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At least 559 records · Page 31

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NASA NTRS1987

Mobile remote manipulator vehicle system

A mobile remote manipulator system is disclosed for assembly, repair and logistics transport on, around and about a space station square bay truss structure. The vehicle is supported by a square track arrangement supported by guide pins integral with the space station truss structure and located at each truss node. Propulsion is provided by a central push-pull drive mechanism that extends out from the vehicle one full structural bay over the truss and locks drive rods into the guide pins. The draw bar is now retracted and the mobile remote manipulator system is pulled onto the next adjacent structural bay. Thus, translation of the vehicle is inchworm style. The drive bar can be locked onto two guide pins while the extendable draw bar is within the vehicle and then push the vehicle away one bay providing bidirectional push-pull drive. The track switches allow the vehicle to travel in two orthogonal directions over the truss structure which coupled with the bidirectional drive, allow movement in four directions on one plane. The top layer of this trilayered vehicle is a logistics platform. This platform is capable of 369 degees of rotation and will have two astronaut foot restraint platforms and a space crane integral.

Bush, Harold G.↗

NASA NTRS1989

Investigation of structural behavior of candidate Space Station structure

Quantitative evaluations of the structural loads, stiffness and deflections of an example Space Station truss due to a variety of influences, including manufacturing tolerances, assembly operations, and operational loading are reported. The example truss is a dual-keel design composed of 5-meter-cube modules. The truss is 21 modules high and 9 modules wide, with a transverse beam 15 modules long. One problem of concern is the amount of mismatch which will be expected when the truss is being erected on orbit. Worst-case thermal loading results in less than 0.5 inch of mismatch. The stiffness of the interface is shown to be less than 100 pounds per inch. Thus, only moderate loads will be required to overcome the mismatch. The problem of manufacturing imperfections is analyzed by the Monte Carlo approach. Deformations and internal loads are obtained for ensembles of 100 example trusses. All analyses are performed on a personal computer. The necessary routines required to supplement commercially available programs are described.

Hedgepeth, John M.↗

NASA NTRS1991

Concepts, analysis and development for precision deployable space structures

Several issues surrounding the development of large Precision Segmented Reflector (PSR) designs are investigated. The concerns include nonlinear dynamics of large unruly masses such as the multi-layer thermal insulation of sunshades for instruments such as the precision pointing 20-m-diameter Large Deployable Reflector (LDR). A study of the residual oscillations after bang-bang reorientation maneuvers of a rigid satellite with a string appendage is presented. Application is made to the design of a sunshade (thermal blanket) for the LDE satellite. Another concern is the development of a deployable truss that has minimum structural redundancy (such as the tetrahedral truss) and that can be configured with planar and doubly curved geometries. A kinematically synchronized articulation scheme for a deployable tetrahedral truss is presented. Called the Tetrapac, this truss is currently limited to a planar configuration that has two rings. The final concern is the development and demonstration of hardware that enables astronauts to attach large, cumbersome, and fragile precision reflector segments to an erectable truss structure. This task must be accomplished with a high degree of precision and with relative ease. A design for a Panel Attachment Device (PAD) was developed and manufactured for neutral buoyancy simulations to be performed by LaRC.

Miller, Richard K.↗

NASA NTRS1990

Design of internal support structures for an inflatable lunar habitat

NASA has a long range goal of constructing a fully equipped, manned lunar outpost on the near side of the moon by the year 2015. The proposed outpost includes an inflatable lunar habitat to support crews during missions longer that 12 months. A design for the internal support structures of the inflatable habitat is presented. The design solution includes material selection, substructure design, assembly plan development, and concept scale model construction. Alternate designs and design solutions for each component of the design are discussed. Alternate materials include aluminum, titanium, and reinforced polymers. Vertical support alternates include column systems, truss systems, suspension systems, and lunar lander supports. Horizontal alternates include beams, trusses, floor/truss systems, and expandable trusses. Feasibility studies on each alternate showed that truss systems and expandable trusses were the most feasible candidates for conceptual design. The team based the designs on the properties of 7075 T73 aluminum. The substructure assembly plan, minimizes assembly time and allows crews to construct the habitat without the use of EVA suits. In addition to the design solutions, the report gives conclusions and recommendations for further study of the inflatable habitat design.

