Systems Engineering Analysis: VA-111 Skvall — A Russian Torpedo That Can Travel 200+ Miles Per Hour
A Systems Engineering analysis of the VA-111 Shkval High Speed Supercavitatingn Vechicle (HSSV): A torpedo that travels at 200+ miles an hour.
In this episode of “The Engineer’s Perspective”, we analyze the Russian VA-111 Shkval (Called Squall in Russian). Specifically we will look into:
- The historical background and context of of the system,
- The Systems Engineering for the system:
- Part 1: Stakeholder Needs
2. Part 2: Derived, High-Level Requirements
3. Part 3: A high level overview of how the system functions and meets the Systems Engineering requirements
- Overall Review and Conclusion
Historical Background and Context:
Developed during the cold war within the Soviet Union, Soviet Submarines at the time were not considered as “quiet” as American Submarines. It was therefore very likely that Soviet Submarines would be targeted and fired upon first during a active war. Thus, the Shkval was created as a countermeasure that Soviet submarine crews could utilize as a “Counter” weapon that could eliminate enemy submarines that attack the Shkval-carrying submarine. It is currently one of the fastest torpedoes ever created, able to travel over 200+ miles an hour with an estimated range of 7km for the first version, and 11–15km for the second version.
Systems Engineering:
Systems Engineering is the analysis of the system and identifying the high-level requirements that are met by the system. This is primarily done by looking at the system and deriving the specific needs and goals of the stakeholders that this system would likely have been developed for. Considering that at the time of the system’s development we would likely have found three stakeholder needs:
Part 1: Stakeholder needs:
Derived stakeholder needs for the Shkval could likely have been the following:
- Stakeholder Need 1: A torpedo system that provides the enemy/target little to no time to react.
- Stakeholder Need 2: A torpedo system that can quickly eliminate a threat without having to worry about the accuracy of the system.
Part 2: Preliminary Rationale and High-Level Requirements:
Requirements for the system are derived from the stakeholder inputs and needs. Knowing the two stakeholder needs mentioned above, the following requirements were derived:
- Requirement 1: The System travel at 300+ kph.
Rationale: Minimize the reaction time the enemy has to counter the torpedo
- Sidenote: Engineering is acknowledging technical limitations of systems and accounting for it. One of the key limitations that would have been acknowledged in the development of the Shkvall is that with the technology at the time, the system would have trouble guiding itself to the target due to its propulsion method.
- Supercaviation = Trouble with sensors: while supercavitation allows for greater velocity, the air bubble created by the system prevents sensors on the torpedo from contacting the water, thus preventing the torpedo from finding, identifying, and tracking targets.
It is very likely then with the Cold War as the background, that Requirement 2 was developed with a specific system in mind.
- Requirement 2: The System Shall have a large warhead
Rationale: Utilize a large enough warhead prevents the enemy from escaping the torpedo’s blast radius, while simultaneously overcoming the inability for the torpedo to guide itself due to its propulsion method of supercavitation. Again, with the Cold War as the background context for the development of the Shkvall, it is very likely that the Derived requirement would have been the following:
- Derived Requirement 2a: The System shall utilize a nuclear warhead.
Part 3: Systems Engineering: The System Functions vs. Given Requirements
To meet the requirements created above for the Shkval, a completely new method of propulsion was developed for the system. This new method of tranportation, called supercavitaiton, reduced water-induced drag on the weapon, essentially, allowing the torpedo to float in a bubble of air as it travelled underwater. A traditional torpedo travels at approximately 80kph through the water., whereas the Shkval has been noted traveling between 380–400kph through the water.
Below are illustrations of a conventional torpedo in comparison to an HSSV type torpedo. Key difference between the two types of torpedos are found in the nose, the propulsion, and control mechanisms, which we will go into detail on.
System Function 1 — Supercavitation vs Requirement 1: System Shall travel 300+ kph
By having the system function via supercavitation, the Shkval meets the 1st requirement of having the system travel at 300+ kph and addresses the stakeholder need of minimizing enemy reaction time. Excessive speed by the Shkval prevents the enemy from possibly escaping the launched Russian torpedo. We go into detail as to how the Shkvall implements the System Function of Supercavitation below:
Shown is a representative drawing of a Shkval, High Speed Supercavitating Vehicle (Hereafter called HSSV) design:
Whereas a conventional torpedo would utilize a propeller to travel through water, the propulsion mechanism for an HSSV is quite different, and utilizes a method called Super Cavitation in order to achieve both propulsion and high speeds to meet Requirement 1: The System Shall travel 300+ kph
Per Huang et al, the HSSV design would consist of a “cavitator, ventilation bowl, fore conic section, cylindrical section, tail section, fins, rudders, and thruster system. The thruster system consists of a water inlet, water pipe, water ramjet, and nozzle”
Super-Cavitation Process:
The method by which the Shkval reaches its high speed is a complicated multi-step process:
- Launch from torpedo tube
- Initiation of Rocket Motor
- Super-Cavitation initiation
- Sustainment via Ramjet and Ventilation
- Launch from Torpedo Tube:
The torpedo is released from the submarine tube prior to the kick-start of its Rocket motor.
2. Initiation of Rocket Motor:
After reaching pre-scribed distance, a rocket motor kicks off the start of the Torpedo’s propulsion process and gets the system up to speed for the Ramjet to start taking effect:
3. Super-Cavitation Initiation:
The high speed of the torpedo created by the rocket engine kick starts the cavitation process. The flat nose (Hereafter called a Cavitator) of the torpedo utilizes high velocity to initiate the creation an area of low pressure in its wake to create a bubble that encloses the entire torpedo.
