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In this chart that I found here (https://i.sstatic.net/f8wOR.jpg)enter image description here

It shows that the price of 1 kg to LEO is cheaper on the Falcon Heavy than the Falcon 9. Also the Falcon Heavy can carry more payload into orbit than the Falcon 9. Why did SpaceX choose to use the Falcon 9 rocket to launch their Starlink satellites?

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    $\begingroup$ Not a definitive answer here, but I have to agree with what is here. The second stage motor and approximately 60 starlinks fills the current large fairing. Without a longer proven fairing, you can’t fit more under the fairing. Heavy is for larger and denser payloads. quora.com/… $\endgroup$
    – Anthony Stevens
    Commented Sep 19, 2022 at 13:47
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    $\begingroup$ I am 100% certain that Falcon Heavy is only cheaper per kg than a Falcon 9 if you are actually using its capabilities. Since Starlink is volume constrained, you will not be able to send more payload with a Falcon Heavy than with a Falcon 9, and (at least the first stage portion of the flight) will almost by definition be three times as expensive. $\endgroup$
    – Jörg W Mittag
    Commented Sep 19, 2022 at 22:57

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That chart likely doesn't account for the fairing reuse. The standard fairing halves are now routinely recovered and reused. There is an extended fairing in development for Falcon Heavy, but it may not be reusable, which would reduce the cost difference. And of course, the extended fairing doesn't exist yet.

However, even assuming a reusable extended fairing, preparing a Falcon Heavy involves readying 3 first stage cores in a special configuration for about double the payload (with full reuse). At the moment, throughput is a bigger issue for them than launch costs, and they can likely put up more satellites in a given time period with Falcon 9. They're averaging better than one launch a week this year, and next year might reach two launches a week. That's likely easier to achieve than one Falcon Heavy a week.

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  • $\begingroup$ There is an extremely remote chance it might be cost-efficient if using a FH allows them to recover all three cores on land. Marine assets are expensive and slow, recovering the cores on land would significantly speed up the turnaround time. For Starlink missions, they are experimenting with a new, accelerated, 5-day refurbishment flow. With this accelerated refurbishment flow, the three days at sea it takes to get the booster back, plus the port operations to lift it off the barge and onto the transporter, plus the transport back to the hangar, add almost 100% overhead to the refurbishment! $\endgroup$
    – Jörg W Mittag
    Commented Sep 25, 2022 at 22:33
  • $\begingroup$ But of course, they would need to build a third landing pad first (or they could station an ASDS just off the beach). $\endgroup$
    – Jörg W Mittag
    Commented Sep 25, 2022 at 22:34
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They are both volume and mass limited on the Falcon 9. The fairing is just not big enough for too many more Starlink satellites.

There is definitely room for some more in the fairing, but considering the mass increases that Falcon Heavy can deliver, it does not scale directly.

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  • $\begingroup$ With Starlink 0.9 and 1.0, they could fit 60, and I believe that was a volume constraint. Now with the current Starlink 1.5, they can fit 54, but it is not quite obvious from the camera views whether that is due to them being bigger or heavier (or both). Either way, even if they are currently mass constrained, they can only increase that number by 10% if they were using a Falcon Heavy. $\endgroup$
    – Jörg W Mittag
    Commented Sep 19, 2022 at 22:55

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