America's Sixth Generation Fighters: The F-X and F/A-XX - I

Image 1: Early sixth generation concept by Lockheed Martin

In recent weeks, senior Air Force, Navy, and Pentagon officials have discussed ambitious plans to design a pair of sixth generation aircraft that will succeed the F/A-18E/F (F/A-XX program) and F-22A (F-X program) in the 2030 to 2035 time frame.

• Part I will discuss the need for a sixth generation fighter given the ongoing development of the capable fifth generation F-35 and the threat environment of 2030. 
• Part II will examine the state of development in both programs, the technologies that will be incorporated into the design which will define sixth generation capabilities. 
• Part III will review key design characteristics and the likely roles and missions of the two aircraft in their respective services. The author will subsequently examine the relative merits of the Air Force and Navy's F-X and F/A-XX concepts given the range of threats posed in an A2/AD environment. Finally, the author will conclude by examining the prospects of upgrading the F-35 with many of the sixth generation capabilities detailed throughout the article.
• Part IV - Works Cited 

The Need for a Sixth Generation Fighter 

Given that the fifth generation F-35 has yet to enter service, it may seem odd that both the Navy and Air Force are planning new sixth generation designs. Four principal of factors have guided the services decision to begin work on the F/A-XX and F-X programs: increasingly sophisticated anti-access threats, the potential compromise of key F-35 program details to China, the age and finite quantity of existing air superiority/air dominance platforms in conjunction with the proliferation of foreign fifth generation aircraft, and industrial base concerns. 

In 2001, Lockheed Martin's X-35 was selected over Boeing's X-32 for the Joint Strike Fighter program and was to be developed into the F-35 which was scheduled to enter service in April of 2010 for the Marines, June 2011 for the Air Force, and April 2012 for the Navy (Anthony Capaccio, 2013). As of 2015, the planned initial operational capability (IOC) dates for the F-35 are 2015 for the Marines, 2016 for the Air Force, and 2018 for the Navy. The significant delay in the development of the F-35 program has enabled US competitors, chiefly China and Russia, to start to develop technologies that would somewhat limit the effectiveness of the F-35's low observability. The proliferation of very high frequency (VHF) radars is a cause for concern as the F-35's airframe is optimized to perform against X and S band radars. As per the Raleigh scattering region, electromagnetic radiation will scatter from bodies smaller than its wavelength (Plopsky & Bozzato, 2014). In comparatively small stealth aircraft that place a premium on maneuverability such as the F-22, F-35, PAK FA, and J-20, the wing edges, tail fins, and other flight surfaces will inevitably be smaller than the 1 to 3 meter wavelength of VHF radars. However, VHF radars are not a panacea type solution to countering stealth aircraft.

Image 2: Raleigh scattering region. Image Credit: Air Power Australia

Historically, VHF radars have been of limited use as the resolution cells are too large too provide a target quality track for weapons systems unlike the X and S bands (Majumdar, 2014). China and Russia have recently applied advances in processing power to improve the quality of their VHF systems. For example, the Type 052D Luyang III destroyer features a Type 518 L-band radar paired with a conventional Type 346 AESA radar which could provide it with nascent anti-stealth capability against aircraft like the F-22 and F-35. At the present level of technological maturity, VHF systems would likely provide an early warning capability against stealth aircraft and could eventually cue X and S band systems which would provide the targeting information to surface to air missile systems. However, the weapon employment range of a VHF radar cued with a X and S band system may not be tactically significant. In the future, a system of VHF radars would be networked via a high speed datalink, the resolution cell could hypothetically be refined enough for a weapon quality track (Majumdar, 2014). Both the USAF and US Navy have made preparations to keep the F-35 relevant in highly contested VHF anti-access area denial (A2/AD) environments into the 2030s and beyond; as VHF systems continue to proliferate the use of electronic warfare in conjunction with low observable aircraft will become a necessity.

Another factor that has led to the development of a sixth generation fighter stems from China's cyber espionage activities. Edward Snowden recently released documents confirming China's role in stealing F-35 program information including the AN/APG-81 design, engine schematics, infrared signature reduction methods, etc. (Gady, 2015). These technical details have not only helped China build its own stealth aircraft, but also the information could be used to potentially facilitate the creation of countermeasures against the F-35. Lockheed Martin insists China has not managed to obtain the "crown jewels" or technical details that would effectively compromise the program. Despite Lockheed Martin's assurances, the data breach is generally regarded as a significant setback for the F-35 program. Chief of Naval Operations (CNO) Admiral Jonathan Greenert recently remarked, "The losing of proprietary data on high technology from cleared defense contractors — it’s just driving me crazy. Cyber theft is just hemorrhaging us". Ultimately, the Department of Defense's (DoD) decision to take the VHF threat seriously is prudent and essential towards maintaining the technological superiority of the American Military: 

senior officials are in the preliminary stages of examining options should stealth—one of the F-35’s key attributes—be compromised by new technology. The idea is to be able to hand off to the next presidential administration both a healthy F-35 program—no small feat, after its years of pitfalls and overruns—and other options should the next president find the aircraft’s technology outdated, the industry source says. The hope is the F-35’s technology will be viable for decades to come. The studies are preliminary and academic at this point, and they do not indicate the Pentagon is backing away from the F-35; its support has been unwavering since the 2011 restructuring. The Pentagon is now planning for a substantial ramp-up in production for the fighter over the next five years. - Amy Butler, 2015 

The emergence of a new threat during the development of a major fighter program is not new. The development of the sixth generation F-X while the fifth generation F-35 has yet to enter service is not dissimilar from how the Advance Tactical Fighter (ATF) program, which eventually led to the fifth generation F-22, was undertaken while the fourth generation F-X program - which led to the F-15A, had only just concluded. US reconnaissance satellites captured images of the T10-1 prototype, the Soviet's fourth generation response to the F-15 which resulted in the Su-27, in 1977 (Goebel, 2014). The Soviets had responded to the F-15 more quickly than anticipated and it was soon apparent that a new fighter aircraft was needed to maintain the US' technological advantage prompting the formulation of the ATF in 1981. Unlike the ATF during the 1980s, the next sixth generation aircraft(s) will be built by up to two of the remaining three US aerospace defense contractors that manufacture combat aircraft assuming the F/A-XX and F-X remain separate programs.

Image 3: Defense industry consolidation after the "last supper" in 1993. Image credit: Ann Markuson, 1998, “The Post-Cold War Persistence of Defense Spending,” in The Defense Industry in the Post-Cold War Era: Corporate Strategies and Public Policy Perspectives, ed G. I. Susman and S. O’Keefe (Amsterdam).

Image 4: Preliminary request for information concepts for the ATF courtesy of YF-23.net.

The consolidation of the US aerospace and defense industry after the Cold War has only been exacerbated in recent years due to the structuring of contemporary US combat aircraft procurement programs. Instead of a diverse set of multiple smaller procurement programs, there are only four major combat aircraft procurement programs over the next decade (UCLASS, T-X, LRS-B, and some F/A-XX and F-X work). Thus, if a major defense contractor fails to secure one of these programs it will be unable to sustain its aircraft manufacturing capability as the wait for another major program opportunity is unsustainable. Northrop Grumman is currently tenuously close to losing its aircraft manufacturing capability with its last combat aircraft manufactured in 1997 (B-2). Should Northrop Grumman lose both the upcoming Long Range Strike Bomber (LRS-B) and next generation trainer (T-X) programs, there is a strong possibility its aircraft division will be sold to either Lockheed Martin or Boeing which would reduce the competitiveness of future defense programs (Aboulafia, 2015). Part of the justification for accelerating the F-X and F/A-XX programs is to provide work for the defense industrial base such that further consolidation can be avoided (Sweetman, Asker, Norris, & Butler, 2015).

The last major reason for starting development of a sixth generation fighter, at least from the Air Force's perspective, is the limited number of high end air superiority platforms currently in service. F-22 production was prematurely terminated with 195 aircraft produced of which only 186 are in the Air Force's current inventory (e.g. not production representative test vehicles and engineering and manufacturing development aircraft). Of these 186 aircraft, only 123 to 149 are combat coded at any one time with the remainder of the aircraft serving in either in an attrition reserve, training, or test and evaluation role.  A total of 300 F-22As were to replace the existing F-15C/D fleet which will now receive an extensive series of upgrades to keep the Eagle fleet operational until at least the late 2020s. While the F-35 will provide robust air to air capabilities, it is not an air dominance fighter like the F-22. A new sixth generation fighter would greatly increase the service's air superiority capabilities upon the retirement of the F-15C/D and F-22A fleets. The USAF will require new sixth generation air superiority aircraft in the 2030s if the service seeks to retain the current disparity in projected kill ratios between Chinese or Russian and US fighters.

