The thread for space cadets!

[Winner]

1) Similar close fly-by events must have occurred hundreds of times in the last half a billion years. If each resulted in a repeat of Late Heavy Bombardment, we wouldn'T be here.

2) What happens in a million years is of no consequence. If humanity still exists, I think there is a fair chance it will not only be able to move comets out of the way, but to move entire stars out of the way.

3) Will it at least be visible in the night sky, I mean the star?

 

[PlutonianEmpire]

1) Similar close fly-by events must have occurred hundreds of times in the last half a billion years. If each resulted in a repeat of Late Heavy Bombardment, we wouldn'T be here.

2) What happens in a million years is of no consequence. If humanity still exists, I think there is a fair chance it will not only be able to move comets out of the way, but to move entire stars out of the way.

3) Will it at least be visible in the night sky, I mean the star?

For 3, yes, it will be visible. At a distance of a light year, its apparent magnitude will be 0.63, more than visible to the naked eye.

To figure that out, I looked up the star on SIMBAD, derived the distance from the parallax, entered the distance and current apparent magnitude into this calculator to get the absolute magnitude and luminosity, and used the given absolute magnitude value for the absolute magnitude entry box, and changed the distance to a light year.

 

[Kaitzilla]

Woo, it might not be ready for constructing a space elevator just yet, but they got carbon nanotube string now.

Like spools of it. Here is demonstration video!

http://news.rice.edu/2013/01/10/new-nanotech-fiber-robust-handling-shocking-performance-2/


So thin, and holds up so much weight. I wonder if you can make fishing line out of it?

 

[Winner]

For 3, yes, it will be visible. At a distance of a light year, its apparent magnitude will be 0.63, more than visible to the naked eye.

To figure that out, I looked up the star on SIMBAD, derived the distance from the parallax, entered the distance and current apparent magnitude into this calculator to get the absolute magnitude and luminosity, and used the given absolute magnitude value for the absolute magnitude entry box, and changed the distance to a light year.

So, about 60% as bright as Vega? According to Wiki, it would be roughly comparable to apparent magnitude of Sun as seen from Alpha Centauri

(These red dwarfs are weird. Is Proxima even really visible from the two main stars of Alpha Centuari?)

 

[hobbsyoyo]

Woo, it might not be ready for constructing a space elevator just yet, but they got carbon nanotube string now.

Like spools of it. Here is demonstration video!

http://news.rice.edu/2013/01/10/new-nanotech-fiber-robust-handling-shocking-performance-2/


So thin, and holds up so much weight. I wonder if you can make fishing line out of it?

Thats really cool. Too bad we can't capture the asteroid that is supposed to bounce off the atmosphere soon to use as an anchor for the elevator.

 

[Borachio]

But wait. A space elevator would have to be 20,000 km long wouldn't it? To get a geostationary orbit.

Is this really feasible?

What kind of bend would it have?

I'd have expected to see vacuum tubes being used for surface transport on Earth first.

 

[warpus]

From my understand the only stumbling block is our present inability to easily and cheaply create large amounts of long carbon nanotubes.

 

[hobbsyoyo]

But wait. A space elevator would have to be 20,000 km long wouldn't it? To get a geostationary orbit.

Is this really feasible?

What kind of bend would it have?

I'd have expected to see vacuum tubes being used for surface transport on Earth first.

It would have zero bend. It certainly is a long way off, but considering our species has hit an exponential growth curve technologically and economically, it may not be that far off.

From my understand the only stumbling block is our present inability to easily and cheaply create large amounts of long carbon nanotubes.

Yeah there are other issues, but this is the principle one (well, that and the cost and any political settlements that will have to be worked out prior to construction). It could be built of other materials, possibly, but the one with the most promise and that is furthest along in development is probably carbon nanotube fibers.

 

[Borachio]

It would have zero bend. It certainly is a long way off, but considering our species has hit an exponential growth curve technologically and economically, it may not be that far off.

So no lateral force from the jet stream?

No thermal effects from the daily warming and cooling?

 

[Winner]

From my understand the only stumbling block is our present inability to easily and cheaply create large amounts of long carbon nanotubes.

