Space Voyage #1 Chatter

[Jay-qu]

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 :phones: clever.

 

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

[TheBigDog]

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)

I think I like God's Eye. But it is up to you JQ. ;)

 

Bill

[Jay-qu]

Though I am not a relegious person and far from beleiving in god - I like the connotations of a 'gods eye view' of the universe. God's Eye's it is - the s is because its an array ;)

[TheFaithfulStone]

Well, hope that didn't screw it up too bad. I think the bump BD felt may have had something to do with the engines. Which if they fire 30 times per second should produce (I think) a low b-flat. Anyway - 60 cycle hum is b-flat below high c, and I think 30 hertz should be near the bottom of the human hearing range - or at least our discrimination range.

 

TFS

[Pyrotex]

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....QUOTE]

Janus,

if this were true, then NO gravity slingshots would work. At any planet, the same would apply--gain speed as fall in, lose it as you climb out.

 

Now, I could be wrong, but my understanding of grav-slings is that as the vehicle passes by the planet (closest approach, highest speed), an additional engine burn is made, adding a small delta-V. The effect is that the time the vehicle spends on the outward leg is much smaller than the time spent on the inward leg. Since the amount of speed added/lost by falling in/out of the gravity well is an integral function over time, if the time in equals time out, then there is no net gain in speed. The additional delta-V reduces the time spent on the climb out of the gravity well, such that far less speed is lost outbound than was gained inbound.

 

Alternate argument: Cassini and Galileo spacecraft both used Earth as grav-slings. So we know it works. Now, the origin of the spacecraft (is it coming from Venus? Is it coming from the Moon?) is immaterial. All that matters is the alignment of the incoming trajectory relative to the Earth's vector in the Earth's orbit. The vehicle must come "from behind" the Earth (in its orbit) and pass on the outward side of the Earth.

[ronthepon]

Whats with the bump? I do not wanna spoil the plot here, but cant think of a way not to...

[Pyrotex]

Whats with the bump? I do not wanna spoil the plot here, but cant think of a way not to...

Doesn't have to be ONE thing. Remember, a malfunction big enough to go BUMP may cause other malfunctions.. Or itself be caused by a predecessor malfunction.

[ronthepon]

Doesn't have to be ONE thing. Remember, a malfunction big enough to go BUMP may cause other malfunctions.. Or itself be caused by a predecessor malfunction.

Yup. I've created a big malfuntion on one of the machines...

[TheFaithfulStone]

Are we to reveal what we're plotting in this thread?

 

Maybe we should.

 

Just to hint: The crawlers transmit an unencrypted 802.11a signal... it wouldn't be difficult at all to spoof it...

 

TFS

[IDMclean]

I hope to god I am not in ring 1... Which rings are hab rings again? It is important to know where I am in all of this.

[Pyrotex]

I hope to god I am not in ring 1... Which rings are hab rings again? It is important to know where I am in all of this.

All habs are in rings 2 and 3. Ring 1 (aft) and 4 (forward) contain most of the special "working" modules, labs, control rooms, sensor displays, internal utilities control. All rings have at least 2 garden modules, but most of these are in rings 2 and 3.

[TheFaithfulStone]

Crap. I might very well be in Ring 1.

[TheBigDog]

I threw on my semi-formal, early-evening silk robe with the embroidered red and taupe dragon (suitable for greeting other officers) and opened the door.

Pyro, I am laughing my *** off here at work. You take the time to choose an appropirate robe for answering the door - while greeting me banging on your door in my boxer shorts.

 

ROFL!

 

Bill

[Janus]

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....QUOTE]

Janus,

if this were true, then NO gravity slingshots would work. At any planet, the same would apply--gain speed as fall in, lose it as you climb out.

 

 

Relative to the planet, yes, the probe always loses the same amount of speed climbing out as it gains falling in. The point is that is does alter its velocity due a change in direction. It is this change of velocity, which when figured relative to the Sun that results in a increase of speed relative ot he Sun. This gain in speed comes from an equal loss of orbital angular momentum of the Planet.

 

Now, I could be wrong, but my understanding of grav-slings is that as the vehicle passes by the planet (closest approach, highest speed), an additional engine burn is made, adding a small delta-V. The effect is that the time the vehicle spends on the outward leg is much smaller than the time spent on the inward leg. Since the amount of speed added/lost by falling in/out of the gravity well is an integral function over time, if the time in equals time out, then there is no net gain in speed. The additional delta-V reduces the time spent on the climb out of the gravity well, such that far less speed is lost outbound than was gained inbound.

 

While a burn at perapis can be used to augment the gain, it isn't needed to get a boost from the planet.

 

 

In our case, however this 'burn while at perigee' trick is of no help.

 

Here's why: If we were in an elipitical orbit with a perigee of altitude 300km and an apogee at moon orbit, it is true that we would only need a delta v of 94 meters per second at perigee to reach escape velocity vs 1255 m/sec at apogee.

 

But we are not in such an orbit, we are sharing the Moon's nearly circular orbit. Now from this orbit it would only take a delta v of 423 m/sec to reach escape velocity. This is still more that the 94 m/sec stated above, but to make use of this smaller delta v burn, we have to get within 300 km of Earth. IOW, we transfer from our circular orbit to the elliptical orbit mentioned above. Here's the kicker, in order to make that transfer we have to apply a delta v of 832 m/sec! this is 409 m/sec greater than the delta v we need to reach escape velocity directly from the Moon's orbit, and would still need to apply an addtional 94 m/ sec at perigee. IOW, from our position in orbit around the Moon we would have to burn more fuel to make a close Earth approach than it does to just directly boost to escape velocity.

 

 

 

Alternate argument: Cassini and Galileo spacecraft both used Earth as grav-slings. So we know it works.

 

Cassini and Galileo were both put into independent solar orbits first. If this was not needed, why was it done? Why didn't they just launch them into an eliptical orbit around the Earth and use the subsequent close swing by Earth to give them their boost? Because it woudn't have worked.

 

Now, the origin of the spacecraft (is it coming from Venus? Is it coming from the Moon?) is immaterial. All that matters is the alignment of the incoming trajectory relative to the Earth's vector in the Earth's orbit.

 

The difference is that an object originating from the the Moon must have a delta v applied to it in order to match that incoming trajectory of an object coming from Venus. The Moon object is not going to assume the trajectory of the incoming Venus object unless we force it to.

[TheFaithfulStone]

:naughty: Ladies and Gentleman! Gather round, gather round!

 

Monday, Monday, Monday -

 

It's an orbital mechanics sh-sh-showdown!! :shrug:

 

But Janus is right. You can only slingshot something you're not currently orbiting and gain momentum. But you can use it to steer.

 

TFS

[ronthepon]

Somebody tell me the plot!!

 

I'm forced to be half dead on R4, and waiting for help.

[IDMclean]

Hold on Ron, Man, I'm on my way, ETA without Interrupt is 5 minutes... ETA with Interrupt is Undefined.