Yesterday’s video from NASA’s Astronomy Picture of the Day website (link) is a short one produced by the National Spaced Society to remind people what’s coming very soon: the first flyby of Pluto. (The images of Pluto shown are of course mere conjecture.) The New Horizons spacecraft will come closest to Pluto on Bastille Day, July 14.

By the way, how old are you? If you were around before March 3, 1972, congratulations: You’re among the minority of humans born before the first interstellar spacecraft from Earth was launched. I’m afraid the rest of you missed it.

I occasionally still hear it said that the vast distance between the stars makes it interstellar travel impossible, overlooking the fact that five interstellar spacecraft are already on their way — Pioneer 10 and 11, Voyager 1 and 2, and New Horizons. Voyager 1 is the farthest away (see this page for the current distance to about the nearest half-second) and will continue to hold the record until a faster spacecraft is launched. (New Horizons was faster for a while, but it has slowed and Voyager 1 is once again the fastest-moving spacecraft from Earth.)

Even Voyager 1 will take about 40,000 years to come anywhere near a star other than our own, passing a little over a light-year from the red dwarf Gliese 445, and that only because Gliese 445 is headed in our direction. Otherwise it would take nearly twice that long to reach the star system currently closest to our own, Proxima Centauri. Either way, that’s several times the length of all of human history. Voyager 1 will stop being a functioning spacecraft long before then, in just a decade or so from now, in fact.

But still, five spacecraft from Earth are headed out among the stars, and that’s something.

Could spacecraft go faster than that? Indeed they could. It’s been suggested, going back at least as far as physicist Robert L Forward’s sf novel Flight of the Dragon Fly (see this Wikipedia entry about it) to use light sails propelled by solar-powered masers or lasers to propel spacecraft to nearby stars in centuries or even decades. The lasers would stay in the solar system, probably orbiting fairly close to the Sun, and their beams would be focused on those distant light sails by lenses also in the solar system by many times farther from the Sun than Earth.

Such a propulsion system would require a number of technological advances and would not be cheap. But based on a calculation I saw, such as system could be cheaper than the Iraq war, and probably a better use of the money.

Incidentally, the total cost of the Voyager 1 mission, from building and launching the probe to the ongoing monitoring and analysis of its transmissions, has averaged less than ten cents a year per American.

All of NASA’s spending combined, from its beginning in the 1950s through early satellites, the Moon landings, the International Space Station, multiple space telescopes, rovers on Mars, New Horizons spacecraft nearing Pluto, and all the other missions of exploration, adjusted for inflation, is roughly comparable to current U.S. defense expenditures for just one single year. (See this earlier post.)

(Updated 2015 July 6 to correct a typo and improve, I hope, some clumsy phrasing.)

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