Author Topic: Stirling Engines in Space?  (Read 20055 times)

Offline venomousbird

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Stirling Engines in Space?
« on: 08/16/2007 07:19 am »
Stirling engines as many probably know, operate by a difference of temperature, which causes a working gas to expand and contract within a fixed space, causing a piston to move back and forth with varying pressures. I'm wondering why power modules for space bother to use a radioactive payload to power a free piston stirling, when such a huge difference exists between temperatures of materials exposed to solar radiation, and those that are shielded.

Also, as a side note, the moon has huge temperature variations and a slightly more stable environment than space itself. . . seems like free power would be a simple thing to achieve in an lunar environment.

Offline Crispy

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Re: Stirling Engines in Space?
« Reply #1 on: 08/16/2007 07:24 am »
I guess because actually dissapating that energy to the 'cold' of space is relatively hard - you'd need large radiators.

Offline venomousbird

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Re: Stirling Engines in Space?
« Reply #2 on: 08/16/2007 07:32 am »
Interesting how in space, too much energy is a problem as often as too little. How do they keep a conventional spacecraft from overheating?

Offline CommanderAce

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RE: Stirling Engines in Space?
« Reply #3 on: 08/16/2007 07:58 am »
This wiki page  contains some informaion on the subject.
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Offline Franklin

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Re: Stirling Engines in Space?
« Reply #4 on: 08/16/2007 12:39 pm »
Quote
venomousbird - 16/8/2007  2:32 AM

Interesting how in space, too much energy is a problem as often as too little. How do they keep a conventional spacecraft from overheating?

On the way to the moon Apollo capsules slowly revolved so that exposed surfaces were always going from sunlight to shadow.

Shuttle uses big radiators.

Offline kevin-rf

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Re: Stirling Engines in Space?
« Reply #5 on: 08/16/2007 12:49 pm »
RTG using stirlings ...

http://www.grc.nasa.gov/WWW/tmsb/stirling/doc/stirl_radisotope.html

Nasa glenn ( http://www.grc.nasa.gov/WWW/tmsb/stirling.html ) did much work on them. There was even talk at one point of doing a solar sterling on the ISS. Sadly, the site has not been updated in a while :(

Also look into Turbo-Brayton Cryo Coolers ( http://www.creare.com/services/cryo/nicmos.html ), one is operating on hubble as we speak.

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Offline kevin-rf

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Re: Stirling Engines in Space?
« Reply #6 on: 09/29/2007 02:18 am »
Interesting article on the AvWeek site about the NASA is fishing for some missions that will use a RTG with a stirling engine converter :

http://www.aviationweek.com/aw/generic/story.jsp?id=news/nukey092807.xml&headline=NASA%20To%20Accelerate%20Space%20Nuclear%20Power&channel=space


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Offline jimvela

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Re: Stirling Engines in Space?
« Reply #7 on: 09/29/2007 03:30 am »
Quote
kevin-rf - 28/9/2007  8:18 PM
Interesting article on the AvWeek site about the NASA is fishing for some missions that will use a RTG with a stirling engine converter :

http://www.aviationweek.com/aw/generic/story.jsp?id=news/nukey092807.xml&headline=NASA%20To%20Accelerate%20Space%20Nuclear%20Power&channel=space

I started a thread here
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=10008&posts=6&start=1
 on that article.  

I searched for any active thread on that topic, but somehow missed this one.  I searched for nuclear, not for stirling...


Offline CFE

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RE: Stirling Engines in Space?
« Reply #8 on: 09/29/2007 03:32 am »
A recent Mars mission concept from SpaceWorks Engineering makes use of a Stirling engine with a radioisotope power source to generate electricity on the Martian surface.
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Offline Jim

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Re: Stirling Engines in Space?
« Reply #9 on: 09/29/2007 02:27 pm »
It was an option for the MMRTG which is powering MSL.   Vibration is a big drawback

Offline G-pit

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Re: Stirling Engines in Space?
« Reply #10 on: 09/29/2007 09:41 pm »
I started another thread on this topic a while ago here:

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=9676&posts=6&start=1
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Offline CuddlyRocket

Re: Stirling Engines in Space?
« Reply #11 on: 09/30/2007 03:37 am »
There might be scope in future to use the difference in temperature between lit and shaded areas of the Moon to power a stirling engine for use on a lunar base (particularly at the South Pole, where such areas may be both permanent and relatively close together), although solar cells will no doubt be simpler in the first instance.

Offline A_M_Swallow

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Re: Stirling Engines in Space?
« Reply #12 on: 09/30/2007 07:41 am »
Quote
CuddlyRocket - 30/9/2007  4:37 AM

There might be scope in future to use the difference in temperature between lit and shaded areas of the Moon to power a stirling engine for use on a lunar base (particularly at the South Pole, where such areas may be both permanent and relatively close together), although solar cells will no doubt be simpler in the first instance.

