Perhaps orbits are overrated. How high could a craft eventually go if it could always maintain a propulsion force of 9.82m/ss?!
If you could just get some kind of thermonukleer rocket with about a hundred thousand times the specific thrust of chemical rockets, then everything becomes (almost) easy.
Ascend to medium earth orbit in 40 minutes, never exceeding 1.3 felt G's, never exceeding 100 M/S in the lower atmosphere. Most of the structural and aerodynamic constraints on the vehicle are removed; it doesn't have to look much like a "rocket" any more.
Reentry? Come back down the same way you went up. Slowly, with rockets burning. None of this fireball-with-thermal-tiles crap.
And you do this by using a few KG's of fuel. The lifting platform is mostly structure and engines, and up to half payload (including human environment, if manned).
And for a few KG more fuel and human provisions, why stop at orbit? A craft like this could take you to the Moon or Mars, and back, almost as easily.
Just a small matter of getting that nukleer rocket technology--and figuring out how to take off and land without burning a hole down to the middle of the planet.
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