STEM Today

STEM TODAY October 2017, No. 25

STEM TODAY October 2017 , No. 25

CONTENTS SM2.1: Determine the changes in sensorimotor function over the course of a mission and during recovery after landing.

The most profound sensorimotor deficits occur during and after gravitational transitions. Given these changes there is a possibility that crew will experience impaired control of the spacecraft during landing along with impaired ability to immediately egress following a landing on a planetary surface (Earth or other) after long-duration space flight.

Editorial Editor: Mr. Abhishek Kumar Sinha Editor / Technical Advisor: Mr. Martin Cabaniss

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Disclaimer ( Non-Commercial Research and Educational Use ) STEM Today is dedicated for STEM Education and Human Spaceflight. This newsletter is designed for Teachers and Students with interests in Human Spaceflight and learning about NASA’s Human Research Roadmap. The opinion expressed in this newsletter is the opinion based on fact or knowledge gathered from various research articles. Appropriate credit is given to its original authors. The results or information included in this newsletter are from various research articles and appropriate credits are added. The citation of articles are included in Reference Section. The newsletter is not sold for a profit or included in another media or publication that is sold for a profit.

Cover Page Northern Lights Over Canada The spectacular aurora borealis, or the "northern lights", over Canada is sighted from the International Space Station near the highest point of its orbital path. The station’s main solar arrays are seen in the left foreground.

This photograph was taken by a member of the Expedition 53 crew aboard the station on Sept. 15, 2017.

Image Credit: NASA

Back Cover A new paper suggests hydrogen-possibly water ice-in the Medusa Fossae area of Mars, which is in an equatorial region of the planet to the lower left in this view.

Scientists taking a new look at older data from NASA’s longest-operating Mars orbiter have discovered evidence of significant hydration near the Martian equator – a mysterious signature in a region of the Red Planet where planetary scientists figure ice shouldn’t exist.

Image Credit: Steve Lee (University of Colorado), Jim Bell (Cornell University), Mike Wolff (Space Science Institute), and NASA

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Editorial Dear Reader

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All young people should be prepared to think deeply and to think well so that they have the chance to become the innovators, educators, researchers, and leaders who can solve the most pressing challenges facing our world, both today and tomorrow. But, right now, not enough of our youth have access to quality STEM learning opportunities and too few students see these disciplines as springboards for their careers.

According to Marillyn Hewson, "Our children - the elementary, middle and high school students of today - make up a generation that will change our universe forever. This is the generation that will walk on Mars, explore deep space and unlock mysteries that we can’t yet imagine". "They won’t get there alone. It is our job to prepare, inspire and equip them to build the future - and that’s exactly what Generation Beyond is designed to do."

STEM Today will inspire and educate people about Spaceflight and effects of Spaceflight on Astronauts.

Editor Mr. Abhishek Kumar Sinha

Editorial Dear Reader The Science, Technology, Engineering and Math (STEM) program is designed to inspire the next generation of innovators, explorers, inventors and pioneers to pursue STEM careers.

According to former President Barack Obama, " Science is more than a school subject, or the periodic table, or the properties of waves. It is an approach to the world, a critical way to understand and explore and engage with the world, and then have the capacity to change that world..."

STEM Today addresses the inadequate number of teachers skilled to educate in Human Spaceflight. It will prepare , inspire and educate teachers about Spaceflight. STEM Today will focus on NASA’S Human Research Roadmap. It will research on long duration spaceflight and put together latest research in Human Spaceflight in its monthly newsletter.

Editor / Technical Advisor Mr. Martin Cabaniss

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Human Health Countermeasures (HHC) SM2.1: Determine the changes in sensorimotor function over the course of a mission and during recovery after landing

The most profound sensorimotor de cits occur during and after gravitational transitions. Given these changes there is a possibility that crew will experience impaired control of the spacecraft during landing along with impaired ability to immediately egress following a landing on a planetary surface (Earth or other) after long-duration space ight.

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Introduction

As reported by NASA, previous studies have shown that the most profound sensorimotor deficits occur during and after gravitational transitions. Given these changes there is a possibility that crew will experience impaired control of the spacecraft during landing along with impaired ability to immediately egress following a landing on a planetary surface (Earth or other) after long-duration space flight.

Dr. Millard F. Reschke captures impressions from a Shuttle commander obtained immediately (<4 hrs) after flight[Paloski et.al.]. The discussion focused on target acquisition tasks the commander performed for Dr. Reschke during the flight and his difficulties with nausea, disorientation, posture, locomotion, etc. after the flight.

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Question: Did you try to limit your head movements?

Ans: Oh yes, definitely.

Question: When you were trying to acquire the targets only, ...did you notice any difficulty in spotting the targets?

Ans: Oh yeah, oh yeah.

Question: Did it seem as though the target was moving or was it you?

Ans: I felt that it was me. I just couldnâ&#x20AC;&#x2122;t get my head to stop when I wanted it to.

Question: So it was a head control problem?

Ans: Yeah, yeah in addition to the discomfort problem it caused.

Question: So when you first got out of your seat today, can you describe what that felt like?

Ans: Oh gosh, I felt so heavy, and, uh, if I even got slightly off axis, you know leaned to the right or to the left like this, I felt like everything was starting to tumble.

Question: When you came down the stairs did you feel unstable?

Ans: Oh yeah, I had somebody hold onto my arm.

Question: Did you feel like your legs had muscle weakness, or ... was it mainly in your head?

Ans: It was mainly in my head.

Every crewmember interviewed by authors[Paloski et.al] on landing day (>200 crewmembers to date) has reported some degree of disorientation/perceptual illusion, often accompanied by nausea (or other symptoms of motion sickness), and frequently accompanied by malcoordination, particularly during locomotion. Of particular relevance to the ability to perform landing tasks, common tilt-translation illusions include an overestimation of tilt magnitude or misperception of the type of motion.

Most also reported having experienced similar symptoms early in flight; however, except in the most severely affected, there seems to be no correlation between the severity of the symptoms following ascent and those following descent. The severity and persistence of postflight symptoms varies widely among crewmembers, but both tend to decrease with increasing numbers of space flight missions. However, both severity and persistence increase with mission duration.

