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Elon estimated a few years ago the dry mass of the Starship as expendable would be 40 tons back when it was still expected to use carbon fiber:

Elon Musk @ElonMusk
Probably no fairing either & just 3 Raptor Vacuum engines. Mass ratio of ~30 (1200 tons full, 40 tons empty) with Isp of 380. Then drop a few dozen modified Starlink satellites from empty engine bays with ~1600 Isp, MR 2. Spread out, see what’s there. Not impossible.
https://x.com/elonmusk/status/1111798912141017089?s=61

After the switch to stainless-steel, Elon said the specialty steel alloy used was actually stronger than carbon fiber so presumably would have less dry mass.

An expendable mass ratio of 30 to 1 would be among the best in history. But the Falcon 9 upper stage has a mass ratio of ca. 28 to 1:

______________________________
Type    Falcon 9 FT Stage 2
Length    12.6m (Separated Length)
Diameter    3.66 m
Inert Mass    4,000 kg (est.)
Propellant Mass    107,500 kg (est.)
Fuel    Rocket Propellant 1
Oxidizer    Liquid Oxygen
LOX Mass    75,200 kg (est.)
RP-1 Mass    32,300 kg (est.)
LOX Tank    Monocoque
RP-1 Tank    Monocoque
Material    Aluminum-Lithium
____________________________

Then, it is known mass ratio improves as you increase the size of stage, Starship being ca. 10 times larger, plus the fact stainless-steel is stronger for weight than aluminum-lithium, can well result in the expendable Starship being ca. 30 to 1 in mass ratio.

The dry mass of the Starship is now estimated as ca. 160+ tons, 4 times what it needs to be as expendable. That higher dry mass makes the ballistic coefficient 4 times greater, i.e., worse. That increases the temperatures reached during reentry for the current Starship.

The X-33 metallic shingle TPS used high temperature Inconel so had better temperature resistance than just iron. It was experimentally verified it could withstand 1,000° C.

However, for the expendable calculation case you have to include the mass of the fairing. The fairing is estimated to weigh 20 tons. So for calculating the ballistic coefficient and reentry temperature for the expendable case you have to use 60 tons as the dry mass.

Bob Clark

The plan appears to use multiple Blue Moon Mk1 landers launched on multiple New Glenns, though not using refueling. It’s likely though it can be launched on a single New Glenn but in expendable format. The reason is a 45 ton payload capability as partially reusable likely means a 60+ ton capability as an expendable. Based on the 21 ton size of the Blue Moon Mk1 with the capability to do land 3 tons on the Moon as a one-way lander, its propellant/dry mass ratio is likely 18 tons/3 tons. Consider then the Delta IV Heavy’s upper stage, the same stage used as the interim upper stage on the SLS Block 1, could serve as the Earth departure stage for this lander. The spec’s on the DIVH upper stage are:

Second stage – DCSS
Height  13.7 m (45 ft)
Empty mass   3,490 kg (7,690 lb)
Gross mass  30,710 kg (67,700 lb)
Propellant mass  27,220 kg (60,010 lb)
Powered by  1×RL10-B-2
Maximum thrust  110 kN (25,000 lbf)
Specific impulse. 465.5 s (4.565 km/s)
Burn time  1,125 seconds
Propellant  LH2 / LOX
https://en.wikipedia.org/wiki/Delta_IV_ … pabilities

Then this can make the ca. 3,000 m/s delta-v needed for translunar injection(TLI):

465.5*9.81Ln(1+27.22/(3.49 + 25)) =3,062.362

Blue Origin could use this stage or, more likely, derive a comparable one from two copies of the Blue Moon Mk1.

  Bob Clark

There will be a special session by NASA’s advanced propulsion section, JANUS, at next week’s AIAA SciTech conference, https://scitech.aiaa.org/

Interestingly all of the advanced propulsion methods being researched now, i.e., anything other than chemical propulsion, have applications to accomplishing nuclear fusion. Then rather than these advanced propulsion methods having just scientific interest to NASA, they have practical importance to achieving the imminent trillion-dollar nuclear fusion economy.

Then they should attract funding from many different commercial investment sectors, not just from NASA. This will serve to advance their development and therefore the development of fusion.

Bob Clark

Blue Origin is rapidly advancing in its space capabilities. It plans in first quarter 2026 to test land a cargo lunar lander in the Blue Moon Mk1, capable of transporting 3 tons payload to the lunar surface. Because of its large cargo capacity, Blue Origin is investigating it as a crewed lander to do Artemis III.

If it succeeds at this test landing in 2026 it will be a watershed moment. Not only is the landing important, but the lander uses hydrolox. In order for this to work the Mk1 will have to employ low boiloff tech. Others have speculated on accomplishing this, notably ULA with their proposed ACES hydrolox upper stage. Blue Origin having a stage with this tech would open up cryogenic stages being used as propellant depots and even for longer missions such as to Mars.

Beyond that, Blue Origin has announced a larger version of the New Glenn capable of 70 tons to LEO. I’m trying to find out if this is with partial reusability, i.e., recovering the booster. If it is, then its expendable payload would be ca. 100 tons. This is important because this is the range commonly thought needed for a “Moon rocket”, one capable of single launch manned Moon missions, a la the Saturn V. Eric Berger has written the upgraded new Glenn might cost only ca. $200 million and be ready by 2027:

Blue Origin revealed some massively cool plans for its New Glenn rocket
“The iterative design from our current 7×2 vehicle means we can build this rocket quickly.”
ERIC BERGER – NOV 20, 2025 1:06

https://arstechnica.com/space/2025/11/b … nn-rocket/

If Blue succeeds at this, it again would be a game changer. This is scarcely more than what we spend just sending astronauts to the ISS. If manned Moon missions could be launched at costs this low it would finally open up the Moon to sustainable habitation and development.

