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The Shuttle was designed with a huge payload of 20 tons. This was supposed to not be a problem since:

  • the reusability would drive down costs until satellite operators dropped expensive space hardware and built large low-cost machines.
  • And if that didn't cut it, the cost would still be so low that wasted capacity would not matter.

That worked out very well.

Now, Elon Musk wants to make money off a vehicle that, at a payload of 100 tons, is several times more capacity. And that too, with a launch price on par with today's smallest rockets — \$2 to \$7 million.

Even if we allow Musk to be off by an order of magnitude, such that his launch price is \$20 to \$70 million — in the same range as Falcon 9 — where is he going to get the payload?

Sure,

  • Starship is not forcibly crewed
  • Its design makes for much less maintenance
  • and thus faster turnaround

Where are the 100-ton satellites?

Especially with that fast turnaround time. Does he really think he can get a 50-ton launch once a week?

We haven't even started talking about how he wants to mass-produce them!

I am looking for justifications for the above based on

  • factual information on design aspects of Starship,
  • past experience with these aspects
  • scientifically plausible predictions on how these would b have on Starship to achieve the above-mentioned results.
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    $\begingroup$ SpaceX has always believed in a "If you build it, they will come" approach, even from day one. They are betting that by the time Starship is operational, the market demand for mega-constellations massing hundreds of tons and other space-infrastructure like stations or tourism will exist. If it doesn't then they'll probably fill that demand gap themselves, similarly to how F9 is currently launching mainly Starlink satellites because they're currently waiting for new companies to mature $\endgroup$
    – Dragongeek
    Apr 20 at 12:42
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    $\begingroup$ "Does he really think he can get a 50 ton launch once a week?" Yes, he does, and more. Elon has stated multiple times that Starships are intended to be capable of multiple launches per day. This isn't a question, it's his professional opinion. $\endgroup$
    – Dragongeek
    Apr 20 at 12:44
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    $\begingroup$ Since they obviously have enough payloads to operate Falcon 9 profitably, it's not clear why you think they'd have a problem with a vehicle that in your worst case assumption is still no more expensive to operate while still being logistically simpler. Especially when it also replaces the Falcon Heavy, gets them a lunar lander contract, delivers large payloads to the surface of Mars, etc. What exactly is problematic about its size? $\endgroup$ Apr 20 at 12:47
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    $\begingroup$ This sounds like the same argument that was made against personal computers back when they were a concept. $\endgroup$
    – Ouroborus
    Apr 20 at 17:52
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    $\begingroup$ You could say that Starship is a bit "Elon-gated" ;) $\endgroup$ Apr 20 at 21:21
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The size is mostly based around missions to Mars as opposed to satellite launch. Where satellite launch is almost a side mission.

Refueling missions for Mars missions will require 7 launches (1 payload, 6 fueling missions) for each vehicle going to Mars. Lunar missions will need 2 or more (not clear this number is settled) refueling launches.

As noted in the comments, SpaceX won the HLS Lunar Lander contract in April 2021, which will use the base Starship modified for NASA's requirements. But not sized down, instead at the same size.

On the satellite front, Starlink has an ultimate need of 4400 for the first phase, 12 thousand plus for the second major phase, and a theoretical need for 44,000 or more for a future phase. You can restate that as SpaceX made their own market for larger launchers. Others will hopefully follow.

In March, 2021, they launched a 15,000kg payload (60 Starlink satellites) almost every week. So to the complaint of a 50,000kg payload every week is not that unreasonable in context.

With Falcon 9 only launching 60 Starlinks at a time (an otherwise astoundingly good number) a larger vehicle can help deploy the constellation. There is no clear number that a Starship can handle, but a simple weight consideration (100,000kg payload (100t) and about 250kg/vehicle) leads to 400 to launch.

The 12K and 44K phases imply smaller mass satellites, so maybe more can fit per launch.

Thus they seem to have created a large market for themselves that only they seem capable of satisfying in an economical fashion.

(If you build it, they will come. And if no one else will build it for you, maybe you have to do it yourself.)

Once they have the vehicle flying at the high rates they require, they are most likely to reduce the costs to make it economical to fly even mostly empty vs the rest of the worlds launch fleet.

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    $\begingroup$ Wouldn't hurt to mention that SpaceX just won a NASA contract to make a Starship variant for lunar landings. Apparently the size is already working in their favor. $\endgroup$
    – Harabeck
    Apr 20 at 15:32
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    $\begingroup$ And that the size of Starship was explicitly called out as an advantage in the Source Selection Document. $\endgroup$ Apr 21 at 5:44
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    $\begingroup$ It hurts seeing 100000 kg, a unit of mass, turned into 100 mT, a unit of magnetic flux density. I know it means metric tonnes but still. $\endgroup$
    – Arsenal
    Apr 21 at 12:35
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    $\begingroup$ @geoffc just a small t. At least that's what used in Germany and what the English Wikipedia is also saying. $\endgroup$
    – Arsenal
    Apr 21 at 12:49
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    $\begingroup$ SpaceX presentations over the years have varied, but generally settled on 6 for Mars, and sometimes 2 for lunar. Not sure there is a totally official number. $\endgroup$
    – geoffc
    Apr 22 at 10:46
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The purpose of Starship is not merely to put satellites into orbit for cheap. If that were its purpose then you'd be correct; it's way overbuilt for that.