Symptoms generally subsided within hours to days following 1-2 week Shuttle missions but persisted for a

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week or more following 3-6 month Mir Station and ISS missions. The degree to which these psychophysical effects might affect piloting skills is difficult to judge, as recent, intensive training may have offset any impact on Shuttle landings, especially under nominal engineering and environmental conditions, and long duration Mir and ISS crewmembers to date have only piloted ballistic entry spacecraft, which parachute in, allowing no human control inputs during the last 15 min before landing.

Shuttle Entry and Landing Spatial Disorientation • Fortunately, on the 120+ Shuttle flights to date, there have been no accidents specifically attributed to spatial disorientation (SD).

• Of all the landings between STS-1 and STS-108, the Shuttle crossed the runway threshold abnormally low 20 times.

• Seven landings touched down abnormally long or short, and 13 had high touchdown sink rates, with three exceeding the 5 ft/sec structural limit.

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• Touchdown speeds during the first 100 Shuttle landings varied widely, with 20% outside of acceptable limits and six equaling or exceeding the maximum speed of 217 knots/hr (main landing gear tires are rated at 225 knots/hr maximum speed)[Moore et. al.].

• The fastest landing on record (224 knots/hr) was linked to the commander’s momentary spatial disorientation, as was the second fastest (220 knots/hr).

• The landing of the 8 day STS-3 mission in 1982. The commander, who was flying visually, took over manual control of the vehicle 30 seconds before landing at White Sands, NM. The vehicle was decelerating at 0.25 g. Starting at flare, when the commander attempted to lower the nose of the Shuttle, the vehicle exhibited a pilot induced oscillation (PIO) of three full cycles with increasing amplitude that continued through touchdown.

The commander denied having any issue with PIO, or misinterpreting pitch attitude. His recollection was that the nose came down earlier than expected as the Shuttle began to slow down. He said the stick was not responsive when he first attempted to pitch the nose back up, but then it seemed to over-respond and pitched up more than he expected. Because he was then concerned about a potential problem with the stick, he brought the nose down and left it down. The commander’s recollection appears to be consistent with the landing video, but not with data from the control stick that showed five large amplitude reversals in the pitch plane command after main gear touchdown. While difficult to reconstruct so long after the event, this may be noteworthy as an unrecognized case of spatial disorientation in a highly experienced pilot.

• McCluskey et al. analyzed data from nine missions, and noted trends, such as a correlation between touchdown sink rate and postflight difficulty performing a sit-to-stand maneuver without using the arms. Scores indicating neuro-vestibular dysfunction generally correlated with poorer flying performances, including a lower approach and landing shorter, faster, and harder.

Postural Equilibrium Control During Landing/Egress (DSO 605) [Paloski. et.al.(1992)] Two experiment paradigms were performed by 40 crew members before, during, and after Shuttle missions of varying duration. The first of these paradigms focused primarily on neuromotor performance by quantifying the response to sudden, stability threatening base-of-support perturbations. The second paradigm focused on neurosensory performance by quantifying postural sway during quiet upright stance with normal, reduced, and altered sensory feedback. All participating subjects performed the two paradigms on at least three occasions before flight to provide an accurate, stable set of unit gravity control data from which postflight changes could be determined. All subjects also performed the two paradigms on up to five occasions after flight to capture the

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full sensory-motor readaptation time course. Postflight tests began on landing day, as soon after Orbiter wheels stop as possible, and were scheduled on an approximately logarithmic time scale over the subsequent 8 days (Table 5.4-1).

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Of the 40 subjects studied: 11 were from short duration (4-7 day) missions, 18 from medium duration (8-10 day) missions, and 11 from long duration (1116 day) missions. Seventeen of the subjects were first time (rookie) fliers, and 23 were experienced (veterans).

Results Inability to Use Vestibular Information Following Spaceflight Sensory organization test results from 34 crew members summarized in Tables 5.4-2 and 3, and in Figures 5.4-2 through 7 and 10. Typical Subject: Preflight and postflight antero-posterior (a-p) center of gravity sway time series traces for a typical subject for each of the six test conditions are presented in Figure 5.42. Each of the traces in this figure represent subject response to a different set of sensory orientation reference conditions. The lower center and lower right panels represent responses to test conditions during which vestibular inputs provided the only theoretically accurate sensory feedback. All other test conditions provided the subject with fully or partially redundant sensory orientation information from the visual, vestibular, and/or proprioceptive systems.

Before flight (Figure 5.4-2, "pre" traces), changes in visual cues had little effect on this subject’s a-p sway amplitude when the proprioceptive cues were left intact, as shown in the upper row-fixed support surface. When the proprioceptive inputs were altered, as shown in the lower row-sway referenced support surface, the subject’s a-p sway amplitude increased for all visual conditions. The greatest increases occurred when visual cues were either absent (eyes closed) or simultaneously sway referenced, forcing the subject to rely on vestibular inputs as the only veridical spatial orientation reference cues. Immediately after spaceflight (Figure 5.4-2, "post" traces), the subject’s a-p sway amplitude increased under all test conditions when compared to preflight values. The increased amplitudes observed under sway referenced support conditions (lower row) were balance threatening. When both visual and proprioceptive cues were sway referenced, this subject’s center of gravity oscillated between his/her forward and backward stability limits.

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Stabilograms corresponding to each of the time series traces in Figure 5.4-2 are shown in Figure 5.4-3. The stabilograms demonstrate that, in addition to the increased ap sway amplitudes, the subjectâ&#x20AC;&#x2122;s mediolateral (m-l) sway amplitudes were also increased on each test condition after flight. The increased center of gravity sway was relatively symmetric about the equilibrium point during tests 1 and 2 (upper left and upper center).

However, under the other four test conditions, the a-p sway amplitudes were clearly larger than the m-l sway amplitudes.

