India is on course to join a very select club of countries that have their own long-flight, High-Altitude Platforms (HAP). On May 7, the CSIR-NAL (National Aerospace Laboratories), test-flew a vehicle first to a height of about 3,000 feet.
- It came back and took off again and flew to 25,000 feet (about 8 km), without the payload.
- HAP is an unmanned aerial vehicle. It is just like a big drone, but with two essential differences — the HAP typically operates at a height of 18-20 km above earth, clearing all air traffic and weather, and is equipped to stay up there for longer periods than drones — from several hours to even months.
- The HAP that NAL is developing is being designed to stay airborne for 90 days — unless other HAP hopefuls get better earlier, NAL’s HAP would set a world record.
- A HAP can do many things that a satellite can — surveillance, imaging the earth below, for both civilian and strategic purposes and can also be used, where economics work out, to provide telecommunications and broadband services over a chosen region — all at a fraction of the cost of a satellite.
- A satellite does not need to be powered for its orbital flight — it does this by gravity. But a HAP needs some propulsion system, with on-board energy generation capability. An HAP would typically be stationed in the upper atmosphere for several months; since it can’t carry its own fuel, the energy must come from solar power.
- HAPs are complex machines. They have to be lightweight because the air at 20 km altitude is very thin — one-16th the density at sea level — so the HAP must be designed for much less ‘lift’; it is the under-wings force that keeps the aircraft in flight.
