Mariner Mars 1964 failure rates computed for use in reliability predictions and cost allocation

Wright, F. H.

English

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N A T I O N A L  A E R O N A U T I C S  A N D  S P A C E  A D M I N I S T R A T I O N  
Technical Report 32-1036 
Failure Rate Computations Based on 
Mariner Mars 1964 Spacecraft Data 
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J E T  P R O P U L S I O N  L A B O R A T O R Y  
C A L I F O R N I A  I N S T I T U T E  O F  T E C H N O L O G Y  
P A S A D E N A ,  C A L I F O R N I A  
January 15, 1967 
https://ntrs.nasa.gov/search.jsp?R=19670006355 2020-03-16T18:45:40+00:00Z
N A T I O N A L  A E R O N A U T I C S  A N D  S P A C E  A D M I N I S T R A T I O N  
Technical Report 32-7036 
Failure Rate Computations Based on 
Mariner Mars 1964 Spacecraft Data 
Frank H. Wright 
Approved by: 
F. A. Paul, Manager 
Reliability Programs Section 
J E T  P R O P U L S I O N  L A B O R A T O R Y  
C A L I F O R N I A  I N S T I T U T E  OF T E C H N O L O G Y  
P A S A D E N A ,  C A L I  F O  R N I A  
January 15, 1967 
Technical Report 32-1036 
Copyright @ 1967 
Jet Propulsion Laboratory 
California Institute of Technology 
Prepared Under Contract No. NAS 7-100 
National Aeronautics & Space Administration 
Acknowledgment 
The author wishes to express his appreciation to Frank F. Baran and Keith L. 
Emberson for their major contributions to the collection of data used for comput- 
ing the failure rates shown in this report. 
JPf TECHNICAL REPORT 32-1036 iii 
Contents 
1 . Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  1 
II . Basis for Deriving Relevant Failure Rates . . . . . . . . . . . . . .  1 
A . Definitions . . . . . . . . . . . . . . . . . . . . . . . .  1 
1 . Parts failure . . . . . . . . . . . . . . . . . . . . . . .  1 
2 . Random failure . . . . . . . . . . . . . . . . . . . . . .  1 
3 . Relevant failure . . . . . . . . . . . . . . . . . . . . . .  1 
B . Relevant Failure Example . . . . . . . . . . . . . . . . . . .  1 
C . Nonrelevant Failure Example . . . . . . . . . . . . . . . . . .  2
D . Ground Rules and Assumptions . . . . . . . . . . . . . . . . .  2
1 . Equipment coverage . . . . . . . . . . . . . . . . . . . .  2 
2 . Wearout failures . . . . . . . . . . . . . . . . . . . . .  2 
3 . Ten-hour burn In . . . . . . . . . . . . . . . . . . . . . .  2 
4 . Parts considered . . . . . . . . . . . . . . . . . . . . .  2 
5 . Length of time measured . . . . . . . . . . . . . . . . . . .  2 
111 . Ground-Based Relevant Failure Rates . . . . . . . . . . . . . . .  2 
A . Failure Rate Format . . . . . . . . . . . . . . . . . . . . .  2 
1 . Class 1 failure rates . . . . . . . . . . . . . . . . . . . .  2 
2 . Class 2 failure rates . . . . . . . . . . . . . . . . . . . .  3 
3 . Class 3 failure rates . . . . . . . . . . . . . . . . . . . . .  3 
IV . lnflight Relevant Failure Rates . . . . . . . . . . . . . . . . . .  4
V . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . .  7 
Tables 
1 . Failure rates. ground-based tests . . . . . . . . . . . . . . . . .  3 
. . . . . . . . . . .  3 2 . Parts. hours and relevant failures (ground-based ) 
3 . Typical industry failure rates (as used in a contractor 
prediction analysis) . . . . . . . . . . . .  . . .  4 
4 . Prelaunch Mariner IV failure rates . . . . . . . . . . . . . . . .  4 
~ JPL TECHNICAL REPORT 32-1036 V 
Contents (contd) 
vi 
Tables (contd) 
5 . Class 3 postlaunch Mariner IV failure rates . . . . . . . . . . . . .  5 
6 . Total Mariner I V  failure rates . . . . . . . . . . . . . . . . . .  5 
5 7 . Class 3 total Mariner 1964 program failure rates . . . . . . . . . . . .  
