Title:
ASPEN Revisited: The Challenge of Nuclear Propulsion for ETO
ASPEN Revisited: The Challenge of Nuclear Propulsion for ETO
Author(s)
Weglian, John E.
Olds, John R.
Marcus, Leland R.
McIntire, James
Nelson, Douglas K.
Blevins, John
Olds, John R.
Marcus, Leland R.
McIntire, James
Nelson, Douglas K.
Blevins, John
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Abstract
ASPEN was a study conducted by Los Alamos National Labs in the early 1960s to examine the benefits of using a Nuclear Thermal Rocket (NTR) for Earth-to-Orbit (ETO) single-stage launch vehicle applications. Using the analysis methods and assumptions of the time, this formerly classified study showed that a significant performance potential might be derived from using NTR engines for the final acceleration phase to orbit (air-breathing engines were used to Mach 11). Given the increased NASA interest in low-cost reusable space transportation, the ASPEN concept has been revisited using contemporary design assumptions and conceptual analysis techniques. The present analysis concludes with a more pessimistic view of NTR propulsion for ETO applications. Aerodynamic drag for the ASPEN configuration was found to be significantly more than that calculated in the original study. The resultant vehicle thrust-to-drag ratio is lower than necessary for high acceleration during the air-breathing acceleration phases. In addition, the NTR reactor power requirements are daunting. In most cases, reactor powers over 10 GW are required. Even with very aggressive assumptions (25 percent drag reduction and NTR thrust-to-weight ratio of 10, including shielding) a 500,000 lb gross weight ASPEN-like vehicle was found to only have a payload mass fraction of 1.6 percent. This is significantly less than the 6 to 15 percent payload mass fractions claimed in the original ASPEN study.
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Date Issued
2001-07
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