Rocket Sled Track Mechanical Parameter Testing
March 2024
Test Objectives
To evaluate the mechanical performance of a rocket sled and its track system through:
Modal testing (natural frequencies/damping ratios)
Impact shock characterization during sled-track collisions
Thermal-strain analysis under high-speed conditions
Test Setup & Methodology
1. Modal Parameter Testing
Sensors: Triaxial accelerometers mounted on sled vehicle and track sections
DAQ System: RE-846U Rugged Data Acquisition System (24-bit, 20kHz/ch)
Procedure:
Excited structure with impact hammer/electrodynamic shaker
Acquired FRFs (Frequency Response Functions) at 50 measurement points
Extracted modal parameters (MAC analysis in ME'scopeVES)
2. Impact & Temperature Monitoring
Instrumentation:
Piezoelectric shock sensors (50k g range) on sled shoes
K-type thermocouples (0-800°C) embedded in track/contact surfaces
Data Collection:
Used rugged standalone loggers (IP67) for unrecoverable high-speed runs
Post-test data retrieval and shock pulse analysis (SRS, pulse duration)
3. Track Strain-Temperature Correlation
Measurement:
Triaxial strain rosettes (120Ω) at track stress-concentration zones
Fiber Bragg grating (FBG) sensors for simultaneous strain/temperature
DAQ: RU-846 Rugged Data Recorder (16-ch, 1kHz sync sampling)
Output: Strain vs. temperature hysteresis loops under cyclic thermal-mechanical loads
Key Results
| Test Type | Parameter | Measured Value | Requirement |
|---|---|---|---|
| Modal | 1st Bending Freq. | 87.5Hz ±2% | >85Hz |
| Impact | Peak Shock (Z-axis) | 12,500g @ 200μs | <15,000g |
| Thermal | Max Track Temp. | 320°C | <400°C |
| Strain | Compressive Strain (εy) | -1,250με | -1,500με |
Engineering Insights
1. Track Dynamics:
Identified 3rd torsional mode at 214Hz requiring stiffening
Sled-track interaction showed 5-8% modal frequency shift vs. FEM
2. Wear Mechanisms:
Localized track heating (>300°C) correlated with plastic strain accumulation
Impact spikes exceeded 10,000g during shoe re-engagement
3. Safety Margins:
Thermal buckling risk confirmed at sustained >350°C
Strain-temperature phase lag indicated viscoplastic behavior
System Advantages
✔ RE-846U – Survived 50g test environment vibrations
✔ RU-846 – 72-hour continuous recording at -40°C to +85°C
✔ FBG Sensors – EMI immunity for electromagnetic launch interference
Next Steps
Track material upgrade (Ti-6Al-4V alloy evaluation)
Active cooling system prototyping
10,000-cycle accelerated fatigue testing
This test series established critical baselines for next-gen rocket sled designs, combining transient dynamics and extreme environment measurements.
Data Availability: Raw time histories (TDMS format), modal shapes (UFF58), and thermal-strain matrices available upon request.
