载人航天器预冷温度的热生理学探讨
作者：虞学军 常绍勇 武建民 邱曼 宋德 杨天德
单位：虞学军.航天医学工程研究所，北京 100094
关键词：载人航天；航天服；体温；热调节
航天医学与医学工程000203
摘要： 目的 探讨载人舱室适宜的预冷温度，以预防或减缓发射、返回段航天器内高温对人体的不利影响。 方法 5名健康男性青年按着航天服时不通风和以通风流率100 L/min(STPD)通风等不同着装条件，在舱温15、l0、5℃环境中进行25人次实验。测量直肠温度(Tr)、平均皮温(Tsk)和平均体温(Tb)等热生理指标。 结果 在舱温15℃航天服通风和不通风状态，实验2 h内人体直肠温度降低不显著(从初始值37.0±0.2℃降为36.7±0.3℃),平均体温、平均皮温显著降低(P<0.05)，受试者有局部的冷紧张；而在舱温和通风温度10℃时，受试者热生理指标随时间延长不断降低，直肠温度从37.0±0.3℃显著下降至36.3±0.3℃,Tsk、Tb显著低于初始值(P<0.05),受试者有全身性冷紧张。 结论 按人体热舒适状态无显著改变的要求，航天器座舱预冷后维持15℃气温对人体较为适宜。
, http://www.100md.com
中图分类号：R852.81；文献标识码：A 文章编号：1002-0837(2000)02-0090-05
Thermal Physiological Consideration of Precooling Procedures in Manned Space Craft
YU Xue-jun,CHANG Shao-yong,WU Jian-min,QIU Man,SONG De,YANG Tian-de
(Institute of Space Medico-Engineering,Beijing 100094,China)
Abstract： Objective To explore a space craft precooling temperature at which excessive thermal stress on the crew member could be prevented or reduced in an overheated launch or reentry module. Method Five young male volunteers wearing a space suit participated in 25 tests at sea level.The space suit was either ventilated in a volume air flow rate of 100 L/min (STPD) with ambient air at temperatures (Ta) of 15℃,10℃,and 5℃,respectively,or not ventilated. Rectal (Tr),mean skin (Tsk) and mean body (Tb) temperatures were measured. Result At Ta 15℃,Tr decreased without significance (from 37.0±0.2℃to 36.7±0.3℃) in 120-min tests,whereas Tsk and Tb decreased significantly,and subjects had local cold strain whether the space suit was ventilated or not; while at Ta 10℃,Tr decreased from 37.0±0.3℃ to 36.3±0.3℃(P<0.05),subjects had a whole body cold strain,and both Tsk and Tb dropped continuously and significantly. Conclusion Ambient temperature 15℃,at which the thermal comfort states of crew was not significantly degraded,was acceptable after precooling in a space craft.
, 百拇医药
Key Words：manned space flight;space suits;body temperature;thermoregulation
American and Russian astronauts used to wear their space suits during the critical phases of launch and reentry in spaceflight.The aerodynamic heating in these periods increases the cabin air temperature that might exceed the limits of human tolerance in the event of the thermal insulation layer being too thin or a failure of heat insulation.Precooling,which was verified by Veghte and his coworkers in 1958[1],is one of the efficient ways to prevent or reduce the thermal strain on the crew member.The Command Module of Apollo mission was precooled prior to reentry to minimize the possible effect of the reentry heating on the internal temperature of the Command Module[2].
, 百拇医药
Although many works on precooling have been done in exercise physiology lab to investigate the effects of improving the lasting time of long distance running or other strenuous sports[3],these experiments mainly focused on the precooling of human bodies rather than on a closed cabin environment.It is impractical to get astronauts precooled in the space cabin because they may catch cold or develop other infectious diseases,or may even cause them difficult to finish flight tasks during the sudden changes of ambient temperature.The purpose of this study was to find out an appropriate precooling temperature in a space craft cabin at which the thermal state of crew wearing space suits would
, 百拇医药
Table 1 Physical characteristics of the 5 subjects(
±s) Ht(cm)
Wt(kg)
Age(yr)
body surface area(m2)
164.6±2.0
57.0±5.1
19.4±0.9
1.6±0.1
not be significantly degraded.Method
, 百拇医药
Subjects Five young male volunteers participated in this study.The physical characteristics of the subjects are given in table 1.
