In December 2003, America’s commemoration of the hundredth anniversary of the Wright brothers’ first heavier-than-air flight took place in Kitty Hawk, North Carolina. I had considered riding down to the Outer Banks from Durham to watch the event, but it turned out to be a cold, rainy day, and I wasn’t too excited about seeing the actor-turned-scientologist John Travolta introduce President Bush. At Duke, the folks in our lab were hoping Mr. Bush would announce NASA’s return to the Moon. I skipped it, nothing happened, and the Wright biplane replica didn’t get off the ground.

The celebration of powered flight...

The space lexicon is famous for acronyms and buzzwords; some are quite useful, but others are peculiar or even confusing. As far as I can tell, the curious nonspecialist needs a simple working vocabulary that can handle three things: an idea of destinations and distances, a nomenclature for the technological and biological aspects of spaceflight, and a framework for the approaches that can limit risk and prevent damage to people who are planning to travel such distances.

Ours is the only habitable planet in our Solar System, so in space, we will be stuck living inside cocoons or artificial space...

A good student of World War II knows that after the Axis’s defeat the United States and the Soviet Union gathered up highly trained German scientists and sequestered them in government laboratories to work on ballistic missile programs. This legendary translocation of scientists, including some avowed Nazis, kindled the breakthroughs in rocketry that produced missiles powerful enough to deliver atomic warheads anywhere in the world with stupefying precision and accuracy. Rocket technology was the heart of the nuclear arms race and the philosophy of nuclear détente that instilled the fear of atomic annihilation into the world. The science of mighty...

The technological history of human spaceflight is heavily chronicled (Compton 1989, NASA 1997, Dick 2007), but this chapter will explain how our knowledge of the problems of putting people into space has evolved and how the remaining issues can be resolved through perseverance, continuity, and international cooperation. Let’s begin with a short synopsis of the development of the key twentieth-century concepts that built on the requirement for hard-shell engineering discussed in the last chapter.

NASA’s seminal manned spaceflight program, Project Mercury, had one objective: to prove that people could survive spaceflight. The obvious first principle was to avoid people suffocating...

America spent $3 billion 1972 dollars for each of the twelve astronauts that went to the Moon—an extraordinary outlay, given the meager scientific return on the Apollo program. This was not lost on the scientific elite of the 1970s, and thirty years later, the Moon-Mars initiative found itself in the same boat, and cost overruns and poor planning prevented it from weathering its own storm. Americans have expectations of a real return on the space program, but no one really seems to know what this means.

Part of the problem is the conquest mindset, a holdover from the Cold...

The vision of a future pantheon of space explorers leading us across vast expanses of space to other worlds mirrors the major historical migrations of societies on Earth. This fantasy of the science fiction writer often deals with overcrowding and the tides of war, but migrations on Earth also fail because of the vicissitudes of geography, climate, and trade. The success or failure to disperse involves many variables, but ultimately, the comportment of the community accounts for all outcomes. Societies that collapse may not be distinguishable at first from durable ones with respect to adaptability and resourcefulness, failing only later...

Biologists and engineers think of dynamic living systems as open or closed. In other words, the inputs are either consumed or conserved, regardless of anything else. However, every living system requires energy as a consumable input. An open system has access to all of its resources—O₂, H₂O, food—and consumes them. As resources are consumed, waste is excreted (or accumulates), and nothing is recycled apart from certain expensive biochemical factors and cofactors that do not concern us here.

Open systems operate in one direction, and waste is disposed of; we consume O₂ and hydrocarbons and eliminate CO₂, ammonia, some...

Every school child is told that Sir Isaac Newton discovered the law of gravity while sitting under an apple tree, but the grip of the ancients, dating to Aristotle, had been broken by Galileo’s demonstration that heavier-than-air objects, regardless of weight, fall with a constant acceleration. This acceleration is caused by gravitational force, g, and the physical attraction between two objects. Gravity is proportional to the masses of the objects and to the inverse square of the distance between them. Objects dropped or thrown always fall to the ground, pulled toward the center of the Earth with a force of...

So far, the challenges of human space exploration may seem to you as if they could be managed through technological and biological innovation. This is a reasonable supposition if we are tenacious enough and if costs can be managed, and the opportunity for future space exploration and exciting new spinoff technologies seems high. However, we have yet to discuss the silent but sizzling showstopper, ionizing cosmic radiation. Unlike the earlier problems, protection from cosmic radiation is a matter for neither simple hard shells nor biological adaptation.

This cosmic ray dilemma, as I say, will take time to solve. Some top...

You might think that by now we could have developed a coherent plan for human space travel, but the lack of information on the hazards of life outside the Van Allen belts, where only a handful of Apollo astronauts have ever been, means that all bets are off. The longer-term effect of radiation on the human body is still a big unknown, and sound statistical thinking points out weaknesses in our understanding rather than a solid estimate of risk. Other unknowns must also be taken into account in putting together a sequence of steps for space exploration. The rationale for...

The title of this chapter echoes a series of symposia as well as Robert Zubrin’s (1996) intriguing book. Zubrin and like-minded people are highly vocal about their view of Mars exploration: within a decade, they claim, current technology could carry us to Mars. Diametrically opposed are the folks who say that sending robots is cheaper and safer, especially since it is looking more likely that there has never been life on Mars. But here again we see the unnecessary dichotomy between man and machines.

Mars activists argue that the so-called Siren of the Moon has seduced NASA into ignoring the...

We are approaching the point in our technological development where large-scale explorations of the Moon and Mars are becoming feasible twenty-first-century objectives. The outer system, however, is six times larger than the inner system, and beyond Mars reside four giants, hundreds of moons, and a tapestry of dwarf planets and small solar-system bodies, a few of which could be intriguing places to explore. We would need a special reason to send people to them, particularly since an entire other world, Mars, could preoccupy us for the next five hundred years.

For better or for worse, astronomers decided finally to define...

You may be scratching your head and wondering what’s next. I have presented hard science and sprinkled it with bits of speculation, but now I must mainly speculate and sprinkle it with bits of science. You might want to visit another planetary system, but just in thinking about how to explore our own I have had to push our technology well into the future. Interstellar travel is notoriously intractable because of the limitations of physics (the speed of light) and of biology (the metabolic rate). This means no wormholes, quantum entanglement, tachyons, multiverses, or other exotic physics that does not...