This is your captain speaking.We are about to take a 5-year journey of 2.4x10^13 miles through a near-vacuum with limited gravity, to the probable location of an alien world wending its way through a trinary star system. Please sit back, relax, and enjoy our trip to Proxima Centauri...oh, and don't eat too much or go crazy. Or get cancer. Thank you for your cooperation.
Yikes, that sounds like a horrible plane trip. You've probably heard about the spectacular hurdles we humans would have to overcome in order to actually reach the nearest non-solar star, the most basic of which is that outer space is going to kill you even inside your flimsy metal spaceship, and you'd need a planet-sized food supply for the journey. I'll run them down real quick, just in case you've forgotten all the gleeful little buzzkills awaiting us:
1. Speed/time/distance
2. Fuel
3. Food
4. Communication
5. Social/psychological problems
6. Microgravity
7. Radiation
8. Space debris
And that's just the big ones. I've left out a few that I didn't have the time or inclination to deal with.
Basically, even if you had a vehicle traveling 9/10 of the speed of light, which would take years to accelerate to and years to decelerate from, you'd still be spending an insane amount of time traveling through space, out of contact with earth, running low on food, your muscles wasting and your bones decomposing as you slowly go mad in a boat full of crazies, dying of cancer and radiation burns from outer space, unable to detect or avoid tiny dust particles that could perforate your ship, arriving on a planet that will probably kill you but you'll need to colonize because you have no fuel, food, or reason to return to earth where your family is already gone and decades have passed while you remain the same age.
I keep thinking about this because there's so much pedantic fact-checking over every single science fiction movie out there these days. It seems like the more accurate a movie tries to be, the more it gets keel-hauled over the glowing glass-sharp cinders of internet technical-knowledge masturbatory watchdogging (think Gravity or Interstellar). What used to be the province of pipe-smoking, smirking ivory tower types, winking condescendingly at "low" culture, is now open to any damn fool who feels the urge to "catch" the writers at some quibbling little unscientific peccadillo. It seems less discouraging to make a brainless Michael Bay-type flick, because at least these get dismissed out of hand, rather than run through the mill.
And the fact is, these fact-checkers, past and present, often don't realize that technology is rapidly catching up with science fiction. They're stuck in a very here-and-now mindset, and develop a sort of tunnel-vision. Science fiction should be about speculation: a casual prognostication on what future human(oid)s will be like, what technologies we'll have, how we'll get to the stars and what we'll find when we get there.
(NB: I'm going to admit, I'm historically more of a Trekkie than a Warsian (Star Trek fan versus Star Wars fan, colloquially); I like the fact that it's more speculative about a realistic future, the characters reminiscing about and idealizing a Past that is our Present. Star Wars is a fantasy set in outer space. The tech is less important than the dream the tech allows for. I mean, space knights? Space rogues? An evil emperor? All they're doing is riding around on modified airplanes instead of unicorns or whatnot. I'm not slamming Star Wars, I'm a huge fan [of the original trilogy]; I'm just saying it's only vaguely speculative, and therefore only vaguely sci-fi).
1. Speed/time/distance
Naturally these three issues are bound together. I won't even attempt to help you understand how big outer space is; no matter how many baseballs inside stadiums are utilized, or driving from New York to Los Angeles, or football fields or city buses or diapers stretching from the earth to the moon three times...you still won't get it. You'll listen politely, and then go back to fantasizing about hopping in your little Ford Intergalactic for a day trip to Mars.
The problem is, even in the black cold depths of space, there's no frame of reference. The stars stay the same, like some kind of three-dimensional screensaver, at least until your reach the Alpha Centauri system, at which point will be four fewer stars in the still-recognizable constellation of Centaurus (it's in the Southern Hemisphere). Hell, you could still navigate by the North Star, if for whatever reason you choose that as your arbitrary reference point. Fire a bullet in a random direction into interstellar space, and there's an overwhelming chance that bullet will go on forever and ever without hitting anything, unable to match even the speed of even our slowest space probes, essentially motionless relative to the size of the universe. Perhaps only lightspeed means anything, and even that's a bit of a stretch: the fastest thing in the universe, a photon, still takes four years to reach Proxima Centauri from earth; traveling onward in a straight line, it would most likely never hit anything else.
Okay, so let's say you think 4.2 years is an acceptable amount of time for space travel. All you need to do is accelerate your spaceship to light speed, correct? Actually, you'd never hit lightspeed - for massive objects, the Universal Constant is an impenetrable barrier. As you approach lightspeed, you begin to literally acquire mass - bizarre, it's true, and seemingly impossible; but this is simply E=mc² here, solved for m - "mass equals the square root of your energy divided by the speed of light". According to this logic, you would eventually have an infinitely massive, infinitely energetic object traveling at the fastest speed possible - such an object cannot exist. It disintegrates. Only its massless particles will be able to achieve lightspeed, while the rest are scattered or annihilated into energy.
Alright, so you achieve 99% lightspeed. Respectable speed. Give it a week or two to ramp up your acceleration to 100g's; continue acceleration for four days until you hit 0.99c, coast for 4 and a half years, then repeat the process in reverse to decelerate. Sweet, now you're at Proxima Centauri. Take a couple pictures, turn the ship around, head back to earth. Total onboard time elapsed: 9 years, four or five months.
Total Earth time elapsed? 80 years.
