Project Enzmann

posted by Kelvin F. Long on March 3, 2012

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. Enzmann Starships by Robert Enzmann (claimed 1949)   Enzmann Starship painting by Don Dixon (1972) Enzmann Starship painting by Syd Mead (1980) The larger Syd Mead painting (1980) with Daedalus Enzmann Starship painting by Bob Eggleton (1986) Enzmann Starship painting by Rick Sternbach (2003, originally painted in 1983) Enzmann Starship painting for October 1972 issue of Analogy by Rick Sternbach

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8 Responses to Project Enzmann

  1. mithril says:

    how big, in terms of physical dimensions, would these proposed spaceships have been? none of the artwork has helpful scale indicators.
    also where would the crew quarters have been on the illustrated designs, and why kind of accomidations were envisioned by the designers?

  2. kelvin says:

    Hi Mithril,
    The basic Enzmann design was said to be around a 1,000 ft (305m) sphere attached to a 1,000 ft spacecraft. The spacecraft is split into three habitat modules, each rotating to roduce artificial gravity. A Central column passes through the sphere and habitats for structural staiblity and fuel movement to the engines at the back. In the original Enzmann design there were 8 engines, but later modifications saw it with up to 24 engines. The crew quarters were illustrated in a magazine article “A Starship is born, Science Digest, May 1983”.

    Our larger ‘Slow Ship ‘ and ‘World Ship’ concepts are factors of 10 and 100 in size although the Deuterium sphere size is conserved.


  3. mithril says:

    i wonder how far you could beleivably take a group of these ‘colony ships’ without sacrificing colony supplies for more supplies for the trip. then again if your taking a group of them (since 200 to 2000 people is pretty small for establishing a viable colony, even with ‘genetic colonists’ in the form of frozen embryo’s or eggs/sperm), i suppose you could include ‘cargo’ versions with colony supplies slaved to the control of the passenger versions to give redundancy.

    i presume that if you didn’t want to try gas giant mining for the fuel, you could use alternative sources of Deuterium, like comets or oceanic processing?

    these kinds of slowboats seem like they’d be a great addition to slower than light space colonization stories. small enough to actually be built in a pluasible midfuture, but large enough to carry the people and supplies you’d actually need to establish a colony.

  4. chuculain says:

    can the broken image links be fixed.

  5. Dimitris K. says:

    Hi! A very interesting concept; I’d also like to take a look at the paper, but…

    It seems impossible to find the paper anywhere on the web. Could you provide a link?

    And could you also take a look at the images? (They don’t seem to load at all…)

  6. the link to enzmannstarship blog is on my website. on his blog are many papers about the starships, there were four designs. There are verisimitudes. There are pictures and paintings and blueprints. Please go there and find what you need, just give him credit. BY the way, none of your images show.

    Michelle Snyder, symbologist, admin on

  7. Steve says:

    All technological speculation as to how fast this 2 Empire State Building long space phallus can go, will be silenced on the first activation of the Viagra Reactor and my revolutionary Jizz Drive.

  8. My recollection is that Harry Stine had the density of deuterium at 10 times the actual density. He was rather miffed when a reader pointed this out in the readers forum. I was very proud the time because I’d spotted the mistake as well. I have since done my share of orders of magnitude mistakes and I am now much more Understanding!

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