Epic Rivalry

by Von Hardesty

  This was the exploration model that NASA adapted for its unmanned moon explorations, an essential precursor to sending astronauts to the lunar surface. First in line was Ranger, designed and constructed by NASA and California Institute of Technology’s storied Jet Propulsion Lab (JPL). Ranger’s mission was to send detailed television pictures and other data to Earth as it approached the moon and then crashed into its surface at high speed. The early Ranger missions did not go well: Rangers 1 and 2, test models launched in 1961, were stranded in low-Earth orbit when Agena upper stages, which would boost them toward the moon, failed to restart. Ranger 3 fared no better in early 1962 on a mission representing the first U.S. attempt to achieve impact on the moon; the engines of its Atlas-Agena booster fired for too long. As a result the Ranger missed the moon by 20,000 miles, ending up in orbit around the sun.44

  More failures followed, although Ranger 4 did at least crash into the lunar surface in April; unfortunately, it lost power en route and sent back neither images nor data. It nonetheless marked the first time the U.S. had hit the lunar surface, three years after Russia’s Luna 2 had done so. After Ranger 5 also missed the moon that fall, NASA voiced serious concerns about JPL’s competence to carry out the Ranger mission. An investigation into the failures resulted in major changes that reduced each mission’s goals. For a time, NASA was concerned that the Apollo landings might be delayed by Ranger’s failures to return photos of potential lunar landing sites. Success finally came in July 1964, when Ranger 7 sent back more than 4,000 clear and impressive images on videotape and film before crashing into the northern rim of the Sea of Clouds. The final picture, taken from 1,500 feet above the lunar surface, revealed craters as small as three feet across. Three additional Rangers each returned thousands more photographs on similarly flawless missions through March 1965. JPL’s reputation had been redeemed, and the data sent back by the Rangers would be used to select landing sites for Surveyor, the next step in reconnoitering the moon.45

  Surveyor was a 600-pound three-legged triangular aluminum structure loaded with instruments. It carried a solid-propellant engine at its base to enable it to make a “soft” landing on the moon. Once there, it would use a sophisticated imaging system to take and transmit close-up color photos of the lunar landscape back to Earth. JPL managed this program as well, though its development took a backseat to the myriad problems encountered by Ranger. Unlike Ranger, though, Surveyor scored a spectacular success on its first launch, a feat made even more impressive by the major delays and difficulties with its Atlas-Centaur launch vehicle. (The Centaur upper stage was powered by new and powerful engines fueled by liquid oxygen and liquid hydrogen to give it heavy-lift capability, but it lagged years behind schedule. Concurrent development of a new launch vehicle and a new lunar probe, both unproven, greatly increased the odds of failure.) Surveyor 1 landed on the Sea of Storms on June 2, 1966, and sent back more than 11,000 high-quality color photos, along with seismological data and other information, over a six-week period. The photographs, the first taken on another celestial body by a U.S. spacecraft, showed a desert-like landscape strewn with rocks.46

  The American robotic probe was not, however, the first spacecraft to achieve a soft landing on the moon or to demonstrate that a spacecraft could land on the lunar surface without sinking into it. Those honors had gone to the Soviet Union four months earlier, when Luna 9 made a soft landing in the same Sea of Storms area as Surveyor 1. Luna 9 opened the metal petals forming the spacecraft to stabilize itself on the lunar surface and soon began to transmit a series of television pictures, which were assembled into a panoramic view of the lunar surface, including the horizon nearly a mile away. However, Surveyor 1’s images were of a much higher quality; in addition, at least five prior Soviet attempts to achieve a soft landing on the moon between April 1963 and the end of 1965 had failed. Each of the five had either impacted at high speed or missed the moon completely.47 Surveyor 2 crashed into the moon, but Surveyor 3 performed perfectly, landing on April 19, 1967, at the edge of a shallow crater, also in the Sea of Storms. It sent back more than 6,300 photographs and used its robotic arm, or claw, to dig trenches in the lunar surface and examine its consistency. Surveyor 3’s achievements would yield the landing site used by Apollo 12 in November 1969. Three more Surveyors performed superbly before the program’s final mission in January 1968, demonstrating the feasibility of manned landings and explorations of the lunar surface.48

