|AA Institute of Space Science & Technology|
Utilising an Asteroid to establish a large off-Earth colony in orbit.|
[A futuristic orbital engineering concept by A. Ahad]
Copyright © 2004 Abdul Ahad. All rights reserved.
Article posted: 29 September 2004
Main Attractions with an Asteroid Interior Space Station Concept
The "Aster-Com" starship concept which I have recently depicted will likely begin its life as an *orbital* engineering project, initially designed to accommodate a large colony living inside the captured asteroid circling Earth, where all technology and biosphere operations will be extensively evaluated. In the medium term, post International Space Station program completion a few decades from now, such an orbital colony venture could be our next realistic goal for a permanent "in space" presence, along side bases on the Moon and on Mars.
In-Situ Excavation Project
I had originally thought the asteroid could be harvested from its heliocentric orbit to a high Earth orbit where it may be subsequently excavated, with the resulting asteroidal debris giving the Earth an awe-inspiring ring system!
However, the combined gravitational forces from an *oblate* Earth along with perturbing influences from the Sun and the Moon would render such an "Earth ring" phenomena totally unstable, as I have noted in my recent astronomy paper. If the debris from such an asteroid excavation project cannot be contained within a neat ring plane of fixed incline, then this will have immense implications for safety of spaceflight in near Earth space.
Hence, carving out the interior habitat space for a potential Earth orbiting colony will require an excavation program in-situ, on the asteroid itself within its heliocentric orbit, prior to transporting the outer framework 'shell' into an Earth orbit. So how do I propose this could be done?
As I described in my interstellar spaceflight proposal, a number of variables must first be considered when deciding "which asteroid?". Close up robotic surveys of a number of asteroids will yield such information as shape, surface mineralogy, density, etc. from which a good choice can be made. An asteroid rich in its surface mineral composition would be economically attractive, since these objects are thought to contain 'rare Earth' metals such as Platinum, Iridium, Rubidium, etc. as part of a mining attraction for the initial orbital venture post orbit capture around the Earth.
Above: Japan's MUSES-C mission closes in on its target asteroid. [Image courtesy: JAXA]
Asteroid missions are currently HOT business in the arena of robotic exploration of our solar system. In February 2001, NASA's Near Earth Asteroid Rendezvous (NEAR) mission achieved a highly successful, gently controlled descent onto the surface of potato-shaped asteroid 433 Eros. Currently, the Japanese MUSES-C mission is on its way to an asteroid to hopefully retrieve a small quantity of surface material by way of a sample return mission.
Above: A small, 20-cm "nanorover" designed for asteroid surface exploration [Image courtesy: JPL]
A nanorover similar to the one shown above, was originally designed to be included on the Japanese mission, but subsequently that plan was cancelled on the grounds of spiralling costs.
A nuclear reactor could easily be deployed on the surface of a small asteroid which would then serve as a power source to not one - but perhaps several - heavy duty rovers, which operate as an autonomously co-ordinated robotic work crew "team". JPL research is well advanced in this area as depicted here. Each rover might be wired via an umbilical to its nuclear power source and utilise various kinds of 'power tools' ranging from drills to axes to sanding and polishing utilities. The Mars Exploration Rovers currently drilling holes into rocks on the surface of the Red Planet are proven examples that we have already mastered the level of robotic articulation necessary to perform such tasks on alien worlds.
By first establishing a robotic outpost on the candidate asteroid, then through a progressive excavation program utilising robots that dig their way into the body, the end result would be a hollowed out asteroid that provides thousands of square metres of habitat space suitable for housing a moderate sized colony. The post-excavated body will have substantially lower (< 10% of initial) mass and the process will have substantially lightened the asteroid's load when it comes to transporting it to an Earth circling parking orbit.
Transporting a Mountain of Rock and Metal through Space
The mechanics for initial capture of a small asteroid from either the main belt, the Amor or the Apollo classifications was briefly discussed in my original article under "Challenges of Assembling a Starship of Viable Size".
