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A multigenerational mission after the sun



LAUREL, Md. – One of the most prestigious awards at the Fort Worth Regional Science Fair, in March 1970 – a calculating rule and a free lunch in Dallas – was awarded to a high school student named Ralph McNutt, who wrote 30 pages on the subject "Interstellar travel: is it feasible?" and built a cardboard model of the spacecraft, he said, could be the first to visit another sun.

Humans had landed on the moon the previous summer, noted the 16-year-old girl in the treatise that her mother transcribed to her on her Royal No. 10 typewriter. Soon, he was certain, we were would venture on all the other planets of the solar system. It would then be time to move on to the next step: "Go to the stars".

On a sweaty summer afternoon, McNutt is sitting in his office at Johns Hopkins University's Applied Physics Lab, aged 65, equipped with a Mickey Mouse wristwatch and fine hair. The latest version of his childhood dream is on his computer screen: a plan for a probe that would travel 1,000 times farther than the Earth will be from the sun, leaving behind the security of our system solar to explore the wild spaces of interstellar space.

From this point of remote observation, Interstellar Probe will help humans finally see themselves what we really are, says McNutt: citizens of a galaxy. Our planet of origin will be only one world among so many others and the sun that gives us life is only another layer of light in the darkness unending.

It's a bold proposition, even in terms of standards of space travel. It would take 50 years for the probe to reach its destination, by which time almost all the people currently involved in the project will have died.

Nevertheless, McNutt and a group of dreamers hope to gain significant support in a few years, when space scientists from the country will publish a list of their top research priorities. For Interstellar Probe to be on the agenda, its supporters must convince their colleagues that its goal is scientifically sound, not to mention its political viability, when there are so many questions inside the solar system and so many questions. unresolved land quarrels.

What makes McNutt believe that it is possible?

The scientist recoils in his chair and crosses his arms. When he responds, it is in the form of poetry.

"I think the reach of the man should go beyond his reach," he says, paraphrasing Robert Browning. "Otherwise, what is heaven for?"

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Our sun sits on a minor arm of the Milky Way star spinning wheel, about 25,000 light-years from the galactic core. Traveling the cosmos at half a million kilometers an hour, the solar system is agitated by gusts of gas and dust and bombarded by energetic particles whose origins are mysterious.

But on Earth, we are partly protected from this chaos by the heliosphere, a balloon-shaped structure inflated by the solar wind. The charged particles flowing from the sun flock to the edge of the solar system – beyond the planets, beyond Pluto, through the frozen halo of the Kuiper belt, to a place called heliopause .

This is the liminal zone between the solar particle river and the ocean of interstellar space; the boundary between our celestial neighborhood and the wider universe.

Only two spacecraft have reached this area and have lived to tell the story: Voyager twin probes, launched in 1977 and taking over 35 years to reach the heliopause. (The Pioneer probes left the solar system but were obsolete at that time.) Now their radio communications are getting weaker and several instruments have failed.

Voyager 1, the most distant object built by man in the universe, now has 145 astronomical units of Earth (one astronomical unit is equal to the distance between the Earth and the Sun). At this rate, it would take 283 years to reach 1,000 AU – 93 billion kilometers from the sun – which McNutt hopes to achieve.

"To really explore what's out there, you want to get out of the solar system as quickly as possible," he said.

And for that, you need a very big rocket.

NASA may soon have one. The space launch system, ultra powerful (but long delayed), capable of propelling almost twice as much weight as the largest rocket in operation, is expected to make its first flight around 2020 or 2021.

With the SLS, Interstellar Probe could leave Earth at a speed of about 9 miles per second. After looping around Jupiter, the probe would retreat to the sun, gaining speed under the gravitational pull of our star. It would pass through the orbits of the inner planets and hover through the solar corona until finally, just above the fiery surface of the sun, it would trigger a second rocket and darken into the darkness at a maximum speed of 60 km / s. At this frantic pace – and certainly ambitious – it would only be a little more than a decade to reach the heliopause.

Travel time would not be lost. Kathy Mandt, a global scientist, explored the potential of an interstellar probe to fly over Uranus, Neptune or an icy body in the Kuiper Belt, called Quaoar.

Abigail Rymer, a physicist, reflects on what the mission could do to help research on exoplanets. An experiment could consist of looking at planets with the same techniques that scientists on Earth use to study extraterrestrial worlds.

"On a background of stars," she says, "we will see our house habitable … and we will understand better what livability means".

