Stealth Technology:

The Potential to Make the Visible, Invisible

Laura Samsó1

Sun Tzu broadly defined the art of war as stealth: “O divine art of subtlety and

secrecy! Through you we learn to be invisible, through you inaudible; and

hence we can hold the enemy's fate in our hands.” to conquer the enemy

without them even realizing it. Stealth, or ‘low-observable technology’, is

currently defined as a complex blend of radar (Radar Detection and Ranging),

infrared (IR), visual, acoustic signature, radio frequency (RF) emissions

reduction and other techniques. It is the potential to make something visible

invisible, not detectable.

Unmanned stealth aircrafts can be used for different purposes such terrorism

incident prevention and recovery. After 9/11, there was a campaign against

terrorist organizations and regimes resulting in a measure that authorized, in

the US, the use of the necessary force to prevent any international terrorism

event.

Some of the first developments began in the early 1900s when Germany and

the URSS (USSR) built planes using transparent materials such emaillit,

cellonrodoid. However, the advent of radar in WWII changed the rules and led

to the development of new stealth technologies: the Horten Ho 229. The first

manned aircraft with pure stealth design was the Defense Advanced Research

Projects Agency (DARPA)/US Air Force (USAF) research Program code-

named HAVE BLUE (1973) that resulted in the Lockheed F-117A fighter.

New developments in optics (metamaterials) could lead to an operative ‘nearly

perfect lens’, enhancing system target tracking capabilities and geospatial data

collection capabilities; hypersonics research being conducted by DARPA

would allow a responding nationality to be anywhere in the world in less than

1h. Some unmanned stealth projects are the X-47B, the Taranis aircraft from

UK, and the Dark Star UAV, among others.

This paper will cover how this technology applies to law enforcement and

intelligence in areas such as terrorism.

INTRODUCTION

Invisibility is a characteristic sought after by humanity since ancient times. Back to Greek

mythology, Hades the God of the underworld received from the Cyclops an invisibility helmet

to fight the Titans. Thanks to this gift, the night before the first battle, he managed to enter the

enemy battlespace unseen and destroyed the weapons of his adversaries, who he defeated after

1 Project Management Institute (PMI) Aerospace and Defense CoP Community Involvement Lead, US.

10 years of war. How has warfare changed since ancient times? Is it possible to predict how

warfare will change in the next 30 years? Is technology changing the way warriors fight? There

are numerous discussions on this topic and there is no one simple solutions.

War unfolds in a battlespace which is defined as a multidimensional realm where operations

take place. Sid Heal describes a dimension as “a realm characterized by a specific feature and

governed by its own rules”. Five dimensions typically define a battlespace: space, which is three

dimensional (length, width and height/depth) time is a non-space and measured in speed and the

fifth, cyberspace, refers not only to networks but to all kinds of information. 1

Each dimension is different and the rules that apply to each one, distinct.

Figure 1: Battle space Concept.2

Barry D. Watts in his paper “The Maturing Revolution in Military Affairs”, concluded that US

would soon see a new Revolution, similar to the one in the 1990s where stealth, precision attack

and networked systems contributed to change the TTP (Tactics, Techniques, and Procedures) of

warfare. He argued that it was time to think about the real utility of aircraft carriers, the

difficulties in deploying large battalions overseas and whether the stealth technologies would be

really useful and effective. It is also important to factor in the nuclear arsenals owned by

different nations, and consider the use of tactical nuclear weapons and their roles. He also

warned about advances in Active Electronically Scanned Array Radars (AESA) and long-

wavelength radars that could impact stealth capabilities 3,4,5

.

It would appear that everything relies on a technological revolution but the rationale behind it is

not that black and white. Why not rely on weapon systems that are more vulnerable or primitive

and adapt them to the 5th dimensional battle space described above?

As technology changes, so does the style of war. Ulysses S. Grant, American Civil War General

and President said: “The laws of successful war in one generation would ensure defeat in

another”1. It is important to analyze, evaluate, adapt and overcome an opponent’s TTP and to

understand that humans learn from a particular event, and that tactics must be changed to offset

new strategies.

