Eve SSTO is impossible!

[horndgmium]

Guys you realize that you can make an SSTO rocket too, right?

[RocketPilot573]

Guys you realize that you can make an SSTO rocket too, right?

Yes, but that's already out of question. Its not possible to make any rocket with that much delta-v while having enough TwR to fly on Eve. An Ion spaceplane is the only hope...

[cerberusti]

If it is managed the end result will no doubt be called an infiniglider by some anyway. No other wing is even close to the lift to weight ratio of small control surfaces, so those are the wings, and you will need a lot of them (with control disabled.)

The question is basically can you loft a 48-7s or two with enough fuel to get you suborbital with enough time to make orbit on the ion glider.

It is still a maybe.

[cantab]

I had some thoughts about this myself the other day, and would like to propose a couple of scoring systems, to make this an incremental challenge rather than just an all-or-nothing affair.

Entries will be on either of two leaderboards. A Top Down entry must start in space, descend through Eve's atmosphere, then reascend to a stable orbit. Scoring is by the lowest altitude reached and returned from, lower is better. A Bottom Up entry must start on the surface of Eve and reach as high an altitude and speed as possible. Scoring is the same as the ion glider challenge, altitude/20 + orbital speed, higher is better.

I also suggest that modded craft and FAR craft, though ineligible for the leaderboard, be granted honourable mentions, since they may be instructive to the ultimate goal.

[horndgmium]

Yes, but that's already out of question. Its not possible to make any rocket with that much delta-v while having enough TwR to fly on Eve. An Ion spaceplane is the only hope...

Did you calculate that to be impossible or just saying it's impossible?

I'm itching so hard to prove it can be done to all the "no it can't be done don't even bother you losers" kind of people, but also totally unwilling to remove FAR from my gamedata.

[cerberusti]

Did you calculate that to be impossible or just saying it's impossible?

I'm itching so hard to prove it can be done to all the "no it can't be done don't even bother you losers" kind of people, but also totally unwilling to remove FAR from my gamedata.

rocket power without ions is impossible even in theory

[horndgmium]

rocket power without ions is impossible even in theory

How so/what theory?

- - - Updated - - -

rocket power without ions is impossible even in theory

How so/what theory?

[cerberusti]

http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

A better link might be:

http://wiki.kerbalspaceprogram.com/wiki/Cheat_sheet#Maximum_.CE.94v_Chart

Or even Better: http://imgur.com/a/iNqmQ#20

Notice how at even at a kerbin relative TWR of 2.0 (not really enough for eve) no engine type can get you over about 5500... and that is the more forgiving vacuum chart.

Even the top of the highest mountain is 8k dv, and you will be carrying a lot of engine to hit the TWR you need to lift off.

Only nuclear engines in vaccum have the possible dv to do it even with an infinitely large rocket, but they do not have this efficiency within the lower atmosphere (and it is a mighty lower atmosphere.) Even then their TWR is low enough that they would require wings, but they are not so high on dv that they can afford the efficiency hit from that ascent profile.

That leaves ion engines as the only possible route, and as an ion engine has a TWR insufficient to lift itself, an ion glider.

Edited July 8, 2014 by cerberusti

[horndgmium]

For some reason Wiki won't load for me right now :/.

Idea: an asparagus staged rocket with higher TWR (lighter engines smaller tanks maybe?) on the outside. Don't drop the stages. Wa-la: SSTO. Nomenclature is a treacherous business.

But to be honest that's overcomplicated and since this is a game, overengineering combined with the new parts could make it possible. All I'm saying is, as the famous quote goes: if you say something is probably not possible, you are most likely right. If you say something is impossible, you are almost certainly wrong.

[cantab]

Or there's this suggestion:

Taking advantage of the obscenely high Isp of Jet Engines via using lots and lots of air intakes, filling them up on Kerbin, bringing them to Eve, and then taking off with Jet Engines

?

The tankage is appalling though. A radial intake weighs 10 kilos (empty I think) and holds 1 unit, which is 5 kilos, of intake air. With your fuel tankage also being worse than for a rocket, I suspect (but haven't proven) that will cancel out the benefit of the high Isp. Not to mention the part count would be insane.

[horndgmium]

Yeah, I also think that the added benefit from the jet engines would get outweighed by their uselessness and added mass fairly quickly when the intakes run out. Can real intakes even hold air like that?

[Red Iron Crown]

For some reason Wiki won't load for me right now :/.

