¶ Introduction
¶ Purpose, Objective and Scope
This document aims to specify and detail the reliability tests to be performed on the pyrocutter devices under flight-representative conditions.
This document is intended for the test, integration, safety teams, as well as system managers. It allows them to:
Understand the objectives of the pyrocutter reliability tests.
Follow the test procedures precisely.
Verify compliance with system requirements.
The documented tests concern the pyrocutter assembly – clamp screw fixation of the separation system. They cover the following environmental conditions: pressure, humidity, temperature, pyrocutter-to-screw distance, and assembly orientation. The document does not include electrical triggering tests or destructive tests post-final integration.
The test plan aims to evaluate the reliability of pyrocutter-type devices used for mechanical separation of two rocket structural elements by controlled screw rupture. These tests simulate environmental (temperature, humidity, pressure) and mechanical (orientation, distance) extremes representative of a real flight between 9 km and 30 km altitude.
¶ Test Documentation
¶ TSP
-
Test specification section explains:
- What part/assembly is being tested during each test.
- What characteristic is being tested.
- Brief description as to how the test is goind to be conducted.
- Explains the Pass/Fail criteria for each step.
- Explains when the test is due to happen and who will be involved in the test.
-
Test procedure serves as a detailed plan for each individual test, it contains (among other things):
- A list of tools and instrument needed for the test.
- A description of the test location and condition.
- A step by step procedure of what needs to be done before, during and after the test.
¶ TR
- The test report contains:
- The "as run procedure", meaning the procedure as planned ~1 week before the test with all of the comments and modiciations which were done the day of the test.
- The results of the test and all of the test data (or at least a link to the test data).
- If applicable, the analysis of the test data.
- The conclusion.
¶ Definitions and Abbreviations
- DOE : Design of Experiments
- ABV : Abbreviations
¶ Requirements to be verified
- 2024_C_SE_ST_REQ_01
The Separation Mechanism shall allow the LV to separate and deploy a drogue parachute or a reefed parachute at apogee.
- 2024_C_SE_ST_REQ_02
The Separation Mechanism shall not interfere in any way with the deployment of the RE systems.
- 2024_C_SE_ST_REQ_03
The Separation Mechanism shall result in a free internal diameter larger than [200]mm.
- 2024_C_SE_ST_REQ_04
The Separation Mechanism shall deploy in less than [3]s.
- 2024_C_SE_ST_REQ_05
The assembly of the Separation Mechanism shall take less than [15]min.
- 2024_C_SE_ST_REQ_06
After it has been used, it shall cost less than [20]CHF to repair the Separation Mechanism.
- 2024_C_SE_ST_REQ_07
The Separation Mechanism shall withstand a bending moment of [3000]Nm around an axis perpendicular to the main LV axis.
- 2024_C_SE_ST_REQ_38
The FH I LV shall resist compression induced by a compression force of [10000]N instead of [15000]N.
¶ Test Specification
¶ Open issue, Assumption and Constraint
Constraints: Limited number of pyrocutter devices available. Each test is destructive.
Method: Design of Experiments (DoE) method is used to reduce the number of tests to 10 representative configurations covering 5 critical factors.
A 4-factor fractional factorial plan (temperature, humidity, pressure, distance to screw) was generated to analyze cross-factor interactions with a reduced number of tests. Two variants considered:
- DOE Level 3: 10 tests
- DOE Level 4: 18 tests
The choice depends on available time and operational pyrocutter availability.
| Factor | Unity | Minimum Value (ECAL-) | Maximum Value (ECAL+) | Comments |
|---|---|---|---|---|
| Temperature | °C | –70 °C | +80 °C | Extreme conditions corresponding to mission spectrum |
| Relative Humidity | % RH | < 20 % | > 80 % | Simulates dry vs saturated atmosphere |
| Pressure | hPa | ~50 hPa (partial vaccum) | 1013.25 hPa (atmos. pressure) | Near-space vacuum vs Earth conditions |
| Orientation of the pyrocutter | Binary | Up | Down |
¶ Test Description
A test session is conducted to evaluate the reliability of screw rupture using the pyrocutter under extreme environmental conditions simulating flight at 9km altitude.
The objective is to understand the cross-influence of multiple environmental factors (temperature, humidity, pressure, orientation, screw-to-charge distance) on the pyrocutter’s ability to sever the fixation screw.
For this purpose, a Design of Experiments (DoE) approach was chosen, in particular a fractional factorial plan that significantly reduces the number of tests required while maintaining robust statistical coverage.
The full plan (2⁶ = 64 configurations) has been reduced to 10 or 18 tests depending on the method chosen:
- Level 3 method → 10 runs
- Level 4 method → 18 runs
The choice between these two methods will depend on: pyrocutter availability, time constraints, and the desired balance between cost, time, and model accuracy.
Type of test: Environmental tests
Parameters tested: Temperature / Pressure / Humidity / Pyrocutter orientation / Screw-to-charge distance
Procedure: The pyrocutter is mounted on a support simulating the actual structural configuration. It is triggered under instrumented observation.
