Structural Analysis and Test Comparison of a 20-Meter Inflation-Deployed Solar Sail

Under the direction of the NASA In-Space Propulsion Technology Office, the team of L Garde, NASA Jet Propulsion Laboratory, Ball Aerospace, and NASA Langley Research Center has been developing a scalable solar sail configuration to address NASA s future space propulsion needs. Prior to a flight experiment of a full-scale solar sail, a comprehensive test program was implemented to advance the technology readiness level of the solar sail design. These tests consisted of solar sail component, subsystem, and sub-scale system ground tests that simulated the aspects of the space environment such as vacuum and thermal conditions. In July 2005, a 20-m four-quadrant solar sail system test article was tested in the NASA Glenn Research Center s Space Power Facility to measure its static and dynamic structural responses. Key to the maturation of solar sail technology is the development of validated finite element analysis (FEA) models that can be used for design and analysis of solar sails. A major objective of the program was to utilize the test data to validate the FEA models simulating the solar sail ground tests. The FEA software, ABAQUS, was used to perform the structural analyses to simulate the ground tests performed on the 20-m solar sail test article. This paper presents the details of the FEA modeling, the structural analyses simulating the ground tests, and a comparison of the pretest and post-test analysis predictions with the ground test results for the 20-m solar sail system test article. The structural responses that are compared in the paper include load-deflection curves and natural frequencies for the beam structural assembly and static shape, natural frequencies, and mode shapes for the solar sail membrane. The analysis predictions were in reasonable agreement with the test data. Factors that precluded better correlation of the analyses and the tests were unmeasured initial conditions in the test set-up

Ground Testing A 20-Meter Inflation Deployed Solar Sail

Solar sails have been proposed for a variety of future space exploration missions and provide a cost effective source of propellantless propulsion. Solar sails span very large areas to capture and reflect photons from the Sun and are propelled through space by the transfer of momentum from the photons to the solar sail. The thrust of a solar sail, though small, is continuous and acts for the life of the mission without the need for propellant. Recent advances in materials and ultra-low mass gossamer structures have enabled a host of useful space exploration missions utilizing solar sail propulsion. The team of L Garde, NASA Jet Propulsion Laboratory (JPL), Ball Aerospace, and NASA Langley Research Center, under the direction of the NASA In-Space Propulsion Office (ISP), has been developing a scalable solar sail configuration to address NASA s future space propulsion needs. The 100-m baseline solar sail concept was optimized around the one astronomical unit (AU) Geostorm mission, and features a Mylar sail membrane with a striped-net sail suspension architecture with inflation-deployed sail support beams consisting of inflatable sub-Tg (glass transition temperature) rigidizable semi-monocoque booms and a spreader system. The solar sail has vanes integrated onto the tips of the support beams to provide full 3-axis control of the solar sail. This same structural concept can be scaled to meet the requirements of a number of other NASA missions. Static and dynamic testing of a 20m scaled version of this solar sail concept have been completed in the Space Power Facility (SPF) at the NASA Glenn Plum Brook facility under vacuum and thermal conditions simulating the operation of a solar sail in space. This paper details the lessons learned from these and other similar ground based tests of gossamer structures during the three year solar sail project

Structural Analysis of an Inflation-Deployed Solar Sail With Experimental Validation

Under the direction of the NASA In-Space Propulsion Technology Office, the team of L Garde, NASA Jet Propulsion Laboratory, Ball Aerospace, and NASA Langley Research Center has been developing a scalable solar sail configuration to address NASA s future space propulsion needs. Prior to a flight experiment of a full-scale solar sail, a comprehensive phased test plan is currently being implemented to advance the technology readiness level of the solar sail design. These tests consist of solar sail component, subsystem, and sub-scale system ground tests that simulate the vacuum and thermal conditions of the space environment. Recently, two solar sail test articles, a 7.4-m beam assembly subsystem test article and a 10-m four-quadrant solar sail system test article, were tested in vacuum conditions with a gravity-offload system to mitigate the effects of gravity. This paper presents the structural analyses simulating the ground tests and the correlation of the analyses with the test results. For programmatic risk reduction, a two-prong analysis approach was undertaken in which two separate teams independently developed computational models of the solar sail test articles using the finite element analysis software packages: NEiNastran and ABAQUS. This paper compares the pre-test and post-test analysis predictions from both software packages with the test data including load-deflection curves from static load tests, and vibration frequencies and mode shapes from structural dynamics tests. The analysis predictions were in reasonable agreement with the test data. Factors that precluded better correlation of the analyses and the tests were uncertainties in the material properties, test conditions, and modeling assumptions used in the analyses

