Showing papers on "Ullage published in 1986"

Orbital spacecraft resupply technology

Abstract: The resupplying of orbital spacecraft using the Space Shuttle, Orbital Maneuvering Vehicle, Orbital Transfer Vehicle or a depot supply at a Space Station is studied. The governing factor in fluid resupply designs is the system size with respect to fluid resupply quantities. Spacecraft propellant management for tankage via diaphragm or surface tension configurations is examined. The capabilities, operation, and application of adiabatic ullage compression, ullage exchange, vent/fill/repressurize, and drain/vent/no-vent fill/repressurize, which are proposed transfer methods for spacecraft utilizing tankage configurations, are described. Selection of the appropriate resupply method is dependent on the spacecraft design features. Hydrazine adiabatic compression/detonation, liquid-free vapor venting to prevent freezing, and a method for no-vent liquid filling are analyzed. Various procedures for accurate measurements of propellant mass in low gravity are evaluated; a system of flowmeters with a PVT system was selected as the pressurant solubility and quantity gaging technique. Monopropellant and bipropellant orbital spacecraft consumable resupply system tanks which resupply 3000 lb of hydrazine and 7000 lb of MMH/NTO to spacecraft on orbit are presented.

Vulnerability Methodology and Protective Measures for Aircraft Fire and Explosion Hazards. Volume 3. On-Board Inert Gas Generator System (OBIGGS) studies. Part 2. Fuel Scrubbing and Oxygen Evolution Tests

Abstract: : A basic consideration in designing an on-board inert gas generator system (OBIGGS) is to manage the evolution of dissolved oxygen in the fuel such that an inert ullage is maintained Fuel scrubbing, in which an inert gas is bubbled through the fuel, is the common method of removing dissolved oxygen Analytical modeling of the scrub gas requirements for fuel scrubbing required experimental data for validation Tests were conducted to determine if a model based on the ideal gas law, published solubility coefficients, and partial pressure relationships was valid The excellent agreement between calculated results and test data verified that such a model is valid Keywords: Fuel scrubbing; Oxygen evolution; Fuel tank inerting; On-board inert gas generator systems; Dissolved gases; Engine fires; Fuel fires

An analysis of ullage heat transfer in the orbital refueling system

Abstract: The Orbital Refueling System was an experiment flown on Shuttle Mission STS 41-G in October, 1984. Liquid hydrazine fuel was transferred back and forth from one spherical bladder tank to another using pressurized nitrogen as the driving force. Compressive heating of the ullage gas in the receiving tank could lead to a hazardous situation if any hydrazine leaked through to the ullage side of the bladder and was heated above about 175 F, where it can undergo spontaneous exothermic decomposition. Early analysis of the flight data indicated that the ullage compression process was much closer to an isothermal than an adiabatic one. In this study, a thorough review of the pertinent literature was used to make an a priori best-estimate for the ullage gas heat transfer coefficient (defining the Nusselt Number as a function of Reynolds and Rayleigh Numbers). Experimental data from the flight were analyzed in detail. It is evident that there is considerably more heat transfer than can be accounted for by conduction alone, but the observed increases do not correlate well with Reynolds Number, Rayleigh Number or vehicle acceleration. There are large gaps in the present understanding of convective heat transfer in closed containers with internal heat generation, especially in the presence of vibrations or other random disturbances. A program of experiments to fill in these gaps is suggested, covering both ground and orbital environments.

The ondek vapor dispersion model

Abstract: During bulk liquid cargo loading of chemicals and petrochemical products, vapors are released at or above deck level by the displacement of the ullage atmosphere in an empty tank. These vapors mix with the air and begin to spread out from the discharge point, becoming more dilute as they move downward. The relative vapor hazards on deck can be determined by estimating the size of the cargo vapor contour at a given concentration over the deck area of the vessel. ONDEK is a computer program designed to compute estimated vapor concentrations and superimpose a plot of the computed contour over a schematic outline of the vessel.

Sizing an emergency venting system for a cryogenic dewar

Abstract: If the vacuum vessel that insulates a cryogenic dewar for a spaceborne experiment prior to launch is damaged, air will leak into the vacuum insulation space. As the sudden heat load causes the pressure to rise in the dewar, a safety disk in the emergency vent line will burst at the design pressure differential to allow vaporized cryogenic fluid to escape. The emergency vent line should be sized such that sufficient gaseous cryogen will be vented to keep the pressure inside the dewar below the design limit. On the other hand, the line should not be so large as to impose an unnecessary heat load on the dewar filled with cryogenic fluid. A vent line computer program was generated to compute the maximum flow rate allowed for a proposed vent line system. Parametric studies have been carried out for different burst disk pressure differentials, liquid cryogen ullage, and vent line sizes. These programs are useful for sizing an emergency venting system for a cryogenic dewar.