New Mars Forums

Thanks for the response. Instead of the exhaust air coming into contact with the ambient air, it could be sent into a heat exchanger to cool ambient air. Doing it this way would allow you to use different gases to be heated, not just air depending on efficiency. The working fluid would then be recycled.

  Bob Clark

I agree with you the price SpaceX charges to the customer, such as NASA, will likely be more than what its build cost is.

However, I’m focusing on three scenarios. Firstly, if you’ll recall Elon once emphasized to the SpaceX staff the importance of getting the Starship up and running because of its importance to maintaining the profitability of the Starlink system. The calculations I showed was it would be beneficial to use the Starship to launch the Starlinks even as expendable because the cost to SpaceX would be less than using the Falcon 9.

Secondly, Elon wants Starship to make his own flights to Mars, not NASA’s. In that case, SpaceX would be using their own build cost in their cost estimations. A flight to Mars at ca. $90 million per flight is absolutely stunning, when you consider that NASA was once considering a total cost of ca. $500 billion for a Mars program.

Thirdly, NASA used to be the only game in town in regards to flights to the Moon. But quite recently Elon has spoken of transitioning to a focus of lunar development first and in a quite rapid time frame, before Mars. Note this is purely for commercial reasons, not NASA’s. This means when SpaceX is making such flights their costs estimations will be their own build cost metrics. Then a $90 million flight to the Moon again is stunning when you consider that all of Apollo, Constellation, and now Artemis always costed several billions per flight.

Note, also SpaceX at such low internal cost could make multiple, operational landed flights to the Moon for their Moon development goals, even at once a month if they chose. This would have the added benefit of proving its reliability to be used for manned flights. I argue to further their Moon development goals SpaceX itself would want to do manned flights. But at an internal cost to SpaceX at ca. $90 billion per flight any reasonable mark up for a NASA mission would be considered a bargain to NASA when it was expecting to pay $4 billion per flight.

And above all those considerations keep in mind this is a capability that SpaceX can do now.
 
   Bob Clark

SpaceX has given a launch price for the Starship:

SpaceX Scores $90M Starship Contract to Launch Starlab Space Station.
https://www.basenor.com/blogs/news/spac … ce-station

Presumably this would be for the reusable version but that is still a stunning price for a Saturn V-class launcher. Remember, for all of Apollo, Constellation, and now SLS the cost of a launch was billions per launch.

Still, there are advantages to launching the expendable version. SpaceX has given the expendable payload of the Starship V3 as 300 tons. Industry experts estimated and Elon has confirmed a build cost, i.e., the cost to SpaceX, of ca. $90 million. This is a per kg cost of ca. $300/kg, nearly a tenth of the Falcon 9 cost.

This is why I disagree with the SpaceX decision not to field the Starship until it achieves full reusability. A large portion of the SpaceX revenue comes from Starlink. SpaceX could launch ten times the number of Starlinks at one-tenth the per kg cost using the Starship even as expendable now. Note that all the while SpaceX would still be investigating progressing to reusability just as it did with the Falcon 9. 

Furthermore, 300 tons is about 3 times the payload of the Saturn V. SpaceX could launch a lunar mission in a single flight now by using the expendable Starship, no multiple refuelings, no problematical TPS required. With so many of the expendable Starship launches taking place, NASA would also get confidence in its reliability as a manned launcher to the Moon. 

And not just the Moon. Robert Zubrin’s Mars Direct proposal could mount a manned Mars mission using two launches of a Saturn V-class rocket. Then the expendable Starship with its 300 ton capacity could do a manned Mars mission in a single launch now.

Here’s another way of thinking about it: the expendable Starship is so low cost at such high payload capacity, we could launch manned missions to both the Moon and Mars for less cost than we are now spending just to get to the ISS(!) And we can launch such manned missions both to the Moon and to Mars every month. And they would be so low cost we could send multiple unmanned full mission landed test flights before the manned flights. And this is a capability we have now.

  Bob Clark

STARSHIP COST ANALYSIS.

Illustration Mars Direct.

I’ll take the increased broadside ballistic coefficient even if it takes a protective engine shroud needing to be extended around the engines during reentry.

  Bob Clark

Thanks for responding. But I was asking in regards to my thesis the reason SpaceX is having such difficulty getting effective Starship TPS for reentry from LEO is because the Starship is so grossly overweight. Elon once estimated an expendable dry mass of Starship as only 40 tons. But with all the multiple systems added on to achieve reusability the dry mass ballooned to over 160 tons, greatly increasing the ballistic coefficient. Ironically, SpaceX’s attempt to make Starship reusable made it impossible for it to do so.

The X-33 metallic shingle TPS withstands 1,000° C temperature. I’m suggesting going back to the 40 ton dry mass of the Starship will make it so X-33’s TPS is sufficient for Starship LEO reentry.