You've lost your family and everything you've known and loved to "time dilation". This is the worst part of E=mc² (among many, many letdowns): the greater the speed of a ship traveling away from Earth, the less time elapses onboard versus time elapsing on earth. You have nothing to go back to. You're a wanderer in time and space, forever young compared to an aging homeworld.
In summary: you can only accelerate up to the brink of the finite speed of light, which isn't that fast in relation to the size of the universe (and we're not even considering how much fuel this would consume), you'll have to spend a few years traveling, consuming food and resources; and when you get back to earth, no one would remember you.
The Solution: Warp Drive
Now hang on, hang on - I'm not talking about magical Faster Than Lightspeed travel, breaking the "Light Barrier" or whatever. This is the Alcubierre Warp Drive I'm talking about here, son, which is not only theoretically possible, it's actually in development at NASA's Eagle Lab. Granted, they've barely started, but there is a chance a working prototype might be available within 50 years. And it solves all of the above problems by sidestepping the whole issue.
Basically, the Alcubierre system doesn't move the ship itself; instead, it moves spacetime around the ship, like a conveyor belt. A huge bubble of energy is generated - "negative" energy in front, "positive" energy behind - and spacetime flows around the vessel in the direction of "travel". This may seem like a horrible idea (you'll break spacetime!) until you consider how vast spacetime actually is - a little warping here and there ain't gonna wrinkle the fabric. Since the ship is subject to no acceleration, and hence no time dilation, the crew would maintain earth-relative time while traveling light-years in weeks. This is the technology I'm probably most geeked about, because we could be taking cruises to Proxima Centauri, or jaunting around Barnard's Star, and get back in time for the Superbowl.
Now, there are enormous hurtles to contend with. One is "negative" energy - we have some faint inklings on how to produce it, but projecting it is a whole other ball game. Then the sheer energy required for the warp bubble is prohibitive. Even with the latest revisions to the design, the envelope required is projected to be the size of a planet. This becomes awkward if you're plowing through a region of debris - disturb the energy bubble even slightly, and you're in for one hell of a spectacular explosion. Also, because the warp bubble itself is warping spacetime, it cannot be activated near a gravity well, or the resulting distortions could tear the ship apart.
I'm an optimist. No - I'm obsessed. I want warp drive to be a feasible mode of travel. For years scientists have told us, with a slightly satisfied smirk, that we'd need some kind of huge damn "earth ship" where people lived and died for a thousand years just to make it to the nearest habitable planet, and that it was a one-way trip because the human race would probably be kaput by the time they made it back to earth.
Well guess what, scientists? I'm warping next to your stupid earth-ship just so I can laugh at you, on my way back from the sunny shores of Kepler 62f, as your reverted-to-cavemen colonists ook at the "bright sky mammoth".
2. Fuel
As any rocket scientist will tell you, one of the huge problems of moving stuff through outer space is that you have to take your own fuel with you - no gas stations, unless you count the great Acetylene Lakes of Titan. Where you'll invariably get price-gouged. At any rate, with current rocket technology - still the quickest and cheapest way to move hundreds of tons of life-sustaining equipment through the unforgiving void - you'd need to drag along tons of fuel. It's the weird conundrum of the horse dragging its own feed in a cart behind it: the further or faster it goes, the more hay it hauls; the more hay it hauls, the more it has to eat...you get the picture. It's a damn headache. Not only that, but alternative fuel types (fusion, antimatter, atom bombs) are dangerous and require massive shielding and containment structures. Ideally you want most of your structure devoted to crew and supplies, not gigantic radioactive engines.
There are ion propulsion systems currently in use - for instance,
So how do we get around this issue? What kind of motor system is the most efficient?
Solution: EM Drive
(Source)
How about a propulsion system that uses no fuel at all?
Check it out here. Apparently, by using microwaves, the EM drive converts electricity directly into thrust. How does it work? Well, scientists don't actually know. All they know is that it produces thrust in a vacuum; barring some seriously stupid math flaws, this thing works. All it needs is enough power. NASA is seriously geeked about this thing; they're talking about reaching the moon in 4 hours, Proxima Centauri (by probe) in 15 years. The current go-to technology for robotic spaceflight, ion propulsion, produces nowhere near the amount of thrust per unit power, and still has to carry some kind of propellant. EM drive is going to revolutionize NASA missions within the next 25 years - maybe less.
3. Food
Food is just fuel for the living crew: the further they have to go, the more fuel they need. The current solution is a bunch of prepackaged pastes and bricks. This stuff is very lightweight. It has a high caloric content, but isn't very filling, tastes dubious, and is expensive to produce. A multi-year mission would require a second ship just to carry the food for the crew.
Cryosleep hibernation is one proposed solution, but I doubt we'll come up with an effective model in the next twenty years. In the meantime, Mars beckons, and we'll have to find a way to feed our crew while they travel there.
Solution: Dehydrated bug powder.
(Source)
Insects are extremely efficient at converting food into mass, and need very little space. Heck, they even grow much larger in microgravity/high oxygen environments! Whee! But even if you don't have room to grow them, you can still grind them up into a dense, dry protein powder that doesn't taste too bad. You can flavor it, boil it, bake it, make little bug-shaped cakes out of it. All kinds of stuff. It may not be as light in weight as the current dehydrated stuff, but it's definitely cheaper, and provides more calories per pound than most other foods.
