WO2018115180A1

WO2018115180A1 - Cubesat bus architecture

Info

Publication number: WO2018115180A1
Application number: PCT/EP2017/083918
Authority: WO
Inventors: Laurent DUSSEAU; Thierry FIOL; Bernard CLOTILDE; Valérie PONSA
Original assignee: Universite de Montpellier
Current assignee: Universite de Montpellier
Priority date: 2016-12-23
Filing date: 2017-12-20
Publication date: 2018-06-28
Anticipated expiration: 2019-06-23
Also published as: ES2806626T3; EP3339188A1; EP3339188B1

Abstract

The present invention relates to a nano-satellite bus, characterized in that it comprises: -a mono-bloc mechanical frame (1) comprising a plurality of posts and edges (2, 2') forming the sides of the said mechanical frame; -a back panel (10) for the connection of electronic components; -at least a connector (23) with spring contacts (24), said connector (23) being connected to the back panel (10) and fixed to the mono-bloc mechanical frame (1), said spring contacts (24) being mounted as a through-hole component through one post (2) of the mono-bloc mechanical frame (1) for the connection of satellite faces. The present invention further relates to a nano-satellite comprising a nano-satellite bus comprising these.

Description

CUBESAT BUS ARCHITECTURE

The present invention concerns an architecture for a bus dedicated to building satellites according to the CubeSat Design Specification.

Started in 1999, the CubeSat Project began as a collaborative effort between Prof. Jordi Puig-Suari at California Polytechnic State University (Cal Poly), San Luis Obispo, and Prof. Bob Twiggs at Stanford University's Space Systems Development Laboratory (SSDL). The purpose of this project is to provide a standard for designing satellites such as nanosatellites and picosatellites, to reduce cost and development time, to increase accessibility to space, and to sustain frequent launches. Presently, the CubeSat Project is an international collaboration of over 100 universities, high schools, and private firms developing picosatellites containing scientific, private, and government payloads. A CubeSat satellite is a 10 cm cube with a mass of up to 1 .33 kg. Developers benefit from the sharing of information within the community.

The CubeSat Design Specification Rev. 13 gives external specification for a Cubesat satellite in order to ensure compatibility with a launch vehicle, the Poly-PicoSatellite Orbital Deployer and the launch proceeding, it is silent on the internal architecture of the satellite itself. This internal architecture is the responsibility of the satellite manufacturer.

The bus of such picosatellite is defined as the common architecture allowing to manufacture different CubeSat satellites. It comprises a hardware mechanical frame used as a structure on which all other parts of the satellite will be fixed. It also comprises an electrical part and electronical components, fixed on the mechanical frame, on which the electrical part and electronical components will be plugged. The bus will be completed with electronical components comprising typically a battery for providing energy, telecommunication modules to communicate with Earth, storage modules to store any collected data. The bus will also be completed with a specific payload, for example a set of specific sensors to collect data, or a specific module for accomplishing the satellite mission. The bus will also receive several satellite faces, typically comprising solar panels to charge the battery and antennas for the telecommunication modules. The bus plus antennas, the satellite faces and the electronic components constitute the complete satellite.

Designing a CubeSat bus architecture is a challenge as the bus needs to fulfil severe constraints. As in any space application, reliability is required, as no human intervention is possible on the satellite once it has been placed in the launch vehicle. The satellite should resist to severe vibrations during the launch.

Thus, the challenge is to design a simple, reliable, cheap and versatile bus that can be used to manufacture as many different satellites as possible. The present invention has been devised to address one or more of the foregoing concerns.

According to a first aspect of the invention, there is provided a nano- satellite bus, comprising:

- a mono-bloc mechanical frame comprising a plurality of posts and edges forming the sides of the said mechanical frame;

- a back panel for the connection of electronic components;

- at least a connector with spring contacts, said connector being connected to the back panel and fixed to the mono-bloc mechanical frame, said spring contacts being mounted as a through-hole component through one post of the mono-bloc mechanical frame for the connection of satellite faces.

In an embodiment of the invention, the spring contacts are mounted through an aperture machined through a post of the mono-bloc mechanical frame. In an embodiment of the invention, the mono-bloc mechanical frame is made in a metal.

Advantageously, a mechanical frame machined within a mono-bloc mechanical frame made in a metal avoids any assembly of several parts, and prevents any possible disassembly during the life of the satellite.

Advantageously, a mechanical frame constituted by a mono-bloc made in a metal avoids the use of welding joints.

