March 18, 2016

# How many Teslas does it take to make up for a SpaceX launch?

Space exploration is awesome and all, and wouldn’t space tourism be even cooler? Who, given the opportunity, wouldn’t want the chance to view the Earth from space?

Commercial spaceflight is in its infancy, but some have speculated that 2016 will be the year space tourism goes mainstream. Mainstream here is relative, of course: moving from the realm of the “very very rich” to that of the “merely really rich.”

So it is a good time to ask: just how carbon intensive is a space launch? Let’s consider the Falcon 9 rocket from SpaceX. According to SpaceFlight101.com, the Falcon 9 v. 1.1 uses about 147,000 kg of RP-1 rocket fuel (similar to kerosene) and 341,000 kg of liquid oxygen, about 80% in the first stage and the rest in the second stage. If we assume the rocket fuel is similar to Jet-A, with a lower heating value of 43.2 MJ/kg and “well to wake” emissions of 85 gCO_{2}-e/MJ (source), then the GHG emissions associated with the fuel are 147,000 * 43.2 * 85 = 540 x 10^{6} gCO_{2}-e or 540 metric tonnes equivalent.

But that’s not all. Producing liquid oxygen takes energy too, to the tune of 638 kWh per tonne. Assuming 470 g of CO_{2} emitted for each kWh of electricity (based on EIA numbers for U.S. generation and emissions in 2015), then the emissions associated with producing the liquid oxygen are 341 * 638 * 470 = 102 x 10^{6} gCO_{2}, or 102 tonnes.

Putting the fuel and oxidant together, we get 640 metric tonnes CO_{2}-equivalent per launch.

To put these numbers in perspective, let’s estimate the lifetime GHG savings of a Tesla Model S P90D (0.36 kWh / mile on electricity) relative to a BMW M5 (17 mpg on gasoline). There are other ways to compare these cars, of course:

… but I digress.

Assuming a 150,000 mile life, and emissions intensity of 0.47 kg/kWh for electricity and 11 kg/gal for gasoline, we can estimate that the M5 will emit 97 tonnes CO_{2}-equivalent over its life, while the Model S will emit 25 tonnes (including upstream emissions in both cases, of course). Thus, a Model S saves the equivalent of about 62 tonnes of CO_{2} over a 150,000 mile life.

In other words, it takes about **10 Teslas** to offset the emissions of one Falcon 9 launch. So, if you’re considering a trip to orbit with 4 of your friends… realize that you’ll each be releasing more GHGs than an EV can save you in 25 years’ worth of driving.

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