Experimental Design Twenty-five experiments were carried out in a climatic chamber.Subjects wearing an intravehicular activity space suit over a pair of cotton underwear (heat insulation value 0.3 clo) sat resting in a simulated launch and reentry seat at sea level.The tests were conducted at ambient temperatures (Ta) of 15℃,10℃,and 5℃respectively,each with a 50% relative humidity.Each test lasted for 120 min.
, 百拇医药
The space suit was used under two different protocols.In protocol 1 (Vet0) the space suit,with helmet open and gloves off,was not ventilated.Following this protocol each subject was exposed once at Ta of 15℃,10℃,and 5℃respectively.In protocol 2 (Vet100) the space suit,with helmet closed and gloves on,was ventilated by the cabin air with a volume flow rate of 100 L/min (STPD).Each subject underwent one test at 15℃ and 10℃separately in Vet100.
Temperature measurements and calculations All measurements were taken at 15 min intervals.Rectal temperature (Tr) was monitored as an index of core temperature.Mean skin temperature was measured at seven sites (forehead,chest,back,forearm,hand,thigh and calf) and calculated using the area weighted formula:
sk=0.07Tforehead+ 0.175(Tchest+Tback)+0.14Tforearm+0.05Thand+0.19Tthigh+0.2Tcalf.Mean body temperature was calculated as b=0.67Tr+0.33sk.Temperatures in middle finger (Tmf) and big toe (Ttoe) were also measured in the same frequency.
, http://www.100md.com
Statistics The data were analyzed by analysis of variance (ANOVA) with repeated measures to evaluate the changes in body temperatures to determine the significant changes with the time in 2 ventilating protocols at selected air temperatures.Paired student-t test was also used where appropriate.Values are given as mean±SD and statistical significance was set at P<0.05.
Result
Mean values of Tr,sk,b Tmf and Ttoe in 5 subjects were decreasing in the tests with exposure time and were lower at lower Ta at the same time.There were no significant differences (P>0.05) in all these body temperature measurements except Ttoe betweenVet0 and Vet100 at the same air temperature of 10 or 15℃ in the same exposure time.
, 百拇医药
Values of Tr measured both in Vet0 and Vet100 at Ta 15℃decreased from the same 37.0±0.2℃to 36.7±0.3℃within 120 min,andsk from 32.9±0.4℃to 32.2±0.5℃ in Vet0 and to 32.1±0.5℃in Vet100 respectively.Similarly within 120 min of cold exposure at Ta 10℃，Tr decreased from 37.0±0.3℃to 36.3±0.5℃ and to 36.3±0.3℃in Vet0 and Vet100 conditions respectively,while sk from 32.1±0.6℃declined to 30.4±0.7℃ and to 30.2±0.6℃respectively.
, http://www.100md.com
As shown in figure 1,when the space suit was not ventilated,Tr and Tmf at 15℃ambient temperature did not decrease significantly during 120 min tests(P>0.05),whileb,Ttoe,and sk decreased significantly in 30,60,and 120 min compared with their initial values respectively.b at all sites declined in the 120-min tests in Vet0 protocol at Ta 10℃and 5℃(P<0.05).At Ta 10℃ in Vet0,all body temperature measurements at the end of the tests significantly decreased compared to those at Ta 15℃.No significant difference in final Tr was found within the same 5℃ fall of Ta from 10℃ to 5℃,but the other body temperatures were significantly decreased.In comparison with Ta 15℃,all body temperature measurements at Ta 5℃significantly decreased (P<0.001).
