← INDEX — FIG. 00 — 21 DECEMBER 2015, LANDING ZONE 1
9 × MERLIN 1D · 33 × RAPTOR
RETURN
FALCON 9, STARSHIP AND REUSABLE ROCKETS
For sixty years almost every rocket was thrown away after one flight.
BEGIN — CHAPTER 01 →CH.01 / 07 — THE MOST EXPENSIVE PART FALLS INTO THE SEA
Reuse saves money, but it costs payload
A first stage carries most of a rocket's engines.
Landing downrange costs 10–20 % of payload; returning to the launch site about half.
CH.02 / 07 — PROPELLANT KEPT FOR THE WAY HOME
Every km/s held back for landing is payload left on the ground
Downrange vs. launch-site landing.
An illustrative two-stage rocket model.
RESERVE PROPELLANT AND PAYLOAD
mres = mdry,1 (eΔvrec/c₁ − 1) · c₁ ln(m₀/m₁) + c₂ ln(m₂/mf) = 9.4 km/s
Assumed masses, not SpaceX data.
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Preset reserves are rough assumptions.
CH.03 / 07 — TOO STRONG TO HOVER
Zero speed at zero height — not a moment earlier
A Merlin 1D throttles down to 108,300 lbf.
The burn must reach zero speed at touchdown.
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Simplified: one engine, constant mass, no drag.
CH.04 / 07 — FROM ONE LANDING TO HUNDREDS
Land it, then fly it again
The first landings, 2015 and 2016.
The first reflight, 2017.
CH.05 / 07 — STARSHIP AND SUPER HEAVY
No legs: the tower catches the booster
Starship reuses both stages.
The tower caught Booster 12 on 13 October 2024.
CH.06 / 07 — TEN YEARS OF COMING BACK
From a single landing to a tower catch
The rocket equation did not change.
CH.07 / 07 — REFERENCES