Nasa lies about Mars atmosphere.Helicopter to fly in Mars" 0.6Percent of earths atmosphere"

a reply to: Zaphod58

CO2 has slightly more mass than O2. The molecular weight of CO2 is 44 grams per mole, while the molecular weight of oxygen is 32 grams per mole. Although CO2 is heavier than O2, the gases do not separate into layers in the atmosphere. Convection and diffusion keep the various atmospheric gases mixed.

So CO2 doesn't affect the lift either then?

originally posted by: Zaphod58
a reply to: M5xaz

The post that I was replying to was about flying a plane on Mars though.

He actually doesn't. You have to take into account the lighter gravity, and the fact that the rotor design provides more lift than a conventional rotor will.

Kamov helicopters have had this twin rotor on single shaft design for decades and have not bested height records of other helicopter designs.

The claimed low pressure for Mars is equivalent to Earth at 35km or 100 000 ft, thin air at which no helicopter operates/could operate even accounting for lower gravity.
Plus, given the low power from the Sun for photovoltaics at Mars distance again seems to suggest something fishy/improbable....

Finally, the compact/small design of the NASA helicopter makes it even more improbable. With low power, you need huge rotors for efficiency, as demonstrated by the team from U of T that built the human powered helicopter that won the AHS Sikorsky prize

Nitrogen — 78 percent
Oxygen — 21 percent

Should the question be about nitrogen, not oxygen.

Well hopefully it works as getting it there is the hard part without it getting smashed to pieces and surviving the changes in temps. As they said, most of the battery is used to keep the batteries temps stable. It will be like Wright Brothers first flight all over again only on a different planet. o-O

originally posted by: 0bserver1
a reply to: Zaphod58

CO2 has slightly more mass than O2. The molecular weight of CO2 is 44 grams per mole, while the molecular weight of oxygen is 32 grams per mole. Although CO2 is heavier than O2, the gases do not separate into layers in the atmosphere. Convection and diffusion keep the various atmospheric gases mixed.

So it CO2 doesn't affect the lift either then?

I'm thinking CO2 needs to be, as your quote says needs to be in a regime of heated gases and mixed, you probably would have convection and diffusion in daytime Mars, one reason why hot air balloons were considered as 'flyer's at one stage as in the video, perhaps not enough though in the current thinking.

The visuals of the dust devils that elevate so easily on Mars could be deceptive though, on the face of it, they are are heavier than air as iron oxides, but they must also be incredibly fine and dry compared to the dust we see on Earth.
something of an enigma, as we can see that the dust storms on Mars can last for some time.
NASA has materials lighter than Balsa wood, and much stronger, maybe that's why they don't use Balsa for Martian flyers....who'd of thunk!

a reply to: SpaceBoyOnEarth

I agree NASA is not very forthcoming about Mars' atmosphere. I don't think it is 70% of Earth's though. NASA will even admit the .6% of Earth's is not a hard #. Just like the fact of water on Mars NASA has changes it's view over the decades.

Hopefully soon private missions will land on Mars and then we can get some real answers. There are some pics from India's Mars orbiter MOM that may interest you.

a reply to: LookingAtMars

Mars atmosphere is over 95 % CO2 , with about 2 1/2 % Nitrogen and about 2 % Argon

CO2 (Mol weight 44) and Argon (Mol weight 40) are fairy heavy compared to Nitrogen (mol weight 28), water vapor (Mol
weight 18) and Oxygen ( Mol weight 32) and are better able to remain in Mars lighter gravity than other gases which are broken up by charged particles from the solar wind and escape from the planet

Meh considering, we really don’t understand how a helicopter can fly, who knows.

At least that is what I was taught. Was never excited about the helicopter ride I took in a Blackhawk once, knowing I was flying in a machine we did not really understand how it was doing it.

I would imagine the blades will have to go faster maybe I dunno to fly.

a reply to: firerescue

Good catch. I was using the .6% of Earth's he was talking about.

Thanks

a reply to: Bicent

we really don’t understand how a helicopter can fly

That is a great point!

a reply to: Bicent

But we do understand.

a reply to: 0bserver1

That's one reason they're using such a large rotor turning at such a high speed.

a reply to: M5xaz

It is so much more complicated than "helicopter x uses the same rotor and can't fly at altitude y". To look at it in a simplified manor, helicopter altitude is determined by rotor diameter, rotor speed, and most importantly weight.

The Kamov Ka-32 uses a coaxial rotor, so lets compare it to the Mars scout.

Ka-27 (the Ka-32 is the civil version) -
Rotor diameter- 51'10
Length- 37'1
Height- 18'1
Empty weight- 14,330 pounds
Gross weight- 24,251
MTOW- 26,455
Rotor RPM- approximately 300 at low speed

Mars Scout-
Rotor diameter- 47 inches
Chassis dimension- 14 cm cube
Weight on earth- 4 pounds
Weight on Mars- 1.5 pounds
Rotor RPM- 1900-2900

Yes the air is the equivalent of 98,000 feet, but you're also talking about a vehicle significantly lighter, with an equivalent rotor diameter to a larger and heavier helicopter, with blades turning close to 10x as fast. That means they're able to generate more lift. You are also talking about extremely short hops at low altitude.

originally posted by: Zaphod58
a reply to: M5xaz

It is so much more complicated than "helicopter x uses the same rotor and can't fly at altitude y". To look at it in a simplified manor, helicopter altitude is determined by rotor diameter, rotor speed, and most importantly weight.

The Kamov Ka-32 uses a coaxial rotor, so lets compare it to the Mars scout.