, 百拇医药
In designated conditions of this study, 5℃ fall of air temperature made the human body temperatures decreased with greater extend than the changes between Vet0 and Vet100 at the same Ta.The final body temperatures except Ttoe between Vet0 and Vet100 were similar at Ta 15℃or 10℃.When the space suit was ventilated in an air flow of 100 L/min at 10℃,Tr significantly decreased after 60 min,but no significant decrease was found until 105 min at the same Ta without ventilation in the space suit.From these comparisons it could be suggested that the final body temperatures were mainly settled by cabin air temperature although ventilation in the space suit made these changes a little faster.
, http://www.100md.com
Fig.1 Body temperatures during 120 min running time trails at 15℃(◆),10℃(■) and 5℃(○) ambient temperatures without ventilation,15℃(△) and 10℃(×) with 100L/min ventilation in space suit.Data points represent means of 5 subjects.(--) not significantly different from initial value (P>0.05); (—) Significantly different from initial value (P<0.05).
Most of the subjects felt that their hands,knees,feet,arms,and legs were slightly cool at ambient temperature 15℃,especially the cool feeling came earlier and more stressful in hands,knees,and feet.In Vet100 at 15℃,subjective assessments were nearly the same as in Vet0 with an exception of no cool sensation in the hands.When the ambient temperature fell to 10℃,subjects had a cold sensation at the back and the cold sensation at the positions mentioned above increased.In Vet100,coldness was complained in torso and limbs especially in hands and feet.What is more,two subjects had a cold induced diuresis.Subjects shivered and complained that the ventilating air (at 10℃) was too cold.At the lowest cabin air temperature of 5℃,more serious cold ratings were reported.All subjects shivered and felt the coldness in the whole body.They complained about the chill in their limbs and ice-cold in their hands and feet.
, 百拇医药
Discussion
If the temperature for space craft precooling were unsuitably near the lower threshold of thermal comfort,there would be no obvious precooling effect.On the other hand,astronauts' health might not be supported when they stayed in an over-cooled space cabin.Thus,there is a trade-off between high and low precooling temperatures.First of all,insuring the crew member's health must be taken into first consideration.Therefore,it is a better way to set a temperature as low as possible provided that the thermal balance required of an astronaut in all his underwear and space suit could be maintained.
, 百拇医药
The finding that there were no significant difference in Tr,s and b at the end of 120 min tests between Vet0 and Vet100 suggested little affection of ventilation in the space suit.In other words,these body temperatures were considerably determined by the temperatures of cabin air.This might related to the combined effects of human body thermoregulation mechanism,by which cutaneous blood flow attenuated and the body heat conductance also reduced thereafter in a cold environment to minimize body heat loss and keep core temperature fixed[4],and the different protocols in donning the space suit.When the space suit was not ventilated radiant heat loss might increase in the head and hands directly exposed to cold air without the protection of helmet and gloves.And the conductive heat loss also increased by the space suit directly reaching the underwear with no pressure to hold the suit up above the underwear in Vet0.In addition,the tightly knitted cotton underwear,about 0.3 clo heat insulation,could additionally contribute to the attenuation of forced convention in ventilating condition.Furthermore,the space suit in this study distributed no ventilating air to nearly a half area of body surface including the back,buttocks and the posterior part of head and neck,which were also closely wrapped by the body shaped seat.Thus,there was little difference between ventilation and no ventilation in heat dissipation on these parts.
, 百拇医药
The tests showed that Tr,s,b,Tmf,and Ttoe kept a dynamic balance and Tr did not differ significantly from their initial states at ambient or ventilated air temperature 15℃,while at 10℃these body temperature measurements dropped continuously and significantly.Subjective feelings were generally in agreement with the thermal physiological measurements in this study.A previous investigation,which showed less stressful ratings of coldness,has been carried out in this lab where subjects were in jacks with the same insulation of 1.6 clo as the space suit[5].The different ratings might be attributed to the space suit,whose insulation is specially distributed with less in arms and legs than chest where metal assemblies are fixed.
