Victoria Coverstone - Academia.edu (original) (raw)
Papers by Victoria Coverstone
AIAA/AAS Astrodynamics Specialist Conference and Exhibit, 2004
Missions to the outer planets for spacecraft with a solar-electric propulsion system (SEPS) and t... more Missions to the outer planets for spacecraft with a solar-electric propulsion system (SEPS) and that uhilize a single Venus gravity assist are investigated. The trajectories rnaximiZe the delivered mass to the target planet for a range of flight times. A comparison of the trajectory characteristics (delivered mass, launch energy and onboard propulsive energy) is made for various Venus gravity assist opportunities. Methods to estimate the delivered mass to the outer planets are developed.
AIAA/AAS Astrodynamics Specialist Conference and Exhibit, 1998
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
UltraSail is a next-generation high-risk, high-payoff sail system for the launch, deployment, sta... more UltraSail is a next-generation high-risk, high-payoff sail system for the launch, deployment, stabilization and control of very large (km 2 class) solar sails enabling high payload mass fractions for high ∆V. UltraSail is an innovative, non-traditional approach to propulsion technology achieved by combining propulsion and control systems developed for formation-flying micro-satellites with an innovative solar sail architecture to achieve controllable sail areas approaching 1 km 2 , sail subsystem area densities approaching 1 g/m 2 , and thrust levels many times those of ion thrusters used for comparable deep space missions. UltraSail can achieve outer planetary rendezvous, a deep space capability now reserved for high-mass nuclear and chemical systems. One of the primary innovations is the near-elimination of sail supporting structures by attaching each blade tip to a formation-flying micro-satellite which deploys the sail, and then articulates the sail to provide attitude control, including spin stabilization and precession of the spin axis. These tip micro-satellites are controlled by 3-axis micro-thruster propulsion and an on-board metrology system. It is shown that an optimum spin rate exists which maximizes payload mass.
Sensors and Systems for Space Applications, 2007
ABSTRACT Small satellites and payloads in the (1-2 kg) class called Cubesats and (20-30 kg) calle... more ABSTRACT Small satellites and payloads in the (1-2 kg) class called Cubesats and (20-30 kg) called Nanosats have been under development at the University of Illinois since fall, 2001. The ION1 Cubesat was a 10x10x21.5 cm3 satellite with the experiment consisting of photometric remote sensing of mesospheric structures (near 94 km) in the O2 (0,0) band airglow at 762 nm. ION1 development began in 2001 and was lost on the failed launch attempt, July 26, 2006. ION2 development began in Fall 2005, and has a remote sensing experiment to measure Halpha (656.3 nm) originating in the Earth's geocorona from which column H densities can be deduced. Taylor University has led the development of a Nanosat called TEST, which was designed to study ionospheric structures. Illinois provided remote sensing payloads including a CCD camera and dual photometers. The development activity is largely implemented by a College of Engineering Interdisciplinary Design class (ENG 491), where students typically participate in the systems engineering experience for two semesters. The students (15-20 average enrollment) are responsible for the design, fabrication, and testing of the systems. This paper describes the development of these Cubesat and Nanosat systems.
The optical properties of the thin metalized polymer films that are projected for solar sails are... more The optical properties of the thin metalized polymer films that are projected for solar sails are assumed to be aected by the erosive eects of the space environment. Their degradation behavior in the real space environment, however, is to a considerable degree indefinite, because initial ground test results are controversial and relevant in- space tests have not been made so
Journal of Spacecraft and Rockets, 2005
Outer-planet mission and systems analyses are performed using three next generation solarelectric... more Outer-planet mission and systems analyses are performed using three next generation solarelectric ion thruster models. The impact of variations in thruster model, flight time, launch vehicle, propulsion and power systems characteristics is investigated. All presented trajectories have a single Venus gravity assist and maximize the delivered mass to Saturn or Neptune. The effect of revolution ratio -the ratio of Venusian orbital period to the flight time between launch and flyby datesis also discussed.
