# Would sterling engines work for intra-solar system space travel? **URL:** \ **Category:** Factual Questions\ **Created:** [September 1, 2003, 11:53am UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954 "2003-09-01T11:53:46Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [September 1, 2003, 11:53am UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954/1 "2003-09-01T11:53:46Z")
My understanding is that, in space, an object will be extremely hot on the side facing the sun and extremely cold on its other side. Given the nature of sterling engines, couldn’t a spaceship be built to take advantage of the hot-cold differences between its front and back? Maybe a sort of saucer shape, but oriented upright? I’m also told that sterling engines take a long time to start up, but couldn’t ships be “parked” in orbit waiting for their inhabitants to arrive via a quick shuttle flight? Then, one of the ships, already “warmed up”, could be taken to a Jovian moon, or whatever? Or is this just crazy? ---
**Author:** ![Michael\_Ellis](https://avatars.discourse-cdn.com/v4/letter/m/977dab/32.png) [@Michael\_Ellis](https://boards.straightdope.com/u/Michael_Ellis)\ **Post date:** [September 1, 2003, 11:59am UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954/2 "2003-09-01T11:59:36Z")
😕 Oh, they’re 1920’s “Death Rays”. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [September 1, 2003, 12:14pm UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954/3 "2003-09-01T12:14:15Z")
Are you planning on using the sterling engine for propulsion? If so, what will it push against? ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [September 1, 2003, 12:18pm UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954/4 "2003-09-01T12:18:51Z")
It’s possible. Some space probes use the Seebeck Effect to generate electricity from the temperature differential. Solar cells would probably be just as effective, though. But if you’re thinking of generating reasonably large amounts of power, then you’d have trouble competing with a nuclear reactor. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [September 1, 2003, 12:20pm UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954/5 "2003-09-01T12:20:38Z")
**Xema** ’s suggestion hadn’t occurred to me. If that’s what you’re thinking of, then yes, it’s just crazy. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [September 1, 2003, 12:45pm UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954/6 "2003-09-01T12:45:03Z")
I don’t get it. Regardless of whether it’s practical, what do you want an engine of any kind in space for? Or are we thinking of opening a laundromat up ther? ---
**Author:** ![Mort\_Furd](https://avatars.discourse-cdn.com/v4/letter/m/8e8cbc/32.png) [@Mort\_Furd](https://boards.straightdope.com/u/Mort_Furd)\ **Post date:** [September 1, 2003, 1:00pm UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954/7 "2003-09-01T13:00:23Z")
Power to run on board systems, for one thing. You might also power an ion drive with it. ---
**Author:** ![refusal](https://avatars.discourse-cdn.com/v4/letter/r/ac91a4/32.png) [@refusal](https://boards.straightdope.com/u/refusal)\ **Post date:** [September 1, 2003, 1:25pm UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954/8 "2003-09-01T13:25:00Z")
One problem is that Sterling engines rely not only on heating one side but being able to cool the other side in order to preserve a temperature differential (as per Carnot, etc). Otherwise you end up with a machine that’s very hot throughout but not producing much power. This means that the design of such a system would be tricky: it couldn’t use convection or conduction to cool itself owing to the vacuum. You would need to release all the heat by radiation, and keep the radiators insulated from solar rays. All this is from basic physics, and I don’t know exactly what sort of design or power output would be realistic. You certainly wouldn’t have a very compact device though, since a large flat radiator would be the most efficient design; although maybe you could put solar panels on the other side 🙂 ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [September 1, 2003, 1:31pm UTC](https://boards.straightdope.com/t/would-sterling-engines-work-for-intra-solar-system-space-travel/198954/9 "2003-09-01T13:31:16Z")
I believe it’s spelled “St **i** rling.” Here is a NASA page that describes their Stirling engine research: [http://www.grc.nasa.gov/WWW/tmsb/stirling.html](http://www.grc.nasa.gov/WWW/tmsb/stirling.html) It looks like they’re mostly interested in using Stirling engines to extract power from radioisotopes.