Five years ago, on an otherwise normal Friday morning in Chelyabinsk, Russia, a six-story meteor—seemingly out of nowhere—burst across the clear blue sky as commuters were making their way to work. This surreal fireball—hurtling toward the Earth at 42,000 miles per hour and burning brighter than the sun—was caught on at least a dozen dashboard cameras before it exploded 19 miles above the city. (Nearly every car in Russia is outfitted with a dashboard camera, with footage typically used to settle traffic disputes.)

The blast from the largest asteroid to pierce the Earth’s atmosphere since the 1908 Tungaska event, which flattened some 800 square miles of Siberian forest, damaged 7,200 buildings in six cities, shattering windows and injuring more than 1,600 people.

Suffice to say, the episode was an effective reminder that about two-dozen meteors pop through the Earth’s atmosphere every year, including on average at least one the size of an automobile. It also proved a wake-up call for Congress, which began holding hearings about the threat to U.S. public safety. After all, the next 7,000-ton, flaming rock could just as likely land on I-95 as a Siberian forest.

NASA eventually announced the creation of the Planetary Defense Coordination Office. The big question they needed to figure out, of course, was how exactly do you divert a rogue asteroid from an orbital collision with Earth? How do you design, model, and fly something into a speeding space rock and then measure the change in its trajectory?

The answer came to Andy Cheng, of the Johns Hopkins Applied Physics Laboratory in Howard County, in his basement during his morning calisthenics routine. Cheng realized the simplest approach was to crash a spacecraft into the smaller of a twin pair of asteroids—whose orbits are linked—and then measure the change in the orbit of the smaller asteroid against its larger twin. Up until that point, leading planetary defense scientists, including those at the European Space Agency, assumed they needed to build two spacecrafts—a prohibitive cost—one to smash into the asteroid and a second to document the change in its orbit. Measuring the changes in the asteroid’s rotation and spin against its twin, however, scientists could manage from their telescopes.

“It was a light bulb moment,” Cheng says with a laugh. “I was at home, stretching, in my normal routine before work, and I thought, ‘I know how to do it.’”

The chief scientist of the Space Department at the Applied Physics Laboratory, Cheng jokes he should be retired by now. He well remembers the year he moved to Baltimore (he currently lives in Potomac) to take a job at JHU’s Applied Physics Lab because it’s the same year the Orioles last won a World Series—1983. Instead, the 66-year-old grandfather is the co-lead investigator on the first-ever mission, nicknamed DART (Double Asteroid Redirection Test), to demonstrate an asteroid deflection in real time, in real space, for planetary defense purposes.

“I’m just having too much fun to quit.”

Given the way the threat of asteroids has permeated pop culture, namely end-of-the-world movies such as Deep Impact and Armageddon, it’s easy to forget that the study of asteroids is really new science. We put a man on the moon a decade before the first scientists theorized a giant asteroid had caused the mysterious extinction of the dinosaurs (not to mention three-quarters of all living species) 66 million years ago. That asteroid, with a diameter half the length of Manhattan, dented the Yucatan Peninsula with such force that it’s estimated 330-foot waves crested the shores of what are now Texas and Florida. More significantly, it ignited such an explosion on impact that the ensuing billow of dust, sulfur, and carbon dioxide blocked out the sun’s rays for years, driving down global temperatures and setting off a chain reaction of ecosystem catastrophes.

Closer to home, it wasn’t until 1983 that scientists discovered the first hint of the 53-mile impact crater buried beneath the Chesapeake Bay—left by the crash of an asteroid more than a mile in diameter.

“You know the saying: ‘The dinosaurs became extinct because they didn’t have a space program,’” says NASA’s Tom Statler, quoting science fiction author Larry Niven and only half-kidding. “Only in hindsight does it seem obvious that all these [previously believed volcanic] craters were the result of asteroids crashing into planets.” All told, Statler adds, about 100 tons of extraterrestrial matter falls onto the Earth every day, mostly in the form of harmless dust, but also the occasional small meteorite.

