DEFINITION:
Following ESA’s technology domains this area includes both launcher propulsion and in space propulsion technologies(separated by NASA in two different technology areas). Under the Advanced Propulsion subdomain, any unconventional system could be included (the ones explicitly included in the description and any other one that could appear in the future). In any case, the description follows the one proposed by ESA.
(Source: PAE own description based on ESA TD 19)