US3324470A

US3324470A - Passive earth satellite reflector

Info

Publication number: US3324470A
Application number: US316804A
Authority: US
Inventors: Thomas M Morse
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1963-10-17
Filing date: 1963-10-17
Publication date: 1967-06-06
Anticipated expiration: 1984-06-06

Description

June 6, 1967 T. M. MORSE PASSIVE EARTH SATELLITE REFLECTOR 2 Sheets-Sheet 1 Filed Oct. 17. 1965 INVBNTOR firms/Z fiomse,

ATTORNEY June 1967 'r. M. MORSE PASSIVE EARTH SATELLITE REFLECTOR 2 Sheets-Sheet 2 Filed Oct. 17, 1963 3,324,470 PASSIVE EARTH SATELLITE REFLECTOR Thomas M. Morse, Santa Maria, Calif assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed Oct. 17, 1963, Ser. No. 316,804 11 Claims. (Cl. 3343-18) This invention relates to a passive earth satellite reflector and more particularly to a reflector utilizing an organized array of needle-like particles for reflecting electromagnetic waves.

It is known in the prior art to use a spherical or balloon-type reflector in an earth orbit for reflecting electromagnetic waves from a transmitting location on earth to a receiving location. A spherical reflector is a relatively ineflicient earth orbit-to-earth reflector, that is, it reflects only a small percentage of electromagnetic wave energy back toward a desired location on earth. A major limitation of the spherical reflector is that its relatively low efficiency is further reduced when the spherical shape is appreciably distorted.

It is also known in the prior art to place an unconfined array of needle-like particles into an earth orbit in an attempt to form a reflective surface for electromagnetic waves. A major disadvantage of this approach is that the particles scatter too widely to be effective as a reflector for electromagnetic waves.

An object of this invention is to provide a new and improved passive earth satellite reflector.

Another object is to provide a passive earth satellite reflector utilizing an organized array of needle-like particles to form a surface for reflecting electromagnetic waves.

Another object is to provide a passive earth satellite reflect-or which is maintained in a predetermined orientation while in a non-polar orbit about the earth by the interaction of the magnetic fields of the earth and the reflector.

A further object is to provide a passive earth satellite reflector utilizing an organized array of magnetized needle-like particles to form a surface for reflecting electromagnetic waves wherein the reflector and surface are maintained in a predetermined orientation while in a non-polar orbit by the interaction of the magnetic fields of the earth and the reflector.

With these and other objects in view, a passive satellite reflector illustrating certain features of the invention may include a plurality of strips having needle-like particles arranged therein to form a surface for reflecting electromagnetic waves. The strips may be maintained in a single plane, for example, the strips may be supported in parallel relationship within an inflatable structure or be radiated outward from a central hub by centrifugal force.

Other objects and advantages of the invention will become apparent by reference to the following detailed specification and accompanying drawings, wherein:

FIG. 1 is a pictorial representation of a sphericalshaped reflector, partially broken away, in a non-polar orbit about the earth, incorporating certain principles of the invention;

FIG. 2 is a schematic representation of the sphericalshaped reflector of FIG. 1 showing the reflector in a nonpolar orbit about the earth;

FIG. 3 is a view showing magnetized, needle-like particles embedded in a strip of elasticized material;

FIG. 4 is a schematic representation of a spherical reflector showing needle-like particles randomly spaced therein;

FIG. 5 is a pictorial representation of a generally wheel shaped reflector in a non-polar orbit about the earth, and

tates Patent 0 FIG. 6 is a schematic representation of the wheelshaped reflector of FIG. 5 showing the reflector in a non-polar orbit about the earth.

General description In FIGS. 1 and 2, a spherical, passive earth satellite reflector, hereafter called spherical reflector 11, and in FIGS. 5 and 6, a wheel-shaped, passive earth satellite reflector, hereafter called wheel reflector 13, are initially placed into an orbit about the earth such that a predetermined plane passing through each of these reflectors is parallel to the surface of the earth. The plane defined by reference numerals 1649 passing through spherical reflector 11 (FIGS. 1 and 2), and the plane defined by reference numerals 21-24 passing through wheel reflector 13 (FIGS. 5 and 6), are initially parallel to the earths surface. A surface, capable of reflecting electromagnetic waves, is maintained in the planes 16-19 and 21-24 to reflect electromagnetic waves from a transmitting location to a receiving location.

