Anyone interested in delta-v design helper

[docfish]

I threw together a script that calculates delta-v for an asparagus staged lifter (with ability to specify static mass of cargo to adjust for that). Seems to nearly perfectly line up with mechjeb, I'm debating cleaning it up enough for others to use but since it's a bit rough wanted to ask if anyone was interested before I did so. Screen shot of current interface: http://imgur.com/EGzCWzx

[Rhomphaia]

Yep, Should save me having to pull off engines and replace them with structural parts of the same mass on more complicated designs that throw mechjebs calculations off.

[Specialist290]

This looks like it could be useful. Keep us posted on how progress goes.

[docfish]

Short version is? When I should have been working on converting it from php to javascript and cleaning up other oddities (don't hate, I just didn't want to deal with browser anything, just raw calculations), I was scattering innocent rockets across the surface of Kerbin, and I'm too tired to get into it now.

Now for the long version: Ok I got a bit overzealous on my calculations, I noticed an inconsistency between my #s and mechjebs, deciding mine were most likely at fault, I traced it back to the weight of my struts & decouplers + a "magic number" that appeared to increment on mechjeb's side one per every stage. Likely a result of one of us rounding differently than the other, but I adjusted for the parts I could explain and figure the rest... 1 dV at sea level, even by 3 stages (when it was cumulatively 6) isn't worth figuring out. Of course then in my first full test where I set out to figure out what would be needed to throw a full orange tank into low orbit, I realized how little even the struts mattered to the real world... as my rocket that should have thrown 1 full tank up, actually threw up 1.5 tanks, plus skipper engine (dV was calculated for sea level, which I knew was going to be below worst case, but wow was it a long ways below worst case). Then it was followed by a series of ignoble failures with the exact same rocket that may have been related to the program crash at the end of the testing run.

I admit, I'd love to be able to scale the ISP for altitude between 1 atmosphere & vacuum, but well, then I'd have to know how the throttles will be set the entire time to scale thrust, oh and does ISP at the same pressure stay the same for different throttle settings? That's about when my brain revolted, crawled out my nose and slapped me hard for even considering simulating a game to play a game that is a simulation to that degree. If you look purely at 1 atm dV even to orbit, you'll do better than you need, if you look at the vacuum... maybe that number should be ignored unless you have a stage you know will be for later maneuvers.

[tavert]

oh and does ISP at the same pressure stay the same for different throttle settings?

Yes it does. Isp depends on atmospheric pressure but not throttle (in KSP anyway).

Pressure drops pretty quickly with altitude, it decreases by a factor of 2.718 every 5000 meters. So it takes less than 3500 meters to get halfway to vacuum efficiency, and by 15 km you're 95% of the way there.