An analysis of engine performances on Eve

[KincaidFrankMF]

Just saw your Eve SSTO vid @astrobond - that's incredible! Would never have thought that was possible. Wonder if you'd be interested in this? 

So far one brave soul's posted a brilliant, enormously complicated solution (I'm in awe), but no one's yet figured out the simpler way of doing it  (Still tricky, but doable.)

 

[herbal space program]

17 minutes ago, KincaidFrankMF said:

So far one brave soul's posted a brilliant, enormously complicated solution (I'm in awe), but no one's yet figured out the simpler way of doing it  (Still tricky, but doable.)

If this is in KSP1, and robotics are allowed, and a propeller plane isn't too much like a rover in your book, I think I built a craft at one time that could do this pretty easily. Alas that KSP1 installation went the way of the wind when I gave the associated Steam account to my son. Propellers really changed the whole game on Eve, since you could fly around with them pretty much indefinitely, and designing a craft that could fly up to 20km and then stage all the wings/props off to fly to orbit was pretty easy to do.

[KincaidFrankMF]

8 minutes ago, herbal space program said:

Propellers really changed the whole game on Eve, since you could fly around with them pretty much indefinitely, and designing a craft that could fly up to 20km and then stage all the wings/props off to fly to orbit was pretty easy to do.

Yeah, you've got it  I was surprised no one posted the solution, but maybe more experienced players aren't looking for challenges as much as the newer ones. Did you see that one craft that got posted though? That is a beast.

[astrobond]

52 minutes ago, KincaidFrankMF said:

Just saw your Eve SSTO vid @astrobond - that's incredible! Would never have thought that was possible. Wonder if you'd be interested in this? 

So far one brave soul's posted a brilliant, enormously complicated solution (I'm in awe), but no one's yet figured out the simpler way of doing it  (Still tricky, but doable.)

 

Thank You  That was a long time ago lol, I made some tries on KSP2 for a SSTO from Olympus Mons on Eve, but from 3000m, that's really hard... not found a solution for now... but i will try with darts on first part ascent xD

Your challenge is excellent !!! I only play KSP2 now, but maybe i will try

[herbal space program]

16 hours ago, KincaidFrankMF said:

Yeah, you've got it  I was surprised no one posted the solution, but maybe more experienced players aren't looking for challenges as much as the newer ones. Did you see that one craft that got posted though? That is a beast.

I'll take a look! The ship I was talking about is sadly gone, but there is still a pic of it on my Imgur account:

 

...So I went and took a look, and that ship is indeed a beast! It's too bad the person never figured out a plane that could land from orbit on Eve.  That makes the whole thing much easier! And it didn't really seem so hard either.  Other than not mounting anything too heat-sensitive on the bottom, I don't recall that I had to do anything special to make it work. The way you can use wings to dissipate speed in KSP1 by turning it into lift rather than heat seems almost like a cheat, but I was only too happy to take advantage of it. I saw also that you apparently had problems with the robotic drift bug affecting your plane.  So did I! If you look closely at the pic above, you can see that my props are at an odd angle, pointing somewhat downwards instead of straight ahead. That is not how I built that plane, but that's how it ended up after I landed, and nothing my onboard engineer could do seemed to be able to correct it.  In the end, I had to make most of my flight back to 20km upside down!

Edited April 5 by herbal space program

[KincaidFrankMF]

21 hours ago, herbal space program said:

I'll take a look! The ship I was talking about is sadly gone, but there is still a pic of it on my Imgur account:

Funny how different your design is, given we took basically the same approach! Here's mine -

I went for a seaplane with fan drives (heavy but fast). The rear cockpit allows access to the science bay, it has another one up front.

As you can see, the foldable wings turned out to be a mistake given the wobbliness of hinges...

21 hours ago, herbal space program said:

That is not how I built that plane, but that's how it ended up after I landed, and nothing my onboard engineer could do seemed to be able to correct it.  In the end, I had to make most of my flight back to 20km upside down!

