DE102012112080B3 - Solar generator for e.g. spacecraft, has light source and light sensors connected to evaluation unit to determine disorder of total reflection properties of internal reflection layer due to collision with space object - Google Patents

Abstract

The generator (100) has a solar panel with a solar cell layer (102) having solar cells for converting an incident electromagnetic radiation into an electric current. A light source is coupled to a total internal light reflection layer (101) arranged on the solar cell layer. Light sensors are arranged at the periphery of the reflection layer to detect the intensity of light reflected in the reflection layer. The light source and the light sensors are connected to an evaluation unit to determine disorder of total reflection properties of the reflection layer due to collision with a space object.

Description

The invention relates to a solar generator for spacecraft or satellites.

As is known, spacecraft and satellites use solar generators to generate energy in space. Solar generators typically include large, generally deployable solar panels with solar cells that convert light into electrical energy, control electronics, and corresponding cabling. Despite extensive soil tests, single or multiple solar cells of the solar generators fail during space missions. The causes are faulty solar cells or damaged during the starting process, aging processes of the solar cells or of the solar generator (for longer space flight missions), and in particular collisions with spatial objects.

Due to their large areal extent, the solar panels are in particular a potential danger of collision with spatial objects, i. H. naturally occurring micrometeorites and space trauma generated by human space activities ("space debris"). While the threat of naturally occurring micrometeorites remains approximately the same in time, the risk of a collision with the so-called space debris, at least in earth orbits, has increased steadily in recent decades. In the present case, micrometeorites and space debris are referred to collectively as "space objects" (MMOD = "micro-meteoroid and orbital debris"). Due to the high relative speed (several kilometers per second), the damage to solar generators resulting from collisions with such spatial objects can be substantial even for small-sized spatial objects and lead to the loss of a mission. Colliding spatial objects often penetrate the solar panels, destroying individual or multiple solar cells.

For risk assessment of space missions, simulation models have been developed (eg MASTER, ORDEM) that allow statements about the distribution of spatial objects. The verification of the analytical methods for the orbital space debris environment plays an essential role. Most spatial objects are too small for ground-based locating methods, the frequency of spatial objects is reciprocal to their size. There is a great need to experimentally validate the on-site space debris distribution and to identify the actual causes of solar cell failure at solar generators.

From the FR 2 641 866 A1 a solar generator for spacecraft or satellites is known, comprising: at least one solar panel having a plurality of planarly arranged side by side on a substrate solar cells that convert impinging electromagnetic radiation into electricity, each solar cell is separated from surrounding solar cells through a gap, and wherein each solar cell has a layer which is arranged above the solar cell and transparent to optical radiation and which conducts light by total reflection. Furthermore, the publication discloses at least one light source which couples light into the respective light-conducting layer of a solar cell via the one gap, and a light sensor (video camera) for detecting a light intensity which is flat on an upper side of the light-conducting layer of each solar cell (and not on Peripheral edge of the light-conducting layer) is coupled out.

From the DE 10 2004v032 047 Al It is known that damage to a glass plate (jump / scratch) by means of a light source, which couples light into the edge of the glass plate, and by means of the Lichteinkoppelort opposite to the edge of the glass plate arranged light sensor, which determines the intensity of the injected light, can be determined. The following applies: Damage to the glass plate leads to a lower light intensity at the light sensor because light is coupled out at the point of damage.

The object of the invention is to provide a solar generator for spacecraft or satellite, which allows an improved evaluation of failure events of individual or multiple solar cells.

The invention results from the features of the independent claim. Advantageous developments and refinements are the subject of the dependent claims. Other features, applications and advantages of the invention will become apparent from the following description, as well as the explanation of embodiments of the invention, which are illustrated in the figures.