  Bob Clark

GW, can you calculate the peak reentry temperature for a Starship at dimensions 50 meter long and 9 meter wide at the current ca. 160+ ton dry mass and at the previous estimate of Elon Musk of the expendable version only 40 ton dry mass?
I have a theory that the reason SpaceX has been unable to find effective TPS for the current Starship is because it is too oveweight at ca. 160+ tons. If it used the previous expendable dry mass of 40 tons then the X-33 metallic shingles that could withstand 1,000C could work.

  Bob Clark

A ziggurat?

  Bob Clark

My irritation at the approach SpaceX is taking to the Starship lunar missions is that it stems not from any engineering reasons. In fact, it doesn't even stem from any logical reason. It stems solely from the Elon's idea that the Starship must be the Be-All-End-All for ALL of spaceflight:

Elon Musk @elonmusk
Once Starship is flying frequently with real payloads next year, then SpaceX will probably deliver >95% of total Earth payload to orbit, despite others, especially China, continuing to grow.

In 2027, maybe as high as 98%.
https://x.com/elonmusk/status/1969988976259092692

Thus, the starship must not admit of any added stage atop it, nor even any in its huge payload bay. And it itself must be the stage that lands at any destination such as the Moon or Mars.

So, in order to maintain this, there arises the idea to do multiple refuelings to allow the entire Starship to be delivered to any of the mission destinations.

But using staging of progressively smaller stages to reach far destinations has been a basic principle of spaceflight since the principle was first recognized by Tsiolkovsky over a hundred years ago. Then Elon is ignoring basic principles of spaceflight engineering in following his approach.

  Apollo using staging used the 3,000 ton gross mass Saturn V to deliver a tiny, in relative terms, 15 ton gross mass lunar lander, a factor of 1/200th the launch vehicle size, in a single launch. SpaceX in contrast wants to use a 6,000 ton gross mass vehicle to deliver a 2,000 ton gross mass lander, i.e., one that's 1/3rd the size of the entire launch vehicle, necessitating multiple launches and multiple refuelings to do it.

Superheavy/Starship is twice the size of the Saturn V and should have twice the capability of Saturn V in a single launch just by using staging. Instead it is multiple times worse needing the equivalent of 20 to 40 Saturn V launches to accomplish the same thing Saturn V did with just one.

  Bob Clark

U.S. Is Losing Race to Return to Moon, Critics Say, Pointing at SpaceX.

The company’s Starship rocket, which has suffered a series of recent test explosions, is still years away from being ready for the mission, former NASA executives say.

The SpaceX Starship rocket has exploded during three of its four recent tests, and its current version can carry only a fraction of its promised payload into orbit.

By Eric Lipton

Reporting from Washington

Sept. 20, 2025

Elon Musk has a history of making promises to rapidly deliver technological breakthroughs, only for them to end up taking longer than predicted or to fail to materialize.

Among these are his promises for fully autonomous self-driving cars or tunnels under Los Angeles to solve traffic congestion. Now some federal government officials worry that his pledges for landing astronauts on the moon will suffer similar delays.

That is why one of the largest federal contracts Mr. Musk has ever secured is now under intense scrutiny: a multibillion agreement with NASA for this crewed mission to the moon, the first in more than five decades.

https://www.nytimes.com/2025/09/20/us/p … -race.html

Bob Clark

Everyday Astronaut suggests a single launch architecture for a Moon mission using an expendable Starship as the launcher, so eliminating the SLS, and using Blue Moon as the lander, and the Orion as the capsule: 

Everyday Astronaut @Erdayastronaut
Call me pessimistic, I honestly think the only way to get humans back on the moon in this decade is likely a single launch approach, but not with SLS. SLS's TLI capacity is insufficient. Honestly, make an expendable Starship upper-stage with a Saturn V style clamshell stage adapter to house a fully fueled Blue Moon Lunar Lander inside and an Orion Capsule on top.

Booster might even be able to be caught and still get all that mass on a TLI with a dedicated expendable upper stage. If not, just ditch the booster for maximum performance, who cares, that's a drop in the bucket compared to even a single RS-25. It could literally be demonstrated in less than one year from today on the Starship side.

Without needing a refueling architecture from Blue Moon, it also simplifies that development process. A stage adapter for Orion is very simple.

Make no mistake, orbital refueling is the future and will be what makes these things more sustainable, but if we're in a race to beat China to the moon, the first return to the moon could be done on a very accelerated timeline without relying on such lofty milestones and infrastructure. 

Maybe I'll do a video breaking down this and other options when I finish my other video.
https://x.com/Erdayastronaut/status/1965141937931120910

  Bob Clark

It would be like spending all the money they did on the Falcon 9 and winding up with a rocket of less payload than the Falcon 1. We would say they took a bad engineering approach to the development of the larger rocket.

  Bob Clark