October 2

 The Mathematics of Reaching Other Worlds

1920 — Giuseppe “Bepi” Colombo Is Born

Time unknown

On October 2, 1920, Giuseppe “Bepi” Colombo was born in Padua, Italy. He would become a mathematician and engineer whose insights helped change the way spacecraft travel through the solar system. Colombo studied mathematics at the University of Pisa, graduating in 1944, and later became a professor at the University of Padua. His interests ranged across celestial mechanics, planetary science, spacecraft trajectories, orbital dynamics, and the behavior of artificial satellites. But his name became particularly associated with Mercury. For many years, astronomers believed that Mercury kept essentially the same face toward the Sun, much as the Moon keeps the same face toward Earth. Radar observations in the 1960s demonstrated otherwise. Mercury rotates once approximately every 59 Earth days, while taking about 88 days to orbit the Sun. At first, that relationship seemed peculiar. Colombo recognized its significance. Mercury was locked into a 3:2 spin-orbit resonance: for every two journeys it makes around the Sun, the planet rotates exactly three times. That realization helped explain one of the solar system's more unusual examples of orbital and rotational dynamics. Colombo's most influential contribution to spaceflight emerged as NASA prepared Mariner 10, the first spacecraft intended to visit Mercury. Getting to Mercury is surprisingly difficult. A spacecraft launched from Earth already shares Earth's enormous orbital velocity around the Sun. To reach Mercury, it must lose substantial orbital energy and fall inward toward the Sun without simply racing past its target. Mariner 10's planned trajectory included a flyby of Venus. Colombo recognized something remarkable about the spacecraft's subsequent orbit. If engineers carefully selected the geometry of Mariner 10's encounter with Mercury, the planet's gravity could reshape the spacecraft's orbit around the Sun so that Mariner 10 would return to Mercury again. NASA's Jet Propulsion Laboratory studied the proposal and confirmed it. The idea worked. Mariner 10 flew past Venus in February 1974, using the planet's gravity to alter its trajectory. It encountered Mercury for the first time on March 29, 1974. Then it came back. Mariner 10 flew past Mercury again in September 1974 and a third time in March 1975. Instead of one encounter, scientists received three. The spacecraft photographed a cratered surface that in some respects resembled the Moon, discovered that Mercury possessed an unexpected intrinsic magnetic field, and greatly improved knowledge of the innermost planet. The trajectory represented an important development in the use of gravity assists. The principle is elegant. A spacecraft approaching a moving planet enters the planet's gravitational influence. As the spacecraft swings past, gravity bends its trajectory. Viewed relative to the Sun, the encounter can transfer orbital energy between the planet and spacecraft, changing the spacecraft's speed and direction without requiring the equivalent amount of rocket propellant. The change to the planet's motion is immeasurably small. For the spacecraft, it can be transformative. Gravity assists became one of the essential tools of interplanetary exploration. The Voyagers used planetary encounters to travel through the outer solar system. Galileo used gravity assists at Venus and Earth to reach Jupiter. Cassini used Venus, Earth, and Jupiter on its journey to Saturn. MESSENGER used repeated encounters with Earth, Venus, and Mercury before entering Mercury orbit. The European-Japanese BepiColombo mission takes the concept even farther, combining solar-electric propulsion with multiple planetary flybys to gradually remove enough orbital energy to enter orbit around Mercury. Colombo contributed to other areas as well. He developed ideas involving long orbital tethers and helped inspire ESA's mission to Halley's Comet, suggesting that it be named Giotto after the medieval Italian artist who depicted the Star of Bethlehem in a manner possibly inspired by a comet. Colombo died in 1984, before Giotto encountered Halley's Comet in 1986. His influence continued. In 1999, the European Space Agency named its ambitious Mercury mission BepiColombo in his honor. The joint ESA-JAXA mission would employ precisely the sort of sophisticated orbital mechanics with which Colombo's name had become associated. Why It Matters: Giuseppe Colombo demonstrated how mathematical insight could dramatically expand what a spacecraft could accomplish. His work helped Mariner 10 turn one planned encounter with Mercury into three and contributed to the development of gravity-assist techniques that became fundamental to planetary exploration. His career illustrates a crucial truth about spaceflight: reaching another world depends as much upon understanding celestial mechanics as upon building powerful rockets.

 

