Author Topic: Starship Expendable Upper Stage?  (Read 42948 times)

Offline kdhilliard

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Re: Expendable Upper Stage?!?
« Reply #40 on: 02/02/2023 02:33 am »
*snip*
ĻDid 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?

Offline c4fusion

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Re: Expendable Upper Stage?!?
« Reply #41 on: 02/02/2023 03:17 am »
*snip*
ĻDid 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?

From what I know, it's currently closer to 120+ tons and you still need fuel to deorbit.  The 2 phases of fuel probably takes up around ~50 tons, then you have the part where for expandable, they may have traditional style payload fairing on top of the other removals that could be done (wings, heatshield header tanks etc), leaving it <50 tons final weight.

Offline Valerij

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Re: Expendable Upper Stage?!?
« Reply #42 on: 02/02/2023 09:54 am »
Letís 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 F9ís 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.

Thatís ~$200/kg, which is  ~7 times cheaper than F9ís ~$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.
« Last Edit: 02/02/2023 09:56 am by Valerij »

Offline kevinof

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Re: Expendable Upper Stage?!?
« Reply #43 on: 02/02/2023 10:00 am »
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.

Letís 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 F9ís 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.

Thatís ~$200/kg, which is  ~7 times cheaper than F9ís ~$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.

Offline Valerij

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Re: Expendable Upper Stage?!?
« Reply #44 on: 02/02/2023 10:13 am »
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.

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.
I think a simplified Starship, stripped of its defense tiles and aerodynamic control planes, will quickly collapse and mostly burn up in the upper atmosphere, but some of its debris will still reach the ocean surface in the designated area. This seems to me to be a solvable problem.

Offline volker2020

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Re: Expendable Upper Stage?!?
« Reply #45 on: 02/02/2023 12:18 pm »
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.

Offline DanClemmensen

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Re: Expendable Upper Stage?!?
« Reply #46 on: 02/02/2023 02:28 pm »
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.
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.




Offline InterestedEngineer

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Re: Expendable Upper Stage?!?
« Reply #47 on: 02/02/2023 03:41 pm »
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.
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.

Offline DanClemmensen

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Re: Expendable Upper Stage?!?
« Reply #48 on: 02/02/2023 04:13 pm »
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.
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.

Offline whitelancer64

Re: Expendable Upper Stage?!?
« Reply #49 on: 02/02/2023 04:23 pm »

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.

Just to post an example, there is Gravatics' concept "StarMax" space station module.

https://twitter.com/brickmack/status/1602425257423429632
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline sevenperforce

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Re: Expendable Upper Stage?!?
« Reply #50 on: 02/02/2023 05:02 pm »
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.
Agree with your point, but I believe that the 250 tonne number is for an expendable Starship on a reusable booster.

Offline DanClemmensen

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Re: Expendable Upper Stage?!?
« Reply #51 on: 02/02/2023 05:11 pm »
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.
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.

Offline Hauerg

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Re: Expendable Upper Stage?!?
« Reply #52 on: 02/02/2023 05:34 pm »

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.

Just to post an example, there is Gravatics' concept "StarMax" space station module.

https://twitter.com/brickmack/status/1602425257423429632

You would not need the header tank in this case, would you?

Offline whitelancer64

Re: Expendable Upper Stage?!?
« Reply #53 on: 02/02/2023 05:43 pm »
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.
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.

Elon Musk's tweet specifies "expendable upper stage," YMMV.

I recall calculations made some years ago that a fully expended booster and stripped-down Starship-derived upper stage would result in a 400+ ton LEO payload capacity, which is probably really out of date compared to the current Starship design.

A lot depends on the exact design of the expendable stages, how stripped down they are compared to the stock Starship launch system. Also whether or not the Starship retains its nose or jettisons it as an expendable fairing.

In general, however, staging as high and fast as possible really helps push up the payload to orbit numbers, because it reduces the amount of work the upper stage has to do. 
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline whitelancer64

Re: Expendable Upper Stage?!?
« Reply #54 on: 02/02/2023 05:44 pm »

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.

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?

I am pretty sure that StarMax is designed to be launched with a fully reusable Cargo Starship.

However, from the drawing, we can visualize that a jettison-able fairing would allow a StarMax type module to be much longer. An expended upper stage would also allow it to be more outfitted and otherwise heavier at launch.
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline DanClemmensen

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Re: Expendable Upper Stage?!?
« Reply #55 on: 02/02/2023 05:50 pm »
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.

Offline whitelancer64

Re: Expendable Upper Stage?!?
« Reply #56 on: 02/02/2023 05:58 pm »
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.

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.

https://twitter.com/DJSnM/status/1197215290699870209
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline DanClemmensen

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Re: Expendable Upper Stage?!?
« Reply #57 on: 02/02/2023 06:02 pm »
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.

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.

I assumed that a funny fairing could fly. I'm asking about fabrication and launch using existing facilities, and in particular the existing launch tower and chopsticks.

Offline sevenperforce

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Re: Expendable Upper Stage?!?
« Reply #58 on: 02/02/2023 07:07 pm »
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.
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.
As whitelancer said, the tweet from Elon specified an expendable upper stage, but there's also the math on it. Back in 2019, Elon said a tank-only Starship would be 40 tonnes empty. We know that the design dry mass for the reusable Starship is in the 85-95 tonne range, not including the 30-40 tonnes of propellant required for deorbit and EDL. So if Starship can deliver 150 tonnes to LEO flying reusable, then simply getting rid of the fairing and header tanks and heat shield and wings and header tank propellant gives you 75-95 more tonnes of margin to LEO, with the exact same flight profile for the booster. That gets you nearly to the 250 tonne number now quoted by SpaceX.

We also know that by expending the booster, SpaceX will be able to send the DearMoon mission to TLI on a single launch. We don't know how heavy the DearMoon Starship will be, but clearly expending the booster is adding a lot of Δv to launch (TLI is 3.2 km/s). If that extra Δv was instead used to loft a heavier payload to LEO, we would expect an enormous increase in the mass of the payload. Falcon 9's boostback takes a ~40% reduction in payload, so while expending Superheavy wouldn't be quite that extreme (it stages lower and slower than Falcon 9), it would still imply something more on the order of 350 tonnes total payload.

Offline marcus79

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Re: Expendable Upper Stage?!?
« Reply #59 on: 02/02/2023 07:07 pm »
Letís 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 F9ís 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.

Thatís ~$200/kg, which is  ~7 times cheaper than F9ís ~$1500/kg cost to LEO.

That in itself revolutionises the industry.

Have been thinking along the same lines. The partially reusable version can sustain NASA's HLS, Starlink, and many other nice things, even up to a NASA-led humans to Mars mission. This would actually be a huge success, and ten years before China aims to field a comparable system.

 

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