Locating spaceports in the UK - a question of safety and vectors

When you launch into space, you need all the help you can get.  That's why communications and weather satellites are launched to geostationary orbit from the equator.  Since the Earth is spinning faster at the equator, it gives a bigger boost, or delta-v, to go towards the final velocity of the satellite in orbit.  The spin of the Earth means that the rockets are given a boost to the East and therefore they are normally launched from the East coast of a country so that should anything fall back to Earth, it will fall over the sea, rather than land.

You can work out this delta-v just by knowing the radius of the Earth (about 6400 km) and the length of the day.  Speed = distance / time gives you 460 metres per second, or around 1,000 mph.  By multiplying by the cosine of the latitude, you can find the speed at any latitude.  So for York, at nearly 54 degrees, this gives 270 m/s. 

Recent government legislation has now made it possible for rockets to be launched to space from the UK.  If you do an online search for UK spaceports, you will find that most of the proposed sites are located on the West coast of the UK.  So why the West coast and not the East, I hear you say?  Well it's because the only satellites we are likely to launch from the UK will go into a polar orbit, rather than geostationary.  With a polar orbit, you want your satellite to be travelling North-South or South-North (doesn't really matter how you say it) - so any East-West velocity vector is actually unwanted.  So if we point our rockets North-West, or South-West when we launch and make sure our West velocity vector cancels out our East vector (due to the spin of the Earth), then we're on our way - and if we are not on our way then at least we are crashing in the sea and not on land. 

Here's a related question to pose to your students: how far from the geographic North Pole would you have to be so that you could run to the West at the same speed as the Earth is rotating to the East?  Effectively running to stand still (cue 1980s U2 track).


Age14-16, 16-19
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