Lt Col Eileen Collins was the first woman ever selected to be a space shuttle pilot and the first to command one. Later this month she will be in command once again as America's space shuttle fleet returns to flight with the launch of Discovery - the first mission since Columbia disintegrated on re-entry into the earth's atmosphere in 2003, killing all seven astronauts on board.
In the 45 years since manned space flight began, nearly 450 people have travelled in space, but only 46 have been women. Some might assume that this is because women's physique and physiology may count against them. But the truth - and the story behind women in space - is much more surprising.
The first woman in space was Soviet cosmonaut, Valentina Tereshkova, who circled the earth in June 1963, instantly becoming a heroine for a nation and the role model for a million little girls. Her flight, a couple of years after that of Yuri Gagarin - the first man in space - proved conclusively that the space-flight rule book need not be rewritten for women. Over in the US, though, preparations to put women in space were proving more difficult.
In 1960, Dr Randy Lovelace II (a name you couldn't make up) invited Jerrie Cobb to take part in the testing regime he had devised to select the original US astronauts, the Mercury Seven. Cobb became the first woman to pass those tests and she and Lovelace then recruited a further 25 women.
The tests to which they were subjected sound horrifying. They had to swallow rubber tubes so their stomach acid could be tested; iced water was shot into their ears to freeze the inner ear and induce vertigo, so doctors could time how quickly they recovered. They pedalled stationary bikes until they were exhausted, and had their lean body mass calculated using a nuclear counter at Los Alamos.
Just 13 - the Mercury 13 - were selected for further testing at the naval aviation centre in Pensacola, Florida. The programme, as with all astronaut training in those cold war days, was deadly secret. Many left their jobs without saying why. But then the testing was abruptly cancelled at the behest of the navy, whose top brass (all men) were appalled that women were being tested for possible spaceflight.
The prejudice against women at the time was immense; they were thought to be weaker, less intelligent and unlikely to be able to handle the complicated tasks of spaceflight. The Americans considered Tereshkova's flight to be nothing more than a stunt.
The oldest of the female recruits was a 41-year-old mother of eight called Janey Hart. She also happened to be the wife of a US Senator and wrote to the president, John F Kennedy, pleading for the First Lady Astronaut Trainees programme to be resumed. A special subcommittee of the House Committee on Science and Astronautics was convened. But Nasa testified that women did not qualify to be astronauts since the entry requirement was that all should be jet test pilots with engineering degrees. Since no women then were jet test pilots, none could meet these requirements.
The US air force did not even begin training women as pilots until 1976, so it was another 20 years before Sally Ride became the first American woman in space and 32 before Eileen Collins became the first woman to pilot the space shuttle. Surprisingly, the first Briton in space was a woman, Helen Sharman. She was selected for the Russian space mission, Project Juno, after answering an advert saying, "Astronaut wanted. No experience necessary", and blasted into space in 1991.
Women do have advantages over men in space, as Jill Richardson of the National Space Centre in Leicester explains. "They're smaller, lighter, more efficient, require fewer calories, produce less waste and, probably because of their oestrogen, are less prone than men to heart problems brought on by the flight." And weightlessness reduces the need for bigger muscles to shift equipment around, making space a level playing field. Interestingly it looks as though women are also more resistant to muscle atrophy - up to 50% reduction in leg strength - which occurs after just two months in space. William Rowe, a professor of medicine at the Medical College of Ohio, believes women are far better suited to long-term, long-distance space travel than men and has called for future missions to Mars to be "womanned", not manned.
So why are there so few women astronauts? The reason is very familiar. "It's the social context that makes space difficult for women," says Dr Kevin Fong, director of the Centre for Aviation and Extreme Medicine at University College London. Although astronauts are always portrayed in films as young and keen, straight out of Top Gun, the truth is that astronauts, of either sex, are not young. The female members of Discovery are typical; Collins will be 49 in November and Capt Wendy Lawrence, the other female crew member, will have just turned 46. "To have achieved everything you need to have achieved to make it as an astronaut means that you are in your late 30s, or even early 40s, by the time you are selected."
Finding time to have children can be very difficult. You can't be pregnant and go into space. "There's no fitting one round the other," says Fong. In their early years, women are too busy clocking up experience. Once women get chosen for a mission - something they've worked for all their lives - pregnancy spells an instant exit. But by the time they've got their space wings, pregnancy may no longer be an option. Efficient planning doesn't help much either. For instance, because of the Columbia disaster, Collins (who is unusual in having two children, the eldest of whom is nine) has been on standby for the past two years. In the tail end of your reproductive life, a two-year delay could turn into a personal disaster.
