Designing the Type-6 Shuttlecraft - By Andrew Probert.
When Star Trek: The Next Generation debuted, everything was redesigned, including the shuttlecraft. The job of updating Walter 'Matt' Jefferies' classic design for the Galileo was given to Andrew Probert, the man who had reinvented the USS Enterprise NCC-1701-D.

Andrew Probert was no stranger to designing small Federation ships; 10 years eariler, he had created the Vulcan shuttle and the Work Bee for Star Trek: The Motion Picture. In fact, even before he was asked to design a shuttle for the new Enterprise, he'd thought about updating his Work Bee concept. "I came up with these small service craft, which Herman [Zimmerman] nicknamed the Sphinx. This would be an extension of the Work Bee, it was designed to be basically a pickup truck that could be used for different purposes." The Sphinx workpods never made it to the screen, but they are still an official part of Star Trek because Rick Sternbach included them in the 'Star Trek: The Next Generation Technical Manual.'

When Probert turned his attention to the shuttle, he reasoned that, since the shuttles would have to make interplanetary journeys, they would need warp engines and all the components associated with them. "I tried to address the fact that the shuttles would need a smaller version of the warp core, so I provided a back section that would have a core in it. My thinking was that there would be an operator's cab separated by a wall that would have the ability to project a barrier in that open area if they needed to seal off the back space." In an effort to make the new shuttles more interesting, Probert originally planned to move the entrance from its traditional position at the side. "Entry into the shuttle was by the front; there's a ramp that lowers between the two operators. The top portion of that would actually slide up - much like a sunroof does on a car - allowing the people to walk straight up into the shuttle between the operators." This shuttle design was approved, but when it was sent down to the construction shop it encountered some unforseen problems; the extremely curved design was simply too difficult for the carpenters on the lot to build at life size. As a result, the design had to be rethought. "They built a shuttle that basically had square edges on it. It was kind of my shape from the side, but it had square edges. Then they came up with the idea of getting into the shuttle from the side." The finished shuttlecraft first appeared in 'Coming of Age'; it was eventually superseded by an even boxier design, but it established the basic design direction for almost all the shuttles we've seen since.
"DESIGNING THE TYPE-6 SHUTTLECRAFT" - JANUARY 2001 ISSUE 21 STAR TREK: THE MAGAZINE COPYRIGHT OF PARAMOUNT PICTURES.