Starship Expendable Upper Stage?

[Asteroza]

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

[su27k]

Some of us saw this coming from a mile away: Launching Orion on SH with Disposable S2

[InterestedEngineer]

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.

[steveleach]

It is probably just marketing, tbh.  Put the biggest payload number they can reasonably justify on the spec sheet.

[TomH]

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.

[Kazioo]

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.

[edzieba]

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.

[JayWee]

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.

[mikelepage]

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 don’t spend decades in transit would be nice too.

[RoboGoofers]

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.

[wannamoonbase]

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.

[DanClemmensen]

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.

[edzieba]

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.

[DanClemmensen]

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.

[wannamoonbase]

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 doesn’t 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, it’s significant. 

The tankage portion will be volume production and possibly highly automated. 

[Robotbeat]

Plus you can put like on Raptor on it and get crazy performance to like any orbit, with a discardable fairing.

[InterestedEngineer]

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 don’t 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.

[volker2020]

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.   

[whitelancer64]

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.

[DanClemmensen]

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.