A N A L Y S I S C E N T E R P A P E R S

by

Robert P. Haffa, Jr. and James H. Patton, Jr.1

June 2002

In Brief

The U.S. Department of Defense plans to invest hundreds of billions of dollars in stealthy aircraft over the next several decades. Will low-observable(LO) capabilities incorporated in military aircraft such as the B-2 bomber, theF-22 air superiority fighter and the F-35 joint strike fighter prove as successfuland enduring as submarine stealth? To address that question, this paper brieflyexplores antisubmarine warfare, examines the development and fielding of low-observable aircraft, and suggests analogues between stealthy platforms in the seaand in the air.

When those analogies are drawn, many of the same reasons the submarine hasproven so difficult to detect, track, fix, and destroy also pertain to stealthy aircraft. The friction of combat, the platform operators ability to modify theirtactics, the technology of denying more than fleeting contacts, and the problemof looking for small things in large volumes all apply. The submarines long-termsuccess suggests that properties inherent in low-observable combat platformsprovide an enduring competitive military advantage to those who produce,maintain and continually improve them. It stands to reason, therefore, thatstealthy aircraft should maintain an enduring edge over anti-aircraft defenses,providing their sponsors constantly study and exploit the environment, and takeprompt and sustained corrective actions to negate enemy countermeasures.

StealthAnalogues of

1 This paper adopts the same title and thesis presented in an article the authors published a decade ago, but explores the issuesquite differently. See Analogues of Stealth in Comparative Strategy (Vol. 10, No. 3) pp. 257-271. Copyright 1991, Taylorand Francis. Now, as then, we acknowledge James G. Roche for encouraging us to examine the similarities between stealthysubmarines and aircraft. We would also like to thank our colleagues in the Northrop Grumman Analysis Center for their assistance, especially John Backschies, Mary Hubbell and Adam Siegel.

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ANALOGUES of STEALTH

Introduction: Analogues of Stealth

Recent claims regarding the detection and vulner-ability of low-observable aircraft like the B-2bomber are reminiscent of similar reports issuedover the years postulating the demise of the sub-marines stealth. Comparing submarines and aircraft employing stealthlow-observable technologies and tacticsresults in several analo-gies useful in refuting these claims: Each system operates in a three-dimensional

environment facilitating low observability: vaststretches of sea and sky.

They can use terrain features (ocean trenches,mountain ranges) to mask their presence fromsensors.

They can vary their immersion within theenvironment (depth, altitude) and use its char-acteristics (i.e., temperature, weather, or dark-ness) to add measures of stealthiness.

They can reduce to varying degrees theirobservable signatures (through sound-deaden-ing techniques, infrared shielding, or cooling).

They can avoid or attack active means ofdetection (sonar, radar) and make themselvesless detectable by spoofing or jamming thosesystems.

Finally, owing to these properties stealth pro-vides, they each enjoy the tactical advantage ofchoosing when to engage the adversary incombat.

With these analogies in mind, this paper exploressimilarities between low-observable submarinesand aircraft with the purpose of examining thestaying power of stealth.2 To accomplish that, wefirst briefly review the history of anti-submarinewarfare (ASW)a story of the search for coun-termeasures against a platform that from the out-set was designed to use the environment to maskits presence. Yet, ever since submarines enteredmilitary operations, claims have emerged thatsome new technology will make them obsolete.Time and again those claims have proved base-less. With continued modernization and modifi-cation, the submarines signature has beenreduced to the point where the noisy nature ofits operational environment hides its position anddramatically reduces or neutralizes the effective-ness of various detection means. Indeed, everynuclear-powered U.S. submarine was quieter, thatis, more stealthy, when decommissioned thanwhen it was launched.

It is our contention that low-observable aircraft,when they reach the end of their service life,should also be retired in a more stealthy condi-tion than that of their first flight. Seeking to sup-port that contention, the paper next outlines thedevelopment and employment of airbornestealth. Although the story of air defense beginswith observers on the ground and in the air, sinceWorld War II air defenses have relied primarily

A N A L Y S I S C E N T E R P A P E R S

2 There are differences as well, most notably that the submarine achieves its stealth primarily by submerging, while a stealthy aircraft operates in the same medium as non-stealthy planes. We believe the comparisons far outweigh the contrasts, particularly with regard to the mutual need to counter detection technologies and the operationaladvantages that accrue to stealthy combat platforms whether in the sea or in the air.

