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Tuesday, August 23, 2022

Astronaut training

From Wikipedia, the free encyclopedia
 
A test subject being suited up for studies on the Reduced Gravity Walking Simulator. This position meant that a person's legs experienced only one sixth of their weight, which was the equivalent of being on the lunar surface. The purpose of this simulator was to study the subject while walking, jumping or running. (1963)

Astronaut training describes the complex process of preparing astronauts in regions around the world for their space missions before, during and after the flight, which includes medical tests, physical training, extra-vehicular activity (EVA) training, procedure training, rehabilitation process, as well as training on experiments they will accomplish during their stay in space.

Virtual and physical training facilities have been integrated to familiarize astronauts with the conditions they will encounter during all phases of flight and prepare astronauts for a microgravity environment. Special considerations must be made during training to ensure a safe and successful mission, which is why the Apollo astronauts received training for geology field work on the Lunar surface and why research is being conducted on best practices for future extended missions, such as the trip to Mars.

Purpose of training

Training flow

The selection and training of astronauts are integrated processes to ensure the crew members are qualified for space missions. The training is categorized into five objectives to train the astronauts on the general and specific aspects: basic training, advanced training, mission-specific training, onboard training, and proficiency maintenance training. The trainees must learn medicine, language, robotics and piloting, space system engineering, the organization of space systems, and the acronyms in aerospace engineering during the basic training. While 60% to 80% of the astronauts will experience space motion sickness, including pallor, cold sweating, vomiting, and anorexia, the astronaut candidates are expected to overcome the sickness. During the advanced training and the mission specific training, astronauts will learn about the operation of specific systems and skills required associated with their assigned positions in a space mission. The mission specific training typically requires 18 months to complete for Space Shuttle and International Space Station crews. It is important to ensure the astronauts’ well-being, physical and mental health prior, during, and after the mission period. Proficiency maintenance aims to help the crew members to maintain a minimum level of performance, including topics such as extravehicular activity, robotics, language, diving, and flight training.

Launch and landing

The effects of launching and landing has various effects on astronauts, with the most significant effects that occur being space motion sickness, orthostatic intolerance, and cardiovascular events.

Space motion sickness is an event that can occur within minutes of being in changing gravity environments (i.e. from 1g on Earth prior to launch to more than 1g during launch, and then from microgravity in space to hypergravity during re-entry and again to 1g after landing). The symptoms range from drowsiness and headaches, to nausea and vomiting. There are three general categories of space motion sickness:

  • Mild: One to several transient symptoms, no operational impact
  • Moderate: Several symptoms of persistent nature, minimal operational impact
  • Severe: Several symptoms of persistent nature, significant impact on performance

About three-fourths of astronauts experience space motion sickness, with effects rarely exceeding two days. There is a risk for post-flight motion sickness, however this is only significant following long-duration space missions.

Post-flight, following exposure to microgravity, the vestibular system, located in the inner ear is disrupted because of the microgravity-induced unresponsiveness of the otoliths which are small calcareous concretions that sense body postures and are responsible for ensuring proper balance. In most cases, this leads to some postflight postural illusions.

Cardiovascular events represent important factors during the three phases of a space mission. They can be divided in:

  • Pre-existing cardiovascular diseases: these are typically selected-out during astronaut selection, but if they are present in an astronaut they can worsen over the course of the spaceflight.
  • Cardiovascular events and changes occurring during spaceflight: these are due to body fluids shift and redistribution, heart rhythm disturbances and decrease in maximal exercise capacity in the micro gravity environment. These effects can potentially lead the crew to be severely incapacitated upon return to a gravitational environment and thus unable to egress a spacecraft without assistance.
  • Orthostatic intolerance leading to syncope during post-flight stand test.

On-orbit operations

Astronauts are trained in preparation for the conditions of launch as well as the harsh environment of space. This training aims to prepare the crew for events falling under two broad categories: events relating to operation of the spacecraft (internal events), and events relating to the space environment (external events)

An internal view of ESA's Columbus module training mockup, located at the European Astronaut Centre in Cologne, Germany. Astronauts must familiarize themselves with all the spacecraft components during their training.

During training, astronauts are familiarized with the engineering systems of the spacecraft including spacecraft propulsion, spacecraft thermal control, and life support systems. In addition to this, astronauts receive training in orbital mechanics, scientific experimentation, earth observation, and astronomy. This training is particularly important for missions when an astronaut will encounter multiple systems (for example on the International Space Station (ISS)). Training is performed in order to prepare astronauts for events that may pose a hazard to their health, the health of the crew, or the successful completion of the mission. These types of events may be: failure of a critical life support system, capsule depressurization, fire, and other life-threatening events. In addition to the need to train for hazardous events, astronauts will also need to train to ensure the successful completion of their mission. This could be in the form of training for EVA, scientific experimentation, or spacecraft piloting.

External events

External events refers more broadly to the ability to live and work in the extreme environment of space. This includes adaptation to microgravity (or weightlessness), isolation, confinement, and radiation. The difficulty associated with living and working in microgravity include spatial disorientation, motion sickness, and vertigo. During long-duration missions, astronauts will often experience isolation and confinement. This has been known to limit performance of astronaut crews and hence training aims to prepare astronauts for such challenges. The long-term effects of radiation on crews is still largely unknown. However, it is theorized that astronauts on a trip to Mars will likely receive more than 1000x the radiation dosage of a typical person on earth. As such, present and future training must incorporate systems and processes for protecting astronauts against radiation.

Science experiments

Scientific experimentation has historically been an important element of human spaceflight, and is the primary focus of the International Space Station. Training on how to successfully carry out these experiments is an important part of astronaut training, as it maximizes the scientific return of the mission. Once on-orbit, communication between astronauts and scientists on the ground can be limited, and time is strictly apportioned between different mission activities. It is vital that astronauts are familiar with their assigned experiments in order to complete them in a timely manner, with as little intervention from the ground as possible.

For missions to the ISS, each astronaut is required to become proficient at one hundred or more experiments. During training, the scientists responsible for the experiments do not have direct contact with the astronauts who will be carrying them out. Instead, scientists instruct trainers who in turn prepare the astronauts for carrying out the experiment. Much of this training is done at the European Astronaut Center.

For human experiments, the scientists describe their experiments to the astronauts who then choose whether to participate on board the ISS. For these experiments, the astronauts will be tested before, during, and after the mission to establish a baseline and determine when the astronaut returned to the baseline.

A researcher using VR headset to investigate ideas for controlling rovers on a planet.

Purpose of virtual reality training

Virtual reality training for astronauts intends to give the astronauts candidates an immersive training experience. Virtual reality has been explored as a technology to artificially expose astronauts to space conditions and procedures prior to going into space. Using virtual reality, astronauts can be trained and evaluated on performing an EVA (extravehicular activity) with all the necessary equipment and environmental features simulated. This modern technology also allows the scenario to be changed on the go, such as to test emergency protocols. The VR training systems can reduce the effects of the space motion sickness through a process of habituation. Preflight VR training can be a countermeasure for space motion sickness and disorientation due to the weightlessness of the microgravity environment. When the goal is to act as a practice tool, virtual reality is commonly explored in conjunction with robotics and additional hardware to increase the effect of immersion or the engagement of the trainee.

Training by region

United States

At NASA, following the selection phase, the so-called "AsCans" (Astronaut candidates) have to undergo up to two years of training/indoctrination period to become fully qualified astronauts. Initially, all AsCans must go through basic training to learn both technical and soft skills. There are 16 different technical courses in:

Astronauts train in the Neutral Buoyancy Facility at the Johnson Space Center in Houston, Texas
 
The Crew of STS-135 practices rendezvous and docking with the ISS in the Systems Engineering Simulator at the Johnson Space Center on June 28, 2011 in Houston, Texas.

AsCans initially go through Basic Training, where they are trained on Soyuz, and ISS systems, flight safety and operations, as well as land or water survival. Pilot AsCans will receive training on NASA's T-38 Trainer Jet. Furthermore, because modern space exploration is done by a consortium of different countries and is a very publicly visible area, astronauts received professional and cultural training, as well as language courses (specifically in Russian).

Following completion of Basic Training candidates proceed to NASA's Advanced Training. AsCans are trained on life-sized models to get a feel of what they will be doing in space. This was done both through the use of the Shuttle Training Aircraft while it was still operational and is done through simulation mock-ups. The shuttle training aircraft was exclusively used by the commander and pilot astronauts for landing practices until the retirement of the Shuttle, while advanced simulation system facilities are used by all the candidates to learn how to work and successfully fulfill their tasks in the space environment. Simulators and EVA training facilities help candidates to best prepare their different mission operations. In particular, vacuum chambers, parabolic flights, and neutral buoyancy facilities (NBF) allow candidates to get acclimated to the micro gravity environment, particularly for EVA. Virtual reality is also becoming increasingly used as a tool to immerse AsCans into the space environment.

The final phase is the Intensive Training. It starts at about three months prior to launch, preparing candidates for their assigned mission. Flight-specific integrated simulations are designed to provide a dynamic testing ground for mission rules and flight procedures. The final Intensive Training joint crew/flight controller training is carried out in parallel with mission planning. This phase is where candidates will undergo mission specific operational training, as well as experience with their assigned experiments. Crew medical officer training is also included to effectively intervene with proactive and reactive actions in case of medical issues.

