Being a member of a space advocacy group and long having an interest in Futurist subjects, I've long been concerned with the problem of economical access to space. But my approach to this problem has tended to be very different from most. Whereas most space advocates are very focussed on visions of elaborate reusable spacecraft intended to send masses of human beings to space, I have been more concerned with how to make space accessible to the small businessman and university researcher. My reasoning is that space development is critically contingent on the ability to demonstrate many ways to earn a living there and to date only one use of space has ever proven profitable; satellite telecommunications. The US space program has long overlooked the significance of space industrial research in favor of grandiose Big Science projects which rationalize manned space flight and large budgets with a kind of circular reasoning. But with a sustainable future in space dependent on being able to commercially exploit it, what is needed is a platform which enables small business -which is responsible for 70% of all technical innovation- to conduct basic industrial research at the lowest possible cost. Thus I have developed a great interest in the concept of ultra-light spacecraft intended to deploy small payloads with a high degree of convenience using technology accessible to the small business.

For a long time I puzzled over what might be the simplest and lightest form for a spacecraft. I long ago realized that spacecraft are, in fact, more like railway systems then they are like aircraft with the vast majority of their operational cost invested in stuff on the ground rather than in the vehicles themselves. If one is to minimize the cost of spaceflight it is the systems on the ground that need to be simplified the most and that means a vehicle system which is very simple to fabricate and very simple to launch.

Conventional rockets are fabricated using the Jet Age technology of welded stressed-skin monocoque hull systems which -truth be known- is a technology whose origins go back to the most ancient sailing ships. It's quite effective but complicated to fabricate, requires more sophisticated engineering the more you push strength-to-weight ratios to the limit, and difficult to devise modular component systems for. It use has been predicated primarily on the premise that a launch vehicle is an aerodynamic container -like the fuselage of an airplane- for its propulsion systems and payloads which must assume a vertical configuration at launch and withstand tremendous loads as it is pushed up from the bottom. This is an architecture which, obviously, pushes the monocoque technology to its practical limits and results in a system which needs extremely sophisticated engineering and manufacture supported by elaborate ground support structures and systems.

I wondered if there were a way to make use of much simpler and more easily modular structural systems and to overcome the need for streamlining, seeing as the period a spacecraft spends in aerodynamically significant atmopsheric density tends to be rather short. Was there a way to make a spacecraft that was inside out? In other words, instead of making a vehicle that is a container for propulsion systems and payloads, could one make a vehicle that was a simpler skeleton structure onto which a payload was attached? In other words, could one evolve the spacecraft into a simpler form in the same way the catamaran or outrigger canoe evolves the mono-hulled sailing ship? And could the spacecraft assume a self-stable form that eliminates the need for complicated ground facilities? Could we make a technology simple enough that one could drive a truck out to a field, unload and plug-together a set of parts, and put a payload into orbit?

Inspiration for such a technology came from the unlikely source of a peculiar musical piece by the composer John Adams and an album called Hoodoo Zephyr. From the moment I heard the first piece on this album the composition seemed to me like some curious soundtrack for a documentary on space travel, evoking the vision of a menagerie of spacecraft. The last title piece, however, inspired a vision of something that was quite new to me. I imagined a caravan of vans and trucks converging on the center of a dry lake bed, deploying a village of temporary structures in the center of which was assembled this improbably machine akin to an airship. Upon completion, this vehicle was released into the air and began a journey to the stratosphere which culminated in the firing of small rockets and the rising of the machine above the arc of the Earth and off into space.

It was from this vision that devised the concept of a dirigible launch system called SkyScraper, my speculative designs dubbed Hoodoo Zephyr in honor of their inspiration. A number of experiments have been done on the technology of balloon assisted rockets, the basic premise being that by getting above the bulk of the atmosphere two basic performance bonuses are gained; the elimination of energy losses due to atmospheric drag and the reduced mass and increased performance of rocket engines which do not have to cope with varying air pressure. But there are some other very significant benefits. Elimination of drag means reduction in sheering forces on the structure of a launch vehicle. This, in turn, means that streamlining is no longer critical and a spacecraft no longer needs to take the form of a container to shelter its components and payload. This further reduces the mass of the vehicle making the performance of supporting structures less demanding and allowing them to be simplified. This gives us the option to create a vehicle based on a light open space frame structure to which the functional components and payload of a spacecraft can be individually packaged and retrofit. This would allow for construction based on modular interchangeable components which can be mass produced and varied in number, type, and scale to suit different payloads.

