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What will space tourism mean for climate change?

The views expressed are those of the author and are not necessarily those of Scientific American.

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SpaceShipTwo test flightIf space tourism ever becomes big business, as plenty of well-heeled backers hope, the danger of the enterprise might not be confined to those who book a ride to the edge of space. A robust suborbital spaceflight industry could deposit enough soot in the stratosphere to cause significant global climate change, according to a new study.

Although the study, set to be published in Geophysical Research Letters, does not mention spaceflight companies by name, the authors seem to have Richard Branson’s Virgin Galactic and its competitors in mind. The researchers modeled climate effects from hybrid motors, the type used by Virgin Galactic, launching repeatedly from southern New Mexico, where Virgin Galactic has a 20-year lease at Spaceport America, a publicly funded commercial spaceport.

Hybrid motors using synthetic solid hydrocarbons as a fuel and nitrous oxide as an oxidizer would inject black carbon soot into the stratosphere, explain the study’s authors, Martin Ross of the nonprofit Aerospace Corporation, Michael Mills of the National Center for Atmospheric Research, and Darin Toohey of the University of Colorado at Boulder.

If the space tourism industry matures to the point that 1,000 hybrid-powered suborbital flights depart annually, those trips would deposit roughly 600 metric tons of soot into the stratosphere each year. Over decades of launches, those emissions would form a persistent and asymmetric cloud over the northern hemisphere that could impact atmospheric circulation and regional temperatures far more than the greenhouse gases released into the stratosphere by those same flights.

In a 40-year climate model incorporating rocket soot, ozone concentrations decreased at the tropics and increased at high latitudes. In midlatitudes of the northern hemisphere, where the carbon cloud would effectively act as a sunshade, temperatures fell by about 0.4 degree Celsius. That might sound like a welcome offset to the effects of rising greenhouse gas concentrations, which are expected to raise average global temperatures in the coming decades, were it not for the fact that rocket soot also had the effect of warming both poles in the researchers’ climate model, boosting temperatures there by nearly a full degree C in local winter.

The specific climate outcomes rest on complex modeling and a series of assumptions that will need refining, specifically regarding the amount of carbon in hybrid exhaust and the interplay between climate changes caused by stratospheric soot and those caused by future increases in global greenhouse gases independent of tourism launches. Nevertheless, the researchers warn, "rocket emissions on this scale clearly cross a threshold to be considered a human-influenced climate impact of global importance."

Photo from a Virgin Galactic glide test: Mark Greenberg/Virgin Galactic

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  1. 1. dvaudio 11:09 am 10/23/2010

    Oh Good Lord….you people worry about the dumbest things! LOL

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  2. 2. BoRon 12:06 pm 10/23/2010

    Those people worry about crazy stuff, invisible demons like UV light, radon gas, lead in paint and gasoline. You, apparently, worry about more important things like your clothing and high tech gadgets. Perhaps you should help them prioritize.

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  3. 3. quincykim 3:54 pm 10/23/2010

    "…to the point that 1,000 hybrid-powered suborbital flights depart annually…"

    That’s 3 per day, every day, all year long. Is that a reasonable estimate? Based on what?

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  4. 4. loopsyel 7:42 pm 10/23/2010

    "If the space tourism industry matures…"

    That’s what it’s based on, the first part of the sentence. That is how many flights it will take to deposit that much soot. No one knows how many flights there will be in a year, and they never said that there would be any certain number. But apparently 1000 per year will make that much soot.

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  5. 5. bloomingdedalus 10:39 pm 10/23/2010

    So, run the space tourism industry on hydrogen like we run spaceflights on now. Of course, one still has to pollute to perform electrolysis on water.

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  6. 6. Orkneygal 7:21 am 10/24/2010

    Why doesn’t this organisation report on real matters of scientific interest/

    Such as-

    Where is the missing Tropical Tropospheric Hot Spot and was is the implication for that for the creditability of the IPCC GCM models of climate?

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  7. 7. dbtinc 8:39 am 10/24/2010

    Oh my, someone has way too much time on their hands. You know what I’m worried about? What happens if we all stop eating beef thus reducing the cow population and simultaneously eliminating cow flatulence thus helping to cause global cooling. OMG, I need to write a senseless article for SA!

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  8. 8. Snowray 1:08 pm 10/24/2010

    I wish that those whom love to see all the bad, WHEN AND IF certain conditions exist, would get a life and live with what does exist! The Earth is a living body that is constantly going through cycles and periods of cooling and heating. Yes, we humans are acting in a way that is not consistent with our position as stewards of the planet. What we must do to bring us to actions that will help the planet does not mean that we should enact laws that would be a cash cow for some individuals or organizations.

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  9. 9. seeqer 11:53 pm 10/24/2010

    The pollutants would be mostly soot and aerosols. While not exactly GOOD for the environment, these produce, mostly cooling effects. Not something to worry about right now, considering the warming effects of CO2 that we’re dealing with. I’d be much more worried about the damage being done to the Ozone layer.

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  10. 10. Dr. Strangelove 10:31 pm 10/29/2010

    I thought about these non-rocket propulsion systems. An abrupt acceleration like the Jules Verne big gun method would kill the passengers, the high g’s will break their bones. A gradual acceleration like a centrifugal rail or slingshot would produce so much force that it would break the steel rail or cable before it reaches orbital speed (18,000 mph). We currently have no material strong enough to withstand the pressure except for carbon nanotubes. But this is not yet produced in large scale.

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