by Chris Impey
Figure 10. A comparison of the Soviet N1/L3 rocket (left) and the US Saturn V rocket (right). The Saturn V was as tall as a thirty-six story building; it had a peak thrust of eight million pounds of force and could lift 60 tons to Earth orbit.
The Moon landings were and still are unprecedented. The twenty-four men who journeyed there are the only people ever to have left the Earth’s gravity, and the twelve who landed are the only people to have set foot on another world.
Despite this feat, and the ingenuity and heroism of the Apollo 13 crew, who in 1970 nursed their crippled spacecraft back to Earth following an oxygen explosion, public interest in the Moon landings waned. Through a misty lens of history, it seems the Apollo program had broad public support. But in fact a majority thought the government was spending too much on space. Both Kennedy and Johnson complained about the enormous cost of the Apollo program, and the final three planned Moon landings were canceled to allow NASA to start work on the Space Shuttle, which was intended to be a “space truck” that could routinely haul astronauts and cargo into low Earth orbit. In effect, it was a retreat from the grandiosity of the Apollo missions.
Yet something profound happened as a result of the Moon landings.
The astronauts were patriots, but they instinctively knew they were representing all of humanity. As they orbited the Earth, many commented on the seamlessness of a planet where no political or cultural boundaries were visible. The iconic image of the fragile Earth hanging in the blackness of space—a blue marble—helped spur the environmental movement in the late 1960s. It is indeed ironic that a supreme feat of the military-industrial complex was embraced by counterculture activists.10 When Frank Sinatra performed “Fly Me to the Moon” on his TV show in 1969, he dedicated it to the astronauts who had “made the impossible possible.” The song’s jaunty melody perfectly captured the lightness of the people who had slipped the bonds of Earth.
Of Mice and Men
The hardest part of space travel is getting there.
For the rocket, the key quantity is Max-Q—the maximum aerodynamic stress due to drag from the atmosphere as the rocket accelerates. The stress is small at low altitude because the speed is lower, and small at high altitude because the atmosphere is thin. Somewhere in between is Max-Q, the moment when engineers watching a launch hold their breaths. For both the Saturn V and the Space Shuttle, Max-Q occurred about a minute after launch, at an altitude of about 40,000 feet.
For any occupant of the rocket, there’s buffeting and vibration, but the maximum hazard is presented by g-forces. We spend our lives subject to a downward acceleration of 9.8 meters per second per second, or 1 g. As flexible, water-filled sacks, we’re fairly tolerant of acceleration, but it depends on the direction. Fighter aircraft pilots can handle a positive 8 or 9 g’s, where the blood is being forced to the feet, as long as it lasts no more than a few seconds. But minus 2 or 3 g’s, when blood is being forced into the head, can cause blackouts and even death. Air Force Colonel John Stapp, a flight surgeon, risked his life to test these limits in the 1950s. Stapp was repeatedly strapped into a rocket sled, and in one test he survived a momentary force forty-six times stronger than normal gravity. The colonel suffered broken limbs and permanent vision loss due to these experiments, but he still managed to die peacefully at home at the age of eighty-nine.
The Apollo astronauts felt a maximum of 4 g’s just before the huge main-stage engines shut off, and close to 7 g’s when they reentered the Earth’s atmosphere. Space Shuttle astronauts, on the other hand, pulled no more than 3 g’s on either ascent or descent, something you could experience on any decent roller coaster. But early in the Space Age, medical science was unsure if people could survive the rigors of space, so a lot of experiments were done using mammals as test cases. This continued a long tradition; in 1783, a sheep, a duck, and a rooster were sent up in the recently invented hot-air balloon.
Laika is one of the unsung heroes of spacefaring. She was a husky-terrier mix, a stray dog found wandering the streets of Moscow. Soviet scientists preferred strays because they thought life on the streets would have made them resilient. Laika was chosen from among ten dogs due to her phlegmatic temperament. After being subjected to centrifuges and noisy environments, she was conditioned for the tiny capsule by being confined in successively smaller spaces for periods of up to three weeks. Nikita Khrushchev put great pressure on mission designers, wanting a launch in time for the fortieth anniversary of the Bolshevik Revolution. So Sputnik 2 was prepared in a hurry and launched, with Laika aboard, less than a month after Sputnik 1.
