Needing Suggestions!!! My attempt on EVE SSTO!

[SpaceFrog]

I have been working on this EVE SSTO for a couple of days. Exploring how aerodynamics work in EVE atmosphere has been a lot of trial and errors. So far, I can get to 12km above sea level using propellers, and from there I switch to the rocket engines. The best I got is about 77km (AP). I have successfully built several SSTOs for Kerbin and Laythe, but EVE is just on a completely different difficulty level. 

How can I perfect this prototype into an actual EVE SSTO? 

More dv? Alternative engine setup? Aerodynamics? Better gravity turn?

 

Drag seems to be a major problem the mk2 cargo bay can generate a lot of drag, but switching to service bay also generate quite the amount of drag too.

(Don't worry about the change in the center of mass, I have altered how fuel gets drained from each parts. The center of mass doesn't change until the last fuel tank starts draining.)

 

Nov 28 Update:

I done did it! Thanks to all your tips, I made it to the low Eve orbit. Scroll down to see the pics and download link 

Edited November 28, 2023 by SpaceFrog
Update on progress

[James Kerman]

Welcome to the forum @SpaceFrog! 

Your thread has been moved from KSP1 Discussion to KSP 1 Gameplay questions.

[miklkit]

MK2 parts are heavy and draggy but provide lift.  MK1 parts are lighter.  I'm not sure about those Big S tail fins.  The wiki says they have wing area but people on this forum say they provide no lift.  Have you heard of the trick of putting reversed nose cones on engines to reduce drag?  It works for the Darts, but I'm not sure about the other engine.

[DennisB]

I'm just in the design process of my first spaceplane, so I can't tell you anything about possible problems of the construction, just looking at your craft.

My suggestion is, if you don't suffer from instability or overheating issues, you could try it with more thrust, to leave the thicker part of the atmosphere faster. Instead of 1 Vecror + 2 Darts you could try 2 Vectors or 1 Vector + 2 Nutshells. With the last combination, you could probably switch off the Vector engine, once you are fast enough and high enough, because I think, the Nutshell has a higher isp, than the Vector engine. If it's still not enough, than you could try it with more dV too.

[SpaceFrog]

8 hours ago, miklkit said:

MK2 parts are heavy and draggy but provide lift.  MK1 parts are lighter.  I'm not sure about those Big S tail fins.  The wiki says they have wing area but people on this forum say they provide no lift.  Have you heard of the trick of putting reversed nose cones on engines to reduce drag?  It works for the Darts, but I'm not sure about the other engine.

Already doing the reverse cone thing to cover up the connection node! :-)

I also put one on the vector, you can kinda see the edge pooping out of the vector engine.

I think you are right about the mk2 parts. I went into debug mode, and they are the draggiest parts on this design, so they are definitely getting swapped out! I just had to try them, they are the most elegant parts in game, but I get is comes with a cost using them. I shall consider a different approach then possibly the all mk3 approach!

[SpaceFrog]

5 hours ago, DennisB said:

I'm just in the design process of my first spaceplane, so I can't tell you anything about possible problems of the construction, just looking at your craft.

My suggestion is, if you don't suffer from instability or overheating issues, you could try it with more thrust, to leave the thicker part of the atmosphere faster. Instead of 1 Vecror + 2 Darts you could try 2 Vectors or 1 Vector + 2 Nutshells. With the last combination, you could probably switch off the Vector engine, once you are fast enough and high enough, because I think, the Nutshell has a higher isp, than the Vector engine. If it's still not enough, than you could try it with more dV too.

Great insight, but the thing with EVE atmosphere and gravity is any attempt trying to add more dv makes the ship size grow exponentially. But I do feel that nuclear engines would help greatly toward the end of the burn.

[DennisB]

7 hours ago, SpaceFrog said:

But I do feel that nuclear engines would help greatly toward the end of the burn.

I don't think so. They don't have enough thrust to accelerate your vessel fast enough to benefit from them, especially, if you can't climb fast enough before (it's still an SSTO, with a higher dry mass, than a normal rocket). Or you would need many of them, which is no option, because of the high mass.

[SpaceFrog]

currently sitting at a total dv of 4200dv.

with the new angled wing design, reaching 90km is fairly easy. But the trajectory is still not optimal, I often end up needing another extra 800dv to circularize.

