Comment by mlindner | Hacker News Reader

Comment by mlindner | Hacker News Reader

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> What people forget is that payloads are deeply coupled to their launch vehicles. The launch vehicle will dictate the maximum weight and dimensions of the payload. You can't just take a payload designed for one vehicle and put it on another.

This is generally (but not always) false. SpaceX has been negotiating a lot of their commercial contracts in a vehicle agnostic fashion. Namely that SpaceX can pick which vehicle to launch a given payload on. This will allow them, as soon as Starship is flying reliably, to swap Falcon 9 payloads on to Starship. Also payloads that were designed for one rocket have been swaped on to Falcon 9. One example: https://spacenews.com/spacex-wins-contract-to-launch-nasa-sm... https://twitter.com/B_Garelick/status/1291029153119178754

> It's likely Starship will launch ISS replacements but is there sufficient demand there for this ambitious launch vehicle? What else will it be used for? That's a bit of an open question.

Starship is being designed with the intent that it will cannibalize all Falcon 9 launches eventually. I don't think it's an open question at all. It's been stated to be the case explicitly in fact.

> This is generally (but not always) false. SpaceX has been negotiating a lot of their commercial contracts in a vehicle agnostic fashion.

Here's another way of putting that: SpaceX has designed it so F9 and Starship payloads will be interchangeable. That's not quite the same thing. You can't just take an F9 payload and bolt it on top of an Ariane rocket.

> Starship is being designed with the intent that it will cannibalize all Falcon 9 launches eventually.

Sure but that's just going to take a long time, particularly if F9 is, say, sub-$15m per launch. There's a lot that still has to be done for Starship (eg the landing system, the crew component).

> but that's just going to take a long time, particularly if F9 is, say, sub-$15m per launch.

1) SpaceX isn't a public company; among other benefits, there's substantially less pressure to maximize profits.

2) Starship launch costs don't need to compete with F9, they only need to compete with the other competition.

Also, it's worth repeating that the goal of this entire endeavor is reaching Mars. The above state of affairs isn't a coincidence, but a very deliberate part of Musk's plan. (Also, luck.)

"The above state of affairs isn't a coincidence, but a very deliberate part of Musk's plan."

To be sure of hitting the target, shoot first, and call whatever you hit the target

Musk has been talking about Mars since SpaceX's infancy.

Correct. Musk has not kept a secret of what his ultimate goals are. Both Tesla and SpaceX have had the plans on their websites for decades.

There is literally a public record that is well document about this strategy. Keeping the company private. Developing the larger vehicle. And so on.

> Sure but that's just going to take a long time, particularly if F9 is, say, sub-$15m per launch.

This rests on the assumption that a starship launch costs SpaceX more than that. The whole starship program is a gamble that they can make cheap, fully and rapidly reusable rockets. If the marginal cost for a starship launch is more than for a partially-reusable falcon 9, then the project has failed (or is still in development)

What does the crew component have to do with payload launches a la F9? They can work out a lot of the kinks with Starship while still launching satellites.

The target cost for starship is $2M per launch for a much bigger payload. If they achieve that (but even if they arrive to several multiple of that) Falcon 9 is dead. It’s as simple as that.

> The target cost for starship is $2M per launch for a much bigger payload. If they achieve that (but even if they arrive to several multiple of that) Falcon 9 is dead. It’s as simple as that.

I wonder if that is entirely true.

There may still be a market for smaller bespoke launches that SpaceX won't want to cede to competitors (though this depends on the cadence of Starship launches, the latency of getting a payload included, and so on), and SpaceX may benefit from keeping F9 around as a platform that allows further iteration on the engines (though this depends on estimates of the increased risk for Starship launches that have a mix of engine versions).

Last I heard, reusable F9 launches cost SpaceX ~$30M. The goal is for Starship launches to cost about $2M, for ~5x the payload mass. Starship is also necessary for Starlink launches to be economical for the full constellation deployment.

I find that utterly mad why would you combine multiple small launches into a big one?

The tyranny of rocket equation suggests to me that you will have to burn a lot more to lift a lot more things to burn for the payloads that would have been in a different rocket.

I would like to be shown the math that it actually takes less fuel with a bigger rocket.

Economies of scale at every stage of the game. Fuel is basically the cheapest part of a launch. Last I checked, the cost of maintaining infrastructure was on roughly the same order as the fuel per launch. More launches per site drives the cost-per down.

Reusability is a spectrum. Falcon requires a nontrivial amount of inspection and refurb between launches, while Starship is aiming for jetliner levels of prep.

Musk is also aiming to drive down the capex costs as well. There's less complexity for unmanned cargo hoist missions. I think the target for Starship is low tens of millions USD, basically cheaper than Falcon Heavy, but more reusable, with more capacity.

I think the only thing that's not cheaper, is liquid methane is a bit more expensive per kJ. They are roughly the same price per kg, with RP-1 being more energy dense. But then again, I could see SpaceX vertically integrating and driving that cost down too.

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