US3460148A

US3460148A - Antenna for space vehicle

Info

Publication number: US3460148A
Application number: US512394A
Authority: US
Inventors: Emeric I Podraczky
Original assignee: Comsat Corp
Current assignee: International Telecommunications Satellite Organization
Priority date: 1965-12-08
Filing date: 1965-12-08
Publication date: 1969-08-05
Anticipated expiration: 1986-08-05
Also published as: DE1541471B2; DE1541471A1; GB1094424A; FR1502296A

Description

g- 1969 E. I. PODRACZKY 3,460,148

ANTENNA FOR SPACE VEHICLE Filed Dec. 8, 1965 INVENTOR EMERIC IMRE PODRACZKY United States Patent Olfice 3,460,148 Patented Aug. 5, 1969 3,460,148 ANTENNA FOR SPACE VEHICLE Emeric I. Podraczky, Bethesda, Md., assignor to Communications Satellite Corporation, Washington, D.C. Filed Dec. 8, 1965, Ser. No. 512,394 Int. Cl. H01q 1/28 US. Cl. 343-705 7. Claims This invention relates to an antenna and more particularly to a despun antenna for a spin-stabilized space satellite.

A spin-stabilized space satellite may be defined as one which is spun about its axis to prevent change in its attitude with relation to the earth axis. Such attitude change would, in the absence of such a spinning arrangement, take place as a result of tumbling of the satellite. One example of a spin-stabilized space satellite is the synchronous satellite Syncom. Such a satellite is controllably positioned in inertial space at a fixed point with relation to the earth. Its radial velocity is the same as that of the earth. In order to prevent tumbling or change in its attitude, a spin is imparted to the satellite. The spin imparting means does not form a part of this invention but for background information this spinning is imparted by the launch vehicle whereby when the satellite is injected into its orbit, it is spinning or rotating about its axis at a speed which may be between 100 and 150 revolutions. This spin rate is of course defined with relation to inertial space. Mechanically associated with the spin-stabilized space satellite is an antenna platform on which an antenna is mounted. This platform may be mounted to the satellite by means such as low-friction bearings. A suitable despinning motor mounted in the satellite and mechanically connected to the antenna may be provided. This motor functions to prevent the antenna platform and therefore the antenna from spinning at the spin rate of the satellite. In this context, the platform is identified as despun and the antenna identified as operating in its despun mode. The radio frequency energy pattern of the antenna is fixed with relation to the earth and has its major axis fixed with relation to a point on the earth during the orbit of the satellite. The motor rotates the antenna platform in a direction opposite to the direction of rotation of the satellite at a speed equal to the rotational speed of the satellite less one revolution per orbit.

Since centrifugal forces are produced when an object is rotated relative to inertial space, a despun platform oriented toward the earth is subject to relatively small centrifugal force. However, should it be desirable for one reason or another to de-energize the despinning motor or should the despinning motor be de-energized inadvertently, the present invention provides means by which the energy pattern of the antenna switches from the despun mode (pencil beam) to an omni mode (toroidal beam). As previously stated, in the despun mode, the energy pattern is a conventional lobe having its major axis directed toward the earth. In the omni mode, the pattern may be substantially doughnut shaped, that is, radiating substantially equally in the directions perpendicular to the spin axis. While this omni mode results in some loss of power, it still defines a pattern which is useable for communication purposes. Were it otherwise, the de-energizing of the despinning motor would result in the despun mode pattern persisting. In this event, a pattern is generated which has little or no utility for communication purposes.

The present invention relates to a fail safe antenna device for spin-stabilized space satellites in which the omni mode antenna energy pattern is automatically achieved upon failure of the despinning motor by direction or by accident. This is done by taking advantage of the centrifugal forces which are produced when the antenna rotates at the spin rate of the satellite due to despinning motor failure. These forces, acting upon the antenna device, change its physical arrangement and more particularly its reflector orientation to achieve the omni mode type of operation. Of course, de-energizing of the despinning motor will result in the antenna platform and consequently the antenna with associated reflectors rotating at the same speed as the satellite.

It is therefore an object of the present invention to provide a fail safe antenna device for a spin-stabilized space satellite having a normally despun section in which means are provided for producing an antenna RF energy pattern useable for communication purposes when the despun section moves away from its normally biased active first position to a passive second position as a result of deenergization of the despinning arrangement using the centrifugal force developed by the normally despun section rotating with the satellite to overcome said bias. The active first position referred to in which the antenna array normally finds itself is of course the despun mode and the passive second position is of course the omni mode.

This, and other objects will become apparent from a more detailed description of the accompanying drawings.

In the drawings:

FIGURE 1 is a perspective view of a spin-stabilized satellite showing the normally despun section including the antenna with reflector and associated RF transparent cylinder, during a despun type of operation;

FIGURE 2 is similar to FIGURE 1, but representing the omni mode type of operation;

FIGURE 3 is similar to FIGURE 2, but illustrating a different type of antenna reflector and transparent means;

FIGURE 4 is similar to FIGURE 3, but representing a despun mode type of operation;

FIGURE 5 is a perspective view of an antenna device but illustrating a diiferent type of reflector and transparent means operating in the despun mode; and

FIGURE 6 is similar to FIGURE 5, but representing an omni mode type of operation.

