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Interstellar travel: From science fiction to reality

Humans may one day travel beyond the solar system on board rockets powered by nuclear fusion.

An artist's impression of the Voyager 1 spacecraft entering interstellar space. Photo: Nasa

Only two probes have reached interstellar space – the region beyond the solar system – since the start of human space exploration .

It took more than three decades for the first spacecraft, Voyager 1 , to cross the heliopause, a boundary scientists believe is where interstellar space begins, after its launch in 1977.

It was an incredible achievement with invaluable data sent back through a medium not influenced by the Sun.

But with its power supply weakening it is almost impossible Voyager 1 will reach our nearest star, Proxima Centauri, which is 4.2 light years away and would take the probe almost 73,000 years.

Les Johnson, a Nasa scientist and author of several scientific and science fiction books, told The National reaching another star could take 50 to 100 years.

“It is possible we might have the technology to send our first robotic probe to another star within the next 50 to 100 years,” said Mr Johnson, who managed the Interstellar Propulsion Research Project at the US space agency.

“Based on the rate of technology growth, after looking at all the propulsion systems that are based on known physics, I believe these first probes will be propelled to the stars using laser light reflecting from a sail, similar to today’s solar sails but driven by intense laser light instead of sunlight.”

Human travel to interstellar space

It could take significantly longer for a crewed mission to travel to another star, as laser light sails would only work for smaller spacecraft.

Nuclear fusion propulsion, a way of powering a spacecraft using high-energy particles created by fusion reactions, is needed to make human missions to interstellar space possible.

“As for humans, that’s a lot more complicated because it takes a lot of mass to keep a group of humans alive for a decade- to centuries-long space journey and that means a massive ship,” Mr Johnson said.

“For a human crewed ship, we will need fusion propulsion at a minimum and antimatter as the ideal.

“While we know these are physically possible, the technology level needed for interstellar travel seems very far away – perhaps 100 to 200 years in the future.”

While scientists dream of antimatter propulsion, which could enable space travel at 70 per cent of the speed of light, nuclear fusion propulsion appears much closer to reality.

The technology could also help reduce the time it takes to reach Mars, the planet to which most space agencies are trying to send their astronauts.

Laura Forczyk, an author and the founder of space consulting firm Astralytical, said nuclear fusion propulsion has the potential to revolutionise space flight.

"We will not be able to achieve interstellar travel until we engineer a faster and more efficient means of accelerating," said Ms Forczyk.

"We also need to develop long-term, self-sustained robust ecosystems for long-duration voyages and a better means of radiation shielding. We are at least a century away from these advances."

While developing nuclear fusion technology is not easy, with the required temperature to achieve it 10 times hotter than the Sun, a few companies have been trying for many years.

California-based start-up Helicity Space recently received $5 million in seed funding to accelerate its fusion propulsion technology projects.

UK-based start-up Pulsar Fusion is also attempting to develop the technology and has started construction on a large nuclear fusion chamber in England.

When the engine is fired, it would, at least temporarily, be the hottest place in the solar system.

China is also trying to advance the development of nuclear fusion, with reports of a new state-owned company that would help accelerate the production of an "artificial Sun".

Is there an Earth-like planet beyond the solar system?

One of the reasons scientists want to explore interstellar space is to learn more about the universe and possibilities of life beyond Earth.

Nasa has been studying exoplanets, or planets outside of the solar system, for decades by using telescopes.

Mr Johnson said he "doubts we will find Earth 2.0 anywhere close" and that discovering another home-like planet was not thought to be a near-term possibility.

"Over time, we might be able to modify another planet to make it habitable but that will likely take additional centuries or millennia," he said.

"That doesn’t mean we shouldn’t go. The job of science is to learn more about the universe in which we live.

"Studying planets around other stars will help us better understand our own solar system and expand our knowledge of this big universe. That alone, in my opinion, makes the journey one we should make."

Interplanetary Exploration

Exploring the Cosmos

Some of NASA's most exciting and productive missions have been conducted by robotic spacecraft that are able to venture much farther into the cosmos than humans dare. These missions explore the planets, comets, and other objects of our solar system as well as the characteristics of the interplanetary medium that lies between them.

There have been many such missions, but several stand out.

Every day, Voyager 1 extends our reach deeper into space than any other human-made object. The craft launched three decades ago and is now more than a hundred times farther from the sun than our own Earth—over 9 billion miles (15 billion kilometers).

Voyager 1 is at the very fringe of our solar system. It is traveling 1 million miles (1.6 million kilometers) a day and, in the next decade, may pass beyond the frontier of the sun's heliosphere and become the first human-made object to reach interstellar space.

Launched in 1977, Voyager 1 and 2 have studied the planets Jupiter, Uranus, Saturn, and Neptune, explored their moons, examined their rings, and revealed much about interplanetary elements such as solar wind.

Now, from deep space, the two craft continue to return data. Scientists expect both Voyagers to function until sometime around the year 2020—an incredible accomplishment for a mission originally designed to run just four years.

Another long-lived spacecraft, Pioneer 10, launched in March 1972 and later that year became the first craft to fly through the asteroid belt, a swath of rocky debris between Mars and Jupiter. Pioneer 10 reached Jupiter in 1973 and captured close-up images of the planet, as well as valuable data on its radiation and magnetic fields.

At the time of its last transmission on January 22, 2003, Pioneer 10 was 82 times farther from the sun than Earth—so far that even a signal traveling at the speed of light took more than 11 hours to reach Earth.

Cassini-Huygens

The Cassini-Huygens mission is an ongoing international effort to explore Saturn and its largest moon, Titan. The mission combines the resources of NASA, the European Space Agency, the Italian Space Agency, and other international experts.

Scientists hope that Titan, as well as Saturn and its rings, may help them understand more about the birth and evolution of our entire solar system.

Titan is one of the solar system's most intriguing destinations. The moon has an Earthlike atmosphere rich in organics and, as revealed by Cassini, it may have oceans or lakes of liquid ethane or methane.

