The safest way to travel long distances in space may be artificial hibernation.
Someday astronauts, stuffed like sprats in rockets cans and flying to other planets, will be protected from radiation and space sickness by a decrease in the rate of metabolism in the body. They will hibernate for months like bears, and spacecraft will carry them through space and time. Probably, they will sleep in white cocoons, similar to coffins, which are shown to us by directors of futuristic science fiction in films such as "2001: A Space Odyssey", "Alien" and "Avatar".
But astronauts and space colonists are likely to learn a thing or two from dehydrated snails, which can survive for over a year without eating anything. Or in giant pandas, which feed on low-calorie bamboo. And also in leeches that can survive in liquid nitrogen; in children who fell into ice water, and then resuscitated; in skiers buried in an avalanche, but then slowly returning to life from a dreamless state of hypothermia.
Scientists call this phenomenon "dazed hibernation." Once upon a time such torpor, or torpor, was considered something strange and outlandish, and was called "insensibility of functions." Now it is being seriously studied, hoping to benefit from long-term space flights.
This interest is partly due to the advances in cryogenic surgery, as well as new knowledge gained in practice. One such case was reported in 1995 in the journal Prehospital and Disaster Medicine. A four-year-old boy fell through ice into cold water on a lake in Hanover, Germany. Rescuers pulled him out of the water, but could not bring him to his senses on the spot. The boy's pupils dilated and his heart stopped for a full 88 minutes. When the victim was taken to the hospital, his body temperature was 20 degrees, which indicated extreme hypothermia.
After 20 minutes, when the doctors began to warm the boy's chest cavity, his heart ventricles began to contract. After another ten minutes, the sinus rhythm returned to normal. In two weeks the boy recovered completely and was discharged from the hospital. The doctors concluded that the ice-cold water rapidly cooled his body to a state of metabolic stupor (torpor), preserving all vital organs and tissues, and at the same time, reducing the need for oxygen for blood circulation. In fact, the cold saved his life. “These kinds of cases lead us to think that very deep hypothermia could allow our patients to survive,” Samuel Tisherman, professor of surgery at the University of Maryland School of Medicine, wrote in an email. - The main thing is to cool the brain either until the blood flow stops,or immediately after stopping. The lower the temperature, the better the brain will cope with the lack of blood flow."
Therapeutic hypothermia is firmly established in surgical practice. Refrigeration experiments began in the 1960s, mainly with newborns and those with cardiovascular disease. Newborns were wrapped in cooling blankets, placed in ice and even in drifts to slow blood circulation and reduce oxygen demand before heart surgery.
Today, doctors use mild hypothermia (approximately 31 degrees) to treat certain newborns in severe cases, such as premature birth or fetal hypoxia. Children are treated in cooling capsules for 72 hours, lowering their metabolism to such an extent that the oxygen requirements of the tissues are met, while the brain and other vital organs are restored.
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Likewise, surgeons use refrigeration and metabolic suppression to treat patients suffering from physical trauma and injury such as heart attack, stroke, gunshot wounds, profuse bleeding, and head injuries that cause cerebral edema. In emergencies, the anesthesiologist can insert a thin catheter tube into the patient's nose, which delivers cooling nitrogen directly to the base of the brain. In one treatment experiment, surgeons insert a heart-lung machine catheter through the chest into the aorta, or through the groin into the femoral artery. These tubes are used to deliver cold saline solution to reduce body temperature and replace lost blood. When the traumatologist stops the bleeding, the heart-lung machine starts the blood flow again and the patient receives a blood transfusion.
“If you apply the cold quickly enough, before the heart stops, then the vital organs, and in particular the brain, will be able to withstand the cold without blood for some time,” Tisherman explains. He is conducting clinical trials with a cold saline solution at a Baltimore Clinic trying to help critically injured patients. Tisherman hopes to continue his research at least until the fall of 2018, and maybe longer.
The resulting hypothermia quickly slows down or stops blood circulation for about an hour. Accordingly, the need for oxygen decreases, and surgeons have time to heal life-threatening wounds, after which they can warm the patient and bring him back to life.
Torpor riddle
Today, many in the aerospace community are pinning their hopes on medically generated hypothermia and the resulting slowdown in metabolism as a way to save space, weight, cargo, fuel, food and depression during long flights to Mars or more distant planets. Research in this direction is just beginning. One problem is purely medical. What's the best way to put healthy astronauts into hibernation? It is well known about therapeutic hypothermia in the operating room, but how to keep people in outer space cool and hibernating for weeks, months and even years? This is a completely unexplored area. Some scientists who study hibernation in animals say that other methods of suppressing metabolism are better. This is a special dietlow-frequency radiation and even the use of proteins that induce hibernation in animals such as bears and Beringian ground squirrels, because they safely regulate the metabolic rate with the possibility of exiting the torpor.
