Author Topic: Starship Expendable Upper Stage?  (Read 43071 times)

Offline Asteroza

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Starship Expendable Upper Stage?
« on: 02/01/2023 02:40 am »
So per Elon

https://twitter.com/elonmusk/status/1620510679424995328


there is talk of a 250 ton expendable commercial option.


If HLS isn't that, what is it?

A stripped baseline Starship with a stretched payload barrel segment, some mutant starship variant, or something substantially different?


What would it be even for?

Very hot Oberth effect launch for high C3?
(a lightly modified tanker variant with a tiny payload bay in the nose?)
(an extra tall starship to accommodate a big but lightweight LH2 fueled third stage, but with tanker variant propellant tanks?)

Oversize (specifically over height) payloads?
(implying an extra tall starship variant)

Half and Half, aka party in the front, business in the rear?
(you bring a custom upper half of starship above the propellant tank line, everything below is a stripped but standard starship)
(useful for a one shot complete space station)


Edit:
Obvious in hindsight, but maybe Elon means a SpaceX branded/manufactured third stage?

Also cursed rocket shoutout
https://twitter.com/TheKSPManiac
« Last Edit: 02/03/2023 12:17 am by zubenelgenubi »

Offline su27k

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Re: Expendable Upper Stage?!?
« Reply #1 on: 02/01/2023 03:32 am »
Some of us saw this coming from a mile away: Launching Orion on SH with Disposable S2

Offline InterestedEngineer

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Re: Expendable Upper Stage?!?
« Reply #2 on: 02/01/2023 05:54 am »
Launching fuel with a disposable Starship make no sense.  Refueling will be the cheapest option even for LH2 (though why LH2 I have no idea, a double-refueled Starship in a GTO has 15km/sec of Vinf with 150t of cargo)

Throwaway Starship takes the base reusable price of $50k/ton and raises it to $400k/ton.  Why would anyone want to pay 8x?

The only thing I can think of is a structure that can't be easily divided into two launches and then assembled in orbit.   Orbital assembly will still be a pretty expensive proposition unless it can be fully automated.  We haven't done that on Earth yet.

Even then the structure would have be very dense, there's only so much room in the payload bay.

Offline steveleach

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Re: Expendable Upper Stage?!?
« Reply #3 on: 02/01/2023 06:34 am »
It is probably just marketing, tbh.  Put the biggest payload number they can reasonably justify on the spec sheet.

Offline TomH

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Re: Expendable Upper Stage?!?
« Reply #4 on: 02/01/2023 08:35 am »
1. Planetary defense, i.e. wayward asteroid impactor for one spotted too late for a small impactor to affect enough ΔV.  Of all extant LVs, SS will become the one most quickly preparable for such a mission and will also be the one able to impart the greatest inertia. You might not have time for refueling. Further, you could have several such impactors in sequence. I think that once SS is in standard service, it would be the go-to LV for such an emergency.

2. Replace SLS as Orion launcher. (In technical theory. Please-no political counterargument.) It would be cheaper and you could use the LAS.

3. Place mid-altitude orbital payloads that wouldn't fit inside SS nosecone, e.g. cluster of Rod-of-God tungsten kinetic energy weapons.

4. You could have an expendable version that is refuelable, very much like HLS. You omit tiles, flaperons, etc., and you build fairings the same dimensions as original nosecone. You refuel the thing and it becomes a gigantic Earth Departure Stage that never comes back. Perfect for sending a miniature nuclear submarine which lands on the surface of an outer solar system moon, melts its way through a frozen ocean, and explores an undersea alien world.
« Last Edit: 02/01/2023 09:51 pm by TomH »

Re: Expendable Upper Stage?!?
« Reply #5 on: 02/01/2023 12:10 pm »
Not sure why some people are surprised. Elon discussed expendable Starship many times over the years, even when it was still called BFR and some presentations had payload mass specs for an expendable option.

Starship turning into a much cheaper mass manufactured stainless steel vehicle makes it even more reasonable than before.

Also any ambitious deep pace mission (that doesn't use some additional kick stage, separate probe) will have to be expendable by definition and there was a tweet from Elon suggesting doing that years ago.

Offline edzieba

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Re: Expendable Upper Stage?!?
« Reply #6 on: 02/01/2023 12:55 pm »
Not sure why some people are surprised. Elon discussed expendable Starship many times over the years, even when it was still called BFR and some presentations had payload mass specs for an expendable option.

Starship turning into a much cheaper mass manufactured stainless steel vehicle makes it even more reasonable than before.

Also any ambitious deep pace mission (that doesn't use some additional kick stage, separate probe) will have to be expendable by definition and there was a tweet from Elon suggesting doing that years ago.
Even after the Starship renaming, the 'Starkicker' expendable stage concept was mentioned by Elon years ago.

Offline JayWee

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Re: Expendable Upper Stage?!?
« Reply #7 on: 02/01/2023 01:49 pm »
Indeed - was mentioned many times. It's pretty logical to have an expandable version if you wish to send something to the outer planets.
"Just" delete heat shield and wings and be done with it.

In any case - I view the publication of 250t figure more of a showcase of the rocket performance than product announcement.

Ie - a number to plug into various architectures people are coming up.

Offline mikelepage

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Re: Expendable Upper Stage?!?
« Reply #8 on: 02/01/2023 02:06 pm »
4. You could have an expendable version that is refuelable, very much like HLS. You omit tiles, flaperons, etc., and you build fairings the same dimensions as original nosecone. You refuel the thing and it becomes a gigantic Earth Departure Stage that never comes back. Perfect for sending a nuclear submarine which lands on the surface of an outer solar system moon, melts its way through a frozen ocean, and explores an undersea alien world.

This. Being able to have Uranus, Neptune (and Pluto?) orbiters that donít spend decades in transit would be nice too.

Offline RoboGoofers

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Re: Expendable Upper Stage?!?
« Reply #9 on: 02/01/2023 02:12 pm »
for and expendable SS the cost is in labor for stacking (and the time tying up the high bay) and raptors. conceivably they'd only have to stack the tanks as the fairing would be a traditional clamshell that would be closed up after the payload is loaded. Expendable wouldn't need any header tanks, of course. So they could churn out expendable upper stages pretty quickly.

They've got how many raptors? >150, right? surely some of those would be serviceable for one time use.

There's also the consideration that the current thermal protection, or even their whole reusability scheme, might not work. It's a good idea to have a plan to make money from all the starship investment while they troubleshoot reusability.


Offline wannamoonbase

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Re: Expendable Upper Stage?!?
« Reply #10 on: 02/01/2023 02:19 pm »
Some of us saw this coming from a mile away: Launching Orion on SH with Disposable S2

Bingo, I'd bet a Tesla share that there are some renders and calcs inside SpaceX of that configuration.

There are plenty of uses for an expendable upper stage.  I know we all love reuse, but before the 'Never Ever' crowd gets all wound up, consider if someone like NASA or ESA is use to billion or multibillion dollar launches tossing a Starship upper stage is a cheap deal.

Then consider how cheap and quickly SpaceX could make a stripped down upper stage and payload fairing?  It would be CHEAP and quick.  And if they reused the 9 meter fairing, wow, 250 tons in one piece.

I love the idea of a huge deep space mission to orbit Neptune or Uranus or something further out. 

If there is a Starship configuration that can handle orion, maybe a 3rd stage with hydrogen on board, then the options for very large deep space missions creates opportunities only the craziest of scientists dare dream about.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Online DanClemmensen

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Re: Expendable Upper Stage?!?
« Reply #11 on: 02/01/2023 02:23 pm »
for and expendable SS the cost is in labor for stacking (and the time tying up the high bay) and raptors. conceivably they'd only have to stack the tanks as the fairing would be a traditional clamshell that would be closed up after the payload is loaded. Expendable wouldn't need any header tanks, of course. So they could churn out expendable upper stages pretty quickly.

They've got how many raptors? >150, right? surely some of those would be serviceable for one time use.

There's also the consideration that the current thermal protection, or even their whole reusability scheme, might not work. It's a good idea to have a plan to make money from all the starship investment while they troubleshoot reusability.
It a matter of timescale. BC can currently build one a month, but Elon want to get to worldwide (not just BC) production of 1000 every two years for the Mars fleets. Popping out a few expendables per year for exotic missions should not be a problem. Maybe dedicate BC for such semi-custom work.

In addition to a traditional expendable cargo SS with a fairing, there is the potential to just customize the SS and use it as the bus for the mission. This is more or less what the HLS is and what the Depot is.

Offline edzieba

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Re: Expendable Upper Stage?!?
« Reply #12 on: 02/01/2023 03:07 pm »
There's no guarantee an expendable Starship would be all that much cheaper than a reusable: Still needs the engines which are the major cost driver. Atill needs to the tank structure to be assembled. Still needs avionics. Still needs the high power electrical subsystem for engine TVC. The flaps and tiles can be omitted, but are unlikely to make up a significant proportion of the cost of the vehicle.


Orion is wildly off topic, and can go be discussed in it's own thread to avoid derailing this one.

Online DanClemmensen

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Re: Expendable Upper Stage?!?
« Reply #13 on: 02/01/2023 03:35 pm »
There's no guarantee an expendable Starship would be all that much cheaper than a reusable: Still needs the engines which are the major cost driver. Atill needs to the tank structure to be assembled. Still needs avionics. Still needs the high power electrical subsystem for engine TVC. The flaps and tiles can be omitted, but are unlikely to make up a significant proportion of the cost of the vehicle.

If you think the engines are a major cost, and you also believe Elon's assertion that each of the 6 engines will ultimately cost $250,000, then the engine cost will be $1.5 million even if they use new engines instead of end-of-life engines.

Offline wannamoonbase

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Re: Expendable Upper Stage?!?
« Reply #14 on: 02/01/2023 03:42 pm »
There's no guarantee an expendable Starship would be all that much cheaper than a reusable: Still needs the engines which are the major cost driver. Atill needs to the tank structure to be assembled. Still needs avionics. Still needs the high power electrical subsystem for engine TVC. The flaps and tiles can be omitted, but are unlikely to make up a significant proportion of the cost of the vehicle.

If you think the engines are a major cost, and you also believe Elon's assertion that each of the 6 engines will ultimately cost $250,000, then the engine cost will be $1.5 million even if they use new engines instead of end-of-life engines.

I agree, one point that doesnít get discussed much is if they are successful at producing SS as cheaply as Elon wants it increases the likelihood of making some expendable. 

I think an expendable SS would be less than half the cost of a full starship.  Flaps, heat shield, extra testing, itís significant. 

The tankage portion will be volume production and possibly highly automated. 
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline Robotbeat

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Re: Expendable Upper Stage?!?
« Reply #15 on: 02/01/2023 04:17 pm »
Plus you can put like on Raptor on it and get crazy performance to like any orbit, with a discardable fairing.
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Offline InterestedEngineer

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Re: Expendable Upper Stage?!?
« Reply #16 on: 02/01/2023 04:20 pm »
4. You could have an expendable version that is refuelable, very much like HLS. You omit tiles, flaperons, etc., and you build fairings the same dimensions as original nosecone. You refuel the thing and it becomes a gigantic Earth Departure Stage that never comes back. Perfect for sending a nuclear submarine which lands on the surface of an outer solar system moon, melts its way through a frozen ocean, and explores an undersea alien world.

This. Being able to have Uranus, Neptune (and Pluto?) orbiters that donít spend decades in transit would be nice too.

An expendable stage you send to the outer planets is all fine and works great, a GTO prop load gives 15km/sec Vinf for 100t of payload, beating Voyager by 30x the mass and much more C3, while costing 10x less than any 3.5 stage throwaway monstrosity from ULA.

But it has nothing to do with lifting 250t to LEO.

Online volker2020

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Re: Expendable Upper Stage?!?
« Reply #17 on: 02/01/2023 05:09 pm »
There's no guarantee an expendable Starship would be all that much cheaper than a reusable: Still needs the engines which are the major cost driver. Atill needs to the tank structure to be assembled. Still needs avionics. Still needs the high power electrical subsystem for engine TVC. The flaps and tiles can be omitted, but are unlikely to make up a significant proportion of the cost of the vehicle.

