Development of Bioregenerative

Life Support for Longer Missions:

When Can Plants Begin to Contribute to

Atmospheric Management?

Raymond M. Wheeler

Surface Systems Office

NASA Kennedy Space Center

Florida, USA raymond.m.wheeler@nasa.gov

https://ntrs.nasa.gov/search.jsp?R=20150022488 2020-04-01T06:55:36+00:00Z

Plant Photosynthesis

light

CO2 + 2H2O* (CH2O) + H2O + O2

*

Edible (food)

(CH2O)

Inedible (waste)

For carbohydrate (CH2O) type crops, Assimilation Quotients (AQs) are ~1.0 (mol CO2 / mol O2)

For fat producing crops, AQ’s are lower, e.g., 0.8-0.9 (Tako et al., 2010)

Nitrogen, NH4 vs. NO3, can also affect AQ, with NO3, resulting in lower AQs (Bloom et al., 1989)

Factors Affecting Plant Photosynthesis and Growth

• Water and Nutrients—Assume these will be optimized but there

are challenges for micro and reduced gravity settings.

• Temperature—Assume this will be optimized for the given crop species.

• Carbon Dioxide—Optimal range for C3 crops probably 1000 to

2000 ppm (0.1 – 0.2 kPa); chambers open to cabin air might be

exposed to “super-elevated CO2”, which can cause some problems.

• Light

1) Light must be intercepted by the leaves or photosynthetic

organs. Light on the floors or walls does no good!

2) Most crops show a linear response of photosynthesis

to light across the lower light range.

NASA’s Biomass

Production Chamber

0

10

20

30

40

50

0 10 20 30 40 50 60 70 80

Photosynthetically Active Radiation (mol m-2 d-1)

Cro

p Y

ield

(g m

-2d

-1)

Total

Biomass

Edible

Biomass

Studies

Include:

Wheat

Soybean

Potato

Lettuce

Tomato

Effect of Light on Crop Yield(Data from NASA Biomass Production Chamber)

Wheeler et al. 1996. Adv. Space Res.

Canopy CO2 Uptake / O2 Production(20 m2 Soybean Stand)

6Wheeler, 1996. Plants in Space Biol. Suge (ed.)

CO2 Exchange Rates of Soybean Stands

-20

-10

0

10

20

30

40

50

0 10 20 30 40 50 60 70 80 90 100

Time (days)

CO

2E

xchange R

ate

(µ

mol m

-2s

-1)

Photosynthesis

Night Respiration

815 µmol m-2 s-1

HPS Lamps

477 µmol m-2 s-1

MH Lamps

Canopy Lodged

Harvest

High Temp

Event

7

Period of

Incomplete

Canopy Cover

Wheeler et al. 2006. EcoEngineering.

0

5

10

15

20

25

30

35

40

45

50

0 200 400 600 800 1000 1200 1400 1600

CO2 (mol mol-1)

CO

2E

xchange R

ate

(

mol m

-2s

-1)

CO

2C

om

pe

nsa

tion

Po

int

Fig. 6

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

90 100 110 120 130 140 150

CO2 Compensation Point

y = 0.15 x - 14.6

R2 = 0.99

CO2 (mol mol-1)

CO

2 E

x.

(m

ol m

-2 s

-1)

(97)

CO2 Exchange Rate vs. CO2 Concentration

Optimal Concentration

Wheeler. 2006. Potato Res.

Effect of Light on Photosynthesis

Wheeler, 1996, Plants in Space Biol. Suge (ed.)

Area for CO2 Removal / O2 Production

for One Person

Radiation

Use

Efficiency

PPF(µmol m-2 s-1)

250 500 750 1000

(g mol-1 PAR)

Daily Light

Integral(mol m-2 d-1)

14.4 28.8 43.2 57.6

0.50 94.4 47.2 31.5 23.6

0.75 63.0 31.5 21.0 15.7

1.00 47.2 23.6 15.7 11.8

* Biomass production data assuming Assimilation Quotient or AQ = 1.0 (i.e., biomass all CH2O)

** Assumes daily O2 requirement of 830 g / person-day (NASA SPP 30262)

*** Assumes a 16 h light / 8 h dark photoperiod

**** Radiation use efficiency data based on Wheeler et al. 2008. Adv. Space Res.

Area Per Person for O2

RUE = 1.0 g mol -1

RUE (Radiation Use Efficiency) Conversions based on Wheeler et al. 2008. Adv. Space Res. 41:706–713 .

Number of Plant Chambers for One

Person’s Oxygen

(with 500 µmol m-2 s-1 PAR and 0.75 RUE)

• VEGGIE (0.15 m2)

210

• Salad Machine (2.0 m2)

16

• Plant Module (10 m2)

3

A “Salad Machine” for Space Station and Transit Missions

MacElroy et al. 1992. Adv. Space Res.

One Human’s Oxygen from 11 m2 of Wheat !

Edeen and Barta. 1995. JSC No. 33636

Harvest Index (%) Ranges for Some Crops*

If inedible biomass recycled aerobically, this will consume some O2.

Hence high harvest index plants benefit gas exchange for life support

30 40 50 60 70 8020

Peanut

Rice

Cowpea

Radish

Sweetpotato

Spinach

Lettuce

Wheat

Tomato Potato Beet

* Data gathered from controlled environment tests at KSC Breadboard Project

and CELSS literature.

Oil Seed

Brassica

Soybean

Wheeler, 2004. Acta Hort.

Role of Bioregenerative Components

for Future Missions

Short Durations Longer Durations Autonomous

(early missions) Colonies

Bioregenerative

Stowage and Physico-Chemical

~1-5 m 2 total ~10-25 m 2 / person ~50 m 2 / person

Plant Growing Area

Wheeler, 2004. Acta Hort.

Conclusions

• Bioregenerative life support components will likely expand as

mission distances and durations increase.

• Near-term missions can benefit from the production of fresh

foods to supplement the crews’ diet.

• Contributions of plants to O2 production and CO2 removal will

be minimal with small, food production systems.

• A plant production module in the range of 10 m2 could begin to

contribute to O2 production.

• The O2 production and CO2 removal by plants is strongly

affected by light.

• Radiation (light) use efficiency (RUE) is an important aspect to

plant performance in future life support systems. Levels up to

1.0 g biomass / mol of photons have been documented and

should be achievable.

Thank you!

Astronaut Steve Swanson

Harvesting Lettuce on the ISS

Light, Productivity, and Crop Area Requirements

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Light (mol m-2 day-1)

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a R

eq

uir

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(m

2/ p

ers

on

)

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Pro

du

cti

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y (

g m

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Bright SunnyDay on Mars