Not too huge. This person[1] did some math and found that a BFR trip across the world should take 40% to 240% as much carbon as a regular plane flight. For short trips this would be worse, though, because a plane's range goes up almost linearly with fuel use while a rocket's goes up much faster than linearly.
Rockets that use solid boosters like the Space Shuttle, SLS, or Atlas V do a good amount of ozone damage as they go up but the ozone damage from cryogenic propellants of the sort that a BFR uses is pretty small.
Did a little googling. Methane is primarily obtained from natural gas fields which are below ground. Atmospheric concentrations are relatively low (on order of parts per billion) although it is still an important greenhouse gas (30x more potent than CO2 per ton). There's a lot of ongoing research into generating CH4 from CO2 using renewable energy but it's relatively energy intensive to date.
So there’s noise pollution on a grand scale, it depends on natural gas extraction or a breakthrough in electrolysis, and it will produce CO2 when burned in flight. Great. It will also cost a fortune, and even SST isn’t viable, yet somehow this will be?
Most people replies are focusing on carbon footprint, but it might also be worth considering noise (e.g. how does the sound of a rocket launching off the coast of California affect whales?) and any atmospheric perturbations caused by the rocket. Launches damage the ionosphere, which hasn't been an issue in the past because as far as we know the damage doesn't have a huge impact, and the ionosphere usually is back to normal within a few hours (or even less depending on trajectory and some other factors). If launches are happening every hour in the same area, that might cause some problems with things like radios.
Does it damage the ionosphere? According to what definition of "damage"?
I honestly don't know, so if someone can explain how it really is damage, please do so by all means. But despite some popular suppositions to the contrary, "affects" != "damage". I know it affects it, probably from the same article from a week or so back as you, but that doesn't mean it's "damaged".
I guess "damage" is a judgement call I'm not really qualified to make. Someone could probably make the argument that humanity can't "damage" a natural system because we're part of nature.
When half the electrons disappear over a few thousand square kilometers, it's not inherently better or worse. It may annoy someone at Arecibo Observatory or a HAM radio operator or a GPS user, but maybe there's also some positive aspects of that temporary depletion.
Depends on how many. Flying airplanes is around 1-2% of our total CO2 footprint. Of course, for an individual, doing 1 intercontinental flight with a full plane is equivalent to months if not a year of driving a car to work every day, but in total, not many people fly.
Depending on the efficiency of the rocket and the reduced number of people doing this, the numbers shouldn't be that much higher.
So, they are actually very efficient transportation for long trips. Absolute worst case flying around the world is 24,901 mi which uses the same fuel per person as a 35 MPG car commuting 26 miles each way for one year.
PS: You can double check this by considering ~1/3 of the cost of a seat as being spent on fuel.
Fuel economy improves at first due to reduced overhead of taxiing, takeoff, and ascent, but as you go farther the fuel consumption increases due to the need to actually carry the fuel.
Efficiency is one way to increase range. Wingtip devices can reduce drag by inhibiting vortex formation, however they increase weight so there is a minimum flight distance before they are a net gain. https://en.wikipedia.org/wiki/Wingtip_device
There is a tradeoff of needing carry more fuel over a portion of the flight, but the aircraft also spends a higher percentage of it's fuel on flying vs taxiing etc.
What is not the case? 1-2% of total CO2 footprint? That flying a full plane is equivalent to months if not a year of driving a nontrivial distance every day?
I'm not saying cars are more efficient. It's just that the distance travelled is huge when one uses an airplane.
Many people use more fuel in a month getting to and from work than a round trip NYC to London flight. It comes down to both distance and fuel economy with some commuters putting in over 1000 miles a week. The range for commuting fuel uses vs transatlantic flight is much wider than 10x months to year.
Pretty similar to the environmental impact of jumbo jets. A 777-200LR burns around 145.5 tonnes of jet fuel to transport around 300 people 15,800 km. That's 31 grams of fuel per passenger-km, about 86% of the fuel is Carbon so that's roughly 27 grams of Carbon emissions per passenger-km. A BFR/BFS contains about 3,240 tonnes of propellant and allegedly will be able to transport around 850 passengers up to 20,000 km. The oxidizer to fuel ratio of the Raptor engine is currently unknown but it's likely it's around 3:1, meaning that 1/4 of the total propellant is Methane while 3/4 is liquid Oxygen, giving 810 of Methane per trip, give or take. Methane is 75% Carbon so a BFR flight should produce roughly 608 tonnes of Carbon emissions, or 36 grams per passenger-km (30% more than a conventional flight, seemingly).
However, it's possible to generate Methane fairly easily using solar power, so such launches have the potential to be nominally carbon neutral with some investment.
The BFR runs on a mix of liquid oxygen and methane, according to Wikipedia.
Ignoring obvious scalability problems, wouldn’t it be possible to manufacture that with a pretty decent environmental footprint from various carbon neutral bio sources?
SpaceX plans to refuel the BFR on Mars with methane and oxygen produced via the Sabatier process and electrolysis [1]. They might do the same thing on Earth, even if only for the bragging rights of being carbon neutral.
It will eventually be very low, much lower than planes. The same technology that is being developed to make propellant on Mars can be used on Earth to extract CO2 from the air and/or sea water. A few squared km of solar panels on floating structures can produce enough propellant for one BFR trip a day.
The same propellant (methane) can also be used on planes, eventually, so BFR will bring many technologies advances independently of the outcome of the project.
Rockets that use solid boosters like the Space Shuttle, SLS, or Atlas V do a good amount of ozone damage as they go up but the ozone damage from cryogenic propellants of the sort that a BFR uses is pretty small.
[1]https://www.quora.com/Elon-Musk-suggested-that-the-SpaceX-BF...