Fixed-wing aircraft used for the delivery of WMD are of significant concern. Most potential proliferants have reasonable numbers of tactical aircraft and have trained pilots to fly them. The aircraft available usually have a short strike range, suitable for their limited geographical area. Longer range capability, while possible with modifications to existing aircraft and the development of in-flight refueling capabilities, involve introduction of new technologies and systems. With the advent of the GPS, proliferants now have a technique to improve the navigational capability of their aircraft significantly. Also, even though state-of-the art signature reduction is not readily available, more conventional countermeasures would still be of considerable value, particularly in regional conflicts.
Three key attributes of an aircraft pose the greatest threat: (1) reliable delivery of WMD, (2) ability to penetrate defenses, and (3) all-weather, day and night capability. The aircraft subsection describes and lists those technologies that allow a proliferant to carry out a targeting objective. The tables first list technologies that assist a country in weaponizing its aircraft fleet to accept WMD. Then they cover technologies that enable all-weather, day and night aircraft operations. Finally, the tables address the hardware and technical expertise that are needed to assist in penetrating defenses. Each of the tables is organized to categorize technologies, or adaptation of technologies, under the specific subsystem of the aircraft: airframe, propulsion, guidance, control, and navigation, and weapons integration.
Proliferants can pursue at least four technological advances to manned aircraft: (1) methods to increase range, (2) methods to weaponize WMD for reliability, (3) methods to mask or otherwise disguise flight signatures to detection networks, and (4) methods to launch an aircraft attack around the clock and in all-weather conditions.
Methods to Extend Range
All the identified proliferants maintain some manned aircraft systems. As total delivery systems, any of these aircraft can carry and drop almost any nuclear, chemical, or biological payload that the proliferant is capable of making or purchasing. Proliferants that possess limited-range aircraft have already begun to upgrade the severity of threat these aircraft pose by investigating the world market for in-flight refueling capability. In 1987, Libya purchased in-flight refueling tankers that are capable of extending the range sufficiently to strike European targets. Libya's only impediment to expanding its aircraft range is the availability of interim staging bases from which the tanker aircraft can fly.
Because of the physical isolation and political posture of many proliferants, few, if any, countries will act as host for proliferants to stage refueling tanker aircraft that could aid any WMD strike against U.S. worldwide interests. To do so would invite retaliation from the United States and the probable loss of the asset to U.S. counterforce operations. Given this geographical constraint, a proliferator may undertake to make modifications to an existing aircraft to extend range without in-flight refueling. To accomplish any range extension to its aircraft fleet, the country must add additional fuel tanks, reduce the aerodynamic drag, or change the propulsion system to consume less fuel. Modifications to the airframe or propulsion subsystem of an aircraft may augment its range at the margins, but none of the realistic modifications a proliferant might make add to the range in the same dramatic way that an in-flight refueling capability does. Thus, if sales of in-flight refueling aircraft are limited and the use of foreign airfields for tanker traffic are monitored, the WMD aircraft threat can be limited to a regional theater of operation. The technology tables have been organized to highlight these considerations.
Methods to Increase Targeting Reliability
With a manned crew, targeting reliability is expected to be high. In the event of any problems en route to the target, the crew may be able to take action to change its target. Similarly, most manned aircraft crews usually visually confirm the position of a target (except when dropping stand-off weapons, such as cruise missiles). Guidance and navigation subsystems are important to aid in navigation to the target. Significant errors in targeting occur from unpredictable winds, incorrect fuzing information, or poor aerodynamic design. The proper weapons integration of WMD warheads can eliminate most of these problems.
An aircraft can often be tracked and shot down by existing defense batteries. At some point, a proliferant aircraft will likely display itself to any tracking sensor as it approaches a target. A proliferant aircraft may, however, delay this detection to radar tracking networks by following contours in the terrain and by employing electronic countermeasures. Neither of these two changes requires modifications to the aircraft's propulsion or airframe and, therefore, they take less effort.
Aircraft can be flown to the target using only visual cues if meteorological conditions permit. A technology that allows an aircraft to operate in any weather condition or during any time of the night or day greatly enhances the threat this delivery system poses. In addition, if a technology allows an airplane to fly outside of its normal operating environment, while following the contours of the terrain, the aircraft then complicates defense strategies. Some technologies that can be fitted onto aircraft to accomplish these objectives are (1) an avionics unit that senses position and position rate; (2) small onboard computers capable of automated flight planning, targeting, en route navigation, and ensured terrain avoidance; and (3) addition of stealth. Many flight-qualified control systems produce sufficient force (sometimes known as command authority) and response time (or phase margin) to steer any existing aircraft autonomously. These actuators must be coupled to a flight computer, which detects position and position rates and compares them to an on-board stored radar or topographical map of the terrain. In a fully autonomous system, the flight computer must predict the course far enough in advance to give the aircraft time to maneuver and avoid any obstacles within performance constraints, such as climb rate and roll rate. Complete guidance and control subsystems and the components that comprise them are sufficient technology to constitute a proliferation threat.
