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.
ā¦That sounds like bull, and quick back-of-the-envelope arithmetic shows thereās probably no way itās true in the general sense.
Falcon9LEOpayload,expended:22.8tPayload,recovered:17.4tStructural material:Variousaero-gradealuminiumalloys.First stage dry mass:25.6tPropellantmass(LOX+RP-1):395.7tSecond stage dry mass:3.9tPropellant mass:92.67tCOāemissions to produce aluminium:2tĀ·COā/tĀ·Alto20+tĀ·COā/tĀ·Al(DependingonwhetherfossilfuelsareusedāAlisveryenergy-intensive.MINIMUM.Doesnotincludemining,alumina,alloying,machining,etc.)COāemissionstoburnLOX+RP-1:~0.8tĀ·COā/tĀ·Fuel
The launch kinematics shouldnāt change too much otherwise, so assume the difference in payload approximately correlates to the fuel amount that must be savedā Oversimplifying and overly linear, I know. (Iām 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 11tĀ·COā/tĀ·A instead of 2tĀ·COā/tĀ·A:
ā¦Then weāre 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.
ā¦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. Iām honestly pretty surprised by this too; Youād think, and Iāve always personally assumed, that the big tank of carbon-based fuel and not the thin sheet of metal around it would release the most COā, 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 youāve 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 donāt 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 youāre āal[l]ocating energy toward putting stuff in spaceā much less efficiently because youāre spending (apparently) much more fuel and energy to replace the rocket.
If you meant ātotal mass and fuel in the rocketā, then frankly thatās an arbitrary and cherry-picked metric in this context. If youāre talking about the social impact and technological history of first NASA then SpaceX developing reusable rockets, then āefficiencyā should include everything that theyāre 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.
ā¦So its ānicheā isā¦ 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 arenāt really relevant to space launch), is āputting satellites into orbitā (regardless of whether those artificial satellites house crew that theyāre then going to ferry Mars, or whether theyāre 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.
āFor certain jobsāā Yeah, no, not really, at least unless you can name those ācertain jobsā.
Sometimes a payload is too heavy for reusable mode but still okay for expendable mode. But thatās not really being āinefficientā, 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 thatās 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 Twitās 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.
Yeahā¦ I feel like youāre getting defensive because I might have come across as trying to dunk on youā¦ Which isā¦ Fair enough, I guess, and sorry if I came across that way.
And I get not wanting to like anything that Muskās tied his name to. But you presented yourself as an authorative/informed speaker on a technical subject, while making a claim that simply isnāt true.
ā¦That sounds like bull, and quick back-of-the-envelope arithmetic shows thereās probably no way itās 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 COā emissions to produce aluminium: 2tĀ·COā/tĀ·Al to 20+tĀ·COā/tĀ·Al (Depending on whether fossil fuels are usedā Al is very energy-intensive. MINIMUM. Does not include mining, alumina, alloying, machining, etc.) COā emissions to burn LOX+RP-1: ~0.8tĀ·COā/tĀ·FuelThe launch kinematics shouldnāt change too much otherwise, so assume the difference in payload approximately correlates to the fuel amount that must be savedā Oversimplifying and overly linear, I know. (Iām 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
11tĀ·COā/tĀ·Ainstead of2tĀ·COā/tĀ·A:(25.6t * (11t/t)) / ((22.8t - 17.4t) * (0.8t/t))ā¦Then weāre 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.
ā¦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. Iām honestly pretty surprised by this too; Youād think, and Iāve always personally assumed, that the big tank of carbon-based fuel and not the thin sheet of metal around it would release the most COā, 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 youāve 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 donāt 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 youāre āal[l]ocating energy toward putting stuff in spaceā much less efficiently because youāre spending (apparently) much more fuel and energy to replace the rocket.
If you meant ātotal mass and fuel in the rocketā, then frankly thatās an arbitrary and cherry-picked metric in this context. If youāre talking about the social impact and technological history of first NASA then SpaceX developing reusable rockets, then āefficiencyā should include everything that theyāre paying for.
ā¦So its ānicheā isā¦ 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 arenāt really relevant to space launch), is āputting satellites into orbitā (regardless of whether those artificial satellites house crew that theyāre then going to ferry Mars, or whether theyāre just there to relay your cat gifs).
āFor certain jobsāā Yeah, no, not really, at least unless you can name those ācertain jobsā.
Sometimes a payload is too heavy for reusable mode but still okay for expendable mode. But thatās not really being āinefficientā, 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 thatās 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 Twitās 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.
Yeahā¦ I feel like youāre getting defensive because I might have come across as trying to dunk on youā¦ Which isā¦ Fair enough, I guess, and sorry if I came across that way.
And I get not wanting to like anything that Muskās tied his name to. But you presented yourself as an authorative/informed speaker on a technical subject, while making a claim that simply isnāt true.