SEARCH · Engineering Papers

Results for “Short circuiting”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54

All sources NASA NTRS DOE OSTI

NASA NTRS2018

Calculation Method for Predicting AM0 Isc from High Altitude Aircraft Flight Data

High altitude aircraft have been used by the space photovoltaic (PV) community to determine the air mass Zero (AM0) performance of solar cells for over fifty years. Relative to in-space measurement opportunities, these methods are generally cheaper and more readily available. The data obtained, however, must be corrected for residual atmospheric effects. This paper details the correction method currently being used for the calculation of the estimated AM0 short-circuit current (Isc) for photovoltaic devices flown on the NASA ER-2 calibration platform. This method would also be applicable to other high altitude methods where Isc data is collected over a sufficiently large range of altitudes. An initial comparison with a four junction (4J) cell flown on the CASOLBA high altitude balloon platform showed an agreement to 0.2%.

AM0↗

NASA NTRS2018

Anomalous Transients in Chip Polymer Tantalum Capacitors

Contrary to MnO2 tantalum capacitors, transient processes in polymer tantalum capacitors after voltage application might result in anomalously high, ampere-level currents when a capacitor might appear as a short circuit for a time that is much greater than a transient time in MnO2 capacitors. In this work, conditions that cause anomalous transients in different types of polymer tantalum capacitors have been analyzed. Related phenomena that included increasing of capacitance and dissipation factors with voltage, parametric surge current test failures without damage to capacitors, and increasing leakage currents at low temperatures are described. It has been shown that anomalous transients increased substantially with applied voltage and with reduction of moisture content in capacitors caused by storage or operation at high temperatures and/or in vacuum. Different types of capacitors exhibited different level of transients and modification of conductive polymers or process of their application might decrease transient leakage currents substantially. For space applications, the risk of failures related to anomalous transients can be mitigated by special testing procedures to select parts with an acceptable level of transients and by voltage derating.

Tantalum Capacitors↗

NASA NTRS2018

Stirling Convertor Controller Development at NASA Glenn Research Center

Over the past decade, NASA Glenn Research Center (GRC) has been supporting the development of Radioisotope Power Systems (RPS). NASA desires higher conversion efficiency RPS options that are reliable and robust with long life design. Dynamic conversion, such as Stirling and Brayton, offer the potential for higher conversion efficiencies but have yet to be demonstrated in a flight application. The RPS program sent out a solicitation to investigate options for dynamic conversion technologies. As a result of this solicitation, four dynamic power convertor (DPC) technologies were selected for design and fabrication of a prototype dynamic convertor. One lesson learned from the Advanced Stirling Radioisotope Generator (ASRG) project is that controller development should start early in the development of a dynamic convertor. As a result of this, NASA GRC has been utilizing hardware from past Stirling convertor projects including that of the ASRG to support controller development for the DPC's. NASA GRC has developed a strong knowledge base on both analog and digital Stirling dynamic power convertor controllers and will continue to expand and apply that knowledge to the four DPC's. Over the past 15 years, controllers were developed in-house at GRC, at Lockheed Martin Coherent Technologies (LMCT) and by the Johns Hopkins University/Applied Physics Laboratory (JHU/APL). Various generations of the controllers, have been developed as lessons were learned through various component and system level tests. Some of the tests performed were fault tolerance, qualification vibration level, electromagnetic interference, Radioisotope Power System Systems Integration (RSIL) tests, and extended operation. The fault tolerance test characterized the controller's ability to handle various fault conditions, including high or low bus power consumptions, total open load or short circuit, and replacing a failed controller card while the backup maintains control of the ASC. The vibration test confirms the controller's ability to control an ASC during launch. The EMI test characterized the AC and DC magnetic and electric fields emitted by the single ASC and if the controller has an impact on the radiated EMI. RSIL testing provided insight into the electrical interactions between the representative RPS, its associated control schemes, and realistic electric system loads. The extended operation test allows data to be collected over a period of thousands of hours to obtain long term performance data of the system. This paper describes the history of controller development at NASA GRC, tests performed on these controllers, and lessons learned.

