Hi LJK

There's some good design studies on Stirling-cycle RPGs with ~ >30% efficiency being available to power very light-weight deep-space probes allowing moderate trajectory assistance from an ion-drive. One mission objective is investigating Jupiter's Trojans but the new planet(s) will be an equally compelling objective for such missions.

Problem is that ~ 100 AU is a LONG way for a probe. New Horizons would take ~20 years to get there and it's close to being the fastest probe launched for a long-time. The new inflatable solar-sails from L'Garde may allow solar "fry-by" hyperbolic boosts and get speeds up to ~ 10 year flight times, but decceleration would be desireable unless we're doing a multi-object swing-by mission.

A sub-probe with a mini-NTR like the proposed MITEE might allow decceleration for an orbiter mission. Or if there's a decent atmosphere for an aerobrake??? Did you know that the Apollo re-entered steeply down to ~ 60 km (200 kilofeet) then effectively flew "level" (with a few shallow hops) for a couple of thousand miles before dropping vertical again? Maximum decceleration was at ~ 60 km up and 6.5 gee.

Adam