Eve SSTO possibility?

[Innuce]

I managed to get a stock, manned, ion-powered/jet-powered SSTO into orbit around Kerbin. I'd have to modify it with a couple aerospikes and some fuel. Probably need to have my refueling station in orbit around Eve to top off the tanks.

The biggest problem will be carrying the dead weight of the jet engines. That is, unless I remove them altogether and replace them with the aerospikes. Hmmm, but that would mean more fuel/weight to get off Kerbin... I know I have seen people make rocket/ion spaceplanes before.

Anyhow, here's a video of my craft going to orbit over Kerbin...

[tavert]

I doubt this is possible, may give it a shot at one point though. I think your best bet might have to result in dropping at least one stage.

SSTO = single stage to orbit. A two stage Eve ascent vehicle is quite a bit less of a challenge, so not what this thread is about.

Unfortunately, I don't think there is a way of refueling SRBs...

As for liquid fuel - I'm getting immence drag due to huge fuel tanks required, which pretty much rules out aerospikes as an initial ascending engine. So the real problem right now is getting to at least 15 000m height, after which LV-Ns work semi-well.

Can anyone post links of good Eve ion planes? I am still considering that option.

Indeed you cannot refuel SRB's in the stock game, so this would be a one-use-only SSTO. Save them till you need them to get off Eve's surface. This would still be a major accomplishment and engineering feat.

I have not personally seen any 100%-ion planes that worked well enough to get all the way to orbit on Kerbin, much less Eve. As I said earlier, in the stock game most ion planes I've seen get more thrust from infiniglide than the ion engine.

[magnemoe]

There are several concepts of "max delta-V," all of which are only strictly valid for a single stage with a single type of engine. One of these concepts just considers the mass ratio of the stock fuel tanks, which is 9 for all bipropellant tanks except the tiny ones. So for bipropellant engines, even in the limit of infinitely many fuel tanks per engine you can never get better than Isp*9.81*ln(9) delta-V.

The other concept also considers mass of the engines, and is the max delta-V to achieve a given acceleration (or TWR for some given planet/moon). You take the thrust of an engine, divide by the required acceleration to get initial rocket mass, subtract the engine mass (and any payload) then multiply by 8/9 to determine how much fuel mass you can carry to achieve the required acceleration for a given engine. So that gives you the max delta-V you can carry for a given engine to, for example, achieve TWR=1 on Kerbin or Eve, which is the minimum you'd need at least for a vertical ascent. Lower TWR is possible with planes, giving a higher max delta-V but requiring a less efficient ascent trajectory.

Both of these concepts can be slightly worked around by what I call "pseudo-staging" (my own completely made up term, take with grain of salt), by which I mean using different combinations of engines at different times of the ascent. It's like a stage since the Isp changes and you can slightly get around the above concepts of "max delta-V" by changing engine types, but not by too much since you still have to carry the empty weight of your initial tanks and disabled engines.

Yes, using an mix of normal and nuclear engines works nice for this, keep nuclear off at liftoff, engage at 1500 meter on kerbin, start turning normal engines off during the middle of gravity turn and finish it on nuclear only.

However I don't think this work so well on Eve because of the brutal TWR requirements.

[Nao]

Yes, using an mix of normal and nuclear engines works nice for this, keep nuclear off at liftoff, engage at 1500 meter on kerbin, start turning normal engines off during the middle of gravity turn and finish it on nuclear only.

However I don't think this work so well on Eve because of the brutal TWR requirements.

Actually i think burning with LV-N from the start is important as any acceleration is welcome in the first part of ascent.

Because even if we have more efficient burn without LV-N burning from the start (less fuel for given Dv) flight profile with LV-N ignited on launch will have less total Dv requirement. Resulting in decrease in net fuel burned for ascent.

Idk how to actually compute the speed at which it's no longer effcient to run LV-N's in dense atmosphere, but for standard 1,6-1,8 TWR rockets i think it will take more time to accelerate the ship than to reach LV-N cutout speed (as it will be increasing with altitude gained).

