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GeneralRe: The odds of being crushed by a rocket has people talking Pin
j snooze15-Aug-22 12:43
j snooze15-Aug-22 12:43 
JokeRe: The odds of being crushed by a rocket has people talking Pin
Daniel Pfeffer15-Aug-22 19:37
professionalDaniel Pfeffer15-Aug-22 19:37 
GeneralRe: The odds of being crushed by a rocket has people talking Pin
Marc Clifton16-Aug-22 2:07
mvaMarc Clifton16-Aug-22 2:07 
GeneralRe: The odds of being crushed by a rocket has people talking Pin
Dan Neely16-Aug-22 4:47
Dan Neely16-Aug-22 4:47 
GeneralRe: The odds of being crushed by a rocket has people talking Pin
Kent Sharkey16-Aug-22 8:14
staffKent Sharkey16-Aug-22 8:14 
GeneralRe: The odds of being crushed by a rocket has people talking Pin
Dan Neely16-Aug-22 9:01
Dan Neely16-Aug-22 9:01 
GeneralRe: The odds of being crushed by a rocket has people talking Pin
Daniel Pfeffer16-Aug-22 9:17
professionalDaniel Pfeffer16-Aug-22 9:17 
GeneralRe: The odds of being crushed by a rocket has people talking Pin
Dan Neely16-Aug-22 12:20
Dan Neely16-Aug-22 12:20 
And now for the longer post I didn't want to write earlier...

Daniel Pfeffer wrote:
It is very difficult to predict (or control) the crash point of a satellite, so they generally fall at random points along their orbital track.


Passive reentry is unpredictable since it's dominated by short term atmospheric density variations. To control where you come down you need to do an engine burn to reenter. All the capsules going to/from the space stations do so. Current best practices - I'm not sure if there's a treaty of any sort, or if it's just voluntary but encouraged at present - are to do the same for upper stages for launches to LEO. This is why the F9 second stage that broke after deploying it's payload and didn't re-enter was notable; as is the Long March 5B heavy lift rocket which takes it's far larger main center core all the way to orbit (the baseline model has a second stage on top and drops the center core like any other booster at suborbital speeds) and then by design leaves to re enter at random a few weeks later are catching so much flak.

Currently no one does controlled deorbits of upper stages sending payloads into Geosynchronous Transfer Orbit. There're a number of reasons here; most come down to cost. A de-orbit burn from GTO takes a lot more fuel than one from LEO which means a significant reduction in payload capacity. It also requires the rocket to remain operational for an extra 6 hours (the reentry burn needs to happen when it's at apogee) requiring larger batteries and measures to keep the propellant lines from freezing. Other than ULA and SpaceX, I'm not sure if anyone else has demonstrated the capability. Those two companies have because the DOD wants some of their satellites carried all the way to GEO by the rocket itself so they're not hanging around in a transfer orbit for a few days to let other countries look at them with telescopes while close to the surface and easy to image.

That's somewhat counterbalanced because IIRC rocket stages in GTO normally reenter via drag while still in eccentric orbits that mean they hit the air going faster and are more likely to fully burn up or at least have fewer and smaller pieces return intact.

Edit: The fact that these stages aren't normally disposed of, and - because they spend only a short period of their orbit in the outer edges of the atmosphere taking drag forces - need years or decades to finally reenter is a large part of why if anything does make it down the equatorial regions are at highest risk.

Daniel Pfeffer wrote:
Unless there is a good reason to do otherwise, launches are preferably toward the East from as close to the equator as possible, into low-inclination orbits (close to the equatorial plane). This gives an extra boost to the rocket due to the Earth's rotation.


Unless you're going into Geosynchronous orbit, or deep space low inclination orbits are mostly useless because all you ever have in line of sight is a narrow strip of the Earth around the equator.

Anything that's doing Earth observation and wants high resolution data (or any of the internet constellations) is going to be in a medium to high inclination orbit. 50-60* gets you most of the populated parts of the planet. Stuff that also cares about the poles, will be in >80* orbits. The optimum latitude to launch into a higher inclination orbit is the same one as the orbit itself; equatorial locations do no favors for them.

Alternately payloads whose designers want to save on needing a large battery to operate on while in shadow - and for camera based platforms to always have the same lighting when overflying locations again will use sun-synchronous orbits, the lowest stable one of these is at ~567km and 97.8* inclination (this is the same as 82.2 but backwards). Normally these launches are done from the west coast, but recently SpaceX has revived an old launch corridor that initially flies south-east along the coast of Florida, before turning south-west once the state's out of the way. This dogleg costs them performance (they have to cancel out the initial eastward part of their velocity) but allows them to fly from Cape Canaveral instead of Vandenberg AFB. The former is preferable because it's more administratively easy to work with. VAFB's still primarily a military site and hasn't streamlined for commercial operations.

This matters because the growth market is in LEO. GEO has been maxed out capacity wise for a long time due to minimum angular spacing requirements (along a single line around the planet) to avoid interference from ground stations radioing up. All the internet constellations and various small sat programs are operating in LEO.
Did you ever see history portrayed as an old man with a wise brow and pulseless heart, weighing all things in the balance of reason?
Is not rather the genius of history like an eternal, imploring maiden, full of fire, with a burning heart and flaming soul, humanly warm and humanly beautiful?
--Zachris Topelius

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GeneralRe: Suck it, Schrödinger: 100-year-old math mistake corrected in new color study Pin
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NewsWhat’s the Go programming language really good for? Pin
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GeneralRe: What’s the Go programming language really good for? Pin
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GeneralRe: What’s the Go programming language really good for? Pin
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