Patent Description:
A vast constellation of spacecraft or satellites orbit the Earth that are employed for many purposes, such as communications purposes, detection purposes, etc., where some of these satellites communicate with each other through satellite cross-link signals and with ground stations through satellite uplink and downlink signals. Some of these satellites are placed in a geostationary orbit above the Earth, where the orbital speed of the satellite and the rotational speed of the Earth cause the satellite to remain above the same location on the Earth.

One specific type of satellite is referred to in the industry as a three-axis satellite, where the satellite body is generally square or rectangular. Solar arrays are often mounted to sides of the satellite that face the north/south direction, referred to as the X-direction, when the satellite is in a geostationary orbit so that when the solar arrays are deployed therefrom they are in a suitable position to be directed towards the sun. The north/south facing sides of the satellite often include a thermal radiator and equipment panel to which various electronics, such as power amplifiers, are mounted to and within the satellite body, where the panels operate as a heat sink and thermal radiator and contain heat pipes to conduct heat. Further, these types of three-axis satellites include a side referred to as the earth deck that faces the Earth in the Y-direction relative to the satellite orbit to which various antennas are mounted, where the opposite surface of the spacecraft is referred to as the zenith deck. In addition, the three-axis satellite includes sides that face the east/west direction, referred to as the Z-direction, relative to the Earth when the satellite is on orbit.

Satellites are constantly being replaced and additional satellites are being added to the constellation as old satellites reach the end of their design lives and new technologies become available. A satellite or spacecraft is typically put into orbit by launching the satellite in a launch fairing on a rocket, where once the rocket reaches a certain altitude, the satellite is released therefrom and on-board propulsion is used to provide the final position of the satellite and the proper orientation relative to the Earth so that the various antennas and other communications devices on the satellite are properly positioned for transmitting and receiving signals.

Launching a spacecraft or satellite in to Earth orbit is expensive, and thus the industry is always attempting to reduce that cost. One way in which the cost of launching a satellite into orbit can be reduced is by launching multiple satellites in a single launch vehicle so that the cost of launching each satellite is spread across all of the satellites. However, as the number of satellites provided in a single launch vehicle goes up, the weight of the launch vehicle also goes up, which also increases the cost.

In order to launch multiple satellites in a common launch vehicle, the satellites need to be mounted to each other or a common structure within the launch vehicle. In one design, multiple satellites are mounted to a common cylindrical dispenser within the launch vehicle that extends through the satellites when in the launch vehicle. Although successful, such a dispenser adds significant weight and volume to the launch vehicle.

It is also known in the art to design a three-axis satellite to have a central cylinder extending therethrough, where that cylinder is coupled to the cylinder of other satellite in the launch vehicle. However, known satellites employing central cylinders orient the cylinder in the Y-direction through the earth deck and the zenith deck of the spacecraft. Because the cylinder extends through the satellite in this direction, there is limited space on the earth deck that could otherwise be used for cross-link antennas, uplink phased arrays (UPA), downlink phased arrays (DPA), gimbal dish antennas (GDA), etc., all of which may be desirable in modern communications geostationary orbiting three-axis satellites. There are also central cylinder stacking-interface related obstructions, which complicate the placement of Earth deck antennas and electronic equipment and interfere with earth deck heat pipe placement and heat removal.

Prior art can be found in <CIT> which generally relates to a modular spacecraft system, in <CIT> which generally relates to a deployed radar panel for space situational awareness and in <CIT> which generally relates to space needles.

The following discussion of the embodiments of the invention directed to a three-axis spacecraft including a central stacking cylinder oriented in an east/west direction is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses. It is noted that the terms spacecraft and satellite are used interchangeably herein.

The invention is set out in the independent claim.

<FIG> is an isometric view of a three-axis spacecraft <NUM> in a deployed configuration and <FIG> is an isometric view of the spacecraft <NUM> in a stowed configuration. The spacecraft <NUM> includes a spacecraft body <NUM> having a general rectangular configuration defining six sides. An X - Y - Z reference frame is shown in <FIG> relative to the spacecraft body <NUM> and is intended to represent the axis of the spacecraft <NUM>. Once the spacecraft <NUM> is on orbit, which will usually be a geostationary orbit, the X-axis will be oriented north and south relative to the Earth, the Z-axis will be oriented east and west relative to the Earth, and the Y-axis will be oriented in to and away from the Earth. As is well understood by those skilled in the art, the enclosure defined by the spacecraft body <NUM> will house most of the electrical circuits, batteries, fuel tanks, cooling systems, etc., none of which are specifically shown in <FIG>. As will be discussed in detail below, a central mounting cylinder <NUM> extends through the spacecraft body <NUM> that is oriented along the Z-axis and extends some distance from the spacecraft body <NUM>, where a mounting flange <NUM> is provided at one end of the cylinder <NUM> and a mounting flange <NUM> is provided at an opposite end of the cylinder <NUM>.