 Mine went even worse - the fan blades ended up rotated 90 degrees so they formed a circle rather than spokes, and gradually drifted outwards in a kind of ever-expanding giant chainsaw of doom. Which weirdly didn't affect the flight characteristics in any way 

21 hours ago, astrobond said:

Thank You  That was a long time ago lol, I made some tries on KSP2 for a SSTO from Olympus Mons on Eve, but from 3000m, that's really hard... not found a solution for now... but i will try with darts on first part ascent xD

The SWERV should help, but yeah the lack of tall mountains might make it impossible 

21 hours ago, astrobond said:

Your challenge is excellent !!! I only play KSP2 now, but maybe i will try

Thanks!  Well, I have been struggling to get interest going for this one in KSP2... 

 

[herbal space program]

28 minutes ago, KincaidFrankMF said:

Funny how different your design is, given we took basically the same approach! Here's mine -

Nice plane! I think the single thing that kept me playing KSP1 the longest was going to the challenges forum and seeing all the different solutions people could come  up with to the same problem.  As to the foldable wings, yeah, I definitely considered those as they would make a prop-driven SSTO at least somewhat reasonable to build, but I could never figure out how to make them both stiff enough to be usable and foldable, so I gave up on that idea pretty quickly. I suppose having an engineer do some wing-walking to change the positions of struts while airborne might have done the trick, but even just setting it up so you could stage the aero parts off all at once and turn the rest of the craft vertical for the flight back to orbit was challenging enough for me.  the heavy fuselage and Mk III capsule also required quite a bit more wing area than you had, which was not evident from the pic above but can be seen in the one below. As to the choice of props, I think I used the ones I did because they gave me the best thrust in thin air on Kerbin, but of course on Eve you'll top out in considerably thicker air due to the higher gravity, so maybe it was not optimal for that situation.  Still, they got me above 20km pretty reliably, which was enough for the rocket part to make orbit.

 

 

Edited April 5 by herbal space program

[KincaidFrankMF]

1 hour ago, herbal space program said:

As to the foldable wings, yeah, I definitely considered those as they would make a prop-driven SSTO at least somewhat reasonable to build, but I could never figure out how to make them both stiff enough to be usable and foldable

They worked initially but gradually drifted out of alignment over time. It still flew, it just got jankier & jankier lol Mine was just a single-seater though, scientist + drone pilot, so it didn't need as much wing area. Lower ceiling, too.

1 hour ago, herbal space program said:

As to the choice of props, I think I used the ones I did because they gave me the best thrust in thin air on Kerbin, but of course on Eve you'll top out in considerably thicker air due to the higher gravity, so maybe it was not optimal for that situation.  Still, they got me above 20km pretty reliably, which was enough for the rocket part to make orbit.

From memory, they're faster at sea level but a lot heavier - so mine topped out around 14k as a result. Just about enough with a tiny rocket carrying basically nothing but a 1k pod and an experiment case.

Love the crazy wings on yours!

[DennisB]

On 4/5/2024 at 2:32 AM, herbal space program said:

...So I went and took a look, and that ship is indeed a beast! It's too bad the person never figured out a plane that could land from orbit on Eve.  That makes the whole thing much easier! And it didn't really seem so hard either. 

I was happy back then, that I could build an airplane and a rocket. And of course, if everyone would know the best solution, no one would do something radical different .

For my Jool 5 I came one step further. It took a long time, but I could build something like a plane, which can land on Laythe and reach Jool's lower atmosphere. It's still not the hardcore one, because it still looks like a plane, when it reaches orbit again, but overall, it looks more like a plane. At the moment, I'm on Laythe, so you can see it in action very soon. I've tried it on Eve too, just for fun, but it didn't survive the entry. I'm sure, it would need more wing area for the higher gravity.

Edited April 6 by DennisB

[herbal space program]

On 4/5/2024 at 9:54 PM, DennisB said:

I was happy back then, that I could build an airplane and a rocket. And of course, if everyone would know the best solution, no one would do something radical different .