4. Communications
Communications in space runs in the same distance problem. This will become even worse once we develop warp technology; how can we report back to Huston if there's a problem? We could fix the problem and warp back to earth before our message even gets there. It's like sending a postcard from Aruba and having your flight touch down before it arrives back home. Not only that, but your transmitter would have to be more and more powerful the further you got from your control base. At a certain distance you might as well send Morse code via pulsar, hoping an amateur astronomer will notice.
Solution: Quantum Entanglement
(Source)
This involves a lot of weird quantum math, and I'm not a quantum mathematician. Here goes: if you bring two elementary particles into close contact, they can become "entangled" - that is, they mirror each other exactly. The weird part is that it's not reliant on distance - no matter where you are in the universe, those two entangled particles will remain entangled. Change one, and the other mirrors its change. You could be 30,000 light-years away, and they'll still be entangled!
Now, I've heard it said that QE is useless for communications because information can't be "sent" from one particle to another. Okay, but what about this? Or this? You can send a fax! Need to send an audio message? Send a visual code that can be read digitally and transferred into audio.
Instantaneous communication can thus occur across light years, even across the universe. There's no reason it couldn't. If I have a problem near Betelgeuse, I can communicate in real time with Huston, and all I have to do is wait for the super-duper slow human engineers to come up with a solution. That's wild and far-out and so mind-boggling I can barely think about it.
This is all just speculation on my part; I'm sure there's some boring buzzkill science explanation as to why we can't use quantum entanglement for this purpose. I just think that at some point, relatively soon, we will be able to use it.
5. Social/psychological problems
Spaceflight is boring. You're trapped in a tiny box with a few other humans. There's nowhere to go except outside, where you can't really feel the wind blowing in your hair. You're never really alone, and yet you're away from everything and everyone you love. The environment is alien, the food is tolerable at best, the view barely changes, and you're stuck doing repetitive tasks. The novelty of "Hey! I'm in outer space!" can only last so long, and then you're basically stuck in the world's loneliest cabin. Naturally, some folks go a little crazy.
There's no real way to test for this, or to predict how people are going to act. Psychological tests can screen out the big, readily apparent stuff; but a lot of issues are latent, and even perfectly healthy, wonderful people can "go toast" (as they say at the South Pole). It's not that people run around murdering each other, it's just that normal cognitive and social function becomes impaired. People walk around like they're asleep, dreams blending into reality; they become like children, forming camps, hoarding food, playing obnoxious games. Truth is, people weren't meant to be cooped up like that. Even the most stoic among us goes crazy, right?
Solution: Spaceborn culture
Star Children? (source)
Except that in some ways, this whole notion of "cabin fever" is somewhat of a cultural thing.
Consider the Inuit - at least traditional Inuit. They don't migrate south for the polar winter, which may have three or four months of complete darkness; instead they wait it out. They spend most of their time inside their dwellings, in very, very close quarters, practically on top of each other. And consider that they're often out hunting or fishing on the ice, where there maybe no one for a hundred miles. They're essentially living in a space capsule. And during this whole time, they never get irritated or try to kill each other.
I might be idealizing the situation; but I think it's relevant that most of the "isolation/confinement" tests were performed on Americans. Americans who, despite our general chuminess, need a lot of elbow-room, and have a combative streak. That's our culture. And despite what you might here, a lot of psychology depends on the culture you grew up in. There are even culture-bound syndromes, strange psychosomatic illnesses specific to a single culture and seen nowhere else.
In addition to cryogenics (nobody can fight or eat or poop while they're in a coma!), I think what's needed for extended space travel is a sort of "spaceborn" culture: humans who were raised in this contained-yet-isolated environment, whose minds are very quiet. They would be able to amuse themselves, and not require constant affirmation from the rest of the group, or feel the need to defend their territory. After a few generations, this culture would be very different from the modern people we're used to; they'd be aloof, efficient, technically minded, and probably have a spiritual life based around their spacecraft, their little world.
This would take a long, long time; we'd probably develop cryogenics before a spaceborn culture arises, and we could avoid the psychological problems that come with long transits.
6. Microgravity
Guess what? Humans were not meant to live in outer space. Weightlessness causes our muscles to atrophy and our bones to rot. Normal bodily functions become problematic. Long-term effects are dramatic and permanent. The problem of microgravity isn't simply being able to walk around normally; it's being able to exist long-term in a normal state.
One solution is to use the force of a ship's constant acceleration to maintain a pleasant 1g of simulated gravity. Problems arise when the ship stops accelerating, or needs to maneuver - everything not velcroed down will proceed to float all over the place. Another idea is the "spinning wheel" that generates 1g of centrifugal force; but this takes up an enormous amount of space, and having moving parts on a spaceship creates all kinds of difficulties.
Solution: Negative energy
(Source)
This one's a bit of a stretch, and I'm probably mangling the physics, but hey - that's what this whole post is about! Quantum physics is a graceful gazelle, and I'm a hyena. Let's chow down.
This relates to Warp Drive (see above). Basically, gravity produces negative energy, which is why mass is attracted by it. It's sort of an odd yin-yang duality, where mass is the positive yang, with gravity as its shadow - the two intertwined and never around without the other. Positive energy rushes toward negative energy, pulled toward its center.
Now, if warp drive is theoretically possible, based on the manipulation of negative and positive energy fields to warp spacetime, and positive and negative energy correlate to mass and gravity respectively, one might postulate that you can generate gravity by creating negative energy. And that you might, through the use of exotic material, manipulate that quasi-gravity into any shape you wanted.
