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Mahesh

14/02/24 14:33 PM IST

India wants to develop high-altitude pseudo-satellite vehicles, powered by the Sun

In News
  • The Bengaluru-based National Aerospace Laboratories (NAL) successfully flew a prototype of a new-generation unmanned aerial vehicle (UAV).
HAPS
  • The primary utility of HAPS vehicles is in the field of surveillance and monitoring, but there are other situations, like disaster management, wherein it can be very useful.
  • HAPS technology is still under development.
  • Several countries, and companies, have developed and flown such vehicles with encouraging success, but none has mastered the technology yet.
  • The world record for a vehicle of this class is held by the Airbus-manufactured Zephyr, which flew continuously for 64 days in August 2022 before crashing.
  • The prototype tested by NAL recently spent eight and a half hours in the air. Next month, NAL, a unit of the Council of Scientific and Industrial Research (CSIR), plans to keep it in flight for at least 24 hours.
  • The full-scale machine that NAL is trying to build, by 2027, would be aiming to remain in the air for 90 days at a stretch.
Need of UAVs
  • The kind of jobs that HAPS are meant to do are currently done by UAVs and satellites, but both have certain limitations.
  • The normal UAVs, or drones as they are commonly called, are mostly battery-powered and cannot remain in the air beyond a few hours.
  • Continuous monitoring is not something these can do very effectively. In addition, they fly at relatively low levels, because of which their vision is restricted to small areas.
  • Satellites can observe much larger areas, but the ones in low-earth orbits are continuously moving with respect to Earth.
  • They cannot be constantly keeping an eye on the target area.
  • Geostationary satellites, located at a height of about 36,000 km above the ground, can keep a constant gaze over one area. But these are fairly expensive, and once deployed, cannot be repurposed or reoriented.
  • HAPS are meant to overcome all these shortcomings, and do more
  • These stratospheric vehicles (flying about 20 km above the ground) are designed to loiter over a region.
  • By standards of flying objects, and in comparison to UAVs for example, they move really slow, at just about 80-100 km per hour.
  • That kind of slow speed 20 km above the ground means that objects on the ground pretty much don’t move for it. You can easily keep an eye over 200 sq km of area.
  • In fact, you can observe everything even over a 400 sq km area with a five metre resolution. If you want to focus only at one sq km, for example, you can get a resolution as high as 15 cm
  • HAPS can be a very powerful solution for this kind of work. They work like geostationary satellites but with added flexibility.
  • They can be easily redeployed over another location, or can be reequipped with a different payload, something that is not possible with a geostationary satellite.
Challenges
  • The primary challenge is to generate enough solar power to keep the aircraft flying, the payloads operating, and the batteries charging.
  • The batteries need to be enough to continue the operations through the night.
  • Then there are design-related challenges. The aircraft needs to be extremely lightweight to minimise the power requirement, but it also has to be stable.
  • This is one of the reasons why this aircraft is meant to fly in the stratosphere.
  • The region between 17 and 23 km above the earth’s surface is climatologically conducive for their flight.
  • The wind speed is very low and ideal for light-weight aircraft to remain stable. It helps that this height, much above the region in which civilian aircraft fly, is favourable for observation and surveillance activities.
  • But temperatures at that height can drop to -50 degree Celsius or lower.
  • Electronics need to be kept warmer, and that is an additional burden on power resources. Also, air density is just about 7 per cent of what it is at sea level.
  • That creates acute complications for the aircraft, for example in producing lift and thrust.
  • Because of limitations of space and weight, solar cells and batteries need to have very high efficiencies.
  • There is one company which has achieved 500 watt-hour/kg, and the battery is commercially available, even though extremely expensive.
  • Even with other aspects of this aircraft, for example, design, materials, aerodynamics and aeroelasticity, we are working at the limits of technology.
India & HAPS
  • For India, HAPS is another technology area where it is entering the race at a relatively early stage.
  • In the last few years, there has been great emphasis on promoting research in emerging technologies, so that the country is not dependent on others for critical technologies of the future.
  • Joining technology development at an early stage also results in capacity building, early adoption of technologies, control over patents, business opportunities and spin-off technologies.
Source- Indian Express

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