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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Novel aerospace mechanisms: A passive tether damping device for tethered satellite, and a pin/latch structural interface system

Presented here is a collection of development tasks that have been accomplished over the past year at the Marshall Space Flight Center's Structures and Dynamics Laboratory. Dissemination of task findings are reported for the following reasons: the task involves new or evolving technology (as in the case of a tethered satellite), and the tasks depict a technique that could have application to extravehicular activity (EVA) or robotic assembly of space structures (the pin/latch system).

Redmon, John W., Jr.↗
NASA NTRS1986

Electrodynamic interactions

The electrodynamic interaction of long metallic tethers with the ionosphere is introduced. Due to the tether's motion across the Earth's field, a polarization electric field is generated along the tether. In a system like the Tethered Satellite System (TSS) where the tether is coated with dielectric and the electrical contact is between its two terminations and the ionosphere, the upper end termination will collect electrons and, in a passive system, the lower end termination will collect ions. Space charge regions will develop around the two terminations of the system, which can be at considerable potential with respect to the unperturbed ionospheric plasma and the current in the tether will be most significantly determined by local processes in such space charge regions. A qualitative view of the global perturbation induced by TSS in the ionosphere is outlined. One of the applications of electrodynamic tethers is that of using them as low frequency wave generators to communicate to the Earth. This application is briefly discussed. An equivalent circuit of the tether system is described. The basic equation of the circuit is given.

Dobrowolny, M.↗
NASA NTRS1986

Plasma contactors for electrodynamic tether

The role plasma contactors play in effective electrodynamic tether operation is discussed. Hollow cathodes and hollow cathode-based plasma sources have been identified as leading candidates for the electrodynamic tether plasma contactor. Present experimental efforts to evaluate the suitability of these devices as plasma contactors, conducted concurrently at NASA Lewis Research Center and Colorado State University, are reviewed. These research programs include the definition of preliminary plasma contactor designs, and the characterization of their operation both as electron emitters and electron collectors to and from a simulated space plasma. Results indicate that ampere-level electron currents, sufficient for electrodynamic tether operation, can be exchanged between hollow cathode-based plasma contactors and a dilute plasma.

Patterson, Michael J.↗
NASA NTRS2004

Graduate Student Researchers Program (GSRP)

An advanced concept in in-space transportation currently being studied is the Momentum-Exchange/Electrodynamic Reboost Tether System (MXER). The MXER system is a permanently orbiting platform designed to boost payloads from low earth orbit (LEO). Unlike conventional rockets that use propellants, MXER acts as a large momentum wheel, imparting a Av to a payload at the expense of its own orbital energy. After throwing a payload, the system reboosts itself using an electrodynamic tether to push against Earth s magnetic field and brings itself back up to an operational orbit to prepare for the next payload. The ability to reboost itself allows for continued reuse of the system without the expenditure of propellants. Considering the cost of lifting propellant from the ground to LEO to do the same Av boost at $10000 per pound, the system cuts the launch cost of the payload dramatically, and subsequently, the MXER system pays for itself after a small number of missions. As such, this technology is a valuable addition to NASA s mission for in-space transportation.

Westerhoff, John↗
NASA NTRS1996

Charged body-plasma interaction research laboratory for the International Space Station

An experiment is proposed for the provision of a fundamental plasma physics facility onboard the International Space Station (ISS) for the investigation of the plasma processes governing the electron current collection processes on a charged electrode. The facility will allow the pre-sheath and sheath physics of a positively biased body to be investigated. These processes are important to the consideration of the use of electrodynamic tether lines for practical applications such as for electrical power generation and to the understanding of the physics of space plasma. A deployment mechanism is required to deploy the charged body to a distance of several 100 m from the space station. The possible solutions are a flexible boom or a short tether line.

Lebreton, Jean-Pierre↗
NASA NTRS1985

Attitude Control Tradeoff Study Between the Use of a Flexible Beam and a Tether Configuration for the Connection of Two Bodies in Orbit

Sometimes it is necessary to mount a payload remotely from the main body of a spacecraft or space station. The reasons for this vary from vibration isolation to avoidance of measurement contamination. For example the SP-100 project, which grew out of the increased interest in nuclear power in space for space stations and for deep space explorations, requires separation of the nuclear reactor from the user because of vibration, heat and radiation. The different attitude control problems for beam and tether configurations are discussed. The beam configuration uses a conservative design approach. The vibration, beam flexibility and deployment concerns are analyzed. The tether configuration offers some very attractive design features, but not without several thorny problems. These problems are analyzed. One configuration will be recommended for the main thrust of the SP-100 design effort based on attitude control considerations.