Cameron, Elizabeth A.↗

NASA NTRS1995

Description of and preliminary tests results for the Joint Damping Experiment (JDX)

An effort is currently underway to develop an experiment titled joint Damping E_periment (JDX) to fly on the Space Shuttle as Get Away Special Payload G-726. This project is funded by NASA's IN-Space Technology Experiments Program and is scheduled to fly in July 1995 on STS-69. JDX will measure the influence of gravity on the structural damping of a three bay truss having clearance fit pinned joints. Structural damping is an important parameter in the dynamics of space structures. Future space structures will require more precise knowledge of structural damping than is currently available. The mission objectives are to develop a small-scale shuttle flight experiment that allows researchers to: (1) characterize the influence of gravity and joint gaps on structural damping and dynamic behavior of a small-scale truss model, and (2) evaluate the applicability of low-g aircraft test results for predicting on-orbit behavior. Completing the above objectives will allow a better understanding and/or prediction of structural damping occurring in a pin jointed truss. Predicting damping in joints is quite difficult. One of the important variables influencing joint damping is gravity. Previous work has shown that gravity loads can influence damping in a pin jointed truss structure. Flying this experiment as a GAS payload will allow testing in a microgravity environment. The on-orbit data (in micro-gravity) will be compared with ground test results. These data will be used to help develop improved models to predict damping due to pinned joints. Ground and low-g aircraft testing of this experiment has been completed. This paper describes the experiment and presents results of both ground and low-g aircraft tests which demonstrate that damping of the truss is dramatically influenced by gravity.

Bingham, Jeffrey G.↗

NASA NTRS2002

STS 110 Mission Highlights Resource Tape

A continuation of 'STS 110 Mission Highlights Resource Tape'. This video, Part 3 of 4, shows footage from flight days 6 through 9 of STS-110. The spacecrew includes Michael J. Bloomfield, Commander Stephen N. Frick, Pilot; Jerry L. Ross, Mission Specialist; Steven L. Smith, Mission Specialist; Ellen Ochoa, Mission Specialist; Lee M.E. Morin, Mission Specialist; Rex J. Walheim, Mission Specialist. On flight day 6, Ross and Morin conduct an EVA (extravehicular activity) to secure a tripod like strut to the S0 Truss of the International Space Station (ISS). They also move the drag link and keel pins from one face of the Truss to the other to free the rail on the truss for a railcar to move. Smith installs a camera onto the CANADARM robotic arm on flight day 7, and on flight day 8 the restraints are removed from the railcar connected to the S0 Truss in preparation for checkout. The checkout of the railcar is shown, including its inaugural run. Ross and Morin conduct another EVA on flight day 9 to complete the outfitting of the S0 Truss Structure. Notable footage includes views of Ross and Morin at work from the helmet-mounted camera on Ross' EVA suit, including close-ups of the pistol grip tool, CANADARM 2 onboard the ISS lit at sunrise, a 'diamond ring' effect formed by the Sun between the Earth's limb and the ISS, a brief shot of the Yucatan peninsula, and a end-to-end pan down the length of the ISS. The activities from other flights days can be seen on "STS 110 Mission Highlights Resource Tape" Part 1 of 4 (internal ID 2002137575), "STS 110 Mission Highlights Resource Tape" Part 2 of 4 (internal ID 2002137573), and "STS 110 Mission Highlights Resource Tape" Part 4 of 4 (internal ID 2002137517).

