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In an effort to help future crewed spacecraft thermal control analysts understand the characteristics of one-and two-loop Active Thermal Control Systems (ATCS), a comparison was made between the one- and two-loop ATCS architectures officially proposed for the Crew Exploration Vehicle (CEV) in Design Analysis Cycle 1 (DAC1) and DAC2, respectively.

The Orion Crew and Service Modules are often compared to the Apollo Command and Service Modules due to their similarity in basic mission objective: both were dedicated to getting a crew to lunar orbit and safely returning them to Earth. Both spacecraft rely on the environmental control, life support and active thermal control systems (ECLS/ATCS) for the basic functions of providing and maintaining a breathable atmosphere, supplying adequate amount of potable water and maintaining the crew and avionics equipment within certified thermal limits.

The Space Station represents an order of magnitude increase in complexity over current Spacecraft technologies and will seriously tax current analysis techniques. This program is capable of simulating atmospheric revitalization systems, water recovery and management systems, and single phase active thermal control systems.

The man-made ecosystem of any spacecraft is distinguished from the natural ecosystem as follows: (a) Man is the decisive part of the system defining the main requirements to its properties, functions and developing laws; (b) the processes of controlled substance turnover are accomplished in the limited number of technical units at rates substantially exceeding those of slow natural processes.

The Comet Rendezvous Asteroid Flyby (CRAF) mission involves seven years of flight from 0.6 to 4.57 Astronomical Units (AU), followed by about 915 days of maneuvering around a comet. Ground testing will characterize the very critical attitude control system thrusters' fuel consumption and performance for all anticipated fuel temperatures over thruster life. The ground test program characterization will support flight condition monitoring. A commercial software application hosted on a commercial microcomputer will control ground test operations and data acquisition using a newly designed thrust stand. The data acquisition and control system uses a graphics-based language and features a visual interface to integrate data acquisition and control.

This paper describes a model-based approach to diagnosing electrical faults in electrical power systems. Until recently, model-based reasoning has only been applied to physical systems with static, persistent states, and with parts whose behavior can be expressed combinatorially, such as digital circuits. Our research is one of a handful of recent efforts to apply model-based reasoning to more complex systems, those whose behavior is difficult or impossible to express combinatorially, and whose states change continuously over time. The chosen approach to representation is loosely based on the idea of the equation network proposed in [6]. This requires a more complex component and behavior model than for simpler physical devices. The resulting system is being tested on fault data from the SSM/PMAD power system breadboard being developed at NASA-MSFC [9].

This paper describes an innovative design of a new biofiltration test lab for investigating the capability of biofiltration process for removal of ersatz multi-component gaseous streams representative of spacecraft contaminants released during long-term space travel. The lab setup allows a total of 24 bioreactors to receive identical inlet waste streams at stable contaminant concentrations via use of permeations ovens, needle valves, precision orifices, etc.

A dual-membrane gas trap is currently used to remove gas bubbles from the Internal Thermal Control System (ITCS) coolant on board the International Space Station (ISS). The gas trap consists of concentric tube membrane pairs, comprised of outer hydrophilic tubes and inner hydrophobic fibers. Liquid coolant passes through the outer hydrophilic membrane, which traps the gas bubbles. The inner hydrophobic fiber allows the trapped gas bubbles to pass through and vent to the ambient atmosphere in the cabin. The gas trap was designed to last for the entire lifetime of the ISS, and therefore was not designed to be repaired. However, repair of these gas traps is now a necessity due to contamination from the on-orbit ITCS fluid and other sources on the ground as well as a limited supply of flight gas traps. This paper describes a novel repair technique that has been developed that will allow the refurbishment of contaminated gas traps and their return to flight use.

A Thermal control system is a necessary component in ensuring survival of the Space Station Freedom (SSF). The hostile space environment can produce surface temperatures from +250°F to −250°F depending upon orbital conditions, thermal control coatings and geometric configuration. The Passive Thermal Control System (PTCS) is required to maintain the interior surfaces above 62°F to prevent condensation and below 113°F to protect the crew. The Passive Thermal Control System includes multilayer insulaton (MLI), thermal control coatings (TCC), electric heaters, thermal isolators, and plumbing insulation. Electrical heaters or thermal isolators are required to prevent condensation at module locations where penetrations occur in the MLI or surfaces with significant exposure such as cupolas. Examples of these penetrations are windows, meteoroid/debris shield support structure, berthing mechanism area, trunnion/keel support structure, grappling fixture attachment, and plumbing lines.

It can further be integrated into a cold plate to receive heat from distributed sources such as spacecraft instruments. Isothermalization of the cold plate can be accomplished by incorporating heat pipes into the cold plate.

The objective of this study is to produce a prototype mixed solid waste pyrolyzer for spacecraft applications. A two-stage reactor system was developed which can process about 1 kg of waste per cycle.

