Many people have a preconceived notion that “sustainment” and “sustainability” only refer to environmental sustainability, which is unfortunate. Sustainment and sustainability are concepts that are much older and broader than just the environmental context that the popular media most often relates them to.
The origin of the word sustain is the Latin word sustenare, which means “to hold up” or “to support”. The modern use of the word sustain is to keeping something going or to extend its duration, , where the most common synonym for sustain is maintain. It is not uncommon for sustain and maintain to be interchangeably used, however, maintenance usually refers to activities that are targeted at correcting problems, while sustainment is a more general term referring to the management of system evolution.
The concept of sustainability is connected to nearly every discipline , e.g., environmental sustainability, business or corporate sustainability and technology sustainment, however, in this blog we are interested in technology sustainment. Although sustainability and sustainment are closely related in a semantic sense, environmental sustainability organizations almost never refer to what they are doing as sustainment or sustainment engineering. However, organizations that maintain systems (sustainment organizations) use both sustainment and sustainability to describe what they do.
Technology sustainment refers to all activities necessary to : a) keep an existing system operational so that it can successfully complete its intended purpose; b) continue to manufacture and install versions of the system that satisfy the original requirements; and c) manufacture and install revised versions of the system that satisfy evolving requirements.
The most widely circulated definition of sustainability is attributed to the Brundtland Report , which is often paraphrased as “development that meets the needs of present generations without compromising the ability of future generations to meet their own needs.” This definition was created in the context of environmental sustainability, however, it is useful and applicable for defining all types of sustainability. For example, for technology sustainment, “present and future generations” in the Brundtland definition can be interpreted as the users and maintainers of a system. Unfortunately, the definition of sustainability has been customized by many organizations to serve as a means to an end, and in some cases it has been abused to serve special interests and marketing.
A good general definition of sustainment is : “development, production, operation, management, and end-of-life of systems that maximizes the availability of goods and services while minimizing their footprint”. In this case the terms in the definition mean:
- “footprint” could represent any kind of impact that is relevant to the system’s stakeholders, e.g., cost (economics), human health, energy required, environmental, and/or other resource consumption (water, materials, labor, expertise, etc.)
- “availability” represents the fraction of time that a good or service is in the right state, supported by the right resources, and in the right place when the customer requires it
- “customer” could be an individual, a company, a city, a geographic region, a specific segment of the population, etc.
Note that this definition is consistent with both environmental and technology sustainment concerns.
A sustainment-dominated system is defined as a system for which the lifetime footprint significantly exceeds the footprint associated with making it . Where "footprint" has the same definition as above. Defining sustainment-dominated systems provides the opportunity to make a distinction between high-volume, low cost consumer products and more complex, higher-cost systems such as airplanes, infrastructure, and institutions. Non-sustainment-dominated products, which tend to be high-volume products, have relatively little investment in sustainment activities and the total time period associated with the product is short (short manufacturing cycle, short field life). Alternatively, sustainment-dominated products, which tend to be relatively low-volume expensive systems, have large sustainment costs and long manufacturing and/or field lives (see my "More Than Acquisition Costs - F-35" blog post in December 2016).
 Sutton, P. (2004). What is sustainability? Eingana, 27(1), pp. 4-9.
 Sandborn, P. and Myers, J. (2008). Designing engineering systems for sustainability, in Handbook of Performability Engineering, K.B. Misra, Editor, pp. 81-103 (Springer, London).
 Brundtland Commission (1987). Our Common Future, World Commission on Environment and Development.
 Sandborn, P. (2017). Cost Analysis of Electronic Systems, 2nd edition, World Scientific.