Modeling and analysis of tethered systems performing orbital maneuvers

Michael Jokic (2005). Modeling and analysis of tethered systems performing orbital maneuvers PhD Thesis, School of Engineering, The University of Queensland.

       
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Author Michael Jokic
Thesis Title Modeling and analysis of tethered systems performing orbital maneuvers
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2005
Thesis type PhD Thesis
Supervisor Dr. Bill Daniel
Prof. James Longuski
Total pages 159
Collection year 2005
Language eng
Subjects L
290299 Aerospace Engineering not elsewhere classified
780102 Physical sciences
Formatted abstract

Tethered systems performing orbital maneuvers offer important benefits to space missions. This has been demonstrated through the investigation of several potential tether applications and modeling approaches. The applications examined in this dissertation include: a tether sling stationed on Phobos, a human transport with artificial gravity, a tethered system performing aerogravity assist and aerobraking maneuvers at Mars, and aerocapture of a tethered satellite system at Neptune. The analysis of a minimum-mass tether sling stationed on Phobos reveals that considerable propellant mass is saved by including the facility in a transportation system between Earth and Mars. The ratio of tether mass to chemical-propellant mass is used as a metric to examine the performance of the sling with respect to various transfer trajectories. The most advantageous application of the tether sling occurs during a Hohmann transfer from Phobos to Earth where the mass ratio is 1.8. Next are semicyclers (ratios of 1.9 and 2.4) and a three-synodic-period cycler (8.7). The tapered tether design methodology of the sling is extended to determine the configuration of a spinning tethered transport for human missions to Mars. Severing the tether is shown to offer a propellant-free boost to return astronauts to Earth in the event of an aborted landing on Mars. Abort trajectory options are found in every Earth-Mars synodic period (2.14 years) between 2014 and 2030. Most of the abort options follow the Earth-Mars-Earth path, but Earth-Mars-Venus-Earth and Earth-Venus-Mars-Earth abort trajectories are also shown to have merit.

 

Aerogravity assist maneuvers with a tethered satellite system are extremely advantageous to interplanetary missions. Unlike traditional single-mass configurations. a tethered system is capable of maintaining part of the system mass outside the sensible atmosphere during an aerogravity assist maneuver. The substantial increase in the velocity change achieved during the flyby relative to a gravity assist maneuver is another advantage. An increase of 57 % in the total velocity change relative to a gravity assist maneuver is determined for a flyby with arrival V of 10 km/s. Releasing the tether end-masses near periapsis of a hyperbolic flyby trajectory is shown to facilitate the arrival of two payloads at two different destinations. In the scenario discussed in this document, atmospheric drag is used to land one of the end-masses on the surface of Mars while the other continues on an escape trajectory. This scenario is referred to as a dual-destination mission. Both the aerogravity assist maneuvers and dual-destination missions are examined using a rigid-rod model of the tether. A finite-element model is developed from contemporary elastodynamic techniques to represent the inherently complex dynamics of a tethered system performing aeroassisted orbital maneuvers. The model is used to simulate aerobraking maneuvers at Mars in two and three dimensions. Results from the two dimensional simulations are shown to be in good agreement with a lumped-mass model propagated in time via the Runga-Kutta- Nyström method. The last aeroassisted orbital maneuver, aerocapture, is demonstrated in the context of a mission to Neptune. Several vehicle architectures are examined for the aerocapture simulations. The arrival conditions are based on an Earth-Venus-Earth- Earth-Jupiter-Neptune trajectory selected from a search of potential ballistic options. 

Keyword Tethered satellites

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
 
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Created: Fri, 24 Aug 2007, 18:48:43 EST