Planning Scenarios for Space Development

Copyright (c) 1995 by Thomas L. McKendree. Placed on the web by the Molecular Manufacturing Shortcut Group for educational and individual use only. No commercial use without prior written permission. All Rights Reserved.


Two scenarios for developing space are presented. The first illustrates how space applications of molecular nanotechnology might be planned for. The second illustrates what could happen if molecular nanotechnology is widely available before the world has planned and prepared for it's application to space. The technical foundations for the scenarios are cited, the scenario development is discussed, and some open questions are indicated.

Note, this paper was originally presented in 1995 at the Space Manufacturing Conference, held by the Space Studies Institute in Princeton.

Table of Contents

  1. Abstract
  2. Introduction
  3. Scenario "Slow and Planned"
    1. Intellectual Currents
    2. Implications for Molecular Nanotechnology
    3. Aerospace Implications
    4. The New Millennium Approaches
    5. Multi-Lateral Negotiations
    6. Privatization
    7. The Coherent Center of MNT Development
    8. Several Years in Space
    9. Progress
    10. Acceleration
    11. Take-off
    12. Full Development
  4. Scenario "Sooners"
    1. Molecular Manufacturing Capabilities Surge
    2. An Opportunity for the Lucky Few
  5. Technical Justification
  6. Scenario Selection
    1. Comments on Slow and Planned
    2. Comments on Sooner
  7. Open Questions
  8. Conclusion
  9. Bibliography


The future is unpredictable. Nonetheless, we must make decisions in the present that make a difference in the future. In recent history, when those decisions have been to pursue specific aerospace projects, they have often taken decades to play out.

Frequently, people make decisions while using only a single mental model of how the future will unfold. If that model proves mistaken, they may have made plans which collapse when circumstances prove different than expected.

Scenarios are a means to deal with this problem. By presenting divergent stories, one can think about an uncertain future. People think in stories, which makes this style of presentation more compelling, and thus more useful, for decision makers. By presenting multiple stories, specific plans can be considered in multiple contexts. If a specific space development project could not adapt well to one of the following scenarios, this suggests that project is vulnerable to uncertainties it cannot control.

This is an unusual AIAA paper, in that it consists primarily of two stories. Neither represents a firm prediction. They were selected to span uncertainties about future space development that appear to be most important. Several other uncertainties about the future also vary across the scenarios.

The intent is to provide a memorable framework in which those concerned about developing space can place and assess specific strategies, missions and systems. The scenarios's titles are "Slow and Planned" and "Sooner."

Scenario "Slow and Planned"

In 1995, traditional space plans continue much as expected. Ongoing programs such as Shuttle, GPS, Geosynchronous communications satellites and space launches, and developmental programs, such as LEO constellations, Space Station Alpha, EOS, X-33, X-34, and various technology efforts, continue their ongoing progress.

Intellectual Currents

"Reality," in academic circles, has an elastic meaning. Show an intricate molecular structure in 1995, and a chemist might say "That's not real," meaning "I can't synthesize that in my lab. There's no way I could write a paper about it." With the same molecular structure a computational chemist might say "That's real," meaning "I could simulate that structure on the computer and write a paper on it. It looks interesting."11

In the mid-90's, those studying space development are like the computational chemists--using scientific knowledge about how the physical world operates to analyze various proposed systems.

While major aerospace projects continue their ongoing progress, in the background molecular nanotechnology (MNT), the idea of designing and building to atomic precision grows as a subject of interest.

Most of the work consists of the form "If we could produce objects to atomic precision, then we could produce this design, which, with this safety factor, offers at least this level of performance."

One simple conclusion is that if one can put every atom in its place, then one can build diamond structures. Indeed, one can build unitary structures with diamond-fiber composites, getting tailored anisontropic near-diamond strengths-to-weights, with strong fracture resistance, and no cracks to propagate.7

Another conclusion is that with a general ability to rearrange molecular structures, it will be possible to take the output (waste) of a human occupied environment, such as a space station or a lunar base, and totally rearrange that waste cleanly into the necessary inputs for the habitat. This is a Closed Environment Life Support System (CELSS).7

A third conclusion is that very high performance interplanetary propulsion, such as space-manufactured thin solar-sails, and very lightweight solar electric ion-engines, could be built.1

Implications for Molecular Nanotechnology

Feasible operating frequencies of mechanical systems are inversely proportional to characteristic lengths.5 Thus, molecular-scale mechanisms can have very high operating frequencies.

Mature molecular manufacturing systems can build most diamondoid objects defined to atomic precision. Molecular manufacturing systems are themselves diamondoid objects defined to atomic precision, and a molecular manufacturing system can build a molecular manufacturing system; it can self-replicate. This allows one to go from a single molecular manufacturing system to tremendously large amounts of molecular manufacturing capability.