The mission, which was launched in 1997, entered Jupiter's orbit and used the massive planet's gravity to slingshot it faster on its route to Saturn. The spacecraft reached Saturn in 2004 and began orbiting the giant planet. Huygens, the detachable probe, landed on the surface of Titan early in 2005 and recorded data on that moon's clouds and atmosphere before landing and beginning surface study.

Comet Studies

In recent years, interplanetary missions have also targeted comets. Many scientists believe that the material that makes up comets is relatively unchanged from the time during which they were formed, billions of years ago when the solar system was young. Because of this ancient nature, comets could provide valuable clues about the origins of planets.

NASA's Stardust mission was the first to visit a comet and return to Earth with samples. In 2004 the spacecraft flew by the comet Wild 2 at a distance of only about 149 miles (240 kilometers), trapping tiny particles from the comet as well as interstellar dust. Though the recovered remnants are small, they could have enormous importance for theories of the solar system's creation.

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From solar sails to hyperspace: Here’s the future of interstellar travel

Will it ever be possible to zip around the cosmos like Baby Yoda and co in The Mandalorian ? A physicist explains.

Stephen Kelly

Hyperspace travel – the ability for spaceships to travel as fast as the speed of light – is an integral part of the Star Wars universe.

The new series of The Mandalorian , for instance, would be quite a different show if Mando and Grogu had to wait 6,000 years to fly from one planet to the next.

But it does raise the question of just how feasible such technology is. Will we ever attain the ability to travel vast distances across space without having to burn through generations of astronauts? Or are we just marooned in our corner of the Galaxy?

To answer that, Prof Patrick Johnson , author of The Physics Of Star Wars , needs to be clear on what, exactly, hyperspace travel is.

“If we’re talking about the idea that spaceships in Star Wars accelerate forward as fast, or faster than, the speed of light, then that is not plausible,” he says.

“The speed of light is the speed limit of the Universe. Once you travel faster than light, cause and effect begin to break down. You could feasibly view an event happening five light-years away, travel faster than the speed of light towards it and get there before it happens. It’s basically time travel.”

A more realistic option, says Johnson, is that instead of ships in Star Wars accelerating at the speed of light, hyperdrive technology enables them to create a wormhole in order to travel from one point in space to another.

“It would be like folding a piece of paper and punching a hole through it so an ant can get to the other side,” he says.

It would also explain why, in certain hyperspace sequences in Star Wars , the ships look like they’re travelling through a blue tunnel. (Although, of course, there are also other scenes, such as Vice-Admiral Holdo flying a ship at light speed through another ship in The Last Jedi , that lend strength to the accelerating theory).

The problem with creating a wormhole, says Johnson, is that no one knows how to do it; it’s more theoretical than practical. “It would perhaps be easier to find a pre-existing wormhole and just hope it leads to somewhere you want to go,” he says.

“As for creating one, that would take decades’ worth of human energy. And that’s before we figure out how to target a particular location.”

Johnson also insists that any wormhole created would have to be far away from Earth.

“Going back to the paper analogy, it’s not going to end well for the ant if it happens to be in the spot where the pencil bursts through. You would need an empty, unoccupied part of space, along with incredibly complex calculations and some sort of up-to-date star map, to ensure that the planet you’re going to is in the right place.”

At this stage, both options seem as unlikely as each other, which means that we are stuck in our Solar System for the foreseeable future.

But Johnson lives in hope that, even if we can’t accelerate at light speed, we can develop ways to travel long distances across the Galaxy.

“Without hyperdrives, I’d say our best bet for getting far, far away in a reasonable amount of time is solar sail technology,” he says. “These would operate like wind sails, but instead use the light from a star to push the ship forward and essentially give it an unlimited supply of fuel. The acceleration would be small at first, but after 10 years you could get up to around 20 per cent of the speed of light, which is very good.”

Promising – but we wouldn’t book that holiday to Tatooine just yet.

About our expert

Patrick Johnson is an associate teaching professor at Georgetown University’s department of physics, and author of The Physics Of Star Wars . Earning his PhD at Washington University in St Louis, Johnson’s work on quantum mechanics has been published in Physical Review journal.

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Universe Today

Space and astronomy news

Pros and Cons of Various Methods of Interstellar Travel

It’s a staple of science fiction, and something many people have fantasized about at one time or another: the idea of sending out spaceships with colonists and transplanting the seed of humanity among the stars. Between discovering new worlds, becoming an interstellar species, and maybe even finding extra-terrestrial civilizations, the dream of  spreading beyond the Solar System is one that can’t become reality soon enough!

For decades, scientists have contemplated how humanity might one-day reach achieve this lofty goal. And the range of concepts they have come up with present a whole lot of pros and cons. These pros and cons were raised in a recent study by Martin Braddock, a member of the Mansfield and Sutton Astronomical Society , a Fellow of the Royal Society of Biology , and a Fellow of the Royal Astronomical Society .

The study, titled “ Concepts for Deep Space Travel: From Warp Drives and Hibernation to World Ships and Cryogenics “, recently appeared in the scientific journal Current Trends in Biomedical Engineering and Biosciences (a Juniper Journals publication). As Braddock indicates in his study, the question of how human beings could explore neighboring star systems has become more relevant in recent years thanks to exoplanet discoveries.

As we reviewed in a previous article, “ How Long Would it Take to Travel to the Nearest Star? “, there are numerous proposed and theoretical ways to travel between our Solar System and other stars in the galaxy. However, beyond the technology involved, and the time it would take, there are also the biological and psychological implications for human crews that would need to be taken into account beforehand.

And thanks to the way public interest in space exploration has become renewed in recent years, cost-benefit analyses of all the possible methods is becoming increasingly necessary. As Dr. Braddock told Universe Today via email:

“Interstellar travel has become more relevant because of the concerted effort to find ways across all of the space agencies to maintain human health in ‘short’ (2-3 yr) space travel. With Mars missions reasonably in sight, Stephen Hawking’s death highlighting one his many beliefs that we should colonize deep space and Elon Musk’s determination to minimize waste on space travel, together with reborn visions of ‘bolt-on’ accessories to the ISS (the Bigelow expandable module ) conjures some imaginative concepts.”