8 . Parts, hour- and failure-summary . . . . . . . . . . . . . . . . .  6 
Figures 
1 . Bar graph of total Mariner I V  failure experience . . . . . . . . . . . .  6 
7 2 . Curve representation of Mariner I V  total program experience . . . . . . .  
J P l  TECHNlCAl REPORT 32- 1036 
L 
. 
Abstract 
This report describes the analysis of spacecraft parts-hours, and failure data 
from the Mariner Mars 1964 program. It contains failure rates for transistors, 
resistors, capacitors, diodes, transformers, relays, and coils, using the JPL Prob- 
lem/Failure Reporting system. Failure data origins, ground rules, and definitions 
are also given. 
I P L  TECHNKAL REPORT 32-1036 vii 
Failure Rate Computations Based on Mariner 
Mars 1964 Spacecraft Data 
1. Introduction 
The purpose of this report is to publish Mariner Mars 
1964 failure rate data for reliability predictions and 
risk/cost allocations of future JPL space programs. To 
obtain these failure rates, over 1500 Problem/Failure 
Reports (P/FRs) written on Mariner C were analyzed to 
see if the P/FR data showed relevant failures. Where 
P/FR data were not clear about the relevancy of the 
failure, cognizant engineers were contacted to obtain 
background information. These P/FR's were then jointly 
re-analyzed with the Mariner spacecraft project design 
personnel to verify their relevancy. Subsystem operating 
hours were obtained from cognizant engineers. Updated 
parts lists were also obtained from subsystem engineers. 
Then, to compute parts-hours, the number of parts were 
muitipiled by the operating hours. Tu cjbtsin fai!uic mtes, 
parts-hours were divided into the applicable relevant fail- 
ures. For convenience of presentation, all failure rates will 
be expressed in %/lo00 hr. 
II. Basis for Deriving Relevant Failure Rates 
A. Definitions 
The term relevant failure must be understood fully to 
make the failure rates of this report meaningful, as well 
as useful. Relevant failure is defined as a JPL-peculiar 
version of what is usually considered a random failure. 
Definitions are as listed below: 
(1) Parts failure. This occurs when a part fails to per- 
form under prescribed conditions. The failure is 
due to its inability to perform a satisfactory func- 
tion within a measurable limit. 
(2) Random failure. This type is caused when a change 
takes place in stress levels that exceed strength lev- 
els, revealing latent quality defects, or exposing 
premature wearout due to undetectable material 
weaknesses. 
(3) Relevant failure. This type is defined as a random 
failure, occuring after power turn-on during mod- 
ule, subsystem, and system testing. Excluded are 
failures due to human error, and operational sup- 
port equipment-induced failures. Also excluded are 
failures due to design errors, mishandling, screen- 
ing rejections, faulty workmanship, and early life 
failures (10 hr). 
6. Relevant Failure Example 
A good example of a relevant failure was recorded in 
a P/FR written on October 21, 1964 against the attitude 
control subsystem. During system test at AFETR, the 
JPL TECHNICAL REPORT 32-1036 1 
I 
I Table 
I 
Typical industry failure rates (as used in a contractor prediction analysis) 
0.03 0.023 0.001 0.015 0.2 0.06 0.01 
I I Transistor I Resistor I Capacitor I Diode I Transformer I Relay I coil I 
0.01 18 
0.027 
t I I I I I I I 
0.381 
0.741 
0.01 18" 
0.01 18 
0.027 
I Besides the failure rate table (Table l), two more 
tables are shown. Table 2 shows part hours and failures 
for the various failure rate categories, to allow the purist 
to compute do-it-yourself failure rates. Table 3 shows 
typical industry failure rates, as used by an independent 
contractor for a reliability prediction analysis in Decem- 
ber 1963, and is included for comparison. While the sta- 
tistical basis of Table 3 failure rates is not known, it is 
thought that they are of point estimate origins. All failure 
rates are expressed in /lo00 hr. 
