Project CST-100

[N_Molson]

I tried 270, it didn't work. Not a big surprise though.

If it works in the 0-180° range, it's OK. There's no point in launching a manned mission in a retrograde orbit.

 

[Urwumpe]

I tried 270, it didn't work. Not a big surprise though.

If it works in the 0-180° range, it's OK. There's no point in launching a manned mission in a retrograde orbit.

Yeah, you need special initialization in your code for handling the other half of the azimuths.

 

[N_Molson]

Works correctly in the 15°-90° range, but not in the 90°-165°'s. Trying to fix that.

 

[N_Molson]

Atlas-412 alpha v0.24

It wasn't easy, but I got it ! Now we have a much more robust first stage guidance program. It should handle all headings from 0° to 180° with accuracy, so you can launch northwards or southwards.

Still works the same : you enter the heading you want in the scenario file, and the program flies the rocket for you.

 

[N_Molson]

Atlas-412 alpha v0.25

Since everything seems to run well, let's go for the v0.25.

New Features :

- Another scenario file included (with settings for a near-polar orbit).
- Guidance Program Trajectory Control Settings (GPTCS as would write NASA ). More values can be entered through the scenario file to adjust the rocket ascent trajectory (first and second stages). See description below, pasted from the Readme included in the package (Doc folder) :

FIRST STAGE TRAJECTORY CONTROL
-----------------------------------

- You can affect the ascent trajectory of the first stage by entering pitch targets through the scenario file.
- There are 5 pitch targets, and those are bound to the following values (in seconds) : 25, 40, 80, 120, 160. As an example :

LC-41:Atlas412_launchpad
  STATUS Landed Earth
  POS -80.582845 28.583361
  HEADING 90.00
  AFCMODE 7
  PRPLEVEL 0:1.000000 1:1.000000
  AZIMUTH 5          
  GUIDANCE 87.2 80 56 22 10         <--- That line : "GUIDANCE a b c d e" ; where a,b,c,d,e are the pitch targets in degrees. 
  NAVFREQ 0 0                            (decimals accepted).
  XPDR 0
END

- So here 25 seconds after liftoff, pitch is set to 87.2° ; 40 sec. after liftoff, to 80° etc...

SECOND STAGE TRAJECTORY CONTROL
-------------------------------------

- The second stage guidance program works in a different way, and is more focused on "altitude keeping".
- Again we have a serie of 5 numbers, but their effect is a little more subtle :

Atlas-412-Stg2:Atlas412_stg2
  STATUS Landed Earth
  POS -80.582845 28.583361
  HEADING 90.00
  ATTACHED 0:0, Atlas-412-Stg1
  AFCMODE 7
  PRPLEVEL 0:1.000000 1:1.000000
  AZIMUTH 5
  GUIDANCE 0 25 350 200000 40       <--- That line : "GUIDANCE a b c d e" (see below for description). Decimals allowed.
  NAVFREQ 0 0
  XPDR 0
END

- "a" : Minimum Pitch (degrees). It is the lowest pitch that the program is allowed to hold. Here 0°. Can be negative.
- "b" : Maximum Pitch (degrees). It is the highest pitch that the program is allowed to hold in normal circumstances. Here 25°. Can be negative.
- "c" : Delay. Value in seconds after liftoff, before which the guidance program will only hold Maximum Pitch.
- "d" : Floor Altitude (meters). If the second stage gets under this altitude (after "c"), it triggers the "contingency mode".
- "e" : Contingency Pitch Value (degrees). A high pitch value used to bleed negative vertical velocity, if the second stage gets too low.


So try to play with those which should give you quite a lot of possibilities. :tiphat:

 

[Mattyv]

This might be a bit unrelated, but are you planning on making other versions of the Atlas V?

 

[N_Molson]

AtlasV-412 alpha v0.26

This might be a bit unrelated, but are you planning on making other versions of the Atlas V?

Yes :yes:. While the first objective is to simulate the Atlas-412, when that one will be done, it will be possible to add/remove boosters and have the Centaur-SE, with 4 meters and 5 meters adapters for payloads. It's a matter of modeling a few more meshes and adjust the guidance settings, nothing very hard. Not sure about AtlasV-Heavy, will do if I get enough time.

---------- Post added at 09:44 PM ---------- Previous post was at 06:35 PM ----------

OK so another release with some little new features before I dig into the heavy stuff (Save/Load support).

New Features :

- Stage 2 PMI adjusted for more realistic behavior.
- Viewpoint of the launchpad adjusted to improve launch experience.
- SRM booster is deleted when it hits the ground (frees simulation resources).
- New camera settings, from the readme :

- Pressing "N" allows you to switch between forward and aft rocketcams when stage 1 or 2 is selected.

