Milestones on the NSS Roadmap to Space Settlement (2001)

Based on our current perspective, the NSS has identified sixteen major Milestones that must be passed to realize the NSS Vision: “People living and working in thriving communities beyond the Earth.” The first four Milestones must be passed en route to the settlement of all destinations: the Moon, Mars, asteroids, O’Neill Habitats, and, eventually, the stars. Specific Milestones then follow for each of these destinations.

These milestones are presented here, with commentary on their current status and the changes and developments necessary to reach them. You can click on the image for specific destinations, or scroll down for all destinations.

nss roadmap milestones to space settlement


1. Commercial Launch Volume

The emergence of an adequate-sized launch market, with efficient vehicles and turnaround times measured in days rather than weeks, will lower the cost of access to space.

To achieve low launch costs, the private sector needs adequate market size and technology enabling efficient vehicles with turnaround time of one day or less. NASA and other government-funded space agencies need to continue their role in developing space transportation technology through flight test demonstrations such as the X-33 and X-34. These activities place the technology “on the shelf” for industrial/commercial uses. Technology developed with government funding must be immediately placed in the public domain. It is a government role that has proved very beneficial in the aviation industry. This is an appropriate area for continued and expanding government technology investment

Expendable launch systems need to get down to about $1,000 per pound to enable human return to the Moon and humans to Mars. Ultimate costs for reusable systems are expected to reach below $100 a pound to enable large-scale settlement. Achieving such low values will require a large volume of traffic demand, very rapid turnaround enabling up to 200 uses per year per vehicle, and vehicle life exceeding 1,000 trips to orbit.

No mechanism for cost reduction is as effective as free market competition, given an adequate market. For this reason the NSS Roadmap envisions that NASA will continue to move in the direction of purchasing launch services from the commercial sector, including human trips to orbit. When commercial entities competitively enter this market arena the current Shuttle fleet will be retired.

Space tourism is also essential for providing incentives to reduce launch costs and make reusable launch vehicles more reliable. Tourism will also be critical in creating the market for space settlement. People will likely not want to settle on the Moon or Mars or elsewhere until many have visited those places. NSS anticipates that space tourism will begin in the near future with suborbital flights to altitudes exceeding 100 kilometers, enabling passengers to briefly view Earth from space and earn astronaut-passenger wings. The next step will be orbit-capable vehicles carrying passengers to orbital trips lasting one to two days in microgravity. Investors and corporations have already discussed construction of hotels, resorts and casinos in orbit around Earth.

2. Legal Protection of Property Rights

…will be enacted to provide prospective off-Earth settlers with the security to take risks.

It is difficult to conceive of successful settlements in space if the settlers are not permitted to own real as well as personal property, and if business enterprises cannot own and run the facilities necessary to operate their businesses in extraterrestrial locations. NSS believes that private individuals and groups who are considering investing their own resources to settle and develop the space frontier will need to know in advance that, if they succeed, they will be rewarded by legally enforceable recognition of their claims of private ownership. Accordingly, NSS strongly endorses the establishment and recognition of such rights.

Current treaties among the nations of Earth prohibit national claims of sovereignty over bodies in space (although some nations have claimed ownership of the portions of the geosynchronous orbit arc over their territories). Therefore, it may be that nations or other terrestrial entities cannot grant ownership of property in space. However, even in the absence of modifications to such treaties, it is possible to expect that a legal regime could be established wherein reasonable claims on extraterrestrial lands, based on beneficial occupancy and development, could be recognized by terrestrial entities.

A legal regime for property rights in space will need to incorporate the usual protections for individuals, businesses, and the natural environment, while also ensuring fair competition for property. These protections include prevention of monopolistic ownership of scarce and valuable resources as well as sensible zoning. The legal regime should take a minimalist approach, not creating volumes of regulation before future space settlers are able to determine, based on actual knowledge and experience, what is reasonable. It should strive for the creation of economic incentives for human expansion into space, access to space for all, and protection of settlers’ rights and space resources.