Methods to Increase Attack Flexibility
Navigation systems traditionally compare either analog or digital representations of the Earth's surface to the radar or topographical scene through which the airplane flies. In recent years, these computers have relied almost exclusively upon digital representations. While reversion to an analogue scene comparison is not ruled out, digital maps are by far the most militarily threatening. They have better resolution, are more accurate, and are updated frequently by contractors, which removes from the proliferant the burden of generating the databases for these maps. Computers that support digital navigation and scene generation require highly sophisticated storage devices and rapid random access to the stored information.
Methods to Increase Penetration
Once an aircraft is within range of defense radars, it may use electronic counter-measures in several ways to spoof defense assets. Sophisticated countermeasures may alter the signal returned to the defense radar to make the aircraft appear to be some other type of aircraft. This technique is especially effective against radars that present thematic rather than actual RCSs to defense personnel evaluating the surroundings. Simpler electronic countermeasures may make an aircraft appear to be much larger or spread out over a greater region of the sky. Consequently, hit-to-kill interceptors may miss the actual aircraft as they fly to intercept the large region within the predicted target area. A proliferant's electronic countermeasures may not prevent the aircraft from being ultimately targeted and eliminated, but they delay the interception to allow the aircraft to release its weapon on the actual target or an adjacent target of near equivalent value. As a result, electronic countermeasures are listed as an important technology to be denied to proliferants.
As a last resort, a proliferant may attempt simply to overwhelm the defense by saturating a target with too many aircraft to intercept. This is a less attractive alternative with aircraft than it is with cruise missiles because of the high cost of purchasing the aircraft, maintaining them, and training a capable crew. Moreover, since a proliferant cannot predict which aircraft will penetrate and which will be intercepted, it must equip all of them with WMD. For chemical and biological agents, this may not be too difficult, but few proliferants can currently manufacture nuclear weapons in sufficient quantities to threaten a saturation attack.
All aircraft require weapons integration, whether they arrive at the point of sale in their weaponized state or not. Indigenously produced WMD will probably differ from their foreign counterparts. A proliferant must discover, on its own, the idiosyncrasies of the interaction of a weapon and the aircraft that carries it to plan for these modifications. For example, bomb bay doors opening at certain velocities sometimes cause severe aircraft vibration. Similarly, once the bomb bay doors are open the airflow around the weapon may cause it to vibrate uncontrollably. Again, modern computational fluid dynamics (CFD) codes and their aerodynamic equivalents streamline the redesign process to achieve clean stores separation under all circumstances. Wind tunnels assist a proliferant in estimating the extent of any needed modifications. The weapons, on the other hand, may need to undergo significant refinements, depending on the ultimate intentions of the country. Some simple standoff weapons, such as glide bombs, may provide a proliferant a unique penetration capability. As an example, a country can target its neighbor without violating its airspace by using a glide bomb that has a lift-to-drag ratio of 5 and dropping it from an aircraft operating at a ceiling of 50,000 ft. The girth of the weapon or its aerodynamic surfaces may create a release problem that forces the proliferant to consider designing folded aerodynamic surfaces. However, a glide bomb is both more accurate than an ordinary gravity bomb and has a greatly reduced RCS compared to the aircraft which drops it, thus solving many of the problems of penetration. To hit in the vicinity of the target, even a large area target such as a city, the post drop vehicle may need an autonomous guidance and control unit. This unit does not need to meet the specifications of a missile-grade IMU, but it must be good enough to provide simple feedback control to the aerodynamic control surfaces. Systems for aircraft using GPSs are being made available on the world market. Many European and U.S. manufacturers make avionics equipment that can control a split flap or simple aileron. The tables include technology items directly tied to accurate aerodynamic bombs, control surfaces for a bomb, and steerable aerodynamic devices suitable for releasing airborne agents.