Data is recorded for each test run.
Notation:
| Run | Temp (X1) | Humidité (X2) | Pression (X3) | Distance vis (X4) |
|---|---|---|---|---|
| 1 | – | – | – | – |
| 2 | – | – | + | + |
| 3 | – | + | – | + |
| 4 | – | + | + | – |
| 5 | + | – | – | + |
| 6 | + | – | + | – |
| 7 | + | + | – | – |
| 8 | + | + | + | + |
(–) = minimum value
(+) = maximum value
This plan is designed to maximize interaction effects between factors, allowing significant trends in the response (screw broken or intact) to be quickly identified.
Analysis and Modeling:
Once the tests are performed, the results will be classified in a binary manner:
- Yes: screw broken
- No: screw intact
These data will then be used to establish a linear statistical model with interactions, which will be developed either in Python (logistic regression or mixed models) or using JMP software.
- Inverted Pyrocutter Test
- Humide Environment Test
- Cold Temperature Test
- Vacuum Chamber Test
The overall objective of these tests is to evaluate the pyrocutter’s ability to sever a fixation screw under various critical configurations, simulating extreme or specific environmental conditions encountered during a space flight.
The specific objectives of each test are:
| Test n° | Name of test | Objectives |
|---|---|---|
| 1 | Inverted pyrocutter test | Check the effectiveness of the device in an inverted orientation (influence of gravity, orientation, and jet positioning). |
| 2 | Test under humide environment | Evaluate the mechanism’s behavior at very low humidty environment or very high. |
| 3 | Cold Test | |
| 4 | Vaccum test | Assess performance under low pressure (simulated space vacuum) |
Each test is executed following a defined experimental protocol, based on a multifactorial factorial design (Multifactor Design) to maximize the statistical relevance of the results.
¶ Controlled electrical triggering of the pyrocutter
Measurement of pressure, temperature, humidity, and position via integrated sensors
Synchronized data acquisition (trigger time, sensor signals)
¶ Test Requirements
Here is a completed version of the Test Requirements section for your document:
-
All tests must be conducted under safety conditions compliant with internal pyrotechnic protocols.
-
Each test configuration must be validated by the responsible engineer before execution.
-
Measurement equipment (cameras, sensors, multimeters) must be calibrated prior to each test series.
-
Data (images, electrical signals, ambient conditions) must be recorded and backed up in two locations (local + internal cloud).
-
Each test must be documented immediately after execution: results, observations, anomalies.
-
Experimental conditions (temperature, pressure, humidity, orientation, screw distance) must be measured and confirmed within defined tolerances before triggering.
-
A minimum delay of 30 minutes is required between tests to allow reconditioning and safety checks.
-
Destructive tests can only be conducted with a validated stock of pyrotechnic charges available.
¶ Test Sequence
The validity of the results can potentially be influenced by residual thermal effects and accumulated mechanical stresses on the test bench. Therefore, the sequence of test configurations has been optimized using the DoE (Design of Experiments) method.
Tests will be conducted according to the run order defined in the factorial plan, in order to avoid any correlation between test conditions and equipment wear or heating.
Special attention will be given to low-temperature and vacuum tests, which require longer stabilization times. These tests will be grouped and scheduled to minimize thermal cycling of the climate chamber.
¶ Pass/Fail Criteria
| Criterion | Type | Condition / Description |
|---|---|---|
| Correct activation of the pyrocutter | Mandatory | The pyrocutter must trigger without failure |
| Effective separation of the component (screw broken) | Mandatory | The screw must be completely severed |
| No unexpected degradation of the structure | Quality | No collateral damage to the structure or neighboring components |
| Screw break within expected time and conditions | Mandatory | The break must occur within the defined time and environmental conditions |
| Compliance with pyrocutter voltage and current limits | Mandatory | The electrical triggering must meet the specifications |
| Conformity of measured parameters | Mandatory | Pressure, temperature, humidity, distance, and orientation must comply with the experimental plan |
| Completeness and usability of measured data | Mandatory | Video, sensors, and voltmeter data must be usable |
| Absence of major technical anomalies | Mandatory | No sensor failures, electrical issues, or other disturbances during testing |
¶ Root Cause Analysis (RCA) in Case of Failure
In case of failure (screw not broken or rupture outside expected conditions), an RCA will be conducted to identify the possible root cause(s):
Material: Screw defect (manufacturing, wear), improper assembly.
Parametric: Experimental conditions not compliant or poorly controlled.
Procedural: Error in the test sequence or method.
Instrumental: Malfunction of measurement equipment.
External factors: Unforeseen environmental disturbances.
¶ Test Organization
Team and Participants
Team:
-
Emma: Responsible for equipment checklist and data collection / Documentation and test report manager.
-
Jules: Responsible for safety and operational compliance / Test setup and installation on site.
