MENG 4137L - NASA TPS Senior Design

Project Overview

As part of a 4-person senior capstone team in active collaboration with NASA, we designed, fabricated, and validated a dual-mode dynamic impact testing platform to quantify the impact resistance of NASA Thermal Protection System (TPS) tiles, the ceramic shielding used on spacecraft during atmospheric re-entry. The system needed to fire projectiles at velocities up to 100 m/s and deliver controlled pendulum impacts across multiple test configurations, all within a fully enclosed safety enclosure.

System Overview

Pellet Launcher

Pellet launcher velocity range: 1–100 m/s (pneumatic, 20–80 PSI operating range)
Projectile types: 2 mm steel (52100), 1.5 mm steel, 3.16 mm silicon carbide
Pellet hopper capacity: 22 projectiles with automated single-shot indexing

Impact Hammer

Impact hammer arm length: 0.75 m; electromagnetic brake for release at any angle
Angular positioning precision: ±0.01°; velocity measurement: ±0.1°/s
Hammer configurations: 2 mm ball point, Charpy/Izod, U-shaped tension/compression head

Sample Holder

Sample stage: 3-axis translation, compatible with 4×4" NASA TPS tiles, glass, and standardized Charpy/Izod specimens

Other

Control system: NI cDAQ-9173 with LabVIEW; stepper motor, solenoid, and ball valve sequencing
Overall enclosure: 2 ft × 5 ft × 4 ft, polycarbonate safety doors on three sides

My Role

Designed and fabricated depth measurement hardware; contributed to barrel assembly and broader mechanical fabrication.
Mapped the full electronics architecture: reviewed datasheets and specifications for every component (NI-9401, Autonics encoder, TB6600 driver, optocoupler module, relay module) to verify signal compatibility, voltage levels, and interface logic before assembly.
Pressure-velocity calibration testing and impact depth data collection across coated (RCG) and uncoated (FRCI) NASA TPS tiles.
Co-authored final technical report documenting design, methodology, and experimental results.

Technical Work

The system was built around two independent but complementary subsystems. The pneumatic pellet launcher used a 5-inch, 7075 aluminum barrel bored to 2 mm ID, fed by a 3D-printed rotary magazine driven by a repurposed 3D printer stepper motor. Each shot was sequenced automatically in LabVIEW: the stepper indexed one pellet into the breach, a motorized ball valve opened and closed to drop it into the barrel, and a 60-bar solenoid valve fired the pressurized air charge. Early testing showed significant shot-to-shot velocity variance; adding a pneumatic accumulator upstream of the solenoid stabilized supply pressure and reduced spread substantially.

The impact hammer was redesigned from a prior iteration. Chanages included switching to a circular cross-section aluminum shaft, removing the pawl-and-ratchet release, and replacing it with an electromagnetic brake controllable to within 0.01° of any release angle. Three interchangeable heads enabled different loading modes: a 2 mm ball point for direct comparison with pellet launcher impacts, a U-shaped steel head for high strain-rate tension and compression loading, and a Charpy/Izod head configurable vertically or horizontally. An Autonics incremental rotary encoder (1024 PPR) mounted coaxially to the pivot shaft measured angular velocity in real time, with impact energy calculated from E = ½Iω². A 24V-to-5V optocoupler isolation module protected the NI-9401 DAQ input from encoder voltage spikes during impact events.

On the materials characterization side, both RCG-coated and uncoated FRCI tile surfaces were impacted at four pressure settings (20, 40, 60, 80 PSI), with impact depth measured via caliper depth gauge and plotted against both velocity and impact energy. The data clearly showed the RCG coating's energy absorption capacity, with shallower craters at equivalent impact energies compared to bare FRCI substrate. The project also engaged directly with NASA materials scientists through monthly progress reviews and an on-site visit to NASA Ames Research Center, where the team presented findings and received feedback on testing methodology.

RCG-coated NASA TPS tile after impact testing across four pressure settings

Microscope cross-section of RCG coating at impact site showing crack propagation

Microscope view of steel pellet impact crater on FRCI substrate

Microscope view of high-energy impact crater with material displacement on RCG surface

Outcome

1st place out of 8 groups in Yale's Mechanical Engineering department capstone competition
Pressure-velocity calibration validated across full operating range
Successfully demonstrated Charpy, Izod, high strain-rate tension, and compression test configurations
Quantified RCG coating energy absorption capacity relative to uncoated FRCI substrate across 20–80 PSI
Visited NASA Ames Research Center; presented results to NASA materials scientists and engineers
Full automated fire sequence operational: index → load → seal → fire, controlled via LabVIEW
Delivered a platform capable of supporting future testing of SuperWood, Corning glass specimens, and additional NASA tile variants

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