[...] if we’re ever going send humans to Mars, or frankly, do more at the Moon than Apollo did, we need heavy launch vehicles (HLVs) with high launch rates.
So the Lunar Starship lander will refuel once from a Starship depot in Earth orbit before heading to the Moon. But that depot requires somewhere between high single digit (according to Musk/SpaceX) and high teen (according to a recent NASA presentation) Starship tanker launches/visits to fuel up.
And my question is how many Moon going Starship can be refueled by the filled Starship depot?
Also from what I understand is what we are seing in the presentation below is the Starship capsule plus the second rocket stage
Will they somehow fill the rocket stage with new fuel ?
Also this is stated as unmanned tasks. Is that not very complicated and risky ?
Yes, and I particularly appreciate your use of the term HLV. In that category I would put Falcon Heavy, DIV-H, SLS Block 1 and perhaps a few others in the past or, like New Glenn, in the near future.Precisely because of on-orbit propellant transfer, we don't absolutely need super-heavy launch vehicles. What we need are launch systems that either through high individual flight capacity and/or through high flight rates provide large amounts of mass delivered to orbit inexpensively.How to get there is still an open question. For optimal efficiency rockets and rocket engines "want" to be big. For optimal manufacturability there's a constraint on vehicle and engine size. If the metric were "tons delivered to orbit per week" it's still unclear what size or type vehicle can do that at the lowest cost..
Quote from: jfri on 12/15/2023 11:25 pmAnd my question is how many Moon going Starship can be refueled by the filled Starship depot?The Starship Depot is essentially a gas station. It can refuel as many Lunar Starship missions as its service life allows. (I don’t how many that is.)If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two. Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant. The wet mass of a Starship at launch is ~1200t. So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.…
-reduced delta-v for disposal burn than the assumed 0.45km/s.
Quote from: Robotbeat on 12/17/2023 04:46 pm-reduced delta-v for disposal burn than the assumed 0.45km/s.First, thanks for sharing the NASA slide comparing LLO and NHRO delta-v requirements! Where's that from?It implicitly makes the assumption that "all delta-v is equal." While true for Starship-like systems that rely solely on methalox in a single-stage vehicle, it could be deceiving for systems that use a combination of e.g. hydrolox and storable propellants for different phases of the mission and discard some stages along the way.Regarding the disposal burn from NHRO, are you estimating that delta-v to escape, or to DRO?
Quote from: sdsds on 12/17/2023 05:39 pmQuote from: Robotbeat on 12/17/2023 04:46 pm-reduced delta-v for disposal burn than the assumed 0.45km/s.First, thanks for sharing the NASA slide comparing LLO and NHRO delta-v requirements! Where's that from?It implicitly makes the assumption that "all delta-v is equal." While true for Starship-like systems that rely solely on methalox in a single-stage vehicle, it could be deceiving for systems that use a combination of e.g. hydrolox and storable propellants for different phases of the mission and discard some stages along the way.Regarding the disposal burn from NHRO, are you estimating that delta-v to escape, or to DRO?I’m just assuming the NHRO to Earth burn in that slide is equivalent to a worst case disposal delta-v requirement.The slide shows the decomposition of the delta-v, so you can of course pick a different Isp for each leg if you like.
Quote from: jfri on 12/15/2023 11:25 pmAnd my question is how many Moon going Starship can be refueled by the filled Starship depot?If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two. Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant. The wet mass of a Starship at launch is ~1200t. So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.
Is it possible that the starship don't need to be fully tanked for going to the Moon ?
Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.
Quote from: VSECOTSPE on 12/17/2023 03:52 pmQuote from: jfri on 12/15/2023 11:25 pmAnd my question is how many Moon going Starship can be refueled by the filled Starship depot?If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two. Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant. The wet mass of a Starship at launch is ~1200t. So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.Is it possible that the starship don't need to be fully tanked for going to the Moon ?Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.