Journal of Spacecraft and Rockets, 2006
Journal of Spacecraft and Rockets, 2006
ABSTRACT Conceptual in-space transfer stages, including those using solar electric propulsion and... more ABSTRACT Conceptual in-space transfer stages, including those using solar electric propulsion and chemical propulsion with aerobraking or aerocapture assist at Mars, were evaluated. Roundtrip Mars sample return mission vehicles were analyzed to determine how technology selections influence payload delivery capability. Results show how specific engine, thruster, propellant, capture mode, trip time, and launch-vehicle technology choices would contribute to increasing payload delivered to Mars or decreasing the size of the required launch vehicles. Low-thrust trajectory analyses for solar-electric transfer were generated with the SEPTOP code.
Journal of Guidance, Control, and Dynamics, 2010
Journal of Guidance, Control, and Dynamics, 2008
ABSTRACT The sail dynamics of spin-stabilized solar sail designs are examined in this paper. The ... more ABSTRACT The sail dynamics of spin-stabilized solar sail designs are examined in this paper. The nonlinear governing equations of motion are derived for four different and progressively more complex dynamical scenarios: pitch (one dimensional); pitch and sweepback (two dimensional); pitch and lead/lag (two dimensional); and pitch, sweepback, and lead/lag (three dimensional). These equations are applied to UltraSail, a novel solar sail design developed at the University of Illinois at Urbana-Champaign, which relies on small-tip satellites to provide tension in rectangular sails. Steady-state and time-dependent characteristics are numerically calculated and discussed. Properties such as the spacecraft acceleration are predicted, and transient sail responses to an applied perturbation are simulated. Results place UltraSail as a strong candidate for future solar sail missions with performance challenging previously proposed concepts.
Journal of Guidance, Control, and Dynamics, 2004
With the growing emphasis on vehicle autonomy, the problem of planning a trajectory in an environ... more With the growing emphasis on vehicle autonomy, the problem of planning a trajectory in an environment with obstacles has become increasingly important. This task has been of particular interest to roboticists and computer scientists, whose primary focus is on kinematic motion planning . Typical kinematic planning methods fall into two main categories, roadmap methods and incremental search methods, both of which find collision-free paths in the state space. Roadmap methods generate and traverse a graph of collision-free connecting paths spanning the state space, while incremental search methods, including dynamic programming [2] and potential field methods [3], perform an iterative search to connect the initial and goal states. For the purely geometric path planning problem, deterministic algorithms have been created that are complete, i.e., they will find a solution if and only if one exists. Unfortunately, these suffer from high computational costs which are exponential in system degrees of freedom. This cost has motivated the development of iterative randomized path planning algorithms that are probabilistically complete, i.e., if a feasible path exists, the probability of finding a path from the initial to final conditions converges to one as the number of iterations goes to infinity. The introduction of the Rapidly-exploring Random Trees (RRTs) of LaValle and Kuffner [4] allowed both for computationally efficient exploration of a complicated space as well as incorporation of system dynamics. The RRT grows a tree of feasible trajectories from the initial condition, or root node. Each node, or waypoint, on the tree represents a system state and has possible trajectories branching from it. Through use of an embedded planning routine, the tree incrementally builds itself in random direc-Associate Fellow AIAA 1 of 12 tions, node by node, until the final conditions are met (within accuracy bounds). Frazzoli demonstrated that a hybrid systems representation of vehicle dynamics, when coupled with the RRT, could be used to address moving obstacles and time-invariant final conditions in a real-time environment. This paper presents a similar approach which provides probabilistic completeness in the presence of both time-varying obstacles and final conditions while using a simpler algorithmic procedure. In addition, a novel approach to provide error mitigation of the embedded planner in a hybrid system-based RRT is presented. An example is then given in which the proposed algorithm is applied to the landing of a spacecraft on an idealized asteroid.
Journal of Guidance, Control, and Dynamics, 2010
ABSTRACT This work focuses on investigating the behavior of the orbit transfer switching function... more ABSTRACT This work focuses on investigating the behavior of the orbit transfer switching function for the two-body problem. Recent work indicated that use of an analytical expression for the switching function could significantly reduce the computational time required to determine when to end coast arcs during trajectory optimization. This analysis of the switching function begins by showing how the printer vector and switching function in various coordinate systems are related, and two representative systems are considered for the remaining analysis. Given that multiple harmonics are manifest simultaneously in the switching function during coast arcs, some possible behaviors of such functions are considered relative to finding bounds containing the desired coast-terminating zero. It is seen that the method proposed in recent work can fail. A relatively simple improvement involving the slope of the switching function at the sampled points is used to make the method more robust and enable the production of example optimal solutions that would not have been possible with the earlier method. In terms or the two chosen systems, analytical expressions for the switching function and its derivative during coasting as well as transformation matrices that relate the systems to each other are therefore presented in Appendices A, B, and C.