[Jod]

I have a bit of a progress regarding aerospikes. I tested a TWR of 1.6 on Kerbin and it took around 4600 delta v to put in orbit. Almost no drag losses. Question is - will 4600 delta v be enough to lift ion engines on Eve up to an altitude where solar panels can be deployed? It should still be able to operate in 1.7 gravity, though the atmosphere density could be a problem.

Here's my proof of concept, consisting of 23 stock parts:

And here it is in polar orbit(it was not controllable very well, i literally whipped it up in an hour or so)

Notice the 2 half-ton landing gear on the wingtips. I could optimize that for more ion engine load.

[Innuce]

Does anyone know what minimum altitude you can deploy solar arrays on Eve? Once you can get your craft to that altitude, ion engines should do the trick!

I know on Kerbin, you can deploy them safely around 27Km.

Sounds to me aerospikes/ions are the way to go, that is, if this is even possible at all.

Edited June 9, 2013 by Innuce

[Jod]

Does anyone know what minimum altitude you can deploy solar arrays on Eve? Once you can get your craft to that altitude, ion engines should do the trick!

I know on Kerbin, you can deploy them safely around 27Km.

Sounds to me aerospikes/ions are the way to go, that is, if this is even possible at all.

I'm guessing around 40 000m. With small craft - you can pave wings in OX-STAT provided it is noon and you have a small craft where less than 300 OX-STAT(enough for 8-12 ion engines max) are enough.

The problem is battling drag and actually stabilizing when switching to ions, I've yet to do it on Kerbin.

Also - I am getting weird results for lift and drag at high altitudes. Can you compensate for Drag with Lift in KSP? As in - add more wings? And how exactly is the Drag vector oriented? Pointing to retrograde?

Edited June 9, 2013 by Jod

[foamyesque]

It's not possible in stock, end of.

I tried with FAR, which shaves the dV requirements pretty immensely; this is the closest I got:

Needed at least another 1.5km/s of dV.

[Innuce]

I have done this on Kerbin. Only with jet engines and ions. Problem is, the jet engines do about 90% of the work getting you up to speed, then it's up to the ions to circularize.

To emulate the same thing on Eve, you'd have to essentially do the same thing I've done on Kerbin, but with aerospikes in place of jet engines.

So, we're talking about a manned SSTO that can take off from Kerbin, make it's way to Eve, land, then take off again back to orbit. A couple of refueling stops along the way of course.

I have been working on another project, but I may have to put that on hold now, haha.

[Jod]

I've found my problem with Drag. According with a formula from the wiki - if you have around 2000m/s speed and 4 tons of mass, ion engines will be entirely unable to compensate for Drag below 40 000m on Kerbin and below 70 000m on Eve. So it's not a question of at what altitude to deploy solar panels but at what altitude the drag won't eat up all the ion engine thrust since the latter is much higher.

[Ekku Zakku]

Does anyone know what minimum altitude you can deploy solar arrays on Eve? Once you can get your craft to that altitude, ion engines should do the trick!

I know on Kerbin, you can deploy them safely around 27Km.

Sounds to me aerospikes/ions are the way to go, that is, if this is even possible at all.

Just wanted to point out that gravity (even on Kerbin) is way too high for ion engines.

If I remember correctly, the highest possible acceleration you can get with ion engines at the ideal maximum TWR is just above 1 m/s^2. Compared to the acceleration due to gravity on Kerbin at 9.81 m/s^2, you've got a massive problem of an impossible TWR situation lol. They can be used to get some efficient Delta-V, but they're nowhere close to being enough for a winged SSTO on Kerbin or Eve; trust me, people have tried.

[Jod]

Just wanted to point out that gravity (even on Kerbin) is way too high for ion engines.

