Hypersonic weapons are defined as able to travel at speeds above Mach 5 and can be broadly classified into two types: hypersonic glide vehicles (HGV) and hypersonic cruise missiles (HCM). The former is launched into the upper atmosphere via ballistic missiles. The HGV is then separated from the booster to glide/maneuver towards its target. The latter can be launched from a jet plane or rocket to reach supersonic speed before igniting its scramjet engine for hypersonic speed.
As the U.S. engages in great power competition with China and Russia, all three countries are racing to field hypersonic weapons. Beijing sees hypersonic weapons as a critical means to shape China’s strategic environment, and has seized the opportunity to gain an edge in this contest. China has reportedly fielded DF-17 missiles mounted on DF-ZF HGVs and is making progress on its Starry Sky-2 HCM.
Chinese Hypersonic Shock Tunnel Development
To aid research and development into hypersonic technology, the Institute of Mechanics (IMECH) of the Chinese Academy of Sciences (CAS) (中国科学院力学研究所, Zhongguo kexue yuan lixue yanjiusuo) launched the “shock tunnel reproducing hypersonic flight conditions” program in 2008. The tunnel became operational in 2012. A news report on the JF-12 hypersonic wind tunnel (复现高超声速飞行条件激波风洞, Fuxian gaochao shengsu feixing tiaojian jibo fengdong), which cited CAS’s National Science Review journal in April 2020, implies that the tunnel is being used for the development of the Starry Sky (星空, Xingkong) HGV (China News, April 20, 2020). According to the South China Morning Post (SCMP), Starry Sky-2 can carry nuclear warheads and travel at six times the speed of sound (SCMP, August 6, 2018). The JF-12 tunnel can duplicate flight conditions between Mach 5-9 speeds and altitudes ranging between 25-50 kilometers (15.5-31 miles) (China News, April 20, 2020; SCMP, August 6, 2018).  The tunnel can sustain test times of more than 130 milliseconds (ms), which is enough to support the data collection of flow field, shock structure, and other high speed aerodynamic parameters (IMECH, November 28, 2017). Based on publicly available information, the shock tunnel is used to analyze thermal characteristics such as flame-holding stability and recovery temperature for combustion. It is possible that the JF-12 tunnel, along with other hypersonic tunnels at the China Aerodynamics Research and Development Center (CARDC) (中国空气动力研究与发展中心, Zhongguo kongqi dongli yanjiu yu fazhan zhongxin), which are located in Mianyang, Sichuan and directly controlled by the People’s Liberation Army (PLA), could be used to help design hypersonic weapons (Baidu).
CARDC has research institutes with revealing names that indicate its key role in the development of hypersonic technology, i.e. Low-speed Aerodynamics, High-speed Aerodynamics, Hypersonic Aerodynamics, Computational Aerodynamics, and Testing Technology. Consequently, it is probable that CARDC is responsible for the PLA’s research and development of hypersonic weapons (CARDC). Given China’s military-civil fusion approach to defense technology, it’s highly likely that IMECH supports CARDC’s simulations and engineering tasks, especially since the former has the country’s most advanced hypersonic shock tunnels.
Chinese media reports have frequently claimed that the JF-12’s performance is superior to NASA’s Hypersonic Tunnel Facility (HTF) (Meiri Toutiao, October 11, 2017; Wen Wei Po, September 3, 2012; Ta Kung Pao, June 2016). Such claims appear dubious in light of contemporaneous emphasis on the JF-12 tunnel’s cutting-edge five degree of freedom mechanism, a technology that NASA has had since the 1980s . The claim that a 130 ms testing time is a world record is also false; NASA’s shock tunnel for the X-43A experimental vehicle can sustain similar test conditions for longer durations.