Idea: an asparagus staged rocket with higher TWR (lighter engines smaller tanks maybe?) on the outside. Don't drop the stages. Wa-la: SSTO. Nomenclature is a treacherous business.

But to be honest that's overcomplicated and since this is a game, overengineering combined with the new parts could make it possible. All I'm saying is, as the famous quote goes: if you say something is probably not possible, you are most likely right. If you say something is impossible, you are almost certainly wrong.

Pure rocket really is mathematically impossible. Take any engine and calculate the maximum amount of fuel that it can lift on Eve, you'll find that no combination can yield enough dV to ascend from Eve's surface.

[The Jedi Master]

Pure rocket really is mathematically impossible. Take any engine and calculate the maximum amount of fuel that it can lift on Eve, you'll find that no combination can yield enough dV to ascend from Eve's surface.

If you say something is impossible, someone will inevitably try it anyway. Nothing you say will convince them otherwise. People just don't seem to understand that when it comes to this topic.

[GoSlash27]

I played around with a pure ion glider last night, and a pure ion glider definitely can't do it. I made a minimal ion glider (smallest probe, single ion, single xenon tank (empty), and a pair of Delta-Deluxe Winglets), and turned on infinite fuel. It topped out at 51km doing around 840 m/s, it also took like an hour to get up to that... which is a lot more than a single xenon tank worth of delta-V. And even that craft is technically abusing infiniglide slightly. The only possible non-cheating method left that I can't eliminate completely is a hybrid ion glider / chemical rocket... but I think it's quite unlikely you can actually lift anything with an ion glider that could then give the boost needed to allow the ions to achieve orbit.

I have already beaten that with 2 tanks of xenon and normal fuel flow. I won't divulge too much, but it's *definitely* not an infiniglider. Best run so far was this morning at over 1,800 M/sec. I've started over with a more dynamically stable (and at least on paper more efficient) design. My second ascent profile run has netted 974 m/sec, and I haven't made a serious run yet.

Best,

-Slashy

[GoSlash27]

I think we need to start this process smaller by first achieving an SSTO ion glider on Kerbin without infiniglide...

[Tsevion]

I have already beaten that with 2 tanks of xenon and normal fuel flow. I won't divulge too much, but it's *definitely* not an infiniglider. Best run so far was this morning at over 1,800 M/sec. I've started over with a more dynamically stable (and at least on paper more efficient) design. My second ascent profile run has netted 974 m/sec, and I haven't made a serious run yet.

Best,

-Slashy

I admit to being extremely curious as to your design, and what your TWR is...

[Tsevion]

For some reason Wiki won't load for me right now :/.

Idea: an asparagus staged rocket with higher TWR (lighter engines smaller tanks maybe?) on the outside. Don't drop the stages. Wa-la: SSTO. Nomenclature is a treacherous business.

But to be honest that's overcomplicated and since this is a game, overengineering combined with the new parts could make it possible. All I'm saying is, as the famous quote goes: if you say something is probably not possible, you are most likely right. If you say something is impossible, you are almost certainly wrong.

The thing you seem to be missing is the problem constraints. We're not saying getting off Eve is impossible, we're not even saying an SSTO is impossible. What we're trying to determine is whether an SSTO made with stock parts can get off of Eve with no funny business/cheating. If we don't need it to be single staged (or we somehow try to use some linguistic trick to have stages anyhow) then it's easy (any standard Eve lifter works). If we ditch the stock parts requirement we can again do it fairly easily, using any number of mods (Hooligan labs balloons, firespitter electric props, the Orion Nuclear Pulse rocket, any number of options from Interstellar). If we ditch the funny business/cheating rules you can hack gravity, use infinite fuel, change some part configs, use an infiniglider, use a Kraken drive, or any number of other methods.

The trick is within the system of constraints we've imposed the problem set becomes effectively finite meaning we can systematically analyze it and actually declare impossibility. The thing is, since among the rules there is essentially a "no funny business" clause, normal creative weasling that can make almost anything possible is not allowed. Our whole discussion here is based on this premise, and our effort is to explore the problem space and systematically eliminate possibilities. We can, with mathematical and logical certainty say a pure chemical rocket is impossible, the math has been done. Just as I can unequivocally state that you cannot add two positive rational numbers and get a negative number. We're now exploring other possibilities, but trying to say "nothing is impossible" is not only not useful, it effectively is working counter to our goal to narrow the problem space.

