Boost-Glide vehicles (BGV) have been around for quite a while, but have suddenly been catapulted (or more accurately, rocketed) into the news by some recent successful and less successful test events. Now, I have to state a disclaimer here – I am not an expert in the field, and have never been involved in any BGV programmes, which, in the context of this article is a good thing, because my comments are based on observations and inferences from open-source material, and cannot be considered to disclose anything classified. Jim ‘Sonic’ Smith reports:
I have, however, been interested in BGV and their related technologies for quite a while, and indicated in earlier articles for @Hush_Kit that BGV were an emerging defence capability that it was important to watch. The first BGV hardware I encountered was at a US Aerospace Materials Conference in 1990 (yes, 30+ years ago). This was a simple, very slender conical structure in Carbon-Carbon, exhibited in an open Conference by Martin-Marietta, and labelled, with no further explanation “BGV nose cone”. So BGVs are real, even if not everyone knows what they are.
Looking into this field from the outside can be somewhat confusing. A number of capabilities are dependent on similar technologies, and, as some of those capabilities are strategic in nature, there tends to be quite substantial obfuscation going on about the purpose of various technology demonstration and maturation activities.
In this article, I will attempt to clarify some aspects of the various programmes which appear to be being pursued; clarify some of the language; and explain the importance of BGV, and how they differ from other hypersonic programmes.
Here I am defining what I mean by various terms in this article. Other sources my use different definitions.
Hypersonic: The word hypersonic is used to describe high-speed flight, typically at Mach numbers greater than 5. Flight at such speed brings potential advantages, but comes with specific technology challenges. The principal advantages are reduced warning time, a more difficult interception by defensive system, and high kinetic energy.
The technical difficulties stem from the interaction of a flight vehicle and the atmosphere at high speeds. These difficulties include thermodynamic heating of structures, requiring the use of advanced materials; predicting, managing and controlling flow behaviour to reduce thermal effects and control and manoeuvre flight vehicles; and managing propulsion, particularly if this is to be air-breathing, rather than rocket-based.
Hypersonic Weapon: A system designed to achieve ‘kinetic effect’, and to operate at hypersonic speeds. Such a weapon may be air or surface-launched, and may be directed against a variety of targets ranging from the fleeting and tactical to the fixed and strategic.
Some examples may help to de-mystify this. The simplest operational hypersonic weapon is the APFSDS (Armour Piercing Fin-Stabilised Dispensing Sabot) anti-tank weapon, otherwise known as a long rod penetrator. These are typically fired from Main Battle Tank guns against other tanks, and fly at about 1.8 km/s, which is a little over Mach 5 at sea level. No guidance after launch or warhead is required – the kinetic effect is achieved through speed and APFSDS mass, which is enhanced through the use of high-density materials.
Moving away from land warfare, recent conflicts have shown that there may be significant tactical advantages in effective guided weapons which are highly reactive, or in other words have a short flash-to-bang time. Other requirements leading to potential hypersonic solutions might include high-speed and long-range anti-air weapons. Hypersonic weapons may vary from the unguided short-range APFSDS, through high-speed cruise missiles and to air-launched ballistic missiles.
Boost-Glide Vehicle: A flying vehicle that is accelerated to very high speeds, but is then un-powered.
This is an intentionally broad definition, and is intended to indicate that BGV concepts have been around for a very long time, and are already in use. The APFSDS is a short-range, unmanned BGV of a sort, with the boost phase provided explosively. The North American X-15, a 1960s rocket-propelled research aircraft able to operate at speeds greater than Mach 6, was an early manned-BGV.
The aim and intent of current BGVs extends well beyond the aspirations of the X-15 program, and I will explore possible current objectives later in this article. BGVs are a special class of hypersonic weapon systems that may prove to be particularly de-stabilising.
The two sections that follow are a quick look at some hypersonic weapons and BGV programs, and these are followed by a discussion of recent US and Chinese BGV test activity. This is an overview. It’s not comprehensive, and doubtless misses some of the reader’s favourite programs, particularly if they are not being reported in the open literature. However, there should be sufficient here to discriminate between hypersonic weapons and BGV programs; to indicate the activities in these areas; and to indicate why BGV might be of broader concern, rather than merely of technical interest.