Early data showed that Laika was agitated but eating her food. However, the temperature-control systems were inadequate, and she died from overheating and stress after seven hours in orbit. There was never any possibility of her surviving the flight; poisoned food had been prepared to euthanize her before the fiery reentry. At the time, it was reported that she died when her oxygen ran out on the sixth day of the flight. Animal rights groups protested at Soviet embassies around the world, and there was a demonstration at the United Nations in New York.11 Years later, when the Soviet Union fell and scientists could speak freely, some did express remorse. Laika’s trainer, Lieutenant General Oleg Gazenko, admitted, “Work with animals is a source of suffering to all of us. We treat them like babies who cannot speak. The more time passes, the more I’m sorry about it. We shouldn’t have done it. . . . We did not learn enough from this mission to justify the death of the dog.”12
While the Soviets used dogs, the Americans preferred monkeys due to their similarity to humans. The first monkey in space was Albert, launched on a V-2 rocket in 1948. Albert died of suffocation. For the first decade of such experiments, the fatality rate was very high. In 1959, Able and Baker became the first US animals to fly into space and return alive, withstanding 32 g’s along the way. Able was a rhesus monkey who died soon afterward during a surgical procedure, but “Miss Baker,” a squirrel monkey, survived another twenty-eight years (Figure 11). She got as many as 150 letters a day from children and was buried on the grounds of the US Space and Rocket Center in Huntsville, Alabama. Three hundred people attended her funeral.
Figure 11. ”Miss Baker,” a female squirrel monkey from Peru, was the first monkey to survive spaceflight. She ascended to an altitude of 360 miles in the nose cone of a US Air Force ballistic missile, surviving 32 g’s and reaching a top speed of 10,000 mph.
Fruit flies were the first animals of any kind sent into space, aboard a captured Nazi V-2 rocket in 1947. They were followed by mice, then monkeys, then men and women.
Since then, a menagerie of animals has made the trip. By the early 1960s, both the Americans and the Soviets had launched mice into space, and the Soviets added frogs and guinea pigs to the launch personnel. France got into the act with rats, and in 1963 they planned to launch Felix the cat, but Felix had other plans and he escaped, so they sent up Félicette instead. In 1968, two tortoises became the first animals to go to the Moon, aboard Zond 5. They were accompanied by wine flies, mealworms, and other biological specimens. A few years later, America sent mice and nematodes to the Moon on Apollo 16 and Apollo 17. The Space Shuttle facilitated animal space travel, and now spiders, bees, ants, silkworms, butterflies, newts, sea urchins, and jellyfish have all been in orbit. Astronauts have had reason to be wary of some of their passengers, especially Madagascar hissing cockroaches and South African rock scorpions.
Most of these hazardous trips were to low Earth orbit, a few hundred miles, or just an afternoon’s drive straight up. Even the round trip to the Moon is less than half a million miles, a distance many business people rack up every few years on atmospheric jet travel.
By contrast, the planets seem far beyond reach.
Exploring the Planets
NASA’s budget never again reached the giddy heights of the mid-1960s. As a percentage of the federal budget, NASA soared from its inception to a peak of 5.5 percent in 1967 and then fell just as rapidly down to 1 percent in 1973. It has
bumbled along below 1 percent ever since.13 In the 1970s, the agency embraced a different challenge, albeit not one as grand and dramatic as having astronauts cavort and drive on the Moon.
A critical transition in the history of ideas is the shift from an Earth-centric worldview, where our planet is seen as special and unique, to a “many worlds” concept, where objects in space are physically and geologically familiar. Space travel brings those worlds into view in a way that can’t be approached by telescopic observation.
Before 1610, the planets were just nontwinkling dots that drifted across a celestial backdrop. The Moon had craters and dark “seas” that the eye could interpret as imaginary figures. When Galileo pointed a telescope at the Moon, he observed a surface that, “. . . just like the face of the Earth itself, is everywhere full of vast protuberances, deep chasms, and sinuosities.”14 But this paled when compared with what we learned when Apollo astronauts went there, walked over the rugged terrain, and returned with 842 pounds of rocks. Now we know the Moon’s age to within an accuracy of a percent, we know its geological history, and we know it formed out of debris from an impact on the infant Earth.
