Hypersonic weapons
Introduction
Humanity has always shaped its discoveries and progress to serve two purposes simultaneously: improving everyday life and strengthening the power of its armies. The wheel carries both harvests and archers; mastery of metallurgy enables the forging of plowshares and swords; aircraft deliver both rescue teams and bombs; satellites monitor the climate and troop movements. Hypersonic‑flight technologies are no exception, as we will see.
The term hypersonic was virtually unknown to the general public until Vladimir Putin thrust it into sudden fame during his annual address to the Russian Parliament in March 2018. In that speech he unveiled new “invincible” weapons with “almost unlimited range,” which he claimed rendered all missile defenses obsolete. Their supposed invincibility stems, he argued, from their hypersonic speed and unpredictable trajectories.
Hypersonics : some hints
Signification
First observation: while the definition of the word supersonic rests on a clearly identified physical phenomenon (the speed of sound in air) and a parameter (the Mach number—the ratio of flight speed to the speed of sound) that allows us to pinpoint the onset of the supersonic regime (Mach > 1), this is absolutely not the case for the word hypersonic.
Even leading experts in the field acknowledge this: for instance, J. D. Anderson highlights in the reference document he authored on the subject [1] a quotation from another renowned scientist who explicitly notes this fact (see Figure 1).
Figure 1 : about the definition of hypersonic flow regime [1]
It has become customary to refer to a flow in air as hypersonic when its Mach number exceeds 5. This is a convenient shortcut and, as a first approximation, perfectly acceptable, but it hides the gradual onset of the phenomena that characterize a hypersonic airflow—or, for stationary air, the speed at which an object moves through it.
Among these phenomena, the most well‑known is probably the ionization of air.”
Air Ionization
When an object moves through air, a shock wave forms ahead of it, compressing the gas to high pressure and temperature near the surface. The faster the object travels, the stronger the shock and the higher the gas temperature become.
Air is composed almost entirely of a mixture of nitrogen and oxygen molecules. Once a certain temperature threshold is reached, the two atoms that make up each nitrogen molecule dissociate.
At still higher speeds, the two atoms of each oxygen molecule also separate, and at yet greater velocities electrons are stripped from the atoms. In the thin layer adjacent to the surface, the air therefore becomes a mixture of neutral atoms, free electrons, and ionized atoms (atoms that have lost one or more electrons).
This process is what we refer to as air ionization. It typically occurs at Mach numbers on the order of 10 (roughly 3 000 m s⁻¹). Air ionization is responsible for the radio‑blackout phenomenon observed during atmospheric re‑entry of capsules and other spacecraft.
Several other physical and chemical phenomena are associated with the hypersonic nature of an object’s speed in air. Readers who wish to explore these topics further can consult Chapter 1 of the cited reference [1].
An already old concept
When did the word hypersonic first appear, and what were the earliest hypersonic objects? Those questions will be addressed in other articles.
For now, it suffices to say that the objects mentioned by V. Poutine are not, far from it, the first hypersonic objects in history. Many others preceded them. Earth‑return capsules such as the crewed capsules of the Apollo program (the 1960s‑70s) belong to this family.
Indeed, a capsule returning from a lunar mission performs atmospheric re‑entry at a speed of roughly 11 000 m/s (≈ 40 000 km/h, Mach > 30). These objects are therefore, without doubt, hypersonic vehicles.
But they also possess another extremely important quality, which is just as crucial for hypersonic weapons, as we will see later: they can maneuver within the atmosphere.
A glimpse of flight mechanics
Drag and Lift
At this point, it is necessary to make a brief digression about the forces exerted by the air on a vehicle moving at high speed, and the principle of trajectory maneuvers that these forces enable. To illustrate this, let’s examine Figure 2.