The self-replicability of molecular manufacturing, combined with the low cost of its necessary inputs (low-purity bulk chemicals of nearly any form, containing the necessary elements), means that the marginal cost of MNT capital is extremely low.

The fundamental general conclusion about MNT is that someday we should have the ability to build a molecular manufacturing system designed to atomic precision. This will provide the ability to create huge quantities of molecular manufacturing systems, which in turn will make feasible extensive and widespread ordering of matter to atomic precision. These capabilities are likely to occur within the current lifetimes of many people.

Aerospace Implications

One aerospace implication is that nearly all current or planned aerospace systems can be redesigned and eventually built to exploit passive structures of near-diamond strength-to-weight ratios. It will also be possible to build active structures of lower strength-to-weight suffused with actuators and intelligence.

Another aerospace implication is that very large and complex aerospace systems will be producible, fully outfitted, at extraordinarily low manufacturing costs.

The main aerospace conclusion is that someday people will have the ability to settle and survive in space, using only the financial resources available to a typical first-world citizen.

The New Millennium Approaches

The aerospace community spends several years re-deriving, reviewing, and convincing itself of these conclusions. Giving added impetus is the continued progress in science and technology along paths which point towards robust control of matter to atomic precision, such as scanning probe microscopy and scanning probe manipulation, protein design, macromolecular chemistry, computational chemistry, and growing explicit interest from these scientific communities in MNT.

Companies work on different parts of developing MNT more vigorously, and those focusing on different areas start forming alliances and partnerships.

It is not clear that near-term space projects require much adjustment. The International Space Station is being assembled in orbit, and already is partially manned. The first EOS satellite is gathering data. Communications satellites continue beaming data, and LEO constellations are booming. A surfeit of space launch vehicles, spooked by successful demonstrations of X-33 and X-34, appear to be in the throes of a shake-out. Every year at least one space probe is launched, although they usually are much smaller than Galileo. None of these programs requires any immediate, dramatic change.

On the other hand, long-range space plans clearly must match the future capabilities. Some someday, the solar system will be heavily settled, and the principal policy question is how to prepare for and accommodate this.

Aerospace communities are closely aligned to their national governments. The aerospace community provides national governments with weapons, governments are large aerospace consumers, although commercial LEO satellites have become the largest share of the space launch market, governments own or control significant portions of aerospace companies in many nations, and personnel frequently move between industry and government. Since aerospace communities are closely aligned to their national governments, their thoughts on MNT are taken seriously.

Multi-Lateral Negotiations

Nations that recognize the potential of MNT recognize arms-control as the most important issue. They legitimately worry that once MNT is developed, other nations might use it to create weapons, and such weapons appear potentially even more fearsome than the Cold-war nuclear arsenals. The problem is that MNT devices seem to offer the only defense against many MNT threats.

In response, a progression of treaties, starting with the "Tsukuba protocol," establish international oversight on the development of MNT armaments, with only "defensive" systems allowed. These "active shields" will be designed, developed and operated multilaterally. The theory and information which guarantees that they are purely defensive will be available for review on-line by the entire world.

These treaty negotiations help create a community with more common views on other aspects of MNT policy. Many aerospace companies took a keen interest in the MNT-weapons issue, and they persuade nations of the need to accommodate space settlement under international law.

What really is needed to accommodate the inevitable space settlement is private ownership of extraterrestrial real estate, where people will live, work and utilize local resources. The owners could in many cases be corporations, Governments, or other organizations, not just individuals. Despite the world trend towards capitalism since the 80's, private ownership of territory in space is a wildly unpopular concept in many areas, especially among third-world government representatives at UN Committee on the Peaceful Uses of Outer Space (UN COPUOS). Efforts at negotiations prove painful and seem fruitless.


Given the difficulties, major space faring nations hint at establishing on their own a multi-lateral regime for allocating private ownership interests in space real-estate, and defending those titles, if no deal can be reached. Rhetoric about "space banditry," "raping the heritage of all Mankind," and "Universal imperialism" becomes even more heated.

Finally, the Czech Republic suggests a model for allocating space assets "to all Mankind," based on its own post-Communist privatization scheme.

