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DRONES By Dr David Maddison, VK3DSM Image source: https://unsplash.com/photos/black-droneon-air-over-cloudy-sky-at-daytime-JPAfSd_acI8 Drones are now commonly used for hobby purposes as well as commercial applications like aerial photography, and for military purposes. This is the result of numerous technological advances, such as satellite navigation for guidance, MEMS accelerometers, high-energy-density batteries and miniaturised control circuitry. T hree-dimensional (3D) printing has also helped to accelerate the proliferation of drones. They are so widespread that they are now often used for criminal purposes and even for terrorist attacks, hence the need for defence against drones. Terminology There are many names for what are popularly known as drones. This article is mostly about the type that fly. Terms for these include: • UAV (unmanned aerial vehicle) • UAS (unmanned aircraft system) • SUAS (small unmanned aerial system) – under 25kg • RPAS (remotely piloted aircraft system) • RPAV or RPV (remotely piloted [aerial] vehicle) • UAVS (unmanned aircraft vehicle system) • UCAV or CAV ([unmanned] combat aerial vehicle) – military types Other types of drones might be landbased and perform jobs such as mowing lawns, agricultural tasks, deliveries, military tasks (eg, reconnaissance or attack/defence) or inspections. Such 16 Silicon Chip devices are called unmanned ground vehicles (UGVs), ground drones or ground robots. Many such drones are used for agricultural purposes. We published an article on drones for agricultural uses in the June 2018 issue (siliconchip.au/Article/11097). There are also unmanned underwater vehicles (UUVs), also known as or autonomous underwater vehicles (AUVs). We covered these in their own article in the September 2015 issue (siliconchip.au/Article/9002). There are also drone ships, known as unmanned/uncrewed surface vehicles (USVs) or autonomous surface vessels (ASVs). Drone is a general, informal term for any of the above. For convenience, we will mostly use that term throughout the remainder of this article to refer to UAVs. Drone history Drones have been around for a surprisingly long time, at least in their more primitive forms. Perhaps unsurprisingly, early drones were mostly for military applications. However, the lack of precision navigation such as Australia's electronics magazine GPS meant that they were generally ineffective at hitting the desired targets or performing other precision tasks, unless they were remotely controlled by an operator within visual range. Some notable examples are as follows (this is not an exhaustive list): 1849 Arguably the first use of a drone-like device in warfare, the Austrian Army attacked Venice with balloon bombs set with half-hour fuses. It was not a success; the expression “own goal” aptly describes the outcome. 1898 Nikola Tesla demonstrated a radio-controlled boat (described in some detail on page 15 of our November 2024 issue; siliconchip.com.au/ Series/427). 1914 The Royal Aircraft Factory in Britain designed an RPV, which they called an Aerial Target (AT) to fool their enemies into thinking it was a test target vehicle. Its true purpose was to attack German airships and as a flying bomb. It was designed by Henry P. Folland, with radio equipment designed by Archibald M. Low. It was first built in 1916 – see Fig.1. It carried around 40kg of explosives and was designed to be controlled siliconchip.com.au either from a ground station or another plane. It was a high-wing monoplane weighing 227kg, launched by catapult and landed on skids. Flight tests in 1917 were unsuccessful, but the feasibility of RPVs was proven. The AT Mark II (Fig.2) was probably built by Sopwith. It was designed to carry 23kg of explosives, but was never tested. 1917 The Hewitt-Sperry Automatic Airplane was first tested by the US Navy; it is considered by some to be the first cruise missile. It was stabilised by Sperry gyroscopes and flew a preset course. However, it was not adopted by the Navy, partly because it had insufficient accuracy to hit a ship. 1918 The Kettering Bug was an experimental unmanned aerial torpedo developed for the US Army that could strike targets at a range of 121km. It was never used in combat. 1935 The DH.82B Queen Bee was a radio-controlled variant of the Tiger Moth, used as a target drone for training antiaircraft gunners. About 470 were built in total. The term drone apparently came into use at this time as a reference to the male bee seeking the queen bee in one fatal flight. 1937 US Navy Curtiss Fledgling trainer aircraft were modified to make radio-controlled target practice drones, designated A3. In 1938, it was also experimentally rammed into a ship; a forerunner of guided weapons. 1939 The Radioplane Company made a variety of radio-controlled target practice drones for the US military, manufacturing them by the thousands. Models included the OQ-1 (RP-4), OQ-2 (RP-5) and OQ-3, among others – see Figs.3, 4 & 5. 1944 (June) The German V-1 flying bomb was the first mass-produced, operational cruise missile. Like the Hewitt-Sperry device, it followed a preset course using gyroscopes and autopilot controls, but unlike its American predecessor, the V-1 was used in combat. Over 9,000 were launched against London alone (more than 30,000 in total), causing substantial damage, injuring and killing many people. Its distinctive buzzing pulse-jet engine earned it the nickname “buzz bomb”. Its success marked a turning point in the military potential of unmanned aircraft. 