THE CHALLENGE OF HYPERSONIC MISSILES

Abstract

The idea of developing a rocket that flies at very high speeds is not new in itself, because such concerns and achievements have existed since the Cold War. The highlighting element is the approach and use of these missiles (overcoming technical flight problems under extreme conditions), in the context of nuclear weapons and ballistic missiles 'existence. During the Cold War, the development of systems using supersonic speed was particularly expensive and complex, so few nations were able to achieve it. However, the development of hypersonic military systems, that can be guided at high altitudes and long distances, with high precision, but also efficiently (not yet demonstrated), is much more difficult and challenging, in terms of securing the necessary resources.

Headnote

The idea of developing a rocket that flies at very high speeds is not new in itself, because such concerns and achievements have existed since the Cold War. The highlighting element is the approach and use of these missiles (overcoming technical flight problems under extreme conditions), in the context of nuclear weapons and ballistic missiles 'existence. During the Cold War, the development of systems using supersonic speed was particularly expensive and complex, so few nations were able to achieve it. However, the development of hypersonic military systems, that can be guided at high altitudes and long distances, with high precision, but also efficiently (not yet demonstrated), is much more difficult and challenging, in terms of securing the necessary resources.

Keywords: hypersonic speed; security threat; counter hypersonic missiles; flight regime; hypersonic missile; ballistic missile; cruise missile; anti-missile systems.

1.Speed and its challenges

Generally, speed is known as a feature of moving objects and it is perceived with both positive connotations (when the result leads to a progress) and negative (when losing control results in a disaster or an anomaly). Identifying the means, by which the speed of a body can be improved, has always been a researchers' concern, both in the civilian field and, especially, in the military. In the latter situation, speed has been an indispensable factor starting with the first known conflict in history.

High-speed movement, occupying combat positions and engaging your opponent at the right time, have always been preferred by military leaders over an expensive war of attrition. Regardless of the nation or military commander, year of operation or technology involved, the used strategy had at least one technique element or category related to the idea of speed or speediness. In these circumstances, the emergence of the first offensive military doctrine, known to the general public as the Lightning War/ Blitzkrieg, tailored by the Germans after the World War I and applied in the next war, followed naturally.

In the military field, the need for speed is more pronounced in the case of aircraft or missiles, the only weapons that have developed thi s feature beyond any thought or imagined limit, only a few decades ago. Achieving the specific effects of using these systems is dependent on the speed feature, its increase could ensure the desired effectiveness, but with the associated resources and costs.

If aircraft have managed to reach supersonic speeds, which has led to a rethinking of how operations can be planned and, above all, conducted, the transition to another level by missiles reaching the hypersonic speed will certainly generate a new revolution in using them, but especially in refuting them. In these circumstances, hypersonic missile, the new concept and system at the same time, emerged in response to the need of enriching military arsenals with weapons that would be both provocative and lethal for opponents, in detecting, tracking and engaging them.

Hypersonic technology is not only applicable for the military, with rockets and space shuttles being just two examples that have been built and used since the middle of the twentieth century1. But when a country has a technology considered revolutionary, tested in different ways that certify its value, identifying military applicability is only a matter of time which, incidentally, is happening with the new hypersonic missile programs.

What is hypersonic speed? It is a fact that an object that flies at a speed of 340 m/s actually reaches the speed of sound or Mach 12. The speed regimes known today were established depending on the speed of sound: subsonic, supersonic and hypersonic. Subsonic speed involves a movement close to the speed of sound (Mach 1). Around the speed of Mach 1 (0.8-1.2), a transonic regime is debated in the published literature. Supersonic involves a speed of movement greater than that of the sound (usually between Mach 1 and Mach 5), and hypersonic is a speed of movement of more than 5 times the speed of sound3. According to the NATO Glossary of Terms and Definitions, hypersonic is defined as "pertaining to speeds equal to, or in excess of, 5 times the speed of sound"4.