If you think the engines are a major cost, and you also believe Elon's assertion that each of the 6 engines will ultimately cost $250,000, then the engine cost will be $1.5 million even if they use new engines instead of end-of-life engines.
I think that even a expandable upper stage will be extremely cheap by today's standards, the major advantage compared with a standard model will be the shape. To land a starship, it needs certain outer properties, which even with a large cargo door add limits.
Wonder how big a pre-assembled replacement for ISS could be (and what it would cost), if you put it on top of the tank section. If there is a use case for space power, a 200 T module would be a great start. I at least could imagine some quite surprising science satelites. Wonder how big a radio telescope could become.
And putting orion and the european service module on top of a Frankenspaceship, should work too.   

Offline whitelancer64

Re: Expendable Upper Stage?!?
« Reply #18 on: 02/01/2023 05:24 pm »
This isn't a novel concept, it's been suggested for years. It would be a bare-bones, no wings, no flaps, no TPS Starship with a jettison-able fairing.

An expendable starship like this would give you MASSIVE payload numbers to the outer planets (or anywhere in the solar system) / interstellar space.

Refueling it before the big yeet, even bigger payload numbers.

Picture from Everyday Astronaut.
« Last Edit: 02/01/2023 05:27 pm by whitelancer64 »
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Online DanClemmensen

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Re: Expendable Upper Stage?!?
« Reply #19 on: 02/01/2023 05:40 pm »
There's no guarantee an expendable Starship would be all that much cheaper than a reusable: Still needs the engines which are the major cost driver. Atill needs to the tank structure to be assembled. Still needs avionics. Still needs the high power electrical subsystem for engine TVC. The flaps and tiles can be omitted, but are unlikely to make up a significant proportion of the cost of the vehicle.

If you think the engines are a major cost, and you also believe Elon's assertion that each of the 6 engines will ultimately cost $250,000, then the engine cost will be $1.5 million even if they use new engines instead of end-of-life engines.
I think that even a expandable upper stage will be extremely cheap by today's standards, the major advantage compared with a standard model will be the shape. To land a starship, it needs certain outer properties, which even with a large cargo door add limits.
Wonder how big a pre-assembled replacement for ISS could be (and what it would cost), if you put it on top of the tank section. If there is a use case for space power, a 200 T module would be a great start. I at least could imagine some quite surprising science satelites. Wonder how big a radio telescope could become.
And putting orion and the european service module on top of a Frankenspaceship, should work too.
For almost all missions there is no need to use an expendable SS. Instead use a customized SS that is also your payload bus, or whatever you want to call it. For example, you don't launch a replacement ISS as a payload. You build your replacement ISS by fitting out a custom SS. The only reason to not do this is if you need to shed some of the SS mass after you expend all of the propellant, after you have refuelled for the last time so you can use a third stage. For almost all missions, refuelling would be a better choice. There might be some extrasolar missions, but even there it may be cheaper to ladder some tankers and expend the last several of them.

Offline whitelancer64

Re: Expendable Upper Stage?!?
« Reply #20 on: 02/01/2023 05:55 pm »
I looked up Elon Musk's tweet from 2019 about this.

@elonmusk
Replying to
@Erdayastronaut
 and
@DiscoverMag

Massive delta velocity slam from highly elliptical Earth orbit using a fully retanked, but lightened up Starship with no heat shield or fins/legs. Best choice for the impatient. Ion engines are too slow.
3:40 PM ∑ Mar 29, 2019



https://twitter.com/elonmusk/status/1111760133132947458
« Last Edit: 02/01/2023 05:55 pm by whitelancer64 »
"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
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Offline TheRadicalModerate

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Re: Expendable Upper Stage?!?
« Reply #21 on: 02/01/2023 07:33 pm »
Launching fuel with a disposable Starship make no sense.  Refueling will be the cheapest option even for LH2 (though why LH2 I have no idea, a double-refueled Starship in a GTO has 15km/sec of Vinf with 150t of cargo)

Throwaway Starship takes the base reusable price of $50k/ton and raises it to $400k/ton.  Why would anyone want to pay 8x?

The only thing I can think of is a structure that can't be easily divided into two launches and then assembled in orbit.   Orbital assembly will still be a pretty expensive proposition unless it can be fully automated.  We haven't done that on Earth yet.

Even then the structure would have be very dense, there's only so much room in the payload bay.

I can't think of a reason to launch 250t in one piece just to LEO, but there are lots of reasons you might want to launch 250t for some kind of non-Mars interplanetary mission that needs lots of storable prop on arrival.  You'd just have to refuel it in its staging orbit before departure.

If you're doing an expendable StarKicker, then what you'd ordinarily consider to be the enclosure for the payload bay becomes a more traditional fairing, which can be jettisoned once q is low enough.  That likely gives you a substantial increase in payload.  If they manage to get the Raptor thrust increased so that it'll handle ~200t reusably, then 250t isn't an unreasonable number.

Note also that, with the fairing gone, you can now assemble even bigger packages by docking them together on the nose.  I can't really think of a mission for this other than the extrasolar missions we discussed here, but there's a lot of flexibility to move huge payloads around in one go if you're willing to expend the Starship.

Offline Oersted

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Re: Expendable Upper Stage?!?
« Reply #22 on: 02/01/2023 07:40 pm »
Starship was always touted as a ship for exploring the whole Solar System, so yeah, sure, there has been lots of ideas about expendable ships aired. Unmanned missions to planets and moons without an athmosphere would of course not have heatshields or fins and would not be coming back to Earth either.

That's the genius of Starship, as compared to the Shuttle: all the reŽntry stuff can be discarded, unlike the Shuttle wings and heatshield. 

Offline Hog

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Re: Expendable Upper Stage?!?
« Reply #23 on: 02/01/2023 07:58 pm »
Starship was always touted as a ship for exploring the whole Solar System, so yeah, sure, there has been lots of ideas about expendable ships aired. Unmanned missions to planets and moons without an athmosphere would of course not have heatshields or fins and would not be coming back to Earth either.

That's the genius of Starship, as compared to the Shuttle: all the reŽntry stuff can be discarded, unlike the Shuttle wings and heatshield.
the genius of SS and STS is that they were designed with the goals of each vehicle system in mind.  Just as you never bring a knife to a gunfight, you never bring wings to an entry lacking atmosphere. 
Paul

Offline InterestedEngineer

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Re: Expendable Upper Stage?!?
« Reply #24 on: 02/01/2023 09:04 pm »

the genius of SS and STS is that they were designed with the goals of each vehicle system in mind.  Just as you never bring a knife to a gunfight, you never bring wings to an entry lacking atmosphere.
[/quote]

STS was designed for cross-range capability.

Which was never used.  Cost of that requirement is in the 10s of billions of dollars.

identifying and throwing away bad requirements is Elon's best insight into good project management.

Now, back to - what could require a 250t one-time LEO launch?

Offline InterestedEngineer

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Re: Expendable Upper Stage?!?
« Reply #25 on: 02/01/2023 09:06 pm »
Launching fuel with a disposable Starship make no sense.  Refueling will be the cheapest option even for LH2 (though why LH2 I have no idea, a double-refueled Starship in a GTO has 15km/sec of Vinf with 150t of cargo)

Throwaway Starship takes the base reusable price of $50k/ton and raises it to $400k/ton.  Why would anyone want to pay 8x?

The only thing I can think of is a structure that can't be easily divided into two launches and then assembled in orbit.   Orbital assembly will still be a pretty expensive proposition unless it can be fully automated.  We haven't done that on Earth yet.

Even then the structure would have be very dense, there's only so much room in the payload bay.

I can't think of a reason to launch 250t in one piece just to LEO, but there are lots of reasons you might want to launch 250t for some kind of non-Mars interplanetary mission that needs lots of storable prop on arrival.  You'd just have to refuel it in its staging orbit before departure.

If you're doing an expendable StarKicker, then what you'd ordinarily consider to be the enclosure for the payload bay becomes a more traditional fairing, which can be jettisoned once q is low enough.  That likely gives you a substantial increase in payload.  If they manage to get the Raptor thrust increased so that it'll handle ~200t reusably, then 250t isn't an unreasonable number.

Note also that, with the fairing gone, you can now assemble even bigger packages by docking them together on the nose.  I can't really think of a mission for this other than the extrasolar missions we discussed here, but there's a lot of flexibility to move huge payloads around in one go if you're willing to expend the Starship.

Agreed and I loved that thread on extra-solar missions, but the launch capability to LEO of 250t is what is being touted on Spacex's website, and nobody can think of any use for that.

Offline TomH

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Re: Expendable Upper Stage?!?
« Reply #26 on: 02/01/2023 09:43 pm »
But it has nothing to do with lifting 250t to LEO.

The 250t figure was only one of several possible metrics mentioned in the op and the linked information. You seem to be grasping at any minutiae you can find simply to be contentious.

Now, back to - what could require a 250t one-time LEO launch?

That is NOT the thread topic! Why are you obsessed with making it so?
« Last Edit: 02/01/2023 10:10 pm by TomH »

Offline whitelancer64

Re: Expendable Upper Stage?!?
« Reply #27 on: 02/01/2023 09:46 pm »
It's just a big number for hype, and most LVs do this. Payload numbers for a 200 km circular Earth orbit are very common, even though such an orbit is essentially useless except as an initial parking orbit. It's extremely rare to ever launch a payload that even comes close to an LV's maximum theoretical LEO performance.

Maximum performance numbers to higher orbits, GEO, and interplanetary, are much more important.
« Last Edit: 02/01/2023 09:49 pm by whitelancer64 »
"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
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Offline TomH

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Re: Expendable Upper Stage?!?
« Reply #28 on: 02/01/2023 09:59 pm »
Orion is wildly off topic, and can go be discussed in it's own thread to avoid derailing this one.

It is not off topic in the least. You are being political rather than focusing on theoretical technical specifications and possible applications. I specified no political counterargument. I agree that the politics of it do not belong in this thread. The fact remains, however, that SH/SS has the technical ability to fill that role in the specified configuration.
« Last Edit: 02/01/2023 10:13 pm by TomH »

Offline wannamoonbase

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Re: Expendable Upper Stage?!?
« Reply #29 on: 02/01/2023 10:14 pm »
Orion is wildly off topic, and can go be discussed in it's own thread to avoid derailing this one.

Wrong! It is not off topic in the least. You are being political rather than focusing on theoretical technical specifications and possible applications.

Agreed, not off topic if you can put Orion in orbit and on it's missions for less than a tenth of an SLS flight.

Regarding what you might want to launch that needs 250 tons, as pointed out above, Starlink.

If it takes more time to develop the cargo Starship, SpaceX can get alot of birds on orbit with expendable SS's.

250 ton Science spacecraft would be amazing, we need some large deep space vehicles to orbit the outer planets.
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Offline TheRadicalModerate

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Re: Expendable Upper Stage?!?
« Reply #30 on: 02/01/2023 10:54 pm »
Agreed and I loved that thread on extra-solar missions, but the launch capability to LEO of 250t is what is being touted on Spacex's website, and nobody can think of any use for that.

I think you're misreading this, or at least not taking the logical next step.  If you have 250t to LEO, then you can refuel and have 250t to anywhere in the solar system.  The trick, though, is to get the 250t into orbit in one piece.Ļ

Why would you want to?  Two broad classes of payloads:

1) Genuine LEO payloads.  A 250t payload that fits in 900m≥ has a density of 280kg/m≥, which is way, way too high for any human spaceflight application.  But I can think of a few applications for such a payload:

a) Any number of ASAT or counter-ASAT systems, which need massive amounts of delta-v to win.

b) I notice that ex-DoD people are writing op-eds about the Chinese looking at FOBS, and how the US should respond.  You can pack a whole bunch of Rods From God into a 250t payload.  Or, even better, 50t of Rods From God and enough prop to do the inclination and RAAN changes needed to have a prompt strike capability within 90 minutes.

c) And of course there are Star Wars-like payloads:  orbital anti-ballistic lasers or other beam weapons, kinetic-kill ABMs, who knows?  But if you tell Space Force, "250t, price no object," they'l think of ways to use it.

d) As for civilian payloads:  280kg/m≥ density is way, way more dense than any human habitation can be (air in livable amounts of volume is not dense), but you could put all the heavy equipment for a really big space station / hotel in one payload and have it reach those kinds of densities--especially if you're trading mass for ease of engineering.

2) Any number of interplanetary probes, but especially icy moon landers.  You can't have a Starship anywhere near an icy moon, for planetary protection reasons.  But, after refueling, an expendable Starship can put a 250t payload into JTO that'll get on-station quickly and do a buttload of science for a very long time.  You might even be able to do a sample return with 250t to play with.

