The UltraLight project would have the simple but challenging objective of developing a ‘minimalist’ rocket based workhorse launch system that can provide unmanned LEO-capable payload support to Modular Unmanned Orbital Laboratory - MUOL development and early Bifrost Space Elevator development. Seeking to realize a lowest-cost system, the UltaLight would employ both alternative vehicle design focused on easy mass production and minimal ground support and a strategy of high acceptable failure rates for low value commodity payloads. In this context it would be somewhat competitive with the MODroc and Exocet projects but may precede them, growing out of work of the Open Space Project, and may seek an even lower unit vehicle cost at the compromise of an initial, perhaps perpetual, limitation to low-value payloads –water, air, raw materials, construction components, and food supply.
Key to this is the notion of high acceptable failure rate. Most spacecraft are designed and built with the notion that failure of any kind is unacceptable, and so they become complex to both engineer and produce due to the extreme effort to build in perfection and fail-proofing. But in the industrial world there is a notion of ‘acceptable yield’ for products that are difficult to make but where unit production costs can be kept low enough that the waste from failures is cost-nominal. For instance, for a very long time the acceptable yields of production for many advanced Liquid Crystal Displays was an astounding 50%. The tolerable market price of these displays was high enough that, compared to the unit production cost, a waste of half of the production was still acceptable. This is not that unusual, even if this is one of the more extreme examples. Most forms of industrial production produce a certain portion of failures that is considered acceptable. So why then is this not also the case in commercial space? Largely because the payloads common today have such extremely high values while rocket failures tend to be especially spectacular and newsworthy. But in the coming era where space structures are increasingly built on-orbit rather than launched whole, and where launches are done increasingly at sea where they pose little to no hazard to people living along their launch trajectories, the value of many payloads will decline along with the need for perfection. Some proponents of very low cost launch systems have postulated that in this context, and given an unmanned system with vehicles of sufficiently low mass production cost, a 1/3 failure rate would still present an acceptable yield. Given the ability to recover lost vehicles for materials recycling, this would also incur a minimal environmental impact. This, then, is the UltraLight’s basic goal.
Building on the experience of the SkyScraper project, the UltraLight would employ a novel combination of pneumatic fuel tanking, simple space-frame structure, and the elimination of control surfaces and mechanical thrust vectoring through the use of a radial aerospike engine. Designed to support payloads based on the type of ‘pallet module’ employed by the MUOL, the UltraLight would employ a core truss – possibly with widened end sections and potentially using pneumatic struts or a tensegrity structure employing nanofiber– with a pallet payload carrier at one end and a radial aerospike engine made using a monolithic fabber-produced ceramic composite. A cylindrical pneumatic oxidizer cell made of flexible composites would be installed in the interior of the core truss while a toroidal cylinder pneumatic fuel cell or array of cylindrical tanks with a membrane streamlining skin would be attached to the exterior. Small spherical composite nitrogen tanks placed in interstitial spaces – along with most of the other active components – would supply gas to maintain continuous pressure in the fuel and oxidizer tanking. A rigid composite nose cap extending to the edge of the outer fuel cell and a thermal insulation blanket on the bottom surrounding the aerospike engine faring would provide streamlining of marginal mass, producing an overall form akin to a squat cylinder. A low launch stand in the form of a frame in a truncated cone shape and with a deflection cone in its bottom-center would support the vehicle for launch from any flat surface. Though not as streamlined as typical rockets with its rather squat shape, the design is intended to maximize the ease of fabrication (and minimization of fabrication facilities) and ground handling while being engineered to ‘muscle’ its way through the short period of trajectory in dense atmosphere thanks to the better performance of its engines at high atmospheric pressure and their very quick non-mechanical attitude control response.
This would be a highly experimental concept for rocket construction at the start and so much experimentation with variant configurations are likely, possibly resulting in a form very different from what is suggested here as one likely possibility. For instance, super-pressure pneumatic rigidization of the fuel cell envelopes by virtue of Kevlar or later nanofiber composites could be sufficient alone to eliminate a core truss, replacing it with short truss pallet frames at either end to interface these tanks to payload and engine modules. The use of homogeneously fiber reinforced structural foams is another possibility. Time will tell. But the basic idea here would be the same throughout: to reduce the cost of fabricating and deploying a launch vehicle to where it’s truly a nominal expense relative to the cost of payloads, making a modest yield of launch success practical for basic supply delivery.
- Mountain Waverider
- Marine Mass Launcher - MML
- Bifrost Space Elevator
- Bifrost Support Systems