All told, Dr. Braddock considers five principle means for mounting crewed missions to other star systems in his study. These include super-luminal (aka/ FTL) travel, hibernation or stasis regimes, negligible senescence (aka. anti-aging) engineering, world ships capable of supporting multiple generations of travellers (aka. generation ships), and cyogenic freezing technologies.

For FTL travel, the advantages are obvious, and while it remains entirely theoretical at this point, there are concepts being investigated today. A notable FTL concept – known as the Alcubierre Warp Drive – is currently being researched by multiple organizations, which includes the Tau Zero Foundation and the Advanced Propulsion Physics Laboratory: Eagleworks (APPL:E) at NASA’s Johnson Space Center.

To break it down succinctly, this method of space travel involves stretching the fabric of space-time in a wave which would (in theory) cause the space ahead of a ship to contract and the space behind it to expand. The ship would then ride this region, known as a “warp bubble”, through space. Since the ship is not moving within the bubble, but is being carried along as the region itself moves, conventional relativistic effects such as time dilation would not apply.

As Dr. Brannock indicates, the advantages of such a propulsion system include being able to achieve “apparent” FTL travel without violating the laws of Relativity. In addition, a ship traveling in a warp bubble would not have to worry about colliding with space debris, and there would be no upper limit to the maximum speed attainable. Unfortunately, the downsides of this method of travel are equally obvious.

These include the fact that there is currently no known methods for creating a warp bubble in a region of space that does not already contain one. In addition, extremely high energies would be required to create this effect, and there is no known way for a ship to exit a warp bubble once it has entered. In short, FTL is a purely theoretical concept for the time being and there are no indications that it will move from theory to practice in the near future.

“The first [strategy] is FTL travel, but the other strategies accept that FTL travel is very theoretical and that one option is to extend human life or to engage in multiple-generational voyages,” said Dr. Braddock. “The latter could be achieved in the future, given the willingness to design a large enough craft and the propulsion technology development to achieve 0.1 x c.”

In other words, the most plausible concepts for interstellar space travel are not likely to achieve speeds of more than ten percent the speed of light – about 29,979,245.8 m / s (~107,925,285 km/h; 67,061,663 mph). This is still a very tall order considering that the fastest mission to date was the Helios 2 mission, which achieved a a maximum velocity of over 66,000 m/s (240,000 km/h; 150,000 mph). Still, this provides a more realistic framework to work within.

Where hibernation and stasis regiments are concerned, the advantages (and disadvantages) are more immediate. For starters, the technology is realizable and has been extensively studies on shorter timescales for both humans and animals. In the latter case, natural hibernation cycles provide the most compelling evidence that hibernation can last for months without incident.

The downsides, however, come down to all the unknowns. For example, there are the likely risks of tissue atrophy resulting from extended periods of time spent in a microgravity environment. This could be mitigated by artificial gravity or other means (such as electrostimulation of muscles), but considerable clinical research is needed before this could be attempted. This raises a whole slew of ethical issues, since such tests would pose their own risks.

Strategies for Engineered Negligible Senescence (SENS) are another avenue, offering the potential for human beings to counter the effects of long-duration spaceflight by reversing the aging process. In addition to ensuring that the same generation that boarded the ship would be the one to make it to its destination, this technique also has the potential to drive stem cell therapy research here on Earth.

However, in the context of long-duration spaceflight, multiple treatments (or continuous ones throughout the travel process) would likely be necessary to achieve full rejuvenation. A considerable amount of research would also be needed beforehand in order to test the process and address the individual components of aging, once again leading to a number of ethical issues.

Then there’s worldships (aka. generation ships), where self-contained and self sustaining spacecraft large enough to accommodate several generations of space travelers would be used. These ships would rely on conventional propulsion and therefore take centuries (or millennia) to reach another star system. The immediate advantages of this concept is that it would fulfill two major goals of space exploration, which would be to maintain a human colony in space and to permit travel to a potentially-habitable exoplanet.

In addition, a generation ship would rely on propulsion concepts that are currently feasible, and a crew of thousands would multiply the chances of successfully colonizing another planet. Of course, the cost of constructing and maintaining such large spaceships would be prohibitive. There are also the moral and ethical challenges of sending human crews into deep space for such extended periods of time.

For instance, is there any guarantee that the crew wouldn’t all go insane and kill each other? And last, there is the fact that newer, more advanced ships would be developed on Earth in the meantime. This means that a faster ship, which would depart Earth later, would be able to overtake a generation ship before it reached another star system. Why spend so much on a ship when it’s likely to become obsolete before it even makes it to its destination?

Last, there is cryogenics, a concept that has been explored extensively in the past few decades as a possible means for life-extension and space travel. In many ways, this concept is an extension of hibernation technology, but benefits from a number of recent advancements. The immediate advantage of this method is that it accounts for all the current limitations imposed by technology and a relativistic Universe.

Basically, it doesn’t matter if FTL (or speeds beyond 0.10 c ) are possible or how long a voyage will take since the crew will be asleep and perfectly preserved for the duration. On top of that, we already know the technology works, as demonstrated by recent advancements where organ tissues and even whole organisms were warmed and vitrified after being cryogenically frozen.

However, the risks also greater than with hibernation. For instance, the long-term effects of cryogenic freezing on the physiology and central nervous system of higher-order animals and humans is not yet known. This means that extensive testing and human trials would be needed before it was ever attempted, which once again raises a number of ethical challenges.

In the end, there are a lot of unknowns associated with any and all potential methods of interstellar travel. Similarly, much more research and development is necessary before we can safely say which of them is the most feasible. In the meantime, Dr. Braddock admits that it’s much more likely that any interstellar voyages will involve robotic explorers using telepresence technology to show us other worlds – though these don’t possess the same allure.

“Almost certainly, and this revisits the early concept of von Neumann replication probes (minus the replication!),” he said. “Cube Sats or the like may well achieve this goal but will likely not engage the public imagination nearly as much as human space travel. I believe Sir Martin Rees has suggested the concept of a semi-human AI type device… also some way off.”