There would be several rounds of sales. The solar system would be divided into eleven categories (NEO carbonaceous asteroids, other NEOs, each inner planetary surface, the non-polar moon, the lunar poles, the asteroid belt and Martian moons, the gas giants, the outer-planetary moons, other). In each round, certificates would be evenly issued to everyone on Earth over eighteen. Certificates would be transferable, salable, and could be grouped into mutual funds and consortia. Entities with certificates could then propose sets of space real estate, and make bids on these sets with their certificates. At the end of the auction, high-bids would be awarded ownership and responsibility for their bidded space real estate, but no more than a certain fraction of real estate in each category could be sold by the end of each round. Ownership of purchased space real-estate would be total, divisible, transferable, salable, and registered.

This basic model is accepted. In tough negotiations, 5 rounds of sales 18 months apart are agreed to, with fractions that sell 50% of each category by the end of the fifth round. Rounds beyond the fifth can be authorized by a majority vote of nations whose nationals control less than the average human per-capita ownership of extra-terrestrial real-estate, weighted by that difference and population, but not until a certain threshold number of people are living off Earth.

Suddenly, questions like "Is there water at the lunar poles?" and "which asteroids have significant amounts of accessible carbon?" are commercially very significant. In the near term, they affect bids, and once space real-estate is sold, speculative values can change dramatically depending on what is found there. Low cost space probes are sent widely. Several lunar polar craters do contain water and carbon.

In the midst of the first round of sales, several groups begin exploring business plans to mine the moon, and build solar power satellites (SPSs), without waiting for MNT. They plan on buying lunar real estate if the financial numbers can be made to work.

At the first round formally closes, Microsoft Corporation announces "The Gates Prize," for the first person to communicate with the company from the Moon, using Microsoft's virtual reality communications software.

The Coherent Center of MNT Development

Most people and nearly all organizations are risk averse. They would like to win big, but they are willing to reduce a bit how big they might win, in order to avoid the chance of losing big. To have MNT, when no one else has, will be to win big. To not have MNT while someone else does, will be to lose big.

Expanding on a base of alliances and partnerships between companies working on different aspects of developing MNT, risk-sharing deals, including joint projects, equity swaps, pre-licensing agreements and research consortia, tie the groups working on MNT projects into a denser web. It makes a great deal of difference to individual researchers and organizations whether or not their specific efforts to make particular breakthroughs succeed, but any step forward can quickly be widely used, and any organization far enough ahead to take the lead in some area necessarily has made so many agreements in order to be ahead that it cannot use a temporary lead to establish and enforce a monopoly. This web of relationships eventually pulls the leading organizations into a coherent center.

Several Years in Space

With secure ownership rights, many investigate how to settle space with current, or near-term technology. Others try to develop less expensive launch capabilities. SSTOs begin entering service, but launch costs are still well over $1000 per kg.

Communications satellites continue as the major portion of the space launch market. Lower launch costs make it cheaper to put bandwidth into space.

For a very limited clientele, space tourism is affordable, but even one tiny orbital hotel, the No Borders Bed & Breakfast, has trouble staying full. (People soon make unfortunate jokes about the "No Boarders B & B.") The majority of space tourists go up, stay in their launch vehicle, and come down.

The initial sales of space real-estate collapses in a speculative slump; there is plenty of real estate, and not much that can be done with it, while more is being sold.

In 2008, after picking up several lunar plots cheap, including one known to have ice and carbon, the Sultan of Brunei puts out an RFP for an unmanned base to develop the site for future settlement from Brunei.

This turns a corner. China, largely for prestige, decides that it will have a lunar base, and sets out to build one. In the upcoming fourth round of sales the Chinese government once again focuses on "guiding" its citizens to acquire large, contiguous plots of land.

The International Space Station is beginning to near the end of its scheduled life. The short term focus is to patch and extend the station's life as a research base. Lower launch costs make it relatively easy to keep the station supplied, reducing maintenance difficulties.

With the idea of SPSs having been bruited for years, NASA, NASDA and ESA set out to build a small demonstration SPS in LEO. The only part more complex than suggested commercial SPSs is the beam slew and pointing mechanism.

In 2010, the first molecular engineered "smart material" appears. Most early smart materials control color or texture. Increasingly, they are intelligent paints and glues. Varieties will proliferate and become wildly popular on Earth, but none offer any immediate utility for space


Over the years, abilities grew to design and control increasingly large systems to atomic precision. On Earth researchers develop self-assembling macro-molecular systems which provide the core for massive, bulk Random Access Memory (RAM). This feeds directly into the ongoing growth in computer capabilities.

Advanced biotechnology develops drugs that ward of space-sickness, and space tourism starts climbing.

Micro Electromechanical Systems (MEMS), often confused with MNT, are put to work as very low cost space probes. First used by investors to assay candidate real estate, the space agencies adopt MEMS probes for science missions, and send swarms of probes to many targets. Humanity's understanding of our solar system and the bodies in it grows.

