Lost amid a large 8,000 box series from the long disestablished Bureau of Aeronautics (Record Group 72 in National Archives-speak) in a classified stack at the National Archives in College Park lies a 500-page document whose ominous mushroom cloud cover artwork supported its Confidential classification marking. The light blue/green cover simply bore the words “Assault” and the official seal and title of the Office of Naval Research in Washington DC. Once inside the cover, though, a reader will find the makings of an extraordinary tale.
In a story that has been retold many times, the U.S. Marine Corps viewed the results of the first nuclear weapons effects test, the July 1946 Operation CROSSROADS, with significant concern. Despite the Navy and Marine Corps’ proven formula of amphibious warfare success during the lately concluded Second World War, the outcome of the two nuclear weapons detonations in Bikini Atoll was that large groupings of amphibious shipping and their support warships that made victory possible in almost every theater of World War II were now frighteningly vulnerable to the new weapon of mass destruction.
The solution was dispersal, spreading shipping, landing craft, support warships, and Marines out along the target coast to defeat the nuclear threat. However, that solution simply caused another problem: how to bring enough Marines to the decisive point to defeat the defenders. If the landing forces were dispersed, a well-disposed defender could annihilate the smaller Marine formations in detail before they could join inland to overwhelm the defenders or capture key terrain.
There were technological solutions seemingly close at hand—the helicopter and large flying boats. A special board appointed by the 20th Commandant of the Marine Corps, General Lemuel C. Shepherd Jr., looked at the dispersal problem in some detail. The board members, Colonels Merrill Twining and Edward Dyer and Lieutenant Colonel Samuel Shaw examined various means of keeping amphibious assault forces out of atomic danger while quickly concentrating Marines to defeat a defending force.
General Shepherd’s special board surveyed this scene and recognized that current helicopter technology was not going to put a lot of Marines on the beach very quickly, and that the flying boat was a longer term option, if it ever was an option at all. They spoke with the helicopter manufacturers, especially with Igor Sikorsky and one Frank Piaseki of Philadelphia, Pennsylvania. Piaseki had some original ideas about large helicopters, and, together, the two men convinced the board members that a helicopter capable of a 5,000 pound payload was possible.
While the Navy’s Bureau of Aeronautics (BuAer) had the mandate to develop the large flying boat program, the Marines took upon themselves the task of sponsoring a large helicopter program through the same Bureau, as BuAer had the authority for the procurement of aircraft for the Marine Corps. As it turned out, the 5,000 pound payload helicopter was a bit ambitious for the technologies of the late 1940’s, so an interim capability of 3,500 pounds was sought for the Marine’s new assault helicopter. A decade later the Marines ended up with the versatile Sikorsky HUS/UH-34 series as the 3,500 pound payload helicopter and the monstrous Sikorsky HR2S/CH-37 as the 5,000 pound payload helicopter. Both aircraft utilized piston engines, so their performances at higher weights and temperatures was always problematic. It was not until the mid-1960’s that designers included compact gas turboshaft engines in their designs, finally manufacturing helicopters capable of consistently meeting Marine requirements first established in 1946.
It must have been sometime in 1947 that the Amphibious Branch of the Navy’s Office of Naval Research (ONR) became involved with the evolution of the new vertical envelopment doctrine that sought a way to overcome the limited payload capabilities of contemporary helicopters. Captured under the title: “A Study of a Third Dimensional Assault Techniques for Amphibious Operations”, this sizeable work was the product of contract N7-ONR-296 Task Order 1 awarded to the Radioplane Company. The final bound report classified CONFIDENTIAL is dated 1 April 1948; however, a perusal of the pages show sections of the report that were completed as early as July 1947.
The Radioplane Company was an unusual choice for this particular contract. Founded in 1934 by British actor Reginald Denny (Anna Karenina, Mr. Blandings Builds His Dream House), the company’s experience up through 1947 was based upon the manufacture of expendable target drone aircraft that were essentially larger versions of hobbyists’ radio-controlled models the company sold during the prewar years. Radioplane’s OQ-2/3 series of target drones were built in the company’s Van Nuys, California facility by the thousands, giving nascent antiaircraft gunners from all of the Armed Services an opportunity to learn key gunnery skills. Outside of the building of target drones, Radioplane’s major claim to fame in being the employer of a young Norma Jeane Dougherty, later known as Marilyn Monroe, who was discovered by an Army Air Forces photographer working in the Radioplane factory. Radioplane had never designed or built a manned aircraft prior to their receipt of the ONR contract.
The ONR study, given the short title of “Project ASSAULT”, sought to overcome the problems of projecting a ground force into an amphibious objective defended by atomic weapons. Radioplane proposed the use of radio-controlled aircraft, each carrying a single Marine above the radioactive contamination on the ground and into the objective. The study broke down into eight sections that dealt with the definition of the mission, flight paths, power plants, aerodynamics, stabilization and control, launching, deceleration and landing, and, finally, structures. There was also a final report that discussed the ASSAULT vehicle.
