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"SpaceX rockets are designed to land back on Earth but the second stage of the Falcon 9 does not parachute down to the ground. Instead, it burns up in the atmos

by zzzeek 4y ago

"SpaceX rockets are designed to land back on Earth but the second stage of the Falcon 9 does not parachute down to the ground. Instead, it burns up in the atmosphere but before doing so it vents its unused fuel which will often take the form of a stunning spiral. " so...we are marveling at how awesome it looks to dump rocket fuel into the atmosphere? cool, cool

arprocter 4y ago
The article contradicts itself about what happens to the second stage "it burns up in the atmosphere" and "deorbit and eventually splash down in the Pacific" Seems like the latter is correct (if it was going to 'burn up' why would you need to dump fuel?) - https://en.wikipedia.org/wiki/Falcon_9#Recovery_of_second_stages_and_fairings https://en.wikipedia.org/wiki/Falcon_9#Recovery_of_second_st... I guess they figure it's better to let the fuel diffuse in the atmosphere than poison the ocean, or less weight to be recovered/sink
- ceejayoz 4y ago
  The fuel dump is to prevent explosions before reentry that could damage the spacecraft it just delivered or create unnecessary space debris. https://sattrackcam.blogspot.com/2018/01/fuel-dump-of-zumas-falcon-9-upper-stage.html https://sattrackcam.blogspot.com/2018/01/fuel-dump-of-zumas-... > Rocket stages always carry excess fuel, as you don't want the engine to cut out prematurely by running out of fuel. So it always has a sufficient fuel margin. Once its work is done, this excess fuel is often vented, also known as "depressurization". > Depressurization and fuel venting avoids the risk of the rocket stage blowing up, for example as a result of static electricity building up in the rocket stage. You do not want your rocket stage to blow up, as it creates an uncontrolable swarm of debris and includes the risk that particles are ejected into orbits where they do not decay quickly, adding to the space debris risk. As for burning up, it's a bit of both. Some material burns up, some larger chunks splash into the ocean. Same thing happened a while back when the US dropped bits of Skylab on Australia. https://www.abc.net.au/news/2020-05-31/nasa-skylab-fell-to-earth-esperance-retrofocus/12282468 https://www.abc.net.au/news/2020-05-31/nasa-skylab-fell-to-e...
kortex 4y ago
I mean, we've gone from stuck squarely on this rock to being able to escape our gravity well in a geological blink of an eye, so yeah, it's quite marvelous.
viraptor 4y ago
What's the expected impact of that much clean kerosene in open air? It's dangerous to breathe in for people in closed spaces, but I couldn't find any estimate of how much of the leftovers would be dumped.
- kortex 4y ago
  Zero. That's not even in the true atmosphere at that point. The kerosene droplets will rapidly evaporate into free molecules and then diffuse around the mesosphere/thermosphere for months/years until radiation breaks it down into first lighter hydrocarbons, then carbon dioxide and water.
- CommieBobDole 4y ago
  As close to none as possible, really - you're diluting probably a ton of kerosene in five and a half quadrillion tons of atmosphere. Plus it's happening ~150km up, mostly outside the atmosphere, so it's got a long time to dilute before it gets to anyone.
- gpm 4y ago
  Planes also dump a ton of kerosene into the air when they need to land early. I'd assume orders of magnitude more than rockets just because there are so many more of them. They also dump it much, much, lower in the atmosphere. Where people and other things are more likely to breathe it.
NotYourLawyer 4y ago
It’s kerosene and liquid oxygen. It’s not like they’re dumping hydrazine.
- kortex 4y ago
  Even if it was hydrazine or UDMH, the half-life of molecules in the upper stratosphere is months/years, anything in the mesosphere isn't coming back down before photolysis breaks it down into NO2, CO2 and H2O. NO2 isn't great for ozone, so hydrazine usage in the mesosphere should be minimized, but not many platforms are using hydrazine still. Oxykero is totally fine.
0xDEF 4y ago
The Falcon 9 second stage uses highly refined jet fuel and liquid oxygen. But it is an absolute trivial amount. The airline industry emits more GHG in a minutes. The reason it is visually spectacular is not because it is burning but because the fume is reflecting sunlight. Rockets that only emit water vapor have caused similar spirals.
- Symmetry 4y ago
  And most competing launch providers use solid boosters whose emissions are way worse via damage to the ozone layer.
shadowgovt 4y ago
Yes, much as we marvel at rocks slicing into the upper atmosphere, solar particle radiation being magnetically bottle-slammed into the poles, and dirty snowballs a hundred million miles away boiling in proximity to the sun. Humans marvel at all kinds of cool-looking things.

