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Marex Proposal for ISS, TurboFan

Hi All:

Subject:	ISS Amateur Radio Turbo Fan Project
Date:		September 26, 2007
From:		Miles at MarexMG

I am working on several amateur radio project
proposals for the International Space Station.  At the
preset time these are only proposals.

Support from the Amateur Radio community:
Marex needs your help.  We are looking for a company
that can donate their time and effort to the design
and manufacture a few pairs of turbo fan heat sinks
systems for the Kenwood TM-D700 transceiver.  These
heat sinks will then be tested with a TM-D700 to
collect thermal performance data that can be used to
support our theory and update our project proposal. 
ARISS keeps asking, “Can you prove it”.  With a few
sets of custom heat sinks we can prove the theory and
then move on to the next phase of the project.  If the
project is approved we could fly the upgrade kit to


Thermal Issues on ISS:
The temperature inside the space station is between
72-74 F (24C) with a typical internal air-pressure of
14.3 psi.  The shirtsleeve environment is nice and
comfortable for humans, however it is not a conducive
environment for electronics.

In space there is no convection cooling, hot air does
not rise in space (see links before regarding cooling
on ISS).  The lack of convection cooling causes most
electronics to run hotter.  What this means for
electronics, is that you need to design your
electronics to compensate for the loss of convection
cooling when you place the electronics inside the ISS.
 Even if your device, in this case an amateur radio
transceiver, has a built in fan and some heat sink
mass that may not be enough to keep the transceiver
cool enough during normal operations in a zero gravity
environment. Most electronics used on ISS were
specifically designed to be used in this zero gravity
environment; the Off-the-Shelf radios for the Amateur
Radio projects were not modified to compensate for
Zero Gravity.

Thermal Problems with the Amateur Radio station:
On ISS we are currently using a Kenwood TM-D700
transceiver for all of our current Amateur Radio
operations.  This is the third Kenwood that we have
used for manned space station operations.  On the
Space Station Mir, we used the Kenwood TM-V7A and the
TM-733.  Both of the Mir radios had good mounting
locations with plenty of available airflow access. In
December 2003, the Radio on ISS was installed inside a
small table. Unfortunately, this location restricted
airflow to the transceiver.  In September 2006 the
radio was moved outside of the table to a location
next to green table where it is would get better
access to cabin airflow.

The Turbo Fan project:
The new Turbo Fan project proposal will add both
Induction cooling and forced air cooling for a total
of 15-CFM (15 cubic feet per minute or more than 1
cubic meter per minute).  The initial plan calls for
the fans to move air from the back of the radio
towards the front of the radio.  This movement will
enhance the performance of the existing single Kenwood
D700 fan, by drawing out the Hot air dissipated by the
stock fan and expelling this hot air out of the bottom
of the table area.  The additional air movement will
draw in more outside air and will also keep the radios
power supply cooler.

The heat sinks will bolt onto existing screw terminals
that are used for the mobile mounting bracket.  Each
heat sink will have a 1.6” square fan attached to the
back of the heat sink.
The additional installation of the Turbo Fans will
significantly improve the cooling of the D700 and
increase its service life.  The two fans will also
help keep other ARISS hardware under the green table
cooler by providing a larger volume of air flowing
under the table.
The Turbo Fans will improve the ability of the TM-D700
to support higher duty cycle modes such as Cross Band
Repeater and Slow Scan TV.

Do you know of a company that can help?
If so, please contact Marex at wf1fgm@comcast.net

 Pictures from ISS:

The D700 is the black box with the gray heat sink
fins.  It is in-between the two green table sections
on the right hand side.  The Gray box with the 3
connectors is the 28 to 12 VDC power converters.  As
you can see from this actual picture, the D700 heat
sink is blocked from a steady source of cool air. 
There are two mounting screws visible on the side of
the D700.  There is where the new heat sink would be
attached.  The D700 was in this location for
approximately 32 months.  It was then moved out from
under the table to just to the right side of the table
in August 2006.  The outside location may be a
temporary location. There is a desire to stuff the
radio back under the table. Extra space in the space
station is in short supply.

The two heat sinks will be custom cut from a single
block of aluminum.  There will be a Left and Right
side heat sinks designed to match the sides of the
D700.  All edges will be polished smooth to prevent
sharp edges

The fans used on most small radios’ and PC are the
same style 40x40x10mm.  There may even be several of
these types of fans already on ISS, including the one
on the existing D700.  The fans will receive their
power from the external power jack on the D700 and
will be controlled by the D700 power switch.  When the
radios turned on, the fans will be running.  When the
radio is turned off, the fans will be off.

The noise generated by most of these types of fans is
extremely small (29dB).  In a normal office
environment, you need to be really close to the fan,
less than 1 meter to tell if the fan is running.  
Once installed in the Ham table, the crew would not be
able to hear it at all in a quite office setting.

The Heat Sinks are being designed to be shorter than
the D700 and the same height of the D700.  The Heat
sinks will make the D700 approximately 3.1 inches
wider (80 mm).  If space becomes a serious issue, we
can attach only 1 turbo heat sink.



Voltage	12 vdc
Rotation speed		6500 rpm
Current	0.13A or 130mA at 12vdc
Rated Power	1.56 watts maximum
Air flow	7.7 CFM
Noise:		29dB
Bearing type:	Sleeve
Size 		1.57” x 1.57” x  0.39”
		40 x 40 x 10 mm

Pictures of the TM-700 installation on ISS

Power Specifications:
The D700 runs on 12 VDC and draws 500 ma while in
receiving mode.  When it is transmitting, the load
will vary depending on the user selectable transmitter
output values. (Note all values are approximate based
on a 13.8 vdc source)

RF settings for the TM-700 on ISS.
Low 5 watts, 3 amps
Medium 10 watts, 4.5 amps
High 25 watts, approximately 8 amps
Note:  The ISS version of the D700 has been modified
not to exceed 25 watts of RF output.  The Terrestrial
version of the D700 has a high power setting of 50

The Space Station is pressurized to approximately 14
PSI, with a room temperature of between 72-74 F.
The D700 (on earth) typically runs at 88-90 F when
sitting idle in receive only mode (with good
ventilation).  When transmitting at 45% duty cycle,
the radio quickly heats up to 100-102 F (On earth with
good ventilation).

After the heat sinks are installed, additional testing
will be conducted to document the new thermal
properties.  From this data, we can better determine
the recommended duty cycle loads for future projects.


Temperature Issues In space.:

Here is some NASA background links on temperature
control inside ISS.
Staying Cool on the ISS

Fan noise stories

Data from ISS:
At the present time we have no base line data for how
hot this radio is operating in its current location. 
That information will be very valuable for current and
future radio projects. 

Radio Table:
The D700 transceiver is mounted inside the Amateur
Radio table.  This table is approximately 16 x 16
inches L x W, and it also has two tables separated by
approximately 4 inches.  All sides of the table are
covered with an insulating type of green padding. The
D700 transceiver is sandwiched in between the two
table sections.  This leaves 4 small side openings
(16x4” approximate) for air ventilation.  The backside
opening is blocked by the ceiling.  The three
remaining side of the table appears to be open for
some air movement.  As a result of the small confined
space, there is a very limited amount of air
circulation under the table layers.  The D700 also
shares this confined space with the radios UN-fanned
power supply. 

73 Miles WF1F


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