What am I doing wrong?

[phoenixr]

Few more tips:

Nuclear engines are HEAVY. They have a very nice ISP but if they need to move a lot of weight, the benefits start to fade. For your tug, the fewer engines you use, the better - but the burn will take a lot longer - so try to balance practicality. In your case, the 3 are probably still ok.

But, your lander is also made with nukes? 4? Well that will make it very heavy, that's why you couldn't slow down. Plus the longer it takes to land, the longer your fuel is wasted fighting gravity's pull. A higher thrust and lower weight engine might be a better idea.

If you still want to go with the nukes, consider adding some airbrakes toward the top of your lander - it will help you keep retrograde so you can burn for the landing, and also help slow you down. Parachutes alone are not enough for heavy landers - so you will need a rocket assisted landing.

Also, you started your landing from a high orbit. You should start from a circular orbit just above the atmosphere (50km for Duna) and burn just a bit - get your Pe to ~40. This way you'll spend more time going sideways through the atmosphere, slowing down, before you reach the ground.

[egoego]

I haven't landed on Duna myself yet, but your landing looks very inefficient. Canceling yout your horizontal movement and takeing a free fall doesn't look safe (I do this on Minmus sometimes, but even on Mun it is dangerous).  

The most efficient landing is an inverse launch (aka gravity turn). Start at a low orbit (just above atmosphere) and burn retrogate to get your PE into the atmosphere (no idea how low you need it on Duna). This way you will travel a long way mostly horizontally through the atmosphere and slow down through air resistance drag. 

You also seem to have way too few parachutes (atmosphere on Duna as very thin). Add more and then some extra and have them open at very low pressure ( see the table here http://wiki.kerbalspaceprogram.com/wiki/Duna#Atmosphere ).

[TubaHorse]

11 hours ago, Streetwind said:

why is there an MX-F.L.A.T. reactor on the transfer stage?

I thought I'd need it, but on my next mission I'll be removing it!

 

9 hours ago, phoenixr said:

Nuclear engines are HEAVY

Thank you! I didn't know that they were so heavy. 

[Spricigo]

3 hours ago, egoego said:

You also seem to have way too few parachutes (atmosphere on Duna as very thin). Add more and then some extra and have them open at very low pressure ( see the table here http://wiki.kerbalspaceprogram.com/wiki/Duna#Atmosphere ).

I’d say quite the opposite bring less parachutes. While the mass of the parachute itself its not much when you consider the the extra fuel you need to haul the parachute its usually better to rely on a powered landing. Also, as noticed in the attempted landings of the op, parachutes are no good if you don’t slow down enough to deploy it safetly.

My suggestion its to get rid of all those parachutes (except the one for landing on Kerbin) and add 2 (to keep it symmetrical) radial Drogue chutes. Use the parachutes to ditch some of the speed and complete the landing with the engines.

Also, deltaV depends on engine Isp and the mass fraction (as explained by @Streetwind ). If you cut the total mass of your vessel in 20% it can do the same (e.g. liftoff from duna) with 20% less fuel. However  lighter craft will turn more easily and loses speed faster(and more) when aerobraking.
 

Some other pointers:

-I strongly suggest to disable yaw, pitch and roll on RCS thrusters and let the reaction wheels handle the rotation. SAS over-correcting itsel and  the rotation caused by thruster misalignment waste a lot of monopropellant. If the idea its to prevent the craft from flipping during the reentry design it to not flip in the first place (heavy parts in front, drag parts in rear).

-mk1-2 command pod is offensively heavy, consider using a different command pod (or probecore) with crew cabins and reaction wheels for the same result.

-When using nuclear engines also use liquid fuel only tanks to reduce the mass and bulk.

-coming directly from high orbits means entering  at higher speed in the atmosphere, lowering your apoasis to 60km and then your periapsis into atmosphere may greatly improve you chances of surviva.

 

 

 

 

 

[TubaHorse]

Well I've gone and tried following the advice given. I took some weight off, changed my lander around, reduced the # of nuke engines, and made sure my window was right. I launched, got to orbit, circularised, and got on my way to Duna with an... 11 minute burn? Okay whatever I had an encounter. I then added a node in the middle of the path to Duna and found that even a single second of burning would make me miss Duna by kilometres. I'm honestly ready to just give up. I don't know what I'm doing and am missing something important I guess.

Thanks for trying everyone. I really appreciate the time taken, even if it didn't work.

Edited March 28, 2017 by TubaHorse

[Streetwind]

8 hours ago, TubaHorse said:

I then added a node in the middle of the path to Duna and found that even a single second of burning would make me miss Duna by kilometres. I'm honestly ready to just give up. I don't know what I'm doing and am missing something important I guess.

...But that's precisely the intended effect. Mid-course correction burns have a massive influence on your point of arrival for no fuel cost worth mentioning. That's why you do them!

If you find that the magnitude of the effect is so large that you can't get enough precision on either your node-making or your burn (or both), then wait a little longer. The closer you are to your destination, the less pronounced the effects of any course corrections get. I personally like to wait until three-quarters of the way there in most cases. Sometimes, when the needed correction is very small, I even wait until I arrive in the target SOI. Radial and normal burns at the edge of the SOI still have a big effect for very little cost... it doesn't work out well for large corrections though.

