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Image: Getty Images/The Spinoff
Image: Getty Images/The Spinoff

ScienceApril 9, 2021

Are rocket launches rubbishing our backyard?

Image: Getty Images/The Spinoff
Image: Getty Images/The Spinoff

Three… two… one… blast-off! They’re an incredible sight, but what’s the impact of rocket launches on the environment? Mirjam Guesgen investigates.

Commercial space flights, moon colonies and missions to Mars are all exciting prospects. Some of them are even being helped along by New Zealand companies

Rocket launches are loud, ground-shaking, smoggy events and after takeoff, rockets will ditch some of their components, leaving them to crash into the ocean. 

Concerns have been raised about the environmental impact of rocket launches, including the effects on our own backyard. So just how bad are they for the environment?

The stuff that comes out the flamey end

Let’s think about the smoggy stuff first. How much of an impact rocket emissions make on the environment depends a lot on the type of fuel used. 

The rockets fired off from New Zealand use a mix of liquid oxygen (LOx) and kerosene fuels. LOx is pretty good environmentally speaking since burning it just produces water vapour. It’s also usually burned in the second stage of launches, where the rocket is higher up in the atmosphere and has less of an impact.

Kerosene is also not terrible as far as rocket fuel goes, but burning it does release carbon dioxide and soot into the atmosphere, both of which break down our UV-shielding ozone layer. A recent scientific review of its effects concluded that kerosene will “likely have a negligible impact on global climate”.

That same review also points out that emissions from rocket launches are dwarfed by emissions from global air travel, even though rocket launches spew out so much more at a time. With commercial space flights on the horizon though, the authors say we’ll need to keep reassessing the fuels’ long-term environmental impact.

As well as what’s happening up in the clouds, there are also impacts locally when a rocket fires off.

Rocket launches are incredibly noisy and release shock waves that can damage the rocket, payload or surrounding launch pad. To muffle the sound, engineers will shoot olympic-swimming-pool amounts of water over the launch pad.

Solid rocket fuels (currently not used for New Zealand’s rockets) can mix with that water and make acid rain. “A heck of a lot of those compounds [in solid rocket fuel] are really nasty and highly toxic,” says Chris Hickey, a marine chemist and toxicologist with Niwa.

But again, fuel type is key. Kerosene has less of a negative effect than these solid rocket fuels, but its effects near the launch site haven’t been studied in detail. LOx will have next to none since all it lets off is water vapour.

All fuels let off nitrogen oxides though. Nitrogen can build up in nearby lakes or estuaries, loading the water up with nutrients that eventually kill the aquatic life in them.

A Rocket Lab launch in Māhia in 2018 (Photo: Supplied)

The noise

The noise from a launch is around 180 decibels (we’re talking louder than the level needed to cause irreversible hearing damage) and lasts for about two minutes. Nasa astronaut Kay Hire has described the sound as physically hitting you.

Studies from New Zealand and abroad show that loud and ongoing noise can directly physically harm animals, leading to hearing loss, as well as making animals more stressed, or flushing them out of areas where they might breed, feed or nest. 

For example, a recent study found that fewer birds hang out in noisy areas of Auckland. In that study “noisy” meant around 58 decibels, which is magnitudes quieter than the near-200 decibels expected from a space launch. 

The effect of noise on ocean life is potentially even more damaging. “All marine life is tuned to its acoustic environment,” says marine scientist Matthew Pine. “Pretty much every single life function, whether it’s feeding, navigating, staying together in a school or looking out for predators is related to sound.” 

Noise has the added disadvantage of travelling really well underwater, up to hundreds of kilometres, says Pine. He suspects that a rocket launchpad near the ocean, like the one at New Zealand’s launch site in Māhia, could create noise loud enough and vibrations strong enough to travel into the water, although he hasn’t tested this theory. 

A recent review of thousands of scientific studies concluded that noise from human sources negatively affects marine life, although animals are unlikely to die from it.

Hapū from around Māhia say they’ve already noticed an absence of local birds and kaimoana.  

The only consolation when it comes to noise is that its effects seem to be reversible. New Zealand’s lockdown was a perfect case study for this, says Pine, as we saw birds and marine life returning to areas where they were seldom or less often seen. “The good thing is that sound doesn’t linger,” he said.

Nasa too has stated that local birds and mice are minimally affected by launches and that the animals seem to act normally afterwards.

The bits that drop off

Part of boosting a rocket into space is ditching the bits that are no longer needed, like used-up fuel tanks. For New Zealand’s launches, it’s estimated that about 40 tonnes of material drops into the ocean per launch, some weighing up to 360kg.

Those chunks could directly hit marine life or could kill animals if they accidentally eat bits of the debris, according to an assessment done by Niwa. The noise from the rocket parts hitting the water could also cause hearing loss or make the animals flee, although temporarily.

The report also notes that ditched lithium ion batteries from inside the rocket could react with the seawater and lower its acidity. That could affect the marine life directly around where the batteries drop, but, again, those effects aren’t likely to last long. 

Niwa also stated that kerosene from ditched fuel tanks isn’t likely to cause much harm, since most of it has burned off during a launch and the rest will probably evaporate on the surface of the ocean.

Overall, the environmental agency believes that the risk of falling rocket debris to sea life would be minor for a single launch and only ramp up for 100 or more launches. That being said, the New Zealand launch site can boost up to 120 rockets each year.

These types of assessment also don’t include what could happen if a rocket failed to launch correctly and the whole thing went up into a fireball. 

Keep going!