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Others have pointed out things wrong with that doomsday predicting Twitter thread. I wanted to add a couple of things * Rocket launches are a rounding error on

by zizee 4y ago

Others have pointed out things wrong with that doomsday predicting Twitter thread. I wanted to add a couple of things * Rocket launches are a rounding error on co2 emissions when compared to passenger aircraft * the worries about Kessler syndrome whilst simultaneously worrying about tonnes of aluminum and rare earth minerals (gasp) due to the short orbital lifetime of the satellites are contradictory. * Presumably astronomers are more worried about light pollution rather than ecological concerns On a side note, what is it about people hyping up rare earth materials? The twitter thread tries to make them sound scary. Others try to make them sound harder to find than gold.

viczsaszbo 4y ago
On the light pollution point, twilight is the worst time for satellite brightness, but as the satellites enter the Earth's shadow their brightness rapidly diminishes. Some estimates are 10%-30% data loss during twilight for Vera Rubin observatory and 2% for vlt. A problem for Vera Rubin, but not so much for other observatories. https://www.economist.com/international/2021/11/25/vast-satellite-constellations-are-alarming-astronomers https://www.economist.com/international/2021/11/25/vast-sate... https://www.economist.com/img/b/640/356/90/sites/default/files/images/print-edition/20211127_IRC301.png https://www.economist.com/img/b/640/356/90/sites/default/fil...
lm28469 4y ago
> Rocket launches > co2 emissions Good thing rockets only release co2 and not a long list of very nasty things Also good thing they stay at low altitude and don't go through every layers of the atmosphere while releasing said nasty things I'm no rocket engineer but your comment is extremely naive
- zizee 4y ago
  Naive eh? What "nasty things" do you think are released into "every layer of atmosphere"? Since we're specifically talking about SpaceX and Starlink, let's talk about Falcon and StarShip rockets. Let's look at the "long list of very nasty things". Falcon 9 is expecting to launch a record number of flights this year, recent reports suggesting 52. Falcon 9 burns RP1 (a refined kerosene, very similar to jet fuel), a hydrocarbon that mostly produces CO2 when burnt, but also Carbon monoxide, and plain old carbon. The Falcon 9 has about 200k litres of fuel when fully loaded. It sounds like a lot, but for perspective a fully loaded Airbus A380 has a fuel capacity of 380k litres. So, they output of a record breaking year will be the equivalent of around 25 long distance flights of a large passenger aircraft. I'm not going to find out how many long distance large plan flights are happening, but many estimates are over 100k a day. So a record breaking year outputs a fraction of a percentage that airline flights do each hour. And the "nasty" stuff is mostly CO2, CO, and C. Starship will burn Methane, and will burn even cleaner than Falcon 9. It will also be fully reusable, resulting in less waste again. On the downside, methane is a potent greenhouse gas, so any unburt fuel would be not great. That said, rockets are designed to make the most efficient of fuel, and any unburt fuel is not going to be released in normal operation. > I'm no rocket engineer Colour me shocked! As for going through "every layer" of the atmosphere, I wouldn't get too worried about that. A lot of a rocket's fuel is burnt at lower altitudes (the same level at which passenger and military Jets operate) and the various zone mix readily, and are really so massive that you would have trouble measuring the impact of hundreds to thousands of flights of Starship per year. https://space.stackexchange.com/questions/13082/calculate-falcon-9-co2-emissions https://space.stackexchange.com/questions/13082/calculate-fa... https://www.sciencefocus.com/space/what-is-the-environmental-impact-of-the-spacex-falcon-heavy-launch/ https://www.sciencefocus.com/space/what-is-the-environmental... https://www.sciencefocus.com/space/what-is-the-environmental-impact-of-the-spacex-falcon-heavy-launch/ https://www.sciencefocus.com/space/what-is-the-environmental... https://space.stackexchange.com/questions/32002/what-percentage-of-overall-fuel-does-a-rocket-burn-up-to-get-to-max-q https://space.stackexchange.com/questions/32002/what-percent...
  - lm28469 4y ago
    They specifically talk about falcon engines here: https://www.space.com/rocket-exhaust-pollution-upper-atmosphere https://www.space.com/rocket-exhaust-pollution-upper-atmosph... https://www.sciencedaily.com/releases/2022/05/220517112210.htm https://www.sciencedaily.com/releases/2022/05/220517112210.h... Anyways, "just one more car", "just one more plane", "just one more coal plant", "just want more launch", "it's not that much worse, just a tiny bit" https://sdup.esoc.esa.int/discosweb/statistics/static/PLtrafficMissionLEO.png https://sdup.esoc.esa.int/discosweb/statistics/static/PLtraf... https://www.eesi.org/images/content/World_Passenger_Traffic_Evolution_-_1945-2022_(Courtesy_ICAO).png https://www.eesi.org/images/content/World_Passenger_Traffic_...
    - zizee 4y ago
      From your links: > When it comes to greenhouse gasses alone, the contribution of rocket launches is rather negligible, accounting for only 1% of aviation's carbon footprint — which in itself only amounts to 2.4% of annual global carbon emissions, according to the Environmental and Energy Study Institute Apart from the fact they overinflated the impact to 1% (there is no way it is close to 1%) there is a reason they chose the adjective "negligible" to describe the impact. > Eventually, the circulation of the atmosphere dissipates those greenhouse gases and brings the concentrations back to "standard" levels. It is, however, unknown how long the concentrations remain elevated and what their impact on the temperature of the mesosphere could be. Reality is that these scientists did a simulation, got some results that can be made to sound alarming, but just don't know if these is any inpact. I'm all for studying this more to see if there is a real issue. My gut says it's not going to be a problem until we have at least a couplr of orders of magnitude increase in launches, but it's worth looking at it further. And I'm not sure why you included the graph of objects in orbit? This looks exciting, but it really is just that companies are now launching clusters of smaller satellites. The good news is that these tend to deorbit in under ten years. Unlike practices of old, this new style of satellite will not result in long lasting space junk. Finally, what is the point of including a graph of airline flights over time? What bearing does it have on rocket launches?

