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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.
Actually, landing is always easy. For example, NASA has landed several spacecraft on Mars in the last few years.
The difficult part is managing to keep your vehicle in one piece as you land.
Well, if there is a game with accurate physics, it would be X-plane. Heck, with this game, you can even land the space shuttle.
The only problem is that right now, we don't have anywhere close to enough data for the other planets. On mars, we got lucky because NASA released all of their data from the explorer.
-- Dan
We have large lifting craft that require almost no runway for takeoff and landing.. they are they relatives to the blimp.
Same laws apply.. sure there is less of an atmosphere.. but you also have one third the gravity to contend with. The main problem with such craft on the martian surface would be the fact that 1) they are huge, and 2) they are light. With the storms that have been witnessed on mars recently, storing such a craft would be a nightmare if you didn't collapse it and store it. Lets not forget the possibility you COULD be in the air when such a storm kicks up.. nothing could save your arse if that happened..
I think this will be the way we go.. because a dirigible could be packed into a small payload area for transport to the martian surface. The added bonus is that Mars has VERY little oxygen in the atmosphere.. so it becomes safe to fill the dirigible with hydrogen as opposed to helium, giving you much more lifting power.. the problem comes with storing compress hydrogen when you deflate these behemoths.. wouldn't want to store the tanks near an oxygen rich environment like say.. in the living structures or greenhouses.. =)
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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?
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).
Also, nasa's probes once they get into the atmosphere still use parachutes and rockets to slow down to a decent speed and then giant inflatable bubbles to bounce along, but you only use that when you're below a few hundred knots. In the article, it says, that you'll be going 400 mph in a well designed plane, there's no way you're gonna just bounce around if you hit the ground like that... Same inertia, right? imagine that its like having 10 times more inertia...
also, I've seen a few articles, he mentions red sky on mars.
I've seen no good proof to believe the sky is red, if its because the ground is red, think about the earth, in the middle of a desert, or forest, is the sky yellow or green? looking at that, you'll often think they'll be bluer than at the beach (where it tends to look grey, I live at a beach town).
Because the colour of the sky is caused by Raleigh scattering (or other scattering effects), the effect (based on the size distribution of particles in the atmosphere) is the same on Mars as it is Earth.
Somewhere, if you hunt around for photos from the surface of mars, and correct using say, photoshop, for the colour (look at the parts of the probe you can see in the picture and return them to their original colours, usually white or metal, unless its an american flag), the sky will be blue.
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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?
Same laws apply.. sure there is less of an atmosphere.. but you also have one third the gravity to contend with. The main problem with such craft on the martian surface would be the fact that 1) they are huge, and 2) they are light. With the storms that have been witnessed on mars recently, storing such a craft would be a nightmare if you didn't collapse it and store it. Lets not forget the possibility you COULD be in the air when such a storm kicks up.. nothing could save your arse if that happened..
.38g gravity of of Mars really helps - landing vertically should be a cinch.
Fortunately, the laws of rocketry also continue to apply. The
As for structural lightness, remember, the air is very thin. What looks like a huge storm on a satellite photo just isn't going to going to blow anything over on the ground. It's true, Martian winds can pick up small particles, and researchers are still trying to figure out how that happens - vortices maybe, and the oarger particles probably don't get very far off the ground. Global dust storms would contain only the finest particles.
Blimps/dirigibles on the other hand... with less than 1% atmosphere, you have less than 1% of the bouyancy. In the end your balloon will have to be 30 times bigger to lift the same mass. This means that, while a balloon might work, a dirigible won't. Too much structure required.
Life's a bitch but somebody's gotta do it.
Wouldn't helicopters work best on mars? Mars is smaller (I forget by how much).. so I doubt anyone's gonna need a 747 up there any time soon :P
RTFA. The basic problem is that you indicated airspeed is 1/10th the acutal airspeed, which means that your lift is 1/10th what it would be if you were on earth.
So of your main rotor is moving at a very conservative 200RPM providing enough lift for takeoff, then that same rotor would have to move at 20,000RPM in order to take off on Mars. This won't work very well because it will be very inefficient and probably make it difficult to keep the body of the helicopter stable.
Designing a helicopter to fly on mars would be a very interesting and difficult task indeed.
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Blimps/dirigibles on the other hand... with less than 1% atmosphere, you have less than 1% of the bouyancy. In the end your balloon will have to be 30 times bigger to lift the same mass. This means that, while a balloon might work, a dirigible won't. Too much structure required.
On the contrary.... here's a little math..
Size of balloon for dirigible (and volume..)
Volume of ellipsoid (a=semimajor, b= semimean, and c=semiminor axes) = (4/3)*pi*abc.
A=100m B=40m C=30m
V=5.03x10^5 M^3
V=5.03x10^8 L
Now for temperature and pressure...
Assuming Tmars to be avg. -50C = 223K
And assuming we inflate to 2atm(mars) = 0.02atm(earth)
PV = nRT
n = PV/RT = (0.02atm * 5.03 x10^8 L) / (0.0821 L atm/mol K * 223 K)
n = 2.75x10^5 moles within balloon...
M(H2)=2 g/mol * n = 5.5x10^5 grams
yeah, that's a LOT of hydrogen.. but lets continue
For the atmosphere this hydrogen is displacing...
Which, BTW, is over 95% CO2, unlike earth which has a much lighter atmosphere for a given pressure..
PV = nRT
n = PV/RT = (0.01atm * 5.03x10^8 L) / (0.0821 L arm/mol K * 223 K)
n = 1.38x10^5 moles of atmoshpere displaced
M(CO2)=44 g/mol * n = 1.21x10^7 grams
Taking the difference, we find that there is 115.5x10^5 grams or...
11550 kg of lifting force here...
Of course we might need to put more H2 into the balloon to have it hold it's shape.. for each martian atmosphere of additional pressure we inflate the craft with, go ahead and reduce the lift by 275 kilograms. Double the local atmospheric pressure should be sufficient.
Now, can we build an airship of that size and keep it's weight under 10000 kg?
(Mind you that IS 30000kg here on earth)...
I think it is safe to say it is more than easily accomplished.
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You're thinking rocket engines.
:)
Rockets carry their own fuel and as such provide their own thrust.
Jets and props require an atmosphere to provide the gas necessary to provide thrust.
Sorta like... imagine outboard motors and water jets out of the water... not much thrust
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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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I hate to nitpick, but this is so wrong I had to point it out.
...
;)
10000kg on earth is still 10000kg on mars.
Taking the difference, we find that there is 115.5x10^5 grams or...
11550 kg of lifting force here..
Now, can we build an airship of that size and keep it's weight under 10000 kg? (Mind you that IS 30000kg here on earth)...
I'll assume based on the rest of the post that you know the difference between mass and weight...
Other than that and the fact that some of the calculations you show have the wrong answer (but strangely the right final answer, where'd you pull that out of?), you're right, a blimp should work ok on mars.