Bug Multistage2 bug

[Sky Captain]

I just discovered multistage2 vessels can take off from Venus with no thrust reduction due to atmospheric pressure. I checked if I had complex flight model enabled and it was on. I also put Deltaglider and XR2 on Venus and both were correctly affected by atmospheric pressure and unable to fly.

Why multistage2 vessels are unaffected by atmospheric pressure?

 

[liber]

I try X-71 on Venus and take off nicely. It could fly but is not config for Venus,so no reaching orbit but fly.

 

[Sky Captain]

I tried spacecraft3 based vessels and they also fly in dense Venus atmosphere with no thrust reduction. Now I`m guessing it`s something to do with how multistage2 and spacecraft3 are coded.

 

[liber]

I tried spacecraft3 based vessels and they also fly in dense Venus atmosphere with no thrust reduction. Now I`m guessing it`s something to do with how multistage2 and spacecraft3 are coded.

You could add more thrust in multistage configuration file.

Maybe double thrust:

[BOOSTER_1]
N=2
MeshName=""
Height=
Diameter=
EmptyMass=
FuelMass=
Thrust= double value
angle=
off=(0,0,0)
BurnTime=

[STAGE_1]
Height=
Diameter=
EmptyMass=
FuelMass=
Thrust= double value
BurnTime=
off=(0,0,0)
MeshName=""
ENG_1=(0,0,0)

 

[simcosmos]

I tried spacecraft3 based vessels and they also fly in dense Venus atmosphere with no thrust reduction. Now I`m guessing it`s something to do with how multistage2 and spacecraft3 are coded.

As far as I'm aware (writing this in a rush, please someone correct / complete as needed), the impact of atmospheric pressure on engine thrust / ISP is not implemented on currently available generic dlls although it seems that it was/is/could be a feature planned for a future eventual version (of multistage.dll):

http://orbiter.dansteph.com/forum/read.php?f=5&i=8323&t=7940

http://orbiter.dansteph.com/forum/read.php?f=5&i=7899&t=7632&page=3


Meanwhile, this might or not bring some impacts to addons, depending of what the developer wishes to simulate. Spacecraft.dll is usually used for stuff already in space; for launchers simulation there are some ways to work around the issue by using the supported [booster] thrust curve function, using and doing automatic guidance 'tweaks' (via thrust commands), assuming adjustments / margins to burnout masses or else assuming average values / highest pressure conditions for the engine specs (if stage / design using such engine is not intended to operate much beyond a given envelope)… but again, these are workarounds for very specific operational constraints


The other solutions would be:
a) wait for Vinka to eventually release new dll versions
b) use other tools (not sure but it seems that Velcro rockets support what you wish)
c) code dll



Hope this helped
(but again, someone feel free to correct)

António

 

[Sky Captain]

Now I tried velcro rocket and it seems to take into account thrust reduction because of atmospheric pressure. For multistage rockets I think it might be possible to roughly simulate thrust reduction by slightly reducing overall thrust of first stage.