----- Original Message ----- From: "David Thomson" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, February 16, 2007 4:08 AM Subject: RE: [Vo]: Lifters
... > My guess is that the potential needs to be increased proportional to the > vacuum. So if you double the vacuum, you need to double the potential. ... Multiply it by root 2 in fact. To maintain the same thrust, every time you halve the pressure you must double the current, as per the thrust formula I*d/mu where ion mobility mu is doubled (inversely proportional to air density). In order to double the current you must indeed increase voltage, but not by a factor two, only root 2 as the I(V) law is quadratic for a corona discharge. There is a brick wall limit to this scheme though: breakdown voltage goes down with pressure, so you can't increase voltage much, hardly at all in fact since a well designed lifter operates as close as possible to the breakdown voltage. Michel
