AAWSAP DIRD, Space Access: Where We’ve Been and Where We Could Go, March 2010

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Adding the switchblade wing (see inset photo in Figure 10) provides a reasonable
takeoff speed for all mass ratios (green triangles). This takeoff speed with the
switchblade wing deployed is approximately the landing speed with the wing stowed.
With the wing deployed (blue diamonds), the landing speed is almost constant, since all
of the launcher vehicles have very similar empty-plus-payload weights (operational
weight empty). Then the landing speed becomes very modest, lower even than that of
most commercial transports and military aircraft. With this approach, the switchblade
wing can be either deployed or stowed, and the landing and takeoff speeds can be
essentially equal, adding a degree of operational simplicity. The switchblade wing was
designed with the expectation that the gliders would return with greater payloads than
they delivered. Landing and takeoff speeds correspond to those of current military
aircraft and commercial transports, at least for the lower mass ratios (5 or less).
Whether the switchblade wing is deployed or stowed, a set of solutions exists in which
the landing and takeoff speeds are similar.
Figure 34 begins with a solution map of vertical takeoff launchers, as represented by
the shaded areas in the lower part of the figure. All of these data are for converged
solutions, whereby the mission requirements are met and the mass and volume of each
solution are converged. These solution areas represent the entire propulsion spectrum,
from all-rocket (far right) to advanced air-breathing systems (far left) . These solution
areas are for vertical takeoff and horizontal landing (VTOHL), with a thrust-to-weight
ratio at takeoff (TWTO) of 1.35 and a Kuchemann tau equal to 0.2.
1500
.........
(/)
C:
B 1000
-
.c­
.2>
~
(/)
~
500
....
CJ
3.0
4.0
5.0
6.0
7.0
8.0
payload = 7 tons
WING LOADING
(kg/m2)
610.2
561 .3 \
\
463.7
~
976.3
TWTO =1 .35
~ = 0.200
2.0
9.0
WR Weight Ratio to Orbital
Figure 34. Horizontal Launch Not Practical Unless Weight Ratio is Less Than Four
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