Eve SSTO is impossible!

[allmhuran]

OK, so there might be something to the SAS helicopter.

The key point seems to be to get the SAS out on the wingtips. They can push more than their own mass, so the further out they are the more torque they can apply.

This one was still slow, but it was faster than the last one and it was slowly accelerating upwards. The biggest problem is that your vision goes weird for staring at the rotating navball trying to keep the TVV centered.

[Tsevion]

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.

From trying to get my electric helicopter working on Eve I learned some things... despite Eve's atmosphere making lift much easier to generate helicopters are a fair bit harder. Gravity fights you harder, and the thick atmosphere makes spinning up the rotors much harder. I think you may actually want larger rotors, so you can spin them slower so you lose less to atmospheric friction.

[Tsevion]

OK, so there might be something to the SAS helicopter.

The problem is, as you're seeing, having it lift any significant payload is extremely difficult... and it definitely needs to carry some sort of rocket to get it to orbit. Also all the wing surface will also likely cause drag in the middle phases, making the rocket even worse. I think there is serious potential to use a helicopter as a base to launch a smaller rocket from a higher altitude on Eve... but I think it's tragically inadequate for an SSTO.

[Tsevion]

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.

Sad... but it matches with previous challenges to get to orbit with ion gliders... it's doable, but they need to use some drop-tanks at the very least, and most of the more effective designs used multiple stages. Not to mention infiniglide concerns, as I've yet to see any ion-glider, staged or otherwise that can get to orbit without having some control surfaces (frequently as the lifting wings).

[GoSlash27]

Sad... but it matches with previous challenges to get to orbit with ion gliders... it's doable, but they need to use some drop-tanks at the very least, and most of the more effective designs used multiple stages. Not to mention infiniglide concerns, as I've yet to see any ion-glider, staged or otherwise that can get to orbit without having some control surfaces (frequently as the lifting wings).

Unfortunately, control surfaces are about the only thing in the proper size range for a lifter this light. I'm going to try a novel concept using a wing, but I'm not hopeful. The parasitic drag is proportional to mass, and wings are massive. I'm pretty sure the difference between making orbit and not is parasitic drag, so...

[Kasuha]

OK, so there might be something to the SAS helicopter.

The key point seems to be to get the SAS out on the wingtips. They can push more than their own mass, so the further out they are the more torque they can apply.

This one was still slow, but it was faster than the last one and it was slowly accelerating upwards. The biggest problem is that your vision goes weird for staring at the rotating navball trying to keep the TVV centered.

http://i.imgur.com/nY1O0CK.png

Since wings have significantly lower drag than other parts I'd suggest to put all reaction wheels to the middle for Eve. The resulting torque will be the same (physics!) but the drag slowing down the rotation will be much smaller.

You may only need to strut wing tips together to prevent oscillations.

[allmhuran]

In the original version I did indeed put the majority of the reaction wheels in the middle, but empirical testing suggested that the more I put on the outer edges, the better. Simply by taking them from the centre and adding them to the wingtips, the thing rotated and ascended noticeably faster. KSP physics! But you're probably right about the additional wingtip drag outweighing this advantage in Eve's thicker atmosphere.

[cerberusti]

You can probably get an ion glider working on kerbin with wings rather than control surfaces, it will just be bigger and closer on fuel (I had about 20% of my xenon left upon reaching orbit with small control surfaces.)

If scaled in weight to that of a swept wing, small control surfaces would have a lift rating of 2.5. Adding enough lift to get it to the same point with wings would be possible, and would weigh about as much as the extra fuel did (so the same ascent profile would work.) It is less granular though, so you may need another ion engine to make the right ratios possible (probably two engines, three xenon containers, and 6 swept wings.)

It would also require some way to control the plane, you may not be able to do that with just the probe torque (although at this weight it would not be affected by a couple of control surfaces much more than most small planes.)

[cantab]

despite Eve's atmosphere making lift much easier to generate

I believe it will always be the case that the denser atmosphere is no real help, because at some point you must ascend through the altitude where it's 1 atm pressure. At that altitude your lift, thrust, and drag all match Kerbin sea level performance, but your weight is much greater.

[HafCoJoe]

Because Eve has a thicker atmosphere planes have WAY more lift so a SAS glider could be more efficient closer to the surface on Eve (don't quote me on that). The real challenge is controlling the thing but I'm not sure how to easily fix that. Helicopters have a very low flight ceiling because as the atmosphere thins the propellers become pretty useless pretty quickly. In reaching orbit that has some good effect because as the atmosphere thins the drag decreases which obviously improves things. If enough liquid fuel is put on the gliders you might be able to lift it to orbit, but we're probably talking about a WhackJob level of ship size.

That's my jot.

[Kasuha]

In the original version I did indeed put the majority of the reaction wheels in the middle, but empirical testing suggested that the more I put on the outer edges, the better.

There's kind of insane amount of reaction wheels on that ship, maybe you just used more. I tested it with a ship with eight reaction wheels both on wingtips and in the middle and did not notice any significant difference.

What's more important, I tested the same "ship" both on Kerbin and on Eve (using Hyperedit to move it there) and you definitely need more torque to get the ship flying on Eve than on Kerbin. What I got somewhat flying on Kerbin was falling down on Eve.

[HafCoJoe]

Maybe Ion engines on the wing tips? Idk.

[GoSlash27]

I believe it will always be the case that the denser atmosphere is no real help, because at some point you must ascend through the altitude where it's 1 atm pressure. At that altitude your lift, thrust, and drag all match Kerbin sea level performance, but your weight is much greater.