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NASA NTRS2003

STS-112 Mission Highlights Resource Tape Part 2 of 3

An overview of the STS-112 Mission is presented. The fourth flight day begins with a view inside of the Destiny Laboratory of the International Space Station where Expedition Five Commander Valery Korzun is shown. The robotics workstation where Mission Specialist Sandra Mangus and Flight Engineer Peggy Whitson operate Canadarm 2 to lift the S(1) Truss segment out of the payload bay of the Space Shuttle Atlantis and maneuver it for installation onto the S(1) Truss is presented. Mission Specialist Piers Sellers is shown preparing for his six and one half hour spacewalk by performing breathing exercises. Animation of the installation of the S(1) Truss, and also the unbirthing of the S(1) truss is also presented. Mission Specialists David Wolf and Piers Sellers are shown getting suited for their spacewalks. During the spacewalk, David Wolf is removing the antenna assembly from its launched position and Piers Sellers is releasing launch restraints from the Radiator Beam Assembly. A beautiful view of the coast of Texas is captured during this spacewalk. Flight day five shows pilot Pam Melroy and Mission Specialist Dave Wolf working inside of the International Space Station's Quest Airlock. Flight day six is shown with Dave Wolf and Piers Sellers exiting their spacesuits inside of the Quest Airlock Module after a successful spacewalk. This presentation ends with views of the International Space Station's installed S(1) Truss, rotation of the radiator assembly and the radiator's coolant tubing.

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NASA NTRS2003

STS-113 Mission Highlights Resource Tape Flight Days 4-6 Tape: 2 of 4

This video, Part 2 of 4, shows the activities of the crew of the Space Shuttle Endeavor on flight days 4-6 of STS-113. The crew consists of Commander Jim Wetherbee, Pilot Paul Lockhart, and Mission Specialists Michael Lopez-Alegria and John Herrington. On flight day 4, The P1 truss was transfered from Canadarm on Endeavour to Canadarm 2 on the ISS, and aligned with the S0 Truss for attachment. The mission specialists connected utility cables between the trusses on an extravehicular activity (EVA). Flight day 5 was Commander Wetherbee's 50th birthday, and the video includes a clip from The Tonight Show in which Jay Leno wishes him a happy birthday. Intravehicular activity on flight day 5 includes Peggy Whitsun of the outgoing Expedition 5 crew of the International Space Station (ISS) showing incoming Expedition 6 crew members Ken Bowersox and Don Pettit how to replace valves on the ISS CO2 removal system. The video also includes an interior tour of Endeavour and the ISS, and an brief exterior tour of the ISS. On flight day 6 Lopez-Alegria and Herrington attach a television antenna to the P1 truss, and are shown using a handcart on the truss several times. The video includes several Earth views, including one of the west coast of South America.

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NASA NTRS1997

Experimental Characterization of Hysteresis in a Revolute Joint for Precision Deployable Structures

Recent studies of the micro-dynamic behavior of a deployable telescope metering truss have identified instabilities in the equilibrium shape of the truss in response to low-energy dynamic loading. Analyses indicate that these micro-dynamic instabilities arise from stick-slip friction within the truss joints (e.g., hinges and latches). The present study characterizes the low-magnitude quasi-static load cycle response of the precision revolute joints incorporated in the deployable telescope metering truss, and specifically, the hysteretic response of these joints caused by stick-slip friction within the joint. Detailed descriptions are presented of the test setup and data reduction algorithms, including discussions of data-error sources and data-filtering techniques. Test results are presented from thirteen specimens, and the effects of joint preload and manufacturing tolerances are investigated. Using a simplified model of stick-slip friction, a relationship is made between joint load-cycle behavior and micro-dynamic dimensional instabilities in the deployable telescope metering truss.

Lake, Mark S.↗

NASA NTRSDate not supplied

Towers: Critical Initial Infrastructure for the Moon, Such as a Power Module Support

