Monday, 31 December 2018

Hypersonic Glide Vehicle


Photo Credit :

December 26th , 2018 marks a watershed moment for Russian Strategic Forces as it culminated with the  third and final successful flight of Avangard ( Project 4202 ) advanced ICBM armed with Hypersonic Glide Vehicle Program.  The project started in 2004 and after  14 long years of R&D and Flight Test program with many challenges and failures the final go ahead for first operational deployment of Avangard Hypersonic Glide Vehicle referred to as Yu-71 ( HGV ) was given the go ahead to be  operationally deployed at Dombarovskiy by the end of 2019

What are Hypersonic Glide Vehicle's ( HGV's ) 

HGV's are technically Reentry Vehicle also sometimes refereed to as Warhead , as the name suggest is a Flying Glider which Glides its way to its target at very high Hypersonic speed and with high degree of maneuverability as it races towards its target. This Glide by a Hypersonic Flying Glider in layman's term is similar to a Stone Skipping over the Water.  The Stone here would be the Glide Vehicle and the Water would be a thin layer of Atmosphere almost at the edge of Space called Kármán line where the Atmosphere and Space  tends to meet.

Hypersonic Glide Vehicle (HGV) is a fusion of multiple scientific discipline involving Advanced Materials that can withstand tremendous heat and dynamic pressure without breaking the structural integrity of Glide Vehicle/Warhead as it glides through this thin layer of atmosphere thousands of kilometers in Range , Aerodynamics similar to an Aircraft but something that flies at Hypersonic Speed ( i.e greater than Mach 6 almost Mach 25 for ICBM Ranges ) while maintaining maneuverability ( laterally and vertically )  as it flies towards its target in a ball of fire due to atmospheric friction , Aero Thermodynamics , Control and Guidance are few aspect of HGV's.
The glide vehicle uses a combination of Hypersonic Blended Wing Design built from materials that can withstand heat of upto 2000 * C as it glides in near space at hypersonic speed along with control surfaces with combination of  Gas-Dynamic Control System/Reaction control system to maintain maneuverability as such hypersonic speeds

Many countries are currently working on Hypersonic Glide Vehicle program or just pure Hypersonic Program using Scramjet Engine and have attained varying degree of experience and success. US leading with DARPA Technology Demonstrator HTV-1 and later HTV-2 and later more military oriented Advanced Hypersonic Weapon , Chinese with DF-ZF HGV , Russian Yu-71 and possibly India with its Hypersonic Technology Development Vehicle (HSTDV) Program.

US has a more advanced program for Hypersonic glide body (HGB) vehicle in form of AHW , it has a conical design with winglets and was designed to fit within the payload assembly. The structure of AHW is made of aluminium, titanium, steel, tantalum, tungsten, carbon fabric, silica and other alloys, including chromium and nickel.

                                             Advanced Hypersonic Weapon ( AHW )

HGB is powered by one lithium-ion actuator battery, two lithium-ion and five nickel manganese hydride batteries. Pressurized nitrogen gas is used as a propellant for the vehicle via its Reaction Control System,Other equipment includes radio frequency transmitters and small electro-explosive devices etc

                                                                    via USAF

The AHW is designed to provide a 6,000km range with 35 minute time-of-flight and achieve less than ten metre accuracy. It delivers a conventional payload at medium and global ranges, using a hypersonic glider. The weapon’s high manoeuvrability allows it to avoid flight over third party nations when approaching the target. It employs a precision guidance system to home in on the target. [9]
US Navy tested its HGV last year ( 2018) as on an Intermediate Ranged weapon as their requirement is to put out tactical Intermediate ranged capability for Submarine and Surface launch and the congressional mandate asks them to do this by late 2020-September 2021. The successful FE-1 which occurred last October (and successfully struck its intended target) was at a 3500 km range which appears to be the design range for the Intermediate Range HGV that the US Navy is fielding into service. The USAF is using the same HGV and will mount it on an Air-Launched weapon in the medium sub 2000 km range class weapon, and the US Army is also likely to look at similar range.

On top of this the 2nd generation HGV is currently being worked on by DARPA under its Tactical Boost Glide program and it will likely form the basis of the next gen. common HGV sometime in the mid to late 2020's once it has been put through its paces. The 2nd gen HGV is expected to be flight tested by September, 2019 and follow on test demonstrations (beyond the first few) would be done by individual services starting with the USAF under its ARRW program. [10]

Avangard ( Yu-71/Project 4202 )

                                                         Photo Credit: Russian MOD

Russia began its own research on Glide Vehicle Program during the time when Soviet Union existed but much of the program was either on drawing board or ended with partial success with Yu-70 HGV program a precursor to the current Yu-71 HGV.

