Paul E. Hintze

Electronic spectroscopy of organic acid dimers

Abstract The UV electronic spectroscopy of acetic, propionic, butyric, isobutyric acid, and their dimers is studied by measurements of the temperature and pressure dependence of their absorption spectra near 205 nm. The binding energy of each dimer is calculated using theoretical methods. The photo-absorption cross-sections for the monomer and dimer of each acid are calculated from 195–220 nm. The dimers are found to have a larger cross-section than the monomers and a peak absorbance that is shifted to higher energy. Theory and experiment are used to compare the strength of the hydrogen bonds in the ground and excited state of these dimers.

Lunar Surface Stabilization via Sintering or the use of Heat Cured Polymers

Two potential methods for lunar surface stabilization are: 1) sintering the regolith into a solid and 2) using heat or UV cured polymers. Sintering, a method in which powders are fused into a solid, has been proposed as a way of building lunar launch pads, roads and other building materials. Polymers are currently used by the military to stabilize sandy soils, and adaptations of this technology may be effective for lunar surface stabilization. This paper describes ongoing work at NASA Kennedy Space Center on these two technologies. A solar concentrator has been built to provide the heat source for sintering. Various solvent free polymers have been investigated. Results of physical testing, including load strength and abrasion resistance, on field and laboratory prepared samples are presented.

Terahertz NDE application for corrosion detection and evaluation under shuttle tiles

Pulsed Terahertz NDE is being examined as a method to inspect for possible corrosion under Space Shuttle Tiles. Other methods such as ultrasonics, infrared, eddy current and microwave technologies have demonstrable shortcomings for tile NDE. This work applies Terahertz NDE, in the frequency range between 50 GHz and 1 THz, for the inspection of manufactured corrosion samples. The samples consist of induced corrosion spots that range in diameter (2.54 to 15.2 mm) and depth (0.036 to 0.787 mm) in an aluminum substrate material covered with tiles. Results of these measurements are presented for known corrosion flaws both covered and uncovered and for blind tests with unknown corrosion flaws covered with attached tiles. The Terahertz NDE system is shown to detect all artificially manufactured corrosion regions under a Shuttle tile with a depth greater than 0.13 mm.

Single-spore elemental analyses indicate that dipicolinic acid-deficient Bacillus subtilis spores fail to accumulate calcium

Dipicolinic acid (pyridine-2,6-carboxylic acid; DPA) is a major component of bacterial spores and has been shown to be an important determinant of spore resistance. In the core of dormant Bacillus subtilis spores, DPA is associated with divalent calcium in a 1:1 chelate (Ca–DPA). Spores excrete Ca–DPA during germination, but it is unknown whether Ca and DPA are imported separately or together into the developing spore. Elemental analysis by scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS) of wild-type spores and mutant spores lacking the ability to synthesize DPA showed that DPA-less spores also lacked calcium, suggesting that the two compounds may be co-imported.

Additive Construction using Basalt Regolith Fines

Planetary surfaces are often covered in regolith (crushed rock), whose geologic origin is largely basalt. The lunar surface is made of small-particulate regolith and areas of boulders located in the vicinity of craters. Regolith composition also varies with location, reflecting the local bedrock geology and the nature and efficiency of the micrometeorite- impact processes. In the lowland mare areas (suitable for habitation), the regolith is composed of small granules (20 – 100 microns average size) of mare basalt and volcanic glass. Impacting micrometeorites may cause local melting, and the formation of larger glassy particles, and this regolith may contain 10-80% glass. Studies of lunar regolith are traditionally conducted with lunar regolith simulant (reconstructed soil with compositions patterned after the lunar samples returned by Apollo). The NASA Kennedy Space Center (KSC) Granular Mechanics & Regolith Operations ( GMRO) lab has identified a low fidelity but economical geo-technical simulant designated as Black Point-1 (BP-1). It was found at the site of the Arizona Desert Research and Technology Studies (RATS) analog field test site at the Black Point lava flow in adjacent basalt quarry spoil mounds. This paper summarizes activities at KSC regarding the utilization of BP-1 basalt regolith and comparative work with lunar basalt simulant JSC-1A as a building material for robotic additive construction of large structures. In an effort to reduce the import or in-situ fabrication of binder additives, we focused this work on in-situ processing of regolith for construction in a single-step process after its excavation. High-temperature melting of regolith involves techniques used in glassmaking and casting (with melts of lower density and higher viscosity than those of metals), producing basaltic glass with high durability and low abrasive wear. Most Lunar simulants melt at temperatures above 1100°C, although melt processing of terrestrial regolith at 1500°C is not uncommon. These temperatures are achievable by laser heating or by using solar concentrators. Similar to volcanic magma, the cooling rate determines the crystallite size – slower cooling develops larger crystals, and rapid quenching can result in fully amorphous glass.