Dugala, Gina M.↗

NASA NTRS2018

Stirling Convertor Controller Development at NASA Glenn Research Center

For nearly two decades, NASA Glenn Research Center has been supporting the development of radioisotope power systems (RPS). NASA desires higher conversion efficiency RPS options that are reliable and robust with long-life design. Dynamic conversion, such as Stirling and Brayton, offer the potential for higher conversion efficiencies than current RPS but have yet to be demonstrated in a flight application. The RPS program sent out a solicitation to investigate options for dynamic conversion technologies. As a result of this solicitation, four dynamic power convertor (DPC) technologies were selected for design and three are proceeding to the fabrication phase of prototype dynamic convertors. One lesson learned from the Advanced Stirling Radioisotope Generator (ASRG) project is that controller development should be coordinated with the development of a dynamic convertor. As a result of this, Glenn has been utilizing hardware from past Stirling convertor projects, including that of the ASRG, to support controller development for the DPCs. Glenn has developed a strong knowledge base on both analog and digital Stirling DPC controllers and will continue to expand and apply that knowledge to the DPCs. Over the past 15 years, controllers were developed at Glenn, at Lockheed Martin (LM), and by the Johns Hopkins University Applied Physics Laboratory (APL). Various generations of the controllers have been developed as lessons were learned through various component- and system-level tests. Some of the tests performed were fault tolerance, flight acceptance vibration, electromagnetic interference (EMI), spacecraft integration, and extended operation. The fault tolerance test characterized the controller’s ability to handle various fault conditions, including high or low bus power consumption, total open load or short circuit, and replacing a failed controller card while the backup maintains control of the Stirling convertor. The vibration test confirms the controller’s ability to control an Advanced Stirling Convertor (ASC) during launch. The EMI test characterized the alternating-current (AC) and direct-current (DC) magnetic and electric fields emitted by the single ASC and if the controller has an impact on the radiated EMI. Spacecraft integration testing in the Radioisotope Power Systems (RPS), System Integration Laboratory (RSIL) provided insight into the electrical interactions between the representative RPS, its associated control schemes, and realistic electric system loads. The extended operation test allows data to be collected over a period of thousands of hours to obtain long-term performance data of the system. This paper describes the history of controller development at Glenn, tests performed on these controllers, and lessons learned.

Dugala, Gina M.↗

NASA NTRS2015

Exploration Architecture with Quantum Inertial Gravimetry and In-Situ ChipSat Sensors

The Dual Exploration Architecture is a mission concept that combines remote sensing and in-situ observations into a single mission to answer planetary science questions that can only be answered with both types of data. Adoption of dual exploration architectures may short circuit the long, slow cycle of missions to inaccessible bodies by eliminating the need for separate precursor and follow-up missions. Additionally, the dual architecture possesses inherent flexibility that enables the design of adaptive, event-driven missions that are very different from traditional, largely pre-planned missions. Five key observations about the state and trends of planetary science exploration lead us to the dual architecture: increasing complexity of observations; scarcity of future mission opportunities; desire to capture transitory events; continued miniaturization of spacecraft components; and the Mars exploration cycle. Our goal in this study is to explore missions that can only happen using the dual architecture concept and find technology development needs that must be filled for those missions to compete. A survey of historical and current missions finds that opportunities for exploration are becoming less frequent, causing the flexibility and dual-nature elements of each mission to become more common. The dual exploration architecture takes these trends to their far conclusion, attempting to eliminate precursor and follow-up missions while still returning more scientific payoff. A study of the future of planetary science goals through the decadal survey reveals broad applicability of dual missions to solve mysteries that cannot be answered with a traditional mission architecture. These missions fall into three broad classes: choosing a local target from a global survey; dynamic/reactive science; and global in-situ networks. Two example missions of each class are notionally described. A deeper look at these dual architecture classes reveals four technology development needs that must be addressed for wide adoption of dual missions: passive landers; guided atmospheric probes; robust sensing packages; and small, precise orbital instruments. This study pursues a specific focus on two examples of such enabling technologies: the ChipSat and cold atom gravimetry. The ChipSat is a fully functional spacecraft-on-a-chip system that has broad versatility in the dual architecture mission space. Initial studies show that ChipSats could survive as passive impactor landers on bodies up to the size of Europa. Furthermore, COTS (Commercial Off-The-Shelf) components could provide an in-situ sensor suite that readily answers a number of pressing planetary science questions. Cold atom gravimetry uses inertial sensors based on light-pulse atom interferometry in a small form factor to map the gravity field of a body to precision equaling what would normally require two full spacecraft to achieve. The cold atom gravimeter provides an example of how advanced remote sensing capability can enable dual missions by providing greater returns in a significantly smaller package. Using the above two technologies, we study an example dual-architecture mission to both characterize and sample the subsurface oceans at Europa. The greatest scientific return in terms of detecting extraterrestrial life is in those regions where Europa’s ice crust is thin. The identification of regions with thin ice should therefore precede the selection of surface targets and dispatch of probes to those targets. This two-step process, if accomplished by separate flagship-scale missions, might take decades. As a result, a combined mission to both identify thin areas of Europa’s ice and follow up with surface observations at those regions is a good candidate for the dual-exploration architecture. This example mission consists of an orbiter spacecraft carrying a cold atom gravimeter capable of sensing or inferring the ice thickness on regional to local scales, along with a number of ChipSat probes capable of landing on the moon. The small size and weight of the ChipSats allows large numbers of them to be carried, ensuring that enough can be dropped to ensure survival of a minimum number of probes and potentially allowing for the in-situ sampling of multiple locations on the moon. The example missions and Europa case study show that amazing scientific return can obtained from dual-exploration architecture missions with a single launch by breaking the long timescales of planetary exploration and providing the flexibility to capturing transitory events and collect data across the local, regional, and global scales.

