Skylon is far more than just a CGI dream. It's actually pretty close to flying. This vast, thunderbird esque plane is a rocket jet hybrid. It takes off like a normal plane, flies into space, delivers a cargo of up to 11 tonnes to the ISS or other stations, then flies home to land, refuel and take off again. The secret to Skylon is the sabre engine. Most planes have big heavy engines which operate at limited power to control their temperature. Skylon doesn't. An innovative cooling system
in the nose freezes air from 1000C down to -150C where it is burned with an onboard hydrogen fuel, allowing the engine to be lighter and run at far higher loads, accelerating to 5.4 times the speed of sound at 16 miles high. Once there, it shuts off the now very thin exterior air supply and uses onboard oxygen to rocket the plane into orbit. If it works, It'll be seriously cheap to mass produce, cheap to run, very efficient (it'll use less than a fifth of the fuel of a comparable rocket), won't require much in the way of infrastructure - because it can just use airports - and should be very reliable. And it's being built. The engine precooler, by far the most difficult part of the engineering project, works and has been signed off by the ESA, freeing up millions of pounds in European and British funding. Millions isn't nearly enough, though. If they get the probably billions they need, Skylon could be flying within just a few years, offering cheap, regular,reliable flights for tonnes of cargo and up to 30 passengers into orbit.
To get into space you need thrust. But what if you had a way of beaming thrust from the ground rather than creating it from fuel carried on board? A much lighter and therefore cheaper and more efficient ship. That's what. Lightcraft have a special mirror on their underside which focusses laser light beamed from the ground to a point in the air directly beneath the craft. Their air is heated to 50,000C, ten times hotter than the surface of the sun. The air explodes, and the shockwave pushes the ship up. All the way back in 2000, a group of private and government bodies used a 10 kilowatt laser to lift a 1.8 oz ship 233 feet off the ground. It's estimated that with a 100 megawatt laser and a 1.4m mirror, supply and satellite payloads of up to 100kg could be sent rapidly and very cheaply to the ISS and other platforms.
3. Space Elevator
Most of the problem with getting things into space is that it takes loads of fuel. Partly because a rocket needs to be going really fast to escape the Earth's gravitational pull, partly because fuel is heavy and needs even more fuel to lift it up. So how about a system that actually gets you into space very slowly, and picks up all its fuel en route? Enter the space elevator. Which does exactly what it says on the tin. A cable, up into an orbital platform, upon which ships and satellites can be lifted and sent off on their way using only the tiniest amounts of fuel. Either the cable can be electrified to provide power, or it can be transmitted from the ground via lasers, which overcomes several engineering
There are some problems though. To work, the cable would have to stay in the same position over Earth. That means that the end platform has to be above geostationary orbit- some 36,000 km from Earth. Then, to make sure the lift car doesn't bring the whole system crashing down with it's weight, the cable has to extend further - twice as far - to act as a counterweight at the other end. That's over 70,000km of cable. You could use a large counterweight closer to the orbit, but it would have to be huge - we're talking either capturing an asteroid, building a VERY big space station, or collecting the first cars that ascend the structure.
But the main problem is that cable. At least 36,000km of it, which has to be strong enough to take its own weight and the force of the counterweight, car and cargo, and flexible enough to withstand weather conditions en route. That's no mean feat. In fact, until recently, there were NO materials on Earth which fitted the bill. Carbon nanotubes show promise, being extremely light, strong and flexible - but as yet no one can produce them in nearly long enough strands to even test the theory. The system has its champions though, Japan holds regular space elevator competitions and has pledged to be a leader in any scheme.
2. Project Orion
To space on nuclear bombs! Sounds like dodgy 1950s science fiction? Well check this out. The department of energy tried it. It was called project Orion. The idea was simple, a ship dropped a bomb behind it, the bomb exploded, and the ship rode the shockwave, potentially reaching speeds that would put Saturn, and possibly even Neptune, Pluto and
beyond, within easy reach of astronauts.
The theory was sound, as you can see from these early tests, which used conventional explosives. The real thing would have been vast, several times the size of a Saturn V rocket for a long trip and weighing up to 10,000 tonnes. 800 bombs weighing anything from hundreds to thousands of tonnes would heft the craft into orbit, but that created a problem. A lot of bombs equals a lot of risks. If you want to avoid killing a lot of people, you have to make sure it's safe, and a long way from humanity. Having said that, each launch would be, relatively, not much more polluting than single early nuclear bomb tests.
The most incredible thing, though, is that it could have been built. Keen for more funding from the military, the team behind Orion designed a missile armed, bomb powered battleship and presented it to the Air Force, who eventually bought into the idea. Fairly quickly, though, the US Government decided there was no military purpose for the Orion battleship, that they actually had no need for any spacecraft so large and powerful, and that it would put an unecessary strain on nuclear relations with Russia.
The project was pretty much dead in the water when nuclear space propulsion was eventually banned by the Partial Test Ban Treaty of 1963, putting an official end to Orion's dreams.
1. Alcubierre Drive
This one is ambitious. Really ambitious. We're talking warp drive. The idea is that you can cheat Einstein's Theory of relativity by creating a sort of space time pressure dip in front of a spacecraft, and a wave behind it, pushing the craft along in a bubble in the middle at speeds which, to us mortals, appears faster than light.
Mathematically, it works. Mathematically. It's also pretty efficient. Initially, the amount of energy required to form a bubble that could transport a ship accross the milky way would have been greater than in all the observable universe combined. Which was a problem. Later calculations and streamlining got that down to less than three solar masses to move a few small atoms. More streamlining, and the journey could be done with a Jupiter's worth of energy. The latest calculations by Nasa's Professor Harold White suggest that a Voyager -1 sized spacecraft could suffice. Interesting, but so far, purely theoretical, right? Well, not quite. Professor White has, with support from Nasa, been trying to warp time in the lab and prove that it can be done.
They are using a device called the Michelson-Morley interferometer, which measures space time. If one of the legs of the sensor appear even very slightly longer than the other, that's proof that the system works, and that the drive is possible. Once you've got that, scaling up is *relatively* easy.
Of course, even if we could build a ship, trying to start, steer and most importantly stop something that exists as a bubble within known reality would be quite tricky. But I'd give it a go.