The object is achieved with a solar generator for spacecraft or satellites, which comprises: at least one solar panel with a solar cell layer, which converts a multiplicity of solar cells arranged side by side, which convert incident electromagnetic radiation into electrical current, and the one arranged above the solar cell layer for optical radiation having transparent and total reflection light-conducting layer; at least one light source with which light can be coupled into the light-guiding layer; a plurality of light sensors arranged on a peripheral edge of the light-conducting layer for detecting an intensity of the light which is coupled into the light-conducting layer and totally reflected light; and a connected to the at least one light source and the light sensors first evaluation means, with which a caused by a collision with a space object disturbance of total reflection properties within the light-conducting layer can be determined.

The term "disturbance" is understood in the present case as any change (change) of the total reflection properties of the light-conducting layer. In this respect, by a first impact / impact of a spatial object, the total reflection properties of the light-conducting layer are changed, which are in turn changed (disturbed) by an impact / impact of another spatial object. The disturbance always refers to a change in the total reflection properties of the light-conducting layer. Since the disturbance of the total reflection properties due to local damage of the light-conducting layer results, the disturbance of the total reflection properties is still locally locatable.

With the solar generator according to the invention, it is, for example, possible to detect the effects of an impinging on the solar generator with high relative speed spatial object that strikes the light-conducting layer or at least mechanically damaged to capture. It is thus possible, in the event of a failure of one or more solar cells, to determine those failure events which are due to a collision of the solar panels with spatial objects.

For this purpose, the solar panels comprises the light-conducting layer, which is preferably arranged on the upper side of the solar panels. The backside of the solar panels typically has a structural layer that provides the solar panels with the required structural strength. The light-conducting layer consists of an electrically insulating optically transparent material. The light-conducting layer is preferably arranged directly adjacent to the solar cell layer, wherein an adhesion-promoting adhesive layer may be present between the solar cell layer and the light-conducting layer. Furthermore, a separating layer is preferably arranged between the solar cell layer and the light-conducting layer, which further preferably has an electrically conductive tissue for electrical shielding. The electrical shield is used in particular for shielding electric fields, such as those caused by electrostatic discharges.

The (mechanical) damage resulting from the impact of a spatial object on the light-conducting layer is, in particular, an emerging breakdown hole or at least a damage to the surface or a portion of the light-conducting layer. In particular, the total reflection properties of the layer are changed / disturbed in that, for example, light is coupled out of the layer at the point of damage, which leads to a reduction in the intensity of the light conducted within the layer. Furthermore, the propagation paths of light within the layer can be changed by damaging the light-conducting layer, for example certain light propagation directions can be blocked by the damage in the layer and / or light scattering and / or light reflections occur at the point of damage. Furthermore, due to the damage, interference patterns or changes of interference patterns may result. The effects of such a disturbance of the total reflection properties are detected by means of the at least one light source and the at least one light sensor.

In a preferred embodiment of the solar generator according to the invention, the at least one light source is designed and arranged so that one or more (bundled, directed, or fan-shaped) light beams can be coupled into the layer at the peripheral edge of the light-conducting layer. These light rays are in the light-conducting layer, if this is not damaged, guided in a straight line by total reflection. Preferably, the light source is a laser or an LED with appropriate bundling optics.

More preferably, a plurality of such, preferably equally spaced light sources are arranged at the peripheral edge, so that the rays emanating from the light sources preferably pass through the layer with parallel beam paths or preferably arranged in a grid-shaped beam paths. Such screens preferably have a rectangular pattern or a diamond pattern. The dimensioning of the distances of adjacent beam paths in the pattern defines a lower dimension limit for the detection of spatial objects. Room objects whose dimension is smaller than this limit can not be resolved and therefore detected.

If a room object collides with the solar panel, the resulting damage depends on the size, the angle of incidence, and the relative speed of the room object. Frequently, the relative velocity of spatial objects is sufficiently large that they penetrate the solar panels even with dimensions in the range of 1 micrometer to several millimeters.

