Keep going Starship Builder Tel!

Kelvin

Vice President (Europe) Icarus Interstellar

This next version of the model was a wooden version that is advertised on ebay. It is claimed to be a “Daedalus NASA Starship spacecraft Wood Model”. Constructed from kiln-dried Wood Mahogany and hand-painted by artists. The origin of the model is unknown but to be fair to the company selling it, I will state that its claimed to be sold by MyAsianArt, an art and antiques gallery based in Manila, the Philippines:

The last of the models, 1 meter tall, was spotted at a Star Wars exhibit in Alaska by Icarus Designer Andreas Tziolas. Again, the origin of the model is unknown but a caption reads:

“In the 1970s, the British Interplanetary Society challenged its members to design an interstellar spaceship using existing and emerging technologies. The result was Daedalus, a two-stage rocket designed to send an unmanned probe on a fifty year trip to Barnard’s Star, a distance of six light years. Daedalus would use tiny fusion reactions to propel itself. A chemical rocket typically burns 800 pounds of fuel for every pound of payload it carries. A nuclear rocket, like Daedalus would use only 100 pounds of fuel per pound of payload.”

The Icarus team has decided to get our own model built for Daedalus which we can use at exhibitions and conference trade stands. We have recruited the excellent British model builder Terry Regan for this challenge. Terry has got started on this ambitious project and we will update you with photographs as he progresses. Meanwhile below shows an image from his early construction of the second stage model, with a payload bay around 120 mm in diameter and 50 mm tall. Well done Terry, this is sure to be a really exciting initiative as the model evolves into the full spacecraft design.

If you know of any other Daedalus models ever built, please let the Icarus team know.

Kelvin
Vice President (Europe) Icarus Interstellar

Fusion processes liberate, on average, about a million times more energy per unit mass than chemical processes. This makes them ideal for propulsion purposes, where minimization of the total mass of the spacecraft and fuel is of paramount importance. Although we have not yet mastered the controlled release of fusion energy, the progress to date indicates that it is simply a matter of time until this new technology can be harnessed.

The Daedalus spacecraft, which was a 1970’s effort to design and interstellar spacecraft, was to be powered by a process known as pulsed fusion whereby small pellets of fusion fuel would be injected at a high velocity into a reaction chamber, and ignited by high energy electron beams. Conceptually, this is not vastly different from a conventional internal combustion engine, where small droplets of gasoline are injected into a combustion chamber and ignited.

The resulting fusion reaction products in the Daedalus reaction chamber would be channeled axially rearward from the main vehicle by a number of field coils acting as a magnetic nozzle. These ejecta would be responsible for an overall momentum transfer mediated by magnetic fields interacting with the reaction chamber. In this article we examine the major elements of the propulsion system, which can be broken down into the following:

• Propellant Storage
• Pellet Injection Gun
• Electron Beams
• Reaction Chamber
• Magnetic Nozzle Coils

Schematic of the Daedalus Propulsion sytem, showing all major components. (Image courtesy of Bond and Martin – Project Daedalus Final Reports)

Propellant Storage

Daedalus was a two stage spacecraft, with stage one carrying 46,000 tonnes of fuel, and stage two carrying 4000 tonnes. The fuel pellets had a mean radius of 19.7 mm for the first stage, and 9.16 mm for the second stage. The core of the pellet, was a  Deuterium Tritium (DT) trigger, which was required to generate a thermonuclear burn wave which would ignite the Deuterium Helium-3 fuel. This core was surrounded by the actual Deuterium Helium-3 fuel which made-up only 10% to 15% of the overall mass of the pellet. The entire pellet was coated with a superconducting shell which  was required so that the pellet could be electromagnetically accelerated from the storage tanks to the reaction chamber by a magnetic gun. A DT trigger was chosen, because it is the easiest fusion reaction to ignite, and ignite the reaction of the Deuterium Helium-3 fuel.

The storage tanks were spherical in shape, and cryogenically cooled to a temperature of 3 K while being maintained at a constant pressure of 0.812 atm. This temperature and pressure combination was required so that the Helium-3 would be in a liquid phase rather than a gaseous phase. This was a requirement since the fusion rate increases with the density of the fuel.

