Matt Wronkiewicz's Weblog» Rockets

Announcing Virtual Range 1.0 for Mac OS X

Matt — Thu, 06 Aug 2009 06:25:51 +0000

I am pleased to announce version 1.0 of Virtual Range, my rocket simulator for Mac OS X. Virtual Range can simulate the flight of a rocket model in real time (on sufficiently powerful CPUs), and tell you if it is stable. It will also record the maximum altitude and acceleration, and the time until apogee. All this is very important information if you have built a rocket and want to know what kind of engine you should put in it. Virtual Range estimates the aerodynamic forces acting on the rocket in flight using the US Air Force DATCOM drag methods and Barrowman’s center of pressure method. The simulated flight is displayed with basic, but accurate graphics. This project could not have been completed without the help of Greg Lyzenga and the Rocketry Organization of California. If you have a Macintosh with a G5 or Intel Core CPU, check it out at Ballistic Aerospace Technologies: Virtual Range.

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PerfectFlite MiniAlt/WD on Mac OS X

Matt — Thu, 25 Jun 2009 07:21:58 +0000

My very understanding wife bought me a rocket altimeter. This handy little device will let me control the descent rate of my higher altitude rockets, so they have less time to drift under the parachute. Less drifting means I won’t have to walk a mile across the dry lake bed to retrieve my rocket, and less chance of losing it. Last ROCstock I flew the upgraded Mean Machine on an Aerotech H128W-M. Gary at Rocketography took a nice photo of the launch. It blasted up and out of sight in seconds. I couldn’t find the rocket after a long search, but I got a call a few days later from someone who found it a couple of miles from the launch pad. Anyway, the altimeter is the MiniAlt/WD (MAWD) from PerfectFlite, ordered from What’s Up Hobbies along with the USB adapter. It doesn’t have as many sensors as some other flight computers, and it’s not very programmable, but several people recommended it as a reliable choice for what I want to do. The USB connection is only supported under Windows and Mac OS 9, but I got it to work under OS X. All I had to do was install the drivers from http://www.ftdichip.com/Drivers/VCP.htm, and then do “screen /dev/tty.usbserial-A9009jvE 38400″ from the terminal to talk to it. I even wrote a little C program to download the flight log over the serial port. We’ll see how well it works when I fly the altimeter on Martian Sunrise 2 in a couple of weeks. If that goes well, I’ll look into connecting it to some pyros for dual parachute deployment, probably on the Mean Machine or the new 4″ rocket I’ve been designing.

(Update) Here’s the MAWD dump program with source code: Dump MAWD.dmg. It’s a command line program that takes the path to the serial port as a single argument.

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Demise of Martian Sunrise

Matt — Sat, 23 Feb 2008 19:06:05 +0000

Joseph and I built an Aerotech Arreaux. He painted it and I named it Martian Sunrise. We took it to Santa Fe Dam to fly it at the SCRA launch. I loaded an E15-7W engine, and the LCO gave a countdown and pressed the button. It fizzled. The igniter popped but didn’t start the engine, probably because I hadn’t attached it securely enough. We tried again and up it flew. And then it continued on a ballistic trajectory back to the Earth. The flight ended after 13 seconds with the nose cone embedded 6 inches into packed dirt. The airframe was shredded. We cleaned up the crash site and flew another rocket before we headed home. Joseph’s beautiful paint job is gone, but the rocket will fly again after I get some replacement body tubes and a new nose cone. See photos and a video at the photo album.387397

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