RU2476833C2 - Method of simulating solar radiation in thermal pressure chamber - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: simulation method involves generating solar radiation simulation flux from light sources outside the thermal pressure chamber. Focusing and input of light flux from the light sources into the thermal pressure chamber are carried out through a light-conducting illuminator in form of a biconex lens which is hermetically mounted on the housing of the chamber. Parallel light flux onto the tested spacecraft is generated by a parabolic collimating reflector while providing flux characteristics with parameters maximally close to real solar radiation on the orbit of the spacecraft, with subsequent reflection thereof from a mixer while splitting the light flux into separate light fluxes with expansion of their light spot incident on the parabolic collimating reflector.

EFFECT: high efficiency and uniformity of exposure of the surface of tested spacecraft or component part thereof.

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Description

The invention relates to methods for simulating solar radiation (ISI) in a thermal vacuum chamber (TCE) and can be used in thermal vacuum testing of a spacecraft (SC) or its components.

The known method of ISI implemented in the TV "General Electric" with ISI non-axial optical design (O. B. Andreychuk, N. N. Malakhov. Thermal tests of spacecraft. Moscow. "Engineering". 1982. P. 23, Fig. 3.1; p. 51, Fig. 3.25), in which a simulating solar radiation flux from light sources outside the pressure chamber is created, focusing and input of light fluxes from light sources inside the pressure chamber through a light-conducting illuminator sealed on its body, creating a parallel light flux to the test space Paratov by collimating parabolic reflector (FFP) ensuring the flow characteristics with parameters as close to the actual solar radiation on the spacecraft orbit.

The disadvantage of this method lies in the low coefficient of performance (COP) and the poor uniformity of irradiation of the surface of the test object. The reason for this is that in the process of its implementation with the successive passage of the light flux from the lamps through a series of optical surfaces, the light flux is significantly weakened and thereby the ICR efficiency is reduced. In addition, the implementation of this method does not contain a special device that provides an increased degree of uniformity of irradiation of the surface of the test object by dividing the total luminous flux into separate ones with an increase in the size of their spots incident on the FFP with an area equal to or close to the area of the said reflector.

As a prototype, the ISI method in TCEs for testing spacecraft implemented by a non-axial simulator of solar radiation in TCEs (O.B.Andreichuk, NN Malakhov. Thermal tests of spacecraft. Moscow. "Engineering". 1982. Pp. 38, fig. .3.10, b). In the indicated method, the condenser lens located in the input unit of the pressure chamber combines light fluxes from individual radiation sources — lamps placed outside the pressure chamber. Next, the combined luminous flux passes through a porthole sealed in the same input unit and enters the FFP with a certain angle of divergence. In this case, the input unit is located in the focus of the FFP. FFP converts the diverging luminous flux arriving at it into a parallel one and directs it to the test spacecraft. The disadvantages of the prototype are similar to the disadvantages indicated in the above analogue.

The objectives of the invention are to increase the efficiency of the ISI and the uniformity of the irradiation of the surface of the test object or its component.

The problems are solved due to the fact that in the proposed ISI method in TCEs for testing spacecraft, the input of the light flux into the thermal chamber is carried out through a biconcave lens porthole to ensure parallel flow rays at its output. Subsequent reflection, mixing and divergence of the flow to the size of the FFP is carried out using a mirror mixer. Moreover, each radiation source is made with an ellipsoid reflector and an auxiliary spherical mirror for returning the rays not covered by the reflector into the zone of passage of the light flux. The calculation of the optimal parameters of the solar radiation simulator for a specific pressure chamber is carried out using the formula for calculating the radius of curvature of a plano-concave lens, which ensures parallel light flux at its output:

Where

R is the radius of curvature of a flat-concave lens;

d is the diameter of the flat-concave lens;

A - half the angle of convergence of the stream entering the biconcave lens (angle of incidence of the "extreme beam" of the stream).

The essence of the proposed method is shown in figures 1, 2, 3 and 4. Figure 1 shows a General view of a non-axis simulator of solar radiation from a thermal vacuum chamber. Figure 2 shows a fragment of a mirror mixer, made in the form of convex mirror lenses with square profiles evenly distributed in the plane of contact with their faces. Figure 3 shows a lamp with an ellipsoid reflector and an auxiliary spherical mirror. Figure 4 shows geometric constructions explaining the methodology for calculating the radius of a flat-concave lens to obtain a strictly parallel stream after it.

