In "Pilots of Borealis" my protagonist’s spacecraft employs an expansive electromagnetic sail to capture the energy of the 1 million mile per hour stream of the solar wind to help build up an efficient interplanetary speed — also picking up a boost by slinging past the minor planet Ceres just right.
Science fiction though is often outdone by scientific facts seemingly more extraordinary than many far-fetched tales. It may well come to pass in this case that the actual flight plans future space-faring vessels might follow — taking advantage of genuine "shipping lanes" connecting interplanetary ports of call — could be remarkable enough to equal quite a few of the fanciful kind.
Those paths through the void would be created by the ever-changing gravitational assist points at which spacecraft could be "slingshot" — instead of expending fuel for the energy.
The entire solar system might be envisioned as being just as complicated as a machine by American author, cartoonist, engineer, inventor, and sculptor Rube Goldberg. A machine in which a free nudge given here by skirting past Mars leads to an assisted boost there in the environs of Ganymede, one of Jupiter’s moons; by circuitously tacking along these corridors a craft could navigate the planets taking advantage of the gravitational potential energy that pervades the solar system with commensurately less reliance on the ever-dominant concern — fuel.
The mode of transit would be to use engines sparingly, firing them only to leap-frog from one gravitational well to the next, in a way analogous to how Tarzan uses his momentum and just the right series of vines to get through the jungle, expending the least amount of effort.
Of course, the mathematics involved in planning an itinerary of such complexity would be sufficiently intimidating to require number-crunching computational power for that very task. And, to be sure, this would certainly not be the fastest way to journey between planetary destinations.
It might, however, be the preferred way to send freight and truly unhurried travelers willing to trade time for reduced cost, booking passage not on a slow boat to China but on a pokey freighter to Titan.
Heavyweight Jupiter, with its massive gravity affecting so much already in the Solar System — from creating and maintaining the Asteroid Belt to protecting Earth by pulling in and subsuming potentially impacting comets and meteors — might develop into the central hub in a system-wide layout of spokes leading to ultimate interplanetary destinations.
The Jovian moons could well turn out to be where to find the crowds of future hostelers, travel agents, freight companies, courier services, and homestead outfitters centuries from now: "Europa or Bust."
Propellant is an overarching problem in space travel. It’s just not possible to bring enough along to keep the engines firing so as to be constantly accelerating to reach the enormous velocities required for the vast gulfs to be traversed in space. One conceivable solution is not to bring the fuel but instead to pick it up along the way, and that may be possible after all.
Even interstellar space isn’t absolutely empty; there’s actually something there. One hydrogen atom is to be found in every cubic centimeter, even in the seemingly abject nothingness of the void between stars.
A ship with a kilometers wide electrostatic funnel could theoretically sweep up this hyper-tenuous gas, ionize it, and then shoot out the stripped protons in a stream to provide miniscule thrust. NASA already has such an ion drive (X3 Hall Thruster) which could be operational on future Mars missions. NASA's plans, at this early stage, certainly include carrying fuel on board though.
Granted, the kind of starship with the capacity to vacuum up its own fuel en route — a vessel of the future with the range to attain the ends of the Solar System and even further beyond — still has quite a number of extremely daunting engineering problems to hurdle, but in space great thrust isn’t required, only never-ceasing nudges that wind up cumulatively pushing the craft to astounding speeds.
A vessel that could manage no more than the snail’s pace of 1 mph acceleration, yet maintain that thrust for two years non-stop, would find itself hurtling through space at the end of twenty four months at some 63.5 million mph — just shy of 10 percent of light speed.
Humanity has always acceded to what nature has graciously offered — mills, looms, mortars, and engines powered by wind and water, funicular trams and railways moved by gravity. Sleek and swift clipper ships have ridden ocean currents and glided on the trade winds while laden barges transported goods pushed along by river flow.
Sunlight has been used to dry, cure, extract and prepare untold thousands of varieties of necessities from Neolithic times to the present. Mankind not only can never repay the debt but doubtlessly is poised to increase the arrears exponentially in the near future.
David Nabhan is a science writer, the author of "Earthquake Prediction: Dawn of the New Seismology" (2017) and three previous books on earthquakes. Nabhan is also a science fiction writer ("Pilots of Borealis," 2015) and the author of many scores of newspaper and magazine op-eds. Nabhan has been featured on television and talk radio all over the world. His website is www.earthquakepredictors.com. To read more of his reports — Click Here Now.
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