GeSp1179

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Number: 1179 Name: ORIGINAL MOONCABLE

Address: J.E.D.CLINE1 Date: 900619

Approximate # of bytes: 22680

Number of Accesses: 16 Library: 3

Description:

Original proposal of Mooncable concept (1972) and NASA reply to it.

Includes " The Mooncable: A Profitable Space Transportation

System" and NASA ICB reply (1972).

Mooncable is a fiberglass tether attached to the Moon's

surface, extending up toward Earth through L-1, with nearly

equal weights on each side of L-1. Superconductors transfer

energy of moving payloads along cable, creating a process analogous

to a siphon. Also describes related application using Mars'

moons for efficient transportation there, too.

Keywords:

mooncable,tether,L-1,fibergalss,glider,foamedsteel,Mars,Phobos

---------------------------------

THE MOONCABLE

J. E. D. Cline

[Note: the following two documents ("The Mooncable: A Profitable Space

Transportation System", and a response to it from NASA Inventions and

Contributions Board) are mostly for historical purposes, although the

project still could be created. For the referenced figures:

Figure No.1: Adjacent Earth and Moon Gravitational Pits

Figure No.2: Cross-sectional area distribution of approximately

"constant-tensile-stress" cable extending to infinity, and having an

input load of 2.5E4lbf pull on the Moon

are available by sending SASE to JED Cline,

5632 Van Nuys Blvd Ste 110,

Van Nuys, CA 91401.]

March 25, 1972

James E. D. Cline

905 Old Topanga Canyon Road

Topanga, California 90290

THE MOONCABLE: A PROFITABLE SPACE TRANSPORTAION SYSTEM

The theoretical basis and major engineering concepts of a unique

space transportation system are being presented. It is intended

primarily for bringing Lunar ans space-environment commercial products

to Earth at potentially very low expense on a long-term, high mass

payload, continuous operation basis. Viewing the moon and Earth

as two adjacent, partially merging gravitational pits in space, a

tensile structural attachment to the Lunar surface is constructed

in the saddle between the two pits of such dimentsions as to remain

in place supported by the upper part of Earth's gravitational pit.

Masses decending down the tensile structure, or cable, into the

Earth's pit are slowed by electromagnetic braking against the cable,

exchanging gravitational energy into electrical energy. The elect-

rical energy is transfered to a conductor system on the cable, which

is preferable superconducting by use of sunward layered foil reflect-

ors. The conductors carry the electrical energy across the grav-

itational hump to the moon-ward part of the cable, where electro-

magnetic traction motors exchange the electrical energy back into

gravitational energy, lifting payload up from the Moon.

The strength limitations of existing engineering materials are

overcome by the creation of a constant-tensile-stress concept, which

makes all parts of the structure carry an equal load by appropriately

varying its cross-sectional area along its length. To show that it

can be done, an example cross-sectional distribution has been worked

out for a cable of 10E4lbf lifting capacity from the Moon's surface,

requiring a maximum area of 21 sqin at the zero-accelleration point

between the two pits, and shrinking to one-hundredth that area at

the point of contact with the Lunar surface. The structural material

used in the example used in the example used in the example is

silica fiberglass, due to the abundance of silica on the Lunar

surface, and assumes a strength of 5E5 lbf and a safety factor of 2.

The emp;acement of the resulting large mass of cable is made feasable

by the concept of a "growing" cable, starting from a "seed" filament

brought from Earth, and p[rogressibely increased in area by electrically

raising new fiberglass up from an expanding fiberglass manufacturing

automatic plant on the Moon, ever-increasing the lifting capacity

of the cable. The initial fiberglass- producing plant landed there

probably would be between the size of Surveryor and Apollo.

With the efficiency allowed by using superconductors, the

Mooncable theoretically can transport payload from Luna to Earth at

zero energy cost, and actually may be able to provide a surplus of

electrical energy during this transportation process, depending

on the length of the cable. Initial Lunar and space environment

product for import to Earth markets involve zero-g foamed-steel

and foamed ceramics cast into glider shapes with cargo compartments

to be dropped off the end of the "mooncable" into Earth's atmosphere.

The structural mass of very large spacecraft for extensive space explor-

ation, made of Lunar materials, can be lifted up out of the Moon's

gravitational pit at an extimated 3 cents per pound, using externally

supplied electrical energy from a small nuclear-electric powerplant

on the Moon or on the cable for this function.

The purpose of this document is to disclose the fundamental

concepts of a unique catagory of transportation in space, which

may enable our declining space industry to revive by creating a

system continuously transporting large quantities of Lunar

environment products to Earth markets at negligible cost.