It should be noted that no individual or company currently has the power to issue “titles” to uninhabited extraterrestrial real estate. NSS regards any past and contemporary offers of “title” to such lands that are not clearly denoted as symbolic and unofficial as unethical and deceptive.

3. Land Grants or Other Economic Incentives

…will be provided to encourage private investment on off-Earth settlements.

Claims of off-Earth land, recognized on the basis of beneficial occupancy and development, could plausibly be broadened to include additional tracts large enough to make feasible subdivision and resale. This measure will increase the potential for private investment in affordable space transportation and facilities and make settlement economically profitable.

Of ideas currently proposed, such extraterrestrial “land grants” appear to be the most likely way to foster privately funded space settlements. Accordingly, the U.S. Congress and the space community need to give efforts to develop an acceptable method of offering land grants as an incentive for such settlements.

4. Technology for Self-Sufficiency

People will leave Earth with the technology and tools needed to settle, survive, and prosper.

The objective of self-sufficiency is to achieve adequate human productivity and diversity of production and service capabilities with a small population on an undeveloped planetary surface so that the colony is not dependent on resupply for critical resources (e.g., air, water, power, shelter, basic foodstuffs). Self-sufficiency implies the development of a broad spectrum of advanced manufacturing, servicing, maintenance, and repair technologies with an underlying structure of advanced automation and robotics.

Our understanding and capabilities in this area are extremely rudimentary. We have some ideas on how to recycle air and water and produce food in a space habitat, but much more research is needed on closed ecological life-support systems. While some have succeeded, self-sufficiency must go much further, reaching the level of producing daily
needs such as energy, clothing, daily-living amenities, and shelter (i.e., habitats) from local resources. NASA has no consequential technology efforts in this important area. NSS believes NASA and other organizations should give high priority to developing the foundations for self-sufficiency technology and that future human missions to the Moon and Mars should focus on demonstrating how these technologies can work in the space environment.


5. Robotic Confirmation of Ice

Robots will determine if water ice is present in adequate quantity.

NASA’s Lunar Prospector mission detected the presence of hydrogen in the regolith in the vicinity of the Moon’s poles. It is widely assumed that this means water is present, but it is not assured; the hydrogen may be in some other form. If it is water, the nature and extent of water deposits will bear on their utility for propellant production and support of human habitation. The nature of the deposits also affects their scientific value and will lead to decisions on how to preserve this resource’s scientific value while obtaining practical benefit from it. Finally, the extent of the resource will affect planning for its use. If deposits are very large, using them for rocket propellant may be practical; if they are modest, it may be preferable to conserve them for life support uses.

6. Research Facility

…will be established to study human habitation and conduct lunar investigations. If appropriate, development, testing, equipment checkout, and training for Mars missions may also be performed here.

A lunar facility for testing planet surface operations is in principle no different than one that is the beginning of a lunar base. NSS views these as the same, and expects that any facility put on the Moon will be designed for long-term use. In order to serve as a test facility for longer planetary surface missions, it must have almost all of the facilities needed for longer-term habitation. So wise investment policy will be to build it with the option of serving many years into the future.

This facility, suitable for initial developmental use, test, checkout and training for Mars missions, will be very similar to a small space station on the Moon. In fact, space station modules could be used with little modification if desired. One can imagine such a facility with a habitat module and a laboratory and operations module. If regenerative food growth were desired, a third module will be necessary.

On the Moon it is essential to provide radiation shielding for the facility. (This is a lesser but still important need on Mars.) Several concepts are available using lunar regolith. Additional mission equipment will be required depending on particular mission purposes. The mission equipment might be prototypes of equipment planned for use on Mars.

Location of the facility near one of the lunar poles will offer a relatively benign thermal environment and access to lunar water and other volatiles detected by the Lunar Prospector spacecraft.

7. Government/Industry Base

The research facility will begin as a government base and evolve to an industry base. The first longer-term residents will begin performing commercial functions.