For the record, the asteroid that exploded over Chelyabinsk is considered “small” by NASA’s near-Earth asteroid tracking standards. As was the fiery 26-pound rock that smashed through the trunk of 18-year-old Michelle Knapp’s Chevrolet Malibu while it was parked in her family’s Peekskill, New York, driveway in 1992, and the 8.5-pound space rock that crashed through an Alabama farmhouse in 1954, injuring Ann Hodges while she was napping on her sofa. Remarkably, there are no known human casualties from asteroids in recorded history, although a dog in a village outside Cairo, Egypt, was reportedly killed by a falling fragment in 1911. (Intercepting these small meteorites isn’t on the table at NASA or the Applied Physics Lab. Planetary defense scientists have their hands full tracking the thousands of near-Earth asteroids five times the size of the most recent Russian asteroid or larger.)

Roughly 95 percent, or about 15,000, of the large near-Earth asteroids have been located, says Statler, who serves as the NASA program scientist overseeing the DART mission. But until Cheng’s breakthrough idea, redirection was considered extremely difficult and borderline unverifiable.

“I wish I had thought of it,” Statler says.

As the timeline stands, the APL-built DART spacecraft will launch in June 2021 and impact Didymoon—the smaller twin to the asteroid Didymos (Greek for twin)—6.8 million miles from Earth on Oct. 7, 2022.

“Each asteroid has been to different places. Each has its own history.”

This summer, the White House released the administration’s 2019 budget request of $150 million for planetary defense, including $90 million for the DART mission. The White House also outlined goals to address the small but “high-consequence” threat posed by near-Earth objects, further developing technologies for deflecting or disrupting potential collisions (including a nuclear missile in the worst case scenario).

Meanwhile, notes Nancy Chabot, an APL project scientist, amateur astronomers will be able to track the DART project’s effect on the orbits of the Didymos asteroids when they are close to Earth. “We welcome anyone with a telescope to help,” she says of what will be the years-long observations of the twin rocks.

Most asteroids that stray near Earth—the Didymos pair, the Chelyabinsk rock, or others—are fragments of larger asteroids, numbering in the millions, from an enormous asteroid belt between the orbits of Mars and Jupiter. Some are rich in precious metals—asteroid mining is predicted as a thing of the future. Some asteroids are actually blown out comets with all the ice gone and just the rocky minerals left behind. Some have eccentric orbits. “Each asteroid has been to different places,” says Columbia resident Andy Rivkin, co-lead investigator with Cheng on the DART mission. “Each one has its own history.”

Rivkin adds that in recent years it has been theorized that most of the water on Earth may have come from asteroids and not comets.

The DART mission is not the only current high-profile project out of the Hopkins lab, which employs more than 6,000 people on its sprawling 20-building, 453-acre campus. The APL designed, built, and operates the recently launched $1.5 billion Parker Solar Probe, which will fly seven times closer to the sun than any previous mission. That spacecraft will explore, among other sun properties, the powerful solar winds that affect Earth, occasionally derailing satellites and GPS systems.

Other recent missions based at the Laurel facility include MESSENGER, the first spacecraft to orbit Mercury, and the New Horizons mission to Pluto. And yes, Pluto is still a planet, although it is now considered a dwarf planet, of which there are many in our solar system. “The question everyone asks at a cocktail party when they find out you’re a planetary astronomer,” says Rivkin.

Meanwhile, APL planetary geophysicist Olivier Barnouin, who worked on the MESSENGER and New Horizons projects, helped write the proposal for another ongoing high-profile project overseen by NASA’s Goddard Flight Center in Greenbelt. The OSIRIS-REx project is the first U.S. mission designed to bring back an asteroid sample, from a primitive asteroid named Bennu, which scientists hope will reveal new information about the formation of the solar system.

“[With the OSIRIS-REx project], we are talking about being able to answer what are religious-type questions in the scientific community,” says Barnouin. “One hypothesis people go for is that in reality we are all aliens—that almost everything that is needed for life on Earth came from outer space.”