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Sensory Test Performances Landing day data were obtained, in all six sensory organization test conditions, for 34 of the 40 subjects (Table STEM Today Page 8

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5.4-2). Cumulative distribution functions for the average p-p sway amplitudes observed in these 34 subjects before and after spaceflight, under each of the six sensory organization test conditions, are presented in Figure 5.4-4. These population data are qualitatively similar to the single subject sway data presented above.

Note that, with the possible exception of the most stable performers on tests 1 and 2 (Figure 5.4-4, upper left and upper center panels), the entire cumulative distribution function for each test condition was shifted to the right, toward higher center of gravity sway, and lower postural stability, values. Furthermore, the preflight and postflight sways were significantly correlated in all but test 2. The correlation coefficients ranged from 0.51 to 0.65 (Table 5.4-3).

Compared to preflight, significant sway amplitude increases were observed early after flight (2.72 Âą 0.13 hrs) in all six test conditions. The mean and standard error values for these data are presented in Table 5.4-3 and plotted in Figure 5.4-5. Under the standard Romberg conditions (Table 5.4-3, tests 1 and 2), the sway amplitude increased by only 0.27 degrees (35%) with eyes open and 0.35 degrees (25%) with eyes closed. Under sensory conflict conditions, the sway amplitude increased by 0.60 degrees (60%) when the visual surround was sway referenced (test 3), by 0.94 degrees (69%) when the support surface was sway referenced and eyes were open (test 4), by 1.97 degrees (63%) when the support surface was sway referenced and eyes were closed (test 5), and by 3.12 degrees (104%) when both the visual surround and the support surface were sway referenced (test 6). While the sway was increased on all sensory organization tests after flight, the increased sway was only stability threatening under the postflight conditions during which vestibular inputs provided the only theoretically accurate sensory feedback (tests 5 and 6).

Sensory Analyses Data from all preflight and postflight sensory organization test conditions were fit to a single ANOVA model to determine the interdependent relationships between sensory inputs in the control of postural stability (p-p sway amplitude). Significant alterations in the main effects of visual, proprioceptive, and vestibular system contributions to balance control were demonstrated (Figure 5.4-6). For all subjects and test sessions combined, altering visual cues (Figure 5.4-6a) approximately doubled sway amplitude, from 1.31 degrees with eyes open to 2.61 degrees with eyes closed, or 2.49 degrees with vision sway referenced (F = 295, df = 2, 64, p < 0.0001). There was no significant difference between the eyes closed condition and the sway referenced vision condition. Mechanically altering proprioceptive cues (Figure 5.4-6b) nearly tripled sway amplitude, from 1.24 degrees with a fixed support surface to 3.25 degrees with a sway referenced support surface (F = 924, df = 1, 32, p < 0.0001). Altering vestibular inputs (Figure 5.4-6c) by 4 to17 days adaptation to microgravity increased sway amplitude by 60%, from 1.61 degrees before flight to 2.56 degrees after flight (F = 156, df = 1, 32, p < 0.0001).

Significant interactions were also observed among the independent variables between the main effects (Figure 5.4-7). For instance, the effects of altering visual cues were exaggerated by simultaneously altering proprioceptive cues (F = 77.8, df = 2, 64, p < 0.0001) (Figure 5.4-7a) and/or vestibular system contributions (F = 10.3, df = 2,64, p < 0.0001) (Figure 5.4-7b). Also, the effects of altering proprioceptive cues were exaggerated by simultaneously altering vestibular system contributions (F = 20.7, df = 1, 32, p < 0.0001) (Figure 5.4-7c).

Time Course of Recovery of Postural Equilibrium Control Following Spaceflight Data presented in Figure 5.4-8, obtained from 13 DSO 605 crew member subjects aboard six separate Shuttle missions ranging from 4 to 10 days in duration, were previously published. Normalized composite equilibrium data from the 10 subjects having landing day measurement sessions were qualitatively similar. Compared to their preflight measurements, which were usually above the 80th percentile scores for a normative population, every subject exhibited a substantial decrease in postural stability on landing day. Four of the 10 had clinically abnormal scores, being below the normative population 5th percentile. All subjects reported similar subjective STEM Today Page 9

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feelings of rapidly increasing stability (initial readaptation) that were corroborated quantitatively in each of the four subjects studied twice on landing day. Although there was some variability in the time required, preflight stability levels were reachieved in all subjects by 8 days after wheels stop.

Based on these results, postflight readaptation was modeled as a double exponential process (Figure 5.4-8).

Normalized composite equilibrium score data were fit to this model using the Levenberg-Marquardt nonlinear

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least squares technique. The results of this exercise demonstrated that (1) at wheels stop, the average returning crew member was below the limit of clinical normality, (2) the initial rapid phase of readaptation had a time constant on the order of 2.7 hrs and accounted for about 50% of the postural instability, and (3) the slower secondary phase of readaptation had a time constant on the order of 100 hrs and also accounted for about 50% of the postural instability.

Head-Trunk Coordination Strategies Following Spaceflight Motor control test results from 28 astronauts aboard 14 separate Shuttle missions of 4 to 10 days in duration were analyzed. The hypothesis that postflight postural biomechanics are affected by adopted strategies aimed at minimizing head movements was investigated to better understand the mechanisms underlying postflight postural ataxia. Subjects were exposed to three sequential sudden support surface translations in the posterior direction before flight.

Ground reaction forces and segmental body motions were monitored and used to compute sagittal plane center of pressure and sway trajectories. Sway responses to translational perturbations were exaggerated on R+0 compared to preflight. The center of force and hip sway trajectories were generally more labile, or underdamped, on R+0 than before flight (Figure 5.4-9), and the learning associated with successive sequential perturbations disappeared in some subjects after flight.

In some subjects, head movements were exaggerated on R+0; however, in other subjects, head movements were substantially reduced compared to preflight. Under these circumstances, hip sway was generally found to be increased while shoulder sway and/or head movement in space were found to be decreased compared to preflight. The strap down and stable platform head trunk coordination strategies postulated by Nashner et.al. were often observed after flight, but rarely observed before flight.

