Dornberger's 'ultra planes' were yesteryear's spaceliners

In 1944, husband and wife Dr. Eugen Sänger and Irene Bredt were desperately trying to find benefactors for their research. In the mid-1930s, the Austrian couple had developed a manned boost-glide vehicle — a piloted spaceplane.

Hitler loved the technology; weaponized, it would make an excellent precision bomber. But the boost-glide vehicle was never built, and when the war ended a decimated Germany didn't have the spare money to develop the system. The boost-glide concept might have died had it not been for Walter Dornberger, a rocket engineer who brought the idea to the United States. But Dornberger didn’t just see it as a possible bomb. He imagined a future where boost-glide commercial aviation carried passengers around the world on a routine basis.

Dornberger, WWII, and the Boost-Glide Vehicle

Walter Dornberger spent most his life working with rockets, mainly under a military umbrella. He joined the German Army in 1914, and in 1925 he was sent to the Charlottenberg Institute of Technology to study ballistics. There he met Wernher von Braun, a young and gifted aeronautical engineer with whom he had a shared passion: both men were members of the German Society for Space Travel.

Having gained this ballistic expertise, the German army put Dornberger in charge of its solid-fuel rocket research and development in the Ordnance Department in 1932. He promptly sought out and courted von Braun, finally persuading his colleague to build rockets for the army rather than for spaceflight. By 1937 Dornberger was military commander of the rocket research station at Peenemunde where von Braun and his team developed the V-2 missile that rained down on London in the closing days of the war.

The V-2 wasn’t the only rocket-based weapon under development at Peenemunde. The Sänger-Bredt boost-glide vehicle was also in the works. The glider — a flat, triangular base with a cockpit on top — was designed to launch on a V-2. The rocket would boost the glider into the upper atmosphere, high enough that its flat bottom would allow it to skip off the atmosphere like a stone across a calm pond. At any point, a pilot could drop a well-placed bomb before reentering the atmosphere and gliding to a landing. It had, at least on paper, an impressive range. It could bomb New York easily after a launch in Germany, a capability that earned the the vehicle the name "Amerika Bomber." Even though the vehicle was never built, Dornberger had seen the plans enough to commit some of the more important details to memory. 

Dornberger came to America as part of Operation Paperclip, which sought German engineers and scientists to bring to the U.S. after the end of World War II. He took a position developing guided missiles for the U.S. Air Force in Ohio, and then went on to work for the Bell Aircraft Corporation, where in 1952 he pitched the idea of a boost-glide bomber. He argued that it would make a formidable addition to the United States’ military, and enough higher-ups agreed that the idea was given a green light. From this initial proposal the Dyna-Soar program was born, one of the Air Force’s failed attempt at a manned spaceflight program. But that wasn’t the limit of the boost-glide technology in Dornberger’s opinion.

Pictured: One of Dornberger's ultra planes, a crewed passegner vehicle is fixed atop a larger crewed launch vehicle.

The Ultra Plane

Walter Dornberger was born on September 6, 1895, in Giessen, Germany. He was one year old when German gliding flight pioneer Otto Lilienthal was killed by his own inventions, and he was eight when the Wright brothers made the first heavier-than-air flight. Throughout his military career, he watched aviation mature before his eyes at a startling pace. Barebone wood-and-canvas airplanes capable of short hops just feet above the ground gave way to sleek fighter jets flying faster than sound at an altitude of over 100,000 feet in just half a century. Civilian aviation also flourished in this era. By 1956, commercial airlines were carrying passengers around the world. Travel by air was a luxury not all could afford, but the trend was towards increased access to flight for the average citizen. 

Comparing the technological developments in aviation with the pace at which the commercial industry developed, Dornberger figured it was only a matter of time before supersonic technology became commonplace in air travel. Writing in 1956, he anticipated turbojet engines would routinely carry passengers faster than the speed of sound between cities worldwide. But until this technology reached maturity, he saw the boost-glide vehicle as a way to introduce supersonic flight to the common man. 

Dornberger called his vehicles "ultra planes," and he expected the benefits of shortened travel time would make commercial rocket flight a profitable business. Rocket flights on ultra planes wouldn’t replace propellor planes for shorter hops between American cities, but they could shrink the distances between major cities like San Francisco, London, Calcutta and Sydney, traveling between these cities in just hours.

Traveling on Ultra Planes

Dornberger’s ultra plane had two parts, a glider and a booster. Both featured flat bottoms and wide wingspans for better gliding capabilities, as well as a rounded passenger cabin in the central fuselage. Both vehicles also had crews, but only the glider was equipped with a passenger cabin. As the workhorse that would carry the glider off the ground at launch, the booster’s main cargo was fuel. 

