Rocket Pollution Speech!

I’m wondering if a key point isn’t missed in comparing starship to airline when you compare strictly passenger capacity to passenger capacity only. Basically it sounds like the fuel comparison your using could get you literally lily half way around the world in starship. An aircraft would require at least one refueling to achieve that I’d think. So are the number per mile bs per mile also, because it didn’t sound like it.

Looking forward to the final version of this!

An excellent presentation, in the Q&A one guy asked an excellent question about manufacture, transport, engine testing and static burn emissions. This was a good point and one that it would be interesting to see some numbers in in the video.

I think Tim is referring to the fact that the commercial aviation sector barely makes a dent on human carbon emissions. You say the aviation sector is "really bad", but that is simply not true. Aviation accounts for only 2.4% of human emissions. Having spaceflight emit as much as commercial aviation won't make much of a difference. Reducing emissions in other areas will have a far greater impact on reducing the effects of climate change than reducing rocket emissions. Besides, the rocket industry is already moving to favor Hydrolox and methalox fuels, which are about as green as you can get when it comes to rocket fuel. The problem is, using that fuel for commercial aviation would be prohibitively expensive, which already is a struggling industry with low profit margins. It's already been demonstrated that jet engines can switch fuels from kerosene to Liquid hydrogen. The key is liquid hydrogen needs to become cheap enough to become profitable, as well as the necessary infrastructure built. Planes would need to be redesigned to be able to hold the fuel as well.

Silly question, perhaps. But does not most of the emissions happen in the lower altitudes where the effect on the atmosphere is minimal?

At some moment in the video, I got the sense that Tim was saying that would be fine to have space flight emit as much as commercial aviation and I don't think that's the right framework to think about it. The aviation sector is really bad and hasn't been investing much in curbing emissions. They should not be the baseline. In addition to that, it's important to point out that work on hydrogen & methane engines would speed up the adoption of that technology for commercial aviation. I do think that we should have a pro-active approach to this problem as opposed to be reactive. We can strive at making the cleanest engines and make it such that we can be proud to see the number of space launches increase. And not in 10 years, be like "Oh, now spaceflights are everywhere but they are a main contributor to making our very own planet inhabitable".

I loved the way you have compiled the facts and how you gave some related facts about everyday transportation that can be said to act in the same space. But it was a bit hard to listen to since you were a bit jerky in your speech and made way to many excuses. After all, you’re not doing it as a space flight lobbyist, you’re an educator and analyst who loves rocket science. Use your strengths to bring the numbers front and center, and make it clearer that rockets and space flight really is not a big contributor to the global warming and environmental changes.

AkeBjorn

Im thinking showing the 2,4% as a pie chart?

This is good. I’ve got a scientific background and nothing wrong was noticed. On the attitude though, what comes through is « we can allow the space industry to pollute as much as the airline one » because it’s fair, somehow. It’s not. Every reduction in pollution is good. The 2.4 % of global emissions from airlines comes a bit late for the effect you seek. Numbers like clothing industry, automobiles would give context and help people realize they too can help and not just blame others for pollution.

Space elevators could have better numbers. People like to assume that materials with the needed strength/wieght ratio to make that work isn't available, but they are always assuming the tether has to be the same thickness from bottom to top. Allow the thickness to be variable and things get quite different, almost practical. (and darn sillly if the materials aren't strong enough, but some are)

Please don't forget about the chemical reaction that SpaceX has proposed would be using on Mars to make fuel there. CO2, H2O, energy --> CH4 & O2 We can do that on Earth too. Our energy source could even be renewable. There's no reason the process would have to run 24x7. They could use solar and the whole launching process would be both energy and carbon neutral. They could operate near any fossil fuel powered electricity plant and benefit from all that free CO2 they are putting out. I am SO looking forward to seeing those methane powered rocket engines put things into space. ....He rose up the chimney with a thunderous fart..., but I regress :-)

23:50, about reusable rockets. This is conceptually jarring because almost all of the previous discussion is about the fuel emissions, not the vehicle structure manufacturing. Of course, there isn't any reusable fuel so far, UNLESS an complete industry is set up to recreate methane (for example) from C02. That industry does not exist now and the economics are presently questionable. Such processes are not anything close to 100% efficient. Please try and separate reusable rocket (structures), which we have now, from reusable fuels which don't exist.

