OHM Delta IV Launch Vehicles 3.0

[virii2k]

I can confirm that is a bug and will be addressed in a patch.

 

[kuddel]

Hello Thomas,

very nice addon! :thumbup:

Only some very minor things that I've noticed so far:

1. Can you possibly increase the drag-coefficient of the 2nd stage a bit?
   When I deorbit that stage it almost doesn't loose any speed in the lower atmosphere (comes in on the ground veeeery fast )
2. Whenever I press the 'J' key (in Orbit) another payload is released.
   This happens at least with the sat-payloads. I haven't tried DG or any other payload. I think one is enough

Don't take this as critics, just as notices to some minor scratches.
I am very impressed by this addon! It's well done, it's complete, it works and it really looks nice! :tiphat:

Best regards,
Kuddel

 

[blixel]

This looks like an amazing add-on.

One quick question though, in the Delta IV Heavy DG scenario, how do you retract the DG's landing gear before launch?

http://i.imgur.com/aS6SB.jpg

 

[virii2k]

Hello Thomas,

very nice addon! :thumbup:

Only some very minor things that I've noticed so far:

1. Can you possibly increase the drag-coefficient of the 2nd stage a bit?
   When I deorbit that stage it almost doesn't loose any speed in the lower atmosphere (comes in on the ground veeeery fast )
2. Whenever I press the 'J' key (in Orbit) another payload is released.
   This happens at least with the sat-payloads. I haven't tried DG or any other payload. I think one is enough

Don't take this as critics, just as notices to some minor scratches.
I am very impressed by this addon! It's well done, it's complete, it works and it really looks nice! :tiphat:

Best regards,
Kuddel

1. Ill check into it. I never really de-orbited the 2nd stage so I,ll try to fix it.
2. Multi payloads? I thought I was going to save that for a future release LOL. I will fix that too :thumbup:



Ive been working on a fix for the dg landing gear deployed at launch, after It gets to the second stage, it crashes so , Ill keep working on that.

 

[MickeyMouse]

Can you use Spacecraft payloads with this?

 

[IronRain]

If you mean spacecraft3 based spacecrafts, yes. But you should first create a config file (*.cfg) in the 'config\vessels' folder for it.

 

[MickeyMouse]

Thanks, I'll give that try.

 

[virii2k]

Ive been trying to get spacecraft3 based vessels to work but it dosent seem to work.
Ive been trying to launch this
[ame="http://www.orbithangar.com/searchid.php?ID=5517"]Deep Space Communications Satellite (DSCS) v0.2[/ame]
But after deploying the payload, its not showing a mesh.

I Havent messed with spacecraft3 much but I dont see why it wouldnt work.
If its confirmed not working, I will try to add compatibility.

 

[boogabooga]

IronRain is right.
Spacecraft3 vessels work fine, if you make a config. See post 11 here:
http://www.orbiter-forum.com/showthread.php?t=26037&highlight=WGS

 

[ggrof]

I´ve tried to make a new .cfg file in the folder config/vessels, but doesn´t work anyway. I´m trying to put a chapman probe in a Delta 4 heavy through the payload configurator after pressing M

 

[Jitar]

This is a Wonderful Addition to my Orbiter Fleet ... GOOD JOB!

I did encounter one small problem though, is that when using these Delta's on my own Launch Pad (or any other) the rocket hangs in the air by about 10 meters. I would like to suggest an option to adjust the position of the rocket on the pad. (One of the other rockets has a PADBIAS option where you specify the offset in meters, or perhaps simpler just 0 the rocket when the DISABLE_BASE_ANIMATION option is specified.)

 

[virii2k]

This is a Wonderful Addition to my Orbiter Fleet ... GOOD JOB!

I did encounter one small problem though, is that when using these Delta's on my own Launch Pad (or any other) the rocket hangs in the air by about 10 meters. I would like to suggest an option to adjust the position of the rocket on the pad. (One of the other rockets has a PADBIAS option where you specify the offset in meters, or perhaps simpler just 0 the rocket when the DISABLE_BASE_ANIMATION option is specified.)

The option to offset the vessels Z position on the pad will be added to the
next release.

 

[Jarod]

Hi Virii2k, thanks for your add-ons, I see you acknowledged several remarks done by people, but you didn't say anything about post #7, http://www.orbiter-forum.com/showthread.php?p=330154&postcount=7
Can you tell if this is something you'll fix too ? Thanks.

 

[virii2k]

Hi Virii2k, thanks for your add-ons, I see you acknowledged several remarks done by people, but you didn't say anything about post #7, http://www.orbiter-forum.com/showthread.php?p=330154&postcount=7
Can you tell if this is something you'll fix too ? Thanks.

I am looking into the idea of holding the prograde direction after a short while. The problem is the autopilot is based on calculations from
http://www.orbiterwiki.org/wiki/Launch_Azimuth.

With some calculations to take in account the earths rotation.

