NASA Advanced Innovations has funded Mach Effect propellantless propulsion, laser power beaming to power ion drives, hybrid Fission-Fusion propulsion and antimatter propulsion.

A Phase 2 project for beaming megawatts of laser power for a next-generation ion drive.

NASA NIAC phase 1 funding to determine the feasibility of a radioisotope positron catalyzed fusion propulsion concept that does not rely on trapped antimatter. Positron Dynamics plans to generate an intense beams of cold positrons using an array of moderators. They use a radioisotope as a source of positrons.

NASA NIAC phase 2 funding for hybrid Fission-Fusion propulsion. This would uses Z-pinches to acheive 30,000 ISP.

Mach Effect Propulsion with NASA NIAC phase 2 funding

For Mach effect propellantless propulsion, it will be better to go to an array of smaller devices.

Woodward, Fearn and SSI expect within 1-5 years to get to 1-5 millinewtons of thrust. They will use better materials and other near-term design improvements. NASA NIAC has given a $500,000 two year phase 2 funding. This may speed up the new materials work and enable the 5 millinewtons of thrust to be achieved within 2 years.

In 5-10 years, have an array of several devices to get to 10-20 millinewtons.
10-20 years, increase thrust to one newton per device.
Test arrays of a hundred one newton devices
In 25 years, the MEGA space propulsion could scale to 1000+ of one newtons devices.

The Brachistochrone orbit travel time columns in the following table describe the trip times within the solar system.

1% acceleration is the fourth column with 0.01G of constant acceleration. This could be 6000 Newtons of thrust with a MEGA drive but a 60-ton spaceship. Anywhere in the solar system out to Pluto within 11 months.

The next column with 0.1G of acceleration could be 60,000 Newtons of thrust and a 60-ton spaceship. Anywhere in the solar system out to Pluto within 4 months.

The next column with 1G of acceleration could be 600,000 Newtons of thrust and a 60-ton spaceship. Anywhere in the solar system out to Pluto within 35 days.