Skip to comments.Astronomy Picture of the Day -- Leaving Earth
Posted on 08/05/2013 3:59:08 AM PDT by SunkenCiv
Explanation: What it would look like to leave planet Earth? Such an event was recorded visually in great detail by the MESSENGER spacecraft as it swung back past the Earth, eight years ago, on its way in toward the planet Mercury. Earth can be seen rotating in this time-lapse video, as it recedes into the distance. The sunlit half of Earth is so bright that background stars are not visible. The robotic MESSENGER spacecraft is now in orbit around Mercury and has recently concluded the first complete map of the surface. On occasion, MESSENGER has continued to peer back at its home world. MESSENGER is one of the few things created on the Earth that has left and will never return -- at the end of its mission MESSENGER will be crashed into Mercury's surface.
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Mercury Messenger movie.
I wonder if it would be scary or fun to do that in a manned craft?
"Well, I sure hope none of the people on Mercury are hurt or killed when Messenger crashes..." - Sheila Jackson Lee
I would think there would be considerable G forces during a gravity assist.
I love, love, love that video!
Thank you so much, SunkenCiv.
I must send that to all my grands!
I doubt anyone on board would feel it. It’s all relative. They’d be traveling at such a high rate that falling into and then out of the gravity well around Earth would be like your driver-side front tire clunking into a pot hole.
I am in Awe!
Thank You, Sunken Civ.
Great. Another parasitic spacecraft coming by just to suck up our gravity! If this keeps up we won’t have enough gravity for the rest of us!
I guess I’m thinking of Centripetal force but I’m not sure you would feel that either without a physical connection to the orbital center.
I’ve read a lot of Robert Forward who wrote extensively on tether assisted maneuvering which creates a physical connection leading to a felt force.
BTTT for later viewing of video
If the orbiting object came into Earth’s gravity well too shallow, it would be slung in the wrong direction away from the planet. If it came in too steep, it would miss the gravity well altogether or have to come back for a second assist later. Fortunately, these calculations are solid formulae tested and confirmed many, many times.
I remember studying the use of gravity assists in the astrophysics part of my physics courses in college. While they used to do the calculations on paper with slide rules, computers can do it all now.
It’s the same sort of thing for which they had to account when sending our boys to the moon. Come in too shallow and they crash into the lunar surface; too steep and they miss the moon’s gravity and careen into space.
As far as “feeling” it, the properties of force in space and force on Earth are different due to the constancy of gravity at the Earth’s surface. We can calculate the acceleration of gravity on Earth as 9.6 m/s^2. Since there’s no atmosphere in space, there’s nothing to hinder the rate of acceleration in space up to the force of thrust. When you hit a gravity well, your trajectory changes slightly, but if you hit it just right, you reach escape velocity of that object’s gravity and gain speed from the ejection, much the same way a NASCAR driver speeds up at the peak of a turn to gain momentum on the downslope.
Sorry, 9.8 m/s^2.
Well as long as it can take a picture of the flag the astronauts planted on Mercury ... its all good
The Juno craft has already been out between the orbit of Mars and Saturn. Seems counter intuitive but the long trip uses less fuel.
I believe the messenger did some thing similar as a means of slowing down.
That is incredible!
It sees to me that unless some counter-thrusts are applied which yield a reactive force, like a booster or maneuvering thruster, the object would follow the geodesic w/o much impact.
We agree on that point fundamentally. There would be little felt impact on a swing trajectory using using gravity assist.