Graff, S. H.↗
NASA NTRS2004

Tethers as Debris: Simulating Impacts of Tether Fragments on Shuttle Tiles

The SPHC hydrodynamic code was used to simulate impacts of Kevlar and aluminum projectiles on a model of the LI-900 type insulating tiles used on Space Shuffle Orbiters The intent was to examine likely damage that such tiles might experience if impacted by orbital debris consisting of tether fragments. Projectile speeds ranged from 300 meters per second to 10 kilometers per second. Damage is characterized by penetration depth, tile surface-hole diameter, tile body-cavity diameter, coating fracture diameter, tether and cavity wall material phases, and deformation of the aluminum backwall.

Evans, Steven W.↗
NASA NTRS1978

Interactions of a tethered satellite system with the ionosphere

The Tethered Satellite System will be the first large structure deployed in space. It will react strongly with the magneto-ionic medium of the Earth's ionosphere and will thus be valuable experimental tool. Experiments planned for the structure are discussed. Emphasis is placed on the structures ability to excite a large variety of wave phenomena in the ionosphere using its electromotive force.

Grossi, M. D.↗
NASA NTRS1984

System definition study of deployable, non-metallic space structures

The state of the art for nonmetallic materials and fabrication techniques suitable for future space structures are summarized. Typical subsystems and systems of interest to the space community that are reviewed include: (1) inflatable/rigidized space hangar; (2) flexible/storable acoustic barrier; (3) deployable fabric bulkhead in a space habitat; (4) extendible tunnel for soft docking; (5) deployable space recovery/re-entry systems for personnel or materials; (6) a manned habitat for a space station; (7) storage enclosures external to the space station habitat; (8) attachable work stations; and (9) safe haven structures. Performance parameters examined include micrometeoroid protection; leakage rate prediction and control; rigidization of flexible structures in the space environment; flammability and offgassing; lifetime for nonmetallic materials; crack propagation prevention; and the effects of atomic oxygen and space debris. An expandable airlock for shuttle flight experiments and potential tethered experiments from shuttle are discussed.

Stimler, F. J.↗
NASA NTRS1986

A review of tether induced dynamical features

The simplest mathematical model used for the simulation of TSS motion is considered in order to review the dynamics of tethers. This model is discussed. Also reviewed are elasticity effects, perturbation sources, orbit eccentricity and natural frequencies. Tethered systems provide a unique opportunity for skilled measurement activities in space. Some of the experiments envisaged require the measurement of very small mechanical quantities. This implies that the level of dynamical noise on instruments output be low or that system response to excitation, either external or internal, be sufficiently known. In this respect, the first TSS flights will be very useful, but much work will be needed in order to have reliable estimates of structural damping in different future systems.

Bergamaschi, S.↗
NASA NTRS1988

Analysis of a rotating advanced-technology space station for the year 2025

An analysis is made of several aspects of an advanced-technology rotating space station configuration generated under a previous study. The analysis includes examination of several modifications of the configuration, interface with proposed launch systems, effects of low-gravity environment on human subjects, and the space station assembly sequence. Consideration was given also to some aspects of space station rotational dynamics, surface charging, and the possible application of tethers.

Queijo, M. J.↗
NASA NTRS2012

The PROPEL Electrodynamic Tether Mission and Connecting to the Ionosphere

The exponential increase of launch system size.and cost.with delta-V makes missions that require large total impulse cost prohibitive. Led by NASA's Marshall Space Flight Center, a team from government, industry, and academia has developed a flight demonstration mission concept of an integrated electrodynamic (ED) tethered satellite system called PROPEL: "Propulsion using Electrodynamics". The PROPEL Mission is focused on demonstrating a versatile configuration of an ED tether to overcome the limitations of the rocket equation, enable new classes of missions currently unaffordable or infeasible, and significantly advance the Technology Readiness Level (TRL) to an operational level. We are also focused on establishing a far deeper understanding of critical processes and technologies to be able to scale and improve tether systems in the future. Here, we provide an overview of the proposed PROPEL mission. One of the critical processes for efficient ED tether operation is the ability to inject current to and collect current from the ionosphere. Because the PROPEL mission is planned to have both boost and deboost capability using a single tether, the tether current must be capable of flowing in both directions and at levels well over 1 A. Given the greater mobility of electrons over that of ions, this generally requires that both ends of the ED tether system can both collect and emit electrons. For example, hollow cathode plasma contactors (HCPCs) generally are viewed as state-of-the-art and high TRL devices; however, for ED tether applications important questions remain of how efficiently they can operate as both electron collectors and emitters. Other technologies will be highlighted that are being investigated as possible alternatives to the HCPC such as Solex that generates a plasma cloud from a solid material (Teflon) and electron emission (only) technologies such as cold-cathode electron field emission or photo-electron beam generation (PEBG) techniques.

