Per definition, many ballistic missile systems could be called hypersonic speed weapons, operating in the mach 5-25 regime.
However the current trend of hypersonic weapons defines something else; operation at hypersonic speeds within the atmospheric layers that allow aerodynamic maneuvering.
Such weapons exploit their kinematic superiority in order to defeat anti-ballistic missile systems. The goal is to force the ABM interceptor to dissipate energy, ultimately an energetic defeat mechanism.
The reason such weapons are developed and now trending so late, is on one side the lower performance of ABM systems in the past and the technological difficulties in terms of thermal-shielding/management.
The Haj Qasem missile is basically a ballistic missile that flies a depressed trajectory, cruising at estimated 35-60km altitude.
The booster stage accelerates a maneuvering re-entry vehicle to mach 12, while its aerodynamic control surfaces remain engaged with the atmosphere. After the carefully controlled cruise phase it impacts at 1400km distance at above mach 5.
This puts the Haj Qasem within the definition of a hypersonic weapon.
Haj Qasem represents a new missile platform for Irans tactical solid fuel arsenal. It started with the Fateh-110, which switched to a composite motor casing variant with the Fateh-313.
It continued with the second platform; the Zolfaghar which was then weight optimized to result in the Dezful variant.
As third platform the Haj Qasem is well in the MRBM range category and offers new growth potential. Compared to the previous platform Zolfaghar, it weights 7000kg instead of 4600kg, has a diamter of ~90cm instead of 67cm but is just ~70cm longer at ~11m.
Like the Zolfaghar, it uses a composite motor casing that is not wound in one piece by carbon-fiber. The fromer is a technology the aerospace industries organization favors for now.
The six months earlier unveiled Raad-500 platform of the IRGC-ASF SSJ organization, itself Fateh-110 derived, has switched to an one piece all carbon fiber filament wound motor casing. A Haj Qasem variant with such a motor casing is an option, to further reduce the structural ratio of the booster stage and so improve its performance.
However even with the technologically inferior AIO composite motor casing technology the calculated structural ratio is at an impressive value of ~0,10 to 0,08, which means 90-92% of the booster weight is fuel and only 8-10% empty-mass.
This value derives from the officially published data on the missile, most importantly its mach 12 burnout velocity. The primary reason for the uncertainties, are the unknown grade of composite solid fuel used and the unknown weight of the maneuvering re-entry vehicle systems.
Since the booster stage does not have added weight due to a thrust vector control system or a thrust termination system, a low value of 8-10% could be well possible. Iranian designers favored an angled launch method to avoid the use of a TVC system as on the Sejil missile or Salman upper stage.
The use of a MaRV that corrects any velocity error created by the booster via constant trajectory re-calculation, allowed to skip a thrust termination system as employed on the Sejil-1. Beside weight, all these measures also improve cost efficiency.
The U.S 1980's, then state of the art Pershing II is a good comparison to the Haj Qasem in terms of booster performance. Both accelerate a payload of 600-750kg to a speed of mach 12.
However the Pershing II with its composite aramid motor casing is thicker, heavier and requires two stages to accomplish that goal. This serves as a hint on what level of technology the Haj Qasem employs and the Pershing II is still not regarded as obsolete technology in 2020.
The high performing booster soon separates from the MaRV, which it puts on a depressed low altitude trajectory. Iranian designers used a modified Zolfaghar/Dezful derived MaRV to reduce costs and risks. This appears to be a reason why the range is restricted to 1400km, since this MaRV platform stemmed from the 700km range Zolfaghar which was later improved to the 1000km range Dezful, designed for significantly lower speeds.
It uses a carbon-carbon composite nosetip, that takes much of the thermal energy which gliding through the atmosphere creates. Four large aerodynamic control surfaces designed for maneuvering in very thin atmospheric layers are also of great importance. Together with the high speed and the ram air pressure velocity creates, it allows the MaRV to maneuver at highest altitudes.
The key to survive the hot journey down to its target, is vast aerothermal scientific knowledge via tests and simulations. An aerothermal management model is necessary, that takes into account the tolerabel speed, maneuvering and altitude at any moment of the flight. Performed in a specific narrow band, the given MaRV or a future hypersonic glide vehicle will reach the target area at the right energy state. Iran explicitly claimed to have mastered such an advanced adaptive flight-dynamic system with the Haj Qasem missile.
