1. High AoA Aerodynamics for Combat Aircraft : 1.3.1

3. Future sight of high AoA

3.1 High AoA capability become useless in future air-warfare? (laser, stealth, hypersonic, etc)

PART A. Future Air-warfare plan of US' 2030

Before we argue about future usage of high AoA on air-warfare, we have to figure out or expect what is going on future air-warfare. Actually, before 2008, full-scale emerge of China and Russia, research or development of future air-war was sluggish due to “War on Terror” against Afghanistan and Iraq. Weapon development had focused reduction of causalities for this war; naturally it leads to emphasize precision rather than speed, stealth, range, altitude, agility, and destruction. 

Advent of J-20, and Pak-Fa, symbol of new-style Cold-war, changed everything around 2008; power of Moskva and Beijing now well prepare for challenge against USAF and USN after long break of collapse of Soviet. In this article, I do not want discuss about geo-political stuff around high powers of the world near 10 years; only what I want to emphasize is that development for preparation of “After F-22” was triggered by the Chinese-and-Russian-made-new-challengers. 

Importance of high AoA or maneuverability was peaked at 70~80’s due to the lessons of the Vietnam war, described in chap. 1 of this article, and emphasizing on this lesson still alive design of F-22, J-20, and Pak-Fa. All those 5th generation fighters have well designed OML to obtain high AoA stability with TVC although long-range missiles, sensors, and stealth also took their pies. Now numerous articles released expectation for future air-warfare which will be performed by 6th generation fighter, after F-22 generation, with new fancy weapons such as laser and hypersonic guided missiles. Noticed things in these articles are that high maneuverability is not ‘1st priority’ performance factor anymore. 

Future fighters described in the articles become bigger and bigger like end age of warships before WWII, and engine manufactures already emphasize obtaining more power from engine turbine in limited fuel usage. Future air-warfare system of US consists of stealth aircraft, DEW, UCAV, Swarm of small UAV, SDB, EMP (http://jaesan-aero.blogspot.kr/2018/03/usaf-2030-commercial.html). Advent of SACM, and DEW presents why maneuverability is not 1st priority option for jet fighter performance; US has confidence about close combat intercept could be done by DEW, MDSM, SACM acting like CIWS, RAM, and ESSM on recent warships as shown in Fig. 3.1. If these ideas of US become true in the future, US could complete multi-layered air-superiority strategy as shown in Fig. 3.2. 

Fig. 3.1. DEW, SACM, MDSM could act like CIWS, RAM, and ESSM?

Fig. 3.2. US’ 2030 strategy for air-superiority (top), possible requirement for 6th generation fighter (bottom)

EMP cruise missile could be spearhead of the possible US’ 2030 strategy air-warfare; which malfunctions enemy electronic devices commanding, sensing, and tracking US assets. It cannot guarantee downing every enemy device however, at least, it could degrade enemy capability of seamless operation. After strike of EMP missiles, remained enemy AD assets try to suppress US’ advance. Information of this kinds of activities are collected by numerous sensors including multi-spectral sensors of satellites, HALE, swarm of small UAVs launched from transport at low altitude, highly stealth 5th and 6th generation fighters. These ‘many hunters’ provides large amount of information for the commanding center or 6th generation fighter if the 6th generation fighter could be capable of taking command center role. 

Killer role is also done by multi-number of platforms like ammunitions from UCAV, 5th, 6th generation fighters or long range conventional missile from 4.5th generation fighters if they still stand for front line. Prior or danger enemy assets like fighters, and radars are primary target of AIM-120D or its replacement, hypersonic ammunition, SACM, MDSM, and DEW pod of UCAV. Enlarged 6th generation fighters usually released hypersonic weapons expected to be too huge for IWB of the conventional 5th generation fighters. These hypersonic cruise missiles target most emergency high value assets for which response time is important. 