Since the end of the Cold War, widespread sales have been made of aircraft capable of delivering WMD. China owns SU-27 Flankers, and North Korea has SU-25 Frogfoots. Syria and Libya possess SU-24s, and Iraq, at one time, had the Mirage F1-C. India has 15 Jaguars. The SU-24 has a combat radius of 1,000 km, giving it the most threatening range capability in a regional conflict. However, since they can trade payload, speed, fuel, and range, any of these aircraft can execute a WMD delivery.
Effective use of aircraft in a combat role requires ongoing training, maintenance, and functioning of a substantial infrastructure. Key needs include trained people, availability of spare parts, and realistic exercises. The case in which Iran lost U.S. support is instructive in the limits to keeping aircraft viable as a means of delivery. China, India, Pakistan, and Israel can maintain and support a tactical aircraft infrastructure, train and recruit pilots, and sustain their aircraft in a threatening posture. North Korea has great difficulty in training pilots and maintaining its aircraft but could mount a single attack against South Korea with its SU-25 Frogfoots. As the Gulf War showed, when the coalition achieved air supremacy, Iraq did not mount even a single sortie against a coalition target, and in all likelihood Iran is in similar straits. Syria has the ability to maintain its aircraft with foreign assistance from either the former Soviet Union or elements of the former Soviet Bloc. The United States has no way of limiting this assistance as it did in post-Revolutionary Iran because its does not control the market for parts and personnel relevant to the air fleet.
All members of the G-7, Sweden, and Poland can supply technical expertise and maintenance personnel to proliferants. South Africa or its agents can funnel spare parts for aircraft to proliferants facing severe shortages. Former Cold War enemy production entities have created licensed co-production facilities for aircraft in China, Israel, South Africa, South Korea, Taiwan, and other countries. Any of these facilities can produce some parts of interest to a proliferator. Many other newly industrialized countries-including Argentina, Brazil, Chile, and Egypt-produce indigenous whole aircraft. A country with an indigenous aircraft production capability may supply custom-made parts or reverse engineered replacement parts for grounded aircraft.
Because of the ubiquity of the aircraft industry in the United States, Russia, and many other countries, virtually every nation in the world has available to it tactical aircraft (or civil aircraft of equivalent range and payload capacity) through legitimate purchase. Smaller aircraft, such as business jets and jet trainers, sold overtly to proliferants can be cannibalized for subsystems, particularly navigation and control subsystems. As a result, no proliferant has a compelling need to build an independent, indigenous aircraft industry solely for delivering its WMD by aircraft. In fact, because of the availability of suitable aircraft on the world market, such an independent capability would be a waste of resources and draw funds away from other needs. A proliferant pursuing aircraft delivery systems needs only the capability to make modest modifications to existing military or civilian aircraft, including bomb bays or bomb racks, associated weapons initiation systems, and research flight conditions for delivering weapons.
To complete the stockpile-to-target delivery cycle at the subsystem level, a proliferant needs to build and test the WMD device that will be delivered by aircraft. Every nation of the FSU, with the exception of Bulgaria, has a trained work force and either existing wind tunnels or structural dynamics laboratories capable of required testing. In the former Yugoslavia, parts of this infrastructure are scattered about the various component states, with most of the research laboratories concentrated in Croatia and Slovenia. India has similar facilities and a tradition of education that can adapt the facilities to unconventional design concepts. The Baltic Republics can perform R&D into flight dynamics and have computer facilities available that can host 1980's vintage U.S. software for advanced structural designs. The industrialized nations of South America (Argentina, Brazil, and Chile) are capable of either building comparable facilities indigenously and performing experiments and analyses for a third party or exporting the technical talent to build such facilities elsewhere.
These same entities can design and build a variety of warhead systems, consistent with tactical aircraft delivery, including aerial bombs, spray systems, glide bombs, terminally steered or guided bombs, and cruise missiles. These devices have the common requirement of aerodynamic flight through a defined mission profile. For chemical and biological weapons, the designer must also provide some mechanism for air braking the warhead, such as fins, or other glide devices that allow the warhead to disseminate agent over a broad area, and a method to keep biological agents in an active condition through the delivery cycle. Failing this, the proliferator must accept the greatly reduced efficiency from dissemination initiated by a burster charge.
At the most rudimentary level, a proliferator must produce an aerodynamic warhead configuration that has a repeatable and predictable flight profile, does not induce severe vibration from air stream buffeting, and can detonate at a predetermined altitude or upon ground contact. Iran, Iraq, Yemen, Indonesia, Bulgaria, the Czech Republic, Slovakia, the Baltic Republics, Pakistan, Mexico, and Cuba can design and build these weapons. Those capabilities that support or further weapon system design are included as "sufficient" technologies.
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