Thursday, March 22, 2012
"If technically advanced alien civilizations can build starprobes and send them to Sol, how long will it be before humanity can construct and launch interstellar messenger vehicles of its own? A small group of engineers and physicists, all members of the British Interplanetary Society (BIS), decided to find out. In February 1973 they initiated Project Daedalus, an impressive four-year feasibility study of a simple interstellar probe mission using only present-day technology or reasonable extrapolations to near-future capabilities. More than 10,000 man-hours were expended directly on the Project, which culminated in April 1977 with a prototype design and finally in 1978 with the publication of the final report. The following is a very brief summary of the design and mission specifications for Project Daedalus (Figure 24.14), the first comprehensive starship design study in the history of mankind.
The basic mission profile involves an unmanned and undecelerated starprobe which executes a flyby of Barnard’s Star at a distance of about 6 light-years from Earth. This particular target was chosen, not because of its inherent superiority to a Centauri (a closer and more likely system to harbor life3224), but rather because it lies near the midpoint of the expected maximum useful range of the Daedalus vehicle -- roughly 10 light-years.
The final design calls for a starship with a total initial mass of 54,000 tons, of which 50,000 tons is propellant in the form of deuterium/helium-3 frozen fuel pellets. The vehicle consists of a two-stage nuclear pulse rocket, a widely discussed conventional interstellar propulsion technique that has been described extensively in the literature. (See Chapter 17.) The trip to Barnard’s Star would require about 20 years of R&D effort (design, manufacture, and vehicle checkout), 50 more years of flight time at about 12%c, followed by another decade of data transmission from the probe relating to approach, encounter, and exit science. Therefore a basic funding commitment over at least the next 80 years would be required for implementation and successful completion of the mission.
As shown in the time-into-mission graph in Figure 24.14, the Daedalus starprobe would leave the Solar System probably from near-Jovian space. This is because the helium-3 needed for fuel is rare on Earth and must be harvested from the atmosphere of Jupiter using "aerostat factories" floating in the jovian air at medium altitudes. (This technology obviously requires at least a mature spacefaring Type I cultural level among humans, which should be attainable in the next century here on Earth.) The boost period, involving three propellant tank drops and a single stage separation, would last 3.8 years. At the end of these events, the starprobe would have achieved a cruising velocity of about 12%c."
If you have been reading Xenology, check out 24.3.4 for info about Project Daedalus.