An existing space simulation test facility was modified by enlarging the solar simulator. Because of the restrictions imposed by existing equipment, the shape of the solar beam was altered from a circular to a rectangular cross section in order to adapt the test facility to test objects of increased size. This modification is described together with the results of preliminary measurements

Feil, O. G.

Frey, H. U.

English

NASA Technical Reports Server

N89- 12605 '
SOLAR SIMULATION WITH A RECTANGULAR BEAM
O. G. Fell and H. U. Frey
IABG, Munich, West Germany
ABSTRACT
An existing space simulation test facility was modified by
enlarging the solar simulator. Because of restrictions imposed by
existing equipment, the shape of the solar beam was altered from a
circular to a rectangular cross section in order to adapt the test
facility to test objects of increased size. This modification is
described together with the results of prelimimary measurements.
INTRODUCTION
Since the beginning of satellite production in West Germany,
approximately 25 years ago, IABG has been involved in the testing of
space hardware. In 1983 a new, relatively large space simulation test
facility became operational 1), a schematic diagram of which is shown in
fig. i; fig. 2 shows a photograph of the open chamber. The main
characteristics of the facility are"
Test Volume Dimensions
- Between Lid and Shutter"
- Between Lid and Mirror"
- Diameter"
7.5 m
12.0 m
approx. 6.2 m
Solar Beam
- Diameter:
- Intensity max.:
- Parallel Beam with Collimation Angle:
3.6m
1.4 solar constants
+20
278
https://ntrs.nasa.gov/search.jsp?R=19890003234 2020-03-20T04:39:12+00:00Z
Shroud
- Temperature Range: <100 K to 400 K
Vacuum
- Pressure"
- Oil free high vacuum pumps
<10 -5 mbar
Motion Simulator"
Two axes of rotation:
- Attitude axis" _200 °
- Spin axis continuous rotation up to 10 rev. per minute
Max. Dimensions of Test Specimen
- Height:
- Diameter:
- Mass:
approx. 5.0 m
approx. 4.0 m
approx. 2000 - 2500 kg
The facility has been used extensively for testing satellites and
subsystems of national and international programmes. It has also been
used for special deformation measurements by means of laser holography
which were reported during the 13th Space Simulation Conference in
19842)
MODIFICATION OF SOLAR SIMULATOR
With the increase of launcher capacities and a corresponding
increase in satellite sizes we began to study the possibilities of
enlarging the usable test volume of our facility. Since the dimensions
of the chamber itself and of the shroud could not be altered, we focused
our attention on the solar beam, which also represented the main
limitation.
279
The solar simulator consists essentially of (see fig. 1)
- the lamp housing with up to 7 lamps of 25 kw each
- the integrator, an array of lenses
- the window as interface between the vacuum inside and the atmospheric
pressure outside the chamber
- the collimation mirror inside the chamber, consisting of hexagonal
segments
This arrangement, the lay-out of which was developed at IABG, yields a
very good intensity distribution across the solar beam (_3 %) with a
collimation angle of +20 . The efficiency is better than 12 %. These
values were obtained by means of extensive analysis and optimisation
using mathematical models. For example, the collector mirrors were
designed for a light source of finite length with a given intensity
distribution.
Each of the integrator lenses distributes the light over the total
beam area; therefore, switching or exchanging of lamps has hardly any
effect on the intensity distribution in the target area.
A further advantage of this solar simulator design is its modular
concept, which allows easy exchange of lamps, power supplies, etc.
Due to restraints imposed by the building and the chamber, it was
not possible to simply increase the number of lamps and,
