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Everything you need to know about space travel (almost)

We're a long way from home...

Paul Parsons

When did we first start exploring space?

The first human-made object to go into space was a German V2 missile , launched on a test flight in 1942. Although uncrewed, it reached an altitude of 189km (117 miles).

Former Nazi rocket scientists were later recruited by both America and Russia (often at gunpoint in the latter case), where they were instrumental in developing Intercontinental Ballistic Missiles (ICBMs) – rockets capable of carrying nuclear weapons from one side of the planet to the other.

It was these super-missiles that formed the basis for the space programmes of both post-war superpowers. As it happened, Russia was the first to reach Earth orbit, when it launched the uncrewed Sputnik 1 in October 1957, followed a month later by Sputnik 2, carrying the dog Laika – the first live animal in space.

The USA sent its first uncrewed satellite, Explorer 1, into orbit soon after, in January 1958. A slew of robotic spaceflights followed, from both sides of the Atlantic, before Russian cosmonaut Yuri Gagarin piloted Vostok 1 into orbit on 12 April 1961, to become the first human being in space . And from there the space race proper began, culminating in Neil Armstrong and Buzz Aldrin becoming the first people to walk on the Moon as part of NASA's Apollo programme .

Why is space travel important?

Space exploration is the future. It satisfies the human urge to explore and to travel, and in the years and decades to come it could even provide our species with new places to call home – especially relevant now, as Earth becomes increasingly crowded .

Extending our reach into space is also necessary for the advancement of science. Space telescopes like the Hubble Space Telescope and probes to the distant worlds of the Solar System are continually updating, and occasionally revolutionising, our understanding of astronomy and physics.

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But there are also some very practical reasons, such as mining asteroids for materials that are extremely rare here on Earth.

One example is the huge reserve of the chemical isotope helium-3 thought to be locked away in the soil on the surface of the Moon . This isotope is a potential fuel for future nuclear fusion reactors – power stations that tap into the same source of energy as the Sun. Unlike other fusion fuels, helium-3 gives off no hard-to-contain and deadly neutron radiation.

However, for this to happen the first challenge to overcome is how to build a base on the Moon. In 2019, China's Chang’e 4 mission marked the beginning of a new space race to conquer the Moon, signalling their intent to build a permanent lunar base , while the NASA Artemis mission plans to build a space station, called Lunar Orbital Platform-Gateway , providing a platform to ferry astronauts to the Moon's surface.

Could humans travel into interstellar space and how would we get there?

It’s entirely feasible that human explorers will visit the furthest reaches of our Solar System. The stars, however, are another matter. Interstellar space is so vast that it takes light – the fastest thing we know of in the Universe – years, centuries and millennia to traverse it. Faster-than-light travel may be possible one day, but is unlikely to become a reality in our lifetimes.

It’s not impossible that humans might one day cross this cosmic gulf, though it won’t be easy. The combustion-powered rocket engines of today certainly aren’t up to the job – they just don’t use fuel efficiently enough. Instead, interstellar spacecraft may create a rocket-like propulsion jet using electric and magnetic fields. This so-called ‘ ion drive ’ technology has already been tested aboard uncrewed Solar System probes.

Another possibility is to push spacecraft off towards the stars using the light from a high-powered laser . A consortium of scientists calling themselves Breakthrough Starshot is already planning to send a flotilla of tiny robotic probes to our nearest star, Proxima Centauri, using just this method.

Though whether human astronauts could survive such punishing acceleration, or the decades-long journey through deep space, remains to be seen.

How do we benefit from space exploration?

Pushing forward the frontiers of science is the stated goal of many space missions . But even the development of space travel technology itself can lead to unintended yet beneficial ‘spin-off’ technologies with some very down-to-earth applications.

Notable spin-offs from the US space programme, NASA, include memory foam mattresses, artificial hearts, and the lubricant spray WD-40. Doubtless, there are many more to come.

Read more about space exploration:

• The next giant leaps: The UK missions getting us to the Moon
• Move over, Mars: why we should look further afield for future human colonies
• Everything you need to know about the Voyager mission
• 6 out-of-this-world experiments recreating space on Earth

Space exploration also instils a sense of wonder, it reminds us that there are issues beyond our humdrum planet and its petty squabbles, and without doubt it helps to inspire each new generation of young scientists. It’s also an insurance policy. We’re now all too aware that global calamities can and do happen – for instance, climate change and the giant asteroid that smashed into the Earth 65 million years ago, leading to the total extinction of the dinosaurs .

The lesson for the human species is that we keep all our eggs in one basket at our peril. On the other hand, a healthy space programme, and the means to travel to other worlds, gives us an out.

Is space travel dangerous?

In short, yes – very. Reaching orbit means accelerating up to around 28,000kph (17,000mph, or 22 times the speed of sound ). If anything goes wrong at that speed, it’s seldom good news.