[miklkit]

21 hours ago, SpaceFrog said:

Already doing the reverse cone thing to cover up the connection node! :-)

I also put one on the vector, you can kinda see the edge pooping out of the vector engine.

I think you are right about the mk2 parts. I went into debug mode, and they are the draggiest parts on this design, so they are definitely getting swapped out! I just had to try them, they are the most elegant parts in game, but I get is comes with a cost using them. I shall consider a different approach then possibly the all mk3 approach!

That does not look like mine at all.  Here is a MK1 with Rapiers and Dart.  You can see the nose cones in the Rapiers and the shroud on the Dart.

[SpaceFrog]

Update on current progress

[Vanamonde]

Mind that the thrust from the LV-Ns is not blocked by the horizontal stabilizers. 

[SpaceFrog]

1 hour ago, Vanamonde said:

Mind that the thrust from the LV-Ns is not blocked by the horizontal stabilizers. 

the side view should clear the doubt on that!

none of them are actually horizontal hahaha

[miklkit]

I hate to be that guy, but when the nosecones are reversed properly those engines will have a shroud over them, and drag will be reduced.

[SpaceFrog]

Thanks everyone! I made it! After days of engineering and fine-tuning, I present you all the Akatsuki!

https://kerbalx.com/DLQ3987/EVE-SSTO-Akatsuki-with-tutorial

[Lt_Duckweed]

I'm honestly quite impressed you made it into orbit carrying so many Mk2 parts on your first Eve SSTO.  Bravo!

If you are looking to improve what it is able to take to orbit andor cut down on mass, I would recommend swapping those mk2 side stacks out for regular 1.25m tanks, and using 1.25m payload bays to hold your propellers instead of the cargo bays.  You will get the same amount of fuel storage for reduced dry mass and reduced drag.

I would also consider swapping from mk3 parts for the center stack to 3.75m parts, they tend to be a little lower drag as well thanks to having a better ratio of fuel mass to surface area.  They also have a little bit lower dry mass as well

I would also recommend seeing if you can replace the big s tails with smaller control surfaces to save a bit of mass.

With all those changes made you can see if you are able to then remove the aerospikes.  They have a lot worse twr than a vector, meaning more dry mass, so if you can get away without using them, it's generally a good idea.

All that said, great work!  Eve SSTOs are a beast to design, and ANY design that works is one to be proud of!

[SpaceFrog]

12 minutes ago, Lt_Duckweed said:

I'm honestly quite impressed you made it into orbit carrying so many Mk2 parts on your first Eve SSTO.  Bravo!

If you are looking to improve what it is able to take to orbit andor cut down on mass, I would recommend swapping those mk2 side stacks out for regular 1.25m tanks, and using 1.25m payload bays to hold your propellers instead of the cargo bays.  You will get the same amount of fuel storage for reduced dry mass and reduced drag.

I would also consider swapping from mk3 parts for the center stack to 3.75m parts, they tend to be a little lower drag as well thanks to having a better ratio of fuel mass to surface area.  They also have a little bit lower dry mass as well

I would also recommend seeing if you can replace the big s tails with smaller control surfaces to save a bit of mass.

With all those changes made you can see if you are able to then remove the aerospikes.  They have a lot worse twr than a vector, meaning more dry mass, so if you can get away without using them, it's generally a good idea.

All that said, great work!  Eve SSTOs are a beast to design, and ANY design that works is one to be proud of!

Thanks for the tips, Mk2 part are extremely draggy when placed horizontally, but I discover that the vertical placement reduce the drag  by a whole lot. I probably won't swap out any part on this SSTO. One reason is that "if it ain't broken, don't fix it", I also just love the aesthetics of the Mk2+ Mk3 part design. I generally have more fun piloting a craft that looks pretty too, and I am more than willing to accept the tradeoffs that come with using these parts. I get more enjoyment out of the process when I limit my self to only design crafts that are aesthetically pleasing. In the future, If I were to make a SSTO using Mammoth engine to carry ISRU components, I will definitely consider the 3.75 and 1.25 parts.  

Edited November 28, 2023 by SpaceFrog
missing a sentence