1. The lab notebook
Ignition! is full of chemists writing down what exploded and why. A propulsion test matrix is the same impulse, only slower and with more paperwork. The Resident wants a matrix that covers the propulsion subsystem from the tank to the nozzle and from the command to the telemetry.
2. Component tests
| Test | Purpose | Key measurements |
|---|---|---|
| Tank pressure cycle | Verify structural integrity and seal | Pressure hold, leak rate, deformation |
| Valve actuation | Confirm valves open, close, and seal | Response time, current draw, leak rate |
| Feed line proof | Confirm plumbing holds pressure | Pressure hold, vibration response |
| Thruster ignition | Confirm startup sequence is repeatable | Ignition delay, voltage/current, thrust |
| Thrust stand mapping | Characterize impulse and stability | Thrust vs time, thrust vs power, noise |
3. Environmental tests
| Test | Purpose | Key measurements |
|---|---|---|
| Thermal vacuum soak | Verify operation at hot/cold limits | Startup at extremes, valve sealing, leak rate |
| Vibration and shock | Survive launch and deployment | No cracks, no leaks, no shifted alignments |
| EMI/EMC | Avoid interfering with other systems | Emissions during firing, susceptibility of thruster electronics |
| Plume impingement | Protect the platform and neighbors | Deposition, heating, force on nearby surfaces |
4. Integrated and operational tests
| Test | Purpose | Key measurements |
|---|---|---|
| Closed-loop firing | Exercise the full command chain | Command latency, state transitions, telemetry |
| Concurrent operations | Confirm other subsystems survive the burn | Power bus stability, compute continuity, comms link |
| Fault injection | Verify safe responses | Stuck valve, pressure anomaly, loss of telemetry, abort |
| Autonomous sequence | Validate state machine and timeouts | Enable, arm, fire, confirm, safe, log |
| Ground override | Confirm human can always stop a burn | Abort at each stage, recovery behavior |
5. Test philosophy
Each test should have a pass/fail criterion written before the test is run. Marginal results are not passes; they are redesign triggers. The matrix is not a checklist to complete; it is a set of questions that must be answered before flight.
6. The hardest tests
The integrated tests are harder than the component tests because they require the platform, or a high-fidelity simulator, to be present. The fault-injection tests are harder than the nominal tests because they require imagining what could go wrong and then proving the system responds. Both are where the real confidence is built.