Good point; how much fuel will it take to get to the same point where you start on Kerbin? Once you get to that point, you have to carry the empty tanks for even more DV than from Kerbin. It'll be a chore.

[cantab]

I did briefly look into using SRBs as a "boost" to get you out of the worst of the atmosphere quicker. They're very light once emptied, which is a good thing when you're not dropping them afterwards, but it's hard to get much delta-V from them. With ion main engines I'm not sure it will ever be a better use of the weight than just adding more xenon and ion thrusters.

[Darthzeus]

Actually started a 3-man group collaboration a week or two ago to do exactly that after my first ever eve mission landed with exactly 0 fuel and some shattered solar panels. We'll step it up though. *Takes gauntlet* *Realizes it'll add excess weight to craft* *Throws it back down on the purple dunes*

[KandoKris]

The closest to this I've seen and tried is a craft by metaphor with he's Eve Ion plane

http://forum.kerbalspaceprogram.com/threads/76153-Lightest-Eve-Lander/page8

I've used it and its nice to use and gets it's pilot to orbit but still not an Ion SSTO

[Tsevion]

Unfortunately, control surfaces are about the only thing in the proper size range for a lifter this light. I'm going to try a novel concept using a wing, but I'm not hopeful. The parasitic drag is proportional to mass, and wings are massive. I'm pretty sure the difference between making orbit and not is parasitic drag, so...

On paper the swept wings (best of the static wings) are pretty good, 1.6 lift for 0.05t mass, for a ratio of 32... and small control surface is 0.5 lift for 0.01t for a ratio of 50.... and both have the same drag rating of 0.02, so they shouldn't be that different. But the small control surfaces, being control surfaces, have an effective parasitic drag of 0... or possibly even negative. I made a craft last night with purely disabled control surfaces that is effectively anti-gravity... cruising at a leisurely 2 m/s and losing no altitude or speed... at all... it's like zeppelin. Interestingly it properly loses speed when climbing, but in level flight it effectively has 0 drag.

[gm537]

Here is a slightly stupid question: How are you guys going about getting your vehicles to Eve for testing? Hyperedit? (A second question would then be: where is the highest peak on Eve? (Lat and Lon))

[Pds314]

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?

With FAR, Eve ascent is much less difficult. The atmosphere, even though 5 times thicker and 40% deeper, is still not even remotely impenetrable, especially when you launch from the top of a tall mountain where nearly 63% of the atmosphere's mass is beneath you.

[Luvodicus]

I didnt see anything in the rules against Refueling the ship once in orbit? Could the SSTO meet with an orbiting fuel dump?

[Red Iron Crown]

Here is a slightly stupid question: How are you guys going about getting your vehicles to Eve for testing? Hyperedit? (A second question would then be: where is the highest peak on Eve? (Lat and Lon))

I've been hyperediting like a filthy cheater to get to Eve's surface attempting this challenge. Highest peak on Eve is just over 7500m and is located at -25.0159 Lat, -158.4558 Long; from this useful site.

I didnt see anything in the rules against Refueling the ship once in orbit? Could the SSTO meet with an orbiting fuel dump?

Doesn't matter. The hard part is getting to low Eve orbit from Eve's surface in one stage, once you're there it doesn't matter what you do.

[allmhuran]

There's kind of insane amount of reaction wheels on that ship, maybe you just used more.

In that picture I have more, but I made a few intermediate steps. One of those steps involved simply moving reactions wheels to the wingtips. I added more when I noticed the increased effectiveness.

It's just a curiosity though, I don't think it makes any kind of SSTO possible for all the reasons already listed by myself and others.

[GoSlash27]

On paper the swept wings (best of the static wings) are pretty good, 1.6 lift for 0.05t mass, for a ratio of 32... and small control surface is 0.5 lift for 0.01t for a ratio of 50.... and both have the same drag rating of 0.02, so they shouldn't be that different. But the small control surfaces, being control surfaces, have an effective parasitic drag of 0... or possibly even negative. I made a craft last night with purely disabled control surfaces that is effectively anti-gravity... cruising at a leisurely 2 m/s and losing no altitude or speed... at all... it's like zeppelin. Interestingly it properly loses speed when climbing, but in level flight it effectively has 0 drag.

I've been doing some "balance beam" testing with wings, and it seems that the #1 criteria for a "best" wing is lift coefficient to induced drag coefficient ratio. The parasitic drag isn't nil, but it's so much less than induced drag that it's neglible. Likewise, the mass of a wing as pure weight is very little compared to the mass of whatever it's lifting, and can be safely ignored.

It's also important to have the correct balance of craft mass to lift coefficient (you don't want too much or too little wing).

According to my preliminary results, the delta wing should yield the best results among non-control surfaces.

Best,

-Slashy

Edited July 11, 2014 by GoSlash27

[cerberusti]

Someone made a lifting surface comparison I find useful a while ago, http://forum.kerbalspaceprogram.com/threads/29788-How-to-calculate-lift/page3

All wings should have no drag when in level flight. I think the only difference between normal wings and control surfaces is in the AOA calculation, but what you mostly notice is that the small control surfaces have a lift to drag ratio twice that of swept wings.

I would consider hyperedit somewhat necessary for this. It will involve some trial and error and generally take a lot of time to test the craft due to the slow ion ascent even with it, without it this would be incredibly tedious.

[zarakon]

Dynamicwarp mod is very helpful when flying ion gliders. Depending on your craft's complexity you can get 2x or 4x warp with no physics distortion, or up to 8x with only 2x physics distortion