Department of the Air Force Report, 1996

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Table 11. Number of Failures for All Vehicles (1186 Flights)
Flight
Phase
1
Fail
2
ure-Res
3
oonse Mode
4
5
'NA'
3&4
Tumble
0
0-1
0-2
0-3
0-4
0-5
0
13
13
13
13
13
0
4
4
4
4
4
0
3­
3
3
3
3
3
68
129
161
165
165
0
15
27
28
28
28
0
11
29
38
45
53
1
19
33
40
42
42
Table 12. Date of Most Recent Failure
Response
Vehicle
Mode
Atlas
Delta
Titan
Thor*
1
03/02/65
none
12/12/59
04/19/58
2
12/18/81
none
05/01/63
12/30/58
3
.04/25/61
none
none
07/21/59
4
08/22/92
05/03/86
10/05/93
03/24//64
5
12/08/80
08/27/69
11/30/65
01/24/62
*Last Thor launch was 02/23/65
For the reasons advanced previously, an exponential filter has been used to estimate
relative probabilities of occurrence for Modes 1 through 5 and the fraction of Mode-3
and Mode-4 failures that tumble while the vehicle is thrusting.
The percentage
weightings for various data samples are shown in Table 13 for values of F from 0.980 to
0.999. Because of the large size of the composite sample (1186), the filter-control
constant of 0.98 used previously to estimate absolute failure probabilities for individual
vehicles does not seem suitable for estimating relative probabilities for the individual
response modes. Use of 0.98 would effectively place 98.2% of the total weight on the
most recent 200 tests thus, in effect, eliminating the earliest 986 tests from the solution.
These are the very tests needed to provide an adequate sample of failures from which
to estimate relative frequencies of occurrence of the individual response modes.
9/10/96
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RTI