Going to Mars on Paper

Not all of the IL's engineers were absorbed in Polaris. After Sputnik, some sought to expand their horizons beyond earthbound missiles. Hal Laning, a mathematician and control engineer, had been at the IL since 1947, and was head of the small but crucial mathematics group. Laning recognized the intrigue and potential of the computer when he worked on Whirlwind, MIT's first computer, specially built for research in real-time control systems. He wrote a program called George, a small compiler for Whirlwind that allowed engineers to write equations for the computer to solve rather than obscure assembly language (features soon incorporated into the high-level language FORTRAN). Another IL engineer, Milt Trageser was a physicist who concentrated in optics. The launch of Sputnik in 1957 convinced Laning and Trageser that there could be a future in engineering for spaceflight. After years of figuring how to guide nuclear missiles to their targets, perhaps they were attracted to the prospect of a scientific mission.

They began a small design study of a Mars probe, a small spacecraft that would fly by the red planet, snap a single picture, and return the film to earth. Today, the idea of a small, free-flying space probe is familiar, and we are used to seeing stunning images from a variety of such devices, several of which have traveled even further than Pluto. At the time, however, the idea seemed innovative, even fanciful.

The design of the Mars probe reflected Laning and Trageser's expertise and also set the basic configuration for the Apollo guidance system several years later. It incorporated the strength of the IL: a set of gyroscopes to keep the probe oriented. In addition, Laning added his own interest: a digital computer. Trageser incorporated an optical telescope with which the probe would orient itself relative to the moon and the stars, and a camera to capture the image of the planet as it flew by. As Laning put it: ''I think we had our own concept of the project. Milt Trageser was a physicist. He, I think, viewed it as a giant eye. I was a computer scientist, and viewed it as an opportunity to put a totally self-dependent machine in the air for a period of time.''16

''Self-dependent'' is a significant phrase—it reflects the IL philosophy of self-contained navigation, inherited from the ballistic missile world. One other group in the country was working on deep-space probes, the Jet Propulsion Laboratory ( JPL) in Pasadena;it emphasized a technique, still used today, of tracking space probes through a network of ground-based antennas. These approaches would evolve and complement each other on Apollo.17

In Laning and Trageser's design, the onboard computer allowed the probe to do more than follow a simple fixed series of events, but to choose ''alternate courses of action'' that would increase the chances of a mission's success. A central computer, they wrote, would serve this function better than controls that were ''distributed among a variety of servo-control systems.''18 The Mars probe navigated by automatically measuring four angles, between the sun, stars, and planets, to determine the spacecraft's position. Unknowingly, Laning and Trageser were providing a counter to the X-15 and Mercury philosophies that human pilots added reliability. They argued instead for an onboard computer that could use complex logic to respond to unforeseen problems, just the type of control system ignored by the air force X-15 study comparing human controls to automatic systems.

The air force continued to fund the Mars probe study, and by 1959 as many as fourteen members of the IL were working on the project. These included Ramon Alonso, who joined the IL from Harvard's Computation Laboratory, led by the pioneering computer scientist Howard Aiken. Also joining the Mars probe group was Richard Battin, an electrical engineer with a Ph.D. in applied mathematics, who became a pioneer in the design of interplanetary trajectories. Battin had worked in the lab from 1951 until 1956, and then left for a career in business. The Sputnik launch convinced Battin the future was in space and he immediately returned to the lab, whence he developed the critical Q-guidance technique. Battin and his colleagues developed the general, abstract methods to bring new computing power to bear on guidance problems in real-time.19

Today, when interplanetary probes accelerate around planets on their way to distant journeys, they are executing Battin's idea for ''a kind of celestial game of billiards.'' Battin's book Astronautical Guidance (1964) laid out the basic ideas for a generation of students.20 Beginning with basic celestial mechanics, he showed how to calculate transfers from one orbit to another, and how to approach a target planet, either for a roundtrip ''reconnaissance'' trajectory or to enter an orbit. Battin developed techniques for taking navigation fixes by measuring the angle between the sun and a planet, between a planet and a star, between a star and a landmark on a planet, and a variety of other observations.

Battin's book culminated in a case study of a lunar reconnaissance mission. In 1960 he began teaching a course called Astronautical Guidance that became foundational to the field (he still teaches at MIT today, after nearly sixty years in the classroom). Nearly a third of the men who walked on the moon took this course. A genial man highly skilled in mathematics, Battin often opens his lectures with lighthearted numerologi-cal analyses of the Apollo program. (For example, he notes that 1961, the year NASA awarded the Apollo computer contract, is an invertible number, meaning it reads the same upside down and backward, like 1881, 1691, and 1111. The next year that would be an invertible number after 1961 is 6009, some indicator of providence for Apollo). Behind the levity lies a serious, creative mathematical mind;one colleague called Battin ''the guiding light in this whole midcourse guidance and lunar navigation theory.''21

With this added brainpower, the Mars probe group produced a more extensive report published in five volumes in 1959. They drew on the initial design but fleshed out a number of other subsystems and added a more complete technical analysis. ''The project was not intended, on anything other than a very superficial level, to be a scientific mission,'' writes Alexander Brown, but rather a demonstration of the IL's skills applied to the new arena of spaceflight. Brown argues that the Mars probe study was not only the design for a piece of flight hardware, but also a ''probe'' enabling MIT/IL engineers to foray into the potential new market of space exploration (figure 5.1).22

Figure 5.1

Milt Trageser (left), Hal Laning (center), and Richard Battin with a mockup of their Mars probe. The capsule-shaped component Battin is holding is to protect the camera film with images of Mars during the return into Earth's atmosphere. (Draper Laboratories/MIT Museum.)

Figure 5.1

Milt Trageser (left), Hal Laning (center), and Richard Battin with a mockup of their Mars probe. The capsule-shaped component Battin is holding is to protect the camera film with images of Mars during the return into Earth's atmosphere. (Draper Laboratories/MIT Museum.)

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