True air/groundspeed vs. actual dynamic pressure

[AphelionHellion]

I've long been interested in the idea of atmospheric flight on Mars (mostly because it's so difficult and involves high
speeds and precise flying) and as an aviation buff first and foremost (armchair space travel only recently being
possible with the advent of Orbiter) I've been wondering if anyone has noticed or addressed some of the atmospheric
discrepancies in Orbiter with a number of addons. Here's an example: I tried to fly the TX on Mars the other day. Hey,
stop laughing! It's not funny!
It flies in the upper atmosphere of earth, so given enough speed, it should fly on Mars, right? Heck, given enough
speed, a brick can fly
Thing is, for safety purposes, the landing gear retracts automatically at something like 190 m/s - leading to a sudden
stop if you're still on the ground. This makes no sense - shouldn't an aircraft use indicated airspeed to determine flight
control configurations? Indicated airspeed is an excellent indicator of dynamic pressure, so it's very useful for
atmospheric reentries, as it tells you how many air molecules you're running into. Atmospheric density being so low on
Mars, dynamic pressure on the landing gear SHOULD be almost nil even at what on earth would be a high atmospheric
speed. I had a similar problem with the DGIII - I tried to take off from Mars using only main engines and aerodynamic
lift, but the landing gear collapsed at 250 m/s. This would certainly make sense on Earth near sea level, but again,
dynamic pressure caused by the thin Martian atmosphere should be pretty darn low even at this velocity. I've heard
estimates that if you take an average airframe from Earth and run it through the Martian atmosphere, you'd need to
get it to over 650 knots true airspeed to generate the equivilent of 50 or 60 knots at sea level on Earth. Shouldn't it
follow then that drag is reduced similarly, and landing gear should be able to survive this sort of speed?

[AphelionHellion]

Er, that should be "to generate the equivalent LIFT as that same airframe moving at 50 or 60 knots at sea level
on Earth."
Um. Bah! My syntax doth sucketh today. You know what I mean, right?

[DanSteph]

AphelionHellion wrote:
I tried to take off from Mars using only main engines and aerodynamic
lift, but the landing gear collapsed at 250 m/s.

Pressure isn't the only problem, in this precise case it's more the vibration of rolling
and the bump that collapse gear, unless you have a real take-off road very plane.
In it's "unrealisme" it's finaly realistic, I doubt anyone can roll on Mars at such speed
without breaking anythings. (I doubt anyone can roll on mars with landing gear as have the DGIII)

Luckily the "ground" gear collapse is the only things based on ground speed, all others things
broke based on dynamic pressure.

Dan

[AphelionHellion]

Dan: Heh, you have a good point A Martian aircraft would to have landing gear built like the wheels on a supersonic
rocketcar. Actually I think in real life they would have some sort of maglev "launcher" as well as a similar sort of
magnetic "chute" that you land in and are slowed down by gas jets or something. This'd eliminate the problem of
vibration and centrifugal force on the wheels, to say nothing of friction.
Either that or just an amazingly flat, smooth plate a number of miles long that you land on with reinforced replaceable
skids. That'd be a bit unnerving, though

Well the thing is, this gear problem occurrs even when you're not on the ground (on Mars). And I'm not just talking
about the DGIII, of course - like I said the TX is another example that uses true relative speed irrespective of
atmospheric density.

Anyway I can't wait until McBrain tells us more about that Mars Flyer model he's got on his site!
*hint*