① | When an axis‑symmetric object such as an Apollo capsule moves through the air with its velocity vector aligned with its symmetry axis, the aerodynamic pressure force acts along that axis. If the object’s center of gravity is also located on the symmetry axis, the motion remains in a straight line, slowed only by the pressure force ( Ftot in the diagram). |
② | If, on the other hand, the center of gravity is offset from the symmetry axis —as was intentionally done with the Apollo capsules—the pressure force not only decelerates the vehicle but also induces a rotation about that offset point. |
③ | This rotation continues until the capsule reaches a stable attitude in which the center of gravity and the pressure force are once again aligned. At that point we say the capsule is traveling with an angle of attack relative to its velocity (the angle between the capsule’s axis and the velocity). In this attitude a braking force—called drag—still acts along the velocity vector and continues to slow the capsule (the “Drag” arrow in the figure). At the same time a force perpendicular to the velocity, known as lift, develops and pushes the capsule away from a purely straight‑line trajectory (the “Lift” arrow in the figure). |
IMPORTANT NOTICE: LIFT over DRAG RATIO: 
The so called lift-over-drag ratio (often referred to as L/D) depends on many parameters—most notably the angle of attack—and has a decisive impact on the capsule’s maneuverability. We will see later that the same holds true for military hypersonic objects.
Maneuvers : how to?
t is the lift force that enables the capsule to perform maneuvers during its descent. The capsule is equipped with so‑called “roll nozzles” that allow it to rotate about its longitudinal axis, thereby steering the direction of the lift force (see Figures 3 and 4):
- Pitching upward or downward to decrease or increase the descent rate
- Yawing left or right to execute turns.
Figure 3 : lift orientation to maneuver
Figure 4 : jet nozzles for roll maneuvers
Maneuvers : what for?
Why steer the capsule when it would be much simpler to go straight in?
That would be perfectly fine for an unmanned capsule, but Apollo‑type capsules carry astronauts whose bodies couldn’t survive excessive deceleration. The forces can reach hundreds of g’s, whereas a young, strong, well‑trained astronaut can tolerate only about ten g’s without injury.
There is indeed a way to reduce the deceleration: enter the atmosphere on a shallow trajectory instead of a steep, straight‑down approach. Figure 5 makes this clear—dropping the flight path angle from 80° to 10° cuts the peak deceleration from over 300 g’s to just a few dozen g’s. Yet even at a 10° angle the crew still experiences far too harsh a braking force.
If we lower the angle just a little more to try to soften the deceleration further, the capsule exits the atmosphere again, embarking on a perilous—and possibly unrecoverable—flight (the curve shown for a 5° angle).
Figure 5 : decelerations applied to a reentry capsule depending on the initial flight path angle.
Maneuvres : the outcome
Does that mean a lunar mission would be impossible—caught between the limits imposed by astronaut survival and the need to bring the crew home?
That’s where the capsule’s ability to maneuver saves the mission, as illustrated in Figure 6.
Apollo 8’s (the first circumlunar flight) initial re‑entry flight‑path angle was 6.5°. The capsule begins its descent at ① with a positive lift (directed upward). In Figure 6 the black curve shows the planned trajectory of the capsule [2]. The blue and red curves are alternative paths:
- The red curve represents a direct re‑entry, like the one in Figure 5. Even though the angle has been reduced further—from 10° to 6.5°—the peak deceleration remains far too high.
- The blue curve depicts a re‑entry that maintains positive lift throughout: you can see that it never reaches the ground but instead climbs back toward space.
The black curve follows the same path as the blue one, but starting at point ② the capsule performs a roll about its longitudinal axis, turning the lift negative (“initiate re‑entry steering”: start of the re‑entry maneuvers) to prevent the vehicle from bouncing. Subsequent maneuvers keep the flight altitude roughly between 50 km and 60 km and hold the deceleration below the critical 10 g threshold (the actual flight recorded a maximum of 6.8 g [3]).
Thus, the maneuverability of the Apollo capsule made lunar missions feasible.
The military vehicles we’ll discuss next employ methods for performing maneuvers during atmospheric flight that are based on essentially the same principle. The implementation, however, differs profoundly.
![Figure 6 : Trajectoire prévisionnelle de rentrée atmosphérique Apollo 8 [2]](https://www.hyfar-ara.org/wp-content/uploads/2025/12/trajectoire-Apollo.jpg)
Figure 6 : Apollo 8 predicted reentry trajectory [2]
Military Hypersonic Vehicles
Ballistic Missiles
Just like civilian hypersonic craft, military hypersonic vehicles didn’t suddenly appear in March 2018 at the Russian parliament. They’ve existed since the 1960s—as the warheads carried by intercontinental ballistic missiles (ICBMs).
