Capacitor sandwich structure containing metal sheets of known thickness for counting penetration rates of meteoroid

Davison, E. H.

English

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REPLY TO 
ATTN OF: GP 
NATIONAL AERONAUTICS AND SPACE AD 
WASHINGTON. D.C. 20546 
October 16, 1970 
TO : USI/Scientific & Technical Information Division 
Attention: Miss Winnie M. Morgan 
FROM z GP/Office of Assistant General 
Counsel for Patent Matters 
SUBJECT: Announcement of NASA-Owned 
U,S, Patents in STAR 
In accordance with the procedures contained in the Code GP 
to Code US1 memorandum on this subject, dated June 8, 1970, 
the attacked NASA-owned U.S, patent is being forwarded for 
abstracting and announcement in NASA STAR, 
The following information is provided: 
U,S. Patent No. 
Corporate Source Lewis Research Center 
Supplementary 
Corporate Source 
NASA Patent Case No,: XLE -0 12 46 
Enclosure: 
Copy of Patent 
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3 
METEOROID SENSING APPARATUS HAVING A COINCIDENCE NETWORK 
CONNECTED TO A PAIR OF CAPACITORS 
Filed Jan. 4, 1963 
P 
INVENTOR 
A'TTORNEUS 
38 ited States Patent 
3,324,388 
METEOROID SENSING APPARATUS HAVING A 
COINCIDENCE NETWORK CONNECTED TO A 
PAIR OF CAPACITORS 
Elmer H. Davison, North Olmsted, Ohio, assignor to the 
United States of America as represented by the Ad- 
ministrator of the National Aeronautics and Space Ad- 
ministration 
Filed Jan. 4, 1963, Ser. No. 249,537 
4 Claims. (Cl. 324-61) 
The invention described herein may be manufactured 
and used by or for the Government of the United States 
of America for governmental purposes without the pay- 
ment of any royalties thereon or therefor. 
This invention relates to apparatus for determining 
meteoroid penetration of space vehicles, and more par- 
ticularly, to  an improved sensor for making direct meas- 
urements of meteoroid damage by recording the pene- 
tration rates of particles through known metal thicknesses. 
Various devices have been proposed for mounting on 
satellites to determine the presence of meteoroids in outer 
space; for example, pressure capsules have been used 
which lose pressure when punctured to activate a switch. 
Another device utilizes a wire or foil grid which has an 
electrical continuity that can be disrupted by a particle 
impacting the grid or penetrating a protective cover over 
the grid. Such devices have been satisfactory where self- 
storing ability is of prime importance to enable the sensor 
to be interrogated at any time. ,However, these devices 
have a disadvantage of not being able to record every 
penetration. 
This prablem has been solved by the apparatus of the 
present invention which inchdes a sensor having a sand- 
wich type construction with a centrally disposed metal 
sheet of known thickness that is electrically grounded. A 
layer of dielectric material covers each surface of the 
metal sheet and a film of metal is deposited on each di- 
electric layer to form a pair of capacitor assemblies. A 
coincidence counting technique is employed to determine 
when a penetration of the sandwich occurs. As a particle 
passes through the sandwich, each capacitor assembly is 
discharged in turn. If two voltage pulses arrive at a diode 
within a given time interval, a pulse is permitted to pass 
and is counted as a penetration. 
It is, therefore, an object of the present invention to 
provide an improved apparatus for determining the 
presence of meteoroids in space which combines simpiic- 
ity of construction with ruggedness. 
Another object of the invention is to provide an im- 
proved apparatus for determining meteoroid damage in 
space vehicles which is inexpensive to manufacture and 
asdaptable for use in various space applications. 
A further object of the invention is to provide an im- 
proved micrometeoroid sensor which counts only the 
punctures which penetrate the entire sensor. 
Other advantages of the invention will be apparent 
from the specification which follows and from the draw- 
ings in which like numerals are used throughout to iden- 
tify like parts. 
In the drawings: 
FIG. 1 is a vertical sectional view through a portion of 
an improved meteoroid sensor constructed in accordance 
with the invention, and 
FIG. 2 is a schematic view showing the improved 
meteoroid sensor and its coincidence counting circuit. 
Referring now to the drawings there is shown a sensor 
Panel 10 for ascertaining the presence of micrometeoroids 
in space and for evaluating the possible damage which 
might be caused by such objects. The sensor panel 10 is 
of the capacitor type and is connected to a suitable detect- 
ing circuit 12 of the diode logic type as shown in FIG. 2. 
The circuit 12 includes a silicon solar cell-battery com- 