Notable training facilities

It can take up to two years for an AsCan to become formally qualified as an astronaut. Usually, the training process are completed with various training facilities available in NASA: Space training facilities try to replicate or simulate the experience of spaceflight in a spacecraft as closely and realistically as possible. This includes full-size cockpit replicas mounted on hydraulic rams and controlled by state of the art computer technology; elaborate watertanks for simulation of weightlessness; and devices used by scientists to study the physics and environment of outer space.

  • Space Vehicle Mock-up Facility (SVMF): located in the Johnson Space Center in Houston, TX. The SVMF consists of life-size models of vehicles of the ISS, the Orion, and different other commercial programs. The purpose of SVMF is to provide a unique simulated experience for astronauts to get familiar with their tasks in space vehicles. Potential training projects include preparation of emergency, on-orbit intra-vehicular maintenance, and airlock operations. The facility also provides experiences for astronauts in real-time communications with the ground team for mission support.
  • KC-135 Stratotanker: the KC-135 is an air-refueling plane designed by Boeing. Known as the “Weightless Wonder” or the “Vomit Comet”, this plane is the most famous of its kind, which has served to simulate reduced or microgravity environments for NASA astronauts since 1994. The “roller coaster” maneuvers that the plane is capable of doing provide people as well as equipment onboard about 20–25 seconds of weightlessness.
  • The Precision Air-Bearing Floor (PABF): located in the Johnson Space Center in Houston, TX. Because of the microgravity environment in space, the resulting lack of friction posts difficulties for astronauts to move and stop large objects. The PABF is a “flat floor” that uses compressed air to suspend typical hardwares or mock-ups that astronauts may encounter in space above the ground. It is used to simulate low-friction environments for astronauts to learn to move large objects.
  • The Neutral Buoyancy Lab: (NBL): located in the Johnson Space Center in Houston, TX. Through a combination of weighting and floating effects, the NBL creates a balance between the tendencies to sink and to float, and therefore simulating the experience of weightlessness. In the NBL, several full-size models of the space vehicles are present in a large “water tank”. Unlike the SVMF, the NBL helps astronauts train on projects such as maintenance, but outside of the space vehicle.

Europe

Astronaut training in Europe is carried out by the European Astronaut Centre (EAC), headquartered in Cologne, Germany. European training has three phases: Basic training, Advanced training, and Increment Specific Training.

Soyuz capsule simulator located at the EAC in Cologne, Germany. ESA astronauts will simulate operations in the capsule at the EAC.

For all ESA selected astronauts, Basic Training begins at the EAC headquarters. This section of the training cycle has four separate training blocks that last 16 months. Astronauts will receive an orientation on the major spacefaring nations, their space agencies, and all major crewed and uncrewed space programs. Training in this phase also looks into applicable laws and policies of the space sector. Technical (including engineering, astrodynamics, propulsion, orbital mechanics, etc.) and scientific (including human physiology, biology, earth observation, and astronomy) basics are introduced, to ensure that all new astronauts have the required base level of knowledge. Training is done on ISS operations and facilities, including an introduction to all major operating systems on board the ISS that are required for its functionality as a crewed space research laboratory. This phase also covers in-depth systems operations for all spacecraft that service the ISS (e.g. Soyuz, Progress, Automatic Transfer Vehicle (ATV), and the H-II Transfer Vehicle (HTV)), as well as ground control and launch facility training. This training phase also focuses on skills such as robotic operations, rendezvous and docking, Russian language courses, human behavior and performance, and finally a PADI open water scuba diving course. This scuba course provides basic EVA training at ESA's NBF before moving onto the larger NASA training facility at the Lyndon B. Johnson Space Center.

Advanced Training includes a much more in-depth look into the ISS, including learning how to service and operate all systems. Enhanced science training is also implemented at this time to ensure all astronauts can perform science experiments on board the ISS. This phase takes around one year to complete and training is completed across the ISS partner network, no longer only at the EAC. It is only upon completion of this phase that astronauts are assignment to a spaceflight.

Increment-Specific Training starts only after an astronaut has been assigned to a flight. This phase lasts 18 months and prepares them for their role on their assigned mission. During this phase crew members as well as backup crews will train together. The crew tasks on the ISS are individually tailored, with consideration to the astronaut's particular experience and professional background. There are three different user levels for all on-board equipment (i.e. user level, operator level, and specialist level). A crew member can be a specialist on systems while also only being an operator or user on others, hence why the training program is individually tailored. Increment Specific Training also includes training to deal with off-nominal situations. Astronauts will also learn how to run the experiments that are specifically scheduled for their assigned missions.

Russia

The grounds of the Gagarin Cosmonauts Training Center

Training for cosmonauts falls into three phases: General Space Training, Group Training, and Crew Training. General Space Training lasts about two years and consists of classes, survival training, and a final exam which determines whether a cosmonaut will be a test or research cosmonaut. The next year is devoted to Group Training where cosmonauts specialize in the Soyuz or ISS as well as professional skills. The final phases, the Crew Training phase, lasts a year and a half and is dedicated to detailed vehicle operations procedures, ISS training, and the English language.

Training primarily takes place at the Yuri Gagarin Cosmonaut Training Center. The center facilities have full size mockups of all major Soviet and Russian spacecraft including the ISS. As with the ISS astronauts, cosmonauts train in the US, Germany, Japan, and Canada for specific training in the various ISS modules.

Japan

The Japanese human spaceflight program has historically focused on training astronauts for Space Shuttle missions. As such, training previously took place at NASA's Lyndon B. Johnson Space Center, and followed that of NASA astronauts and other international participants in the Space Shuttle program.

H-II rocket outside the Tsukuba Space Center where training of JAXA astronauts takes place

Since the development of domestic training facilities at the Tsukuba Space Center, training has increasingly taken place in Japan. With Japan's participation in the ISS, the training of Japanese astronauts follows a similar structure to that of other ISS partners. Astronauts carry out 1.5 years of Basic Training mainly at Tsukuba, followed by 1.5–2 years of Advanced Training at Tsukuba and ISS partner sites. Training for any international ISS astronauts involving the Kibo module will also be carried out at Tsukuba Space Center.

Advanced Training is followed by Increment-Specific Training, which, along with any Kibo training, will be carried out at Tsukuba. EVA training for Kibo takes place in the Weightless Environment Test System (WETS). WETS is a Neutral Buoyancy Facility featuring a full-scale mock-up of the Kibo module on the ISS. The Tsukuba Space Center also includes medical facilities for assessing suitability of candidates, an isolation chamber for simulating some of the mental and emotional stressors of long duration spaceflight, and a hypobaric chamber for training in hull breach or Life Support System failure scenarios resulting in a reduction or loss of air pressure.

China

Although official detail of the selection process for the Shenzhou program is not available, what is known is that candidates are chosen by the Chinese National Space Administration from the Chinese air force and must be between 25 and 30 years of age, with a minimum of 800 hours flying time, and a degree-level education. Candidates must be between 160 cm and 172 cm in height, and between 50 kg and 70 kg in weight.

For China's Shenzhou astronauts, training begins with a year-long program of education in the basics of spaceflight. During this period, candidates are also introduced to human physiology and psychology. The second phase of training, lasting nearly 3 years involves extensive training in piloting the Shenzhou vehicle in nominal and emergency modes. The third and final stage of training is mission specific training, and lasts approximately 10 months. During this phase of training, astronauts are trained in the high fidelity Shenzhou trainer, as well as the Neutral Buoyancy Facility located at the Astronaut Center of China (ACC), in Beijing. As well as time spent in the Neutral Buoyancy Facility (NBF), training for EVA takes place in a high vacuum, low temperature chamber that simulates the environmental conditions of space. At all stages of training, astronauts undergo physical conditioning, including time in a human centrifuge located at the ACC, and a program of micro gravity flights, carried out in Russia.

India

The Indian human space flight program still awaits a formal go ahead. Once cleared the mission is expected to take two Indians in a Soyuz-type orbital vehicle into low Earth orbit. The training for these astronauts should be based on the lessons learned from training India's only Cosmonaut Wing Commander Rakesh Sharma (See Salyut-7 1984) and through India's international co-operation with NASA and Roscosmos. This would allow India to gain insights from their rich experiences in human spaceflight. There also lies a possibility that India may go proceed through its human spaceflight program individually, necessitating the Indian Space Research Organisation (ISRO) to develop its own training program. For astronaut training, India is deciding a place which is at a distance of 8 to 10 km from Kempegowda international airport. This land is under the ownership of ISRO. Astronaut training and biomedical engineering centers will be built on it. Though India's first man mission training will take place in USA or in Russia, this place can be used for future training. Moreover, center will have chambers for radiation regulation, thermal cycling and centrifugal for the acceleration training.

Future training

Suborbital astronaut training

Ecuadorian Civilian Space Agency (EXA)

While the first generation of non-government spaceflight astronauts will likely perform suborbital trajectories, currently companies like Virgin Galactic and Xcor Aerospace are developing proprietary suborbital astronaut training programs. However, the first official Suborbital Astronaut Training program was a joint effort between two government agencies. The Ecuadorian Air Force and the Gagarin Cosmonaut Training Center developed the ASA/T (Advanced Suborbital Astronaut Training) program which lasted up to 16 months between 2005 to 2007 and focused on command and research duties during short missions with suborbital trajectories up to 180 kilometers. This program had one Ecuadorian citizen graduate in 2007, the Ecuadorian Space Agency made a call for a new class of ASA/T training candidates, accordingly to the EXA, they will focus on renting commercial suborbital vehicles in order to perform crewed space research

Commercial astronauts

Human centrifuge at DLR in Cologne, Germany used for human physiological tests. The high accelerations experienced during suborbital flights may necessitate testing or even training on human centrifuges to determine if participants are fit for space flight

Looking ahead, the emergence of commercial space tourism will necessitate new standards for flight participants that currently do not exist. These standards will be to ensure that medical screenings are done properly in order to ensure safe and successful flights. This process will differ from that for space agency astronauts because the goal is not to fly the best individual, but to ensure a safe flight for the passengers. The main considerations for this type of travel will be:

  • What type and extent of training is sufficient?
  • Who will qualify space tourists as fit for travel?
  • How will new regulations comply with existing medical boards?
  • What selection-out criteria need to be employed to reduce dangers to space tourists?

