Eve ∞ (Hard)

[AHHans]

On 9/5/2019 at 5:34 PM, AHHans said:

The accident investigation is still ongoing. After finding only low to moderate amounts of part clipping, the investigators are currently looking into the Kraken attracting properties of autostruts.

The accident investigation team has finished its analysis of the incident. Careful study of the wreckage showed that no remains of the central fuel tank could be found, disintegration of this central part of the craft can also explain the scatter of the recovered wreckage parts. Therefore the investigation team considers the following chain of events to be the most probable course of the accident.

1. At the time of the accident the small (FL-T100) fuel tank at the bottom of the main fueselage was the root part of the craft. It was connected to the central fuel tank (a model X200-32 from Rockomax) via a TD-12 decoupler and a BZ-52 attachment point.
2. When the small fuel tank was detached by triggering the TD-12 decoupler the X200-32 tank became the root part of the craft because the specialized construction of the BZ-52 makes it an integral part of the X200-32.
3. The main cause for the disintegration of the X200-32 tank are still unclear, but it is assumed that the rapidly changing loads of several autostruts snapping to it (including an autostrut from itself) exceeded the structural limits of the X200-32 tank.
4. Once the central tank stopped connecting the different parts of the vessel, the reinforcing EAS-4 strut connectors between the - now separate - parts of the vessel disconnected. Leading to a complete collapse of the structure.

It was concluded that the underlying cause of the incident was the change of the design to work around a limitation of the FMRS time-jumping technology. In this change the root part of the overall craft was changed from being on the carrier plane to being on the orbital module. This cause the small connecting part becoming the root part of the carrier plane after the initial separation of the two crafts. As the FMRS time-jumping technology has still proven to be unreliable even in this configuration, this change is now discouraged.

[Guest]

Hey nice @EveMaster!  You're a better pilot than I am, I haven't managed to land them anywhere near that close together.

I made a few tweaks to improve the thermal performance of the craft, unfortunately one of these  needs a Making History part as well -- it's not a critical part though. Main change was to move the Mk 1 utility bay from the nose of the orbiter module to the tail: this means I can re-enter at a slightly tail-first angle, having the bay take most of the heat. Now it survives atmospheric entry no problem.

I also swapped out the aero nose cone on the nose of the lifter module with a Making History service bay, which has just a bit higher thermal tolerance -- this made it easier to enter the combination plane from Eve orbit. It's not a blocker though as you can always pack a bit more fuel and burn retrograde to make the entry less severe.

Anyway, I made a round trip (surface to orbit and back, everything intact) in the improved version, and updated the file on KerbalX.

 

Edited September 8, 2019 by Guest

[EveMaster]

Nice to see, that you also made the round trip. The shielded docking port also has a very high heat tolerance. Unfortunately it has no attachment node so you cannot assemble it in the hangar. With the shielded docking port I could even bring back down the empty lifter safely during testing from a vertical dive of 2km/s.

[AHHans]

After many tries the engineers at AHTech industries have managed to wrestle the FMRS time-jumping technology into submission. The clou was not to modify the craft but to change the mission strategy: by pre-positioning a refueling tanker in Eve orbit, the orbital module can rendezvous with it and once it is in physics range on can switch control without FMRS resetting. (And once the orbital module has landed FMRS is willing to merge it into the save with the landed carrier plane.)

The (mostly) full photo story of the trip can be seen on imgur: https://imgur.com/gallery/qRW7TlA here are some highlights:

The Eve Reusable 3 (yes, a totally ingenious name, I agree) on the runway.

And on landing approach after cheating into Eve orbit, de-orbit burn, and aerobraking.

After craft separation, ditching of the temporary interconnect, and re-attaching with the Klaw. Using the mining gear on the carrier plane for refueling.

It can go under electrical power to above 10 km asl. the next stage is using the rocket engines on the carrier plane to get even higher. This is also when we need to arm FMRS.

After separation and most of the burn into orbit. The orbital module coasts to its circularization burn. (With about 250 m/s dV left to rendezvous with the tanker in orbit.)

[Note, the following screenshots are from another run. The images above are from before I figured out how to deal with the FMRS issues. For the following I loaded a save with the craft landed on Eve and ready for take-off after refueling with the mining equipment. Unfortunately I also lost the screenshots with the return of the carrier plane to ground.]

The rendezvous maneuvers to meet the tanker in Eve orbit have to be done with the orbital module. But once the tanker is in physics range one can switch to it to finalize the docking without FMRS resetting.

Refueling the orbital module, de-orbiting, and landing the orbital module is then comparatively trivial. Once the orbital module has landed one can use FMRS to join it with the carrier plane, and the carrier plane can come and pick up the orbital module for another go.

