When it comes to sources of climate change, a handful of activities have the most impact. For American consumers, the current leading causes are energy use in the home, driving and plane travel. Now, something new is set to join the group of worst offenders: space tourism. Virgin Galactic will launch its first rockets next year, and space tourism may soon affect the global climate as much as the world’s entire fleet of subsonic airplanes.

A New Polluting Industry Takes Flight

Space tourism officially began in 2001, when businessman Dennis Tito paid a reported $20 million to take a ride to the International Space Station on a Russian Soyuz spacecraft. By 2004, SpaceShipOne, the world’s first privately funded and operated space vehicle, had been successfully tested. Space Adventures Inc. has been taking reservations for space flights since 1998. But it’s only now that space tourism — also known as “personal spaceflight,” or “citizen space exploration” — is taking off on a larger scale.

In southern New Mexico, Virgin’s new launch base, Spaceport America, is getting ready for its first commercial flights. Virgin Galactic already has more than 500 reservations for the flights, which will take customers higher than 60 miles above the surface of the Earth, where the planet’s atmosphere ends and space begins. Each spaceplane, attached to a jet-powered mothership, flies faster than 2,400 miles per hour. When customers reach space, they’ll have six or seven minutes to float weightlessly in the cabin and view Earth below; then the spaceplane will begin its return to Earth.

Virgin is not alone. XCOR, based in the Mojave desert in California, is developing a spacecraft that can take off and land like a plane. Unlike Virgin’s spaceplane, which seats six passengers, XCOR’s flights will seat just one customer each. They’ve also already booked more than 500 customers. Trials will start this year, and commercial launches are set to begin in 2014. SpaceX was recently cleared for its first standard cargo flight to the International Space Station. In Texas, Armadillo Aerospace is developing a rocket that will take sub-orbital flights, and eventually full-orbital flights. International space tourism companies include Orbital Technologies, a Russian company that is building a four-room guesthouse where customers can stay for several days.

The SpaceX Dragon approaches the International Space Station in May. Image by NASA.

In total, the industry estimates that 13,000 people will have been space tourists by 2021. That pales in comparison to the number of passengers on ordinary airplanes — in the U.S. alone, there will be more than 700 million air passengers in 2012, and by 2024, there will be one billion per year. But the impacts from one rocket flight are so much worse that total airplane and spaceplane travel may be roughly equal contributors to climate change in a decade.

Bringing Soot to Space

Though spaceplanes create carbon dioxide, the biggest impact will come from black carbon, or, as it’s more commonly known, soot. While commercial rockets run on kerosene and liquid oxygen, companies like Virgin Galactic plan to use “hybrid” rocket engines. Not to be confused with hybrid cars, these engines have nothing to do with electricity — they run on synthetic hydrocarbon and nitrous oxide. The engine makes the spaceplanes cheaper to run than typical rockets, but the new spacecraft also emit substantially more black carbon.

Closer to ground, other sources of black carbon are also major contributors to global warming. In the developing world, for example, smoke from open cooking fires is responsible for as much as one-fifth of all human sources of climate change globally. While soot rising from Earth poses serious challenges, the impacts are slightly lessened because rain and other weather helps wash black carbon particles out of the atmosphere. Even black carbon from jets stays in the atmosphere for only days or weeks. In the stratosphere, where there is no rain, particles can remain as long as ten years.

Soot pours off a very different type of rocket—in this case, a toy. Black carbon (the main ingredient of soot) is formed from the incomplete combustion of fuel. Image by Steve Jurvetson/Flickr.

The impacts of black carbon in the stratosphere will be significant. In a 2010 study funded by NASA and the Aerospace Corporation, researchers Martin Ross, Michael Mills and Darin Toohey modeled a potential scenario based on the amount of space traffic expected in coming years. Their computer model examined what would happen if 600 metric tons of black carbon were sent into the atmosphere at Spaceport America in Las Cruces, N.M., where Virgin Galactic will be basing its flights.

Though the black carbon emissions only came from one location, the model showed global impact. The soot stayed within a 10 degree latitude of the launch site, and the majority also stayed in the Northern Hemisphere. But the model showed climates everywhere changed as a result: temperature increased at the poles between 0.2 and 1° Celsius, melting ice caps 5-15 percent; temperature decreased in the tropics and subtropics; and the ozone layer changed in both regions. Globally, the net effect in the model was increased solar energy reaching the Earth. According to the study, effects from the black carbon will far outpace climate change contribution from the spacecrafts’ carbon dioxide emissions (CO2 emissions, according to Virgin Galactic, are roughly similar to an airplane flight across the Atlantic, per passenger).