In the case of a breakdown of the spatial object by the light-conducting layer, solar cells of the solar cell layer arranged in the impact area underneath the layer are possibly mechanically destroyed and thereby fall out. Furthermore, by a different electrostatic charge of adjacent areas of the surface of the solar panels at the impact caused by a material ejection occurring at the impact site, a plasma discharge, the surrounding solar cells, ie solar cells that are not mechanically affected by the collision with the space object, disturbs in their function or even destroyed, so that these by the collision or the impact also fail. The adjacent areas must have a different electrical potential. As a result of the impact, locally electrically conductive plasma is formed, which conductively connects the regions of different potential, so that short circuit occurs.

It may also be that by the impact itself short circuits occur at the impact point z. As carbon fibers (conductive material). Due to the plasma discharges, the number of solar cells affected by the failure or their solar cell area can be many times greater than a cross-sectional area of the breakdown channel.

Preferably, a second evaluation means is provided with which the functioning of the solar cells is monitored or a failure of one or more solar cells is detected. For this purpose, the solar cells are preferably connected individually or as solar cell groups (for example as individual columns or rows) to the second evaluation means. The electrical circuits which can be used for monitoring or for failure detection are known to the person skilled in the art. The second evaluation means thus detects only the failure of one or more solar cells, the failure cause is not determined by the second evaluation. This may be due to the fact that the affected solar cell itself fails due to, for example, aging or that the failure is caused by a collision with a room object.

For clarification, it is assumed that in the event of a collision of the solar panels with a room object, the room object completely penetrates the solar panels and thereby forms a breakdown channel in the solar panels. During breakdown, a local disturbance of the total reflection properties is generated in the light-conducting layer, which is preferably determined with respect to the position and dimension of the breakdown channel by the first evaluation means or detected by the light source and the light sensor connected thereto.

In order not to have to analyze local disturbances in the entire light-conducting layer at each collision event, in a preferred embodiment the first evaluation means is connected to the second evaluation means and designed and arranged such that in the event of a failure of one or more solar cells detected by the second evaluation means, the analysis of the light-conducting layer is carried out with respect to further local disturbances of the total reflection properties only for the areas of the light-conducting layer which are arranged above undamaged solar cells. This significantly reduces the energy required for monitoring and analysis.

In particular, when the light-conducting layer is scanned for local changes in the total reflection properties by means of a plurality of closely adjacent and intersecting light beams (scanning beams), the dimension of a spatial object that has penetrated the layer can be estimated. This information can be stored and / or sent to one Central (for example, a ground control center or a spacecraft) are transmitted for further evaluation. There are a variety of possible patterns of beam guidance of the scanning beams in the light-conducting layer. The following applies: the smaller the distance between individual scanning beams in the layer and the smaller their diameter, the greater is the local resolution for detecting spatial objects or the dimension of the breakdown channels generated by them.

Preferably, opposite to the position of a respective light source in the coupling-in direction of the respective light beam, a light sensor is arranged at the peripheral edge of the light-conducting layer, with which an intensity of the light beam coupled into the light from the respective light source can be determined in a time-dependent manner.

In a further embodiment of the solar generator according to the invention, the at least one light source is integrated into the light-conducting layer and embodied such that it preferably couples undirected light into this layer. By way of example, the light source is arranged as geometrically as possible centrally in the areally extended light-conducting layer. In this case, a plurality of light sensors are preferably arranged distributed on the peripheral edge of the light-conducting layer.

The light sensors preferably have an aperture (aperture) which serves to detect only light from a given direction of incidence. Thus, the total reflection properties can be monitored along a beam path. The aperture diaphragms delimiting an aperture angle of the light sensor are preferably arranged between the light sensors and the peripheral edge.

In a further embodiment of the solar generator according to the invention, the light source is designed as a line light source which couples light into this along a part of the peripheral edge of the light-conducting layer. Also in this case, a plurality of light sensors are preferred at the peripheral edge of the layer, preferably at the Line light source opposite peripheral edge of the layer arranged.

