sevenperforce

Reusable Staging Off Eve

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Eve is always the one problem planet that trips everyone up when they want to do grand tours. Trying to establish any kind of long-term presence on Eve is fraught with the need for expendable multistage landers.

I've seen @Kergarin's amazing suborbital catch he uses to get off Eve and reuse his ISRU-equipped everywhere-lander, but that kind of precise timing is way beyond my capabilities, and I'm interested to see if there are any other ways of doing it. Now, I've toyed around with stock props to try and make a propeller-based SSTO, and some designs are promising, but it still stretches the boundaries of what's actually feasible.

What about reusable staging, SpaceX or Stratolaunch or Energia style? If we could use the Klaw to mate a first and second stage together, then the first stage could get suborbital, release the second stage, and fly back to the launch site to land and refuel. After reaching orbit, the second stage could rendezvous with a waiting tanker/station, refuel if necessary, then head back down to do it all over again.

I've tried it two ways so far: one with a HTOL Vector-powered Stratolaunch carrying an LV-N based upper stage underneath, and one with a VTOL first stage with the second stage slung alongside providing a parallel boost. In both cases, I've been able to make orbit on the second stage, but not before the first stage fell out of render range.

Any other ideas? Anyone else want to take a try at it?

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Well it certainly is an interesting idea, and with the right massaging it should work.  I'll play around with things and see, although I might rely on KER's readouts to determine if it works.  I'm the type to spend 90% of my KSP time in the VAB or SPH designing.

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Posted (edited)

I could think of some 2 stage designs, but the first stage would have to be rather tall and massive, hard to land and hard to mate the second stage back to. 

 

Hmm, maybe an EVE Seadragon, if we could land both stages in the Sea and grab them with boats, we might be able to dock them together while floating. Then we "only" need a mechanism to raise the floating rocket upright to launch it. The refueling would also require boats. That'd be a good way to utilize stock props.

Something like this

5lyDrPr.jpg

Edited by Physics Student
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37 minutes ago, Physics Student said:

I could think of some 2 stage designs, but the first stage would have to be rather tall and massive, hard to land and hard to mate the second stage back to. 

 

Hmm, maybe an EVE Seadragon, if we could land both stages in the Sea and grab them with boats, we might be able to dock them together while floating. Then we "only" need a mechanism to raise the floating rocket upright to launch it. The refueling would also require boats. That'd be a good way to utilize stock props.

Something like this

5lyDrPr.jpg

Good idea. I hadn't thought of using the water to help.

The Klaw makes docking much easier, but it also means you can't use crossfeed for a parallel-staged design. It's also harder to get the alignment right, though I suppose some sort of alignment struts might come in handy.

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or this: 

 

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15 minutes ago, Physics Student said:

or this: 

 

Well, of course any number of mods enable Eve SSTO.

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Posted (edited)
On ‎1‎/‎5‎/‎2018 at 3:33 PM, sevenperforce said:

Well, of course any number of mods enable Eve SSTO.

As the author of that mod, I haven't succeeded in making an Eve SSTO space plane with it yet. (Guess what? I succeeded!) Mind you, I haven't used Kerbal Engineer before this month either, and I really didn't have a clue about how much delta-v was needed to orbit Eve from sea level.

One day, I hope to accomplish this. Perhaps the most recent release of ExV Engines with the stronger high-density thrust will help. So I'd say, let's start by allowing this part mod, and then gradually allow others. What's the minimum modding needed to accomplish Eve single stage to orbit?

Also consider installing Alien Space Programs so you can start from Eve. If you do this though, this by default replaces the atmosphere with the one from Realistic Atmospheres, but has a config switch that puts back Eve's stock atmosphere.

Edited by Gordon Fecyk
I succeeded! With a lot of asterisks...
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3 minutes ago, Gordon Fecyk said:

As the author of that mod, I haven't succeeded in making an Eve SSTO space plane with it yet. Mind you, I haven't used Kerbal Engineer before this month either, and I really didn't have a clue about how much delta-v was needed to orbit Eve from sea level.

