@nyrath Criticisms (3) Like the early 20th century focus on dirigibles aka "airships" following a false paradigm of extending naval traditions to the air, spaceplanes try to extend the paradigm of aeronautics to orbital launch. Reusable VTO&L concepts being dismissed until SpaceX.
@nyrath Criticisms (2b)
III. What the paper writer is envisioning: aerospace vehicles that uses ramjet/scramjet air breathing for a significant part of their performance, like the long-proposed Skylon. VERY difficult to build (21st century and we still haven't done it), and possibly strong limitations on vehicle size and hence resulting payload.
@nyrath Criticisms (2a) "Spaceplane" is covering three or so different concepts here:
I. A gliding reentry vehicle boosted by conventional rocket like the X-37b; convenient for recovery but no real savings in cost.
II. Airplane-shaped rocket stages- 1, 2, or 3-stage designs going back to Von Braun's Ferry Rocket. Increased dry mass, developmental risk associated with weight overruns, and unknown unknowns with high speed and altitude aerodynamics. Includes drop-tank versions like the Shuttle.
@nyrath Okay, my criticisms: (1) "Rockets are terribly inefficient and expensive." The way the military/aerospace contractor paradigm built them, yes. Equivalent to using aircraft carriers as cargo ships. As long ago as the 1970s proponents of "Big Dumb Boosters" pointed out that if you ignored efficiency- squeezing the last iota of performance out of a rocket- and instead focused on minimum construction and operating cost, cost to orbit could be dropped by an order of magnitude.
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