The costs of space exploration

Investigating the carbon footprint of intergalactic flights

For several years now, several of the world’s most influential entrepreneurs have had their sights set on space travel. The likes of Jeff Bezos and Richard Branson are sure of it: they’re going to make interplanetary tourism a thing – and make a huge success of it, too.

This week, we’ll be dissecting the impact of this bizarre trend, which has already become a reality, with the first Blue Origin and Virgin Galactic flights having taken off in 2021. If one thing’s clear, it’s that the vision of these businesses are directly opposed to the pragmatic aims of Midnight Trains, striving simply to revamp the sleeper-train industry. And one thing that really hasn’t been investigated enough is the likely effects of the space-tourism sector on the climate.

In this new kind of space race, the environmental question could be what ends up preventing the industry from really taking off. In the case of Blue Origin, run by Jeff Bezos, and Virgin Galactic, by Richard Branson, the space ships will head out on suborbital flights, reaching the invisible barrier between our planet’s atmosphere and space. Virgin Atlantic’ aim is to surpass that frontier (80km up), while Blue Origin wants to go further, reaching 100km into space. And all that will require a heck of a lot of energy.

The propulsion force of space flights must be sufficiently powerful to carry them beyond the limits of the Earth’s atmosphere, with a speed somewhere between 3,500 and 4,000km/h. This would require that the vehicles burn a colossal amount of rocket fuel. A number of chemical pollutants will be pumped out into the atmosphere during this process. CO2 is among the worst of these: a greenhouse gas largely responsible for the climate catastrophe.

Let’s take the example of Virgin Galactic. SpaceShipTwo – that’s its name – breaks off from a carrier plane, after the latter whisks it out into space for a good hour or so, producing quite a bit of pollution en route. To propel itself forward, the vessel has to burn a mix of nitrogen protoxyde and by-product of polybutadiene.  

Even if those terms mean nothing to you, it suffices to know that an estimate from the Federal Aviation Administration (FAA), that they would produce 27.17 tonnes of CO2 during a full flight. If it were to carry six passengers, that would mean a whopping 4.52 tonnes are emitted per passenger. That would be the equivalent of a round-the-world trip by car. Worst still, the luxury of air travel – we have a few less impactful to suggest to them – on board SpaceShipTwo would represent the equivalent of more than two times the annual individual carbon emission limit, according to the Intergovernmental Panel on Climate Change (IPCC), if we are to keep temperatures just two degrees celsius above pre-industrial levels.

On the surface, things look a little rosier at Jeff Bezos’s Blue Origin. Its New Shepard aircraft will be powered by a mix of liquid oxygen and hydrogen: much greener energy sources, you’d think. In fact, the company boasts: ‘the only side-product of the motor combustion will be water vapour, with no carbon emissions.’ Really?

That’s the question posed by the TreeHugger website, recognised around the world for its studies on climate change. It points out that ‘the hydrogen used has a significant carbon footprint. It concerns grey hydrogen largely obtained by reforming with vapour from natural gas: a process which produces 7kg of CO2 per kilo of hydrogen.’ If a New Shepard flight was to require 24 tonnes of fuel, including a decent proportion of oxygen, TreeHugger concluded that the amount of CO2 produced would be some 93 tonnes. So yet again, if just six passengers were carried by the New Shepard, that would be 15.5 tonnes of CO2 per passenger.

The space-tourism sector may appear to be a rather marginal attraction intended only for a lucky few at this point in time, but that trend could reverse in the years to come, much to the chagrin of the scientific community, given its likely adverse effects on the planet. Tempted? Stick here on Earth, we say, and take the train instead.

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