JP Aerospace is America’s other Space Program, independent of NASA. They have a unique approach for reaching space that doesn’t involve high-powered rockets or high “G” forces: a series of blimp-like airships and stations.
Excerpt from ATO — Airship to Orbit (PDF):
The first part is an atmospheric airship. It will travel from the surface of the Earth to 140,000 feet. The vehicle is operated by a crew of three and can be configured for cargo or passengers. This airship is a hybrid vehicle using a combination of buoyancy and aerodynamic lift to fly. It is driven by propellers designed to operate in near vacuum.
The second part of the architecture is a suborbital space station. This is a permanent, crewed facility parked at 140,000 feet. These facilities, called Dark Sky Stations (DSS), act as the way stations to space. The DSS is the destination of the atmospheric airship and the departure port for the orbital airship. Initially, the DSS will be the construction facility for the large orbital vehicle.
The third part of the architecture is an airship/dynamic vehicle that flies directly to orbit. In order to utilize the few molecules of gas at extreme altitudes, this craft is big. The initial test vehicle is 6,000 feet (over a mile) long. The airship uses buoyancy to climb to 200,000 feet. From there it uses electric propulsion to slowly accelerate. As it accelerates it dynamically climbs. Over several days it reaches orbital velocity.
According to the ATO document, they should reach their goal in only 7 years using currently available technology.