Youtube tutorial that I can't find for the life of me!

[JDCollie]

Hey all, I'm trying to find a Youtube tutorial about calculating delta V using a circular graph thingy by hand. It was very in depth, and discussed how to estimate delta v for various orbital using this graph-ruler-thingy, but I can't remember the name, and it isn't in my view history. Can anyone help me out finding this?

( I know it wasn't Scott Manley or Bob Fitch, just so you know)

[WanderingKid]

You'll have to be a bit more specific then "Circular Graph Thingy", I fear. dV is usually simply calculated via the full and dry mass of your ship, Isp, and a gravity constant (9.82 for Kerbin). Is it a way to calculate dV required going to particular orbital heights or something like that?

[Epthelyn]

This thing?

Not sure that's exactly what you want, but it fits the "circular graph" description, sort of.

[Musil]

, and a gravity constant (9.82 for Kerbin).

Are you sure? I am not an expert, as some people here, but I think the gravity constant is only relevant for TWR.

[Deutherius]

Are you sure? I am not an expert, as some people here, but I think the gravity constant is only relevant for TWR.

It's necessary to calculate exhaust velocity V_e, which in turn is needed for the calculation of dV.

The equation for dV is:

dV = V_e * ln(M_f/M_e)

We are not given the exhaust velocity V_e in KSP, but we do know the I_sp, which can be converted into V_e by this equation:

V_e = I_sp * g₀

Quite relevant.

[SmashingKirby148]

This thing?

http://deltavmap.com/

[Red Iron Crown]

I bet the "circular graph thingy" is a circular slide rule.

[Musil]

Ah, good to know.

[Deutherius]

This thing?

http://deltavmap.com/

Is it just me, or does that calculator make little sense? The individual node numbers seem reasonable, but the final number it gives after selecting a celestial body is ludicrously overblown. For example, why would it take 10km/s dV to just land on Minmus? At worst that's 5 km/s to orbit, 1 km/s to transfer, 1 km/s to circularise and land = 7 km/s dV.

On topic: I tried my best google-fu, but alas, to no avail. Sorry OP.

[nekogod]

Is it just me, or does that calculator make little sense? The individual node numbers seem reasonable, but the final number it gives after selecting a celestial body is ludicrously overblown. For example, why would it take 10km/s dV to just land on Minmus? At worst that's 5 km/s to orbit, 1 km/s to transfer, 1 km/s to circularise and land = 7 km/s dV.

On topic: I tried my best google-fu, but alas, to no avail. Sorry OP.

It just doubles the one way trip to get the round trip number, which is clearly wrong, there are better deltav tools out there

[Red Iron Crown]

It just doubles the one way trip to get the round trip number, which is clearly wrong, there are better deltav tools out there

Doubling the number to get the round trip is correct if you ignore aerobraking (though counting 4500m/s for landing on Kerbin makes that highly questionable). I think there is something odd with the tool, when I tried it on Chrome earlier it was saying 10km/s to get to Minmus one-way, but trying again now in Firefox it gives 5740m/s, which is more or less correct. Odd.

[Starhawk]

Doubling the number to get the round trip is correct if you ignore aerobraking (though counting 4500m/s for landing on Kerbin makes that highly questionable). I think there is something odd with the tool, when I tried it on Chrome earlier it was saying 10km/s to get to Minmus one-way, but trying again now in Firefox it gives 5740m/s, which is more or less correct. Odd.

That's strange, it just gave me 6140 for Minmus one-way.

The first time I tried to use it, I clicked on Kerbin and then on Minmus and it showed 10000.

Happy landings!

edit: There's a glitch in the tool. It doesn't seem to reset when a new target is clicked, and the number is invalid. If you reload the page and then click on a target, it seems to work properly.

Edited April 4, 2015 by Starhawk

[JDCollie]

Thanks for the replies, guys. Sorry I wasn't more specific

I don't think the graph in question was a slide rule per se, though it was similar. This graph was circular like a slide rule, but had lines drawn out from the center, with regular tick marks for values on them. The version the youtuber I'm trying to find was using was intended to be written on, and was used to easily estimate the delta v necessary for things like inclination changes. I'm also fairly sure the graph tool thingy was named after someone, and not just a generic name like circular slide rule.

I wish I could remember it better, but then again if I could, I probably wouldn't be hunting for the video

EDIT:

I FOUND IT!!!

It's called a Maneuvering Board, and the Youtuber is PurpleTargets.

Edited April 5, 2015 by JDCollie