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Space simulators—prelude to manned space flight
SPACE SIMULATORS-PRELUDE
TO MANNED SPACE FLIGHT
A. B. THOMPSON Vought Astronautics,
and W. B. LUTON
Division of Chance Vought Corporation
Abstract-Before man travels in space as an active member of a man-machine system, considerable additional knowledge must be gained as to his capabilities under the combined stresses of space flight and in the particular vehicle configurations being considered. Combination flight control-navigationenvironment simulators are proposed as a tool to verify and aid analytical studies of man’s performance. A review is made of two recent simulator programs (a centrifuge simulator and a six degree of freedom fixed base simuiator) which studied human performance in orbital vehicles. Results of these studies are presented as examples of information on man’s capabilities that may be obtained through simulation. Need for more complete environmental simulation is shown and a study presented to show the degree of simulation which can be reasonably obtained in such a specialized laboratory. One concept for a space simulation laboratory is detailed. Conclusions are drawn as to the urgency of need for such tools.
Before man ventures into space as an active member of a man-machine system, a thorough knowledge must be available as to his capability adequately to control and navigate the vehicle throughout the entire mission profile and to cope successfully with emergency situations. Although a considerable amount of data is available on human capability and tolerances when exposed to individual stresses, almost none exists for the multiple stress situations which will be encountered in space flight. Degradation of pilot performance under the combined stresses of noise, vibration, acceleration, high temperature, reduced pressure, isolation and extreme tension -to mention only a few-must be thoroughly evaluated and then compensated for insofar as practicable by optimum integration of the man with the machine. Theoretical analyses based on past tests establishing human tolerances to individual stresses are not sufficient to provide assurance that the pilot of an orbital vehicle will be capable of reliable decision, command and control throughout all phases of flight. The first rocket boosted flights of a manned space vehicle will be roughly equivalent to taking a new, very high performance aircraft to the extremes of its flight envelope on its first flight completely on instruments and without the benefit of a chase plane. It becomes increasingly apparent that relatively complex flight control-navigationenvironment simulators must be utilized ex-
tensively from the study and design phases of vehicle development up to and including complete mission flights. In the past, simulators have been used primarily for training purposes, being available to user activities in an after-the-fact fashion. Currently, they are being utilized on an everincreasing scale for research in man-machine integration and optimization of vehicle parameters. However, the approach is in bits and pieces, i.e. pressure chamber type space cabins, heat chambers, acceleration via centrifuges and high-speed sleds, and fixed base flight simulators. Of course, these are logical first steps toward realization of manned space flight, but they fall short of determining man’s usefulness under combined stresses and in the particular vehicles under consideration. During 1959 two such simulators were designed, built and operated by Chance Vought Aircraft, Inc., as aids in establishing the needs and capabilities of the pilot of an orbital hypersonic vehicle. The first of these was an acceleration flight control simulator (Fig. 1) which operated both fixed base (static) and under boost acceleration fields in the Aviation Medical Acceleration Laboratory centrifuge at Johnsville, Pennsylvania. Its purpose was to determine the pilot’s accuracy of control during acceleration representative of an orbital vehicle’s exit flight, evaluate a new concept in pilot operated control
324
SPACE SIMULATORS
Fig. I. Acceleration space flight simulator Johnsville, centrifuge.
Fig. 2. Typical
in AMAL,
pilot control
devices and verify general physiological tolerance aspects to the rocket-boosted flight of a space vehicle. Previous tests had indicated that optimum tolerance to high transverse acceleration fields was obtained with a slightly forward leaning
325
seat position, and as rudder control became ineffective at approximately 6 “G” while wrist and finger control was effective to beyond 12 “G”, a three-axis wrist controller would probably be necessary for manual vehicle control. However, all side sticks developed to this time were two-axis types-pitch and roll only. After studies were made as to wrist bone structure, pivot angle limits and force capabilities along all axes, a three-axis side stick was designed and initially evaluated versus the conventional center stick-rudder pedal arrangement in a C-l 1B simulator. With a minimum familiarization period pilots were able to make equally accurate instrument approaches and landings with either type of control. Both the selected seat angle and side stick were integrated into the centrifuge simulator along with the appropriate instruments necessary for the pilot to fly a command boost profile. The tracking task was a closed loop simulation of vehicle dynamics and response through the controls and instruments. Transient moments of wind shear and uneven thrust termination were introduced in pitch at
of vehicle boost trajectory.
appropriate times for added realism. In addition to manually flying the entire trajectory into orbit the pilot was required to initiate and terminate last stage thrust. Four experienced pilots flew twelve recorded runs each under 1 “G” conditions and twelve
A. B. THOMPSON
326
Fig. 3. Pilot
performance degradation transverse acceleration.
