Research and development of fuel cell materials often focuses on designing and discovering materials which will reduce the cost or improve the durability of an individual subcomponent. Examples of ...recent focus areas include non-Pt group metal catalysts, noncarbon catalyst supports, and nonfluorinated membranes. These studies rarely look at the entire system to comprehend the impact of these materials on the cost of ownership to the customer, including vehicle and fuel costs. This perspective takes a holistic look at the impact of functional materials on automotive fuel-cell systems and provides direction on which material properties will provide the greatest benefit. It also provides guidance on which material classes are the most likely to enable the achievement of systems which will result in the successful commercialization of light-duty fuel-cell vehicles.
With NASA's direction set to further explore Mars with both robotic and human exploration, an Entry, Descent and Landing (EDL) vehicle with the ability to place large payloads on the Martian surface ...is essential. The scheme utilized by Curiosity has limitations. Work being done by Masten along with several NASA centers and other commercial firms on a dual thrust axis lander, known as XEUS, provides the basis for an economical Martian EDL vehicle. The XEUS program was conceived as a result of the Augustine Commission's observation that a lander is not affordable in an effort to produce an affordable lander. The general approach is to add a mission specific kit to an upper stage that includes additional landing thrusters and landing gear to conduct a rocket powered vertical landing while the vehicle is in a horizontal attitude. The addition of aerodynamic structures and thermal protection systems to the mission kit allow aerocapture, entry, descent, and landing on worlds with a significant atmosphere such as Mars. Using the current Centaur used on Atlas V, the planned Advanced Common Evolved Stage (ACES) which is to be used on both Atlas and Delta launch vehicles, or NASA's Cryogenic Propulsion Stage (CPS) for SLS, we found that payloads ranging in size from 1.5mT to 60mT can be landed on Mars and returned to orbit. The use of shared propulsion stages that would be used for launch vehicles, including Centaur, ACES, and SLS CPS allow high mass fraction landers with large payload capability without designing and manufacturing new large vehicles. The large mass fraction reduces the number of launches required and reduces or eliminates the need for additional in-space stages. The large mass fraction also reduces the number of propulsive stages needing to be designed by handling both descent and ascent with a single vehicle. For long term sustainability, the use of a single descent/ascent stage eliminates the clutter of descent stages left on the surface. The large cryogenic propellant tanks ease the aerodynamics and thermal conditions of aerocapture and entry. Landing with the primary vehicle axis in a horizontal attitude, astronaut and equipment access to the Martian surface is made far easier and safer.
Research and development of fuel cell materials often focuses on designing and discovering materials which will reduce the cost or improve the durability of an individual subcomponent. Examples of ...recent focus areas include non-Pt group metal (PGM) catalysts, non-carbon catalyst supports, and non-fluorinated membranes. These studies rarely look at the entire system to comprehend the impact of these materials on the cost-of-ownership to the customer, including vehicle and fuel costs. This perspective takes a holistic look at the impact of functional materials on automotive fuel cell systems and provides direction on which material properties will provide the greatest benefit. Furthermore, it also provides guidance on which material classes are the most likely to enable the achievement of systems which will result in the successful commercialization of light-duty fuel cell vehicles.
The Autonomous Ascent and Descent Powered-Flight Testbed (ADAPT) is a closed-loop, free-flying testbed for demonstrating descent and landing technologies of next-generation planetary landers. The ...free-flying vehicle is the Masten Space Systems Xombie vertical-takeoff, vertical-landing suborbital rocket. A specific technology ADAPT is demonstrating in the near-term is Guidance for Fuel-Optimal Large Diverts (G-FOLD), a fuel-optimal trajectory planner for diverts during powered descent, which is the final kilometers of descent to landing on rocket engines. Previously, ADAPT used Xombie to fly optimal large-divert trajectories, extending Xombie's divert range to 750 m. However, these trajectories were planned off-line with G-FOLD. This paper reports the successful Xombie flight demonstrations of large diverts using G-FOLD on board to calculate divert trajectories in real time while descending. The culminant test flight of the last year was an 800 m divert that was initiated at an altitude of 290 m while moving away from and crosswise to the landing pad. Hence, G-FOLD had to calculate a constrained divert trajectory that reversed direction, was fully three-dimensional, with horizontal motion nearly three times the initial altitude, and it did so in ∼100 ms on board Xombie as it was descending. Xombie then flew the divert trajectory with meter-level precision, demonstrating that G-FOLD had planned a trajectory respecting all the constraints of the rocket-powered vehicle. The steps to reach this flight demonstration of on-board generation of optimal divert trajectories and the system engineering for future ADAPT payloads are also presented.
