Stretching directions in cislunar space: Applications for departures and transfer design

in Astrodynamics (2022)

Stable or nearly stable orbits do not generally possess well-distinguished manifold structures that assist in designing trajectories for departing from or arriving onto a periodic orbit. For some ... [more ▼]

Stable or nearly stable orbits do not generally possess well-distinguished manifold structures that assist in designing trajectories for departing from or arriving onto a periodic orbit. For some potential missions, the orbits of interest are selected as nearly stable to reduce the possibility of rapid departure. However, the linearly stable nature of these orbits is also a drawback for their timely insertion into or departure from the orbit. Stable or nearly stable Near Rectilinear Halo Orbits (NRHOs), Distant Retrograde Orbits (DROs), and lunar orbits offer potential long-horizon trajectories for exploration missions and demand efficient operations. The current investigation focuses on leveraging stretching directions as a tool for departure and trajectory design applications. The magnitude of the state variations along the maximum stretching direction is expected to grow rapidly and, therefore, offers information for efficient departure from the orbit. Similarly, maximum stretching in reverse time enables arrival with a minimal maneuver magnitude. [less ▲]

Autonomous control for satellite rendezvous in near-Earth orbits

Scientific Conference (2022, July)

CubeSats are being deployed for a number of activities including Earth observation, telecommunications, scientific experiments, and due to their low cost and flexibility, more often than not, they are ... [more ▼]

CubeSats are being deployed for a number of activities including Earth observation, telecommunications, scientific experiments, and due to their low cost and flexibility, more often than not, they are even being considered for use in On-Orbit Servicing (OOS) and debris removal missions. This investigation focuses on using the CubeSat technology to perform autonomous proximity operations with passive target bodies including satellites or space debris. The nonlinear coupled attitude and orbit dynamics for the chaser and the target bodies are modelled and simulated. A nonlinear optimal controller identifies an appropriate rendezvous path. A vision-based navigation system on the chaser satellite records the pose of the target body. The pose observations with stochastic uncertainties are processed using a Kalman filter, and offer state feedback along the satellite path. Such observations in conjunction with the postulated linear control algorithm anchor the chaser to approach the target by maintaining appropriate relative configuration. The linear controller delivers regular maneuvers to compensate for any deviations from the identified reference path. A close-range rendezvous operation is illustrated in a Mission Design Simulator (MDS) tool. [less ▲]

Stretching Directions in Cislunar Space: Stationkeeping and an Application to Transfer Trajectory Design

Doctoral thesis (2021)

The orbits of interest for potential missions are stable or nearly stable to maintain long-term presence for conducting scientific studies and to reduce the possibility of rapid departure. Near ... [more ▼]

The orbits of interest for potential missions are stable or nearly stable to maintain long-term presence for conducting scientific studies and to reduce the possibility of rapid departure. Near Rectilinear Halo Orbits (NRHOs) offer such stable or nearly stable orbits that are defined as part of the L1 and L2 halo orbit families in the circular restricted three-body problem. Within the Earth-Moon regime, the L1 and L2 NRHOs are proposed as long-horizon trajectories for cislunar exploration missions, including NASA's upcoming Gateway mission. These stable or nearly stable orbits do not possess well-distinguished unstable and stable manifold structures. As a consequence, existing tools for stationkeeping and transfer trajectory design that exploit such underlying manifold structures are not reliable for orbits that are linearly stable. The current investigation focuses on leveraging stretching direction as an alternative for visualizing the flow of perturbations in the neighborhood of a reference trajectory. The information supplemented by the stretching directions are utilized to investigate the impact of maneuvers for two contrasting applications; the stationkeeping problem, where the goal is to maintain a spacecraft near a reference trajectory for a long period of time, and the transfer trajectory design application, where rapid departure and/or insertion is of concern. Particularly, for the stationkeeping problem, a spacecraft incurs continuous deviations due to unmodeled forces and orbit determination errors in the complex multi-body dynamical regime. The flow dynamics in the region, using stretching directions, are utilized to identify appropriate maneuver and target locations to support a long lasting presence for the spacecraft near the desired path. The investigation reflects the impact of various factors on maneuver cost and boundedness. For orbits that are particularly sensitive to epoch time and possess distinct characteristics in the higher-fidelity ephemeris model compared to their CR3BP counterpart, an additional feedback control is applied for appropriate phasing. The effect of constraining maneuvers in a particular direction is also investigated for the 9:2 synodic resonant southern L2 NRHO, the current baseline for the Gateway mission. The stationkeeping strategy is applied to a range of L1 and L2 NRHOs, and validated in the higher-fidelity ephemeris model. For missions with potential human presence, a rapid transfer between orbits of interest is a priority. The magnitude of the state variations along the maximum stretching direction is expected to grow rapidly and, therefore, offers information to depart from the orbit. Similarly, the maximum stretching in reverse time, enables arrival with a minimal maneuver magnitude. The impact of maneuvers in such sensitive directions is investigated. Further, enabling transfer design options to connect between two stable orbits. The transfer design strategy developed in this investigation is not restricted to a particular orbit but applicable to a broad range of stable and nearly stable orbits in the cislunar space, including the Distant Retrograde Orbit (DROs) and the Lunar Orbits (LO) that are considered for potential missions. Examples for transfers linking a southern and a northern NRHO, a southern NRHO to a planar DRO, and a southern NRHO to a planar LO are demonstrated. [less ▲]