Then there’s the growing cloud of space junk to contend with in Earth's orbit – defunct satellites, discarded rocket stages and other detritus – all moving just as fast. A five-gram bolt hitting at orbital speed packs as much energy as a 200kg weight dropped from the top of an 18-storey building.

And getting to space is just the start of the danger. The principal hazard once there is cancer-producing radiation – the typical dose from one day in space is equivalent to what you’d receive over an entire year back on Earth, thanks to the planet’s atmosphere and protective magnetic field.

Add to that the icy cold airless vacuum , the need to bring all your own food and water, plus the effects of long-duration weightlessness on bone density, the brain and muscular condition – including that of the heart – and it soon becomes clear that venturing into space really isn’t for the faint-hearted.

When will space travel be available to everyone?

It’s already happening – that is, assuming your pockets are deep enough. The first self-funded ‘space tourist’ was US businessman Dennis Tito, who in 2001 spent a week aboard the International Space Station (ISS) for the cool sum of $20m (£15m).

Virgin Galactic has long been promising to take customers on short sub-orbital hops into space – where passengers get to experience rocket propulsion and several minutes of weightlessness, before gliding back to a runway landing on Earth, all for $250k (£190k). In late July 2020, the company unveiled the finished cabin in its SpaceShipTwo vehicle, suggesting that commercial spaceflights may begin shortly.

Meanwhile, Elon Musk’s SpaceX , which in May 2020 became the first private company to launch a human crew to Earth orbit aboard the Crew Dragon , plans to offer stays on the ISS for $35k (£27k) per night. SpaceX is now prototyping its huge Starship vehicle , which is designed to take 100 passengers from Earth to as far afield as Mars for around $20k (£15k) per head. Musk stated in January that he hoped to be operating 1,000 Starships by 2050.

10 Short Lessons in Space Travel by Paul Parsons is out now (£9.99, Michael O'Mara)

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The History of Space Exploration

During the time that has passed since the launching of the first artificial satellite in 1957, astronauts have traveled to the moon, probes have explored the solar system, and instruments in space have discovered thousands of planets around other stars.

Earth Science, Astronomy, Social Studies, U.S. History, World History

Apollo 11 Astronauts on Moon

A less belligerent, but no less competitive, part of the Cold War was the space race. The Soviet Union bested its rival at nearly every turn, until the U.S. beat them to the finish line by landing astronauts on the moon.