An asteroid estimated to be 4.5 billion years old with a diameter of the Empire State Building, Bennu, named after a mythological Egyptian bird, takes a close orbit to the Earth every six years. It is also noteworthy because it’s one of the large near-Earth asteroids with the best odds of impacting Earth, albeit sometime late next century. Granted, it’s a slim shot—an estimated 1 in 2,700 chance—but that’s still twice the probability of the average little leaguer making it to the big leagues. It’s also better odds than getting struck by lightning, which kills a couple dozen people in the U.S. each year.

Space, which is sometimes depicted as a great void and at other times as an asteroid and comet superhighway, is actually neither.

It’s both.

“Space is big,” says Rivkin. “But if you wait around long enough, something will come by.”

As far as celebrating New Year’s Eve in Iraq goes, the holiday was going well for Jonathan Kuniholm. He had spent the last evening of 2004 with a few dozen fellow Marines and Army soldiers, taking a break from the war to enjoy a talent show at the chow hall. Using a borrowed acoustic guitar, he played and sang “Driver 8” by R.E.M., and a bluegrass version of “Greensleeves.”

The next day, while investigating a grove of palm trees along the Euphrates River, an improvised explosive device blew up in the middle of a clearing and knocked Kuniholm to the ground. The blast broke his rifle in half and nearly severed his lower right arm. A medic applied a tourniquet to the shattered arm, which was later amputated below the elbow.

He doesn’t like to talk about it. “I’m glad I’m not dead,” says Kuniholm, 35. “Anything after that is a gift.”

But get him talking about his life since, and the words flow much more freely. When he’s not working as a Duke University doctoral student in biomedical engineering—he may eventually benefit from his own research into grasp control—he works at an industrial design firm he co-founded almost four years ago in Durham, North Carolina. But every day, he is still making the transition to life as an amputee.

“If I need to test the bathwater to see if it’s too hot for my son, I’m going to do it with my other hand,” he says. “If I’m going to hold my son’s hand, I’ll use my other hand.” His son will still hold the prosthesis without complaint, and so will other children. But he has to look at where his prosthetic hand is to see if anyone is on the other end. “It takes me a little longer to tie my shoes. It takes me a little longer to put on my pants. As long as I know and understand and don’t let it frustrate me, there’s not a whole lot I can’t do.”

When he plays guitar now, his left hand’s fingers press the strings against the frets, changing chords like always. But the guitar pick goes in a prosthetic hand that strums only—no finger picking. “It chews up my guitar a little bit. If I miss with the pick, I gouge it all up,” he says.

Like many amputees, Kuniholm has a different prosthesis for different tasks. There’s his body-powered prosthesis, which operates with cables and rubber bands. When he moves the rest of his arm, the hand end opens and closes based on the distance between the hand and harness strapped to his opposite shoulder.

He also has a myoelectric prosthesis, activated by electrical impulses from his forearm muscles, but he doesn’t wear it because other prosthetics work better. The one he uses for flying airplanes is shorter than a regular arm and doesn’t bend. And he has another with a basic hand prosthetic, complete with a cosmetic covering, which helps minimize the stares of strangers. He uses yet another to control a stylus when he is doing his design work.

“Prosthetics tend to do very few things well,” he says.

Despite the swath of medical marvels and technological strides made in helping patients, prosthetic hands have long been left behind on the evolutionary ladder. Hand and arm prosthetics have evolved very little from simple, crude approximations of the natural limb developed decades ago. Look at the current technology for prosthetic legs, for example: The devices let amputees climb stairs, run a marathon, drive a car, or kick a ball with a child.

“Why can’t we do that for the arm and the hand?” asks Colonel Geoffrey Ling, program manager at the Defense Advance Research Projects Agency (DARPA), which is overseeing a project to improve prosthetics. “The best hand prosthetic one can get is a hook, right out of Peter Pan.”

Its functions are limited, and it’s inflexible. “It’s heavy, it’s clumsy, [and] cosmetically, it’s just horrid,” says Ling.