Also on This Day

1962 — Explorer 14 Launches to Investigate Earth's Space Environment

Launch time not established

On October 2, 1962, NASA launched Explorer 14, also known during development as S-3a, aboard a Thor-Delta rocket from Cape Canaveral. The spacecraft was designed to investigate an environment that scientists had only recently discovered was far more complicated than expected. Before the Space Age, the region surrounding Earth was sometimes imagined as comparatively empty. The first Explorer satellites changed that picture. Measurements beginning with Explorer 1 in 1958 revealed intense populations of energetic charged particles trapped by Earth's magnetic field—the Van Allen radiation belts. Explorer 14 continued the investigation. Its scientific instruments included detectors for cosmic rays, solar particles, trapped radiation, ions, plasma, and magnetic fields. Its highly elliptical orbit carried it from a few hundred kilometers above Earth to roughly 100,000 kilometers away, allowing instruments to sample very different regions of Earth's magnetic environment. The mission was especially timely. The Sun was capable of releasing streams and eruptions of energetic particles into interplanetary space. When those particles encountered Earth's magnetic field, they could dramatically change conditions around the planet. Understanding that environment was important scientifically, but it also had practical consequences. Astronauts and spacecraft electronics could be exposed to radiation. Radio communications could be disrupted. Satellites would have to operate within an environment shaped simultaneously by Earth and the Sun. Explorer 14 returned roughly 6,500 hours of scientific data during about ten months of useful operation. Among its contributions were observations helping scientists understand the shape of Earth's magnetosphere and the behavior of charged particles within it. The scientific field would eventually become central to what we now call space weather.

Why It Matters: Explorer 14 helped reveal that the space surrounding Earth is not empty but a dynamic environment filled with charged particles and shaped by Earth's magnetic field and the Sun. Understanding that environment became essential both to heliophysics and to the safe operation of spacecraft.

1991 — Soyuz TM-13 Launches an International Crew Toward Mir

Launch time not established

On October 2, 1991, Soyuz TM-13 launched from the Baikonur Cosmodrome carrying a crew that reflected the rapidly changing political geography of Europe and the Soviet Union. Commander Aleksandr Volkov was accompanied by Toktar Aubakirov of Kazakhstan and Franz Viehböck of Austria. Aubakirov became the first Kazakh in space. Viehböck became the first Austrian in space. Their destination was the Soviet space station Mir. The flight occurred at an extraordinary historical moment. Only weeks earlier, an attempted coup against Soviet leader Mikhail Gorbachev had failed. Several Soviet republics were moving rapidly toward independence. The Soviet Union itself had only months left to exist. Aubakirov's presence was therefore especially symbolic. He had been born in the Kazakh Soviet Socialist Republic, while the Baikonur launch complex from which he departed was located on Kazakh territory. Viehböck's mission, meanwhile, grew from Austrian-Soviet scientific cooperation. During his time aboard Mir, he conducted experiments involving medicine, physics, materials, and other fields. Aubakirov and Viehböck remained aboard Mir only briefly before returning to Earth with cosmonaut Anatoly Artsebarsky. Volkov stayed. He joined Sergei Krikalev, who had already been living aboard Mir since May. Then history overtook the mission. In December 1991, the Soviet Union ceased to exist. Volkov and Krikalev had launched under one political system and would return in March 1992 to a transformed world. Baikonur itself was now located in the independent nation of Kazakhstan. The spacecraft continued orbiting Earth while borders, governments, and national identities changed beneath it.

Why It Matters: Soyuz TM-13 expanded human spaceflight to Kazakhstan and Austria while also becoming part of one of the most remarkable political transitions ever experienced during a space mission. Mir continued operating even as the Soviet state that had created it disappeared, demonstrating how spaceflight institutions and international partnerships could survive profound changes on Earth.

 

The Bigger Picture

October 2 reminds us that exploration depends upon learning how to navigate environments that cannot be controlled. For Bepi Colombo, that environment was the gravitational architecture of the solar system. Planets are not simply destinations. They are moving masses whose gravity can become part of the spacecraft itself—a kind of invisible propulsion system available to anyone who can calculate the trajectory precisely enough. Explorer 14 confronted another invisible environment. Earth appears to orbit through empty space, but the planet is actually surrounded by magnetic fields and energetic particles interacting continuously with the Sun. Spacecraft entering that environment must understand it rather than ignore it. And Soyuz TM-13 encountered an environment of another kind. While its crew traveled to Mir, the political world beneath them was changing dramatically. The Soviet Union that launched the mission would soon disappear, yet the station remained in orbit and its crews continued working. There is an intriguing common thread: exploration succeeds by adapting to forces larger than the spacecraft itself. Gravity cannot be switched off. The solar wind cannot be stopped. History on Earth does not pause because people are living in orbit. The explorer therefore learns the environment and works within it. Colombo's great insight made this especially clear. Early thinking about interplanetary flight could easily emphasize rocket power: if another world is difficult to reach, build a more powerful rocket and carry more fuel. Celestial mechanics offers a subtler answer. Sometimes the solar system itself can help. A planet's gravity can accelerate a spacecraft, slow it, redirect it, or arrange another encounter years later. The planets become not merely destinations on the journey. They become part of the road.

At a Glance

1920 — Time unknown — Giuseppe “Bepi” Colombo is born in Padua, Italy; his later work on Mercury and spacecraft trajectories helps establish gravity-assist techniques as an essential tool of planetary exploration.

1962 — Launch time not established — NASA launches Explorer 14 to investigate energetic particles, plasma, cosmic radiation, and Earth's magnetosphere.

1991 — Launch time not established — Soyuz TM-13 launches Aleksandr Volkov, Toktar Aubakirov, and Franz Viehböck toward Mir; Aubakirov and Viehböck become the first people from Kazakhstan and Austria, respectively, to travel in space.