Consider this: negative energy plates placed on the inner surface of a starship. Essentially it would be a shielded, layered matrix of exotic matter, with the "active" surface generating a negative energy field, while the "nonactive" surface would have a positive energy field canceling out its effect. The negative energy would be projected to only effect the surface of that plate.
This finagling is necessary because a spacetime is three-dimensional (well, 4-D) though we represent it as a flat sheet: a point of negative energy would pull on everything around it. You'd have to do some clever warping to ensure it only affects a certain area, i.e. the active surface. There's also the question of whether producing negative energy would give off a fatal amount of radiation, or use up too much power. What's necessary is a sort of semipassive system: exotic materials that naturally produce negative energy when a light current runs through them, then disarrange when the current is turned off - sort of like LED crystals.
7. Radiation
(Source)
I'm going to start this off by stating something kind of awful: we aren't going to Alpha Centauri. We're not going to Mars. Hell, the best we can do right now is the moon.
The reason is, quite simply, radiation.
"Radiation?" you say, assumed reader. "But I thought we can shield from that! Just throw some lead on it, you're golden."
Here's the trick: we can successfully shield ourselves from radiation...inside the Earth's magnetosphere. Which conveniently extends out to encompass the moon. Even then, astronauts receive an enormous dose, the effects of which are not yet entirely known. But step outside the magnetopause (where the effects of the magnetic field drop off exponentially), and you're in for a world of hurt. Cosmic rays, composed of exotic particles rarely seen on earth, blast through outer space, filling the vacuum.
To imagine how prevalent cosmic rays are in the void, imagine the noise filling a music hall - the rise and fall and wave and blast from each particular instrument. Now imagine every audience member has a rapid-fire Airsoft gun and infinite ammunition, and is required to spray pellets at random throughout the entire performance. Now imagine that someone has one of those toy air-burst guns, and fires from one spot on the balcony every minute. Now imagine the hall is outfitted with disco lights and rave lasers. Now imagine that every single one of these effects, from the sound waves to the plastic pellets to the swirling, streaking lights, causes mutations in the human body. Sounds fun, right? Welcome to outer space. And that's on a normal day - if there isn't a solar event, or a gamma ray burst, or a planet (such as Jupiter) nearby which produces deadly amounts of radiation.
You can shield from this radiation, which is mostly high-energy protons; however, it would require something like several feet of lead shielding embedded with water on every exterior surface. Thus EVA would be next to impossible. Space ships could only be manufactured at "space docks" orbiting the earth, because such heavy vehicles could never achieve escape velocity. Transporting all that shielding would also be a daunting task.
Now, you've probably heard of metamaterials - the so-called "invisibility cloak" materials that can bend waves around themselves, rendering them "invisible" to that particular wavelength. Simple stuff: just make the reflective surface smaller than the wavelength of the EM radiation (same principle for sound or seismic waves). Problem is, cosmic radiation is mostly particles. Particles ignore metamaterials, unless you can somehow shield for mass, which isn't going to happen anytime soon. High-energy-particles (usually protons, but there's a lot of antimatter) smash into a spaceship hull and generate a shower of exotic particles (much like at CERN) which then crash into our gooshy bits and create even more particles, which slowly burn and mutate us from the inside. In order to protect from particles, you need some kind of a magnetic field, like on earth. But that in itself could adversely effect the human crew.
Solution: Plasma shielding, genetic modification/nanobots
(Source)
I think the best idea is to somehow charge the hull with plasma. A flow of ionized particles across the surface could neutralize the particles before they penetrate the hull. Superconductors and metamaterials could be utilized to sustain the plasma flow while protecting the crew from the plasma at the same time. But this would require a bit of power, when a ship needs all the power it can get.
The best thing might be to get at the root of the problem: our fragile human bodies. We need to either be a) genetically engineered to withstand radiation, like cockroaches; or b) carry nanobots around with us to repair our cells. I think that a mix of both is best. Future humans will be sort of superhuman anyway, with much tougher (maybe even mechanical) bodies that heal extraordinarily quickly. Nanobots will not only repair our cells and weed out cancer, they could also bolster our immune systems, clear out toxins, help us live longer. Genetic engineering could alter humans to survive on otherwise inhospitable planets, rather than waiting for evolution or adaptation to take hold. Our current problem is that genetic engineering, while commonplace, is still in its infancy - we can make bug-resistant wheat, but radiation-resistant humans are another kettle of fish. And nanobots are still a sort of gee-whiz toy - we can make tiny gears turn and itty bitty bugs crawl around, but they don't quite have things figured out yet.
8. Space debris
If you've seen the movie Gravity, you know that space debris is a huge problem, especially in Low Earth Orbit. Earth is circled by a landfills' worth of space junk, carelessly tossed up there and left to hurl around the planet faster than bullets forever. Gravity dramatized the situation by having the characters detect the debris cloud before it hit, but in reality you'd never see it coming - the only sign that you'd found the powerdrill you lost on your last EVA would be a pair of hilariously power-drill shaped holes in your hull, followed by a less-than-hilarious loss of atmosphere and whatever else it had gone through. Even harmless dust particles become miniature missiles.
Solution: Plasma force field
(Source)
Yes, plasma force fields are a real thing. They're little more than university papers at this point, and have significant problems, but could see real development in the next twenty years. And they might be essential for interstellar travel. Remember the radiation mentioned above? A plasma forcefield could absorb the charged particles bombarding us from outer space, as well as vaporizing larger debris. Practical warp travel would require a shield around its warp bubble, because a single impact could collapse the bubble and destroy the ship.