By a suitable arrangement of light sources and light sensors on the layer, a plurality of beam paths of light coupled into the layer can be monitored. Preferably, the beam paths intersect in the manner of a regular pattern (rectangular or quarter-shaped or diamond-like pattern). The activation of the light sources is preferably carried out in such a way that only one light source is active at a time, and the light coupled from this light source into the light-conducting layer can be received by the at least one light sensor, preferably by several or all light sensors. Preferably, the light sources are serially activated, i. H. one light source after the other, so that the total reflection properties along the different optical paths are serially scanned.

A further preferred refinement of the solar generator according to the invention is characterized in that the first evaluation means is designed to determine a transit time of a light pulse emitted by the light source until it is detected by the light sensor in order to determine a change in the total reflection properties on the basis of an occurring change in the transit time , This development makes use of the circumstance that a damage of the layer, for example. By a breakdown hole, a propagation of a light beam from the light source is interrupted in a straight path to a corresponding light sensor, and the light beam, if necessary by scattering and / or reflection over a longer Path to the light detector passes, which causes a longer duration of the light beam compared to the shortest path. Thus, changes the duration for a light pulse emitted from the light source to an associated light sensor, this is an indication of a change / disturbance of the total reflection properties of the light-conducting layer.

The solar generator according to the invention is particularly characterized in that a plurality of light sensors connected to the first evaluation means are arranged on the light-conducting layer at the peripheral edge. In a particularly preferred embodiment, the first evaluation means is designed and set up for determining a position of a disturbance in the light-conducting layer caused by a collision with a spatial object.

If, for example, the light-conducting layer has a rectangular peripheral edge, then the light sources are preferably arranged on two adjoining sides of the peripheral edge. The light sensors are arranged at the peripheral edge opposite to the light sources. If the light sources in the light-conducting layer in each case couple light rays perpendicular to the peripheral edge, a rectangular grid of light paths through the light-conducting layer results in this embodiment.

If a collision with a spatial object at a position of the solar panels, and thus at a position of the light-conducting layer, a local damage of the layer, eg. Produced a breakdown hole, this position, with a correspondingly close arrangement of adjacent light sources / light sensors, by the interruption of respective light paths passing through the punch-through hole are detected. The smaller the lattice constant of the aforementioned lattice, the higher the spatial resolution in determining the position of the damage by the spatial object.

In a further preferred embodiment, the first evaluation means is designed and set up for determining a dimension of the damage of the light-conducting layer. The term "dimension" in the present case refers to the size / extent (length and width) of the damage present in the light-conducting layer. In particular, it is thus possible, for example, to determine the diameter of a breakdown hole through the light-conducting layer.

In a preferred embodiment, the first evaluation means for determining a dimension of the spatial object is executed and set up. For this purpose, for example, on the basis of the previously determined dimension of the damage and known damage equations on the particle size of the spatial object can be concluded, as for example in the ESA Final Report: "METEOROID and DEBRIS FLUX and EJECTA MODELS"; ESA CONTRACT NO. 11887/96 / NL / JG; FINAL REPORT "is described.

A further preferred development of the solar generator according to the invention is characterized in that the light-conducting layer has a peripheral edge, which is a uniform polygon, and at the peripheral edge a plurality of light sensors are arranged substantially opposite of light sources. The light-conducting layer preferably consists of glass or Plexiglas or, in particular, of an optically transparent material which, if possible, does not tend to fragment.

A further preferred development of the solar generator according to the invention is characterized in that the evaluation unit is designed and set up such that after detection and evaluation of an nth disturbance, the total reflection properties of the light-conducting layer are stored and used as a reference for detecting an n + 1-th fault can be used. The total reflection properties can be specified in the form of measurable characteristic optical parameters of the layer (time of flight, interference pattern, light intensity distribution, etc.).

A further preferred development of the solar generator according to the invention is characterized in that the first evaluation unit has a memory unit in which the detected disturbances of the total reflection properties and their evaluation, for example. The parameters describing the total reflection properties are stored, and current and / or stored Disturbances and their evaluations are provided for transmission to a ground station.