NASA photograph

We human beings have been venturing into space since October 4, 1957, when the Union of Soviet Socialist Republics (U.S.S.R.) launched Sputnik, the first artificial satellite to orbit Earth. This happened during the period of political hostility between the Soviet Union and the United States known as the Cold War. For several years, the two superpowers had been competing to develop missiles, called intercontinental ballistic missiles (ICBMs), to carry nuclear weapons between continents. In the U.S.S.R., the rocket designer Sergei Korolev had developed the first ICBM, a rocket called the R7, which would begin the space race. This competition came to a head with the launch of Sputnik . Carried atop an R7 rocket, the Sputnik satellite was able to send out beeps from a radio transmitter. After reaching space, Sputnik orbited Earth once every 96 minutes. The radio beeps could be detected on the ground as the satellite passed overhead, so people all around the world knew that it was really in orbit. Realizing that the U.S.S.R. had capabilities that exceeded U.S. technologies that could endanger Americans, the United States grew worried. Then, a month later, on November 3, 1957, the Soviets achieved an even more impressive space venture. This was Sputnik II, a satellite that carried a living creature, a dog named Laika. Prior to the launch of Sputnik, the United States had been working on its own capability to launch a satellite. The United States made two failed attempts to launch a satellite into space before succeeding with a rocket that carried a satellite called Explorer on January 31, 1958. The team that achieved this first U.S. satellite launch consisted largely of German rocket engineers who had once developed ballistic missiles for Nazi Germany. Working for the U.S. Army at the Redstone Arsenal in Huntsville, Alabama, the German rocket engineers were led by Wernher von Braun and had developed the German V2 rocket into a more powerful rocket, called the Jupiter C, or Juno. Explorer carried several instruments into space for conducting science experiments. One instrument was a Geiger counter for detecting cosmic rays. This was for an experiment operated by researcher James Van Allen, which, together with measurements from later satellites, proved the existence of what are now called the Van Allen radiation belts around Earth. In 1958, space exploration activities in the United States were consolidated into a new government agency, the National Aeronautics and Space Administration (NASA). When it began operations in October of 1958, NASA absorbed what had been called the National Advisory Committee for Aeronautics (NACA), and several other research and military facilities, including the Army Ballistic Missile Agency (the Redstone Arsenal) in Huntsville. The first human in space was the Soviet cosmonaut Yuri Gagarin, who made one orbit around Earth on April 12, 1961, on a flight that lasted 108 minutes. A little more than three weeks later, NASA launched astronaut Alan Shepard into space, not on an orbital flight, but on a suborbital trajectory—a flight that goes into space but does not go all the way around Earth. Shepard’s suborbital flight lasted just over 15 minutes. Three weeks later, on May 25, President John F. Kennedy challenged the United States to an ambitious goal, declaring: “I believe that this nation should commit itself to achieving the goal, before the decade is out, of landing a man on the moon and returning him safely to Earth." In addition to launching the first artificial satellite, the first dog in space, and the first human in space, the Soviet Union achieved other space milestones ahead of the United States. These milestones included Luna 2, which became the first human-made object to hit the Moon in 1959. Soon after that, the U.S.S.R. launched Luna 3 . Less than four months after Gagarin’s flight in 1961, a second Soviet human mission orbited a cosmonaut around Earth for a full day. The U.S.S.R. also achieved the first spacewalk and launched the Vostok 6 mission, which made Valentina Tereshkova the first woman to travel to space. During the 1960s, NASA made progress toward President Kennedy’s goal of landing a human on the moon with a program called Project Gemini, in which astronauts tested technology needed for future flights to the moon, and tested their own ability to endure many days in spaceflight. Project Gemini was followed by Project Apollo, which took astronauts into orbit around the moon and to the lunar surface between 1968 and 1972. In 1969, on Apollo11, the United States sent the first astronauts to the Moon, and Neil Armstrong became the first human to set foot on its surface. During the landed missions, astronauts collected samples of rocks and lunar dust that scientists still study to learn about the moon. During the 1960s and 1970s, NASA also launched a series of space probes called Mariner, which studied Venus, Mars, and Mercury. Space stations marked the next phase of space exploration. The first space station in Earth orbit was the Soviet Salyut 1 station, which was launched in 1971. This was followed by NASA’s Skylab space station, the first orbital laboratory in which astronauts and scientists studied Earth and the effects of spaceflight on the human body. During the 1970s, NASA also carried out Project Viking in which two probes landed on Mars, took numerous photographs, examined the chemistry of the Martian surface environment, and tested the Martian dirt (called regolith ) for the presence of microorganisms . Since the Apollo lunar program ended in 1972, human space exploration has been limited to low-Earth orbit, where many countries participate and conduct research on the International Space Station. However, unpiloted probes have traveled throughout our solar system. In recent years, probes have made a range of discoveries, including that a moon of Jupiter, called Europa, and a moon of Saturn, called Enceladus, have oceans under their surface ice that scientists think may harbor life. Meanwhile, instruments in space, such as the Kepler Space Telescope , and instruments on the ground have discovered thousands of exoplanets , planets orbiting other stars. This era of exoplanet discovery began in 1995, and advanced technology now allows instruments in space to characterize the atmospheres of some of these exoplanets.

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History of Space Travel

Learn about the history of humans traveling into space.

The first earthling to orbit our planet was just two years old, plucked from the streets of Moscow barely more than a week before her historic launch. Her name was Laika. She was a terrier mutt and by all accounts a good dog. Her 1957 flight paved the way for space exploration back when scientists didn’t know if spaceflight was lethal for living things.

Humans are explorers. Since before the dawn of civilization, we’ve been lured over the horizon to find food or more space, to make a profit, or just to see what’s beyond those trees or mountains or oceans. Our ability to explore reached new heights—literally—in the last hundred years. Airplanes shortened distances, simplified travel, and showed us Earth from a new perspective. By the middle of the last century, we aimed even higher.

Our first steps into space began as a race between the United States and the former Soviet Union, rivals in a global struggle for power. Laika was followed into orbit four years later by the first human, Soviet Cosmonaut Yuri A. Gagarin. With Earth orbit achieved, we turned our sights on the moon. The United States landed two astronauts on its stark surface in 1969, and five more manned missions followed. The U.S.’s National Aeronautics and Space Administration (NASA) launched probes to study the solar system. Manned space stations began glittering in the sky. NASA developed reusable spacecraft—space shuttle orbiters—to ferry astronauts and satellites to orbit. Space-travel technology had advanced light-years in just three decades. Gagarin had to parachute from his spaceship after reentry from orbit. The space shuttle leaves orbit at 16,465 miles an hour (26,498 kilometers an hour) and glides to a stop on a runway without using an engine.

Space travel is nothing like in the movies. Getting from A to B requires complex calculations involving inertia and gravity—literally, rocket science—to "slingshot" from planet to planet (or moon) across the solar system. The Voyager mission of the 1970s took advantage of a rare alignment of Jupiter, Saturn, Uranus, and Neptune to shave off nearly 20 years of travel time. Space is also dangerous. More than 20 astronauts have died doing their job.

