ASI W9900326r1.1

Moon Miners' Manifesto

#107 July 1997

Section 6.9.3.2.107.of the Artemis Data Book

Seattle Lunar Studies Group Part2

Concept Papers from Seattle Lunar Group Studies, Part II.

Concept Papers from Seattle Lunar Group Studies, Part II.

Cislunar Ferry
Magsail Asteroid Survey Mission
Magsail Mars Missions
Magsail Stabilization of Lagrange Point Structures
Remote Lunar Geological Survey
Clear Span Lunar Base Structures
Survey of Earth-Crossing Objects
Food Animals in Biological Life Support Systems
An Artificial Lunar Magnetic Field
Magnetic Radiation Shields
Regolith as Propellant for Mars Missions

A Major Contribution of Seminal Concept Papers to MMM. These are the work of a significant brainstorming group in Seattle which has continued over a span of many years. MMM thanks David Graham and Hugh Kelso for permission to reprint these papers. The first installment was published in MMM # 106. We will finish republication of these papers in MMM #108

Whether the paper was in response to a request for input for the Space Exploration Initiative (SEI) or for the Stafford Commission, is indicated in the byline for each.


Cislunar Ferry
(SEI; Stafford) by Gordon Woodcock and Joe Hopkins

We propose a vehicle be developed to utilize swing orbits (Woodcock, 1). The vehicle would be designed to travel in the lunar plane between Earth and Luna, providing frequent and regular access to both bodies.

This vehicle could be viewed as a cislunar ferry. In its initial form, the orbiter would be a small, no gravity, passenger/freight carrier. The cycling orbiter could be configured to provide radiation shielding for the passenger section. If gravity becomes necessary, it could be simulated by spinning equal massed compartments opposite each other on a tether.

Actually, it is not necessary that both opposing components be equal in mass - unless equal levels of artificial gravity are required at both ends. If this is not required and the two components are unequal in mass, the center of gravity or fulcrum simply lies proportionately closer to the heavier mass while the gravity felt in the lighter more distant component will be the greater. - Editor.

Regular, inexpensive transportation between the Earth and Moon is the main purpose of the orbiter. Cargo and passengers would be transported on and off of the orbiter in specially designed taxi modules. Passengers would generally remain on board for only one leg of the trip at a time; three to five days.

Over time, with a system like the cislunar ferry, transshipments from the Moon to low Earth orbit would become cheaper than such shipments from Earth. Early shipments could include oxygen, unprocessed lunar rock (for shielding) and agricultural products. As lunar bases develop, processed metals and glasses could be included.

Shipments from Earth to the Moon would be precision tooling equipment and electronic supplies. Organic waste generated onboard the cislunar ferry and in low Earth orbit could be sold to Moonbase farms. The orbiter would also be valuable as a research facility. (SLuGS)

(1) Woodcock, Gordon R., Transportation Networks for Lunar Resources Utilization, Space Manufacturing 5; Engineering with Lunar and Asteroidal Materials, American Institute of Aeronautics and Astronautics, New York, Proceedings of the 7th Princeton/AIAA/ Space Studies Institute Conference, May 8-11, 1985.
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Magsail Asteroid Survey Mission
(SEI; Stafford) by Stan Love and Dana G. Andrews

The asteroids, lying principally between the orbits of Mars and Jupiter, have long been considered one of the best potential sites for near term access to extraterrestrial resources. To fully assess the value of asteroids for commercial use, and also to gain scientific knowledge about them which is critical to our understanding of the formation of the solar system, it is necessary to examine a large number of them a very close range, perhaps even collecting samples of their surfaces for analysis on Earth. Such a mission is unthinkable with current chemical rockets, however. Each flyby would require a few km/s of velocity change (hence approximately doubling the initial mass of the spacecraft) and no surface landings could occur without expending a prohibitive amount of propellant.

