WHY THIS MATTERS IN BRIEF
As Elon Musk “tries to save the planet” on one hand, on the other people criticise him for SpaceX’s rocket emissions but there’s a twist to the story.
One of the most common questions I get asked when showing audiences Elon Musks’ latest SpaceX innovations, such as his inter-continental rocket system which will transport people from one side of the planet to the other in 40 minutes or less at Mach 27, is how much damage their emissions will do to the environment. And it’s a great question because as everyone knows rocket emissions aren’t environmentally friendly in any way – including the so called “green” ones developed by NASA and SpaceX that you can FedEx.
As it turns out though Musk foresaw this problem and has been developing Methane powered Raptor engines which, as you’ll see, amazingly are carbon neutral. Methane also happens to be a fuel that the Russian space program first experimented with in the 1960’s but that noone else could get to work. History, it seems, has a funny way of repeating itself – in this case for the better.
Currently we are unsure as to exactly how much spaceflight accounts for total greenhouse gas emissions per year, but there is consensus that it would be a very small number, several orders of magnitude less than 1%. And while not zero this is an extremely negligible amount especially when compared to emissions that come from agriculture which accounts for 24%, or energy production which accounts for 25%.
Despite this small number though the concern is that this number will rise “astronomically” as rocket reusability drives launch prices down and launches become increasingly more common – something that’s going to be compounded by SpaceX’s plans to take on the airline industry come 2024 and use its newest Starship rocket, which just successfully completed its tests, for point-to-point transportation here on Earth. And at face value all this seems like it could be catastrophic for the environment. But as it turns out it needn’t be that way thanks to some science, engineering, and good old human ingenuity.
At SpaceX’s event late last month they unveiled their plan for clean fuel production. The idea is that Starship will unconventionally run on Methane and Oxidizer. One of the reasons why SpaceX chose Methane (CH4) as the fuel is because it can be readily produced on Mars, as well as Earth, although it’s worth noting, however, that methane is incredibly abundant on earth, so SpaceX will likely not need to produce it here. During the presentation Musk gave a brief synopsis of the process they will be using, but left out a few details.
In order to create both the oxygen and methane fuel on Mars, SpaceX will need to collect water and carbon dioxide. Mars’ atmosphere is 95% carbon dioxide, and frozen water is plentiful on the poles, making them both relatively easy to collect. Then, they will split the water into hydrogen and oxygen gas through a process known as electrolysis. Electrolysis is naturally energy intensive, which is where their plan to use solar energy comes into play. After that, they will add the hydrogen gas to carbon dioxide that they’ve collected from either Mars or Earth and run them both through something called the Sebatier Process, which will produce methane, and water as a side product. All that’s left is to liquify the methane and oxygen gas through a cryogenic system, and the rocket has all the fuel it needs!
Since SpaceX will use solar power to provide energy to pull carbon dioxide out of the atmosphere on both Earth and Mars, this would have the effect of mitigating emissions here on our planet – as well as altering the atmosphere of Mars.
Furthermore, when the fuel burns, it releases water and carbon dioxide back into the atmosphere, leaving both open to re-collection by SpaceX who can then theoretically recycle the same materials over and over again without creating any net emissions!
So, as you can see, by using this method SpaceX has essentially developed a carbon-neutral propulsion system, which is not only a first for the space industry, but it would also, ironically, make travelling from one side of the planet to the other by rocket more environmentally friendly, and a hell of a lot faster, than taking the same journey by plane. Until planes turn electric … but that’s another story.