Re: Discovery Channel

[Bruce Moomaw]

----- Original Message ----- From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Sunday, October 27, 2002 12:31 AM Subject: Re: Discovery Channel In a message dated 10/26/2002 10:58:54 PM Alaskan Daylight Time, [EMAIL PROTECTED] writes: I did some more thinking about the 'steam issue'.  I agree, steam is not necessary, considering that if/when this thing gets ice frozen over it, it will generate hydraulic pressure.  So, the model has got to be very sturdy, and very streamlined.  Speed is not the issue, and too much heat would possibly be counterproductive, as the model might hit a rock, stop, and then be so damned hot that a cavity is created around it before it can get around the rock, thereby stranding the model in a water bubble under 50' of ice. It's got to move, but it's got to move SLOW.  Temperature of the model should probably be about 30 degrees faranheit warmer than the ice. ____________________________   There's a VERY serious misconception developing here -- every Cryobot design ever developed simply melts the ice beneath its nose, and then uses gravity to descend.  Rear steam-jet propulsion would be incredibly inefficient in providing a very small amount of additional downward motive force, given the amount of energy needed to boil ice (fully 8 times more than is needed to melt it) -- you'd do infinitely better just to use any heat source powerful enough to do that to just melt the ice below the Cryobot's nose faster instead.   (By the way, the Cryobot does NOT generate "hydraulic pressure" when it melts ice -- quite apart from the fact that any such pressure would be in every direction anyway, remember that water ice is one of the very few substances that SHRINKS when it melts.) ______________________________ ______________________________     Can the transponders relay a signal?  Would it help if they were wired together with a thin filament? ______________________________   They certainly wouldn't be wired together in any real Europa Cryobot -- the whole reason for using them rather than a thin communcations cable from the cryobot to the surface is that (1) any such cable, even if very thin, will add a huge chunk to the Cryobot's weight and volume; and (2)  given that there are probably slow motions within Europa's ice layer, any cable that wasn't elastic would be quickly broken by shear stress.  (The plan is to space the transponders about 1 km apart.)