Uncertainty is a quality that surrounds war and creates the so-called fog of war, defined by Carl

Von Clausewitz in his book On War: “War is an area of uncertainty; three quarters of the things

on which all action in War is based are lying in a fog of uncertainty to a greater or lesser extent.

The first thing (needed) here is a fine, piercing mind, to feel out the truth with the measure of its

judgment”. So our warriors are taught basic warfare methods that are inapplicable in the midst

of a conflict that changes constantly: the non-linearity and unpredictability of war. Contrary to

the way a war appears at first, asymmetric conflicts are more common than symmetric ones.

Terrorism could be considered as a form of asymmetric conflict when practiced outside the laws

of war.6 The 9/11 terrorist attacks on the United States homeland had a profound impact and

resulted in a new phase of warfare in terms of globalism. There are different definitions of

terrorism; it could be defined “as political violence in an asymmetrical conflict that is designed

to induce terror and psychic fear (sometimes indiscriminate) through the violent victimization

and destruction on noncombatant targets.” 7

On the other hand, the U.S. Code of Federal Regulations defines the word as “the unlawful use

of force and violence against persons or property to intimidate or coerce a government, the

civilian population, or any segment thereof in furtherance of political or social objectives.”8

Terrorism has been used not only by individuals or small groups but also by anarchist

organizations as ‘propaganda of the deed’. Historically, Marxism has always opposed terrorist

methods, believing rather in mass action, general strikes and others to overthrow dictatorial

regimes9 The terrorist approach is to remove a person or a government using violent methods,

but does this action bring about real social change? 10,11,12,13,14

Armed UAS, commonly known as UCAV (Unmanned Combat Air Vehicle) had been used not

only in armed conflicts in Afghanistan, Iraq and Lybia to fight insurgent groups but also to fight

al-Qaeda terrorism in Pakistan, Yemen and the al-Shabaab movement in Somalia15

. This

technology is used as a tool to dissuade terrorism and revolutionaries, but as mentioned

previously, there is not much information about how effective they are when the insurgent

organizations are large and resilient enough to withstand the deaths of their leaders.

STEALTH TECHNOLOGY: THE ORIGINS

There are different approaches to describing the term ‘stealth’ or ‘low-observable technology’

but a complete definition is: a complex blend of radar, infrared (IR), visual, acoustic signature

RF emissions reduction and other techniques. It is the potential to make something visible

invisible, undetectable. The philosophy behind these features is to fool hostile air, sea and land

defense systems, to diminish an adversary’s capability to detect, track and attack.

Some of the first developments began in the early 1900s when Germany and the URSS built

planes using transparent materials such emaillit, cellon, rodoid, etc. but the advent of radar and

sonar during WWII changed the rules and made the development of new stealth systems

possible, like the Horten Ho 229. The performances obtained through this design were the result

of a combination of its external shape and the use of the Radar Absorbent Materials (RAM) and

Radar Absorbent Structure (RAS) 16, 17

.

By the late thirties, the introduction of first-early warning radars changed the air combat

philosophy and air defense became dependent on them. Advances in speed and altitudes largely

surpassed human eye capabilities and electronics mechanisms, developed in parallel with radar

technology, opened up possibilities for attack scenarios not even contemplated until now, such

as night or bad weather. A relatively recent discovery was the fact that radar signals could be

distorted, counterfeited or jammed using electronic noise and this marked the birth of Electronic

Warfare (EW) 18

.

For many years, the secret test site Area 51 located in Nevada has been the stage not only for

different black project developments, but it has also played an important role in the

development of the US Air Force (USAF) secret stealth programs from the 1970s to the 1980s

and during the Cold War 19

. In 1955, Lockheed Corporation’s Skunk Works developed an

unarmed reconnaissance aircraft (this might be a better choice) named the U-2 (code-named

Black Angel/Dragon Lady) that was a joint effort between the Central Intelligence Agency

(CIA) and USAF. It was flown over Soviet territory and also over China, Cuba, and Vietnam

between others. Before the end of 1958, a new advanced aircraft appeared the A-12 or

OXCART.

