A little backstory: when I was in grade school I remember a big to-do about the space shuttle (Columbia?) being shipped from one launch pad to another, I think from Florida to California. The shuttle was simply set right on top of what must’ve been a Boeing 777, as it can’t take off like a plane.
My 7-year-old mind just assumed that those smart astronauts just figured a better way to launch the shuttle: just strap it onto the back of a plane, plane goes up, up, up, shuttle get out of the atmosphere, they cut the lines, and presto! it’s in orbit. I was baffled to learn that it was just a means of transport, and that puzzlement has always stuck with me.
Obviously a 777 isn’t really equipped for extreme altitude flight, but a plane could be modified for this, even with liquid fuel rockets in low orbit. My question is this: wouldn’t it expend less energy to launch this way rather than starting from a dead stop and shooting straight up? It seems that with the fuel burnt in the first 15 seconds of a normal launch you could fly a plane (yes, even a very heavy one) for a considerably long time/distance.