Carbonaceous Chondrite asteroids remain the favorite candidate for space real-estate expected to become valuable as MNT is fielded. In the interim, small robotic precursors are sent to further explore and then prepare some of these sites for future utilization. Advanced chemical engineering, often drawing on MNT-related research, helps in processing the local resources.

Lunar bases grow. The Chinese have the largest, and Japan's is also substantial. The Mormons are building up a presence, and several private individuals have started lunar outposts. It seems certain that a lunar hotel will be established, once adequate round-trip transportation is available between the Earth and Moon.

Several nations push for the next UN round of space real-estate "privatization," but most poorer countries decide that if they wait a little longer, they will get significantly more money, so nothing happens yet.

After several years of refinement, and fully recovery of investment costs, space launch prices to LEO drop to near $500 per kg.


Simple molecular mechanisms designed on Earth, combined with the practical experience culled from living with space biospheres, yields robust CELSS. The ability to have essentially zero wastage from life-support systems increases the demand for space habitats, and the desire to expand existing space habitats, actually leading to a significant increase in demand for organic elements for space habitats, especially as more groups and families start settling in space.

The polar lunar mines grow in importance. To satisfy the demand for organics, owners of several very small asteroids consider bringing them to Earth orbit.

To satisfy increasing space traffic, an international joint venture, legally headquartered in Moscow, begins offering the services of nuclear-electric space tugs.

A few early smart materials had some abilities to control their shape, but in general none were not well suited for space. Eventually, however, a smart material is developed that can exert forces, and that holds up well under vacuum and space background radiation. This proved very useful in very-low g environments, such as on asteroid bases.

In 2015, MNT "assemblers," general purpose manufacturing robots capable of self-replication, are announced with great fanfare. Despite fantastic predictions, they do not instantly transform the world. The problem is that they are "general purpose" in theory only. In practice, the software to make them produce much of anything is nonexistent, and coming slowly. International restrictions designed to prevent abuse of "self-replicating devices or their output" makes work even more burdensome, and progress even slower.

The LEO SPS works, and a consortium of power companies along with several large international aerospace companies launches a project to build a "lunar mine" and a demonstration geosynchronous SPS. They soon revise their plan and merely contract lunar mining services from existing lunar bases.

ESA, NASA and NASDA invite the Russians and Chinese to join them in turning the LEO SPS into a new international space station.


Despite slow progress, advancing molecular processing reaches the point where diamond-diamond composites can be made industrially. To a person's eyes, the process appears to be one of "casting" in a mold. The long-anticipated ability to produce large diamondoid structures leads to lighter space-launch vehicles. Several operating companies take large losses, retiring old SSTO's, but the new vehicles drop launch costs to under $200 per kg, and that's while companies rapidly recover their recent investment costs.

Anyone who can, for example, sell their house and net well over a hundred-thousand dollars per family member, can move into space. Developers start creating massive tract's of "homestead" on the Moon, and sell package deals to get people started. MNT provides robust environmental life support, the ability to produce needed tools remotely, and every year, more amenities.

"Hard core" settlers target the asteroids, outer planets, or even just Mars, if they can afford the transport, finding Lunar colonization is becoming too tame.

Exploding traffic quickly covers investment costs, and the price to LEO falls in a couple years to below $50 per kg. This proves fortunate for the developers; a significant fraction of the homesteaders are not thrilled to be in "lunar suburbs," but the vanishing market they represent is more than made up by people buying inexpensive lunar homesteads.

Full Development

Increasingly, sophisticated assembler software is available. The massive capabilities of MNT-based computers provide powerful automated design capabilities through shear brute force. What would have been considered a miracle thirty years ago is often common-place. There is no body in the solar system, outside of the Sun and on the Gas Giants, which cannot be settled.

In 2022, nations finally authorize further rounds of space real-estate "privatization," and this time, no one doubts that their certificates are valuable.

One group, which has automated a large belt asteroid, announces a plan to build a Space Elevator. They will establish a geostationary satellite, supply it with carbon from their asteroid, and grow a diamond cable up and down, until the cable reaches the Earth's atmosphere.

The cable will then draw carbon from the atmosphere to thicken itself along it's whole length, and then extend to the ground. At that point, "elevators" will lift people and payloads into space, and bring others down. Launch costs to LEO will be minuscule.

This project will clearly take years, which gives them time to negotiate the rights to the atmospheric carbon they plan on using, and for the Earth orbital trajectories the cable will block.

Meanwhile, research probes are launched towards several nearby solar systems, and humanity begins a discussion of how it will allocate rights to settle the stars.