Quote from: jfri on 12/18/2023 02:34 pmQuote from: VSECOTSPE on 12/17/2023 03:52 pmQuote from: jfri on 12/15/2023 11:25 pmAnd my question is how many Moon going Starship can be refueled by the filled Starship depot?If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two. Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant. The wet mass of a Starship at launch is ~1200t. So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.Is it possible that the starship don't need to be fully tanked for going to the Moon ?Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.Even for one-way missions to both destinations, it actually takes less propellant to send stuff to land on Mars than it does the Moon, due to Mars’ atmosphere.Measured by propulsive delta-v, travel to Mars is “closer” than traveling to the Moon. Doubly so for round trip missions because volatiles are more readily available on Mars than the Moon (we’ve already demonstrated making oxygen and CO fuel on Mars from the Martian CO2 atmosphere), cutting the delta-v potentially in half.The Delta-V from LEO to NHRO and to the moon’s surface and back to NHRO is about the same as the delta-v from LEO to Mars’ surface and back to Mars orbit.So once SpaceX demonstrates Artemis 3 and 4 plus successful Earth recovery of a Starship from orbit, they basically are ready for Mars (uncrewed to start).
Quote from: Robotbeat on 12/18/2023 03:31 pmQuote from: jfri on 12/18/2023 02:34 pmQuote from: VSECOTSPE on 12/17/2023 03:52 pmQuote from: jfri on 12/15/2023 11:25 pmAnd my question is how many Moon going Starship can be refueled by the filled Starship depot?If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two. Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant. The wet mass of a Starship at launch is ~1200t. So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.Is it possible that the starship don't need to be fully tanked for going to the Moon ?Is double amount fuel sufficient for going to Mars ? They claim that Starship can reach Mars aand even beyond that.Even for one-way missions to both destinations, it actually takes less propellant to send stuff to land on Mars than it does the Moon, due to Mars’ atmosphere.Measured by propulsive delta-v, travel to Mars is “closer” than traveling to the Moon. Doubly so for round trip missions because volatiles are more readily available on Mars than the Moon (we’ve already demonstrated making oxygen and CO fuel on Mars from the Martian CO2 atmosphere), cutting the delta-v potentially in half.The Delta-V from LEO to NHRO and to the moon’s surface and back to NHRO is about the same as the delta-v from LEO to Mars’ surface and back to Mars orbit.So once SpaceX demonstrates Artemis 3 and 4 plus successful Earth recovery of a Starship from orbit, they basically are ready for Mars (uncrewed to start).Two things come to my mind.Moon gravity is less than MarsMars atmosphere is very thin. Does that not limit aerobraking significantly ?
Precisely because of on-orbit propellant transfer, we don't absolutely need super-heavy launch vehicles. What we need are launch systems that either through high individual flight capacity and/or through high flight rates provide large amounts of mass delivered to orbit inexpensively.
Quote from: sdsds on 12/15/2023 09:33 pmPrecisely because of on-orbit propellant transfer, we don't absolutely need super-heavy launch vehicles. What we need are launch systems that either through high individual flight capacity and/or through high flight rates provide large amounts of mass delivered to orbit inexpensively.But economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.Something F9R has well and truly proven. Most of mass any BLEO mission is fuel, dry mass of vehicles isn't that great unless wanting to place skyscraper on lunar surface . 20mt to LEO is more than enough for dry mass of crew OTV, crew lander, in space tankers and depots.
But economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.
Quote from: DanClemmensen on 12/19/2023 04:56 pmBut economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both). Throughput is what matters in the end. You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).Also, infrastructure, nature, and neighbors put limitations on physical size. Yeah, there are some really big supertankers, but they can only visit certain ports. If they’re honest, Airbus will tell you that the A380 was a mistake. Australians can run several trailers behind their tractors, but you can’t do that on US roads. Etc.To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else. I’m just saying that in the abstract, big is not always better. NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.FWIW...
I would prefer a metric involving rate, e.g. dollars per ton per week, $/(t⋅wk). Less focus on a ton of cargo delivered; more on the rate at which tons of cargo are delivered.