Several hundred years of observations with telescopes uncovered a handful of additional planets but revealed almost nothing about their true nature. They remained small, blurry disks of light. The exception was Mars, which had pale poles and a network of features that, in the wishful thinking of amateur astronomer Percival Lowell, represented an irrigation system of a Martian civilization. Even a nearby planet like Mars is so far away that telescopes reveal little of its physical reality. As recently as 1966, scientists still argued over whether or not Mars was covered with vegetation.
The context for understanding planetary exploration is the vastness of space. When we progressed from orbiting the Earth to landing on the Moon, it was like leaving our backyard to explore another city. Earth orbit is a few hundred miles up, while the Moon is a quarter of a million miles away. That increase of a factor of a thousand severely taxed our ingenuity. Compared to the Earth–Moon distance, the distance to Mars at its closest approach is 200 times greater, and the distance to Jupiter at its closest approach is 1,600 times greater. Jumping to the edge of the Solar System is another factor of a thousand.
While sending men to the Moon was the Space Race’s big prize, the Americans and the Soviets could test their technology and expand their knowledge of the Solar System by guiding robotic spacecraft to targets hundreds of millions of miles from Earth. Failures were common. In 1958, the Army and the Air Force saw four failed launches of the Pioneer series of probes. Meanwhile, the first three launches of the Luna program also failed, and the Soviets got in the habit of not disclosing launches that failed to reach orbit and not even assigning them a Luna number. But with persistence came success. In January 1959, less than two years after Sputnik shocked the world, Luna 1 was the first manmade object to leave Earth’s gravity. By the end of 1959, its successors Luna 2 and Luna 3 had crashed into the Moon’s surface and taken photos of its crater-pitted dark side. The scientific payoff from these probes was substantial, yielding information on the chemical composition, gravity, and radiation environment of the Moon.
In 1962, the United States achieved the first planetary flyby, as Mariner 2 swooped within 20,000 miles of Venus. Two years later, Mariner 4 executed the first flyby of Mars. Getting a planetary probe to its target was a technical tour de force. In a golfing analogy, the flybys were like hitting the ball 400 yards off the tee to within an inch of the hole.
Landing spacecraft and returning data from these planets was much harder.
The Soviets succeeded first, when Venera 7 landed on Venus and sent back twenty-three minutes of data in 1970. But that was after fifteen attempts. Before the Venera series, three spacecraft failed to leave Earth orbit and another exploded. When the Soviet Mars 3 lander sent back less than twenty seconds of data in 1971, it came after seven failed missions. The Soviets had such trouble with their Mars missions that they gave up trying to get there for more than a decade.
As NASA engineers started to apply their expertise to exploration of the Solar System, the agency realized they had no one there to do the science. So they cajoled and bribed universities into hiring faculty and postdocs, and the academic field of planetary science was born. The field was an amalgam of geology and astronomy and attracted its fair share of iconoclasts and larger-than-life figures.
The learning curve for planetary exploration was brutal, but the results were spectacular. In the wake of Apollo, a young and ambitious cadre of planetary scientists worked with NASA to launch twin orbiters and landers to Mars (Viking 1 and Viking 2), probes to Jupiter and Saturn (Pioneer 10 and Pioneer 11), and probes to outer planets Uranus and Neptune (Voyager 1 and Voyager 2). These missions from the 1970s were hugely successful. The Pioneer 10 and 11 probes, launched in 1972 and 1973, respectively, both flew by Jupiter and its moons; Pioneer 11 got a close look at Saturn too. They each carried a golden plaque etched with human figures and information about the origin of the probes, in case aliens would one day find them. Both have left the Solar System, and Pioneer 10 is more than 10 billion miles from home. The Voyager spacecraft are both still transmitting data more than thirty-six years after their launch in 1977. Voyager 2 visited Uranus and Neptune and Voyager 1 is the most distant human artifact, coasting through interstellar space 12 billion miles from Earth. The Viking spacecraft launched in 1975 released twin landers to different locations on Mars, where they conducted the first and only tests of life in the Martian soil. This was indeed the “golden age” of planetary science (Figure 12).