Scenario "Sooners"

As this scenario starts, traditional space plans continue much as expected. Constellations of LEO satellites go up in the late 1990s, and world-wide communications continues booming. The International Space Station's schedule slips, and slips again, but by the turn of the century, pieces are actually in orbit, being put together.

The real scientific tour-de-force, however, is on the ground. A group of researchers designs and produces a molecular robot. It is built from a carefully engineered set of designed proteins, is much smaller than a human cell, and is controlled in solution using acoustic signals.

The reaction is incredible. Most researchers decide that molecular nanotechnology (MNT) is on its way, and this robot is the first step. Ordinary citizens, as they hear what this nanotechnology is, decide they like it, as long as it can be made to work safely.

The DNA sequences for the robot proteins were published in the initial work. Any reasonably equipped lab can produce the robots, and it seems every lab with pretensions of doing something important does so. A mad scramble follows to extend the work, produce better robots, and use them.

Pharmaceutical companies put a number of well-known but previously hard to make drugs into mass production. In just over a year, the first computer related products come out, and the historical double-every-two-years growth rate of computers accelerates.

This progress continues, drawing in fresh investment, feeding on itself. Expectations grow. The Economist estimates that over one percent of Gross World Product will be invested in molecular nanotechnology over the next year, and that may double the year after.

There is massive debate over what policies to follow and laws to enact as the revolution unfolds. Powerful groups take strong positions on opposing sides, and there is no consensus. New miracles seem to appear every few months, then every few weeks and the scientists continue their furious debate over what will be feasible. With no agreement on what can be done, it is hard to agree on what should be allowed. The problem is really that technical progress is faster than society's ability to evolve rules can keep up.

Some say the goofiest idea is to sell off the solar system. Pundits point to computers, and then nanotechnology, as areas that grow tremendously on their own, and point to NASA as another institution whose future has passed it by.

Molecular Manufacturing Capabilities Surge

A little over three years after the first molecular robot was announced, the technological race in hardware is tight. Everyone started with the same molecular robot design, much of the work was published, leaked or shared, and a lot of effort had been copying what others were doing.

Systems exist that produce arbitrarily shaped large structures out of diamond. More advanced versions of the original protein robots build special diamond-building robots. These limited, second-generation devices link up in solution, forming scaffolding. Interaction with nearest neighbors and external signals allows the robots to locate themselves in three dimensions, creating a registered matrix in space. Using downloaded object descriptions, the robots build diamond as appropriate in their immediate region, and the arbitrary structure, usually a structural component, is built.

Several somewhat general purpose manufacturing systems, that can build limited ranges of products and self replicate, are also widespread. Some use second-generation robots similar to the diamond-robots, with more advanced on-board computers. Others use microscopic assembly lines to build atomically precisise, standard building blocks assembled into complex, three-dimensional objects.

A significant minority of products are provided as software instructions for popular manufacturing architectures, and it appears that standards are starting to emerge for software descriptions of molecular manufactured products.

An Opportunity for the Lucky Few

Then someone hides a curious file on-line. No one who could have done it ever claims responsibility. While the vast majority of people on Earth do not have the technical sophistication and the hardware necessary to take advantage of this file, dozens of individuals use it, and molecular manufacturing labs where they work, to produce rockets. Each rocket launches a probe, which flies to a carbonaceous chondrite asteroid and delivers a molecular manufacturing system that self-replicates until it takes over the asteroid. The second half of the file is used to guide the production of a two-stage, personal space vehicle. Seven are in space following their precursor probes before authorities realize to be suspicious of anyone with a stockpile of magnesium (fuel for the second stage's ion engine in the original design).

By then, it is too late. One meticulous student edits the software, and settles Phobos. As the squatters start arriving at their asteroids, they begin communicating, and trading improvements in the designs of their habitation and equipment. An entire village in China rockets into space, and goes to the colony established by their favorite son. While every nation officially bans unauthorized space travel, the land rush is on, and most nations tacitly condone their citizens occupying what they can. Soon every body in the solar system known or suspected to have carbon is targeted with probes. Not that long thereafter, they are all occupied with settlers.

There are more people who want to go into space than well-suited destinations. A trivial modification of the probe software turns it into a kinetic weapon which can fly in at 40 km/sec or more. Disorganized battles over desirable asteroids and other bodies break out. More sophisticated weapons, on both sides, are developed.

In general, the defenders win by virtue of their massive resources. The original squatters form a rough alliance to hold on to their original claims, and trade strategies and designs to deal with the evolving threats. Over time the fighting settled down, and people grudgingly accept the status quo in space

By then, many people off Earth feel that the Solar System is getting too crowded, but, there are already probes on their ways to the stars.