An obvious question for an interplanetary probe is, "Since you have to refuel to get to JTO anyway, why can't you assemble the pieces-parts in LEO?"  There are a couple of answers to that:

a) Planetary protection regulations make us certify the whole probe is clean before we put it on the rocket, and we can't certify that more than one piece will remain clean when we put them together.  (A weak engineering excuse, but bureaucracies don't care that much about engineering.)

b) EOR assembly comes with risk, and we don't want to take any risks we don't have to with Flagship programs.  (250t is almost certainly a Flagship program.)  We want to integrate the whole thing on the ground and have done with it.

c) We need a lot of arrival and post-arrival prop, and we can't use methalox, because:
i) We can't load cryogenics on the pad and guarantee cleanliness.
ii) We're super-conservative and don't want to count on multi-year cryogenic storage.

d) You're not getting the Starship back on an outer planets mission no matter what, so why do you care if we push the payload mass limits?

____________
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?

Offline whitelancer64

Re: Expendable Upper Stage?!?
« Reply #31 on: 02/01/2023 11:01 pm »
*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."

IIRC, with expended booster and expended stripped-down Starship-derived upper stage, LEO payload should be more like 400+ tons.
« Last Edit: 02/01/2023 11:04 pm by whitelancer64 »
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Offline InterestedEngineer

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Re: Expendable Upper Stage?!?
« Reply #32 on: 02/01/2023 11:02 pm »
But it has nothing to do with lifting 250t to LEO.

The 250t figure was only one of several possible metrics mentioned in the op and the linked information. You seem to be grasping at any minutiae you can find simply to be contentious.

Now, back to - what could require a 250t one-time LEO launch?

That is NOT the thread topic! Why are you obsessed with making it so?

Because some of us read the actual Twitter thread - 250t to Earth Orbit was the thread. Don't believe me, believe pic from the Twitter thread the OP linked to

Offline InterestedEngineer

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Re: Expendable Upper Stage?!?
« Reply #33 on: 02/01/2023 11:14 pm »
Agreed and I loved that thread on extra-solar missions, but the launch capability to LEO of 250t is what is being touted on Spacex's website, and nobody can think of any use for that.

I think you're misreading this, or at least not taking the logical next step.  If you have 250t to LEO, then you can refuel and have 250t to anywhere in the solar system.  The trick, though, is to get the 250t into orbit in one piece.Ļ

Why would you want to?  Two broad classes of payloads:

1) Genuine LEO payloads.  A 250t payload that fits in 900m≥ has a density of 280kg/m≥, which is way, way too high for any human spaceflight application.  But I can think of a few applications for such a payload:

a) Any number of ASAT or counter-ASAT systems, which need massive amounts of delta-v to win.

b) I notice that ex-DoD people are writing op-eds about the Chinese looking at FOBS, and how the US should respond.  You can pack a whole bunch of Rods From God into a 250t payload.  Or, even better, 50t of Rods From God and enough prop to do the inclination and RAAN changes needed to have a prompt strike capability within 90 minutes.

c) And of course there are Star Wars-like payloads:  orbital anti-ballistic lasers or other beam weapons, kinetic-kill ABMs, who knows?  But if you tell Space Force, "250t, price no object," they'l think of ways to use it.

d) As for civilian payloads:  280kg/m≥ density is way, way more dense than any human habitation can be (air in livable amounts of volume is not dense), but you could put all the heavy equipment for a really big space station / hotel in one payload and have it reach those kinds of densities--especially if you're trading mass for ease of engineering.

2) Any number of interplanetary probes, but especially icy moon landers.  You can't have a Starship anywhere near an icy moon, for planetary protection reasons.  But, after refueling, an expendable Starship can put a 250t payload into JTO that'll get on-station quickly and do a buttload of science for a very long time.  You might even be able to do a sample return with 250t to play with.

An obvious question for an interplanetary probe is, "Since you have to refuel to get to JTO anyway, why can't you assemble the pieces-parts in LEO?"  There are a couple of answers to that:

a) Planetary protection regulations make us certify the whole probe is clean before we put it on the rocket, and we can't certify that more than one piece will remain clean when we put them together.  (A weak engineering excuse, but bureaucracies don't care that much about engineering.)

b) EOR assembly comes with risk, and we don't want to take any risks we don't have to with Flagship programs.  (250t is almost certainly a Flagship program.)  We want to integrate the whole thing on the ground and have done with it.

c) We need a lot of arrival and post-arrival prop, and we can't use methalox, because:
i) We can't load cryogenics on the pad and guarantee cleanliness.
ii) We're super-conservative and don't want to count on multi-year cryogenic storage.

d) You're not getting the Starship back on an outer planets mission no matter what, so why do you care if we push the payload mass limits?

____________
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?

Good stuff, thanks.  Great point about density.  280kg/m^3 is pretty dense.

I'm not sure what the difference between 250t for many of these missions are and 250/150 more launches (e.g. LEO space station was already built with multiple launches).  The additional launch is 8 times cheaper.

The reason to not do outer planet with 250t payload is simply a deltaV problem.  the same fuel can push 150t a lot faster than 250t.  Sure, both expend a Starship, but the 150t (or 50t for that matter) will go much faster.

Can 250t of Starlinks fit into Starship's payload bay?  Maybe, but requires what is probably a custom stuffing setup, probably not worth it.

What might make sense is a large nuclear reactor or a submarine for Europa.  Those might exceed 280kg/m^3
« Last Edit: 02/01/2023 11:16 pm by InterestedEngineer »

Offline JayWee

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Re: Expendable Upper Stage?!?
« Reply #34 on: 02/02/2023 12:08 am »
Another way of reading the 250t figure is: It "costs" 100t to reuse the stage. That's about 40% of payload capacity.


« Last Edit: 02/02/2023 12:09 am by JayWee »

Offline TrueBlueWitt

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Re: Expendable Upper Stage?!?
« Reply #35 on: 02/02/2023 12:14 am »
If, as someone before stated, full expendable mode can put 400t in LEO, is that enough for a single launch stripped down ship moon landing attempt(one way HLS test tri)?

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Re: Expendable Upper Stage?!?
« Reply #36 on: 02/02/2023 01:32 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.

Offline TomH

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Re: Expendable Upper Stage?!?
« Reply #37 on: 02/02/2023 01:33 am »
Because some of us read the actual Twitter thread - 250t to Earth Orbit was the thread. Don't believe me, believe pic from the Twitter thread the OP linked to

I read that too. It was only a small part of what was attached to the OP. There was a whole lot more and that is NOT title of this thread. The OP presented a much wider spectrum, yet you are trying to police the thread and limit it to one small factor. Stop.
« Last Edit: 02/02/2023 01:35 am by TomH »

Offline sevenperforce

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Re: Expendable Upper Stage?!?
« Reply #38 on: 02/02/2023 01:51 am »
It's just a big number for hype, and most LVs do this. Payload numbers for a 200 km circular Earth orbit are very common, even though such an orbit is essentially useless except as an initial parking orbit. It's extremely rare to ever launch a payload that even comes close to an LV's maximum theoretical LEO performance.

Maximum performance numbers to higher orbits, GEO, and interplanetary, are much more important.
Often, payload numbers for a 200 km circular orbit are quoted as inclusive of residual propellant. If you have a restartable upper stage and you know your specific impulse and stage dry mass, it's a quick way to characterize BLEO capabilities.

Offline Malatrope

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Re: Expendable Upper Stage?!?
« Reply #39 on: 02/02/2023 02:16 am »
Well, an "expendable" upper stage would certainly be an appropriate way to start building "Tycho Station" in some high orbit or another, so we can start building really big ships.  :D
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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.

Online 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.

Online 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.

Online 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
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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.

Online 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

Online 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

Online 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.

Offline TheRadicalModerate

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Re: Expendable Upper Stage?!?
« Reply #60 on: 02/02/2023 09:29 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.

From the Starship User Guide (which is probably stale, but I doubt they've changed the payload bay static envelope), see attached.  Note also that there's an "extended" configuration with a 22m height, which I suspect is an expendable Starship without header tanks, but could be a different outer mould line.

Offline TheRadicalModerate

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Re: Expendable Upper Stage?!?
« Reply #61 on: 02/02/2023 09:33 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.

There's nothing particularly expensive about the Starship stage, other than the engines.  If you have lighter payloads, you can de-engine the silly thing, rip the elonerons and TPS off, and it's not much more than a bunch of stainless steel with some avionics and (fewer) engines.  You don't need new stages; you just need a dumber Starship.

Offline TheRadicalModerate

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Re: Expendable Upper Stage?!?
« Reply #62 on: 02/03/2023 03:37 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?

It's very close to 1:1, but you've left off a biggie:  You can jettison the whole nose fairing pretty early in the ascent.  I suspect that's good for close to 50t-70t extra payload right there.  I've been assuming that all the elonerons, TPS, header tanks, and residuals are good for at least 25t, so now we're getting pretty close.

This of course assumes that the vanilla-flavored Starship can actually get 150t to LEO, which isn't a done deal yet.  And I'd also guess that the baseline for the 250t claim assumes the existence of "Raptor Full-Thrust", as well, which reputedly takes the vanilla mass to LEO to almost 200t.

Online M.E.T.

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Re: Expendable Upper Stage?!?
« Reply #63 on: 02/03/2023 03:57 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?

It's very close to 1:1, but you've left off a biggie:  You can jettison the whole nose fairing pretty early in the ascent.  I suspect that's good for close to 50t-70t extra payload right there.  I've been assuming that all the elonerons, TPS, header tanks, and residuals are good for at least 25t, so now we're getting pretty close.

This of course assumes that the vanilla-flavored Starship can actually get 150t to LEO, which isn't a done deal yet.  And I'd also guess that the baseline for the 250t claim assumes the existence of "Raptor Full-Thrust", as well, which reputedly takes the vanilla mass to LEO to almost 200t.

This is the important point that the ď400t expendableĒ proponents are missing.

Starship in its current format is likely not down to 85t dry mass, and Raptor in its current form is likely gonna operate well below Elonís optimised, aspirational levels.

So I would not be surprised if reusable Starship is initially just a 75t to LEO vehicle.

With optimisation gradually pushing it towards the 100t mark. With 150t the distant stretch goal, assuming a lot of aspirational progress.

So 250t is likely the realistic fully expendable  capacity, if I had to put money on it - for the 2020ís at least.
« Last Edit: 02/03/2023 03:58 am by M.E.T. »

Offline Valerij

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Re: Expendable Upper Stage?!?
« Reply #64 on: 02/03/2023 10:42 am »
The "250 tonne expendable" refers to a payload delivered by an expendable SS atop an expendable booster.

I, like all of us, cannot confirm my words with a calculation due to the lack of accurate initial data. But I got the impression that 250 tonns in orbit is a expendable Starship on a reusable booster. I'll try to explain why I have such an opinion.
     
Yes, I agree, a expendable Starship should not have thermal protection tiles, aerodynamic planes, part of the fuel plant, intended for return, but this is a lot less than a hundred tonns in total.
   
As I understand it, a reusable Starship must have about 40 tonns of fuel in its tanks to return to Earth. Unlike it, the expendable Starship can use these forty tonns of fuel to enter orbit, and therefore may have an additional supply of fuel in excess of these forty. In my opinion, due to an increase in the available fuel supply and a decrease in the mass of the Starship itself, its maximum carrying capacity is growing to 250 tonns.
   
That is, the starting mass of a expendable Starship may be more due to for more fuel and more payload.
   

Offline Valerij

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Re: Expendable Upper Stage?!?
« Reply #65 on: 02/03/2023 10:55 am »
   
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.
   
Of course, this is pure speculation, but I assume that after some time we will see a custom Starship with an "over-caliber" payload bay. That is, on the usual section of engines and tanks with a diameter of 9 meters there will be a payload compartment, or fairing, with a diameter of 12-15 meters. I think, this is a very interesting configuration for space stations...

Offline eriblo

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Re: Expendable Upper Stage?!?
« Reply #66 on: 02/03/2023 11:11 am »
The "250 tonne expendable" refers to a payload delivered by an expendable SS atop an expendable booster.

I, like all of us, cannot confirm my words with a calculation due to the lack of accurate initial data. But I got the impression that 250 tonns in orbit is a expendable Starship on a reusable booster. I'll try to explain why I have such an opinion.
     