1944 (August) The United States, under the Army Air Force’s Aphrodite siliconchip.com.au Fig.1: the Aerial Target RPV, built in 1916. Source: https://shvachko.net/?p=1378 Fig.2: the British Aerial Target Mark II RPV, likely built by Sopwith. Source: https://w.wiki/EDQ7 Fig.3: Norma Jeane Dougherty, later known as Marilyn Monroe, assembles an RP-5 (OQ-2) drone in 1944 or 1945. Source: https://w.wiki/EDQ8 Fig.4: a Radioplane OQ-3 target drone in 1945, ready for launch. Source: https://w.wiki/EDQ9 Fig.5: the OQ-2A aerial target of 1941. Source: www.nationalmuseum.af.mil/Upcoming/Photos/igphoto/2001562776 Australia's electronics magazine September 2025  17 and Navy’s Anvil programs, modified worn out B-17, B-24 and PBY4-1 bombers to operate under remote control from another ‘mothership’ aircraft, filled them with explosives and flew them into heavily defended German targets. Television pictures of the controlled aircraft’s instrument panel were relayed to the mothership. However, the program was a huge failure. 1951 The Ryan Firebee series of target drones led to the development of the highly successful Ryan Model 147 “Lightning Bug” reconnaissance drone series, which were used from 1962, including in the Vietnam war. Archibald Montgomery Low, 1888-1956 Archibald is known as the “father of radio guidance systems”. He designed the control system for the first drone, the British “Aerial Target”, as well as guided rockets and torpedoes. He was a prolific inventor, author and futurist and was also involved in the early development of television. 1962 The SDI Surveillance System was used by the British Royal Artillery for observation over the battlefield, and to locate targets, although there is little information available about it. 1969 Israel used a drone to photograph enemy positions on the 7th of July 1969. Conventional aircraft were useless because they had to fly too high to avoid ground-to-air missiles, so the photos showed little. An officer called Shabtai Brill conceived the idea of using a radio-controlled aircraft purchased in a toy store that he fitted with a 35mm film camera, with a timer to take pictures every ten seconds. The mission was a huge success, but it was forgotten until after the 1973 Yom Kippur war. That led to Israel becoming a dominant player in the drone industry; it still is today. 2001 After the September 11th terrorist attacks, the United States General Atomics MQ-1 Predator saw widespread (and heavily publicised) use in Afghanistan, bombing enemy positions. 2013 Jeff Bezos announced that Amazon was considering using drones as a package delivery method. 2022 Russia’s invasion of Ukraine marked the first large-scale conflict with widespread use of both purpose-­ built military and improvised civilian drones. Ukraine used consumer-grade quadcopters for reconnaissance and artillery spotting, while both sides deployed loitering munitions, kamikaze drones and electronic warfare systems. The war demonstrated how lowcost drones could be highly effective in modern combat, revolutionising battlefield tactics. Thousands of expensive military targets have been destroyed by drones to date in this war, including numerous tanks, surface-­ to-air missile systems, ammunition depots and more. Drone types Drones come in a variety of sizes, from the size of an insect to full-size fighter jets and bombers. They include the following: ● Tricopter – a relatively rare type of drone with three rotors. ● Quadcopter – an aircraft with four rotors, designed for vertical take-off and landing (VTOL). ● Multirotor – similar to a quadcopter but with more than four rotors. These include hexacopters (with six rotors) and octocopters (eight rotors). ● Fixed-wing – similar to a conventional aircraft. ● Hybrid-VTOL – these can take off and land vertically but fly horizontally, like a conventional aircraft. They may or may not have tilting rotors. ● Balloon drones – these use hydrogen or helium for buoyancy. They may float with the wind, or have guidance using propellers. An example is the “h-aero” (more on that later). ● Passenger drones – also known as autonomous aerial vehicles (AAVs), they are pilotless and designed to carry passengers short or medium distances, such as from an airport to a city centre. ● Ground drones with wheels or tracks. ● Sea drones in the form of a boat or submarine. While most drones are intended to be reused, some drones are regarded as expendable, especially some used in military applications. Drone categories and uses The US Department of Defense categorises drones according to the scheme shown in Table 1. The higher the group number, the more capable the drone is. Among the many uses of drones are recreation, aerial photography (eg, real estate & sports events), surveillance, Fig.6: a few possible examples of civilian uses for drones. Source: www.gao.gov/drone-operations 18 Silicon Chip Australia's electronics magazine siliconchip.com.au package delivery, search & rescue, rail inspection, power line inspection, agricultural inspection & spraying, maintenance (eg, washing buildings, solar panels or mowing lawns), military and others uses. Fig.6 depicts some of these applications. Drone navigation More basic drones, such as toys and early models, are guided by a human operator who can observe the vehicle directly or via a video link. More advanced drones can be programmed with a flight path, which the drone follows using satellite navigation (GNSS; eg, GPS). Most drones also use inertial measurement units (IMUs) to ensure they are orientated correctly. Advanced drones may include altimeters (usually based on air pressure) and electronic compasses (often integrated into the IMU). As drones can be disabled by disruption of their data links or GNSS (global navigation satellite system) signals, more advanced drones, especially military ones, can be autonomous, using artificial intelligence (AI) to guide them. They may also use sensors like LiDAR (light detection and ranging), cameras, radar and other inputs. Optical flow sensors can be used; these analyse images from the drone camera to determine its movement over time. They can also use a system called SLAM (simultaneous location and mapping) to determine their position and movement. Data from LiDAR and IMUs is used in this type of navigation, among other inputs. SLAM is also used Table 1 – US DoD drone categories Group Maximum weight Typical altitude Speed 1 0-9kg <366m (1200ft) <185km/h 2 9.5-25kg <1067m (3500ft) <463km/h 3 <599kg <5486m (18,000ft) <463km/h 4 >599kg <5486m (18,000ft) Any 5 >599kg >5486km (18,000ft) Any in self-driving cars and even robotic vacuum cleaners. Some drones, which we will discuss later, have fibre optic data links to enable them to operate without wireless data links or GPS/GNSS, and without needing to be autonomous. For hobbyist drones, there are many navigation systems to choose from, including open-source software like ArduPilot (https://ardupilot.org) and flight controller hardware like that shown in Figs.8 & 7. Even though ArduPilot was developed by hobbyists, it can control some very advanced drones and is used commercially. Even Boeing has used it for experimental cargo delivery drones. Apart from UAVs, it can also control UGVs (ground), USVs (water) and UUVs (underwater). Power sources Drones can be powered by a variety of sources: ● Batteries, typically rechargeable lithium-ion/LiPo types. These are the norm for hobby drones. For a non-fixed-wing (VTOL) drone, a typical flight duration is up to 10 minutes, although military or commercial drones can last 30-60 minutes. A fixed-wing electric drone may have an endurance of several hours. These drones are relatively quiet and have low maintenance requirements. ● Internal combustion engine (ICE) drones use a fuel like petrol, diesel or kerosene. They have much longer flight durations due to the higher energy density of liquid fuels compared to batteries, but may be noisier and require more maintenance. Their flight duration can be up to around 16 hours for a fixed-wing type or eight hours for a VTOL type, like the IAI APUS 25 (siliconchip.au/link/ac6x). ● External combustion engine drones use a turbojet engine. They are fast but have high fuel consumption compared to ICE drones. An example is the Boeing MQ-28 Fox Bat being developed for the RAAF. ● Fuel cell powered drones are relatively new and experimental. They may have better endurance than battery types. They can use hydrogen as the fuel, kept as a gas in high-­pressure cylinders. Storage of hydrogen as a cryogenic fluid is possible but requires a lot of infrastructure and management. Australian company Stralis has developed a hydrogen fuel cell they Fig.7: drone mission planner software. Source: www.ardupilot. co.uk Fig.8: an ArduPilot Mega (APM) flight controller. Source: www.ardupilot.co.uk siliconchip.com.au Australia's electronics magazine September 2025  19 say can power a hydrogen-electric aircraft for ten times longer than batteries. ● Hybrid drones operate much like hybrid cars, with an ICE to produce power, driving electric motors and/ or recharging batteries. An unusual implementation of a hybrid commercial/military drone is the Jabiru JCQ50 “Donkey”, which has coaxial rotors for vertical lift directly driven by an ICE, plus electric motors for directional control. ● Solar power – some specialised fixed-wing drones are solar-powered but they have to be high-efficiency, lightweight drones designed for long endurance. The solar cells can charge batteries and drive propellers during the day, while batteries drive the propellers at night. ● Nuclear – a nuclear power source will be used to power the Dragonfly drone to explore Saturn’s moon Titan (more on that later). Such systems are not considered suitable for use on Earth for several reasons. ● Balloon drones require no power to provide lift; it is provided by a lifting gas like helium or hydrogen. So they have an almost indefinite flight duration, until the gas eventually leaks out (no lightweight material can hold these gases indefinitely). Control for onboard electronics or propellers for station-keeping can be provided by solar panels. Example drones Some notable examples of drones are as follows: drones (see Fig.11). It operates in the Tolleson, Arizona area and can deliver packages of around 2.3kg within an hour of placing an order. The drone was designed for package delivery, with redundant systems, including a second flight controller. This ensures there is no single point of failure that will allow loss of control of the drone. It has also been designed to minimise noise. It has a camera and uses machine learning to identify obstacles such as clotheslines, trampolines, humans, animals and other aircraft which may not show up in satellite imagery. It has received regulatory certification with the US FAA for beyond-line-of-sight operations. Fig.9: an anti-drone gun at the Pope’s funeral. Source: https://x.com/ma777hew/ status/1916067221488480319/photo/1 300 (www.avinc.com/lms/switchblade) or so-called kamikaze drone is used by the Australian military – see Fig.10. Its procurement was announced in 2024. It is a precision loitering drone; it can fly to an area and a decision can be made whether to engage a target or call off the mission. It weighs 1.7kg, has a range of 30km or a loitering time of 20 minutes, flies at up to 150m altitude and has a loiter speed of 101km/h. It