Looking at the development of air-to-surface strike capabilities over the last several decades, one can determine two trends of interest. Those targets which cannot be readily moved, including for example, airfields, command centres, communication hubs and so on, have been buried or hardened where possible. This has led to continuing efforts to improve the capability of (largely) conventional weapons against hardened targets.
Where hardening is not achievable to a sufficiently effective level, effort has been put into making key assets mobile, or moveable at short notice and in unpredictable ways. This has created a class of targets which are high-value, yet for which the engagement opportunities may be short-lived, or “fleeting”. The advent of conflicts prosecuted by non-state actors, insurgents, and other unconventional forces, has further increased the pressure to be able to locate and take rapid action on the occasions when targets are apparent and can be engaged.
This type of issue has become a strong driver for real-time and near real-time reconnaissance and intelligence systems, capable of alerting the command structure to the presence of such targets. Responding to such targets is another matter, and depends on the availability of suitable weapons systems; their presence in or near the engagement area; and a sufficiently flexible and responsive command structure to ensure a timely engagement. In a word, having a hypersonic strike weapon is not enough – the rest of the target discovery, identification, command and authorization chain has also to be in place.
That said, by maintaining standing strike patrols of B-1B aircraft, with precision guided weapons on board, the US has achieved very rapid response times when targets have become apparent. However, this may not be practical in circumstances where weapons platforms themselves are threatened by ground or air threats, and a long-range, high-speed strike weapon may be required. This appears to be the objective of the majority of visible US programmes.
Other nations see the world somewhat differently. The Russians appear to me to be rather more defensively minded than the US, but are also perpetually nervous about NATO, the US and various other perceived threats. The strength of US Naval Forces, and their mobility, is a particular concern, so it is no surprise that the Russians appear to have a strong interest in hypersonic anti-shipping weapons. In addition, it is clear that much NATO and US Air capability is dependent on high-value air assets such as AEW&C aircraft, air-to-air refuelling tankers, and high-flying and long endurance reconnaissance systems. To counter these, it is possible that future hypersonic anti-air systems will be developed.
In respect of China, key potential flashpoint areas appear to be in the South China Sea, on the island of Taiwan, as well as a generally difficult relationship with several of its neighbouring countries. Area denial would appear to be a strong driver for recent military developments, and it is possible that the large and capable J-20 will eventually be equipped with hypersonic air-to-surface and anti-air weapons, to have at least a deterrent, and possibly an area-denial effect. China is also said to be concerned that recent US hypersonic technology developments may threaten its nuclear deterrent.
Some hypersonic weapons programess are identified below:
· U.S. Air Force—Hypersonic Attack Cruise Missile (HACM);
and · DARPA—Hypersonic Air-breathing Weapon Concept (HAWC, pronounced “hawk”).
The USAF program is presumed to derive from the DARPA demonstrator, and relies on a Supersonic Combustion Ramjet (SCRAMJET) to provide sustained hypersonic propulsion. SCRAMJET technology is one of the high-risk areas for hypersonic weapons, and significant international efforts are underway to demonstrate viable systems. The benefit gained through the use of air-breathing propulsion is that the weapon is smaller, and could perhaps be carried by the F-15 as well as the B-52. An additional advantage is that it may be easier to integrate sensors and seekers into hypersonic cruise missiles, suggesting that these are intended to achieve more tactical effects.
The Air Force is also examining proposals for the Expendable Hypersonic Air-Breathing Multi-Mission Demonstrator Program, alternatively known as Project Mayhem, which is seeking to achieve significantly longer range than current systems.
The detail below has been derived from a report Hypersonic Weapons – Background and Issues for Congress – Congressional Research Service https://crsreports.congress.gov R45811
Russia is developing the Avangard BGV and the 3M22 Tsirkon (or Zircon) hypersonic cruise missile, and has reportedly fielded the Kinzhal (“Dagger”), a maneuvering air-launched ballistic missile.
The Tsirkon is a ship-launched hypersonic cruise missile capable of traveling at speeds of between Mach 6 and Mach 8 (Russian sources state Mach 8 to 9, and claim a range of up to 1000km). Tsirkon is reportedly capable of striking both ground and naval targets. Tsirkon can be fired from the vertical launch systems mounted on a number of Naval vessels as well as 885 Yasen-class submarines, and other platforms.