For a brief overview illustration of the astrodynamics requirements, I will choose near Earth asteroid 887 Alinda which is thought to be just 4 km across (2.5 miles), and approaches the orbit of the Earth to within 0.14 AU (20 million km) at perihelion.
Above: The AA Institute's proposed "Three-Impulse Strategy" for capturing asteroid 887 Alinda into Earth orbit! - click to see a larger image. [Credit: JPL orbit simulator / Abdul Ahad]
The above diagram presents a "three-impulse strategy" that could be used with this particular rock to achieve an initial Earth capture. 'A' is an orbit change impulse, which will be initiated at a pre-perihelic point whose heliocentric radius vector is 1.3 AUs, which will achieve a delta-V of - 1.9 km/s, braking 887 Alinda's orbital speed from 31.7 km/s to match Earth's 29.8 km/s. 'B' is an orbit matching impulse which would keep Alinda on the same orbit as the Earth until a favourable meetup point at 'C', which is an Earth capture impulse. At 'C' a close flyby of the Moon would result in a gravity assisted slowdown, along with further retro impulse to make the Earth-relative velocity zero, leading to a provisional capture orbit.
This is a somewhat simplistic illustration, since the orbit of Alinda is inclined at 9.3 degrees relative to Earth's, and in actual practice the number of dynamical variables requiring optimisation would be large, making favourable operations windows highly constrained and limited. On the flip side, there are over 20,000 candidate near Earth asteroids (NEAs) to pick and choose from with all manner of shapes, sizes and orbital geometries that prospective launch and capture windows are plentiful.
The fuel requirements to step-change the steep heliocentric orbital velocity and momentum of what is in essence a hollowed out 'celestial mountain' of rock and metal, are non-trivial. Perhaps several missions would be required to stockpile a bank of propellant either on the asteroid's surface or in an orbit around the body. Its weak gravity will demand some kind of anchoring mechanism for surface operations. A further option in braking the asteroid's speed via the "3-impulse strategy" I describe above could perhaps consist of detonating nuclear weapons in its path. The shock waves emanating from such precision targetted explosions would serve to alter the speed and course of the body toward an eventual parking orbit around our planet.
Yet further options may include guiding the asteroid toward close fly-bys of either Venus or Mars, where an 'atmospheric aerobraking' maneouvre (whereby the body skims through a thin layer of the planet's upper atmospher) could be used to reduce its heliocentric orbital velocity so as to facilitate a subsequent Earth rendezvous and capture. Options are plentiful through and through!
EVEN BETTER STILL would be to capture nearby asteroids, known as "corck screw asteroids" or "coorbitals" that occasionally drift into the vicinity of the Earth and then share a common orbit with our planet as it moves around the Sun. Several such objects have been detected in recent years measuring anything up to 200 meters in diameter, and effectively acting as an adittional "moon" to the Earth. Such bodies describe a strange cork-screw type orbit of usually a million or so mile radius centered on the Earth that would be easier to maneouver down to a lower orbit that's closer in reach to humanity.
A final near circular orbit around Earth of 40,000 km in altitude would ensure zero orbital decay and keep the asteroid hab within reach of geostationary satellite-bound rockets of our present era like the 4-stage Russian Proton. Assuming such a capture process has been successfully carried out and the asteroid is placed into an orbit around the Earth, I describe here a possible route to its successful transformation into a potentially habitable body.
Mining Operations on the Surface
If the asteroid had been carefully chosen with a robotic, cross-sectional analysis of its surface mineral composition, then the economic attractions of its mining could be overwhelming. Okay, there may not exactly be the celestial diamonds, rubies and emeralds to attract pirates... but the 'rare Earth' metals which are needed for many critical industrial processes on Earth could make their mining appear like gold dust to a future spacefaring community and more than make up.