The biomechanical changes appeared to follow recovery trajectories similar to those found in the sensory test performance measurements, with preflight patterns returning by R+4 or R+8 days. We conclude that postflight postural instabilities resulted in part from new constraints on biomechanical movement caused by the CNS adopting strategies designed to minimize head movement.

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Effects of Previous Spaceflight Experience Comparisons of performances on sensory organization tests between the rookie and veteran groups demonstrate significant differences between subjects having previous spaceflight experience and those having none (Figure 5.4-10).

Preflight performances were statistically indistinguishable between these groups on every sensory organization test. Similarly, postflight performances on tests 1, 2, 3, and 4 were not different between rookies and veterans.

On the postflight conditions in which vestibular inputs provided the only theoretically accurate sensory feedback (tests 5 and 6), however, rookies exhibited significantly higher (p=0.02) sway than veterans.

These observations demonstrate that experienced space travelers were better able to use vestibular information immediately after flight than first time fliers. Since experienced astronauts had previously made the transitions between unit gravity and microgravity, they may have been partially dual-adapted and able to more readily transition from one set of internal models to the other.

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The fact that no differences were observed between rookies and veterans on tests 1 through 4 further supports our assertion that altered processing of vestibular system inputs is the primary mechanism of postflight postural ataxia.

Effects of Mission Duration and Demographic Factors Postflight p-p sway amplitude was not significantly affected by mission duration, subject height, or subject weight for any test condition. There were weak, but not significant relationships between postflight sway amplitude and age on test 3 (slope = -0.04 deg/yr, p = 0.04, r2 = 0.31) and test 6 (slope = -0.19 deg/yr, p = 0.006, r2 = 0.41), in which vision was sway referenced with and without accurate proprioceptive cues. As there were only two female crew members studied, no gender effects could be examined.

A significant effect of mission position was found only for test 6 (sway referenced vision and support surface; F = 4.7, df = 2, 30, p < 0.02). Mission commanders had the most stable landing day performances on this test condition (mean ± sem = 4.9 ± 0.61 deg), followed by mission specialists (mean ± sem = 6.3 ± 0.44 deg), and mission pilots (mean ± sem. = 7.4 ± 0.55 deg). The number of payload specialists studied was too small to allow their inclusion in this analysis.

DSO 605 represents the first large n study of balance control following spaceflight. Data collected during DSO 605 confirm the theory that postural ataxia following short duration spaceflight is of vestibular origin.

Balance control is disrupted in all astronauts immediately after return from space.

The most severely affected returning crew members performed in the same way as vestibular deficient patients exposed to this test battery.

Authors conclude that otolith mediated spatial reference provided by the terrestrial gravitational force vector is not used by the astronauts’ balance control systems immediately after spaceflight.

DSO 605 Questionnaire Attached is a blank questionnaire that was given to crewmembers in a one hour preflight training sessions for motion perception reporting.

The training sessions included: 1) Review and definition of motion perception vocabular terms, categories of motion perception disturbances and examples of previously report inflight, entry, and postflight motion perception disturbances; 2) Demonstrations of perceptual illusory phenomena; 3) Practice using the motion perception vocabulary while experiencing altered sensory conditions.

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APOLLO FLIGHT CREW VESTIBULAR ASSESSMENT Motion sickness histories of individual Apollo crewmen, as well as motion sickness symptoms and vestibular related illusions experienced by Apollo crewmen during space flight, are summarized in table 1.

All three Apollo 7 crewmen had positive motion sickness histories. During their mission, however, none of these crewmen-including the Lunar Module Pilot (LMP), who performed purposeful spinning and tumbling maneuvers in the Command Module-experienced any symptoms of motion sickness. While donning his space suit, the Apollo 7 LMP did experience a brief tumbling illusion once, as indicated in table 1.

All three Apollo 8 astronauts had some history of motion sickness. During flight, soon after leaving their couches, all three crewmen experienced nausea apparently as a result of rapid body movements. For the Commander (CDR), these symptoms progressively worsened; and, shortly after waking from his first sleep period, he vomited. ln this particular case, the severe symptoms experienced were in part caused by gastroenteritis. The antimotionsickness drug, Marezine, was ineffective for the CDR, but it did alleviate the stomach awareness and nausea experienced by the other two crewmen.

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The first clear episode of a severe vestibular related motion sickness problem occurred during the Apollo 9 mission. Because this incident is unique, a detailed account is given. The crewman involved, the LMP, had fewer flying hours than the average astronaut and a definite history of motion sickness. Also, he was making his first space flight. Because he was concerned about his previous history, he took one 50-mg Marezine tablet three hours before lift-off and another one 1-1/2 hours after orbital insertion. Upon rising from the couch later on the first day, he observed that when he turned his head rapidly, he experienced mild dizziness. The dizziness did not seem to interfere with his performance, and he was able to control it by executing all movements slowly and by turning at the waist instead of turning his head. He did not experience any nausea with the dizziness that was produced by head movements.

Shortly after donning his pressure suit for transfer from the CM to the LM at approximately 40:00 ground elapsed time, the Apollo 9 LMP vomited suddenly. The characteristic prodromal symptoms of motion sickness were not experienced. He was, however, able to retain the vomitus in his mouth long enough to use a disposal bag effectively. In the postflight medical debriefing, he could not recall whether he felt nauseated after vomiting or whether he experienced some relief. About four hours later, he vomited again after he had transferred to the LM. Again, the vomiting was sudden and was not preceded by much warning. Aspiration of the vomitus did not occur on either occasion. Just before vomiting the second time, he had been closing circuit breakers and cycling switches located in different areas of the cabin. Such activities require considerable movement within the LM. Immediately following the second episode of vomiting, he felt much better and noted a marked improvement in his ability to move around freely. The only residual symptom was a loss of appetite and an aversion to the odor of certain foods. Until the sixth day of the mission, he subsisted exclusively on liquids and freeze-dehydrated fruits (Apollo 9 Mission Report, 1969).

