[Old Thread] KRE - Kerbal Reusability Expansion

[Rhedd]

All of these parts are 100% awesome! Thanks!

I would love to see one "simple" addition. Do you think we could get a docking port like yours without the nosecone cover? I'd love to have one that matched the style for mounting on space stations, etc.

[EmbersArc]

I've spent some more time on the textures to (hopefully) make them more stockalike:

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The oscillation problem with the ITS legs is fixed. Apparently the attachment node was too high up. I mean obviously it had to be something like that.. 

On 10/21/2016 at 5:25 PM, Senior Slaphead said:

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. 

I've observed that on those legs too, but it's not that strong. Did you test it in 1.2?

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On 10/26/2016 at 4:59 AM, Rhedd said:

I would love to see one "simple" addition. Do you think we could get a docking port like yours without the nosecone cover? I'd love to have one that matched the style for mounting on space stations, etc.

I really don't know about that one. The focus should be on reusability and that might be a bit too far away from that. The IDA port on the station is actually quite different from the one on the Dragon. It's not even that different from the stock docking port in my opinion.

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Version 2.1 will be out soon. One question before that though: The medium sized ITS legs are currently a bit bigger than the small Falcon legs. Would you also like to see a smaller version or a larger one? Or maybe both?

Edited October 27, 2016 by svendii

[Deimos Rast]

holy cow you've really grown this mod since I last checked in here. Everything looks great!
Now I just have to build rockets worth reusing, haha.

Keep  up the good work.

As for your question: which are the ITS legs? The one on the left, correct? I haven't used them in game, but looking at their profile in the picture, I'd assume they fold down similarly to the Falcon legs - and if they're the same size, then you have unnecessary overlap. Not saying you can't have that, just might make more sense to make them more unique. I guess I would vote larger, as they seem - visually - like they could handle more weight.

But like I said, I'm not terribly familiar with their real world counterparts, and I have yet to try them in game; I'm just giving you a generic opinion, take it or leave it.

I really like all of what I see though!

[EmbersArc]

<< different name, different picture, same guy 

Update 2.1

• Added landing legs based on the SpaceX ITS concept (large and very large variants)
• Adjusted textures of New Glenn and Falcon Legs
• Updated heat shield config and model
• Added a bit of drag to grid fins in stowed position and to SuperDracos

 

[EmbersArc]

Also, does anyone else have this bug:

After reloading and deploying the legs their rotation is off by 90°. It also happens with the stock legs and has been around for quite a while. It surprisingly doesn't seem to be in the bug tracker though so I'll report it later.

Edited November 3, 2016 by EmbersArc

[CobaltWolf]

Oh snap I didn't catch that it was you. I thought you'd died.

[mostlydave]

On 10/25/2016 at 10:59 PM, Rhedd said:

All of these parts are 100% awesome! Thanks!

I would love to see one "simple" addition. Do you think we could get a docking port like yours without the nosecone cover? I'd love to have one that matched the style for mounting on space stations, etc.

Yeah, this would be great!

[EmbersArc]

5 hours ago, CobaltWolf said:

Oh snap I didn't catch that it was you. I thought you'd died.

Which is the logical conclusion I get it, but all fine here.

Call off my funeral though.

[CobaltWolf]

Just now, EmbersArc said:

Which is the logical conclusion I get it, but all fine here.

Call off my funeral though.

But I already made a casserole to leave at the house...

[Enorats]

So, I played around with this mod a bit and really like it. I want to use it on every bloody craft I make, but I just.. can't. I can't bring myself to include so much extra weight. I play with a mk1-2 pod that has been slightly reduced in weight so that it is just barely below the mk1 pod's weight times 3, the idea being that increasing the volume of an object actually only increases its surface area by a lesser proportion and that the larger pod should have a more efficient crew/pod mass ratio than the smaller one.

Switching to the propulsive landing equipment (from simple parachutes, typically 4 radial ones) increases the weight of the craft by a whopping 57 percent! I've been trying to think of a way I could modify the numbers to allow me to reasonably justify using this over parachutes (aside from the simple cool factor, which is considerable), but I just can't come up with a way.

Looking over what I could find for the superdraco's real world specs, you seem to have matched them fairly well. The thrust is a wee bit lower in the real world, and the burn time is about half as long (at full thrust). No clue on propellant flow rates or the mass of the engine itself, but the mass of the entire craft isn't too terribly far off from reality using KSP's stock numbers (the real one is a good half ton or so lighter). The delta-v is around 600-630 m/s, which seems to be fairly similar to reality (real one stops in ~3 seconds from terminal at full thrust, which is about half the total burn time it can manage). So.. it all looks "real".

The problem, so far as I can figure.. is that KSP just isn't real. In the stock game, things are 1/10th scale.. so it takes far less delta-v to get places, so rockets are far smaller. Normally that is true all around, so it doesn't matter at all in the end. This isn't true of a propulsive landing system though. Because terminal velocity is nearly the same (or possibly even higher I think) on Kerbin as it is on Earth, it's going to take the same delta-v to land in the 1/10th scale KSP as it does in reality. Thus, you're going to be lugging around a propulsive landing system that is roughly 10 times "more" than it really should be if it scaled at an equal level to the rest of the rocket.

