dV Needed to land on Minmus?

[Evenger14]

I'm building a rover that will be put into a very low (Less than 10KM) orbit around Minmus via an orbital assist stage, which will then do the retrograde burn before separating off. The rover will then fire it's Rockomax 48-7S and land under it's own power. How much dV will I need to just land, that is ONLY landing, not the retro burn or taking off.

[cantab]

http://wiki.kerbalspaceprogram.com/wiki/File:KerbinDeltaVMap.png

The figures there tend to be best case scenarios without gravity assists, so add a bit of a margin for targeting higher, inclined, or retrograde orbits.

The big factor though is that the delta-v splitting between the deorbit burn and the landing burn is largely up to you. Most efficient overall is a small deorbit burn, a descent that goes halfway round Minmus, then a big landing burn to kill the horizontal speed. But also perfectly viable is a big deorbit burn and a near-vertical descent, then a smaller landing burn to kill the vertical speed. In that case, you need about 100 m/s of dV if you fall from 10km up. (I assumed constant gravity, so that'll be a slight overestimate, but then you want a safety margin anyway).

Edit: Something I noticed on safety margins. Delta-v maps give about 3.2 to 3.4 km/s needed to go from (real world) lunar orbit to the Moon's surface and back. The Apollo LM had 4.7 km/s, around 40% extra. And remember that Neil landed with less than 30 seconds worth of fuel left on board Apollo 11. Now, while many of us aren't so bothered about killing or stranding our Kerbals, if you don't want trial-and-error gameplay don't cut your dV margins too thin.

Edited March 14, 2014 by cantab

[Superfluous J]

Your problem will not be bringing enough fuel, it'll be bringing too much.

Oh, and your rover flipping over because it'll weigh as much as a piece of paper on Kerbin would.

[helaeon]

Minmus is suuuupper forgiving. I wonder if you could do the landing entirely with RCS (probably not... but maybe... if you can it would be awesome and that's the Kerbal way)... then use those same RCS ports for down-force and flip rover back over control when necessary.

[cantab]

You probably could. The RCS thrusters have a TWR of 40:1 in Minmus's gravity. The only real gotcha is not having smooth throttle control, but since low-gravity worlds are forgiving you can probably get away with it.

[Superfluous J]

I got a Kerbal to a pinpoint landing at a Kethane base way up near the North Pole of Minmus, from a 25km equatorial orbit, using nothing but his jet pack. I'm pretty sure you can land almost anything on Minmus without too much trouble

[SRV Ron]

Minmus is suuuupper forgiving. I wonder if you could do the landing entirely with RCS (probably not... but maybe... if you can it would be awesome and that's the Kerbal way)... then use those same RCS ports for down-force and flip rover back over control when necessary.

Landing probes using RCS is easy. Flipping back upright risky.

If the probe is light enough, a Mun landing is also possible. (Version 0.21)

[vidboi]

I'm building a rover that will be put into a very low (Less than 10KM) orbit around Minmus via an orbital assist stage, which will then do the retrograde burn before separating off. The rover will then fire it's Rockomax 48-7S and land under it's own power. How much dV will I need to just land, that is ONLY landing, not the retro burn or taking off.

From a 10km orbit, landing in Minmus takes an absolute minimum of 184m/s. This is of course an ideal case, so I'd take atleast 250m/s to give a reasonable margin.

[pauix]

From a 10km orbit, landing in Minmus takes an absolute minimum of 184m/s. This is of course an ideal case, so I'd take atleast 250m/s to give a reasonable margin.

So, assuming an EVA pack has around 500m/s of Delta-V, does this mean I can deorbit from a 10km orbit, plant a flag and go up again in EVA mode? I'm gonna try it as soon as I get home.

[wasmic]

So, assuming an EVA pack has around 500m/s of Delta-V, does this mean I can deorbit from a 10km orbit, plant a flag and go up again in EVA mode? I'm gonna try it as soon as I get home.

If you land on a mountain, yes. If you land on the plains, I'm not sure. Maybe.

[Superfluous J]

If you land on a mountain, yes. If you land on the plains, I'm not sure. Maybe.

You don't even need to do that. You can quite easily do it for any equatorial location on the planet. I am not 100% positive but you may even be able to reach the poles from an equatorial orbit and then get back to that equatorial orbit.

Would make for an interesting (and profitable) first or second career mode mission

[pauix]

Would make for an interesting (and profitable) first or second career mode mission

If my kerbals agree to do it, I'll try it on my next career. Right now, they are growing suspicious about the whole "for SCIENCE!" thingy:

[cantab]

So, assuming an EVA pack has around 500m/s of Delta-V, does this mean I can deorbit from a 10km orbit, plant a flag and go up again in EVA mode? I'm gonna try it as soon as I get home.

Absolutely. Limited instruments makes it a bit more challenging (no altimeter or speedo, but you can hit M for the map view).

I see from your ribbons you already did it. Hopefully you remembered a surface sample!

[pauix]

I see from your ribbons you already did it. Hopefully you remembered a surface sample!

I did indeed take a sample (I was in sandbox, but hey, it's SCIENCE! ), but I messed up the rendez-vous and there's a 70º angle between Kirrim's orbit and his spacecraft's orbit, so I can't send the data back. Once I rescue him and the samples, I'll probably be prepared to attempt a trip to Duna and an "Ikewalk"

[Kryxal]

Minimus, where "take a running start" might actually be a viable way to reach orbit...