Delta II Mission mod. (Phoenix)

[Kemo]

It now seems impossible to nail Mars in the phoenix scenario. I followed the read-me that was in the mod and no matter how spot on I am, The Delta-V is off the chart! (250m just after earth departure burn!?). :huh:

PS: The Delta II autopilot in the original phoenix add-on was fine. I don't know why Brian decided to add a parking orbit AP in the second stage but I can easily get myself accustomed to it.

Other than that, this mod has even more eye candy than the original. :lol:

 

[BrianJ]

Hi Kemo,
I just had another go at launching Phoenix using the Delta II Mission Mod.
I ended up only 4.19m/s off the required dV (PeA at Mars 196.6M), using IMFD5.1m.

As per the readme, from parking-orbit set up the burn using IMFD "Target Intercept" and "Orbit Eject" programs.

Start the 2nd stage ~250s before the IMFD nominal burn time. Over-burn the 2nd stage by 20m/s so the remaining dV for the 3rd stage burn is 3319m/s.

You should still have about 50s left until the IMFD nominal burn time.

Advance (increase) the IMFD nominal burn time (you'll see the required dV for the burn increase) until the required dV is 3334m/s.

The IMFD nominal burn time should now be about 120s away.

You can hit the IMFD "Orbit Eject" AutoBurn [AB] button to keep the 2nd stage pointing accurately.

At 100s before IMFD nominal burn time, spin-up and jettison the 3rd stage. At exactly 50s before IMFD nominal burn time - light up the 3rd stage!

That's about all I can say - works for me

P.S. The reason I put the auto-pilot in the 2nd stage is that, since the 2nd stage has it's own .dll it is no longer controlled by the multistage2.dll and thus cannot use the multistage2.dll auto-pilot function.

Hope this helps your Phoenix launch - good luck!

BrianJ

 

[Kemo]

Thanks for the help, but these directions are quite a handful to remember. I'm the type of guy who's not that hot when it comes to following complex instruction to precise timing/orienting for burn. Is there a way to make more use of the IMFD?

 

[BrianJ]

Is there a way to make more use of the IMFD

Not that I can think of.

Since the 3rd stage has no attitude control and will burn until fuel is finished, you can't set up the burn in IMFD while in parking orbit and just hit the AutoBurn button - IMFD will try to throttle down the 3rd stage when you've acheived the desired dV but will have no effect - the engine will just keep burning regardless.

So, the idea is to use the 2nd stage to set up the orbit so that the dV that IMFD requires for the final burn of the 3rd stage is equal to the dV available from the 3rd stage (you can see the available dV of the 3rd stage displayed on the HUD of the 2nd stage).

Well, I don't know if that makes things any clearer for you!

Launching this way is more challenging than just setting up the burn in IMFD and hitting AutoBurn, but a bit more realistic for the DeltaII. And you do have to know your way around IMFD "Target Intercept" / "Orbit Eject" / "Burn Vector" view.

Why not just print out the instructions above and tick 'em off as you go?

All the best,
Brian

 

[flying coffin]

Hey Brian!

Thanks for these instructions. I now also can do an accurate 3rd stage burn.
I think the part I was missing before was

"Advance (increase) the IMFD nominal burn time (you'll see the required dV for the burn increase) until the required dV is 3334m/s."

Now it all makes sense and works great. I did the real launch with the un-modded version so I wouldn't have to cheat and add fuel with the scenario editor. Once again you have taught me something important.

Thanks again

-Chris

 

[Kemo]

Mission success! It all payed off but I wished it was somewhat easier. I really don't want to resort back to the original delta mission, gotta love the spin stage.

Thanks, Brian!

Would love to see improvements, updates, and other addons from you!

 

[BrianJ]

Well done, guys

It all payed off but I wished it was somewhat easier.

"We do not do these things because they are easy...."

All the best,
Brian