Successful Experiment Series under Weightlessness

Fig. 1: CFRP Boom in packed configuration

Scientists from the DLR’s Institute of Composite Structures and Adaptive Systems performed several experiments onboard of the A300 Zero-G test aircraft, at February 13th.

 

This flying test laboratory offers the possibility to generate 22 seconds of weightlessness usable for all experiments that fit into the 5 m x 20 m large experiment bay.

 

The experiment focuses on the verification of ultra lightweight deployable booms (masts) as displayed in Fig. 1. Due to its material thickness of only 0.1 mm, an 8 m long boom of the current design weighs less than 500 gram. In spite of the light weight, the booms are very stiff and can be used as basic modules for various large space structures at future space missions. Potential applications for those booms are deployable solar sails for propellant less propulsion or even solar arrays and low frequency radar antennas.

 

Thanks to their special geometry, the booms can be pressed flat and rolled around a core to stow them space saving during launch and orbit transfer. Thus, one of the used 14 m long test booms can be stored in a volume comparable to two shoe boxes.

 

Related to this packing principle, the booms tend to deploy their self by their stored elastic energy. Hence, the boom needs a restraining force that prevents an unwanted self deployment during launch and transfer but offers a safe method to deploy the boom controllable as well. The experiments shall verify two possible control principles for such a save storage and deployment.

Fig. 2: Successful deployment of a 14 m hybrid deployable/inflatable boom

Fig. 2 displays the successful deployment of a 14 m long boom that was equipped with deployment inhibiting Velcro layers and an internal inflation bladder that is required to deploy it in a controllable manner by inflation. Both the metallic looking bladder and the black thin Velcro stripes are visible in Fig. 1. Depending on the gas flow rate, the total deployment of this long boom can be done in 9 seconds.

The second control principle uses a special construction that deploys the boom using an electrically driven mechanism (visible in the upper left corner of Fig. 3). It consists of a light aluminum cage that caries the coiled boom and two plastic wheels that pulls the boom out of the storage region. The most interesting feature of this mechanism is the jettisoning of the mechanism at the end of the deployment. Since weight is an important criterion for solar sail missions, this deployment principle could offer the possibility to deploy a sail support structure for a 40 m x 40 m solar sail that weights below 20 kg.

 

 

 

 

 

Fig. 3: Successful deployment of an 8 m boom, using an electrically driven mechanism

As displayed in Fig. 3 this mechanism has been successfully demonstrated as well.