Pellet Injection Gun

The fuel pellet injection gun was designed to channel the fuel pellets into the main reaction chamber at a rate of 250 per second by using a travelling magnetic wave, which is a wave of magnetic energy that is capable of  imparting momentum to the pellet. The magnetic gun consisted of a number of field coils, in series, where each imparted an equal amount of kinetic energy into the fuel pellet. Both stage one and stage two injection guns were to have a field strength of 15 Tesla, and would accelerate the pellets at a rate of 3.83 x 107 m/s2 (1st stage) and 8.21 x 107 m/s2 (2nd stage). To minimize energy dissipation in the coils, they were to be cryogenically cooled to about 20 K. The pellet injection system was a particularly massive component in the overall propulsion system, with the bulk of the mass being in the cooling system mass (40 tonnes 1st stage, 4 tonnes 2nd stage) and the capacitor mass (29.6 tonnes for stage 1, 0.79 tonnes for stage 2).

Schematic of the Fuel Pellet Injection gun.(Image courtesy of Bond and Martin – Project Daedalus Final Reports)

Relativistic Electron Beams

Once accelerated, the pellets would be ignited within the reaction chamber. A number of diodes capable of emitting beams of relativistic electrons were focused on to the specific location where the injected pellets would pass. At the instant the pellet reached the focus, the beams would be discharged and the outer layers of the pellet would be ablated as a consequence of the the electron beam collisions, which would heat it to a high temperature. This heating would result in a strong coupling of the pellet to the electron beams and lead to high heat transfer rates to the surface of the pellet. A convergent shock wave would result from the ablated material, focusing on the pellet center with sufficient pressure to ignite the thermonuclear trigger of DT. The driver energy for the first stage would be 2.7 GJ, and 400 MJ for the second. Due to the high gain of the system, each cycle would generate enough energy to power the subsequent cycle, and the process would continue as required.

Reaction Chamber

The ignited fusion fuel would reduce the pellet to an expanding plasma radiating from ignition point. The basic concept of the reaction chamber was to enclose the electromagnetic field of the plasma in a conducting shell. The hemispherical shell would perform as a shock absorber, which would absorb the momentum of the plasma and transmit it to the vehicle. The process would occur rapidly, over a few microseconds, and the rise and fall in magnetic pressure would be received by the shell as an impulse which set it in motion. The shell would then relax, and become set in motion once again, by the next pellet. The reaction chamber would experience a constant forced oscillatory motion for the duration of the acceleration.

The reaction chamber would need to have a low density to conserve mass. It would also need a high temperature capability, and a high electrical conductivity. For the Daedalus spacecraft, Molybdenum was chosen since it met all the requirements. The first stage reaction chamber had a mass of 218.7 tonnes, and the second reaction chamber mass would be 25 tonnes.

Magnetic Nozzle Coils

External field coils were required since the reaction chamber was to have a weak magnetic field which was required for the plasma compression. The field was to be shaped such that it did not interfere with the propagation of the electron beams to the target. The field also had to run parallel to the reaction chamber walls, and diverge downstream, so as to guide the plasma for propulsive purposes. This is what is typically referred to as a ‘magnetic nozzle’. The Daedalus team selected a configuration of four field coils, which they believed provided the desired field configurations. The field coils would be superconducting with a peak field of 14 Tesla. The stage one coils had a total mass of 124.7 tonnes, and the stage two coils had a total mass of 43.6 tonnes. For comparison, the dry mass of the space shuttle orbiter is only 85 tonnes, so one immediately appreciates the sheer scale of the Daedalus.

Conclusion

The first stage engine cycle involved the ignition of 16 billion pellet cycles lasting a total of 2.05 years, and a second stage cycle lasting 1.76 years. This made for a total boost period of 3.81 years, and a top speed of 12.2% the speed of light. What is particularly fascinating about this propulsion system is that it is within the realms of credible science since no new physics is required. This in itself does not imply that the task of building a Daedalus class spacecraft would be easy, since the engineering and economical costs are quite staggering, but it is certainly encouraging that this design could theoretically be built, given sufficient ambition.

One of the reasons was to investigate the Fermi Paradox first postulated by the Italian Physicist Enrico Fermi in the 1940s. This supposes that there has been plenty of time for intelligent civilizations to interact within our galaxy when one examines the age and number of stars, as well as the distances between them. Yet, the fact that extra-terrestrial intelligence has never been observed leads to a logical paradox where our observations are inconsistent with our theoretical expectation. This original question from Fermi seemed to also reinforce the prevailing paradigm at the time that interstellar travel was impossible.