Medical regulations for commercial space flight might mitigate commercial space company risk by selecting only those capable of passing standard medical criteria, as opposed to allowing anyone who can purchase a ticket to fly. The first generation of commercial space flight will likely be suborbital trajectories which invoke significant acceleration changes, causing cardiovascular and pulmonary issues. Because of this any future medical criteria for commercial spaceflight participants needs to focus specifically on the detrimental effects of rapidly changing gravitational levels, and which individuals will be capable of tolerating this.

A fundamentals of scientist-astronaut formative program along with additional Bioastronautics, Extravehicular activity, Space Flight Operations, Flight Test Engineering and Upper-Atmospheric Research courses have been conducted by Project PoSSUM scientist-astronaut candidates since 2015.  As of January 2021, the program has attracted members from 46 different countries and published research on mesospheric dynamics, human performance in space suits, microgravity research in various fields, and post-landing environments. The programs are run by the International Institute of Astronautical Sciences that has also partnered with Embry-Riddle Aeronautical University, Final Frontier Design Spacesuits, Survival Systems USA, National Research Council of Canada, Canadian Space Agency and the National Association of Underwater Instructors.

Current research on fitness training and strategies for commercial astronauts conducted by Astrowright Spaceflight Consulting, the first commercial firm to offer dedicated fitness training for space tourists, suggests that conventional fitness training is inadequate to support safe movement in microgravity, and that training utilizing reduced points of stability should be emphasized.

Long-duration missions to the Moon or Mars

Astronaut during virtual reality training

Astronauts for long term missions–such as those to the Moon or Mars–need to carry out multiple tasks and duties, because on such missions the astronauts will need to function largely autonomously, and will need to be proficient in many different areas. For these types of missions, the training to prepare astronauts will likely include training as doctors, scientists, engineers, technicians, pilots, and geologists. In addition there will be a focus on the psychological aspects of long-duration missions where crew is largely isolated.

Currently a six-month mission to the ISS requires up to five years of astronaut training. This level of training is to be expected and likely to be expanded upon for future space exploration missions. It may also include in-flight training aspects. It may be possible that the ISS will be used as a long-duration astronaut training facility in the future.

A powerful tool for astronaut training will be the continuing use of analog environments, including NASA Extreme Environment Mission Operations (NOAA NEEMO), NASA's Desert Research and Technology Studies (Desert RATS), Envihab (planned), Flight Analog Research Unit, Haughton-Mars Project (HMP), or even the ISS (in-flight). In fact, at NEEMO a total of 15 mission astronauts (known as aquanauts) have been trained for future missions to asteroids. The use of virtual reality will also continue to be used as a means of training astronauts in a cost-effective manner, particularly for operations such as extra-vehicular activity (EVA).

Robonaut2 onboard ISS

These missions are not completely independent without the presence of robots. This opens up a new avenue towards Human-Robot Interaction which has to be thoroughly understood and practised to develop a harmonious relationship between astronauts and robots. These robots would aid the astronauts from being their personal assistants to next generation of extreme environment explorers. Currently there is a robot on the ISS aiding the astronauts in their mammoth tasks with a human touch. Intercultural and human robot interaction training is the need of the hour for long duration missions.

Training also has to be evolved for future Moon landings to a human mission to Mars. Factors like crew dynamics, crew size, and crew activities play a crucial role as these missions would last from one year to Moon to three years on Mars. The training required for such missions has to be versatile and easy to learn, adapt, and improvise.

A journey to Mars will require astronauts to remain in the crew capsule for nine months. The monotony and isolation of the journey present new psychological challenges. The long period spent in the crew capsule is comparable to other forms of solitary confinement, such as in submarines or Antarctic bases. Being in an isolated and confined environment generates stress, interpersonal conflict, and other behavioral and mental problems. However, natural scenery and communication with loved ones has shown to relax and lessen these effects. A Network of Social Interactions for Bilateral Life Enhancement (ANSIBLE), which provides natural scenery and socialization in a virtual reality environment, is being researched as a solution to behavioral health.

Researchers are looking into how current mental health tools can be adjusted to help the crew face stressors that will arise in an isolated, confined environment (ICE) during extended missions. The International Space Station uses a behavioral conflict management system known as the Virtual Space Station (VSS) to minimize conflict between crew members and address psychological challenges. The program has modules that focus on relationship management, stress and depression that guide astronaut’s through a virtual therapy session in space.

Virtual reality astronaut training

History

Virtual reality technologies first came to a commercial release in the 1990s. It is not until then did people realize that VR can be used in training astronauts. The earlier VR gears for astronaut training are dedicated to enhance the communication between robot arm operators and the astronaut during Extravehicular Activities (EVA). It brings EVA crew members and robot arm operators together, in live, even when they are on board a spacecraft. It is also used to replace some of the oversized models that cannot fit in the Neutral Buoyancy Lab (NBL).

In 1993, astronauts were trained and evaluated on working on the Hubble Space Telescope through a virtual reality training tool, Research in Human Factors Aspects of Enhanced Virtual Environments for EVA Training and Simulation (RAVEN). However, the aim of RAVEN was not to train astronauts but to evaluate the efficacy of training using virtual reality versus underwater and other setup.

Through the years of technological development in VR, the hardware for the VR Lab in NASA has also significantly improved. Both the material and the resolution of the display are being renovated:

  • 1991: Liquid-Crystal Display (LCD) - 320x420
  • 1992: Cathode Ray Tube (CRT) - 1280x1024
  • 2005: Micro Organic Light-Emitting Diode (micro-OLED) - 800x600
  • 2012: LCD - 1280x720
  • 2015: OLED - 1920x1080

Virtual reality has also been adopted to a much wider range of fields in space exploration throughout the history of technology renovation. The newer applications of VR include but are not limited to:

  • Mission planning
  • Cooperative and interactive designing
  • Engineering problem-solving
  • Data modeling
Astronauts Tom Marshburn, left, and Dave Wolf train for a spacewalk in the Integrated EVA-RMS Virtual Reality Simulator Facility at Johnson Space Center

Current virtual reality training

While the extravehicular activities (EVAs) training facility can simulate the space conditions, including pressure and lighting, the Micro-g environment cannot be fully reconstructed in the Earth’s 1-G environment. Virtual reality is utilized during EVA training to increase the immersion of the training process. NASA Johnson Space Center has facilities such as the Space Vehicle Mockup Facility (SVMF), Virtual Reality Laboratory (VRL), and Neutral Buoyancy Laboratory (NBL).

The SVMF uses the Partial Gravity Simulator (PGS) and air bearing floor (PABF) to simulate the zero-gravity and the effects of Newton's laws of motion. Similar training systems originated from the Apollo and Gemini training. Virtual reality enhances an astronaut’s senses during training modules like fluid quick disconnect operations, spacewalks, and the orbiter’s Space Shuttle thermal protection system (TPS) repairs.

NASA Virtual Reality Laboratory utilizes virtual reality to supplement the Simplified Aid For EVA Rescue (SAFER) as simplified aid. The VR training offers a graphical 3-dimensional simulation of the International Space Station (ISS) with a headset, haptic feedback gloves, and motion tracker. In 2018, two Expedition 55 astronauts Richard R. Arnold and Andrew J. Feustel, received virtual reality training and performed the 210th spacewalk. The Virtual Reality Laboratory offers astronauts an immersive VR experience for spacewalks before launching into space. The training process combines a graphical rendering program that replicates the ISS and a device called the Charlotte Robot that allows astronauts to visually explore their surroundings while interacting with an object.  The Charlotte robot is a simple device with a metal arm attached to the side that allows a user to interact with the device. The user wears haptic feedback gloves with force sensors that send signals to a central computer. In response, the central computer maneuvers the device using a web of cables and calculates how it would act in space through physics. While objects are weightless in space, an astronaut has to be familiar with an object's forces of inertia and understand how the object will respond to simple motions to avoid losing it in space. Training can be completed individually or with a partner. This allows astronauts to learn how to interact with mass and moments of inertia in a microgravity environment.

The Neutral Buoyancy Laboratory (NBL) has advantages in simulating a zero-gravity environment and reproducing the sensation of floating in space. The training method is achieved by constructing a low gravity environment through Maintaining the Natural buoyancy in one of the largest pools in the world. The NBL pool used to practice extravehicular activities or spacewalks is 62 meters (202 feet) long, 31 meters (102 feet) wide, and 12 meters (40 feet) deep, with a capacity of 6.2 million gallons. Underwater head-mounted display virtual reality headset is used to provide visual information during the training with a frame rate of 60 fps and screen resolution of 1280 by 1440. The underwater VR training system has a reduced training cost because of the accessibility of the VR applications, and astronauts need less time to complete the assigned practice task.