That hasn’t stopped people from signing up and blasting off. NASA’s shuttle program has ended, but private companies are readying their own space programs. A company called Planetary Resources plans to send robot astronauts to the Asteroid Belt to mine for precious metals. Another company named SpaceX is hoping to land civilian astronauts on Mars—the next human step into the solar system—in 20 years. NASA and other civilian companies are planning their own Mars missions. Maybe you’ll be a member of one? Don’t forget to bring your dog.

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First to visit all four giant planets

Voyager 2 is the only spacecraft to visit Uranus and Neptune. The probe is now in interstellar space, the region outside the heliopause, or the bubble of energetic particles and magnetic fields from the Sun.

Mission Type

What is Voyager 2?

NASA's Voyager 2 is the second spacecraft to enter interstellar space. On Dec. 10, 2018, the spacecraft joined its twin – Voyager 1 – as the only human-made objects to enter the space between the stars.

• Voyager 2 is the only spacecraft to study all four of the solar system's giant planets at close range.
• Voyager 2 discovered a 14th moon at Jupiter.
• Voyager 2 was the first human-made object to fly past Uranus.
• At Uranus, Voyager 2 discovered 10 new moons and two new rings.
• Voyager 2 was the first human-made object to fly by Neptune.
• At Neptune, Voyager 2 discovered five moons, four rings, and a "Great Dark Spot."

In Depth: Voyager 2

The two-spacecraft Voyager missions were designed to replace original plans for a “Grand Tour” of the planets that would have used four highly complex spacecraft to explore the five outer planets during the late 1970s.

NASA canceled the plan in January 1972 largely due to anticipated costs (projected at $1 billion) and instead proposed to launch only two spacecraft in 1977 to Jupiter and Saturn. The two spacecraft were designed to explore the two gas giants in more detail than the two Pioneers (Pioneers 10 and 11) that preceded them.

In 1974, mission planners proposed a mission in which, if the first Voyager was successful, the second one could be redirected to Uranus and then Neptune using gravity assist maneuvers.

Each of the two spacecraft was equipped with a slow-scan color TV camera to take images of the planets and their moons and each also carried an extensive suite of instruments to record magnetic, atmospheric, lunar, and other data about the planetary systems.

The design of the two spacecraft was based on the older Mariners, and they were known as Mariner 11 and Mariner 12 until March 7, 1977, when NASA Administrator James C. Fletcher (1919-1991) announced that they would be renamed Voyager.

Power was provided by three plutonium oxide radioisotope thermoelectric generators (RTGs) mounted at the end of a boom.

Voyager 2 at Jupiter

Voyager 2 began transmitting images of Jupiter April 24, 1979, for time-lapse movies of atmospheric circulation. Unlike Voyager 1, Voyager 2 made close passes to the Jovian moons on its way into the system, with scientists especially interested in more information from Europa and Io (which necessitated a 10 hour-long “volcano watch”).

During its encounter, it relayed back spectacular photos of the entire Jovian system, including its moons Callisto, Ganymede, Europa (at a range of about 127,830 miles or 205,720 kilometers, much closer than Voyager 1), Io, and Amalthea, all of which had already been surveyed by Voyager 1.

Voyager 2’s closest encounter to Jupiter was at 22:29 UT July 9, 1979, at a range of about 400,785 miles (645,000 kilometers). It transmitted new data on the planet’s clouds, its newly discovered four moons, and ring system as well as 17,000 new pictures.

When the earlier Pioneers flew by Jupiter, they detected few atmospheric changes from one encounter to the second, but Voyager 2 detected many significant changes, including a drift in the Great Red Spot as well as changes in its shape and color.

With the combined cameras of the two Voyagers, at least 80% of the surfaces of Ganymede and Callisto were mapped out to a resolution of about 3 miles (5 kilometers).

Voyager 2 at Saturn

Following a course correction two hours after its closest approach to Jupiter, Voyager 2 sped to Saturn, its trajectory determined to a large degree by a decision made in January 1981, to try to send the spacecraft to Uranus and Neptune later in the decade.

Its encounter with the sixth planet began Aug. 22, 1981, two years after leaving the Jovian system, with imaging of the moon Iapetus. Once again, Voyager 2 repeated the photographic mission of its predecessor, although it actually flew about 14,290 miles (23,000 kilometers) closer to Saturn. The closest encounter to Saturn was at 01:21 UT Aug. 26, 1981, at a range of about 63,000 miles (101,000 kilometers).

The spacecraft provided more detailed images of the ring “spokes” and kinks, and also the F-ring and its shepherding moons, all found by Voyager 1. Voyager 2’s data suggested that Saturn’s A-ring was perhaps only about 980 feet (300 meters) thick.

As it flew behind and up past Saturn, the probe passed through the plane of Saturn’s rings at a speed of 8 miles per second (13 kilometers per second). For several minutes during this phase, the spacecraft was hit by thousands of micron-sized dust grains that created “puff” plasma as they were vaporized. Because the vehicle’s attitude was repeatedly shifted by the particles, attitude control jets automatically fired many times to stabilize the vehicle.

