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The posts are in reverse chronological order, and are pegged by topic on the links to the left. For more of an introduction, please see the About this site page listed above.

Thursday, 25 October 2012

Getting into orbit, and what to consider...

We begin with the idea that for some reason you want to get into space.

Why? I don’t know. Maybe you’re bored, maybe you just saw Felix Baumgartner’s record-breaking freefall from 39 km up and you were inspired to do better. (I have issues with the coverage of this event, which I'll talk about later.)

Or maybe, like me, you want to explore the final frontier.

For whatever reason you like best, this series of posts begins with the idea that you want to get to space, and stay there. So, how do we get there?

Well, jumping doesn’t work. Building really tall buildings doesn’t work, and for a reason which will be made clear soon, balloons and airplanes won't work. Not too long ago, a French writer by the name of Jules Verne wrote a story about how we could do it.

In his novel, From the Earth to the Moon, a gun club in Baltimore decides to undertake a project to make a giant cannon which can fire a hollow bullet, carrying people, to the Moon.

It would sound ridiculous except that’s what we do, essentially.

When people like you started wondering how to get up there, how to explore that final frontier, they started looking at what stood in their way, namely gravity.

Since the days of Newton, we’ve had theories, laws, and ideas as to why and how we’re kept Earth-bound. Basically, it all comes down to the Force.

No, not that force; the force of gravity. And while we’re pretty certain living beings don’t actually create it, we’re still uncertain as to how it works, exactly. I have my ideas, but that’s for another time.

In order to figure out how to get to space, we need to have a clear definition of where space begins. The generally accepted definition is that space starts approximately 100 km above sea level. At this point, the atmosphere thins out and an object in this region cannot remain aloft aerodynamically, as planes do. That's why you can't simply use balloons or planes to get into, or rather stay in, space, as they rely upon the surrounding atmosphere to keep them flying. Although several companies are looking into doing something to that effect by essentially diving into space and then coming back down. For more information on that, check this video out! The makers of this, Sci Show, have a lot of great videos and I highly recommend checking them out.

I like this definition of where space begins, so let’s go with it. Obviously, it is up for debate, and one of the reasons it is so difficult to define is because the atmosphere is made of layers of flying particles and gases, which like to mix and don’t just stop at an arbitrary “You are now in space” line. But, for the sake of argument, we'll pretend they do, at 100 km.

Remember when I said I had issues with the news coverage of Felix Baumgartner’s jump? Well, here is an article from a popular science/science fiction website,, perfectly articulating this. While it was a record-breaking achievement, and an awesome testament to the creativity and audacity of humankind, it was not exactly the edge of space, his jump being from the statrosphere, and only about 40% of the way there.

Anyway, before I venture too far off topic, we're looking to get into space, which we now know is about 100 km up. I've included a diagram below, which outlines the situation.

Being in orbit is the ultimate game of tag, except the Earth is always it, always trying to get you, but if you move fast enough, you'll constantly miss the Earth as you go around. Essentially, anything in orbit is in constant freefall, but it's also moving fast enough to stay there. The usual analogy is to imagine you're holding a bucket of water. If you swing it over your head fast enough, the water will stay in the bucket as it flies around. That's like being in orbit. If you don't swing it fast enough, the the water dumps all over you. A simple example, but effective.

So, how fast do you have to move? Well, I've included my calculations below, but at the end of it all, you would have to move at a speed of 7.84 kilometres/second, or 28 000 km/hr, or 15 000 mph in order to achieve orbit at 100 km!

So now you might understand why Jules Verne was not too far off when he imagined giant cannons shooting us into space. The extreme speed alone to overcome Earth's gravity makes getting into space quite difficult.

However, you can get away with moving slightly slower if you cheat and launch toward the east. How does that work? 

Well, imagine a merry-go-round. If you were to jump off a spinning merry-go-round, it's easier and you'll land much farther if you jump in the same direction it's spinning. By doing so, the merry-go-round helps to throw you. If, however, you try jumping against the direction of spin, you won't go as far, and will have a harder time of it. The Earth works the same way. It spins to the east, so you can afford to put less energy into things if you fly in that direction. The Earth will help throw you and you save effort, not a lot, but some.

But, still, getting yourself to that speed is quite difficult and requires a lot of energy. Attached are my calculations for the amount of energy required, but I think it more interesting to think about the sheer amount of fuel.

Looking at all the fuels out there, solid propellent, liquid hydrocarbon, liquid hydrogen/oxygen, even if we choose the fuel with the greatest potential for thrust, the most efficient at getting us to the speeds we need, we still need a lot of it.

Imagine, if you will, that you weigh about 165 pounds, or 75 kg, and that Tony Stark (aka Iron Man), upon hearing about your dream, has given you rocket boots! Using standard equations relating the speed you want to achieve, and the best fuel typical space programs can buy, you would need about 660 kg, 1 456 pounds, half a tonne, or 2 500 gallons of fuel to get into orbit!

Now, you are getting the idea as to why space programs can be so expensive. Things don't always work out as nicely as they do on paper, and while the idea behind a typical launch vehicle is the same as you wearing rocket boots, the implementation is much more complex, not to mention weighs a lot more. Comparing launch vehicles here, the range of the cost to mass ratio is between $2 000-$20 000/kg. Of course, this cost takes into account more things than just fuel, but as you've seen above, even when you limit the thought-experiment to a pretty girl with rocket boots, you'd still have to wear a backpack carrying half a tonne of fuel.

So there you have it! A quick, hard, and dirty look at what it takes to get into space. Moving at a speed of 7.84km/s, using about 9 800 litres, one could achieve orbit at 100 km, in space.

Next time, we'll look into specific orbits and what you need to consider before choosing a launch site. Eventually, we'll address the issue as to why a green dress might not be suitable enough for space.

I hope you've enjoyed our time together, and if you have any questions, thoughts, or concerns, leave a comment here or email me at

Thanks for reading!


Daly, M. "Propulsion", [lecture notes], York University, 2011

Dvorsky, G. "Infographic reveals just how far Felix Baumgartner really was from space", io9, Oct. 2012,

Pickup, A. "Spacewatch: Where does space begin?", Guardian News and Media Limited, 2012,

"Space Tourism", Sci Show,

"Comparison of orbital launch systems", Wikipedia, Oct. 2012,

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