It won't rise but some of the ions will go round or even through the paper so you'll get some remaining thrust, it's very hard to insulate high voltages.
Anyway no one serious in the field still doubts the ion wind hypothesis, for thousands of reasons, not the least of them being that it has been experimentally shown that you get no thrust in vacuum. But some people do entertain the doubt on their websites, deliberately or not. What convinced me personnally is the fact that experimental thrusts are equal to what is expected from ion wind theory (the formula I gave earlier on). So any contribution of other effects is minimal at most. Anyway EHD experiments are great fun and easy to do, so by all means experiment and form your own opinion. Beware though that high voltages (25kV for a typical computer screen power supply) at any sizeable current (more than a few mA) can be lethal, and hurt a lot in the very least (feels a bit like having your arm caught in a meat chopper I was told). Michel ----- Original Message ----- From: "Harry Veeder" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Sunday, February 04, 2007 9:50 PM Subject: Re: [Vo]: Re: Fred's Van de Graaff Antics > Michel Jullian wrote: > >> >> ----- Original Message ----- >> From: "Harry Veeder" <[EMAIL PROTECTED]> >> To: <vortex-l@eskimo.com> >> Sent: Sunday, February 04, 2007 2:01 AM >> Subject: Re: [Vo]: Re: Fred's Van de Graaff Antics >> >> >>> Michel Jullian wrote: >>> >>>> Sure Harry it's ion wind. Naudin's comment, athough somewhat misleading, is >>>> correct too. The collector (bottom negative armature) is indeed attracted >>>> upwards to the "parachuting" positive ion cloud _generated by_ the corona >>>> wire >>>> (the ion cloud, dragging ambient air along, is pulled downwards with an >>>> equal >>>> and opposite force, hence the wind). This upwards pull constitutes most of >>>> the >>>> lift, because most of the positive charge (whose total value is equal and >>>> opposite to the collector's negative charge due to charge conservation) is >>>> in >>>> the air, so the wire itself carries a comparatively small positive charge, >>>> so >>>> it's contribution to the lift (upwards push from the positive ion cloud >>>> below) >>>> is comparatively small. >>>> >>>> Same reasoning holds if you reverse polarity, in all cases you get thrust >>>> in >>>> the direction from the collector to the wire (not necessarily upwards BTW). >>>> >>>> Michel >>> >>> >>> >>> For sake of argument assume there is no ion wind. What you have >>> are two oppositely charged bodies where one (the wire) is above the other >>> (the tube). Each will be attracted to the other. The tube will accelerate >>> upwards and the wire will accelerate downwards. If the attractive forces are >>> opposite AND equal the lifter will not take off, but since tube has some >>> freedom to move it will rise until it is stopped by the cross member. >> >> If the force is sufficient, yes. >> >>> However, if these forces are opposite but not equal the lifter will either >>> want to ascend or descend depending on the polarity. >> >> If there is no ion wind there are no positive charges in the air so they are >> all on the wire, so the forces are necessarily equal. The thing becomes an >> ordinary capacitor, it doesn't fly. >> >>> On the other hand if an ion wind is the cause of this net force then it >>> should be possible to reduce the net force by inserting a horizontal neutral >>> (e.g. paper) shield in the gap between the wire and the tube. This shield >>> would be fixed to the struts of the lifter. >> >> Sure, but why reduce the net force? >> >> Michel > > This tests the ion wind hypothesis. > Is the hypothesis sufficient to explain > the motion of the lifter? If the lifter > still rises then it is insufficient. > > Harry >
