Robotic In-Space Assembly Simulator

Target structure

Modules required 12

Per-step reliability 97.0%

Mission readout

Assembly steps needed

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Steps completed

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Overall mission success probability (all steps)

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This run's outcome

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Success probability vs. total required steps, at current per-step reliability

How it works

A rocket's payload fairing has a fixed maximum diameter, so any single pre-assembled structure is capped in size. Robotic in-space assembly gets around that ceiling: the target structure is launched as many small modules, and a robotic arm docks and joins them in orbit one joint at a time until the full structure is complete.

Each individual joint-attachment step has its own success probability p (a robotic-arm positioning error or a latch failing to seat can each end the mission). Because every joint must succeed for the finished structure to be functional, the overall mission success probability compounds multiplicatively:

P(mission) = p ^ steps
steps = modules − 1

Modules required — a bigger target structure (larger antenna, array or mirror) needs more compact modules launched and joined, so it needs more assembly steps.
Per-step reliability — how often a single robotic docking/joint step succeeds on its own; this is normally very high, but is never 100%.
Even at a high fixed per-step reliability, stacking enough steps drives the compounded overall probability down — the chart shows this decay as required steps grow.

Real programs facing exactly this tradeoff: NASA's OSAM-1 robotic servicing/assembly demonstrator, Made In Space/Redwire's Archinaut in-space manufacturing, and DARPA's SPIDER assembly demonstrator — all designed to build structures far larger than any single fairing could launch.

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