Entry Vehicle Research Articles

Nature-based tourism in Indian protected areas: New challenges for park management

Previous research indicates that numbers of visits to protected areas (PAs) are declining in wealthy countries while foreign visitation is increasing in less-wealthy countries. We focus on India to discern trends and implications of nature-based tourism in an emerging economy. We interviewed 91% of tourist facilities around 10 PAs to assess visitation, employment, and practices. Average growth rate was 14.9% (from −7% in Bandipur to 44% in Periyar from 2002 to 2008) and 80% are domestic tourists. Many facilities (72% post 2000) are recently constructed and 85% occur within 5 km of PAs. Clustering of facilities in some PAs might facilitate easier management of resource use and establishment of best practice guidelines. Contributions of facilities to local employment are marginal. Rules governing entry of people and vehicles vary widely. Domestic nature-based tourism potentially generates public support for conservation but adds to existing challenges of managing PAs already facing pressure from livelihood needs of local populations. Based on these trends, the increasing middle class in India is likely to generate future demand for nature-based tourism counter to trends in industrialized countries. There is urgent need for establishing and enforcing regulations to manage tourists, resource use, and land-use change around PAs.

Analysis of predictive entry guidance for a Mars lander under high model uncertainties

The problem of precision landing on Mars is now considered to be an essential challenge in the planned Mars missions. The paper focused on the guided atmospheric entry as a predominant phase in achieving a desired target state, as compared with the following parachute and powered descent. The predictive algorithms for the longitudinal guidance of a low-lift entry vehicle are treated. The purpose is to investigate applicability of the predictive strategy under possible high discrepancies between the on-board dynamic model and real environment while in entry trajectory. The comparative performance analysis based on computer simulation has been made between the standard one-parametric “shooting” predictive algorithm and a more complex two-parametric algorithm providing lower final velocity and, thus, expanding the interval of admissible downrange. However, both algorithms display considerable degradation of downrange accuracy in the cases when the actual drag force is larger than the modelled one. An acceptable solution has been found by including to both predictive guidance schemes an identification algorithm that repeatedly adapts the on-board model to varied environment in real time scale.

Zirconium diboride based coatings for thermal protection of re entry vehicles: Effect of MoSi 2 addition

The possibility of improving the performances of new generation re-entry vehicles as well as reducing the mission costs is closely connected to the development of new thermal protection systems: innovative heat shield materials, able to withstand higher temperature during the lift re-entry manoeuvre, would permit to improve reusability and easiness of maintenance as well as to increase the manoeuvrability and the payload of vehicles. UHTC materials, and, among them, Zirconium diboride based materials, exhibit outstanding oxidation and thermal shock resistance, high emissivity and very high melting temperature: all these properties make ZrB 2 based materials possible candidates for thermal protection systems of atmospheric re-entry vehicles. The experimental activities described in the present work were focused on ZrB 2 based coatings deposited by plasma spray, containing SiC and MoSi 2 in different ratios: the work aimed at understanding the role of MoSi 2 addition in the oxidation resistance. XRD analysis was carried out on starting powders and plasma sprayed coatings, in order to evaluate the transformations of crystalline phases induced by thermal deposition and to analyse the possible presence of amorphous phase; XPS was also used to study the coatings surface composition and to obtain information about chemical bonds in the materials. Oxidation behaviour was studied carrying out exposure tests up to 1800 °C in static air to compare and model the oxidation kinetics of the different compositions: results show the better behaviour of materials containing MoSi 2. Microstructure of as sprayed and oxidised samples was observed by means of SEM and analysed by EDS to understand the link between dispersion of Mo containing phases and the improved oxidation resistance.

The influence of size and charge of chitosan/polyglutamic acid hollow spheres on cellular internalization, viability and blood compatibility

Polymeric hollow spheres can be tailored as efficient carriers of various therapeutic molecules due to their tunable properties. However, the entry of these synthetic vehicles into cells, their cell viability and blood compatibility depend on their physical and chemical properties e.g. size, surface charge. Herein, we report the effect of size and surface charge on cell viability and cellular internalization behaviour and their effect on various blood components using chitosan/polyglutamic acid hollow spheres as a model system. Negatively charged chitosan/polyglutamic acid hollow spheres of various sizes 100, 300, 500 and 1000 nm were fabricated using a template based method and covalently surface modified using linear polyethylene glycol and methoxyethanol amine to create a gradient of surface charge from negative to neutrally charged spheres respectively. The results here suggest that both size and surface charge have a significant influence on the sphere’s behaviour, most prominently on haemolysis, platelet activation, plasma recalcification time, cell viability and internalization over time. Additionally, cellular internalization behaviour and viability was found to vary with different cell types. These results are in agreement with those of inorganic spheres and liposomes, and can serve as guidelines for tailoring polymeric solid spheres for specific desired applications in biological and pharmaceutical fields, including the design of nanometer to submicron-sized delivery vehicles.

