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One to two Starlink satellites are falling back to Earth each day

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Re: One to two Starlink satellites are falling back to Earth each day

#91

Post by JumpCrisscross »

nicce wrote: post #89
JumpCrisscross wrote: post #78

Earlier quoted context omitted.

> closer to earth you are, less space there is Humans are bad at intuiting exponents. There is roughly 200x more volume in LEO than there is between the ground and cruising altitude. Plane changes, moreover, take a lot of energy--you aren't going to get enough energy out of a collision to pollute nearby orbits.

> going to get enough energy out of a collision to pollute nearby orbits. There is no infinite space. The problem is exactly defining the number objects when that "small" amount of energy is actually enough to cause problems.

> There is no infinite space

Straw man.

> problem is exactly defining the number objects when that "small" amount of energy is actually enough to cause problems

The exercise, maybe. The problem? No. In LEO, which is where Starlink orbits, there is no known solution for causing a Kessler cascade that causes more than a few billion in damage. Space isn't infinite, but it's really big.

Again, a few hundred thousand planes land every day [1]. They operate in a volume less than 1% that of LEO. To approach the object densities where we start controlling an airspace, you'd need tens of millions of objects in LEO alone. We simply do not have--not have any roadmap to having--the sort of launch capacity required to keep 30 million objects in LEO at a time.

There are real problems with more Starlinks in space. Kessler cascades are not one of them.

[1] https://www.travelandleisure.com/airlines-airports/number-of...

Re: One to two Starlink satellites are falling back to Earth each day

#92

Post by JumpCrisscross »

dgs_sgd wrote: post #34
nicce wrote: post #31

Earlier quoted context omitted.

There is a limit how much satellites LEO/GEO can hold unless every satellite has perfect dodging system. Called as Kessler syndrome [1], and one estimate is around 70k satellites. So it is a race who can get the most satellites orbiting, because after a certain point, there is no "space" anymore, and anyone who tries to launch after that point, will be blamed for destroying the satellites of the others. Winner takes…

I’m just a layman, but why can’t they increase the orbital radius to solve this problem? Like, if the current “layer” is too full, have the new satellites orbit further out?

> why can’t they increase the orbital radius to solve this problem?

Because there isn't a problem. LEO contains more than 200x the volume of commercial airspace.

We run out of spectrum and launch capacity well before Kessler cascades become a problem.

Re: One to two Starlink satellites are falling back to Earth each day

#93

Post by JumpCrisscross »

nicce wrote: post #86
JumpCrisscross wrote: post #76

Earlier quoted context omitted.

> threshold we are speaking of cannot allow any fragments, because they start chain reaction and destroy more satellites Kessler cascades are localised to specific orbits. In low-earth orbit, they're a problem for a few years. They're going to be annoying. But not catastrophic. > there is always one which is on the highest level Highest level?

> Kessler cascades are localised to specific orbits. In low-earth orbit, they're a problem for a few years. > They're going to be annoying. But not catastrophic. I think there is a misunderstanding about the whole term. If it is not a big problem, then it does not meet the definition. So there must be some threshold where they aren't problem. What is that threshold? Because certainly there isn't space for infinite am…

> What is that threshold?

Way beyond anything we can currently achieve with current and planned launch capacity or radio technology.

> that object can get destroyed; which means it will start deorbiting and with a chance to hit some other object below

Got it, altitude.

Yes, in theory. In practice, the odds of that happening are vanishingly low. If it did happen, the volumes we're talking about are still so big that you'd struggle to come up with a way to cause a third collision even if we remove satellites' abilities to marginally change their orbits.

Re: One to two Starlink satellites are falling back to Earth each day

#94

Post by JumpCrisscross »

whazor wrote: post #77
superkuh wrote: post #17

Short lifetime and quick re-entry is a great feature of vLEO constellations. No long term space junk. Compare that to MEO or GEO where sats are there pretty much forever (hundreds to thousands of years). Or even high LEO with many tens of years.

Yes, it is much better to error on the side of losing satellites, versus making future space travel impossible.

> versus making future space travel impossible

Not a real thing. (It was proposed as a possibility. We searched the parameter space. Mostly in the context of militaries trying to figure out how to deny orbits to an adversary. It's really difficult, to the point that even if one were intentionally trying to cause Kessler cascades, they wouldn't deny an adversary access to orbit.)

Re: One to two Starlink satellites are falling back to Earth each day

#95

Post by JumpCrisscross »

advisedwang wrote: post #68
trenbologna wrote: post #3

Does this create pollution? I don't think I want to inhale satellite dust.

