Low energy transfers
Encyclopedia
A low energy transfer, or low energy trajectory
, is a route in space which allows spacecraft to change orbit
s using very little fuel. These routes work in the Earth
-Moon
system and also in other systems, such as traveling between the satellites of Jupiter. The drawback of such trajectories is that they take much longer to complete than higher energy (more fuel) transfers such as Hohmann transfer orbit
s.
Low energy transfer are also known as weak stability boundary trajectories, or ballistic capture trajectories.
Low energy transfers follow special pathways in space, sometimes referred to as the Interplanetary Transport Network
. Following these pathways allows for long distances to be traversed for little expenditure of delta-v
.
Missions that have used low energy transfers include:
Proposed missions using low energy transfers include:
, which was designed to swing by the moon but not to enter orbit. The Hagoromo subsatellite was released by Hiten on its first swing-by and successfully entered lunar orbit, but suffered a communications failure.
Edward Belbruno
and James Miller of the Jet Propulsion Laboratory
had heard of the failure, and helped to salvage the mission by developing a ballistic capture trajectory that would enable the main Hiten probe to itself enter lunar orbit. The trajectory they developed for Hiten
used Weak Stability Boundary Theory and required only a small perturbation to the elliptical swing-by orbit, sufficiently small to be achievable by the spacecraft's thrusters. This course would result in the probe being captured into lunar orbit using zero delta-v, but required five months instead of the usual three days for a Hohmann transfer.
For rendezvous with the Martian moons, the savings are 12% for Phobos and 20% for Deimos. Rendezvous is targeted because the stable pseudo-orbits around the Martian moons do not spend much time within 10 km of the surface.
Trajectory
A trajectory is the path that a moving object follows through space as a function of time. The object might be a projectile or a satellite, for example. It thus includes the meaning of orbit—the path of a planet, an asteroid or a comet as it travels around a central mass...
, is a route in space which allows spacecraft to change orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
s using very little fuel. These routes work in the 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...
-Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
system and also in other systems, such as traveling between the satellites of Jupiter. The drawback of such trajectories is that they take much longer to complete than higher energy (more fuel) transfers such as Hohmann transfer orbit
Hohmann transfer orbit
In orbital mechanics, the Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbits, typically both in the same plane....
s.
Low energy transfer are also known as weak stability boundary trajectories, or ballistic capture trajectories.
Low energy transfers follow special pathways in space, sometimes referred to as the Interplanetary Transport Network
Interplanetary Transport Network
The Interplanetary Transport Network is a collection of gravitationally determined pathways through the solar system that require very little energy for an object to follow. The ITN makes particular use of Lagrange points as locations where trajectories through space are redirected using little...
. Following these pathways allows for long distances to be traversed for little expenditure of delta-v
Delta-v
In astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....
.
Missions that have used low energy transfers include:
- HitenHitenThe Hiten Spacecraft , given the English name Celestial Maiden and known before launch as MUSES-A , part of the MUSES Program, was built by the Institute of Space and Astronautical Science of Japan and launched on January 24, 1990...
, from JAXA - SMART-1, from ESAEuropean Space AgencyThe European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
- Genesis, from NASANASAThe 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...
.
Proposed missions using low energy transfers include:
- European Student Moon OrbiterEuropean Student Moon OrbiterThe European Student Moon Orbiter is planned to be the first European student mission to the Moon. Currently student teams from 19 universities throughout Europe are working on the program....
(ESMO)
History
Low energy transfers to the Moon were first demonstrated in 1991 by the Japanese spacecraft HitenHiten
The Hiten Spacecraft , given the English name Celestial Maiden and known before launch as MUSES-A , part of the MUSES Program, was built by the Institute of Space and Astronautical Science of Japan and launched on January 24, 1990...
, which was designed to swing by the moon but not to enter orbit. The Hagoromo subsatellite was released by Hiten on its first swing-by and successfully entered lunar orbit, but suffered a communications failure.
Edward Belbruno
Edward Belbruno
Edward Belbruno is a mathematician whose interests are in celestial mechanics, dynamical systems, dynamical astronomy, and aerospace engineering....
and James Miller of the Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
had heard of the failure, and helped to salvage the mission by developing a ballistic capture trajectory that would enable the main Hiten probe to itself enter lunar orbit. The trajectory they developed for Hiten
Hiten
The Hiten Spacecraft , given the English name Celestial Maiden and known before launch as MUSES-A , part of the MUSES Program, was built by the Institute of Space and Astronautical Science of Japan and launched on January 24, 1990...
used Weak Stability Boundary Theory and required only a small perturbation to the elliptical swing-by orbit, sufficiently small to be achievable by the spacecraft's thrusters. This course would result in the probe being captured into lunar orbit using zero delta-v, but required five months instead of the usual three days for a Hohmann transfer.
Delta-v savings
From low-earth orbit to lunar orbit, the delta-v savings approach 25% and allow for a doubling of payload.For rendezvous with the Martian moons, the savings are 12% for Phobos and 20% for Deimos. Rendezvous is targeted because the stable pseudo-orbits around the Martian moons do not spend much time within 10 km of the surface.
See also
- Orbital mechanics
- Interplanetary Transport NetworkInterplanetary Transport NetworkThe Interplanetary Transport Network is a collection of gravitationally determined pathways through the solar system that require very little energy for an object to follow. The ITN makes particular use of Lagrange points as locations where trajectories through space are redirected using little...
- Gravitational slingshotGravitational slingshotIn orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement and gravity of a planet or other celestial body to alter the path and speed of a spacecraft, typically in order to save propellant, time, and expense...