1. When the system has to fail well
Neal Stephenson’s Snow Crash returns as the recalled work because its digital systems fail in ways that are often more interesting than their normal operation. The desktop’s degraded-mode test is about failing well: when a segment is cut off, the remaining systems must not collapse, and the separated segment must not die.
This entry defines success and failure for the platform segment split and degraded-mode test.
2. Minimum success
The test passes if:
- The platform and the separated segment both establish stable independent operation after a commanded or fault-triggered split.
- Critical functions continue on both sides without data loss or corruption.
- The segment sheds non-critical loads in a controlled way when resources are reduced.
- The main platform reconfigures its federation and services without cascading failures.
- Ground-link loss on the segment does not cause unrecoverable state or data loss.
- Both sides return to a stable state after each transient and degraded condition.
This minimum says the desktop can survive becoming two platforms under expected degraded conditions.
3. Full success
A stronger result would add:
- The segment maintains margin after shedding loads, rather than operating at its limit.
- Service recovery is automatic and predictable.
- The segment can communicate with the main platform through a backup path.
- Degraded-mode behavior matches the predictions from the end-to-end mission simulation.
- Test data supports claims of split-ready flight readiness.
This stronger result supports a claim that the platform could survive a real on-orbit split.
4. Failure modes
The test fails if any of the following occur:
- A critical function is lost on either side during a nominal or degraded split.
- The segment experiences a power or thermal emergency that would damage hardware.
- The main platform loses services or data because of the split.
- A service hangs or crashes instead of failing over cleanly.
- The segment cannot recover ground contact or autonomous operation.
- The platform does not return to a stable state after the split or transient.
Each failure mode points to a fix in architecture, software policy, or operations procedure.
5. What this changes
- The segment split and degraded-mode test has clear pass and fail criteria.
- The criteria separate platform survival from segment survival.
- The next entry will close the test arc.