Technical Justification

This paper can only point to discussions which provide technical justifications for systems used in the scenarios. A number of systems mentioned are current projects. That status makes these reasonable candidates for future deployment, and they are not discussed further here.

Projects which are not currently underway, but which have been examined, include SPSs, lunar bases, and nuclear electric space tugs.

Space elevators are a widely discussed concept, arguably feasible if one can provide adequate diamond as structure.2 MNT will be able to provide large diamondoid structures, given adequate designs and sufficient supplies of carbon.

Work by Drexler discusses diamondoid structures1,5,7,8, CELSS7, Solar sails1,7 and ion engines1. Drexler7,8 and others3 discuss smart materials.

Jeffery Soreff discusses RAM as an early MNT product.13 Designed, self-assembling macromolecular systems are an obvious candidate for producing such devices, which would reasonably come in the early stages of MNT development.

Space sickness is a medical condition subject to ongoing research. An anti-space sickness drug is a plausible result of substantial biotechnology research.

Friedman has suggested sending automated precursors "seeds in space" to prepare for human activity in space.9 Both MEMS probes and small robot precursors refining raw materials fall into this concept.

Specific SSTO launch prices are speculative. Diamondoid structures, however, would offer increased performance with greatly increased safety factors, which should allow lower operating costs.

Drexler5 discusses a limited molecular robot using a Stewart platform. He also discusses building molecular machinery through self-assembled proteins fabricated using traditional biotechnology.7 It does not take much imagination to combine these two concepts into the molecular robots in Sooner.

Molecular Manufacturing (MM) systems, including assembler-based systems, would be automated, and thus very software dependent. It is quite plausible that early MNT hardware would lack much utility without adequate embedded software. The availability of adequate software depends on efforts during development.

The systems in Sooner that produce arbitrarily shaped large structures out of diamond are similar to the manufacture of a rocket engine described by Drexler.7

Given the initial molecular robot in Sooner, second generation systems would be a natural progression before developing mature MNT. Chapter 16 of Drexler discusses analogous intermediate systems.5

Using LH2/LOx for propulsion, a mass ratio of 15 is more than adequate for single-stage injection into an interplanetary trajectory. Solar electric ion engines1 offer specific thrusts and impulses quite sufficient for asteroid rendezvous from highly non-optimal interplanetary trajectories. Diamondoid structures and engines would require only a small portion of the rocket's dry mass. 1 kg is grossly oversized for an MNT-based asteroid development payload. This allows a rocket for an Earth-launched asteroid development probe of less than 15 kg gross lift-off weight (GLOW). Issues with covert launch in the scenario might suggest adding a small zero stage.

Drexler has sketched out the basic approach of applying his assembler concept to developing the mass of an asteroid.6 The necessary operating period is on the order of weeks, and the mass requirement for delivered payload is quite small.

Drexler discusses a personal Earth-to-orbit vehicle, and two methods of interplanetary propulsion.1 Combining these into a two-stage vehicle provides a personal transport system to target asteroids. The ground launch would not need to be covert if the passengers are escaping without return.

Phobos appears similar to chondritic asteroids. If Phobos is compositionally similar to carbonaceous chondrites, then, given the asteroid settlement system described in Sooner, it would be a minor modification to apply that system to Phobos.

Drexler has looked at interstellar probes exploiting MNT.6 More conventional interstellar designs could also be made affordable by exploiting the cost reductions in hardware MNT offers.5,8

Scenario Selection

Schwartz's method12 calls for developing two to four scenarios which span the critical, driving uncertainties. Other uncertainties are to be varied across the scenarios, as much as can be made to fit within the natural flow of the respective plots.

Fig. 1 The space over which the scenarios directly vary

The critical uncertainties for space development are how widely available MNT will be when it is applied to Space, and how much is the development of space using MNT prepared for, as opposed to simply left to happen. This plane of possibilities is illustrated in figure 1 above, with the selected scenarios shown as well.

Sooner was developed because it made sense for a scenario with low pre-planning of space development being a scenario in which MNT is developed early. Slow and Planned was developed because it made sense that scenario in where it takes longer to development MNT, it could be better planned for. (Nonetheless, note that by 2000 MNT is already being better planned for in Slow and Planned than in Sooner.) It also seemed likely that with slower development and more planning MNT would be more widely available.

A third scenario, "Imminent Catastrophe," is also shown in figure 1. This scenario posits the discovery of an asteroid on a multi-year collision course with Earth, and a very delayed development of MNT. It is an illustrative wildcard which was removed so this paper would fit the page limit. Since "Imminent Catastrophe" was removed, "Sooner" was modified to reduce how widely available MNT was when applied to space development, and "Slow and Planned" was designed to extend the development period of MNT.

