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The Orion spacecraft. Via Wikipedia

One day, for whatever reason… we will have to leave this Solar System

The human race, as it has always been, is on course for extinction. The Sun will lumber through its life cycle and, in the process of this, will engulf the Earth and destroy everything on it. This isn’t exactly new information and it’s one of the reasons why the continuing development of space exploration is essential to the survival of our species (and all others bound to this planet for that matter). One day, for whatever reason, without the creation of an invulnerable shield and a way to get energy without the Sun, we will have to leave this Solar System.

A design for Orion Pulse Unit. Via Wikipedia

This idea was slightly covered in xkcd’s “What If” weekly post entitled Everybody Out. This piece attempted to answer the question of whether or not there is enough energy to remove the entire population off of Earth. After some calculations in regards to the use of chemical propulsion (ie the same technology we use now to launch satellites and spaceships), just to move the weight of all the people (not including the rocket, fuel or anything else) we would need 8 petawatt-hours, or 5% of the world’s annual energy consumption.

. One of the fundamental issues surrounding [rocket science] is the fact that rockets need to carry the weight of the fuel itself.

Rocket science, as you probably know, is not exactly simple. One of the fundamental issues surrounding it is the fact that rockets need to carry the weight of the fuel itself. This suggest the creation of a never ending loop of increasing the necessary amount of fuel to carry the increasing overall weight due to extra fuel. This problem is solved using calculations based on the fact that the weight of the ship will decrease as fuel is burnt. As you can imagine, it is not the most efficient of methods.

At the end of the “What If” piece, we are given an estimation for the amount of fuel necessary to lift the entire weight of the population (roughly 400 million tons of flesh, bones and hair) would amount to tens of trillions of tons of fuel.It would take up a huge proportion of all hydrocarbon fuels on the planet. Of course, you could suggest we could use alternative fuels, but we still have to consider the weight for the ship, water, food and anything else we’d like to bring (xkcd’s article points out that there are about a million tons of pet dog just in the US). The article sums its verdict up with this sentence, “It’s not necessarily completely impossible, but it’s certainly outside the realm of plausibility.”

Obviously, the above example is taking things to the extreme, but it highlights the point that current propulsion systems are generally not that great. In the event of a global exodus, we would have to leave a hell of a lot of people behind without some new technology or, in this case, the revival of an old one.  In my opinion, the most viable alternative is also the one that sounds the most insane. It is the idea that we should launch ourselves into space by riding the shock waves of nuclear bombs.

Freeman Dyson summing up the mad genius stereotype. Via Wikipedia

Led by physicists Ted Taylor and Freeman Dyson, Project Orion began in 1958 and is a perfect example of how close madness and genius become. The idea of nuclear propulsion was first proposed by Stanislaw Ulam way back in 1946. A year later, Ulam and F. Reines made the first calculations. The project came to end in 1963 in response to a lack of political support due to fears of nuclear fallout and the introduction of the Partial Test Ban Treaty. Admittedly, in a world continuously in fear of all-out nuclear war, the idea of propelling spaceships with radioactive bombs was hard for people to get behind.

So how does it work? You would expect anything within the vicinity of a nuclear explosion would be destroyed, but not in this case. Project Orion designed a shield that would be able to harness the propulsion of the shockwave and thus keep itself ahead of the explosion itself. On the face of it, it is a pretty simple concept. Of course meticulous calculations had to be done to get a viable design completed. Dyson was very hopeful about this project saying, “…a Saturn V bears the same relation to an Orion ship as the majestic airships of the 1930’s bore to the Boeing 707”.

Why would an Orion spaceship be so much better? Well, it is the fact that it can combine a high exhaust velocity with massive levels of thrust, which is something rocket propulsions cannot do easily. This means a nuclear propulsion system is by far much more efficient and requires significantly less fuel as seen in this table looking at possible payload weights demonstrates:

As you can see, as the journey length increases the Saturn V rocket becomes more and more laughable. Of course, you might say that the Saturn V is out of date and that surely more modern rockets perform better. Well, in fact,  to this day, the Saturn V holds the record for the heaviest launch vehicle payload. If ever tested, an Orion spaceship would have blown it out of the water.

Governments should be investing more and more in viable interplanetary technology

It is a shame the project was discontinued when it was. It was clearly a visionary idea that would have revolutionised space travel for the future. What’s the problem with a bit of fallout when the Earth is going to be destroyed? Dyson managed to work out the essentials for lifting 8,000,000 tons (easily the weight of a city) into space using Orion methods. This could easily be achieved considering the stockpiles of nuclear weapons around the world. Carl Sagan himself made the point that it would be a good way to use them up.

The solution to saving mankind is the thing that came closest to ending it. Governments should be investing more and more in viable interplanetary technology and I would wager that nuclear propulsion is our best shot. Paranoid fears about radiation should be dismissed can considered in a more reasoned way. We should not be eschewing technology because of outdated Cold War fears.