By the end of 1959, Area 51 became a radar test site focused on the detection of vulnerabilities

in different reconnaissance aircraft programs and on the development of technologies to evade

radar detection. During the mid-70s, activities in Area 51 were focused on trying to reduce the

aircraft Radar Cross Section (RCS) resulting in derivations of the OXCART program such the

SR-71 (codenamed Blackbird). Its main characteristics were its high speed and cruising altitude

and it was the first generation of aircraft that were not purely stealth, but which were designed

from the outset with that philosophy in mind.

The SR-71 was the result of a public tender launched by the CIA in 1958 and 1959 in which

companies such Boeing, General Dynamics, North American and Lockheed all participated.

In the 60s, the Russian physicist and mathematician Pytor Ufimtsev developed a theory for

predicting the reflection of electromagnetic waves from simple 2D shapes20, 21

. Only two years

later, in 1962, he published the paper Method of Edge Waves in the Physical Theory of

Diffraction which represented the Holy Grail for stealth technology14

. The first manned aircraft

considered to have a pure stealth design was the DARPA/USAF research program code-named

HAVE BLUE (1976), the first attempt to convert Ufimtsev’s theoretical equations into a pure

stealth technology demonstrator that later, in 1978, resulted in the first Lockheed F-117A fighter

(code-named Nighthawk). Declared operational in October 1983, it was subsequently used in

different conflicts such as Operation Just Cause and mainly in Operation Desert Storm in Iraq to

name but a few. In order to present a high degree of stealth, the F-117 had to accept some

compromises in its aerodynamic and engine performances. The aircraft was tested using

different types of radars such bi-static and low and high-frequency types, among others, and

produced promising results. In 2008, the USAF withdrew that aircraft mainly due to the

development and introduction of the F-22 Raptor and the F-35. The B-2, or The Advanced

Strategic Penetrating Aircraft (ASPA) in 1981, was the 4th generation of stealth and it

combined F-117’s survivability with the range/payload of the B-52, capable of nuclear payload

and was constructed with an innovative blend of stealth technology.

CW: Continuous Wave

FMCW: Frequency Modulated Continuous Wave

CW: Continuous Wave

FMCW: Frequency Modulated Continuous Wave

PRF: Pulse Repetition Frequency

MTI: Moving Target Indicator

In May 1960, a U-2 was shot down over Russia resulting in a crucial political resolution

adopted by US: the abandon of manned flight over foreign territory. However the U-2 was still

needed for gathering intelligence22

.At this point, satellite imagery and RF monitoring seemed to

be the most helpful solution but this technology presented certain drawbacks: cost, limited

mission lifetime, slow, etc. and the Unmanned Aircraft Systems (UAS) appeared to be the most

reliable solution to all these problems. It was when Ryan Aeronautical offered the USAF

different updates of previous Remotely Piloted Aircrafts (RPA) versions used as target drones

or unmanned systems from the 50s to 2000.

TECHNOLOGY

During an anti-terrorist operation, being stealthy and remaining undetected while

performing intelligence, surveillance, target acquisition, and reconnaissance (ISTAR) activities

is a must. Each mission is unique and each one will impose different requirements that will be

transformed to produce a definitive blend of stealthy features.

As mentioned above, stealth technology is defined as a compound of technologies that, when

blended, offer the ability to evade detection or reduce the detectability signature. Modern stealth

aircraft trade-off developments are focused on the following areas: acoustic, visual or electronic,

heat, IR and radar. Depending on the type of operation, one factor will become more prevalent

and be given a higher priority than the others. In that case, air superiority is dominated by radar

when thinking in terms of air warfare but a balance needs to be achieved. It is important to note

that the degree of stealth is always changing due to continuous progress in counter-stealth

measures23

.

Radar Principles and Radar Cross Section (RCS)

Radar consists in a method using radio waves to locate, detect, track and identify different

targets. They can be classified into different types depending on the location of the receiver and

transmitter:

Bistatic: transmission and reception antennas are at different locations viewed from the

target.

Monostatic: the transmitter and receiver are collocated as viewed from the target.

Quasi-Monostatic: transmission and reception antennas are some way apart but appear

to be in the same place viewed from the target.