Nonlinear Structural Analysis Methodology and Dynamics Scaling of Inflatable Parabolic Reflector Antenna Concepts

Ultra-light weight and ultra-thin membrane inflatable antenna concepts are fast evolving to become the state-of-the-art antenna concepts for deep-space applications. NASA Langley Research Center has been involved in the structural dynamics research on antenna structures. One of the goals of the research is to develop structural analysis methodology for prediction of the static and dynamic response characteristics of the inflatable antenna concepts. This research is focused on the computational studies to use nonlinear large deformation finite element analysis to characterize the ultra-thin membrane responses of the antennas. Recently, structural analyses have been performed on a few parabolic reflector antennas of varying size and shape, which are referred in the paper as 0.3 meters subscale, 2 meters half-scale, and 4 meters full-scale antenna. The various aspects studied included nonlinear analysis methodology and solution techniques, ways to speed convergence in iterative methods, the sensitivities of responses with respect to structural loads, such as inflation pressure, gravity, and pretension loads in the ground and in-space conditions, and the ultra-thin membrane wrinkling characteristics. Several such intrinsic aspects studied have provided valuable insight into evaluation of structural characteristics of such antennas. While analyzing these structural characteristics, a quick study was also made to assess the applicability of dynamics scaling of the half-scale antenna. This paper presents the details of the nonlinear structural analysis results, and discusses the insight gained from the studies on the various intrinsic aspects of the analysis methodology. The predicted reflector surface characteristics of the three inflatable ultra-thin membrane parabolic reflector antenna concepts are presented as easily observable displacement fringe patterns with associated maximum values, and normal mode shapes and associated frequencies. Wrinkling patterns are presented to show how surface wrinkle progress with increasing tension loads. Antenna reflector surface accuracies were found to be very much dependent on the type and size of the antenna, the reflector surface curvature, reflector membrane supports in terms of spacing of catenaries, as well as the amount of applied load

Test and Analysis of an Inflatable Parabolic Dish Antenna

NASA is developing ultra-lightweight structures technology for large communication antennas for application to space missions. With these goals in mind, SRS Technologies has been funded by NASA Glenn Research Center (GRC) to undertake the development of a subscale ultra-thin membrane inflatable antenna for deep-space applications. One of the research goals is to develop approaches for prediction of the radio frequency and structural characteristics of inflatable and rigidizable membrane antenna structures. GRC has teamed with NASA Langley Research Center (LaRC) to evaluate inflatable and rigidizable antenna concepts for potential space missions. GRC has completed tests to evaluate RF performance, while LaRC completed structural tests and analysis to evaluate the static shape and structural dynamic responses of a laboratory model of a 0.3 meter antenna. This paper presents the details of the tests and analysis completed to evaluate the radio frequency and structural characteristics of the antenna

Hydraulic Performance and Mass Transfer Efficiency of Engineering Scale Centrifugal Contactors

Annular centrifugal contactors (ACCs) are being evaluated for process-scale solvent extraction operations in support of Advanced Fuel Cycle Initiative (AFCI) separations goals. Process-scale annular centrifugal contactors have the potential for high stage efficiency if properly employed and optimized for the application. Hydraulic performance issues related to flow instability and classical flooding are likely unimportant, especially for units with high throughputs. However, annular mixing increases rapidly with increasing rotor diameter while maintaining a fixed g force at the rotor wall. In addition, for engineering/process-scale contactors, elevated rotor speeds and/or throughput rates, can lead to organic phase foaming at the rotor discharge collector area. Foam buildup in the upper rotor head area can aspirate additional vapor from the contactor housing resulting in a complete loss of separation equilibrium. Variable speed drives are thus desirable to optimize and balance the operating parameters to help ensure acceptable performance. Proper venting of larger contactors is required to balance pressures across individual stages and prevent vapor lock due to foam aspiration

