Aircraft - Introduction
Source: American Federation of Scientists 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, 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, 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 ca-pable 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.
Systems
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.
Subsystems
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 vin-tage 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.
http://www.fas.org/nuke/intro/aircraft/intro.htm
(2) ability to penetrate defenses, and
(3) all-weather, day and night capability.
(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.