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A Hybrid Engine For Rockets To Keep Space Clean

Hybrid engines are not just for cars. New hybrid rocket engines, a mixture of solid and liquid fuels, are emerging as one one of the cheapest and cleanest ways to launch into space.

A Hybrid Engine For Rockets To Keep Space Clean
NASA

You might not imagine it, given all the explosive fire you associate with rocket launches, but the propulsion system that launched the world’s first civilian astronaut into space aboard Scaled Composites’ SpaceShipOne in 2004 was a hybrid engine. It’s not the same thing you’d fine in your Prius. Instead, it’s an engine that uses both solid and liquid fuel, which means less cost and less pollution. Virgin Galactic’s own suborbital vehicle, SpaceShip Two, is using the dual system to do away with many of the disadvantages from using just solid or liquid fuel: toxic exhaust, sky-high costs, a tendency to accidentally explode, and an inability to shut down engines after ignition.

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One of the companies pushing this technology, the California-based Space Propulsion Group (SPG), recently test-fired its new hybrid engines, powered by liquid oxygen and paraffin (a simple hydrocarbons used in sculptor’s wax), for 20 seconds at Butte, Montana. The design is lighter, and more powerful than previous versions. Most importantly, says the company, it’s cheaper: five to 10 times cheaper than existing rocket engines.

“We believe propulsion drives the cost of access to space and that complexity generally drives propulsion system cost,” said SPG president and chief technical officer Arif Karabeyoglu said in a statement after the test-fire at Space.com. “By using a commercially available paraffin-based fuel, we have created an economically viable alternative that could significantly reduce the price of space accessibility, as well as help preserve the environment.”

Once refined, this technology could make commercial space travel far more economical and environmentally friendly as space-related industries such as tourism, transportation, defense, and suborbital research get underway. But if the industry does ever take off, it will need to clean up its act. Nature and the Geophysical Research Letters report that even a modest number of private space flights using today’s technology could harm the stratosphere by altering global atmospheric circulation, creating ozone and warming the Earth’s climate reducing polar sea ice by 5–15%.

“There are fundamental limits to how much material human beings can put into orbit without having a significant impact,” says Martin Ross, an atmospheric scientist at the Aerospace Corporation in Los Angeles, California and an author of the study, in Nature.

But the industry is racing ahead. The first private space craft, launched by the Space Exploration Technologies Corporation, or SpaceX of Hawthorne, California, docked with the International Space Station in May 2012. Virgin Galactic also recently signed up its 529th passenger, a milestone that surpasses the total number of people that have entered space since the Russians first sent humans to space in 1961. Commercial flights, said Virgin’s chief Richard Branson, will begin by 2013.

About the author

Michael is a science journalist and co-founder of Publet: a platform to build digital publications that work on every device with analytics that drive the bottom line. He writes for FastCompany, The Economist, Foreign Policy and others on science, economics, and the environment.

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