If I remember correctly, the highest possible acceleration you can get with ion engines at the ideal maximum TWR is just above 1 m/s^2. Compared to the acceleration due to gravity on Kerbin at 9.81 m/s^2, you've got a massive problem of an impossible TWR situation lol. They can be used to get some efficient Delta-V, but they're nowhere close to being enough for a winged SSTO on Kerbin or Eve; trust me, people have tried.

Thank you, Captain. We've established that several times on the first page.

As I said, the problem with ion engines is the inability to counter Drag. With the current Lift model we can counter gravity acceleration all day using a matchstick for propulsion.

Looks like it's back to LV-Ns for me. Though I'm pretty sure their weight will screw things up with this ridiculous Drag equation. What bugs me the most is it probably would have been possible(a dry to full ratio of just around 1/5) to SSTO Eve if it had no atmosphere. Aerodynamics are useless.

Does anyone have an elevation map of Eve in its current form? I've been watching Scott Manley videos and noticed it took him only 8000 delta v when taking off from 10 000m. I'm aware that the plateau is gone, but is there anything close enough?

Edited June 9, 2013 by Jod

[Ekku Zakku]

Thank you, Captain. We've established that several times on the first page.

Sorry, came into the thread on the fourth page past midnight being half asleep, didn't bother reading the other pages XD entirely my fault, as well as the poster who I replied to I suppose. I simply wanted to inform is all =3

[tavert]

Does anyone have an elevation map of Eve in its current form? I've been watching Scott Manley videos and noticed it took him only 8000 delta v when taking off from 10 000m. I'm aware that the plateau is gone, but is there anything close enough?

kerbalmaps.com - there are a few locations over 6000 meters, I used the 6400 meter mountain at roughly -11.9, -2

You can do it from those high mountains for around 8500 m/s, but only if your TWR is high enough to stay near terminal velocity. An SSTO design, if possible, will not be able to match the TWR that staged Eve ascent vehicles have.

[Jod]

Thank you.

Yeah... 6000 delta v is the best I got from my TWR 1.0-1.7 SSTO designs without using jet engines for that pesky ascent through the thick parts of the atmosphere. Will keep trying though.

[Innuce]

It's not an issue of whether ion engines can compensate, but at which point they would contribute.

The unique problem with ion/jet engines on Kerbin is the inability of throttling up the ions to full-throttle at the same time you need to throttle-down the jet engines. Once I was well over 40Km, I was able to shut down the jet engines entirely and finish the orbit with ion alone.

In this case, on Eve, we can supplement the main engine(s) with ion at around 40Km (once the solar arrays can be deployed), at full power. Presumably, exhausting rocket fuel after 70Km, then switching to 100% ion drive and perhaps RCS for docking (unless you have a docking port on the nose).

[Jod]

In this case, on Eve, we can supplement the main engine(s) with ion at around 40Km (once the solar arrays can be deployed), at full power.

I tried that on Kerbin. Unfortunately, there is a huge power gap between even LV-Ns and ions and unless you have more than 8 ion engines, the contribution while in atmosphere will be less than 100 delta v for a lot of weight which could've otherwise been fuel. Using more than 8 ion engines is even less productive due to their mass. So far - the only part of ascent where ion engines have proven themselves to be useful is the last few hundred delta v when you circularize your orbit. Maybe a thousand. That's still 1500 dv short of a feasible SSTO.

[Innuce]

So it might not even be worth using ion engines at all?

Getting a manned, horizontally launched, ion/jet engine powered spaceplane into orbit probably wasn't the best solution either. Probably could have replaced all the ion engines with a couple aerospikes and a tank of fuel to accomplish the same thing.

I think I did it just to see if it was possible, not for the sake of efficiency.

[Jod]

I'm not saying Ion engines are not worth using. I'm saying I can't get to a height where they can be useful. If I will miraculously come up with a design that can get me to at least 80 000 m on Eve I will totally use 2-4 Ion engines to circularize since all fuel will probably be used up at that point even with LV-Ns.