Yikes, that sounds like a horrible plane trip. You've probably heard about the spectacular hurdles we humans would have to overcome in order to actually reach the nearest non-solar star, the most basic of which is that outer space is going to kill you even inside your flimsy metal spaceship, and you'd need a planet-sized food supply for the journey. I'll run them down real quick, just in case you've forgotten all the gleeful little buzzkills awaiting us:
1. Speed/time/distance
2. Fuel
3. Food
4. Communication
5. Social/psychological problems
6. Microgravity
7. Radiation
8. Space debris
And that's just the big ones. I've left out a few that I didn't have the time or inclination to deal with.
Basically, even if you had a vehicle traveling 9/10 of the speed of light, which would take years to accelerate to and years to decelerate from, you'd still be spending an insane amount of time traveling through space, out of contact with earth, running low on food, your muscles wasting and your bones decomposing as you slowly go mad in a boat full of crazies, dying of cancer and radiation burns from outer space, unable to detect or avoid tiny dust particles that could perforate your ship, arriving on a planet that will probably kill you but you'll need to colonize because you have no fuel, food, or reason to return to earth where your family is already gone and decades have passed while you remain the same age.
I keep thinking about this because there's so much pedantic fact-checking over every single science fiction movie out there these days. It seems like the more accurate a movie tries to be, the more it gets keel-hauled over the glowing glass-sharp cinders of internet technical-knowledge masturbatory watchdogging (think Gravity or Interstellar). What used to be the province of pipe-smoking, smirking ivory tower types, winking condescendingly at "low" culture, is now open to any damn fool who feels the urge to "catch" the writers at some quibbling little unscientific peccadillo. It seems less discouraging to make a brainless Michael Bay-type flick, because at least these get dismissed out of hand, rather than run through the mill.
And the fact is, these fact-checkers, past and present, often don't realize that technology is rapidly catching up with science fiction. They're stuck in a very here-and-now mindset, and develop a sort of tunnel-vision. Science fiction should be about speculation: a casual prognostication on what future human(oid)s will be like, what technologies we'll have, how we'll get to the stars and what we'll find when we get there.
(NB: I'm going to admit, I'm historically more of a Trekkie than a Warsian (Star Trek fan versus Star Wars fan, colloquially); I like the fact that it's more speculative about a realistic future, the characters reminiscing about and idealizing a Past that is our Present. Star Wars is a fantasy set in outer space. The tech is less important than the dream the tech allows for. I mean, space knights? Space rogues? An evil emperor? All they're doing is riding around on modified airplanes instead of unicorns or whatnot. I'm not slamming Star Wars, I'm a huge fan [of the original trilogy]; I'm just saying it's only vaguely speculative, and therefore only vaguely sci-fi).
1. Speed/time/distance
Naturally these three issues are bound together. I won't even attempt to help you understand how big outer space is; no matter how many baseballs inside stadiums are utilized, or driving from New York to Los Angeles, or football fields or city buses or diapers stretching from the earth to the moon three times...you still won't get it. You'll listen politely, and then go back to fantasizing about hopping in your little Ford Intergalactic for a day trip to Mars.
The problem is, even in the black cold depths of space, there's no frame of reference. The stars stay the same, like some kind of three-dimensional screensaver, at least until your reach the Alpha Centauri system, at which point will be four fewer stars in the still-recognizable constellation of Centaurus (it's in the Southern Hemisphere). Hell, you could still navigate by the North Star, if for whatever reason you choose that as your arbitrary reference point. Fire a bullet in a random direction into interstellar space, and there's an overwhelming chance that bullet will go on forever and ever without hitting anything, unable to match even the speed of even our slowest space probes, essentially motionless relative to the size of the universe. Perhaps only lightspeed means anything, and even that's a bit of a stretch: the fastest thing in the universe, a photon, still takes four years to reach Proxima Centauri from earth; traveling onward in a straight line, it would most likely never hit anything else.
Okay, so let's say you think 4.2 years is an acceptable amount of time for space travel. All you need to do is accelerate your spaceship to light speed, correct? Actually, you'd never hit lightspeed - for massive objects, the Universal Constant is an impenetrable barrier. As you approach lightspeed, you begin to literally acquire mass - bizarre, it's true, and seemingly impossible; but this is simply E=mc² here, solved for m - "mass equals the square root of your energy divided by the speed of light". According to this logic, you would eventually have an infinitely massive, infinitely energetic object traveling at the fastest speed possible - such an object cannot exist. It disintegrates. Only its massless particles will be able to achieve lightspeed, while the rest are scattered or annihilated into energy.
Alright, so you achieve 99% lightspeed. Respectable speed. Give it a week or two to ramp up your acceleration to 100g's; continue acceleration for four days until you hit 0.99c, coast for 4 and a half years, then repeat the process in reverse to decelerate. Sweet, now you're at Proxima Centauri. Take a couple pictures, turn the ship around, head back to earth. Total onboard time elapsed: 9 years, four or five months.
Total Earth time elapsed? 80 years.
You've lost your family and everything you've known and loved to "time dilation". This is the worst part of E=mc² (among many, many letdowns): the greater the speed of a ship traveling away from Earth, the less time elapses onboard versus time elapsing on earth. You have nothing to go back to. You're a wanderer in time and space, forever young compared to an aging homeworld.