The spacecraft body <NUM> includes a side panel or wall at each of the six sides of the body <NUM>, where one of the side walls facing the Z-direction has been removed so as to expose the cylinder <NUM> extending through the body <NUM>. In the orientation shown in <FIG>, one of the panels facing the Y-direction is an earth deck <NUM> that will face the Earth when the spacecraft <NUM> is on orbit and an opposing panel is a zenith deck <NUM> that will face away from the Earth. The spacecraft <NUM> includes a north thermal radiator/equipment panel <NUM> that defines the north facing panel when the spacecraft <NUM> is on orbit and a south thermal radiator/equipment panel <NUM> that defines the south facing panel when the spacecraft <NUM> is on orbit. Various electrical components (not shown), such as high power amplifiers, are mounted to an inside surface of the panels <NUM> and <NUM> within the body <NUM> and generate significant heat. The outer surface of the panels <NUM> and <NUM> is directed towards cooler space, away from sunlight to provide thermal radiative cooling for those components. Depending on the power requirements of the communications system within the spacecraft <NUM>, the size of the spacecraft body <NUM>, etc., the panels <NUM> and <NUM> will have a certain size where they may extend some distance beyond the earth deck <NUM> and the zenith deck <NUM>. The length of panels <NUM> and <NUM> can also be extended in the Z-direction.

The spacecraft <NUM> includes two opposing solar panels, specifically a first solar panel <NUM> mounted to the north panel <NUM> and a second solar panel <NUM> mounted to the south panel <NUM>. In one embodiment, the solar panels <NUM> and <NUM> are folded into the stowed configuration, where they are positioned adjacent to the panels <NUM> and <NUM>, as shown. When the solar panels <NUM> and <NUM> are deployed, they are able to rotate about the X-axis so they can be oriented perpendicular to the direction of the sun as the spacecraft <NUM> orbits and the Earth turns to provide maximum power efficiency.

Because the mounting cylinder <NUM> extends along the Z-axis in the east/west direction and the solar panels <NUM> and <NUM> are mounted to the north/south panels <NUM> and <NUM>, the earth deck <NUM> is completely open for providing real-estate to which multiple antennas can be mounted, where modern satellites require many communications antennas often operating at different frequency bands. A downlink phased array <NUM> and an uplink phased array <NUM> are configured at a central location on the earth deck <NUM>, as shown, and can be used for beam steering downlink signals and uplink signals, respectively, as is well understood by those skilled in the art. Additional antennas on the earth deck <NUM> may include three cross-link dish antennas <NUM>, <NUM> and <NUM> for transmitting and receiving signals to and from other spacecraft on orbit. The antenna dishes <NUM>, <NUM> and <NUM> are shown in their deployed configuration facing away from the spacecraft <NUM> in <FIG> and their stowed configuration turned inward to reduce the space requirements for launch. Additionally, two gimbal dish antennas <NUM> and <NUM> are shown mounted to the earth deck <NUM> for transmitting and receiving uplink and downlink signals at a different frequency band than the phased arrays <NUM> and <NUM>.

As mentioned above, the mounting cylinder <NUM> allows the spacecraft <NUM> to be mounted to other spacecraft in a single launch fairing to be launched for deployment in orbit around the Earth. <FIG> is an isometric view of a launch vehicle <NUM> including an engine section <NUM>, a launch fairing <NUM> and a nose cone <NUM>. The spacecraft <NUM> is mounted to two other identical three-axis spacecrafts by securing the flange <NUM> or <NUM> of the spacecraft <NUM> to an identical flange of an adjacent spacecraft. As is well understood by those skilled in the art, any suitable device for securing the flanges of adjacent spacecraft together can be used, such as exploding bolts, to separate the spacecraft <NUM> once the launch vehicle <NUM> is on or near the appropriate orbit for the deployment spacecraft <NUM>. As is apparent, the axis of the cylinders <NUM>, i.e., the east/west Z-axis, is in the same direction as the launch velocity vector of the launch vehicle <NUM>, where the earth deck <NUM> is perpendicular to the velocity vector, contrary to the known stackable spacecrafts where the earth deck <NUM> faces the velocity vector of the launch vehicle <NUM>.

