Date of Award

Summer 2006

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Aerospace Engineering

Committee Director

Brett Newman

Committee Member

Robert L. Ash

Committee Member

Chuh Mei

Call Number for Print

Special Collections; LD4331.E535 F56 2006

Abstract

Design of orbital trajectories using patched conic approximation methodology for short duration missions to newly detected, incoming near Earth asteroids, which are on close approach trajectories with Earth, is the focus of this thesis. The primary purpose for such missions is two fold. First, near Earth asteroids provide unique mission opportunities for solar system science where the celestial body of interest transits to Earth proximity and is studied in situ by probes having short duration trajectories, rather than sending long distance probes to the celestial body. Second, improved characterization of asteroid properties, compositions, and orbital states for reduction of uncertainties concerning potential future impact threats with Earth are available from such missions. Cases with near Earth asteroid minimum distance of approach being equal to or less than the Earth's sphere of influence, with respect to the Sun, are analyzed. Major assumptions are that all motion is within the ecliptic plane, all bodies are idealized point masses, and asteroid motion is sufficiently known for targeting purposes. The asteroid approach conditions are arbitrary in the sense that the incoming flight path and speed can be of any value consistent with earlier assumptions and fundamental mechanics. Several mission trajectory types namely, impact, flyby, capture, and free return, are investigated. The accuracy of the patched conic approximation technique in computing trajectories to asteroids located very close to Earth is validated by comparing the results against multi-body (Earth, Moon, Asteroid, and Spacecraft) non-linear simulations. In this process, the results of the patched conic approximation are compared with the non-linear simulation outputs for validation. Simplified single-body non-linear spacecraft trajectory simulations including the effect from a third-body (Moon, Asteroid, and Sun) perturbation on the spacecraft is also considered using special perturbation techniques. Investigations found that the Keplerian computations using the patched conic approximation provide trajectories that reflect non-linear solutions, depending on asteroid penetration depth within the Earth's sphere of influence, as well as relative asteroidal-lunar geometry. Inclusion of third-body and higher effects introduces perturbations in the patched two-body trajectories that vary from slight to significant. On the whole, the patched conic approximation technique is found to be an easy, dependable, and advantageous tool, particularly useful for preliminary mission planning, for short duration near Earth asteroid missions like those presented in this thesis.

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DOI

10.25777/nfbq-4609

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