The magnetic sail (Andrews, D.G. and Zubrin, R.M., "Progress in Magnetic Sails," AIAA Paper 90-2367, 1990) suggests a solution to this problem. It would derive its thrust from the interaction of the solar wind with the magnetic field around a loop of super conducting cable several dozen km in diameter. As long as current flows in the cable (once set up, it will continue to flow indefinitely) the sail would develop a small amount of thrust, which could be directed by altering the orientation of the loop or by changing the current, easily accomplished with a modest-sized solar array. Since it would produce a continuous force without expending any propellant, a magsail could orbit the sun in the asteroid belt indefinitely, visiting tens or hundreds of objects at a relative velocity of a few km/s.

Asteroids possess no magnetic fields to hinder the use of a magsail. Neither do they have strong gravitational gradients, which are difficult for any low-thrust vehicle to overcome. If the mission profile allowed the necessary deceleration time, the spacecraft could rendezvous with asteroids to take samples of their surfaces. Proper alignment of the sail and the asteroid could be arranged so that the sail force and the gravitational attraction of the asteroid exactly balance one another, allowing samples to be taken of the surface from a motionless spacecraft. After sampling a number of asteroids, the spacecraft could return to Earth to drop off material samples and undergo routine maintenance. It could then return to the asteroid belt for further exploration. (SLuGS)
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Magsail Mars Missions
(SEI; Stafford) by Dana G. Andrews, Stan Love, and Joe Hopkins

Regular round trip missions to Mars could be undertaken using a magnetic sail, or magsail, spacecraft. A magsail would derive its thrust from interaction between the thin plasma of the solar wind and the magnetic field surrounding a current-bearing loop of superconducting cable roughly 100 km in diameter. Once a current was established in the loop, it would continue to flow indefinitely, providing thrust until the current was cut.

Directing the thrust could be accomplished by changing the orientation of the loop or by altering the current; both easily accomplished with a modest-sized solar array. The magnetic sail concept was originated by D. G. Andrews in 1968, but was not feasible until recent developments in superconductors that allow for cable that could be kept below its critical temperature with a simple and lightweight passive cooling system.

An additional advantage of the magsail is that the current loop would generate its own magnetosphere, much like that of the Earth, but on a much smaller scale. The magnetic field of the sail would protect the spacecraft's payload (and, in particular, its living passengers) from most charged particle radiation, decreasing the requirement for massive and costly radiation shielding on manned missions.

A recent paper (Andrews, D.G. and Zubrin, R.M., "Progress in Magnetic Sails," AIAA Paper 90-2367, 1990) describes a manned mission to Mars in 2007 with an initial mass of 200 tons and a payload of 140 tons. This payload is comparable with the payloads of other low-thrust manned systems currently under consideration.

A flyby of Mars is projected 164 days after departure from Earth. The payload and crew taxi would return to high Earth orbit after a total of 668 days. The spacecraft could then be refitted for the next launch window, occurring 90 days after arrival. Since proper alignment of the two planets occurs at regular intervals and the magsail could make the round trip with time to spare, it could be used as a permanent facility cycling between Earth and Mars. (SLuGS)
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Magsail Stabilization of Lagrange Point Structures
(SEI; Stafford) by Stan Love

In numerous schemes for the development of cislunar space, propellant depots, mass catchers, and other facilities have been proposed at the various Lagrange points of the Earth-Moon system. Of these five points, only two, L4 an L5 (at 60° leading and trailing the Moon in its orbit) are stable against the small, constant gravitational perturbations present in the system. The two Lagrange points nearest the Moon, L1 and L2, are probably the most useful for lunar missions. Facilities constructed there would have to be constantly supplied with propellant to compensate for gravitational perturbations, or they would soon drift into other, less useful orbits.

The magnetic sail (Andrews, D.G. and Zubrin, R.M., "Progress in Magnetic Sails," AIAA Paper 90-2367, 1990) suggests a solution to this problem. It would derive a small amount of thrust from the interaction of the solar wind with the magnetic field around a loop of super conducting cable roughly 100 km in diameter.

As long as current flows in the cable (once set up, it will continue to flow indefinitely) the sail would develop a small amount of thrust, which could be directed by altering the orientation of the loop or by changing the current, easily accomplished with a modest-sized solar array. It would be capable of making the necessary continuous orbit modifications without expending any propellant at all, hence eliminating the need for large resupply missions. Operating a magsail in the near-Earth environment would require that some consideration be made of the Earth's magnetotail, but this would probably not impact the sail's usefulness.

