This decline is due to the accumulation of knowledge and the development of improved alternative techniques for evaluating missile systems. In addition, continually increasing computational capabilities streamline the development process by aiding design, development and evaluation. Political considerations have also driven down the numbers and restricted the possibilities for testing. For example, over flights of the continental United States are problematic, and a static testing procedure called Simulated Electronic Launch of Minuteman was introduced to compensate partially for the lack of flight tests fired from active-duty silos. The transfer of knowledge from non-military space activities to military missiles may also reduce flight testing requirements.
Redundancy means dead weight, and a multiplication of system cost and complexity.
A typical commercial launch is carried out only under the best weather conditions, and only after the rocket has been examined by an army of technicians. Moreover, the continuing series of unmanned launches, using rockets with long histories such as Atlas, Titan and Delta, is itself a de- facto testing program from which information is obtained to improve the rockets and their operational use. Even so, major upgrades of these systems have been accompanied by an expensive and embarrassing series of failures. Without flight testing, every new weapon or component risks catastrophic failure with a high probability. In the past few years the US military has diverted increasing intelligence assets to cover developing countries and regions considered dangerous.