Another obvious problem is financing. How much money will NASA allocate to study the metabolic slowdown in animals and humans if the agency is cut the budget even for space flights? Former director of the Ames Research Center in California, Pete Worden, now executive director of the Breakthrough Starshot project, says that because NASA places great emphasis on synthetic biology and the survival and functioning of organisms in unusual environments like Mars, “what is hibernation will be financed, it is almost inevitable."
This optimism is not shared by everyone. “People are disappointed,” said Yuri Griko, a NASA-trained radiobiologist and leading researcher in the space biology division of the Ames Center. - When a satellite flew into space in 1957, my generation rejoiced and rejoiced. We believed that we would fly to Mars already in the 20th century. But … it's the 21st century, and we never flew to Mars. People like me have a sense of personal resentment as we expected to go much further than we are now."
Griko admits that research on lowering metabolism is currently in limbo. He came to work at NASA in 2005, and before that he worked for five years at the biotechnology firm Clearant, Inc., where he, using ionizing radiation, blocked the activity of pathogens in medicinal blood products, in organs for transplantation and in biologics. The space agency then invited Griko to conduct research to protect astronauts from space radiation. It turned out that slowing down metabolism is one of the most effective mechanisms given to us by nature.
When animals go into hibernation, their body carries radiation without significant harm to cells. Griko believes that a decrease in metabolism leads to a decrease in damage from radiation, since biochemical processes are slowed down, and oxidative stress is weakened. Hypoxia, or low oxygen levels in blood and tissue, is one possible explanation for the radiation shielding effect. With hypoxia, the formation of free oxygen and hydroxyl radicals is reduced. Since ionizing radiation releases free radicals, causing damage to cells, slowing down metabolism and reducing oxygen consumption work in the opposite direction. These processes interfere with the death of normal cells and prolong the life of healthy cells. This protective effect is much more pronounced at lower temperatures.
Griko believes that hibernation can also protect animals from muscle and bone atrophy, which usually occurs in zero gravity. According to him, a normally eating person, after spending 90 days in bed, loses more than half of his muscle strength. But a bear that does not eat anything and sleeps in its den for about the same time or a little longer loses only 25% of its muscle strength, and it shows no signs of bone loss. The scientist notes that hibernating animals such as turtles and marsupials have not been sent into space for decades.
NASA has denied its request to fund space experiments with hibernating animals. Today, Griko's scientific work is limited to the analysis of research conducted on hibernation, and he also conducts his own laboratory studies, studying stasis in mice, snails and leeches. The scientist proposed organizing an international conference on torpor in 2015, inviting leading world experts to it, and discussing the question of how hibernation can be found in outer space. NASA has refused to fund it, but Griko still hopes to raise the necessary money.
“There are significant obstacles to the study of torpor, although without this we cannot seriously talk about long-distance space flights,” says former NASA astronaut and ISS crew commander Leroy Chiao, who spent 193 days in orbit from October 2004 to April 2005. of the year. Animal research is a particularly challenging topic because NASA has criticized animal advocates in the past. “Even research on primates is viewed with hostility by humans,” Chiao notes.
The solution is in two planets
NASA's Innovative Advanced Concepts (NIAC) Program Manager Jason Derleth sees reason for hope. Under his leadership, the program has awarded two innovation grants since 2013, supporting one company's detailed plans to create an intermediate laboratory dwelling on Mars using artificial hibernation techniques. The lead company for this project, SpaceWorks Enterprises, is an aerospace designer and contractor for NASA and the Department of Defense. It is located in Dunwoody, Georgia, 30 kilometers from Atlanta. The company participated in the creation of the CubeSat format for small artificial earth satellites. But it was the torpor that attracted the special attention of the president and chief engineer of this company, John Bradford (John Bradford).
“I've been asking myself for 15 years about how to design the materials, structures and propulsion systems that will allow us to fly to Mars and its satellites,” says Bradford. He is a Ph. D. and an aerospace engineer. Bradford has led several projects by NASA, the Defense Advanced Research Projects Agency, and the Air Force Research Laboratory to build military spaceplanes. He was also a consultant for the science fiction movie Passengers, which came out in 2016. There, interplanetary settlers, played by Jennifer Lawrence and Chris Pratt, wake up from artificial sleep ahead of time. “We're not filming the Apollo mission anymore,” explains Bradford. - No flags and footprints. We must become a two-planetary species."
Bradford's medical engineering team used the first Innovative Advanced Concepts grant in 2013 to design a zero-gravity compact living module from rigid structures, based on the ISS habitation module. In this space house, a closed cycle system for the production of oxygen and water was provided, direct access to the takeoff and landing module for landing on Mars, as well as a life support complex for six people who were supposed to plunge into a torpor state for the entire flight time (from six to nine months).