Despite the NASA training modules, commercial spaceflight training also uses virtual reality technology to improve their training systems. Boeing’s virtual reality team develops a training system for Boeing Starliner to train astronauts to transport between the Earth and the ISS. The VR training system can simulate high-speed situations and emergency scenarios, for instance, launching, entering the space, and landing at an unexpected location.

Advantages of virtual reality training

Visual reorientation is a phenomenon that happens when the perception of an object changes because of the changing visual field and cues. This illusion will alter the astronaut’s perception of the orienting force of gravity and then lose spatial direction. The astronauts must develop good spatial awareness and orientation to overcome visual reorientation. In the traditional disorientation training, for instance, the Yuri Gagarin Cosmonaut Training Center trains the astronaut by simulating a microgravity environment through a centrifuge. In contrast, VR training requires less gear, training the astronauts more economically.

Virtual reality training utilizes the mix-realistic interaction devices, such as cockpits in flight simulators can reduce the simulation sickness and increase user movement. Compared to traditional training, VR training performs better to minimize the effects of space motion sickness and spatial disorientation. Astronauts who received VR training can perform the task 12% faster, with a 53% decrease in nausea symptoms.

While VR is used in astronaut training on the ground, immersive technology also contributes to on-orbit training. VR head-mounted display can help the astronaut maintain physical well-being as part of proficiency maintenance training. Moreover, VR systems are used to ensure the mental health of the crewmembers. The simulations of social scenarios can mitigate the stress and establish the connectedness under the isolated and confined environment (ICE).

Virtual reality acclimates astronauts to environments in space such as the International Space Station before leaving earth. While astronauts can familiarize themselves with the ISS during training in the NBL, they are only able to see certain sections of the station. While it prepares astronauts for the tasks they are performing in space, it does not necessarily give them a full spatial understanding of the station’s layout. That’s where Virtual Reality plays an important role. The Virtual Reality Lab uses a system known as the Dynamic Onboard Ubiquitous Graphics program (DOUG) to model the ISS’s exterior including decals, fluid lines, and electrical lines, so that the crew can acclimate to their new environment. The level of detail goes beyond the exterior of the station. When a user enters space, they see pure black until their pupil’s dilate and the sky fills with stars in an occurrence called the ‘blooming effect’.

Disadvantages of virtual reality training

While virtual reality prepares astronauts for the unfamiliar tasks they will face in outer space, the training is unable to replicate the psychological and emotional stress that astronauts face on a daily basis. This is because virtual tasks do not hold the same repercussions as the real task and the technology does not produce strong psychological effects, like claustrophobia, that often occurs in enclosed environments.

Stimulating a virtual microgravity environment can be costly due to additional equipment requirements. Unlike commercialized virtual reality, the equipment that NASA uses cannot be produced at a large scale because the systems require supplemental technology. Several VR programs work in combination with the Neutral Buoyancy Lab or the Charlotte Robot in the Virtual Reality Lab which requires expensive facilities and does not eliminate the travel component that VR can minimize. NASA’s Charlotte robot is restricted by cables that simulate the microgravity environment and the Virtual Reality Lab only has two machines in their possession. This particular training system requires a virtual glovebox system (GVX) that has been incorporated into training at NASA and the EVA virtual system at the Astronaut Center of China. Using sensors embedded in the fabric, the gloves can sense when the wearer  decides to  grasp an object or release it, but the technology needs to be further developed to integrate precise user movements into virtual programs. These gloves have been reported to be uncomfortable and only capture limited movements. Full-body motion sensors have also been incorporated into training and tend to be expensive but necessary in order to have effective tactile feedback in response to the astronauts movements. While virtual reality programs have been developed that do not require full-body sensors, the absence reduces the degree to which a user can interact with the virtual world.

Future

The primary focus of future research of virtual reality technologies in space exploration is to develop a method of simulating a microgravity environment. Although it has been a goal since the beginning of VR being used in astronaut training, minor progress has been made. The current setup uses a bungee rope attached to a person’s feet, a swing attached to the body, and finally a head mounted VR display. However, from participants in experiments that use this setup to simulate reduced gravity environments, they only experience the feel of moving around in space with the help of VR, but the experience does not resemble a real zero-gravity environment in outer space. Specifically, the pressure from the bungee rope and the swing because of the participants’ own weight creates an unreal and unpleasant feeling. The current technology may be enough for the general public to experience what moving around in space is like, but it is still far from being formally used as an astronaut training tool.

These efforts of simulating micro-gravity serve a similar purpose of creating an increasingly immersive environment for astronaut training. In fact, this is a developing trend for the entire VR industry. The ultimate scene VR experience that we are imagining will eventually be marked by the elimination between the real and the virtual world.

Prophecy

From Wikipedia, the free encyclopedia

16th century woodcut of a soothsayer delivering a prophecy to a king, deriving it from stars, fishes, and noises from the mountains

In religion, a prophecy is a message that has been communicated to a person (typically called a prophet) by a supernatural entity. Prophecies are a feature of many cultures and belief systems and usually contain divine will or law, or preternatural knowledge, for example of future events. They can be revealed to the prophet in various ways depending on the religion and the story, such as visions, divination, or direct interaction with divine beings in physical form. Stories of prophetic deeds sometimes receive considerable attention and some have been known to survive for centuries through oral tradition or as religious texts.

Etymology

The English noun "prophecy", in the sense of "function of a prophet" appeared from about 1225, from Old French profecie (12th century), and from prophetia, Greek propheteia "gift of interpreting the will of God", from Greek prophetes (see prophet). The related meaning, "thing spoken or written by a prophet", dates from c. 1300, while the verb "to prophesy" is recorded by 1377.

Definitions

The revolution of 1831. As prophesied by that learned astrologer General Ikey Wether-Bridge
  • Maimonides suggested that "prophecy is, in truth and reality, an emanation sent forth by Divine Being through the medium of the Active Intellect, in the first instance to man's rational faculty, and then to his imaginative faculty".
  • The views of Maimonides closely relate to the definition by Al-Fârâbî, who developed the theory of prophecy in Islam.
  • Much of the activity of Old Testament prophets involved conditional warnings rather than immutable futures. A summary of a standard Old Testament prophetic formula might run: Repent of sin X and turn to righteousness, otherwise consequence Y will occur.
  • Saint Paul emphasizes edification, exhortation and comfort in a definition of prophesying.
  • The Catholic Encyclopedia defines a Christian conception of prophecy as "understood in its strict sense, it means the foreknowledge of future events, though it may sometimes apply to past events of which there is no memory, and to present hidden things which cannot be known by the natural light of reason".
  • According to Western esotericist Rosemary Guiley, clairvoyance has been used as an adjunct to "divination, prophecy, and magic".
  • From a skeptical point of view, a Latin maxim exists: "prophecy written after the fact" (vaticinium ex eventu). The Jewish Torah already deals with the topic of the false prophet (Deuteronomy 13:2-6, 18:20-22).

In religion

Baháʼí Faith

In 1863, Bahá'u'lláh, the founder of the Baháʼí Faith, claimed to have been the promised messianic figure of all previous religions, and a Manifestation of God, a type of prophet in the Baháʼí writings that serves as intermediary between the divine and humanity and who speaks with the voice of a god. Bahá'u'lláh claimed that, while being imprisoned in the Siyah-Chal in Iran, he underwent a series of mystical experiences including having a vision of the Maid of Heaven who told him of his divine mission, and the promise of divine assistance; In Baháʼí belief, the Maid of Heaven is a representation of the divine.

Buddhism

The Haedong Kosung-jon (Biographies of High Monks) records that King Beopheung of Silla had desired to promulgate Buddhism as the state religion. However, officials in his court opposed him. In the fourteenth year of his reign, Beopheung's "Grand Secretary", Ichadon, devised a strategy to overcome court opposition. Ichadon schemed with the king, convincing him to make a proclamation granting Buddhism official state sanction using the royal seal. Ichadon told the king to deny having made such a proclamation when the opposing officials received it and demanded an explanation. Instead, Ichadon would confess and accept the punishment of execution, for what would quickly be seen as a forgery. Ichadon prophesied to the king that at his execution a wonderful miracle would convince the opposing court faction of Buddhism's power. Ichadon's scheme went as planned, and the opposing officials took the bait. When Ichadon was executed on the 15th day of the 9th month in 527, his prophecy was fulfilled; the earth shook, the sun was darkened, beautiful flowers rained from the sky, his severed head flew to the sacred Geumgang mountains, and milk instead of blood sprayed 100 feet in the air from his beheaded corpse. The omen was accepted by the opposing court officials as a manifestation of heaven's approval, and Buddhism was made the state religion in 527.

Christianity

According to Walter Brueggemann, the task of prophetic (Christian) ministry is to nurture, nourish and evoke a consciousness and perception alternative to the consciousness and perception of the dominant culture. A recognized form of Christian prophecy is the "prophetic drama" which Frederick Dillistone describes as a "metaphorical conjunction between present situations and future events".

Later Christianity

In his Dialogue with Trypho, Justin Martyr argued that prophets were no longer among Israel but were in the Church. The Shepherd of Hermas, written around the mid-2nd century, describes the way prophecy was being used within the church of that time. Irenaeus confirms the existence of such spiritual gifts in his Against Heresies. Although some modern commentators claim that Montanus was rejected because he claimed to be a prophet, a careful examination of history shows that the gift of prophecy was still acknowledged during the time of Montanus, and that he was controversial because of the manner in which he prophesied and the doctrines he propagated.