Exploration↗

NASA NTRS2017

Safe, High Specific Energy & Power Lithium Ion Cell Designs

The higher energy content (265 Wh/kg, 725 Wh/L) of the newer cell designs from LG, Panasonic, and Samsung have made them susceptible to side wall ruptures (SWR) during thermal runaway, rather than venting through the intended vent path in the cell header. This is also due to higher reaction kinetics of the electrochemistry, thinner can walls, tight crimp enclosure of the cell header, and inadequate flow rate through the header vent. This effort determined that bottom vents and thicker cell can walls both are necessary for reducing the risk of SWR. Compelling evidence was obtained using novel test methods that included an on-demand internal short circuit device, high speed X-ray videography, and cell thermal runaway calorimetry.

side wall rupture↗

NASA NTRS2019

Metallized Plastic Current Collectors

Metallized plastic current collectors are an innovation patented by the Soteria Battery Innovation Group with the promise of isolating active material involved in an internal short by vaporizing and isolating the short from the rest of the cell electrode jellyroll or stack. Partnering with NREL, UCL, Coulometrics, and Soteria, NASA is leading a research effort into demonstrating the merits and understanding the phenomena of this safety innovation using prototype 18650 cylindrical cells vs control cells with standard metal foil current collectors. Cells with and without the plastic collector, with and without the on-demand internal short circuit device, and with polymer or cellulose separators were made. Safety evaluations were done with driving cells into thermal runaway (TR) with thermal and nail penetration triggers while inside our TR calorimeter and with ultra high speed X-ray videography provided at Synchrotrons. Preliminary results suggests that the thermally unstable plastic current collector innovation has great promise for preventing TR or reducing the severity of the TR output.

Li-ion cell↗

NASA NTRS2019

Dust Abrasion Damage on Martian Solar Arrays: Experimental Investigation and Opportunity Rover Performance Analysis

Here we investigate the effects of erosion and weathering that occur on III-V cover-glass interconnected cells (CICs) after exposure to Mars dust storm conditions. The durability of these materials in a Martian environment is not well characterized so we perform analogous experimentation. To replicate the dust impingement, test coupons were placed in an enclosure and sandblasted with Mars dust simulant. We show the J-V response dependency on both incident angle and exposure times. We find that the simulated Martian dust storm often results in damage to the anti-reflective coating and subsequent reduced short circuit current. Reduction in the open circuit voltage is observed, likely caused by structural damage to the crystal lattice after CIC fracture. We employ data-driven modeling to determine a performance degradation rate that is consistent with zero within uncertainty. We also quantify the soiling contribution and power degradation of the photovoltaic cells on Mars through analysis of 4.95 Martian years of report-out power conditions from the Opportunity rover. We find that atmospheric dust suspended due to a weather event does not result in instantaneous settled dust on the PV cells. We calculate via autocorrelation function that the dust settling rate is approximately 21 Sols from atmospheric dust suspension. The findings presented here deliver a realistic approximation for the insolation values and subsequent PV power expected over time on the Martian surface thus informing future dust abatement systems.