Advantageously, a mechanical frame constituted by a mono-bloc metallic structure prevents deformations and/or the appearance of structural weaknesses. In an embodiment of the invention, the metal is an aluminium alloy such as 7075, 6061 , 5005 and 5052 aluminum.

Advantageously, a mono-bloc mechanical frame made in a metal, and in particular, comprising a 7075, 6061 , 5005 and/or 5052 aluminum alloy has a light weight and a large resistance.

In an embodiment of the invention, the nano-satellite bus comprises one connector with spring contacts for the connection of each face of the nano- satellite.

In an embodiment of the invention, the nano-satellite bus further comprises:

- at least a deployment switch operated by a sliding rod cooperating with a spring mounted within a post of the mechanical frame and acting as a push button. In an embodiment of the invention, a stroke of the sliding rod is longer than 2 millimeters.

In an embodiment of the invention, the nano-satellite bus further comprises:

- at least a second redundant deployment switch with the same function.

In an embodiment of the invention, the nano-satellite bus further comprises:

- faces mounted to the mono-bloc structure comprising current sources connected to the back-panel through said connectors.

In an embodiment of the invention, the nano-satellite bus further comprises:

- at least an antenna connected to said mechanical frame;

said antenna comprising a warming device to cut a nylon wire to free the antenna; said antenna high frequency circuit being connected to the back panel through a connector; said warming device being connected to the back panel through the antenna fixing screws.

In an embodiment of the invention, the nano-satellite bus further comprises:

- a central plate fixed to lateral posts of the mechanical frame and to the back panel.

In an embodiment of the invention, the nano-satellite bus further comprises:

- lugs for receiving spacers through a rod for the fixation of the top of daughter boards.

In an embodiment of the invention, the central plate further comprises: a place to receive a battery for the alimentation of the nano-satellite.

In an embodiment of the invention, the central plate further comprises: - a shield to protect the battery.

In an embodiment of the invention, the battery comprises a flange ensuring a contact between a sensor and the said battery.

In an embodiment of the invention, the nano-satellite bus is compatible with the specifications of the Cubesat Design Specification Rev. 13.

According to a second aspect of the invention, there is provided a nano- satellite comprising a nano-satellite bus comprising any of the preceding features.

Embodiments of the invention will now be described, by way of example only, and with reference to the following drawings in which:

Figure 1 illustrates a mechanical frame for a nano-satellite bus in an embodiment of the invention;

Figure 2 illustrates a back panel for a nano-satellite bus in an embodiment of the invention;

Figure 3 illustrates a back panel with connectors and electrical connections for a nano-satellite bus in an embodiment of the invention;

Figure 4 illustrates an assembly of spring contacts on the mechanical frame for a nano-satellite bus in an embodiment of the invention;

Figure 5 illustrates a connection of spring contacts for a nano-satellite bus in an embodiment of the invention;

Figure 6 illustrates a detail of the bus featuring a deployment switch for a nano-satellite bus in an embodiment of the invention;

Figure 7 illustrates an internal structure of a deployment switch for a nano-satellite bus in an embodiment of the invention; Figure 8 illustrates a central plate for a nano-satellite bus in an embodiment of the invention;

Figure 9 illustrates a central plate fixed on a back panel for a nano- satellite bus in an embodiment of the invention;

Figure 10 illustrates a central plate with daughter boards for a nano- satellite bus in an embodiment of the invention;

Figure 11 illustrates a cross section of a central plate with daughter boards for a nano-satellite bus in an embodiment of the invention;

Figure 12 illustrates a central plate along with a battery for a nano- satellite bus in an embodiment of the invention;

Figure 13 illustrates a battery with a control board for a nano-satellite bus in an embodiment of the invention;

Figure 14 illustrates an access port mounted on a central plate for a nano-satellite bus in an embodiment of the invention;

Figure 15 illustrates a stop-off switch for a nano-satellite bus in an embodiment of the invention;

Figure 16 illustrates a bundle of connectors connecting an access port for a nano-satellite bus in an embodiment of the invention;

Figure 17 illustrates bounding pads of a bundle of connectors for a nano- satellite bus in an embodiment of the invention;

Figure 18 illustrates a temperature sensor of a battery for a nano- satellite bus in an embodiment of the invention;

Figure 19 illustrates a temperature sensor of a battery with a flange for a nano-satellite bus in an embodiment of the invention;

Figure 20 illustrates a complete bus with a mounted battery for a nano- satellite bus in an embodiment of the invention;

