Development of space motion sickness in a ground-based human centrifuge

Adaptation of the vestibular system, specifically the otolith organs, to a non-terrestrial environment can result in space motion sickness-like symptoms when the human is reintroduced to the normal, 1 Gz, terrestrial environment. This premise was investigated by exposing nine subjects to 90 min of sustained 2 Gz acceleration in a human centrifuge and then observing and evaluating them at 1 Gz. Five of the subjects developed slight SMS symptoms, three developed moderate, and one developed frank sickness. Postural instabilities in two of the most affected subjects were also observed using the Equitest System post exposure. Long duration exposure to a non-terrestrial G(2Gz) appears to be a potential means for developing SMS-like symptoms in a ground-based human centrifuge.     

Italy's contribution, from a medical standpoint, to the space safety of payload scientists, and perspectives for the future

In Italy, the selection of the Italian payload scientists has been performed according to the Spacelab Program of ESA. Twenty-four subjects underwent a screening performed by the Health Service of Italian Air Force. They were requested to pass an exercise test on treadmill and another ten-minute test on centrifuge, subject to the effect of +3 Gz. The authors briefly describe the results of the test. Noteworthy is the determination of Central Flicker Fusion Frequency. This parameter makes it possible to assess the endurance level of the subject, much earlier than other techniques (e.g. EKG). The importance of an accurate preliminary screening is emphasized as well as of successive training periods. Future studies will be undertaken to compare evoked cortical potentials with behaviour parameters of space safety, with a view to setting up a subtle tool of evaluation for both future candidates and payload scientists.     

Effects of repeated long duration +2Gz load on man's cardiovascular function

Usefulness of a short-arm human centrifuge is expected when it is used in space as a countermeasure against cardiovascular deconditioning, problem of bone-calcium metabolism, etc. However, nothing is solidly established regarding the most desirable program for artificial G application. Accordingly, this study was designed to analytically evaluate the effects of repeated long duration +Gz load on human cardiovascular function. Recently heart rate spectral analysis has been recognized as a powerful tool for quantitatively evaluating parasympathetic and sympathetic activity separately in human. It is reported that power of the high frequency component (HF-p) is mediated selectively by parasympathetic activity and the power ratio of low to high frequency components(LF/HF) is indicative of cardiac sympathetic activity or cardiac sympathovagal balance. Sequence method is developed to examine spontaneous baroreceptor reflex sensitivity (BRS). We studied cardiovascular control function by using these methods in 9 healthy men before and after 7 days of daily repeated 1hour +2Gz load. When compared with the data of pre-G load period, post-G load period, decrease of HR, increases of HF-p and BRS were statistically significant. SBP, DBP and LF/HF tended to decrease, however, these changes were not statistically significant. This results indicate that repeated +2Gz load increases parasympathetic activity and arterial baroreceptor-cardiac reflex sensitivity. In recent years, many investigators suggest that space flight and head-down bedrest leads to impaired baroreceptor-cardiac reflex responses and decrease of parasympathetic activity, which may contribute to orthostatic intolerance. So our results suggest that daily repeated 1hour +2Gz load would be useful in preventing post-flight orthostatic intolerance.     

Usefulness of daily +2Gz load as a countermeasure against physiological problems during weightlessness.

Adaptation to head-down-tilt bed rest as a simulated microgravity leads to an abnormality of reflex control of circulation, hypovolemia and reduction of exercise capacity. We hypothesized that this cardiovascular deconditioning and reduction of exercise capacity could be prevented by a daily 1 hr centrifugation at +2Gz. To test this hypothesis, twenty healthy male subjects underwent 4 day of 6 degrees head-down-tilt bed rest. Ten of them were exposed to a +2Gz load for up to 30 min twice per day (the Gz group). The remaining 10 were not exposed to a Gz load (the no-Gz group). We estimated autonomic cardiovascular control by power spectral analysis of blood pressure and R-R interval variability, and baroreflex regulation by the transfer function analysis and the sequence method, before and after bed rest. Further, we measured hematocrit as an index of changes in plasma volume and maximal oxygen consumption as an index of exercise capacity, before and after bed rest. Result: In the no-Gz group, heart rate increased after bed rest. The high frequency power of R-R interval variability as an index of cardiac parasympathetic nervous activity, baroreflex gains estimated by transfer function analysis and the sequence method as index of the integrated arterial-cardiac baroreflex function decreased significantly. Associated with these changes, the ratio of low to high frequency power of R-R as an indicator of cardiac sympathovagal balance tended to increase after bed rest in the no-Gz group. However, those showed no significant changes after bed rest in the Gz group. Hematocrit increased after bed rest in the no-Gz group. It also tended to increase in the Gz group, however it did not achieve statistical significance. Maximal oxygen consumption decreased significantly to similar extent in both the groups. Conclusion: This result suggested that 1) a daily 1hr +2Gz load produced by a centrifuge might eliminate the changes in autonomic cardiovascular control during simulated weightlessness; 2) furthermore, it might partly reverse hypovolemia induced by bed rest; 3) however, it could not prevent the decreases in exercise capacity.     