Initial mineral mining on the surface of the asteroid could be either performed robotically or with manned missions, since the body is in a conveniently accessible orbit around the Earth. Futuristic space shuttle orbiters, which may be just a touch more enhanced over the kinds in use today (designed with improved safety and 'high Earth orbit' (HEO) reach capability), could be used for manned missions to and from the asteroid.
Setting up Habitat inside the Celestial Titanic
Once the entrance to the interior habitat has been sealed and isolated from the surrounding vacuum of space with airlocks and such like, the interior could be pressurised to one atmosphere of breatheable air, by feeding oxygen/nitrogen in Earthly proportions. Spin thrusters mounted around the asteroid's framework would maintain artificial gravity at one-g (9.81 m/s^2) equivalent of Earth's. Initially, it would be necessary to establish a 'controlled ecological life support system' (CELSS), with artificial lighting, plants and animals as depicted in my original interstellar blue print.
A thin layer of soil transported up from Earth would overlay the hard rock/metal composite of the interior 'walls' (floors) of the cylindrically shaped asteroid habitat. We know from microbial actions on Earth how sands can be transformed into growable soils over time... deserts turned into oasis... by carefully controlled microorganismic processes.
These same processes, if carefully applied on the Celestial Titanic, will gradually remove the stark division between growable top soil and the hard asteroidal rock underneath, making its floors suitable for growing plants and trees in abundance, where, under artificial gravity, roots grow from the inside outward in this imaginary asteroid ship of the future.
Above: An engineering schematic of the Ahad-AsterCom starship. The "Celestial Titanic", envisioned here, will be identical to this - minus the comet-mining robotic arms! [Copyright: Abdul Ahad]
Initially computerised monitoring, sampling and adjustments would be necessary to establish and maintain the correct balance between the various components of the CELSS via 'fine-tuning' the recycling drivers. An in-situ nuclear power station will provide all the electricity needs for much of this recycling work and be more than ample in meeting power needs. However, over time, the biosphere will transform itself into an accommodating environment and hopefully start to run under its own steam. Through careful selection of plants and animals that contribute favourably to this process, we can create a "miniature Earth" environment to support a natural ecosystem and food chain. All transportation activities to take large trees, shrubs, birds, insects, people... from the ground up to an Earth circling asteroid hab would be immeasurably easier than to take such things up to a totally barren Moon or all the way to a much more 'Earth-like' Mars.
When it comes to *natural* bio-engineering, we have done something similar on Earth for thousands of years. All farm animals like cows, horses, chickens, turkeys and geese did not come about through a total miracle in nature. Over thousands of years of artificial selective breeding, humans adapted them to provide our communities with a reliable supply of food. The sweet smelling roses in their variety of awe inspiring colours and fragrances you encounter as you walk through an empty park on a fresh summer's day, did not happen totally by accident!
We shaped - and up to an extent - *created* our world here. We have every potential to create our world up there, in the glittering starlit skies we see at night, too. Though as a lifelong naturalist, I feel it important to stress here that I would never support any *genetic* manipulations; natural processes are tried and trusted and will work best.
Setting Sail for the Planets and Stars
Some day, once the orbital colony gets tired of seeing the same monotonous features, facing the same planetary cradle of blue oceans and swirling white clouds day in day out, it might decide to venture off toward other more interesting parts of our solar system. This would be made possible thanks to the 'high Earth orbit' (HEO) altitude and high-energy nuclear propulsive capabilities of this ingeniously designed space station of the future.
The escape velocity V of an object departing from Earth's gravity well is dictated by:
V = (2GM/r)^1/2
[ where V = escape velocity, M = mass of Earth = 5.9742 x 10^24 kg, r = geocentric distance, G = universal constant of gravitation = 6.67 x 10^-11 N m^2 / kg^2 ]
For an orbital space station like the one I envision here at 40,000-km in altitude with a roughly circular orbit, V = 4.1 km/sec. In terms of the true propulsive effort necessary to achieve an interplanetary escape trajectory, this would be just a tiny fraction of that of the present day International Space Station's 400-km orbit, where V = 10.8 km/sec.