Figure 21 illustrates an antenna and a connection for a nano-satellite bus in an embodiment of the invention. Figure 1 illustrates a mechanical frame 1 in an embodiment of the invention. The mechanical frame 1 comprises a set of posts 2 forming, in the example a cube, the posts being located on the sides of the cube. At least some of the posts 2 and of the edges 2' are provided with an aperture 3 intended for receiving connectors with spring contacts. The posts 2 and the edges 2' can also be provided with holes 4 containing one or several pitch forming nuts for the fixation of some faces to the mechanical frame. Advantageously, the frame is provided with mounting lugs 5 for the fixation of lateral posts. The mechanical frame 1 further comprises a set of edges 2' connecting the posts 2. In an embodiment of the invention, the mechanical frame 1 comprises four posts 2 and eight edges 2'. Figure 2 illustrates a back panel 10 in an embodiment of the invention.

The back panel 10 comprises a printed circuit board (PCB) 11 intended to be fixed to the mechanical frame 1 as an internal face of the cube with screws 12. The screws 12 correspond to associated nuts machined in the posts 2 and the edges 2' of the mechanical frame 1. The printed circuit board 11 is provided with connectors 13 to connect different electronic components typically formed by electronic daughter boards. A place 14 is provided for the fixation of a central plate which will be described in more details below.

Figure 3 illustrates a back panel 10 with connectors and electrical connections in an embodiment of the invention. The back panel 10 is provided with a bundle of connectors 21 connecting a battery and feeding the different electronic components of a satellite. This bundle of connectors 21 has bounding pads for fixation 22 of the bundle to the central plate (not represented). The back panel is also provided with connectors 23 for the connection to faces of a satellite. These faces typically comprise solar panels adapted to charge the battery. They are connected to the back panel 10 using connectors which are not represented on figure 3. The connectors 23 are provided with a set 24 of spring contacts, such as a compressible elastomer, or a compressible composite material, for the connection with the faces. The connectors 23 are screwed to the posts in order to allow the spring contacts to fit into through- holes provided within the posts. Screwing the faces to the posts will bring the spring contacts in contact with corresponding contacts provided in the faces to the posts 2 and the edges 2'. By doing so, a good connection is provided between the back panel 10 and the faces of the satellite by simply screwing the faces on the posts of the mechanical frame. There is no need to connect dedicated connectors when fixing the faces. At least a deployment switch 25 is connected to the bundle of connectors 21. This deployment switch, which will described in more details below, aims at cutting a power circuit during a launch of the satellite and can be automatically switched on after launch to allow operating the satellite. It is fixed to a post of the mechanical frame and cooperates with a sliding rod and a spring to allow the automatic switch on of the satellite at liberation.

Figure 4 illustrates the assembly of spring contacts on the mechanical frame 1 in an embodiment of the invention. The connector 23 is fixed to the post 2 with screws 31 and a spacer 32 in order to have the spring contacts 24 to fit the hole in the post 2 and to go through the post 2 and the extremity 33 of the spring contacts. Advantageously, each face of the cube comprises one connector 23.

Figure 5 illustrates a connection of spring contacts in an embodiment of the invention. Figure 5 is a cross-section of four posts 2 at the level of the spring contacts 24 showing the spring contacts 24 and the connector 41 connecting the spring contacts 24 together.

Figure 6 and Figure 7 illustrate a deployment switch in an embodiment of the invention. The deployment switch 25 is fixed on a plate that is screwed using screws 51 on a post 53 of the mechanical frame on a first side and on the mounting lug 5 on the other side. The deployment switch cooperates with the sliding rod 52 which is mounted within the post 54. An extremity of the sliding rod 52 projects outside the post 54. A spring 61 , such as a compressible elastomer or a compressible composite material, pushes the sliding rod 52 in the direction of the outside of the post 54. Alternatively, the spring 61 can be an electromagnet or a gas piston. The stroke of the sliding rod is limited in a way to allow the sliding rod 52 to act as a push button. When the sliding rod 52 is pushed within the post 54, a stopper within the sliding rod 52 pushes an actuator 62 of the deployment switch in order to cut the power of the entire electronic system of the satellite. When the satellite is placed in a launch vehicle, the sliding rod 52 is maintained in the pushed position. At the liberation of the satellite, the sliding rod 52 is released and the power is switched on. It is important to avoid unwanted switch on of the power accidentally during the flight of the launch vehicle due to vibrations. Advantageously, the stroke of the sliding rod 52 is at least two millimeters to avoid accidental switch on. In the described example, the stroke is 10 millimeters.