If pulling on the maneuver node markers isn't precise enough, try using the mouse scrollwheel. When you hover the cursor over a marker and scroll, it will add or subtract to that marker (depending on which direction you scroll). You want to scroll very, very slowly, because the amount added goes up exponentially with scroll speed, and you just want tiny amounts. Also, if you are having trouble seeing the results of your node editing, try focusing on Duna while editing your node. Beyond that - there are mods that let you input numerical values directly.

There are some tricks to increase your burn precision as well. For example, if you have RCS thrusters, you can use those to execute the node instead of the main engine. Alternatively, if your ship features a multi-engine cluster, you can manually shut down all but one engine (just don't forget to re-enable the others afterwards). Or, if there's just a single main engine, you can throttle it down to as little as 5% output via the thrust limiter accessible while rightclicking the engine. All of these tricks make your ship work with a lot less thrust, which can make tiny burns much more manageable. For example, let's take the 7-NERV cluster you used in the video. That's 420 kN of thrust. But if you disable all but the center engine, then limit that engine to 5% output, and then only gently tap the shift key once, you might be thrusting with as little as 0.1 kN. That certainly won't throw your trajectory off target anytime soon.

Edited March 29, 2017 by Streetwind

[phoenixr]

18 hours ago, TubaHorse said:

Thank you! I didn't know that they were so heavy. 

You're welcome . Sarcasm aside, you can save a lot of weight on your lander if it's not nuclear.

You can look at some others' landers to get some idea of a working design. Some shameless self-promotion - my own first Duna lander mission: 

Nukes have low thrust and lots of weight, causing a low TWR, which is not very good for a lander - a low TWR will leave very little room for error. They even have a low ISP in atmosphere, so again not much sense in using them for a lander. Add some oxygen tanks to your tug and then you can even refuel a rocket lander for multiple landings.

There is no best engine in KSP, each engine has it's niche.

http://wiki.kerbalspaceprogram.com/wiki/Parts#Engines

 

Edited March 29, 2017 by phoenixr

[TheKorbinjer]

On 3/27/2017 at 2:47 AM, TubaHorse said:

So, I've always known that KSP isn't an easy game, and I'm not the best at it. I kinda picked it up and fiddled until I learned it. However, I feel I'm lacking something. If I ever try to go to any other body that isn't the Mun or Minmus, the mission never works out. I've watched countless videos seeing people do things that seem impossible, and yet I can't get to Duna with an overpowered rocket without cheating. Just recently I installed Space Y and some near future mods. I made a rocket to send to Duna, waited for a window, and went on my way. Things went great for the most part. Getting into orbit was easy, circularising was no problem, and the Duna encounter was a piece of cake. However, when I got there (after a 6 min. burn with 7 nuke engines), the game told me it would take a 15 minute burn to get into Duna's orbit.

 

So, what am I doing wrong? I really want to enjoy this game and eventually land on every planet/moon, but it seems currently it's just a $30 Kerbin orbit simulator.

From the video you posted, i can suggest aerobraking on duna for one, it would save you huge amounts of fuel,

And for landing  on duna, unless it's under ~1.5 tons, ALWAYS MAKE IT A POWERED LANDING. 

Duna's atmosphere is thiiiiin, so it's not enough to slow you down to a soft parachuted landing.

If you want a close encounter with the planet, after you leave Kerbin's SOI, add a maneuver node on the  orbit trajectory (around the sun) and focus your camera on Duna. You will be able to see just where your Duna encounter will wind up going.

 

 

The following aerobraking altitude  numbers should be good for you.

Eve: 65-75 km

Kerbin: 20-30 km

Duna: 7-15 km

Laythe: 20 km

Jool: 160-170 km

if the planet has an atmosphere, use it to slow yourself down.

[Hodo]

On 3/27/2017 at 6:14 PM, TubaHorse said:

The video is up! 

 

 

My only suggestion would be to use Duna's atmosphere to slow you down and bring you into orbit.  Atmospheric braking is a real thing and is used to cut the actual delta velocity expenditure down to a more manageable level.   For Duna set your target PE for 20-30km with a good heat shield at the front of your craft, and some kind of fins at the rear to keep your craft stable during the maneuver.   

Then all you have to do after you complete your skip through the atmosphere is a simple adjustment burn which will be MUCH less than the actual deceleration burn to get in orbit normally.  I use it to this day on all planets with atmospheres.  

[Jarin]

People are talking about mid-course correction burns, but honestly? You'd still save a ton of dV, and a headache, if you just wait until you cross into Duna's SoI, then - while still at the very edge of its space - burn radial-in until your PE is low enough. The edge of SOI is far enough out that this is still pretty easy to do. I mean, no, it's not nearly as efficient as doing this correction a couple months earlier, but it's still waaay better than trying to circularize at the edge of SOI. And if you play around a bit, you might get a gravity-braking assist from Ike.

[TubaHorse]

On 3/29/2017 at 3:14 AM, Streetwind said:

...But that's precisely the intended effect. Mid-course correction burns have a massive influence on your point of arrival for no fuel cost worth mentioning. That's why you do them!