With the right amount of maneuvering during the late cruise phase, the Haj Qasem's MaRV would dissipate kinetic energy in the thinner atmospheric layers to sufficiently slow down and finally impact with >mach 5 at 1400km distance.
This means instead of gaining range due to the strong body lift "wave riding" effect of a HGV, as used in the Chinese DF-17, the Haj Qasem maneuvers to reduce speed, so that it's MaRV can survive the journey.
A positive side effect here is, that the true target trajectory can be masked due to significant course changes, confusing the defending adversary. Most importantly, having mastered the science package of this hypersonic weapon, opens the door to a better MaRV or HGV beyond the Zolfaghar origin MaRV platform.
The Chinese DF-17 hypersonic weapon is an advanced and relatively expensive solution equipped with a radar seeker as terminal sensor, indicating an anti-shipping role. Iranian missiles, even long-range ones, achieve hits with pin-point accuracy levels of 10-30m CEP without a terminal sensor.
This raises the question whether a mid-course GNSS/GPS/GLONASS update of the INS is used, or something exotic such as an astro-navigation system, or simply if new Iranian gyroscopes and accelerometer enable a highly accurate INS. External mid-course updates for the INS in a secure form could also include ground based positioning system on Iranian soil or ground radar position update.
Skipping the terminal sensor, bars the missiles from use against moving targets but also significantly simplifies the MaRV design, foremost thermal shielding.
A problem related to this, are the immense g-loads at re-entry and terminal anti-ABM maneuvering, which can easily destroy sensitive avionic such as the INS. Hence it's possible that a secondary lower accuracy solid-state mechanically robust MEMS based INS, designed to survive the high g-loads is used for the short terminal phase.
Whether it is GNSS that allows the Haj Qasem to perform a pin-point strike at 1400km distance or systems that can't be externally influenced at all; the threat it poses is immense, the destructive power devastating. As example a mid-course GLONASS update at 60km altitude and 300km distance to the target area would be almost impossible for the opponent to jam or spoof.
Its time to arrival is extremely fast due to the shorter depressed trajectory; only shoot-and-scoot level mobile systems could change their position fast enough, certainly not large aperture ABM radars.
Anti-ABM defeat mechanism
The weapon system qualities of the Haj Qasem missile described up to this point, could also be performed by a MaRV'ed ballistic missile for example a MaRV Sejil-2.
The Russian Iskander is the most famous SRBM counter to NATO ABM systems. Despite not falling into the hypersonic weapons category, primary because it slows down below mach 5 at impact, it almost does everything hypersonic weapons use for ABM defeat.
A very fast missile, in a superior kinematic state performs pseudo-random maneuvers when reaching predicted ABM system envelope. A constant change of its vector, forces the ABM interceptor to react to those changes, which the interceptor must initially perform in dense atmospheric layers, fighting against gravity. The attacking missile is doing its course changes in thin atmospheric layers and is assisted by gravity on its path down. Each reaction of the interceptor happens with a tiny sensor-, relay- and actuator- delay which has significant adverse impact at those high speeds.
The kinetic energy reserve a > mach 6 SRBM like the Iskander can tap into for such maneuvering is very limited compared to the mach 12 Haj Qasem.
Western fighter pilot know the energy defeat mechanism as the F-pole maneuver, primary used to defeat BVR AAMs by changing the the fighters vector and forcing the AAM to bleed its energy when updating its course. The same situation occurs if an ABM interceptor engages a MaRV or a Iskander-like missile.
The other method to exploit western ABM interceptors weaknesses is by operating in regimes for which they were not designed. Often because they were made to counter common non-maneuvering ballistic missile RV's.
ABM interceptors such as SM-3, THAAD and Arrow-3 are restricted by altitude, they can't operate below a certain altitude threshold due to air friction. These exo-atmospheric interceptors have little effective usage against hypersonic or Iskander type missiles.
