1. When the burn is the failure mode

James S. A. Corey’s The Expanse returns as the recalled work because the Rocinante’s crew treats every burn as a commitment: once thrust is applied, the ship is on a new trajectory, and a wrong burn costs remass, time, and sometimes lives. A LEO desktop is smaller, but the same rule applies. A stuck valve, a cracked thruster, or a miscomputed delta-v can place the platform in the wrong orbit, point it dangerously, or exhaust the propellant budget.

This entry explains why the propulsion fault recovery and maneuver verification test matters.

2. Why propulsion needs its own fault injection

The propulsion reading arc established that the desktop should choose between electric, chemical, and cold-gas thrusters according to mission needs. The autonomous orbit maintenance arc decided that the platform should plan and execute burns within ground-approved policy. Both are design claims. The propulsion fault recovery and maneuver verification test is the experiment that validates them.

Without propulsion fault testing, the desktop might discover these problems only after launch:

  • A thruster fails to ignite, and the platform does not detect the missed burn in time to re-plan.
  • A valve sticks open, venting propellant until the tank is empty.
  • A pressure regulator drifts, causing thrust to be lower than commanded, and the maneuver underperforms.
  • A burn is aborted by software but the thruster keeps firing because the cutoff command did not reach the driver.
  • The platform executes a maneuver with the wrong attitude, applying delta-v in a direction that worsens the orbit.

3. The failures that only appear when thrust is commanded

Propulsion fault injection exposes behaviors that do not appear in nominal testing:

  • A thruster’s actual impulse is half the predicted value; the orbit correction falls short.
  • A multi-thruster maneuver continues after one thruster fails, creating an unwanted torque.
  • A planned collision avoidance burn is rejected at the last second, and the platform must choose between a late burn and no burn.
  • Propellant slosh after a burn changes the center of mass and upsets attitude control.
  • A fault during a long electric-thrust arc leaves the platform on an unintended spiral trajectory.
  • Ground cannot diagnose the problem because propulsion telemetry is sparse or delayed.

4. What this test must cover

The propulsion fault recovery and maneuver verification test must exercise:

  • Thruster faults: failed ignition, degraded thrust, erratic thrust, stuck-on, stuck-off.
  • Valve and pressure faults: stuck valve, leaking seal, regulator drift, tank pressure anomaly.
  • Maneuver verification: pre-burn attitude check, delta-v prediction, abort before execution, commit criteria.
  • Burn monitoring: real-time thrust estimation, early termination, fallback re-planning.
  • Propellant isolation: isolating a leaking branch, protecting deorbit reserves, cross-feed reconfiguration.
  • Safe-mode interaction: propulsion faults that trigger safe mode, and safe mode that inhibits burns.

The goal is to prove that the platform can detect a propulsion fault, stop or reconfigure the burn, and return to a safe state without ground intervention for faults within the designed set.

5. What this changes

  • Propulsion fault recovery and maneuver verification testing is identified as the next qualification step for the desktop.
  • The test must verify detection, safe termination, reconfiguration, and recovery, not just nominal maneuver execution.
  • The next entry will define the test matrix.