Directed reflectivity, long life AMTEC condenser (DRC). Final report of Phase II SBIR program[Alkali Metal ThermoElectric Converter] Page: 30 of 33
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Fabrication of DRC cylinders.
Fabrication of DRC surfaces was first carried out as planar arrays because this is a simple geometry to
make. For use on the walls of cylindrical cells, where we expect it to be effective based on the analysis
described above, it is necessary to use a different approach. Clearly this cannot be achieved by wrapping
a planar array around a cylindrical form. The initial step taken, was to produce a CAD drawing of the part
in which all of the right angles could be directly specified, with the constraint that the apices of the corner
cubes must lie on the surface of a right circular cylinder. This was done in AutoCad and the drawings
converted to IGES format so that they could be used to drive an electrodischarge machine (EDM)
automatically. The fabrication was carried out by 3-Dimensional Services s (3-D) on a purchase order.
While the details of the process were kept proprietary by 3-D, it was basically a multi-step process in which
1) a mold was initially EDM cut on the inside of 3 nesting pie shaped sections of a cylinder; 2) this mold
was used to cast a 'positive' mandrel using a low melting alloy - probably one of the Cerro-Bismuth alloys
(Bismuth, lead, tin, cadmium with melting
points well below 100 C); 3) a layer of nickel
(approximately 0.10 mm thick) was then
electroplated onto this mandrel; 4) the cast
object was then heated to melt and remove the
mandrel leaving the finished hollow cylinder
with the corner cube pattern impressed on the
inside (and outside) forming a DRW. In this
way the expensive, EDM cut parts could be
reused multiple times.
3-D made 6 cylindrical shells for us. Two
of these were not usable since they had
deformed edges. For each of the 6, the
surface finish was quite poor by optical
standards, but with the angles made as
required, they should be usable for testing and
for establishing the proof of principle. These
shells remain available for incorporation into
PX style converters. Two of them are shown DRC Ce Cylinders
in the photograph in Figure 28 .
9. Remaining Tasks Figure 28 Nickel Corner Cube Cylindrical Converter Wall Liners.
In order to complete a proof of principle
for the directed reflectivity radiation transfer control strategy, an experimental test of the efficiency gain
possible with the DRW concept should be carried out. This should be done first with a DRW surface
inserted into the colder end of the low pressure region of a standard cylindrical AMTEC converter on which
substantial efficiency data has been or can be obtained. The data obtained in the experiments should then
be compared to the predictions of the analytical models generated in this program. If the experimental results
are in reasonable agreement with the analysis, further experiments and analytical effort would become
worthwhile in the context of high performance AMTEC systems for high value added applications.
Spacecraft power for technical missions to deep space destinations may be the best example of this sort of
application. If the analytical approach is verified successfully it can then be used to investigate the potential
s 3-Dimensional Services, Inc, 2547 Product Drive, Rochester Hills, MI 48309.
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Hunt, Thomas K. Directed reflectivity, long life AMTEC condenser (DRC). Final report of Phase II SBIR program[Alkali Metal ThermoElectric Converter], report, September 10, 2001; United States. (https://digital.library.unt.edu/ark:/67531/metadc717643/m1/30/: accessed April 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.