Mass-produced rocket engines no larger than a fingernail may one day lift payloads cheaply into orbit. MIT aerospace engineer Adam London is etching a microrocket motor just 3 millimeters thick and 1.5 cetimeters across into a silicon wafer. Thanks to microscale physics of the sort that allows ants to haul potato chips, the rocket-on-a-chip should pro-vide 20 times as much thrust per unit weight as the space shuttle's main engine.

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