As here used, the term polar orbit means an orbit which passes directly over, or very nearly over, the North and South poles of the earth. it follows that the term non-polar orbit includes all orbits which do not pass over, or very nearly over, the North and South poles of the earth.

Although any plane in outer space is parallel to some surface on the earth, the term parallel to the ear-ths surface is used in reference to the parallel plane which is closest to the surface of the earth for a given distance measured perpendicularly from the surface of the earth.

The term reflection and its derivatives include reradiation from small particles which is present only at the resonant frequency or harmonics of the particles as well as mirror-type reflection in which all frequencies of electromagnetic radiation are reflected by the particles.

The term electromagnetic wave means a wave of electromagnetic radiation, characterized by variations of electric and magnetic fields, and the term electromagnetic radiation as here used means radiation associated with a periodically varying electric and magnetic field that is traveling at or near the speed of light, including radio waves, light waves, X-rays, and gamma radiation. It is to be understood that the scope of the invention is not limited to use with any of the illustrative types of radiation above noted. It is contemplated that this invention may be employed with any electromagnetic radiation capable of being reflected.

Detailed description Referring to FIG. 1, spherical reflector 11 has a spherical body 25 constructed of a strong, non-porous, material which is transparent to electromagnetic waves, for example rubber, or plastic such as a polyester film sold under the trademark name of Mylar by the E. I. Du Pont de Nemours and Co., Inc.

A plurality of strips 31 are secured in parallel relationship with respect to each other to the inner walls of body 25 and are spaced a short distance apart. Strips 31 form a surface in the shape of a disc, hereafter called the reflective disc 26, in the plane 1619. Strips 31 may be flat tapes of rectangular cross section, strings or tapes of circular cross section, or the like.

In FIG. 3 there is shown one of the strips 31, each of which is composed of an elastic material characterized in' that the strip will stretch along its length when subjected to two opposing pulling forces and capable of returning to its original length when the forces are released.

Blunt-ended, needle-like particles 32 are embedded, or placed in any suitable manner, in end to end relation within or on each strip 31. The term needle-like is indioative of a class of articles, such as pins, slender rods,

flat foil strips, needles, or the like. Pins, slender rods, or the like would be used where re-radiation is desired. Flat foil strips would be used where mirror-type reflection is desired. Flat foil strips can be designed to provide both mirror-type and re-radiation type reflection.

Particles 32 are made of a magnetized material which is an eflicient reflector of electromagnetic waves and are spaced a small distance apart within each strip 31 such that a north pole is opposite a south pole. One such magnetizable material is an alloy approximately composed of 42.2% iron, 24% cobalt, 18% nickel, 8.5% aluminum, 5% titanium, and 3.3% copper. It is to be understood that there are other magnetizable materials available which one skilled in this art could employ for particles 32. Also, certain ceramic-type magnetic materials, known as ferrites, may also be used. It is to be understood, however, that particles 32 need not be made of any particular material; it is only necessary that the particles be magnetizable and eflicient reflectors of the frequencies of electromagnetic radiation to be employed.

Spherical reflector 11 and strips 31 are folded into a small package and placed in a nose cone of a rocket prior to launching into an earth orbit. After the packaged spherical reflector is placed into a preselected earth orbit, it is unfolded and inflated in space by injection of an inflating medium, for example a gas under pressure may be released from a cylinder into the spherical reflector upon actuation of a valve by a time or radio controlled mechanism. An example of a system for launching a space vehicle and inflating it in outer space is shown in US. Patent 2,996,212, issued to W. J. OSullivan, Jr. Strips 31 stretch out to a length greater than their unstretched length when spherical reflector 11 is fully inflated to form disc 26.