In March 2018, the same group responsible for the IMECH’s JF-12 began work on the JF-22 “detonation-driven ultra-high-speed and high-enthalpy shock tunnel” (爆轰驱动超高速高焓激波风洞, Baohong qudong chao gaosu gao han jibo fengdong) (IMECH, January 2021). The JF-22 can reportedly achieve higher speeds and altitude conditions than the JF-12. Located in Beijing’s Huairou District, the program passed a major milestone (roughly equivalent to the U.S. DoD’s Production Readiness Review [PRR] and System Verification Review [SVR]) in December 2020. The IMECH press release claims that the JF-12 and JF-22 combined can cover all hypersonic flight profiles, although the timeline for the JF-22 to achieve initial operational capability is uncertain.
Taking Advantage of U.S. Knowledge and Technology
In the past, innovative computational fluid dynamics (CFD) algorithms developed by U.S. institutions such as the NASA Glenn Research Center were published and openly discussed at academic conferences. The Chinese and American CFD communities frequently overlap; the principal investigator of both JF-12 and JF-22 shock tunnels, Jiang Zonglin (姜宗林), received the Ground Testing Award from the American Institute of Aeronautics and Astronautics (AIAA) in 2016 (Guancha, May 25, 2016). Chinese experts have likely acquired much-needed knowledge from such CFD community events. In addition to powerful wind tunnels, hypersonic vehicle design requires sophisticated CFD computer simulations. The U.S.’s open sharing of advances in CFD has aided China’s hypersonic research and development efforts. The powerful computer simulations requiring computation-intensive algorithms are run on indigenous supercomputers built with U.S.-designed GPUs, CPUs, and memory chips. (Washington Post, April 9, 2021) This kind of knowledge diffusion is currently not preventable under existing national security safeguards such as the U.S. Economic Espionage Act.
PLA Thinking on Defense against Hypersonic Weapons
PLA strategists fear that the U.S. may deploy hypersonic weapons on the first island chain and/or the second island chain, directly threatening China. In particular, they recognize that Chinese long-range kinetic interceptors lack precision to kill, and precision interceptors lack the range to strike targets at long distance. As early as 2012, the China Aerospace Science & Industry Corporation (CASIC) Academy of Defense Technology (中国航天科工防御技术研究院, Zhongguo hangtian ke gong fangyu jishu yanjiuyuan) proposed an architecture capable of defending against hypersonic weapons.
The first component of the proposed 2012 CASIC defense architecture is an efficient and optimized detection network comprised of various sensors covering a distance of 800-1000 km (497-621 miles). The second is a high-speed information center capable of processing large amounts of heterogeneous data and discriminating against noise and other interference in real-time. The third element of the hypersonic defense plan is a high-performance command and control system to support an integrated air picture with rapid sensor-to-shooter cycle. The fourth component is a mixture of fast response airborne and near space-based interceptors. CASIC advocates air-to-air missiles for this purpose. However, hypersonic cruise missiles also pose significant technical challenges for low-angle detection and tracking over long distance, and the 2012 CASIC proposal does not seem to have reached sound solutions to this problem.
Researchers from the China Air-to-Air Missile Research Institute (中国空空导弹研究院, Zhongguo kong kong daodan yanjiuyuan) recommended a similar architecture in 2016. They also advocate implementing airborne interceptors using both kinetic and direct energy, because of their advantages of low risk, low R&D and deployment cost, as well as the ability to offer rapid response with maximum operational flexibility. One challenge involved with air-to-air interceptors is their reliance on powerful airborne fire control radar to lock onto targets hundreds or even thousands of kilometers away. Whether China has fully developed this technology is unknown.
Researchers from the Space Engineering University (航天工程大学, Hangtian gongcheng daxue) under the command of the PLA Strategic Support Force (SSF) (战略支援部队, Zhanlue zhiyuan budui) indicated that they could use existing surveillance assets consisting of early warning aircraft and ground radars for early detection. Additionally, they propose fielding ground-based and ship-borne high power, high resolution, and long-range phased array radars that can detect and track small, high-speed targets such as ballistic missile warheads and hypersonic vehicles. For warfighting, they envisage “forward deployment” of air-to-air missiles for head-on intercept, though due to the HGV’s high maneuverability, the deployment area would need to be quite large, and the rate of success would likely be small.