The glider and booster would begin their journeys in a large hangar sitting horizontally like traditional airplanes. The first step was to mate the vehicles. The glider was designed to slide into guide rails on the booster’s upper fuselage and lock into place, and arrangement that made it look as though the booster was giving the booster a piggy-back ride. In both the glider and the booster, the pilots’ cockpit is in the nose of the vehicle. The passengers’ section in the glider is in the vehicle’s mid section, a placement that keeps its center of gravity more or less consistent throughout the flights. 

Once mated, the booster-glider stack would be flipped on its end. This launch configuration would be impressive, a black monolith towering 90 feet above the ground. The stack would be mounted on a mobile launch platform that would carry it from the hangar to its launch site by rail — a transportation system Dornberger had pioneered at Peenemunde before NASA adopted the method. The whole phase would have looked like the shuttle, ready for launch, moving slowly from the Vehicle Assembly Building to the launch pad on the crawler.

On its way to the launch site, a specially dug crater large enough to keep the exhaust away from travelers in the airport, the ultra plane would stop at a canyon. Here, gantries projecting from the walls would give maintenance crews access to all levels of the booster and the glider for pre-flight checks. The railway would then take the ultra plane into its launch crater where both vehicles would be fueled before passengers could board. 

For the passengers, boarding the ultra plane would be just like boarding a traditional plane. The launch canyons, which would be dug a ways from the terminal but still at regular airports, would be assigned ordinary gate numbers. They would be driven to the launch crater by van — it would be far too dangerous to connect the launch site to the terminal by a jetway. They would take an elevator 20 feet down into the crater walls where a special would give them access to the hatch opening into the glider’s passenger cabin. 

Once on board, passengers would take their seats inside smaller cabins. These would rotate freely, ensuring the passengers are always oriented “normally” regardless of the glider’s orientation. But this was the end of the onboard comforts — the cost of fuel would make carrying excess cargo like flight attendants impossible, and because the flights would be so short there would be no meal service. But to make up for the lack of amenities — and in keeping with 1950s airline standards of giving flyers spectacular aerial views to make their flights special — windows with pilot-controlled sun screens would give passengers awesome sights of black space and the Earth’s curvature during the flight.  

With both vehicles fueled and loaded with passengers and crew, the ultra plane would rotate so its wings sliced into any oncoming wind — a measure to limit any jostling. Then the booster’s five rocket motors would light, delivering 760,000 pounds of thrust. Though fuel and oxygen tanks would absorb some of the sound and vibrations, it would still be a noisy ride as passengers would feel 25 percent heavier thanks to the increased g-forces. The shaking, noise, and g-forces would increase throughout the ascent, peaking at an uncomfortable but manageable 3g. Then, just over two minutes after launch, it would be time for staging. 

It would fall to the glider pilot to engage the release mechanism and separate the glider from the booster; the small passenger vehicle would slide off the rails on the booster’s upper fuselage. The booster’s pilots would take control of their vehicle and turn back towards the airport. They’d make a smooth gliding landing near their launch point before being towed back to the hangar to prepare and fuel for another launch. 

With the booster gone, the glider’s pilot would ignite the three rocket motors, which would fire for another two minutes, accelerating the glider more than 140,000 feet above the Earth at speeds greater than 8,400 miles per hour. Then, as suddenly as they’d kicked in, the three engines would cut out. In an instant passengers would go from weighing three and a half times their normal body weight to weighing just three-quarters. 

The total powered portion of the flight, from launch through staging, would be over in just four and a half minutes. The remaining hour and ten minutes would be the unpowered gliding descent to the airport. With all engines off, the cabin would be nearly silent. Passengers would be able to sit back and watch the Earth rush up at them or look out at stars shining as brightly as the full Moon.  

Far too soon, it would be time for landing. The glider’s pilots would make an unpowered landing on a runway, just as though it were a traditional airplane. From its horizontal position, passengers would be able to disembark down a rolling staircase right on to the tarmac. Another bus or shuttle would drive them to the terminal where they could catch a connecting plane or ultra plane, or else leave and visit their destination city.

Pictured: A vision for more activity in Earth's orbit by space artist Chesley Bonestell, with a Dornberger-like spaceplane to the left and a "wheel" space station right, as imagined by Wernher Von Braun.

Beyond the Ultra Plane

Ultra planes would have been a fantastic opulence had they made their debut in the 1960s. But, like commercial air travel, Dornberger imagined a future where it wasn’t a means reserved for the elite. Eventually, intercontinental flights would be dominated by rocket planes.  

But it wasn’t just commercial air travel that could benefit from ultra plane flights. Dornberger, the former member of the German Society for Space Travel, saw ultra planes and other suborbital rocket flights as the first step in starting man’s outward push from the Earth to other planets. He suspected that by shrinking our own planet, more people would be inclined to look past the Earth and out into space. A commercial demand for large boosters would parlay into technology capable of launching planetary probes. 

Once rocket flights became commonplace, Dornberger imagined a future where the sky was no longer the limit. 

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