Training Duna landings?

[RealDarko]

I started doing Duna trips, but goind to Duna costs time, putting the lander in orbit, flying there... Is there any way I can try If my landers will work and can achieve a Duna landing without having the play all the sequence?

[Gianni1122]

Open the debug window and use cheats to "set orbit" around Duna 

Alternatively, you can get MechJeb's current dev build and use all of its autopilot features to do everything from launch from Kerbin to land on Duna with minimum effort 

Edited November 23, 2016 by Gianni1122

[Tex_NL]

3 minutes ago, Gianni1122 said:

Open the debug window and use cheats to "set orbit" around Duna

Exactly. And if you do it in a separate sandbox game it won't affect your career game.

And if that's too difficult for you just save your game before you attempt a landing. When you cock-up, and you most likely will, simply load your save and try again.

Edited November 23, 2016 by Tex_NL

[RealDarko]

And how can I do that? I never mixed with "debugging"

[Rocket In My Pocket]

4 minutes ago, RealDarko said:

And how can I do that? I never mixed with "debugging"

Alt + F12 or whatever Alt is on Mac if you have a Mac.

[Daveroski]

1 minute ago, Rocket In My Pocket said:

Alt + F12 or whatever Alt is on Mac if you have a Mac.

Or Right Shift + F12 if you have linux

[Leafbaron]

I would highly recommend using the debug menu in a sandbox game. I always start with a career save and name the sandbox game "Proving Grounds" it basically acts like a simulator in which I can test designs free of penalty before I actually implement complicated designs in my career mode. 

[septemberWaves]

Here's an alternative if you want to do it without cheating but also without sending your vehicle all the way to Duna:

Design your Duna lander, make sure it's reasonably pointy, and send it to a low Mun orbit (about 10km). Land it on the Mun, get back into a 10km orbit, and then land it on the Mun again. If that works, then it has enough fuel for a Duna ascent. Return to a 10km orbit and then land another time, and you should have enough to propulsively land on Duna too.

If it's a two-stage lander (with a descent stage and ascent stage), the descent stage (with ascent stage attached) should be able to land on the Mun from a 10km orbit and then return to that orbit. The ascent stage should then be able to land on the Mun, return to a 10km orbit, and land on the Mun again.

It's a very approximate method, but it should give you some indication of what you need for a Duna landing (if you don't use delta-v calculating). Also, it does assume that your design is draggy enough to aerobrake in Duna's atmosphere (which most of the time is true) and will land without using parachutes.

[Rocket In My Pocket]

12 minutes ago, Daveroski said:

Or Right Shift + F12 if you have linux

Apologies, didn't mean to leave out the penguins.

[Chiron0224]

I recently accomplished my first Duna landing and here's how I did it.  I build the lander and then packed on a ton of parachutes.  I had 4 drogues, 4 radials, and 4 of the biggest nosecone style (my lander had 4 radial fuel tanks so each one was capped with a big chute).  I used my thrusters to decelerate in the upper atmosphere until my drogues could open.  Then I opened the drogues and let them slow me down and then opened the mains.  I then relaxed until the drag on the chutes killed my horizontal and vertical momentum and I was falling slowly.  Then I extended gears and used a little bit of thrust to bring my descent speed down to 5m/s at the last moments.  Easy peesy.

 

EDIT: Imgur album of the mission http://imgur.com/gallery/BCeWu

Edited November 23, 2016 by Chiron0224
added album

[AeroGav]

Don't sweat it.  Just keep your lander small and lightweight,  pack plenty of parachutes,  and whatever you do don't forget the ladders. 

 

[Gianni1122]

2 hours ago, Rocket In My Pocket said:

Alt + F12 or whatever Alt is on Mac if you have a Mac.

 

2 hours ago, Daveroski said:

Or Right Shift + F12 if you have linux

Mac is fn + alt + F12 if your system preferences are default. Just figured I'd mention that.

 

[Scarecrow]

I have found that any of my landers that can land on Mun and return to a 15k orbit is capable of landing on Duna and returning to orbit if you add some drogue and main chutes.  Aerobraking and the chutes mean that you use way less fuel to land on Duna than you would on Mun, so all the fuel you save is now available for the ascent.

[hms_warrior]

While using the cheat-menu is most likely the easiest way, you CAN simulate a Duna landing on Kerbin.

Step 1: adjust the fuel-level/payload of your lander so that it weights about 38% of it's "real weight". You just have simulated the lower gravity on Duna!

