The ship described at BuildTheEnterprise is at its core inspired by the Star Trek science fiction ship named the USS Enterprise with registry NCC-1701-x (where x can be left blank, or be A, or B, etc.). However, many changes are needed inside the Gen1 ship to make the ship compatible with the technologies of the first half of the 21st century. Keep in mind that the Star Trek adventures in the NCC-1701-x Enterprise ships take place starting in the year 2245. Our technology today is just not up to building a starship; that will have to wait for a Gen4 ship or later.
But this doesn't mean that the Gen1 Enterprise will not be awe-inspiring and similar in many fundamental ways to the Enterprises of the future. The Gen1 Enterprise will be the same size as future Enterprises or larger. It will have 1g artificial gravity like the future ships and ample comfortable living space. It will have a bridge with 1g gravity where the captain and key crew members will often work. It will have a huge number of sensors for probing whatever the ship encounters in space. It can launch landers that descend to a planet below and then return to the ship. It will move beyond the brute-force rocket engines of the 20th century by using ion propulsion engines powered by on-board nuclear reactors. Yes, this may still be a long way from warp drives powered by anti-matter, but it will be a respectable start.
Things get moved around and reworked quite a bit inside the Gen1 Enterprise compared to the Enterprises of Star Trek. For example, in the NCC-1701-x ships the hangar deck is located in the back of the lower hull, as seen in the figure above, and this serves as the launch and entry port for shuttlecrafts. But in the Gen1 Enterprise this lower hull section instead houses the main engine and main nuclear reactor. For the Gen1 ship, the spaceport entry doors are on the underside of the saucer hull. The reason for this is that in the Gen1 Enterprise every bit of the three hull sections to the rear of the Enterprise are needed to house the three engines and nuclear reactors that will be needed to provide enough power to move the massive ship with the required .0001g constant acceleration.
Another example of a change is that the bridge is not at the top center of the saucer hull as it is shown in the figure above. If it was there in the Gen1 Enterprise then there would be no gravity on the bridge. Having the ship's captain and crew floating around inside the bridge just makes no sense. Thus, in the Gen1 Enterprise the bridge is in a dedicated section of the gravity wheel so that they will work in 1g gravity.
While things get moved around quite a bit inside the Gen1 Enterprise when compared to the ships from Star Trek, they are not moved around upon a whim. They are moved around because the Gen1 ship's technological capabilities demand certain changes.
Check out this site about building a Star Ship Enterprise with today’s technology. It is interesting to consider what we could really do.