Something is, finally, being done. Ling and Kuniholm are both part of a $70 million effort by the federal government to change that frustrating fact. And they’re just two of hundreds of people attempting to build a better arm for the many American soldiers who have undergone amputation following injury while serving in Iraq or Afghanistan.

Spearheading this work is the Johns Hopkins University’s Applied Physics Laboratory (APL) in Laurel, just down the road from Baltimore. The legendary facility—one that is known for its innovative military and aerospace technology—is leading an international 250-person effort to create an artificial arm that works as well as a natural one.

The project’s goals are lofty: APL hopes to design an arm that can sense temperature, touch, and vibration, and that can sense the position of the arm and hand relative to the body. An arm that can tolerate heat, cold, water, humidity, and dust. An arm that will allow an amputee to regain the fine motor control needed to thread a needle, use a computer keyboard, or play a piano or a guitar. And a hand that will not just strum a guitar, but one that will let the wearer use the prosthetic fingers to perform fretwork and change chords.

The arm must also fit comfortably enough to use for 18 hours a day, and have the internal power to work for at least 24 hours.

Right now, “the best hand prosthetic one can get is a hook, right out of Peter Pan,” says Colonel Ling.

And it has to last for 10 years.

The first phase of the project—dubbed Revolutionizing Prosthetics 2007—aims to integrate existing technologies and map out areas of research for a new kind of mechanical arm. Last year, the APL won a $30.4 million grant to develop an entirely new arm that works like a biological limb. APL is serving as the project’s lead institution, working with dozens of colleges and universities in the U.S. and Europe, plus research and industry leaders such as Otto Bock Health Care of Germany and the Rehabilitation Institute of Chicago. Hopkins’ schools of medicine, engineering, and public health are working on the project as well.

If DARPA officials like the results, the lab will get another $24.4 million toward the project’s second phase. That project—called Revolutionizing Prosthetics 2009—will create an arm that transmits data to and from the brain; it aims to create an arm that is sensitive enough to sense temperature and texture, yet strong enough to lift a suitcase.

Possibly the earliest evidence of amputation and prosthetic surgery came from the Egyptian pyramids at Giza, where archaeologists uncovered a mummy dated to between 1550 and 700 B.C. According to The Lancet, the London-based medical journal, the woman’s big toe had been amputated and replaced with a wooden prosthesis that was painted dark brown. Two wooden plates and seven leather strings held in place a perfectly shaped big toe, even including the nail.

Centuries later, in 484 B.C., the Greek historian Herodotus wrote about an imprisoned Persian soldier named Hegesistratus. With one foot bound in wooden and iron stocks, he cut off part of his own foot and escaped. Later, he wore a wooden replacement and became an enemy to Sparta.

In the U.S., prosthesis technology advanced during the Civil War, which produced some 50,000 amputees. Government funding for Civil War veterans and the discovery of anesthetics allowed longer surgeries to attach more functional prosthetics. World War II produced nearly 7,500 major amputations, spurring development of currently used technology. Today, prosthetics consist mostly of body-powered mechanical parts made of straps, bands, metal, wood, and plastic—and no matter how they are assembled, they are a poor substitute for one of the human body’s most dynamic and elegant devices.

“The human limb system is an incredibly complex and very amazing system,” says Stuart D. Harshbarger, program director at the Applied Physics Lab. “Look at how strong a human hand is. For its volume, it’s fast, dexterous. It’s silent when you move it. Its skin covering doesn’t leave big baggy areas when you move it,” he continues. “It’s a very highly integrated biological system that’s remarkably capable.”

The big challenge, explains Harshbarger, is to copy the arm’s mechanical systems and fit them into the space of a human limb. In this case, the goal is to make something no heavier than a woman’s arm (which weighs an average of seven pounds) that can lift up to six times as much as its weight. An arm made of existing mechanical parts would weigh six times that much.

Part of the problem facing developers is that arms and hands are far more complicated than legs and feet. Hands have between 20 and 30 tiny muscles and joints that allow someone to type, button a shirt, pick up a pencil, or carry a grocery bag. Toes and feet help with a much smaller range of balance and mobility tasks.