Yes, I agree, a expendable Starship should not have thermal protection tiles, aerodynamic planes, part of the fuel plant, intended for return, but this is a lot less than a hundred tonns in total.
   
As I understand it, a reusable Starship must have about 40 tonns of fuel in its tanks to return to Earth. Unlike it, the expendable Starship can use these forty tonns of fuel to enter orbit, and therefore may have an additional supply of fuel in excess of these forty. In my opinion, due to an increase in the available fuel supply and a decrease in the mass of the Starship itself, its maximum carrying capacity is growing to 250 tonns.
   
That is, the starting mass of a expendable Starship may be more due to for more fuel and more payload.
   
Unless they spend a lot more time hovering than they did during the test flights deorbit + landing is < 400 m/s which is ~30 t of propellant even with full payload. Quoting from another thread:
 
Expendable payload has been estimated as ~2x reusable which gives HLS + 2 tankers with quite a bit of margin for boiloff and residuals.
There's no way it takes an extra 100t of propellant to reuse a Starship.

1.2x I'd believe, but not 2x
It's not just the propellant. If SS is designed to be expendable it does not have TPS or Elonerons.
Do the math, you still don't get 2x
Have you done the math? flightclub.io has a Starship profile (120 t payload, 119 t + 250 t dry mass, 1200 t + 2970 t of propellant) that gets to a ~200 km orbit with 12 t of residuals/landing propellant.

Expending the booster gets ~50 t of residuals. Loading the booster fully with 3400 t gets ~87 t of residuals.

If we say that TPS + flaps + actuators + smaller batteries + payload bay is a conservative 23 t that would mean a stripped down tanker would deliver 230 t of propellant even before extending it and launching it heavy.

Offline TheRadicalModerate

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Re: Starship Expendable Upper Stage?
« Reply #67 on: 02/03/2023 07:19 pm »
FWIW, here's a Silverbird calculation with:

SuperHeavy, with somewhat improved thrust (255.1tf):
dry=200t, prop=3400t, Thrust=33 x 2500kN = 82,500kN, launch Isp=333s

Expendable Starship with 50t jettisonable fairing, 9 engines, and avg 265.3tf thrust:
dry=95t, prop=1200t, Thrust=9 x 2600kN avg = 23,400kN, avg vac Isp=370s

Launched from Canaveral into 200km x 200km x 28.5ļ.

Midpoint is 213t payload to LEO.  95% CI is 164.2t - 271.5t

This is de facto a fully expendable (both SH and SS) calculation, with (assumed) nominal residuals.  It is of course possible that Silverbird's set of approximations doesn't work very well with something this big, but it implies that 250t might be... aspirational?

Offline InterestedEngineer

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Re: Starship Expendable Upper Stage?
« Reply #68 on: 02/03/2023 07:31 pm »
FWIW, here's a Silverbird calculation with:

SuperHeavy, with somewhat improved thrust (255.1tf):
dry=200t, prop=3400t, Thrust=33 x 2500kN = 82,500kN, launch Isp=333s

Expendable Starship with 50t jettisonable fairing, 9 engines, and avg 265.3tf thrust:
dry=95t, prop=1200t, Thrust=9 x 2600kN avg = 23,400kN, avg vac Isp=370s

Launched from Canaveral into 200km x 200km x 28.5ļ.

Midpoint is 213t payload to LEO.  95% CI is 164.2t - 271.5t

This is de facto a fully expendable (both SH and SS) calculation, with (assumed) nominal residuals.  It is of course possible that Silverbird's set of approximations doesn't work very well with something this big, but it implies that 250t might be... aspirational?

50t seems like very heavy for a faring, but dropping it in half only helps about 10t.

when I set the fairing to 10t and the dry mass of SS to 70t I get 250t.

(I also set Isp for first stage to 345.  It's only 333 the first few kilometers, vacuum Isp is 355).

Second stage is 365, which is what you get with all vacuum engines 100% and the regular at 50% thrust.
« Last Edit: 02/03/2023 07:35 pm by InterestedEngineer »

Offline TheRadicalModerate

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Re: Starship Expendable Upper Stage?
« Reply #69 on: 02/03/2023 08:08 pm »
FWIW, here's a Silverbird calculation with:

SuperHeavy, with somewhat improved thrust (255.1tf):
dry=200t, prop=3400t, Thrust=33 x 2500kN = 82,500kN, launch Isp=333s

Expendable Starship with 50t jettisonable fairing, 9 engines, and avg 265.3tf thrust:
dry=95t, prop=1200t, Thrust=9 x 2600kN avg = 23,400kN, avg vac Isp=370s

Launched from Canaveral into 200km x 200km x 28.5ļ.

Midpoint is 213t payload to LEO.  95% CI is 164.2t - 271.5t

This is de facto a fully expendable (both SH and SS) calculation, with (assumed) nominal residuals.  It is of course possible that Silverbird's set of approximations doesn't work very well with something this big, but it implies that 250t might be... aspirational?

50t seems like very heavy for a faring, but dropping it in half only helps about 10t.

when I set the fairing to 10t and the dry mass of SS to 70t I get 250t.

(I also set Isp for first stage to 345.  It's only 333 the first few kilometers, vacuum Isp is 355).

Second stage is 365, which is what you get with all vacuum engines 100% and the regular at 50% thrust.

I was assuming that the dry mass included the fairing, which was then subtracted after the jettison time.  The fairing would be the entire nose of the vehicle.  There will be no header tanks, but the nose is really designed to maximize payload bay volume, rather than minimizing dynamic pressure loads.  I guess they could make a radically different fairing and slap it onto the propulsion section, but that seems like quite a bit more work.

I was also assuming that you plugged in SL Isp for the first stage, but it appears that's wrong and it should be vac Isp.  That takes the midpoint up to 235.8t.

Offline InterestedEngineer

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Re: Starship Expendable Upper Stage?
« Reply #70 on: 02/03/2023 08:18 pm »
FWIW, here's a Silverbird calculation with:

SuperHeavy, with somewhat improved thrust (255.1tf):
dry=200t, prop=3400t, Thrust=33 x 2500kN = 82,500kN, launch Isp=333s

Expendable Starship with 50t jettisonable fairing, 9 engines, and avg 265.3tf thrust:
dry=95t, prop=1200t, Thrust=9 x 2600kN avg = 23,400kN, avg vac Isp=370s

Launched from Canaveral into 200km x 200km x 28.5ļ.

Midpoint is 213t payload to LEO.  95% CI is 164.2t - 271.5t

This is de facto a fully expendable (both SH and SS) calculation, with (assumed) nominal residuals.  It is of course possible that Silverbird's set of approximations doesn't work very well with something this big, but it implies that 250t might be... aspirational?

50t seems like very heavy for a faring, but dropping it in half only helps about 10t.

when I set the fairing to 10t and the dry mass of SS to 70t I get 250t.

(I also set Isp for first stage to 345.  It's only 333 the first few kilometers, vacuum Isp is 355).

Second stage is 365, which is what you get with all vacuum engines 100% and the regular at 50% thrust.

I was assuming that the dry mass included the fairing, which was then subtracted after the jettison time.  The fairing would be the entire nose of the vehicle.  There will be no header tanks, but the nose is really designed to maximize payload bay volume, rather than minimizing dynamic pressure loads.  I guess they could make a radically different fairing and slap it onto the propulsion section, but that seems like quite a bit more work.

I was also assuming that you plugged in SL Isp for the first stage, but it appears that's wrong and it should be vac Isp.  That takes the midpoint up to 235.8t.

When I use what i think are reasonable numbers the reusable config easily gets 150t


Online MickQ

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Re: Starship Expendable Upper Stage?
« Reply #71 on: 02/03/2023 10:14 pm »
Would there be any noticeable gain / loss in deleting the sea level engines and just running
the RVACís ??
« Last Edit: 02/03/2023 10:16 pm by MickQ »

Offline Steve D

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Re: Starship Expendable Upper Stage?
« Reply #72 on: 02/03/2023 10:16 pm »
If you want an expendable or non returnable starship could you lighten it by building it out nof aluminum?

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Re: Starship Expendable Upper Stage?
« Reply #73 on: 02/03/2023 10:38 pm »
One payload that comes to mind is a bigger and much more capable optical space telescope.
Imagine a 7+ metre monolithic mirror 🤔

Offline TheRadicalModerate

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Re: Starship Expendable Upper Stage?
« Reply #74 on: 02/03/2023 11:33 pm »
Would there be any noticeable gain / loss in deleting the sea level engines and just running
the RVACís ??

With only 3 RVacs and no gimbaling, doing control just by throttling is dicey.  And things get really dicey if one of the RVacs fails.

On the other hand, if they really go to 6 RVacs + 3 RSLs, then deleting the 3 RSLs leaves a pretty robust system.  You might get into T/W trouble with extremely heavy payloads, though.  There's still some gravity drag to be incurred after SuperHeavy is gone.

Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #75 on: 02/03/2023 11:58 pm »
One payload that comes to mind is a bigger and much more capable optical space telescope.
Imagine a 7+ metre monolithic mirror 🤔
It appears That Subaru is the largest monolithic mirror on Earth. The mirror is 8.2 m diameter with a mass of 22.8 tonnes. Should easily fit in a standard reusable SS.  But why?  A bigger segmented mirror is probably a better choice.
   https://subarutelescope.org/en/about/

Offline livingjw

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Re: Starship Expendable Upper Stage?
« Reply #76 on: 02/04/2023 02:18 am »
If you want an expendable or non returnable starship could you lighten it by building it out nof aluminum?

- No, the strength to weight of 300 series SS used in Starship is higher than most high strength aluminum alloys.

John
« Last Edit: 02/04/2023 02:26 am by livingjw »

Online Zed_Noir

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Re: Starship Expendable Upper Stage?
« Reply #77 on: 02/04/2023 03:55 am »
One payload that comes to mind is a bigger and much more capable optical space telescope.
Imagine a 7+ metre monolithic mirror 🤔
It appears That Subaru is the largest monolithic mirror on Earth. The mirror is 8.2 m diameter with a mass of 22.8 tonnes. Should easily fit in a standard reusable SS.  But why?  A bigger segmented mirror is probably a better choice.
   https://subarutelescope.org/en/about/
Not really. IIRC the internal diameter of the Starship is about 8 meters. Something like the Subaru monolithic mirror needs to be mounted in a telescope structure that is likely to have a bigger diameter than the 9 meter external diameter of the Starship .

Of course a 15-ish meter diameter mirror could fitted in a large asymmetric payload fairing shaped like an arrowhead on top of an expendable Starship variant.

Offline su27k

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Re: Starship Expendable Upper Stage?
« Reply #78 on: 02/04/2023 04:11 am »
One payload that comes to mind is a bigger and much more capable optical space telescope.
Imagine a 7+ metre monolithic mirror 🤔
It appears That Subaru is the largest monolithic mirror on Earth. The mirror is 8.2 m diameter with a mass of 22.8 tonnes. Should easily fit in a standard reusable SS.  But why?  A bigger segmented mirror is probably a better choice.
   https://subarutelescope.org/en/about/
Not really. IIRC the internal diameter of the Starship is about 8 meters. Something like the Subaru monolithic mirror needs to be mounted in a telescope structure that is likely to have a bigger diameter than the 9 meter external diameter of the Starship .

That's why it may be a job for expendable Starship: Use the ship structure itself as telescope structure and leave the ship in space (since it _is_ the telescope). Pretty sure Elon mentioned something like this before.

Online Zed_Noir

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Re: Starship Expendable Upper Stage?
« Reply #79 on: 02/04/2023 05:09 am »
One payload that comes to mind is a bigger and much more capable optical space telescope.
Imagine a 7+ metre monolithic mirror 🤔
It appears That Subaru is the largest monolithic mirror on Earth. The mirror is 8.2 m diameter with a mass of 22.8 tonnes. Should easily fit in a standard reusable SS.  But why?  A bigger segmented mirror is probably a better choice.
   https://subarutelescope.org/en/about/
Not really. IIRC the internal diameter of the Starship is about 8 meters. Something like the Subaru monolithic mirror needs to be mounted in a telescope structure that is likely to have a bigger diameter than the 9 meter external diameter of the Starship .

That's why it may be a job for expendable Starship: Use the ship structure itself as telescope structure and leave the ship in space (since it _is_ the telescope). Pretty sure Elon mentioned something like this before.

