Eve SSTO is impossible!

[Tsevion]

That isn't Eve though.

Yeah... I kinda just realized that...

[Sirine]

I'm sorry to interrupt this 'discussion'/challenge.

Please bear in mind, that.. having F.A.R. mod versus not having one, are having huge impact on the atmosphere environment.

OP please stated this challenge/ discussion are base on which ground. With the FAR mod, or without one?

[Red Iron Crown]

Crosspost from the other thread:

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.

[Kasuha]

In the current state of the game, infiniglide is pretty much law of physics rather than a bug. You may place some limits on how many control surfaces you may or want to use but with each control surface you get some unavoidable propulsion as long as it is in atmosphere under correct orientation. It's not like you get infiniglide when you have 10 control surfaces or 10 control surfaces per ton of your vehicle, the only way to completely avoid it is to not use any control surfaces at all and only steer using torque. But then you're restricting yourself off perfectly valid stock parts.

[zarakon]

It's not like you get infiniglide when you have 10 control surfaces or 10 control surfaces per ton of your vehicle, the only way to completely avoid it is to not use any control surfaces at all and only steer using torque.

Even with no control surfaces, you can infiniglide using torque

[cerberusti]

There are a few ways in stock to get infinite propulsion from nowhere, I think the rule is asking for a reasonable attempt not to do so.

The criteria for an ion plane are similar to those for an infiniglider though (very small, with high lift to weight), so there will be more infiniglide going on than normal for craft which have a reasonable shot at making this work. With an ion glider you can see the speed increase a few m/s from a single flap when making a heading change, which really has more to do with how light these craft are than active cheating.

I am taking it to mean that control surfaces which are not used for control should be locked, and control input should be minimized (no flapping.)

It should also be fairly obvious if infiniglide is a primary contributor to making orbit if there are pictures, as you would want high speed in the mid atmosphere to reach orbital velocity with the infiniglider. An ion plane has a different ascent profile.

[rtxoff]

Well here is an perfect explaination from KerikBalm why this challenge is not possible:

Problem:

SSTO means your "wet mass" : "dry mass" ratio can never be any better than the best fuel tank (which is not the ARM tanks). When you plug that into the Tsiolkovsky rocket equation, you will find the maximum deltaV a single stage rocket can get.

It is below that required for eve ascent.

http://en.wikipedia.org/wiki/Tsiolko...ocket_equation

That goes for all the "chemical" engines.

That leaves us with the ions and the nukes.

The nukes get a worse ISP than the chemical until very high on eve, because its atmosphere is very thick.

Ions have plenty of ISP for the tank empty/dry weight

So then the next problem is TWR and gravity drag.

The low nuke TWR knocks them out (even though the low atmospheric ISP already knocked them out of the running).

The stupidly OP'd ions still can't even lift themselves off the ground as a rocket.

So you'd have to use a wings,

In real life, wings can negate gravity drag and provide for a more efficient ascent

That can get you around the TWR requirement.

But then we run into another problem, the KSP aerodynamics model, where drag is proportional to the square of velocity, but lift is proportional to only velocity,

Thus, drag increases much faster than lift, and soon far too much drag is produced just to generate the lift needed, and you don't get to orbit. (at least not with ions, somethign with a better TWR can counteract more drag while still only requiring the same amount of lift, and once you get going fast enough, you don't need so much lift as you're close to orbit anyway, but if you never get close to orbital speed, that wont apply)

It is not possible with stock parts and stock aeordynamics.

Just like in real life its not possible to SSTO with a water+baking soda powered rocket.

Nor is it possible to SSTO from kerbin using just sepratrons

If you want to SSTO on eve, mod yourself an engine with 2,000 atmospheric ISP, and a 50:1 TWR, then you should be able to easily do it.

None of the parts have enough performance to SSTO from eve.

It is impossible without taking advantage of a glitch (like the demonstrated ladder thing, or an infiniglider)

[Kasuha]

Even with no control surfaces, you can infiniglide using torque

That's not infiniglide, that's flapping your wings. You spend electricity on that. Birds fly like that.

[cerberusti]

Which fuel tank did you use? I have a craft with an FL-T200 I was going to try, but am only aiming for 30 - 40k on ions alone before I kick in the somewhat long rocket burn.

[Red Iron Crown]

Which fuel tank did you use? I have a craft with an FL-T200 I was going to try, but am only aiming for 30 - 40k on ions alone before I kick in the somewhat long rocket burn.

If that was in reference to my attempt, I used 4 Oscar-Bs with a single 48-7S, it gave just under 600m/s in a 30s burn. More rocket fuel is definitely needed, but everything else gets bigger then, too.

[cerberusti]

It was to you, I hit reply and assumed it would note that somehow in the post.

There is also some question as to if a short high twr burn or a long barely sufficient twr burn is better. Terminal velocity at 40k is 1km / s, and it climbs from there somewhat quickly.

Really I want at least 2k dv on the rocket, but that will be hard to do. For now I am making the assumption that a .35 TWR will reach orbit (it does on kerbin) and went for the long burn.

[kmMango]

He who achieves this becomes a LEGEND:D

[allmhuran]

There is one kind of craft that hasn't been mentioned yet, but I'm curious if anyone has tried (or considered trying): A torque powered helicopter.

[Kasuha]

There is one kind of craft that hasn't been mentioned yet, but I'm curious if anyone has tried (or considered trying): A torque powered helicopter.

I was definitely thinking about one when I was writing my previous post.

[Red Iron Crown]

There is one kind of craft that hasn't been mentioned yet, but I'm curious if anyone has tried (or considered trying): A torque powered helicopter.

