Colonizing Luna, part 3: Energy


Originally written: 8 August 2005. Previous | Overview | Next


Earth-built photovoltaic panels, batteries, fuel-cell/electrolysis pairs.


Luna-built photovoltaic arrays, parabolic solar ovens for manufacturing, possibly thermoelectric.

Massive, solar-powered?compulsators; alternators capable of delivering massive pulses of electricity.


At present the most efficient photovoltaic cells are still p/n-doped monocrystalline silica wafers. Hopefully the necessary rare metals are available on Luna for their production. Large PV arrays should remain low low and wide so that flying vehicles do not hit them. Near the south pole, one simple geometry is a circular fence of outward-facing, fixed-position panels. These can be placed on hills, and around both habitats and compulsators. This simple, no-moving-parts configuration is inefficient, but its simplicity and reliability may offset the cost once PV wafers can be manufactured on Luna in large quantities.


Initial flywheels will be disks of iron just light enough for an astronaut to lift (carefully) under Lunar gravity. These disks can be stacked together on spindles, like gymnastic freeweights, to make high-mass cylindrical flywheels. In addition to powering compulsators, flywheels can store mechanical energy for direct use in machinery such as roller-slabs.

The massive compulsators needed to drive the mag-launcher will require flywheels the size of gravitats. These should also be situated in craters, so that if they malfunction and disintegrate the debris will impact the crater walls, and not threaten the rest of the base. The spindle may include an electric motor/generator assembly, or a separate ‘spin-up’ motor if the winding of the compulsator needs to be a different geometry.


The temperatures in the lunar shade are low enough for ‘high-temperature’ superconductivity to be sustained so long as materials are insulated from heat-conduction and perhaps refrigerated slightly. This makes Meisser bearings, mag-lev tracks, and the movement of large amounts of electricity feasible. At this point the main constituent elements in higher-tempreature superconductors are either copper, titanium and oxygen for cuprate-perskovite materials, or ytrrium (La), copper, oxygen, and barium (YBCO). So an important early feasibility-test will be the availability of these materials and their refinability.

Colonizing Luna, Part 2: Gravitats


Originally written: 8 August 2005. Previous | Overview | Next

Luna’s gravity is too low for humans to maintain long-term health. Therefore, like long-term residents of microgravity environments, lunar settlers will need to live in ‘gravitats’ where gravity is simulated by spin (centripetal acceleration).

The good news is that the design requirements for lunar gravitats and deep-space gravitats are very similar, so many lessons and techniques can be learned once and shared. Science-fiction authors have proposed that large types of gravitats such as O’Neill cylinders be used for multi-generational voyages. I think we can start small by working out all the problems and details of gravitats on Luna and in low-earth orbit (just as 1950s sci-fi artwork proposed). Once we have a reliable model, an engine cah be mounted on the spindle-axis of the gravitat to push humans out on very long-term missions. These might not be the first missions to Mars (that could be done using capsules, especially by a dedicated nation-state such as China). But a mobile gravitat could support a multi-year mission to the Jupiter and Saturn systems.

Initial gravitat:

This is a dumbell form, about 100 m (300 ft) radius.

A pair of pressurized vessels are spun around a central tower. The vessels probably will be the upper stages of heavy-lift vehicles. They will be suspended by cables or rigid swing-arms. Access/egress is most difficult, either by stopping the spin of the whole habitat or by an EVA climb up/down a ladder to the central spindle.

Full gravitat:

This is a “bicycle-wheel” form.

To eliminate vertigo caused by inner-ear sensation of the coriolis effect of spin, I think a full gravitat will have to have a radius of 500 m, and therefore a diameter of 1000m (1 km). The rim, 3142 meters in circumference, could begin as an open truss-work that gets filled in by opposing/balancing modules over time. The spin rate would have to be about 1 rpm, thus a speed of almost 200 kph at the rim.

The ring would be a sequence of links and modules. The links would be open trussworks attached to the radial suspension cables, and attached to each module. To access the ring from the Lunar exterior, one must board a “synchro railcar” located in a trench underneath the structure. The railcar is accessed via an underground passage network, which leads out beyond the rim and inward to the central hub. The railcar would accelerate up to matching speed with the ring and mate with an airlock in the bottom of a link-truss.

The suspension cable network consists of upper and lower planes of radial suspension cables, cross-tied for redundancy. Thus the overall appearance of the gravitat would be very similar to a bicycle wheel–except the tires would look like a string of sausages.

