Fission sail

Fission sail

The fission sail is a type of spacecraft propulsion proposed by Robert Forward that uses fission fragments to propel a large solar sail-like craft. It is similar in concept to the fission-fragment rocket in that the fission by-products are directly harnessed as working mass, and differs primarily in the way that the fragments are used for thrust.

In the fission sail, the "rocket" is built in the form of a two-layer sheet, with some sort of absorber on one side, and nuclear fuel on the other. Atoms in the fuel that decay will release their fragments in random, but opposite, directions. In the simple case where the decay releases the fragments "front" and "rear", the rearward moving fragment generates thrust directly, while the frontward moving one is absorbed in the front half of the sail, also contributing thrust. The system must be built very large in order to ensure that those fragments that are not moving directly to the front of rear nevertheless tend to hit the sail somewhere. A sail several kilometers on a side would have fairly good "capture ratios".

The sail is not a nuclear reactor, and relies on natural decay rates for energy release. The thrust from such a system will always be very low, albeit extremely efficient. Another problem is that the sail receives the energy equally over the entire sail surface, and thus can't be steered. This differs from a solar sail, where tilting the sail to the sunlight can produce a sideways thrust for steering.

Forward proposed the system as an "add on" to existing solar sails. Close to stars where the light density is high the sails work fine, but as they move past about 2 AU their thrust is too low to be useful. Forward suggested that coating the sail with fissionable material would provide thrust in this region, where maneuvering is no longer as important. Such a system would accelerate and maneuver based on solar energy for the start of its flight, and then continue to accelerate at a lower rate for long periods of time.


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Magnetic sail — A magnetic sail or magsail is a proposed method of spacecraft propulsion which would use a static magnetic field to deflect charged particles radiated by the Sun as a plasma wind, and thus impart momentum to accelerate the spacecraft.[1][2] A… …   Wikipedia

  • Propulsion par fragments de fission — Cet article concerne l utilisation directe de l énergie cinétique des fragments de fission pour la propulsion . Pour pour le chauffage direct d un fluide propulsif, voir Propulsion nucléaire thermique#Réacteur à fragments de fission. La… …   Wikipédia en Français

  • Nuclear salt-water rocket — A nuclear salt water rocket (or NSWR) is a proposed type of nuclear thermal rocket designed by Robert Zubrin that would be fueled by water bearing dissolved salts of Plutonium or U235. These would be stored in tanks that would prevent a critical… …   Wikipedia

  • Nuclear pulse propulsion — An artist s conception of the Project Orion basic spacecraft, powered by nuclear pulse propulsion. Nuclear pulse propulsion (or External Pulsed Plasma Propulsion, as it is termed in one recent NASA document[1]) is a proposed method of spacecraft… …   Wikipedia

  • Gas core reactor rocket — Gas core reactor rockets are a conceptual type of rocket that is propelled by the exhausted coolant of a gaseous fission reactor. The nuclear fission reactor core may be either a gas or plasma. They may be capable of creating specific impulses of …   Wikipedia

  • Nuclear photonic rocket — In a nuclear photonic rocket, a nuclear reactor would generate such high temperatures that the blackbody radiation from the reactor would provide significant thrust. The disadvantage is that it takes a lot of power to generate a small amount of… …   Wikipedia

  • Spacecraft propulsion — A remote camera captures a close up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is any method used to accelerate spacecraft and artificial… …   Wikipedia

  • Nuclear thermal rocket — Sketch of nuclear thermal rocket …   Wikipedia

  • Fusion rocket — A fusion rocket is a theoretical design for a rocket driven by fusion power which could provide efficient and long term acceleration in space without the need to carry a large fuel supply. The design relies on the development of fusion power… …   Wikipedia

  • Nuclear electric rocket — In a nuclear electric rocket, nuclear thermal energy is changed into electrical energy that is used to power one of the electrical propulsion technologies. Technically the powerplant is nuclear, not the propulsion system, but the terminology is… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”