Figure 8 illustrates a central plate 70 in an embodiment of the invention. The central plate 70 is provided with mounting lugs 72 for the fixation of the central plate 70 to laterals posts. The lateral posts are fixed to mounting lugs 5 of the mechanical frame. The central plate 70 comprises a placement 71 for the battery of the satellite. It also provides lugs 75 for receiving spacers 73 through a rod 74 for the fixation of the top of daughter boards 91. The central plate 70 is intended for rigidifying the whole structure while providing a central location for the battery which is an heavy part of the satellite that is advantageously located near the centre of gravity of the satellite.

Figure 9 illustrates a central plate 70 fixed on the back panel 10 in an embodiment of the invention. On this figure the fixation of the central plate on the lateral posts 81 is illustrated. The central plate is screwed on the back panel 10 and to lateral posts 81.

Figure 10 illustrates a central plate 70 with daughter boards 91 in an embodiment of the invention. The bottom of the daughter boards 91 is fixed to connectors 13 of the back panel 10. The top of the daughter boards 91 is fixed to the central plate through spacers 73 secured with screws 92. Advantageously, a washer 93 is used between the screw 92 and the daughter board 91. Figure 11 illustrates a cross section of the central plate 70 with daughter boards 91 in an embodiment of the invention. This figure shows more clearly the fixation of the top of daughter boards 91 to the central plate 70 using spacers 73 and the screws 92. This figure also shows the screw 101 fixing the central plate to the back panel 10.

Figure 12 illustrates a central plate 70 along with a battery 111 in an embodiment of the invention. The battery 111 is fixed to the central plate 70 with a shield 112 fixed to the central plate 70 with screws 113. Advantageously, the battery is surrounded by a lining that favours thermic exchanges with the whole structure. This lining may be made of CHO-THERM (registered trademark). This lining may comprise a thermal paste, or a braze of a conductive drain on the battery 111.

Figure 13 illustrates a battery 111 with a control board 121 in an embodiment of the invention. The control board is fixed to the central plate 70 with screws 122 and connected to the battery 111. Figure 14 illustrates an access port 131 mounted on a control board 121 in an embodiment of the invention. The aim of the access port 131 is to allow the connection to the system for testing, setting parameters, monitoring, providing external energy and charging the battery 111 once the satellite is mounted.

Figure 15 illustrates a stop-off switch 141 mounted on a control board 121 in an embodiment of the invention. The aim of the stop-off switch 141 is to switch off the system before the flight. The stop-off switch is operated with a "Remove Before Flight" pin that is inserted into the stop-off switch to guarantee that the system is switched off while the pin is inserted. Before the launch, the pin should be removed to allow the switch-on of the system by the deployment switch 25. Figure 16 illustrates a bundle of connectors 21 connecting an access port signal to the different electronic components in the system, in an embodiment of the invention. The bundle of connectors 21 is connected to a connector 151 placed on the back of the control board 121.

Figure 17 illustrates the bounding pads 161 of the bundle of connectors 21 in an embodiment of the invention. The bounding pads 161 are used to secure the bundle of connectors to the central plate.

Figure 18 illustrates the temperature sensor 171 of the battery 111 in an embodiment of the invention. The temperature sensor 171 is placed in contact with the battery through a cavity 172 and connected to the back panel 10. Figure 19 illustrates the temperature sensor 171 of the battery 111 comprising a flange 181 in an embodiment of the invention. The aim of the flange 181 is that the sensor 171 is in contact with the battery 1 1 1 to ensure the thermal connection. The flange 181 is fixed with screws 182. A thermal pase, or CHO-THERM, can also be used to ensure the thermal connection.

Figure 20 illustrates a complete nano-satellite bus equipped with a battery and a mounted central plate 70 in an embodiment of the invention. The lateral posts 81 are fixed to the posts 2 of the mechanical frame 1. The back panel 10 is fixed on the bottom posts of the mechanical frame 1. The central plate 70 is mounted on the back panel 10 and fixed to the lateral posts 81. The battery is installed in the central plate 70 and provided with a control board 121 and a shield 112.

Figure 21 illustrates an antenna 201 and its connection in an embodiment of the invention. The antenna 201 is screwed with screws 205 to a support plate 202. The support plate 202 is fixed to a lateral post 81. The support plate 202 is provided with nuts 204. A signal is provided through the connector 203 connected to the antenna 201 . Advantageously, the antenna is provided with a self-deployment capacity. This self-deployment capacity consists in a warming device adapted to cut a nylon wire to free the antenna 201 . When the antenna 201 , which is first wrapped and maintained by the nylon wire, is freed, the antenna automatically unwraps. Advantageously, the warming device is supplied through the fixation screws 205. The high frequency circuit of the antenna is connected to a dedicated connector 203. Alternatively, the antenna is mounted on a face of the satellite, and both the alimentation of the warming device and the high frequency signal are transmitted via the spring contacts 24 connecting the face to the back panel.

