To Moho and back.

[koshelenkovv]

Last time I've attempted Moho landings was back in 0.17. I could not stop exploding and abandoned the idea.

Now, without evil atmosphere and with all new fancy tiny shiny parts it turned out to be not hard at all.

This is 125 ton Mohosity, the hugest rocket I've ever built.

It have a bunch of aerospikes and central Skipper for controllability.

Second staging event

There is several tricks to lower delta-V requirements.

Ideal intercept must occur near Moho aphelion. Such way you must lower your orbit less and will save dV.

Also, it must occurs in ascending/descending node, so plane alignment burn is not needed, and it saves a lot of dV too.

Sunbeam the interplanetary ship scratching Kerbin atmosphere for better ejection trajectory.

1500 m/s dV burn took over 6 minutes.

Billy Bobny look at Kerbin, Moon and Minmus maybe for the last time.

There is also one trick with circularization at intercept.

Relative velocities on the edge of SoI and close to Moho will be almost equal. But at the edge you must kill velocity down to near zero to get captured and lower periapisis and then also lower apoapisis.

Whilst if you get really close intercept, you must kill velocity down to orbital, and only once.

12 minutes capture burn

Billy-Bobny decided to land on the edge of this huge solidified lava field.

He took a seat in the Raylet lander and separated from return stage.

At 3350m and 350m/s panic attack stroke. Billy-Bobny started to brake like mad.

And it was too early.

It not easy to land, controlling lander from rover seat because pro- and retrograde markers are shifted. Actually, it's very hard and lander vent explodey.

Billy-Bobny discovered that he is alive.

Billi-Bobny discovered that he have a probe core in rover and could land safely, but forgot about it in panic.

Turning over Sundog rover.

After taking samples on a lava field B-B decided to climb a mountain nearby.

It was higher then appeared to be from afar.

While solar panels delivers 6 times more electricty than on Kerbin, rover terribly lacks wheels and crawling uphill at measly 2.8m/s

Summit at last!

Moho got flagged.

After some rest Billy-Bobny preparing Emmergency Rescue Donut Photon Elevating Device for ascend.

Liftoff!

Floating over the peaks.

Return to Sunbeam

There is other trick for delta-V saving - ejection burn must occur near the Moho perihelion, when your speed is higher and where you must raise apoapisis less, thus saving the fuel.

Billi-Bobny had more then enough fuel and decided not to wait for months.

Hitting the atmosphere in retrograde direction. G-forces peaked at 6.4 g.

Home, wet home!

delta-V expendages:

Kerbin orbit - 4600 m/s

Moho intercept - 1600 m/s

Moho capture in low orbit - 3400 m/s

Corrections and further lowering - 200 m/s

Landing - 1100 m/s

Back to orbit - 900 m/s

Rendezvous (using too powerful engine with TWR over 20 instead of EVA pack due to Billy-Bobny cowardice) - 350 m/s

Return to Kerbin on a wasteful way- 3500 m/s

TOTAL: 15650 m/s.

About 800 m/s was wasted and 400 m/s exploded in the lander.

I could make the rocket smaller.

Edited June 17, 2013 by koshelenkovv

[DMagic]

Nice work, getting to Moho and back is tough. I really like your vehicles, they all make very efficient use of mass.

But I think you might have it backward about when to start your ejection burn to Moho. I think it's best to intercept Moho at its perihelion. It requires a bit more delta-v for the initial ejection burn, but the capture burn is much less. You only have to lower your orbit to Moho's aphelion instead of its perihelion. This can save a lot of delta-v.

My other suggestion is, instead of trying to intercept Moho at a node with Kerbin, to launch into an inclined orbit and perform the ejection burn at a node with Moho. My strategy is to wait until I'm at the descending node with Moho, then launch into about a 20^o inclined orbit (launching when KSC is on the side of Kerbin opposite from the sun). Doing this gets me to within 0.5 - 1.0 of Moho's inclination after the ejection burn (it requires a bit more delta-v to launch into an orbit like this, but not much). Launching at the descending node also allows me to intercept Moho's orbit near its perihelion. Most of the time I don't try for a direct intercept with Moho, instead I treat it more like an orbital rendezvous, this can add 500 - 1000 m/s to the total delta-v, but I think it's easier than waiting for everything to line up perfectly.

My record doing this is about 4300 m/s from LKO to a 100km polar orbit above Moho, but most of the time I get more like 4500 - 4800 m/s. And for return a good delta-v is around 2300 m/s. Assuming you're landing on Kerbin the inclination doesn't really matter.

But really, anything that makes good use of a rescue donut deserves recognition.

[koshelenkovv]

I think you might have it backward about when to start your ejection burn to Moho. I think it's best to intercept Moho at its perihelion. It requires a bit more delta-v for the initial ejection burn, but the capture burn is much less. You only have to lower your orbit to Moho's aphelion instead of its perihelion. This can save a lot of delta-v.

Oh, thanks! I'll try this way.

My other suggestion is, instead of trying to intercept Moho at a node with Kerbin, to launch into an inclined orbit and perform the ejection burn at a node with Moho. My strategy is to wait until I'm at the descending node with Moho, then launch into about a 20^o inclined orbit (launching when KSC is on the side of Kerbin opposite from the sun). Doing this gets me to within 0.5 - 1.0 of Moho's inclination after the ejection burn (it requires a bit more delta-v to launch into an orbit like this, but not much). Launching at the descending node also allows me to intercept Moho's orbit near its perihelion. Most of the time I don't try for a direct intercept with Moho, instead I treat it more like an orbital rendezvous, this can add 500 - 1000 m/s to the total delta-v, but I think it's easier than waiting for everything to line up perfectly.

My record doing this is about 4300 m/s from LKO to a 100km polar orbit above Moho, but most of the time I get more like 4500 - 4800 m/s.

Better than 5000 m/s, but sounds somewhat tricky On the other hand, waiting is not hard in any way (if arrange intercept at Kerbin), but somewhat tedious.

[Geschosskopf]

Great story! I love the orbit-capable donut thingy. That pic of it flying over the mountains still has me laughing.

So, where do you get this rescue donut?

[koshelenkovv]

I've built it.

Smaller one suitable for Mun, Eeloo and other smaller moons. It is just OKTO2 core with a seat on top, round tank and ant engine. Solar panel is useful, but not mandatory.

Bigger one suitable for Vall, Moho and Duna. It have two circular tanks and 24-77 engine instead of Ant. 24-77 attaches naturally on top and bottom of anything, if you turn this anything in 90 deg. position like in SPH. Don't forget to rotate engine 5 deg. because it is inclined by default.

[koshelenkovv]

Here the crafts.

http://yadi.sk/d/JW1bNN825vV_y

http://yadi.sk/d/BJigVZUq5vVaS

Kerbal Engineer Redux needed.

When launching double-Donut, first start the engine, then decouple, because engine can stuck inside octostrut. Or just replace octostrut with 2 additional decouplers. (+29 kg!)

Do not forget to switch control from probe body - it not easy to make ascend from lander seat, because Navball is shifted on 90 degrees.