To see why they’re classified as hypersonic, we need to pause and look at how they operate.
Whether launched from a submarine or a land‑based silo, strategic warheads ride on massive missiles—much like satellites hitch a ride on a launch vehicle—and are released near the end of the boost phase (well above Earth’s atmosphere).
From there they travel through space like high‑altitude cannonballs: soaring at extreme speed, covering vast distances, and then falling back to Earth far away, re‑entering the atmosphere in a manner akin to Apollo capsules—but without any active maneuvering.
Figure 7’s animation illustrates this sequence in a very pedagogical way.
Because their missions demand extremely long ranges, these warheads must start out at very high velocities. As with the Apollo capsules, that high entry speed forces a hypersonic atmospheric re‑entry (roughly 7 km s⁻¹, Mach > 20, to cover about 10 000 km).
Figure 7 : trajectory of a strategic warhead embarked in a ballistic missile
Maneuverable hypersonic vehicles
The flight paths taken by objects carried on ballistic missiles are, however, highly predictable, and their flight times are long enough (sometimes more than half an hour) to give an adversary ample time to prepare a defense.
Other trajectories that exploit the maneuverability of purpose‑built hypersonic vehicles (as opposed to purely ballistic warheads) were conceived in the first half of the 20th century to extend range and/or produce less predictable paths:
- Skip‑entry trajectories
- Boost‑glide trajectories
All three trajectory families are sketched in Figure 8. Each starts the same way—with a powered phase followed by a ballistic coast—but they diverge during the atmospheric re‑entry phase.
- Skip entries: the vehicle “bounces” one or more times off the atmosphere before making a final plunge to the ground.
- Boost‑glide trajectories: the vehicle begins re‑entry much like a conventional ballistic path, but at a certain altitude it pulls up into the atmosphere (the “pull‑up” phase) and then follows a gently descending glide, sustained by aerodynamic drag, until it reaches its target (the “glide” phase).
In both cases the vehicle is not propelled all the way to its destination: it completes its entire flight solely thanks to the velocity imparted by the launch rocket at the moment of separation.
A further similarity is that both trajectories enter the atmosphere at much shallower angles than classic ballistic warheads. Such low entry angles are mandatory to allow the vehicle to execute the bounces or the sustained glide.
Figure 8 : three kinds of hypersonic military vehicles trajectories.
Skip entries
The idea of using a “skip” trajectory for a weapon system was first theorized in the shadowy years of the 1940s by Austrian engineer Eugen Sänger for his long‑range bomber project, the “Silbervogel.” The concept called for a vehicle that could launch from Germany, skip along the upper atmosphere to reach New York, and then return to its point of origin (see Figures 9 and 10 and technical note [4]).
The “skip” re‑entry concept was also considered for Apollo capsules, although it was never used. It remains relevant today: China’s Chang’e probe employs this type of entry, and NASA’s Orion capsule— the first crewed spacecraft ever to perform such a maneuver—demonstrated an autonomous skip‑entry on 11 December 2022 (no astronauts aboard) [5].
![Figure 10 : la trajectoire circumterrestre du Silbervogel [4]](https://www.hyfar-ara.org/wp-content/uploads/2025/12/Sanger-hyfar-400px.jpg)
Figure 10 : round the World trip of the Silbervogel vehicle [4])]
Figure 9 : E. Sänger “Silbervogel”
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Figure 11 : some « skip entries » considered for the ORION capsule
Boost Glide trajectories
The earliest references to boost‑glide trajectories are credited to Chinese engineer Qian Xuesen, who reportedly imagined them in the late 1940s while working in the United States (MIT, Caltech) after several years of study there.
Both he and Sänger led extraordinary lives—stories that fall outside the scope of this article but that we intend to explore later.
What does make them unique
Boost‑glide paths have a distinctive feature that sets them apart from the other flight profiles: the glide phase occurs at altitudes of roughly 40 km – 60 km. At those heights the vehicle stays well below the radio‑frequency horizon of the radars defending the target area, unlike the two other trajectories.