The utilization of the Flat nose of the Cavitator, combined with the three ventilation Bowls, creates the initial cavitation bubble:
Ventilation + Ramjet = Sustained Supercavitation
Once the rocket engine is activated and the cavitation bubble is created, the ramjet kicks on to sustain the high speed of the torpedo through the water.
The following cutout shows the path of the water as it enters through the cavitator, passes through the fore conic section and cylindrical section before entering the water ramjet:
The ramjet takes in the water from the surrounding environment and according to tvzvezda.ru uses the sea water as an oxidizer “hydro-reactive fuel containing aluminum, magnesium, [and ]lithium”). The violent reaction creates gases that are used for two different purposes:
- Ventilation for sustainment of the super-cavitation bubble
- Exhaust thrust that exit out of the rear nozzles.
Ventilation:
The gases created from by taking the ramjet water and mixing with aluminum are vented back to the front of the Torpedo through the Ventilation Bowls highlighted below:
The gases supplement the initial bubble created by the Cavitator and Ventilation Dishes, helping to sustain and enlarge the bubble as shown in the animation below:
Exhaust Thrust:
According to Huang et al, “water ramjets using aluminum as fuel can obtain the highest specific impulse of up to 3 490 N·s/kg when the water-fuel ratio is 3.5”, this specific impulse can be expelled out of the nozzles of the torpedo:
The resulting thrust created out of the nozzles when combined with the reduced drag of the Supercavitation results in a torpedo that travels over 300kph, and meets the 1st requirement:
- The System Shall Travel over 300kph:
Side note: How to does the Torpedo Stay Level:
One of the interesting photos I have found of the Shkval is shown immediately below:
One can see that there are push-rod and hinge mechanism that can orient the direction of the Cavitator in the close-up image seen below:
Further analysis of a paper on MDPI indicates that sustained movement forward for the torpedo requires optimization of the position and angle of the cavitator to maximize the size of the supercavitation bubble that envelopes the torpedo. Via MDPI, the approximate angle can be seen below:
Seeing this, it makes sense that there is a tilting mechanism for the flat nose of the cavitator to angle the position and shape of the bubble formed to envelope the torpedo.
How does the Torpedo Turn?
The torpedo turns by extending the control fins found in the back of the torpedo as seen in this example photo of the Iranian “Hoot” Supercavitating Torpedo, itself believed to be a copy of the Shkval:
These control fins extend outside of the cavitation bubble created by the torpedo and create drag by placing the torpedo’s control fin into the water draft as shown in the image below from Popular Science:
System Function 2 — Nuclear weapon vs Requirement 2: System Shall utilize a nuclear warhead
For obvious reasons, I will not go into the details of how to create a nuclear warhead, but will say that the first version of the Shkvall was indeed designed to utilize one.
The original requirement was:
“The System Shall have a large warhead”, with a derived requirement of “The System shall utilize a nuclear warhead”.
A fair rationale can be assumed that combined with a high velocity and little time to react, a large warhead
- Prevents the enemy from escaping the Shkval, while simultaneously
- Overcoming the inability for the torpedo to guide itself due to its high speed.
The function of the nuclear warhead was incorporated during the Cold War when nuclear weapons were a newly system, and nuclear submarines were being newly minted and added to the U.S. and Soviet Navies.
Update: System Function and Requirements for advanced Shkvall
This requirement however may have been deprecated or Obsolesced By Events as it has been reported that the updated version of the system according to the National Interest: “…employs a compromise method, using supercavitation to sprint to the target area, then slowing down to search for its target”
Knowing this is the updated Shkvall, which foregoes a nuclear weapon altogether, we can look at this Function and Requirements as eliminated with new ones in place:
System Function 2A: The System Shall Supercavite to a designated location proximal to the target and then slow down to X kph
System Function 3: The System Shall Search for, identify and lock onto designated target upon arriving at designated location.
Knowing what current systems Russia has this system then may utilize a more modern forms of guidance, such as, active and passive acoustic/wake homing capabilities.
While not as effective at the prevention of the target system escaping, this set of functions allows the system to be used in more conventional naval and engagement settings, and lowers the overall costpoint for the system for mass-adaption by the Russian Navy.
The Shkvall was a breakthrough Soviet technology for Soviet Torpedoes that to this day does not have an analogue in the United States Navy. It’s ability to travel at unprecedented speeds to this day has no openly acknowledged countermeasure by Western Navies.
It was fun looking at this system and applying high-level systems engineering principles to the system such as identifying its primary functions and requirements, and then tracing how the system’s specific implementations met those requirements and functions, and identifying how those requirements and functions may have changed as we transition from Cold-War to Post-Cold War era history and effective policy with the removal of Nuclear Weapons requirements.
The updated version of the system seems to imply that there was no effective engineering solution for system targeting and guidance while in supercavitation mode, and it is possible that the lessons learned from the Shkvall will provide guidance for future Russian torpedoes.
References:
Supercavitating Torpedo: A rocket torpedo that swims in an air bubble
How this super-fast Russian torpedo could be a US carrier killer
Cavitator Design for Straight-Running Super-Cavitating Torpedoes
Influence of Ramjets’ water inflow on supercavity shape and cavitator drag characteristic
Russia developing Khishchnik high-speed torpedo to replace VA-111 Shkval supercavitating torpedo
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