Once the Celestial Titanic has successfully managed to escape the gravity well of our own planet, the distant worlds of the outer solar system may be an eye-catching destination for its inhabitants. A journey through the asteroid belt would be made safe by the tough rock/metal outer body of the station-turned-ship. Imagine the exotic worlds and fine vistas that await the colonists. Flying over the icy oceans of Europa and the volcanos of Io... safely trekking through a gap in the Saturnian ring system, peering over the icy canyons of Tethys... and exploring what intense horrors may lurk inside the dark, frozen caves of Triton via a brave surface excursion!
Above: Voyager 2 photo of Saturn [Image courtesy: NASA/JPL]
And when the ship docks into an orbital rendezvous with Pluto - a world quite literally "on the edge of forever" - half of its orbit would be looking inward toward the inner solar system with our distant Sun and the Earth lost somewhere in its overwhelming glare. The other half of the ship's orbit would open up a forebodingly endless gulf of interstellar space, with shores reaching out to near eternity whose nature and inhabitants no human mind can ever hope to truly imagine...
An artist's impression of the Sun as viewed from the icy surface of Pluto, a tiny world on the remote edge of our solar system. The Sun's light intensity from this distance is drastically reduced, although still above that of the full moon seen from Earth. [Picture credit: Don Dixon]
Looking even further out into the far distant future, once all the worlds within our solar system are fully explored and the time is right, the colonists might opt in favour of an outright interstellar oceanic voyage, whereupon the Celestial Titanic could re-invent itself as the 'Aster-Com' starship and wander off beyond the outer reaches of our solar system in a general direction headed toward the third brightest star in our night sky...
The Destiny of our Species Rests on the Simple Toss of a Coin...
At this present juncture here in the early 21st century, humanity's cosmic adventures into the great unknown face a situation of three << hopefully parallel >> choices: embarking on an orbital colony program (like the one envisioned here), setting up a base on the Moon and making strides toward a manned settlement of the Red Planet. Each of these avenues will stretch human spaceflight accomplishments of the past 40 years to pioneering new heights of identical grandeur.
In the grand scheme of going into the complete 'unknown' and the steepness of new financial, social and technological demands we face, the scales are fairly evenly balanced for each option. A single toss of a coin might decide an outcome between a manned base on the Moon or setting up a robotic outpost, as a precursor to a manned settlement, on Mars. A further toss of that same coin might decide delaying any further manned endeavours out into the hostile environment of space until the 22nd century, in favour of setting up a robotic outpost on each of two near Earth asteroids with a view to building a Celestial Titanic (like the one I envision here) within the interior of one of them.
The future of our planet, of our species and of as yet unborn billions hangs in the balance and will be determined by the choices we make today. Superficial inventions of man such as our national divisions, inefficient economic, financial and political frameworks and the pride and prejudices of individuals, could all act as shackles to human progression and make choosing a sound future direction in space no more informed than that of the simple toss of a coin...
First Ark to Alpha Centauri - A novel by A. Ahad
"An epic fantasy voyage carrying the hopes and dreams of everyone who ever was, everyone who ever is and everyone who ever will be... on a journey spanning 2,000 generations and lasting for no less than 50,000 years into the future!"
Click on the book's cover image for a fuller, more condensed version of the synopsis for this first novel in the series. You will also find information there on how to order your own copy!
"First Ark to Alpha Centauri" - A motion picture concept!
Public discussions on this concept
About the author
Copyright © 2004 by Abdul Ahad. All intellectual property rights on this article and the spaceflight concept depicted herein are fully reserved by the author under contract with his literary agents in the United Kingdom. Any sharing of this work is only permitted for personal, non-profit and educational use.