The proposed technique of artificial hibernation is based on the techniques used by surgeons to induce hypothermia in a patient. For example, the cooling gas nitrogen can be supplied to an astronaut through a nasal tube, lowering the temperature of the brain and body to 31 degrees. This is enough to maintain hibernation, but at the same time the heart does not overcool and there is no risk of other complications. With cooling, blood clotting decreases, Tisherman notes. He also noticed that patients who are exposed to moderate hypothermia (33 degrees) for two or more days are more likely to have infections than non-refrigerated people.
At SpaceWorks Enterprises 'space home, modular mechanical manipulators are programmed to do chores, exercise astronauts' limbs, check body sensors, empty urine containers and monitor nutrient delivery. The robots must send electrical impulses to the astronauts' muscles, keeping them in good shape, and also inject sedatives to suppress the natural tremors. Astronauts also need to receive complete parenteral nutrition with substances such as electrolyte, D-glucose, lipids, vitamins, and so on. They are supplied to the body with fluid through a catheter that is inserted into the chest or thigh. In the experimental module, stocks of total parenteral nutrition were created for 180 days. But if the flight to Mars lasts longer,in the module, you can create a supply of food for another 500 days.
Overall, SpaceWork was able to reduce the total weight of the Compact Habitat to 19.9 tonnes, including consumables and consumables (low Earth orbit weight). By comparison, NASA's TransHab housing unit, along with supplies and supplies, weighs 41.9 tons. This is 52% more than SpaceWork. Compared to NASA's SpaceWork module, the total inventory weight has been reduced by 70%.
The NIAC program management was intrigued. “SpaceWorks made an interesting proposal,” says Derlet. “People have studied hibernation for medical purposes. But as far as we know, no one is currently carrying out a constructive study of the use of hypothermia or torpor in space flights."
In 2013, NIAC management provided SpaceWorks with the first part of a $ 100,000 grant to develop an exemplary platform for artificially sleeping research flights to Mars and its satellites. The crew was supposed to include four to eight people. However, the space agency opposed the proposal to put all crew members in artificial sleep for the entire duration of the flight. What if there will be medical complications or malfunctions in the spacecraft? How long will it take until astronauts begin to suffer psychological and physical damage? What if complications on board require them to wake up early? And what about the gradual and slow waking up and rewarming of the body while awakening the astronaut from hibernation?
These questions pushed the SpaceWorks team back to work. They designed a compartment for the crew to stay in a state of artificial sleep, while providing that several astronauts would take turns awake to pilot the ship and carry out the necessary work (as in "Space Odyssey", where two crew members on the way to Jupiter were awake, while while the rest were in artificial hibernation).
Bradford's team went further. By designing three interconnected living modules for 100 displaced passengers (to populate Mars), she created a spacecraft with a living compartment that is completely unlike anything NASA had planned. The SpaceWorks displaced bay contains two compact rotating housing units, each containing 48 torpor passengers. Rotation at different speeds creates an artificial gravitational force that prevents bone loss.
But the Bradford team had another, more daring proposal. In a separate living module, she decided to place four astronauts on duty, who should serve the ship and crew throughout the flight. While one sleeps, three work, thus maintaining their strength.
Flight to Mars by SpaceX
“Rotating the sleeping crew and waking up some astronauts to watch is more beneficial than having all the astronauts hibernate for six months,” Bradford said. A spaceship with settlers in a torpor state will be lighter, which will greatly increase its speed, reduce flight time, and possibly also provide more reliable protection from radiation due to a slowdown in metabolism. Further, says Bradford, sleeping astronauts will not experience motion sickness, which is a common problem for ISS residents.
Bear hibernation
But what will be the sensation of torpor in outer space? No, this is not about freezing to death in a cryogenic unit and then revitalizing, says obstetrician-gynecologist and SpaceWorks consultant Doug Talk, who uses therapeutic hypothermia to treat oxygen-deprived children. “Cryogenics has zero success here,” he explains. - The human body is not intended to be frozen; it consists mainly of water, and when water increases in volume [this happens when it freezes], it leads to the destruction of cells."
Rather, the astronauts will hibernate like a coma. This is a cross between dreamless sleep and a semi-conscious state. “Patients in coma have cycles of brain activity from seeming wakefulness to deep, dreamless sleep,” explains Tock. Although patients in a coma are unable to move, their brains remain active and even respond to external stimuli, including verbal commands.
Hibernating bears experience something similar. Their body temperature drops by only a few degrees (as with moderate hypothermia in humans), and their metabolism is reduced by 75%. Bears in northern climates can hibernate for seven to eight months without eating or drinking anything; and pregnant females give birth to offspring and feed them even in hibernation.
“People in torpor will behave like bears,” Tok suggests. “They will have cycles from wakefulness to deep dreamless sleep. And like bears, when they wake up they will show signs of sleep deprivation."