If you find that the magnitude of the effect is so large that you can't get enough precision on either your node-making or your burn (or both), then wait a little longer. The closer you are to your destination, the less pronounced the effects of any course corrections get. I personally like to wait until three-quarters of the way there in most cases. Sometimes, when the needed correction is very small, I even wait until I arrive in the target SOI. Radial and normal burns at the edge of the SOI still have a big effect for very little cost... it doesn't work out well for large corrections though.

If pulling on the maneuver node markers isn't precise enough, try using the mouse scrollwheel. When you hover the cursor over a marker and scroll, it will add or subtract to that marker (depending on which direction you scroll). You want to scroll very, very slowly, because the amount added goes up exponentially with scroll speed, and you just want tiny amounts. Also, if you are having trouble seeing the results of your node editing, try focusing on Duna while editing your node. Beyond that - there are mods that let you input numerical values directly.

There are some tricks to increase your burn precision as well. For example, if you have RCS thrusters, you can use those to execute the node instead of the main engine. Alternatively, if your ship features a multi-engine cluster, you can manually shut down all but one engine (just don't forget to re-enable the others afterwards). Or, if there's just a single main engine, you can throttle it down to as little as 5% output via the thrust limiter accessible while rightclicking the engine. All of these tricks make your ship work with a lot less thrust, which can make tiny burns much more manageable. For example, let's take the 7-NERV cluster you used in the video. That's 420 kN of thrust. But if you disable all but the center engine, then limit that engine to 5% output, and then only gently tap the shift key once, you might be thrusting with as little as 0.1 kN. That certainly won't throw your trajectory off target anytime soon.

So, I may not be Duna-worthy, but just tonight I got a com sat around Eve and a com tower landed on Gilly with no heartbreak at all. I finally figured out how to use ΔV and what the numbers mean. The communication dishes may be overkill but it's better to be safe than sorry. I'm pretty proud!  

[Blaarkies]

On 3/29/2017 at 4:59 PM, TheKorbinger said:

Eve: 65-75 km

Kerbin: 20-30 km

Duna: 7-15 km

Laythe: 20 km

Jool: 160-170 km

if the planet has an atmosphere, use it to slow yourself down.

"Jool: 160-170 km"  when last did you update KSP? Going below 190km at Jool instantly explodes anything except heatshields.
Kerbin below 30km results in unintended landing with anything else than a spaceplane...say, are you using FAR by any chance?

Edited March 31, 2017 by Blaarkies

[Streetwind]

49 minutes ago, TubaHorse said:

So, I may not be Duna-worthy, but just tonight I got a com sat around Eve and a com tower landed on Gilly with no heartbreak at all. I finally figured out how to use ΔV and what the numbers mean. The communication dishes may be overkill but it's better to be safe than sorry. I'm pretty proud!  

Congratulations, and welcome to the Interplanetary Club!

[FloppyRocket]

50 minutes ago, TubaHorse said:

So, I may not be Duna-worthy, but just tonight I got a com sat around Eve and a com tower landed on Gilly with no heartbreak at all. I finally figured out how to use ΔV and what the numbers mean. The communication dishes may be overkill but it's better to be safe than sorry. I'm pretty proud!  

 

Nice work!

[TubaHorse]

1 minute ago, FloppyRocket said:

Nice work!

 

4 minutes ago, Streetwind said:

Congratulations, and welcome to the Interplanetary Club!

Thanks a ton! It was a nice feeling being able to do the thing finally.

Also, I sent up a polar Kerbin scanner since my last message

okay I'll stop spamming now

[Wanderfound]

On 29 March 2017 at 9:48 AM, TubaHorse said:

Edited to delete as redundant

Edited March 31, 2017 by Wanderfound

[TheKorbinjer]

8 hours ago, Blaarkies said:

"Jool: 160-170 km"  when last did you update KSP? Going below 190km at Jool instantly explodes anything except heatshields.
Kerbin below 30km results in unintended landing with anything else than a spaceplane...say, are you using FAR by any chance?

It's been a minute sicne i've been to Jool. All my spacecraft are very large when they get there though xD

[Matt Lowne]

On 2017-3-27 at 11:10 AM, TubaHorse said:

I see people like Matt Lowne doing amazing things and I try to do similar things and end up never being able to get the simple stuff done

We were all there too at one point. All about practice. Something something the masters have failed more times that students have ever tried. Stick at it, you'll get there one day!

[Joseph Kerman]

I *just* got a 100-seat SSTO to Duna, and now I am not so sure after all my modifications.

[Spricigo]

1 hour ago, Matt Lowne said:

We were all there too at one point. All about practice. Something something the masters have failed more times that students have ever tried. Stick at it, you'll get there one day!

On the same vane,  a student may still need to learn what the master already forgot.

While we are learning we frequently need to deal with 'newbie mistakes'. Much of what experienced people learned is how to perceive and avoid such mistakes. A problem you avoid is a problem you don't need to solve. 

Another point is that we usually don't notice how many mistakes experienced people still do and how much effort takes to do things rigth.