Deep Field

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Deep Field
29 September 2026 2518 stories tracked

Glossary · Launch & Flight

Thrust-to-weight ratio

Whether the rocket can lift itself, expressed as a number that must exceed one.

Divide the thrust by the weight on the pad. Below 1.0 the vehicle does not move; at 1.2 it climbs slowly and wastes propellant fighting gravity; much above 1.5 and it hits thick air too fast and pays in drag. Most launchers leave the pad between 1.2 and 1.4 and rise steeply as the tanks empty, which is why the same engines that struggle off the pad are throttled down late in the burn to keep the acceleration survivable — around 3g on a crewed flight, more on a cargo one.

Related terms

Delta-v The currency of spaceflight: how much you can change your velocity, in metres per second. NET (no earlier than) A launch date that is a lower bound, not a promise. Max-Q The moment of peak aerodynamic pressure on an ascending rocket. Staging Throwing away the empty part of the rocket so you stop accelerating it.

Questions

What is Thrust-to-weight ratio?

Whether the rocket can lift itself, expressed as a number that must exceed one.

Why does it matter?

Below 1.0 the vehicle does not move; at 1.2 it climbs slowly and wastes propellant fighting gravity; much above 1.5 and it hits thick air too fast and pays in drag. Most launchers leave the pad between 1.2 and 1.4 and rise steeply as the tanks empty, which is why the same engines that struggle off the pad are throttled down late in the burn to keep the acceleration survivable — around 3g on a crewed flight, more on a cargo one.

Written and computed by . Corrections and errors to hello@cantinalabs.dev.