In May 2016, NIAC management approved the second phase of the SpaceWorks project, this time providing it with $ 250,000 to continue engineering research, as well as operational and medical research. “Phase 1 projects have proven that our vision is real,” says Derlet. "We're glad Dr. Bradford is making progress."
The SpaceWorks team suggested some design improvements to the living module, as well as an experiment with artificial sleep for a period of two to three weeks with several healthy pigs. Pigs, like humans, do not hibernate in their natural environment, and therefore their physiological reaction to artificial sleep will better help people understand what to expect from torpor than experiments on mice and snails. But according to Derleth, NASA rules prohibit funding research on pigs.
Therefore, SpaceWorks came up with an alternative proposal: to comprehensively study the already conducted and ongoing experiments to suppress metabolism, on this basis, to create a program of action for the near future to develop the necessary technologies that will allow the transition to human trials, including more systematic animal studies. This summer, NIAC is due to conduct an interim review of SpaceWorks and decide whether or not to allocate another $ 250,000 in funding.
“We continue to believe in the need for research on living things to develop torpor technologies and apply them over the long term,” wrote SpaceWorks founder and CEO John Olds. "And this step may require the participation of private sponsors."
Whoever pays for this work will be difficult to conduct experiments on animals because it raises ethical questions.
“I think NASA is right to act slowly and gradually,” says Arthur Caplan, director of medical ethics at New York University Medical Center. While many are enthusiastic about the promise of artificial sleep during extended space missions, NASA doesn't need the additional hassle that animal advocates can get, he said.
“Pigs are quite similar in physiology to humans, so it makes sense to use them for experiments,” says Kaplan. "And to the critics, we can say this: the number of pigs that will be recruited for this kind of research will be less than the average American eats in a week for breakfast."
Human factor
In science fiction films and books, torpor is idealized and romanticized, Kaplan says. They give the impression that a person can easily enter and leave this coma-like state. But the reality may be different.
According to Kaplan, the first experiments will be carried out with the participation of very unusual people - most likely, these will be test pilots. “These people risk their lives every day; they understand the physiological hazards because they test planes and know that many of their colleagues have died. Astronauts told me that they are ready to participate in any experiment, just to fly into space. Our job is to contain them,”he says.
Human experimentation will be an unprecedented step. No one has ever used hypothermia to slow down metabolism in people who are not sick or injured, much less in exceptionally healthy astronauts.
“We have a lot of healthy people who have expressed a desire to participate in long-term experiments with artificial sleep,” says Tok. - There is a pent-up demand for people who are ready to disconnect from life for six months. I'm sure the health authorities will not approve of this."
Meanwhile, Tok has recruited two therapeutic hypothermia specialists to the SpaceWorks research team: Alejandro Rabinstein, medical director of the Neurology Intensive Care Unit at Mayo Clinic, and neuroscientist Kelly Drew, who works at Fairbanks at the University of Alaska, specializing in hibernation. animals. Drew, along with other scientists at the University of Alaska Institute of Arctic Biology, is studying the hibernation patterns of warm-blooded animals such as hedgehogs, Beringian ground squirrels, and bears. They hope to solve the mystery of healthy hibernation and the brain signals that trigger it, believing it will help astronauts adapt without side effects.
For example, in the Beringian ground squirrel (evrazhka) in winter, the body temperature drops to zero degrees. No scientist knows exactly what triggers the hibernation mechanism. True, there is an assumption that a special brain and muscle receptor - the A1 adenosine receptor - leads to a decrease in the body temperature of the ground squirrel and causes him to sleep, from which he awakens eight months later with minimal loss of bone and muscle mass.
“Adenosine is a neuromodulator that plays a role in stimulating sleep and reducing brain excitability,” says Drew. "It is ubiquitous in animal brains." She injected into hibernation euras with a drug that stimulates their A1 adenosine receptors. Drew can also wake up gophers by using another drug that blocks these receptors.
But the signaling cascade and the set of genes in humans are much more complicated and very difficult to decipher. Complicating the task is that hibernating animals sleep in different ways.
The only primate that hibernates is the Madagascar pygmy lemur, which spends eight months a year in torpor, mostly in hot weather. He lives off fat deposits in the tail. A decrease in metabolism in this animal does not require a decrease in body temperature.
Meanwhile, Rabinstein, who plans to conduct a mild hypothermia analysis to induce torpor, says the techniques used in intensive care in space may not be as reliable.
“The fact that young children are 'drowning' in icy water and then come to their senses is remarkable, and it gives us hope,” he says. - But can we apply our knowledge [of deep hypothermia] to create milder hypothermia, so that people can stay in this state much longer without harmful consequences, without psychological and physiological stress? It remains to be seen, but we think there is a chance."
Arielle Emmett