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1
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Transfer Rate of Moisture from Bath Towel to Human Skin During
Hyper & Microgravity Conditions
Engr. Dr. Mohd Harridon bin Mohamed Suffian
1
, Mohd Helmy bin Hashim
2
, Muhamad
Zaim bin Ismail
3
, Muhammad Zaim bin Mahd Nor
4
1
Universiti Kuala Lumpur, Malaysia mdharridon@unikl.edu.my
2
National Space Agency of Malaysia (ANGKASA) helmy@angkasa.gov.my
3
Universiti Kuala Lumpur, Malaysia
4
Universiti Kuala Lumpur, Malaysia
Abstract
The cleaning process in space involves the usage of bath towel. The bath towel would
function in zero gravity in space. It would transfer moisture to the human skin. This is
the process that astronauts go through. We are interested upon the rate of transfer of
moisture from the bath towel to the human skin during microgravity condition as this
would aid in the process of producing a more effective bath towel to be used by
astronauts. We had performed several parabolic flight cycles and results were obtained
during hyper and microgravity conditions which gave us an opportunity to make
comparison. Comparisons with 1G data were also made.
2
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Introduction
The team performed several parabolic flights during the concourse of 2 days over the
airspace of Nagoya in order to collect data in hyper and micro gravity conditions. During
the first day, data from 10 parabolic cycles were collected. During the second day, data
from 9 parabolic cycles were collected.
The parabolic flights were performed using a Gulfstream Aircraft owned by Diamond
Air Services (DAS). Collaboration between the National Space Agency of Malaysia
(ANGKASA), Japanese Aerospace Exploration Agency (JAXA), and Universiti Kuala
Lumpur enable the team to perform the parabolic experiments. Each parabolic flight
gave 20 seconds of microgravity condition which is an ample time to record the results
of moisture transfer.
Schramek in his paper stated that the absorption of water for a particular towel
depends upon yarn material, yarn type and fabric construction [1]. For our experiments,
we constrict ourselves to only 2 types of towel, thus designating the towel as the control
parameter. The corresponding section details out the characteristic of the towels of our
experiments.
We also had positioned our towels at horizontal and vertical positions. This gave us a
wide breadth of observation on whether orientation plays a role or not in propagating
the transfer rate of moisture. We ran through several papers which were particularly
fond of using the horizontal setup. This gave us precedents of data (horizontal in nature
and in 1G) which we could compare upon. Masoodi in his experiment used the
horizontal setup to investigate the absorption rate of certain towels [2]. Ours in
different as we were also actuating the experiment in hyper and microgravity
conditions in contrast to 1G as performed by Masoodi. Nevertheless we will take his
experiment as a platform for comparison
Governing Equation
We are dealing with the transfer of fluid from one body to another. We measured the
rate of transfer via the transfer of mass in a particular time and area. We designated the
area as 1cm
2
as this is the “best” area captured by our sensors. The sensors captured the
readings every one second.
Washburn Equation, which is shown below, governs our experiments.
L
2
= ( γ d t ) / ( 4 µ )
L is the distance a liquid has travelled in time t , γ is the surface tension of the liquid, d is
the pore diameter, and µ is the liquid viscosity. This can be re-written in terms of the
mass (M) of fluid absorbed, the permeability, K , and driving pressure ΔP.
3
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
M = ρ T W √(2K ΔP/ µ ) √t
T and W are the thickness and width of the porous material and ρ is the liquid density,
and the relationship of fluid absorbed vs. time is a square root relationship for a one-
dimensional linear flow [3]. Our experiments measured the values of M. All other
parameters of the equation are controlled parameters. We have a simplistic view and
postulated that a change in gravitational value would affect the driving pressure ΔP,
thus altering the value of M. Pressure as equated by (mass * gravitational
acceleration)/area and (mass * gravitational acceleration * height) comprises of the
gravitational component [4][5].
