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A few things to bear in mind here. The payload of a rocket is far less of that of a 747, so you aren't remotely comparing like-with-like. Unlike planes rockets aren't typically reused, the energy cost of manufacturing is considerable. (SpaceX's reusable first stages are impressive, but there is a fuel and payload cost.) Finally, taking a flight is about the highest carbon-emitting activity we do - one transatlantic trip is roughly equivalent to driving a car for a year.

Agreed. Thank you for adding this, to paint a fuller picture.

Space industry definitely isn't emissions-free, but right now it doesn't even register. We might have a problem in the future, but there's hope in switching to cleaner fuels planetside and eventually sourcing fuel for space operations from space. As it is today, in my opinion space industry has very good value proposition in terms of utility/carbon emitted.

Charge wise they are closer than you might think.

The 747’s net cargo of passengers plus luggage probability amounts to around 300-400 lb per passenger. 22,800 / 400 ~= 57 passanger equivalent to 22,800 / 300 ~= 76 passanger equivalents.

Further people take much longer trips than your benchmark getting them even closer.

> 300-400 lb per passenger

Maybe less if you're not talking about Americans. Even counting 40lb of luggage those are pretty porky passengers. :)

I was thinking luggage for long haul flights + clothing + carry on was extremely heavy. But, your right the average is probably far below that.

I was going by the max for a checked piece of luggage. The carryon will add some to that (20lbs?) but it's still a pretty generous weight allowance.

The 500 ton figure also includes the oxidizer which contain no carbon. The equivalent of a plane's jetfuel, RP-1, in a current Falcon 9 is just 123+32=155 metric tons [1].

[1] http://spaceflight101.com/spacerockets/falcon-9-ft/

> "A jumbo jet (Boeing 747-400) flying from London to New York burns approximately 70,000 kilograms of fuel"[0]

If numbers like this were regularly given to laypeople, the climate change discussion situation would be much better. That number for a single flight is ENORMOUS!

It would also help hammer home to people/politicians that we'll never have battery powered jumbo jets.

if you make a (square) "balloon" a bunch of km large you can use concrete and vacuum. :D

No, but it's not inconceivable to consider electric cars and biofuel powered jets. It's certainly possible to go mostly carbon neutral on our major transportation systems, but it's a lot of work.

747s burn a lot of fuel because they haul a lot of people over a long distance.

Per passenger you are getting something like 50mpg.

It's 2-3 tons carbon emitted per person, per flight. One flight like that would be approx. a quarter of the average carbon usually emitted per person. Shorter flights are much less efficient as a large chunk of fuel is used to simply take off.

Perhaps it's better to restrict oneself to flying OR driving that kind of distance. And it adds up - if you drive: do you ever look at your total mileage, then calculate your carbon emissions?

You are off by a few orders of magnitude. Total fuel load is 70,000kg and a 747-400 carries 416 passengers in a typical 3-class configuration[0]. That comes to only 168kg/passenger.

[0]https://en.wikipedia.org/wiki/Boeing_747

I was basically paraphrasing this:

https://www.nytimes.com/2013/01/27/sunday-review/the-biggest...

"For many people reading this, air travel is their most serious environmental sin. One round-trip flight from New York to Europe or to San Francisco creates a warming effect equivalent to 2 or 3 tons of carbon dioxide per person. The average American generates about 19 tons of carbon dioxide a year; the average European, 10."

Seems like there's some tricky math going on, notice: "equivalent" in the above quote:

http://www.carbonindependent.org/sources_aviation.html

This calculates 180 kg CO2/hour per passenger. So 8 hours or so between NYC and Paris? 1,440 kg. 1.6 tons. Not quite a few orders of magnitude.

Once through all the calculations, the above then states, "The CO2 emissions are therefore rounded up and the Carbon Independent calculator takes a values of 250 kg i.e. ¼ tonne CO2 equivalent per hour flying."

So that's more like 4 tons to Paris. (on Basis 1)

No idea what they mean by "Equivalent" either, I was just doing the math with the figures quotes up-thread.

Look at the correction at the bottom of the NYT piece:

> "A news analysis article last Sunday about the impact of air travel on global warming referred imprecisely to the environmental impact of one round-trip flight from New York to Europe or to San Francisco. It has a warming effect equivalent to 2 or 3 tons of carbon dioxide per person, but does not generate that much carbon dioxide per person. (The estimate also includes warming from other greenhouses gases.)"

So actual carbon output per person was correctly calculated, but there is some "carbon equivalent" multiplier slapped on other gasses that brings their totals up from 170kg/px to 2-3T/px.

Jet fuel is 840kg/m^3 so 70,000kg is ~146m^3 which is a cube roughly 5.2m/side.

I personally would not consider that a "enormous" amount of fuel to move 400+ people 5,500km.

How can there be fuels that don't emit CO2? Don't they burn?

By oxidizing something other than carbon, e.g. hydrogen. (Keep in mind that this is similar to calling EVs "zero emission": the vehicle itself does not emit carbon, but providing the energy source of course does; making hydrogen doesn't exactly have low energy demand).

Some hypergolic fuels don't even contain any carbon. For example, hydrazine and nitrogen tetroxide. Mostly what you're interested in rocket fuel is an oxidizer and lots of hydrogen.

Combustion is exothermic oxidization; that's something completely unrelated to carbon. E.g. hydrogen burns in presence of oxygen, releasing water. Or magnesium burns into magnesium oxide. It so happens that most of the fuels we burn have carbon in them, but that's not a requirement.

Huh, yeah, when you put it that way I guess oxidization requires oxygen but obviously does not require carbon. I'd never thought of that, thanks!

It does not require oxygen either. Oxidization happens when a substance reacts to any other one that attract more electrons.

Ah, that I didn't know at all, thank you.

That's a little thing that they tell you in high school chemistry classes (remember "reduction–oxidation reactions", or "redox"?), which you then promptly forget. I only remembered because of an unhealthy interest in home-made rocket propellants :).

> remember "reduction–oxidation reactions", or "redox"?

Clearly no :P Also I realized that, unless I have a specific problem I need to solve, I don't remember or like reading about things. I have been taught things in school/uni that I thought were terribly boring and was bad at, until I needed to solve a problem with that information and then I had to re-learn everything. Kind of a waste of time, but I can't change my brain!

Some common carbonless rocket fuels are hydrogen, hydrazine, and aluminum in solid rockets (boosters; ICBMs).

That said, they usually have an even larger CO2 footprint because processes used to make them take natural gas an an input, or use lots of electricity mostly coming from fossil fuels. The main reasons they're chosen are for their specific impulse (hydrogen) or long-term stability and readiness (solid fuel in ICBMs), rather than their CO2 emissions.