Scenarios could plausibly differ on a tremendous number of other factors. Other uncertainties considered in the process of developing these scenarios included:

A ground rule for this effort was that there would be no scenario in which the world, Homo Sapiens, or technological civilization is wiped out, since that makes planning for space development pointless. Note, despite this ground rule, such scenarios are possible. Some even use MNT to deliver the coup de grace. Planning on how to avoid such scenarios is a valid, and perhaps crucial, exercise. Given the ground rule, however, there is no uncertainty as to whether or not technological civilization will be wiped out.

The key driving force in future space development appears to be the development of MNT. There is no scenario, short of a collapse of human society, in which MNT is not developed. When MNT is developed, it provides the technical capability for robust and extensive space development. Even if the development of MNT is delayed as long as plausible, and the space activities are accelerated as much as possible, pre-MNT space development is dwarfed by post-MNT space development.

Numerous reasons why MNT might be impossible have been suggested. Many are design issues which must be addressed, but analysis has not shown any to be fatal. Issues include thermal excitation, thermal and quantum positional uncertainty, quantum-mechanical tunneling, bond energies, strengths and stiffnesses, feasible chemical transformations, electric field effects, contact electrification, ionizing radiation damage, photochemical damage, thermomechanical damage, stray reactive molecules, device operational reliabilities, device operational lifetimes, energy dissipation mechanisms, inaccuracies in molecular mechanics models, limited scope of molecular mechanics models, limited scale of accurate quantal calculations, inaccuracy of semiempirical models, and providing adequate safety margins for modeling errors.5

It is not surprising that no one has found a fundamental limit which makes MNT impossible, since living organisms operate using a form of MNT.

When MNT is developed does not appear to have great direct impact on how space is developed. If MNT is well-planned for and developed widely, that has much more ultimate impact that whether MNT is developed soon or developed late. It is true, however, that the later MNT is developed, the more time from now we have to prepare for it.

Drexler has made the observation, however, that if what matters is how long it takes from when we take MNT very seriously to when it is developed, then the sooner we take MNT very seriously, the less we will know when that occurs, and thus the longer it will take from that point to full development. If one imagines that we will only take MNT very seriously when we launch a concerted effort to develop it, then Drexler observes it will take longer to develop MNT (from this time frame), the sooner we launch a concerted effort to develop it, even if this means that in an absolute time frame MNT will come sooner.

The actual development path MNT takes is of obvious great concern to researchers in the area, but that is of much less concern to space development.

One can argue it is inevitable that the capability and implications of MNT will be generally accepted well before it's major capabilities are demonstrated. Indeed, signs already suggest it is growing as an expressed research goal in related fields. If this is taken as predetermined factor, it narrows the scope of possible scenarios.

Table 1, below, compares the two scenarios along various uncertainties.

Table 1. Comparison of scenarios

Space Development is planned/unplanned Unplanned Planned
How widely available is MNT when it is applied to space? Limited to dedicated experts fortuitously placed in skill and time at the right moment "Very widely available throughout the dominant consortium, which any group contributing to MNT could join, and for purchase from the dominant consortium"
MNT is initially deployed peacefully or aggressively? Mostly peacefully Peacefully
Prior establishment of property rights? No (Space is settled by squatters) Yes (Privatization equally distributes tradable rights to all adults on Earth)
MNT emerges competitively or cohesively? "Competitively (but key precursor is available to everyone, providing some cohesion)" Cohesively
Who develops MNT? Groups in competition A dominant consortium
Who Settles Space? "Individuals and small groups with MNT, on their own initiative" "First governments, and very wealthy individuals, then corporations, individuals and small groups, in all cases paying for the right"
What is in Space before MNT is developed? "Communications satellites, International Space Station" "Communications satellites, International Space Station, remote precursor probes, preliminary lunar bases"
When does popular thought orient to MNT? After the development of the molecular robot (~2000) In tandem with its recognition by their governments (~2003)
How is MNT developed? Demonstration of molecular robot launches a huge competitive race "Internationally, jointly, and competitively through risk-sharing alliances "
Developing MNT proves easy or hard? Easy Hard
What is average NASA budget level? Nominal "Nominal, but grows with privatization"
What research path is used to develop MNT? Protein design Macromolecular chemistry
When is MNT developed? 2005 "First ""assembler"" in 2015; robust capability by 2020"

Comments on Slow and Planned

Slow and Planned is designed to illustrate how "Rules of the road" could be established for exploiting space and what that might mean. It also presents a scenario in which the ability to use MNT is very widespread as it is applied to space development, and illustrates a long development period for MNT.

