NASA NIAC 2020 virtual meetings has an update on the affordable SGL (Solar Gravitational Lens) mission architecture design.
National nonprofit The Aerospace Corp the Solar Gravity Lens concept received a phase III $2 million grant by NASA’s Innovative Advanced Concepts program. They described a roadmap for building the required SGL mission capability, beginning with a technology demonstration mission in the 2023–24 time frame.
It reduces cost:
1) It cuts the cost of each participant by enabling multiple entities broad choices of funding, building, deploying, operating, analyzing system elements at their choice.
2) It delivers economy of scale in an open architecture designed for mass production to minimize recurring costs.
3) It drives down the total mass (and thereby both NRE/ recurring costs) by using smallsats.
4) It uses realistic-sized solar sails (~16 vanes of 10^3 m^2) to achieve the needed high velocity at perihelion (~150 km/sec).
5) It applies maturing AI technologies for virtually autonomous mission execution eliminating the need for operator-intensive mission management,
(6) It reduces launch costs by relying on “ride share” opportunities to launch the smallsats, avoiding the costs of large dedicated launchers.