The device, taken as an example of the implementation of the proposed method, contains an input porthole 1, a parabolic collimating reflector 3, solar radiation sources 5 and a mirror mixer 7. The input porthole 1 is made in the form of a biconcave lens and is hermetically integrated into the housing 2 of the thermal vacuum chamber. FFP 3 is used to reflect simulated solar radiation on the test object 4, located in a thermal vacuum chamber. Sources of solar radiation 5 are lamps with ellipsoid reflectors and auxiliary spherical mirrors located outside the thermal vacuum chamber. The ellipsoid reflector directs the part of the lamp radiation that arrives at its surface to the biconcave lens 1. The auxiliary spherical mirror 6 returns the remaining part of the lamp radiation that does not fall on the reflector surface, reflecting it again to the reflector, and then to the biconcave lens 1. Mirror mixer 7 located along the luminous flux between the PKO 3 and the biconcave lens 1 and is made in the form of convex mirror lenses 8 with square profiles uniformly arranged in the plane of their contacting faces. Each of the convex mirror lenses 8 reflects the part of the parallel light flux received after the biconcave lens 1 in the form of a diverging beam of rays at the FFP 3, occupying its entire surface.

To ensure increased efficiency and uniformity of irradiation of the surface of the test object 4 due to the optimal operation of the system as a whole, the biconcave lens 1, convex mirror lenses 8 with square profiles and parabolic collimating reflector 3 are made with optimal parameters (for the condition that the test object is large product, e.g. spacecraft):

- the outer and inner radii of curvature of the biconcave lens are respectively minus 1,050 and plus 1,050 m;

- the diameter of the biconcave lens is 0.6 m;

- half the angle of convergence of the stream entering the biconcave lens (angle of incidence of the "extreme beam" of the stream) is equal to 14 degrees;

- the dimensions of convex mirror lenses with square profiles are 0.04 × 0.04 m, the radii of their curvature are 0.16 m.

- the dimensions of the FFP are 2.5 × 2.588 m.

- the radius of curvature and the diameter of the auxiliary spherical mirrors of the lamps are 0.11 and 0.12 m, respectively.

A method of simulating solar radiation, we consider the example of its implementation in a device simulating solar radiation.

The proposed device operates as follows. The test object (SC) 4 is installed in the TCE motionless for conducting a stationary thermal regime or with the possibility of rotation using a rotary device (not shown) relative to the direction of the simulated solar radiation flux, respectively, of the developed variant of the motion of the SC 4 in its orbit for unsteady thermal regime. At the same time, the lamps are turned on and the luminous flux of a given total power from them is focused on the biconcave lens 1, passes through it and enters the mirror mixer 7 with parallel light rays, located at a distance of 4.5 m along the optical axis from the biconcave lens 1.

In the proposed device, along the path of the light flux between the PSC 3 and the biconcave lens 1, a mirror mixer 7 is installed, made in the form of convex mirror lenses 8 with square profiles that are uniformly located in contact with their faces to reflect the simulated solar radiation incident on each of them on the PSC 3 in the form of a diverging beam of rays with an area incident on the FFP 3 spots equal to or close to the area of the FFP 3. With the specified reflection of the light flux from each convex mirror lens 8 and their reflection with the increase in the size of the light flux to an area equal to the surface area of the FFP 3, the uniformity of the irradiation of the surface of the test object 4 is increased.

The mirror mixer consists of 400 identical mirror lenses 8 (mixer elements) of a square profile with dimensions of 0.04 × 0.04 m, thickness 0.01 m and radius of curvature 0.16 m. Given the small divergence of the flow due to a really “non-point” source, the dimensions of the mirror of the mixer, 0.8 × 0.8 m are taken. The radii of curvature of the mirror lenses 8 are calculated so that the parallel flow coming to the surface of one mirror lens 8 is reflected from it with a divergence angle of 26 degrees, occupying the entire surface of the FFP 3. Thus, the mirror the mixer t is the function of 2 elements: the reversal of the flow with its subsequent increase by a collimating mirror 3 and its 400-fold mixing. Since at least two optical elements are required to perform these functions, respectively, the efficiency loss on these elements would be approximately 16% on the mirror and 8% on the mixer. In this case, potential losses on two surfaces of the mixer elements are eliminated. This gives a total increase in the efficiency of the simulator of solar radiation by about 8%.

Each of the 400 mirror lenses 8 reflects the luminous flux at the FFP 3 and increases it to sizes close to the size of the FFP. With this reflection, the beam of rays from each mirror lens is mixed 400 times with the beams of rays of other lenses, which provides a high degree of uniformity of the incident flux at the FFP and further on the surface of the test object (SP) 4 with a simultaneous high degree of parallelism of the light flux.

