"...His dreams have lost some grandeur coming true,
There'll be new dreams, maybe better dreams and plenty..."

I can empathize with Dr. Bell. In 1968 I stood beside my father inside KSC watching the first crewed Saturn V thunder into the heavens. In 1972 I went to the public viewing area outside KSC to watch the night launch of our first and last scientist sent to the moon.

My father chose to stay at home. Dad, a U of F dept. of EE professor who taught NASA engineers at KSC via closed circiut TV, told me way back then that the age of human space exploration had already ended.

As unwelcome as those words were to the ears of an adolescent full of SciFi dreams, Dad was correct. The robotic space exploration future had already begun with Mariner and Pioneer.

Since then, international commercial launch costs have come down only modestly, while available computing power has expanded exponentially. The advantages of robotic explorers continue to increase.

Since the return of Dr. Harrison Schmidt from the Moon, nothing has been done in space by humans that could not have been done more economically by machines. The centerpiece of the Shuttle program was Hubble servicing.

Yet it is easy to demonstrate that both astronomers and taxpayers would have been better served by a series of expendable Hubbles launched by expendable boosters.

I agree with Dr. Bell that the best chance to establish a sustained human presence in space has long passed, if it ever even existed in the first place.

The mid 20th century dreams incubated by Tsiolkovsky, Goddard, Von Braun, and Disney were the end product of Victorian astronomy and science fiction.

In that era, it was still believed by many that Mars was little worse than Mongolia, Venus was little worse than Brazil. It was reasonable to dream of humans traveling to nearby worlds suitable for human settlement.

And we could have done it with our old chemical rockets. If an Earth twin had existed in our solar system, we would have colonized it in the 1980s despite the risks and high capital investment cost. But, thanks to our excellent robots and telescopes, we know better now.

Mars is a frigid desert, a near vacuum with the additional annoyances of blowing corrosive dust and space radiation hazard. Die hard dreamers still engage in fantastical speculations about terraforming Mars, but the difficultly of doing so is seldom confronted.

The dream is usually based on the idea that if Mars could be warmed up with orbiting mirrors and maybe a little freon, all the dry ice would sublime, and the atmosphere would thicken fifty fold. Then at least, colonists could live in unpressurized surface dwellings and grow plants in the open. Nice pipe dream, but not possible.

In recent news, it was reported that the Martian polar caps are almost entirely water ice. There isn't enough dry ice on Mars to even double the present meager atmospheric pressure, much less increase it fifty fold.

Perhaps in the far distant future, with extravagant use of fusion power, Kuiper belt bodies could be robotically mined for atmospheric volatiles which, with delta V of a few hundred km/sec, could be dispatched to Mars on cometary trajectories...perhaps. (Of course it would be most foolish to waste energy shipping cometary iron, silicates, and water ice to Mars, which already has these commodities in great abundance.)

The cost of shipping around a million gigatons of refined liquid nitrogen from the Kuiper belt to Mars is left to the imagination. Of course this new atmosphere would have to be continually replenished as a warm Mars would more rapidly lose atmosphere by Jeans escape.

Slightly less outrageously, Titan could be colonized by humans using nuclear power, even old fashioned fission.

The atmosphere is thick enough to afford good protection from space radiation and would allow unpressurized surface dwellings and farms. Biogenic elements are available in abundance.

Colonists could stay as long as they could afford to buy nuclear fuels and manufactured goods. But, it is unclear what products could be exported from Titan to pay the considerable heating and lighting bills.

So let us face the facts. There are not any other sustainable habitable environments in our solar system, and will not be for millinea, if ever. Our astronauts do not have any hospitable destinations.

Eventually, the crust of Mars will need to be drilled to search for evidence of fossil life in ancient sediments or surviving microbial life in underground aquifers.

Advocates of humans in space assert that this could not be done without humans on Mars. Yet, since any such Mars drilling expedition is decades away, it is far from clear that future robots will not be up to the task.

More importantly, the risk of biological contamination of Mars by astronauts might be greater than the benefit of having astronauts present on an astrobiology drilling mission.

The deep subglacial ocean of Europa is another important target for astrobiology research. Yet the extremely high radiation levels on Europa would seem to make human exploration indefinitely impractical.

Our radiation hardened robots will have to drill or melt through the ice on Europa. And we will have to be content with what we might someday learn from robotic probes of Europa's ocean.

If astrobiology on Europa must wait for better robots, why should astrobiology on Mars not wait for robots as well?

No matter what one might wish to do in space, with humans or robots, radically reducing transportation costs is vital. For decades space activists have dreamed of replacing expendable chemical rocket boosters with a fully reusable transportation system that could make frequent routine trips to orbit with little more servicing between flights than a commercial jet.

It was asserted that such a system could provide orbital access comparable in cost to trans-Pacific air transport. No such system has been forthcoming. In the wake of the Columbia tragedy, such a system of routine Mach 25 atmospheric operations seems more unlikely than ever.

The suborbital stunts of the X-prize competition are entertaining, but it is far from clear that these schemes will ever advance orbital transportation. The old space exploration dream is dying.

In fact, the 1950s dreams of a solar system full of human explorers are already dead. We need new dreams for a new century. And we shall have them, better dreams, and plenty.

In this new century, a new generation has accepted the challenge of creating an entirely different type of space transportation. Once a SciFi curiosity, the space elevator is increasingly gaining credibility in materials science and engineering circles.

It is entirely possible that carbon nanotube based fibers with the tensile strength needed for an orbital elevator could be developed within a decade Rice Refining Production Of Pure Nanotube Fibers.