Have doubts that the Starship structure is stable enough for use as a telescope structure without a lot of modifications. Might just be cheaper to not use the Starship as a telescope and build a new space telescope instead.
« Last Edit: 02/04/2023 06:56 am by Zed_Noir »

Offline whitelancer64

Re: Starship Expendable Upper Stage?
« Reply #80 on: 02/04/2023 06:17 am »
One payload that comes to mind is a bigger and much more capable optical space telescope.
Imagine a 7+ metre monolithic mirror 🤔

Large monolithic mirrors are really expensive to make.

The Subaru space telescope cost about $377 million to build. The Keck telescopes each cost about $90 million, they have 10 meter diameter mirrors of 36 segments each.

It's cheaper to mass produce many small mirrors, make it segmented and fold it up. Why not dream big, make it 15 meters in diameter.

https://twitter.com/NASAGoddard/status/1116310431969239040
« Last Edit: 02/04/2023 06:26 am by whitelancer64 »
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Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #81 on: 02/04/2023 01:29 pm »
One payload that comes to mind is a bigger and much more capable optical space telescope.
Imagine a 7+ metre monolithic mirror 🤔
It appears That Subaru is the largest monolithic mirror on Earth. The mirror is 8.2 m diameter with a mass of 22.8 tonnes. Should easily fit in a standard reusable SS.  But why?  A bigger segmented mirror is probably a better choice.
   https://subarutelescope.org/en/about/
Not really. IIRC the internal diameter of the Starship is about 8 meters. Something like the Subaru monolithic mirror needs to be mounted in a telescope structure that is likely to have a bigger diameter than the 9 meter external diameter of the Starship .

That's why it may be a job for expendable Starship: Use the ship structure itself as telescope structure and leave the ship in space (since it _is_ the telescope). Pretty sure Elon mentioned something like this before.

Have doubts that the Starship structure is stable enough for use as a telescope structure without a lot of modifications. Might just be cheaper to not use the Starship as a telescope and build a new space telescope instead.
This thread is about "expendable SS" and includes custom non-EDL SS. The designer of a huge telescope has two options: do the engineering to design a standalone free flyer, or do the engineering to use the SS as part of the structure. You have stability problems to solve either way. Not being a telescope engineer, I have no idea which is the better solution.

Offline KSHavre

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Re: Starship Expendable Upper Stage?
« Reply #82 on: 02/04/2023 05:23 pm »
One payload that comes to mind is a bigger and much more capable optical space telescope.
Imagine a 7+ metre monolithic mirror 🤔
It appears That Subaru is the largest monolithic mirror on Earth. The mirror is 8.2 m diameter with a mass of 22.8 tonnes. Should easily fit in a standard reusable SS.  But why?  A bigger segmented mirror is probably a better choice.
   https://subarutelescope.org/en/about/
Not really. IIRC the internal diameter of the Starship is about 8 meters. Something like the Subaru monolithic mirror needs to be mounted in a telescope structure that is likely to have a bigger diameter than the 9 meter external diameter of the Starship .

That's why it may be a job for expendable Starship: Use the ship structure itself as telescope structure and leave the ship in space (since it _is_ the telescope). Pretty sure Elon mentioned something like this before.

Have doubts that the Starship structure is stable enough for use as a telescope structure without a lot of modifications. Might just be cheaper to not use the Starship as a telescope and build a new space telescope instead.
This thread is about "expendable SS" and includes custom non-EDL SS. The designer of a huge telescope has two options: do the engineering to design a standalone free flyer, or do the engineering to use the SS as part of the structure. You have stability problems to solve either way. Not being a telescope engineer, I have no idea which is the better solution.

The minimal modified variant then, has bits of the telescope as part of the door (folds out to support shields or mirrors) with other telescope bits folding out of the bay.


Or, a totally new SS as the telescope variant would add up the mass of:

*   TPS and Fins and any addition supporting structure for those bits
*   1, 2 or 3 sea level Raptors not required to get to orbit
*   All fueling infrastructure required to "land", anywhere
*   All current nosecone structures to add cargo or passengers

Telescope design parameters could then include:

*   The mass available for cargo plus all the bits above
*   The diameter of Starship
*   The maximum length of a nosecone the OLP can support


If the 'go anywhere' version keeps all three RVacs, a special purpose version would make available the mass of engines and infrastructure removed.

A telescope location that would not require refueling provides a little more mass to the telescope. The challenge is to optimize stretching tanks vs. telescope mass to get there in one go.

Offline Reynold

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Re: Starship Expendable Upper Stage?
« Reply #83 on: 02/04/2023 09:56 pm »
That's why it may be a job for expendable Starship: Use the ship structure itself as telescope structure and leave the ship in space (since it _is_ the telescope). Pretty sure Elon mentioned something like this before.

Have doubts that the Starship structure is stable enough for use as a telescope structure without a lot of modifications. Might just be cheaper to not use the Starship as a telescope and build a new space telescope instead.
This thread is about "expendable SS" and includes custom non-EDL SS. The designer of a huge telescope has two options: do the engineering to design a standalone free flyer, or do the engineering to use the SS as part of the structure. You have stability problems to solve either way. Not being a telescope engineer, I have no idea which is the better solution.

I would suspect the designer would go with a standalone free flyer, because it would be hard to get funding for "another of the same telescope", so scientists design custom instrumentation for each telescope, which takes a long time, and SpaceX may not be willing to freeze a design for years to design their Starship structure into the telescope. 

That is one reason SpaceX has not iterated the F9 much since it became reliable, because customers don't want them to change things to much and have to requalify everything.  SpaceX had the Starship to work on for their next generation, so it is easier for them and customers to leave the F9 largely alone.  Starship will clearly have more variations, because at a minimum it has to do several things like orbital depot, HLS lander, etc. but there is probably some limit SpaceX will apply. 

Offline edzieba

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Re: Starship Expendable Upper Stage?
« Reply #84 on: 02/05/2023 08:44 pm »
This thread is about "expendable SS" and includes custom non-EDL SS. The designer of a huge telescope has two options: do the engineering to design a standalone free flyer, or do the engineering to use the SS as part of the structure. You have stability problems to solve either way. Not being a telescope engineer, I have no idea which is the better solution.
Trying to build a giant precision optical instrument kitbashed from parts of an unrelated spaceship is about as difficult as trying to build a large ground telescope from bits of the semi trailers that transported it to site. The structural requirements for an optical assembly are pretty radically different from those of Starship (thermal bridging, thermal stability CoTE, flex when repointing, internal emissivity, etc. etc.), and trying to incorporate Starship into the telescope assembly is just adding more headaches unnecessarily.

Offline sevenperforce

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Re: Starship Expendable Upper Stage?
« Reply #85 on: 02/06/2023 03:28 pm »
Trying to build a giant precision optical instrument kitbashed from parts of an unrelated spaceship is about as difficult as trying to build a large ground telescope from bits of the semi trailers that transported it to site. The structural requirements for an optical assembly are pretty radically different from those of Starship (thermal bridging, thermal stability CoTE, flex when repointing, internal emissivity, etc. etc.), and trying to incorporate Starship into the telescope assembly is just adding more headaches unnecessarily.
I take your point, but what about building a large ground telescope by mounting it inside the semi trailer, using the semi trailer as the structural frame, so that once you get to your destination you can simply jettison the top of the trailer box and start observing?
« Last Edit: 02/06/2023 03:28 pm by sevenperforce »

Offline whitelancer64

Re: Starship Expendable Upper Stage?
« Reply #86 on: 02/06/2023 03:51 pm »
Trying to build a giant precision optical instrument kitbashed from parts of an unrelated spaceship is about as difficult as trying to build a large ground telescope from bits of the semi trailers that transported it to site. The structural requirements for an optical assembly are pretty radically different from those of Starship (thermal bridging, thermal stability CoTE, flex when repointing, internal emissivity, etc. etc.), and trying to incorporate Starship into the telescope assembly is just adding more headaches unnecessarily.
I take your point, but what about building a large ground telescope by mounting it inside the semi trailer, using the semi trailer as the structural frame, so that once you get to your destination you can simply jettison the top of the trailer box and start observing?

Rather like installing a telescope in an airplane and putting a huge  door on the side of the airplane so you can fly the telescope around and make observations anywhere in the world. Neat idea in theory, but we've seen how cost-effective that was in practice.

I think the "Starship as a satellite bus" idea is pretty bad overall. In virtually every case you're better off using Starship for its designed purpose - to launch the satellite. You're not saving any time or money in the long run by building your instruments into the LV.
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Offline TheRadicalModerate

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Re: Starship Expendable Upper Stage?
« Reply #87 on: 02/06/2023 06:58 pm »
I think the "Starship as a satellite bus" idea is pretty bad overall. In virtually every case you're better off using Starship for its designed purpose - to launch the satellite. You're not saving any time or money in the long run by building your instruments into the LV.

More likely it's bad for some applications, good for others.

It's not a great platform for anything requiring precision optics, extreme pointing accuracy, or a stable thermal environment.  It's also really, really bad for anything requiring Category III or IV icy moon planetary protection.

But if you have a heavy industrial application, building it straight into a Starship, either with or without a fairing, will be a lot easier than having to design, build, and deploy a free-flying bus for a heavy application.  I suspect that there are also a fair number of scientific packages that are easier to put together in a rack-mounted format, rather than a bus-mounted one.  Having a Starship, either expendable or not, with the power and thermal systems to support rack-mounted stuff sounds like a pretty good idea to me.

One of my favorite industrial apps is a self-contained methalox plant for Mars.  Just land it, deploy power and heat rejection, and use the existing LCH4 and LOX tanks, with suitable cryo-cooling, as storage.  You can build versions that work with water delivered to them, but you can also work a bunch of the bugs out simply by carrying some LH2 feedstock.  Of course, this requires getting some planetary protection relief, but it seems that everybody agrees that's a requirement.  Getting from the current guidelines to relaxed guidelines will likely take a few years, but my guess is that's about how long we have before SpaceX tries anything with Mars in the first place.

Offline JayWee

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Re: Starship Expendable Upper Stage?
« Reply #88 on: 02/06/2023 07:39 pm »
But if you have a heavy industrial application, building it straight into a Starship, either with or without a fairing, will be a lot easier than having to design, build, and deploy a free-flying bus for a heavy application.  I suspect that there are also a fair number of scientific packages that are easier to put together in a rack-mounted format, rather than a bus-mounted one. 
Aka - Spacehab II.

Offline Valerij

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Re: Starship Expendable Upper Stage?
« Reply #89 on: 02/06/2023 09:48 pm »
But if you have a heavy industrial application, building it straight into a Starship, either with or without a fairing, will be a lot easier than having to design, build, and deploy a free-flying bus for a heavy application.  I suspect that there are also a fair number of scientific packages that are easier to put together in a rack-mounted format, rather than a bus-mounted one.  Having a Starship, either expendable or not, with the power and thermal systems to support rack-mounted stuff sounds like a pretty good idea to me.
   
With this I completely agree.
     
One of my favorite industrial apps is a self-contained methalox plant for Mars.  Just land it, deploy power and heat rejection, and use the existing LCH4 and LOX tanks, with suitable cryo-cooling, as storage.
     
You canít argue with this either, but it must be borne in mind that an energy source is needed to produce fuel. Solar panels and a rover that will install and connect them can be brought on the same or on another Starship.
         
You can build versions that work with water delivered to them, but you can also work a bunch of the bugs out simply by carrying some LH2 feedstock.  Of course, this requires getting some planetary protection relief, but it seems that everybody agrees that's a requirement.  Getting from the current guidelines to relaxed guidelines will likely take a few years, but my guess is that's about how long we have before SpaceX tries anything with Mars in the first place.
     
But here I disagree. Since we're going to have a pretty powerful energy source one way or another, it's much better to bring in rovers with a rig and ice and/or water extraction equipment. Better to spend the time to find water/ice and to develop methods for extracting it.
   
We can continue this discussion in a more appropriate thread.
   
« Last Edit: 02/06/2023 09:51 pm by Valerij »

Offline TheRadicalModerate

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Re: Starship Expendable Upper Stage?
« Reply #90 on: 02/07/2023 05:10 am »
You can build versions that work with water delivered to them, but you can also work a bunch of the bugs out simply by carrying some LH2 feedstock.  Of course, this requires getting some planetary protection relief, but it seems that everybody agrees that's a requirement.  Getting from the current guidelines to relaxed guidelines will likely take a few years, but my guess is that's about how long we have before SpaceX tries anything with Mars in the first place.
     
