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Post-Challenger Assessment of
Space Shuttle Flight Rates and Utilization
The following 4 assessments were requested by Congressman
Edward P. Boland in a letter dated April 21, 1986, to NASA Acting
Administrator William E. Graham. The request for information is
stated, followed by the response of the ad hoc study panel.
ASSESSMENT ONE
An assessment of the possible flight rate assuming a
baseline of an 18-~onth delay in shuttle operations. The
analysis should be based on the assumed flight rate and
manifest most recently promulgated by NASA.
Note: Subsequent to the request for this report, hASA announced that
the delay would be 24 months from the time of the Challenger accident,
and the following responses are based upon that estimate.
Utilizing the current 3-Orbiter inventory, NASA can sustain a
flight rate--following a transition phase ot approximately 2 years
after resumption of shuttle operations--of 8-10 flights per year
(Appendix B) from the KSC* under the following conditions:
o
o
o
no Orbiter is lost or rendered inoperable,
sufficient logistic support is available to meet the
scheduled manifest with reasonable confidence, and
structural or other system problems requiring substantial,
recurring downtime do not occur.
With a 4-Orbiter fleet, the sustainable flight rate would be 11-13
per year; however, there are additional qualifications. The principal
*The U.S. Air Force announced that the Vandenberg Launch Site would
not be used before 1992. Should it be used for DoD missions
thereafter, the yearly flight rates for either 3- or 4-Orbiter fleets
would be reduced by approximately one.
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constraints to launch rates higher than 8-10 are limits on
launch-processing facilities at KSC, limits on mission operations
facilities and skilled personnel at JSC, additional time demanded by
increased program review and oversight, yet-to-be-defined new safety
rules, need for improvement in crew-training facilities, and necessary
logistic support (Appendix C).
The importance of the -logistics requirements needs emphasis: to
sustain any shuttle flight rate with reasonable continence requires an
adequate inventory of' spares, including line replaceable units (LBUs),
shop replacement units (SRUs), and expendable parts.* Such items must
be available on demand in the shuttle turnaround process. One other
limitation should be mentioned: Columbia (OV 109) does not have the
performance of the other Orbiters. Many of the Department of Defense
(DoD) and NASA payloads require either Atlantis or Discovery, which is
effectively a 2-Orbiter fleet for these payloads.
If structural or system problems do occur--contrary to our basic
assumption--the sustained flight rate will diminish immediately. This
lower rate cannot be calculated because it is dependent upon the
particular mission scenario and the severity of the problem. If
Orbiters were to require downtimes of several months every few years,
outside of planned maintenance, the sustained flight rate for ~
Orbiters would be lower than the 8-10 range. For 4 Orbiters the rate
would be lower than 11-13 per year.
Under special conditions, the 3-Orbiter flight rate might surge to
approximately 12 per year for a limited period of time, if the major
shuttle cargos have standard Payload Assist Module (PANS or equivalent
upper stages, are repeat missions with few flight plan changes, and
are launched and landed at KSC. Any mix of other cargo or missions
such as classified payloads, Vandenberg Air Force Base (VAFB)
-launches, Edwards Air Force Base landings, Spacelab flights,
rendezvous, or first-of-a-kind missions will reduce the rate to less
than 12. For a 4-Orbiter fleet the surge rate may reach 15 flights
per year, with stringent operational limitations such as reasonably
standard payloads and relatively short mission durations.
The most critical assumption in estimating flight rates is that no
Orbiter will be lost or become inoperable for a significant time. The
,
possibility of a loss or irreparable damage to an Orbiter cannot be
discounted. In case of loss, the options are to replace the Orbiter
or to reduce the flight rate proportionately and permanently. To
preclude having a launch capability based on only 2 functional
Orbiters for a period that would be at least 5 years, a replacement
Orbiter will have to be on order by 1987 for delivery in the early
l990s. Procurement of a fourth Orbiter as announced by the President
would fill this need until 1992. Beyond that, some continuing
-
*Line replaceable units are shuttle components that can be replaced on
the line, e.g., on the launch pad. Shop replacement units are shuttle
components that cannot be replaced on the line, but need to be sent
back to the shop or the manufacturer.
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9
production level to provide replacements will be required since an
unutilized manufacturing base will vanish in a very short time.
While maintaining an efficient industrial base implies an order
rate for new Orbiters higher than payload demand suggests (Appendix
C), it is clear that an accommodation between production and
requirements must be reached if replacement vehicles are to be had.
The need for additional Orbiters flay increase in the l990s in response
to Space Station and other demands, and thus may bring supply and
demand into balance. Alternately, the industrial base may function at
somewhat less than optimal conditions with spread out production
rates. Further study of the maintenance of a viable industrial base
is well warranted.
