Friday, May 22, 2009

Rockets in Cyberspace and Meatspace

Cyberspace: I've got my rocket simulation program on my calculator back up past 90% functionality. The main simulation is up and required only one quick bug fix (accidentally using diameter instead of radius while calculating drag), and since it's completely rewritten, it's almost twice as fast as the old loop. Variables are handled faster, less time-consuming 'store to variables' are used, and instead of a clunky loading bar, it displays the real-time calculations of altitude and velocity. Useful for long calculations (low gravity, no drag, large motors) so I have some idea of how long it'll take.
I've got MMX-D motors up, plus the E6, G80, and J570 for test purposes. The only part of the old program that I haven't re-added, besides the motor files I haven't put in yet, is the handling for staging rockets. The motor data subroutine displays propellant type, size / reload casing, and available delays for all motor in th program grouped by size, plus the ability to display initial weight, propellant mass, average thrust, maximum thrust, burn time, total impulse, and thrust curves for all 80-odd motors. (All Estes, Apogee, and Quest motors minus the D5, all 18mm-29mm AT SU motors, and 18mm, 24mm (non-RC), and most 29mm reloads, plus a smattering of larger motors: I435, J570, K550, L1420, M1939, N2000).
I also completely rewrote the descent calculator today. I calculated the relative areas for circular, square (side and diagonal), hex (side-to-side and diagonal), and x-form chutes. I also derived the equations for descent rate in terms of weight, air density, chute drag coefficient, and chute area, and the program can now derive the descent rate from chute size, or vice versa, with all the other parameters the same. The calculations were fairly simple: just set weight (9.8N per kg) equal to drag (0.5pCDV2A) and solve for whatever variable you want. (p (rho) is the air density (1.2062 at sea level); CD is the drag coefficient of the chute (between 0.75 and 1 for parasheets (can lay out flat) and about 1.5 for parachutes (actual half-spheres)).

If you want the code, just drop me a line and I'll send a text file, or maybe an actual file to download to your calculator once I get TiConnect on my laptop.

Meatspace: I started gluing the first fin on the Machnum force tonight. I'll use one layer of wood glue to attach each fin (12+hr drying time) and 2 to 3 per fillet (24+hr drying). This is the last truly tricky step (before came cutting and wood-glue-smoothing-and-strengthening the fins), and from here on out it should be pretty easy. I hope to fly it at NERRF in August along with the Mozzie which'll be my cert flight.

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