[GoSlash27]

Test run #3 got me 1,877 M/sec. I'm almost there and I haven't made a serious run yet...

[cantab]

I think we need to start this process smaller by first achieving an SSTO ion glider on Kerbin without infiniglide...

I recall there being a ding-dong row in the ion glider challenge thread over this. It seems it's quite hard to be sure you're not benefiting from infiniglide, since it can occur even with locked control surfaces. That said, it's easy to be sure you're not deliberately and actively infinigliding.

[Tsevion]

Test run #3 got me 1,877 M/sec. I'm almost there and I haven't made a serious run yet...

http://i52.photobucket.com/albums/g13/GoSlash27/testgliderrun3_zpsc070c7bd.jpg

I'm pretty sure there's infiniglide going on there... or something else hinky... otherwise it doesn't make a ton of sense. The TWR of this I'm guessing is pretty close to optimal, but optimal is still under 0.5... meaning your maximum speed should be about 1/2 terminal velocity... and terminal velocity at that height on Eve is about 1000 m/s.

Edit: Ignore that, I'm an idiot who can carefully calculate the maximum speed based on altitude and potential TWR, and totally miss the fact that I'm looking at the wrong planet.

Edited July 9, 2014 by Tsevion

[GoSlash27]

I'm pretty sure there's infiniglide going on there... or something else hinky... otherwise it doesn't make a ton of sense. The TWR of this I'm guessing is pretty close to optimal, but optimal is still under 0.5... meaning your maximum speed should be about 1/2 terminal velocity... and terminal velocity at that height on Eve is about 1000 m/s.

After I make orbit (*IF* I make orbit) I will give you a copy of the file and a detailed ascent profile. You will see that infiniglide is not a part of this design.

Best,

-Slashy

[Tsevion]

After I make orbit (*IF* I make orbit) I will give you a copy of the file and a detailed ascent profile. You will see that infiniglide is not a part of this design.

Best,

-Slashy

The problem is, with the weight of that craft, 3 of those control surfaces will give considerable infiniglide power... it's near unavoidable, even (and I don't know why this is true, but it measurably IS) if you disable control on them. I'm definitely not saying you're trying to use infiniglide... you're probably trying quite hard to avoid it, but I've only found 1 way to not be leveraging infiniglide, and that is to not have control surfaces on your craft.

Just one thing to check, take your craft near the ground and nose up until you're pure vertical... I bet you'll see your craft magically hover, even if you cut the engine... or at the very least fall very very slowly, in a magic anti-stall.

Another thing you could try is use B9, or procedural wings, or modify the configs on some of the base wings to be the same size/lift as the flaps you're using as wings, and then try your craft and see if the results are the same.

And I should add, I honestly hate to be telling you these things... as I feel like I'm kicking a puppy and robbing you of earned accomplishment. I just ran into this a TON myself when working on stock electric helicopters and ornithopters. I thought I had some great designs until I realized they were deriving more power from infiniglide than my intended propulsion... and literally the only stock solution I've found is to not use control surfaces... hence both my final helicopter and ornithopter rocking tons of SAS but nary a control surface between them.

A side corollary, give me a plane with a glide slope of 10:1 or better and control surfaces on it, and I'll show you me flying it from KSC to the island with no power after takeoff... and if it has a minimum takeoff speed of 50 m/s or less, or a fairly large number of control surfaces, I'll do it without ever turning the engine on.

[GoSlash27]

Just one thing to check, take your craft near the ground and nose up until you're pure vertical... I bet you'll see your craft magically hover, even if you cut the engine... or at the very least fall very very slowly, in a magic anti-stall.

Yeah... no.

Just hold your horses until I make orbit and give you a copy.

[Rhomphaia]

I'm pretty sure there's infiniglide going on there... or something else hinky... otherwise it doesn't make a ton of sense. The TWR of this I'm guessing is pretty close to optimal, but optimal is still under 0.5... meaning your maximum speed should be about 1/2 terminal velocity... and terminal velocity at that height on Eve is about 1000 m/s.

That isn't Eve though.

Atmospheric pressure at 40km on Eve would be around the same as at 20.5km on Kerbin.

You would have to be above 67km on Eve before you started seeing that.

Edited July 9, 2014 by Rhomphaia

[Tsevion]

Yeah... no.

Just hold your horses until I make orbit and give you a copy.

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.