Some concern exists in 3 additional areas that the panel believes
need further study: (1) the adequacy of simply upgrading existing
training flight simulators when additional, more modern equipment may
be required as well, (2) the repeated late addition of payloads to the
manifest at the expense of maintaining schedules, and (3) the nature
of the shuttle processing contract and the possible need for clearer
contractor responsibilities vis-a-vis NASA in quality assurance,
spares planning and acquisition, and design change demands on shuLtl
component designers and manufacturers for reliability and reduced
turnaround costs. Until NASA establishes a complete operating
organization or elects to contract the total function, these
inconsistencies in responsibility will remain a problem.
ASSESSMENT TWO
An assessment of the assumptions made in..
[partitioning] between payloads manifested on expendable
launch vehicles and payloads manifested on the shuttle and
whether such assumptions are reasonable.
e
The following assumptions regarding potential partitioning of
payloads between ELVs and the shuttle were deduced by the panel, based
upon NASA presentations. The panel did not receive any explicit
baseline definitions regarding the partitioning.
It is understood that the manifest for the period from resumption
of shuttle flights to approximately 3 years later will be determined
on a case-by-case basis within classes of payloads (national security,
NASA science and other, and commercial). A number of payloads
originally scheduled for the shuttle could be launched by ELVs if
these boosters were available; however, only the DoD is committed to
build ELVs for this purpose. In the absence of firm shuttle or ELV
manifests, the panel examined NASA assumptions regarding payload
off-loading, commercial satellites, and availability of launch
vehicles.
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Pavload Off-T~oadin~
~ .
.
, .
The DoD has made a major attempt to off-load free-flying payloads
from the shuttle, for example, the Defense Meteorological Satellite
Program (DMSP), Defense Support Program (DSP), MILSTAR, and certain
classified payloads. Further, DoD may off-load certain additional
satellites such as the Defense Satellite Communications System III
(DSCS) and Global Positioning Satellites (GSP) replacements. Looking
into the far future (mid-199Os), relatively few DoD free-flying
payloads will require shuttle launch provided ELVs are available and
operational. NASA estimates only 4 such shuttle-unique DoD payloads
between resumption of flight and 1993. To this must be added SDI
experiments (1 to ~ shuttle equivalents per year beginning in 1989)
and potential SDI deployment later. The DoD seems well on its way to
relieving its total dependence on the shuttle through ELV procurement.
NASA estimates that approximately 22 of its own payloads could be
off-loaded between now and 1993 leaving approximately 110 for shuttle
launch. The panel has no reason to doubt the validity of this
partitioning. However, in the longer-term future, many payloads could
be designed for ELV launch. Based upon the criticality of the
Tracking, Data, and Relay Satellites (TDRS) in supporting other
missions, NASA should seriously consider launching the TDRS by an
appropriate ELV such as the Titan IV. Two TDRSs are presently
contemplated for early shuttle launch.
In reference to the planned manifest, the panel notes that no
action has been taken by NASA to procure ELVs for its payloads. Lack
of funding is one cause for this inaction. Another is the apparent
confusion of responsiblities between the space transportation charters
of the Departments of Commerce and Transportation and NASA. Also NASA
has not as yet stated a policy for partitioning its payloads between
the shuttle and ELVs. It seems true that many people in the space
science community* would prefer ELV launch because of past experience
with shuttle uncertainties and costs. This preference is not yet
being taken into account by NASA. It is important to note here that,
as presently designed, the NASA Space Station alone could require 8-10
shuttle flights per year for deployment and support in the middle
l990s .
Commercial Satellites
-
The commercial satellite situation is confused by existing
contractual commitments for launch by NASA. The assumption is that
shuttle launches of commercial satellites with existing contracts will
continue. It is hoped, but not yet planned, that significant numbers
of ELVs will become available in the future for the commercial
*This is with the exception of scientists involved in some aspects of
earth, life, and astronomical sciences and in space-processing
research.
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market. The competitors for the proposed DoD medium-lift launch
vehicles (NLVs) have indicated these vehicles could be ready by early
1989; however it will be several years after that before new ELVs
become available to users other than DoD. The primary requirement of
commercial satellite users, in addition to a launch reliability of
more than 93 percent (the approximate reliability of past ELVs), is
availability of timely launch. Assuming availability, most commercial
satellite suppliers and operators now express preference for ELVs.
The panel believes that the assumption of availability is open to
question. The economic viability of commercial launch suppliers may
not be decided for many years because of the long transition period
from total shuttle dependence to some combination of foreign and
speculative domestic suppliers.