What is a hypersonic missile? The current sources present it in the form of a weapon that brings to the foreground the speed and range of ballistic missiles and the manoeuvrability of cruise missiles. If the main feature of ballistic missiles is the re-entry speed into the atmosphere, hypersonic missiles add an increased manoeuvrability to it, in a way that the warning and countering measures are reduced to zero. Therefore, it should be kept in mind that it represents a new type of weapon, and thus a new threat with increased potential for manoeuvre, and the very high speed provide increased possibilities of striking a variety of targets, in a very short period of time.

The hypersonic missiles are very fast and manoeuvrable, with the possibility of flying about 5,000 to 25,000 kilometres per hour (for comparison, these missiles fly at speeds between 6 and 25 times higher than modern airplanes), and the flight altitude is unusual: between a few tens and 100 kilometres5. At this time, these characteristics of speed, manoeuvrability and altitude provide hypersonic missiles certain advantages over existing air defence systems, simply because the latter were not constructed to counter such threats.

The speed and precision of a weapon, plus the absence or the inefficiency of countering measures, are desirable characteristics in any operating environment and, consequently, this type of missile has caught the attention of the world's great powers. At the same time, these new weapons and the interest in their development have triggered a new concern among military analysts regarding the possibility of initiating a new race arms between the great powers, one that can overcome, in ambition and destruction, the same period of the Cold War. Furthermore, these missiles the development and ownership will lead to new challenges to the operating environment and global security, in addition to a much greater threat of the existing ballistic and cruise missiles.

The published literature brings to the foreground the existence and development of two types of hypersonic missiles: Hypersonic Glide Vehicles/ HGVs and Hypersonic Cruise Missiles/ HCMs. While Hypersonic Glide Vehicles/ HGVs are launched into space using other missiles where, from altitudes between 50 km and 100 km (or higher), are released for hypersonic flight from the upper layers of the atmosphere to the set targets, Hypersonic Cruise Missiles/HCMs have their own advanced jet engines (scramjets) necessary for target-directed flight, which they usually perform at relatively low altitudes6.

The development of a weapon with the same characteristics of speed and range of ballistic missiles, but with improved performance in accuracy and manoeuvrability, while at the same time causing significant destruction without nuclear warheads, is a goal for most military powers. Thus, it is normal for a weapon with such declared performance - but still in the development and testing phase - to become a "hot topić" for most military publications and a topic of debate for political and military analysts. The reality that it is considered a revolutionary weapon, as were, in turn, aircraft carriers, "invisible" aircraft, ballistic missiles etc., can no longer be denied, and the possibility of radically changing the way of future conflicts are thought and carried out is more and more increasing. US Senator Angus King makes, in this respect, an expressive comparison between the hypersonic missiles and the use of the long bow at the Battle of Agincourt in the 14th century, when the English army manned with such bows succeeded to defeat a four times larger French army7.

However, the development of such missiles, especially those that are launched into space, cannot be done without overcoming technical problems specific to the propagation medium8. First of all, from the aerodynamics point of view, it is necessary to ensure a stable flight in an aerodynamic regime that is not very well known, because there are differences between the flight of ballistic missiles which, upon entering the atmosphere, are designed to reach the target as quickly as possible, and that of hypersonic glide vehicles, which must glide towards the target with very high accuracy. Secondly, the thermal management must be carried out so that the heat released due to the very high speed and friction with the atmosphere does not affect the aerodynamic properties of the missile. At the same time, it should not be overlooked that the orientation, navigation and control, especially in case of the use of kinetic energy, must be achieved in such a way as to ensure that the optimum point of impact is achieved in order to produce the desired effects.

2.Threat of hypersonic missiles

In order to understand the implications arising from the interest in the development of hypersonic missiles, it is necessary to understand the (relative) advantage that these missiles offer, compared to existing missiles. Clearly, their purpose is not to threaten nations that do not have and cannot develop such technology, since they are already vulnerable to existing and already traditional threats (ballistic and/or cruise missiles).