Russia has also fielded Kinzhal, a maneuvering air-launched ballistic missile, which was successfully test fired from a modified MiG-31 fighter in July 2018—striking a target at a distance of approximately 500 miles. Russian media has reported Kinzhal’s top speed as Mach 10, with a range of up to 1,200 miles when launched from the MiG-31. The Kinzhal could eventually be fitted with a nuclear warhead.
According to U.S. defense officials, China successfully tested Starry Sky-2 (or Xing Kong2), a nuclear-capable hypersonic vehicle prototype, in August 2018. China claims the vehicle reached top speeds of Mach 6 and executed a series of in-flight maneuvers before landing. Starry Sky-2 is described as a “waverider” that uses powered flight after launch and derives lift from its own shockwaves.
There has been, and continues to be, very extensive international interest in hypersonic technologies, and related programs are in place in (at least) Australia, France, Germany, India, and Japan.
When I first encountered the term BGV, it was in the context of one of those forward-looking papers the USAF occasionally put out on technology trends and aspirations, indicating that the USAF had a desire to achieve Global Reach, and, moreover, to be able to deliver capability anywhere on the Globe in two hours. This would be in around 1990, and this highly ambitious target was to be approached through testing and development of Boost-Glide Vehicles.
As time has passed, events have demonstrated the need for systems capable of reacting quickly to respond to rapidly changing military situations, or to attack high-value fleeting targets. Recent aspirations suggest the desire is now to be able to strike anywhere on the globe within one hour rather than two. Current BGV systems offer the prospect of being able to do that, and moreover, using delivery systems that are much less predictable than ballistic missiles, and hard to counter.
The key aspect is the use of the space and near-space environment. Two alternative approaches have been described, the first of which may be thought of as a hypersonic glider. Such a vehicle is launched using a booster rocket and delivered at high speed into the upper atmosphere or near-space environment. After separation from the booster, the BGV descends and transits for significant distances in the upper atmosphere at hypersonic speed.
In this cruise mode, the vehicle can manoeuvre to change course, and, although in the upper atmosphere, will be below the target radar horizon for much of its flight, which might extend for a few thousand miles. This increases unpredictability, reduces warning time, and makes defensive engagement more difficult.
Placeholder for insertion of FOBS vs Hypersonic Glider figure
The second approach is more ambitious, and requires a launch system capable of putting the BGV into low-earth orbit. Re-entry may be achieved at a location of choice, which may be extended by a skipped re-entry, allowing cross-track manoeuvre and increasing unpredictability. Because a partial orbit is used to deliver the flight path, systems like this are referred to as Fractional Orbit Bombardment Systems or FOBS. The nature of the flight path provides truly global reach.
Pairing a BGV hypersonic glider payload with a FOBS delivery system massively increases unpredictability because of the range and manoeuvrability of the BGV after it has entered the atmosphere, coupled with the global reach and unpredictable flightpath of the FOBS delivery vehicle.
Naturally, there is nothing to prevent the BGV carrying a nuclear payload, rather than a conventional strike warhead.
Some Boost-Glide Vehicle programs are identified below:
· DARPA—Tactical Boost Glide (TBG);
· DARPA—Operational Fires (OpFires);
The DARPA programs are closely related. TBG is Air Force and air-launched in focus, but is also looking at compatibility with Navy Vertical Launch systems, while OpFires is focussed on ground-launched, vehicle-based systems for Army.
· U.S. Navy—Conventional Prompt Strike (CPS);
· U.S. Army—Long-Range Hypersonic Weapon (LRHW), otherwise known as ‘Dark Eagle’;
The US Army and Navy programs are intended to use a Common Hypersonic Glide Body (C-HGB) with a Navy developed booster. The Navy system would be submarine based, while the Army would use a mobile launch platform. The Army system is stated to have a range of “more than 1725 miles”
· U.S. Air Force—AGM-183 Air-Launched Rapid Response Weapon (ARRW)
The USAF program builds on the DARPA Tactical Boost Glide program, with the BGV being derived from the Falcon
Interestingly, US hypersonic programs have been described as being “mostly non-nuclear”, which is scarcely reassuring.