The DoD estimates the People's Liberation Army Air Force (PLAAF) will have its first operational J-20 unit between 2017 and 2018 (Sweetman, 2014). Similarly, the Russian Air Force will deploy its first fifth generation PAK FAs in 2016 with 55 units operational by 2020 (Novichkov, 2014). A new sixth generation air superiority fighter is needed  in the 2030s to hedge against a decline in expected US exchange ratios against increasingly advanced Russian and Chinese aircraft. A US Air Force official interviewed by the National Interest discussed the narrowing disparity in performance between US and Chinese aircraft which is a concern given China's regional numerical superiority:

I think we can probably keep a slight advantage for quite some time, but a slight advantage means significant losses and less of a deterrent...Lets pretend the F-22 confronts current air-to-air threats outside of a SAM [surface-to-air missile] environment and has a 30 to one kill ratio today versus a [Sukhoi] Su-30 or [Shenyang] J-11. When the J-20 and J-31 come around, even a three to one kill ratio advantage becomes costly...Our competitors know the current reality and are working very hard to avoid the wide gap we have created by investing in those planes,they represent their attempt and creating parity in the skies.

In an Australian Parliamentary hearing within the Foreign Affairs, Defense And Trade Joint Committee, Garry Liberson who is the Technical Lead of Operations Analysis and Strategic Studies at Lockheed Martin indicated the F-35 would have a six to one exchange ratio against "advanced red threats" in the 2015 to 2020 time frame (Source 69, page 5).The red threats described by Mr. Liberson are likely to be either upgraded Su-30s or Su-35s. Thus the author would surmise the F-35 would perform less favorably against the J-20 and Pak Fa when compared to the F-22 as discussed above. In order to the maintain its edge, the Air Force must inevitably invest in new platforms, upgrades for its existing platforms, and innovate new tactics techniques and procedures (TTP) with respect to its employment of those systems.

The A2/AD Strategic Environment of 2030

Image 5: Chinese A2/AD anti-surface warfare weapons in the Asia-Pacific. Image Credit: CSBA, 2014

It is important to emphasize the context in which American sixth generation aircraft will operate in conjunction with other American and allied aircraft rather than merely analyzing various tactical air to air combat scenarios between individual adversary and US platforms. The sixth generation development programs take place within the broader context of the third offset strategy and new concepts like distributed lethality all of which are geared towards mitigating advancements made by Russia and China to limit US power projection operations. To provide a brief overview, China began to develop systems to inhibit US power projection after the overwhelming victory of the United States in the Persian Gulf War:

...the consensus that U.S. forces were unbeatable in a conventional force-on-force conflict became the dominant global lesson learned. As the previous study notes [Conduct of the Persian Gulf War], 'while the Vietnam syndrome might always have been exaggerated and misinterpreted, the display of U.S. power in the Persian Gulf had the effect of creating an image of overwhelming power'. For nations, non-state actors, and other entities opposed to U.S. influence and contemplating violent means toward achieving their international political aims, conventional warfare seemed almost a closed option. - Tangredi, pg.29, 2013 

The general deterioration of Sino-US relations following Tienanmen Square in 1989, the Third Taiwanese Strait Crisis in 1996, and the US bombing of the Chinese embassy in Kosovo in 1999 all provided the impetus for China's development of its A2/AD strategy (Erikson, 2013). To constrain US power projection near its shores, China has implemented a host of systems including: sea mines, anti-ship cruise missiles (ASCMs), electronic &GPS jamming, submarines, anti-satellite weapons, conventional land attack and anti-ship ballistic missiles, and extensive surface to air missile systems networked with air power. These systems collectively limit how close US forces can safely operate in proximity to China and allow Chinese forces to avoid a conventional force on force engagement which favors US forces as described above. In order to further push US forces out of the region in wartime conditions, many Chinese source publications such as, The Science of Second Artillery Campaigns, emphasize the need to destroy US logistics assets in the Western Pacific which are the enablers of US power projection. These assets include aircraft carriers, ports, allied air bases, pre-positioned stockpiles (e.g. at Guam and Diego Garcia) tankers, etc. Note the explicit abstention from referring to the United States directly and the term "powerful enemy" is substituted for the United States instead (presumably for political reasons):

When the powerful enemy uses allied military bases in our periphery and aircraft carriers as aircraft launch platforms to implement various forums of military intervention; and when the powerful enemy's allied military bases around are periphery are beyond our air arm's firing range, and when the carrier battle groups are away from our shores, thus making it difficult to carryout out the overall operational advantages associated with firepower coordination among the service arms, conventional missiles can be used to implement harassment strikes against the military bases of the enemy's allies around our periphery as well as the carrier battle groups. - 401 (See source 55)

China's A2/AD strategy will force the US to operate its land and carrier based aircraft far from China's stores during the opening stages of the conflict. New technologies developed under the Defense Innovation Initiative and the National Aerospace Initiative will permit sixth generation aircraft to operate in in this heavy contested environment.

PART II - Development Status and Technology 
PART III - Roles and Missions
PART IV - Works Cited 

America's Sixth Generation Fighters: The F-X and F/A-XX - II

Part I 

Program Development Status

Image 6: Lockheed Martin YF-22 technology demonstrator 

Pentagon acquisition chief Frank Kendall reported the FY 2016 budget request will allocate funds towards the development of sixth generation aircraft under the aerospace innovation initiative. The Air Force has set aside $8 million for its next generation air dominance program while the Navy has set aside $5 million for the F/A-XX program (Parsons, 2015). However, neither of these sums represent the total budgeted amount which is under the black budget. Within the Air Force's $7 billion black research development and procurement budget, funds have been allocated towards the Defense Advanced Research Projects Agency (DARPA) which recently completed its Air Dominance Initiative study (Sweetman, Asker, Norris, & Butler, 2015). Frank Kendall estimates that $150 million to $500 million will be allocated towards the development of a sixth generation X plane over the next few years.

The aerospace innovation initiative will be led by DARPA and will produce an X plane type technology demonstrator aircraft. A senior DARPA official speaking to Aviation Week compared the current classified X plane program to the earlier Joint Advanced Strike Technology (JAST) program which produced a technology demonstrator related to the F-35. DARPA will create an aircraft with a similar size to what the services might procure, that would incorporate the desired technologies, and would be capable of flight but it would not be as mature as the YF-22 as to the F-22 in terms of program development (Sweetman, Asker, Norris, & Butler, 2015). 

Higher level defense initiatives such as the Third Technological Offset strategy, the Long-Range Research and Development Program (LRRDPP), Full Spectrum Dominance, and Better Buying Power 3.0 give some indication of how the F-X and F/A-XX programs will proceed and which technologies both planes will incorporate. Deputy Defense Secretary Robert Work, who is (in the view of the author) among the most intelligent and competent individuals within the DoD's leadership, has been tasked with leading the Pentagon's third offset strategy. The first offset strategy focused on developing US nuclear capabilities early in the Cold War and the second offset drove US investments in information technology, stealth, and guided weapons. The third strategy will seek to preserve the US' technological superiority and power projection capabilities in the face of increasingly hostile A2/AD environments posed by near peer military competitors (Work, 2014). A November 2014 press release by then Secretary of Defense Chuck Hagel stated four technologies would take priority but the list is not holistic due to classification concerns: robotics, miniaturization, big data, and advanced manufacturing. In an interview with Defense News, Robert Work outlined the objectives of the Defense innovation initiative and how LRRDPP fits in within the broader Defense Innovation Initiative and the United State's national security strategy:

"within the long range [LRRDPP], we have the advanced capabilities and deterrence panel, which is really focused on state actors. And, as part of the advanced capabilities and deterrence panel, we have similar lines of efforts, strategy, war gaming concepts. But the long-range research and development planning program is designed to tell us how we would want to use technology to gain an advantage over time...We want to remain a resident Pacific power. We want China to accept that, and over time we’re building confidence-building measures, which were just announced by the president. And, we believe that we can do this peacefully. But, we also need to hedge. They are developing certain capabilities that would be very problematic for our allies, and for us in the Western Pacific, and it is important that we create capabilities that deter their use."

