– Subodh Sharma & Aman Routray
An Alpha Defense Exclusive
The Aeronautical Development Establishment (ADE), a premier lab of Defence Research & Development Organisation (DRDO) is all set to power its flagship medium-altitude long-endurance unmanned aerial vehicle (MALE UAV) – TAPAS-BH-201 with a 220 HP Diesel Engine. Currently, UAV is powered by two wing-mounted turboprop engines that can produce 98.63 hp each. (Through some reports suggests it was 115 HP Rotax engine).
220 HP Engine for Tapas
All the modern systems are designed for scalability and a proportionate increase in size, fuel carrying capacity, and engine power can result in a system with greater payload and endurance. This new engine that ADE is working with CVRDE will be almost twice as powerful as the existing engine.
In 2017 it was reported, that Rustom 2 which was later called TAPAS BH 201 after many alterations will be powered by two 180 HP engines. However, since then a lot has changed, the UAV is now completely revamped. It offers increased range because of SATCOM (Satellite Communication) against a regular line of sight communication. The system also offers automatic landing and take-off that was missing in the initial Rustom 2 prototype.
These additions naturally require more power and to meet the increased power demand now the UAV will require a more powerful powerplant. These new UAV engines will not only provide Tapas more power but also increase its endurance as these diesel engines will be more efficient than existing engine.
Diesel Engine vs Turboprop Engine
Piston engines are the most efficient option for small aircraft and diesel is even better. the compression-ignition design, also known as diesel engines, can achieve ignition via compression of the fuel/air mixture. These engines offer a higher compression ratio, which allows more efficient use of energy contained in the fuel. The efficient combustion results in improved burning efficiency and lower fuel consumption.
Lower fuel consumption is a property of significant importance for a UAV that requires long endurance. Other advantages that a diesel engine offers are simplicity, lighter weight, improved environmental credentials, and less operating costs.
However, like all other engineering solutions, this also comes with pros and cons. The problem with jet-fuel diesel engines is that they run very coarsely compared to turboprop designs. The uneven torque distribution causes vibrations that eventually fatigue the propeller. This reduces its lifespan and increases the risk of failure. Though, this risk can be mitigated with a purpose-made propeller and a dampening device that can reduce vibrations significantly.
Looking at the trade-offs, the diesel engine is best suited for this type of requirement. These are fuel-efficient, lighter, and cheaper. Though designers will have to add a damper and improve the propeller design to mitigate the vibration issues.
New UAV vs Improved UAV?
Historically, DRDO has developed multiple UAVs but none of that system could see services of Indian armed forces. This journey started with Nishant, which was a multi-mission Unmanned Aerial Vehicle with Day/Night capability used for battlefield surveillance and reconnaissance, target tracking & localization, and artillery fire correction. The launcher was a truck-based Mobile Hydro pneumatic Launcher. Whereas the air vehicle has autonomous flight capabilities, and it was controlled from a user-friendly Ground Control Station. Nishant was a highly mobile, compact, and easily deployable system. The recovery mechanism had an Aero Conical Parachute and impact attenuation system. This was the system that came closest to induction, 4 of these were delivered to the Indian army for the user trials and all 4 crashed during these trials.
Based on the Inputs from the user a conventional takeoff and landing version of this UAV was designed, and it was called Panchi. This system took its first flight in September 2014 but much before that a more powerful MALE was taking shape in ADE which was later called Rustom.
Rustom-I took its first flight on 16 November 2009, the UAV crashed after flying for a brief period. Through ADE was ready with another prototype with improvements to demonstrate this UAV in less than a years’ time. The second flight took place on 15 Oct 2010. In this test flight, the UAV flew for 30 minutes at an altitude of 910 m (3,000 ft). It was reported that Indian army officials present at the demonstration were impressed with Rustom-1. Recently this drone was undergoing user trials with (Most likely) CRPF and it was crashed into walls of the airfield.
Many believe Rustom 2 is the latest system from the house of DRDO. However, the system that was initially planned as Rustom 2 was significantly inferior to the current Tapas BH 201. The journey of Rustom 2 to become Tapas BH 201 has gone through Rustom H. These are three variants of the same system with significant changes. The technological advancement that resulted in Automatic take-off and Landing (ATOL) and satellite communication (SATCOM) mode makes this system significantly more capable than baseline Rustom 2.
That leaves us to a new question.
Armed Tapas BH 201?
Tapas in it’s current form can carry a payload of around 350 KG. The payload will certainly increase with a 180HP engine as they are almost twice as powerful as the existing engine. This improvement will allow Tapas to carry more payloads. Therefore, its regime of operation can be expanded from just surveillance to armed surveillance. DRDO has already integrated an anti-tank guided missile with Rustom-I.
Rustom-I with a payload-carrying capacity of 95KG could carry 2 anti-tank guided missiles (Likely Helina). Each anti-tank-guided missile Helina weighs 43 KGs and has a range of 7KM. Tapas in its current form can theoretically carry 8 of these missiles. Though it’s not clear how it will impact its endurance. Even though this number looks impressive, but today’s warfare requires larger standoff ranges. This is where laser-guided bombs come in, Tapas powered by a high-power engine can carry much more ordinance resulting in a solution for today’s battlefield, only if the system is ready before better technology surfaces.
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