Saturday, March 10, 2007

Aero-Structural Update

The aero-structural team has been keeping quite busy recently as the whole design comes together. We are near the end of our design phase, transitioning into procurement and manufacturing. Here are a few of the main projects we are working on.

Cross-Braced Frames
The main structural components of the rocket are these 1' or 2' long frame sections. Modularity in the design makes it easier to manufacture, store, and transport. With the limited storage space we have available, this is an important concern. Currently we have all the material we need for the ring parts and cross braces (refer to the picture below). The picture does not show the array of holes for fastening or the fillet welds. We hit a snag with the c-channel parts when it became apparent that our supplier did not carry that stock. Currently, lighter c-channels are being analyzed using methods described in "Analysis and Design of Flight Vehicle Structures" by E. F. Bruhn. We did not even know of this book before and it has proved to be quite useful. Future revisions of the rocket could be more efficient, load bearing wise. Back to the present, we will get new c-channel in and get these frames machined and welded.

Nose Cone
The nose cone design is currently being looked after by Tom. Back in the day we had decided upon an ogive shaped nose cone, based on what we knew. Tom has been looking at different shapes and how they impact our performance.

One of the main unknowns that we had not addressed before was heating of the nose. We have always wanted a composite nose cone and we do not want it "melting" in flight. Temperature distribution over the nose cone is different depending on which shape we use and over the last week, temperatures have been estimated. Next week we plan to settle on a shape. The tip of the nose cone has always been an area of concern due to the fact that it will experience the highest temperature. There is also the problem of laying-up the nose cone by hand. None of us are carbon fibre experts so the quality of the composite at the tip may be sketchy at best. To rectify this problem, we plan on having a metal tip that threads into the rest of the nose cone. This should help with the temperature issue and should make manufacturing easier.

What has yet to be completed is a design for the internal structure of the nose cone. I imagine a simple frame that will help keep the shape of the cone and will make mounting to the rocket easier. Some of the recovery system will be located in the nose cone and mounting points are required for that as well. Insulation is important in the nose cone especially if we have a parachute packed neatly inside it. I like the spec's I see at the Aerogel website.

We have had a general shape and size for a while. We like the clipped delta configuration, slightly swept back, with a short span. We also have a nice stack of books, articles, etc. to look through regarding fins in supersonic flow, etc. Arash is working on completing the aerodynamic and structural design. For the fins we will also have an internal structure with a skin over top. Tom's heating analysis will determine whether we can use composite skin for the fins or not.

Other projects the aero-structural team is involved with include the fuel system and the rocket skin. The fuel system components have been spec'd and a BOM has been completed. Swagelok® is being contacted for most of our plumbing needs. Fuel system testing can be integrated with engine testing. The skin has been temporarily left on the back burner as the other major aspects are being completed. Several solutions have been proposed for attaching the skin to the entire rocket frame. This is next on the to-do list.

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