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Technical Paper

“Derivation of Conduction Heat Transfer in Thin Shell Toroids”

2000-07-10
2000-01-2487
This paper presents the derivation of the equations for circumferential, longitudinal and radial heat transfer conductance for a thin shell toroid or a segment of the toroid. A thin shell toroid is one in which the radius to thickness ratio is greater than 10. The equations for the surface area of a toroid or of a toroidal segment will also be derived along with the equation to determine the location of the centroid. The surface area is needed to determine the radial conductance in the toroid or toroidal segment and the centroid is needed to determine the heat transfer center of the toroid or toroidal segment for circumferential and longitudinal conductance. These equations can be used to obtain more accurate results for conductive heat transfer in toroid which is a curved spacecraft components. A comparison will be made (1) using the equations derived in this paper which takes into account the curvature of the toroid (true geometry) and (2) using flat plates to simulate the toroid.
Technical Paper

‘Bigelow Aerospace® Life Support Laboratory - Planning and Status’

2004-07-19
2004-01-2474
This Life Support Laboratory consists of a simulator of the spacecraft called Nautilus, which houses Air Revitalization Subsystem, Atmospheric Control and Supply, and Fire Detection and Suppression in the Equipment Area. There are supporting facilities including a Human Metabolic Simulator, simulated Low and Moderate Temperature Coolant Loop, chemical analysis bench, purified water supply, vacuum and gas supplies. These facilities are scheduled to be completed and start to operate for demonstration purposes by March 2005. There are an ARES Ground Model (AGM) and a Trace Contaminant Control Assembly in the ARS. The latter will be integrated with the AGM and a Condensing Heat Exchanger. The unit of AGM is being engineered, built, and will be delivered in early 2005 by EADS Space Division. These assemblies will be operated for sensitivity analysis, integration and optimization studies. The main goal is the achievement for optimal recovery of oxygen.
Technical Paper

some development problems with Large Cryogenic Propellant Systems

1960-01-01
600022
HEAT TRANSFER causes loading and starting design problems in large missile systems powered by cryogenic propellants. This manifests itself during loading as effective density variation, violent surface conditions, boiloff, and ice formation — problems which may be solved by insulating the tank. During starting it causes overheating and caviation — effects which may be reduced by recirculators and subcooled charge injections. The study described in this paper centers around liquid oxygen and its variations in heat flux rate, which affect liquid density, surface condition, and replenishing requirements. The problem areas are made apparent by consideration of a hypothetical missile system.*
Technical Paper

Zone of Influence of Porous Suction Tubes in Condensing Heat Exchanger for Space Systems

2008-06-29
2008-01-2075
A “next generation” condensing heat exchanger for space systems has to satisfy demanding operational requirements under variable thermal and moisture loads and reduced gravity conditions. Mathematical models described here are used to investigate transient behavior of wetting and de-wetting dynamics in the binary porous system of porous tubes and porous cold plate. The model is based on the Richard's equation simplified for the zero-gravity conditions. The half-saturation distance or the zone of influence of the porous annular suction tubes on the cold-plate porous material will be in the range of 1 to 10 cm for the time scales ranging from 100 to 10,000 seconds and moisture diffusivity in the range of D = 10-4 to 10-6 m2/s.
Technical Paper

Zero Gravity Phase Separator Technologies - Past, Present and Future

1992-07-01
921160
Spacecraft life support equipment is often challenged with two phase flow, where liquid and gas exist together. In the zero gravity environment of an orbiting spacecraft, the behavior of a liquid/gas interface is dominated by forces not usually observed in one “G” due to the overwhelming effects of gravity. The normal perceptions no longer apply. Water does not run down hill and bubbles do not rise to the surface. Surface energy, capillary forces, wetting characteristics and momentum effects predominate. Techniques and equipment have been developed to separate the liquid/gas mixture into its constituent parts with various levels of efficiency and power consumption.
Standard

