Reread what I typed, reusablle rockets have their place but they can become rather inefficient or even outright wasteful depending on the circumstances. Remember it takes about a lot of energy to land something coming down from orbit, that means more fuel, more fuel means more weight. And sometimes it better to put that fuel and weight into putting more shit into orbit.
Remember it takes about a lot of energy to land something coming down from orbit, that means more fuel, more fuel means more weight. And sometimes it better to put that fuel and weight into putting more shit into orbit.
…That sounds like bull, and quick back-of-the-envelope arithmetic shows there’s probably no way it’s true in the general sense.
Falcon 9 LEO payload, expended: 22.8t
Payload, recovered: 17.4t
Structural material: Various aero-grade aluminium alloys.
First stage dry mass: 25.6t
Propellant mass (LOX+RP-1): 395.7t
Second stage dry mass: 3.9t
Propellant mass: 92.67t
CO₂ emissions to produce aluminium: 2t·CO₂/t·Al to 20+t·CO₂/t·Al
(Depending on whether fossil fuels are used— Al is very energy-intensive. MINIMUM. Does not include mining, alumina, alloying, machining, etc.)
CO₂ emissions to burn LOX+RP-1: ~0.8t·CO₂/t·Fuel
The launch kinematics shouldn’t change too much otherwise, so assume the difference in payload approximately correlates to the fuel amount that must be saved— Oversimplifying and overly linear, I know. (I’m not breaking out Tsiolkovsky for this. You do it, if you want.):
In even the most conservative scenario, the carbon footprint of the extra fuel to land a Falcon 9 will be somewhere in the neighbourhood of 12X less than even just the raw material costs to replace the aluminium in it.
If we assume a more typical US aluminium production process for a US company, resulting in 11t·CO₂/t·A instead of 2t·CO₂/t·A:
…Then we’re looking at the carbon footprint of the fuel to reuse a rocket being 65X lower the carbon footprint of replacing it. This is still not even counting either the actual mining, preprocessing, and alloying of the aluminium ore nor the machining nor the rocket structure, so the real number will be even higher.
…In fact, it looks like nearly half of all the carbon emissions from a rocket launch are likely to come from just manufacturing the rocket, not even the fuel it burns. I’m honestly pretty surprised by this too; You’d think, and I’ve always personally assumed, that the big tank of carbon-based fuel and not the thin sheet of metal around it would release the most CO₂, but apparently not.
I guess it makes sense when you remember that GHG costs for other types of vehicles are usually amortized over the useful lifespan of the vehicle in question.
Reusable rockets are just kinda inefficient for a lot of shit.
Remember it takes about a lot of energy to land something coming down from orbit,
This entire premise is somewhere between false and dishonest or misinformed. It costs basically zero energy to land something coming down from orbit, compared to what you’ve already spent to send it up there in the first place, because all you have to do is lower your periapsis into the atmosphere and then fire a quick thrust burst for a couple seconds to land at the end once air drag has done all the hard work of bringing you down from hypersonic to subsonic terminal velocity. The Saturn V had to be millions of tonnes to get to the Moon, but the command module and capsule to get back was kinematically basically one step above an inert rock with a couple of whoopee cushions strapped to the back.
Call out the shitty labour practices, security risks, and deeply problematic political and economic injustices. But don’t try to lie about physics.
Firstly I wasnt even thinking about co2 emisions and was thinking almost exclusively in total mass movement. Secondly when I was refering to the amount of fuel required for slow down for landing I was more so thinking yet again in total mass. Almost all of my points on the matter had to do with the idea of alocating energy toward putting stuff in space.
If you can realocate fuel toward moving stuff further into space for example. I doubt think the falcon is completely bad either, just that it has its niche. If memory serves me right its mostly doing things like putting satalites into orbit, thats a great use of a reuasble rocket.
All I was stating is that such rockets can be kinda inefficient for certain jobs. To put it in nautical terms you wouldnt use a fishing trawler as heavy cargo ship.
Perhaps this is showing my ignorance for arospace shit, IDK but as I understand it more fuel and less mass means you can get shit farther. Thats all I was really thinking.
