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

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Propellant Weight
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-
LACE Constant OWE
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---a- Rocket Constant O WE
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5,000
10,000
15,000
20,000
25,000
30,000
Flight Speed Along Trajectory (ft/sec)
Figure 31. LACE Air-Breathing Rocket Reduces Gross Liftoff Weight by 150 Metric Tons and Uses
Existing Rocket Engines
The LACE or deeply cooled cycle could
also be adapted to operate in the FDL­
7 /Model 176 if it were a first stage to a
two-stage-to-orbit system, 25 as shown in
Figure 32 with a retractable, inward-
turning inlet.26 In this case, there is
another version of the precooled air­
breathing engine concept, called the
KUN cycle, that was invented by V. V.
Balapin. 27 Like the LACE and deeply
cooled systems, the KUN cycle can
significantly reduce the size and weight
Inlet Heal
of a launcher. The KUN™ Deeply Cooled
Exchanger
Turbojet/Rocket Cycle incorporates a
heat exchanger upstream of the
Figure 32. The FDL-7 Class of Vehicles With An
compressor to thermally control the air
Anthony DuPont Variable Capture and a Retractable
Inlet Tested to Mach 5 Employing an Air-Breathing
to the compressor so a lower corrected
KLIN Cycle Rocket
speed of the compressor can be
maintained with the increasing mach number. The cycle also thermally integrates an
expander cycle rocket engine, one in which rejected thermal energy is used to drive the
turbopumps and accessories. The initial cycle calculations have shown good results for
hypersonic vehicle space launcher applications. For mach numbers less than mach 5.5,
the turbojet and rocket operate as a single system providing the required total thrust
for acceleration .
Turbojet
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29