But here I disagree. Since we're going to have a pretty powerful energy source one way or another, it's much better to bring in rovers with a rig and ice and/or water extraction equipment. Better to spend the time to find water/ice and to develop methods for extracting it.
   
We can continue this discussion in a more appropriate thread.
   

FWIW, there was a very long thread on some of this starting about here.  It's pretty much zombified at this point--and should rest in peace, since it became a quite a food fight, albeit an interesting one.

Offline su27k

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Re: Starship Expendable Upper Stage?
« Reply #91 on: 02/08/2023 12:17 am »
https://twitter.com/SpaceHaxx/status/1621877068001681410

Quote
Starstack 2 Orion Special: "Princess Flies Coach"

Starstack isn't a "design".  It's a menu.  Like Mexican food.  Same few ingredients, many dishes.

Here we open the fridge and pull out the perfect concoction to send Orion safely off to TLI.

Offline TomH

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Re: Starship Expendable Upper Stage?
« Reply #92 on: 02/08/2023 04:21 am »
Obviously, there are doubts it could ever happen in terms of business cooperation, but from a technical POV only, I have to wonder if the National Team lander would fit beneath the CSM for a single launch architecture like Apollo/Saturn V. Enough ΔV? TLI? LOI? Tank stretch?
« Last Edit: 02/08/2023 04:22 am by TomH »

Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #93 on: 02/08/2023 04:49 am »
Consider this mission plan:
  *Launch a "standard" EDL cargo Starship and have it consume all of its fuel during launch to put itself and a max payload to the least energetically expensive LEO.
  *Refuel in this orbit, deliver the payload to its desired orbit, and then EDL.

Does this allow delivery of a larger payload than the simple reusable single-launch case? It should be cheaper than an expendable.


Offline TheRadicalModerate

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Re: Starship Expendable Upper Stage?
« Reply #94 on: 02/08/2023 04:17 pm »
Consider this mission plan:
  *Launch a "standard" EDL cargo Starship and have it consume all of its fuel during launch to put itself and a max payload to the least energetically expensive LEO.
  *Refuel in this orbit, deliver the payload to its desired orbit, and then EDL.

Does this allow delivery of a larger payload than the simple reusable single-launch case? It should be cheaper than an expendable.

It's probably a bit larger payload, but I'm pretty sure that the 250t to LEO is with an expendable SuperHeavy as well.  Also, by removing the TPS, header tanks, elonerons, and jettisoning the fairing, all that mass goes into the payload number.

The issue isn't getting the payload from LEO to its final target orbit.  It's getting it to LEO in the first place.

Finally, if lift tankers don't actually have the refueling hardware on them, then you need a depot at the inclination and RAAN of the target orbit.  That's a major expense.

Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #95 on: 02/08/2023 04:41 pm »
Consider this mission plan:
  *Launch a "standard" EDL cargo Starship and have it consume all of its fuel during launch to put itself and a max payload to the least energetically expensive LEO.
  *Refuel in this orbit, deliver the payload to its desired orbit, and then EDL.

Does this allow delivery of a larger payload than the simple reusable single-launch case? It should be cheaper than an expendable.

It's probably a bit larger payload, but I'm pretty sure that the 250t to LEO is with an expendable SuperHeavy as well.  Also, by removing the TPS, header tanks, elonerons, and jettisoning the fairing, all that mass goes into the payload number.

The issue isn't getting the payload from LEO to its final target orbit.  It's getting it to LEO in the first place.

Finally, if lift tankers don't actually have the refueling hardware on them, then you need a depot at the inclination and RAAN of the target orbit.  That's a major expense.
Understood: that's what I thought, but if a standard reusable launch is 150 tonne, then what would we expect of this launch? The increment will be at least equal to the mass of the fuel needed for EDL including the safety reserve.

I think a depot is needed in all refuelling cases. Direct tanker-to-target does not make sense to me. If depot is needed, it's production and launch cost is a one-time expense. It would be placed in the minimum-energy stable LEO for a particular launch site and would serve all launches from that site that need it. I envision the payload launch going to a barely-stable altitude and the depot descending to this altitude for the refuelling, and ascending back to a reasonable altitude after refuelling, while the payload carrier goes on its merry way. One depot would support hundreds of missions over its lifetime, and tanker flights are shared when the payload missions don't need exact multiples of a tanker.

This idea is on this thread because if this scheme works it raises the lower bound for the mass that requires an expendable launch, and that in turn changes the economics.

Offline TheRadicalModerate

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Re: Starship Expendable Upper Stage?
« Reply #96 on: 02/08/2023 06:58 pm »
I think a depot is needed in all refuelling cases. Direct tanker-to-target does not make sense to me. If depot is needed, it's production and launch cost is a one-time expense. It would be placed in the minimum-energy stable LEO for a particular launch site and would serve all launches from that site that need it. I envision the payload launch going to a barely-stable altitude and the depot descending to this altitude for the refuelling, and ascending back to a reasonable altitude after refuelling, while the payload carrier goes on its merry way. One depot would support hundreds of missions over its lifetime, and tanker flights are shared when the payload missions don't need exact multiples of a tanker.

Only if all of those missions have the same inclination and RAAN.  And they won't, especially for the vanilla-flavored reusable missions.

Quote
This idea is on this thread because if this scheme works it raises the lower bound for the mass that requires an expendable launch, and that in turn changes the economics.

Let's assume we need 250m/s for EDL, with zero down-mass.  At sea-level Isp=333s and 120t dry mass, that's 9.6t of prop.  Let's ignore sump and boiloff losses and assume that payload to LEO is nominally 150t.  To get to LEO, that mass ratio needs to be the same as the mass ratio for the system with the 9.6t of prop put back in.  If we represent the improved payload mass as x, then they have to have the same mass ratios:

(120+1200+150)/(120+9.6+150) = (120+1200+x)/(120+x)
x = 161.9t

A 7.9% payload improvement.  Nothing to sneeze at.

That said, unless your already-quite-exotic payload happens to need to go to an inclination that's popular enough to already have a depot (and that's likely only at a fairly low inclination that's good for TLI), you're incurring the cost of a depot launch, which you probably have to amortize all by your lonesome.  In effect, the depot becomes an expendable component.

Instead, if you expend your launch Starship, you can strip off all the EDL crap, which can then be turned into payload.  I've been arm-waving the EDL crap at 25t, so instead you get 186.9t of payload, a 24.6% improvement over the presumptive 150t for the fully-reusable system with no refueling.

Bottom line:  What you're saying makes sense if you can amortize the cost of the depot.  If not, it's much better to go with an expendable Starship stage.

PS:  I'm gonna poke at the "only depots can refuel targets" idea.  Unless there are things that require bizarro stuff to be added to the ventral side of a depot for refueling (note that refueling doesn't necessarily imply long-term storage), then you should be able to design all the dorsal stuff that needs to be added as a deployable "kit".  If the depot can deploy that kit, then a lift tanker ought to be able to deploy it as well.  There are a variety of cases where that would be handy.  The most notable is for doing cislunar refueling without a depot, but it would also nicely solve your problem with getting the last few tonnes of performance to LEO by using the EDL residuals.
« Last Edit: 02/08/2023 07:48 pm by TheRadicalModerate »

Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #97 on: 02/08/2023 07:53 pm »
I think a depot is needed in all refuelling cases. Direct tanker-to-target does not make sense to me. If depot is needed, it's production and launch cost is a one-time expense. It would be placed in the minimum-energy stable LEO for a particular launch site and would serve all launches from that site that need it. I envision the payload launch going to a barely-stable altitude and the depot descending to this altitude for the refuelling, and ascending back to a reasonable altitude after refuelling, while the payload carrier goes on its merry way. One depot would support hundreds of missions over its lifetime, and tanker flights are shared when the payload missions don't need exact multiples of a tanker.

Only if all of those missions have the same inclination and RAAN.  And they won't, especially for the vanilla-flavored reusable missions.

Quote
This idea is on this thread because if this scheme works it raises the lower bound for the mass that requires an expendable launch, and that in turn changes the economics.

Let's assume we need 250m/s for EDL, with zero down-mass.  At sea-level Isp=333s and 120t dry mass, that's 9.6t of prop.  Let's ignore sump and boiloff losses and assume that payload to LEO is nominally 150t.  To get to LEO, that mass ratio needs to be the same as the mass ratio for the system with the 9.6t of prop put back in.  If we represent the improved payload mass as x, then they have to have the same mass ratios:

(120+1200+150)/(120+9.6+150) = (120+1200+x)/(120+x)
x = 161.9t

A 7.9% payload improvement.  Nothing to sneeze at.

That said, unless your already-quite-exotic payload happens to need to go to an inclination that's popular enough to already have a depot (and that's likely only at a fairly low inclination that's good for TLI), you're incurring the cost of a depot launch, which you probably have to amortize all by your lonesome.  In effect, the depot becomes an expendable component.

Instead, if you expend your launch Starship, you can strip off all the EDL crap, which can then be turned into payload.  I've been arm-waving the EDL crap at 25t, so instead you get 186.9t of payload, a 24.6% improvement over the presumptive 150t for the fully-reusable system with no refueling.

Bottom line:  What you're saying makes sense if you can amortize the cost of the depot.  If not, it's much better to go with an expendable Starship stage.
No, the whole idea is that all such launches go the the same orbit and then refuel, so they all use the same depot. The refuelling provides enough  delta-v to do a plane change, so you can hit a fairly large range of RAAN from a particular depot. I suppose you might need several depots  (three?) in strategically-placed orbits so the payload-bearing SS can change planes and refuel several times. All of this assumes that tanker operations are really, really cheap.

And all of this, including any expendable SS, leaves open the question: how many unitary payloads greater than 150 tonne are there?

Offline TheRadicalModerate

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Re: Starship Expendable Upper Stage?
« Reply #98 on: 02/08/2023 08:02 pm »
No, the whole idea is that all such launches go the the same orbit and then refuel, so they all use the same depot. The refuelling provides enough  delta-v to do a plane change, so you can hit a fairly large range of RAAN from a particular depot. I suppose you might need several depots  (three?) in strategically-placed orbits so the payload-bearing SS can change planes and refuel several times. All of this assumes that tanker operations are really, really cheap.

And all of this, including any expendable SS, leaves open the question: how many unitary payloads greater than 150 tonne are there?

I suggest you crank through some numbers on what the plane-change costs, and then convert it to tanker launches.  That's crazy talk.  And it's especially crazy talk because there won't be very many unitary payloads greater than 150t.  (Unless DoD decides to do Rods From God if they can't convince the Chinese to back away from FOBS.  Then depots--plural--would make all kinds of sense.)

One other thing:  If somebody's launching unitary 160t payloads to LEO, there's a pretty good chance that it's some kind of multi-squintillion-dollar DoD thing, and those guys really don't want their baby nuzzling up to another spacecraft if they can avoid it.  They'll happily pay for the expendable Starship to avoid it.

Offline whitelancer64

Re: Starship Expendable Upper Stage?
« Reply #99 on: 02/08/2023 08:21 pm »
*snip*
And all of this, including any expendable SS, leaves open the question: how many unitary payloads greater than 150 tonne are there?

Expendable starship does not necessarily assume a 150+ ton payload.

With an expendable Starship-derived upper stage you could maximum yeet a 10 ton probe on an outer planets mission, so it won't take 10 years to fly by the outer planets. For reference, Cassini (at launch, with Huygens probe) was 5 metric tons, the New Horizons probe to Pluto was less than 500 kg.
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Offline Robotbeat

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Re: Starship Expendable Upper Stage?
« Reply #100 on: 02/08/2023 09:12 pm »
*snip*
And all of this, including any expendable SS, leaves open the question: how many unitary payloads greater than 150 tonne are there?

Expendable starship does not necessarily assume a 150+ ton payload.

With an expendable Starship-derived upper stage you could maximum yeet a 10 ton probe on an outer planets mission, so it won't take 10 years to fly by the outer planets. For reference, Cassini (at launch, with Huygens probe) was 5 metric tons, the New Horizons probe to Pluto was less than 500 kg.
Yup, although starship even stripped down has high dry mass so would benefit from a third stage for small payloads, even like a solid kick motor or something.
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Offline TheRadicalModerate

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Re: Starship Expendable Upper Stage?
« Reply #101 on: 02/08/2023 09:16 pm »
*snip*
And all of this, including any expendable SS, leaves open the question: how many unitary payloads greater than 150 tonne are there?