A REAL-TIME LICENSE PLATE DETECTION SYSTEM FOR PARKING ACCESS

The automatic and real-time license plate detection system can be used as an access control entry of vehicles into the parking area. The problem is how to recognize the vehicles that will go into the parking lot and how to recognize various types of license plates in various light conditions quickly and accurately. In this research, the prototype was developed with a detection system to recognize the vehicles that will enter the parking area, and a license plate recognition system. In the license plate recognition system, the Fourier transform and Hidden Markov model method have proposed to detect location of license plate and as characters segmentation to recognize Indonesia license plates. The research results have shown that the developed prototipe system has successfully recognized all Indonesia license plates in several of light condition and camera position. The percentage of plate recognition in the real-time experiment is 84.38%, and the average execution time for all recognition process is 5.834 second.

Traffic Operation Performances at Roundabout Weaving Sections

There are frequent confluence and diffluence operations at roundabout weaving sections. The operation performances are complicated because the entry vehicles of turn-left and run-straight travel around the circle center. On the basis of the Shuma square in Dalian city roundabout survey using video cameras, some parameter performances were analyzed, which included the velocity distribution, the distance distribution of lane changing, the headway distribution of confluence vehicles, and vehicles on circulating lanes, as well as the application of accepted headways. Besides, some conclusions were drawn, for example, the vehicle velocity of outer circulating lane is larger than the inner circulating lane; the confluence vehicle velocity is smallest; the diffluence operation occurs later than the confluence operation; the confluence vehicle velocity has a tendency to increase with the accepted headway increase; the posterior gap is usually larger than the frontal gap in one accepted headway; the equivalent critical gap of multilane roundabouts is smaller than the critical gap of single-lane roundabouts.

Rapid Generation of Accurate Entry Landing Footprints

Rapid and reliable generation of the landing footprint of an entry vehicle is the key capability required for on-board determination of landing options. Under the conventional formulation of the maximum crossrange problem at specified downranges, the footprint problem is difficult to numerically solve. When inequality trajectory constraints are imposed, accurate determination of footprints becomes even more challenging. Using the quasi-equilibrium glide condition (QEGC) in entry flight, a near-optimal, closed-form bank angle control law is first developed for the class of problems including maximum-crossrange problem. Then it is shown that the footprint problem is equivalent to seeking the solutions of a series of much simpler problems of closest approach to a moving virtual target. The closest-approach problem is a univariate root-finding problem using the near-optimal control law. Common inequality entry trajectory constraints are enforced without any additional difficulty with appropriate velocity-dependent bounds of the bank angle by using the QEGC. As a result, an accurate and fully constrained landing footprint from any feasible initial condition can be obtained rapidly and very reliably. The validity of the method is verified with independent trajectory optimization software. Footprints for an entry vehicle in several different mission scenarios and constraint settings are generated to demonstrate the method.

Application of a Fault Accommodation Approach to a Re-***entry Vehicle

AbstractIn this paper a fault accommodation approach especially suitable for nonlinear dynamic inversion controllers is presented and applied to an atmospheric re-entry vehicle. The approach is based on the nominal/robustness decoupling principle used in recent high-performance architectures, reminiscent of anti-windup compensator approaches, and is well connected to the Youla-Kucera controller parameterizations used in the field of fault tolerant systems. The applicability of the approach is exemplified through its application to a high-fidelity nonlinear simulator of a reusable launch vehicle during re-entry which includes a nonlinear dynamic controller and an H-infinity based fault detection and isolation filter.

Nonequilibrium Radiation in Shocked Martian Mixtures

Shock-tube experiments are carried out to study the radiation emitted during a vehicle entry in the Mars atmosphere. CN and C 2 emission absolute intensity measurements are performed behind a strong shock wave in a CO-N 2 mixture with two different conditions of initial pressure and velocity. The CN violet system bands are shown to be self-absorbed. Temperatures and CN mole fractions are derived using this phenomenon in the nonequilibrium part of the shocked gas. C 2 absolute emission intensities are measured in different mixtures: CO-N 2 , CO 2 -N 2 , and pure CO 2 . Some comparisons with two-temperature calculations are presented. Such a two-temperature model fails to correctly reproduce CN and C 2 experimental radiative flux densities but is suitable for mole fraction predictions.

Experimental study of factors influencing maturing data phenomenon in warranty performance indicators

Warranty performance indicators are extensively used for comparison, prediction, and prioritisation purposes to support warranty cost reduction efforts. These efforts, however, are made challenging due to data maturation phenomena. Data maturation causes value of warranty performance indicators to change as new data become available, making comparison, prediction, and prioritisation tasks complex. Although this phenomena has been discussed in literature, there is a lack of understanding about the contributing factors. This paper provides an experimental simulation study involving three factors viz., staggered entry of vehicles, failure rate and months-in-service, and reports the findings of the study with managerial implications.

