New Mars Forums

I’d like to get some feedback on these estimates I made after I heard Robert Zubrin say Elon told him the Starship, i.e., the upper stage only, could be made for ~$10 million production cost:

https://twitter.com/spacewatchgl/status … 6932841756

I was surprised that Elon estimates a Starship only cost of ~$10 million. At a ~$10 million Starship cost, SpaceX should investigate it as 1st stage of a smaller system, with a mini-Starship as the 2nd stage at perhaps only ~$2 million additional cost, due to its proportionally smaller size. Get ~100 ton to LEO Saturn V-class launcher at only ~$12 million cost(!)

As the first stage now, Starship loses only a proportionally small payload by reusing if you land it down range. Then close to a 100 ton partially reusable launcher for only ~$3 million(!) Say, payload reduced to 80 tons with partial reusability. Then price per kilo only $3 million/80,000kg = $37.5 per kilo(!)

  Bob Clark

Commercial
Starship Super Heavy booster came within one second of aborting first “catch” landing.
Jeff Foust
October 25, 2024
https://spacenews.com/starship-super-he … h-landing/

This illuminates why I argue it’s likely SpaceX will ultimately decide to go with landing legs and landing on a landing pad anyway. Landing legs can be optimally designed to be lightweight to add only a small amount to the dry mass. Then it won’t be worth risking a launch tower worth hundreds of millions of dollars for such a small loss in payload.

Also it’s mentioned there wasn’t the expected amount of pressure in the Raptor. This could have been due to a fuel leak. Fuel leaks and the resulting fires have been a recurring problem with the Raptor:

What Happened to Starship SN11? | SpaceX Starship SN11 Test Flight & Explosion Cause Analysis.
https://youtube.com/clip/UgkxziHi2GsiVo … _ussOY9bhT

Then the giant plume of flame seen shooting up the side of the booster may in fact have been due to a fuel leak.

Additionally, its mentioned one of the chine covers blew off exposing valves that are sources of single-point failure if they had been damaged. Notably the landing video shows the cover blew off before the engine restart began. It was speculated it was due to atmospheric forces, but it may have been due to a fire within the engine compartment releasing pressurized gas.

  Bob Clark

The elephant in the room everybody is ignoring. A 25 meter, 80 foot, long plume of flame shooting up the side of a rocket is a pretty big thing to ignore.

  Bob Clark

I would be interested in seeing that video. Perhaps it would appear in your web history? The ship didn’t explode before landing. But it did catch on fire before the landing, like the booster did.

  Bob Clark

Thanks for the refs.

  Bob Clark

The estimated cost of the Artemis landing missions will be in the range of $8 billion per mission. This is an unsustainable cost. However, there is an approach to returning to the Moon that would only be ca. $100 million(!) per launch, comparable to the cost NASA is spending just getting to the ISS. This is to use the Starship in expendable mode. According to SpaceX it would have a payload capacity of ca. 250 tons to LEO. Moreover, it could be done literally now. Just strip off the reusability systems to get the full 250 ton to LEO capability and put an existing smaller stage such as the Falcon 9 upper stage atop it to act as a 3rd stage/lander.

However, NASA and SpaceX are too wedded to their SLS and multiple Starship refueling approach. Remember at the beginning of the U.S. space program in the late 50’s when our rockets kept failing, while the Soviet Union kept succeeding, made famous in the book and movie the Right Stuff? We weren’t able to finally succeed until we gave it over to the military to manage. In view of the strategic importance of returning to the Moon, the DoD might want to pay for this low cost, independent approach to returning to the Moon that has the distinct advantage of allowing a sustainable lunar presence and at high flight cadence.

Should the DoD be involved in returning us to the Moon?
https://exoscientist.blogspot.com/2024/ … ng-us.html

  Bob Clark

Is China planning to weaponize the Moon?

https://youtu.be/eElDqTNe4oE?si=hv8Y3tgo9gBDfbF_

China wants to build a 1 megawatt nuclear reactor on the Moon, 10 times the size the U.S. is planning on. Why? Evidence suggests it’s for their electromagnetic launcher they want to use for sending resources from the Moon to Earth.

This is analogous to the SpinLaunch™ being constructed on Earth for reducing the cost to LEO. But on the Moon with no atmosphere and much reduced gravity it can send the payload all the way to lunar orbit and even all the way to Earth. Being just electrically powered the launches will be at just the cost of generating the electricity.

But it needs to be kept in mind it could send anything, anywhere on the surface of Earth. When you realize the Chinese space program is just an off-shoot of their military the possibility arises it could be used as a weapon.

“Mr. President, we must not ALLOW a spin launch gap!”
(With apologies to “Dr. Strangelove”.)

  Bob Clark

For the manned Artemis missions, SLS and Orion cost $2 billion each per launch. SpaceX got a $4 billion contract for 2 Starship HLS’s, so $2 billion each. Boeing EUS, Advanced SRB’s, Gateway, at least total another billion and likely closer $2 billion. Then manned Artemis ~$8 billion per launch. This is clearly not a sustainable approach to lunar habitation.