One day, I hope to accomplish this. Perhaps the most recent release of ExV Engines with the stronger high-density thrust will help. So I'd say, let's start by allowing this part mod, and then gradually allow others. What's the minimum modding needed to accomplish Eve single stage to orbit?

Also consider installing Alien Space Programs so you can start from Eve. If you do this though, this by default replaces the atmosphere with the one from Realistic Atmospheres, but has a config switch that puts back Eve's stock atmosphere.

The only mod I play with is Tweakscale but I may think about trying yours out.

Anyway, for the time being this isn't a standard, scored challenge so much as it is a challenge to try and do the impossible: namely, get to Eve orbit with a reusable system, in stock.

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You might be able to use any kind of docking port to connect the stages reusably (not just klaw), but how do you land the first stage and ensure that the second stage continues to orbit with the way the physics bubble works in stock?

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20 minutes ago, Wcmille said:

You might be able to use any kind of docking port to connect the stages reusably (not just klaw), but how do you land the first stage and ensure that the second stage continues to orbit with the way the physics bubble works in stock?

With a high enough apoapse at separation, you should be able to push the second stage into a stable orbit (or at least a nearly-stable one) before the first stage is unloaded. Depending on the trajectory, you can probably manage to switch back over to the first stage and fly it to a landing as long as you get to it before it hits 45-50 km.

I recently used this trick to launch a Falcon Heavy clone and recover all three boosters, in stock.

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1 hour ago, sevenperforce said:

Well, of course any number of mods enable Eve SSTO.

A fun one I briefly considered, once, was SXT's Nuclear Ramjet. Still requires soe other propulsion to bring it up to speed first, preferably supersonic.

As for a Sea Dragon, I guess KIS fuel lines will make it a whole lot easier. If the rocket doesn't stand up from the mass of fuel alone, add ore ballast tanks and an action group to purge the contents as soon as you have gimbal control (tweakable everything?)

1 minute ago, sevenperforce said:

With a high enough apoapse at separation, you should be able to push the second stage into a stable orbit (or at least a nearly-stable one) before the first stage is unloaded.

Pretty impractical on Eve. Besides, if you have infrastructure (separate mining rig, refueling barge, ...) you want to return to it.

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2 minutes ago, Laie said:

A fun one I briefly considered, once, was SXT's Nuclear Ramjet. Still requires soe other propulsion to bring it up to speed first, preferably supersonic.

As for a Sea Dragon, I guess KIS fuel lines will make it a whole lot easier. If the rocket doesn't stand up from the mass of fuel alone, add ore ballast tanks and an action group to purge the contents as soon as you have gimbal control (tweakable everything?)

Build a ring-shaped set of flotation tanks with a ballast tank and a Klaw underneath. Distribute the ballast to tip the whole affair on its side and dock the Klaw to the back end of the first stage. Dock the second stage, move the ballast (ore) back to the lower tank to erect it. Fuel the whole affair, then set up the engines, throttle up and disengage the Klaw simultaneously, and you should be good to go.

And very easily testable in the oceans of Kerbin.

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49 minutes ago, Laie said:

Pretty impractical on Eve. Besides, if you have infrastructure (separate mining rig, refueling barge, ...) you want to return to it.

That's what a boostback burn is for.

Also, in my testing, the first stage is pretty much just going to go straight up and straight down. The second stage needs to carry all the dV for the actual orbit; the first stage merely acts to lift it up out of the dense atmosphere.

Plus, if you are using a Stratolaunch-style approach, then you have enough crossrange to get back to the launch site anyway.

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Only makes it even more impractical. All planets but Kerbin have a pretty thick upper atmosphere, don't expect that you can translate your Kerbin experience to Eve just like that.

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My current thinking is to use a Seadragon like assembly method and have a first stage with wings for the cross-range capability.  It would be harder, but having two first stage boosters split off improves the efficiency.