Step 2: The atmospheric pressure of Kerbin at 20 km height is comparable to the atmospheric pressure of Duna at sea-level. So if you want to test if your parachutes(for example) are enough for a soft duna landing, just put your weight-reduced lander on some SRBs, go straight up to 25-30km, activate your parachutes and see what your speed is at 20 km height.

Edited November 24, 2016 by hms_warrior

[Sharpy]

[del]

Edited November 24, 2016 by Sharpy

[baberbot]

all of this is for testing in a separate carea save there are 2 options i used in the past

15km kerbin atmosphere = surface atmosphere of duna

1) use debug menu to reduce gravity to 30%/0.3G and try to achieve under 10 m/s speed by 15 km and then try return to orbit (may need action groups to cut parachutes as well as need to edit their deployment height in the VAB prior to launch) 

2) other option is use the set orbit command in debug menu to teleport a test lander to duna orbit then attempt do land and launch

prefer second one as is better and more accurate but option 1 requires less effort

[RealDarko]

I have the feeling my landers are short on fuel, I want a lander capable of retunring all by himself to Kerbin, what will be a minimum kander for that with a bit of spare fuel just to be safe a error will not strand me there?

[KerikBalm]

On 11/23/2016 at 9:50 PM, eloquentJane said:

Here's an alternative if you want to do it without cheating but also without sending your vehicle all the way to Duna:

Design your Duna lander, make sure it's reasonably pointy, and send it to a low Mun orbit (about 10km). Land it on the Mun, get back into a 10km orbit, and then land it on the Mun again. If that works, then it has enough fuel for a Duna ascent. Return to a 10km orbit and then land another time, and you should have enough to propulsively land on Duna too.

If it's a two-stage lander (with a descent stage and ascent stage), the descent stage (with ascent stage attached) should be able to land on the Mun from a 10km orbit and then return to that orbit. The ascent stage should then be able to land on the Mun, return to a 10km orbit, and land on the Mun again.

It's a very approximate method, but it should give you some indication of what you need for a Duna landing (if you don't use delta-v calculating). Also, it does assume that your design is draggy enough to aerobrake in Duna's atmosphere (which most of the time is true) and will land without using parachutes.

That sounds way over engineered. Orbital velocity at low Duna orbit is less than 1,000 m/s. With chutes you only need ~50 m/s for a propulsive landing (or even less)..You can figure about another 400 m/s lost due to air pressure and drag (depending on where you take off from)... but this is very conservative. You only lose about 1,000 m/s to drag + increasing potential energy on a Kerbin ascent (if done right, it can be done for 3,200 vac dV, orbital velocity is ~2350, and you get about ~150 from going east). 1,400 m/s vac dV should give you a big margin.

Just going to the surface of Mun and back to orbit takes a minimum of 1,100 m/s, and thats with perfect execution and infinite TWR. Generally speaking, if you send a craft with a pair of radial drogues/airbrakes, and a main chute (the airbrakes/drogue are good to slow down sooner so there's more time for the main chute to safely deploy), to mun orbit and can land it and get back to orbit, it will work on Duna. Just to be sure, its only a couple (few?) hundred m/s to go from low munar orbit back to kerbin. If you can get your craft to low munar orbit with some basic aerodynamic equipment, land it on Mun and get it back to kerbin, it can land on Duna and get back to Duna orbit.

Lastly, you can test the TWR by setting the thrust limiters on your craft to 50% , since Mun gravity is 0.165 and Duna gravity is 0.3

A 2 stage duna lander doesn't make much sense, and can't really be tested on Mun (only the ascent stage), because any reasonable Duna lander is going to make use of aerodynamics, and even with a propulsive landing, the fuel used will be so little that it makes no sense to add a 2nd engine, and the propulsive landing will be done with the engine used by the ascent stage

On 11/24/2016 at 9:02 AM, hms_warrior said:

While using the cheat-menu is most likely the easiest way, you CAN simulate a Duna landing on Kerbin.

Step 1: adjust the fuel-level/payload of your lander so that it weights about 38% of it's "real weight". You just have simulated the lower gravity on Duna!

Step 2: The atmospheric pressure of Kerbin at 20 km height is comparable to the atmospheric pressure of Duna at sea-level. So if you want to test if your parachutes(for example) are enough for a soft duna landing, just put your weight-reduced lander on some SRBs, go straight up to 25-30km, activate your parachutes and see what your speed is at 20 km height.

Theres some problems here with step 2.

* Since 1.0 came out, atmospheric pressure is not the same thing as atmospheric density. the MW of Duna's atmospheric gas is 43, compared to 28.8 for kerbin. Its also a bit colder but we'll ignore that. At the same atmospheric pressure, Duna's atmo is 50% denser than kerbin's. So you actually want to compare it to the alttude at which kerbin's atmospheric pressure is 0.1 - this occurs around 12km - also FYI your original 20km stat should have actually been 15km.