Towers are an efficient structure commonly used to elevate systems against a gravity field, such as above the surface of a planet or the Moon. Towers can be used to elevate antennas, transmitters and sensors for communication, navigation, and observation infrastructure in support of surface operations. Near the Lunar poles, elevation of rotating solar panels enables nearly continuous panel illumination for solar power production despite the Sun remaining near the horizon year-round. Further, once technology is developed for tower assembly, this same technology can be extended to the assembly of a variety of structures including rocket blast containment shields, bridges, shelters, and habitats from either Earth-sourced or Lunar-sourced structural members. Environmental factors on the Lunar surface are vastly different than those found on Earth and have significant impact on the design of towers. Towers designed for the Lunar surface have no heritage nor Earth analog. The designs discussed herein are therefore breaking new ground creating a fundamentally new class of structures outside of current experience and intuition. The purpose of this paper is to: a) describe the unique environmental factors affecting tower design on the Lunar surface compared to Earth-based systems, b) evaluate two structural forms for the tower; telescoping tubes and an assembled truss, as well as c)provide recommendations on when each structural form is most suitable. A major contribution presented in the current paper is to provide parametric plots and supporting equations of mass and volume versus module power level and blanket height above the Lunar surface for the solar array application, to enable system level studies of optimum power module distribution and size. A secondary contribution are plots of the mass and volume of aluminum or structural glass required for assembled truss towers formed from Lunar derived structural members. An objective of achieving 1 MW of total power has been used to enable comparison of structural forms, because the total mass of solar arrays is consistent. It will be shown that for moderate module sizes, up to ~50 kW power modules, based on a telescoping tube tower have advantages, but for power modules from 50 kW to 200 kW an assembled truss tower can be created with half to one third of the tube tower mass. More significantly, when shipped from Earth, an assembled truss tower can be packed into 1/14th to 1/25th of the tube tower volume. Truss designs in the 100 kW to 200 kW range will be shown to be a favorable when assembled from either graphite-epoxy angles shipped from Earth or aluminum angles fabricated from Lunar materials. 50 kW towers are an attractive choice for both a telescoping or assembled tower with the solar arrays elevated 10 m above the Lunar surface, while increased solar array elevation favors 100 kW to 200 kW power modules.

assembly↗

NASA NTRS1981

Progress in composite structure and space construction systems technology

The development of deployable and fabricated composite trusses for large space structures by NASA and private industry is reviewed. Composite materials technology is discussed with a view toward fabrication processes and the characteristics of finished truss beams. Advances in roll-forming open section caps from graphite-composite strip material and new ultrasonic welding techniques are outlined. Vacuum- and gravity-effect test results show that the ultrasonic welding of graphite-thermoplastic materials in space is feasible. The structural characteristics of a prototype truss segment are presented. A new deployable graphite-composite truss with high packaging density for broad application to large space platforms is described.

Bodle, J. B.↗

NASA NTRS1980

Accuracy potentials for large space antenna structures

The relationships among materials selection, truss design, and manufacturing techniques in the interest of surface accuracies for large space antennas are discussed. Among the antenna configurations considered are: tetrahedral truss, pretensioned truss, and geodesic dome and radial rib structures. Comparisons are made of the accuracy achievable by truss and dome structure types for a wide variety of diameters, focal lengths, and wavelength of radiated signal, taking into account such deforming influences as solar heating-caused thermal transients and thermal gradients.

Hedgepeth, J. M.↗

NASA NTRS1983

System identification of large flexible structures by using simple continuum models

Simple continuum models for the representation of large truss beams and truss platforms are constructed and employed in the solution of system identification problems permitting the significant reduction of the number of structural parameters. Two simple and easily computer-implemented algorithms are presented for the estimation of a simple model's equivalent structural parameters, and analytical and numerical solutions are given for the truss beam and truss platform cases in order to illustrate the basic concepts. It is found that model simplicity, in conjunction with the principle of least square erors, yields a feasible integration of structural and identification problems.

Juang, J. N.↗

NASA NTRS1981

SPF/DB primary structure for supersonic aircraft (T-38 horizontal stabilizer)

The structural integrity and potential cost savings of superplastic forming/diffusion bonding (SPF/DB) titanium structure for future Supersonic Cruise Research (SCR) and military aircraft primary structure applications was demonstrated. Using the horizontal stabilizer of the T-38 aircraft as a baseline, the structure was redesigned to the existing criteria and loads, using SPF/DB titanium technology. The general concept of using a full-depth sandwich structure which is attached to a steel spindle, was retained. Trade studies demonstrated that the optimum design should employ double-truss, sinewave core in the deepest section of the surface, making a transition to single-truss core in the thinner areas at the leading and trailing edges and at the tip. At the extreme thin edges of the surface, the single-truss core was changed to dot core to provide for gas passages during the SPF/DB process. The selected SPF/DB horizontal stabilizer design consisted of a one-piece SPF/DB sinewave truss core panel, a trunnion fitting, and reinforcing straps. The fitting and the straps were mechanically fastened to the SPF/DB panel.