Journal of Guidance, Control, and Dynamics, 2004
Journal of Guidance, Control, and Dynamics, 2008
ABSTRACT The sun/Earth-moon L1 point is a growing target for space missions. This paper assumes a... more ABSTRACT The sun/Earth-moon L1 point is a growing target for space missions. This paper assumes a need to place an object directly between the Earth and the sun. Possible purposes for such a mission include a type of shield to intercept some portion of the sun's rays, or conversely a lens or mirror to focus them. In addition, this paper requires a launch directly from the moon instead of a traditional orbit-to-orbit transfer. A detailed case using accurate positional and velocity data for all planetary bodies is used in this paper. Instead of focusing solely on trajectories defined as optimal by minimum fuel consumption, we looked for trajectories with low sensitivity to initial conditions to additionally minimize the frequency and magnitude of course corrections. We first analyzed the reverse problem to identify solution areas of low sensitivity to launch conditions. Using the determined restricted solution space, we were successfully able to determine a launch site on the moon that could reach L1 with the greatest number of low-cost trajectories and launch windows within the resolution of the solution space.
Journal of Guidance, Control, and Dynamics, 1995
Minimum-fuel, impulsive, time-fixed solutions are obtained for the problem of orbital rendezvous ... more Minimum-fuel, impulsive, time-fixed solutions are obtained for the problem of orbital rendezvous and interception with interior path constraints. Transfers between coplanar circular orbits in an inverse-square gravitational field are considered, subject to a circular path constraint representing a minimum or maximum permissible orbital radius. Primer vector theory is extended to incorporate path constraints, and the optimal number of impulses along with their times and positions are determined. The existence of constraint boundary arcs is investigated as well as the optimality of a class of singular arc solutions. A bifurcation phenomenon is discovered in a maximum-radius solution as the transfer time is increased. To illustrate the complexities introduced by path constraints, an analysis is made of optimal rendezvous in field-free space subject to a minimum radius constraint.
Journal of Guidance, Control, and Dynamics, 1998
Journal of Guidance, Control, and Dynamics, 1994
Minimum-fuel rendezvous of two power-limited spacecraft is investigated. Both vehicles are active... more Minimum-fuel rendezvous of two power-limited spacecraft is investigated. Both vehicles are active and provide thrust to complete the rendezvous. Total propellant consumption is minimized. A direct-minimization method, direct collocation with nonlinear programming, is used to obtain cooperative rendezvous solutions in an inversesquare gravitational field. Unconstrained and constrained circular terminal orbits are considered. The optimal solutions depend upon the power-to-mass ratios of the spacecraft, the initial orbits, and the specified transfer time. Optimal cooperative rendezvous solutions are compared with optimal active-passive solutions and with previously reported linearized solutions.
Advances in Space Research, 2011
The CubeSail mission is a low-cost demonstration of the UltraSail solar sailing concept ), using ... more The CubeSail mission is a low-cost demonstration of the UltraSail solar sailing concept ), using two near-identical CubeSat satellites to deploy a 260 m-long, 20 m 2 reflecting film. The two satellites are launched as a unit, detumbled, and separated, with the film unwinding symmetrically from motorized reels. The conformity to the CubeSat specification allows for reduction in launch costs as a secondary payload and utilization of the University of Illinois-developed spacecraft bus. The CubeSail demonstration is the first in a series of increasingly-complex missions aimed at validating several spacecraft subsystems, including attitude determination and control, the separation release unit, reel-based film deployment, as well as the dynamical behavior of the sail and on-orbit solar propulsion. The presented work describes dynamical behavior and control methods used during three main phases of the mission. The three phases include initial detumbling and stabilization using magnetic torque actuators, gravity-gradient-based deployment of the film, and steady-state film deformations in low Earth orbit in the presence of external forces of solar radiation pressure, aerodynamic drag, and gravity-gradient.
