Quote from: TheRadicalModerate on 02/01/2023 10:54 pm*snip*¹Did we get an answer for whether 250t to LEO is with only an expendable Starship, or does it require expending the SuperHeavy as well?Probably with expendable Starship only. Musk does specify in the Tweet "expendable upper stage." ...
*snip*¹Did we get an answer for whether 250t to LEO is with only an expendable Starship, or does it require expending the SuperHeavy as well?
Quote from: whitelancer64 on 02/01/2023 11:01 pmQuote from: TheRadicalModerate on 02/01/2023 10:54 pm*snip*¹Did we get an answer for whether 250t to LEO is with only an expendable Starship, or does it require expending the SuperHeavy as well?Probably with expendable Starship only. Musk does specify in the Tweet "expendable upper stage." ...If only the upper stage is expended, then isn't there a 1:1 correspondence between the additional payload to orbit and the landing propellant, header tanks, heat shields, and body flaps which are not needed for an expendable mission?Where is the 100t found (to increase payload from 150t reusable to 250t expendable) if the dry Starship only weighs ... what? ~ 85 - 100t? How much landing propellant are we talking about?
Let’s say the heat shield issue can never be reliably solved for rapid, cheap upper stage reuse.In that case, Starship can still be a greatly improved evolution of F9. My interest is, how much cheaper can a partially reusable Starship be than a partially reusable F9, on a kg to LEO basis?That would largely depend on the cost of expending the upper stage. So I then ponder on how the upper stage can be easily redesigned to be as cheap as possible? Does it simply become an upsized F9 upper stage? In that case you can have a flared out, detachable and recoverable fairing (upsized from F9’s fairing), allowing for payloads significantly exceeding 9m in diameter.In my view, even if such a partially reusable configuration is the best Starship ever achieves, it can still probably get to around a $30M launch cost, for 150t to LEO.That’s ~$200/kg, which is ~7 times cheaper than F9’s ~$1500/kg cost to LEO.That in itself revolutionises the industry.
Quote from: M.E.T. on 02/02/2023 01:32 amLet’s say the heat shield issue can never be reliably solved for rapid, cheap upper stage reuse.In that case, Starship can still be a greatly improved evolution of F9. My interest is, how much cheaper can a partially reusable Starship be than a partially reusable F9, on a kg to LEO basis?That would largely depend on the cost of expending the upper stage. So I then ponder on how the upper stage can be easily redesigned to be as cheap as possible? Does it simply become an upsized F9 upper stage? In that case you can have a flared out, detachable and recoverable fairing (upsized from F9’s fairing), allowing for payloads significantly exceeding 9m in diameter.In my view, even if such a partially reusable configuration is the best Starship ever achieves, it can still probably get to around a $30M launch cost, for 150t to LEO.That’s ~$200/kg, which is ~7 times cheaper than F9’s ~$1500/kg cost to LEO.That in itself revolutionises the industry. If the development of a reusable and repeatable Starship fails or takes a long time, a simplified, single-use Starship could be used to quickly fill the Starlink-2 constellation of satellites.
What's the risk involved in splashing a Starship in the pacific? I realize Skylab/Mir were big and splashed but they were thin walled structures. SS is solid stainless and a lot of it so wondering how much would make it back to sea level.Quote from: Valerij on 02/02/2023 09:54 amIf the development of a reusable and repeatable Starship fails or takes a long time, a simplified, single-use Starship could be used to quickly fill the Starlink-2 constellation of satellites.
If the development of a reusable and repeatable Starship fails or takes a long time, a simplified, single-use Starship could be used to quickly fill the Starlink-2 constellation of satellites.
People seem to forget, that they have 2 expandable upper stages on the books.The storage depot and the moon lander are exactly this.And I don't get, why people here don't see the advantages for building an ISS replacement (it is due soon).The ISS has 420t took years and ~40? launches to get operational status and did cost around 100.000.000.000 $.Using an expendable Starship, you could be able to archive the same with just 2 launches, possibly ready for usage from day 1.
