How Much Do Rockets Pollute? Are They Bad For Our Air?

- Hello, it's me, Tim Dodd, your everyday astronaut. I'm here at the Kennedy Space Center Visitor Complex in its magnificent rocket garden. I mean, look at this place. How wonderful is it to talk to you about rocket pollution? Because there's no arguing that

rockets

aren't incredible pieces of machinery. I mean, let's forget the fact that

they

are currently really the only way we have to put anything meaningful into orbit. But seeing and hearing a rocket launch is simply an unforgettable experience. We are in this. We are doing this! Yeah! But as impressive as those flames and sounds are, what's not amazing is when you stop and think about how

much

a single rocket

pollute

s.

I mean, some find it ironic that an organization like NASA that studies our atmosphere is okay with

rockets

polluting it so

much

. Or isn't it strange that Elon Musk, the same person who pushes so much for sustainable energy with Tesla, also owns a rocket company that basically runs on fossil fuels? And let's not forget about Jeff Bezos, who literally just pledged $10 billion to help combat climate change and is also simultaneously working on a huge rocket that's almost the size of the Saturn V moon rocket he'll be launching all the time. I mean, isn't this all a little hypocritical?

So today we are going to delve into all of this. Let's find out how much of it really comes out of the flaming end of a rocket. Then we'll see how much different fuels and different engines change that equation. And then we'll compare rockets to other forms of transportation and other industries. And we'll even find out what would happen if SpaceX's proposed Starship point-to-point transportation system here on Earth actually replaced airliners. Would that be an improvement or a big step backwards when it comes to emissions? But that's not the only environmental impact rockets have, right? I mean, what happens when a rocket hits the ocean or land?

That can't be good, right? Or what about space debris? I mean, we're putting a lot of things into orbit. Shouldn't we talk about that too? Well, those will be the next video topics. But for today, we'll just focus on the environmental impact it has on our air. So by the end of this video, we hope to have a really healthy understanding of the environmental impact that rockets have on our atmosphere. Let's find out if launching rockets is really reckless or not. Or yes, in the grand scheme of things, it's not a big deal. And finally, we'll look at the things the aerospace industry is doing today to improve rockets for the future.

Let us begin. (bright music) - Three, two one. (upbeat music) - This is a question I get asked all the time. And, frankly, it's a fantastic question. And there are actually some other articles out there, but

they

can tend to be misleading and barely scratch the surface. So you don't really have the context or the concrete numbers of all the material to really answer the question, right? So I think it's time to get to the bottom of this and finally find out how important emissions from rocket launches really are. So I spent about five months trying to gather as much information as I could.

I even ended up hiring a researcher, Lisa Stojafoski, to help me do additional research. As I continue to study this topic, because, I mean, as far away as I am from being a rocket scientist, I'm even further away from being a climate scientist. But now I have spoken to experts. I've read one research paper after another, and I constantly have to update the stupid script, because I keep learning things almost every day, because this is a really, really deep, complicated, nuanced, but actually very interesting topic. So stay until the end because I promise you this is pretty fascinating.

But right off the bat, let me address one thing. I'm certainly opening a huge can of Internet worms here. But listen to me. We'll just go through a bunch of numbers and compare them to other numbers so you can form your own opinion about it. I guess somehow climate change and pollution have become a political issue. Honestly, it doesn't make any sense to me. But regardless of what you think about words like climate change, greenhouse gases or CO2, let's all agree that we probably don't want to live in a terribly

pollute

d world and that we physically cannot live in a world that is uninhabitable.

So, with that in mind, keep the comments section free of politics and useless internet arguments about climate change and all that kind of stuff and look at the raw numbers here with me. And we will use it to shape our knowledge about the impact rockets have on our planet. And this video is really going to focus primarily on what actually comes out of the flaming end of a rocket. And we will ignore manufacturing, transportation, ground operations, etcetera, etcetera, etcetera. Not to ignore them and act like it doesn't matter, but because that would turn an already incredibly long video into the longest video ever.

And many of those things are not unique to rockets either. This video will be a roller coaster of good and bad. You'll say, oh, that's not so bad. But oh, that's really bad. I guess it's really no big deal, over and over again. But there are a lot of little side notes and interesting facts in this video. Then we will go to the tangent city. I'm sorry, I'm not sorry. But because this video has so many topics and tangents, here are the timestamps for them. There are also some quick links and a version of the article that has some additional resources, methodology, and numbers that you can check out in the description as well.

So grab a drink, a notebook, and your periodic tables because we've got a lot of science to talk about. (bright, upbeat music) So to begin, let's make one thing clear. Humans won't abandon traditional rockets too soon. There is simply no other form of propulsion feasible with our current technology. As much as I want to believe in the anti-gravity warp driven magnetic superdrives that my comments section seems to constantly tell me about. Until the lizard lords bless us with access to those things, rockets are really all we have. After all, rockets are simply machines whose sole purpose is to extract as much kinetic energy as possible from chemical bonds.

