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Originally Posted by Rude Dude
I'm glad someone else is following the Mercury probes. I have a few questions about the issues getting to the planet.
#1) Why does it take as much fuel to get to Mercury as it does to get to Saturn??
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Getting out of Earth's gravity well is a large energy expenditure regardless of destination. It takes very little additional fuel to get TO Mercury. It takes a LOT of energy to slow down enough to be captured by Mercury's gravity.
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#2) Why so many gravity assists? Wouldn't it be faster with less? The ESA space craft is using ION propulsion so I understand why it takes forever to get there and needing the gravity assists.
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Again, the problem isn't getting TO the planet, it's slowing down enough to take more than a few fleeting snapshots. Those weren't gravity assists, they were gravity brakes; the opposite of outward bound probes get.
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#3) Wouldn't a straighter path take less fuel and save money??
The probe is treking almost 5 billion miles to get to a planet that is only about a third the Earth's distance from the Sun.
I know its close proximity to the Sun has unique challenges but.... the stats seem way out of whack......
Can someone educate me on the specifics please??
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This isn't about simply flying by Mercury. Mercury is very small and close to the sun. Any probe simply pushed toward the Sun will accelerate so much that Mercury will never be able to capture it. We could go straight to Mercury and fire retro-rockets to slow the probe down, but the probe would have to be the size of the original launching rocket. Which means that the original launching rocket would have to have been something the size of the Saturn rockets that launched Apollo.