Duna lander help!

[nascarlaser1]

hi guys!

For my first ever interplanetary mission (not including the one where I managed to fly past eeloo due to a failed trip to Minimus ... don't ask) I want to go to Duna!

But.... I cant figure out how to build a lander . All my test landers cant even get into orbit around kerbin. I would prefer if I  could get to Duna and back without needing to dock (refueling it ok though) but I wont care if its a 1 way trip since its my first time. Anyone have any tips/examples for a basic dune lander? I am playing in sandbox so science parts do not matter. 

 

Thxs!

[DD_bwest]

i have one on my computer but im stuck at work.. lol wish i could upload a shot of it.

 

lander can and material bay +4 sparks.  24 of the smallest tanks, divided into groups of 6 and placed in 4 part symmetry around the bay. sparks on the bottom. 4 chutes on the top of them.   3 drogue chutes on the side.  crank the min pressure as low as it goes.  ooen the drogues nice and high, set the mains for 3k.  you'll need a bit of thrust to soften landing but not much.

[nascarlaser1]

4 minutes ago, DD_bwest said:

i have one on my computer but im stuck at work.. lol wish i could upload a shot of it.

 

lander can and material bay +4 sparks.  24 of the smallest tanks, divided into groups of 6 and placed in 4 part symmetry around the bay. sparks on the bottom. 4 chutes on the top of them.   3 drogue chutes on the side.  crank the min pressure as low as it goes.  ooen the drogues nice and high, set the mains for 3k.  you'll need a bit of thrust to soften landing but not much.

yay thanks you! since you included material bay I'm going to assume that you are using the mk1 lander can? if so do you think replacing the material bay with a crew cabin would affect it much? I want to bring 3 of my kerbals with me if possible (if not I'll happily settle for 1 kerbal).

 

[DD_bwest]

1 minute ago, nascarlaser1 said:

yay thanks you! since you included material bay I'm going to assume that you are using the mk1 lander can? if so do you think replacing the material bay with a crew cabin would affect it much? I want to bring 3 of my kerbals with me if possible (if not I'll happily settle for 1 kerbal).

 

i cant remember the weight difference for the crew cabin so youll have to build it and rerun the deltav calc.  i dont THINk it should be a problem, but not sure.

[nascarlaser1]

Just now, DD_bwest said:

i cant remember the weight difference for the crew cabin so youll have to build it and rerun the deltav calc.  i dont THINk it should be a problem, but not sure.

ok thxs!

[Spricigo]

54 minutes ago, nascarlaser1 said:

yay thanks you! since you included material bay I'm going to assume that you are using the mk1 lander can? if so do you think replacing the material bay with a crew cabin would affect it much? I want to bring 3 of my kerbals with me if possible (if not I'll happily settle for 1 kerbal).

 

+800kg, for a craft that small it may cut a lot of the deltaV budget.

1 hour ago, nascarlaser1 said:

 All my test landers cant even get into orbit around kerbin.

 

Post a picture and give us more detail, so we can try to diagnose what is wrong. maybe all you need its a few pointers in the right direction.

 

[nascarlaser1]

14 hours ago, Spricigo said:

Post a picture and give us more detail, so we can try to diagnose what is wrong. maybe all you need its a few pointers in the right direction.

 

I'm not at ksp right now so no pics (will post later today or over the weekend if I can) but my lander is a mk2 command pod,heatshield,1 medium sized rockomax fuel tank (can never remember the names). Around this is 4 radially attached small rockomax tanks with decoupler. The middle stack has a mainsail engine and the four detachable drop tanks have poodle engines. I have fuel lines going from the 4 drop tanks to the main engine. On each fuel tank there are at least 2 drogue chutes and 2 regular, and there is 1 parachute on the command pod.

[Cpt Kerbalkrunch]

1 hour ago, nascarlaser1 said:

I'm not at ksp right now so no pics (will post later today or over the weekend if I can) but my lander is a mk2 command pod,heatshield,1 medium sized rockomax fuel tank (can never remember the names). Around this is 4 radially attached small rockomax tanks with decoupler. The middle stack has a mainsail engine and the four detachable drop tanks have poodle engines. I have fuel lines going from the 4 drop tanks to the main engine. On each fuel tank there are at least 2 drogue chutes and 2 regular, and there is 1 parachute on the command pod.