Also, the longer-term demand for commercial launches is nebulous
at best. At the present, 44 commercial payloads are contracted for
NASA launch; another 46 have made lesser commitments. Though many of
these will fall by the wayside because of the delay and uncertainty,
others will retain their reservation and lobby for shuttle launch if
the contracted costs are maintainted. Still others will move to
Ariane or other foreign launchers. However, demand will decline
because of the difficulties: launch supply and demand will tend to
come into balance. As contemplated today, approximately 15 commercial
shuttle launches are anticipated between resumption of flight and
1993. To the panel, this rate of commercial utilization seems
significantly too low if additional DoD and NASA off-loading to early
ELVs becomes possible.
Availability of Launch Vehicles
. ~
It has been implicitly assumed that launch vehicle production
(whether of shuttles or ELVs) could keep up with demand' regardless of
the mix of shuttle and ELV launches. The matter of shuttle production
and support was addressed earlier. ELV procurement is limited at
present to DoD. Representatives from the launch vehicle industry
indicate adequate numbers of ELVs for DoD, NASA, and commercial needs
could become available, with present or slightly expanded production
facilities within 3 to 4 years of orders. Thus ELV production
capability does not seem to be a limit, at least in the long run, to
future space activities. As for timing, ELVs for the military will be
available within 3 years after the contracts are signed. However,
because of DoD needs, and government budget limitations, it seems
unlikely that ELVs could be available for commercial payloads before
the early 1990s.* Arianespace representatives stated that Ariane is
completely booked until after 1990 as well. Thus, there is a time gap
of several years before a commercial launch capability could be
*It is noted that in September 1986 a commercial company contracted
with Federal Express to launch a private payload in 1989.
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available to meet the needs of commercial payloads, despite adequate
production and launch facilities.
ASSESSMENT THREE
An assessment of the impact on both flight rate and
manifest of the existing 3-Orbiter fleet with no fourth
Orbiter replacement. This assessment should include
manifest requirements for both launch and operation of a
Space Station. This assessment should also be based on the
assumption that the shuttle will fly at least one-third of
the average number of commercial satellites launched over
the manifest period.
As stated in the the first assessment, the panel believes that a
sustained flight rate of 8-10 per year for a 3-Orbiter inventory and
11-13 for 4 Orbiters can be maintained only under the conditions
previously noted. Support of a Space Station requires a robust
shuttle fleet, even were a new Space Station design to reduce launch
requirements. The panel does not consider a 3-Orbiter fleet robust
because of accident possibilities and other needs for downtime. Given
the assumptions presented by the Space Station office, the entire
3-shuttle capability would be absorbed by this project, i.e. a need
for 32 shuttle flights is projected for the initial 3-year
construction phase. However, the construction and operation of the
station is still under study and these estimates may be modified.
Although some ELVs could be used for purely cargo flights, operating
The Space Station adds another requirement, nearly the same weight
must be returned from orbit as was originally launched to orbit in the
operational phase, a requirement not met in ELV designs.
Estimates of the number of commercial satellites that will be
shuttle-launched in the l990s are difficult in today's uncertain
launch and insurance environment. However, NASA has indicated that
some 15 commercial launches will be available between resumption of
flight and 1993. This is about one-third of the 44 contracted
launches. Others beyond contracted payloads number 46. To launch
one-third of all commercial payloads would require 30 launches. This
number is not possible given the current situation. However, a
resolute effort by the federal government to accelerate production,
and procurement of ELVs would allow for more commercial launches in
the period before potential privately supplied launches could become
available. Clearly, there is a need to proceed with ELV procurement
for NASA payloads and for fulfilling contractual obligations to
commercial operators. Competitive pricing of ELV launches with
shuttle and foreign suppliers should be a principal consideration.
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ASSESSMENT FOUR
An estimate, based on available data, of the various
cost trade-offs of the above assumptions.
Due to the many political, financial, and market variables in the
immediate post-Challenger environment, it is not possible to make
detailed cost trade-off analyses at this time. Nonetheless, one
general statement can be made.
Total national space launch costs depend principally upon the size
l
of the nationls space program. Perhaps surprisingly' the total launch
costs are relatively independent of the particular mix between
shuttles, Titan IVs, MLVs and Titan IIs (for example) for a given
total weight to orbit in equivalent shuttle loads (Appendix E). In
other words, policy decisions such AS the long-term commitment to
man's presence in space (Appendix F), the timing and cost of a Space
Station, the nature of the SDI, and the robustness (spares on orbit
and survivability) of national security space systems will have a
greater effect on national launch costs than the shuttle/ELV mix.
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Representative terms from entire chapter:
space station
