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How to land a spaceship | Space



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No matter what mission is sent to the astronauts, the engineers who send them must solve two basic problems: how to get space travelers out of Earth (and put them in orbit or way to the Moon or Mars) and how to bring them back another time. With decades of experience in pushing payloads into space, the space powers of the world have decided unanimously with chemical rockets as the best way to launch astronauts. The question that engineers are still debating is: What is the best way to get them?

Boeing and SpaceX have been asked, through NASA's Commercial Crew Program, to send astronauts to the International Space Station next year, to respond to the two basic problems of space flight with ingenuity, economy and technology. vanguard for the cosmic challenges that lie ahead. . However, one of the most visible elements of your private design spaceship will go back to the depths of the last century: they are shaped like capsules, and have their blunt, high-drag shapes and a pair of parachutes to slow them down from a speed orbital of 17,000. mph at a speed that human occupants can survive when they hit the surface of the Earth.

It was assumed that the space shuttle would end all of that when it took its first flight in 1981, providing comfort like a passenger plane during its smooth landing on the runway. And by creating the next generation of space transport, SpaceX, at first, really tried to lean on the future. Elon Musk and his team searched for a new type of lander, one that relied on propulsion rockets, rather than parachutes, to slow the ship and the extendable legs to balance it at the time of landing, the so-called propulsion landing. "This is how a 21st century spacecraft should land," Musk boasted in 2014, "anywhere on Earth with the precision of a helicopter." SpaceX has been very successful with the propulsive landing for its payload delivery rockets: the first stage of the Falcon 9 regularly. and impressively, it lands upright on an ocean barge or back at Cape Canaveral. But such advances with astronauts in the interior require time and money that NASA was not willing to commit to a mission whose key selling point was economics. At least that's what space observers guess about the laconic abandonment of Musk in the approach in 2017. So the parachutes came out again.

NASA astronaut spatters have acquired a nostalgic, if not mystical, tint at the distance of half a century. But they were hairy issues in real life. Gus Grissom almost drowned after the second Mercury flight in 1961: a famous incident that became more famous for his inaccurate interpretation in the 1983 movie The right thing. The following year, Scott Carpenter landed 250 miles away and spent three hours in a life raft before being rescued by the USS. Bold.

The adventures of Splashdown continued after the missions to the Moon, even after more than a decade of accelerated technological progress. The crews of the Skylab 4 mission of 1974 and the Apollo-Soyuz Test Project a year later ended up face down in the ocean for a while, while the heavy seas captured their parachutes and overturned the landing craft. The problems of Apollo-Soyuz were aggravated by an escape leak of the propeller in the cabin that forced the astronauts to grab oxygen masks, which were more difficult to reach while they were face down. Crew member Vance Brand fainted during the revolt, and one of his crew had to put on the mask. In both cases, the inflatable "straightening spheres" outside the capsule worked as intended. The ships turned back to the surface, and the astronauts left relatively unharmed.

Of course, there is an alternative to landing at sea: landing on land, which the Soviet and then Russian space program has been doing since its inception. The Soyuz spacecraft, launched for the first time in 1967 and still strong, returns to Earth in the vast and flat steppes of Kazakhstan. It is not the most comfortable experience, the former passengers report. "It's like a series of explosions followed by a car accident," says Michael Lopez-Alegria, a former NASA astronaut who returned from the International Space Station on a Soyuz in 2007. "After seven months in space, it's not Well, feel great. "

Soyuz had an almost fatal accident in 1976, when the re-entry capsule lost its way and landed in a partially frozen lake, five miles offshore, at night, in the midst of a snowstorm. Rescuers, who arrived at the ship partially submerged nine hours later, did not bother to open the hatch for two hours because they assumed that the cosmonauts had died of death. The sturdy Soviets survived, though they never flew again.






Ah, the good old days, when the American astronauts landed in the ocean and the Russian cosmonauts, on land. In the photo: an unmanned Apollo capsule in 1968

(POT)

A Soyuz fires its retrothrusters just before impact. Soon the United States capsules will do both.