LRRDPP has outline five core areas of focus: air, missile and precision guided munition defense, air superiority, space, undersea, and emerging technologies. The following technologies will be developed in the context of the aforementioned broad DoD defense innovation programs with the intent of operating in highly contested A2/AD environments: variable cycle engines, directed energy weapons, GaN avionics & electronic warfare systems, autonomous system integration, and broadband stealth. It is important to note that there are ongoing discussions within the DoD to incorporate some of these technologies into the F-35 as a means to keep it more competitive against developing threats (Sweetman, Asker, Norris, & Butler, 2015).

Sixth Generation Technologies 

Adaptive-Cycle Engines 

Image 7: General Electric ADVENT

Adaptive cycle engines have the potential to revolutionize future fighter aircraft propulsion. Adaptive engines incorporate a third stream of air within the engine which manipulates its bypass ratio enabling supercruise at more fuel efficient rates. Furthermore, the pilot has the option to exit cruise mode and significantly increases thrust as needed. Substantial progress has been made in adaptive cycle or variable cycle engines as a result of the Air Force's Adaptive Versatile Engine Technology (ADVENT) program: 

One of the key technologies behind the adaptive-cycle engine is the adaptive fan, which allows the engine to vary its bypass ratio depending on its altitude and speed due to a third stream of air. Air flows through the third stream as needed to increase or decrease the bypass ratio of the engine—or alternatively use the extra airflow for cooling. 'We can effectively vary the performance of the engine across the flight envelope,' Kenyon said. At high-supersonic speed, the third stream can reduce spill drag by letting the excess air flow through the engine—however performance above about Mach 2.2 is still limited by the physics of air inlet geometry. 'The third stream does help supersonically very much,' McCormick said. The General Electric ADVENT engine has an adaptive-fan, which creates a third stream of air, an extremely high-pressure compressor, a new combustion system, various new materials such as ceramic matrix composites and cooling technologies...the ADVENT demonstrator engine is actually exceeding expectations in many cases including for fuel burn. The fuel efficiency target for ADVENT was to reduce fuel-burn by 25 percent. The AFRL’s follow-on Adaptive Engine Technology Development (AETD) program is intended to bring the technologies developed under ADVENT into a flight-worthy design." - Dave Majumdar, 2014 

Aviation Week's Guy Norris explained sixth generation fighters equipped with adaptive cycle engines could lead to a 25%-30% increase in range and up to a 10%  increase in thrust over conventionally configured turbofan fighter aircraft. Part of the impetus behind funding variable cycle technology is the 500-600 nautical mile unrefueled combat radius of existing aircraft is insufficient in A2/AD environments, particularly in the Pacific theatre (this point will be examined in depth during the roles and missions section). However, the Navy is not as convinced variable cycle engine technology would make a valuable addition to the F/A-XX (Majumdar, 2014).The Navy should adopt variable cycle engine technology given it synergizes with many other potential technologies discussed for sixth generation aircraft. The third stream of air provides additional heat sink capacity that both reduces the aircraft's infrared signature and enables the aircraft to accommodate directed energy weapons (Norris, 2015).

Directed Energy Weapons 

Image 8: Lockheed Martin Falcon 10 test aircraft equipped with Aero-Adaptive/Aero-Optic Beam Control (ABC) laser

Despite the stigma associated with directed energy weapons as a result of the Strategic Defense Initiative (nicknamed STAR WARS), laser technology has steadily progressed since the 1980s to the point at which it is feasible for combat in limited roles. Sydney Freedburg recently explaied, "Not only have lasers gotten better, the military’s expectations have gotten lower — and the urgency of the threat has gotten higher". The Navy, Air Force, and DARPA have concurrently researched high energy aircraft mounted solid and liquid state lasers in the 100kw to 150kw range. In a request for information issued by the Air Force's Research Laboratory, the service seeks:

"The emphasis of this effort is to identify potential laser systems that could be integrated into a platform that will provide air dominance in the 2030+ highly contested Anti-Access/Area Denial (A2/AD) environments,..Laser and beam control systems are being investigated independent of platform in the flight regime from altitudes Sea Level to [65,000ft] and speeds from Mach 0.6 to 2.5,"

Should programs such as DARPA's High Energy Liquid Laser Area Defense System (HELLAD) come to fruition, it is highly likely that both the F/A-XX and F-X aircraft will be equipped with directed energy weapons. As for the tactical usage of lasers on fighter aircraft, lasers would likely be employed as defensive weapons at ranges of 10-15 nautical miles against incoming missiles or small enemy unmanned aerial vehicles. Lasers of the 150kw class can burn through the casings of enemy missiles which will cause them to veer off course or damage the missile's seeker rendering the missile unable to function (Clark, 2014). As lasers continue to improve in power, cooling, and miniaturization, it is conceivable they could be employed against enemy fighter aircraft in the far future.

"[if] a laser weapon can burn a hole through the skin of its target, success is practically assured. Aircraft with wet wings are doomed, similarly fuel cells not protected by substantial amounts of airframe structure. Missiles with solid propellant engines and warheads are also left with little potential to survive. The damage that can be done to guidance or control systems is also vast." - Karlo Kopp, 2005 

An ongoing concern with the F-35 is its limited ammo capacity for its GAU-22 at 180 rounds which fires at a rate of roughly 50 rounds per second. In contrast, lasers are only limited by power and cooling constraints rather than physical ammunition which is both a performance and logistics benefit. Further discussion on how both the F/A-XX and F-X will employ lasers will be discussed in the roles and mission section.

Image 9: Concept of Lockheed Martin ABC fitted to the F-35. Conceivably, a laser system could be fitted to the F-35 in a future upgrade.

Broadband All Aspect Stealth

Image 10: Aviation Week concept of Northrop Grumman's RQ-180. Image Credit: Aviation Week

Amy Butler reported in February of 2015 that, "[DoD] planners are considering broadband stealthiness for sixth-generation fighters—the F/A-XX for the Navy and F-X for the Air Force". Aircraft such as the LRS-B, B-2, and RQ-180 incorporate broadband stealth and do not share the potential vulnerability to VHF systems like smaller aircraft using planform alignment. Bill Sweetman explains how the RQ-180's shape enables it to achieve broadband stealth: [emphasis mine]  

A key feature of the RQ-180’s design is an improvement in all-aspect, broadband radar cross-section reduction over Lockheed Martin’s F-117, F-22 and F-35. This is optimized to provide protection from low- and high-frequency threat emitters from all directions. The design also merges stealth with superior aerodynamic efficiency for increased altitude, range and time on station. The aircraft uses a version of Northrop’s stealthy “cranked-kite” design, as does the X-47B, with a highly swept centerbody and long, slender outer wings. Northrop Grumman engineers publicly claimed (before the launch of the classified program) that the cranked-kite is scalable and adaptable, in contrast to the B-2’s shape, which has an unbroken leading edge. The RQ-180’s centerbody length and volume can be greater relative to the vehicle’s size.

It will be difficult to design a broadband stealth aircraft that is also maneuverable, none of the aforementioned broadband stealth aircraft were optimized for air dominance roles. Rather, all previously mentioned broadband stealth aircraft are intended to cruise at high altitude and perform either bombing or intelligence, surveillance, and reconnaissance (ISR) missions. Northrop Grumman is exploring a tailless concept for the F-X competition and Boeing has similarly shown tailless F/A-XX concepts. The removal of the aircraft's tail could reduce the number of small exposed flight surfaces with respect to the Raleigh scattering region but it remains to be seen if a high degree of broadband stealth is achievable in a maneuverable platform. Furthermore, the Navy and Air Force have diverging opinions on what level of stealth is appropriate for their sixth generation concepts.