Fig. 4. Six degree
due
to
of freedom
recorded runs under the selected acceleration profile. Oscillograph records were made of integrated error in pitch, roll and yaw; pilot input in pitch, roll and yaw; instantaneous error in pitch, roll and yaw; radial acceleration; and
and
W. B. LUTON
flight path angle. Also a variplotter operated each run and plotted altitude versus velocity, a typical dynamic run being shown in Fig. 2. The four subjects’ integrated pitch control error (from the commanded profile) was averaged for each run, static and dynamic, and a comparative plot made (Fig. 3). It indicated that after a short centrifuge learning period (four runs), the subjects’ accuracy of control under the high “G” conditions was within 5 per cent of the accuracies obtained under 1 “G” conditions. The subjects’ time of response to attitude errors averaged onethird greater under the boost conditions, however, this apparently did not significantly affect the probability of achieving a successful orbit. It was concluded that with the seat position and side controller used in this experiment and with proper flight information, a pilot could be an effective redundant controller to an automatic system during the boost phases of space vehicle flight. As much of the remainder of an orbital mission was well beyond the regions which have been explored by and are familiar to engineering and
fixed
base space flight
simulator.
flight personnel as regards the human component in the system, a six degree of freedom fixed base space flight simulator (Fig. 4) was constructed. Specific objectives were to determine what control capability the pilot will have as well as
Fig. 5. Six degree
of freedom
space flight simulator
block diagram.
328
A. B. THOMPSON
what displays are required-both optimum and minimum-to manage energy, effect safe reentry and navigate to destination. Some idea of the complexity required to achieve such simulation is illustrated in the block diagram (Fig. 5). This particular simulator was driven by 290 amplifiers and 16 function generators and was capable of simulating in real time the mission from the end of boost, throughout orbit, re-entry, hypersonic glide and finally supersonic approach
and W. B. LUTON pilot controlling temperature during re-entry and managing the vehicle’s kinetic energy to arrive at destination. An orbital space vehicle requires a completely different concept of managing energy than pilots have used in the past. For example, at 500,000 ft altitude the potential energy (which is familiar to pilots) is 500,000 ft-lb/lb of vehicle weight, while the kinetic energy is twenty times that value or 10,000,000 ft-lb/lb of vehicle weight. The major
Fig. 6. Pilot ability to manually fly orbital
to a point over the destination. All instruments were activated that were required for these phases-vertical situation, horizontal situation, distance to go, range tolerance, inertial velocity, inertial altitude, vehicle temperature, normal acceleration, reaction control fuel and time. The simulator contained the vehicle equations of motion, aerodynamic and reaction control parameters, long and short period dynamics, temperature and navigation equations, as well as full pilot control capability through the three-axis side stick. In addition to standard pen recorder records of specific parameters, four variplotters recorded flight profile data. An altitude versus distance trace (Fig. 6) recorded the entire orbital mission as flown by the pilot. The deviations from the predicted trajectory are the result of the
mission.
problem now is how to manage the velocity rather than the altitude. An energy management plot (Fig. 7) recorded inertial velocity versus distance. The pilot of an orbital vehicle may vary his range upon re-entry by as much as 6000 miles by varying the vehicle angle-of-attack between the limits of LIDmax and CLAIM. Provided with an adequate display of this information, a wide range of destinations may be reached. Another parameter of critical concern during re-entry is vehicle temperature. A lifting vehicle (during a non-equilibrium re-entry) re-enters with a series of long period bounces off the dense lower atmosphere. A recording of altitude versus velocity (Fig. 8) illustrates this condition. As maximum lower surface temperature occurs at the bottom of each plunge and it is a function of angle-of-attack, it was found
SPACE SIMULATORS
Fig. 9. With proper energy management and navigation information, the pilot may correct for relatively large azimuth launch errors or turn to reach alternate destinations.
that the pilot could effect safe re-entry from above the normal or equilibrium recovery ceiling. This was accomplished by holding phase and allowing CL maK during the descending
Fig.
