BS ISO 27875 pdf free download

BS ISO 27875-2019 pdf free download.Space systems – Re-entry risk management for unmanned spacecraft and launch vehicle orbital stages.
4.5 Re-entry risk management concept
The scoring schemes for the severity of consequence of re-entry hazards are defined by the national authority. Based on lSQJ.Zb66. risk Is assessed by the risk magnitude expressed as the conthination of its severity and likelihood (see Annex B. and ISO 17666).
The scoring is typically related to the casualty area (see 5.5.1.2) in the case of casualty risk, damage of properties in the case of social risk, or pollution on the ground in the case of environmental risk (for example, see Table B.1. or ISO 17666). Generally, a risk index will he defined as a combination of severity and likelihood, and a risk magnitude will be defined for each risk index.
For assessing re-entry risk:
— In the case of natural re-entry. Ec is calculated as a function of the casualty area, orbital inclination, and population density. Since the re-entry cannot be avoided without control, likelihood Is fixed as the probability of occurrence of 1,0, and the risk index is equivalent to the Ec. Sub-clause 5..,5 describes assessment procedures for casualty risk in the case of natural re-entry. Sub-clause £6 for environmental risk.
— In the case of controlled re-entry, Ecis calculated in the same manner as for the natural re-entry (I.e., is a function of the casualty area, orbital inclination and population density), but the Ec is weighted by reliability of functions and sufficiency of propellants needed for controlling the re-entry. (See Annex.B or 15Q 17666). Sub-clause 24 describes assessment procedures for casualty risk in the case of controlled re-entry.
Proposed actions may be defined for each risk index (See Table 11.3 and 11.4. or lS.OJ166.)
5 Risk assessment for the case of natural re-entry
5.1 General
A safety assessment shall be conducted to evaluate the risks associated with an uncontrolled re-entry and to determine the need for design improvements or a controlled re-entry. The safety assessment should include the following:
a) identification of the safety requirements;
b) identification of a standardized process and resources for analysis;
c) identification of system/mission dependent parameters;
d) estimation of risk; and
e) risk decision and actions.
NOTE Because the general concept for risk assessment is given In ISO 17666. this clause supplements specific requirements related to re-entry using terms (risk scenario, risk magnitude, risk decision and actions, etc.) defined in iSO 17666.
5.2 Identification of safety requirements
5.2.1 IdentificatIon of requirements
Specific re-entry safety requirenwnts imposed contractually, voluntarily, or by national or international authorities shall be identified, and where possible, quantified with threshold parameters.
5.2.2 Risk assessment plan
Re-entry risk assessment actions (analyses, reports, etc.) shall be defined and scheduled, and a compliance matrix that correlates safety requirements against the system design and operation plan, which includes achieved quantitative results, threshold values, consequences of violating thresholds, and the probability that those consequences would be realized, shall be maintained.
The expected output Is the assessment parameters (e.g., risk to people on the ground and its associated mathematical parameters) and their thresholds, or the concept for risk decision and the actions according to the severity of consequences and the likelihood of occurrence.
NOTE I Several national governments and space agencies adopt 0,000 1 persons as an acceptable upper limit for Ec.
NOTE 2 Generally, on-board radioactive substances, toxic substances, and any other hazardous materials are considered when evaluating and limiting the potentially adverse effects of re-entry on the Earth’s environment.
5.3 Identification of standardized process and resources for analysis
A standardized process, to identify the safety requirements established by national or international authorities, shall be Implemented by the entity which conducts the analysis. The standardized process shall designate methods, tools, models, and physical characteristics and properties of materials, as in the examples shown below.
a) Analysis tools, models, and approach, including:
1) algorithms for trajectory, aerodynamic, aerothermodynamic, and thermal analyses for reentry trajectory and thermal analyses;
2) requisite physical characteristics, aerodynamic properties, and thermal properties for trajectory and thermal analyses;
3) Earth model and atmospheric model;
4) any constants or formulae for perturbations on the decaying trajectory;
5) human population distribution model;
6) definition of casualty area (see 5.5.1.2 for a typical definition of casualty area);
7) reduction in mass and size, and deformation due to ablation during re-entry; and
8) definition of the techniques and assumptions used to estimate the Ec (e.g., year of re-entry, population model, casualty area).
b) Analytic conditions, assumptions, or criteria for assessment
Due to the complexity of re-entry physics and material responses, detailed analyses will he necessary to obtain accurate estimates of aerodynamic and thermal phenomena. If there are technical uncertainties or Insufficient resources, then simplified models, analytic conditions, criteria, or assumptions may be applied.
The following conditions may he assumed as given, for example:
1) attitude mode (e.g., tumbling, side-on stable, etc.).BS ISO 27875 pdf download.