The Roman Solution: Fixing the Shuttle safety problems at NASA
by Steven Schear
12 February 2003
Since Columbia's untimely destruction the popular media have been filled
with stories about the possible failures of systems designed to assure the
safety of NASA's Space Transportation System (STS). Engineers at NASA
often decry the qualifications and motives of management, especially the
politically appointed. As in most such failures the roots often lie in
unrealistic expectations and human shortcomings.
The Lesson from Challenger
When Nobel laureate Richard Feynman was investigating the Challenger
explosion he received conflicting views about safety from engineers and
management. There were enormous differences of opinion as to the
probability of a failure with loss of vehicle and of human life. The
estimates ranged from roughly 1 in 100 to 1 in 100,000. The higher figures
came from the working engineers, and the very low figures from management.
What were the causes and consequences of this lack of agreement? Since 1
part in 100,000 would imply that one could put a Shuttle up each day for
300 years expecting to lose only one, we could properly ask "What was the
cause of management's fantastic faith in the machinery?"
Management maintained that the higher figures are for unmanned rockets but
since the Shuttle is a manned vehicle "the probability of mission success
is necessarily very close to 1.0." It is not very clear what this phrase
meant. Did it mean it is close to 1 or that it ought to be close to 1? They
went on to explain "Historically this extremely high degree of mission
success has given rise to a difference in philosophy between manned space
flight programs and unmanned programs; i.e., numerical probability usage
versus engineering judgment."
Richard found that the certification criteria used in Flight Readiness
Reviews often developed a gradually decreasing strictness. The argument
that the same risk was flown before without failure is often accepted as an
argument for the safety of accepting it again. Because of this, obvious
weaknesses were accepted again and again, sometimes without a sufficiently
serious attempt to remedy them, or to delay a flight because of their
continued presence.
I posit that, despite the efforts of a generation of NASA engineers and the
implied attention to STS safety from both Congress and succeeding
management, not much has changed in the risks or the manner in which risks
are assessed and important decisions made. And why should it? The basic
Shuttle technology, while incrementally improved since Challenger, is
fundamentally the same. Key incentives to Congress and management have
been left unchanged. The fix is simple: honesty and consequences.
The Roman Solution
Two thousand years ago the Roman Empire built what are unarguably some of
the finest structures. Their roads, bridges and aqueducts were
suburb. Many remain in constant operation with little or no repair. Some
were only recently replaced. How were the Romans able to create such
lasting edifices from then leading edge materials, design and fabrication
techniques?
In Roman times its architects were some of the best paid and most revered
in the empire (perhaps second only to leading gladiators). The invention
of concrete and the perfection of the arch were Rome's greatest gifts to
architecture. Structures using arches often were designed so that
load-bearing parts were in compression against one another and depended on
each other for stability. For arches to be sturdy the stones had to be cut
and positioned precisely. Even minor mistakes could spell disaster. It
was found that due to the arch's nature faulty designs and construction
were almost always immediately apparent. The arch components were held in
place until completion by a sturdy scaffolding system. When the
scaffolding was taken down if the arch stood it would endure. If not,
entire structures often immediately failed. To insure that such accidents
were rare Roman law decreed that architects would stand beneath the
scaffold when it was removed. As a result there were few failures.
I think its time that Congress and NASA treat the Shuttle program as if
they were actuaries with an insurance company. They need to publicly
accept the risks originally calculated by engineers for STS: about 1 loss
per 100 (events may indicated even that figure may even be optimistic). If
both Congress and management continue to tell the public that the STS is
far safer than results have indicated, that the problems can and will be
fixed, and that going forward astronaut lives are much less likely be to be
lost then they should put their money and their lives where their mouths
are. My recommendations are:
1. That Congressmen on Senate Commerce, Science and Transportation
Committee and the House Science Committee be required by Congressional
measure to place a substantial portion of their wealth, including future
retirement benefits, in a trust which is compensated based measured safety
performance of the STS versus the projected safety accepted by Congress
from their NASA management appointees. The rewards or punishments would be
on a steep sliding scale.
2. That all senior NASA management of sound health be required to
participate in a kind of draft in which those randomly selected would be
inducted into the astronaut core and required to fly on missions or forfeit
their positions and retirement. The goal should be that each flight
contains one such manager.
Copyright 2003 Steve Schear
"Reality must take precedence over public relations, for nature cannot be
fooled."
-- Richard P. Feynman