  The final space probe in NASA’s pre-Apollo exploratory triad was the Lunar Orbiter, managed by the Langley Research Center. Its mission was to photograph the moon so that accurate maps could be prepared and the best landing sites for the coming Project Apollo landings selected. Five Lunar Orbiters, each weighing 800 pounds, were launched between August 1966 and August 1967. All were highly successful, returning 200 pictures each. In addition to mapping nearly all of the lunar surface, Lunar Orbiters also mapped the moon’s gravitational field and provided data on radiation levels on and around the moon. Once in lunar orbit, the robotic probe used its velocity-control rocket to adjust its orbital parameters, allowing it, for example, to draw closer to the lunar surface for more detailed photographic coverage.49

  Eastman Kodak, the pioneering giant of American photography, developed a special camera for Lunar Orbiter that enabled it to take blur-free images as it flew around the moon at thousands of miles an hour. A complex system monitored the spacecraft’s altitude and velocity above the lunar surface, adjusting the film as each picture was taken to compensate for the camera’s motion. Kodak’s system produced photos of extraordinary quality, with resolution down to three feet, a vital aspect in helping select Apollo landing sites.50 The pictures were so good that the Soviet Union used them to map out its own potential manned lunar landing sites beginning in 1968, since they were better than any captured by their own spacecraft. Some NASA officials objected to making the Ranger, Surveyor, and Lunar Orbiter images public, fearing that the details could help the Soviet Union fly to the moon. But they were overruled because the 1958 legislation creating NASA mandated the “widest practical and appropriate dissemination of information…for the benefit of all mankind.”51

  Even as NASA’s vast and successful program of scouting the moon was concluding, the Soviet Union continued with its own unmanned lunar missions under two programs, Luna and the later Zond series. Beginning with Luna 1 in 1959, the Russians carried out 20 successful missions of their own, including a number of important firsts: first probe to hit the moon; first flyby and photographs of the far side of the moon; first soft landing; first lunar orbiter; and first probe to circle the moon and return to Earth. Several of these feats were repeated as many as four times. Like the American space probes, several Luna lander missions were tasked with obtaining close-up photographs of the moon’s surface to help assess the feasibility of manned lunar landings.52

  Both sides also moved aggressively to send robotic space vehicles beyond the moon, to explore Venus and Mars, Earth’s two neighboring planets. Both have fascinated mankind for centuries. Mars, with its mysterious surface “canals” fueling endless speculation about the possibility of life there, was the first planetary target of the space age. The Soviet Union launched two unsuccessful Mars probes in 1960, and three more, one intended as a Mars lander, were attempted in 1962. Though its communications failed en route, one of these, Mars 1, was the first spacecraft to fly past the red planet, at a distance of more than 122,000 miles, in June 1963. Two NASA Mariner spacecraft launched in 1964 to fly past Mars yielded a major success in July 1965, when one of them, Mariner 4, passed within 6,118 miles of the planet, returning 22 photos showing Mars’ cratered surface and confirming the composition of its thin atmosphere. Mariner 3 failed, but the overall mission nonetheless was considered a great success in terms of increasing human knowledge of one of the Earth’s closest planetary neighbors. Mariner 6 and Mariner 7 continued America’s Martian exploration successes when both flew by the planet in 1969, sending home hundreds more
surface photographs and additional surface and atmospheric temperature and pressure information. Both sides have continued sending spacecraft toward Mars, though the Russians have had very limited success despite their many attempts. Only one of its probes, Mars 5, successfully orbited and photographed the planet, in 1974.53

