Stennis Space Center (SSC) is one of three government-operated rocket engine test facilities in the United States and is the primary center for testing and flight-certifying rocket propulsion systems for future space vehicles. Safety is a top priority at NASA-SSC. To safely test and certify rocket engines, monitoring technologies for rocket test stands, which (1) verify compliance with federal, state, and local government guidelines; (2) ensure a safe work environment for its personnel at ground testing facilities; as well as (3) monitor environmental impacts, are all required. Additionally, NASA has a need to monitor engine combustion efficiencies and engine health of a variety of launch vehicle configurations utilizing liquid oxygen, liquid hydrogen, isopropanol, and kerosene. Multi-analyte measurement technology is essential for a safe and effective working environment. Therefore, for the advancement in multi-analyte technology in the rocket testing industry, a device was created that integrates multi-analyte measurements into a single sensor unit.

The multi-analyte optical sensor for rocket testing (MOSRT) device developed consists of a miniaturized optoelectronic platform, which uses light-emitting diodes (LEDs), alleviating complications and drawbacks often associated with the use of an ordinary fiber bundle design. Significant improvements to the sensor unit’s optoelectronics and the operating software were made, resulting in the fabrication of a highly sensitive instrument. These included fine-tuned adjustments to the MOSRT formulations to optimize sensor performance and to enhance the features for temperature compensation and signal-to-noise ratio. To accomplish this, an evaluation of a variety of immobilization matrices including polymers and sol-gel-based materials was conducted to find the best performance capabilities for thin-film sensors because a simple sol-gel matrix would not produce the desired signal-to-noise ratio. Therefore, an organically modified sol-gel matrix was applied. Additionally, the use of organically modified silane formulations enabled accelerated curing. Then, sensor formulations using organically modified sol-gel matrix were cast into thin film so that long-term drift could be minimized/eliminated for the production of the necessary signal-to-noise ratio. A pin-printed multi-analyte sensor chip was integrated with a fiber bundle to achieve remote-sensing capability. The pin-printing technique also provides assurance in sensor reproducibility so that the device can be reproduced and manufactured consistently.

Compared to existing technologies, this sensor substantially reduces operational costs and provides a significant improvement in detection capability over the lifetime of the detection system. Additionally, a unique feature not available in other commercially available products in the marketplace is that the sensors can be custom designed to specifically suit a variety of clients’ differing needs. The compact size and multi-analyte capabilities of the MOSRT sensors offer feasible adaptation for a vast range of gaseous detection systems ranging from environmental monitoring to process control.

This work was done by Kisholoy Goswami of InnoSense LLC for Stennis Space Center. For more information please contact InnoSense at (310) 530-2011 and refer to SSC-00416.

NASA Tech Briefs Magazine

This article first appeared in the January, 2015 issue of NASA Tech Briefs Magazine.

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