AIAA/AAS Astrodynamics Specialist Conference and Exhibit, 2004
Missions to the outer planets for spacecraft with a solar-electric propulsion system (SEPS) and t... more Missions to the outer planets for spacecraft with a solar-electric propulsion system (SEPS) and that uhilize a single Venus gravity assist are investigated. The trajectories rnaximiZe the delivered mass to the target planet for a range of flight times. A comparison of the trajectory characteristics (delivered mass, launch energy and onboard propulsive energy) is made for various Venus gravity assist opportunities. Methods to estimate the delivered mass to the outer planets are developed.
AIAA/AAS Astrodynamics Specialist Conference and Exhibit, 1998
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
UltraSail is a next-generation high-risk, high-payoff sail system for the launch, deployment, sta... more UltraSail is a next-generation high-risk, high-payoff sail system for the launch, deployment, stabilization and control of very large (km 2 class) solar sails enabling high payload mass fractions for high ∆V. UltraSail is an innovative, non-traditional approach to propulsion technology achieved by combining propulsion and control systems developed for formation-flying micro-satellites with an innovative solar sail architecture to achieve controllable sail areas approaching 1 km 2 , sail subsystem area densities approaching 1 g/m 2 , and thrust levels many times those of ion thrusters used for comparable deep space missions. UltraSail can achieve outer planetary rendezvous, a deep space capability now reserved for high-mass nuclear and chemical systems. One of the primary innovations is the near-elimination of sail supporting structures by attaching each blade tip to a formation-flying micro-satellite which deploys the sail, and then articulates the sail to provide attitude control, including spin stabilization and precession of the spin axis. These tip micro-satellites are controlled by 3-axis micro-thruster propulsion and an on-board metrology system. It is shown that an optimum spin rate exists which maximizes payload mass.
Sensors and Systems for Space Applications, 2007
ABSTRACT Small satellites and payloads in the (1-2 kg) class called Cubesats and (20-30 kg) calle... more ABSTRACT Small satellites and payloads in the (1-2 kg) class called Cubesats and (20-30 kg) called Nanosats have been under development at the University of Illinois since fall, 2001. The ION1 Cubesat was a 10x10x21.5 cm3 satellite with the experiment consisting of photometric remote sensing of mesospheric structures (near 94 km) in the O2 (0,0) band airglow at 762 nm. ION1 development began in 2001 and was lost on the failed launch attempt, July 26, 2006. ION2 development began in Fall 2005, and has a remote sensing experiment to measure Halpha (656.3 nm) originating in the Earth's geocorona from which column H densities can be deduced. Taylor University has led the development of a Nanosat called TEST, which was designed to study ionospheric structures. Illinois provided remote sensing payloads including a CCD camera and dual photometers. The development activity is largely implemented by a College of Engineering Interdisciplinary Design class (ENG 491), where students typically participate in the systems engineering experience for two semesters. The students (15-20 average enrollment) are responsible for the design, fabrication, and testing of the systems. This paper describes the development of these Cubesat and Nanosat systems.
The optical properties of the thin metalized polymer films that are projected for solar sails are... more The optical properties of the thin metalized polymer films that are projected for solar sails are assumed to be aected by the erosive eects of the space environment. Their degradation behavior in the real space environment, however, is to a considerable degree indefinite, because initial ground test results are controversial and relevant in- space tests have not been made so
Journal of Spacecraft and Rockets, 2005
Outer-planet mission and systems analyses are performed using three next generation solarelectric... more Outer-planet mission and systems analyses are performed using three next generation solarelectric ion thruster models. The impact of variations in thruster model, flight time, launch vehicle, propulsion and power systems characteristics is investigated. All presented trajectories have a single Venus gravity assist and maximize the delivered mass to Saturn or Neptune. The effect of revolution ratio -the ratio of Venusian orbital period to the flight time between launch and flyby datesis also discussed.
