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The Invention of Space Sailing

This section describes the history of the invention of space sailing and related events on the theory of light. It appears that Jules Verne may have been the first to recognize the space sailing concept in 1865, although Johannes Kepler might have been first with the idea around 1610.

JOHANNES KEPLER observed that comet tails point away from the Sun and suggested that sunlight caused the effect. In a letter to Galileo in 1610, he wrote, "Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void." He might have had the comet tail phenomenon in mind when he wrote those words, although his publications on comet tails came several years later. (Ad vitellionem parali pomena, Frankfort, 1604; De cometis liballi tres, Augsburg, 1619; he possibly referred to sunlight effects in New Astronomy, 1609.)

RENE DESCARTES in 1638 suggested that light is a pressure wave propagating through a special type of matter, giving rise to the ether concept.

OLE ROMER made the first rather accurate determination of the speed of light in 1675 based on observations of Jovian satellites.

ISSAC NEWTON published his three laws of motion in 1687 (Principia). His Second Law equates a motive force to a change in momentum, which is the principle used in determining the force resulting from the reflection, absorption, and emission of radiation. His Third Law equates that to a propulsive force on a sail.

JAMES BRADLEY measured the abberation of starlight as an angle of 20" (= 0.006 deg) in 1728 and used Romer's data to explain the effect as being due to the orbital motion of Earth.

JAMES CLERK MAXWELL, in 1864, published his theory of electromagnetic fields and radiation, which shows that light has momentum and thus can exert pressure on objects. His work provides the theoretical foundation for sailing with light pressure.

JULES VERNE, in From the Earth to the Moon, published in 1865, wrote "there will some day appear velocities far greater than these [of the planets and the projectile], of which light or eletricity will probably be the mechanical agent...we shall one day travel to the moon, the planets, and the stars." This is possibly the first published recognition that light could move ships through space. Given the date of his publication and the widespread, permanent distribution of his work, it appears that he should be regarded as the originator of the concept of space sailing by light pressure, although he did not develop the concept further. Verne probably got the idea directly and immediately from Maxwell's 1864 theory (although it cannot be ruled out that Maxwell or an intermediary recognized the sailing potential and became the source for Verne). If he had written a story around space sailing, Verne might have caused the beginning of space exploration to be quite different from what it was.

WILLIAM CROOKES built his radiometer in 1873, which he thought would demonstrate the pressure exerted by light, but actually failed to do so. Six years passed before Maxwell and Osborne Reynolds provided the correct explanation for the radiometer, which is thermal transpiration around the edges of the vanes.

ALBERT MICHELSON and EDWIN MORLEY conducted their interferometry experiment in 1887 and obtained null results, beginning the end of the ether concept and setting the experimental basis for the Lorentz Contraction and the Theory of Relativity.

GEORGES LE FAURE and HENRI DE GRAFFIGNY published a four-volume science fiction novel in 1889, The Extraordinary Adventures of a Russian Scientist, which included a spacecraft propelled by solar pressure. The ship is a hollow selenium sphere ten meters across, surrounded by a selenium disk 30 meters across. For its launching from the surface of the moon, the spacecraft is placed in the center of a 250-meter reflector made of separate, movable mirrors. By using this system to focus sunlight onto the disk, the spaceship is repelled at a speed of 28,000 km/h. It makes a journey to Venus where the selenium ring converts to a parachute for descent to the surface.

PYOTR LEBEDEV was first to successfully demonstrate light pressure, which he did in 1901 with a torsional balance; Ernest Nichols and Gordon Hull conducted a similar independent experiment later that same year.

JOHN POYNTING and HOWARD ROBERTSON developed the Poynting-Robertson effect. In 1903, Poynting predicted that the abberation of sunlight causes dust grains larger than about 1 um to experience a retarding force from solar pressure, causing them to spiral into the Sun. In 1937, Robertson extended the concept by tying it to relativity theory. This effect has incorrectly been said to apply to solar sailing ships on inward spirals. (The drag caused by sunlight abberation applies to both outward and inward motion of spacecraft, but is ignored in calculating solar sailing trajectories because of its small magnitude.)

ALBERT EINSTEIN developed the concept of light quanta (the photon) in his work on the photoelectric effect and showed its equivalence to the wave description of light. He also established the speed of light as a limiting speed in his Special Relativity theory. Both were published in 1905.

SVANTE ARRHENIUS published Worlds in the Making in 1908, in which he predicted the possibility of solar pressure distributing life spores across interstellar distances, the concept of panspermia. He apparently was the first scientist to state that light could move objects between stars.

B. KRASNOGORSKII published On the Waves of the Ether in 1913. In his story backed by technical calculations, a small, bullet-shaped capsule is surrounded by a circular mirror 35 meters in diameter. It travels through space by means of solar pressure on the mirror. Steering is accomplished by changing the angle of the ring relative to the direction the sunlight. Screens of black silk are pulled over sections of the mirror to moderate the radiation pressure. A sequel, Islands in the Ether Ocean, was published in 1914. His stories are thought to have been read by Tsiolkovsky and Tsander.

KONSTANTINE TSIOLKOVSKY proposed the concept of using light to propel ships by means of photonic engines around 1920.