Space Station Freedom employs a pump module to provide fluid pumping, fluid pressure and temperature regulation, and fluid management in its active thermal control system. The pump module utilizes a multifunction pitot pump for fluid pumping, a servo actuated vapor regulator for fluid pressure and temperature regulation, and an accumulator to aid with fluid management. Pump module component designs are tailored to the specific requirements of the thermal control system. Prior to use on the Space Station, the pump module will undergo a comprehensive test program that includes engineering development tests and flight qualification tests.

It is designed to remove every class of contaminants found in spacecraft cabin air, including alcohols, aldehydes, aromatics, ethers, esters, chlorocarbons, halocarbons, fluorosilanes, hydrocarbons, ketones, silicones, sulfides, and inorganics, and it is designed to operate continuously with minimal maintenance or periodic replacement major components.

The on-orbit automation currently planned for the Environmental Control and Life Support System (ECLSS) and the Internal Thermal Control System (ITCS) of the United States on-Orbit Segment (USOS) habitable modules of the International Space Station (ISS) are examined. The discussion includes an overview of the ECLSS, ITCS, and Command and Data Handling (C&DH) system, and features the direct applicability of the planned real-time software control functions to the planned on-orbit ECLSS/ITCS functions.

The system is comprised of a manipulator whose end-effector rigidly grasps a functional spacecraft, a six-axis force/moment (F/M) sensor placed at the interface of the spacecraft and the manipulator, and a control system. ...The controller takes the values of the force/moment as well as the manipulator's joint angles and velocities and issues torque command to drive the manipulator so that the motion of the spacecraft model in the presence of external forces replicates 0-g motion dynamics of a flight spacecraft. The control system can also modify the inertial properties of the spacecraft so as to match those of an actual spacecraft, even if the latter is flexible and the former is rigid. ...A system emulation that can be used for testing a spacecraft control system with all of its hardware in place, in a 1-g laboratory environment, is presented.

The Internal Thermal Control System (ITCS) has been developed jointly by Boeing Corporation, Huntsville, Alabama and Honeywell Engines & Systems, Torrance, California to meet the internal thermal control needs for the International Space Station (ISS). The ITCS provides heat removal for the critical life support systems and thermal conditioning for numerous experiment racks. The ITCS will be fitted on a number of modules on the ISS. The first US Element containing the ITCS, Node 1, was launched in December 1998. Since Node 1 does not contain a pump to circulate the fluid it was not filled with ITCS fluid until after the US Laboratory Module was installed. The second US Element module, US Laboratory Module, which contains the pumps and all the major ITCS control hardware, was launched in February 2001. The third US Element containing the ITCS, the US Airlock, was launched in July 2001.

The Early External Thermal Control System (EETCS) is the temporary system used to collect, transport, and reject waste heat from habitable volumes on the International Space Station (ISS). The EETCS collects heat from the Interface Heat Exchangers (IFHX) located on the US Laboratory module, circulates the working fluid, anhydrous ammonia, via the Pump and Flow Control Subassembly (PFCS), and rejects heat to space via two orthogonal stationary radiators. This temporary system has been active for over three years and is nearing the end of its utilization as a means of waste heat rejection for ISS pressurized modules. This paper provides a summary of the operational history of the EETCS and presents data from several interesting nominal and off-nominal events.

Long term space exploration poses considerable challenges in logistics since launch costs, weight, and volume are all limited. In space life support systems contaminants are generated due to the off-gassing of materials of construction and are also a by-product of crew metabolism. While carbon dioxide is a metabolic contaminant, its control is typically accomplished by a dedicated system, whereas the rest of the contaminants are controlled using a trace contaminant control system (TCCS). Currently, NASA employs various TCCS approaches depending on the mission type and duration. In the Extravehicular Mobility Unit (EMU) this is accomplished with activated carbon as well as strict control on materials of construction. The activated carbon is thermally regenerated in some EMU applications and the adsorbed contaminants are purged to the International Space Station (ISS) where they are subsequently removed.

The routine extravehicular activity (EVA) anticipated from the United States Space Station dictates that productivity be maximized for astronaut accessibility to information during the EVA, Ideally for Space Station EVA, this requires a “hands-free” operation, especially for intensive EVA scenarios such as satellite servicing and emergency or contingent operations. This hands-free access to information will be provided to the crewmember via a voice recognition & control system and a helmet-mounted projection display in the Space Station Extravehicular Mobility Unit (EMU). To demonstrate the capabilities of the combined system, a simulation program has been created which addreses the human factors required to effectively provide the crewmember with productive information during an EVA.

Because of the capability of extended accuracy, digital systems are indicated for guidance and control of spacecraft. Furthermore, by implementing these systems with integrated microelectronic components, substantial improvement in reliability can be expected. ...A study and experimental evaluation program was performed to apply such digital techniques to the spacecraft stabilization and control problem. Of major consideration were the selection of appropriate mathematical techniques for system analysis and the development of suitable fabrication methods for hardware implementation. ...A discrete state model of a spacecraft reaction wheel and jet attitude control system was developed and computer simulations were performed.