Wednesday, January 30, 2013

The Next 25 Years of Spaceflight.

The next twenty-five years in spaceflight will be fascinating.

At time of writing, Chris Hadfield circles the Earth in the International Space Station.

The next period of microgravity experiments in physics and chemistry, medicine and botany, microbiology, entomology, (yes, ants in space!) crystallography, will bring results we can’t foresee, for many of the most important discoveries in history were accidental. But there will be results.

More powerful motors needed

With Hubble finding new exoplanets almost weekly, there is more of an incentive to do the research into interstellar drives. The power units we have now make for slow trips within our solar system. They’re simply not suitable for interstellar flight. While a Moon base is often bandied about as an alternative to Mars, it looks mostly like a military proposition. For that reason it is more likely to happen than an immediate Mars expedition. Mars doesn’t command the high ground of a terrestrial battlefield. The Moon does. The Moon offers certain advantages for surface-based telescopes of any wavelength. Mars has none of these advantages, its only attraction is for long-term colonization. It has an atmosphere,  the Moon does not.

Here’s the thing with Mars colonization. It’s completely unnecessary assuming we learn to manage and conserve our terrestrial resources of air, water and topsoil. As a backup to Earth, maybe there is some logic in it. Looking for life on Mars does not require colonization, only probes of increasing sophistication.

A colony on Mars

A colony on Mars would in some ways be a lot easier than a Moon colony. While there must be ice or water somewhere under the Moon’s surface, the fact is that the Martian atmosphere has small quantities of water vapour, surely an easier proposition in terms of harvesting it. Mars has tons of water in a hundred cubic kilometres of the Martian air. All you need is an air pump. You would need to process hundreds of tons of Moon rock or soil to extract one litre of water. The difference is a technical challenge—the Moon is a lot easier to get to. It’s quicker, two days as opposed to two or three years.

We already have the technology, which is part of the attraction.

Several companies have been formed for the commercial exploration of space, more specifically the asteroids. At an economical Delta-V, an accessible asteroid might take four years round trip for a sample to be returned to Earth.

433 Eros
The elements we take for granted in modern industrial processes, platinum, gold, antimony, and others, will possibly run out in the next sixty years. Mining the asteroids, processing the materials in space, and then shipping the refined product to the Moon or to Earth could be profitable for the firms involved. With modern industrial growth, even at one hundred percent efficiency of recycling, stocks will eventually run out. Totally robotic ships could be designed to mine and refine the ore. I recall an Isaac Asimov story with Martian colonists engaged in ice-mining and asteroid-finding. What was once science fiction is now within the realm of possibility, if not immediate probability.

The space elevator

A space elevator might be feasible within a few years. The cost per ton of getting materials into low orbit would be phenomenally low compared to chemical launch vehicles. Building it might be like trying to build a spider’s web—a lot harder than it looks. The first filament makes all things possible. Initially, we would either have to unroll a filament on launch from the pad, and keep it intact until orbit is achieved, or anchor one end somehow in space and then descend to Earth, again keeping the filament intact. Once one filament is in place, it must be strong enough to haul up one that is twice as thick, the full length required to be properly anchored or counterbalanced on the ends.

Yet ultimately, I think that’s how it will be done. Much like a cable-laying ship of the nineteenth century, with no need to join short lengths. It will all be one piece. I see something like a tungsten leader—just like on the end of a fishing line. This will take the heat of the rocket exhaust, and the actual filament, likely of nano-carbon tubes or something similar, will be attached to the end of it. The actual cable will be on a motor driven reel, unwinding as the rocket climbs out so as to reduce drag and directional input from the towed filament.

The only other way to do it would be to build the full structure from the ground up, stabilizing the top with gyros, or even drive units holding it in place against the winds, which would be variable at different altitudes. It would take a lot of computer power, super instrumentation and a flexible control system just to keep the thing upright. If the cable is 38,000 miles long, the problems seem insuperable. Different types of flying machines, including high-altitude helicopters and airships need to be developed for construction of this type.

New kinds of flying machines

Part of the weight initially could be borne by tethered balloons, with drive units of their own to help maneuver and steady the structure on the way to completion. My big idea, which seems more practical than hot chemical rockets, is to use a machine shaped much like a jumping-jack to get that first filament into space. The central spindle has the cable or filament attached at the bottom end. The central spindle is the working body of the ship with propellant tanks and small reaction motors for later use in space. Once the cable is up and self-sustaining due to centrifugal force, the ship itself is useful on its own. On the arms of the jumping-jack are a minimum of four laser targets. The ship is propelled by a ground-based array of laser machine guns of great power.

They must go through the charge and discharge very quickly and the pulses would be controlled by computer software. The people of North America might be willing to give up electricity for a day or so to get the thing up to its destination. And that first filament makes all other things possible…we need to avoid heat transfer from the targets to the body of the ship. Here’s the interesting thing mathematically. Once you push your package to the halfway point, the power required, which was increasing at an exponential rate, begins to taper off in terms of increasing power requirements. It originally went up due to the increasing weight of the cable.

But gravity varies inversely with the square of the distance. One end of the cable is weightless, but it still has mass. What that means, at the halfway point, centrifugal/centripetal force begins to tug some portion of the cable away from the earth, like a ball on a string swung at arm’s length. At that point you are away to the races. By doubling the size of the cable, each one strong enough to pull up its replacement, you eventually end up with cables not unlike those used to suspend the Golden Gate Bridge, and by having an array of launchers, all using a common laser array, you can build a structure that looks ultimately like an Eiffel Tower made of carbon cables, one that doesn’t stop with an antenna and a flag on top, but one that just keeps going up and up and up…until it gets all the way out into space.

Photos: Wiki Commons, NASA.


  1. Louis,
    Like the Shuttle Program, what will kill, or at the very least hamper, enterprising engineers from taking the next step are the tight fisted bean-counters holding the purse strings...

  2. The key thing is to show how the rich could get richer using these technologies. Then we might see some movement.

    1. Ain't that the truth Louis. I've just finished reading a scifi novel concerning the first mineral mining venture on Mars and how it quickly goes pear shaped when they realise they aren't alone. :)




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