ESA: space tourism greener than ordinary airline flights

Suborbital rocketplane flights of the type planned by Virgin Galactic - and other nascent space-tourism ventures - would have a lower carbon burden than ordinary airline journeys, according to the European Space Agency.

Flight International reports that a preliminary ESA study indicates less CO₂-equivalent emissions per passenger on a suborbital flight than would be produced by a transatlantic crossing in a widebody jet. The ESA isn't yet ready to release details, however, and plans to investigate in more detail.

"I don't want to release our figures before we do the more detailed work," the ESA's Geraldine Naja-Corbin told a symposium last week.

Some part of a suborbital flight would consist of a ballistic trajectory outside the atmosphere, with the spacecraft travelling very fast and subject to very low - almost insignificant - levels of drag. This is why satellites can travel round and round the world for years using no thrust (and emitting no carbon). So there's nothing counter-intuitive about a ballistic flight emitting less exhaust overall than a normal in-atmosphere one, where the plane must keep thrusting the whole time to overcome air resistance.

That said, in order to achieve suborbital speeds and get above the atmosphere in the first place a tourist rocketplane must expend a lot of energy. The ballistic phase of currently-planned services such as Virgin Galactic would be quite brief, too - but then these aren't useful place-to-place journeys, so a comparison of CO₂ equivalent per passenger mile isn't really possible. (Virgin Galactic flights will take off from and return to land at the same place, the New Mexico spaceport.)

Then, if one wants to be picky, one might note that for a typical space-tourism ride a normal customer will make long journeys by normal airline to and from the launch facility, and probably beforehand to undergo training. Such people fly a lot anyway, though.

Still, if the ESA is right about the carbon footprint of space-joyride flights, it would seem at least possible that proper suborbital aerospace vehicles - able to hop mostly exo-atmosphere from London to Sydney, say - would not only be faster than ordinary ones, but potentially greener too.

Unfortunately the only mainstream configuration for such vehicles at present is multi-stage rocket stacks without any ability to land (and the payload area full of nuclear warheads). The present drawing-board generation of tourist spaceplanes won't be making long trips, at least to start with.

Still, not only is there some mild irony in the idea that a nuclear missile is potentially greener than an airliner; there's also the pleasing note that Richard Branson's transport operations may finally have achieved a slight unexpected tint of green from Virgin Galactic, of all things. The bearded would-be right-on biz kingpin's efforts to make his airlines eco-friendly - or anyway give them such an appearance - have mostly been unsuccessful thus far.

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