Saturday, October 31, 2009

µMLAS - The First of the Parts

My µMLAS build officially started with an e-mail to Gordon Agnello requesting another Forward Fairing and CM - oh, and while you have your lathe all set up, Gordy, can you do an airframe of the correct diameter too? Gordon was happy to produce more parts, though I'm not sure he stayed that way as we progressed. MLAS was done as a "concurrent design-build" project, which is another way of saying we were ordering hardware and putting it together while the designers were still grinding out drawings. Parts usually showed up on the shop floor just in time for installation. That moved things along much more quickly than they otherwise would have, but we occasionally found ourselves doing some rework when the design changed after some piece of first-generation hardware had been machined. Gordon got a taste of that while working on the µMLAS fairing: the MLAS aero team kept tweaking the original Sears-Haack (SH) profile, and every change resulted in another e-mail to Gordy. MLAS ultimately ended up with a "modified" SH shape ... flattened at the top for minimal drag below mach 1 (max velocity expected of MLAS in flight was about mach 0.6) and flared slightly at the bottom for a smooth transition to the cylindrical Coast and Boost Skirts. The mid section had a slightly more pronounced "flat cone" shape than a true SH - that and the aft flare helped move the aerodynamic Center of Pressure aft slightly. Gordon did an amazing job capturing all those details ... you'll find a link to his working drawing posted here under "Resources: µMLAS Drawings."

The results of Gordon's work are shown at right. The Forward Fairing and CM are both of fiberglass-over-foam construction in 1:20 scale to the actual MLAS. Gordon made the cylindrical section shown from a piece of 12" PML phenolic tubing by cutting out a section lengthwise, pulling the free edges together, and applying a fiberglass patch inside the tube. The CM was identical to the one he produced for µMRA with an open 2-1/2" core up the center, filled in this picture with a piece of scrap Estes BT-80. As with the previous parts, Gordon provided the fairing and CM primed and ready for finishing.

While Gordon was turning parts, I started working on drawings of my own. Those evolved as work on µMLAS progressed, and are posted here in their native MicroSoft Visio format along with a pdf conversion. Feel free to download with the usual caveats: these are for personal use only, I won't guarantee they're free of errors (though I really did try - if you do find something wrong let me know), and if you poke an eye out using them, hey, you were warned.