User:Hjpospie/System requirements (Spacecraft system)

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[edit] General

Spacecraft systems are normally developed under the responsibility of space agencies as NASA, ESA etc. In the space area standardized terms and processes have been introduced to allow for unambiguous communication between all partners and efficient useage of all documents. For instance the life cycle of space systems is divided in phases

  • Phase A: Feasibilty Study
  • Phase B: Requirements Definition
  • Phase C/D: Design / Manufacturing / Verification
  • Phase E: Operational useage.

At the end of phase B the sytem requirements together with a statement of work are sent out requesting proposals from industry.

The customer technical system requiremts documented in the System Specification stay on mission level

  • System functions and performances
  • Orbit
  • Launch vehicle
  • etc.

wheras the non-technical system requiremts

  • Cost and progress reporting
  • Documentation maintenance
  • etc.

are contained in the statement of work.

The customer (requirements) specification is answered by the contractor by a design-to specification.

For example the requirement "Columbus shall be launched by the Space Shuttle." is detailed in the contractor system specification "Columbus shall be a cylindrical pressurized module with max. length of 6.9 meters and 4.5 meters diameter as agreed in the Shuttle/Columbus ICD."

[edit] System specification structure

A typical industry generated system specification for a spacecraft has the following structure

  • Document change record
  • 1. Scope
    • 1.1 Purpose
    • 1.2 Summary description
    • 1.3 Classification
    • 1.4 Applicability
  • 2. Related documents
    • 2.1 Applicable documents (incl. order of precedence)
    • 2.2 Reference documents
  • 3. Functional /Performance Requirements
  • 4. Support requirements
    • 4.1 Product assurance
    • 4.2 Electro-magnetic compatibility
    • 4.3 Contamination
    • 4.4 etc.
  • 5. Interface requiremts
    • 5.1 System interfaces
      • 5.1.1 Launcher
      • 5.1.2 Ground stations
      • 5.1.3 etc
    • 5.2 Subsytem interfaces
      • 5.2.1 Electrical power
      • 5.2.2 Data
      • 5.2.3 etc.
  • 6. Implementation requirements
    • 6.1 Configuration
    • 6.2 Budget Allocations
      • 6.2.1 Mass
      • 6.2.2 Electrical power
      • 6.2.3 etc
  • 7. Preparation for delivery
  • Attachments (Abbreviation list etc.)

Each requirement paragraph consists of the requirement to be fulfilled by the product to be delivered and the verification requirement (Review of design, analysis, test, inspection).

[edit] Specification tree

The spacecraft system specification defines also the subsystems of the spacecraft e.g.

  • Structure
  • Data management subsystem incl. software
  • Electrical Power
  • etc.

For each subsystem a subsystem specification is prepaired by the Prime Contractor with the same specification structure shown above inluding references to the parent paragraph in the system specification. In the same way the subsystem contractor prepares an assembly or unit specification. All these specifications are listed in a so-called specification tree showing all specifications and their linkage as well as the issue / date of each specification.

[edit] Links

Verification of system requirements