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Old 09-26-2016, 11:09 AM   #31
jedidia
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No, if the mesh is positioned like that, they are at the correct height. The other ones at -2.164 wouldn't be, though.
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Old 09-26-2016, 12:12 PM   #32
gattispilot
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Thanks. So how do I get it to drive on the surface. The thrust is at 0,0,0. Without the flipping.

I did notice that effect. When the vessel is added no issues but when thrust is applied it tends to sink down a bit.

On Dans cars How can you drive them if you can't get them in? Depending on which pad they do sink in.
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Old 09-26-2016, 12:43 PM   #33
jedidia
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Quote:
On Dans cars How can you drive them if you can't get them in? Depending on which pad they do sink in.
Just from external view. They sink in a little bit depending on evenness of the terrain, that's unavoidable, but I haven't seen anything extreme.
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Old 09-26-2016, 12:48 PM   #34
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Ok. So not sure if adjusting the dampness would help. In the real world. If the dampness was weak on a car. The car would be bouncing. I guess if enough bounce it could leave the surface. Maybe that is whats happening.

Ideally the vessel should hug the surface.
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Old 10-02-2016, 07:01 PM   #35
mike-c
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Default touchdown points in cfg

Hope i didn't missed it in orbiter2016's doc:
is there a new Syntax/semantic for defining TD-Points (n>4) in a (Vessel).cfg

Thank's in advance
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Old 10-02-2016, 07:41 PM   #36
N_Molson
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Quote:
below standard sea-level.
"datum" as they say
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Old 10-03-2016, 12:36 PM   #37
gattispilot
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Yes. There is a new definition:http://www.orbiter-forum.com/showthr...12&postcount=4

So maybe it is not the touchdown points that cause my ground vessels to flip,....

But maybe the dampness....
"Low stiffness makes the vessel jump more. It's the equivalent of a soft spring, so exerts a low force at large spring displacement.

However, be careful when increasing the stiffness. A higher stiffness also increases the eigenfrequency of the system, which can lead to numerical instabilities in particular at higher time accelerations (large forces even at small displacements).

Regarding damping: look up "critical damping" for computing damping values that return the spring to equilibrium fastest and don't induce oscillations. "


https://en.wikipedia.org/wiki/Damping

Last edited by gattispilot; 10-03-2016 at 12:40 PM.
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Old 10-03-2016, 03:36 PM   #38
mike-c
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In the process of getting a Velcro-Atlas flying i got some strange behavioure on launchpad: sinking into the ground like a needle, tipping over and then lying flat on the ground, bouncing a few meters into the air; all immediate at sim start.

After some trying i found these params working for a middlesize rocket:
static TOUCHDOWNVTX tdvtx0[ntdvtx0] = {
{currTD1, 1e8, 1e6, 3, 1},
{currTD2, 1e8, 1e6, 3, 1},
{currTD3, 1e8, 1e6, 3, 1},
{_V(0.0,0.0, 1.0), 1e8, 1e6, 3},
};

tdvtx0[3] is constant, since i cannot yet hand it over to the vessel from
Config\Vessels\*.cfg
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Old 10-14-2016, 10:56 AM   #39
gattispilot
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Ok. I can't figure this out.

So the mesh is oriented correctly.

Code:
DWORD ntdvtx = 3;
static TOUCHDOWNVTX tdvtx[3] = {
	{ _V(0, .001, 20), 1e5, 1e2, 0.5, 0.005 },
	{ _V(-15, .001, -20), 1e5, 1e2, 0.5, 0.005 },
	{ _V(15, .001, -20), 1e5, 1e2, 0.5, 0.005 },
	//{ _V(0, 5, 0), 1e5, 1e2, 0.5 }// new point just to make a closed shape (more are not needed as the crawler is unlikely to get upside down)
};
Code:
void SLSCRAWLER::clbkSetClassCaps(FILEHANDLE cfg) {
	// physical specs
	SetSize(6.08);
	SetEmptyMass(MASS);
	SetCW(0.9, 0.9, 2, 1.4);
	SetWingAspect(0.1);
	SetWingEffectiveness(0.1);
	SetCrossSections(_V(12.16, 15.99, 9.39));
	SetRotDrag(_V(0.1, 0.1, 0.1));
	if (GetFlightModel() >= 1) {
		SetPitchMomentScale(1e-4);
		SetBankMomentScale(1e-4);
	}
	SetPMI(_V(3.75, 3.48, 2.23));
	SetTrimScale(0.05);
	SetCameraOffset(_V(0, .7, 3.121));
	SetTouchdownPoints(tdvtx, ntdvtx);

