Journal of Space Safety Engineering最新文献

In order to evaluate the possible casualty area caused by the atmospheric re-entry of a vehicle, CNES develops its own certification tool named DEBRISK. For more than 7 years, an important work has been carried out in the frame of DEBRISK v3 with the aim of reducing as much as possible the uncertainties on all the models influencing the survivability of debris.

Given the significant advances in terms of modelling and observations from ground experiments, the methodologies and recommendations are evolving and improving. Several recommendations are discussed, specifically related to how to model a satellite and problematic equipment from a survivability point of view. Representative satellite test cases are presented, showing the evolution of the debris survivability with DEBRISK V3.

Several commercial companies, as well as various nations, have proposed to deploy or are deploying many satellites in Low Earth Orbit (LEO). These large constellations will greatly increase the number of satellites operating in relatively narrow altitude regions of space. The added space traffic in these regions will create many close approaches between the members of the large constellations and other space operators. These close approach situations can necessitate maneuver(s) to avoid a potential collision. Should both satellites have maneuvering capability, the question of how the overall collision avoidance procedures should be executed is raised. Some constellations may employ automated collision avoidance systems which interact differently than conventional human-in-the-loop systems. Interactions between an automated system and another operational satellite, between two automated systems or two nonautonomous systems present new challenges for executing effective collision avoidance. Additionally, the existence of non-maneuverable satellites and space debris continues to pose additional challenges. This paper is the first of several papers that will be documenting an International Academy of Astronautics study on this topic.

Geospatial and celestial datasets are used extensively to support safety-critical applications across multiple industries. Examples include aircraft navigation aids, charts, terrain elevation data, and many others. In commercial space, examples include star positions, micrometeoroid, and orbital debris data (MMOD), terrestrial or lunar navaids, lunar terrain data. Depending on its application, this data has the potential to cause hazards and therefore needs to be assured. Approval of this data cannot be achieved by any one company or body alone; the international commercial space industry needs to develop an ecosystem of interlocking standards and oversight. The aviation industry provides a good example of how this might be accomplished.

Over the last few years, both the space debris population and the number of active satellites in orbit has dramatically increased. The risk of collision for satellite missions is a problem to an increasing extent targeted thoroughly by all agents involved in space situational awareness (SSA) & spacecraft operations. In the frame of the European Union Space Surveillance and Tracking (EU SST), the CA service is provided on a hot redundancy scheme involving the French and Spanish Operations Centres (FR-SSA Centre and S3TOC, respectively), to more than 50 organizations and 390 satellites at the time of writing.

Given the dynamic space environment, EU SST CA service must evolve continuously to face the increase of the number of registered users and spacecraft, the diversity of users’ needs and the increasing number of close approaches.

As we aim for deep space exploration, supporting vital systems, such as the Temperature and Humidity Control System (THCS) in the Environmental Control and Life Support System (ECLSS), through timely onboard fault detection and diagnosis becomes paramount for mission success. Many existing fault diagnosis approaches assume that the function that models the relationship between faults and associated symptoms (fault-symptom relationships) will remain constant throughout the THCS’ lifetime. Therefore, many of these diagnosis methods are not robust enough to automatically account for changes in fault-symptom relationships as a result of changes in the habitat (e.g., system reconfiguration). The work highlighted here is on (i) surveying existing work on adaptable fault diagnosis methods and (ii) showcasing a real-life case study, in which we identified the need for an automatically adaptable fault diagnosis method. The case study focuses on a reconfigured terrestrial THCS analog, the Heating, Ventilation, and Air Conditioning (HVAC) system, where the original fault-symptom relationship is revealed to be no longer accurate. We then apply current adaptable fault-symptom relationship generation methods, such as Model-Based Dependability Analysis (MBDA) methods and data-driven causal discovery methods. Through this analysis, we detail our procedure in (i) identifying relevant fault-free system information, such as redundancy, to revise fault-symptom relationships used in fault diagnosis and (ii) evaluating the fault diagnosis performance in a THCS with the original and revised fault-symptom relationship. Our contribution lies in identifying the shortcomings of current methods and pinpointing future steps in creating an adaptable fault diagnosis framework. We found that although the MBDA methods can automatically generate fault-symptom relationships given system flow information and fault mode of components, they also required manual revision of the aforementioned information to create fault-symptom relationships that reflect redundancies. On the other hand, we concluded that the causal discovery methods can detect fault-free system information, such as redundancies, that may help us revise fault-symptom relationships, but suspect variables that contribute to redundancies may have to be hand-picked.

The capture of the space debris (SD) occurs after the tether is delivered from the space tug (ST) to the SD with the help of an autonomous docking module (ADM). During tether stretching, motion impulses are exchanged between the ST and the "ADM + SD" system, after which a rotating space tether system (RSTS) is created.

Under the influence of two factors, i.e., the difference in relative velocities of the ST and the "ADM + SD" system (up to 200 m/s) and the centrifugal force, significant longitudinal deformations of the tether occur, which can lead to its breakage. The presence of a significant value of the relative velocity projection on the tether line is the peculiarity of this RSTS which has a significant effect on the tether loading in comparison to the action of centrifugal force. In traditional RSTS, only centrifugal forces are considered.

This paper introduces a novel method of damping the longitudinal oscillations of the tether for the proposed type of RSTS, based on two active control strategies: by changing the natural length of the tether and by the thrust force of the ST propulsion system acting opposite to the centrifugal force. A comparative analysis of the dynamics of the RSTS under different methods of active control has been performed.

Significance of the developed methodology is determined by the possibility of using it for further research in planning various active interorbital space missions. The contribution to the solution of the problem under study consists of the possibility of creating RSTS formed by exchanging the impulses of the ST motion and the "ADM + SD" conjunction at significant relative velocities, unlike traditional RSTS, such as star, triangle, etc.

Space is once again an arena of global competition and rivalry, but now more actors and technologies affecting the dynamics. Russia remains a relevant, yet relatively declining space power, eager to preserve both status and capabilities. Space domain is seen as both an opportunity and a threat, and both technological and political efforts are being invested to shape the environment so it will be favorable for Russian interests. However, the interests themselves are defined rather vaguely, yet the threats are seen as immediate, thus some overreaction is a real possibility. The actual and possible developments in the area are researched, and some solutions to keep things manageable are proposed. Moreover, relations of space domain with other major topics, including Strategic Offensive Arms, Missile Defense and Cyber/Electronic Warfare are addressed.