Guest-blog by Flight Dynamics officer and space capsule electronics lead Steen Andersen.
Soon to be launched active guided rocket Sapphire has three main electronic systems on-board:
- Guidance and Navigation Computer (GNC). The main objective of this unit is to calculate steering commands to the servo rudders in the jet exhaust enabling the computer to keep the rocket on a vertical flight path. The unit is also responsible for deploying the drogue and main parachute after apogee. The unit is basing the flight path calculations on an IMU (Inertial Measurement Unit). The overall goal of this launch is to test this unit capability to control the flight path of the rocket during the powered ascent. This is the responsibility of our guidance wizard Flemming Nyboe.
2) Autonomous Abort Unit (AAU). This unit is a prototype of an AAU which will be able to determine the attitude and altitude of the rocket and in case of the rocket flying out of a predetermined range corridor, this system should stop the engine in order to avoid any range safety issues. The unit has an IMU and a GPS on-board.
- The Radio which is used to send telemetry acquired from the two units mentioned above down to Mission Control (MC) during the flight. The bandwidth of the radio is approximately 100 kbit.
The radio receiver is placed in MC on-board the vessel Vostok which in return sends decoded data to two different computers. One is used to show the FIDO monitor and the other is used to show telemetry from GNC. The rest of this blog is presenting the various information which can be seen on the FIDO monitor. The word FIDO is an acronym for Flight Dynamics Officer and the FIDO monitor is therefore the application which is presenting the flight information to the Flight Director and the Flight Dynamics officer.
The rocket will be launched from the mobile launch platform Sputnik, which is our marine vessel designed especially for this purpose. The area is called ESD139 in the Baltic Sea east of Bornholm (a small island in Denmark). The challenges of getting a successful launch of the rocket are not only concerning the rocket itself, but also performing the launch and recovery operations at sea using dedicated marine vessels. The FIDO monitor is used to support these operations by showing various parameters of telemetry and AIS information. AIS (Automatic Identification System) is an international maritime radio based system used by ships larger than 300 tons to broadcast their positions and other parameters to each other.
The FIDO monitor
Below is a screen-dump of the FIDO monitor. Please note that all data seen are just test data.
The FIDO application has four main purposes:
1) Running the countdown clock which is used to synchronize the launch of the rocket by the Flight Director. 2) Presenting different flight parameters send to mission control from the rocket itself. 3) Monitoring the positions of all the vessels in the area. 4) Plotting positions of the rocket during flight and recovery.
All data shown on the monitor originates from either the AAU (IMU and GPS) or the AIS receiver.
Rocket telemetry
The telemetry originating at the AAU (Accelerometer and GPS) is shown in the left side of the screen:
Next to word ‘Telemetry” the last known time for correct data-packet received (from the rocket) is shown. In other words, this tells us how old the data are. The number of good and bad packages are also shown. This gives an indication of how the data down-link is performing.
In addition we have the position of the rocket in absolute coordinates as well as a bearing and distance from mission control. In addition we calculate and ETA – if the vertical speed is negative. “Flying” says either Yes or No indication if the AAU has registered that the rocket has been launched. Finally, we have two house-keeping parameter showing if the AAU writes to the SD card correctly and how many volts that is supplied to the AAU electronics unit.
In the second column we have altitude (defined by the GPS position), the down-range from the lift off position, course over ground (COG), the quality of the GPS positioning (either No fix, 2D or 3D fix). Next we have the combined speed as well as vertical and horizontal speed of the rocket. And finally we have readings from the accelerometer in the AAU.
When Sapphire reaches apogee we are hopefully able to verify a terminal vertical velocity of app 20 m/s and Y-axis g-forces app 1 g, indicating the rocket hanging safely in the main parachute. If the rocket is not hanging in the parachute the vertical speed will be much higher and the rocket will tumble down. On the map to the right you see the overall screen-dump of the position and the rocket trajectory (over ground) shown with the green dot/arrow.
AIS information
The lower left panel displays AIS information of the mobile launch platform Sputnik and mission control vessel Vostok. Furthermore, we have a time stamp, showing how old the data are, the position, COG, speed over ground, true heading and relative bearing and distance of Sputnik seen from mission control.
The map
On the right we have a large map displaying marine vessels position in the area. This is a tool for ensuring range safety (only allowed vessels can be in the area during launch) and a guide to help the recovery teams finding the rocket post splashdown. A vessel is indicated by an arrow showing the position and heading of the vessel. The rocket is shown as the green dot and if the rocket has a horizontal speed the COG of the rocket will be shown as well. All this information, except the Sapphire rocket, is based on an AIS receiver in mission control. Small boats with no AIS transponder cannot be seen on this monitor and we must rely on visual identification for range safety purposes. As depicted on the map we’re able to measure distances and headings using the mouse.
Software
The FIDO monitor is implemented in Java using Netbeans as IDE and you can download it all using the following two links:
FIDO lib (contains all panels, com port interfaces etc): https://github.com/SteenAndersen/FIDOLib And the main application: https://github.com/SteenAndersen/FIDO
So, please feel free to download and build your own FIDO monitor.
Acknowledgement
I would like to thank Daniel Leong, UK, for doing several excellent reviews of the FIDO source code. He has provided valuable suggestions for improvements as well as ensuring a more robust application. Thanks.
Steen Andersen Copenhagen Suborbitals
Steen Andersen joined Copenhagen Suborbitals in 2009. He is the mission control Flight Dynamics Officer, taking part in test measurements and space capsule electronics lead. He has previously been working with software development for a Danish space company and as an IT consultant.