Quote from: VSECOTSPE on 12/19/2023 06:38 pmQuote from: DanClemmensen on 12/19/2023 04:56 pmBut economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both). Throughput is what matters in the end. You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).Also, infrastructure, nature, and neighbors put limitations on physical size. Yeah, there are some really big supertankers, but they can only visit certain ports. If they’re honest, Airbus will tell you that the A380 was a mistake. Australians can run several trailers behind their tractors, but you can’t do that on US roads. Etc.To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else. I’m just saying that in the abstract, big is not always better. NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.FWIW...That's the reason I said "The measure for tanker rockets will be total cost/kg of delivered propellant." All of your points get rolled into total cost/kg. As of now, we are beginning to see limits on the number of launches per year from a site. This scarcity will begin to increase the cost of using a launch slot, in which case bigger is better, aside from any intrinsic economies of scale.
Quote from: DanClemmensen on 12/19/2023 06:45 pmQuote from: VSECOTSPE on 12/19/2023 06:38 pmQuote from: DanClemmensen on 12/19/2023 04:56 pmBut economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both). Throughput is what matters in the end. You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).Also, infrastructure, nature, and neighbors put limitations on physical size. Yeah, there are some really big supertankers, but they can only visit certain ports. If they’re honest, Airbus will tell you that the A380 was a mistake. Australians can run several trailers behind their tractors, but you can’t do that on US roads. Etc.To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else. I’m just saying that in the abstract, big is not always better. NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.FWIW...That's the reason I said "The measure for tanker rockets will be total cost/kg of delivered propellant." All of your points get rolled into total cost/kg. As of now, we are beginning to see limits on the number of launches per year from a site. This scarcity will begin to increase the cost of using a launch slot, in which case bigger is better, aside from any intrinsic economies of scale.I'm not sure that we're near the limits of number of launches per year. The FAA and the range have drastically increased launch rate capacity, higher than they had even planned for this year. And SpaceX has not chosen to invest in more droneships or upper stage reuse, even though both would probably help increase launch rate... Because they believe Starship is the future and those other investments would either distract from Starship (opportunity cost) or they wouldn't have time to pay back given that they think Starship will be ready soon. Maybe we're seeing a limit to the *rate of increase* in launches per year.
Quote from: Robotbeat on 12/20/2023 03:28 amQuote from: DanClemmensen on 12/19/2023 06:45 pmQuote from: VSECOTSPE on 12/19/2023 06:38 pmQuote from: DanClemmensen on 12/19/2023 04:56 pmBut economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both). Throughput is what matters in the end. You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).Also, infrastructure, nature, and neighbors put limitations on physical size. Yeah, there are some really big supertankers, but they can only visit certain ports. If they’re honest, Airbus will tell you that the A380 was a mistake. Australians can run several trailers behind their tractors, but you can’t do that on US roads. Etc.To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else. I’m just saying that in the abstract, big is not always better. NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.FWIW...That's the reason I said "The measure for tanker rockets will be total cost/kg of delivered propellant." All of your points get rolled into total cost/kg. As of now, we are beginning to see limits on the number of launches per year from a site. This scarcity will begin to increase the cost of using a launch slot, in which case bigger is better, aside from any intrinsic economies of scale.I'm not sure that we're near the limits of number of launches per year. The FAA and the range have drastically increased launch rate capacity, higher than they had even planned for this year. And SpaceX has not chosen to invest in more droneships or upper stage reuse, even though both would probably help increase launch rate... Because they believe Starship is the future and those other investments would either distract from Starship (opportunity cost) or they wouldn't have time to pay back given that they think Starship will be ready soon. Maybe we're seeing a limit to the *rate of increase* in launches per year.Of course. SpaceX has chosen to go big. The counter-argument seems to be that lots of smaller LVs will be or would have been more cost-effective. I don't see it. SpaceX also claims that Starship (specifically including its "stage 0") is designed for full and rapid reuse. They seem to have about a 5-year head start. They have designed for multiple launches per day from a single pad, which translates to at least 600 launches per year from each pad. I just don't see a path for a competitor to beat them in sending propellant to orbit, by any measure. Certainly not in the Artemis III context.