 

In conclusion: this craft has two major drawbacks. One is the strict limits on what you can do while in orbit: no switching to another vessel outside physics range, no going back to the KSC to launch a tanker or so. You are in a state of limbo until the orbital module has landed and FMRS can join the saves. The other one is that the combination of the telescoping pistons and the landing gear doesn't work too well. When loading the craft with the pistons locked, then the actual extension of the pistons is not the target extension that was set. So when they are unlocked they "jump" to their target, and this tends to over-stress the landing gears. And when not locked the pistons are fairly wobbly... But it works!

I already have another craft in development, which is kind of the merger of this one and the Eve Infinity by EveMaster. So I don't plan to put the craft file on KerbalX (unless you ask me to), but you can download it here:  craft file

[EveMaster]

Nice craft @AHHans, I'm also interested in seeing the combination of your craft an my craft.

I also build a craft named "Eve Reusable 3" some while ago:

The upper stage seems to lack parachutes. Maybe they were added for the Eve Reusable 4. With the command chair in the fairing I managed to reach orbit from 550m above sea level once. Unfortunately when disembarking from the command seat the kerbal often got trapped within the fairing and I had to destroy the fairing.

I also managed to put a kerbal in a command chair on into orbit without protection of the fairing. Reentry without fairing however would not be survivable for the kerbal.

[Guest]

2 hours ago, EveMaster said:

Nice to see, that you also made the round trip. The shielded docking port also has a very high heat tolerance. Unfortunately it has no attachment node so you cannot assemble it in the hangar. With the shielded docking port I could even bring back down the empty lifter safely during testing from a vertical dive of 2km/s.

Yeah, I know, the shielded docking port is terrific. I was considering it as a last resort, but that characteristics makes it really undesirable. 

BTW, about that ground infrastructure...

[AHHans]

[Hmmm... maybe I got a bit carried away there, but now I'm tired. So I just copy and paste my sales-pitch from Kerbalx:]

AHTech Industries proudly presents:

The Eve Transportation System (ETS)

This latest entry in our Flying Eve class of Eve exploration vessels is intended to facilitate recurring transport between Eves surface and low Eve orbit (LEO)

The craft consists of the carrier plane that can fly to every place on Eve on solar power and contains a fully independent refueling setup, and of the orbital module. Working together both parts of the ETS can carry 6 Kerbals with all their personal survival gear and science results from anywhere on Eves (solid) surface into low Eve orbit. Where the passengers can transfer to further transportation.

After both parts are joined and refueled the ETS can ascend to 10 km asl on solar power alone, from where it can fire its rocket engines and boost itself into a suborbital trajectory. There it can release the orbital module which can circularize into low Eve orbit before the carrier plane falls back too far into Eves atmosphere. The carrier plane can then re-enter the atmosphere and land on solar power. With an optimized ascend profile the orbital module has more than 300 m/s dV left in LEO for in-orbit maneuvering it also has a fully functional RCS system and 15 units of monopropellant for final docking maneuvers. After refueling in orbit the orbital module can re-enter Eves atmosphere and glide to a save landing, where it can be picked up by the carrier plane to repeat the process.
To ease docking of the two crafts the carrier plane is equipped with a movable docking port and a craft alignment system.
As a bonus feature the carrier plane is equipped with party lights to entertain the ground crew while waiting for the next mission.

Notes from the engineering department:

There are still some issues that could be improved, but the marketing department said something along the lines: "Do we have to actually shoot one of you before we can have this thing shipped?" And now most of the engineering department is taking a well earned rest, while staying as far away from anyone from marketing as possible.

One problem is is that this thing is hughe! Nearly 700 tons. I wanted to have a more capable orbiter that has some fuel left for in-orbit maneuvers. That meant a big carrier, that needed a larger wing, that needed more propeller power, that needed a larger booster, etc. On the other hand: this thing works! And getting into orbit and the carrier landed safely is pretty easy. The latter is also the reason for using the "Skiff" engines from Making History. It probably could also work with the aerospike, but the greater thrust of the Skiff makes the circularization so much easier.

But the biggest problem is that the many propellers make the carrier plane (without the orbiter) aerodynamically unstable when they are not used for propulsion. I just resigned myself for the time being to let the craft tumble through the atmosphere until it is below 10 km altitude and them power up the props to get it to fly straight.

 

[Guest]

Work on the service plane continues. I've now gotten to the point where I've tested all of the subsystems and phases of the mission separately and they work. There's still a lot of work to do to work out the kinks but at this point all of the major challenges have been solved, now it's "just" working out the kinks.

Pictures related...

[Guest]

All right, I published the service plane. I haven't yet used it for a real mission but I have thoroughly tested it. It will work.

https://kerbalx.com/Brikoleur/BAK-9012-Elvira-L

(I had a certain real-life workhorse in mind when tweaking how it looks although this is obviously not a replica, just an "inspired by..." but I think there is something about the wing and the tail that evoke it...)

Edited September 11, 2019 by Guest