During the encounter, Voyager 2 also photographed the Saturn moons Hyperion (the “hamburger moon”), Enceladus, Tethys, and Phoebe as well as the more recently discovered Helene, Telesto and Calypso.

Voyager 2 at Uranus

Although Voyager 2 had fulfilled its primary mission goals with the two planetary encounters, mission planners directed the veteran spacecraft to Uranus—a journey that would take about 4.5 years.

In fact, its encounter with Jupiter was optimized in part to ensure that future planetary flybys would be possible.

The Uranus encounter’s geometry was also defined by the possibility of a future encounter with Neptune: Voyager 2 had only 5.5 hours of close study during its flyby.

Voyager 2 was the first human-made object to fly past the planet Uranus.

Long-range observations of the planet began Nov. 4, 1985, when signals took approximately 2.5 hours to reach Earth. Light conditions were 400 times less than terrestrial conditions. Closest approach to Uranus took place at 17:59 UT Jan. 24, 1986, at a range of about 50,640 miles (81,500 kilometers).

During its flyby, Voyager 2 discovered 10 new moons (given such names as Puck, Portia, Juliet, Cressida, Rosalind, Belinda, Desdemona, Cordelia, Ophelia, and Bianca -- obvious allusions to Shakespeare), two new rings in addition to the “older” nine rings, and a magnetic field tilted at 55 degrees off-axis and off-center.

The spacecraft found wind speeds in Uranus’ atmosphere as high as 450 miles per hour (724 kilometers per hour) and found evidence of a boiling ocean of water some 497 miles (800 kilometers) below the top cloud surface. Its rings were found to be extremely variable in thickness and opacity.

Voyager 2 also returned spectacular photos of Miranda, Oberon, Ariel, Umbriel, and Titania, five of Uranus’ larger moons. In flying by Miranda at a range of only 17,560 miles (28,260 kilometers), the spacecraft came closest to any object so far in its nearly decade-long travels. Images of the moon showed a strange object whose surface was a mishmash of peculiar features that seemed to have no rhyme or reason. Uranus itself appeared generally featureless.

The spectacular news of the Uranus encounter was interrupted the same week by the tragic Challenger accident that killed seven astronauts during their space shuttle launch Jan. 28, 1986.

Voyager 2 at Neptune

Following the Uranus encounter, the spacecraft performed a single midcourse correction Feb. 14, 1986—the largest ever made by Voyager 2—to set it on a precise course to Neptune.

Voyager 2’s encounter with Neptune capped a 4.3 billion-mile (7 billion-kilometer) journey when, on Aug. 25, 1989, at 03:56 UT, it flew about 2,980 miles (4,800 kilometers) over the cloud tops of the giant planet, the closest of its four flybys. It was the first human-made object to fly by the planet. Its 10 instruments were still in working order at the time.

During the encounter, the spacecraft discovered six new moons (Proteus, Larissa, Despina, Galatea, Thalassa, and Naiad) and four new rings.

The planet itself was found to be more active than previously believed, with 680-mile (1,100-kilometer) per hour winds. Hydrogen was found to be the most common atmospheric element, although the abundant methane gave the planet its blue appearance.

Images revealed details of the three major features in the planetary clouds—the Lesser Dark Spot, the Great Dark Spot, and Scooter.

Voyager photographed two-thirds of Neptune’s largest moon Triton, revealing the coldest known planetary body in the solar system and a nitrogen ice “volcano” on its surface. Spectacular images of its southern hemisphere showed a strange, pitted cantaloupe-type terrain.

The flyby of Neptune concluded Voyager 2’s planetary encounters, which spanned an amazing 12 years in deep space, virtually accomplishing the originally planned “Grand Tour” of the solar system, at least in terms of targets reached if not in science accomplished.

Voyager 2's Interstellar Mission

Once past the Neptune system, Voyager 2 followed a course below the ecliptic plane and out of the solar system. Approximately 35 million miles (56 million kilometers) past the encounter, Voyager 2’s instruments were put in low power mode to conserve energy.

After the Neptune encounter, NASA formally renamed the entire project the Voyager Interstellar Mission (VIM).

Of the four spacecraft sent out to beyond the environs of the solar system in the 1970s, three of them -- Voyagers 1 and 2 and Pioneer 11 -- were all heading in the direction of the solar apex, i.e., the apparent direction of the Sun’s travel in the Milky Way galaxy, and thus would be expected to reach the heliopause earlier than Pioneer 10 which was headed in the direction of the heliospheric tail.

In November 1998, 21 years after launch, nonessential instruments were permanently turned off, leaving seven instruments still operating.

At 9.6 miles per second (15.4 kilometers per second) relative to the Sun, it will take about 19,390 years for Voyager 2 to traverse a single light year.

