Bue, Grant

Colunga, Aaron

Makinen, Janice V.

Vogel, Matthew

NASA Technical Reports Server

National Aeronautics and Space Administration
Mini-Membrane Evaporator for 
Contingency Spacesuit Cooling
Janice V. Makinen, NASA JSC
Grant Bue, NASA JSC
Aaron Colunga, Matthew Vogel, Jacobs Technology
TFAWS 2014
August 7, 2014
https://ntrs.nasa.gov/search.jsp?R=20140010656 2019-08-31T20:08:58+00:00Z
Introduction-Advanced PLSS
 A new Portable Life Support System is being developed at NASA JSC.
 Includes new technology development hardware;
• Spacesuit Water Membrane Evaporator for heat rejection
• High-speed ventilation fan
• Primary and Secondary oxygen regulators
• Rapid-Cycle Amine (CO2 removal)
 Integrated PLSS testing completed at a breadboard level in 2011 (PLSS 1.0)
 Packaging the PLSS into ‘backpack’ began in 2013 (PLSS 2.0)
2
PLSS 1.0 Testing
Introduction
 The current Extravehicular Mobility Unit (EMU) utilizes a secondary 
oxygen vessel (SOV) for contingency breathing oxygen and cooling of 
the crewmember during an EVA anomaly.
• Sublimator failure
• Power failure
 The SOV flows high pressure oxygen through the LCVG to cool the 
crewmember.
 Some drawbacks of the SOV include:
• Very high pressure charge: 6000 psi
 Primary oxygen vessel (POV) is charged only to 3000 psi and is 
smaller
• Cannot be recharged on orbit after use—must be returned for service
• Provides only 30 minutes of get-back time
3
Introduction-PLSS 2.0
 During packaging analyses for PLSS 2.0, it became clear that more 
space was needed to package all of the components
 A proposed solution was to eliminate the SOV and replace it with a 
smaller tank, identical to the POV. 
• Rely on new, smaller SOV for contingency breathing oxygen only
• Create an Auxiliary Cooling Loop (ACL), which relies on a small 
membrane evaporator for heat rejection.
 Advantages to identical Primary and Secondary oxygen tanks include;
• More available volume inside of PLSS package
• Component similarity
• Rechargeable on-orbit
4
Auxiliary Cooling Loop Overview
 Auxiliary Cooling Loop consists of;
• Small Membrane Evaporator, Mini-ME, utilizing same technology as 
the primary heat rejection device for the PLSS, the Spacesuit Water 
Membrane Evaporator (SWME)
• Independent pump
• Independent power supply
• Independent LCVG tubing in the vest area only
• Independent feedwater assembly
• Independent controller
 Advantages of the ACL
• Can be recharged on orbit
• Can provide more get-back time
• Completely independent system
5
Auxiliary Cooling Loop Overview
6
 Mini-ME is an evaporative cooler
• 8000 porous microfibers
 300 microns in diameter
Process
 Water in LCVG absorbs body heat while 
circulating 
 Warm water pumped through Mini-ME
 Valve is opened
 Mini-ME evaporates water vapor, while 
maintaining liquid water
• Cools water
 Cooled water is then recirculated through LCVG.
 LCVG water lost due to evaporation (cooling) is 
replaced from feedwater 
Warm water from 
LCVG pumped 
into Mini-ME
Water vapor is exhausted 
to space from Mini-ME, 
removing heat
Cooled water 
is pumped 
back into 
LCVG
Mini-ME
ACL & Mini-ME
 Proposed operation of ACL
• During a contingency event, the crewmember will turn-on the ACL via 
a switch on the Display Control Module (DCM)
• The switch will turn on the independent controller
• The pump will start
• The valve will fully open, exposing fibers to vacuum, rejecting heat
 Goals for first generation of hardware:
• Accommodate a 1200 BTU/hr crewmember metabolic rate
• Provide 60 minutes of heat rejection
• Package into PLSS 2.0—rectangular cross section preferred