Zero Acceptance Number Sampling Procedures and Tables for Inspection by Attributes of A Continuous Manufacturing Process

2015-07-01
CURRENT
EIA584
Conventional attribute sampling plans based upon nonzero acceptance numbers are no longer desirable. In addition, emphasis is now placed on the quality level that is received by the customer. This relates directly to the Lot Tolerance Percent Defective (LTPD) value or the Limiting Quality Protection of MIL-STD-105. Measuring quality levels in percent nonconforming, although not incorrect, has been replaced with quality levels measured in parts per million (PPM). As a result, this standard addresses the need for sampling plans that can augment MIL-STD-105, are based upon a zero acceptance number, and address quality (nonconformance) levels in the parts per million range. This document does not address minor nonconformances, which are defined as nonconformances that are not likely to reduce materially the usability of the unit of product for its intended purpose.
Technical Paper

ZERO-ODP REFRIGERANTS FOR LOW TONNAGE CENTRIFUGAL CHILLER SYSTEMS

1996-05-01
961320
This paper investigates the use of several zero-ozone depleting potential (zero-ODP) HFC refrigerants, including HFC-134a, HFC-227ca, HFC-227ea, HFC-236ea, HFC-236cb, HFC-236fa, HFC-245cb, and HFC-254cb, for centrifugal chiller applications. We took into account the thermodynamic properties of the refrigerant and aerodynamic characteristics of the impeller compression process in this evaluation.. For a given operating temperature lift, there are significant differences in the pressure ratio required by each refrigerant and this variation in pressure ratio directly affects compressor size, efficiency, and performance. A comparison of the HFC refrigerant candidates with CFC-114 shows that HFC-236ea, HFC-227ca and HFC-227ea are viable alternatives for centrifugal water chillers. HFC-236ea has properties closest to CFC-114, and will result in comparible performance, but will require a slightly larger impeller and a purge system.
Technical Paper

X-29 Fuel/Auxiliary Oil Systems Thermal Management

1986-07-14
860913
The X-29 Fuel/Auxiliary Oil Thermal Management System provides total aircraft accessory oil cooling, including both flight and combined hydraulics, Integrated Drive Generator oil, and Accessory Drive Gearbox oil, with onboard fuel. Fuel cooling rates that are independent of engine demand are achieved through the use of a recirculation loop. Recirculation is minimized by maintaining the engine fuel inlet temperature at the maximum allowable. Fuel cooling results in lower, more uniform subsystem oil temperatures, less ram drag, and smaller, lighter-weight heat exchangers. Initial design studies and laboratory development testing will be discussed, along with comparisons of analytical predictions with flight test results.
Technical Paper

Working Fluid De-freezing in Radiator on Base of LHP

2007-07-09
2007-01-3199
Selection of working fluid is one of the main criterions for designing of heat pipes thermal control systems (TCS) for space application. In this paper we will describe how we solved the task of development of the TCS with working fluid of high thermal physical properties. In 2004-2006 we developed the Engineering model of Deployable Radiator based on Loop Heat Pipe by CAST purchase order. It was developed for qualification tests. Ammonia application as LHP working fluid is stipulated by its high thermal physical properties. However Ammonia freezing temperature is of minus 77ºC. Such fact impedes Ammonia application when operation temperatures of LHP Radiator are lower than this value, for example, It takes several tens of hours to orbit a spacecraft and prepare it for work (at that moment the spacecraft is out of power supply) and the working fluid can be frozen in a condenser-radiator when the spacecraft being in the shadow over a long period of time.
Technical Paper

Wind and Temperature Database for Flight Planning

1981-10-01
811068
This paper discusses the importance of enroute wind conditions and the need for a wind measurement system which provides accurate and timely observations of wind and temperature conditions aloft. Recent advances in remote measurement of winds, temperature, and humidity such as the Stratospheric-Tropospheric radars and profilers developed at the National Oceanic and Atmospheric Administration’s Environmental Research Lab form the basis of such a system. A domestic system could and should be established using these devices together with a near real time winds aloft data dissemination network. Estimates of the saving in aircraft fuel consumption benefits range from 1 to 3 percent per year, or from $ 100 to $ 300 million for U.S. aviation system users at current prices and consumption.
Technical Paper