7.
Pilot management
of re-entry
the angle-of-attack to decrease as the temperature limit was approached and then holding Z,/Dmaxduring the ascending portion of the bounce. Such a maneuver is relatively easy for
26
21
22
20
18 INERTIAL
Fig. 8. Typical
pilot control
329
16 “ELOCLTY
Conclusions drawn from the operation of this simulator were that the human component, equipped with a display comparable to that used in the simulator, can manually fly the
14
L2
1”
8
6
4
1000 F’PS
of vehicle temperature
a pilot and relatively complex and less reliable for automatic equipment. The ability of the pilot to turn off the orbital path during re-entry to reach particular destinations is illustrated in
energy.
kinetic
during
re-entry.
orbital, re-entry and hypersonic glide phases of a one-orbit mission and can manage kinetic and potential energy and navigate to various destinations. The capability of the pilot, assuming,
330
A. B. THOMPSON
and W. B. LUTON 40”
3P
200
IO0
0”
100
200
I
I 170°
180°
I 11P
I l&P
Fig. 9. Typical pilot controlled
I
I
I
I
1500
1400
1300
1200
1 30” 110°
heading change to reach destination.
adequate training, is limited only by the performance capability of the vehicle. The only reservation in reaching these conclusions is that several other human factors-combined stresses, etc.-were not simulated and were therefore beyond the scope of the analysis.
simulation facility for every type of spacecraft is not necessary. Many of the parameters are the same for all crafts and missions, and many others differ so slightly that the apparatus would be readily convertible to each configuration. Studies were made to determine what degree of
700
T
850
P 2
300
200
100
115
I@@!
I-
”
Fig. IO. Relative cost of degree of simulation
Although the work to date on space flight simulators is significant as indicated above, it represents only a millesimal fraction of what is required before space flight becomes even relatively commonplace. As the next step, a most urgent need exists for a moving base environmental flight simulator. To build a near-total
for space vehicles.
simulation could be achieved at reasonable cost; the results of which are shown in Fig. 10. The basic fixed base simulator would simulate on a real time basis in six degrees of freedom all phases of the mission boost, orbit, re-entry, glide, approach and landing. The addition of a moving base would give the proper direction of
SPACE SIMULATORS
the acceleration forces existing at all times as well as the translational motions due to vehicle short period dynamics. External vision in the form of a planetarium type display would add very little to the total cost. The important crew environmental stresses-noise, vibration, temperature, internal atmosphere and pressure, and lighting-could be included for a reasonable price. Only when an attempt is made to include the magnitude of acceleration does the cost go out of reason. This is due to the extremely large centrifuge required to carry the heavy simulator. And, of course, the weightless condition is not obtainable at this time in surface-based simulators. Conceptual studies were made to determine how best to achieve the above. One such concept is illustrated in Figs. 11 and 12. This particular simulation laboratory consists of a spherical dome, 40 ft in diameter, attached to a two-story building, 40 ft square. In the center of the dome is a moving base pressure-tight gondola which duplicates the space vehicle crew’s flight control station. It contains the instruments, controls and genera1 cockpit arrangement of the space vehicle under investigation The environment stresses of various space missions are reproduced therein : re-entry heat is produced by heating elements which can raise the inner wall temperature to 350°F; rocket noise up to 130 dB is produced by tapes and projected by a speaker system into the cabin ; vibrations to 50 c/s and & in. double amplitude are programmed as a function of flight condition by a signal generating device which drives the seats’ vibrations bases; and the internal atmosphere in its principle elements of composition and mixture ratio, cabin pressure altitude, humidity and circulation rate is generated by systems of pumps, valves, supply bottles and regulators. The entire cabin environment is programmed as a function of the particular mission profile. External vision is projected on the interior of the spherical dome by a planetarium type star field-Sun-Earth-Moon projection system, which is attached to the upper surface of the gondola. It is servo driven by signals from the computer.