CNO Greenert indicated stealth may be less of a priority for the F/A-XX when compared to its ability to suppress enemy air defenses with a high weapons payload and powerful sensors, "You know that stealth maybe overrated...I don’t want to necessarily say that it’s over but let’s face it, if something moves fast through the air and disrupts molecules in the air and puts out heat – I don’t care how cool the engine can be – it’s going to be detectable...It has to have an ability to carry a payload such that it can deploy a spectrum of weapons. It has to be able to acquire access probably by suppressing enemy air defenses". The CNO's statement is consistent with the view of several Navy officials who are skeptical of stealth which is a contributing factor in its prioritization of endurance over stealth the UCLASS' (Unmanned Carrier Launched Surveillance and Strike) requirements and the Navy's decision to slow F-35C buys in its FY 2016 budget submission (Sweetman, 2015). Unlike the Air Force which has operated stealth aircraft since the early 1980s, the Navy has had to rely on its electronic warfare aircraft to carry out suppression of enemy air defense (SEAD) missions. The Navy would have received stealth aircraft prior to 2018 if it were not for the cancellation of the McDonnell Douglas A12 and A/FX programs in the 1990s. Despite the CNO's comments, the F/A-XX will assuredly have some level of stealth but it may not have the same degree of stealth as the F-X. In contrast to the Navy, the Air Force continues to be bullish on the future of stealth and Air Combat Command's General Herbert "Hawk" Carlisle indicated stealth would be incredibly important for the F-X (Butler, 2015).

Gallium Nitride (GaN) Avionics & Electronic Warfare Systems

Image 11: Next generation jammer pod featuring GaNs components. Image Credit: Raytheon

GaN based AESAs and electronic warfare systems will revolutionize fighter avionics over the next two decades with substantial increases in performance and cooling over existing Gallium Arsenide(GaA) based arrays:

"GaN has anywhere from five to 10 times the power density, which is the amount of electrical energy a chip can handle relative to its size. A GaN chip can handle more than double the voltage and amperage of a similarly sized GaAs chip. GaN also has up to seven times the thermal conductivity of the older material, which allows it to run hotter. That means lower cooling requirements and greater amounts of electrical power. In basic terms, Rosker said, a radio transmitter based on GaN technology could put out "an order of magnitude more" power than a similar GaAs-based transmitter, or conversely, produce the same power yet take up a fraction of the volume. It could also operate over far more frequency bands...Colin Whelan, a Raytheon engineer who works on GaN technology, said a GaN-based active electronically scanned array radar could search five times the volume as a similarly sized GaAs-based radar, or at a 50 percent greater range. You could even halve the size of the radar and still deliver greater performance." - Dave Majumdar, 2011 

The addition of a GaN AESA to both the F/A-XX and F-X would greatly increase the detection range of enemy fifth generation aircraft and other low observable targets. The power of a large GaN based fighter AESA would likely result in detection ranges for targets well beyond the range of current weapons like the AIM-120D range. As the roles and missions section will discuss, the power of GaNs will synergize with the Naval Integrated Fire Control-Counter Air—or NIFC-CA concept.

As discussed previously, the emergence of more powerful radars and capable VHF radars will make the employment of electronic warfare in conjunction with stealth a necessity. Defense One's Patrick Tucker reports sixth generation aircraft will likely employ a more advanced version of cognitive electromagnetic weapons:

"Cognitive electromagnetic weapons autonomously find new wave forms to use against planes, tanks, or other threats (or, defensively, find ways to detect new wave forms being used against the system). Full spectrum dominance will mean more of that. It could include intelligence gathering equipment we can’t fathom. 'Today it’s radar but it might be something more in the future,' said Adm. Jonathan Greenert, chief of naval operations, at the expo. Tomorrow’s innovations in radar, jamming and sensing, will emerge from a variety of research outfits but particularly the DARPA Microsystems Technology Office, MTO, designed specifically to tackle those sorts of problems."

Autonomous and semi-autonomous sensors and components, such as cognitive electromagnetic weapons, will be a prominent feature of both the F-X and F/A-XX.

Unmanned & Autonomous System Integration

Image 12: DARPA Collaborative Operations in Denied Environment (CODE) concept

The DoD has hinted at an "optionally manned" F-X or F/A-XX. While there is certainly an institutional desire to leverage the United States' advantage in unmanned systems as part of the third offset strategy, particularly in the Air Force, the possibility of the next sixth generation fighter being fully autonomous is minimal. However, some form of artificial intelligence that integrates sensors and information is plausible and the addition of systems that would facilitate the operation of manned and unmanned systems is a near certainty. Both the Air Force and Navy are looking at integrating  Unmanned Combat Air Vehicls (UCAVs) with fighter aircraft.

USAF Col. Michael W. Pietrucha published, "The Next Lightweight Fighter - Not Your Grandfather’s Combat Aircraft" in which he argued the Air Force should procure a low cost UAV which would act as a force multiplier for manned fighter aircraft. Advances in datalinks would enable UAVs to act as "missile trucks" for the sixth and fifth generation assets which would provide targeting information. The additional supply of air to air missiles provided by UAVs would be advantageous given the limited probability of kill (pk) of most air to air missiles in a digital radio frequency memory (DRFM) jamming environment. Half a dozen Air Force officials interviewed by the Daily Beast stated they expect the pk of the AIM-120D to be reduced by DRFM jammers such that two to three missiles will be required to destroy a single target. Lieutenant General Ellen Pawlikowski is tasked with the Air Force's R&D, procurement, and modernization programs; she is a staunch advocate for usage of UAVs similar to what is described above, "I can see a scenario where you’ve got an F-35 orchestrating an attack with 20 RPAs [remotely-piloted aircraft] that are weapons-equipped and that F-35, with all its sensors and communications, is essentially an orchestrator".

DARPA's CODE program will facilitate the integration of semi-autonomous UAVs with manned assets in contested A2/AD environment's:

"Just as wolves hunt in coordinated packs with minimal communication, multiple CODE-enabled unmanned aircraft would collaborate to find, track, identify and engage targets, all under the command of a single human mission supervisor...CODE aims to decrease the reliance of these systems on high-bandwidth communication and deep crew bench while expanding the potential spectrum of missions through combinations of assets—all at lower overall costs of operation. These capabilities would greatly enhance survivability and effectiveness of existing air platforms in denied environments." -Jean-Charles Ledé, DARPA program manager

As for specific UAV platforms that could serve in this role, a high end requirement UCLASS, configured QF-16 (unmanned target drone variant of the F-16), and optionally manned variant of the F-35 are all possible candidates. DARPA has already discussed the possibility of using an aircraft like the QF-16 in an air to ground role (Bell, 2014). It is plausible that with further modifications Boeing could permit the QF-16 to integrate with manned platforms via datalinks like the advanced tactical data-link (ATDL) or tactical targeting network technology (TTNT) waveform. With respect to an unmanned F-35, Lockheed Martin's Skunk Works has neither confirmed nor denied working on an optionally manned variant of the F-35. Once sufficient economies of scale has been reached with respect to F-35 air frame production, an optionally manned variant could become more feasible in the future. 

Part I - The Need for 6th Gen. and 2030 A2/AD

PART III - Roles and Missions 

PART IV - Works Cited 

America's Sixth Generation Fighters: The F-X and F/A-XX - III

Part I - The Need for 6th Gen. and 2030 A2/AD

PART II - Development Status and Technology 

Key Characteristics, Roles, and Missions F-X

Image 13: Early Lockheed Martin F-X concept. Image Credit: Lockheed Martin, 2012.  

The primary role of the aircraft produced as a result of the F-X program will be air superiority as a replacement for the F-22 (Majumdar, 2014). The Air Force has been comparatively more bullish on the future of adaptive cycle engines, stealth, and UAVs when compared to the Navy. The greater emphasis placed on air superiority over a deep strike role, as described in the F/A-XX section, will greatly impact the F-X's design as described by Air Force and defense industry officials interviewed by Dave Majumdar:

“'I would expect our requirements to be a lot different from the Navy’s,' Col. Tom Coglitore, who heads Air Combat Command’s Air Superiority Core Function Team and the F-X program, told the trade journal Aviation Week in its Oct. 13 issue. 'Our system of systems would be more offensively minded and operate in more difficult and highly contested areas of operation than the areas the Navy will likely be operating in'...The Navy may need to be content with ceding the uber-air dominance mission to the USAF due to the geometric constraints of their ‘mobile airbases’"

Air Force officials consistently uses the term "systems of systems" (SOS) when describing their vision for a new a sixth generation aircraft. General Carlisle explained the Air Force is reviewing the prospect of making significant changes to communications, capabilities from space, standoff and stand in options under a comprehensive assessment of air superiority in 2030 (Butler, 2015). Similarly,  Lt. Gen. James Holmes said, "[ the Air Force] not want to jump straight to the idea of a sixth-generation fighter". Given the service's aforementioned stance on the future of UAVs, the author surmises the air force plans to integrate UAVs with manned sixth generation aircraft in future air-to-air missions. However, the service has yet to release R&D or procurement plans, at least in the public domain, for a UCAV that would act as a force multiplier for sixth generation aircraft. The canceled MQ-X program likely have produced a UCAV with similar capabilities required to act as a force multipler but the program was canceled in 2012. The General Atomics Avenger did not meet MQ-X requirements (Axe, 2013).