(NASA / Bill Ingalls)

When a capsule loses its mark on the earth, astronauts are not allowed to spend hours so that they rise and fall in the waves. But they can cool down. Here, a Soyuz recovery team meets the crew on a day in Kazakhstan with snowstorms.

(NASA / Bill Ingalls)

However, López-Alegría would prefer to return from space to mainland, given the option. "Landing on the water seems to make a gigantic stomach failure, so I'm not sure the impact is much less," he says. "And afterwards, I think I would be happier on land than in the ocean." Ken Bowersox, another Soyuz landing veteran, also thinks that the earth is safer than water. "On land you can have a bit of a hard landing and still get out of the vehicle," he says. "If things do not go well in the water, it can be exciting pretty fast." Describing the re-entry of Bowersox's Soyuz in 2003 as a "bit of a hard landing" could be an understatement. The capsule veered into a ballistic landing that took him hundreds of miles from the target. But "we only wait a few hours," he recalls. "In the water, it would have been much less comfortable." Regarding the impact, Bowersox compares it to the aircraft carrier landings that he practiced as a Navy pilot. "Get your attention, but it's not worse than a carnival ride," he says.

NASA studied the land landing at various points in the pre-shuttle era, but rejected it for several reasons. At that time, the agency came to the conclusion that the United States lacked a flat, vast, properly wide area in the contiguous states. At least compared to the undifferentiated open space of the Kazakh plain, even the southwestern desert could not compete, with its canyons, plateaus and cities and remote reserves. The orientation in the descent was simply not accurate and reliable enough. What the country had was a lot of open water: abundant access to two oceans, a coastal launch site and existing maritime infrastructure to recover water astronauts.

Another important consideration in these terrestrial studies was the weight of the spacecraft. A landing in the water can end with a dive, but the liquid still has a little energy; returning to shore requires some additional feature to compensate for the hard stop, such as the retro rockets that Soyuz fires when it is several feet off the ground for a final brake in the seconds before impact. However, that equipment makes it a heavier vehicle, and in the early 1960s, NASA's mental confidence, pressed by time, did not believe they could carry all that weight to the Moon (see sidebar).

But the technology improves and the objectives change. So Boeing reviewed the question about the land landing when he started designing his commercial crew vehicle, the Starliner, around 2010. "The return on land has an advantage over the sea by having immediate access to the crew and the entire cargo to board, "says Michael McCarley, a career man from Boeing who worked on the shuttle on his last flight before moving on to the Starliner project as the chief engineer for re-entry. But the weight of this type of capsule remains a problem, or as McCarley calls it, "the massive challenge."

Soyuz could have solved its massive challenge the year the Beatles recorded Sergeant Pepper, but the Russian ship can only cram three astronauts, half the crew of a space station. One of the keys to the expanded seven-passenger land vehicle was to replace those retro rockets with airbags. The Starliner will be based on six of them (a seventh, in the center, is deployed only for an emergency landing on the water). They are inflated with nitrogen and oxygen like those of automobiles, but designed as bicycle tires with discreet internal and external layers. The outer bag has ventilation holes that release pressure when landing, while the inner tube remains firm. Hopefully.

McCarley says that not only is the airbag system lighter than Soyuz rockets, but it should be easier for bodies that have already run out of space for half a year. Ken Bowersox is an enthusiast. "If you look at the specialists who jump off buildings and land in airbags, that should be a reasonable landing," he says.

Then there's McCarley's personal project: the seat. One way or another, a space capsule that returns to Earth under parachutes is slowing through the atmosphere around 4 G before its sudden stop, says López-Alegria, who is still on the advisory board for human exploration. of NASA. That compares to a tolerable 1.5 Gs for the space shuttle from slip to landing. But the impact on astronauts' bodies depends, literally, on where and how they sit. Or actually lie, since the backbone of a human and other vital organs are not designed to absorb 4 Gs in an upright position. The Soyuz passengers already land reclined, with an individually designed seat cover. But McCarley was determined to improve that with modern ergonomics. He started with a pile of plywood in his garage.

