LASSO: Lunar Asteroid Salvage by Slower-impact Operation — delivering a co-orbital near-Earth asteroid to the lunar surface by uncontrolled low-velocity impact

Everything we want to build in space is made of iron, and the Moon has almost none of it in usable form — lunar iron is oxide, chemically bound, and the most efficient plant anyone has modelled needs about 109 kWh to make a kilogram of metal from it. Asteroids carry iron that was already reduced four and a half billion years ago. Every proposal for getting it to the Moon has assumed you must slow the asteroid down: fly out and mine it, or brake it into orbit and park it. Both pay for every metre of the descent, and neither closes economically for structural metal. This preprint proposes the opposite. Don't land it — drop it. Let the asteroid hit the Moon, unbraked, and let the impact do the ore processing. The crater and its ejecta blanket are the mine. What makes this work rather than merely destructive is that arrival speed at the Moon cannot be chosen: it has a hard floor of 2.42 km/s set by lunar escape velocity and the geometry of the Earth–Moon system, and — the central result — it barely rises above that floor no matter what the approach. Across a 2.5 km/s range of encounter velocity, arrival speed varies by only 0.6 km/s. Two design choices push it to the bottom of that range at zero propellant cost: pursuit geometry, striking the trailing lunar hemisphere so the Moon is running away as the body falls, which is worth 32%; and selecting for asteroids with a Tisserand parameter near 3, meaning orbits so close to Earth's that the object is barely moving relative to us. That second choice is where the argument turns. An asteroid cheap to nudge is cheap because it is co-orbital with Earth — and a co-orbital asteroid is, necessarily, one that arrives slowly. The property that makes it affordable to move is the same property that makes its metal survive the landing. There is no trade-off to balance, because there is only one variable. At every reachable speed the body is shattered by a factor of 10–45 over its failure strength and stays a factor of 2.2–15 below whole-rock melting; iron, with the largest melting margin of anything present, is what the impact sorts out. Kamil crater in Egypt is the field calibration: a metallic impactor at or above this velocity left roughly 3,400 kg of recoverable metal gravel, with only 1.5–3.5% of the surviving mass lost to microscopic melt. Filtering the 42,062 known near-Earth asteroids on size, orbit, minimum orbit intersection distance, co-orbital envelope, orbit quality, focusing aperture and nudge cost leaves exactly one object: 2026 AC4, arriving 27 July 2058 at 2.50 km/s for a 0.71 m/s impulse applied 32 years early — about 269 kg of xenon, less than Dawn carried. Median delivered metal is ~120 t, roughly twice everything ever soft-landed on the Moon by all nations, with a 75% band of 5–1,020 t and about a one-in-three chance the object fails its own propellant filter once its mass is known. Three quantities remain unmeasured and are carried as explicit free parameters: fragment size distribution, composition (every small co-orbital yet characterised has returned a lunar signature, which may mean the orbital filter selects against value), and recoverable fraction. All catalogue queries are given verbatim and were re-run on 14 August 2026. Section 15 states the disclosure in enumerated form. One action is time-critical: 2026 AC4 is observable on 14 October 2026 and then not for 29.6 years.