It is possible that these weapons bring that something extra, necessary to the great powers, that would guarantee their separation from the others, which inevitably leads to a new race to obtain and possess the weapons, followed inevitably, by the specific crisis. Under these circumstances, several arguments naturally arise, which may form the basis for the non-proliferation of these types of missiles, first by starting from the existence of the treaties regulating this problem.

The emergence of new types of weapons and the threat of their use led to a change at doctrinal level, in the way of managing a crisis and conducting a conflict, in light of identifying solutions to counter them, particularly in the context of reducing the time available. The range of missions that can be assigned to these missiles leads to their establishment between strategic and conventional/ tactical boundaries. According to the aimed effect, their use may be justified when trying to annihilate an insurgent group in a location that is crowded or protected and unjustified and difficult to understand in situations with major, mass destructive consequences.

The swift development of this new type of weapons brings forward any discussion of its characteristic danger, and simply putting them into the equation of a crisis can lead to its escalation. At the moment, there are no international agreements on regulation of the use of these missiles or plans to start such discussions between countries that want this kind of weapons9.

The development, possessing and use of new types of missiles shall be considered a threat to future international crises, both by the countries that are interested and possibly owners, and by countries which cannot afford the resources for their development. The main three reasons are:

* their existence in the arsenal of a state make them strong in a negotiation or crisis situation;

* incorrect assessment of a crisis situation, to which a possible and, ultimately normal human error can be added, an ordinary example can be a false launch of such a missile10 that may lead to the maximum shortening the time to make a correct decision and the possibility of triggering a brutal response with catastrophic consequences;

* during a conflict or crisis situation, the use of such a missile can set up the conditions for employment of other types of weapon systems, with disastrous consequences for the entire planet.

By considering the possibility of using this type of weapon systems, the pros (considered from the viewpoint of a potential hypersonic missile owner state) can be identified, but also cons (from the international community perspective).

Pro-arguments for the use of hypersonic missiles:

* early warning loses its characteristics, as the time available to respond to a possible attack is short, thus surprising on the offensive actions carried out;

* missile features ensure the possibility of changing the target during flight, which leads to a greater number of targets being maintained under threat, thus a dissipation of the air defence effort;

* the execution of simultaneous attacks, under the protection of jamming and combined with the use of other weapons systems, has very high chances of achieving the set objectives, in a short time and with minimal losses;

* the psychological effect has a great impact on the military and political system.

Arguments against the use of hypersonic missiles:

* the perception over the offensive potential of these missiles, as well as the possibility that the owner states will use them in the first phase of a conflict (to paralyze the entire military, economic and social system) may lead to a fierce race for obtaining such weapons or, possibly other types, but with the same destructive effect;

* their presence in a country's arsenal can lead to the exacerbation of a crisis;

the time between the identification of a missile launch and the effective measures to counter it does not allow for an effective defence of military and non-military objectives, especially when the identification of the target needing defence is difficult; in this context, the response of the nation under attack may be of the last resort' or even nuclear;

* uncertainty about the nature of the warhead of these missiles can generate a response with far more destructive consequences than the attack itself.

The topicality of hypersonic missiles can lead to a quite difficult situation to imagine two decades ago: their use at the expense of nuclear weapons, with the same paralyzing effect of the adversary, but perhaps without the radioactive consequences and international blame, possible in the case of nuclear weapons11. Thus, one can speak of a possible paradox of hypersonic missiles - states are blamed for their development and possession, but possible use may not be criticized as much as in the case of nuclear weapons or ballistic missiles, even if the effects of their use may fall within the same range of destruction.

3.Global concerns

Currently, there are three actors in the world highly concerned about the research, development and testing of such capabilities: the U.S., Russia and China12. Each of them stands out for initiatives, programmes or actions that are defining elements of their efforts in the field of hypersonic missiles.

For the United States, the development of hypersonic missiles constitutes a significant part of the Conventional Prompt Global Strike program, which would allow the U.S. hit targets located anywhere in the world, in less than an hour13. The U.S.'s concerns are directed not only towards developing and possessing such capabilities, but also towards identifying the systems that provide defence against hypersonic missiles. Thus, the Missile Defense Agency (MDA) has requested 206,832 million dollars in the fiscal year 2021, for the development of hypersonic missile defence systems, as Russia and China have reported considerable progress in the development of this technology14.