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1 hour ago, Laie said:

Only makes it even more impractical. All planets but Kerbin have a pretty thick upper atmosphere, don't expect that you can translate your Kerbin experience to Eve just like that.

I've already tested the assembled LV on Eve using the cheat menu. My initial first-stage booster (with the second stage slung alongside, Energia-style) wasn't quite big enough to get a high apoapse, but that just means I need to go a touch bigger. The upper stage makes orbit without too much trouble.

30 minutes ago, Thor Wotansen said:

My current thinking is to use a Seadragon like assembly method and have a first stage with wings for the cross-range capability.  It would be harder, but having two first stage boosters split off improves the efficiency.

No way you can recover the side boosters in stock.

A VTHL core stage, using the oceans to go vertical for launch, is one promising architecture I hadn't considered. See, this is why I made a challenge out of it!

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6 minutes ago, sevenperforce said:

No way you can recover the side boosters in stock.

What I meant was two first stage boosters supporting a central orbital stage, like a three part parallel stage system but with vacuum optimized engines on the orbital bit.

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I haven't tested this, but my first thought for reusable Eve infrastructure is to have a ISRU equipped rocket spaceplane with a detachable, winged second stage. The first stage of the rocket plane would take off horizontally and then climb into a suborbital trajectory where it would deploy the second stage. The second stage would reach orbit, while the first stage would glide back down to a flat, high altitude landing site (>5000 m). From here the first stage could use ISRU to refuel, and the second stage could deorbit and glide back down to this landing site. Since they are both horizontal when landed, they can be redocked and the arrangement can take off again without too much trouble.

Alternatively, you can setup a ring of high altitude ISRU bases around the planet for the plane to land at. This would require more setup, but would enable better payload fractions.

2 hours ago, sevenperforce said:

Build a ring-shaped set of flotation tanks with a ballast tank and a Klaw underneath. Distribute the ballast to tip the whole affair on its side and dock the Klaw to the back end of the first stage. Dock the second stage, move the ballast (ore) back to the lower tank to erect it. Fuel the whole affair, then set up the engines, throttle up and disengage the Klaw simultaneously, and you should be good to go.

And very easily testable in the oceans of Kerbin.

While this may work on Kerbin, it probably won't work as well on Eve. This is because Eve's oceans are much denser than Kerbin's: An ore tank on Kerbin will sink just fine, but will barely sink on Eve. If you want ballast for Eve, you pretty much need to use Vectors, or the I-beams to be effective. And even then, you need a surprising amount to get something to sink, much less sit upright in the water. 

Not to discourage you from this approach, just be sure to do your testing on Eve first because their oceans are quite different.

 

 

 

 

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Posted (edited)
11 hours ago, Stratzenblitz75 said:

While this may work on Kerbin, it probably won't work as well on Eve. This is because Eve's oceans are much denser than Kerbin's: An ore tank on Kerbin will sink just fine, but will barely sink on Eve. If you want ballast for Eve, you pretty much need to use Vectors, or the I-beams to be effective. And even then, you need a surprising amount to get something to sink, much less sit upright in the water. 

Not to discourage you from this approach, just be sure to do your testing on Eve first because their oceans are quite different.

 

 

Correct, but sinking isn‘t the only option. You could also have a „booster boat“, a designated craft (or even two of them) that have very high thrust and burn for just a second or two to lift the rocket up to a vertical position. They detach at the same time as the main engines ignite. I did something like this once where I wanted my Eve Ascent rocket landed in a horizontal position, so it could drive around like a rover. I call it „assisted horizontal takeoff“. The problem with all of this is of course the massive requirements in infrastructure.

Edited by Physics Student

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2 hours ago, Physics Student said:

Correct, but sinking isn‘t the only option. You could also have a „booster boat“, a designated craft (or even two of them) that have very high thrust and burn for just a second or two to lift the rocket up to a vertical position. They detach at the same time as the main engines ignite. I did something like this once where I wanted my Eve Ascent rocket landed in a horizontal position, so it could drive around like a rover. I call it „assisted horizontal takeoff“. The problem with all of this is of course the massive requirements in infrastructure.

