Interestellar ships in Avatar-surprisingly well thought over ?

[Toymaker]

Yes I realise there is a thread about the movie, but I wanted to touch upon a specific issue. While I didn't like the movie and consider it a anti-science fantasy, I was surprised by description of of the interstellar ship in the movies. It seems that besides the mineral used and high speed(70.c, but the description mentions that is very dangerous) the ship has been very detailed and well thought over. Actually I would say it's one of the best designed in SF I have encountered ? Does anybody know who advised Cameron on this ? What are your opinions ?

For interested
http://www.pandorapedia.com/doku.php/isv_venture_star?s[]=venture&s[]=star

[IsaacKuo]

James Cameron hired Charles Pellegrino (http://www.charlespellegrino.com/index.htm) as tech consultant. The ISV Venture Star design is a combination of Pellegrino's Valkyrie concept with some aspects of Robert Forward's laser sailship concepts.

[eburacum45]

So Avatar uses the Valkyrie, eh? Excellent!
Here's a bit more information about the Valkyrie concept, from Project Rho.
http://www.projectrho.com/rocket/rocket3aj.html#valkyrie

and here's a picture of the Venture Star from the film
http://www.pandorapedia.com/lib/exe/detail.php/isventurestar.jpg?id=isv_venture_star

[LotusExcelle]

I'm curious as an aside - what about it was anti-science?

[John Jaksich]

Yes I realise there is a thread about the movie, but I wanted to touch upon a specific issue. While I didn't like the movie and consider it a anti-science fantasy, I was surprised by description of of the interstellar ship in the movies. It seems that besides the mineral used and high speed(70.c, but the description mentions that is very dangerous) the ship has been very detailed and well thought over. Actually I would say it's one of the best designed in SF I have encountered ? Does anybody know who advised Cameron on this ? What are your opinions ?

For interested
http://www.pandorapedia.com/doku.php/isv_venture_star?s[]=venture&s[]=star

There seems to be a listing at Wikipedia about the movie:

AVATAR (http://en.wikipedia.org/wiki/Avatar_(2009_film))

It might answer some questions.

[eburacum45]

The Valkyrie design is efficient because it is lightweight; the rockets are at the front, and pull the payload along on a wire, so that the ship is in tension rather than compression.

My problem with this sort of design is that you've got to divert the thrust so that it doesn't melt the wire; this cuts down on the efficiency somewhat (your rockets are thrusting sideways somewhat, to avoid hitting the thin cable dragging the payload behind).

[IsaacKuo]

The Valkyrie design is efficient because it is lightweight; the rockets are at the front, and pull the payload along on a wire, so that the ship is in tension rather than compression.

My problem with this sort of design is that you've got to divert the thrust so that it doesn't melt the wire; this cuts down on the efficiency somewhat (your rockets are thrusting sideways somewhat, to avoid hitting the thin cable dragging the payload behind).
It cuts down on efficiency quite a bit. For example, with a 15 degree outward diversion angle, you lose 3.4% of your delta-v. That means at best a 3.4% increase in fuel requirements; due to the exponential aspect of the rocket equation an increase of perhaps 10% is more like it.

However, there is actually a pretty easy fix for this problem. Instead of diverting the thrust off at an angle, simply divert the payload off to the side at an angle.

This is done by slowly spinning the tether. Instead of hanging straight behind the thruster, the tether hangs off to the side at an angle. As it spins around, it traces the surface of a cone. The thruster stays mostly at the center, thrusting straight along the centerline of this cone. The tether and its payload are along the surface of this cone.

This increases the strength requirement of the tether by 3.4%; this increases the mass of the tether by 3.4%. This is a negligible penalty compared to the alternative of increasing the fuel tanks by 10%.

[eburacum45]

A good idea. You could have two tethers, to keep the ship balanced. Maybe more. Interesting...

[SkepticJ]

I'm curious as an aside - what about it was anti-science?

Not a thing.