Because the vehicle remains inside the atmosphere for the entire glide phase and can actively maneuver, it can execute evasive actions that make its path far less predictable. Those two capabilities alone create exploitable opportunities to disrupt a defender’s response, which is why boost‑glide trajectories are especially attractive.
Range extension
But that’s not the whole story. Like skip‑entry paths, boost‑glide trajectories can theoretically extend range far beyond a conventional ballistic trajectory. The primary factor influencing that range is the aerodynamic L/D ratio of the vehicle (as defined earlier): the higher the L/D ratio, the larger the range gain.
Any evasive maneuvers performed en route to the target, however, incur additional velocity loss and therefore reduce the theoretical maximum range.
Illustration
Figure 12 illustrates all of these points. It compares several vehicles initially accelerated to 7 000 m s⁻¹, showing the difference between a plain ballistic flight and a boost‑glide flight, and, in the boost‑glide case, the effect of having a medium versus a high L/D ratio.
Increasing the entry speed would stretch boost‑glide ranges even further, producing a vehicle that matches many elements of the “hypersonic weapon” sketch presented by V. Putin in 2018.
Various classes of hypersonic weapons
The hypersonic objects described here are collectively known as BGRV – Boost Glide Re‑entry Vehicles. More recently, the designation Hypersonic Glide Vehicles (HGV) has emerged to designate such vehicles.
As Figure 12 demonstrates, they can achieve very long ranges, placing them squarely in the “strategic weapons” category.
Other classes of hypersonic weapons exist that remain propelled all the way to their target. Their design challenges differ markedly, but, once again, we will leave that discussion for a future article so as not to overload the present text.
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Figure 12 : comparison of « ballistic » and« boost-glide » trajectories.
BGRVs: a few examples
In the past decade, hypersonic‑glide programs (now commonly referred to as HGV – Hypersonic Glide Vehicles, superseding the older BGRV terminology) have proliferated in the United States, China, and Russia.
France is also active in this field. In 2023 it achieved its first successful flight test with the VMAX vehicle, developed by the French Defense Procurement Agency (DGA) under the engineering leadership of ArianeGroup.
Below we illustrate, with two concrete examples, how the principles discussed earlier can be realized in practice.
BGRV 122E
The first example is the experimental vehicle BGRV 122E, which gave its name to this class of craft (see Figures 13 and 14).
The 122E was a very elongated cone weighing close to one ton and measuring about 7 m in length. Its outer skin was made of colombium—a material that retains strength at extremely high temperatures—and it was backed with thermal insulation.
Cooling of the forward tip, which endured the highest heat flux, was accomplished by liquid transpiration (circulating coolant that evaporates through the skin to remove heat).
The vehicle was set at an angle of attack to generate the necessary lift, and to prevent the same side from constantly bearing the greatest thermal load, it was spun about its longitudinal axis for the entire flight.
On 26 February 1966, after being launched atop an Atlas rocket “at the limit of its structural and thermal capability” [6], the 122E successfully linked Vandenberg Air Force Base in California with Wake Island on a trajectory that was estimated [7] to exceed 7 000 km (see Figure 17).
Figure 13 : BGRV 122E on display at Wright-Patterson AFB
![Figure 14 : vue schématique du BGRV 122E [6]](https://www.hyfar-ara.org/wp-content/uploads/2025/12/BGRV-sketch-300x264.jpg)
Figure 14 : schematic view of the BGRV 122E [6]
Common Hypersonic Glide Body (C-HGB)
The C‑HGB is a hypersonic warhead jointly developed for the U.S. Army and the U.S. Navy. The Army version—Long‑Range Hypersonic Weapon (LRHW) “Dark Eagle”—is mounted on a transporter‑erector‑launcher (TEL) truck that carries two missiles equipped with this head (see Figure 15).
Exact specifications of the C‑HGB vehicle are, of course, classified. However, external shapes have been released repeatedly, showing a tri‑conical object about 2 m long with control fins for in‑flight maneuvering (Figure 16).