Researchers started by looking at current leading-edge technologies ranging from state-of-the-art prosthetic limbs to robotics to spacesuits that allow astronauts to manipulate their hands. By the end of last year, they finished Prototype 1, which was designed to have “seven degrees of freedom.” Proto 1, as developers call it, can move at the shoulder and in two ways at the elbow, flex and rotate the wrist, and pinch fingers together or with the thumb at the top—as if holding keys or a dollar bill.

“Look at how strong a human hand is. It’s a very highly integrated biological system that’s remarkably capable.”

On a rainy Friday in January, in a squat, painted-brick office park in Laurel, researchers at APL are packing up Prototype 1 for a trip to Chicago, where a double amputee from an electrical accident is waiting to test it.

On the floor, a worker sifts through a plastic tub of startlingly lifelike prosthetic arm covers, selecting one for the strapping mannequin representing the modern American soldier. Under harsh fluorescent lights, a half-dozen researchers and developers click at computers nestled amid piles of papers, empty soda bottles and a half-eaten package of Oreos.

The mannequin towers at 6 feet, 4 inches tall, wearing black combat boots, sand-colored fatigues, helmet, and sunglasses. Computer cables jut out from the left shoulder, which joins a dark gray upper arm the size and shape of a potato chip can. The mechanical hand looks like something out of a Terminator movie.

Presiding over Proto 1’s final workout before getting its first human test, deputy project manager John Bigelow smiles as he describes the action as a programmer manipulates the device using a computer and mouse. The arm rises up and down, the palm turns upward and down, and the fingers slowly open and close. The arm moves a little too fast in first tests, so developers put speed thresholds in place.

“It’s quite peppy,” Bigelow says.

By August, the APL team must deliver and demonstrate Prototype 2, which must show even greater capability. If DARPA likes it, then the group will spend the next two years getting this new technology—which will become the new standard—ready for commercial manufacturing and for Food and Drug Administration review by the end of 2009. Working with Otto Bock, one of the world’s largest prosthetics makers, parts of the new technology will become commercially available along the way.

“What we’re most excited about is the technology that will be developed,” says Dr. Ross E. Andersen, an associate professor at the Johns Hopkins University School of Medicine. “It will have a phenomenal effect on the field of prosthetics.”

Researchers are collecting input from the people who know best what a better artificial arm needs. Andersen has gone to Walter Reed Army Medical Center in Washington, D.C. three times to meet with amputees, physicians, and therapists to ask them their opinions. Soldiers are talking about the kinds of activities they want to do, like skeet shooting, fishing, and water skiing. They want better looks, fit, and function without weightier limbs, Andersen says. “We’re getting some good feedback that will help the engineers come up with something that won’t sit on the shelf.

“We’re not developing some one-shot bionic limb,” he says. “The last thing we want to develop is a limb that on paper looks good but that a patient won’t use.”

Like the human arm, a prosthetic limb has many parts. The “terminal device,” a term borrowed from robotics, is the piece a wearer uses to interact with the world. A hand or a hook usually attaches to some kind of wrist, then a frame that attaches to the wearer’s remaining arm. Different terminal devices do different jobs, whether holding a guitar pick or a stylus. And while one prosthesis might let the wearer pick up a suitcase, it would crush an egg.

Individual prostheses are as different as the people who wear them and the myriad tasks humans do. Some amputees want a prosthesis to help them pursue their passions—playing piano, quilting, or hiking. Looks are most important for others, who want only to avoid cruel or curious stares.

Experts say the commercial incentive is slim to develop a better prosthetic arm. Research and development is slow (but is being sped up by these DARPA projects), and it takes years for any business to recoup product design costs. Researchers have abandoned numerous innovations over the years because there aren’t a lot of people to buy them.

