Description
98t to 100x100km, single-stage recoverable rocket. 97.937/484.144=20.23%
Launch: throttle full, SAS stability on, stage, switch SAS to prograde at 57.5m/s, deactivate mammoth & vectors at 28km (AG1), burn until apoapsis at 100km, circularise.
Recovery: stage parachutes (needed again after payload separation), enable brakes to deploy inflatable heatshield, set SAS retrograde. There should be plenty fuel left to decelerate for reentry, aim for 50-55km and let it aerobrake. Try aim for land, water landings break the rocket. Parachutes will deploy in sets to avoid ripping off the top, and can land it softly.
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A stock rocket called MassFraction-Rocket-D2. Built in the VAB in KSP version 1.2.2 with 127 of the finest parts, its root part is probeStackLarge.
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An entry to the Stock Payload Fraction Challenge: the single-stage recoverable rocket D2, delivering a 97.937t payload to 100x100km orbit for a 20.23% mass fraction.