“MOVEMENT APPARATUS FOR AN ARTIFICIAL SATELLITE”
FIELD OF THE INVENTION
The present invention concerns a movement apparatus for an artificial satellite able to orbit Earth. The movement apparatus comprises an articulated arm which, in correspondence with one free, unconstrained end thereof, is connected to one or more propulsion units which allow to move the satellite itself.
BACKGROUND OF THE INVENTION
Artificial satellites orbiting Earth are provided with movement apparatuses that comprise respective articulated arms with the unconstrained, free ends of which there are associated one or more propulsion units for moving the satellites.
Such propulsion units are usually Hall Effect Thruster propulsion engines, or thrusters, known in the state of the art, in which the thrust process is driven thanks to the ionizing effect of electrons that are first imprisoned and accelerated within a magnetic field and then neutralized during discharge. Specifically, the magnetic field is obtained by means of a cylindrical anode and a cathode formed from a negatively charged plasma.
Usually, the articulated arms of a satellite are provided with rotational joints that allow to rotate and move the articulated arm to make it assume various operating positions, so as to orient the propulsion units as desired.
For the operation of the propulsion units and the rotational joints, in such movement apparatuses there are a plurality of operating cables disposed along the articulated arm and comprising, for example, drive wiring, power cables for the propulsion units and the joint drive members, sensor cables, etc. In particular, these cables have to be protected with adequate shielding to prevent them from being damaged by impact with micro-meteorites that frequently intercept the orbit of the artificial satellite.
The shielding, usually, is made with additional protection parts disposed externally to the articulated arm, for example panels and protective sheaths, and if on the one hand it allows to protect the aforementioned operating cables, on the other it has the disadvantage of making the articulated arm significantly heavier.
The disposition of this shielding has to also take into account the possible movement of the articulated arm in order to avoid hindering its movement; this operation can therefore become even very complex to perform and - in the event that the shielding is not disposed correctly - it can significantly limit the movement of the articulated arm.
In addition, both the cables and also the propulsion units have to be adequately protected and thermally insulated so that they are operational in Earth orbit, where temperatures, in circumstances where solar rays are absent and do not affect these components with their heating effect, are comprised between about -250°C and about -300°C.
Furthermore, the propulsion engines are connected to corresponding auxiliary control and drive systems which are installed substantially close to said engines and which comprise, for example, auxiliary filtering and valve members.
A disadvantage related to the proximity between propulsion engines and auxiliary systems is that propulsion engines produce a high amount of heat, reaching temperatures even above l,500°C; the auxiliary systems, on the other hand, have operating temperature ranges well below propulsion engines, therefore, they have to be adequately shielded and/or thermally protected, otherwise malfunctions, faults, or breakages can occur.
There is therefore the need to provide, or perfect, a movement apparatus for an artificial satellite that can overcome at least one of the disadvantages of the state of the art.
To do this it is necessary to solve at least the technical problem of providing a movement apparatus for an artificial satellite in which the operating cables that run along the articulated arm are adequately protected without using additional protection parts external to the articulated arm itself.
In particular, one purpose of the present invention is to provide a movement apparatus for an artificial satellite which is ergonomic, and which allows a correct and effective movement of the articulated arm for the correct orientation of the propulsion units.
Another purpose of the present invention is to provide a movement apparatus for an artificial satellite in which both the operating cables and also the propulsion units are effectively protected and thermally insulated for operation in Earth orbit.
Another purpose of the present invention is to provide a movement apparatus for an artificial satellite which has lower production costs than the state of the art. The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.
SUMMARY OF THE INVENTION The present invention is set forth and characterized in the independent claim. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.
In accordance with the above purposes and to resolve the technical problem disclosed above in a new and original way, also achieving considerable advantages compared to the state of the prior art, a movement apparatus according to the present invention is configured to move an artificial satellite able to be put into Earth orbit, and comprises both an articulated arm provided with a first, a second and a third rotational joint which are operatively connected to each other, and also a cable assembly connected to the first, second and third joint for the respective drive.
In accordance with one aspect of the present invention, the first, second and third joint are provided with a first, a second and a third cavity, respectively, which are connected to each other in order to define a hollow conduit able to let the cable assembly pass through it, thus guaranteeing a physical and thermal protection and shielding therefor.
