There is a little known and poorly understood natural phenomenon that was discovered late in the 20th Century which offers the possibility for a very unusual and compelling elegant way of reaching space. It is called the Stratospheric Mountainwave and consists of a natural updraft of such scale and force that it blows air like a fountain well into the stratosphere. Though much is still unknown about the physics of this phenomenon, it is known that mountainwaves are a fairly frequent occurrence and appear in larger numbers in certain areas near the Equator. I first learned of this phenomenon from the NASA Tech Briefs journal in which was published a short article on research by a meteorologist who was proposing the adaptation of a conventional sailplane so that it could ride these mountainwaves and gain access to the stratosphere for atmospheric research.

This got me thinking. I have long had an interest in the development of ultra-light spacecraft which would allow cheap access to space for small payloads at a cost that could be affordable to small business and universities. Key to achieving this is being able to simplify the form and operation of a spacecraft so that it has the minimum operating overhead on the ground. With my SkyScraper dirigible spacecraft concept this was achieved by exploiting the ability of lighter-than-air lift to get a spacecraft to an altitude where atmospheric drag was so reduced that an ultra-light and modular spacecraft structure could be used while allowing a safe low-g acceleration to orbital velocity by simple and small rockets. By exploiting the Stratospheric Mountainwave it might also be possible to achieve this same thing using a smaller and even simpler vehicle, albeit one so small as to be limited to perhaps only a couple hundred pounds or so of payload.

This system, which I dubbed the Mountainwave Rider, would consist of a fairly conventional sailplane of the usual composite construction. However, it would feature a tail fuselage containing a solid rocket booster and a forward capsule designed for separation like the payload capsule of a conventional rocket. Piloted by remote control using a ground based guidance system equipped with an array of dopplar radar sensors, the Mountainwave Rider would cruise around a region prone to mountainwaves -perhaps being towed by a conventional powered aircraft- until it encountered a mountainwave of sufficient potential power and altitude in the path of a suitable launch vector. It would then enter this massive updraft and 'surf' it to the edge of the atmosphere whereupon it would ignite its rocket engine and, using its slender wings to skip at the edge of the atmosphere, accelerate to orbital velocity.

The obvious limitation of this technology is that launches occur on Mother Nature's schedule since it relies on the random occurrence of mountainwaves. This requires that the launch team and vehicle operating in a 'cruising' mode for days or weeks and then scramble to intercept an appropriate mountainwave encounter. But in an age where launch payloads typically wait years to get to the launch pad, this is not a terribly great problem and, since the vehicle itself never expends fuel or the like as it cruises and can be brought safely back to the ground and re-launched any number of times, there's no particular hazard to the payload. And ground facilities are quite minimal. A launch tow plane, a hangar, and a portable command center and atmospheric scanner system accommodated by a few trucks is all that would be needed.

To maximize the utility of such a small spacecraft I also considered the idea of using more of the flight structure as integral components on-orbit. This would be particularly useful with a microsatellite platform. The tail section of the spacecraft could double as a telecommunications boom with tail fins articulated and fashioned with integrated antenna components. The long sailplane wings could be mounted on articulated joints and covered with photovoltaic flexcells to serve as solar power arrays. There is also the intriguing possibility that this vehicle, in its largest form, could serve as a single-man launch vehicle with a front gondola capsule designed to function as a ballistic reentry capsule. This might be marketable as kind of sporting spacecraft or used as an emergency launch vehicle. One can imagine a new form of sport competition based on a race to be the first amateur astronaut to orbit the Earth.

The most compelling aspect of this concept is that this is a spacecraft which, potentially, could be developed by any of the hundreds of companies which today now make conventional sailplanes, since it is a derivative of conventional sailplane technology. But much more research needs to be done to determine the feasibility of this concept, work which I sadly do not have the time for at present.