Starship wasn't created to put satellites into orbit though, it was created to construct a self-sustaining city on Mars. Achieving that goal will likely require lifting hundreds of megatons of mass to orbit every year.

In an interview with Ars Technica in February 2020, Elon Musk had this to say on the matter:

No, it’s absolutely mad, I agree.

The conventional space paradigms do not apply to what we’re doing here. We’re trying to build a massive fleet to make Mars habitable, to make life multi-planetary. I think we need, probably, on the order of 1,000 ships, and each of those ships would have more payload than the Saturn V—and be reusable.

[...]

The point at which one says the goal is to make life multi-planetary, it means that we need to have a self-sustaining city on Mars. That city has to survive if the resupply ships stop coming from Earth for any reason whatsoever. Doesn’t matter why. If those resupply ships stop coming, does the city die out or not? In order to make something self-sustaining, you can’t be missing anything. You must have all the ingredients.

This echos similar statements Musk made on Twitter (1, 2, 3, 4) earlier in the year:

Megatons per year to orbit are needed for life to become multiplanetary

[...]

Starship design goal is 3 flights/day avg rate, so ~1000 flights/year at >100 tons/flight, so every 10 ships yield 1 megaton per year to orbit

Building 100 Starships/year gets to 1000 in 10 years or 100 megatons/year or maybe around 100k people per Earth-Mars orbital sync

That’s the goal

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    $\begingroup$ And really, we will need way more than one city on Mars to approach 'multi-planetary' in a meaningful way. One city on Mars is still reducing things down to a single point of failure if ships stop coming from Earth. $\endgroup$
    – TylerH
    Apr 20 at 18:55
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    $\begingroup$ Starship may actually be near the lower size limit for a practical reusable launch system. The Shuttle had a payload of only ~20 t, but the orbiter alone had a dry mass of 78 t, despite discarding an external propellant tank. Starship is targeting a dry mass only about 1.5 times higher, though with a maximum payload 5-7 times higher. And keep in mind that Starship is what they scaled the system down to in order to make it competitive for satellite launch duty, the original concepts were several times larger. $\endgroup$ Apr 20 at 23:10
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    $\begingroup$ So it isn't really Starship that's mad, it's the idea of a self-sustaining city (or even a non-self-sustaining one) that's mad. Starship is merely a consequence of that madness. $\endgroup$
    – jamesqf
    Apr 21 at 3:18
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    $\begingroup$ @jamesqf : mad? Back in a time where the biggest watercraft was a tree trunk you could barely use to cross a small river, it would have sounded surely mad if someone suggested constructing a boat big enough to travel across the sea, and take a look at what lies beyond that seemingly endless water stretching to the horizon. Yet here we are, and it's actually good we're a multi-continent species now. $\endgroup$
    – vsz
    Apr 21 at 6:10
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    $\begingroup$ @vsz: On the contrary, some of my ancestors managed to walk here (I assume you mean to the Americas), others probably used kayaks or similar. But the point is that they could live perfectly well once they got here. On Mars they couldn't, barring the really extensive terraforming that we are far from having the technical capabilities to carry out. Until you can give Mars (or any other place) a self-sustaining biosphere, any habitation would need to be supported from Earth. Think of Antarctic research bases, which have the advantage of a breathable atmosphere and plenty of water. $\endgroup$
    – jamesqf
    Apr 21 at 15:35
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The reason why SpaceX exists is to Make humanity a multiplanetary species. https://www.spacex.com/human-spaceflight/mars/index.html

And unlike the mission statements of other companies which are often just sound bites, this really is what SpaceX is all about and why they do things the way they do. For most companies the primary goal is to make money. But for SpaceX money is just an important means to an end, not an end in itself.

Viewed from the perspective of making humanity a multiplanetary species it is obvious that the rockets used will have to be reusable, will have to be capable of traveling to and from Mars with a lot of cargo and will need to be relatively cheap to run. So SpaceX is working to make a launch system to do just that.

Where are the 100 ton payloads* you ask? SpaceX will probably use the majority of payloads themselves. The primary cargo will be bound for Mars carrying the crews and equipment needed to build a human presence there, plus dozens of tanker flights to re-tank Starships in orbit before departing to Mars.

So in one sense SpaceX simply doesn’t care if anyone has a 100 ton payload to launch, they have built Starship for their own purposes and have plenty to launch on it. I will qualify that to say they don’t care provided they have enough money to run the Starship program and get to Mars and that will be expensive. So in another sense they would like to sell Starship services if at all possible as it could be a good source of income.

