Lightcraft

As with the orbital-ring, ProjectRho does have a placeholder for the Lightcraft... but that's about all it offers, sketches. As we await new content over there, and for that matter at the ToughSF / Matter Beam blog, ToughSF happens to run a Twitter account... hence how I found out about this.

The Lightcraft is a revolutionary design from 1987-8 in the wake of the Challenger disaster. Dissidents in NASA proposed to replace the Shuttle with something cheaper. As in... a LOT cheaper. It also borrowed design from the Apollo project, back when NASA were getting stuff to work right.

You can read the 166 page spec at archive.org. Assuming Earth: The gross liftoff mass is 5550 kg, of which 500 kg is the payload and 300 kg is the LH2 propellant. The first stage is retrievable (after burning through its fuel). So they were promising payload delivery cost of $3.11/lb meaning $6.86/kg in Reaganbux. (Their metric was the 100kg "person", kek.)

That propellant wasn't even to go to its maximum aero (Mach 25!). The liquid molecular hydrogen was to boost from aero to orbit. Honestly I would not be married to that propellant. Launch could be cheaper overall with the newer propellants or just Elon's methalox. UPDATE 12/15: If we have an eccentric-orbit tether we might not need even that. UPDATE 1/18/21: The Ionic Ramscoop? ...anyone?

As to why nobody picked up on the Lightcraft plan, well... it needs external platforms to fire lasers at the stratosphere, to get this thing to that Mach 25 (where I guess the ramscoop might take over). Quite a few moving-parts, here. Jordin Kare in 1991 followed up with a laser thermal rocket a.k.a. the heat exchanger (HX) thruster ... but it hasn't been much looked-at, since.

The researchers were hoping to get those lasers into space - eventually. I imagine the Soviet Union although moribund would have objected to space lasers penetrating near to spyplane- and scramjet-altitude. I know that horrible movie Real Genius so objected.

Mainly I suspect that "in the wake of the Challenger" also meant (ironically perhaps) more conservatism at NASA and less general interest in alternatives to NASA. So all we got was a safer Shuttle. Until, you know, that second disaster, two decades later.

Times have changed and the present concern is, how to compete with the Starship. For that, the Lightcraft may find its niche. We might not need ground or space platforms if we can float the laser(s) on balloons right up close. Or fly them on Aether. Nuclear ramjets, if over Venus.