Firstly I wasnt even thinking about co2 emisions and was thinking almost exclusively in total mass movement. Secondly when I was refering to the amount of fuel required for slow down for landing I was more so thinking yet again in total mass. Almost all of my points on the matter had to do with the idea of alocating energy toward putting stuff in space.
What do you think the GHG from the manufacturing comes from? Expendable rockets means you’re “al[l]ocating energy toward putting stuff in space” much less efficiently because you’re spending (apparently) much more fuel and energy to replace the rocket.
If you meant “total mass and fuel in the rocket”, then frankly that’s an arbitrary and cherry-picked metric in this context. If you’re talking about the social impact and technological history of first NASA then SpaceX developing reusable rockets, then “efficiency” should include everything that they’re paying for.
I doubt think the falcon is completely bad either, just that it has its niche. If memory serves me right its mostly doing things like putting satalites into orbit, thats a great use of a reuasble rocket.
…So its “niche” is… Literally the entire thing that space launch rockets are scientifically and economically useful for???
Literally every space mission, outside of like upper atmospheric research sounding rocket launches (which aren’t really relevant to space launch), is “putting satellites into orbit” (regardless of whether those artificial satellites house crew that they’re then going to ferry Mars, or whether they’re just there to relay your cat gifs).
All I was stating is that such rockets can be kinda inefficient for certain jobs. To put it in nautical terms you wouldnt use a fishing trawler as heavy cargo ship.
“For certain jobs”— Yeah, no, not really, at least unless you can name those “certain jobs”.
Sometimes a payload is too heavy for reusable mode but still okay for expendable mode. But that’s not really being “inefficient”, just too small, and would be more efficiently solved with a bigger reusable rocket. And there are certification and supply chain concerns which mean that expendable systems like SLS and Ariane 6 still sorta have a place for now, but that’s not really an efficiency issue either.
But overall, from tiny cubesats to massive moon landings, reusable rockets are consistently and increasingly demonstrating significant efficiency advantages in all areas of spaceflight, because as it turns out, despite all of Chief Twit’s mistakes and harms, throwing away the rocket after you use it once was in fact just a sorta dumb way to do things in the first place.
Perhaps this is showing my ignorance for arospace shit, IDK but as I understand it more fuel and less mass means you can get shit farther. Thats all I was really thinking.
Yeah… I feel like you’re getting defensive because I might have come across as trying to dunk on you… Which is… Fair enough, I guess, and sorry if I came across that way.
And I get not wanting to like anything that Musk’s tied his name to. But you presented yourself as an authorative/informed speaker on a technical subject, while making a claim that simply isn’t true.
Reread what I typed, reusablle rockets have their place but they can become rather inefficient or even outright wasteful depending on the circumstances. Remember it takes about a lot of energy to land something coming down from orbit, that means more fuel, more fuel means more weight. And sometimes it better to put that fuel and weight into putting more shit into orbit.
…That sounds like bull, and quick back-of-the-envelope arithmetic shows there’s probably no way it’s true in the general sense.
Falcon 9 LEO payload, expended: 22.8t Payload, recovered: 17.4t Structural material: Various aero-grade aluminium alloys. First stage dry mass: 25.6t Propellant mass (LOX+RP-1): 395.7t Second stage dry mass: 3.9t Propellant mass: 92.67t CO₂ emissions to produce aluminium: 2t·CO₂/t·Al to 20+t·CO₂/t·Al (Depending on whether fossil fuels are used— Al is very energy-intensive. MINIMUM. Does not include mining, alumina, alloying, machining, etc.) CO₂ emissions to burn LOX+RP-1: ~0.8t·CO₂/t·FuelThe launch kinematics shouldn’t change too much otherwise, so assume the difference in payload approximately correlates to the fuel amount that must be saved— Oversimplifying and overly linear, I know. (I’m not breaking out Tsiolkovsky for this. You do it, if you want.):
(25.6t * (2t/t)) / ((22.8t - 17.4t) * (0.8t/t))In even the most conservative scenario, the carbon footprint of the extra fuel to land a Falcon 9 will be somewhere in the neighbourhood of 12X less than even just the raw material costs to replace the aluminium in it.
