[Old Thread] KRE - Kerbal Reusability Expansion

[EmbersArc]

6 hours ago, Delta_8930 said:

The thrust from the superdraco engines is asymmetric and always want to make the vehicle curve north immediately after launching when placed with 4x symmetry. In orbit, when I try to burn prograde, the ship always wants to curve. Is there a solution to this problem?

You're using Ven's right?

The problem is the capsule's offset center of mass. Here are some ways around it:

• Use 2 engines in 2-way symmetry
• Use 3 engines in 3-way symmetry
• Use no symmetry and adjust the thrust for each engine to balance your capsule
• Edit the mk1-2's config to move the CoM
• Don't use Ven's mk1-2 capsule (The texture from KSPRC looks great too without changing anything else)

 

[Benji13]

Looks nice. Looking forward to using this in my new career save once 1.2 drops. 

[Delta_8930]

2 hours ago, svendii said:

You're using Ven's right?

The problem is the capsule's offset center of mass. Here are some ways around it:

• Use 2 engines in 2-way symmetry
• Use 3 engines in 3-way symmetry
• Use no symmetry and adjust the thrust for each engine to balance your capsule
• Edit the mk1-2's config to move the CoM
• Don't use Ven's mk1-2 capsule (The texture from KSPRC looks great too without changing anything else)

 

How do you move the CoM in the cfg file? (sorry I am a noob to all of this)

[EmbersArc]

7 minutes ago, Delta_8930 said:

How do you move the CoM in the cfg file? (sorry I am a noob to all of this)

Open Command.cfg in VenStockRevmap/Squad/Parts. The first patch is the one for the Mark1-2Pod. There change the CoMOffset to 0, 0, 0 and save the file.

[Palaceviking]

12 hours ago, CobaltWolf said:

Well it is a LAS...

?

[Senior Slaphead]

I've been looking again at reusable launch vehicles and - within the limitations of my current career tech - have come up with a new craft that uses parts from this mod.  So I have some observations specific to my particular experience that you may like to consider.

For a while I experimented with using two stages and returning the first one directly to the launchpad.  This provides 100% reusability (or rather 80% once the lost fuel is taken into account).  But it means flying two craft, using Flight Manager for Reusable Stages (or Dark Multiplayer in my case). If you want to return the second stage, then you're talking about much higher velocities, landing on the next continent (and therefore getting less funds back) or doing a full orbit to the KSC and coming in really fast.

Then I realised I was doing it wrong.  Most of the value is in the engines and the various whistles and bells on the rocket core.  If you can get all the engines back anyway then the logical thing is to combine the first and second stages, go large on the engines and use drop tanks. In reusability terms you lose about 10% at most, but you save yourself lots of time and effort. I hope you are listening, Elon...

Once you are at orbital velocity you cannot come in engines first and therefore have to come in head first, using a heat shield.  To do this you need weight (fuel) pumped forward to balance out the weight of the engines. If your engines are heavy this requires a lot of fuel... more than you need for a propulsive landing.  The logical thing therefore is to add some aerodynamic control (gridfins) to the back on the craft to keep it pointing in the right direction.

So... what I don't like is the extent of the drag on the grid fins (which is the reason why I do not use stock airbreaks, which are just ridiculously overpowered).  I think grid fins should provide good control (so you can fight against the flipping) but less drag.  Is this possible?  As you can see from the vid we're actually only talking about a short perilous period where the weight distribution is fighting against the aerodynamics.  Hey look! Gameplay!

I should point out that I'm not moving to 1.2 until the majority of my many mods are playing nice, so if you've changed something for 1.2 I've probably missed it.

 

 

Edited October 8, 2016 by Senior Slaphead

[EmbersArc]

@Senior Slaphead thanks for sharing the mission, I really like the approach.

On 10/8/2016 at 7:57 PM, Senior Slaphead said:

So... what I don't like is the extent of the drag on the grid fins (which is the reason why I do not use stock airbreaks, which are just ridiculously overpowered).  I think grid fins should provide good control (so you can fight against the flipping) but less drag.  Is this possible?  As you can see from the vid we're actually only talking about a short perilous period where the weight distribution is fighting against the aerodynamics.  Hey look! Gameplay!

