Video Games

Over the weekend I returned to my Jool exploration mission and got the Explorer transferred from Tylo to Bop.

It took about two hours of real time and required three burns. A 10 minute burn to leave Tylo, a 6 minute burn to match inclination with Bop’s orbit and get an intercept, and a final 6 minute burn to get into orbit around Bop. Docking turned out to be easier than I expected but was quite slow.

Overall I’m pretty disappointed with the VASIMR engine on the ship. I tried an alternate design in the VAB with two reactors and engines which did help with the TWR of the craft but not enough to offset the hit to the available deltaV. Instead, I’ve started looking at a new version of the Explorer that uses nuclear engines. The current design looks very promising. It has better TWR and roughly the same deltaV. The ship is smaller because nuclear engines run on liquid fuel not hydrogen which takes more volume, and there’s no nuclear reactor required which saves a lot of mass as well.

Speaking of mass, I drastically overestimated the amount of supplies I would need for the crew. Or really I under estimated how well the hydroponics modules would do at recycling waste. Three years into the mission, and the crew still has a full set of supplies. The next mission should easily be able to get away with half the number of supply containers or more.

So now that the Explorer is docked at the refinery I have to make a decision about whether to cut the mission short and return to Kerbin or continue on to Pol, Laythe, and Vall. I’m leaning to cutting things short and coming back to Jool with a redesigned Explorer with better TWR. Either way, I can send Jeb down to the surface as planned and then leave the lander at the refinery.

 

Continuing my extended weekend in KSP, I left off yesterday with the crew of the Jool Explorer 1 starting their two year journey to the outer edges of the Kerbol system. I time warped the game through most of that journey, slowing down to complete a few research missions and check in on a science lab in orbit around Kerbin’s second moon, Minmus. I use a mod called Kerbal Alarm Clock which is invaluable when running multiple missions at once. It does just what it sounds like it does. I can set alarms for various events like a ship is coming up on a sphere of influence change or a maneuver node. In this case I had an alarm set to remind me when the JE1 was getting close to Jool’s gravity well.

Getting to your destination is only half of the challenge for interplanetary travel. You also have to slow down somehow to get into orbit. In the above picture the solid blue line shows the trajectory of the JE1 coming into the Jool system and then escaping. Not only that, but the ship would have picked up a little velocity because of how it was passing Jool. In previous versions of KSP, the easiest way to get into orbit of Jool was called aerobraking, and involved dipping into the upper layer of Jool’s atmosphere and using that to slow down. In the current version that just causes you ship to overheat and explode. Instead of using atmosphere, it’s possible to use gravity. Jool has three decent sized moons with nearly Kerbin levels of gravity, which makes them excellent candidates for this.

In the map screenshot above there’s a maneuver node at the top left of the blue orbit which creates the new dotted orange orbit. That orbit intersects with Jool’s third moon Tylo (which is highlighted in a peach color). Because the JE1 comes in on the backside of Tylo’s orbit, instead of picking up speed the craft instead sheds it, and after exiting Tylo’s gravity well the JE1 will be in the third green dotted orbit. This let’s me get the JE1 into an elliptical Jool orbit for only 73 m/s, compared to spending 250 or more burning on the periapsis marker of the blue orbit.

This kinds of stuff is very cool to me and one of the reasons why I enjoy KSP so much. Of course it’s fun to launch rockets, fly planes, and blow stuff up, but I have really enjoyed learning about orbital mechanics and getting a deeper appreciation for the science and work involved in space navigation.

Finally in orbit of the Jool system, it was time to transfer to the moon Tylo and the initial moon landing. The Tylo rendezvous wasn’t difficult, but it was pretty tedious. First I had to push JE1’s periapsis out to intersect with Tylo’s orbit for 418 meters per second delta V which was about an 8 minutes and 30 second burn. Second, I needed to match inclination with Tylo, so we were orbiting at the same angle, which was another 192 m/s and 4 minutes. It’s not strictly necessary to match inclination but it makes rendezvous far easier to do and I’ve never had any luck without doing it. Lastly I needed to wait two orbits and then burn to bring down my apoapsis (point an orbit furthest from the center) to match Tylo’s orbit, which required 183 m/s and a 3 minutes 47 seconds burn. Again, time warp can’t be used while the ship is under acceleration, so I had about 16 minutes of real time waiting to sit through.

While it was really nice to have a design that included so much delta V, it hasn’t really been offset by a much lower TWR, which is why all of these maneuvers were taking so long. I’ll probably not be using this same design on my next big ship. Despite the slight frustration over waiting, I was finally in orbit around Tylo. The first really exciting part of the mission was about to begin.

Jeb transferred over to the lander and undocked from the Jool Explorer. After making a save point, because nothing ever goes right the first time, Jeb made a small burn to bring his orbit down close to the planet above a landing site that  I selected semi-randomly. My only criteria was to get a different biome than an earlier probe mission so that I could run a full set of science experiments. After passing around the far side of the moon and making a second burn, I create a maneuver for the deorbit burn and waited as the Jool 5 Lander came back around to the daytime side of Tylo.

The deorbit burn was 1,495 meters per second, which was 67% of what I had in the descent stage. My plan had been to use that stage for most of the descent and jettison it just before landing. I had a minor moment of panic though because I wasn’t sure how much I would need before actually touching down. In the end I had almost a perfect amount. The remaining 33% was enough to keep my speed down for most of the descent after the deorbit burn finished. I ended up jettisoning the main descent stage and using about 460 m/s of my ascent stage touching down on the surface. But I had budgeted a few hundred extra meters per second on my ascent stage just for that reason. I thought it might be close, but I was pretty confident Jeb wouldn’t be stuck on the surface.