SSBN GeorgeWashington

(598)

SSBN Ethan Allen(608)

SSBN Permit(594)

SSBN Permit(594)

SSBN Lafayette(616)

SSBN Sturgeon(637)

SSN Los Angeles(688)

SSBN Ohio(726)

US Attack Submarines

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SSBN Lafayette(616)

SSN Sturgeon(637)

SSN Los Angeles(688)

SSBN Ohio(726)

US Attack Submarines

SSN Nautilus(571)

Merchant Ship

Seawolf andVirginia Class

US Ballistic Missile Submarines

DieselSubmarineon Battery

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Adapted from Tom Stephanic,Strategic Anti-Submarine Warfare and

Naval Strategy (New York: Lexington, 1987), p. 278.

Figure 1. This estimate of total radiated sound levels for US nuclear submarines suggests a noise reduction of 60 dB over45 years. Modern submarines emit about one-millionth of acoustic energy as did their predecessors.

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ANALOGUES of STEALTH

survive, must be accorded the attention and theresources it deserves.

Anti-Submarine Warfare: CounteringUnderwater Stealth

Attempts to degrade the submarine's inherentstealthiness through ASW have evolved throughnumerous techniques and technologies. Initially,ASW relied on a submarine compromising itsstealth by operating in a non-submerged mode orraising its periscope above the oceans surface.Before World War II, technological innovationsled to active means of detection (e.g., sonar) tosearch for submerged submarines. During WorldWar II, ASW exploited the nonstealthy aspects ofa submarine's behavior by employing radar whenthe sub was required to operate on the surface,

and by using direc-tion-finding equip-ment when subma-rine transmissionsbroke radio silence.Finally, since WorldWar II, more sophis-ticated detection

techniques have emphasized passive detectiontechnologies, such as listening for the sounds of asubmarine, detecting its metallic hull, or pickingup the trail it leaves behind.

Seeking nonstealthy signatures. Although someobservers anticipated the submarines militarypotential before World War I, a more typicalopinion was that the submarine was a cowardlyweapon employed only by weak naval powers.Even after three British cruisers had been torpe-doed and sunk in a matter of minutes by aGerman U-boat on September 22, 1914, themedia coverage about the event concluded thatthe submarine threat was likely to be short lived.Mining harbors, torpedo nets, better armor,careful lookouts (including aircraft) and highspeeds and frequent course changes were seen ascountermeasures likely to negate any advantagesthe submarine could achieve by wrapping itself inthe cloak of the sea.3

The 1918 British development of sonar, forSOund Navigation And Ranging, strengthenedthe belief that the submarine would become

A N A L Y S I S C E N T E R P A P E R S

on radar to detect, track, and subsequentlyengage hostile aircraft. That said, optical detec-tion is still pursued, as are detection techniquesseeking other aircraft signatures such as heat,radio communications, and even turbulent wakesin the atmosphere.

Although the atmosphere provides some naturalhiding places for aircraft, such as clouds anddarkness, an airplanes signature must be loweredto survive in a hostile environment. Using stealthtechnology, aeronautical engineers reduce an air-crafts susceptibility to radar detection and miti-gate its observable infrared, electromagnetic, visu-al and acoustic signatures. Indirect or passivemeasures diminish the contrast between an air-crafts profile and its physical or electromagneticsurroundings. For example, camouflage paintallows an aircraft toblend into the back-ground, while aircraftthreat-warning systemsenable search radar eva-sion. Countermeasuresinclude presenting anincoming anti-aircraftmissile with a false signature to lead it astray,using focused light, flares or lasers to lure aninfrared seeker, and employing active jamming ordeploying a towed decoy to deflect radar terminalguidance. Using these multi-spectral signatureredu