Prophecy and other spiritual gifts were somewhat rarely acknowledged throughout church history and there are few examples of the prophetic and certain other gifts until the Scottish Covenanters like Prophet Peden and George Wishart. From 1904 to 1906, the Azusa Street Revival occurred in Los Angeles, California and is sometimes considered the birthplace of Pentecostalism. This revival is well known for the "speaking in tongues" that occurred there. Some participants of the Azusa Street Revival are claimed to have prophesied. Pentecostals believe prophecy and certain other gifts are once again being given to Christians. The Charismatic Movement also accepts spiritual gifts like speaking in tongues and prophecy.

Since 1972, the neo-Pentecostal Church of God Ministry of Jesus Christ International has expressed a belief in prophecy. The church claims this gift is manifested by one person (the prophesier) laying their hands on another person, who receives an individual message said by the prophesier. Prophesiers are believed to be used by the Holy Ghost as instruments through whom their God expresses his promises, advice and commandments. The church claims people receive messages about their future, in the form of promises given by their God and expected to be fulfilled by divine action.

Apostolic-Prophetic Movement

In the Apostolic-Prophetic Movement, a prophesy is simply a word delivered under the inspiration of the Holy Spirit that accurately communicates God's "thoughts and intention".

The Apostolic Council of Prophetic Elders was a council of prophetic elders co-convened by C. Peter Wagner and Cindy Jacobs that included: Beth Alves, Jim Gool, Chuck Pierce, Mike and Cindy Jacobs, Bart Pierces, John and Paula Sanford, Dutch Sheets, Tommy Tenny, Heckor Torres, Barbara Wentroble, Mike Bickle, Paul Cain, Emanuele Cannistraci, Bill Hamon, Kingsley Fletcher, Ernest Gentile, Jim Laffoon, James Ryle, and Gwen Shaw.

Latter Day Saint movement

The Latter Day Saint movement maintains that its first prophet, Joseph Smith, was visited by God and Jesus Christ in 1820. The Latter Day Saints further claims that God communicated directly with Joseph Smith on many subsequent occasions, and that following the death of Joseph Smith God has continued to speak through subsequent prophets. Joseph Smith claims to have been led by an angel to a large hill in upstate New York, where he was shown an ancient manuscript engraved on plates of gold metal. Joseph Smith claimed to have translated this manuscript into modern English under divine inspiration by the gift and power of God, and the publication of this translation are known as the Book of Mormon.

Following Smith's murder, there was a succession crisis that resulted in a great schism. The majority of Latter-day Saints believing Brigham Young to be the next prophet and following him out to Utah, while a minority returned to Missouri with Emma Smith, believing Joseph Smith Junior's son, Joseph Smith III, to be the next legitimate prophet (forming the Reorganized Church of Jesus Christ of Latter Day Saints, now the Community of Christ). Since even before the death of Joseph Smith in 1844, there have been numerous separatist Latter Day Saint sects that have splintered from the Church of Jesus Christ of Latter Day Saints. To this day, there are an unknown number of organizations within the Latter Day Saint movement, each with their own proposed prophet.

The Church of Jesus Christ of Latter-day Saints (LDS Church) is the largest Latter Day Saint body. The current Prophet/President of the LDS Church is Russell M. Nelson. The church has, since Joseph Smith's death on June 27, 1844, held a belief that the president of their church is also a literal prophet of God. The church also maintains that further revelations claimed to have been given through Joseph Smith are published in the Doctrine and Covenants, one of the Standard Works. Additional revelations and prophecies outside the Standard Works, such as Joseph Smith's "White Horse Prophecy", concerning a great and final war in the United States before the Second Coming of Jesus Christ, can be found in other church published works.

Islam

The Arabic term for prophecy nubū'ah (Arabic: نُبُوْءَة) stems from the term for prophets, nabī (Arabic: نَبِي; pl. anbiyāʼ from nabā "tidings, announcement") who are lawbringers that Muslims believe were sent by God to every person, bringing God's message in a language they can understand. But there is also the term rasūl (Arabic: رسول "messenger, apostle") to classify those who bring a divine revelation (Arabic: رسالة risālah "message") via an angel. Knowledge of the Islamic prophets is one of the six articles of the Islamic faith, and specifically mentioned in the Quran. Along with Muhammad, many of the prophets in Judaism (such as Noah, Abraham, Moses, Aaron, Elijah, etc.) and prophets of Christianity (Adam, Zechariah the priest, John the Baptist, Jesus Christ) are mentioned by name in the Quran.

In the sense of predicting events, the Quran contains verses believed to have predicted many events years before they happened and that such prophecies are proof of the divine origin of the Qur'an. The Qur'an itself states "For every announcement there is a term, and ye will come to know." [Quran 6:67] Muslims also recognize the validity of some prophecies in other sacred texts like in the Bible; however, they believe that, unlike the Qur'an, some parts of the Bible have been corrupted over the years, and as a result, not all of the prophecies and verses in the Bible are accurate.

Judaism

David and Saul, detail from an 1878 oil painting, Nationalmuseum, Stockholm

The Hebrew term for prophet, Navi (נבוא), literally means "spokesperson"; he speaks to the people as a mouthpiece of their God, and to their god on behalf of the people. "The name prophet, from the Greek meaning "forespeaker" (πρὸ being used in the original local sense), is an equivalent of the Hebrew Navi, which signifies properly a delegate or mouthpiece of another."

According to Judaism, authentic Nevuah (נבואה, "Prophecy") got withdrawn from the world after the destruction of the first Jerusalem Temple. Malachi is acknowledged to have been the last authentic prophet if one accepts the opinion that Nechemyah died in Babylon before 9th Tevet 3448 (313 BCE).

The Torah contains laws concerning the false prophet (Deuteronomy 13:2-6, 18:20-22). Prophets in Islam like Lot, for example, are false prophets according to Jewish standards.

In the Torah, prophecy often consisted of a conditioned warning by their God of the consequences should the society, specific communities, or their leaders not adhere to Torah's instructions in the time contemporary with the prophet's life. Prophecies sometimes included conditioned promises of blessing for obeying their god, and returning to behaviors and laws as written in the Torah. Conditioned warning prophecies feature in all Jewish works of the Tanakh.

Notably Maimonides, philosophically suggested there once were many levels of prophecy, from the highest such as those experienced by Moses, to the lowest where the individuals were able to apprehend the Divine Will, but not respond or even describe this experience to others, citing in example, Shem, Eber and most notably, Noah, who, in biblical narrative, does not issue prophetic declarations.

Maimonides, in his philosophical work The Guide for the Perplexed, outlines twelve modes of prophecy from lesser to greater degree of clarity:

  1. Inspired actions
  2. Inspired words
  3. Allegorical dream revelations
  4. Auditory dream revelations
  5. Audiovisual dream revelations/human speaker
  6. Audiovisual dream revelations/angelic speaker
  7. Audiovisual dream revelations/Divine speaker
  8. Allegorical waking vision
  9. Auditory waking revelation
  10. Audiovisual waking revelation/human speaker
  11. Audiovisual waking revelation/angelic speaker
  12. Audiovisual waking revelation/Divine speaker (that refers implicitly to Moses)

The Tanakh contains prophecies from various Hebrew prophets (55 in total) who communicated messages from God to the nation of Israel, and later the population of Judea and elsewhere. Experience of prophecy in the Torah and the rest of Tanakh was not restricted to Jews. Nor was the prophetic experience restricted to the Hebrew language.

Native American prophecy

There exists a problem in verifying most Native American prophecy, in that they remain primarily an oral tradition, and thus there is no way to cite references of where writings have been committed to paper. In their system, the best reference is an Elder, who acts as a repository of the accumulated wisdom of their tradition.

In another type of example, it is recorded that there are three Dogrib prophets who had claimed to have been divinely inspired to bring the message of Christianity's God to their people. This prophecy among the Dogrib involves elements such as dances and trance-like states.

China

In ancient Chinese, prophetic texts are known as Chen (谶). The most famous Chinese prophecy is the Tui bei tu (推背圖).

Nostradamus

Esoteric prophecy has been claimed for, but not by, Michel de Nostredame, popularly referred to as Nostradamus, who claimed to be a converted Christian. It is known that he suffered several tragedies in his life, and was persecuted to some degree for his cryptic esoteric writings about the future, reportedly derived through a use of a crystal ball. Nostradamus was a French apothecary and reputed seer who published collections of foreknowledge of future events. He is best known for his book Les Propheties ("The Prophecies"), the first edition of which appeared in 1555. Since Les Propheties was published, Nostradamus has attracted an esoteric following that, along with the popularistic press, credits him with foreseeing world events. His esoteric cryptic foreseeings have in some cases been assimilated to the results of applying the alleged Bible code, as well as to other purported pseudo-prophetic works.

Most reliable academic sources maintain that the associations made between world events and Nostradamus's quatrains are largely the result of misinterpretations or mistranslations (sometimes deliberate) or else are so tenuous as to render them useless as evidence of any genuine predictive power. Moreover, none of the sources listed offers any evidence that anyone has ever interpreted any of Nostradamus's pseudo-prophetic works specifically enough to allow a clear identification of any event in advance.

Explanations

According to skeptics, many apparently fulfilled prophecies can be explained as coincidences, possibly aided by the prophecy's own vagueness, and others may have been invented after the fact to match the circumstances of a past event (an act termed "postdiction").

