Kethane Scanning Calculation. I must be doing something wrong

[Sokar408]

You want a formula to calculate absolute optimal altitude?

Number of seconds the mun take to rotate once

divided by:

number of hexes across the munar surface along the equator.

that gives you the number of sec you want your orbit to take. (one orbit pr hex)

call that number (T)

Look up the muns GM (newtons gravitational constant x mass of the mun)

and look up the radius of the mun, referred to in the formula as ®

calculate: cuberoot((T²xGM)/4pi²) - r = your optimal scanning altitude.

If that's inside the mun (ie "-something"), simply double (T) in your formula and you're all good.

this will simply make you complete the surface scan in 2 munar "days".

(if the number of hexes across the surface is an even number,

instead of doubling it, multiply it by 1,5 or 3 to avoid scanning the same lines twice)

Place your craft in a perfect circular polar orbit at your calculated altitude and you shouldn't miss a single hex.

happy counting..

I have now plugged in all the values, and gotten an answer that just cant not be true. At "T*11250", which means after 11250 orbits, at 73.980,18 meters, with the assumption of 160 hexagons around the planet (Kerbin in this case), you'd have everything scanned on. This is the lowest amount orbits its can be done in, with the "set it up and let it run" mentality. That would take almost 3 solid REAL days at warp speed 1000 to complete (If you can even scan reliably going that fast). I must be doing something wrong.

This is the spreadsheet I use to calculate it. (red values are either constant or self calculating, grey is inputs and green is results)

http://www./download/1t5jn9xrh644mhq/KSP+Calculators.xlsx

Thanks in advance

[Spyritdragon]

I have no idea just what the optimal altitue is, or what you're doing wrong, but you are doing something wrong. I can scan the entire planet five times over with a turbojet craft in that time.

Why do you need these precise calculations, to be very honest? Can't you just... put it in a polar orbit and synch it so every N orbits you advance one line of hexagons? Im not sure just how fast Kerbin rotates at the altitudes you're scanning, but if you just make an orbit that passes over the same spot after the same amount of orbits as you have lines of hexagons going from North to South, you should scan them all.

[mhoram]

For the altitude calculation of ideal resonance-free orbits there is a thread:

http://forum.kerbalspaceprogram.com/threads/27999-ISA-Mapsat-Ideal-and-Non-Ideal-Altitudes

Initially it was intended for ISA Mapsat. Since the scan-angle for Kethane is smaller, the results may differ.

[Geschosskopf]

First off, it depends on what you want to use the Kethane for. Is it to make a refueling depot for ships in space, or is it only for surface use? Of course, Minmus is better than Mun for the depot thing, just saying.

Anyway, if the plan is to end up with rocket fuel in Munar orbit to refuel ships there, then doing a polar scanning orbit is a waste of time. You really don't care about any Kethane more than about 20^ off the equator because you waste so much fuel with the plane changes needed first to reach high-latitude sites, then back into equatorial where the fueling station is. So in this case, just put your satellite into about a 20^ inclination orbit and scan only the equatorial belt. Fly at a high enough orbit that you can do 100x warp and let it run. If you find yourself covering a lot of the same ground, tweak your orbit (or just 1 end of it) up or down a little.

You only need to do a polar scan if you seriously plan to use high-latitude Kethane, or have put the Kethane scanner on a terrain-mapping satellite which needs a polar orbit anyway. In this case, start with the ISA MapSat orbits linked by mhoram above. But because the Kethane scanner beam is so narrow (maybe changed in the newest version 0.8.1), you're forced into a choice. Do you want to have the job take the least amount of realtime or the least amount of gametime? Less realtime means it's less of a boring chore for you, but less gametime might be important in relation to other missions you have going on. The problem is, these work at cross-purposes; decreasing 1 increases the other.

The basic issue is that because the scanning beam is so narrow and doesn't vary with altitude, the amount of GAMEtime required to scan a planet is solely a function of orbital velocity. Thus, the lower you fly, the quicker the job gets done from the POV of Kerbals. HOWEVER, the lower you fly, the less you can warp, so the longer the job takes from YOUR POV. The best compromise I've found is to scan at an altitude where you can warp 100x, which is the limit for a single large scanner getting anything like decent coverage. Any lower and it's just WAY too much REALtime to do it. IIRC, you need to be about 60km up to warp 100x at Mun. So look at the ISA table and get in an orbit in the 60s or 70s and see if that works.

The alternative strategy is to get in a very high orbit where you can warp 1000x. The problem here, however, is that the large scanner drops from about 80% coverage at 100x to about 5% coverage at 1000x. This means you need like 8 scanners on the satellite, PLUS the electricity to run them all at once (4 RTGs each), so they can somewhat fill in each other's gaps. This makes for a rather hefty probe, but greatly reduces the time YOU have to spend watching it happen. However, years or even decades might pass in GAMEtime while you do this.