Are rockets contributing to climate change?

It’s an interesting conundrum: how does funding for space exploration, which might well hold the solution to many of our problems, account for costs which may be inflicted on the environment? To help shed some light, I’ve enlisted Xander Byrne from the University of Cambridge’s Institute of Astronomy…

Xander - Thanks James. Frank’s question raises a few interesting points. Rocket launches do have an impact on the greenhouse effect - but it's actually not because of the greenhouse gases they emit.

A lot of rockets use kerosene as their fuel which releases CO2 when it's burned. But kerosene is also used to power jet engines. Whereas in a given week there might be 3 or 4 rocket launches, there will also be about 800,000 flights, so compared to that, rocket launches aren't a huge problem.

The difference is that in a rocket launch, the fuel has to be burned so quickly that we have what's called incomplete combustion. The fuel doesn't burn all the way, and you end up with a load of soot being released into the upper atmosphere.

James -  You might not know that soot is actually the second-biggest contributor to global warming after greenhouse gases.

So although some rocket companies will say that the emissions of their rocket launches are much lower than from commercial flights, the amount of soot that they produce is really starting to have an effect, especially since it's partly being released way up in the stratosphere where it tends to stick around for a long time, interfering with the ozone layer and so on.

And the problems don’t stop there…

Xander - There's another fuel which is often used in rocket launches called UDMH (unsymmetrical dimethylhydrazine).

Now this is absolutely horrible stuff - it's very carcinogenic, but it doesn't actually need an ignition system, so it's very easy to power a rocket with it.

But just like kerosene, UDMH also doesn't usually burn completely.

So when the early stages of the rocket fall back to Earth, they often contain a lot of unburned UDMH which just gets spilled out into soil and rivers and so on.

James - In Kazakhstan - where a lot of Russian rockets launch from - they've found very high rates of cancer in towns hundreds of miles away from the launch sites.

So rockets which use this fuel are really bad for people living even remotely nearby.

But space exploration continues nevertheless: the potential upside is huge. After all, humanity’s innate urge to push the boundaries, to go where we haven’t before, has served us fairly well to this point.

Thanks for sending that one in, Frank.