In summary: you can only accelerate up to the brink of the finite speed of light, which isn't that fast in relation to the size of the universe (and we're not even considering how much fuel this would consume), you'll have to spend a few years traveling, consuming food and resources; and when you get back to earth, no one would remember you.
The Solution: Warp Drive
Now hang on, hang on - I'm not talking about magical Faster Than Lightspeed travel, breaking the "Light Barrier" or whatever. This is the Alcubierre Warp Drive I'm talking about here, son, which is not only theoretically possible, it's actually in development at NASA's Eagle Lab. Granted, they've barely started, but there is a chance a working prototype might be available within 50 years. And it solves all of the above problems by sidestepping the whole issue.
Basically, the Alcubierre system doesn't move the ship itself; instead, it moves spacetime around the ship, like a conveyor belt. A huge bubble of energy is generated - "negative" energy in front, "positive" energy behind - and spacetime flows around the vessel in the direction of "travel". This may seem like a horrible idea (you'll break spacetime!) until you consider how vast spacetime actually is - a little warping here and there ain't gonna wrinkle the fabric. Since the ship is subject to no acceleration, and hence no time dilation, the crew would maintain earth-relative time while traveling light-years in weeks. This is the technology I'm probably most geeked about, because we could be taking cruises to Proxima Centauri, or jaunting around Barnard's Star, and get back in time for the Superbowl.
Now, there are enormous hurtles to contend with. One is "negative" energy - we have some faint inklings on how to produce it, but projecting it is a whole other ball game. Then the sheer energy required for the warp bubble is prohibitive. Even with the latest revisions to the design, the envelope required is projected to be the size of a planet. This becomes awkward if you're plowing through a region of debris - disturb the energy bubble even slightly, and you're in for one hell of a spectacular explosion. Also, because the warp bubble itself is warping spacetime, it cannot be activated near a gravity well, or the resulting distortions could tear the ship apart.
I'm an optimist. No - I'm obsessed. I want warp drive to be a feasible mode of travel. For years scientists have told us, with a slightly satisfied smirk, that we'd need some kind of huge damn "earth ship" where people lived and died for a thousand years just to make it to the nearest habitable planet, and that it was a one-way trip because the human race would probably be kaput by the time they made it back to earth.
Well guess what, scientists? I'm warping next to your stupid earth-ship just so I can laugh at you, on my way back from the sunny shores of Kepler 62f, as your reverted-to-cavemen colonists ook at the "bright sky mammoth".
2. Fuel
As any rocket scientist will tell you, one of the huge problems of moving stuff through outer space is that you have to take your own fuel with you - no gas stations, unless you count the great Acetylene Lakes of Titan. Where you'll invariably get price-gouged. At any rate, with current rocket technology - still the quickest and cheapest way to move hundreds of tons of life-sustaining equipment through the unforgiving void - you'd need to drag along tons of fuel. It's the weird conundrum of the horse dragging its own feed in a cart behind it: the further or faster it goes, the more hay it hauls; the more hay it hauls, the more it has to eat...you get the picture. It's a damn headache. Not only that, but alternative fuel types (fusion, antimatter, atom bombs) are dangerous and require massive shielding and containment structures. Ideally you want most of your structure devoted to crew and supplies, not gigantic radioactive engines.
There are ion propulsion systems currently in use - for instance,
So how do we get around this issue? What kind of motor system is the most efficient?
Solution: EM Drive
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How about a propulsion system that uses no fuel at all?
Check it out here. Apparently, by using microwaves, the EM drive converts electricity directly into thrust. How does it work? Well, scientists don't actually know. All they know is that it produces thrust in a vacuum; barring some seriously stupid math flaws, this thing works. All it needs is enough power. NASA is seriously geeked about this thing; they're talking about reaching the moon in 4 hours, Proxima Centauri (by probe) in 15 years. The current go-to technology for robotic spaceflight, ion propulsion, produces nowhere near the amount of thrust per unit power, and still has to carry some kind of propellant. EM drive is going to revolutionize NASA missions within the next 25 years - maybe less.
3. Food
Food is just fuel for the living crew: the further they have to go, the more fuel they need. The current solution is a bunch of prepackaged pastes and bricks. This stuff is very lightweight. It has a high caloric content, but isn't very filling, tastes dubious, and is expensive to produce. A multi-year mission would require a second ship just to carry the food for the crew.
Cryosleep hibernation is one proposed solution, but I doubt we'll come up with an effective model in the next twenty years. In the meantime, Mars beckons, and we'll have to find a way to feed our crew while they travel there.
Solution: Dehydrated bug powder.
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Insects are extremely efficient at converting food into mass, and need very little space. Heck, they even grow much larger in microgravity/high oxygen environments! Whee! But even if you don't have room to grow them, you can still grind them up into a dense, dry protein powder that doesn't taste too bad. You can flavor it, boil it, bake it, make little bug-shaped cakes out of it. All kinds of stuff. It may not be as light in weight as the current dehydrated stuff, but it's definitely cheaper, and provides more calories per pound than most other foods.
4. Communications
Communications in space runs in the same distance problem. This will become even worse once we develop warp technology; how can we report back to Huston if there's a problem? We could fix the problem and warp back to earth before our message even gets there. It's like sending a postcard from Aruba and having your flight touch down before it arrives back home. Not only that, but your transmitter would have to be more and more powerful the further you got from your control base. At a certain distance you might as well send Morse code via pulsar, hoping an amateur astronomer will notice.
