Starship-Based HLS Iterations and Design Considerations

[clongton]

 SpaceX has committed to the Starship HLS form for both Lunar and Martian landing. For the foreseeable future, Starship HLS will be the SpaceX lander of record. The purpose of this thread is to discuss ongoing design changes, proposed design changes, potential design changes and design iterations as the HLS goes forward and matures. This thread is also open to suggesting, and discussing, any and all suggested design changes that NSF members may have, but must retain the basic Starship form of record. Any suggested design changes that deviate from this form, such as a completely different style lander design, are off topic, unless it is a design that SpaceX itself has suggested or committed to. Discussion of the lander designs from any other company, excepting context-only points, are also off topic. This thread is for Starship-based HLS design discussion only. Feel free to suggest any design changes you like, so long as it is Starship-based. There are several NSF members who have thoughts in this regard but until now there was nowhere to actually present them for discussion. This will be the home for such suggestions and discussions.

[clongton]

Ditch the Ogive Nose Cone. Replace it with 6 barrels and a 2:1 ellipsoid dome.
A 2:1 Ellipsoidal Dome is a better fit for a Purpose-Built Lunar Starship HLS

For a lunar-only Starship HLS that never reenters an atmosphere, the ogive nose is carrying design baggage it no longer needs. Replacing it with a 2:1 ellipsoidal forward dome converts the forward section into a structurally efficient, fully usable pressure volume optimized for launch loads and habitation rather than hypersonic lift. A 2:1 ellipsoid is a proven launch-vehicle geometry: it offers excellent pressure efficiency while handling combined internal pressure and axial compression better than a pure hemisphere, and it ties cleanly into the 9-meter barrel with a robust knuckle ring. The modest ascent drag penalty for its initial launch from Starbase or KSC, relative to the ogive, is operationally negligible for an HLS that already relies on on-orbit refueling, while the structural simplification (no flaps, no TPS, no lifting-body constraints) reduces mass, mechanisms, and certification complexity.

From a crewed-systems standpoint, the geometry is even more compelling. The flatter crown of a 2:1 ellipsoid dramatically improves usable headroom and deck integration compared to a spherical cap or tapered nose, enabling a clean multi-deck layout, a structurally efficient axial docking port at the apex, and straightforward load paths into the primary barrel. Instead of wasting volume in a narrowing ogive, the vehicle gains practical habitable space, better airlock placement options, and more rational mass distribution for lunar operations. In short, a 2:1 ellipsoidal dome turns HLS into what it actually is: a deep-space, pressure-vessel-centric lander optimized for launch and lunar service—not atmospheric reentry.

From a manufacturing capability perspective, SpaceX’s existing stainless-steel dome fabrication facilities are capable of building a 2:1 ellipsoidal forward dome for an HLS variant, but there are important qualification and tooling distinctions between current tank dome production and what an HLS habitation-dome would require.

SpaceX already routinely forms large stainless-steel domes and dish components for Starship’s cryogenic tanks and Super Heavy cupolas using incremental forming, press brakes, and robotically guided welders. These processes scale well with diameter and curvature, and the metallurgy (300-series stainless) doesn’t change just because you flatten the curvature into a 2:1 ellipsoid instead of a near-hemisphere. In other words, the basic fabrication technology (forming, trimming, fit-up, and automated TIG/GMAW welding of large curved panels) is the same whether you’re making a tank cap or a forward pressurized shell.

In short, the physical manufacturing plant and welding automation SpaceX uses for Starship tanks is already capable of producing a 2:1 ellipsoidal dome of the same diameter with modest adaptation of tooling and programming. What’s not already in place yet, because it isn’t needed for the current vehicle, is the qualification framework and habitation-level integration tooling that would make that dome a flight-certifiable pressurized module.

So the manufacturing capability already exists and is in use, while programmatic qualification and tooling setup would be the new work. SpaceX has already demonstrated its ability to efficiently pivot in this direction several times. The result, should SpaceX implement this kind of change, ESPECIALLY now that the company has shifted it focus for the foreseeable future to the moon in lieu of Mars, would be a human spacecraft that is structurally and dynamically better suited to the space and lunar environment in which it needs to continually operate.

