Ariane 6: solid vs. liquid

[deltaV]

And ballast steel isn't really that expensive so there is rarely ever a reason to _exactly_ match a payload mass with a capability.

I hereby nominate that sentence for understatement of the day. Enough steel ballast to use an entire Ariane 5's GTO capacity costs around $10k. Even in Elon's dreamworld where most of the cost of a rocket launch goes to propellant that's still a small fraction of the cost of the launch!

[quanthasaquality]

Exactly this was the problem.
They investigated only concepts with strap-on-boosters. But strap-on-boosters are expensive! Really expensive! You can kill every concept by adding boosters.
Adding a third Vulcain to the core and throw out the boosters entirely, as we did last year in the NELS study, would probably have resulted in another Ariane 6 baseline concept.
But concepts without boosters were never taken into account by CNES.

Spacediver

Solid strap ons seem to work on cost in America for the EELVs. The Atlas V 501 can put 10 tons to LEO, and the 551 can put 20 tons to LEO. In the USA, liquid cores get the expensive bureaucratic treatment to ensure reliability. The solids don't need as much expensive oversight to ensure reliability.

With your logic, a larger Delta IV, without SRBs, complete with ablative nose cone, would be cheap to GTO.