Scientists at the CSIR-National Aerospace Laboratories (NAL) have successfully tested an unmanned aerial vehicle, called High Altitude Pseudo Satellite (HAPS) at Challakere, Karnataka, earlier this month. HAPs are like drones, except that they are expected to be in the stratosphere – well above where commercial planes fly – and can be powered enough by solar cells and a battery-system to be able to hover for days on end. A fully working HAPS can be used for a variety of applications, from surveillance to beaming 5G waves. They can double up as “towers in the sky” and have more flexibility than satellites, in being able to map a piece of land from above.
The NAL system is currently far from these goals. The HAPS that was flown this month is a scaled-down HAPS. The 5-metre-long system, with a wingspan of 11 metres and weighing 23 kg, rose to about 3 km and stayed put for about eight hours. This prototype, scientists associated with the project told The Hindu, “met or exceeded all the performance metrics set out for it.” However a series of tests have been planned and they are expected to culminate in a full-bodied craft – with a wingspan of 30m (nearly as much as a Boeing 737) – by 2027. It will be able to rise to 23 km and stay airborne for at least 90 days. “There are very few proven systems anywhere in the world that can do this and given the variety of potential applications, India ought to be able to have such capabilities of its own,” said Abhay Pashilkar, Director, CSIR-NAL.
While HAPS may look elementary, it requires a fair bit of engineering prowess. They are unmanned and must fly days and nights on end, meaning they need solar-powered batteries – and not jet fuel - capable of lifting the airframe up to the stratosphere (which extends from 6-50 km above the earth’s surface). This ascent into the sky is challenging, given the air turbulence in the atmosphere, and the fact that these are relatively light planes. “The weight of the airframe is only 8 kg but the entire system’s weight is nearly 23 kg. Most of the weight is of the batteries,” said Dr. Pashilkar. Unlike the familiar solar panels on rooftops, those used to power the plane are extremely thin solar films. “There are only one or two companies in the world capable of making solar-cell films that thin,” said L. Venkatakrishnan, Chief Scientist and Head, NAL, and in-charge of the HAPS programme. “It’s like the Hero Honda of the skies. Our test this month gave us the information required to design a bigger system, particularly on how can we ensure that the drone remains balanced given the forces it will be subject to,” he told The Hindu.
CSIR-NAL aims to design and build the HAPS’ propellers, battery management system, carbon-composite airframe, flight-control system, and the high-powered electric motors that can withstand extreme temperature ranges.
Last month, in an unrelated project, Bengaluru-based private company, NewSpace Research and Technologies Pvt. Ltd. (NRT) reported carrying carried out the first test-flight of a solar-powered, long-endurance drone that flew for 21 hours. This was part of a demonstration project funded by the Defence Ministry. However details of the height achieved by the plane and whether it carried a payload isn’t publicly known.