Shuttle Reaction Control Research Articles

History of Space Shuttle Rendezvous and Proximity Operations

Space Shuttle rendezvous missions present unique challenges that were not fully recognized when the Shuttle was designed. Rendezvous targets could be passive (i.e., no lights or transponders), and not designed to facilitate Shuttle rendezvous, proximity operations, and retrieval. Shuttle reaction control system jet plume impingement on target spacecraft presented induced dynamics, structural loading, and contamination concerns. These issues, along with limited reaction control system propellant in the Shuttle nose, drove a change from the legacy Gemini/Apollo coelliptic profile to a stable orbit profile, and the development of new proximity operations techniques. Multiple scientific and on-orbit servicing missions, and crew exchange, assembly and replenishment flights to Mir and to the International Space Station drove further profile and piloting technique changes. These changes included new proximity operations, relative navigation sensors, and new computer generated piloting cues. However, the Shuttle's baseline rendezvous navigation system has not required modification to place the Shuttle at the proximity operations initiation point for all rendezvous missions flown.

Lessons Learned During Redesign of Shuttle Reaction Control Thruster Pilot Seat Assembly

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.

Shuttle Diplomacy

The article highlights key points of a special National Research Council (NRC) committee on Space Shuttle upgrades’ ‘Upgrading the Space Shuttle’ report. The NRC committee reviewed two $1 billion-plus proposals for changing what NASA uses to propel the orbiters to space, and found that these could be broached only if more flights were planned, much more design review was done, and the Shuttle would be in service after 2012. The committee used NASA's grouping of the proposed upgrades into phases, with one being the least expensive, time-consuming, and risky, and four being the most costly, long term, and risk-prone. The committee studied another upgrade that would eliminate a hazardous material. The upgrade would modify the Shuttle's orbital manoeuvring and reaction control systems to use liquid oxygen and ethanol propellants instead of current engines' toxic N2O4 and monomethyl hydrazine propellants.

Neural Network for Positioning Space Station Solar Arrays

As a Shuttle approaches the Space Station Freedom for a rendezvous, the Shuttle's reaction control jet firinga pose a risk of excessive plume impingement load of Freedom solar arrays. The current solution to this problem, in which the array. are locked in a feathered position prior to the approach, may be neither accurate nor robust, and is also expensive. An alternative solution it proposed here: the active control of Freedom's. beta gimbals during the approach, positioning the arrays dynamically in such a way that they remain feathered relative to the Shuttle jet molt likely to cause an impingement load. An artificial neural network is proposed as a means to determining the gimbal angles that would drive plume angle of attack to zero.Such a network would be both accurate and robust, and could be less expensive to implement than the current solution. A network was trained via backpropagation, and results, which compare favorably to the current solution as well as to some other alternative, are presented. Other training options are currently being evaluated.

Active Vibration Damping of the Space Shuttle Remote Manipulator System

Controls-structures interaction is a technology currently under development for application to large flexible space vehicles. The goal of this technology is the improvement of spacecraft performance through active control of the structural dynamic response of the vehicle. This goal is particularly important for modern spacecraft designs where large size and reduced stiffness make structural response a significant contributor to vehicle dynamics. Analysis and design methods have been developed to analyze and predict flexible spacecraft performance, but the technology remains largely unvalidated by hardware experiments, demonstrations, or applications, particularly in-space flight applications. One potential application considered is to provide active damping augmentation of the Space Shuttle remote manipulator system. The objective of actively damping the manipulator is to demonstrate improved structural dynamic response following payload maneuvers and Shuttle reaction control system thruster firings. This paper describes an initial analysis effort to determine the feasibility of controlling the flexible dynamic response of the arm. The approach to the study is summarized and results from both linear and nonlinear performance analyses of candidate control laws are presented. Results indicate that significant improvement in dynamic response can be achieved through active control if measured arm tip acceleration was made available for feedback.

The Development and Testing of the Space Shuttle Reaction Control System

The Space Shuttle Reaction Control System design requirements, regimes of operation, and physical characteristics are described to show how they influenced the subsystem design. An overall RCS description and discussion of several components including the thruster, propellant tank, AC propellant isolation valves, and burst disc pressure relief valve assembly are presented. The current status of the Forward Reaction Control System development tests at the NASA-White Sands Test Facility are discussed including test results and unique developments encountered as a part of the test program.