Full name:  
Password:  
Register 
It is currently Fri Aug 17, 2018 2:34 pm

All times are UTC - 6 hours





Post new topic Reply to topic  [ 12 posts ] 
  Print view Previous topic | Next topic 
Author Message
 Post subject: physics of radiators
PostPosted: Wed Feb 22, 2006 9:37 pm 
Offline
User avatar

Joined: Wed Sep 21, 2005 11:09 am
Posts: 198
Location: Tallahassee, FL
I thought radiating fins or spikes were only marginally effective in space. Any gain is lost by the energy being absorbed by another fin. IIRC they require a heat conductive media to function.

Is this incorrect?

_________________
Roger Books


 Profile E-mail  
 
 Post subject: Re: physics of radiators
PostPosted: Wed Feb 22, 2006 9:51 pm 
Offline

Joined: Thu Sep 08, 2005 10:00 am
Posts: 5095
Location: Milwaukee, WI
Roger Books wrote:
I thought radiating fins or spikes were only marginally effective in space. Any gain is lost by the energy being absorbed by another fin. IIRC they require a heat conductive media to function.

Is this incorrect?


That is the case - however, "marginally effective" is not the same as "requires a heat conductive medium to function". They still work by radiating waste heat; they're just grossly less efficient than most folks consider.

For every J of useful power, you need to dispose of 4 J of waste heat, which is what that thermo proof in the rulebook covers. :)

_________________
Ken Burnside
President
Ad Astra Games


 Profile  
 
 Post subject:
PostPosted: Wed Feb 22, 2006 10:51 pm 
Offline
User avatar

Joined: Wed Sep 07, 2005 2:11 pm
Posts: 347
Location: Portland, Oregon
You have to be very careful that the radiators don't "re-radiate" onto another surface. In practice, this means that your radiators can't be closer than 90 degrees offset from each other (and preferably 120 degrees offset). In my own fictional universe, my radiators have an "X" cross section when viewing the ship from fore or aft. This gives the maximum possible radiating surface with minor re-radiation.

_________________
-Matt P.
Errata Coordinator
Olympian Advocate
Commentor-at-large


 Profile  
 
 Post subject:
PostPosted: Thu Feb 23, 2006 9:05 am 
Offline
User avatar

Joined: Wed Sep 07, 2005 12:49 pm
Posts: 639
Location: the praeternatural tower
They can correct me if I am wrong, but I believe that Charles Oines and Ken were fully aware of the 90 degree rule, but the dramatic visual image of a warship looking like a spiked mace was just too good a picture to pass up.


 Profile  
 
 Post subject: Radiators and Art
PostPosted: Thu Feb 23, 2006 10:07 am 
Offline

Joined: Thu Sep 08, 2005 10:00 am
Posts: 5095
Location: Milwaukee, WI
Winchell Chung wrote:
They can correct me if I am wrong, but I believe that Charles Oines and Ken were fully aware of the 90 degree rule, but the dramatic visual image of a warship looking like a spiked mace was just too good a picture to pass up.


More or less true. The spike radiators on the engines are trading some re-radiation effects for artistic license. :)

As a general rule, you want your radiators 180 degres apart if possible; particularly if they're retractable. Less duplication of machinery to get broken.

_________________
Ken Burnside
President
Ad Astra Games


 Profile  
 
 Post subject:
PostPosted: Thu Feb 23, 2006 11:30 am 
Offline
User avatar

Joined: Wed Sep 07, 2005 2:11 pm
Posts: 347
Location: Portland, Oregon
NASA has adopted the 180 and 120 rules in all their advanced concept designs, and the original "dragonfly" drawings of the Discovery in the "2001" movie pre-production art shows a 120 degree radiator design.

I don't think the engine radiators on the AV:T ships are too bad - re-radiation is minimal since the radiators are small, and the drive cage is pretty open anyway.

Interestingly, the designs for MTF (Magnetically Targetted Fusion) look a lot like an AV:T drive cage.