bination 14 for supplying the desired potential to the 
sensor 10, and the solar cells are mounted on the surface 
of an instrumentation package carried by a satellite or 
other space vehicle. 
According to the present invention the sensor 10 com- 
prises a sandwich type construction forming a pair of 
capacitors 16 and 18 that are charged by the power 
source 14. The sensor 10 includes a ground plate 20 in 
the form of a thin metal sheet having a known thickness 
lo and layers 22 and 24 of a dielectric material are bonded 
to opposite surfaces of this metal sheet. These layers 22 
and 24 are very thin and preferably comprise sheets of 
Mylar. However, it is also contemplated that the dielec- 
tric layers 22 and 24 may be a vapor deposit of silicon 
Aluminum films 26 and 28 engage the outer surfaces 
of the die!ectric layers 22 and 24 respectively, and these 
films are vapor deposited. The sensor IO is temperature 
controlled by using a thermal control coating 30 com- 
' O  prising a coating of silicon monoxide or other suitable 
material over the vapor deposit of aluminum 26. This 
combination of A1 plus S i 0  limits the maximum tem- 
perature of the sensor 10 by controlling the ratio of solar 
25 absorptivity to low temperature emissivity. Fluctuations 
from the maximum temperature to much lower temper- 
atures can be tolerated, but it is necessary to limit the 
maximum temperature. 
The resulting sandwich is quite thin, and can be folded 
or rolled for compactness during the launching of the 
space vehicle. For example, sensor panels 10 have been 
successfully tested in which the ground plate 20 has a 
thickness in the range between approximately 1 and 10 
mils while the dielectric layers 22 and 24 are Vi mil thick 
35 Mylar sheets. The aluminum films 26 and 28 are vapor 
deposited to a thickness of about 1,000 Angstroms. A 
typical thermal control coating 30 has a thickness in the 
range between about 1,000 Angstroms to about 10,COO 
Angstroms, depending upon the maximum temperature 
Because of the extreme thinness of both the aluminum 
films 26 and 28 as well as the dielectric layers 22 and 24 
penetration of the entire sandwich corresponds, in effect, 
to penetrations of only the metal, and it is possible to 
45 apply an effective coincidence counting technique to the 
sensor 10 because the complete penetration of the entire 
sandwich occurs in less than a microsecond. Also by 
using the coincidence circuit arrangement, only those 
punctures that penetrate the entire thickness of the sensor 
5o 10 are recorded, and this arrangement eliminates counts 
resulting from discharges due to other causes such as the 
aluminum vapor deposit burnoff when the dielectric is 
punctured or breakdown of the dielectric because of 
minor flaws. 
A further advantage of this type of construction is that 
both sides of the metal surface exposed can be effective 
for measuring penetration if it is so desired. The sensor 
panel 10 may act as its own structural support Which, 
when both sides are utilized for penetration measurement 
as in the aforementioned embodiment, reduces the weight 
In operation, the capacitor assemblies 16 and 18 are 
charged through resistors 32 and 34 respectively by the 
solar cell power supply 14 in the battery portion of the 
65 circuit 12 so that the stainless steel ground plate 20 has a 
negative charge. In a typical sensor panel 10 in which the 
various components have the aforementioned thicknesses, 
the potential of each of the aluminum layers 26 and 28 is 
raised to approximately 100 volts. The capacitor assem- 
As a particle, such as a micrometeoroid M shown in 
FIG. 1, passes through the sensor 10, each capacitor 16 
5 
l5 monoxide or other suitable vapor deposited coatings. 
4o requirements. 
55 
6o per unit area exposed to  a minimum. 
7o blies 16 and 18 have a capacitance of from 1 to 2 mf. 
3,324,3 88 
3 
and 18 is discharged in turn, and if two voltage pulses 
arrive at a diode 36 in the counting circuit 12 in a given 
time interval, a pulse is permitted to pass through diodes 
38 and 40 to a bistable multivibrator 42 whereupon it is 
recorded on a counter 44. The diodes 36, 35 and 40 are 
preferably silicon; however, a zener diode may be sub- 
stituted for the pair of silicon diodes 38 and 40. The 
multivibrator 42 is capable of operating under space en- 
vironment conditions and consumes less than 100 micro- 
watts of power. 
In the situation where the micrometeoroid M does not 
pass through the entire sandwich but only discharges the 
capacitor assembly 16 for example, the resulting dis- 
charge of a capacitor 46 sends a pulse along the circuit 12 
through a resistor 48 which is not passed by diode 36. 
