I’ve heard numbers such as $200/kg to LEO for Starship. I’m trying to understand this.
I figure that the Falcon Heavy is already about 96.5% reusable (at least 27 of 28 engines are reused). Based on the recent Roman telescope deal ($255M), Falcon Heavy costs $4000/kg.
How is Starship, which is basically only 3.5% “more reusable”, going to cost 20X less? Is methane massively better than RP5? Is stainless steel way better than aluminum? Is it because it’s taller? Fatter? Is it the tower catch? Is it because the booster returns to the launch pad instead of landing on a drone ship?
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It reduces costs through economy of scale. It is a very large rocket, with a smaller cost to turn around and launch again. It’s like comparing to cost to drive a car across country against riding in a bus/train/plane. Getting 300 other people to agree to go with you on the train is a huge economy of scale impact.
It doesn’t. Not yet.
There’s a concept called “economy of scale”. The more stuff you produce, the cheaper it is. If you hired a guy to custom-build you a sports car, it would be crazy expensive. He’d have to know what he was doing (so highly skilled labor), he’d have to design the thing, and he’d have to make a lot of the parts himself. It’s much, much cheaper to just buy a Corvette. Those are produced on an assembly line in huge quantities, and tens of thousands of them are sold each year. The costs are spread out amongst all the buyers.
Right now, space travel is closer to the “hire some people to custom build it by hand” end of the scale, rather than the “buy one from the dealership” end. Musk hopes that Starship will lower the costs enough so that governments will buy more of them. And then private companies will buy some. And gradually the cost will come down, as they set up factories to mass produce them.
Elon also talks about Starship being “rapidly reusable”. It is possible that despite being over 90% reusable, the cost of operating the drone ships and faring recovery ships is significant. But if you use off-shore platforms for launching Starship then you will still need ships to get payloads and fuel out to them, so either way you need to operate a fleet of ships.
Falcon9 and Falcon Heavy also jettison their fairings once they leave the atmosphere whereas Starship takes them all the way to orbit. That has to eat into Starship’s payload ratio.
I do think it would be interesting to see some kind of detailed breakdown of where all money goes when a customer buys a launch. I would be interested in hearing what other people think about this.
For Starship the key thing is achieving a “fully and rapidly reusable” second stage. At this time no second stage is reusable.
Methane engines will combust “cleaner” with RP1 you have to worry about coking and soot in the engines, Merlin engines on the Falcon 9 need to be cleaned between launches.
Stainless steel is cheap, it has better strength and other properties the temperature ranges needed for a fully reusable conditions. (Cryogenic temperatures and reentry heating)
When you have a bigger rocket a proportionally smaller amount of the mass you’re lofting to orbit is “rocket” when you increase the diameter of a cylinder the volume on the interior increases much more rapidly than the surface area does.
You have a right to be puzzled. This $200/kg to LEO number is yet to become real. Economies of scale will bring down Starship launch costs, but to go from $4,000 to $200 is quite the leap.
You cant count reusability costs like that.
A rocket is more than the engine it is a whole second stage that is expended. Even if an engine is resued there is maintance need on it and that can differ between engine models.
Even if you just look at the engine is 1 engine expended per flight. So if you do two flights you have expended 2 of 29 engines, after three flights it is 3 of 30.
The number you use for Falcon Heavy assumes all three cores land and can be reused. Space X has had a problem with center stage recovery because it travels faster than the Falcon 9 first stage. There has been 3 flight of the system and only one center core manage a landing. The stage that manage the landing was lost during the recovery operation. It was if I remember correctly because of bad weather, the center stage land farther out than the sea so there is a higher risk during recovery.
So the reusability in engine Space X has managed for the Falcon 9 is 18 of 29.
Reusability does not mean no maintenance is done. The engine needs to be checked between flights. The move from RP1 (refined jet fuel) in the Merlin engine to methane in the Raptor engine will likely result in a lot less fouling so less maintenance is needed.
I suspect the number $200/kg to LEO for Starship is a number for cost for Space X if everything works as they hope. That will no be what you sell a launch for you like to make money. Space X did talk about Falcon 9 launch costs would drop below $10 million but they are around $67 million today. Part of that is too optimistic a prediction.
Another part is the cost of something primary depends on what the customers are prepared to pay and what competitors chare for a alternative. So Space X is like other companies will not sell their product too cheap that will price it to optimise its profit. So even if Space X manage $200/kg they will charge more because they can.
If you look at extimation that likely are closer to what the cost will be if Starship works are around $1,500/kg to $2,500/kg to LEO. A lower cost than that will just reduce your own profit.
https://arstechnica.com/science/2022/05/rocket-report-meet-the-gravity-1-rocket-will-starship-really-cut-launch-costs/3/
My understanding is that currently only the first stage of falcon heavy rockets is reusable and that the intention is to make both the first and second stages of the starship rockets reusable.
Falcon Heavy requires significant refurbishment work after every launch and they need to build a full new 2nd stage.
The goal with Starship is it won’t need that refurbishment, it will land and the only work needed will be a refuel.
It’s kind of like the difference between having to do a full engine rebuild of your car every single time you drive it vs having to do an oil change every 10,000 miles. In both cases you’re still reusing the car, but one’s a whole lot cheaper.
And with that, you can service more launches with fewer rockets, so that also saves you money (it’s cheaper to build and maintain one vehicle than 10). Combine that with the fact that most parts on Starship are also designed to be cheaper, and you save even more. If you’re cheap enough that demand goes up then that means overhead becomes a smaller percentage of cost, so that saves some money too.
All the small (and not so small) things combine and add up to significant savings.
There’s a basic rule of reusability that says that your incremental cost can never go below the cost of the parts that you throw away. The second stage for Falcon 9 is roughly a $10 million piece of hardware, so Falcon 9 can never get any cheaper than that, no matter how many times you fly a booster or how cheap it is to do refurbishing.
Engine count isn’t really a very good way to look at price; the second stage is probably about 20% of the overall cost.
The goal of starship is to be fully reusable, so there is floor on the cost because of throwing away parts. It also avoids the cost of the drone ship, the cost of fairings, and – with any luck – the higher cost of engine maintenance.
How much cheaper it will be is something we don’t know yet. An initial target is probably the same cost as a Falcon 9 launch, or about $50 million. Starship will be around 6 times the payload, so about that much cheaper, after a couple of years or so.
That’s assuming SpaceX can get reuse to work they way they hope to.
>*How … only 3.5% “more reusable”, going to cost 20X less?*
This is simply not the correct way to count. If the 3.5% which are currently thrown away cost X million dollars, and 0% will costs zero, then the cost of thrown away equipment goes down by an infinite ratio (X divided by zero), not just by 3.5%. So there is no paradox with “just” a 20-fold improvement.
(Others have already answered about $200/kg being an inspirational goal, and also about economy of scale.)
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