Post 1.0 - Lightest sea level* Eve ascent challenge

[Moonk]

@Moonk: Impressive Eve ship you have there! It never would have occurred to me to do an intentional flip during descent. I would have expected such a flip to yank the ship to pieces. Did you have much trouble getting that to work safely?

Getting it landed in one peace was as much hard as getting to orbit. Thanks for asking. Flip was done after drogue shuts fully deployed to slow down descent. And first main chuts are opening very gently, 15 seconds time to full radius by schedule. Even touching ground was a problem with such weight, usually one landing leg explode on rough ground. Launching is a bit trikky too, i have to off the ground with all landing equipment and decouple it couple moments after launch, otherwise the missile mislaid on its side.

[Nefrums]

You are getting close now astrobond.

I tried to get it to work by adding nukes but that did not work.

I wonder if adding aerospikes could help. The mammoth could in theory be throttled down in the later stages of the assent and the 8% higher isp of the aerospikes might do the trick.

[Moonk]

You are getting close now astrobond.

I tried to get it to work by adding nukes but that did not work.

I wonder if adding aerospikes could help. The mammoth could in theory be throttled down in the later stages of the assent and the 8% higher isp of the aerospikes might do the trick.

I am not sure, but looks like we need at least 0.75 TWR for getting altitude flying on wings 10 degrees above the horizon? or maybe it is possible with 0.5 twr?

And Nukes are too heavy to pull a significant amount of fuel, i did some calculations, looks like they almost totally useless on Eve, but not so useless as Xenon. Xenon cant pull even themselves.

btw what do u think, do we need wings if we use mamonth? Because on my opinion wings purpose to let climbing with TWR less then 1, but they also generate drag. We have mamonth, so TWR is not a problem. I wonder how astobond getting so close with wings.

[Nefrums]

Becouse the lift from the wings alow the engins to burn at a lower angle to prograde.

[astrobond]

You are getting close now astrobond.

I tried to get it to work by adding nukes but that did not work.

I wonder if adding aerospikes could help. The mammoth could in theory be throttled down in the later stages of the assent and the 8% higher isp of the aerospikes might do the trick.

Yes that's an excellent idea Nefrums

And Spikes are lighters than Nukes, that could be the solution...

No time to test that now grrr

I'll continue tonight !

[KerikBalm]

Yea, the Nuke nerf makes this not so great.... They only have a 2:1 TWR on Kerbin, so that is just a 1.2:1 vacuum TWR for Eve...

Still, you've got a lot of LF storage in those wings anyway. If you could even get a single pair to orbit, that should be the ticket for actually having some dV to maneuver in space - though any eve SSTO is probably just going to get up there, and wait for a fuel tanker to come, or a tug to push it to a fuel depot.

So the Aerospikes have a better Isp than the mammoth from above 14.3 km, and below 5.3km (irrelevant here)...

I think the bigger issue with aerospikes or LV-Ns, is the added drag, because now you need to radially attach things.

If only there were some sort of cargo bay + robotics where you could open the bay and deploy the engines at high altitude when there isn't that much drag.

I wonder if you couldn't construct some sort of reusable rocket launch sled... like something that you drive up behind the parked SSTO, maneuver into position, lower landing gear(to lift it up from the rover wheels you were using) and then fire the sled's rockets and have it push the SSTO so that the SSTO leavs the top of the mountain at over 100 m/s.

As the sled crests the top of the mountain, braking chutes deploy and you switch to the SSTO and fire its engines.

The launch sled then gets refueled by ISRU on the surface...

Saving 100m/s of atmospheric dV will translate to more than 100m/s of vacuum dV.

Heck, if you got to within 80m/s of making orbit, then a sled that pushes your SSTO off the top of the mountain at 80m/s should allow you to do it, and actually have a margin for error.

Edited August 28, 2015 by KerikBalm

[Nefrums]

The aerospikes have 9 times the vac. twr of the nukes, and more importantly they work in the lower eve atmosphere, where nukes are completely useless.