Journal of Spacecraft and Rockets, 2006
Journal of Spacecraft and Rockets, 2006
ABSTRACT Conceptual in-space transfer stages, including those using solar electric propulsion and... more ABSTRACT Conceptual in-space transfer stages, including those using solar electric propulsion and chemical propulsion with aerobraking or aerocapture assist at Mars, were evaluated. Roundtrip Mars sample return mission vehicles were analyzed to determine how technology selections influence payload delivery capability. Results show how specific engine, thruster, propellant, capture mode, trip time, and launch-vehicle technology choices would contribute to increasing payload delivered to Mars or decreasing the size of the required launch vehicles. Low-thrust trajectory analyses for solar-electric transfer were generated with the SEPTOP code.
Journal of Guidance, Control, and Dynamics, 2010
Journal of Guidance, Control, and Dynamics, 2008
ABSTRACT The sail dynamics of spin-stabilized solar sail designs are examined in this paper. The ... more ABSTRACT The sail dynamics of spin-stabilized solar sail designs are examined in this paper. The nonlinear governing equations of motion are derived for four different and progressively more complex dynamical scenarios: pitch (one dimensional); pitch and sweepback (two dimensional); pitch and lead/lag (two dimensional); and pitch, sweepback, and lead/lag (three dimensional). These equations are applied to UltraSail, a novel solar sail design developed at the University of Illinois at Urbana-Champaign, which relies on small-tip satellites to provide tension in rectangular sails. Steady-state and time-dependent characteristics are numerically calculated and discussed. Properties such as the spacecraft acceleration are predicted, and transient sail responses to an applied perturbation are simulated. Results place UltraSail as a strong candidate for future solar sail missions with performance challenging previously proposed concepts.
Journal of Guidance, Control, and Dynamics, 2004
With the growing emphasis on vehicle autonomy, the problem of planning a trajectory in an environ... more With the growing emphasis on vehicle autonomy, the problem of planning a trajectory in an environment with obstacles has become increasingly important. This task has been of particular interest to roboticists and computer scientists, whose primary focus is on kinematic motion planning . Typical kinematic planning methods fall into two main categories, roadmap methods and incremental search methods, both of which find collision-free paths in the state space. Roadmap methods generate and traverse a graph of collision-free connecting paths spanning the state space, while incremental search methods, including dynamic programming [2] and potential field methods [3], perform an iterative search to connect the initial and goal states. For the purely geometric path planning problem, deterministic algorithms have been created that are complete, i.e., they will find a solution if and only if one exists. Unfortunately, these suffer from high computational costs which are exponential in system degrees of freedom. This cost has motivated the development of iterative randomized path planning algorithms that are probabilistically complete, i.e., if a feasible path exists, the probability of finding a path from the initial to final conditions converges to one as the number of iterations goes to infinity. The introduction of the Rapidly-exploring Random Trees (RRTs) of LaValle and Kuffner [4] allowed both for computationally efficient exploration of a complicated space as well as incorporation of system dynamics. The RRT grows a tree of feasible trajectories from the initial condition, or root node. Each node, or waypoint, on the tree represents a system state and has possible trajectories branching from it. Through use of an embedded planning routine, the tree incrementally builds itself in random direc-Associate Fellow AIAA 1 of 12 tions, node by node, until the final conditions are met (within accuracy bounds). Frazzoli demonstrated that a hybrid systems representation of vehicle dynamics, when coupled with the RRT, could be used to address moving obstacles and time-invariant final conditions in a real-time environment. This paper presents a similar approach which provides probabilistic completeness in the presence of both time-varying obstacles and final conditions while using a simpler algorithmic procedure. In addition, a novel approach to provide error mitigation of the embedded planner in a hybrid system-based RRT is presented. An example is then given in which the proposed algorithm is applied to the landing of a spacecraft on an idealized asteroid.
Journal of Guidance, Control, and Dynamics, 2010
ABSTRACT This work focuses on investigating the behavior of the orbit transfer switching function... more ABSTRACT This work focuses on investigating the behavior of the orbit transfer switching function for the two-body problem. Recent work indicated that use of an analytical expression for the switching function could significantly reduce the computational time required to determine when to end coast arcs during trajectory optimization. This analysis of the switching function begins by showing how the printer vector and switching function in various coordinate systems are related, and two representative systems are considered for the remaining analysis. Given that multiple harmonics are manifest simultaneously in the switching function during coast arcs, some possible behaviors of such functions are considered relative to finding bounds containing the desired coast-terminating zero. It is seen that the method proposed in recent work can fail. A relatively simple improvement involving the slope of the switching function at the sampled points is used to make the method more robust and enable the production of example optimal solutions that would not have been possible with the earlier method. In terms or the two chosen systems, analytical expressions for the switching function and its derivative during coasting as well as transformation matrices that relate the systems to each other are therefore presented in Appendices A, B, and C.