And just look at a rocket launch. There is an incredible amount of energy involved. Well, from the beginning, we have something to keep in mind. Notice that when a rocket takes off, it leaves behind a giant cloud of white smoke. That seems pretty disgusting, right? And then watch as the rocket ascends, the cloud doesn't actually follow it. The exhaust will end up looking much clearer very quickly. What's going on here? Well, luckily that giant white cloud of smoke isn't actually smoke at all. It is almost entirely a giant cloud of vapor. And that's because many rockets and their launch pads use a water deluge/sound suppression system to not only keep the launch pad intact, but also dampen the sound energy of the rocket.

So it doesn't actually harm itself. By dumping over a million liters of water during the initial launch sequence, most of that water is vaporized and turned into steam. And in doing so, it absorbs a lot of energy. Then you'll notice that many rockets, when they clear the pad, no longer have that thick cloud of smoke following them. Although some still do it. But we'll talk more about that in a second. Below I'll list basically everything that can come out of the flaming end of a rocket. Then we will organize and classify those things. Then we will show which rocket engines produce what.

And sum it all up by showing how much of what each vehicle and each system produces based on its engines, its size and its fuels. Rockets can produce many different emissions. But here's the list of usual suspects. You have CO2, water vapor, carbon soot, carbon monoxide, which will almost always bind together and become carbon dioxide, nitrous oxide, chlorine, alumina, and sulfur compounds. Now, I should point out that I accidentally kept saying nitrous oxides instead of nitrogen oxides or nitrogen oxides. So if you hear me say nitrous oxides, I'm actually referring to the more generic term which is nitrogen oxides.

So keep that in mind. There are many other trace gases, but they are literally insignificant. You can barely measure them compared to these main ones. So in the future we will focus on these primary elements instead of getting into the weeds with all these little trace gases. Of these main gases, the United States Environmental Protection Agency or EPA considers nitrogen oxides, sulfur oxides and carbon monoxides as pollutants. Think of most of these things like the bad stuff that comes out of cars or like smog in a big city. Chlorine, alumina, and nitrous oxides can actually destroy ozone and are therefore considered ozone-depleting substances, or ODS, and have been closely monitored and restricted since 1996.

You may have heard the term punch a hole in the ozone layer or something like that. That's it, but it's an incorrect term because it's not a layer and you don't actually make holes in it. CO2, nitrogen oxides, soot and water vapor are greenhouse gases, or act as such, since soot is not a gas. These are just elements that absorb more heat than the current balance of our atmosphere. This is called radiative forcing. And we'll get into that a little bit later. But simply put, if there are more of these substances in our atmosphere, our atmosphere will have the ability to trap more heat from the sun.

It's really that simple. In fact, the EPA considers chlorine to be a dangerous air pollutant. And sulfuric compounds and nitrogen oxides can cause acid rain. And that's really bad for marine life and trees and well, I guess for almost anything living. So which rocket fuels produce which emissions? Let's compare RP-1, hydrogen, methane, solid rocket fuel, and even hydrazine-based hypergolic fuels. Going over them will pretty much cover the vast majority of rockets and the fuels they actually use. So let's start with the dirtiest rocket pollution. And those are solid rocket boosters. You'll usually see solid rocket boosters in the first stage of rockets, where high thrust really matters.

Perhaps the most famous solid rocket boosters were those two giant white boosters on the side of the space shuttle. They produced more than 85% of the space shuttle's thrust at liftoff. But there are also two huge, powerful solid rocket boosters on ESA's Ariane V. Those huge solid rocket boosters make the rocket jump off the platform in a hurry. SRBs are also seen attached to the first stage of many rockets to give it a little extra boost. Solid rocket propellants are typically composed of ammonium perchlorates of hydrochloric acid and perchloric acid ammonia salt, which are powerful oxidants. And then there is also aluminum or magnesium powder.

Then they are held together by a binder, by a bunch of words that I know I'm not going to pronounce anywhere near correctly. They are usually hydroxyl-terminated polybutadiene, known as HTPB, or polybutadiene acrylopytrile known as PBAN, which converts the propellant into a rubber-like mixture. Please don't make fun of me too much. I'm a terrible pronouncer. This means that they mainly emit aluminum oxide, soot or black carbon, CO2, hydrogen chloride, nitrogen oxides, hydrogen and some other trace gases. Since we mentioned the space shuttle, let's take a look at its main engines. The RS-25, which ran on hydrogen, or more specifically hydrogen and liquid oxygen or also known as hydrolox.

The Delta IV, Ariane V mid-engine and Centauro upper stage are also powered by hydrogen. Hydrogen is perhaps the cleanest burning fuel. When you burn hydrogen with oxygen, you literally only get water vapor. But there is a small amount of nitrous oxides, also known as NOx, while the vehicle is in the lower atmosphere, also known as troposphere, as an after-effect of the combustion of the hot flame that comes into contact with our air. Because literally all rocket engines that are hot, which is pretty much all of them, will do this to some degree when they're in our troposphere, which is mostly made up of nitrogen.

Next, let's look at a very common booster, which has been quite common throughout the entire history of space flight and this is the RP-1. But again, it's mixed with liquid oxygen, which is why it's known as kerolox. The first stage of the Saturn V used RP-1, as well as Falcon 9 and Falcon Heavy. The core stage of Rocket Lab's Atlas V, Soyuz, and Electron, to name just a few. HeRP-1 is basically a highly refined jet fuel that itself is just a highly refined kerosene. When burned, RP-1 will produce carbon dioxide, water vapor, nitrous oxide, carbon soot, and carbon monoxide, which in turn will be converted mostly to CO2 and a little to sulfur compounds.