, 百拇医药
As has been noted,Tr,sk,and b maintained lower levels in the last 60 min and subjects had a local cold strain at Ta 15℃ with or without ventilation in the space suit; while at Ta 10℃subjects had a whole body cold strain and their body temperatures were falling all the time in the tests.According to a standard of General medical requirements for thermal environment of working room (GJB898-90)[6],thermal state of the subjects' were between “thermal comfort maintenance" and “performance insurance" at 15℃and in "degraded performance" at 10℃.
, 百拇医药
Because of the importance of hand operation in spaceflight, it is necessary to pay attention to the skin temperature in hand.In thermal comfort zone,the skin temperature in hand is about 28℃,this is the initial figure in this study.The swiftness and touch sense of hand begin to reduce at the skin temperature of 15～20℃,significant decrease in hand performance such as rope knotting can be resulted when the skin temperature in hand falls to 15～16℃[7].Thus,operative performance might be impaired unexpectedly at Ta 10℃,where the skin temperature in hand were 16.0±2.2℃(in Vet0) or 17.0±0.7℃(in Vet100),but it could be guaranteed at Ta 15℃where skin temperatures in hand were kept on above 20℃in all the test conditions in this study.Although not guaranteed in a comfort state (29～33℃) suggested by Fanger[8],foot skin temperatures in all the tests were at least above 15℃which was more than two times higher than the skin temperature 7℃—the threshold of cold induced numbness in foot[9].It could be accepted for there is no problem of operation performance with foot in space flight.
, 百拇医药
In summary,ambient or ventilated air temperature,as a main factor,affects human thermal states more greatly than the air flow rate in the space suit.Precooling at 15℃could keep a better thermal state than at 10℃so far as the conditions in this study are concerned.No ventilation or ventilation with a flow rate of 100 L/min in the space suit at 15℃could be selected as there is no significant difference between the two conditions from the thermal physiological point of view.
, 百拇医药
A final plan for space craft precooling should also take the maximum temperature and its lasting time in launch or entry period into consideration.If the thermal strain were so severe that exceeds human tolerance,a lower precooling temperature might be needed in search for an optimal effects on preventing heat strain in thermal emergency situations.
[References]
[1] Veghte JH,Webb P.Extending human tolerance to extreme heat by prior body cooling[R].WADC Technical Report No.58-415,1958, Wright-Patterson AFB,Ohio
, 百拇医药
[2] National Aeronautics and Space Administration.Skylab mission report[R],first visit,1973, NASA JSC-08414
[3] Booth J,Marino F,Ward JJ.Improved running performance in hot humid conditions following whole body precooling[J].Med Sci Sports Exerc,1997, 29(7): 943～949
[4] Robinson S,Wiegman DL.Heat and humidity.In: Slonim NB eds.Environmental physiology[M].Saint Louis: The C V Mosby Co,1974, 84～113
, 百拇医药
[5] CHANG Shaoyong,CUI Daixiu,WU Jianmin et al.Physiological effects of cabin temperature decrease on human[J].Space Medicine & Medical Engineering,1997，10(3): 177～181
常绍勇,崔代秀,武建民等.舱温降低对人体的影响[J].航天医学与医学工程,1997，10(3): 177～181
[6] 顾鼎良.工作舱(室)温度环境的通用医学要求[S].GJB 898-90
[7] PANG Cheng,CHEN Jingshan.Effects of EVA space glove on manual performance and resolution[J].Chinese Space Science and Technology,1997，17(6):34～39
, http://www.100md.com
庞 诚,陈景山.舱外航天手套对手动作业的影响及解决办法[J].中国空间科学技术,1997，17(6):34～39
[8] Fanger PO.Thermal comfort [M].McGraw-Hill Book company,1970:95～106
[9] Vanggaard L.Protection of hands and feet[C].In: Research study group 7 on biomedical research aspects of military protective clothing eds.Handbook on clothing.Brussels: NATO,1988:7a-1～7a-12
