Best way to slow down approaching surface of Minmus

[JackBush]

I've been trying to land on Minmus but the horizontal approach is causing me trouble. I consistently haven't enough fuel to spend on slowing down sufficiently (and still have enough left to get back home) and am wondering how others handle the approach.

[Red Iron Crown]

Get as low a periapsis as possible on your intercept (adjust this right after completing the transfer burn if necessary), then burn retrograde at that periapsis. There's not any more trick to it than that.

[Gojira1000]

I suspect your rocket just doesn't have enough delta-V. The obvious fix is more fuel or less weight. You'd have to post your rocket or dV totals, though, for specific advice.

[Tex_NL]

Minmus is one of the easiest bodies to land on. Low gravity so it won't take a big heavy lander to land but enough gravity to stay in control. Your approach might not be the issue, it could very well be the design of your craft.
Could you please post some pictures of your craft. Both on the launchpad and how it arrives at Minmus. If you have dV numbers to share with them even better.

Edit: Double ninja. [IMG]http://www.animaatjes.nl/smileys/smileys-en-emoticons/overig/ninja01.gif[/IMG][IMG]http://www.animaatjes.nl/smileys/smileys-en-emoticons/overig/ninja01.gif[/IMG] Edited November 18, 2015 by Tex_NL

[JedTech]

Wait really? Just aim retrograde and quickly and gently tap "Shift" followed by quickly punching the "x" key.
That always helps me stop and even go the reverse direction on Minmus.

[JackBush]

Okay, thanks. My DV is something in the 4300 total range (according to MJ).

[Nathair]

[quote name='JackBush']Okay, thanks. My DV is something in the 4300 total range (according to MJ).[/QUOTE]That [I]just[/I] won't do it. I wouldn't try for Minmus with less than 4500 and even then it would leave very, very little room for sloppiness.


Edit: Plus, you know, fuel for getting home might be nice.

[DeMatt]

On 11/18/2015, 1:14:19, JackBush said:

Okay, thanks. My DV is something in the 4300 total range (according to MJ).

Is that "on the launchpad" or "approaching Minmus"?

If the former, then you definitely need more fuel. A typical rocket launching to low Kerbin orbit (LKO) takes about 3500 m/s dV. That leaves you about 800 m/s to get to Minmus, land, and return. This dV map thinks you'll need more than that just to get to Minmus, so if you're actually able to touch down successfully, then you're doing fine on the piloting front, but need a bigger rocket.

If the latter... then you need to work on your piloting, instead. 4300 m/s dV, when entering Minmus's Sphere of Influence, is enough to let you bounce around Minmus like a ping-pong ball.

Either way, a screenshot of your rocket (in the VAB) will let us give you more pointers on design and pilotage.

Edited November 30, 2015 by DeMatt
New forum formatting.

[JackBush]

MJ says I have 4350 Delta V on the launchpad. Here's the ship:

[URL]http://imgur.com/UJTSr69[/URL]

[Snark]

Most efficient way to land on Minmus (or any vacuum body) is a suicide burn. A search on that term will turn up plenty of KSP tutorials.

That said... Minmus is very easy to land on, once you've achieved orbit; very little dV required to land and take off. Sounds like your main problem is not Minmus landing per se, but rather the overall dV for the whole mission. You just need more.

Be aware that as a last resort, if you've successfully landed and don't quite have enough fuel to go home, a Kerbal on EVA who's standing on the surface of Minmus can easily achieve Minmus orbit and even head home to Kerbin without a ship, using only EVA thrusters.

Previous to 1.0.5, that EVA kerbal could then re-enter Kerbin's atmosphere just fine (as long as Pe is set somewhere high, like around 45-50 km), fall out of the sky, and land unharmed. 1.0.5 made reentry heating tougher, though, so I don't know whether that's still the case (haven't tried it yet). I wouldn't be surprised if EVA kerbals can no longer reenter unharmed.

But even without reentry, the fact remains that a kerbal on EVA is packing 300+ m/s of dV, so you can use that to go home. You could always send up a rescue ship to intercept the kerbal as he/she approaches Kerbin.

[Nathair]

[quote name='JackBush']MJ says I have 4350 Delta V on the launchpad.[/QUOTE]The map linked to by DeMatt should illustrate the problem. It's suggesting 4670 to land on Minmus and then you'll want another 400(ish) to get off again.

[vixr]

[quote name='Snark']Most efficient way to land on Minmus (or any vacuum body) is a suicide burn. A search on that term will turn up plenty of KSP tutorials.

That said... Minmus is very easy to land on, once you've achieved orbit; very little dV required to land and take off. Sounds like your main problem is not Minmus landing per se, but rather the overall dV for the whole mission. You just need more.

Be aware that as a last resort, if you've successfully landed and don't quite have enough fuel to go home, a Kerbal on EVA who's standing on the surface of Minmus can easily achieve Minmus orbit and even head home to Kerbin without a ship, using only EVA thrusters.

