© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm

24.3.4  Project Daedalus

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.²⁹⁵³

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.

Figure 24.14 Project Daedalus: Mission to the Stars²⁹⁵³

The Daedalus starship takes shape in orbit around Callisto, near Jupiter. A new frontier is about to open.

JOVIAN AEROSTAT FACTORY. Factory modules floating in the atmosphere of Jupiter harvest the isotope Helium-3 for use as fuel in the Daedalus starship. At far left is the overall scheme, with ascent vehicle docked. At near left is detail of the factory complex.

BASIC VEHICLE CONFIGURATION OF DAEDALUS STARSHIP

SCHEMATIC DIAGRAM OF DAEDALUS NUCLEAR PULSE PROPULSION SYSTEM,
USING FUEL PELLET IMPLOSION

COMPLETE DAEDALUS VEHICLE PRIOR TO THE START OF THE BOOST PHASE

LEFT: At low thrust, the Daedalus starship leaves Callisto’s orbit. Soon it will have escaped from Jupiter and the Sun and head into interstellar space on its half-century flight to another star. RIGHT: Results of stellar target ranking out to 12 light years.

BASIC DAEDALUS STARSHIP MISSION PROFILE: Basic mission profile to Barnard’s Star, giving distance from the Solar System as a function of time into mission.

DAEDALUS VEHICLE SECOND STAGE, AFTER SEPARATION

The main Daedalus vehicle, already well into the encounter with the planetary system of the target star, detects new phenomena on the star and deploys a high-velocity-gain subprobe to attempt a closer look.

DEPLOYMENT OF DAEDALUS PLANETARY PROBE AT ENCOUNTER
WITH PLANET HAVING TWO SATELLITES

During the flight out the payload remains active, making continuous measurements and constantly reporting data back to Earth. A wide variety of "coast phase" scientific investigations would be undertaken, including direct detection and observation of interstellar particles and fields and innumerable detailed astrometric very-long-baseline measurements of distances to other stars and of the size of the Galaxy. At the time of encounter with the Barnard’s Star system, a dispersible payload would be deployed much like the multiprobe Pioneer Venus (1978) spacecraft or the warheads of a MIRV’ed missile.

As the vehicle approaches Barnard’s Star, two onboard large space telescopes (Palomar-size 5-meter reflectors) swing into action, beginning the search for planets and an accurate determination of their orbits. Once these orbits are established, heavily instrumented subprobes would be launched on close-intercept trajectories for more detailed observations. The main ship carries 40 tons of extra fuel for this purpose, and the main propulsion system would be used for each maneuver. Throughout the encounter period the subprobes -- up to 18 in number -- would pass their data back to the mother ship, which receives the transmissions on each of eight 10-meter-diameter radio dishes studding the starprobe’s exterior. This information is processed and condensed by Daedalus’ semi-intelligent computer system, which is housed in a central core running through the payload. Later it is relayed back to Earth during the post-encounter period using the bowl of the dormant second-stage engine as a giant radio communications dish.

The total mission payload is about 500 tons, a large fraction of which is in the dispersible subprobes. A typical subprobe weighs more than 10 tons and measures 20 meters in length. Prior to deployment each is shaped like a narrow conical frustrum in order to facilitate radial packing into the cargo bay. Each subprobe’s communication channel, operating on a 1-kilowatt transmitter, can beam as much as 11 million bits/second of data back to the main vehicle in "video" mode. When talking to Earth, the starprobe uses a 1-megawatt radio transmitter operating at 2-3 GHz with a maximum bit rate of 864,000 bits/second. (See encounter scenario, Figure 24.14.)

The Daedalus starship design includes many necessarily innovative features too numerous to mention here. One example is the "wardens," created to help ensure the vehicle’s self-sufficiency:

The requirement for a high degree of reliability suggested that a system of "Self Test and Repair" philosophy should be adopted. Also, the payload effectiveness could be enhanced if it were possible to re-organize experiments when required en route. Further, in order to avoid the contaminated environment of the main vehicle it became desirable to place the particles and fields experiments a long way (several thousand kilometers) from the main vehicle. These requirements led to the concept of robot self-propelled vehicles carrying specialized tools and general manipulators. These vehicles would have a limited degree of data processing and machine intelligence, but any high level decision making would be carried out by the main mission computer on the main ship. Two of these "wardens" would be provided, each having a mass of about 5 tons. A total mass of spares of 15 tons would be available.²⁹⁵³

Starprobe Daedalus may never be built, but it is perhaps a primitive prototype design for the exploratory interstellar spacecraft of the coming century. It provides a firm basis for discussion of the plausibility of Bracewell probes and other artifacts that may find there way into our Solar System at the hands of alien adventurers. To those who remain skeptical of the ambitions of the BIS’s Project Daedalus, let them recall that it was the same British Interplanetary Society that conceived a model for a manned moon lander mission a mere 30 years before Armstrong and Aldrin first set foot on lunar soil.

Last updated on 6 December 2008