This has the advantage that it is not necessary to prepare other covering elements, or parts, external to the articulated arm, in order to protect and insulate the cable assembly.
In accordance with another aspect of the present invention, the articulated arm comprises a connection pipe interposed between the first and second joint and provided with a fourth cavity connected to the first and second cavity for the passage of the cable assembly. The first joint being connected to a central body of the satellite.
In accordance with another aspect of the present invention, the first, second and third joint each comprise a first part and a second part, respectively, which are rotatably coupled to each other in such a way as to determine a relative movement with respect to each other.
In particular, the first joint comprises a first part integral with the central body and a second part rotatable around a first axis of rotation by means of a first drive member and connected to the connection pipe.
The second joint comprises a first part integral with the connection pipe and a second part rotatable around a second axis of rotation by means of a second drive member.
Moreover, the third joint comprises a first part integral with the second part of the second joint and a third part rotatable around a third axis of rotation by means of a third drive member.
In accordance with another aspect of the present invention, in the first, second, third and fourth cavity there are one or more support plates configured to guarantee the correct disposition of the cable assembly and each provided with a plurality of through holes able to house and allow the passage of at least one cable of the cable assembly.
In accordance with another aspect of the present invention, the first, second and third joint and the connection pipe are covered with a multilayer coating able to guarantee an effective thermal insulation against temperature fluctuations in Earth orbit.
In accordance with another aspect of the present invention, the movement apparatus comprises a propulsion assembly able to be orientated for the correct movement of the satellite and configured to be connected to the third joint and to the cable assembly.
In accordance with another aspect of the present invention, the propulsion assembly comprises a support structure provided with a connection shaft associated with the third joint, and two or more propulsion units which are associated with the support structure and are connected to a corresponding auxiliary control and drive system.
In accordance with another aspect of the present invention, the propulsion units are mounted in housing seatings of a flat element of the support structure, the flat element having the function of a radiator and being provided with a plurality of ribs which branch out radially from the housing seatings and have the function of increasing the area for the dispersion of the heat generated by the propulsion units toward the outside.
In accordance with another aspect of the present invention, the auxiliary systems each comprise one or more auxiliary filtering members and one or more auxiliary valve members which are disposed, on the opposite part with respect to the respective propulsion units, on a separation panel of the support structure.
The separation panel is provided with a first plate facing toward the flat element and distanced therefrom, and a second plate distanced from the first plate and on which the auxiliary systems are mounted.
In accordance with another aspect of the present invention, the flat element and the separation panel are associated and kept distanced from each other by means of the connection shaft and a plurality of elongated spacer elements. In accordance with another aspect of the present invention, between the flat element and the separation panel there is a further multilayer coating having the function of thermally insulating the auxiliary systems, shielding them from the heat generated by the propulsion units.
In accordance with another aspect of the present invention, in correspondence with zones of attachment between the connection shaft and the flat element, between the flat element and the elongated elements, and between the auxiliary filtering and valve members and the second plate, there are respective thermal insulation elements for insulation from the heat generated by the propulsion units and absorbed by the flat element. In accordance with another aspect of the present invention, the support structure also comprises a protective housing for the auxiliary systems which is disposed on the opposite part with respect to the propulsion units and is made of a fiber- reinforced material. Preferably, the protective housing can also comprise a layer of graphite that facilitates the passage and dispersion of heat. According to another aspect, a propulsion assembly is provided comprising a support structure with which there are associated two or more propulsion units connected to corresponding auxiliary control and drive systems. The propulsion units are mounted on a flat element of the support structure, and the auxiliary systems are disposed, on the opposite part with respect to the respective propulsion units, on a separation panel of the support structure. In particular, the flat element and the separation panel are associated with and kept distanced from each other by means of a plurality of elongated spacer elements, and between the flat element and the separation panel there is a further multilayer coating having the function of thermally insulating the auxiliary systems, shielding them from the heat generated by the propulsion units.
The propulsion assembly can be provided alone, or in combination with the articulated arm. DESCRIPTION OF THE DRAWINGS
These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:
- fig. 1 is a schematic and simplified perspective view of an articulated arm for an artificial satellite according to the present invention;
- fig. 2 is a schematic and simplified section view of the articulated arm of fig. 1 ;
- fig. 3 is a detail view, enlarged and out of scale, of a detail of the articulated arm of fig. 1;
- fig. 4 is a schematic and simplified perspective view of a propulsion assembly of the articulated arm of fig. 1 ;
- fig. 5 is a schematic and simplified section view of the propulsion assembly of fig- 4.
