The jet propelled RQ-4 Global Hawk UAV was the first large jet powered UAV to enter service and did so over Afghanistan three years after its first flight in 1998 while still technically under development. What was remarkable about the RQ-4 was that it could fly across oceans quickly because its cruise speed was 570 kilometers an hour. Weighing 14.6 tons, it could carry a lot of sensors (up to 1.3 tons worth) but most of the eight-ton carrying capacity is fuel, giving it a max range of 22,800 kilometers and total air time of nearly 40 hours for long distance fights and closer to 30 hours for operational (carrying sensors) flights. Five of the first 42 put into service crashed. The U.S. Air Force plans to retire its remaining RQ-4Bs by 2027. Despite the air force plans, by now (2022) nearly a hundred RQ-4s have been built or are on order.
RQ-4 is strictly a combat support aircraft and was never equipped with weapons. The RQ-4 design was flexible and it greatly evolved. That means any time there was a new need for large, long range unmanned aircraft, Global Hawk was usually the fastest and cheapest way to get what was needed. A current need is for a long range, relatively fast unmanned aircraft to monitor a test range for hypersonic missile testing and thereby avoid giving advance notice to hostile powers (China and Russia) to get their own monitoring ships out into the remote Pacific areas where the tests are held. With the twenty “Range Hawk” UAVs at work, short notice is needed to warn innocent ships operating near the missile impact zone. There’s not enough time to get monitoring ships out there and Russia and China have nothing like the Global Hawk.
A more specialized, if temporary use of Global Hawk was in Afghanistan, where three Global Hawks were equipped with BACN (Battlefield Airborne Communications Node) tech and used to provide continuous long-range communications for army units operating in Afghanistan, among so many hills and mountains that often block radio signals. The air force put BACN equipment in aerial refueling aircraft as well as smaller manned surveillance aircraft. When most American troops left Afghanistan by 2014, there were fewer refueling aircraft over Afghanistan and the larger (45 ton) manned E-11A twin-jet business jet aircraft were used to carry BACN gear. Soon it was realized the Global Hawk could also do this at less cost and stay in the air longer. The manned E-11A was limited by crew fatigue while the RQ-4B had a ground-based monitoring crew of three personnel which, because of a satellite data link, could be anywhere in the world, but usually at an air force base in the United States where most large UAV operations are monitored. Ground crews for these UAVs were based near where they were operating.
The ground crews would refuel and maintain the aircraft. Early model RQ-4s had a lot of problems and ground crews were often larger than usual to handle problems found before or after flights. The first version was the RQ-4A and only sixteen were built. Many of the problems were solved with the slightly larger and structurally stronger RQ-4B. About half the hundred RQ-4s built or on order were the 4B version. Most of the rest are the slightly heavier RQ-4C naval patrol version, also known as Triton.
There were also eight RQ-4D Phoenix ground surveillance models ordered by NATO and five RQ-4E Euro Hawk models built for Germany. All but one RQ-4Es were canceled because collision avoidance systems for UAVs could not be developed quickly enough. Such systems have since been developed and accepted into service, mainly for armed UAVs but also for the RQ-4Ds. Germany no longer sees a need for the larger RQ-4D.
Other foreign customers, such as South Korea and Japan, still saw a need and ordered RQ-4Bs for land and naval surveillance. NASA and DARPA (Defense Advanced Research Projects Agency) have used several RQ-4Bs to support research efforts in various areas requiring a high-altitude aircraft. RQ-4B has a max altitude of 18,000 meters (60,000 feet).
Since Global Hawk entered service the navy and air force have developed smaller and stealthier jet powered UAVs like the RQ-170 and RQ-180 as well as the carrier-based X-47B attack aircraft and the MQ-25A aerial tanker UAV that will refuel manned attack aircraft as well as perform recon and surveillance. The X-47B and a similar air force land- based fighter used the same stealthy design seen with the B-2 bomber, while MQ-25A has a conventional straight wing design and is to enter service by 2025.
Stealthy design attack UAVs are planned for use as “loyal wingman” UAVs. These look like small F-35s but are not as stealthy, are subsonic (about 1,000 kilometers an hour), weigh a few tons and carry a 250 kg (550 pound) payload of smaller short-range decoys or a smart bomb. Loyal Wingman UAV are meant to be cheap and expendable when used with F-22s or F-35s. The goal for the Loyal Wingman UAV is to weigh a few tons, cost a few million dollars each and be only sturdy enough to last five or six missions. That’s a difficult design goal to achieve and whoever can achieve it will have a large contract for a UAV that is used somewhat like ammunition that flies near the aircraft using it.
Meanwhile older UAV designs like Global Hawk prove themselves flexible and sturdy enough to adapt to many new uses, many of which didn’t even exist when Global Hawk entered service while still in development because it was adaptable and as a UAV, more expendable than a manned aircraft. Only one Global Hawk has been lost to enemy fire. That was in 2019 when an RQ-4A belonging to the U.S. Navy was shot down near the Iranian border with a missile in 2019. The UAV was an early model RQ-4A used by the Navy to develop its MQ-4C Triton maritime surveillance UAV. The navy RQ-4A was apparently testing some surveillance equipment when the Iranians fired at it.
The MQ-4C is meant to operate far out to sea and not in a combat zone. Many nations are interested in buying MQ-4Bs for coastal and off-shore patrol to detect smugglers and poachers. The RQ-4B is seen as a cheaper alternative to manned aircraft or ships. Some countries use it for inland border patrol. Demand for these naval and land surveillance RQ-4Bs is what is keeping the Global Hawk in production.
New reconnaissance UAVs have been less successful. The Navy’s MQ-25A may fill a similar role for carrier-based UAVs. Meanwhile the stealthy 5-ton RQ-170 and 15-ton RQ-180 were built in smaller numbers. Fewer than 30 RQ-170s were built and it has less endurance (about six hours) than Global Hawk but is less detectable and useful for secret missions. RQ-170 entered service in 2007 and one operated by the CIA and flying along the Afghan border crashed inside Iran in 2011. The Iranians say they hacked its data-link but that has never been proven. Iran reverse engineered the downed RQ-170 as the Shahed 171. This UAV first flew in 2014 and was little seen after that. One was sent to Lebanon where the Israelis detected it crossing the border into Israel and shot it down. It was made of fiberglass and could be used for surveillance or, carrying explosives, as a cruise missile. Iran appeared to lose interest in Shahed 171 after the loss to Israel. The RQ-180 has also served as a secret surveillance UAV and entered service in 2015.
Its missions have been kept secret although it was apparently intended to serve duties earlier performed by the manned SR-71. This was an expensive manned aircraft that entered service in 1966. Only 32 were built and they were used by the air force and NASA until 1999. It was very fast and could fly very high but was expensive to maintain and operate. It was retired because the older U-2 and more effective space satellites could do the same work.
The SR-71 had impressive capabilities. It was a 78-ton twin-engine jet with a top speed of 3,500 kilometers an hour and max altitude of 26,000 meters (85,000 feet). That was the edge of space, about as high as an air-breathing jet could go. It had a crew of two and endurance of a few hours. Twelve of the 32 SR-71s were lost due to operational accidents but only one crew member died. The RQ-180 is smaller, slower and has more endurance than the SR-71 and is cheaper to operate. RQ-180 is being used for classified missions and little of that activity has been made public. None have apparently been lost and apparently not many (perhaps six) have been built so far.