Return from Laythe

[Bishop149]

So I am well into the process of establishing a colony on Laythe, no actual Kerbal's there yet but an absolute heap of rovers, aircraft, refueling tankers, fuel depots etc etc.

The base is the next thing to go.

BUT it was always planned as a one-way trip for the guys I sent. . .the prospect of building a craft to return them always seemed quite daunting.

But hell, I feel I need to give the little guys some way of getting back!

So how much of a shoestring can I do it on?

Operation Name : Return from Laythe

Purpose: Design a craft capable of being delivered to Laythe and once there able to re-launch and return a Kerbal to Kerbin. Weight must be kept as low as possible due to the fact that my current launch systems suck a bit.

Aims for initial test phase.

1) Design craft and get to Kerbin orbit, I figure if it can make Kerbin it will probably make Laythe. . although this assumtion may be flawed . . . won't know until I get to Laythe and try it

2) Once in orbit test minimal interplanetary module by examining it's DeltaV profiles when leaving Kerbins Sphere of influence.

I guess the obvious way to get this lightly to orbit is an SSTO Spaceplane, but upon initial design phase I hadn't gotten the hang of those yet.

Phase I

Soooooo after much refinement I built an odd Jet / Rocket Hybrid:

As you can see it sits on the launch pad supported by its own landing struts.

It Flies!

Off Jets and on to rockets

Jet Stage separation

Orbit Achieved!

Now to test the interplanetary module. . . which is INCREDIBLY minimal! Separation:

Interplanetary module ready!

It took 3 orbits worth of burning on near Kerbin Periapsis side of the orbit (Ion engines are slow!) but eventually I arranged and escape from the Kerbin's Sphere of influence with the help of the Mun:

Mun Flyby:

Bill is in interplanetary space. . . . in an ion powered tin can!

After some more Ion Burning, Bill arranges his return to Kerbin sphere of influence, once again with the help of the Mun

Gratuitous Mun + Kerbin shot

Successful re-entry and landing. . . . module isn't actually designed to land very intact. . .I couldn't squeeze decent landing legs on but I didn't try the VERY small ones. I may see if I can fit them on.

So Phase is a success. . . a craft has been built that can get the interplanetary return module into orbit, the module itself is perfectly capable of inter-planetary flight and its DeltaV capacity seems impressive. Whole flight used up less than 30% of the Xenon it carried and total DeltaV changes for all the many burns must have been over 2000 m/s, maybe even 3000m/s.

It should be more than capable of getting from Laythe to Kerbin intact.

Problems:

- Ion burns are very slow. . . to be accepted. I could maybe cram another engine on but it wouldn't help much. Sunlight out at Laythe will be much lower too. Drives will not run at 100% I'd guess.

- Craft is still pretty heavy. . .probably too heavy for my current lifters

- Craft lacks un-powered decent system to bring it down to Laythe, this will add a fair bit more weight and I really don't have much space on the craft to fit the chutes!

[Bishop149]

Phase II

Right so its still heavy. . . and a chutes system to drop it on Laythe was proving very difficult to cram on.

So lets do this properly. Time to get an SSTO spaceplane up and running!

I started with my standard aircraft and after some faffing with weight and lifting surfaces came up with a version that may work, it gets off the ground (take off speed is a bit high!), is stable in flight and is carrying a decent amount of rocket fuel.

So lets try a flight! From what I read formula for SSTO is High and fast as possible on jets, switch to rocket to raise apoesis and circularise orbit.

23Km Up and at 1400 m/s (orbit), ship maxes out (with me flying!) at around 25km and 1700m/s (orbit)

Orbit!! My first SSTO! With a whole 10 units of Oxidiser left . . .

Here we see the MkII nearly at orbit, it replaced the Jet fuel only containers with some equivalent rocket fuel ones. . . quite a bit heavier but the extra fuel is nice:

Interplanetary module separation and deployment

And this is the MkIII, lower take off speed / better lift profile and with a "mobility system" to actually allow ground based Kerbals to board it.

SSTO is a fair old bit lighter than the craft in Phase I although not as much lighter as I hoped. Current lifter should be able to get it to Laythe. . . it just need a chute system to bring it down now!

Phase III will be development of the chute system to drop it (likely fairly easy) and the onwards to test on Laythe itself!