Currently, there is only one proposed mission for sending an interstellar space craft to a nearby star system. This would be Breakthrough Starshot , a proposal to send a laser sail-driven nanocraft to Alpha Centauri in just 20 years. After being accelerated to 4,4704,000 m/s (160,934,400 km/h; 100 million mph) 20% the speed of light, this craft would conduct a flyby of Alpha Centauri and also be able to beam home images of Proxima b .

Beyond that, all the missions that involve venturing to the outer Solar System consist of robotic orbiters and probes and all proposed crewed missions are directed at sending astronauts back to the Moon and on to Mars. Still, humanity is just getting started with space exploration and we certainly need to finish exploring our own Solar System before we can contemplate exploring beyond it.

In the end, a lot of time and patience will be needed before we can start to venture beyond the Kuiper Belt and Oort Cloud to see what’s out there.

Further Reading: ResearchGate

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4 Replies to “Pros and Cons of Various Methods of Interstellar Travel”

The multi-generation starship looks like a big sperm cell …. which is perhaps fitting.

Redefining the speed of light ? 299792458 m/s, not 107925285 or 107925285000, whichever was intended.

Ditto with “4,4704,000” m/s being 5% of c; it’s not. Sloppy.

Not sure of the point of starships that cut one portion of the human race off from the other effectively forever. How would things go if they ever did return? I can’t see it ending well. In any case, we’re never going to build a massive ship or garner enough energy to tackle the physics of space from down here, we need to get out there in the Solar System big time, only then will we have the tools to start thinking seriously of travelling interstellar.

Comments are closed.

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How Humans Could Go Interstellar, Without Warp Drive

Faster-than-light (ftl) travel is possible..

The field equations of Einstein’s General Relativity theory say that faster-than-light (FTL) travel is possible, so a handful of researchers are working to see whether a  Star Trek -style warp drive, or perhaps a kind of  artificial wormhole , could be created through our technology.

But even if shown feasible tomorrow, it’s possible that designs for an FTL system could be as far ahead of a functional starship as Leonardo da Vinci’s 16th century drawings of flying machines were ahead of the Wright Flyer of 1903. But this need not be a showstopper against human interstellar flight in the next century or two. Short of FTL travel, there are technologies in the works that could enable human expeditions to planets orbiting some of the nearest stars.

Picking the Target

Certainly, feasibility of such missions will depend on geopolitical-economic factors. But it also will depend on the distance to nearest Earth-like exoplanet. Located roughly 4.37 light years away, Alpha Centauri is the Sun’s closest neighbor; thus science fiction, including  Star Trek , has envisioned it as humanity’s first interstellar destination.

In 2012, a planet was  identified  orbiting closely around Alpha Centauri B, one of three stars comprising the Alpha Centauri system. Three years later, astronomers were unable to find that same planet, but if it exists it would be too hot for life anyway. What we really want to know is whether planets exist further out from the two main stars, or whether their much smaller, dimmer companion star, Proxima Centauri, located just 4.24 light years from Earth, has planets of its own.

Very soon, these questions will be answered by the  James Webb Space Telescope (JWST) that NASA will be launching into space in 2018, and by other instruments that will follow, instruments capable of more than merely detecting a planet’s presence. They will also be able to read the chemical composition of planetary atmospheres.

Imagine this: If there’s an Earth-like planet around Alpha Centauri or another nearby star system, astronomers will know about it within a decade or two — certainly long before we can build a ship like the  Enterprise .

Maybe we could consider flying under the speed of light.

Propulsion 

It is not widely known, but the US government spent real money, tested hardware and employed some of the best minds in late 1950s and early 60s to develop an idea called  nuclear pulse propulsion .

Known as  Project Orion , the work was classified because the principle was that your engine shoots a series of “nuclear pulse units” — atomic bombs of roughly Hiroshima/Nagasaki power — out the back. Each unit explodes and the shockwave delivers concussive force to an immense, steel pusher plate, which is connected to the most immense shock absorber system that you could imagine.

The researchers calculated that the ship could reach five percent the speed of light (0.05  c ), resulting in roughly a 90-year travel time to Alpha Centauri. The Nuclear Test Ban Treaty of 1963, which forbade nuclear explosions in the atmosphere, and the Outer Space Treaty of 1967, which forbade nuclear explosive devices in space, effectively ended  Orion .

In his epic TV series Cosmos, Carl Sagan noted such an engine would be an excellent way to dispose of humanity’s nuclear bombs, but that it would have to be activated far from Earth. But back when  Orion  was being funded, amazingly, the plan was to use the nuclear pulse engine even for launching the vessel, in one massive piece, from the surface of Earth. Suffice it to say it does not seem likely that we’ll every build a nuclear pulse ship, but it’s something that we already have the technology to build.

A Cleaner System

But what about a less explosive, cleaner propulsion system that could achieve the same end? The British Interplanetary Society took on this goal in the 1970s with Project Daedalus . Named for the inventor from Greek mythology who built wings to escape the island of Crete, the design was based on projected development of inertial confinement fusion (ICF), one of two main strategies for generating nuclear fusion energy on Earth.

The other strategy is magnetic confinement fusion (MCF), and similar to ICF, designs exist for  adapting MCF to space propulsion . Like  Orion , a  Daedalus  craft would have to be rather large. But using deuterium and helium-3 (obtained from the lunar surface, or from Jupiter’s atmosphere) as fuel,  Daedalus  craft could reach 0.12  c , cutting travel time to Alpha Centauri to something like 40 years.

There are other ingenious ideas, such as the  Bussard ramjet  that could approach the speed of light, but the size of the engines and technological gaps that we must fill become so large that they may not seem easier than warp drive. So let’s limit our discussion to capabilities up to the neighborhood of the 0.12  c  of  Daedalus  as we consider what form a human interstellar voyage might take

The Generation Starship

It has been said that if you want to go fast, go alone, but if you want to go far, go together. This proverb characterizes the strategy of building an interstellar ship so large that you don’t worry so much about the travel time.

