Super Heavy & Ship Blocks

The block logic

Each Block Is a Redesign, Not a Trim

Falcon evolved in place over a decade. Starship changes generation about once a year, and each one reworks tanks, engines and control surfaces together.

A block is a coordinated redesign of both stages, flown as a batch and then retired whole. Block 1 proved the stack could fly and be caught. Block 2 stretched the tanks and reshaped the flaps but never reached its payload goal. Block 3, flying since May 2026, is the first built around Raptor 3, refueling hardware and the grid-fin catch. Block 4, planned for 2027, stretches the whole vehicle and adds engines to the ship. The through-line is the same across all four: the airframe kept gaining mass as heat shield, reinforcement and reuse hardware were added, so SpaceX stopped chasing weight down and scaled the vehicle up instead.

The pattern that matters for everything downstream: payload to low Earth orbit went from 15 t on Block 1 to a planned 200 t on Block 4, an order of magnitude in four generations, while the diameter never moved off 9 m. The growth came from taller tanks, denser engines and lighter structure, not a wider vehicle. Building

Stack at a glance

The Whole Vehicle, Block by Block

Integrated figures for the full stack. Booster and ship detail follow in their own sections.

Block 2’s 35 t is the figure it retired at. Its original target was at least 100 t; the ship never flew an orbital mission before it was retired after Flight 11. Block 4 height, payload and mass are SpaceX estimates, not flown numbers.

Super Heavy by block

The Booster: Same 33 Engines, a Deeper Redesign Underneath

Engine count held at 33 through Block 3. What changed was the interstage, the grid fins, the shielding and the engine generation.

Three Block 3 changes carry most of the weight. The interstage folds into the methane tank instead of being a separate vented ring that was thrown away in flight, which removes a jettison event. The grid fins drop from four to three, grow about half again in size, sit lower on the vehicle, and now serve as the tower catch points — so the separate catch hardware the earlier boosters carried is gone. And because Raptor 3 moves its own plumbing inside the engine, most of the engine-bay shielding comes off, saving over a tonne per engine. All 33 Block 3 engines can relight, where Block 1 and 2 could only relight the inner 13 for boostback.

Ship by block

The Ship: Where the Flaps, Tiles and Refueling Hardware Changed

The upper stage is also the spacecraft, so its blocks carry the heat shield, the flaps and, from Block 3, the docking gear for orbital refueling.

Block 2’s signature change was the forward flaps: moved leeward, made thinner, and set at roughly 140° instead of 180°, after Block 1 ships took repeated flap burn-through on reentry — near-total loss on Flight 4. Block 3 keeps that flap geometry and adds what the beyond-LEO mission needs: docking ports and a redesigned quick disconnect for ship-to-ship refueling, plus a revised tile design. The Block 3 ship also carries a “crunch wrap” felt between tiles, added after Flight 10, to stop heat seeping through the gaps. Block 4 adds three more Raptor Vacuum engines, taking the ship from six engines to nine.

Raptor generations

The Engine Generation Sets the Block

Full-flow staged combustion on subcooled methalox throughout. Each Raptor generation removes external hardware and raises thrust.

The jump that changed the airframe was Raptor 3. By internalizing the plumbing it let SpaceX strip the engine-bay shielding from both stages — the single biggest reason a Block 3 vehicle looks cleaner around the engines than a Block 2 one. Full engine detail lives on the Raptor page.

Grid fins and catch

Four Fins Became Three, and the Fins Became the Catch Point

The most visible Block 3 change is also a recovery change: the booster no longer carries dedicated catch hardware.

Block 1 and 2 boosters had four grid fins near the top of the vehicle and separate protruding hardpoints for the tower arms to grab. Block 3 goes to three larger fins in a 90/90/180 arrangement, set lower on the booster, with the catch pins integrated into the fins themselves. SpaceX says the lower position reduces the heat the fins take during stage separation. Removing the separate catch structure saves mass, but it also means the fin and the catch point are now one part — a fin failure and a catch failure are no longer independent.

This is why no Block 3 booster has yet been caught: the three catches on record — Boosters 12, 14 and 15, from October 2024 on — were all Block 1 and Block 2 vehicles with the four-fin, separate-hardpoint layout. The Block 3 catch is unproven, and it is the recovery milestone Flight 15 may attempt. Recovery in full is on the hub’s recovery section.

Retirement sequence

Blocks Retire Whole, on the Flight That Ends Them

SpaceX does not phase blocks together. A generation flies its batch and stops on a named flight.

Booster 18, the first intended Block 3 booster, was scrapped after test damage, so Block 3 debuted on Booster 19. That is why the first Block 3 flight is Flight 12 rather than an earlier number, and why the booster and ship serial numbers no longer track the flight number.

Contested

Deliberately Not Claimed

The load-bearing uncertainties, tagged with the confidence they actually earn.

Record

Provenance and Data Sources