Recieved date:1999-06-27, 百拇医药
单位：虞学军.航天医学工程研究所，北京 100094
关键词：载人航天；航天服；体温；热调节
航天医学与医学工程000203
摘要： 目的 探讨载人舱室适宜的预冷温度，以预防或减缓发射、返回段航天器内高温对人体的不利影响。 方法 5名健康男性青年按着航天服时不通风和以通风流率100 L/min(STPD)通风等不同着装条件，在舱温15、l0、5℃环境中进行25人次实验。测量直肠温度(Tr)、平均皮温(Tsk)和平均体温(Tb)等热生理指标。 结果 在舱温15℃航天服通风和不通风状态，实验2 h内人体直肠温度降低不显著(从初始值37.0±0.2℃降为36.7±0.3℃),平均体温、平均皮温显著降低(P<0.05)，受试者有局部的冷紧张；而在舱温和通风温度10℃时，受试者热生理指标随时间延长不断降低，直肠温度从37.0±0.3℃显著下降至36.3±0.3℃,Tsk、Tb显著低于初始值(P<0.05),受试者有全身性冷紧张。 结论 按人体热舒适状态无显著改变的要求，航天器座舱预冷后维持15℃气温对人体较为适宜。
, http://www.100md.com
中图分类号：R852.81；文献标识码：A 文章编号：1002-0837(2000)02-0090-05
Thermal Physiological Consideration of Precooling Procedures in Manned Space Craft
YU Xue-jun,CHANG Shao-yong,WU Jian-min,QIU Man,SONG De,YANG Tian-de
(Institute of Space Medico-Engineering,Beijing 100094,China)
Abstract： Objective To explore a space craft precooling temperature at which excessive thermal stress on the crew member could be prevented or reduced in an overheated launch or reentry module. Method Five young male volunteers wearing a space suit participated in 25 tests at sea level.The space suit was either ventilated in a volume air flow rate of 100 L/min (STPD) with ambient air at temperatures (Ta) of 15℃,10℃,and 5℃,respectively,or not ventilated. Rectal (Tr),mean skin (Tsk) and mean body (Tb) temperatures were measured. Result At Ta 15℃,Tr decreased without significance (from 37.0±0.2℃to 36.7±0.3℃) in 120-min tests,whereas Tsk and Tb decreased significantly,and subjects had local cold strain whether the space suit was ventilated or not; while at Ta 10℃,Tr decreased from 37.0±0.3℃ to 36.3±0.3℃(P<0.05),subjects had a whole body cold strain,and both Tsk and Tb dropped continuously and significantly. Conclusion Ambient temperature 15℃,at which the thermal comfort states of crew was not significantly degraded,was acceptable after precooling in a space craft.
, 百拇医药
Key Words：manned space flight;space suits;body temperature;thermoregulation
American and Russian astronauts used to wear their space suits during the critical phases of launch and reentry in spaceflight.The aerodynamic heating in these periods increases the cabin air temperature that might exceed the limits of human tolerance in the event of the thermal insulation layer being too thin or a failure of heat insulation.Precooling,which was verified by Veghte and his coworkers in 1958[1],is one of the efficient ways to prevent or reduce the thermal strain on the crew member.The Command Module of Apollo mission was precooled prior to reentry to minimize the possible effect of the reentry heating on the internal temperature of the Command Module[2].
, 百拇医药
Although many works on precooling have been done in exercise physiology lab to investigate the effects of improving the lasting time of long distance running or other strenuous sports[3],these experiments mainly focused on the precooling of human bodies rather than on a closed cabin environment.It is impractical to get astronauts precooled in the space cabin because they may catch cold or develop other infectious diseases,or may even cause them difficult to finish flight tasks during the sudden changes of ambient temperature.The purpose of this study was to find out an appropriate precooling temperature in a space craft cabin at which the thermal state of crew wearing space suits would
, 百拇医药
Table 1 Physical characteristics of the 5 subjects(
±s) Ht(cm)Wt(kg)
Age(yr)
body surface area(m2)
164.6±2.0
57.0±5.1
19.4±0.9
1.6±0.1
not be significantly degraded.Method
, 百拇医药
Subjects Five young male volunteers participated in this study.The physical characteristics of the subjects are given in table 1.
