Daniel F. Berisford

Thermal Testing of the Compositional InfraRed Imaging Spectrometer (CIRIS)

The CIRIS device is a Fourier Transform (FT) spectrometer that utilizes a rotating refractor to induce the time-varying path length difference in split light beams. This design allows the spectrometer to be extremely compact, and eliminates linear accelerations associated with traditional Michelson FT spectrometers. Compared to grating spectrometers, CIRIS is inherently radiation-tolerant and has high signal-to-noise in the mid- to thermal IR, making it ideal for outer planetary and primitive body missions. We have developed a small-scale thermal/vacuum testing facility for rapid testing of the CIRIS prototype and similar instruments in cryogenic conditions relevant to an outer planetary orbital environment. Here we present results from testing the CIRIS prototype and several infrared detectors, including thermal and electrical performance of the system.

Design and Testing of an Active Heat Rejection Radiator with Digital Turn-Down Capability

NASAs proposed lunar lander, Altair, will be exposed to vastly different external environment temperatures. The challenges to the active thermal control system (ATCS) are compounded by unfavorable transients in the internal waste heat dissipation profile: the lowest heat load occurs in the coldest environment while peak loads coincide with the warmest environment. The current baseline for this fluid is a 50/50 inhibited propylene glycol/water mixture with a freeze temperature around -35 C. While the overall size of the radiators heat rejection area is dictated by the worst case hot scenario, a turn-down feature is necessary to tolerate the worst case cold scenario. A radiator with digital turn-down capability is being designed as a robust means to maintain cabin environment and equipment temperatures while minimizing mass and power consumption. It utilizes active valving to isolate and render ineffective any number of parallel flow tubes which span across the ATCS radiator. Several options were assessed in a trade-study to accommodate flow tube isolation and how to deal with the stagnant fluid that would otherwise remain in the tube. Bread-board environmental tests were conducted for options to drain the fluid from a turned-down leg as well an option to allow a leg to freeze/thaw. Each drain option involved a positive displacement gear pump with different methods of providing a pressure head to feed it. Test results showed that a start-up heater used to generate vapor at the tube inlet held the most promise for tube evacuation. Based on these test results and conclusions drawn from the trade-study, a full-scale radiator design is being worked for the Altair mission profile.

Fluid Line Evacuation and Freezing Experiments for Digital Radiator Concept

The digital radiator technology is one of three variable heat rejection technologies being investigated for future human-rated NASA missions. The digital radiator concept is based on a mechanically pumped fluid loop with parallel tubes carrying coolant to reject heat from the radiator surface. A series of valves actuate to start and stop fluid flow to di erent combinations of tubes, in order to vary the heat rejection capability of the radiator by a factor of 10 or more. When the flow in a particular leg is stopped, the fluid temperature drops and the fluid can freeze, causing damage or preventing flow from restarting. For this reason, the liquid in a stopped leg must be partially or fully evacuated upon shutdown. One of the challenges facing fluid evacuation from closed tubes arises from the vapor generated during pumping to low pressure, which can cause pump cavitation and incomplete evacuation. Here we present a series of laboratory experiments demonstrating fluid evacuation techniques to overcome these challenges by applying heat and pumping to partial vacuum. Also presented are results from qualitative testing of the freezing characteristics of several di erent candidate fluids, which demonstrate significant di erences in freezing properties, and give insight to the evacuation process.

A 5 kWht Lab-Scale Demonstration of a Novel Thermal Energy Storage Concept With Supercritical Fluids

An alternate to the two-tank molten salt thermal energy storage system using supercritical fluids is presented. This technology can enhance the production of electrical power generation and high temperature technologies for commercial use by lowering the cost of energy storage in comparison to current state-of-the-art molten salt energy storage systems. The volumetric energy density of a single-tank supercritical fluid energy storage system is significantly higher than a two-tank molten salt energy storage system due to the high compressibilities in the supercritical state. As a result, the single-tank energy storage system design can lead to almost a factor of ten decrease in fluid costs. This paper presents results from a test performed on a 5 kWht storage tank with a naphthalene energy storage fluid as part of a small preliminary demonstration of the concept of supercritical thermal energy storage. Thermal energy is stored within naphthalene filled tubes designed to handle the temperature (500 °C) and pressure (6.9 MPa or 1000 psia) of the supercritical fluid state. The tubes are enclosed within an insulated shell heat exchanger which serves as the thermal energy storage tank. The storage tank is thermally charged by flowing air at >500 °C over the storage tube bank. Discharging the tank can provide energy to a Rankine cycle (or any other thermodynamic process) over a temperature range from 480 °C to 290 °C. Tests were performed over three stages, starting with a low temperature (200 °C) shake-out test and progressing to a high temperature single cycle test cycling between room temperature and 480 °C and concluding a two-cycle test cycling between 290 °C and 480 °C. The test results indicate a successful demonstration of high energy storage using supercritical fluids.Copyright

