Brown's Lunar Exploration Working Group

Michael's Paper on a "Parking Orbit"

The Rendezvous Committees

Houbolt's First Crusade

The Feelings Against Lunar-Orbit Rendezvous

The Space Task Group's Early Skepticism

Mounting Frustration

President Kennedy's Commitment

Houbolt's First Letter to Seamans

A Voice in the Wilderness

The LOR Decision



Key Documents
(pdf version)


  Michael's Paper on a "Parking Orbit"

Meanwhile at Langley, members of Brown's lunar exploration group were already studying ways for landing on the Moon someday. They explored several options and ideas, but in one of these studies, by Bill Michael, the group examined the benefits of "parking" the Earth-return propulsion portion of a spacecraft in orbit around the Moon during a landing mission. The spark for Michael's interest in what eventually was called a "parking orbit," a spacecraft in a "waiting" orbit around the Moon or some other celestial body, involved his own calculations to determine whether there was any advantage in a lunar mission to some additional "staging." Staging was a proven and necessary technological concept, first explained by Tsarist Russia's space visionary Tsiolkovskiy in the late 1800s, by which a self-propelled, staged-rocket vehicle (Tsiolkovskiy called it a rocket "train") could ascend to greater and greater heights as its different stages expended their fuel and separated.

In a lunar landing mission, Michael speculated, one would not want to fly a big rocket directly from the Earth to the Moon, as Jules Verne’s popular book and other science fiction fantasies envisioned. The big rocket would result in too much unnecessary weight being taken down to the surface. It would be much wiser to take "an intermediate step" and go into lunar orbit, where much of the total weight remained behind—the structure of the interplanetary spacecraft, its heavy fuel load for leaving lunar orbit and heading home, and its massive heat shield necessary for a safe reentry into the Earth's atmosphere. "It's very expensive to accelerate any type of mass to high velocity," Michael reasoned. "Any time you do not have to do that, you save a lot of fuel and thus a lot of weight."12

The upshot of his calculations, which he documented in early 1960 in a never-to-be-published paper titled, "Weight Advantages of Use of Parking Orbit for Lunar Soft Landing Mission," was to identify one of the most basic advantages of what eventually was known as the concept of "lunar-orbit rendezvous." Michael had to make several assumptions about what might entail a lunar landing mission—the spacecraft's engines, the structural weights, and so forth. But his results implied that by going into orbit around the Moon rather than going directly to the lunar surface, one could save an impressive 50 percent or more of the total mission weight. Figuring the numbers did not require any difficult or sophisticated calculations.13 Nor did it require any knowledge of the writings of Russian rocket theoretician Yuri Kondratyuk and British scientist and Interplanetary Society member H.E. Ross, both of whom had expressed the fundamentals of the lunar-orbit rendezvous concept (Kondratyuk in 1916 and Ross in 1948).14 Neither Michael nor anyone else at Langley at this point, so they have always maintained, had any knowledge of those precursors.

The Langley scientists also had not yet known anything about competition from contemporaries. That did not take long, however. Later the same morning that Michael first presented his rough "parking orbit" calculations in Clint Brown's office, a team led by Thomas E. Dolan from Vought Astronautics, a division of the Chance-Vought Corporation in Dallas, gave a briefing at Langley. This briefing concerned Vought's ongoing company-funded, confidential study of different problems related to "Manned Lunar Landing and Return" (acronym "MALLAR") and, specifically, its plans for a manned spaceflight simulator and its possible application for research under contract to NASA.

During the briefing, Dolan's team members mentioned an idea for reaching the Moon. Although the Vought representatives focused their analysis on the many benefits of what they called a "modular spacecraft"—one in which different parts, including a lunar landing module, were designed for certain tasks—Brown and Michael understood what was being advertised: the essentials of the lunar-orbit rendezvous concept. "They got up there and they had the whole thing laid out," Brown remembers. "They had scooped us" with their idea of "designing a spacecraft so that you can throw away parts of it as you go along." For the next several days, Michael walked around "with his face hanging down to the floor."

Nevertheless, the chagrined Langley engineer wrote a brief paper, confident that he had spawned his idea simultaneously and independently of all others. Furthermore, the word spread around Langley that Dolan had developed the idea of using a detachable lunar-landing module for the actual landing operation after an earlier visit to Langley when engineers in the Pilotless Aircraft Research Division, who were somehow familiar with Michael's embryonic idea, had suggested a parking orbit. This explanation, however, may simply have been "sour grapes." On the other hand, Dolan had made several visits to Langley in late 1959 and early 1960, and Michael remembered having already mentioned his idea to a few people at the laboratory, "so it shouldn’t have been any surprise to anybody here at Langley that such a possibility existed."15 The truth about this will probably never be known.

What is known is that Michael’s paper, at least in retrospect, had some significant limitations. It was only two pages long and presented little analysis. Its charts were difficult to follow and interpret. There was no mention of "Earth-escape weights," although an informed reader could infer such numbers by a type of inverse reasoning. Perhaps most importantly, the paper did not explicitly mention either the need for a separate lunar lander or the additional weight savings derived from using one and then discarding it before the return trip home. In sum, one would already have to have been familiar with the subject even to recognize, let alone fully fathom, what was being implied.

Michael’s paper had one last problem: it was never published. Therefore, it was hardly a fully developed articulation of a lunar landing mission using lunar-orbit rendezvous. Nonetheless, Michael’s unpublished paper on the weight advantages of a parking orbit made a fundamentally important contribution: for NASA researchers contemplating lunar missions, it zeroed in on the central theme of rendezvous. As his paper concluded, the chief problems in a lunar landing mission were the "complications involved in requiring a rendezvous with the components left in the parking orbit."16

Although disappointed that Vought had already hit on the idea of lunar-orbit rendezvous, the Langley researchers were hardly demoralized. Staffers in and around Brown's division quickly began making lunar and planetary mission feasibility studies of their own. John P. Gapcynski, for example, considered "factors involved in the departure of a vehicle from a circular orbit about the Earth." Wilbur L. Mayo calculated energy and mass requirements for missions to the Moon and even to Mars. Robert H. Tolson studied the effects on lunar trajectories of such geometrical constraints as the eccentricity of the Moon's orbit and the oblate shape of the Earth; he also analyzed the influence of the solar gravitational field. John D. Bird, who worked across the hall from Michael, began designing different "lunar bugs," "lunar schooners," and other types of small excursion modules that could land on the surface of the Moon after departing a "mother ship." "Jaybird" (as Bird was called by his peers) became an outspoken advocate of the lunar-orbit rendezvous concept. When a skeptical visitor to Langley offered, with a chuckle, that lunar-orbit rendezvous was "like putting a guy in an airplane without a parachute and having him make a midair transfer," Bird set that visitor straight. "No," he corrected, "It’s like having a big ship moored in the harbor while a little rowboat leaves it, goes ashore, and comes back again."17

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