We finished the long airbeam for the High Beam mission. We pressure tested and it held fine under the full load. It’s has enough strength however it wants to snap into an arch given any chance. Something new to tackle. High aspect ratio airbeam stabilizing.
Eek! I accidentally deleted the comment suggesting putting a carbon support within the beam.
The deflection load may be to great for even a carbon structural tube to take. We thinking about bundling the tubes. It’s going to take some experimenting.
No problem about the deletion.
There are two possible main approaches to the problem that I can see, looking at the problem from a mechanical designer’s standpoint.
1. 4 linear tubes along the length of the air beam, inserted thru loops in the fabric, either inside the beam or outside. One length of tube in each of the 4 corners. The advantage of the outside approach is that the tubing will be easier to insert, but the tubing will be exposed to the upper atmospheric conditions. The advantage of the inside approach is that the tubes are not directly exposed to the vacuum, but it would be more difficult to insert the rods.
2. Building a framework of 4 tubes that are fastened together at each end to form a box of sorts. If there were cross supports inside the framework, that would increase the rigidity with only a small increase in weight. But the obvious drawback is that the air beam would be a bit long for transport with this structure. There are possible solutions to this that might help with the transport, ways of breaking down the structure.
1A, 2A. Putting extra lengths of the tubing at the center for extra rigidity, where the flexing is most apparent, or using a larger OD tube in the center section.
I can do quick and dirty solid models at work on the CAD system if you are interested in an outside volunteer’s help. Feel free to contact me at the email address listed. My wife and I think that your approach to getting us into space is very clever and imaginative(we have “Balloons to Space”).
I am nowhere near as knowledgeable as Don here, but:
Building on his idea, would it be possible to attach a similar structural support using not carbon supports but high-pressure air beams ribbed with nylon as seen in this post?:
http://jpaerospace.com/blog/?p=660
You would have to construct smaller and stronger end caps as well as vacuum test the beams, but should it work, it may be far lighter and easier to transport than any other alternative. Yes, I recognize that the entire point of this mission is to test the viability of air beams in the upper atmosphere, but even if the structural supports fail the added mass should not skew the test results by any significant amount.