And that seems to be off to a good start. They have already signed up one billionaire for a flight around the Moon in Starship and they have just (last Friday) won the NASA HLS contract for landing the first woman and the next man on the Moon (around $3 billion) using Starship.

But a lot of the initial finance for the Mars program will come from Existing Falcon 9 and heavy launch profits as well as the new Starlink global internet service which is just starting to come on line (which incidentally will be much cheaper to launch on Starship when that comes on stream).

  • 100 tonnes is the minimum payload they are actually aiming for anything up to 150 tonnes and judging by previous plans if Musk could quickly, reliably, safely and reasonably cheaply build a 250ton payload rocket he would do just that.

https://www.spacex.com/vehicles/starship/

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Starship will not be launching many satellites at \$2 million a launch. I don't think there will ever be enough of a market to justify that. Let's just assume that Starship reliability can get to the point where the cost to launch will be \$2 million/ launch, something on the order of 1000 launches per Starship. The launch market would have to be 1000 launches per year, which simply won't be satisfied for carrying satellites to space. Where it might shine is the following types of applications:

  1. Space industry- Anything remotely involving manufacturing in space with a constant need to bring goods up/ down from the factory.
  2. Space habitats- Again, large scale continuing. This includes Mars, orbital, lunar, etc.
  3. Earth-to-Earth transportation- Assuming they can reduce the chance of death to something around 1 in a million or less.

Really those are the only applications I can think of that might justify such a high launch cadence. The cost still might be able to drop to around \$10 million a launch, if one can justify 150 launches a year. That might be sustainable with mega constellations, space tourism, and similar types of missions. That's where I suspect Starship will go in the next few years, but time will tell. They won't drop the revenue to support Starship from Falcon, so expect the cost to be no less than (35 * \$60 million = \$2.1 billion) / (# of launches per year).

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Another factor:

By making the price per pound to orbit a lot cheaper you can make satellites cheaper, also. In the space business you bend over backwards to shave off every bit of weight you can because it's so expensive to lift it. All that weight-shaving costs money, lots of it. Lets call the per-launch price $5 million--that cuts the price per pound 50x, that can translate into a lot of savings on how you build your space hardware.

It also means it's reasonable to mandate that everything heading at least into a reasonably low orbit includes independent deorbit capability.

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  • $\begingroup$ Another angle on the last part: it also means it's a lot cheaper to make tugs to haul defunct satellites into disposal orbits or deorbit them entirely (or to carry devices to capture and contain smaller bits of debris), and plenty of room to put them up alongside other payloads. Especially since tugs are mostly propellant, which is only expensive in orbit due to its launch costs. $\endgroup$ Apr 24 at 21:44
  • $\begingroup$ @ChristopherJamesHuff If you can lift a large enough craft for deorbiting you can do it without much propellant. Throw out a grapple, capture something. Give it a yank, the junk goes into a lower orbit, you climb--aiming for the next piece of junk. You only need to burn if there's no suitable target, or when you've climbed above the junk and need to go back down. $\endgroup$ Apr 25 at 1:04
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    $\begingroup$ That kind of momentum exchange will be difficult enough with cooperative targets designed for it, and even that will require precisely matching your target's orbit to a degree you're unlikely to achieve moving on from a previous one. Try it with anything else and you're likely to tear your target to bits. $\endgroup$ Apr 25 at 3:24
  • $\begingroup$ @ChristopherJamesHuff So long as the velocity difference is low (you go for something in a similar orbit) the grapple can absorb the velocity difference. $\endgroup$ Apr 25 at 4:11
  • $\begingroup$ No, it can't. You're unavoidably going to be applying high accelerations to the target, or you're not slinging it anywhere. Realistically, that's going to end with you applying high accelerations to part of the target, while other parts of the target fly in every direction. You need targets with a grapple fixture that were structurally designed specifically to operate with momentum exchange tethers and which are still active and functioning enough to handle their side of the required maneuver. That makes it fairly useless for debris disposal. $\endgroup$ Apr 25 at 11:32
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The key thing is, Starship is really not comparable with STS in terms of reusability. Or with anything existing so far, actually.

The shuttle wasn't really reusable, it was refurbishable, but that was a huge cost and turnaround was several months at best. More importantly, the main tank was not reusable, and refurbishing SRBs was actually more costly than producing new ones, so from economical perspective it's like they were not reusable too.

The goal for Starship is to have all the hardware reusable for several flights with no refurbishment. This is the huge difference between Starship and anything else. This means that once you built a Starship and flown it once, you get the next, say, 10 flights for little more than the cost of the fuel (which is peanuts, compared to e.g. building the tank (STS) or second stage (Falcon)).

And at this point this rocket becomes an appealing option not just for launching 20t load, but for launching 10 cubesats.

I mean, if the cost of a Starship launch is as high as for Falcon, this would be a massive failure of the program. And so unless the program is a failure, it can simply do the Falcon's job, but cheaper - there is no need to look for bigger payloads.

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