correspondingly, the size of the collimation mirror in order to enlarge
the solar beam. Instead, the following modifications were made after a
number of calculations aimed at an optimised solution:
o The integrator was replaced by a new one containing rectangular
instead of circular lenses.
o The collimation mirror was enlarged by a number of hexagonal segments.
280
These measures yielded a solar beam with a cross section of 3.05 m by
4.5 m, suitable for larger spacecraft than the 3.6 m dia beam, which
covers square shaped spacecraft cross sections of up to 2.5 m side
length.
The essential parameters of the two solar beams are listed in fig.
3. It can be seen that an increase of illuminated area of approximately
35 % is gained compared to a "loss" of maximum intensity of 7 %. This
reduction was considered acceptable since 1.36 SC leaves a comfortable
margin above the standard 1SC. The gain is mainly achieved by the
improved packing factor of the rectangular integrator (27 %), a
geometrical effect as shown in fig 4. The area covered by the support
structure of the lenses, which does not transmit any light, is larger
for the circular lenses than for the rectangular ones.
Fig. 5 shows photographs of the new integrator which was designed
and manufactured by C. Zeiss at Oberkochen, West Germany.
Preliminary measurements of the rectangular solar beam show that
the intensity distribution is better than +3 % with the exception of the
edges and very few points in the middle (Fig. 6). It should be noted
that some mirror segments at the corners of the collimation mirror had
not yet been installed at the time of these measurements; also the upper
left corner of the beam is obstructed by the support structure of a
radiometer.
These measurments were performed with an intensity of 0.83 kw/m2;
with full power of the 7 X 25 kw lamps a value of 1.8 kw/m2 = 1.36 SC
will be obtained.
281
CONCLUSION
By a relatively simple modification and with relatively low cost,
the usable test volume of IABG,s space simulation test facility was
considerably enlarged (e.g. for ARIANE 3 spacecraft) and the range of
potential customers increased. A further advantage is that changeover
between the two solar beams can be achieved easily by exchanging the
integrator only; no other modifications are required.
REFERENCES
1) H. E. Nuss und J. Reimann: The new space simulation and thermal vacuum
facility WSA/TVA. Proc. of the International Symposium on
Environmental and Thermal Systems for Space Vehicles, 1983, ESA SP-
2O0
2) H. U. Frey: Distortion Measurement of Antennas under Space Simulation
Conditions, 13th Space Simulation Conference, 1984, NASA Conference
Publication 2340.
282
bJ
Oo
(_ = vessel
(_ = shroud
(_) = collimator
(_) = window
(_) = integrator
(_) = lamps
(_) = motion simulator
13m
o_
|
_m
|
Fig. I: Space Simulation Test Facility
OR/G]NAE PA-G_ IS
DE I_OR QUAL[T_
t,
4_
tD
_D
F--
c-
0
°r-
4_
e_
E
°t-
O
<3)
c-
q--
O
(D
-r-
>
g_
°r-
D-
284
smeaflJeLoS _o s_a_awe_ed :_ "613
<
3s 9£" -[
6'0
S3SN37 _tV7N9NV193_I _9 X
w c;,_; x w g'b
b_
w q'bxw _0'_-
DS tTb'I
TL'O
S3SN3q _lVqAOlYl9 I{X
T9
w 9'_ vlo
3NVqJ 1S31 NI
ALISN3/NI WqOS NflWIXVW
aO13V3 9NINDVJ -
_01V_931NI
_tOLVWI-1-109 30 SI/OISN314I(I
SLN3N93S _t01VWIq-IO3 30 >J3_tNnN
V3UV f131VIQVUUl
SNOISN3WIQ WV3_
t¢3
O0
('4
OO
Rectangular
Lenses
Circular
Lenses
Fig. 4: Packing Factor of Integrator
ORIGINAE PAGE [_
OF POOR QUALITI_
Fig. 5: Rectangular Integrator
287
,k , •
ORIGINAL PAGE IS
OF POOR QUALt'I_.
Meanval ue I*
833 14/m2
Radiated surface
11.67 m2
Grid Size[]
100 X 100 mm2
I=Local value
[] 4Z <I< = 10Z
[] 3Z <I< = 4Z
[] 2Z <I< = 3Z
[] -2Z <I<= 2Z
m -3Z <I<= -2Z
-4Z <I<= -3Z
[]-IOZ <I< = -4Z
PRE TEST
MERSUREMENT
Fig. 6: Intensity Distribution - Rectangular Beam
288


Solar simulation with a rectangular beam

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server