A website I recently visited described the Cassini Probe flight as requiring two loops around Venus and one around the Earth prior to its flight to Saturn because no launcher was powerful enough to send the probe on a direct route to Saturn. Does this mean that the loops reduced the required flight time, or does it mean that we are unable to launch a probe that can fly direct to Saturn? What was or is the limiting factor? I was under the impression that once the probe was on its way through space there was nothing to stop its progress on such a mission.
2007-09-03 12:24:13 · 6 answers · asked by zahbudar 6 in Science & Mathematics ➔ Astronomy & Space
The loops were to gain "gravity assist" boosts from those planets.
Its a common technique - its like "stealing" a tiny bit of additional momentum from the planet. Sometimes called a "slingshot" when orbiting a planet and then leaving orbit at just the right point.
If we hadn't done that, the probe would still be travelling to Saturn. These gravity assists serve to increase the speed of the probe and to angle its trajectory (without using a lot of steering fuel along the way to adjust the direction).
We did the same thing with New Horizons - it flew by Jupiter and at just the right moment it fired rockets to escape Jupiter, giving it an extra boost of speed.
By doing that, the travel time to Pluto was reduced by about 4 years.
2007-09-03 15:36:03 · answer #1 · answered by Anonymous · 1⤊ 0⤋
Let's look at it this way. The sun is at the center of the solar system, and we are orbiting quite close to it, compared to Saturn.
If you toss a rock in the air, it will come down. If you toss it harder, it will get higher before it comes down. This is the same thing with the solar system (I am simplifying here, there is also the fact gravity decreases the further you are, but we can skip this for now). Now, we are on earth, how strongly (fast) do you need to toss something up for it to reach Saturn before it falls back towards the sun (being on earth is like being atop a building on earth, ti simply puts up higher to start, but that is it, we still have to break free of the sun's attraction).
So, in comes the sling shot effect: by sending the probe on a carefully selected path, the probe will come from one direction and swing by in the opposite direction relative to the planet, with a change of velocity relative to the sun! Essentially, Venus was slowed down a minuscule amount, and the probe gained a lot of velocity.
So, in the end, you gained enough speed to make it all the way up to Saturn, but since the speed you have to make it there is the same that it would have been if you had the rocket needed to make it directly, what you did is take a lot of time to gain that speed. So you did not make the mission any shorter, you took a lot of time to build up the necessary speed.
2007-09-03 12:38:40 · answer #2 · answered by Vincent G 7 · 2⤊ 0⤋
The main factor holding back probes to the outer planets is the gravity of the Sun itself. The cassini probe is very large — about the size of a school bus — so using the gravitational slingshot effect in the inner planets allowed much less fuel to be used. Indeed, for such a heavy craft it's probably impossible to speed it up sufficiently without slingshot passes.
2007-09-03 12:32:23 · answer #3 · answered by poorcocoboiboi 6 · 2⤊ 0⤋
Left to orbit Saturn on it's own, Cassini would probably not crash into Saturn's atmosphere as Galileo did on command from mission controllers. It would however probably crash into one of the satellites, likely after circling the planet for many thousands of years or even longer. The spacecraft is carrying Plutonium 238, which has a half-life of 87 years, so by the time it does crash into either Saturn or one of it's moons, the plutonium aboard the probe would have decayed completely into it's daughter isotopes. Because of the vastness of the Saturnian system, Cassini will be wandering around the planet for a long, long time as an interplanetary Flying Dutchman.
2016-04-03 01:49:51 · answer #4 · answered by Anonymous · 0⤊ 0⤋
It's already been said, but the gravitational slingshot around Venus and Earth wasn't the only grav assist in the Cassini mission - it also made use of Jupiter, which is what propelled it the rest of the way. Now it's using some of Saturn's gravity, as well as its larger moons, to reduce the amount of fuel it needs.
2007-09-03 16:12:24 · answer #5 · answered by ryttu3k 3 · 1⤊ 0⤋
The gravitational sling shot maneuver takes more time, but considerably less fuel.
2007-09-03 12:35:38 · answer #6 · answered by kris 6 · 1⤊ 0⤋