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The danger to orbiting satellites from space debris has been known for decades, yet accidents and intentional anti-satellite weapon tests still pose serious threats. Better rules are needed to govern increasingly busy near-Earth space. [ABSTRACT FROM AUTHOR]

Abstract: The spatial problem of the aerophysics of a superorbital entry of the Apollo-4 command module into the dense layers of the Earth’s atmosphere at an angle of attack of 25°, an entry velocity V∞ = 10.7 km s-1, and altitudes of 91.5 and 76.2 km has been solved. The distributions of the spectral and integral radiative heat flux densities along the entire streamlined surface have been derived. A significant role of the electronic bands of diatomic molecules in the radiative heating of the surface has been shown. [ABSTRACT FROM AUTHOR]

On 6 February 2018, SpaceX launched a Tesla Roadster on a Mars-crossing orbit. We perform N-body simulations to determine the fate of the object over the next 15 Myr. The orbital evolution is initially dominated by close encounters with the Earth. While a precise orbit can not be predicted beyond the next several centuries due to these repeated chaotic scatterings, one can reliably predict the long-term outcomes by statistically analyzing a large suite of possible trajectories with slightly perturbed initial conditions. Repeated gravitational scatterings with Earth lead to a random walk. Collisions with the Earth, Venus and the Sun represent primary sinks for the Roadster's orbital evolution. Collisions with Mercury and Mars, or ejections from the Solar System by Jupiter, are highly unlikely. We calculate a dynamical half-life of the Tesla of approximately 15 Myr, with some 22%, 12% and 12% of Roadster orbit realizations impacting the Earth, Venus, and the Sun within one half-life, respectively. Because the eccentricities and inclinations in our ensemble increase over time due to mean-motion and secular resonances, the impact rates with the terrestrial planets decrease beyond a few million years, whereas the impact rate on the Sun remains roughly constant. [ABSTRACT FROM AUTHOR]

In its report on the SpaceShipTwo accident the National Transportation Safety Board (NTSB) included in its recommendations that the Federal Aviation Administration (FAA) “in collaboration with the commercial spaceflight industry, continue work to implement a database of lessons learned from commercial space mishap investigations and encourage commercial space industry members to voluntarily submit lessons learned.” In its official response to the NTSB the FAA supported this recommendation and indicated it has initiated an iterative process to put into place a framework for a cooperative safety data sharing process including the sharing of lessons learned, and trends analysis. Such a framework is an important element of an overall commercial human spaceflight safety system. As the industry matures and approaches a time of regular operational flights carrying paying commercial passengers, the time is right to consider the development of an industry-wide safety reporting system focused on operational hazards, incidents, and close calls. Mature safety reporting systems of this nature exist, both in the aerospace sector and in other industries. For example: • The Aviation Safety Reporting System (ASRS) in the United States • The Federal Railroad Authority Confidential Close Call Reporting System • The NASA Safety Reporting System (NSRS) • Aviation Safety Reporting Systems operated by several civil aviation authorities around the globe These successful systems offer a number of lessons learned and operational best practices that might be applied to a prospective commercial human spaceflight safety reporting system. Through a review of these programs, focusing on systems in the U.S., this paper will describe elements of a safety reporting system that might be developed in support of the commercial human spaceflight industry. Factors to be addressed include: • Origins and motivations for the system • Organizational and operational approaches • Treatment of confidentiality, both for reporters' personally identifiable information, and for proprietary or commercially sensitive information • Relationship to lessons learned and safety data exchange programs • Authority to act upon information received One element that these systems often have in common is that they were established following a tragic incident involving the loss of multiple lives. The FAA's efforts to analyze and implement a commercial spaceflight; safety lessons learned database offers a window to develop a safety reporting system, in consultation with; industry, prior to similar tragic incidents involving commercial spaceflight participants; [ABSTRACT FROM AUTHOR]

Space debris of millimeter dimensions is almost not detectable by normal methods of observation from Earth. However, particles of such sizes can cause damage to the spacecraft. and even eliminate it. Estimating the status of impurity of near-Earth space mainly based on mathematical models, which are confirmed only for large particles. The millimetric fractions of space debris elements remain unexplored. In case of invasion of debris particles into the planet's atmosphere, they burn down as well as meteoric particles of natural origin. In this work, the observation technique of separation of debris particles and particles of natural origin is described. Also, the results of the detection of particles from space debris received during the TV observations on the wide-angle camera patrol camera FAVOR (Russia, Northern Caucasus). [ABSTRACT FROM AUTHOR]

A new approach to the estimation of atmospheric parameters affecting the movement of space rocket fragments in case of accident launches is proposed by the example of the Plesetsk Cosmodrome. Due to the absence of operational information on the vertical distribution of atmospheric parameters above 30 km, the method is considered which allows using available archival aerological data and the statistical characteristics of air density and wind speed components computed from the rocket sounding of the atmosphere for ballistic calculations. [ABSTRACT FROM AUTHOR]

This paper researches an optimal problem of orbital evasion with considering space geometry by using an analytical approach. Firstly, an angles-only relative navigation model is built and the definition of completely nonobservable maneuver is proposed. After algebraic analysis of relative space geometry, it is proved that the completely nonobservable maneuver is nonexistent. Based on this, the angle measurements of orbit without evasion are set as reference measurements and an analytical solution is derived to find the minimum difference between measurements and the reference measurements in a constant measuring time. Then, an object function using vector multiplication is designed and an optimization model is established so as to prove the optimality of analytical solution. At last, several numerical simulations are performed with different maneuver directions, which verify the effectiveness of the analytical method of this paper for orbital evasion problem. This method offers a new viewpoint for orbital evasion problem. [ABSTRACT FROM AUTHOR]

This paper presents a suboptimal continuous control algorithm that would enable an active spacecraft to avoid collision with inactive space objects. To prevent collision, a penalty function whose value soars as a spacecraft is about to collide with other objects is inserted into the cost functional of an optimal control problem. Then, a two-point boundary value problem for a Hamiltonian system is constructed, and is solved with the generating functions. This algorithm can be coded step-by-step to obtain suboptimal feedback continuous control laws as truncated power series with no initial guess or iteration. This advantage over direct optimizations, however, requires moderate efforts to develop higher-order generating functions and update the penalty function parameters heuristically. In the illustrative examples, the above process allows an active satellite to smoothly circumvent other space objects or forbidden regions. The overall process is also useful for obtaining an appropriate initial guess for the direct optimization approaches in case of numerically sensitive problems because of the definiteness in its solution procedure. [ABSTRACT FROM AUTHOR]

For the application of robotically assembling large space structures, a feedback control law is synthesized for transitional and rotational maneuvers of a ‘tug’ spacecraft in order to transport a flexible element to a desired position without colliding with other space bodies. The flexible element is treated as a long beam clamped to the ‘tug’ spacecraft modelled as a rigid hub. First, the physical property of passivity of Euler-Lagrange system is exploited to design the position and attitude controllers by taking a simpler obstacle-free control problem into account. To reduce sensing and actuating requirements, the vibration modes of the beam appendage are supposed to be not directly measured and actuated on. Besides, the requirements of measuring velocities are removed with the aid of a dynamic extension technique. Second, the bounding boxes in the form of super-quadric surfaces are exploited to enclose the maximal extents of the obstacles and the hub-beam spacecraft. The collision avoidance between bounding boxes is achieved by applying additional repulsive force and torque to the spacecraft based on the method of artificial potential field. Finally, the effectiveness of proposed control scheme is numerically demonstrated via case studies. [ABSTRACT FROM AUTHOR]