The mystery of SpaceX ship 26.

 Copyright 2023 Robert Clark

 Interesting article:

SpaceX rolls naked Starship prototype to test site. 
SHIP 26 JOINS SHIP 25 FOR PROOF TESTING. (NASASPACEFLIGHT - STARBASE LIVE)
By Eric Ralph
Posted on February 12, 2023
https://www.teslarati.com/spacex-rolls-naked-starship-prototype-to-test-site/

   Much web discussion is going on on space forums about the Starship version Ship 26. This surprised everyone in being a completely expendable format. It has no top or bottom flaps, heat shield, or legs. Since it is to be expendable it likely also has no ballast tanks. The most frequent speculation is its a test vehicle for orbital refueling. But it has no visible external connections for linking up to another Starship.

 The key clue is it’s moved to the suborbital launch pad. This means it can launch without the SuperHeavy booster. With 6 Raptor 2 engines it can launch fully fueled unlike the previous Starship test flights meant just to test landing.

 The key question: what is the dry mass of this expendable version without flaps, legs, heat shield, or ballast tanks? If you know that you can calculate how much payload it can lift to orbit in a single stage.

 Elon said the expendable version with only 3 engines might mass only 40 tons:

https://twitter.com/elonmusk/status/1111798912141017089?s=61&t=A46qVnS2GH4VVA-pQSUlkg

 Add another 5 tons for 3 more engines and this version might mass 45 tons. However, the increased thrust may require strengthening of the tanks which would increase the dry mass. On the other hand, this version would have to support far less payload atop it than the max 250 tons of the full two-stage so would need reduced tank strengthening.

  The argument can be made that just being moved to the suborbital launch pad does not mean it is going to be launched. It might be just used for pressure testing for example.

 However, the “Angry Astronaut” did a video from Boca Chica showing the Raptor work station being moved towards Ship 26:

 He says that’s only done if you are installing engines on the Starship. You don’t do that if you are only doing pressure testing. He notes though that it could be putting engines either on S26 or S25. Probably we’ll know by the end of today which ship is having engines installed.

  

       Robert Clark