Exoscientist

I am arguing that NASA was blindsided by the low 40 to 50 ton capability of the current version of the SuperHeavy/Starship. A couple of reasons why I say this. First, while Elon was extolling the “success” of the latest test flight in his recent update at Starbase on the Starship development, NASA soon after wards started making plans for use Starship in Artemis III that won’t use the Starship as a lander. (NASA did not openly reveal this; it had to be leaked.) Note also the proposed options NASA is considering also would not use refueling of the Starship. The low 40 to 50 tons to orbit would cause impractically large number of refueling missions. Then V2 or even V3 would be needed for this and I’m suggesting NASA believes neither of those would be ready by Artemis III. Note the SpaceX plan for a lander using multiple refuelings absolutely can not work if the Raptor can not operate reliably for both boostback and landing burns. Relighting, apparently, successfully at boostback is not sufficient if a Raptor explosion on landing causes vehicle RUD. So I’m also arguing NASA has no confidence SpaceX can solve the relighting reliability issue, that requires three Raptor firings per flight both for the booster and ship, by Artemis III. Beyond that, another key reason why I say NASA was blind-sided by the low payload capability of the current version is if you run the numbers SpaceX cited for the specifications on the current version, it should easily make 100+ tons to orbit even as a reusable. That it makes at best half that suggests the dry mass or Raptor values or more likely both are significantly worse than the values cited by SpaceX. Bob Clark

NASA is now opening up the Mars Sample Return mission to the commercial space approach. The usual NASA government financed approach is estimated to cost ~$10 Billion. But following the commercial space approach it probably could be done at literally 1/100th that at ~$100 million including launch cost. I had estimated it as less than ~$200 million using the Falcon Heavy as launcher: Low cost commercial Mars Sample Return.
 http://exoscientist.blogspot.com/2023/07/low-cost-commercial-mars-sample-return.html This could get ~750 kg back from Mars with the Falcon Heavy as the launcher. However, it probably could in fact be launched on the Falcon 9. The Falcon 9 can launch about a quarter of the mass of the Falcon Heavy to Mars, for all the in-space stages, so estimate the sample size returned from Mars of ca. 180kg. At a $40 million launch cost of the reused F9, then all together with all the in-space stages, the mission cost probably could be less than than ~$100 million. Such a low mission cost probably could be paid for by advertising alone. But to encourage participants to take up the task of such a fully privately financed mission, NASA could offer a prize of say $200 to $500 million to whoever could accomplish it, with some smaller incentive prizes to those who accomplish some key required steps. Bob Clark

An article on the Starship performance shortcomings for the Artemis missions: Starship Faces Performance Shortfall for Lunar Missions by Alex Longo https://www.americaspace.com/2024/04/20/starship-faces-performance-shortfall-for-lunar-missions/ Bob Clark

Reading the article it’s clear the delay in the development in the Starship specifically in the refueling capability is a primary reason for why these alternative missions for Artemis III are being considered. “An unrealistic timeline The space agency's date for Artemis II is optimistic but potentially feasible if NASA can resolve the Orion spacecraft's heat shield issues. A lunar landing in September 2026, however, seems completely unrealistic. The biggest stumbling blocks for Artemis III are the lack of a lander, which SpaceX is developing through its Starship program, and spacesuits for forays onto the lunar surface by Axiom Space. It is not clear when the lander or the suits, which NASA only began funding in the last two to three years, will be ready.” Note the alternative missions being mentioned now for the Starship in Artemis III will require no refueling flights. Bob Clark

The sea level Raptor 2 sea level thrust is 230 tons. For its vacuum thrust estimate it as proportionally higher by how much higher the vacuum Isp is over the sea level Isp: 230*(353/327) = 248 tons. The Raptor Vacuum thrust is given as 258 tons. Then the total thrust for the 3 sea level Raptors and 3 vacuum Raptors should be 1,520 tons. But the thrust for the ship of the current version is given as only 1,250 tons: So it was started at 82% of full thrust. Commonly, you throttle down a rocket engine as most of the propellant burned off. The result is the overall average thrust was less than 75%. Bob Clark

