eve propeller test 1

[antipro]

hi, I'm trying to assembly a rocket that is able to launch in eve orbit an Mk1-3 Pod.
This prototype is currently able to reach an altitude of 18km with the electric engines, then a 90,90 orbit, even if with some difficulties.
So, I'm looking for some tips to modify it in a more efficient way.

Edited January 12 by antipro

[Blaarkies]

If you did that on Kerbin, you are looking at some +5000 m/s dv needed to do it at Eve. Because of the thick atmosphere, you can go pretty high before it thins out too much. I got a ducted fan launch close to 30 km altitude on Eve, and i'm sure a better design can go higher. The problem is that Mk1-3 Pod at the top. It is heavy, and heavy things are a luxury for any Eve launcher. If you are comfortable replacing that MK1-3 pod instead with 3 kerbal seats protected inside in a fairing, the mission becomes much simpler.

If you intend on getting that Mk1-3 pod up there, you should try a wider base (3m parts near the bottom) to get the necessary fuel or dry/wet mass ratio to improve the delta-v capability. It is also worth experimenting with more stages and less TWR, but you might have to make this rocket shorter to successfully land so that will be difficult.

Unless it is for aesthetics, you won't need such big fins at the bottom. Those propeller ducts are pretty light weight so the rocket should point nicely prograde.

[antipro]

13 minutes ago, Blaarkies said:

If you did that on Kerbin, you are looking at some +5000 m/s dv needed to do it at Eve.

I never tried it on kerbin, only from eve sea level.

 

14 minutes ago, Blaarkies said:

Because of the thick atmosphere, you can go pretty high before it thins out too much. I got a ducted fan launch close to 30 km altitude on Eve, and i'm sure a better design can go higher.

30km is very high, I've never reached such altitude, even with the pod only on top of the propellers.
How you did it? which electric engines and blades did you use?
 

 

17 minutes ago, Blaarkies said:

The problem is that Mk1-3 Pod at the top. It is heavy, and heavy things are a luxury for any Eve launcher. If you are comfortable replacing that MK1-3 pod instead with 3 kerbal seats protected inside in a fairing, the mission becomes much simpler.

well, if the mass is the main problem I think I can maybe replace it with an mk2 pod and smaller fuel engines. I'm going to try to modify it in a lighter way.

 

20 minutes ago, Blaarkies said:

If you intend on getting that Mk1-3 pod up there, you should try a wider base (3m parts near the bottom) to get the necessary fuel or dry/wet mass ratio to improve the delta-v capability. It is also worth experimenting with more stages and less TWR, but you might have to make this rocket shorter to successfully land so that will be difficult.

I'll try it but if with this rocket mass I can reach 18k only, if I add more mass won't it be worse?


 

24 minutes ago, Blaarkies said:

Unless it is for aesthetics, you won't need such big fins at the bottom. Those propeller ducts are pretty light weight so the rocket should point nicely prograde.

ok, I'll try to replace them with smaller ones. anyway I don't think it will change a lot regarding the max altitude reachable with the propellers.

[king of nowhere]

I doubt the fins at the bottom make any real difference. they are detached when the rocket detaches the helicopter blades. and while it's climbing as an helicopter, there is a full rocket to lift, and the weight of two big fins is mostly irrelevant.

 

So, the main mass reduction is to put three seats and a fairing instead of the pod, but that's not always possible.

Another small improvement, I discovered that the Mk 3 parachute is bad. It's 3 times heavier than the regular parachute, and it is NOT three times as effective. Using smaller parachutes would be more efficient. And discarding your parachute after landing on eve; if you have regular chutes, you can discard them with some eva construction if you bring all the crew to help. Unless you need those chutes to land back on kerbin.

the last stage (marked with 2 in the vab) looks a bit overpowered, twr >1 on eve is a lot for the orbital stage. So maybe you could shift fuel a bit, add some 20% fuel to it and remove some 600 m/s from the first stage; if you save enough mass this way, you may be able to get away with a smaller engine than the vector. but unlikely. if you have troubles getting in a 90x90 orbit, you may want to add 20% fuel to that last stage and leave everything else the same, the weight increase on the full rocket is very small so the helicopter part and the first stage should behave just the same, and you should gain some 300 m/s that will give you extra safety.