Personally I think the amount of drag is fine. Landing stages is hard enough as it is and increasing the terminal velocity doesn't help with that. Of course I could remove the drag but not as long as that would make the stock airbrakes a better choice for landing stages.. 
Now the control of the grid fins (or any kind of control surface) increases the further back they are placed on a long stage. On a normal first stage that makes for more than enough control. I found that increasing it would make them too strong and lead to all kinds of funky behavior. So they're not really made for a short stage high up in the atmosphere.
If you want to decrease the drag anyway, there is a commented line for the drag cube A in the grid fin configs. That's the real drag the fins would provide. Remove the // from those and add them to the next line.

[EmbersArc]

Something I'm working on:

You know you've made many landing legs when it only takes five minutes of banging your head against a wall until it works.

 

[Senior Slaphead]

Having done more landings now the drag is not as excessive as I first thought, I think there were other factors at play in the other vid. You can see from the Trajectories mod here how much difference they make. With practice it's easy enough to estimate how far short you will land and deliberately plot a course that's going to overshoot a bit. I'm also going to try using the small gridfins rather than medium which might be just enough.

 

[Senior Slaphead]

I've noticed that sometimes I get a twisting motion on craft landed on your legs (not just on the launchpad).  Is this a known or stock problem?  I've only seen it on Kerbin, my various craft landed on Minmus are fine.  It's a very minor thing and might easily be related to another mod, but I thought I'd mention it.  Full modlist in the video description.

 

Edited October 12, 2016 by Senior Slaphead

[Senior Slaphead]

Full process from launch, to deployment, to return.  The trajectory was perfect but I choked and flipped it a moment too soon.  Hey, I got it on the green in one... so I think I'm under par for the course.  With a lot of pilot input the small gridfins were just enough to keep things under control while inflicting minimal drag.

 

[Ali_Army107]

I did download this but I didn't find the landing legs

I was using it on KSP 1.2 pre-release.

4 hours ago, Senior Slaphead said:

Full process from launch, to deployment, to return.  The trajectory was perfect but I choked and flipped it a moment too soon.  Hey, I got it on the green in one... so I think I'm under par for the course.  With a lot of pilot input the small gridfins were just enough to keep things under control while inflicting minimal drag.

 

nice

[Giuliano]

Hi, im an user of your mod, and im playing 1.2. After saw you update with ITS, I have two suggestions:

1-More sizes for ITS landing Legs.

2-Make a New Shepard Landing Leg (one that i want in your mod).

 

[EmbersArc]

On 10/11/2016 at 10:19 PM, Senior Slaphead said:

I've noticed that sometimes I get a twisting motion on craft landed on your legs (not just on the launchpad).  Is this a known or stock problem?  I've only seen it on Kerbin, my various craft landed on Minmus are fine.  It's a very minor thing and might easily be related to another mod, but I thought I'd mention it.  Full modlist in the video description.

I haven't seen this before. Might be a version of "landers walking up a hill" which is supposed to be fixed.

The legs are still "Newtonian nonsense" but it's not that bad anymore in 1.2. Maybe try it there.

 

5 hours ago, Senior Slaphead said:

Full process from launch, to deployment, to return.  The trajectory was perfect but I choked and flipped it a moment too soon.  Hey, I got it on the green in one... so I think I'm under par for the course.  With a lot of pilot input the small gridfins were just enough to keep things under control while inflicting minimal drag.

I like that.

 

55 minutes ago, Ali_Army107 said:

I did download this but I didn't find the landing legs

I was using it on KSP 1.2 pre-release.

Could you provide some more information? Does it show no parts at all? Maybe try CKAN for the installation.

 

2 minutes ago, Giuliano said:

Hi, im an user of your mod, and im playing 1.2. After saw you update with ITS, I have two suggestions:

1-More sizes for ITS landing Legs.

I will probably make two sizes of the ITS legs, not sure how big they will end up being.

 

3 minutes ago, Giuliano said:

2-Make a New Shepard Landing Leg (one that i want in your mod).

Maybe when I get bored but I can't tell you when that will happen. 

[EmbersArc]

Update 2.0.3

• Adjusted mass, cost, etc.
• Added sound to landing legs
• Added WIP version of ITS landing legs (check .zip folder)

Download also available on SpaceDock now.

Note that this will move the position of the landing legs on existing craft from 1.1.3 (Sorry about that, happened when I redid the setup.)
Black variant of landing legs hidden. Use FirespitterCore to change leg color.
Craft from the 1.2 prerelease will not be changed.

