The Lunar Dozer Project


The dream of human colonization of space is one many of us share.
From Hollywood we see images of Star Trek and a rich, enlightened
society cruising the galaxy in search of new life forms and knowledge.
Unfortunately, in the years following the Apollo moon landings,
we have abandoned many of near-term dreams on colonizing Earth orbit,
the lunar surface, and Mars.  One of the main reasons for this is the
dramatic costs of getting mass out of Earth's gravity well.

There are two approaches to dealing with this problem.  The first is
to lower the cost of getting into orbit.  Currently the price runs
about $4000/kg of mass into Low Earth Orbit (LEO), where the Space
Shuttle typically ventures.  Even the venture being studied here would
end up costing over $100,000,000 to actually be launched.  However,
after several decades and attempts by a variety of countries and
commercial ventures to bring the price down, the price remains high.

The second approach, as a complement to the first, is to utilize mass
which is already outside of Earth's gravity well.  Non-terrestrial
materials processing is one of the most important activities of our
time because it offers a cheaper way to build things in space or on
the lunar surface.  Utilizing materials found on-site will be a
significant savings if ways can be found to process them cheaply,
with machines of low initial mass and few consumables.

Ideas for a project begin as follows - build a machine which does some
useful work on raw lunar materials.  It might be in one of three areas
(oxygen, free iron, or glass production).  Each might need an oven for
the refining of the materials.  In each case, the consumers of the
products would be envisioned as other lunar activities.  Iron, once
refined into rebar or sheet might serve in a variety of applications.
Oxygen might be used for fuel, water, or for breathing.  Glass might
be useful in place of plastic, good as a building material, or for a
variety of low-strength, maleable building blocks.  In this role, it
need not be highly pure.

Each of the three categories satisfies a philosophy of replacement
mass, mass that would not have to be shipped up from the surface of
the earth.  Versus complex and massive schemes which require HF leech
or other such chemical engineering approaches, I like the idea of
Replacement Mass.  If one can put in place simple processes to
construct comparatively crude parts which save mass in an overall
machine, then one can at least begin the cycle of manufacturing using
local materials.  Small is beautiful in the modern space program,
because of the extreme expense otherwise incurred.  The properties of
the materials obtainable in such a scenario are not nearly so good as
in the HF leech scenario, but at least we can begin getting
non-terrestrial mass in the loop.

One typical student assignment might be to envision applications for
shaped glass.  What trick can be used to improve its properties?
Containers are certainly a first application.  But even here, there
are the difficulties of shaping the product.  A lego approach,
followed by a welding step, may improve the situation.  For iron, the
horizons are larger, perhaps because of the improved strength of the
material.  Yet forging and shaping are as much, if not more, of a
problem.  With both materials, the construction of products is
relatively bulk oriented, and the resulting products would seem to be
passive.  Yet if one designed a machine for which certain massive
parts were to be crafted on the moon out of local resources, there
might well be savings.

Another possibility is the idea of constructing a large electic motor,
where all the parts, except for the iron core, are hauled up from the
Earth.  What would the mass savings be?  Could one construct a
scenario in which the iron refining and shaping mechanisms paid for
themselves?  What standardized parts of glass or iron could be
produced such that a general advantage could be gained by having a
stockpile of them?

A limited project might be the child's iron filing refiner.  Given
input dirt, the child would turn a crank, and a small set of iron
filings would collect in a bin, as dirt was run thru the mechanism.
As a small toy, it could be sold as a novelty, as well as pioneering a
possible iron collection method for the lunar surface.

After contemplating these and other proposals, the following project
arises as one I would like to have explored for this semester.

The overall project can be broken down into three parts:
1. The magnetic separator for recovery of free iron from the lunar soil
2. The foundary for heating and casting iron parts
3. The design of a piece of heavy machinery (Lunar Dozer)

The goal of the project would be to support manned and unmanned lunar
operations through the early use of locally derived lunar materials.
The overall mass of such a system would need to small, as the probability
of any mission being sent to the lunar surface varies inversely
with its mass.

1. Isolation of Free Iron

Construct a magnetic separator for the isolation of iron particles
which are to be found in the lunar soil.  The device should be
electrically powered, and should be less than 30 kg in mass.  Designed
to operate in 1/6th G and in a hard vacuum, it should also perform
under Earth-normal conditions.  When provided with lunar soil or a
suitable substitute, say finely weathered granite or basalt, it should
be able to process a considerable volume to isolate the free iron
fraction.

As it will be exposed to hard vacuum and temperature extremes, the
devices should have as few moving parts as possible.  Power
distribution may also be a problem.  Could the magnetic separator be
placed at a fixed location, and material transported back and forth by
other means?  I say it is better to have the separator move, leaving
most of the soil where it lies.


2. Lunar Foundary

A key to the utilization of lunar iron and glass will be the heating
of these materials in a furnace past their melting points.  Design and
construct such a furnace, utilizing solar and electrical sources of
energy, and a system by which raw materials can be melted and poured
(smelted and cast) into awaiting molds.  Explore techniques for
reliably maintaining the processing even if it is operated remotely.
Consider thermodynamic considerations, crucible size, shape and
composition, as well as delivery of raw and finished materials.

One option for the creation of parts is that of sand-casting.  Because
of the wide availability of powdered silicates on the moon, it would
not be difficult to make use of raw or slightly refined lunar soil to
prepare a mold or form which had the desired characteristics.  There
might be complications arising from getting the soil to take and hold
a particular shape, given the lack of moisture for adhession.
However, simple vacuum sintering or the localized melting of surface
features might make this possible.  It might be possible to utilize a
numericaly controlled instrument to form the mold in a desired pattern,
which when used in casting, would render a part of a desired shape.


3. A Lunar Dozer

The question is, why not go all the way on this project, and have a
group study the feasibility of casting our own complete bulldozer.
The iron filling collector robot, if nothing else, could gather
sufficient quantities of ore into one spot, until we figured out how
to do the rest of the process.

If this is to be a separate project, then there are a variety of
questions we would like students to solve.  First, which is the better
material to make it out of, Iron or Glass?  Second, what are the
pieces going to look like?  How big should it be?  How much energy
will it need/consume?  What parts would be shipped from the Earth, and
what would be manufactured on the moon?  What are the tolerences
needed for the lunar-made parts?  What measures can be made of its
capacity?  Like with wind-tunnels, can simulations be made of its
performance in 1/6th gravity?

A friend suggested that Catapiller might be interested in the lunar
dozer, or that at least they would be a good source of information.
From articles gathered and photocopied in SDSU and UCSD's libraries,
one learns of the complications in lunar materials processing.  Glass
utilization.  Difficulties in machinery operation.  Use of steel
derived from lunar sources.

If you were specific, concerning the dozer, they would probably spend
their time looking at how it operates, and/or its design.  If you were
less specific, they will spend their time wondering about it.  Best to
be specific.  And if so, could you get them to build a mock-up or
scale model?  To divide up the systems into those locally produced and
those which are brought from the Earth, this would be cool.