It will be apparent to one skilled in this art that body 25 of spherical reflector 11 serves merely as a supporting and containing structure for the extended strips 31 which make up disc 26. Therefore, body 25 need not necessarily be spherical, but may be disc-shaped, pancake-shaped, or other suitable shape.

In FIGS. 1 and 2, reflective disc 26 is shown oriented to a position such that the north and south poles of particles 32 are aligned with the North-South axis of the earth. Reflective disc 26 presents an effective north pole along its periphery defined by

numerals

36, 37, and 38, and presents an effective south pole along its periphery defined by

numerals

38, 39, and 36.

When spherical reflector 11 is placed into a non-polar orbit, for example the orbit about the equatorial belt of the earth shown in FIGS. 1 and 2, the magnetic field of the earth interacts with the magnetic field of reflective disc 26 to maintain the reflective disc (made up of the organized array of magnetized particles 32) in the orientation shown. The interaction of the magnetic fields of the earth and reflective disc 26 maintain the reflective disc, and hence spherical reflector 11, stable against rotation about its East-West axis, identified as E-W, and about its vertical axis, identified as V-V. However, the spherical reflector is free to rotate about its North-South axis, identified as N-S.

While in orbit in outer space, the small mass of particles 32 is weightless in an almost frictionless medium. Hence, when spherical reflector 11 is in a non-polar orbit, the magnetic field of the earth exerts suflicient influence on the magnetized particles 32 of disc 26 to maintain the North-South axis of the spherical reflector aligned with the earths magnetic field.

To realize the maximum reflective efficiency of the organized array of particles 32 embedded in strips 31 for reflecting electromagnet waves, it is necessary to maintain reflective disc 26 in parallel relationship to the earths surface. This can be done by modifying the structure of spherical reflector 11 only slightly. Two valves 41 and 42 (shown in block schematic form) may be placed about the East-West circumference of spherical reflector 11 such that an appropriately directed exhaust of the gas contained within the spherical reflector from one or the other valves rotates the spherical reflector in a direction necessary to maintain disc 26 parallel to the earths surface. Alternatively, valve controlled cylinders of gas may be mounted on the East-West circumference to accomplish this result. The valves can be controlled by radio signals from earth in a known manner, for example a solenoid may be controlled by a radio receiver responsive to a predesignated signal to operate the valves. It will be apparent to one skilled in the art that any of a number of conventional devices can be used to rotate spherical reflector 11 to maintain disc 26 parallel to the earths surface.

Radio equipment on the earth can readily determine how often reflective disc 26 is rotating about its North- South axis. It can readily be determined how often reflective disc 26 should rotate about the North-South axis to maintain the reflective disc parallel to the surface of the earth. Valves 41 and 42 can be operated as above indicated to exhaust gas from spherical reflector 11 to increase or decrease rotation of the spherical reflector to maintain the reflective disc parallel to the earths surface.

In this manner, spherical reflector 11 gradually loses gas and elastic strips 31 slowly contract to their unstretched length to decrease the size of the spherical reflector. Even when all of the gas is exhausted, the spherical reflector decreases only to a size dictated by the unstretched lengths of elastic strips 31. Due to the interacting magnetic fields of the magnetized particles 32, strips 31 exert an effective outward force which after total exhaustion of the gas, prevents the reflector 11 from collapsing around the periphery of the reflective disc 26. Since the remainder of the reflector 11 has neither interior nor exterior forces acting upon it, it should retain its spherical shape unless it is hit by a meteorite or some other object which causes it to distort. However, this distortion has no effect on the efficiency of the reflector. As previously mentioned, disc 26 has an effective north pole and south pole, therefore, each strip 31 tends to maintain its North-South alignment in the earths magnetic field and exerts an outward force around the periphery of the reflective disc 26 of the uninflated reflector. The pressure required to maintain the shape of the reflective disc 26 in outer space is extremely minute.

