Live data from Hacker News

Starlink satellites being lowered from 550 km to 480 km

twitter.com

21–30 of 46 posts

Re: Starlink satellites being lowered from 550 km to 480 km

#21
post #12

I wonder if this will improve latency and signal strength

It seems plausible that it would help with latency, but not by a game changing amount. This is 70/550 or 13% closer. Not all of the latency is caused by distance to the the satellites (e.g., terrestrial latency is not 0), so my guess would be that the latency experienced by users would improve by less than 13%.

Re: Starlink satellites being lowered from 550 km to 480 km

#22
post #12

I wonder if this will improve latency and signal strength

It seems plausible that it would help with latency, but not by a game changing amount. This is 70/550 or 13% closer. Not all of the latency is caused by distance to the the satellites (e.g., terrestrial latency is not 0), so my guess would be that the latency experienced by users would improve by less than 13%.

[dead]

Re: Starlink satellites being lowered from 550 km to 480 km

#23

great move, we're continually about 2 days away from kessler if we lost maneuvering control on a constellation like starlink (ofc that's vanishingly unlikely, but it's important to understand that continual maneuvering is what keeps space accessible to humanity) anything we can do to lower that risk is a good move, and dropping 70km of elevation for the largest satellite constellation is definitely going to make a de…

The paper says we are 2.8 days away from a collision. It doesn't say we're '2 days away from kessler'. In fact, the paper explicitly warns against your interpretation.

> We emphasize that the CRASH Clock does not measure the onset of KCPS, nor should it be interpreted as indicating a runaway condition.

Re: Starlink satellites being lowered from 550 km to 480 km

#24
post #7

Usually orbits are reserved years in advance. AFAIK this kind of move is unprecedented (although everything about Starlink is unprecedented since it's the first megaconstellation). Two weeks ago, a Starlink satellite exploded. SpaceX believes it wasn't caused by a collision which means the explosion was probably caused by a malfunction in the satellite itself. Now 4,400 Starlink satellites are moving to a lower orbit…

> Usually orbits are reserved years in advance Because planning missions took years to plan. Holidaygoers book hotels months and sometimes a year or more in advance. Business travelers don’t. That doesn’t make the latter unusual, just a different use case. > Is this an emergency change to account for a design flaw that they just discovered? Zero evidence or precedent for this.

If the existing orbit is safe enough, why bother "increasing space safety"? The cost of this reconfiguration must be quite large. And why have no public comment period?

Re: Starlink satellites being lowered from 550 km to 480 km

#25
post #6
post #5

Earlier quoted context omitted.

It sounds like this corresponds to an atmospheric contraction. They are lowering to avoid extending the lifetime of possible debris, but that also probably means the regular lifetime is not shortened. They are just staying in the designed density to match their designed service lives. The field of view of the satellites will be reduced, but presumably they have enough units up there to maintain full coverage. This is…

At 480km there will be increased drag, even as we get closer to the solar minimum. The trade-off may be between using propellant for collision avoidance vs using it to counter altitude loss and for station keeping. Maybe it is also linked to the falling altitude of the ISS? 480km is about the upper bound of its altitude but they seem unlikely to actually raise it that high before it is deorbited.

is it conceivable that collision avoidance maneuvers become cheaper in fuel consumption by using the slightly less thin atmosphere to steer a satellite (only use propellant for attitude control, less direct linear acceleration?

i.e. if the propellant consumption for collision avoidant steering at 550 km in practice turns out to be higher than the consumption to negate the drag incurred for using atmosphere for steering, it could be a logical choice.

Re: Starlink satellites being lowered from 550 km to 480 km

#27
post #23

great move, we're continually about 2 days away from kessler if we lost maneuvering control on a constellation like starlink (ofc that's vanishingly unlikely, but it's important to understand that continual maneuvering is what keeps space accessible to humanity) anything we can do to lower that risk is a good move, and dropping 70km of elevation for the largest satellite constellation is definitely going to make a de…

The paper says we are 2.8 days away from a collision. It doesn't say we're '2 days away from kessler'. In fact, the paper explicitly warns against your interpretation. > We emphasize that the CRASH Clock does not measure the onset of KCPS, nor should it be interpreted as indicating a runaway condition.

Thanks, I stand corrected. I'll do a better job reading next time.

Re: Starlink satellites being lowered from 550 km to 480 km

#29
post #14

That would surely also mean their expected lifespan is shorter too? Faster decay doesn’t just affect dead satellites Idk seems like a strange move and the stated reason seems flimsy

Yes, it’s absolutely a trade off against prop (argon) lifetime, energy spent thrusting, and atomic oxygen degradation of plastic components. The benefits of increased drag for these shells of thousands of vehicles must be worth it.

Re: Starlink satellites being lowered from 550 km to 480 km

#30

great move, we're continually about 2 days away from kessler if we lost maneuvering control on a constellation like starlink (ofc that's vanishingly unlikely, but it's important to understand that continual maneuvering is what keeps space accessible to humanity) anything we can do to lower that risk is a good move, and dropping 70km of elevation for the largest satellite constellation is definitely going to make a de…

> we're continually about 2 days away from kessler if we lost maneuvering control on a constellation like starlink To be clear, we’d be at risk of losing those specific orbits for a few years. Nothing would block all orbits much less access to space. And nothing above those orbits would be any more statistically likely to suffer an impact afterwards.

For these large constellations, vehicles are generally raised slowly at the beginning of their lives, and debris spreads out as it decays downwards. A significant increase in debris at 550km would have an impact on all orbits below it, including all vehicles raising through that debris zone.
Post reply on HN