Effectively, the ship is a space colony. It contains a large population — current estimates are that a minimum of tens of thousands of colonists are needed for a  healthy gene pool — and all that is needed for people to live comfortably, but it follows a trajectory out of the solar system. Ideas for an interstellar ark taking millennia to reach a destination date back to the fathers of the Space Age — Russia’s Konstantin Tsiolkovsky and America’s Robert Goddard— — the idea really set sail with mid 20th century science fiction writers.

In a two-part novel series written in 1941, Robert A. Heinlein wrote of a vessel that took so long to reach its destination that the people aboard had forgotten they were on a ship. Instead, they believed the large craft to be their natural world.

Sending colonists on a voyage lasting centuries or millennia raises social questions, such as whether it is ethical to commit unborn generations to live out their lives in transit between planets.

10,000 years is a rather long time and means a large number of generations to commit to the interstellar void. But if we’re talking 40 or even 90 years, that’s probably more palatable to many more people. Still, it raises questions as to who would volunteer for such an expedition.

But what about people with shorter attention spans and what if we have no will to build enormous, moving colonies?  

Here’s another science fiction strategy: sending cryopreserved human embryos, or gametes (ova and sperm) into deep space. Upon reaching the destination star system, the embryos would be developed. This would require an artificial uterus, which we don’t have yet, but like fusion, here we’re also talking in terms of a matter of decades.

At some point in this century,  motherless birth  could become a technological reality. Theoretically, we’ll be able to send cryopreserved embryos through space, for centuries if needed due to propulsion limitations, and set them to develop into full-term infants on the new planet.

Then, all you need are robot nannies to raise and educate the infant colonists. And if there’s one area of technological progress that people are supremely confident will keep advancing at warp speed, it’s robots and artificial intelligence.

The egg ship concept is loaded with ethical questions, which can be hashed out in the comments section.

Suspended Animation

As technically ambitious as it may sound, medical science is making incremental progress toward a safe form of human hibernation.

Currently, it’s routine to lower a patient’s body temperature intentionally by a few degrees, thereby inducing a mild hypothermic coma, following cardiac arrest. This enables the brain to recover after oxygen has been cut off, whereas remaining at normal body temperature results in what’s called reperfusion injury.

Not routine yet, but now under clinical trials, trauma surgeons are cooling patients down to just above freezing temperature in cases of severe blood loss. This is true  suspended animation . It’s done just for two hours, or possibly three, stalling death so that injuries can be repaired and blood replaced, but the person is basically hibernating during that time.

With incremental progress, the procedure may eventually be extended to time frames of many hours, and eventually days or weeks to treat other conditions. Perhaps, in time, we’ll put people to sleep long enough, and with enough supervision by computers, to slumber away for an entire interstellar voyage the way you now doze off for a transoceanic flight.

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How Interstellar Space Travel Works (Infographic)

Even the fastest humans and spacecraft launched thus far would take many thousands of years to reach the closest stars. Speeds about 75 times faster than this would be required if we hope to make an interstellar trip in less than a hundred years.

To understand the difficulty of interstellar travel, one must comprehend the incredible distance involved. Even the closest star is more than 266,000 times farther away than our own sun. Consider the speed of light . Light, the fastest thing known, takes only 8 minutes to travel to us from the sun, but requires more than four years to get to the nearest star. A handgun bullet travels at 720 miles per hour, but would take nearly 4 million years to get to the nearest star. The fastest object ever launched into space is the Voyager 1 probe , and it would take nearly 75,000 years to make the trip. Today’s chemical rockets are far too slow for interstellar travel . To have a hope of reaching the closest star in less than a hundred years, we would have to accelerate a starship to nearly 30 million mph. Rockets using nuclear fusion or antimatter propulsion could do the job, but they would have to be developed. It is theoretically possible that by warping space, a starship might travel faster than light without violating the laws of physics within its own bubble of space-time.

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Karl's association with Space.com goes back to 2000, when he was hired to produce interactive Flash graphics. From 2010 to 2016, Karl worked as an infographics specialist across all editorial properties of Purch (formerly known as TechMediaNetwork).  Before joining Space.com, Karl spent 11 years at the New York headquarters of The Associated Press, creating news graphics for use around the world in newspapers and on the web.  He has a degree in graphic design from Louisiana State University and now works as a freelance graphic designer in New York City.

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Ramin Skibba

These Sci-Fi Visions for Interstellar Travel Just Might Work

In a month or two, NASA will launch its massive Space Launch System rocket from the Kennedy Space Center. While the spacecraft atop it will travel around the moon—the farthest from Earth a crew-capable craft will have ever gone—the rocket will also deploy a bunch of little CubeSats , including one called NEA Scout that will be propelled by a solar sail toward a nearby asteroid.

That project has come to fruition thanks to Les Johnson, head of that mission’s technology team at NASA’s Marshall Space Flight Center in Huntsville, Alabama. It’s a milestone for Johnson, who has been working on solar sails and other advanced propulsion systems for years.

Outside his day job at NASA, Johnson also writes nonfiction and science fiction books for popular audiences, many of which envision future interstellar voyages. His latest, A Traveler’s Guide to the Stars , explores the kinds of propulsion systems that could one day make these deep-space expeditions a reality.

This conversation has been edited for length and clarity.

WIRED: What inspired you to study space propulsion systems?

Johnson: Star Trek , if you go way back. I’ve been a science fiction fan and an advocate for space exploration and space travel since I was in elementary school. I was 7 years old when I watched Neil Armstrong walk on the moon. I was asleep probably, and I was in footie pajamas, and my parents woke me up to come watch this. And later, my older sister allowed me to stay up with her late to watch Star Trek reruns, and Lost in Space , so I was kind of hooked.

I decided at that age that I wanted to study physics and be a scientist. I always had bad vision and had been a scrawny kid, so I knew I wouldn’t be an astronaut—but I wanted to work for NASA. 

One of the first projects I was assigned was to work on something called a space tether. Those are long wires that are deployed on spacecraft, and they can be used for scientific measurements. But there was a secondary effect in test flights: You could actually get propulsion in low Earth orbit using these wires, without electricity orfuel. So I got really excited: “Hey, this is a way to travel through space, at least in Earth orbit, where you may not ever run out of gas.” 

