No abstract

No abstract

No abstract

No abstract

No abstract

Microvibration management onboard spacecraft with high stability requirements has drawn increasing interest from engineers and scientists, and this paper discusses a reaction wheel design that allows a significant reduction of mid-to high-frequency microvibrations and that has been practically implemented in industry. Disturbances typically induced by mechanical systems onboard a spacecraft (especially rotating devices such as reaction wheel assemblies and momentum wheel assemblies) can severely degrade the performance of sensitive instruments. Traditionally, wheel-induced high-frequency (over 100-200 Hz) vibrations, generated by a combination of phenomena from bearing noise to dynamic amplifications due to internal resonances, are especially difficult to control. In this paper, the dynamic behavior of a newly designed wheel assembly, with a cantilevered flywheel configuration supported by a soft-suspension system, is investigated. The wheel assembly's mathematical model is developed and later verified with vibration tests. Wheel-assembly-induced lateral and axial microvibrations are accurately measured using a seismic-mass microvibration measurement system, which represents an alternative to typical microvibration measurement setups. Finally, the performance of this wheel assembly in terms of microvibration emissions is compared with a traditional design (with a rigid suspension) through comparison of frequency spectra, and it is shown that this design produces significantly lower vibrations at high frequency. = at wheel-assembly/seismic-mass interface, in x and y directions md = dynamic imbalance condition ms = static imbalance condition r = torsional (spring and dashpot) s = wheel and seismic system s xx , s yy , s zz = orthogonal directions of wheel-assembly and seismic-mass system sx, sy, sz = orthogonal directions of wheel-assembly and seismic-mass system t = linear (spring and dashpot) w = flywheel x, y, z = orthogonal directions

An investigation on the structural performance of inserts within honeycomb sandwich panels is presented. The investigation considers metallic inserts in all aluminum sandwich panels and emphasis is placed on the structural performance difference between hot bonded and cold bonded inserts. The former are introduced during panel manufacture while the latter are potted into existing panels. The investigation focuses on the static performance of the two insert systems subject to loads in the normal direction to the facing plane. The experimental part of the work presented involved carrying out pullout tests on hot bonded and cold bonded reference samples by loading them at a centrally located insert. The experimental results were compared with results from an analytical model and results from a finite element model. Contrary to what was expected it was found from the experiments that the cold bonded inserts outperformed the hot bonded inserts in terms of load carrying capability. From the finite element study it was found that this was mainly due to the difference in stiffness of the different filler materials used in the two insert systems.

This is the second of two companion papers that describe the development of the RemoveDEBRIS space mission. This second article describes the in-orbit operations that were performed to demonstrate technologies to be used for the active removal of space debris, whereas the first paper described the development of the satellite's hardware. The RemoveDebris mission has been the world's first Active Debris Removal (ADR) mission to successfully demonstrate, in orbit, some cost effective technologies, including net and harpoon capture; and elements of the whole sequence of operations, like the visionbased navigation. The satellite was launched the 2 nd of April 2018, to the International Space Station (ISS) and from there, on the 20 th of June 2018, was deployed via the NanoRacks Kaber system into an orbit of 405 km altitude. During the mission, two 2U CubeSats have been released by the mothercraft platform as artificial debris targets, to demonstrate net capture and cameras to be used for vision based navigation. Harpoon capture has been demonstrated by deploying a target and then firing at it a harpoon tethered to the platform. The various phases of the missions have been monitored using relevant telemetry and video cameras, and this paper reports the results of the various demonstrations.