Vanes, box shealding & landing frame

John Carmack,

I was wandering if you folks had any concerns about the deep 
enclosure around the jet vanes?  It seems to me it may cause 
some problems with the gas dynamics for controlling the thrust 
vectoring.  It seems that as the vanes deflect a significant amount 
the gases are going to impinge on the side of the box and basically 
have the steering effects basically canceled out.  Also it would 
seem that at extreme vane deflection the back pressure behind and 
to the side of the vane and the box could be the cause of the 
stress failures of the shaft and vane that might not of other wise 
have happened in such a constricted volume.

Have you considered instead of the shielding box, instead covering 
the bearing and servo motor with a low profile as possible high 
temperature flexible thermal insulation blanket, perhaps made of 
fiberglass or  nominex?  Also perhaps the servos could be moved 
further up and away from the exhaust backwash by coupling them 
the the vane shaft by a universal joint and thus moving the servos 
up and way, say up to 60 degrees.

I know that the system is now an experimental steeping stone to 
your next vehicle, and thus your trying to keep it as simple as 
possible.  The landing gear looks to have a very narrow foot print 
and only a modest amount of sideways motion on touchdown 
would result in the vehicle toppling over.  Have you considered for 
at least the first free flights putting 'training' struts out on the 
landing structure?

I know its probably going to be a while but when you plan on having 
the vehicle going to higher speeds and altitude, have you 
considered putting a angled down facing camera with a RF link?  
The idea is that if the vehicle encounters control problems or 
unexpected drift and possibly has to land out of direct view of the 
ground control station, such as having to land it on the other side of 
a hill or tree.  This would make possible last minute adjustment to 
avoid undesirable landing locations that the auto land code would 
have no way of knowing about.  Also along those lines any 
thoughts about some sort of close range terrain sensors such as a 
IR or ultra sonic ranger.  I know you have a GPS system but it 
can't take into account the odd little topography issues if you have 
to land further away from your takeoff point.

Just some thoughts, from my own experience in technology 
developments I empathize with you on the frustrations and joys of 
such an effort.

 - Edward Rupp