0.1905" 
0.1905 
0.44 
IV. lnflight Relevant Failure Rates 
Getting an accurate count of relevant failures on the 
Mariner IV spacecraft during flight was obviously more 
difficult than during its ground-based assembly and test, 
because more conjecture, simulation, and engineering 
judgment entered into data analysis of inflight problems 
or failure, with failure data collection also becoming a 
problem. Fortunately, an extremely thorough job of 
problem/failure reporting and analysis was done within 
the Mariner project and the supporting divisions during 
the Mariner ZV flight. 
By using the results of this P/FR system a s  a basis of 
failure-occurrence analysis, it appeared that two definite 
part failures occurred during the flight (there are still 
several P/FR's without sufficient information to make a 
failure/no-failure decision). The two definite primary 
failures were a film resistor in the plasma probe and the 
Geiger-Mueller tube in the ion chamber. However, these 
two "definite" failures break down into no relevant fail- 
ures under the ground rules described in Section 11. 
Under these ground rules, analysis definitely indicated 
that the resistor failure in the plasma probe must be 
classified a design failure, and not a relevant failure. The 
Geiger-Mueller tube failure is a borderline case between 
a relevant failure or a wear-out failure, but it makes littIc 
difference because this analysis does not compute failure 
rates for tubes. Therefore, for the seven part groups un- 
der consideration on the postlaunch Mariner ZV, there are 
no known inflight relevant failures. 
This analysis does not use any of the brief inflight data 
from Mariner ZII because the terminal nature of this mis- 
sion precluded the collection of significant data. 
For computing the flight time (from launch date to 
Octobcr 1, 1965) for Mariner ZV, a figure of 7392 hr was 
used. However, while some subsystems worked for all 
this time (e.g., portions of the radio, CC&S, etc.), others 
had only brief activation (such a s  the television, tape 
recorder, etc.) and appropriate operating times for these 
subsystems were used. Compensations were also made 
for that part of the flight electronics that were not 
act i vat cd . 
TYPO 
Class 1 
Point estimate 
Best estimate 
One sided 90% confidence limit 
Class 3 
Point estimate 
Best estimate 
One sided 90% confidence limit 
'One failure assumed. 
Table 4. Prelaunch Mariner IV failure rates 
Transistor 
0.0259 
0.05 19 
0.101 
0.0259 
0.051 9 
0.101 
Resistor 
0.0151 
0.0227 
0.04 
0.0151 
0.0227 
0.04 
Capacitor 
0.055 
0.0733 
0.121 
0.01 83 
0.0366 
0.071 
0.01 18" 0.1905 
Relay 
0.9781" 
0.9781 
2.28 
0.978 1 " 
0.9781 
2.28 
Coil 
8.8476 
1 1.0595 
17.9 
2.21 19" 
2.2119 
5.18 
I 
4 JPL TECHNICAL REPORT 32- 1036 
The rates shown in the following tables are based on 
computations made in this analysis. Table 4 shows the 
failure rate history of Mariner ZV before its launch on 
November 28, 1964. Table 5 shows the failure rate history 
of Mariner ZV after its launch to October 1, 1965. Because 
this is flight configuration hardware, only the Class 3 
failure category applies. Table 6 gives the failure rate 
history of Mariner ZV from first assembly and test to 
October 1, 1965. It combines the failures and parts hours 
of Table 4 and Table 5. Table 7 gives failure rates com- 
puted from a combination of prelaunch Mariner 1964 
Program failure data and the flight data from Mariner N 
that is current to October 1, 1965. 
Type Transistor 
Point estimate" 0.0043 
Best estimate" 0.0043 
One sided 90% confidence limit 0.01 
All failure rates are expressed in %/lo00 hr. Table 8 
shows the various parts hours and failure combinations 
used as a basis for the contents of this section, and allows 
those with stamina to compute variations on the failure 
rates given. Figures 1 and 2 give Mariner ZV failure fre- 
quency in graph form. Figure 1 is a histogram plotting 
failures versus time, while Fig. 2 is a freehand curve of 
the monthly peaks of Fig. 1 which, when logically ex- 
tended, is impressively similar to the well-known re- 
liability "bathtub curve. The dotted lines at the end 
of the curve represent an extrapolation of the expected 
Mariner ZV performance, with the time to wear-out 
unknown. 