Figure 1. Radar Bands and Usage (left) & Classification by Waveform (right)

24.

Figure above (left) shows the different bands, their range and usage. Another type of radar

classification is based on the type of radar (right): Continuous Wave (CW) and Pulsed with

different sub levels.

RCS can be defined in several ways, one of them being that it represents the ability to be seen or

detected by radar and determines the range within which a given radar can detect and track it.

RCS is a function of several factors: material properties, target geometry, radar frequency and

waveform, polarization of the original wave and the target aspect with respect to the radar. It is

calculated as follows:

Where: is the incident power density.

is the scattered power density at a distance r from the target.

RCS values are represented by square meters or decibels (dB), more specifically it is expressed

in dBsm or decibel square meters.

Figure 2. Example of RCS

16.

Figure 2 shows that RCS does vary depending on the angle at which radar energy strikes the

aircraft and on the wavelength of the radar. If the radar waves were directed at the side or

bottom of the aircraft, the RCS would be larger than head-on RCS 24

.

Figure 3. Examples of typical RCS values of several targets

at microwave frequencies 25

.

Figure 3 above presents a more generalist example of the typical RCS value of different targets

in square meters and dBsm. The F-117 was thought to be between 0.001 and 0.0001 sq. meters,

F-35, not shown in the image, seemed to be better than a B-2. Due to the strategic importance of

those values, the real numbers are closely held and classified by the US government, however

these capabilities continue to evolve to lower RCS values and more stealthy systems. It is said

that current developments of stealthy aircrafts are pursuing values ranging from 0.0001 to

0.00001 m2

22.Nonetheless, the figure shows that RCS of bombers (i.e. B-52) were about 1000

sq. meters, which is an extremely high value.

Figure 4. RCS vs. Detection Range 26

.

RCS could also be defined as the size of a reflective sphere that returns the same amount of

energy (see Figure 4).

Taking into account the parameters that affect RCS, different techniques and trade-offs exist to

diminish RCS, such as the shape of the aircraft, the use of special materials for external skins or

for internal coverings (i.e. Radar Absorbent Materials - RAMs) and increasing the effectiveness

of Electronic Counter Measures (ECM).

Figure 5. Aircraft shaping: Radar reflections 26,27

.

Modifying the shape of the aircraft to reduce RCS is possible, but has limitations, as the

aerodynamic performance of the aircraft could be affected. RCS depends on the angle from

which it is viewed, but in general stealth aircraft are designed to decrease their frontal RCS.

Figure 5, on the left, presents the typical schema of waves reflected to the antenna from a

rounded airplane nose; and on the right, a stealth aircraft composed of flat surfaces and sharp

edges. Notice how the waves from radar in this case are scattered and there is no return to the

radar antenna.

Figure 6. Reflection of incoming signals in limited number of directions 27

.

A second method is to reflect the incoming signals in a limited number of directions and the last

one is modeling the aircraft with changing curves geometry (see Figure 6).

Internal structures such metal spars, ribs and bulkheads, engine installation, vertical stabilizers,

external payloads, cockpit instruments, corners and cavities also contribute to the RCS value.

These surfaces can be treated with RAM and RAS in order to absorb the radar energy. Some

examples of RAM materials are epoxy, urethane, polytherimide, Magnetic Radar Absorbing

Material (MAGRAM) and resistive card (R-card) between others. While RAM can help to

reduce the RCS, they do not constitute a complete solution. Other principles to reduce RCS are

active (plasma technology) and will be covered later on in the paper 25

.

Visual Stealth

Camouflage is the oldest method used to deceive the enemy eye. The classical method consisted

in the use of paint to make the aircraft blend in with its environment.

Apart from the standard method, in the early 1900s certain optical transparent materials were

introduced to cover aircraft surfaces, including emaillit and cellon among others, but the results

were not really conclusive. The materials could not withstand certain meteorological effects

which meant that engines and circuitry were exposed to extreme temperatures or to impacts,

leaving the aircraft vulnerable to a general failure.