Quote from: DanClemmensen on 12/20/2023 03:45 amQuote from: Robotbeat on 12/20/2023 03:28 amQuote from: DanClemmensen on 12/19/2023 06:45 pmQuote from: VSECOTSPE on 12/19/2023 06:38 pmQuote from: DanClemmensen on 12/19/2023 04:56 pmBut economies of scale are real. That's the reason container ships have grown ever larger even though the size of a container has not changed, or why supertankers grew to ridiculously large sized before finally running into physical limits. The measure for tanker rockets will be total cost/kg of delivered propellant.Economies of scale are real, but they can take the form of physical dimensions or of quantity (or both). Throughput is what matters in the end. You can try to build the biggest, most capable HLV with the tech base you’ve got, but if it can only puts 70-130t into LEO once every year or two (cough...SLS...cough), you’re better off going with a less capable HLV that can put 60t to LEO 5+ times a year for 300t+ annually (cough...F9H actually did or will do this in 2023...cough).Also, infrastructure, nature, and neighbors put limitations on physical size. Yeah, there are some really big supertankers, but they can only visit certain ports. If they’re honest, Airbus will tell you that the A380 was a mistake. Australians can run several trailers behind their tractors, but you can’t do that on US roads. Etc.To be clear, I have no idea if Starship will prove too big or launch too infrequently or something else. I’m just saying that in the abstract, big is not always better. NASA human space flight has paid dearly by not heeding that advice and doing the analysis before going down blind alleys on STS size, Orion size, Ares V, and now SLS.FWIW...That's the reason I said "The measure for tanker rockets will be total cost/kg of delivered propellant." All of your points get rolled into total cost/kg. As of now, we are beginning to see limits on the number of launches per year from a site. This scarcity will begin to increase the cost of using a launch slot, in which case bigger is better, aside from any intrinsic economies of scale.I'm not sure that we're near the limits of number of launches per year. The FAA and the range have drastically increased launch rate capacity, higher than they had even planned for this year. And SpaceX has not chosen to invest in more droneships or upper stage reuse, even though both would probably help increase launch rate... Because they believe Starship is the future and those other investments would either distract from Starship (opportunity cost) or they wouldn't have time to pay back given that they think Starship will be ready soon. Maybe we're seeing a limit to the *rate of increase* in launches per year.Of course. SpaceX has chosen to go big. The counter-argument seems to be that lots of smaller LVs will be or would have been more cost-effective. I don't see it. SpaceX also claims that Starship (specifically including its "stage 0") is designed for full and rapid reuse. They seem to have about a 5-year head start. They have designed for multiple launches per day from a single pad, which translates to at least 600 launches per year from each pad. I just don't see a path for a competitor to beat them in sending propellant to orbit, by any measure. Certainly not in the Artemis III context.Need someone to pay for missions that use all the propellant delivered to orbit. At this stage its just odd NASA manned lunar mission which requires use of SLS+Orion.
Isn't there is another downside of smaller launchers to assemble a "structure" is that you have to design and link the sections in space, which is still a labour intensive operation?
The US main structure part of ISS could have been assembled with a few (5?) Saturn V class launches. Instead of maybe 20 Shuttles (structure) and lots of supporting flights to connect things up.
Then you end up with a more complex end product.
