U.S. patent application number 15/535900 was filed with the patent office on 2017-11-30 for spacecraft.
The applicant listed for this patent is AIRBUS DEFENCE AND SPACE SAS. Invention is credited to Patrick Coutal, Fabrice Mena.
Application Number | 20170341781 15/535900 |
Document ID | / |
Family ID | 53191753 |
Filed Date | 2017-11-30 |
United States Patent
Application |
20170341781 |
Kind Code |
A1 |
Mena; Fabrice ; et
al. |
November 30, 2017 |
SPACECRAFT
Abstract
The invention relates to a spacecraft comprising a body having
two opposite faces; a first radiator carried by at least one face;
the first radiator having an outer face; a first supporting arm
extending substantially perpendicularly to the outer face of the
first radiator; a drive motor suitable for rotating the first
supporting arm about its longitudinal axis a first assembly carried
by the first supporting arm, said first assembly comprising a
plurality of slats stationary with respect to the first supporting
arm; said slats being attached one above the other and separated
from each other by a free space.
Inventors: |
Mena; Fabrice; (Teulat,
FR) ; Coutal; Patrick; (Renneville, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AIRBUS DEFENCE AND SPACE SAS |
Les Mureaux |
|
FR |
|
|
Family ID: |
53191753 |
Appl. No.: |
15/535900 |
Filed: |
December 15, 2015 |
PCT Filed: |
December 15, 2015 |
PCT NO: |
PCT/FR2015/053502 |
371 Date: |
June 14, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64G 1/503 20130101;
B64G 1/506 20130101; B64G 1/50 20130101; B64G 1/222 20130101; B64G
1/446 20130101 |
International
Class: |
B64G 1/50 20060101
B64G001/50; B64G 1/44 20060101 B64G001/44; B64G 1/22 20060101
B64G001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2014 |
FR |
14 62565 |
Claims
1. A spacecraft comprising: a body having a face +Y and a face -Y
opposite the face +Y; a first radiator carried by at least one face
out of the face +Y and the face -Y; said first radiator having an
outer face; a first supporting arm extending substantially
perpendicularly to the outer face of the first radiator, said first
supporting arm having a longitudinal axis; a drive motor suitable
for rotating the first supporting arm about said longitudinal axis
of the first supporting arm, the speed of rotation of the first
supporting arm being substantially equal to the speed of revolution
of the sun around the spacecraft; a first assembly carried by the
first supporting arm, said first assembly having at least one
absorption face suitable for absorbing a portion of the incident
solar radiation during the vernal and autumnal equinoxes, said
first assembly being suitable for transmitting heat generated by
said portion of the incident solar radiation absorbed to the first
radiator; said absorption face being inclined with respect to the
outer face of the first radiator by an angle substantially between
20.degree. and 26.degree., wherein said first assembly comprises at
least two slats attached one above the other and separated from
each other by a free space, said at least two slats being
stationary with respect to the first supporting arm.
2. The spacecraft according to claim 1, wherein said first radiator
is carried by the face -Y and wherein said at least two slats of
the first assembly are substantially parallel to the direction of
the solar radiation during the summer solstice.
3. The spacecraft according to claim 1, further comprising: a
second radiator carried by the other face out of the face -Y and
the face +Y, said second radiator having an outer face; a second
supporting arm extending substantially perpendicularly to the outer
face of the second radiator, said second supporting arm having a
longitudinal axis; a drive motor suitable for rotating the second
supporting arm about said longitudinal axis of the second
supporting arm, the speed of rotation of the second supporting arm
being substantially equal to the speed of revolution of the sun
around the spacecraft; a second assembly carried by the second
supporting arm, said second assembly having at least one absorption
face inclined with respect to the outer face of the second radiator
by an angle substantially between 20.degree. and 26.degree., and
wherein said second assembly comprises a plurality of slats
stationary with respect to the second supporting arm; said slats
are attached one above the other and separated from each other by a
free space, and said slats of the second assembly are substantially
parallel to the direction of the solar radiation during the winter
solstice.