On 1st March 2018, Vladimir Putin, the President of the Russian Federation, gave an important speech to the Council of the Russian Federation, the upper house of the Russian Parliament, where he also presented an update on some of the important developments in the country's strategic arsenal. During the speech, President Putin provided technical details (which is quite surprising) about several ongoing strategic programs, including the hypersonic glide vehicles (called 15Yu71/Avangard), which can be launched using ballistic missiles, such as the RS-28 Sarmat (still in the testing phase), the intercontinental ballistic missile which, according to the president, "practically has no range restrictions"15. A year later, the Russian Ministry of Defence announced, according to TASS news agency, that the first regiment of intercontinental ballistic missiles equipped with the Avangard hypersonic glide vehicles missiles became operational on December 27, 201916.

In the case of China, the hypersonic glide vehicle program is quite advanced, by 2014 China had conducted seven tests, six of which were successful. The development of hypersonic missiles is considered a potential capability to strike, with use in A2/AD17 concept implementation or for force projection18. The advance of hypersonic missile programs is also likely to be due to the paradigm shift in this country, as in June 2017, the Chinese Academy of Sciences highlighted the shift from the phrase "copied in China" to "created in China", through a list of seven science and technology premieres, made in China between 2012 and 2017. Among them, relevant to this article, is "the World's largest shockwave hypersonic wind tunnel", thus demonstrating experience in supersonic and hypersonic speed flights, as well as an interest in the development of hypersonic missiles19.

Apart from the three important actors, other states express their interest in this direction. Thus, according to a study conducted by RAND Corporation in 2017, France and India are among the most interested in developing capabilities in the field, both based on cooperation with Russia, followed, in terms of the effort made, by Australia, Japan and countries in the European Union20. The same source states that there are concerns regarding hypersonic research in Brazil, Canada, Iran, Israel, Pakistan, Singapore, South Korea and Taiwan, but the actions are only at the academic research level or proposals made by various entrepreneurs, with fairly small allocated budgets. The exception is Brazil, which is involved in both development and testing21.

In terms of combat load, the hypersonic missiles can carry both conventional and nuclear payloads, which make them even more fearsome in relation to their characteristics. At the same time, hypersonic missiles have the potential to use kinetic energy to destroy or damage targets, which is possible due to the very high speed and materials from which they are made. The kinetic energy of such a missile at the time of impact, at a speed of at least 1,900 km/h, is strong enough to penetrate any building material or armour, representing the equivalent of the detonation of three to four tonnes of TNT22. Even if, on a declaratory level, the U.S. is pursuing the development of hypersonic missiles with conventionally load, while the counter-candidates Russia and China intend to equip the same missiles with both conventional and nuclear warheads23, the estimated possibilities of these missiles almost make these differences so irrelevant. The competition for the possession of these weapons is fiercer for the three major players, as a simple calculation demonstrates that launching such a missile from anywhere in these countries can hit any target in the territory of the other two.

However, the materialization of the use of these new weapons is not possible in the near future, as potential developers and users must identify solutions for overcoming the technical barriers related to missile control at high speeds and altitudes or identifying materials that meet the existing conditions during the flight24. At the same time, we can add the problems related to their testing in real conditions and, finally, yet very important, those relating to the costs and justification of the construction and possession of these missiles in relation to the expected outcomes. RAND Corporation specialists estimate that both types of missiles could be used for military purposes within a decade or less25.

4.Countering hypersonic missiles

Identifying the possibilities ofbuilding a missile that is as manoeuvrable as a cruise missile, but with a much higher speed and which, at the same time, has the same speed or even greater than a ballistic missile, but a much better manoeuvrability, logically leads to concerns for the development of defence systems against them. Regardless of the choice made (the development of hypersonic missiles or the development of defence systems against them), the necessary investments must be identified, which are often significant. Only in the U.S., testing such a missile at Mach 5 speed cost 160 million dollars, and the Missile Defense Agency suggested a 600-million dollars budget in 2017, for a five-year programme, to identify the technological solutions needed to counter hypersonic threats26.