Nice presentation! I agree with Q&A to include the light-lift vehicles (e.g., RocketLab's Electron, Blue Origin, etc.). Also, since you note that aircraft don't fly their entire fuel loads, it would be good to characterize the 737 & 747 emissions in context of a typical flight (e.g., a 6 hour transcontinental flight).

Seems like there’s a small mistake in the slide for co2 per kg to LEO. Falcon 9 should do 16.8 ton to LEO on reusable, not 14.

From 22:10 Please enlarge on methalox rockets potentially being net-zero, perhaps emphasizing it again in the conclusion. And acknowledge currently methane is a fossil fuel, from natural gas. The hopeful future of Starship or any methalox vehicles being carbon-neutral bears a lot of emphasizing, including Starship can have LOX and methane production near the launch sites, solar or wind powered. Near enough for short pipelines, so near-zero transportation costs.

Regarding the debate about CO2 in higher atmosphere: The air is much thinner up there, so if the in one m3 air at 10 meter is 400 ppm of a gas, the number of molecules in 50km might be 1/100, meaning 400ppm would span many m3's. Here are some formulas: https://www.engineeringtoolbox.com/air-temperature-pressure-density-d_771.html#Units

Interesting. I have to say, though, that it disappoints me a 'great deal', that the focus turns to 'CO2' as a 'pollutant' (it is, to be fair, 1/3 of the basis for life on the planet!) and you completely ignores all the actual toxic stuff that some fuel-types emits. If this is going to be the focus of your video, I would recommend that you change the title to 'rocket emission facts', give the numbers of all the emissions and then let the viewer decide if they think one or the other is the 'bad stuff'. To be honest, I would much rather have rockets emit H2O & CO2 than al the other actual-toxic stuff, since H2O & CO2 can return in the natural cycles of nature without human interaction. For some perspective, here is some basic CO2-levels, all ppm: 160-180: The low level where plants can't breath anymore. The planet dies. 280: The 'pre-industrial' level, everybody thinks we should back to.. ~400: The level today.. 800-1000: The level used in greenhouses. Plants simply grow much better at this level. 1000+: The level where The Danish Working Environment Authority starts to raise eyebrows when office levels reach it.. but mostly due to indication of bad air circulation 😉 2000: Seen many times in nature, according is ice-cores from Greenland and Antarctica. 8000: Highest level allowed in US submarines (as far is I can find) Looking forward to a great video! 😀

Overall this was a very comprehensive and detailed presentation. As you mentioned you're working on some of the fine details and I look forward to the full video. It would also be interesting to see some of the other pollutants involved in a rocket launch such as recovery vehicles, transporting the rockets, etc. and how that contributes to the overall impact of a launch.

🙋‍♂️ I'm a chemist! I also work in the quality department so I apologise in advance 😂 Minor technical point in the way you abbreviate carbon dioxide; it should be a subscript '2'. And I spotted one slide that had 'CO2' and carbon dioxide in the same sentence. Good effort with the tricky pronunciations though, you were almost there! I enjoyed the talk and it's great to see some numbers to back up how insignificant the emissions from rockets are versus what I consider are valuable scientific and technological advances (even the space cookie!). Thanks Tim 🙏

I think the comment about the whole process of launching a rocket with construction, transportation, testing, possibly even the infrastructure around it being the main source of pollution was good. With airplanes, it's mainly show up, sit around for a while, then fly off. Airports are set up to handle hundreds or thousands of flights per day, whereas the whole launch complex is usually preparing for a single launch for days. It would probably be much, much more difficult to find these numbers, but you could at least mention it and make it a point that that may or may not be a significant portion of the emissions of the space flight industry. By the way, I was in the audience, and you did a great job! It was a ton of fun, as was OLF live!