Quote from: M.E.T. on 06/11/2021 05:37 amCould a fully fuelled F9 2nd stage (without the need for fairings) not fit inside the Starship cargo bay? What trajectories can you achieve with say a 10 ton payload if you have a fully fuelled F9 2nd stage in LEO?Please correct me if I'm wrong, but as far as I know, for a third stage packing Starship, wouldn't the best maneuver involve refueling the ship in LEO, burning to a highly eccentric orbit, and dropping the third stage off for a massive Oberth burn while the Starship returns to Earth?
Could a fully fuelled F9 2nd stage (without the need for fairings) not fit inside the Starship cargo bay? What trajectories can you achieve with say a 10 ton payload if you have a fully fuelled F9 2nd stage in LEO?
That's why they think the minimum reasonable cost for Starship will be as much as the F9, but not below that.
Quote from: soyuzu on 06/11/2021 06:48 am...There is a limit for every rocket, Starship included, and adding a third stage can break that limit.Agree. But that is not an SS issue, it is a payload issue. As payload owner, you have 100-150t delivered to LEO to play with. Knock yourself out (and stop throwing shade at SS because it does not satisfy all payload owner desires).
...There is a limit for every rocket, Starship included, and adding a third stage can break that limit.
Also, Starship suffer from high empty mass, even a stripped down expendable version will weights 40t, which is not very efficient when the payload mass is on the order of several tons.
Quote from: Pipcard on 06/11/2021 06:37 amThat's why they think the minimum reasonable cost for Starship will be as much as the F9, but not below that.Not sure who this amorphous "they" is you are referring to.
Quote from: soyuzu on 06/11/2021 06:29 amAlso, Starship suffer from high empty mass, even a stripped down expendable version will weights 40t, which is not very efficient when the payload mass is on the order of several tons. where did you get the 40 t mass? I'm not saying it is wrong.
I don’t think so, just as SpaceX provides equipment handling Methalox at LC-39A for Nova-C (and results in a delay), SpaceX would also be included in the process of integrating a third stage to Starship.
It's a particular community of people (which I am a part of) who play Kerbal Space Program with the Real Solar System and Realism Overhaul mods (which as you can tell, make the game much more realistic but not as much as professional simulation software), and sometimes like to discuss real-world spaceflight history and current events. The zeitgeist over there right now is one of skepticism about Starship and how it's only practical as an LEO tug unless it has a high energy upper stage.
Quote from: Pipcard on 06/11/2021 07:31 amIt's a particular community of people (which I am a part of) who play Kerbal Space Program with the Real Solar System and Realism Overhaul mods (which as you can tell, make the game much more realistic but not as much as professional simulation software), and sometimes like to discuss real-world spaceflight history and current events. The zeitgeist over there right now is one of skepticism about Starship and how it's only practical as an LEO tug unless it has a high energy upper stage.High energy upper stage for what? Current conops include cislunar and Mars with standard SS. Again, you have 100-150t to LEO to work with as payload owner. Why does SS need an intrinsic capability beyond that? Those missions are going to be few and far between for the foreseeable future. This attitude that, because SS cannot alone solve all high C3 needs is a canard.
Can’t we just say that “Starship can carry a third stage as payload”? This sidesteps the semantic controversy and gives impressive delta V numbers for final, conventional-size payloads.
The cost of an expendable version of starship is extremely unclear: even if refueling is as cheap as hoped for you are still expending the vehicle and the Raptors that power it. Can't see this selling for less that $100M....
The cost of an expendable version of starship is extremely unclear: even if refueling is as cheap as hoped for you are still expending the vehicle and the Raptors that power it. Can't see this selling for less that $100M.
Quote from: DreamyPickle on 06/11/2021 11:21 amThe cost of an expendable version of starship is extremely unclear: even if refueling is as cheap as hoped for you are still expending the vehicle and the Raptors that power it. Can't see this selling for less that $100M.The aspirational numbers are 2 million to refly, and 5 mil to build a new ship, including all 6 raptors on the upper stage and all the fin actuators. SpaceX is aiming to get the cost of each raptor down to half a million dollars or less, or about twice what a merlin currently costs them.This sounds crazy to someone used to pork- funded, 8-engines-a-year traditional aerospace prices. SpaceX isnt like that.
Quote from: rakaydos on 06/11/2021 12:28 pmQuote from: DreamyPickle on 06/11/2021 11:21 amThe cost of an expendable version of starship is extremely unclear: even if refueling is as cheap as hoped for you are still expending the vehicle and the Raptors that power it. Can't see this selling for less that $100M.The aspirational numbers are 2 million to refly, and 5 mil to build a new ship, including all 6 raptors on the upper stage and all the fin actuators. SpaceX is aiming to get the cost of each raptor down to half a million dollars or less, or about twice what a merlin currently costs them.This sounds crazy to someone used to pork- funded, 8-engines-a-year traditional aerospace prices. SpaceX isnt like that.When Musk gives eye-popping numbers like "2 million marginal cost" per flight, one has to remember that that's not the total cost, that's the marginal cost. You still have to add fixed costs.For example, suppose the Starship development program costs $1.5 billion per year. (Estimate based on 4 years for the Lunar Starship program with a total cost of $6 billion.)If SpaceX launches 12 times in a year, that's $125 million in fixed costs per launch. Even if SpaceX manages 100 launches in a year, that's $15 million per launch in fixed costs. Now, maybe development costs shouldn't be considered part of fixed costs. But assuming development is ongoing and they don't lay off much of the development staff, the amount of revenue they'd need in order not to go broke would be $15 million per launch plus marginal costs. In any case, one must be careful not to confuse marginal costs and fixed costs. The great value of marginal costs, and the reason Musk thinks that way IMHO, is that total cost approaches that marginal cost when the number of reflights is high and the number of flights per year gets huge, well into the 1000s of flights per year.
The aspirational $2M launch price is for flying a reused vehicle to LEO and back. An expendable custom version will be much more expensive and you need to add something like 6-8x marginal price just for the refueling flights.