4. The spacecraft according to claim 1, further comprising at least
one solar panel and wherein at least one of said first supporting
arm and said second supporting arm supports said at least one solar
panel.
5. The spacecraft according to claim 1, wherein said slats comprise
a polyimide film and rods suitable for rigidifying said polyimide
film.
6. The spacecraft according to claim 1, wherein said absorption
face has a coating having high solar absorptivity.
7. The spacecraft according to claim 1, wherein the outer face of
said radiator has a non-specular coating.
8. The spacecraft according to claim 1, wherein each of said at
least two slats has a thickness of less than one millimetre.
9. The spacecraft according to claim 1, wherein said at least two
slats of the first assembly are parallel to each other.
10. (canceled)
11. (canceled)
12. (canceled)
13. (canceled)
14. (canceled)
15. (canceled)
16. (canceled)
17. (canceled)
18. (canceled)
19. (canceled)
20. The spacecraft according to claim 6, wherein said coating is a
black coating.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a spacecraft and in
particular to a geostationary satellite.
BACKGROUND OF THE INVENTION
[0002] Because of the revolution of the Earth around the sun, the
various faces of a geostationary satellite do not receive the same
quantity of solar radiation over the seasons. As a result, there
are cyclical variations in temperature on the face +Y and on the
face -Y. Thus, during the winter and summer equinoxes (EQ), the
faces -Y and +Y have lower temperatures than during the winter (WS)
and summer (SS) solstices, as illustrated in FIG. 1. Moreover, the
temperature of the faces of the satellite also fluctuates over
time. This temperature is approximately equal to 20.degree. C. at
the beginning of the life of the satellite and is 70.degree. C. at
the end of the life of the satellite. These variations in
temperature over the seasons and over time are reproduced on the
ground in a vacuum atmosphere during satellite validation
tests.
[0003] These validation tests are long and complex to carry
out.
[0004] To facilitate the validation tests on the ground, reducing
the variations in temperature over the seasons and over time was
envisaged.
[0005] For this purpose, the faces +Y and -Y of the satellite were
heated by electric heaters during the equinox. Nevertheless, the
heaters have limited effectiveness and require the electric power
system of the satellite to be oversized. This oversizing notably
increases the cost of the satellite.
[0006] Moreover, to regulate the temperatures of the faces of
Earth-observation satellites, louvers were attached opposite
radiators mounted on the outer faces of the satellites. These
louvers obscure the outer face of the radiator more or less
according to the cooling needs of the satellites. The louvers are
mounted pivotably about an axis positioned along a longitudinal
edge of the louvers. In the closed position, such louvers obscure
all of the outer face of the radiator. The only function of these
louvers is to prevent solar radiation from reaching the radiator.
Moreover, these louvers require a complex mechanism allowing the
rotation of the louvers. This mechanism must have good strength in
a variable thermal environment.
[0007] Document JP H03 109999 discloses a satellite comprising a
device that allows a portion of the incident solar radiation (Ie)
to be absorbed mainly during the vernal and autumnal equinoxes and
transferred via radiation to the adjacent radiator. This device
comprises two heat-radiating plates, each mounted on a supporting
arm of a solar panel. Over the course of a day, the two supporting
arms and the two heat-radiating plates are rotated about the
longitudinal axis of the supporting arms.
[0008] Each plate is solid. It has a high-absorptivity,
high-emissivity face and an opposite, low-absorptivity face. This
latter face is suitable for reflecting solar radiation. The plates
are rotated about an axis perpendicular to the longitudinal axis of
the supporting arm that supports it. The amplitude of rotation is
approximately 180.degree.. The rotation is carried out during
certain seasons. Thus, at the vernal and autumnal equinox, the
high-absorptivity faces of the two heat-radiating plates are
pivoted in such a way as to form an angle of 23.degree. with the
radiators.