By crossing the border in interstellar space, the probe could search for dust and particles in suspension to help researchers understand the structure of the heliosphere and the material from which our solar system he's trained.

And once out of the protective bubble of the sun, she could finally study the phenomena obscured by the heliosphere: galactic cosmic rays of stars exploding; the light of the glow of the big bang; Debris discs where planets form around other suns.

For now, the interstellar probe only exists in the form of PowerPoint presentations and a twinkle in McNutt's eyes. His team received about $ 700,000 for concept studies. It is waiting to see if NASA will give them $ 6.5 million over the next three years to develop a more detailed science plan and mission design.

Their decisive moment will come in 2023, when the National Academies of Science, Engineering and Medicine are about to publish their next ten-year survey on solar and space physics. These assessments, conducted every 10 years at the request of Congress and NASA, represent the official consensus on the country's space science goals and guide the NASA budget in subsequent years.

If the interstellar probe is to be launched during McNutt's lifetime, it must be classified as a top priority.

"It was always something we could not do right away, but maybe set aside for the future," says Caltech physicist Richard Mewaldt, who chaired the solar and heliospheric physics task force at the conference. the latest decennial survey published in 2013. This report ranked the "advance planning" for an interstellar spacecraft as the eighth of NASA's nine requirements.

Mewaldt notes that the heliophysics division of NASA – which would oversee an interstellar mission – receives the least funding from either branch of the agency's scientific divisions. The interstellar spacecraft may be more effective if planners get the endorsement of the global scientific community, which could profit from flights beyond the ice giants or the Kuiper belt. Still, the scientific world tends to be compartmentalized, he says, making it difficult to fund missions in several NASA divisions.

Even if the project continues, we do not see how a spacecraft could survive the solar flyover. The best heat shield man has ever made, currently using NASA's Parker solar probe, is designed to protect a spacecraft within 3.8 million kilometers of the sun's surface. To reach the desired speed, the interstellar probe should be more than twice as close.

"There is a moment for every big mission, almost a moment" aha ", when the technology is ready and you have a plan, that it makes sense and that it will answer the scientific questions", said Nicky Fox, director of NASA. heliophysical division. The problem with the heat shield, she says, is always between the interstellar probe and that moment.

But then again, she adds, every major mission also has a moment when scientists simply decide that the time has come to try.

Another question that weighs on the mission is the one that goes beyond the questions of budget and bureaucracy, but also the limits of what humans can accomplish.

By 2050 – the year the probe reaches the interstellar environment – the Intergovernmental Panel on Climate Change at the United Nations estimated that the global average temperature would already be higher than more than 2 degrees Celsius to that of the pre-industrial era. Unless the world radically lowers its carbon consumption, we are facing a future in which cities will be submerged by a sea level rise of several feet or will be heated to unbearable extremes. But most major emitters are far from achieving their climate goals.

– – –

The gap between what the world can do and what it will do has rarely seemed so vast.

But perhaps, says Mandt, the seeming audacity of an interstellar mission is what makes it worthwhile to try.

"This would be an example of a large group of people working together on something multigenerational," she says. "Which is the same thing we need with climate change."

The members of the interstellar probe team, she noted, range from Fellows who have just completed their graduate studies to people avoiding retirement. They come from at least eight countries. They include planetary scientists, astronomers, engineers and a particle physicist.

Last fall, Mandt invited Janet Vertesi of Princeton, who conducted ethnographic studies of spacecraft teams, to advise the team on organizational issues. It's the first time that they know that a sociologist has been involved in designing a NASA mission.

His job is to "remind them of the human side," says Vertesi: how to solve a conflict. Where to store the data. How to conduct an awareness campaign so that the demographic data of the project team reflect today the more diverse country that will launch the probe in the coming decades.

"We test the idea that you can actually plan a mission in advance to achieve certain social goals," said Vertesi.

In these "uncertain times," she adds, it's an intoxicating feeling to take part in something so fundamentally optimistic. Watch as a computer calculates the precise location of the planets on the date 50 years from now. See scientists dedicating the remnants of their careers to an idea that they could never live in practice.

"These people," she says, "they just can not wait for the future to come."

In his Maryland office, McNutt turns away from the unfinished plan on his computer screen and tries to visualize the moment Interstellar Probe reaches the void between the stars.

There is no way of knowing what he will find there, beyond the veil of the solar wind. But of one thing, he is certain.

When the probe will turn to Earth to return the data that it has collected, it will have as its objective "one of the most special places in the universe," says McNutt: the small watery world in which he was imagined.


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