Journal of Guidance, Control, and Dynamics, 2004
Journal of Guidance, Control, and Dynamics, 2008
ABSTRACT The sun/Earth-moon L1 point is a growing target for space missions. This paper assumes a... more ABSTRACT The sun/Earth-moon L1 point is a growing target for space missions. This paper assumes a need to place an object directly between the Earth and the sun. Possible purposes for such a mission include a type of shield to intercept some portion of the sun's rays, or conversely a lens or mirror to focus them. In addition, this paper requires a launch directly from the moon instead of a traditional orbit-to-orbit transfer. A detailed case using accurate positional and velocity data for all planetary bodies is used in this paper. Instead of focusing solely on trajectories defined as optimal by minimum fuel consumption, we looked for trajectories with low sensitivity to initial conditions to additionally minimize the frequency and magnitude of course corrections. We first analyzed the reverse problem to identify solution areas of low sensitivity to launch conditions. Using the determined restricted solution space, we were successfully able to determine a launch site on the moon that could reach L1 with the greatest number of low-cost trajectories and launch windows within the resolution of the solution space.
Journal of Guidance, Control, and Dynamics, 1995
Minimum-fuel, impulsive, time-fixed solutions are obtained for the problem of orbital rendezvous ... more Minimum-fuel, impulsive, time-fixed solutions are obtained for the problem of orbital rendezvous and interception with interior path constraints. Transfers between coplanar circular orbits in an inverse-square gravitational field are considered, subject to a circular path constraint representing a minimum or maximum permissible orbital radius. Primer vector theory is extended to incorporate path constraints, and the optimal number of impulses along with their times and positions are determined. The existence of constraint boundary arcs is investigated as well as the optimality of a class of singular arc solutions. A bifurcation phenomenon is discovered in a maximum-radius solution as the transfer time is increased. To illustrate the complexities introduced by path constraints, an analysis is made of optimal rendezvous in field-free space subject to a minimum radius constraint.
Journal of Guidance, Control, and Dynamics, 1998
Journal of Guidance, Control, and Dynamics, 1994
Minimum-fuel rendezvous of two power-limited spacecraft is investigated. Both vehicles are active... more Minimum-fuel rendezvous of two power-limited spacecraft is investigated. Both vehicles are active and provide thrust to complete the rendezvous. Total propellant consumption is minimized. A direct-minimization method, direct collocation with nonlinear programming, is used to obtain cooperative rendezvous solutions in an inversesquare gravitational field. Unconstrained and constrained circular terminal orbits are considered. The optimal solutions depend upon the power-to-mass ratios of the spacecraft, the initial orbits, and the specified transfer time. Optimal cooperative rendezvous solutions are compared with optimal active-passive solutions and with previously reported linearized solutions.
Advances in Space Research, 2011
The CubeSail mission is a low-cost demonstration of the UltraSail solar sailing concept ), using ... more The CubeSail mission is a low-cost demonstration of the UltraSail solar sailing concept ), using two near-identical CubeSat satellites to deploy a 260 m-long, 20 m 2 reflecting film. The two satellites are launched as a unit, detumbled, and separated, with the film unwinding symmetrically from motorized reels. The conformity to the CubeSat specification allows for reduction in launch costs as a secondary payload and utilization of the University of Illinois-developed spacecraft bus. The CubeSail demonstration is the first in a series of increasingly-complex missions aimed at validating several spacecraft subsystems, including attitude determination and control, the separation release unit, reel-based film deployment, as well as the dynamical behavior of the sail and on-orbit solar propulsion. The presented work describes dynamical behavior and control methods used during three main phases of the mission. The three phases include initial detumbling and stabilization using magnetic torque actuators, gravity-gradient-based deployment of the film, and steady-state film deformations in low Earth orbit in the presence of external forces of solar radiation pressure, aerodynamic drag, and gravity-gradient.