Yu-70 was tested few times approximately 4 times but the initial test ended in failures with either Glide Vehicle not separating from booster or if it did the HGV burnt up during atmospheric reentry since then the program remained frozen for most part of the 90's due to funding constrains and lack of interest by political leadership of the time.[1]

A major impetus on building a Hypersonic Glide Vehicle arose when US withdrew from the ABM Treaty and subsequently the Corner Stone of Cold War treaties in limiting the deployment of Offensive and Defensive system was nullified and US was free to develop its ABM system deployed nationally and globally.

A  test vehicle for HGV was presented to country leadership during a major nuclear exercise in 2004 in which President Putin was present and Yu-70 HGV was tested from SS-19 launch platform and in President Putin's words, were capable "hitting targets at an intercontinental depth," "with a hypersonic speed, high precision and the opportunity of deep manoeuvre in terms of height and course".[2]   The HGV subsequently disintegrated upon re-entry

                                               Avangard Launch ( via Russian MOD )
A new HGV program Project 4202/Yu-71 was initiated and it took over a decade of  R&D  to test these new HGV with SS-19 ICBM as a primary launch platform to carry the Glider atop.  SS-19 Mod 3 variant were capable of carrying 4.3 Ton of Throw Up Weight ( Warhead and Decoys ) to a range greater than 11,000 Km. 

Yu-71 program had its own share of technology challenges and after few failures in 2014 the program was on the verge of getting mothballed , Quoting Russian Deputy Prime Minister Yuri Borisov who held the post of Deputy Defense Minister in 2014

"This complex was born quite hard. Four years ago, at a meeting of the Supreme Commander, the question was to continue or close this work, because, unfortunately, this is a very difficult job ... I remember well how the Supreme Commander asked a direct question to the general designer and got enough convincing answer: “Give us another chance.” And they used this chance, ”said Borisov. [4]

                                                                Credits: Russian MOD

He noted that the test on December 26 was the third test,it confirmed all the main declared characteristic. Borisov recalled that the serial contract for the production of Avangard complexes was concluded in 2017. From next year(2019 ) , it would be operationally deployed [3]

Borisov also mentioned in interview with MOD Press Red Star " Russian scientists had to overcome a number of difficulties associated with the fact that the temperature on the surface of the combat unit reaches 2 thousand degrees. "It really flies in the plasma, so the problem of managing this object and the issues of protection were very acute, but solutions were found," Borisov said.  Avangard HGV carries a ThermoNuclear warhead with a blast yeald of more than 2 megaton[8]

HGV versus Ballistic Missile ( BGRV/MRV ) 

A logical question to ask and answer would be what makes a Hypersonic Glide Vehicle different from a Ballistic Re-entry Vehicle like those carried by ICBM i.e  MRV/MaRV/MIRV or Boost Glide Reentry Vehicle ( BGRV )

While the Hypersonic Glide Vehicle and ICBM with  MRV/MaRV/MIRV/BGRV payload travels at Hypersonic Speed and post Boost Phase during Mid-course Phase of ICBM it travels at  more than Mach 18-20 speed and re-enters the atmosphere at about the same speed that it flies during its mid-course phase and post 3rd stage burn out  in case of MIRV when the BUS gets deployed. Post re-entry of Warhead which begins at ~ 100 km altitude the Warhead  speeds to its target experiencing great atmospheric drag/friction and burns in a flame of fire as it gushes through atmospheric drag and gradually slows down to ~ 4- 6 km/sec as it hits the target , in the case of advanced vehicle like Boost Glide Re-entry Vehicle , The warhead post - reentry boost glides to its target a form of Maneuvering in the atmosphere to avoid ABM system , due to BGRV long cross range ,high speed in multiple mach numbers and extreme High G forces as it maneuvers and boost glides it makes intercepting via ABM system extremely complex and time sensitive task . In both cases the re-entry phase though do not last beyond couple of minutes.

A Hypersonic Glide Vehicle on the contrary post launch of the ICBM and after the termination of Boost Phase and 2nd stage  would get ejected by the launch platform ( eg SS-19 in case of Avangard ) and would then deep dive till it reaches ~ 100 km Altitude which is edge of space where the atmosphere exist though thinly and space environment just begins known as Kármán line a boundary between Earth's atmosphere and outer space as starts its long complex journey towards its target . The HGV glides at this altitude for extended period of time at IRBM/ICBM ranges as it travels in a ball of fire due to formation of Plasma and maneuvers in what can be termed loosely as  Zig-Zag fashion towards its target. The HGV experiences extreme heat and pressure that would last tens of minutes and temperature approaching 2000 degree centigrade , compare this to re-entry time of few minutes in case of MRV/MIRV/BGRV warhead post re-entry the technology complexity to design an HGV becomes more clear.

