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OCR for page 3
Preamble
This report was requested following the Challenger loss and
several months before the President's August 15, 1986, statement
announcing intent to build a fourth space shuttle and to end NASA's
launching of comnerc~al satellites. The assessments requested in the
letter of April 21, 1986, from Congressman Boland to the Administrator
of NASA (Appendix A), in the opinion of the an hoc panel, remain
timely but with a few minor changes in assumptions. The 18-month
stanadown Is replaced by a >4-month standdown. The assumption on
shuttle launching of commercial satellite payloads is modified to
reflect both the near-term shuttle program and manifest and the
longer-term intent expressed in the Presioent's statement.
Early in its deliberations, the ad hoc panel found that it had to
make an assumption regarding whether the national intent was to have a
sustained manned spacetlight program--one in which manned flight was a
regular and continuing occurrence year in and year out--or to treat
the shuttle fleet as a declining resource (Like the Apollo), which in
due course would, through use or accident, diminish to zero. It also
had to decide whether the requested assessments should apply to the
transition period between now and 1991 or to the period
thereafter when both the shuttle and ELV fleets presumably would be
available for launch.
The panel, considering the nature of the requested assessments,
decided to assume a sustained manned flight program and to consider
flight rates in both the post-l991 time frame and the build up before
1991. Discussions of these assumptions can be found in the appendixes.
It is the understanding of the panel that the purpose of the
assessments is to estimate flight rates for a 3- or 4-Orb~ter fleet.
Both fleet sizes are therefore addressed without making any
recommendation on which fleet size is preferable or needed. (It is
clear, however, that the Space Station program has assumed the
existence of a "robust shuttle fleet" of at least the 3- or 4-Orbiter
size, from which its own flight rate demands would have to be
satisfied.)
Congressman Boland's letter also asks for an examination of th
assumptions behind the shuttle manifest for the foreseeable future
This matter raises the issue of expendable launch vehicle (ELV)
availability--for ELVs are the alternative to shuttle launches.
3
OCR for page 4
4
Air Force has recently procured a number of heavy-lift ELVs (Titan
IVs) and is negotiating to begin production of a medium-lift ELV
(MLV). The early production of these vehicles seems likely to be
devoted to DoD payloads. Even were production lines for existing ELVs
to be reactivated immediately, it would take several years for
vehicles to become available. Thus, the availability of ELYs as a
shuttle alternative for other than DoD payloads is likely to be
severely limited until at least around 1990. DANA and commercial
interests have yet to decide to procure ELVs. Thus, particularly in
the coming interim period, hASA and commercial interests that have
contracted for launch service will be depending on the shuttle as the
most immediate launch capability, with corresponding pressure on its
manifest.* For activities requiring the specialized use of people,
the shuttle cannot be replaced -by ELVs.
Before addressing the questions raised by the House Appropriations
Committee, the panel will state certain fundamentals drawn from its
members' association with research, development, operations,
logistics, fleet maintenance, and space activities. These
fundamentals must be recognized it shuttle flight rates and manifests
are to be discussed without misunderstanding.
One fundamental is that in addressing flight rate, there is an
essential distinction between capability and demand. Capability
refers to the number of flights that can be mounted given the
equipment, people, spare parts, and facilities available. Capability
is thus the available supply of launch services. Demand, on the other
hand, refers to the number and configuration of payloads to be
launched. While this distinction is clear enough, there is often
confusion since both capability and demand are discussed in terms of
flight rates.
The panel will address the shuttle capability in terms of the
sustainable flight rate. This is the rate of flights that can be
sustained over a substantial period of time and after buildup from the
cautious resumption of flight subsequent to the Challenger accident.
This buildup will, of course, require some period of time, perhaps 2
years, before the sustainable rate can be reached.
For short periods of time, a launch rate in excess of that
sustainable can be achieved with adequate planning, lead time, and a
minimum of changes. The panel will refer to this as the surge rate,
recognizing that it places severe stresses on people and facilities.
It cannot be sustained for longer than a brief period, approximately 4
months.
