Clean Power

Published on June 1st, 2020 |
by Michael Barnard

June 1st, 2020 by  

SpaceX and NASA did something awesome over the weekend. They successfully launched two astronauts, Bob and Doug — cue Canadian humor clip — to the ISS on the SpaceX Crew Dragon from American soil. This is the first time since July 8th, 2011, when the last Shuttle launch occurred.

This led me to dust off some old calculations I’d done around powering the Shuttle entirely with renewable energy. At the time, I figured that we could turn water into rocket fuel sufficient for a Shuttle launch using a month’s wind power from a small wind farm at a cost of about $285,000, a bit more than market prices but a drop in the bucket compared to the $450 million to $1.5 billion per Space Shuttle launch.

Space Shuttle launching

Space Shuttle launch image courtesy

How does that work out? Let’s start with what most rocket propellant is.

“LOX and liquid hydrogen, used in the Space Shuttle orbiter, the Centaur upper stage of the Atlas V, Saturn V upper stages, the newer Delta IV rocket, the H-IIA rocket, and most stages of the European Ariane 5 rocket.”

LOX is not something you eat with bagels and cream cheese, but liquid oxygen.

So, basically one form of rocket fuel is oxygen and hydrogen. And one of the most common chemical compounds around is H2O, or two hydrogen and one oxygen bound together to form water, which is about as non-combustible as things get. It’s so non-combustible that it’s the most common mechanism used for putting out fires.

Okay, so far, so good. We have water which contains only the two things we need to make rocket fuel. But what about getting at it? Could we do that with renewable energy?

Absolutely, it turns out. Turning water into hydrogen and oxygen gases is done by a process called electrolysis, which unsurprisingly uses electricity. And it’s easy and cheap to make lots of electricity with wind and solar energy, that’s why they are the fastest growing sources of energy globally, with China, for example, having put in almost as much solar energy in the first three months of 2015 [guess when I wrote this Quora answer originally] as exists in the US, and China’s wind power at 115 GW now has more nameplate capacity than all of the US’ nuclear plants and is expected to reach 200 GW by 2020. Then more electricity is required to supercool the hydrogen and oxygen into liquids.

So we can get sufficient electricity and we can use it to turn water into rocket fuel. And hey, when we burn them shoving rockets into space we get water back. That sounds pretty good!

So what’s the kicker? Well, rockets use a lot of fuel. For this, I’ll just turn to the space expert and NASA engineer, Robert Frost, and his detailed assessment of the number of pounds of rocket fuel necessary to propel a pound of mass in Earth’s orbit from sea level.

“So, if our imaginary rocket with a final mass of 1 kg started off at 10.39 kg, then 90.3% of the mass of the rocket was propellant. Our rule of thumb was pretty darn close.”

Even that is a bit of an understatement, because a lot of stuff you throw into orbit is just there to contain the actually useful payload, whether that’s a military stealth satellite that can catch people cheating on their taxes or an as

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