Several scientifically interesting asteroids could be visited by astronauts with flight times ranging from six months to a year and a half using a 200-kilowatt (kW) electric propulsion system, which is a reasonable advance over our present capability; the ISS currently has 260 kW of solar arrays installed. Such a mission would break the deep-space barrier, while taking a crucial step toward the two- to three-year flight times and 600-kW systems that would be needed for Mars exploration.
The second governing principle of our plan is that NASA does not have to invent completely new systems for everything as it did in the 1960s. Some systems, most notably zero-g and deep-space radiation protection, will require new research. Everything else can derive from existing spacefaring assets. The deep-space vehicle can be assembled by combining a few specialized elements. For instance, the structure, solar arrays and life-support systems could be adapted from designs that have been implemented on the space station. And many private companies and other nations’ space agencies have expertise in these areas that NASA could tap.
The third principle is to design a program that can maintain forward momentum even if one component runs into problems or delays. This principle should be applied to the most debated component of the space policy adopted by Congress: the launch vehicle that will ferry the crew and exploration vehicles from the surface of Earth into orbit. Congress directed NASA to build a new heavy-lift rocket, the Space Launch System (SLS). As announced this past September, NASA plans to develop this vehicle in steps starting at roughly half the capacity of the Apollo Saturn V and working up to just beyond the full launch capability of that rocket. The first SLS launcher, plus the Orion capsule now in the works, could carry astronauts on three-week excursions to lunar orbit and the Lagrangian points but can take astronauts no farther without the development of a new system.
Fortunately, journeys to deep space do not need to wait for the SLS to be completed. Preparations could begin now with the development of the life-support and electric propulsion systems that will be needed for trips beyond the moon. By making these systems an early priority, even while the new rockets are still under development, NASA would be better able to refine details of the SLS design to make it better suited to deep-space missions. These components could even be designed to fit on commercial or international launchers and then assembled in orbit, just as the ISS and the Mir space station were. The use of existing rockets would generate momentum toward deep-space exploration. With the flexibility from a portfolio of options, NASA could fit more exploration into its increasingly limited budget.
Mission: 2008 EV5
In our plan, NASAs renaissance begins by constructing the means for people to travel between the planets—the deep-space vehicle. A solar-powered ion drive provides the oomph, and a new transit habitat provides a safe haven away from home. The most basic deep-space vehicle would consist of two modules that could both be lofted into low Earth orbit with a single launch of the smallest of NASA’s new SLS rockets. Alternatively, three commercially available rockets could do the trick, two for the vehicle components and one with supplies for the trip.
The maiden voyage is, ironically, its most boring. For two years the ship, without crew, is remotely piloted to follow a slow spiral from low Earth orbit through the Van Allen radiation belts and up to a high Earth orbit—a trip that goes easy on propellant but is too long and radioactive for astronauts. Once the spaceship is poised on the outer edge of Earth’s gravity well, just one push away from interplanetary space, it can undertake lunar flybys and other maneuvers to reshape the orbit for efficient departure. The astronauts then fly up from the ground on a conventional chemical booster.