We must clarify that the phraseology and terminology used in the present description, as well as the figures in the attached drawings also in relation as to how described, have the sole function of better illustrating and explaining the present invention, their purpose being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.
To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications. DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION
With reference to figs. 1 and 2, these represent a movement apparatus 100 configured to move an artificial satellite 200 orbiting Earth. The movement apparatus 100 comprises an articulated arm 10 provided with a first rotational joint 11 associated with the central body 201 of the satellite 200, a second rotational joint 12 operatively connected to the first joint 11, and a third rotational joint 13 operatively connected to the second joint 12. According to preferred embodiments, the first joint 11 and the second joint 12 are connected to each other by means of a connection pipe 15. The second joint 12 and the third joint 13 can be connected to each other directly, as in the example shown, or - in other variants - by means of another connection pipe. Preferably, the first and second joint 11, 12 are disposed in such a way as to have respective axes of rotation XI, X2, that is, a first axis of rotation XI and a second axis of rotation X2, parallel to each other.
The third joint 13 is disposed in such a way as to have the respective axis of rotation, that is, the third axis of rotation X3, perpendicular to the first and second axis of rotation X 1 , X2.
The movement apparatus 100 also comprises a propulsion assembly 30 able to be oriented for the correct movement of the satellite 200.
The propulsion assembly 30 is configured to be connected to the third joint 13 on the opposite part with respect to the second joint 12, as will be described in detail below.
Each joint 11, 12, 13 essentially comprises a first part I la, 12a, 13a and a second part 1 lb, 12b, 13b, which are rotatably coupled to each other so as to determine a relative movement with respect to each other.
In particular, the first joint 11 (fig. 1) comprises a first part 1 la integral with the central body 11 , and a rotatable second part 11b connected to a first end 15a of the connection pipe 15, which allows a first rotation R1 of the articulated arm 10 around the first axis of rotation XI. According to possible embodiments, the first rotation R1 has an angular amplitude comprised between 0° and about 150°, considering the central body 201 of the satellite 200 as a reference. The second joint 12 comprises a corresponding first part 12a connected to a second end 15b of the connection pipe 15, and a corresponding rotatable second part 12b connected to the third joint 13, which allows a second rotation R2 of the articulated arm 10, or of a part thereof, around the second axis of rotation X2. According to possible embodiments, the second rotation R2 has an angular amplitude comprised between about -5° and about 130°, considering as a reference the orientation of a longitudinal axis around which the connection pipe 15 develops coaxially.
The third joint 13 comprises a respective first part 13a, integral with the rotatable second part 12b, and a respective rotatable second part 12b, which is connected to the propulsion assembly 30 and which allows a third rotation R3 of the articulated arm 10, or of a part thereof, around the third axis of rotation X3. According to possible embodiments, the third rotation R3 has an angular amplitude comprised between about -25° and about 90°, considering a generic plane parallel to the connection pipe 15 as a reference.
According to preferred embodiments, each joint 11, 12, 13 comprises a respective drive member 16, 17, 19 for determining a relative rotation between the first part I la, 12a, 13a and the second part 1 lb, 12b, 13b of the respective joint (fig. 2). Specifically, there are provided:
- a first drive member 16 for driving the first joint 11 , that is, for rotating the second part 1 lb with respect to the first part 1 la of the first joint 11 ;
- a second drive member 17 for driving the second joint 12, that is, for rotating the second part 12b with respect to the first part 12a of the second joint 12; - a third drive member 19 for driving the third joint 13, that is, for rotating the second part 13b with respect to the first part 13a of the third joint 13.
The drive members 16, 17, 19 are of any known type whatsoever, or which will be made in the future, and are connected to one or more control and drive units of the satellite 200, not shown in the drawings. The movement apparatus 100 comprises an assembly of operating cables 20 (fig. 2) which depart from the central body 201 of the satellite 200 and which are connected to the first, second and third joint 11, 12, 13 and to the propulsion assembly 30 for the respective drive and operation. The cable assembly 20 comprises, for example, drive wiring, power cables, sensor cables, etc. We must clarify that the connection between the cable assembly 20 and the propulsion assembly 30 occurs in a known manner and for simplicity has not been shown in the drawings. By way of example, the cable assembly 20 can also be provided with secondary, or spare, drive cables for driving the propulsion assembly 30, which are used in the event of malfunctions and/or failures of the primary drive cables.