[0009] Thus, the high-absorptivity faces absorb solar radiation and
emit heat to the radiators. During the summer solstice, the
heat-radiating plate of the supporting arm located on the North
side is rotated in order for its low-absorptivity face to be
directed towards the solar radiation and be perpendicular to the
North radiator. This face is thus exposed towards the sun in order
to not heat the South radiator of the satellite when it is exposed
to direct solar radiation.
[0010] Finally, during the winter solstice, the heat-radiating
plate of the supporting arm located on the South side is rotated in
order for its low-absorptivity face to be directed towards the
solar radiation and be perpendicular to the South radiator.
[0011] This device, however, requires one or two additional
electric motors. This or these motors make the satellite heavier
and increase its manufacturing cost.
[0012] Moreover, the satellite of document JP H03 109999 is not
secure. If a part or one of the motors for rotating the
heat-radiating plates breaks down during a mission, it is difficult
to repair them. If, in addition, this breakdown takes place during
the solstices, the heat-radiating plates remain in a position that
will increase the temperature differences during the other seasons
and will endanger the operation of the on-board electronic
equipment.
SUMMARY OF THE INVENTION
[0013] The purpose of the present invention is to propose a system
that has a lower cost, is more reliable, and would allow the
variations in temperature between the North and South faces of a
satellite during the equinoxes and during the solstices to be
limited.
[0014] For this purpose, the object of the invention is a
spacecraft comprising: [0015] a body having a face +Y and a face -Y
opposite the face +Y; [0016] a first radiator carried by at least
one face out of the face +Y and the face -Y; said first radiator
having an outer face; [0017] a first supporting arm extending
substantially perpendicularly to the outer face of the first
radiator, said first supporting arm having a longitudinal axis
(A-A); [0018] a drive motor suitable for rotating the first
supporting arm about said longitudinal axis (A-A) of the first
supporting arm, the speed of rotation of the first supporting arm
being substantially equal to the speed of revolution of the sun
around the spacecraft; [0019] a first assembly carried by the first
supporting arm, said first assembly having at least one absorption
face suitable for absorbing a portion of the incident solar
radiation during the vernal and autumnal equinoxes, said first
assembly being suitable for transmitting said absorbed heat to the
first radiator; said absorption face being inclined with respect to
the outer face of the first radiator by an angle substantially
between 20.degree. and 26.degree.; said first assembly 34 comprises
at least two slats 36 attached one above the other and separated
from each other by a free space e, said slats being stationary with
respect to the first supporting arm 32.
[0020] Advantageously, in the present invention, the slats are
stationary with respect to the supporting arm. This results in a
system that is simpler, less costly and more reliable.
[0021] Advantageously, the assembly according to the invention has
a surface containing holes that variably and selectively (1% to
100%) absorbs the incident solar radiation. Indeed, the solar
radiation "passes through" the assembly during the solstices. This
gives it the quality of being discrete during the desired season
and allows its "stationary" nature.
[0022] Although the slats obscure a portion of the radiation during
the solstices, their thickness is so small that the resulting loss
of heat is highly negligible since it represents a few percent of
the heat collected, typically approximately 5%.
[0023] Advantageously, in the assembly according to the invention,
only the absorption face is exposed to the incident solar
radiation, and this face is always vertically in line with the
adjacent radiator.
[0024] Advantageously, the assembly according to the invention is
less costly to manufacture. Moreover, it is passive and does not
require an electric power supply.
[0025] Advantageously, the assembly according to the invention is
small and has a very low mass of approximately several kilograms,
typically approximately one kilogram.
[0026] According to specific embodiments, the spacecraft comprises
one or more of the following features: [0027] The first radiator is
carried by the face -Y and wherein said slats of the first assembly
are substantially parallel to the direction of the solar radiation
during the summer solstice.
[0028] Advantageously, since said at least slat is inclined by an
angle corresponding to the angle formed between the outer face of
the radiator and the direction taken by the solar radiation during
the solstice, said at least slat is not heated during the solstice.