For the Apollo missions I asked ChatGpt what were the per launch costs in current dollars. It’s response was:

The Apollo program, which included a total of 17 missions (from Apollo 1 through Apollo 17), cost approximately $25.4 billion in 1973 dollars. To estimate the cost per flight in today’s dollars, we’ll follow these steps:

    1.    Adjust the total cost for inflation:
    •    The cumulative inflation rate from 1973 to 2024 is approximately 5.8 times. This means that $1 in 1973 is worth about $5.80 in 2024 dollars.

Total cost in 2024 dollars = $25.4 billion x 5.8 = $147.32 billion

    2.    Calculate the cost per flight:
    •    There were 17 Apollo missions, including the uncrewed and crewed missions.

Cost per flight = $147.32 billion/17 = $8.67 billion per flight

Summary:

The Apollo program cost approximately $147.32 billion in today’s dollars, which breaks down to about $8.67 billion per flight on average.

And we already know Apollo was not sustainable.

In contrast, ~$100 million for expendable SuperHeavy/Starship at 200+ ton capability gets single launch missions to the Moon at costs nearly two orders of magnitude cheaper than Apollo or Artemis. This is in the same range of what NASA spends for just flights to the ISS.

For Mars, NASA once presented a plan to the Bush administration for a Mars program for a total cost of $500 billion. This was promptly rejected by the administration. These large cost estimates led Robert Zubrin to propose in the early 90’s his Mars Direct approach, where propellant for the return flight would be generated at Mars.

This would require only 2 launches of Saturn V class launchers at 100+ ton capability. With the development of the Starship at 100+ ton ability reusable, Zubrin proposed using it in his Mars Direct 2.0 proposal. He contrasted this from the SpaceX approach of using multiple refuelings here:

Mars Direct 2.0 - Dr. Robert Zubrin - IAC 2019.
https://www.youtube.com/watch?v=z5k7-Y4nZlQ

Zubrin notes by just using a small 3rd stage/lander you would need no refueling flights.

But you have to wait until the time the Starship becomes reliable for reusable manned flights. In contrast the expendable version with its higher payable capability can launch now and needs only a single launch, not two.

Demo flights to either the Moon or Mars can literally launch in a month on IFT-5 if stripped of its reusability systems to get the 200+ ton payload capability.

  Bob Clark

Controversy coming from someone on Twitter posting an image claiming to show the IFT-4 booster exploding after water landing:

BOCA'S?BRAIN @BocasBrain
Here comes a 12 hour ban from X
Sorry, you don't get the footage.
See you tomorrow after the scolding :

https://x.com/BocasBrain/status/1809390911782367455

  Bob Clark

We can estimate using the Silverbirdastronautics.com payload estimator. Some quirks of the program have to be noted though. First, always use the vacuum thrust and vacuum Isp, even for first stages. This is because the program already takes into account the diminution at sea level. Note in the images below the engine thrust and Isp fields have the vacuum values even though this is for the Falcon 9 first stage.
Secondly, input the “Inclination” for the launch as the latitude of the launch site. This is just a fact of orbital mechanics that the launch angle should match the sites latitude to maximize payload. So for a launch from Cape Canaveral I input 28.5 degrees.
Third, for the “Restartable upper stage?” Option, select “No”. Selecting “Yes” often reduces payload, perhaps because it keeps some propellant on reserve for a restart.

Then this is what the input and results screens look like:

About 3,400 kg to LEO for the Falcon 9 first stage as an expendable SSTO. About the expendable scenario, note I subtracted 2,000 kg from the dry mass input field taking the dry mass down from 22,000 kg to 20,000 kg since reportedly the landing legs add about 2,000 kg to the dry mass of the first stage.

The question arises then why subtract that off if you’re aiming for a reusable system? A few reasons. It is my opinion that the opposition to SSTO’s is so engrained that just doing a launch carrying a payload would be an important thing to do. So first accomplish the expendable case then proceed to the reusable case.

[Sidebar: this is one of the reasons why I disagree with the approach SpaceX is taking with the Starship. SpaceX was spectacularly successful by first getting the expendable Falcon 9 then proceeding to reusability. If they had taken that approach to the Starship, they would already be flying expendable rockets to orbit at a profit. Moreover, they would already have rockets capable of single flight missions now to the Moon or Mars. No refueling flights nor SLS required. I mean they could do that literally like tomorrow.]

Secondly, the margins for a SSTO are slim, so you want to maximize the payload. So for the operational SSTO you want to use the known technology of altitude compensation. Using this instead of the vacuum Isp for the Merlin being 311s you could get the highest known possible vacuum for a kerolox engine, ca. 360s, while still having an engine able to fire at sea level.

This will greatly increase the payload possible, at least to 10,000 kg possibly higher, simply by having a variable nozzle. Now, when you have that higher payload then you can add on reusability systems.

  Bob Clark