I did that once for a Sea Dragon challenge, before I understood buoyancy in the Kerbin oceans. Assembled the rocket in the SPH, drove it out into the drink with rover wheels, decoupled the rover wheels, then used pairs of Hammers at the fore and aft ends to flip vertical before staging to release the Hammers and ignite the first stage. Took a lot of doing, but I managed it.

Of course, that's not the most reuse-friendly architecture, especially when you have to assemble it manually.

In testing the two different architectures I've attempted so far (Energia-style with parallel staging, and Stratolaunch-style with a winged second stage), I relearned the importance of vertical thrust on Eve. I had thought that using a winged vehicle would enable takeoff with TWR<1, and it does, but rocket engines are so inefficient on Eve that you don't really climb appreciably before your mass drops and your TWR is enough to just point radial-out and be done with it. 

So it would seem the primary advantage of using HTOL is "free" crossrange/landing and presumably easier vehicle mating, but nothing really in the ascent department, since you need to be pointing radial before any actual progress is made. VTHL would have the same advantages with none of the disadvantages, but getting it erect would be very challenging.

And we still have to make sure the first stage is beefy enough to have the dV for significant suborbital hang time, or there's no way to get the second stage orbital and switch back in time.

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2 hours ago, sevenperforce said:

I did that once for a Sea Dragon challenge, before I understood buoyancy in the Kerbin oceans. Assembled the rocket in the SPH, drove it out into the drink with rover wheels, decoupled the rover wheels, then used pairs of Hammers at the fore and aft ends to flip vertical before staging to release the Hammers and ignite the first stage. Took a lot of doing, but I managed it.

Of course, that's not the most reuse-friendly architecture, especially when you have to assemble it manually.

In testing the two different architectures I've attempted so far (Energia-style with parallel staging, and Stratolaunch-style with a winged second stage), I relearned the importance of vertical thrust on Eve. I had thought that using a winged vehicle would enable takeoff with TWR<1, and it does, but rocket engines are so inefficient on Eve that you don't really climb appreciably before your mass drops and your TWR is enough to just point radial-out and be done with it. 

So it would seem the primary advantage of using HTOL is "free" crossrange/landing and presumably easier vehicle mating, but nothing really in the ascent department, since you need to be pointing radial before any actual progress is made. VTHL would have the same advantages with none of the disadvantages, but getting it erect would be very challenging.

And we still have to make sure the first stage is beefy enough to have the dV for significant suborbital hang time, or there's no way to get the second stage orbital and switch back in time.

Indeed, having a TWR <1 on Eve is a bad idea. You really need to be ascending as quickly as possible to start out. However, my point with a horizontal take off isn't to try gradually climbing to orbit, but instead, is a different way of getting the vehicle vertical. After a horizontal take-off, you can quite easily leverage the engine gimbals + lift to point yourself upwards. You could even use the upward slope of a hill to help out too. Of course, as you said, during this initial pull up maneuver, you aren't making any progress, but the horizontal take off isn't as bad as it seems.

Also, yeah the suborbital hang-time is a problem for the second stage. To get around this, I think you could build the first stage so that it is almost an SSTO (maybe 500-1000 m/s of orbit). From here, you should be able to get the second stage into orbit before leaving KSP's 40 Km unload range. 

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Posted (edited)

Thanks for mentioning me, but it was @Stratzenblitz75s Eve Unlimited which first used suborbital docking at Eve.


The idea is really nice, I was thinking of a spaceplane desgin too, because putting the second stage back to the upright standing rockets nose would be harder than anything else.

Besides this, i have just checked what my old Eve SSTOs could do with a second stage on top. Using 4 side mounted Aerospikes i can get a Mk3 pod quick enough into orbit, to switch back to the first stage. 