Edited June 9, 2013 by Jod

[foamyesque]

I'm not saying Ion engines are not worth using. I'm saying I can't get to a height where they can be useful. If I will miraculously come up with a design that can get me to at least 80 000 m on Eve I will totally use 2-4 Ion engines to circularize since all fuel will probably be used up at that point even with LV-Ns.

Getting to 80km isn't the problem. The problem is you get to 80km and need a km/s+ of dV to even approach a circular orbit, or you fall right back down. You simply won't have the time to manage it with ions.

[Innuce]

Seems to me it will take a very massive craft to do this. Especially if we're talking a true SSTO from KSC.

Maybe reduce some size if it were allowed to be carried to Kerbin orbit first using a lifter stage...

[Jod]

Getting to 80km isn't the problem. The problem is you get to 80km and need a km/s+ of dV to even approach a circular orbit, or you fall right back down. You simply won't have the time to manage it with ions.

That is why standard procedures require to start leveling the craft as early as 40 000m. I'm talking about circularizing an orbit that covers at least 1/4th of the equator.

Massive crafts are out of the question though, ion engines simply won't move them fast enough. Something in the range of 6-10 tons when all fuel is depleted can theoretically gain some good delta v from ions, anything heavier will not accelerate fast enough and lose orbit.

And I'm talking really small. Like, Rockomax 24-77 small. I'm going to test a 2 Rockomax 24-77 + 1 ion engine setup soon. So far, 1 LV-N + 4 Rockomax 24-77 are quite a bit more efficient than 1 aerospike, provided 24-77 are not used all the time but only when needed.

Here are some screens of my test flights:

Made it into Kerbin orbit with some fuel to spare on an LV-N with four 24-77 boosters. The fuel left was enough to push apoapsis up to 500 000m.

Taking off with all boosters enabled. Half of the fuel is consumed in the first 4000m.

Also - I found out that aircraft landing gear weighs 0 kg for some reason. So all my efforts at attaching rover wheels were in fact making the TWR worse, will revert to aircraft landing gear soon.

Taking an SSTO without jet engines into Kerbin orbit should be a challenge or something... With winners trying their craft on Eve. Anyone wants to start one?

Edited June 10, 2013 by Jod

[Sephta]

So I made a short test with the Kethane Turbine and I'm not really convinced, it'll make sense to use them on EVE:

* You have a fixed amount of KIntakeAir per turbine, as there aren't any single intakes, you could slap on your plane, so you can't compensate higher altitudes with more intakes to keep the turbines running efficient.

* a small craft with 2 Turbines only (15t, 2 turbines, 1 nerva with fuel for both) would go max 450m/s at 14000m on Kerbin.

* there was a instant flameout, when I exceeded 15000m (not exact, have to test this further) after adding the nerva to go higher.

So... I don't exactly know, how these numbers translate to Eve, but I doubt, you could make an orbit with Kethane jets as you could with the normal turbo jets.

Edited June 10, 2013 by Sephta

[Jod]

Well, it is possible with mods, there is a challenge for that. This topic is more about Stock parts.

The Rockomax 24-77 + ion engine combo is a bust. It is possible to make Kerbin orbit but ion engines have no effect whatsoever during ascent and even circularization due to empty fuel tank mass they have to tow. I used 24-77 specifically because their weight is very very low so all I had to deal with was empty fuel tanks. Along the distance of 1/4 of the equator the ion engine failed to increase delta v sufficiently.

Also tried the aerospike + 2 ion engines combination, same result. Liquid engines require a lot of fuel tanks that even when depleted hinder ion engine thrust.

I will check the math to see if creating a pure ion-powered glider is possible. I think I saw one of those on the wiki, though I'm not sure if it can reach the needed speeds before getting to the dark side of the planet(or driving the pilot to insanity). Something tells me that getting sunlight would be the least of the problems.

Edited June 10, 2013 by Jod

[foamyesque]

The problems with a pure ion ship are twofold:

1. Partcount

2. You're flying on infiniglide anyway