Project NASA Viking

[Buck Rogers]

What I got from the pdf's is the attitude is managed by RCS until 91km alt. when its just left to find its equilibrium attitude of AoA -11.1. Specificaly, it sets the AoA -20 at 9 mins before entry and keeps it there until entry alt. At that point I think it just nulls out any rotation - if you do that, you find it hits AoA -11.1 just as you get to 91km and the atmosphere kicks in to keep it stable.
Thats my interpretation

Sounds good, your last .cfg works very well, parachute was also nearly vertical before sep.(ground contact), looking good. It's also not directly relevant for the addon, it was just the explicit use of the word trim that got me wondering.

As much detail as you need in those .pdf's.

Indeed, I wish I had that detail on some other projects, but sifting through and understanding is another... What would be nice to have though is the exact timing of the deorbit burn for the individual missions, I'm sure they didn't perform identicaly and this would be the biggest difference in flight profile.

Yes, no problem with that, if you do any documentation might be worth making a note though.

Good documentation is important, I'll put a draft together as soon as I have time.

I had a look around the interweb and a lot of Mars landers, e.g. Mars Rovers, hit 6-8g but one (I forget which) hit ~18g.
I had go at finding a trajectory that hit 13g but I couldn't make it work. Given that the add-on entry range and chute deploy velocity are pretty close to nominal, I'm prepared to leave the 13.6g as a ?

OK, cool, I'll start trying to read a bit about the lander descent - it had some kind of azimuth pointing requirement but I can't find what.

The only thing I could find is a tip-up maneuver to align the x-axis with the total relative velocity vector (p.88)?

 

[Buck Rogers]

Hi @BrianJ , I've spent most of the day working on the textures and have encountered many problems and am having to redo the entire mesh, this also breaks all the animation ,td points and thruster positions. I've no idea how I put it together using 3dsmax (I'll just say thanks that there's Blender and Blakes plugin).
If you've made a lot of progress and have encountered no problems I'll halt and do only changes to the tex. files.
On the other hand if you are not so far then give me a day or two and I'll try and get it straightened out.

 

[BrianJ]

Hi @BrianJ , I've spent most of the day working on the textures and have encountered many problems and am having to redo the entire mesh, this also breaks all the animation ,td points and thruster positions. I've no idea how I put it together using 3dsmax (I'll just say thanks that there's Blender and Blakes plugin).
If you've made a lot of progress and have encountered no problems I'll halt and do only changes to the tex. files.
On the other hand if you are not so far then give me a day or two and I'll try and get it straightened out.

Great! No problem at all - I haven't had time to do anything much.
Take as much time as you like, no worries.
Looking forward to seeing the updated models
Cheers,
Brian

 

[Buck Rogers]

Good news, after mirroring it on 2 axis and cancelling out the offsets (I don't have the orig. files so I have to import) it fits back in place. Had to go through the whole mesh but could also fix some bad geom. and normals, and UV map everything. I've corrected and added shadows so it hopefully looks a bit more polished.

@BrianJ So the old .cfg is still good to go, this has been a bit of a slow burner anyway and there's still a lot to do so no rush. I'll try to set up DOI and EI .scn files next.

Mesh and tex. update attached.

 

[Buck Rogers]

Small update: BrianJ pointed out some major errors with the model and so there has been a partial rework, changes and lots of corrections. BrianJ has also provided invaluable input and brought the project far beyond my expectations.
Next year is the 50th anniversary of the Viking landing and this August 20th the launch of Viking1. Hope to have a release up soon!

 

[BrianJ]

During the course of getting the lander to land properly, we discovered there was quite a discrepancy between the historical landing site altitudes (both below Mars "sea level" ) using the default Orbiter2016 Mars elevation or using the Mars Hi-Res elevation available from orbit.medphys.ucl.ac.uk .

The landing sites are much further below 0 alt. when using Mars Hi-res elevation than they are with the default elevation.

I think I got a handle on why this is so.

I'm leaving a copy of my message to @Buck Rogers here as it may be useful for others using the Mars Hi-res elevation.

I think the difference between the default Mars terrain and hi-res terrain is down to Mars oblateness.

Default elevation data is "elevation relative to Mars geoid(oblate)" and applied to perfectly spherical Mars. So Orbiter2016 default Mars is not oblate but the surface features have the correct elevation relative to Orbiter2016 Mars surface (spherical).

Hi-res elevation data is "elevation relative to a perfect sphere" and applied to perfectly spherical Mars. So Orbiter2016 hi-res Mars IS oblate but the surface features have the "wrong" elevation relative to Orbiter2016 Mars surface (spherical).

Actually its not "wrong" - its just that Orbiter altitude is always measured from the mean radius. And the atmosphere properties (and rendering) are relative to a perfect sphere, so they are out of whack with the hi-res elevation.

In a nutshell: the hi-res elevation is more correct (you get an oblate Mars) but the MFDs, atmosphere properties and rendering get thrown out of whack because they are all relative to a perfect sphere.

Evidence:

landing site             latitude           alt.error (Orbiter MFD/HUD readout) with Hi-Res elev.

Phoenix                   68    15.61km
Viking2                   48    9.98km
Viking1                   23    4.02km
Insight                   4     0.31km

I predict an error of 20km at the poles, and 0 at the equator.

Cheers,
Brian

 

[Buck Rogers]

It's release Tues/Sat/Whatever-day!
Big shout out to BrianJ who made this possible
To all real-time flight fans the 50th anniversary launch of the Viking 1 is next Wednesday on the 20 August.