Two engineers from PLA Units #31002 and #32032 of the Strategic Support Force (SSF) recommend a similar architecture for hypersonic defense systems, but propose to deploy layered global networks for early warning and kinetic interception. They indicate that though an infrared sensor cannot render precise three-dimensional target coordinates, it can still effectively provide early warning capabilities. The PLA Rocket Force (PLARF) Engineering University (火箭军工程大学, Huojianjun gongcheng daxue), previously known as PLA Second Artillery Engineering University, divides the engagement of hypersonic weapons into four stages. In the first stage, early warning satellite constellations detect the launch of an enemy weapon, immediately issue alerts and begin tracking the projectile. In the second stage, early warning radar detect and track the incoming target based on satellite data feeds. During the third stage, surveillance systems distinguish targets from decoys and report to the command and control center. Lastly, the command center directs weapon platforms to intercept the incoming projectile.
Based on these four stages, researchers from PLARF Engineering University identify a few capabilities requiring improvement, namely, early warning, positioning and tracking, and interceptor guidance. They largely follow the U.S. Missile Defense Agency’s thinking on interception, and separate the trajectory of a hypersonic target into boost, midcourse, and terminal phases and proposed technologies they could develop in each phase accordingly.  Perhaps more importantly, PLA experts recommend shortening a long chain of command to build a flat command and control organization that optimizes information flow and reduces response time. 
Chinese researchers at the First Aircraft Institute of Aviation Industry Corporation of China (AVIC) (中国航空工业集团公司, Zhongguo hangkong gongye jituan gongsi) recognize that laser weapons can be valuable in hypersonic defense because they can illuminate a target instantaneously using laser beams. Laser weapons installed on aircraft, however, are susceptible to vibration and noise, which creates technical difficulties for beam control, high-precision aiming, tracking, and rapid damage assessment. Additionally, hypersonic vehicles are typically shielded by ceramic matrix composites, which protect their structures from extreme heat, especially in the nose cone section. The ceramics would be naturally effective at diffusing heat from laser beams for a prolonged period, rendering the laser weapon less effective. (Weapon News; MDPI Open Science)
In general, Chinese strategists assess that hypersonic defense systems based on airborne platforms are advantaged by flexible deployment, high initial launch speed of kinetic interceptors, and incoming targets’ relatively weak maneuverability in the cruise/glide phase. Some Chinese researchers believe these limitations can be remedied by the use of unmanned aerial systems (UAS).
China’s Air Force Engineering University (空军工程大学, Kongjun gongcheng daxue) has studied the feasibility of deploying a cluster of widely spaced UASs to intercept hostile hypersonic strikes. The conceptual design makes use of high-altitude, long-endurance (HALE) UAS that can loiter in the forward theater. Because UAS payloads are smaller than manned warplanes, Chinese researchers envisage that the drone cluster will be divided between two missions: early warning and interception.
In order to provide effective early warning, the UAS that are involved need collaborative decision-making, networked target acquisition, and beyond visual range communications to provide long-range detection and tracking capabilities. The early warning UAS cluster would be part of the networked sensors comprising space-based infrared satellites, land-based early warning radars, and early warning aircraft. Per the Air Force Engineering University’s conceptual design, the interceptor UAS will carry six 250 kg, 200 km range airborne missiles. The proposed defense architecture also calls for robust battle management and C2 systems. The researchers divide warfighting into four stages: patrol and combat readiness, early warning, target acquisition, and intercept capabilities. They have conducted systems analysis to determine the optimal deployment strategy for both early warning and interceptor UASs.
The Chinese open source literature summarized above provide a very high-level concept of operations (CONOPS) and warfighting applications against hypersonic weapons. Applied with systems engineering, CONOPS can be refined and transformed into top-level systems requirements for design, development, integration, testing, and IOC. This does not mean that China is on the verge of developing these missile defense systems, but the extensive research undertaken thus far, nevertheless brings China a step closer to achieving a hypersonic defense capability.