 The dimensions for the first Mini-ME were dictated by available volume 
in the PLSS.
7
First Generation Mini-ME
 A rectangular membrane evaporator was designed and constructed in-
house. 
 A clear, acrylic housing was chosen in order to evaluate membrane 
integrity
 The fiber cartridge was constructed with 8000 fibers, utilizing a new, 
layered technique
 Gate valve with small stepper motor
• Gate valve chosen due to volumetric constraints within the PLSS 
volume.
8Mini-ME Fabrication
Preliminary Mini-ME testing
9
Completed Mini-ME unit
 Two units were constructed.
 Preliminary testing results showed heat rejection performance of 95-
110W (325-375 BTU/hr)at 50kg/hr flow rate with a 10 degree Celsius 
outlet temperature.
 Approximately ~10 W of heat leak was observed across the closed gate 
valve
• This could cause fiber freezing and loss of feedwater during system 
standby
 Following preliminary testing, one Mini-ME was installed into the PLSS 
2.0 backpack.
PLSS 2.0
10
PLSS 2.0
Mini-ME (left), RVP SWME (right)
Subsequent Mini-ME Testing
 Following the preliminary testing of Mini-ME, a study was conducted to:
• investigate ideal fiber density and packaging in terms of heat rejection 
• Determine smallest valve throat area needed to reject at full capability
 9 Fiber Density Test Articles (FDTA’s) were constructed with different fiber 
densities and with replaceable valve throat areas.
 Each unit was tested for a total of 24 hours.
 Data from these tests allowed analysts to correlate models to data
 Ideal configuration: 16 bundles of 6 layers (9413 fibers), which produced 
165W of heat rejection with a 55kg/hr flow rate
11
Fiber 
Density 
Test Article 
(FDTA)
Bundle 
Count Layers
Nominal 
Fiber 
Count
2 16 5 7844
5 14 6 8236
1 16 6 9413
3 16 6 9413
8 12 7 8236
6 14 7 9609
4 16 7 10982
9 12 8 9413
7 14 8 10982
Nominal bundle width (in) 1.85
Nominal fiber density (fibers/inch) 53
Nominal fiber exposed length (in) 2.25
Day 4, 0.75 in2 
Orifice Plate, 
10°C Outlet Heat 
Rejection (W)
FDTA Outlet 
Water Mass 
Flow (kg/hr)
Normalized (10°C 
Tout, 55 kg/hr mdot) 
FDTA Day 4, 0.75 in2 
Orifice Plate Heat 
Rejection (W)
127 55.05 127
127 54.95 127
164 54.3 166
158 55.55 156
118 55.2 118
138 54.25 140
158 54.5 159
148 55.2 147
135 54.4 136
FDTA Analysis
 Valve throats of 0.75in2 , 1 in2 
and 4in2 were investigated.
• No difference between 
0.75in2 and 4 in2
 Fiber density and packaging:
• Most data points show that 
fewer layers yield greater 
heat rejection for same fiber 
count
• Strongly suggests optimum 
packaging is higher bundle 
count and fewer layers
• Limits of this approach 
would require additional 
testing
12
115
120
125
130
135
140
145
150
155
160
165
170
175
180
7400 7800 8200 8600 9000 9400 9800 10200 10600 11000 11400
H
e
a
t
 
R
e
j
e
c
t
i
o
n
 
(
W
)
Total Fiber Count
Mini‐ME 2 FDTA Test Heat Rejections Normalized to 10 °C, 55 kg/hr Outlet Water
0.75 in2 Orifice Plate Configuration
5 layer
6 layer
7 layer
8 layer
5 layer?
5 layer?
FDTA
13
Fiber Density Test Article (FDTA)
Forward Work
 The Mini-ME and ACL will be tested as an integrated system in PLSS 
2.0, beginning in September.
 The next generation of Mini-ME hardware (Mini-ME2) is currently being 
designed.
• Goals:
 New valve with 0W heat leak
 More heat rejection (350W)
 Mini-ME2 will be tested independently, and ultimately integrated into the 
next round of PLSS testing (PLSS 2.5).
14
Acknowledgments
 Grant Bue
 Matt Vogel
 Aaron Colunga
 Colin Campbell
 Carly Watts
 Ian Anchondo
15


Mini-Membrane Evaporator for Contingency Spacesuit Cooling

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server