Browsing by Author "Carpenter, Lemuel"
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Item Application of Composite Materials to Reduce Mass of Internal and External Exploration Habitat Structures(49th International Conference on Environmental Systems, 2019-07-07) Simon, Matthew; Carpenter, Lemuel; Hrinda, Glenn; Bergan, Andrew; Samareh, Jamshid; Mitrou, AnatoliHabitats for human exploration missions to the Moon and Mars (including rovers and surface ascent cabins) are often massive elements, which must be pushed through many propulsive burns. Small increases in habitat mass can translate into large mass changes in launch vehicle and propulsion stage masses, which often drive the affordability and complexity of missions. Targeted investments in technologies that substantially reduce mass of habitats, such as lightweight, composite structures, are impactful for any human exploration mission. In previous studies, composite structures have been proposed to significantly reduce the mass of habitat primary structures over traditional aluminum structures. However, these designs faced challenges including certification, damage tolerance, inherited requirements, a lack of early consideration of required joints, and challenges manufacturing large-scale sealed structures. There is an opportunity to achieve substantial mass savings by implementing multiple-composite habitat structures, which apply different, optimal composite materials and structural concepts for each part of the habitat structure (e.g., acreage, discontinuities, secondary structure, interior equipment cases) customized to its unique structural requirements (e.g., strength, loads, and damage tolerance). This paper describes the current progress of a study into composite habitat structures to identify those beneficial composite materials and layups that enable substantial mass savings (target of >20%) at similar cost and risk of existing metallic structures. Composite material systems and structural concepts are assessed for their desirable structural properties, ease of manufacture, technical maturity, cost, and ability to join efficiently with other composite and metallic structures using a representative Mars Transit Habitat. The differences and implications for a lunar ascent module application are briefly discussed.Item Concept Evaluation of Minimal In-Space Vehicles in Support of Exploration External Operations(48th International Conference on Environmental Systems, 2018-07-08) Carpenter, Lemuel; Akin, DavidExperience gained with International Space Station has demonstrated the need for both planned and contingency external operations to maintain system functions. As the focus shifts to operations beyond low Earth orbit such as the Deep Space Gateway and eventually Mars transit vehicles, the need for external operations will not decrease, but the remoteness, communications limitations, and implications of an EVA accident will change the approach taken. One factor would be the proposed space exploration vehicle (SEV), currently envisioned as a two-person vehicle capable of supporting EVA via suitports and designed for extended duration sorties. However, the current SEV concepts are spacecraft of a scale comparable in mass to Dragon or Starliner vehicles, and therefore unlikely to be affordable in a cost- and mass-constrained exploration architecture. In addition to a simple mass-based cost estimate, some of the more recognizable features of the current concepts, such as multiple large windows, will further amplify the development and production costs of the system. As an outgrowth of ongoing research into single-person space utility vehicles, the University of Maryland has performed a number of studies of the potential roles of small vehicles to support external operations in microgravity. In this paper, we consider how direct ``eyes-on'' vision compares to various forms of video in the control of dexterous robotics. Tests to date have demonstrated that direct vision is generally inferior to multiple high-resolution video views, calling into question the need for large and/or multiple windows.Item Design of a Multipurpose Extensible Space Habitat - Vanguard(47th International Conference on Environmental Systems, 2017-07-16) Joyce, Ryan; Carpenter, Lemuel; Chang, Jian-Ming; Akin, DavidThis paper documents recent design activities at the University of Maryland in the engineering development of a multirole habitation system designed for an initial low Earth orbit application, but capable of being replicated for or moved to deep-space locations as well. The design effort started with the development of a set of detailed requirements with specific applicability in parallel for each of four reference locations: low Earth orbit, low lunar orbit, a distant lunar retrograde orbit, and Mars orbit co-orbital with (or moored to) Phobos. Each of these locations has different implications for power, propulsion, and thermal control designs, as well as communications and and associated avionics systems. A series of trade studies examined critical design decisions, such as the choice of inflatable or fixed-shell habitat structure, type and emplacement of power systems, and accommodation for additional modules and/or hosted vehicles. The detailed design of the baseline habitat included trade studies driving the selection of life support systems and other crew accommodations, with emphasis on contingency planning for life support system failures remote from Earth in terms of both distance and time required until resupply. Internal layouts examined alternative placement of crew accommodations, life support systems, airlocks, windows, and other crew systems. Operations issues considered include attitude control system design and analysis, number, location, and type of docking interfaces, energy storage for all potential orbits, as well as transport options for moving the spacecraft between low Earth orbit and other destinations of interest. A