scope:

This is the first level standard of a three level standard set defining a human spaceflight (HSF) spacecraft ontology from architectural and system engineering viewpoints. It provides guidance for systems and architecture design emphasizing human-system integration (HSI) requirements and constraints. While adopting a holistic approach, this complex domain is stratified using a three-dimensional roadmap (Figure 5) that guides the user to a high-level, fundamental and context-specific design requirement based on the HSF program, mission and spacecraft goals.

Examples:

- The International Space Station is a spacecraft in Low Earth Orbit (LEO).

- NASA's Space Transportation System (STS) is an example of another HSF program yielding a specific type of reusable spacecraft, the Space Shuttle, enabling transport between the ground and LEO.

A human spaceflight mission involves a variety of activities from concept development to manufacturing and operations to full mission realization. The architecture of a mission consists of various elements such as the mission concept; ground segment; command, control and communications; orbit and trajectory design; launch system; payload; and spacecraft systems. While this standard is focused on the spacecraft element, other elements will need to be considered.

This first level standard describes a Human Spaceflight ontology that captures the spacecraft architecture via three high-level areas: development activities or processes related to the spacecraft lifecycle (e.g., concept and engineering design activities, simulations, testing, etc.), a specific application or function of the spacecraft (e.g., space transportation, tourism, exploration, resource mining, construction, etc.) and destination or operating environment of the spacecraft (e.g., suborbital, orbital, cis-lunar, lunar surface, etc.). It provides organizational guidance for effective spacecraft architecture development. The first and second levels focus on the more specific design requirements definition, while the third level identifies specific values for the engineering of subsystems and the HSI process.

The three levels composing this three level standard set are organized in the following manner:

1st level - Ontology of HSF spacecraft domain. This serves to structure the HSF domain by defining categories of spacecraft, fundamental environmental requirements within a specific phase of the spacecraft lifecycle, and their relationship, and provides a guide to a systematic design requirements definition (see Figure 6).

2nd level - Spacecraft types and their properties related to HSI. This includes human-imposed vehicle requirements, and environmental constraints of vehicles vis-à-vis mission and duration, e.g., suborbital point A to point A vehicle (returning to the departure spaceport), long duration habitat.

3rd level - Human requirements and subsystems properties related to HSI (e.g., atmosphere requirements, radiation shielding).

The 2nd level standard develops spacecraft types drawn from the 1st level document (S-153-2021). It describes the specific requirements for each category of spacecraft and its components related to the spacecraft operational environment in form of typical scenarios and typical requirements on the vehicle. The 2nd level standard also references existing standards by third parties. The scope of the 2nd level standard includes:

- Spacecraft function

- Duration of spaceflight

- Details of the operational environment, destination

- Spacecraft occupancy, etc.

The 3rd level further develops the 2nd level by focusing on the technical details of individual components or parameters of the spacecraft and its operator, and other occupants. It describes specific tasks and their allocation in nominal, off-nominal and emergency scenarios for all occupants and other artificial agents. All necessary subsystems are defined in a higher level of detail according to 2nd level requirements and HSI considerations, such as physical and cognitive ergonomics, social interaction and medical requirements. Examples include:

- Spacecraft autonomy (self-sufficiency)

- Spacecraft automation (levels of control)

- Radiation detection and protection

- Atmosphere requirements, generation and recycling

- Human body consumables and waste (refer to existing ISO 16157-2018 "Space systems - Human-life activity support systems and equipment integration in space flight - Techno-medical requirements for space vehicle human habitation environments")

- G-load (acceleration) dependent restraint principles and requirements