Right now, the FAA is taking public comments for SpaceX’s environmental review of the upcoming Starship Orbital launch. While I generally support space exploration and hope SpaceX succeeds, it’s important to consider the environmental impacts of space activities and find ways to reasonably minimize the environmental impacts.

Your support makes a big difference! Please let the FAA know your opinion. https://t.co/4T3NaemoCr

— Elon Musk (@elonmusk) October 23, 2021

The Use of Methane For Rockets Is Mostly Defensible

From an environmental perspective, a rocket should be powered by hydrogen. Burning hydrogen combines hydrogen with oxygen from the atmosphere, producing only water vapor in the exhaust. The water vapor harmlessly diffuses in the atmosphere, and doesn’t contribute to climate change or any other environmental harms. Hydrogen rockets are also a proven technology that took the United States to the moon, so it’s entirely possible to use hydrogen for space launches.

But hydrogen does have some serious drawbacks.

Being a small molecule, it’s very difficult and expensive to make sure a rocket doesn’t simply leak its fuel out. Every weld must be absolutely perfect. Every seam must be carefully sealed. All joints and fittings from tanks to engines must have perfect seals. All of that need for perfection means a lot more work, expense, and even danger.

The second problem with hydrogen is that it makes metal more brittle. This again drives up the cost of safely building a hydrogen rocket. Other problems include the low energy density compared to other fuels, temperature control, expense, and complexity of the systems needed to handle it properly. It’s also not easy to produce on Mars, so it wouldn’t be suitable for a Mars colony.

Methane (the purest form of “natural” gas) is the next best thing. It does produce carbon dioxide when it’s burned, but that’s basically all it produces (other than water vapor, like any combustion reaction). Unlike RP-1 or other rocket fuels, it does contribute some to greenhouse gases, but doesn’t spew out other pollutants.

Given the costs of hydrogen and the fact that methane is only a little worse, going with methane was the obvious choice, even if not perfect for the environment.

All The Methane Has To Come From Somewhere, Though

While assessing environmental impacts, the FAA didn’t factor one thing in: the source of the natural gas that would feed SpaceX’s Starbase.

The obvious thing they’ll need natural gas for is the rockets. For those unfamiliar, natural gas is mostly methane, and while it’s good enough for things like furnaces and power plants, the gas that’s normally in pipes just isn’t pure enough for use in rockets. So SpaceX needs a facility to take natural gas in, purify it, and then cool it down until it changes to a liquid state. Then, it’ll be ready to pump into a rocket’s tank and use for launches.

But they didn’t mention the source of all this natural gas in the report. Theoretically, they could truck the natural gas in using tanker trailers, but that would be expensive, cumbersome, and would take a LOT of trucks. The other, more reasonable, option would be to reactivate a natural gas pipeline that runs through the Lower Rio Grande Valley National Wildlife Refuge. The pipeline, which was abandoned in 2016, is currently holding fiberoptic cables for a local educational institution.

So, SpaceX may still be able to use the pipeline, or it may have to build a new one.

The other thing that hasn’t been considered in the report is that the gas has to get put in the pipeline from somewhere, and the areas near Brownsville just don’t produce enough gas to feed the needs of  SpaceX at Starbase, so more gas will be needed from at least 80 miles away. That means more wells, more pipelines, and more environmental impact that isn’t currently being considered.

SpaceX Is Also Building a 250-Megawatt Gas Power Plant

Getting methane for rockets would probably be something the nearby wells could supply, with minimal gas needs from elsewhere in the state, and that would be reasonable. But, add the needed fuel for a 250-megawatt power plant that runs on natural gas, and you end up in the situation described above. There just isn’t enough local gas to power the rockets plus a big power plant.

According to TechCrunch and ESG Hound (both linked above), the power plant will be needed to power a desalination plant to provide for Starbase’s water needs, as well as to provide for the base’s other electrical needs.

Desalination makes sense, given the limited water supplies in the area and the abundance of salt water, but the equipment to do that isn’t picky about where its electrons come from. Whether it comes from natural gas, or comes from wind and solar, as long as the power keeps coming in, they’ll be able to produce the needed water.

So, Why Isn’t SpaceX Using Renewables?

Given that the company is already planning on piping in gas, and getting more gas is relatively cheap, it’s probably the cheapest solution overall.

But, really, south Texas has great solar resources.

Image provided by the National Renewable Energy Laboratory (NREL). Public Domain.

Sure, it’s not as red hot as it is in El Paso, but Brownsville still has better quality sunlight for solar power production than most of the country. There’s not much in the way of excuse to not build a big solar power plant with storage to supply the desalination plant’s needs, as well as other needs at Starbase. You probably couldn’t build a plant that big right next to Starbase, but you could find some vacant land in the region to supply enough power.

Brownsville only has 223 sunny days per year, which could make an issue, but there’s no reason to not go further away in Texas for power. El Paso and other parts of far west Texas, as close as Big Bend, have over 300 sunny days per year.

Getting the power from the vacant land to Starbase, whether from nearby or farther away, is an issue, but so is the issue of building pipelines. If you can build pipelines, then you can build power lines. Plus, power lines don’t leak and cause other environmental harms the way that gas lines do.

The cost of doing 250 megawatts of solar is probably higher than 250 megawatts of gas, but it doesn’t make sense to be trying to save the species with Tesla and then turn around and burn natural gas for SpaceX’s space colonization efforts.

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