A jaunt to Jool

[ncw33]

Exclusive news report! Our brave Kerbonauts have returned from Jool.

Since year 25, Jeb, Val, Bill, and Bob have been bravely exploring the Jool system. Now they return to tell their tale!

The journey begins

The trip consisted of two launches, both launched on the same day of the Jool transfer window in year 25.

The launch vehicles were similar: a 6× Vector lower stage, with SRBs; a SWERV transfer stage, and a payload on top.

The first launch (below) contained an unmanned (or so we thought!) Tylo lander, with a Mk-1 lander can on top of an ascent stage, a payload bay for science, and a descent stage to be dropped just before landing the upper stage.

 

The robotic upper stage was sent from a 120km circular orbit on a fairly unremarkable transfer to Jool, in fact, not even using up all the Methalox:

Bill says, "we slapped the rocket together according to Jeb's design, without precalculating the δv. Naturally we ended up with 800m/s too much Methalox and about 1000m/s too little Hydrogen. But our fuel tanks have remarkably little fuel boil-off so who cares!"

Next, the crewed stage launched (below). The lower stages were the same, with an upper stage consisting of a Mk-3 capsule, a docking port, and a honking big Tuba engine. We put an Orbital Science module in the cargo bay.

In true Kerbal style, Jeb says: "I used some parts from my junkyard to build a fairing over the docking port on the nose, because Bob said he needed to make 2000 more scientific discoveries before he could work out how to put a hatch over the docking port. I don't know what 2000 discoveries means, but my fairing worked fine".

Val commented, "I put plenty of fuel in the crewed stage, so that we could refuel the lander as we visited different Joolian müns. After the Tylo ascent, the lander will definitely need a refill, but the upper stage (that we didn't expend on Tylo) will have plenty of capacity to hop around the other müns."

Our Kerbonauts made another unremarkable transfer, pretty efficient with the outward trajectory from Kerbin almost parallel to Kerbin. Val chose to include a radial component in the ejection burn, as she normally does, to reduce the relative inclination for later.

Val admits, "I'm still waiting for Bob to learn how to calculate transfer angles, so I eyeballed the transfer window in the Tracking Station. Honestly, when our KSC GUI gets that update we'll all be glad. It's remarkable how much δv you waste on radial adjustments if you've 5-10° out in the transfers."

For the interest of our readers, Jeb insists on showing you his mid-course corrections, for both the lander and crewed capsule in their convoy. The editor apologises that we didn't have time to commission high-quality infographics.

The mid-course correction to Jool is done at the AN, and here we spent some δv on adjusting the encounter to get a nice flyby of Tylo, on the near side of Jool, for both vehicles. Although the KSC GUI doesn't show it very well, we have got a free Jool capture for each vehicle.

Arrival at Jool

Finally, many months (many müns?) later, our Kerbonauts arrived at Jool.

Jeb apologises that he forgot to capture the manoeuvres performed there!

Jeb does not believe that it is efficient to do a capture burn around Tylo. Instead he does a zero-burn flypast of Tylo to reach an elliptical Jool orbit with roughly the same semi-major axis to Tylo (with RCS adjustments perhaps to get the inclination to zero on the way past). Then, Jeb burns at Jool Ap/Pe to "rendezvous" with Tylo (waiting one orbit of Jool...) and the capture burn around Tylo is then very cheap.

Both our vehicles reach Tylo orbit, then rendezvous, and dock. Val did remember to grab some pictures of this, at least (using her magic camera mounted goodness-knows-where outside the ship).

We transferred the remaining Hydrogen into a single tank, using an EVA to set up one of Bob's long cryogenic fuel hoses that was stored somewhere on board, then jettisoned the SWERV that we didn't need.

Disaster strikes!

Now at this point, our crew made a surprise discovery. Bob was on the "uncrewed" lander! Cheeky stowaway... after testing our rockets a few times, he must have snuck on board. [Editor: yes, doing "Revert to VAB" can repopulate your Kerbals... watch out!]

So, the crew chanted "Kraken's fate, kraken's fate, kraken's fate" [Editor: Alt+F8] until he disappeared back to Kerbin in a puff of magic Kraken dust. Too much time was spent on this mission to start again [Ed: I have no shame working around a bug with F8].

Descent to Tylo

Tim C bravely used his lower-stage Trumpet to do a tiny de-orbit burn, then a 2000m/s suicide burn on a precise trajectory to reach the source of a strange signal.

The lower stage, thankfully, had about 1000m/s of extra fuel. Tim C knew that Tylo needed "2000 down, 2000 up" but budgeted an extra 1000 for hovering around near the ground to adjust the precision landing.

Tim C adds, "Bill, you'd better work out how to add targets to our navball fast, or I'm going to go crazy. Even 1000m/s of wasted δv on the wretched landing was only just enough to get close to the target. We worked our RCS to the max on some crazy switches between horizontal and vertical burns to move a few km closer to the target while minimizing time spent hovering."

But, we did it:

Spoiler

Disaster strikes again!

To take a sample from the monument, Tim C had to go on an EVA to walk a few 100m closer. But his feet got stuck in the Tylo regolith!

Totally stuck.

After lots of fiddling with his suit controls [Ed: timewarp] Tim C gave up again and chanted "Kraken Fate" until he teleported close enough to grab a sample, then headed back to the lander the same way. [Ed: yes really, no shame using F8 if the Kerbals can't walk on flat ground.]

Transfer to Pol

After docking and refueling the lander, the crew headed out to Pol, using the last of the Hydrogen and then moving on to the Tuba's big Methalox tank.

There were not many opportunities to save (or waste) fuel on the way, so it was a gentle ride.

Tim C landed on each biome of Pol (only one shown below for brevity):

Then, Tim C entered a polar orbit at 4km Ap/Pe and started looking for fun objects to explore.

One was found rather quickly:

Spoiler

One took an incredibly long time to find:

[Ed: the timewarp speeds are ludicrously limiting on Pol. We need to be able to orbit faster if we're going to stand a chance of finding all the discoverables without cheating for coords from Discord.]

Spoiler

The journey home

Finally, our crew re-united, ditched the lander, and with the weight saved from that, had plenty of fuel left to return.

Val comments: "I was sad not to be allowed to land on this trip. But next time I'll get my chance!"

After a standard return transfer (after a long wait!) Jeb & Val made the following small mid-course correction burn.

And here they are, the brave heros!

 

[Editor's appendix - Bugs/issues encountered]

• Issues with "Revert to VAB" changing the Kerbal complement of capsules
• Couldn't use the SWERV layout I wanted due to δv bugs
• Encounters sometimes not showing up properly made it hard to get the free capture from Tylo
• Lack of UI for transfers a bit of a pain. Also Manoeuvre mod is a must.
• Lack of navball assist on Tylo monument landing a total pain. Not enough δv to hover while trying to move closer.
• Kerbals can't walk on Tylo?
• Timewarp limits made Pol discoverables a total pain.
• Lots of savefile issues. I encountered the infamous "Landed state in orbit" bug, and some weird ones where vessels disappeared or had their orbits badly messed up (into crashing trajectories) on save/load.
• I also had the "vessel throttle set to max on switching vessel" bug.

I upvoted all the relevant bugs, as usual.