The concept for the so-called Dyson-Harrop satellite begins with a long metal wire loop pointed at the sun. This wire is charged to generate a cylindrical magnetic field that snags the electrons that make up half the solar wind. These electrons get funnelled into a metal spherical receiver to produce a current, which generates the wire’s magnetic field – making the system self-sustaining.

Any current not needed for the magnetic field powers an infrared laser trained on satellite dishes back on Earth, designed to collect the energy. Air is transparent to infrared so Earth’s atmosphere won’t suck up energy from the beam before it reaches the ground.

Back on the satellite, the current has been drained of its electrical energy by the laser – the electrons fall onto a ring-shaped sail, where incoming sunlight can re-energise them enough to keep the satellite in orbit around the sun.

A relatively small Dyson-Harrop satellite using a 1-centimetre-wide copper wire 300 metres long, a receiver 2 metres wide and a sail 10 metres in diameter, sitting at roughly the same distance from the sun as the Earth, could generate 1.7 megawatts of power – enough for about 1000 family homes in the US.

A satellite with the same-sized receiver at the same distance from the sun but with a 1-kilometre-long wire and a sail 8400 kilometres wide could generate roughly 1 billion billion gigawatts (10²⁷ watts) of power, “which is actually 100 billion times the power humanity currently requires”, says researcher Brooks Harrop, a physicist at Washington State University in Pullman who designed the satellite.

Since the satellites are made up mostly of copper, they would be relatively easy to construct. “This satellite is actually something that we can build, using modern technology and delivery methods,” Harrop says.

Satellites laden with solar panels that can beam their energy down 24 hours a day have been discussed for decades. California agreed last December to a deal involving the sale of space-based solar power. Solar panels cost more per pound than the copper making up the Dyson-Harrop satellites, so according to Harrop, “the cost of a solar wind power satellite project should be lower than a comparative solar panel project”.

So far so good, but there is one major drawback. To draw significant amounts of power Dyson-Harrop satellites rely on the constant solar wind found high above the ecliptic – the plane defined by the Earth’s orbit around the sun. Consequently, the satellite would lie tens of millions of kilometres from the Earth. Over those distances, even a sharp laser beam would spread to thousands of kilometres wide by the time it reached Earth.

“Two megawatts spread across areas that large are meaningless, less than moonlight,” says John Mankins, president of consultancy firm which specialises in space solar power. To beam power from a Dyson-Harrop satellite to Earth, one “would require stupendously huge optics, such as a virtually perfect lens between maybe 10 to 100 kilometres across,” he says.

He also points out that the wire could burn out due to the huge current coursing through it, although he has not performed the calculations to gauge the probability of that occurring. But he does say that a smaller version of this “clever and interesting” satellite could help power some space missions. “I could imagine uses for this idea outside of the plane of the ecliptic, such as helping generate power for something like the Ulysses spacecraft, which went around the poles of the sun.”

Journal reference:

Update on 7 February 2012: Red Bull says the jump attempt is back on for sometime in 2012. The legal challenge to the jump was resolved out of court and the jump, from a planned altitude of 36.6 kilometres, will occur above Roswell, New Mexico.

Update: On 12 October 2010, Red Bull stopped work on this project, a multi-million-dollar lawsuit by an entrepreneur who claimed rights to the idea.

A “space diver” will try to smash the nearly 50-year-old record for the highest jump this year, becoming the first person to go supersonic in freefall. The stunt could help engineers design escape systems for space flights.

On 16 August 1960, US Air Force Captain Joe Kittinger made history by jumping out of a balloon at an altitude of some 31,333 metres. “I stood up and said a prayer and stepped off,” he recalled (see Space diving: The ultimate extreme sport).

Since then, many have tried to break that record but none have succeeded – New Jersey native Nick Piantanida actually died trying in 1966. Now Austrian skydiver has announced he will make the attempt, with help from Kittinger and sponsorship from the energy drink company Red Bull.

Baumgartner, who became the first person to cross the English Channel in freefall in 2003, will be lofted to a height of 36, 575 metres in a helium balloon. After floating up for roughly three hours, he will open the door of a 1-tonne pressurised capsule, grab the handrails on either side of the exit, and step off, potentially breaking records for the highest parachute jump, as well as the fastest and longest freefall.

Shock wave

He will face extreme peril. He should reach supersonic speeds 35 seconds after he jumps, and the resulting shock wave “is a big concern”, the project’s technical director, Art Thompson, said at a press briefing on Friday. “In early aircraft development, they thought it was a wall they couldn’t pass without breaking apart. In our case, the vehicle is flesh and blood, and he’ll be exposed to some extreme forces.”

Still, project medical director Jonathan Clark noted there has been one known instance of a pilot surviving the destruction of a plane at three times the speed of sound. “We know it’s not just theoretically possible, it’s possible,” he said.

After falling for about six minutes, Baumgartner should open his parachute at roughly 1520 metres.

The jump height is above a threshold at 19,000 metres called the Armstrong line, where the atmospheric pressure is so low that fluids start to boil. “If he opens up his face mask or the suit, all the gases in your body go out of suspension, so you literally turn into a giant fizzy, oozing fluid from your eyes and mouth, like something out of a horror film,” Thompson explained. “It’s just seconds until death.”

Flexible suit

To protect himself, Baumgartner will wear a more flexible version of the airtight, pressurised spacesuit currently used aboard the space shuttle (see Future spacesuits to act like a second skin). That will let him bend to achieve the standard, belly-down skydiving position needed to decelerate.

Another concern is uncontrolled spin, which could knock him unconscious. Sensors all over the suit will constantly monitor his acceleration for signs of spinning, as well as checking on his heart rate and position, relaying data to the ground team via a radio in a pack mounted on his chest. If needed, a drogue parachute can be deployed to stabilise his flight.

Two practice flights will be conducted at about 20,000 and 27,000 metres. Currently Baumgartner is undergoing rigorous tests in the suit at extreme cold, in vacuum chambers and in vertical wind tunnels to simulate falling.

Red Bull would not reveal the cost of the project. And though it says it will launch this year from North America, it has not yet specified a date or launch site. This uncertainty depends in part on finding the ideal weather conditions for the flight, Thompson said.

By showing that a person can safely return to Earth from that speed and altitude, the “Stratos” mission team hopes to show that astronauts might survive with similar systems if they needed to bail out of spacecraft.

“It’s human nature to want to go faster and further,” Kittinger noted, but he added he would not have signed on without the promise of getting scientific data. “We’re testing the next-generation full-pressure suits.”

The teeth of ancient hominids commonly have curved grooves on their roots. It has been suggested that these marks were made by an implement used to pick teeth. But critics of this theory point out that the teeth of today’s regular toothpick users have no such marks.

Resolving this conundrum has surprisingly wide implications. Similar grooves have been found on fossil teeth dating back 1.8 million years. If the individuals made them by using toothpicks, the habit would qualify as the oldest human custom yet recorded. It could also reveal details about ancient diets and oral health.

To help settle the debate, palaeontologist Leslea Hlusko of the University of Illinois at Urbana-Champaign hit upon grass stalks as likely to have left the mystery grooves.

Unlike wood, grass contains large numbers of hard, abrasive silica particles. This may explain the grooves seen on ancient teeth. And grass stalks are the right size to leave the marks, between 1.5 to 2.6 millimetres wide, that have been found on ancient teeth.

Hlusko spent eight hours grinding a piece of grass along a tooth taken from a baboon. She then replicated the experiment for three hours on a modern human tooth. In both, the grass left marks almost identical to those seen in scanning electron microscopic images of early hominid teeth.

Journal reference: Current Anthropology (vol 44, p 738)