Quote from: volker2020 on 02/02/2023 12:18 pmPeople seem to forget, that they have 2 expandable upper stages on the books.The storage depot and the moon lander are exactly this.And I don't get, why people here don't see the advantages for building an ISS replacement (it is due soon).The ISS has 420t took years and ~40? launches to get operational status and did cost around 100.000.000.000 $.Using an expendable Starship, you could be able to archive the same with just 2 launches, possibly ready for usage from day 1.I think we need to distinguish an "expendable second stage" from a "Custom non-EDL SS". Depot and HLS are custom SSs and are no more expendable than is ISS or a Mars rover. They launch into space and then perform an ongoing function. An "expendable second stage" delivers its payload to orbit and then has no further use. The "250 tonne expendable" refers to a payload delivered by an expendable SS atop an expendable booster. A custom SS delivered by an expendable booster will be heavier than that by quite a bit, so the comparison to the 420 tonne ISS needs some interpretation. Qualitatively, quite a bit of the ISS mass is in the walls and other elements of the pressurized structure, and this function will be done by the walls and structure of the SS, not by its "payload". ISS currently has a lack of storage space. A custom SS design can include a method to convert the tanks into storage space. schemes for converting tanks into anything more sophisticated have been considered and rejected in the past, but storage space should be feasible.The most cost-effective way to replace ISS is likely to be one or more custom SS using reusable boosters.
Quote from: DanClemmensen on 02/02/2023 02:28 pmQuote from: volker2020 on 02/02/2023 12:18 pmPeople seem to forget, that they have 2 expandable upper stages on the books.The storage depot and the moon lander are exactly this.And I don't get, why people here don't see the advantages for building an ISS replacement (it is due soon).The ISS has 420t took years and ~40? launches to get operational status and did cost around 100.000.000.000 $.Using an expendable Starship, you could be able to archive the same with just 2 launches, possibly ready for usage from day 1.I think we need to distinguish an "expendable second stage" from a "Custom non-EDL SS". Depot and HLS are custom SSs and are no more expendable than is ISS or a Mars rover. They launch into space and then perform an ongoing function. An "expendable second stage" delivers its payload to orbit and then has no further use. The "250 tonne expendable" refers to a payload delivered by an expendable SS atop an expendable booster. A custom SS delivered by an expendable booster will be heavier than that by quite a bit, so the comparison to the 420 tonne ISS needs some interpretation. Qualitatively, quite a bit of the ISS mass is in the walls and other elements of the pressurized structure, and this function will be done by the walls and structure of the SS, not by its "payload". ISS currently has a lack of storage space. A custom SS design can include a method to convert the tanks into storage space. schemes for converting tanks into anything more sophisticated have been considered and rejected in the past, but storage space should be feasible.The most cost-effective way to replace ISS is likely to be one or more custom SS using reusable boosters.Not only more cost effective, there's no way to fit an ISS into Starship's payload bay.
The "traditional" alternative would be to send ISS modules that will fit into the SS cargo bay and assemble them in space. Nominal SS cargo payload volume is listed at 9 meter diameter by 18 meter "height", but I suspect the actual payload must be a bit smaller: call it 8 meters in diameter. One module would be at least 5 times the volume of an existing ISS module.
I think we need to distinguish an "expendable second stage" from a "Custom non-EDL SS". Depot and HLS are custom SSs and are no more expendable than is ISS or a Mars rover. They launch into space and then perform an ongoing function. An "expendable second stage" delivers its payload to orbit and then has no further use. The "250 tonne expendable" refers to a payload delivered by an expendable SS atop an expendable booster.
Quote from: DanClemmensen on 02/02/2023 02:28 pmI think we need to distinguish an "expendable second stage" from a "Custom non-EDL SS". Depot and HLS are custom SSs and are no more expendable than is ISS or a Mars rover. They launch into space and then perform an ongoing function. An "expendable second stage" delivers its payload to orbit and then has no further use. The "250 tonne expendable" refers to a payload delivered by an expendable SS atop an expendable booster.Agree with your point, but I believe that the 250 tonne number is for an expendable Starship on a reusable booster.
