Calculating DV is "hard"??

[arkie87]

Part list in xlsx format.

I don't have any of the massless parts included on the list, but I did update it to include all the wing parts (I had left them out before). I also don't have air-breathing Isps included, the calculations for those make my head hurt and vary greatly with both altitude and speed.

Edit: I did include one massless part, the O-10, because its needed for RCS powered designs.

Thank you muchly!

Maybe you want to work with GoSlash27 and put together a tutorial for making a spreadsheet? The compiled parts list is a huge help for those working to create their own spreadsheet.

Now I can replace "bananas" with actual LFO tanks

[LethalDose]

Part list in xlsx format.

I don't have any of the massless parts included on the list, but I did update it to include all the wing parts (I had left them out before). I also don't have air-breathing Isps included, the calculations for those make my head hurt and vary greatly with both altitude and speed.

Edit: I did include one massless part, the O-10, because its needed for RCS powered designs.

Well, hello... I this saves me a lot of data entry for my Mission record DB in Access. Have some rep, RIC.

[RuBisCO]

Ok I got a hard question: how would I go about calculated nozzle diameters and lengths to match a specific thrust and ISP, knowing only chamber pressure, throat temperature, gas chemistry and mass flow?

[Bill Phil]

Ok I got a hard question: how would I go about calculated nozzle diameters and lengths to match a specific thrust and ISP, knowing only chamber pressure, throat temperature, gas chemistry and mass flow?

Well, the ISP is dependent on thrust and mass-flow. So if you can find the thrust you should get a good estimate.

Btw, what about expansion ratio?

[WafflesToo]

This is exactly what I'd set out to get across (badly)

If the newbie is asking how to use the formula, don't say "it's really tricky, use a mod"

Likewise, if the newbie is asking how to use a mod, don't say "suck it up and learn the maths".

Thanks,

-Slashy

THANK YOU! I cannot count the number of times I've seen someone ask "how do I maths" and see them bombarded by links to mods, webpages, and tools, following being somewhat mistreated when they clarify that they want the maths, not the tools (doubly irksome if I'm interested in learning about the same maths).

To be honest, I don't really see the opposite happen all that often (though I'm sure it happens).

---

KER is an awesome tool that I use on a regular basis, but it is completely useless if I'm designing vehicles that are using RCS blocks for primary propulsion and it there are times it is WORSE than useless when docking ports get involved (very often presenting wildly incorrect results). It doesn't take long to get a back-of-a-napkin calculation to double-check the figure KER is giving me; especially since the stage mass KER returns is reliable.

Shame the stock game doesn't have in-editor mass and TWR readouts.

[RuBisCO]

Yeah well ISP also depends on expansion ratio

[GoSlash27]

THANK YOU! I cannot count the number of times I've seen someone ask "how do I maths" and see them bombarded by links to mods, webpages, and tools, following being somewhat mistreated when they clarify that they want the maths, not the tools (doubly irksome if I'm interested in learning about the same maths).

To be honest, I don't really see the opposite happen all that often (though I'm sure it happens).

---

KER is an awesome tool that I use on a regular basis, but it is completely useless if I'm designing vehicles that are using RCS blocks for primary propulsion and it there are times it is WORSE than useless when docking ports get involved (very often presenting wildly incorrect results). It doesn't take long to get a back-of-a-napkin calculation to double-check the figure KER is giving me; especially since the stage mass KER returns is reliable.

Shame the stock game doesn't have in-editor mass and TWR readouts.

I haven't seen it happen the second way, either... but that's not to say it doesn't. That first scenario happens all the time, tho'.

Thanks and have a splendid weekend,

-Slashy

[GoSlash27]

Ok I got a hard question: how would I go about calculated nozzle diameters and lengths to match a specific thrust and ISP, knowing only chamber pressure, throat temperature, gas chemistry and mass flow?

Hahaha well.. none of that stuff applies to KSP and certainly not anything going on in this thread. You might want to pose that in the Science Labs forum. I do recall that NASA has a pretty good tutorial and interactive Java applet on the subject, though.

http://www.grc.nasa.gov/WWW/k-12/airplane/nozzled.html

Good search terms to start with are "CD nozzle" "DeLaval nozzle" "Convergent Divergent Nozzle" and "ConDi nozzle".

I did some research on this subject a few months back on a subject completely unrelated to rockets, and there was lots of info out there.

Best,

-Slashy

Edited December 13, 2014 by GoSlash27

[LethalDose]

Shame the stock game doesn't have in-editor mass and TWR readouts.

WARNING! WARNING!! INCOMING SARCASM DETECTED!!!

ohhhh, you must be one of "those people" who like numbers. The dev's have decided that numbers aren't fun, didn't you get that memo?

But seriously, the devs have stated this repeatedly and, unless something has changed recently, reject the idea that Mass/TWR/dV information should be provided in the stock game.

Even though tons of people ask for it, and it could be turned off.

[Red Iron Crown]

Ok I got a hard question: how would I go about calculated nozzle diameters and lengths to match a specific thrust and ISP, knowing only chamber pressure, throat temperature, gas chemistry and mass flow?

I have found this site particularly useful for more advanced rocketry/spaceflight questions. I think this page in particular should be of interest to you, starting around equation 1.26.

[RuBisCO]

i have found this site particularly useful for more advanced rocketry/spaceflight questions. I think this page in particular should be of interest to you, starting around equation 1.26.

f5,f5,f5,f5,f5,f5!

[RocketBlam]

The long and short of it is, the last thing I want to be doing when designing a rocket is math. Maybe it doesn't take a whiz, but who cares? I don't want to do it! This app definitely needs some kind of way to easily calculate Delta-V, like MechJeb (without the autopilot) or Engineering Redux.