TEACHER RESOURCE SCIENCE CONTENT/ CURRICULUM LINK EXPLORE A STARDOME OBSERVATORY & PLANETARIUM TECHNOLOGICAL OR BIOLOGICAL FACTS, RESOURCES AND ACTIVITIES ON... APPLICATION ASSIST OF PHYSICS. GRAVITY Gravity assist, or gravitational slingshot is a manoeuvre used in space exploration. It uses the gravitation pull of astronomical JUPITER bodies, usually planets, to speed up or slow down a spacecraft. Jul 1979 Using this technique, we can send spacecraft much further into space by using less fuel. A gravity assist works by flying a spacecraft close to a planet. As the spacecraft approaches the planet, the gravity from the planet speeds it up. But then it flies away, and it slows down SATURN EARTH again. So, the speed increase equals the speed decrease. This Aug 1981 Aug 1977 doesn’t speed the spacecraft up at all! So how does it work? Remember, the planet is both spinning on its axis and orbiting the Sun. So as the spacecraft gets close enough to the planet, it catches up with the speed that the planet is orbiting around the Sun. It is this orbital momentum that gives the spacecraft so much speed. If the spacecraft now fires its rockets at the closest point of encounter with the planet, the Using this technique, approach will multiply we can send the effect of the rockets. This immense momentum URANUS spacecraft much however, comes at a Jan 1986 further into space cost. Energy cannot be less fuel. created or destroyed, only by using transferred. So when the
spacecraft uses the planet’s orbital momentum to speed up, the planet loses a minute amount of orbital velocity. If we did this gravitational slingshot enough times (think NEPTUNE many, many, many trillions of times) we could eventually Aug 1989 cause the planet to crash into the Sun. This however, isn’t really a concern at all but if you’re worried, the gravity assist works backwards too. So if we had a spacecraft fly Journey of Voyager 2 using towards the planet in the opposite direction to its orbit gravity assists from planets. around the Sun, it would decelerate and the planet would speed up a tiny amount.
We’ve used gravity assists to send many spacecraft further into space. The two Voyager crafts flew by Jupiter and Saturn. Cassini flew by Venus twice to this other resource... use its orbital momentum, and then past Earth and Check out Rosetta’s Twelve-Year Journey to Land on a Comet: Jupiter for a third and fourth gravity assist. The MESSENGER spacecraft needed, two Earth flybys, https://www.youtube.com/watch?v=ktrtvCvZb28 two Venus flybys and three Mercury flybys to slow down enough to finally insert itself into orbit around Mercury. DISCUSSION POINTS we use Why do Why does the gravity assist? spacecraft speed up? STARDOME.ORG.NZ 09 624 1246 ACTIVITY
STARDOME OBSERVATORY & PLANETARIUM ASSIST GRAVITY EXTRA FOR GRAVITY ACTIVE EXPERTS ACTIVITY Objective... ASSISTING To simulate gravity assist Objective... manoeuvres and learn about BIRDS To try and borrow energy previous space-crafts that Objective... from an object to go faster have used this strategy. To understand the trajectory for space-crafts and their You’ll need... You’ll need... gained momentum. A computer Three students in total You’ll need... Instructions... An Apple or Android device Instructions... 1. Two students face each 1. Visit the following website: Angry Birds in Space App other and hold hands with http://www.messenger- outstretched arms. One education.org/Interactives/ child is the Sun, and the ANIMATIONS/grav_assist/ Instructions... other is a planet. gravity_assist_menu.html 1. Download and install the app 2. Both students lean back to 2. Look at the different 2. As you catapult the bird create some tension, and distances that a spacecraft into space, try to get it the planet starts to orbit can be from the planet. within the gravitational the Sun at a moderately 3. Does this make a difference? pull of the planet. quick speed. 4. Why do you think? As the bird approaches the 3. 3. The third student, the planet, watch the bird, fly spacecraft, approaches the off into space, faster and planet. Touch the planet’s in a different direction. shoulder to borrow some energy! (remember, in reality, the spacecraft doesn’t have to touch the planet!) 4. As the spacecraft touches the planet, the Sun and the planet should feel a bit of a loss of energy through drag. The spacecraft should get a bit of a boost helping the go faster!
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