Quote from: DanClemmensen on 02/02/2023 04:13 pmThe "traditional" alternative would be to send ISS modules that will fit into the SS cargo bay and assemble them in space. Nominal SS cargo payload volume is listed at 9 meter diameter by 18 meter "height", but I suspect the actual payload must be a bit smaller: call it 8 meters in diameter. One module would be at least 5 times the volume of an existing ISS module.Just to post an example, there is Gravatics' concept "StarMax" space station module. https://twitter.com/brickmack/status/1602425257423429632
Quote from: sevenperforce on 02/02/2023 05:02 pmQuote from: DanClemmensen on 02/02/2023 02:28 pmI think we need to distinguish an "expendable second stage" from a "Custom non-EDL SS". Depot and HLS are custom SSs and are no more expendable than is ISS or a Mars rover. They launch into space and then perform an ongoing function. An "expendable second stage" delivers its payload to orbit and then has no further use. The "250 tonne expendable" refers to a payload delivered by an expendable SS atop an expendable booster.Agree with your point, but I believe that the 250 tonne number is for an expendable Starship on a reusable booster.Why do you think this? You may very well be correct, but I assumed that SpaceX was publishing the largest credible number they can as an apples-to-apples comparison to fully-expended SLS and Saturn V. It's not as if there are any actual unitary 250 tonne payloads that fit into an SS payload bay.
Quote from: whitelancer64 on 02/02/2023 04:23 pmQuote from: DanClemmensen on 02/02/2023 04:13 pmThe "traditional" alternative would be to send ISS modules that will fit into the SS cargo bay and assemble them in space. Nominal SS cargo payload volume is listed at 9 meter diameter by 18 meter "height", but I suspect the actual payload must be a bit smaller: call it 8 meters in diameter. One module would be at least 5 times the volume of an existing ISS module.Just to post an example, there is Gravatics' concept "StarMax" space station module. *snip tweet*You would not need the header tank in this case, would you?
Quote from: DanClemmensen on 02/02/2023 04:13 pmThe "traditional" alternative would be to send ISS modules that will fit into the SS cargo bay and assemble them in space. Nominal SS cargo payload volume is listed at 9 meter diameter by 18 meter "height", but I suspect the actual payload must be a bit smaller: call it 8 meters in diameter. One module would be at least 5 times the volume of an existing ISS module.Just to post an example, there is Gravatics' concept "StarMax" space station module. *snip tweet*
The 250 tonne number is fairly silly due to payload density unless the payload volume can be increased. If someone wants a huge payload on an expendable SS (or custom) SS, how large could the fairing (or SS body above the tanks) be? They don't need to worry about EDL. They are however constrained by the launch system and by the fabrication technique (e.g., high bay height, if used) So how wide, and how long? There is also a problem with CoM during stacking. I guess you could in theory make this part of the SS wide instead of circular if necessary.
Quote from: DanClemmensen on 02/02/2023 05:50 pmThe 250 tonne number is fairly silly due to payload density unless the payload volume can be increased. If someone wants a huge payload on an expendable SS (or custom) SS, how large could the fairing (or SS body above the tanks) be? They don't need to worry about EDL. They are however constrained by the launch system and by the fabrication technique (e.g., high bay height, if used) So how wide, and how long? There is also a problem with CoM during stacking. I guess you could in theory make this part of the SS wide instead of circular if necessary.An empty nose cone that can split in half and be jettisoned would be the most direct and straightforward way to do it. Also, hammerhead fairings are very common. But in theory, you can make a fairing just about any shape you need it to be to accommodate a payload of any awkward shape. A fun example is the asymmetric fairing which was actually developed to the point of wind tunnel testing for use on Atlas V Heavy.