Beyond: Our Future in Space (8 page)

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.
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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.”
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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.

The Space Shuttle flew 135 times between 1981 and 2011, sending 300 astronauts into space. In its early years, it was used for a mixture of scientific and military payloads; in its later years, it was used to complete assembly of the International Space Station. It also served as a reminder of the danger and the high cost of space travel.
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On January 28, 1986, a nationwide TV audience was stunned when the Space Shuttle Challenger broke up and exploded in a clear blue winter sky, just seventy-three seconds after launch. Later investigation showed that a leak from an O-ring seal on one of the solid-fuel boosters had led to extreme aerodynamic stress on the spacecraft as it traveled at twice the speed of sound. Millions of schoolchildren were watching because NASA had selected Christa McAuliffe to be the first teacher in space. Chillingly, the crew cabin was intact as the vehicle broke up, so the seven crew members most likely died from subsequent impact in the ocean (
Figure 13
).
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The grief was repeated seventeen years later when the Space Shuttle Columbia disintegrated as it reentered the Earth’s atmosphere at twenty times the speed of sound. During launch, a piece of foam insulation had broken off from the external fuel tank and ruptured the leading edge of the left wing. Fourteen crew members died in these twin disasters.

The Space Shuttle was never as cheap and nimble as planned. Instead of the planned flight each week, the Shuttle managed one flight every two or three months. Over the course of the program, a launch cost about $1 billion, which works out to $80,000 per kilogram placed in orbit. Commercial entities were only able to use the Shuttle with massive subsidies from the government. The US military lost patience with the anemic launch schedule and the fact that two out of five orbiters had been lost catastrophically, so they developed their own heavy-lift capability using rockets without any astronauts.

However, the Space Shuttle did provide case studies in the importance of having astronauts rather than robots work in space. Robots are not versatile or reliable enough to match a well-trained astronaut. We can all admire the “seat-of-the-pants” problem-solving skills demonstrated by Neil Armstrong as he guided Apollo 11 over a boulder field with hardly any fuel left, and by the Apollo 13 crew as they nursed their crippled spacecraft around the Moon and home to safety. In particular, the five servicing missions of the Hubble Space Telescope defined the state of the art for astronauts, with multiple long space walks, challenging technical jobs, and difficult decisions made under time pressure. NASA administrator Mike Griffin had nixed a final Hubble servicing mission, worried about the risk to the astronauts. But in the end he determined that a robot servicing mission was so difficult that it was destined to fail, so astronauts were called on to give Hubble its final upgrade in 2009.

The choice between robots and humans is a false dichotomy. Machines are pathfinders and advance scouts, learning as much as they can and setting the stage for humans to eventually follow. We’ve explored the Solar System with robotic probes so far, but they’re limited in what they can do. Machines are extensions of us as we explore; when we eventually live in space, they will be our partners.