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Because of great concern about the inflight problems of the Apollo 9 LMP, a decision was made to perform comprehensive vestibular tests on him at the Naval Aerospace Medical Institute, Pensacola, Florida. Functional tests of the labyrinth included audiometry, measurements of semicircular canal sensitivity (caloric irrigation and oculogyral illusion), ocular counterrolling, and ataxia/postural equilibrium. Provocative tests included the "dial test" (performance of head and arm movements in the slow rotating room), a coriolis motion sickness test (performance of programmed head movements while rotating in a chair), an off-vertical rotation test, and a cineramic motion picture.

On the basis of these tests, it was concluded that the Apollo 9 LMP had normal function of the vestibular apparatus. The provocative tests, including parabolic flight test data, indicated that he had no greater than average susceptibility to motion sickness. Furthermore, he showed an ability to adapt or to gain increased tolerance with repeated exposures to provocative stimuli.

As a result of the Apollo 9 vestibular problem, increased attention was given to developing techniques for predicting and preventing any such future occurrences. Insufficient time prevented individual crewmen from engaging in any special preflight vestibular adaptation activities. However, on the basis of research performed using the slow rotating room at the Naval Aerospace Medical Institute, it was determined that vestibular adaptation to the weightless environment might progress more rapidly if the crewmen executed planned head movements very early during their flights. Also, the antimotion-sickness drug was champed from Marezine to a combination of scopolamine and Dexedrine.

During the first day of the Apollo 10 flight, the LMP executed the recommended head movements in an attempt to hasten vestibular adaptation. The head movements quickly induced stomach awareness and nausea, and he was compelled to stop. He tried these head movements again on the second day and again had to stop after one minute because of the rapid onset of symptoms. After the second day of flight, he apparently had

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adapted and experienced no further difficulties. On the seventh day of the mission, he experimented with the head movements again and was able to perform them for five minutes before symptoms began to appear. No other Apollo 10 crewmam experienced any inflight symptomatology.

Although several of the Apollo 11 and Apollo 12 astronauts had positive motion sickness histories, none of these crewmen reported any difficulties either during weightless flight or on the lunar surface. The complete absence of vestibular problems during lunar surface activity throughout the Apollo Program has proved significant. Before the Apollo 11 mission, many predictions had been made regarding possible disorientation and postural stability problems that might occur on the lunar surface.

Very early in the Apollo 13 flight, vestibular problems were experienced by two of the crewmen, including the LMP, who vomited on the second day. All available information indicated that both of these crewmen had negative motion sickness histories. The CDR, who had a definite history of motion sickness, experienced no vestibular symptomatology during this flight. Although comprehensive historical data are not available for the Apollo 14 flight crew, at least two of the crewmen had some past experience with motion sickness. This history was especially true of the CDR, who, several years before the Apollo 14 flight, underwent successful corrective surgery for Ménière’s disease. No crewmam encountered vestibular difficulties during the Apollo 14 mission.

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Complete historical data are not available for the Apollo 15 flight crew; however, at least two of the crewmen had some minimal past experience with motion sickness. During the flight, the CDR and the Command Module Pilot (CMP) had no illusions or symptoms. The LMP reported, however, that he experienced a sensation of impending vestibular difficulties and therefore limited his motions during the first several days of the flight.

This condition cleared, and he bad no subsequent problems during lunar extravehicular activity and return to Earth.

Following splashdown and recovery, however, he developed some unusual symptoms that probably were partly vestibular in origin. He reported a feeling of dizziness or lightheadedness that persisted for seven days following recovery. This condition was not accompanied by any type of gastrointestinal disturbance. Locomotion was not impaired, nor was any tinnitus reported.

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In addition, be commented on a 30 degree head-down, tilted sensation experienced when supine. This sensation was most apparent during periods of "twilight" sleep and persisted even when he turned onto his side.

The tilted sensation was not present when be was fully awake, regardless of postural position. This condition gradually lessened; the degree of tilt appeared to decline and disappeared entirely after the fifth postrecovery day.

At about the same time that his symptoms disappeared, he was subjected to several different clinical vestibular tests, which were conducted by an otolaryngologist. The tests included a standard Hallpike (measurement of the amount of nystagmus produced by alternate irrigation of the right and left ear canals with warm or cold water), positional nystagmus, postrotary nystagmus, and standard audiometry. The crewmanâ&#x20AC;&#x2122;s responses on all of the tests were normal All Apollo 16 and Apollo 17 crewmen had positive motion sickness histories. However, only the Apollo 17 CDR and LMP experienced inflight disturbances. In both of these cases, the symptoms were mild and disappeared after the third day of flight An overall summary of Apollo motion sickness findings is presented in table 2. Eleven of the 33 individuals who have flown on Apollo flights have experienced apparent vestibular difficulties. Of these eleven, nine had positive motion sickness histories. Conversely, 18 of 27 individuals with positive histories had no inflight symptomatology. Six of the eleven crewmen with inflight problems experienced minor symptoms, two experienced moderate symptoms, and three bad severe symptomatology. As previously stated, it is questionable whether the vomiting experienced by one of these latter individuals was vestibular in origin or due primarily to gastroenteritis. Six (40 percent) of the 15 individuals making their first space flight developed inflight symptoms. Of the 18 veteran pilots, only five (approximately 28 percent) experienced symptoms.

Special Laboratory Measurements Because no postflight tests were performed on the Apollo 17 flight crew, complete laboratory data for the Apollo 16 crewmen only are described.

Test results showing the ability of each Apollo 16 crewman to balance on rails of various widths are presented in figure 1. Preflight findings for all three crewmen are within the range of performance typically exhibited by young, healthy, pilot-type subjects. Examination of figure I indicates that during the first (R + 3) and second (R + 7) postflight test periods, postural equilibrium with eyes open was nearly identical to preflight performance for all crewmen. The CDR actually demonstrated a slight progressive improvement on this task with time. At R + 3, however, the CDR and the CMP exhibited a marked decrease in postural stability when deprived of all visual sensory cues. When these two individuals were tested again at R + 7, there was a definite improvement in postural stability with eyes closed compared to their R + 3 performance. The CMP bettered his preflight, eyes-closed scores, whereas the performance of the CDR was approximately midway between his two previous scores.