Of these three only THAAD has a aerodynamically formed nose seeker that can take dynamic pressure and thermal loads to a certain extend. To what altitude and at which speeds this is possible is unclear. However even with the seeker not being a limiting factor e.g via late jettisoned protection shroud: THAAD is a TVC steered system and its kill-vehicle's altitude control thrusters offer only very limited course correction reserves. Hence against Haj Qasem it can counter react to course changes as long as its booster is active, but afterwards its lack of aerodynamic control surfaces degrade its course correction capacity, as large vector changes will deplete its KV fuel reserves.
The second category; the endo-atmospheric interceptors, are represented by e.g Patriot PAC-2 and PAC-3, Arrow-1/2, SM-2/6, S-300/-400 and David Sling. Its these interceptors against which the energy defeat maneuvering is used. Goal of the interceptor is to be at one point in time close enough to the attacking missile and additionally fast and maneuverable enough, for an endgame high-g turn and finally hit, or trigger its HE-frag warhead.
The more energy the interceptor is forced to dissipate by counter/reaction maneuvering, the smaller its engagement envelope becomes. The area it is able to protect becomes smaller, to a point, at which it will never reach the attacking missiles rendezvous position at all.
In the case of the mach 12 Haj Qasem missile, energy must be dissipated in order to slow it down to below mach 6 at impact. Hence the kinetic energy equivalent of 6 mach numbers is available to its MaRV for late cruise phase and terminal phase maneuvering. The dissipated energy will heat up the MaRV and cause the desired positional changes.
Relatively low g maneuvers that change the heading angle by few degrees will, at those high speeds, create large difference in distance of missile to interceptor. The more energy reserve/speed is available, the more such heading angle change cycles can be performed, to which the interceptor must react, since it doesn't know what the intended target is.
As the maneuvers become more intense the closer the missile comes to its target, it suddenly goes vertical with highest intensity maneuvering to hit the intended object from above. This vertical dive maneuver increases the unpredictability and makes interception more difficult.
The Iskander can only perform late and relatively few maneuvering cycles during its vertical dive, primary intended to defeat PAC-3 and David Sling type terminal ABM interceptors. Haj Qasem starts earlier, with more cycles, of more severe vector variations.
This improves its performance against high kinematic capability, area-defense interceptors like the Arrow-2 and further reduces engagement envelopes to points where the ABM system itself can be attacked.
To degrade ABM sensor performance and the early warning system, it must be understood that hypersonic missiles can be seen as high flying cruise missiles. While space based IR sensors can pick up the boost phase of the Haj Qasem at launch and initial trajectory, its high energy level can be used to drastically alter its trajectory after boost phase.
This, combined with the small MaRV of low RCS, especially compared to the whole Iskander missile body, creates a target that is difficult to discover and track. Pseudo-random maneuvering means that the final destination of the MaRV can't be predicted either.
This creates a set of problems, where warning is late and not specific.
One of the few benefits of ABM systems against hypersonic weapons, is the denied usage of light decoys and effective "traveling" chaff and aerosol clouds.
Basing options: Missile farms
The preceding platform, namely the Zolfaghar missile was used on transporter erector launchers which had a single or two missiles each. There is a high possibility that we will see such twin launchers for the Haj Qasem missile in future as well.
The most intriguing basing method however, was unveiled by the IRGC-ASF in summer 2020; the so called "missile farm" basing method.
A canister with a missile is buried up to meters deep in earth. Once launched, the hot gases exiting the top of the canister throwing away covering earth, and the missile exits the canister. A deeper, open shaft where the missile travels through was also claimed to be possible.
Compared to Irans "missile cities" tunneled into hard mountain rock, this concept is not a hardened basing method. But ambiguity via the potential for decoy launch sites creates a relative soft but survivable basing concept.
Without resorting to a nuclear counter-force strike to neutralize the buried missiles, the concepts requires a very low CEP weapon to hit the launch site, to destroy it. Flat featureless terrain is selected for the launch sites, tens to hundreds meters away from each other. This creates serious problems to achieve a <5m CEP hit in an environment where GPS signal is likely degraded by jamming, as optical/IIR terrain matching is difficult.
As conventional blast over-pressure doesn't work against against a missile buried in flat terrain, a very direct hit by a heavy weapon is needed to neutralize the missile. Decoy sites can't be identified by any physical air or space based principle known, leaving HUMINT as only mean to identify where real missiles are buried.