After, AD commanding center or radars are destroyed by EMP and hypersonic missiles, remained enemy fighter, unfortunately unorganized, will be hunted by front-line 5th generation and UCAV fighters. If some stealth enemy fighters have fortune to close range between US and enemy ones, DEW and CUDA like missiles, SACM and MDSM, could provide overwhelmed magazine and self-defense tools for friendly assets. While numerous platforms from space to airborne spot location of enemy, 2nd swarm of UAV provides missing spot information of enemy stealth platforms. These swarmed UAV sometimes will be used as ‘Kamikaze’ style attack when situation is in urgency. US thinks this multi-layered defense and attack could handle any kind of non-nuclear AD threat; it seems that air-warfare evolves as naval-warfare without aircraft-carrier. Each 6th, 5th generation and UCAV corresponds to cruiser, frigate, and destroyer while performance of the fight is determined by what they carry. 

It is why US’ commercial for future warfare did not emphasize maneuverability of platform itself. Finding, tracking, hunting, and even evading could be done by sensors and ammunitions launched from the fighters. Fighters do not have to show their extreme turning performance because kill or killed will be decided by magazine of DEW and MDSM. Someone could argue that this is revival of ‘missile fantasy’ of 60’s before break of Vietnam war; difference is completeness of technologies underneath of the missiles and DEW is much higher than the past one. So, now high maneuverability enters the technology of the past? Like big-gun technologies of WWII battleship? When we limit our discussion about future air-warfare in 2030, it looks correct. However, from Part B, I will present counter-technologies of US’ 2030, and possible revival of high maneuverability in future air-warfare. 

PART B. How to counter Air-warfare plan of US' 2030

US’ strategy described in Part A reminds us multi-layered defense tactics like air-defense system of WWII warship without carriers or big-box formation of WWII bombers believed to provide perfect coverage for all directions and enough depth. One of the strategy to follow this one is just build better or bigger than any other; building bigger, stealthier, and more fighters than enemy. However, that kinds of strategy already seem to arrive in final destination as shown in F-35 case; many countries feel too much burden on building or buying F-35s. How many countries buying enough number of 6th generation fighters having lots of functions proportional to the cost? It is very probable that divergence of cost and function of the next generation jet fighter limit the number of production itself. Because of this reason, similar to fate of big battle ships of WWII, only limited number of countries like US, USSR, Chinese, Japan, and EU is capable of having limited number of 6th generation fighters. 

 Counter method of this vicious circle is combination of relatively cheap method from the un-expected directions; asymmetric power method was usually used as weaker side. One of the famous example of the asymmetric power is usage of U-boat developed and well-used by Kreigsmarine in WWII; Nazi German tried to compensate advantage of Royal Navy by using the highly stealth weapon at its time. Lessons from the famous history is well reflected in the current US’ strategy that US want to use stealthier fighter and invest their assets on ‘finding-enemy’ very generously. Indeed, asymmetric approach should be come from other than stealth method which US has most confidence about. Possible approaches for the asymmetric method are aggressive usage of ‘Hypersonic’, and ‘EMP’ missiles. Hypersonic and EMP concept are also adopted by US already as one their teeth, however, as shown in the U-boat case, submarine itself was not first invented or used by Germans, similarly. 

 How to use hypersonic and EMP missiles more aggressive than US’? Fig. 3.3~3.5 summarize usage of Hypersonic MIRV ballistic and conventional EMP missiles for air-to-air combat. The missile consists of one big booster, delivering MIRV warheads to semi-orbital altitude, heat shield, protecting MIRV from strong shock of hypersonic, and MIRV warheads having small scramjet engine to preserve kinematic energy and maneuverability to kill enemy fighters. In a similar altitude of air-to-air combat against US’ strategy is not easy task as described above; solution should be coming from vertical advantages. If threats were coming from horizontally, US’ strategy, multi-layered and deep magazines of missiles and DEW, works well. Hypersonic ballistic missile could break this by reduction of response time via speed, direction, and multi-warhead while EMP cruise missile intrudes in horizontal direction to divide situation-awareness resources and down the UCAV power of US. 

