THE one small step for mankind is about to get smaller. Engineers designing Nasa’s next generation of spacecraft will require astronauts with an “optimum height” as short as 5ft 7in.

The American space agency says no final decisions have been made, but it confirmed last week that it was rethinking its astronauts’ physical profile because the cone-shaped Orion crew module currently being designed is only 11ft long compared with the 120ft shuttle it is designed to replace.

“The next class of around a dozen people will probably be shorter than today’s astronauts who are all shapes and sizes,” said Duane Ross, Nasa’s head of astronaut selection, last week.

Astronauts selected under the new rules will be graduating when the space shuttles Endeavour, Discovery and Atlantis are grounded in 2010. The other two, Columbia and Challenger, both blew up in flight.

Some of the new astronauts will then hitch a ride to the space station on the tiny Russian Soyuz craft before the £5 billion Orion is expected to come into service in 2014.

The new seating specifications, proposed by contracted engineers at Lockheed Martin, are likely to favour women astronauts as well as short men, like the all-American actor Tom Cruise who nudges 5ft 7in.

Some veterans, such as the 6ft 2in Scott Parazynski, were not allowed on board the Soyuz until it was modified for his legs. In the 1990s he and Wendy Lawrence, his fellow American, were nicknamed “Too Long” and “Too Short”. Lawrence, at 5ft 3in, could not reach some of the controls.

Historically, America’s space pioneers have been relatively tall men. Chuck Yeager, the 6ft 2in test pilot, broke the sound barrier in 1947, paving the way for the Mercury and Apollo programmes. In 1961 Alan Shepherd, the first American into space, was 5ft 11in. Eight years later, when Neil Armstrong walked on the moon and announced “One small step for [a] man, one giant leap for mankind”, he was 5ft 9in; his fellow astronaut Buzz Aldrin was 5ft 10in.

The former Soviet Union, which led much of the early space race using relatively small craft, recruited cosmonauts to fit: Yuri Gagarin, who in April 1961 became the first man into space, was just 5ft 2in.

Americans are growing taller, but their space pioneers have been getting smaller. Until 1978, Nasa crew members were usually white male fighter pilots, but since then they have included women, Asian and Hispanic crew, who are on average 3in shorter than the earlier heroes.

The spaceships are also getting smaller. The Orion looks similar to the designs of the 1960s Apollo missions and will be lifted into space by conventional rockets. But despite this return to old technology, Nasa and Lockheed Martin are seeking to make it the most fuel-efficient vehicle in space history After test missions in 2013, Orion is scheduled to return man to the moon in 2020 and then, potentially, onward to Mars.

Lockheed’s specifications, which aim for astronauts between 5ft 7in and 5ft 9in, would have made Aldrin and Armstrong only just acceptable to Nasa, which will announce its rules this summer. Nor will it apply to tourists paying £100,000 to go into space on Virgin’s VSS Enterprise from 2009.

“Bigger astronauts will still be essential on space walks, which require a lot of stamina, but on a journey to the moon or Mars, where we are looking at four-person crews, there are complex calculations about what an extra inch of height would cost in fuel,” said one Lockheed engineer. “The tall Chuck Yeager type was the cowboy hero, but today a shorter, lighter astronaut makes sense.

“An especially skilled 5ft 10in astronaut would still make it and the cabin configuration is far from set, but I think we are seeing the last of the giants.”

Big test for Einstein’s theories

More than 90 years after Einstein published his general theory of relativity, scientists this week hope to announce whether or not he got it right, writes Jonathan Leake.

They are to release the early results from Gravity Probe B, one of the most complicated Nasa satellites. Since its launch in April 2004 the probe has been using four ultra-precise gyroscopes to measure two effects vital to Einstein’s theory.

One is the “geodetic” effect, the amount by which the Earth warps space and time. The other, called frame-dragging, is the amount by which the Earth “twists” space around with it as it spins. Both effects were predicted by Einstein in 1905 but are so tiny that it only recently became possible to measure them.

Francis Everitt, a physicist at Stanford University in California who is leading the team assessing data from the probe, said the preliminary results would be announced at a meeting of the American Physical Society.

But he warned that the final verdict would come only after more data-crunching. “It is apparent that several more months of data analysis will be required to achieve the lowest possible margin of error,” he said.

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