Pressurized Modules:

Modules will tend toward a generic, standardized construction. Habitable space will be enveloped by at least two if not three outer wrappings, held rigid by internal gas pressure. These sacks wrap around a rigid trusswork which is connected to the link at either end. Human-occupied space is built as decks within that truss.
Insack: The innermost sack is held rigid at human-comfortable atmospheric pressure, which I think is at least 800 mB of nitrogen-oxygen mix.
Midsack: I think the second sack would contain argon gas, at maybe 400 mB; it serves as an emergency backup if the inner bag fails.
Outsack: The outermost sack is coated with material to reflect alpha-rays, and very tear-resistant to absorb micrometeorites. Whatever it is inflated with should be a good beta- and maybe gamma-ray absorber, but the pressure must be low enough that the bag can deform to absorb impact energy without putting too much strain on the fabric.

The interior each module has three decks, listed from top to bottom:

1. Topside: built on top of the truss. This deck is open to the fabric roof of the insack. Hydroponics, recreation, informal meeting areas. Include a projector to show stars, images, movies. (slightly less than 1g)
2. Main deck: work labs/stations, sleeping and showering (1.00g)
3. The hold: hydroponics, water recycling, tanks and other heavy equipment (slightly more than 1g).

Assembling the first full gravitat

This is a massive structure, and the vast majority of the material needed to build it must me extracted and refined on Luna. (The main worry here is the flexible sacks. What can they be made from? Probably a woven metal mesh, coated to make it airtight.) This means the full gravitat will not be built until refining and manufacturing facilities on Luna are well-developed.

Protective Covering Dome:

Permanent gravitats should be placed under protective cover to shield from micrometeorites, hard X-rays, and mistargeted landing vehicles. As resources permit, the domes should be:

a. A lightweight, open geodesic framework which anchors the upper end of the gravitat-spindle. This initial dome can also serve as the construction-scaffolding for a second, heavier, outer dome.

b. A heavier dome which includes enclosing panels.

c. A very strong dome which is buried over with soil or refinery slag.

Locating the habitats in small craters will provide a head-start in terms of lateral protection, and reduce the amount of material needed for covering dome assemblies.

Long-Voyage Vehicle Development:

The design needs of a permanent Lunar gravitat are almost identical to those of a long-voyage vehicle. Either the dumbbell or bike-wheel design would serve, with fuel tanks, engines, and communication equipment attached to the central spindle. Given a large enough, powerful enough launcher, the whole vessel could be flung out from the Lunar surface at escape velocity in one or two pieces; minimal in-flight assembly required.

Colonizing Luna, Part 1: Bootstrapping

Originally written: 3 August 2005.

A. From 2006 to permanent, productive lunar base

The good news from this spring was NASA’s decision to replace the space shuttle with separate, simple-configuration heavy-lift and crew-lift vehicles, Ares I and Ares V. This should lower both the cost and risk of getting from earth’s surface to low earth orbit (LEO). It is also very encouraging to see successful private projects to get humans to LEO and geosynchronous orbit (GEO).

But how to really get humans into space? Some people want to go to Mars. It may strike the imagination now, but in the long run I think Mars will be a disappointment. Too small to terraform and inhabit, too big to use as a platform for further space exploration. In fact, I think humans will do best in gravitats–‘wheels in space’–in the long run. The minimum-size gravitat which does not produce a spin-sensation in the average human is one kilometer across, so it is not small. But once built, gravitats can be used in many locations: as stations at Lagrange points, as bases on low-gravity bodies like the moon, and as slow interplanetary vehicles.

Furthermore, we can built most of a gravitat on the moon, as well as many other handy items like monocrystalline silica wafers for semiconductors and efficient photovoltaic cells. Once we build a mass-driver on the moon, we can also lob products off the surface and either glide them down to earth or nudge them out to other orbits or other planets.

The problem is imagining the transition ‘from A to B’: from our present general indifference to space, to having a viable, productive lunar base that manufactures reflectors for massive far-side optical telescopes; wire and bars for structures and machines; and liquid hydrogen and oxygen for propellants.

The following pages are thought-pieces on issues and designs necessary to make that step.

B. First bits

The main challenge in developing a major lunar base is thinking phase-wise about scaling up. The first bits of equipment will need to be manufactured on earth, lifted all the way to the moon, and landed under controlled power. The equipment should be chosen to enable ‘bootstrapping’ up to larger and larger capacities.