is launched from a tube, after which its wings fold out. Anti-drone device On a news item about the Pope’s funeral, we saw a security official holding an apparent anti-drone device (Fig.9). It is the CPM-­ WATSONPLUS by CPM Elettronica (www. cpmelettronica.com). Australia Post parcel delivery Australia Post is looking at concepts of future mail and parcel delivery via drones. One idea is a ground drone (Fig.12). Another is a UAV (see https://x.com/auspost/­ status/720786994511491072). Balloon drones Balloon drones have the advantage of extremely long flight times as their lift comes from a gas like helium or hydrogen. They can be stationed in the upper atmosphere, where wind is minimal, so they can stay on station using small amounts of solar power and AeroVironment Switchblade The AeroVironment Switchblade Amazon delivery drones In November 2024, Amazon released its MK30 delivery drone, with twice the range of its previous delivery Fig.10: the launch of a SwitchBlade 300 drone, used by the Australian Army. Source: https://w.wiki/EDQA Fig.11: an Amazon MK30 delivery drone, now in service in Arizona, USA. Source: www.aboutamazon.com/news/operations/mk30-drone-amazondelivery-packages 20 Silicon Chip Australia's electronics magazine siliconchip.com.au propellers. This was covered in detail in our August 2023 article on High-­ Altitude Aerial Platforms (HAAPs; siliconchip.au/Article/15894). These drones can be used for tasks like bushfire surveillance (or other types of surveillance), radio relays, and scientific research. In our June 2025 Airshow article (siliconchip.au/Article/18303) we mentioned that the Australian company Stratoship (https://stratoship.au) is developing balloon drones. Another company that produces balloon drones for lower altitude use is h-aero (https:// h-aero.com/en) – see Fig.13. Black Hornet 4 nano drone The Black Hornet 4 (Fig.14) is a miniature drone built by Teledyne (www.flir.com) with thermal imaging and optical cameras, the latter having low-light capability. It is tolerant of wind, flies at up to 36km/h, has obstacle avoidance capabilities, weighs 70g and can fly for 30 minutes. Most other specifications of this model are not published, but earlier models had a transmission range of 1km. These are used by numerous militaries, including Australia’s. According to Wikipedia, in 2015, the original model cost US$195,000 each. A recent video claims the cost as US$40,000. Such is the cost of military procurement. You can buy a similar-looking one for $100-200 online, but perhaps with a little less capability. For more information, see the video at https:// youtu.be/DMJgq2tpNJA Boeing MQ-28 Ghost Bat Boeing Australia is developing the MQ-28 Ghost Bat for the RAAF. We reported on this vehicle in our article on the Avalon Airshow (June 2025; siliconchip.au/Article/18303). It is a stealthy, multi-role UCAV. Fig.12: Australia Post’s idea of using a ground-based drone to deliver mail and parcels in the future, compared with a traditional postie on a motorcycle. Source: https://auspost.com.au/content/dam/corp/startrack-insights/customerexperience/photo-robot-delivery-machine.jpg Fig.13: the h-aero balloon drone. Source: https://cloud.aicanfly.de/index.php/s/xfnayzmeKJzPs8P Building maintenance drones Drones can be used to wash buildings or solar panels. An example is the Joyance JTC30T (https://joyance.tech), shown washing solar panels in Fig.15. DefendTex D40 The DefendTex D40 is an Australian-­ made drone for military purposes (see Fig.16). The manufacturer states it can be launched from a standard 40mm grenade launcher; it is low in cost, can carry an intelligence gathering payload, can swarm with other drones, siliconchip.com.au Fig.14: the Black Hornet Nano drone. Source: www.techeblog.com/teledyne-flir-black-hornet-4-nano-drone Australia's electronics magazine September 2025  21 Fig.15 (left): Joyance’s JTC30T cleaning drone. Source: www.spreaderdrone.com/Solar-panel-washing-drone-roofcleaning-drone-in-USA-pd524419658.html Fig.16: the DefendTex D40. Source: www.defendtex.com/uav can perform autonomous flight and is waterproof. Little else about it is known. De-icing wind turbines A Latvian company, Aerones (https://aerones.com), has developed a drone for deicing wind turbine blades (Fig.17). This can be a problem in North America and Europe. The drone is supplied with electricity from a cable, and hot water or deicing fluid via a hose to clean the turbine blades. It has multiple redundancy and safety features, such as onboard batteries, so that the drone can land safely in the event of a power failure. For more details, see the video at https://youtu. be/mP5LZYpFggM Dragonfly drone Dragonfly (https://dragonfly.jhuapl. edu), shown in Fig.18, is a multi-rotor drone that will be used to explore one of Saturn’s moons, Titan. It is planned to be launched in 2028 and will land in 2034. It will use a nuclear power source, a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), like the Curiosity rover on Mars. The nuclear power source is too weak to power the drone in real-time. Therefore, the plan is for the MMRTG to charge a lithium-ion battery, which will power it in flight, up to a distance of 16km with a duration of 30 minutes on each battery charge. When Dragonfly lands, the 134Ah battery will be recharged. Dragonfly will carry various scientific instruments. It is surprisingly large, weighing 450kg, and each of its eight rotors is 1.35m in diameter. Each ‘corner’ of the quadcopter will have two rotors and two motors; the 22 Silicon Chip aircraft is designed to be able to tolerate the loss of one rotor and/or one motor. It will be launched on a SpaceX