We however did not consider radial absorption as it is not within our scope to measure
how fast the moisture spread at a particular area. We concentrated upon our objective
of measuring transfer between 2 separated bodies.
Experiment Apparatus
The primary structures are 2 plates at horizontal and vertical positions. Figure 1 shows
the setup.
Figure 1. Horizontal & Vertical Plate
Both plates are infested with holes which bleeds fluid when a switch is actuated. Towels
are attached to both plates and an artificial skin is attached to each towel. The sensors
are clad throughout the artificial skin. The skin is shown in Figure 2.
4
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 2. The Artificial Skin
The skin that we used mimics the skin of a human to a certain degree. It is a spandex
made of polyurethane which exhibits almost human like characteristics [6]. Table 1
gives details of the skin.
Table 1
Mechanical / Physical
Properties
Artificial Human Skin
(Polyurethane)
Tensile Strength (LW)
100,000
psi
Flexural Strength (
LW
)
100,000 psi
Interlaminar Shear
7,500 psi
Bearing Strength (LW)
45,000 psi
Water Absorption
0.3 % Max
Density
0.07 lb/in
3
Notched Izod Impact (LW)
78
ft
-
lb/inch
Our towels are of 2 types. They differed in several categories. Table 2 shows the details.
5
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Table 2
Towel Type 1
Towel Type 2
Hp
4.9
5.7
Density, Yarn/cm
(Weft)
20
17
Density, Yarn/cm
(Warp)
28
24
Porosity (ratio)
0.56
0.38
Experiment Procedures
The team was given 2 days of parabolic flights. On the first day, 10 readings were
recorded where each reading was recorded each parabolic cycle and towel type 1 was
used. On the second day, 9 readings were recorded where each reading was recorded
each parabolic cycle and towel type 2 was used. Table 3 gives details on the
experiments.
Table 3
Towel Type 1
Towel Type 2
Day
First
Second
Horizontal Position
1
st
, 2
nd
, 3
rd
, 4
th
, and
5
th
parabolic cycle
1
st
, 2
nd
, 3
rd
, 4
th
, and 5
th
parabolic cycle
Vertical Position
6
th
, 7
th
, 8
th
, 9
th
, and
10
th
parabolic cycle
6
th
, 7
th
, 8
th
, and 9
th
parabolic cycle
Anomalies
Vertical Position (8
th
and 9
th
parabolic
cycles)
Horizontal Position (4
th
and 5
th
parabolic cycles)
Microgravity Reading
1
st
, 2
nd
, 3
rd
, 4
th
,
5
th
,
6
th
, 7
th
, 8
th
, 9
th
, and
10
th
parabolic cycle
1
st
, 2
nd
, 3
rd
, 4
th
,
5
th
,
6
th
,
7
th
, 8
th
, and 9
th
parabolic
cycle
Hypergravity Reading
1
st
, 2
nd
, 3
rd
, 4
th
,
5
th
,
6
th
, 7
th
, 8
th
, 9
th
, and
10
th
parabolic cycle
1
st
,
2
nd
, 3
rd
, 4
th
,
5
th
,
6
th
,
7
th
, 8
th
, and 9
th
parabolic
cycle
6
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Results & Discussions
As shown in Table 3, there are anomalies in the readings at certain cycles. We would
show in this section the results which are acceptable and comment upon them. The
anomalies are shown in another section with comments attached. We have produced
several graphs of the acceptable results which are shown in this section.