McMillon-Brown, Lyndsey↗

NASA NTRS2019

Dust Abrasion Damage on Martian Solar Arrays: Experimental Investigation and Opportunity Rover Performance Analysis

McMillon-Brown, Lyndsey↗

NASA NTRS2019

Sublimation Protection Coatings for Thermoelectric Materials for Space Power Applications

The compounds such as Yb14MnSb11 are relatively new p-type thermoelectric materials, respectively. NASA's interest in these material are to replace the state-of-the-art Si-Ge legs of the current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000 degrees C in the vacuum of space. These materials, however, suffer from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of present work is to develop sublimation protection coatings for Yb14MnSb11 at temperatures up to 1000 degrees C. Coatings for Yb14MnSb11 present many challenges. The coating must not significantly react or interdiffuse with the substrate thereby degrading the substrate or consuming the coating, must remain intact and not crack or spall during thermal cycling prior to launch, and must be a good insulator both electrically and thermally so as not to provide a short circuit for either electron flow or heat through the coating rather than through the leg. Based on these requirements, several oxides have been selected as possible coating candidates. This paper discusses the development of slurry processes to deposit these oxides coatings on thermoelectric materials.

Sublimation↗

NASA NTRS2019

Development of Solid State Electrolytes for Li-Metal Based High Capacity Battery

NASA future missions demand safe, high specific energy (>400 Wh/kg) batteries. Current state-of-the-art (SOA) lithium-ion batteries (LIBs) can only provide ~150-200 Wh/kg in energy capacity, which is unable to meet NASA's future energy goals, and also pose safety issues due to the use of liquid flammable electrolyte. There are intense on-going development activities to increase battery energy density. The use of Li metal as an anode material has emerged as one highly attractive option for achieving high-energy, next generation batteries. This is because Li has many advantages. It is the lightest metal, but also has the highest theoretical capacity. It also has the lowest potential, which boosts whole cell voltage, and Li metal is 100% active material and requires no binder. Thus, Li metal is an ideal anode material for high energy battery chemistries. Lithium metal based advanced battery chemistries are envisioned to be mission enhancing and, in many cases, mission enabling for future space and aeronautic applications. However, the reliable use of this exceptionally high capacity anode in a commercial rechargeable battery has not been achieved due to safety and reliability concerns resulting from thermal runaway and short-circuit issues due to dendritic growth on the Li metal anode from lithium plating during charge-discharge cycles. A solid state electrolyte, such as garnet/ceramic or solid polymer nanocomposite electrolyte, is a promising approach to make Li metal safely cycling. The solid state electrolyte is non-flammable and eliminates leakage and fire hazard by replacing the liquid flammable electrolyte. However, the low-ionic conductivity and high interfacial impedance are the key issues to be overcome. In this presentation, the research activities on solid state electrolyte development funded by the NASA Advanced Energy Storage System program and by the NASA Center Innovative Fund will be presented, and the progress and results will be also discussed.

Wu, James J.↗

NASA NTRSDate not supplied

Comparative Analysis of Thermal Runaway Heat Output as a Function of Trigger Mechanism and Cell Format

High demand for energy storage systems across many fields drives the need for safe and reliable Li-ion batteries. In order to assess the risk of using such batteries in various applications, many types of abuse tests have been developed to push battery cells to their limits and learn how they fail. In this work, internal short circuit (ISC) tests, nail penetration tests, and thermal tests were used to trigger thermal runaway in D-cell, 18650, and 21700 Li-ion cells. High-speed radiography was used to gain insight to the propagation of thermal runaway throughout the cell, while calorimetric and thermal data were recorded in real time. Post-test disassembly of the calorimeter allowed for any mass ejected from the cell to be analyzed and the distribution of mass through the calorimeter to be determined. The impact of cell geometry and trigger mechanism on post-test mass distribution, thermal runaway propagation and internal cell temperature are discussed.