Delmundo, A. R.↗

NASA NTRS1985

ACCESS (Assembly Concept for Construction of Erectable Space Structure) - A Shuttle flight experiment

ACCESS is a planned Shuttle flight experiment to assess the potential of an on-orbit construction concept designed for efficient manual assembly of a space truss. The experiment, which is scheduled for launch November 27, 1985, on the Space Transportation System (STS) flight 61-B, uses two astronauts secured in fixed foot restraints located in the Shuttle cargo bay to assemble a 45-foot long aluminum truss beam from 93 tubular struts and 33 nodal joints. Neutral buoyancy simulations of the flight experiment indicate the truss can be assembled in less than thirty minutes. Structural assembly, structural repair, flexible cable attachment and manual manipulation of the truss is also planned for the experiment using an astronaut secured in the Manipulator Foot Restraint attached to the Remote Manipulator System arm. Flight assembly data will be generated for correlation of the neutral buoyancy ground test data. This paper describes the ACCESS flight experiment and presents results of the neutral buoyancy development and training tests.

Heard, W. L., Jr.↗

NASA NTRS1986

A space station Structures and Assembly Verification Experiment, SAVE

The Space Station structure has been baselined to be a 5 M (16.4 ft) erectable truss. This structure will provide the overall framework to attach laboratory modules and other systems, subsystems and utilities. The assembly of this structure represents a formidable EVA challenge. To validate this capability the Space Station Structures/Dynamics Technical Integration Panel (TIP) met to develop the necessary data for an integrated STS structures flight experiment. As a result of this meeting, the Langley Research Center initiated a joint Langley/Boeing Aerospace Company study which supported the structures/dynamics TIP in developing the preliminary definition and design of a 5 M erectable space station truss and the resources required for a proposed flight experiment. The purpose of the study was to: (1) devise methods of truss assembly by astronauts; (2) define a specific test matrix for dynamic characterization; (3) identify instrumentation and data system requirements; (4) determine the power, propulsion and control requirements for the truss on-orbit for 3 years; (5) study the packaging of the experiment in the orbiter cargo bay; (6) prepare a preliminary cost estimate and schedule for the experiment; and (7) provide a list of potential follow-on experiments using the structure as a free flyer. The results of this three month study are presented.

Russell, R. A.↗

NASA NTRS1987

Equivalent beam modeling using numerical reduction techniques

Numerical procedures that can accomplish model reductions for space trusses were developed. Three techniques are presented that can be implemented using current capabilities within NASTRAN. The proposed techniques accomplish their model reductions numerically through use of NASTRAN structural analyses and as such are termed numerical in contrast to the previously developed analytical techniques. Numerical procedures are developed that permit reductions of large truss models containing full modeling detail of the truss and its joints. Three techniques are presented that accomplish these model reductions with various levels of structural accuracy. These numerical techniques are designated as equivalent beam, truss element reduction, and post-assembly reduction methods. These techniques are discussed in detail.

Chapman, J. M.↗

NASA NTRS1986

Space station structures development

A study of three interrelated tasks focusing on deployable Space Station truss structures is discussed. Task 1, the development of an alternate deployment system for linear truss, resulted in the preliminary design of an in-space reloadable linear motor deployer. Task 2, advanced composites deployable truss development, resulted in the testing and evaluation of composite materials for struts used in a deployable linear truss. Task 3, assembly of structures in space/erectable structures, resulted in the preliminary design of Space Station pressurized module support structures. An independent, redundant support system was developed for the common United States modules.

Teller, V. B.↗