The 6-barrel + dome nose design maximizes pressurized volume while reducing structural mass, all within the current Starship HLS ogive length.
This configuration dramatically increases usable volume, reduces dry mass, and stays within ogive length limits, making it the most effective forward nose design for lunar HLS missions.

Metric	Current HLS Nose	6-Barrel + Dome
Length (m)	13–15	~13.95
Pressurized Volume (m³)	400–5001	~782
Dry Mass (t)	20–25	10.9–16.3
Volume/Length Efficiency	1	1.9–2×

1. Especially toward the top much of this volume is wasted and completely unusable, while the 2:1 ellipsoid maximizes every cubic meter of space.

[sdsds]

The modest ascent drag penalty for its initial launch from Starbase or KSC, relative to the ogive, is operationally negligible

Is drag the only consideration during ascent? What about structural loads? Aerodynamic stability? And finally esthetics: it wouldn't look like a cool rocket! ;-)

[punder]

The modest ascent drag penalty for its initial launch from Starbase or KSC, relative to the ogive, is operationally negligible

Is drag the only consideration during ascent? What about structural loads? Aerodynamic stability? And finally esthetics: it wouldn't look like a cool rocket! ;-)

Thor!

[sanman]

Hey, thanks for this nifty idea!

Give us Eagle Transporter, Elon -- add trusses!

The modest ascent drag penalty for its initial launch from Starbase or KSC, relative to the ogive, is operationally negligible

Is drag the only consideration during ascent? What about structural loads? Aerodynamic stability? And finally esthetics: it wouldn't look like a cool rocket! ;-)

But ellipsoid shape could look very cool & stylish -- anybody care to do a quick sketch and post it in here, just for visualization & discussion purposes?

I was even imagining an ellipsoid body could be quite cool looking and useful for non-HLS Starship, because it could provide even more drag during skydiver bellyflop descent. Ellipsoid should be stronger than circular under asymmetric load.

But regarding Lunar HLS, it then provides that broader footprint when lying on its side on the lunar surface, unlike the cylindrical fuselage that can roll.

[catdlr]

The ellipsoid shape that's being discussed is only as a replacement for a ship's pointed top, kinda like a bullet-point pen?

[clongton]

The ellipsoid shape that's being discussed is only as a replacement for a ship's pointed top, kinda like a bullet-point pen?

Yes. Six additional barrels plus the ellipsoid dome are approximately the same length as, and replaces, the current ogive shaped nosecone. Everything below the nosecone remains unchanged, so this modified HLS is ~the same total length as the HLS of record. The current nosecone is the best shape from the aerodynamics pov, launch, and especially for reentry EDL. The downside of the nosecone is a tremendous waste of volume. So much is completely unusable as you approach the top. This isn't a problem for a vehicle that needs to reenter the atmosphere; it's the correct trade. But the HLS will never do that. So why restrict yourself just to retain a capability that will never be used? Instead, maximize the volume and make it ALL available for use. This suggested configuration does exactly that. PLUS, the mass is actually less! That translates directly into an additional ~10 tonnes of payload with no penalty, in available space you can actually use! This additional payload capacity itself more than justifies this configuration change.

[darkenfast]

A few years ago, Musk said that the Tanker version of Starship could look a little odd (I'm paraphrasing from dim memory). Maybe they were thinking about this kind of nose for the tankers. Could that shape handle reentry?

[DanClemmensen]

The ellipsoid shape that's being discussed is only as a replacement for a ship's pointed top, kinda like a bullet-point pen?

So why restrict yourself just to retain a capability that will never be used?

This is an excellent question in retrospect. It's useful to remember the answer. In 2021, SpaceX' HLS bid was $2.9 B, less than half the cost of the next-lowest bidder. The bid was low because SpaceX  was just charging for the incremental design and build costs of the HLS itself, based on the Starship that they were already designing. The result far exceeded the requirements in every way. The contract was for a total of two flight articles: Demo and Artemis III. All that extra volume was completely unused. Changing the ogive would cause an increase in the cost of the design and fabrication of the two HLS vehicles.