Visual low observability in daylight is an important issue in modern air forces, and

developments are based on obtaining the appropriate luminance difference between its

backgrounds or the amount of light scattered from it. Today’s experiments with

electroluminescence find their roots in August 1942 when, during Operation Snowflake, a

Whitley flew with “lights along the leading edges of wings to mask its head-on visual signature” 28

. The Tornado CR1 named Houdini carried a computer on board capable of measuring

ambient light and of adjusting the intensity of light emissions using a fiber optic cable

embedded in the leading edges of the wings.

Operations during the day, night or bad weather will define the type of camouflage required for

the aircraft. Glints, smoke and contrails are some options to be considered when designing these

systems.

IR Stealth

IR stealth procedures are focused on reducing or masking the IR emissions generated mainly in

the aircraft engines through shielding, using active and passive cooling, using different

materials to absorb or reflect and deplete IR radiation, flying at supercruise speed without

afterburning, curved jet pipes, curved air intake, limiting maximum supersonic speed, or

through other systems such as IR jammers (US Army Disco Ball), flares and decoys, etc.

SU-27 and the F-35 II are equipped with passive systems such as the IR Search and Track

(ISRT) and Electro Optical (EO) systems. The F-117 and B-2 were designed without

afterburners because these systems increased the IR radiation; the F-22 can also fly at

supersonic speeds without afterburners and the SR-71 was designed prioritizing high Mach

velocity 22

.

Radio Frequency (RF) Emissions

In order to prevent possible leaks from avionic systems onboard emissions they should be

shielded from harmful electromagnetic pulses (EMP or HIRF) and RAM coating should be

applied on and around avionic bays. However, the radar inside the stealth aircraft should be

used in non-standard modes. F-117 used Forward Looking IR (FLIR) but it is unclear whether it

used Low-Light Television (LLTV) sensors.29,30

Acoustic Stealth

Stealth acoustic reduction signature procedures are focused on the engines also contributing to

reduce IR signatures. Most of the modern stealth aircrafts use turbine engines which are

generally noisy. Some alternatives to diminish this signature are flight at high altitudes, and

flight at velocities approaching the speed of sound, which implies some design complications.

Previous developments have shown that acoustic signature reduction has not been a priority in

stealth aircraft designs, i.e. in the SR-71 speed and altitude were more important.

ELECTRONIC WARFARE (EW)

This section presents an overview of Electronic Warfare and its relation with stealth

technologies.

Figure 7. Overview Electronic Warfare 18

Airborne equipment is exposed to external electromagnetic radiation sources that can reduce its

performance and compromise its survivability. Electromagnetic interference (EMI) sources can

be natural or man-made. An overview of Electronic Warfare is provided in Figure 7. These

elements of EW all have a connection to and/or association with any employment of stealth

technology.

EW is a key element in stealth technology effectiveness. By providing EW effects in concert

with the inherent radar detection capabilities the total system vulnerability to threat weapons

systems is reduced significantly. This EW component of the total system protection can be

employed by denying, intercepting and disrupting enemy information and data links. While

stealth technology can be employed to minimize an aircraft’s radar cross-section, it cannot

eliminate the fact that the aircraft exists as well as system function that requires onboard

transmit and receive of information and data. EW systems can be used to disrupt detection

and/or engagement by transmitting false targets, range gate pull-off, basic noise jamming or IR

countermeasures that minimize detection system accuracy and/or sensitivity as well as hand-off

of tracking/targeting data to associated engagement systems.

An example of the requirement for an EW capability to be provided as a complimentary aspect

of the use of stealth technology is provided in a recent Aviation Week article by Amy Butler. In

this article the recent emergence of VHF radars which can be used to detect stealth aircraft is

discussed 31

.

Integrating EW technologies into unmanned aircraft that employ stealth technologies will be

inherently complicated as the two system protect/attack techniques diametrically oppose each

other. While an unmanned aircraft can act autonomously, it still requires off-board navigation

data as well as the ability to interact with other systems within its operating environment. This

interaction must be accomplished via some sort of data transmission utilizing the RF spectrum.