Falcon Heavy. Dragonfly will navigate using an optical system to recognise visual landmarks as a reference; LiDAR to detect hazards; inertial measurement units (IMUs) to track the drone’s orientation, velocity, and acceleration; plus pressure and wind sensors. It will make autonomous flight and landing decisions. Delivery drones Apart from the Australia Post and Amazon delivery drones mentioned above, we covered the Australian Quickstep Brolga (www.quickstep. com.au) and Jabiru’s JCQ50 “Donkey” cargo drone (https://jabiru.aero/jcq50) in our most recent Airshow article. Domestic ground drones Common domestic ground drones include robotic lawn mowers, robotic vacuums and mops. Energy-harvesting drone Danish researchers at the University of Southern Denmark have developed a self-charging drone that finds and attaches to high voltage power cables using millimetre-wave radar and then inductively charges its onboard batteries. The purpose of these drones is to inspect the same cables they harvest energy from. See Fig.19, siliconchip.au/link/ac66 and the video at https://youtu.be/C-uekD6VTIQ for more details. Fibre-optic guided drones In the Russia-Ukraine war, both sides are actively developing and using drones that are controlled via optical fibres. According to Forbes (siliconchip.au/link/ac67), the Kalashnikov subsidiary company ZALA makes “Product 55”, an unjammable quadcopter. Such a drone was discovered by the Ukrainian military blogger Serhii, who asked what the ‘egg-shaped’ Fig.19: a Danish energy-harvesting power line inspection drone attached to a power line to recharge. Source: https://youtu.be/C-uekD6VTIQ Australia's electronics magazine siliconchip.com.au Fig.17: Aerones’ wind turbine deicing drone. Source: https://wonderfulengineering.com/this-giant-drone-cande-ice-wind-turbines-in-few-minutes contraption was (see Fig.20). It turned out to be a spool of optical fibre for data and control, which held over 10km of cable! This is necessary as both sides field extensive RF and GNSS jamming technology to make the other sides’ use of drones difficult or impossible. There is actually a long history of guiding torpedoes and missiles with wire or optical fibre like this. For example, the Germans experimented with wire guidance for missiles in 1944, and US TOW (tube-launched, optically tracked, wire-guided) antitank missiles are in common use, even today. Fishing drones Drone fishing is a style of fishing where a drone is used to deliver the rig and bait far further than it can be manually cast. Distances of up to 500m are possible. This enables the fisher to get access to deeper water, and perhaps a different species of fish. According to the August 2013 issue Fig.18: a rendering of Dragonfly drone to be used on Saturn’s moon, Titan. Source: https://science.nasa.gov/wp-content/ uploads/2024/04/dragonfly-inflight.jpg of Popular Mechanics, the first person to catch a fish with a drone was Dave Darg, in 2013. Drones also allow visual examination of a proposed fishing area. Some drone fishers hang the line and bait directly from the drone rather than using the drone to haul the line out from a rod and reel. Considerations are the line release mechanism and whether to purchase a water-resistant drone. Various companies sell drones and accessories for fishing; try searching for “fishing drones”. If in Australia, make sure to follow CASA’s rules. Floor-cleaning drones Many commercial operations such as airports, hospitals and supermarkets now have their floors cleaned by drones. An example is the Gausium Phantas; see https://gausium.com Ingenuity helicopter The Ingenuity helicopter (Fig.21) was the first flying vehicle on another planet. It was delivered as part of the Mars 2020 mission, along with the Perseverance ground rover. It was intended to last only five flights, but completed 72 flights before a rotor blade failure. The failure was attributed to a blade strike on the ground due to the inability of the navigation system to cope with an area of featureless terrain. It weighed 1.4kg, had a motor power of 350W and used the Zigbee protocol for communications back to the rover. It was powered by six Sony/Murata US18650VTC4 lithium-ion batteries (which anyone can buy), which were recharged by a solar panel between flights. Its cumulative flight time was just over two hours, and it covered 17km. Due to the extremely low air pressure on Mars, the rotor blades had to spin extremely fast; between 2400 and 2900 RPM despite their large diameter of 1.2m. Surprisingly, this is comparable with small model helicopters on Earth, such as the Blade Fusion 480, which Fig.20 (left): Serhii’s photo of a Russian optic-fibre guided drone found in Ukraine. The optical fibre spool is outlined. Source: https://t.me/serhii_flash/2413 Fig.21 (above): the Ingenuity helicopter drone on Mars. Source: NASA siliconchip.com.au Australia's electronics magazine September 2025  23 has a 1.1m rotor diameter with rotor speeds up to 3000 RPM. General Atomics MQ-1 Predator This US drone became famous for its use in 2001 in Afghanistan, with other appearances in Bosnia, Iraq, Libya, Pakistan, Somalia, Syria, Yemen and Yugoslavia – see Fig.22. It was in production from 1995 to 2018, and could be used for either reconnaissance or attack. It had a cruise speed of 130km/h, a 24 hour endurance, a range of 1250km, a service ceiling of 7600m and an 86kW Rotax four-cylinder air-cooled turbocharged engine. Fig.22: an MQ-1 Predator surveillance/attack drone. Source: https://w.wiki/EDQG Fig.23: an artist’s impression of the Lockheed Martin RQ-170 Sentinel stealth drone. Source: https://w.wiki/EDQH Lockheed Martin RQ-170 Sentinel The