The Saturn V used for the Apollo missions burned 203,000 gallons of RP-1 (basically kerosene) in its first stage. At 820 kg/m^3, that’s 630 metric tons of fuel. Liquid hydrocarbons tend to be close to CxH2x, or about 85% carbon by mass, so that’s 536 metric tons of carbon, which yields 1965 tons CO2 when burned, or 655 TonCO2/astronaut. Obviously that’s not personal consumption, but it is a lot of carbon in the atmosphere.
The emerging space tourism industry, on the other hand, is primarily personal consumption. I’d love to take the trip, but I’d be a little put off if the consequences of seeing the big blue marble from above were to make a major contribution to climate change. So, what are the consequences?
Apparently, I’m not the only one to wonder. Steven Fawkes writes at The Space Review, “A calculation for the carbon dioxide emissions of an orbital trip to the ISS on a Soyuz launcher suggests the emissions are 143 tonnes per passenger.” I’m guessing that’s tons of CO2 rather than carbon, given the lower orbital ambitions than Apollo. Fawkes goes on, ” Clearly any scaling up of orbital tourism will not use Soyuz technology.” Hope not.
The Astrium space plane is one alternative. I’ve read that half of its 18 ton takeoff weight is fuel, a mix of methane and conventional jet fuel. Presumably that accounting also includes oxidizer, so a wild guess might be 5 tons carbon or 19 tons CO2, divided by four passengers is a little less than 5 TonCO2/astronaut.
It’s harder to find information on other options, but for Virgin Galactic’s SpaceShipTwo, Richard Branson claims,
“If you’re going to build a spaceship, you’ve got to build a green spaceship,” Branson said, adding that the carbon dioxide output from a single spaceflight is on par with those of a business class seat aboard commercial aircraft.
Hmm … a business class seat to where? Apparently, transatlantic: ‘Eight people [on SS2] will have the same CO2 output, quite precisely, as a business-class seat on Virgin Atlantic on a New York-to-London flight.’ A nice review of offset companies indicates that Atmosfair and myclimate use emissions factors of 1.4x and 1.5x for business class, based on seat space allocation, but that “Further research has shown that first class travel on long haul flights could have an impact 6 times as large as an economy traveler.” Presumably the latter is a revenue-based allocation, which makes more sense. Depending on the accounting then, that would put SpaceShipTwo somewhere between 1 and 6 TonCO2/astronaut. SpaceShipOne burned rubber and nitrous oxide, so there may also be non-carbon greenhouse gases involved.
Relative Emissions, TonCO2/person (Guesstimates)
So, it looks like space tourism isn’t dramatically worse than other exotic tourism (like an Antarctic expedition, my yardstick for “it became necessary to destroy the place in order to photograph the place” irony). In fact, given the outlandish cost ($200,000 for a ride on SpaceShipTwo), the cost of emissions offsets would hardly be noticed. One could allay concerns about additionality and leakage by purchasing, say, 100 tons of offsets for less than 1% of the spacefare.