Jool 5 in a single launch

[Lyra]

Hello everyone! I recently flew a Jool 5 mission that, as the title says, was done in one launch. Here's how it went.

I'll be uploading the report in seven parts, with (hopefully) one per day, for each leg of the mission: from Kerbin to Jool (this one), one for each moon, and return to Kerbin.

Part 1: Launch!

We begin on the pad with this massive rocket - nicknamed the "Colossus" - that appears to be almost half fairing. I don't have either DLC, so Mammoth spam (Spammoth?) it is. The two boosters, connected to the core via fuel pipes, will get the rocket off the pad before separating and letting the core carry it to a suborbital trajectory. There's also an extra Vector that's been attached to the bottom of the core stage, because the TWR was far too low with only the Mammoth.

All systems are nominal, staging triple-checked, and Val, Bill, and Bob are all on board. We are clear to launch.

Liftoff!

A fairly standard gravity turn.

Booster separation! The core stage will carry us to a roughly 100km altitude.

The core stage is empty now and the Rhino will take us to orbit and beyond. Our apoapsis is just above 100 km.

Fairing deployed and the interplanetary craft is revealed! It has a small SSTO for Laythe, a two-stage Tylo lander that will refuel for Vall, and an ion lander for the two outer moons.

A 350 m/s circularization burn puts us into LKO. Launch happened at a Jool transfer window, so we're able to plan our Kerbin escape burn immediately.

Two staging events will happen during this burn - the Rhino engine and the lower liquid fuel tank will both be dropped.

And here are those staging events now.

Goodbye Kerbin!

The crew plans a correction burn and Tylo gravity assist in deep space. We want our periapsis to be nice and close to Laythe's orbit, and the apoapsis not too far out. As you can see, this required a close scrape with Tylo.

(the second maneuver there is only because KSP doesn't like to show my trajectory beyond Tylo's SOI when plotting an assist from Kerbin or interplanetary space unless I put a maneuver node in Tylo's SOI. I deleted it right after the correction burn.)

Hello Jool!

And hello Tylo, too!

The aforementioned close scrape of Tylo. The crew will be getting much closer soon with that lander in the back, but for now the moon has done its job. Val, Bill, and Bob are safely captured around Jool.

And with that, the crew is in a stable orbit around the green giant. This is all for today, but I'll be back tomorrow with what was arguably the most annoying part of the whole mission: the Laythe landing.

[fulgur]

Looks great! Can't wait to see that spaceplane
If you open up the settings (ESC -> Settings from in-game) and scroll down a bit, there should be a setting called Conic Patch Limit. If you increase that setting, you will see your trajectory more than 3 SoI's in the future. I also like to turn on Advanced Tweakables and the Extended Burn Indicator.

[Lyra]

Just now, fulgur said:

If you open up the settings (ESC -> Settings from in-game) and scroll down a bit, there should be a setting called Conic Patch Limit. If you increase that setting, you will see your trajectory more than 3 SoI's in the future. I also like to turn on Advanced Tweakables and the Extended Burn Indicator.

Thank you! I'll definitely do that for my next mission. I already had the other settings on, thankfully 

[Lyra]

Part 2: Laythe Landing

Planning an encounter with Laythe was fairly easy. I initially wanted to do a flyby first, but the game didn't want to display encounters correctly after that, so I loaded up a quicksave from just after when I captured into Jool's SOI and planned a regular encounter.

The capture burn is relatively short. In total, circularization cost about 700 dV.

Plane change to a more equatorial orbit.

Val's view out the command pod window. She'll get to see it up close soon in that spaceplane!

The final circularization burn, about halfway done.

The main ship will remain in a 61 km orbit while Val and the spaceplane visit Laythe's surface.

Undocked and ready to enter Laythe's atmosphere. Periapsis is about 45 km. I ended up skipping off the atmosphere at one point, which wasn't too fun.

Land coming up on the horizon - it's the island that I tried to aim for. I've landed on that island many times, and it has a nice flat beach on the south end for craft to land on. Will my speed drop in time for me to land on it?

Nope. Flying right past it. Ah well, there's still plenty of land ahead.

We're in the thicker atmosphere and aiming for the flatter parts of that crater rim. Hopefully I can make it...

Gliding above the mountains. At this point I quicksaved in case I crash-landed.

Gear down!

I did in fact end up crashing. A lot. About 15 times, actually. Easily the most infuriating part of the whole mission. I was so focused on landing that I didn't take any more screenshots until I had touched down safely...

...which we can now see here. The now-used parachutes on the back helped a LOT.

First flag planted!

Now for ascent; it's not shown but I timewarped to a point where the main ship was just behind the plane. We're actually facing westward, so once the plane is in the air I'll have to do a quick turn to get us on track.

Flung myself off a hill with not quite enough lift to get airborne yet. This little maneuver helped avoid ANOTHER crash into Laythe's mountainsides.

Turn complete. It's a fairly normal ascent from here.

And just like that, we're back in low Laythe orbit.

Got a near-perfect encounter for docking, and with over 500 m/s in the tank it should be easy to dock.