Asif Siddiqi

Beyond Earth: A Chronicle of Deep Space Exploration

Through the turn of the century, NASA's Jet Propulsion Laboratory (JPL) continued to receive ultraviolet and particle fields data. For example, on Jan. 12, 2001, an immense shock wave that had blasted out of the outer heliosphere on July 14, 2000, finally reached Voyager 2. During its six-month journey, the shock wave had plowed through the solar wind, sweeping up and accelerating charged particles. The spacecraft provided important information on high-energy shock-energized ions.

On Aug. 30, 2007, Voyager 2 passed the termination shock and then entered the heliosheath. By Nov. 5, 2017, the spacecraft was 116.167 AU (about 10.8 billion miles or about 17.378 billion kilometers) from Earth, moving at a velocity of 9.6 miles per second (15.4 kilometers per second) relative to the Sun, heading in the direction of the constellation Telescopium. At this velocity, it would take about 19,390 years to traverse a single light-year.

On July 8, 2019, Voyager 2 successfully fired up its trajectory correction maneuver thrusters and will be using them to control the pointing of the spacecraft for the foreseeable future. Voyager 2 last used those thrusters during its encounter with Neptune in 1989.

The spacecraft's aging attitude control thrusters have been experiencing degradation that required them to fire an increasing and untenable number of pulses to keep the spacecraft's antenna pointed at Earth. Voyager 1 had switched to its trajectory correction maneuver thrusters for the same reason in January 2018.

To ensure that both vintage robots continue to return the best scientific data possible from the frontiers of space, mission engineers are implementing a new plan to manage them. The plan involves making difficult choices, particularly about instruments and thrusters.

National Space Science Data Center: Voyager 2

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Space in our time: a brief history of space travel

October 1957: USSR launches Sputnik 1, the first man-made object to orbit the earth. November 1957 A dog called Laika orbits the earth for seven days in Sputnik 2.

January 1958: Explorer 1, the first US satellite, lifts off from Cape Canaveral and discovers the earth's radiation belt.

October 1958: The National Aeronautics and Space Administration (Nasa) is set up in the US. The US probe Pioneer 1 reaches a height of 70,700 miles.

January 1959: The USSR launches Luna 1, the first man-made satellite to orbit the sun.

March 1959: The US Pioneer 4 passes within 37,000 miles of the moon.

September 1959: Luna 2, carrying a copy of the Soviet coat of arms, becomes the first man-made object to hit the moon.

October 1959: Luna 3 photographs some 70% of the far side of the moon.

April 1960: The US launches Tiros 1, the first successful weather satellite, and Discoverer XIV, the first camera-equipped spy satellite.

April 1961: The USSR launches Vostok 1. It carries Yuri Gagarin, who becomes the first man in space when he orbits the earth once.

May 1961: Mercury Freedom 7 carries Alan Shepard into a sub-orbital space, making him the first American in space.

August 1961: Gherman Titov, aboard Vostok 2, undertakes the first day-long space flight.

February 1962: John Glenn becomes the first American to orbit the earth.

July 1962: US satellite Telstar 1 beams the first live transatlantic telecast.

December 1962: US Mariner 2, the first successful planetary spacecraft, flies past Venus.

June 1963: Soviet cosmonaut Valentina Tereshkova becomes the first woman in space. She orbits the earth 48 times.

July 1964: US Ranger 7 relays the first close-up pictures of the moon.

March 1965: Soviet cosmonaut Aleksey Leonov undertakes the first space walk. It lasts 12 minutes.

June 1965: Edward White II makes the first US space walk - duration 22 minutes.

July 1965: US Mariner 4 returns the first close-range images from Mars.

November 1965: Launch of Soviet Venus 3. Four months later, it becomes the first craft to hit Venus.

December 1965: Frank Borman and James Lovell make 206 orbits around the earth, proving that a trip to the moon is possible. American astronauts make the first space rendezvous with another craft.

February 1966: Soviet Luna 9 is the first spacecraft to soft-land on the moon.

March 1966: Soviet Luna 10 is the first spacecraft to orbit the moon.

June 1966: Surveyor 1 is the first US spacecraft to soft-land on the moon.

August 1966: US Lunar Orbiter 1 enters moon orbit, and takes the first picture of the earth from such a distance.

April 1967: Vladimir Komarov is the first person to die in space.

September 1968: Launch of Soviet Zond 5, the first spacecraft to orbit the moon and return.

October 1968: Apollo 7 is the first manned Apollo mission. It orbits the earth once.

December 1968: Apollo 8, carrying Frank Borman, James Lovell and William Anders, is the first manned spacecraft to orbit the moon.

January 1969: Soyuz 4 and 5 perform the first Soviet spaceship docking, transferring cosmonauts between vehicles.

July 1969: Neil Armstrong and Edwin Aldrin make the first manned soft-landing on the moon, and the first moonwalk, using Apollo 11. Mariner 6 returns to earth high-resolution images of the Martian surface.

