Engineering topics

Bush, Harold G.

Publications and source records attributed to Bush, Harold G..

32 records · Page 2

NASA NTRS1990

An articulated-truss space crane concept

An articulated-truss space-crane concept is described, and four articulating-joint (AJ) concepts are evaluated. The space-crane concept uses the same truss structure hardware as Space Station Freedom. The joint concepts are compared according to their actuator stroke ratio, actuator authority, and part count. One AJ concept is selected as a candidate space-crane joint because of its better performance and lower part count. The space-crane reach envelope is determined as a function of the number of AJs and the number of fixed-length booms. A space crane with three booms, three AJs, and one rotary joint provides an adequate reach envelope for an expected work area. The space-crane tip velocity, because of an allowable truss strut compressive load, is limited to approximately 1.0 in./sec for a 300,000-lbm payload. The displacement response is also shown for an emergency stop scenario as a function of the payload mass. The space-crane tip deflection is on the order of 12 in. for a 300,000-lbm payload.

Sutter, Thomas R.↗

NASA NTRS1990

The versatility of a truss mounted mobile transporter for in-space construction

The Mobile Transporter (MT) evolution from early erectable structures assembly activities is detailed. The MT operational features which are required to support astronauts performing on-orbit structure construction or spacecraft assembly functions are presented and discussed. Use of the MT to perform a variety of assembly functions is presented. Estimated EVA assembly times for a precision segmented reflector approximately 20 m in diameter are presented. The EVA/MT technique under study for construction of the reflector (and the entire spacecraft) is illustrated. Finally, the current status of development activities and test results involving the MT and Space Station structural assembly are presented.

Bush, Harold G.↗

NASA NTRS1989

Endjoints For Structural Elements

Endjoint and connecting-node system designed for use in erection of frames. System structurally sound and simple to operate. All nodes and struts interchangeable. Nodes and struts attach to form cubic cell structures to produce beams, platforms, towers, or combinations of these. Design suitable for use in construction of space structures and such terrestrial skeletal frameworks as antenna-reflector supports, roof structures for large buildings, lookout towers, radio-transmitter towers, powerline pylons, and scaffolds.

Bush, Harold G.↗

NASA NTRS1989

A comparison of two trusses for the space station structure

The structural performance of two truss configurations, the orthogonal tetrahedral and a Warren-type, are compared using finite element models representing the November Reference Phase 1 Space Station. The truss torsional stiffness properties and fundamental torsion frequency are determined using cantilever truss-beam models. Frequencies, mode shapes, transient response, and truss strut compressive loads are compared for the two space station models. The performance benefit resulting from using a high modulus truss strut is also presented. Finally, assembly and logistics characteristics of the two truss configurations are evaluated.

Sutter, Thomas R.↗

NASA NTRS1988

Lightweight structural design of a bolted case joint for the space shuttle solid rocket motor

The structural design of a bolted joint with a static face seal which can be used to join Space Shuttle Solid Rocket Motor (SRM) case segments is given. Results from numerous finite element parametric studies indicate that the bolted joint meets the design requirement of preventing joint opening at the O-ring locations during SRM pressurization. A final design recommended for further development has the following parameters: 180 one-in.-diam. studs, stud centerline offset of 0.5 in radially inward from the shell wall center line, flange thickness of 0.75 in, bearing plate thickness of 0.25 in, studs prestressed to 70 percent of ultimate load, and the intermediate alcove. The design has a mass penalty of 1096 lbm, which is 164 lbm greater than the currently proposed capture tang redesign.

Dorsey, John T.↗

NASA NTRS1988

Results of EVA/mobile transporter space station truss assembly tests

Underwater neutral buoyance tests were conducted to evaluate the use of a Mobile Transporter concept in conjunction with EVA astronauts to construct the Space Station Freedom truss structure. A three-bay orthogonal tetrahedral truss configuration with a 15 foot square cross section was repeatedly assembled by a single pair of pressure suited test subjects working from the Mobile Transporter astronaut positioning devices (mobile foot restraints). The average unit assembly time (which included integrated installation of utility trays) was 27.6 s/strut, or 6 min/bay. The results of these tests indicate that EVA assembly of space station size structures can be significantly enhanced when using a Mobile Transporter equipped with astronaut positioning devices. Rapid assembly time can be expected and are dependent primarily on the rate of translation permissible for on-orbit operations. The concept used to demonstate integrated installation of utility trays requires minimal EVA handling and consequentially, as the results show, has little impact on overall assembly time.