Conclusion: Implications for U.S.-China Arms Control
Hypersonic vehicles are not currently subject to existing arms control treaties on ballistic missiles. The U.S. extended the bilateral New Strategic Arms Reduction Treaty (START) with Russia in February 2021, and still hopes to persuade China to join future strategic arms control negotiations. China presently has little incentive to be encumbered by any arms control treaty as it lags behind the U.S. and Russia in long-range intercontinental ballistic missiles (ICBMs) and nuclear warhead stocks, while simultaneously maintaining a vast stockpile of short and intermediate range ballistic missiles that could potentially give it the edge in a Western Pacific contingency. China is not a signatory of the Missile Technology Control Regime (MTCR), a multilateral export control regime. Consequently, Beijing is not bound by missile nonproliferation obligations and has proliferated missile technologies to Pakistan, Iran, Saudi Arabia, and Syria. (USNI News, May 18, 2021)
However, the current situation, which is characterized by China’s long range missile disadvantage vis-à-vis the U.S. and Russia, and huge advantage in short and medium range missiles, may be beginning to shift. In August 2019, the U.S. withdrew from the Intermediate-Range Nuclear Forces Treaty (INF Treaty) because of repeated Russian violations and Chinese arms buildup in the Pacific and the South China Sea. The withdrawal has introduced the possibility of new U.S. land-based, conventional, intermediate-range, and hypersonic missile deployments in Asia.
The PLA Rocket Force believes hypersonic weapons possess powers of deterrence unmatched by nuclear weapons that can alter the strategic balance and affect an opponent’s intent and determination.  Indeed, China’s early interest in developing a hypersonic defense system demonstrates its concern over the U.S.’s development of hypersonic weapons. As a result, concerns over U.S. hypersonic weapons’ development and missile deployments, along with revisions to the MTCR that enable allies and partners like Taiwan, Japan, and Australia to build long-range land-based offensive capabilities, could combine to alter Beijing’s strategic calculus on arms control. President Reagan’s secretary of state, George Shultz, believed that the U.S. deployment of short-range nuclear missiles in Western Europe played a key role in driving the former Soviet Union to join INF negotiations. (NBR, February 20, 2021) U.S. deployment of hypersonic weapons on either one of the Western Pacific island chains could induce Beijing to perceive a change in the strategic balance to its disadvantage, and compel it to participate in arms control negotiations with the U.S., Russia, and potentially other nuclear weapons states.
Mr. Holmes Liao (廖宏祥) has over 30 years of professional experience in U.S. aerospace industries. He previously served as an adjunct distinguished lecturer at Taiwan’s War College.
 Han Guilai (韩桂来)，Mou Qianhui (牟乾辉), “ Shock wave wind tunnel to reproduce hypersonic flight conditions” [复现高超声速飞行条件的激波风洞], Bulletin of the Chinese Academy of Sciences, [中國科學院院刊], 33 (2018): 37-40. Note also that an unauthoritative website stated that CAS scientists previously supported the PLA to build wind tunnels including the JF-4 (1962), JF-4A (1964) and JF-10 (1998) at CARDC. “Only China’s shock tunnel technology has enabled Chinese missiles to surpass the U.S. and lead the world,” [仅中国掌握的激波管技术，使中国导弹超越美国领先世界], Military Hobby (军事爱好), January 14, 2020, http://www.chinaha.net/html/202001/20200174387.php.
 Note that the original post from the China Academy of Aerospace Aerodynamics (CAAA, 中国航天空气动力技术研究院, Zhongguo hangtian kongqi dongle jishu yanjiuyuan) referenced by the SCMP article has been removed from the internet. CAAA is a unit under the China Aerospace Science and Technology Corporation (CASC), which is the main contractor for China’s space program.
 Note that while China News states the JF-12 can replicate conditions ranging between Mach 10-25 and altitude 35-90 km, CAS’s own publication (cited in the SCMP article) returns a more conservative numbers, which are cited in this piece.