8% more isp is not mush but it might be enough to squeeze out the last 100 dV.

The added drag should be compensated by the added thrust of the aerospikes, to allow same amount of fuel/total mass

Edited August 28, 2015 by Nefrums

[KerikBalm]

The aerospikes have 9 times the vac. twr of the nukes, and more importantly they work in the lower eve atmosphere, where nukes are completely useless.

8% more isp is not mush but it might be enough to squeeze out the last 100 dV.

The added drag should be compensated by the added thrust of the aerospikes, to allow same amount of fuel/total mass

Well, its really about the ballistic coefficient.... how much drag for how much mass.

The lower TWR means that they can push less mass in a single stage than the mammoth can. I'm not sure it will work out (especially considering the mammoth limbo craft dominated over the aerospike limbo craft).

I guess we'll see. I still think that some from of reusable launch assist is the key here.

Besides, if you want to have a reusable craft to get kerbals down to eve, you'll need a way to maneuver it in position, because even the best pilot or mech jeb won't always land it to be perfectly aligned for takeoff, and it will have next to no dV to spare to line up correctly.

Something will be needed to move it around on the surface after it lands near the top of that mountain.

If that something can also catapult it off the top of the mountain at 80 m/s... then a working reusable system to get kerbals down the the surface of eve and back up becomes trivial to develop from there.

[Nefrums]

yes, the question that needs to be put to the test is if the small increase in isp in the later stages offsets the decrease in ballistic coefficient in the earlier stages of the assent.

[astrobond]

yes, the question that needs to be put to the test is if the small increase in isp in the later stages offsets the decrease in ballistic coefficient in the earlier stages of the assent.

From all the things (but the wings) i tested with the mammoth, each time you add something, at the end you need more dV than without added things

But i hope someone will find something working soon

[KerikBalm]

A launch sled... send me the craft file please, I'd like to try making a reusable launch vehicle for this.

If I can make something to send it off the edge of the cliff at 80 m/s, then it should be able to make orbit.

[Nich]

Have you done any tinkering with the ascent profile? Perhaps extrapolating the results from the Goddard Problem I suspect you might be hitting air friction maxes in the middle accent when TWR is really high but air density is still pretty thick. This is compounded by the fact you have wings so now drag is even more important.

[astrobond]

A launch sled... send me the craft file please, I'd like to try making a reusable launch vehicle for this.

If I can make something to send it off the edge of the cliff at 80 m/s, then it should be able to make orbit.

Hi KerikBalm

Here is the last version:

Eve-104-SSTO-4.craft

Eve-104-SSTO-6.craft

Eve Ascent:

Nose 35°, prograde at 20km = 52m/s missing... for my best try

(reduce throttle to avoid too much heat at about 30km, then full throttle, unlock fuel tank one by one from rear to front when big tanks are out, stop throttle when AP at over 90km, try to circularize at AP ^^)

Edit: I let the plane go rear down from the Foxster's HE coordinates and then i stop the plane before takeoff, that lets a good distance to speed up and takeoff at the mountain top with about 10° AOA

- - - Updated - - -

Have you done any tinkering with the ascent profile? Perhaps extrapolating the results from the Goddard Problem I suspect you might be hitting air friction maxes in the middle accent when TWR is really high but air density is still pretty thick. This is compounded by the fact you have wings so now drag is even more important.

Hi Nich

No real tinkering, only throttle down to avoid exploding, but feel free to test the plane too !!!

52m/s missing in manual ascent... i'm sure a good pilot can do the orbit with it !!! ^^

Edited September 17, 2015 by astrobond
another tip

[Moonk]

If only there were some sort of cargo bay + robotics where you could open the bay and deploy the engines at high altitude when there isn't that much drag.

Something like this could work?

You have to open container, launch engine, then close container.Zero drag as result.

[astrobond]

A new quick test... missed for 36m/s !!! i think i'll ask to Jeb to push the ship in EVA lol

[KerikBalm]

The problem is the container is blunt at the back, and rear nose cones are needed nearly as much as front nose cones.

