A good summary of state-of-the-art advanced propulsion technologies
Space Access Society 2019 April 19 – 21
Day 1 – The Entrepreneurial Revolution In Smallsat Launch
http://space-access.org/updates/sa2019schedule.html#Thursday
Day 2 – Reusable Rocket Transport Networks in Earth-Moon (and Mars, and Nearby Asteroids) Space
http://space-access.org/updates/sa2019schedule.html#Friday
Day 3 – After Rockets, Getting There Faster: High Energy Propulsion Possibilities
http://space-access.org/updates/sa2019schedule.html#Saturday