Although the present invention has been described hereinabove with reference to specific embodiments, the present invention is not limited to the specific embodiments, and modifications will be apparent to a skilled person in the art which lie within the scope of the present invention.

Many further modifications and variations will suggest themselves to those versed in the art upon making reference to the foregoing illustrative embodiments, which are given by way of example only and which are not intended to limit the scope of the invention, that being determined solely by the appended claims. In particular the different features from different embodiments may be interchanged, where appropriate.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be advantageously used.

Claims

A nano-satellite bus, characterized in that it comprises:

- a mono-bloc mechanical frame (1 ) comprising a plurality of posts and edges (2, 2') forming the sides of the said mechanical frame;

- a back panel (10) for the connection of electronic components;

- at least a connector (23) with spring contacts (24), said connector (23) being connected to the back panel (10) and fixed to the mono-bloc mechanical frame (1 ), said spring contacts (24) being mounted as a through-hole component through one post (2) of the mono-bloc mechanical frame (1 ) for the connection of satellite faces.

The nano-satellite bus according to claim 1 , characterized in that said spring contacts (24) are mounted through an aperture (3) machined through a post (2) of the mono-bloc mechanical frame (1 ).

The nano-satellite bus according to anyone of claims 1 to 2, characterized in that said mono-bloc mechanical frame (1 ) is made in a metal.

The nano-satellite bus according to claim 3, characterized in that said metal is an aluminium alloy such as 7075, 6061 , 5005 and 5052 aluminum.

The nano-satellite bus according to anyone of claims 1 to 4, characterized in that it comprises one connector (23) with spring contacts (24) for the connection of each face of the nano-satellite.

6. The nano-satellite bus according to anyone of claims 1 to 5, characterized in that it further comprises: - at least a deployment switch (25) operated by a sliding rod (52) cooperating with a spring (61 ) mounted within a post (2) of the mechanical frame (1 ) and acting as a push button.

7. The nano-satellite bus according to claim 5, characterized in that a stroke of the sliding rod (52) is longer than 2 millimeters.

8. The nano-satellite bus according to anyone of claims 6 to 7, characterized in that it further comprises:

- at least a second redundant deployment switch (25) with the same function.

9. The nano-satellite bus according to anyone of claims 6 to 8, characterized in that it further comprises:

- faces mounted to the mono-bloc structure comprising current sources connected to the back-panel through said connectors (23).

10. The nano-satellite bus according to anyone claim 6 to 9, characterized in that it further comprises:

- at least an antenna (201 ) connected to said mechanical frame (1 );

- said antenna (201 ) comprising a warming device to cut a nylon wire to free the antenna;

- said antenna high frequency circuit being connected to the back panel (10) through a connector (203);

- said warming device being connected to the back panel (10) through the antenna fixing screws (205).

1 1 . The nano-satellite bus according to anyone claim 6 to 9, characterized in that it further comprises:

- at least an antenna (201 ) connected a face of the satellite; - said antenna (201 ) comprising a warming device to cut a nylon wire to free the antenna;

- said antenna high frequency circuit and said warming device being connected to the back panel (10) through the connector (24) connecting the face.

12. The nano-satellite bus according to any of the preceding claims, characterized in that it further comprises:

- a central plate (70) fixed to lateral posts (81 ) of the mechanical frame (1 ) and to the back panel (10).

13. The nano-satellite bus according to claim 12, characterized in that the central plate (40) further comprises:

- lugs (75) for receiving spacers (73) through a rod (74) for the fixation of the top of daughter boards (91 ).

14. The nano-satellite bus according to anyone of claims 12 to 13, characterized in that the central plate (40) further comprises:

- a place to receive a battery (1 1 1 ) for the alimentation of the nano- satellite.

15. The nano-satellite bus according to claim 14, characterized in that the central plate (40) further comprises:

- a shield (1 12) to protect the battery (1 1 1 ).

16. The nano-satellite bus according to claim 15, characterized in that the battery (1 1 1 ) comprises a flange (181 ) ensuring a contact between a sensor (171 ) and the said battery (1 1 1 ).

17. The nano-satellite bus according to any of the preceding claims, characterized in that said nano-satellite bus is compatible with the specifications of the Cubesat Design Specification Rev. 13.

18. A nano-satellite comprising a nano-satellite bus according to any of the preceding claims.