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#126 2019-04-01 19:57:48

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 3,486

Re: Airplanes on Mars

for SpaceNut #125

Magnesium strips the oxygen away from the carbon, leaving carbon behind.  The text said the engine is being (has been?) redesigned to avoid coating the turbine blades with carbon. 

From https://en.m.wikipedia.org/wiki/Composition_of_Mars

Based on these data sources, scientists think that the most abundant chemical elements in the Martian crust, besides silicon and oxygen, are iron, magnesium, aluminum, calcium, and potassium. These elements are major components of the minerals comprising igneous rocks

The exhaust from an engine running on magnesium would (I would think) be on the sooty side.  The carbon would exhaust as soot, and magnesium oxide would (presumably) float for some time in the atmosphere as a fine powder. 

To my surprise, magnesium oxide is used on Earth for medical purposes:
https://www.rxlist.com/consumer_magnesi … dition.htm

Magnesium oxide is an over-the-counter mineral effective as treatment for

The article also reports that magnesium is needed for normal human health.

(th)

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#127 2019-04-02 20:23:13

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,717

Re: Airplanes on Mars

SpaceNut,

Thanks for the interesting find.  I learned something new today.  I'm going to read more about that.

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#128 2020-06-10 16:19:04

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,681

Re: Airplanes on Mars

Another good post to add into a topic where it fits...

kbd512 wrote:

tahanson43206,

The primary problem with wings on Mars is that the air density at Mars sea level ranges between the Earth-equivalent of 100,000 to 130,000 feet.  Look at the ratio between gravity and atmospheric pressure.  The atmospheric pressure and forward velocity will determine the actual lifting force and drag generated as you fly through the air for any given wing design.  Sure, Mars' gravitational pull is only 38% of Earth's gravity, but the air pressure at Mars sea level is 11.5 millibars vs Earth's 1,013 millibars.  Are you going to be flying or stalling and falling from any greater altitude?  That's like 1/88th of Earth's atmospheric pressure, which you only get at Mars sea level, so your wings are going to be truly huge (and therefore heavy) or you're going to be flying really fast when you land.  No airliner wings would generate sufficient lift at subsonic speeds to keep the generated lifting force at or above the mass of the airliner at the atmospheric pressure at Mars sea level.  So, you either have to have an enormous wing that must be incredibly light and stiff or you have to have quite a bit of velocity to stay airborne at any altitude while staying subsonic, or some combination of both.  Mach 1 on Mars is also significantly lower velocity than on Earth.

The U2 was basically a jet-powered glider, but at 70,000+ feet, even with its enormous wings, it was basically 11 mph away from either exceeding the wing's structural integrity and ripping the wings off or stalling / diving / then ripping the wings off.  Modern carbon fiber composites are much better than Aluminum when strength / stiffness / mass per unit area of wing are considered, but still not good enough.  The Airbus Perlan II glider can actually do what you're talking about, meaning stay aloft at altitudes above 100,000 feet.  Perlan II has a pressurized cockpit with just enough room for 2 pilots wearing flight suits.  That glider's Vne is 434 mph and I think it can stay aloft at a bit more than half that speed at 100,000 feet.  Landing something that delicate faster than the Space Shuttle would be VERY interesting.  If it was made from CNT and BNNT, then perhaps it could land at normal airliner landing speeds.

If you break Mach, you'll probably rip the wings off the glider, so the numbers shown in the link below are not mere suggestions for any prospective Mars glider designers:

Speed of Sound on Mars

Airbus paid for the Perlan Project, but Windward Performance fabricated the machine for them:

Windward Performance Perlan II

Perlan II has an 84 foot wingspan and weighs 1,800 pounds.  If it was made from CNT and BNNT, it could weigh less than half of that and most likely land about as fast as an airliner does, at Mars sea level.  I'd love to see how that thing is packaged behind a heat shield of some kind.  Your guess about how well that would work is as good as mine, but the wings would likely have to fold.  Still, it would be cool to actually "fly" rather than "fall" to the surface of Mars.  I think airliners are pretty much out of the question, though.  Airships are doable, but also huge for the payload lifted.

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