As the expansion of maneuvers, assets, and access into space increases, the risk of fire aboard a spacecraft or other vessel becomes an unavoidable concern. There is an inability of existing technology to detect fire and concerns with the limited types of combustible materials which can be sensed rapidly. To better position the growth of this economic sector, there is a need to ensure rapidly implementable and standardized components which can address this common need across flight and mission platforms. This work is about developing the optical system for an LED-based absorption spectroscopy, an early-fire detection sensor that identifies CO and CO2. The proposed design consists of restricted LED emitters with corresponding spectral bandpass filters along each beam path for CO2 and CO, respectively.
Airborne meteorological instruments are key to climate science, of which understanding cloud formation is an important component. Cloud formation involves the entrainment of air with dissimilar convective, thermal, and humidity properties. Improved understanding of these meteorological parameters can improve forecasting. The National Oceanic and Atmospheric Administration (NOAA) currently relies on outboard sensors with 25 Hz sampling, giving 10 m spatial resolution during nominal fixed wing aircraft flights. Higher-resolution humidity and temperature data are needed. We describe a novel laser absorption-based instrument that can make high sensitivity airborne measurements with 25 cm spatial resolution. The use of mid-infrared (MIR) quantum cascade lasers (QCLs) enables high sensitivity humidity measurements based on strong fundamental vibrations of water vapor. Sampling at 1 MHz (averaged data output exceeding 1 kHz) enables the high spatial resolution from a jet platform that accesses near the ground to 45,000 ft. This technology could be extended using complementary lasers to identify any Chemical, Biological, Radiological, and Nuclear (CBRN) threats, or hazardous material incidents, based on their MIR absorption features. Additional applications could also include highly accurate information for combating wildfires and high-speed identification of anomalous gas-phase species in semiconductor processing.
Ensuring the operating temperature regime of optoelectronic (EO) components, such as detectors and emitters, is paramount for the accurate performance of any instrument comprised of, or relies on, those devices. The semiconductors’ band gaps enable the photoelectric conversion to dilate as a function of temperature, on the order of magnitude variation per 10°C near 300K. Semiconductor infrared (IR) detectors benefit from compact cooling with thermoelectric coolers (TECs), which rely on the Peltier Effect and an input current direction to force heat flow to/from the device to which they are attached. When coupled with a closed-loop control system, this bi-directional capability can enable temperature stability on the order of 0.01°C of the regulated device. Heat sinks and thermally conductive adhesives are required to facilitate the TEC to source and sink heat with the environment. In aerospace applications, it is necessary to design a compact cooling fin architecture that maximizes heat transfer capabilities within a given envelope of system size, weight, and power (SWaP) limitations. These design envelopes persist where an operating environment requires atypical radiation and convection heat transfer consideration. This paper compares two different wire mesh models and assesses their ability to assist in a TEC’s ability to cool an IR detector. Commercial finite element software, Siemens NX, and Simcenter Thermal are used to explore how two different meshes perform in steady-state operating conditions comparing reduced convection coefficients attributable to microgravity and radiative heat dissipation.
KEYWORDS: Sensors, Light emitting diodes, Space operations, Analog electronics, Photodiodes, Flame detectors, Microcontrollers, Signal detection, Interfaces, Embedded systems
As the value of assets in space increases, the need for protection from internal system faults and fires becomes necessary. The rapid nature of commercial space advancement contrasts the approach NASA utilized, and there is a paramount need for a Federal Aviation Administration (FAA) approved commercial off the shelf (COTS) solution to fire detection in space. Our objective is to develop a low size weight and power (SWaP) solution for an early fire detection system implemented as an industry standard. This work highlights the electrical systems which drive LED-based absorption spectroscopy earlyfire detection sensor which targets CO and CO2. The unit’s core logic is executed using a PIC24HJ series microcontroller with custom libraries that interface with several devices through analog, I2C, and SPI communication protocols. The prototype unit is slated for an upcoming sub-orbital flight test which will record and log measurements data onto a microSD card for subsequent post-flight analysis.
Additive manufacturing (AM, 3D printed) enables, among other advantages, the in-house fabrication of optomechanical components with minimal tooling investment and labor hours per finished part. Currently, supply chains for high-value optomechanical components are delicate and can be a potential area of concern for scheduling; there is an advantage from using bulk sourced filament and commercial off-the-shelf (COTS) components to meet design needs. Additionally, spacebased manufacturing can incorporate AM, where a remote design engineer transmits a part file to a permanent orbiting, Lunar, or Martian platform to facilitate and optimize the use of personnel hours. Herein, we describe the design objectives, process, and test evaluation for a versatile optomechanical positioner to incorporate an optical component (emitter, mirror, beam-splitter, etc.) to a precision instrument at a fixed location honed surface normal. The designed AM optical positioner (OP) is manufactured from low off-gassing nylon 6,6. It has incorporated low-mass components such as silicon carbide (SiC) to reduce further the mass of the kinematic systems with a minimum number of secondary tensioners and actuators. This positioner provides one degree of translational freedom (infinite translation), either along the optical path or normal to it, with two degrees of angular degrees of freedom (Δαmax= 189.2 mrad and Δβmax= 375.9 mrad) with minimal off-axis shift about the rotation center. We have verified the designs in static tests and isothermal shake table tests.
3D printing is a rapid manufacturing methodology which provides low turnaround times greatly advancing the efficacy of low technology readiness level (TRL) prototyping of opto-electric sensors. Herein, we describe the design and evaluation of a discrete adjustable optical prototyping system, refered to as the Rapid Indexable Positioning System which can be utilized in conjunction with formfitting 3D printed opto-mechanical components to aid in the development of aerospace payloads. “Grid holes” are integrated to an enclosure wall using a grid pattern of holes on every face of a payload enclosure. This works in conjunction with various components that can be semi-permanently positioned with the use of “studs,” allowing for rapid validation of layout within an enclosure. The demonstration of this technique is conducted on prints using both PLA and ABS with the use of a Raise3D Pro2 Printer with the print properties of 20% honeycomb infill and .2mm layer height. The use of this technique in payload enclosure development facilitates rapid and indexable changes to be made, requiring that only a single enclosure, which requires nearly 24 hours to print. This print can be utilized with multiple iterations of each part to be indexed, requiring only about 1 hour. Additional Dynamic oscillation simulations can be conducted to ensure that the optical components would remain within a necessary manifold of deflection once the viability of their final location was verified.
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