Figure 3. Data during Microgravity Condition – Towel Type 1
In Figure 3, there are series of graphs which indicate the transferred liquid during the
period of microgravity. Below is shown the correlation between series of graph and the
parabolic cycles.
i. Series 2 : 1
st
Parabolic Cycle (Horizontal Position)
ii. Series 3 : 2
nd
Parabolic Cycle (Horizontal Position)
iii. Series 4 : 3
rd
Parabolic Cycle (Horizontal Position)
iv. Series 5 : 4
th
Parabolic Cycle (Horizontal Position)
v. Series 6 : 5
th
Parabolic Cycle (Horizontal Position)
vi. Series 7 : 6
th
Parabolic Cycle (Vertical Position)
vii. Series 8 : 7
th
Parabolic Cycle (Vertical Position)
viii. Series 9 : 10
th
Parabolic Cycle (Vertical Position)
7
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 4. Data during Hypergravity Condition – Towel Type 1
In Figure 4, there are series of graphs which indicate the transferred liquid during the
period of hypergravity. We only captured the readings for 10 seconds during the
hypergravity period. Below is shown the correlation between series of graph and the
parabolic cycles.
i. Series 2 : 1
st
Parabolic Cycle (Horizontal Position)
ii. Series 3 : 2
nd
Parabolic Cycle (Horizontal Position)
iii. Series 4 : 3
rd
Parabolic Cycle (Horizontal Position)
iv. Series 5 : 4
th
Parabolic Cycle (Horizontal Position)
v. Series 6 : 5
th
Parabolic Cycle (Horizontal Position)
vi. Series 7 : 6
th
Parabolic Cycle (Vertical Position)
vii. Series 8 : 7
th
Parabolic Cycle (Vertical Position)
viii. Series 9 : 10
th
Parabolic Cycle (Vertical Position)
8
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 5. Data during 1G Condition – Towel Type 1
In Figure 5, there are series of graphs which indicate the transferred liquid during the
period of 1G. We only captured the readings for 10 seconds during the 1G period which
were actuated on the ground. Below is shown the information of the series of graph.
i. Series 2 : Horizontal Position
ii. Series 3 : Horizontal Position
iii. Series 4 : Horizontal Position
iv. Series 5 : Vertical Position
v. Series 6 : Vertical Position
vi. Series 7 : Vertical Position
9
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 6. Averaged Data during Microgravity Condition – Towel Type 1
We took all of the graphs in Figure 3 and concatenated and averaged them and the
result is shown in Figure 6. We will use Figure 6 for comparison with conditions of
hypergravity and 1G.
Figure 7. Averaged Data during Hypergravity Condition – Towel Type 1
We took all of the graphs in Figure 4 and concatenated and averaged them and the
result is shown in Figure 7. We will use Figure 7 for comparison with conditions of
microgravity and 1G.
10
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 8. Averaged Data during 1G Condition – Towel Type 1
We took all of the graphs in Figure 5 and concatenated and averaged them and the
result is shown in Figure 8. We will use Figure 8 for comparison with conditions of
microgravity and hypergravity.
Figure 9. Comparison of Transferred Mass during Microgravity, Hypergravity, and 1G
Conditions – Towel Type 1
We took the graphs from Figures 6, 7, and 8 and produced a comparison as shown in
Figure 9. During the comparison, we noted that there are distinct variations (even
though small) upon the transfer rate of moisture. We are satisfied with this and
reasoned out that our postulation earlier that gravity affects the driving pressure is not
farfetched. We intend to parlay more reasons of these occurrences in another paper as
this is not within the scope of this paper.
11
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 10. Data during Microgravity Condition – Towel Type 2
In Figure 10, there are series of graphs which indicate the transferred liquid during the
period of microgravity. Below is shown the correlation between series of graph and the
parabolic cycles.
i. Series 2 : 1
st
Parabolic Cycle (Horizontal Position)
ii. Series 3 : 2
nd
Parabolic Cycle (Horizontal Position)
iii. Series 4 : 3
rd
Parabolic Cycle (Horizontal Position)
iv. Series 5 : 6
th
Parabolic Cycle (Vertical Position)
v. Series 6 : 7
th
Parabolic Cycle (Vertical Position)
vi. Series 7 : 8
th
Parabolic Cycle (Vertical Position)
vii. Series 8 : 9
th
Parabolic Cycle (Vertical Position)
12
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 11. Data during Hypergravity Condition – Towel Type 2
In Figure 11, there are series of graphs which indicate the transferred liquid during the
period of hypergravity. We only captured the readings for 10 seconds during the
hypergravity period. Below is shown the correlation between series of graph and the
parabolic cycles.