Design and Modeling of a Radiator with Digital Turn-Down Capability under Variable Heat Rejection Requirements

Future NASA human-rated near Earth missions impose severe demands on a radiator to be capable of responding to variable heat loads in challenging environments. The capability requires the rejection of peak loads during the warmest environment as well as the rejection of the lowest loads during the coldest environment. Conservation of mass and power becomes a challenge while maintaining the cabin environment and equipment temperatures. A radiator with digital turn-down capability is under development at JPL to manage the transient environments and heat loads. Designed for the worst case hot scenario, the radiator can satisfy any turn-down ratio by isolating sections of the radiator using active valving and varying mass flow rate. Of particular complication is the demand during Low Lunar Orbit (LLO) when environmental temperatures vary the most. Additional concerns involve stagnation of fluid in the closed lines and the time needed to perform turn-down and turn-up operations. A closed loop thermal management system with a representative lunar mission profile and heat loads has been modeled using Thermal Desktop/SINDA Fluint. The fluid selected for the study was a 50/50 propylene glycol/water mixture by weight. Panel size, tube quantity, tube spacing, and tube diameter were traded in order to satisfy the worst case hot scenario and provide options for various other mission phases. Stepping through the mission timeline allows the performance to be predicted as the radiator “reacts” to changes in heat load and environment. Results from the trade study will be used to generate a prototype digital radiator system for testing purposes.

An integrated SoC for science data processing in next-generation space flight instruments avionics

We present here an integrated SoC platform, called APEX-SoC, that is aimed at speeding-up the design of next-generation space flight instruments avionics by providing a convenient infrastructure for hardware and software based science data processing. We use a case-study drawn from the JPL Compositional Infrared Imaging Spectrometer (CIRIS) to illustrate the process of integrating instrument-dependent data acquisition and processing stages in this platform. In order to enable the use of APEX-SoC-based instruments in deep space missions, the platform implements Radiation Hardening By Design (RHBD) techniques and offers support for instantiating multiple processing stages that can be used at runtime to increase reliability or performance, based on the requirements of the mission at each particular stage. Finally, in the specific case of CIRIS, the data processing includes a stage to cope with radiation affecting the instrument photo-detector.

Designing a SoC to control the next-generation space exploration flight science instruments

SoC technology permits to integrate all the computational power required by next-generation space exploration flight science instruments on a single chip. This paper describes the Xilinx Zynq-based Advanced Processor for space EXploration SoC (APEX-SoC) that has been developed at the Jet Propulsion Laboratory (JPL) in collaboration with ARM. The paper discusses the APEX-SoC architecture and demonstrates its main capabilities when used to control JPLs Compositional InfraRed Imaging Spectrometer (CIRIS). As the CIRIS instrument is intended to explore harsh space environments, the paper also deals with the Radiation Hardened By Design (RHBD) features that have been implemented in the APEX-SoC.

The airborne snow observatory during NASA snow experiment (SnowEx) year 1: Mapping of snow water equivalent and snow albedo and constraining understanding of the physical environment

We present Airborne Snow Observatory (ASO) measurements in support of the fist NASA SnowEx field campaign. The fall 2016 campaign collected snow-free data using multiple in-situ and remote sensing platforms at two distinctly different sites in western Colorado: Grand Mesa (flat, high, partially forested plateau), and Senator Beck Basin (steep, complex sub-alpine and alpine mountain terrain). The ASO flies a scanning lidar and imaging spectrometer to measure snow depth and albedo. For the SnowEx snow-free campaign, the ASO surveys produced high-resolution digital surface models of the underlying terrain with full-waveform laser returns. These data will be used to calculate snow depths during subsequent winter surveys, and provide insight to the impact of forest canopy structure on snow accumulation and melt.