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Duna Excursion Module


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I am trying to make the Duna Excursion Module (ala Von Braun), but I am unable to get the ascending vehicle to Duna orbit from Duna surface

To my understanding, based on IMIP (and Raptor9's EV-3), The Ascent module double as Earth return vehicle, hence the heat shield at the bottom of the command pod. Otherwise everything is limited to 2.5m in order to get it fit inside a Mk-3 Payload bay (There is a reason for that)

The craft is as follow: https://drive.google.com/file/d/0B_pbFy_PSy99SnNiOUxnblFHYzA/view?usp=sharing

Edited by Jestersage
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What's your TWR on takeoff?  You might want a bigger engine,  like the Poodles.

You're also probably getting a lot of drag from all those little tanks.  As I understand it, parts in cargo bays are only shielded if they're attached at the central node,  or attached to a part attached to the node.   So attaching to the cargo bay floor does not work. I would consider simplifying and just using 2.5m fuel tanks. 

The docking port at the front is also fairly draggy. 

Do you really need monopropellant and thrusters?  Is this thing docking with anything else?  If not,  that's dead weight and drag. 

Iso there a second heat shield at the very bottom?  Seems like you can cut that ashe well.  You can probably also cut a bit of ablation from the upper heat shield to save weight.

You can probably also lose the radiators.

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The TWR looks OK at 1.88 so it gets off the surface of Duna OK. 

I'd say the problems are down to all the junk you are carting about.

There's radiator panels, science experiments, RCS tanks and jets, air brakes, solar panels, docking ports, extra capsule, etc all contributing mass and drag. If you dumped most of that either entirely or before lifting off Duna then you'd almost certainly make orbit.

...

Now look what happened...

cInw7tR.png?1

I'll have to go and fetch the poor little green idiots. <sigh>

....

Yay, rescue finally arrived!

nhpcXpB.png?1

Edited by Foxster
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Hey, that looks like my screenshot :P

As some of you probably guessed, it was based on the LV-4 as made by Raptor9, in concept at least.

I thought It was stage so only the 4 man capsule goes up. I do have to rearrange the oscar tank attached to the descent module as they made the terrier of the upper stage get stuck.

5 hours ago, Aegolius13 said:

You're also probably getting a lot of drag from all those little tanks.  As I understand it, parts in cargo bays are only shielded if they're attached at the central node,  or attached to a part attached to the node.   So attaching to the cargo bay floor does not work. I would consider simplifying and just using 2.5m fuel tanks. 

The docking port at the front is also fairly draggy. Do you really need monopropellant and thrusters?  Is this thing docking with anything else?  If not,  that's dead weight and drag. Iso there a second heat shield at the very bottom?  Seems like you can cut that ashe well.  You can probably also cut a bit of ablation from the upper heat shield to save weight.

It was based on Von braun's STS-Mars, which in turn is based on Boeing's IMIS. The duna excursion Module will be at the tip end, which will be carried by Nuclear shuttle (1 in the case on STS, 3 stages in the case of Boeing). Upon arrival, the excursion module will detach (hence the docking port), then after using the de-orbitign pack, will enter Duna atmosphere (hence the bottom heatshield)  and land with the help of parachutes and Fuels. Departure from Mars surface involves just the upper stage, which I replicate by (looking over at Raptor9's LV-4) using a single terrier.

That being said, I can replace it with a covered dock, as it is suppose to be carried from Kerbin to Kerbin's orbit by a STS shuttle, and transfer with the help of space tugs.

The question I guess is: in the original IMIS on von Braun STS-Mars, does the Mars excursion module's ascent module double as Earth return vehicle? That's the reason for the upper heatshield.

Edited by Jestersage
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One quick fix for a lot of the drag issues might be to put a fairing around most of the ship (maybe closing to at the base of the command pod)  Those are supposed to be better about occluding drag from the objects inside.   But that might make it hard for your crew to get up and down on EVA.

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Also, do people just base a craft's performance on the pictures only? For all I know I may have hide some decouplers around

Anyway, can someone give me the figure to reach to Duna 100k orbit? According to the map I need 1810 for dv, but what about TWR?

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I based my comments on flying your craft on Duna. 

You want about 1750-1800 dV to make Duna orbit, depending on how efficient your lift is and the starting altitude. 

A launch TWR of about 1.3-2.0 should work OK. 

I did see you have a kind-of hidden stage in there. Using it meant dumping the science experiments so I wasn't sure if it was supposed to be used to reach orbit. It did have a problem in that the small tanks were too close to the engine and they became stuck to the engine, preventing proper separation of the spent stage. 

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9 hours ago, Jestersage said:

Also, do people just base a craft's performance on the pictures only? For all I know I may have hide some decouplers around

Anyway, can someone give me the figure to reach to Duna 100k orbit? According to the map I need 1810 for dv, but what about TWR?

Craft files usually works best, however not everyone have access to KSP while answering your question. (I would rather be playing if I had access to KSP rigth now). Pictures are a good starting point. However if there is something unusual or 'hidden' its up to you to point out. Posting pictures and good description its just 'good practice' that facilitate to get advice.

 

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10 hours ago, Foxster said:

I based my comments on flying your craft on Duna.

I did see you have a kind-of hidden stage in there. Using it meant dumping the science experiments so I wasn't sure if it was supposed to be used to reach orbit. It did have a problem in that the small tanks were too close to the engine and they became stuck to the engine, preventing proper separation of the spent stage. 

Sorry about the picture issue...

As for the results, they will be transfer to a recording container that I will add eventually. I have not even put the rover in the bottom bay yet!

And I am aware of the issue with the tanks making engine stuck, but thanks for the heads up.

I will sort through everyone's answer and select one as the best one. Thanks anyway.

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