Experimental Design Twenty-five experiments were carried out in a climatic chamber.Subjects wearing an intravehicular activity space suit over a pair of cotton underwear (heat insulation value 0.3 clo) sat resting in a simulated launch and reentry seat at sea level.The tests were conducted at ambient temperatures (Ta) of 15℃,10℃,and 5℃respectively,each with a 50% relative humidity.Each test lasted for 120 min.
, 百拇医药
The space suit was used under two different protocols.In protocol 1 (Vet0) the space suit,with helmet open and gloves off,was not ventilated.Following this protocol each subject was exposed once at Ta of 15℃,10℃,and 5℃respectively.In protocol 2 (Vet100) the space suit,with helmet closed and gloves on,was ventilated by the cabin air with a volume flow rate of 100 L/min (STPD).Each subject underwent one test at 15℃ and 10℃separately in Vet100.
Temperature measurements and calculations All measurements were taken at 15 min intervals.Rectal temperature (Tr) was monitored as an index of core temperature.Mean skin temperature was measured at seven sites (forehead,chest,back,forearm,hand,thigh and calf) and calculated using the area weighted formula:
sk=0.07Tforehead+ 0.175(Tchest+Tback)+0.14Tforearm+0.05Thand+0.19Tthigh+0.2Tcalf.Mean body temperature was calculated as b=0.67Tr+0.33sk.Temperatures in middle finger (Tmf) and big toe (Ttoe) were also measured in the same frequency., http://www.100md.com
Statistics The data were analyzed by analysis of variance (ANOVA) with repeated measures to evaluate the changes in body temperatures to determine the significant changes with the time in 2 ventilating protocols at selected air temperatures.Paired student-t test was also used where appropriate.Values are given as mean±SD and statistical significance was set at P<0.05.
Result
Mean values of Tr,
sk,b Tmf and Ttoe in 5 subjects were decreasing in the tests with exposure time and were lower at lower Ta at the same time.There were no significant differences (P>0.05) in all these body temperature measurements except Ttoe betweenVet0 and Vet100 at the same air temperature of 10 or 15℃ in the same exposure time., 百拇医药
Values of Tr measured both in Vet0 and Vet100 at Ta 15℃decreased from the same 37.0±0.2℃to 36.7±0.3℃within 120 min,and
sk from 32.9±0.4℃to 32.2±0.5℃ in Vet0 and to 32.1±0.5℃in Vet100 respectively.Similarly within 120 min of cold exposure at Ta 10℃，Tr decreased from 37.0±0.3℃to 36.3±0.5℃ and to 36.3±0.3℃in Vet0 and Vet100 conditions respectively,while sk from 32.1±0.6℃declined to 30.4±0.7℃ and to 30.2±0.6℃respectively., http://www.100md.com
As shown in figure 1,when the space suit was not ventilated,Tr and Tmf at 15℃ambient temperature did not decrease significantly during 120 min tests(P>0.05),while
b,Ttoe,and sk decreased significantly in 30,60,and 120 min compared with their initial values respectively.b at all sites declined in the 120-min tests in Vet0 protocol at Ta 10℃and 5℃(P<0.05).At Ta 10℃ in Vet0,all body temperature measurements at the end of the tests significantly decreased compared to those at Ta 15℃.No significant difference in final Tr was found within the same 5℃ fall of Ta from 10℃ to 5℃,but the other body temperatures were significantly decreased.In comparison with Ta 15℃,all body temperature measurements at Ta 5℃significantly decreased (P<0.001)., 百拇医药
In designated conditions of this study, 5℃ fall of air temperature made the human body temperatures decreased with greater extend than the changes between Vet0 and Vet100 at the same Ta.The final body temperatures except Ttoe between Vet0 and Vet100 were similar at Ta 15℃or 10℃.When the space suit was ventilated in an air flow of 100 L/min at 10℃,Tr significantly decreased after 60 min,but no significant decrease was found until 105 min at the same Ta without ventilation in the space suit.From these comparisons it could be suggested that the final body temperatures were mainly settled by cabin air temperature although ventilation in the space suit made these changes a little faster.
