Let's build a full scale StarTrek USS Enterprise in space

[Tim330]

Gene Vincent said:

Bedazzled said:

(Putting practicalities aside) that's not how it works at all. The most efficient means to escape the solar system is to wait until Earth is at perihelion (nearest point to sun) and then thrust forwards (along the trajectory of Earth's orbit) to increase speed until the apoapsis (furthest point on the far side of the Sun) leaves the solar system and intersects the target star. When you approach apoapsis you will be captured by the gravity of that object. It's a bit more complicated because of the gravitational influence of the other planets, but it's basically how Apollo went to the moon.

The stuff about the Earth being attracted to snap back into its natural place and going straight into the sun is rubbish, the Earth's orbit depends entirely on its mechanical energy (KE+PE). If you speed up the Earth it will increase the mechanical energy, so the far side of its orbit will move further away from the Sun (translating KE into PE). Thrusting perpendicular to its trajectory doesn't change the mechanical energy of the orbit at all, it just changes the shape to become more elliptical.

Any speeding up of the Earths present course will mean we career into a closer orbit and the sort of increase we are talking about (11x present) means we are travelling 6x faster than Mercury in its orbit.

This is the 'prime mover' in this matter and as such over powers any/other effects.

Your ideas work only for objects that are small in scale or rather comparison, a Saturn 5 is big to us but minute in this comparison.

The orbits of the planets determine their speed in that orbit and is a balancing act, accelerate and you get closer... now if you slowed us we would move out gradually, halve our orbit speed and we are in the same orbit as Jupiter, halve it again and we're beyond Neptune.

We're too massive to get a 'slingshot' as the Apollo mission did.

I'm not a Physicist as it may soon become clear but I would think that if "the hand of God" slowed the earth down or a (big) rocket on the surface fired against the direction of orbit thereby reducing the speed of the earths orbit we would move closer to the sun?

[Tim330]

My understanding with the moon orbit is that the loss of energy from the earths rotation is effectivly boosting the moons orbital velocity & in so doing causing it to move further away from earth.

Taken from
http://en.wikipedia.org/wiki/Orbit_of_the_Moon

"The tidal bulges on Earth are carried ahead of the Earth–Moon axis by a small amount as a result of the Earth's rotation. This is a direct consequence of friction and the dissipation of energy as water moves over the ocean bottom and into or out of bays and estuaries. Each bulge exerts a small amount of gravitational attraction on the Moon, with the bulge closest to the Moon pulling in a direction slightly forward along the Moon's orbit, because the Earth's rotation has carried the bulge forward. The opposing bulge has the opposite effect, but the closer bulge dominates due to its comparative closer distance to the Moon. As a result, some of the Earth's rotational momentum is gradually being transferred to the Moon's orbital momentum, and this causes the Moon to slowly recede from Earth at the rate of approximately 38 millimetres per year. In keeping with the conservation of angular momentum, the Earth's rotation is gradually slowing, and the Earth's day thus lengthens by about 23 microseconds every year (excluding glacial rebound). Both figures are valid only for the current configuration of the continents."

[Use Psychology]

PW said:

Heading out into space, in technology totally unproven to endure the time scales the journey is planned to take, with no idea what is at the other end, an expedition spanning a time longer than all of Human civilisation so far... EXACTLY the same as going to America on a creaky sailboat. How very dare anyone question the idea!

the attitudes required by the participants are basically identical/

the (first) people who sailed to america didn't even know how far they had to go, and had limited food, water, etc., so the comparison is very valid

[hairykrishna]

Bedazzled said:

I can think of an example which supports what GV is saying; our moon is moving away from the Earth slightly due to drag from the tidal forces slowing it down. Interesting, so if you slow down a small object like a satellite its orbit will decay, speed it up and its orbit increases, but with a planet/moon the opposite happens? Damn, looks like I need to read up on Kepler's Laws again I thought I'd got my head around that stuff, obviously not.