So that’s what got me interested in advanced propulsion. From there it spread out to solar sails, and to nuclear propulsion. As a result of that, I got involved with some groups outside of NASA, people thinking about how we might go to the stars. They’d ask me, “What’s a viable method to go to Proxima Centauri?” So things kind of snowballed from there.

How does a solar sail work?

It’s not the solar wind—that’s an unfortunate naming problem. A solar sail is propelled only by light. Light is made up of photons, and those photons don’t have mass. But they do have momentum, like a molecule of air in the wind. And just like a sailboat on a lake or the ocean, when the wind blows against the sail, some of the momentum of the air particles is absorbed by the sail, which causes it to recoil, which is pushing on the sail. And through the mast, it pulls the boat with it. 

Charlie Wood

Juliane Bergmann

Kathy Gilsinan

Julian Chokkattu

Out in space, as photons of light reflect from the sail, the light gives up a little of its energy and momentum, and that momentum goes into the motion of the sail and it pushes it.

How far from the sun can you go while still getting a significant amount of energy from it?

This is why solar sails are really cool, and this is why I like them for interstellar travel. Let’s go out the Earth’s distance from the sun, 1 AU, 93 million miles. When you unfurl a sail of any size, say it’s 100 square meters, the sunlight falling on it pushes on it. As you move away from the sun, the intensity of sunlight falls off pretty rapidly, and so does the thrust. But if you deploy a sail closer to the sun, the thrust level goes up dramatically. 

If you have a light enough sail, you can get a really big acceleration. If you get well inside the orbit of Mercury and you have a sail that only weighs 1 or 2 grams per square meter—which is about 20 times better than we can do today—and you have a sail that’s like a square kilometer, if you add a laser to boost it, you can get enough thrust to go out of the solar system at a significant fraction of the speed of light, like 10 percent. It’s unbelievable. That’s where you can get a trip that will get you to Alpha Centauri in hundreds of years, as opposed to thousands or tens of thousands with chemical rockets.

When I first saw these numbers, I thought, “That’s great, but we have no material that can stand those loads that’s that lightweight. That material is ‘unobtainium.’” That was pure science fiction. Then in 2004, graphene was found. The discoverers of that got a Nobel Prize for it in 2010. That’s a single layer of carbon. It has all the thermal and mechanical properties you need to build this huge sail; you just have to put something on it to make it reflective, like a layer of aluminum. And suddenly, this looks possible. 

We don’t know how to engineer anything that big yet . But we’ve gone from a material that doesn’t exist to one that does exist in the last two decades. And if you augment that with a high-power laser, like the folks at the Breakthrough Starshot want to do, it’s like a lot more suns falling on it, which means you can accelerate it to much higher speeds, potentially up to 5, 10, 20 percent the speed of light. And all of this without violating the laws of physics. The only laws you’re violating are known engineering. Nobody knows how to build these things, but we will! We’ll figure it out.

How did you get involved with the NEA Scout’s solar sail?

I have been working on solar sails since the early 2000s. It was one technology of many, in a portfolio of advanced propulsion that I was working on at my day job at NASA. It involved electric propulsion, nuclear propulsion, sail propulsion, some chemical work, and solar sails were a part of that. That was about the time little CubeSats were being flown, small, bread-loaf-sized spacecraft that a lot of universities now fly in low Earth orbit. NASA was trying to figure out, “Hey, can we do useful things with these? Does anybody have a payload?” We said, “We have some solar sail hardware. Let’s test a sail deployment in Earth orbit.” 

So in 2010, we flew a 10-square-meter sail called Nanosail-D . And that was successful. Then the Space Launch System was starting to move forward, and someone at NASA said, “This rocket’s going into deep space. It will have extra payload capability, we can take some of these CubeSats.” So I led a team and we wrote the proposal for NEA Scout using a scaled-up version of the Nanosail-D.

Tell me about some speculative propulsions you’ve explored, such as pulsed fusion and antimatter.

Oh, it’s all cool! I could talk for hours! I’ll start with the things I think are possible within the known laws of physics. I don’t want to be arrogant here: Scientists throughout history have made the mistake of saying, “Oh, that’s impossible,” and then 50 years later somebody proves them wrong.

There are a few ways to get to the stars. One is sails—light sails, solar sails. Chemical rockets just don’t have the energy density to do it. Nuclear-thermal rockets basically use a small version of the reactor that produces electrical power in a power station near you. You miniaturize it and put it on a rocket and use fuel, and it’s superheated by the nuclear reactor. That’s an improvement in performance over a chemical rocket, and it’s something I think we ought to be doing for the exploration of our solar system, but it won’t take you to the stars. You can’t carry enough fuel in the mass you have available to make it work.

Its descendant, fusion, which people are working on to try to have a cleaner source of power on Earth, is: Instead of splitting atoms, you’re combining them, like the way the sun produces energy. You’re squeezing hydrogen atoms so tightly until they become helium, and then they give off energy. If you can do that in a controlled reaction, you get a lot more energy out than you put in. You could use that as a propulsion system to build a rocket. It would have to be a really big rocket, because you’d have to carry a lot of fuel: Think of a rocket bigger than the Empire State Building. But it would work. You could get to the nearest few stars, like maybe Proxima Centauri, but not Ross 248, which is 10 light-years away.

One of my favorites after that is antimatter. People hear that and think, “That’s out of Star Trek .” Which it was. But it’s real. In high-energy reactions, like at the CERN collider in Europe and other particle accelerators, when we smash atoms together at high speed, lots of things break apart and fly off. But a curious thing people discovered is that there are things that look like a proton, have the mass of a proton, but have a negative charge. And then they discovered these lighter-weight things that look like electrons, but they have a positive charge. So scientists have taken these antiprotons, combined them with positrons, and made anti-hydrogen. That’s in small quantities, because when these anti-particles encounter their normal matter counterparts, they undergo—in physics terms—annihilation. That mass gets turned into energy. They explode and give off gamma rays, all kinds of secondary particles—it’s a very energetic explosion. A tablespoon of antimatter would basically destroy a city—that’s how much energy is packed into antimatter. 