 Zhou Xiaogang (周晓刚), Hu Minglun (胡明伦), Bai Benqi (白本奇), Ling Zhongwei (凌忠伟), Zhang Wei (张伟)，“Improvements of Five Degree of Freedom Support Mechanism in Hypersonic Wind Tunnel” [高超声速风洞五自由度机构技术改造]，Ordnance Industry Automation [兵工自动化]，10 (2013): 66-68; XuXiaobin (许晓斌)，Shu Haifeng (舒海峰), Xie Fei (谢飞), Wang Xiong (王雄)，Guo Leitao (郭雷涛)，“Research progress on aerodynamic test technology of hypersonic wind tunnel for air breathing aircraft” [吸气式飞行器高超声速风洞气动力试验技术研究进展]，Journal of Experiments in Fluid Mechanics [实验流体力学 ]，5 (2018): 29-40.
 Zhou, et al., “Improvements of Five Degree of Freedom Support Mechanism in Hypersonic Wind Tunnel,” 2013.
 Liang Xiaogeng (梁晓庚), Tian Hongliang (田宏亮), “Analysis of the Development Status and the Defense Problem of Near Space Hypersonic Vehicle” [临近空间高超声速飞行器发展现状及其防御问题分析], Aero Weaponry [航空兵器], 4 (2016): 3-10.
 Bao Yunxia, (包云霞), Zhang Weigang (张维刚), Li Junlong (李君龙 ), Chen Yong(陈勇), “Challenge and consideration of early warning detection and guidance technique of near space weapons” [临近空间武器对预警探测制导技术的挑战], Modern Defense Technology [现代防御技术], 1 (2012): 42-47. Note that the authors are affiliated with the Beijing Institute of Electronic System Engineering (北京电子工程总体研究所), also called the Second Research Academy of CASIC or the CASIC Academy of Defense Technology (中國航天科工防禦技術研究院 (第二研究院)).
 Liang Xiaogeng, et al., “Analysis of the Development Status and the Defense Problem of Near Space Hypersonic Vehicle”, 2016.
 刘晓慧 [Liu Xiaohui]，聂万胜 [Nie Wanshen]，“反临近空间高速机动目标策略研究” [“Strategy for interception of near space high speed maneuvering target”]，兵器装备工程学报 [Journal of Ordnance Equipment Engineering]，1 (2017): 75-78
 韩洪伟 [Han Hongwei]，王鹏坡 [Wang Pengpo]，“高超声速武器发展及防御策略研究” [“Research on development of hypersonic weapon and defense strategy”]，飞航导弹 [Aerodynamic Missile Journal]，12 (2019): 12-15。Note that the lead author is affiliated with the PLA Unit, #31002 which is a research and development institute. The second author is with Unit #32032 under the PLA SSF.
[11[ Liu Xiaohui, “Strategy for interception of near space high speed maneuvering target”, Op. Cit.
 杨明映 [Yang Mingying]，朱昱 [Zhu Yu]，张笋 [Zhang Sun]，“防抗高超声速武器作战体系建设思考” [“Strategy for the construction of combat system for anti-hypersonic weapons”]，飞航导弹 [Aerodynamic Missile Journal]，7 (2019): 21-25
 张同鑫 [Zhang Tongxin] ，李权 [Li Ouan] ，“对抗高超声速武器的机载激光武器发展研究” [“Research on the development of airborne laser weapons against hypersonic weapons”] ，航空科学技术 [Aeronautical Science＆ Technology] ，3 (2018): 5-8
 肖吉阳 [Xiao Jiyang]， 康伟杰 [Kang Weijie]， 陈文圣 [Chen Wensheng]，“无人机集群反高超声速武器作战概念设计” [“Conceptual Design of UAV Cluster Anti-hypersonic Weapon Operations”]，飞航导弹 [Aerodynamic Missile Journal]，10 (2018)
 The maximum takeoff weight of PLA’s largest UAS, WZ-7翔龍 Xianglong, is about half of the U.S. RQ-4 Global Hawk. The CH-7 彩虹 Caihong UAS makes debut at Airshow China 2021 in Zhuhai in September 2021 seems capable of carrying heavier payload than WZ-7.
 Xiao Jiyang, et. al., “Conceptual Design of UAV Cluster Anti-hypersonic Weapon Operations”, Op. Cit.
 Yang Mingying, “Strategy for the construction of combat system for anti-hypersonic weapons”, Op. Cit.