Has it been proved, mathematically, that an Eve SSTO is impossible?

[metaphor]

I got an ion glider to about 20km on Eve, but then ran out of xenon. It's very hard to have the thrust needed to overcome the drag at higher altitudes/speeds and also have all the fuel to get the needed delta-v.

[GoSlash27]

I restarted from baseline with a new design. I tried and tried to make the rudder unnecessary, but no dice. No matter what I did, it was dynamically unstable in yaw. I basically built it backwards so that the drag of the okto 2 would have a stabilizing effect instead of a destabilizing effect, deleted 1 unnecessary control surface, and reverted to the small control surfaces as wings. I think it's under the optimal lift/ weight now, but I'm seeing if it can work as-is.

I'm testing different ascent profiles now, and this happened on my third flight. 1,878 M/sec and it was steady as a rock. I think Kerbin SSTO is in the can...

[GoSlash27]

I'm going to bed. Best ascent profile so far is 45* climb. 1,963 m/sec. I'm gonna try varying the lift tomorrow to see what effect (if any) it has.

[Red Iron Crown]

I had a go at Eve last night with a twin ion/single 48-7S unmanned design, got to about 50km on ions alone but the rocket wasn't enough to kick it out of the atmosphere (Ap of ~72km). The toughest thing about this challenge is how long each attempt takes.

[GoSlash27]

Nothing new to report today. I found a lot of ways to not go to space

[Claw]

Nothing new to report today. I found a lot of ways to not go to space

Have you checked the ion SSTO glider thread? It seems there is a pretty limited set of configurations that work for getting off of Kerbin. I'm not sure if that same basic config will get you off of Eve, but it might be a place to start looking for refinements for your ion plane.

[GoSlash27]

Claw,

After exhausting the thread, none of the successful attempts were done SSTO without infiniglide. In fact, if it weren't for my shameless battery-hogging, I'd be on the leaderboard with this design.

The most successful SSTO attempts consistently had absolute minimum part count for physics parts. Only 2 wings.

This gives me an idea...

[GoSlash27]

IRT to the OP, I don't think an Eve SSTO can be proven conclusively impossible mathematically. Not because it's possible, mind you, but because the math doesn't work in a way that allows proof.

You're never going to get to LEO using an ion glider (without infiniglide), but the closest thing to "proof" is in the outcome.

Efficiency in ion gliders is all about the ratios. A certain number of engines per wing and a certain number of tanks per engine. If you keep the ratios the same and double everything, you don't get any gain beyond diminishing the effect of the payload. And more importantly, approaching the ideal ratio of parts only creates a small improvement in performance. It's never going to get to Eve orbit no matter what you do. I doubt it will ever make Kerbin orbit, and I'm the closest to that achievement as of this writing.

So long-short, brute force rocket is mathematically impossible. Ion glider without infiniglide isn't mathematically impossible, but you're never gonna see it happen. Ion glider using infiniglide is virtually certain.

Best,

-Slashy

[Sanguine]

Macey Dean did it back in .18.

[Red Iron Crown]

Macey Dean did it back in .18.

That's single stage from Kerbin's surface to Eve, a much simpler accomplishment (still hard, but not as hard). This thread is about getting from Eve's surface to low Eve orbit in a single stage.

[GoSlash27]

^ Also accomplished using jet engines and control surfaces as wings.

[GoSlash27]

I'm still tinkering with this concept. I believe an Eve SSTO *is* just barely possible, but only if you cheat. My current design harnesses infiniglide to do most of the work and ion engines to complete the job. After I make that work (or give up trying), we're going to collaborate on an infinigliding kraken drive. And of course... ladder lifters are proven successful at getting a Kerbal into Eve orbit.

Other than that, no... not possible. And I'll tell ya why...

Most of the ascent from Eve in a glider is spent trying to overcome "the wall"; accelerating painfully slowly and barely climbing. In this regime, the aircraft only has about a 20% delta V efficiency. Once past that, the situation improves, but only to 40% efficiency until you're out of the atmosphere.

Even an ion glider can't make enough delta v to overcome that. From a high point on the surface, you're looking at somewhere in the neighborhood of 34,000 m/sec. Eve is a tall order even with infinigliding. Impossible without it.