You could take a lot of this antimatter, store it in a perfect vacuum, and then as you need it for your reaction mass to propel your spaceship, you have a stream of it that goes in and annihilates with normal matter and you use that energy. We don’t know how to do that, but nature says it’s possible. Now, I don’t think I want to build this on Earth, because you’re going to need tons of antimatter. If you lost control of it, that would be a disaster. 

Buried in there is another pretty interesting idea that is not as good as antimatter or fusion, but it’s really close. That’s something called a fission pulse. You may have heard of Project Orion. That was a really cool project in the Cold War, in the late ’50s and into the ’60s, where some scientists including the late Freeman Dyson said, “Maybe instead of using a rocket to put a spacecraft into space, what would happen if we used a series of controlled explosions under a big steel plate?”

It’s like, if you put a rock on top of a firecracker, the rock gets launched, right? Imagine a series of explosions under a steel plate. It’ll start getting off the ground—“Boom, boom, boom!”—to higher and higher speeds as you keep detonating these explosions. You could potentially get this plate or whatever’s on it—a spacecraft—moving to really high speeds. These scientists figured out, if you have a spacecraft the size of an aircraft carrier and you put extremely large plates under it, that are big enough to shield it from the radiation from the bomb going off, and you started exploding atomic bombs every three seconds under it, you could get tremendous speeds and you could use this to send a spacecraft, with a trip time of a few hundred years, to the nearest star. Of course you destroy the ecosystem while you’re launching it. But in theory, yeah, that ought to work!

According to a figure in your book, it looks like it’s hard to strike a balance to achieve both efficiency and thrust—and to also not have something cost a gazillion dollars.

Unfortunately, if we’re talking about building something at the scale to send a reasonably sized spacecraft to the nearest star, it’s going to be—with today’s capabilities—a really expensive endeavor. But over time, the capability evolves.

That curve you’re talking about limits rockets. It applies to any rockets that have fuel on board: chemical rockets, electric rockets, nuclear-thermal, fusion, and even antimatter. You’ve got the mass of your spacecraft, and to get it moving, it requires a certain amount of fuel at a certain thrust level. To keep it going faster, you have to load more fuel on it, which increases the weight, which means you need more fuel to move it initially. Eventually it gets to a point where you get diminishing returns.

That’s why I like sails, where the energy is not on the ship; it comes from somewhere else, so you don’t have to worry about that efficiency curve getting you. That’s a beautiful way to get around that problem.

For very long interstellar trips—things that are farther than the closest star—continuous fusion, antimatter, and sails are the only thing that will let you get there. But the better the thrust performance, the worse the efficiency it has, with every system we’ve looked at.

What motivated you to write this book, A Traveler’s Guide to the Stars ?

I go back to what motivated me to study science: It was our achievements in space, going to the moon. It was the dreamers, science fiction writers, and television shows, and this notion that in this big universe, as we look out and we discover exoplanets and we find that some of these exoplanets live in regions around their star where there might be liquid water, there might be a place where life could go and exist. 

I am a believer that life is good and that it’s a morally good thing to try to preserve and protect and spread life. We as a species, as humans, should strive to use space resources to make life better on Earth and expand our presence in the solar system, and eventually start sending our children to spread life into the rest of the universe, which sure looks like it’s a cold, dead universe. If it is, then let’s go fill it up with people who have hopes, dreams, aspirations, to create art and be human.

How long will it take humanity to design and send a robotic probe to another star system?

Part of that’s going to be a function of how hard we try. If we keep going on the path we’re going—which isn’t a bad path, but it’s taking longer than we thought it would to get the costs of launch down—I think it’ll be 300 years.

But if someone were to come along and say, “Here’s a blank check. Let’s go figure this out,” we could do it probably in less than 100 years. It’s a challenge limited by engineering knowledge, but interest, enthusiasm, and funding could accelerate it. 

Now if it’s the public purse, politicians have to balance that with all the other things: health care, police. I’m just thankful our society places a value on science and exploration at any level. So it’s a balance of priorities.

What might a crewed space journey to another star system look like?

Let’s assume we’re not going to fundamentally change our own biology through genetic engineering, that 100 years from now, people are still people as we’d recognize them today, but maybe living longer, maybe with better health care. I think it would be a voyage of hundreds of years, in a ship where there would be generations that are born and die, before you ever reach the nearest star. It would be a concept like in the movie Passengers , but not with suspended animation, because I’m really skeptical of that. 

Now if we have breakthroughs in medical research that allow us to engineer ourselves to be adapted to spaceflight, perhaps engineer ourselves to be like bears, where we could go into hibernation, and then you combine that with rocket science and propulsion science, a voyage of hundreds of years might still be the case, but wouldn’t necessarily be generations. It might open the possibility of the people who get on the ship being the ones who get off the ship. But that’s two levels of revolutionary breakthroughs.

What are your thoughts about sending robots versus people into space? That seems to be the eternal debate—with the moon, asteroids, and Mars?

It’s going to be both. I think that’s what history has shown. Before we sent people into space, we sent Sputnik and Explorer 1 and other robotic spacecraft. Before we went to the moon, there were the Surveyor missions that we sent, and the Soviets sent spacecraft, and then we sent people. For decades we’ve been sending robotic spacecraft to Mars. I think we will send people to Mars. I’m hoping that will be in my lifetime.

When I look at that debate, I think it’s a false dichotomy. And I’ve got a story in the book: I went to a meeting probably eight to 10 years ago on new strategies for exploring Mars. There was a debate going on there, with panelists on stage, about whether we should send people to Mars. Is it really worth it? There was this reserved chair in the first row that was empty. And then in walks Buzz Aldrin. Buzz, the second man to walk on the moon, makes his entrance, and sits down. And he’s there for like five minutes. He stands up, and raises his hand. He looked at all of us and said, “OK, let’s suppose we had a way to do this tomorrow. How many of you would sign up for a one-way trip to Mars?” I was stunned. I want to go as a tourist, but I want to go back home. But it was over half the people, and a lot of them who raised their hands were those who had been arguing we should only send robots. But as soon as they were given the thought, “Oh, we could send people—then of course I’d go.” That moment crystallized in my head that if the capability exists, we’re going to do both. It will first be the robots, then we’ll send people.