Sorry, I had no intention whatsoever of minimizing the significance of what you accomplished  there. It's actually quite impressive, especially considering how few hours of gameplay you had under your belt at the time. I don't think I could ever  have done such a thing so early in my KSP1 career! As to the Laythe plane, I look forward to seeing it. I posted my own KSP2 Jool5 here a while back in the "What did you do today" thread, and you can see there that I used a plane for my Laythe segment: 

 

 In KSP1 it's actually not so hard to build a plane that can make it all the way to Laythe and back on its own in a single stage, using only 1.25m parts. In KSP2, I'm finding I need to move up to Mk3 to do the same thing, because the hydrogen tanks are total drag monsters compared to the LF tanks you could use for the nukes in KSP1.

Edited April 7 by herbal space program

[DennisB]

6 hours ago, herbal space program said:

Sorry, I had no intention whatsoever of minimizing the significance of what you accomplished  there.

It's OK, I know. The reason for my comment wasn't that.

[MirageNL]

This week I tested some of the engines for additional altitudes. The Dart has pretty constant performance as expected, though it weirdly decreasse a bit between 2 and 8 km. The nuclear engines have constant Isp up to 9 km, then start to climb, stall a bit at 15 km and then increase again; also pretty odd behaviour. It might have something to do with the fact that 15 km corresponds to Kerbin sea level Isp values. Other engines also have a slight nod at 15 km, but otherwise behave as expected. The Rapier turns out to have better Isp than the Mammoth up till 16 km and between 5 and 11 km it's even higher than that of the Vector. Its lack of thrust still makes it a poor choice for a vertical launch, but an SSTO from Kerbin to Eve and back might be feasible. Above 25 km Isp's start to approach their maximum and at 50 km all Isp's are at vacuum levels.

[MirageNL]

I also ran some simulations using the variable Isp and including models for air density and resistance.  Though the drag coefficient has a large influence on the maximum altitude, it seems to have little effect on the optimal starting mass. Starting with too much fuel also turns out to be much worse than having a suboptimal amount. You could start off with tons of less fuel, only costing you a few km of altitude.

Also interesting: from the KSP 1 wiki I found an Eve SL pressure of 5 atm and temperature of 420 K. However, to get the pressure at 15 km to around 1 atm from that, I had to give the air at Eve a low molar mass of just 20 g/mol. For comparison: a CO2-rich atmosphere like that of Venus would be 44 g/mol, while Earth air is 29 g/mol. Lowering the temperature lapse rate could increase the molar mass, but only up to 22 g/mol. The temperature would have to increase with altitude to get higher, but it would have to be 1400 K at 15 km to get a value of 44 g/mol. If KSP 2 still has the same SL values for Eve, then Ammonia (17 g/mol), Methane (16 g/mol) or even water (18 g/mol) would have to be pretty large components of Eve's atmosphere.

[leos101]

On 4/5/2024 at 3:32 AM, herbal space program said:

I'll take a look! The ship I was talking about is sadly gone, but there is still a pic of it on my Imgur account:

 

...So I went and took a look, and that ship is indeed a beast! It's too bad the person never figured out a plane that could land from orbit on Eve.  That makes the whole thing much easier! And it didn't really seem so hard either.  Other than not mounting anything too heat-sensitive on the bottom, I don't recall that I had to do anything special to make it work. The way you can use wings to dissipate speed in KSP1 by turning it into lift rather than heat seems almost like a cheat, but I was only too happy to take advantage of it. I saw also that you apparently had problems with the robotic drift bug affecting your plane.  So did I! If you look closely at the pic above, you can see that my props are at an odd angle, pointing somewhat downwards instead of straight ahead. That is not how I built that plane, but that's how it ended up after I landed, and nothing my onboard engineer could do seemed to be able to correct it.  In the end, I had to make most of my flight back to 20km upside down!

Awesome Design !!!