Author Topic: Starship Expendable Upper Stage?  (Read 44695 times)

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
"There are lies, damned lies, and launch schedules." - Larry J

Online TheRadicalModerate

  • Senior Member
  • *****
  • Posts: 4466
  • Tampa, FL
  • Liked: 3344
  • Likes Given: 641
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.

Online Oersted

  • Member
  • Senior Member
  • *****
  • Posts: 2903
  • Liked: 4110
  • Likes Given: 2779
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

  • Senior Member
  • *****
  • Posts: 2846
  • Woodstock
  • Liked: 1700
  • Likes Given: 6866
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

  • Senior Member
  • *****
  • Posts: 2333
  • Seattle
  • Liked: 1816
  • Likes Given: 2962
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

  • Senior Member
  • *****
  • Posts: 2333
  • Seattle
  • Liked: 1816
  • Likes Given: 2962
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.

Online TomH

  • Senior Member
  • *****
  • Posts: 2940
  • Vancouver, WA
  • Liked: 1868
  • Likes Given: 911
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
"There are lies, damned lies, and launch schedules." - Larry J

Online TomH

  • Senior Member
  • *****
  • Posts: 2940
  • Vancouver, WA
  • Liked: 1868
  • Likes Given: 911
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 »

Online wannamoonbase

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 5432
  • Denver, CO
    • U.S. Metric Association
  • Liked: 3121
  • Likes Given: 3879
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.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5 (Welp a little early on IFT-4, but still have a shot at 5)

Online TheRadicalModerate

  • Senior Member
  • *****
  • Posts: 4466
  • Tampa, FL
  • Liked: 3344
  • Likes Given: 641
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 »
"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 InterestedEngineer

  • Senior Member
  • *****
  • Posts: 2333
  • Seattle
  • Liked: 1816
  • Likes Given: 2962
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

  • Senior Member
  • *****
  • Posts: 2333
  • Seattle
  • Liked: 1816
  • Likes Given: 2962
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

  • Full Member
  • ****
  • Posts: 1000
  • Liked: 998
  • Likes Given: 1854
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

  • Space Nut
  • Senior Member
  • *****
  • Posts: 2242
  • Mars in my lifetime!
  • DeWitt, MI
  • Liked: 300
  • Likes Given: 487
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)?

Offline M.E.T.

  • Senior Member
  • *****
  • Posts: 2318
  • Liked: 2921
  • Likes Given: 508
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.

Online TomH

  • Senior Member
  • *****
  • Posts: 2940
  • Vancouver, WA
  • Liked: 1868
  • Likes Given: 911
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

  • Full Member
  • ****
  • Posts: 1474
  • Liked: 969
  • Likes Given: 599
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

  • Member
  • Posts: 74
  • Backwoods, Idaho
  • Liked: 131
  • Likes Given: 163
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
Space is hard. Hard is fun.

 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1