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Probes, slingshots and interstellar nakedness

December 19, 2010

This week a significant event was announced by the Jet propulsion Laboratory at CalTech. The Voyager 1 spacecraft, after 33 years and 10.8 billion miles of travel, has reached a region of our outer solar system called the Heliosheath – where the propelled ionised gas of the solar wind finally runs out of steam. This means that the little craft is now on the verge of leaving the solar system for good, and heading off into the vastness of interstellar space.

The Heliosheath

As someone lucky (old?)  enough to remember the glory years of the Voyager program, the event is bittersweet. Soon that venerable machine will finally shut down, becoming a dead hunk of seventies technology and decaying Plutonium. To say it exceeded our expectations is a ludicrous understatement. It delivered science at its most breathtaking. But there are two human aspects regarding Voyager that will stay with me after the power turns off. One concerns the collective human race, the other is a single man. Both are connected to each other, and to the events 10.8 billion miles above us.

Voyager represents a ‘message in a bottle’ about humanity for any intelligent species that may find it in future. The significance of this was clear to Carl Sagan and the seventies minds that built it. The Pioneer spacecraft of 1972 and 1973 contained a plaque which showed very basic information on human beings and the location of their planet. I loved the press criticism which objected to the use of naked male and female figures on the plaque. Apparently, folk objected to lewd aliens copping a look at our genitalia in some future epoch. Interesting to think that of all the human characteristics to influence the plaque, prudishness should remain high amongst them. Or perhaps that’s a more telling message?

Pioneer plaque

The diagram on the plaque of the Pioneer probes

By 1977, things were more ambitious. In 40,000 years time, it was calculated that Voyager 1 would approach a star in the constellation of Ophiuchus. This time a golden record was to be included on the craft – a time capsule that would contain music, images, languages – even a UN speech. Recordings from this fascinating collection can be heard here. The idealistic greetings reflected an optimism regarding extra-terrestrial communication in popular culture at that time. Spielberg’s movie ‘Close Encounters of The Third Kind‘ was a smash hit that year – an uplifting tale of  beneficent aliens contacting our world. More recently, Stephen Hawking has suggested that promoting contact with aliens might be rather unwise, and should be avoided. Have aliens become more deadly in the wake of movies such as ‘Independence day’ and ‘Alien’? Or are we just more coy about the relative nakedness of our early idealism?

Whatever the truth, these considerations would have remained pure science fiction had it not been for the ground-breaking work of a single young mathematician in 1961 – Dr Michael Minovitch. Until Minovitch, the received scientific wisdom on interplanetary spaceflight was grim. Basically, the sums didn’t add up. Carrying the rocket fuel necessary to propel a spacecraft to the outer reaches of the solar system would mean unfeasibly huge payloads. Minovitch’s brilliance was in realising a way to avoid taking all that fuel, by using the gravitational fields of the major planets as a huge “slingshot”. If a craft passed close to a planet, it could steal enough orbital energy to propel it on to another planet. And then another. All you needed was the fuel to get you to the first planet.

This was bold, brilliant stuff. Trouble was, Minovitch was just a lowly UCLA grad student at the time, working at the Jet Propulsion Lab. It took till 1962 before his theory was taken seriously by the  establishment. But the implementation of his ideas changed everything. All the great planetary missions – Mariner, Pioneer, Voyager, Cassini – have used Minovitch’s slingshot. Without him there would be no photographs of Jupiter’s moons. No fly-by of Saturn’s rings. No Golden Record for aliens to find.

Minovitch in 1960

Dr Michael Minovitch in 1960

And yet there is a bittersweet edge to his story. Recently, Minovitch announced that he was making copious data on his ‘Gravity Propelled Interplanetary Space Travel’ available for free on his Gravity Assist website. It is a wonderful resource. But the tone of the site feels like an argument – a declaration of ownership – rather than a testament to acknowledged achievement. Minovitch was nominated for a Nobel Prize in 1991, but not successful. And there were others who claimed to have had a hand in gravitational propulsion, which Minovitch strongly refuted. One cannot avoid the impression that Minovitch – now approaching the end of his life – feels he has not received adequate recognition for the revolution in planetary exploration his work made possible.

Big deal, you might say. Scientist feels work is unappreciated. Hardly new! And yet I’m struck by the poignancy of his quiet protestation. Because what he desires is a claim to posterity. The association of his work with something lasting and significant. Immortality. His own Golden Record.

The quaint collective conceit of the Voyager time capsule is little different from the aspiration of the scientist who made the flight possible. We humans are partial to throwing pebbles into the ocean of time. To justify our baffling existence in a lasting declaration – naked or otherwise. For all the science that made Voyager possible, the message received by aliens in 40,000 years time will be a wholly human appeal.

‘We were here. And what we did mattered’.

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