On June 17, before the Augustine Commission, Shuttle Program Manager John Shannon described this "Sidemount" development of the Space Shuttle. This is very similiar to Shuttle-C, a cargo version of the Shuttle that was unfortunately never built. By removing the winged orbiter, Shuttle-C could bring twice as much payload to orbit. ISS could have been built with half as many launches and less risk to crews. When Norman Augustine was proposing a course for NASA 20 years ago, Shuttle-C was part of the plan.
The Sidemount booster uses components that are proven and human-rated, like the standard External Tank and 4-segment Solid Rocket Boosters. Because so much is common with Shuttle, this could be built for about 6.6 billion, far less than Ares I. The huge, expensive Ares V would not be needed. Instead of one big and one little rocket, a Moon mission would require 2 launches of one medium-sized booster. Orion would launch with an extra stage to boost the crew into lunar orbit, where it would rendezvous with the lander. Launch Complex 39 and much of the Shuttle workforce would be maintained.
There are some tradeoffs: The weight of the lander is reduced from 48 tons to 28 tons. The Apollo Lunar Module weighed 16 tons. There is a question whether the Space Shuttle Main Engines would be used, and whether those engines would be recovered after flight. Putting an escape tower alongside the External Tank could raise separation issues. At first glance, the Sidemount appears to offer many advantages over the current Constellation architecture. In a limited time of limited budgets, this proposal needs to be examined seriously.