 

By the way, congratulations for giving detailed information. I don't think I've ever seen anyone asking for help include in the picture the twr of the various stages

[antipro]

49 minutes ago, king of nowhere said:

I doubt the fins at the bottom make any real difference. they are detached when the rocket detaches the helicopter blades. and while it's climbing as an helicopter, there is a full rocket to lift, and the weight of two big fins is mostly irrelevant.

in fact. and btw I just tried to replace them with smaller fins and the rocket became really unstable.
 

 

49 minutes ago, king of nowhere said:

the last stage (marked with 2 in the vab) looks a bit overpowered, twr >1 on eve is a lot for the orbital stage.
...

I just reduced the total mass from 50 to 30tons, using mk2 and smaller stages, even using only 2 ducted fans,
but I always reach the same max altitude, around 18k.
even in this video down below, which we all have already seen, he starts the fuel burn at 18k and by using smaller rotors/propellers.
How did @Blaarkies reached 30k? 30k is a lot more and it will save a lot of fuel compared to 18k.

So what is the max altitude reachable on eve with an electric engine system?

 

Edited January 12 by antipro

[Blaarkies]

1 hour ago, antipro said:

I just reduced the total mass from 50 to 30tons, using mk2 and smaller stages, even using only 2 ducted fans,
but I always reach the same max altitude, around 18k.
even in this video down below, which we all have already seen, he starts the fuel burn at 18k and by using smaller rotors/propellers.
How did @Blaarkies reached 30k? 30k is a lot more and it will save a lot of fuel compared to 18k.

So what is the max altitude reachable on eve with an electric engine system?

 

Sorry, please have a grain of salt with the 30 km altitude claim 

So it is definitely possible to go 30 km high on Eve with ducted fans:

Spoiler

But as can be seen this craft has almost no payload, and it probably lost lift by 29 km already (so 30 km was just the ballistic apex due to velocity). Realistically with a pod/payload, i would not aim for more than 25km. But looking closely at the video, i think that craft maybe still has some lift above 18 km?

What i did here was max out the props, and use a KAL-1000 controller. I'm not sure how well adept you are at the propellers in game, apologies if im just repeating stuff you already know, but here goes, this is what i use:

• The electric motors have a editor toggle for how many blades can be attached. I don't think KSP cares about too many blades in the same airstream (in real life this here probably has some bad side effects), so just max out the blades for now.
  • Blades can be set to have pitch/yaw/roll controls. I disabled them for this, they work better on helicopters with long blades
  • I gizmo moved the blades out from the moter a bit, hoping it helps
• Set the blades as "Deployed"
• Then we are going to use the "Deploy Angle" with the KAL-1000, so it transitions those between 0-14°
• Then connect the KAL controller to the main-throttle. Now we have smooth control over the pitch of the blades
  • Propeller pitch works a lot like higher/lower gears in a car. The faster you go, the more you should pitch those blades
  • But the current pitch should match the speed, else the blades stall (much like the car engine in 5th gear at a traffic light...but the stall reasons are way different of course )
• I added the motors' "Torque" value to the "Custom 1 Axis", which like like a secondary throttle for robotics things (there are actually 4 alternative throttle axis stuff in the settings)
  • When you launch, just max out those torque values. You can do it with these PAW windows as well if you prefer

Nothing much more to it, i just leave the RPM at max, and torque at max, and then keep the throttle(blade pitch) in line with the current speed. 

 

The last prop attempt for Eve I did used a lander that was like ~8t (or even less, but i would lie if i had to guess now). It only took a single kerbal up in a fairing chair and everything selected to be miniature. I think it was 4 stage? The last stage was an Ant engine, and the Kerbal did not have to use their jetpack.

The weight savings really made everything else soo much easier, even the Eve re-entry and landing was a breeze. Before props my best attempt got down to the 40ton range.

 

[18Watt]

I have launched the MK2 capsule from Eve with propellers.  I used 4 rotors, each with 6 (or was it 8?) fan blades.  I did not use the ducts, as I could not see any improvement by using them, just added weight.

I was able to reach about 17 km, but I really was happy at 15 km.  There is absolutely still atmosphere at 17 km, my design just wasn’t able to take advantage of it.

At 17 km I ditched the propellers, and a 2-stage LFO rocket took me to orbit.  Lower stage used a Vector engine, upper stage is a couple of sparks and just enough fuel to circularize above 90k.

This could be done with the Mk3 capsule as well.  However, keep in mind every extra kg of mass you try to lift from Eve will take hundreds or even thousands of extra kg to lift to orbit.

