On December 14, the US Air Force Research Laboratory released a snippet of information about a highly secretive programme called Mayhem, or officially, the hypersonic multi-mission ISR and strike programme.
More than this is not publicly known. One such hypersonic system could be the SR-72 Darkstar, a drone that is billed as being capable of flying faster than Mach 5 – five times the speed of sound – the minimum speed for something to be classed as hypersonic.
The SR-72 was previewed, albeit in CGI form, in a US air force video in November (see the end of the video below at 2.30 for a glimpse of the concept).
This is now a trend: drones are becoming better armed, bigger and faster, and capable of extremely long-range missions.
This has become explicitly clear through 2021: in May, Aevum outlined the role for its huge Ravn X drone that is intended to launch satellites into space, before launching them into low-Earth orbit, a critical operation for the US Space Force.
Drones are also increasingly being used in long-range naval operations. In early December, an MQ-25 Stingray drone arrived for testing on the US aircraft carrier USS George H W Bush.
It was a landmark event: the drone has successfully refuelled US Navy aircraft, including the F-35 and could play a vital role in extending the range of aircraft over vast distances.
The next generation of unmanned aerial vehicles will be distinct from slower systems currently used for counter-terrorism missions, reconnaissance and in some cases, suicide drone attacks – so-called loitering munitions.
Earlier this month, US Air Force Secretary Frank Kendall said that the US was seeking funds for two classified drone programmes in 2023.
The drones will operate alongside the F-35 stealth fighter, as well as a new, highly classified fighter aircraft and the B-21 stealth bomber, a forthcoming, long range aircraft that will cruise at high subsonic speed.
The new drones will need to be "unique and highly capable unmanned aerial vehicles", Mr Kendall said.
A counter-terrorism platform
Today, unmanned aircraft can fly at near supersonic speeds, making the Predator – a 1,000 kilogram aircraft with a top speed of 220 kilometres per hour, seem like a biplane in comparison.
They are increasingly being flown using autonomous systems and paired with manned aircraft to multiply the force of a combat mission.
These “Loyal Wingman” drones, pioneered by Boeing and specialist US drone company Kratos, are now being developed by China, the UK, Russia, Turkey and Japan.
They are smaller than manned fighter jets, but that could change soon.
Northrop Grumman’s Model 437, announced in September, is based on their manned stealth fighter, the secretive Model 401, while Japan’s Ministry of Defence has hinted that high performance unmanned fighters could follow its current Loyal Wingman projects.
The huge drone has a take-off weight of almost 25,000kg, part of a new class of very large UAVS.
In March, US Vice Admiral James Kilby said that in future drones could comprise almost half of all aircraft on a given US aircraft carrier.
Other drones such as the stealthy X-47B – the first experimental combat drone to land on an aircraft carrier and the first drone to successfully complete air-to-air refuelling with a tanker, are clearly influencing foreign designs.
These drones are large – the X-47B has an 18.9 metre wingspan, six metres wider than the F/A-18 Hornet , the US Navy’s main carrier aircraft. Its take-off weight is almost 20 times that of the Predator.
Furthermore, they have a high endurance – the X-47B can fly for almost 4,000km on a tank of fuel.
Their increased capability – and a growing range of roles envisioned by designers, could bring us to a future where the majority of aerial combat missions are unmanned.
It is still not clear if the trend to larger and faster UCAVs will continue – US research agency Darpa’s LongShot programme envisions small drones that can be launched from planes that fire long-range missiles.
That said, here are some of the biggest, fastest unmanned aircraft in existence or scheduled for testing next year:
The SR-72 “Son of Blackbird”, is inspired by the manned Blackbird SR-71 spy plane that smashed speed records in September 1974, flying from New York to London in one hour 54 minutes, cruising at an average speed of 2,900kph.
The Blackbird eventually left service because of its extremely high operational costs, improved satellite reconnaissance and the development of a high altitude Russian jet, the MiG-31, that posed a risk to the aircraft, even at its high operational ceiling of 85,000 feet, more than twice the cruising altitude of an airliner.
The SR-72 could theoretically evade current fighter jets, zipping in and out of enemy airspace at Mach 6, or six times the speed of sound.
More importantly, new anti-satellite weapons being developed could give extremely fast spy planes like the SR-72 a critical role.
Developers Lockheed Martin hope the aircraft can be test flown next year.
Sukhoi S-70 Okhotnik-B
On December 14, a new version of Russia's stealth SU-70 drone was displayed by the Novosibirsk Aircraft Production Association.
First test flown on August 7, 2019, the Sukhoi S-70 Okhotnik-B is a multi-role aircraft designed for reconnaissance and combat with low observable, or stealthy, design features – in other words, it has a small radar signature, in theory making it hard to shoot down.
According to Russian news agency Tass, up to four S-70s could be controlled by a two-seater variant of the Su-57 fighter jet. Russia hopes the drone will enter service in 2024.
Photos of the drone near the Su-57 show that it is indeed a large aircraft, almost the size of the multi-role fighter jet.
Very little is known about the enormous RQ-180, but it s thought to have a wingspan of about 40 metres, almost as wide as the Second World War B-29 bomber.
That is just an estimate based on plane spotter sightings near the US Area 51 Air Force facility and more recently, in Philippine airspace.
The secretive stealth aircraft is designed to fly at high altitude over long distances and was recently shown, albeit briefly, in a video by the US Air Force's Profession of Arms Centre of Excellence.
The Global Hawk was one of the first large-scale, high-altitude long-endurance drones, entering service in 2001 with a flight endurance of up to 30 hours.
With a 40-metre wingspan, it is almost nine metres wider than a Second World War B-17 bomber. Its synthetic aperture radar can map terrain in 3D over vast areas, helped by its operational ceiling altitude of 65,000ft-plus, or more than 19km.
While high flying, the aircraft is lumbering and made headlines in 2018 when Iran shot down an RQ-4 over the Strait of Hormuz – probably with a Russian-made SA-3 missile which can reach the upper limit of the RQ-4’s altitude.
With a V-shape “flying wing” stealth design and intended for reconnaissance and air combat, the Hongdu first flew in 2013 and has a wingspan of 14 metres. A scale model of the aircraft was displayed at the China 2021 air show, featuring an open bomb bay and four munitions which, according to the state affiliated Global Times, resembled “guided precision air-to-ground glide bombs”.
Recently displayed at Dubai Air Show 2021, Russia’s new SU-75 Checkmate stealth fighter jet can carry 7,400kg of weapons, including five air-to-air missiles in an internal weapons bay, flying at speeds of up to Mach 2. That is impressive for a stealth aircraft – weapons are normally stored internally to preserve stealth characteristics, limiting munitions load.
Sukhoi says an unmanned variant is in the offing, potentially reducing the comparative cost of the stealth system even further.
Test flown with armaments for the first time in June, the massive Altius has a 28.5 metre wingspan. The heavy, twin engine propeller driven drone is claimed to have a 48-hour endurance window, according to developers Kazan Simonov Design Bureau, in addition to a range of 3,500km.
As well as having a reconnaissance role, Russia hopes the plane – which first flew in 2016 – will also carry an array of missiles and bombs into battle.