Space assembly interruptability with applications to Space Station Freedom

The task of assembling large structures in space creates the possibility of construction interruptions. The unscheduled interruption of the assembly process may require abandoning the Station and returning to Earth. This interruption may be due to: crew illness/injury, Shuttle Orbiter mechanical failure, Orbiter or Station pressure loss, space debris damage, etc. If not handled properly these interruptions may jeopardize crew safety, Orbiter operations and the recoverability of the structure being assembled. The problem of space assembly interruptability was first addressed in January 1989 by astronaut Vance Brand (NASA-JSC) to Dr. George Morgenthaler at the University of Colorado - Boulder, at which time an Interruptability Team was organized at the University to study the problem of Space Station Freedom assembly interruptability. The approach which is being undertaken at the University of Colorado is to create a methodology capable of analyzing generic structures. This is being accomplished by developing a software tool, DYCA, to plan assembly sequences, and will be used in conjunction with INTERPRO, the INTERrupatbility PROgram, to analyze the Space Station Freedom assembly interruptability problem. Using an automated networking approach with some human interaction, the most favorable near-term safing plus options will be calculated in the event of an interruption. PERT network techniques are employed to analyze which of these near-term improvements provide the optimal long-term response, as far as impact on the time and cost of the overall project are concerned.