What is the temperature of the moon in permanent shade?
We can easily arrange shade, particularly behind the mirrors.  The local lunar surface temperature would depend on conduction from a few feet away.

Offline imcub

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RE: Stirling Engines in Space?
« Reply #13 on: 09/30/2007 08:59 am »
Quote
venomousbird - 16/8/2007  12:19 AM

Stirling engines as many probably know, operate by a difference of temperature, which causes a working gas to expand and contract within a fixed space, causing a piston to move back and forth with varying pressures. I'm wondering why power modules for space bother to use a radioactive payload to power a free piston stirling, when such a huge difference exists between temperatures of materials exposed to solar radiation, and those that are shielded.

Also, as a side note, the moon has huge temperature variations and a slightly more stable environment than space itself. . . seems like free power would be a simple thing to achieve in an lunar environment.

I don't know if you received that answer you were looking for ... so here is my attempt ...

Like you stated ... Stirlings work on temperature differences.  Both a continuous heat source and a cold sink. Without the radioactive core, the core cools .... no active stirling cycle.

Offline Bill White

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RE: Stirling Engines in Space?
« Reply #14 on: 09/30/2007 04:31 pm »
Like you stated ... Stirlings work on temperature differences. Both a continuous heat source and a cold sink. Without the radioactive core, the core cools .... no active stirling cycle.


On the Moon, fashion a parabolic mirror out of a few square meters of mylar using an inflatable structure to provide the curve. Perhaps use a few thousand dollars worth of material having total mass less than 100 kg.  

Place the "hot end" at the focal point of the concentrated sunlight. The "cold end" will face the same challenges, no matter what the heat source. A network of pipes run in or on shaded regolith is one possibility

This heat source would be far, far less expensive than nuclear power.

As for lunar night, find a big boulder and blast it with several passive solar furnaces during the lunar day. Then, encapsulate it with an aerogel blanket laced with working fluid capillaries.

= = =

I am not anti-nuclear.

BUT nuclear reactors are rather heavy (high IMLEO requirements) and have the same heat dissipation issues and do need to be re-fueled.

Lowe's grade Mylar and some inflatable parabolic mirrors (1/10th sea level air pressure shuld be sufficient hold the mirror shape) and you can generate over 1000 C at the focal points pretty much for free.

Thereafter, the power generation side (turbines, working fluids, electric generators) will face the same challenges whether nuclear or passive solar.
EML architectures should be seen as ratchet opportunities

Offline Jim

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RE: Stirling Engines in Space?
« Reply #15 on: 09/30/2007 04:47 pm »
Quote
Bill White - 30/9/2007  12:31 PM

On the Moon, ...........
P

Why bother going for all the energy conversions, just use solar cells.  
And what do you for the other 14 days of the month.  Solar power is not a long term (> 20 days) option for the lunar surface

Offline CFE

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RE: Stirling Engines in Space?
« Reply #16 on: 09/30/2007 04:55 pm »
Quote
Bill White - 30/9/2007  10:31 AM

I am not anti-nuclear.

BUT nuclear reactors are rather heavy (high IMLEO requirements) and have the same heat dissipation issues and do need to be re-fueled.

Reactors will be heavy, but the power output per unit of mass is higher than other power systems.  They're also reliable, to the extent that you won't have to worry about degradation, or not operating during lunar night.  These are all factors that will stunt the performance of solar energy on the moon.
"Black Zones" never stopped NASA from flying the shuttle.

Offline imfan

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RE: Stirling Engines in Space?
« Reply #17 on: 09/30/2007 05:16 pm »
Quote
Jim - 30/9/2007  6:47 PM

Quote
Bill White - 30/9/2007  12:31 PM

On the Moon, ...........
P

Why bother going for all the energy conversions, just use solar cells.  
And what do you for the other 14 days of the month.  Solar power is not a long term (> 20 days) option for the lunar surface

Are you sure that solar cells have better efficiency than stirling combined with parabolical mirror of  the same size as fotovoltaic panels?

Offline A_M_Swallow

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Re: Stirling Engines in Space?
« Reply #18 on: 09/30/2007 05:32 pm »
A solar village can can have both power sources.

A furnace or sling may only need to work half the time.

Offline meiza

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Re: Stirling Engines in Space?
« Reply #19 on: 09/30/2007 06:26 pm »
On the pole you could have solar power for four weeks, if you mount the panels vertically and high enough. The sun stays at about 0 degrees height and makes a full circle along the horizon in four weeks.

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