Kevin Sites in the Hot Zone - Chapter 15: Coming HomeIn this final chapter of "A World of Conflict," Kevin Sites returns home to the U.S., only to confirm what he suspected -- that in the year that he was gone little had changed.

Kevin Sites in the Hot Zone - Chapter 14: Israel-Hezbollah WarThe war between Israel and Hezbollah shook the landscape in the Middle East.

Kevin Sites in the Hot Zone - Chapter 13: Sri LankaKevin Sites covered Sri Lanka as violence erupted between the government and Tamil Tiger rebels, pushing a nation with so much to lose back to the brink of all-out war. In rebel-held territory Sites interviewed Tiger fighters about their tactics and reported on the many effects of war still seen in the region.

Kevin Sites in the Hot Zone - Chapter 12: Nepal and KashmirKevin Sites covered Nepal during a time of sweeping political change that followed mass nationwide protests, forcing the autocratic King to cede power.

Kevin Sites in the Hot Zone - Chapter 11: Child BrideIn Afghanistan, Kevin Sites met a 12-year-old girl named Gulsoma, whose incredible story of resilience resonated with millions of people worldwide. She was only six years old when she was sold to a neighbor family in Kandahar as a child bride.

Kevin Sites in the Hot Zone - Chapter 10: AfghanistanReporting from Afghanistan in spring 2006, more than four years after the U.S.-led coalition ousted the Taliban, Kevin Sites found that war is not over in the country.

Kevin Sites in the Hot Zone - Chapter Nine: ChechnyaIn Chechnya during the winter of 2005-2006, Kevin Sites reported on a region still reeling from lingering conflict between Russia and Islamic separatists. The conflict engulfed Chechnya in the 1990s, and even now, half of the population is yet to return. Those that have eke out a living amid the rubble.

Kevin Sites in the Hot Zone - Chapter Eight: Iran

Kevin Sites in the Hot Zone - Chapter Seven: IsraelIn Israel, Kevin Sites interviewed Kinneret Boosany, a victim of a suicide bombing at a Tel Aviv cafe in 2002.

When skin cells from a dead pit bull named Booger gave rise to five healthy-looking puppies with a $50,000 price tag, it marked the formal beginning of a commercial dog-cloning industry.

But for all the attention given to these and other clones, little was paid to the behind-the-scenes science. For every successfully cloned animal thrust into the spotlight, how many failures were quietly ushered out of sight?

"What we're seeing with the clones they present are the ones that look good," said Jaydee Hanson, an animal-cloning analyst at the Center for Food Safety, a Washington, D.C.-based liberal nonprofit.

In March, the U.S. Humane Society and American Anti-Vivisection Society released a report castigating pet cloning for "serious animal suffering and disreputable activities." Critics point to the general tendency of animal embryos to fail before they're born, and for survivors to develop debilitating diseases. And dogs, it's widely agreed, are among the hardest of all animals to clone.

These are serious charges for a nascent industry comprising, for now, just two startup companies: the South Korea-based RNL Bio -- Booger's cloners -- and California-based BioArts International, who in July promised clones to four high bidders and a contest winner.

RNL Bio's charge of $50,000 for Booger's clones was heavily discounted, and BioArts' bidders paid $150,000 apiece, but prices could drop if the procedure becomes popular. That could make cloning an option for many of the United States' 50 million dog owners, but disfigured and diseased outtakes would turn the joy derived from copying their canine into horror.

Yet defenders of the industry say that it's wrong to apply analogies taken from other species' clones: Despite the difficulties, they insist, cloned dogs tend to be healthy, not least because scientists have spent the last decade figuring out how to do it.

"Clone enough dogs, and occasionally you have offspring that aren't perfect," said Lou Hawthorne, CEO of both BioArts and the late Genetic Savings and Clone. "But it's comparable to what you have through conventional breeding."

At cloning's root is a procedure called somatic cell nuclear transfer: Scientists scoop the nucleus out of a fertilized egg, then replace it with the nucleus of a cell taken from a pet. It's the same process used to generate genetically matched human embryonic stem cells for therapeutic purposes. But unlike those embryos, which are destroyed after a few days, the canine embryos are implanted in the hope of eventually becoming adults.

The developmental process magnifies any flaws, the most fundamental of which involve epigenetic programming -- patterns of genetic activation and inactivation that are acquired rather than inherited. A sperm cell involved in traditional reproduction undergoes extensive changes during development, but the donor cells used in cloning come from so-called adult sources, such as skin. They underwent completely different programming.