In particular, the first, second and third joint 11, 12, 13 are made so as to have inside them a first, a second and a third central cavity 21, 22, 23, respectively. The connection pipe 15 is also provided with a respective cavity, or fourth central cavity 25. In the event that a further connection pipe is provided between the second joint 12 and the third joint 13, this pipe is also provided with a further cavity, suitable to house the cable assembly 20.
The first, second, third and fourth cavity 21, 22, 23, 25 (fig. 2) are connected to each other in order to define a hollow conduit able to house and let the cable assembly 20 pass through it, thus guaranteeing a physical and thermal protection and shielding therefor.
In this way, advantageously, the cable assembly 20 is protected, for example from the impact of micro-meteorites, without needing to make an additional protection or coating and thus add additional weight to what is necessary for the structure itself.
In order to prevent any damage caused by excessive bending of the cable assembly 20, the cavities 21, 22, 23 and the corresponding joints 11, 12, 13 have been designed and sized taking into account both the maximum allowable bending for the cables in the longitudinal direction, and also the maximum allowable torsional component for the cables that can be generated when the joints 11, 12, 13 rotate around their axis of rotation XI, X2, X3.
On the other hand, to prevent any damage caused by excessive rubbing of the cable assembly 20, there are one or more support plates 26 inside the first, second, third and fourth cavity 21, 22, 23, 25 of each joint 11, 12, 13 and the connection pipe 15 (figs. 2 and 3), which are configured to guarantee the correct disposition of the cable assembly 20 and prevent unwanted twisting.
Each support plate 26 is provided with a plurality of through holes 27, of different sizes, able to house and allow the passage of at least one respective cable of the cable assembly 20, thereby accurately distancing them from each other. In the example shown in fig. 3, only two types of through holes 27 are shown, specifically first central through holes 27a and second perimeter through holes 27b; however, in other embodiments, there may also be three or more types of through holes 27. According to possible preferred embodiments, the support plates 26 are made of polytetrafluoroethylene (PTFE), that is, a polymer material that has a very low friction coefficient and a high degree of anti-adhesion.
The first, second and third joint 11, 12, 13 and the connection pipe 15 are covered with a multilayer coating 29 (fig. 2), for example of the MLI (Multi Layer Insulation) type, which guarantees an effective thermal insulation against temperature fluctuations in Earth orbit, mainly due to exposure to solar radiation, or lack thereof. Advantageously, the cable assembly 20, since it is inside the joints 11, 12, 13 and the connection pipe 15, benefits from the same insulating and mitigating effect of the temperatures present in Earth orbit.
The propulsion assembly 30 (figs. 4 and 5) essentially comprises a support structure 31 provided with a connection shaft 32, and two or more propulsion units 33, 35 for moving the satellite 200, which are associated with the support structure
31 and connected to a corresponding auxiliary control and drive system 36, 37.
Advantageously, the connection shaft 31 is associated with the third joint 13, specifically with the second part 13b thereof.
According to preferred embodiments, the propulsion units 33, 35 are Hall Effect Thrusters (HET), known in the state of the art, which during their respective operation reach temperatures even greater than l,500°C inside them.
The propulsion units 33, 35 are mounted on a flat element 39 of the support structure 31.
The flat element 39 (fig. 4) is shaped in such a way as to have two housing seatings 40 of the propulsion units 33, 35 and has the function of a radiator. The element 39 is provided with a plurality of ribs 41 (fig. 5) of various sizes which branch out radially from the housing seatings 40 and have the function of increasing the area for the dispersion of the heat generated by the propulsion units 33, 35 toward the outside. According to preferred embodiments, the flat element 39 is made of 7075 aluminum material, very resistant, light and with a high thermal conductivity, so as to allow a good planar diffusion of the generated heat. For example, the flat element has a thermal conductivity coefficient K of about 155 W/mK.
