ISO 17851:2016 pdf free

ISO 17851:2016 pdf free.Space systems – Space environment simulation for material tests – General principles and criteria
During ground-based tests of materials, two principle approaches are applied. The first approach implies the reproduction of the characteristics of the space environment at laboratory facilities in the full correspondence with space conditions and requires no initial assumption or additional data on the nature and type of processes under investigation. However, in laboratory conditions, it is practically impossible to reproduce characteristics of certain space environment components (e.g. space radiation component because of the complexity of energy spectra and composition of cosmic rays) and to provide simultaneous impact of the whole set of space environment components.
For these reasons, the second approach to the simulation of the space environment impact on spacecraft materials is used more frequently. In this case, the choice of one or several space factors that have the most damaging effects is made on the basis of certain assumptions and the data of physical mechanisms of degradation of objects under study.
As a rule, within this approach, the duration of accelerated tests is substantially shorter with respect to the period of material usage in space. The monoenergetic sources and the replacement of certain types of radiation with other ones are often applied. However, this approach requires the detailed knowledge of physical mechanisms of space environment component impact on objects under study, because the insufficient scientific validity of accelerated tests and indicated replacements may lead to false results.
It shall also be noted that degradation rate may not be linearly related with the acceleration ratio.Models of the space environment are used for solving all the totality of tasks of studying the space environment impact on spacecraft with experimental and theoretical methods. The important request is the development of universal models with the full set of data and functionality for solving all the tasks. For applied problems, it is very promising to create computerized expert systems including complex models of the space environment along with databases on various effects of the spacecraft/environment interaction. Requests to these expert systems shall be realized in technical terms, such as orbit parameters, duration of spacecraft flight, etC. Higher-level expert systems may obtain online data on the current state of the near-Earth space using communication channels with Earth’s satellites (e.g. velocity of the solar wind, interplanetary magnetic field, charged particles fluxes,etc.) and ground-based observation centres (e.g. geomagnetic indices, solar electromagnetic radiation,neutron monitor data, and so on). In this case, expert systems can operate in real time, and this will enable to predict the possible adverse effects of space environment components on spacecraft and to develop recommendations on the spacecraft operation to prevent these unfavourable effects. ISO 17851 pdf free.