Project Icarus has its origins in late 2008 during discussions between Kelvin Long and NASA physicist Marc Millis, who left NASA to become President of the Tau Zero Foundation. These discussions led to a proposal for a study based upon a redesign of Daedalus. The study was to include an examination of the fundamental assumptions, for example, of whether Daedalus should be strictly a flyby mission, or should participate in mining Jupiter for Helium-3.
In 2008, several members of the original Daedalus Study Group were approached and asked to participate in a new study. Project Icarus was born. To increase the visibility of Project Icarus, a presentation was given by Long at a special session on interstellar flight at the Charterhouse Space Conference during 2009. After several months of recruitment, over a dozen volunteer designers and consultants joined the project.
The official launch of Project Icarus was recorded in Spaceflight magazine, and a number of the original Project Daedalus study group were in attendance. These included Alan Bond, Bob Parkinson, Penny Wright, Geoff Richards, Jerry Webb and Tony Wight. The founding members of Project Icarus at this event also included Martyn Fogg, Richard Obousy, Andreas Tziolas and Richard Osborne. Others present who were later recruited to the team included Pat Galea, Ian Crawford, Rob Swinney and Jardine Barrington-Cook. The membership continues to grow.
Icarus was a character from ancient Greek mythology. In an attempt to escape the labyrinth prison of King Minos, his father Daedalus fashioned a pair of wings made of feathers and wax for both himself and his son. Icarus, so the story goes, flew too close to the Sun and the wax on his wings melted. He fell into the sea and died after having touched the sky.
To paraphrase Sir Arthur Eddington from Stars and Atoms, the standard interpretation of the Icarus myth is that he was a man performing a stunt who met his ill-fated doom due to his antics. However, an alternative interpretation of the myth is that he is the man who illuminated a serious constructional deficiency in the flying machines of his era. Perhaps there is also a lesson for science here. A more cautious Daedalus applies his theories only where he feels confident they will succeed; but by his overindulgent caution, their veiled faults remain undiscovered. Conversely, Icarus will drive his theories to the threshold of collapse, and we may at least hope to learn from his flight how to construct a better machine.
Project Icarus, as the successor to Project Daedalus, is a theoretical engineering design study for an unmanned interstellar craft. Its overall purpose can be summarized as follows:
• To design a credible interstellar probe that embodies the essential concepts for a successful mission in the coming centuries.• To allow a direct technology comparison with Daedalus and provide an assessment of the maturity of fusion-based space propulsion for future precursor missions.• To generate greater interest in the real term prospects for interstellar precursor missions that are based on credible science.• To motivate a new generation of scientists to be interested in designing space missions that go beyond our solar system.
Using these four purposes as a guide, the collective scope of the project is codified in the Icarus Terms of Reference:
1. To design an unmanned probe that is capable of delivering useful scientific data about the target star, associated planetary bodies, solar environment and the interstellar medium.2. The spacecraft must use current or near-future technology and be designed to be launched as soon as is credibly determined.3. The spacecraft must reach its stellar destination within as short a time as possible, not exceeding a century and ideally much sooner.4. The spacecraft must be designed to visit any one of a variety of target stars.5. The spacecraft propulsion must be mainly fusion based (e.g. Daedalus).6. The spacecraft mission must be designed so as to allow some deceleration for increased encounter time at the destination.
One of the main differences between Daedalus and Icarus is the requirement that there be some deceleration at the target system. Daedalus had a cruise velocity 12% of light speed, and would have raced through the target system within days. It would have been in close proximity to any planet for only a matter of seconds. This short encounter time would severely restrict the scientific return from the mission, and so Icarus is committed to address the issue of deceleration.
Project Icarus is clearly a highly scientific endeavor whose success will be measured by the credibility and quality of the work that is created. Despite these academic ambitions, there are additional motives behind the project that are worthy of further examination.
One such motive is to use Icarus as a vehicle for training a new generation of interstellar engineers. The field of interstellar propulsion is sprinkled with luminaries whose names have become synonymous with the field of interstellar propulsion. These visionaries include VIPs such as Robert Bussard, Bob Forward, Greg Matloff, Robert Frisbee and Alan Bond, whose names will be immediately recognizable to interstellar aficionados. To maintain the healthy vision of a future where interstellar travel is possible, a new generation of capable enthusiasts is required. Project Icarus was designed with this specific motive in mind, and a quick glance at the Icarus designers reveals an average age close to thirty. Thus, one hope is that, upon completion of the project, an adept team of competent interstellar engineers will have been created, and that this team will continue to kindle the dream of interstellar flight for a few more decades until, presumably, they too become grey and find their own enthusiastic replacements.
Another parallel objective of Project Icarus is to evolve the possibility of interstellar flight from being merely feasible to actually being practical. The Daedalus design demonstrated that, with sufficient determination, a craft could be built using known principles of physics that could reach another star system in approximately fifty years. However, some critical components to Daedalus may lead a conservative spectator to believe that Daedalus was too ambitious.
Two impractical aspects of the original Daedalus spring to mind. The first is a feature of the propulsion system which necessitates the firing of marble-sized pellets, consisting of mainly deuterium and Helium-3, into a reaction chamber at a rate of 250 pellets per second. These pellets would then be ignited by high powered relativistic electron beams in a process known as inertial confinement fusion (ICF). Though considered a credible way to liberate energy from the fusion fuel, the fusion ignition rate of 250 hertz is difficult to be taken seriously given that the National Ignition Facility (NIF), a large U.S. fusion ignition project located at the Lawrence Livermore Laboratory, will likely accomplish only one such event per day under ideal conditions! Thus, an improvement on this rate by a factor of approximately twenty-one million would be required to achieve Daedalus fusion pellet ignition rates. While certainly not impossible, this pellet frequency requires a rather vast improvement on current technology. However, it’s important to recognize that the NIF is a physics demonstrator, and that it is not designed to be optimized for rapid ignition rates.