Peter A. Warren

Experimental Characterization of Lightweight Strain Energy Deployment Hinges

Elastic, lenticular hinges have been used for many years to provide simple, reliable, repeatable deployment of spacecraft structural components. Recent advances in high performance elastically flexible composites have opened up the application field for this useful deployment component by providing lighter, more thermally stable hinges as well as designs that can meet a much wider range of requirements. This paper describes recent advances in composite hinge performance through a combination of analysis and testing.

Experimental characterization of deployable outer barrel assemblies for large space telescopes

Several variations of large space-based observatories have been hypothesized using different approaches to deploying the primary and secondary mirrors on orbit. Careful consideration must also be given to the design and implementation of the shield that protects these observatories from thermal extremes, micro-debris, and controls stray light entry into the optical train. One approach to the shield architecture is use of an Optical Barrel Assembly (OBA), such as that used on the Hubble Space Telescope (HST). For space telescopes much larger than the HST, an OBA will need to be deployed or assembled to form an adequately large structure to fully shield both the primary mirror and secondary mirror. This paper describes the design, prototyping, characterization tests, and test results from two different OBA development efforts. The first design is a combined barrel and secondary mirror support structure. This system was designed for a fixed primary mirror and deploys straight upward along the optical axis, carrying the Secondary Mirror Assembly (SMA) with it. The second OBA design is of a structurally independent OBA that deploys out from behind the Primary Mirror Assembly (PMA) (itself deployed or assembled) and extends forward along the optical axis to completely enclose the optical train, pulling along the shroud material. Examples of both systems were built out of prototype materials, tested, and the test results were compared against modeled predictions of system performance. The designs, test procedures, and test results are presented along with recommendations for future work.

Dynamic Modeling of the Folding of Multi-Shell Flexible Composites

Flexible composite structural members have been key features in many deployable space structure designs. However designers of deployment systems that require complex folds, tighter packaging, more deployment torque and higher stiffness when deployed have been slow in adopting flexible composites. One reason for this is the difficulty in analyzing the complex strain field in flexing composite shells. This difficulty is exacerbated when multiple, separate shells come in contact with each other. This paper describes Finite Element modeling techniques used to analyze the strain and deployment force in multi-shell flexing composites. In the paper two Finite Element codes are compared with respect to the affect of various solution parameters on solution accuracy and time.

Experimental Characterization of an Extremely High Expansion Deployable Gossamer Structure

A wide variety of structural architectures have been explored to provide very lightweight or “gossamer” boom systems for several different space missions. For very large solar sails, antennae and other systems to be packaged into launch shrouds, they must have very low stowed volume and mass. In order to capitalize on the mass efficiency of tubular truss structures, these structures should have a deployed length to stowed length ratio of 200:1 or better. This paper describes the structural performance of a 323:1 expansion truss structure as determined by ground testing of a 10.7 meter prototype structure.

The Strain Energy Deployed High Expansion Outer Barrel Assembly

Future large aperture telescopes will require several deployable subsystems, including Primary Mirrors (PM), Secondary Mirror Support Structures (SMSS), and Optical Barrel Assemblies (OBA). The three subsystems must be specifically designed to package together but then deploy separately and operate without disturbing each other. This work presents a point design for a combined SMSS and OBA deployable structure for a non-deployed PM telescope. The architecture uses elastic strain energy composites to provide high precision, lightweight, reliable, and repeatedly verifiable deployment. A full scale proof of concept was built using non-flight materials and successfully stowed and deployed many times. Component and full system tests and analyses were performed to estimate the performance for an equivalent system using flight materials.

Strain Energy Deployment of Telescope Outer Barrel Assemblies

While some work has been done on the packaging and deployment of large space telescopes, the design of the accompanying Optical Barrel Assemblies (OBAs) that act as thermal and light shrouds for the telescopes have been relatively neglected. These systems must be lightweight, stiff, strong, reliable, and function without disturbing the overall telescope system. To investigate this problem, a modular, deployable structural system based on lightweight flexible composites has been developed. This system is called the Strain Energy Deployable OBA (SEDOBA). This paper describes the design, fabrication and testing of a deployable OBA based on this modular system approach for a 2-3m diameter telescope.

Lightweight Optical Barrel Assembly Structures for Large Deployable Space Telescopes

Future space based telescopes will need apertures and focal lengths that exceed the dimensions of the launch vehicle shroud. In addition to deploying the primary mirror and secondary mirror support structure, these large telescopes must also deploy the stray light and thermal barriers needed to ensure proper telescope performance. The authors present a deployable light and thermal optical barrel assembly approach for a very large telescope with a variable sun angle and fast slew rate. The Strain Energy Deployable Optical Barrel Assembly (SEDOBA) uses elastic composite hinges to power the deployment of a hierarchical truss structure that supports the thermal and stray light shroud material that form the overall system. The paper describes the overall design approach, the key component technologies, and the design and preliminary testing of a self deploying scale model prototype.

Structural Characterization of Carbon Nanotube Rope Films for Gossamer Structure Applications

Recent work has focused on making macroscopic materials from carbon nanotubes (CNTs) with the goal of maintaining the impressive structural characteristics of individual CNT. This paper presents a comparison of three-point bending and tensile extension methods for measuring the modulus of the new macroscopic epoxy infiltrated film samples made from aligned and unaligned CNT ropes. A method for measuring the film thickness to within 10 µm is also presented. Two processing variations are used in making the samples: incorporating micro-particles in the CNT network and densifying the aligned samples. The measured tensile moduli fall between 5 and 8 GPa for aligned and up to 10.5 GPa for unaligned samples with tensile moduli being between 40% and 100% larger than the bending