[Ali_Army107]

54 minutes ago, svendii said:

I haven't seen this before. Might be a version of "landers walking up a hill" which is supposed to be fixed.

The legs are still "Newtonian nonsense" but it's not that bad anymore in 1.2. Maybe try it there.

 

I like that.

 

Could you provide some more information? Does it show no parts at all? Maybe try CKAN for the installation.

 

I will probably make two sizes of the ITS legs, not sure how big they will end up being.

 

Maybe when I get bored but I can't tell you when that will happen. 

I use Mac book any the only thing I can't get are landing legs and the Engines. the rest are fine for me.

I tried installing it twice but same result.

 

[nosirrbro]

Oh man I really needed this, I hated having to throw out my Kerbals after a single use. Just so wasteful

 

Wait, you mean that kind of re-useability? Oh!

Edited October 13, 2016 by nosirrbro

[bmyers831]

I just tried this with 1.2 for the first time and quickly noticed something that must be a bug.... but as a first time user let me know if I'm just suffering from Noob's syndrome.

I think both Glenn Leg Mounts are missing their top and bottom attachment nodes?  I'm not seeing any appear anywhere...

Bryan

[EmbersArc]

3 hours ago, bmyers831 said:

I just tried this with 1.2 for the first time and quickly noticed something that must be a bug.... but as a first time user let me know if I'm just suffering from Noob's syndrome.

I think both Glenn Leg Mounts are missing their top and bottom attachment nodes?  I'm not seeing any appear anywhere...

Bryan

Hey Bryan, it's meant to be surface attached because it gives more flexibility and doesn't block the node.

[EmbersArc]

Update 2.0.4

• Fixed offset behavior of Falcon legs
• Increased strength of Falcon legs to allow for heavier lander designs like this one:

Sorry to everyone who flew across half the solar system to have their legs explode on landing 

 

[bmyers831]

5 hours ago, svendii said:

Hey Bryan, it's meant to be surface attached because it gives more flexibility and doesn't block the node.

And we have a winner!  Thanks Svendii!

The first time I tried I had the engine attached to the bottom of the tank and no knowing it was intended to be surface attached, the engine shape was giving it fits.  Once I removed that and used the smooth tank surface it worked perfectly.  Nice mod =)

[ionn]

Awesome!! Thanks!

[Senior Slaphead]

A much more expensive reusable first stage (due to the vector engines) returns to the KSC at orbital speed. Although of course, it doesn't matter how expensive it is if you are getting the pricey components back. The slight sideslip prior to deploying the gridfins is what put me the other side of the runway... just as well really.

There are very marginal benefits to having this engine configuration. It can deliver about 25t to LKO without mishap, rather than 23t with the previous launcher. I do have a more powerful vessel available in my career but it has not proved necessary yet.

On 16/10/2016 at 11:28 AM, svendii said:

Hey Bryan, it's meant to be surface attached because it gives more flexibility and doesn't block the node.

Make this thy mantra!

[EmbersArc]

Texturing on the legs is done:

Last chance to make suggestions for improvements!

One problem has come up though:

Somehow certain landers start oscillating. On this one it only happens when the upper tank is empty and the center of mass is low.
Changing the damping or spring ratio on the legs doesn't change anything. It's not the SAS. My guess is that it happens when the CoM is underneath the vector of the reaction force from the legs. The only difference of those legs to the stock LT-2 is the deployment angle. With the LT-2 it's fine no matter where the CoM is

Does anyone have an idea how to avoid that? I'm at a loss..

 

 

 

[Senior Slaphead]

40 minutes ago, svendii said:

One problem has come up though:

Somehow certain landers start oscillating. On this one it only happens when the upper tank is empty and the center of mass is low.
Changing the damping or spring ratio on the legs doesn't change anything. It's not the SAS. My guess is that it happens when the CoM is underneath the vector of the reaction force from the legs. The only difference of those legs to the stock LT-2 is the deployment angle. With the LT-2 it's fine no matter where the CoM is

Does anyone have an idea how to avoid that? I'm at a loss..

 

@svendii this looks similar to the phantom torque issue I mentioned earlier.  That it's related to the CoM would make sense in that I never get the issue on fully loaded rockets held up by legs on the launchpad... it's always been when I've landed after expending most or all of the fuel weight, or when testing something with empty tanks on the launchpad.