Exploring the Physics of a Hobby: Investigating Lift in Vacuum Chambers

[Altune]

I am interested in this Hobby.
I have seen several experiments and it looks pretty easy to do.
I am wondering what exactly lifts this?
Is it Ions or ??
They had done a test in a vacuum chamber and it was still working, are ions present in a vacume?
If it's not ions, then what makes the model rise? And I wonder how high it would rise if it did not need the power line connected?
They say it's high voltage, low wattage 30k
Anybody taking this seriously?
I heard they are using this technology in the leading edges of the B1 Bomber to create more lift.
Anybody?

 

[Hurkyl]

http://www.blazelabs.com/nasatest.pdf

 

[Mech_Engineer]

I am wondering what exactly lifts this?
Is it Ions or ??

Ions created in the air from the high-voltage areas of the lifter provide a repulsive effect on one end and an attractive effect at the other that propels the model.

http://en.wikipedia.org/wiki/Ionocraft

When the corona wire is at approximately 30 kV, it causes the air molecules nearby to become ionised by stripping the electrons away from them. As this happens, the ions are strongly repelled away from the anode but are also strongly attracted towards the collector, causing the majority of the ions to begin accelerating in the direction of the collector. These ions travel at a constant average velocity termed the drift velocity. Such velocity depends on the mean free path between collisions, the external electric field, and on the mass of ions and neutral air molecules. If this were the only effect present, there would be no movement; as the ions impact the second electrode, they create another equal and opposite force that cancels out the initial movement.

They had done a test in a vacuum chamber and it was still working, are ions present in a vacume?

EHD Lifters do NOT work in a vacuum, no matter what you think you have seen or heard on the internet. It is a myth propogated by anti-gravity nut jobs. No fluid surrounding the model means no thrust.

I heard they are using this technology in the leading edges of the B1 Bomber to create more lift.

Well that's a weird thing to think. Where exactly did you hear that?

 

[Hurkyl]

EHD Lifters do NOT work in a vacuum, no matter what you think you have seen or heard on the internet.

Clarification -- they do not work in a 'hard' vacuum. If the quality of the vacuum is sufficiently poor, enough fluid remains to allow them to work.

 

[Mech_Engineer]

Clarification -- they do not work in a 'hard' vacuum. If the quality of the vacuum is sufficiently poor, enough fluid remains to allow them to work.

The point is they are NOT an anti-gravity device, they require a medium like air to create ions for thrust. Saying they work in some vacuums might be technically correct for a very poor vacuum (if you like measuring thrust in micro-Newtons), but propogates the wrong idea. As it is, a relatively poor vacuum is really just a very low-pressure gas. Unfortunately in the real world, the distinction between gas and lack of it (vacuum) is an infinite gradient of gray.

I think the really important thing to take away from "lifters do not work in a vacuum" is "lifters do not work in space."

 

[Hurkyl]

The point is they are NOT an anti-gravity device, they require a medium like air to create ions for thrust. Saying they work in some vacuums might be technically correct for a very poor vacuum (if you like measuring thrust in micro-Newtons), but propogates the wrong idea. As it is, a relatively poor vacuum is really just a very low-pressure gas. Unfortunately in the real world, the distinction between gas and lack of it (vacuum) is an infinite gradient of gray.

I think the really important thing to take away from "lifters do not work in a vacuum" is "lifters do not work in space."

I believe several demonstrations have been performed in (poor) vacuums, in which the lifter does work. I was being pedantic on this point because the layperson could easily get the wrong impression from the claim "lifters do not work in a vacuum", and then reject what the scientists say when they see one of these demonstrations.

 

[russ_watters]

http://www.blazelabs.com/nasatest.pdf

Great link - I'd been wondering if anyone did any real tests of one of these in a vacuum (there is a crackpot claiming he did). I wish they had more there, though.