Energy-Based Control For an Over-Saturated Three-phase Intersection

Using the energy concept, the traffic flow controlled by traffic lights on an oversaturated single intersection is addressed in this paper. By regarding the flow entry of vehicles as the energy stored in the system, we show that the dissipative system theory can be applied. As a result, a state feedback control law is found in terms of the solution of an associated dissipation equation that renders the system non-accumulative, Le., to get out the over-saturation situation. The simulation results indicate that our control strategy guarantees a high degree of control benefit.

Hypersonic Wind Tunnel Test of a Flare-type Membrane Aeroshell for Atmospheric Entry Capsules

A flexible aeroshell for atmospheric entry vehicles has attracted attention as an innovative space transportation system. In this study, hypersonic wind tunnel tests were carried out to investigate the behavior, aerodynamic characteristics and aerodynamic heating environment in hypersonic flow for a previously developed capsule-type vehicle with a flare-type membrane aeroshell made of ZYLON textile sustained by a rigid torus frame. Two different models with different flare angles (45o and 60o) were tested to experimentally clarify the effect of flare angle. Results indicate that flare angle of aeroshell has significant and complicate effect on flow field and aerodynamic heating in hypersonic flow at Mach 9.45 and the flare angle is very important parameter for vehicle design with the flare-type membrane aeroshell.

An efficient drug delivery vehicle for botulism countermeasure

BackgroundBotulinum neurotoxin (BoNT) is the most potent poison known to mankind. Currently no antidote is available to rescue poisoned synapses. An effective medical countermeasure strategy would require developing a drug that could rescue poisoned neuromuscular synapses and include its efficient delivery specifically to poisoned presynaptic nerve terminals. Here we report a drug delivery strategy that could directly deliver toxin inhibitors into the intoxicated nerve terminal cytosol.ResultsA targeted delivery vehicle was developed for intracellular transport of emerging botulinum neurotoxin antagonists. The drug delivery vehicle consisted of the non-toxic recombinant heavy chain of botulinum neurotoxin-A coupled to a 10-kDa amino dextran via the heterobifunctional linker 3-(2-pyridylthio)-propionyl hydrazide. The heavy chain served to target botulinum neurotoxin-sensitive cells and promote internalization of the complex, while the dextran served as a platform to deliver model therapeutic molecules to the targeted neurons. Our results indicated that the drug delivery vehicle entry into neurons was via BoNT-A receptor mediated endocytosis. Once internalized into neurons, the drug carrier component separated from the drug delivery vehicle in a fashion similar to the separation of the BoNT-A light chain from the holotoxin. This drug delivery vehicle could be used to deliver BoNT-A antidotes into BoNT-A intoxicated cultured mouse spinal cord cells.ConclusionAn effective BoNT-based drug delivery vehicle can be used to directly deliver toxin inhibitors into intoxicated nerve terminal cytosol. This approach can potentially be utilized for targeted drug delivery to treat other neuronal and neuromuscular disorders. This report also provides new knowledge of endocytosis and exocytosis as well as of BoNT trafficking.

A probabilistic sizing tool and Monte Carlo analysis for entry vehicle ablative thermal protection systems

Implicit ablation and thermal response software was developed to analyse and size charring ablative thermal protection systems for entry vehicles. A statistical monitor integrated into the tool, which uses the Monte Carlo technique, allows a simulation to run over stochastic series. This performs an uncertainty and sensitivity analysis, which estimates the probability of maintaining the temperature of the underlying material within specified requirements. This approach and the associated software are primarily helpful during the preliminary design phases of spacecraft thermal protection systems. They are proposed as an alternative to traditional approaches, such as the Root-Sum-Square method. The developed tool was verified by comparing the results with those from previous work on thermal protection system probabilistic sizing methodologies, which are based on an industry standard high-fidelity ablation and thermal response program. New case studies were analysed to establish thickness margins on sizing heat shields that are currently proposed for vehicles using rigid aeroshells for future aerocapture missions at Neptune, and identifying the major sources of uncertainty in the material response.