Another aspect of this novel basing concept innovated by Iran is, that the missiles are ready to fire. In a realistic scenario the bulk of the missiles buried would have been launched instantly before an campaign to neutralize the missile farms could start.
Multiple simultaneous launches against pre-programmed targets at the start of hostilities, saturating ABM systems, is the realistic scenario this basing concept enables.
In terms of logistics it offers the benefit, that dangerously explosive solid fuel missiles are not stored in tunnel systems or specifically built bunkers, where an incident or inflicted damage could cause a catastrophic cascade effect. The effort for a safe storage container and a bunker or even tunnel is instead invested in a launch container that is simply buried in a vast secured area.
The fixed basing also offers the benefit of an accurately known initial position, which increases accuracy if an all-INS guidance is employed.
Tactically most attractive of all features, is the on-demand availability for launch. A target detected by any means can be instantly attacked without preparation time.
The IRGC-ASF first military satellite, the Noor that is apparently working in the infrared band, is a hint of future capabilities for target detection. A constellation of such expandable IR or SAR satellites, detecting a target and able to communicate the targets position fast enough, would enable an instant attack. The chain of action from detection, to data transmission, to analysis and launch order would greatly benefit from a weapon instantly ready to fire and with a very short time to arrival.
The mobile, compact Qased SLV gives a hint that Iran is interested to acquire an expandable cubesat-size and inexpensive satellite constellation capability. In a conflict that would degrade such a constellation by the opponents ASAT capabilities, on-demand wartime launches of replacement satellites, randomly launched by compact mobile SLVs, would be the primary mean to find targets for the long range missile forces.
The attractive features of this new basing concept, required technological breakthroughs for Iran. First and foremost advances in missile internal energy supply, all-electric servo actuators and advances in the guidance systems that need to orient the missile in 3D space.
Pneumatic actuators of previous generation systems are replaced by storable all electric ones. These in turn need batteries that retain their power for years, batteries that need to provide sufficient energy for the intensive maneuvering, hypersonic weapons perform. Common 2D-plane guidance algorithms that required the missile in the right rotation angle are not applicable anymore. The missile must survive hot gas environment that is employed to throw away the protecting top earth layer.
The Haj Qasem's compact 8 rear stabilizer fin configuration is clearly because it is meant to be used in this buried container hot launch basing mode. For ease of the manufacturing process, the stabilizer configuration of previous generations with a vortex generator assisting the stabilizer is omitted in the Haj Qasem. While still possible to be applied in the Zolfaghar and Dezful composite motor casings, the vortex generator won't be applicable anymore in a future Raad-500-like all carbon-fiber filament motor casing.
The Haj Qasem can be described by two features: First, it is a new high performance booster platform made to stay within Irans 2000km self-proclaimed range restriction. Second, it is a demonstration of the scientific package needed for hypersonic weapons, foremost in the aerothermal field.
A third point that will certainly result in a more potent variant in the future, is thermal resistent materials and their economic application in the manufacturing process. It will result in a DF-17 like weapon, although the Haj Qasem booster is apparently already better performing than that used on the DF-17.
A lifting body HGV will exploit range benefits, which results in a 7-8 ton, single stage missile with a significant weight conventional high-energy explosive warhead to have a range of ~2000km. That range is a threshold from which tactical airpower can't be effectively employed anymore, leaving strategic airpower as option left in this category.
The missile farm concepts allows ready to launch missile to be stored for years or even more than a decade in relatively protected buried containers. Therefore survivability of the Haj Qasem arsenal can be regarded as very high. Relatively small 8x8 off-road TELs with two missiles each of MRBM range capability is another feature of this kind of next generation weapon.
Although it could be described as nearly immune to any current deployed ABM system in the western world, a better thermally shielded HGV variant would reinforce its capabilities in this field, due to its ability to fly at an even lower altitude band of between 40-50km.
Haj Qasem represents a new kind of assets and while in the past, e.g Israel, had a countering system ready or near completion against new Iranian long range missile types, this is the first time there is not even a system announced to be in development to counter it.