The exhaust is a little unpleasant, but it's really not that different from what a normal internal combustion engine produces. Speaking of nasty, let's take a look at hypergolic fuels. Hypergolic fuels are those that ignite spontaneously when the fuel and the oxidant come into contact with each other. This helps make rocket engines extremely reliable by simplifying the ignition sequence. They are also very stable at room temperature, meaning you can load fuel into a rocket and it will happily sit there ready to launch for long periods of time, which made hypergolic fuels the perfect choice for the Titan missiles and other missiles.

They need to be able to launch literally with the push of a button. But hypergolic fuels are also used in the Proton rocket, in the abort engines of SpaceX's Crew Dragon Capsule and Boeing's Starliner, and also in the space shuttle's orbital maneuvering system. It is also very common in reaction control systems and long duration coastal stages for the same reasons; being simple, reliable and stable. But hypergolic fuels include hydrazine or one of its relatives whose name I know I won't pronounce correctly, such as monomethylhydrazine or asymmetric dimethylhydrazine, which are extremely toxic. Breathe too much of any of them and you probably won't live to tell the tale. - The lung tissue burns, blisters form and the resulting accumulation of moisture causes fixation. - The biggest concern is especially if you have unburned hydrazine or if you spill something while trying to handle it.

So maybe handling the fuel is a bigger concern than burning it. However, when burned, hypergolics are quite similar to RP-1, producing mainly CO2, water vapor, soot, sulfur-containing compounds, and slightly more nitrogen oxides than other fuels, since nitrogen is a compound found in the oxidant, which is usually nitrogen tetroxide. Lastly, let's talk about the new kid on the block, methane, or when burned with liquid oxygen, metalox. Three of the newest rockets coming online in the next two years will run on methane. That SpaceX spacecraft, the first stage of Blue Origin's new Glenn and also the first stage of ULA's Vulcan.

Methane is probably the next cleanest compound after hydrogen, which makes sense since it is a very similar compound. So when burned, methane turns into CO2 and water vapor, over and over again, along with some nitrous oxides. Now this might be contrary to what you've heard. I mean, it's common to talk about how cow burps or farts are just methane and how bad a greenhouse gas that is. Well, that's true. But that's because it's not burned. Methane in the atmosphere is a really powerful greenhouse gas. So it's actually better if it is burned and split into CO2 and H2O.

Well, at least when it comes to greenhouse gases. (bright, upbeat music) So let's look at some real facts about some real-world rockets. To do this, let's look at a variety of rockets with a variety of different fuels. And in fact we will see how much of what each rocket produces. Let's compare the Titan II rocket which is powered by hypergolic thrusters, the Soyuz FG, which is powered by RP-1 and has a hypergolic upper stage, the Atlas V N22, which has two solid rocket boosters and a main core powered by RP-1 and a hydrogen-powered upper stage and then the Falcon 9 powered by RP-1.

So let's compare the Delta IV Heavy, which runs entirely on hydrogen, the space shuttle, which runs on hydrogen and two huge solid rocket boosters, the SLS or the Space Launch System, which is basically a larger scale space shuttle without the orbiter, and works by transitioning to even larger solid rocket boosters and a huge hydrogen tank and hydrogen upper stage. And finally, we'll look at Starship and the super heavy booster, which are completely methane-powered. Now you may have noticed a few things about these options. First of all, I chose these rockets because they are all rockets that have flown or will fly well with humans, except for the Delta IV Heavy, but you'll see why I wanted to include that one in just a second.

But you'll also notice that this selection of rockets covers virtually all fuel options. But I should point out here that my numbers are pretty accurate. But even direct observation recordings of rocket exhaust are confusing because of how the exhaust ends up interacting with ambient air. There are lots of little things, like how carbon monoxide almost immediately converts to carbon dioxide, or how exhaust heat converts atmospheric nitrogen to nitrous oxide. Now, because of all these variables, I have simplified its production by grouping carbon monoxide and carbon dioxide into just carbon dioxide, which is quite normal. All other carbon sources clump together into soot and we have simply ignored the slight oxygen production that some engines can produce.

Now, we generally combine various sources and our own calculations to get a fairly accurate total for each vehicle. I guess we're probably within five or 10%. And it seems like our numbers tend to line up pretty well with some of the other numbers that for this purpose are good enough for comparison, and at least for relative purposes, when comparing all of these rockets together. But put a little mental thought behind all these numbers, just in case. The hypergolic Titan II produced mainly CO2, then some water vapor, nitrous oxide, soot and sulfur. The Soyuz FG and Atlas V N22 again produce mainly CO2, some water vapor, soot and nitrous oxides.

But because the Atlas V uses those solid rocket boosters, we see a big jump in chlorine and alumina. The Falcon 9 produces almost twice as much as the Soyuz does and that makes sense since it burns about twice as much fuel. It should be noted that the Falcon 9 and Soyuz use RP-1 in open cycle for their engines. This means that there is a gas generator that is very rich in fuel. Therefore, you will see much darker smoke coming from the side of the engine as you have much less complete combustion in the gas generator compared to the main engine.

