Friday, December 21, 2012

The newest near space flight computer from NearSys is the NearSpace Simple-18. It’s a PICAXE-18M2 based datalogger in parallel with a TinyTrak 3 APRS tracker. Input/output devices, like sensors, connect to the NearSpace Simple-18 through its four ports. 1. Analog Port: used to digitize the voltages of three sensors 2. Digital Port: used to interface three digital devices or sensors 3. GPS Port: shares GPS data with both the APRS tracker and the PICAXE-18M2 4. Camera Port: used to operate two cameras Analog sensors are supplied +5 volts and ground as soon as you connect them to the Analog Port. The PICAXE-18M2 can digitize sensor voltages with either eight or ten bits of resolution. The Digital Port is a two way port. You can connect input (like sensors) or output devices to this port. An example of a digital sensor is the Geiger counter. The cameras operated by this flight computer need by-passed shutter switches. Alternatively, a single camera with a by-passed shutter and power switch can be operated through the Camera Port. The flight computer also includes a Commit Pin. This is used to prevent the flight computer from recording data prior to launch. When launch is immanent, the pin is removed, signally the PICAXE to begin collecting data. Data from the four analog and digital sensors is stored in a 24LC256 I2C memory chip. This gives the flight computer enough memory to record 256 kb of data. The chip can be replaced with a larger version if additional data storage is required. The flight computer has four LED status indicators. These indicate when the flight computer has power, when the tracker side is transmitting a position report, the status of the GPS Receiver (when its connected and when it has a satellite lock), and the current status of the flight computer. The last indicator, the status indicator is a programmable bi-color LED. The PICAXE-18M2 is programmed to illuminate the LED as desired. The NearSpace Simple-18 flight computer kit also includes a two meter antenna kit. The antenna connects to the flight computer through an SMA connector. The NearSpace Simple-18 makes a great first flight computer. It’s simple plug and fly operation makes collecting data in near space quite simple.

Wednesday, December 12, 2012

The Assembled NearSys GPS Simulator

NearSys LLC now sells a GPS Simulator. It allows you to test a near space APRS tracker or flight computer for its behavior during a mission. It's a way to simulate a mission on your bench top, saving you money and difficulty should something go awry.

The GPS Simulator models all the events of a GPS that's making a trip to near space. These events include GPS lock and loss of lock, launch and ascent of the balloon, balloon float, balloon burst, descent, and landing. The GPS lock can be lost at any time during the mission and can be regained at will. The ascent rate, landing speed, float altitude, and burst altitude of the mission are easy to set and vary by adjusting four well-described variables at the top of the GPS Simulator program.

This level of functionality is useful if you programmed your flight computer to respond to conditions like too slow of an ascent rate, unexpected loss of GPS lock, unplanned for neutral bouyancy, passing specific altitudes, balloon burst, approaching landing, or touchdown.

The NearSys GPS Simulator lets you test and debug these programmable features of your near space mission.

You can view the kit and its instructions at the GPS Simulator page at

Monday, December 10, 2012

Vacuum Cannon

What can you accelerate using a vacuum? How about a ping pong ball to several hundred miles per hour? The vacuum cannon evaculates the air from a PVC tube. Both ends of the tube are sealed using sheets of aluminized mylar and inside is a ping pong ball. After the air is evacvuated, you puncture the mylar film closest to the ping pong ball. As the air rushes back in, it creates a force on the ping pong ball. Since the air pressure is 101.3 kP and the ping pong ball has a low mass of three grams, the ball's acceleration can exceed 1,000 g's. By the time the ping pong ball reaches the end of the tube, it bursts through the other mylar film cap with a loud bang.

The kinetic energy of the ping pong ball is equal to the energy required to evacuate the PVC, minus losses due to friction and drag. Still, a ping pong ball capable of flying through an aluminum can is mightly impressive.

You can see a video of my vacuum cannon on my YouTube channel

Friday, December 7, 2012

NearSys has updated its BalloonSat Mini flight computer to version 4.0. This version is more convenient to program and to interface sensors. Rather than programming the flight computer through a serial adapter cable, the flight computer now incorporates a DB-9 connector. Interfacing sensors is easier because sensor arrays are available with simple to solder connectors that plug right into the flight computer’s I/O port.

Like the older versions, the BalloonSat Mini v4.0 also operates a camera. The flight computer can operate any electronic camera with a by-passed shutter switch. Cameras modified to work with the BalloonSat Mini v4.0 are available from NearSys.

The BalloonSat Mini v4.0 has memory to record 256 sensor readings. Since it can collect data from two sensors, the BalloonSat Mini v4.0 can record one reading per sensor per minute for the entire ascent of a typical high altitude balloon. However, it will not begin recording data until after the BalloonSat crew removes the Commit Tag.

The BalloonSat Mini v4.0 kit is available from NearSys for $23.50. The kit contains all the necessary parts except for solder. Directions for the kit and sample code are available from the NearSys website at, http://nearsys/catalog/balloonsat/mini.htm.