Another advantage of the magnetic sail is that it could generate its own magnetosphere, much like that of the Earth, but on a much smaller scale. The magnetic field of the sail would provide good shielding against charged particle radiation for anything in its immediate vicinity, and would thus lessen the need for heavy and expensive radiation shielding of manned outposts.(SLuGS)
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Remote Lunar Geological Survey
(SEI; Stafford) by Stan Love and Robert Lilly

For the development of a manned presence on the Moon, it is critical to determine the mineral resources available locally. The Moon is too large and travel across it is too difficult for a detailed, ground based global geologic survey to be feasible in the near term. An alternative to the collection of soil samples on the surface is determination of the soil composition via remote means. This could be done in a crude manner by observing the spectrum of sunlight reflected from the Moon. A more sophisticated method would be the use of laser Raman spectroscopy, wherein a laser is directed at the surface, with the spectrum of light scattered at wavelengths near that of the incident laser providing accurate determination of the composition of the surface. Laser Raman spectroscopy is commonly used at close range in the laboratory, but could be applied at longer distances.

Placing a satellite equipped with a 100 W laser in polar orbit around the Moon would allow a Raman survey of the entire body with a resolution as small as 25 cm. At 100 km altitude, the Raman signal (10-6 of the incident intensity) would outshine full Earthlight. Sunlit regions could not be surveyed. A 10 cm telescope with a spectrograph and CCD detector aboard the craft would be able to obtain a spectrum, with a signal-to-noise ratio of 10, in roughly 200 seconds, less than the 1200 seconds it would take for the satellite to travel across the sky of a given point. Both telescope and laser would have to track with an accuracy of 0.5 arcsec.

Each spectrum, one CCD frame, would contain about 20 M bits of information. The spacecraft must be able to store at least 20 frames of data while out of sight of Earth, requiring roughly 50 M bytes of storage, perhaps on tape. Transmission of data to Earth would require a rate of at least 200 k bits per second for a continuous survey.

The most difficult aspect of this mission would be providing power for the laser, which would operate only over shadowed terrain. The power requirement of the rest of the electronic equipment is small in comparison with the laser's consumption, several kilowatts. Power must come from solar panels via fuel cells, batteries or other suitable sources. The expense of such a system would certainly be less that of a ground-based survey of similar scope, and the spacecraft could be retrieved at the end of its mission and redeployed to other bodies in the solar system.(SLuGS)
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Clear Span Lunar Base Structures
(SEI; Stafford) by Hugh Kelso, Joe Hopkins, et. al.

We present a design for a lunar base that provides a generic, multipurpose environment; the location of which is not dependent upon natural geological features. Clear-span construction creates large open spaces that can be subdivided according to use and need. It could be developed along the lines of an industrial park with the flexibility to accommodate a wide variety of uses while at the same time providing varied services to its customers.

This design is of steel construction and is divided into upper and lower pressure areas. The upper area provides a pressure environment equivalent to two miles above sea level (9.5 psi) for agricultural use while the lower area provides an atmospheric pressure equivalent to one mile above sea level (12 psi) for habitation and work areas. Elevators which service the base also act as air locks between the pressurized areas.

Our design encloses a space 30 meters high and 50 meters square. A layer of excavated regolith would be spread over the top of the base and compacted to a depth of 10 meters. This would serve as both a shield against radiation and as a dead load to counter balance some of the atmospheric pressure within the base. Other uses for the excavated material might include the extraction of iron, oxygen, and hydrogen. The construction process of the base would be similar to that of a building on Earth, and could be repeated as growth requires.

This base concept permits many interior configurations. Services the base would provide include such things as the basic maintenance of the base itself, power, lighting, air, waste disposal, food, living quarters, recreational areas, communications facilities, computer support, and medical services. Modules could be configured to include fabrication and processing facilities, a gymnasium, park areas, conference rooms, media production studios, and whatever else was needed or desired. Heavy industrial processes, such as smelting, and other activities which may harbor health risks would be carried out in modules separated from those that house personnel.(SLuGS)
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Survey of Earth-Crossing Objects
(Stafford) by Stan Love

Asteroids whose orbits carry them across the orbit of the Earth are of extreme interest for a number of reasons. Only half of the estimated 1,000 such objects with diameters greater than 1 km have been discovered. Since Earth-crossing asteroids present a direct threat to all life on Earth, a large-scale astronomical survey should be undertaken to detect as many of them as possible.