The principal characteristics of the spontaneous nystagmus-as well as the lag, the maximum velocity, the maximum frequency, and the duration of nystagmus elicited from each Apollo 16 crewman in response to the two irrigation temperatures-are summarized in table 3. Lag is defined as the time between the onset of irrigation and the first measurable nystagmus. Maximum velocity was obtained by selecting the ten-second epoch of a given record that contained the greatest preponderance of high-velocity, slow-phase nystagmus, and by calculating the average slow-phase velocity value for that epoch. Maximum frequency was obtained similarly. The duration of nystagmus is the interval between onset and complete cessation of nystagmus.

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In general, the preflight responses indicate that all crewmen possess normally functioning canals bilaterally.

The nystagmus produced was always in the expected direction. Spontaneous nystagmus was present in all three Apollo 16 crewmen, but no meaningful trends were observed with this parameter. Also, all of the crewmen exhibited an asymmetry or labyrinthine preponderance which, with the exception of a slight reversal in the CMP at R + 7, remained unchanged.

To facilitate more discernible intersubject and intrasubject comparisons, the primary parameters of lag, maximum velocity, maximum frequency, and duration of nystagmus are plotted in the form of bar graphs for each Apollo 16 crewman at each irrigating temperature in figures 2 to 4. Right and left ear data are shown separately in each figure.

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Examination of figure 2 indicates that during the first test period (R + 3), the nystagmic responses of the LMP were very similar to his preflight responses, particularly at 303.65 degree K. The tendency toward shorter lag times, higher velocities and frequencies, and longer durations of nystagmus with the more stressful water temperature (307.15 degree K) is also quite apparent in these data, as is the consistent right-greater-than-left response asymmetry.

Because no postflight changes were detected with either postural equilibrium or caloric irrigation procedures, the Apollo 16 LMP was not tested further. Changes in the CDRâ&#x20AC;&#x2122;s responses to caloric irrigation at R + 3 are readily observable in figure 3. With two exceptions that occurred with the 307.15 degree K stimulus, all of the R + 3 response parameters arc elevated compared to the F - 30 baseline. When tested again four days later, the CDRâ&#x20AC;&#x2122;s nystagmic responses had essentially returned to preflight values. Figure 4 indicates that, although a few parameters were elevated at R + 3 compared to F-30 and R + 7, the data for the CMP are scattered and no overall trends are apparent. Left/right asymmetry, which is pronounced in the first two crewmen, is not well defined in this individual.

Although no provocative tests were administered, a motion experience questionnaire completed before flight by each crewman indicated that all had low susceptibility to motion sickness under one-g conditions. As stated previously, none of the Apollo 16 crewmen reported experiencing any symptoms of motion sickness during the flight.

Apollo 16 Special Study In evaluating the results of the Apollo 16 special study, the type of tests that were used and the manner in which they were performed should be considered. Postural equilibrium with eyes open served as a control condition for the eyes-closed portion of the test. Whereas none of the crewmen at any time showed appreciable change in postural stability with eyes open, a performance change was noted in two crewmen (CDR and CMP) when they were deprived of visual cues, and were required to balance solely on the basis of vestibular and proprioceptive sensory cues.

This finding suggests that subtle alterations in these nonvisual sensory modalities were present at R + 3. The fact that the eyes-open scores did not change suggests that visual cues compensated for the relative decrease in performance observed in the eyes-closed task. This finding is not unusual. When minor changes occur in the vestibular system, they often can be overridden by vision, which normally dominates human spatial orientation.

It can reasonably be assumed that the relative improvement seen in these two individuals at R + 7 represented a return to normal of the sensory mechanisms involved.

It is also recognized that the postural stability test employed in this study is primarily a behavioral task and, as such, is subject to learning effects. Examination of the data indicates that a slight amount of learning may have occurred. The only clear evidence, however, is in the ease of the CDR on the eyes open portion of the test. Even if a learning effect was present, it could only have biased the postflight performance in a positive direction, and it is clear that a decline in eyes-closed performance occurred in two of the crewmen at R + 3.

The significant improvement in eyes-closed postural stability observed in these two crewmen at R + 7 undoubtedly is more representative of a return to normal function of the sensory systems involved than of a simple learning effect. An alert mental state is conducive to the elicitation of nystagmus. Apparent y as a result of an understandable emotional letdown following their mission, the crewmen exhibited some difficulty in maintaining an alert mental state during the calorie test at R + 3. This condition should have tended to suppress nystagmus; however, the CDR did show a very clear elevation in nystagmic activity at R + 3, indicative of a labyrinthine hypersensitivity. The somewhat erratic nystagmic activity observed in the CMP is also suggestive of unstable postflight vestibular function.

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The finding of both decreased postural stability and increased nystagmic activity in the same two crewmen at R + 3 corresponds well to a study reported previously . Using procedures very similar to those employed in this study, these investigators found a high positive correlation between tests of ataxia and caloric irrigation. The majority of their subjects who performed poorly on the ataxia tests, particularly with eyes closed, also yielded abnormal responses to calorie stimulation.

On the basis of the data, a tentative conclusion is that the postflight responses observed in two of the Apollo 16 crewmen reflected changes in vestibular function brought about by exposure to the conditions encountered during their mission. Because of the limitations inherent in this study, it is not possible to generalize from these data or to identify causal factors with any degree of certainty. Although lack of a gravitational stimulus was probably the most important environmental factor, other physiological stressful events such as launch, entry, and recovery activities may have contributed to the observed changes.

Overall Assessment of Apollo Series • Increased mobility, and thus increased head movements as afforded by the larger volume of the Apollo CM/LM, resulted in a higher incidence of vestibular disturbances in the Apollo Program than in previous programs.

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• In most eases in which symptoms did occur, they were mild to moderate and could be controlled by limiting head movements the first few days in flight.

• Adaptation of the vestibular receptors to the weightless environment apparently occurred within the first several days of flight for most individuals. However, on the basis of these Apollo data alone, one can only speculate whether or not adaptive processes will lead to complications of a different nature during long duration missions.