A further preferred refinement of the solar generator according to the invention is characterized in that two layers which are transparent to optical radiation and are guided by total reflection are arranged above the solar cell layer, each of which at the peripheral edge couples at least one light source which couples light into the respective light-guiding layer and several at Have respective peripheral edge of the light-conducting layers arranged light sensors, for detecting the intensity of the coupled into the respective light-conducting layer totally reflected light, and which is connected to the light sensors and the light sources first evaluation means is adapted from determined for the respective layers positions of a respective Damage to the layer to determine a direction from which a spatial object has collided with the solar panels, wherein the spatial object has thereby penetrated the at least outer light-conducting layer.

Of course, space objects from different directions, d. H. especially on the bottom (back) of the solar panels. If, in a first case, a room object only penetrates into the light-conducting layer and does not destroy any solar cell (s) in its functionality, or if in a second case one or more solar cells of the solar cell layer fail, without the light-conducting layer being damaged, this may be present of the first or the second case can be determined by means of the first and second evaluation means.

With the solar generator according to the invention, it is possible to detect damage to the light-conducting layer, which are caused by very small space objects (depending on the scan resolution / line density of the scanning beams up to a diameter of 1 micron) .. Furthermore, by detecting the damage, or the resulting disturbances of the total reflection properties at the light-conducting layer, also the clouding and thus a degradation of the solar generator, d. H. a reduction in the efficiency of the solar generator can be determined. The light source and the light sensor must degrade slower than the light-conducting layer.

Further advantages, features and details will become apparent from the following description in which an embodiment is described with reference to the drawings. The same, similar and / or functionally identical parts are provided with the same reference numerals.

Show it:

1 a vertical section through a solar generator 100 .

2 a view of a light-conducting layer 101 according to a first embodiment,

3 a view of a light-conducting layer 101 according to a second embodiment.

1 shows a vertical section through a solar generator 100 comprising a structural layer 103 , a solar cell layer disposed thereon 102 , and one on the solar cell layer 102 arranged light-conducting layer 101 , Between these layers 101 . 102 . 103 Additional connection layers can be arranged. Between the structural layer 103 and the solar cell layer 102 In particular, one or more layers containing electrical conductors may be arranged. The structural layer 103 serves to generate a sufficient structural strength of the solar panels.

2 shows a plan view of a transparent to optical radiation and by total reflection light-conducting layer 101 a solar generator according to the invention 100 according to a first embodiment. The light-conducting layer 101 covers the solar cell layer 102 flat completely and has a rectangular peripheral edge. On two adjacent sides of the peripheral edge are equally spaced light sources 201 arranged. In the present case are the light sources 201 each carried out a straight light beam perpendicular to the peripheral edge in the light-conducting layer 101 couple. The light rays are each shown as arrows. Opposite to the light sources 201 are at the peripheral edge of the layer 101 light sensors 202 for detecting an intensity and / or a transit time in the light-conducting layer ( 101 ) coupled and totally reflected light, which have an aperture diaphragm, so that they can specifically detect only light from an incident direction, which is also perpendicular to the peripheral edge. The light sources 201 and the light sensors 202 are connected to a first evaluation means (not shown) with which a disturbance of total reflection properties in the photoconductive layer caused by a collision with a space object 101 can be determined. Preferably, a second evaluation means (not shown) is provided, with which a failure of individual solar cells can be determined.

Also shown is a collision with a spatial object in the light-conducting layer 101 Arisen puncture hole 204 , This punch hole 204 blocks the propagation paths of light rays in the direction of the light sensors 203a . 203b , By evaluation of measurement data of the light sensors 202 Thus, it is possible the position and the dimension of the punch hole 204 in the layer 101 and, on the basis of well-known damage equations, continue to determine the dimension of the spatial object that is the breakthrough hole 204 has generated.