Solution: Quantum Entanglement
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This involves a lot of weird quantum math, and I'm not a quantum mathematician. Here goes: if you bring two elementary particles into close contact, they can become "entangled" - that is, they mirror each other exactly. The weird part is that it's not reliant on distance - no matter where you are in the universe, those two entangled particles will remain entangled. Change one, and the other mirrors its change. You could be 30,000 light-years away, and they'll still be entangled!
Now, I've heard it said that QE is useless for communications because information can't be "sent" from one particle to another. Okay, but what about this? Or this? You can send a fax! Need to send an audio message? Send a visual code that can be read digitally and transferred into audio.
Instantaneous communication can thus occur across light years, even across the universe. There's no reason it couldn't. If I have a problem near Betelgeuse, I can communicate in real time with Huston, and all I have to do is wait for the super-duper slow human engineers to come up with a solution. That's wild and far-out and so mind-boggling I can barely think about it.
This is all just speculation on my part; I'm sure there's some boring buzzkill science explanation as to why we can't use quantum entanglement for this purpose. I just think that at some point, relatively soon, we will be able to use it.
5. Social/psychological problems
Spaceflight is boring. You're trapped in a tiny box with a few other humans. There's nowhere to go except outside, where you can't really feel the wind blowing in your hair. You're never really alone, and yet you're away from everything and everyone you love. The environment is alien, the food is tolerable at best, the view barely changes, and you're stuck doing repetitive tasks. The novelty of "Hey! I'm in outer space!" can only last so long, and then you're basically stuck in the world's loneliest cabin. Naturally, some folks go a little crazy.
There's no real way to test for this, or to predict how people are going to act. Psychological tests can screen out the big, readily apparent stuff; but a lot of issues are latent, and even perfectly healthy, wonderful people can "go toast" (as they say at the South Pole). It's not that people run around murdering each other, it's just that normal cognitive and social function becomes impaired. People walk around like they're asleep, dreams blending into reality; they become like children, forming camps, hoarding food, playing obnoxious games. Truth is, people weren't meant to be cooped up like that. Even the most stoic among us goes crazy, right?
Solution: Spaceborn culture
Star Children? (source)
Except that in some ways, this whole notion of "cabin fever" is somewhat of a cultural thing.
Consider the Inuit - at least traditional Inuit. They don't migrate south for the polar winter, which may have three or four months of complete darkness; instead they wait it out. They spend most of their time inside their dwellings, in very, very close quarters, practically on top of each other. And consider that they're often out hunting or fishing on the ice, where there maybe no one for a hundred miles. They're essentially living in a space capsule. And during this whole time, they never get irritated or try to kill each other.
I might be idealizing the situation; but I think it's relevant that most of the "isolation/confinement" tests were performed on Americans. Americans who, despite our general chuminess, need a lot of elbow-room, and have a combative streak. That's our culture. And despite what you might here, a lot of psychology depends on the culture you grew up in. There are even culture-bound syndromes, strange psychosomatic illnesses specific to a single culture and seen nowhere else.
In addition to cryogenics (nobody can fight or eat or poop while they're in a coma!), I think what's needed for extended space travel is a sort of "spaceborn" culture: humans who were raised in this contained-yet-isolated environment, whose minds are very quiet. They would be able to amuse themselves, and not require constant affirmation from the rest of the group, or feel the need to defend their territory. After a few generations, this culture would be very different from the modern people we're used to; they'd be aloof, efficient, technically minded, and probably have a spiritual life based around their spacecraft, their little world.
This would take a long, long time; we'd probably develop cryogenics before a spaceborn culture arises, and we could avoid the psychological problems that come with long transits.
6. Microgravity
Guess what? Humans were not meant to live in outer space. Weightlessness causes our muscles to atrophy and our bones to rot. Normal bodily functions become problematic. Long-term effects are dramatic and permanent. The problem of microgravity isn't simply being able to walk around normally; it's being able to exist long-term in a normal state.
One solution is to use the force of a ship's constant acceleration to maintain a pleasant 1g of simulated gravity. Problems arise when the ship stops accelerating, or needs to maneuver - everything not velcroed down will proceed to float all over the place. Another idea is the "spinning wheel" that generates 1g of centrifugal force; but this takes up an enormous amount of space, and having moving parts on a spaceship creates all kinds of difficulties.
Solution: Negative energy
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This one's a bit of a stretch, and I'm probably mangling the physics, but hey - that's what this whole post is about! Quantum physics is a graceful gazelle, and I'm a hyena. Let's chow down.
This relates to Warp Drive (see above). Basically, gravity produces negative energy, which is why mass is attracted by it. It's sort of an odd yin-yang duality, where mass is the positive yang, with gravity as its shadow - the two intertwined and never around without the other. Positive energy rushes toward negative energy, pulled toward its center.
Now, if warp drive is theoretically possible, based on the manipulation of negative and positive energy fields to warp spacetime, and positive and negative energy correlate to mass and gravity respectively, one might postulate that you can generate gravity by creating negative energy. And that you might, through the use of exotic material, manipulate that quasi-gravity into any shape you wanted.