• Extravehicular activity in one sixth g on the lunar surface resulted in no disorientation or vestibular disturbances. Apparently, one-sixth g is an adequate stimulus for the otolith organs to provide sensory information regarding gravitational upright and, hence, maintenance of posture.

• With one important exception on the Apollo 15 mission, no crewmen experienced pronounced vestibular disturbances after returning from space flight. This finding suggests that adaptive processes that occur during weightless space flight missions of up to two weeks in duration do not render the vestibular system significantly hyposensitive or hypersensitive following sudden return to a one-g environment. Again, on the basis of these data alone, one can only speculate whether or not this condition will be true following very long exposure to zero g.

• Whether or not an individual is likely to develop inflight vestibular problems cannot be predicted reliably from his previous history of motion sickness. However, astronauts making their first space flight appear to be slightly more susceptible to the development of inflight symptoms than are experienced astronauts.

The Mercury flight series, the Gemini flights, including those involving extravehicular activity, were free of significant vestibular problems. Results of quantitative preflight, inflight, and postflight tests performed during the Gemini 5 and 7 missions indicated that lifting the gravitational load from the otolith organs did not result in any disturbance of the integrative processes of the central nervous system that might have influenced the crewmen’s spatial orientation.

Also, there were no significant differences between preflight and postflight measurements of ocular counterrolling. A phenomenon that occurred during the Gemini Program, and that has been reported routinely by American flight crews since that time, was a feeling of "fullness of the head" upon entering weightlessness.

Some astronauts described this sensation as a feeling of "hanging upside down." As a result, the idea was quickly adopted that these men had experienced am inversion illusion or a spatial disorientation. On the basis of better descriptions from the crewmen involved, the investigators are reasonably certain that this phenomenon was not an inversion illusion, but the result of a redistribution of extravascular and intravascular fluids.

The Apollo Program included several significant changes from Project Mercury and the Gemini Program in the type of vehicle and the type of mission being flown. The Apollo Command Module (CM) had a considerably larger habitable volume than had either the Gemini or the Mercury spacecraft. Therefore, for the first time in the American space program, crewmen were able to move about freely within the spacecraft. Beginning with

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the Apollo 9 flight, the CM and the Lunar Module (LM) were docked in flight, and crewmen were able to move back and forth between two vehicles for the first time.

Beginning with the Apollo 11 flight, the first lunar landing, crewmen made transitions from zero g in flight to activity in one-sixth g on the lunar surface and back to zero g. With these changes, particularly the greater mobility permitted by the larger volume of the CM and the LM, the first serious vestibular problems became evident. The purpose of this report is to present and discuss all available information on vestibular system function during the Apollo series of space flights.

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Vestibular function and Sensory interactions in MIR Space Station Statistical analysis of questionnaire data on in-flight subjective reactions performed by L. N. Kornilova demonstrated that 75% of cosmonauts experienced spatial illusions and orientation disturbances. In-flight vestibular discomfort occurred in 12% of cosmonauts. Postflight vestibular evidence was present in 38% of cosmonauts when not tested and in 31% of subjects when executing active head movements. Illusions were noted by 50% of cosmonauts.

Examinations of vestibular function in microgravity revealed a significant transformation of spontaneous and visual-vestibular stimulation induced oculomotor reactions. On the 3rd day of flight oculographic measurements revealed development of a spontaneous vertical nystagmus (especially with eyes closed), disturbances of eye tracking motions, and a decreased threshold for optokinetic and vestibular nystagmus in the majority of 9 cosmonauts examined within the Salyut 7 and Mir space programs. Combined vestibulo-optokinetic stimulation induced a predominant vestibular nystagmus. On day 5 of flight the severity of changes decreased, but again recurred on days 116 and 164 of flight with this level of severity maintained up to days 7-8 after returning to Earth gravity.

Observed changes in spontaneous and induced oculomotor activity, particularly during the early stages of flight, can result in the development of inflight specific sensory reactions. Examination of 14 crewmembers after longterm stays aboard Salyut-7 and Mir space stations revealed the presence of postgravitational dysmetric and dysrhythmic nystagmus associated with the vertical (mainly a downward motion) and horizontal (shift to the right) electro-oculographic (EOG) leads both at rest and during executing active and passive movements.

Simultaneously in most cases the pattern of oculomotor reactions for different tests and the visual tracking reflex were changed. Vestibulo-oculomotor reactions returned to the norm in almost all cosmonauts within 2 weeks. It was noted that in 17% of cases disturbances of the vestibular function and the vestibulo-oculomotor interaction correlated well with hemodynamic changes (r = 0.85, P < 0.05). In 22% these disturbances were concerned with altered activity of the vestibular input proper and on other sensory systems interacting with it.

Both factors were of significance in 61% of cases.

Statokinetic measurements (on days 3, 5, 63 and 193 in flight) during graded force tests revealed significant changes in the precision of applied strength and rate of movement. Incidence of findings were greater (approx.

2 times more) in an "eyes closed" position. The postural-motor coordination test demonstrated distinct changes in the standard (for a 1g environment) pattern of muscle activity.

However, on the 193rd day of flight the coordination patterns of posture synergies and postural control demonstrated a trend to return to an Earth-based standard. This was most likely due to the regular use of countermeasures and is interpreted to indicate adaptability of the motor control system during prolonged space missions.

Postflight shifts were manifested as 4-8 changes in sensory inputs and spinal automatisms in the form of an increased sensitivity (a decline in threshold levels) to support (vibration effects on the feet) and stimulate muscle (graded T-reflex) and as interextremity synergy disturbances; a decrease in lateral stiffness of muscles and muscular strength velocity parameters; subatrophy and atrophy of antigravitational muscle groups; decrements of vertical posture stability; locomotor disorders; and changes in coordination precision parameters revealing a declined effectiveness of precision regulation.

The severity and duration of manifesting the abovementioned shifts in crewmembers after flights of various durations were different, but did not correlate with flight duration and had a marked dependence on the amount, intensity and profile of inflight exercise usage.

