Modularity as an Enabler for Evolutionary Acquisition

SBIRS4 High (Crock, 2002; DSB/AFSAB, 2003) is an excellent example of how
requirement instability can lead to cost growth. Conceived in the mid-1990’s as an early warning system for missile defense, SBIRS High suffered from a series of management mis-steps. The original requirements called for detection of long-range missile launches. As the program progressed, the Air Force and new users levied additional requirements. For example, intelligence agencies wanted ground surveillance capability to detect rocket-engine tests. The Army wanted short-range missile such as SCUDs to be detected. Tracking and decoy/warhead detection was also desired.These additional missions led to conflicting needs. For example, detecting rocket tests requires high acuity sensors that can
discern small, low-contrast details; such sensors however have too high a false positive rate to be useful for a missile warning system. Solving/settling such conflicts is one of the reasons for cost growth from new/changed requirements (see Figure 1-1).