by jjk166 | 2025-07-21 19:07:56+00:00
> SpaceX could have easily done this. They already proved they could land a 1st stage/Booster with the Falcon 9, and Falcon 9’s Booster could launch a 1/10 scale Starship into orbit. Tests of such a scaled-down model would help SpaceX determine the best compromise for using the bellyflop manoeuvre and retro rockets to land. It would help them iteratively improve the design around such a compromise, especially as they will be far cheaper and quicker to redesign and build than the full-scale versions. Not only that, but these tests would highlight any of the design’s shortcomings, such as the rocket engines not having enough thrust-to-weight ratio to enable a high enough payload. This allows engineers to do crucial, complete redesigns before the large-scale version is even built.

> Well, developing a Starship like this would expose that making a fully reusable rocket with even a barely usable payload to space is impossible. Musk knows this: Falcon 9 was initially meant to be fully reusable until he discovered that the useful payload would be zero. That was his iterative design telling him Starship was impossible over a decade ago, as just making the rocket larger won’t solve this!

The author clearly isn't very knowledgeable about rocket design. Rockets do not scale linearly. While some lessons can be learned with scale models, other lessons simply have to be learned with a full scale test, which is why all rockets get full scale tests. This is also why small amateur rockets are incapable of achieving orbit, no matter how small the payload. Conversely, making rockets bigger does increase payload.

Further, Starship isn't simply a bigger Falcon 9, and Falcon 9 was not designed from the beginning to be fully reusable. Falcon 9, like Falcon 1, was designed to be fully expendable. SpaceX's original plan was to focus on low cost, mass producible rockets. When this didn't work out as planned, they pivoted to reusability. There was a concept video showing 100% reusability (as well as dragon capsule flyback and propulsive landing), but no serious effort at ever actually achieving that. The booster was the only thing they tried to make work, and they did several serious redesigns to first add landing legs and then optimize the booster for flyback.

Starship was from the ground up designed to be fully reusable, and its design is very different - it uses different, higher performance propellant, it uses larger engines with a different thermodynamic cycle, it is made from different structural materials, it lands by a different method. Of course lessons learned from Falcon 9 were incorporated, and you can clearly see some of that legacy for example in the control fins, but this includes learned lessons about the limitations of the Falcon 9's design that they needed to shed. The idea that Falcon 9 proves Starship can't work is asinine, by that logic why would we ever try to improve upon things if we couldn't achieve it with an earlier version that was never designed to do so?

> Simple. Musk isn’t an engineer and doesn’t understand iterative design, and now SpaceX and NASA are facing a sunk cost fallacy.

> You never achieve iterative design with a full-scale prototype. It is incredibly wasteful and can lead you down several problematic and dead-end solutions. I used to engineer high-speed boats — another weight- and safety-sensitive engineering field. We would always conduct scale model tests of every aspect of design, iteratively changing it as we went so that when we did build the full-scale version, we were solving the problems of scale, not design and scale simultaneously.

This isn't iterative design. This is waterfall. It's progressing linearly through stages without going back to incorporate lessons learned. Yes, it is cheaper to work out all the bugs on scale prototypes than full scale tests, just as it would be cheaper still to get it right the first time at the design stage, but that doesn't mean it's a good project management strategy. What SpaceX did quite successfully with its Falcon 9 development is iterative design.