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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 2l, l986, 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 l8-month 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, NASA 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 rateâfollowing a transition phase of approximately 2 years after resumption of shuttle operationsâof 8-l0 flights per year (Appendix B) from the KSC* under the following conditions: o no Orbiter is lost or rendered inoperable, o sufficient logistic support is available to meet the scheduled manifest with reasonable confidence, and o structural or other system problems requiring substantial, recurring downtime do not occur. With a 4-Orbiter fleet, the sustainable flight rate would be ll-l3 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 l992. 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.
8 constraints to launch rates higher than 8-l0 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-uefined 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 confidence requires an adequate inventory of spares, including line replaceable units (LRUs), 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 (0V l02) 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 occurâcontrary to our basic assumptionâthe 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 3 Orbiters would be lower than the 8-l0 range. For 4 Orbiters the rate would be lower than ll-l3 per year. Under special conditions, the 3-Orbiter flight rate might surge to approximately l2 per year for a limited period of time, if the major shuttle cargos have standard Payload Assist Module (PAM) or equivalent upper stages, are repeat missions with tew 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 l2. For a 4-Orbiter fleet the surge rate may reach l5 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 l987 for delivery in the early l990s. Procurement of a fourth Orbiter as announced by the President would fill this need until l992. 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.
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 may 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: (l) 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 tor clearer contractor responsibilities vis-a-vis NASA in quality assurance, spares planning and acquisition, and design change demands on shuttle 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. 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.
l0 Payload Off-Loading 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-l990s), 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 l993. To this must be added SDI experiments (l to 2 shuttle equivalents per year beginning in l989) 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 l993 leaving approximately ll0 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 (TORS) in supporting other missions, NASA should seriously consider launching the TORS 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-l0 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.
ll market. The competitors for the proposed DoD medium-lift launch vehicles (MLVs) have indicated these vehicles could be ready by early l989; 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 l5 commercial shuttle launches are anticipated between resumption of flight and l993. 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 l990s.* Arianespace representatives stated that Ariane is completely booked until after l990 as well. Thus, there is a time gap of several years before a commercial launch capability could be *It is noted that in September l986 a commercial company contracted with Federal Express to launch a private payload in l989.
l2 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-l0 per year for a 3-Orbiter inventory and ll-l3 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 l9903 are difficult in today's uncertain launch and insurance environment. However, NASA has indicated that some l5 commercial launches will be available between resumption of flight and l993. 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.
l3 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 of the nation's space program. Perhaps surprisingly, the total launch costs are relatively independent of the particular mix between shuttles, Titan IVs, MLVs and Titan Us (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.