I used the patented Lowne Lazy Method™ of docking for the spaceplane - almost no RCS needed.

We're docked! The remaining liquid fuel will be transferred to the main ship, while the dead weight of the oxidizer will stay in the plane when it's ditched to save on mass.

Goodbye, spaceplane. You served us well...

Now it's time for our escape burn to Tylo, leaving the ocean moon behind. Goodbye Laythe!

Tomorrow I'll post the Tylo landing - surprisingly much easier than Laythe. See you then

 

 

[Lyra]

Part 3: Taking on Tylo

Tiny correction burn on our way to Jool's largest moon.

Circularization to low Tylo orbit was split into three parts, each about 200-300 m/s. This here is the initial capture burn.

The six nuclear engines fire up for the second periapsis burn as Jool vanishes behind the limb of the massive moon.

Just before the last burn, circularizing the mothership into a 30 km Tylo orbit.

Now in a nice low orbit, Bill Kerman jets his way over to the two-stage lander - nicknamed "Teeny Tiny Tylo 5" - and decouples from the mothership. The lander's lower stage will both land and provide the first ~600 or so dV for ascent, and the upper stage will be reused for the Vall landing.

The descent to Tylo's surface. Holding retrograde, Teeny Tiny Tylo 5 burns off its speed until it's going about 400-500 m/s, then cuts off its engines til about 7500 m above the ground, where it fires them again for landing.

Second flag planted!

I didn't get a screenshot of the stage separation in time, as the timing of the ascent and separation is quite precise, but here's the top stage/future Vall lander on its way to orbit again.

Got a really good approach almost right away - this whole mission had some of the smoothest dockings I've ever had.

The lander is stuck on the side of the ship like a barnacle, ready for the inter-moon journey after some refueling.

An 800 m/s burn takes us to the edge of Tylo's SOI. The transfer window for Tylo to Vall means that you can only encounter the latter after just barely escaping the former, and careful planning is required to make sure one doesn't completely overshoot Vall. I did a short burn right after the last screenshot to finally escape.

Tomorrow will be the last of the three inner moons, and also the one I'm most familiar with - Vall. See you then

 

 

 

 

[Lyra]

Part 3: The Vall Landing

Since Tylo's SOI is large enough to make a direct burn to Vall very, very difficult, a 190 m/s correction burn is needed right after escaping Tylo.

As Vall drifts into view, the capture burn is set up. Unlike the last two captures, I can capture directly into low Vall orbit; not only because Vall is much smaller, but also because the TWR of the main craft has significantly increased.

Capture burn in progress. I ended up in a slightly-eccentric, roughly 30 km orbit - my go-to height for large vacuum bodies.

It's only natural that we send Val to Vall, so she uses her EVA pack to seat herself in the Tylo lander's upper stage.

At this point I was ready to land, but I wasn't quite sure where. I am very familiar with how to land craft on Vall, especially with high TWR craft like this one, and didn't want to bore myself to death doing yet another landing near my colony site in my main save. So I put a poll on my Tumblr about where I should land - main save colony site, flats, or a mountain - and looked at the results after an hour...

Mountain was the winner, so I planned my descent to a large blob of peaks just ahead of the craft's orbit.

Val descends to the icy blue surface of Vall...

And the third flag is planted! You can't really tell, but the darker blue in the distance is Vall's plains. The mountain was almost 5 km tall!

Takeoff was fairly standard, although for some reason the navball switched to Target mode less than halfway through the ascent.

Circularization and docking were quite trivial, and I got some nice shots of it too.

And once again, the little top stage/lander is attached to the side like a barnacle. Valentina is safe on board and over half the mission is done!

Tomorrow I'll post the Pol mission. Until next time!

[Lyra]

Part 4: Landing on Pol

The Pol leg of the mission begins not over Pol or in deep space, but rather still in low Vall orbit. Bill goes on EVA to take a seat on the tiny ion lander that will carry out the last two landings, transfer and all.

A 400 m/s burn with the ion lander gets Bill on an escape trajectory from Vall. The lander has a single RTG for passive electrical generation, and six fuel cells for running the ion engine continuously. The fuel cells' consumption of liquid fuel/oxidizer also messes up the dV readouts and it appears to somehow gain dV out of thin air (or well, thin vacuum) - looking at the resource readouts should help make sense of it.

160 m/s correction burn planned in deep space

Pol comes into view as the capture burn is planned and executed.

A few minutes later, we're descending to the surface.

Landing burn, touchdown, and the fourth flag planted!

Time to head back to Pol orbit now. Pol has some of my favourite landscapes of KSP, so flying over these mountains and lowlands was a treat.

After some timewarping, it's time to do the transfer back to Vall. Another big correction burn was needed, but as you can see this lander has plenty of delta-v left - if you factor in the fuel cells' consumption, it's well over 2000 in total.

Vall capture cost around 500 m/s, and docking was very easy for such a low TWR craft coming in from a hyperbolic trajectory.

With both landers now looking like barnacles on the mother ship, it's time to refuel both the xenon and LF/OX tanks for the final leg - the Bop landing. I'll post that tomorrow!