  Bob Clark

NASA and the military brass are becoming increasingly disenchanted with the SpaceX progress on the Starship HLS lunar lander. Eric Berger in an article discussed some possible alternative options being offered that NASA could use to beat or match China in getting back to the Moon. The one deemed most likely would use Blue Origin’s Blue Moon Mk1 cargo lander instead as a manned lander:

How America fell behind China in the lunar space race—and how it can catch back up.
Thanks to some recent reporting, we've found a potential solution to the Artemis blues.
ERIC BERGER – OCT 2, 2025 7:30 AM |
“Here comes the important part. Ars can now report, based on government sources, that Blue Origin has begun preliminary work on a modified version of the Mark 1 lander—leveraging learnings from Mark 2 crew development—that could be part of an architecture to land humans on the Moon this decade. NASA has not formally requested Blue Origin to work on this technology, but according to a space agency official, the company recognizes the urgency of the need.”
https://arstechnica.com/space/2025/10/h … h-back-up/

This plan would not need any refueling launches, unlike the larger Blue Moon Mk2 manned lander. I’m puzzled though by the statement in the article it would use “multiple” Mk1’s. Presumably that would take multiple New Glenn launches?

I had suggested it might be doable using a single Blue Moon Mk1 launched on a single New Glenn. This though would require New Glenn reaching its intended payload capacity of 45 tons reusable, 60+ tons expendable:

Could Blue Origin develop a lander for Artemis III?
https://www.reddit.com/r/BlueOrigin/s/DjyRJUVC2E

  Bob Clark

The total number launches of Starship for the lunar mission with all the refuelings has been cited as from 10 to 20. But since SuperHeavy/Starship is twice the size of the Saturn V this is the equivalent to 20 to 40 launches of the Saturn V for a single Moon mission.

  Bob Clark

Former NASA administrator Jim Bridenstine also saying U.S. unlikely to win race back to the Moon against China because of the too complex multi-refueling approach to a lander:

Ex-NASA chief revealed the Real Problem with SpaceX Starship to get back to the Moon while China
https://youtu.be/eA1uS4SgAwU

  Bob Clark

It would be like NASA spending billions on the Saturn V to take man to the Moon. And the Saturn V they came up with had less payload than the Gemini-Titan that could only get the Gemini capsule to LEO.

  Bob Clark

SpaceX spent billions developing Starship version V1 getting a rocket 10 times the size of the Falcon 9 and it wound up having less payload than the Falcon 9.

   Bob Clark

More uncertainty on the viability of the Starship:

AUGUST 22, 2025
Can SpaceX Solve Its ‘Exploding Starships’ Problem?
After a string of fiery failures, SpaceX’s biggest rocket faces another test flight with sky-high stakes for U.S. space ambitions
BY ADAM ROGERS EDITED BY LEE BILLINGS
https://www.scientificamerican.com/arti … exploding/

SpaceX schedules 10th test flight for Starship, details recent setbacks
August 16, 2025 Will Robinson-Smith
https://spaceflightnow.com/2025/08/16/s … -setbacks/

  Bob Clark

Robert Zubrin again gives his argument why Starship should have a smaller third stage to do the actual landing on Mars:

Crewed Mars missions will require a new ascent vehicle.
by Robert Zubrin
August 12, 2025
https://spacenews.com/crewed-mars-missi … nt-vehicle

  Bob Clark

A majorly important advantage of the new Invictus reboot of Skylon is it will use an existing jet-fuel turbojet rather than a hydrogen-fueled one that Skylon had been supposing. A hydrogen-fueled turbojet engine still does not exist and in fact the leading jet engine manufacturer studying them Rolls Royce has stated one won’t be fielded for another 20 years.

On the other hand, having the engine and precooler actually in place and undergoing testing means you can vary the different parameters of both and confirm, or disconfirm, its estimated performance values.

By the way an interesting question occurred to me looking at those performance curves: can precooling break the Mach 6 ramjet barrier?

Prior analysis of ramjet propulsion had led to the conclusion they can only be effective up to the range of ca. Mach 5.5 to Mach 6.

After that, you need scramjets to get positive net thrust with airbreathers. The problem is nobody has been able to get scramjets to provide positive net thrust for longer than just a few seconds.

But if you look at the graphs of the T/W ratio and Isp of the precooled Sabre engine compared to that of ramjets approaching Mach 6, you notice the Isp for the ramjets is rapidly trending downwards to that of just rockets, while the Sabre’s Isp is gradually leveling off. Does this mean the precooled Sabre could still get effective thrust past Mach 6?

The attached image here show specs for the original Sabre that used a high level of cryogenic precooling, while the image in my previous post was for a later version of Sabre with lower precooling. The first version with the high precooling has higher thrust but lowered Isp. But what’s notable is the Sabre’s Isp graph seems to be leveling off approaching Mach 6, while the ramjet’s Isp graph is rapidly dropping off.

So there arises the question: Is there a combination of precooling level at a prescribed outside air pressure level that would allow the Sabre to maintain positive net thrust even past Mach 6?

  Bob Clark