If you're using a 2.5m body, I think I would put 1.25m tanks radially attached with Dart engines rather than more 2.5s with Poodles. This is quite a bit lighter, and you can put 4, 6, or 8, depending on how heavy your lander is. The Dart is a good engine. It has pretty decent power and a really good ISP. Plus, they're really short, so they're good for landers. Their drawback is that they don't gimbal, so you'll need reaction wheels or RCS for good control. It'll get you off of Duna pretty easily, though, so I think it's worth a look.

Edited May 25, 2017 by Cpt Kerbalkrunch

[Ohm is Futile]

45 minutes ago, Cpt Kerbalkrunch said:

Their drawback is that they don't gimbal, so you'll need reaction wheels or RCS for good control. It'll get you off of Duna pretty easily, though, so I think it's worth a look.

If you are using them mostly for orbital maneuvers and to soften a chute landing, I'd say you should be more than fine with the average torque a small reaction wheel provides, even maybe only the pod.

 

2 hours ago, nascarlaser1 said:

I'm not at ksp right now so no pics (will post later today or over the weekend if I can) but my lander is a mk2 command pod,heatshield,1 medium sized rockomax fuel tank (can never remember the names). Around this is 4 radially attached small rockomax tanks with decoupler. The middle stack has a mainsail engine and the four detachable drop tanks have poodle engines. I have fuel lines going from the 4 drop tanks to the main engine. On each fuel tank there are at least 2 drogue chutes and 2 regular, and there is 1 parachute on the command pod.

I wouldn't use the Mk 2 Command Pod ever as it is horribly weight inefficient. You can bring 4 kerbals instead of 3 if you use a Hitchhiker's crew quarter and a probe core instead and it saves you nearly half the tonnage of the Mk 2 Command Pod.
Note that parachute landing is quite viable for Duna and will save you a ton of fuel (thus, weight) if you do so. Just make sure you go with at least double what you would use for a Kerbin parachute landing due to the thinner atmosphere.

[nascarlaser1]

58 minutes ago, Cpt Kerbalkrunch said:

If you're using a 2.5m body, I think I would put 1.25m tanks radially attached with Dart engines rather than more 2.5s with Poodles. This is quite a bit lighter, and you can put 4, 6, or 8, depending on how heavy your lander is. The Dart is a good engine. It has pretty decent power and a really good ISP. Plus, they're really short, so they're good for landers. Their drawback is that they don't gimbal, so you'll need reaction wheels or RCS for good control. It'll get you off of Duna pretty easily, though, so I think it's worth a look.

 

10 minutes ago, Ohm is Futile said:

If you are using them mostly for orbital maneuvers and to soften a chute landing, I'd say you should be more than fine with the average torque a small reaction wheel provides, even maybe only the pod.

 

I wouldn't use the Mk 2 Command Pod ever as it is horribly weight inefficient. You can bring 4 kerbals instead of 3 if you use a Hitchhiker's crew quarter and a probe core instead and it saves you nearly half the tonnage of the Mk 2 Command Pod.
Note that parachute landing is quite viable for Duna and will save you a ton of fuel (thus, weight) if you do so. Just make sure you go with at least double what you would use for a Kerbin parachute landing due to the thinner atmosphere.

Thxs!

[Spricigo]

43 minutes ago, Ohm is Futile said:

Note that parachute landing is quite viable for Duna and will save you a ton of fuel (thus, weight) if you do so. Just make sure you go with at least double what you would use for a Kerbin parachute landing due to the thinner atmosphere.

 

Actually I suggest to bring less parachutes than  for Kerbin. Parachutes also have mass and so requires fuel to move all the way to Duna. But just a few can ditch most of the velocity allowing for a trivial burn to finalize the landing.

[Ohm is Futile]

1 minute ago, Spricigo said:

Actually I suggest to bring less parachutes than  for Kerbin. Parachutes also have mass and so requires fuel to move all the way to Duna. But just a few can ditch most of the velocity allowing for a trivial burn to finalize the landing.

I see the merit in your suggestion, but I think parachute mass shouldn't be that significant anyway. Parachutes also affect your terminal velocity without any added cost over time, whereas engines do cost fuel. It's also worth noting that Duna's geography is not flat either and if you land on one of the higher areas with very few chutes, you may have... surprises... I guess that could also be an argument for landing with minimal amount of chutes.

That said, given that you can quite realistically achieve a final descent speed in the 20-30m/s range with chutes, I have to wonder how that compares in fuel tonnage to slow the vehicle down. Also, OP may reuse those chutes on Kerbin if he has an engineer to repack them.

Anyways, I would say it's mostly a matter of preference with a pinch of confidence in suicide burn skills.

