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NASA Bulletin Warns Hydrazine Freeze–Thaw Cycles Threaten Spacecraft Systems
Key Takeaways
- Hydrazine freezes near 1.6°C, and the resulting phase transition is a documented risk to flight hardware in propulsion and auxiliary systems.
- NASA cites Space Shuttle APU lines that could burst from freeze-induced contraction and thaw-induced over-expansion, with flight rules limiting systems to two freeze–thaw cycles before being considered degraded or failed.
- Voyager thermal analyses showed that temperatures approaching 0.1–1.6°C risked line freezing, blockage, and thruster malfunction, requiring detailed modeling rather than simple temperature reads.
- The bulletin identifies six risk categories: structural damage from superpacking, valve and seal compromise, slush-driven blockage, hazardous leaks, lost reliability, and uncertain thermal margins.
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DT Editorial Team··via nasa.gov