Gate 1: a testable specification
Write the mission need, selected architecture, system boundary and comparison metric. Identify the momentum partner and power source. Produce a parameter table with measured, sourced, assumed and unknown entries. The exit requirement is an independently understandable prediction with an uncertainty target. A rendering or a broad statement about geometry does not close this gate.
Gate 2: a qualified measurement
Design and commission the measurement chain before testing a novel improvement. Use known loads or impulse references appropriate to the range, characterize drift, and document the influence of cables, gas lines and chamber conditions. The exit requirement is an archived calibration and control dataset that supports the intended resolution. Instrument sensitivity claims must be supported by operation, not only a sensor datasheet.
Gate 3: a reproducible comparison
Freeze the analysis and run the reference and candidate under matched conditions. The proposed screening goal is a meaningful improvement with an uncertainty interval that excludes no improvement, repeated across operating sessions. Report power, flow, geometry and all exclusions. If the outcome is null, publish the tested range and use it to narrow the design space rather than simply renaming the claim.
Gate 4: engineering endurance
A short measurement does not establish lifetime. Test starts, stops, thermal cycles, contamination, erosion and control behavior relevant to the intended mission. Compare the complete subsystem mass and power. The exit requirement is a reviewed performance envelope with unresolved risks explicitly assigned. A commercially available component’s heritage does not automatically transfer to a new assembly or environment.
Gate 5: independent reproduction and mission review
Arrange reproduction with separately assembled hardware and independently processed data. Only after that evidence should a flight demonstration be scoped around a specific vehicle and environment. NASA readiness guidance distinguishes component evidence from relevant-environment and operational demonstrations. Our roadmap uses that distinction but assigns no unsupported readiness level to Metric Flight. Procurement, staffing and a schedule follow a reviewed scope; no station launch date depends on a speculative propulsion result.
What a stage review decides
A stage review should record continue, revise, pause or stop, with the evidence that supports the decision. It should also state which uncertainty the next expenditure will reduce. Passing one gate does not authorize every later purchase. A deliberately small next experiment is appropriate when it can resolve the critical question more directly than a large integrated prototype.
PRIMARY SOURCES / FOLLOW THE EVIDENCE
Research behind the study
- NASA: Appendix G, Technology Assessment and Insertion ↗Readiness requires evidence about a specific technology and its demonstrated environment.Institutional or primary research link · bibliographic details pending verificationConsult the linked record; no full-text access claim.
- Polk et al.: Recommended Practice for Thrust Measurement in Electric Propulsion Testing ↗Pendulum-stand design, calibration, error sources and uncertainty analysis; DOI 10.2514/1.B35564.Institutional or primary research link · bibliographic details pending verificationConsult the linked record; no full-text access claim.
- NASA: Electric Propulsion Qualification Guidelines and Best Practices for Small Spacecraft Missions ↗Qualification and integration considerations for small-spacecraft electric propulsion.Institutional or primary research link · bibliographic details pending verificationConsult the linked record; no full-text access claim.
References checked 24 October 2026. External research is not a Metric Flight result or an institutional endorsement. Source abstracts, records and accessible full text support this synthesis; individual links may require publisher access.