Maybe they could point it towards a spacecraft to get above Low Earth Orbit. The idea here is to get high ISP and high thrust directed at a spacecraft in order to increase useful mass fraction.
It would work on similar principles as the nuclear thermal, but instead of nukes doing the work, a solar thermal solution is employed instead. This would be a variation on the Parkins device.
A solar collector as described in an earlier post would supply the energy. It would focus the energy on an aeroshell, which would get heated up to high temperatures. Liquid hydrogen would be used to keep the aeroshell from melting, and the heated hydrogen would be used as the reaction mass.
An ISP of a thousand seconds would reduce the amount of fuel needed. Compared to a hypergolic engine used in Apollo the mass fraction might well be tripled.
If a fast transit to Mars is desired, then one can post it at a LaGrange point, and have to accelerate the spacecraft to Mars at a high velocity. Perhaps it would get there in 45 days.
The spacecraft could be kept light, so the amount of fuel would needed would not be excessive. However, you'd need to slow down once you got there. Therefore, post another one at one of the Martian moons that would slow down the spacecraft once it got there.
The idea here is really to use the sun as the energy source as opposed to onboard fuel. You'd need a series of "stations" that would boost the spacecraft up from low orbit, and from there to interplanetary destinations. At the destination, you could have a station that would help the craft slow down in the same manner-- a retro rocket type deceleration maneuver.