Tidal drag is increasing the moons energy - it's taking it from the earths rotation. Atmospheric drag on satellites is decreasing their energy.

Edit to add; think in energy terms. Velocity just makes it harder to visualize in a simple problem.

I dunno what the answer to the 'earth thrust' question is. Not sure I followed when and what direction the thrust is applied in. Orbital mechanics are complicated.

[jmorgan]

Bit OTT either way. Now then, any one read footfall?

http://www.up-ship.com/apr/michael.htm

[Gene Vincent]

Tim330 said:

I'm not a Physicist as it may soon become clear but I would think that if "the hand of God" slowed the earth down or a (big) rocket on the surface fired against the direction of orbit thereby reducing the speed of the earths orbit we would move closer to the sun?

I know it is counter-intuitive, but that is the rule of the spheres.

Stole this off the net...

Mercury - 47.8725 km/sec = 107,000MPH
Venus - 35.0214 km/sec = 78,350 MPH
Earth - 29.7859 km/sec = 66,630 MPH
Mars - 24.1309 km/sec = 54,000 MPH
Jupiter - 13.0697 km/sec =29,240 MPH
Saturn - 9.6724 km/sec = 21,640 MPH
Uranus - 6.8352 km/sec = 15,290 MPH
Neptune - 5.4778 km/sec = 12,250 MPH
Pluto (TNO, or dwarf planet) = 10,700 MPH

Read more: http://wiki.answers.com/Q/At_what_speed_does_each_...

[Simpo Two]

OK, I can see that as a body slows perhaps instead of falling in it wanders out to a new stable/slower orbit.

So why do satellites fall back to Earth and not gradually spiral away? A few wisps of air resistance?




(And would the Antikythera mechanism predict it?)

[Gene Vincent]

I think the confusion or counter-intuitive nature of it is that we don't ever experience this on Eartg, we can attach something to a string and spin it and as we spin it faster it tensions the string further and further until it snaps.

The planets do not mimic this, the orbits are a trade off of their desire to fall into the sun (gravity) and the counter balance of velocity that mitigates it.

If you look at Low Earth and other orbits, the object travel faster the closer they are to the surface...

I couldn't remember the numbers so another shameless steal from Wiki...

Low Earth orbit:- circular orbit: 7.2 km/s [1000km above surface]

Geo:_ 3.1 km/s [42,000km above surface]

Orbit of the Moon:- 1.0 km/s [380,000km above surface]

[SystemParanoia]

like a boat.. but in 3D

[PugwasHDJ80]

realistically the only way we'll move very long distances isn't to move a long way in sapce, but move space to connect 2 points in space- then you move a short distance between the two.

Whether this is even theoretically possible is open to debate.

[Simpo Two]

PugwasHDJ80 said:

realistically the only way we'll move very long distances isn't to move a long way in sapce, but move space to connect 2 points in space- then you move a short distance between the two.

I tend to agree. And hence 'warp' drive. I think it would be possible - the theory is there but not the technology.

[SystemParanoia]

Simpo Two said:

PugwasHDJ80 said:

realistically the only way we'll move very long distances isn't to move a long way in sapce, but move space to connect 2 points in space- then you move a short distance between the two.

I tend to agree. And hence 'warp' drive. I think it would be possible - the theory is there but not the technology.

Frame Shifting

( frame dragging recently being proven to exist etc )

now we just need to hurry up and get the grand unifying formula for everything together so we can properly understand gravity and how to manipulate it without using biblical amounts of mass!

[Squirrelofwoe]

PW said:

Use Psychology said:

so the comparison is very valid

Oh yes, when you put it like that it becomes entirely clear that the comparison is indeed very valid between spending a few months on a sailing ship, and many thousand of years travelling on a space ship.

I'm surprised they didn't skip America in the first place, and go straight to Barnard's Star, seeing as how it is basically identical.

I think the point Use Psychology was making is that the attitudes of the participants would have to be broadly similar- i.e venturing into the unknown, without being able to accurately predict what will be found.

