Meet the TDR-1: one of the world's first ever deployed combat UAVs

During WW2, the U.S. actually developed and used an early UAV.
Christopher McFadden
Interstate TDR-1 at the National Museum of Naval Aviation, Florida. Greg Goebel/Wikimedia Commons

The use of drones for combat is nothing new, but early examples would pale in comparison to the sophistication of modern ones. However, there were some shining lights in the history of this technology that would reveal the potential for this technology for future generations. 

One such craft was the Interstate TDR-1. Developed by the United States towards the end of the Second World War, this interesting craft is a fascinating one to explore briefly. 

What was the Interstate TDR-1?

The Interstate TDR was an early uncrewed combat aerial vehicle built by the Interstate Aircraft and Engineering Corporation for use by the United States Navy during WWII. Dubbed as an "attack drone" at the time, around 2000 aircraft were ordered.

Each TDR-1 had a very simple design, with a steel-tube frame built by the Schwinn Bicycle Company and a molded wooden skin made by the Wurlitzer Musical Instrument Company. Two non-military Lycoming flat-head 6s provided the power with 230 horsepower each. The drone was built using few strategic resources so as not to obstruct the manufacture of higher-priority planes.

The TDR-1 was capable of carrying bombs or torpedoes, but only about 200 were ever completed, and even fewer were used in combat. The TDR-1 saw some action against the Japanese in the Pacific Theater, with mixed success.

early UAV TDR-1
Interstate TDR-1 assault drone in flight, circa 1944. Source: U.S. Navy/Wikimedia Commons

Throughout their use, around 50 drones were launched over the course of two months, with 31 hits on anti-aircraft positions, bridges, airfields, and grounded ships recorded. The drone would be released by a ground control crew and then handed over to the TBM pilot already flying above the field, guided by a modified TBM-1C Avenger torpedo bomber. The TBM pilot would be connected to the drone and pass control to the controller in the rear cockpit. The controller would guide the drone to its target using TDR's nose-mounted camera signals.

Because of ongoing developmental challenges with the aircraft and the success of operations utilizing more conventional weaponry, the attack drone program was canceled in October 1944.

Vital statistics of the Interstate TDR-1

Several variants of the Interstate TDR program were built like many other aircraft. However, the only production model was the TDR-1. For this reason, we will provide the statistics for that particular model. 

Entered service: July 1944

Retired: November 1944

Crew: 0–1 (optional pilot)

Wingspan: 48 ft (15 m)

Gross weight: 5,900 lb (2,676 kg)

Powerplant: 2 × Lycoming O-435-2 opposed-piston engines, 220 hp (160 kW) each

Cruise speed: 140 mph (230 kph)

Range: 425 mi (684 km)

Armament: One 2,000-pound (907 kg) bomb or aerial torpedo

What is the history of the TDR-1?

In 1942, the U.S. embarked on a mission to develop low-cost, easy-to-use drones in order to help save its highly valuable and irreplaceable human crews. With the war's conclusion seemingly far off, such a far-fetched and experimental technology was pushed to the bottom of the military's priority list. 

pilot variant TDR-1
Interstate XBQ-4 assault drone prototype (a U.S. Army variant). Source: U.S. Army Air Force/Wikimedia Commons

However, enough U.S. military officials did foresee how such a technology would be beneficial if successfully developed, especially in the Pacific Theatre against the Empire of Japan. 

To this end, Interstate Aircraft was tasked with developing the drones, which were mostly made of wood stretched over a metal frame. Each TDR possessed two engines and a detachable cockpit, giving them the option to be piloted by humans if and when required. However, from the outset, their primary function was to serve as an uncrewed drone. 

Each drone was controlled remotely by a master Grumman TBM-1C Avenger torpedo bomber that would follow the drone and control it using technologies that were very sophisticated for the time.

What technology was added to the TDR 1 that made it different from all previous UAS?

The TDR-1's secret was a new type of top-secret technology called an RCA television. Images from a camera installed in the drone's nose were sent to a five-inch screen in the Avenger's rear cockpit. The picture quality was admittedly poor, but it was more than sufficient for the pilot to see large targets like enemy ships.

Once developed and built, the first batches of them were supplied to three Special Task Air Groups (STAGs) specially established to operate them. However, problems with these early drones quickly arose. For example, when they landed in the Solomon Islands, it was rapidly discovered that the tropical climate and lack of sophisticated infrastructure proved to be a nightmare for electrical equipment on the drones. 

However, these early problems were overcome, and the TDRs were put into action soon after. 

On June 30, 1944, they were put to the test against a Japanese cargo ship, the Yumasuki Maru, that had been beached near Guadalcanal in the Solomon Islands. A total of four drones were used, three of which collided with the ship. Two of them were successfully detonated.

tdr-1 silouette
A three-view drawing of the Interstate TDR-1 assault drone. Source: Greg Goebel/Wikimedia Commons

Another test also proved promising when four drones were launched to Bougainville in September of the same year on a mission to destroy another beached Japanese vessel. That ship, unlike the first, was made a little tougher and had been provided with some Japanese defenses, like an anti-air battery. Each drone was armed with a 2,000-pound (907 kg) bomb and had to travel a total of 55 miles (88.5 km) to reach the objective.

This test was a little more mixed, with one drone being lost along the route, another came close to hitting the ship but didn't explode, and a third hit the ship but didn't detonate. The final aircraft slammed into the ship, successfully detonating its enormous explosive payload.

Further tests followed, with more flights performed over the next month, some of which were sent to targets more than 100 miles away from their base. 

The drones were largely successful in attacking numerous military targets, but they were widely despised by U.S. Navy leadership, and by November 1944, the project was duly canceled. This was most likely due to politics, distrust, and lack of knowledge of such a new and radical technology rather than any severe design flaws. There had been no American lives lost as a result of their use.

Following the war, some TDR-1s were converted for operation as private sports planes.

And that, UAV enthusiasts, is your lot for today.

The Interstate TDR-1 was a revolutionary aircraft for its day, but like most cutting-edge tech throughout history, it likely came a little too early to be fully appreciated. It would, in part, show the world how valuable uncrewed aircraft could be in combat, ultimately leading to the development of modern combat UAVs we are all too familiar with today. 

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