With the development of hypersonic missiles currently being in the research and experimentation stage, the technological effort of the highly interested countries is seriously considered, and, thus, the identification of measures to counter this type of missiles is required. Even though hypersonic missiles are currently presented as invincible, there are certain vulnerabilities that can be exploited to identify means of countering and neutralisation. At the same time, combat solutions can consist not only of the development of missile defence systems that have the possibility of physically destroying a hypersonic missile, but also of systems that can influence its performance (the most well-known technique of "functional destruction" of a system is GPS denial technology, with which its guidance system can be affected/disabled27).

Countering hypersonic missiles is a problem not only for states that cannot afford a weapon of this kind, because in addition to counter the missile itself (which is extremely difficult to do with the current technology), their level of proliferation must also be taken into account. Even for major powers, the proliferation of hypersonic missiles will create new threats to national and global security, because of the impossibility of protecting all military and civilian objectives and facilities and, above all, urban congestion.

Hypersonic missiles differ from ballistic missiles and cruise missiles in the characteristics of speed, altitude and manoeuvrability, in the sense that, for the former, the point of impact and the trajectory may undergo changes during the flight regime. In a RAND Corporation study on hypersonic missile issues, these differences are presented and exemplified in a graph, presented in Figure No.1. In these circumstances, the possibilities of warning, identification, tracking and countering are different and even more difficult.

Possible targets for hypersonic missiles can be identified in the same range as those for ballistic missiles, but taking into account specific requirements related to their distance, available time, target value, level of protection and level of collateral damage. Thus, possible targets could be military command and control structures, strategic forces, naval groups, air bases, facilities for the production or possession of weapons of mass destruction, nuclear infrastructure (production, testing, storage and use facilities etc.), leaders of terrorist groups, A2/AD systems etc.

The hypersonic missiles effectiveness is closely related to how increased speed and manoeuvrability characteristics are managed at an appropriate level. Because of that, the two types of hypersonic missiles intended to be developed (hypersonic glide vehicles and hypersonic cruise missiles) are much more difficult to counter than existing ballistic missiles. The flight altitude and speed they can develop make the warning of their use very difficult to achieve, with implications on the time available for effective combat, while increased manoeuvrability increases the degree of uncertainty about the objective to be defended. All aspects presented represent the main problem of countering these missiles: the physical possibility of neutralizing a missile that has a hypersonic speed is discovered too late and has increased possibilities for manoeuvring. Currently, it is quite likely that the most important mean of countering be deterrence, but for this, there must exist the proper means to produce the desired effect. As it is known, the best defence is the attack, so, it is possible that the defence against hypersonic missiles is the credible possession of these weapons itself. The counter of hypersonic missiles is primarily linked to the possibilities of detection, which involves the development or improvement of air, space and ground sensor systems that can detect their launch or flight. Even with these capabilities available in the military arsenal, the time decisionmaking on how to act and the time of combat itself are quite limited29.

Countries with only ground sensor systems (radars) in their inventory will have to cope with a harsh reality, during which the decision-making process must be rapidly carried through and the time for countering is extremely limited. In this context, it is a certainty that the rapid rate of hypersonic missiles development must require an alert rate of identification of new missile defence solutions. It is expected that, in the first phase, the solution be the current systems and programmes that can counter ballistic and cruise missile, but brought into a configuration and range of performance commensurate with the threat. However, their effectiveness against hypersonic missiles can only be proven under similar conditions such as the ones of a conflict. The current ballistic missile counter technology can also be a solution to underpin future hypersonic missile counter systems, supported by highperformance early warning capabilities. It is certain that, regardless of the proposed and chosen solution, defence systems must also be viable in case of multiple attacks, under the protection of jamming or combinations with other lethal systems.