Previous to 1.0.5, that EVA kerbal could then re-enter Kerbin's atmosphere just fine (as long as Pe is set somewhere high, like around 45-50 km), fall out of the sky, and land unharmed. 1.0.5 made reentry heating tougher, though, so I don't know whether that's still the case (haven't tried it yet). I wouldn't be surprised if EVA kerbals can no longer reenter unharmed.

But even without reentry, the fact remains that a kerbal on EVA is packing 300+ m/s of dV, so you can use that to go home. You could always send up a rescue ship to intercept the kerbal as he/she approaches Kerbin.[/QUOTE]

Jeb takes one last look at his stranded lander, fires up the MMU and flies home without it... That scene just makes me smile.

[eddiew]

The lander's very un-aerodynamic... not going to be helping your fuel efficiency during launch. Definitely want some nosecones on them, top and bottom ideally, so's not to have any exposed connection nodes.

But as others have said, it doesn't have the overall delta-v for the trip anyway. Could the lander's side pods be on decouplers, so you can dump them (and the legs) on the surface and return with just the lander core?

[Kerbart]

The question tells me you're fairly new to KSP
The design tells me you're playing career mode

My advice would be to start in Sandbox mode instead, and practice the [ ] out of KSP with building ships, orbiting them, docking, making transfers to Mun, Minmus, dock there, land there, maybe go even to Duna.

Career, in my eyes, is a challenge, not a way getting eased into the game. It's hard enough to master many of the required game basics in the first place; being hampered by a very limited choice of parts is not going to make it easier.

[Mastikator]

[quote name='JackBush']MJ says I have 4350 Delta V on the launchpad. Here's the ship:

[URL]http://imgur.com/UJTSr69[/URL][/QUOTE]

Bigger fuel tanks on the upper stage, replace the fl-100 with fl-200 should do the trick to be honest.
Also you don't need to jettison the heatshield, it has a higher crash tolerance than the science jr so you can safely land on it.
Alternatively you could put the heat shield on the pod directly. When you're done doing the experiments have the pilot go EVA, collect the science data (it will render the parts useless, but you'll get all the science).

[Captain H@dock]

[quote name='vixr']Jeb takes one last look at his stranded lander, fires up the MMU and flies home without it... That scene just makes me smile.[/QUOTE]
Except that in 1.0.5 Jeb now catches fire quite high in the atmosphere even after a suborbital hop. So I would say these days are gone (and rightly so). :wink:

[JackBush]

[quote name='Kerbart']The question tells me you're fairly new to KSP
The design tells me you're playing career mode[/QUOTE]

New but in Science mode. I'd like to stay there but I recognise I'm limited in parts. I still think I should be able to make it.

[eddiew]

[quote name='Captain H@dock']Except that in 1.0.5 Jeb now catches fire quite high in the atmosphere even after a suborbital hop. So I would say these days are gone (and rightly so). :wink:[/QUOTE]

Turn off heating and it's probably viable, especially with the new water... IIRC a naked kerbal falls pretty slowly :)

[COLOR="silver"][SIZE=1]- - - Updated - - -[/SIZE][/COLOR]

[quote name='JackBush']New but in Science mode. I'd like to stay there but I recognise I'm limited in parts. I still think I should be able to make it.[/QUOTE]

Yes, don't worry too much about it. The fact that you're getting into Kerbin orbit means you have the hardest part (rocket stability) of a Minmus craft sorted anyway :)

I'd suggest looking into staging - stage everything. The lander's side pods are a prime example; leave them on the surface, because the core tank is ample to get that payload home. Might actually give you the extra delta-v you need ^^

[Seajay]

Looking at your ship, you seem to have fuel lines for asparagus staging but your staging is onion. You should be able to get a couple of hundred more dv from that. Also fire your core engine (currently on stage 4) right from the beginning,that will give you more thrust on the ground so you can add more fuel to your upper stage while keeping your current twr.

[Geschosskopf]

[quote name='JackBush']I've been trying to land on Minmus but the horizontal approach is causing me trouble. I consistently haven't enough fuel to spend on slowing down sufficiently (and still have enough left to get back home) and am wondering how others handle the approach.[/QUOTE]

These are 2 separate problems: piloting and ship design. Ship design as in building enough fuel for the round trip into the thing, piloting as in being able to land safely. Landing on Minmus is technically easy and forgiving because the gravity is very low, and as a result even inefficient landing trajectories don't cost much fuel. Or at least, not enough to worry about if you've designed enough into the ship to make the round trip in the 1st place :).

As to actually landing on Minmus, at least to start with, the EASIEST (but far from the most efficient) way is to get into a circular orbit at about 15km. Your ship will be moving about 250m/s. As you start to pass over a nice, flat area, [b]make sure your navball is in surface mode, not orbit[/b] then burn full throttle retrograde until you kill off your horizontal velocity. You'll know when you've done that because the retrograde marker will be at the center of the blue end of the navball. And you can tweak it there by putting your nose on the opposite side of the retrograde marker from the center of the navball and burning a little. So now your ship is falling straight down. Rotate so its pointing straight up so it will hit on its feet and burn gently now and then to keep your speed between 30-50m/s. As you get close to the ground, burn a bit harder and more often to slow down to about 10m/s, then just above the ground burn some more to touch down as gently as possible. Welcome to Minmus.