Furthermore, the flat element 39 can advantageously be coated with a high emissivity white paint, having for example an emissivity coefficient £ equal to about 0.8, such as to allow an efficient radiation of heat toward the outside.
According to preferred embodiments, the auxiliary systems 36, 37 (fig. 5) each comprise one or more auxiliary filtering members 42 and one or more auxiliary valve members 43 which are disposed, on the opposite part with respect to the respective propulsion units 33, 35, on a separation panel 45, parallel to and distanced from the flat element 39; the panel 45 forming part of the support structure 31.
It should be noted that the operating thermal ranges of the auxiliary filtering members 42 are comprised between about -55°C and about 85°C, while those of the auxiliary valve members are comprised between about -15°C and about 85°C; therefore, they have to be adequately shielded both from the heat generated by the propulsion units 33, 35 and also from the temperatures present in Earth orbit, in order to guarantee these operating ranges, as will be described in detail below.
According to preferred embodiments, the separation panel 45 (fig. 5) is provided with a first plate 46 facing the flat element 39 and a second plate 47 distanced from the first plate 46 and on which the auxiliary systems 36, 37, that is, the auxiliary filtering members 42 and the auxiliary valve members 43, are mounted. There are reinforcing blocks 48 between the first plate 46 and the second plate 47.
The flat element 39 and the separation panel 45 are associated with and kept distanced from each other by means of the connection shaft 32 and a plurality of elongated spacer elements 49, for example having the shape of small columns or pipes.
Between the flat element 39 and the separation panel 45 there is a further multilayer coating 50 which has the function of thermally insulating the auxiliary systems 36, 37, shielding them from the heat generated by the propulsion units 33, 35.
The support structure 31 also comprises a protective housing 51 for the auxiliary systems 36, 37, which is disposed on the opposite part with respect to the propulsion units 33, 35.
The protective housing 51 has the function of protecting and shielding at least the auxiliary systems 36, 37, in particular the auxiliary filtering members 42 and the auxiliary valve members 43, from any micro-meteorites.
Preferably, without any limitation to generality, the protective housing 51 is made of a fiber-reinforced material, which can comprise, or consist of, carbon fiber reinforced polymers (CFRPs). Furthermore, the protective housing 51 can advantageously also comprise a graphite layer that facilitates the passage and dispersion of heat.
Advantageously, the protective housing 51 is attached to corresponding perimeter reinforcement blocks 48 of the separation panel 45.
Moreover, the protective housing 51 can advantageously be coated with the aforementioned high-emissivity white paint, having for example an emissivity coefficient £ equal to about 0.8, so as to promote the emission of the heat stored therein.
Advantageously, in correspondence with the zones of attachment between the connection shaft 32 and the flat element 39, between the flat element 39 and the elongated elements 49 and between the auxiliary filtering and valve members 42, 43 and the second plate 47 of the separation panel 45 there are respective thermal insulation elements 53 for insulation from the heat generated by the propulsion units 33, 35 and absorbed by the flat element 39.
The thermal insulation elements 53 can be of various shapes and sizes and have the function of creating thermal bridges to thermally decouple the flat element 39, with which the propulsion units 33, 35 are associated, from the rest of the support structure 31. Advantageously, the thermal insulation elements 53 also allow the auxiliary systems 36, 37 to be thermally decoupled from the separation panel 45, which faces the flat element 39 and the propulsion units 33, 35. Preferably, without any limitation to generality, the thermal insulation elements 53 are made of fiberglass. For example, the thermal insulation elements 53 can have the shape of a washer.
It should be noted that the attachment between the connection shaft 32 and the flat element 39, between the flat element 39 and the elongated elements 49, between the auxiliary filtering and valve members 42, 43 and the second plate 47 of the separation panel 45 and between the separation panel and the protective housing 51 is achieved by means of attachment means of any known type whatsoever, or which will be made in the future, and which are used in the aerospace field. It should also be noted that the auxiliary filtering and valve members 42, 43 are attached to the second plate 47 in correspondence with the internal reinforcement blocks 48 of the separation panel 45, which can provide a stable anchoring point for the aforementioned attachment means. It is clear that modifications and/or additions of parts may be made to the movement apparatus 100 as described heretofore, without departing from the field and scope of the present invention, as defined by the claims.
It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will be able to achieve other equivalent forms of movement apparatuses for artificial satellites, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.
In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.