Orbit Maintenance Strategy for Earth-Moon Halo Orbits

Scientific Conference (2021, February)

The L1 and L2 Near Rectilinear Halo Orbits (NRHOs) are proposed long horizon trajectories for cislunar exploration missions. Due to unmodeled forces as well as orbit determination errors in this ... [more ▼]

The L1 and L2 Near Rectilinear Halo Orbits (NRHOs) are proposed long horizon trajectories for cislunar exploration missions. Due to unmodeled forces as well as orbit determination errors in this dynamically sensitive region, the spacecraft deviates from the desired path. The current investigation focuses on an extended analysis of an impulsive stationkeeping technique to maintain the spacecraft near a long horizon virtual reference orbit. The dynamics in the halo orbit region are explored to identify suitable maneuver and target locations for stationkeeping. Furthermore, phasing constraints are incorporated to maintain spacecrafts on orbit where position and velocity states are sensitive to epoch time. [less ▲]

Tracking neighboring quasi-satellite orbits around Phobos

in IFAC-PapersOnLine (2020, July)

We consider the orbital maintenance problem on a quasi-satellite orbit about the Martian moon, Phobos. The orbit is computed using a high-fidelity ephemeris model so that the major sources of disturbances ... [more ▼]

We consider the orbital maintenance problem on a quasi-satellite orbit about the Martian moon, Phobos. The orbit is computed using a high-fidelity ephemeris model so that the major sources of disturbances are due to measurement error. Two types of orbit maintenance schemes are considered. The first is based on asymptotically tracking the desired trajectory and the second is based on stabilizing to the manifold of trajectories that share the same Jacobi constant as the reference trajectory. The latter can be done because trajectories with the same Jacobi constant are in the neighborhood of one another. The results show that the trajectory-tracking scheme has lower fuel consumption when tracking must be precise and that the approach of stabilizing to a manifold has better fuel consumption at the expense of tracking. [less ▲]

Orbit Maintenance Strategies for Sun-Earth/Moon Libration Point Missions: Parameter Selection for Target Point and Cauchy-Green Tensor Approaches

Bachelor/master dissertation (2017)

The libration point orbits in the Sun-Earth/Moon system are formed by concurrent gravitational influences by various celestial bodies, originating in a nonlinear dynamical regime. Coupled with the ... [more ▼]

The libration point orbits in the Sun-Earth/Moon system are formed by concurrent gravitational influences by various celestial bodies, originating in a nonlinear dynamical regime. Coupled with the unstable nature of the orbit, the impact of any perturbations are expected to increase rapidly. The feasibility of a flow-based, Cauchy-Green tensor control strategy for station-keeping is examined. An orbit consistent with the mission objectives is selected for examination. The station-keeping process is stochastic, thus Gaussian random errors are introduced for simulation. The evolution of a velocity perturbation over time is monitored, beyond which the attainable state in the accessible region nearest to the target state is employed as a feedback to compute the necessary full, three-component corrective maneuver. The application and appropriateness of single axis control maneuvers for orbit maintenance are also evaluated. The selection procedure for certain parameters such as tolerances and weighting values are developed to incorporate the available dynamical information, yielding a versatile and straightforward strategy. Weighting matrices within the target point approach are effective in influencing the station-keeping costs as well as size and direction of maneuvers. Moreover, selection of appropriate tolerance values in the application of the Cauchy-Green tensor exploits the dominant stretching direction of the perturbation magnitude to inform the maneuver construction process. The work is demonstrated in the context of the upcoming Aditya-1 mission to a Sun-Earth/Moon L1 halo orbit for solar observations and the James Webb Telescope to a Sun-Earth/Moon L2 halo orbit for astronomy. [less ▲]

Design optimization of front and rear aerodynamic wings of a high performance race car with modified airfoil structure

in 2015 International Conference on Nascent Technologies in the Engineering Field (ICNTE) (2015, January)

Formula Student Racing competitions are international events organized by Society of Automotive Engineers globally at various Formula SAE Circuits. Teams comprising of college students worldwide thrive to ... [more ▼]

Formula Student Racing competitions are international events organized by Society of Automotive Engineers globally at various Formula SAE Circuits. Teams comprising of college students worldwide thrive to build a Formula style race car to compete at these events. In this high octane racing event every team tries to have an inch over their opponents by reducing lap timings. The best way for minimal lap timings is better performance along the straights and a good cornering. It becomes difficult for cars to get good traction when traveling at high speeds as well as they need to reduce their speeds drastically to take sharp corners. To maximize the performance of team NITK Racing car for such events an aerodynamic wings package at the front and the rear is proposed which produces sufficient down-force when accelerating in the straights as well as allowing sharp corners at relatively higher speeds. Being a student based competition intense amount of care is given to the safety precautions. Cars having sharp corners and protrusions are liable to be disqualified and hence the wing tip needs to be modified in order to satisfy the safety rules of the competition. [less ▲]