离心机气动产热及其影响因素的理论研究

为深入解析离心机气动产热的影响因素和变化规律，理论推导建立产热模型，并通过与文献中离心机的气动产热实验和仿真结果的对比，验证了理论模型的有效性。利用该模型对实际的离心机产热问题进行分析计算发现:在所研究的工况范围内，机室内空气的随流比随转子转速ω_r的增加而增加；产热总功率与转子转速呈指数上升关系，与机室压力呈正比例关系；机室侧壁的摩擦产热功率在离心机气动产热热源中的占比最大，且随着ω_r的增加而增加。建议将离心机的换热器布置在机室侧壁内表面并人为提高机室内空气的随流比，以利离心机散热控温。     

Efficacy of periodic centrifugation of primates during 4-week head-down tilt.

Creation of artificial force of gravity (AFG) to counteract the negative consequences of microgravity in manned space missions of extended duration is one of the high-priority problems of space biology and medicine. However, there are a number of especial effects of AFG (namely, structural changes in muscles and bones, and some other system) which need implantation of electrodes and sensors and are possible only with animals. That is why it is of particular interest to make studies with monkeys whose reactions to changed gravity bear much resemblance with human. The purpose of the investigation was development of a protocol of periodic gravity loads as a counter-measure against the hypokinetic syndrome in Macaca mulatta. Two series of experiments were performed. In the series, animals were split into two groups of 6 species each who were motor restrained with the head end tilted downward at 5 degrees (HDT) for 28 days. Monkeys of group-2 were periodically subjected to centrifugation (HDT+G). During the first series of experiments rotation was conducted in the +Gz direction at g-loads from 1.2 to 1.6 units for 30-40 minutes 4-5 times a week. In the second series, g-load was equal to 1.2 units and the animals were rotated 30 min. 2-3 time a week. The criterion of Y-training protocol efficacy was a test +Gz run at 3 units for 30 s. during which functioning of the cardiovascular systems and its controls was evaluated. The test run was performed prior to and after HDT. Following HDT the animals of group HDT+G were more resistant to the test than their counterparts who had not been trained on the centrifuge. Data of the investigation imply that following HDT and HDT+G alike reduced the amount of total bodily fluids (by approximately 5%), the intracellular component (approximately 4%), and plasma volume (by 6-7%). Yet, there are radical differences between the groups in the levels of reduction in extracellular fluids (by 11% and 6.5%, respectively, P<0.05) and the interstitial component (by 11.5% and 6.5, respectively, P<0.05). Prophylactic centrifugation during HDT was also positive to the muscular blood flow in lower extremities.     

First results from experiments performed with the ESA Anthrorack during the D-2 Spacelab mission

In 1993 four astronauts performed physiological experiments on the payload "Anthrorack" during the second German Spacelab mission D-2. The Anthrorack set-up is a Spacelab double rack developed under the management of the European Space Agency. It consists of an ECHO machine, a respiratory monitoring system (gas analyzer with flow meter), a blood centrifuge, an ergometer, a finger blood pressure device, ECG, body impedance measurement device and a respiratory inductance plethysmograph. Experiment-specific equipment was used as well. Nineteen investigators performed experiments in the cardiovascular, pulmonary, fluid-renal and nutritional physiology area. Results on central venous pressure, ocular pressure, vascular resistance, cardiac output, tissue thickness and orthostatic intolerance are presented in the cardiovascular area. In the pulmonary area first results are mentioned on O2 transport perfusion and ventilation distribution and breathing pattern. From the fluid-renal experiments, data from diuresis, sodium excretion and hormonal determinations are given. Finally results from glucose metabolism and nitrogen turnover experiments are presented.     

