11.2 General Design Process

General Design Process

Remember the V&V model? You’ll never escape this diagram because this diagram shows all the phases of project definition to implementation and the connection between phases upstream and downstream.

System Implementation (buy, build, re-use)

We don’t talk much about the fabrication subphase of Phase C: Final Design and Fabrication because fabrication is a relatively straightforward process. Fabrication includes the verbs: buy, build, and re-use. Buying refers to procuring standalone components that engineers/scientists specified in the final design. Building refers to the creation of structures, avionics, or software from more basic components, like stock metal. Re-using refers to the repurposing of heritage components that are already in possession, like the Perseverance mission in re-using Curiosity’s leftover components to minimize cost.

^{An overview of NASA’s PerseveranceRover, the rocket that will take it there, the timeline, the landing sequence, and then compare it to its older sibling, Curiosity to see what’s changed and what has stayed the same including its instruments and mission. Video by Everyday Astronaut.} 

Artemis Kit Specific

Integration, Verification & Validation

Within NASA’s Project Phase D: System Assembly, Integration, and Test, Launch is sequential integration and testing from components to subsystems to the whole system. The NASA Systems Engineering Handbook describes the activity as “assembl[ing] and integrat[ing] the system (hardware, software, and humans), meanwhile developing confidence that it will be able to meet the system requirements. Perform system end product implementation, assembly, integration, and test, and transition to using” [NASA SE Handbook].

 ^{Time-lapse footage of engineers assembling the two halves of the James Webb Space Telescope together at Northrop Grumman in Redondo Beach, CA from GoPro camera 3. Video courtesy of NASA.} 

Further, typical activities and products include:

• Update documents developed and baselined in previous phases
• Monitor project progress against plans
• Identify and update risks
• Integrate/assemble components according to the integration plans
• Perform verification and validation on assemblies according to the V&V Plan and procedures
  • Perform system qualification verifications, including environmental verifications
  • Perform system acceptance verifications and validation(s) (e.g., end-to-end tests encompassing all elements; i.e., space element, ground system, data processing system)
  • Assess and approve verification and validation results
  • Resolve verification and validation discrepancies
  • Archive documentation for verifications and validations performed
  • Baseline verification and validation report

Integration and testing are not isolated processes. Integration happens bit by bit and testing happens every time a new component or subsystem is integrated, such that the system is verified at every configuration. The complexity of a system, like a spacecraft, can become overwhelming. Imagine yourself with all the components of a spacecraft. You decide to put them all together without seeing if the payload itself can measure anything. You power on the spacecraft and command the payload to take a measurement but it cannot. In this fully integrated configuration, your inability to receive a payload measurement could be due to a multitude of factors: the software has a bug, the onboard computer isn’t wired to the payload correctly, the power distribution system did not power on the payload correctly, or the payload itself is not functional. For this reason, to mitigate any kind of ambiguity of what components worked or at what stage of the configuration the spacecraft is still functional, we verify, validate, and document as we integrate. If your requirements are comprehensive, your verification methods from your components to your system should lay out a rough roadmap for how you will verify as you go.

^{To test the James Webb Space Telescope’s readiness for its journey in space, technicians successfully commanded it to deploy and extend a critical part of the observatory known as the Deployable Tower Assembly. In this test, the deployable tower was commanded to extend 48 inches (1.2 meters) over the course of several hours to ensure that the observatory will be able to complete this process once in space. Producer, Videographer, Editor – Michael McClare (KBRwyle).Video courtesy of NASA Goddard Space Flight Center.}

Testing processes include vibration, shock, acoustics (VS&A), thermal, and mechanisms. These tests intend to exercise the spacecraft in an aggressive, relevant environment that the spacecraft would see in space but hasn’t seen yet on the ground. Vibration, shock, and acoustics testing stem from launch conditions. Thermal testing in thermal vacuum chambers aims to imitate space’s vacuum and consequential radiation-dominant heat transfer. Testing mechanisms with gravity off-loading mechanisms and frictionless testbeds produce spacecraft behavior closer to the ultimate microgravity space environment. To conduct these tests, you will need access to specialized testbeds, like the ones that the Malaysian Space Agency has created: