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1、How to Establish a Bioregenerative Life Support Systemfor Long-Term Crewed Missions to the Moon or MarsYuming Fu,1,2,3,*Leyuan Li,1,2,3,*Beizhen Xie,1,2,3,*Chen Dong,1,2,3,*Mingjuan Wang,1,3,*Boyang Jia,1Lingzhi Shao,1,2Yingying Dong,1,3Shengda Deng,1,2Hui Liu,1,3Guanghui Liu,1,2Bojie Liu,1,2Dawei H

2、u,1,3and Hong Liu1,2,3AbstractTo conduct crewed simulation experiments of bioregenerative life support systems on the ground is a criticalstep for human life support in deep-space exploration.An artificial closed ecosystem named Lunar Palace 1was built through integrating efficient higher plant cult

3、ivation,animal protein production,urine nitrogenrecycling,and bioconversion of solid waste.Subsequently,a 105-day,multicrew,closed integrative bio-regenerative life support systems experiment in Lunar Palace 1 was carried out from February through May2014.The results show that environmental conditio

4、ns as well as the gas balance between O2and CO2in thesystem were well maintained during the 105-day experiment.A total of 21 plant species in this system kept aharmonious coexistent relationship,and 20.5%nitrogen recovery from urine,41%solid waste degradation,and a small amount of insect in situ pro

5、duction were achieved.During the 105-day experiment,oxygen andwater were recycled,and 55%of the food was regenerated.Key Words:Bioregenerative life support systems(BLSS)Space agricultureSpace life supportWaste recycleWater recycle.Astrobiology 16,925936.1.IntroductionCurrent strategies to further ex

6、plore space,such asNASAs Design Reference Architecture or Chinaslunar exploration program(Zheng et al.,2008;Drake et al.,2010),strongly suggest the development of bioregenerativelife support systems(BLSS)that can be fully incorporatedinto space stations,transit vehicles,and eventually habitatson the

7、 Moon and Mars(Dempster et al.,2004;Tong et al.,2011).Utilization of BLSS would decrease resupply massby regenerating essential resources for human use throughbiologicalprocesses.WithinBLSS,thecultivationofhigherplants takes a crucial role,as they can contribute to all majorfunctional aspects(e.g.,f

8、ood production,carbon dioxidereduction,oxygen production,water recycling,and wastemanagement)(Wheeler et al.,1993;Tikhomirov et al.,2003).The ultimate goal of this technology is to create asustainable life support ecological environment that is openwith respect to energy but closed with respect to m

9、ass(Massa et al.,2007).Technological innovation of BLSSunit components for biomass production and waste re-cycling is of particular interest for a number of researchersfrom various countries,including the United States,Russia,Japan,Canada,Germany,and China.Recent advances inunit technologies,particu

10、larly in the development of high-efficiency plant cultivation(Fu et al.,2013;Dong et al.,2014c),animal protein production(Yu et al.,2008b;Liet al.,2016),nitrogen recovery from urine(Kabdasli et al.,2006),and bioconversion of solid wastes into soil-likesubstrate(Yu et al.,2008a;He et al.,2010;Tikhomi

11、rovet al.,2011),provide unparalleled opportunities to improvetheclosurecoefficientofBLSSforthereductionofstowage,the resupply of life support materials,and the provision ofmore reasonable and balanced diets for crews.As a simple model,BLSS address the interactions amongorganisms and their environmen

12、t as an integrated systemthrough the study of factors that regulate the pools andfluxes of materials and energy through the ecosystem.Theflow of energy and materials through organisms and thephysical environment provides a framework for under-standing the diversity of form and functioning of Earthsp

13、hysical and biological processes.The unique contributionof BLSS is their focus on biotic and abiotic factors as in-teracting components of a single integrated system.Despite progress in the technology of BLSS unit compo-nents,the development of feasible bioregenerative systems1School of Biological S

14、cience and Medical Engineering,Beihang University,Beijing,China.2Institute of Environmental Biology and Life Support Technology,Beihang University,Beijing,China.3International Joint Research Center of Aerospace Biotechnology and Medical Engineering,Beihang University,Beijing,China.*These authors con

15、tributed equally to this work.ASTROBIOLOGYVolume 16,Number 12,2016 Mary Ann Liebert,Inc.DOI:10.1089/ast.2016.1477925requires the integration of these units into a single system.Russian(BIOS-3,36 months)(Gitelson et al.,1989;Salis-bury et al.,1997)and Japanese investigators(CEEF,14weeks)(Tako et al.,

16、2008,2011)have conducted crewedsimulation experiments by integrating several BLSS unitcomponents on the ground.These studies demonstrate thatthe different biological components and operational methodsresult in changes of mass circulation and migration in BLSS(Nelson et al.,2009;Tong et al.,2012).The

17、 information onBLSS mass flow integrated with currently available new unittechnologies,as mentioned above,is therefore needed toestablish realistic BLSS in the future.In the present study,we established a ground-based ex-perimental BLSS platform(Lunar Palace 1)by integratingatmospheric management,cr

18、op production,insect breeding,waste recovery,and water-processing compartments.Withthis system,we performed a 105-day,multicrew,closedintegrative experiment wherein several new technologies forBLSS that comprise high-efficiency plant cultivation,ani-mal protein production,urine nitrogen recycling,an

19、d bio-conversion of solid wastes into soil-like substrate wereapplied.The mass flow of the system was analyzed andcompared with other published reports.Moreover,we alsoexplored the quantitative relationships of material fluxamong different components of the system.Efforts likeLunar Palace 1 will yie

20、ld important information in prepa-ration for missions to the Moon or Mars.2.Materials and Methods2.1.Sealed research facilityThe integrative,ground-based,experimental facility forPermanent Astrobase Life-support Artificial Closed Ecosys-tem(P.A.L.A.C.E.)was rigorously designed according to thedefini

21、tion of BLSS and is referred to as Lunar Palace 1.Lunar Palace 1 comprises a comprehensive cabin and twoplant cultivation cabins.Its construction was divided intotwo stages.The first stage included construction of a1432.5m comprehensive cabin and a 105.83.5mplant cabin,which have the capacity to pro

22、vide three crewmembers with a life support environment.In the secondstage,another plant cabin will be built,with a capacity forfive members to live.The present study was conducted byusing the Lunar Palace 1 first-stage facility.The compre-hensive cabin included four private bedrooms,a living room,a

23、bathroom,and a room for waste treatment.The plant cul-tivation cabin was subdivided into two rooms,that is,plant-culture room 1 and 2.The environmental conditions withinthese two plant rooms were controlled separately,accordingto the growth demands of different plants.To provide ahermetic environmen

24、t,the facilitys shell was welded stain-less steel plates,and all cabin doors were tightly sealed withsilicon gaskets.We used far higher CO2concentrationchanges to test the leakage rate of the closed system(Dempster et al.,2009;Tong et al.,2011),and a leakage rateof 0.04%per day was obtained(Dong et

25、al.,2016a).2.2.Key modulesNew unit technologies,including nitrogen recovery fromurine,soil-like substrate preparation by co-fermentation ofstraw and human feces,and animal protein production usingplant wastes were integrated into Lunar Palace 1.In terms offunction,Lunar Palace 1 was divided into thr

26、ee key modules:a higher plant cultivation module,a water treatment module,and a solid waste bioconversion and animal-rearing module.2.3.Higher plant cultivation moduleA spatial multilayer planting method was employed in theplant cultivation module to improve space-utilization effi-ciency of the plan

27、t cabin(Dong et al.,2015b).The plantcultivation module was composed of 13 three-layer planttrays,where five food crops,15 vegetables,and one fruit werecultivated(Dong et al.,2016b).The total growing area forcrops was 69m2.Here,the plant species and abundance weredesigned based on a set of criteria o

28、f human nutritional re-quirements and dietary variety(Yang et al.,2002;Hu et al.,2010).The cultivation schedule for all varieties of plants isshown in Supplementary Table S1(Supplementary Data areavailable online at variety ofplants were introduced into the system as seeds and conveyor-type cultivat

29、ed with uniform and sustained oxygen production.A red-white light-emitting diode(LED)with full light spectraarrays was used as a light source for plant growth(Dong et al.,2014a).The illumination conditions were set as follows:inroom 1,continuous lighting was provided,with a light in-tensity of 500lm

30、ol$m-2$s-1(as tested from 20cm below thelight source)(Dong et al.,2014b);in room 2,a 16h$d-1lighting period(light:dark=16:8h)was employed with thesame light intensity as room 1.All plants were irrigated reg-ularly with 1 or 2 a time-strength modified Hoagland solution(Dong et al.,2015a),and the pH w

31、as kept at 5.86.0.ModifiedHoagland solution was prepared by stored plant minerals thatwere supplied into the system periodically.2.4.Water treatment moduleThis module was subdivided into three units,that is,ahumidity condensate water processing unit,a sanitary waste-water treatment unit,and a urine

32、treatment unit.The waterprocessing procedures of the system are shown in Fig.1.Withair cooling facilities,plant transpiration of the plant cabinproduced a large amount of humidity condensate water.Thecondensed water from the plant cabin and the comprehensivecabin was collected and pumped through wat

33、er purificationequipment.The purified water was then stored in a cleanwater tank.Most of the purified water was used for plantnutrient solution preparation,and the rest served as drinkingwater and sanitary water for the crew.The urine collectedfrom the crew was treated with low-pressure distillation

34、 torecover water and part of the nitrogen.The recovered waterwas mixed with sanitary wastewater from the comprehensivecabin before going through a biological activated carbonmembrane reactor for purification.The purified water wasthen collected into a gray-water tank before being pumpedinto the nutr

35、ition tank for the preparation of plant nutrientsolution.The solid residual urine obtained from distillationwas collected,stored,and periodically sent out of the system.2.5.Solid waste bioconversionand animal-rearing moduleThe inedible crop biomass(mainly stalks)was dried andground into powder after

36、 the plants were harvested.A total926FU ET AL.of 85.8%of the straw powder was stored for fermentation,13.9%as bedding for human feces,and 0.3%for insect(yellow mealworm,Tenebrio molitor L.)food fermentation,along with some old vegetable leaves produced in the sys-tem.The stored straw powder,the huma

37、n feces with strawbedding,and worm frass were sent collectively into a solidwaste bioconverter that contained microbial inoculants thatare able to degrade plant waste.The CO2-enriched gas re-leased from the solid waste bioconverter was passed throughan air purifier and into the plant cabin to supply

38、 CO2forplant photosynthesis.Moreover,to control and limit CO2fluctuation,the CO2emission rate from the bioconverter tothe plant cabin was regulated by controlling the amount ofrunning heat units inside the bioconverter based on a feed-back signal of CO2concentration.Compressed solid resi-dues that r

39、emained after fermentation were stored andperiodically exported from the system.The technologicalprocess of solid waste treatment is shown in Fig.2.2.6.Crew and substitutionsTo test the toleration capacity of Lunar Palace 1 for crewmembers,a total of five volunteers was selected and trainedto partic

40、ipate in a 105-day closed test experiment.The basicphysical information gathered from these volunteers is listedin Table 1.The volunteers maintained good health and goodpsychological compatibilities and were devoid of habitsdetrimental to their overall health(e.g.,smoking,drinkingalcohol).The 105-da

41、y experiment was performed fromFebruary 3 to May 20,2014.The study was approved by theCommittee of the School of Biological Science and MedicalEngineering in Beihang University,Beijing,China(Ap-proval ID:20140203,approval date January 15,2014).Thisstudy was carried out in strict accordance and compl

42、iancewith the Statement on Ethical Conduct in Research Invol-ving Humans guidelines of the Science and Ethics Com-mittee of the School of Biological Science and MedicalEngineering in Beihang University.Written informed con-sent was obtained from all volunteers.2.7.Environmental monitoringand control

43、 of the systemWithin the entire closed experiment,environmental param-eters that included cabin temperature,humidity,air pressure,and air composition(O2and CO2concentrations)were moni-tored continuously by a series of sensors located at a variety ofpositions within the system(Fig.3).Accordingly,cabi

44、n tem-perature and humidity were controlled in real-time by air-conditioners and dehumidifiers.Furthermore,levels for 14kinds of harmful trace gases were determined weekly with gaschromatographymass spectrometry,using the EPA TO-14FIG.1.Water recovery procedures during the 105-day experiment in Luna

45、r Palace 1.LUNAR PALACE 1 EXPERIMENT927method(EPA/625-96/010b).Seven representative air samplingpoints were selected in the plant chamber and comprehensivechamber.For crew and plant safety,air purification deviceswere installed in system ventilation pipes for removing harmfulgases.The air purificati

46、on devices were composed of anelectrostatic precipitator,an activated charcoal matrix,and acatalytic reactor,and were run continuously for 24h$d-1without maintenance during the entire experimental period.2.8.Dynamic monitoring and balancecontrol in gas and waterBy distributing the sensors at multipl

47、e points within thesystem,dynamic changes in CO2and O2concentrationswere monitored and recorded in real-time.When the con-centration of internal CO2exceeded 5000ppm(i.e.,lmol/mol),the concentrations of O2and CO2were regulated byadjusting the solid waste bioconverter temperature,thelighting period of

48、 plants,and the intensity of crew activities.With respect to the water,no extra water was imported intothe system during the experiment.The water consumptionby the crew and plant irrigation,as well as water recoveredfrom air condensation,urine,and sanitary wastewater,weremonitored and recorded.2.9.B

49、iomass and waste measurementsThe edible biomass,inedible biomass,and nutritionalelements of the crops were measured after harvesting eachbatch of crops.The O2production efficiencies were calcu-lated with stoichiometric models(Tikhomirov et al.,2003;Hu and Bartsev,2010).Urine and feces from the crew

50、andworm frass were collected and weighed.The O2consump-tion and CO2production rates during the process of solidwaste treatment were calculated by testing the elementcomposition of each material and building stoichiometricmodels(Hu et al.,2010).2.10.Crew basal metabolic rate measurementsand external