The pace slowed and planetary science was in the doldrums in the 1980s, but Cassini was launched in 1997 and is still exploring the Saturn system. Cassini is the size of a bus and bristles with a dozen scientific instruments. The spacecraft that traveled a billion miles to view new worlds for the first time saw amazing sights: fractured ice on top of an ocean on the water world Europa, lakes of ethane and methane on Titan, volcanoes on Io coating the tiny moon with an inch of sulfur every year, moons as dark as soot and as bright as a mirror. Cassini dropped the Huygens probe for a soft landing on Titan in 2005, revealing an exotic world with lakes and rivers, clouds and rain. Huygens was a 300-kilogram spacecraft that sampled the atmosphere and took pictures of the surface for a few hours before its battery died. It’s still the most distant landing of any manmade craft.15
Figure 12. The first image ever returned from the surface of another planet. Viking 1 landed on Mars on July 20, 1976. The close-up view of Mars as an arid, frigid desert replaced decades of speculation about the red planet. The rock near the center is 10 cm across.
Digital cameras on planetary probes showed that these remote worlds had distinctive features and “personalities.” Instead of a single pixel, the new cameras transmitted millions of pixels. In 1990, when Voyager 1 got to the edge of the Solar System after traveling for twelve years and four billion miles, it reversed the usual situation. Looking back, it snapped a picture of the Earth, which was no more than a mote of light on a dark backdrop. Carl Sagan called this evocative image the “Pale Blue Dot,” and he used it to issue a clarion call for humanity to get its house in order: “Our planet is a lonely speck in the great enveloping cosmic dark. . . . there is no hint that help will come from elsewhere to save us from ourselves. . . . This distant image of our tiny world . . . underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.”16
Man versus Machine
The difficulties we have getting there remind us of the fact that we weren’t made to live in space. Let’s consider what happens to an unprotected human there.
Imagine you’re at one end of a large space station in a room with air but no food or water. You have no spacesuit. Safety lies at the end of a long tunnel whose wall has been ruptured by a meteorite impact, leaving pure vacuum inside. You estimate it will take you five seconds to
propel yourself to the end of the tunnel and perhaps another ten to open the air lock and get into a pressurized zone. Would you make it?
Not if you took a deep breath. Vacuum is lethal because it makes the air in your lungs expand, rupturing delicate tissue, so emptying your lungs would be a better strategy. Water in your tissues would vaporize and bubbles would form in your veins, but your skin would likely stop you from exploding. It would be unlikely, however, that you could get to safety before lack of oxygen flow to the brain caused you to pass out, which takes roughly fifteen seconds. Death follows in a minute. Compared with these indignities, adjusting to zero gravity is a walk in the park.
Humans have proved capable of living and working in space, but their fragility and the cost of keeping them safe has spurred a long debate over whether it’s better to explore space with men or with machines. Robots have the advantages of being strong, compact, durable, and relatively cheap, but humans have the ability to adapt to any situation and exercise real-time, complex judgments.
The United States thought it had accomplished what it needed to after the excitement and expense of the Moon landings. As NASA funding was dialed back, the agency modified the remaining Saturn V rockets to launch and send astronauts to the Skylab space station. Meanwhile, they began developing a reusable vehicle designed to carry astronauts and equipment into low Earth orbit roughly once a week. The Space Shuttle could carry up to eight astronauts and 25 tons of cargo. Meanwhile, the Soviets gave up on getting men to the Moon after four consecutive failures of their huge N1 rocket; the second exploded on the launchpad with the power of 5,000 tons of TNT. In 1971, they were first to launch a space station dubbed Salyut. But in a chilling example of the hazards of the vacuum of space, the second three-man crew to visit Salyut suffered depressurization of their capsule as they prepared for reentry. They died of asphyxiation in just forty seconds. With the slow thaw in relations between the two superpowers, the Space Race ended. Détente in space was symbolized by the docking of the Apollo and Soyuz spacecraft in 1975 and a historic handshake between Tom Stafford and Alexey Leonov.