I opened a scenario and added it and located it at the sh02;
Code:
SH-02:ShuttleA
  STATUS Landed Earth
  BASE Cape Canaveral:5
  POS -80.6745295 28.5197189
  HEADING 100.00
  ALT 2.912
  AROT -62.051 -79.897 124.244
  AFCMODE 7
  PRPLEVEL 0:1.000000 1:1.000000
  NAVFREQ 0 0
  XPDR 0
  PODANGLE 0.0000 0.0000
  DOCKSTATE 0 0.0000
  GEAR 0 0.0000
  PAYLOAD MASS 0.0 0
  ATTREF 0 0 0
  ADI_LAYOUT 0
END
crawler:SLSCRAWLER
  STATUS Landed Earth
  POS -80.6745300 28.5197190
  HEADING 100.00
  ALT -60.000
  AROT -28.841 8.183 95.517
  AFCMODE 7
  PRPLEVEL 0:1.000000
  NAVFREQ 0 0
END
Notice the ALT -60

So the craft is below the surface and rotated straight up. The points work in sc4
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Old 10-14-2016, 11:07 AM   #40
Urwumpe
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Syntax error.

Also ALT is no standard parameter of Orbiter.
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Old 10-14-2016, 11:20 AM   #41
gattispilot
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Quote:
Originally Posted by Urwumpe View Post
 Syntax error.

Also ALT is no standard parameter of Orbiter.
Syntax error in the code?


Well how do you adjust the ALT then?
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Old 10-14-2016, 11:48 AM   #42
Urwumpe
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Quote:
Originally Posted by gattispilot View Post
 Well how do you adjust the ALT then?
By the touchdown points.

And yes, syntax error in the code: Your comment removes the last line and does not remove the comma ahead of it.
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Old 10-14-2016, 11:51 AM   #43
martins
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Quote:
Originally Posted by Urwumpe View Post
 Also ALT is no standard parameter of Orbiter.
Actually I think it probably is in Orbiter 2016 (haven't got the sources handy at the moment to check).
The reason is that due to the compressible touchdown points in Orbiter 2016, the touchdown points are no longer sufficient to determine the equilibrium position of an idle (landed) vessel. Instead, Orbiter now uses the ALT and AROT entries to determine those parameters.

The alternative would be to start the scenario with each vessel active, allowing it time to settle in its equilibrium state before switching it back to idle. But that has its own problems.

Quote:
Code:
  ALT -60.000
  AROT -28.841 8.183 95.517
So where are these values coming from, and how do you know that they don't reflect correctly what you see in the simulation?
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Old 10-14-2016, 11:55 AM   #44
Urwumpe
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Quote:
Originally Posted by martins View Post
 Instead, Orbiter now uses the ALT and AROT entries to determine those parameters.
Oh ... that's problematic with all those add-ons that use the new API and a ALT parameter, didn't know it yet.

So, the "spring forces" are not saved per vertex?
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Old 10-14-2016, 12:15 PM   #45
gattispilot
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Quote:
Originally Posted by martins View Post
 So where are these values coming from, and how do you know that they don't reflect correctly what you see in the simulation?

So ALT and AROt are calculed based off touchdown point info?


Don't know. I had another vessel the slstower I added and it was above the surface.

Well I would saw since the y value on the touchdown point is .01 then -60 is wrong.

I will fix that comma and see it is rights the vessel

Last edited by gattispilot; 10-14-2016 at 12:30 PM.
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