What Is MECO? Main Engine Cut-Off Explained

Quick answer

MECO — main engine cut-off — is the moment a rocket's main engines shut down, ending the first phase of powered ascent. It precedes stage separation and hands the flight to the upper stage; on reusable boosters, everything after MECO is the flight home.

📘 Full definition✓ Reviewed 2026-09-07

MECO (main engine cut-off) is the scheduled shutdown of a launch vehicle's main engines — on a two-stage rocket, the end of first-stage thrust, typically around two and a half to three minutes into flight at roughly 2–3 km/s, followed within seconds by stage separation and upper-stage ignition. The abbreviation belongs to a family narrating every ascent: SECO (second-stage engine cut-off, often the moment of orbital insertion), BECO (booster engine cut-off) for strap-on configurations, and SES/SECO-2 pairs for missions whose upper stages relight after coasts. Cut-off timing is a designed quantity — propellant-depletion versus commanded shutdown, with guidance refining the instant to hit the staging state precisely — and on ascent profiles for reusable boosters MECO is deliberately set earlier and slower, reserving propellant for the boostback, entry and landing burns that follow. For crewed vehicles MECO edges are abort-mode boundaries; for telemetry watchers everywhere, the sudden fall of acceleration to zero and the callout "MECO" is the ascent's first exhale.

Falcon 9 MECO

2.5 min / 80 km

Followed By

Stage separation → SES-1

Shuttle MECO

8.5 min into flight

Falcon 9 Speed

6,000 km/h at MECO

Understanding MECO

The ascent, told in callouts

A modern webcast's script is the event sequence: lift-off; max-Q (peak aerodynamic pressure, engines briefly throttled); BECO and booster jettison where applicable; MECO; stage separation; upper-stage ignition; fairing separation once the air is too thin to matter; SECO into a parking orbit; optional relight; spacecraft separation. Each event is a telemetry edge — acceleration, chamber pressures, rates — and the sequence's exact times, published pre-flight, are the mission's skeleton.

Cut-off precision and insurance

Guidance computes cut-off to deliver a target state vector, not a stopwatch time: the engines burn until position and velocity match the staging or insertion solution, absorbing performance dispersions along the way. Insertion accuracy quoted by launch providers — tens of kilometres and hundredths of a degree — is ultimately cut-off precision, and anomalies at these edges (early shutdown, failed relight) are the classic sources of "off-nominal orbit" headlines.

Frequently Asked Questions

Why does MECO happen so early for reusable boosters? ▼

Recovery propellant. A booster that must boost back, re-enter and land keeps a reserve, so it stages earlier and slower — around 1.7–2.3 km/s for return-to-launch-site profiles versus faster, hotter staging for droneship recoveries and full expendable performance when the mission demands it.

What happens between MECO and upper-stage ignition? ▼

Seconds of choreography: thrust tails off, separation devices fire, springs or pushers open the gap, and the upper stage lights clear of the falling booster. Some vehicles ullage-settle propellants first; hot-staging designs overlap the sequence, igniting before release.

Is SECO the same as reaching orbit? ▼

Usually the first SECO marks insertion into the initial orbit — the "we are in orbit" call. Missions to higher targets then coast and relight: SES-2 and SECO-2 bracket the burn that stretches the orbit toward GTO or escape, so a flight may count several cut-offs before spacecraft separation.

MECO (Main Engine Cut-Off)

Understanding MECO

The ascent, told in callouts

Cut-off precision and insurance

Frequently Asked Questions

Sources & References