This may be a multipurpose facility in the spirit of the International Space Station, with programmatic features that encourage early industry investment and involvement. The lunar facility described above could directly evolve to a government-industry base with delivery of a few more modules and installation of additional infrastructure equipment. The timing of such a base depends upon funding available, resources required for other missions (such as human missions to Mars), industry interest, and definition of technology initiatives, all of which will be needed to make a small lunar settlement economically self-sufficient.

8. Moon Settlement

Settlement will grow with the base as the commercial center.

Investors and corporations have already discussed construction of hotels, resorts and casinos in orbit around the Moon. Tourist travel to the Moon itself will follow. The first long-term residents may arrive in support of hospitality businesses.

NSS visualizes that continuously occupied bases on the Moon will likely operate for 10 to 20 years, reaching higher and higher levels of self-sufficiency, until enough confidence is gained to expand the true settlement process.


9. Mission Goal for Settlement

Exploration will accelerate with the clear purpose of eventual settlement. “Flags and Footprints” will not be the objective.

Current NASA study activities on Mars missions do not emphasize settlement. Early human Mars missions, though not settlements in their own right, will include among their objectives the conduct of engineering tests to verify the self-sufficiency technologies to enable settlement. In order to get on the right track, even the first human Mars mission must have settlement-derived mission goals, which need to be decided before detailed mission design begins.

10. Robotic Exploration

…will precede human explorers.

Robotic missions to gather key scientific and engineering information relevant to design of the human missions must precede the first human missions. The robotic mission activities envisioned will develop a clear understanding of resources and obtain information leading to an assessment of the biological risks associated with human missions to Mars. NASA is presently conducting a focused series of Mars robotic missions aimed at garnering scientific knowledge of Mars. These missions are presently being planned and designed with limited consideration of human missions.

Issues have been raised regarding the biological risks of human missions. These include: (1) the return to Earth of possible harmful biological agents from Mars, and (2) contamination of Mars and risk to possible Mars biota by human missions and the inevitable release by leakage from human-occupied systems of Earth organisms into the Mars environment. While these risks are low, they cannot be entirely disregarded.

Human missions will need to use resources on Mars and to operate in the Mars environment in ways not important for modest robotic missions. Examples include production of propellant and construction and equipment emplacement operations on Mars’ surface. Note that propellant production is also relevant to a robotic Mars sample return mission.

NSS believes the Mars robotic exploration program should include experiments leading to propellant production, greater and broader assessment of Mars’ biological environment, and specific evaluation of the biological risks by the scientific community.

11. Research Facility

Development, testing, equipment checkout and training for Mars missions will likely be performed close to home, in Earth orbit or on the Moon. Effects of long space missions will also be studied close to home before sending humans such a great distance.

A human Mars mission is likely to entail a stay on Mars’ surface of a year or more, a wait for the alignment of Mars and Earth that requires the return spacecraft to use the least possible amount of energy (fuel), and a return that requires many months. A commitment to embrace such a Mars mission will likely be viewed as placing people and their “can’t-test-them-too-much” machines on a very unforgiving mission profile. An equipment or other failure on or near Mars will need to be handled there — beyond the point of easy return. By comparison, a return from a lunar research testing facility can occur almost any time and requires only a few days. An unexpected failure, whether a hardware failure, an overlooked operational necessity, or a human failure, that would likely be fatal on Mars might be recoverable on the Moon.

12. Human Explorers to Mars

Human explorers will follow robots to Mars after field testing on the Moon, in low Earth orbit, or directly from Earth. A base will be established.

NSS views the first mission to Mars as a precursor to a settlement. The human trip will be preceded by infrastructure emplacement so that the initial visit can stay on Mars for over a year. The first mission to Mars, like all missions in NSS’s view, should use launch services from Earth purchased from the commercial sector. The first mission will conduct experiments not only on scientific topics but also on self-sufficiency technology.

Several architectures have been proposed to send the first mission to Mars. Candidates include a solar electric propulsion system, nuclear propulsion, the Mars Direct architecture or some variation of it, and cryogenic aerobraking architectures intended to evolve to use propellants produced from materials from the Martian moon Phobos or asteroids. Following a shakedown cruise on the Moon to test equipment, operations, and crew performance, the first mission to Mars should use the conjunction profile and stay on the surface of Mars for about a year and a half.