- You can preset the default camera through the config file :

Atlas-412-Stg2:Atlas412_stg2
  STATUS Landed Earth
  ... (all the other stuff)
  CAMERA 0              <------- That line : "CAMERA x", where x = 0 (aft camera) or x = 1 (forward camera).
  NAVFREQ 0 0
  XPDR 0
END

- There is a setting for the launchpad called "autofocus". It decides if yes or no the focus will be automatically switched
from the launchpad to the rocket on liftoff.

LC-41:Atlas412_launchpad
  STATUS Landed Earth
  ... (all the other stuff) 
  AUTOFOCUS 0         <------------- That line : "AUTOFOCUS x", where x = 0 (no autofocus) or x = 1 (autofocus activated).     
  NAVFREQ 0 0                            
  XPDR 0
END

 

[Capt_hensley]

We're closing in. With a few fixes, the dimensions will be fairly close from the original.

Looks Great!

 

[N_Molson]

AtlasV-412 - alpha v0.27

Here's the v0.27.

New Features :

- Now supports Save/Load (no more CTDs). Expect weird behavior from the stage 2 guidance, though, this is normal for the moment. Stage 1 guidance don't like to be Save/Loaded during initial roll (strange idea anyway), but will find it's way back after a few aerobatics.
- Centaur (stage 2) mesh enhanced (side umbilicals added).

A "VARS" line will be added in the scenario file after saving. You're not supposed to modify anything there (or expect CTD).

Thank you for testing this Save/Load thing in various conditions at various stages of the flight ; errors there can become nasty later. Feel free to report anything suspect, it helps. Reporting it works helps as well

 

[N_Molson]

Soon : launchpad spotlights :

 

[ky]

Ok, after quicksaving and loading at 108 seconds into the scenario (I launched at 37 seconds in), the MET clock restarted, and the booster didnt fall off for another 79 seconds after loading the scenario.

 

[N_Molson]

the MET clock restarted

The focus was set on the first stage ? If yes I think I see what it is.

 

[ky]

The focus was set on the first stage ? If yes I think I see what it is.

Yes, it was.

 

[N_Molson]

AtlasV-412 alpha v0.28

Right, here's the v0.28

New Features :

- Launchpad lights, can be toggled on/off with the "L" key (if focus set on the launchpad).
- A night launch scenario to enjoy those lights. Also notice how the mighty RD-180 illuminates a great area of KSC, creating an artificial sunrise for a minute or so.

Bugfixes :

- Save/Load now works for Stage 1 and Stage 2, the previous problems should be fixed (SRM separation, MET timer not working properly). Most critical point of that update.
- There was something wrong with the first stage mass that wasn't updated correctly after the SRM separation. Fixed ; as a result the rocket performance is slightly improved.


So thanks for watching closely the mission timer and the rocket mass at various stages of flight. Here's a recap of the elements of the rockets (Propellant Mass + Empty Mass, figures from Astronautix) :

CCB (Stage1) : 284,453 + 22,461 kg
SRM : 36,824 + 4,000 kg
Centaur (Stage2) : 20,799 + 2,026 kg
DemoCap : 10,000 kg
LES : not accounted for yet (anyway, the CST-100 has its own abort SRMs).

And as usual, thank you for any constructive feedback. This is quite an "open alpha" since the files are available on the forum, feel free to contribute :tiphat:

Edit : I've found this document which is a real mine of data on that rocket !

 

[ky]

Pad lights are not functional

 

[N_Molson]

AtlasV-412 alpha release v0.29

Here's another, they should work. Also the rocket will now throttle up 3 seconds before liftoff and reach a maximum of 99.1% thrust, as it is done IRL. Also there is now a throttle down to 60% several seconds before separation.

BTW, make sure you have "Local Light Sources" checked in the "Visual Effects" tab. (if you test on a clean install, that option is unchecked by default after installation).

 

[N_Molson]

There is one thing I need to know : what is the G limit set to the AtlasV manned version ? 4G ? 5G ? That way I'll be able to implement accurately a throttleback that will avoid to the astronauts to be compressed too much. :lol:

 

[ky]

It looks like 4.6 G is the maximum, according to this

 

[N_Molson]

It looks like 4.6 G is the maximum

Seems wrong, as the document I posted above, section 2-2 (by Lockheed Martin) says :

At the end of alpha-biased steering, closed-loop guidance steering is enabled. Near the end of the CCB phase, the RD-180 engine is continuously throttled so that a 5.5 ±0.5-g axial acceleration level is not exceeded.

http://spacecraft.ssl.umd.edu/design_lib/Atlas5.pl.guide.pdf

And 5.5g +/- 0.5g seems quite a lot for a "commercial" vehicle. I'm sure I've seen somewhere that they have decided with the advice of NASA a lower limit to keep into man-rating standards.

 

[ky]

Some progress on a VC

That is just the shell of the VC, it will fit inside the CST model, almost like this:

Another pic