As for getting home, that depends on how much use you make of Kerbin's atmosphere. We will assume you landed near Minmus' equator so have minimal need for a plane change on the way home and make several aerobraking passes. So, the return trip will need about 250m/s to get back into low orbit around Minmus, then about 250m/s to transfer back to Kerbin with a Pe there of about 37km. That Pe will make you land on your 2nd time around Kerbin, although you have very little control over where you come down, and you'll be fire on reentry heat.

So, when your lander is on the surface of Minmus, it needs an average of about 500m/s still in the tanks to be able to get home the quick and easy way. with a bit or reserve. It will need a bit more if it's far from Minmus' equator, and it will need a few hundred more if you want to circularize your orbit at Kerbin, then de-orbit at a spot you choose to land in a specific area (near KSC or at least not in mountains). And you might also want some margin for error. So design it for something between 500-1000m/s depending on how confident you feel and how exactly you want to come home.

OK, that's getting home. Then, if you do the very inefficient landing profile outlined above, you need about 350-450m/s for the landing itself (providing some reserve). Thus, your lander design needs a total of about 1000m/s (if you're confident in your abilities) to 1500m/s if you're not. So that's the lander. Next step back in the mission is getting from Kerbin into orbit at Minmus. It's about 1000m/s for the transfer burn to get there and about 300m/s to achieve orbit on arrival. Call it 1500 to be safe, in case the inclination causes problems, and put the lander on top of a transfer stage with that amount of fuel. All that's left is getting this off the ground, which takes a lifter with about 3300-3700m/s these days, depending on ascent profile. Edited November 19, 2015 by Geschosskopf

[MrOsterman]

[quote name='Kerbart']

My advice would be to start in Sandbox mode instead, and practice the [ ] out of KSP with building ships, orbiting them, docking, making transfers to Mun, Minmus, dock there, land there, maybe go even to Duna.

Career, in my eyes, is a challenge, not a way getting eased into the game. It's hard enough to master many of the required game basics in the first place; being hampered by a very limited choice of parts is not going to make it easier.[/QUOTE]

Career does add the challenge of having to watch your funds and upgrade your buildings but it also doles out the parts to you slower than you do in pure sandbox. I personally think that starting off with limited parts and limited potential is good because it gets you working with various mechanisms in small scale before you start trying to do the big scale stuff.

[Snark]

[quote name='Captain H@dock']Except that in 1.0.5 Jeb now catches fire quite high in the atmosphere even after a suborbital hop. So I would say these days are gone (and rightly so). :wink:[/QUOTE]

Oh, thank goodness. That particular aspect of kerbal toughness always bugged me.

Even if Jeb can't re-enter on his own, though, the EVA return can still be useful. He can take off from Minmus surface and head back to Kerbin, he just can't re-enter. You still need a rescue ship, but it only needs enough dV to get to LKO, plus another 920 m/s or thereabouts to match orbit with Jeb as he's incoming. Therefore the rescue ship doesn't have to pack the dV to enter Minmus orbit, land, take off, and head home. Thus, Jeb's ability to head home on his own shaves a good 500-600 m/s off the dV requirements for the rescue ship.

[quote name='eddiew']Turn off heating and it's probably viable, especially with the new water... IIRC a naked kerbal falls pretty slowly :)[/QUOTE]

Doesn't even need the new water. A kerbal can fall out of the sky and land unharmed. Worked just fine in 1.0.4 water. Works just fine on land, for that matter. Kerbals are [I]tough[/I].

[eddiew]

[quote name='Snark']Doesn't even need the new water. A kerbal can fall out of the sky and land unharmed. Worked just fine in 1.0.4 water. Works just fine on land, for that matter. Kerbals are [I]tough[/I].[/QUOTE]

Well. Now I just want to turn off heating for my next career and have the ONLY return method being to jump from space...

[Delta-Cheese]

I think this will help: [URL]http://forum.kerbalspaceprogram.com/threads/104638-Reverse-gravity-turn-landing-technique-for-airless-bodies[/URL]

It's basically a tutorial on landing "reverse gravity turn style". It's overkill for your needs, but I recommend testing it out. If you master this you won't have any problems landing in the future.

Note: This is NOT the most efficient way of landing, if you want that use the zero descent rate technique. Personally I still think the reverse gravity landing is better because it's easy to learn and because the zero descent rate technique is VERY inaccurate Edited November 20, 2015 by Delta-Cheese

[Hysterrics]

Don't forget engine choice to up your Delta V. Don't put mainsails on all your stages. You want high thrust for your ascent profile and high efficiency for just about everything else. I quite like the poodle engine, they have a good ISP.