Resistor Capacitor Diode Transformer Relay Coil 
0.001 2 0.003 0.002 0.0388 0.1603 0.4035 
0.0012 0.003 0.002 0.0388 0.1603 0.4035 
0.0029 0.0071 0.0047 0.091 0.37 0.94 
TY Pe Transistor Resistor Capacitor Diode Transformer Relay 
Point estimate 0.01 12 0.0009 0.0032 0.002 0.0098" 0.0421 
Best estimate 0.0123 0.001 2 0.004 0.0025 0.0098 0.0843 
One sided 90% confidence limit 0.01 72 0.0022 0.0066 0.0041 0.022 0.1 65. 
Class 1 
Point estimate 
Best estimate 
One sided 90% confidence limit 
Class 3 
Point estimate 
Best estimate 
One sided 90% confidence limit 
failure assumed. 
Coil 
0.1 11:' 
0.1 1 1  
0.258 
Table 6. Total Mariner IV failure rates 
~ ~~ 
Transistor 1 Resistor 
0.0036 
0.0073 
0.0143 
0.0036 
0.0073 
0.01 43 
0.0021 
0.0031 
0.0056 
0.0021 
0.0031 
0.0056 
Capacitor 
0.0078 
0.01 04 
0.0175 
0.0026 
0.0052 
0.0102 
Diode 
0.0017" 
0.0017 
0.004 
0.0017" 
0.0017 
0.004 
Transformer I Relay 
0.0322 
0.0644 
0.124 
0.0322" 
0.0322 
0.074 
0.1377" 
0.1377 
0.315 
0.1 377" 
0.1377 
0.315 
Coil 
1.3651 
1.7064 
2.72 
0.3412" 
0.341 2 
0.78 
~~ ~~ 
JPL TECHNICAL REPORT 32-1036 5 
Table 8. Parts,hour-and failure-summary 
Type 
Prelaunch Mariner I V  part hours 
Postlaunch Mariner IV part hours" 
Total Mariner I V  part hours" 
Total Mariner 1964 part hours" 
Class 1 prelaunch Mariner I V  failures 
Class 3 prelaunch Mariner I V  failures 
Class 3 postlaunch Mariner I V  
failures 
Class 1 total program Mariner I V  
failures 
Class 3 total program Mariner IV 
failures 
Class 3 total Mariner 1964 program 
failures 
"To October 1, 1965 
Transistor 
3,847,480 
23.1 98,442 
27,045,922 
88,741,399 
1 
1 
0 
1 
1 
10 
~~ 
Resistor 
13,203,842 
80,935,046 
94,138,888 
109,3 16,230 
2 
2 
0 
2 
2 
3 
~ 
Capacitor 
5,45 1,111 
32,964.356 
38,415,467 
124,139,330 
3 
1 
0 
3 
1 
4 
~~ 
Diode 
8,411,010 
49,646,268 
58,057,278 
193,807,690 
0 
0 
0 
0 
0 
4 
Transformer 
524,839 
2,576,558 
3,101,397 
10,165,600 
1 
0 
0 
1 
0 
0 
10223 1 
~ 3 , 6 8 8  
725,919 
2,372,226 
0 
0 
0 
0 
0 
1 
Coil 
45.21 0 
247,798 
293,008 
899,430 
4 
0 
0 
4 
0 
0 
TIME 
Fig. 1. Bar graph of total program Mariner IV failure experience 
6 JPL TECHNICAL REPORT 32- 1036 
10 
e -  
Fig. 2. Curve representation of Mariner IV total program experience 
- 
1 I I I t 
- 
- 
V. Conclusions 
This report represents ;i first attempt at parts failure 
statistics and recommendation for a Jlariricr M a r s  
spacecraft rvliability analysis. The various failure rate 
configurations given should have real v:ilue if wisely used 
in relialdity models and studies of future JPL space pro- 
grams. These failure rates illustrate JPL assembly, test, 
and flight experience; they also give ;in approximate 
(juantitative representation of the worth of the parts 
screening program ;md the effectiveness of JPL circuit 
derating techniques. 
