NASA has accepted the greatest challenge in its history — the Vision for Space Exploration (VSE). With the Ares and Orion projects, the flagships of the future exploration fleet are taking shape. What NASA should not overlook is the contributions to be made by spacecraft at the opposite end of the size scale.
A program of long-term exploration, as opposed to an Apollo-type sortie, requires scouts, rescue parties and other ancillaries to support its main parties and bases. In the VSE, many of these roles are well suited for spacecraft in the 100-kilogram or smaller range. The need to provide unprecedented capabilities with minimal launch mass and manageable cost should drive planners to thoroughly examine the potential role of microspacecraft throughout the VSE.
In a recent paper for the American Institute of Aeronautics and Astronautics/Utah State University Conference on Small Satellites, we dubbed microspacecraft doing VSE tasks Pioneering Robotic Microspacecraft Scouts (PRISMs).
The PRISM concept, based on a VSE architecture using the optimal mix of large and small spacecraft, suggests the best approach would be to have a single entity examine microspacecraft utility across the breadth of the VSE and guide the development and integration of microspace technology as that architecture evolves. The existing guidance for the VSE has a number of requirements for which PRISMs could be candidate solutions.
First, PRISMs could inspect the exterior of larger vehicles (crewed and uncrewed) for damage. This is a mature application, demonstrated by the U.S. Air Force’s XSS series and Surrey Satellite Technology Ltd. ‘s 5kg SNAP-1.
Second, PRISMs could assist astronauts on extra-vehicular activity by fetching tools and equipment, recovering dropped items and even taking a backup safety line to an astronaut whose tether has failed. The technology has been demonstrated in NASA’s AERCam project and is being further tested on the international space station with two prototype Synchronized Position Hold Engage and Reorient Experimental Satellites, or SPHERES.
A third idea is servicing larger vehicles (transferring components, connecting propellant lines, etc.). This concept has not been demonstrated, only examined in studies like the Air Force Research Lab’s Aircraft Structural Testing and Evaluation Center project, and would need further study. An example of one type of servicing mission a PRISM might perform came during the 1973 Skylab 2 mission, when two astronauts had to be sent on a spacewalk to cut a metal strap jamming a solar panel.
Fourth, PRISMs could provide communications services, remote sensing and navigation signals from lunar and martian orbit. This is a concept well-proven around Earth in programs from Transit to Orbcomm. NASA Ames Research Center Director Simon “Pete” Worden has embraced small, low-cost spacecraft as a promising approach to establishing “lunar utilities.”
Fifth, PRISMs could explore space and celestial bodies ahead of the large exploration vehicles. A historical example is the Particles and Fields Subsatellite deployed into lunar orbit on two Apollo missions. NASA’s 3-kg GeneSat-1 is designed to examine radiation effects on living cells near Earth: it could do the same wherever in space a human presence is planned. This concept extends to probing landing sites for conditions and resources. The NASA Advanced Concept Institute has funded several proposals for micro-sized martian probes that could be deployed in large numbers.
Finally, microspacecraft can help fulfill the oft overlooked call in the VSE for a concurrent program of unmanned science spacecraft. The use of microspacecraft in this role began in 1958 with America’s 38-kg Pioneer 1 lunar probe. Given the drastic shrinkage in NASA’s science mission budgets, smaller missions, often carried as secondary payloads, may become the only practical method for continuing unmanned exploration.
Funding issues make it vital to maximize the leveraging of technology developed by sources both inside and outside NASA. Fortunately, a great deal of relevant technology, at the spacecraft system and subsystem levels, is available or in development from other programs, internal and external.
Most NASA centers, including Goddard Space Flight Center, Greenbelt, Md.; Ames Research Center, Moffett Field, Calif.; Marshall Space Flight Center, Huntsville, Ala.; Johnson Space Center, Houston; and the Jet Propulsion Laboratory, Pasadena, Calif. , have experience and/or current programs relevant to microspacecraft.
Several c ompanies including SpaceDev, Orbital, Swales, Microcosm, AeroAstro and the Space Dynamics Lab have built microspacecraft for government or private customers. Additional contributors include the Defense Advanced Research Projects Agency , military laboratories, universities, the Aerospace Corp. , national labs and international partners.
PRISM missions also offer the opportunity to test new technology and new operational concepts before committing to the expense and time involved in a large mission. This fits in well with the Aldridge Commission’s emphasis on developing technology through a series of affordable iterations.
NASA has shown some interest in PRISM-type ideas. The Jet Propulsion Laboratory was funded to design a new microsat inspector, although not to build the prototype. At the Small Satellite conference, NASA Administrator Mike Griffin strongly endorsed small science craft and described a “solar system infrastructure” concept similar to our PRISM network proposal. There are several specific proposals for relevant NASA microspacecraft programs, but no one has the responsibility to look at microspacecraft technology across the breadth of the VSE and share that technology in accordance with a common vision.
Laying out this vision should be a synergistic activity coupled to the development of the VSE architecture. NASA’s Exploration Systems Mission Directorate could begin by issuing a Solicitation for Microspacecraft Concepts in response to identified VSE requirements, hosting a workshop to gather and discuss ideas on this topic, and establishing or designating an office to coordinate work on PRISM technologies across the VSE.
There are two fundamental challenges involved in the VSE: it must be executed within practical cost limits; and given that constraint, it must succeed in a mission that would be daunting under any circumstances. Those carrying out the vision — in NASA, in industry, in academia and internationally — must study every practical option for technologies that save money, increase safety or improve the science to be done in the VSE.
The capabilities displayed in microspacecraft programs warrant examining the many requirements of the VSE in a cross-cutting effort to determine where microspacecraft offer optimal solutions. From our preliminary examination, it does indeed appear our smallest spacecraft can help carry out NASA’s grandest challenge.
Matt Bille and Kris Winkler are freelance space writers and researchers in Colorado and Virginia, respectively.