Supermoon eclipse: Scooting about the solar system

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Updated: September 10, 2015 8:15:16 PM

News of the supermoon eclipse due on the night of September 27-28 has recommended the heavens yet again to public attention. It’s a rarity, a blood moon about 14% bigger than normal.

News of the supermoon eclipse due on the night of September 27-28 has recommended the heavens yet again to public attention. It’s a rarity, a blood moon about 14% bigger than normal. Like all celestial orbits, the moon’s path around the earth is elliptical and the difference between apogee and perigee, the furthest and closest points of the orbit, is in the range of 30,000 miles. That can make a difference to the apparent size of the moon and the effect can be remarkable. This has not happened after 1982 and the next occurrence will be in 2033.

By that time, there should be many more interesting ways to look at the solar system. A couple of advances in space probe technology should open up a new era of spacefaring vehicles and landers with very low fuel requirements, which hitch rides and use gravity wells to get about. They are children of the Philae, the vehicle that is now riding the comet 67P/Churyumov-Gerasimenko as it swings through the perihelion of its orbit around the sun.

The harpoon that was to tether it to the 67P had failed to fire, and the craft had bounced into an area of darkness. Its solar panels deprived of sunlight, the Philae shut down for months.

Whether by accident or design, the developments in propulsion technology would prevent such possibilities, and would help to develop craft to explore the Kuiper Belt, the mass of icy jetsam from the making of the solar system, beyond the orbit of the Neptune, whose biggest member is the Pluto. It could have a big brother, according to a paper by Scott Sheppard and Chad Trujillo in the Nature last year, an invisible giant whose presence was inferred by its gravitational effect, and which has become the next Holy Grail.

It turns out that bouncing about can be a good way for space vehicles to manoeuvre in low gravity situations, like on an asteroid or comet—where the wheels of a lander would not find purchase. Even more beguiling is the idea of using harpoons to sling a craft across the gulf of space like some interplanetary Tarzan of the Apes.

Comet Hitchhiker received initial funding last year from NASA Innovative Advanced Concepts, which backs disruptive technologies which promise to accelerate space exploration. While conventional landers like the Philae have to carry fuel for decelerating and landing and can target only one body in space, the Hitchhiker would fire off a harpoon with a cable up to 1,000-km long, to snag its target and some of its kinetic energy too, and use that to reel itself in, or to sling itself away to another object. The weight of fuel required for soft landings retards space exploration and if this concept proves to be practical, there would be a new, low-cost way to run long missions with multiple landings.

Meanwhile, a collaboration between NASA’s Jet Propulsion Laboratory, Stanford University and the Massachusetts Institute of Technology has produced the Hedgehog, a cubical concept vehicle which can operate no matter which of its six faces it lands on. Propulsion is provided not by wheels, which is what the Curiosity uses to get about on the Mars, but internal gyroscopic flywheels, which are spun up and suddenly braked to create a reaction that sets the vehicle tumbling, by Newton’s Third Law.

This would be a most inefficient way of getting around under earth’s gravity—even a dung beetle would look more graceful—but in the low gravity of most Kuiper Belt objects, this could actually be a sophisticated mode of transport. Not only would it be more accurately steered than wheeled traction, the hopping action would allow the Hedgehog to clear obstacles effortlessly and range much wider than a conventional rover.

Science has replaced science fiction’s imperative to travel to the most distant galaxies with the practical need to explore, exploit and understand humanity’s home system first, and as cheaply and efficiently as possible.

Interestingly, this refocus is prompting the innovation of small, beautiful propulsion systems. The scale is in the tiny range of kilojoules, a fraction of the kilotons of yield which, it was imagined, would power the nuclear ships of the future.

The history of space propulsion is littered with proposals for improbable drives, magic carpets which would send humanity to the stars, guaranteed. The most unlikely was a little tube under a spacecraft which stood on a base plate.

Bombs popped out of the tube and exploded in space like so many eggs hatching. The force of the explosions against the plate propelled the craft forward. It appeared in the 1970s and was simply incredible, but after ideas like the Hitchhiker and the Hedgehog, one would not be surprised to see it scooting about the solar system sometime soon.

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