Starship
DraftA fully reusable super-heavy launch vehicle in development by SpaceX. It is the largest technical bet in the industry and the one whose outcome most affects everything else in this site.
- Configuration
- Super Heavy first stage plus Ship second stage, both intended to be reusable
- Propellant
- Methalox
- Engines
- Raptor, full-flow staged combustion; roughly 33 on the booster
- Structure
- Stainless steel
- Target payload
- Over 100 t to low Earth orbit, reusable
The distinguishing choices
Three decisions separate it from conventional practice, and each has a specific rationale.
Full-flow staged combustion. Raptor is the first engine of this cycle to fly. All fuel passes through one preburner and all oxidiser through the other, so both turbines run on gas at lower temperature for the same power, and neither turbopump handles both fluids. That removes the interpropellant seal, a classic failure point, and it is a cycle chosen for reusability rather than for peak performance. See Engine cycles.
Methalox. Methane does not coke, which limits how many times a kerolox engine can fly without teardown. It is a mild enough cryogen to share thermal design with liquid oxygen. And it can be manufactured on Mars via the Sabatier reaction, which is the long-term rationale. See Chemical propulsion.
Stainless steel. Heavier than aluminium-lithium or composites, and chosen anyway. It is cheap, weldable in the open without a clean room, and retains strength at high temperature, which reduces the thermal protection required on the windward side. This is a manufacturing-cost and operability decision that accepts a mass penalty, which is unusual in launch vehicle design and consistent with a vehicle intended to be built in quantity.
Flight test approach
The development approach is iterative and public: build vehicles quickly, fly them, accept failures, and incorporate what is learned into the next article. This differs sharply from the analysis-heavy approach described in Spacecraft systems engineering, where a single article is verified exhaustively before flight.
Both approaches are defensible and they suit different situations. Iterative testing works when articles are cheap enough to lose and the failure is contained; exhaustive verification is necessary when there is one article and no second chance. A programme that will build hundreds of vehicles can amortise learning across them in a way a flagship science mission cannot.
The flight test campaign has progressed through ascent, stage separation, orbital velocity, controlled re-entry and booster recovery, with failures at various stages along the way.
The critical dependency
Starship in low Earth orbit does not have the propellant to reach the Moon, land, ascend and return. A lunar mission requires orbital refuelling: a series of tanker Starships launched separately, transferring cryogenic propellant in microgravity.
| Unproven step | Difficulty |
|---|---|
| Cryogenic transfer in microgravity | No bottom to the tank; requires settling or capillary management |
| Tank chilldown | The receiving tank is warm and flash-boils the first propellant in |
| Boil-off during a campaign | Propellant loaded early evaporates while later tankers launch |
| Launch cadence | The whole campaign must complete within the boil-off window |
| Gauging | Knowing how much actually transferred, to a few per cent at best |
None of these is impossible and none has been demonstrated at scale. Together they are a chain of unproven steps on the critical path of a crewed mission, which is where the Artemis schedule most plausibly slips. See Refueling and propellant depots.
What changes if it works
The consequences are broad enough that much of this site’s economics would need revision.
| Domain | Effect |
|---|---|
| Launch cost | Another order of magnitude reduction is the stated goal; unproven |
| Fairing volume | A 9 m diameter changes what can be designed, not just how much is carried |
| Spacecraft design | Mass and volume constraints relax, permitting less optimised and cheaper designs |
| In-space infrastructure | Depots, large assemblies and stations become affordable |
| Space solar power | The economics depend directly on launch cost |
| Mars architecture | The vehicle is designed around it, contingent on refuelling and on landing tens of tonnes |
The fairing point deserves emphasis independently of cost. As noted in In-space manufacturing and assembly, the launch fairing constrains what can be designed far more often than mass does, and JWST’s folding architecture with its 344 single-point failures exists because of it. A 9 m fairing removes that constraint for a large class of missions.
The honest position
The vehicle has flown, reached orbital velocity and demonstrated booster recovery. Full reuse of both stages, orbital refuelling, and the operational cadence the economics require have not been demonstrated.
The reasonable position is therefore that this is a programme with genuine progress and unproven core claims, whose success would change the field substantially and whose failure would leave the field roughly where it is. Statements about the future of space that assume Starship works as advertised are making a contingent bet and should say so.
References
- SpaceX published Starship material and FAA licensing documentation.
- NASA Human Landing System award documentation and source selection statements.
- FAA Office of Commercial Space Transportation flight test licences and mishap reports.
- Gradl, P. R. et al. on full-flow staged combustion and additive manufacturing in engine development.