So.. what can be done to make this work "equally" to how it does in reality? I could make them ultra-efficient so that they use less fuel, then make the fuel pod carry far less fuel so that the overall mass of the system is more representative of the ratio of superdraco system mass / falcon 9 mass.. but then they'd be massively overpowered with other tanks. Stick a couple of these on a stock fuel tank and you're going god mode. I suppose I could make them have a super high atmospheric isp so that they're only ultra efficient during the landing phase, which I'd be a bit less likely to.. er, abuse.. but then they'd be useless on non-atmospheric bodies. Red Dragon would be.. fail. I honestly just can't come up with a way to make them able to pump out enough delta-v to land on while also significantly lowering the weight to make them more "stockish" without making them utterly overpowered in all other aspects. Anyone have any ideas?

[EmbersArc]

Thanks to @Enorats I just learned a thing or two about my own mod .
I normally use it to get to a 100km orbit and circularising after decoupling the second stage which reenters the atmosphere. Mostly RCS fuel is used for orbital adjustments and getting to the station. The Dracos are then used for deorbit which leaves about 1/2 to 2/3 of the fuel for a landing. You're right that the margins are somewhat tight but I found it to work quite well. The high TWR gives the ability to do the suicide burn very late and minimise gravity losses. KER gives you a readout when to start your burn.
That's about all it's meant to do. Get to a station with a trunk and some cargo/crew and then come back for a cool landing. I remember the Crew Dragon having about 400 m/s of deltaV. So in the game you have 50% more than in reality.
Can you explain how you use the Dragon?

[PickledTripod]

You need a third of your fuel for deorditing?! Dude what do you think heatshields are for, you're supposed to aerobrake. From the side of the planet exactly opposite to KSC burn retrograde to lower your periapsis to ~30000 to 35000m above the surface. It takes about 60 m/s from 125km orbit then the atmosphere will do the rest. To precisely land at KSC without using more fuel just change your angle of attack to alter your trajectory, with some practice it's doable even without a mod like Trajectories. (I play in FAR though, not sure if body lift is possible in stock aero.)

With that you have enough fuel to perform your suicide burn at only 50% thrust and keep acceleration to a comfortable 3.5Gs, with a ~100 m/s of extra fuel at sea level.

[EmbersArc]

11 minutes ago, PickledTripod said:

You need a third of your fuel for deorditing?!

Dude no. For circularisation, orbital maneuvers and deorbiting.

12 minutes ago, PickledTripod said:

From the side of the planet exactly opposite to KSC burn retrograde to lower your periapsis to ~30000 to 35000m above the surface.

I do that.

13 minutes ago, PickledTripod said:

To precisely land at KSC without using more fuel just change your angle of attack to alter your trajectory, with some practice it's doable even without a mod like Trajectories.

And that.

13 minutes ago, PickledTripod said:

(I play in FAR though, not sure if body lift is possible in stock aero.)

It is, but FAR gives way more control.

14 minutes ago, PickledTripod said:

With that you have enough fuel to perform your suicide burn at only 50% thrust and keep acceleration to a comfortable 3.5Gs, with a ~100 m/s of extra fuel at sea level.

Yep. Suicide burn only if really necessary.

[PickledTripod]

Oh that's the part I missed, you circularize on the Dracos. I either read too fast or just dismissed it subconsciously because it seems so weird to me . Sorry if it seemed condescending.

I just put a probe core on the upper stage so I can achieve full orbit before separating and deorbiting it, then I rendezvous with my space station using only RCS (having launched as close as possible it doesn't take a lot of monoprop.) Margins would indeed be pretty thight if I used any SuperDraco fuel for these maneuvers.

[EmbersArc]

27 minutes ago, PickledTripod said:

Oh that's the part I missed, you circularize on the Dracos. I either read too fast or just dismissed it subconsciously because it seems so weird to me . Sorry if it seemed condescending.

I just put a probe core on the upper stage so I can achieve full orbit before separating and deorbiting it, then I rendezvous with my space station using only RCS (having launched as close as possible it doesn't take a lot of monoprop.) Margins would indeed be pretty thight if I used any SuperDraco fuel for these maneuvers.

No worries. It's certainly possible to save fuel in many different ways. It really depends on the sloppiness of the launch and how quickly you want to get there. The 1/2 to 1/3 estimate is probably for an inefficient launch and rendezvous. Just wanted to say that it can be done even with plenty of room for error, just as long as you're not trying to get to the moon and back with it.

[Enorats]

Hmm. Using about half the fuel for orbital maneuvers and the like would make them significantly less of a burden compared to using them solely for the final landing. I typically use the upper stage engines and leftover fuel for those sorts of maneuvers. By ditching the upper stage and using these you're left with a more efficient spacecraft once in orbit at the cost of a less efficient launch.

Now that I consider it though, the launch vehicle I've used prior getting this mod would work very well with this. It's effectively a falcon 9 like design, except the main booster goes all the way to orbit before turning around and landing in the water (stock legs are crap, and that extra 3% or recovery just isn't  worth it)  just offshore of KSC with a few chutes and 1 of its 9 vector engines softening the splashdown. Pairing it with a Dragon V2-like craft would give a nearly entirely reusable LKO crew transport with around 400 delta-v and enough leftover for a powered landing. That might be a good use for this tech.