航天器公路运输包装箱环境监测系统研制

为掌握运输过程中航天器的环境状态，确保过程受控，研制了一套运输环境监测系统，以NI cDAQ和LabVIEW为软硬件平台，设计软硬件架构与软件工作流程，能实现加速度、温湿度、车速多种类型信号的协同监测、实时超差警示与数据回放；并可利用北斗定位实现车速测量，针对高频采集的加速度信号，实现全程低速存储与触发高速存储。在实际运输道路上进行测试验证的结果表明，该监测系统功能完善，满足使用要求。     

借助TADT技术对中继卫星实现高准确的非相干多普勒跟踪

用非相干多普勒跟踪系统取代相干多普勒跟踪系统是可能的,只需消除其振荡器频率漂移对测速的有害 影响即可。TADT技术能使之达到相干系统的准确度。文中介绍TADT方法的数学原理及其在TDKSS网中的应用。结 论认为,TADT方法是解决非相干多普勒跟踪系统高精度和高可靠性这一矛盾的有效方法,从而使航天器的多普勒跟踪 技术取得突破性进展。     

On reliability of determining the orbital parameters of exoplanets by the Doppler method

As a part of the program of searching for exoplanets, the hypothetical influence of changeable velocity of light (due to parameters of motion of a radiation source) on the results of spectrometric measurements of stars is considered. Accelerations of stars relative to the barycenter of a system star-planet (planets) are taken into account. It is shown that the dependence of velocity of light on the barycentric radial velocity and on the component of barycentric radial acceleration of stars should result in significant increase (up to an order of magnitude) of semimajor axes of the found candidates for exoplanets. Consequently, a correct comparison of the spectral method with other known modern methods of finding exoplanets would allow one to use the results obtained in this paper as a reliable test for inspection of invariance of the velocity of light.     

星载合成孔径雷达的运动效应

对星载合成孔径雷达的运动效应进行了详细的分析，给出了雷达回波的多普勒参数和距离徒动特性的一般关系式。详细论证了卫星运动对多普勒参数和成像的影响，导出了描述速度误差、加速度误差和姿态误差的一系列定量计算公式，并就运动误差的补偿方法进行了阐述。     

Kinematics of maneuverable relativistic starship

Maneuvering a relativistic starship is not as easy as it appears. The closer is its velocity to the speed of light the less maneuverable it appears to be relative to the rest frame. The relativistic kinematic equations are derived and the examples of starship trajectories are calculated on the condition of a constant proper acceleration and taking into account the required protection from hard radiation caused by the oncoming relativistic flow of interstellar gas. Possible navigation methods are also outlined shortly.     

Effects of 12 days exposure to simulated microgravity on central circulatory hemodynamics in the rhesus monkey

Central circulatory hemodynamic responses were measured before and during the initial 9 days of a 12-day 10 degrees head-down tilt (HDT) in 4 flight-sized juvenile rhesus monkeys who were surgically instrumented with a variety of intrathoracic catheters and blood flow sensors to assess the effects of simulated microgravity on central circulatory hemodynamics. Each subject underwent measurements of aortic and left ventricular pressures, and aortic flow before and during HDT as well as during a passive head-up postural test before and after HDT. Heart rate, stroke volume, cardiac output, and left ventricular end-diastolic pressure were measured, and dP/dt and left ventricular elastance was calculated from hemodynamic measurements. The postural test consisted of 5 min of supine baseline control followed by 5 minutes of 90 degrees upright tilt (HUT). Heart rate, stroke volume, cardiac output, and left ventricular end-diastolic pressure showed no consistent alterations during HDT. Left ventricular elastance was reduced in all animals throughout HDT, indicating that cardiac compliance was increased. HDT did not consistently alter left ventricular +dP/dt, indicating no change in cardiac contractility. Heart rate during the post-HDT HUT postural test was elevated compared to pre-HDT while post-HDT cardiac output was decreased by 52% as a result of a 54% reduction in stroke volume throughout HUT. Results from this study using an instrumented rhesus monkey suggest that exposure to microgravity may increase ventricular compliance without alternating cardiac contractility. Our project supported the notion that an invasively-instrumented animal model should be viable for use in spaceflight cardiovascular experiments to assess potential changes in myocardial function and cardiac compliance.     

