The implications of the advent of hypersonic
weapon systems for strategic stability
1. First things first: What are hypersonic missiles?
1.1 Hypersonic missiles are a new type of missile which possesses speed and
manoeuvring capabilities that make them a game-changer in nuclear (and conventional)
inter-state competition
. They are much faster than existing cruise missiles and much more
manoeuvrable than existing ballistic missile re-entry vehicles (RVs). They can reach and
maintain hypersonic speeds, i.e. speeds exceeding Mach 5
. However, this characteristic
is not unique to them: ICBM RVs also travel at hypersonic speeds
.
Hypersonic missiles follow a non-ballistic trajectory, flying between 18 miles and 60 miles in
altitude. Their manoeuvrability allows them to change course up to the last minutes of flight
and achieve a high degree of targeting precision. These characteristics have implications
for detection.
The unusual altitude and flight path of hypersonic missiles can result in their being invisible
to existing missile early-warning radars for much of their trajectory. Some varieties
RAND, Hypersonic Missile Nonproliferation: Hindering the Spread of a New Class of Weapons (RAND Corporation, 2017),
p. 1; RICHARD R. HALLIONS, CURTIS M. BEDKE AND MARC V. SCHANZ, Hypersonic Weapons and US National Security: a 21st
Century Breakthrough (The Mitchell Institute for Aerospace Studies, 2016), p. 2.
JAMES ACTON, Silver Bullet? Asking the Right Questions about Conventional Prompt Global Strike (Carnegie Endowment
for International Peace, 2013), p. 5;
RAND (n.1); The terminal phase is the portion of flight when the warhead reenters the atmosphere which lasts
approximately thirty seconds. ROBERT CHEN, JASON SPEYER, Terminal and Boost Phase Intercept of Ballistic Missile
Defense (AIAA Guidance, Navigation and Control Conference and Exhibit 18 - 21 August 2008) p.1. Nevertheless, once
the RV reenter from outer space would be greatly slowed down by the Earth’s atmosphere. It is estimated that an average
ICBM RV would travel at more than 1,8 m/s (approximately Mach 8) at impact point. AMITAV MALLIK, Technology and
Security in the 21st Century: A Demand-side Perspective (Oxford University Press, 2004), p. 110.
RAND (n.1), p. 8. See also ‘Hyper-glide Delivery Systems and the Implications for Strategic Stability and Arms Reductions’
(James Martin Center for NonProliferation Studies, 2015), p. 8.
At the time of this writing it is not certain if Hypersonic Cruise Missiles (HCM) will be detected by satellites during their
boost-phase. HCMs are a two-stage weapon system, the first-stage is a small rocket booster that will accelerate the missile
at the right supersonic speed needed for properly starting the second stage. During the firing of the first-stage there could
be the possibility for a boost-phase detection. It is still not certain if the infrared signature of the first stage of HCM could
be detected by infrared satellites used for missile warning. See JAMES ACTON (n.2), p. 68.
