Sun Yacht Racer Diana piloted by John Merton, sponsored by Cosmodyne Corporation. ("The Wind From The Sun" by Arthur C. Clarke)

In the early 22nd century, racing of sun yachts powered by solar sails became the cutting edge of extreme sports. John Merton had popularized the sport while Chief Engineer of Cosmodyne Corporation as a means of promoting solar sailing for hauling heavy cargoes throughout the solar system.

After many years of trial and effort, Merton, newly retired from Cosmodyne, piloted his own racer Diana in the decadal race from Earth orbit to Lunar orbit. To conserve mass, Merton chose to fly solo, while all other yachts had two person crews. In the race, all contestants started from geosynchronous Earth orbit, and followed a spiral solar driven orbit to the Moon. Start to finish would be about seven days.

Challenging orbital changes, risks of collision, artificial eclipses, and the rigors of spaceflight faced the crews of all seven yachts (Gossamer, Santa Maria, Sunbeam, Woomera, Lebedev, Arachne, & Diana). Entries included ships from Earth and the Martian colonies.

Diana was pulled by two square miles of sail, configured in a flat disc 1.6 miles in diameter, on rigging two miles long. Braced by spars and rigging, the thin foil sail provided the "engine" for Cosmodyne Corporation's Diana. All sun yachts were very lightly built, rather like a present-day endurance balloon racers or racing bicycles, to maximize velocity. Each yacht was an amalgam of space tested components, plus cutting edge technology.

The Model

My model of Diana is built to 1:48 scale. Based on the sketchy details from the story, my engineering background, and an interest in spacecraft, the concept emerged as a small but functional sail craft.

Combining elements of spacecraft engineering, high altitude balloon gondolas and a healthy respect for solar thermal loads, Diana emerged as a foil covered craft. Spinning the sail could lead to uncontrollable gyroscopic effects, so the yachts could not use "barbecue mode" to distribute thermal loads. Diana became a glittering craft covered in multilayer thermal insulation. Since the solar sail would be 176 feet across in 1:48 scale, only the passenger end was modeled!

The crew capsule is a ping-pong ball (36 mm diameter). It has two side looking portholes, made of ¼ inch Evergreen styrene tubing with Micro Crystal Clear windows. A periscope is provided, built of aluminum and brass tube, for Merton to check out his sail and competitors during the race. A searchlight for artificial light during Earth eclipse for sail inspection was fashioned from ¼ inch styrene tubing, with five minute epoxy as a lens. Orange colored Rollo candy foil covers the sides attached with Micro Scale Foil adhesive. The capsule itself is covered with Ultra Bright Bare Metal Foil, and sealed with Testors gloss coat.

The personnel sphere carries a forward equipment module, made from a 30 mm diameter pill bottle cut down to 8 mm high, covered in gold gift wrap foil. I used Micro Scale Foil adhesive to fasten the gold foil, before gluing it to the sphere with five minute epoxy. This module holds the winches for the sail control lines and the main rigging attachments. Holes on the top are for (invisible) control lines. This model will eventually be in a display box, so the four main rigging lines are .015 inch steel K&S steel wire, epoxied through the pill bottle and into the ping pong ball.

The hexagonal main equipment module is built of .030 inch styrene sheet. It is 40 mm across the flats, is 11 mm high, and is cemented with liquid styrene cement. The module is covered with Matte Aluminum Bare Metal Foil, and gloss coated. Thermal radiators for the life support and electrical systems are made of Plastruct corrugated sheet, attached with epoxy. Four styrene strip emergency thrusters are mounted on the rear, along with an umbilical connector for preflight servicing.

Two omni directional antenna booms were made from .015 steel wire with a drop of five minute epoxy at the end to create the active antenna element. These are placed on opposite sides of the equipment module for full sky coverage.

Although not mentioned in the story, for a seven day flight batteries would be too heavy, so two advanced solar panels are attached to the equipment module with 1/16 inch K&S brass tubes. Small sections of 3/32 inch square brass tubes are epoxied to the panel, which the boom fits through. The panels are .030 inch white styrene sheet, 25 mm square, with paper decals for the solar cells. I designed the cell pattern with a drafting program, shrank it to size, and printed them on bond paper with a laser printer. I attached the decals using Krylon photo adhesive. To control panel thermal loads, and provide additional antispin capability (as mentioned in the story) to the yacht and sail system, each panel can be rotated about its boom. (Note: Solar sailing using rotating solar panels was first used by Mariner 10 after it ran low on attitude control fuel during Mercury flybys.)

Arthur Clarke has John Merton bail out through an airlock. The airlock is a 21 mm tube, 40 mm long, and thermoformed from .010 inch styrene sheet over a plastic calculator paper roll, then cemented back on itself with Zap-A-Gap CA. The plastic roll deformed in the hot water giving a wavy surface to the plastic. Covered with orange colored Rollo candy foil, and sealed with gloss coat, it creates a nice thermal blanket appearance.

Internal and external hatches made of .015 inch styrene are detailed with styrene latches and staple handles. I used a drafting divider to scribe out the hatches and hatch coamings. Small 2 mm eye ports are also included in each hatch, and are filled with Micro Crystal Clear. The airlock also has an internal handgrip made from a 5/8 inch steel staple. The external hatch, since it resists opening against an internal pressure, is braced with styrene strip and tube reinforcements, and is covered with gold gift wrap foil. The gold foil was glued on with Micro Scale Foil Adhesive and sealed with Testors gloss coat.

The airlock hatch is open, just as Merton left her, showing Diana heading for the stars.

Decals (Diana, John Merton, Cosmodyne, and the number 7) were printed using word processing software on bond paper, and glued in place with Avery permanent glue stick. I had to use paper decals after my first attempt at creating my own decals failed. Next time, I'll order the right decal film for laser printers!

The model is 67 mm long, ignoring the sail rigging. The width across the solar panels is 120 mm. At full scale this would be 3.07 meters long by 5.76 meters across.

Everything used in the model came from my stockpile of styrene, brass, aluminum, foil, and the ever-present found object box, plus Zap-A-Gap CA, Testors styrene cement, and Duro five minute epoxy.

References

• Arthur C. Clarke; "The Wind From The Sun"; Boys Life Magazine; Boy Scouts of America; 1963
• Arthur C. Clarke ed.; Project Solar Sail; Penguin Books; NY, NY; 1990

Image: Front view

Image: Rear view

Image: Side view

Image: Top view