This document will be limited to a brief presentation of

the fundamental transportation concept along with ane set of

engineering concepts which might be used to implement the system.

Materials and other products from the unique space and Lunar

environments, such as "foamed steel" would be marketable profitably if

the cost of bringing them to Earth markets were sufficiently

reduced. Foamed steel is expected to be a building construction

material of outstanding usefulness.

Chemically-fueled fueled rocket propulsion transportation, such as

used by the Apollo project, is too inefficient to provide inexpen-

sive transportation to market, because nearly all of the fuel energy

is used just to lift the fuel mass itself.

An alternative Lunar-Earth transportation system concept

is now being proposed, which potentialluy can reduce the transportation

energy cost to a negligible expense, althougjh some of the features

of the concept stagger the imagination. No chemical energy fuels

need be brought from the Earth to the Moon, or be made on the Moon.

It is necessary to the understanding of the concept to change

one's visualization of what lies between Moon and Earth. Analogously

imagine a small model of two adjacent pits in the ground, the

shallower one containing water. Then note that the water from the

shallower pit may be siphoned into the deeper one without addition

of external energy, provided that a hose is provided and the siphoning

process is started. Such a siphoning process will power

itself provided that the work applied to the mass being transfered

down the deeper slope is greater than the work required to lift

the mass up from the shallower side. The Earth and its moon, Luna,

may be pictured as two adjacent gravity pits in space, the pit

corresponding the the Moon being much less deep than that of the Earth.

The total work of lifting mass from R0 to R is the area under

the curve representing the force of gravitational attraction,

W = I GMm dr = GMm ( -1 1 )

R0 r 2 R0 R

The work involved in getting in or out of the Moon's gravity pit is

2.9E6 joule per kg, or 807 watt-hours per kg. Similarly, the

work energy received going down Earth's gravtty pit is 6.2E7joule

per kg, or 17.3 KW per Kg. Also, in going from the Moon to Earth

an orbital kinetic energy of 140 wHr must be given up. The resulting

algebraic sum of energy is 16.5 KwHr per Kg surplus energy. Therefore,

a siphon-like process could continuously move Moon-mass payload to Earth

without further input of energy, theoretically.

A siphon-like process can anologously be formed by a continuous

balancing interchange of electrical energy and gravitational energy

between masses going up and down gravitational slopes. Electrical

energy can be converted into gravitational energy such as by an

electric traction motor powering an attached payload up a cable;

gravitational energy is converted to electrical energy by a pauyload

pushing a traction-coupled electric generator down a cable; and

electric power is coupled between up- and down-moving masses by

electically conducting tracks along the cable.

A cable, or other tension structure, if it is attached to

the Moon's surface and extends up out of the Moon's gravity pit

toward Earth far enough so that part of it hangs down part way

into Earth's gravity pit, will stay there in place without external

energy applied, if the weight of the part of the cable in Earth's

pit is at least as great as the weight in the Moon's pit.

A constant cross-section tension structure, such as a common

rope or cable, must have a tensile strenght-to-density ratio which

excludes most known engineering materials. However, a "constant-

tensile-stress" structure concept produces a varying cross-section

cable which easily has sufficient strength for this purpose,

being larger in cross-section where tension is greater in the cable.

This tension is greatest at the point where the Moon-Earth

gravitational accellerations with the angular centrifugal accelleration

cancel out one another, and is less than the tension bearing the

weight of an infinitely long cable extending out from the Moon's

surface.

To prove that a constant-cross-section cable can be strong

enough for this purpose, an imaginary cable extending from the

Moon to infinity was divided into sections of constant-crosssection

area, the area of each section being that required to support the

weight of that section plus the weight of the cable below it plus

the attached conductor weight and live loads, expressed by the

following equation:

F = (A)(S) = (Fn)(S)

n+1

(S)- (d)(r0)(1g/6) integral rn to rn+1 1/r 2 dr

Where Fn = Force atop a section of cable

Fn+1 = Force atop next higher section of cable

S = working tensile stress of cable material

d = density of tensile material

r0 = radius of planet or moon

An outside figure for the mass of an example rope was deter-

mined by applying the above equation in 23 cable sections to find

the maximum required cross-sectional area at infinity. The

assumptions were:

(a) A maximum upward pull on the Moon by the rope of

2.5 X 10E4lbf (1.1 X 10E5 newtons)

(b) A niobium-copper superconductor constant-cross-section

equal to a pair of #12 wires,

of 10E4 lbf (4.4E4 newtons)

(d),A density of 8.3E-2 lbm/in 3 fiberglass

(e) A working tensile stress in the fiberglass of 2.5E5 lbf/in 2

which assumes a strength of 5E5 lbf/in 2 and a safety

factor of 2.