The programs appear to be based around the hypersonic glider rather than FOBS concept – but given the unclassified nature of the paper describing them, this is no surprise. Given US space capability generally, it would be surprising if a US FOBS program does not exist.
The detail below has been derived from a report Hypersonic Weapons – Background and Issues for Congress – Congressional Research Service https://crsreports.congress.gov R45811
Russia is developing the Avangard BGV and the 3M22 Tsirkon (or Zircon) hypersonic cruise missile, and has reportedly fielded the Kinzhal (Dagger), a maneuvering air-launched ballistic missile.
Avangard is a hypersonic glide vehicle launched from an intercontinental ballistic missile (ICBM), giving it “effectively ‘unlimited’ range.” Reports indicate that Avangard is currently deployed on the SS-19 Stiletto ICBM, though Russia plans to eventually launch the vehicle from the Sarmat ICBM. Avangard features onboard countermeasures and will reportedly carry a nuclear warhead. Russian news sources claim that Avangard became operational in December 2019.
China has conducted a number of successful tests of the DF-17, a medium-range ballistic missile specifically designed to launch BGVs. U.S. intelligence analysts assess that the missile has a range of approximately 1,000 to 1,500 miles and may now be deployed. China has also tested the DF-41 intercontinental ballistic missile, which might also be modified to carry a conventional or nuclear BGV.
China has tested the DF-ZF BGV (previously referred to as the WU-14) at least nine times since 2014. The U.S. officials have identified the range of the DF-ZF as approximately 1,200 miles and have stated that the vehicle may be capable of performing “extreme manoeuvres” during flight.
Recent test activity
Recently, the US attempted a BGV test from Alaska. The material disclosed by the US suggests that this was a test of the Common Hypersonic Glide Body (C-GHB), in support of the Army Dark Eagle and Navy Conventional Prompt Strike Programs.
The test apparently failed due to a problem with the booster rocket, and it appears likely that this booster was new, and differed from the USN booster rocket used previously. It may be that this is the first test of a three-stage booster with the C-GHB payload.
Previous reporting has suggested a range of 1725+ miles for the Dark Eagle system, using a two-stage booster, but the trial warning and airspace notification for the failed test identified possible landing zones for three booster stages, and an overall range of about 4000 miles. This suggests that new longer-range applications are being sought for the C-GHB and its launch system, and coming, as it does, a few days after a successful Chinese BGV test, one cannot help wondering whether new scenarios for the use of such systems are being examined.
China was recently reported in the Financial Times as having conducted a successful BGV test in August, using a Long March 2C rocket as the launch vehicle, and presumably carrying the DF-ZF BGV as payload. The system was reported as completing an orbit of the Earth before re-entry of the BGV, which landed near its intended target.
Although the miss distance was of the order of 40 km, this might not be regarded as too significant, particularly if the intended future application is nuclear weapon delivery.
The significance of this test is immense, as it confirms the capability of combining a FOBS delivery with a manoeuvring hypersonic BGV payload. The upshot, were this to be developed into a fully capable system, would be a Chinese ability to deliver global nuclear reach using hitherto unpredicted and undefended flightpaths.
In an environment of increasing tension between three global super-powers, the US, China and Russia, it is a matter for concern that all three are actively developing BGV-based strike systems. It is highly likely that all three are considering the use of such systems in the context of both conventional and nuclear conflicts. To describe these developments as de-stabilising seems a mild use of the term.
There would, of course, be extreme dangers should any Nation seek to deploy and use even a conventional variant of a future FOBS-BGV capability. The unpredictable flightpath, coupled with low warning time available, would be likely to result in any target Nation regarding such an attack as Strategic in nature, and responding accordingly, with very high risk of escalation.
It is perhaps no coincidence that these capabilities are becoming public at a time when the US DoD will be seeking funding for detection, tracking and defensive systems capable of defeating such threats, particularly as defensive concepts remain largely to be defined.
It is also no coincidence that proliferation is an immediate concern. Given the technologies required to possess a ballistic missile-delivered nuclear system, it is perhaps a relatively minor step from there to add a BGV capability to the payload. One need only consider the list of states, outside the big three, that are known to possess nuclear weapons, to recognise the danger that the relevant technologies could represent if developed elsewhere.