Bill Whitcomb in The Magician's Companion observes,

One point to remember is that the probability of an event changes as soon as a prophecy (or divination) exists. . . . The accuracy or outcome of any prophecy is altered by the desires and attachments of the seer and those who hear the prophecy.

Many prophets make a large number of prophecies. This makes the chances of at least one prophecy being correct much higher by sheer weight of numbers.

Psychology

The phenomenon of prophecy is not well understood in psychology research literature. Psychiatrist and neurologist Arthur Deikman describes the phenomenon as an "intuitive knowing, a type of perception that bypasses the usual sensory channels and rational intellect."

"(P)rophecy can be likened to a bridge between the individual 'mystical self' and the communal 'mystical body'," writes religious sociologist Margaret Poloma. Prophecy seems to involve "the free association that occurred through the workings of the right brain."

Psychologist Julian Jaynes proposed that this is a temporary accessing of the bicameral mind; that is, a temporary separating of functions, such that the authoritarian part of the mind seems to literally be speaking to the person as if a separate (and external) voice. Jaynes posits that the gods heard as voices in the head were and are organizations of the central nervous system. God speaking through man, according to Jaynes, is a more recent vestige of God speaking to man; the product of a more integrated higher self. When the bicameral mind speaks, there is no introspection. In earlier times, posits Jaynes, there was additionally a visual component, now lost.

Child development and consciousness author Joseph Chilton Pearce remarked that revelation typically appears in symbolic form and "in a single flash of insight." He used the metaphor of lightning striking and suggests that the revelation is "a result of a buildup of resonant potential." Pearce compared it to the earth asking a question and the sky answering it. Focus, he said, feeds into "a unified field of like resonance (and becomes) capable of attracting and receiving the field's answer when it does form."

Some cite aspects of cognitive psychology such as pattern forming and attention to the formation of prophecy in modern-day society as well as the declining influence of religion in daily life.

Poetry and prophecy

For the ancient Greeks, prediction, prophesy, and poetry were often intertwined. Prophecies were given in verse, and a word for poet in Latin is “vates” or prophet. Both poets and oracles claimed to be inspired by forces outside themselves. In ancient China, divination is regarded as the oldest form of occult inquiry and was often expressed in verse. In contemporary Western cultures, theological revelation and poetry are typically seen as distinct and often even as opposed to each other. Yet the two still are often understood together as symbiotic in their origins, aims, and purposes.

Middle English poems of a political nature are linked with Latin and vernacular prophecies. Prophecies in this sense are predictions concerning kingdoms or peoples; and these predictions are often eschatological or apocalyptic. The prophetic tradition in English derives in from Geoffrey of Monmouth's History of the Kings of Britain (1136), otherwise called "Prophecies of Merlin;" this work is prelude to numerous books devoted to King Arthur. In 18th century England, prophecy as poetry is revived by William Blake who wrote: America: A Prophecy (1783) and Europe: A Prophecy (1794).

Contemporary American poetry is also rich in lyrics about prophesy, including poems entitled Prophecy by Dana Gioia and Eileen Myles. In 1962, Robert Frost published "The Prophets Really Prophesy as Mystics the Commentators Merely by Statistics". Other modern poets who write on prophets or prophecy include Carl Dennis, Richard Wilbur, and Derek Walcott.

Autophagy

From Wikipedia, the free encyclopedia

A Diagram of the process of autophagy, which produces the structures autophagosomes (AP), and autolysosomes (AL); B Electron micrograph of autophagic structures AP and AL in the fat body of a fruit fly larva; C Fluorescently-labeled autophagosomes AP in liver cells of starved mice.

Autophagy (or autophagocytosis; from the Ancient Greek αὐτόφαγος, autóphagos, meaning "self-devouring" and κύτος, kýtos, meaning "hollow") is the natural, conserved degradation of the cell that removes unnecessary or dysfunctional components through a lysosome-dependent regulated mechanism. It allows the orderly degradation and recycling of cellular components. Although initially characterized as a primordial degradation pathway induced to protect against starvation, it has become increasingly clear that autophagy also plays a major role in the homeostasis of non-starved cells. Defects in autophagy have been linked to various human diseases, including neurodegeneration and cancer, and interest in modulating autophagy as a potential treatment for these diseases has grown rapidly.

Four forms of autophagy have been identified: macroautophagy, microautophagy, chaperone-mediated autophagy (CMA), and crinophagy. In macroautophagy (the most thoroughly researched form of autophagy), cytoplasmic components (like mitochondria) are targeted and isolated from the rest of the cell within a double-membrane vesicle known as an autophagosome, which, in time, fuses with an available lysosome, bringing its specialty process of waste management and disposal; and eventually the contents of the vesicle (now called an autolysosome) are degraded and recycled. In crinophagy (the least well-known and researched form of autophagy), unnecessary secretory granules are degraded and recycled.

In disease, autophagy has been seen as an adaptive response to stress, promoting survival of the cell; but in other cases, it appears to promote cell death and morbidity. In the extreme case of starvation, the breakdown of cellular components promotes cellular survival by maintaining cellular energy levels.

The word "autophagy" was in existence and frequently used from the middle of the 19th century. In its present usage, the term autophagy was coined by Belgian biochemist Christian de Duve in 1963 based on his discovery of the functions of lysosome. The identification of autophagy-related genes in yeast in the 1990s allowed researchers to deduce the mechanisms of autophagy, which eventually led to the award of the 2016 Nobel Prize in Physiology or Medicine to Japanese researcher Yoshinori Ohsumi.

History

Autophagy was first observed by Keith R. Porter and his student Thomas Ashford at the Rockefeller Institute. In January 1962 they reported an increased number of lysosomes in rat liver cells after the addition of glucagon, and that some displaced lysosomes towards the centre of the cell contained other cell organelles such as mitochondria. They called this autolysis after Christian de Duve and Alex B. Novikoff. However Porter and Ashford wrongly interpreted their data as lysosome formation (ignoring the pre-existing organelles). Lysosomes could not be cell organelles, but part of cytoplasm such as mitochondria, and that hydrolytic enzymes were produced by microbodies. In 1963 Hruban, Spargo and colleagues published a detailed ultrastructural description of "focal cytoplasmic degradation", which referenced a 1955 German study of injury-induced sequestration. Hruban, Spargo and colleagues recognized three continuous stages of maturation of the sequestered cytoplasm to lysosomes, and that the process was not limited to injury states that functioned under physiological conditions for "reutilization of cellular materials", and the "disposal of organelles" during differentiation. Inspired by this discovery, de Duve christened the phenomena "autophagy". Unlike Porter and Ashford, de Duve conceived the term as a part of lysosomal function while describing the role of glucagon as a major inducer of cell degradation in the liver. With his student Russell Deter, he established that lysosomes are responsible for glucagon-induced autophagy. This was the first time the fact that lysosomes are the sites of intracellular autophagy was established.

In the 1990s several groups of scientists independently discovered autophagy-related genes using the budding yeast. Notably, Yoshinori Ohsumi and Michael Thumm examined starvation-induced non-selective autophagy; in the meantime, Daniel J. Klionsky discovered the cytoplasm-to-vacuole targeting (CVT) pathway, which is a form of selective autophagy. They soon found that they were in fact looking at essentially the same pathway, just from different angles. Initially, the genes discovered by these and other yeast groups were given different names (APG, AUT, CVT, GSA, PAG, PAZ, and PDD). A unified nomenclature was advocated in 2003 by the yeast researchers to use ATG to denote autophagy genes. The 2016 Nobel Prize in Physiology or Medicine was awarded to Yoshinori Ohsumi, although some have pointed out that the award could have been more inclusive.

The field of autophagy research experienced accelerated growth at the turn of the 21st century. Knowledge of ATG genes provided scientists more convenient tools to dissect functions of autophagy in human health and disease. In 1999, a landmark discovery connecting autophagy with cancer was published by Beth Levine's group. To this date, relationship between cancer and autophagy continues to be a main theme of autophagy research. The roles of autophagy in neurodegeneration and immune defense also received considerable attention. In 2003, the first Gordon Research Conference on autophagy was held at Waterville. In 2005, Daniel J Klionsky launched Autophagy, a scientific journal dedicated to this field. The first Keystone Symposia Conference on autophagy was held in 2007 at Monterey. In 2008, Carol A Mercer created a BHMT fusion protein (GST-BHMT), which showed starvation-induced site-specific fragmentation in cell lines. The degradation of betaine homocysteine methyltransferase (BHMT), a metabolic enzyme, could be used to assess autophagy flux in mammalian cells. Macro, micro, and Chaperone mediated autophagy are mediated by autophagy-related genes and their associated enzymes. Macroautophagy is then divided into bulk and selective autophagy. In the selective autophagy is the autophagy of organelles; mitophagy, lipophagy, pexophagy, chlorophagy, ribophagy and others.

Macroautophagy is the main pathway, used primarily to eradicate damaged cell organelles or unused proteins. First the phagophore engulfs the material that needs to be degraded, which forms a double membrane known as an autophagosome, around the organelle marked for destruction. The autophagosome then travels through the cytoplasm of the cell to a lysosome in mammals, or vacuoles in yeast and plants, and the two organelles fuse. Within the lysosome/vacuole, the contents of the autophagosome are degraded via acidic lysosomal hydrolase.

Microautophagy, on the other hand, involves the direct engulfment of cytoplasmic material into the lysosome. This occurs by invagination, meaning the inward folding of the lysosomal membrane, or cellular protrusion.

