Can We Sail To Our Neighboring Star By The Century’s End?

The Firefly, designed by Robert Freeland, has a glowing rear, illuminated by the Z-pinch fusion drive.

I

If the Yellow Brick Road went all the way from Oz to our nearest stellar neighbor, 4.3 light-years away, and we were driving along it at a modest 55 m.p.h.—guided perhaps by an astral version of our G.P.S., which might have said, “Entering Kuiper Belt … Now, Turn Left”—it’d take us 50 million years to get there. (For perspective: one light-year is about six trillion miles.)

Even if we spun away at the speed of New Horizons, at a blistering 36,000 m.p.h., it’d still take us about 80,000 years.

And that’s why star-to-star voyages are so difficult to undertake. The gulf that separates one system from another is so enormous that making such a trip within a human lifetime is simply, out of the question.

II

But Icarus Interstellar is bold enough (or loopy enough) to dream that it can make that happen. A project that has the blessings of the British Interplanetary Society and the Tau Zero Foundation, it brings together a group of scientists and space enthusiasts to brainstorm a design for a no-crew starship that can travel to our closest foreign “solar system” by the end of the 21st century or the beginning of the next.

The Daedalus probe, designed in 1978.

The effort, which began in 2009, in London, renews from a previous study conducted by the British Interplanetary Society in the 1970s. Its mission was to create a blueprint for a probe—named Daedalus—which would fly to Bernard’s Star, a star much older than our own, located some six light-years from Earth, believed, at the time, to host a couple of promising planets. But by the time Icarus Interstellar came about, it’d been discovered to be barren. A different destination was, therefore, chosen: Alpha Centauri, a three-star system.

Roundish and Cyclopean, half as tall as the Empire State Building, Daedalus resembled two inverted colanders, held together by a ring of enormous globe grapes. Sure, it didn’t have the architectural oomph of the Millennium Falcon or the Battlestar Galactica.

But in its speed, it outshone any vehicle built by humankind. Propelled by fusion—the energy that powers the Sun and other stars—it’d attain 12 percent of the speed of light, a feat far beyond the scope of our conventional chemical rockets.

III

The past November, Icarus Interstellar took the lid off the much-awaited model of the new-generation starship. Dubbed the Firefly, it’s named after a class of spaceship, featured in the short-lived American science-fiction series, “Firefly,” whose rear glowed like that of a firefly when it pushed the pedal to the metal.

A gargantuan, pencil-thin, dart-like projectile, it makes the huge, Apollo-era, Saturn V rocket look like a three-story condominium next to the Burj Khalifa. But even at nearly 33,000 feet and 178,000 tonnes, it’s small and light by the standards of interstellar clippers.

Even though Firefly looks nothing like its “father,” it has its DNA, in the form of a nuclear engine. But where Daedalus would’ve used pellets of deuterium (a heavier cousin of hydrogen, with one proton and one neutron) and helium-3 (a lighter sibling of helium, with two protons and one neutron), Firefly would burn a combination of deuterium and deuterium.

IV

As a fuel, helium-3 is a cleaner choice than deuterium. But its drawback is its acute paucity. There’s so little of it on Earth that it’d have to be harvested from the gas giants, the two best depots being Jupiter and Uranus.

One option to mine it is to have a floating robotic factory, high up in the Jovian sky, from which a very long, hollow pipe would descend below. It’d hoover up the gaseous atmosphere, just like a vacuum cleaner would, and bring it up, where helium-3 would be extracted from it. Tankers could then either haul the fuel back to Earth or store it in orbiting “gas pumps,” from where the ship could collect it on its way out.

But this arduous schlep to merely get gas seemed neither profitable, nor doable in the near future. So, the decision to go with deuterium, a substance we have no shortage of in our oceans, and can be procured easily.

But the fly in the ointment of a deuterium-deuterium reaction is that it emits neutrons and x-rays, which are deeply hazardous not just to flesh and bones, but also to metals.

And that’s the chief reason Firefly is so strikingly dissimilar in appearance to Daedalus. Being narrow, its body is less exposed to the deadly emissions from its own engine as well as to whirling debris that it might encounter in space.

Draping it in a thick protective padding, it was reckoned, would result in an unworkably unwieldy vessel. Firefly does away with Space Shuttle-esque shields. It’s fashioned so as to let the bulk of the harmful exhaust escape directly out into space.

At the speed at which it’s expected to sail, even a mote of dust can tear a rent in its hull. Making it smooth and streamlined reduces the risk of its being struck by stray cosmic pebbles.

Also, its immensely long form enables sensitive payload to be placed amidships, at a reasonably safe distance from the inferno at its stern.

All the action happens in its tail. It’s where the “Z-pinch” drive is. A cylindrical reactor, it sparks off fusion by cracking a whip of electricity through a column of searing plasma, held in captivity, in a skinny tube, and kneaded by magnetic muscles.

Other than profuse radiation, another inescapable byproduct of this process is titanic heat—in the range of 1,800 degrees Fahrenheit. To cool the scorching machinery, giant radiators spread out like insect wings from the kernel.

Unlike Daedalus, whose fuel tanks stuck out conspicuously from its structure, Firefly, incorporates them seamlessly into its frame. About 15,400 tonnes of liquid deuterium would be housed in 20 cylindrical tanks, positioned along the spine.

Firefly will achieve 4.5 percent of the speed of light in about four years, after which it’ll coast at that speed for 93 years, and once in the proximity of its terminus, it’ll put the brakes on, and jettison a swarm of sensors—all of it within 100 years.

V

Michel Lamontagne writes in Discovery News that “this is faster than needed.” Expanding the trip time to several centuries would take many of the technological thorns out of the way. Besides, the stars aren’t going anywhere, anytime soon. But gliding at a leisurely pace would raise the challenge of setting up an organization of matching longevity , which would provide the starship key infrastructural backbone after departure.

After all, a spaceflight, long-haul or not, is made possible not alone by pieces of equipment and a team of astronauts, but by the people on the ground, who keep a close watch over their destiny from their stations in mission control. With that in mind, the team behind Daedalus had designed their 1978 probe for a 50-year flyby mission as this was deemed the upper limit for a NASA engineer’s career.

Firefly would be constructed piece-by-piece, in an orbital shipyard—a structure so sprawling that it might be an exciting destination for space tourists, eager for a taste of the celestial assembly.

Materials will be delivered to it by Skylon, an amphibian transport that can maneuver both in air and in vacuum, and is being developed by Reaction Engines. Half-jet and half-rocket, it can take off from an airport runway, and fly through the atmosphere straight to space.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s