The use of drones for military purposes has a long history. The concept dates to World War I, and pilotless explosive-laden aircraft were used extensively by Germany in World War II. Remotely controlled precision attack drones were developed by the United States near the end of World War II, but despite predictions in the many decades after that war, crewed combat aircraft continued to rule the combat zone. The experience in Ukraine this year, however, suggests that there may be a radical change in that military doctrine. Swarms of accurate, low-cost combat and reconnaissance drones may now make it possible for a warring nation to overwhelm even sophisticated air defence systems, including piloted fighter aircraft. This shift in the definition of air superiority would be the first change in the doctrine of aerial warfare in a century. And cost engineering is key.
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Like the early attempts at weapon-carrying drones, the primary problem was guidance. Sperry was a pioneer in gyroscopes, which helped with stability, and the invention of the radio altimeter let early autopilots maintain a steady altitude. But heading, azimuth, was a much more difficult problem to solve.
American developments like the Interstate TDR–1 got around this problem by using a television camera installed in the drone, and radio control from a drone operator in a trailing aircraft. The system was crude, but it worked, although only a handful were used in combat.
A practical solution came in the 1950s with inertial guidance systems. Accelerometers measuring forces in pitch, roll and yaw could send information to a relatively simple computer comparator, which could determine error from a preprogrammed path and send corrective signals to the autopilot.
In the 1950s, this could produce an accuracy, expressed as circular error probable, of perhaps half a mile. That meant that the drones needed to carry nuclear weapons, which were themselves heavy at that time. That required a large aircraft, which was necessary anyway to house the early guidance systems plus fuel. This Matador is an example.
There were experiments in the 1960s and 1970s, notably from the Teledyne Ryan Corporation, but the last 20 years have seen an explosion in growth of the use of drones for military purposes. A major reason is the considerable improvement in navigation and the use of satellite-based control, as well as improved standoff weapons that are themselves smart enough to not require pinpoint positioning accuracy from the carrying drone. These drones are still vulnerable, just as crewed aircraft are.
The current conflict in Ukraine, however, is demonstrating a new game-changing tactical use of drones: drone swarms. The concept is simple. Use small, very low-cost preprogrammed drones, then send them in dozens or even hundreds to saturate enemy air defenses. Not only are great numbers difficult to suppress, but the use of a quarter million-dollar surface-to-air missile to down a $25,000 drone is itself militarily useful for the attacker.
But how have engineers managed to reduce the cost to the point where drone swarms are affordable? The answer is the combination of low-cost computational power, GPS and smaller, lighter stabilization systems and inertial navigation. GPS is a major cost saver. With accuracy and repeatability in civilian GPS now approaching the military levels of a decade ago, commercially available technology can be used to create effective small combat drones.
GPS signals can be jammed, and satellite networks can even be switched off to prevent this use, but there are now multiple independent satellite networks that use this technology, and defending nations need the capability for military purposes as well.
Airframes are simplified, with extensive use of plastics, and often simple piston engine propulsion with fixed pitch propellers. They’re slow, but they’re cheap and there can be a lot of them.
Recent news reports that Russian forces in Ukraine are using Iranian-made Shahed-136 small drones that operate with this tactical philosophy. Launched in groups of 10 to 15, Ukrainian forces have made claims that they are capable of shooting down approximately half of the incoming drones, and those that get through have caused extensive damage.
Can conventional fighter aircraft deal with this threat? Probably not, for several reasons.
Modern military combat aircraft designed for air defence are generally fast jets, and are not designed to operate low and slow, in the world of small drones. They are designed to carry weapons capable of knocking down similar large jet aircraft, meaning expensive missiles and cannons, both of which would have difficulty engaging a very small, low radar signature, slow moving target at treetop height.
The potential for altering military planning is significant. It’s possible that in the battlefield of the future, a warring nation can lose control of the airspace over the battlefield, yet still exploit that airspace to launch damaging attacks through drone swarms launched from very mobile and simple vehicle-mounted launchers.
Possible countermeasures have been developed, notably Israel’s Iron Dome system, but they are expensive and it would require a large number of those systems to cover all potential targets. Airborne or ground-based lasers may be an answer, which will make the economics of drone engineering the most important consideration.
Design for low cost is now as important as design for speed or accuracy, or even payload. The conflict in Ukraine suggests that wars of the future may not be fought with a few, high-tech aircraft costing dozens of millions of dollars apiece, but rather with thousands of low-cost, mass-produced and tiny drones, swarming like bees.
Military strategists and the engineering community are watching the Ukrainian conflict with keen interest. The days of the combat pilot just might be numbered.