Don't reinvent the wheel revisited

I didn't know this before I wrote the original post- that the shuttle external tank reaches 98% of orbital velocity.  With a little more power, it can get into orbit instead of being sent back to a fiery doom during reentry from space.  So, why not use this as a resource as opposed to wasting it?  That's what I was writing about before, so I'll return to that subject again.

The Augustine Commission considered a Shuttle derived system as one of the possible heavy lift vehicles that will replace the Shuttle.  With a little less mass, as would be the case without a shuttle to put into orbit, the Shuttle derived system could reuse its external tank.  Since the tank already has 98% velocity with more mass, the reduction in mass (from not having to lift the shuttle) should make virtually the entire system  reusable.  But not as it is.  Once it arrives in space, it will need a little work to set it up as a permanent facility in space.

The external tank can be remodeled into a useful bit of machinery that could save a lot of money and do something useful.  Instead of putting extra rocketry on its sidemount, it could carry equipment and supplies that would be transferred to the inside of the tank so it can do the remodeling job.  How can you do that?  Well, I think that it would take a few modifications to the external tank in order to make this possible.  You would need to make a large door at end of the tank so that stuff could be put inside the tank after its launched into space.  Think of it as a hood and/or trunk type setup.

Each subsequent launch would add more equipment and supplies, but not a duplicate of what was sent earlier.  Instead, after the first tank was finished, launch the next tank into space.  Transfer the equipment that was no longer needed on the first, and equipment from the second is tranferred to the first for further work on the first.

In such a manner, an assembly line could be set up in space which would build a fleet of large habitats in space for future missions.  All that would be required after construction of one habitat is for a crew to come up in a separate vehicle and transfer to the large habitat.  Not only would the big external tank be a habitat, it would still have a large powerful rocket that could take it on missions back and forth.