Saturday, 21 July 2007
A critical milestone in for the Pathfinder 01 development program was scheduled to take place July 24th, when the newly designed liquid propellant motor was to undergo qualification firings. However last minute logistical issues required that our team postpone the planned firing, pending a new safety review.
The term VaPak has been applied to propulsion systems that utilise the vapor pressure of one or more volatile propellants, to deliver said propellants to the rocket motor. Thus negating the need for separate high pressure feed or pump systems to deliver propellants to the rocket motor, leading to greater overall simplicity and reduced cost.
Our innovative design uses a high vapor pressure liquid oxidizer (Nitrous Oxide) and standard Methylated Spirits (95% Ethanol), to provide a simple, safe and efficient propulsion system. And is based on the proven heritage of Nitrous Oxide based hybrid rocket developments of the last 10 years.
Potential hazards associated with other forms of propulsion are largely eliminated due to the following.
1/ Nitrous Oxide is loaded remotely with operators more than 50 meters from loaded flight tank.
2/ There is no explosive or toxic agents used, and ignition is only possible via the introduction of oxygen gas and high voltage spark. This is again facilitated remotely from a safe distance.
3/ Nitrous Oxide is non-toxic except for slight narcotic effect (Laughing Gas), as to is Ethanol.
Above is the motor hardware showing the outer casing, injector, phenolic chamber liner and nozzle housing closure.
The team did complete critical testing of the Nitrous Oxide Fill & fire system and the static test stand assembly, and are ready for rescheduling of qualification trials.
The Inertial Measurement Unit (IMU) being designed for the rocket consists of 3 single axis MEMS rate gyros, 2 dual axis accelerometers, 2 dual axis magnetic sensors and a GPS unit. The magnetometer and the GPS provide absolute heading and position reference to minimize accumulated error in the inertial measurements. The IMU has been designed together with a CAN bus expansion module on a PC104 form factor. The base board has two smaller boards connecting at right angles to provide inertial sensing in all 3 axis. This board will be mounted on top of a PC104 XScale based single board computer(SBC) interfacing via two high speed UARTs (one for CAN bus, one for IMU). The board design has been completed and all components have been source courtesy of RS Components.
The eCos real-time operating system has been ported to run on the Arcom Vulcan board sponsored to the project by RS Components. eCos is a deeply embedded operating system designed for applications requiring fast deterministic response time.
Currently a Kalman Filter implementation is being to developed to run on the SBC along with a roll control algorithm to drive the discontinuous reaction jets.
Monday, 9 July 2007
Through out the holidays the Uni of Adelaide team has been working hard to get all the items ready for the static test rig.
The ST development board kindly donated by ST along with other tools has been excellent to work with. It has offered an easy medium to develop & test software. Also lessons learned from the board will give invaluable insight into the development of our own STR7 based microcontroller boards.
The test stand load cell and pressure transducer have had there circuitry developed and built. Each apparatus has had simple tests to verify there functionality, with excellent results.
The real time data capture and wireless control systems are being continually developed. Currently the real time graphing we wish to use through the test fire is almost complete. Next the graphical control will have it output linked to the microcontroller.
Our nitrous components have arrived.
The nitrous oxide solenoids draw 8amps. Because of this and also the need to have a mechanical interlock, a control box was made to take a signal as input from the microcontroller. The box then outputs the function to the appropriate relay via a transistor switching arrangement, to cycle 3 solenoids ( 1 for NOX fill/ 1 for NOX purge / 1 for O2 flood ). The solenoids have been connected to the control box and tested successfully. Completed box is shown above.
An ignition test was completed to test how much time is needed for the ignition spark to take effect and to cause burning on the nylon hose. This nylon hose will hold the fuel and we are relying on it to burn to open the lines and allow the fuels to mix to produce a burn. To test a small section of nylon hose was taped to the ignition wire, it as placed in an oxygen rich beaker. As you can see in the movie it took very little time for it to burn. The shorter the sparks time the better as it reduces the EMC on small sensitive devices such as microcontrollers.
The team at University of Adelaide thank RS Components, Coregas & STMicroelectronics for thier generous support, of the A.S.L.I 2007 program.