Another possibility implied by SOS would be to integrate the LRS-B with the F-X. The LRS-B would be loaded with stand-off range air-to-air missiles and the F-X with a high power GaN AESA radar which would provide targeting information; the LRS-B has also frequently been referred to as a SOS or "family of systems". The LRS-B's bomb bay will accommodate at least 30,000 pounds in ordinance and its extensive signature reduction methods coupled with extended range air-to-air missiles would reduce risk to the aircraft (Hodge, 2013). It is also possible the SOS term refers to Air Force plans to integrate the F-X with ISR assets like the RQ-180 to perform electronic attack and suppression of enemy air defense (SEAD) missions which will be discussed later. Regardless of SOS, the physical F-X platform will rely upon its variable cycle engines to overcome the "tyranny of distance" between US facilities in the Pacific and they likely area of operations in the Western-Pacific. 

Image 14: Key US air bases with respect to their distance from the Taiwanese Strait. Image Credit: RAND, 2008. 

The Air Force's sixth generation air superiority fighter will likely be based from Andersen air force base at Guam which is 1,500 nautical miles from China's mainland. Air bases closer than 1,500 nautical miles will be subject to cluster munition strikes from Chinese ballistic missiles. The limited number of hardened aircraft shelters and exposed fuel storage depots at these locations would entail a high risk to US aircraft (RAND, 2008). The extended range from Guam to mainland China will put a heavy strain on tanker aircraft supporting fifth generation aircraft. For example, F-22s with a full load of air-to-air weapons would have to refuel six times (to destination and return) with a total fuel consumption rate of 2.6 million gallons per day to support 120 F-22s with 69 KC-135s. Raptors based at Guam would only be able to conduct 1.15 combat air patrol sorties per day meaning China would maintain a 10:1 numerical advantage at any given time over the Taiwanese strait with Andersen based aircraft and 3:1 from Kadena (RAND, 2008). The F-X will be able to more easily operate from Andersen given its variable cycle engines and will be better suited to face large numbers of J-20s in the 2030s than its fifth generation counterparts. Futhermore, the F-X will work alongside the LRS-B and RQ-180 in SEAD and Destruction of Enemy Air Defense (DEAD) missions.

As a result of the increment 3.1 upgrades, the F-22 is among the most capable SEAD/DEAD platforms in the USAF and it is likely the F-X will be tasked with similar roles. Working in conjunction with the RQ-180 and LRS-B, the F-X will play a vital role in disabling VHF radars, C2 nodes, missile batteries, and DF-21 launch sites within China's integrated air defense system (IADS). The addition of powerful GaN based electronic warfare systems, broadband stealth, and energy weapons will allow the F-X to support fifth generation assets to operate further within the A2/AD zone than would otherwise possible. In summary, the F-X concept and design characteristics are highly relevant to the expected threat environment of the late 2030s to 2040s.

Key Characteristics, Roles, and Missions F/A-XX

Image 15: Boeing F/A-XX concept 

Navy official have released few details as to the role and capabilities of the F/A-XX. Navy Rear Adm. Mike Manazir vaguely described the F/A-XX,

"You have to have something that carries missiles, you have to have something that has enough power and cooling for directed energy weapons and you have to have something that has a weapons system that can sense the smallest radar cross-section targets...We’re looking to replace the F/A-18E/F with an understanding already of what the F-35C has brought to the air wing, what the UCLASS mission set is,"

Adm. Mike Manazir indicated that as a replacement for the F/A-18E/F, the F/A-XX will focus on a strike role rather than air superiority which is the F-35C's role under NIFC-CA (Tucker, 2015). Similarly, changes made to the UCLASS program requirements underscore the emphasis of the F/A-XX as a deep strike platform. UCLASS was conceived as a 2,000 nautical mile range low observable platform which would enable carriers to operate outside of enemy A2/AD weapons employment range. However, the Navy altered its requirements for UCLASS from a low observable strike platform to a limited ISR platform in order to justify the role of the F/A-XX:

"The striking power and stealth of the U.S. Navy’s Unmanned Carrier Launched Airborne Surveillance and Strike (UCLASS) concept was reduced to protect the role of the service’s next-generation of manned fighters, USNI News has learned. In particular, the change in UCLASS from a deep strike stealthy penetrator into the current lightly armed intelligence, surveillance and reconnaissance (ISR) focused aircraft was — in large part — to preserve a manned version of the F/A-XX replacement for the Boeing F/A-18E/F Super Hornet, several Navy, Pentagon and industry sources confirmed to USNI News. Industry, Pentagon and Navy sources outlined a, 'bureaucratic and cultural resistance to the introduction of unmanned aircraft onto the carrier.'" - Dave Majumdar and Sam LaGrone, 2014 

The Navy's decision to delay the acquisition of a high-end stealthy carrier strike platform is, in the author's view, shortsighted. Depending upon how the fight for UCLASS program requirements unfold, the role of the F/A-XX may be subject to change. Deputy Secretary of Defense Robert Work currently chairs the Defense Acquisitions Board and he has been a longtime supporter of a high end UCLASS (he advocated for a high-end UCLASS as early as 2007 while working for the Center for Strategic and Budgetary Assessments). Furthermore, Congressional support for a high-end UCLASS remains strong with the backing of chairman of the House subcommittee on Seapower Randy Forbes. The Navy should embrace UCLASS as its low observable strike platform and subsequently adjust the F/A-XX to be geared towards its premier carrier based long range interceptor as a fleet defense asset with both robust sea control and offensive anti-air warfare capabilities similar to how the F-14 was utilized under its "Outer Air Battle" concept in the Cold War.

Image 16: F-14A fires a long range AIM-54 Phoenix missile

Several US Navy concepts developed during the 1980s were in response to the Soviet's use of sea denial platforms to keep the US Navy from being able to conduct transatlantic resupply operations (Tangredi, pgs. 36-38). With the rise of China as a near military competitor to the United States whose military will employ A2/AD methods, many of the Cold War concepts developed to protect US carrier battle groups are becoming increasingly relevant. Under the Outer Air Battle concept, F-14s would be guided by E-2Cs to intercept Soviet Tu-22 "Backfire" and Tu-95 "Bear" bombers at extended ranges away from the carrier group (Clark, 2014). Soviet bombers employed too many anti-ship cruise missiles (ASCMs) for individual missile interceptors to be cost effective but the combination of the F-14 armed with its 100 nautical mile range AIM-54 and the E-2C enabled the Navy to, "shoot the archer before he shoots his arrows". By destroying the launch platform of the ASCMs before they can fire at the carrier group, rather than targeting individual ASCMs, the F-14 would have been able to cost effectively protect the carrier battle group from air based threats. The basics of Outer Air Battle could be reimplemented with the F/A-XX, E2-D, and a yet to be developed long range air-to-air missile. This future assortment of systems could target Chinese and Russian air launched ASCM platforms at extended ranges as well as A2/AD enablers such as enemy Command and Control (C2) and ISR assets. For example, by destroying Chinese UAVs like the Chengdu Tian Yi and other ISR assets, the DF-21 "carrier killer" would be unable to receive mid-course guidance updates required to successfully hit American carriers.

As for why a new platform is needed to fulfill this fleet defense role rather than the F-35C, the variable cycle engines on the F/A-XX and presumably larger fuel capacity would grant it the ability to perform long duration combat air patrols at extended ranges further from the carrier strike group than the F-35C. Furthermore, the addition of a directed energy weapon on the F/A-XX would enable the aircraft to intercept any ASCMs launched against the carrier group which would subsequently reduce the strain on the limited number ship based interceptors like the SM-6 and evolved sea sparrow missile. Ideally, the F/A-XX would also be an exceedingly capable air dominance platform similar to the terminated A/F-X concept in order to enforce sea control and conduct offensive anti-air warfare missions.