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Long-term space flightsâ&#x20AC;&#x201C;personal impressions by Polyakov VV On August 29, 1988, I was launched together with the Soviet-Afghan crew and on August 31 after docking we found ourselves onboard the "Mir" orbital complex where we were given a hearty welcome

by Vladimir Titov and Musa Manarov, who had been staying there for 8 months and who were faced with completing a record-setting flight of one year in duration.

In six days the Soviet-Afghan space flight was terminated, but Titov, Manarov and I were still on orbit. On November 28, 1988, we were joined by a Soviet-French crew and the crew of six worked aboard the "Mir" complex together, including a French cosmonaut, general Jean-Loup Chretien, till December 21, when he together with Titov and Manarov returned to Earth, and Alexander Volkov, Sergei Krikalyov and I stayed for an extra 4 months in space, that is, till April 27, which is Volkovâ&#x20AC;&#x2122;s and my own Birthday.

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The result of my work during the 8-month space mission and the most important personal impression is that I was able to preserve performance, good physical form, orthostatic and vestibular tolerance and finally health itself. What was the cost of it?

It was probably equivalent to that deficit of physiological and biological effects on the human body produced by Earth gravity. My experience in space medicine makes it possible to formulate and apply tactical principles of using inflight countermeasures and a system to prevent an adverse effect of a long-term stay in microgravity on the body, which was creatively complemented by elements based on my personal impressions associated with weightlessness effects and on the results of observing and examining my spacemates.

The principle of this tactic is simple - "do not allow the body to be adapted to weightlessness" - as far as possible, of course. And I think this vestibular system is a single one which is desired to be adapted to microgravity as soon as possible.

However, none of the spacemates experienced motion sickness problems. It is known that in these individuals who are susceptible to space motion sickness its symptoms disappear and therefore an adaptation of vestibular analyzer persists for 3-5 days, in rare cases it occurs for a longer period of time and fmally the cosmonauts forget all about it and think of it only after landing, when during post-flight examinations the physicians reveal a particular level of vestibular or orthostatic intolerance practically in all cosmonauts.

Following the above concept "to prevent a cosmonaut from being fully adapted", but rather desiring a vestibular readaptation when preparing for the return to the Earth I, already having stayed in orbit for six months, have embarked on a vestibular training.

During the first minutes of rotation I observed pronounced vestibulo-vegetative reactions, even more severe than that which I have experienced during experiments or ground-based trainings, although I considered myself a rather tolerant man. In just that very flight, I became aware of the importance of this problem for the Shuttle, Buran, Hermes type spacecraft pilots who after more than a week stay in orbit suddenly have to land a manually controlled spacecraft.

But soon my alarm gave place to optimism because in subsequent trainings the severity of vestibulovegative and somatic responses was less pronounced even in a third training session which lasted for 10 minutes. I understood that I would not exprience motion sickness problems in the descent stage but after landing it occurred as expected.

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References Paloski, W.H., C.M. Oman, J.J. Bloomberg, M.F. Reschke, S.J. Wood, D.L. Harm, B.T. Peters, A.P. Mulavara, J.P. Locke, and L.S. Stone. Risk of sensory-motor performance failures affecting vehicle control during space missions: a review of the evidence. J. Grav. Physiol. 15(2):1-29, 2008

McCluskey, R., J. Clark, and P. Stepaniak. Correlation of Space Shuttle landing performance with cardiovascular and neurovestibular dysfunction resulting from space flight. In: Human Systems 2001. Clear Lake City, TX, 2001

Moore, S.T., H.G. MacDougall, X. Lescue, J.J. Speyer, F. Wuyts, and J.B. Clark. Head-eye coordination during simulated orbiter landings. Aviat. Space Environ. Med. 79:888-898, 2008.

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Paloski WH, Reschke MF, Black FO, Doxey DD, Harm DL. Recovery of postural equilibrium control following spaceflight. Ann N Y Acad Sci. 1992 May 22;656:747-54. PubMed PMID: 1599180.

Postural Equilibrium Control During Landing/Egress (DSO 605), NASA.

CHAPTER 8, APOLLO FLIGHT CREW VESTIBULAR ASSESSMENT, SP-368 Biomedical Results of Apollo , NASA.

Grigoriev AI, Bugrov SA, Bogomolov VV, Egorov AD, Polyakov VV, Tarasov IK, Shulzhenko EB. Main medical results of extended flights on space station Mir in 1986-1990. Acta Astronaut. 1993 Aug;29(8):581-5. Review.

PubMed PMID: 11541636.

Polyakov VV. Long-term space flightsâ&#x20AC;&#x201C;personal impressions. Adv Space Res. 1992;12(1):339-41. PubMed PMID: 11536977.

Polyakov VV. The physician-cosmonaut tasks in stabilizing the crew members health and increasing an effectiveness of their preparation for returning to Earth. Acta Astronaut. 1991;23:149-51. PubMed PMID: 11537117.

O. G. Gazenko, A. I. Grigoriev, S. A. Bugrov, A. D. Egorov, V. V. Bogomolov, I. B. Kozlovskaya and I. K. Tarasov, Main medical results of the second prime crew flight on Mir: a review. Kosm. Biol. aviakosm. Med. 24, No. 4, 3-11 (1990) (in Russian).

A. I. Grigoriev, S. A. Bugrov, V. V. Bogomolov, A. D. Egorov, I. B. Koziovskaya, I. D. Pestov and I. K. Tarasov, Medical results of the 366-day manned mission on Mir: an overview. Kosm. Biol. aviakosm. Med. 24, No. 5, 3-10 (1990) (in Russian).

A. I. Grigoriev, V. V. Polyakov, V. V. Bogomolov, A. D. Egorov, I. D. Pestov and I. B. Kozlovskaya, Medical results of the fourth prime expedition on the orbital station Mir. In Proceedings of the Fourth European Symposium on Life Sciences Research in Space, Trieste, Italy, pp. 19-22. ESA, France (1990).