The shuttle fleet concept is also fundamental. The fleet Orbiter
inventory is the number of Orbiters on hand at any given time; today
it is 3. The number of schedulable Orbiters is fewer than the
inventory because of a number of fundamental factors, some common with
*The statement by the President, dated August 15, 1986, precludes
continuing launch of commercial satellites by space shuttle. It
appears at this time that certain contracted commitments will be
honored.
6
OCR for page 5
5
fleets of other flight vehicles such as those operated by the Air
Force and commercial airlines (e.g., age of hardware, availability of
spares, damage, normal wear). The panel's experience suggests that
the schedulable Orbiter fleet is smaller than the inventory by almost
one Orbiter. Thus today, the schedulable fleet is only a bit in
excess of 2. Therefore, the Orbiter fleet flight rate in the
remainder of this report will be calculated on that basis. The
reasons for this discounting of the Orbiter inventory arise from
essential scheduled maintenance of the flight articles and the
possibility of damage or needed modifications to an Orbiter that would
keep it or the whole fleet out of service for a significant period.
Reliable, sustainable flight rates hinge upon other factors as
well. Underfunded logistics has been a recognized problem for the
shuttle program in the past. Today there is still not an adequate
complement of spares on hand. This has necessitated cannibalization
to keep the fleet flying and has lengthened the turnaround interval
for individual Orbiters. In this report the panel attempted to
estimate sustainable flight rates based on certain conditions, e.g.,
adequate spares, logistics, and all the facilities needed for
turnaround and training. These conditions will not be necessarily
satisfied under programs now in place at NASA. If they are not, a
further decrease of sustainable flight rates would be in order.
Another fundamental concern is the industrial base for the
manufacture of Orbiters. Because there is a sufficient probability of
an Orbiter-involved accident over the operational lifetime of the
Orbiter fleet, the capability to produce and repair Orbiters should be
maintained. Without it, there will be no viable shuttle fleet. With
a small number of flight articles, such as the inventory of Orbiters,
no management can sustain a reliable flight schedule since
contingencies and new requirements will surely arise from
unanticipated events. In other words, the partial equivalent of a
contingency Orbiter (one available within a time period that would not
seriously disrupt schedules, perhaps 2 years at maximum) should be in
the construction process. This is consistent with the President's
declaration for a fourth Orbiter and with the panel's judgment that
over a period of years (15-20) there must be replacements available
because of possible Orbiter wearout (there are no reliable statistics
at present on Orbiter life)* or irreparable damage in an accident.
There have been suggestions that a new-technology reusable launch
vehicle is in prospect for the 1990-2000 time frame. Even then, any
such vehicle is likely to be shuttlelike. Barring an unforeseen, new,
space initiative, the panel believes that the shuttle fleet, with
improvements, will be required until at least the year 2000 and
probably well beyond if the United States is to have a sustained
manned space program.
*Regarding wearout, it is well to note that the Orbiter is stressed
near its design limits each time it is launched and returns to Earth.
An ordinary airliner is rarely, if ever, so stressed.
6
OCR for page 6
6
On the demand side of shuttle launches, the situation is quite
fluid. An important point is that the payload backlog from today's
extended launch standdown is not as large as it may appear to be.
Many payloads now listed will not be launched at all since they will
have missed a window of opportunity. Lack of reliable launch
schedules and available insurance for payloads will depress not only
future demand. but also the backlog. Just how large this effect will
The Drincinal point is that supply and
be is difficult to judge.
tend ~
r ~ rid
demand will always tend to come into balance.
As launches using shuttles resume, there will be a buildup phase
before reaching a sustainable flight rate. This report comments on
both chases halt HOPE not attempt to evaluate in detail the buildup
i t ; a! ~ ~ a; I ~ ~ ~ ~ 1—~ ~ ~ _ ~ ~ ~ I ~ ~ ~ ~ ~
phases but does ~ r
operations. However, it is evident that a period of caution will be
prudent regardless of the apparent demand for launches and the
unavailability of ELYs. Present NASA planning appears to reflect this
philosophy.
6
Representative terms from entire chapter:
flight rate