[0029] the spacecraft comprises a second radiator carried by the
other face out of the face -Y and the face +Y; said second radiator
having an outer face; a second supporting arm extending
substantially perpendicularly to the outer face of the second
radiator, said second supporting arm having a longitudinal axis
(B-B); [0030] a drive motor suitable for rotating the second
supporting arm about said longitudinal axis (B-B) of the second
supporting arm, the speed of rotation of the second supporting arm
being substantially equal to the speed of revolution of the sun
around the spacecraft; [0031] a second assembly carried by the
second supporting arm, said second assembly having at least one
absorption face inclined with respect to the outer face of the
second radiator by an angle (.alpha.) substantially between
20.degree. and 26.degree.,
[0032] and wherein said second assembly comprises a plurality of
slats stationary with respect to the second supporting arm; since
said slats are attached one above the other and separated from each
other by a free space, said slats of the second assembly are
substantially parallel to the direction of the solar radiation
during the winter solstice [0033] The craft comprises at least one
solar panel, and wherein said supporting arm supports said at least
one solar panel.
[0034] Since the solar panels are generally rotated about an axis
perpendicular to the outer face of the radiator at a speed equal to
the speed of revolution of the sun around the spacecraft, the use
of this supporting arm to carry the assembly of slats allows an
additional rotation mechanism to not be added. This implementation
is very advantageous from an economic point of view. [0035] The
slats comprise a polyimide film and rods suitable for rigidifying
said polyimide film. [0036] Said at least absorption face has a
coating having high solar absorptivity, for example a black
coating. [0037] The outer face of said radiator has a non-specular
coating. [0038] Each slat has a thickness of less than one
millimetre. [0039] The slats of one assembly out of the first
assembly and the second assembly are parallel to each other.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] The invention will be better understood after reading the
following description, given only as an example and made in
reference to the drawings, in which:
[0041] FIG. 1 are two curves representative of the variations in
temperature of the faces +Y and -Y of a spacecraft according to the
prior art over one year;
[0042] FIG. 2 is a perspective view of the spacecraft according to
a first embodiment of the invention in geostationary orbit;
[0043] FIG. 3 is a cross-sectional view of an assembly of
heat-transfer slats;
[0044] FIG. 4 is a schematic perspective view illustrating the
operating mode of the first embodiment of the invention during the
summer solstice;
[0045] FIG. 5 is a schematic perspective view illustrating the
operating mode of the first embodiment of the invention during the
equinox; and
[0046] FIG. 6 is a simplified schematic view of an embodiment of
the satellite according to the invention at the vernal equinox EP,
at the summer solstice SE, at the autumnal equinox EA and at the
winter solstice SH.
DETAILED DESCRIPTION OF THE INVENTION
[0047] The present invention is defined with respect to an
orthogonal reference frame R (X, Y, Z) shown in FIGS. 2 to 5. The
direction of the vectors X, Y and Z is defined as being the
positive direction. The opposite direction is defined as being a
negative direction.
[0048] In the various drawings, the same reference signs designate
identical or similar elements.
[0049] In reference to FIG. 2, a spacecraft 2 according to the
first embodiment of the invention is in the form of a
parallelepipedic body 4. This body 4 always has the same face
oriented towards the Earth, this face being called the Earth face
6. The face opposite and parallel to the earth face 6 is called the
anti-Earth face 8.
[0050] The face -X, also called East face 10, and the face +X, also
called West face 12, are opposite faces parallel to each other and
perpendicular to the direction of movement of the spacecraft 2.
Communication antennas 14 are generally attached to the faces -X 10
and +X 12. The face -Y, also called North face 16, and the face +Y,
also called South face 18, are two other faces of the body. They
are opposite, parallel to each other and perpendicular to the
North-South axis of the Earth.
[0051] The spacecraft 2 comprises a first radiator 22 and a second
main radiator 24 in order to cool electronic equipment contained in
the body. This electronic equipment not shown in the drawings is
thermally connected to the first and to the second radiator, for
example via heat pipes also not shown.
[0052] The first radiator 22, having a generally parallelepipedic
shape, has four lateral faces 26, an inner main face 28 attached to
the face -Y 16, an outer main face 30 opposite the inner main face
and located on the side of the space outside of the spacecraft. The
inner 28 and outer 30 main faces extend in the plane (X, Y). The
second radiator 24 is identical to the first radiator 22. It will
not be described in detail. It is attached to the face +Y 18.
