I've flown 3 types of 500 series Citations with the nose wheel spin up kit, most recently the C560 V. It uses the bleed air from the windshield heat to spin the wheel with vanes. The valve is adjustable from the cockpit to keep the speed between green and red light limits. The fairing also uses ram air to spin the wheel, so it actually rotates without bleed air. I'm told it was developed for a Lear. It weighs 10lbs when installed. Remarkably few stone chips in the leading edge, bottom wing skin, and virtually no fan damage in decades of use on gravel. The nose wheel casters so it touches down straight and kicks up fewer rocks.
The kit imposes a 200 knot gear speed limit and is removed in winter so it doesn't get packed with snow. The gravel is usually firm and not loose then. Nothing helps you when the gravel is soft in the spring and runway condition reports are 2 days old!