April 1970: Apollo 13 is launched, but suffers an explosion. Its moon landing is aborted, and the crew return safely.

September 1970: Soviet Luna 16 is launched, conducting the first successful return of lunar soil samples by an automatic spacecraft.

November 1970: Luna 17 lands on the moon with the first automatic robot, Lunokhod 1, driven from controls on earth.

April 1971: The Salyut 1 space station is launched by the USSR.

June 1971: Soyuz 11 carries the first crew to occupy an orbital station. On June 29, they die on re-entry.

July 1971: David Scott and James Irwin drive the first moon rover.

March 1972: The US fires Pioneer 10 towards Jupiter with the intention of familiarising alien life with humans.

July 1972: The first probable black hole is discovered.

May 1973: Launch of US Skylab Workshop.

June 1974: USSR launches Salyut 3, its first military space station.

December 1974: USSR launches Salyut 4, its first civilian space station.

July 1975: The American Apollo 18 and Soviet Soyuz 19 dock - it is the first international spacecraft rendezvous.

September 1976: Viking 2 lands on Mars and finds ice.

December 1978: Two Pioneer spacecraft reach Venus.

September 1979: Pioneer 11 flies within 13,000 miles of Saturn.

March 1982: The USSR obtains the first Venusian soil analysis.

April 1982: The Soviet Salyut 7 space station is launched.

May 1982: Soviet cosmonauts begin a 211-day occupation of a space station, a new record.

August 1982: Voyager 2 completes its fly-by of Saturn.

November 1982: The space shuttle Columbia deploys two satellites, its first operational mission.

April 1983: The space shuttle Challenger lifts off for its first mission, which marks the first American space walk in nine years.

June 1983: Sally K Ride becomes the first American woman in space.

November 1983: The space shuttle Columbia carries the European Space Agency (ESA) Spacelab-1 into orbit. Its crew includes the German Ulf Merbold, the first ESA member in space.

January-November 1983: The Infrared Astronomical Satellite finds new comets, asteroids, galaxies and possible planets.

February 1984: Bruce McCandless takes the first untethered space walk.

December 1984: Soviet/International Vega 1 and 2 are launched, dropping probes into Venus's atmosphere before continuing to Halley's Comet.

January 1985: The Sakigake probe is launched by Japan's Institute of Space and Aeronautical Science, and makes a rendezvous with Halley's Comet.

April 1985: The space shuttle Challenger carries the ESA Spacelab-3 into orbit.

July 1985: The ESA launches the Giotto spacecraft from an Ariane rocket.

October 1985: Spacelab D1 becomes the first joint German/ESA mission.

January 1986: Voyager 2 flies past Uranus. The space shuttle Challenger explodes shortly after liftoff.

February 1986: The core unit of the Soviet space station Mir is launched.

May 1989: The space shuttle Atlantis is launched, deploying the spacecraft Magellan, bound for Venus.

October 1989: The US Galileo spacecraft sets off for Venus and Jupiter.

April 1990: The space shuttle Discovery deploys the Edwin P Hubble Space Telescope.

August 1990: Magellan arrives at Venus.

February 1992: The US spacecraft Ulysses flies around Jupiter on its way to the sun.

February 1994: A Russian cosmonaut flies on a US space shuttle for the first time.

February 1995: The US space shuttle Discovery prepares to dock with the Russian space station Mir. It is the first shuttle mission to be flown by a female pilot.

March 1995: Cosmonaut Valery Polyakov returns to earth after a 438-day mission aboard Mir, setting a new space endurance record.

December 1995: Galileo reaches Jupiter.

March 1996: Shannon Lucid becomes the first female astronaut to crew a space station.

November 1996: A Russian spacecraft bound for Mars ignites prematurely and crashes into the ocean off Chile carrying 270g plutonium.

July 1997: Pathfinder lands on Mars, the first landing on the red planet since the Viking missions in 1976.

January 1998: Launch of joint ESA/Nasa Cassini mission to explore Saturnian system. Lunar Prospector arrives on moon in search of information that could one day help scientists plan a lunar base.

March 1998: Lunar Prospector discovers ice on the moon.

July 1998: Japan launches a probe to reach Mars in 2003.

October 1998: John Glenn, now a 77-year-old senator, returns to space aboard the space shuttle Discovery.

November 1998: Assembly work begins on the International Space Station.

May 1999: A shuttle docks with the International Space Station for the first time.

July 1999: Colonel Eileen Collins becomes the first woman to command a shuttle mission.

July 2000: Russia launches a living quarters module, its contribution to the International Space Station.

October 2000: A 10-day mission to the International Space Station marks the 100th shuttle flight.

November 2000: The first permanent crew sets up home aboard the International Space Station.

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The latest on the massive solar storm

By Angela Fritz, Elise Hammond and Chris Lau, CNN

Incredible lighthouse picture from Maine

From CNN's Chris Lau

Among a flurry of surreal images capturing the dazzling auroras is one taken by Benjamin Williamson of a lighthouse in Portland, Maine.