Referring first to FIGURES 1 and 2, FIGURE 1 represents a spin-stabilized satellite 10 with antenna platform 11 mounted by bearing means 12 to the satellite. Mounted by spring-loaded hinges 16 to the platform 11 are the metallic parabolic reflector 14 and the RF transparent parabolic cylinder 15. The antenna is identified at 13. The platform 11 is mounted by some conventional means to a despinning motor (not shown) carried by the satellite. FIGURE 1 is illustrative of the despun mode type of operation in which the

members

14 and 15 are biased by the springs 16 toward their active first position (the despun mode) and away from a passive second position (omni mode). Since the despinning motor substantially prevents spinning of the platform with relation to inertial space, the antenna device does not generate a significant amount of centrifugal force. However, should the despinning motor be de-energized, then the platform and associated antenna device will rotate along with the satellite 10 and the resultant centrifugal forces generated overcome the bias springs to move the

members

14 and 15 into the omni Inode type of operation shown in FIG- URE 2.

Of course it should be understood that springs are illustrative only. Any mechanical means performing a similar function may be employed. In fact, arrangements such as shown in FIGURES 3 through 6 may be employed.

Referring first to FIGURE 3, there is shown a satellite 10 operating in the omni state. The antenna 13 is in this figure associated with flexible metallic wire reflectors 17 and flexible RF transparent wires 18. The de-energizing of the despinning motor causes the antenna platform and device to rotate with the satellite and to generate centrifugal force whereby these Wires move from the despun mode as shown in FIGURE 4 to the omni mode shown in FIGURE 3.

FIGURES 5 and 6 illustrate respectively despun mode and omni mode types of operation in which the reflectors are constituted of a plurality of flexible metallic petals :19 and the RF transparent means is in the form of a parabolic supporting cylinder 20.

With relation to all of the figures, the specific type of antenna array, reflector or RF transparent means is not critical to the invention. As to the materials employed, the metallic reflector may be of any suitable type commonly used in the art and the RF transparent means may be made of Fiberglas. The flexible metallic wires referred to in FIGURES 3 and 4 may be of conventional beryllium-copper type. This is also true in connection with the flexible metallic petals shown in FIGURES 5 and 6.

The bearing means by which the antenna platform is mounted to the satellite may be conventional. These bearings should be as frictionless as possible. The despinning motor mounted within the satellite and connected to the antenna platform may also be conventional and forms no part of this invention.

The functioning of the RF transparent member is only for dynamic balancing purposes.

What has been disclosed are various embodiments to the present invention. Other embodiments obvious to those skilled in the art from the teachings herein are contemplated to be within the spirit and the scope of the following claims.

What is claimed is:

1. A fail safe antenna device for a spin-stabilized space satellite having a normally despun section comprising: a radiator/collector member mounted on the despun section and wave reflector means mounted on the despun section adjacent the radiator-collector member and biased toward an active first position and away from a passive second position whereby centrifugal force overcomes the biasing to move the reflector means to the passive second position whenever the normal despun section rotates with the satellite.

2. A fail safe antenna device as claimed in claim 1 wherein said normally despun section comprises a platform means for carrying said radiator/ collector member, and substantially frictionless bearing means mounting said platform to said satellite.

3. A fail safe antenna device as claimed in claim 2 wherein said wave reflector means comprises a metallic parabolic cylinder.

4. A fail safe antenna device as claimed in claim 3 further including hinge means connecting said platform and said wave reflector means.

5. A fail safe antenna device as claimed in claim 1 wherein said wave reflector means comprises a plurality of flexible metallic wires.

6. A fail safe antenna device as claimed in claim 1 wherein said wave reflector means comprises a plurality of flexible metallic petals.

7. A fail safe antenna device as claimed in claim 1 further including an RF transparent means mounted to said despun section adjacent said radiator/collector oriented opposite to said wave reflector means.

References Cited UNITED STATES PATENTS 3,341,151 9/1967 Kampinsky 343705 ELI LIEBERMAN, Primary Examiner U.S. Cl. X.R. 343724, 729

Claims

1. A FAIL SAFE ANTENNA DEVICE FOR A SPIN-STABLIZED SPACE STATELLITE HAVING A NORMALLY DESPUN SUCTION COMPRISING: A RADIATOR/COLLECTOR MEMBER MOUNTED ON THE DESPUN SECTION AND WAVE REFLECTOR MEANS MOUNTED ON THE DESPUN SECTION ADJACENT THE RADIATOR-COLLECTOR MEMBER AND BIASED TOWARD AN ACTIVE FIRST POSITION AND AWAY FROM A PASSIVE SECOND POSITION WHEREBY CENTRIFUGAL FORCE OVERCOMES THE BIASING TO MOVE THE REFLETOR MEANS TO THE PASSIVE SECOND POSITION WHENEVER THE NORMAL DESPUN SECTION ROTATES WITH THE SATELLITE.