How difficult is interstellar travel?

[rockoon]

Yep.

What do you mean I can't see the Sun/Moon/Stars now??

What do you mean there's only one gravity??

People doubt me when I say that there will easily be more humans living between the stars, planets, and moon than living on planets and moons.

I dont know why it seems obvious to me but not to most people. I see it as inevitable.

 

[RecoveringYuppy]

People doubt me when I say that there will easily be more humans living between the stars, planets, and moon than living on planets and moons.

I dont know why it seems obvious to me but not to most people. I see it as inevitable.

Seems obvious to me too. Even if only a miniscule fraction of the humans leaves Earth and most stay here wondering what the attraction might be, that miniscule fraction will be able to grow without limit. And, unless something wipes us all out first, someday some of them will grow without limit.

 

[Cuddles]

The energy densities don't have to be outrageous. Bright sunlight is about a GW per square kilometer which I expect would work for a sail. Not sure if a sail would work for interstellar travel though.

Solar power is pretty much useless for space travel. It's nice for things that hang around close to the Sun, but even as close as Jupiter it's too weak to be of any real use. Pointing lasers at sails can improve things a little, if you can find enough energy to throw at it, but even they will be useless past a fairly short distance.

The only real option for sails is similar to that from "The Moat Around Murcheson's Eye" (sequel to "The Mote in God's Eye") by Larry Niven. You have to dump a huge amount of energy into the sail very early on and then just coast along until you reach somewhere capable of slowing you down. Assuming you haven't been there before that means firing yourself straight at a star and hoping you stop before hitting it. This makes the energy issue rather more of a problem, since 1.5GW averaged over a few years is no problem, but concentrating that amount into a much shorter time is (in the story it took a large part of a civilisation's resources to send one small ship).

The other problem is that once you are away from your propulsion you have essentially no control. We can just about manage to send powered probes a few million miles with several corrections along the way, sending something several light years without any opportunity for correction just isn't an option. Especially since there is no chance of compensating for any new knowledge or events along the way. If we were really lucky we might just about manage to hit the right system, but would probably sail straight through it. More likely would be missing it entirely.

 

[whiteyonthemoon]

In that case, you realize that the collecting station wont be supplying force, right?

The force will be applied by the energy "beam" or whatever (laser?) .. which will be traveling at the speed of light relative to everything that isnt.

Wavelengths will change based on the relative motion of the emitter to the reciever (red shift) and that will effect efficiency in some manner, but probably not nearly as much as distance will.

The relativistic mass of the ship still shouldn't apply... *shrug*

I would argue that this methodology is flawed. How do you decelerate?

I think the calculation for loss due to redshift and the calculation for increase in required energy due to relativistic mass increase give the same result. Can anyone who knows something about relativity confirm this?

The article is meant to be an extremely conservative in terms of what is required for interstellar travel, and includes no energy for deceleration, and no method for propulsion at any point.

 

[RecoveringYuppy]

I think the calculation for loss due to redshift and the calculation for increase in required energy due to relativistic mass increase give the same result. Can anyone who knows something about relativity confirm this?

Yes, that's a point of view issue.

 

[Hellbound]

Solar power is pretty much useless for space travel. It's nice for things that hang around close to the Sun, but even as close as Jupiter it's too weak to be of any real use. Pointing lasers at sails can improve things a little, if you can find enough energy to throw at it, but even they will be useless past a fairly short distance.

The only real option for sails is similar to that from "The Moat Around Murcheson's Eye" (sequel to "The Mote in God's Eye") by Larry Niven. You have to dump a huge amount of energy into the sail very early on and then just coast along until you reach somewhere capable of slowing you down. Assuming you haven't been there before that means firing yourself straight at a star and hoping you stop before hitting it. This makes the energy issue rather more of a problem, since 1.5GW averaged over a few years is no problem, but concentrating that amount into a much shorter time is (in the story it took a large part of a civilisation's resources to send one small ship).