Consider this: negative energy plates placed on the inner surface of a starship. Essentially it would be a shielded, layered matrix of exotic matter, with the "active" surface generating a negative energy field, while the "nonactive" surface would have a positive energy field canceling out its effect. The negative energy would be projected to only effect the surface of that plate.
This finagling is necessary because a spacetime is three-dimensional (well, 4-D) though we represent it as a flat sheet: a point of negative energy would pull on everything around it. You'd have to do some clever warping to ensure it only affects a certain area, i.e. the active surface. There's also the question of whether producing negative energy would give off a fatal amount of radiation, or use up too much power. What's necessary is a sort of semipassive system: exotic materials that naturally produce negative energy when a light current runs through them, then disarrange when the current is turned off - sort of like LED crystals.
7. Radiation
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I'm going to start this off by stating something kind of awful: we aren't going to Alpha Centauri. We're not going to Mars. Hell, the best we can do right now is the moon.
The reason is, quite simply, radiation.
"Radiation?" you say, assumed reader. "But I thought we can shield from that! Just throw some lead on it, you're golden."
Here's the trick: we can successfully shield ourselves from radiation...inside the Earth's magnetosphere. Which conveniently extends out to encompass the moon. Even then, astronauts receive an enormous dose, the effects of which are not yet entirely known. But step outside the magnetopause (where the effects of the magnetic field drop off exponentially), and you're in for a world of hurt. Cosmic rays, composed of exotic particles rarely seen on earth, blast through outer space, filling the vacuum.
To imagine how prevalent cosmic rays are in the void, imagine the noise filling a music hall - the rise and fall and wave and blast from each particular instrument. Now imagine every audience member has a rapid-fire Airsoft gun and infinite ammunition, and is required to spray pellets at random throughout the entire performance. Now imagine that someone has one of those toy air-burst guns, and fires from one spot on the balcony every minute. Now imagine the hall is outfitted with disco lights and rave lasers. Now imagine that every single one of these effects, from the sound waves to the plastic pellets to the swirling, streaking lights, causes mutations in the human body. Sounds fun, right? Welcome to outer space. And that's on a normal day - if there isn't a solar event, or a gamma ray burst, or a planet (such as Jupiter) nearby which produces deadly amounts of radiation.
You can shield from this radiation, which is mostly high-energy protons; however, it would require something like several feet of lead shielding embedded with water on every exterior surface. Thus EVA would be next to impossible. Space ships could only be manufactured at "space docks" orbiting the earth, because such heavy vehicles could never achieve escape velocity. Transporting all that shielding would also be a daunting task.
Now, you've probably heard of metamaterials - the so-called "invisibility cloak" materials that can bend waves around themselves, rendering them "invisible" to that particular wavelength. Simple stuff: just make the reflective surface smaller than the wavelength of the EM radiation (same principle for sound or seismic waves). Problem is, cosmic radiation is mostly particles. Particles ignore metamaterials, unless you can somehow shield for mass, which isn't going to happen anytime soon. High-energy-particles (usually protons, but there's a lot of antimatter) smash into a spaceship hull and generate a shower of exotic particles (much like at CERN) which then crash into our gooshy bits and create even more particles, which slowly burn and mutate us from the inside. In order to protect from particles, you need some kind of a magnetic field, like on earth. But that in itself could adversely effect the human crew.
Solution: Plasma shielding, genetic modification/nanobots
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I think the best idea is to somehow charge the hull with plasma. A flow of ionized particles across the surface could neutralize the particles before they penetrate the hull. Superconductors and metamaterials could be utilized to sustain the plasma flow while protecting the crew from the plasma at the same time. But this would require a bit of power, when a ship needs all the power it can get.
The best thing might be to get at the root of the problem: our fragile human bodies. We need to either be a) genetically engineered to withstand radiation, like cockroaches; or b) carry nanobots around with us to repair our cells. I think that a mix of both is best. Future humans will be sort of superhuman anyway, with much tougher (maybe even mechanical) bodies that heal extraordinarily quickly. Nanobots will not only repair our cells and weed out cancer, they could also bolster our immune systems, clear out toxins, help us live longer. Genetic engineering could alter humans to survive on otherwise inhospitable planets, rather than waiting for evolution or adaptation to take hold. Our current problem is that genetic engineering, while commonplace, is still in its infancy - we can make bug-resistant wheat, but radiation-resistant humans are another kettle of fish. And nanobots are still a sort of gee-whiz toy - we can make tiny gears turn and itty bitty bugs crawl around, but they don't quite have things figured out yet.
8. Space debris
If you've seen the movie Gravity, you know that space debris is a huge problem, especially in Low Earth Orbit. Earth is circled by a landfills' worth of space junk, carelessly tossed up there and left to hurl around the planet faster than bullets forever. Gravity dramatized the situation by having the characters detect the debris cloud before it hit, but in reality you'd never see it coming - the only sign that you'd found the powerdrill you lost on your last EVA would be a pair of hilariously power-drill shaped holes in your hull, followed by a less-than-hilarious loss of atmosphere and whatever else it had gone through. Even harmless dust particles become miniature missiles.
Solution: Plasma force field
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Yes, plasma force fields are a real thing. They're little more than university papers at this point, and have significant problems, but could see real development in the next twenty years. And they might be essential for interstellar travel. Remember the radiation mentioned above? A plasma forcefield could absorb the charged particles bombarding us from outer space, as well as vaporizing larger debris. Practical warp travel would require a shield around its warp bubble, because a single impact could collapse the bubble and destroy the ship.
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