There is however a significant difference in the sense that at the time of the voyages to America in the 15th century, long distance voyages by boat were reasonably common-place, and the fundemental basics of spending time at sea had been understood for hundreds of years previously.

If we were to compare this to space travel only a handful of us have ever even dipped our toes in the water, with an even smaller number venturing out to a couple of hundred meters from the shore. Once we are travelling fairly regularly around the inner planets of the solar system, and have been doing so for some time, 'then' I would say it's a fair comparison!

Use Psychology's point about it not happening so easily in this day and age is extremely relevant though- the way our health & safety society is progressing we will soon be prevented from proceeding with any undertaking where the results cannot be predicted to 99.9%, and where any risk- financial as much as human, cannot be eliminated/mitigated in it's entirety.

[SystemParanoia]

if you put an advert on tv asking people to apply for this once in a lifetime mission to the stars. they will apply in droves.

add to the advert that they will never see the destination, nor will their kids, or their kids kids, but then cut to oppulent views of the interior they wont care, they will still come.

then finally, say that all transport costs will be free for them, and you'll have a stampede on your hands!

I would go, leave it all behind and not have a single regret. you dont need many people to feel like that before you've crewed 4, 5 or even 10 similar generation ships

[Squirrelofwoe]

SystemParanoia said:

if you put an advert on tv asking people to apply for this once in a lifetime mission to the stars. they will apply in droves.

add to the advert that they will never see the destination, nor will their kids, or their kids kids, but then cut to oppulent views of the interior they wont care, they will still come.

then finally, say that all transport costs will be free for them, and you'll have a stampede on your hands!

I would go, leave it all behind and not have a single regret. you dont need many people to feel like that before you've crewed 4, 5 or even 10 similar generation ships

x 1 million!

I believe if they ever got serious about setting up a 1-way colonisation mission to Mars, they would have applicants falling over themselves to get a chance.

However it seems that the powers that be are so wapped up in the ethics of such endeavours that they feel people would be incapable of making such a decision.

[Simpo Two]

If you want to have a viable colony, you won't want it full of attention-seekers and Big Brother types. They're exactly the kind you're trying to leave behind!

[SystemParanoia]

Simpo Two said:

If you want to have a viable colony, you won't want it full of attention-seekers and Big Brother types. They're exactly the kind you're trying to leave behind!

they make good grunts..

they wont survive long tho which is also good

( look at that shiny thing/ picture of you / present to you because you're so awesome in the airlock room... PTSHHHHHHHHHHHHH!!! ) lol

[Simpo Two]

SystemParanoia said:

they wont survive long tho which is also good

I'd feed them one by one into the ion engine... chav in the top, ions out the bottom


Wonder how many light years per chav you get? Do they burn well?

[Squirrelofwoe]

Couldn't agree more.

PW said:

Until reaching the ultimate destination, people's lives would consist of making sure nothing breaks, keeping everyone sane & scrubbing the toilets

This bit I had to smile at because as of 5 minutes ago I just finished watching a re-run of the Red Dwarf episode- 'Queeg'

After watching that your comment seemed rather appropriate!

[Simpo Two]

PW said:

I'm willing to bet that their reasons for going were not strongly tied to the notion of spending all eternity cooped up in a very small environment with very little to do, and more along the lines of striking out, discovering that new flora, fauna, climate and peoples, returning them home to great acclaim and fabulous riches. The thing about interstellar space though... there's nothing, almost literally, out there to "explore".

I agree, though the first polar explorers were different - they knew there was only going to be ice and snow, plant a flag and hopefully get home alive. No exotic fruits, native girls or gold coins for them.

PW said:

Until reaching the ultimate destination, people's lives would consist of making sure nothing breaks, keeping everyone sane & scrubbing the toilets - I really doubt Columbus, Cortés or Cook would be at the head of that queue

No, that's what the crew were for