Dixon, Michael A.

Stasiak, Michael A.

Wehkamp, Cara Ann P.

Wheeler, Raymond M.

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Produced by the NASA Center for Aerospace Information (CASI) 
https://ntrs.nasa.gov/search.jsp?R=20130009997 2019-08-31T00:03:40+00:00Z
Why Reduced Pressures for

Space Missions? 
• Reduced gas leakage and hence reduced 
resupply costs 
• Reduced structural mass 
• Increased potential for finding transparent 
materials for space "greenhouses" 
• Rapid egress for EVAs (spacewalks) without 
prolonged prebreathing and acclimation
1
Plant Responses to Reduced Pressures 
• Increased transpiration although there can stomatal acclimation (Gale, 
1972; Daunicht and Brinkjans, 1992; Andre and Massimino, 1992; Iwabuchi 
and Kurata, 2003). 
• Increased photosynthesis with sufficient pCO 2 but results vary with 
conditions (Iwabuchi et al., 1995; Corey et al., 1997). 
• No effect on growth down to 25 kPa but only with sufficient p0 2 (Goto 
etal., 2002; He et al., 2007). 
• Plant survival down to 7 kPa and 10 kPa--barley and wheat (Andre 
and Richaud, 1985; Massimino and Andre, 1999). 
• Wheat seeds did not geminate at 1 kPa of simulated Mars 
atmosphere (SMA) but did germinate and survive at 1 kPa SMA plus 
5 kPa 02 = 6 kPa total pressure (Schwartzkopf and Mancinelli, 1991). 
• Based on the literature, it appears the survival 
threshold for plants is 6-7 kPa. 
• But what would happen if there is a catastrophic 
pressure loss in the plant greenhouse / chamber 
in a life support system? 
• To study this, we exposed lettuce, radish, and 
wheat plants to a rapid depressurization to -1.5 
kPa and held them there for 30 min and then 
restored the original pressure.
2
Plant Growing Procedures 
• Radish (Raphanus sativa L. cv. Cherry Bomb II), lettuce (Lactuca sativa L. cv. Grand Rapids) and wheat (Triticum 
aestivum L. cv. Sable) used for study 
• All plants grown in 140 x 40 cm stainless steel troughs in 
rockwool with recirculating NFT (two troughs of radish, 
two of lettuce, and one of wheat). 
• Wheat sown at 574 plants rn-2; lettuce at 13 plants rn-2, 
and radish at 38 plants rn-2. 
• Seeds germinated under ambient pressure (-98 kPa)

then thinned at 3 days before closing the chambers. 
Environmental Conditions 
• Plants grown at -98 kPa or 33 kPa 
pressure with 20 kPa 
°2' and 0.12 kPa 
Co2. 
• Light at 300 iimol m 2
 s PAR with HPS 
lamps, 16-h photoperiod (17.3 mol m 2
 d1) 
• Temperature at 22°C. 
• Relative Humidity at 65% or 1.7 kPa, 
giving a VPD = 0.9 kPa.
3
Experimental Treatments 
• At 20 after planting, chambers pumped down as 
rapidly as possible, reaching -5 kPa after 5 mm 
and -1.5 kPa after 10 mm. 
• Chambers held at -1.5 kPa for 30 mm. 
• Pressure then restored to 33 kPa (over 30 mm) 
or 98 kPa (over 60 mm). 
• Temperature and humidity control engaged 
throughout the pressure drop although some 
adiabatic cooling was apparent. 
Hypobaric Test Chamber
University of Guelph, CESF
4
11 VI i :: T
I 
-I.'."	
a
jRapid Pressure Drop Test (33 kPa) 
.c35-___-__--_-------
Pressure (kPa)Jllf ) 
0.
25
Vapor 
OL 
CL	 VPD 
.E	 -1,4kPa 
0	 20	 40	 60	 80	 100 
Time (mm) 
Day 20 After Planting
Rapid Pressure Drop Test (98 kPa) 
bC 
>
esu,e (kPa) 
so 
CL
4U CL 
E Lowest Pressure 
0	 20	 40	 60	 80	 100 
Time (mm) 
Day 20 After Planting
	_______	
I	
IL:: 7 
	
______	
"e:• 
,
----' 
Measuring weights, dimensions, and health status of plants after rapid depressurization
8
80 
70
I (jControl
Lettuce Fresh Mass (27 days) 
Pressure Drop  
-+ 
40  
m 
.0 30 
LLI-
20 
10  
0
Growth Environment (kPa)
Lettuce Dry Mass (27 days) 
35
J Control 
• Pressure Drop 
3.0 
2.5 
20_—	 I	 I 
15  
0.5 - 
00	
-	 98 
Growth Environment (kPa)
9 
Lettuce Head Diameter (27 days) 
30
IControl 
U Pressure Drop 
25 __________________  
I—' 
20 
E 
U 
4) 15 
E 
0
10 
5	 - 
0 ___
33
Growth Environment (kPa) 
Radish Root Fresh Mass (27 days) 
80
Control 
	
70	
• Pressure Drop 
	
60	 1T 
50 
'I 
	
!30
	 -U. 
0 
& 20
	
10	 --
	
0	 ------ --
33	 38 
Growth Environment (kPa)
10
Radish Total DM (27 days) 
50
I Con" 
• Pressure Drop 
4.0 
C
30	 --
20.
98 
Growth Environment (kPa) 
Wheat Fresh Mass (27 days) 
800
IContrc 
• Pressure Drop 
;600 
(5
500
 
400__-
C 
co 0. 300-	 - . 
2
100  
0
33
Growth Environment (kPa)
11
Wheat Dry Mass (27 days) 
80
ii Control 
70	 U Pressure Drop 
60
 
so 
1:11	 1ii 
Growth Environment (kPa) 
SOlid 1th'	
rompre.s.sihle	
siipercriiital 11111(1 
liquid 
critical pressure
liquid	 crltILil	 nnl 
1)/laIr 
triple p1)1lit	
siijeiluati'€I vrqur 
1'U 51051 S /1/ti) se
rttiaI 
temperature 
Tr	 T
Temperature 
The triple point is the sire combination of pressure and temperature at which pure water, pure ice, and pure water vapor can 
coessi in a stable equilibrium. This occurs at exactly 273 16K (001 C) and a pressure of 611 73 Pa (061173 kPa, or 
0.0060373057 atm)
12
Phase Change of Water 
70 ---------
60 Vapour	 -	 -	 - 
50 --
I,
40 Plants Held - 
Here for - 
co 30 min 
°
I Liquid 4 20 
10 Trp!e Point of Water 
:
:°:°: 10	 12	 14	 16	 18	 20	 22	 24 
Pressure (kPa)
13 
*1 
Questions? 
- — —
a 
I,	 9. 
R9seate Spoonbill at Kennedy Space Center


Plants Survive Rapid Decompression: Implications for Bioregenerative Life Support

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