Search Results

This paper discusses some of the analytical decisions that an investigator must make during the course of a life support system trade study. Equivalent System Mass (ESM) is often applied to evaluate trade study options in the Advanced Life Support (ALS) Program. ESM can be used to identify which of several options that meet all requirements are most likely to have lowest cost. It can also be used to identify which of the many interacting parts of a life support system have the greatest impact and sensitivity to assumptions. This paper summarizes recommendations made in the newly developed ALS ESM Guidelines Document and expands on some of the issues relating to trade studies that involve ESM.

A summary of waste processes and waste process data is presented in the context of mission equivalent system mass. Storage, size reduction, drying, aerobic and anaerobic biodegradation, chemical oxidation, pyrolysis, and post processing are evaluated in the context of probable long-duration missions beyond LEO, and the probable quantities and types of wastes and of the other on-board systems. An assessment of the waste systems described in the ALS Reference Missions Document is presented, and rationale for some changes to these systems is provided.

Equivalent system mass (ESM) was defined in 1997 as an integral part of the Advanced Life Support project metric. It is particularly suited to comparing technologies that differ in mass, volume, power, cooling, and crew time during the early phases of a program. In principle, ESM can also be used to compare technologies that differ in other parameters. In practice, the necessary data is generally not available, and this limits this application. ESM has proven to be a useful tool. Like any tool, its strengths and weaknesses must be understood. This paper documents the history, capability and methods used in connection with ESM.