Issue 10 Volume 41 May 16, 2003

technology R&D program include catalysis, ceramic processing methods, and the design of a separation unit operating under
high pressure. Multiphase materials with maximum ambipolar conductivity will be developed and supported thin film
membranes of promising materials will be fabricated and tested. Conductivity characteristics and hydrogen separation rates
will be determined for selected membrane structures and candidate compositions will be employed in laboratory-scale
high-pressure hydrogen separation units. Information gained during laboratory testing will be used to develop a prototype
hydrogen separation unit and generate a strategy for scale-up.
NTIS
Fossil Fuels; Hydrogen; Gas Mixtures; Membranes; Separators
20030033909 Air Force Research Lab., Edwards AFB, CA, USA
Energy Conversion in Laser Propulsion III
Larson, C. W.; Mead, F. B., Jr.; Kalliomaa, Wayne M.; Feb. 2002; 15 pp.; In English
Contract(s)/Grant(s): AF Proj. 1011
Report No.(s): AD-A410650; AFRL-PR-ED-TP-2002-038; No Copyright; Avail: CASI; A03, Hardcopy
Conversion of pulses of CO2 laser energy (18 microsecond pulses) to propellant kinetic energy was studied in a Myrabo
Laser Lightcraft (MLL) operating with laser heated STP air and laser ablated delrin propellants. The MLL incorporates an
inverted parabolic reflector that focuses laser energy into a toroidal volume where it is absorbed by a unit of propellant mass
that is subsequently expanded in the geometry of the plug nozzle aerospike. With Delrin propellant, measurements of the
coupling coefficients and the ablated mass as a function of laser pulse energy showed that the efficiency of conversion of laser
energy to propellant kinetic energy was ^54\%. With STP air, direct experimental measurement of efficiency was not possible
because the propellant mass associated with measured coupling coefficients was not known. Thermodynamics predicted that
the upper limit of the efficiency of conversion of the internal energy of laser heated air to jet kinetic energy, alpha, is ^0.30
for EQUILIBRIUM expansion to 1 bar pressure. For FROZEN expansion alpha ^0.27. These upper limit efficiencies are
nearly independent of the initial specific energy from 1 to 110 MJ/kg. With heating of air at its Mach 5 stagnation density (5.9
kg/m3 as compared to STP air density of 1.18kg/m3) these efficiencies increase to about 0.55 (equilibrium) and 0.45 (frozen).
Optimum blowdown from 1.18 kg/m3 to 1 bar occurs with expansion ratios ^1.5 to 4 as internal energy increases from 1 to
100 MJ/kg. Optimum expansion from the higher density state requires larger expansion ratios, 8 to 32. Expansion of laser
ablated Delrin propellant appears to convert the absorbed laser energy more efficiently to jet kinetic energy because the
effective density of the ablated gaseous Delrin is significantly greater than that of STP air.
DTIC
Thermodynamics; Laser Applications; Rocket Propellants
20030034688 Air Force Research Lab., Edwards AFB, CA, USA
Predicting the Initial Crack Length in a Solid Propellant
Liu, C. T.; Kwon, Y. G.; Hendrickson, T. L.; Mar 2001; 11 pp.; In English
Contract(s)/Grant(s): Proj-2302
Report No.(s): AD-A410508; AFRL-PR-ED-VG-2001-049; No Copyright; Avail: CASI; A03, Hardcopy
No abstract available
DTIC
Crack Propagation; Solid Propellants; Mathematical Models; Mechanical Properties
20030034696 Air Force Research Lab., Edwards AFB, CA, USA
Energy Conversion in Laser Propulsion
Larson, C. W.; Mead, F. B., Jr.; Jan. 2001; 23 pp.; In English
Contract(s)/Grant(s): AF Proj. 1011
Report No.(s): AD-A410649; AFRL-PR-ED-TP-2001-003; No Copyright; Avail: CASI; A03, Hardcopy
Analysis of energy conversion in laser propulsion is reported and compared to experimental studies of a laboratory scale
propulsion device that absorbs laser energy and converts that energy to propellant kinetic energy. The propellants studied were
air and Delrin, a solid with the composition of formaldehyde H2CO that vaporizes cleanly upon laser irradiation. The Myrabo
Laser Lightcraft (MLL) was studied. It incorporates an inverted parabolic reflector that focuses laser energy into a toroidal
volume where it is absorbed by a unit of propellant mass that is subsequently expanded in the geometry of the plug nozzle
aerospike. The results showed that between 30 and 50\% of the incident laser energy is converted to propellant kinetic energy.
This overall absorption/expansion efficiency was examined in terms of the thermodynamic predictions of conversion of
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