Quote from: VSECOTSPE on 12/17/2023 03:52 pmQuote from: jfri on 12/15/2023 11:25 pmAnd my question is how many Moon going Starship can be refueled by the filled Starship depot?The Starship Depot is essentially a gas station. It can refuel as many Lunar Starship missions as its service life allows. (I don’t how many that is.)If you’re asking how many Lunar Starships could be refueled at a Starship Depot before the depot needs refueling, it may be two. Don’t quote this, but I’ve seen numbers bandied about that the Starship Depot will hold ~2500t of propellant. The wet mass of a Starship at launch is ~1200t. So if a Lunar Starship is also refueled with 1200t of propellant after reaching orbit, a full Starship Depot could do that twice before needing refueling itself.…So actually I don’t think the depot can do 2 lunar starship fills, at least not for a round trip.If we look at the LEO-NHRO-Surface-NHRO-disposal delta-v, it’s actually about 9.6km/s. A filled out Starship (ie with 100tonnes of furnishings/cargo/etc) can do “only” 6.9km/s. Where does that 2.7km/s come from?-lower cargo/furnishings for HLS than 100t-slower transit (doesn’t help much since you have cryogen boiloff to keep in mind)-reduced delta-v for disposal burn than the assumed 0.45km/s.Even with all that, there’s still likely a 2-2.5km/s gap to make up.So the solution is the refueling happens in a GTO-like orbit, not LEO. Alternatively, the Depot acts like a stage and boosts HLS to a GTO-like orbit.With such a strategy, the 2500t of capacity is enough to refuel HLS *and* put it in a near-GTO-like elliptical orbit. But not to do so twice. (On the other hand, you could still do 2 LEO refuelings of one-way cargo HLSes.)
To close, there’s just a lot of unreality ignored reality in that video. If a refuelable industry lander is too operationally complex, then where does the money come from to afford a non-refuelable one?
2) The other major problem is that there's no way (currently) to reload the HLS Starship with large, unpressurized cargo for the next mission. You can bring pressurized cargo up and transfer it through the Orion docking tunnel, but that constrains its dimensions and weight. On the other hand, if the HLS Starship launches from Earth, it can carry large payloads like rovers, habs, etc., which can then be deployed by the crew. That's a pretty big advantage.
On the contrary, sending large cargo on dedicated cargo landers is both the plan, and the better solution. If NASA and partners ever manages to get the money to do so, that is.Rovers, both pressurized like the expected JAXA rover, and unpressurized like the not-yet-awarded Lunar Terrain Vehicle, are better delivered before the crew arrives. That way they can be tested without crew, and be used for reconnaissance, exploration, and/or other scientific examinations before crew arrival. (And consistent with NASA trying to not buy a rover, but contracting rover-as-a-service, it will be the responsibility of the LTV provider to deliver their rover to the Moon.)Habitat modules are unlikely to even fit in the "garage" of the HLS Starship and fit through the planned door (approximately 3m×3m), and are certainly not going to fit on the planned elevator. A dedicated cargo ship can deliver much larger modules. (Besides, there's currently no money in sight for separate habitats.)Likewise any power systems: better to deliver and deploy them robotically before sending crew on the expensive and rare (once per year) SLS+Orion.
Fair point that very large systems aren't going to fit in the garage, and that dedicated HDL or CLPS missions are the way to go there. But there's almost certainly a wide array of equipment that's too big to go through an IDSS docking ring and safely stow in microgravity, but small enough to be stowed in the garage, using payload processing best practices, and deployed via the elevator. That class of stuff could probably be batched together and transported with one large-ish HDL mission, but it'll likely be cheaper to co-manifest it with a crewed mission.
(BTW: We haven't seen what an automated deployment of a large module off of a cargo LSS would look like. I suspect they'll blow the nose and fairing off early in the flight, then land with the payload exposed. That still leaves the question of how you get a payload that's 30m above the ground deployed: Internal crane with counterweight or counter-cantilever? Ramp? Super-gigando elevator, also with counterweight? External crane?)
Do you have any concrete examples of such equipment? (And remember that it needs to be equipment that NASA would like to use within the Artemis program, and can potentially afford.)
On the last page of the Starship Users Guide there is a picture of Starship delivering two or possibly four Space Exploration Vehicles to the Moon, using an elevator. (There exists a larger version of that picture, but I'm too lazy to find a copy right now.) Granted, that is an early concept picture, and the SEV probably doesn't count as a large module in this context.
Beyond that, you probably have to think about how large and heavy individual modules will be. A 30 tonne module should not be too difficult to hoist down using an internal crane. And I think it will be quite some time until we are sending larger singular pieces of cargo to the Moon.