The discussion above of the spacecraft <NUM> is merely representative of one possible configuration of the elements that may be included in a modern three-axis spacecraft, where the configuration of the various components discussed herein can be varied within the scope of the present invention. <FIG> is an isometric view of a three-axis spacecraft <NUM> in a deployed configuration and <FIG> is an isometric view of the spacecraft <NUM> in a stowed configuration, where like elements to the spacecraft <NUM> are identified by the same reference number. The illustrations of the spacecraft <NUM> are specifically intended to show antenna being deployed off of the sides of the spacecraft <NUM>, which may require the antenna to be deployed from the zenith deck <NUM>. The spacecraft <NUM> includes a spacecraft body <NUM> having a slightly different shape and size than the spacecraft body <NUM>, but still having six sides including the earth deck <NUM> and the zenith deck <NUM>. Further, the thermal radiator panels <NUM> and <NUM> have been replaced with thermal radiator panels <NUM> and <NUM> having a larger size than the panels <NUM> and <NUM> to show that different spacecraft have different heat removal requirements. It is noted that the solar panels <NUM> and <NUM> have been removed merely for clarity purposes. In this configuration, the phased arrays <NUM> and <NUM> and the cross-link antenna dish <NUM> are still mounted to the earth deck <NUM>, but the antenna dishes <NUM> and <NUM> are mounted to the zenith deck <NUM>. Further, a con-focal main reflector <NUM> is mounted to the zenith deck <NUM> and a con-focal sub-reflector <NUM> is mounted to the earth deck <NUM>.

<FIG> is an isometric view showing a launch fairing <NUM> for a launch vehicle <NUM> and including three spacecraft <NUM>, <NUM> and <NUM> mounted therein for launch, where the cylinders <NUM> of adjacent spacecraft are coupled together in the manner discussed above. <FIG> is intended to illustrate that different three-axis spacecraft can be stacked together in a common launch fairing, where the spacecraft may have different sized thermal radiator panels, different sized earth decks, different components, different configuration of antennas, etc. For example, the spacecraft <NUM> may be a medium power geostationary orbit spacecraft configured with a con-focal uplink phased array, the spacecraft <NUM> may be a high power geostationary orbit spacecraft configured with multi-beam downlink phased arrays and high gain multi-beam uplink phased arrays, and the spacecraft <NUM> may be a low power high earth orbit or geostationary orbit spacecraft.

Claim 1:
A three-axis spacecraft (<NUM>, <NUM>) comprising:
a spacecraft body (<NUM>, <NUM>) being generally rectangular in shape and including first and second opposing radiator/equipment panels (<NUM>, <NUM>), first and second opposing mounting panels, an earth deck (<NUM>) thermally coupled to the first radiator/equipment panel (<NUM>) and a zenith deck (<NUM>) thermally coupled to the second radiator/equipment panel (<NUM>), wherein the first and second radiator/equipment panels (<NUM>, <NUM>) generally face a north and south direction relative to the Earth when the spacecraft (<NUM>,<NUM>) is on orbit, the first and second mounting panels generally face an east and west direction relative to the Earth when the spacecraft (<NUM>, <NUM>) is on orbit, the earth deck (<NUM>) faces the Earth when the spacecraft (<NUM>, <NUM>) is on orbit, the zenith deck (<NUM>) faces away from the Earth when the spacecraft (<NUM>, <NUM>) is on orbit;
a mounting cylinder (<NUM>) extending through the spacecraft body (<NUM>, <NUM>) and out of the first and second mounting panels, wherein the mounting cylinder (<NUM>) includes a mounting flange (<NUM>, <NUM>) at each end of the cylinder (<NUM>) and being operable to be mounted to a mounting flange of a mounting cylinder of other spacecraft,
wherein a plurality of antennas including a downlink phased array (<NUM>) and an uplink phased array (<NUM>) is mounted to the earth deck (<NUM>) at a central location on the earth deck (<NUM>).