[0053] In reference to FIGS. 1 and 6, the spacecraft 2 comprises a
first 32 and a second 33 supporting arm extending substantially in
the Y direction, a first 20 and a second 21 solar panel attached to
a distal end of the first 32 and the second 33 supporting arm, and
one or two gear motors 50, 51 suitable for rotating the first 32
and respectively the second 33 supporting arm at a speed
substantially equal to the speed of revolution of the sun around
the spacecraft. Thus, the solar panels 20,21 are aimed at the sun
all day long.
[0054] The first supporting arm 32 has a longitudinal axis (A-A).
The gear motor 50 is suitable for rotating the first supporting arm
32 about the longitudinal axis (A-A). The second supporting arm 33
has a longitudinal axis (B-B). The gear motor 51 is suitable for
rotating the second supporting arm 33 about the longitudinal axis
(B-B).
[0055] Alternatively, a single gear motor is suitable for driving
the first supporting arm 32 and the second supporting arm 33.
[0056] The spacecraft 2 further comprises a first assembly 34 of
slats 36 and a second assemblies 35 of slats 36 attached to the
first supporting arm 32 and to the second supporting arm 33,
respectively, between the body 4 and the first solar panel 20 and
the second solar panel 21. Each assembly 34,35 of slats is
stationary with respect to the supporting arm 32,33 that carries
it. Each assembly 34,35 of slats is rotated by the supporting arm
32,33 that carries it.
[0057] The slats 36 of the assemblies of slats transfer heat. They
are suitable for absorbing solar radiation during the equinox and
transferring, via radiation, the heat generated by this solar
radiation to the first radiator 22 and to the second radiator 24,
as explained below.
[0058] The heat-transfer slats 36 are plates having a very small
thickness of approximately one millimetre or less. They are, for
example, made from a sheet and rigidifying rods attached to a face
of the sheet. The sheet is made, for example, from a polyimide film
designated by the registered trademark Kapton or from graphite
layers. The rods are, for example, made from carbon.
[0059] As visible in FIG. 3, the heat-transfer slats 36 are
attached one above the other. They are superimposed in the Y
direction. A free space e is arranged between two heat-transfer
slats 36 superimposed on one another. The heat-transfer slats 36 of
the assembly are advantageously attached in a frame 38.
[0060] The heat-transfer slats 36 have a flat main face 40, called
absorption face 40, positioned facing the outer face 30 of the
first radiator or of the second radiator 24 and an outer face 42
opposite the absorption face 40. The absorption face 40 of the
first assembly 34 of slats mounted on the face -Y 16 is inclined
with respect to the outer main face 30 of the first radiator by a
dihedral angle .alpha. approximately equal to 23.5.degree..
Likewise, the absorption face 40 of the second assembly 35 of slats
mounted on the face +Y 18 is inclined with respect to the outer
main face 30 of the second radiator by a dihedral angle .alpha.
approximately equal to 23.5.degree.. The opening of said dihedral
angle .alpha. extends on the side of the direction of the incident
solar radiation Is.
[0061] As visible in FIGS. 4 and 6, the value of this dihedral
angle .alpha. corresponds to the maximum angle formed between the
outer main face 30 of the first radiator 22 and the direction of
the incident solar radiation Is.sub.E during the summer solstice
SE. Likewise, this value corresponds to the maximum angle formed
between the outer main face 30 of the second radiator 24 and the
direction of the incident solar radiation Is.sub.H during the
winter solstice SH.
[0062] During operation, during the summer solstice SE, the
direction of the solar radiation I.sub.SE is substantially parallel
to the heat-transfer slats 36 of the first assembly 34, as visible
in FIGS. 4 and 6. Since the heat-transfer slats have a small
thickness, their presence does not lead to a loss of thermal
rejection capacity for the first radiator 22. Almost all of the
incident solar radiation I.sub.SE reaches the first radiator 22.
