Probing Urlum (from Outer Planets Mod - pic heavy)

[Randazzo]

With the recent update of the Outer Planets Mod released by CaptRobau and Eudae55, three new moons were added to Urlum: Polta, Priax, and Wal. Eager for something new to do, I decided to send probes to these new bodies. Initially assuming one could not land on Urlum itself, a system which carried three separate landing-capable probes would be sent. "Goliath" was born. Since I was going in blind, I opted to err on the side of caution and give it loads of Delta V. The probe-bearing vehicle would have two stages: An interplanetary transfer stage with 2850 m/s Delta V, and a primary stage with 8000 m/s for moving about the planetary system (since this was calculated with the fairings attached, it turned out to be slightly more). Each probe would also have two stages. One for orbital maneuvers and a landing stage. Each stage possessed ~1400 m/s. Borrowing Stealing from the fuel tank design of the Kron series by Lajoswinkler (Kron Series), the probes would be attached to a narrow section of the main body, keeping them mostly inside the profile of the vessel. There would be no heat shield included as the weight of the necessary width of shield would reduce the total Delta V by more than I believed it would save by aerobraking, assuming it was even possible to do so. The complete vehicle on the pad weighed in at just over 1000 tons and had a total cost of 491256 funds.

Goliath utilizes parts from NovaPunch, Modular Rocket Systems, Procedural Parts, and Procedural Fairings

Goliath launched directly into a 645km orbit around Kerbin to facilitate 100,000x time warp since I had no idea when the window would be arriving. The vessel was so over-designed that even after establishing circular orbit at this altitude, the second stage of the lifter assembly was used for over half of the transfer burn. There would be a window in a little over 270 days at ~2680 m/s, and the trip would take more than 9 Kerbal years.

My experiences with visiting Eeloo had fortunately led to including RTGs on each probe and three on the main vessel. The Outer Planet Mod also alters solar panels a bit to make them less magical at tremendous distances from Kerbol. After passing Jool, solar panels with 100% exposure were producing zero electricity.

Having disregarded the suggestion in the Outer Planets Mod thread to download a timewarp mod, I spent a LOOONG time at 100,000x warp. But, at last, Goliath arrived at Urlum. Since Urlum possessed rings (which I later discovered were harmless, probably made of vapor), a periapsis with a slight inclination and altitude higher than the rings was set, and a braking burn executed. Not planning on staying at Urlum itself, orbit was not circularized. As Priax and Polta both occupy the same orbital plane around Urlum, the plan was to transfer first to Polta, then directly to Wal, and finally directly to Priax.

Once arriving at Polta, the transfer stage had very little fuel left (~30 m/s) and was jettisoned. Polta had a unique appearance that I found intriguing and I wanted to land on an interesting portion of the moon which was just entering the dark side (and warping was very slow at the orbital altitude I had set), so I decided to move on to Wal and come back to Polta later. The first Goliath probe was deployed and left in orbit.

Once arriving at Wal, I found it to be quite interesting as well. There is a ridge of mountains around the equator and it's quite yellow. A probe was deployed and headed toward the surface. I was using Mechjeb to try and hit what appeared to be a tiny flat area atop one of these mountains, but upon getting closer I discovered that it was in fact not flat at all. Switching off the landing guidance, I maneuvered the probe to a lower plateau that still had a decent view. Readings were taken for science, and a transfer to Priax was set.

The probe is near the edge of the plateau: zoomed out for the view

It was past 1am at this point, and I was getting a bit tired and careless. I set up the transfer to Priax and warped as fast as possible to try and speed things up. Naturally, I hit an encounter with Polta (which is ahead of Priax in the same plane) and got thrown into an escape trajectory at 100,000x warp (which was WAY too fast, It was a stupid mistake). By the time I clumsily smashed the "SLOW THE F DOWN!!!!" button, I was well on my way out of the SOI. Fortunately I engineer things with my stupidity in mind, and the main vessel still had over 7,000 m/s of Delta V (it gained a boost with each probe it dropped off). I reversed course and did a full burn until a ridiculously elliptical orbit was established. Goliath would now spend ~70 days returning from this blunder. Fortunately I was able to get a gravity assist around Polta on the ingress which resulted in a much better orbit, with a fairly close approach to Priax afterward. With some fiddling, I finally got an encounter.

Arriving at Priax, I found it to resemble Gilly. I hate Gilly. So far as I know, it's the only place that you have to burn towards the ground to land. Well, you might not have to, but it will take ages otherwise. At any rate, the resemblance was fleeting. Priax is oddly shaped and looks like somebody used it for target practice. The final probe was deployed and sent to the surface. More science was gathered, and it was time to switch back over to Polta (after going to sleep!) and execute a landing.

As the probe was already standing by in orbit here, there were no shenanigans. I picked a site with green dirt and headed to the surface. It was a nice change of pace visually.

With probes on each of the moons, I decided to use the main vessel for some experimentation on Urlum itself. Specifically I wanted to find out what those rings were, and if in fact it was possible to land on the surface. The rings turned out to be harmless, probably gas.

With that detail covered, I embarked on what turned out to be the most interesting part of the trip: Landing on Urlum. The info box on the side of the screen told me it's atmosphere started at ~124km, so I set a periapsis at 70 for entry. This was probably a touch reckless as I could have burned up, but it turned out to be a rather strange planet. Compressive heating began at around 110km but it was extremely mild. It became a bit more concerning at ~100km, but did not start in earnest until about 85km. By 80km it was approaching dangerous levels, so I fired the engine to start slowing down. Not having a mechjeb unit on this assembly I can't say precisely what the TWR was, but it was enough to slow me down fairly quickly. By 72km, I had slowed down to a little over 1,100 m/s and heat levels were dropping.

Judging by my descent, I believe Urlum has a dense atmosphere and low gravity. I arrived at this conclusion from how slowly I descended. With no additional engine burns, Goliath had slowed down to barely over 72 m/s by 30km altitude. This continued to drop; at 20km I was under 40 m/s, and by 10km I was at 22 m/s. My head started to fill with all the cool things I could send here since landing was going to be so easy. I could probably land things with Drogue chutes alone!

I was starting to become concerned I might smack into the ground as it was so foggy and bright I could barely see. That, however, would not be an issue. My hopes and dreams of a vast Urlum empire were dashed when I saw this:

Yes, chronologically this was taken before the fog shot above, but I wanted to put the fog shot in that group. Deal with it, chief.

I had seen this before. I saw it while "landing" on Jool. The surface wasn't there! Still, I hoped maybe it was just a graphical glitch. At 1km, I engaged the engine at one-quarter and slowed the descent down to 10 m/s and gradually reduced it to a little over 2 m/s before I reached zero altitude. Alas, as I suspected, there was nothing there to catch Goliath, and I kept on going. Finally I decided to turn prograde and burn to see if I could get out the other side. That resulted in death at 259m below the surface.

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And So the mission to probe Urlum has come to an end. There will be no Urlum empire. Still, the moons are neat and there's always Sarnus to visit! You can check out the Kron 3's journey there in the Kron Series thread.

Thanks for reading or skipping the text and looking at the pictures! Complete album link is below, and a seven minute video of the Goliath going up. Literally. Just going up.

Complete full-sized image album

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Edited March 19, 2015 by Randazzo

[Tommygun]

Good report, I need to get back to the Outer Planets Mod, it adds a lot to the game.

[Interplanet Janet]

You could have lessened your delta-V had you used gravity assists (JGA, KJGA, KJSGA, EKKJSGA).