Likewise, if the micrometeoroid M strikes the sensor 10 
from the opposite side and discharges only the capacitor 
assembly 18, the resulting discharge of a capacitor 50 
similarly sends a pulse along with the circuit through re- 
sistors 52 and 54. Because the resistance of the resistor 
54 is much greater than that of the resistors 48 and 52 
only a very weak signal reaches the diode 38. This signal 
is not strong enough to be passed by the diodes 38 and 40 
that are in series. 
While only one embodiment of the invention has been 
disclosed and described, various modifications may be 
made to the disclosed structure without departing from 
the spirit of the invention or the scope of the subjoined 
claims. For example, it is contemplated that the counting 
circuit 12 may be adapted to count separately the par- 
ticles that penetrate only one condenser assembly 16 or 
18 to obtain added information on much smaller particles 
than those required for complete penetrations. 
What is claimed is: 
1. Apparatus for determining the presence of meteor- 
a metal sheet having a thickness in the range from 1 
to 10 mils between opposed surfaces, 
a one-quarter mil thick layer of dielectric material in 
contact with each of said opposed surfaces, 
a vaporized aluminum layer having a thickness of 
about 1,000 Angstrom units on each dielectric layer, 
said aluminum layers and said metal sheet forming 
with said dielectric layers a pair of capacitors the 
penetration of which corresponds to the penetration 
of only said metal sheet, 
means for charging said pair of capacitors, each of 
said capacitors being discharged when penetrated by 
a meteoroid whereby a pair of electrical pulses is 
generated by the passage of a meteoroid through 
said metal sheet, 
a coincidence network electrically connected to said 
pair of capacitors for receiving said pair of pulses, 
and 
recording means connected to said network for re- 
ceiving a single pulse therefrom generated by said 
pair of pulses arriving thereat within a predeter- 
mined short time interval. 
2. Apparatus for determining the presence of meteor- 
oids as clamed in claim 1 inclusding 
oids comprising, 
5 
10 
15 
20 
25 
30 
35 
40 
4 
a thermal control coating covering the vaporized alumi- 
num layer to limit the maximum temperature of the 
capacitors by control!ing the ratio of solar absorp- 
tivity to low temperature emissivity. 
3. Apparatus for determining meteoroid damage to 
a pair of capacitors positioned on the space vehicle in 
means for charging said pair of capacitors, 
each of said capacitors being discharged by the pene- 
tration thereof by a meteoroid whereby an elec- 
trical pulse is generated, 
a coincidence network electrically connected to each 
of said capacitors for receiving said e!ectrical pulses 
and generating a single pulse in response to the 
receipt of a pair of substantially simultaneous elec- 
trical pulses generated by the substantially simul- 
taneous discharge of both said capacitors by the 
penetration thereof by a meteoroid, and 
recording means for counting said single pulses as 
meteoroid penetrations. 
4. Apparatus for determining meteoroid damage com- 
a pair of capacitors having a common ground plate 
positioned to be struck by meteoroids, 
means for charging said pair of capacitors, each of said 
capacitors being discharged when penetrated by a 
meteoroid whereby a pair of substantially simul- 
taneous electrical pulses is generated by the passage 
of said meteoroid through said common ground 
plate, 
a coincidence network electrically connected to said 
pair of capacitors for receiving said pair of simul- 
taneous electric pulses and passing the same as a 
single pulse, and 
recording means connected to said coincidence net- 
work for receiving each of said single pulses there- 
from and counting the same as a single penetration 
of said common ground plate. 
space vehicles, said apparatus comprising, 
close proximity with one another, 
prising, 
References Cited 
UNITED STATES PATENTS 
45 2,703,857 3/1955 Engelhardt _ _ _ _ _ _ _ _ _  317-261 
2,984,745 5/1960 Scherbatskoy _ _ _ _ _ _  250-71.5 
3,004,735 10/1961 Kinard _ _ _ _ _ _ _ _ _ _ _ _ _  244-14 
3,004,763 10/1961 Knapp _ _ _ _ _ _ _ _ _ _ _  273-102.2 
50 3,159,029 12/1964 Ruderman _ _ _ _ _ _ _ _ _ _  73-170 
3,222,596 12/1965 Meyer et al. _ _ _ _ _ _ _ _ _  324-70 
FOREIGN PATENTS 
2,944,250 2/1960 Outt _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  73-170 
58,159 8/1946 Netherlands. 55 
WALTER L. CARLSON, P&nary Examiner. 
W. H. BUCKLER, E. E. KUBASIEWICZ, 
Assistant Examiners. 
00 


Meteoroid sensing apparatus having a coincidence network connected to a pair of capacitors Patent

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