Best,

-Slashy

[CakeNinjaProductions]

What if- as you got higgher into the atosphere, your thrust ddecreased and your isp increased? Like switching from liquid power to ion midway?

[MarvinKitFox]

Is EVE SSTO impossible?

(from sealevel, using stock parts, no alt-f12 cheats)

*Using purely rockets: proven impossible

*Using valid aerodynamics (wings): 'Proven' impossible by somewhat fuzzy extrapolation. Seems to require such obscene scaling that your plane may outmass eve. Seems to be plausible from a high-altitude start, but...

*using physics glitch- infiniglide: Theoretically possible, have not seen a demonstrated success.

*using physics glitch- kraken drive: was possible. .24 seems to have fixed the K-drive glitches sufficiently to make it impractical?

*using physics glitch- ladder: Very possible, there is a video of it being done on here somewhere.

[CakeNinjaProductions]

But what about switching from rocket to ion midway?

[Red Iron Crown]

But what about switching from rocket to ion midway?

Not enough TWR. A xenon drive can't even lift itself on Eve. No chance of it pulling a dead rocket and tanks into orbit, wings or not.

The opposite I think has a slight chance: An ion glider used for the initial ascent, then a rocket to kick it out of the atmosphere and circularize. I couldn't make it work, maybe you'll have better luck.

[sedativechunk]

Okay, I am not the greatest math person however I am majoring in IT and put close to 400 hours in this game now. From my understanding (and own experimentation in this game with the engineering mod) it's pretty much impossible to get off of Eve using SSTO design, even with most of the modded part packs out there. I can tell you now in particular it's just not possible with the stock parts including the ion engine. If I'm not mistaken, the MK1 lander can is the lightest stock vehicle that contain a kerbal, and with a single ion engine (with a small xenon container) does not give you enough thrust-to-weight ratio to leave Eve or even get off of the ground for that matter. Ion engines are practically useless on Eve. Maybe someone will prove me wrong but I have yet to come up with a design that would work on Eve with ion engines.

Let's assume you are okay with using mods, however (not "cheating" or debugging crap but fair-play mods). From my own experimentation, the most efficient and close to single stage you might be able to make is to use the KW Rocketry pack. The KW rocketry pack (if I'm not mixing it up with interstellar) contains liquid methane rocket engines and fuel tanks. Compared to all the other engines (including ion, nuclear, and even some of the interstellar engines) they seem to give the most thrust-to-weight ratio out of all engines particularity for Eve. They are extremely powerful engines. Even in reality, Space X I believe is experimenting with liquid methane rockets for first stages.

I think one fuel tank and methane engine would get you about 4,000m/s of ÃŽâ€v. The number to leave the orbit of Eve (from one of it's higher mountains/peaks) would be about 8,000m/s, so technically it may be possible using the liquid methane rocket to leave in a single stage. It's just it would be like a small building on Eve in terms of height, however. IT could tip over very easy and also (if you haven't tried it before) it's VERY HARD to do precision landings on Eve if you were trying to land on a high valley in an exact location.

[MarvinKitFox]

I think one fuel tank and methane engine would get you about 4,000m/s of ÃŽâ€v.

Riddle me this:

If one (tank + engine) gives you about 4,000m/s of ÃŽâ€v, what will 10000 * (tank + engine) give you, when you are not allowed to drop anything?..... about 4,000m/s of ÃŽâ€v!!

[sober667]

if somebody still thinking about

http://forum.kerbalspaceprogram.com/threads/78857-0-23-5-Planitron-Reloaded-Update-(25th-may-14-v0-3-7)

mod that could help with testing

work for me

i think rocket-like was to early shoted out haveing now realy big rocket(NASA parts) could give us nice dV and enough TWR having one huge engine and pair or more nuclear for final ascending and circulizacjon

[Starman4308]

i think rocket-like was to early shoted out haveing now realy big rocket(NASA parts) could give us nice dV and enough TWR having one huge engine and pair or more nuclear for final ascending and circulizacjon

For a homogenous engine setup, easily proven mathematically impossible. The most mass-efficient tanks have a fueled/empty mass ratio of 9/1. In the rocket equation, that puts a hard cap of 2.197*G*Isp on how much dV a single stage can have. A short calculation assumes 390 Isp and zero payload/engine mass, for 8414 m/s delta-V. This is just barely enough to get to orbit from a high altitude, and completely and utterly neglects engine/payload mass.

