Stopping a hypersonic missile

Stopping a hypersonic missile is one of the most difficult problems facing modern defence planners. Hypersonic weapons — including boost-glide vehicles and air-launched high-speed cruise missiles that travel at many times the speed of sound while manoeuvring unpredictably at low altitude — combine extreme velocity, short warning times and flight profiles designed to complicate detection, tracking and interception. Any credible solution is therefore multi-layered: there is no single technological silver bullet. The most realistic approach blends improved sensing, novel intercept concepts, operational resilience and political measures to reduce both the likelihood of use and the damage if one gets through.

Detection and tracking

The first and most fundamental requirement is reliable detection and continuous tracking. Hypersonic glide vehicles often fly below traditional early-warning radars and may manoeuvre unpredictably, invalidating simple ballistic predictions. Persistent, multi-domain observation — in particular space-based infrared and optical sensors that can observe both a rocket boost and the subsequent glide, together with improved ground, airborne and sea radars — is central to any defence architecture. Those sensors must be linked by rapid, secure command and control so that a threat can be transitioned quickly from initial detection to a shooter that can engage it.

Technical primer: flight phases, signatures and defensive opportunities

To make the practical problem concrete, it helps to distinguish the principal phases of a typical hypersonic weapon’s flight and to consider what each phase means for detection and defeat. This primer is written at a non-technical level so that the operational implications are clear.

1. Boost phase

What happens: The weapon is accelerated by a rocket motor or booster from launch until it reaches hypersonic speed. This is the phase when the vehicle is brightest in infrared terms and when rocket plumes and launch signatures are most conspicuous.

Why it matters for defence: Boost phase offers the longest single opportunity to detect and to attempt an interception before the weapon attains sustained hypersonic speed and manoeuvrability. The disadvantages are practical: boost interceptors must be close to the launch area and must react quickly. Space-based sensors and airborne early warning are most useful here because they can detect the hot signature of the booster despite the briefness of the event.

What can be done: Diplomatically, restricting the geography and warning of launches helps. Operationally, locating interceptors or high-power directed-energy systems close to probable launch corridors or investing in persistent space sensors to cue theatres of action improves the odds of a boost-phase defeat.

2. Glide (or mid-course) phase — for boost-glide vehicles

What happens: After boost, a glide vehicle enters the upper atmosphere and travels toward its target at hypersonic speed, often following a depressed or quasi-ballistic trajectory while using manoeuvres to alter course and evade prediction. At these altitudes the vehicle is fast and relatively small against ground clutter; the thermal and radar signatures are reduced compared with the boost.

Why it matters for defence: The glide phase is short in absolute time but offers potentially the last realistic window to intercept before terminal approaches begin. The principal difficulty is that manoeuvring invalidates simple predictive intercept solutions; a single detection must be continuously tracked to support an engagement.

What can be done: Persistent space sensors that track the boost and hand off continuous positional updates, high-altitude radars with rapid revisit rates, and long-range interceptors able to engage at high closure rates are the primary tools. Concepts that seek to intercept during the glide phase aim to defeat the vehicle before it commits to terminal manoeuvres; they demand excellent sensor fusion and automated cueing.

3. Terminal phase

What happens: In the final approach, the vehicle descends to lower altitude and performs final manoeuvres to alter its trajectory and terminal point. Warning time is minimal, and the closure speed against a defender is extremely high.

Why it matters for defence: Terminal interception is hardest because the defender has the least time to react and must counter both speed and last-second manoeuvre. Terminal intercepts thus typically require sensors that are locally dense (for example shipboard radars or local high-altitude radars) together with very fast, agile interceptors or directed-energy systems.

What can be done: Defenders can harden likely targets, use active decoys and confuse the weapon’s terminal guidance, and rely upon very short-range, extremely fast interceptors and point defences. Distributed, redundant protection of critical nodes makes a single successful strike less strategically decisive.

Cross-phase implications

• Signature economics: the weapon is most conspicuous during boost and least so during the glide. Hence persistent space-based infrared sensors that detect boost remain of central importance.

  
  

• Manoeuvre and prediction: because hypersonic vehicles can manoeuvre, interception requires continuous tracking and frequent updates rather than a single ballistic prediction.

  
  

• Time economics: high velocity shortens the time available at each phase, increasing the premium on automation, secure sensor fusion and pre-planned engagement options.

  
  

• Geography and basing: defences are easier if they can be placed near likely launch axes or if allied coverage produces overlapping sensor fields and shooter options.

This primer explains why defenders place disproportionate emphasis on persistent space sensors, rapid data links and layered, overlapping shooters — and why no single interceptor, radar or laser is a complete answer on its own.

