Aerocapture Guidance Research Articles

Flight control methodologies for Neptune aerocapture trajectories

In this work, a comparison of potential flight control methodologies for Neptune aerocapture trajectories is presented. Lifting trajectories pertaining to bank angle modulation and direct force control as well as ballistic trajectories pertaining to continuously-variable drag modulation are investigated. A parametric study of vehicle configurations is explored to quantitatively compare the flight envelope between lifting and ballistic trajectories. A closed-loop numerical predictor–corrector aerocapture guidance architecture is utilized to unify each flight control technique for trajectory comparisons. A series of Monte Carlo simulations of blunt body Neptune aerocapture trajectories are conducted to assess each flight control’s robustness to uncertainties in vehicle aerodynamics, atmospheric knowledge, and entry state. Direct force control can achieve 100% successful science orbit insertion within a 120 m/s total ΔV budget. Bank angle modulation can achieve 100% successful science orbit insertion within a 300 m/s total ΔV budget. Continuously-variable drag modulation can achieve 99.3% successful science orbit insertion within a 190 m/s total ΔV budget but at 3 times lower peak stagnation point convective heating rate.

Characteristic model and its applications in Mars aerocapture guidance

Mars exploration has been a hot spot around the world in the field of deep space exploration in recent years. Low-cost space transport is one of the key factors in space exploration and development, and aerodynamic assisted orbit change will reduce space vehicle design costs. Aerocapture is a form of aerodynamically assisted orbit shift, referring to the use of the aerodynamic force generated by the planetary atmosphere to minimize the energy of the orbit and the transfer of the hyperbolic orbit to the target orbit. There is only one opportunity to fulfill the aerocapture mission, and the criterion for reliability is very high. Because the aerocapture guidance and accuracy and robustness of the control are very poor, a smart and autonomous guidance system is required. The characteristic model-based guidance approach has a broad application potential and has high adaptability, robustness, and autonomy. The research status and progress of the theory of characteristic model and its application in Mars aerocapture guidance are reviewed, and the problems to be solved are put forward, which provides the basis for further research.

Analytical Predictor-Corrector Guidance Algorithm Based on Drag Modulation Flight Control System for Mars Aerocapture

Aerocapture is one of the essential technologies for future large-scale space exploration missions, as it can significantly reduce the Δv and fuel requirement. The performance and robustness of two different aerocapture control methods are analyzed around Mars exploration, and then an analytic predictor-corrector guidance algorithm for drag modulation flight control system is proposed. A piecewise linear function between velocity and flight path angle is established by appropriate approximations and assumptions, and then the state at atmosphere interface can be predicted by an analytical method; therefore, aerocapture guidance can be realized by feedback control. Numerical simulation is used to evaluate performance and robustness of the algorithm. The simulation results show that the guidance algorithm is accurate and robust, which can effectively overcome the influence of atmospheric density error, aerodynamic parameter error, and initial state uncertainty.

Connecting atmospheric science and atmospheric models for aerocapture at Titan and the outer planets

Many atmospheric measurement systems, such as the sounding instruments on Voyager, gather atmospheric information in the form of temperature versus pressure level. In these terms, there is considerable consistency among the mean atmospheric profiles of the outer planets Jupiter through Neptune, including Titan. On a given planet or on Titan, the range of variability of temperature versus pressure level due to seasonal, latitudinal, and diurnal variations is also not large. However, many engineering needs for atmospheric models relate not to temperature versus pressure level but atmospheric density versus geometric altitude. This need is especially true for design and analysis of aerocapture systems. Drag force available for aerocapture is directly proportional to atmospheric density. Available aerocapture “corridor width” (allowable range of atmospheric entry angle) also depends on height rate of change of atmospheric density, as characterized by density scale height. Characteristics of hydrostatics and the gas law equation mean that relatively small systematic differences in temperature versus pressure profiles can integrate at high altitudes to very large differences in density versus altitude profiles. Thus, a given periapsis density required to accomplish successful aerocapture can occur at substantially different altitudes ( ∼ 150 –300 km) on the various outer planets, and significantly different density scale heights ( ∼ 20 –50 km) can occur at these periapsis altitudes. This paper will illustrate these effects and discuss implications for improvements in atmospheric measurements to yield significant impact on design of aerocapture systems for future missions to Titan and the outer planets. Relatively small-scale atmospheric perturbations, such as gravity waves, tides, and other atmospheric variations can also have significant effect on design details for aerocapture guidance and control systems. This paper will discuss benefits that would result from improved understanding of Titan and outer planetary atmospheric perturbation characteristics. Details of recent engineering-level atmospheric models for Titan and Neptune will be presented, and effects of present and future levels of atmospheric uncertainty and variability characteristics will be examined.