Well, the lack of proper space infrastructure doesn't help either. I think space elevators are quite a long way off, but they will potentially transform spaceflight.

 

[Borachio]

A 20,000 km structure straight up is a bit of an engineering challenge. No matter what the material. I think.

People baulk at 50 km tunnels, for goodness sake.

 

[hobbsyoyo]

So no lateral force from the jet stream?

No thermal effects from the daily warming and cooling?

My apologies, I thought you meant 'bend' as some sort of desing feature, i.e. how much it has to bend to get to geostationary orbit, which is none.

Wind stress will only be a very local issue as the atmosphere will only appreciably act on a very small (almost trivial) amount of the total length of 20k km. The atmosphere really only matterd below 100-150km.

Also, the cable will likely be very small in diameter so even the parts that are in the atmosphere will be pretty small overall. Also, the stress force created by turbulance will be insignificant compared to the tension force keeping the cable taught and it will therefore be unlikely such a force will be able to bend it much.

Finally, any material that can handle the load of 20k km of cable will surley be unaffected by something like the force of even a hurricane acting on a very thin line. The two forces would be orders of magnitude apart.

As for thermal strain (which is stretch or compression), they could either install heat exhchanging systems into it to keep the temperature rather consistent or could allow the cable mounts to flex at either in to allow it to streych or contract daily.

Both solutions seem enormous in all respects until you compare them to the overall project, which dwarfs them.

 

[PlutonianEmpire]

So, about 60% as bright as Vega? According to Wiki, it would be roughly comparable to apparent magnitude of Sun as seen from Alpha Centauri

(These red dwarfs are weird. Is Proxima even really visible from the two main stars of Alpha Centuari?)

Barely. Looking at it in Celestia, Proxima registers as apparent magnitude 4.47, regardless of the positions of A and B in their orbits. My favorite star is apparent magnitude 4.85 from here on Earth, and I have to look really hard to see it with my eyes, given my location, when I go out at night.

 

[warpus]

It would have zero bend. It certainly is a long way off, but considering our species has hit an exponential growth curve technologically and economically, it may not be that far off.

Yeah there are other issues, but this is the principle one (well, that and the cost and any political settlements that will have to be worked out prior to construction). It could be built of other materials, possibly, but the one with the most promise and that is furthest along in development is probably carbon nanotube fibers.

Well, the lack of proper space infrastructure doesn't help either. I think space elevators are quite a long way off, but they will potentially transform spaceflight.

I should have probably specified technological stumbling block in that post, that makes a lot more sense. I mean, the scope of the project seems daunting, Borachio is right, but I don't think there is anything there we don't have the means to do (if not the money or will) other than the actual construction of the amount of nanotubes required.

What other sort of material would work, hobbsyoyo? I was under the impression that it was pretty much "nanotubes or nothing"

 

[hobbsyoyo]

Wikipedia mentions boron nitride nanotubes and graphene sheets.

It doesn't say anything else, so I guess there's only 3 choices and none of them have been researched.

It's an interesting article, I have to read a lot more of it.

 

[warpus]

I read that as bacon nitride nanotubes at first

Here's a nifty graphic outlining present and en-route missions to other planets

Spoiler :

Uranus: No exploration since 1986



and so close to Valentine's day too..

 

[LamaGT]

If the counterweight of a space elevator is held above GEO, how is it possible that the cable stays vertical ?

 

[hobbsyoyo]

i read that as bacon nitride nanotubes at first

Here's a nifty graphic outlining present and en-route missions to other planets

Spoiler :

uranus: No exploration since 1986



and so close to valentine's day too..

usa#1!

 

[Winner]

usa#1!

I like when Americans say that, especially when the topic is gun crime or teen pregnancy



Anyway, to be fair, the US share is going to decline now, which is both a good and a bad thing. Good because it means more agencies and countries are beginning to contemplate launching probes *beyond* Earth orbit/the Moon - most notably China and India - and bad because the US planetary exploration is losing pace.

As of now, the only two agencies with a serious planetary exploration programme are NASA and ESA. Japan is third, but has had some extraordinarily bad luck in that regard.

 

[hobbsyoyo]

I resent your misquote.

That is all.