Review on Transforming TiO 2 into a Visible-Light- Responsive Catalyst for Water and Air Purification

Photocatalytic oxidation (PCO) of organic contaminants is a promising air and water quality management technique which offers energy and cost savings compared to thermal catalytic oxidation (TCO). The most widely used photocatalyst, anatase TiO2, has a wide band gap (3.2 eV) requiring UV photons to activate it. Solar radiation consists of ~4-6% UV and 45% visible light at the Earth’s surface. Therefore, catalysts capable of utilizing these visible photons need to be developed to make PCO approaches more efficient, economical, and safe. Many approaches have been taken to make TiO2 visible-light-active (VLA) with varied degrees of success. Strategies attempted thus far fall into three categories based on their electrochemical mechanisms: 1) photosensitizing TiO2 with Dyes; 2) altering the band gap of TiO2; and 3) coupling TiO2 with a narrow band gap semiconductor. There are diverse technical approaches to implement each of these strategies. This paper presents a brief review of these approaches and their outcomes in terms of the photocatalytic activity and photonic efficiency of the resulting products under visible light. Although resulting visible-light-responsive (VLR) photocatalysts show promise, there is very few comparative studies on the performance of unmodified TiO2 under UV and the modified TiO2 under visible light. It was found that the UV-induced catalytic activity of unmodified TiO2 is much greater than the visible-light-induced catalytic activity of the VLR catalyst at the current state of technology. Furthermore, VLR-catalysts have much lower quantum efficiency than UV-catalysts. This stresses the need for continuing research in this area.

Smart Coatings for Autonomous Corrosion Detection and Control

Corrosion is the degradation of a material that results from its interaction with the environment. The environment at the Kennedy Space Center’s (KSC) Beachside Atmospheric Exposure Test Site near the launch pads have been documented by ASM International (formerly American Society for Metals) as the most corrosive in the United States. The 70 tons of highly corrosive hydrochloric acid that are generated by the solid rocket boosters during a launch exacerbate the natural corrosiveness of the coastal environment at the pads. Numerous failures at the pads are caused by corrosion of stainless steels, rebar corrosion, and the degradation of refractory concrete. Corrosion control of launch pad structures relies on the use of coatings and materials that can withstand the marine atmosphere as well as the launch conditions. Coatings are selected from the qualified products list (QPL) of the NASA Standard 5008A for Protective Coating of Carbon Steel, Stainless Steel, and Aluminum on Launch Structures, Facilities, and Ground Support Equipment. This standard was developed to establish uniform engineering practices and methods and to ensure the inclusion of essential criteria in the coating of ground support equipment (GSE) and facilities used by or for NASA. This standard is applicable to GSE and facilities that support space vehicle or payload programs or projects and to critical facilities at all NASA locations worldwide. In recent years, environmental regulation changes have dramatically reduced the availability of conventional corrosion protective coatings. Current attrition rate of qualified KSC coatings will drastically limit the number of commercial off the shelf (COTS) products available for future ground operations in support of launch operations at KSC. For this reason, corrosion detection and control technologies have been identified as a critical, initial capability technology need for ground processing of future launch vehicles, reduced ground processing complexity, streamlined integrated testing, and operations phase affordability and sustainability. Researchers at NASA’s Corrosion Technology Laboratory at KSC are developing a smart, environmentally friendly coating system for early corrosion detection, inhibition, and self healing of mechanical damage without external intervention. This coating is being developed using corrosion sensitive microcapsules and particles designed to deliver corrosion indicators, corrosion inhibitors, and self healing agents on demand when corrosion or mechanical damage to the coating occurs. This paper presents the results from progress made to date in developing a coating for the smart corrosion control of launch pad structures and GSC.

Regolith-Derived Heat Shield for Planetary Body Entry and Descent System with In Situ Fabrication

In this paper we will discuss a new mass-efficient and innovative way of protecting high-mass spacecraft during planetary Entry, Descent & Landing (EDL). Heat shields fabricated in situ can provide a thermal-protection system (TPS) for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from regolith materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Three regolith processing and manufacturing methods will be discussed: 1) oxygen & metal extraction ISRU processes produce glassy melts enriched in alumina and titania, processed to obtain variable density, high melting point and heat-resistance; 2) compression and sintering of the regolith yield low density materials; 3) in-situ derived high-temperature polymers created to bind regolith particles together, with a lower energy budget.

Refractory Materials for Flame Deflector Protection

Fondu Fyre (FF) is currently the only refractory material qualified for use in the flame trench at KSCs Shuttle Launch Pads 39A and 3913. However, the material is not used as it was qualified and has undergone increasingly frequent and severe degradation due to the launch blasts. This degradation is costly as well as dangerous for launch infrastructure, crew and vehicle. The launch environment at KSC is unique. The refractory material is subject to the normal seacoast environment, is completely saturated with water before launch, and is subjected to vibrations and aggressive heat/blast conditions during launch. This report presents results comparing two alternate materials, Ultra-Tek FS gun mix and Kruzite GR Plus, with Fondu Fyre. The materials were subjected to bulk density, porosity, compression strength, modulus of rupture and thermal shock tests. In addition, test specimens were exposed to conditions meant to simulate the launch environment at KSC to help better understand how the materials will perform once installed.

Application of Terahertz Radiation to the Detection of Corrosion under the Shuttle's Thermal Protection System

There is currently no method for detecting corrosion under Shuttle tiles except for the expensive process of tile removal and replacement; hence NASA is investigating new NDE methods for detecting hidden corrosion. Time domain terahertz radiation has been applied to corrosion detection under tiles in samples ranging from small lab samples to a Shuttle with positive results. Terahertz imaging methods have been able to detect corrosion at thicknesses of 5 mils or greater under 1” thick Shuttle tiles and 7‐12 mils or greater under 2” thick Shuttle tiles.