Although the invention has been further illustrated and explained in detail by way of preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention. It is therefore clear that a multitude of possible variations exists. It is also to be understood that exemplified embodiments are really only examples that are not to be construed in any way as limiting the scope, applicability, or configuration of the invention. Rather, the foregoing description and description of the figures enable one skilled in the art to practice the exemplary embodiments, and those skilled in the art, having the benefit of the disclosed inventive concept, can make various changes, for example, to the function or arrangement of individual elements recited in an exemplary embodiment, without Protected area, which is defined by the claims and their legal equivalents, such as further explanation in the description.

LIST OF REFERENCE NUMBERS

100

solar generator

101

Light-conducting layer

102

solar cell layer

103

structural layer

201

light source

202

Light sensor / s

203a, b

Light sensor which due to a disturbance does not receive direct light from an associated opposite light source

204

Punch hole through the light-conducting layer

Claims (9)

Solar generator ( 100 ) for spacecraft or satellites comprising: - at least one solar panel with a solar cell layer ( 102 ), which convert a multiplicity of solar cells lying side by side, which convert incident electromagnetic radiation into electrical current, and one above the solar cell layer (FIG. 102 ) transparent to optical radiation and by total reflection light-conducting layer ( 101 ), - at least one light source ( 201 ), which are in the light-conducting layer ( 101 ) Light, - several at a peripheral edge of the light-conducting layer ( 101 ) arranged light sensors ( 202 ), for detecting an intensity of the light-conducting layer ( 101 ) coupled and totally reflected light, and - one with the light source ( 202 ) and the light sensors ( 201 ) associated with the one caused by a collision with a spatial object disturbance of total reflection properties in the light-conducting layer ( 101 ) can be determined. Solar generator ( 100 ) according to claim 1, characterized in that the first evaluation means for determining a transit time of one of the light source ( 201 ) emitted light pulse until its detection by the light sensors ( 202 ) is designed to determine a change in the total reflection properties on the basis of an occurring change in the transit time. Solar generator ( 100 ) according to one of claims 1 to 2, characterized in that the first evaluation means for determining a position of a caused by a collision with a space object, the disturbance of the total reflection properties causing damage ( 204 ) of the light-conducting layer ( 101 ) is executed and set up. Solar generator ( 100 ) according to one of claims 1 to 3, characterized in that between the light sensors ( 202 ) and the peripheral edge one each an opening angle of the respective light sensors ( 202 ) limiting aperture stop is arranged. Solar generator ( 100 ) according to one of claims 1 to 4, characterized in that the first evaluation means for determining a dimension of the disturbance of the total reflection properties causing damage ( 204 ) of the layer ( 101 ) is executed and set up. Solar generator ( 100 ) according to one of claims 1 to 5, characterized in that the first evaluation means is designed and set up for determining a dimension of the spatial object. Solar generator ( 100 ) according to any one of claims 1 to 6, characterized in that the first evaluation means is designed and arranged such that after occurrence and evaluation of an n-th disorder, the total reflection properties of the light-conducting layer ( 101 ) and used as a reference to detect an n + 1th perturbation, where n = 1, 2, .... Solar generator ( 100 ) according to one of claims 1 to 7, characterized in that the first evaluation means comprises a memory unit in which the detected total reflection properties and their evaluation are stored, and current and / or stored total reflection properties and / or their evaluations provided for transmission to a ground station become. Solar generator ( 100 ) according to one of claims 1 to 8, characterized in that - above the solar cell layer ( 102 ) two optical radiation transparent and total reflection light conductive layers ( 101 ) are arranged, each at the peripheral edge at least one light source ( 201 ), which in the respective light-conducting layer light ( 101 ) and several at the respective peripheral edge of the light-conducting layers ( 101 ) arranged light sensors ( 202 ), for detecting the intensity of the light-conducting layer ( 101 ) have coupled total reflect light, and - that with the light sensors ( 202 ) and the light sources ( 201 ) connected first evaluation means is arranged to off for the respective layers ( 101 ) determined positions of the respective disturbance causing damage ( 204 ) of the layer ( 101 ) to determine a direction from which a spatial object has collided with the solar panels, wherein the spatial object thereby the at least external light-conducting layer ( 101 ) has penetrated.

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