Most of the exhaust seen in the Falcon 9's exhaust trail is likely coming from its gas generators. Although all rocket engines run on rich fuel in the main combustion chamber, to achieve the right balance between heat management and performance. Therefore, unburned fuel is likely to be expelled regardless of the cycle type, but much more so when dealing with an open cycle engine. Now, if you're sitting there confused right now and have no idea what I'm talking about, and you need a good overview of the gasoline generator and the different types of engine cycles, be sure to watch my Raptor video because I break down.

All the different cycles and I think making them really easy to understand. Okay, now let's go back to our graph. The Delta IV Heavy is really cool because it produces no CO2 and only shoots over 600 tons of water vapor, but as mentioned, it will of course produce some nitrous oxides in the lower atmosphere and a small amount of carbon from its ablative nozzles, which makes its exhaust glow orange instead of the light blue exhaust we see on the space shuttle main engines. The space shuttle and its wingless big brother, the SLS, produce mostly CO2, a lot of water vapor, a little soot, nitrous oxide, and a lot of chlorine and alumina because of those huge solid rocket boosters.

Lastly, Starship will produce by far the most CO2 and water vapor simply due to its enormous size, and of course it will produce some nitrogen oxides. It's worth quickly noting that these figures actually differ from those SpaceX published last year for its Starship environmental impact assessment. But they were probably worst-case scenarios and for a potentially much larger rocket, and our calculations are based on the nine-meter-wide Starship 2019 design. But of course, simply looking at his production doesn't tell the whole story, right? What about its payload capacity? This is a number that will vary drastically between vehicles. So for this, let's look at its tons to low Earth orbit capacity.

So for the Titan II we get 3.5 tons. The Soyuz FG was seven years old. The Atlas V at 13. The Falcon 9 at 15.5 while being reused as it almost always does now. But it should be noted that its expendable payload is a little higher, 22.8. The Delta IV Heavy with 29 tons. The space shuttle weighs 28 tons. The SLS cited here is Block 1 with 95 tons to LEO. And finally, Starship will currently be the king of this group at 100 tons. And now that we have all these numbers on the screen, this is where the fun begins. We can really do some fun ratios here to really see how much work each rocket does compared to its emissions.

So let's start with your CO2 payload ratio to low Earth orbit. That means the lower the number here, the less CO2 they will produce to actually get the job done. The Titan II emitted 10 tons of CO2 per ton of payload in low Earth orbit. The Soyuz at 35, the Atlas V at 20, the Falcon 9 at 27 when it is reused or 19 when it is expendable, the Delta IV Heavy at zero, the space shuttle at 16, SLS at six and Starship at 27. Next let's see its water. Vapor payload ratio to low Earth orbit. Again, the lower the number here, the less water vapor they put into the atmosphere to do the same amount of work.

The Titan II produced four tons of H2O per ton of payload at LEO, the Soyuz FG and Atlas V N22 are at nine tons, the Falcon 9 is at 10 tons when reused or seven when expendable, the Delta IV Heavy produces 22 tons, the Space Shuttle will weigh 35 tons, the SLS will produce 14 tons and the Starship, 22 tons. Now, finally, let's compare their ozone-depleting compounds. Again, these were nitrogen oxides, alumina and chlorine for their payload capacity. Again, the lower the number here, the less ozone will be depleted to put things into space. All rockets without solid propellants produce almost zero tons per ton in orbit, while the Atlas V N22 produces four tons, the space shuttle, 21.7, and the SLS, 7.7.

Now you may notice that the SLS here performs much better than the space shuttle in terms of emissions to payload capacity, because the SLS has a much larger payload capacity than the space shuttle. Now this is mainly because the space shuttle had to put that huge orbiter into orbit, which wasn't really considered part of its payload capacity. And we're also only comparing the Block 1 version of SLS, which only has a small and much less capable upper stage. So things are pretty interesting here, right? Rockets don't seem like a very environmentally friendly way to transport things, do they?

There's actually a lot of stuff coming out of the back per kilogram of every rocket, except a rocket powered exclusively by hydrogen. But there are a lot of notes here. Here we go. We're going to the city tangent. Of course, putting something into orbit requires an incredible amount of energy. So as we move forward, keep this in mind. We're not talking about long-haul trucks here. We're talking about accelerating huge payloads 10 times faster than a bullet. Now, you may have also noticed that I quote what happens when you wear out a Falcon 9 instead of reusing it. And you might be tempted to think, oh wow, it emits quite a bit more per ton of payload when you try to reuse it.

Well, this is a topic we're not really going to talk about much here because it's a huge, huge rabbit hole. But manufacturing a rocket is much worse for the environment than the launch itself. But this is where I didn't want to go into too much detail because aluminum and steel manufacturing is a completely different topic and is by no means exclusive to rockets. If we wanted to debate the impact manufacturing has on our planet, that's a completely different topic that I don't think we need to address in this video. We're just focusing on the actual flight of the rocket and what comes out of that burning end.

That said, in the case of the Falcon 9, it is much better to reuse a rocket so that the pollution and carbon output of the manufacturing process can be amortized over several flights, rather than just one. I said I wouldn't go down a rabbit hole and here I am, down the biggest rabbit hole in history, because we actually also need to calculate how muchemissions from the fleet of recovery vessels, before actually knowing the total emissions over their useful life. of a dispensable rocket versus a reusable one. But a fun little note here is that rockets could be a solution to industrial pollution and CO2 emissions.