Lithium-ion battery; thermal runaway; calorimetry;↗

NASA NTRSDate not supplied

Battery Failure Databank

The Battery Failure Databank contains thermal runaway results gathered from nearly 300 small format fractional thermal runaway calorimetry (S-FTRC) experiments. A majority of these experiments were conducted at synchrotron facilities where high-speed x-ray videography was conducted of the cell while tested inside of the S-FTRC. The databank is a two-component system which consists of a Microsoft ExcelTM spreadsheet which provides S-FTRC results in tabular format and a radiographic video library containing the high-speed x-ray videos. Overall, the databank provides thermal results from S-FTRC experiments conducted on a mixture of commercially available lithium-ion (Li-ion) cells and specialized Li-ion test cells with varying cell format (18650, 21700, and D-cell) and trigger mechanism (heaters, heaters plus internal short circuiting device, and nail penetration). The radiography video component provides insight into the initiation and propagation of TR in the cells, in addition to consequences of TR measured by the FTRC. Fractions of mass ejected for the cell types are separated into regimes based on the different failure modes of the cells, such as purely venting, partial ejection, and total ejection. With knowledge of the rate and characterization of the internal degradation of the cells during TR, and the amounts of mass ejected and unrecovered, the extent of TR, and therefore the mitigation of TR, is revealed relative to cell types and failure modes.

Lithium-ion battery↗

NASA NTRS2020

Popcorning Failures in Polymer and MnO2 Tantalum Capacitors

Popcorning is a well-known effect in plastic encapsulated microcircuits (PEM) and it occurs in chip tantalum capacitors. The sensitivity of components to the presence of moisture during soldering is characterized by the moisture sensitivity level (MSL); however, contrary to PEMs, there is no standard procedure for establishing MSL for tantalum capacitors.The effect of absorbed moisture on soldering related degradation and failures in tantalum capacitors have not been studied properly yet, and there is no sufficient information regarding the difference in the sensitivity to soldering between polymer and MnO2 capacitors. In this work, 16 types of polymer and 9 types of MnO2 tantalum capacitors with different moisture content have been tested before and after reflow soldering. The level of moisture release during soldering has been estimated and thermo-mechanical analysis used to assess deformation of capacitorsduring soldering simulations. Results show that moisture uptake in similar parts is approximately two times greater in polymer than in MnO2 capacitors. Cracking of the case and degradation of parameters can occur in both types of parts, but MnO2 capacitors are much more likely to fail catastrophically with a short circuit and possible ignition during the first power-on cycle. This type of failure in MnO2 capacitors is lot-related, can occur even at derated voltages and relatively low levels of moisture sorption that corresponds to room conditions. Baking before soldering is an effective measure to prevent failures even in lots susceptible to popcorning damage.

Capacitor↗

NASA NTRS2021

Effect of Soldering on Polymer and MnO2 Tantalum Capacitors

Soldering might have a strong effect on performance and reliability of most surface mount technology components, including tantalum capacitors. High quality tantalum capacitors are likely the only type of components where soldering simulation is the first step during screening. Nevertheless, post-soldering failures of tantalum capacitors happen and require additional analysis. Popcorning is a well-known effect in plastic encapsulated microcircuits (PEM) and it occurs also in chip tantalum capacitors. The sensitivity of parts to the presence of moisture during soldering is characterized by the moisture sensitivity level (MSL); however, contrary to PEMs, there is no standard procedure for establishing MSL for tantalum capacitors. The effect of absorbed moisture on soldering related degradation and failures in tantalum capacitors have not been studied properly yet, and there is no sufficient information regarding the difference in the sensitivity to soldering between polymer and MnO2 tantalum capacitors. In this work, 16 types of polymer and 9 types of MnO2 cathodes tantalum capacitors with different moisture content have been tested before and after reflow soldering. The level of moisture release after soldering has been estimated and thermo-mechanical analysis used to assess deformation of capacitors during soldering simulations. Results show that moisture uptake in similar parts is approximately two times greater in polymer than in MnO2 capacitors. Cracking of the case and degradation of parameters can occur in both types of parts, but MnO2 capacitors are much more likely to fail catastrophically with a short circuit and possible ignition during the first power-on cycle. This type of failure in MnO2 capacitors is lot-related, can occur even at derated voltages and relatively low levels of moisture sorption corresponding to room conditions. Baking before soldering is an effective measure to prevent failures even in lots susceptible to popcorning damage. Recommendations for baking and testing to establish MSL are suggested.

