Sounding rockets

Sounding rockets for weightless experiments: © EADS Astrium

Sounding rockets are used to carry scientific payloads, mostly for measuring the Earth’s atmosphere, ionosphere and aurora, to sub-orbital altitudes above that possible for balloons and below that of satellites. They follow parabolic trajectories, the duration of which is determined by the apogee reached by the rocket, and provide a valuable vibration-free microgravity environment for experiments into material properties and behaviour. For some experiments the microgravity timeframe afforded by the sounding rocket flight is sufficient to obtail self-standing results, while in other cases the sounding rocket experiments are conducted as a precursor to longer-term research in space (aboard the ISS).

Astrium operates missions with sounding rockets on a commercial basis, as prime contractor to ESA or the German Aerospace Centre (DLR). All sounding rockets for microgravity research are launched from Esrange in northern Sweden.

European sounding rocket activities for microgravity research started in 1976 with the TEXUS Sounding Rocket Programme (Technologische Experimente unter Schwerelosigkeit) as a preparatory programme for the first Spacelab mission in 1983. With TEXUS 17 and 18 (launched in May 1988) the TEXUS project was commercialised and Astrium in Bremen has taken on overall responsibility.

The MAXUS long-duration sounding rocket programme is a joint venture between Astrium and the Swedish Space Corporation. This programme was initiated in 1990 to extend the microgravity time achievable with sounding rockets to 10-15 minutes. For MAXUS, a single-stage solid-fuel rocket motor, Castor 4B, with a steerable nozzle is used to launch a gross payload of typically 800 kg to an apogee of more than 700 km. This corresponds to some 13 minutes of microgravity conditions. As its apogee is above the limit of 300 km, the Esrange safety regulations require (for MAXUS) the use of a guidance control system and a self-destruct system.

The TEXUS rockets are launched with the new Brazilian VSB-30, a two-stage rocket motor which performed its maiden operational flight from Esrange in December 2005. With a typical gross payload weight of 400 kg, an apogee of more than 250 km is reached, and microgravity conditions are achieved for a period of 390 seconds.

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Sounding rockets