SOUGHT-AFTER STEALTH CHARACTERISTICS

Hypersonics

The idea of hypersonics can be found back in the 50s with the concept design of the X-20 Dyna-

Soar which was developed for vertical launch on a rocket and then glided back to Earth. In the

60s, the CIA were working on designs to replace A-12/SR-71 that would allow travel at Mach

20, but operating risks and costs forced the project to be abandoned.

Figure 8. FALCON HTV-2 32

.

To have the capability to be in any part of the world within 1-2 h and act in any threat is the idea

behind such projects. The DARPA/USAF joint effort called Force Application & Launch from

Continental (FALCON) US was a project part of the Prompt Global Strike Program. It consisted

in a small launch vehicle and the hypersonic vehicle itself 33

.

On the other hand, at such speeds different thermodynamics and aerodynamics issues must be

taken into account.

Metamaterial Cloaking and the ‘Nearly Perfect Lens’

Metamaterials are a new kind of artificial materials that exhibit properties not found in nature.

One of the main studies on such materials focused on their ability to reverse the refractive index

which implies bending or refracting light in unusual and unexpected ways.

This theory about left-handed or negative index materials was first proposed by Victor Veselago

in 1967 33,36

. He demonstrated that all geometrical optics would need to be reevaluated to open

up new possibilities for optical devices: superlenses that would allow the enhancement of

optical resolution beyond conventional capabilities. Pendry concludes that it seems feasible to

obtain images of large regions of space with a flat lens 34,35,37,38,39,40

which is not possible with a

curved lens. Pendry has supporters and detractors concerning his theories, and he maintains that

a solution could be developed in the next 5 to 10 years.

Another exciting characteristic of the use of negative index metamaterials is invisibility. Who

has never dreamt about this property? Developments are under way and some milestones are

claimed to have been reached by Hyperstealth Biotechnology Corporation, a Canadian

company, with this type of technology 41.

In addition Veselago noted that all electromagnetic and optical phenomena would be impacted

by negative index materials. In his time, no such material had yet been developed, but

pinpointed different ideas for the creation of a negative index material, including magnetic

semiconductors 42.

Active Stealth Technology or Plasma Stealth

This technology uses ionized gas to reduce the RCS of the aircraft by creating a layer or a cloud

of plasma around the vehicle using RF or laser discharges. The history behind that technology is

thought to have begun in 1957 when the Soviets launched Sputnik. In 1963, the IEEE published

an interesting paper 43

explaining the effects of plasma on the RCS of aircraft based on the data

from Sputnik. Interactions between various types of electromagnetic radiation and plasma fields

were studied for many years in Russia, along with the US and other parts of the world. The US

Navy developed a plasma stealth antenna for use on LO aircraft.

In early 1999, Dr. Anatoliy Koroteyev, a Russian physicist, announced a plasma stealth device

developed by his organization, the Keldysh Research Center. This system was based on the

same concept, but it was applied in a different way: the aircraft was surrounded by a plasma

field that could absorb part of the enemy radar energy or bend the aircraft. Russians claimed to

have obtained results in which RCS was reduced by up to 100 times, and to have equipment

weighing just 100 kg 26

.

Later in 2002, it is said that the Russians tested the system in a Su-27 and that the results were

extremely promising. The Sukhoi Su-35 and the MiG-35 were the first to benefit from this

technology.

Figure 9. Example of Plasma Stealth System.

Those plasma stealth systems could control and adjust their properties such density, temperature

and composition on the fly. However, this technology has some drawbacks because it emits EM

radiation in the form of a visible glare, visible aircraft trail and, at high speeds, there are

problems generating the plasma- stealth field to cover the entire aircraft 44,45,46

.

COUNTERS TO STEALTH

This section presents some counter-stealth measures that pose different threats to current stealth

technology developments.

Low-Frequency (long wavelength) Radars

Low frequency radars use frequencies lower than 1 GHz and, below 900 MHz, the RCS

increases exponentially, which means that signal radar return comes from sources such cloud

cover and rain. These highly-sensitive radars were used to shoot down an F-117, but they can

handle a lot of information in near real time. Some of the latest advances were to develop and

apply digital signal processing to diminish the burden of data radar. It is important to note that

long-wave radar can detect a target but not identify it, so there is a lack of precision that does

not justify sending out an attack.