Image 17: Lockheed A/F-X concept. The A/F-X program would have produced a twin engine low observable carrier based air superiority fighter second only to the F-22. The A/F-X would have replaced the A6 Intruder, F-14, F-15E, and F-111.

Sea control is the prerequisite to power projection operations which carriers are often associated with. The Navy defines sea control as the deployment of naval and air forces with the intent of establishing local military superiority, defending critical sea lines of communication, destruction of enemy naval vessels, and suppression of enemy sea commerce (Naval Operations Concept, pg. 52). Carrier based fighter's air-to-air capabilities would perform vital roles assisting surface action groups achieve sea control such as protecting surface action groups, tanker aircraft, ISR assets, and Airborne Early Warning aircraft. Jon Solomon further explains how carrier air wings would facilitate sea control in tandem with surface combatants:

"...carrier-based fighters—supported by battleforce-organic Airborne Early Warning (AEW) and aerial refueling assets, with augmentation by land-based AEW and tanker aircraft as possible—might screen SAGs throughout their contested zone missions. Carrier-based fighters might likewise be sortied forward if a SAG makes heavy contact with adversary forces, or be used to cover an ordnance-depleted SAG’s retirement from the contested zone. The same would be true for providing similar support to maritime forces operating at the ‘frontline’ at the beginning of a war. Fighters based on land within the contested zone could also render this support, but because their doing so would be predicated on their basing’s survivability and logistical lines of communications’ defensibility, carrier-based fighter support remains a necessary hedge within operational plans." - 2014 

As the F-X section describes, sixth generation aircraft will be needed when the mass deployment of Russian and Chinese fifth generation aircraft would severely reduce US exchange rates; the reduced US exchange rates in conjunction with the adversary's in thetare numerical advantage limits the prospect of the US being able to establish air superiority. As an author, I have been a staunch supporter of the F-35 program and I have often sought to defend its substantial air to air capabilities in the midst of mostly unfounded criticism. With a capable pilot, the F-35 is able to engage foreign stealth aircraft such as the J-20 and PAK FA as discussed ad nauseam in many of my articles. However, the F/A-XX will serve in the 2035-2050s time frame under a strategic environment where US competitors are likely to obtain both a numerical advantage and reduce the existing performance disparity between their fifth generation aircraft and the F-22 and F-35. The carrier air wing of 2030 requires a high-end air dominance platform to complement the F-35C strike fighter in order for the carrier to remain relevant in extremely hostile A2/AD environments. The United States' will have to respond to the aforementioned developments with higher quality air superiority aircraft given the finite space of the carrier flight deck in conjunction with new concepts and unmanned systems.

Image 18: Carrier air wing of the 2020s. Image Credit: Center for New American Security, 2014

Future Ford-class and upgraded Nimitz-class aircraft carriers will host only 44 strike fighters (20 F-35Cs and 24 F/A-18E/Fs) and possibly 6 UCLASS with limited strike capability under current procurement plans. In recent conflicts, the US Navy has at most deployed six carrier strike groups at any one time including surged units (Erdossy, 2012). Thus, at best the Navy could field 264 aircraft that could serve in an air-to-air role (300 with high-end UCLASS as a "missile truck" linked via NIFC-CA) .

The proposed F/A-XX's relationship to the F-35C would be similar to the F-22's complementary role to the F-35A in the Air Force or how the F-14 complemented the legacy F/A-18A/B Hornet in older carrier air wings. Without a high-end air superiority fighter, the carrier air wing will become less relevant to great power conflicts. During the Cold War, well armed and highly maneuverable F-14s provided the carrier group with an effective  air superiority and fleet defense capability. The F-14 was replaced in 2006 by the F/A-18E/F Super Hornet which was designed and built after the collapse of the Soviet Union when the US held uncontested dominion of the seas and the threat of a major great power conflict had subsided. Ideally, the F/A-XX should be thought of as an opportunity to replace the F-14 with A/F-X elements (such as low observability and supermaneuverability) rather than a replacement for the F/A-18E/F.

Upgrading the F-35

Image 19: F-35

Both the Air Force and Navy will examine the prospect of significantly upgrading the F-35 (and F-22) with the aforementioned sixth generation capabilities such as directed energy weapons and variable cycle engines as part of their analysis of alternatives (AOA) to building a new sixth generation fighter. However, Air Force and Navy officials speaking with Dave  Majumdar were not confident the F-35 will be upgraded to preform air dominance missions:

"The Navy will start its formal AOA in 2015 while the Air Force’s analysis will start a little later—in about a year and a half from now [December 2014] .The Air Force hopes to enter into a technology development phase in 2018...It will likely be one of the alternatives in the Analysis of Alternatives,” said a senior Air Force official...The Air Force official added that another alternative will be to modify and upgrade the tiny 186 aircraft-strong F-22 Raptor fleet. 'Modifying the Raptor will be an option too,' he said. 'I doubt either the F-22 or F-35 will win.’" -  Majumdar , 2014 

A host of new weapons and planned upgrades such as Lockheed Martin's CUDA, the AIM-9X Block III (pending its possible cancellation in the Navy's FY 2016 budget request), and Block 4 upgrades to increase the weapons bay capacity for internally carried AIM-120Ds to six paired with new sixth generation technologies would make the F-35 significantly more effective in an air-to-air role. Depending upon the cost of the individual upgrades, both the Navy and Air Force should consider adding some sixth generation technologies into their F-35 fleets in the late 2020s to early 2030s. For example, Block 6 improvements indicate the F-35 will receive a propulsion upgrade and the F-35 will likely be the first operational fighter aircraft with an adaptive cycle engine. However, upgrading the F-35 in lieu of developing a sixth generation fighter is not a plausible option unless the Pentagon is willing to facilitate further consolidation of the military aerospace industry which is likely to have detrimental effects of the competitiveness of future contracts. Ultimately the decision to significantly upgrade the F-35 will depend upon fiscal resources and the next presidential administration's management of the DoD.

Conclusion

In summary, the natural progression of threats from Russia and China necessitates a proactive US response to regain a technological advantage. The natural progression of threats does not reflect poorly on either the development of the F-22 or F-35 which are necessary programs the Air Force and Navy must sustain. Both fifth generation aircraft will be able to provide robust air-to-air capabilities over the next decade but as VHF systems evolve electronic warfare support will become increasingly important in the 2030s. As the F-X and F/A-XX programs progress, the DoD must be cognizant of the health of the US defense industrial base with respect to consolidation and the deeply unnerving bureaucratic/institutional constraints that currently inhibit the development of Naval UAV systems. Furthermore, the Navy should not cede the high-end air dominance mission to the Air Force and should subsequently re-adjust its F/A-XX concept to provide a more robust fleet defense and air-to-air capability. Lastly, upgrading both the F-22 and F-35 with sixth generation technology without building new sixth generation aircraft is not a plausible option. The addition of directed energy weapons, variable cycle engines, and GaN avionics would greatly increase the capabilities of fifth generation aircraft but such upgrades would be dependent on the fiscal environment of the late 2020s to 2030s.

Author's Note: Feel free to let me know if you have any comments, concerns, or suggestions.

Part I - The Need for 6th Gen. and 2030 A2/AD

PART II - Development Status and Technology 

PART IV - Works Cited 

America's Sixth Generation Fighters: The F-X and F/A-XX - IV Works Cited

Sources 

Author's Note: Full citations coming soon. Thank you for your patience.

Part I - The Need for 6th Gen. and 2030 A2/AD

PART II - Development Status and Technology 

PART III - Roles and Missions 

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Article Announcement - America's Sixth Generation Fighters: The F-X and F/A-XX

Image 1: Early Lockheed Martin concept for the F-X. Image Credit: Lockheed Martin, 2012.

On either Tuesday the 17th or Wednesday the 18th I will publish "America's Sixth Generation Fighters: The F-X and F/A-XX ". The article will extensively discuss the need for a sixth generation fighter given the ongoing development of the fifth generation F-35, the state of development in both programs, the technologies that will be incorporated in the design to define sixth generation capabilities, and the likely roles and missions of the two aircraft in their respective services. This article will be my second longest after the "Canada and the F-35" article as I spent an extensive period of time researching and writing it. Thus, I hope you guys will enjoy it!