Gilchrist, Brian↗
NASA NTRS2010

Electrodynamic Propulsion System Tether Experiment (T-REX)

A Japanese-led international team is developing a suborbital test of orbital-motion-limited (OML) bare wire anode current collection for application to electrodynamic tether (EDT) propulsion. The tether is a tape with a width of 25 mm, thickness of 0.05 mm, and is 300 m in length. This will be the first space test of OML theory. The mission will launch in the summer of 2010 using an S520 Sounding Rocket. During ascent, and above approximately 100 km in attitude, the tape tether will be deployed at a rate of approximately8 m/s. Once deployed, the tape tether will serve as an anode, collecting ionospheric electrons. The electrons will be expelled into space by a hollow cathode device, thereby completing the circuit and allowing current to flow. The total amount of current collected will be used to assess the validity of OML theory. This paper will describe the objectives of the proposed mission, the technologies to be employed, and the application of the results to future space missions using EDTs for propulsion or power generation

Johnson, L.↗
NASA NTRS2019

Rotary-motion-extended Array Synthesis (R-MXAS)

R-MXAS is a revolutionary aerospace architecture for realizing a synthetic aperture imaging radiometer (SAIR) with dramatically lower SWaP than existing state-of-the-art (SOTA) methods. The space-based component of the RMXAS system (Figure 1) is a single platform comprising a 1-D sparse / decimated antenna array on a rigid tether (deployed parallel to the horizon) and one or more additional tethered antennas that rotate in a plane orthogonal to the 1-D array.The processing that correlates the data from these two antenna systems and performs image reconstruction has both space-based and ground-based components. The processing exploits the interferometric baselines formed between the rotating tethered antenna at radius R and each of the antennas of the 1-D array on the rigid tether.

Radiometer↗
NASA NTRS2018

Comet Hitchhiker: NIAC Phase 1 Final Report

Summary of Activities-Developed the Comet Hitchhiker concept, which is to hitch rides on small bodies (asteroids and comets) using a tethered spacecraft. (Section 2)-Identified five scientifically important missions that would be enabled or significantly benefited by the Comet Hitchhiker concept.The five mission concepts are: KBO rendezvous, Centaur rendezvous, Trojan rendezvous, Damocloid rendezvous, and Main asteroid belt tour to rendezvous with multiple (10) objects. (Section 3)-Derived the Space Hitchhike Equation, or "the rocket equation for hitchhiker", which relates the specific strength of tether, mass ratio, and V. (Section 4.1)-Performed in-depth feasibility analysis of the critical components of the concept through: Finite-element simulations of tether and spacecraft dynamics, as shown in Figure 1 (Section 4.4); Supercomputer simulations of the hypervelocity impact of harpoon on a small body, as shown in Figure 2. (Section 6)-Performed public outreach activities including the collaboration with a concept artist of the Museum of Science Fiction, exposure to media, and public presentations. (Section 8)

Deep Space↗
NASA NTRS1988

Outer atmospheric research

The region above the earth from about 90 km to 150 km is a major part of the upper or outer atmosphere. It is relatively unexplored, being too high for balloons or aircraft and too low for persistent orbiting spacecraft. However, the concept of a tethered subsatellite, deployed downward from an orbiting, more massive craft such as the Space Shuttle, opens the possibility of a research capability that could provide global mapping of this region. The need for research in this thick spherical shell above the earth falls into two major categories: (1) scientific data for understanding and modeling the global atmosphere and thereby determining its role in the earth system, and (2) engineering data for the design of future aerospace vehicles that will operate there. This paper presents an overview and synthesis of the currently perceived research needs and the state-of-the-art of the proposed tethered research capability.

Anderson, John L.↗
NASA NTRS2006

MISSE Materials Results for Applications in the Vision for Space Exploration

Marshall Space Flight Center has a role in the development of the Crew Launch Vehicle and Crew Exploration Vehicle, as well as the Robotic Lunar Exploration Program (RLEP-2) and In-Space Propulsion. The success of these programs depends upon understanding the space environment, the requirements imposed on the spacecraft materials, and data gleaned from materials returned from space. Station Experiment (MISSE) were analyzed at the Marshall Space Flight Center. Changes in mass, optical properties, and mechanical integrity for these samples can indicate which materials may be suitable for use on exploration spacecraft, which materials need further testing, and which materials should not be recommended for long term missions. A number of materials for in-space propulsion were flown on MISSE. These include the conductive, insulative, and non-conductive tether materials selected for the ProSEDS mission. Also included were candidate solar sail materials. The solar sail materials were flown underneath a magnesium fluoride window that allowed ultraviolet radiation through to the sample but blocked any atomic oxygen. Over two hundred materials samples from the Materials on International Space

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