The launch vehicle is composed of an Improved Orion motor with exhaust nozzle extension, a tailcan, three stabilising fins and a motor adapter with an integrated separation system.

The total mass of the rocket is around 515 kg comprising a propellant mass of 290 kg, motor and vehicle hardware of around 125 kg and a payload mass of around 100 kg. The total rocket vehicle has a length of 5.6 m and the diameter is 356 mm.

The standard configuration of this payload comprises the recovery module, the service system, an ejectable nosecone and two experiment modules. The mass of each experiment module structure and bulkhead is approximately 5 kg. The total available mass for the student experiments is normally about 30 kg.

The rocket accelerates the payload for 26 seconds with a peak acceleration of ~20 g during the boost phase. During flight one rocket configuration will have a spin of approximately 4 Hz (no microgravity environment!). The other rocket configuration uses a yo-yo despin system that will reduce the spin to a maximum spin rate of 0.08 Hz (30°/s). The rockets will usually be launched during daylight. A night launch is possible in case of special requirements of an experiment.

The motor burnout is usually at an altitude of around 23 km. The motor separation timedepends on the experiment requirements but will not be performed before the nosecone ejection which can take place at altitudes above 55 km. Motor separation is usually performed before apogee which is between 90 -100 km, depending on the payload mass. For reasons of stabilisation, the payload can be separated later. The latest separation altitude is about 60 km on descent, before the vehicle enters the lower atmosphere.

During the descent phase in the lower atmosphere, at an altitude of about 26 km, the payload is decelerated with a maximum acceleration of about 6 g. The recovery sequence is initiated after about 7 minutes of flight, at an altitude of about 5 km. A parachute system decelerates the payload to a terminal velocity of ~10 m/s before landing.

a) Mechanical Accommodation
The experiments are mounted in the experiment modules. A standard experiment module is an aluminium cylinder of 400 mm height, 356 mm in diameter and a mass of about 3.5 kg.

The experiments can be placed on bulkheads in the experiment modules or directly on the module skin (see Fig. 5).

Hatches in the module skins can be provided to give an experiment the possibility to take measurements outside the module (see Figure 6).

One experiment can be mounted below the ejectable nosecone on an adapter structure (see Figure 7). It is possible to release this experiment from the payload during the flight. This separated experiment follows the same ballistic trajectory as the total payload but will not usually be recovered.

b) Environmental Conditions
The experiment modules of a standard REXUS payload are not pressurised. During flight the air escapes from the modules through openings while the ambient pressure decreases to 10-4 mbar.

The integration of the modules and payload is carried out at normal room temperature of approx. 20 °C. After integration, the payload is mounted on the motor. The ambient temperature at the launcher can be low (down to -30 °C) depending on the launch date and time.

The thermal environment of the outer structure of a front-end positioned parallel bay module on the launcher can reach 110 °C at 50 seconds after lift-off. Peak temperatures above 200 °C are reached during the re-entry phase.

After landing, the payload will be subjected to snow and cold air in the impact area for a period of typically one to two hours. The temperature during the season when REXUS is launched is normally between 0 °C and -30 °C.

c) Electrical Interface
The service system provides five 28 V power lines. One experiment cannot use more than one line. The average current is 1 Ampere and the peak current is 3 Amperes. Please check the REXUS Manual for further details.

d) Experiment Control and Data Acquisition
A Telemetry/Telecommand serial data interface is available for 5 experiments (RS422 transparent data Interface). One experiment can use a TV channel that will usually be switched to the recovery camera before the parachute deployment.

• Position and Velocity (GPS)
• Acceleration data (3-axis accelerometer)
• Angular rate (3-axis rate gyros)