If we assume a more typical US aluminium production process for a US company, resulting in
11t·CO₂/t·Ainstead of2t·CO₂/t·A:(25.6t * (11t/t)) / ((22.8t - 17.4t) * (0.8t/t))…Then we’re looking at the carbon footprint of the fuel to reuse a rocket being 65X lower the carbon footprint of replacing it. This is still not even counting either the actual mining, preprocessing, and alloying of the aluminium ore nor the machining nor the rocket structure, so the real number will be even higher.
…In fact, it looks like nearly half of all the carbon emissions from a rocket launch are likely to come from just manufacturing the rocket, not even the fuel it burns. I’m honestly pretty surprised by this too; You’d think, and I’ve always personally assumed, that the big tank of carbon-based fuel and not the thin sheet of metal around it would release the most CO₂, but apparently not.
((25.6t + 3.9t) * (11t/t)) / ((395.7t + 92.67t) * (0.8t/t))I guess it makes sense when you remember that GHG costs for other types of vehicles are usually amortized over the useful lifespan of the vehicle in question.
This entire premise is somewhere between false and dishonest or misinformed. It costs basically zero energy to land something coming down from orbit, compared to what you’ve already spent to send it up there in the first place, because all you have to do is lower your periapsis into the atmosphere and then fire a quick thrust burst for a couple seconds to land at the end once air drag has done all the hard work of bringing you down from hypersonic to subsonic terminal velocity. The Saturn V had to be millions of tonnes to get to the Moon, but the command module and capsule to get back was kinematically basically one step above an inert rock with a couple of whoopee cushions strapped to the back.
Call out the shitty labour practices, security risks, and deeply problematic political and economic injustices. But don’t try to lie about physics.
Firstly I wasnt even thinking about co2 emisions and was thinking almost exclusively in total mass movement. Secondly when I was refering to the amount of fuel required for slow down for landing I was more so thinking yet again in total mass. Almost all of my points on the matter had to do with the idea of alocating energy toward putting stuff in space.
If you can realocate fuel toward moving stuff further into space for example. I doubt think the falcon is completely bad either, just that it has its niche. If memory serves me right its mostly doing things like putting satalites into orbit, thats a great use of a reuasble rocket.
All I was stating is that such rockets can be kinda inefficient for certain jobs. To put it in nautical terms you wouldnt use a fishing trawler as heavy cargo ship.
Perhaps this is showing my ignorance for arospace shit, IDK but as I understand it more fuel and less mass means you can get shit farther. Thats all I was really thinking.
What do you think the GHG from the manufacturing comes from? Expendable rockets means you’re “al[l]ocating energy toward putting stuff in space” much less efficiently because you’re spending (apparently) much more fuel and energy to replace the rocket.
If you meant “total mass and fuel in the rocket”, then frankly that’s an arbitrary and cherry-picked metric in this context. If you’re talking about the social impact and technological history of first NASA then SpaceX developing reusable rockets, then “efficiency” should include everything that they’re paying for.
…So its “niche” is… Literally the entire thing that space launch rockets are scientifically and economically useful for???
Literally every space mission, outside of like upper atmospheric research sounding rocket launches (which aren’t really relevant to space launch), is “putting satellites into orbit” (regardless of whether those artificial satellites house crew that they’re then going to ferry Mars, or whether they’re just there to relay your cat gifs).
“For certain jobs”— Yeah, no, not really, at least unless you can name those “certain jobs”.
Sometimes a payload is too heavy for reusable mode but still okay for expendable mode. But that’s not really being “inefficient”, just too small, and would be more efficiently solved with a bigger reusable rocket. And there are certification and supply chain concerns which mean that expendable systems like SLS and Ariane 6 still sorta have a place for now, but that’s not really an efficiency issue either.
But overall, from tiny cubesats to massive moon landings, reusable rockets are consistently and increasingly demonstrating significant efficiency advantages in all areas of spaceflight, because as it turns out, despite all of Chief Twit’s mistakes and harms, throwing away the rocket after you use it once was in fact just a sorta dumb way to do things in the first place.
Yeah… I feel like you’re getting defensive because I might have come across as trying to dunk on you… Which is… Fair enough, I guess, and sorry if I came across that way.
And I get not wanting to like anything that Musk’s tied his name to. But you presented yourself as an authorative/informed speaker on a technical subject, while making a claim that simply isn’t true.