"The overall concept of the seat has not changed with respect to the plywood model, but we have added some more advanced materials," says McCarley. The company also added 3D printing technology to shape a complete custom seat for every Starliner passenger. Given the compact space available, this involved an intensive study of human body types.

McCarley, who is a sturdy 6 & # 39; 1 ", and Starliner systems engineer Melanie Weber, who stays a little more or less about five feet, modeled themselves for the outer limits of the allowed size. in the nuances, the engineers worked to adapt to a range of body types, which gave him names of pets such as The Orangutan ("long arms that can practically pass through the capsule", clarifies McCarley), or The T-Rex (wide torso) with short arms.) By designing the range of extremes, the team will be in a better position to adapt each seat with the explorations of an astronaut's body.

The Boeing team also wanted to improve the parachutes of the Soyuz era. For reasons now lost in the scientific history of the Cold War, the parachute series of the Russian ship (pilot, drug and finally the main ramp) opens from one side of the capsule, followed by the pyrotechnic release of a rig system. which forces Capsule to hang down. Lopez-Alegria describes the result as "a very violent side-by-side movement, like Toad's Wild Ride." Boeing promises to soften the process with two drogue hoppers for symmetry, followed by three main chutes for stability, not to mention redundancy.

As for where the capsule will be placed, the Starliner team feels more comfortable with its precision landing than the first NASA engineers. The company has a list of five sites in the West: two at the White Sands Missile Range in New Mexico, the Dugway Proving Ground in Utah, the Edwards Air Force Base in California and Wilcox Beach in Arizona, among which they will choose the main and backup locations shortly before the end of each mission. Ground crews have been looking for telephone poles and other long-forgotten obstacles, and have conducted extensive environmental and cultural studies to ensure both the safety of astronauts and the integrity of the earth. The Dugway test field, for example, was established by the Army during World War II to test chemical and biological weapons, and is also an archaeological treasure trove of Native American artifacts dating back 13,000 years.






When Starliner astronauts, Eric Boe (sitting on the left), Chris Ferguson (sitting on the right) and Nicole Mann, return to Earth after the first crew mission next year, each of them will be cushioned by seats totally made of his body. explorations

(NASA / Bill Ingalls)

Instead of the heavy Soyuz retrothrusters, Boeing designed six lightweight airbags for the Starliner (which is being tested here at the Langley Research Center) that should make a somewhat more comfortable rebound on his return to Earth.

(POT)

In Nevada, Boeing tests the landing system on its Starliner capsule.

(Boeing)

* * *

While Boeing engineers thought a lot about the earthly details of their capsule's descent to the hard ground, SpaceX began its work dreaming of Mars. In January 2011, the company released a 15-second futuristic video showing a neat trapezoidal spacecraft that makes a vertical landing without hurry without a parachute, driven by the flames that emerge from the four corners of its base at angles of approximately 30 degrees . Elon Musk, in the voiceover, describes it as "a propulsive landing with equipment, something like [how Apollo 11’s] The eagle landed on the moon. It seemed very cool.

But those SuperDraco thrusters that fire the flames, as Musk later named them, aimed at more than lowering a 14,000-pound Crew Dragon capsule to a helicopter platform anywhere on Earth. SpaceX insisted they could carry a ship of similar mass to the surface of Mars, where the atmosphere is too thin to land some of that weight with a parachute. The heaviest object to be dropped there to date was the NASA Curiosity rover, which had about one seventh of that mass and, of course, no fragile human passengers.

SpaceX unveiled a Crew Dragon prototype in 2014 with high hopes for its prospects on two planets. In 2016, he posted a video of a test model that confidently moved several yards over a platform in Texas. Then Musk suspended him. While the Crew Dragon was still technically capable of propulsive landing, he said at a space station research and development conference in July 2017, it would require "a tremendous effort to qualify that for safety." In addition, since then he had guessed a "A much better approach" to land on Mars, whose details he has kept secret. The capsule still has SuperDraco engines, but will only be used in case of a launch abortion. (See "Abort!", October and November 2018.) A routine power-driven landing crew dragon seems destined to become a footnote in the history of exploration, although SpaceX continues to work on its technology. other vehicles, including the next generation BFR. rocket: a spacebus still unproven that promises to transport up to 100 passengers to the Moon or beyond. The first customer who paid for that trip, the Japanese billionaire Yusaku Maezawa, was announced in September.

