Theresa Kowalkowski

Implementation of a Low-Thrust Trajectory Optimization Algorithm for Preliminary Design

A tool developed for the preliminary design of low-thrust trajectories is described. The trajectory is discretized into segments and a nonlinear programming method is used for optimization. The tool is easy to use, has robust convergence, and can handle many intermediate encounters. In addition, the tool has a wide variety of features, including several options for objective function and different low-thrust propulsion models (e.g., solar electric propulsion, nuclear electric propulsion, and solar sail). High-thrust, impulsive trajectories can also be optimized.

Planetary Protection Trajectory Analysis for the Juno Mission

Juno is an orbiter mission expected to launch in 2011 to Jupiter. Junos science orbit is a highly eccentric orbit with a period of about 11 days and a nominal duration of one year. Initially, the equatorial crossing near apojove occurs outside Callistos orbit, but as the mission evolves the apsidal rotation causes this distance to move much closer to Jupiter. This motion could lead to potential impacts with the Galilean satellites as the ascending node crosses the satellite orbits. In this paper, we describe the method to estimate impact probabilities with the satellites and investigate ways of reducing the probabilities for the Juno mission.

Analysis of System Margins on Deep Space Missions Using Solar Electric Propulsion

NASAs Jet Propulsion Laboratory has conducted a study focused on the analysis of appropriate margins for deep space missions using solar electric propulsion (SEP). The purpose of this study is to understand the links between disparate system margins (power, mass, duty cycle, etc.) and their impact on overall mission performance and robustness. It is shown that the various sources of uncertainty and technical risk associated with electric propulsion mission design can be summarized into three relatively independent parameters 1) Electric Propulsion Power Margin, 2) Propellant Margin and 3) Duty Cycle Margin. The overall relationship between these parameters and other major sources of uncertainty is presented. A detailed trajectory analysis is conducted to examine the impact that various assumptions related to power, duty cycle, destination, and thruster performance including missed thrust periods have on overall performance. Recommendations are presented for system margins for deep space missions utilizing solar electric propulsion.

Mars Sample Return Orbiter concepts using Solar Electric Propulsion for the post-Mars2020 decade

Since the selection of the proposed Mars 2020 mission as a Rover with the capability of sample collection and caching, there has been renewed interest in subsequent mission concepts to return Mars samples to Earth. The general architecture for this series of missions is outlined in the Planetary Science Decadal Survey of 2011. The role of the Sample Return Orbiter (SRO) in The 2011 Decadal Survey MSR architecture was to collect an orbiting sample (OS) from low Mars orbit and deliver it to Earths surface. The architecture focused on chemical propulsion orbiters with ballistic and aerobraking trajectories that were dedicated entirely to the capture of orbiting samples and returning them to the surface of the Earth. Recent concepts have explored the use of Solar Electric Propulsion (SEP) to Mars and for the return to Earth. SEP could enable significant mission flexibility which includes: lower launch mass or increased mass delivery capability to Mars orbit and return to Earth; longer launch periods for both launch and Earth return; consistency of design across launch opportunities; access to both high and low Mars orbit altitudes; increased on-orbit ΔV budgets for orbit changes and sample rendezvous; and greater control over Earth arrival speed and geometry. With this flexibility come opportunities to: save launch cost; add functions such as remote sensing observations, secondary payload deployment, and relay telecommunications; and choose between direct return of Mars samples to the Earths biosphere or capturing them to a stable long-term orbit around the Earth. This paper compares the previous SRO chemical-ballistic concepts with the recent SEP orbiter concepts. We will show the potential benefits gained by the inherent flexibility of SEP as applied to launch mass, launch periods, Earth return opportunities, on-orbit ΔV and other architectural drivers.

Electric Propulsion System Selection Process for Interplanetary Missions

† Engineer, Trajectory Design and Navigation, M/S 301-121, Member AIAA. ** Staff Engineer, Flight Systems Engineering, M/S 264-623, Member AIAA. ‡‡ Senior Engineer; Guidance, Navigation, & Control; M/S 301-150; Member AIAA. * Senior Engineer, Flight Systems Engineering, M/S T1722, Senior Member AIAA. ‡ Project Element Manager, Propulsion and Materials Engineering, M/S 125-109, Senior Member AIAA. †† Principle Member of Engineering Staff, Guidance Navigation and Control, M/S 301-121, Senior Member AIAA. § Senior Power Systems Engineer, Power Systems, M/S 303-310K.