Orbital Re-Entry into Atmosphere

[Turtle]

Originally Posted by Grains

Thanks Turtle!!! That is exactly what I was curious about.

De nada.

Originally Posted by Grains

I like the other link you sent that was very helpful. I didn't mean an actual helicopter I was just trying to describe the movement I was thinking about (up-down).....bad example on my part

A bit off topic, but further note on flying in the Martian atmosphere, as there is in fact a plan for a Martian plane. To fly in thin atmosphere you need a big surface area wing, and with the lower Mars gravity the engineering is feasible.
>> http://asl.epfl.ch/aslInternalWeb/AS...aper-Final.pdf

[InfiniteNow]

Originally Posted by Overdog

Yes, I believe it would. When the spacecraft first enters the atmosphere, the atmosphere is too thin for the helicopter blades to work, so there would be nothing to slow down the space craft except the resistance of the atmosphere itself.

Maybe it could work like this helicopter:

YouTube - The Anti-Gravity Helicopter

It's a pretty cool video ultimately demonstrating the stroboscopic (wagon wheel) effect. The rotor speed and the film speed are matched (to some ratio) so there is no apparent movement of the blades for each frame of the camera. It's not on topic, but I thought it was really sweet and that this was a good opportunity to share it since the OPs questions has been answered.

[Moontanman]

Not sure if this is relevent but a nuclear light bulb rocket could land by slowly descending on it's own exhaust and avoid the dangerous slowing down by friction that craft like the space shuttle experiences.

BRUCE BEHRHORST ARTICLE LIST

I think they do have either plans for or a working scale model of a space craft that descends on helicopter type blades but I'm not sure if that concept would work on the almost vacuum of the mars atmosphere.

[Overdog]

Originally Posted by Moontanman

Not sure if this is relevent but a nuclear light bulb rocket could land by slowly descending on it's own exhaust and avoid the dangerous slowing down by friction that craft like the space shuttle experiences.

BRUCE BEHRHORST ARTICLE LIST

Wow. A nuclear light bulb. I want one of those.

[Grains]

Originally Posted by Moontanman

Not sure if this is relevent but a nuclear light bulb rocket could land by slowly descending on it's own exhaust and avoid the dangerous slowing down by friction that craft like the space shuttle experiences.

BRUCE BEHRHORST ARTICLE LIST

I think they do have either plans for or a working scale model of a space craft that descends on helicopter type blades but I'm not sure if that concept would work on the almost vacuum of the mars atmosphere.

Would the concept work on Mars if you reversed the blades of the helicopter so they were pulling the other way. Much like the way you change a fan setting? Would that not counter-act the effect of the vacuum?

[Grains]

Originally Posted by Moontanman

Not sure if this is relevent but a nuclear light bulb rocket could land by slowly descending on it's own exhaust and avoid the dangerous slowing down by friction that craft like the space shuttle experiences.

BRUCE BEHRHORST ARTICLE LIST

I think they do have either plans for or a working scale model of a space craft that descends on helicopter type blades but I'm not sure if that concept would work on the almost vacuum of the mars atmosphere.

So if were to reverse the blades of a helicopter and caused a reverse effect (almost like reversing the flow of a home fan) would that counter-act the effect of the almost vacuum on the mars atmosphere?

[Moontanman]

Originally Posted by Grains

So if were to reverse the blades of a helicopter and caused a reverse effect (almost like reversing the flow of a home fan) would that counter-act the effect of the almost vacuum on the mars atmosphere?

Helicopters need air to work, the thicker the air the better they work, the air on mars is so thin (it's close to what we would think is a pretty good vacuum) no matter which direction the turned they wouldn't be able to generate any lift.

[Turtle]

Originally Posted by Grains

Would the concept work on Mars if you reversed the blades of the helicopter so they were pulling the other way. Much like the way you change a fan setting? Would that not counter-act the effect of the vacuum?

First, Mars has a thin atmosphere, but it is not a vacuum. Propellers will work there and a helicopter with large rotors likely the same. Reversing the rotor direction would push the craft down to a crash, as that thrust is then added to the acceleration due to the gravity.

Here's that link again on a Mars airplane: >>

Page #5...The propeller is composed of two 60 [cm] diameter blades with a Goe795 profile. The calculated specifications of the
propeller, at high altitude on Earth for speed similitude with Mars, are listed in Table 4. ...

http://asl.epfl.ch/aslInternalWeb/AS...aper-Final.pdf

[TheBigDog]

Helicopters push the blades to create lift. When the engines fail they reverse the angle of attack of the blades to autogyro to the ground. As the craft falls it causes the blades to spin, and this causes the fall rate to slow. This was the principle employed by the company that wanted to use the rotary space craft to win the original x-prize. It ended up burning up do to rocketry issues, but the descending worked as they had hoped as I recall.

Rotary Rocket - Wikipedia, the free encyclopedia

Oops! Not x-prize, but a commercial venture.

Bill

[Moontanman]

Guys, yes Mars has an atmosphere, I didn't say it didn't but at 1% of Earths it would be considered a pretty good vacuum to us, not complete but better than most of us would be able make here on Earth without special equipment. Helicopters do not work at high altitudes on Earth, the power requirements are just too great, they would not work on Mars due to the "thin" atmosphere either. Yes a very light airplane with huge wings could fly on mars but a helicopter would not. The engineering of a helicopter that would work on Mars would be a challenge to say the least and almost certainly wouldn't be much of a help for a space craft trying to land.