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Comment by ripvanwinkle | Hacker News Reader

Hate to be that guy but what's the environmental impact of flying folks to orbit "just for kicks" if this were to become a business

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Per capita, a lot. In absolute terms, effectively zero.

Do you know roughly how many "car-hours" this flight would be in terms of green house emissions?

Not car-hours, but a Falcon 9 launch apparently has similar impact to a 777 crossing the Atlantic. Not nothing, but surprisingly little all things considered.

https://www.treehugger.com/spacex-launch-puts-out-much-co-fl...

Yea that is surprisingly low, if accurate.

I mean, they're both 200 foot long tubes full of fuel that gets used up by the end of the flight. Only so much carbon you can fit into a set volume.

Agreed, though without considering it as such if someone asked me to compare to an airliner I would have placed it between 10-100x the emissions, and would not have been surprised at more!

Remember 3/4 of the rocket is just the oxygen for combustion!

Difference being the per person emissions. 4 people, vs upwards for 250. But still not nearly as bad as I thought it might be.

per capita, sure. Another way to think about it is this capsule is flying what, twice a year? One 777 will do 2 trips in 24 hrs, 365 days a year. Then add up the thousands of planes doing that a day. I'd be worried if we ALL had a reason (and the means) to take frivolous space flights. Which may come some day out of all this, who knows anymore!?!

About 8.4 car seconds of fuel.

Data: Us burns about 390,000,000 gallons of gas per day.

SpaceX Falcon9 uses about 38,000 gallons of RP-1.

390000000/86400 = 4513 (gallons per second of fuel in the US).

38,000/4500 = 8.4 seconds.

On the day this launches, it will represent about 0.0097% of the fuel used for that day in the US.

There are about 280 cars in this photo: https://cimg0.ibsrv.net/ibimg/hgm/450x253-1/100/226/parking-...

If you printed out this image 40 times, you could delete ONE car from this image for one day. That's the difference that this launch will make.

This caused me to look up largest parking lots. You can fit approximately that many cars in the parking lots at Disney in Florida on any given day (11k+ spots). Though I don't know how full they actually get.

Depends a lot on the fuel used. Solid boosters are terrible. Kerosene, like on the Falcon not too bad, but not great. Methane is better, it can in theory be made carbon neutral. Hydrogen is the best because it only produces water, but it’s not great as a first stage.

> Methane is better, it can in theory be made carbon neutral.

Methane is a much stronger greenhouse gas than the amount of CO2 you get when you burn it. Most sources/uses of it are a net positive in terms of greenhouse effect.

Here's some back of the envelope calculations.

The Raptor engine uses a propellant mixture (methalox = liquid methane + liquid oxygen) that is slightly fuel rich. In other words, the reaction resultants are not just CO2 and H2O, but CH4 as well. Since CH4 is a very potent greenhouse gas (the EPA says it's 25 times more potent than CO2), this makes a difference.

Anyway, here's the numbers: the mass of the propellant is about 500 tons, and the mass of the equivalent CO2 emissions is about 650 tons per flight.

For comparison, the humankind puts about 30 billion tons of CO2 in the air every year. A Boeing 777 flight puts about 500 tons on a long haul trip.

The Falcon 9 is equipped with Merlin engines which burn Kerosene fuel.

Becoming space faring could allow us to have a trillion humans and have the planet be effectively a nature preserve. So long term net positive environmental impact I expect.

There's no need for a specific number of humans larger than what's necessary to continue the species indefinitely. We can easily become sustainable on Earth as we were for thousands of years with or without space colonization.

There's no need for a specific number of humans larger than what's necessary to continue the species indefinitely.

"continuation of the species" is an arbitrary, and arguably pointless, goal though. I think we should be aiming higher than that. If exploring the universe is a possibility then a trillion people might well be necessary - the universe is a big space. Heck, we'll probably need a trillion times that number.

A trillion would need a decent amount of automation that has not yet been invented, and that same automation would make quintillions possible even just in this solar system.

Can someone help me understand why I was down voted. Is there anything wrong about thinking of the impact of something like this becoming a commonplace luxury.

Most likely because we're not anywhere remotely close to this becoming a commonplace luxury, and the impact of this happening twice a year is essentially zero.

Also on an tangent, advances in launch industry = moving industries to space. This could reduce pollution drastically on Earth. So the net carbon footprint of the launch industry could even become negative.

Starting with

> Hate to be that guy but

will give some readers immediate negative connotations (i.e. that you are in fact 'that guy'). Asking the question without the 'that guy' preamble might still be seen as an off-topic downer but may have raised fewer hackles amongst the downvoters.

Perhaps.

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