Expendable starship does not necessarily assume a 150+ ton payload.

With an expendable Starship-derived upper stage you could maximum yeet a 10 ton probe on an outer planets mission, so it won't take 10 years to fly by the outer planets. For reference, Cassini (at launch, with Huygens probe) was 5 metric tons, the New Horizons probe to Pluto was less than 500 kg.

Dan was looking explicitly at LEO payloads, but with a refueling so that a reusable Starship didn't have to hold back the landing residuals.  It makes a non-trivial difference.

Offline Robotbeat

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Re: Starship Expendable Upper Stage?
« Reply #102 on: 02/08/2023 09:27 pm »
That plus droneship landing could make a pretty big difference for Starship reusable performance.
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Offline baddux

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Re: Starship Expendable Upper Stage?
« Reply #103 on: 02/14/2023 12:00 am »
Maybe one option for expendable Starship would be cargo Mars lander, ship with maybe one Raptor and header tanks lands on Mars, the "usual" Starship stage with 3 vacuum Raptors just sends it to TMI. It would be shorter so easier to access the surface. Of course that would require redesign of the flaps, or maybe expendable heatshield on the bottom.

Offline Brigantine

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Re: Starship Expendable Upper Stage?
« Reply #104 on: 09/16/2023 10:09 am »
To flip this old thread on its head... I'm pondering Starship backloading as a way of recovering otherwise expendable upper stages from other launch vehicles.

You space-tug an empty Falcon 2nd stage or Centaur etc. to the future orbit of a Starship commercial payload launch, integrate into the payload bay in orbit, then extract it after landing.
(the concept is this is low cost as the the Starship needs to land anyway and there isn't much demand for down-mass)

Falcon 2nd stage is 13.8m high, Centaur V is 12.7m, Starship payload bay is 17m tall - so they would fit vertically.
Falcon 2nd stage is 3.7m diameter, Centaur III is 3.05m diameter. payload bay interior approx 8m (Ī ??)
Depending on the exact details of the payload bay you could fit 2 or 3. (or in theory 1 Falcon and 3 Centaurs - or 1 Centaur V)

I'm assuming the upper stages being recovered would be from GTO missions, so not directly competing with Starship and not from wildly different inclinations. The space tug side could be its own whole discussion, but this is about the Starship part.

Since the upper stages are empty, the mass is well within the down-mass Starship can land.


Q1) Does this seem feasible? (other than the space tug part)
Q2) What technical challenges? e.g. robotic loading & securing, pressurizing them before they get crushed...
Q3) How much potential value? is the marginal upper stage replacement cost much?
Q4) Would 3rd parties even pay a competitor for this service? Or would it be in-house only?
Q5) Or could you kill 2 birds with 1 stone and just re-fuel an old upper stage in orbit and re-use it as a kick stage? (I doubt it)
« Last Edit: 09/16/2023 10:27 am by Brigantine »

Offline TomH

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Re: Starship Expendable Upper Stage?
« Reply #105 on: 09/17/2023 01:37 am »
Q1) Does this seem feasible?

My WAG is that SX would have no interest in considering it simply because they intend to retire Falcon completely when SS is fully online. The investment required would soon be lost.
« Last Edit: 09/17/2023 02:07 am by TomH »

Offline whitelancer64

Re: Starship Expendable Upper Stage?
« Reply #106 on: 09/17/2023 01:54 am »
To flip this old thread on its head... I'm pondering Starship backloading as a way of recovering otherwise expendable upper stages from other launch vehicles.

You space-tug an empty Falcon 2nd stage or Centaur etc. to the future orbit of a Starship commercial payload launch, integrate into the payload bay in orbit, then extract it after landing.
(the concept is this is low cost as the the Starship needs to land anyway and there isn't much demand for down-mass)

Falcon 2nd stage is 13.8m high, Centaur V is 12.7m, Starship payload bay is 17m tall - so they would fit vertically.
Falcon 2nd stage is 3.7m diameter, Centaur III is 3.05m diameter. payload bay interior approx 8m (Ī ??)
Depending on the exact details of the payload bay you could fit 2 or 3. (or in theory 1 Falcon and 3 Centaurs - or 1 Centaur V)

I'm assuming the upper stages being recovered would be from GTO missions, so not directly competing with Starship and not from wildly different inclinations. The space tug side could be its own whole discussion, but this is about the Starship part.

Since the upper stages are empty, the mass is well within the down-mass Starship can land.


Q1) Does this seem feasible? (other than the space tug part)
Q2) What technical challenges? e.g. robotic loading & securing, pressurizing them before they get crushed...
Q3) How much potential value? is the marginal upper stage replacement cost much?
Q4) Would 3rd parties even pay a competitor for this service? Or would it be in-house only?
Q5) Or could you kill 2 birds with 1 stone and just re-fuel an old upper stage in orbit and re-use it as a kick stage? (I doubt it)

Starship's payload bay would need a robotic arm, and some highly specialized structures to support - any captured object - from the forces of reentry. They'd be unique to the object being captured. Whether the costs involved would make it worthwhile is something to look closer at. If hiring a Starship and paying for designing, building, testing, and installing a unique fixture costs $15 million to return $10 million of hardware, it's not going to be worth it.

ULA is already studying in-space refueling of a future long-duration Centaur V. A Starship tanker carrying hydrogen would make some sense.
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Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #107 on: 09/17/2023 01:57 am »
To flip this old thread on its head... I'm pondering Starship backloading as a way of recovering otherwise expendable upper stages from other launch vehicles.
 Q1) Does this seem feasible? (other than the space tug part)
My guess: no, it is not feasible. Existing upper stages are not designed to handle the lateral forces they would experience during the re-entry inside the SS cargo bay. SS re-enters in a belly-forward attitude and probably decelerates at 2 G or more, but existing upper stages are designed to withstand axial forces, not lateral forces. If you are going to design new upper stages, for this, I think the money is better spent on just flying on Starship in the first place.

Offline mikelepage

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Re: Starship Expendable Upper Stage?
« Reply #108 on: 09/17/2023 03:06 am »
To flip this old thread on its head... I'm pondering Starship backloading as a way of recovering otherwise expendable upper stages from other launch vehicles.

You space-tug an empty Falcon 2nd stage or Centaur etc. to the future orbit of a Starship commercial payload launch, integrate into the payload bay in orbit, then extract it after landing.
(the concept is this is low cost as the the Starship needs to land anyway and there isn't much demand for down-mass)

Falcon 2nd stage is 13.8m high, Centaur V is 12.7m, Starship payload bay is 17m tall - so they would fit vertically.
Falcon 2nd stage is 3.7m diameter, Centaur III is 3.05m diameter. payload bay interior approx 8m (Ī ??)
Depending on the exact details of the payload bay you could fit 2 or 3. (or in theory 1 Falcon and 3 Centaurs - or 1 Centaur V)

I'm assuming the upper stages being recovered would be from GTO missions, so not directly competing with Starship and not from wildly different inclinations. The space tug side could be its own whole discussion, but this is about the Starship part.

Since the upper stages are empty, the mass is well within the down-mass Starship can land.


Q1) Does this seem feasible? (other than the space tug part)
Q2) What technical challenges? e.g. robotic loading & securing, pressurizing them before they get crushed...
Q3) How much potential value? is the marginal upper stage replacement cost much?
Q4) Would 3rd parties even pay a competitor for this service? Or would it be in-house only?
Q5) Or could you kill 2 birds with 1 stone and just re-fuel an old upper stage in orbit and re-use it as a kick stage? (I doubt it)

I agree with other commenters that recovering spent upper stages still in orbit is probably a bridge too far for now, but having done a fair bit of study on the space debris issue, I'd say the low hanging fruit would be using the expendable upper stages to do controlled capture, de-orbit and disposals of 200+ spent rocket stages in excess of a ton. Seems kind of wasteful on first glance, but realistically, many of the rocket stages that cause the main risk aren't likely to be in any condition to be reused. Doing this alone would eliminate the main part of the risk of Kessler syndrome for the foreseeable future.

Offline Brigantine

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Re: Starship Expendable Upper Stage?
« Reply #109 on: 09/17/2023 03:17 am »
If they can support 150+ tonnes at 4(?) g axially (FH payload & fuel at MECO), but can't support their own empty mass of 4 tonnes at 2 g laterally even with the aid of "highly specialized structures"... that would be quite a result for a horizontally-integrated LV

---------
Whitelancer64 has some good points, even if it is feasible, the setup won't be cheap. You'd need to build a few cradles and fly them over and over, eventually recovering & re-using dozens of the same model of upper stage.

You'd need a continuing market for F9 and/or ULA launches for years in parallel with Starship, despite space tugs being in operation at least for specific uses.

---------
How quickly would Falcon and competitors really be retired?
(I don't have answers, only questions)

Supply:
Even if they shut the factory, SpaceX already have a fleet of boosters with a combined remaining life of *a lot* of launches. The same could be true of upper stages. If they write down the capital value of that fleet, they can operate profitably at reduced prices for many years. (at a fraction of 100 launches/year, TBF)

Demand:
- Are classified F9-sized defense payloads going to still want dedicated launches?
- When will Starships fly to polar orbits? Until then - depending on the state of space tugs - F9s will have demand (re-use, no recovery)
→ Lunar polar orbit doesn't count! Either SS flying from a launch site like Vandenberg, or else pay for orbital refueling and plane-change
- Express freight to GEO - How cost-effective will it be to bulk-carry to GEO on Starship? Can cut-price FH/F9/ULA still compete?
→ (Possibility that snail freight to GEO flies on Starship to LEO and electric space tug to GEO, so the express market is low volume)
→ "in-space refueling of a future long-duration Centaur V" might kill here, as an efficient LEO-GEO chemical/express space tug. Just add H2

--------
Clarification: The proposal here is to recover recently flown upper stages, which would include a space tug in their payload in lieu of de-orbiting.

Cleaning up old rocket bodies from past eras is a worthwhile but separate topic - though yes if it offers orbital stages a valuable terminal mission extension, then it reduces the value of my proposal.
« Last Edit: 09/17/2023 03:56 am by Brigantine »

Offline Vahe231991

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Re: Starship Expendable Upper Stage?
« Reply #110 on: 09/17/2023 03:45 am »
Given the weight of the Starship's upper stage, the scheme by SpaceX to fit the Starship Cargo version's upper stage with a large cargo door that opens to release payloads into orbit and closes upon reentry makes more sense than leaving the Starship upper stage in orbit because if SpaceX wishes to re-use the upper stage for a future Starship mission, repairs or other intricate fine-tuning of silica tiles on the upper stage could be easily made.

Offline TomH

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Re: Starship Expendable Upper Stage?
« Reply #111 on: 09/17/2023 04:55 am »
On Sept. 7, the GAO released (another) report stating that SLS costs are unsustainable. Of course, they've always said that.

If hot staging proves to be successful, and increases standard SS payload by 10 tons, I wonder how much it would increase payload for a stripped down expendable SS US. If you add in downrange drone ship landing for SH, you increase payload even further. (I acknowledge landing legs issue.)

If GAO and other budget watchdogs put serious cost reduction pressure on NASA re. Artemis, I really can see Orion atop a SS stack and the full National Team Lander (including transfer module) tucked below, a la Apollo, for a single launch architecture. I could also envision a tank stretch (Elon tweeted that full stack will grow 10%-20% in height) for the US, which might possibly eliminate the transfer module. Of course, there is also the possibility of remaining with a 2 launch architecture, but both are SS. One carries Orion and the other carries SS HLS.

I do not see NASA launching astronauts (from Earth) on SS (sans capsule with LAS) for a long time. I do not see F-9/Dragon ferrying them, nor do I see Dragon going to Luna. I can see NASA giving up SLS for a fully tested SS stack, but I just don't see them giving up Orion for a number of years. Of course, SS does have do show improvement in the coming months.

And I do think SX would go for this if they knew it meant the death of SLS.

GAO report on SLS: https://www.gao.gov/assets/gao-23-105609.pdf

« Last Edit: 09/18/2023 06:21 am by TomH »

Online volker2020

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Re: Starship Expendable Upper Stage?
« Reply #112 on: 09/17/2023 01:10 pm »
On Sept. 7, the GAO released (another) report stating that SLS costs are unsustainable. Of course, they've always said that.

If hot staging proves to be successful, and increases standard SS payload by 10 tons, I wonder how much it would increase payload for a stripped down expendable SS US.
...