13. Mars Settlement

Settlers will follow the explorers.

Missions to Mars will continue on the evolutionary path to a fully reusable in-space transportation system employing advanced technology and will demonstrate enough self-sufficiency to enable a decision to begin establishment of a settlement.

One distinguishing characteristic of a settlement is that settlers emigrate without clear and specific plans for a return. The emigration will begin when self-sufficiency on basic life-support needs including food growth has been demonstrated, and it becomes practical to construct human habitation facilities and supporting infrastructure from lunar or Mars resources.

True settlement cannot begin until assurance has been demonstrated that indigenous food growth can be productive and stable over long periods of time. Before we can commit to sending people to a space settlement without firm and definite plans to return them, we must know that long-term survival and quality of life is assured.

Another major issue for true settlement is who will pay the way for the settlers. Historically, in most cases, settlers have paid their own way. Transportation costs to space to settlements will probably (at least in the beginning) be too high for settling families to pay their own way. Therefore it is essential to develop an approach, that can raise enough funds to pay for sellers to emigrate without placing a large burden on public tax revenues.


14. Exploration & Settlement of Asteroids

Robots will identify the asteroids for potential settlement and development. Human explorers will follow and confirm robotic information. Settlers will follow to those asteroids offering economic opportunity.

Asteroids may prove to be practical sources of resources including metals, nonmetals, and volatiles. Exploration of specific asteroids that are reasonably accessible from Earth or Mars is needed to develop a catalog of resource availability and a mission time schedule. This exploration may be entirely robotic. The robot spacecraft will land on the asteroids and perform resource exploration and assays. These robots may be launched directly from Earth and probably will be compact enough for direct launch by a contemporary expendable launch vehicle. Human explorers will follow to confirm the best prospects, and engineers and miners will settle those asteroids that offer real economic opportunity.


15. Construction of O’Neill Habitats

Once settlers can leave planetary bodies, these “cities in space” will be built.

In 1974, Dr. Gerard O’Neill proposed the construction of large pressurized habitats in space from resources obtained from the Moon. These habitats will be something like giant space stations, but large enough that the interior will be treated as real-estate land on which crops will be grown and houses constructed. People will live in a manner similar to a region of small villages and cities. The habitats will be cylindrical, rotating around their axes so that the inner surfaces will experience centrifugal acceleration similar to the gravity force on the surface of Earth.

Suffice it to say that construction of these habitats represents an enormous space enterprise similar to building a city. It is difficult to project when space engineering and construction techniques will make such projects feasible in a practical sense. It is, however, probably very safe to say it will be feasible long before interstellar travel becomes possible. Therefore, NSS recognizes construction of O’Neill-style habitats as an evolutionary step in humanity’s development, growth, and expansion into the universe.


16. New Propulsion Methods

…will be developed to carry humans to the stars.

Human travel much beyond Mars will not be practical with propulsion technologies now in use or now in development. Solar-electric systems quickly run out of sunlight beyond Mars’ orbit, and chemical propulsion systems have too low specific impulse. Some sort of advanced approach involving nuclear energy or off-board energy sources is clearly required.

NASA currently has a modest program seeking scientific breakthroughs in propulsion physics concepts such as compact efficient fusion, antimatter, and even gravitational effects. These are not necessarily needed for settlement of the Moon and Mars, exploitation of asteroid resources, or construction of O’Neill-style habitats from lunar or asteroid resources. However, they are needed to open up the Mars transportation windows so that travel to and from Mars becomes possible other than during the optimal, “low-energy” Mars-Earth alignments occurring every 2.2 years. They are certainly needed for our eventual ambitions of travel to the stars. This NASA program should be expanded, to conduct significant experiments where analysis shows a potential for progress.

These propulsion technologies are an important aspect of long-range research. It is essential to focus most of the effort on concepts well enough understood to have some promise of success. That success can be characterized as adequate specific impulse and thrust-to-weight performance to represent a quantum step forward beyond what can be achieved with current and developmental technologies.