On contradiction between the cost of development and the cost of maintenance/support

Y. B. Karasik,
Thought Guiding Systems Corp.,
Ottawa, Canada.

Abstract:Some readers accused us in criticizing other authors without providing anything positive instead. We heeded to their concerns and decided to start publishing some educational materials as well. Our first essay is on the hot topic of the technical contradictions.

There are at least four different costs associated with any technical system. The cost of development, the cost of manufacturing, the cost of maintenance/support, and the cost of disposal/removal/destroying/deactivating/recycling. How are they inter-related ? Here we are primarily concerned with the inter-relations between the cost of development and the cost of maintenance.

It is well known that there is cheap design and costly design . How does it affect the cost of maintenance ? Would the expensive design make system easier/cheaper to maintain ?

Generally, there are no relationships between the costs. One can spend fortunes on design but it will not guarantee inexpensive maintenance. Nevertheless, a hasty design is, usually, more error prone (and, hence, results in more money spent on fixing problems afterwards). On the other hand, a thorough design usually results in a higher quality system, which requires less attention at the stage of exploitation.

There is a limitation to the thoroughness, of course. Too thorough design borders on convoluted design, which may give rise to a less reliable system. Thus, it is highly probable that for the same group of designers it will turn out that the cost of maintenance initially decreases and then increases [1] as the function of the time/effort spent on design.

Besides this, other circumstances may also cause the cost of development and the cost of support to become contradictory. For example, it is known from practice that the solid fuel rocket is easier ( and faster) to develop than a liquid fuel rocket. However, should it be reusable, the solid fuel rocket is more difficult/expensive to maintain. Nevertheless, when designing Shuttle, NASA opted for solid fuel reusable boosters because its R&D expenses were capped by $5 billion [2]. It is despite the NASA specialists knew in advance that such boosters would be more difficult to maintain than the ones that utilize the liquid fuel.

R E F E R E N C E S:

1. Darrell Mann, "C... increases and then decreases", The TRIZ-journal, January 2003.

2. Columbia accident investigation board report, Vol. 1, August 2003.