Supersonic Transport vehicles will be needed IF we plan to perform interspace transport, as a vehicle will need to
accelerate to supersonic speeds to gain access to transport transfer stations in low orbit, then return with passengers.
These may not be very big, limited to mabye 20 passengers and crew for sub-orbital short term docking
& personel transfer with glide path return to earth station terminal ports.
I don't see them as a 'shuttle' like vertical launch operation consuming vast amounts of fuels to reach a service orbit,
but more of a 'piggy-back' platform where a mother ship takes off conventionally from a space support operations port,
flies to high speed and altitude and then releases it's corrier craft with an aerospike hypersonic drive engine to
acheive a velocity that will allow it to climb & shortly hesitate in space at the upper terminus of earth's gravity well.
duration without docking would be under 30 minutes in the proximity of a pre-positioned space port station.
Mechanical docking before orbit decay may extend it's linger time to over an hour becore breaking contact and re-entry of the vehicle.
The orbiting station will loose energy from each docking with a transport vehicle and will have to be re-accelerated daily to extend it's orbital capability.
We should be able to place and maintain orbital mechanics in the 350 mile altitude range and reach that position rather easily.
For example: most ICBM missles are flown to reach an altitude of approximately 750 miles before positioning
and release of the RV warhead, and from launchg/boost to final impact takes 25 minutes or less.
The Shuttle itself has effectivley reached it's low orbit position in 9 minutes from launch.
We should be able to use a combination of mother ship to carry a transport vehicle to altitude in less than 20 minutes,
Aerospike thrust to reach 5,000 MPH & inertial coasting to reach nearly 100 miles altitude in another 10 minutes,
then the use of peroxide reactors (or hypergolic engines) to intercept and dock with the station in another 15 minutes or so.
Food for thought - technically we can do this now, (Rutan proved it) but the orbital transfer platforms have to be there first.