, http://www.100md.com
Fig.1 Body temperatures during 120 min running time trails at 15℃(◆),10℃(■) and 5℃(○) ambient temperatures without ventilation,15℃(△) and 10℃(×) with 100L/min ventilation in space suit.Data points represent means of 5 subjects.(--) not significantly different from initial value (P>0.05); (—) Significantly different from initial value (P<0.05).
Most of the subjects felt that their hands,knees,feet,arms,and legs were slightly cool at ambient temperature 15℃,especially the cool feeling came earlier and more stressful in hands,knees,and feet.In Vet100 at 15℃,subjective assessments were nearly the same as in Vet0 with an exception of no cool sensation in the hands.When the ambient temperature fell to 10℃,subjects had a cold sensation at the back and the cold sensation at the positions mentioned above increased.In Vet100,coldness was complained in torso and limbs especially in hands and feet.What is more,two subjects had a cold induced diuresis.Subjects shivered and complained that the ventilating air (at 10℃) was too cold.At the lowest cabin air temperature of 5℃,more serious cold ratings were reported.All subjects shivered and felt the coldness in the whole body.They complained about the chill in their limbs and ice-cold in their hands and feet.
, 百拇医药
Discussion
If the temperature for space craft precooling were unsuitably near the lower threshold of thermal comfort,there would be no obvious precooling effect.On the other hand,astronauts' health might not be supported when they stayed in an over-cooled space cabin.Thus,there is a trade-off between high and low precooling temperatures.First of all,insuring the crew member's health must be taken into first consideration.Therefore,it is a better way to set a temperature as low as possible provided that the thermal balance required of an astronaut in all his underwear and space suit could be maintained.
, 百拇医药
The finding that there were no significant difference in Tr,
s and b at the end of 120 min tests between Vet0 and Vet100 suggested little affection of ventilation in the space suit.In other words,these body temperatures were considerably determined by the temperatures of cabin air.This might related to the combined effects of human body thermoregulation mechanism,by which cutaneous blood flow attenuated and the body heat conductance also reduced thereafter in a cold environment to minimize body heat loss and keep core temperature fixed[4],and the different protocols in donning the space suit.When the space suit was not ventilated radiant heat loss might increase in the head and hands directly exposed to cold air without the protection of helmet and gloves.And the conductive heat loss also increased by the space suit directly reaching the underwear with no pressure to hold the suit up above the underwear in Vet0.In addition,the tightly knitted cotton underwear,about 0.3 clo heat insulation,could additionally contribute to the attenuation of forced convention in ventilating condition.Furthermore,the space suit in this study distributed no ventilating air to nearly a half area of body surface including the back,buttocks and the posterior part of head and neck,which were also closely wrapped by the body shaped seat.Thus,there was little difference between ventilation and no ventilation in heat dissipation on these parts., 百拇医药
The tests showed that Tr,
s,b,Tmf,and Ttoe kept a dynamic balance and Tr did not differ significantly from their initial states at ambient or ventilated air temperature 15℃,while at 10℃these body temperature measurements dropped continuously and significantly.Subjective feelings were generally in agreement with the thermal physiological measurements in this study.A previous investigation,which showed less stressful ratings of coldness,has been carried out in this lab where subjects were in jacks with the same insulation of 1.6 clo as the space suit[5].The different ratings might be attributed to the space suit,whose insulation is specially distributed with less in arms and legs than chest where metal assemblies are fixed., 百拇医药