THE TESTING OF COMMERCIALLY AVAILABLE ENGINEERING AND PLANT SCALE ANNULAR CENTRIFUGAL CONTACTORS FOR THE PROCESSING OF SPENT NUCLEAR FUEL

Annular centrifugal contactors are being evaluated for process scale solvent extraction operations in support of United State Advanced Fuel Cycle Initiative goals. These contactors have the potential for high stage efficiency if properly employed and optimized for the application. Commercially available centrifugal contactors are being tested at the Idaho National Laboratory to support this program. Hydraulic performance and mass transfer efficiency have been measured for portions of an advanced nuclear fuel cycle using 5-cm diameter annular centrifugal contactors. Advanced features, including low mix sleeves and clean-in-place rotors, have also been evaluated in 5-cm and 12.5-cm contactors

Testing of a 10-meter Quadrant Solar Sail

The purpose of this paper is to address the technical challenges and requirements of modal testing a solar sail system (Fig. 1). Specific objectives of this work are to investigate the effectiveness (i.e. accuracy, precision, repeatability, etc.) of laser vibrometer measurements obtained on solar sail components (i.e. sail membrane quadrant and masts) actuated with various excitation methods in vacuum conditions. Results from this work will be used to determine the appropriate test technique for testing large scale full quadrant flight-like solar sail system hardware in vacuum conditions. This paper will focus on the dynamic tests conducted in-vacuum on a 10-meter solar sail quadrant development by AEC-ABLE as part of a ground demonstrator system development program funded by NASA's In-Space Propulsion program. One triangular shaped quadrant of a solar sail membrane (Fig. 2) was modal tested in a 1 Torr vacuum environment using various excitation techniques including, shaker excitation through the masts, magnetic excitation (Ref. 3), and surface-bonded piezoelectric patch actuators (Ref. 4 & 5). The excitation methods are evaluated for their applicability to in-vacuum ground testing and their traceability to the development of on-orbit flight test techniques. The solar sail masts (Fig. 3) were also tested in ambient atmospheric conditions and vacuum using various excitation techniques and these methods will also be assessed for their ground test capabilities and traceability to on-orbit flight testing

In-Space Structural Assembly: Applications and Technology

As NASA exploration moves beyond earth's orbit, the need exists for long duration space systems that are resilient to events that compromise safety and performance. Fortunately, technology advances in autonomy, robotic manipulators, and modular plug-and-play architectures over the past two decades have made in-space vehicle assembly and servicing possible at acceptable cost and risk. This study evaluates future space systems needed to support scientific observatories and human/robotic Mars exploration to assess key structural design considerations. The impact of in-space assembly is discussed to identify gaps in structural technology and opportunities for new vehicle designs to support NASA's future long duration missions

Hydraulic and Clean-in-Place Evaluations for a 12.5-cm Annular Centrifugal Contactor at INL

Hydraulic and Clean-in-Place Evaluations for a 12.5 cm Annular Centrifugal Contactor at the INL Troy G. Garn, Dave H. Meikrantz, Nick R. Mann, Jack D. Law, Terry A. Todd Idaho National Laboratory Commercially available, Annular Centrifugal Contactors (ACC) are currently being evaluated for processing dissolved nuclear fuel solutions to selectively partition integrated elements using solvent extraction technologies. These evaluations include hydraulic and clean-in-place (CIP) testing of a commercially available 12.5 cm unit. Data from these evaluations is used to support design of future nuclear fuel reprocessing facilities. Hydraulic testing provides contactor throughput performance data on two-phase systems for a wide range of operating conditions. Hydraulic testing results on a simple two-phase oil and water system followed by a 30 % Tributyl phosphate in N-dodecane / nitric acid pair are reported. Maximum total throughputs for this size contactor ranged from 20 to 32 liters per minute without significant other phase carryover. A relatively new contactor design enhancement providing Clean-in-Place capability for ACCs was also investigated. Spray nozzles installed into the central rotor shaft allow the rotor internals to be cleaned, offline. Testing of the solids capture of a diatomaceous earth/water slurry feed followed by CIP testing was performed. Solids capture efficiencies of >95% were observed for all tests and short cold water cleaning pulses proved successful at removing solids from the rotor