Space Shuttle External Tank Research Articles

An improved approach for tank purge modeling

Many launch support processes use helium gas to purge rocket propellant tanks and fill lines to rid them of hazardous contaminants. As an example, the purge of the Space Shuttle's External Tank used approximately 1,100kg of helium. With the rising cost of helium, initiatives are underway to examine methods to reduce helium consumption. Current helium purge processes have not been optimized using physics-based models, but rather use historical ‘rules of thumb’. To develop a more accurate and useful model of the tank purge process, computational fluid dynamics simulations of several tank configurations were completed and used as the basis for the development of an algebraic model of the purge process. The computationally efficient algebraic model of the purge process compares well with a detailed transient, three-dimensional computational fluid dynamics (CFD) simulation as well as with experimental data from two external tank purges.

Millimeter-Wave Detection of Localized Anomalies in the Space Shuttle External Fuel Tank Insulating Foam

The Space Shuttle Columbia's catastrophic accident emphasizes the growing need for developing and applying effective, robust, and life-cycle-oriented nondestructive testing (NDT) methods for inspecting the shuttle external fuel tank spray on foam insulation (SOFI). Millimeter-wave NDT techniques were one of the methods chosen for evaluating their potential for inspecting these structures. Several panels with embedded anomalies (mainly voids) were produced and tested for this purpose. Near-field and far-field millimeter-wave NDT methods were used for producing images of the anomalies in these panels. This paper presents the results of an investigation for the purpose of detecting localized anomalies in several SOFI panels. To this end, continuous-wave reflectometers at single frequencies of 33.5, 70, or 100 GHz representing a relatively wide range of millimeter-wave spectrum [Ka-band (26.5-40 GHz) to W-band (75-110 GHz)] and utilizing different types of radiators were employed. The resulting raw images revealed a significant amount of information about the interior of these panels. However, using simple image processing techniques, the results were improved in particular as it relates to detecting the smaller anomalies. This paper presents the results of this investigation and a discussion of these results.

System for Orbital Recovery of Space Shuttle's External Tank

The orbital recovery of the external tank (ET), backbone of the U.S. space transportation system, can be considered enormously important for the future development and colonization of space. America's ability to respond to the many space opportunities on the horizon of research, commercialization and planetary science depend on the resiliency of the space transportation system, and especially on the use of the external tank in space. The use of ETs—as launch stages for planetary exploration, as large platforms in either low Earth orbit or geosynchronous Earth orbit to coorbit with other payloads requiring human interaction, or as an element of support for the next part of space station Freedom—could be of fundamental importance. The purpose of this paper is to describe a method for the orbital construction of the device and the corresponding recovery of the ET.

A millimeter wave technique for measuring ice thickness on the Space Shuttle's external tank

The external fueltank of the Space Shuttle contains extremely lowtemperature propellents. A layer of material known as SOFI (Spray-On Foam Insulation) covering the outside of the fueltank provides thermal insulation between the aluminum surface of the fueltank and the ambient air. In spite of this insulation, under certain conditions ice formation will occur on the surface of the SOFI. Ice on the external fueltank can be detrimental to the launch and it is important to detect its presence and measure its thickness. This paper describes the design of a millimeter-wave radiometer technique developed for this purpose. The design is based on model calculations and measurements of the emission properties of a panel from the external fueltank performed at 35, 94 and 140 GHz. Two sets of measurements were performed, one for the unmodified rough-surface SOFI panel and another for a panel whose surface was sanded down to produce a smooth surface interface with the ice cover. The latter was used to evaluate the results of radiative transfer calculations which are much easier to perform for multilayer structures with plane boundaries. We present experimental evidence demonstrating that the technique developed can accurately predict ice thickness in the case of the smooth-surface SOFI panel. For the original (rough-surface) panel, the emission levels observed were considerably higher than predicted by the model. Both cases however exhibited comparable sensitivities to ice thickness (∼ K/mm at 35 GHz, 4 K/mm at 94 GHz, and 5 K/mm at 140 GHz).

Lunar habitat concept employing the Space Shuttle external tank

The space shuttle external tank, which consists of a liquid oxygen tank, an intertank structure, and a liquid hydrogen tank, is an expendable structure used for approximately 8.5 min during each launch. A concept for outfitting the liquid oxygen tank-intertank unit for a 12-person lunar habitat is described. The concept utilizes existing structures and openings for both man and equipment access without compromising the structural integrity of the tank. Living quarters, instrumentation, environmental control and life support, thermal control, and propulsion systems are installed at Space Station Freedom. The unmanned habitat is then transported to low lunar orbit and autonomously soft landed on the lunar surface. Design studies indicate that this concept is feasible by the year 2000 with concurrent development of a space transfer vehicle and manned cargo lander for crew changeover and resupply.

Utilization of space shuttle external tank materials by melting and powder metallurgy

The Crucible Melt Extraction Process was demonstrated to convert scraps of aluminum alloy 2219, used in the Space Shuttle External Tank, into fibers. The cast fibers were then consolidated by cold welding. The X-ray diffraction test of the cast fibers was done to examine the crystallinity and oxide content of the fibers. The compressive stress-strain behavior of the consolidated materials was also examined. Two conceptual schemes which would adapt the as-developed Crucible Melt Extraction Process to the microgravity condition in space were finally proposed.

Aeroelastic characteristics of the Space Shuttle external tank cabletrays

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

PERUN—Space shuttle external tank used as a space station

This paper describes the results of a study project which has been conducted by a Student Working Group for Astronautics of the Planetarium of Praha. It deals with the possibility of converting an expended Space Shuttle External Tank into a space station, a permanently manned orbital facility. The space station was designed economically by using much off-shelf hardware developed for earlier space projects. It is compatible with the Space Transportation System which will operate in the 1980s. It is proposed that mission dependent experimental equipment be carried aboard Spacelab modules which should be exchanged during periodic revisits by the Space Shuttle. The key functions of the proposed space station are discussed, such as power supply, thermal control, trajectory corrections, logistics, etc. In our project we have arrived at a Space Station carrying a permanent crew of 8 people, orbiting the Earth at an altitude of 390 km, resupplied by STS every 80 days.