As has been noted,Tr,
sk,and b maintained lower levels in the last 60 min and subjects had a local cold strain at Ta 15℃ with or without ventilation in the space suit; while at Ta 10℃subjects had a whole body cold strain and their body temperatures were falling all the time in the tests.According to a standard of General medical requirements for thermal environment of working room (GJB898-90)[6],thermal state of the subjects' were between “thermal comfort maintenance" and “performance insurance" at 15℃and in "degraded performance" at 10℃., 百拇医药
Because of the importance of hand operation in spaceflight, it is necessary to pay attention to the skin temperature in hand.In thermal comfort zone,the skin temperature in hand is about 28℃,this is the initial figure in this study.The swiftness and touch sense of hand begin to reduce at the skin temperature of 15～20℃,significant decrease in hand performance such as rope knotting can be resulted when the skin temperature in hand falls to 15～16℃[7].Thus,operative performance might be impaired unexpectedly at Ta 10℃,where the skin temperature in hand were 16.0±2.2℃(in Vet0) or 17.0±0.7℃(in Vet100),but it could be guaranteed at Ta 15℃where skin temperatures in hand were kept on above 20℃in all the test conditions in this study.Although not guaranteed in a comfort state (29～33℃) suggested by Fanger[8],foot skin temperatures in all the tests were at least above 15℃which was more than two times higher than the skin temperature 7℃—the threshold of cold induced numbness in foot[9].It could be accepted for there is no problem of operation performance with foot in space flight.
, 百拇医药
In summary,ambient or ventilated air temperature,as a main factor,affects human thermal states more greatly than the air flow rate in the space suit.Precooling at 15℃could keep a better thermal state than at 10℃so far as the conditions in this study are concerned.No ventilation or ventilation with a flow rate of 100 L/min in the space suit at 15℃could be selected as there is no significant difference between the two conditions from the thermal physiological point of view.
, 百拇医药
A final plan for space craft precooling should also take the maximum temperature and its lasting time in launch or entry period into consideration.If the thermal strain were so severe that exceeds human tolerance,a lower precooling temperature might be needed in search for an optimal effects on preventing heat strain in thermal emergency situations.
[References]
[1] Veghte JH,Webb P.Extending human tolerance to extreme heat by prior body cooling[R].WADC Technical Report No.58-415,1958, Wright-Patterson AFB,Ohio
, 百拇医药
[2] National Aeronautics and Space Administration.Skylab mission report[R],first visit,1973, NASA JSC-08414
[3] Booth J,Marino F,Ward JJ.Improved running performance in hot humid conditions following whole body precooling[J].Med Sci Sports Exerc,1997, 29(7): 943～949
[4] Robinson S,Wiegman DL.Heat and humidity.In: Slonim NB eds.Environmental physiology[M].Saint Louis: The C V Mosby Co,1974, 84～113
, 百拇医药
[5] CHANG Shaoyong,CUI Daixiu,WU Jianmin et al.Physiological effects of cabin temperature decrease on human[J].Space Medicine & Medical Engineering,1997，10(3): 177～181
常绍勇,崔代秀,武建民等.舱温降低对人体的影响[J].航天医学与医学工程,1997，10(3): 177～181
[6] 顾鼎良.工作舱(室)温度环境的通用医学要求[S].GJB 898-90
[7] PANG Cheng,CHEN Jingshan.Effects of EVA space glove on manual performance and resolution[J].Chinese Space Science and Technology,1997，17(6):34～39
, http://www.100md.com
庞 诚,陈景山.舱外航天手套对手动作业的影响及解决办法[J].中国空间科学技术,1997，17(6):34～39
[8] Fanger PO.Thermal comfort [M].McGraw-Hill Book company,1970:95～106
[9] Vanggaard L.Protection of hands and feet[C].In: Research study group 7 on biomedical research aspects of military protective clothing eds.Handbook on clothing.Brussels: NATO,1988:7a-1～7a-12
Recieved date:1999-06-27, 百拇医药