Subsystems Present:
- Pyrocutters (main component under test)
- Prototype structure simulating actual fixture
- Sensors (pressure, temperature, humidity)
- Multimeter for measuring electrical triggering
- Climate chamber and vacuum tent for environmental control
External Partners:
No external participants are planned at this stage. However, a supplier may be involved for delivery of pyrocutters or specific components, which could impact the schedule.
Planning and Constraints
- Planned Test Period:
Tests scheduled between June and July 2025, depending on pyrocutters availability.
- Main Constraints:
Limited availability of pyrotechnic charges requires a strict schedule to avoid exceeding the allowed number of tests.
Possible delay due to prototype pyrocutters delivery, which could postpone test start.
Environmental conditions require coordination with the laboratory equipped with climate and vacuum chambers.
Final choice between experimental Level 3 method (10 tests) and Level 4 method (18 tests) will depend on available time and equipment availability.
¶ Test Procedure
¶ Item Under Test
| Sub-System | Part Name/ID | Type of Part | Version ID |
|---|---|---|---|
| Structure | 115201_Pyrocutter_Body | Test Flight hardware | / |
| Structure | 115201_Pyrocutter_Chamber | Test Flight hardware | / |
¶ Test Set-up
Tests will be conducted in a climatic chamber equipped with a vacuum bag to simulate extreme conditions (temperature, pressure, humidity). The pyrocutter will be mounted on the prototype structure, with the screw to be cut positioned according to the required configuration (distance, orientation). Sensors will be placed to continuously measure environmental conditions and electrical voltage/current during triggering.
¶ Test Equipment Checklist
| Equipment | Bag | Responsible | |
|---|---|---|---|
| ☐ | Camera | ||
| ☐ | Temperature/Pressure Sensors | ||
| ☐ | Trigger Multimeter | ||
| ☐ | Power Supply | ||
| ☐ | Installation |
¶ Test Location and Conditions
Tests are conducted in the climatic chamber built by ourself using welding and a lathe. The Conditions vary according to the experimental plan: temperature from -70°C to +80°C, atmospheric pressure from 1013 hPa to ~50 hPa (vacuum bag), humidity from <20% to >80%. Tests will be scheduled based on the availability of the chamber and equipment.
¶ Participants
¶ Test Safety
¶ Main Risks
| Safety Concern | Probability | Impact | Severity | Mitigation | Post-Mitigation Probability | Post-Mitigation Impact | Post-Mitigation Severity |
|---|---|---|---|---|---|---|---|
| Cartridge fails to fire | Medium | High | High | Double check connections and voltage | Low | Low | Low |
| Partial screw break | Low | Medium | Moderate | Camera + post-test inspection | Low | Low | Low |
¶ Main Hazards
| Safety Concern | Probability | Impact | Severity | Mitigation | Post-Mitigation Probability | Post-Mitigation Impact | Post-Mitigation Severity |
|---|---|---|---|---|---|---|---|
| Pyrotechnic trigger | Medium | High | Very High | Secure area, mandatory PPE | Low | Medium | Moderate |
¶ Tasks and Step-by-Step Procedure
¶ Before Test
¶ Tasks
| ✔ ? | Step | Tool |
|---|---|---|
| ☐ | Check power supply voltage + wiring continuity | Multimeter |
| ☐ | Mount pyrocutter on the test bench | Wrenches/Bolts |
| ☐ | Set chamber (T°, P, H%) according to test plan | Test console |
| ☐ | Verify screw position and orientation | Goniometer |
| ☐ | Install sensors and camera | - |
¶ Step-by-step procedure
| ✔ ? | Step | Tool |
|---|---|---|
| ☐ | Arm the pyrotechnic activation system | Trigger console |
| ☐ | Start the camera | Camera |
| ☐ | Confirm environmental parameters (T, P, H) | Test console |
| ☐ | Check electrical supply | Multimeter |
¶ During Test
¶ Tasks
| ✔ ? | Step | Tool |
|---|---|---|
| ☐ | Trigger the pyrocutter | Switch |
| ☐ | Turn off power | Console |
| ☐ | Extract the screw | Pliers |
| ☐ | Inspect structural damage | Visual |
| ☐ | Save measurement files | PC |
| ☐ | Clean chamber | Team |
¶ Step-by-step procedure
| ✔ ? | Step | Tool |
|---|---|---|
| ☐ | Trigger the pyrocutter | Switch |
| ☐ | Observe and record screw breakage | Camera + sensors |
| ☐ | Turn off power after test | Console |
| ☐ | Extract and inspect the screw | Pliers + inspection |
| ☐ | Save all recorded data | PC |
¶ After Test
¶ Tasks
| ✔ ? | Step | Tool |
|---|---|---|
| ☐ | Analyze video footage | Software |
| ☐ | Record observations | Report |
| ☐ | Store and secure equipment | Boxes |
| ☐ | Clean and prepare for next test | Team |
¶ Step-by-step procedure
| ✔ ? | Step | Tool |
|---|---|---|
| ☐ | Review video and extract data | Video software |
| ☐ | Write test report | PC |
| ☐ | Store equipment | Boxes |
| ☐ | Prepare setup for next test | Team |