Project Daedalus was a bold way to examine the Fermi Paradox head on and gave a partial answer – interstellar travel was possible. The basis of this belief was the demonstration of a credible engineering design just at the outset of the space age that could in theory, cross the interstellar distances. In the future scientific advancement would lead to a refined and more efficient design. The absence of alien visitors would therefore require a different explanation because Project Daedalus demonstrated that with current, and near future, technology, interstellar travel was feasible. Therefore, another solution to the absence of extra-terrestrial visitation was necessary. Although Project Daedalus was ostensibly focused on designing an interstellar flyby probe, the underlying motives were to frame discussions about the Fermi paradox.

In the years after Project Daedalus, a member of the Daedalus team Alan Bond plunged himself into researching biology to understand how species evolve from a single celled organism to something as complex as human beings. He argued that historically pure guess work had been used to determine the number of intelligent civilizations in our galaxy. The culmination of his research resulted in the publication of a paper ‘On the improbability of intelligent extraterrestrials‘ in 1982 in the Journal of the British Interplanetary Society. He concluded that organisms with the complexity of human beings may be rare and only occur with a probability below much less than once per galaxy.

This startling conclusion was based upon the development of a biological model assuming an observed exponential growth in the complexity of biological life in the fossil records over time. Bond had addressed the probability of Earth-like planets with Carbon based biology existing in our galaxy. Proteins, the complete set of genes which pass from a parent to an offspring, were seen as the fundamental mechanism of biochemistry on all worlds. The genome would increase in size over time and the establishment of intelligence would require a certain level of intelligence and therefore a minimum size of genome; the more complex an organism then the larger the genome required for its specification. Attainment of an intelligence level like us would take merely a few million years, for species which had a similar genome size.

Bond himself stated in the paper that a lot of assumptions had been made with inaccurately known parameters and that more work needed to be done. He said further that there was clear potential for an order of magnitude variation around the estimates that were derived. His actual numbers suggested that a planet with the development level of the Earth only occurs once in 50,000 galaxies.

He concluded that “whilst we are sufficiently rare to inhibit contact, at least with the Galaxy at its present age, we are not so rare as to defy phenomenological explanation”. The conclusions of this paper are a disappointment for those who believe intelligent life to be prolific. But it is interesting that in the Cosmos television series Carl Sagan also expresses the view that although life may occur purely as a function of chemistry and on most worlds where the environment is suitable, intelligent life in complex beings like us may be rare. When two great thinkers share a similar vision this requires contemplation. The rare intelligence hypothesis paints a very different picture of intelligent life in the universe to that of shows like Star Trek.

As a literature search on the internet shows, there are many potential answers to the Fermi Paradox and it may remain unresolved for some time. Although, advances in observational techniques for looking at distant extra-solar planets may lead us to an answer sooner than we think. One thing is for certain though, the contribution of Project Daedalus to the debate was first rate, demonstrating the possibility of star travel and forcing us to consider other more profound answers. It was no surprise that Alan Bond would also be one of the pioneers in searching for alternative explanations. There is one way we will know for sure, and that it to build something like Daedalus or Icarus in the coming decades, and then go see for ourselves.

If you have found this article to be of value then please consider donating a small amount to Project Icarus to assist us with our ambitions of creating a credible starship design.

Alternatively take a look around the remainder of the Icarus site.

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Useful Links

Visit the Project Icarus website

Project Icarus a Starship for the 21st Century

Project Daedalus, a Nuclear Starship

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The idea behind Project Orion is to detonate a nuclear charge at some distance from a vehicle. The detonation creates an expanding plasma wave which transfers momentum to the vehicle by hitting a pusher plate. This detonation process is repeated, and the rocket achieves thrust. In 1965, the Test Ban Treaty, which prohibits the detonation of nuclear devices in space, put a stop on the development of the nuclear pulse rocket.

Several years later, Alan Bond of the British Interplanetary Society, believed that the time was right to investigate the feasibility of an interstellar mission. He discussed the idea with members of the Society and Project Daedalus was born.

Project Daedalus began on 10^th January 1973 and the final reports were published 15^th May 1978 taking just over 64 months or over 5 years. Approximately  10,000 man hours were used by 13 core designers and several additional consultants.

In essence, Project Daedalus was a feasibility study for an interstellar mission, using 1970’s capabilities and credible extrapolations for near-future technology. One of the major objectives was to establish whether interstellar flight could be realized within established science and technology.

The conclusion of the report was that Interstellar flight is feasible.

If you have found this article to be of value then please consider donating a small amount to Project Icarus to assist us with our ambitions of creating a credible starship design.

Alternatively take a look around the remainder of the Icarus site.

Useful Links

Visit the Project Icarus website

Interstellar Propulsion and the Fermi Paradox

Project Icarus, a Nuclear Starship

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