Project Longshot
Encyclopedia
Project Longshot was a conceptual design for an interstellar spacecraft, an unmanned probe intended to fly to Alpha Centauri
powered by nuclear pulse propulsion
. Developed by the US Naval Academy and NASA
from 1987 to 1988, Longshot was designed to be built at Space Station Freedom
, the precursor to the existing International Space Station
. Unlike the somewhat similar Project Daedalus
, Longshot was designed solely using existing technology, although some development would have been required.
Unlike Daedalus' closed-cycle fusion
engine, Longshot would use a long-lived nuclear fission
reactor for power. Initially generating 300 kilowatts, the reactor would power a number of laser
s in the engine that would be used to ignite inertial confinement fusion
similar to that in Daedalus. The main design difference is that Daedalus would rely on the fusion reaction being able to power the ship as well, whereas in Longshot the internal reactor would provide this power.
The reactor would also be used to power a laser for communications back to Earth, with a maximum power of 250 kilowatts. For most of the journey this would be used at a much lower power for sending data about the interstellar medium
, but during the flyby the main engine section would be discarded and the entire power capacity dedicated to communications at about 1 kilobit per second.
Longshot would have a mass of 396 metric tonnes at the start of the mission, including 264 tonnes of Helium-3
/Deuterium
pellet fuel/propellant. The active mission payload, which includes the fission reactor but not the discarded main propulsion section, would have a mass of around 30 tonnes.
A difference in the mission architecture between Longshot and the Daedalus study is that Longshot would go into orbit about the target star while Daedalus would do a one shot fly-by lasting a comparatively short time.
The journey to Alpha Centauri B
orbit would take about 100 years, at an average velocity of approx. 13411 km/s, about 4.5% the speed of light, and another 4.39 years would be necessary for the data to reach Earth
.
Alpha Centauri
Alpha Centauri is the brightest star in the southern constellation of Centaurus...
powered by nuclear pulse propulsion
Nuclear pulse propulsion
Nuclear pulse propulsion is a proposed method of spacecraft propulsion that uses nuclear explosions for thrust. It was first developed as Project Orion by DARPA, after a suggestion by Stanislaw Ulam in 1947...
. Developed by the US Naval Academy and NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
from 1987 to 1988, Longshot was designed to be built at Space Station Freedom
Space Station Freedom
Space Station Freedom was a NASA project to construct a permanently manned Earth-orbiting space station in the 1980s. Although approved by then-president Ronald Reagan and announced in the 1984 State of the Union Address, Freedom was never constructed or completed as originally designed, and after...
, the precursor to the existing International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...
. Unlike the somewhat similar Project Daedalus
Project Daedalus
Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible unmanned interstellar spacecraft. Intended mainly as a scientific probe, the design criteria specified that the spacecraft had to use current or near-future technology and had to...
, Longshot was designed solely using existing technology, although some development would have been required.
Unlike Daedalus' closed-cycle fusion
Fusion power
Fusion power is the power generated by nuclear fusion processes. In fusion reactions two light atomic nuclei fuse together to form a heavier nucleus . In doing so they release a comparatively large amount of energy arising from the binding energy due to the strong nuclear force which is manifested...
engine, Longshot would use a long-lived nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
reactor for power. Initially generating 300 kilowatts, the reactor would power a number of laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s in the engine that would be used to ignite inertial confinement fusion
Inertial confinement fusion
Inertial confinement fusion is a process where nuclear fusion reactions are initiated by heating and compressing a fuel target, typically in the form of a pellet that most often contains a mixture of deuterium and tritium....
similar to that in Daedalus. The main design difference is that Daedalus would rely on the fusion reaction being able to power the ship as well, whereas in Longshot the internal reactor would provide this power.
The reactor would also be used to power a laser for communications back to Earth, with a maximum power of 250 kilowatts. For most of the journey this would be used at a much lower power for sending data about the interstellar medium
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
, but during the flyby the main engine section would be discarded and the entire power capacity dedicated to communications at about 1 kilobit per second.
Longshot would have a mass of 396 metric tonnes at the start of the mission, including 264 tonnes of Helium-3
Helium-3
Helium-3 is a light, non-radioactive isotope of helium with two protons and one neutron. It is rare on Earth, and is sought for use in nuclear fusion research...
/Deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
pellet fuel/propellant. The active mission payload, which includes the fission reactor but not the discarded main propulsion section, would have a mass of around 30 tonnes.
A difference in the mission architecture between Longshot and the Daedalus study is that Longshot would go into orbit about the target star while Daedalus would do a one shot fly-by lasting a comparatively short time.
The journey to Alpha Centauri B
Alpha Centauri
Alpha Centauri is the brightest star in the southern constellation of Centaurus...
orbit would take about 100 years, at an average velocity of approx. 13411 km/s, about 4.5% the speed of light, and another 4.39 years would be necessary for the data to reach Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
.
External links
- Project Longshot: An Unmanned Probe To Alpha Centauri (Please note that the article cited here refers to an Alpha and Beta Centauri as the orbital target of the mission, but the correct nomenclature for these two components of the Alpha Centauri binary star system is Alpha Centauri A and B. Beta CentauriBeta CentauriBeta Centauri , also known as Hadar or Agena, is the second brightest star in the constellation Centaurus and the tenth brightest star in the night sky. Beta Centauri is a B1 III blue-white giant star that the astrometric Hipparcos satellite calculates as about 161 parsecs or 525 light-years from...
is an entirely different unassociated star.)