In fact, Jeff Bezos, founder of Amazon and Blue Origin, paints a very interesting picture of what he thinks the future should look like. In May 2019, during a speech about Blue Origins' proposed Blue Moon lunar lander, Bezos shared his vision of using rockets to move energy production and heavy industry off Earth, which would then sustain Earth. as a sanctuary in the future. Now, I think this is actually a really cool concept and has almost nothing to do with this video. I'm sorry. I keep doing this. But you should definitely watch that speech because it has some really compelling ideas.

But here's another interesting note. A rocket that runs on hydrogen or methane can become practically carbon neutral if the fuel production is powered by renewable energy. Unfortunately, most hydrogen is produced from fossil fuels through steam reforming of natural gas, methane, or coal gasification. When hydrogen is produced this way, it is not a very sustainable fuel source. But hydrogen can be made through electrolysis to extract it from water, although it is relatively inefficient. And in fact, methane can be created simply by extracting carbon dioxide from the air and adding it to hydrogen using the sabatier process. This means that you can extract the CO2 from the air emitted by the rocket or, I guess, anything, and turn it back into rocket fuel for your next flight.

Now, I know this sounds a little obtuse, like, come on. That can't be right. I mean, won't it take a lot of energy to do that and that will just create more emissions? Again, not if the fuel production is done with renewable energy. This is something SpaceX will likely implement as a cost-effective way to not only refuel its Starship, but also as good practice for a vital refueling process needed to return home from Mars. That's how it is. To return from Mars, SpaceX will need to perform this exact process. So it will probably make a lot of sense for them to use the sabatier process basically right away so that they can become experts at it when humans depend on it to get home.

But it is worth noting. If you're relying on solar energy to refuel a spacecraft on Mars, a lot of solar panels will be needed. And boy, I mean a lot. Mars Society founder and Martian exploration evangelist Robert Zubrin told Elon Musk that he is concerned about how much solar energy is actually needed to refuel a single Starship, stating that it must be a solar field the size of six to 10 football fields. To that, Elon said, "So be it." (upbeat music) Now, before we try to compare rockets to anything else, like airliners, we should probably talk about how rocket emissions have different effects at different altitudes.

Now, because rockets burn their propellant in all layers of the atmosphere, including the upper atmosphere known as the stratosphere, and even beyond that, their effects can last much longer since they don't actually end up cycling as much. quickly. like at sea level. And since CO2, soot and water vapor are greenhouse gases, the longer they are in the air, the more time they have to warm our planet due to a process known as radiative forcing. Water vapor in the lower atmosphere transforms very quickly into clouds and rain and is regulated almost automatically by nature. No problem. Although CO2 does not circulate as quickly or as easily as water vapor, over time it can circulate in the troposphere, becoming delicious food for trees.

But when you put any of these things very high in the atmosphere, they tend to stick around much longer. In reality, water vapor is a much more powerful greenhouse gas than CO2. You can think of CO2 as a thermostat and water vapor as a heater. But regardless, CO2 emissions in the stratosphere from rockets are not really that different from CO2 emissions in the troposphere, or lower atmosphere. But what should worry us most is placing carbon, soot and alumina in the stratosphere instead of water vapor or CO2. So rockets that have, say, SRB or RP-1 will produce a fair amount of soot or aluminum.

And one study showed that they can generate about 30 times more atmospheric warming or radiative forcing than a Hydrolox rocket. And it's actually a little more confusing here because when it comes to emissions in the stratosphere versus, say, the troposphere, there are actually certain places where there are huge impacts. Researchers discovered that when planes fly in conditions that will create those condensation trails, which is the right combination of altitude, humidity and temperature, those clouds of frozen ice like streaks in the sky will end up trapping a surprising amount of heat on our planet. . atmosphere. A study published in February 2020 by a group of researchers at Imperial College London found that minor changes in aircraft altitude can have drastic changes in their effects on emissions.

But all researchers tend to agree that they really need to study this more to accurately calculate and model the impact that stratosphere commissions have because, honestly, it's all very confusing. (bright, happy music) So this is all starting to get pretty interesting. I think it's time we compare rockets to airliners and get an idea of ​​how bad rockets are, especially when used to transport people. And I know we've already thrown out a lot of numbers, a lot. And there really hasn't been much context for these numbers. But I really wanted to lay it all out so you know exactly what is thrown into the air when a rocket is launched.

So let's do a little comparison of six different vehicles, six very different vehicles. We are going to compare the three vehicles that can currently transport astronauts to the International Space Station, which are the Falcon 9, the Atlas V N22 and the Soyuz. Then we will also add Starship, along with two very common airliners, the Boeing 747-8 and the Boeing 737-800. The reason I chose these vehicles is because, again, they all carry passengers and, even more fun, the Falcon 9, the Soyuz and the Atlas V booster and the two planes run on virtually the exact same fuel . The Jets run on Jet-A fuel, which is again just a highly refined kerosene, while the Rockets run on RP-1, which is an even more refined kerosene.