_________________
-Matt P.
Errata Coordinator
Olympian Advocate
Commentor-at-large


 Profile  
 
 Post subject: Re: Radiators and Art
PostPosted: Thu Feb 23, 2006 12:03 pm 
Offline
User avatar

Joined: Wed Sep 21, 2005 11:09 am
Posts: 198
Location: Tallahassee, FL
Ken Burnside wrote:
Winchell Chung wrote:
They can correct me if I am wrong, but I believe that Charles Oines and Ken were fully aware of the 90 degree rule, but the dramatic visual image of a warship looking like a spiked mace was just too good a picture to pass up.


More or less true. The spike radiators on the engines are trading some re-radiation effects for artistic license. :)


Artistic license is an excellent reason. I have to admit the ships look great. Of course I would think this because they looksimilar to the ore prospecting ship I use for my Avatar. It was designed years ago for an anime RPG.

_________________
Roger Books


 Profile E-mail  
 
 Post subject:
PostPosted: Thu Feb 23, 2006 12:15 pm 
Offline

Joined: Wed Sep 07, 2005 4:40 pm
Posts: 242
In general, reradiating problems are dependent on what portion of the 'sky' is obscured from a view on the surface of the radiator. The spike radiators aren't too bad, though there's no real advantage unless we assume there's another technical reason for how they're designed (probably related to the fuel ignition or containment system).


 Profile  
 
 Post subject:
PostPosted: Fri Mar 03, 2006 11:11 pm 
Offline

Joined: Fri Jan 20, 2006 12:27 am
Posts: 18
Anthony Jackson wrote:
In general, reradiating problems are dependent on what portion of the 'sky' is obscured from a view on the surface of the radiator. The spike radiators aren't too bad, though there's no real advantage unless we assume there's another technical reason for how they're designed (probably related to the fuel ignition or containment system).


Another reason to scatter radiators around the bell is resistance to damage. If you have 2 radiator wings one laser or kinetic shot could disable half your heat rejection capacity. Scattering spikes on the surface of the engine bell gives considerable redundancy, which is important since it is difficult to armour radiators.

- Bill Seney


 Profile  
 
 Post subject:
PostPosted: Sat Mar 04, 2006 1:10 pm 
Offline
User avatar

Joined: Wed Sep 07, 2005 11:45 am
Posts: 109
Location: Redmond, WA
Matt Picio wrote:
Interestingly, the designs for MTF (Magnetically Targetted Fusion) look a lot like an AV:T drive cage.
That's actually what I based the design on. It had the overwhelming artistic advantage of not looking like the standard sci-fi rocket cluster. Using the fusion cage thingy gave the AV:T ships a look that's unique and instantly recognizeable.

_________________
Charles Oines
Emergency Stunt Artist
Products of a Disordered Mind


 Profile  
 
 Post subject:
PostPosted: Sat Mar 04, 2006 1:40 pm 
Offline
User avatar

Joined: Wed Sep 07, 2005 2:11 pm
Posts: 347
Location: Portland, Oregon
I think you're going to see a lot more designs like that in the future - the ICAN II is similar, and a number of NASA's future design concepts seem to be converging on that type of nozzle.

_________________
-Matt P.
Errata Coordinator
Olympian Advocate
Commentor-at-large


 Profile  
 
 Post subject:
PostPosted: Fri Mar 30, 2007 11:15 pm 
Offline

Joined: Sun Feb 11, 2007 12:17 am
Posts: 192
Location: Calgary
One niggling question came to me as I waded through the various steps needed to determine that heating up liquid metals was or was not better than a total loss steam cooling system (depending on how pressurised your system and whether you run the steam through an energy recovery turbine, the argument can go either way; unless replenishing the water in a timely fashion is an issue).

How do you get the heat out of the heat sinks once the temperature of the metal drops to the designed operating temperature of the radiators?

The likely and unpleasant possibility is that the whole ship warms to the point that the rate of heat leaking from the sinks to the ship match the rate of radiation off of the ship's hull.

[edit]
I have since determined that you just run the radiators at a lower temperature. The thermal radiation rate goes down, but you can keep running the radiators at decreasing effectiveness for as long as the metal remains a liquid.


 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ] 

All times are UTC - 6 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron







Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
mile200 v1.0 desgined by CodeMiles Team (msi_333)