[1D-1()T]

I like the Ion powered interplanetary stage. I never thought of something like that. Also, congratulations for your first SSTO!

[Bishop149]

Phase III

Phase III will be development of the chute system to drop it (likely fairly easy) and the onwards to test on Laythe itself!

Well that turned out to be an awful statement. . . it was not easy. . . . at all.

In fact for the SSTO it was a nightmare, the extra weight from the chutes made it too heavy to reach orbit . . . I went through many stages of refinement bulking it up and I got to the point of "I need a 3rd turbojet". . . now the original jet/rocket hybrid had 4 normal jet engines. . . the weight of 3 turbojets would approach equivalency . . . which made be question the whole idea of the SSTO being more weight efficient, and they sure as hell are more difficult to fly.

So I went back to the jet/rocket and much more quickly refined it into the below:

Which is almost as light as the SSTO was becoming and a WAY easier to fly, has enough chutes to land safely fully loaded with fuel.

Its nicely staged to shed as much weight as possible on the way up as well, which I'm quite happy with. . .

1st stage separation ditches the cone with the landing legs on and exposes the rocket engine. The legs are not required more as soon as its off the ground, and covering the rocket like this also had the added advantage of solving the "rocket engines sometimes fall off on landing from chutes" problem.

2nd stage is the switch to rockets on an action group, it shuts down and ditches the jet engines but keeps the fuel tanks they are attached to, fires the rocket and closes all the air intakes.

3rd stage ditches the two former jet attached fuel tanks when they are empty . . this also gets shot of all weight associated with most of air intakes and chutes.

Its then just the central fuel tank rocket and payload to orbit.

The next stage is to get it into orbit attached to a nuclear powered tug to get it to Laythe.

My current heavy lifter isn't up to the task. . . but its also very badly designed, the next phase will be refinement of the lifter.

I always have the option launching separately and linking the Laythe return Jet/Rocket to the tug in orbit . . . . I've done orbital rendezvous' before but never docked before.

[Bishop149]

Phase IV

So refinement of the heavy lifter to get it to Laythe.

My old heavy lifter was awful. . . a mass of HUGE fuel tanks lots of mainsails and 2 stages. HORRIBLY inefficient and rather unstable too, but hey it worked up to a point and served me well so I never changed it. This payload however really is too much for it so its time for a new one!

My first attempt was interesting. . . I was rather enamored of the idea of Jets as a first stage, so wondered how far I could take it. . . . this far apparently:

The thing is bat**** insane but it works. It gets to 19-20 km up before you really have to ditch the jets, which is best done early, one spark out in that lot and you have a tumbling fireball. The three mainsails then ignite and can carry it all the way to orbit (or very close):

The Nuke powered interplanetary stage then kicks in (finishes circularizing if required) and begins the push to Jool.

That craft is on its way and has completed its burn to give it a nice Jool intercept, but I'm a little worried the interplanetary stage is under-fueled . . . Hopefully with some good areobraking to minimise deltaV it will make it to Laythe. We shall see.

So, interplanetary stage is a little weedy and jet powered rockets, whilst they work well are a little silly. So I thought I'd build a proper big rocket lifter.

And after several stages of refinement this is what I got:

7 mainsails and staged to hell and back.

The small tanks around the big orange ones asparagus staged, all the fuel is gone from those about 7.5k up, last ones being ditched below:

Then I have 3 of the big tanks + mainsails further asparagus staged to the other three. Those need to go around 10km up:

The last three big outer tanks are onion staged to the one in the middle, together these remaining 4 mainsails get Ap to 70-80km before I ditch the remaining 3 outer tanks and cruise to orbit on the remaining central:

Then its on to Laythe, the interplantary stage has undergone some refinement, it carries more fuel and is staged to ditch about half the tanks engines when empty. . this is usually about 2/3 of the way through the Jool burn.

The payload I am using here is a test, a big air droppable jet fuel tank designed to dock nicely with my fuel tanker rovers. It weighs about 19.4 units.

The inter planetary stage weighs in the region of 65 units.

So my heavy lifter can put ~85 units into Kerbin orbit and I hope get 20 odd units to Laythe orbit.

Well see how it goes.

I actually have 2 of these tanks on the way, the first version had no RCS. . . . which as I discovered on such a large craft makes controlling it a nightmare.

Second on has RCS!

Edited October 11, 2013 by Bishop149