Space; I’m not sure if you’ve noticed, but it’s pretty big.
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So, when you’re choosing how to get somewhere, your choice of transport is rather important. For example, if you wanted to drive the 400,000 km to the moon, it would take you about six Months.
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In August, they announced the discovery of a new planet orbiting our nearest neighbouring star, Proxima Centuari, that has the possibility of being habitable.
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The big question is; can we realistically get there and when we do will it be made of cheese? Because as tasty as that would be, it’s not very practical. Proxima Centuari is just over 4 light years away, which is nothing relative to the size of the universe.
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However, the fastest spacecraft we’ve ever sent out Voyager 1, has only covered 1/600th of a light-year in 30 years.
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At this rate it would take us over 80,000 years to reach Proxima Centauri. So quite a long journey…
But the biggest problem of all is fuel. There is no way we could carry enough mass for regular rocket propulsion so what are the other options? How do you make a futuristic space drive?
The first, very elegant option is a sail. Obviously there is no air out there in vacuum of space but it’s certainly not empty, there are all kinds of particles and waves shooting around. A solar sail works through solar radiation pressure. When a light particle, a photon, hits a mirrored surface, it reflects but the mirror gets a tiny backwards reflection reaction force as well, like if you threw a tennis ball at an elephant when it was sitting on the ice, the elephant would slide away ever so slightly.
It was Johannes Kepler who first noticed this phenomenon in 1610
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when he saw that all comet tails pointed away from the sun, no matter where in the solar system they came from.
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The force behind all these particles reflecting on the sails realy move up.
Any mission to Mars would need to account for a few thousand miles of displacement thanks to this photon wind. The IKAROS was launched in May 2010 and using a super thin sail, 7.5-micrometres thick and 14 by 14 meters square, it reached Venus in 6 months, passing by at almost 400 km/h.
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Since it will keep accelerating, it’s probably 5 or 6 times that speed by now as it carries on out into space.
Photons are not the only part of the wind we could use them though since there are proposals for magnetic sails and electric sails that would harness the charged particles emitted by the Sun. Similarly to the solar sail, they could use the particle reflections from a magnetic or electric field to gain momentum.
NASA is currently working on an E-sail idea that would have around 20 wires sticking out of a central hub.
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The wires would be just a millimeter thick but almost 20 km long and the sail would spin to keep them all stretched out. Like a gigantic spider web propelling the spacecraft along, as terrifying as that would be for arachnophobes, it sure makes for a really futuristic looking space vessel.
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Sure a sail is basically free power but by the time you’ve blown your way across the high seas from Dublin to New York, you’re definitely too late for check in and you may have lost a leg to sharks. So we might need something a little bit faster in space.
Introducing ion thrusters;
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Ions are atoms or molecules that have a positive or negative charge because their number of protons and electrons don’t match as they do in a regular atom or molecule. Most ion drives involve bombarding the fuel with electrons, so to knock free other electrons and create a plasma of positive ions and free Electrons.
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The plasma is like a gas but it can be controlled by an electric field so the drive accelerates this plasma out the exhaust to create thrust.
It’s nowhere near the power of a rocket drive, you wouldn’t even be able to push over a mouse, let alone launch a spacecraft within Earth’s atmosphere. Deep Space 1 launched in 1998
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and it had an ion drive but its thrust was about the same strength as the downward force exerted by earth’s gravity on one sheet of paper.
The Dawn probe was sent out to explore Vesta and then Ceres, an asteroid and dwarf planet out in the asteroid belt. Its ion drive used just 385 kg of xenon, which is the normal fuel, to increase its velocity by 10 kilometers a second. So it all adds up, but we’re still a few years off being able to use ion thrusters to travel vast distances.
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But an increasingly more exciting prospect is the emergence of the EM drive. British scientist, Roger Shawyer,
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designed the drive in 2001 and it appears to create thrust without releasing any propellant, something we had thought was impossible. Well, most scientists still do believe it’s impossible and have treated it highly suspiciously. The way it works is… I’m going to be honest here, I don’t understand this one, because it seems to break physics so clearly that I think Roger Shawyer has made a deal with Space Satan.
But, here’s the general overview. The Em drive would use solar power to create Microwaves. These microwaves go into a blunted cone chamber called a resonant cavity thruster. The microwaves bounce off the walls and exert a larger force on the wide end than on the narrow end, creating thrust. Why it does this is the big argument and some say it’s down to an as-yet-unproven concept called Unruh radiation, which is predicted by Einstein’s General Relativity but hasn’t been observed so far.
Trying to understand this is like being 4 years old and listening to your parents spell things they don’t want you hear. What is this B-E-D and why am I going? Is it good? Can I take teddy? Does it obey Newton’s Second Law? There are now plans to soon send an Em Drive into space to see if it really does work up there in the vacuum so we can argue about something else instead.
Roger Shawyer is exactly what you’d expect a scientist to look like, a disheveled white haired old man.
But occasionally, ideas come from much more unexpected places.
At just 19, Egyptian physicist Aisha Mustafa
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proposed an idea for a drive that would use the very vacuum of space itself to provide thrust. Now, a vacuum is not as empty as we initially believed. Every part of space is filled with virtual particles. Despite the name, they do exist, just for incredibly tiny periods of time.
In 1948, Hendrik Casimir
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predicted that these virtual particles could result in real physical forces. The way to observe them is to put two reflective mirrors just nano-meters apart, in a vacuum.
Their close proximity means that you limit the ways electromagnetic vibration can happen in this space, compared to the space on the outside of the two mirrors, where there are more modes of vibration so you get more pressure on the outside and a force is created, pushing the mirrors together. It’s called the static Casimir Effect.
In 1970, Gerald Moore
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came up with the dynamic Casimir Effect, that involved moving this pair of mirrors at very high speed, close to light speed. The field would not have time to adjust at this velocity and it could produce real photons. This is where the thrust comes from in Mustafa’s Drive.
These are just a few of the leading ideas for futuristic space drives, there are plenty of others banging around. There’s the Bussard ramjet which would use thousand-kilometer-wide fields to scoop up all the hydrogen atoms that are scattered through space, before compressing them enough so that you get nuclear fusion.
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There’s the proposed Alcubierre warp drive
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which would contract space in front of it and expand space behind it, possibly moving faster than the speed of light.
It’s actually mathematically possible but that doesn’t mean it’s going to happen. It would require “exotic matter”, and not the kind that you find under a teenage boy’s bed. Of course, scientists are a complicated bunch and maybe they have overlooked an obvious solution; if mankind really want to travel to the stars, perhaps we just all need to get out and push.
But seriously, it’s only a matter of time before we can travel as fast or even faster than the speed of light, it will happen. The solution could come from a leading scientist or one of those annoyingly genius-level kids at a school science fair. When it does happen we will have a whole universe to explore Thanks for the reading