The reason I put Starship in this mix is ​​mainly because, A, it's incredibly huge. And for now it represents a worst-case rocket in terms of total emissions and B, SpaceX really wants to use it as point-to-point transportation on Earth. So we will cite the Starship in two configurations: Starship and super heavy for orbital spaceflight missions and also just Starship for rapid ground-to-Earth transport that could one day directly compete with the airline industry. One more note here. We first calculated the worst-case scenario for a passenger plane, as if it were flying with all its fuel and had used it up on each and every flight.

But it would be a really bad flight if your plane ran out of fuel. And the planes only fill a little more than they really need for their route. That said, we take their maximum potential production as if their tanks were full to the brim and then divide that in half, as it's a much better representation of the overall average amount of fuel used by these airliners in, say, half. . or long-distance route. What I should really mention, if we compare it to Starship, we should really only compare the long distance routes. But I thought it was a pretty decent estimate.

And since we can compare CO2 between rockets and airplanes quite well, let's focus on the CO2 emissions of all these vehicles. But we want to keep in mind that rockets that emit carbon or alumina into the stratosphere, like the Falcon 9, Atlas V, and Soyuz, are definitely not a good thing. So as we showed before: Falcon 9 releases 425 tons of CO2 per flight, Atlas V 259 tons, Soyuz 243 tons, and Starship releases 2,683 tons for the full stack, and Starship alone releases 716 tons. Now compare that to a 747 with 302 tons of CO2 and 60 tons for the 737. But now remember, these numbers make planes only use half their fuel per flight.

So these numbers could vary greatly, and in reality, sometimes, they will probably be much lower than that. But I thought it was still a decent estimate of the average CO2 emissions of each different route. And furthermore, that can also vary, depending on how many people are on each flight. But yeah, that's not exclusive to airlines either. And now what about the passengers? The Falcon 9 can carry up to four passengers and a Dragon Crew capsule, the Starliner atop an Atlas V can also carry four passengers. The Soyuz and Soyuz Capsule can carry three passengers. Starship can carry up to 100 passengers to low Earth orbit.

And then after they refuel it, it could take those same 100 people to the Moon or on really long trips to Mars. For Starship point-to-point, we don't have an exact number. But considering that there are almost 1,000 cubic meters of pressurized payload capacity, let's say that 400 passengers could be comfortable on a 45-minute flight. Now let's compare this with a 747 that can accommodate up to 416 passengers and only 756 cubic meters of volume. You'll notice that 400 on a spaceship for a short period was quite conservative. And finally, the 737 can carry up to 180 passengers. So what about CO2 per passenger? Well, this is where some of these rockets really aren't an ideal form of transportation.

With the Falcon 9 with 106.25 tons of CO2 per passenger, the Atlas V with 64.75 per passenger and the Soyuz with 81 tons of CO2 per passenger per flight. But don't forget that low Earth orbit and Dallas are very different destinations. Now compare that to the 26.83 tonnes of an orbital spacecraft with 100 people on board and you'll realize that we can actually make some pretty drastic improvements to the per passenger numbers. And then look at Starship doing suborbital trips with 400 people, it would drop to just 1.79 tons per passenger. Actually, that's not so bad. I compare it to a 747 with 0.73 tons per passenger and the 737 is the king here with only 0.33 tons per passenger.

So Starship is actually pretty close to a 747, at least when it comes to CO2 emissions per passenger. On certain longer routes with certain passenger loads, it could be very comparable. Sure, in general, it could be twice as bad on certain routes and things. But at least it's not two orders of magnitude worse, like some of the other rockets. But let's not forget now, with carbon capture, we could almost completely negate an entire Starship flight. And that's something you simply can't do with RP-1 or Jet-A jet fuel, although synthetic jet fuels are being worked on. But with continued improvements, can we ever make rockets as efficient as airliners?

Now, one might be tempted to think that because rockets only burn fuel for a few minutes and then glide through the frictionless vacuum of space, they might actually be a really efficient form of transportation. Well, the problem lies in two main issues. First, a rocket has to counteract gravity in order to fly. So to take off, it has to at least create its own thrust path before the being even starts moving. This is called gravity drag. Imagine if a rocket had a thrust-to-weight ratio of 1.2. The relative acceleration is only 0.2 g because gravity pulls it down with one g.

If you gave that same rocket a thrust-to-weight ratio of 2.0, you would essentially accomplish five times the amount of work because the relative acceleration is a full g in addition to the g pulling against the rocket. This is something that airplanes don't really need to deal with. Its aerodynamic lift is what counteracts and overcomes gravity. Although this lift can actually induce drag, the engines themselves do not need to waste energy to directly counteract gravity, so aircraft can fly with a thrust-to-weight ratio of less than one. Although some fighter aircraft can and do have a thrust-to-weight ratio greater than one.

And that rules. The other issue between rocket engines and jet engines is engine efficiency. Chemical rocket engines, although some are becoming quite efficient, can't really exceed 450 seconds of specific impulse in a vacuum, which is their measure of how much work can be done with X amount of fuel. Here it iswhere jet engines have a huge advantage as their specific impulse is usually measured in thousands. And they can cheat by using oxygen from the atmosphere and also using air as a reaction mass. So a jet engine can simply do much, much more work with the same amount of fuel.

