The Aspire II avionics consists of 4 units. The first unit, the Telemetry and Control System, forms the heart of Aspire II's avionics and is connected to all the other units and the payloads via the Aspire Intermodule Bus (AIB), a fast digital serial link. The units are as follows:
| 1. Telemetry and Control System (TCS) |
The TCS performs two functions:
i. Telemetry and monitoring.
The TCS collects data from the payloads carried by Aspire II. It also gathers information about the operational status of all the other onboard systems, such as the engine and its propellant supply system. The TCS also collects data from its own Standard Sensor Array (SSA). This is a bank of sensors which are flown on every mission to collect importantdata about the rockets' flight such as airspeed, altitude, attitude and acceleration.
The TCS formats all this data and sends it to the ground via a UHF radio transmitter. The data is sent in digital form using Frequency Shift Keying (FSK) modulation. At the ground station, the data is displayed to the ground crew and also stored on disk for post-flight analysis.
ii. Telecommand, control and sequencing
The other function of the TCS is to act as a central controller and sequencer for the other systems and payloads on the rocket. Despite this, most of Aspire II's systems are designed to run autonomously if necessary.The TCS allows the ground crew to control various systems on the rocket remotely during pre-flight procedures and, if necessary, during flight. This is accomplished using a VHF radio uplink from the ground station to a receiver in the TCS.
The TCS is based around a 68332 microcontroller chip.
The GS stabilises the rocket and ensures its progression along the correct trajectory. It is based around a 68332 microcontroller chip. The GS contains an inertial reference (gyroscope) to provide data about the rocket's attitude.This is processed using fuzzy logic algorithms to produce correction signals which are fed to the thrust vectoring actuators. Thrust vector control (TVC) will probably be accomplished by gimballing the motor, though other TVC techniques are being investigated.
The GS is referred to as a "Genetically Adaptive Active Control Guidance System".
The gyroscopes and accellerometers which make up the inertial reference, have been scratch built by AspireSpace in order to reduce costs. This goal has been achieved without sacrificing accuracy of themeasurements. Comprehensive bench testing and flight testing on smallrockets, has validated this approach.
| 3. Recovery System Controller (RSC) |
The RCS contains circuitry for initiating and sequencing the operation of the vehicle's recovery parachute system.
| 4. Engine Management System (EMS) |
The EMS contains circuitry for sequencing the start-up and running of the hybrid rocket motor and its propellant supply system. The EMS also contains a controller to regulate the propellant feed pressure and provide a programmed sequence of throttle (thrust) settings during flight.
The payloads are connected to the TCS via the AIB. To give the payload providers a simple, user-friendly interface, there is no direct access to the AIB. Instead, they are connected to the AIB through a Payload Interface Unit (PIU). The PIU has a number of analogue and digital data lines for the payload provider to connect to. Every payload has its own PIU.