This paper investigates the history and current state of commercial robotic launch vehicle testbeds available to demonstrate landing technologies required for extraterrestrial vertical landing.
The decomposition of hydrazine (Nsub 2Hsub 4) in near-critical and supercritical water is studied by in situ Raman spectroscopy. A high-pressure, high-temperature optical cell equipped with diamond ...windows allows us to perform Raman measurements at up to 430degreeC and 350 atm of water. Using the optical cell as a steady-state flow reactor, the decay of hydrazine and the production of ammonia are followed optically as a function of reaction time to yield an effective first-order rate constant for decomposition of 0.32 ssup minus1 at 400degreeC. 20 refs., 3 figs.
The Experimental Enhanced Upper Stage (XEUS) offers a path to reduce costs and development time to sustainable activity beyond LEO by equipping existing large cryogenic propulsion stages with MSS ...VTVL propulsion and GNC to create a large, multi-thrust axis lander. Conventional lander designs have been driven by the assumption that a single, highly reliable, and efficient propulsion system should conduct the entire descent, approach, and landing. Compromises in structural, propulsion, and operational efficiency result from this assumption. System reliability and safety also suffer. The result is often an iterative series of optimizations, making every subsystem mission-unique and expensive. The XEUS multi-thrust axis lander concept uniquely addresses the programmatic and technical challenges of large-mass planetary landing by taking advantage of proven technologies and decoupling the deorbit and descent propulsion system from the landing propulsion system. Precise control of distributed, multi-thrust axis landing propulsion units mounted on the horizontal axis of a Centaur stage will ultimately enable the affordable deployment of large planetary rovers, uncrewed base infrastructure and manned planetary expeditions. The XEUS lander has been designed to offer a significantly improved mass fraction and mass to surface capability over conventional lander designs, while reducing airlock/payload to surface distances and distributing plume effects by using multiple gimbaled landing thrusters. In utilizing a proven cryogenic propulsion stage, XEUS reduces development costs required for development of new cryogenic propulsion stages and fairings and builds upon the strong heritage of successful Centaur and MSS RLV flights.
The decomposition of CH
OH and C
OH in supercritical water was studied in a flow reactor tube (Ni/Mo/Cr/Fe alloy) in the temperature range 597 ≤
/K ≤ 797 at a pressure of
= 315 bar for technical ...application of scH
O for hazardous chemical waste destruction. The CH
OH and C
OH concentrations in the liquid as a function of the residence times were determined by a Raman spectrometer.
The CH
OH and C
OH resp. decay followed first order kinetics and a rate constant
(653 K) = 1.3 × 10
s
for CH
OH and
(653 K) = 5.5 × 10
s
for C
OH was determined. The rate constant
was found to be independent of the initial CH
OH concentration in the mass fraction range 0.002 ≤
≤ 0.04. The rate depended on the history of the reactor. Treatment with NH
OH, C
OH or with H
at
= 653 K, did not change the rate. Treatment with HNO
/H
, however, at
= 838 K reduced the rate by about a factor of 1000.
The Arrhenius-activation energy over the above temperature range was determined to be
= 164 kJ/mol for methanol and
= 145 kJ/mol for ethanol.
The major products from methanol decomposition were CH
, H
, and CO
as observed by gas chromatography and CH
and CO
by FTIR-spectrometry. No other products were found. The products were not effected by the pretreatment of the reactor wall. A non-radical mechanism, which explains the formation of only these products, will be discussed.
An analysis of the importance of digital ethnography in the modern world. The article discusses how the business world embraces digital ethnography, examines its benefits, and includes a case study ...on the topic (a project focused on Valentine's Day).
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