331
The Earth’s and Moon’s orbs may be varied in size from a pure horizon to spheres (including phasing) of the proper size when viewed from the vehicle’s space position. Black light would be used to simulate the high contrast conditions of space. The moving base has pivot points in pitch, roll and yaw at a point far enough behind the gondola to provide realistic short period translational and rotational motions. The entire gondola and gimbled structure is mounted on a yoke which pivots to provide the proper direction of the acceleration fields throughout the mission. Atop the gondola is a pressure-tight hatch and tunnel which mates with a space cabin laboratory at the conclusion of the boost phase. This space cabin is a fixed base chamber, 8 ft wide and 25 ft long, which contains the same atmosphere and pressure as the gondola. When large vehicle long term space missions are being studied, the gondola and space cabin are used as a single vehicle, however, they may be used separately. The entire simulator is driven by an analog digital computer complex capable of computing, in real time, the flight mechanics in six degrees of freedom, the navigation equations, rotating Earth, winds, programs for the environment generating systems, and such functions as required by the work stations in the space cabin. The equations of motion, aerodynamic and reaction control parameters, orbital mechanics, etc., are computed in a nearly total sense with only minor linearizations and compromises to simplify the apparatus. None of the parameters which might have a realizable effect on the crew would be omitted. The master control station in the center of the laboratory consists of a large console which contains all the controls and monitoring devices (including closed circuit television) required to direct the simulated flights. Variplotters, pen and tape recorders record all the essential and crew parameters for crew monitoring proficiency evaluation on a continuous basis. This entire facility is completely versatile in that it would be adaptable to any spacecraft configuration from a single-man orbital craft to
332
A. B. THOMPSON
and W. B. LUTON
-
LI
I
,- / __---__/J/
SPACE SIMULATORS
333
334
A. B. THOMPSON and W. B. LUTON
a three-man space voyaging craft, ballistic or lifting, and would be likewise adaptable to any mission within the capability of these craft. The computer is designed for universal application and the parameters and functions may be changed or reset to conform to the particular vehicle under study. The gondola and all apparatus associated with it are independent of the apparatus associated with the space cabin. Thus, the two units may be used together or separately. No doubt there are other simulator concepts which could evaluate man’s performance on space missions as well as the one described.
However, to obtain valid data on man’s performance on space missions, the simulator must have as many as practicable of the following basic parameters : combined stresses, vehicle dynamics, visual stimuli, moving base, and vehicle displays and controls. Although initial results indicate that man can assume a much more responsible role in space vehicles than previously thought possible, until such a total simulation program is implemented, man’s true capability in an integrated man-machine space system can only be surmised.
TO MANNED SPACE FLIGHT
A. B. THOMPSON Vought Astronautics,
and W. B. LUTON
Division of Chance Vought Corporation
Abstract-Before man travels in space as an active member of a man-machine system, considerable additional knowledge must be gained as to his capabilities under the combined stresses of space flight and in the particular vehicle configurations being considered. Combination flight control-navigationenvironment simulators are proposed as a tool to verify and aid analytical studies of man’s performance. A review is made of two recent simulator programs (a centrifuge simulator and a six degree of freedom fixed base simuiator) which studied human performance in orbital vehicles. Results of these studies are presented as examples of information on man’s capabilities that may be obtained through simulation. Need for more complete environmental simulation is shown and a study presented to show the degree of simulation which can be reasonably obtained in such a specialized laboratory. One concept for a space simulation laboratory is detailed. Conclusions are drawn as to the urgency of need for such tools.
Before man ventures into space as an active member of a man-machine system, a thorough knowledge must be available as to his capability adequately to control and navigate the vehicle throughout the entire mission profile and to cope successfully with emergency situations. Although a considerable amount of data is available on human capability and tolerances when exposed to individual stresses, almost none exists for the multiple stress situations which will be encountered in space flight. Degradation of pilot performance under the combined stresses of noise, vibration, acceleration, high temperature, reduced pressure, isolation and extreme tension -to mention only a few-must be thoroughly evaluated and then compensated for insofar as practicable by optimum integration of the man with the machine. Theoretical analyses based on past tests establishing human tolerances to individual stresses are not sufficient to provide assurance that the pilot of an orbital vehicle will be capable of reliable decision, command and control throughout all phases of flight. The first rocket boosted flights of a manned space vehicle will be roughly equivalent to taking a new, very high performance aircraft to the extremes of its flight envelope on its first flight completely on instruments and without the benefit of a chase plane. It becomes increasingly apparent that relatively complex flight control-navigationenvironment simulators must be utilized ex-
tensively from the study and design phases of vehicle development up to and including complete mission flights. In the past, simulators have been used primarily for training purposes, being available to user activities in an after-the-fact fashion. Currently, they are being utilized on an everincreasing scale for research in man-machine integration and optimization of vehicle parameters. However, the approach is in bits and pieces, i.e. pressure chamber type space cabins, heat chambers, acceleration via centrifuges and high-speed sleds, and fixed base flight simulators. Of course, these are logical first steps toward realization of manned space flight, but they fall short of determining man’s usefulness under combined stresses and in the particular vehicles under consideration. During 1959 two such simulators were designed, built and operated by Chance Vought Aircraft, Inc., as aids in establishing the needs and capabilities of the pilot of an orbital hypersonic vehicle. The first of these was an acceleration flight control simulator (Fig. 1) which operated both fixed base (static) and under boost acceleration fields in the Aviation Medical Acceleration Laboratory centrifuge at Johnsville, Pennsylvania. Its purpose was to determine the pilot’s accuracy of control during acceleration representative of an orbital vehicle’s exit flight, evaluate a new concept in pilot operated control
324
SPACE SIMULATORS
Fig. I. Acceleration space flight simulator Johnsville, centrifuge.