Though the first operational deployment of HGV warhead is currently limited to ICBM system , HGV is also getting developed for IRBM and MRBM class of missile by US China and possibly India. As IRBM and MRBM travels at much lower speed ( 3-5 km/sec ) the HGV would consequently travel at similar lower speed ,lower ranges and at altitude ~ 80 -100 km but would still represent a very potent system versus the ABM

ABM versus HGV Advantage   

What makes HGV even more dangerous compared to a very capable BGRV or MIRV is its ability to dodge ABM defenses which is HGV's pièce de résistance and  a USP of this program.  Current ABM defense works on the basis of ABM Radar constantly tracking the target which can be a ballistic missile or warhead and computes an optimum path of interception and sends the data to the ABM missile interceptor which then at high speed approaches the target. If the target maneuvers to some degree or drops in altitude or speed  the radar keeps track of it and data is sent to missile interceptor via Mid-course Guidance or data links to set the interceptor missile on a path into a narrow box of intercept envelop.  

As the ABM interceptor missile reaches a narrower box of  its intercept envelop then the on-board Radar or IIR Seeker of the interceptor would then track the target and try to hit the target head on to destroy it completely  a process no different to intercepting a fighter by a SAM but more complex due to Speed , Time , Distance and Low RCS of Warhead.  Unlike a SAM interceptor the ABM Interceptor does not need a warhead to obliterate the target as the closing velocity between ABM Interceptor its target can be as high as 10 km/sec which is good enough to destroy any target without using warhead.

The entire sequence of launch to intercept is a very complex mechanism where Speed , Maneuvering , Distance /Altitude ,G Forces and Time is a key factor.  A delay in intercept of just 1 second  by an ABM interceptor would be a miss distance of 3-4 km for a target approaching  speed of 3-4 km/sec ( Mach 12- 14 ).  It is similar to hitting a bullet with another bullet albeit far more complex. 

Intercepting HGV adds up to a far greater challenge to ABM system to the already complex mechanism of ABM interception

1 )  Due to formation of Plasma on the entire Warhead as it boost glides at high speed , this makes any Radar Tracking a daunting task as Radio waves cannot penetrate the thick plasma screen nor can the glide vehicle transmit any kind of radio signal outside the plasma screen it travels under making ABM  Radar Tracking of the Glide Vehicle/Warhead a difficult task.   

2 ) As HGV travels at extremely high speed which is greater than Mach 20 ( top speed of Yu-71 approaches Mach 27 ) and maneuvers  Laterally ( side ways ) and in Altitude ( Height ) a kind of Zig Zag maneuver when loosely defined , The ABM Radar cannot compute an optimum intercept path for a random Zig Zag manouvering target which  can constantly keeps changing its direction and height and  due to  its ability to maneuver in a random manner the interception compute point is impossible to predict , to add the complexity of intercepting a Laterally moving target at extremely high speed of Mach 20 and above which is difficult due to High G Load Factor an ABM interceptor would experience while intercepting such targets ( as a thumb rule an interceptor has to pull in 3-4 times as much G as the target it is intercepting )  which would cause a ABM interceptor  missile to simply miss the interception as the target can out maneuver the interceptor 

3 ) As it travels at Low Altitude  of around 100 km for the Ground Based Early Warning Radar the warning time would reduce as  detection time of  low flying HGV Warhead due to its lower Horizon and for Space Based Early Warning Satellite which would generally predict an approximate impact point of a BM as soon as it is launched giving ABM Radar system advanced warning to cue its Radar may not be able to predict this approximate impact point as HGV keeps changing its direction and like a Sub-Orbital vehicle could simply break out or de-orbit any time and could hit any target on to its path and from any direction a concept similar to Fractional Orbital Bombardment System (FOBS ) .