FREDERIK TSANDER published his solar sailing work in 1924, the first technical publication on the subject. He identified several useful configurations and made calculations of interplanetary trajectories by solar sailing spacecraft. He coined the term "solar sailing". He also showed the optimal method of transfer between circular orbits before Hohmann and showed how spacecraft could perform gravity-assist maneuvers.

J.D. BERNAL wrote The World, the Flesh & the Devil in 1929 in which he stated, "A form of space sailing might be developed which used the repulsive effect of the sun's rays instead of wind. A space vessel spreading its large, metallic wings, acres in extent, to the full, might be blown to the limit of Neptune's orbit. Then, to increase its speed, it would tack, close-hauled, down the gravitational field, spreading full sail again as it rushed past the sun." This popular work appears to be the first Western publication in the 20th Century on solar sailing, and shows a good understanding of the principles.

HERMANN OBERTH proposed the use of large reflectors in orbit to direct sunlight onto Earth for illumination, weather modification, and as a weapon. He did not apparently propose their use for transportation. The idea was revived during the Vietnam War as a battlefield illuminator and as a directed-energy weapon. NASA administrator James Fletcher mentioned the use of large reflectors on the Lunar surafce as directed-energy weapons in 1969.

CARL WILEY, writing as Russell Saunders, described the concept of solar sailing in "Clipper Ships of Space", published in Astounding Stories in 1951, the first U.S. publication on space sailing. His "light-jammer" configuration resembles a parachute, being a magnesium hemisphere 80 km in diameter and 0.15 um thick.

RICHARD GARWIN made the first U.S. professional publication on solar sailing in 1958 in the journal Jet Propulsion.

RAD GEORGEVIC created the first comprehensive model of the effects of solar pressure on spacecraft, published in 1973.

JEROME WRIGHT published Solar Sailing: Evaluation of Concept and Potential in 1974, beginning the modern solar sailing activity. He discovered artificial balance points using sails around planets in 1974-75. His development of a method to rendezvous with Halley's Comet led to the first substantial solar sail development work, done at JPL in 1976-77. He led the construction of the first prototype solar sail, done through the World Space Foundation, sponsored by the Lindberg Foundation.

ROBERT FORWARD invented the concept of using laser and microwave radiation sources for driving sailing ships across interstellar distances (foreshadowed by Arthur Clarke's laser to provide power to an interstellar ship in The Promise of Space, 1968).  

Early Developmental Work

Fabrication of 15-m sail, 1980-81 (© WSF)

Fabrication of 15-m sail, 1980-81 (© WSF)

Deployment of 15-m sail at The Planetary Society's Planetfest in 1981 (© WSF)

Deployment of 15-m sail, 1981 (© WSF)

After NASA terminated all solar sail funding in 1977, the World Space Foundation and the predecessor company to General Astronautics built two solar sails.  This work was sponsored by the Charles A. Lindbergh Foundation.  JPL provided booms without cost to the project.  One sail was 15 meters across (225 m2) and one was 30 meters (900 m2).  The latter may still be the largest sail to be built.

The 15-m sail was successfully deployed, furled, and deployed a second time without problems.  This was considered to be an adequate ground demonstration.  The 30-m sail was fabricated and folded, intended for a deployment demonstration in space.  The WSF sought funding and a launch for the 30-m sail.  Negotiations for a demonstration from a Shuttle Orbiter had been in progress for several months when Challenger was lost.  This ended hopes of a near-term space deployment.  While in storage, the sails and manufacturing equipment were damaged and subsequently scrapped.

Transolar Satellite Corporation was incorporated in California in 1980 by Jerome Wright for the purpose of developing space in a commercial manner through development of solar sailing and low-cost spacecraft. This venture was succeeded by General Astronautics Corporation, a Florida company established in 1989 by Jerome Wright for the purpose of developing space in a commercial manner through development of solar sailing and low-cost launch vehicles. These two companies are the first established for the development and operation of space sailing ships. Transolar was possibly the first company established with the intent of developing space on a commercial basis rather than through participation in government-led development.

In the late 1980's and early 1990's, several teams formed to enter solar sailers in a proposed race in celebration of Columbus' discovery of the New World.  This activity generated interest and some hardware, but no launches.  

Current Activities

A few projects exist today aimed at deployment demonstrations in space.  The chances of a demonstration happening appear better now than at any time in the past 20 years.

DLR, the German research organization, is working toward an in-space demonstration late in 2001 or 2002. The Planetary Society worked toward arranging an orbital demonstration. Both suborbital and orbital tests failed due to launcher problems.  

Future Activities

General Astronautics and Surrey Satellite Technology Ltd. (SSTL) have agreed to jointly offer low-cost solar sailing craft. This combines General Astronautics' solar sail experience with SSTL's experience in small spacecraft. SSTL has built and launched 15 satellites. SSTL's MINISAT 400 is included in GSFC's Rapid Spacecraft catalog. SSTL's successful SNAP-1 nanosat has been submitted for approval for the catalog.

Using the SNAP-1 spacecraft and a solar sail module, a fully functional solar sail spacecraft can be delivered for a very modest price. The SNAP-1 spacecraft includes video, communications, GPS-based navigation, and Sun sensors. Sail areas of 1000 to 4000 m2 are avaialble. This solar sail spacecraft is capable of escaping from Earth and operating in interplanetary space.