But if I do remember this right, it is still possible to build a manned Eve SSTO in 1.3. I just wasn't able to include the ISRU equipment in the SSTO. So if you don't mind having some kind of ground bases ISRU refuelling, you can still have an EVE SSTO to get your crew back to orbit. (from the highes point)

EDIT:

Just a small hint:

does a second stage have to be mounted on top of the rocket? :wink:

If you mount it at the bottom of your first stage, you can just give it wheels an drive it back under the frist stage, and then lift it until the docking ports connect, using some landing legs (which you will need anyway).
This way you can also use the second stages enginge during the whole ascend. 
Also you dont need so much ladders this way.
I would go for 3-4 Mammoths plus one Rhino for the second stage.

This should bring you so high up. that you will have enough time to undock the bottom mounted second stage. The Rhino will bring it to Orbit in seconds

 

 

Edited by Kergarin
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Posted (edited)

Soon after this thread started (not yet having found this thread) I started a similar thread, and got some good advice.

PelicanFish.jpgI am happiest myself with a two-stage design (craft file) using horizontal takeoff and landing for the sake of control, especially for the landings.

Fueled mass is 175 tonnes and TWR starts at 1.1 at Eve's high-point.  I can hold an AoA around 3° and gradually transition to vertical.  I take off heading west, then rotate just past vertical to exit the atmosphere, so that the first-stage re-enters not too far east of the high-point, within gliding distance for landing, without needing to save any fuel for boost-back.  

The second stage then needs to provide essentially all the orbital speed to circularize, but it can do so with 2--4 G acceleration before the first stage gets too deep in the atmosphere, so I can switch back to land the first stage, without any stage-recovery mods.  The orbital stage took its canard with it, so the booster stage is left with wings further back, closer to its unfueled CoM.

When it is time for the orbital stage to return to the surface, it has wing-strakes forming a feathered tail and deployable control surfaces for drag, all of which were shielded in the cargo ramp during ascent.

For re-docking, both craft point slightly uphill, the orbiter rolls into the cargo ramp, and then the lifter gulps it down, like a pelican swallowing a fish.  The module-manager patch to enable angle-snap on docking ports is very helpful to make the joined craft fly straight.  After docking, the cargo ramp can close around the orbiter, shielding its tail feathers and engine from drag during the next ascent, but leaving its nose and canard active (and causing drag, which is only fair).  I am happy to imagine this is some custom fairing that the Kerbals can fit while they are preparing the craft for flight.

Not that I'm finally happy with the shuttle in 'the simulator' (hyperedit) I can time-warp to the transfer window and send the full expedition.

Edited by OHara
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That's a nice design @OHara!

Can it be landed fully fuelled, or do you have to land it empty and refuel on the ground? 

Does it reach orbit with open "mouth" or does this generate to much drag?

You could get rid of the angle snap mod if you use two docking ports.

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9 hours ago, Kergarin said:

Can it be landed fully fuelled, or do you have to land it empty and refuel on the ground? 

Does it reach orbit with open "mouth" or does this generate to much drag?

Each part on its own, and the docked combination, can land fully fueled, but the booster alone is very nose-heavy and extremely hard to flare.   The difficulty is re-entry.  Only the orbiter stage can re-enter with any significant fuel; it is mass-balanced so it can hold a high AoA but parts still overheat.

Having the mouth open creates significant drag, but it still accelerates. It might work with the mouth open, but it is no fun to fly that way.

I decided that I like the way the cargo bay shields just the parts that lie visibly inside it, and found it interesting to see how I could use that.  Using a full-size in-line docking port could also work, re-attaching the parts in the manner we dock bases on the surface, but my attempts in that direction were looking ugly.

9 hours ago, Kergarin said:

You could get rid of the angle snap mod if you use two docking ports.

Maybe.  I was not sure if I could get two ports to dock simultaneously with Eve's gravity pulling on the craft.  Instead I made fittings inside the cargo bay that rub against the tail feathers to guide the 'fish' into the proper orientation in the 'mouth'.  That aligns things well enough to fly. The angle-snap module-manager config just makes things tidy, and everybody knows that docking ports should work that way by default.

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