RQ-170 (Fig.23) is a stealth reconnaissance drone introduced in 2007. Very little is known about it. It is a flying wing design, somewhat like the Northrop B-2 Spirit; about 20-30 are believed to be in service. It was produced at the famous Skunkworks facilities, where America’s most advanced and secret aerospace projects are developed. It has a wingspan of 11.6m and a length of 4.5m. It is powered by a turbofan engine and is thought to have an endurance of 5-6 hours and a service ceiling of 15,000m (49,000ft). Long-range consumer drones We saw a quadcopter drone available in Australia at https://au.aeroodrones. com/products/aeroo-pro that is stated to be able to deliver a 1kg payload with a flight time up to 45 minutes and a 10km range (note CASA rules, see below, when considering the flight range). Lunar drones We mentioned the Australian-made lunar rover Roo-ver in our article on the 2025 Airshow. Another interesting lunar drone is the Micro Nova “Grace”, a unique hopping drone that uses a rocket engine to move about – see Fig.25. It landed on the moon on the 6th of March 2025, as part of the IM-2 mission. Unfortunately, the lander carrying it fell over and the mission failed. Fig.24: an ornithopter drone. Source: www.hackster.io/news/swifts-provideinspiration-for-lightweight-quiet-and-maneuverable-ornithopter-droned0e2f8a0785c Medical drones Some drones are used to deliver medical supplies or equipment, such as defibrillators. These are designed so non-specialists can use them to Australia's electronics magazine siliconchip.com.au 24 Silicon Chip provide first aid before emergency services arrive. Ornithopter drones Ornithopters are aircraft that fly by flapping wings like birds, bats and insects. Researchers at Nanyang Technological University, the Defence Science and Technology Group, Qingdao University of Technology, the University of South Australia and National Chiao Tung University developed a 26g, 200mm-long ornithopter flapping wing drone (see Fig.24). It is quiet and energy efficient, consuming 40% less energy than the production of equivalent thrust from a propeller. Passenger drones Companies that are developing unpiloted drones to convey passengers as air taxis include: ● Archer Aviation (https://archer. com) ● Boeing (https://wisk.aero) ● CityAirbus (siliconchip.au/link/ ac6a) ● Ehang (www.ehang.com) ● Joby Aviation (www.jobyaviation.­ com) ● Volocopter (www.volocopter. com/en) The VoloCity by Volocopter (Fig.26) may be furthest down the certification pathway, and will commence operations with a pilot soon. It is intended to be pilotless in the future. It has two seats, 18 rotors, nine swappable batteries for a fast turnaround, a maximum takeoff weight of 1000kg, a range of 20km and a cruise speed of 90km/h. It has undergone 2000 test flights to date. Power line inspection Drones can be equipped with UV cameras for inspecting of power lines. Ultraviolet light emanates from a corona discharge, which can indicate a faulty power line. Solar-powered micro drones Researchers at Beihang University have produced a tiny solar powered drone weighing just 4.21g with a diameter of 20cm (see Fig.27). The vehicle is called the CoulombFly and uses an electrostatic motor rather than a traditional AC or DC motor. An electrostatic motor utilises the attraction and siliconchip.com.au repulsion of electric charges rather than magnetic fields. Electrostatic motors require high voltages to operate, so the CoulombFly contains a boost converter to boost less than 100V from the solar cells to over 9kV. This prototype device does not carry a payload. Solar surveillance drone Some drones using solar panels have an especially long flight time. The Zephyr High Altitude Platform Station (HAPS) is a high-persistence solar-powered surveillance drone that has been developed by Airbus subsidiary AALTO (www.aaltohaps.com). It has a 25m wingspan, weighs 75kg, operates above 18km (59,000ft) and runs on batteries that are charged by solar panels during the day. It has a potential mission duration of many months. See our August 2023 article on High-Altitude Aerial Platforms (HAPS; siliconchip.au/Article/15894). Stealthy drones Is it a bird? Is it a plane? Guard from Above (https://guardfromabove.com) have developed the Evolution Eagle UAS for covert surveillance. It blends into the natural environment – that’s a fancy way of saying it looks like a bird ( s e e the photo on the left). Its suggested uses are intelligence, border patrol, public safety, wildlife control and detection of poachers. Swarming drones Swarming drones act in groups and can have either military or civilian applications. A robotic swarm is a group of robots that behave in a swarm-like manner (like a flock of birds or swarm of insects) without centralised control (except perhaps overall direction). The members interact with other members of the swarm and the environment at large. Robotic swarms can exhibit complex behaviour, but are governed by a small set of principles as follows: maintain separation to avoid collisions, coordinate movement to maintain the average heading of neighbours (alignment), and keep the group together as a whole by maintaining a group ‘centre of mass’. To accomplish this, there may be many simple robots of limited ability Australia's electronics magazine Fig.25: the Micro Nova “Grace” lunar hopping drone. Source: www. intuitivemachines.com/micro-nova Fig.26: VoloCity is said to be quieter than a helicopter. Source: www. volocopter.com/en/newsroom/vc-jetsystems Fig.27: the prototype solar-powered CoulombFly drone, which uses an electrostatic motor. Source: Xinhua News – siliconchip.au/link/ac6d September 