"It's one of the most incredible things I've ever seen, the awe and wonder," Williamson told CNN.

He said he used a long-exposure technique to snap the shot, but did not edit it.

Watch the full interview with Williamson here .

Things could be about to ramp up

If you still haven't seen the aurora, hold on for another 30 minutes to an hour, according to CNN meteorologist Chad Myers.

The next wave of coronal mass ejections, or CMEs, which cause the aurora, is about to arrive, he said.

"Just wait a minute because things are going to start to ramp up here," he said, adding that the increase could arrive "anytime now." "When it comes, get outside, get ready, put your coat on."

For those who are too busy to witness the phenomenon tonight, Myers said the aurora is expected to last three nights.

Why does the aurora last for a weekend?

By CNN's Chris Lau

Generally, it takes just eight minutes for light to travel 93 million miles to the Earth from the sun, but astrophysicist Janna Levin said the energized particles causing the current wave of aurora travel a lot slower, causing the phenomenon to last for the weekend.

"Some of these mass ejections are trillions of kilograms," she said. "They're slower. So they're taking longer, but still hours, maybe tens of hours."

Here's how the solar storm looks in the South and on the East Coast

The aurora was visible across the East Coast and in the South Friday.

Here's how it looked in Chester, South Carolina.

Down in Florida, waves of color swam through the sky.

Up north in New Jersey, a purple-ish haze could be seen in the sky.

Will solar storms get more intense and risky in the future?

The answer is probably not in the short term, according to astrophysicist Hakeem Oluseyi.

He said scientists study what is constantly happening on the surface of the sun and have found a pattern.

“Geological data shows us that in the past the sun was way more active than it is today. It has cycles where it goes very quiet ... and you have events that show that the solar activity was much, much greater,” he told CNN. “So there's no evidence that we're going to see those big maxima this cycle." 

But the astrophysicist also spoke of a caveat - the limitations of modern science.

“Even though it's predictable in the short term, we still don't quite understand what creates the magnetic fields in the sun,” he said, adding: “That's why NASA has so many satellites looking at the sun.”

In Pictures: Auroras light the sky during rare solar storm

From CNN Digital's Photo Team

A series of solar flares and coronal mass ejections from the sun are creating dazzling auroras across the globe .

The rare solar storm may also disrupt communications. The last time a solar storm of this magnitude reached Earth was in October 2003, according to the National Oceanic and Atmospheric Administration's Space Weather Prediction Center.

See more photos of the aurora from tonight.

Behind dazzling aurora could lie “real danger,” Bill Nye the Science Guy says

The massive solar storm could present “a real danger,” especially with the modern world relying so much on electricity, according to Bill Nye the Science Guy , a science educator and engineer.

Scientists are warning an increase in solar flares and coronal mass ejections from the sun have the potential to disrupt communication on Earth into the weekend. Solar flares can affect communications and GPS almost immediately because they disrupt Earth’s ionosphere, or part of the upper atmosphere. Energetic particles released by the sun can also disrupt electronics on spacecraft and affect astronauts without proper protection within 20 minutes to several hours.

In comparison to tonight's event, Nye drew comparisons with another incident in 1859, known as the Carrington Event, when telegraph communications were severely affected.

“The other thing, everybody, that is a real danger to our technological society, different from 1859, is how much we depend on electricity and our electronics and so on,” Nye said. "None of us really in the developed world could go very long without electricity."

He noted that there are systems in place to minimize the impact, but “stuff might go wrong,” stressing that not all transformers are equipped to withstand such a solar event.

“It depends on the strength of the event and it depends on how much of our infrastructures are prepared for this the sort of thing,” he said.

Bill Nye breaks down significance of the solar storm | CNN

This post has been updated with more details on solar flares' impact on electronics.

Here's where clouds will block the view of the northern lights in the US

From CNN's Angela Fritz

After an incredibly stormy week, most of the Lower 48 has clear skies to see the northern lights. But there are some areas where clouds and rainy weather are spoiling the view.

A deck of clouds is blocking the sky in the Northeast, from parts of Virginia into Maine, as an area of low pressure spins off the East Coast.

In the Midwest, the aurora will be hard to see through thick clouds in parts of Wisconsin, Michigan — including the Upper Peninsula — and Illinois.

A stripe of clouds is tracking across Texas, including Dallas-Forth Worth, and into Louisiana.

And in the Southwest, patchy clouds across the the Four Corners region could make the northern lights difficult to spot.

Aurora seen at least as far south as Georgia

Barely visible to the naked eye, the aurora can be seen in Atlanta in the 10 p.m. ET hour. 

It is easier to see through photographs using a long exposure. The photos below, taken by CNN's Eric Zerkel and Emily Smith, used 3- and 10-second exposures.

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