Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Let Gravity Assist You...

23.10.2003


’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:
http://www.esa.int/export/esaSC/SEMXLE0P4HD_exploring_0.html

More articles from Physics and Astronomy:

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

nachricht Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>