The other problem is that once you are away from your propulsion you have essentially no control. We can just about manage to send powered probes a few million miles with several corrections along the way, sending something several light years without any opportunity for correction just isn't an option. Especially since there is no chance of compensating for any new knowledge or events along the way. If we were really lucky we might just about manage to hit the right system, but would probably sail straight through it. More likely would be missing it entirely.

Gah!!!!!

Get outta my ****** head!!!!!




I'm currently in the process of reading "The Mote in God's Eye". Started it two days ago. It had the solar sail ship in the beginning, by the way, so that may be what you're thinking of.

Anyway, spooooooooooky

 

[RecoveringYuppy]

Relevant article.

http://www.space.com/adastra/070802_adastra_spacesettlement.html

 

[RecoveringYuppy]

[duplicate post]

 

[RatBoy]

When I think about interstellar travel, I wonder about two things:

* At what point will we have the capacity to travel fast enough for enough people to actually back a mission? Structures like the pyramids and the gothic cathedrals of Europe took a long time to build - if I remember correctly, some of the cathedrals were still unfinished long after the original designers died (pls feel free to correct me!) The people were sufficiently motivated (by whatever means) to contribute to the project. So if we could go to Alpha Centauri or Sirius or Vega, explore and gather resources, and return within 50 years, would there be sufficient motivation to do so? 100? 500? 1000? And at what point does our lack of resources or pending incineration meet our capability to carry out a manned mission with a generation ship?

* Collisions. What thought and advancement has gone into proximity warning, debris avoidance or destruction systems? Between here and the nearest star systems, wouldn't there be billions or trillions of rocks, balls of ice, or combinations thereof? If we're hurtling toward Sirius at 1-20% of the speed of light, would we be capable of detecting and either swerving to avoid or destroying a room- or building-sized object prior to impact?

 

[Jimbo07]

Between here and the nearest star systems, wouldn't there be billions or trillions of rocks, balls of ice, or combinations thereof? If we're hurtling toward Sirius at 1-20% of the speed of light, would we be capable of detecting and either swerving to avoid or destroying a room- or building-sized object prior to impact?

Possibly. Space is so unimaginably big that it's hard to comprehend just how much 'stuff' is floating around out there. We can't even track all of the asteroids on an intercept path with Earth in our own neighbourhood. On the other hand, space is so unimaginably unimaginably big that the average density is very low. You wouldn't have to manage too many contacts at any one time.

 

[rockoon]

Possibly. Space is so unimaginably big that it's hard to comprehend just how much 'stuff' is floating around out there. We can't even track all of the asteroids on an intercept path with Earth in our own neighbourhood. On the other hand, space is so unimaginably unimaginably big that the average density is very low. You wouldn't have to manage too many contacts at any one time.

The thing is that it is hard to "manage" a contact that you have no opportunity to react to.

A good earth-based analogy here is the SR-71 "spy plane." This thing is so fast that by the time the enemy knows its there, they cannot do anything about it. They cannot intercept it and its too late to conceal whatever they are trying to hide.

"Management" vs the SR-71 is not an option. Over 1000 attempts to shoot 'em down all failed. But we did lose some of them, for the very same reason. It was too fast for its own good on several occasions where the pilots could not react fast enough to the changing weather conditions as it jetted through the atmosphere.


Now these bits of space rock arent announcing themselves either. The only forseable solution that allows for extremely high speeds relative to the interstellar medium seems to be an extremely thick and dense shield, or simply to "gamble."

 

[Davo]

Shame the SR-71 flights ended. The fastest production plane of all time. Speed of aircraft hasn`t improved since then back in the 70`s. Improvements in rocketry won`t give us enough sustainable power for interstellar travel. Hopefully science will come up with a new possible form of propulsion.

The Ian Banks culture novels and his recent book "the algebraist" give an intelligent view of how mankind would slowly spread out through the stars.

 

[Cuddles]

I'm currently in the process of reading "The Mote in God's Eye". Started it two days ago. It had the solar sail ship in the beginning, by the way, so that may be what you're thinking of.

Really? I could have sworn it was in the second one. I think I'll have to find copies somewhere, haven't read them for ages.