I've read complaints of "New Ageism" being present in the movie, but the "supernatural" stuff is clearly presented as having its origin in something that violates no know physics.

I'd say the movie is a positive depiction of scientists and what they do.

[LotusExcelle]

See that was my take on it, too. Which is why I get a quizzical look on my face when it gets brought up.

[noncryptic]

Not a thing.

I've read complaints of "New Ageism" being present in the movie, but the "supernatural" stuff is clearly presented as having its origin in something that violates no know physics.

I'd say the movie is a positive depiction of scientists and what they do.

Agreed.
If the movie is anti anything, it's anti-imperial, anti-military, anti my-resources-are-on-your-soil attitude. And it's pro-environment.
So it's no surprise it gets flak from certain directions.

[SolusLupus]

Agreed.
If the movie is anti anything, it's anti-imperial, anti-military, anti my-resources-are-on-your-soil attitude. And it's pro-environment.
So it's no surprise it gets flak from certain directions.

Indeed. And it's no surprise it gets support from other directions.

[dohbot]

i was dissapointed with avatar.

they didn't show the spaceships that much. the spaceship at the start of the movie was shown only for a few seconds. the shuttle and the scorpion helicopters also looked good.

i didn't care about the navi, their cgi is inferior to the cgi of master yoda.

avatar should have focused the story more about the ships like in 2001 or 2010

[SolusLupus]

i didn't care about the navi, their cgi is inferior to the cgi of master yoda.

Well, if cgi is that important to you... :)

[Strange]

My problem with this sort of design is that you've got to divert the thrust so that it doesn't melt the wire; this cuts down on the efficiency somewhat (your rockets are thrusting sideways somewhat, to avoid hitting the thin cable dragging the payload behind).

Why not just make the wire out of something that doesn't melt at those temperatures?

[IsaacKuo]

Why not just make the wire out of something that doesn't melt at those temperatures?
Melt isn't the proper word for what happens to a solid substance bombarded by a relativistic particle stream. Spallation is more like it. Chemical bonds simply aren't strong enough to prevent relativistic particles from stripping away affected atoms.

[Strange]

Melt isn't the proper word for what happens to a solid substance bombarded by a relativistic particle stream. Spallation is more like it. Chemical bonds simply aren't strong enough to prevent relativistic particles from stripping away affected atoms.

Ah. I hadn't read the background and didn't realise it wasn't a chemical rocket.

But if the tether is hollow and you pump more self-assembling unobtanium nano-particles down the center...

[IsaacKuo]

I wouldn't worry about it, since a small amount of spin can be used to make the tether and payload to hang off at a safe angle.

[tracer]

I've read complaints of "New Ageism" being present in the movie, but the "supernatural" stuff is clearly presented as having its origin in something that violates no know physics.

I'd say the movie is a positive depiction of scientists and what they do.

Yes. But. The science was conveniently arranged to support the pseudo-scientific culture of the Na'vi, so as to tug on the heartstrings of the viewing audience.

And, frankly, the portrayal of the native wildlife was practically Disney-esque. Thousands of flying banshees suddenly helping the heroes because the planet-spanning tree-brain "heard the cry for help"? (And how did such a planet-spanning tree-brain even evolve in the first place?) A ginormous predator letting the heroine ride it when it showed no compunction against eating other Na'vi? Tree seed pods dancing around the hero because he has a "good heart"? What next, birds helping Cinderella on with her ball gown?

[karadan]

I always liked the concept of the Bussard engine. There's a book called Tau Zero by Poul Anderson which i found utterly fascinating.

http://en.wikipedia.org/wiki/Bussard_ramjet

I liked avatar even though i'm a hard SF nutter. I think what Cameron did was to make sci-fi accessible to people who don't usually give it a second glance. This is telling by the 2 billion plus dollars it made. I turned my brain off and watched the pretty 3D movie for what it was - a James Cameron film.

[publiusr]

Scott Lowther is working on a new book to be released by ARA press on Nuclear propulsion.
Visit www.up-ship.com for more