Structure and Mechanisms

Main structure

The main structure of the Flying Laptop is designed to be a hybrid structure. The lower part consists of integral aluminium parts and therefore offers a cost-effective and precise assemply, adjusted force transmission and good thermal properties. The upper part, where the optical systems are installed, consists of carbon-fibre reinforced sandwich structures. These offer a low mass, high stiffness as well as low thermal longitudinal expansion to provide a stable calibrated alignment of the cameras in the satellite and to each other.

The satellite is divided into three segments. The launch adapter is attached to the lowest module, the service module, in which the so-called service components like on-board computer, the battery and the power control and distribution unit are located. The second module, the core module, is located in the middle of the satellite and houses systems components like reaction wheels, the components of the data downlink system and the fibre optical gyros. The payload module forms the upper segment of the satellite main structure. In this module, the panoramic camera, the optical link OSIRIS as well as both of the optical benches containing the optical camera system MICS and the camera heads of the star trackers are located. To ensure the proper alignement of the camera systems to each other sandwich structures are used in the payload module.

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The three segments are connect by a shear wall crossing and two outer shear walls. The shear wall crossing between service and core module consists also of integral aluminium parts. All other shear walls consist of sandwich structures to reduce the effects of thermal deformation on the payload module as far as possible. The sandwich and aluminium components are connected with full floating fasteners, which compensate the occuring inner tension caused by different thermal expansion coefficients.

Solar panel deployment mechanism

Due to the high energy consumption and the limited integration volume in the launcher the Flying Laptop features two deployable solar panels, which need to be retracted during the launch. After successful separation those panels will be deployed and form a plane with the body-mounted center solar panel. The deployment will be accomplished by a newly developed mechanism consisting of two hinges and two binders per panel.

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The holding-down clamp features a melting wire mechnism is used and an escapement. The bolts retaining the solar panels during the launch are attached to the satellite using a split pod. This pod is held together by a melting wire during launch.  For deployment the wire is melt via a heat resistor, releasing the split pod. The bolt gets pulled out of the pod by a compression spring, so that the solar panels are unfolded by the prestressed hinges.

scharnier-180The hinges are partly designed as fixed joints and partly as plunging joints and they are prestressed by leg springs. The rotation energy during the deployment is absorbed by a damper so that transient oscillation is suppressed. After deployment the panels are held in place by the pretension of the mechanisms' leg springs. By using ball joints the hinge mechanism can compensate axis aberrations up to 1°.

 

The entire deployment mechanism has a mass of under 2 kg and a power consumption of 64 W for approx. 30 seconds.

 

 

 

De-orbit mechanism

In 2002 the "Inter-Agency Space Debris Coordination Committee" of the United Nations adopted a code of conduct on the prevention of space debris. It states that the owners of object in the low earth orbit have to ensure, that their object will reenter in the Earth's atmoshere within 25 years after its life time. This prevention of space debris reduces the risk of collisions between objects in low Earth orbit.

In orer to adhere to the UN regulation the FLP will carry a de-orbiting mechansim. The satellite system will deploy a 2.5 x 2.5 m² plain foil which increases the aerodynamic drag of the satellite in the residual atmosphere. Thus, the orbit height will decrease rapidly. The size of the foil is designed in a way that the Flying Laptop reenters into Earth's atmosphere within 25 years and will burned up there.

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The de-orbit mechanism is a purchase part and was developed in a cooperation of Tohoku University, Japan and the company Nakaschimada Engineering Works Ltd.