Bi-static Radars47,48,49,50,51

Monostatic radars share the same antenna, but in the case of Bi-Static radars, the transmitter and

receiver are separated by a considerable distance in order to obtain technical, operational and

cost benefits. These types of radars have potential advantages concerning the detection of

stealthy aircrafts which are shaped to avoid detection by mono static radars.

Figure 10: Bistatic Angle 47

.

Figure 10 above presents the Bistatic angle calculation; this parameter is important in

calculating the RCS of the target.

Figure 11: Bistatic Radar Equation 47

.

Some types of bistatic radars include Pseudo-Monostatic, forward scattered, multi-static and

passive radars.

Emitter Locating Systems: ELINT Systems 52

These systems date back to the Second World War, our aircraft in Vietnam were covered by

active and passive Elint Systems developed to detect, locate, evaluate and track aircraft, ships,

radar sites, missile launches, missile sites, Jammers, satellites, bi-static and Monostatic receivers

and anything in general that emitted RF. Sometimes they are incorrectly termed as Passive Anti

Stealth radars but they are passive Electronic Support Measures (EMS) built to provide an ELS

capability against forces emitting radio frequency signals.

Some examples are the Czech Tesla-Parbudice KRTP-86 TAMARA or the ERA Vera Emitter

Locating Systems (ELS) or the Ukranian Topaz Kolchuga series of ELS.

Figure 12: (left) Kolchuga and TAMARA (right).

Some Russian systems are the 85V6 Vega/Orion ELINT system, the Kvant 1L222 Avtobaza

and the PLA systems.

Quantum Radar

The overall approach relies on devising a gravimetric radar system for detecting massive

moving objects based on the time variation that these objects produce in the local gravitational

field measured by several detectors.

Multi-Band 3D Radar 53, 54

This technology was developed in late 2008 by Russia and comprises three to four radars

operating on different frequency bands, and a Processing and Command center. One example of

this kind of system is the NEBO-M.

Figure 13. NEBO-M: Multi-band 3D Radar.

Multiple Input Multiple Output (MIMO) Radar

This technology is a variation of the Multi static concept. This type of radar can process signals

received at multiple antennas and uses multiple transmit waveforms.

Figure 14: MIMO Radar.

One of the characteristics in its performance is that the average Signal to Noise Ratio (SNR) is

more constant when compared to conventional systems.

Light Detection and Ranging (LIDAR) Technology

Countermeasures LIDAR technology techniques can be divided into multi-band and multi-static

systems. LIDAR has a short wave length 55

, high beam quality, strong directionality, large

measuring capacity, high resolution and anti-jamming characteristics which indicate that this

technology is a good candidate for target detection, track and range.

IR Search and Track (IRST)

This is a passive method to track an aircraft’s IR radiation and, in comparison to the radar, it has

a limited range, and its accuracy is better at close range.

Detection through Secondary Effects

-Schlieren Signature62, 63

The Schlieren effect helps detect anything that disturbs the atmosphere, so it is possible to

detect a stealth aircraft using this type of detection.

STEALTH PROJECTS

Intelligence and defense agencies together with defense contractors have been paving the way to

changing how wars will be fought in the near future, but as discussed above, will be that

enough? Modern warfare is constantly changing owing to progress in stealth and counter stealth

technologies to cover the different gaps. For example the B-2 and the F-22 are able to drop

GPS-inertial weapons with precision.

Some unmanned stealth projects are briefly described below in order to show how fast stealth

technology is advancing.

Tier III Minus UAV or code name DarkStar 56,57

This system was the result of a joint effort between Boeing and Lockheed Martin which, in

1994, teamed and designed a stealthy plane for the US Department of Defense (DoD) Tier III

Minus program. The first flight took place in March 1996 but the project was canceled in 1999

due to budget cuts and the preference over the range of the Global Hawk.

Figure 15: DarkStar UAV (Source: FAQS)

X-47B 58

The X-47B is a variant of Pegasus X-47A which was developed in 2001 as a joint USAF and

USN program, called J-UCAS. This aircraft is an Unmanned Combat Air Vehicle (UCAV)

demonstrator program developed by Northrop Grumman, designed for carrier-based operations

and developed under the Unmanned Combat Air System Demonstration (U-CLAS) program.