The key, though, is to conveniently get this vehicle to the edge of the atmosphere where all these benefits can be exploited. The balloon assisted launch experiments relied on the use of conventional super-pressure balloons which dragged a small conventional rocket behind them on a cable. On the moment of launch the rocket was disconnected and pierced and exploaded the balloon which was designed to rupture in a safe fashion. This approach is not very effective for a larger more complex vehicle and doesn't get the vehicle to the very edge of the atmosphere thus I devised the concept of a system of modular tensegrity structure vacuum dirigible cells with a metalized mylar skin which could be attached to the structural space frame just like its other components, making the vehicle into a rigid core dirigible airship. These cells transition from a lighter-than-air lift phase to a vacuum lift phase as the vehicle ascends -such light materials being unable to contain a vacuum at sea level but quite capable of it at stratospheric air pressures. Upon reaching maximum altitude, the vehicle would assume a horizontal attitude and then ignite its rocket engines for a slow low-g acceleration to orbital velocity, providing a much safer flight for more delicate payloads.

Since the mass of the lift cells is marginal and they present no problem of air resistance when the vehicle is launching from the edge of the atmosphere, they could either be jettisoned as the vehicle reached sufficient velocity or they could be retained on the flight to orbit, perhaps serving additional duty as a mount for flex-cell photovoltaic panels, components of a solar thermal power system, or as a possible component of a pneumatic re-entry shield system -though in general I was not concerned about the vehicle being reusable at all.

While working on a practical design for this spacecraft I also devised the concept of a tractor engine strategy rather than the conventional pusher engine approach, the rocket engines taking the form of a set of nacels on booms near the middle or front of the vehicle. Pulling is more efficient and stable than pushing and so by placing these engines more forward further power-to-mass performance might be gained. But this presents the problem of pumping against inertial forces, though this is not a great problem for this kind of spacecraft since it would launch in a vertical position and have a slow rate of acceleration. Still, looking for a way to make this issue as nominal as possible I have considered the possibility of using rotating engine booms with a simpler gyroscopically fed electric arc driven rocket engine. Such technology has already been demonstrated by the Roton rotary rocket project. An additional benefit from this is that it offers a very effective thrust vectoring system by electronically varying the engine thrust at different points during the revolution of the booms. This would afford further reduced mass due to elimination of turbopumps, greater attitude control, while also presenting the interesting visual effect of the spacecraft being pulled along by a halo of fire around its front. A most unusual looking spacecraft indeed!

The SkyScraper launch system is basically intended to provide a platform for deploying small relatively light or very fragile payloads to LEO using an extremely cheap disposable vehicle that needs very little on-ground launch support. The vehicle could be readily fabricated with fairly low-tech aircraft component fabrication capability and assembled at launch point from quick-connect parts easily shipped and transported anywhere by conventional means. It needs no special launch facilities and, since it's rockets are never fired until it is airborne and are small to begin with, it presents no particular hazard to residential areas near its launch point. It could literally be built on a college campus and launched from its football field. Though not intended to be reusable, it may offer this possibility through the use of the recently developed pneumatic reentry shield technology which would exploit the vast area of the lift cells as a huge heat sink to safely disperse the great heat of atmospheric friction. Of course, since it would retain vacuum lift buoyancy during reentry this process is a much less demanding one of aerobraking rather than full reentry, the vehicle simply skipping lightly around on the edge of the atmosphere until it slowed to a stop and descended by taking on air ballast. It's certainly no alternative to the Space Shuttle but then the Space Shuttle has little relevance to small business commercial use anyway. It's job is to make doing research in space as cheap as possible so that products for space-based manufacture can be developed and create a practical purpose for pursuing the development of more robust launch systems.

I have presented this spacecraft concept to the NASA Advanced Propulsion Technology office and they confirmed that it was in fact technically feasible and worth further study. Unfortunately, as with all my other interests, this has been forced to take a back seat to my quest for non-toxic housing.