The precise range is also confidential: reference [8] mentions 2 800 km, while a Pacific test conducted in June 2024 flew from Hawaii to the Marshall Islands, a distance of roughly 3 800 km [9] (see Figure 17). The Army announced that the first battery fielding would start by the end of 2025 [10], and was expected to wrap up in early 2026 at the time this article was written. [14]
A full test of the naval version was carried out from Cape Canaveral in May 2025, validating integration onto Zumwalt‑class destroyers. Two ships are currently being modified to accommodate the new missiles [11] [12]. Sea trials are expected to begin in 2027 [11]. An attack‑submarine variant for Virginia‑class submarines is also planned [13].
Figure 15 : an LRHW unit of the US Army
Figure 16 : mockup of the maneuverable hypersonic warhead “Common‑Hypersonic Glide Body (C‑HGB)” used by the U.S. Army for the LRHW (Long‑Range Hypersonic Weapon) system, displayed during a demonstration at the House Army Caucus Breakfast in Washington, DC on 27.02.2020
![Figure 17 : trajectoires supposées du BGRV 122E (ref [6] et [7]) et du LRHW](https://www.hyfar-ara.org/wp-content/uploads/2025/12/BGRV-trajectory-2.jpg)
What to remember
As noted in the introduction, the articles in this series are aimed primarily at non‑specialists affiliated with the HyFAR‑ARA association who want to learn a bit more than what mainstream media typically provide.
For their benefit, we’ve distilled below the key take‑aways from the material presented:
- There isn’t a sharp dividing line between the supersonic and hypersonic regimes the way there is between subsonic and supersonic flow. Instead, as speed increases, a host of increasingly complex physical phenomena emerge gradually, marking the transition into the hypersonic regime.
- Mainstream media often conflate “hypersonic vehicle” with “maneuverable vehicle.” We have shown that a system can be one without being the other, or it can be both simultaneously.
- It was maneuverability (among other factors) that made the Apollo lunar missions possible.
- Maneuverable hypersonic vehicles—whether civilian or military—are not a recent invention. Numerous experimental and operational objects have been designed and deployed for more than half a century.
We have sprinkled throughout the article various orders of magnitude—speeds, accelerations, ranges, altitudes, dimensions, etc.—that we hope will prove useful to readers when they analyze information obtained from other sources.
Finally, if this article has sparked any questions for you, we consider our goal achieved, and we invite you to submit those questions through the contact forms available on this site.
References
[1] | Hypersonic and High-Temperature Gas Dynamics J.D. Anderson AIAA Education series – second edition – 2006 |
[2] | Apollo 8 NASA Press Kit NASA news release 68-208 – 15/12/1968 |
[3] | Apollo 8 mission report NASA MSC-PAR-69-1, February 1969 |
[4] | Uber einen Raketenantrieb für Fernbomber (Deuxième édition allemande inchangée) (a) Eugen Sänger, lrene Bredt VERLAG FLUGTECHNIK/ ERNST VON OLNHAUSEN STUTTGART – October 1957 |
[5] | ORION Artemis I entry performance Jeremy Rea and Luke McNamaray and Mark Kane 46th Annual American Astronautical Society Guidance, Navigation and Control Conference 1-7 February 2024 |
[6] | Engineering the Space Age – A Rocket Scientist Remembers Robert V. Brulle Air University Press – Maxwell Air Force Base, Alabama 2008 |
[7] | Lightning bolts – first manuevering reentry vehicles William YENGST Tate publishing 2010 |
[8] | The U.S. Army’s Long-Range Hypersonic Weapon (LRHW): Dark Eagle Congressional Research Service, update n°36 from 12 June 2025 |
[9] | DOD Completes Flight Test of Hypersonic Missile 28 June 2024 |
[10] | US Army Long-Range Hypersonic Weapon: Programme status Sidney A. Dean 8 October 2025 |
[11] | First U.S. Warship Fitted for Hypersonic Missiles Back in the Water 6 December 2024 |
[12] | US Navy Begins Hypersonic Integration on USS Lyndon B. Johnson 16 January 2025 |
[13] | Breaking News: US Navy funds first Block VI Virginia-class submarines with hypersonic strike capability. 12 July 2025 |
| [14] | First U.S. Ground-Based Hypersonic Weapon Dark Eagle Delayed Again as Army Misses 2025 Target 19 January 2025 |
(a) First version issued in 1944
