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Flying on Mars
jimharris submitted a bunch of links about flying on Mars: "X-Plane's author Austin Meyer is working out the details of flying on Mars. Meyer has taken his system and adapted it for the conditions on Mars and has discovered a lot about what it would take to fly on Mars, where the atmospheric pressure is 1 percent of Earth, and gravity one third, but laws of flight remain the same. Flying becomes difficult, and landing almost impossible. Other people are working with NASA to create Entomopters engineered to meet Mars conditions. More ideas about the concept can be found at PBS's Scientific American Frontiers. A quick search at Google will reveal many people are thinking about flying on Mars." It's a beautiful challenge - how to fly in a situation where everything you "know" about flight is wrong.
Helicopters won't work well on mars, you'll need to have your props spinning 10 times faster to get the same lift, which will be somewhat diffucult, no?
/. article) they're probably strong enough to make a helicopter, right?
It might work actually, but AFAIK there aren't any easily manufacturable materials that will stand up to the centripetal forces, since there will be 100 times as much force on the end of the prop (centripetal force is the square of velocity). You might be able to do this by increasing the surface area of the prop (longer blades, or more blades).
Sounds like another potential use for carbon nanotubes. After all, if they're strong enough to build a space elevator (see earlier
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... who read that article and thought "too bad they didn't call these vehicles 'ornithopters' "?
- Mike
And more. For example...If you want to convert the surface of the planet to a temperature where you can stay outside without a space suit you need to heat upo the atmosphere. The best way to do that is to use Carbon Dioxide as it is a natural greenhouse gas. However, if your eventual goal is to make the atmosphere breathable, you need to do something about the vast quantities of Carbon Dioxide.
How about a huge focusing lens positioned in a aerosynchornous orbit that collects those solar rays that woud just miss Mars and focuses them back toward the3 planet to heat it up.
How about drilling huge holes in the surface to realease Geothermal energy into the atmosphere to heat things up.
And so on. If you are interested in Mars, read the book. He addresses a lot of the major issues . Even if he is off on certain topics (it is a novel after all), it is a great step forward in Science Fiction
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I was surprised that Austin Meyer doesn't understand that the thrust of jet engines in either direction doesn't depend on the atmosphere density, unlike prop engines. Am I missing something?
Disclaimer, I am not an aeronautical engineer.
Actually, you are incorrect. The challenges for jet and prop engines are different in very thin atmospheres, but the basic problem is that with 1% of the earth's atmosphere, you cannot take enough O2 into your engine to get the engine running. OK. Crash course in turbofan engines:
The engine containes a few parts:
compressor->combustion chamber->turbine
The turbine runs the compressor, often generates electricity and usually also runs a secondary compressor or fan ourside fo the combustion pipeline used for increased thrust.
THe secondary compressor's thrust output, like a propellor's is purportional to the strength of the atmosphere (less air, less thrust). This is the first main problem. Unlike the propellor, the fan's thrust is mostly in the form of reaction mass and there is no real Bernouli's effect. Again, this reduces probably 10fold at 1% atmosphere.
The second in in the jet pipeline. The turbine compresses air in the combustion chamber which is mixed with fuel and burns. The jet of hot gasses pass by the turbine which runs the compressor and produces thrust in the form of reaction mass (for each action...). The combustion is limited by the oxygen intake which goes down as the air supply goes down, but not as fast as it does for a propellor (assuming adequate O2).
For take-off and landing, the turbofan engines also produce thrust in a third way. If you have been reading this so far and asked, "what about the shape?" I will answer this question. The shape is designed to produce a ducted fan effect, drastically increasing thrust at low speeds. Basically, as air gets sucked into the engine, it forms a low-pressure ring around the lip of the rim which means that the rim of the engine gains forward lift (similar in principle to the Hillard Flying Platform). This thrust would also be decreased 10 fold in the thin martian air.
So yes, jet engines do depend on atmospheric density. Their curve is just flatter than that of a propellor (which are basically forward spinning wings similar to helicopter rotors, but with more fan and less wing).
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