Other variations of spherical reflector 11 are within the contemplation of the invention. For example, particles 32 embedded in strips'31 (FIG. 3) might be unmagnetized. In such a case, particles 32 embedded in strips 31 nevertheless form a reflective disc 26. This variation is limited with respect to spherical reflector 11 abovedescribed, in that it does not have the feature of maintaining reflective disc 26 and spherical reflector stabilized against rotation about its East-West axis and its vertical axis. This variation of spherical reflector 11 is a less efficient reflector of electromagnetic waves because the reflector and reflective disc 26 are free to rotate about all axes. Such rotation would result in a lower percentage of electromagnetic waves being reflected to a desired target. This variation can be used in a polar as well as a non-polar orbit since unmagnetized particles 32 are unaffected by the earths magnetic fields.

If re-radiation of electromagnetic waves is desired, another variation of spherical reflector 11 employs a plurality of discs 26 stacked one above the other in such a manner that the re-radiation from the discs reinforces each other.

In FIG. 4, magnetized, needle-like particles 32 are coated with an insulating material, for example, the plastic known as Mylar. Particles 32 are placed unconfined within a spherical body 44 of a passive earth satellite reflector, hereafter called the balloon reflector 46, and float randomly at different horizontal levels with respect to each other within the body when the balloon reflector is in outer space. Balloon reflector 46 is initially placed into a non-polar orbit about the earth. The magnetic field of the earth exerts suflicient influence on the individual, magnetized, particles 32 to align the particles in end to end relation to form strings, in much the same manner that a magnet aligns iron filings. As with spherical reflector 11, body 44 of balloon reflector 46 need not be spherical, since the body serves merely as a containing structure.

As long as balloon reflector 46 is not in a magnetic field reversal area near the earths magnetic poles, magnetized particles 32 remain aligned in the earths magnetic field regardless of the rotation of the body of the balloon reflector about any of its axes. Even if this embodiment is placed into a polar orbit, particles 32 will be out of alignment for only a short interval when the earths magnetic field reverses itself near the magnetic poles.

Balloon reflector 46 is somewhat less efficient than spherical reflector 11 because some of the electromagnetic waves reflected by particles 32 at different horizontal levels tend to cancel instead of re-inforcing reflections from other particles. Nevertheless, balloon reflector 46 is a simple arrangement which may be economically practicable in a given application.

A variation of balloon reflector 46 does not use strips 31 or magnetized needle-like particles 32. Unmagnetized particles, for example flat aluminum foil strips, or copper, steel, or alloy needle-like particles, or the like, are placed within body 44 and float randomly therein when balloon reflector 46 is in orbit in outer space. The reflective efficiency of this confined random array of particles 32 is unaffected by changes in the shape of body 44 of balloon reflector 46 or its attitude with respect to the earths surface. Also, this variation of the second embodiment may be used in any orbit since unmagnetized particles 32 are relatively unaffected by the earths magnetic fields.

This variation of balloon reflector 46 is relatively ineflicient; however, the efiiciency could be slightly improved by transmitting electromagnetic waves at a frequency corresponding to the natural resonant frequency, or harmonics thereof, of the particles 32 contained within body 44. In this manner, the particles would re-radiate at their natural resonant frequency and present a larger effective reflecting surface.

In FIG. 5, Wheel reflector 13 is generally wheel-shaped and has openings 54 spaced about the periphery of a central hub 53. Behind each opening 54 and mounted in hub 53 is a reel 61 (shown schematically) of dielectric tape 52, made for example of Mylar or other plastic. As shown, tapes 52 may be unreeled from reels 61 to emanate through openings 54 and radiate therefrom in spoke-like fashion. Tapes 52 are similar in construction to strips 31 depicted in FIG. 3 except that unmagnetized needle-like particles 56 are embedded therein and the tapes need not be elasticized. A small mass 57 is attached to the end of each tape 52.

Braking facilities are provided to prevent the unwinding of reels 61 until a desired time. For example, these facilities may include a solenoid controlled brake which is energized by an electronic circuit responsive to a predesignated signal from earth or to a signal generated internally in the satellite based either on time, rotational speed of the satellite, on on centrifugal force. Another example of such braking facilities may simply include a blocking mass which is initially pressing against each reel 61 and is movable away from each reel by centrifugal force.