The resulting cross-sectional distribution is shown in figure 2.

The length of the cable will be less than that distance between

Moon and Earth, 3.8E5 Km; and the average area will be less than

that of the maximum if at infinity, which is 21 in 2 (1.3E-2 m 2).

With a glass specific gravity of 2.3, this makes a mass of 2.6E9lbm.

Raising this mass from the moon is made reasonable by using

a special construction technique of using an initial filament brought

from Earth and emplaced by chemical rocket transportation. This

filament is gradually built up exponentially in dimensions and strength

by electrically raising the fiberbeing added as it is made by an

appropriately growing glass manufacturing plant on the Moon.

Earth-launch mass of the "seed" fiberglass filament, starting

with two strands at the Moon's surface, is 2.5E4 lbm if

5E-4 inch diameter fibers are used, or 4.4E3 lbm if 1.5E-4 in

diameter fibers are used. This does not include weight of reels,

control equipment, and auxilliary equipment.

Assuming nuclear-electric energy at the Moon at a long term

average cost of 10c per KwHr, the energy cost of raising this ropes

or cable's mass is less than 10E9 KwHr, or 10E8 dollars, assuming

also that the conductor is superconducting at the major phases of

construction, and that generator efficiency is 99%, and an average

electric traction motor efficiency of 91%.

The fiberglass is manufactured from the silica so plentiful

on the Moon"s surface, making it the ideal cable material. Heat

energy needed to melt it may come from solar reflectors. Mechanical

energy needed to form the fibers may come from the use of solar energy

being used to expand a gas, or from the nuclear-electric

powerplant. The size of the initial glass plant accompanying the

emplacement of the "seed" fiber filament cable may be similar to that of

the Surveyor spacecraft which were soft-landed on the Moon

many years ago. Earth-made parts for later larger glass manufact-

uring facilities would use the p[artly-built rope or cable to reduce

the cost of transportation to the Moon. The manufacture of strong

fiberglass filaments would be greatly assisted by the vacuum so

plentiful on the Moon, since contact with air reduces fiberglass

strength during manufacture on earth. Space-rated fiberglass

rope was for sale several years ago with a strength of 5E5 lbf/in 2

so a working tensile stress in the rope of 2.5E5 lbf/in 2 was used

in the preceding example rope calculations, using a safety factor

of 2, which is very conservative compared with a safety factor

of 1.6 normally used in construction practice. The total mass of

the rope needed would go down rapidly when the working tensile

stress allowed is increased. Glass fibers drawn and baked in a

vacuum have been measured as strong as 1.8E6 lbf/in 2, so there

is a good possibility that, for a given maximum payload lifted, the

size of the cable may be greatly reduced over the "outside" value

determined in the example calculation.

The area of the mooncable's cross-section would best be

distributed in the form of a net or thin hollow tube, to prevent

the cable from being completely severed by smaller hurtling objects.

The conductors would best be distributed around the tensile

supporting structure for the same reason, allowing continuous power

for repair activities, and for bidirectional traffic during normal

use of the system. A widely distributed cross-section would also

help in case the mooncable was ever severed, helping increase the

amount of atmosphere which dissapates the falling cable's mass energy.

THE CONDUCTOR AND MOTOR TYPES: The conductors wiuld need

to be superconducting to enable the energy balance equations to

approach reasonable accuracy, avoiding resistance heating losses

in the conductor. Multiple layers of reflecting, insulating

foils kept on the solar side of the rope may be sufficient to

allow rediation losses to adequately cool the superconductors.

the conductors might be still further cooled by having each tractor

spray the conductor with cryogenic liquids from "lunar cryostats"

during each passage along the rope.

The configuration of the conductors might be in the form of

linear stripes for rolling or wiping electrical contacts to drive

conventional traction motors, or spiral for use in a linear

electric motor system. Direct current is assumed to be used, as

the hysterisis loop in hard superconductors prevent the use of

alternating currents and linear induction motors. If the conduct-

tors are difficult to cool sufficiently to be superconducting,

energy losses would need to be minimized by using high voltages

between conductors. A-C linear induction motors or conventional

electric track propulsion concepts apply during the climb up the

cable, with conversion of the motors to generators during the

fall down the other end of the cable. Additional electrical

energy might need to be supplied from nuclear-electric or solar-

electric powerplants along the rope or on the Lunar surface, to

overcome conductor resistance losses. This would still be high-

efficiency transportation, requiring no chemical energy fuels to

be made on the Moon, or to be brought from Earth.