That was 2021, but now it's 2026. I think you are right, and this relatively minor change is a big improvement. You get some combination of increased payload mass, increased cargo volume, and increased crew size. Most importantly, it's useful beyond just the first two vehicles, so the design cost is amortized across many vehicles.

Minor quibble: we think the current design has its IDSS port on the nose. The IDSS port must stick out from the body of the vehicle to allow for docking with Gateway and Orion and possibly other vehicles such as Crew Dragon. The ogive is pointy enough for this but the ellipsoid is probably not. I think it is quite simple to fix this with a short cylinder at the top of the ellipsoid.

[sanman]

The ellipsoid shape that's being discussed is only as a replacement for a ship's pointed top, kinda like a bullet-point pen?

Yeah, I'd got that - I guess I expanded beyond that scope while pondering it.

Sphere is best in static space vacuum, where there are no loads from other things like gravity or acceleration.

And come to think of it - why can't we use more truss structures in spacecraft?
They're only seen as a liability during atmospheric ascent, which should be a one-time thing for HLS.
They could be covered up during ascent by fascia-panels which would be discarded after clearing the atmosphere.

To facilitate hot-staging, lattices are already used in interstages, while not overly compromising aerodynamics.

So use lightweight truss structures covered by fascia panels for lower drag during ascent, then discard those panels afterwards as parasitic mass.
Then once you're in space -- well, you have trusses, which offer more structural strength relative to mass, even if they're not able to enclose pressurized contents (although even a bladder might work find inside a mesh)
You might be able to manage just fine around cis-lunar space without the need for full-blown metal skin.

(I apologize if it seems like I'm trying to let aesthetics or form dictate function, when I was just trying to argue for allowing further possible deviations from the classical Starship design)

Starship was designed primarily with Mars in mind, and with the Moon being the main priority for the foreseeable future, then it seems the design priorities need to be flipped towards catering to the lunar environment, so that these become predominant in their thinking.

[sdsds]

It might be useful to quantify the increase in drag forces at max-q. Is it correct to think drag forces produce loads carried from the nose into the top ring of the structure below it? Is there an easy way to verify the structure can handle those loads?

[clongton]

But ellipsoid shape could look very cool & stylish -- anybody care to do a quick sketch and post it in here, just for visualization & discussion purposes?

Not pretty, but very, VERY efficient. Perfect for this application.
AND ~10 tonnes lighter! The image is deceiving, mass-wise, but the Ogive nosecone has a lot of additional interior structure to strengthen it specifically for reentry, which is not needed for a vehicle that never reenters. Additionally, the nosecone material is thicker than the barrels. The tapered ogive experiences more complex stress patterns during launch (axial compression, bending, and vibration) than a straight cylinder. Even without aerodynamic loads for HLS, structural conservatism usually adds thickness. The cylindrical barrel sections are simpler because they carry mostly hoop stress from pressurization. For the same stainless steel grade, you can often reduce wall thickness by 10–20 % versus the nosecone and still meet structural requirements.

I drew the quick sketch for you in Sketchup, but to make it prettier for discussion, I fed the dimensions into ChatGPT and asked it to create an image of the difference, side-by-side. The ChatGPT image dimensions themselves aren't correct, but it serves the purpose. I hope this helps.

[catdlr]

But ellipsoid shape could look very cool & stylish -- anybody care to do a quick sketch and post it in here, just for visualization & discussion purposes?

Not pretty, but very, VERY efficient. Perfect for this application.

Some variants of THOR had that design in mind

[catdlr]

Here is a THOR Blunt nosecone launch ...oops...NOT

Space Intelligence
@SpaceIntel101
·
6h
Absolutely chilling images of Operation Bluegill Prime.  This is not just a rocket exploding. It is the explosion of the Thor DSV-2E on July 26, 1962, over Johnston Island. Its particularity? Under the nose cone was a 400-kiloton W50 nuclear warhead.

https://twitter.com/SpaceIntel101/status/2022657014292181272