Wind Gusts - 0 - 300 ft Altitude - Homogeneous Terrain

1970-02-01
700342
This paper is concerned with the development of statistical models for the gust field in the lowest 300 ft of the atmosphere. It presents some of the highlights of the underlying physics principles, what is known about gusts, and how gusts affect aircraft. The difficulties of developing gust models are accounted for by the lack of data in particular areas and thus direct attention to the work required to provide the needed information.
SAE MOBILUS Subscription

Wiley SAE MOBILUS® eBook Package

2018-03-23
Committed to being the primary source for aerospace and ground vehicle engineering resources, SAE International has added the full compilation of our Wiley eBook collections to the SAE MOBILUS® technical resource platform. Purchasable as an annual subscription and containing the titles from the Wiley Aerospace Collection, the Wiley Automotive Collection, the Wiley Computer Systems Collection, and the Wiley Cyber Security Collection.
SAE MOBILUS Subscription

Wiley Aerospace Collection

2018-03-23
Purchasable as an annual subscription and containing 30 eBook titles, the Wiley Aerospace Collection covers valuable engineering subject matter, such as aircraft fuel systems, aerodynamics, and propulsion. The series also goes beyond engineering, including eBooks on planning, logistical issues, and how human behavior can be managed and controlled while operating aircraft.
Standard

White Paper to Support Supersession of MIL-S-8879C With AS8879C

2003-03-19
CURRENT
AIR5926
This paper was prepared to support supersession of MIL-S-8879C with Screw Thread Conformity Task Force selected industry standard AS8879C, published by the Society of Automotive Engineers (SAE). Other documentation changes will be covered by separate papers. Separate papers are anticipated for thread gaging issues, and thread gage calibration procedures. The STC-TF decided that the thread design standard needed to be completed before thread gage definition could be addressed. Thread gage definition has to be known before calibration procedures can be addressed.
Technical Paper

Weight Optimization of Fork and Axle of Main Landing Gear for an Unmanned Aerial Vehicle by Finite Element Analysis

2017-07-10
2017-28-1949
Unmanned Aerial Vehicles (UAV) are being deployed in military, law enforcement, search & rescue, scientific research, environmental & climate studies, reconnaissance and other commercial and non-commercial applications on a large scale. A design and development of landing gear system has been taken up for a UAV. This paper presents the design optimization of structural components of Wheel-Brake & Fork assembly pertaining to the Main Landing Gear (MLG) for a UAV. The wheel, fork, axle and brake unit constitute the wheel assembly. The wheel-brake assembly is assembled with the strut assembly and forms the Landing gear system. The Fork is the connecting member between the shock strut and the axle containing the wheel-brake assembly. As the fork and axle are subjected to shock loads while landing, the strength of these components are very much essential to withstand the dynamic loads.
Technical Paper

Weibull/Weibayes Analysis of Hydraulic Pump Malfunction Data

1983-10-03
831542
Premature wearout of augmentor hydraulic fuel pumps was being experienced in service on a fighter aircraft engine. The removal times ranged from 150 to 800 engine operating hours. Considerable effort had gone into the understanding of the physics of failure and overcoming this problem in a modified pump. However, there still remained the question of how best to proof test the new pump. The challenge was to demonstrate that the redesigned pump was significantly better than the old pump. The problems faced during design verification will be discussed in this case study. For example, does an accelerated test duplicate the service failure mode? When has an accelerated test run long enough to prove the redesign is in fact better than the old product? This paper illustrates the application of new technology to solve these research and development program problems through the use of Weibull and Weibayes Analysis.
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