2025  25 that can communicate with all the others to follow the above principles. These principles apply to swarming animals too. Robotic swarms have some benefits: ● Fault tolerance; the failure of one device does not have a major impact. ● The swarm can be scaled up or down in size as required. ● A swarm is flexible and can be programmed to perform many different tasks. ● The swarm may be more cost-­ effective than a few more expensive drones. Military applications include surveillance and/or attack. Civilian applications include drone shows (see Fig.28). the event the cable is severed. Typical altitudes achieved by tethered drones are 60-120m, or even as high as 200m, depending on regulatory limits. Various hobby or professional drones can be converted to tethered operation with appropriate accessories. Example accessories to convert some DJI drones to tethered operation can be seen at siliconchip.au/ link/ac6b WASP The WASP AE, built by AeroVironment (https://avinc.com), was introduced in 2012 and is used by the US military and Australian Army, among others – see Fig.29. It is in the process of being phased out. It weighs 430g, has an endurance of 45 minutes, a Tethered drones range of 5km, an altitude of up to 300m These are like conventional free-­ (1000ft) and a top speed up to 65km/h. flying drones, but they have a wire connecting them to the ground, over Drones in warfare which power and data can be transMilitary drones need no longer be mitted. This theoretically gives them multi-million-dollar machines used an indefinite flight duration; or at least by well-funded militaries; cheap conuntil the motors or other components sumer or home-made drones can be need maintenance or wear out. easily adapted or constructed for miliThere are obvious limitations on the tary purposes. Hobby drones are plenlength of wire that can be supported tiful, cheap, easy to transport and easy (but also see the section on drones with to set up. The cost benefit is hugely optical fibre data links). Advantages asymmetrical. include relative ease of operation; no As an example, a properly equipped RF emissions (making them stealthy); $300 drone can destroy a $30 million imperviousness to jamming; the abil- asset like a parked aircraft or tank. For ity to perform persistent surveillance; example, see the video about Ukraine’s and the ability to be attached to a mov- use of hobby drones at https://youtu. ing vehicle. be/hWxUt41DlB4 One application is as a self-­ Ukraine has developed its own contained radio relay, like the MPU5 indigenous drone capability and Mobile Ad Hoc Networking (MANET) makes its own drones without reliance radio (www.persistentsystems.com/ on imported components, or at least mpu5). Tethered drones usually have can use generic imported components a backup battery to return home in with no reliance on just one or a few suppliers (https://en.victory-drones. com). Ukraine has also converted conventional aircraft such as small Cessnas into drones. Australia also supplies cardboard ‘flat pack’ drones to Ukraine (www. sypaq.com.au). In Ukraine, inexpensive ground and sea-based drones are also being used for military purposes. Drone rules The rules for usage of recreation and other drones are constantly evolving. Notably, for recreational use, there are height restrictions, highly restricted or prohibited usage in public parks and national parks, a ban on beyond-­ visual-range flying, transmitter power and frequency limits, and many other restrictions. If you plan to fly a drone in Australia, familiarise yourself with the rules and regulations. There is information at www.casa.gov.au/drones and www. casa.gov.au/drones/drone-rules Commercial drone operators need to be licensed. Also, in Australia, any drone used for commercial purposes needs to be registered. There was a proposal for hobbyist drones over 250g to be registered, but this has been delayed. At the time of writing, the CASA website states, “In some cases, you don’t need to register your drone, such as when: … you don’t intend to fly it … you’re only flying for sport or recreation, including at CASA-approved model airfields”. Approved commercial drone delivery services in Australia include the Australian company Swoop Aero, now called Kite Aero (https://kite.aero) and Wing Aviation (https://wing.com). Kite Aero’s drone can deliver a 3kg payload Fig.28: a drone show made using Skybrush. Fig.29: soldiers from the Australian Army with a WASP AE drone on left and a PD-100 Black Hornet drone on right. Source: Sgt. Janine Fabre, Australian Defence 26 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.30 (left): the R&S Ardronis protection package. Depending on the model, it can detect the radio signal from a drone, even before it is launched; can determine the position of the drone; and can disrupt radio signals from the drone. Source: www.rohde-schwarz.com/de/unternehmen/magazine/drohnenabwehr_251858.html Fig.31 (right): the Discovair CUAS acoustic detection sensor. Source: www.sqhead.com/drone-detection over 175km at a speed of 122km/h (see Fig.32). Wing’s drone can deliver a 2.3kg payload over 10km at a speed of 105km/h. Kite Aero is approved to deliver goods in Toowoomba & Goondiwindi (Qld), while Wing Aviation (owned by the parent company of Google) is approved to deliver goods in areas of East Melbourne (Vic), North Canberra (ACT) and Logan (Qld). Defending against drones Defence against hostile drones can be either active or passive. The best approach depends on whether the drone is using radio control and satellite navigation (GPS or other GNSS) or is fully autonomous. An autonomous drone cannot be disabled by