The first supporting arm 32 pivots about its longitudinal axis
(A-A) (about the Y direction) at a speed equal to the speed of
revolution of the sun around the spacecraft. Thus, the direction of
the solar radiation Is.sub.E is parallel to the heat-transfer slats
throughout the day.
[0063] During the winter solstice SH, the direction of the solar
radiation I.sub.SH is parallel to the heat-transfer slats of the
second assembly 35 of slats attached to the second supporting arm
33 located on the side having the face +Y 18. The presence of the
heat-transfer slats do not lead to heat loss for the second
radiator 24.
[0064] In reference to FIGS. 5 and 6, during the vernal equinox EP
and during the autumnal equinox EA, the direction of the incident
solar radiation I.sub.E extends in the plane (X, Y). This direction
I.sub.E forms an angle of approximately 23.5.degree. with the
median plane of the heat-transfer slats 36. Consequently, the
absorption faces 40 of the heat-transfer slats that are facing the
outer face 30 of the first radiator and the absorption faces 40 of
the heat-transfer slats that are facing the outer face 30 of the
second radiator absorb the UV portion of the incident solar
radiation I.sub.E and are heated. The heat-transfer slats 36 can
thus reach a temperature of approximately 90.degree. C. When the
heat-transfer slats 36 are hot, they radiate this heat towards the
radiator located on the side having the supporting arm carrying the
heat-transfer assembly. Thus, during the vernal equinox EP and
during the autumnal equinox EA, the first radiator 22 and the
second radiator 24 are heated and heat the faces +Y 18 and -Y 16 of
the body. Just like for the summer solstice, the first supporting
arm 32 and the second supporting arm 33 pivot about their
longitudinal axis at a speed equal to the speed of revolution of
the sun around the spacecraft in order for the incident solar
radiation IE to heat the absorption faces 40 of the heat-transfer
slats throughout the day.
[0065] An increase in temperature of approximately 15.degree. C.
can, for example, be achieved using an assembly of twenty-five
heat-transfer slats having a size of 2,300 by 50 millimetres, two
adjacent slats being spaced apart by a distance of 19.9
millimetres.
[0066] Thus, the variations in temperature between the equinoxes
and the solstices are reduced.
[0067] Preferably, the absorption faces 40 of the heat-transfer
slats 36 have a coating having high solar absorptivity in order to
absorb as much solar radiation as possible. They are, for example,
black. A person skilled in the art in the field of thermal
engineering in the space industry chooses a suitable material
according to multiple criteria besides absorptivity. In general the
materials and the chosen coating will have with a solar
absorptivity greater than 0.6.
[0068] Preferably, the first radiator 22 and the second radiator 24
are coated with a non-specular or not very specular material in
order for the radiators to not heat the heat-transfer slats 36
during the solstices by reflecting solar radiation.
[0069] Preferably, the heat-transfer slats 36 are plates having a
thickness of less than one millimetre.
[0070] It should be noted that contrary to louvers, the
heat-transfer slats 36 are not mobile about an axis contained in
their median plane or parallel to their median plane. They are
stationary with respect to the frame and the supporting arm 32 that
carries them.
[0071] Alternatively, the heat-transfer slats 36 have a median
plane inclined with respect to the outer main face 30 of the first
and second radiators by a dihedral angle between 20.degree. and
26.degree..
[0072] Each assembly 34, 35 comprises at least two heat-transfer
slats 36. In each assembly, the main faces 40 of the slats are
positioned parallel to each other. In each assembly 34, 35, the
free space e between two adjacent superimposed heat-transfer slats
is between 0.5 cm and 10 cm for slats having a width of 50 mm.
[0073] The heat-transfer slats 36 of the first assembly 34 are
substantially parallel to the direction of the solar radiation
I.sub.SE during the summer solstice SE.
[0074] The heat-transfer slats (36) of the second assembly (35) are
substantially parallel to the direction of the solar radiation
(I.sub.SH) during the winter solstice (SH).
* * * * *