Also, there is no node at the back of a Mammoth, and you can't stick that at the front of a stack, so it must go radial, and then you get the same drag as if you stuck a mk short fusalage on the side.

Tonight, I'm going to get to work on a launch sled that is reusable and compatible with Astrobond's craft.

When 1.0 comes out, the rear ramp part should get around the drag issue from an open rear node, but we'd still have no place to put it with a mammoth at the back.

I'm imaging something in an in-line cargobay, that extends a pair of engines outward radially once the air is thinner

BTW, this is getting a little off topic, I wonder if we should start an Eve SSTO thread.

In the meantime, I think this craft could get a winning entry in the Eve limbo thread.

Edited August 28, 2015 by KerikBalm

[Moonk]

btw HyperEdit "ship lander" turns ship upside down. Do u have any suggestions?

[astrobond]

btw HyperEdit "ship lander" turns ship upside down. Do u have any suggestions?

Just upside down the ship in orbit before clicking "ship lander"

Don't know if there is a better tip, but that's how i do xD

- - - Updated - - -

...In the meantime, I think this craft could get a winning entry in the Eve limbo thread.

Ok, Ok, i'll try the "standard" limbo challenge with this ship lol, but i'm not sure to beat Nefrums...

Edit: I dream of a "touch and go" at 200m/s speed at the top of the big mountain !!!

Edited August 28, 2015 by astrobond

[Nefrums]

The limbo challenge requires your ship to survive the decent... I had to add air brakes in order to do that.

[astrobond]

The limbo challenge requires your ship to survive the decent... I had to add air brakes in order to do that.

I'll try AOA breaking... I think i made a test that worked with almost the same ship

[Moonk]

Just upside down the ship in orbit before clicking "ship lander"

Don't know if there is a better tip, but that's how i do xD

I used to "land" on 2000 m, and then use chutes. But SSTO is to heavy for this

[astrobond]

I used to "land" on 2000 m, and then use chutes. But SSTO is to heavy for this

Or you can turn the ship (very slow but that works too) while in "landing mode" with enough height

Edit: Don't forget to press F5 key when you are ready to takeoff......

[astrobond]

The limbo challenge requires your ship to survive the decent... I had to add air brakes in order to do that.

Well... More difficult than i thought Another problem to solve lol

[KerikBalm]

Yea... a SSTO from eve isn't very useful if it can't be re-used.

Its even less usefull if it can't get to the surface of eve in the first place

Although... I can imagine a lot of claws with airbrakes attaching to your ship to help it get down.

Want to get another kerbal to the surface of eve? send a new shipment of airbrakes on claws....

It should end up cheaper than a new disposable eve lander.

I wonder if we should list cost of landers here...

I'm thinking we'll fix a cost of 500 funds per ton to get the ship to eve, so that a larger but cheaper lander could win.

I know I can get a ton to Eve orbit for far less than 500 funds/ton (less than 250 funs/ton to orbit for oversize payload... much lower for fuel or stuff that fits in a cargo bay, or does not require a fairing.

One obvious cost cutting method would be to replace the shock cones with just advanced nose cones,

[Foxster]

I think we have kinda derailed the challenge a little here. Not that that is a terribly bad thing but might be a tad unfair to KerikBalm. We are trying for some/any kind of SSTO from the surface of Eve rather than worrying about the challenge.

We could either de-camp to another thread or beg KerikBalm's indulgence.

Just a tip for what I do to get a craft down to where I want it with HE: Starting from the KSC, use the landing tool with a height of 100,000m over Eve and then cancel the landing. Get the craft upright. Change the height to 20m and let it land.

I think I have just about managed to get a craft from the mountain-top to a stable orbit with no staging except to drop stabilising landing legs. However!...I cheated by simulating staging by blowing up a bottom section by overheating. I just can't quite seem to get there without this. It's soooo frustrating. It's like Squad designed it to be bloody annoyingly just out of reach!