Right now, the FAA is gathering public comment on SpaceX’s environmental review of the upcoming Starship Orbital launch. While I generally support space exploration and hope SpaceX is successful, it is 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 report your opinion to the FAA. https://t.co/4T3NaemoCr
– Elon Musk (@elonmusk) 23 October 2021
The use of methane for rockets is largely defensible
From an environmental point of view, a rocket should be powered by hydrogen. The combustion of hydrogen combines hydrogen with oxygen in the atmosphere, producing only water vapor in the exhaust gases. Water vapor diffuses harmlessly into the atmosphere and does not contribute to climate change or other environmental damage. Hydrogen rockets are also a proven technology that took the United States to the Moon, so it is entirely possible to use hydrogen for space launches.
But hydrogen has serious drawbacks.
Being a small molecule, it is very difficult and expensive to ensure that a rocket does not just leak its fuel. Each weld must be absolutely perfect. Each seam should be carefully sealed. All joints and connections from tanks to engines must have a perfect seal. All this need for perfection means a lot more work, expense, and even danger.
The second problem with hydrogen is that it makes the metal more brittle. This further increases the cost of safely building a hydrogen rocket. Other issues include low energy density compared to other fuels, temperature control, expense, and the complexity of the systems required to manage it properly. It’s also not easy to produce on Mars, so it wouldn’t be suitable for a Martian colony.
Methane (the purest form of “natural” gas) is the second best thing. It produces carbon dioxide when burned, but that’s basically all it produces (aside from water vapor, like any combustion reaction). Unlike RP-1 or other rocket fuels, it contributes in part to greenhouse gases, but does not emit other pollutants.
Considering the costs of hydrogen and the fact that methane is only a little worse, the choice of methane was obvious, even if it wasn’t perfect for the environment.
All the methane must come from somewhere, however
When assessing the environmental impacts, the FAA only considered one thing: the source of the natural gas that would power SpaceX’s starbase.
The obvious thing they’ll need natural gas for are rockets. For those who aren’t familiar, natural gas is mostly methane, and while it’s good enough for things like furnaces and power plants, the gas that is normally found in pipes just isn’t pure enough to be used in rockets. SpaceX therefore needs a facility to absorb natural gas, purify it, and then cool it until it turns liquid. Then it will be ready to be pumped into a rocket tank and used for launches.
But they didn’t mention the source of all that natural gas in the report. Theoretically, they could haul natural gas by truck using tank trailers, but it would be expensive, cumbersome, and require LOTS of trucks. The other, more reasonable option would be to reactivate a pipeline that crosses the Lower Rio Grande Valley National Wildlife Refuge. The pipeline, which was scrapped in 2016, currently contains fiber optic cables for a local educational institution.
So SpaceX may still be able to use the pipeline or may need to build a new one.
The other thing that was not factored into the report is that the gas has to be put into the pipeline from somewhere, and the areas near Brownsville just aren’t producing enough gas to meet SpaceX’s needs. at Starbase, so more gas will be needed at least 80 miles away. This means more wells, more pipelines and more environmental impact that is not currently taken into account.
SpaceX is also building a 250 megawatt gas power plant
Getting methane for rockets would likely be something neighboring wells could provide, with minimal gas requirements elsewhere in the state, and that would be reasonable. But, add the fuel needed for a 250 megawatt natural gas power plant, and you end up in the situation described above. There just isn’t enough local gas to power rockets and a large power plant.
According to TechCrunch and Dog ESG (both linked above), the power plant will be needed to power a desalination plant to meet the starbase’s water needs, as well as to meet the base’s other power needs.
Desalination makes sense, given the region’s limited water supplies and abundance of salt water, but the equipment to do it isn’t fussy about where its electrons come from. Whether it comes from natural gas or wind and solar, as long as the electricity continues to flow, they will be able to produce the water they need.
So why isn’t SpaceX using renewable energy?
Since the company is already planning to ship the gas, and getting more gas is relatively cheap, it’s probably the cheapest solution overall.
But, really, South Texas has excellent solar resources.
Of course, it’s not as hot as El Paso, but Brownsville still has better quality sunshine for solar power generation than most of the country. There aren’t many excuses not to build a large solar power plant with storage to meet the needs of the desalination plant, as well as other Starbase needs. You probably couldn’t build such a large factory right next to Starbase, but you might find some vacant land in the area to provide enough electricity.
Brownsville only has 223 sunny days a year, which could be a problem, but there’s no reason not to go further into Texas for electricity. El Paso and other parts of far west Texas, as close as Big Bend, have over 300 sunny days a year.
Getting electricity from the vacant lot to the starbase, whether nearby or further away, is a problem, but so is the construction of pipelines. If you can build pipelines, you can build power lines. Plus, power lines don’t leak and cause other environmental damage like gas lines do.
The cost of 250 megawatts of solar power is probably more than 250 megawatts of gas, but it doesn’t make sense to try to save the species with Tesla and then turn around and burn natural gas for SpaceX’s space colonization efforts.
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