Chaperone-mediated autophagy, or CMA, is a very complex and specific pathway, which involves the recognition by the hsc70-containing complex. This means that a protein must contain the recognition site for this hsc70 complex which will allow it to bind to this chaperone, forming the CMA- substrate/chaperone complex. This complex then moves to the lysosomal membrane-bound protein that will recognise and bind with the CMA receptor. Upon recognition, the substrate protein gets unfolded and it is translocated across the lysosome membrane with the assistance of the lysosomal hsc70 chaperone. CMA is significantly different from other types of autophagy because it translocates protein material in a one by one manner, and it is extremely selective about what material crosses the lysosomal barrier.

Mitophagy is the selective degradation of mitochondria by autophagy. It often occurs to defective mitochondria following damage or stress. Mitophagy promotes the turnover of mitochondria and prevents the accumulation of dysfunctional mitochondria which can lead to cellular degeneration. It is mediated by Atg32 (in yeast) and NIX and its regulator BNIP3 in mammals. Mitophagy is regulated by PINK1 and parkin proteins. The occurrence of mitophagy is not limited to the damaged mitochondria but also involves undamaged ones.

Lipophagy is the degradation of lipids by autophagy, a function which has been shown to exist in both animal and fungal cells. The role of lipophagy in plant cells, however, remains elusive. In lipophagy the target are lipid structures called lipid droplets (LDs), spheric "organelles" with a core of mainly triacylglycerols (TAGs) and a unilayer of phospholipids and membrane proteins. In animal cells the main lipophagic pathway is via the engulfment of LDs by the phagophore, macroautophagy. In fungal cells on the other hand microplipophagy constitutes the main pathway and is especially well studied in the budding yeast Saccharomyces cerevisiae. Lipophagy was first discovered in mice and published 2009.

Targeted interplay between bacterial pathogens and host autophagy

Autophagy targets genus-specific proteins, so orthologous proteins which share sequence homology with each other are recognized as substrates by a particular autophagy targeting protein. There exists a complementarity of autophagy targeting proteins which potentially increase infection risk upon mutation. The lack of overlap among the targets of the 3 autophagy proteins and the large overlap in terms of the genera show that autophagy could target different sets of bacterial proteins from a same pathogen. On one hand, the redundancy in targeting a same genera is beneficial for robust pathogen recognition. But, on the other hand, the complementarity in the specific bacterial proteins could make the host more susceptible to chronic disorders and infections if the gene encoding one of the autophagy targeting proteins becomes mutated, and the autophagy system is overloaded or suffers other malfunctions. Moreover, autophagy targets virulence factors and virulence factors responsible for more general functions such as nutrient acquisition and motility are recognized by multiple autophagy targeting proteins. And the specialized virulence factors such as autolysins, and iron sequestering proteins are potentially recognized uniquely by a single autophagy targeting protein. The autophagy proteins CALCOCO2/NDP52 and MAP1LC3/LC3 may have evolved specifically to target pathogens or pathogenic proteins for autophagic degradation. While SQSTM1/p62 targets more generic bacterial proteins containing a target motif but not related to virulence.

On the other hand, bacterial proteins from various pathogenic genera are also able to modulate autophagy. There are genus-specific patterns in the phases of autophagy that are potentially regulated by a given pathogen group. Some autophagy phases can only be modulated by particular pathogens, while some phases are modulated by multiple pathogen genera. Some of the interplay-related bacterial proteins have proteolytic and post-translational activity such as phosphorylation and ubiquitination and can interfere with the activity of autophagy proteins.

Molecular biology

Autophagy is executed by autophagy-related (Atg) genes. Prior to 2003, ten or more names were used, but after this point a unified nomenclature was devised by fungal autophagy researchers. Atg or ATG stands for autophagy related. It does not specify gene or a protein.

The first autophagy genes were identified by genetic screens conducted in Saccharomyces cerevisiae. Following their identification those genes were functionally characterized and their orthologs in a variety of different organisms were identified and studied. Today, thirty-six Atg proteins have been classified as especially important for autophagy, of which 18 belong to the core machinery

In mammals, amino acid sensing and additional signals such as growth factors and reactive oxygen species regulate the activity of the protein kinases mTOR and AMPK. These two kinases regulate autophagy through inhibitory phosphorylation of the Unc-51-like kinases ULK1 and ULK2 (mammalian homologues of Atg1). Induction of autophagy results in the dephosphorylation and activation of the ULK kinases. ULK is part of a protein complex containing Atg13, Atg101 and FIP200. ULK phosphorylates and activates Beclin-1 (mammalian homologue of Atg6), which is also part of a protein complex. The autophagy-inducible Beclin-1 complex contains the proteins PIK3R4(p150), Atg14L and the class III phosphatidylinositol 3-phosphate kinase (PI(3)K) Vps34. The active ULK and Beclin-1 complexes re-localize to the site of autophagosome initiation, the phagophore, where they both contribute to the activation of downstream autophagy components.

Once active, VPS34 phosphorylates the lipid phosphatidylinositol to generate phosphatidylinositol 3-phosphate (PtdIns(3)P) on the surface of the phagophore. The generated PtdIns(3)P is used as a docking point for proteins harboring a PtdIns(3)P binding motif. WIPI2, a PtdIns(3)P binding protein of the WIPI (WD-repeat protein interacting with phosphoinositides) protein family, was recently shown to physically bind Atg16L1. Atg16L1 is a member of an E3-like protein complex involved in one of two ubiquitin-like conjugation systems essential for autophagosome formation. The FIP200 cis-Golgi-derived membranes fuse with ATG16L1-positive endosomal membranes to form the prophagophore termed HyPAS (hybrid pre-autophagosomal structure). ATG16L1 binding to WIPI2 mediates ATG16L1's activity. This leads to downstream conversion of prophagophore into ATG8-positive phagophore via a ubiquitin-like conjugation system.

The first of the two ubiquitin-like conjugation systems involved in autophagy covalently binds the ubiquitin-like protein Atg12 to Atg5. The resulting conjugate protein then binds Atg16L1 to form an E3-like complex which functions as part of the second ubiquitin-like conjugation system. This complex binds and activates Atg3, which covalently attaches mammalian homologues of the ubiquitin-like yeast protein ATG8 (LC3A-C, GATE16, and GABARAPL1-3), the most studied being LC3 proteins, to the lipid phosphatidylethanolamine (PE) on the surface of autophagosomes. Lipidated LC3 contributes to the closure of autophagosomes, and enables the docking of specific cargos and adaptor proteins such as Sequestosome-1/p62. The completed autophagosome then fuses with a lysosome through the actions of multiple proteins, including SNAREs and UVRAG. Following the fusion LC3 is retained on the vesicle's inner side and degraded along with the cargo, while the LC3 molecules attached to the outer side are cleaved off by Atg4 and recycled. The contents of the autolysosome are subsequently degraded and their building blocks are released from the vesicle through the action of permeases.

Sirtuin 1 (SIRT1) stimulates autophagy by preventing acetylation of proteins (via deacetylation) required for autophagy as demonstrated in cultured cells and embryonic and neonatal tissues. This function provides a link between sirtuin expression and the cellular response to limited nutrients due to caloric restriction.

Functions

Nutrient starvation

Autophagy has roles in various cellular functions. One particular example is in yeasts, where the nutrient starvation induces a high level of autophagy. This allows unneeded proteins to be degraded and the amino acids recycled for the synthesis of proteins that are essential for survival. In higher eukaryotes, autophagy is induced in response to the nutrient depletion that occurs in animals at birth after severing off the trans-placental food supply, as well as that of nutrient starved cultured cells and tissues. Mutant yeast cells that have a reduced autophagic capability rapidly perish in nutrition-deficient conditions. Studies on the apg mutants suggest that autophagy via autophagic bodies is indispensable for protein degradation in the vacuoles under starvation conditions, and that at least 15 APG genes are involved in autophagy in yeast. A gene known as ATG7 has been implicated in nutrient-mediated autophagy, as mice studies have shown that starvation-induced autophagy was impaired in atg7-deficient mice.

Infection

Vesicular stomatitis virus is believed to be taken up by the autophagosome from the cytosol and translocated to the endosomes where detection takes place by a pattern recognition receptor called toll-like receptor 7, detecting single stranded RNA. Following activation of the toll-like receptor, intracellular signaling cascades are initiated, leading to induction of interferon and other antiviral cytokines. A subset of viruses and bacteria subvert the autophagic pathway to promote their own replication. Galectin-8 has recently been identified as an intracellular "danger receptor", able to initiate autophagy against intracellular pathogens. When galectin-8 binds to a damaged vacuole, it recruits an autophagy adaptor such as NDP52 leading to the formation of an autophagosome and bacterial degradation.

Repair mechanism

Autophagy degrades damaged organelles, cell membranes and proteins, and insufficient autophagy is thought to be one of the main reasons for the accumulation of damaged cells and aging. Autophagy and autophagy regulators are involved in response to lysosomal damage, often directed by galectins such as galectin-3 and galectin-8.