Layered, integrated engagements

Given the short reaction times, defences must be layered and tightly integrated. Layering means overlapping sensors and effectors: space sensors handing off to high-altitude radars, which feed sea- and land-based interceptors and directed-energy systems. Integration requires automated, secure command-and-control channels so that a tracked threat can be passed rapidly from the sensor that first saw it to the shooter best placed to engage it. Glide-phase intercept concepts attempt to defeat manoeuvring glide vehicles earlier in flight rather than relying solely on terminal intercepts; these concepts demand a high degree of sensor fusion and rapid decision-making.

Kinetic interceptors and alternative kinetic concepts

Traditional hit-to-kill interceptors remain part of the toolkit, but their employment against hypersonics is technically demanding. Interceptors must match very high closure rates and possess exceptional agility and guidance to collide with or otherwise neutralise a manoeuvring, high-speed target. To expand the available options, defence agencies are exploring alternatives: hypervelocity projectiles, glide-phase interceptors launched from ships or high-altitude platforms, and other kinetic concepts that rely on very high closing speeds or extended-range engagement. These are promising, but they are not yet mature enough to be relied upon as the sole solution.

Directed energy and non-kinetic measures

Directed-energy weapons — principally high-power lasers — offer an attractive complement because they can, in principle, engage multiple targets at the speed of light and with relatively low per-shot marginal cost. In practice, current directed-energy devices face challenges: atmospheric propagation, the need for sustained power and thermal management, and the difficulty of delivering enough energy quickly enough against a hypersonic surface that may present only a small aiming window. Nonetheless, in constrained environments (for example protecting a forward base, port or naval group) lasers and high-power microwave systems may degrade sensors, blind seekers or damage airframes. Electronic attack and cyber measures that degrade an adversary’s command, control or guidance are another non-kinetic layer — useful for disruption but not, by themselves, a comprehensive defence.

Sensor and radar modernisation

Improving ground and sea radar capability remains essential. Newer radars built with advanced semiconductors, faster digital processing and improved discrimination algorithms can detect and track smaller, faster targets at greater ranges. However radars alone cannot substitute for persistent wide-area coverage and the unique boost-phase and mid-course visibility that space sensors provide. The modern approach therefore fuses space, airborne and surface sensors to present a continuous operational picture.

Operational measures and force posture

Technology must be combined with operational changes. Dispersal of high-value assets, hardening of critical infrastructure, adaptive patrol patterns and redundancy in command networks reduce the attractiveness of any single target. For expeditionary forces and bases, kinetic defences should be paired with active camouflage, physical hardening and passive countermeasures so that the operational cost of a successful strike is minimised. Exercises and realistic testing against representative surrogate threats are necessary both to validate concepts and to train decision-makers to operate under compressed timelines.

Allied cooperation, doctrine and intelligence

Hypersonic defence is inherently collective. Sensors, interceptors and political will are distributed across alliances; cooperation enables burden sharing and more comprehensive regional coverage. Doctrine must be updated so that senior political leaders understand the timelines involved and can provide clear rules of engagement. Intelligence work, including measurements to detect proliferation and launch preparations, is equally important because the best technical defence is sometimes denial of the adversary’s ability to prepare a strike.

Dissuasion, arms control and risk reduction

Technical defences alone will not eliminate the danger. Diplomatic engagement, arms control measures and confidence-building steps that limit deployments and reduce incentives for pre-emptive use are critical. Transparency measures, dialogues about no-first-use or mutual limits on certain delivery classes, and negotiated restraints on the basing of such systems could lower operational pressure and reduce the chances of destabilising escalation during crises.

Resilience and civil preparedness

Planners must prepare for the possibility that some hypersonic strikes will succeed. Civil preparedness, rapid damage mitigation and resilient infrastructure design limit the strategic effects of a strike. Investing in redundancy for power, communications and logistics, protecting population centres and critical nodes, and planning rapid medical and emergency responses are necessary complements to technical defence investments.

Conclusion

Defending against hypersonic missiles is not a binary problem with a single technical fix. It requires a coherent, sustained programme that spans sensors in space and on the ground, improved radars, new intercept concepts, directed-energy research, allied integration, operational change and political engagement to reduce the risks of use. The technical primer above shows why persistent space-based detection and continuous tracking matter so much, and why glide-phase and terminal-phase intercepts present distinct and difficult challenges. Progress is being made — principally in better tracking from space and in layered architectures that combine kinetic and non-kinetic effectors — but the field remains immature. Policymakers should plan for an extended period of investment and experimentation rather than quick solutions, and couple those investments with diplomacy, redundancy and resilience so that when a hypersonic weapon is used it produces the least possible strategic effect.