Ka-27 (the Ka-32 is the civil version) -
Rotor diameter- 51'10
Length- 37'1
Height- 18'1
Empty weight- 14,330 pounds
Gross weight- 24,251
MTOW- 26,455
Rotor RPM- approximately 300 at low speed

Mars Scout-
Rotor diameter- 47 inches
Chassis dimension- 14 cm cube
Weight on earth- 4 pounds
Weight on Mars- 1.5 pounds
Rotor RPM- 1900-2900

Yes the air is the equivalent of 98,000 feet, but you're also talking about a vehicle significantly lighter, with an equivalent rotor diameter to a larger and heavier helicopter, with blades turning close to 10x as fast. That means they're able to generate more lift. You are also talking about extremely short hops at low altitude.

So far, we are somewhat on the same page.

I still think the rotor size for the NASA copter is too small if the Mars atmosphere is that thin, and the available power is that low

Where it really breaks down is power.
Sure given enough power, anything is possible
But the chassis is very small, and on that small chassis are the photovoltaics that must produce power to lift the copter for a significant distance/altitude where the Sun is far less bright on Mars, affecting power production.

Again, something fishy @ NASA

a reply to: M5xaz

They're talking about 5 flights in 30 days. It's theoretically capable of one 90 second flight a day, with each flight having a maximum altitude of 1300 feet, and maximum forward range of 2000 feet. This thing isn't going to go any kind of significant distance or altitude. If they go the maximum of 2000 feet on each flight, it'll get roughly 2 miles from where it's dropped off.

a reply to: M5xaz

Where it really breaks down is power. Sure given enough power, anything is possible But the chassis is very small, and on that small chassis are the photovoltaics that must produce power to lift the copter for a significant distance/altitude where the Sun is far less bright on Mars, affecting power production.

It runs off the battery not the solar cells. The solar panels are used to recharge the battery.

originally posted by: Bicent
Meh considering, we really don’t understand how a helicopter can fly, who knows.

As a former Naval helicopter mechanic, I will tell you we know exactly how they fly.

originally posted by: SpaceBoyOnEarth

Continued:
Mars gravity is: 38% of earths. Will use this later.


Well lets go deeper:
Because mars gravity is 38% of earths, we get:

We divide 100 with 0.38. It is 2.63. So a craft can be 2.63 times lighter and have same lift capability as on earth and it will still fly, if atmosphere is same. Remember, atmosphere is atoms, as gas, and rotors spin through it like a screw.

Did you mean to say heavier? Since Mars Gravity is only 38% of earths a craft can be 2.63 times "heavier" and still have same lift capacity as on earth?

Other question is if you took into account reduced air resistance? Obviously a boat propeller running on dry land uses less energy and accelerates and spins faster without the resistance of water.

Still reading...

a reply to: SpaceBoyOnEarth

"The Martian atmosphere is only about one percent the density of Earth's," said Aung. "Our test flights could have similar atmospheric density here on Earth - if you put your airfield 100,000 feet (30,480 meters) up. So you can't go somewhere and find that. You have to make it."

Aung and her Mars Helicopter team did just that in JPL's Space Simulator, a 25-foot-wide (7.62-meter-wide) vacuum chamber. First, the team created a vacuum that sucks out all the nitrogen, oxygen and other gases from the air inside the mammoth cylinder. In their place the team injected carbon dioxide, the chief ingredient of Mars' atmosphere.

"Getting our helicopter into an extremely thin atmosphere is only part of the challenge," said Teddy Tzanetos, test conductor for the Mars Helicopter at JPL. "To truly simulate flying on Mars we have to take away two-thirds of Earth's gravity, because Mars' gravity is that much weaker."

The team accomplished this with a gravity offload system - a motorized lanyard attached to the top of the helicopter to provide an uninterrupted tug equivalent to two-thirds of Earth's gravity. While the team was understandably concerned with how the helicopter would fare on its first flight, they were equally concerned with how the gravity offload system would perform.

"The gravity offload system performed perfectly, just like our helicopter," said Tzanetos. "We only required a 2-inch (5-centimeter) hover to obtain all the data sets needed to confirm that our Mars helicopter flies autonomously as designed in a thin Mars-like atmosphere; there was no need to go higher. It was a heck of a first flight."

The Mars Helicopter's first flight was followed up by a second in the vacuum chamber the following day. Logging a grand total of one minute of flight time at an altitude of 2 inches (5 centimeters), more than 1,500 individual pieces of carbon fiber, flight-grade aluminum, silicon, copper, foil and foam have proven that they can work together as a cohesive unit.

www.jpl.nasa.gov...

This is relatively simple. The equation for lift of a rotor blade is:

L=Cl·(p·V^2·S)/2

Lift = Coefficient of lift x (pressure x velocity squared x surface area)/2

Coefficient of lift is a unitless number that will vary with the specific shape of the airfoil and angle of attack. Typically, it will fall somewhere between 0 and 2).

Pressure is the air pressure.

Velocity refers to the velocity of the air moving over the airfoil, which necessarily varies with the RPM of the rotor.

Surface area is area of the surface of the rotor disk.

As can be seen, lift varies linearly with air pressure. That is, all other things being equal, a rotor operating in in the Martian atmosphere with a density of 0.6% that of Earth's will produce 0.6% of the lift as it would operating on Earth.

However, we see that the lift also varies with the square of the velocity. Again, all other things being equal, a rotor spinning at 1500 RPM will produce 75 times the lift of a rotor spinning at 300 RPM.

This is why the Mars Helicopter's rotor spins so fast. Accounting for the differences, the Mars Helicopter's rotor, spinning at 2900 RPM in the Martian atmosphere and gravity, can lift the same mass as the same rotor spinning at ~365 RPM in Earth's atmosphere and gravity.