Fig. 2. Typical
in AMAL,
pilot control
devices and verify general physiological tolerance aspects to the rocket-boosted flight of a space vehicle. Previous tests had indicated that optimum tolerance to high transverse acceleration fields was obtained with a slightly forward leaning
325
seat position, and as rudder control became ineffective at approximately 6 “G” while wrist and finger control was effective to beyond 12 “G”, a three-axis wrist controller would probably be necessary for manual vehicle control. However, all side sticks developed to this time were two-axis types-pitch and roll only. After studies were made as to wrist bone structure, pivot angle limits and force capabilities along all axes, a three-axis side stick was designed and initially evaluated versus the conventional center stick-rudder pedal arrangement in a C-l 1B simulator. With a minimum familiarization period pilots were able to make equally accurate instrument approaches and landings with either type of control. Both the selected seat angle and side stick were integrated into the centrifuge simulator along with the appropriate instruments necessary for the pilot to fly a command boost profile. The tracking task was a closed loop simulation of vehicle dynamics and response through the controls and instruments. Transient moments of wind shear and uneven thrust termination were introduced in pitch at
of vehicle boost trajectory.
appropriate times for added realism. In addition to manually flying the entire trajectory into orbit the pilot was required to initiate and terminate last stage thrust. Four experienced pilots flew twelve recorded runs each under 1 “G” conditions and twelve
A. B. THOMPSON
326
Fig. 3. Pilot
performance degradation transverse acceleration.
Fig. 4. Six degree
due
to
of freedom
recorded runs under the selected acceleration profile. Oscillograph records were made of integrated error in pitch, roll and yaw; pilot input in pitch, roll and yaw; instantaneous error in pitch, roll and yaw; radial acceleration; and
and
W. B. LUTON
flight path angle. Also a variplotter operated each run and plotted altitude versus velocity, a typical dynamic run being shown in Fig. 2. The four subjects’ integrated pitch control error (from the commanded profile) was averaged for each run, static and dynamic, and a comparative plot made (Fig. 3). It indicated that after a short centrifuge learning period (four runs), the subjects’ accuracy of control under the high “G” conditions was within 5 per cent of the accuracies obtained under 1 “G” conditions. The subjects’ time of response to attitude errors averaged onethird greater under the boost conditions, however, this apparently did not significantly affect the probability of achieving a successful orbit. It was concluded that with the seat position and side controller used in this experiment and with proper flight information, a pilot could be an effective redundant controller to an automatic system during the boost phases of space vehicle flight. As much of the remainder of an orbital mission was well beyond the regions which have been explored by and are familiar to engineering and
fixed
base space flight
simulator.
flight personnel as regards the human component in the system, a six degree of freedom fixed base space flight simulator (Fig. 4) was constructed. Specific objectives were to determine what control capability the pilot will have as well as
Fig. 5. Six degree
of freedom
space flight simulator
block diagram.