The approach could compensate the reach advantage of US achieved by long range ISR assets and stealth performance of the platforms. Sensors of the platform mostly focus on lower direction than upper one because sensing the high altitude object is very clear task. However, story goes little bit different when object is in the altitude higher than ozone or sub-orbital layer. Ion-object interaction could interrupt object detection, and IR sensor became main method to detect the object. As we know, performance of IR sensor, angular resolution or range estimation, is lower than that of radar in similar condition; more importantly, US asset is not heavily depending on the IR sensors. Indeed, if hypersonic MIRV ballistic missile could achieve higher altitude than US assets, detection capability against missile is significantly reduced due to that only limited assets like satellite and HALE could detect the missile. 

Fig. 3.3 High Alt attack from hypersonic MIRV

Fig. 3.4. high speed + high AoA for unmanned missile or platform

Fig. 3.5. Specific details of hypersonic ballistic MIRV for counter of 6th generation fighter

After, the missiles avoid detections of the US assets (number 1 phase in Fig. 3.3) and enter the enough high altitude, conventional assets could not intercept the missile, except missile used for MD like SM-6, or THAAD. However, usually, launchers of these MD missiles are not coming with aerial platform until now. Even if they carry it, weight of the missiles limits magazine of the missiles. The missiles start to cruise in hypersonic speed with its scramjet engine which maximize range of the missile via weight reduction of oxidizer carried internally in the conventional rocket engine. When the fuel of the scramjet booster is consumed, missile now separates its warhead as shown in Fig. 3.5. Actually, impact of shock wave at re-entry phase is magnificent, and heat shield acts as front-runner to face the shock wave to protect MIRV warheads. MIRV falls to lower altitude where re-entry phase is over, then heat-shield acts as dummy to harass interception system of US assets. Other hidden MIRV parts activates its scramjet thruster to engage 5th or 6th generation fighters from the upper head of them; MIRV could be changed to one unitary EMP warhead to shut down enemy electric assets. 

There are few reasons why I choose way of intercept in this complex method. MIRV could do counter-act against close combat defense of 6th generation fighters, combination of DEW and MSDM. They have high speed and are coming from upper altitude reducing effective range of MSDMs. If MIRV flythrough whole the altitude from the start, cost of material and sensor is increased to sustain the load of high speed. This is why heat shield act as front runner in front of the MIRVs during dive re-entry. Cost of the MIRV is also reduced by choosing free-fall type warheads, however, even small scramjet thruster is required to maintain its maneuverability at terminal phase. Cost of making this kind of missile is expensive compare to conventional one; not expensive than 5th or 6th generation fighters. 

Although these missiles could be operated in any platform which could reach altitude higher than few kilo feet from the sea level, stealth, long-endurance platform is preferred to flexibility of operation. Possible operation platform is suggested as shown in Fig. 3.6; contrary to US’ 2030 one, expensive options like DEW and MSDM could be avoided. Detachable wing-extension and engine pod could be also suggested for flexible operation of speed and altitude in emergency situations. 

Fig. 3.6. Platform of hypersonic ballistic MIRV; 

 After, complete readiness of US’ 2030 is broken, possibility of close combat between aerial platform is increased. Remained air-asset fights like combat-knife style among UCAV, few manned 5th, 6th generation fighters; in this combat, UCAV, SACM, and MSDM are required to have high maneuverability against for each other. Indeed, US’ 2030 strategy try to rule out usage of high maneuverability in combat due to its uncertainty of winning, fatigue on airframe, and pilot; DEW, SACM, MSDM is result of this research. I supposed the idea of spear for this strategy, and core of the idea is hypersonic ballistic MIRV missile which open the narrow path to US assets. 

 In a future aerial combat, high AoA maneuver is probably not done by manned vehicle, maximum of which was already overtaken by missiles since advent of R-73s. However, legacy of Vietnam war lessons was remained until F-22 generation for emergency or perfect preparation; US’ 2030 strategy shows US will out of this trauma. High AoA maneuverability should be performed by missiles like SACM, MSDM, or the supposed hypersonic ballistic MIRV or UCAVs in future combat, and it means high maneuverability should pursue endless goal for more than 9G and could perform its maneuverability in high supersonic or hypersonic speed.