At the same time with combat actions, it is necessary to carry out actions limiting the consequences of the hypersonic missiles use. These actions may relate to: command and control decentralization, dispersion of forces and, in particular, structures providing their command and control, prioritization of objectives to be defended, existence or establishment of reserve command posts to take over the tasks of the main ones as soon as possible, thinking and applying tactics, techniques and procedures that use the most of the mobility of forces, the defensive measures specific to the technique and the terrain.

Conclusions

History has proven that this is not the first time that the great powers have ignored the risks arising from the desire to have miraculous solutions regarding the military threat. The nuclear weapon is just one of many examples of military programs with which the U.S. and the U.S.S.R. threatened each other during the Cold War. However, the existence of such weapons in a country's military arsenal leads to a change in its perception of the resolution of future crises, but also a positioning of the country at another level of military power. The mere presence of these missiles can lead to an escalation of a conflict, and the deployment of hypersonic missile systems, even with a declared conventional load, can put an end to good intentions to peacefully resolve a crisis situation.

Perhaps the main problem with these missiles is not their development (it is quite possible that the tests that are currently being carried out show that all technical and construction problems can be overcome), but the continuous interest that more and more states have in them. As a competition involving at least three superpowers, the results are expected to emerge very soon and increasingly convincing, contrary to the opinion of military analysts who consider this race harmful to the security environment.

The possession of hypersonic missile construction technology may be equivalent to the possession of the nuclear weapon, unless measures are taken to limit access to it. The resources involved for the construction and possession of such weapons are not fully known yet, but it is certain that there are large funds allocated to research of hypersonic missiles programmes.

Research, development and use of hypersonic missiles does not create the prerequisites for a safer planet, but merely provides a state of relative quietness for the holders and a new concern for those who want them, but cannot afford them. At the same time, the possession of these weapons by states that normally do not have other equally large threats in their arsenal, leads to a situation where hypersonic missiles can pose a real threat to the great powers, further complicating the equation of the poles of power or the peaceful resolution of crises.

Footnote

1A.N.: the X-15 became the first manned vehicle that reached hypersonic speed, in 1959 under the X-Plane Program (URL: https://history.nasa. gov/x1/appendixa1.html); in April 1961, Yuri Gagarin became the first man that had traveled at hypersonic speed during the world's first piloted orbital flight. In the same time, there were other manned vehicles that used hypersonic speed (Apollo and Soyuz).

2 A.N.: the Mach number comes after the Austrian physicist and philosopher Ernst Mach, who made important contributions to the study of shock waves.

3 ···, "Mach number", NASA, URL: https:// www.grc.nasa.gov/www/k-12/airplane/mach. html; ···, "Flight Regimes", Globalsecurity, URL: https://www.globalsecurity.org/military/ systems/aircraft/intro-regimes.htm, accessed on 20.03.2020.

4 ···, AAP-06, NATO Glossary of Terms and Definitions (English and French), North Atlantic Treaty Organization, NSO, 2019, p. 64, URL: https://nso.nato.int/nso/nsdd/listpromulg.html

5···, Hypersonic Missile Nonproliferation, Hindering the Spread of a New Class of Weapons, RAND Corporation, Published by the RAND Corporation, Santa Monica, 2017, p. xi.

6···, Hypersonic Missile Nonproliferation, Hindering the Spread of a New Class of Weapons, RAND Corporation, Published by the RAND Corporation, Santa Monica, 2017, p. 2.

7 Russ Read, "Nightmare weapon", Washington Examiner, URL: https://www.businessinsider. com/king-hypersonic-missiles-nightmareweapons-and-us-carriers-vulnerable-2019-8, accessed on 23.03.2020.

8 A.N.: more details are provided in James M. Acton, Silver Bullet: Asking the Right Questions about Conventional Prompt Global Strike, Washington DC, Carnegie Endowment for International Strength, 2013, pp. 59-61, URL: https://camegieendowment.org/files/cpgs. pdf, accessed on 18.02.2020.

9 R. Jeffrey Smith, "Speed Kills", URL: https:// publicintegrity.org/national-security/future-ofwarfare/scary-fast/hypersonic-weapons-race/, accessed on 18.03.2020.