The optimal engine for a TWR of 1.7 (Eve surface gravity) is the KR-2L, with a vacuum Isp of 380s and an Eve TWR of 23.03. This means an upper bound of 22.03t of fuel tank per ton of KR-2L, or you will literally sit on the surface burning fuel until you can get off the ground. Take the inverse, and you've got to add 0.0454t of KR-2L for each ton of fuel tank, thus your fueled/empty ratio is now 9.0454/1.0454, for 8.65. Plug that into the rocket equation, and you now have 8052.29 m/s delta-V. In practice, you will lose a lot of this delta-V to a combination of gravity drag and sea-level Isp values, because this rocket is literally just barely capable of getting itself off the ground when full. You will not get to orbit with this rocket.

While the math is more complicated for a heterogenous engine setup, there are practical arguments to suggest it is impossible: every ton of LV-N will reduce your fuel ratio for the KR-2Ls, and the KR-2Ls will add a lot of dry weight for the LV-Ns to haul when you switch over. I strongly suspect you'd never be able to make a KR-2L/LV-N setup work; the KR-2Ls don't have the efficiency, and the LV-Ns don't have the thrust, and using both exacerbates both of these problems.

Edited November 10, 2014 by Starman4308

[GoSlash27]

Is EVE SSTO impossible?

(from sealevel, using stock parts, no alt-f12 cheats)

*Using purely rockets: proven impossible

*Using valid aerodynamics (wings): 'Proven' impossible by somewhat fuzzy extrapolation. Seems to require such obscene scaling that your plane may outmass eve. Seems to be plausible from a high-altitude start, but...

*using physics glitch- infiniglide: Theoretically possible, have not seen a demonstrated success.

*using physics glitch- kraken drive: was possible. .24 seems to have fixed the K-drive glitches sufficiently to make it impractical?

*using physics glitch- ladder: Very possible, there is a video of it being done on here somewhere.

-Using valid aerodynamics with ion gliders, still out. Until it's proven possible with infinigliders, it's impossible for normal wings. We've barely been successful with pure wing SSTO ion gliders from Kerbin. Eve is far worse and nobody currently working the Kerbin effort would consider Eve plausible at this point.

Using infiniglide with ion engines, I haven't had any luck. I suspect the required part count would be prohibitive.

Using infiniglide with kraken drive, That one's confirmed for .25. KrakBadger 2.5

Using ladder lifters, that one's been confirmed many times over.

Anything short of these is a mathematical impossibility.

Best,

-Slashy

Edited November 11, 2014 by GoSlash27

[sober667]

Stock without exploiting bugs is probably imposible (but i saw working stock elecrical helicopter so who knows?)

[UmbralRaptor]

Not sure why this needed a bump, but...

0.90's Mk3 plane parts will mock you. They have mass ratios slightly better than the "normal" stock tanks (9.333 vs 9), which makes the numbers look slightly better. Not enough to matter, but better.

[panzer1b]

Ive managed a 2 stage to orbit eve craft, but yeah, SSTO is just not happening. The biggest issue is the fact that any engine with anywhere near the required ISP has terrible TWR, and any engine with enough TWR has crap ISP. Without mods/hacks/exploits, SSTOs cant be done at all.

Perhaps 1.0's atmosphere will make it possible, or not, who knows.

[GoSlash27]

Ive managed a 2 stage to orbit eve craft, but yeah, SSTO is just not happening. The biggest issue is the fact that any engine with anywhere near the required ISP has terrible TWR, and any engine with enough TWR has crap ISP. Without mods/hacks/exploits, SSTOs cant be done at all.

Perhaps 1.0's atmosphere will make it possible, or not, who knows.

^ This is the key. If the new 1.0 aerodynamics reduce the DV requirement to an attainable level, then SSTO will be at least theoretically possible.

Best,

-Slashy