Fortunately, the company had a proven Plan B to take the crew to the space station. While SpaceX was playing with the futuristic system for a crewed ship, when this magazine went to press its cargo ship, it has flown silently 15 successful missions to and from the space station, the capsule has been splashed without incident. So far, the company has managed to reuse four of the capsules despite immersion in salt water.

The Crew Dragon is approximately 50 percent heavier than the cargo model, so SpaceX is compensating the extra mass with a system of four parachutes that are thrown symmetrically above the vehicle, offering more resistance than the classic triangle that is deployed above the capsules of the sixties. More than Bolin Starliner too, a statement from the company implies: "The Crew Dragon parachute system is the most efficient system ever designed in terms of packing density and aerodynamic braking capability."

An even more remarkable difference of the days of yesteryear will be the modest flotilla that SpaceX implements to recover the astronauts Dragon at sea. The published plans require a single ship of 164 feet, the Go search engine, with the support of several inflatable boats that can maneuver closer to the splashed capsule. the Go search engine will be equipped with a heliport to transport the astronauts quickly to land if necessary.

That is a dramatic contrast to the United States Navy fleet that took to the water to meet the space travelers of the sixties and seventies. No less than 24 naval vessels awaited the fall of John Glenn after the first orbital flight of the United States in 1962, with the Air Force in the most avid reserve. However, the landings became more accurate quickly, and the welcome party was reduced to four boats on the last lunar flight of the Apollo in 1972. So the SpaceX recovery team is not as minimalist as it seems. (The company has a more elaborate system, through an association with the Air Force's pararescado teams, for the recovery of the astronaut after a launch abortion).

SpaceX is also predictably eager to expand its reusable technology to the Dragon Crew. The team has gained extensive experience in water sealing and corrosion prevention by refining four of its cargo ships. But at this time, SpaceX is only approved to fly a crew with a new spacecraft, creating a somewhat ironic situation where the rival Boeing deploys a reusable capsule before SpaceX. Rocket observers are guessing that the delay will be temporary.

* * *

Human space flight inevitably involves stopping in the worst scenarios. "I'm always thinking: is there something hidden that we do not know?" Says Mike McCarley of Boeing. "Have I looked behind each door and in the back of each closet? It is a kind of personal neurosis, but also a professional neurosis. " Since the space race of the 1960s, human space flight seems to involve inevitable delays and frustrating mid-course corrections, from adjustments that only engineers can imagine to setting aside promising systems. as the SpaceX propulsive landing scheme. At the beginning of the program, commercial crew missions were optimistic targets for 2015. They are currently targeting mid-2019.

None of that should hide the fact that private contractors are gaining confidence from NASA, and from past and future astronauts, in whatever path they follow. "For me, I do not care, they both go to work," concludes Ken Bowersox. "Going down by land or sea is more an economic decision."

The delays of the program also do not invest a clear direction: the flights of the commercial crew, the systems of retro landing and everything, indicate the way towards a new and exciting chapter in the space exploration, where the private companies assume futuristic projects from the extraction of asteroids until the colonization of Mars. "This is revolutionary in many ways," says López-Alegría. "This is the first time the government has loosened the reins of what size the washing machine should be used in. It will be a kind of rebirth." That is a door that opens and that he, and many others, are eager to go through. The current work of López-Alegría is the head of commercial development of Axiom Space, which wishes to build a successor to the space station financed with private funds at a projected cost of $ 1.5 billion.

First, however, the new commercial vehicles and their dramatic parachute returns will come, not only to Earth, but for the first time in almost a decade, to their own country.

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