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Douglas HATV

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World Circling Space Credit: © Mark Wade

Status: Design 1946. Gross mass: 45,350 kg (99,970 lb). Height: 27.40 m (89.80 ft). Diameter: 4.57 m (14.99 ft).

In July 1946, the US Army Air Force had concluded that a single-stage-to-orbit earth satellite was impossible based on a Rand Corporation report. The Office of Naval Research gave Douglas Aircraft manager Ed Heinemann a copy of the report. He in turn handed the report to Douglas scientist Dr. William F Ballhaus. Ballhaus was asked to visit Rand and verify the conclusions of the report. After visiting the Rand people, Ballhaus returned and concluded that the difficulty with the Rand designs were that they were all based upon conventional aircraft and missile structures.

Ballhaus knew that a new approach was demanded. He realized that, if all critical structures were subjected only to tensile stresses, there would be no need for stringers, rings, or bulkheads, as in the conventional designs, and a significant amount of structural weight could be saved. He conceived of a steel balloon, pressurized when empty to support the payload, and further pressurized to accept the loads required for fuel and oxidizer during the entire flight to orbit. He designed a vehicle using this approach while assuming the same payload, propulsion, and control systems applied to the Rand designs. Detailed calculations were made regarding load factors, velocities, weight and drag. Ballhaus' conclusions were handed over to Heinemann and published as 'Preliminary Design of a Satellite', Douglas, El Segundo, Report ES 20636, on 7 August 1946. This was the first proof that a single stage earth satellite was indeed possible.

However prior to publication Heinemann had the title page re-typed to remove "Prepared By William F Ballhaus" from the report. In his autobiography Heinemann claimed to have conceived the idea and took full credit for the study when introduced to Wernher von Braun in later years. Ballhaus noted that Heinemann always bragged that he had only a high school education and yet he was able to manage a number of highly educated people. Heinemann did not have the mathematical capability to analyze the critical aspects of the first single stage earth satellite, yet he claimed authorship of the design approach.

In the post-war military cutbacks there were no funds for development of space launch vehicles. Ballhaus' 'metal balloon' concept would be later 'invented' again by Charles Bossart at Convair and applied to the Atlas rocket; and also by the German team in Russia in one alternative G-4 design.

In his memoirs Heinemann takes full credit for the invention and mentions Ballhaus only as 'refining' Heinemann's 'rough calculations':

Shortly after World War II Dr Harvey Hall, a scientist with the Office of Naval Research, contacted me on a matter concerning satellites -- a subject treated with discretion because it dealt with the "unknown".

"In a nutshell," he said, "We would like you to try designing a single-stage satellite."

Harvey explained that the Rand organization, among others, and Dr. Wernher von Braun, who created the V-2 rocket for Germany during World War II and who was involved in various projects for the US government, were examining satellite possibilities. Studies heretofore indicated that two or three stages were necessary, but Harvey believed a single-stage design was feasible.

"What structural weight fraction are Von Braun and the others using?" I asked.

"Twenty-six percent," answered Harvey.

Which meant that after fuel had been exhausted in propelling the satellite orbit, the structure and components that remained weighed 26 percent of the device's total weight.

I agreed to work up something and enlisted the help of Douglas engineer, Dr. Ballhaus, who was engaged in special projects at the time.

Harvey, Bill, Leo Devlin, and I reviewed the problem and outlined the concept. For a base figure we began with an arbitrary 100,000 pounds takeoff weight and from there incrementally subtracted pounds for the engine, fuel, instrumentation, controls, and so on. After these items had been subtracted, the weight of the structure remained. We took this figure and divided it by the surface area required to house the fuel, payload, and engines, and obtained a unit weight.

This gave us a skin strong enough to contain the fluid but not stiff enough for handling purposes. A rather swift review of the figures showed that just a few pounds of internal pressure would be sufficient to hold what we called the "metal balloon" in shape for handling without exceeding its bursting strength. The device was ninety-feet high with a fifteen-foot diameter.

Bill Ballhaus refined the rough calculations and confirmed the principle to be sound. Harvey went back to Washington and we proceeded with the details at El Segundo. After several weeks we had a design and presented it to Harvey who was as pleased with the results as we were. This was 1946; unfortunately, the project never proceeded beyond the drafting boards for a variety of reasons, not the least of which were lack of money and the navy's disinclination at the time to become immersed in such exotic programs as artificial satellites.

Fifteen years later I went to see Wernher Von Braun in Huntsville, Alabama, on a different matter. We had met casually a few times during the interim, so it wasn't a first for me. His secretary asked that I wait since Wernher was busy, but when he did emerge from his office he was with Harvey Hall.

"Well," said Harvey, "here's the guy who designed the single-stage satellite."

"Oh I know Ed," said Wernher.

In the discussion that followed Harvey asked Wernher why he used a 26 percent structural weight fraction ratio on the V-2.

"Well," Von Braun said, "I built the structure strong enough to hold together, and frankly, it just came out that way."

We had differed from Wernher in our approach in that we worked backwards. We began with a weight and designed components to remain within that weight. Wernher, on the other hand, designed the components and then arrived at a weight. His circumstances were far different from ours, of course, since he was building a weapon which had to be very rugged. If there was a lesson in the satellite project, it was that by starting out with a clean piece of paper and a different approach, suitable results could be achieved, regardless of what approach others might have taken to reach the same goal.

The metal balloon concept, incidentally, was in evidence later when Convair designed the Atlas missile for the Air Force. The Atlas had very thin skin but was pressurized internally, using the same principle we proposed, and became a very successful metal balloon.