A spacecraft that can provide the propulsion necessary to reach other planets while also being reproducible, relatively light, and inexpensive would be a great boon to larger missions in the inner solar system.
The idea is called Hummingbird, and it’s basically an engine and fuel tank with slots in it for mounting CubeSats. The whole thing was set to weigh 80 kg fully-fuelled. The idea, however, is eleven years old and nobody tried it. I imagine it’s being resurfaced now because people are thinking about the US presidential transition and the seesaw potential between either NASA getting superfunded or being essentially folded into a superfunded SpaceX. If you want to make a future NASA-as-SpaceX-service still look like NASA, lofting a hundred cheap exploratory probes looks virtuous and science-y.
Maybe they can go and find dark comets.
Like the Saunders-Roe test site at High Down, the Ansty (space rocket) test bed used thousands of gallons of water running through a curved duct to soak up the heat from the engine. Huge columns of steam rose up into the Midlands sky. There were occasional complaints from the maternity hospital nearby, not about the danger, but the noise. Sometimes, if a cloud already heavy with vapour passed overhead, the extra steam was just enough to make the droplets precipitate out and start a very localised shower. One memorable day, an inspection team from the Ministry of Supply were soaked by a downpour a hundred yards across and never wondered why they had been placed at that exact spot on the tarmac to witness a firing.
BACKROOM BOYS, Francis Spufford