The study was the first detailed look at how space tourism will impact climate change. Surprisingly, despite the scale of the problem, no further studies have followed. Virgin Galactic has indicated that it thinks the study was inconclusive.

“The report is from a well-respected source and looks at an area of potential environmental impact which is certainly important to study,” the company states on its website. “However it is also an early stage, speculative discussion paper by and for the scientific research community. The lack of any real data and the many unknowns mean that the range of uncertainty in the models is enormous.”

Ross, Mills and Toohey agree that further research is needed. “Overall, these results should not be taken as a precise forecast of the climate response to a specific launch rate of a specific rocket type,” the study states. Instead, the authors say, the simulation should be used to demonstrate how sensitive the atmosphere is to black carbon coming from rockets. Though the numbers from the simulation may end up being different than data from actual rockets, it seems clear that they will have a significant impact.

No Progress After Study’s Results

What are companies doing now to address the challenge? It’s a little surprising that Virgin Galactic isn’t doing more, since the company appears committed to improving sustainability as a whole. The company’s mission includes “transformation in safety, cost and environmental impact of access to space.”

“Virgin Galactic is concerned about the whole environmental impact of space access,” a company representative said. “Using 21st century design and technologies to transform what has been a relatively dirty industry, has been one of our key objectives.”

Virgin Galactic has sought innovative solutions for other environmental challenges; for example, by using a carbon composite material instead of steel, they’ve cut the weight of launch aircraft and spaceships by 75 percent, drastically reducing energy requirements. By launching spacecraft from the air, Virgin has avoided polluting ground-based rocket booster systems. They’ve even built their facilities to LEED standards. But the challenge of black carbon remains to be solved.

Virgin Galactic’s hanger for SpaceShip Two, located in Mojave, Calif., is LEED certified. Image by Virgin Galactic.

The company points out that in comparison to the Space Shuttle, which uses 2.5 million pounds of solid fuel, SpaceShip Two uses only 15,000 pounds of fuel and therefore is responsible for far fewer emissions. But the difference is frequency. The Space Shuttle, which costs around $450 million for each launch, flew only three or four times per year. As space tourism becomes accessible and more common, it could potentially reach 1,000 flights a year or more, making a significant difference in total emissions.

“While the stratospheric emissions from a single suborbital rocket will be small compared to an orbital rocket, total suborbital fleet emissions could become comparable to present day rocket emissions within a decade,” Ross, Mills and Toohey concluded in their 2010 study.

Is six minutes in space, for a handful of very wealthy individuals, worth the potential costs to our atmosphere? Virgin argues that there are some climate benefits to the launch of SpaceShip Two, saying that their vehicles “will provide a unique and near perfect environmental research platform to capture the currently unavailable data that would help the whole industry better understand the effects black carbon as well as many other environmental issues. We have already seen high levels of interest from the science community, including NASA, for SpaceShipTwo as a research platform and it is not unreasonable to expect that work will be undertaken in the early years of commercial flights to help us understand the environmental impact of  black carbon emissions.”

It does not appear that Virgin is actively seeking a solution to reduce black carbon, though they say that their vehicles will continue to improve in terms of environmental performance.

“We are happy that the vehicles we currently have under development represent a major step forward in cleaning up access to space,” said a Virgin representative. “We fully expect the vehicles to evolve over time and improving overall environmental efficiency will certainly be one of the key drivers in that respect for Virgin Galactic.  As explained above – we think our principle initial contribution to the black carbon debate will be to provide the means to make it one that is more informed. Understanding the issue more fully will help the whole industry to seek appropriate solutions.”

Though personal spaceflight companies don’t yet have a solution for black carbon emissions, and there is no new research in the area, study co-author Toohey remains hopeful.

“I trust that these companies, which are headed by highly intelligent, socially responsible entrepreneurs, will demonstrate a high degree of integrity and transparency when it comes to disclosing their environmental footprint,” Toohey said. “I look forward to the eventual release of high-quality observations directly within exhaust plumes in the upper atmosphere that will demonstrate these activities have a negligible impact on the environment.”

Main photo credit: Virgin Galactic