Wheel reflector 13 is placed into an orbit about the earth such that plane 21-24 (FIGS. and 6) passing through the wheel reflector is initially parallel to the surface of the earth. Wheel reflector 13 is illustratively shown in an equatorial orbit, however, the wheel reflector is operative in any orbit. Facilities are provided for rotating the wheel reflector about its V-V axis. At the desired time, the braking facilities are removed from the reels to free the reels for rotation. For the examples of braking facilities above suggested, the solenoid controlled brake is energized by the circuit responsive to the predesignated signal, or the blocking mass is moved away from the reels when sufficient centrifugal force is developed by rotating the Wheel reflector about its V-V axis.

Small mass 57 in the end of each tape 52 initiates the nreeling action much in the same way that a line plays out from a fishing reel when wheel reflector is rotated about its V-V axis. In this manner, tapes 52 are unreeled to their full length under the impetus of centrifugal force to form a surface in the shape of a reflective discs 58 (FIG. 6) for reflecting electro-magnetic Waves.

To realize the maximum reflective efficiency of the organized array of needle-like particles 56 embedded in tapes 52, it is necessary to maintain reflective disc 58 parallel to the earths surface. For example, if the wheel reflector is placed in an equatorial orbit (FIG. 6), facilities must be provided for rotating the wheel reflector about its E-W mis and its N-S axis to maintain the plane 21-24 parallel to the surface of the earth.

In theory, once wheel reflector 13 has been rotated sufliciently to create the desired centrifugal force, it should continue to so rotate indefinitely. However, should wheel reflectors 13- rotational speed decrease to a point where insuflicient centrifugal force is developed to sustain strips 52 in the shape of a disc, facilities may be provided for rotating the wheel reflector about its V-V axis to maintain sufiicient centrifugal force. These facilities may comprise valve controlled gas jets responsive to predesignated appropriately directed signals.

Since the braking facilities and the facilities for rotating the wheel reflector about its three principal axes are known in this art, these facilities are not shown and do not form a part of the invention. The reflectors can be as large as necessitated by the particular application and are limited in size only by the capacity of available launching equipment.

It is to be understood that the above-described em-bodiments and variations are illustrative of the principles of the invention and many others could be devised without departing from the scope of the invention.

What is claimed is:

1. A passive earth satellite reflector for reflecting electromagnetic Waves, comprising a plurality of magnetized, needle-like particles, each particle capable of reflecting electromagnetic waves,

a satellite vehicle for confining and limiting the maximum relative spacing of the particles to form an effective surface larger than any individual particle to reflect the electromagnetic waves, and

strip means mounted to said satellite vehicle for maintaining theparticles in parallel rows with said particles arranged in north pole-to-south pole relationship in each row.

2. A passive earth satellite reflector for reflecting elec tromagnetic waves, comprising a plurality of dielectric strips having magnetized,

needle-like particles secured thereto in north poleto-south pole relationship for reflecting electromagnetic waves, said strips arranged to form a substantially planar surface, and

means for maintaining the strips in the planar surface.

3. A passive earth satellite reflector capable of being packaged in a small container and subsequently inflatable to provide a surface for reflecting electromagnetic waves, comprising a plurality of strips,

a plurality of spaced, magnetized, needle-like particles mounted in north pole-to-south pole relationship on each strip for reflecting electromagnetic waves, and

a body, transparent to electromagnetic waves, for supporting the strips in a substantially flat plane.

4. A passive satellite reflector capable of being folded into a small package and subsequently inflatable to provide a surface for reflecting electromagnetic waves, comprising an inflatable body which is transparent to electromagnetic waves,

a plurality of strips secured within the body and placed under tension in parallel rows to define a single plane when the body is inflated, and

a plurality of spaced, magnetized, needle-like particles mounted in north pole-to-south pole relationship on each strip for reflecting electromagnetic waves.

