In any defense system, the various elements have to be alerted and generally "told what to do" before they can even begin to perform their functions. Always difficult, this problem is compounded enormously in the case of the multilayered system contemplated under SDI. A master command, control, communications, and intelligence (C3 I) system, in this case usually referred to as a battle-management system, must not only alert and instruct the first layer and initiate the entire defensive process, but it must also somehow instruct each layer in sequence, "handing off" the problem from one layer to the next as the attack progresses. In addition to the usual problems such systems face, a special problem, called "kill assessment," assumes importance here. Many of the proposed defensive systems either leave the RVs and other objects more or less intact, but nonfunctional, or break them into large fragments that may still look threatening. The overall battle-management system must somehow determine which RVs have been put out of action—that is, it must make a kill assessment and pass this assessment on to succeeding layers in order not to waste ammunition over and over again on objects that are already out of the battle. (The problem of kill assessment has been combined by SDIO with surveillance, acquisition, and tracking in a program package called SATKA.) Large quantities of data from the sensors and the battle satellites must be rapidly processed and the results assimilated and communicated to the satellites and to ground controllers.
The entire supersystem, battle management included, must perform all of its functions correctly the first time under actual battle conditions, and it must have an overall sensitivity threshold such that the entire defensive process is certain to be set in motion when the alarm is real
while, in the event of a false alarm, nothing at all is done. And there will be many opportunities for false alarms, especially if both sides deploy space-based defenses. Under such circumstances there would be a great many objects in space, and plenty of launchings from enemy territory to set the alarms ringing. Even if only one side has space-based defenses, operating and replenishing them involves events that might trigger operation of the entire system in a sort of autoimmune-like reaction.
Another unique problem of battle-management derives from the extremely short response times following a launch warning. The response times for space-based defenses are very much shorter than those associated with ground-based BMD. The fifteen- to thirty-minute response time for the latter allows for at least the possibility of human intervention. The record shows that, so far, when false alarms have been sounded, the human operators of the system have used the time available to determine that the alarms were indeed false, and thus avoided a catastrophic reaction. In the case of space-based defenses, response times drop to minutes or seconds or even less. Moreover, the entire system must be fully automated if it is to have any chance of responding in a timely manner. This obviously means that the false-alarm suppression mechanism must also be both purely automatic and much more finely set than it would ever need to be for ground-based terminal defenses of the classical kind.
The need for quick reaction poses the question of whether the defensive shield would have to operate automatically, without a human being "in the loop." SDIO officials have assured Congress that an "affirmative" human decision would be required before any lethal element of a space shield could be activated. Congress has mandated, in P.L. 100-180, that SDIO must not develop command-and-control systems that would make it possible "to initiate the directing of damaging or lethal fire except by affirmative human decision at an appropriate level of authority." In order for an interception to be made successfully, however, the time for such "affirmative human decision" will inevitably be extremely short—on the order of minutes or even seconds. The "appropriate level of authority" is therefore likely to reside not with the commander-in-chief but with a designated subordinate, very likely a military officer directly in charge of the space shield who would have been "preprogrammed" to know what to do in a variety of contingencies.
The battle-management systems must be designed and programmed so as to avoid the difficulties and to solve these problems. It has been estimated by experts that the necessary software program would involve
ten million or more lines of code. SDI opponents point out that no such program has ever been constructed and that experience would indicate that even if it could be built, it would be rife with untestable and undetectable errors. Proponents say the software could be assembled in smaller pieces, which could probably be tested adequately or otherwise made "fault-tolerant." In such a fast-moving field, there is no sure way to predict the outcome of this issue. Clearly, however, the experts are hardly in agreement that the battle-management problem can be solved. One acknowledged expert, Frederick P. Brooks, has said he sees "no reason why we could not build the kind of software system that SDI requires with the software engineering technology that we have today." Others share the view bluntly expressed by Robert Taylor, formerly the director of computer research programs for DARPA, and currently head of the research center at the Digital Equipment Corporation: "I think it's pretty clear that it can't be done. The goals of the SDI put demands on software that are just absurd in terms of the state of our knowledge." After examining the problem in detail, the Office of Technology Assessment concluded that even if the system could be designed and built, it would be highly prone to failure: "In OTA's judgment, there would be a significant probability (i.e., one large enough to take seriously) that the first (and presumably only) time the BMD system were used in a real war, it would suffer a catastrophic failure"—defined in the study as "a decline of 90 percent or more in system performance." The OTA also found that no existing software system (such as the long-distance telephone network or the Aegis ship-defense system) provides an adequate model for developing, testing, producing, or maintaining the software required for a BMD system.