Watson, Judith J.↗

NASA NTRS1988

The versatility of a truss mounted mobile transporter for in-space construction

Bush, Harold G.↗

NASA NTRS1988

Lightweight structural design of a bolted case joint for the Space Shuttle Solid Rocket Motor

This paper presents the structural design of a bolted joint with a static face seal which can be used to join Space Shuttle Solid Rocket Motor (SRM) case segments. Results from numerous finite element parametric studies indicate that the bolted joint meets the design requirement of preventing joint opening at the O-ring locations during SRM pressurization. A final design recommended for further development has the following parameters: 180 1-inch-diameter studs, stud center line offset of .5 inches radially inward from the shell wall center line, flange thickness of 0.75 inches, bearing plate thickness of 0.25 inches, studs prestressed to 70 percent of ultimate load, and the intermediate alcove. The design has a mass penalty of 1096 lbm, which is 164 lbm greater than the currently proposed capture tang redesign.

Dorsey, John T.↗

NASA NTRS1988

Astronaut/EVA construction of Space Station

Four early space construction tests performed in neutral buoyancy and/or on-orbit to evaluate EVA for assembly of truss structures are reviewed and astronaut observations are presented. In addition, two ongoing ground test programs that address EVA assembly of full scale Space Station truss structure using a mobile transporter equipped with astronaut positioning arms are described. A truss joint design that enables EVA assembly while meeting structural design goals is also discussed.

Heard, Walter L., Jr.↗

NASA NTRS1988

Space truss construction studies

The ACCESS Shuttle Flight Experiment, designed to evaluate EVA for on-orbit assembly of erectable truss structure, is reviewed and principal results are summarized. In addition, two on-going ground test programs that address EVA assembly of full scale Space Station truss structure using a mobile transporter are described. A typical truss joint design that enables EVA assembly while satisfying structural requirements is also presented. Preliminary results indicate that assembly rates in excess of one strut/min are achievable.

Heard, Walter L.↗

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 NTRS1987

Design, construction, and utilization of a space station assembled from 5-meter erectable struts

The primary characteristics of the 5-meter erectable truss is presented, which was baselined for the Space Station. The relatively large 5-meter truss dimension was chosen to provide a deep beam for high bending stiffness yet provide convenient mounting locations for space shuttle cargo bay size payloads which are approx. 14.5 ft (4.4 m) in diameter. Truss nodes and quick attachment erectable joints are described which provide for evolutionary three dimensional growth and for simple maintenance and repair. A mobile remote manipulator system is described which is provided to assist in station construction and maintenance. A discussion is also presented of the construction of the Space Station and the associated extravehicular active (EVA) time.

Mikulas, Martin M., Jr.↗

NASA NTRS1987

Metal-Clad Graphite/Epoxy Tubes

Structural parts feature low weight, low thermal expansion, and high stiffness. Unique, non-labor-intensive manufacturing process developed for fabricating aluminum-clad graphite/epoxy (Gr/E) struts which meet Space Station requirements. Method of manufacturing struts provides procedure for using Gr/E material system in very efficient manner. Technique places all fibers in longitudinal direction for stiffness and strength. Aluminum surfaces provide transverse strength and resistance to atomic oxygen in environment.

Bush, Harold G.↗

NASA NTRS1987

Structural design of an in-line bolted joint for the space shuttle solid rocket motor case segments

Results of a structural design study of an in-line bolted joint concept which can be used to assemble Space Shuttle Solid Rocket Motor (SRM) case segments are presented. Numerous parametric studies are performed to characterize the in-line bolted joint behavior as major design variables are altered, with the primary objective always being to keep the inside of the joint (where the O-rings are located) closed during the SRM firing. The resulting design has 180 1-inch studs, an eccentricity of -0.5 inch, a flange thickness of 3/4 inch, a bearing plate thickness of 1/4 inch, and the studs are subjected to a preload which is 70% of ultimate. The mass penalty per case segment joint for the in-line design is 346 lbm more than the weight penalty for the proposed capture tang fix.

Dorsey, John T.↗