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Various concepts for advanced manned launch systems are examined for delivery missions to space station and polar orbit. Included are single-and two-stage winged systems with rocket and/or air-breathing propulsion systems. For near-term technologies, two-stage reusable rocket systems are favored over single-stage rocket or two-stage airbreathing/rocket systems. Advanced technologies enable viable single-stage-to-orbit (SSTO) concepts. Although two-stage rocket systems continue to be lighter in dry weight than SSTO vehicles, advantages in simpler operations may make SSTO vehicles more cost-effective over the life cycle. Generally, rocket systems maintain a dry-weight advantage over air-breathing systems at the advanced technology levels, but to a lesser degree than when near-term technologies are used. More detailed understanding of vehicle systems and associated ground and flight operations requirements and procedures is essential in determining quantitative discrimination between these latter concepts. NomenclatureAl-Li = aluminum-lithium g = acceleration due to gravity, 32.2 ft/s 2 GLOW = gross liftoff weight, Ib H 2 = hydrogen h = altitude, ft LHk = liquid hydrogen LC>2 = liquid oxygen O 2 = oxygen Ti-Al = titanium aluminide T/W = thrust-to-weight ratio t = time, s a.-angle of attack, deg y r = relative flight-path angle, deg A V = incremental velocity, ft/s s = rocket-engine expansion ratio