10 A.N.: a real case concerning the alarm of the population of The State of Hawaii regarding the launch of a ballistic missile (proven to be false): Adam Nagourney, David E. Sanger and Johanna Barr, "Hawaii Panics After Alert About Incoming Missile Is Sent in Error", URL: https://www. nytimes.com/2018/01/13/us/hawaii-missile. html, accessed on 23.03.2020

11R. Jeffrey Smith, op. cit.

12 A.N.: the order is random and does not reflect any particular progress in the field

13 ···, Conventional Prompt Global Strike and Long-Range Ballistic Missiles: Background and Issues, URL: https://crsreports.congress.gov, accessed on 20.03.2020.

14 ···, "US Missile Defense Agency requests funds to counter hypersonic threats", Jane's International Defence Review, April 2020, URL: https://emagazines.janes.com/webviewer/#jane sinternationaldefencereviewapril2020, accessed on 20.03.2020.

15 ···, Strategic effect, Jane's Defence Weekly, November 28, 2018, URL: https://emagazines. janes.com/ihsj-defence-weekly, accessed on 20.03.2020.

16 ···, Russia declares first Avangard regiment operational, Jane's Defence Weekly, January 08, 2020, URL:<https://emagazines.janes.com/webv iewer/#janesdefenceweekly8january2020/cover>, accessed on 20.03.2020.

17 A.N.: Anti-Access/Area-Denial.

18 Tate Nurkin et. al., "China's Advanced Weapons Systems, Jane's by IHS Markit", May 12, 2018, URL: https://www.uscc.gov/sites/default/files/ Research/Jane's%20by%20IHS%20Markit_ China's%20Advanced%20Weapons%20 Systems.pdf, accessed on 20.03.2020.

19 ···, "7 'firsts' in China's sci-tech achievements in 2012-17", China Daily, URL: http://www.chinadaily.com.cn/china/201706/15/content_29752320.htm, accessed on 12.03.2020.

20 ···, Hypersonic Missile Nonproliferation, Hindering the Spread of a New Class of Weapons, RAND Corporation, Published by the RAND Corporation, Santa Monica, 2017, p. xii.

21 ···, Hypersonic Missile Nonproliferation, Hindering the Spread of a New Class of Weapons, RAND Corporation, Published by the RAND Corporation, Santa Monica, 2017, p. 14.

22 R. Jeffrey Smith, op. cit.

23 ···, "Hypersonic Weapon Basics", Missile Defense Advocacy Alliance, URL: https:// missiledefenseadvocacy.org/missile-threatand-proliferation/missile-basics/hypersonicmissiles/#_ednref2, accessed on 18.03.2020.

24 A.N.: given the experience and challenges that have arisen during the development of ballistic missiles, it is somewhat likely to be overcome.

25 ···, Hypersonic Missile Nonproliferation, Hindering the Spread of a New Class of Weapons, RAND Corporation, Published by the RAND Corporation, Santa Monica, 2017, p. xii.

26 Jason L. Sherman, "The Hypersonic Arms Race Heats Up", URL: https://www.thedailybeast.com/ the-hypersonic-arms-race-heats-up, accessed on 22.02.2020.

27 James M. Acton, Silver Bullet: Asking the Right Questions about Conventional Prompt Global Strike, Washington DC, Carnegie Endowment for International Peace, 2013, p. 71, URL: https:// carnegieendowment.org/files/cpgs.pdf

28 Hypersonic Missile Nonproliferation, Hindering the Spread of a New Class of Weapons, RAND Corporation, Published by the RAND Corporation, Santa Monica, 2017, p. 4.

29 A.N.: according to the RAND Corporation study, states equipped with performance earth and space sensors have a few minutes to know that the missiles are in their airspace; see: Hypersonic Missile Nonproliferation, Hindering the Spread of a New Class of Weapons, RAND Corporation, Published by the RAND Corporation, Santa Monica, 2017, p. 14.

References

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