critical design factor identified was that of launch vehicle choice, primarily due to volumetric constraints of available payload fairings. The paper also discusses near-term analog studies of habitat designs in virtual reality, Earth gravity, and neutral buoyancy to evaluate and validate habitability design choices.Item Developing Technologies and Techniques for Additive Manufacturing of Spacesuit Bearings and Seals(48th International Conference on Environmental Systems, 2018-07-08) Garner, Sarah; Carpenter, Lemuel; Akin, DavidHuman exploration beyond low Earth orbit will require increasing self-sufficiency in light of the logistics support challenge. One critical area is in spacesuit maintenance, parts replacement, and eventually in-situ manufacturing. An ongoing project at the University of Maryland (UMd) is exploring additive manufacturing (AM) for space suits, both “hard suits” entirely fabricated from feed stock, and “hard” elements of conventional hybrid suits. The current technology development focus is on the integral structural elements of bearings, and seals, and interfaces to the suit envelope. Prior work investigated the feasibility of “printing” full bearings, and led to the realization that current AM techniques are of insufficient precision to allow the fabrication of the bearing balls directly. Complete bearings were assessed for joint friction under varying loads, and tested to destruction to verify the ability to meet both pressurization and human loads with adequate factors of safety. Seals were fabricated of elastomeric 3D printed materials and tested for sealing performance and friction. Complete suit bearing prototypes consisting of both AM bearings and seals were fabricated and subjected to hydrostatic pneumatic load tests, as well as tested in the UMd glove box and cycled to determine operating lifetime. Based on these results, the best performing design that met all requirements was selected for the fabrication and test of a complete AX-5-type four-roll elbow module, which was integrated to soft goods upper and lower arm segments and terminated with a glove box sealed bearing on the proximal end and a standard glove disconnect on the distal end. This arm segment was then used for human factors evaluations in the UMd glovebox, including quantifying dexterity via a Fitts’ law protocol .Item Experimental Investigation of Configurations and Capabilities of a Space Utility Vehicle(48th International Conference on Environmental Systems, 2018-07-08) Akin, David; Carpenter, LemuelThe concept of a space utility vehicle (SUV), also termed “single person spacecraft” or “man-in-a-can”, has been around since the mid-1950’s. However, in the intervening time, little or no experimental investigation has taken place into the feasibility of the concept in comparison to traditional EVA, telerobotics, or other space operations. To address this lack, the University of Maryland (UMd) has undertaken an extensive program to better understand the capabilities and limitations of the SUV concept. Multiple prior UMd studies dating back to 1993 have examined the SUV concept on paper, and concluded that the most advantageous configuration would incorporate spacesuit arms as well as robotic manipulators to allow full human manual dexterity to be applied at the space worksite. Analyses also indicated the advantage of single-crew spacecraft capable of docking and supporting two crew for enhanced survival in contingency situations. This paper documents the latest phase of SUV research performed at UMd, focusing on the design and construction of a neutral buoyancy-compatible mockup of the current baseline design. AX-5 type “hard suit” arms were fabricated using additive manufacturing, including integral bearings, and tested for range and ease of motion. The mockup was outfitted with notional controls and displays for laboratory testing, and four different control locations identified for various flight phases. The mockup was then reconfigured for underwater testing, and concepts for reconfigurable crew restraints tested and evaluated in each location. A primary focus of this testing will be to obtain quantitative data on the utility of spacesuit arms in a vehicle of this type, and to test concepts for simultaneous manual manipulation and robotic arm control. The paper details tests conducted and results obtained, along with plans for future development activities.Item Experimental Investigation of Vertical Translation Design Commonality Across Differing Gravitation Levels(48th International Conference on Environmental Systems, 2018-07-08) Carpenter, Lemuel; Hanner, Charles; Akin, DavidCurrent knowledge of human habitation in partial-gravity is limited to six brief sorties to the lunar surface. As interest in human exploration and longer-term habitation of the Moon and Mars increases, methods must be created to better understand how to design a living environment for humans in differing gravity levels. This paper presents the results of recent studies at the University of Maryland on human accessibility between different floors of a habitat in various gravity levels, based on the use of body segment parameter ballasting in the underwater environment to represent the gravitational force on each body segment in ascending and descending ladders and staircases. This has culminated in the development of a dedicated test apparatus which allows full reconfiguration of the angle and tread spacing on staircases, and can be used both underwater and in the laboratory environment. Test subjects ascend and descend the ladder at various gravity conditions to determine the effect of differing apparent gravity levels, with data collected on both performance and gaits as measured by motion capture systems. Extensions to this work are proposed that focus on part-task simulations such as servicing and repair of equipment racks, and focused studies on the habitat design implications of rotating habitats for artificial gravity.