i. Series 2 : 1
st
Parabolic Cycle (Horizontal Position)
ii. Series 3 : 2
nd
Parabolic Cycle (Horizontal Position)
iii. Series 4 : 3
rd
Parabolic Cycle (Horizontal Position)
iv. Series 5 : 6
th
Parabolic Cycle (Vertical Position)
v. Series 6 : 7
th
Parabolic Cycle (Vertical Position)
vi. Series 7 : 8
th
Parabolic Cycle (Vertical Position)
vii. Series 8 : 9
th
Parabolic Cycle (Vertical Position)
13
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 12. Data during 1G Condition – Towel Type 2
In Figure 12, there are series of graphs which indicate the transferred liquid during the
period of 1G. We only captured the readings for 10 seconds during the 1G period which
were actuated on the ground. Below is shown the information of the series of graph.
i. Series 2 : Horizontal Position
ii. Series 3 : Horizontal Position
iii. Series 4 : Horizontal Position
iv. Series 5 : Vertical Position
v. Series 6 : Vertical Position
vi. Series 7 : Vertical Position
14
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 13. Averaged Data during Microgravity Condition – Towel Type 2
We took all of the graphs in Figure 10 and concatenated and averaged them and the
result is shown in Figure 13. We will use Figure 13 for comparison with conditions of
hypergravity and 1G.
Figure 14. Averaged Data during Hypergravity Condition – Towel Type 2
We took all of the graphs in Figure 11 and concatenated and averaged them and the
result is shown in Figure 14. We will use Figure 14 for comparison with conditions of
microgravity and 1G.
15
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 15. Averaged Data during 1G Condition – Towel Type 2
We took all of the graphs in Figure 12 and concatenated and averaged them and the
result is shown in Figure 15. We will use Figure 15 for comparison with conditions of
microgravity and hypergravity.
Figure 16. Comparison of Transferred Mass during Microgravity, Hypergravity, and 1G
Conditions – Towel Type 2
We took the graphs from Figures 13, 14, and 15 and produced a comparison as shown
in Figure 16. During the comparison, we noted that there are distinct variations (even
though small) upon the transfer rate of moisture. We are satisfied with this and
reasoned out that our postulation earlier that gravity affects the driving pressure is not
farfetched. We also, as stated earlier, intend to parlay more reasons of these
occurrences in another paper as this is not within the scope of this paper.
16
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 17. Comparison between Towel 1 and 2 – Microgravity Condition
We made a comparison between Towel 1 and 2 by comparing Figures 6 and 13 and the
comparison is shown in Figure 17. During microgravity condition, it seems there’s only
a small difference of reading between Towel 1 and 2. These differences occurred due to
the different nature of both towels as outlined in Table 2.
Figure 18. Comparison between Towel 1 and 2 – Hypergravity Condition
We also made another comparison between Towel 1 and 2 by comparing Figures 7 and
14 and this comparison is shown in Figure 18. During hypergravity condition, it seems
there’s only a small difference of reading between Towel 1 and 2. We concurred with
our previous assessment which is these differences occurred due to the different nature
of both towels as outlined in Table 2.
17
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
Figure 19. Comparison between Towel 1 and 2 – 1G Condition
We also made another comparison between Towel 1 and 2 by comparing Figures 8 and
15 and this comparison is shown in Figure 19. During 1G condition, it seems there’s only
a small difference of reading between Towel 1 and 2. We concurred with our previous
assessment also which is these differences occurred due to the different nature of both
towels as outlined in Table 2.