Though cloners try to reverse-engineer the original process, it often proves difficult, if not impossible. There's also a mismatch between the DNA of a cloned embryo's new nucleus and the DNA of its energy-regulating mitochondria, which come directly from the mother and are already present in the egg.

For these reasons, getting a cloned embryo to survive to birth is tricky and often results in failure. Among livestock, where animal-cloning efforts have been concentrated, many surviving clones die shortly after birth; if they live to adulthood, they often suffer from organ malfunction, metabolic disorders and cancer.

"Most of the animals die in utero," Hanson said. "Then another group dies within a few days right after birth. And of the ones that live 150 days, about half of those die."

"The biological abnormalities inherent to the cloning procedure will always make cloning inferior to natural breeding," said Konrad Hochedlinger, a Harvard Medical School cloning expert. "I don't think we will ever be able to fix the biological problems. The process of fertilization is fundamentally different from sticking DNA into an egg and generating clones."

Adding to the challenges, dogs are notoriously hard to clone. Females ovulate rarely and randomly, and their eggs are fully mature for just a couple hours out of a six- to 12-month cycle, making them difficult to collect. The eggs are also coated in opaque fats that make them tough to work with.

The first cloned dog, an Afghan hound named Snuppy, was the end result of 1,095 implanted embryos, of which just three developed into pregnancies. One of these resulted in a miscarriage, and Snuppy's only brother died of pneumonia after three weeks.

But according to Hawthorne, there's a silver lining to the complications of canine cloning: Flawed embryos are miscarried or fail to develop altogether.

"The extreme sensitivity of the canine reproductive system means you have to have an absolutely perfect pregnancy," he said. "In other systems, you can just put a flawed embryo in, and get offspring out."

Hawthorne also headed Genetic Savings and Clone, a pioneering company whose six-year run ended in 2006 after producing just three cats and no dogs.

Researchers at that company -- who'd already started canine-cloning work three years before the company's founding -- produced just a single canine pregnancy, and it ended in a naturally caused stillbirth.

"The idea that there's a holocaust of malformed offspring and all these miscarriages is false," said Hawthorne, who insisted that his researchers have learned from a decade of painstaking, often frustrated efforts.

Overseeing BioArts' cloning efforts is Woo Suk Hwang, the former leader of a South Korean research team disgraced for its fraudulent human stem cell findings, but only after cloning Snuppy. Another member of that team was Lee Byeong-chun, who now directs science at RNL Bio.

Hawthorne cited unpublished data showing that 90 percent of his company's cloned dogs are born healthy, a figure comparable to traditional dog breeders. The dogs are given full veterinary exams after birth and again at eight to 12 weeks of age; if they're free of defects that long, said Hawthorne, they should stay healthy.

Carol Keefer, a University of Maryland animal-cloning expert, said that safe dog cloning should be scientifically possible, though she cautioned that conclusive studies haven't yet been conducted.

"There are cases where something appears to go wrong later," she said. "You get that with natural breeding, too. The question is, what's the rate, the big picture? There haven't been that many clones made to get a true feel."

Indeed, cloners have only produced about 40 dogs to date, and all since 2005.

"It is still unknown how the surviving animals will do later in life," reads the Humane Society's report, "as no cloned cat or dog has lived long enough to assess."

Many believe that humanity's destiny lies with the stars. Sadly for us, rocket propulsion experts now say we may never even get out of the Solar System.

At a recent conference, rocket scientists from NASA, the U.S. Air Force and academia doused humanity's interstellar dreams in cold reality. The scientists, presenting at the Joint Propulsion Conference in Hartford, Connecticut, analyzed many of the designs for advanced propulsion that others have proposed for interstellar travel. The calculations show that, even using the most theoretical of technologies, reaching the nearest star in a human lifetime is nearly impossible.

"In those cases, you are talking about a scale of engineering that you can't even imagine," Paulo Lozano, an assistant professor of aeronautics and astronautics at the Massachusetts Institute of Technology and a conference attendee, said in a recent interview.

The major problem is that propulsion -- shooting mass backwards to go forwards -- requires large amounts of both time and fuel. For instance, using the best rocket engines Earth currently has to offer, it would take 50,000 years to travel the 4.3 light years to Alpha Centauri, our solar system's nearest neighbor. Even the most theoretically efficient type of propulsion, an imaginary engine powered by antimatter, would still require decades to reach Alpha Centauri, according to Robert Frisbee, group leader in the Advanced Propulsion Technology Group within NASA's Jet Propulsion Laboratory.

