Another concept likely to be of interest at a very early stage of the Bifrost program, the Mountain Waverider would employ the same basic philosophy of the SkyScraper but would employ a natural phenomenon as a means to achieve a stratospheric altitude. In a number of parts of the globe there exists a natural phenomenon known as the Stratospheric Mountain Wave. It is a natural updraft of such size and power that it throws a column of air right to the edge of space. Scientists have proposed the development of large sailplanes based on conventional sailplane technology that would be designed to ride these mountain waves in order to reach the stratosphere for the purposes of performing high-altitude research.
The Mountain Waverider would employ this same strategy with the intent of reaching orbital space, combining a largely conventional but minimalist sailplane structure made with conventional carbon composites with a simple rocket or SCRAM jet thruster to create a very compact spacecraft that would ‘surf’ a natural mountain wave to get it to a stratospheric altitude and fairly high velocity, then launch to LEO on a long period modest acceleration trajectory. Initial flight would rely on a tow vehicle. During launch the vehicle would rely on Doppler radar guidance from ground support vehicles to aid it in profiling the mountain wave it rides in 4D so that guidance computers can optimize its climb and velocity along its flight path. The Mountain Waverider would be a minimalist system and so would not be able to carry large payloads in a conventional sense. Instead, it would seek to employ every portion of its sailplane structure to double-duty, turning it whole into a satellite or research platform. This would be accomplished by such schemes as applying flex cells to its wings to turn them into solar panels, using its tubular tail member as a fuel tank and antenna array, and using its forward gondola as an equipment chassis with opening or ejected top and bottom cover panels or designed as a detachable ballistic re-entry capsule.
Because it would employ a not entirely reliable natural phenomenon for launch assist, the Mountain Waverider would not be suited to a regular launch schedule. And since even the largest of conventional sailplane structures would have relatively limited payload capacity, it is not likely to be usable for more than LEO access or for more than a single human passenger, if any. It would also not be a reusable vehicle – any passenger variants likely needing to employ a gondola designed as a simple ballistic re-entry capsule. But it could prove very practical as a research platform that can employ modest scale fabrication facilities, might spawn a new generation of personal manned rocketry, and would provide valuable experience with composite structure and propulsion engineering. Again, this is a launch system potentially achievable for the university or space advocacy group.