Anomalies
As mentioned in Table 3, there exist anomalies in our readings. For Towel Type 1, the
anomalies occurred during parabolic cycles 8
th
and 9
th
(both vertical position
measurement). The graphs of these anomalies are shown in Figure 20.
Figure 20. Anomalies for Towel Type 1
18
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
For Towel Type 2, the anomalies occurred during parabolic cycles 4
th
and 5
th
(both
horizontal position measurement). The graphs of these anomalies are shown in Figure
21.
Figure 21. Anomalies for Towel Type 2
At this moment we could not offer a concrete reason on the existence of anomalies. We
however suspected that a surge or under surge of current occurred in the circuitry that
produced several snags as shown in the graphs. We intend to investigate further this
phenomenon.
Conclusions
We have several conclusions. We noted that there exist differences in readings (of
transfer rate of moisture) when comparison are made between 3 different conditions :
microgravity, hypergravity, and 1G. The highest difference is around 2 grams for Towel
Type 1. For Towel Type 2, the highest difference is also around 2 grams.
Both towels also exhibit differences in transfer rate of moisture. However these
differences are minute where the highest difference is around 0.8 grams (from Figure
17). We had earlier indicated that the characteristics of the towel, as outlined in Table 2,
played a role in producing these differences. We however cautioned that induced
vibration during flights could also be a contributing factor. Other factors also come into
play.
We nevertheless are satisfied with our results even though several anomalies existed.
Overall these anomalies did not affect our entire results. We can perhaps make a
judgement that, in relation to the mathematics that governed our experiment,
gravitational values which instigate driving pressure play a role in determining the
transfer rate of moisture from bath towel to human skin. We are cautious however as
19
Universiti Kuala Lumpur, 1016 Jalan Sultan Ismail, 50250 Kuala Lumpur, Malaysia.
National Space Agency of Malaysia (ANGKASA), Level 8, PJH Commercial Building 4C11, Persiaran
Perdana, Precint 4, 62100 Putrajaya, Malaysia.
we did not dwell deeper onto the reason for such differences occurred during
microgravity, hypergravity, and 1G conditions. We put forward several
recommendations to put our worries at ease.
Recommendations
We would recommend the positioning of the towel at different angles. We in this
experiment only tried 2 positions : horizontal and vertical. Using angles at 30 degrees or
45 degrees or 70 degrees would give perhaps different results.
We had used an artificial human skin and in the market there exist numerous materials
that mimic human skin. We encourage future researchers to try materials different from
ours. Perhaps different materials would give “optimum” results or “worse” results.
The parabolic flight that we undertook went from hypergravity to microgravity and
when we peered upon the hypergravity and microgravity graphs, we observed a
transition which is significant when condition changes from hypergravity to
microgravity. We are interested in this transition period where values of transfer rate of
moisture changed rapidly. Further research should look upon this.
Acknowledgement
The team would like to express extreme gratitude to several organizations, listed below
in alphabetical order, for their support and aid.
i. Diamond Air Services Japan
ii. Japanese Aerospace Exploration Agency
iii. National Space Agency of Malaysia
iv. Universiti Kuala Lumpur, Malaysia
With their support, the team managed to perform the experiments and collect relevant
data.
References
[1] Schramek G, 2009. Konzepte zur kostenbewussten produktion von Frottierwaren.
Melliand Textilberichte, 90(6): 236-237
[2] Masoodi 2010, Effect of Externally Applied Liquid Pressure on Wicking in Paper
Wipes, Journal of Engineered Fibers and Fabrics, Volume 5, Issue 3
[3] Washburn, E.V.; The Dynamics of Capillary Flow; Phys. Rev. 1921, 17, 273.
[4] Clark, J. 1995, “The Encyclopedia of Physics”, Andromeda Oxford, Oxfordshire.
[5] Chang, R. 1993, “Chemistry in Action”, McGraw-Hill, LA.
[6] Shawna S, “Data Sheet Polyurethane Pultrusions Series 4000”, Creative Pultrusions,
2005.