Project Enzmann

Sometime in the 1960s the physicist Robert Duncan Enzmann came up with the idea of using huge spheres of frozen Deuterium, mined from the gas giants, as the main fuel for so called ‘Slow Boats’. These are large vessels but much smaller than conventional world ships. Enzmann seems to have imagined these vessels travelling at around 0.09c and taking a crew of 200 to the Alpha Centauri star system in around 60 years. By the time of arrival in the target system, the crew population would have grown to something as large as 2000. In the 1970s the space artist David Hardy had painted the Enzmann Starships, although the original picture was lost to history. So in 2011 one of us (Long) commissioned Hardy to repaint the Enzmann and this is shown in the picture below. Enzmann Starships at Jupiter (David Hardy) About 1.5 years ago, Adam Crowl first apprised some of us of the Enzmann Starship design and pointed out that not much was known about it. In addition, its origins needed to be clarified and its actual design was surrounded by ambiguity and grandiose claims. In particular, an October 1973 Analog article by G.Harry Stine expanded the concept to an unjustified performance domain. So it was that three of us set about initiating a new design study, called Project Enzmann. Adam Crowl was the Chief Designer on the project and Kelvin Long the Project Leader. Richard Obousy was one of the team members. This very small team, set out with a simple task in mind: clarify the Enzmann Starship history and assess its design. Thus we now come to nearly the end of this journey. A paper on our preliminary findings were presented at the August 2011 British Interplanetary Society World Ship Symposium. The long awaited paper is now nearing completion and is about to be submitted to the BIS technical Journal for peer review. The title of the paper is: “The Enzmann Starship: History and Engineering Appraisal”, A.Crow, K.F.Long, R.K.Obousy. The table below shows what we think is the original Robert Enzmann design:

Enzmann Starship (Slow Boat) Configuration & Performance



Dry spacecraft mass (tons)


Propellant mass (tons)


Start population


End population


Total Mass Ratio


Mass Ratio


Exhaust Velocity (km/s)


Total Delta.V (km/s)

54,000 (0.18c)

Cruise Velocity (km/s)

27,000 (0.09c)

Total acceleration time (years)


Mass Flow Rate (kg/s)


Start Acceleration (m/s2)

0.019 (0.002g)

Total Cruise time (years)


TotalMissiontime (years)


More information is contained in our paper including of a scale Slow Ship” and “World Ship” design. Although the project didn’t necessary start out explicitly as an Icarus Interstellar initiative, we are pleased to declare it as one of the organizations official projects in collaboration with the BIS Technical Committee. The publication of the paper will represent the completion of this small project and indeed, the first completion of a project under the Icarus Interstellar umbrella. We invite others to take our paper, and expand on it to produce a more credible design concept. We have merely laid the foundations for what may also be a useful baseline for our sister initiative Project Hyperion. We hope this demonstrates that the members of Icarus Interstellar continue to break now ground in pushing our ideas to fruition as we attempt to reach for that long desired interstellar frontier. Kelvin F.Long Vice President (Europe) Icarus Interstellar The images below show various reproductions of the Enzmann Starship by others. (more…)