So even though a jet engine needs to run for hours and hours to actually cover the same distance that a rocket can travel in just seven minutes of burning a rocket engine, a jet engine actually consumes much, much less fuel all the time. phase, because their wings provide lift and jet engines are so efficient. While the rocket will need to consume much more fuel in a very short period of time to do the same amount of work. I mean, just look at a rocket and a plane. A rocket is basically all fuel and a small payload and an airplane is basically the exact opposite.

That pretty much tells the whole story, so the Skylon hybrid rocket plane concept would definitely be quite attractive. It's mixing the best of both worlds. While in the atmosphere, your SABER engine uses oxygen in the air to perform an efficient air breathing cycle. He also uses winged wallets in the atmosphere. Once the atmosphere becomes too thin for its engine or wings to run on that cycle, the engine switches to a closed-loop system where it operates more like a traditional rocket engine. This would be a really interesting concept that could help bridge the gap between rockets and airliners.

I certainly need to make an updated version of my video on single stage vehicles in orbit and debate whether we will actually see them fly or not. So hang on because I think this is definitely a video I need to redo. (bright, upbeat music) So I think it's time we look at how many launches there are per year and compare it to the number of flights per year in the commercial airline industry. In 2018, there were 114 orbital launch attempts, which was actually the most orbital launches in almost 30 years. The majority of launches came from China that year, closely followed by the United States and only SpaceX, which accounted for the vast majority of American launches.

However, in that same year there were 37,800,000 commercial aircraft departures. That's 331,579 times more flights than rocket launches. CO2 emissions from all commercial aviation in 2018 amounted to 918 million tons of CO2. Now compare that to the aerospace industry's 22,780 tons in that same year and we realize that we need to fly 40,300 times as many rockets per year to match the production of airliners. This is equivalent to 4,594,200 rocket launches per year or 12,586 launches per day. And that's the same proportion of dirty solid rocket propellants, hypergolic rockets or kerolox that we had in 2018, rather than this new trend we're seeing toward cleaner metalox or hydrolox alternatives.

Although in 2018, with China launching the most solid and hypergolic rockets and dramatically increasing their launch rates, it might be a while before the cleaner rockets truly surpass the dirtier ones. Well, now we know what it would be like to continue launching fairly small rockets, like those of 2018 with their modest CO2 emissions. Now, how many Starship launches per day would it take for there to be two identical aircraft? The answer: 937 full Starship/super heavy launches, or 3,512 point-to-point Starship launches per day. But wait, let's pause and remember that we still need to study more the effects that water vapor and CO2 have on our stratosphere in order to better understand them.

But even if we found out that they are an order of magnitude worse than we previously thought, we would still be launching an enormous number of megarockets per day before it even begins to compare to the airline industry. Now, believe it or not, the nitrogen oxides that form during reentry can have a quite negative effect on stratospheric ozone. In fact, returning for reentry may be as bad for the ozone as the actual ascent. So if a vehicle like Starship flew 5,000 times a year, it would produce as much ozone damage as all the meteorites during that same period of time.

So if we started to see Starship flying as frequently as a passenger airliner, ozone depletion due to re-entry and nitrogen oxide emissions during ascent would certainly become a really big concern that airliners face. of passengers would not have to deal with. (bright, upbeat music) And now I think it's time to put airplanes into perspective, since we've been using them as a benchmark for CO2 emissions. CO2 emissions from the airline industry accounted for only 2.4% of global CO2 emissions. That means that in 2018, global CO2 production from rockets was only 0.0000059% of all CO2 emissions. In other words, there are a lot of bigger fish to sort out.

Worrying about the current CO2 output of rockets compared to the rest of the world's contributions would be like worrying about focusing on a single leaf of a forest fire. There are much worse criminals we should be focusing on. Maybe there's something we should focus on before worrying about rockets. 2-stroke internal combustion engines. Those cheap little engines that power leaf blowers, chainsaws, lawnmowers and some jet skis. They only burn cleanly about 70% of the gas you put in them. The rest actually turns into pollutants like carbon monoxide, nitrous oxide, and hydrocarbons. Tests found that a 2-stroke eco-friendly leaf blower is actually a terrible polluter.

It generates 23 times more carbon monoxide and almost 300 times more non-methane hydrocarbons or NMHC than a Ford F-150 SVT Raptor. So, to put this in perspective, the hydrocarbon emissions from about a half hour of yard work with a two-stroke leaf blower are about the same as driving 1,300 miles from Florida to Portland, Maine, in a Ford F-150. SVT Raptor 2011. And when it comes to the transportation industry, old cars and light vehicles on the roads account for more than 50% of the transportation industry's global CO2 emissions. So let's assume that Starship actually ends up launching and producing as much as the entire airline industry currently does.

And it doesn't reduce airline demand, all we have to do is reduce total car missions by just 15% globally. Now forget about semis, buses, trains, planes, shipping, don't touch any of that. Only passenger cars. In fact, it would offset the launches of the entire Starship Point to Point fleet more than 3,500 times a day. And I'm going to go ahead and personally guess that by the time Starship point-to-point flies consistently in a decade or two, the cars will have made a much bigger improvement in their overall emissions. And if Elon Musk really has his way, the world will transition to more sustainable cars sooner rather than later.