So how did Collins do it? The woman is a phenomenon. As a 21-year-old, she famously ate carrots for two weeks, turning the tips of her fingers orange in the process, in order to pass the 20/20 vision test requirements. Only the second woman to enter the air force test-pilot school in 1989, she admits to being terrified of rollercoasters yet has logged more than 6,280 hours of flying in 30 types of aircraft, including 540 hours (22 days) in space. She conceived immediately after space missions: Bridget arrived the same year she piloted the shuttle in 1995 and Luke was born after she became the first woman to command a space mission in 1999. Her call sign is "Mom".
Pre-flight contraception, however, is mandatory for women astronauts. This is partly because no one has any idea as to what the effects of space might be on a developing baby, but mainly because of the threat to a mission that could be posed by pregnancy complications. Discovering that a crew member has an ectopic pregnancy in orbit doesn't bear thinking about.
Therefore, women astronauts are put on the pill during flights, taking it back to back without a break to abolish their cycles. This isn't just about convenience. Some problems, such as those that affect balance and cause debilitating space sickness, get worse during periods.
There are more differences between men and women in space than simply those affecting balance. For instance, something called orthostatic intolerance (it causes near fainting or fainting when attempting to stand following a space flight) affects only one in five men, but nearly all women.
But with fewer than 50 women astronauts, precious little is known as to why this should be. "It's a big, dark continent out there, as far as women's bodies are concerned," says Fong.
Another major unknown relates to the bone loss induced by microgravity, which runs at about 2% a month in both men and women. This can be recovered on returning to Earth. However, at the menopause, women experience a 90% drop in oestrogen levels anyway, which affects bone metabolism, leading to osteoporosis in those who are vulnerable. This has led to concerns about astronauts close to the menopause being sent on long space flights: would they be able to recover lost bone on their return? Or would the flight condemn them to a painful future of brittle bones?
There is a real need for information on the long-term effects of space. Flights to Mars are likely to take at least a couple of years and there is no question of excluding women from these missions. As Dr Sarah Duncan, a space scientist involved with Aurora (the preparatory stages for manned missions to Mars), says, "Women have an important role to play because of their training in physics and space science." She didn't actually say, "And just let 'em try excluding us", but one suspects that the European Space Agency has already heard this message loud and clear from the increasing number of female space scientists.
Three years ago, Nasa, with the University of Missouri, ran a workshop aimed at prioritising sex differences in human responses to challenging environments. Janice Meck, director of Nasa's cardiovascular laboratories and one of the scientists involved in the workshop, thinks the reason why women wobble so much on return from space is that they're not "vascular responders", which means that they respond to the orthostatic stress caused by space flight by increasing heart rate, rather than by increasing the stiffness of the blood vessels (the response of men). More information is clearly needed. "We are doing bed-rest studies to try and determine more of the mechanisms of the differences in men and women. We're keeping them in the head-down tilt position for 90 days and measuring many parameters."
Twelve women have also taken to their beds in Toulouse as part of the Women's International Space Stimulation for Exploration project. They too are lying at a six-degree downwards slant (a position in which they eat, wash and sleep). This simulates the response to space. It makes fluids shift to the head, causing puffy face and headaches. Lack of stimulation to the soles of the feet causes dizziness and nausea. There's a risk of kidney stones as calcium leaches from bones, heart muscles shrink and, with blood glucose control confused by lack of exercise, diabetes may set in.
Britain has decided not to be involved in the manned aspects of Aurora but is contributing to the robotic exploration stages. This has meant space medicine now has little priority here. But this is a lost opportunity - especially for women, says musculoskeletal physiologist, Professor Michael Rennie of the University of Nottingham. "Being able to do muscle experiments in space would be 100 times more efficient with 1,000 times more benefit for understanding muscle and bone wasting - the biggest sufferers of which are women." Fong agrees: "Space medicine has many knock-ons for human health, not just for astronauts." And women could be the greatest beneficiaries.
It may not be for its research benefits, but space switches girls on as much as it does boys. Alison Boyle of the Science Museum is quite clear what Eileen Collins's effect on today's schoolgirls will be. "She's the inspiration for this generation, as Tereshkova was to hers in the 60s."