328
A. B. THOMPSON
what displays are required-both optimum and minimum-to manage energy, effect safe reentry and navigate to destination. Some idea of the complexity required to achieve such simulation is illustrated in the block diagram (Fig. 5). This particular simulator was driven by 290 amplifiers and 16 function generators and was capable of simulating in real time the mission from the end of boost, throughout orbit, re-entry, hypersonic glide and finally supersonic approach
and W. B. LUTON pilot controlling temperature during re-entry and managing the vehicle’s kinetic energy to arrive at destination. An orbital space vehicle requires a completely different concept of managing energy than pilots have used in the past. For example, at 500,000 ft altitude the potential energy (which is familiar to pilots) is 500,000 ft-lb/lb of vehicle weight, while the kinetic energy is twenty times that value or 10,000,000 ft-lb/lb of vehicle weight. The major
Fig. 6. Pilot ability to manually fly orbital
to a point over the destination. All instruments were activated that were required for these phases-vertical situation, horizontal situation, distance to go, range tolerance, inertial velocity, inertial altitude, vehicle temperature, normal acceleration, reaction control fuel and time. The simulator contained the vehicle equations of motion, aerodynamic and reaction control parameters, long and short period dynamics, temperature and navigation equations, as well as full pilot control capability through the three-axis side stick. In addition to standard pen recorder records of specific parameters, four variplotters recorded flight profile data. An altitude versus distance trace (Fig. 6) recorded the entire orbital mission as flown by the pilot. The deviations from the predicted trajectory are the result of the
mission.
problem now is how to manage the velocity rather than the altitude. An energy management plot (Fig. 7) recorded inertial velocity versus distance. The pilot of an orbital vehicle may vary his range upon re-entry by as much as 6000 miles by varying the vehicle angle-of-attack between the limits of LIDmax and CLAIM. Provided with an adequate display of this information, a wide range of destinations may be reached. Another parameter of critical concern during re-entry is vehicle temperature. A lifting vehicle (during a non-equilibrium re-entry) re-enters with a series of long period bounces off the dense lower atmosphere. A recording of altitude versus velocity (Fig. 8) illustrates this condition. As maximum lower surface temperature occurs at the bottom of each plunge and it is a function of angle-of-attack, it was found
SPACE SIMULATORS
Fig. 9. With proper energy management and navigation information, the pilot may correct for relatively large azimuth launch errors or turn to reach alternate destinations.
that the pilot could effect safe re-entry from above the normal or equilibrium recovery ceiling. This was accomplished by holding phase and allowing CL maK during the descending
Fig.
7.
Pilot management
of re-entry
the angle-of-attack to decrease as the temperature limit was approached and then holding Z,/Dmaxduring the ascending portion of the bounce. Such a maneuver is relatively easy for
26
21
22
20
18 INERTIAL
Fig. 8. Typical
pilot control
329
16 “ELOCLTY
Conclusions drawn from the operation of this simulator were that the human component, equipped with a display comparable to that used in the simulator, can manually fly the
14
L2
1”
8
6
4
1000 F’PS
of vehicle temperature
a pilot and relatively complex and less reliable for automatic equipment. The ability of the pilot to turn off the orbital path during re-entry to reach particular destinations is illustrated in
energy.
kinetic
during
re-entry.
orbital, re-entry and hypersonic glide phases of a one-orbit mission and can manage kinetic and potential energy and navigate to various destinations. The capability of the pilot, assuming,
330
A. B. THOMPSON
and W. B. LUTON 40”
3P
200
IO0
0”
100
200
I
I 170°
180°
I 11P
I l&P
Fig. 9. Typical pilot controlled
I
I
I
I
1500
1400
1300
1200
1 30” 110°
heading change to reach destination.
adequate training, is limited only by the performance capability of the vehicle. The only reservation in reaching these conclusions is that several other human factors-combined stresses, etc.-were not simulated and were therefore beyond the scope of the analysis.
simulation facility for every type of spacecraft is not necessary. Many of the parameters are the same for all crafts and missions, and many others differ so slightly that the apparatus would be readily convertible to each configuration. Studies were made to determine what degree of
700
T
850
P 2
300
200
100
115
I@@!
