By Group Captain Anupam Banerjee (r)
The development of present-day Lighter Than Air (LTA) platforms dates back to the first hot air balloon flight by Joseph and Étienne Montgolfier of France in 1783. From then on till now, the LTA platforms have seen a myriad of military and civil commercial uses. For instance, balloons raised scouts several hundred feet into the air to observe troop movements during the American Civil War. Towards the end of the 19th century, Count Ferdinand von Zeppelin developed the first rigid shell airship, which weighed more than ten tons and was the first LTA platform for passenger travel and was later used by the German military in the Zeppelin bombing campaigns of World War-I and as defence assets, surveying harbours and protecting convoys.
LTAs were quite an attractive option during the early days of military aviation. The airships flew because of the buoyancy provided by hydrogen or helium, and the engines were only needed to provide enough power to steer the aircraft at low speeds. The airframe was also less complicated as it required only enough strength to support its own weight and withstand the relatively mild stresses associated with low-speed flight. In contrast, conventional fixed-wing aeroplanes required more robust airframe structures and powerful and reliable engines.
The interest of military planners in LTA vehicles was mainly because of their ability to support persistence, loitering, weapons delivery of specific kind and potential logistics mission capabilities. The role of LTA vehicles in the history of various military engagements depended on the technological advancements of that time and the ability of various adversaries to mount defences against them.
During the Second World War, LTA production gained momentum, and they played an essential role in sweeping mines, performing search and rescue, escorting convoys and various ISR tasks such as scouting, photographic reconnaissance, and anti submarine patrols. The airships also took part in a few bombing campaigns, but substantial losses to fighter planes led the airships to assume a defensive role. Other than the USA, Japan also used LTA technology in incendiary bombs called Fu-Go, a thousand of which were floated across the Pacific using balloons, though they failed to cause any damage.
Post Second World War, the interest in the LTA platform waned for a few decades. However, the LTA vehicles received a fresh look in the 1980s when several tethered aerostats came into service for counter-narcotics and drug interdiction missions on the USA-Mexico border. Tethered aerostat platforms since then have been successfully used to provide persistent ISR and force protection capabilities across the globe. Efforts are also underway to develop airships capable of airlift and logistics capabilities.
LTA vehicles could be categorised as unpowered and powered. Unpowered includes balloons and tethered aerostats, whereas powered LTA vehicles are airships that can be classified further as either conventional or hybrid designs. Conventional airships, also known as blimps, rely on buoyancy for lift, whereas hybrid strategies use the structure and variable directional thrust to create lift.
In India, the Indian Airforce (IAF), as far back as 1996, projected the requirement of a few aerostat systems to provide gap-free low-level surveillance coverage across its western border. The procurement of aerostats was also part of a series of recommendations to streamline border management and enhance surveillance capabilities in the aftermath of the 1999 Kargil conflict. Finally, in the mid-2000s, the IAF procured two aerostats manufactured in the USA and fitted with Israeli payloads from Israel for surveillance of border areas.
An aerostat is a helium-filled balloon tethered above the ground and equipped with surveillance and communication payloads. It can remain deployed for several days at a stretch, scan a wide swath of area and is particularly effective for detecting low-flying objects, making it a cost-effective alternative to aircraft, especially during peacetime.
Tethered aerostats used in India remain anchored to the ground by one or more cables. The main tether holds the aerostat in position and provides power to the aerostat’s payload and data link to provide communications between the payload and the ground control station. An aerostat’s main envelope is filled with helium, with an air chamber called a ballonet inside catering for expansion and contraction of the gas while changing altitude without compromising the shape of the aerostat.
The stabilising tail fins are normally filled with air. The primary payload is in a ventral dome under the envelope, with other payloads fixed at various points of the external envelope. The shape of the envelope and the tail fins are designed aerodynamically to provide a stable platform that can sustain modest winds and gusts. When moored to the ground, the aerostats are anchored to a rotating mast along a circular rail so that they can freely weathervane in the wind.
Around 2015, the IAF again drew up plans to procure a few more aerostats. Meanwhile, attempts were on to design and develop aerostats indigenously. Though the aerostats cannot replace the Airborne Warning And Control System (AWACS) in view of their very high mobility in the air, the aerostat radars play a vital role in the overall air defence of the country.
However, the aerostat radars are considered more vulnerable to air attack in view of their fixed location; however, their advantage far outweighs the vulnerability, and the cost of operation is minuscule compared to aircraft. No surprise that the aerostats are called the poor man’s AWACS.
The IAF Aerostats have payloads consisting of Advanced Programmable Radar (APR), Electronic Intelligence (ELINT), Communication Intelligence (COMINT) and V/UHF radio telephony payloads and Identification Friend or Foe (IFF).
Though the Defence Research and Development Organisation (DRDO) has taken a step in developing an aerostat radar, we still cannot claim self-sufficiency in advanced aerostat radar systems. The DRDO system, having a detection range of 100 nautical miles and endurance of one month, carries electro-optic and communication intelligence payloads, designed, developed, and integrated by the Aerial Delivery Research and Development Establishment (ADRDE), Agra.
India has unique security challenges with a 7,000 km long coastline and almost 14,000 km long international border with various countries that require constant monitoring. The development of Unmanned Aerial Systems (UAS) systems worldwide rapidly has increased the challenges of protecting these long borders and equipping the security forces with all the relevant intrusion detection systems to effectively counter any intruding object. The aerostat radars can substantially boost this capability and act as a force multiplier in these surveillance roles. Planners at security establishments must weigh all possible options.
The future of LTA platforms looks promising with the emergence of High-altitude platforms (HAP) and High-Altitude Pseudo Satellites (HAPS). These are systems equipped with various payloads for applications ranging from surveillance, environmental monitoring, and communication to navigation. These systems can stay aloft for long durations at more than 50,000 feet altitudes. HAPs are typically positioned in the stratosphere. The HAPs are much more cost-effective when compared to satellites used for similar applications requiring less operating and maintenance expenditure while offering compatibility with the existing infrastructure.
The current geopolitical conflicts clearly demonstrate that modern wars will be influenced by costly high-tech platforms and innovative use of low-cost and niche technology-driven platforms with disruptive potential. The future use of LTA vehicles can easily form a part of this transformation.
Gp Capt. Anupam Banerjee (r) is a former IAF Spokesperson and is now a Senior Consultant at SIDM
