Two-stage-to-orbit vehicles discard a heavy first stage after it exhausts its propellant in the lower atmosphere, leaving a smaller second stage to carry the payload into orbit. This staging approach sheds dead weight, drastically improving the mass fraction and payload capacity compared to single-stage designs. It remains the standard architecture for orbital rockets because it balances engineering complexity with payload efficiency.
The new heavy lifter is a classic TSTO design, relying on a reusable booster and an expendable upper stage.
Related terms
SSTO
A single-stage-to-orbit vehicle that reaches space without dropping hardware.
Launch vehicle
A rocket or other system used to carry a payload from the Earth's surface into space.
Multistage
A multistage vehicle uses two or more distinct rocket sections that fire and discard sequentially.
Interstage
The structural ring or cylinder that connects two stages of a multi-stage rocket.