It should not be lost sight of the fact the delays in Stasrship are a primary cause in these delays in the Artemis landing missions. Who in space reporting will put to NASA the tough questions: Was NASA aware the current version of Starship could only get 40 to 50 tons to orbit, so they would have to wait for V2 or even V3 to do Artemis? Did SpaceX inform them they throttled down the Raptor for reliability on IFT-2 and IFT-3? Bob Clark

A route to aircraft-like reusability for rocket engines. https://exoscientist.blogspot.com/2024/04/a-route-to-aircraft-like-reusability.html An interesting discussion on longevity of jet engines: The question I raise is whether this could also increase the reuse capability of rocket engines. Near the end I suggest, SpaceX is using this principle of running the engines at lowered power to increase engine life for the purpose of increasing the reliability of the Raptors. If they are, then they should explore the potential of this principle to also extend rocket engine reuse capability. Bob Clark

The trouble is if you run the numbers for the specifications SpaceX has cited for the SuperHeavy and Starship, i.e., their dry and propellant masses, and Raptor thrust and Isp, SH/SS should well be able to make 100+ tons to orbit as a reusable. I think NASA engineers were able to take the SpaceX proposal as a viable solution for an Artemis lander because their numbers checked out. But now we find the reusable payload for the current version is only 1/3rd the originally predicted 150 tons to orbit. What explains the drastically reduced payload capacity? This is a major issue because the current version can not perform the refueling functions of the Artemis lander missions at that low payload value. My opinion: I think NASA was blind-sided by that low announced payload value. SpaceX and NASA will have to be open about what that severe loss in payload, by 100 tons, stems from. Bob Clark

SpaceX should withdraw its application for the Starship as an Artemis lunar lander, Page 3: Starship has radically reduced capability than promised. https://exoscientist.blogspot.com/2024/04/spacex-should-withdraw-its-application.html Robert Clark

About 31 minutes in Elon suggests the current version V1 would be capable of 40 to 50 tons to orbit. This is bad because SpaceX sold NASA on the idea the Starship HLS could serve as an Artemis lander based on 150 tons to orbit reusable and “10ish” refueling flights. If the capability is max 50 tons, then it would take “30ish” refueling flights. If they intend to use version V2 then this is bad because it would require further qualification flights for the larger version and more importantly further qualification of the more powerful Raptor 3 engine needed. This last is doubly bad because I’d be willing to bet dollars to donuts that they never informed NASA that the current version couldn’t do it and further development would be required for the larger version. Bob Clark

I’d like to see them get some actual payload to orbit, even if it’s inert like water or liquid nitrogen. Bob Clark

SpaceX has completely dismantled the second OLM, located at the Kennedy launch site: Chris Bergin - NSF @NASASpaceflight The final Orbital Launch Mount (OLM) leg at KSC 39A has been demolished ahead of a likely pad redesign prior to East Coast Starship launches. https://twitter.com/NASASpaceflight/status/1775529100335108442 Evidently, NASA or SpaceX or more likely both were unhappy with the level of damage on an OLM after a Starship launch. They started dismantling it just one week after IFT-3. Rumor has it the new design will have a flame diverter. Bob Clark

SpaceX Starship has a serious problem that no one is talking about! https://www.youtube.com/watch?v=9SUbx3IkfRA His argument is the pad damage after each flight might take a month or more to repair. That would extend the time for all the refueling flights for the Artemis missions to a year or more. But when you have cryogenic propellant stored in orbit that long it results in severe boiloff problems. That means additional refueling flights to replace the propellant lost to boiloff. But at a month or more between flights, that means even longer time in orbit for the propellant and additional boiloff, so even more refueling flights. The result is the number of refueling flights becomes impracticality large. The answer might be you need a full flame diverter like used by Apollo to prevent pad damage. Gee, those Apollo guys really were smart. Bob Clark

Multiple sources give a 3,400 ton propellant load for the booster and 1,200 tons for the ship, for 4,600 ton max propellant load. The 4,500 ton total given in the SpaceX tweet is only 2% off this value. That could be just round off error or it could be you don’t want literally the tanks to be filled to the very top to allow for boiloff of the cryogenic propellant. Bob Clark

Oddly, not just suggesting it could reach orbit before the mission, Elon said it did reach orbital velocity after the flight: What max propellant load are you saying SH/SS could carry? Bob Clark