I don't think, that you can translate this to SS. The reason why Starship get's a higher payload, is that the ullage gas in the booster does not collapse, allowing it to use the spared fuel to boost starship further.

Since the first stage of SS is expandable, those effects play no role. All you get is a few seconds of gravitational lost.

Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #113 on: 09/17/2023 02:24 pm »

If hot staging proves to be successful, and increases standard SS payload by 10 tons, I wonder how much it would increase payload for a stripped down expendable SS US. If you add in downrange drone ship landing for SH, you increase payload even further. (I acknowledge landing legs issue.)

If you just want to replace SLS while retaining Orion and the rest of the Artemis architecture, then why bother with re-usability at all? Just fly an expendable SH and a custom expendable SS with an Orion stuck on top as you pictured. Since Orion only flies once a year, recovery has low ROI. SLS costs at least $2 B. An expendable SH will be a whole lot cheaper and even the custom SS should be fairly cheap: a wild guess would be the SH is less than $100 M and the custom SS is less than $100 M. SS cost is mostly the amortized development cost.

Any Orion-on-SS will require some customization of the launch tower to add a crew access arm. I assume the plan will be to stack the Orion atop the SS in the Megabay and then stack this mess atop the SH on the OLM using the chopsticks: this may be "interesting".


Online Zed_Noir

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Re: Starship Expendable Upper Stage?
« Reply #114 on: 09/17/2023 10:31 pm »
<snip>
Any Orion-on-SS will require some customization of the launch tower to add a crew access arm. I assume the plan will be to stack the Orion atop the SS in the Megabay and then stack this mess atop the SH on the OLM using the chopsticks: this may be "interesting".

Think it is cheaper and easier to build a mobile service gantry with crew access than to modified the launch and integration tower.

It isn't a customized SS that is needed. Just an austere SS with a few extra ring segments with lifting attachments  above the propellant tanks and an adopter ring segment to the Orion stack. Don't think the chopsticks should have too much difficulties with the SS & Orion integrated stack.

Will also point out that the Orion capsule don't need the current launch escape system design to outrun the SRBs. Something less capable and much less in mass will do.

Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #115 on: 09/18/2023 12:01 am »
<snip>
Any Orion-on-SS will require some customization of the launch tower to add a crew access arm. I assume the plan will be to stack the Orion atop the SS in the Megabay and then stack this mess atop the SH on the OLM using the chopsticks: this may be "interesting".
Think it is cheaper and easier to build a mobile service gantry with crew access than to modified the launch and integration tower.
That would be a really tall gantry. I disagree with you, but I'm just guessing.
Quote
It isn't a customized SS that is needed. Just an austere SS with a few extra ring segments with lifting attachments  above the propellant tanks and an adopter ring segment to the Orion stack. Don't think the chopsticks should have too much difficulties with the SS & Orion integrated stack.
I consider that degree of modification to be "customization". Feel free to pick your own terminology.

Offline Vahe231991

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Re: Starship Expendable Upper Stage?
« Reply #116 on: 09/18/2023 01:01 am »

If hot staging proves to be successful, and increases standard SS payload by 10 tons, I wonder how much it would increase payload for a stripped down expendable SS US. If you add in downrange drone ship landing for SH, you increase payload even further. (I acknowledge landing legs issue.)

If you just want to replace SLS while retaining Orion and the rest of the Artemis architecture, then why bother with re-usability at all? Just fly an expendable SH and a custom expendable SS with an Orion stuck on top as you pictured. Since Orion only flies once a year, recovery has low ROI. SLS costs at least $2 B. An expendable SH will be a whole lot cheaper and even the custom SS should be fairly cheap: a wild guess would be the SH is less than $100 M and the custom SS is less than $100 M. SS cost is mostly the amortized development cost.

Any Orion-on-SS will require some customization of the launch tower to add a crew access arm. I assume the plan will be to stack the Orion atop the SS in the Megabay and then stack this mess atop the SH on the OLM using the chopsticks: this may be "interesting".
The Starship being designed to carry up to 100 people on long-duration, interplanetary flights begs one simple question: is a special access arm would be required for a large number of people to safely board the Starship stage?

Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #117 on: 09/18/2023 01:12 am »

If hot staging proves to be successful, and increases standard SS payload by 10 tons, I wonder how much it would increase payload for a stripped down expendable SS US. If you add in downrange drone ship landing for SH, you increase payload even further. (I acknowledge landing legs issue.)

If you just want to replace SLS while retaining Orion and the rest of the Artemis architecture, then why bother with re-usability at all? Just fly an expendable SH and a custom expendable SS with an Orion stuck on top as you pictured. Since Orion only flies once a year, recovery has low ROI. SLS costs at least $2 B. An expendable SH will be a whole lot cheaper and even the custom SS should be fairly cheap: a wild guess would be the SH is less than $100 M and the custom SS is less than $100 M. SS cost is mostly the amortized development cost.

Any Orion-on-SS will require some customization of the launch tower to add a crew access arm. I assume the plan will be to stack the Orion atop the SS in the Megabay and then stack this mess atop the SH on the OLM using the chopsticks: this may be "interesting".
The Starship being designed to carry up to 100 people on long-duration, interplanetary flights begs one simple question: is a special access arm would be required for a large number of people to safely board the Starship stage?
I see that as a completely separate application. I was just discussing the SLS replacement using and Orion atop a funny SH/SS. I have no idea how SpaceX intends to get 100 people onto an interplanetary SS. I see that as off-topic for the "expendable SS" thread.

Offline jimvela

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Re: Starship Expendable Upper Stage?
« Reply #118 on: 09/18/2023 02:44 am »
If NASA were to slightly delay Artemis 4 and 5, then a SH/SS version could be developed to not just carry the Orion but also use strap-on solid-fuel rocket boosters to allow it to fly past max-q velocity in a much shorter period of time than a basic SH/SS.

That's chatbot nonsense.

Offline Vahe231991

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Re: Starship Expendable Upper Stage?
« Reply #119 on: 09/18/2023 03:54 am »

If hot staging proves to be successful, and increases standard SS payload by 10 tons, I wonder how much it would increase payload for a stripped down expendable SS US. If you add in downrange drone ship landing for SH, you increase payload even further. (I acknowledge landing legs issue.)

Any Orion-on-SS will require some customization of the launch tower to add a crew access arm. I assume the plan will be to stack the Orion atop the SS in the Megabay and then stack this mess atop the SH on the OLM using the chopsticks: this may be "interesting".
How much would it cost for SpaceX to add a crew access arm to the launch tower for the Starship?

Offline TomH

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Re: Starship Expendable Upper Stage?
« Reply #120 on: 09/18/2023 06:27 am »
How much would it cost for SpaceX to add a crew access arm to the launch tower for the Starship?

Elon recently tweeted that the full stack will likely grow by 10%-20% in height. This will require tower modifications. IDK for sure, but I believe this tower is much more easily modified than SLS tower. I think it was designed with simplicity of future modifications in mind.

Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #121 on: 09/18/2023 02:56 pm »
How much would it cost for SpaceX to add a crew access arm to the launch tower for the Starship?

Elon recently tweeted that the full stack will likely grow by 10%-20% in height. This will require tower modifications. IDK for sure, but I believe this tower is much more easily modified than SLS tower. I think it was designed with simplicity of future modifications in mind.
My guess: stretching an existing tower would be fairly expensive. The massive cap would need to be removed, and new section added, and the cap replaced. Changing the design prior to building a new tower would add very little cost. However, it is not clear that  a 10% stack stretch would need a taller tower. The lift points on the stretched SS would need to be the same distance from the SS base as they are now, which would put them farther from the nose. We have already seen how they handle an increase in SH height. All of this is actually relevant to this "expendable SS" thread. An expendable SS can be heavier than a non-expendable SS, and thus could might need to be taller to handle some large exotic payload.

A crew access arm for an Orion would be conceptually similar to the existing SS QD arm. I doubt it would be much if any heavier.

Offline Twark_Main

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Re: Starship Expendable Upper Stage?
« Reply #122 on: 09/25/2023 03:45 am »
If they can support 150+ tonnes at 4(?) g axially (FH payload & fuel at MECO), but can't support their own empty mass of 4 tonnes at 2 g laterally even with the aid of "highly specialized structures"... that would be quite a result for a horizontally-integrated LV

It's not that the Falcon upper stage can't support 2 g laterally in general. The question is more about where specifically you want to transfer 2 g laterally into the vehicle.

Unless you want to fill the entire payload bay with expanding foam and push on the whole outside surface of S2 evenly (and I'd love to have eight pages of discussion on that btw), then you'll need to figure out a set of hard points on S2 you'll use to attach it to Starship. All the complexity comes in how that structural adapter is designed and built, how it gets attached to S2 in orbit, and what happens in case of various off-nominal contingencies.
« Last Edit: 09/25/2023 03:51 am by Twark_Main »
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Offline Paul451

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Re: Starship Expendable Upper Stage?
« Reply #123 on: 10/14/2023 08:10 am »
If they can support 150+ tonnes at 4(?) g axially (FH payload & fuel at MECO), but can't support their own empty mass of 4 tonnes at 2 g laterally even with the aid of "highly specialized structures"... that would be quite a result for a horizontally-integrated LV

Examples of the required structures below.

First image in the internal support for the bottom of the upper stage and its engine, on the lower stage. Second image shows the external supports required.

Offline BitterJim

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Re: Starship Expendable Upper Stage?
« Reply #124 on: 11/19/2023 05:20 pm »
It will be interesting to see how SpaceX intend to land both vehicles to make the system fully reusable as stated.  The Super Heavy goes higher and faster than the Falcon 9 first stage but they haven't tested such a landing.  As far as the second stage is concerned assuming it will have the capability to do a controlled landing from LEO escape velocity is a different story.  Currently, a ballistic re-entry is the only possibility.

(Bold mine)

Isn't the opposite true? I thought Starship did more of the work than the Falcon 9 second stage, allowing the booster to stage lower/slower/not as far downrange

Offline Brigantine

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Re: Starship Expendable Upper Stage?
« Reply #125 on: 11/20/2023 11:04 am »
This telemetry comparison (from IFT-2 Updates thread) agrees with BitterJim (mostly).

SH burns longer, but F9 pulls more G's after Max Q and so gets more done in less time.

Eyeballing:
At staging, F9 velocity is ~1800 m/s (T~⁺140), SS is ~1600 m/s (T~⁺160)
However, F9 altitude is ~550 hm (i.e. 55 km) at staging, and although SS altitude is lower at a given time, it increases to ~600 hm (i.e. 60 km) in the extra time it has before MECO.

I don't know which F9 mission that was, YMMV depending on whether F9 is doing LEO or GTO etc.
« Last Edit: 11/20/2023 11:07 am by Brigantine »

Offline BringBackSuperHeavies!

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Re: Starship Expendable Upper Stage?
« Reply #126 on: 12/28/2023 09:18 pm »
You might need to expend the starship for higher delta-v, instead you could just fill the spacecraft inside with a big fuel tank and let that do some of the work.

Offline TomH

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Re: Starship Expendable Upper Stage?
« Reply #127 on: 12/28/2023 11:30 pm »
You might need to expend the starship for higher delta-v, instead you could just fill the spacecraft inside with a big fuel tank and let that do some of the work.

No reason to do that. The LV is designed such that they refill the propellant tanks from a fuel depot.

Offline JaimeZX

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Re: Starship Expendable Upper Stage?
« Reply #128 on: 12/29/2023 01:28 am »
Here's a fun one I don't recall seeing before, but may well have overlooked:

Could SH SSTO with a simple nose cone for low-altitude aerodynamics?

If so, with orbital refueling you could stack a payload after the fact and REALLY expend a booster.

Online DanClemmensen

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Re: Starship Expendable Upper Stage?
« Reply #129 on: 12/29/2023 01:38 am »
Here's a fun one I don't recall seeing before, but may well have overlooked:

Could SH SSTO with a simple nose cone for low-altitude aerodynamics?

If so, with orbital refueling you could stack a payload after the fact and REALLY expend a booster.
You could also go completely crazy and stack an SS on your SH after the fact, but why do any of this? We need SH (33 engines) to get from Earth to space. After you are in space, it's mostly about the total energy (more or less, the total propellant mass), not about the number of engines. just send your payload (presumably in an SS), together with as many full depots as you wish, to whatever destination you wish.

 

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