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Comment by ortusdux | Hacker News Reader

For the record, these satellites are inserted in groups of 60 at half their orbital height. They have onboard thrusters to boost up to the final operational orbit. There is high atmospheric drag at lower altitudes, so they deploy their solar panels horizontally during this boost period, which usually lasts less than a month. These horizontal panels reflect the sun just after sunset and just before dawn. Once they are at their final height they rotate the panels so they are much less reflective. Basically, the constellation's effect on the night sky is proportional to the number of launches in the last month, not the total number in orbit.

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>Basically, the constellation's effect on the night sky is proportional to the number of launches in the last month, not the total number in orbit.

For what it's worth, in order for the constellation to reach steady state the number of launches in the last month will need to be proportional to the total # of orbit. So if the constellation has 42,000 satellites and the satellites last 10 years on average (IMO that's an optimistic lifespan), you need to launch around 350/month just to maintain the size of the constellation.

By that time they'll also have a launch vehicle capable of launching around 300 satellites in a single launch.

Additionally, 42,000 was a worst case for the number needed and only if things go exceedingly well with the service. I think people quote that number too much when in reality there's likely to be under 5000 (from SpaceX at least).

I think number of launches was used as a proxy for number of satellites launched in the last month - more satellites/launch shouldn't impact it that much.

I think it would as the satellites would be closer together with fewer launches so as a percentage of sky the issue would be reduced.

What about when competing services launch, as they will if this is successful? What are the total numbers going to look like if EU, Russia, China, Japan, and India all launch starlink services?

> I think people quote that number too much when in reality there's likely to be under 5000 (from SpaceX at least).

Why? I think it's much more likely that they either fail, or (eventually) launch every single satellite that their licenses allow. More satellites increases the proportion of the market they can address, and if they can profitably launch a satellite, they can profitably launch a second.

Thanks for the info!

Absolutely! Things will be really interesting when they can use Starships to launch batches. I've seen estimates that they could launch 600 starlink satellites at a time. They could theatrically also launch fewer, but put them all the way into their final orbit, skipping the few weeks of light pollution.

> They could theatrically also launch fewer, but put them all the way into their final orbit

I wonder if they might choose to do this so the sats keep more of their onboard fuel, and will be able to keep themselves in orbit a bit longer before the inevitable re-entry burn up.

I'd guess it is more efficient to have them boost themselves, so that they act as an additional rocket stage. (and so not need the delta V to elevate and then de-elevate starship's orbit.)

There is certainly someone doing the optimization problem for the orbit insertion and fuel loads and picking the right set of tradeoffs.

The optimization problem also includes drag losses at the lower altitudes.

And those drag losses are a lot lower keeping all the satellites inside the rocket rather than having each experience its own drag.

Might be worth putting an ion drive on the f9 2nd stage for that reason...

That's a tradeoff that could be made, but the onboard ion thrusters are about 5x as efficient as the rocket. They'd probably be much better off making the onboard tanks a bit larger and launching to the same low orbit.

Re-entry is a bit of a feature, though - should a satellite be DOA, it will be in a low orbit and burn up faster.

I wonder if they could use another satellite to sweep a DOA satellite. They all start in almost identical orbits, so unlike most orbital degree cleanup plans there aren't huge relative velocities to deal with or anything...

It would mean that 1 DOA satellite means bringing down 2, but that might be worth it if the DOA rate is low.

Absolutely, but for the ones that are not DOA, having more fuel on board means they can re-boot themselves for a longer time, thus staying up for longer and getting a longer service life per sat...

Or they could do it theatrically and once in a while make the most sats possible as bright as possible for a pre announced one orbital period with good ground visibility in inhabitted areas. Would be quite a sight! :)

They are getting a bit too good at reducing Starlink visibility lately so I could definitely welcome an event like that. :)

They could start doing shapes and messages. Throw in some colors. Maybe provide a service where you can get them to show a message of your choice.

> They could theatrically also launch fewer

I'd love to see a theatrical launch. :)

> Basically, the constellation's effect on the night sky is proportional to the number of launches in the last month, not the total number in orbit.

For the major brightness issues sure, but they are not invisible or undetectable while in operation. Surely the effects are proportional to both the recent launches and the whole size.

I think it's a bit early to dismiss the whole sky effect of multiple Starlink-style constellations in operation.

Also isn't Starlink intending to do launches for the rest of time? There is always a value for the last month of launches- they'll never stop launching right?

Just thinking out loud.

There is also the (no help at the moment) fact that the more money that Starlink's parent company makes, the more likely we are to get the world's cheapest heavy lift orbital booster soon, and the more likely we are to soon have multiple large orbital telescopes that far exceed ground-based capabilities.

Basically, if SpaceX makes it, we'll probably have a Starship-launched lunar observatory quite soon, in the grand scheme of things.

This doesn't help the situation now, although there is so much screaming from the anti-Musk people as well as the pro-Musk people that it's hard to tell what the actual impact of the now-somewhat-albedo-mitigated starlink v.whatever satellites are. All of the coverage is breathless sky-is-falling stuff.

In any case, the situation is temporary. Either SpaceX makes it and we get a far side of Luna observatory and LEO/MEO telescopes besides, or they don't and in a few years Starlink all falls down and burns.

Would cheaper/larger launch vehicles significantly change the economics of deploying space based observatories? The James Webb space telescope has cost about $10 billion, and you can afford even today's largest/most expensive launch vehicle (Delta Heavy) for a relatively small fraction of that ($350M).

It'd be a lot cheaper if they iterated and could service the machine if needed. Waterfall is the most expensive way of doing something.

I'm reminded of Earth orbit from the film Wall-E for some reason.

That's distinctly completely impossible in this case.

The current satellite version (VisorSat) has a magnitude of about 6, which is generally considered to be the limit of what is visible with the naked eye in a light-pollution free area.

Once you start using any optics they will be visible.

https://arxiv.org/ftp/arxiv/papers/2101/2101.00374.pdf#:~:te....

https://earthsky.org/astronomy-essentials/what-is-stellar-ma...

I might sit down and do the math to see how 1500 satellites at mag 6 compares to 60 at mag 2.

> I think it's a bit early to dismiss the whole sky effect of multiple Starlink-style constellations in operation.

I wasn't trying to dismiss their effect, just address the people who say "you think those 60 are bad, imagine when there are 20,000", or "there go the Americans, ruining the night sky for the whole world".

I have no idea how oneweb or blue origin will handle this issue.

> Also isn't Starlink intending to do launches for the rest of time?

Their satellites are designed for a 5 year lifespan. Without constant boosts, they will deorbit and burn up fully in the atmosphere. This is great, because they will not become space junk, and they can't cause the dreaded kessler syndrome. The downside is that they will need to be constantly replenished. Hopefully this will be streamlined when they can launch 600 at a time, reducing the number of launches by a factor of 10.

>I might sit down and do the math to see how 1500 satellites at mag 6 compares to 60 at mag 2.

Every 5 astronomical magnitudes corresponds to a factor of 100 difference in brightness, so magnitude 2 is (100^0.2)^4 or about 40 times brighter than magnitude 6. So they're pretty similar, 1500 satellites at magnitude 6 are about 2/3 as bright as 60 satellites at magnitude 2.

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