Single-stage-to-orbit. This is a theoretical or developmental spacecraft that can launch from Earth and achieve orbital velocity without jettisoning boosters, fuel tanks, or other stages during ascent. Achieving this requires extremely high mass fractions and highly efficient engines, making it one of the hardest engineering challenges in aerospace.
Heard on the job
If they can perfect the aerospike engine, an SSTO might actually be viable.
Related terms
TSTO
Two-stage-to-orbit refers to a launch vehicle that uses two distinct propulsion stages to reach space.
Multistage
A multistage vehicle uses two or more distinct rocket sections that fire and discard sequentially.
Delta-v
The total change in velocity a spacecraft can achieve using its available propellant.