But for the engineers in the cleanroom, the mission’s most stressful moment isn't the liftoff. It happens 24 hours earlier, inside a climate-controlled high bay, when a stack of painted steel or aluminum—utterly inert and devoid of electronics—is bolted to the top of a million-dollar rocket.
The ingot is mounted to the top of the kick stage or the center of the rideshare stack. Engineers perform a “mass moment of inertia” (MMI) test, spinning the stack to ensure the simulated weight matches the flight software. launch ingot
For now, it is indispensable. Without ballast masses, the economics of rideshare collapse. You cannot fly a variable menu of small satellites without a fixed counterweight. But for the engineers in the cleanroom, the
This is the ingot’s moment of sacrifice. The upper stage performs a “ballast jettison” burn. Explosive bolts fire. Pneumatic pushers shove the ingot away from the stack at 1.5 meters per second. Engineers perform a “mass moment of inertia” (MMI)
Until then, the next time you watch a launch webcast and hear the commentator say, “Payload deployment confirmed,” spare a thought for the last object to separate.
He taps the metal. “This thing will outlast every satellite on this manifest. Long after the last telemetry packet dies, the ingot will still be up there. Circling. Waiting.” Is the launch ingot a necessary evil or a reckless source of debris?
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