Currently, knowing that such an object was on a collision course with the Earth would be of no use, as there exists no capability to alter its course. This unhappy state of affairs will change in the future, however, so a good knowledge of the population of 1 km objects in the inner solar system could prevent a disaster the likes of which have not been seen on Earth in millions of years.

Although the impact of a 1 km object would have dire consequences for most life on Earth, the chances of such a collision are comfortably remote: only about 1 in 100,000,000 per year. Some Earth-crossing asteroids are of interest for reasons other than fear of collision.

Many of these objects can be reached with only a few kilometers per second of velocity above Earth escape, and hence represent an important and relatively accessible source of extraterrestrial materials. Many such objects are thought to contain, among other useful resources, several weight percent of water present in hydrated minerals. An astronomical survey of such objects can determine not only their orbital parameters and hence ease of access, but can also produce indications of their basic chemical composition and likely available resources. (SLuGS)
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Food Animals in Biological Life Support Systems
(Stafford) by Stan Love

A great deal of research has been done regarding the use of plants as part of life-support systems for space habitats. Plants are excellent recyclers of air and water, and if the system is planned carefully enough and the substantial startup mass is allowable, a vegetable garden (equipped with a few mechanical devices, such as an oxidation reactor for waste products) in a space habitat can perform complete recycling of air and water for the crew, and also provide almost all of their nutritional needs.

In typical biological life support systems of this kind, about 3 percent of the dietary needs of the crew are left to be filled by outside sources, primarily as vitamin and amino acid supplements. The bulk of the diet, however, would necessarily be vegetarian, which may not appeal to all astronauts.

It is interesting to note the changes necessary in a biological life support system if it is required to produce even a modicum of animal protein for crew consumption. Let us assume that 10 percent of the crew's diet is to be derived from animals, such as rabbits or fish, grown along with the vegetables in a biological system. A generous estimation of the fraction of a meat animal that is edible and palatable (i.e. not hair or bones or viscera) is 50 percent.

Let us also assume that the a mass of living food animals equal to the mass of a person metabolizes air, water, and food at the same rate as the person does, again a generous assumption since small animals have higher metabolic rates than human beings. A general rule of thumb quoted in ecology is that raising an animal takes ten times the animal's weight in food. Using these very general rules, if 10 percent of mass in the crew's diet is animal products, twice that mass of animals (because the whole animal is not used) must be raised continuously, requiring 20 times that mass of plants to be fed to the animals.

The life-support system for the animals, then, requires 20 times 10 percent, or two times, the "acreage" as that for the human crew, effectively tripling the mass of the entire system.

In conclusion, it is probably not feasible to have a closed biological life-support system provide meat for its crew if mass is a deciding factor in the design. Astronauts in such missions will be largely vegetarian, in spite of any personal preferences. (SLuGS)
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An Artificial Lunar Magnetic Field
(Stafford) by Stan Love

The Moon possesses no magnetic field of its own. As a consequence of this, and the fact that it has no atmosphere, it is constantly bombarded by cosmic rays both from deep space and from the Sun. For human activity on the Moon over any length of time, great care will have to be taken to provide shielding from harmful cosmic rays. The Moon's bulk itself can provide more-than-adequate shielding from solar cosmic rays during local night, but solar flares cannot be counted on to occur only when the sun is below the horizon.

A far-fetched but effective solution to the shielding problem is to gird the Moon with a loop of superconducting cable bearing enough current to generate an artificial "bubble" in the solar wind large enough to contain the entire Moon. A current on the order of 1 million amperes should suffice. Once the current is induced in the cable, it will continue to flow undiminished forever, so the power requirements for such a system are negligible. The magnetic field would protect the whole surface of the Moon, greatly reducing the flux of charged particle radiation both for permanent habitats and for astronauts working on the surface. It would also allow compasses to be used for orientation on the Moon .

