Nonlinear breathing vibrations of eccentric rotating composite laminated circular cylindrical shell subjected to temperature, rotating speed and external excitations

The Soil Moisture Active Passive1 (SMAP) instrument includes a conically scanning 6-m diameter deployable Astromesh reflector and feedhorn that rotates relative to a de-spun spacecraft at 14.6 RPM. This is the first application of a spinning Astromesh reflector. This paper describes the design and performance of the Reflector/Boom Assembly (RBA) under multiple constraints and requirements that are inherent to a spinning large flexible reflector/structure. The deployed RBA has stringent mass property control and knowledge requirements, structural natural frequency separation requirements, and all other typical ones including the antenna performance. Finally the validation of the design on the ground by analysis/test and its difficulties due to gravity are discussed.

Design and performance of Astromesh reflector onboard Soil Moisture Active Passive spacecraft

We study the multi-pulse jumping double-parameter homoclinic orbits and chaotic dynamics of the eccentric rotating ring truss antenna under combined the parametric and external excitations for the first time. Considering combined the parametric and external excitations, the averaged equations of the eccentric rotating circular cylindrical shell are obtained in the case of the primary parametric resonance-1/2 sub-harmonic resonance and 1:2 internal resonance by using the perturbation analysis. From the averaged equation, the theory of normal form is applied to find the explicit expression of the eccentric rotating circular cylindrical shell under combined the parametric and external excitations. Based on the extended Melnikov method, we study the multi-pulse double-parameter homoclinic bifurcation and chaos of the eccentric rotating circular cylindrical shell under combined the parametric and external excitations and also estimate the double-parameter chaotic threshold. Numerical simulations are utilized to study double-parameter chaotic dynamic behaviors of the eccentric rotating circular cylindrical shell under combined the parametric and external excitations based on the double-parameter Lyapunov exponents. When one of the excitations is constant, it is found that the temperature parametric excitation directly decides the occurrence of the chaotic motion and the external excitation determines the paths to chaos. It is also known that the topology shapes of the chaotic motions are similar when the excitations corresponding to the chaotic motions change in a small range. Otherwise, there exists the obvious difference of the shapes for the topological structure of the double-parameter chaotic motions in the eccentric rotating circular cylindrical shell.

Multi-pulse jumping double-parameter chaotic dynamics of eccentric rotating ring truss antenna under combined parametric and external excitations

Large deployable space antennas may be exposed to severe thermal environments in future space missions; extreme heat loads will result in considerable thermal stresses and deformations which seriously affects the accuracy of the antenna's parabolic surface. In this study, thermal–structural finite element analysis of a deployable AstroMesh antenna under extreme heat loads was presented. Considering position and orientation with respect to the Sun and Earth, the antenna's temperature changing law under orbital heat fluxes was first evaluated to find the worst condition as loading point. Analyses for the antenna under different levels of extreme heat loads were then performed to obtain the temperature distributions utilizing an equivalent quarter antenna model. Based on the temperature calculation results and prestress designs, structural analyses were finally made to gain the resulting stresses and deformations. The analysis results show that the existing antenna may generate significant performanc...

Thermal–structural analysis of large deployable space antenna under extreme heat loads

In recent and future space applications, affordability is becoming increasingly important, hence new kinds of large deployable mesh reflectors are being considered and used for satellite communications. We propose a new conceptual structure design for large deployable spaceborne antennas based on a folded fixed truss hoop reflector. Through analysis and simulation, this new structure is shown to have good mechanical performance and good electromagnetic performance. By comparing this new design with typical large deployable antenna structures, we show that our folded fixed truss hoop reflector is a potentially good selection for future affordable large deployable antennas in satellite communications.

New Conceptual Structure Design for Affordable Space Large Deployable Antenna

This paper will discuss the rationale, methodology, and principal results from a Solar Thermal Vacuum (STV) test of a deployable mesh reflector that was performed in the Jet Propulsion Laboratory's twenty-five foot Space Simulator.12 The test was performed in support of several Earth Science Missions to provide an empirical understanding of the thermoelastic behavior of a modern deployable mesh reflector. A state-of-the-art photogrammetry system was utilized to measure deformations of the reflector under various illuminations up to one full sun (1420 W/m2) in order to correlate and validate existing predictive analytical models. Photogrammetric resolution of 0.025 mm RMS (0.001″) was achieved over the entire 5 meter aperture for each test case. The resulting validated models will increase our confidence that Earth science mission instruments utilizing large aperture deployable mesh reflectors will perform as predicted. Furthermore, this testing has raised our deformation analysis capability for this reflector from Technology Readiness Level (TRL) 3 to TRL 6.

Solar Thermal Vacuum testing of deployable mesh reflector for model correlation

NASA's proposed Soil Moisture Active and Passive (SMAP) mission would provide global soil moisture content and freeze/thaw state measurements with a minimum repeat period of three days at the equator. To do so, the SMAP instrument would employ a conically scanning synthetic aperture radar (SAR) and a radiometer operating at L-band (1.20 GHz – 1.41 GHz) through a common feed assembly. The proposed mission profile plans to employ a near polar sun-synchronous orbit that would periodically allow for solar impingement upon the internal surfaces of the feed horn, which could result in solar entrapment. If left unaddressed, this solar entrapment would cause the instrument to exceed its tight thermal stability requirements. These thermal stability requirements result from the sensitivity of the radiometer electronics and their proximity to the feed assembly. As a result of these stability requirements, a radome was incorporated into the design to act as a thermal barrier. As such, this paper will discuss the material selection process, design rationale, analysis, and material property test campaign for the SMAP antenna feed radome.12

SMAP antenna feed radome: Design, development, and test

On September 10, 2008, a 36-hour Solar Thermal Vacuum Test of a 5m deployable mesh reflector was completed in JPL's 25' Space Simulator by the Advanced Deployable Structures Group at JPL. The testing was performed under NASA's Innovative Partnership Program (IPP) as a risk reduction effort for two JPL Decadal Survey Missions: DESDynI and SMAP. The 5.0 m aperture Astromesh reflector was provided by Northrop Grumman Aerospace Systems (NGAS) Astro Aerospace, our IPP industry partner. The testing utilized a state-of-the-art photogrammetry system to measure deformation of the reflector under LN2 cold soak, 0.25 Earth sun, 0.5 sun and 1.0 sun. An intricate network of thermocouples (approximately 200 in total) was used to determine the localized temperature across the mesh as well as on the perimeter truss of the reflector. Half of the reflector was in a fixed shadow to maximize thermal gradients. A mobility system was built for remotely actuating the cryo-vacuum capable photogrammetry camera around the circumference of the Solar Simulator. Photogrammetric resolution of 0.025 mm RMS (0.001") was achieved over the entire 5 meter aperture for each test case. The data will be used for thermo-elastic model correlation and validation, which will benefit the planned Earth Science Missions.

Matthew D. Stegman

Papers

Solar Thermal Vacuum testing of deployable mesh reflector for model correlation

SMAP antenna feed radome: Design, development, and test

Solar Thermal Vacuum Test of Deployable Astromesh Reflector