You're kind of making me curious, though. I have a Duna lander that weighs about 8 tons, fully fueled, of which 4 tons is fuel. It has almost exactly 2000m/s dV. It uses 4 of the radial Mk 2 chutes and 4 of the smaller radial drogue chutes. It reduces my dV by about 25m/s per chute, but its final descent speed is around 15m/s, allowing me to land for practically free beyond deorbit costs. You might be right that the extra chutes are somewhat pointless and cost you extra dV on the non-lander stages. With that said, my lander docks with a space station where an engineer repacks the chute, saving me the braking fuel every time I land, which probably more than makes up for what it cost me extra to send it there in the long run.

I'd have to test how much speed a parachute can shed on descent.

[Spricigo]

18 minutes ago, Ohm is Futile said:

You're kind of making me curious, though. I have a Duna lander that weighs about 8 tons, fully fueled, of which 4 tons is fuel. It has almost exactly 2000m/s dV. It uses 4 of the radial Mk 2 chutes and 4 of the smaller radial drogue chutes. It reduces my dV by about 25m/s per chute, but its final descent speed is around 15m/s, allowing me to land for practically free beyond deorbit costs. You might be right that the extra chutes are somewhat pointless and cost you extra dV on the non-lander stages. With that said, my lander docks with a space station where an engineer repacks the chute, saving me the braking fuel every time I land, which probably more than makes up for what it cost me extra to send it there in the long run.

 

If you don't mind, send a picture or a craft file and set some performance parameter you want it to meet. Let's see what we can design within those parameters.

[Ohm is Futile]

2 minutes ago, Spricigo said:

 

If you don't mind, send a picture or a craft file and set some performance parameter you want it to meet. Let's see what we can design within those parameters.

Has a KER part:

https://www.dropbox.com/s/twamkkz9oat7yxv/DLV - Mk I.craft?dl=0

Works like a charm, launches from and docks back with a station at 100km orbit with one tank. The antennae die on entry if they are not pulled back in, but much to my surprise, the can's integrated comms are enough to reach a relay so I don't need a pilot, I can send a scientist down. Science canister hidden between the engines allows to bring back up multiple copies of the same experiments for maximum efficiency.

Re-reading the topic, I feel as though you might be addressing the wrong person, but hey, it wouldn't be polite not to reply.

[Spricigo]

40 minutes ago, Ohm is Futile said:

Re-reading the topic, I feel as though you might be addressing the wrong person, but hey, it wouldn't be polite not to reply.

Well, in some sense I really am. But my intent its more to add to what you said and offer a more ample view for the OP (or anyone interested).

The request for a craft file is because I find interesting (an opportunity to learn) to try designing/optimizing a ship according with a different 'directive' than mine and what works to someone else its a good starting point. Also I'm curious if for a reusable lander parachutes will be an advantage or a hindrance (at this point I'm slightly more inclined to think it will save more in the long run.)

[Scarecrow]

I have found that if a lander can land on the Mun and get back to orbit, it's almost certain it can land on Duna and get back to orbit by simply adding a few parachutes.  Virtually all of the fuel on board is then available for the launch back to orbit as only a small amount is required for the initial de-orbit burn and a bit more to soften the landing.

I built an Apollo style rocket for missions to the Mun, including a 2-stage lander, and I used the same rocket to go to Duna and back after adding parachutes to the lander.

 

This is a single stage that carries two rovers, but it does need to dock with the CSM to get everyone home.

 

This one is a there and back all in one design.

Edited May 27, 2017 by Scarecrow

[nascarlaser1]

2 hours ago, Scarecrow said:

(snipped for space)

How long does it take for the second version of your lander to return to Kerbin (in real life time)?

Thanks for your help guys!

[Scarecrow]

In real time, a few minutes to get back to orbit around Duna.  It then takes a few more minutes to time warp for a transfer window, and set up the transfer and burn.  A few more minutes of time warping again, and then final adjustments for capture and landing.

So I guess from the surface of Duna to landing back at Kerbin will take around 20 - 30 minutes of real time play, maybe a bit less.

[nascarlaser1]

On ‎5‎/‎27‎/‎2017 at 6:49 PM, Scarecrow said:

In real time, a few minutes to get back to orbit around Duna.  It then takes a few more minutes to time warp for a transfer window, and set up the transfer and burn.  A few more minutes of time warping again, and then final adjustments for capture and landing.