Figure 16: X-47B.

It is equipped with electro optics (EO), IR, synthetic aperture radar (SAR), inverse SAR, ground

moving target indicator (GMTI), electronic support measures (ESM) and maritime moving

target indicator (MMTI) sensors. The first flight took place early 2011 from Edwards AF base

and up to now different sets of tests have been run to confirm its capabilities.

Taranis 59

This is an UCAV demonstrator program led by BAE Systems for the UK MoD. According to

BAE press, the concept behind Taranis is to “develop an autonomous and stealthy unmanned

aircraft capable of striking targets with real precision at long range, even in another continent, is

even possible.”

Figure 17: Taranis (Source: BAE Systems).

An Aviation Week magazine analysis indicates that it has been designed to defeat new counter-

stealth radars, and may use thrust vectoring as a primary means of flight control and an

innovative high-precision, passive navigation and guidance system.

RQ-180 60,61

This aircraft was developed by Northrop Grumman and it is seen as a continuation of

Intelligence, Surveillance and Reconnaissance (ISR) missions previously addressed by the

retired SR-71 in 1998. This new UAS will work in a more denied or contested environment,

rather than the previous permissive Iraq or Afghanistan scenarios.

Figure 18: RQ-180

This new UAS could be jointly controlled by the USAF and the CIA if the previous ISR

operations model is repeated.

Some improvements include RCS reduction compared to F-117, F-22 and F-35; use of a

scalable and adaptable ‘cranked-kite’ design, design philosophy based on laminar flow and

efficiency, better engine integration and enhancement in operations between others. Other

details are classified due to the secrecy of the project. It seems (Source: aviation week

magazine) that it will enter production for the USAF and could already be operational by 2015.

In general, all these kinds of stealth programs will need to propose solutions for maintainability,

sustainability, and of course reliability, logistics support, training for operators and maintenance

personnel.

CONCLUSIONS

Conflicts are always diverse, they are rarely equal, and the TTP used in one conflict will not be

useful for the next, because war is neither linear nor predictable.

So just how effective will stealth technologies actually be? Is it a matter of a new technological

revolution or can warriors and commanders rely on more vulnerable weapon systems and adapt

them to the 5th dimensional battlespace? Are they prepared for that? This discussion has been

heard for years and it is still going on.

UAS/UCAV have been used not only to fight insurgent groups but also to combat Al-Qaeda

terrorism, but are they truly effective? Perhaps the Marxism concept of terrorism is more

appropriate? It is not easy to quantify

UAS systems brought into such conflicts use stealth or low observable technologies. They are a

blend of different capabilities: radar, LIDAR, IR, visual and acoustic signature and RF among

others. Depending on the mission and the type of operations, the blend of sensors and

capabilities will be different.

Some considerations when designing stealthy UAS are to factor in different methods and trade -

them off: how to reduce the RCS, obtain visual, IR, and acoustic signatures reduction, mask RF

emissions, protect airborne equipment from EW. In parallel, counter stealth technologies are

quickly evolving to fight stealth capabilities in a never ending game: low-frequency radars, bi-

static radars, ELINT systems, multi-band 3D radar, MIMO radar, LiDAR technology, quantum

radar, ISRT and detection using secondary effects.

Integrating EW technologies into UAS that use stealth technologies will be complicated because

the functionalities of the two systems are opposed.

Some technologies that will change the game and are currently under development are the idea

of hypersonics, the obtention of metamaterial cloaking, a nearly perfect lens, and advances in

active plasma stealth development.

On the other hand, these so-called “game changers”, disruptive and revolutionary technologies

such UAS are giving the military planners and strategists food for thought.

ACKNOWLEDGEMENTS

I would like to thank you Mr. Jim Atkinson, from Atkinson Aeronautics, for his EW expert

help, to Mr. Aloysio Vianna, PMP, PMI Aerospace & Defense Communications Lead for his

general review and to M. Cathy Brewerton for her assessments.

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