Author Topic: Starship Expendable Upper Stage?  (Read 44755 times)

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.

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« Last Edit: 02/04/2023 06:26 am by whitelancer64 »
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Offline 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.

Online 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. 

Online 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.

Online 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 »

Offline 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.

Offline 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 »

Offline 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.
"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

 

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