pt3maf1

PART 3-Manufacturing and Fabrication

Sankar Sastri, Michael B. Duke, and Larry A. Haskin

Introduction

The ability to use nonterrestrial materials and energy and to utilize the special properties of space environments will allow the space enterprise to grow at an increased rate. We can envision a self- sufficient space economy, with centers of resource extraction and manufacturing off Earth that provide sustenance to colonies of people. However, in the next 25 years, the infrastructure for using space resources will concentrate on more limited goals, those that will have high leverage on the space economy.

Four general goals for use of non terrestrial resources are

To decrease the cost of transporting various systems beyond low Earth orbit (LEO) by providing propellant or reaction mass at a reduced cost

To reduce or eliminate the transportation costs for systems emplaced on other planetary surfaces and in space by using indigenous materials

To increase supplies of energy to Earth orbit and the Earth

To provide previously unattainable products by utilizing the special materials and unique processing capabilities afforded by space environments

Several possibilities exist to make major augmentations to our space capability by providing access to materials in space:

Provision of liquid oxygen can significantly reduce the need to transport propellant from Earth to low Earth orbit and reduce the cost of transportation to and from a lunar base.

Provision of material can decrease the costs of insulation and of shielding against radiation and impact for satellites in Earth orbit and human habitats beyond low Earth orbit.

Structural material, including pressurizable volumes, could be provided for Earth orbit or lunar bases.

Byproducts from nonterrestrial processing systems could begin to make living in space easier.

Energy collected in space could be used directly or by conversion to electricity to carry out space manufacturing enterprises.

Space debris could be recovered and reused or put to a new use.

This report is deliberately conservative. Previous studies (Criswell 1980) have demonstrated that nearly anything one wants to make in space can be made from the raw materials available on the Moon or on near-Earth asteroids. We have looked instead at what is most easily accomplished in the next 25 years.

The accessibility of material and energy off the Earth and the leverage that these nonterrestrial resources can exert on the space transportation system are important influences on the long-term goal of exploring the solar system. The next 25 years will provide the learning experience necessary to advance that activity more rapidly. The concept of "bootstrapping"- using the production capability to manufacture additional production equipment and expand production more rapidly than if all the production equipment had to be transported from Earth-can be tested and the ability to sustain human settlement beyond Earth can be demonstrated.

Research on separation of lunar materials and manufacture of useful products from them is in its infancy. Many avenues are left to be investigated. A few possible processes and products are described below.

Products

The least complicated technologies will not necessarily be the most cost-effective ones to manufacture products from nonterrestrial materials. It is nevertheless appealing to imagine that early space manufacture can be done by simple means. It seems that simplicity ought to correlate with economy or at least with probability of early application. Thus, we have chosen to explore the oxygen, metal, and silicate products that might be obtained from simple treatment of well-characterized materials from near-Earth space.

The ground rules of the exercise are these:

Starting materials are those substances found in greatest abundance at the lunar sites visited by the Apollo astronauts. More exotic lunar ores and water at the poles are excluded from consideration. So are all asteroidal materials, their exact nature being still unknown.

Raw materials for manufacture are materials in ''as found" condition or materials upgraded or separated by only the simplest means.

Products are for use on the Moon or in orbit, not on Earth.

The additives, catalysts, and processing materials that must be supplied from Earth will be kept to a mlhimum.

Oxygen, perhaps extracted from ilmenite-rich material, will be an important early lunar product.

Materials used in space applications will be those available and adequate, not necessarily those traditionally envisioned or preferred.

The quality of material used may not match that of similar material produced on Earth, and sizes and quantities will be adjusted accordingly.

The complex components that are necessary will be imported from Earth.

Steps in manufacture must be few, easy, and reliable.

Assembly and application of products must be simple and rapid and tolerances relatively loose.

All processes up through assembly should be reasonably automated but tended. Equipment should be easy for its operators to repair, optimize to actual conditions, and adapt to new feedstocks and applications.

The scenario that could result from application of these ground rules to common materials at Apollo sites is limited but far from stifling. To make the problem tractable for this exercise, we have chosen to constrain our list of materials and products even more narrowly than the rules specify. Nevertheless, the examples we treat should be sufficient to illustrate the possibilities and the limitations.

The following are designated as starting materials:

I. Unprocessed lunar regolith

A. Bulk soil

1. Mare-derived; high-iron, high-silicon, low-aluminum. low-calcium

2. Highland-derived; low-iron, high-silicon, high- aluminum, low-calcium

3. Mixed origin; intermediate- composition

B. Rocks

1. Mare basalt [CaAl2Si20g (plagioclase} and (Mg,Fe)SiO3 (low-calci\;Jm pyroxene) ]

2. Highland igneous-rocks

a. Anorthite (primarily plagioclase)

b. Dunite [primarily (Mg,Fe)2SiO4 (olivine)]

c. Troctolite (mixtures of plagioclase and olivine)