Problems with Atlas V

[mbartley]

I think part of the problem is that Astronautix.com doesn't factor in the throttle-down towards the end of the first stage burn. I crunched some numbers, and I came up with an actual burn time for the first stage of 227 seconds. That might help you get more accurate results.

I'll try it.

Given complications like aerodynamic drag, air pressure reducing the thrust and/or (?) ISP of the engines, and throttling for Max-Q limiting and G limiting, it seems unlikely that the 1st stage can be accurate. However I'd think the 2nd stage should be able to get very close, since only G limiting would apply, to normal flight profiles anyways.

 

[clive bradbury]

The problem I have with realistic Atlas V is more fundamental. For some reason I cannot launch a saved scenario. Whilst I can run a supplied scenario with no problem, if I save it with a different name, or even close orbiter and re-load the 'current state' scenario and it crashes.

Does anyone know hwy this might be?

 

[Jrquinlisk]

The problem I have with realistic Atlas V is more fundamental. For some reason I cannot launch a saved scenario. Whilst I can run a supplied scenario with no problem, if I save it with a different name, or even close orbiter and re-load the 'current state' scenario and it crashes.

Does anyone know hwy this might be?

I think it's a bug with multistage.dll. Open the .scn files in your favorite text editor, and wherever it says

:multistage/multistage

change it to

:multistage/multistage[B]2[/B]

That should solve your problems with saving.

I'll try it.

Given complications like aerodynamic drag, air pressure reducing the thrust and/or (?) ISP of the engines, and throttling for Max-Q limiting and G limiting, it seems unlikely that the 1st stage can be accurate. However I'd think the 2nd stage should be able to get very close, since only G limiting would apply, to normal flight profiles anyways.

Actually, I used some equation involving mass flow, specific impulse, and some other stuff. I found it on Wikipedia, if memory serves.

 

[mbartley]

Actually, I used some equation involving mass flow, specific impulse, and some other stuff. I found it on Wikipedia, if memory serves.

Referring to the mission planners guide at Lockheed's www page
http://www.lockheedmartin.com/ssc/commercial_launch_services/MissionPlannersGuide.html

Specifically this file:
http://www.lockheedmartin.com/data/assets/14161.pdf
(Warning: 33 megabyte PDF)

On page 51 (AKA 2-19) there is a graph showing the thrust percentage vs time during 1st stage for a typical Atlas V 401 launch. It should be possible to estimate from that how long the burn would be if it was all at 100%. I wonder if that would match the way you estimated it.