  The Russians were more successful in their effort to explore Venus, even though the first successful mission there—actually the first machine from Earth to reach another planet—was the American Mariner 2 spacecraft. It flew past Venus in December 1962 at a distance of 21,600 miles, returning information on the planet’s temperature and the thick clouds that covered it. However, the Soviets achieved a major coup in March 1966, when the Venera (“Venus”) 3 spacecraft, a product of Korolev’s design bureau, crashed on the Venusian surface. It was the first space probe ever to hit another planetary body. Venera 2, launched four days before Venera 3, flew past the cloud-shrouded planetary hot house at a distance of 15,000 miles. In 1970, Venera 7 became the first probe to send back data from the surface of another planet, an especially impressive achievement considering that Venus’s surface temperature is roughly 932°F. The Russians’ remarkable successes with Venus probes continued unabated into the 1970s and well beyond, including the first photos sent from the planet’s surface in 1975 and later orbital missions to map the planet. The United States also continued to explore Venus.54

  Only a handful of planetary probes, all of them American, have ventured beyond Venus, Mars, and Mercury. Given the vastness of space, trips to the outer planets—Jupiter, Saturn, Uranus, Neptune, and Pluto—require space probes able to survive a journey of years. The first of this hearty genre was Pioneer 10, launched in 1972. It flew past Jupiter in December 1973 to become the first spacecraft to reach the outer planets, going on to achieve another first as well when it left the solar system. In December 1974, Pioneer 11 also flew past Jupiter. Both probes provided color photos of Jupiter’s clouds. Continuing its astonishing space journey, Pioneer 11 passed Saturn nearly five years later, in September 1979, providing information on the ringed planet’s environment.55

  Closer to home, Earth satellites continued to revolutionize life on a global scale, providing highly accurate weather forecasts and radio and television links. Other satellites mapped the Earth’s surface and spied on the Soviet Union, monitoring its military activities. Of all these spacecraft, communications satellites have had perhaps the greatest significance for the lives of average Americans.

  Arthur C. Clarke, noted author and scientist, predicted a future where artificial Earth satellites would link the globe electronically, a prophecy he made in 1945. He advocated placing three satellites in geosynchronous orbit. (Such satellites are placed directly above the Equator at a height of 22,240 miles. They remain over the same spot on Earth, circling the planet once each day.) Three such satellites could “cover” the Earth’s entire surface, Clarke posited, and therefore be able to relay communications globally. With the advent of the space age, implementation of Clarke’s concept became possible, though not right away. The earliest communications satellites were much less ambitious, starting with the Air Force’s 1958 orbiting of an entire Atlas missile carrying a tape recorder that broadcast a message from President Eisenhower. That was followed in 1960 by Echo, an orbiting mylar-covered balloon that relayed radio signals bounced off its surface from one point on Earth to another.

  The next major advance in satellite telecommunications was Telstar, an experimental satellite launched into orbit by NASA for American Telephone and Telegraph (AT&T) in July 1962. Telstar successfully relayed television signals for the first time from Europe (France) to the United States, a feat not possible with traditional TV broadcast signals. These signals travel in a straight line rather than follow the curve of the Earth, with a range of only about 50 miles from the point of broadcast. Telstar made international television a reality by amplifying and retransmitting the television signals across the Atlantic. By 1965, Hughes Aircraft had developed and orbited “Early Bird,” the world’s first operational commercial communications satellite, or comsat, as it came to be known. Early Bird, just as Clarke had written two decades earlier, was placed in geosynchronous orbit. It provided the capacity to handle hundreds of telephone calls simultaneously, offering a more economic alternative to the undersea cables. There was, however, one interesting exception to Clarke’s original proposal: Signals from geosynchronous comsats do not transmit well to Earth’s northern regions. This was an important issue for the Soviet Union, since much of its landmass lies in the far north. The Soviets solved this problem by developing their own system of Molniya (“lightning”) comsats, which use a highly elliptical, or egg-shaped, orbit carrying them high over the northern hemisphere.56

  From the mid-1960s comsats proliferated in number, capability, and sophistication. They permanently have altered human communication by voice and data transmission and have provided entertainment and news in the form of television and other electronic signals. Among all the changes that came with the space race, communications satellites have had a profound and continuing influence on modern life.

