SMALL LAUNCH VEHICLES FOR EOS AND NPOESS

This section covers launch vehicles capable of launching to the Earth Observing System (EOS) and National Polar-orbiting Operational Environmental Satellite System orbits with mass performance capabilities up to and including the Delta II. While the Delta II may be considered excessive for the launch of individual 500 kg payloads (the upper limit of what this report defines as a small satellite), its capacity for launching multiple small spacecraft on a single launch vehicle merits its inclusion. Also, Boeing Corporation (which recently acquired McDonnell Douglas Co.) is developing a downsized version of the Delta II (Delta II-7320) to extend the utility of this reliable launch vehicle. However, this will still be a fairly high-performance launch vehicle with a relatively high absolute cost compared with the alternatives, suitable primarily for medium-sized or multiple small satellites. Within these guidelines, the launch vehicles considered here are the Delta II, Pegasus, Taurus, Athena (previously known as the Lockheed-Martin Launch Vehicle), and Conestoga. Further detail on these launch vehicles is provided in Appendix C, which also addresses the Eagle family of launch vehicles—the Eclipse Express and Astroliner, the PacAstro, and the Kistler booster. These launch vehicles, while all still in development, are included because of their potential for significant cost savings and market impact.

Pertinent data for the U.S. launch vehicles evaluated are presented in Tables 5.1 and 5.2. Table 5.1 summarizes their mass performance to a 700 km polar Sun-synchronous orbit, approximate cost, and performance history; Table 5.2 provides data on their fairing dimensions and launch environments. Table 5.1 also provides data for relevant foreign launch vehicles.

Generally, mission planners look to minimize mission costs. Because absolute launch vehicle costs increase with launch vehicle size and performance, the lowest performance (and hence lowest cost) launch vehicle that accomplishes the mission should be used. Preferably, the mission designer would have a series of launch vehicle options with increments in performance filling the gap between the low-capacity Pegasus and the high-capacity Delta II. Small launch vehicles such as the Pegasus and Athena 1 have limited capacity to put payloads into EOS orbit. However, these launch vehicles can be used for Earth observation missions by supplementing them with spacecraft on-board propulsion to enable them to reach the desired orbit (e.g., the Total Ozone Mapping Spectrometer Earth Probe). This approach is being used, but it results in some increase in spacecraft cost. The development of intermediate-capacity launch vehicles, such as the Taurus XL and Athena 2, helps fill this gap and offers more opportunity to optimize missions.

Fairing size is sometimes another criteria in selecting a suitable launch vehicle for a mission in that it must accommodate the stowed payload. It is preferable that launch vehicle candidacy not be limited by fairing size but by performance to orbit. Thus, most manufacturers are developing larger fairings for their vehicles for added utility. The fairing size for the Pegasus, however, which does impose significant size constraints, is limited by its airplane launcher system.

Figure 5.1 plots the cost and performance data for operational and planned U.S. launch vehicles as the specific cost per unit payload (satellite) mass to the EOS orbit versus launch capacity. For operational launchers, the minimal cost per unit mass to orbit is achieved with the Delta II and increases with decreasing or increasing launch vehicle capacity. The cost per pound penalty is severe for small launchers with payloads under 500 kg. It is this superior cost efficiency of the Delta II, along with its excellent reliability, which makes launching multiple satellites on a single Delta II an attractive alternative to multiple smaller launch vehicles when possible. In fact, early experiences (failures) with new, smaller launch vehicles indicate that reliability is a major concern, as indicated by the success rates shown in Table 5.1. It will probably take several years and more failures before any small launch vehicle achieves the reliability of the Delta II (>95 percent).

   

same time, a major issue is cooperation with and technology transfer to China. Complicating this issue is a policy debate within the administration and the Congress on how to balance competing economic and foreign policy interests with concerns over technology transfer—issues that resonate particularly with respect to China.



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