Because of the small consumer market, prosthetics makers must wait for other industries to develop new technologies that are adaptable to their field, says Gary Berke, president of the American Academy of Orthotists and Prosthetists, a 2,500-member organization based in Alexandria, Virginia. Batteries to power artificial limbs used to be huge, but cell phones and other electronics slimmed them down. “We basically leech off of those,” Berke says. Current prices start around $7,000 for a basic above-the-elbow prosthesis, reaching as high as $75,000 to $120,000 for what DARPA is developing, he estimates.

“We’re not developing some one-shot bionic limb,” says Hopkins professor Ross Andersen.

While the federal government is pouring millions of dollars into building a better prosthesis, nobody at Hopkins is going to get rich off the project. Prosthetics is a notoriously low-margin industry. “One of our colleagues was joking,” Andersen recalls, “‘if we’re really successful, we’ll make thousands of dollars.'”

Each year, 82 percent of amputations occur because of diabetes and other complications of the vascular system, the body’s network of blood vessels, according to the National Limb Loss Information Center, based in Knoxville, Tennessee. Nearly all of those amputations—97 percent—happen to the leg. More than two-thirds of trauma-related amputations, however, happen to the arms.

Among the 1.9 million people living with limb loss in the U.S., most of them don’t need a better arm. But the project became a priority at DARPA—which was founded after the launch and orbit of the Soviet Sputnik spacecraft surprised the Western world—after the U.S. went to war in Iraq and Afghanistan. Improvements in body armor saved lives, but left survivors with missing limbs. By January 2, Walter Reed had treated 383 amputees from the war in Iraq and 38 from Afghanistan, a hospital spokeswoman says.

“Before the war . . . we didn’t have young people losing their arms,” says Colonel Ling, the DARPA program manager, who served in Afghanistan in 2003 and Iraq in 2005. “In Afghanistan, there wasn’t a day that went by that I didn’t see a kid who lost a hand or a foot from a Russian land mine.”

Part of the new research is looking into how to pick up a stronger signal from the brain when it tells the arm and fingers what to do. In a way, it’s like someone in Takoma Park trying to tune into broadcast television from Baltimore. The signal is clear enough, but not as good as in Fells Point. In prosthetics research, TV Hill is the brain, Fells Point is the shoulder, and Takoma Park is the elbow. The elbow gets the signal, but the shoulder gets it stronger.

In the amputee who will be testing Prototype 1, surgery remapped his remaining nerves at the shoulder to the pectoral muscles (or between the spinal cord), which act like an amplifier of the brain’s signal. Surface electrodes on his chest then pick up nerve impulses—and the brain’s instructions to the arm. In Prototype 2, developers are picking up the brain’s signal in new ways, such as by implanting sensory capsules the size of two grains of rice under the skin. The tiny devices wirelessly transmit sensory data—temperature or touch—back to the nerves.

“The trick is to put the signals back in the brain,” Ling says. “We’ve got to hack into the central nervous system itself.”

Paul Goszkowski changes his prosthesis like he changes his shirt. He wears a different artificial leg depending on whether he’s walking his dog, cutting his grass, or building a pond out of three tons of Pennsylvania bluestone—the project he chose to pull him from a post-amputation funk. “You have to try something so out of the ordinary just to convince yourself that the loss is not going to affect your life,” says Goszkowski, 47, a chiropractor in Federal Hill. “I had to learn how to use a shovel without a leg.”

A diabetic since age 4, Goszkowski developed two small blisters on his toes that wouldn’t heal. Two toes were amputated after bone infection set in; a subsequent surgery led to infection that eventually cost him most of his right leg in 2001. Coming out of the hospital, Gozskowski found little help for a new amputee. He quickly realized he can’t wear his prosthesis in the shower—the mechanical parts will rust—but he didn’t know where to find items for everyday activities, such as a shower chair.

“I was told by the occupational therapist in the hospital, ‘I think Sears carries that.’ I was just appalled. They had taken this leg but couldn’t tell me how to live without it,” Goszkowski says.

After three years of trying to find adaptable wheelchairs and exercise equipment he could use, Goskowski and fellow amputee John Yanke founded the Amputee Center of Maryland, an information network and support group. The center’s website, amputeecenterofmaryland.org, features a handy 120-item glossary of amputee-related terms plus a list of doctors, homebuilders and exercise equipment makers who cater to amputees.

