At an advanced high-speed test in the New Mexico desert Nov. 26, Boeing Phantom Works and the U.S. Air Force Research Laboratory began attempting to solve the problem of safely releasing ordnance from inside an airframe traveling at high supersonic speeds. The test was a small but potentially important step toward the Pentagon's long-range goal of establishing the capability to strike at intercontinental distances with conventional weapons.
At an advanced high-speed test in the New Mexico desert Nov. 26, Boeing Phantom Works and the U.S. Air Force Research Laboratory began attempting to solve the problem of safely releasing ordnance from inside an airframe traveling at high supersonic speeds. The test was conducted on the High-Speed Test Track at Holloman Air Force Base by a program with a name so long its acronym has to be abbreviated: the High Frequency Excitation Active Flow Control for Supersonic Weapon Release (known simply as HIFEX). The test is a small but potentially significant step in the Pentagon's cultivation of the capability to strike anywhere in the world on short notice. Now in its sixth year, HIFEX is attempting to solve a pesky problem that plagues supersonic military aircraft: ordnance released from an internal weapons bay at sufficiently high speeds will be forced back up into the bay by the airflow beneath the aircraft. In some cases, at lower speeds, this can be controlled by adding a passive weapons bay spoiler; HIFEX is developing a way to manipulate airflow actively to release munitions safely at higher supersonic speeds. In the Nov. 26 test, an active airflow system forced a piece of dummy ordnance approximating a 500-pound satellite-guided bomb up and out of a test sled traveling at nearly twice the speed of sound. HIFEX has more tests to conduct, and at higher speeds. But this series of tests may be of crucial importance for the U.S. Air Force's next-generation strategic bomber, currently scheduled for testing in about a decade. That bomber has yet to be designed — or even to have very clear design objectives defined — but there is good chance that higher supersonic speeds will come into play. Whether the design will eventually entail releasing ordnance at unprecedented speeds remains to be seen. But the work done under HIFEX has more immediate applications. It is already being incorporated into what the Air Force calls the Prompt Global Strike mission — the objective of being able to strike a specific piece of territory anywhere on the earth's surface in very short order. Or, more simply stated: the rapid delivery of conventional weapons at intercontinental ranges. Of course, intercontinental ballistic missiles (ICBMs) can do this already, with (very roughly) a thirty-minute flight time — but so far, ICBMs have only been fielded with nuclear warheads, not conventional ones. The reason is that initially, given the long distances involved, the only way an ICBM delivery system could hit a target with a meaningful degree of accuracy was with the massive destructive power of a nuclear weapon. However, improved precision guidance — and especially the maturity of the Global Positioning System — has made that level of devastation unnecessary. But whether the Pentagon decides to push forward with conventional warheads for the submarine-launched Trident missile (a highly controversial program strongly opposed by arms-control groups) is really beside the point. Such a measure would simply be temporary. The real solution is the use of hypersonics — either as delivery vehicles or as weapons themselves. Current research by NASA (on the X-43 test vehicle) and the U.S. Department of Defense (on the X-51 test vehicle) suggests that hypersonic flight will be sustained by scramjet engines. Scramjets are an elegant and simple design, but they only function at extremely high velocity — they must first be boosted to sufficiently high speed by more conventional rocketry. Scramjet designs thus far have required careful management of airflow along the entire underside of the airframe. Because of this, there is a good chance that the constraints of hypersonic design will favor or perhaps even require an internal weapons bay (externally mounted weapons are unlikely given the airspeeds involved) located on the top side of the aircraft. In other words, the ordnance will need to be pushed up and out rather than simply being dropped from underneath. This type of upward release was part of the Nov. 26 HIFEX test. Whatever form the weapons and vehicles ultimately take, current Pentagon thinking is — and has been for some time — very dedicated to such ideas. It is very likely that the kind of system envisioned by HIFEX (or something like it) will eventually become a key part of the U.S. strategy to maintain its military advantage.