Fire Detection and Meteorology from MALE and HALE Ultralight UAVs

Problem Statement

Wildfires cause massive trauma and damage, and are getting more intense as Global Warming increases. Swift detection and intervention allows most such fires to be put out while they are still confined to a few trees. Present approaches try to synergize large and small assets from GEO, LEO and other orbits, with citizens calling 911 Emergency, ground-based towers, fire spotter Ranger stations, daytime fire-spotter aircraft, Medium and High Altitude Long Endurance (MALE and HALE) UAVs, Aerostats and high-altitude balloons. Each has severe limitations. Of greatest interest to us, MALE and HALE UAVs require fuel and maintenance. Coming from military genesis, they are expensive. One estimate is that coverage of just California would require over 420 such HALE craft, costing several billions of dollars. Still small compared to the cost of even one massive fire that can be stopped early, but daunting.

Cloud cover is a serious obstacle. Helicopters and small aircraft can fly under clouds given safe weather conditions, but are usually constrained at night over mountainous areas where fires may start on slopes that are hidden from ground observers in the nearest community. However, in daytime, smoke plumes precisely mark fire locations, and spreading haze points to general fire locations. Swift detection and communication at night is the difficult target, along with UAV response that delivers fire suppressants most promptly and precisely while the fire is still small.

In some cases such as where downed power lines in high winds, or a fast-moving front with thousands of lightning strikes trigger many fires simultaneoulsy, weather may prevent low-level observation flights, and smoke plumes may spread at low altitude. In such conditions, swift “triage” could identify the most serious threats to the limited resources available for fast response. This is generally a problem in residential areas where dry interiors can fuel fire even if it is raining heavily outside. During the day local 911 calls may suffice, but not at night.

Solution Approach

In prior work at AMS, we sought community input to design instrumentation payloads for a new class of ultralight, reflective MALE and HALE vehicles as part of the Glitter Belt architecture. This was to help alleviate Global Warming, starting with the ability do to Continuous Atmospheric Mapping with long residence times over remote ocean areas. Smaller scale models of the Glitter Belt Flying Leaflets (FLT) and Flying Leaf (FL) platforms, developed as part of the scale-up process, provide unique solutions for MALE and HALE based detection respectively. The solar-powered FLTs are designed for daytime meteorology up to the tropopause but can come to lower altitudes, even under light cloud cover, given wind safety. The FLs can stay up between 18km (dawn minimum) and 32km (dusk maximum) indefinitely, so that they offer excellent night-time detection platforms, albeit constrained to stay well above clouds. Both use GPS-based navigation and connect to ground and Space communications. The paper considers the synergy between requirements as well as results for meteorology and fire detection.

Meteorology data are used to help identify areas and times of high fire risk. FL trajectories are adjusted to increase persistence over such areas. Since most wildfire risk is in summer weather, daytime duration is significantly longer. FLT flights are scheduled during high-risk times, able to launch and recover from most playgrounds or open roads.

Use of these vehicles eliminates the long delays inherent in LEO based imaging, while retaining the communication and geographical precision advantages. Precision and image resolution are improved by an order of magnitude, reducing false-positives due to reflected sunlight. The large wing span enables use of multiple detectors for accuracy. The relatively low altitude compared to LEO, enables swift communication and coordination with local authorities. The same craft, due to their long persistence, can also augment disaster response and evacuation strategies.

Also from the last AMS meeting, we are extending work on Virtual Aperture Antennae formed by several FLs flying in formation. This is at high enough altitude to ensure smooth air for precise spatial alignment. Prior work looked upwards at the radiation from re-entering satellites, starting with Space Shuttle (STS) Orbiter re-entry images, but then moving on to images of small cubesats. Now we present results looking downwards, with the distance reduced by an order of magnitude. Clouds and haze still post difficulties for which solutions are being explored.

Conclusions: 1) HALE and MALE ultralight craft provide an inexpensive solution for most of the problems in detecting wildfires 2) Integrating routine Meteorology and Remote Sensing functions into the same architecture helps to justify their acquisition and routine deployment for all purposes. 3) Cloud cover and haze still pose difficult problems 4) Virtual-Aperturture antennae formed by formation flight of HALE swarms, opens opportunities to improve resolution and precision by orders of magnitude.

Acknowledgement:

We acknowledge generous partial support from Taksha Institute, as well as the Amrita Visva Vidyalaya, and guidance from Prof. Satyanarayana Chakravarthy of Indian Institute of Technology, Madras, Chennai, India

The attached Concept Figure shows a swarm of Flying Leaf ultralight UAVs examining fire spots in virtual aperture antenna collaborative mode, including multispectral imaging with long span of each. Each FL is formed from 7 to 9 Flying Leaflets(FLTs) with all but 3 of FLT power units returning after rendezvous of the sheet-frames. Thus for instance, a swarm of 30 FLs would take 270 launches of FLTs but only 90 full FLTs to remain at high altitude.