And we are still not even close to talking about the biggest polluters. Again, if we are concerned about pollution or CO2 emissions, there are many bigger fish to sort out. I mean, rockets don't even begin to tip the scales or put a blip on the global emissions radar. (bright, happy music) So rockets are just a small drop in the grand scheme of today's emissions. But that doesn't mean we should just give them a pass, right? I mean, shouldn't all industries work to improve? So what steps can the aerospace industry take to achieve tangible improvements? As far as each rocket is concerned, the most obvious thing to do is to stop using solid rocket boosters.

SRBs are very harmful to our environment. They emit unpleasant toxic compounds and deplete ozone. So we should probably stay away from hypergolic and fossil fuel-based fuels like RP-1. That would be another good step. Using methane or hydrogen could be more sustainable either by producing hydrogen from electrolysis or by continuing that process and removing CO2 from the atmosphere and producing methane. But if we go a step further, the industry should use closed cycle engines such as the RD-180, RS-25, RD-181, full flow stage combustion cycle Raptor engine and BE-4, They will have a more complete combustion and do not pollute as much as an open cycle engine with a gas generator, especially when burning RP-1.

Closed cycle engines also tend to have a higher specific impulse, meaning they can actually do more work with the same amount of fuel because it's like the fuel economy of a rocket. Improving it is a total win. But perhaps the most important thing by far would be to stop raving about it. Again, as I briefly mentioned, making a rocket produces a lot of CO2 and pollution itself. We're not even halfway there. In fact, steel manufacturing is a huge global producer of CO2, producing around 8% of global CO2 emissions. But using steel might be a better option than using carbon composites or carbon fiber, because you will produce a lot of CO2 in production or in the autoclave when you cure it.

Now, again, because the manufacturing process produces all of these emissions, when a rocket is scrapped at each launch, we would need to add those emissions to the launch to get the total output of the rocket. If a rocket is reused over and over again, those manufacturing emissions can be spread over the life of the rocket, which would greatly reduce the rocket's total emissions more than any fuel change or choice could achieve. motor. But in terms of improving rockets, we should change the fuels, change the engines and reuse them. Honestly, it's that simple. And of course, these are all trends in the aerospace industry.

Really, it's a win-win situation. Or maybe we should all just plant a few billion trees. # Team trees. Sorry I'm very late to this. But in reality, now is probably as good a time as any to shut down and plant some more trees at teamtrees.org. Because whether it is or not, rockets are really that important to our air. No one can argue that trees are not a really good thing. (upbeat music) To summarize. How bad are rockets for our air and climate? Well, compared to other forms of transportation, every rocket that is launched is not great in and of itself.

I mean, you probably don't want to start sending simple packets via rockets. But the cost will probably always keep it off the table anyway. But compared to even a small player in total CO2 emissions like the airline industry, rockets currently don't even compare at all. We would need several orders of magnitude more releases to even begin to take into account their contributions compared to other industries. Obviously, rockets are not ideal. But for now, they're all we have. And it will be a long, long time before we have to worry about the environmental impact they have on our air, at least compared to, frankly, almost everything else.

And not to mention the possibility of removing heavy industry from our planet using rockets. Perhaps its slight emissions could end up being our planet's greatest savior. And furthermore, if it were not for rockets, we would not have the observation and data collection satellites that we can use to monitor our planet and other worlds well to further shape our knowledge about our place in the universe and our effects on our little planet. . So what do you guys think? Do you think rockets are something terrible and that we should stop launching them immediately? Do you think there's something we should just pay attention to and tweak and hope we can get better at?

Or do you think they're actually not that important compared to everything else? Let me know your opinion in the comments below. I have some very special things to give for this video because it was very difficult. And if it weren't for people like Lisa Stojafoski, who helped me research a lot of these topics, or Maryliz Bender and Ryan Chylinski from Cosmic Perspective for helping me film some of those scenes and some of these beautiful rocket launches, I would. I haven't had such an amazing video. Or, especially, many thanks to the Kennedy Space Center Visitor Complex for allowing me to come out and shoot in the rocket garden.

I mean, what a dream come true. How wonderful was that? But of course, I still owe a huge thank you to my Patreon supporters. Guys, this one almost ruined me. And you were very patient in helping me discover all these strange details and small nuances of this topic. And you really gave me great feedback. So I owe you the biggest thank you for not only being patient butalso for helping me with the script and research. If this is something you want to help do if you're sitting here wishing you could contribute or maybe add your opinion on the script before it comes out, consider becoming a Patreon member.

Well, you'll also get access to our exclusive subreddit, our exclusive Discord channel, and monthly live streams at patreon.com/everydayastronaut. Or if you'd like another fun way to support what I do, consider visiting dailyastronaut.com/shop. We'll find awesome t-shirts like the Full Flow Stage Combustion Cycle T-shirt, which is, I guess, one of Elon Musk's favorite t-shirts. And you can find other things like the aerospike t-shirt or the flaming tip and down t-shirt. And don't forget, there's also our scheduled quick markdown section where you can get some really good deals on leftover inventory. And if you work in the aerospace industry, click the link in the apparel section and you can get 25% off any apparel as a thank you for helping us get off this planet.

So keep up the good work. We are all counting on you. That's dailyastronaut.com/shop. Thank you all. That will be enough for me. I'm Tim Dodd, your everyday astronaut. Bringing space closer to earth for everyday people. (bright and happy music)