Space Voyage #1 Chatter

[TheBigDog]

I am minutes away from the weekend. I am making a full fledged effort to get a post of our last orbit of earth written, and to begin compiling the story together into a single document. I will post that document to the sticky and it will become Space Voyage #1 - Part 1. We are just beginning Part 2. I am going to use illustrations that people provided, along with the story peices everyone wrote for compiling the whole thing together.

I will take some liberty in sewing some of the story together. I am open to everyone's input. If you want an advace copy before I post so you can proof read it please let me know.

It is going to be a busy weekend! All that plus taking #4 to the swimming pool.

Bill

[Jay-qu]

kilometers is a well recognised unit of length - units of millions of km are a bit more tangible to peoples minds than a billion meters

and pyro I have to go with number 9 - I was out getting drunk last night and slept in this morning

[Jay-qu]

Again, all women. So we now had a crew of 100. And now we had 31 women and 69 men. Huh… sixty nine…

Ratio's not to good.. I call shotgun!

errr I didnt bring any *protection* with me.. there didnt happen to be any floating around in the recreational supplies?

[ronthepon]

The ratio's fine... realistic seeming... for some reason...

Parts one and two? huh?

I'd love a copy of the story... but oh shoot... what difference would it make...

[ronthepon]

Something needs to be done about posts which wont be all that story advancing being put up in the main thread now...

[TheBigDog]

Jay-Qu, funny you should mention the name of the telescope as "thee eyes of god". I was going to call it "God's Eye", but decided against it. I couldn't think of a proper mythology reference. Sauron?

Bill

[Janus]

Originally Posted by TheBigDog

We were going to run the engine all the way to the earth, and use her gravity to slingshot us at even higher speed out away from earth and toward Jupiter.

Bill (T+18)

The thing is that this won't result in any net gain of speed. Sure, you'll gain speed as fall in towards the Earth, but you'll lose it again as you climb back out.

A gravitational slingshot works by transfering orbital momentum from one object to another. In order for this tranfer to take place, however, there must be a initial difference in orbital speed between the objects. In this case, since our object is to reach Jupiter, the difference must be in their Solar orbits. Since the Moon. (our Starting point) orbits the Sun along with the Earth, Its mean solar orbital velocity is equal to that of the Earth's.

A gravitational slingshot in simplest terms is like an elastic collision between objects. Put an object in an orbit with a velocity of 30 km/sec. Place a second smaller object in its path with an orbital velocity of 20 km/sec in the same direction. The relative velocity between the two is 10 km/sec.

Let the first object catch up to and collide with the second object. They will hit at 10 km per second realtive to each other, and rebound from each other at that same speed. If the second object is much smaller than the first, the vast majority of this rebound will be in the manner of a change of velocity in this object. After the collision the two objects still have the same relative speed (10 km/sec) but now away from each other. The first object will be moving at slightly less than 30 km in the same direction it was before and the Second will moving at slighty less than 40 km in the same direction. The second object gains 20 km/sec by virtue of the transfer of momentum from the collision. And assuming that the first object was in a circular orbit, this is enough to boost the second object into a solar escape trajectory.

The only difference between this and a gravititational slingshot is that gravity gives us a way to swing around a planet in a hyperbolic trajectory to get this same "rebound" effect without a collision. The gain in speed does not come from the gravity, it comes from the transfer of momentum. Gravity just provides the mechanism for this transfer.

So, going back to our scenerio, our ship is in orbit around the Moon, and thus has the same Solar orbital velocity as the Earth. No velocity difference, no means of transfering momentum. (of course we can use our engines to make a difference, but since the velocity "gained" would be only equal to the velocity change caused by our engines, it would be a wash.)

Another point is that even if we could steal some orbital momentum from the Earth, in our present case, it would do us no good. This gain of velocity would have to be in the same direction as the Earth's orbital motion, and with Juipiter's present position relative to Earth, the Earth is moving in the wrong direction.

All that being said, there is a legitimate reason why we might want to swing in close to the Earth. Right now, the Moon is in its last quarter, which means that it is in that part of its orbit where it is "in front" of the Earth in its orbital path, and on the "opposite" side of the Earth with respect to Jupiter . By passing in close to the Earth on the right hyperbola, we can use its gravity to "steer" us onto the correct heading to Jupiter. ( like a roller skater using a lamp post to change direction.)

[TheBigDog]

Thanks Janus!

I learn something new every day. I had been wondering about how gravitational slingshotting worked. Now I know. I guess we do exactly as is written, but instead of a slingshot it is for steering purposes. Still works for me. I will make not of the engineering and be sure to correct it in the compiled version I am making.

Bill

[TheBigDog]

We are on our way to Jupiter. How long to get there? That is yet to be determined. Determined by all of us. I have been driving this story forward at a determined pace since the beginning. Now I am stopping. Lets see where we end up, shall we?

Bill

[Jay-qu]

Originally Posted by TheBigDog

We are on our way to Jupiter. How long to get there? That is yet to be determined. Determined by all of us. I have been driving this story forward at a determined pace since the beginning. Now I am stopping. Lets see where we end up, shall we?

Bill

cool, should be interesting. I could see how in your last post you where trying to encourage others to join in by asking them questions about their parts of the mission clever.

So do you not like God's Eye or Through God's eyes (TGE)