Not holding the heading until seco puts the vessel off course.
Im guessing it would put the vessel in the correct orbital plane but the wrong
inclination.
Copying the orbital elements of another vessel and ending up in the same inclination and orbital plane is the ultimate goal.
I am always trying to improve on the autopilot as it is one of my favorite features of this addon.

 

[boogabooga]

Uhhh...
O.K one of us is confused.

Here is the way I understand it.
The equation Wikipedia gives is for instantaneous launch azimuth. If you use that plus take into account the Earth's rotation, then with a decent assumption about final orbital velocity you should get fairly close to the correct inclination.

Except for launches due east or west from the equator, as you head downrange, your latitude is constantly changing. So if you are holding your original launch heading, then you will be at the wrong heading for the latitude you are at at any given instant. This is an error that will keep adding up as your head downrange and you latitude differs more and more from the launch latitude. You burn more and more out of your launch plane. I don't understand how this error could be smaller than launching at the proper azimuth and holding prograde, unless there is a problem accounting for the earth's rotation.

Take the extreme example. A launch due north from Alaska for a 90 degree inclination. During launch, you start heading about 0 degrees north (actually a bit west of that due to the earth's rotation) . At some point you cross the north pole. You are now heading about 180 degrees south. That's natural. But if you are holding your launch heading, would you turn back to 0 degrees north? No, because then you would be flying loops over the north pole until you run out of fuel.

Perhaps the code could keep checking your current latitude and keep updating your heading according to your equations?

I don't understand how a vessel can be in the correct orbital plane but the wrong inclination unless it is heading in exactly the opposite direction as it should be.

As a side note,

Delta IV mediums from Cape Canaveral are more likely than not launching something to geostationary transfer orbit instead of just LEO. In those cases, since the inclination has to be reduced, they sometimes do launch eastward and the second stage burns out of plane. If you watch launch coverage with the STK animations, you can see the inclination drops when the second stage lights and goes below 28.5 degrees by seco. In that sense, the autopilot is pretty much correct

 

[virii2k]

Uhhh...
O.K one of us is confused.

LOL. Im gonna guess its me.:facepalm:

So your suggesting recalculate heading every once in a while?
Ive tryed so many ways of reaching the desired inclination and what I have now seems to work but, try launching to the ISS. You will get the same inclination but the orbital plane is off. I still don't fully understand the relationship between inclination and orbital plane.
What the launch azmuth code dosen't take into account is
thrust, vessel weight, and payload weight. This was fixed by small changes in the heading due to the fact that a lighter payload will reach the desired inclination a little earlier. If you launch different versions of the Delta IV at the same desired inclination, you will see they have slightly different headings.
The autopilot has definatley been the most challenging part of this addon
and any suggestions on its improvement are much appreciated.:thumbup:
What I need to look for is a good tutorial on direct assent to the ISS and figure out where the autopilot is going wrong.

---------- Post added at 02:51 AM ---------- Previous post was at 02:50 AM ----------

Also from what I understood, was the launch azmuth is the heading you need to hold.

 

[boogabooga]

[ame="http://en.wikipedia.org/wiki/Orbital_elements"]Orbital elements - Wikipedia, the free encyclopedia[/ame]

There is inclination, and longitude of the ascending node (LAN). Both together constitute the "orbital plane." Longitude of the ascending node, in an equatorial frame is where you cross the equator going toward the northern hemisphere. "Longitude" here refers to a direction relative to fixed stars, not geographic longitude.

To intercept, say, ISS, you match inclination by launching to the correct heading (as in the equations you provided). You match LAN by waiting for the correct time (the so called launch window) when the earth will rotate you to directly under the orbital plane of the ISS.

You should only need to worry about inclination. We have LaunchMFD, TransX, etc. to find launch windows, and get LAN correct. The azimuth should not depend on thrust to weight so much. I bet your lighter payload vehicles were doing better at getting the inclination right simply because they accelerate to orbital velocity faster, and weren't wrong as long.

I believe launch azimuth is instantaneous for you launch latitude, and not held through launch.

Have you tried to look at other rockets with autopilot in Orbiter to see how they behave?

 

[Jarod]

Check SpaceX or Soyouz autopilot, they're quite good, there is still some weird behavior in pitch for SpaceX at the end or in yaw and pitch for Soyouz but they're doing the job for the inclinaison, well at least for the cases I tried.

 

[virii2k]

Payload weight and thrust do have an impact on the launch azmuth.
The launch azmuth can be off by as much as 0.1 degrees per 1000kg of payload weight.
The auto pilot makes minor adjustments to the launch azmuth depending on the payload weight. If you launch the Delta IV Heavy with an 8000kg payload then again with a
13000kg payload you will see that they launch with a different heading.

---------- Post added at 06:41 PM ---------- Previous post was at 06:27 PM ----------

The SpaceX vehicles autopilot states it was created for a payload mass close to maximum. I am going to check other autopilots and see how they work.

 

[virii2k]

Yes the coodinates are in the equatorial frame.
When in the orbit mfd for the ISS click the FRM button on the left.