5. In a system for transmitting electromagnetic waves at a first location and receiving the waves at a second location, a passive earth satellite reflector capable of being folded into a small package and subsequently inflated, comprising an inflatable, body which is transparent to electromagnetic waves,

a plurality of elastic strips secured within the body and placed under tension in parallel rows to define a single plane when the body is inflated, and

a plurality of spaced, magnetized, needle-like particles mounted in north pole-to-south pole relationship on each strip for reflecting electromagnetic waves, the strips forming a reflective disc having an effective north and south pole for interacting with the magnetic field of the earth to maintain the reflective disc in a predetermined orientation relative to the earth.

6. A passive earth satellite reflector for reflecting electromagnetic waves capable of being folded into a small container and subsequently inflatable, comprising an inflatable body which is transparent to electromagnetic waves, and

a plurality of magnetized, needle-like particles within the body, the particles being unconnected so as to be free to interact with the earths magnetic field and align in end to end relationship to form strings of particles for reflecting electromagnetic waves.

7. A passive earth satellite reflector for reflecting electromagnetic waves, comprising a central body,

a plurality of tapes extensible from and spaced about the periphery of the central body to define a single plane, and

a plurality of spaced needle-like particles mounted on each tape for reflecting electromagnetic Waves.

8. A passive earth satellite reflector for reflecting electromagnetic waves, comprising a hub-shaped body having openings spaced about the outer periphery of the body,

a tape mounted for extension from each opening to radiate in a substantially flat plane about the hubshaped body, and

a plurality of spaced needle-like particles mounted in end to end relationship on each tape for reflecting incident electromagnetic waves.

9. A passive earth satellite reflector operable abovethe earths surface, capable of being compacted in size while on the earth, and extensible when placed above the earths surface to form a surface for reflecting electromagnetic waves, comprising a hub-shaped body having a plurality of openings spaced about the outer periphery thereof,

a reel mounted behind each opening of the body and having a length of tape Wound thereon, the tape being extensible upon rotation of the body to define a generally planar surface, and

a plurality of spaced, needle-like particles mounted in end to end relationship on each tape for reflecting electromagnetic waves.

10. A passive earth satellite reflector for reflecting electromagnetic waves, comprising:

an inflatable body which is transparent to electromag netic waves;

a plurality of strips attached within said body in parallel relationship to define a plurality of parallel planes when the body is inflated, each plane being spaced a predetermined distance away from the adjacent plane so that the reflection from one plane reinforces reflections from other planes; and,

11. A passive earth satellite reflector for reflecting electromagnetic waves comprising:

a supporting structure;

means including a plurality of parallel strips mounted on the supporting structure for forming a substantially planar surface; and

a plurality of spaced, magnetized, needle-like particles mounted in parallel rows on said planar surface with said particles arranged in each row in north poleto-south pole relationship.

References Cited RODNEY D. BENNETT, Primary Examiner.

LEWIS H. MYERS, CHESTER L. JUSTUS, Examiners.

J. P. MORRIS, Assistant Examiner.

Claims

1. A PASSIVE EARTH SATELLITE REFLECTOR FOR REFLECTING ELECTROMAGNETIC WAVES, COMPRISING A PLURALITY OF MAGNETIZED, NEEDLE-LIKE PARTICLES, EACH PARTICLE CAPABLE OF REFLECTING ELECTROMAGNETIC WAVES, A SATELLITE VEHICLE FOR CONFINING AND LIMITING THE MAXIMUM RELATIVE SPACING OF THE PARTICLES TO FORM AN EFFECTIVE SURFACE LARGER THAN ANY INDIVIDUAL PARTICLE TO REFLECT THE ELECTROMAGNETIC WAVES, AND STRIP MEANS MOUNTED TO SAID SATELLITE VEHICLE FOR MAINTAINING THE PARTICLES IN PARALLEL ROWS WITH SAID PARTICLES ARRANGED IN NORTH POLE-TO-SOUTH POLE RELATIONSHIP IN EACH ROW.