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MBSE Case Studies

Aerospace Industry: Modeling & Simulation of CubeSat Mission

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MBSE Solution for NASA and INCOSE

Challenge

Conventional Systems Engineering approaches often neglect subsystem interaction, fail to capture the dynamic aspects of mission analysis, and are built as one-off solutions.

These challenges are particularly problematic for CubeSats where components are usually physically integrated, the entire spacecraft is extremely constrained, and orbits are often unknown during mission design. MBSE addresses these challenges through the formal application of modeling to Systems Engineering processes. Successful application of MBSE requires integrating design, analysis, and simulation into a common framework.

About CubeSat

  • CubeSats are a class of research spacecraft called nano satellites
  • The cube-shaped satellites are approximately:
    • 10 cm long,
    • have a volume of about 946 cm3,
    • weigh about 1.4 kg
  • CubeSats are flown as auxiliary payloads on previously planned missions

Solution

The International Council on Systems Engineering (INCOSE) Space Systems Working Group (SSWG) established the Space Systems MBSE Challenge team in 2007. The SSWG Challenge team has been investigating the applicability of MBSE for designing CubeSats since 2011. It is the fourth phase of development of a CubeSat model.

MBSE is used in CubeSat to create a system model that helps integrate other discipline specific engineering models and simulations. The system level model provides consistent source of system requirements, design, analysis, and verification. SysML is used to model all aspects of a system.

MBSE applicability in four CubeSat phases:

The first phase of SSWG CubeSat project created a CubeSat reference model that was applied to the Radio Aurora Explorer (RAX), a three unit CubeSat developed by SRI International and the Michigan Exploration Laboratory at the University of Michigan.

The second phase focused on expanding the RAX CubeSat model to include modeling behaviors and interfacing with several Commercial Off the Shelf (COTS) simulation tools.

The third phase was comprised of two activities. The first was the development of a CubeSat enterprise model to capture cost and product lifecycle aspects for the mission spacecraft and problem domain. The second activity incorporated additional design and operational characteristics into the RAX model.

The modeling effort starts anew in this fourth phase. The objective is a generic CubeSat reference model to provide a model that other projects can use as a starting point for their mission specific CubeSat model.

Challenge

  • How do satellite states evolve throughout mission?
  • Does the vehicle design/operations meet all mission requirements?
  • How do changes in spacecraft mission parameters impact performance and requirements satisfaction?

Results

  • Generic CubeSat reference model which other projects can use as a starting point for their mission specific CubeSat model.
  • Coupled analytic models with simulation capabilities.
  • Mission and Design Trade-Offs.
  • Achieved requirements verification for full end-to-end missions.

Solution

  • Model-Based Systems Engineering (MBSE) is a key practice to advance systems engineering that can benefit CubeSat missions.
  • SysML as a graphical modeling language is used to model all aspects of a system.
  • CubeSat model including behavior part and interfacing with several simulation tools.
  • MBSE Tools:
    • Modeling: MagicDraw + SysML,
    • Simulation: Cameo Simulation Toolkit,
    • Integration: Phoenix Model Center,
    • Analytical Models: STK, and Matlab.

Integrated models and tools are critical to design and plan for these missions!