The launches are probably significantly worse!

> launches are probably significantly worse

Kerosene rockets produce soot. Methalox rockets (like Starship) produce plain CO2 and water.

Re: One to two Starlink satellites are falling back to Earth each day

#96

Post by schiffern »

perihelions wrote: post #90
schiffern wrote: post #64

Earlier quoted context omitted.

>0.01% of anthropogenic ozone depletion The sheer percentage increase in stratospheric AlO is still alarming.[0] Satellite reentries in 2022 (ie mostly pre-megaconstellation) were already raising stratospheric AlO levels by 29.5% above normal levels (with satellites adding 'only' 17 t/year), but megaconstellations could raise that to ~480% above natural levels (360 t/year). This isn't a rounding error, it's a non-tri…

That's still much less than the aluminum from solid rockets, which have been ongoing since the 1970's. Per your own link, > "In situ measurements showed evidence of a 1,000% increase in stratospheric aluminum levels from 1976 to 1984 (Zolensky et al., 1989), which was associated with the emission of hundreds of tons of such particles from solid rocket motors (SRM) during atmospheric ascent (Brady et al., 1994)" If yo…

As I understand it, the concern is not just AlO but specifically nanoparticles with high reaction surface area and long lofting lifespans.

The importance of this distinction is acknowledged in Brady et al (1994):

  >The exact chemical nature, as well as size distribution (and total surface area) of particles formed in rocket exhaust in the stratosphere is currently unknown. Preliminary experiments at Aerospace by L. R. Martin indicate that plausible particle compositions give highly variable rates of direct ozone destruction.
The 17 t/year and 360 t/year figures are specifically for AlO nanoparticles (formed by hypersonic ablation), whereas Brady et al gives numbers for all AlO particles, regardless of size.

Nice username btw.

Re: One to two Starlink satellites are falling back to Earth each day

#97

Post by JumpCrisscross »

londons_explore wrote: post #72
oceanplexian wrote: post #10

Earlier quoted context omitted.

A single terminal could serve an entire African village. It's also serving use cases in the Ukraine war, ships at sea, Antarctic research stations, numerous aerospace and military use cases, and so on. DTC is provide texting and emergency services to countless people who might need it in an emergancy, like we saw in North Carolina. Last and most importantly, Starlink exists is to create revenue for SpaceX and to fund…

> The value to humanity of Starship succeeding at its goals is extremely high. If humanity agreed with this statement, humanity would fund the program directly through investment, donations or taxes, the same way we fund roads and schools which we also value highly.

> If humanity agreed with this statement, humanity would fund the program directly through investment, donations or taxes, the same way we fund roads and schools which we also value highly

...Starlink and SpaceX are funded through investments and taxes. When they launch a non-profit's satellite I guess, indirectly, through donations, too.

Also, what? Why is the funding source a measure of value?

Re: One to two Starlink satellites are falling back to Earth each day

#99

Post by JumpCrisscross »

leptons wrote: post #70
bryanlarsen wrote: post #30

Earlier quoted context omitted.

The primary benefit of Starship is a sizable reduction of the cost of getting mass to orbit, not Mars dreams.

That's a bit of a re-branding. How does "getting mass to orbit" benefit all of humanity more than what we have now? Not that much, I think, but maybe you have some inside scoop that the rest of us don't know about.

> That's a bit of a re-branding

No, it isn't. Starlink's entire commercial value is in being able to perform high-mass / low-latency launch to LEO. There is some fun stuff on the Moon. And a long-term pitch on Mars. But the commercial branding has always been about LEO.

> How does "getting mass to orbit" benefit all of humanity more than what we have now?

Better Earth observation. Better space observation. Communications outside our ecology versus based on wires strung through it.

Let's reverse the question. For the environmental impact of space launch, what else do we do that's more-agreeably useless?

Re: One to two Starlink satellites are falling back to Earth each day

#100

Post by zwily »

michaelmior wrote: post #51
dgs_sgd wrote: post #34

Earlier quoted context omitted.

I’m just a layman, but why can’t they increase the orbital radius to solve this problem? Like, if the current “layer” is too full, have the new satellites orbit further out?

Not with a geostationary orbit. That must have a fixed radius. The problem is that satellites have to move to counteract the force of gravity to avoid falling out of orbit. But if they move too much or too little, then the satellite moves with respect to the earth and the orbit is no longer geostationary. (Caveat: Not an expert by any means, just someone who had a similar question and did some reading, so my answer m…

Starlink satellites aren't geostationary.
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