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

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I
UNCLASSIFIED/ /POI\ 8PPl@lsTd:. Ulili Otl! Y
the
u Tube, or uperrube, is somewhat conrrovcrsial.
According co the inventor (Patenl
o. 6,132,823) and to
claims by the company and their quoted rcsul of rescs
conducred by ranfurd Research lnslirute, it reportedly
has an effective thermal conductivicy of the order of J0
co J00 times grearer than cha ofconventional liquid-va­
por heat pipes, and over 30,000 tim
char fan equiva­
lemly sized solid rod of silver. Repons cited also have
indicated puzzling temperature di tribtttions
n. o ur
with these rubes unlike conventional thermal condu ­
cor and liquid-vapor heat pip . 11,e tube al o app ar
to h ve the ability co function at v ry high re.mperatures,
even up ro the melting point of the material used, nd
ro supporrvery high heat .Auxes.
ur cesrs to dare sup­
port the high tempera.cure capabilities in addition co
the high thermal conductivities. However, the thermal
ondu ivity is so high chac accurately measuring the
value i very difficult. We have ther fore acquired nine
10' long uperrubes, 5/16" in diameter, and have er up
a method for decermining the thermal conductivity us­
ing high heat flux, a water cooled ca.lorimcte.r, and a rake
of over 30 carefully ca.librared thermistor . Thi appara•
tus should provide an accurate means ofd rermining the
thermal conductivity, and will also allow us 10 1eck the
high heat flux capabiliiy of ch rube and co
po •
ible puzzling rempe.rarure di rributions.
Figure 17 shows a data sec in which the ccmpe cure
across the length ofa 1O' long cube hear.ed rom the end
and cooled in air is essenrially connanr, wh r s similar
si.ze copper tube would have the tcmpe cure djsuibu­
tion shown in the bocrom curve. Increasing the th rmaJ
conductivicy, k, of che copper by fuctors fr m I 000 to
30,000 shows agreement becween the analysis and the
daca ar 30,000 times chat of the copper, akhough chi is
only a lower limit on the actual condu tiviry. Increas­
ing the fucror even more do s nor produ ea di
mibl
cllange in the curve relative to the data. We have also
tried ocher methods to estimate the high th rmal con­
ductivities we have measured, such
the lngenhouss
rechniq_ue; these results also indicate very high th rmal
conductivities. However, we needed a more accurate
mean than previous tests with free conv
ion o led
rubes with thermocouples, and therefor
d ·sed the
rest appararus shown in Figure I .
The 10 fr Superrubes are heaced by three 2kW oil
rs. Power for the heaters comes from a -ph
2
:\mps.
output power concroUer with two I gs fu ed at 20
For saf-ccy reasons the pow r contr0l1cr and fus
placed in an endosure along with a Watmode" power
meter. A water calorimeter is used ro measure the h~
conducred along rhe Supertube. Fins, hown in Figu
19, are necessary ro transfer the high heal Bux ro d1e
warer; these were fabricaced in such a way that they can
be easily auaclled to the uperrub
using hos clamps.
A1 o the fin design increases turbulence in the flow
through the heat exchanger. Having the turbulent Aow
increases the heat transfer rate inro the warer, and also
di ourages boiling, which could oc ur with rJ1e high
heat .Auxes used.
CnlA l•111ptealb2: Dt£ribulon Afon;Qu l'11oeaidCClflPII' f1,1blful
0111• U.t:S.oi ec,..- and 'ID,,2045 tvptl'l:11
,a-------------
, - -~-
--r--
-r----r--r---,
:(
,c
l3
u
ll
• :.t..1-;a
__,__,_,,
~°!Altl"l
.:.......On
~tk.-•e.u...,m
X ""'
--c:i..-:.....mi-:­
_,_..,.
_____..,,..
~,-c...-.. tC'
Figure 17. Compari.Jon of&enrially Co,uwu Superrube
Tt:mperarure Dfrtribution with 1heort:ticai Dutribution
for a Standard Copper Tithe and Rod. Showing that the
7herma/. Conductivity Must be at Len.st 30,000 limts that
ofCopper.
Figure 18. Fxperimmra/. Appararusfor 10 ft Qu Super­
tubes.
UNCLASSIFIED//FOR OfifilCl.t.k Wlili 9rtLlf
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