Module beneath 

The crates under the builder, for what it doesn’t offer.

The builder makes the same things the crates below it use, and hands them over:

• Rocket::design is the design tree, an hpr_design::Rocket, as a design file holds it. Add what the builder can’t (clusters, pods, launch lugs, rail buttons, stages) with hpr_design, and make a rocket of it again with Rocket::from_design.
• FlightBuilder::simulation is the hpr_sim::Simulation a flight runs. Its methods add a stage separation, events of your own, moving or released masses, or another tool’s drag table; run flies it.
• Environment::sim is the hpr_sim::Environment, and Environment::from_sim wraps one built directly, with a geoid undulation, say.

Every crate of the workspace is re-exported by name: hpr::hpr_aero is the aerodynamics, hpr::hpr_motor the motors, hpr::hpr_io the file formats, and so on. The site’s API reference page lists them all.