APPLICATION OF THE SYSTEM

The path from the Moon to the Earth is interrupted by the gap from

the end of the mooncable to the surface of the Earth,

so one way of bridging the gap is to modify the form of the larger

imported products, such as the foamed materials, into shapes that

can independently survive the drop into Earth's atmosphere and

landing. For example, the importaion of "foamed steel" might be

made possible by lifting Lunar siderite steel up the cable to the

zero accelleration point where it would be melted in a solar-

reflector furnace and foamed into a mold which casts it into the

shape of a giant low-density glider which then continues along the

cable to Earth-end, where it drops off it into Earth's atmosphere

into the ocean where it would float until collected, or glided

under control to more accurately determined market sites for delivery to

foamed-steel purchasers or conventional steel producers

around the world. this steel operation alone may be able to

support an expanding space industry, with the other space environment

products being extra value. The "mooncable" also could lift the bulk of

immense spacecraft, made of lunar materials, to the zero-g

potential point on the cable for assembly and launching toward

ambitious space exploration efforts such as a manned landing on

Mars or collection of gasses from Jupiter's atmosphere, and perhaps

an exploratory trip to a nearer star.

(Incidentally, Mars' two moons Phobos or Deimos could be used

in a similar way in bidirectional transportation between Mars and

points distant from its concentrated gravity field by electrically

powering elevators operating between moon orbit altitudes and several

miles above Mars' atmosphere, although a running start of about

1000 mph would be necessary to catch the end of a rope attached to

Phobos, and much less if attached to the more distant Deimos.)

SUMMARY: This document has presented a concept of a new catagory

in space transportation, along with some of the engineering concepts

which could be applied to implement and use the transportation system.

The ideas contained herein are hoped to be both the starting point

and the goals for the labors required of the many talented and

imaginative people who are needed to make the transportation system

a reality. But it can be made a real, working, and useful system

only if the people who create it are determined to make it work.

Figure No. !: Adjacent Earth and Moon Gravitational Pits

Figure No. 2:

Cross-sectional area distribution of approximated "constant-

tensile-stress" cable extending to infinity, and having an

input load of 2.5X10^4 lbf pull on the moon

--------------------------------------------------------------------

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

Washington, D. C. 20546

Reply to attn of: KB June 23, 1972

Mr. James E. D. Cline

905 Old Topanga Canyon Road

Topanga, California 90290

Dear Mr. Cline:

Your letter of June 3, 1972, which was addressed to Dr. George M.

Low, Deputy Administrator fo the National Aeronautics and Space

Administration and which briefly described your concept entitled

"The Mooncable: Gravitational-Electric Siphon in Space", was

referred to the Inventions and Contributions Board for review and reply.

We are also in receipt of related correspondence and a

document entitled "The Mooncable: A Profitable Space Transporta-

tion System", which was forwarded to this office by Mr. Monte Mott,

Patent Counsel of the NASA Pasedena Office. A review has now been

completed of all of your material that has been received, and we

should like to provide you with the following explanatory comments

and suggestions.

The proposal which you have outlined in your correspondence is obvi-

ously conceptual in nature, and describes a project which, if under

taken, would involve a significant expenditure of time and money to

transport materials from the lunar surface to the earth. For your

information, the lunar landing of the Apollo 17 mission which is

now scheduled to take place in December, 1972, will conclude NASA's

program to investigate the lunar surface, at least so far as the

immediate future is concerned. Following termination of the Apollo

program, we shall move on during the remainder of this decade to the

Skylab program and subsequently, to the Space Shuttle program. You

will find enclosed a copy of NASA EP-81 entitled: Man in Space

(Space in the Seventies), which explains how NASA plans to accomplish

the objectives of these programs. Present and future budgetary com-

mittments to attain the goals outlined in this booklet will not per-

mit the consideration of expentitures for extensive new projects such

as the one you have submitted, and we are therefore not able to make

a favorable recommendation with respect to your proposal.

In your letter to Dr. Low, we inferred that you were requesting that

NASA contribute funds for the promotion of the project you have

proposed. We believe you should be aware of the regulations that

apply to joint projects involving the expenditure of NASA funds

and, for that purpose, are also sending you a copy of a NASA

booklet entitled "Guide to Policies and Procedures for Sponsored

Research" which we believe you will find informative and helpful.

The successful completion of the concept which you have proposed

would depend upon the verification of a number of unsubstantiated

assertions that are made in your presentation, and there is, of course

no certainty that such confirmation could be established. This is

an additional and importatnt reason for deferring consideration of

your concept. Although we cannot make a favorable recommendation

in response to your proposal, we do want to thank you for permitting us

to examine its contents, and to express our appreciation for your

interest in contributing to the advancement of NASA's future program.

(signed)

Francis W. Kemmett

Director of the Staff

Inventions and Contributions Board

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