I am intrigued by your ideas and wish to subscribe to your newletter.

I'm not sure that's a feasible strategy. With the ions the plane goes faster as you get into the thinner atmosphere, with the helicopter you'd go slower, I think. Though you might be able to lug more of a rocket up to a higher altitude than the mountaintop. Hmm.

[zarakon]

That's not infiniglide, that's flapping your wings. You spend electricity on that. Birds fly like that.

What we call infiniglide is the same thing, just flapping control surfaces. I guess spending electricity is the difference, but that still creates an unintended infinitely-renewable propulsion source, which IMO goes against the spirit of most challenges

[Tsevion]

There is one kind of craft that hasn't been mentioned yet, but I'm curious if anyone has tried (or considered trying): A torque powered helicopter.

I actually was trying one of these last night, as I've got a fair amount of helicopter experience... it was not going well. While you can build one relatively easily, they seem to top out around 20km at best, and that's with little to no load, and the helicopter weighs a fair amount. Trying to carry enough rocket fuel to boost the helicopter further just cuts down efficiency. It could be a neat strategy for an Eve launch vehicle, but not useful for an SSTO.

[Tsevion]

What we call infiniglide is the same thing, just flapping control surfaces. I guess spending electricity is the difference, but that still creates an unintended infinitely-renewable propulsion source, which IMO goes against the spirit of most challenges

The trick is, with torque powered helicopters or flapping, the gains are strictly limited to the energy expended, placing hard limits on their capabilities... they are really only functional at extremely low speeds. Infinigliders are NOT the same... they exploit the math of control surfaces so they generate thrust proportional to current speed, essentially generating energy. It is NOT the flapping action that makes infinigliders function... that's just one of the easier ways to see it... I can design infinigliders that function with you just holding the control stick in a single direction.

[allmhuran]

I actually was trying one of these last night, as I've got a fair amount of helicopter experience... it was not going well. While you can build one relatively easily, they seem to top out around 20km at best, and that's with little to no load, and the helicopter weighs a fair amount. Trying to carry enough rocket fuel to boost the helicopter further just cuts down efficiency. It could be a neat strategy for an Eve launch vehicle, but not useful for an SSTO.

Agreed, I quickly put this together as a proof of concept. Maybe with some tweaking on the ratios, types, and positions of wing and SAS parts it could be improved slightly, but it took me 6 minutes to lift it to 1500m at a climb rate of about 3m/s.

Edit: And of course this is Kerbin, I have no idea how to translate the effectiveness to the different environment of Eve. Best guess, one would need fewer SAS parts to keep the weight down, but also fewer/stubbier wings because of the dense atmosphere.

Edited July 10, 2014 by allmhuran

[robopilot99]

Are ornithopters acceptable?

[Cannon_Fodder]

Just to make sure I understand the challenge. I read that as Single stage FROM Eve to Low-Kerbin-Orbit? I can use a mother-ship or stages to get to Eve and I don't have to land on Kerbin?

[GoSlash27]

Just to make sure I understand the challenge. I read that as Single stage FROM Eve to Low-Kerbin-Orbit? I can use a mother-ship or stages to get to Eve and I don't have to land on Kerbin?

Negative. The challenge is to get from the surface of Eve to low Eve orbit.

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I'm sorry to interrupt this 'discussion'/challenge.

Please bear in mind, that.. having F.A.R. mod versus not having one, are having huge impact on the atmosphere environment.

OP please stated this challenge/ discussion are base on which ground. With the FAR mod, or without one?

Without. Stock parts, stock environment.

-Slashy

[cantab]

Single stage from the surface of Eve to low Eve orbit.

[GoSlash27]

Ah... I've realized the primary problem, we're talking past each other a bit... totally my fault. You responded to my numbers which was a test I conducted on Eve. Going back and checking, I was unclear on that. Since those are what you responded to, I assumed you were on Eve as well. Rereading your earlier posts, and looking at the picture again (to see the big BLUE planet that is totally not Purple) I realize you're still doing the Kerbin testing. You numbers suddenly make much more sense, and no longer require anything bizarre to explain them. I still worry about infiniglide polluting results when using flaps as wings... but it's significantly less of a concern to me knowing this, it's likely mostly just providing some bonus lift/speed during the early phases of the launch but at 40k on Kerbin the effects should be negligable. When I used my craft on Kerbin (Still infinite fuel cheating), it achieved orbit easily... so I'm hopeful for you to get a positive result on Kerbin. My numbers unfortunately still stand for Eve though... it's just not possible to get a pure ion-craft to orbit there.

Sadly, nothing new to report today. I found a lot of new ways to not go to space

My record for Kerbin SSTO remains at 1,963. Pretty sure I can get that to orbit, but Eve looks highly unlikely to me.

[GoSlash27]

How so/what theory?

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This would be going by the rocket equation. DV= 9.81 Isp ln(Mw/Md).

You need at least 8,500 DV to get from the surface of Eve to LEO. Nothing stock in this game can achieve that, even composed of infinite tanks. Especially not with the t/w demanded for Eve. A chemical rocket to do that job would need an Isp of at least 394 atmospheric.

As others have said, if it's possible at all it'll be using an ion glider. Ion engines can make the DV easily, but they lack the t/w to pick themselves up let alone anything else. So it's a glider. unfortunately, gliders are grossly DV inefficient since you spend practically your whole launch fighting drag.

Your fuel becomes time. You know exactly how long your engines will provide thrust and how much drag you can push. The question is does a glider exist that is efficient enough to get you to orbit before the clock runs out...

How so/what theory?