But there is plenty of work to do in the meantime. The first prize competition for climber, tether and power beaming hardware will be held in California within nine months Elevator 2010 Competition. As with the early rocket experiments of Goddard and Von Braun, governments and giant corporations are not yet significantly involved.

It is up to a new generation of dreamers to lead the way. Imagine a world where the cost of lifting payloads to geosynchronous orbit drops more than three orders of magnitude, from over $10,000/kg to under $10/kg.

With these low freight costs, space solar power stations would not only be possible, but would free the world from dependence on fossil fuels forever, creating a sustainable future for all humanity. A better dream indeed, and only a beginning.

In the old stories, starship captains would cross interstellar space in hours or days, and then search for planets upon arrival in a stellar system. The same writers who imagined routine faster than light space travel also believed that the five meter Hale telescope at Palomar was the best that could ever be built.

Planet detection across interstellar distances was assumed to be impossible. Now, we know of over a hundred extrasolar planets. The next several generations of ground based and space based telescopes will exponentially increase planet detection.

Dr. Bell is correct that adaptive optics have allowed our best ground based telescopes to in some respects equal Hubble in visible light observations. But ground based telescopes are blind in the very infrared wavelenghts that will be most useful for detecting and analyzing terrestrial extrasolar planets.

The clarity of the local interstellar medium permits building instruments with microarcsecond resolution. Once we have solved the pesky problem of high freight costs to orbit, we will begin building interferometer telescope constellations, eventually hundreds of kilometers in baseline.

Such instruments would not only be able to use spectroscopy to detect life bearing terrestrial planets, but could image oceans and continents of worlds up to 100 light years away. This volume encompasses over ten thousand stars, several hundred of which are sunlike.

If there are other terrestrial worlds in the neighborhood with liquid water, temperate climates, and tolerable atmospheric pressures, we will find them. And few astronomers doubt that terrestrial planets are going to be at least as common as gas giant planets.

Discovering other Earths around sunlike stars, that is a wonderful dream for this century. Fortunately, both the ESA and NASA have fully embraced this particular vision.

The skeptic will now wonder what will be the utility of detecting Earthlike planets tens of light years away, forever out of reach. Warp drive, wormholes, stargates and all other speculative forms of faster than light travel are indeed all just literary devices for SciFi writers.

But there will be other ways to fly. In a few months, the Planetary Society, a private group, hopes to launch humanity's first functional solar sail The Solar Sail. The same advances in development of carbon nanotubes that could give us a space elevator by mid-century could also give us the technology to build ultra-thin solar sails 333Christensen. Assuming that solar sails could be made with a reflective mesh of doped carbon nanotubes, it would be possible to attain a payload terminal velocity of one percent of lightspeed, under human tolerable accelerations, by using sunlight alone.

Why should we care about human acceleration tolerance? If robots are better than humans for exploration of Mars and Europa, their advantage for interstellar flight should be even greater. Well, the difference is the quality of the destinations.

It is unlikely that anyone will ever wish to live on Europa. In the case of habitable Earth-like planets, humans would certainly wish to go. The biological lure of human colonization would be irresistable. Robots of many types would, of course, be needed and welcome.

So there is no need to exponentially increase humanity's energy production for centuries, no need to strip mine first the Moon, and later the atmospheres of Uranus and Neptune for helium-3 fusion fuel for starships.

Indeed, there is no need to massively industrialize any place in the solar system beyond the elevator terminals and power stations at geosynchronous orbit. We can sail to the stars directly from the elevator ribbon for the price of doped carbon nanotube mesh.

There is no need to build ultra-massive starships either. Any number of small starsailers could depart as a great flotilla with the redundancy increasing chances of success.

Such starsailers cound, in theory, journey from star to star without refueling for as long as the half-life of the isotope used (longer lived than the isotope we used on Cassini) in their radioisotope thermal generators for payload heating and onboard electric power.

Taking along a reel of elevator ribbon, along with climbers, solar panels, and lasers for power beaming would allow our human explorers to ride an elevator down to the surface of their destination planet. No transporter beam or Mach 25 atmospheric aircraft required.

Obviously, our waking attention spans and current lifespans will not tolerate trips of several centuries. This problem also has a promising solution.

Several mammals, including at least one primate, can hibernate, in some cases with a hundred fold decrease in metabolism. ESA is already funding research to better understand this metabolic state in hopes of eventually duplicating it in humans.

Could astronauts sleep their way to the stars?

Travel at one percent of metabolism at one percent of lightspeed is metabolically equivalent to lightspeed travel. One would only consume one year of oxygen and provisions per light year traveled.

These are managable logistics. Drugged hibernation would also prevent in-flight boredom. Anti-aging techniques to extend human metabolic lifespan would be nice but are not essential.

Human interstellar travel, towards Earth-like extrasolar planets could begin by the close of this century. There are no laws of physics, astronomy, or biology preventing it.

Imagine space elevators, a sustainable energy economy, extrasolar terrestrial planet detection, solar sails, human hibernation, and eventually human interstellar colonization, not as Sci-Fi fantasies, but as actual possibilities.

I no longer rage or mourn for the well justified shelving of Von Braun's outdated dreams.

These are new dreams, better dreams, and plenty. But, ossified government bureaucracies and risk averse giant corporations alone can not realize these dreams for us. We each have much work to do before our last revolving year is through. Ad Astra.

Joy Shaffer is a physician in San Jose, California. She holds a Biology degree from Caltech and a Medicine degree from Stanford. Related Links
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