 

 

[fulgur]

I love the tiny ion lander design, and I can't wait to see the end of your journey!

The reason the dV indicator is wrong is as follows:

Spoiler

ΔV is derived from rate of change of momentum of your ship. Fuel of mass dm is chucked out the back at a constant velocity, and your ship accelerates according to conservation of momentum by an amount dV. You then add up all the small changes dV and dm, to find the total ΔV of your ship when the mass has a total change Δm.

This derivation assumes that all the change in mass of your ship comes from you throwing the fuel out of the back. If instead some of the mass is lost from being burnt in a fuel cell, the dV calculations will not reflect that. You are losing mass, and therefore gaining acceleration, which the equation has not accounted for. So the actual change in velocity is higher than the equation predicts.

Finding the actual ΔV of a ship using ion engines and fuel cells is a (fairly easy) exercise in calculus left to the reader.

Edited June 25, 2023 by fulgur

[Lyra]

14 hours ago, fulgur said:

The reason the dV indicator is wrong is as follows:

  Hide contents

ΔV is derived from rate of change of momentum of your ship. Fuel of mass dm is chucked out the back at a constant velocity, and your ship accelerates according to conservation of momentum by an amount dV. You then add up all the small changes dV and dm, to find the total ΔV of your ship when the mass has a total change Δm.

This derivation assumes that all the change in mass of your ship comes from you throwing the fuel out of the back. If instead some of the mass is lost from being burnt in a fuel cell, the dV calculations will not reflect that. You are losing mass, and therefore gaining acceleration, which the equation has not accounted for. So the actual change in velocity is higher than the equation predicts.

You said it more clearly than I ever could. To be entirely fair it was something like 12:30 AM when I wrote it and I had been out hiking for half the day lol

The lander was super fun to design and test, and it got me thinking about the practical limits of ion craft too! My ultimate goal is to make one capable of landing on Vall - the designs I made simply didn't have enough TWR to do so

[Lyra]

Part 6: Bop Landing

(side note: I messed up with the numbers! Vall and Pol should be 4 and 5 instead of 3 and 4, respectively. Anyways...)

Bob was feeling a little left out, and his name is similar to that of Jool's second smallest moon, so off he goes to Bop!

Ejection cost abour 330 m/s.

A long correction burn (~750 m/s!) in deep space puts us on course for the lumpy moon.

Capture is quite expensive as well - thankfully this lander has loads of dV to spare. I used one maneuver to get myself right to the edge of Bop's SOI, and one to circularize into a 30km orbit.

Landing was, again, fairly trivial, and Bob gets some spectacular mountain views.

Final flag planted!

Ascent was easy as well. I became a little worried about not having enough dV to get back to Vall, as the map I used showed around 1550 m/s total for a perfect low-orbit-to-low-orbit transfer. Thankfully, the fuel cells' gradual lightening of the craft meant that resource consumption was on my side!

I didn't need to do a correction burn on the way back, since Vall's SoI is so huge. Ejection had already been done at this point for something like 900-1000 m/s of dV - that maneuver is for Vall capture.

Vall grows bigger as Bob in his tiny chair gets closer and closer.

The plane change to match up with the main craft was done in a highly eccentric Vall orbit - much less costly this way.

Docking was just as easy as before, and both landers are once again attached to the side of the mothership.

Bob jets his way over to the mothership and with that, all five landings have been completed!

All that's left is the journey back to Kerbin, which I'll leave for tomorrow.

[Lyra]

Part 7: The Long Journey Back Home

In orbit above Vall at an optimal transfer window, the two remaining landers are drained of their liquid fuel, and the excess oxidizer and xenon aboard the mothership's refueling tanks is transferred to the landers. They are then jettisoned to save weight. No more barnacles!

Jool disappears behind Vall one last time as the escape burn begins...

...and rises for the last time as the crew climbs away from the icy blue moon.

Once we're out of Vall's SOI, a 1200 m/s burn is set up to escape Jool and almost encounter Kerbin again.

Goodbye Laythe...

The last screenshot I got with all three of the major moons. Laythe is eclipsing Tylo as we speed out of the Joolian system.

Days later, the green giant is now a tiny dot in the distance, slowly growing smaller.

A 260 m/s correction burn is made in deep space to get a Kerbin periapsis of 35 km, but the nuclear stage just didn't have enough to complete it on its own - so the second-to-last staging occurs, and the last engine fires up to finish the last bit of the burn.

Kerbin approaches fast - it's time for reentry.

The last stage separates, and not a moment too soon as only a few seconds later we hit the atmosphere and the crew is treated to some nice, er.... "fireworks" as it explodes below them.

Reentry is intense! The crew gets subjected to some absolutely ludicrous G-forces, but thankfully Kerbals are a lot more durable than us humans and are able to tolerate it.

Safely landed with a beautiful Kerbin sunset!

Val, Bill, and Bob take off their helmets and breathe fresh Kerbin air for the first time in several years as they watch the Mun rise. It was fun out there, but it's also good to be back home.

 

And that concludes the single-launch Jool 5 mission! Feel free to ask any questions or point things out that you thought were interesting. Thank you for reading!