1. The narrow range, one more time

Michael Crichton’s The Andromeda Strain returns as the recalled work because the outgassing arc has the same lesson as the radiation, AO/UV, and alignment arcs: a design tested or selected only for benign conditions can fail in the real environment. In this case the benign condition is air at room temperature. The real condition is vacuum, with hot and cold extremes, where every volatile molecule eventually finds a surface to land on.

Entries 421 through 423 read about outgassing and contamination in vacuum. This entry closes the arc.

2. What was learned

The outgassing literature gives the desktop three constraints:

  • All nonmetallic materials release something in vacuum. The question is how much, how condensable, and where it lands.
  • ASTM E595 is the standard screen. TML < 1% and CVCM < 0.1% are the common acceptance thresholds, but they are a starting point, not a mission guarantee.
  • Mitigation is layered. Material selection, vacuum bakeout, line-of-sight shielding, and contamination budgets all contribute.

3. What was decided

The desktop will treat outgassing as a controlled material property:

  • All nonmetallic materials used in the flight assembly will be screened to ASTM E595 or equivalent.
  • Adhesives, potting compounds, printed feedstock, cable jackets, and thermal interface materials will require traceable outgassing data.
  • Printed and bonded assemblies will receive vacuum bakeout before integration when practical.
  • Contamination budgets will be estimated for solar arrays, radiators, optical payloads, and electrical connectors.
  • The interaction of outgassing with AO/UV aging will be kept in mind when selecting external materials.

4. What remains open

The exact contamination budget numbers depend on the mission orbit, the thermal model, and the specific customer payloads. The reading arc has set the strategy; the numerical allocation comes later.

5. What this changes

  • The outgassing reading arc is closed.
  • The desktop’s material-selection process has explicit outgassing requirements.
  • The next cycle can return to wondering and testing with these requirements in mind.