Monday, October 20, 2014

Successful parachute ejection

After a break I'm back now with an update on the project. In the mean time some work has been done on the project. Basic navigation software and ground station communication has been completed. Implementing the parachute ejection mechanism was quite a challenge because of the limited space on the plane. Finally after testing a bunch of concepts a working solution comes up. A hot gas propelled latch releases now the lit on the parachute bay.

The plane is ready now for the first fest flight from low altitude. Therefore I’m looking for an Quadrocopter pilot who likes to support the project and can lift the Near Space Plane to a suitable altitude for releasing it. A servo based release mechanism is already available. The weight of the plane is approximately 450 g.
 
 

Saturday, November 17, 2012

Parachute ejection system

Some experimental work has been carried out on the parachute ejection system. The Following video shows two tests of an airbag-like ejection system that will be placed under the parachute. On the first test some gas from the gas generator bypassed the metal mesh that cools the gas. The hot gas damaged the nylon bag so it doesn’t inflate. That issue has been fixed on the second test.


Wednesday, October 17, 2012

The SRTM elevation model

Beside working on the parachute ejection system, I spend two more evenings on the (onboard) above ground level estimation software. Therefore data from GPS, barometric pressure sensor and from the SRTM elevation model is used. In the Shuttle Radar Topography Mission from 2000 the elevation of most of the earth’s surface was captured. The following (Hi Res) Image shows some visualized elevation data. Who guesses which region is shown here?
 
 
The processed SRTM-Data is sourced from:
Jarvis A., H.I. Reuter, A.  Nelson, E. Guevara, 2008, Hole-filled  seamless SRTM data V4, International Centre for Tropical  Agriculture (CIAT), available  from http://srtm.csi.cgiar.org.

Friday, September 21, 2012

Back from holidays

I'm back from holidays and started with the parachute bay and ejection system. The parachute itself is already  finished. It is made from 11 pieces of 37 g/m² Ripstop-Nylon and has a diameter of 730 mm. The following image shows the folded parachute:

 

In the next posts I will go into detail of a specific komponent. Here is a block diagram that gives an overview of all installed electronic components:



Saturday, August 18, 2012

Status Update

Today the Electronic mounting has been almost finished. The Picture shows the electronic bay with assembled main board, battery, servos and connection tubing for barometer and Pitot tube.


The battery is a single cell 5 Ah rated Li-Po from China. A measurement shows up a capacity of more than 6 Ah on 600 mA discharge current (That's the consumption of the plane electronics including GPS and Transceiver but without Servos). A circuit using the MAX1708 is used to step-up the cell voltage to 5 V.

 

Sunday, July 29, 2012

Testing the IMU on the airfraime

Wings and fuselage have been merged now, servos and control surfaces linkage are installed.  I replaced my own IMU code by a implementation from Sebastian Madgwick he developed during his PhD. His C# implementation is significant faster than my implementation and much more accurate too, especially for low update rates. Simple PID controllers are used to calculate the control surface angles.



More information to Sebastian Madgwicks implementation you can find on: www.x-io.co.uk

Thursday, July 19, 2012

Some Photos


The following photos shows the naked airframe and the mostly finished mainboard. From left to right you can see the GPS-receiver, barometer, IMU-board (with 3-axis gyro, 3-axis accelerometer and 3-axis magnetometer), pilot tube pressure sensor, mini SD-card, CPU and step-up converter.