* Maximum full deployment altitude for any chute, without modding, is 5km above the ground. You can't test that at 20km, or 15km, and it would be really hard to test for deployment at 12km, because you'd need to go right over one of the highest peaks on kerbin to get full deployment at 12km... even then by the time the chute decelerates you, you'll be well below 12km, and the test will show you to be slower than you actually will be on Duna.

Instead... just use math. Drag is proportional to v^2. Duna sea level atmosphere is 0.067 atmospheres, duna atmo density at the same pressure is 1.5x kerbin's. Duna's "sea level" atmosphere is 0.1x as dense as kerbin sea level. Duna's gravity is 0.3x that of Kerbin.

This means you'll land sqrt (10*0.3) = 1.73x faster under chutes on Duna. Take whatever speed you'd like chutes to slow you down to on Duna, multiply by 0.55, and try to achieve that speed under chutes with your craft on Kerbin.

 

 

 

Edited November 25, 2016 by KerikBalm

[Gianni1122]

1 hour ago, RealDarko said:

I have the feeling my landers are short on fuel, I want a lander capable of retunring all by himself to Kerbin, what will be a minimum kander for that with a bit of spare fuel just to be safe a error will not strand me there?

Fuel is not necessarily your main concern. Delta-V, on the other hand, is the number you should be focusing on. I suggest getting a mod like Mechjeb or KER (KER isn't updated for 1.2 yet I think) to do deltaV calculations for you.

In case you don't know, deltaV-to put it as simply as I can-is a number used to describe the "distance" your ship can travel based on its weight, engine efficiency and whether it's in an atmosphere or vacuum. For example; You need ~3500m/s of delta-v to get from Kerbin surface to Kerbin orbit.

 

[Sharpy]

On 23.11.2016 at 11:06 PM, AeroGav said:

Don't sweat it.  Just keep your lander small and lightweight,  pack plenty of parachutes,  and whatever you do don't forget the ladders. 

 

1) You don't need plenty parachutes for Duna, just a couple, mounted in such a way that you land engines-down. Perform a short burn right before touchdown, and you'll be better off mass-wise than packing plenty of parachutes - and for Duna that really means plenty, because its atmosphere is very thin. Also, set the parachutes' parameters to safer values. 2-3km altitude, lowest pressure available. In Duna's thin atmosphere the 1000m are gone in a blink of an eye. But with a parachute or two, and enough time for it to work, you will lose great most of the speed, and the engine will cover the last 40m/s or so.

2) Duna is the heaviest planet where you don't need the ladder. You can hover on jetpack, albeit barely so. Note if you use KIS, you may be unable to take off if you carry anything of considerable mass.

Also, Duna's thin atmosphere and low gravity mean LV-N, the nuclear engine, works at almost full efficiency on the surface and is well capable of lifting moderate-sized lander. That allows for some awesomely efficient designs. (just watch out, the poor TWR means losing that 40m/s out of remaining speed on a single parachute may take a while!)

[RealDarko]

How muh Delta-V will I need for the landing and back? Imagine I can put my lander ready for catching Duna, landing and then back.

[Tex_NL]

[RealDarko]

Great, does that include the trip back?

[AeroGav]

5 hours ago, Sharpy said:

1) You don't need plenty parachutes for Duna, just a couple, mounted in such a way that you land engines-down. Perform a short burn right before touchdown, and you'll be better off mass-wise than packing plenty of parachutes - and for Duna that really means plenty, because its atmosphere is very thin. Also, set the parachutes' parameters to safer values. 2-3km altitude, lowest pressure available. In Duna's thin atmosphere the 1000m are gone in a blink of an eye. But with a parachute or two, and enough time for it to work, you will lose great most of the speed, and the engine will cover the last 40m/s or so.

2) Duna is the heaviest planet where you don't need the ladder. You can hover on jetpack, albeit barely so. Note if you use KIS, you may be unable to take off if you carry anything of considerable mass.

Also, Duna's thin atmosphere and low gravity mean LV-N, the nuclear engine, works at almost full efficiency on the surface and is well capable of lifting moderate-sized lander. That allows for some awesomely efficient designs. (just watch out, the poor TWR means losing that 40m/s out of remaining speed on a single parachute may take a while!)

I was being a tad facetious, i didn't follow much of my own "advice" in the video.   Though ladders would have helped my Kerbonaut retain a little more dignity. 

[Gianni1122]

5 hours ago, RealDarko said:

Great, does that include the trip back?

I don't think it does.