I-
”
Fig. IO. Relative cost of degree of simulation
Although the work to date on space flight simulators is significant as indicated above, it represents only a millesimal fraction of what is required before space flight becomes even relatively commonplace. As the next step, a most urgent need exists for a moving base environmental flight simulator. To build a near-total
for space vehicles.
simulation could be achieved at reasonable cost; the results of which are shown in Fig. 10. The basic fixed base simulator would simulate on a real time basis in six degrees of freedom all phases of the mission boost, orbit, re-entry, glide, approach and landing. The addition of a moving base would give the proper direction of
SPACE SIMULATORS
the acceleration forces existing at all times as well as the translational motions due to vehicle short period dynamics. External vision in the form of a planetarium type display would add very little to the total cost. The important crew environmental stresses-noise, vibration, temperature, internal atmosphere and pressure, and lighting-could be included for a reasonable price. Only when an attempt is made to include the magnitude of acceleration does the cost go out of reason. This is due to the extremely large centrifuge required to carry the heavy simulator. And, of course, the weightless condition is not obtainable at this time in surface-based simulators. Conceptual studies were made to determine how best to achieve the above. One such concept is illustrated in Figs. 11 and 12. This particular simulation laboratory consists of a spherical dome, 40 ft in diameter, attached to a two-story building, 40 ft square. In the center of the dome is a moving base pressure-tight gondola which duplicates the space vehicle crew’s flight control station. It contains the instruments, controls and genera1 cockpit arrangement of the space vehicle under investigation The environment stresses of various space missions are reproduced therein : re-entry heat is produced by heating elements which can raise the inner wall temperature to 350°F; rocket noise up to 130 dB is produced by tapes and projected by a speaker system into the cabin ; vibrations to 50 c/s and & in. double amplitude are programmed as a function of flight condition by a signal generating device which drives the seats’ vibrations bases; and the internal atmosphere in its principle elements of composition and mixture ratio, cabin pressure altitude, humidity and circulation rate is generated by systems of pumps, valves, supply bottles and regulators. The entire cabin environment is programmed as a function of the particular mission profile. External vision is projected on the interior of the spherical dome by a planetarium type star field-Sun-Earth-Moon projection system, which is attached to the upper surface of the gondola. It is servo driven by signals from the computer.
331
The Earth’s and Moon’s orbs may be varied in size from a pure horizon to spheres (including phasing) of the proper size when viewed from the vehicle’s space position. Black light would be used to simulate the high contrast conditions of space. The moving base has pivot points in pitch, roll and yaw at a point far enough behind the gondola to provide realistic short period translational and rotational motions. The entire gondola and gimbled structure is mounted on a yoke which pivots to provide the proper direction of the acceleration fields throughout the mission. Atop the gondola is a pressure-tight hatch and tunnel which mates with a space cabin laboratory at the conclusion of the boost phase. This space cabin is a fixed base chamber, 8 ft wide and 25 ft long, which contains the same atmosphere and pressure as the gondola. When large vehicle long term space missions are being studied, the gondola and space cabin are used as a single vehicle, however, they may be used separately. The entire simulator is driven by an analog digital computer complex capable of computing, in real time, the flight mechanics in six degrees of freedom, the navigation equations, rotating Earth, winds, programs for the environment generating systems, and such functions as required by the work stations in the space cabin. The equations of motion, aerodynamic and reaction control parameters, orbital mechanics, etc., are computed in a nearly total sense with only minor linearizations and compromises to simplify the apparatus. None of the parameters which might have a realizable effect on the crew would be omitted. The master control station in the center of the laboratory consists of a large console which contains all the controls and monitoring devices (including closed circuit television) required to direct the simulated flights. Variplotters, pen and tape recorders record all the essential and crew parameters for crew monitoring proficiency evaluation on a continuous basis. This entire facility is completely versatile in that it would be adaptable to any spacecraft configuration from a single-man orbital craft to
332
A. B. THOMPSON
and W. B. LUTON
-
LI
I
,- / __---__/J/
SPACE SIMULATORS
333
334
A. B. THOMPSON and W. B. LUTON
a three-man space voyaging craft, ballistic or lifting, and would be likewise adaptable to any mission within the capability of these craft. The computer is designed for universal application and the parameters and functions may be changed or reset to conform to the particular vehicle under study. The gondola and all apparatus associated with it are independent of the apparatus associated with the space cabin. Thus, the two units may be used together or separately. No doubt there are other simulator concepts which could evaluate man’s performance on space missions as well as the one described.
However, to obtain valid data on man’s performance on space missions, the simulator must have as many as practicable of the following basic parameters : combined stresses, vehicle dynamics, visual stimuli, moving base, and vehicle displays and controls. Although initial results indicate that man can assume a much more responsible role in space vehicles than previously thought possible, until such a total simulation program is implemented, man’s true capability in an integrated man-machine space system can only be surmised.