Programmed cell death

One of the mechanisms of programmed cell death (PCD) is associated with the appearance of autophagosomes and depends on autophagy proteins. This form of cell death most likely corresponds to a process that has been morphologically defined as autophagic PCD. One question that constantly arises, however, is whether autophagic activity in dying cells is the cause of death or is actually an attempt to prevent it. Morphological and histochemical studies have not so far proved a causative relationship between the autophagic process and cell death. In fact, there have recently been strong arguments that autophagic activity in dying cells might actually be a survival mechanism. Studies of the metamorphosis of insects have shown cells undergoing a form of PCD that appears distinct from other forms; these have been proposed as examples of autophagic cell death. Recent pharmacological and biochemical studies have proposed that survival and lethal autophagy can be distinguished by the type and degree of regulatory signaling during stress particularly after viral infection. Although promising, these findings have not been examined in non-viral systems.

Exercise

Autophagy is essential for basal homeostasis; it is also extremely important in maintaining muscle homeostasis during physical exercise. Autophagy at the molecular level is only partially understood. A study of mice shows that autophagy is important for the ever-changing demands of their nutritional and energy needs, particularly through the metabolic pathways of protein catabolism. In a 2012 study conducted by the University of Texas Southwestern Medical Center in Dallas, mutant mice (with a knock-in mutation of BCL2 phosphorylation sites to produce progeny that showed normal levels of basal autophagy yet were deficient in stress-induced autophagy) were tested to challenge this theory. Results showed that when compared to a control group, these mice illustrated a decrease in endurance and an altered glucose metabolism during acute exercise.

Another study demonstrated that skeletal muscle fibers of collagen VI in knockout mice showed signs of degeneration due to an insufficiency of autophagy which led to an accumulation of damaged mitochondria and excessive cell death. Exercise-induced autophagy was unsuccessful however; but when autophagy was induced artificially post-exercise, the accumulation of damaged organelles in collagen VI deficient muscle fibres was prevented and cellular homeostasis was maintained. Both studies demonstrate that autophagy induction may contribute to the beneficial metabolic effects of exercise and that it is essential in the maintaining of muscle homeostasis during exercise, particularly in collagen VI fibers.

Work at the Institute for Cell Biology, University of Bonn, showed that a certain type of autophagy, i.e. chaperone-assisted selective autophagy (CASA), is induced in contracting muscles and is required for maintaining the muscle sarcomere under mechanical tension. The CASA chaperone complex recognizes mechanically damaged cytoskeleton components and directs these components through a ubiquitin-dependent autophagic sorting pathway to lysosomes for disposal. This is necessary for maintaining muscle activity.

Osteoarthritis

Because autophagy decreases with age and age is a major risk factor for osteoarthritis, the role of autophagy in the development of this disease is suggested. Proteins involved in autophagy are reduced with age in both human and mouse articular cartilage. Mechanical injury to cartilage explants in culture also reduced autophagy proteins. Autophagy is constantly activated in normal cartilage but it is compromised with age and precedes cartilage cell death and structural damage. Thus autophagy is involved in a normal protective process (chondroprotection) in the joint.

Cancer

Cancer often occurs when several different pathways that regulate cell differentiation are disturbed. Autophagy plays an important role in cancer – both in protecting against cancer as well as potentially contributing to the growth of cancer. Autophagy can contribute to cancer by promoting survival of tumor cells that have been starved, or that degrade apoptotic mediators through autophagy: in such cases, use of inhibitors of the late stages of autophagy (such as chloroquine), on the cells that use autophagy to survive, increases the number of cancer cells killed by antineoplastic drugs.

The role of autophagy in cancer is one that has been highly researched and reviewed. There is evidence that emphasizes the role of autophagy as both a tumor suppressor and a factor in tumor cell survival. Recent research has shown, however, that autophagy is more likely to be used as a tumor suppressor according to several models.

Tumor suppressor

Several experiments have been done with mice and varying Beclin1, a protein that regulates autophagy. When the Beclin1 gene was altered to be heterozygous (Beclin 1+/-), the mice were found to be tumor-prone. However, when Beclin1 was overexpressed, tumor development was inhibited. Care should be exercised when interpreting phenotypes of beclin mutants and attributing the observations to a defect in autophagy, however: Beclin1 is generally required for phosphatidylinositol 3- phosphate production and as such it affects numerous lysosomal and endosomal functions, including endocytosis and endocytic degradation of activated growth factor receptors. In support of the possibility that Beclin1 affects cancer development through an autophagy-independent pathway is the fact that core autophagy factors which are not known to affect other cellular processes and are definitely not known to affect cell proliferation and cell death, such as Atg7 or Atg5, show a much different phenotype when the respective gene is knocked out, which does not include tumor formation. In addition, full knockout of Beclin1 is embryonic lethal whereas knockout of Atg7 or Atg5 is not.

Necrosis and chronic inflammation also has been shown to be limited through autophagy which helps protect against the formation of tumor cells.

Tumor cell survival

Alternatively, autophagy has also been shown to play a large role in tumor cell survival. In cancerous cells, autophagy is used as a way to deal with stress on the cell. Induction of autophagy by miRNA-4673, for example, is a pro-survival mechanism that improves the resistance of cancer cells to radiation. Once these autophagy related genes were inhibited, cell death was potentiated. The increase in metabolic energy is offset by autophagy functions. These metabolic stresses include hypoxia, nutrient deprivation, and an increase in proliferation. These stresses activate autophagy in order to recycle ATP and maintain survival of the cancerous cells. Autophagy has been shown to enable continued growth of tumor cells by maintaining cellular energy production. By inhibiting autophagy genes in these tumors cells, regression of the tumor and extended survival of the organs affected by the tumors were found. Furthermore, inhibition of autophagy has also been shown to enhance the effectiveness of anticancer therapies.

Mechanism of cell death

Cells that undergo an extreme amount of stress experience cell death either through apoptosis or necrosis. Prolonged autophagy activation leads to a high turnover rate of proteins and organelles. A high rate above the survival threshold may kill cancer cells with a high apoptotic threshold. This technique can be utilized as a therapeutic cancer treatment.

Therapeutic target

New developments in research have found that targeted autophagy may be a viable therapeutic solution in fighting cancer. As discussed above, autophagy plays both a role in tumor suppression and tumor cell survival. Thus, the qualities of autophagy can be used as a strategy for cancer prevention. The first strategy is to induce autophagy and enhance its tumor suppression attributes. The second strategy is to inhibit autophagy and thus induce apoptosis.

The first strategy has been tested by looking at dose-response anti-tumor effects during autophagy-induced therapies. These therapies have shown that autophagy increases in a dose-dependent manner. This is directly related to the growth of cancer cells in a dose-dependent manner as well. These data support the development of therapies that will encourage autophagy. Secondly, inhibiting the protein pathways directly known to induce autophagy may also serve as an anticancer therapy.

The second strategy is based on the idea that autophagy is a protein degradation system used to maintain homeostasis and the findings that inhibition of autophagy often leads to apoptosis. Inhibition of autophagy is riskier as it may lead to cell survival instead of the desired cell death.

Negative regulators of autophagy

Negative regulators of autophagy, such as mTOR, cFLIP, EGFR, (GAPR-1), and Rubicon are orchestrated to function within different stages of the autophagy cascade. The end-products of autophagic digestion may also serve as a negative-feedback regulatory mechanism to stop prolonged activity.

The interface between inflammation and autophagy

Regulators of autophagy control regulators of inflammation, and vice versa. Cells of vertebrate organisms normally activate inflammation to enhance the capacity of the immune system to clear infections and to initiate the processes that restore tissue structure and function. Therefore, it is critical to couple regulation of mechanisms for removal of cellular and bacterial debris to the principal factors that regulate inflammation: The degradation of cellular components by the lysosome during autophagy serves to recycle vital molecules and generate a pool of building blocks to help the cell respond to a changing microenvironment. Proteins that control inflammation and autophagy form a network that is critical for tissue functions, which is dysregulated in cancer: In cancer cells, aberrantly expressed and mutant proteins increase the dependence of cell survival on the “rewired” network of proteolytic systems that protects malignant cells from apoptotic proteins and from recognition by the immune system. This renders cancer cells vulnerable to intervention on regulators of autophagy.

Parkinson’s disease

Parkinson’s disease is a neurodegenerative disorder partially caused by the cell death of brain and brain stem cells in many nuclei like the substantia nigra. Parkinson's disease is characterized by inclusions of a protein called alpha-synuclien (Lewy bodies) in affected neurons that cells cannot break down. Deregulation of the autophagy pathway and mutation of alleles regulating autophagy are believed to cause neurodegenerative diseases. Autophagy is essential for neuronal survival. Without efficient autophagy, neurons gather ubiquitinated protein aggregates and degrade. Ubiquitinated proteins are proteins that have been tagged with ubiquitin to get degraded. Mutations of synuclein alleles lead to lysosome pH increase and hydrolase inhibition. As a result, lysosomes degradative capacity is decreased. There are several genetic mutations implicated in the disease, including loss of function PINK1 and Parkin. Loss of function in these genes can lead to damaged mitochondrial accumulation and protein aggregates than can lead to cellular degeneration. Mitochondria is involved in Parkinson's disease. In idiopathic Parkinson's disease, the disease is commonly caused by dysfunctional mitochondria, cellular oxidative stress, autophagic alterations and the aggregation of proteins. These can lead to mitochondrial swelling and depolarization.

Type 2 diabetes

Excessive activity of the crinophagy form of autophagy in the insulin-producing beta cells of the pancreas could reduce the quantity of insulin available for secretion, leading to type 2 diabetes.

Significance of autophagy as a drug target

Since dysregulation of autophagy is involved in the pathogenesis of a broad range of diseases, great efforts are invested to identify and characterize small synthetic or natural molecules that can regulate it.

Entropy (information theory)

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