The privatization of space real-estate, creating a market to effectively allocate targets among projects, is only one model that could be used. Another model would be homesteading, wherein individuals file claims to particular bits of space real estate, and secure full title after living on a developing the property over a period of years.

Comments on Sooner

The purposes of the Sooner scenario are to illustrate, the problems that will occur in space development if MNT becomes available before "Rules of the road" are established for moving into space, including unplanned, unbridled settlement, and a very early plausible development of MNT.

When in Sooner MNT is used to rapidly develop space, is narrowly available to those who were technically skilled in related areas when the initial molecular robot development bursts upon the world around the turn of the century.

MNT could be even less widely available. For example, the design of for the initial robot might be kept a proprietary secret, giving some group a decisive lead. Indeed progress might not even be announced until more mature tools are available.

In a scenario where some group has a decisive lead in MNT, that lead could be used to establish a dominant position in the development of space. That lead could also be a major cause of fear in others.

Open Questions

A number of important research questions related to MNT and space remain open. Several are mentioned below.

Most on space applications of MNT have examined the implications of mature capabilities. Immature capabilities will come first, and may have great impact. A vast amount of work remains to be done in designing aerospace systems that exploit capabilities on the path towards mature MNT, and assessing these applications for intermediate MNT.

There remains a need for detailed analysis and exposition of system reliability, adding dynamic component replacement via onboard remanufacture4 to the basic tools of high component reliability and active and passive component redundancy. This is particularly of interest since the background radiation environment in deep space is substantially heavier than the Earth environment Drexler analyzed.5

Well worked out estimates of MNT technical capabilities are available.5 There remains a crying need for conceptual designs of systems using MNT performance parameters.10 The estimated performance of these conceptual designs would provide a basis for refining strategies and operational concepts, which in turn may suggest further system concepts to investigate.

In particular, an MNT-based comet (or carbonaceous asteroid) exploitation system appears to be a very high-leverage target system, and an analysis of the appropriate system architecture, feasibility, and estimated performance, should prove very significant.

Existing MNT work focuses on carbon-based chemistry. Many solar bodies, however, offer limited supplies of carbon, but often, as is the case with the Moon, have abundant silicon. Extending existing work where possible to analogous silicon-based designs remains to be done.

A closely related open question is whether extend the existing work to consider silicon offers more to space development than simply working to further the work in carbon-based MNT.

Also, MNT work to date generally ignores primarily metallic molecular systems. What is feasible with MNT and metals is an open question, with particular applicability to how MNT can exploit a primarily metal object, such as a Nickel-Iron asteroid.


People can think about an uncertain future by thinking about representative stories, or scenarios, about the future. Two scenarios about space development present either a future in which MNT comes upon an unprepared world, leading to an unplanned, mad scramble to settle space, or in which societies foresee MNT and develop policies which accommodate the likelihood of tremendous changes, leading to widely availability of the opportunity to settle space, and more ability to avoid conflicts and dangers.

Finally, indications are MNT should enable interstellar probes. There are many important issues in space applications beyond the solar system, but this paper leaves those for another time.


1 British Interplanetary Society, Journal of the British Interplanetary Society, Vol. 45, No. 10, October, 1992.

2 Clark, Arthur C., Fountains of Paradise, Bantam, 1991.

3 Crandall, B.C., ed., Nanotechnology: Speculations on the Emerging Culture of Abundance, MIT Press, (forthcoming).

4 Drexler, K. Eric, personal communications, 1995.

5 Drexler, K. Eric, Nanosystems: Molecular Machinery, Manufacturing, and Computation. John Wiley & Sons, New York, 1992.

6 Drexler, K. Eric, "Nanotechnology and the Challenge of Space Development," 1988.

7 Drexler, K. Eric, Engines of Creation. Anchor Press/Doubleday, Garden City, New York, 1986.

8 Drexler, K. Eric, Peterson, Chris and Pergamit, Gayle, Unbounding the Future: The Nanotechnology Revolution. William Morrow & Company, New York, 1991.

9 Friedman, George J., "An Expanded Agenda for SSI," SSI Update, Vol XXI Issue 1, Jan/Feb 1995.

10 McKendree, Thomas, "Educating Systems Engineers For an Impending Metatechnology in Product and Process Systems," Proceedings of the Third Annual Symposium of the National Council On Systems Engineering, James E. McAuley and William H. McCumber, ed., 1993, pp. 417-424.

11 Merkle, Ralph, personal communications, 1995.

12 Schwartz, Peter, The Art of the Long View. Doubleday, New York, 1991.

13 Soreff, Jeffrey, "Scenario:'Sooners'," posting to sci.nanotech, 4 April 1995.