wouldn't be able to model the interaction of the insert and the abs.

7-If necessary i can upload the results for the orthogonal load after the deadline in the comments. FOS was 2,29 for this load.

8-It is possible to change the materials of handrails to one with less tensile strength, since the highest von-misses stress happens in the pins. But the Young´s modulus should be close in order to keep secondary stress effects in check.

9-The contact adopted in the FEA simulations was frictionless. This type of contact allow that the distance between parts change with the time, but don't allow one part to go inside the other. I tried to reproduce the best of the real system, but this had a cost in processing time, when compared with one-piece model.

10-It wast possible to perform a mesh convergence analysis due the insufficient memory of my workstation.


Judging criteria:

Description of system : OK
STEP/IGES: OK
Assembly Procedure: OK
Sharp Human edge criteria : OK
Factor of Safety: OK
Deflection: OK
Force and Moment Reactions: OK
EAS Envelopoe: OK
Launch Envelope : OK
Mass: OK
Materials : OK
Captive fasteners, retaining pins: OK