disrupting radio signals, as it does not use any. Active approaches for drones under external control and navigation include disruption or jamming of radio signals or navigation signals, causing the drone to crash; or spoofing of GNSS to make the drone think it is somewhere other than the intended place. Another approach is to ‘hack’ into the drone to assume control of it (see D-Fend Solutions; https://dfendsolutions.com). Other defences involve the destruction of the drone using a laser or projectiles. The ‘obsolete’ German Flakpanzer Gepard anti-aircraft system has been found to be especially effective at destroying at ranges of up to 4km. High-power microwave beams or electromagnetic pulses can also be directed at a drone to destroy the device’s electronics, assuming they aren’t shielded. Systems exist that ‘fry’ drone electronics using focused beams of radio-frequency energy. These directed energy weapons (DEWs) or high-powered microwave (HPM) systems typically only work over a range of a few hundred metres, though, so they are best for point defence of critical infrastructure. Physical barriers are another option. Fig.32: the Kite Aero Kite delivery drone. Source: https://kite.aero/technology/kite/ siliconchip.com.au Australia's electronics magazine In some cases, such as jails, netting is reported to be used to prevent drone landings. Devices that fire a net at a drone are also available. An unusual approach is the use of a trained predatory bird to attack drones. Passive approaches include detecting drones using sensors like radar, cameras and microphones. RF analysers can also detect control signals, if present, and reveal the make and model of drone. In some cases, it’s possible to use triangulation to locate the drone with multiple RF receivers, to provide an early warning of an approaching drone. All of these approaches have advantages and disadvantages; it is best to use a combination of them. Commercial anti-drone systems The Rohde & Schwarz Ardronis (see www.rohde-schwarz.com/au/ home_48230.html) is a drone protection package which, depending on the model, can detect the radio signal from a drone and identify the model, even before it is launched – see Fig.30. It can also determine the position of the drone and disrupt radio signals. The Squarehead Technology Discovair CUAS detection sensor (www. sqhead.com) is an acoustic array that uses machine learning to acoustically detect drones – see Fig.31. Multiple sensors can be coupled together to provide more extensive coverage and triangulation of the position. The CPM-WATSON-PLUS is a device to disrupt drone control and GNSS navigation signals (see Fig.9). DIEHL Defence (www.diehl.com/ defence/en) makes the HPEM (HighPower Electro-Magnetics) Skywolf, September 2025  27 which produces high-power electromagnetic pulses directed at a drone to disrupt its electronics – see Fig.33. Dutch firm Guard From Above (https://guardfromabove.com) trains eagles to attack drones – see Fig.34. Fig.35 shows a system from Rafael (https://rafael.co.il) for a kinetic means to destroy drones, especially autonomous ones that don’t use a data or navigation link. Australian company RedTail Technology (www.redtailtech.com.au) has developed a range of directed-­energy laser weapons to combat unfriendly drones, especially autonomous types. Fig.33: the Diehl Defence HPEM Skywolf produces high-power electromagnetic pulses to disrupt drone electronics. Source: www.diehl.com/defence/en/ products/reconnaissance-and-protection Drone shows & sports Skybrush (https://skybrush.io) is open-source drone show software. It can be used to create spectacular shows with groups of swarming drones, as previously shown in Fig.28. Drone racing is a sport governed internationally by the Fédération Aéronautique Internationale. The drones used are typically small, high-powered quadcopter-style aircraft with an FPV (first person view) camera. This allows the operator to view the live video feed on a headmounted display. The first FPV drone races were held in Australia and New Zealand in 2014, but drone racing without FPV equipment was first held in Germany in 2011 (siliconchip.au/link/ac68). Normally, humans race each other, but you can see a human-vs-AI race at siliconchip. au/link/ac6e The AI drone taught itself a faster way through the course than the human. For more details, see www. droneracingaustralia.com.au and www.droneracing.nz Future concerns Fig.34: a trained eagle attacks a drone. Existing and future airspace management concerns include how to integrate drone operations, such as deliveries, with existing air traffic control. It’s also necessary to protect against the use of drones by terrorist groups, requiring the development and use of counter-drone technology. Hobbyists and experimenters should also not be unnecessarily restricted by such considerations. Accidents During the recent Los Angeles wildfires, one plane was hit by a drone. Fortunately, the damage was not severe and no-one was hurt. This is why strict rules against flying hobby drones near airports and in controlled airspace need to be observed. Further reading/viewing Fig.35: Raphael Typhoon 30 for defence against drones, at a test site. The projectile is fired from the barrel on the left; the tower hosts the sensors. 28 Silicon Chip Australia's electronics magazine ● More information about the US Army Air Force’s Aphrodite and the US Navy’s Anvil programs is at siliconchip.au/link/ac6c ● How Ukraine’s grenade-­dropping drones changed war (Daily Mail): https://youtu.be/qtF2dOic0Y4 ● How Ukraine tries to change the battlefield with ground drones: https:// SC youtu.be/NXqt9dRfqQM siliconchip.com.au