It is possible though remains untested at a speed more than 8- 9 km/sec or Mach 27 as the final test experienced for Yu-71 the HGV/Warhead would have the capability to orbit at LEO for few days before it can re-enter the earth atmosphere on command giving it a FOBS like capability which was considered a very destabilizing in 70's and was withdrawn from service. The technical capability do exist for Yu-71 to act as FOBS though the possibility of exercising remains non-existent due to its destabilizing nature of FOBS

4 )  The effort though seems well worth the time and money , according to estimate of  Viktor Bondarev, chairman of the Federation Council Committee on Defense and Security, it would need many dozens of  ABM interceptor to intercept one single  HGV making the exchange ratio highly uneconomical for any adversary. [6]  Compare this to mid 90's deployed Topol-M with a BGRV Warhead which would according to Russian SRF commander Viktor Yesin would need around 5-7 GBI interceptor to intercept a single Topol-M [7]

ABM versus HGV Disadvantage

1 )  As currently HGV are heavy for ICBM Ranges it needs to be carried by Heavier Launch Platform like SS-19 which has a throw up weight of 4.2 Tons but this makes the system limited to Silo Launch impacting its Mobility which is offered by TEL and makes the TEL vulnerable to potential bolt from blue strike by any adversary.

2 )  Due to tailored trajectory that HGV follows  it needs a  limited stage  launch vehicle ( typically 3 stages launch vehicle for ICBM plus BUS in case of MIRV/MaRV ) it is not possible to carry Decoy and Jammers which a ICBM carrying MRV/MIRV/MaRV or BGRV does employ as part of its ABM mid-cource defense , making the vehicle vulnerable to Boost Phase Intercept or early mid-course intercept when 1st Stage is initiated , Deployment of advanced Decoys that can re-enter the atmosphere with the warhead , it is not possible due to HGV trajectory , speed and maneuvering. 

3 ) Only a single HGV can be carried by Launch Platform due to size and weight limitations making its application limited to Very High Value Target in a potential Nuclear Conflict . 

                                  Sarmat ICBM configuration with 5 HGV  ( via ) 

It is planned that next generation of Heavy ICBM Sarmat will carry multiple upto 5 Heavy HGV due to its larger throw up wight ~ 10 T and  more new generation lighter HGV with possibly lower yeald warhead.[11]

The Test and Deployment of Advanced Hypersonic Glide Vehicle like Russian Yu-71 , US AHW , Chinese DF-ZF and possibly Indian HSTDV can be regarded as the next stage in development of a constant battle between ABM and Offensive system but this also opens the gate to deployment of similar system by other countries in coming years leading to an open ended Arms Race in absence of ABM or similar Treaty , with INF demise  all but a certainty both Russia and US followed by China and India would deploy HGV on IRBM and ICBM class of  ballistic missiles and  Semi-Strategic Air and Ground Launched variants of it.

                                                                                                                             - Austin Joseph


[5]Interiew with Deputy Defence Minister Deputy Defense Minister Yuri BORISOV
[10] via BRF/brar  ( )

P.S. Kindly note that the Information and Analysis in this article are mine and official references provided where ever available.


Anonymous said...

I've always thought they were different, Project Avangard was first used on the Rubezh IRBM project (to the point that the missile project was called Avangard), while Object 4202 was a warhead delivery capsule (HGV). Avangard was the 'bus-less' delivery system where, instead of using a bus to point each warhead to its target before release, each warhead capsule (4202/HGV) gets its own 'engine (propulsion)' and is released simultaneously. Avangard was tested with Rubezh but with a more 'conventional' warhead system than 4202. And they were using Topol to test 4202.

Austin said...

Hello Anonymous,

Rubezh was in ICBM system ( and demonstrated to US as mentioned by Russian officials ) that did not have BUS but used Advanced BGRV that would self propelled and guide to its target making the BUS redundant, Rubezh was more of a test platform to prove a BUSLESS system using Advanced BGRV design but retaining all stages of Yars.

Avangard is a HGV which is more advanced than was was tested on Rubezh

bennedose said...

This is the best and most detailed explanation I have seen on this topic - much of which was unclear to me. Thanks Austin

Austin said...

Thank You Shiv , Much appreciate your feedback and glad you liked it.

This is a work in progress so would keep adding to it as I get more information , I am more keen on DRDO HGV program , Hopefully if you are at AI this time you may get some information and I would like to write on DRDO advances on this.

Unknown said...

You should probably point out the fact that current ABM systems have essentially no realistic capability against even one mirv/ICBM.

Austin said...

Ryan , certainly not a proven much less combat proven one if you add MIRV plus decoys but ABM too is not at standstill and at some point it would have such capability against limited strikes.

Anonymous said...

Austin maybe you are with problems with the URL Change in the Russian defence forum, so this is the new link


Enforcement Logix said...

This is the best and most detailed explanation I have seen on this topic - much of which was unclear to me. Interceptor Speed Camera System