Spherical mirrors 6 are located at a distance of 0.05 m along the optical axis from the first foci of ellipsoid reflectors, in which there are arcs of vertically mounted lamps, almost immediately behind the quartz bulbs of the lamps. The proposed device uses lamps of the type XBO 10000 W / HS OFR. The manufacturer (OSRAM) provides for both vertical (relative to the horizon) and horizontal installation of lamps - at the discretion of the developer of the optical system. However, horizontal (or at an angle) installation requires the installation of additional elements in the structure - magnets to stabilize the arc. The vertical installation of embedding magnets does not require and, in addition, since the lamp has an elongated shape (Fig. 3), it allows you to place spherical mirrors immediately behind the bulb.

The diameters of the spherical mirrors are 0.12 m, the radii of curvature are 0.11 m. Without the use of auxiliary spherical mirrors, the efficiency of the “Reflector-lamp” bundle would be about 60% - this is approximately how an ellipsoid reflector covers the rays evenly emanating in all directions from the lamp. The introduction of an auxiliary spherical mirror into the “Reflector-lamp” bundle allows you to return that part of the lamp radiation that did not hit the surface of the ellipsoid reflector, again to this reflector, and then to the biconcave lens 1.

Thus, the efficiency of the “Reflector-Lamp” bundles is increased by about 30% due to the collection of rays not covered by the reflector and returning them to it.

In addition, the efficiency of the device is increased due to the fact that the porthole is made in the form of a biconcave lens 1. The indicated positive effect is obtained due to the fact that the power loss of the light flux is reduced by reducing the number of surfaces of the light guide elements that reduce its power.

The calculation of the specified parameters of the biconcave lens 1, based on the requirements for providing the spot area of the light flux of simulated solar radiation to the test object 4, was carried out according to the newly developed calculation methodology below.

Figure 4 shows a flat-concave lens, incident and refracted rays. In accordance with the law of refraction, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant and is the refractive index of the second medium relative to the first (G. Schroeder, H. Traiber. Technical Optics. Moscow: Technosphere, 2006). In the case of an air-glass refraction, the refractive index is 1.5. In the case of an uneven surface, the angle of incidence is the angle between the incident beam and the perpendicular to the tangent at the point of incidence, and the angle of refraction is the angle between the perpendicular to the tangent and the refracted beam, respectively.

Thus, in relation to a flat-concave lens to obtain a parallel flow behind it (figure 4) we have:

Where

A - angle of incidence of the "extreme" beam of the light flux;

B is the angle between the perpendicular to the tangent and the refracted “extreme” ray.

To determine the radius R of the plane-concave lens, we first find the angle B (angle of refraction).

Having expanded the sine of the sum and carried out the corresponding transformations, we obtain:

From here:

From the relations in a right triangle (Fig. 5) we also have:

where d is the diameter of the lens.

Applying ratio

between inverse trigonometric functions (Bronstein I.N., Semendyaev K.A. Math reference book for engineers and students of technical colleges. M: Nauka, 1986), we obtain:

Converting the denominator of a fraction:

we get:

To find the radius R, we equate the arguments of two arcsines calculated for finding B in accordance with formulas (3) and (4) earlier:

Hence:

,

,

From here:

If it is necessary to calculate a biconcave lens with the same optical power, it is necessary, keeping the focal length f and setting R ₁ , apply the formula:

,

,

Here:

f is the focal length of the lens;

n ₂₁ is the refractive index of the second optical medium relative to the first;

R ₁ , R ₂ - respectively, the radii of the surfaces of the lens.

When deriving the necessary mathematical formulas, the information of their official sources was used (G. Schroeder, H. Traiber. Technical optics. Moscow: Technosfera, 2006 and I. Bronstein, K. A. Semendyaev. A reference book on mathematics for engineers and students of technical schools. M. : Science, 1986).

The proposed method for simulating solar radiation in TCEs for testing a spacecraft (SC) or its components is currently undergoing implementation in the design documentation developed for a newly built TCE enterprise.

Claims (3)

1. A method for simulating solar radiation in a thermal pressure chamber by supplying a simulating light flux from light sources to a thermal pressure chamber through a porthole hermetically installed in its body, reflection of this light stream with focus on a parabolic collimating reflector (FFP) and on the test product, characterized in that they use a window in the form of a biconcave lens, providing at its output a parallel light flux, which is then divided into separate beams of rays, mix and reflect them with increased I eat on the SSP. 2. The method according to claim 1, characterized in that to ensure parallel light flux at the output of the biconcave lens, its parameters are calculated by the formula:

where R is the radius of curvature of a flat-concave lens;
d is the diameter of the flat-concave lens;
A - half the angle of convergence of the stream entering the biconcave lens (angle of incidence of the "extreme beam" of the stream). 3. The method according to claim 1 or 2, characterized in that lamps with reflectors are used as light sources, each of which is equipped with a spherical mirror, which allows to capture that part of the lamp radiation that did not fall on the reflector surface and return it to the reflector again and further on to the biconcave lens.

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