W 
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a 
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1 
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I I I I -  0 - - - - -- ---- 
J A N ' 6 4  JUN'64 DEC'64 JUN'65 OCT'65 
Another interesting result of the flight analysis is the 
comparison of the relevant part failures on the Mariner Iv 
spacecraft (no known relevant failures) to the ground- 
which adds significant data to the growing evidence that 
once a spacecraft passes the launch environment, the 
probability of mission success being degraded by random 
failures is greatly lowered, perhaps by severai ordtx > 0:' 
magnitude. This contrasts the belief (held until recently) 
that the random failure frequency in space was about 
equal to that in a well-controlled laboratory environment 
I based experience of this spacecraft (1 1 relevant failures); 
1 on Earth. 
I Significantly, Figs. 1 and 2 show that the dominant 
failure experience period centered on JUIX of 1964 and 
lasted approximately four months. This time period CO- 
incided with the major period of spacecraft testing at JPL 
before shipment of the flight spacecraft to Cape Ken- 
I 
ncdy. Relevant failure frequency became significant 
\vhen this testing began, n i~d  stopped when the flight 
spiiccuxft were shipped to the Cape. This would tend 
to indicate that the greatest incidence of hardware failure 
(not only relevant failures, but failures caused by design, 
workmanship, and human error), will occur during final 
subsystem testing and ful l  systems test, which is ordinar- 
ily the time period when schedule and manpower coii- 
strnints are the most critical. 
It w a s  not possible to make this analysis ;is thorough 
3s originally intended. Therefore, in coilcludiilg this re- 
port, it seems appropriate to mention specific areas not 
accomplished in this analysis that should lie considered 
in future JPL analyses of this type. 
Future studies should probe deeper into failure rate 
analysis of the parts group. As mentioned in Section 2. 
because of priority constraints it was not possible in this 
study to break ;i broad part group down into its subsets; 
e.g., iio ana!j.:;i..: 1.v;~  m:adr-. of the failure frequency of 
power diodes, computer diodes, zener diodes-but just (111 
diodes. This type of generality extended to d l  seven 
part categories. This created a good margin for bias, be- 
cause the application, complexity, and manufacturer of 
various part types often is a good indication of their 
failure rate. For example, reliability analysis on other pro- 
grams has sho\vn zener diodes to fail with greater regu- 
larity than computer diodes, yet this analysis grouped 
these members of the diode family together and it was 
unfortunately not possible to make such fine distinctions. 
JPL TECHNICAL REPORT 32- I036 7 
The relay and coil failure rate given should also be 
considered with statistical doubt. First, due to the diffi- 
culty in accumulating accurate data, relay failure rates 
were based on straight operating time failures. Relay 
actuations were not considered, which is unfortunate, 
because the number of actuations of cycles before failure 
is the best measure of relay reliability. Secondly, statis- 
tically small relay and coil part hour totals were accumu- 
lated due to a low number of these devices on the 
spcecriift, which gave a poor statistical failure rates base 
for predictions (especially true with the cxxprience of 
coils during the Afarincr ZV iinalysis). 
Other vduahlc future spacccraft analyses would cal- 
culate and compare relrvant failure frequencies for 
pirts, subsystems, ;ind systems during bench testing, 
subsystem and system type approvd (TA) testing, for 
flight acceptance (FA) testing, and during flight. An- 
other interesting analysis would explore the part history 
of the relevant part failures on future programs; i.e., how 
many were screened, not screened, hi rel, etc. 
Therefore, the reliability analyses made or recom- 
mended in this report would be considerably enhanced 
if made during future JPL space programs, and not just 
on the spacecraft system, but on all specid mission ele- 
ments brought into existence with it. 
As Mariner ZV continues its dcep spacc orbit around 
the Sun, xlditional parts-hr data has become available 
which will not be shown in this publication. The flight 
experience will be reflected in an updated version of this 
report to be published in early 1968. 
8 J P l  TECHNICAL REPORT 32-1036 


Failure Rate Computations Based on Mariner Mars 1964 Spacecraft Data

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