Best,

Matt 

Sea Denial: Analysis of the CSBA's Proposal The Case for Taiwanese Midget Submarines - Part I

Image 1: Hai Lung class diesel electric attack submarine.

In December of 2014, Taiwanese Deputy Defense Minister Chiu Kuo-cheng indicated he had approved a preliminary design review for a new class of domestically built conventionally powered attack submarine. The Taiwanese Navy currently maintains a force of four submarines including two US World War II Guppy class submarines. The seventy year old boats are relegated to training duties and are not capable of conducting combat missions. Thus, the ROCN effectively operates only two capable attack submarines which are Hai Lung class vessels. The Dutch built submarines are a modified variant of the last US produced diesel electric submarine, the innovative Barbel class which was first deployed by the US Navy in 1959. In 2001, the Bush Administration had promised to supply Taiwan with eight US built diesel electric submarines but the deal has effectively been canceled. Chief of Naval Operations, Admiral Jonathan Greenert, discussed the prospect of US assistance with Taiwanese officials in September of 2014 but refused to comment on the extent of potential US assistance which is likely to be minimal (Defense Industry Daily, 2015).

In theory, the acquisition of eight submarines would greatly augment Taiwan's defense capabilities. The widening disparity of resources between the Taiwanese and Chinese militaries has forced Taiwan to adopt am increasingly asymmetric defense posture in recent years e.g. the fielding of platforms like the HF-2E and HF-3 anti-ship cruise missiles (ASCM) and the Tuo Chiang class "carrier killer" corvette. The stealthiness and lethality of modern attack submarines makes them uniquely suited to Taiwan's strategic situation. Even if Taiwanese forces loose control of the air and the Republic of China Navy (ROCN) surface fleet has been destroyed, Taiwanese submarines could derail any invasion force by sinking Chinese amphibious assault ships en route to the island. Furthermore, the high survivability of these submarines would enable Taiwan to launch retaliatory cruise missile strikes against the Chinese mainland in the event that its land based cruise missile deterrent is destroyed. In 2013, Taiwan received a shipment of 32 submarine launched UGM-84L Harpoon missiles, each missile has a range of 150 nautical miles. Additionally, Taiwanese submarines would also provide crucial intelligence surveillance and reconnaissance (ISR) capabilities for other platforms such as land based ASCMs.

Despite the sound doctrinal justifications for the acquisition of new submarines, most foreign observers are deeply skeptical of the argument that Taiwan's defense industrial base is capable of producing capable 1,500 - 3,000 ton attack submarines. Submarines are among the most difficult defense platforms to design, build, and maintain with only a handful of countries dominating global submarine production including: Russia, Germany, France, and the United States. Even advanced industrialized nations such as Israel and South Korea have relied on foreign manufacturers to produce or facilitate license built production of their submarine fleets. Given Taiwan has no prior experience in building submarines and has had an increasingly flat annual defense budget of $10.5 billion in recent years, the Centers for Strategic and Budgetary Assessments (CSBA) - an influential US Defense policy institute, recommends Taiwan to built a greater number of midget submarines in lieu of the much more expensive and technologically demanding conventional attack submarines:

"With no existing domestic submarine industry, this could prove a serious technical challenge and would likely be more expensive and time consuming than buying directly from foreign suppliers. While it certainly possesses the shipbuilding prowess needed to launch such a program, the ROC would depend heavily on technical assistance from foreign manufacturers, which might not be forthcoming...Furthermore, the costs of acquiring modern diesel- electric submarines, especially if they were equipped with AIP [Air-Independent Propulsion], would most likely consume a large portion of Taiwan’s small defense procurement budget. Assuming Taiwan could overcome the technical challenges of creating a new SSK design and that it could produce them at the same cost per ton as existing SSKs, then procuring eight new submarines would cost approximately $4.47 billion, which constitutes close to half of Taiwan’s total annual defense budget. If they had the same ratio of crew per displaced ton as existing submarine designs, then these eight submarines would require a total of 336 sailors to man them. At any given time, no more than six of the eight submarines would be available for patrol, with the others undergoing refit or modernization"

This article will examine the key capabilities required in modern submarines (stealth, range & endurance, and armament), feasibility of Taiwanese production of conventionally powered 1,500-3,000 ton submarines, and the relative merits of the CSBA recommendation for midget submarines.

Key Capabilities 

Stealth

Image 2: Acoustic signatures for US and Russian submarines. Image Credit: Federation of American Scientists.

Stealth, first and foremost, is the most critical aspect of an attack submarine as it determines the submarine's relative survivability and is a prerequisite to the submarine acting as an effective area denial, power projection, or ISR platform. Quieting technology has progressed steadily since the end of the Second World War with the advent of improved anechoic tiles, integrated electric drive systems (over mechanical), X-shaped stern control surfaces, pump jet propulsion systems (over conventional propellers), AIP technology, etc. The acoustic signature of a submarine, which is measured in decibels, is an indicator of a submarine's relative detectability to passive sonar systems. The following is from the article "China's Anti Access Strategy: Submarine Force - Part I":

A decibel is "a unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale" (American English in Oxford dictionary, 2013). Decibels do not scale linearly. A 3db change is signifies a doubling power and a change of 10 db signifies the power increasing by a factor of ten. Therefore, the 636 Kilo class with an acoustic signature of 105 decibels is 10 times as loud as the 95 decibel acoustic signature of the Virginia class submarine.

The United States is widely recognized as fielding the most capable and stealthiest submarines with the Virginia and Seawolf class submarines. The following is from  Chinese Evaluations of the U.S. Navy Submarine Force by Andrew S. Erickson, William Murray, and Lyle Goldstein:

"Chinese observers are intensely interested in and closely follow other modern U.S. nuclear submarines, including the USS Jimmy Carter, Seawolf, and Hawaii. Highly detailed, full-page color photos of Seawolf- and Virginia-class submarines appear in China’s most prominent naval journals. These photos are usually accompanied by articles that imply an advanced state of technology and advanced acoustic quieting...Chinese authors believe Seawolf possesses 'beyond-first-class performance' and is regarded as the most sophisticated and lethal submarine yet to go to sea, despite its 'tortuous development history'. The Chinese also respect Virginia-class submarines for their advanced technology and quietness...'Its acoustic signature is lower than that of the improved model of Russia’s Akula-class attack submarine and Russia’s fourth-generation attack submarine that will hereafter be in active service'. Another analyst, in discussing the Virginia class’s acoustic achievements, reports, 'The Virginia-class has been called the world’s quietest submarine,’ with a cruising sound level that is only '1/10 that emitted by a Los Angeles class boat pierside'. The construction techniques used to build Virginia and its sister ships also evoke respect'" 

The following acoustic signature figures are from Chinese Evaluations of the U.S. Navy Submarine Force and China’s Future Nuclear Submarine Force:

Ocean background noise - 90 decibels
Seawolf-class - 95 decibels
Virginia-class - 95 decibels
636 Kilo class - 105 decibels
Akula-class - 110 decibels
Improved Los Angeles -105 - 110 decibels
Type 093 - 110 decibels
Type 094 - 120 decibels

The possibility of the United States providing assistance in reducing the acoustic signature of Taiwan's domestically produced submarines will be discussed in part II.

Image 3: Relative detectability of Russian and Chinese diesel and nuclear powered submarines. Image Credit: Office of Naval Intelligence, 2009.

Taiwan's new indigenous submarines must feature a low acoustic signature as noisy submarines will be unable to provide Taiwan with substantial asymmetric capabilities. As part II will discuss, nations with no prior experience in building submarines have often had major difficulties in producing minimally detectable submarines. However, the limitations of Taiwan's ship building industry must also be put in the context of China's significant anti-submarine warfare (ASW) shortcomings.

Range

The need for extended range on a submarine varies in importance depending upon the country's defense needs. For example, Taiwanese submarines would not need to conduct power projection missions off the coast of a distant continent as their primary purpose would be to defend Taiwan and its nearby waters. In contrast, the United States requires extremely long range submarines given its global strategic interests. Depending upon the relative need for range as well as budgetary and technological issues, a country will field either nuclear or diesel electric powered submarines. The later is far more prevalent but has limited range, endurance, and is unable to operate continuously underwater as the diesel engine requires air to operate. It is important to note that while a submarine is at the surface, it is more vulnerable to detection. The solution in older diesel submarines was to incorporate large lead batteries that could be charged by the engine; the use of these batteries would permit the submarine to function for a few hours without having to surface for air. Snorkels could also be used to feed the engine air while remaining under water but the submarine still had to remain close to the surface. Despite these limitations, diesel electric submarines tend to be significantly cheaper and are less difficult to make stealthy when compared to nuclear submarines. Furthermore, recent advances in AIP technology have increased the time in which a diesel electric submarine can stay submerged.