by zizee 4y ago

viczsaszbo 4y ago

On the light pollution point, twilight is the worst time for satellite brightness, but as the satellites enter the Earth's shadow their brightness rapidly diminishes. Some estimates are 10%-30% data loss during twilight for Vera Rubin observatory and 2% for vlt. A problem for Vera Rubin, but not so much for other observatories. https://www.economist.com/international/2021/11/25/vast-satellite-constellations-are-alarming-astronomers https://www.economist.com/international/2021/11/25/vast-sate... https://www.economist.com/img/b/640/356/90/sites/default/files/images/print-edition/20211127_IRC301.png https://www.economist.com/img/b/640/356/90/sites/default/fil...

lm28469 4y ago

> Rocket launches > co2 emissions Good thing rockets only release co2 and not a long list of very nasty things Also good thing they stay at low altitude and don't go through every layers of the atmosphere while releasing said nasty things I'm no rocket engineer but your comment is extremely naive

zizee 4y ago
Naive eh? What "nasty things" do you think are released into "every layer of atmosphere"? Since we're specifically talking about SpaceX and Starlink, let's talk about Falcon and StarShip rockets. Let's look at the "long list of very nasty things". Falcon 9 is expecting to launch a record number of flights this year, recent reports suggesting 52. Falcon 9 burns RP1 (a refined kerosene, very similar to jet fuel), a hydrocarbon that mostly produces CO2 when burnt, but also Carbon monoxide, and plain old carbon. The Falcon 9 has about 200k litres of fuel when fully loaded. It sounds like a lot, but for perspective a fully loaded Airbus A380 has a fuel capacity of 380k litres. So, they output of a record breaking year will be the equivalent of around 25 long distance flights of a large passenger aircraft. I'm not going to find out how many long distance large plan flights are happening, but many estimates are over 100k a day. So a record breaking year outputs a fraction of a percentage that airline flights do each hour. And the "nasty" stuff is mostly CO2, CO, and C. Starship will burn Methane, and will burn even cleaner than Falcon 9. It will also be fully reusable, resulting in less waste again. On the downside, methane is a potent greenhouse gas, so any unburt fuel would be not great. That said, rockets are designed to make the most efficient of fuel, and any unburt fuel is not going to be released in normal operation. > I'm no rocket engineer Colour me shocked! As for going through "every layer" of the atmosphere, I wouldn't get too worried about that. A lot of a rocket's fuel is burnt at lower altitudes (the same level at which passenger and military Jets operate) and the various zone mix readily, and are really so massive that you would have trouble measuring the impact of hundreds to thousands of flights of Starship per year. https://space.stackexchange.com/questions/13082/calculate-falcon-9-co2-emissions https://space.stackexchange.com/questions/13082/calculate-fa... https://www.sciencefocus.com/space/what-is-the-environmental-impact-of-the-spacex-falcon-heavy-launch/ https://www.sciencefocus.com/space/what-is-the-environmental... https://www.sciencefocus.com/space/what-is-the-environmental-impact-of-the-spacex-falcon-heavy-launch/ https://www.sciencefocus.com/space/what-is-the-environmental... https://space.stackexchange.com/questions/32002/what-percentage-of-overall-fuel-does-a-rocket-burn-up-to-get-to-max-q https://space.stackexchange.com/questions/32002/what-percent...
- lm28469 4y ago
  They specifically talk about falcon engines here: https://www.space.com/rocket-exhaust-pollution-upper-atmosphere https://www.space.com/rocket-exhaust-pollution-upper-atmosph... https://www.sciencedaily.com/releases/2022/05/220517112210.htm https://www.sciencedaily.com/releases/2022/05/220517112210.h... Anyways, "just one more car", "just one more plane", "just one more coal plant", "just want more launch", "it's not that much worse, just a tiny bit" https://sdup.esoc.esa.int/discosweb/statistics/static/PLtrafficMissionLEO.png https://sdup.esoc.esa.int/discosweb/statistics/static/PLtraf... https://www.eesi.org/images/content/World_Passenger_Traffic_Evolution_-_1945-2022_(Courtesy_ICAO).png https://www.eesi.org/images/content/World_Passenger_Traffic_...
  - zizee 4y ago
    From your links: > When it comes to greenhouse gasses alone, the contribution of rocket launches is rather negligible, accounting for only 1% of aviation's carbon footprint — which in itself only amounts to 2.4% of annual global carbon emissions, according to the Environmental and Energy Study Institute Apart from the fact they overinflated the impact to 1% (there is no way it is close to 1%) there is a reason they chose the adjective "negligible" to describe the impact. > Eventually, the circulation of the atmosphere dissipates those greenhouse gases and brings the concentrations back to "standard" levels. It is, however, unknown how long the concentrations remain elevated and what their impact on the temperature of the mesosphere could be. Reality is that these scientists did a simulation, got some results that can be made to sound alarming, but just don't know if these is any inpact. I'm all for studying this more to see if there is a real issue. My gut says it's not going to be a problem until we have at least a couplr of orders of magnitude increase in launches, but it's worth looking at it further. And I'm not sure why you included the graph of objects in orbit? This looks exciting, but it really is just that companies are now launching clusters of smaller satellites. The good news is that these tend to deorbit in under ten years. Unlike practices of old, this new style of satellite will not result in long lasting space junk. Finally, what is the point of including a graph of airline flights over time? What bearing does it have on rocket launches?