How far can spacecraft fly?

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In summary: MFP = (1/4)*10^15 km = 10^12 km.This means that the spacecraft would slowly decelerate and eventually reach the center of the galaxy after tens of thousands of years.
  • #1
mreq
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How far can spacecraft fly? Why ?
 
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  • #2
Until they run into something?
 
  • #3
Given that the mean free path of stars in the universe is many orders of magnitude larger than the size of the universe, the answer is essentially forever. I suppose there would be some kind of thermodynamic breakdown due to interactions with the interstellar medium, but I'm not sure how to calculate that.
 
  • #4
Note that we are assuming that you get into space, where there is very little matter to cause friction, and then cut off the engines. The spacecraft would continue along the same trajectory with almost constant speed (relative to the earth). Of course, with with no other bodies near by, how would tell if you "came to a stop"?
 
  • #5
Well the farthest distance was Cassini to Saturn. And why it can't explore any further ?
 
  • #6
mreq said:
Well the farthest distance was Cassini to Saturn.
Incorrect. Voyager 1, Voyager 2 and Pioneer 10, all launched in the 1970s, have all left the solar system. Voyager 2 provided pretty pictures of Neptune when it passed in 1989.
And why it can't explore any further ?
We can explore as far as we want. We can send a probe to another galaxy if we want...it'll just take a very long time to get there, so we don't bother.
 
  • #7
russ_watters said:
We can send a probe to another galaxy if we want...it'll just take a very long time to get there, so we don't bother.
Aha. That's what i wanted to know.
 
  • #8
russ_watters said:
We can explore as far as we want. We can send a probe to another galaxy if we want...it'll just take a very long time to get there, so we don't bother.
Would we be able to overcome the milky way's gravity?
 
  • #9
Er...good point. I'm not actually sure. Googling, I find the Milky Way's escape velocity is 525 km/sec, which is about an order of magnitude greater than we've done so far. It's probably possible, but would take a lot of effort.
 
  • #10
I didn't knew about the Milky Way's gravity.
 
  • #11
How much fuel do you have? Anything is possible with enough rocket power. The problem is you would need the equivalent of an Earth mass of fuel just to reach nearby stars in less than a thousand years. For example, Voyager will take around 70,000 years to travel 4 light years.
 
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  • #12
Interesting, I wasn't aware of the average mean path of stars being that large (by this you do, loosely speaking mean the amount of empty space between stars on average is so great that you have a very unlikely chance of colliding with anything, right?) though I kind of had a feeling it must be. That probably conclusively answers a question I was pondering in the past. I was thinking about line of sight and stars. I thought about visible objects at the edge of the visible universe and I realize that due to technological limitations we're looking at very large and/or bright objects (galaxies, supernovae) but presuming that we could resolve individual stars from that distance. I would think that perhaps it would be puzzling that we could see anything so far because of other, much closer stars that appear much larger to us blocking the line of sights. But I figured that, as you said the average mean path of stars must be great enough that this would not be the case. Also considered the sheer distance between the star blocking sight and the one we were looking at would mean that the one blocking the sight could be incredibly close to 'perfectly' (I realize you can go possibly for an infinite amount and closer to perfect, or at least the Planck scale so I don't use the term very loosely) blocking it from our line of sight but again due to the very long distance even the tiniest deviation would be big enough that it wouldn't shield out the other star.

Can someone clarify that for me? Thanks.

Also, as for the gravity well of the milky way: what would happen, if, say, voyager one were to make it out of our galaxy presuming that it were just escaping now, so for ease let's say that the galaxy were in the same state that it is in now. Would it just eventually slow down to the point of reversing direction and then accelerate back towards the center of the galaxy?
 
  • #13
If we assume the spacecraft doesn't escape the disk of the Milky Way and use an estimate I found for the density of stars in the galactic disk of .05 solar masses per cubic parsec, the mean free path is:

MFP = 1/(n*A_g) where n = .05 solar masses/parsec^3 and A_g is the gravitational cross section of the sun.

Using conservation of momentum and energy, we get for the effective gravitational radius of the sun:

R_g = R_s * f * sqrt(1 + 2*G*M/R * 1/v^2 * 1/f )

Here v is the speed of the spacecraft far away from the star, M and R are the mass and radius of the sun. I have used the factor f to represent the multiple of the radius of the sun at which the spacecraft would burn up. So we get for gravitational cross-sectional area:

A_g = pi * R_s^2 * f^2 * (1 + 2*G*M/R * 1/v^2 * 1/f )

Using v = 17 km/s (speed of Voyager 1), f = 10 because some googling made that factor sound reasonable, I get

A_g = 2 * 10^22 m^2

Plugging this into the formula above we have

MFP = 1/A_g * 1/ (.05 stars/parsec^3) =~ 3 trillion light years

So this means the spacecraft will travel for about 5*10^16 years before it collides with a star!
 
  • #14
TheTechNoir:

Google "Olber's Paradox."
 
  • #15
Do we know everything that's surround us ?
 
  • #16
Of course not. But what do you mean by that question?
 
  • #17
Direction of the scientists? I don't understand the question.
 
  • #18
Regarding cosmology and astronomy.
 
  • #19
Certainly not! It's impossible to know everything about the universe! We don't know what is lying under our bed!
 
  • #20
Trevorwin said:
Certainly not! It's impossible to know everything about the universe! We don't know what is lying under our bed!

Have you looked?
 

1. How far can spacecraft travel in our solar system?

Spacecraft can travel to the farthest reaches of our solar system, including the outer planets and their moons. The furthest spacecraft from Earth is Voyager 1, which has traveled over 13 billion miles and is currently in interstellar space. However, the exact distance a spacecraft can travel within our solar system depends on its speed, fuel supply, and the gravitational pull of other objects.

2. Can spacecraft travel beyond our solar system?

Yes, some spacecraft have the capability to travel beyond our solar system. Voyager 1 and Voyager 2 are currently on a trajectory to leave our solar system and enter interstellar space. However, it would take thousands of years for them to reach the nearest star outside of our solar system.

3. How do spacecraft navigate and control their distance from Earth?

Spacecraft use a variety of navigation techniques to control their distance from Earth. These include tracking their position using radio signals, using sensors to detect the position of stars and other celestial objects, and utilizing gravity assists from planets to change their trajectory.

4. What is the maximum speed a spacecraft can travel?

The maximum speed a spacecraft can travel depends on its propulsion system and the force of gravity acting upon it. The fastest spacecraft ever launched was NASA's New Horizons probe, which reached a speed of over 36,000 miles per hour during its journey to Pluto. However, spacecraft can potentially reach much greater speeds if they are able to utilize gravity assists or other advanced propulsion technologies.

5. How long can spacecraft continue to function and communicate with Earth?

The lifespan of a spacecraft depends on various factors, including its design, mission objectives, and maintenance. Some spacecraft, such as NASA's Opportunity rover, have far exceeded their intended lifespan and continue to operate for many years. However, over time, the equipment and systems on a spacecraft can degrade, and it may eventually lose communication with Earth.

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