Some drawbacks to this idea are the large initial cost of producing and laying the cable, and the fact that the artificial magnetosphere would probably generate zones of intense radiation similar to the Earth's Van Allen belts, creating radiation hazards in lunar orbit. It would also prevent the solar wind from striking the Moon's surface, thus eliminating the primary remover of gaseous pollutants from the Lunar environment.(SLuGS)
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Magnetic Radiation Shields
(Stafford) by Stan Love

The powerful and wide-reaching magnetic field of a magnetic sail (Andrews, D. G. and Zubrin, R. M., Progress in Magnetic Sails, AIAA Paper 90-2367,1990) provides good protection against charged-particle radiation for its payload, and indeed anything inside its magnetosphere, as a secondary effect of the thrust it produces. There will be many applications in near-term space exploration for which thrust will not be required, but cosmic-ray shielding will: namely, any fixed activity taking place outside the Earth s magnetosphere. In such cases, shielding could be provided with a loop of superconducting material similar to a magnetic sail, but with a smaller dipole moment. The resulting magnetic field could protect an area a few kilometers across, and would produce negligible thrust.

Stations in geosynchronous or other high Earth orbit, permanent installations at the Lagrange points or in orbit around planets such as Mars or Venus, and bases on the surfaces of the Moon , the Asteroids, or any airless body without a magnetic field will all need to provide shielding for their inhabitants. Vehicles that travel routinely through the Van Allen belts would also benefit from having effective charged-particle radiation shielding. Surface bases may block radiation with thick layers of local material, but transporting large amounts of massive material for shielding is not economically sound for orbital bases when a lightweight loop of superconducting cable could do the job equally well.(SLuGS) Back to List at Top of Page

Regolith as Propellant for Mars Missions
(Stafford) by Brian Tillotson

This is a proposal to use a coaxial electromagnetic accelerator (a.k.a. coil gun or mass driver) as a rocket engine for a Mars mission. The proposed propellant for the outbound journey to Mars is regolith (dirt) from the Moon, and the propellant for Mars orbital maneuvers and for return to Earth is regolith from Demos or Phobos.

O'Neill proposed use of a coil gun or mass driver as a rocket motor which ejects inert material at high speed to produce thrust. Recent coil gun demonstrations show that technology is in hand to realize this propulsion concept. With this concept, raw regolith is a suitable propellant. Regolith is less expensive than other proposed extraterrestrial propellants, which require heavy equipment delivered from Earth to chemically process raw materials.

Value: Use of planetary regolith addresses two needs for Mars mission design: low IMLEO and protection of the crew from galactic cosmic radiation (GCR). The concept avoids the cost of launching propellant from Earth, and the regolith can be used as shielding for most of the mission.

Several other advantages are realized. Propellant is stored in a bag which is folded and launched empty from Earth; this gives less launch volume than liquid propellants which are launched in rigid pressure tanks. Neither cryogenic storage nor in-space fluid transfer technology is required. Smaller power systems are required than for ion-propelled vehicles. Crews need not crowd into a storm shelter during solar flares. The proposed Moonbase finds a clear purpose.

Performance Characteristics: Using assumptions described in the background paper, the proposed vehicle's Earth mass (including lunar infrastructure) is 24% lower than a solar electric ion-propelled vehicle's mass. GCR dose to the crew is cut by more than half. The required electrical power is only 26% as large as for an ion vehicle.

Enabling Technologies: Coil gun launcher technology is advancing rapidly. Development should be directed to two new areas: 1) coil guns as flight-qualified rocket engines, and 2) a coil gun launcher on the lunar surface.

Relation to Mission Objectives: This concept may be enabling or enhancing for a manned Mars mission in two major ways. First, it may be cost enabling or enhancing by reducing the mass of Earth material launched into space. Second, it may be medically enabling or enhancing due to reduction of crew radiation dose. By providing a rationale for lunar support of a Mars mission, the concept increases the political likelihood of a permanent manned return to the Moon (SLuGS)

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