Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Let Gravity Assist You...


’Fly-bys’, or ’gravity assist’ manoeuvres, are now a standard part of spaceflight and are used by almost all ESA interplanetary missions.

Imagine if every time you drove by a city, your car mysteriously picked up speed or slowed down. Substitute a spacecraft and a planet for the car and the city, and this is called a ’gravity assist’. These manoeuvres take advantage of the fact that the gravitational attraction of the planets can be used to change the trajectories, or the speed and direction, of our spacecraft on long interplanetary journeys.
As a spacecraft sets off towards its target, it first follows an orbit around the Sun. When the spacecraft approaches another planet, the gravity of that planet takes over, pulling the spacecraft in and altering its speed. The amount by which the spacecraft speeds up or slows down is determined by the direction of approach, whether passing behind or in front of the planet.

When the spacecraft leaves the influence of the planet, it once again follows an orbit around the Sun, but a different one from before, either on course for the original target or heading for another fly-by.

’Slingshot’ effect

The first spacecraft to experience a gravity assist was NASA’s Pioneer 10. In December 1973, it approached a rendezvous with Jupiter, the largest planet in the Solar System, travelling at 9.8 kilometres per second. Following its passage through Jupiter’s gravitational field, it sped off into deep space at 22.4 kilometres a second – like when you let go of a spinning merry-go-round and fly off in one direction. This kind of acceleration is also called the ‘slingshot effect’.

Mission: Impossible?

Even before this encounter, Italian astronomer Giuseppe ‘Bepi’ Colombo had realised the potential of such manoeuvres and had used them to design a ‘Mission: Impossible’ to Mercury, the innermost planet of our Solar System. To reach Mercury, a spacecraft launched from Earth needed to lose more energy than a conventional rocket would allow.

Colombo’s brilliant idea was to realise that gravity assists could also be used to slow a spacecraft. On 10 March 1974, the NASA Mariner 10 spacecraft flew past Venus, lost speed and fell into its rendezvous orbit with Mercury.

Extraordinary manoeuvre

The ESA/NASA Ulysses mission used one of the most extraordinary gravity assists to allow it to see the polar regions of the Sun, places that are forever hidden from any observing location on Earth.

In October 1990, the Ulysses spacecraft left Earth to voyage towards Jupiter. There, it used a gravity assist to throw it out of the plane of the planets into a gigantic loop that passed over the south pole of the Sun in 1994, and then the north pole 13 months later.

More manoeuvres coming up

Also in 2004, ESA’s Huygens probe will arrive at the Saturn’s moon Titan. It is carried on the NASA spacecraft Cassini which used four gravity assists (one with Earth, two with Venus and one with Jupiter) to accelerate it towards Saturn. ESA’s comet-chaser Rosetta will use a similar number of gravity assists to speed it to Comet Churyumov-Gerasimenko.

Over the next eighteen months ESA’s lunar scout SMART-1 will become the first spacecraft to use gravity assists in conjunction with a revolutionary propulsion system, the solar-electric ion engine. This will pave the way for ESA’s Mercury mapper, appropriately called BepiColombo, which will use the same technique to orbit the inner planet early in the next decade.

As well as affecting spacecraft, the gravitational influence of planets also affects the distribution of asteroids and comets. There are families of small bodies, for example the Apollo and the Plutino asteroids, which converges on a particular shape and size of orbit because their members have been repeatedly subjected to small gravitational attractions from the planets.

There are also individual, one-off gravitational effects that can send objects such as comets either plummeting into the inner Solar System or hurtling out beyond the planets. Watching for these ‘wild cards’ is a prime area of study for ESA, as the geological record on Earth shows that asteroids have occasionally collided with our planet in the past.

Monica Talevi | ESA
Further information:

More articles from Physics and Astronomy:

nachricht Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)

nachricht Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>