High-Efficiency Interplanetary Probe / Pixie

Perhaps the most efficient craft in its class.
Mid-tech, two stage, JVP-friendly, sustainable in long missions.
Launched correctly, will offer over 6 km/s dV budget from low circular orbit.

Launch procedure:
- heading lock to 80 deg pitch, direction as needed (East for general case);
- THR 100%, stage to lift off;
- when 80 deg pitch reached, switch to prograde;
- keep going full power, but if velocity goes over ~3.5 Mach, throttle down a bit;
- when apoapsis reaches 90..100 km - THR 0%, ballistic trajectory;
- coming to apoapsis, 40 sec prior set pitch to 0 deg;
- 30 sec prior THR 100%;
- switch to map (orbit) view, watch periapsis rapidly raising, cut THR when it's 80+ km (do at 1/4 time or drop gradually for precision);
- enjoy 700..900 m/s remaining in the 1st stage + 5300 m/s in command module.

Upon staging, solar panel will expose. As Pixie runs electric fuel pumps, and the module itself drains power, always orient the craft toward the star to keep battery charged in free flight.