Alexander Teverovsky↗

NASA NTRS2021

Effect of Preconditioning on Post-Soldering Failures in Tantalum Capacitors

Soldering have a strong effect on performance and reliability of most surface mount technology components, including tantalum capacitors. High quality tantalum capacitors are likely the only type of components where soldering simulation is the first step during screening. Nevertheless, post-soldering failures of tantalum capacitors do happen and require additional analysis. Popcorning is a well-known effect in plastic encapsulated microcircuits (PEM) and it occurs also in chip tantalum capacitors. The sensitivity of parts to the presence of moisture during soldering is characterized by the moisture sensitivity level (MSL); however, contrary to PEMs, there is no standard procedure for establishing MSL for tantalum capacitors, and standard J-STD-020 is applicable partially only. In this work, the effect of absorbed moisture on soldering related degradation and failures in tantalum capacitors have been studied using 22 types of polymer and 11 types of MnO2 cathodes tantalum capacitors including single and multianode parts. The amount of moisture released during soldering has been estimated by measurements of mass and capacitance variations. Results show that moisture uptake in similar parts is approximately two times greater in polymer than in MnO2 capacitors. Cracking of the case and degradation of parameters can occur in both types of parts, but MnO2 capacitors are much more susceptible to catastrophic short circuit failures and their ignition is possible during the first power-on cycle. This type of failure in MnO2 capacitors is lot-related, can occur even at derated voltages and relatively low levels of moisture sorption corresponding to room conditions. Baking before soldering is an effective measure to prevent failures even in lots susceptible to popcorning damage. Recommendations for testing to establish MSL and for baking to reduce the probability of failures are suggested.

tantalum polymer capacitors↗

NASA NTRSDate not supplied

Design Considerations for Practical Li-S Batteries for Electric Aviation

The development of high-energy, high-safety, and high-power batteries beyond electric automotive standards is critical for future electric aviation applications. Non-volatile solid-state electrolytes (SSE) offer many promising advantages over traditional flammable liquid electrolytes. Solid-state electrolytes may be an enabling technology for certain battery chemistries by preventing detrimental interactions with liquid electrolytes, for example prevention of the dissolution of intermediates in lithium-sulfur common in traditional liquid organic solvents. However, significant manufacturing challenges must be overcome before the adoption of such technology. This research was conducted to identify processing techniques for producing solid-state battery components with practical dimensions and weights for enabling high specific energy cells. Traditional research has identified a range of very high theoretical ionic conductivities but are impractical due to their instability or inability to be manufactured. Electrolytes explored in this study were produced as sulfide-polymer composites with densified thicknesses below 40 micron using a tape-casting technique and thermoplastic elastomer binder. The combination of high chemical compatibility and flexibility produced robust films that had moderate impact on the ionic conductivity but was capable of dramatically reducing the parasitic mass. Despite minimal conductivity losses, films were produced 10-15 times thinner than comparable bulk powder electrolytes thus leading to overall lower film resistance. Conductivity is maintained above 0.2mS/cm for composite electrolytes. Through the analysis of materials based on their physical properties, such as density, practical cells can be designed. Based on this, low density sulfide-solid-state electrolytes are a promising candidate for achieving the energy and safety metrics for electric aviation, however, further optimization of cathode microstructure and composite processing will be required to achieve the high power metrics and will be the focus of further studies. Additionally, fabrication challenges arise when utilizing metallic lithium foil, due to its soft nature, as overflow and mechanical short circuit can occur on assembly which remains a challenge to overcome before metallic lithium anodes can be fully realized.

batteries↗

NASA NTRS2021

Challenges with Heat Flux Calorimeters used in Arc Jets

Occasionally large errors have occurred in some of the calorimeters used in the arc jet facilities. Some slug calorimeters would measure twice the expected heat flux and some Coaxial TC calorimeters would measure half the expected heat flux. While these errors in heat flux measurements are easy to identify and discard / dismiss, the concern is that less spectacular errors are difficult to detect. This inspired a critical look at the calorimetry used to measure stagnation heat flux in the NASA Ames Arc Jet facilities. Numerous sources of error were investigated, and the culprit in the case of slug calorimeters was determined to be leaks in the stagnation calorimeter assembly resulting in flow along the side of the slug. In the case of the coaxial TC calorimeter, it is hypothesized that in some calorimeters there is a partial electrical short circuit in the Coaxial TC sensor element somewhere in the middle of the calorimeter.

Calorimeter↗