These are guesses. But it seems like the earth-made equipment needed to begin the base are:
A pressurized habitat which can be buried under lunar soil.
A small tele-operated robot which can be used in lieu of human space-suited exterior activities (HEAs).
A large tractor which can operate as an earthmover. Call it a crawler.
A strong photovoltaic array.
Big mirrors which can focus enough sunlight to vaporize lunar soil.
Some refining equipment (will have to read up on what is needed here to start with).

C. Second step: bulk refining, basic manufacturing

The lunar base needs, first of all, to develop the capacity to refine and mold metals (aluminum, titanium, and iron) and crystals (mostly silica), and extract and contain gases (oxygen, hydrogen, and whatever else is available).

D. Third step: machining and assembly

In this third phase, the base will need to:

  • form basic metal stock into machined members for structures,
  • weave wire into cable and fabric, and
  • build large, simple machines.

Among the large machines will be bigger crawlers used for paving, mining, and moving items; compulsators and mass-driver components; electric distribution network components; and the parts for gravitats.

E. Beyond the bootstrap phase

After this point, the critical projects become multiple, parallel, and overlapping. The electrical system and mass-driver are highest priority, but at the same time components need to be built and stockpiled so they can be lobbed as soon as the mass-driver is completed. Likewise the gravitat needs to be built, so that longer-term experimentation in closed-loop life-support can begin. Paving the area around the base will be a slow process, and once the mass-driver is online, the same team and equipment will proceed to lay more mag-lev track to other locations around the moon. At this point the purposes and processes of the lunar base will be too complex to predict at the moment. What get learned from ‘bootstrapping’ the base into operation will probably open many possibilities.

One likely ongoing project will be astronomy, particularly in the electromagnetic bands ranging from visible light out to radio waves. All of these require larger collection mechanisms, either reflectors or conductive arrays. The far side of the moon is an excellent location for these telescopes.

The second ongoing project will be as a major factory, building robots, satellites, deep-space probes, and gravitats. As more mag-lev tracks are built in various directions, payloads can be launched in various directions, including straight out from the far side of the moon. This will facilitate not just a Mars mission, but also roving gravitats which can support extremely complex, long-term exploration.

F. Location

I agree with the various authors who recommend that the first Luna base should be located at one of the poles, where sunlight is always available. With the information available in 2005, I think the south pole is a slightly better choice. In part because the astronomy of the southern hemisphere is very interesting; in part because there is a crater right at the south pole (Shackleton) which may be very useful.

Colonizing Luna: Overview

Next Steps in Using Near-Earth Space and Luna

First written: August 3, 2005

This is the fist in a set of conceptual essays to design a permanent, self-supporting, productive Lunar base.

As I thought it through, I have been realizing that the whole zone from low-earth orbit (LEO) out past the moon is crucial to future human deep-space exploration.


Most of the description here is of a substantially-developed base, and so the obvious first problem is getting from here to there. This problem can be broken into four parts:

1. Cost, mainly in the form of political acceptability. This is an issue which NASA deals with constantly, so I have little to contribute except in the specific proposals and promise of this base.

2. Environmental impact. Mainly this is the atmospheric damage caused by rocket launches. Part of this is atmospheric disruption, part of it is the chemicals used as propellants. LOX and kerosene are better than the solid propellant used on the shuttle boosters, but we need to carefully study how to minimize atmospheric harm from rocket launches.

3. Scaling-up, or ‘bootstrapping.’ This is the main challenge for a permanent Lunar base. To become self-supporting I think it will require very substantial facilities for mining, refining, manufacturing, and return-to-earth systems. As quickly as possible, ‘bulky’ items should be produced on Luna.

Scaling-up should be the driving principle in designing the interim stages to get us to a permanent Lunar base. Systems should be designed for multiple use and re-use, and maximum-value items should be pursued first, to subsidize the development of ‘beach-head infrastructure’ in the early stages, where the greatest uncertainties exist. Examples:

a. chemicals, medicines, and crystals which can only be grown in microgravity.
b. permanent storage of highly-radioactive nuclear waste.

4. Surprises and unknowns. This should also be regarded as an opportunity; as we face unknowns we learn. The challenge then is how much a taxpaying public is willing to underwrite the financial risks of fundamental research. This will depend upon political persuasion. It could, in time, become a major rationale for the U.S. government itself. Since the FDR administration, we have rationalized massive government investment through the ‘war-mobilization’ model. If, instead, we used government resources in an ‘exploration-mobilization’ model, we would continue to develop both technology and economic growth which will justify the effort and very likely maintain U.S. military supremacy without the belligerence.