Modern diesel electric submarines incorporate greatly enhanced AIP capability which enables them to remain underwater for much longer periods of time (Whitman, 2001). AIP is most often achieved in modern diesel electric submarines with the addition of fuel cells (e.g. hydrogen-oxygen fuel cells) or lithium ion batteries. Depending upon the speed at which the submarine is traveling while AIP is activated, the AIP equipped submarine could remain submerged for more than a week as opposed to a few hours with lead batteries. As an added benefit, the use of fuel cells greatly reduces the noise generated by boat as the engine is not used for propulsion while AIP is activated.

Endurance is how long the submarine can continue to operate at sea. Nuclear submarines have unlimited endurance with the only constraint being the limited space for consumables on board as the nuclear reactor has enough fuel to run for 25 to 40 years depending upon the class of submarine. US nuclear submarines undergo six month deployments with enough food on board for three months (the ship is resupplied). In contrast, diesel electric submarines such as the Kilo class and Type 209 are limited by their finite on board fuel and food storage and have an endurance of 45 and 50 days respectively (Federation of American Scientists & Global Security, 2011). AIP has somewhat narrowed the gap in terms of endurance between nuclear and diesel electric submarines with advanced diesel electric boats such as the Type 214 capable of 84 day deployments. Taiwan's only option would be to pursue a diesel electric submarine given technological, political, and budgetary issues associated with nuclear propulsion. AIP would be required to lengthen the endurance of the submarines.

Sensors

Image 4: Sonar arrays of the Virginia class submarine

Modern attack submarines typically incorporate a mix of passive and active sonar arrays which are usually mounted in the bow (front of the submarine), mast, or are towed behind the submarine. Passive sonar arrays detect ships by listening to the sound of the surrounding ocean which is then filtered for ambient background noise and marine life. Each ship has its own unique acoustic signature from which it can be identified and tracked. However, the use of passive sonar arrays requires extensive crew training and conditioning even with the use of automated acoustic classification systems (Clark, 2015). Furthermore, passive detection systems have become less effective in recent decades against submarines due to advances in quieting technology, the sound radiated by submarines operated by US strategic competitors has fallen significantly. For example, the details provided by John Walker (arguably the greatest American intelligence failure of the Cold War), enabled the Soviet's to learn the extent in which their nuclear submarine force was vulnerable. Prior to the late 1970s, Soviet nuclear submarines were on average 20 dB to 40 dB louder than their American counterparts resulting in an American detection range advantage by a factor of up to 100 (Tyler, 1992). The US Sound Surveillance System (SOSUS) network, a system of undersea passive sonar arrays based in both the Atlantic and Pacific, enabled the US to track Soviet submarines for the entirety of their deployment across thousands of nautical miles. Once the Soviet's became aware of their vulnerability, the Soviet Navy mounted an aggressive quieting effort resulting in a 30 dB drop in radiated noise of Soviet submarines from 1975 to 1988 or a reduction in radiated noise by a factor of 1,000. The significant advancements made by the Soviet's in quieting technology resulted in the United States developing low frequency active sonar systems which are not dependent upon the level of radiated noise of emitted by enemy submarines.

Image 5: Atlantic SOSUS network. Image credit: CSBA, 2015.

Active sonar systems emit sound waves using the ocean as a medium, the emitted signal reflects off of the target's hull and is subsequently received by hydrophones on the array (Tyler, 1992). While active sonar arrays provide significantly improved detection ranges against minimally detectable submarines when compared to passive systems, the emission of signals betrays the location of the active sonar system to emitter location systems. Thus, many low frequency active sonar systems are towed several kilometers behind  the submarine as not to betray the submarine's location (Kopp, 2004).

The primary mission of ROCN submarines would be to conduct anti-shipping missions against PLAN amphibious assault ships, the more senor intensive task of ASW is a secondary concern. It would not be difficult for Taiwan to obtain a system capable of detecting surface ships, the senors employed by its current Hai Lung class submarines are likely more than capable at tracking surface targets:

“one Type 1001 surface-search and navigation radar, one Krupp-Atlas low-frequency active bow sonar [DSQS 21], one medium-frequency sonar, one WM-8/7 underwater weapons fire-control system, one SEWACO VIII active information system, one ESM system, and extensive communication and navigation systems.” - Chant, 1987

The pervasive use of sonar technology in the commercial sector should ease Taiwan's development process for its own military sonar systems. For example, all US nuclear attack submarines incorporate commercial off the shelf (COTS) components as part of the Acoustic Rapid Commercial-Off-The-Shelf Insertion (A-RCI) program. A-RCI makes significant improvements to the submarine's processing power and adds new algorithms with respect to analyzing data from the ships sonar arrays (Defense Industry Daily, 2014). Other dual use technologies could aid Taiwan in building its own submarines as suppliers would have some degree of deniability when compared to overt arms sales. China has exploited dual use technologies from Europe as a means to circumvent the current US and EU arms export ban enacted after Tiananmen Square protests (Lague, 2013).

Armament

"There are two types of naval vessel: submarines and targets"  -unattributed 

Modern attack submarines are often armed with a mix of torpedoes, ASCMs, land attack cruise missiles (LACM), and sea mines.

Video 1: Canadian submarine fires a MK 48 ADCAP torpedo at RIMPAC 2012. Torpedo impact at 36 second mark. 

 Despite their enormous destructive power, nearly all submarine launched torpedoes are wire guided which limits their maximum range to between 20 - 30 nautical miles. Taiwan's Hai Lung class submarines are currently equipped with German designed SUT 264 heavyweight torpedoes but in 2010 Taiwan requested delivery of 40 US Mark 48 ADCAP torpedoes to replace the SUT 264s. The MK 48 is among the most capable 533 mm size torpedoes and its deployment will significantly increase the lethality of Taiwanese submarines:

"Chinese naval observers regard American torpedo technology highly. Noting an enviable six decades of torpedo experience, one Chinese author observes, 'Since World War II and for a relatively long period, U.S. torpedo technology has always been among the best in the world.' With specific reference to the Mark 48 heavyweight torpedo, another analyst assesses that 'the [Mark 48] torpedo’s outstanding effectiveness in all combat circumstances has been proven and it can be used to attack surface ships, nuclear submarines, and also diesel electric submarines.' The same author describes the aggressive U.S. torpedo-testing program: 'The USN has already carried out more than 6500 exercises and warshot firings [with the Mark 48], in addition to 20,000 simulations and 9 million mathematical simulations, so that this torpedo reaches a high state of reliability.'” - Andrew S. Erickson, William Murray, and Lyle Goldstein

Video 2: The P-800 hypersonic ASCM has a range of 200 nautical miles and caries a 250kg warhead. The Russian Severodvinsk class nuclear attack submarine can carry up to 24 P-800 missiles.

ASCMs provide submarines with much longer range anti-ship weapons; submarine launched anti-ship missiles such as the Harpoon Block II and 3M-54 Klub have ranges in excess of 100 nautical miles. The additional range provided by ASCMs is especially useful when an adversary has a robust ASW capability around the target and the use of a short range torpedo would present a significant risk to the submarine.

The inherent survivability of modern submarines enables them to serve as effective second strike platforms with LACMs. Israel's Dolphin class submarines are rumored to be armed with nuclear tipped popeye turbo cruise missiles and effectively provide a second strike nuclear capability. Taiwan's future domestic submarines could be equipped with submarine launched versions of the HF-2E which would provide Taiwan with a robust conventional deterrent.

The deployment of sea mines near PLAN ports or other high traffic areas could be cost effective means to enact high costs on China during a conflict. Sea mines are relatively cheap and the US could likely assist Taiwan in developing a submarine deployed sea mine system.

Part II will discuss the feasibility of Taiwanese production of conventionally powered 1,500-3,000 ton submarines and the relative merits of the CSBA recommendation for midget submarines.

Sources

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