[PickledTripod]

@Enorats I'm really confused reading your posts again... At first I thought you were saying that you don't get enough delta-v for landing with your Dragon-alike capsule even with a reduced weight Mk1-2 pod, but you said yourself that you get about 600 m/s which is the same I get, and now you say that you're not using the capsule's fuel for circularization and orbital maneuvers. Can you post a picture of your craft and launcher, and tell us in detail what you're trying to do with them?

[Enorats]

Ah, sorry. With the stock parts I manage a good 600-630 delta-v, which is several times what is needed for landing. No issues there. With my modified pod it's slightly higher, again no issues.

The issue I'm seeing is that propulsive landing in general seems useless in KSP due to the delta-v required for landing (what's needed to cancel terminal velocity) not going down to 10% of reality like everything else in game does. The result is that the mass of a propulsive landing system in KSP is disproportionately high compared to similar systems in reality, making them rather silly to use over simple parachute systems. As I said, using these parts increases the weight of my "payload" for a simple crew delivery mission by a whopping 57%.

I've tried to come up with a way to change the numbers to make them work better, but just can't come up with a way to do so without making them utterly overpowered in the parts of the game that do scale normally (everything other than landing basically).

[PickledTripod]

Oh I see. The reason why it's so disproportionate is that planets and moons in KSP have the same surface gravity and pressure as their real-life counterparts. They would have to scale proportionally to the size to allow crafts to be proportionned the same way as IRL.

Personally I don't mind these differences between KSP and real life, if anything it forces you to be creative instead of just building straight replicas and expecting them to work. My Falcon-alike can launch my Dragon-alike and return the first stage to KSC just like Falcon 9 IRL so I'm happy.

[Enorats]

Exactly. The landing velocities don't scale appropriately, else Kerbin would have super low gravity and the game wouldn't work.

It'd be interesting to try this in RO, as it'd probably work perfectly there since it's already so close to reality. Never really cared for RSS/RO though, so I wish I could just find a way to make this a viable alternative to parachutes. Maybe dropping the mass of the engines down to match the stock radials (.09 instead of .25), increase their ISP, but drop the fuel in the tank down and lower their thrust to something more similar to the stock radials (20-30 each). That'd lower the overall mass of the system significantly, without altering the TWR of the vessel too much.. I'd just be wary of making them better than something like the LV-909 efficiency wise, though I don't want them to be miles behind either or I'll never use them. Hmm.

[AmpCat]

To make this more like real-life, I'd agree. Rather than matching weights and whatnot to real life, you want to match thrust-to-weight ratios and things like that. In real life, they also only need to fire for a very short time (5 seconds?) to stop the vessel.

So basically, design the thrust and weights and fuel for the engine to stop your pod from an orbital fall, in 5 seconds, given the ISP of 240. May have to end up tweaking ISP or something to make it work.

Edited November 3, 2016 by AmpCat

[Enorats]

That's more or less where it's at now, though it has several times the delta-v (and thus like triple the fuel) that it really needs at a minimum. The problem is that the landing IS realistic while the rest of the game isn't. Making the engine powerful enough to work realistically while not being super OP in the unrealisitic section (or super overweight due to its realistic-ness) is.. difficult.

Might just have to settle for it being super OP (aka Vector) but super expensive to compensate.

[AmpCat]

Yeah, you're kinda stuck with weights of fuel and your pod, so just making the engine have a huge thrust won't necessarily work. And you can't make the engines weigh less than zero, so you probably more or less get stuck with making the ISP higher.

[FrancisDillinger]

Hey I was thinking of suggesting the addition of rcs pods for the 1st stage to this mod. It's a part I always struggle with and end up using parts from other mods. Do you have any plans for adding these?

Falcon 9 cold gas thrusters

[EmbersArc]

13 hours ago, Enorats said:

Exactly. The landing velocities don't scale appropriately, else Kerbin would have super low gravity and the game wouldn't work.

It'd be interesting to try this in RO, as it'd probably work perfectly there since it's already so close to reality. Never really cared for RSS/RO though, so I wish I could just find a way to make this a viable alternative to parachutes. Maybe dropping the mass of the engines down to match the stock radials (.09 instead of .25), increase their ISP, but drop the fuel in the tank down and lower their thrust to something more similar to the stock radials (20-30 each). That'd lower the overall mass of the system significantly, without altering the TWR of the vessel too much.. I'd just be wary of making them better than something like the LV-909 efficiency wise, though I don't want them to be miles behind either or I'll never use them. Hmm.

I guess your basic misconception is that propulsive landing in KSP makes financial sense. It doesn't. In reality you do it to keep that corrosive salt water from touching your spacecraft and also to avoid landing out in the desert somewhere. The Crew Dragon will have parachutes for emergencies as well. KSP doesn't care about the water and you can land close to the space center even with parachutes. It's really for style and to give an additional challenge. If that's not your thing then you can just use parachutes instead.