“It’s the frustration level that gets to people. That frustration level is so high,” says Goszkowski, 47. “Imagine your life right now. If you’re driving or talking on the phone, you limit yourself to only half of what you can do.”

Goszkowski and Yanke developed a handbook to answer questions for new amputees, and they wrote pamphlets about how to clean and care for the residual limb. A prosthesis sometimes relies on a sort of sleeve that rolls up over the stump, gripping like a scuba diver’s suit. Halting air circulation around a stump can trigger bruising and infection, and amputees constantly have to care for the residual limb, Goszkowski says.

Many of the amputees who have come to Goszkowski’s group started as healthy people with no major health problems. One man was a sailor sanding his boat. He cut his leg and stayed in the Chesapeake Bay all day; infection claimed the limb. Another was a carpenter who cut his leg on a piece of old timber. One woman in her 30’s slipped and got a splinter when she fell—ironically—down a wheelchair ramp. A few months later, she lost the leg.

Sometimes Goszkowski almost forgets he’s an amputee. Women and children fawn over his 3-year-old dog, a Corgi named George, when the two go for a walk. “If I go in my shorts, and I don’t have a covering on my prosthesis,” Goszkowski says, “it’s like I’ve grown a third eye, and they don’t want to let their kid touch my dog.”

In past decades, the small consumer market forced the abandonment of lots of innovative ideas for prosthetics. The DARPA project ends in 2009, but it will take many years for the advances made at APL and other centers to reach the general public, officials say. When it does, it will cost about as much as a new Mercedes, estimates Ling.

“If I go out in my shorts, and I don’t have a covering on my prosthesis, it’s like I’ve grown a third eye.”

That will be too expensive for people like Sarah Mallon. She was born with her left arm ending five inches below the elbow; therefore, all her mosquito bites end up on her right arm. And neither a prosthesis—nor her left arm—is any good for scratching those itches. Also, since buttons on women’s shirts are on the left side, she says it’s aggravating to button a shirt with the “wrong” hand.

Mallon, 34, got her first prosthetic as a 6-month-old orphan. Her occupational therapist adopted her and raised her in Simsbury, Connecticut; she always wore her prosthesis except when sleeping, bathing, or swimming.

In first grade, as the only kid with a visible handicap who wasn’t in special ed, her teacher had her present her artificial arm for show-and-tell. “Kids asked me how I turned on a light switch,” she says. Using her stump, “I walked over and turned on the light. All you have to do is put it under the switch and push it up.”

“Someone asked me how I tied my shoes,” she says. “I just sat down on the floor and told them to watch when I did it. Ask me how I do something with a prosthesis, and it’s like asking someone how they use two hands.”

Mallon hasn’t bought a prosthesis since age 18 because they are too expensive: Insurance will only pay half the cost of the $8,000 limb. She stopped wearing the device once in the early 1990’s, during a year in Mexico, where a prosthesis would have labeled her as rich and a target for muggings.

A few years later, working at a home for children with mental and physical problems, she accidentally cut a boy with her prosthesis, and stopped wearing it around children. “Since I have my own kids, that means I don’t wear it anymore,” she says.

But last month, Mallon decided to give it another try: her youngest child is now 4, and she feels the risks are now very small—plus her mother offered to pay half of the cost.

Mallon was fitted for her first new prosthesis in 16 years. With straps and a closeable hook powered by back and shoulder movement, “it’s almost exactly like the one I had when I was younger,” she says. One improvement is that it attaches with a sort of silicone “sock” that will prevent it from sliding around so much.

Since she’s not a veteran, she probably won’t see the expensive benefits of the APL’s work for many, many years—and there’s no guarantee that she’ll be able to afford a new prosthetic arm even when one becomes available. But she knows what she wants it to do.

“When I dream, I have two hands,” Mallon says. “My mom says that’s because I see my prosthesis as a hand. It would be so neat to have one with nails that can scratch.”