弹道目标中段平动补偿与微多普勒提取

弹道目标高速平动会使微多普勒产生平移、倾斜和折叠,必须进行补偿处理。针对弹道目标中段平动补偿问题,本文提出了一种基于多普勒极值点信息的平动参数提取和平动补偿方法。通过将平动近似为多项式描述,将微动等效为锥旋运动,推导了瞬时多普勒极值点与多项式参数和微动参数的关系。在此基础上,利用最小二乘参数辨识方法估计了平动参数,实现了平动补偿和微多普勒的高精度实时提取。仿真实验验证了本文算法的有效性。     

轨道机动过程中推力加速度的实时最小方差估计

飞行器轨道机动过程中，为跟踪、定位机动目标和干预机动控制过程，需要统计处理离散的雷达观测量实时估计推进发动机的推力，进而确定飞行器的瞬时轨道参数。本文所述算法是该工程问题的探讨和解决方案。文章建立了轨道机动过程中连续变质量运动模型和离散雷达量测模型，推进发动机的质量秒耗量作为表征推力加速度的一个近似常量，应用扩展卡尔曼滤波对离散的雷达测量数据进行顺序统计处理给出秒耗量的最小方差估计；文章详细地推导了线性化量模型的变分方程和观测矩阵；仿真结果表明该算法能快速、准确地估计推进发动机的质量秒耗量和向机动目标施加的实际推力。     

The feasibility of Doppler monitoring during EVA

During extravehicular activities (EVA) outside the spacecraft, astronauts have to work under reduced pressure in a space suit. This pressure reduction induces the risk of decompression sickness (DCS) by the formation of gas bubbles from excess nitrogen dissolved in the organism by breathing air at normal pressure. Under laboratory conditions the gas bubbles moving in the blood stream can be detected by the non-invasive ultrasonic Doppler method. By early detection of excessive bubble formation the development of DCS symptoms may be prevented by early application of preventative measures. The method could also be useful when applied in the space suit in order to compare the results of laboratory tests with operational results, because there is a discrepancy according to the DCS risk of laboratory experiments and actual EVA missions, where no symptoms have been reported yet. A prototype Doppler sensor has been developed and implemented in the Russian Orlan suit. To investigate the feasibility of this method under simulated space conditions, the equipment has been used in a series of 12 thermovacuum chamber tests with suited subjects, where intravenous bubble formation was compared to unsuited control experiments. In more than 50% of the suited tests good Doppler recordings could be achieved. In some cases with unsatisfying results the signal could be improved by breathholding. Although the results do not yet allow any conclusion about a possible difference between suited and unsuited subjects due to the small number of tests performed, the method proved its feasibility for use in EVA suits and should be further developed to enhance the safety of EVA procedures.     

航天器自旋对测轨数据影响的修正方法

从测量原理上分析了航天器自旋对地基无线电测轨数据的影响,提出了测距和多普勒测速自旋影响修正方法,该方法也可用于估算航天器天线安装位置与自旋轴的距离。利用修正方法对嫦娥二号地月转移飞行段的地基测距与多普勒测速数据进行处理,解算的嫦娥二号天线安装位置精度在厘米量级。使用修正后的测距和多普勒测速数据,并融合时延与时延率测量数据,进行定轨计算,结果表明,使用修正后的测轨数据对事后定轨计算有近50m的精度提高。     

Medical considerations for extending human presence in space

The prospects for extending the length of time that humans can safely remain in space depend partly on resolution of a number of medical issues. Physiologic effects of weightlessness that may affect health during flight include loss of body fluid, functional alterations in the cardiovascular system, loss of red blood cells and bone mineral, compromised immune system function, and neurosensory disturbances. Some of the physiologic adaptations to weightlessness contribute to difficulties with readaptation to Earth's gravity. These include cardiovascular deconditioning and loss of body fluids and electrolytes; red blood cell mass; muscle mass, strength, and endurance; and bone mineral. Potentially harmful factors in space flight that are not related to weightlessness include radiation, altered circadian rhythms and rest/work cycles, and the closed, isolated environment of the spacecraft. There is no evidence that space flight has long-term effects on humans, except that bone mass lost during flight may not be replaced, and radiation damage is cumulative. However, the number of people who have spent several months or longer in space is still small. Only carefully-planned experiments in space preceded by thorough ground-based studies can provide the information needed to increase the amount of time humans can safely spend in space.     

Influence of simulated high-G on the weld size of aL–lI alloy

Whether welding processes are used on earth or in space, they have the same objective: to obtain defect-free welds. To fully understand the effect of gravity on the weld pool geometry and solidification one should perform experiments within a broad range of gravitational acceleration. High-gravity arc welding experiments were done on Al–Li alloy using the centrifuge called Multi-Gravity Research Welding System (MGRWS). At a high “g” level, buoyancy-driven flow is the dominant force in the weld pool over the Marangoni and the electromagnetic forces. Preliminary results show that the average grain size in the fusion zone at 1g is smaller that at 5g.