by zzzeek 4y ago

arprocter 4y ago

The article contradicts itself about what happens to the second stage "it burns up in the atmosphere" and "deorbit and eventually splash down in the Pacific" Seems like the latter is correct (if it was going to 'burn up' why would you need to dump fuel?) - https://en.wikipedia.org/wiki/Falcon_9#Recovery_of_second_stages_and_fairings https://en.wikipedia.org/wiki/Falcon_9#Recovery_of_second_st... I guess they figure it's better to let the fuel diffuse in the atmosphere than poison the ocean, or less weight to be recovered/sink

ceejayoz 4y ago
The fuel dump is to prevent explosions before reentry that could damage the spacecraft it just delivered or create unnecessary space debris. https://sattrackcam.blogspot.com/2018/01/fuel-dump-of-zumas-falcon-9-upper-stage.html https://sattrackcam.blogspot.com/2018/01/fuel-dump-of-zumas-... > Rocket stages always carry excess fuel, as you don't want the engine to cut out prematurely by running out of fuel. So it always has a sufficient fuel margin. Once its work is done, this excess fuel is often vented, also known as "depressurization". > Depressurization and fuel venting avoids the risk of the rocket stage blowing up, for example as a result of static electricity building up in the rocket stage. You do not want your rocket stage to blow up, as it creates an uncontrolable swarm of debris and includes the risk that particles are ejected into orbits where they do not decay quickly, adding to the space debris risk. As for burning up, it's a bit of both. Some material burns up, some larger chunks splash into the ocean. Same thing happened a while back when the US dropped bits of Skylab on Australia. https://www.abc.net.au/news/2020-05-31/nasa-skylab-fell-to-earth-esperance-retrofocus/12282468 https://www.abc.net.au/news/2020-05-31/nasa-skylab-fell-to-e...

kortex 4y ago

I mean, we've gone from stuck squarely on this rock to being able to escape our gravity well in a geological blink of an eye, so yeah, it's quite marvelous.

viraptor 4y ago

What's the expected impact of that much clean kerosene in open air? It's dangerous to breathe in for people in closed spaces, but I couldn't find any estimate of how much of the leftovers would be dumped.

kortex 4y ago
Zero. That's not even in the true atmosphere at that point. The kerosene droplets will rapidly evaporate into free molecules and then diffuse around the mesosphere/thermosphere for months/years until radiation breaks it down into first lighter hydrocarbons, then carbon dioxide and water.
CommieBobDole 4y ago
As close to none as possible, really - you're diluting probably a ton of kerosene in five and a half quadrillion tons of atmosphere. Plus it's happening ~150km up, mostly outside the atmosphere, so it's got a long time to dilute before it gets to anyone.
gpm 4y ago
Planes also dump a ton of kerosene into the air when they need to land early. I'd assume orders of magnitude more than rockets just because there are so many more of them. They also dump it much, much, lower in the atmosphere. Where people and other things are more likely to breathe it.

NotYourLawyer 4y ago

It’s kerosene and liquid oxygen. It’s not like they’re dumping hydrazine.

kortex 4y ago
Even if it was hydrazine or UDMH, the half-life of molecules in the upper stratosphere is months/years, anything in the mesosphere isn't coming back down before photolysis breaks it down into NO2, CO2 and H2O. NO2 isn't great for ozone, so hydrazine usage in the mesosphere should be minimized, but not many platforms are using hydrazine still. Oxykero is totally fine.

0xDEF 4y ago

The Falcon 9 second stage uses highly refined jet fuel and liquid oxygen. But it is an absolute trivial amount. The airline industry emits more GHG in a minutes. The reason it is visually spectacular is not because it is burning but because the fume is reflecting sunlight. Rockets that only emit water vapor have caused similar spirals.

Symmetry 4y ago
And most competing launch providers use solid boosters whose emissions are way worse via damage to the ozone layer.

shadowgovt 4y ago

Yes, much as we marvel at rocks slicing into the upper atmosphere, solar particle radiation being magnetically bottle-slammed into the poles, and dirty snowballs a hundred million miles away boiling in proximity to the sun. Humans marvel at all kinds of cool-looking things.