So I guess from the surface of Duna to landing back at Kerbin will take around 20 - 30 minutes of real time play, maybe a bit less.

Thxs!

 

On ‎5‎/‎25‎/‎2017 at 2:22 PM, Spricigo said:

 

If you don't mind, send a picture or a craft file and set some performance parameter you want it to meet. Let's see what we can design within those parameters.

Here is a picture ! sorry it took so long I took like 20 of these but couldn't figure out where it was saving too .

Note: the other side of this craft is a just a copy of what you see. I have 2 of each kind of parachute on each side, 4 landing legs, a poodle engine (under the heat shield fairing) and 1 big parachute on top.

Basic requirements I'd like to try to achieve to complete this mission:

Landing on Duna

getting back into orbit around Duna

 

Advanced requirements (stuff that I don't need in order to complete the mission, but would make future missions easier):

Be able to return this craft to kerbin

be able to hop around Duna with it so I can look for easter eggs. Thxs!

[Scarecrow]

I've had another look at that all-in-one lander, and think it may be from an earlier version of KSP with different aerodynamics.  I tried replicating the build in the latest version, but it's very marginal on fuel, and that's not how I normally build my craft.

I do have a different Duna craft that has a single stage lander, but it does needs to dock with an orbiting CSM.  I flew that one to Duna and back yesterday.  In real time it took me 31 minutes to get there, and 35 to get back.  It took slightly longer to get back due to messing about with manoeuvre nodes and timing for a burn that wasn't influenced by Ike during departure. 

 

This is an image of the complete launch vehicle, which hopefully shows that you don't need to too mad in order to get to Duna and back.

 

The Duna lander this vehicle carries features the following, which is enough to get it to the surface and back to orbit.

Mass : 10.242t

Fuel ox/lf  :  539/441

Chutes  :  2 radial main and one normal drag

Engine  :  LV-909 Terrier

Total part count  :  48

 

Looking at your own design, I would say you could lose 2 of the drogue chutes as the remaining two will be sufficient to slow you down enough to deploy the mains.  You could probably lose two of the radial main chutes as well.  I would also suggest that the ablator at the bottom isn't necessary for Duna unless you intend coming in very low from your insertion burn to maximise atmospheric braking.  Landing from normal orbital altitudes shouldn't need an ablator.

The Poodle may also be overkill.  I'm sure a Terrier would be enough.  Making those changes would shave nearly 3t off the mass of your lander, which would be a great help to your overall dV.  Having said that, I've just built your lander as shown in your image - with the Poodle it only has marginally more dV than my own lander design, and I know that won't get back to Kerbin.  Even making the changes I have suggested, whilst it does considerably improve your dV, I still think it's marginal for a safe return.

If you substitute one of the smallest decouplers in place of the Rockomax, you will gain a bit more dV, which may be enough, but I reckon it would be very tight.

Unfortunately, I don't see any batteries or solar panels on your lander, so a lack of electricity may also be a problem.

I know it's possible for a Duna lander to get to the surface and eventually back to Kerbin, because I have done it, but a more efficient way would be for the lander to be designed for just that purpose, with an orbiting craft waiting for the return journey back to Kerbin, but that does mean you need to be able to rendezvous and dock to fly that sort of mission profile.

Good luck anyway.

Edited May 29, 2017 by Scarecrow

[Scarecrow]

OK - quick update.  I've just built your lander with the modifications I suggested.  I landed it on Duna from a 60km orbit, and returned to a 57km orbit with just over 900 dV remaining, which should be enough to get back to Kerbin and then perform a capture burn.

You can download the craft from Dropbox if you want to take a look.  https://www.dropbox.com/s/7y6rke7mdh229ac/Duna Return Lander.craft?dl=0

[Spricigo]

https://www.dropbox.com/s/fc37tpa8w594pke/Old Spice.craft?dl=0

auto gravity turn, just press space and let it fly to space (stagging as necessary) raise apoapsis to 85km and coast to circularize.

transfer to duna, aerobrake with 18km periapsis to capture, at apoapsis raise periapis to 25km and procede to landing.

Returns to low duna orbit with 800m/s left

 

[nascarlaser1]

Thxs @Scarecrow and @Spricigo!

[Spricigo]

BTW,  Old Spice have some extras you may not use (RTG,  monopropellant,  RCS thrusters,  docking port),  feel free to strip it if you don't care about those.  However the craft as is can be left in Duna for use of future missions, using the docking port /RCS to couple with a tanker between landings. However doing so means you need a dedicated transfer vehicle (sold separately).