The study began with a foreword written by CAPT W. H. Leahy, the Assistant Chief for Research for ONR. Leahy was the son of Fleet Admiral William D. Leahy, then Chief of Staff to the Commander in Chief, President Harry Truman. The foreword contained the six performance objectives that established the preliminary requirements for the study:
- A vehicle payload of 300 pounds
- Flight controlled by remote or forward position or ground remote station
- Adaptable for rapid launch from a ship or limited launching area
- Capable of rapid deceleration for safe landings in areas with natural obstacles such as forests and irregular terrain
- Flight range of 25 mile radius
- Vehicle can be used for logistics support with a payload of 300 pounds
The study then continues with five detailed sections that discussed the amphibious warfare mission, possible ASSAULT craft flight paths, possible power plants for ASSAULT craft, the aerodynamics of various ASSAULT craft, and, finally, stabilization and control of the proposed ASSAULT aircraft. The bottom line for the proposed ASSAULT vehicles became:
It can then be seen that the ideal situation would be one in which the Assault trooper could step into a vehicle which would then be launched to deliver him automatically to his destination.
The final report offered a range of technical concepts, each concept differing by its designed cruising speed, which ranged from 250 mph, to 400 mph, and finally to 550 mph. A fourth concept embraced the use of an assault pod to be launched by a parent aircraft. All of the proposed ASSAULT vehicles shared the characteristics of being easily controlled in flight, tough enough to make a rough landing while preserving the occupant, and cheap enough to be built in some quantity.
The proposed 250 mph aircraft resembled an up-scaled target drone, sized large enough to carry one Marine safely from ship to objective. The recommended power plant was air-cooled Continental E 185-1 opposed 6-cylinder engine of 250 hp, most famously used in the Beechcraft Bonanza general aviation aircraft and deemed capable of moving the proposed ASSAULT vehicle at 250 mph. The landing gear was two skids attached to the fuselage ahead of the straight 32-foot wings. The aircraft was to be catapult-launched, and, when reaching its objective, would have been slowed by a parachute-like controllable sleeve and an air-launched arresting gear—essentially a harpoon driven into the ground and attached to the airframe by a nylon rope.
The proposed 400 mph aircraft was a bit more daring in design, being based upon a turbojet-powered airframe. The fuselage was of a high mid-wing type with a pod-and-boom layout for the twin endplate tail. The author identified the Flader Model XJ-55-FF-1 engine with 700 pounds of thrust as the power plant. The XJ-55 was proposed as the propulsion for a postwar drone aircraft called the XQ-2, so it seemed to be a natural fit in a small airframe designed by a company with radio-controlled aircraft experience. Landing a faster vehicle within tight space constraints required even more ingenuity than the 250 mph proposal, so wings contained split flaps and the fuselage sported skids underneath, a 28 foot airfoil parachute, and, finally, ten 2,000 pound thrust retro-rockets. After the flaps slowed the aircraft to an appropriate speed, the parachute would deploy, suspending the fuselage in a horizontal attitude below the canopy. A proximity device would trigger the retrorockets, thus ensuring a relatively soft landing for the embarked Marine.
Radioplane continued their report with a description of a 550 mph aircraft, showing what design compromises were necessary to produce a faster vehicle. To gain the desired speed, this third ASSAULT design depended upon rocket power; however, the specific type of rocket engine was not mentioned, unlike the engines on the 250 mph and 400 mph proposals. The final report of the study only mentioned the fact that the two engines would be bi-liquid propellant, one engine to be of 1,150 lbs thrust and the second to be of 500 lbs thrust, and would be similar to the type manufactured by Reaction Motors, Inc or of equivalent design and performance. For landing this high performance vehicle, split flaps on the narrow, tapered wings would again be needed. As in the 400 mph proposal vehicle, the aircraft would deploy a tail-mounted parachute. This time the aircraft would be lowered nose-first to the ground rather than using the complicated parachute suspension system on the 400 mph aircraft that kept the fuselage horizontal. The 550 mph ASSAULT vehicle would then use twelve retro-rockets fitted in the tail to slow the aircraft further. A hydraulically-buffered nose probe would take the remaining landing shock, the probe sticking into the ground to keep the airframe upright after landing.
The final ASSAULT vehicle was a simple pod with no wings. However, deceleration and landing processes would be similar to the aircraft-configured ASSAULT vehicles—a parachute to initially slow down the vehicle, a retro-rocket to slow the pod completely, an air-launched arresting gear system, landing leg skids to take the impact of landing, and, finally, a fixed wooden skid to take the punishment of an emergency landing. The report included sketches of the pod as well as its carrier aircraft, in this case a Grumman F7F-1. The drawing suggests that the aircraft carry two pods, one on pylons under each wing. The study’s report made it clear that the preferred aircraft type for an ASSAULT pod mission was a fighter aircraft. The ASSAULT pod required none of the radio controls necessary for the other vehicles mentioned in the report, and it would require the services of an escort carrier (CVE) to base the fighter aircraft, the pods, and the Marines necessary to conduct the ASSAULT pod operation.
While there were many unsolved problems with Radioplane’s concept for conducting vertical envelopment operations in the first decade after World War II, ideas generated by such unconventional thinking foreshadowed the great changes in aerospace and defense technology that took place over the next fifty years. Indeed, in the world in which we live it is difficult to be unaware of drones and their impact on military operations, intelligence, surveillance, and reconnaissance (ISR)operations, and even in commercial delivery services and popular culture. However, all of this technology had to start someplace, and Radioplane is one of the places where it started.