I"

NASA-CR-]91802

Final Technical Report

NAG8-39131 Delivery Order Number 10

HYPERVELOCITY IMPACT EFFECTS ON SOLAR CELLS

Submitted by:

M. Frank Rose

Space Power Institute

231 Leach Science Center

Auburn University, AI. 36849-5320

(205) 844-5894 - Fax (205) 844-5900

Submitted to: NASA

Marshall Space Flight Center

Huntsville, AI.

(NASA-CR-191802) HYPERVELOCITY

IMPACT EFFECTS ON SOLAR CELLS Final

Technical Report, 30 Mar. - 29 Sep.

1992 (Auburn Univ.) 6 p

N93-16680

Unclas

G3/44 0141019
m.tr..o_d_u_r, JJ.o_

One of the space hazards of concern is the problem of natural matter and

space debris impacting spacecraft. This phenomena has been studied since

the early sixties and a methodology has been established to determine the

relative abundance of meteoroids as a function of mass. As the mass

decreases, the probability of suffering collisions increases, resulting in a

constant bombardment from particles in the sub-micron range. The composition

of this "cosmic dust" is primarily Fe, Ni, AI, Mg, Na, Ca, Cr, H, O, and Mn. In

addition to mechanical damage, impact velocities greater than 5 k rrgsec can

produce shock induced ionization effects with resultant surface charging and

complex chemical interactions. The upper limit of the velocity distribution for

these particles is on the order of 70 km/sec.

The second source of particulate matter is due to the presence of man

and the machinery needed to place satellites in orbit. This "man made"

component of the space debris consists of waste, rocket exhaust, and debris

caused by satellite break-up. Most of the particles are small. However as the

size increases, debris purposefully thrown overboard such as garbage and

human waste, combined with paint chips, plastic, wire fragments, bolts, etc.,

become formidable hazards which completely dominate the distribution function

for some orbits. These larger fragments can produce penetration and spalling

of the thick metallic structures associated with spacecraft. Of course, at the

upper limit of the man made contribution is derelict satellites and spent

boosters. While the probability of impact with thesei_,r-ge-r objects is small, it

has been necessary to "move the Space Shuttle" to avoid possible impact. The

calculated debris spectrum as a function of altitude is shown in figure 1.

Figure 1. Space Debris Environment

I • i

lO

I

I

I km

I

I krll

v

I

i0"7 l

I

10-8 I __

I0"2 lo'l 1 lO1 lo2

Diameter (crn)

lo3
The "man-made" contribution to the space debris problem is increasing

and dominates the distribution for some altitudes. The particles most often

encountered is aluminum oxide, associated with fuel residue, and paint chips

and can have a wide range of particle sizes. It has been stated that the design

of spacecraft will have to take the debris evolution into account and provide

additional suitable armor of key components in the near future.

The purpose of this work was to subject samples from solar power arrays,

one of the key components of any spacecraft, to debris flux typical of what it

might encounter in space, and measure the degradation of the power panels

after impact.
Exoerimental

The facility used to conduct the impact tests is a "plasma drag"

hypervelocity (HYPER) accelerator located in the Space Power Institute facility

at the Auburn University. The facility is shown schematically in figure 2.

_ Conlrol / and Oiagnostic$

I '1 IP,oiec,"eSource High CurrenlCapacitor Bank F-1 Chamber DrillTube 'I Target Chamber ]

I 1

Vacuum

Syslems

Figure 2(a). Facility Schematic

POWER

SUPPt.Y

50kV

t00kW

L.&-

So4idDielecuic

c,,_git_ Swi=ch

Relay R /Trigger

0%

T

ExplodingF_

Driver

/

L_._

r'---

RightTul_

Figure 2(b). Current Source Circuit
With this device, particle velocities as high as 15 km/sec have been

measured for particles on the order of 100 microns. For these experiments,

particles as large as 400 microns in diameter were used. The diagnostics used

to characterize the impacts were "streak camera" records, electrical diagnostics

as required and a sub-micron ballistic membrane for measuring the

approximate particle size. Each specimen was scanned for impact events and

the scans recorded on VHS tape for analysis. The sizes of the craters and the

depth of the damage zone was recorded for later analysis with the technical

staff of the Rocketdyne Laboratories. The table below is a listing of the

experiments conducted, the diagnostics used, the impacting material, and the

analysis done for each experiment.

Table 1

SHOT #!

C 19

C 20

C21

C 22

C U

C SS

C S7

DATE TARGET TEST TYPE

2-25-82 CELL 11-219 Passive

2/25/92 CELL 11-221 Passive

2/25/92 CELL 11-232 Passive

2/26/92 FCC-Test I Passive

11/6/92 FCC-Tesl 2 Active

11/S/g2

FCC-TesI 3 Active

11/SR2

TEST DIAGNOSTIC

CELL 11-376 Passive

Streak Camera Olivine

Streak Camera

Streak Camera Numinum Oxide 7(; micron nora. Streak Photo

Plasma; Bias Volts Pre.Test Photo

Streak Camera Aluminum Oxide 122 micron nora.

Plasma; Bias Volts

Streak Camera

PARTICLE TYPE PARTICLE SIZE

Aluminum Oxide 100 micron nom.

Aluminum Oxide

Aluminum Oxide

Aluminium Oxide 122 micron horn.

Pre-Test Photo

40 micron nora. Post.Test Photo

X-Y Streak Data

100 micron nora. X-Y Site Log

Site Physical Data

Site Velocity

100 micron nom.

DATA PROVIDED

Streak Photo

Projectile Size

Velocity Distrib.

Site Video Log

Wdeographs

Spreadsheet

Data Disk

Streak Photo

Pre.Test Photo

Post-Test Photo

X-Y Site Log

Site Physical Data

Velocity Distrib.

Site Video Log

Spreadsheet

Data Disk

Velocity Distrib.

Spreadsheet

Data Disk

Streak Photo

Pre-Test Photo

Velocity Distrib.

Spreadsheet

Dala Disk

Streak Camera

Streak Camera
Results

The analysis of the photocells under illumination was done by the

Rocketdyne staff. In general, the results of this work can be summarized as

follows:

• The velocity range up to 10 km/sec was covered in the impact events

characterized in these experiments.

• The number of impacts on each specimen in this series of

experiments represents several years of space exposure.

• Cover plate damage and some damage to the underlying cells does

take place over the range of velocities investigated.

• On the cable bundles, no arcing to the simulated space plasma was

observed for the potentials used in the experimental set-up.

Extrapolated degradation of a solar power system such as that of the

Space Station is minimal for the range of exposure covered in these

experiments.