This Tylo landing was one of the more intense things I’ve done in KSP recently. It reminded me quite a bit of when I was first learning to do Mun landings and orbital docking. Trying to keep track of remaining fuel, heading, and descent velocity all while the surface is rushing up to meet you. These are some of the most exhilarating and rewarding activities I’ve ever done in gaming.

After planting a flag and running some experiments, I was a little anxious to get Jeb back into space and see if I could get him docked up with the JE1. Taking off from a moon with no atmosphere is pretty straight forward. You throttle up and point the craft to the east at a 45° pitch. East because then you get to add the rotational velocity of the body you’re on to your orbital velocity, and 45° is a good rule of thumb although you can always go lower or higher depending on the terrain.

It turned out that my fuel situation was a lot tighter than I realized. The Jool 5 Lander ended up in a 53.5 km by 17.5 km orbit with only 34 m/s fuel remaining. That’s not much, but this was after I had already gotten an intersect of 2.9 km with the Jool Explorer, so all I really needed was for my relative velocity to not be too much over 34 m/s when I got to my rendezvous point. I still have a bunch of monopropellant for RCS thrusters, but those aren’t create for slowing down more than 10 m/s or so.

After a last orbit of Tylo, Jeb’s Lander intercepted the Explorer and had a relative velocity of 45 m/s. Ideally it would have been 34 or less, but the remaining 11 m/s after I exhausted the lander’s fuel was easy to take care of with RCS. Docking went smoothly and then Jeb transferred back to the Explorer’s crew module bringing along all of the science he’d collected on the surface.

The next stage of the mission was to head to Laythe and land, but I ended up using more hydrogen than I expected getting from Kerbin to Tylo. So instead the crew of the JE1 will make for Bop which is where the orbital refinery that I had previously sent out is located. Bop is inclined and the fourth moon in the system, but it has very little gravity which made more sense for mining operations.

My intentions going into the weekend were to launch my Jool exploration expedition, meet up with my local Golem Arcana group, and restart on my multi-tasking experiment. Two out of three isn’t bad right? I ended up playing two Golem Arcana matches using my Dread Vanguard army, winning both so my Ashmogh remains undefeated, and playing a lot of Kerbal Space Program. A lot. Maybe 20 hours worth? I wish Steam showed detailed play statistics. Raptr kind of does, but it’s not as good at that as it used to be. As a matter of fact, if I think about it Raptr is past the point where its usefulness to me outweighs its memory footprint. I should probably find an alternative that just tracks gaming time.

Crew Transfer

The last phase of preparation for my Kerballed Jool exploration mission was to send up the crew and perform some minor structural maintenance.

The transfer vehicle was designed to send up a three Kerbal crew, the standard pilot, engineer, and scientist complement. It also had a probe core so that it could be remotely piloted and set to rendezvous and dock with the space station in orbit while the Jool mission was underway, and then be reused to bring the crew back Kerbin-side when they returned.

The crew launched at night in order to have the shortest rendezvous with the Jool Explorer 1. That means most of the launch and rendezvous was in the dark so there isn’t much in the way of pictures from that part of the mission. The actual crew transfer took place in the daytime as EVA’s, since there’s only one docking port on the Explorer and it was in use by the lander.

Our pilot, Jebediah Kerman, enjoyed the whole process a little too much.

With the crew aboard and some struts applied to the docking connection between the crew and engine modules by the ship’s engineer, Bill Kerman, it was finally time to deploy the habitat ring, heat radiators, and fire up the nuclear reactor.

This was my first time using such a large ship as well as a VASIMR engine. With a TWR (thrust to weight ratio) of 0.10 I was expecting it to be slow to get underway, but I wasn’t really prepared for how slow. I was also surprised that the Kerbal Engineer Redux (KER) mod that I use to provide flight details wasn’t working correctly with the VASIMR engine. After plotting a maneuver to transfer from Kerbin to Jool, the built-in numbers were telling me the burn would take 27 minutes while KER was saying 6 minutes and 28 seconds. Sadly KER was wrong. It also meant that I had to break the 27 minute burn down into 4 to 6 minute chunks, which was about the maximum length I could burn at my current altitude without causing my orbit to dip into the atmosphere.

So for about five orbits I would start burning at three minutes before the periapsis (lowest point on my orbit, and the most efficient place to burn from) and keep it up for six minutes total. KSP doesn’t allow time warping while a craft is under acceleration either, so I had to do all of the burns in real-time. Well that’s not totally true, KSP does allow for physical warping by a factor of 2, 3, or 4 times but physical time warp can do very bad things to a large craft and I didn’t want to risk it. Eventually the maneuver was completed and my Kerbals were finally on their way to Jool with the trip set to take roughly two years and 48 days.

Getting back to my mission preparation for my first Kerballed mission to Jool, the next piece that needed to get into orbit was the Jool 5 Lander (since it’s going to land on five different moons, not that it took five designs to get it right).

 

The launch went well, although I had to jettison the fairings below 20 kilometers which isn’t usually a good idea, but could have been much worse. I did end up using quite a bit more fuel than I expected. I still had plenty for rendezvous, but I knew then that wouldn’t have enough on the Explorer to completely refill the lander.

So of course that mean I needed to launch a refueling ship. I do have a refinery set up in orbit around Bop in the Jool system, but my plan was to go there last to refuel the ship before returning to Kerbin. I didn’t want to have to go there first, hit the remaining moons, and then  go back again. Far easier to do the refueling in Kerbin orbit instead. I happened to have a large refueling rocket design already that was over kill for  my current needs, but that’s kind of how you’re intended to play KSP anyway.

 

The refueler launch and rendezvous went off without a hitch. I always enjoy watching booster stages separate and drop away. Here’s the completed ship, fully fueled, and ready to receive crew once the transfer window arrives.