Blunted-Cone Heat Shields of Atmospheric Entry Vehicles

Spacecraft entry into the atmosphere of a planet requires protection against the extreme temperatures that result from aerodynamic heating. This is normally achieved through use of a heat shield, which also provides the necessary aerodynamic braking and stability. The shape of the heat shield used varies considerably between spacecraft, and spherical and blunted-cone geometries are often employed. Theblunted-cone' heat shield has been developed through experimental design and computational simulation. Here, we demonstrate that this generic shape can be derived mathematically and yields the maximum stabilizing aerodynamic torque of all possible shapes (1). The derived single shape is universal, depending only on the center-of- mass, and provides invariance in static stability due to minor heat shield damage. The derived universal shape is obtained by requiring the aerodynamic torque be insensitive to small shape changes. Importantly, this heat shield shape gives the maximum stabilizing torque in both the continuum and free molecular (FM) regimes. For continuum flows, the obtained shape is always stable, regardless of the position of the center-of-mass. For FM flows, stability is dependent on the nature of the gas interactions with the surface and the position of the center-of-mass - even though the heat shield shape remains unchanged. This establishes that static stability may not be possible for some vehicle configurations, since the solution gives the shape that yields the maximum torque and this is unstable in some cases. Importantly, the design of practical heat shields involves numerous competing factors, which include the expected heat load and the craft volumetric efficiency, in addition to aerodynamic stability (2, 3). We thus emphasize that the presented results focus on only one component of this multi-objective problem. Nonetheless, the derived shape shows good agreement with the heat shields of previous entry vehicles, a comparison of which shall be given.

Shock Radiation Measurements for Mars Aerocapture Radiative Heating Analysis

NASA's In-Space Propulsion Technology program is supporting the development of shock radiation transport models for aerocapture missions to Mars and Venus. Phenomenological models of nonequilibrium shock radiation will be incorporated into high-fidelity flowfield computations used to predict the aerothermal environments for a Mars or Venus aerocapture entry vehicle. These models are validated with shock radiance measurements obtained at flight-relevant conditions. A comprehensive test series in the NASA Ames Electric Arc Shock Tube facility at a representative freestream condition was recently completed. The facility's optical instrumentation enabled spectral measurements of shocked gas radiation from the vacuum ultraviolet to the near infrared. The instrumentation captured the nonequilibrium postshock excitation and relaxation dynamics of dispersed spectral features. A description of the shock tube facility, optical instrumentation, and examples of the test data are presented.

Using Pressure- and Temperature-Sensitive Paint on the Aftbody of a Capsule Entry Vehicle

Pressure-sensitive and temperature-sensitive paint were used to visualize and quantify the surface interactions of reaction control system jets on the aftbody of capsule reentry vehicle shapes. The first model tested was an Apollo-like configuration and was used to focus primarily on the effects of the forward facing roll and yaw jets. The second model tested was an early Orion crew module configuration blowing only out of its forward-most yaw jet, which was expected to have the most intense aerodynamic heating augmentation on the model surface. This paper will present the results from the experiments, which show that with proper system design, both pressure-sensitive and temperature-sensitive paint are effective tools for studying these types of interaction in hypersonic testing environments.

Lightweight measures for electric vehicles

The two major hurdles for a successful market entry of electric vehicles are the limited range and the costs. The main cost driver is the electrochemical storage of the vehicle. Besides a decrease in production costs, the reduction of the energy consumption of the vehicle is an important adjusting lever to reduce costs. Hence, lightweight design is seen as a key aspect for the economical success of electric vehicles. Therefore, the “Institut fur Kraftfahrzeuge” (ika) of the RWTH Aachen University quantifies the saving potential of lightweight measures as well as their areas of application within an electric vehicle concept development.

A Simulation Tool for Hurricane Evacuation Planning

Atlantic hurricanes and severe tropical storms are a serious threat for the communities in the Gulf of Mexico region. Such storms are violent and destructive. In response to these dangers, coastal evacuation may be ordered. This paper describes the development of a simulation model to analyze the movement of vehicles through I-65, a major US Interstate highway that runs north off the coastal City of Mobile, Alabama, towards the State of Tennessee, during a massive evacuation originated by a disastrous event such a hurricane. The constructed simulation platform consists of a primary and two secondary models. The primary model is based on the entry of vehicles from the 20 on-ramps to I-65. The two secondary models assist the primary model with related traffic events such as car breakdowns and accidents, traffic control measures, interarrival signaling, and unforeseen emergency incidents, among others. Statistical testing was performed on the data generated by the simulation model to indentify variation in relevant traffic variables affecting the timely flow of vehicles travelling north. The performed statistical analysis focused on the closing of alternative on-ramps throughout the Interstate.

Diode-laser-based near-resonantly enhanced flow visualization in shock tunnels

Two new near-resonantly enhanced flow visualization techniques suitable for hypersonic low-density flows in shock or arc tunnels have been developed using seeded lithium (Li) metal as the refractivity-enhancing species. Two semiconductor lasers, single-longitudinal-mode and multimode, are compared with respect to their suitability as light sources for the technique. Transient wake-flow structures around a cylinder and a model of a planetary entry vehicle are visualized to demonstrate the capabilities of this comparatively inexpensive and simple visualization system. The images show flow features which are undetectable with conventional schlieren, shadowgraph, or interferometry techniques. Furthermore, the effect of density inhomogeneities along the line-of-sight outside the region of interest can be reduced by enhancing the refractivity only in selected parts of the flowfield.