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  GETTING HOME

  When asked to name the most beautiful thing he had ever seen on a space mission, astronaut Wally Schirra replied, “The parachute opening.” A spacecraft in orbit has reached a kind of summit, an achievement won through great effort. However, like a mountaineer on the peak, a spacecraft in orbit has accomplished only half of the journey. “We established very clearly at the outset that this was supposed to be a round trip,” Schirra used to say. Getting home, from a summit or from orbit, takes getting down, and the route back must be negotiated with care, for it can prove just as fatal as the route up.

  To return to Earth from space, a spacecraft must line itself up on a precise approach trajectory to hit the Earth’s atmosphere at just the right angle. Much like a jet lining up on a short runway in the Andes, the spacecraft has very little room for error. Too shallow an angle, and the spacecraft could shoot back out of the atmospheric curvature and fly off into space without the power to return. Too steep an angle, and the spacecraft will burn up. An Apollo spacecraft had to hit the atmosphere within half a degree of 6.49 degrees in order for it to begin a successful reentry run.

  The main problem of reentry from orbit into the Earth’s atmosphere is like the problem of getting there in the first place: It is not so much the height as it is the speed. If a spacecraft at orbital altitude could simply free-fall straight down to Earth like a skydiver, reentry wouldn’t really be so difficult. The orbiting spacecraft cannot do this, however, because of the high speed at which it is moving. The spacecraft could fire braking rockets to slow it to a gentle speed—if it carried strong enough engines and sufficient fuel. But it took the strength of an entire rocket booster to accelerate the spacecraft from zero to orbital velocity of 17,500 miles per hour. The energy to cut that speed back down to zero has to come from somewhere. No space vehicle yet built has been able to bring that kind of rocket power with it into orbit, so rocket engineers use atmospheric friction to slow the returning spacecraft for a survivable landing.

  Home from the moon: Apollo 8 photographed during Earth reentry, December 1968.

  Air friction offers a considerable braking force, but friction causes heat, just as you can quickly heat your hands with a vigorous rub. At the “vigorous” speed of a supersonic airliner, the nose of the Concorde commonly reached 260°F, with the rest of the plane’s fuselage topping out at around 200°F, almost hot enough to boil water. The Concorde encountered this boiling heat at Mach 2. From an orbital velocity of Mach 25, a spacecraft dropping into the atmosphere must endure air-friction temperatures in the thousands of degrees. Constructing spacecraft to survive this harrowing trial challenged both Soviet and American engineers, and while the basic problems were the same, each side worked out slightly different solutions.

  American space capsules took the form of squat cones with a roun
ded blunt end built as a heat shield designed to take the brunt of reentry punishment. The Apollo moon missions raised the challenge even higher than orbital reentry, increasing spacecraft speeds up to Mach 32, or some 25,000 miles per hour. The capsule and its returning astronauts would be surrounded by temperatures reaching 5,000°F, as hot as the sun’s corona. Nothing that we could engineer could long endure the full force of such an assault, so Apollo engineers built the spacecraft’s heat shield on the principle of ablative material: Phenolic resin in the cells of a honeycomb shield was designed to melt, absorb the tremendous heat, and then flake away, taking the heat with it.

  To reduce the force of the reentry, Apollo spacecraft used small maneuvering thrusters to afford it some steering control through its orientation. Blunt face on, the capsule produced maximum drag and fell. Designed with the center of gravity offset, the ship would tilt forward slightly, and in this orientation the capsule produced some lift, and could “surf” upward for a limited time. With these techniques an Apollo capsule traced a roller-coaster path, plunging the capsule into the thick of the atmosphere to burn off speed, but then tilting it upward to rise and cool before turning down again for another plunge. Two such peaks cut down on the maximum heat levels and reduced the required thickness of the heat shield.