And then there's the issue of fuel. It would take at least the current energy output of the entire world to send a probe to the nearest star, according to Brice N. Cassenti, an associate professor with the Department of Engineering and Science at Rensselaer Polytechnic Institute. That's a generous figure: More likely, Cassenti says, it would be as much as 100 times that.

"We just can't extract the resources from the Earth," Cassenti said during his presentation. "They just don't exist. We would need to mine the outer planets."

A 160-Million-Ton Needle

Interstellar propulsion systems are not a new idea. Rocket scientists, aeronautical engineers and science-fiction enthusiasts have proposed such designs for several decades.

In 1958, U.S. scientists explored the possibility of a spaceship propelled by dropping nuclear bombs out the back, a so-called nuclear-pulsed rocket. The research, called Project Orion, was killed by the signing of the Nuclear Test Ban Treaty and the budgetary requirements of the Apollo Project.

In 1978, the British Interplanetary Society designed a mission to Barnard's Star, almost 6 light years away, using a pulsed fusion rocket fueled by deuterium. Building such a spaceship would require mining the outer planets for fuel for at least two decades, scientists said at the Joint Propulsion Conference this year.

But the thought experiments continue. At the conference, Frisbee presented a theoretical design for a ship using antimatter to propel its way to nearby stars.

Frisbee's design calls for a long, needle-like spaceship with each component stacked in line to keep radiation from the engines from harming sensitive equipment or people.

At the rocket end, a large superconducting magnet would direct the stream of particles created by annihilating hydrogen and antihydrogen. A regular nozzle could not be used, even if made of exotic materials, because it could not withstand exposure to the high-energy particles, Frisbee said. A heavy shield would protect the rest of the ship from the radiation produced by the reaction.

A large radiator would be placed next in line to dissipate all the heat produced by the engine, followed by the storage compartments for the hydrogen and antihydrogen. Because antihydrogen would be annihilated if it touched the walls of any vessel, Frisbee's design stores the two components as ice at one degree above absolute zero.

The systems needed to run the spacecraft come after the propellant tanks, followed by the payload. In its entirety, the spaceship would resemble a large needle massing 80 million metric tons with another 40 million metric tons each of hydrogen and antihydrogen. In contrast, the Space Shuttle weighs in at a mere 2,000 metric tons.

"Interstellar missions are big," Frisbee said, in part because of the massive amounts of energy (and hence fuel) required to get moving fast enough to make the trip in anything like a reasonable amount of time. "Any time you try to get something up to the speed of light, Newton is still God."

With that fuel, it would still take nearly 40 years to travel the 4.3 light years to Earth's nearest neighbor, Alpha Centuri, he said.

Down and Out On Earth

Even improving humans' access to near space is not easy.

Scientists have all but discarded ideas for rockets that can reach orbit using a single stage. Instead, private space ventures have focused on lightening the payload and rocket and on increasing reliability. If space tourism comes into vogue, then launch providers could benefit from economies of scale.

But alternative-propulsion systems? They are not in short supply in people's imaginations, but most fail the test of reality, Marcus Young, a researcher at the U.S. Air Force Research Lab's Advanced Project Group, told conference attendees. Young and his team surveyed ideas for launch vehicles that could be accomplished in the next 15 to 50 years and found most to be unworkable.

Space elevator? Even if the engineering made sense, the design requires a breakthrough in materials science to create cables long and strong enough. Rail guns? A vehicle would have to shoot down a 100-kilometer track at 50 times the force of gravity to achieve orbit. Nuclear power? Radioactivity would limit its use to outside Earth's atmosphere and the politics are positively toxic.

"There are a lot of ideas that initially you say, 'Hey, that might work,'" Young said. "But after a little research, you quickly find that it won't."

Yet, just because science fiction is not yet a reality is not a reason to make science suffer, said MIT's Lozano.

"There is a lot of interesting stuff that you cannot do even in the solar system," he said. "We have the technical means to do it. But some of the most sophisticated technologies ... we have not developed. Not because we can't, but because we have not made it a priority."

As for interstellar travel, even the realists are far from giving up. All it takes is one breakthrough to make the calculations work, Frisbee said.

"It's always science fiction until someone goes out and does it," he said.