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Could We Become an Interplanetary Species? What’s next for space travel?

BBC Two’s Stargazing: Moon Landing Special (15 July) explores the future of space travel. Series Producer Rob Liddell reveals what he’s learnt about the next big step for mankind.

Over the next few years it looks like there will be a revolution in space travel

50 years ago two astronauts, Neil Armstrong and Buzz Aldrin, achieved something that many thought was completely impossible. Their historic journey to the surface of the Moon must be considered one of the greatest engineering achievements of all time. However as the anniversary of this event is celebrated it is clear today the scope of human space travel seems much reduced from what it was in the 1970s.

Right now America, the only nation to have sent astronauts to the surface of another world, has no rockets or spacecraft capable of carrying humans into space at all, let alone into deep space.

But that is about to change.

Over the next few years it looks like there will be a revolution in space travel that will transform how astronauts get into space, where astronauts travel, and even who gets to become an astronaut in the first place.

Getting back to the Moon

On 8th July 2011 Space Shuttle Atlantis blasted off into orbit for the final time, marking the end of NASA’s most successful and complex spacecraft. This incredible vehicle built the International Space Station, or ISS, a laboratory in Low Earth Orbit that has been continuously occupied for 18 years. In total there were 135 Space Shuttle missions, but since its retirement America has had to pay Russia to take its astronauts to space.

In the meantime NASA has been exploring new goals and has set its sights beyond the ISS and into deep space again. The plan is to return humans to the Moon and eventually to Mars.

The goal is as ambitious as it was 50 years ago. And to achieve it NASA is calling for a fundamental change in space travel. The space agency wants to focus its efforts on sending humans to deep space and that means handing over the more ‘routine’ activity of flying to Low Earth Orbit to commercial companies.

Tickets to the International Space Station?

In the next 12 months two companies are hoping the make this a reality. Elon Musk’s SpaceX has developed pioneering self-landing rockets. This makes them reusable and means they have slashed the cost of getting cargo into space. In March 2019 the company achieved a major milestone by successfully testing their Crew Dragon spacecraft. The uncrewed test proved it could dock with the International Space Station.

Hot on Crew Dragon’s heels is Boeing’s Starliner spacecraft. Boeing has been awarded a $4.7 Billion contract from NASA to build the Starliner that will take up to 7 astronauts per flight to the ISS. It’s being built on site at Kennedy Space Center in Florida.

The Spaceship factory

Step inside the Starliner spacecraft factory.

Both companies are commercial enterprises and both plan to sell tickets to private citizens allowing for short stays on the ISS at a cost of 10s of millions of pounds. In doing so they will help make ‘space tourism’ a reality. It is also quite possible commercial companies will be given a role in running the space station itself.

SLS will eventually tower to 111 meters and will be the most powerful rocket ever launched to space

How to get a human into deep space

To aid its deep space missions, NASA is planning a successor to the ISS when its funding runs out – currently expected to be in 2025. It’s exploring creating the Deep Space Gateway, a smaller space station that would orbit near the Moon and could act as a staging post to get down to the lunar surface.

But to reach this new space station NASA needs to build a rocket capable of flying astronauts beyond Earth orbit. A feat that was last achieved by the mighty Saturn V rocket that powered the Apollo programme. So NASA is building the Orion spacecraft and the Space Launch System, or SLS rocket. SLS will eventually tower to 111 meters and will be the most powerful rocket ever launched to space, capable of carrying Orion and its crew of 4 to 24,500 mph, the speed needed to escape Earth's gravity.

Right now the rocket is being built in Michoud, Mississippi and is expected to launch for the first time in 2020.

The World's Most Powerful Rocket

SLS will be the worlds most powerful rocket, here the collosal fuel tanks are being built.

First stop Moon Camp, next stop... Mars?

this new moon programme is aiming to create a lunar base

The goal is to do more than just repeat the feats of Apollo – this new moon programme is aiming to create a lunar base – something the European Space Agency is already committed to. And the Moon will become an important testing ground that could pave the way for future crewed missions to Mars.

As part of this new approach a team at an experimental NASA research facility – Swampworks - has been building robots that could mine the Moon. This isn’t about finding precious metals to return to Earth and make someone very rich. It’s about trying to minimise the amount of cargo need to be blasted into space from our planet. Every kilo costs thousands of pounds in fuel. Instead the idea is the robots could mine the Moon for building materials to create lunar bases. The team is even able to 3D print structures using lunar material.

The most precious resource of any mission is fuel – and even this could be harvested from the Moon. Most rocket fuel is made up of hydrogen and oxygen – two of the most abundant elements in the universe and which bind together to form water – H₂0. Whilst at first glance the Moon appears to be an arid desert there is actually water ice in the shade of many of its craters and there’s surface ice near the poles. With 1/6th the gravity of Earth getting this fuel off the Moon is a lot easier and cheaper than carrying it from Earth. So robots could make fuel on the Moon which could be used power rockets back to Earth or on to Mars.

Mining the Moon

Meet the autonomous robots built to mine the Moon.

It all seems very outlandish but so did the idea of having a human stand on the Moon in 1961 when John F Kennedy committed America to the Moon programme. As Robert Mueller, Chief Technologist at NASA’s Swampworks lab says “ Everything is there, the only two things missing are technologies and imagination. If we can put those two things together and harness the materials and the energy we have in space, we have all the resources of space we need. We just need to be clever enough to know how to use them. ”

It all seems very outlandish but so did the idea of having a human stand on the Moon in 1961

This could be the dawn of a new era of space travel. In the future historians might look back to this moment as the first step of many that lead to humans becoming an interplanetary species, expanding beyond the Earth. Whatever happens the next 10 years look to be an incredibly exciting period.

Watch Stargazing Live: Moon Landing Special on Monday the 15th of July at 9pm

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