By the way, I needed fins during the climb to 17 km, the rocket was not even remotely stable enough without them.  The weight of fins is insignificant, especially if you stage them away when you light the chemical engines.

Getting a capsule (or really any useful payload) higher than 17 km is going to be very difficult.  I would look at that as diminishing returns.  15 km will allow you to get to orbit, anything higher is just icing on the cake.  Trying to get to 30 km begs the question, why?  You still need LFO engines,  your payload still needs to be small, and you still won’t have enough fuel to do much other that reach Eve orbit.

For me the hardest part of the Eve lander is getting it through the atmosphere without overheating.

[antipro]

Thanks all for the tips, I'll try with some other configurations.
About the settings of the blades I only assign the "change angle" to the main throttle and I regulate them by small throttle adjustments depending on the altitude,
not the speed, for example from 10km they need to be set up differently, with a lower angle.

only for fun and  to see what is the max reachable altitude I tried to push a small pod using low energy rotors and medium blades, it had reached 40k.
Like @18Watt said, I noticed is almost impossible to pass the 18k limit with a useful payload.

Edited January 12 by antipro

[Lt_Duckweed]

6 hours ago, antipro said:

Thanks all for the tips, I'll try with some other configurations.
About the settings of the blades I only assign the "change angle" to the main throttle and I regulate them by small throttle adjustments depending on the altitude,
not the speed, for example from 10km they need to be set up differently, with a lower angle.

only for fun and  to see what is the max reachable altitude I tried to push a small pod using low energy rotors and medium blades, it had reached 40k.
Like @18Watt said, I noticed is almost impossible to pass the 18k limit with a useful payload.

If you look carefully in your screenshot, it says in the top middle of the screen "physics easing in progress".  This means the crat does not weigh the full amount, as it was trying to ease the physics as you landed, but presumably you never touched the ground.

[antipro]

10 hours ago, Lt_Duckweed said:

presumably you never touched the ground.

thank you  for noticing, yes, you're right, I used the "set position" tool starting from 16k or so, in order to save time and batteries but forgetting to remove the "ease to ground".
in fact, the max correct altitude with that test pod is only around 24k and even with the biggest rotors/blades the max is the 30k limit.

Edited January 13 by antipro

[camacju]

For once I actually have some Eve-related expertise that may help with this.

It turns out that the tiny basic fins actually make quite good propeller blades. I recently did an ultra low mass Eve mission where the Eve lander uses a propeller to ascend out of the thick part of the atmosphere. A ducted fan prop could only get me to 22 km, while a basic fin prop (weighing less than the ducted fan) was actually able to climb all the way to 35.1 km.

The same propeller with no extra payload can go even further.

 

Edited January 15 by camacju

[Blaarkies]

That's insane, what is the equivalent 35 km pressure-altitude for Kerbin? (Trying to figure out how thin of an atmosphere these fins can use)

How do you handle the pitch angle on those, do you just place a static angle on the fins and then vary the RPM limiter?

[antipro]

nice altitude @camacju, new record! anyway we are talking about a non-ordinary assembly, with intersected floating parts attached in the vacuum.
On Youtube I've seen a big ship assembled more less the same way using shields as propellers, capable of reaching hi-horizontal speed and the orbit.
This is not my way of building rockets, but anyway interesting.
For my test I've added an extra stage which let me to reach 120km eq orbit with an MK1-3 Pod.

edit: I can't figure out what are those 3 for fin, kind of pins/pivots/screws, I know they have a specific name but can't remember at the moment,
anyway I've never see them before.

Edited January 15 by antipro

[camacju]

11 hours ago, Blaarkies said:

That's insane, what is the equivalent 35 km pressure-altitude for Kerbin? (Trying to figure out how thin of an atmosphere these fins can use)

From AeroGUI you can see that static pressure is 809 Pascals. Since Eve gravity is higher than Kerbin gravity, it's likely that the min pressure is even lower on Kerbin. I haven't actually tested this assembly on Kerbin though.

11 hours ago, Blaarkies said:

How do you handle the pitch angle on those, do you just place a static angle on the fins and then vary the RPM limiter?

It's even simpler than that, I place a static angle on the fins and keep the RPM limiter on 100% the entire ascent.

By the way, here is the altitude this same craft reaches with a useful payload. This upper stage rocket can actually bring a kerbal all the way into Eve orbit with most of his jetpack to spare.